Is it possible to replace gnome-keyring-daemon with ssh-agent?

edit

It turned out to be easier than I expected. First, some background:

When you log into gdm, it starts up your X session by running /etc/gdm/Xsession, which is a symlink to /etc/X11/xinit/Xsession. This is a shell script that receives a single parameter from the display manager -- for Gnome, this is gnome-session. There's an ugly case statement in this script that figures out the next step based on the display manager in use; for Gnome, it ends up doing this:

    gnome|gnome-session)
        # lack of SSH_AGENT is intentional, see #441123.  though
        # the whole thing should really happen in xinitrc.d anyway.
        exec -l $SHELL -c gnome-session
        exec /bin/sh -c "exec -l $SHELL -c \"gnome-session\"" 
        ;;

I thought at first I was going to have to modify this script, which would have been an ugly hack -- future package updates would probably revert my changes. Fortunately, earlier on in the script is this snippet of code:

XCLIENTS_D=/etc/X11/xinit/Xclients.d
if [ "$#" -eq 1 ] && [ -x "$XCLIENTS_D/Xclients.$1.sh" ]; then
    exec -l $SHELL -c "$CK_XINIT_SESSION $SSH_AGENT $XCLIENTS_D/Xclients.$1.sh"
else

This looks in /etc/X11/xinit/Xclientds.d for a display-manager specific Xclients script, and runs that instead of the case statement if one is available. So I created `/etc/X11/xinit/Xclients.d/Xclients.gnome-session.sh with the following contents:

#!/bin/sh
exec -l $SHELL -c "$SSH_AGENT gnome-session"

This takes advantage of the SSH_AGENT variable set earlier by xinitrc-common. This gets me a session running under ssh-agent, which is just what I wanted.

There was another problem, however: files in /etc/xdg/autostart were still starting up the gnome-keyring-daemon agent. It's possible to modify or remove these files, but since they're not marked as configuration files in the gnome-keyring package they'll come back to haunt me in the event this packages gets updated.

So for the time being, I've wielded the Hammer of Chmod:

chmod 0 /usr/bin/gnome-keyring-daemon

It's not pretty, but it gets me what I want: the ability to load SSH certificates in my desktop environment.