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2 Help For Users

From the user's perspective, there's nothing to the GnuTLS integration. It Just Works for any Emacs Lisp code that uses open-protocol-stream or open-network-stream (see Network Connections). The two functions are equivalent, the first one being an alias of the second.

There's one way to find out if GnuTLS is available, by calling gnutls-available-p. This is a little bit trickier on the W32 (Windows) platform, but if you have the GnuTLS DLLs (available from http://sourceforge.net/projects/ezwinports/files/ thanks to Eli Zaretskii) in the same directory as Emacs, you should be OK.

— Function: gnutls-available-p

This function returns t if GnuTLS is available in this instance of Emacs.

Oh, but sometimes things go wrong. Budgets aren't balanced, television ads lie, and even TLS and SSL connections can fail to work properly. Well, there's something to be done in the last case.

— Variable: gnutls-log-level

The gnutls-log-level variable sets the log level. 1 is verbose. 2 is very verbose. 5 is crazy. Crazy! Set it to 1 or 2 and look in the *Messages* buffer for the debugging information.

— Variable: gnutls-algorithm-priority

The gnutls-algorithm-priority variable sets the GnuTLS priority string. This is global, not per host name (although gnutls-negotiate supports a priority string per connection so it could be done if needed). The priority string syntax is in the GnuTLS documentation.

— Variable: gnutls-trustfiles

The gnutls-trustfiles variable is a list of trustfiles (certificates for the issuing authorities). This is global, not per host name (although gnutls-negotiate supports a trustfile per connection so it could be done if needed). The trustfiles can be in PEM or DER format and examples can be found in most Unix distributions. By default four locations are tried in this order: /etc/ssl/certs/ca-certificates.crt for Debian, Ubuntu, Gentoo and Arch Linux; /etc/pki/tls/certs/ca-bundle.crt for Fedora and RHEL; /etc/ssl/ca-bundle.pem for Suse; /usr/ssl/certs/ca-bundle.crt for Cygwin. You can easily customize gnutls-trustfiles to be something else, but let us know if you do, so we can make the change to benefit the other users of that platform.

— Variable: gnutls-min-prime-bits

The gnutls-min-prime-bits variable is a pretty exotic customization for cases where you want to refuse handshakes with keys under a specific size. If you don't know for sure that you need it, you don't. Leave it nil.