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E.1 Core TLS API

The prototypes for the following functions lie in gnutls/gnutls.h.

gnutls_alert_get

Function: gnutls_alert_description_t gnutls_alert_get (gnutls_session_t session)

session: is a gnutls_session_t type.

This function will return the last alert number received. This function should be called when GNUTLS_E_WARNING_ALERT_RECEIVED or GNUTLS_E_FATAL_ALERT_RECEIVED errors are returned by a gnutls function. The peer may send alerts if he encounters an error. If no alert has been received the returned value is undefined.

Returns: the last alert received, a gnutls_alert_description_t value.

gnutls_alert_get_name

Function: const char * gnutls_alert_get_name (gnutls_alert_description_t alert)

alert: is an alert number.

This function will return a string that describes the given alert number, or NULL . See gnutls_alert_get() .

Returns: string corresponding to gnutls_alert_description_t value.

gnutls_alert_get_strname

Function: const char * gnutls_alert_get_strname (gnutls_alert_description_t alert)

alert: is an alert number.

This function will return a string of the name of the alert.

Returns: string corresponding to gnutls_alert_description_t value.

Since: 3.0

gnutls_alert_send

Function: int gnutls_alert_send (gnutls_session_t session, gnutls_alert_level_t level, gnutls_alert_description_t desc)

session: is a gnutls_session_t type.

level: is the level of the alert

desc: is the alert description

This function will send an alert to the peer in order to inform him of something important (eg. his Certificate could not be verified). If the alert level is Fatal then the peer is expected to close the connection, otherwise he may ignore the alert and continue.

The error code of the underlying record send function will be returned, so you may also receive GNUTLS_E_INTERRUPTED or GNUTLS_E_AGAIN as well.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_alert_send_appropriate

Function: int gnutls_alert_send_appropriate (gnutls_session_t session, int err)

session: is a gnutls_session_t type.

err: is an integer

Sends an alert to the peer depending on the error code returned by a gnutls function. This function will call gnutls_error_to_alert() to determine the appropriate alert to send.

This function may also return GNUTLS_E_AGAIN , or GNUTLS_E_INTERRUPTED .

If the return value is GNUTLS_E_INVALID_REQUEST , then no alert has been sent to the peer.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_alpn_get_selected_protocol

Function: int gnutls_alpn_get_selected_protocol (gnutls_session_t session, gnutls_datum_t * protocol)

session: is a gnutls_session_t type.

protocol: will hold the protocol name

This function allows you to get the negotiated protocol name. The returned protocol should be treated as opaque, constant value and only valid during the session life.

The selected protocol is the first supported by the list sent by the client.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

Since 3.2.0

gnutls_alpn_set_protocols

Function: int gnutls_alpn_set_protocols (gnutls_session_t session, const gnutls_datum_t * protocols, unsigned protocols_size, unsigned int flags)

session: is a gnutls_session_t type.

protocols: is the protocol names to add.

protocols_size: the number of protocols to add.

flags: zero or a sequence of gnutls_alpn_flags_t

This function is to be used by both clients and servers, to declare the supported ALPN protocols, which are used during negotiation with peer.

See gnutls_alpn_flags_t description for the documentation of available flags.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

Since 3.2.0

gnutls_anon_allocate_client_credentials

Function: int gnutls_anon_allocate_client_credentials (gnutls_anon_client_credentials_t * sc)

sc: is a pointer to a gnutls_anon_client_credentials_t type.

Allocate a gnutls_anon_client_credentials_t structure.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_anon_allocate_server_credentials

Function: int gnutls_anon_allocate_server_credentials (gnutls_anon_server_credentials_t * sc)

sc: is a pointer to a gnutls_anon_server_credentials_t type.

Allocate a gnutls_anon_server_credentials_t structure.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_anon_free_client_credentials

Function: void gnutls_anon_free_client_credentials (gnutls_anon_client_credentials_t sc)

sc: is a gnutls_anon_client_credentials_t type.

Free a gnutls_anon_client_credentials_t structure.

gnutls_anon_free_server_credentials

Function: void gnutls_anon_free_server_credentials (gnutls_anon_server_credentials_t sc)

sc: is a gnutls_anon_server_credentials_t type.

Free a gnutls_anon_server_credentials_t structure.

gnutls_anon_set_params_function

Function: void gnutls_anon_set_params_function (gnutls_anon_server_credentials_t res, gnutls_params_function * func)

res: is a gnutls_anon_server_credentials_t type

func: is the function to be called

This function will set a callback in order for the server to get the Diffie-Hellman or RSA parameters for anonymous authentication. The callback should return GNUTLS_E_SUCCESS (0) on success.

gnutls_anon_set_server_dh_params

Function: void gnutls_anon_set_server_dh_params (gnutls_anon_server_credentials_t res, gnutls_dh_params_t dh_params)

res: is a gnutls_anon_server_credentials_t type

dh_params: The Diffie-Hellman parameters.

This function will set the Diffie-Hellman parameters for an anonymous server to use. These parameters will be used in Anonymous Diffie-Hellman cipher suites.

gnutls_anon_set_server_known_dh_params

Function: int gnutls_anon_set_server_known_dh_params (gnutls_anon_server_credentials_t res, gnutls_sec_param_t sec_param)

res: is a gnutls_anon_server_credentials_t type

sec_param: is an option of the gnutls_sec_param_t enumeration

This function will set the Diffie-Hellman parameters for an anonymous server to use. These parameters will be used in Anonymous Diffie-Hellman cipher suites and will be selected from the FFDHE set of RFC7919 according to the security level provided.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error value.

Since: 3.5.6

gnutls_anon_set_server_params_function

Function: void gnutls_anon_set_server_params_function (gnutls_anon_server_credentials_t res, gnutls_params_function * func)

res: is a gnutls_certificate_credentials_t type

func: is the function to be called

This function will set a callback in order for the server to get the Diffie-Hellman parameters for anonymous authentication. The callback should return GNUTLS_E_SUCCESS (0) on success.

gnutls_auth_client_get_type

Function: gnutls_credentials_type_t gnutls_auth_client_get_type (gnutls_session_t session)

session: is a gnutls_session_t type.

Returns the type of credentials that were used for client authentication. The returned information is to be used to distinguish the function used to access authentication data.

Returns: The type of credentials for the client authentication schema, a gnutls_credentials_type_t type.

gnutls_auth_get_type

Function: gnutls_credentials_type_t gnutls_auth_get_type (gnutls_session_t session)

session: is a gnutls_session_t type.

Returns type of credentials for the current authentication schema. The returned information is to be used to distinguish the function used to access authentication data.

Eg. for CERTIFICATE ciphersuites (key exchange algorithms: GNUTLS_KX_RSA , GNUTLS_KX_DHE_RSA ), the same function are to be used to access the authentication data.

Returns: The type of credentials for the current authentication schema, a gnutls_credentials_type_t type.

gnutls_auth_server_get_type

Function: gnutls_credentials_type_t gnutls_auth_server_get_type (gnutls_session_t session)

session: is a gnutls_session_t type.

Returns the type of credentials that were used for server authentication. The returned information is to be used to distinguish the function used to access authentication data.

Returns: The type of credentials for the server authentication schema, a gnutls_credentials_type_t type.

gnutls_buffer_append_data

Function: int gnutls_buffer_append_data (gnutls_buffer_t dest, const void * data, size_t data_size)

dest: the buffer to append to

data: the data

data_size: the size of data

Appends the provided data to the destination buffer.

Returns: GNUTLS_E_SUCCESS on success, otherwise a negative error code.

Since: 3.4.0

gnutls_bye

Function: int gnutls_bye (gnutls_session_t session, gnutls_close_request_t how)

session: is a gnutls_session_t type.

how: is an integer

Terminates the current TLS/SSL connection. The connection should have been initiated using gnutls_handshake() . how should be one of GNUTLS_SHUT_RDWR , GNUTLS_SHUT_WR .

In case of GNUTLS_SHUT_RDWR the TLS session gets terminated and further receives and sends will be disallowed. If the return value is zero you may continue using the underlying transport layer. GNUTLS_SHUT_RDWR sends an alert containing a close request and waits for the peer to reply with the same message.

In case of GNUTLS_SHUT_WR the TLS session gets terminated and further sends will be disallowed. In order to reuse the connection you should wait for an EOF from the peer. GNUTLS_SHUT_WR sends an alert containing a close request.

Note that not all implementations will properly terminate a TLS connection. Some of them, usually for performance reasons, will terminate only the underlying transport layer, and thus not distinguishing between a malicious party prematurely terminating the connection and normal termination.

This function may also return GNUTLS_E_AGAIN or GNUTLS_E_INTERRUPTED ; cf. gnutls_record_get_direction() .

Returns: GNUTLS_E_SUCCESS on success, or an error code, see function documentation for entire semantics.

gnutls_certificate_activation_time_peers

Function: time_t gnutls_certificate_activation_time_peers (gnutls_session_t session)

session: is a gnutls session

This function will return the peer’s certificate activation time. This is the creation time for openpgp keys.

Returns: (time_t)-1 on error.

Deprecated: gnutls_certificate_verify_peers2() now verifies activation times.

gnutls_certificate_allocate_credentials

Function: int gnutls_certificate_allocate_credentials (gnutls_certificate_credentials_t * res)

res: is a pointer to a gnutls_certificate_credentials_t type.

Allocate a gnutls_certificate_credentials_t structure.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_certificate_client_get_request_status

Function: int gnutls_certificate_client_get_request_status (gnutls_session_t session)

session: is a gnutls session

Get whether client certificate was requested on the last handshake or not.

Returns: 0 if the peer (server) did not request client authentication or 1 otherwise.

gnutls_certificate_expiration_time_peers

Function: time_t gnutls_certificate_expiration_time_peers (gnutls_session_t session)

session: is a gnutls session

This function will return the peer’s certificate expiration time.

Returns: (time_t)-1 on error.

Deprecated: gnutls_certificate_verify_peers2() now verifies expiration times.

gnutls_certificate_free_ca_names

Function: void gnutls_certificate_free_ca_names (gnutls_certificate_credentials_t sc)

sc: is a gnutls_certificate_credentials_t type.

This function will delete all the CA name in the given credentials. Clients may call this to save some memory since in client side the CA names are not used. Servers might want to use this function if a large list of trusted CAs is present and sending the names of it would just consume bandwidth without providing information to client.

CA names are used by servers to advertise the CAs they support to clients.

gnutls_certificate_free_cas

Function: void gnutls_certificate_free_cas (gnutls_certificate_credentials_t sc)

sc: is a gnutls_certificate_credentials_t type.

This function will delete all the CAs associated with the given credentials. Servers that do not use gnutls_certificate_verify_peers2() may call this to save some memory.

gnutls_certificate_free_credentials

Function: void gnutls_certificate_free_credentials (gnutls_certificate_credentials_t sc)

sc: is a gnutls_certificate_credentials_t type.

Free a gnutls_certificate_credentials_t structure.

This function does not free any temporary parameters associated with this structure (ie RSA and DH parameters are not freed by this function).

gnutls_certificate_free_crls

Function: void gnutls_certificate_free_crls (gnutls_certificate_credentials_t sc)

sc: is a gnutls_certificate_credentials_t type.

This function will delete all the CRLs associated with the given credentials.

gnutls_certificate_free_keys

Function: void gnutls_certificate_free_keys (gnutls_certificate_credentials_t sc)

sc: is a gnutls_certificate_credentials_t type.

This function will delete all the keys and the certificates associated with the given credentials. This function must not be called when a TLS negotiation that uses the credentials is in progress.

gnutls_certificate_get_crt_raw

Function: int gnutls_certificate_get_crt_raw (gnutls_certificate_credentials_t sc, unsigned idx1, unsigned idx2, gnutls_datum_t * cert)

sc: is a gnutls_certificate_credentials_t type.

idx1: the index of the certificate chain if multiple are present

idx2: the index of the certificate in the chain. Zero gives the server’s certificate.

cert: Will hold the DER encoded certificate.

This function will return the DER encoded certificate of the server or any other certificate on its certificate chain (based on idx2 ). The returned data should be treated as constant and only accessible during the lifetime of sc . The idx1 matches the value gnutls_certificate_set_x509_key() and friends functions.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error value. In case the indexes are out of bounds GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE is returned.

Since: 3.2.5

gnutls_certificate_get_issuer

Function: int gnutls_certificate_get_issuer (gnutls_certificate_credentials_t sc, gnutls_x509_crt_t cert, gnutls_x509_crt_t * issuer, unsigned int flags)

sc: is a gnutls_certificate_credentials_t type.

cert: is the certificate to find issuer for

issuer: Will hold the issuer if any. Should be treated as constant.

flags: Use zero or GNUTLS_TL_GET_COPY

This function will return the issuer of a given certificate. If the flag GNUTLS_TL_GET_COPY is specified a copy of the issuer will be returned which must be freed using gnutls_x509_crt_deinit() . In that case the provided issuer must not be initialized.

As with gnutls_x509_trust_list_get_issuer() this function requires the GNUTLS_TL_GET_COPY flag in order to operate with PKCS11 trust lists in a thread-safe way.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error value.

Since: 3.0

gnutls_certificate_get_ours

Function: const gnutls_datum_t * gnutls_certificate_get_ours (gnutls_session_t session)

session: is a gnutls session

Gets the certificate as sent to the peer in the last handshake. The certificate is in raw (DER) format. No certificate list is being returned. Only the first certificate.

Returns: a pointer to a gnutls_datum_t containing our certificate, or NULL in case of an error or if no certificate was used.

gnutls_certificate_get_peers

Function: const gnutls_datum_t * gnutls_certificate_get_peers (gnutls_session_t session, unsigned int * list_size)

session: is a gnutls session

list_size: is the length of the certificate list (may be NULL )

Get the peer’s raw certificate (chain) as sent by the peer. These certificates are in raw format (DER encoded for X.509). In case of a X.509 then a certificate list may be present. The list is provided as sent by the server; the server must send as first certificate in the list its own certificate, following the issuer’s certificate, then the issuer’s issuer etc. However, there are servers which violate this principle and thus on certain occasions this may be an unsorted list.

In case of OpenPGP keys a single key will be returned in raw format.

Returns: a pointer to a gnutls_datum_t containing the peer’s certificates, or NULL in case of an error or if no certificate was used.

gnutls_certificate_get_peers_subkey_id

Function: int gnutls_certificate_get_peers_subkey_id (gnutls_session_t session, gnutls_datum_t * id)

session: is a gnutls session

id: will contain the ID

Get the peer’s subkey ID when OpenPGP certificates are used. The returned id should be treated as constant.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

Since: 3.1.3

gnutls_certificate_get_verify_flags

Function: unsigned int gnutls_certificate_get_verify_flags (gnutls_certificate_credentials_t res)

res: is a gnutls_certificate_credentials_t type

Returns the verification flags set with gnutls_certificate_set_verify_flags() .

Returns: The certificate verification flags used by res .

Since: 3.4.0

gnutls_certificate_get_x509_crt

Function: int gnutls_certificate_get_x509_crt (gnutls_certificate_credentials_t res, unsigned index, gnutls_x509_crt_t ** crt_list, unsigned * crt_list_size)

res: is a gnutls_certificate_credentials_t type.

index: The index of the certificate list to obtain.

crt_list: Where to store the certificate list.

crt_list_size: Will hold the number of certificates.

Obtains a X.509 certificate list that has been stored in res with one of gnutls_certificate_set_x509_key() , gnutls_certificate_set_key() , gnutls_certificate_set_x509_key_file() , gnutls_certificate_set_x509_key_file2() , gnutls_certificate_set_x509_key_mem() , or gnutls_certificate_set_x509_key_mem2() . Each certificate in the returned certificate list must be deallocated with gnutls_x509_crt_deinit() , and the list itself must be freed with gnutls_free() .

The index matches the return value of gnutls_certificate_set_x509_key() and friends functions, when the GNUTLS_CERTIFICATE_API_V2 flag is set.

If there is no certificate with the given index, GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE is returned. If the certificate with the given index is not a X.509 certificate, GNUTLS_E_INVALID_REQUEST is returned. The returned certificates must be deinitialized after use, and the crt_list pointer must be freed using gnutls_free() .

Returns: GNUTLS_E_SUCCESS (0) on success, or a negative error code.

Since: 3.4.0

gnutls_certificate_get_x509_key

Function: int gnutls_certificate_get_x509_key (gnutls_certificate_credentials_t res, unsigned index, gnutls_x509_privkey_t * key)

res: is a gnutls_certificate_credentials_t type.

index: The index of the key to obtain.

key: Location to store the key.

Obtains a X.509 private key that has been stored in res with one of gnutls_certificate_set_x509_key() , gnutls_certificate_set_key() , gnutls_certificate_set_x509_key_file() , gnutls_certificate_set_x509_key_file2() , gnutls_certificate_set_x509_key_mem() , or gnutls_certificate_set_x509_key_mem2() . The returned key must be deallocated with gnutls_x509_privkey_deinit() when no longer needed.

The index matches the return value of gnutls_certificate_set_x509_key() and friends functions, when the GNUTLS_CERTIFICATE_API_V2 flag is set.

If there is no key with the given index, GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE is returned. If the key with the given index is not a X.509 key, GNUTLS_E_INVALID_REQUEST is returned.

Returns: GNUTLS_E_SUCCESS (0) on success, or a negative error code.

Since: 3.4.0

gnutls_certificate_send_x509_rdn_sequence

Function: void gnutls_certificate_send_x509_rdn_sequence (gnutls_session_t session, int status)

session: a gnutls_session_t type.

status: is 0 or 1

If status is non zero, this function will order gnutls not to send the rdnSequence in the certificate request message. That is the server will not advertise its trusted CAs to the peer. If status is zero then the default behaviour will take effect, which is to advertise the server’s trusted CAs.

This function has no effect in clients, and in authentication methods other than certificate with X.509 certificates.

gnutls_certificate_server_set_request

Function: void gnutls_certificate_server_set_request (gnutls_session_t session, gnutls_certificate_request_t req)

session: is a gnutls_session_t type.

req: is one of GNUTLS_CERT_REQUEST, GNUTLS_CERT_REQUIRE

This function specifies if we (in case of a server) are going to send a certificate request message to the client. If req is GNUTLS_CERT_REQUIRE then the server will return an error if the peer does not provide a certificate. If you do not call this function then the client will not be asked to send a certificate.

gnutls_certificate_set_dh_params

Function: void gnutls_certificate_set_dh_params (gnutls_certificate_credentials_t res, gnutls_dh_params_t dh_params)

res: is a gnutls_certificate_credentials_t type

dh_params: the Diffie-Hellman parameters.

This function will set the Diffie-Hellman parameters for a certificate server to use. These parameters will be used in Ephemeral Diffie-Hellman cipher suites. Note that only a pointer to the parameters are stored in the certificate handle, so you must not deallocate the parameters before the certificate is deallocated.

gnutls_certificate_set_flags

Function: void gnutls_certificate_set_flags (gnutls_certificate_credentials_t res, unsigned int flags)

res: is a gnutls_certificate_credentials_t type

flags: are the flags of gnutls_certificate_flags type

This function will set flags to tweak the operation of the credentials structure. See the gnutls_certificate_flags enumerations for more information on the available flags.

Since: 3.4.7

gnutls_certificate_set_known_dh_params

Function: int gnutls_certificate_set_known_dh_params (gnutls_certificate_credentials_t res, gnutls_sec_param_t sec_param)

res: is a gnutls_certificate_credentials_t type

sec_param: is an option of the gnutls_sec_param_t enumeration

This function will set the Diffie-Hellman parameters for a certificate server to use. These parameters will be used in Ephemeral Diffie-Hellman cipher suites and will be selected from the FFDHE set of RFC7919 according to the security level provided.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error value.

Since: 3.5.6

gnutls_certificate_set_ocsp_status_request_file

Function: int gnutls_certificate_set_ocsp_status_request_file (gnutls_certificate_credentials_t sc, const char * response_file, unsigned idx)

sc: is a credentials structure.

response_file: a filename of the OCSP response

idx: is a certificate index as returned by gnutls_certificate_set_key() and friends

This function sets the filename of an OCSP response, that will be sent to the client if requests an OCSP certificate status for the certificate chain specified by idx .

This is a convenience function which may be inefficient on busy servers since the file is opened on every access. Use gnutls_certificate_set_ocsp_status_request_function2() to fine-tune file accesses.

Note: the ability to set multiple OCSP responses per credential structure via idx was added in version 3.5.6 with the GNUTLS_CERTIFICATE_API_V2 flag.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

Since: 3.1.3

gnutls_certificate_set_ocsp_status_request_function

Function: void gnutls_certificate_set_ocsp_status_request_function (gnutls_certificate_credentials_t sc, gnutls_status_request_ocsp_func ocsp_func, void * ptr)

sc: is a gnutls_certificate_credentials_t type.

ocsp_func: function pointer to OCSP status request callback.

ptr: opaque pointer passed to callback function

This function is to be used by server to register a callback to handle OCSP status requests from the client. The callback will be invoked if the client supplied a status-request OCSP extension. The callback function prototype is:

typedef int (*gnutls_status_request_ocsp_func) (gnutls_session_t session, void *ptr, gnutls_datum_t *ocsp_response);

The callback will be invoked if the client requests an OCSP certificate status. The callback may return GNUTLS_E_NO_CERTIFICATE_STATUS , if there is no recent OCSP response. If the callback returns GNUTLS_E_SUCCESS , it is expected to have the ocsp_response field set with a valid (DER-encoded) OCSP response. The response must be a value allocated using gnutls_malloc() , and will be deinitialized by the caller.

It is possible to set a specific callback for each provided certificate using gnutls_certificate_set_ocsp_status_request_function2() .

Since: 3.1.3

gnutls_certificate_set_ocsp_status_request_function2

Function: int gnutls_certificate_set_ocsp_status_request_function2 (gnutls_certificate_credentials_t sc, unsigned idx, gnutls_status_request_ocsp_func ocsp_func, void * ptr)

sc: is a gnutls_certificate_credentials_t type.

idx: is a certificate index as returned by gnutls_certificate_set_key() and friends

ocsp_func: function pointer to OCSP status request callback.

ptr: opaque pointer passed to callback function

This function is to be used by server to register a callback to handle OCSP status requests that correspond to the indexed certificate from the client. The callback will be invoked if the client supplied a status-request OCSP extension.

The callback function prototype is:

typedef int (*gnutls_status_request_ocsp_func) (gnutls_session_t session, void *ptr, gnutls_datum_t *ocsp_response);

The callback will be invoked if the client requests an OCSP certificate status. The callback may return GNUTLS_E_NO_CERTIFICATE_STATUS , if there is no recent OCSP response. If the callback returns GNUTLS_E_SUCCESS , it is expected to have the ocsp_response field set with a valid (DER-encoded) OCSP response. The response must be a value allocated using gnutls_malloc() , and will be deinitialized by the caller.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

Since: 3.5.5

gnutls_certificate_set_params_function

Function: void gnutls_certificate_set_params_function (gnutls_certificate_credentials_t res, gnutls_params_function * func)

res: is a gnutls_certificate_credentials_t type

func: is the function to be called

This function will set a callback in order for the server to get the Diffie-Hellman or RSA parameters for certificate authentication. The callback should return GNUTLS_E_SUCCESS (0) on success.

gnutls_certificate_set_pin_function

Function: void gnutls_certificate_set_pin_function (gnutls_certificate_credentials_t cred, gnutls_pin_callback_t fn, void * userdata)

cred: is a gnutls_certificate_credentials_t type.

fn: A PIN callback

userdata: Data to be passed in the callback

This function will set a callback function to be used when required to access a protected object. This function overrides any other global PIN functions.

Note that this function must be called right after initialization to have effect.

Since: 3.1.0

gnutls_certificate_set_retrieve_function

Function: void gnutls_certificate_set_retrieve_function (gnutls_certificate_credentials_t cred, gnutls_certificate_retrieve_function * func)

cred: is a gnutls_certificate_credentials_t type.

func: is the callback function

This function sets a callback to be called in order to retrieve the certificate to be used in the handshake. The callback will take control only if a certificate is requested by the peer. You are advised to use gnutls_certificate_set_retrieve_function2() because it is much more efficient in the processing it requires from gnutls.

The callback’s function prototype is: int (*callback)(gnutls_session_t, const gnutls_datum_t* req_ca_dn, int nreqs, const gnutls_pk_algorithm_t* pk_algos, int pk_algos_length, gnutls_retr2_st* st);

req_ca_dn is only used in X.509 certificates. Contains a list with the CA names that the server considers trusted. This is a hint and typically the client should send a certificate that is signed by one of these CAs. These names, when available, are DER encoded. To get a more meaningful value use the function gnutls_x509_rdn_get() .

pk_algos contains a list with server’s acceptable signature algorithms. The certificate returned should support the server’s given algorithms.

st should contain the certificates and private keys.

If the callback function is provided then gnutls will call it, in the handshake, after the certificate request message has been received.

In server side pk_algos and req_ca_dn are NULL.

The callback function should set the certificate list to be sent, and return 0 on success. If no certificate was selected then the number of certificates should be set to zero. The value (-1) indicates error and the handshake will be terminated. If both certificates are set in the credentials and a callback is available, the callback takes predence.

Since: 3.0

gnutls_certificate_set_verify_flags

Function: void gnutls_certificate_set_verify_flags (gnutls_certificate_credentials_t res, unsigned int flags)

res: is a gnutls_certificate_credentials_t type

flags: are the flags

This function will set the flags to be used for verification of certificates and override any defaults. The provided flags must be an OR of the gnutls_certificate_verify_flags enumerations.

gnutls_certificate_set_verify_function

Function: void gnutls_certificate_set_verify_function (gnutls_certificate_credentials_t cred, gnutls_certificate_verify_function * func)

cred: is a gnutls_certificate_credentials_t type.

func: is the callback function

This function sets a callback to be called when peer’s certificate has been received in order to verify it on receipt rather than doing after the handshake is completed.

The callback’s function prototype is: int (*callback)(gnutls_session_t);

If the callback function is provided then gnutls will call it, in the handshake, just after the certificate message has been received. To verify or obtain the certificate the gnutls_certificate_verify_peers2() , gnutls_certificate_type_get() , gnutls_certificate_get_peers() functions can be used.

The callback function should return 0 for the handshake to continue or non-zero to terminate.

Since: 2.10.0

gnutls_certificate_set_verify_limits

Function: void gnutls_certificate_set_verify_limits (gnutls_certificate_credentials_t res, unsigned int max_bits, unsigned int max_depth)

res: is a gnutls_certificate_credentials type

max_bits: is the number of bits of an acceptable certificate (default 8200)

max_depth: is maximum depth of the verification of a certificate chain (default 5)

This function will set some upper limits for the default verification function, gnutls_certificate_verify_peers2() , to avoid denial of service attacks. You can set them to zero to disable limits.

gnutls_certificate_set_x509_crl

Function: int gnutls_certificate_set_x509_crl (gnutls_certificate_credentials_t res, gnutls_x509_crl_t * crl_list, int crl_list_size)

res: is a gnutls_certificate_credentials_t type.

crl_list: is a list of trusted CRLs. They should have been verified before.

crl_list_size: holds the size of the crl_list

This function adds the trusted CRLs in order to verify client or server certificates. In case of a client this is not required to be called if the certificates are not verified using gnutls_certificate_verify_peers2() . This function may be called multiple times.

Returns: number of CRLs processed, or a negative error code on error.

Since: 2.4.0

gnutls_certificate_set_x509_crl_file

Function: int gnutls_certificate_set_x509_crl_file (gnutls_certificate_credentials_t res, const char * crlfile, gnutls_x509_crt_fmt_t type)

res: is a gnutls_certificate_credentials_t type.

crlfile: is a file containing the list of verified CRLs (DER or PEM list)

type: is PEM or DER

This function adds the trusted CRLs in order to verify client or server certificates. In case of a client this is not required to be called if the certificates are not verified using gnutls_certificate_verify_peers2() . This function may be called multiple times.

Returns: number of CRLs processed or a negative error code on error.

gnutls_certificate_set_x509_crl_mem

Function: int gnutls_certificate_set_x509_crl_mem (gnutls_certificate_credentials_t res, const gnutls_datum_t * CRL, gnutls_x509_crt_fmt_t type)

res: is a gnutls_certificate_credentials_t type.

CRL: is a list of trusted CRLs. They should have been verified before.

type: is DER or PEM

This function adds the trusted CRLs in order to verify client or server certificates. In case of a client this is not required to be called if the certificates are not verified using gnutls_certificate_verify_peers2() . This function may be called multiple times.

Returns: number of CRLs processed, or a negative error code on error.

gnutls_certificate_set_x509_key

Function: int gnutls_certificate_set_x509_key (gnutls_certificate_credentials_t res, gnutls_x509_crt_t * cert_list, int cert_list_size, gnutls_x509_privkey_t key)

res: is a gnutls_certificate_credentials_t type.

cert_list: contains a certificate list (path) for the specified private key

cert_list_size: holds the size of the certificate list

key: is a gnutls_x509_privkey_t key

This function sets a certificate/private key pair in the gnutls_certificate_credentials_t type. This function may be called more than once, in case multiple keys/certificates exist for the server. For clients that wants to send more than their own end entity certificate (e.g., also an intermediate CA cert) then put the certificate chain in cert_list .

Note that the certificates and keys provided, can be safely deinitialized after this function is called.

If that function fails to load the res type is at an undefined state, it must not be reused to load other keys or certificates.

Note that, this function by default returns zero on success and a negative value on error. Since 3.5.6, when the flag GNUTLS_CERTIFICATE_API_V2 is set using gnutls_certificate_set_flags() it returns an index (greater or equal to zero). That index can be used to other functions to refer to the added key-pair.

Returns: On success this functions returns zero, and otherwise a negative value on error (see above for modifying that behavior).

Since: 2.4.0

gnutls_certificate_set_x509_key_file

Function: int gnutls_certificate_set_x509_key_file (gnutls_certificate_credentials_t res, const char * certfile, const char * keyfile, gnutls_x509_crt_fmt_t type)

res: is a gnutls_certificate_credentials_t type.

certfile: is a file that containing the certificate list (path) for the specified private key, in PKCS7 format, or a list of certificates

keyfile: is a file that contains the private key

type: is PEM or DER

This function sets a certificate/private key pair in the gnutls_certificate_credentials_t type. This function may be called more than once, in case multiple keys/certificates exist for the server. For clients that need to send more than its own end entity certificate, e.g., also an intermediate CA cert, then the certfile must contain the ordered certificate chain.

Note that the names in the certificate provided will be considered when selecting the appropriate certificate to use (in case of multiple certificate/key pairs).

This function can also accept URLs at keyfile and certfile . In that case it will use the private key and certificate indicated by the URLs. Note that the supported URLs are the ones indicated by gnutls_url_is_supported() .

In case the certfile is provided as a PKCS 11 URL, then the certificate, and its present issuers in the token are imported (i.e., forming the required trust chain).

If that function fails to load the res structure is at an undefined state, it must not be reused to load other keys or certificates.

Note that, this function by default returns zero on success and a negative value on error. Since 3.5.6, when the flag GNUTLS_CERTIFICATE_API_V2 is set using gnutls_certificate_set_flags() it returns an index (greater or equal to zero). That index can be used to other functions to refer to the added key-pair.

Returns: On success this functions returns zero, and otherwise a negative value on error (see above for modifying that behavior).

Since: 3.1.11

gnutls_certificate_set_x509_key_file2

Function: int gnutls_certificate_set_x509_key_file2 (gnutls_certificate_credentials_t res, const char * certfile, const char * keyfile, gnutls_x509_crt_fmt_t type, const char * pass, unsigned int flags)

res: is a gnutls_certificate_credentials_t type.

certfile: is a file that containing the certificate list (path) for the specified private key, in PKCS7 format, or a list of certificates

keyfile: is a file that contains the private key

type: is PEM or DER

pass: is the password of the key

flags: an ORed sequence of gnutls_pkcs_encrypt_flags_t

This function sets a certificate/private key pair in the gnutls_certificate_credentials_t type. This function may be called more than once, in case multiple keys/certificates exist for the server. For clients that need to send more than its own end entity certificate, e.g., also an intermediate CA cert, then the certfile must contain the ordered certificate chain.

Note that the names in the certificate provided will be considered when selecting the appropriate certificate to use (in case of multiple certificate/key pairs).

This function can also accept URLs at keyfile and certfile . In that case it will use the private key and certificate indicated by the URLs. Note that the supported URLs are the ones indicated by gnutls_url_is_supported() . Before GnuTLS 3.4.0 when a URL was specified, the pass part was ignored and a PIN callback had to be registered, this is no longer the case in current releases.

In case the certfile is provided as a PKCS 11 URL, then the certificate, and its present issuers in the token are imported (i.e., forming the required trust chain).

If that function fails to load the res structure is at an undefined state, it must not be reused to load other keys or certificates.

Note that, this function by default returns zero on success and a negative value on error. Since 3.5.6, when the flag GNUTLS_CERTIFICATE_API_V2 is set using gnutls_certificate_set_flags() it returns an index (greater or equal to zero). That index can be used to other functions to refer to the added key-pair.

Returns: On success this functions returns zero, and otherwise a negative value on error (see above for modifying that behavior).

gnutls_certificate_set_x509_key_mem

Function: int gnutls_certificate_set_x509_key_mem (gnutls_certificate_credentials_t res, const gnutls_datum_t * cert, const gnutls_datum_t * key, gnutls_x509_crt_fmt_t type)

res: is a gnutls_certificate_credentials_t type.

cert: contains a certificate list (path) for the specified private key

key: is the private key, or NULL

type: is PEM or DER

This function sets a certificate/private key pair in the gnutls_certificate_credentials_t type. This function may be called more than once, in case multiple keys/certificates exist for the server.

Note that the keyUsage (2.5.29.15) PKIX extension in X.509 certificates is supported. This means that certificates intended for signing cannot be used for ciphersuites that require encryption.

If the certificate and the private key are given in PEM encoding then the strings that hold their values must be null terminated.

The key may be NULL if you are using a sign callback, see gnutls_sign_callback_set() .

Note that, this function by default returns zero on success and a negative value on error. Since 3.5.6, when the flag GNUTLS_CERTIFICATE_API_V2 is set using gnutls_certificate_set_flags() it returns an index (greater or equal to zero). That index can be used to other functions to refer to the added key-pair.

Returns: On success this functions returns zero, and otherwise a negative value on error (see above for modifying that behavior).

gnutls_certificate_set_x509_key_mem2

Function: int gnutls_certificate_set_x509_key_mem2 (gnutls_certificate_credentials_t res, const gnutls_datum_t * cert, const gnutls_datum_t * key, gnutls_x509_crt_fmt_t type, const char * pass, unsigned int flags)

res: is a gnutls_certificate_credentials_t type.

cert: contains a certificate list (path) for the specified private key

key: is the private key, or NULL

type: is PEM or DER

pass: is the key’s password

flags: an ORed sequence of gnutls_pkcs_encrypt_flags_t

This function sets a certificate/private key pair in the gnutls_certificate_credentials_t type. This function may be called more than once, in case multiple keys/certificates exist for the server.

Note that the keyUsage (2.5.29.15) PKIX extension in X.509 certificates is supported. This means that certificates intended for signing cannot be used for ciphersuites that require encryption.

If the certificate and the private key are given in PEM encoding then the strings that hold their values must be null terminated.

The key may be NULL if you are using a sign callback, see gnutls_sign_callback_set() .

Note that, this function by default returns zero on success and a negative value on error. Since 3.5.6, when the flag GNUTLS_CERTIFICATE_API_V2 is set using gnutls_certificate_set_flags() it returns an index (greater or equal to zero). That index can be used to other functions to refer to the added key-pair.

Returns: On success this functions returns zero, and otherwise a negative value on error (see above for modifying that behavior).

gnutls_certificate_set_x509_simple_pkcs12_file

Function: int gnutls_certificate_set_x509_simple_pkcs12_file (gnutls_certificate_credentials_t res, const char * pkcs12file, gnutls_x509_crt_fmt_t type, const char * password)

res: is a gnutls_certificate_credentials_t type.

pkcs12file: filename of file containing PKCS12 blob.

type: is PEM or DER of the pkcs12file .

password: optional password used to decrypt PKCS12 file, bags and keys.

This function sets a certificate/private key pair and/or a CRL in the gnutls_certificate_credentials_t type. This function may be called more than once (in case multiple keys/certificates exist for the server).

PKCS12 files with a MAC, encrypted bags and PKCS 8 private keys are supported. However, only password based security, and the same password for all operations, are supported.

PKCS12 file may contain many keys and/or certificates, and this function will try to auto-detect based on the key ID the certificate and key pair to use. If the PKCS12 file contain the issuer of the selected certificate, it will be appended to the certificate to form a chain.

If more than one private keys are stored in the PKCS12 file, then only one key will be read (and it is undefined which one).

It is believed that the limitations of this function is acceptable for most usage, and that any more flexibility would introduce complexity that would make it harder to use this functionality at all.

Note that, this function by default returns zero on success and a negative value on error. Since 3.5.6, when the flag GNUTLS_CERTIFICATE_API_V2 is set using gnutls_certificate_set_flags() it returns an index (greater or equal to zero). That index can be used to other functions to refer to the added key-pair.

Returns: On success this functions returns zero, and otherwise a negative value on error (see above for modifying that behavior).

gnutls_certificate_set_x509_simple_pkcs12_mem

Function: int gnutls_certificate_set_x509_simple_pkcs12_mem (gnutls_certificate_credentials_t res, const gnutls_datum_t * p12blob, gnutls_x509_crt_fmt_t type, const char * password)

res: is a gnutls_certificate_credentials_t type.

p12blob: the PKCS12 blob.

type: is PEM or DER of the pkcs12file .

password: optional password used to decrypt PKCS12 file, bags and keys.

This function sets a certificate/private key pair and/or a CRL in the gnutls_certificate_credentials_t type. This function may be called more than once (in case multiple keys/certificates exist for the server).

Encrypted PKCS12 bags and PKCS8 private keys are supported. However, only password based security, and the same password for all operations, are supported.

PKCS12 file may contain many keys and/or certificates, and this function will try to auto-detect based on the key ID the certificate and key pair to use. If the PKCS12 file contain the issuer of the selected certificate, it will be appended to the certificate to form a chain.

If more than one private keys are stored in the PKCS12 file, then only one key will be read (and it is undefined which one).

It is believed that the limitations of this function is acceptable for most usage, and that any more flexibility would introduce complexity that would make it harder to use this functionality at all.

Note that, this function by default returns zero on success and a negative value on error. Since 3.5.6, when the flag GNUTLS_CERTIFICATE_API_V2 is set using gnutls_certificate_set_flags() it returns an index (greater or equal to zero). That index can be used to other functions to refer to the added key-pair.

Returns: On success this functions returns zero, and otherwise a negative value on error (see above for modifying that behavior).

Since: 2.8.0

gnutls_certificate_set_x509_system_trust

Function: int gnutls_certificate_set_x509_system_trust (gnutls_certificate_credentials_t cred)

cred: is a gnutls_certificate_credentials_t type.

This function adds the system’s default trusted CAs in order to verify client or server certificates.

In the case the system is currently unsupported GNUTLS_E_UNIMPLEMENTED_FEATURE is returned.

Returns: the number of certificates processed or a negative error code on error.

Since: 3.0.20

gnutls_certificate_set_x509_trust

Function: int gnutls_certificate_set_x509_trust (gnutls_certificate_credentials_t res, gnutls_x509_crt_t * ca_list, int ca_list_size)

res: is a gnutls_certificate_credentials_t type.

ca_list: is a list of trusted CAs

ca_list_size: holds the size of the CA list

This function adds the trusted CAs in order to verify client or server certificates. In case of a client this is not required to be called if the certificates are not verified using gnutls_certificate_verify_peers2() . This function may be called multiple times.

In case of a server the CAs set here will be sent to the client if a certificate request is sent. This can be disabled using gnutls_certificate_send_x509_rdn_sequence() .

Returns: the number of certificates processed or a negative error code on error.

Since: 2.4.0

gnutls_certificate_set_x509_trust_dir

Function: int gnutls_certificate_set_x509_trust_dir (gnutls_certificate_credentials_t cred, const char * ca_dir, gnutls_x509_crt_fmt_t type)

cred: is a gnutls_certificate_credentials_t type.

ca_dir: is a directory containing the list of trusted CAs (DER or PEM list)

type: is PEM or DER

This function adds the trusted CAs present in the directory in order to verify client or server certificates. This function is identical to gnutls_certificate_set_x509_trust_file() but loads all certificates in a directory.

Returns: the number of certificates processed

Since: 3.3.6

gnutls_certificate_set_x509_trust_file

Function: int gnutls_certificate_set_x509_trust_file (gnutls_certificate_credentials_t cred, const char * cafile, gnutls_x509_crt_fmt_t type)

cred: is a gnutls_certificate_credentials_t type.

cafile: is a file containing the list of trusted CAs (DER or PEM list)

type: is PEM or DER

This function adds the trusted CAs in order to verify client or server certificates. In case of a client this is not required to be called if the certificates are not verified using gnutls_certificate_verify_peers2() . This function may be called multiple times.

In case of a server the names of the CAs set here will be sent to the client if a certificate request is sent. This can be disabled using gnutls_certificate_send_x509_rdn_sequence() .

This function can also accept URLs. In that case it will import all certificates that are marked as trusted. Note that the supported URLs are the ones indicated by gnutls_url_is_supported() .

Returns: the number of certificates processed

gnutls_certificate_set_x509_trust_mem

Function: int gnutls_certificate_set_x509_trust_mem (gnutls_certificate_credentials_t res, const gnutls_datum_t * ca, gnutls_x509_crt_fmt_t type)

res: is a gnutls_certificate_credentials_t type.

ca: is a list of trusted CAs or a DER certificate

type: is DER or PEM

This function adds the trusted CAs in order to verify client or server certificates. In case of a client this is not required to be called if the certificates are not verified using gnutls_certificate_verify_peers2() . This function may be called multiple times.

In case of a server the CAs set here will be sent to the client if a certificate request is sent. This can be disabled using gnutls_certificate_send_x509_rdn_sequence() .

Returns: the number of certificates processed or a negative error code on error.

gnutls_certificate_type_get

Function: gnutls_certificate_type_t gnutls_certificate_type_get (gnutls_session_t session)

session: is a gnutls_session_t type.

The certificate type is by default X.509, unless it is negotiated as a TLS extension.

Returns: the currently used gnutls_certificate_type_t certificate type.

gnutls_certificate_type_get_id

Function: gnutls_certificate_type_t gnutls_certificate_type_get_id (const char * name)

name: is a certificate type name

The names are compared in a case insensitive way.

Returns: a gnutls_certificate_type_t for the specified in a string certificate type, or GNUTLS_CRT_UNKNOWN on error.

gnutls_certificate_type_get_name

Function: const char * gnutls_certificate_type_get_name (gnutls_certificate_type_t type)

type: is a certificate type

Convert a gnutls_certificate_type_t type to a string.

Returns: a string that contains the name of the specified certificate type, or NULL in case of unknown types.

gnutls_certificate_type_list

Function: const gnutls_certificate_type_t * gnutls_certificate_type_list ( void)

Get a list of certificate types.

Returns: a (0)-terminated list of gnutls_certificate_type_t integers indicating the available certificate types.

gnutls_certificate_verification_status_print

Function: int gnutls_certificate_verification_status_print (unsigned int status, gnutls_certificate_type_t type, gnutls_datum_t * out, unsigned int flags)

status: The status flags to be printed

type: The certificate type

out: Newly allocated datum with (0) terminated string.

flags: should be zero

This function will pretty print the status of a verification process – eg. the one obtained by gnutls_certificate_verify_peers3() .

The output out needs to be deallocated using gnutls_free() .

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error value.

Since: 3.1.4

gnutls_certificate_verify_peers

Function: int gnutls_certificate_verify_peers (gnutls_session_t session, gnutls_typed_vdata_st * data, unsigned int elements, unsigned int * status)

session: is a gnutls session

data: an array of typed data

elements: the number of data elements

status: is the output of the verification

This function will verify the peer’s certificate and store the status in the status variable as a bitwise or’d gnutls_certificate_status_t values or zero if the certificate is trusted. Note that value in status is set only when the return value of this function is success (i.e, failure to trust a certificate does not imply a negative return value). The default verification flags used by this function can be overridden using gnutls_certificate_set_verify_flags() . See the documentation of gnutls_certificate_verify_peers2() for details in the verification process.

The acceptable data types are GNUTLS_DT_DNS_HOSTNAME , GNUTLS_DT_RFC822NAME and GNUTLS_DT_KEY_PURPOSE_OID . The former two accept as data a null-terminated hostname or email address, and the latter a null-terminated object identifier (e.g., GNUTLS_KP_TLS_WWW_SERVER ).

If a DNS hostname is provided then this function will compare the hostname in the certificate against the given. If names do not match the GNUTLS_CERT_UNEXPECTED_OWNER status flag will be set. If a key purpose OID is provided and the end-certificate contains the extended key usage PKIX extension, it will be required to be have the provided key purpose or be marked for any purpose, otherwise verification status will have the GNUTLS_CERT_SIGNER_CONSTRAINTS_FAILURE flag set.

Returns: GNUTLS_E_SUCCESS (0) when the validation is performed, or a negative error code otherwise. A sucessful error code means that the status parameter must be checked to obtain the validation status.

Since: 3.3.0

gnutls_certificate_verify_peers2

Function: int gnutls_certificate_verify_peers2 (gnutls_session_t session, unsigned int * status)

session: is a gnutls session

status: is the output of the verification

This function will verify the peer’s certificate and store the status in the status variable as a bitwise or’d gnutls_certificate_status_t values or zero if the certificate is trusted. Note that value in status is set only when the return value of this function is success (i.e, failure to trust a certificate does not imply a negative return value). The default verification flags used by this function can be overridden using gnutls_certificate_set_verify_flags() .

This function will take into account the OCSP Certificate Status TLS extension, as well as the following X.509 certificate extensions: Name Constraints, Key Usage, and Basic Constraints (pathlen).

To avoid denial of service attacks some default upper limits regarding the certificate key size and chain size are set. To override them use gnutls_certificate_set_verify_limits() .

Note that you must also check the peer’s name in order to check if the verified certificate belongs to the actual peer, see gnutls_x509_crt_check_hostname() , or use gnutls_certificate_verify_peers3() .

Returns: GNUTLS_E_SUCCESS (0) when the validation is performed, or a negative error code otherwise. A sucessful error code means that the status parameter must be checked to obtain the validation status.

gnutls_certificate_verify_peers3

Function: int gnutls_certificate_verify_peers3 (gnutls_session_t session, const char * hostname, unsigned int * status)

session: is a gnutls session

hostname: is the expected name of the peer; may be NULL

status: is the output of the verification

This function will verify the peer’s certificate and store the status in the status variable as a bitwise or’d gnutls_certificate_status_t values or zero if the certificate is trusted. Note that value in status is set only when the return value of this function is success (i.e, failure to trust a certificate does not imply a negative return value). The default verification flags used by this function can be overridden using gnutls_certificate_set_verify_flags() . See the documentation of gnutls_certificate_verify_peers2() for details in the verification process.

If the hostname provided is non-NULL then this function will compare the hostname in the certificate against it. The comparison will follow the RFC6125 recommendations. If names do not match the GNUTLS_CERT_UNEXPECTED_OWNER status flag will be set.

In order to verify the purpose of the end-certificate (by checking the extended key usage), use gnutls_certificate_verify_peers() .

Returns: GNUTLS_E_SUCCESS (0) when the validation is performed, or a negative error code otherwise. A sucessful error code means that the status parameter must be checked to obtain the validation status.

Since: 3.1.4

gnutls_check_version

Function: const char * gnutls_check_version (const char * req_version)

req_version: version string to compare with, or NULL .

Check the GnuTLS Library version against the provided string. See GNUTLS_VERSION for a suitable req_version string.

See also gnutls_check_version_numeric() , which provides this functionality as a macro.

Returns: Check that the version of the library is at minimum the one given as a string in req_version and return the actual version string of the library; return NULL if the condition is not met. If NULL is passed to this function no check is done and only the version string is returned.

gnutls_cipher_get

Function: gnutls_cipher_algorithm_t gnutls_cipher_get (gnutls_session_t session)

session: is a gnutls_session_t type.

Get currently used cipher.

Returns: the currently used cipher, a gnutls_cipher_algorithm_t type.

gnutls_cipher_get_id

Function: gnutls_cipher_algorithm_t gnutls_cipher_get_id (const char * name)

name: is a cipher algorithm name

The names are compared in a case insensitive way.

Returns: return a gnutls_cipher_algorithm_t value corresponding to the specified cipher, or GNUTLS_CIPHER_UNKNOWN on error.

gnutls_cipher_get_key_size

Function: size_t gnutls_cipher_get_key_size (gnutls_cipher_algorithm_t algorithm)

algorithm: is an encryption algorithm

Get key size for cipher.

Returns: length (in bytes) of the given cipher’s key size, or 0 if the given cipher is invalid.

gnutls_cipher_get_name

Function: const char * gnutls_cipher_get_name (gnutls_cipher_algorithm_t algorithm)

algorithm: is an encryption algorithm

Convert a gnutls_cipher_algorithm_t type to a string.

Returns: a pointer to a string that contains the name of the specified cipher, or NULL .

gnutls_cipher_list

Function: const gnutls_cipher_algorithm_t * gnutls_cipher_list ( void)

Get a list of supported cipher algorithms. Note that not necessarily all ciphers are supported as TLS cipher suites. For example, DES is not supported as a cipher suite, but is supported for other purposes (e.g., PKCS8 or similar).

This function is not thread safe.

Returns: a (0)-terminated list of gnutls_cipher_algorithm_t integers indicating the available ciphers.

gnutls_cipher_suite_get_name

Function: const char * gnutls_cipher_suite_get_name (gnutls_kx_algorithm_t kx_algorithm, gnutls_cipher_algorithm_t cipher_algorithm, gnutls_mac_algorithm_t mac_algorithm)

kx_algorithm: is a Key exchange algorithm

cipher_algorithm: is a cipher algorithm

mac_algorithm: is a MAC algorithm

Note that the full cipher suite name must be prepended by TLS or SSL depending of the protocol in use.

Returns: a string that contains the name of a TLS cipher suite, specified by the given algorithms, or NULL .

gnutls_cipher_suite_info

Function: const char * gnutls_cipher_suite_info (size_t idx, unsigned char * cs_id, gnutls_kx_algorithm_t * kx, gnutls_cipher_algorithm_t * cipher, gnutls_mac_algorithm_t * mac, gnutls_protocol_t * min_version)

idx: index of cipher suite to get information about, starts on 0.

cs_id: output buffer with room for 2 bytes, indicating cipher suite value

kx: output variable indicating key exchange algorithm, or NULL .

cipher: output variable indicating cipher, or NULL .

mac: output variable indicating MAC algorithm, or NULL .

min_version: output variable indicating TLS protocol version, or NULL .

Get information about supported cipher suites. Use the function iteratively to get information about all supported cipher suites. Call with idx=0 to get information about first cipher suite, then idx=1 and so on until the function returns NULL.

Returns: the name of idx cipher suite, and set the information about the cipher suite in the output variables. If idx is out of bounds, NULL is returned.

gnutls_compression_get

Function: gnutls_compression_method_t gnutls_compression_get (gnutls_session_t session)

session: is a gnutls_session_t type.

Get currently used compression algorithm.

Returns: the currently used compression method, a gnutls_compression_method_t value.

gnutls_compression_get_id

Function: gnutls_compression_method_t gnutls_compression_get_id (const char * name)

name: is a compression method name

The names are compared in a case insensitive way.

Returns: an id of the specified in a string compression method, or GNUTLS_COMP_UNKNOWN on error.

gnutls_compression_get_name

Function: const char * gnutls_compression_get_name (gnutls_compression_method_t algorithm)

algorithm: is a Compression algorithm

Convert a gnutls_compression_method_t value to a string.

Returns: a pointer to a string that contains the name of the specified compression algorithm, or NULL .

gnutls_compression_list

Function: const gnutls_compression_method_t * gnutls_compression_list ( void)

Get a list of compression methods.

Returns: a zero-terminated list of gnutls_compression_method_t integers indicating the available compression methods.

gnutls_credentials_clear

Function: void gnutls_credentials_clear (gnutls_session_t session)

session: is a gnutls_session_t type.

Clears all the credentials previously set in this session.

gnutls_credentials_get

Function: int gnutls_credentials_get (gnutls_session_t session, gnutls_credentials_type_t type, void ** cred)

session: is a gnutls_session_t type.

type: is the type of the credentials to return

cred: will contain the credentials.

Returns the previously provided credentials structures.

For GNUTLS_CRD_ANON , cred will be gnutls_anon_client_credentials_t in case of a client. In case of a server it should be gnutls_anon_server_credentials_t .

For GNUTLS_CRD_SRP , cred will be gnutls_srp_client_credentials_t in case of a client, and gnutls_srp_server_credentials_t , in case of a server.

For GNUTLS_CRD_CERTIFICATE , cred will be gnutls_certificate_credentials_t .

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

Since: 3.3.3

gnutls_credentials_set

Function: int gnutls_credentials_set (gnutls_session_t session, gnutls_credentials_type_t type, void * cred)

session: is a gnutls_session_t type.

type: is the type of the credentials

cred: the credentials to set

Sets the needed credentials for the specified type. E.g. username, password - or public and private keys etc. The cred parameter is a structure that depends on the specified type and on the current session (client or server).

In order to minimize memory usage, and share credentials between several threads gnutls keeps a pointer to cred, and not the whole cred structure. Thus you will have to keep the structure allocated until you call gnutls_deinit() .

For GNUTLS_CRD_ANON , cred should be gnutls_anon_client_credentials_t in case of a client. In case of a server it should be gnutls_anon_server_credentials_t .

For GNUTLS_CRD_SRP , cred should be gnutls_srp_client_credentials_t in case of a client, and gnutls_srp_server_credentials_t , in case of a server.

For GNUTLS_CRD_CERTIFICATE , cred should be gnutls_certificate_credentials_t .

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

gnutls_db_check_entry

Function: int gnutls_db_check_entry (gnutls_session_t session, gnutls_datum_t session_entry)

session: is a gnutls_session_t type.

session_entry: is the session data (not key)

This function has no effect.

Returns: Returns GNUTLS_E_EXPIRED , if the database entry has expired or 0 otherwise.

gnutls_db_check_entry_time

Function: time_t gnutls_db_check_entry_time (gnutls_datum_t * entry)

entry: is a pointer to a gnutls_datum_t type.

This function returns the time that this entry was active. It can be used for database entry expiration.

Returns: The time this entry was created, or zero on error.

gnutls_db_get_default_cache_expiration

Function: unsigned gnutls_db_get_default_cache_expiration ( void)

Returns the expiration time (in seconds) of stored sessions for resumption.

gnutls_db_get_ptr

Function: void * gnutls_db_get_ptr (gnutls_session_t session)

session: is a gnutls_session_t type.

Get db function pointer.

Returns: the pointer that will be sent to db store, retrieve and delete functions, as the first argument.

gnutls_db_remove_session

Function: void gnutls_db_remove_session (gnutls_session_t session)

session: is a gnutls_session_t type.

This function will remove the current session data from the session database. This will prevent future handshakes reusing these session data. This function should be called if a session was terminated abnormally, and before gnutls_deinit() is called.

Normally gnutls_deinit() will remove abnormally terminated sessions.

gnutls_db_set_cache_expiration

Function: void gnutls_db_set_cache_expiration (gnutls_session_t session, int seconds)

session: is a gnutls_session_t type.

seconds: is the number of seconds.

Set the expiration time for resumed sessions. The default is 3600 (one hour) at the time of this writing.

gnutls_db_set_ptr

Function: void gnutls_db_set_ptr (gnutls_session_t session, void * ptr)

session: is a gnutls_session_t type.

ptr: is the pointer

Sets the pointer that will be provided to db store, retrieve and delete functions, as the first argument.

gnutls_db_set_remove_function

Function: void gnutls_db_set_remove_function (gnutls_session_t session, gnutls_db_remove_func rem_func)

session: is a gnutls_session_t type.

rem_func: is the function.

Sets the function that will be used to remove data from the resumed sessions database. This function must return 0 on success.

The first argument to rem_func will be null unless gnutls_db_set_ptr() has been called.

gnutls_db_set_retrieve_function

Function: void gnutls_db_set_retrieve_function (gnutls_session_t session, gnutls_db_retr_func retr_func)

session: is a gnutls_session_t type.

retr_func: is the function.

Sets the function that will be used to retrieve data from the resumed sessions database. This function must return a gnutls_datum_t containing the data on success, or a gnutls_datum_t containing null and 0 on failure.

The datum’s data must be allocated using the function gnutls_malloc() .

The first argument to retr_func will be null unless gnutls_db_set_ptr() has been called.

gnutls_db_set_store_function

Function: void gnutls_db_set_store_function (gnutls_session_t session, gnutls_db_store_func store_func)

session: is a gnutls_session_t type.

store_func: is the function

Sets the function that will be used to store data in the resumed sessions database. This function must return 0 on success.

The first argument to store_func will be null unless gnutls_db_set_ptr() has been called.

gnutls_deinit

Function: void gnutls_deinit (gnutls_session_t session)

session: is a gnutls_session_t type.

This function clears all buffers associated with the session . This function will also remove session data from the session database if the session was terminated abnormally.

gnutls_dh_get_group

Function: int gnutls_dh_get_group (gnutls_session_t session, gnutls_datum_t * raw_gen, gnutls_datum_t * raw_prime)

session: is a gnutls session

raw_gen: will hold the generator.

raw_prime: will hold the prime.

This function will return the group parameters used in the last Diffie-Hellman key exchange with the peer. These are the prime and the generator used. This function should be used for both anonymous and ephemeral Diffie-Hellman. The output parameters must be freed with gnutls_free() .

Note, that the prime and generator are exported as non-negative integers and may include a leading zero byte.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_dh_get_peers_public_bits

Function: int gnutls_dh_get_peers_public_bits (gnutls_session_t session)

session: is a gnutls session

Get the Diffie-Hellman public key bit size. Can be used for both anonymous and ephemeral Diffie-Hellman.

Returns: The public key bit size used in the last Diffie-Hellman key exchange with the peer, or a negative error code in case of error.

gnutls_dh_get_prime_bits

Function: int gnutls_dh_get_prime_bits (gnutls_session_t session)

session: is a gnutls session

This function will return the bits of the prime used in the last Diffie-Hellman key exchange with the peer. Should be used for both anonymous and ephemeral Diffie-Hellman. Note that some ciphers, like RSA and DSA without DHE, do not use a Diffie-Hellman key exchange, and then this function will return 0.

Returns: The Diffie-Hellman bit strength is returned, or 0 if no Diffie-Hellman key exchange was done, or a negative error code on failure.

gnutls_dh_get_pubkey

Function: int gnutls_dh_get_pubkey (gnutls_session_t session, gnutls_datum_t * raw_key)

session: is a gnutls session

raw_key: will hold the public key.

This function will return the peer’s public key used in the last Diffie-Hellman key exchange. This function should be used for both anonymous and ephemeral Diffie-Hellman. The output parameters must be freed with gnutls_free() .

Note, that public key is exported as non-negative integer and may include a leading zero byte.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_dh_get_secret_bits

Function: int gnutls_dh_get_secret_bits (gnutls_session_t session)

session: is a gnutls session

This function will return the bits used in the last Diffie-Hellman key exchange with the peer. Should be used for both anonymous and ephemeral Diffie-Hellman.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_dh_params_cpy

Function: int gnutls_dh_params_cpy (gnutls_dh_params_t dst, gnutls_dh_params_t src)

dst: Is the destination parameters, which should be initialized.

src: Is the source parameters

This function will copy the DH parameters structure from source to destination. The destination should be already initialized.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

gnutls_dh_params_deinit

Function: void gnutls_dh_params_deinit (gnutls_dh_params_t dh_params)

dh_params: The parameters

This function will deinitialize the DH parameters type.

gnutls_dh_params_export2_pkcs3

Function: int gnutls_dh_params_export2_pkcs3 (gnutls_dh_params_t params, gnutls_x509_crt_fmt_t format, gnutls_datum_t * out)

params: Holds the DH parameters

format: the format of output params. One of PEM or DER.

out: will contain a PKCS3 DHParams structure PEM or DER encoded

This function will export the given dh parameters to a PKCS3 DHParams structure. This is the format generated by "openssl dhparam" tool. The data in out will be allocated using gnutls_malloc() .

If the structure is PEM encoded, it will have a header of "BEGIN DH PARAMETERS".

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

Since: 3.1.3

gnutls_dh_params_export_pkcs3

Function: int gnutls_dh_params_export_pkcs3 (gnutls_dh_params_t params, gnutls_x509_crt_fmt_t format, unsigned char * params_data, size_t * params_data_size)

params: Holds the DH parameters

format: the format of output params. One of PEM or DER.

params_data: will contain a PKCS3 DHParams structure PEM or DER encoded

params_data_size: holds the size of params_data (and will be replaced by the actual size of parameters)

This function will export the given dh parameters to a PKCS3 DHParams structure. This is the format generated by "openssl dhparam" tool. If the buffer provided is not long enough to hold the output, then GNUTLS_E_SHORT_MEMORY_BUFFER will be returned.

If the structure is PEM encoded, it will have a header of "BEGIN DH PARAMETERS".

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

gnutls_dh_params_export_raw

Function: int gnutls_dh_params_export_raw (gnutls_dh_params_t params, gnutls_datum_t * prime, gnutls_datum_t * generator, unsigned int * bits)

params: Holds the DH parameters

prime: will hold the new prime

generator: will hold the new generator

bits: if non null will hold the secret key’s number of bits

This function will export the pair of prime and generator for use in the Diffie-Hellman key exchange. The new parameters will be allocated using gnutls_malloc() and will be stored in the appropriate datum.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

gnutls_dh_params_generate2

Function: int gnutls_dh_params_generate2 (gnutls_dh_params_t dparams, unsigned int bits)

dparams: The parameters

bits: is the prime’s number of bits

This function will generate a new pair of prime and generator for use in the Diffie-Hellman key exchange. This may take long time.

It is recommended not to set the number of bits directly, but use gnutls_sec_param_to_pk_bits() instead. Also note that the DH parameters are only useful to servers. Since clients use the parameters sent by the server, it’s of no use to call this in client side.

The parameters generated are of the DSA form. It also is possible to generate provable parameters (following the Shawe-Taylor algorithm), using gnutls_x509_privkey_generate2() with DSA option and the GNUTLS_PRIVKEY_FLAG_PROVABLE flag set. These can the be imported with gnutls_dh_params_import_dsa() .

It is no longer recommended for applications to generate parameters. See the "Parameter generation" section in the manual.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

gnutls_dh_params_import_dsa

Function: int gnutls_dh_params_import_dsa (gnutls_dh_params_t dh_params, gnutls_x509_privkey_t key)

dh_params: The parameters

key: holds a DSA private key

This function will import the prime and generator of the DSA key for use in the Diffie-Hellman key exchange.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

gnutls_dh_params_import_pkcs3

Function: int gnutls_dh_params_import_pkcs3 (gnutls_dh_params_t params, const gnutls_datum_t * pkcs3_params, gnutls_x509_crt_fmt_t format)

params: The parameters

pkcs3_params: should contain a PKCS3 DHParams structure PEM or DER encoded

format: the format of params. PEM or DER.

This function will extract the DHParams found in a PKCS3 formatted structure. This is the format generated by "openssl dhparam" tool.

If the structure is PEM encoded, it should have a header of "BEGIN DH PARAMETERS".

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

gnutls_dh_params_import_raw

Function: int gnutls_dh_params_import_raw (gnutls_dh_params_t dh_params, const gnutls_datum_t * prime, const gnutls_datum_t * generator)

dh_params: The parameters

prime: holds the new prime

generator: holds the new generator

This function will replace the pair of prime and generator for use in the Diffie-Hellman key exchange. The new parameters should be stored in the appropriate gnutls_datum.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

gnutls_dh_params_import_raw2

Function: int gnutls_dh_params_import_raw2 (gnutls_dh_params_t dh_params, const gnutls_datum_t * prime, const gnutls_datum_t * generator, unsigned key_bits)

dh_params: The parameters

prime: holds the new prime

generator: holds the new generator

key_bits: the private key bits (set to zero when unknown)

This function will replace the pair of prime and generator for use in the Diffie-Hellman key exchange. The new parameters should be stored in the appropriate gnutls_datum.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

gnutls_dh_params_init

Function: int gnutls_dh_params_init (gnutls_dh_params_t * dh_params)

dh_params: The parameters

This function will initialize the DH parameters type.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

gnutls_dh_set_prime_bits

Function: void gnutls_dh_set_prime_bits (gnutls_session_t session, unsigned int bits)

session: is a gnutls_session_t type.

bits: is the number of bits

This function sets the number of bits, for use in a Diffie-Hellman key exchange. This is used both in DH ephemeral and DH anonymous cipher suites. This will set the minimum size of the prime that will be used for the handshake.

In the client side it sets the minimum accepted number of bits. If a server sends a prime with less bits than that GNUTLS_E_DH_PRIME_UNACCEPTABLE will be returned by the handshake.

Note that this function will warn via the audit log for value that are believed to be weak.

The function has no effect in server side.

Note that since 3.1.7 this function is deprecated. The minimum number of bits is set by the priority string level. Also this function must be called after gnutls_priority_set_direct() or the set value may be overridden by the selected priority options.

gnutls_digest_get_id

Function: gnutls_digest_algorithm_t gnutls_digest_get_id (const char * name)

name: is a digest algorithm name

Convert a string to a gnutls_digest_algorithm_t value. The names are compared in a case insensitive way.

Returns: a gnutls_digest_algorithm_t id of the specified MAC algorithm string, or GNUTLS_DIG_UNKNOWN on failure.

gnutls_digest_get_name

Function: const char * gnutls_digest_get_name (gnutls_digest_algorithm_t algorithm)

algorithm: is a digest algorithm

Convert a gnutls_digest_algorithm_t value to a string.

Returns: a string that contains the name of the specified digest algorithm, or NULL .

gnutls_digest_get_oid

Function: const char * gnutls_digest_get_oid (gnutls_digest_algorithm_t algorithm)

algorithm: is a digest algorithm

Convert a gnutls_digest_algorithm_t value to its object identifier.

Returns: a string that contains the object identifier of the specified digest algorithm, or NULL .

Since: 3.4.3

gnutls_digest_list

Function: const gnutls_digest_algorithm_t * gnutls_digest_list ( void)

Get a list of hash (digest) algorithms supported by GnuTLS.

This function is not thread safe.

Returns: Return a (0)-terminated list of gnutls_digest_algorithm_t integers indicating the available digests.

gnutls_ecc_curve_get

Function: gnutls_ecc_curve_t gnutls_ecc_curve_get (gnutls_session_t session)

session: is a gnutls_session_t type.

Returns the currently used elliptic curve. Only valid when using an elliptic curve ciphersuite.

Returns: the currently used curve, a gnutls_ecc_curve_t type.

Since: 3.0

gnutls_ecc_curve_get_id

Function: gnutls_ecc_curve_t gnutls_ecc_curve_get_id (const char * name)

name: is a curve name

The names are compared in a case insensitive way.

Returns: return a gnutls_ecc_curve_t value corresponding to the specified curve, or GNUTLS_ECC_CURVE_INVALID on error.

Since: 3.4.3

gnutls_ecc_curve_get_name

Function: const char * gnutls_ecc_curve_get_name (gnutls_ecc_curve_t curve)

curve: is an ECC curve

Convert a gnutls_ecc_curve_t value to a string.

Returns: a string that contains the name of the specified curve or NULL .

Since: 3.0

gnutls_ecc_curve_get_oid

Function: const char * gnutls_ecc_curve_get_oid (gnutls_ecc_curve_t curve)

curve: is an ECC curve

Convert a gnutls_ecc_curve_t value to its object identifier.

Returns: a string that contains the OID of the specified curve or NULL .

Since: 3.4.3

gnutls_ecc_curve_get_pk

Function: gnutls_pk_algorithm_t gnutls_ecc_curve_get_pk (gnutls_ecc_curve_t curve)

curve: is an ECC curve

Returns: the public key algorithm associated with the named curve or GNUTLS_PK_UNKNOWN .

Since: 3.5.0

gnutls_ecc_curve_get_size

Function: int gnutls_ecc_curve_get_size (gnutls_ecc_curve_t curve)

curve: is an ECC curve

Returns: the size in bytes of the curve or 0 on failure.

Since: 3.0

gnutls_ecc_curve_list

Function: const gnutls_ecc_curve_t * gnutls_ecc_curve_list ( void)

Get the list of supported elliptic curves.

This function is not thread safe.

Returns: Return a (0)-terminated list of gnutls_ecc_curve_t integers indicating the available curves.

gnutls_error_is_fatal

Function: int gnutls_error_is_fatal (int error)

error: is a GnuTLS error code, a negative error code

If a GnuTLS function returns a negative error code you may feed that value to this function to see if the error condition is fatal to a TLS session (i.e., must be terminated).

Note that you may also want to check the error code manually, since some non-fatal errors to the protocol (such as a warning alert or a rehandshake request) may be fatal for your program.

This function is only useful if you are dealing with errors from functions that relate to a TLS session (e.g., record layer or handshake layer handling functions).

Returns: Non-zero value on fatal errors or zero on non-fatal.

gnutls_error_to_alert

Function: int gnutls_error_to_alert (int err, int * level)

err: is a negative integer

level: the alert level will be stored there

Get an alert depending on the error code returned by a gnutls function. All alerts sent by this function should be considered fatal. The only exception is when err is GNUTLS_E_REHANDSHAKE , where a warning alert should be sent to the peer indicating that no renegotiation will be performed.

If there is no mapping to a valid alert the alert to indicate internal error is returned.

Returns: the alert code to use for a particular error code.

gnutls_est_record_overhead_size

Function: size_t gnutls_est_record_overhead_size (gnutls_protocol_t version, gnutls_cipher_algorithm_t cipher, gnutls_mac_algorithm_t mac, gnutls_compression_method_t comp, unsigned int flags)

version: is a gnutls_protocol_t value

cipher: is a gnutls_cipher_algorithm_t value

mac: is a gnutls_mac_algorithm_t value

comp: is a gnutls_compression_method_t value

flags: must be zero

This function will return the set size in bytes of the overhead due to TLS (or DTLS) per record.

Note that this function may provide inacurate values when TLS extensions that modify the record format are negotiated. In these cases a more accurate value can be obtained using gnutls_record_overhead_size() after a completed handshake.

Since: 3.2.2

gnutls_ext_get_data

Function: int gnutls_ext_get_data (gnutls_session_t session, unsigned type, gnutls_ext_priv_data_t * data)

session: a gnutls_session_t opaque pointer

type: the numeric id of the extension

data: a pointer to the private data to retrieve

This function retrieves any data previously stored with gnutls_ext_set_data() .

Returns: GNUTLS_E_SUCCESS on success, otherwise a negative error code.

Since: 3.4.0

gnutls_ext_get_name

Function: const char * gnutls_ext_get_name (unsigned int ext)

ext: is a TLS extension numeric ID

Convert a TLS extension numeric ID to a printable string.

Returns: a pointer to a string that contains the name of the specified cipher, or NULL .

gnutls_ext_register

Function: int gnutls_ext_register (const char * name, int type, gnutls_ext_parse_type_t parse_type, gnutls_ext_recv_func recv_func, gnutls_ext_send_func send_func, gnutls_ext_deinit_data_func deinit_func, gnutls_ext_pack_func pack_func, gnutls_ext_unpack_func unpack_func)

name: the name of the extension to register

type: the numeric id of the extension

parse_type: the parse type of the extension (see gnutls_ext_parse_type_t)

recv_func: a function to receive the data

send_func: a function to send the data

deinit_func: a function deinitialize any private data

pack_func: a function which serializes the extension’s private data (used on session packing for resumption)

unpack_func: a function which will deserialize the extension’s private data

This function will register a new extension type. The extension will remain registered until gnutls_global_deinit() is called. If the extension type is already registered then GNUTLS_E_ALREADY_REGISTERED will be returned.

Each registered extension can store temporary data into the gnutls_session_t structure using gnutls_ext_set_data() , and they can be retrieved using gnutls_ext_get_data() .

This function is not thread safe.

Returns: GNUTLS_E_SUCCESS on success, otherwise a negative error code.

Since: 3.4.0

gnutls_ext_set_data

Function: void gnutls_ext_set_data (gnutls_session_t session, unsigned type, gnutls_ext_priv_data_t data)

session: a gnutls_session_t opaque pointer

type: the numeric id of the extension

data: the private data to set

This function allows an extension handler to store data in the current session and retrieve them later on. The set data will be deallocated using the gnutls_ext_deinit_data_func.

Since: 3.4.0

gnutls_fingerprint

Function: int gnutls_fingerprint (gnutls_digest_algorithm_t algo, const gnutls_datum_t * data, void * result, size_t * result_size)

algo: is a digest algorithm

data: is the data

result: is the place where the result will be copied (may be null).

result_size: should hold the size of the result. The actual size of the returned result will also be copied there.

This function will calculate a fingerprint (actually a hash), of the given data. The result is not printable data. You should convert it to hex, or to something else printable.

This is the usual way to calculate a fingerprint of an X.509 DER encoded certificate. Note however that the fingerprint of an OpenPGP certificate is not just a hash and cannot be calculated with this function.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_fips140_mode_enabled

Function: unsigned gnutls_fips140_mode_enabled ( void)

Checks whether this library is in FIPS140 mode.

Returns: return non-zero if true or zero if false.

Since: 3.3.0

gnutls_global_deinit

Function: void gnutls_global_deinit ( void)

This function deinitializes the global data, that were initialized using gnutls_global_init() .

Since GnuTLS 3.3.0 this function is no longer necessary to be explicitly called. GnuTLS will automatically deinitialize on library destructor. See gnutls_global_init() for disabling the implicit initialization/deinitialization.

gnutls_global_init

Function: int gnutls_global_init ( void)

Since GnuTLS 3.3.0 this function is no longer necessary to be explicitly called. To disable the implicit call (in a library constructor) of this function set the environment variable GNUTLS_NO_EXPLICIT_INIT to 1.

This function performs any required precalculations, detects the supported CPU capabilities and initializes the underlying cryptographic backend. In order to free any resources taken by this call you should gnutls_global_deinit() when gnutls usage is no longer needed.

This function increments a global counter, so that gnutls_global_deinit() only releases resources when it has been called as many times as gnutls_global_init() . This is useful when GnuTLS is used by more than one library in an application. This function can be called many times, but will only do something the first time.

A subsequent call of this function if the initial has failed will return the same error code.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

gnutls_global_set_audit_log_function

Function: void gnutls_global_set_audit_log_function (gnutls_audit_log_func log_func)

log_func: it is the audit log function

This is the function to set the audit logging function. This is a function to report important issues, such as possible attacks in the protocol. This is different from gnutls_global_set_log_function() because it will report also session-specific events. The session parameter will be null if there is no corresponding TLS session.

gnutls_audit_log_func is of the form, void (*gnutls_audit_log_func)( gnutls_session_t, const char*);

Since: 3.0

gnutls_global_set_log_function

Function: void gnutls_global_set_log_function (gnutls_log_func log_func)

log_func: it’s a log function

This is the function where you set the logging function gnutls is going to use. This function only accepts a character array. Normally you may not use this function since it is only used for debugging purposes.

gnutls_log_func is of the form, void (*gnutls_log_func)( int level, const char*);

gnutls_global_set_log_level

Function: void gnutls_global_set_log_level (int level)

level: it’s an integer from 0 to 99.

This is the function that allows you to set the log level. The level is an integer between 0 and 9. Higher values mean more verbosity. The default value is 0. Larger values should only be used with care, since they may reveal sensitive information.

Use a log level over 10 to enable all debugging options.

gnutls_global_set_mutex

Function: void gnutls_global_set_mutex (mutex_init_func init, mutex_deinit_func deinit, mutex_lock_func lock, mutex_unlock_func unlock)

init: mutex initialization function

deinit: mutex deinitialization function

lock: mutex locking function

unlock: mutex unlocking function

With this function you are allowed to override the default mutex locks used in some parts of gnutls and dependent libraries. This function should be used if you have complete control of your program and libraries. Do not call this function from a library, or preferably from any application unless really needed to. GnuTLS will use the appropriate locks for the running system.

Note that since the move to implicit initialization of GnuTLS on library load, calling this function will deinitialize the library, and re-initialize it after the new locking functions are set.

This function must be called prior to any other gnutls function.

Since: 2.12.0

gnutls_global_set_time_function

Function: void gnutls_global_set_time_function (gnutls_time_func time_func)

time_func: it’s the system time function, a gnutls_time_func() callback.

This is the function where you can override the default system time function. The application provided function should behave the same as the standard function.

Since: 2.12.0

gnutls_handshake

Function: int gnutls_handshake (gnutls_session_t session)

session: is a gnutls_session_t type.

This function does the handshake of the TLS/SSL protocol, and initializes the TLS connection.

This function will fail if any problem is encountered, and will return a negative error code. In case of a client, if the client has asked to resume a session, but the server couldn’t, then a full handshake will be performed.

The non-fatal errors expected by this function are: GNUTLS_E_INTERRUPTED , GNUTLS_E_AGAIN , GNUTLS_E_WARNING_ALERT_RECEIVED , and GNUTLS_E_GOT_APPLICATION_DATA , the latter only in a case of rehandshake.

The former two interrupt the handshake procedure due to the lower layer being interrupted, and the latter because of an alert that may be sent by a server (it is always a good idea to check any received alerts). On these errors call this function again, until it returns 0; cf. gnutls_record_get_direction() and gnutls_error_is_fatal() . In DTLS sessions the non-fatal error GNUTLS_E_LARGE_PACKET is also possible, and indicates that the MTU should be adjusted.

If this function is called by a server after a rehandshake request then GNUTLS_E_GOT_APPLICATION_DATA or GNUTLS_E_WARNING_ALERT_RECEIVED may be returned. Note that these are non fatal errors, only in the specific case of a rehandshake. Their meaning is that the client rejected the rehandshake request or in the case of GNUTLS_E_GOT_APPLICATION_DATA it could also mean that some data were pending. A client may receive that error code if it initiates the handshake and the server doesn’t agreed.

Returns: GNUTLS_E_SUCCESS on success, otherwise a negative error code.

gnutls_handshake_description_get_name

Function: const char * gnutls_handshake_description_get_name (gnutls_handshake_description_t type)

type: is a handshake message description

Convert a gnutls_handshake_description_t value to a string.

Returns: a string that contains the name of the specified handshake message or NULL .

gnutls_handshake_get_last_in

Function: gnutls_handshake_description_t gnutls_handshake_get_last_in (gnutls_session_t session)

session: is a gnutls_session_t type.

This function is only useful to check where the last performed handshake failed. If the previous handshake succeed or was not performed at all then no meaningful value will be returned.

Check gnutls_handshake_description_t in gnutls.h for the available handshake descriptions.

Returns: the last handshake message type received, a gnutls_handshake_description_t .

gnutls_handshake_get_last_out

Function: gnutls_handshake_description_t gnutls_handshake_get_last_out (gnutls_session_t session)

session: is a gnutls_session_t type.

This function is only useful to check where the last performed handshake failed. If the previous handshake succeed or was not performed at all then no meaningful value will be returned.

Check gnutls_handshake_description_t in gnutls.h for the available handshake descriptions.

Returns: the last handshake message type sent, a gnutls_handshake_description_t .

gnutls_handshake_set_hook_function

Function: void gnutls_handshake_set_hook_function (gnutls_session_t session, unsigned int htype, int post, gnutls_handshake_hook_func func)

session: is a gnutls_session_t type

htype: the gnutls_handshake_description_t of the message to hook at

post: GNUTLS_HOOK_ * depending on when the hook function should be called

func: is the function to be called

This function will set a callback to be called after or before the specified handshake message has been received or generated. This is a generalization of gnutls_handshake_set_post_client_hello_function() .

To call the hook function prior to the message being sent/generated use GNUTLS_HOOK_PRE as post parameter, GNUTLS_HOOK_POST to call after, and GNUTLS_HOOK_BOTH for both cases.

This callback must return 0 on success or a gnutls error code to terminate the handshake.

Note to hook at all handshake messages use an htype of GNUTLS_HANDSHAKE_ANY .

Warning: You should not use this function to terminate the handshake based on client input unless you know what you are doing. Before the handshake is finished there is no way to know if there is a man-in-the-middle attack being performed.

gnutls_handshake_set_max_packet_length

Function: void gnutls_handshake_set_max_packet_length (gnutls_session_t session, size_t max)

session: is a gnutls_session_t type.

max: is the maximum number.

This function will set the maximum size of all handshake messages. Handshakes over this size are rejected with GNUTLS_E_HANDSHAKE_TOO_LARGE error code. The default value is 128kb which is typically large enough. Set this to 0 if you do not want to set an upper limit.

The reason for restricting the handshake message sizes are to limit Denial of Service attacks.

Note that the maximum handshake size was increased to 128kb from 48kb in GnuTLS 3.5.5.

gnutls_handshake_set_post_client_hello_function

Function: void gnutls_handshake_set_post_client_hello_function (gnutls_session_t session, gnutls_handshake_simple_hook_func func)

session: is a gnutls_session_t type.

func: is the function to be called

This function will set a callback to be called after the client hello has been received (callback valid in server side only). This allows the server to adjust settings based on received extensions.

Those settings could be ciphersuites, requesting certificate, or anything else except for version negotiation (this is done before the hello message is parsed).

This callback must return 0 on success or a gnutls error code to terminate the handshake.

Since GnuTLS 3.3.5 the callback is allowed to return GNUTLS_E_AGAIN or GNUTLS_E_INTERRUPTED to put the handshake on hold. In that case gnutls_handshake() will return GNUTLS_E_INTERRUPTED and can be resumed when needed.

Warning: You should not use this function to terminate the handshake based on client input unless you know what you are doing. Before the handshake is finished there is no way to know if there is a man-in-the-middle attack being performed.

gnutls_handshake_set_private_extensions

Function: void gnutls_handshake_set_private_extensions (gnutls_session_t session, int allow)

session: is a gnutls_session_t type.

allow: is an integer (0 or 1)

This function will enable or disable the use of private cipher suites (the ones that start with 0xFF). By default or if allow is 0 then these cipher suites will not be advertised nor used.

Currently GnuTLS does not include such cipher-suites or compression algorithms.

Enabling the private ciphersuites when talking to other than gnutls servers and clients may cause interoperability problems.

gnutls_handshake_set_random

Function: int gnutls_handshake_set_random (gnutls_session_t session, const gnutls_datum_t * random)

session: is a gnutls_session_t type.

random: a random value of 32-bytes

This function will explicitly set the server or client hello random value in the subsequent TLS handshake. The random value should be a 32-byte value.

Note that this function should not normally be used as gnutls will select automatically a random value for the handshake.

This function should not be used when resuming a session.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

Since 3.1.9

gnutls_handshake_set_timeout

Function: void gnutls_handshake_set_timeout (gnutls_session_t session, unsigned int ms)

session: is a gnutls_session_t type.

ms: is a timeout value in milliseconds

This function sets the timeout for the TLS handshake process to the provided value. Use an ms value of zero to disable timeout, or GNUTLS_DEFAULT_HANDSHAKE_TIMEOUT for a reasonable default value. For the DTLS protocol, the more detailed gnutls_dtls_set_timeouts() is provided.

This function requires to set a pull timeout callback. See gnutls_transport_set_pull_timeout_function() .

Since: 3.1.0

gnutls_heartbeat_allowed

Function: int gnutls_heartbeat_allowed (gnutls_session_t session, unsigned int type)

session: is a gnutls_session_t type.

type: one of GNUTLS_HB_LOCAL_ALLOWED_TO_SEND and GNUTLS_HB_PEER_ALLOWED_TO_SEND

This function will check whether heartbeats are allowed to be sent or received in this session.

Returns: Non zero if heartbeats are allowed.

Since: 3.1.2

gnutls_heartbeat_enable

Function: void gnutls_heartbeat_enable (gnutls_session_t session, unsigned int type)

session: is a gnutls_session_t type.

type: one of the GNUTLS_HB_* flags

If this function is called with the GNUTLS_HB_PEER_ALLOWED_TO_SEND type , GnuTLS will allow heartbeat messages to be received. Moreover it also request the peer to accept heartbeat messages.

If the type used is GNUTLS_HB_LOCAL_ALLOWED_TO_SEND , then the peer will be asked to accept heartbeat messages but not send ones.

The function gnutls_heartbeat_allowed() can be used to test Whether locally generated heartbeat messages can be accepted by the peer.

Since: 3.1.2

gnutls_heartbeat_get_timeout

Function: unsigned int gnutls_heartbeat_get_timeout (gnutls_session_t session)

session: is a gnutls_session_t type.

This function will return the milliseconds remaining for a retransmission of the previously sent ping message. This function is useful when ping is used in non-blocking mode, to estimate when to call gnutls_heartbeat_ping() if no packets have been received.

Returns: the remaining time in milliseconds.

Since: 3.1.2

gnutls_heartbeat_ping

Function: int gnutls_heartbeat_ping (gnutls_session_t session, size_t data_size, unsigned int max_tries, unsigned int flags)

session: is a gnutls_session_t type.

data_size: is the length of the ping payload.

max_tries: if flags is GNUTLS_HEARTBEAT_WAIT then this sets the number of retransmissions. Use zero for indefinite (until timeout).

flags: if GNUTLS_HEARTBEAT_WAIT then wait for pong or timeout instead of returning immediately.

This function sends a ping to the peer. If the flags is set to GNUTLS_HEARTBEAT_WAIT then it waits for a reply from the peer.

Note that it is highly recommended to use this function with the flag GNUTLS_HEARTBEAT_WAIT , or you need to handle retransmissions and timeouts manually.

The total TLS data transmitted as part of the ping message are given by the following formula: MAX(16, data_size )+gnutls_record_overhead_size() +3.

Returns: GNUTLS_E_SUCCESS on success, otherwise a negative error code.

Since: 3.1.2

gnutls_heartbeat_pong

Function: int gnutls_heartbeat_pong (gnutls_session_t session, unsigned int flags)

session: is a gnutls_session_t type.

flags: should be zero

This function replies to a ping by sending a pong to the peer.

Returns: GNUTLS_E_SUCCESS on success, otherwise a negative error code.

Since: 3.1.2

gnutls_heartbeat_set_timeouts

Function: void gnutls_heartbeat_set_timeouts (gnutls_session_t session, unsigned int retrans_timeout, unsigned int total_timeout)

session: is a gnutls_session_t type.

retrans_timeout: The time at which a retransmission will occur in milliseconds

total_timeout: The time at which the connection will be aborted, in milliseconds.

This function will override the timeouts for the DTLS heartbeat protocol. The retransmission timeout is the time after which a message from the peer is not received, the previous request will be retransmitted. The total timeout is the time after which the handshake will be aborted with GNUTLS_E_TIMEDOUT .

Since: 3.1.2

gnutls_hex2bin

Function: int gnutls_hex2bin (const char * hex_data, size_t hex_size, void * bin_data, size_t * bin_size)

hex_data: string with data in hex format

hex_size: size of hex data

bin_data: output array with binary data

bin_size: when calling should hold maximum size of bin_data , on return will hold actual length of bin_data .

Convert a buffer with hex data to binary data. This function unlike gnutls_hex_decode() can parse hex data with separators between numbers. That is, it ignores any non-hex characters.

Returns: GNUTLS_E_SUCCESS on success, otherwise a negative error code.

Since: 2.4.0

gnutls_hex_decode

Function: int gnutls_hex_decode (const gnutls_datum_t * hex_data, void * result, size_t * result_size)

hex_data: contain the encoded data

result: the place where decoded data will be copied

result_size: holds the size of the result

This function will decode the given encoded data, using the hex encoding used by PSK password files.

Initially result_size must hold the maximum size available in result , and on return it will contain the number of bytes written.

Returns: GNUTLS_E_SHORT_MEMORY_BUFFER if the buffer given is not long enough, GNUTLS_E_PARSING_ERROR on invalid hex data, or 0 on success.

gnutls_hex_decode2

Function: int gnutls_hex_decode2 (const gnutls_datum_t * hex_data, gnutls_datum_t * result)

hex_data: contain the encoded data

result: the result in an allocated string

This function will decode the given encoded data, using the hex encoding used by PSK password files.

Returns: GNUTLS_E_PARSING_ERROR on invalid hex data, or 0 on success.

gnutls_hex_encode

Function: int gnutls_hex_encode (const gnutls_datum_t * data, char * result, size_t * result_size)

data: contain the raw data

result: the place where hex data will be copied

result_size: holds the size of the result

This function will convert the given data to printable data, using the hex encoding, as used in the PSK password files.

Note that the size of the result includes the null terminator.

Returns: GNUTLS_E_SHORT_MEMORY_BUFFER if the buffer given is not long enough, or 0 on success.

gnutls_hex_encode2

Function: int gnutls_hex_encode2 (const gnutls_datum_t * data, gnutls_datum_t * result)

data: contain the raw data

result: the result in an allocated string

This function will convert the given data to printable data, using the hex encoding, as used in the PSK password files.

Note that the size of the result does NOT include the null terminator.

Returns: GNUTLS_E_SUCCESS on success, otherwise a negative error code.

gnutls_idna_map

Function: int gnutls_idna_map (const char * input, unsigned ilen, gnutls_datum_t * out, unsigned flags)

input: contain the UTF-8 formatted domain name

ilen: the length of the provided string

out: the result in an null-terminated allocated string

flags: should be zero

This function will convert the provided UTF-8 domain name, to its IDNA mapping in an allocated variable. Note that depending on the flags the used gnutls library was compiled with, the output of this function may vary (i.e., may be IDNA2008, or IDNA2003).

To force IDNA2008 specify the flag GNUTLS_IDNA_FORCE_2008 . In the case GnuTLS is not compiled with the necessary dependencies, GNUTLS_E_UNIMPLEMENTED_FEATURE will be returned to indicate that gnutls is unable to perform the requested conversion.

Note also, that this function will return an empty string if an empty string is provided as input.

Returns: GNUTLS_E_INVALID_UTF8_STRING on invalid UTF-8 data, or 0 on success.

Since: 3.5.8

gnutls_idna_reverse_map

Function: int gnutls_idna_reverse_map (const char * input, unsigned ilen, gnutls_datum_t * out, unsigned flags)

input: contain the ACE (IDNA) formatted domain name

ilen: the length of the provided string

out: the result in an null-terminated allocated UTF-8 string

flags: should be zero

This function will convert an ACE (ASCII-encoded) domain name to a UTF-8 domain name.

If GnuTLS is compiled without IDNA support, then this function will return GNUTLS_E_UNIMPLEMENTED_FEATURE .

Note also, that this function will return an empty string if an empty string is provided as input.

Returns: A negative error code on error, or 0 on success.

Since: 3.5.8

gnutls_init

Function: int gnutls_init (gnutls_session_t * session, unsigned int flags)

session: is a pointer to a gnutls_session_t type.

flags: indicate if this session is to be used for server or client.

This function initializes the provided session. Every session must be initialized before use, and must be deinitialized after used by calling gnutls_deinit() .

flags can be any combination of flags from gnutls_init_flags_t .

Note that since version 3.1.2 this function enables some common TLS extensions such as session tickets and OCSP certificate status request in client side by default. To prevent that use the GNUTLS_NO_EXTENSIONS flag.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_key_generate

Function: int gnutls_key_generate (gnutls_datum_t * key, unsigned int key_size)

key: is a pointer to a gnutls_datum_t which will contain a newly created key

key_size: the number of bytes of the key

Generates a random key of key_size bytes.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, or an error code.

Since: 3.0

gnutls_kx_get

Function: gnutls_kx_algorithm_t gnutls_kx_get (gnutls_session_t session)

session: is a gnutls_session_t type.

Get currently used key exchange algorithm.

Returns: the key exchange algorithm used in the last handshake, a gnutls_kx_algorithm_t value.

gnutls_kx_get_id

Function: gnutls_kx_algorithm_t gnutls_kx_get_id (const char * name)

name: is a KX name

Convert a string to a gnutls_kx_algorithm_t value. The names are compared in a case insensitive way.

Returns: an id of the specified KX algorithm, or GNUTLS_KX_UNKNOWN on error.

gnutls_kx_get_name

Function: const char * gnutls_kx_get_name (gnutls_kx_algorithm_t algorithm)

algorithm: is a key exchange algorithm

Convert a gnutls_kx_algorithm_t value to a string.

Returns: a pointer to a string that contains the name of the specified key exchange algorithm, or NULL .

gnutls_kx_list

Function: const gnutls_kx_algorithm_t * gnutls_kx_list ( void)

Get a list of supported key exchange algorithms.

This function is not thread safe.

Returns: a (0)-terminated list of gnutls_kx_algorithm_t integers indicating the available key exchange algorithms.

gnutls_load_file

Function: int gnutls_load_file (const char * filename, gnutls_datum_t * data)

filename: the name of the file to load

data: Where the file will be stored

This function will load a file into a datum. The data are zero terminated but the terminating null is not included in length. The returned data are allocated using gnutls_malloc() .

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

Since 3.1.0

gnutls_mac_get

Function: gnutls_mac_algorithm_t gnutls_mac_get (gnutls_session_t session)

session: is a gnutls_session_t type.

Get currently used MAC algorithm.

Returns: the currently used mac algorithm, a gnutls_mac_algorithm_t value.

gnutls_mac_get_id

Function: gnutls_mac_algorithm_t gnutls_mac_get_id (const char * name)

name: is a MAC algorithm name

Convert a string to a gnutls_mac_algorithm_t value. The names are compared in a case insensitive way.

Returns: a gnutls_mac_algorithm_t id of the specified MAC algorithm string, or GNUTLS_MAC_UNKNOWN on failure.

gnutls_mac_get_key_size

Function: size_t gnutls_mac_get_key_size (gnutls_mac_algorithm_t algorithm)

algorithm: is an encryption algorithm

Returns the size of the MAC key used in TLS.

Returns: length (in bytes) of the given MAC key size, or 0 if the given MAC algorithm is invalid.

gnutls_mac_get_name

Function: const char * gnutls_mac_get_name (gnutls_mac_algorithm_t algorithm)

algorithm: is a MAC algorithm

Convert a gnutls_mac_algorithm_t value to a string.

Returns: a string that contains the name of the specified MAC algorithm, or NULL .

gnutls_mac_list

Function: const gnutls_mac_algorithm_t * gnutls_mac_list ( void)

Get a list of hash algorithms for use as MACs. Note that not necessarily all MACs are supported in TLS cipher suites. This function is not thread safe.

Returns: Return a (0)-terminated list of gnutls_mac_algorithm_t integers indicating the available MACs.

gnutls_memcmp

Function: int gnutls_memcmp (const void * s1, const void * s2, size_t n)

s1: the first address to compare

s2: the second address to compare

n: the size of memory to compare

This function will operate similarly to memcmp() , but will operate on time that depends only on the size of the string. That is will not return early if the strings don’t match on the first byte.

Returns: non zero on difference and zero if the buffers are identical.

Since: 3.4.0

gnutls_memset

Function: void gnutls_memset (void * data, int c, size_t size)

data: the memory to set

c: the constant byte to fill the memory with

size: the size of memory

This function will operate similarly to memset() , but will not be optimized out by the compiler.

Returns: void.

Since: 3.4.0

gnutls_ocsp_status_request_enable_client

Function: int gnutls_ocsp_status_request_enable_client (gnutls_session_t session, gnutls_datum_t * responder_id, size_t responder_id_size, gnutls_datum_t * extensions)

session: is a gnutls_session_t type.

responder_id: array with gnutls_datum_t with DER data of responder id

responder_id_size: number of members in responder_id array

extensions: a gnutls_datum_t with DER encoded OCSP extensions

This function is to be used by clients to request OCSP response from the server, using the "status_request" TLS extension. Only OCSP status type is supported. A typical server has a single OCSP response cached, so responder_id and extensions should be null.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

Since: 3.1.3

gnutls_ocsp_status_request_get

Function: int gnutls_ocsp_status_request_get (gnutls_session_t session, gnutls_datum_t * response)

session: is a gnutls_session_t type.

response: a gnutls_datum_t with DER encoded OCSP response

This function returns the OCSP status response received from the TLS server. The response should be treated as constant. If no OCSP response is available then GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE is returned.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

Since: 3.1.3

gnutls_ocsp_status_request_is_checked

Function: int gnutls_ocsp_status_request_is_checked (gnutls_session_t session, unsigned int flags)

session: is a gnutls session

flags: should be zero or GNUTLS_OCSP_SR_IS_AVAIL

When flags are zero this function returns non-zero if a valid OCSP status response was included in the TLS handshake. That is, an OCSP status response which is not too old or superseded. It returns zero otherwise.

When the flag GNUTLS_OCSP_SR_IS_AVAIL is specified, the function returns non-zero if an OCSP status response was included in the handshake even if it was invalid. Otherwise, if no OCSP status response was included, it returns zero. The GNUTLS_OCSP_SR_IS_AVAIL flag was introduced in GnuTLS 3.4.0.

This is a helper function when needing to decide whether to perform an explicit OCSP validity check on the peer’s certificate. Should be called after any of gnutls_certificate_verify_peers*() are called.

Returns: non zero if the response was valid, or a zero if it wasn’t sent, or sent and was invalid.

Since: 3.1.4

gnutls_oid_to_digest

Function: gnutls_digest_algorithm_t gnutls_oid_to_digest (const char * oid)

oid: is an object identifier

Converts a textual object identifier to a gnutls_digest_algorithm_t value.

Returns: a gnutls_digest_algorithm_t id of the specified digest algorithm, or GNUTLS_DIG_UNKNOWN on failure.

Since: 3.4.3

gnutls_oid_to_ecc_curve

Function: gnutls_ecc_curve_t gnutls_oid_to_ecc_curve (const char * oid)

oid: is a curve’s OID

Returns: return a gnutls_ecc_curve_t value corresponding to the specified OID, or GNUTLS_ECC_CURVE_INVALID on error.

Since: 3.4.3

gnutls_oid_to_mac

Function: gnutls_mac_algorithm_t gnutls_oid_to_mac (const char * oid)

oid: is an object identifier

Converts a textual object identifier typically from PKCS5 values to a gnutls_mac_algorithm_t value.

Returns: a gnutls_mac_algorithm_t id of the specified digest algorithm, or GNUTLS_MAC_UNKNOWN on failure.

Since: 3.5.4

gnutls_oid_to_pk

Function: gnutls_pk_algorithm_t gnutls_oid_to_pk (const char * oid)

oid: is an object identifier

Converts a textual object identifier to a gnutls_pk_algorithm_t value.

Returns: a gnutls_pk_algorithm_t id of the specified digest algorithm, or GNUTLS_PK_UNKNOWN on failure.

Since: 3.4.3

gnutls_oid_to_sign

Function: gnutls_sign_algorithm_t gnutls_oid_to_sign (const char * oid)

oid: is an object identifier

Converts a textual object identifier to a gnutls_sign_algorithm_t value.

Returns: a gnutls_sign_algorithm_t id of the specified digest algorithm, or GNUTLS_SIGN_UNKNOWN on failure.

Since: 3.4.3

gnutls_openpgp_send_cert

Function: void gnutls_openpgp_send_cert (gnutls_session_t session, gnutls_openpgp_crt_status_t status)

session: a gnutls_session_t type.

status: is one of GNUTLS_OPENPGP_CERT, or GNUTLS_OPENPGP_CERT_FINGERPRINT

This function will order gnutls to send the key fingerprint instead of the key in the initial handshake procedure. This should be used with care and only when there is indication or knowledge that the server can obtain the client’s key.

gnutls_packet_deinit

Function: void gnutls_packet_deinit (gnutls_packet_t packet)

packet: is a pointer to a gnutls_packet_st structure.

This function will deinitialize all data associated with the received packet.

Since: 3.3.5

gnutls_packet_get

Function: void gnutls_packet_get (gnutls_packet_t packet, gnutls_datum_t * data, unsigned char * sequence)

packet: is a gnutls_packet_t type.

data: will contain the data present in the packet structure (may be NULL )

sequence: the 8-bytes of the packet sequence number (may be NULL )

This function returns the data and sequence number associated with the received packet.

Since: 3.3.5

gnutls_pem_base64_decode

Function: int gnutls_pem_base64_decode (const char * header, const gnutls_datum_t * b64_data, unsigned char * result, size_t * result_size)

header: A null terminated string with the PEM header (eg. CERTIFICATE)

b64_data: contain the encoded data

result: the place where decoded data will be copied

result_size: holds the size of the result

This function will decode the given encoded data. If the header given is non null this function will search for "—–BEGIN header" and decode only this part. Otherwise it will decode the first PEM packet found.

Returns: On success GNUTLS_E_SUCCESS (0) is returned, GNUTLS_E_SHORT_MEMORY_BUFFER is returned if the buffer given is not long enough, or 0 on success.

gnutls_pem_base64_decode2

Function: int gnutls_pem_base64_decode2 (const char * header, const gnutls_datum_t * b64_data, gnutls_datum_t * result)

header: The PEM header (eg. CERTIFICATE)

b64_data: contains the encoded data

result: the place where decoded data lie

This function will decode the given encoded data. The decoded data will be allocated, and stored into result. If the header given is non null this function will search for "—–BEGIN header" and decode only this part. Otherwise it will decode the first PEM packet found.

You should use gnutls_free() to free the returned data.

Note, that prior to GnuTLS 3.4.0 this function was available under the name gnutls_pem_base64_decode_alloc() . There is compatibility macro pointing to this function.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

Since: 3.4.0

gnutls_pem_base64_encode

Function: int gnutls_pem_base64_encode (const char * msg, const gnutls_datum_t * data, char * result, size_t * result_size)

msg: is a message to be put in the header (may be NULL )

data: contain the raw data

result: the place where base64 data will be copied

result_size: holds the size of the result

This function will convert the given data to printable data, using the base64 encoding. This is the encoding used in PEM messages.

The output string will be null terminated, although the output size will not include the terminating null.

Returns: On success GNUTLS_E_SUCCESS (0) is returned, GNUTLS_E_SHORT_MEMORY_BUFFER is returned if the buffer given is not long enough, or 0 on success.

gnutls_pem_base64_encode2

Function: int gnutls_pem_base64_encode2 (const char * msg, const gnutls_datum_t * data, gnutls_datum_t * result)

msg: is a message to be put in the encoded header (may be NULL )

data: contains the raw data

result: will hold the newly allocated encoded data

This function will convert the given data to printable data, using the base64 encoding. This is the encoding used in PEM messages. This function will allocate the required memory to hold the encoded data.

You should use gnutls_free() to free the returned data.

Note, that prior to GnuTLS 3.4.0 this function was available under the name gnutls_pem_base64_encode_alloc() . There is compatibility macro pointing to this function.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

Since: 3.4.0

gnutls_perror

Function: void gnutls_perror (int error)

error: is a GnuTLS error code, a negative error code

This function is like perror() . The only difference is that it accepts an error number returned by a gnutls function.

gnutls_pk_algorithm_get_name

Function: const char * gnutls_pk_algorithm_get_name (gnutls_pk_algorithm_t algorithm)

algorithm: is a pk algorithm

Convert a gnutls_pk_algorithm_t value to a string.

Returns: a string that contains the name of the specified public key algorithm, or NULL .

gnutls_pk_bits_to_sec_param

Function: gnutls_sec_param_t gnutls_pk_bits_to_sec_param (gnutls_pk_algorithm_t algo, unsigned int bits)

algo: is a public key algorithm

bits: is the number of bits

This is the inverse of gnutls_sec_param_to_pk_bits() . Given an algorithm and the number of bits, it will return the security parameter. This is a rough indication.

Returns: The security parameter.

Since: 2.12.0

gnutls_pk_get_id

Function: gnutls_pk_algorithm_t gnutls_pk_get_id (const char * name)

name: is a string containing a public key algorithm name.

Convert a string to a gnutls_pk_algorithm_t value. The names are compared in a case insensitive way. For example, gnutls_pk_get_id("RSA") will return GNUTLS_PK_RSA .

Returns: a gnutls_pk_algorithm_t id of the specified public key algorithm string, or GNUTLS_PK_UNKNOWN on failures.

Since: 2.6.0

gnutls_pk_get_name

Function: const char * gnutls_pk_get_name (gnutls_pk_algorithm_t algorithm)

algorithm: is a public key algorithm

Convert a gnutls_pk_algorithm_t value to a string.

Returns: a pointer to a string that contains the name of the specified public key algorithm, or NULL .

Since: 2.6.0

gnutls_pk_get_oid

Function: const char * gnutls_pk_get_oid (gnutls_pk_algorithm_t algorithm)

algorithm: is a public key algorithm

Convert a gnutls_pk_algorithm_t value to its object identifier string.

Returns: a pointer to a string that contains the object identifier of the specified public key algorithm, or NULL .

Since: 3.4.3

gnutls_pk_list

Function: const gnutls_pk_algorithm_t * gnutls_pk_list ( void)

Get a list of supported public key algorithms.

This function is not thread safe.

Returns: a (0)-terminated list of gnutls_pk_algorithm_t integers indicating the available ciphers.

Since: 2.6.0

gnutls_pk_to_sign

Function: gnutls_sign_algorithm_t gnutls_pk_to_sign (gnutls_pk_algorithm_t pk, gnutls_digest_algorithm_t hash)

pk: is a public key algorithm

hash: a hash algorithm

This function maps public key and hash algorithms combinations to signature algorithms.

Returns: return a gnutls_sign_algorithm_t value, or GNUTLS_SIGN_UNKNOWN on error.

gnutls_prf

Function: int gnutls_prf (gnutls_session_t session, size_t label_size, const char * label, int server_random_first, size_t extra_size, const char * extra, size_t outsize, char * out)

session: is a gnutls_session_t type.

label_size: length of the label variable.

label: label used in PRF computation, typically a short string.

server_random_first: non-zero if server random field should be first in seed

extra_size: length of the extra variable.

extra: optional extra data to seed the PRF with.

outsize: size of pre-allocated output buffer to hold the output.

out: pre-allocated buffer to hold the generated data.

Applies the TLS Pseudo-Random-Function (PRF) on the master secret and the provided data, seeded with the client and server random fields. For the key expansion specified in RFC5705 see gnutls_prf_rfc5705() .

The label variable usually contains a string denoting the purpose for the generated data. The server_random_first indicates whether the client random field or the server random field should be first in the seed. Non-zero indicates that the server random field is first, 0 that the client random field is first.

The extra variable can be used to add more data to the seed, after the random variables. It can be used to make sure the generated output is strongly connected to some additional data (e.g., a string used in user authentication).

The output is placed in out , which must be pre-allocated.

Note: This function produces identical output with gnutls_prf_rfc5705() when server_random_first is set to 0 and extra is NULL .

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_prf_raw

Function: int gnutls_prf_raw (gnutls_session_t session, size_t label_size, const char * label, size_t seed_size, const char * seed, size_t outsize, char * out)

session: is a gnutls_session_t type.

label_size: length of the label variable.

label: label used in PRF computation, typically a short string.

seed_size: length of the seed variable.

seed: optional extra data to seed the PRF with.

outsize: size of pre-allocated output buffer to hold the output.

out: pre-allocated buffer to hold the generated data.

Apply the TLS Pseudo-Random-Function (PRF) on the master secret and the provided data.

The label variable usually contains a string denoting the purpose for the generated data. The seed usually contains data such as the client and server random, perhaps together with some additional data that is added to guarantee uniqueness of the output for a particular purpose.

Because the output is not guaranteed to be unique for a particular session unless seed includes the client random and server random fields (the PRF would output the same data on another connection resumed from the first one), it is not recommended to use this function directly. The gnutls_prf() function seeds the PRF with the client and server random fields directly, and is recommended if you want to generate pseudo random data unique for each session.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_prf_rfc5705

Function: int gnutls_prf_rfc5705 (gnutls_session_t session, size_t label_size, const char * label, size_t context_size, const char * context, size_t outsize, char * out)

session: is a gnutls_session_t type.

label_size: length of the label variable.

label: label used in PRF computation, typically a short string.

context_size: length of the extra variable.

context: optional extra data to seed the PRF with.

outsize: size of pre-allocated output buffer to hold the output.

out: pre-allocated buffer to hold the generated data.

Applies the TLS Pseudo-Random-Function (PRF) on the master secret and the provided data, seeded with the client and server random fields, as specified in RFC5705.

The label variable usually contains a string denoting the purpose for the generated data. The server_random_first indicates whether the client random field or the server random field should be first in the seed. Non-zero indicates that the server random field is first, 0 that the client random field is first.

The context variable can be used to add more data to the seed, after the random variables. It can be used to make sure the generated output is strongly connected to some additional data (e.g., a string used in user authentication).

The output is placed in out , which must be pre-allocated.

Note that, to provide the RFC5705 context, the context variable must be non-null.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

Since: 3.4.4

gnutls_priority_certificate_type_list

Function: int gnutls_priority_certificate_type_list (gnutls_priority_t pcache, const unsigned int ** list)

pcache: is a gnutls_prioritity_t type.

list: will point to an integer list

Get a list of available certificate types in the priority structure.

Returns: the number of certificate types, or an error code.

Since: 3.0

gnutls_priority_cipher_list

Function: int gnutls_priority_cipher_list (gnutls_priority_t pcache, const unsigned int ** list)

pcache: is a gnutls_prioritity_t type.

list: will point to an integer list

Get a list of available ciphers in the priority structure.

Returns: the number of curves, or an error code.

Since: 3.2.3

gnutls_priority_compression_list

Function: int gnutls_priority_compression_list (gnutls_priority_t pcache, const unsigned int ** list)

pcache: is a gnutls_prioritity_t type.

list: will point to an integer list

Get a list of available compression method in the priority structure.

Returns: the number of methods, or an error code.

Since: 3.0

gnutls_priority_deinit

Function: void gnutls_priority_deinit (gnutls_priority_t priority_cache)

priority_cache: is a gnutls_prioritity_t type.

Deinitializes the priority cache.

gnutls_priority_ecc_curve_list

Function: int gnutls_priority_ecc_curve_list (gnutls_priority_t pcache, const unsigned int ** list)

pcache: is a gnutls_prioritity_t type.

list: will point to an integer list

Get a list of available elliptic curves in the priority structure.

Returns: the number of curves, or an error code.

Since: 3.0

gnutls_priority_get_cipher_suite_index

Function: int gnutls_priority_get_cipher_suite_index (gnutls_priority_t pcache, unsigned int idx, unsigned int * sidx)

pcache: is a gnutls_prioritity_t type.

idx: is an index number.

sidx: internal index of cipher suite to get information about.

Provides the internal ciphersuite index to be used with gnutls_cipher_suite_info() . The index idx provided is an index kept at the priorities structure. It might be that a valid priorities index does not correspond to a ciphersuite and in that case GNUTLS_E_UNKNOWN_CIPHER_SUITE will be returned. Once the last available index is crossed then GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE will be returned.

Returns: On success it returns GNUTLS_E_SUCCESS (0), or a negative error value otherwise.

Since: 3.0.9

gnutls_priority_init

Function: int gnutls_priority_init (gnutls_priority_t * priority_cache, const char * priorities, const char ** err_pos)

priority_cache: is a gnutls_prioritity_t type.

priorities: is a string describing priorities (may be NULL )

err_pos: In case of an error this will have the position in the string the error occurred

Sets priorities for the ciphers, key exchange methods, macs and compression methods. The priority_cache should be deinitialized using gnutls_priority_deinit() .

The priorities option allows you to specify a colon separated list of the cipher priorities to enable. Some keywords are defined to provide quick access to common preferences.

Unless there is a special need, use the "NORMAL" keyword to apply a reasonable security level, or "NORMAL:%COMPAT" for compatibility.

"PERFORMANCE" means all the "secure" ciphersuites are enabled, limited to 128 bit ciphers and sorted by terms of speed performance.

"LEGACY" the NORMAL settings for GnuTLS 3.2.x or earlier. There is no verification profile set, and the allowed DH primes are considered weak today.

"NORMAL" means all "secure" ciphersuites. The 256-bit ciphers are included as a fallback only. The ciphers are sorted by security margin.

"PFS" means all "secure" ciphersuites that support perfect forward secrecy. The 256-bit ciphers are included as a fallback only. The ciphers are sorted by security margin.

"SECURE128" means all "secure" ciphersuites of security level 128-bit or more.

"SECURE192" means all "secure" ciphersuites of security level 192-bit or more.

"SUITEB128" means all the NSA SuiteB ciphersuites with security level of 128.

"SUITEB192" means all the NSA SuiteB ciphersuites with security level of 192.

"NONE" means nothing is enabled. This disables even protocols and compression methods.

"@KEYWORD1,KEYWORD2,..." The system administrator imposed settings. The provided keyword(s) will be expanded from a configuration-time provided file - default is: /etc/gnutls/default-priorities. Any attributes that follow it, will be appended to the expanded string. If multiple keywords are provided, separated by commas, then the first keyword that exists in the configuration file will be used. At least one of the keywords must exist, or this function will return an error. Typical usage would be to specify an application specified keyword first, followed by "SYSTEM" as a default fallback. e.g., " LIBVIRT ,SYSTEM:!-VERS-SSL3.0" will first try to find a config file entry matching "LIBVIRT", but if that does not exist will use the entry for "SYSTEM". If "SYSTEM" does not exist either, an error will be returned. In all cases, the SSL3.0 protocol will be disabled. The system priority file entries should be formatted as "KEYWORD=VALUE", e.g., "SYSTEM=NORMAL:+ARCFOUR-128".

Special keywords are "!", "-" and "+". "!" or "-" appended with an algorithm will remove this algorithm. "+" appended with an algorithm will add this algorithm.

Check the GnuTLS manual section "Priority strings" for detailed information.

Examples: "NONE:+VERS-TLS-ALL:+MAC-ALL:+RSA:+AES-128-CBC:+SIGN-ALL:+COMP-NULL"

"NORMAL:+ARCFOUR-128" means normal ciphers plus ARCFOUR-128.

"SECURE128:-VERS-SSL3.0:+COMP-DEFLATE" means that only secure ciphers are enabled, SSL3.0 is disabled, and libz compression enabled.

"NONE:+VERS-TLS-ALL:+AES-128-CBC:+RSA:+SHA1:+COMP-NULL:+SIGN-RSA-SHA1",

"NONE:+VERS-TLS-ALL:+AES-128-CBC:+ECDHE-RSA:+SHA1:+COMP-NULL:+SIGN-RSA-SHA1:+CURVE-SECP256R1",

"SECURE256:+SECURE128",

Note that "NORMAL:%COMPAT" is the most compatible mode.

A NULL priorities string indicates the default priorities to be used (this is available since GnuTLS 3.3.0).

Returns: On syntax error GNUTLS_E_INVALID_REQUEST is returned, GNUTLS_E_SUCCESS on success, or an error code.

gnutls_priority_kx_list

Function: int gnutls_priority_kx_list (gnutls_priority_t pcache, const unsigned int ** list)

pcache: is a gnutls_prioritity_t type.

list: will point to an integer list

Get a list of available key exchange methods in the priority structure.

Returns: the number of curves, or an error code.

Since: 3.2.3

gnutls_priority_mac_list

Function: int gnutls_priority_mac_list (gnutls_priority_t pcache, const unsigned int ** list)

pcache: is a gnutls_prioritity_t type.

list: will point to an integer list

Get a list of available MAC algorithms in the priority structure.

Returns: the number of curves, or an error code.

Since: 3.2.3

gnutls_priority_protocol_list

Function: int gnutls_priority_protocol_list (gnutls_priority_t pcache, const unsigned int ** list)

pcache: is a gnutls_prioritity_t type.

list: will point to an integer list

Get a list of available TLS version numbers in the priority structure.

Returns: the number of protocols, or an error code.

Since: 3.0

gnutls_priority_set

Function: int gnutls_priority_set (gnutls_session_t session, gnutls_priority_t priority)

session: is a gnutls_session_t type.

priority: is a gnutls_priority_t type.

Sets the priorities to use on the ciphers, key exchange methods, macs and compression methods.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_priority_set_direct

Function: int gnutls_priority_set_direct (gnutls_session_t session, const char * priorities, const char ** err_pos)

session: is a gnutls_session_t type.

priorities: is a string describing priorities

err_pos: In case of an error this will have the position in the string the error occurred

Sets the priorities to use on the ciphers, key exchange methods, macs and compression methods. This function avoids keeping a priority cache and is used to directly set string priorities to a TLS session. For documentation check the gnutls_priority_init() .

To simply use a reasonable default, consider using gnutls_set_default_priority() .

Returns: On syntax error GNUTLS_E_INVALID_REQUEST is returned, GNUTLS_E_SUCCESS on success, or an error code.

gnutls_priority_sign_list

Function: int gnutls_priority_sign_list (gnutls_priority_t pcache, const unsigned int ** list)

pcache: is a gnutls_prioritity_t type.

list: will point to an integer list

Get a list of available signature algorithms in the priority structure.

Returns: the number of algorithms, or an error code.

Since: 3.0

gnutls_priority_string_list

Function: const char * gnutls_priority_string_list (unsigned iter, unsigned int flags)

iter: an integer counter starting from zero

flags: one of GNUTLS_PRIORITY_LIST_INIT_KEYWORDS , GNUTLS_PRIORITY_LIST_SPECIAL

Can be used to iterate all available priority strings. Due to internal implementation details, there are cases where this function can return the empty string. In that case that string should be ignored. When no strings are available it returns NULL .

Returns: a priority string

Since: 3.4.0

gnutls_protocol_get_id

Function: gnutls_protocol_t gnutls_protocol_get_id (const char * name)

name: is a protocol name

The names are compared in a case insensitive way.

Returns: an id of the specified protocol, or GNUTLS_VERSION_UNKNOWN on error.

gnutls_protocol_get_name

Function: const char * gnutls_protocol_get_name (gnutls_protocol_t version)

version: is a (gnutls) version number

Convert a gnutls_protocol_t value to a string.

Returns: a string that contains the name of the specified TLS version (e.g., "TLS1.0"), or NULL .

gnutls_protocol_get_version

Function: gnutls_protocol_t gnutls_protocol_get_version (gnutls_session_t session)

session: is a gnutls_session_t type.

Get TLS version, a gnutls_protocol_t value.

Returns: The version of the currently used protocol.

gnutls_protocol_list

Function: const gnutls_protocol_t * gnutls_protocol_list ( void)

Get a list of supported protocols, e.g. SSL 3.0, TLS 1.0 etc.

This function is not thread safe.

Returns: a (0)-terminated list of gnutls_protocol_t integers indicating the available protocols.

gnutls_psk_allocate_client_credentials

Function: int gnutls_psk_allocate_client_credentials (gnutls_psk_client_credentials_t * sc)

sc: is a pointer to a gnutls_psk_server_credentials_t type.

Allocate a gnutls_psk_client_credentials_t structure.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_psk_allocate_server_credentials

Function: int gnutls_psk_allocate_server_credentials (gnutls_psk_server_credentials_t * sc)

sc: is a pointer to a gnutls_psk_server_credentials_t type.

Allocate a gnutls_psk_server_credentials_t structure.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_psk_client_get_hint

Function: const char * gnutls_psk_client_get_hint (gnutls_session_t session)

session: is a gnutls session

The PSK identity hint may give the client help in deciding which username to use. This should only be called in case of PSK authentication and in case of a client.

Returns: the identity hint of the peer, or NULL in case of an error.

Since: 2.4.0

gnutls_psk_free_client_credentials

Function: void gnutls_psk_free_client_credentials (gnutls_psk_client_credentials_t sc)

sc: is a gnutls_psk_client_credentials_t type.

Free a gnutls_psk_client_credentials_t structure.

gnutls_psk_free_server_credentials

Function: void gnutls_psk_free_server_credentials (gnutls_psk_server_credentials_t sc)

sc: is a gnutls_psk_server_credentials_t type.

Free a gnutls_psk_server_credentials_t structure.

gnutls_psk_server_get_username

Function: const char * gnutls_psk_server_get_username (gnutls_session_t session)

session: is a gnutls session

This should only be called in case of PSK authentication and in case of a server.

Returns: the username of the peer, or NULL in case of an error.

gnutls_psk_set_client_credentials

Function: int gnutls_psk_set_client_credentials (gnutls_psk_client_credentials_t res, const char * username, const gnutls_datum_t * key, gnutls_psk_key_flags flags)

res: is a gnutls_psk_client_credentials_t type.

username: is the user’s zero-terminated userid

key: is the user’s key

flags: indicate the format of the key, either GNUTLS_PSK_KEY_RAW or GNUTLS_PSK_KEY_HEX .

This function sets the username and password, in a gnutls_psk_client_credentials_t type. Those will be used in PSK authentication. username should be an ASCII string or UTF-8 strings prepared using the "SASLprep" profile of "stringprep". The key can be either in raw byte format or in Hex format (without the 0x prefix).

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_psk_set_client_credentials_function

Function: void gnutls_psk_set_client_credentials_function (gnutls_psk_client_credentials_t cred, gnutls_psk_client_credentials_function * func)

cred: is a gnutls_psk_server_credentials_t type.

func: is the callback function

This function can be used to set a callback to retrieve the username and password for client PSK authentication. The callback’s function form is: int (*callback)(gnutls_session_t, char** username, gnutls_datum_t* key);

The username and key ->data must be allocated using gnutls_malloc() . username should be ASCII strings or UTF-8 strings prepared using the "SASLprep" profile of "stringprep".

The callback function will be called once per handshake.

The callback function should return 0 on success. -1 indicates an error.

gnutls_psk_set_params_function

Function: void gnutls_psk_set_params_function (gnutls_psk_server_credentials_t res, gnutls_params_function * func)

res: is a gnutls_psk_server_credentials_t type

func: is the function to be called

This function will set a callback in order for the server to get the Diffie-Hellman or RSA parameters for PSK authentication. The callback should return GNUTLS_E_SUCCESS (0) on success.

gnutls_psk_set_server_credentials_file

Function: int gnutls_psk_set_server_credentials_file (gnutls_psk_server_credentials_t res, const char * password_file)

res: is a gnutls_psk_server_credentials_t type.

password_file: is the PSK password file (passwd.psk)

This function sets the password file, in a gnutls_psk_server_credentials_t type. This password file holds usernames and keys and will be used for PSK authentication.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_psk_set_server_credentials_function

Function: void gnutls_psk_set_server_credentials_function (gnutls_psk_server_credentials_t cred, gnutls_psk_server_credentials_function * func)

cred: is a gnutls_psk_server_credentials_t type.

func: is the callback function

This function can be used to set a callback to retrieve the user’s PSK credentials. The callback’s function form is: int (*callback)(gnutls_session_t, const char* username, gnutls_datum_t* key);

username contains the actual username. The key must be filled in using the gnutls_malloc() .

In case the callback returned a negative number then gnutls will assume that the username does not exist.

The callback function will only be called once per handshake. The callback function should return 0 on success, while -1 indicates an error.

gnutls_psk_set_server_credentials_hint

Function: int gnutls_psk_set_server_credentials_hint (gnutls_psk_server_credentials_t res, const char * hint)

res: is a gnutls_psk_server_credentials_t type.

hint: is the PSK identity hint string

This function sets the identity hint, in a gnutls_psk_server_credentials_t type. This hint is sent to the client to help it chose a good PSK credential (i.e., username and password).

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

Since: 2.4.0

gnutls_psk_set_server_dh_params

Function: void gnutls_psk_set_server_dh_params (gnutls_psk_server_credentials_t res, gnutls_dh_params_t dh_params)

res: is a gnutls_psk_server_credentials_t type

dh_params: is a structure that holds Diffie-Hellman parameters.

This function will set the Diffie-Hellman parameters for an anonymous server to use. These parameters will be used in Diffie-Hellman exchange with PSK cipher suites.

gnutls_psk_set_server_known_dh_params

Function: int gnutls_psk_set_server_known_dh_params (gnutls_psk_server_credentials_t res, gnutls_sec_param_t sec_param)

res: is a gnutls_psk_server_credentials_t type

sec_param: is an option of the gnutls_sec_param_t enumeration

This function will set the Diffie-Hellman parameters for a PSK server to use. These parameters will be used in Ephemeral Diffie-Hellman cipher suites and will be selected from the FFDHE set of RFC7919 according to the security level provided.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error value.

Since: 3.5.6

gnutls_psk_set_server_params_function

Function: void gnutls_psk_set_server_params_function (gnutls_psk_server_credentials_t res, gnutls_params_function * func)

res: is a gnutls_certificate_credentials_t type

func: is the function to be called

This function will set a callback in order for the server to get the Diffie-Hellman parameters for PSK authentication. The callback should return GNUTLS_E_SUCCESS (0) on success.

gnutls_random_art

Function: int gnutls_random_art (gnutls_random_art_t type, const char * key_type, unsigned int key_size, void * fpr, size_t fpr_size, gnutls_datum_t * art)

type: The type of the random art (for now only GNUTLS_RANDOM_ART_OPENSSH is supported)

key_type: The type of the key (RSA, DSA etc.)

key_size: The size of the key in bits

fpr: The fingerprint of the key

fpr_size: The size of the fingerprint

art: The returned random art

This function will convert a given fingerprint to an "artistic" image. The returned image is allocated using gnutls_malloc() , is null-terminated but art->size will not account the terminating null.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_range_split

Function: int gnutls_range_split (gnutls_session_t session, const gnutls_range_st * orig, gnutls_range_st * next, gnutls_range_st * remainder)

session: is a gnutls_session_t type

orig: is the original range provided by the user

next: is the returned range that can be conveyed in a TLS record

remainder: is the returned remaining range

This function should be used when it is required to hide the length of very long data that cannot be directly provided to gnutls_record_send_range() . In that case this function should be called with the desired length hiding range in orig . The returned next value should then be used in the next call to gnutls_record_send_range() with the partial data. That process should be repeated until remainder is (0,0).

Returns: 0 in case splitting succeeds, non zero in case of error. Note that orig is not changed, while the values of next and remainder are modified to store the resulting values.

gnutls_record_can_use_length_hiding

Function: int gnutls_record_can_use_length_hiding (gnutls_session_t session)

session: is a gnutls_session_t type.

If the session supports length-hiding padding, you can invoke gnutls_range_send_message() to send a message whose length is hidden in the given range. If the session does not support length hiding padding, you can use the standard gnutls_record_send() function, or gnutls_range_send_message() making sure that the range is the same as the length of the message you are trying to send.

Returns: true (1) if the current session supports length-hiding padding, false (0) if the current session does not.

gnutls_record_check_corked

Function: size_t gnutls_record_check_corked (gnutls_session_t session)

session: is a gnutls_session_t type.

This function checks if there pending corked data in the gnutls buffers –see gnutls_record_cork() .

Returns: Returns the size of the corked data or zero.

Since: 3.2.8

gnutls_record_check_pending

Function: size_t gnutls_record_check_pending (gnutls_session_t session)

session: is a gnutls_session_t type.

This function checks if there are unread data in the gnutls buffers. If the return value is non-zero the next call to gnutls_record_recv() is guaranteed not to block.

Returns: Returns the size of the data or zero.

gnutls_record_cork

Function: void gnutls_record_cork (gnutls_session_t session)

session: is a gnutls_session_t type.

If called, gnutls_record_send() will no longer send any records. Any sent records will be cached until gnutls_record_uncork() is called.

This function is safe to use with DTLS after GnuTLS 3.3.0.

Since: 3.1.9

gnutls_record_disable_padding

Function: void gnutls_record_disable_padding (gnutls_session_t session)

session: is a gnutls_session_t type.

Used to disabled padding in TLS 1.0 and above. Normally you do not need to use this function, but there are buggy clients that complain if a server pads the encrypted data. This of course will disable protection against statistical attacks on the data.

This functions is defunt since 3.1.7. Random padding is disabled by default unless requested using gnutls_range_send_message() .

gnutls_record_discard_queued

Function: size_t gnutls_record_discard_queued (gnutls_session_t session)

session: is a gnutls_session_t type.

This function discards all queued to be sent packets in a TLS or DTLS session. These are the packets queued after an interrupted gnutls_record_send() .

Returns: The number of bytes discarded.

Since: 3.4.0

gnutls_record_get_direction

Function: int gnutls_record_get_direction (gnutls_session_t session)

session: is a gnutls_session_t type.

This function provides information about the internals of the record protocol and is only useful if a prior gnutls function call, e.g. gnutls_handshake() , was interrupted for some reason. That is, if a function returned GNUTLS_E_INTERRUPTED or GNUTLS_E_AGAIN . In such a case, you might want to call select() or poll() before restoring the interrupted gnutls function.

This function’s output is unreliable if you are using the same session in different threads, for sending and receiving.

Returns: 0 if interrupted while trying to read data, or 1 while trying to write data.

gnutls_record_get_max_size

Function: size_t gnutls_record_get_max_size (gnutls_session_t session)

session: is a gnutls_session_t type.

Get the record size. The maximum record size is negotiated by the client after the first handshake message.

Returns: The maximum record packet size in this connection.

gnutls_record_get_state

Function: int gnutls_record_get_state (gnutls_session_t session, unsigned read, gnutls_datum_t * mac_key, gnutls_datum_t * IV, gnutls_datum_t * cipher_key, unsigned char seq_number[8])

session: is a gnutls_session_t type

read: if non-zero the read parameters are returned, otherwise the write

mac_key: the key used for MAC (if a MAC is used)

IV: the initialization vector or nonce used

cipher_key: the cipher key

seq_number[8]: – undescribed –

This function will return the parameters of the current record state. These are only useful to be provided to an external off-loading device or subsystem.

In that case, to sync the state you must call gnutls_record_set_state() .

Returns: GNUTLS_E_SUCCESS on success, or an error code.

Since 3.4.0

gnutls_record_overhead_size

Function: size_t gnutls_record_overhead_size (gnutls_session_t session)

session: is gnutls_session_t

This function will return the size in bytes of the overhead due to TLS (or DTLS) per record. On certain occasions (e.g., CBC ciphers) the returned value is the maximum possible overhead.

Since: 3.2.2

gnutls_record_recv

Function: ssize_t gnutls_record_recv (gnutls_session_t session, void * data, size_t data_size)

session: is a gnutls_session_t type.

data: the buffer that the data will be read into

data_size: the number of requested bytes

This function has the similar semantics with recv() . The only difference is that it accepts a GnuTLS session, and uses different error codes. In the special case that the peer requests a renegotiation, the caller will receive an error code of GNUTLS_E_REHANDSHAKE . In case of a client, this message may be simply ignored, replied with an alert GNUTLS_A_NO_RENEGOTIATION , or replied with a new handshake, depending on the client’s will. A server receiving this error code can only initiate a new handshake or terminate the session.

If EINTR is returned by the internal pull function (the default is recv() ) then GNUTLS_E_INTERRUPTED will be returned. If GNUTLS_E_INTERRUPTED or GNUTLS_E_AGAIN is returned, you must call this function again to get the data. See also gnutls_record_get_direction() .

Returns: The number of bytes received and zero on EOF (for stream connections). A negative error code is returned in case of an error. The number of bytes received might be less than the requested data_size .

gnutls_record_recv_packet

Function: ssize_t gnutls_record_recv_packet (gnutls_session_t session, gnutls_packet_t * packet)

session: is a gnutls_session_t type.

packet: the structure that will hold the packet data

This is a lower-level function than gnutls_record_recv() and allows to directly receive the whole decrypted packet. That avoids a memory copy, and is intended to be used by applications seeking high performance.

The received packet is accessed using gnutls_packet_get() and must be deinitialized using gnutls_packet_deinit() . The returned packet will be NULL if the return value is zero (EOF).

Returns: The number of bytes received and zero on EOF (for stream connections). A negative error code is returned in case of an error.

Since: 3.3.5

gnutls_record_recv_seq

Function: ssize_t gnutls_record_recv_seq (gnutls_session_t session, void * data, size_t data_size, unsigned char * seq)

session: is a gnutls_session_t type.

data: the buffer that the data will be read into

data_size: the number of requested bytes

seq: is the packet’s 64-bit sequence number. Should have space for 8 bytes.

This function is the same as gnutls_record_recv() , except that it returns in addition to data, the sequence number of the data. This is useful in DTLS where record packets might be received out-of-order. The returned 8-byte sequence number is an integer in big-endian format and should be treated as a unique message identification.

Returns: The number of bytes received and zero on EOF. A negative error code is returned in case of an error. The number of bytes received might be less than data_size .

Since: 3.0

gnutls_record_send

Function: ssize_t gnutls_record_send (gnutls_session_t session, const void * data, size_t data_size)

session: is a gnutls_session_t type.

data: contains the data to send

data_size: is the length of the data

This function has the similar semantics with send() . The only difference is that it accepts a GnuTLS session, and uses different error codes. Note that if the send buffer is full, send() will block this function. See the send() documentation for more information.

You can replace the default push function which is send() , by using gnutls_transport_set_push_function() .

If the EINTR is returned by the internal push function then GNUTLS_E_INTERRUPTED will be returned. If GNUTLS_E_INTERRUPTED or GNUTLS_E_AGAIN is returned, you must call this function again, with the exact same parameters; alternatively you could provide a NULL pointer for data, and 0 for size. cf. gnutls_record_get_direction() .

Note that in DTLS this function will return the GNUTLS_E_LARGE_PACKET error code if the send data exceed the data MTU value - as returned by gnutls_dtls_get_data_mtu() . The errno value EMSGSIZE also maps to GNUTLS_E_LARGE_PACKET . Note that since 3.2.13 this function can be called under cork in DTLS mode, and will refuse to send data over the MTU size by returning GNUTLS_E_LARGE_PACKET .

Returns: The number of bytes sent, or a negative error code. The number of bytes sent might be less than data_size . The maximum number of bytes this function can send in a single call depends on the negotiated maximum record size.

gnutls_record_send_range

Function: ssize_t gnutls_record_send_range (gnutls_session_t session, const void * data, size_t data_size, const gnutls_range_st * range)

session: is a gnutls_session_t type.

data: contains the data to send.

data_size: is the length of the data.

range: is the range of lengths in which the real data length must be hidden.

This function operates like gnutls_record_send() but, while gnutls_record_send() adds minimal padding to each TLS record, this function uses the TLS extra-padding feature to conceal the real data size within the range of lengths provided. Some TLS sessions do not support extra padding (e.g. stream ciphers in standard TLS or SSL3 sessions). To know whether the current session supports extra padding, and hence length hiding, use the gnutls_record_can_use_length_hiding() function.

Note: This function currently is only limited to blocking sockets.

Returns: The number of bytes sent (that is data_size in a successful invocation), or a negative error code.

gnutls_record_set_max_size

Function: ssize_t gnutls_record_set_max_size (gnutls_session_t session, size_t size)

session: is a gnutls_session_t type.

size: is the new size

This function sets the maximum record packet size in this connection. This property can only be set to clients. The server may choose not to accept the requested size.

Acceptable values are 512(=2^9), 1024(=2^10), 2048(=2^11) and 4096(=2^12). The requested record size does get in effect immediately only while sending data. The receive part will take effect after a successful handshake.

This function uses a TLS extension called ’max record size’. Not all TLS implementations use or even understand this extension.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

gnutls_record_set_state

Function: int gnutls_record_set_state (gnutls_session_t session, unsigned read, unsigned char seq_number[8])

session: is a gnutls_session_t type

read: if non-zero the read parameters are returned, otherwise the write

seq_number[8]: – undescribed –

This function will set the sequence number in the current record state. This function is useful if sending and receiving are offloaded from gnutls. That is, if gnutls_record_get_state() was used.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

Since 3.4.0

gnutls_record_set_timeout

Function: void gnutls_record_set_timeout (gnutls_session_t session, unsigned int ms)

session: is a gnutls_session_t type.

ms: is a timeout value in milliseconds

This function sets the receive timeout for the record layer to the provided value. Use an ms value of zero to disable timeout (the default), or GNUTLS_INDEFINITE_TIMEOUT , to set an indefinite timeout.

This function requires to set a pull timeout callback. See gnutls_transport_set_pull_timeout_function() .

Since: 3.1.7

gnutls_record_uncork

Function: int gnutls_record_uncork (gnutls_session_t session, unsigned int flags)

session: is a gnutls_session_t type.

flags: Could be zero or GNUTLS_RECORD_WAIT

This resets the effect of gnutls_record_cork() , and flushes any pending data. If the GNUTLS_RECORD_WAIT flag is specified then this function will block until the data is sent or a fatal error occurs (i.e., the function will retry on GNUTLS_E_AGAIN and GNUTLS_E_INTERRUPTED ).

If the flag GNUTLS_RECORD_WAIT is not specified and the function is interrupted then the GNUTLS_E_AGAIN or GNUTLS_E_INTERRUPTED errors will be returned. To obtain the data left in the corked buffer use gnutls_record_check_corked() .

Returns: On success the number of transmitted data is returned, or otherwise a negative error code.

Since: 3.1.9

gnutls_rehandshake

Function: int gnutls_rehandshake (gnutls_session_t session)

session: is a gnutls_session_t type.

This function will renegotiate security parameters with the client. This should only be called in case of a server.

This message informs the peer that we want to renegotiate parameters (perform a handshake).

If this function succeeds (returns 0), you must call the gnutls_handshake() function in order to negotiate the new parameters.

Since TLS is full duplex some application data might have been sent during peer’s processing of this message. In that case one should call gnutls_record_recv() until GNUTLS_E_REHANDSHAKE is returned to clear any pending data. Care must be taken, if rehandshake is mandatory, to terminate if it does not start after some threshold.

If the client does not wish to renegotiate parameters he should reply with an alert message, thus the return code will be GNUTLS_E_WARNING_ALERT_RECEIVED and the alert will be GNUTLS_A_NO_RENEGOTIATION . A client may also choose to ignore this message.

Returns: GNUTLS_E_SUCCESS on success, otherwise a negative error code.

gnutls_safe_renegotiation_status

Function: unsigned gnutls_safe_renegotiation_status (gnutls_session_t session)

session: is a gnutls_session_t type.

Can be used to check whether safe renegotiation is being used in the current session.

Returns: 0 when safe renegotiation is not used and non (0) when safe renegotiation is used.

Since: 2.10.0

gnutls_sec_param_get_name

Function: const char * gnutls_sec_param_get_name (gnutls_sec_param_t param)

param: is a security parameter

Convert a gnutls_sec_param_t value to a string.

Returns: a pointer to a string that contains the name of the specified security level, or NULL .

Since: 2.12.0

gnutls_sec_param_to_pk_bits

Function: unsigned int gnutls_sec_param_to_pk_bits (gnutls_pk_algorithm_t algo, gnutls_sec_param_t param)

algo: is a public key algorithm

param: is a security parameter

When generating private and public key pairs a difficult question is which size of "bits" the modulus will be in RSA and the group size in DSA. The easy answer is 1024, which is also wrong. This function will convert a human understandable security parameter to an appropriate size for the specific algorithm.

Returns: The number of bits, or (0).

Since: 2.12.0

gnutls_sec_param_to_symmetric_bits

Function: unsigned int gnutls_sec_param_to_symmetric_bits (gnutls_sec_param_t param)

param: is a security parameter

This function will return the number of bits that correspond to symmetric cipher strength for the given security parameter.

Returns: The number of bits, or (0).

Since: 3.3.0

gnutls_server_name_get

Function: int gnutls_server_name_get (gnutls_session_t session, void * data, size_t * data_length, unsigned int * type, unsigned int indx)

session: is a gnutls_session_t type.

data: will hold the data

data_length: will hold the data length. Must hold the maximum size of data.

type: will hold the server name indicator type

indx: is the index of the server_name

This function will allow you to get the name indication (if any), a client has sent. The name indication may be any of the enumeration gnutls_server_name_type_t.

If type is GNUTLS_NAME_DNS, then this function is to be used by servers that support virtual hosting, and the data will be a null terminated IDNA ACE string (prior to GnuTLS 3.4.0 it was a UTF-8 string).

If data has not enough size to hold the server name GNUTLS_E_SHORT_MEMORY_BUFFER is returned, and data_length will hold the required size.

index is used to retrieve more than one server names (if sent by the client). The first server name has an index of 0, the second 1 and so on. If no name with the given index exists GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE is returned.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, on UTF-8 decoding error GNUTLS_E_IDNA_ERROR is returned, otherwise a negative error code is returned.

gnutls_server_name_set

Function: int gnutls_server_name_set (gnutls_session_t session, gnutls_server_name_type_t type, const void * name, size_t name_length)

session: is a gnutls_session_t type.

type: specifies the indicator type

name: is a string that contains the server name.

name_length: holds the length of name

This function is to be used by clients that want to inform (via a TLS extension mechanism) the server of the name they connected to. This should be used by clients that connect to servers that do virtual hosting.

The value of name depends on the type type. In case of GNUTLS_NAME_DNS , a UTF-8 null-terminated domain name string, without the trailing dot, is expected.

IPv4 or IPv6 addresses are not permitted to be set by this function. If the function is called with a name of name_length zero it will clear all server names set.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

gnutls_session_channel_binding

Function: int gnutls_session_channel_binding (gnutls_session_t session, gnutls_channel_binding_t cbtype, gnutls_datum_t * cb)

session: is a gnutls_session_t type.

cbtype: an gnutls_channel_binding_t enumeration type

cb: output buffer array with data

Extract given channel binding data of the cbtype (e.g., GNUTLS_CB_TLS_UNIQUE ) type.

Returns: GNUTLS_E_SUCCESS on success, GNUTLS_E_UNIMPLEMENTED_FEATURE if the cbtype is unsupported, GNUTLS_E_CHANNEL_BINDING_NOT_AVAILABLE if the data is not currently available, or an error code.

Since: 2.12.0

gnutls_session_enable_compatibility_mode

Function: void gnutls_session_enable_compatibility_mode (gnutls_session_t session)

session: is a gnutls_session_t type.

This function can be used to disable certain (security) features in TLS in order to maintain maximum compatibility with buggy clients. Because several trade-offs with security are enabled, if required they will be reported through the audit subsystem.

Normally only servers that require maximum compatibility with everything out there, need to call this function.

Note that this function must be called after any call to gnutls_priority functions.

gnutls_session_etm_status

Function: unsigned gnutls_session_etm_status (gnutls_session_t session)

session: is a gnutls_session_t type.

Get the status of the encrypt-then-mac extension negotiation. This is in accordance to rfc7366

Returns: Non-zero if the negotiation was successful or zero otherwise.

gnutls_session_ext_master_secret_status

Function: unsigned gnutls_session_ext_master_secret_status (gnutls_session_t session)

session: is a gnutls_session_t type.

Get the status of the extended master secret extension negotiation. This is in accordance to draft-ietf-tls-session-hash-01

Returns: Non-zero if the negotiation was successful or zero otherwise.

gnutls_session_ext_register

Function: int gnutls_session_ext_register (gnutls_session_t session, const char * name, int type, gnutls_ext_parse_type_t parse_type, gnutls_ext_recv_func recv_func, gnutls_ext_send_func send_func, gnutls_ext_deinit_data_func deinit_func, gnutls_ext_pack_func pack_func, gnutls_ext_unpack_func unpack_func, unsigned flags)

session: the session for which this extension will be set

name: the name of the extension to register

type: the numeric id of the extension

parse_type: the parse type of the extension (see gnutls_ext_parse_type_t)

recv_func: a function to receive the data

send_func: a function to send the data

deinit_func: a function deinitialize any private data

pack_func: a function which serializes the extension’s private data (used on session packing for resumption)

unpack_func: a function which will deserialize the extension’s private data

flags: must be zero

This function will register a new extension type. The extension will be only usable within the registered session. If the extension type is already registered then GNUTLS_E_ALREADY_REGISTERED will be returned.

Each registered extension can store temporary data into the gnutls_session_t structure using gnutls_ext_set_data() , and they can be retrieved using gnutls_ext_get_data() .

Returns: GNUTLS_E_SUCCESS on success, otherwise a negative error code.

Since: 3.5.5

gnutls_session_force_valid

Function: void gnutls_session_force_valid (gnutls_session_t session)

session: is a gnutls_session_t type.

Clears the invalid flag in a session. That means that sessions were corrupt or invalid data were received can be re-used. Use only when debugging or experimenting with the TLS protocol. Should not be used in typical applications.

gnutls_session_get_data

Function: int gnutls_session_get_data (gnutls_session_t session, void * session_data, size_t * session_data_size)

session: is a gnutls_session_t type.

session_data: is a pointer to space to hold the session.

session_data_size: is the session_data’s size, or it will be set by the function.

Returns all session parameters needed to be stored to support resumption. The client should call this, and store the returned session data. A session may be resumed later by calling gnutls_session_set_data() .

This function will fail if called prior to handshake completion. In case of false start TLS, the handshake completes only after data have been successfully received from the peer.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_session_get_data2

Function: int gnutls_session_get_data2 (gnutls_session_t session, gnutls_datum_t * data)

session: is a gnutls_session_t type.

data: is a pointer to a datum that will hold the session.

Returns all session parameters needed to be stored to support resumption. The client should call this, and store the returned session data. A session may be resumed later by calling gnutls_session_set_data() .

The returned data are allocated and must be released using gnutls_free() .

This function will fail if called prior to handshake completion. In case of false start TLS, the handshake completes only after data have been successfully received from the peer.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_session_get_desc

Function: char * gnutls_session_get_desc (gnutls_session_t session)

session: is a gnutls session

This function returns a string describing the current session. The string is null terminated and allocated using gnutls_malloc() .

If initial negotiation is not complete when this function is called, NULL will be returned.

Returns: a description of the protocols and algorithms in the current session.

Since: 3.1.10

gnutls_session_get_flags

Function: unsigned gnutls_session_get_flags (gnutls_session_t session)

session: is a gnutls_session_t type.

This function will return a series (ORed) of flags, applicable for the current session.

This replaces individual informational functions such as gnutls_safe_renegotiation_status() , gnutls_session_ext_master_secret_status() , etc.

Returns: An ORed sequence of flags (see gnutls_session_flags_t )

Since: 3.5.0

gnutls_session_get_id

Function: int gnutls_session_get_id (gnutls_session_t session, void * session_id, size_t * session_id_size)

session: is a gnutls_session_t type.

session_id: is a pointer to space to hold the session id.

session_id_size: initially should contain the maximum session_id size and will be updated.

Returns the current session ID. This can be used if you want to check if the next session you tried to resume was actually resumed. That is because resumed sessions share the same session ID with the original session.

The session ID is selected by the server, that identify the current session. In all supported TLS protocols, the session id is less than GNUTLS_MAX_SESSION_ID_SIZE .

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_session_get_id2

Function: int gnutls_session_get_id2 (gnutls_session_t session, gnutls_datum_t * session_id)

session: is a gnutls_session_t type.

session_id: will point to the session ID.

Returns the current session ID. The returned data should be treated as constant.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

Since: 3.1.4

gnutls_session_get_master_secret

Function: void gnutls_session_get_master_secret (gnutls_session_t session, gnutls_datum_t * secret)

session: is a gnutls_session_t type.

secret: the session’s master secret

This function returns pointers to the master secret used in the TLS session. The pointers are not to be modified or deallocated.

Since: 3.5.0

gnutls_session_get_ptr

Function: void * gnutls_session_get_ptr (gnutls_session_t session)

session: is a gnutls_session_t type.

Get user pointer for session. Useful in callbacks. This is the pointer set with gnutls_session_set_ptr() .

Returns: the user given pointer from the session structure, or NULL if it was never set.

gnutls_session_get_random

Function: void gnutls_session_get_random (gnutls_session_t session, gnutls_datum_t * client, gnutls_datum_t * server)

session: is a gnutls_session_t type.

client: the client part of the random

server: the server part of the random

This function returns pointers to the client and server random fields used in the TLS handshake. The pointers are not to be modified or deallocated.

If a client random value has not yet been established, the output will be garbage.

Since: 3.0

gnutls_session_get_verify_cert_status

Function: unsigned int gnutls_session_get_verify_cert_status (gnutls_session_t session)

session: is a gnutls session

This function returns the status of the verification when initiated via auto-verification, i.e., by gnutls_session_set_verify_cert2() or gnutls_session_set_verify_cert() . If no certificate verification was occurred then the return value would be set to ((unsigned int)-1).

The certificate verification status is the same as in gnutls_certificate_verify_peers() .

Returns: the certificate verification status.

Since: 3.4.6

gnutls_session_is_resumed

Function: int gnutls_session_is_resumed (gnutls_session_t session)

session: is a gnutls_session_t type.

Check whether session is resumed or not.

Returns: non zero if this session is resumed, or a zero if this is a new session.

gnutls_session_resumption_requested

Function: int gnutls_session_resumption_requested (gnutls_session_t session)

session: is a gnutls_session_t type.

Check whether the client has asked for session resumption. This function is valid only on server side.

Returns: non zero if session resumption was asked, or a zero if not.

gnutls_session_set_data

Function: int gnutls_session_set_data (gnutls_session_t session, const void * session_data, size_t session_data_size)

session: is a gnutls_session_t type.

session_data: is a pointer to space to hold the session.

session_data_size: is the session’s size

Sets all session parameters, in order to resume a previously established session. The session data given must be the one returned by gnutls_session_get_data() . This function should be called before gnutls_handshake() .

Keep in mind that session resuming is advisory. The server may choose not to resume the session, thus a full handshake will be performed.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_session_set_id

Function: int gnutls_session_set_id (gnutls_session_t session, const gnutls_datum_t * sid)

session: is a gnutls_session_t type.

sid: the session identifier

This function sets the session ID to be used in a client hello. This is a function intended for exceptional uses. Do not use this function unless you are implementing a custom protocol.

To set session resumption parameters use gnutls_session_set_data() instead.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

Since: 3.2.1

gnutls_session_set_premaster

Function: int gnutls_session_set_premaster (gnutls_session_t session, unsigned int entity, gnutls_protocol_t version, gnutls_kx_algorithm_t kx, gnutls_cipher_algorithm_t cipher, gnutls_mac_algorithm_t mac, gnutls_compression_method_t comp, const gnutls_datum_t * master, const gnutls_datum_t * session_id)

session: is a gnutls_session_t type.

entity: GNUTLS_SERVER or GNUTLS_CLIENT

version: the TLS protocol version

kx: the key exchange method

cipher: the cipher

mac: the MAC algorithm

comp: the compression method

master: the master key to use

session_id: the session identifier

This function sets the premaster secret in a session. This is a function intended for exceptional uses. Do not use this function unless you are implementing a legacy protocol. Use gnutls_session_set_data() instead.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

gnutls_session_set_ptr

Function: void gnutls_session_set_ptr (gnutls_session_t session, void * ptr)

session: is a gnutls_session_t type.

ptr: is the user pointer

This function will set (associate) the user given pointer ptr to the session structure. This pointer can be accessed with gnutls_session_get_ptr() .

gnutls_session_set_verify_cert

Function: void gnutls_session_set_verify_cert (gnutls_session_t session, const char * hostname, unsigned flags)

session: is a gnutls session

hostname: is the expected name of the peer; may be NULL

flags: flags for certificate verification – gnutls_certificate_verify_flags

This function instructs GnuTLS to verify the peer’s certificate using the provided hostname. If the verification fails the handshake will also fail with GNUTLS_E_CERTIFICATE_VERIFICATION_ERROR . In that case the verification result can be obtained using gnutls_session_get_verify_cert_status() .

The hostname pointer provided must remain valid for the lifetime of the session. More precisely it should be available during any subsequent handshakes. If no hostname is provided, no hostname verification will be performed. For a more advanced verification function check gnutls_session_set_verify_cert2() .

If flags is provided which contain a profile, this function should be called after any session priority setting functions.

The gnutls_session_set_verify_cert() function is intended to be used by TLS clients to verify the server’s certificate.

Since: 3.4.6

gnutls_session_set_verify_cert2

Function: void gnutls_session_set_verify_cert2 (gnutls_session_t session, gnutls_typed_vdata_st * data, unsigned elements, unsigned flags)

session: is a gnutls session

data: an array of typed data

elements: the number of data elements

flags: flags for certificate verification – gnutls_certificate_verify_flags

This function instructs GnuTLS to verify the peer’s certificate using the provided typed data information. If the verification fails the handshake will also fail with GNUTLS_E_CERTIFICATE_VERIFICATION_ERROR . In that case the verification result can be obtained using gnutls_session_get_verify_cert_status() .

The acceptable typed data are the same as in gnutls_certificate_verify_peers() , and once set must remain valid for the lifetime of the session. More precisely they should be available during any subsequent handshakes.

If flags is provided which contain a profile, this function should be called after any session priority setting functions.

Since: 3.4.6

gnutls_session_set_verify_function

Function: void gnutls_session_set_verify_function (gnutls_session_t session, gnutls_certificate_verify_function * func)

session: is a gnutls_session_t type.

func: is the callback function

This function sets a callback to be called when peer’s certificate has been received in order to verify it on receipt rather than doing after the handshake is completed. This overrides any callback set using gnutls_certificate_set_verify_function() .

The callback’s function prototype is: int (*callback)(gnutls_session_t);

If the callback function is provided then gnutls will call it, in the handshake, just after the certificate message has been received. To verify or obtain the certificate the gnutls_certificate_verify_peers2() , gnutls_certificate_type_get() , gnutls_certificate_get_peers() functions can be used.

The callback function should return 0 for the handshake to continue or non-zero to terminate.

Since: 3.4.6

gnutls_session_supplemental_register

Function: int gnutls_session_supplemental_register (gnutls_session_t session, const char * name, gnutls_supplemental_data_format_type_t type, gnutls_supp_recv_func recv_func, gnutls_supp_send_func send_func, unsigned flags)

session: the session for which this will be registered

name: the name of the supplemental data to register

type: the type of the supplemental data format

recv_func: the function to receive the data

send_func: the function to send the data

flags: must be zero

This function will register a new supplemental data type (rfc4680). The registered supplemental functions will be used for that specific session. The provided type must be an unassigned type in gnutls_supplemental_data_format_type_t .

If the type is already registered or handled by GnuTLS internally GNUTLS_E_ALREADY_REGISTERED will be returned.

Returns: GNUTLS_E_SUCCESS on success, otherwise a negative error code.

Since: 3.5.5

gnutls_session_ticket_enable_client

Function: int gnutls_session_ticket_enable_client (gnutls_session_t session)

session: is a gnutls_session_t type.

Request that the client should attempt session resumption using SessionTicket.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, or an error code.

Since: 2.10.0

gnutls_session_ticket_enable_server

Function: int gnutls_session_ticket_enable_server (gnutls_session_t session, const gnutls_datum_t * key)

session: is a gnutls_session_t type.

key: key to encrypt session parameters.

Request that the server should attempt session resumption using SessionTicket. key must be initialized with gnutls_session_ticket_key_generate() , and should be overwritten using gnutls_memset() before being released.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, or an error code.

Since: 2.10.0

gnutls_session_ticket_key_generate

Function: int gnutls_session_ticket_key_generate (gnutls_datum_t * key)

key: is a pointer to a gnutls_datum_t which will contain a newly created key.

Generate a random key to encrypt security parameters within SessionTicket.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, or an error code.

Since: 2.10.0

gnutls_set_default_priority

Function: int gnutls_set_default_priority (gnutls_session_t session)

session: is a gnutls_session_t type.

Sets the default priority on the ciphers, key exchange methods, macs and compression methods. For more fine-tuning you could use gnutls_priority_set_direct() or gnutls_priority_set() instead.

Returns: GNUTLS_E_SUCCESS on success, or an error code.

gnutls_sign_algorithm_get

Function: int gnutls_sign_algorithm_get (gnutls_session_t session)

session: is a gnutls_session_t type.

Returns the signature algorithm that is (or will be) used in this session by the server to sign data. This function should be used only with TLS 1.2 or later.

Returns: The sign algorithm or GNUTLS_SIGN_UNKNOWN .

Since: 3.1.1

gnutls_sign_algorithm_get_client

Function: int gnutls_sign_algorithm_get_client (gnutls_session_t session)

session: is a gnutls_session_t type.

Returns the signature algorithm that is (or will be) used in this session by the client to sign data. This function should be used only with TLS 1.2 or later.

Returns: The sign algorithm or GNUTLS_SIGN_UNKNOWN .

Since: 3.1.11

gnutls_sign_algorithm_get_requested

Function: int gnutls_sign_algorithm_get_requested (gnutls_session_t session, size_t indx, gnutls_sign_algorithm_t * algo)

session: is a gnutls_session_t type.

indx: is an index of the signature algorithm to return

algo: the returned certificate type will be stored there

Returns the signature algorithm specified by index that was requested by the peer. If the specified index has no data available this function returns GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE . If the negotiated TLS version does not support signature algorithms then GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE will be returned even for the first index. The first index is 0.

This function is useful in the certificate callback functions to assist in selecting the correct certificate.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise an error code is returned.

Since: 2.10.0

gnutls_sign_get_hash_algorithm

Function: gnutls_digest_algorithm_t gnutls_sign_get_hash_algorithm (gnutls_sign_algorithm_t sign)

sign: is a signature algorithm

This function returns the digest algorithm corresponding to the given signature algorithms.

Since: 3.1.1

Returns: return a gnutls_digest_algorithm_t value, or GNUTLS_DIG_UNKNOWN on error.

gnutls_sign_get_id

Function: gnutls_sign_algorithm_t gnutls_sign_get_id (const char * name)

name: is a sign algorithm name

The names are compared in a case insensitive way.

Returns: return a gnutls_sign_algorithm_t value corresponding to the specified algorithm, or GNUTLS_SIGN_UNKNOWN on error.

gnutls_sign_get_name

Function: const char * gnutls_sign_get_name (gnutls_sign_algorithm_t algorithm)

algorithm: is a sign algorithm

Convert a gnutls_sign_algorithm_t value to a string.

Returns: a string that contains the name of the specified sign algorithm, or NULL .

gnutls_sign_get_oid

Function: const char * gnutls_sign_get_oid (gnutls_sign_algorithm_t sign)

sign: is a sign algorithm

Convert a gnutls_sign_algorithm_t value to its object identifier.

Returns: a string that contains the object identifier of the specified sign algorithm, or NULL .

Since: 3.4.3

gnutls_sign_get_pk_algorithm

Function: gnutls_pk_algorithm_t gnutls_sign_get_pk_algorithm (gnutls_sign_algorithm_t sign)

sign: is a signature algorithm

This function returns the public key algorithm corresponding to the given signature algorithms.

Since: 3.1.1

Returns: return a gnutls_pk_algorithm_t value, or GNUTLS_PK_UNKNOWN on error.

gnutls_sign_is_secure

Function: int gnutls_sign_is_secure (gnutls_sign_algorithm_t algorithm)

algorithm: is a sign algorithm

Returns: Non-zero if the provided signature algorithm is considered to be secure.

gnutls_sign_list

Function: const gnutls_sign_algorithm_t * gnutls_sign_list ( void)

Get a list of supported public key signature algorithms.

Returns: a (0)-terminated list of gnutls_sign_algorithm_t integers indicating the available ciphers.

gnutls_srp_allocate_client_credentials

Function: int gnutls_srp_allocate_client_credentials (gnutls_srp_client_credentials_t * sc)

sc: is a pointer to a gnutls_srp_server_credentials_t type.

Allocate a gnutls_srp_client_credentials_t structure.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, or an error code.

gnutls_srp_allocate_server_credentials

Function: int gnutls_srp_allocate_server_credentials (gnutls_srp_server_credentials_t * sc)

sc: is a pointer to a gnutls_srp_server_credentials_t type.

Allocate a gnutls_srp_server_credentials_t structure.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, or an error code.

gnutls_srp_base64_decode

Function: int gnutls_srp_base64_decode (const gnutls_datum_t * b64_data, char * result, size_t * result_size)

b64_data: contain the encoded data

result: the place where decoded data will be copied

result_size: holds the size of the result

This function will decode the given encoded data, using the base64 encoding found in libsrp.

Note that b64_data should be null terminated.

Warning! This base64 encoding is not the "standard" encoding, so do not use it for non-SRP purposes.

Returns: GNUTLS_E_SHORT_MEMORY_BUFFER if the buffer given is not long enough, or 0 on success.

gnutls_srp_base64_decode2

Function: int gnutls_srp_base64_decode2 (const gnutls_datum_t * b64_data, gnutls_datum_t * result)

b64_data: contains the encoded data

result: the place where decoded data lie

This function will decode the given encoded data. The decoded data will be allocated, and stored into result. It will decode using the base64 algorithm as used in libsrp.

You should use gnutls_free() to free the returned data.

Warning! This base64 encoding is not the "standard" encoding, so do not use it for non-SRP purposes.

Returns: 0 on success, or an error code.

gnutls_srp_base64_encode

Function: int gnutls_srp_base64_encode (const gnutls_datum_t * data, char * result, size_t * result_size)

data: contain the raw data

result: the place where base64 data will be copied

result_size: holds the size of the result

This function will convert the given data to printable data, using the base64 encoding, as used in the libsrp. This is the encoding used in SRP password files. If the provided buffer is not long enough GNUTLS_E_SHORT_MEMORY_BUFFER is returned.

Warning! This base64 encoding is not the "standard" encoding, so do not use it for non-SRP purposes.

Returns: GNUTLS_E_SHORT_MEMORY_BUFFER if the buffer given is not long enough, or 0 on success.

gnutls_srp_base64_encode2

Function: int gnutls_srp_base64_encode2 (const gnutls_datum_t * data, gnutls_datum_t * result)

data: contains the raw data

result: will hold the newly allocated encoded data

This function will convert the given data to printable data, using the base64 encoding. This is the encoding used in SRP password files. This function will allocate the required memory to hold the encoded data.

You should use gnutls_free() to free the returned data.

Warning! This base64 encoding is not the "standard" encoding, so do not use it for non-SRP purposes.

Returns: 0 on success, or an error code.

gnutls_srp_free_client_credentials

Function: void gnutls_srp_free_client_credentials (gnutls_srp_client_credentials_t sc)

sc: is a gnutls_srp_client_credentials_t type.

Free a gnutls_srp_client_credentials_t structure.

gnutls_srp_free_server_credentials

Function: void gnutls_srp_free_server_credentials (gnutls_srp_server_credentials_t sc)

sc: is a gnutls_srp_server_credentials_t type.

Free a gnutls_srp_server_credentials_t structure.

gnutls_srp_server_get_username

Function: const char * gnutls_srp_server_get_username (gnutls_session_t session)

session: is a gnutls session

This function will return the username of the peer. This should only be called in case of SRP authentication and in case of a server. Returns NULL in case of an error.

Returns: SRP username of the peer, or NULL in case of error.

gnutls_srp_set_client_credentials

Function: int gnutls_srp_set_client_credentials (gnutls_srp_client_credentials_t res, const char * username, const char * password)

res: is a gnutls_srp_client_credentials_t type.

username: is the user’s userid

password: is the user’s password

This function sets the username and password, in a gnutls_srp_client_credentials_t type. Those will be used in SRP authentication. username and password should be ASCII strings or UTF-8 strings prepared using the "SASLprep" profile of "stringprep".

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, or an error code.

gnutls_srp_set_client_credentials_function

Function: void gnutls_srp_set_client_credentials_function (gnutls_srp_client_credentials_t cred, gnutls_srp_client_credentials_function * func)

cred: is a gnutls_srp_server_credentials_t type.

func: is the callback function

This function can be used to set a callback to retrieve the username and password for client SRP authentication. The callback’s function form is:

int (*callback)(gnutls_session_t, char** username, char**password);

The username and password must be allocated using gnutls_malloc() . username and password should be ASCII strings or UTF-8 strings prepared using the "SASLprep" profile of "stringprep".

The callback function will be called once per handshake before the initial hello message is sent.

The callback should not return a negative error code the second time called, since the handshake procedure will be aborted.

The callback function should return 0 on success. -1 indicates an error.

gnutls_srp_set_prime_bits

Function: void gnutls_srp_set_prime_bits (gnutls_session_t session, unsigned int bits)

session: is a gnutls_session_t type.

bits: is the number of bits

This function sets the minimum accepted number of bits, for use in an SRP key exchange. If zero, the default 2048 bits will be used.

In the client side it sets the minimum accepted number of bits. If a server sends a prime with less bits than that GNUTLS_E_RECEIVED_ILLEGAL_PARAMETER will be returned by the handshake.

This function has no effect in server side.

Since: 2.6.0

gnutls_srp_set_server_credentials_file

Function: int gnutls_srp_set_server_credentials_file (gnutls_srp_server_credentials_t res, const char * password_file, const char * password_conf_file)

res: is a gnutls_srp_server_credentials_t type.

password_file: is the SRP password file (tpasswd)

password_conf_file: is the SRP password conf file (tpasswd.conf)

This function sets the password files, in a gnutls_srp_server_credentials_t type. Those password files hold usernames and verifiers and will be used for SRP authentication.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, or an error code.

gnutls_srp_set_server_credentials_function

Function: void gnutls_srp_set_server_credentials_function (gnutls_srp_server_credentials_t cred, gnutls_srp_server_credentials_function * func)

cred: is a gnutls_srp_server_credentials_t type.

func: is the callback function

This function can be used to set a callback to retrieve the user’s SRP credentials. The callback’s function form is:

int (*callback)(gnutls_session_t, const char* username, gnutls_datum_t *salt, gnutls_datum_t *verifier, gnutls_datum_t *generator, gnutls_datum_t *prime);

username contains the actual username. The salt , verifier , generator and prime must be filled in using the gnutls_malloc() . For convenience prime and generator may also be one of the static parameters defined in gnutls.h.

Initially, the data field is NULL in every gnutls_datum_t structure that the callback has to fill in. When the callback is done GnuTLS deallocates all of those buffers which are non-NULL, regardless of the return value.

In order to prevent attackers from guessing valid usernames, if a user does not exist, g and n values should be filled in using a random user’s parameters. In that case the callback must return the special value (1). See gnutls_srp_set_server_fake_salt_seed too. If this is not required for your application, return a negative number from the callback to abort the handshake.

The callback function will only be called once per handshake. The callback function should return 0 on success, while -1 indicates an error.

gnutls_srp_set_server_fake_salt_seed

Function: void gnutls_srp_set_server_fake_salt_seed (gnutls_srp_server_credentials_t cred, const gnutls_datum_t * seed, unsigned int salt_length)

cred: is a gnutls_srp_server_credentials_t type

seed: is the seed data, only needs to be valid until the function returns; size of the seed must be greater than zero

salt_length: is the length of the generated fake salts

This function sets the seed that is used to generate salts for invalid (non-existent) usernames.

In order to prevent attackers from guessing valid usernames, when a user does not exist gnutls generates a salt and a verifier and proceeds with the protocol as usual. The authentication will ultimately fail, but the client cannot tell whether the username is valid (exists) or invalid.

If an attacker learns the seed, given a salt (which is part of the handshake) which was generated when the seed was in use, it can tell whether or not the authentication failed because of an unknown username. This seed cannot be used to reveal application data or passwords.

salt_length should represent the salt length your application uses. Generating fake salts longer than 20 bytes is not supported.

By default the seed is a random value, different each time a gnutls_srp_server_credentials_t is allocated and fake salts are 16 bytes long.

Since: 3.3.0

gnutls_srp_verifier

Function: int gnutls_srp_verifier (const char * username, const char * password, const gnutls_datum_t * salt, const gnutls_datum_t * generator, const gnutls_datum_t * prime, gnutls_datum_t * res)

username: is the user’s name

password: is the user’s password

salt: should be some randomly generated bytes

generator: is the generator of the group

prime: is the group’s prime

res: where the verifier will be stored.

This function will create an SRP verifier, as specified in RFC2945. The prime and generator should be one of the static parameters defined in gnutls/gnutls.h or may be generated.

The verifier will be allocated with gnutls_malloc () and will be stored in res using binary format.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, or an error code.

gnutls_srtp_get_keys

Function: int gnutls_srtp_get_keys (gnutls_session_t session, void * key_material, unsigned int key_material_size, gnutls_datum_t * client_key, gnutls_datum_t * client_salt, gnutls_datum_t * server_key, gnutls_datum_t * server_salt)

session: is a gnutls_session_t type.

key_material: Space to hold the generated key material

key_material_size: The maximum size of the key material

client_key: The master client write key, pointing inside the key material

client_salt: The master client write salt, pointing inside the key material

server_key: The master server write key, pointing inside the key material

server_salt: The master server write salt, pointing inside the key material

This is a helper function to generate the keying material for SRTP. It requires the space of the key material to be pre-allocated (should be at least 2x the maximum key size and salt size). The client_key , client_salt , server_key and server_salt are convenience datums that point inside the key material. They may be NULL .

Returns: On success the size of the key material is returned, otherwise, GNUTLS_E_SHORT_MEMORY_BUFFER if the buffer given is not sufficient, or a negative error code.

Since 3.1.4

gnutls_srtp_get_mki

Function: int gnutls_srtp_get_mki (gnutls_session_t session, gnutls_datum_t * mki)

session: is a gnutls_session_t type.

mki: will hold the MKI

This function exports the negotiated Master Key Identifier, received by the peer if any. The returned value in mki should be treated as constant and valid only during the session’s lifetime.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

Since 3.1.4

gnutls_srtp_get_profile_id

Function: int gnutls_srtp_get_profile_id (const char * name, gnutls_srtp_profile_t * profile)

name: The name of the profile to look up

profile: Will hold the profile id

This function allows you to look up a profile based on a string.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

Since 3.1.4

gnutls_srtp_get_profile_name

Function: const char * gnutls_srtp_get_profile_name (gnutls_srtp_profile_t profile)

profile: The profile to look up a string for

This function allows you to get the corresponding name for a SRTP protection profile.

Returns: On success, the name of a SRTP profile as a string, otherwise NULL.

Since 3.1.4

gnutls_srtp_get_selected_profile

Function: int gnutls_srtp_get_selected_profile (gnutls_session_t session, gnutls_srtp_profile_t * profile)

session: is a gnutls_session_t type.

profile: will hold the profile

This function allows you to get the negotiated SRTP profile.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

Since 3.1.4

gnutls_srtp_set_mki

Function: int gnutls_srtp_set_mki (gnutls_session_t session, const gnutls_datum_t * mki)

session: is a gnutls_session_t type.

mki: holds the MKI

This function sets the Master Key Identifier, to be used by this session (if any).

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

Since 3.1.4

gnutls_srtp_set_profile

Function: int gnutls_srtp_set_profile (gnutls_session_t session, gnutls_srtp_profile_t profile)

session: is a gnutls_session_t type.

profile: is the profile id to add.

This function is to be used by both clients and servers, to declare what SRTP profiles they support, to negotiate with the peer.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error code is returned.

Since 3.1.4

gnutls_srtp_set_profile_direct

Function: int gnutls_srtp_set_profile_direct (gnutls_session_t session, const char * profiles, const char ** err_pos)

session: is a gnutls_session_t type.

profiles: is a string that contains the supported SRTP profiles, separated by colons.

err_pos: In case of an error this will have the position in the string the error occurred, may be NULL.

This function is to be used by both clients and servers, to declare what SRTP profiles they support, to negotiate with the peer.

Returns: On syntax error GNUTLS_E_INVALID_REQUEST is returned, GNUTLS_E_SUCCESS on success, or an error code.

Since 3.1.4

gnutls_store_commitment

Function: int gnutls_store_commitment (const char * db_name, gnutls_tdb_t tdb, const char * host, const char * service, gnutls_digest_algorithm_t hash_algo, const gnutls_datum_t * hash, time_t expiration, unsigned int flags)

db_name: A file specifying the stored keys (use NULL for the default)

tdb: A storage structure or NULL to use the default

host: The peer’s name

service: non-NULL if this key is specific to a service (e.g. http)

hash_algo: The hash algorithm type

hash: The raw hash

expiration: The expiration time (use 0 to disable expiration)

flags: should be 0 or GNUTLS_SCOMMIT_FLAG_ALLOW_BROKEN .

This function will store the provided hash commitment to the list of stored public keys. The key with the given hash will be considered valid until the provided expiration time.

The store variable if non-null specifies a custom backend for the storage of entries. If it is NULL then the default file backend will be used.

Note that this function is not thread safe with the default backend.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error value.

Since: 3.0

gnutls_store_pubkey

Function: int gnutls_store_pubkey (const char * db_name, gnutls_tdb_t tdb, const char * host, const char * service, gnutls_certificate_type_t cert_type, const gnutls_datum_t * cert, time_t expiration, unsigned int flags)

db_name: A file specifying the stored keys (use NULL for the default)

tdb: A storage structure or NULL to use the default

host: The peer’s name

service: non-NULL if this key is specific to a service (e.g. http)

cert_type: The type of the certificate

cert: The data of the certificate

expiration: The expiration time (use 0 to disable expiration)

flags: should be 0.

This function will store the provided (raw or DER-encoded) certificate to the list of stored public keys. The key will be considered valid until the provided expiration time.

The store variable if non-null specifies a custom backend for the storage of entries. If it is NULL then the default file backend will be used.

Unless an alternative tdb is provided, the storage format is a textual format consisting of a line for each host with fields separated by ’|’. The contents of the fields are a format-identifier which is set to ’g0’, the hostname that the rest of the data applies to, the numeric port or host name, the expiration time in seconds since the epoch (0 for no expiration), and a base64 encoding of the raw (DER) public key information (SPKI) of the peer.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error value.

Since: 3.0.13

gnutls_strerror

Function: const char * gnutls_strerror (int error)

error: is a GnuTLS error code, a negative error code

This function is similar to strerror. The difference is that it accepts an error number returned by a gnutls function; In case of an unknown error a descriptive string is sent instead of NULL .

Error codes are always a negative error code.

Returns: A string explaining the GnuTLS error message.

gnutls_strerror_name

Function: const char * gnutls_strerror_name (int error)

error: is an error returned by a gnutls function.

Return the GnuTLS error code define as a string. For example, gnutls_strerror_name (GNUTLS_E_DH_PRIME_UNACCEPTABLE) will return the string "GNUTLS_E_DH_PRIME_UNACCEPTABLE".

Returns: A string corresponding to the symbol name of the error code.

Since: 2.6.0

gnutls_supplemental_get_name

Function: const char * gnutls_supplemental_get_name (gnutls_supplemental_data_format_type_t type)

type: is a supplemental data format type

Convert a gnutls_supplemental_data_format_type_t value to a string.

Returns: a string that contains the name of the specified supplemental data format type, or NULL for unknown types.

gnutls_supplemental_recv

Function: void gnutls_supplemental_recv (gnutls_session_t session, unsigned do_recv_supplemental)

session: is a gnutls_session_t type.

do_recv_supplemental: non-zero in order to expect supplemental data

This function is to be called by an extension handler to instruct gnutls to attempt to receive supplemental data during the handshake process.

Since: 3.4.0

gnutls_supplemental_register

Function: int gnutls_supplemental_register (const char * name, gnutls_supplemental_data_format_type_t type, gnutls_supp_recv_func recv_func, gnutls_supp_send_func send_func)

name: the name of the supplemental data to register

type: the type of the supplemental data format

recv_func: the function to receive the data

send_func: the function to send the data

This function will register a new supplemental data type (rfc4680). The registered data will remain until gnutls_global_deinit() is called. The provided type must be an unassigned type in gnutls_supplemental_data_format_type_t . If the type is already registered or handled by GnuTLS internally GNUTLS_E_ALREADY_REGISTERED will be returned.

This function is not thread safe.

Returns: GNUTLS_E_SUCCESS on success, otherwise a negative error code.

Since: 3.4.0

gnutls_supplemental_send

Function: void gnutls_supplemental_send (gnutls_session_t session, unsigned do_send_supplemental)

session: is a gnutls_session_t type.

do_send_supplemental: non-zero in order to send supplemental data

This function is to be called by an extension handler to instruct gnutls to send supplemental data during the handshake process.

Since: 3.4.0

gnutls_system_recv_timeout

Function: int gnutls_system_recv_timeout (gnutls_transport_ptr_t ptr, unsigned int ms)

ptr: A gnutls_transport_ptr_t pointer

ms: The number of milliseconds to wait.

Wait for data to be received from the provided socket ( ptr ) within a timeout period in milliseconds, using select() on the provided ptr .

This function is provided as a helper for constructing custom callbacks for gnutls_transport_set_pull_timeout_function() , which can be used if you rely on socket file descriptors.

Returns -1 on error, 0 on timeout, positive value if data are available for reading.

Since: 3.4.0

gnutls_tdb_deinit

Function: void gnutls_tdb_deinit (gnutls_tdb_t tdb)

tdb: The structure to be deinitialized

This function will deinitialize a public key trust storage structure.

gnutls_tdb_init

Function: int gnutls_tdb_init (gnutls_tdb_t * tdb)

tdb: A pointer to the type to be initialized

This function will initialize a public key trust storage structure.

Returns: On success, GNUTLS_E_SUCCESS (0) is returned, otherwise a negative error value.

gnutls_tdb_set_store_commitment_func

Function: void gnutls_tdb_set_store_commitment_func (gnutls_tdb_t tdb, gnutls_tdb_store_commitment_func cstore)

tdb: The trust storage

cstore: The commitment storage function

This function will associate a commitment (hash) storage function with the trust storage structure. The function is of the following form.

int gnutls_tdb_store_commitment_func(const char* db_name, const char* host, const char* service, time_t expiration, gnutls_digest_algorithm_t, const gnutls_datum_t* hash);

The db_name should be used to pass any private data to this function.

gnutls_tdb_set_store_func

Function: void gnutls_tdb_set_store_func (gnutls_tdb_t tdb, gnutls_tdb_store_func store)

tdb: The trust storage

store: The storage function

This function will associate a storage function with the trust storage structure. The function is of the following form.

int gnutls_tdb_store_func(const char* db_name, const char* host, const char* service, time_t expiration, const gnutls_datum_t* pubkey);

The db_name should be used to pass any private data to this function.

gnutls_tdb_set_verify_func

Function: void gnutls_tdb_set_verify_func (gnutls_tdb_t tdb, gnutls_tdb_verify_func verify)

tdb: The trust storage

verify: The verification function

This function will associate a retrieval function with the trust storage structure. The function is of the following form.

int gnutls_tdb_verify_func(const char* db_name, const char* host, const char* service, const gnutls_datum_t* pubkey);

The verify function should return zero on a match, GNUTLS_E_CERTIFICATE_KEY_MISMATCH if there is a mismatch and any other negative error code otherwise.

The db_name should be used to pass any private data to this function.

gnutls_transport_get_int

Function: int gnutls_transport_get_int (gnutls_session_t session)

session: is a gnutls_session_t type.

Used to get the first argument of the transport function (like PUSH and PULL). This must have been set using gnutls_transport_set_int() .

Returns: The first argument of the transport function.

Since: 3.1.9

gnutls_transport_get_int2

Function: void gnutls_transport_get_int2 (gnutls_session_t session, int * recv_int, int * send_int)

session: is a gnutls_session_t type.

recv_int: will hold the value for the pull function

send_int: will hold the value for the push function

Used to get the arguments of the transport functions (like PUSH and PULL). These should have been set using gnutls_transport_set_int2() .

Since: 3.1.9

gnutls_transport_get_ptr

Function: gnutls_transport_ptr_t gnutls_transport_get_ptr (gnutls_session_t session)

session: is a gnutls_session_t type.

Used to get the first argument of the transport function (like PUSH and PULL). This must have been set using gnutls_transport_set_ptr() .

Returns: The first argument of the transport function.

gnutls_transport_get_ptr2

Function: void gnutls_transport_get_ptr2 (gnutls_session_t session, gnutls_transport_ptr_t * recv_ptr, gnutls_transport_ptr_t * send_ptr)

session: is a gnutls_session_t type.

recv_ptr: will hold the value for the pull function

send_ptr: will hold the value for the push function

Used to get the arguments of the transport functions (like PUSH and PULL). These should have been set using gnutls_transport_set_ptr2() .

gnutls_transport_set_errno

Function: void gnutls_transport_set_errno (gnutls_session_t session, int err)

session: is a gnutls_session_t type.

err: error value to store in session-specific errno variable.

Store err in the session-specific errno variable. Useful values for err are EINTR, EAGAIN and EMSGSIZE, other values are treated will be treated as real errors in the push/pull function.

This function is useful in replacement push and pull functions set by gnutls_transport_set_push_function() and gnutls_transport_set_pull_function() under Windows, where the replacements may not have access to the same errno variable that is used by GnuTLS (e.g., the application is linked to msvcr71.dll and gnutls is linked to msvcrt.dll).

gnutls_transport_set_errno_function

Function: void gnutls_transport_set_errno_function (gnutls_session_t session, gnutls_errno_func errno_func)

session: is a gnutls_session_t type.

errno_func: a callback function similar to write()

This is the function where you set a function to retrieve errno after a failed push or pull operation.

errno_func is of the form, int (*gnutls_errno_func)(gnutls_transport_ptr_t); and should return the errno.

Since: 2.12.0

gnutls_transport_set_int

Function: void gnutls_transport_set_int (gnutls_session_t session, int fd)

session: is a gnutls_session_t type.

fd: is the socket descriptor for the connection.

This function sets the first argument of the transport function, such as send() and recv() for the default callbacks using the system’s socket API.

This function is equivalent to calling gnutls_transport_set_ptr() with the descriptor, but requires no casts.

Since: 3.1.9

gnutls_transport_set_int2

Function: void gnutls_transport_set_int2 (gnutls_session_t session, int recv_fd, int send_fd)

session: is a gnutls_session_t type.

recv_fd: is socket descriptor for the pull function

send_fd: is socket descriptor for the push function

This function sets the first argument of the transport functions, such as send() and recv() for the default callbacks using the system’s socket API. With this function you can set two different descriptors for receiving and sending.

This function is equivalent to calling gnutls_transport_set_ptr2() with the descriptors, but requires no casts.

Since: 3.1.9

gnutls_transport_set_ptr

Function: void gnutls_transport_set_ptr (gnutls_session_t session, gnutls_transport_ptr_t ptr)

session: is a gnutls_session_t type.

ptr: is the value.

Used to set the first argument of the transport function (for push and pull callbacks). In berkeley style sockets this function will set the connection descriptor.

gnutls_transport_set_ptr2

Function: void gnutls_transport_set_ptr2 (gnutls_session_t session, gnutls_transport_ptr_t recv_ptr, gnutls_transport_ptr_t send_ptr)

session: is a gnutls_session_t type.

recv_ptr: is the value for the pull function

send_ptr: is the value for the push function

Used to set the first argument of the transport function (for push and pull callbacks). In berkeley style sockets this function will set the connection descriptor. With this function you can use two different pointers for receiving and sending.

gnutls_transport_set_pull_function

Function: void gnutls_transport_set_pull_function (gnutls_session_t session, gnutls_pull_func pull_func)

session: is a gnutls_session_t type.

pull_func: a callback function similar to read()

This is the function where you set a function for gnutls to receive data. Normally, if you use berkeley style sockets, do not need to use this function since the default recv(2) will probably be ok. The callback should return 0 on connection termination, a positive number indicating the number of bytes received, and -1 on error.

gnutls_pull_func is of the form, ssize_t (*gnutls_pull_func)(gnutls_transport_ptr_t, void*, size_t);

gnutls_transport_set_pull_timeout_function

Function: void gnutls_transport_set_pull_timeout_function (gnutls_session_t session, gnutls_pull_timeout_func func)

session: is a gnutls_session_t type.

func: a callback function

This is the function where you set a function for gnutls to know whether data are ready to be received. It should wait for data a given time frame in milliseconds. The callback should return 0 on timeout, a positive number if data can be received, and -1 on error. You’ll need to override this function if select() is not suitable for the provided transport calls.

As with select() , if the timeout value is zero the callback should return zero if no data are immediately available. The special value GNUTLS_INDEFINITE_TIMEOUT indicates that the callback should wait indefinitely for data.

gnutls_pull_timeout_func is of the form, int (*gnutls_pull_timeout_func)(gnutls_transport_ptr_t, unsigned int ms);

This callback is necessary when gnutls_handshake_set_timeout() or gnutls_record_set_timeout() are set, and for calculating the DTLS mode timeouts.

In short, this callback should be set when a custom pull function is registered. The callback will not be used when the session is in TLS mode with non-blocking sockets. That is, when GNUTLS_NONBLOCK is specified for a TLS session in gnutls_init() . For compatibility with future GnuTLS versions it is recommended to always set this function when a custom pull function is registered.

The helper function gnutls_system_recv_timeout() is provided to simplify writing callbacks.

Since: 3.0

gnutls_transport_set_push_function

Function: void gnutls_transport_set_push_function (gnutls_session_t session, gnutls_push_func push_func)

session: is a gnutls_session_t type.

push_func: a callback function similar to write()

This is the function where you set a push function for gnutls to use in order to send data. If you are going to use berkeley style sockets, you do not need to use this function since the default send(2) will probably be ok. Otherwise you should specify this function for gnutls to be able to send data. The callback should return a positive number indicating the bytes sent, and -1 on error.

push_func is of the form, ssize_t (*gnutls_push_func)(gnutls_transport_ptr_t, const void*, size_t);

gnutls_transport_set_vec_push_function

Function: void gnutls_transport_set_vec_push_function (gnutls_session_t session, gnutls_vec_push_func vec_func)

session: is a gnutls_session_t type.

vec_func: a callback function similar to writev()

Using this function you can override the default writev(2) function for gnutls to send data. Setting this callback instead of gnutls_transport_set_push_function() is recommended since it introduces less overhead in the TLS handshake process.

vec_func is of the form, ssize_t (*gnutls_vec_push_func) (gnutls_transport_ptr_t, const giovec_t * iov, int iovcnt);

Since: 2.12.0

gnutls_url_is_supported

Function: unsigned gnutls_url_is_supported (const char * url)

url: A URI to be tested

Check whether the provided url is supported. Depending on the system libraries GnuTLS may support pkcs11, tpmkey or other URLs.

Returns: return non-zero if the given URL is supported, and zero if it is not known.

Since: 3.1.0

gnutls_utf8_password_normalize

Function: int gnutls_utf8_password_normalize (const unsigned char * password, unsigned plen, gnutls_datum_t * out, unsigned flags)

password: contain the UTF-8 formatted password

plen: the length of the provided password

out: the result in an null-terminated allocated string

flags: should be zero

This function will convert the provided UTF-8 password according to the normalization rules in RFC7613.

If the flag GNUTLS_UTF8_IGNORE_ERRS is specified, any UTF-8 encoding errors will be ignored, and in that case the output will be a copy of the input.

Returns: GNUTLS_E_INVALID_UTF8_STRING on invalid UTF-8 data, or 0 on success.

Since: 3.5.7

gnutls_verify_stored_pubkey

Function: int gnutls_verify_stored_pubkey (const char * db_name, gnutls_tdb_t tdb, const char * host, const char * service, gnutls_certificate_type_t cert_type, const gnutls_datum_t * cert, unsigned int flags)

db_name: A file specifying the stored keys (use NULL for the default)

tdb: A storage structure or NULL to use the default

host: The peer’s name

service: non-NULL if this key is specific to a service (e.g. http)

cert_type: The type of the certificate

cert: The raw (der) data of the certificate

flags: should be 0.

This function will try to verify the provided (raw or DER-encoded) certificate using a list of stored public keys. The service field if non-NULL should be a port number.

The retrieve variable if non-null specifies a custom backend for the retrieval of entries. If it is NULL then the default file backend will be used. In POSIX-like systems the file backend uses the $HOME/.gnutls/known_hosts file.

Note that if the custom storage backend is provided the retrieval function should return GNUTLS_E_CERTIFICATE_KEY_MISMATCH if the host/service pair is found but key doesn’t match, GNUTLS_E_NO_CERTIFICATE_FOUND if no such host/service with the given key is found, and 0 if it was found. The storage function should return 0 on success.

Returns: If no associated public key is found then GNUTLS_E_NO_CERTIFICATE_FOUND will be returned. If a key is found but does not match GNUTLS_E_CERTIFICATE_KEY_MISMATCH is returned. On success, GNUTLS_E_SUCCESS (0) is returned, or a negative error value on other errors.

Since: 3.0.13


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