When installing for a software distribution, it is often desirable to preconfigure GnuTLS with the system-wide paths and files. There two important configuration options, one sets the trust store in system, which are the CA certificates to be used by programs by default (if they don’t override it), and the other sets to DNSSEC root key file used by unbound for DNSSEC verification.
For the latter the following configuration option is available, and if not specified GnuTLS will try to auto-detect the location of that file.
To set the trust store the following options are available.
--with-default-trust-store-file --with-default-trust-store-dir --with-default-trust-store-pkcs11
The first option is used to set a PEM file which contains a list of trusted certificates, while the second will read all certificates in the given path. The recommended option is the last, which allows to use a PKCS #11 trust policy module. That module not only provides the trusted certificates, but allows the categorization of them using purpose, e.g., CAs can be restricted for e-mail usage only, or administrative restrictions of CAs, for examples by restricting a CA to only issue certificates for a given DNS domain using NameConstraints. A publicly available PKCS #11 trust module is p11-kit’s trust module2.