Comment 15 for bug 823775

Okay, digging through the lightdm code a little, I'm looking at:

in src/display.c, the start_user_session() function does:
...
    g_debug ("Starting user session");
    user = pam_session_get_user (authentication);
    /* Load the users login settings (~/.dmrc) */
    dmrc_file = dmrc_load (user_get_name (user));
...

And in src/dmrc.c, the dmrc_load() function:
...
    /* Load from the user directory, if this fails (e.g. the user directory
     * is not yet mounted) then load from the cache */
    path = g_build_filename (user_get_home_directory (user), ".dmrc", NULL);
    have_dmrc = g_key_file_load_from_file (dmrc_file, path, G_KEY_FILE_KEEP_COMMENTS, NULL);
    g_free (path);
...

Basically, if the user's home directory is not mounted, then something is *wrong*, and we shouldn't be proceeding yet. Lightdm should be blocking until the pam session start completes successfully.

Further down, this is just wrong:
...
    /* Update the users .dmrc */
    if (user)
    {
        path = g_build_filename (user_get_home_directory (user), ".dmrc", NULL);
        g_file_set_contents (path, data, length, NULL);
        if (getuid () == 0 && chown (path, user_get_uid (user), user_get_gid (user)) < 0)
            g_warning ("Error setting ownership on %s: %s", path, strerror (errno));
        g_free (path);
    }
...

This is creating the ~/.dmrc file in a read-only $HOME directory as the root user, and then chowning it over to $USER. This leaves un-encrypted files in the user's home directory, which is very much undesirable, if a user is encrypting their home.

I haven't found a solution yet as I'm only looking at this a little bit while at a conference, but I thought I'd leave a few notes here :-)