GnuPG 2.1.x changed the way the gpg-agent works, and that new approach no
longer requires (or even supports) the "start everything as a child of the
agent" scheme we've implemented in NixOS for older versions.
To configure the gpg-agent for your X session, add the following code to
~/.xsession or some other appropriate place that's sourced at start-up:
gpg-connect-agent /bye
GPG_TTY=$(tty)
export GPG_TTY
If you want to use gpg-agent for SSH, too, also add the settings
unset SSH_AGENT_PID
export SSH_AUTH_SOCK="${HOME}/.gnupg/S.gpg-agent.ssh"
and make sure that
enable-ssh-support
is included in your ~/.gnupg/gpg-agent.conf.
The gpg-agent(1) man page has more details about this subject, i.e. in the
"EXAMPLES" section.
This has some advantages:
* You get ssh-agent regardless of how you logged in. Previously it was
only started for X11 sessions.
* All sessions of a user share the same agent. So if you added a key
on tty1, it will also be available on tty2.
* Systemd will restart ssh-agent if it dies.
* $SSH_AUTH_SOCK now points to the /run/user/<uid> directory, which is
more secure than /tmp.
For bonus points, we should patch ssh-agent to support socket-based
activation...
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.
