[gdm/wip/oh-god-environment-variables-again] gdm-{wayland, x}-session: protect more session variables

[Ray Strode <halfline src gnome org>]

commit 68aac5ed238c28223c50eda1cbf9e752e0acc081
Author: Ray Strode <rstrode redhat com>
Date:   Wed Aug 28 11:20:07 2019 -0400

    gdm-{wayland,x}-session: protect more session variables
    
    since commit 2802e92d27450d86d81b6356dd532ec80e797223 we allow users
    to override the session environment with systemd's environment.d
    mechanism.
    
    That is great for PATH, but not so great for XDG_CURRENT_DESKTOP
    and other potentially lingering session variables.
    
    This commit adds more variables to the blacklist of things that
    aren't allowed to be preempted by systemd's environment.
    
    Closes https://gitlab.gnome.org/GNOME/gdm/issues/505

 daemon/gdm-wayland-session.c | 22 ++++++++++++++++++----
 daemon/gdm-x-session.c       | 28 +++++++++++++++++++++-------
 2 files changed, 39 insertions(+), 11 deletions(-)
---
diff --git a/daemon/gdm-wayland-session.c b/daemon/gdm-wayland-session.c
index 79922664..650e180f 100644
--- a/daemon/gdm-wayland-session.c
+++ b/daemon/gdm-wayland-session.c
@@ -283,11 +283,22 @@ spawn_session (State        *state,
         gboolean             is_running = FALSE;
         int                  ret;
         char               **argv = NULL;
-        static const char  *session_variables[] = { "DISPLAY",
-                                                    "XAUTHORITY",
+        static const char  *session_variables[] = { "DESKTOP_SESSION",
+                                                    "DISPLAY",
+                                                    "GDMSESSION",
+                                                    "GDM_LANG",
+                                                    "GNOME_SHELL_SESSION_MODE",
+                                                    "LANG",
                                                     "WAYLAND_DISPLAY",
                                                     "WAYLAND_SOCKET",
-                                                    "GNOME_SHELL_SESSION_MODE",
+                                                    "WINDOWPATH",
+                                                    "XAUTHORITY",
+                                                    "XDG_CURRENT_DESKTOP",
+                                                    "XDG_SEAT",
+                                                    "XDG_SESSION_ID",
+                                                    "XDG_SESSION_CLASS",
+                                                    "XDG_SESSION_DESKTOP",
+                                                    "XDG_VTNR",
                                                     NULL };
 
         g_debug ("Running wayland session");
@@ -326,8 +337,11 @@ spawn_session (State        *state,
                 /* Don't allow session specific environment variables from earlier sessions to
                  * leak through */
                 for (i = 0; session_variables[i] != NULL; i++) {
-                        if (g_getenv (session_variables[i]) == NULL) {
+                        const char *value = g_getenv (session_variables[i]);
+                        if (value == NULL) {
                                 g_subprocess_launcher_unsetenv (launcher, session_variables[i]);
+                        } else {
+                                g_subprocess_launcher_setenv (launcher, session_variables[i], value, TRUE);
                         }
                 }
         }
diff --git a/daemon/gdm-x-session.c b/daemon/gdm-x-session.c
index 9714da3e..8ca396fa 100644
--- a/daemon/gdm-x-session.c
+++ b/daemon/gdm-x-session.c
@@ -608,12 +608,23 @@ spawn_session (State        *state,
         GError              *error = NULL;
         gboolean             is_running = FALSE;
         const char          *vt;
-        static const char   *session_variables[] = { "DISPLAY",
-                                                     "XAUTHORITY",
-                                                     "WAYLAND_DISPLAY",
-                                                     "WAYLAND_SOCKET",
-                                                     "GNOME_SHELL_SESSION_MODE",
-                                                     NULL };
+        static const char  *session_variables[] = { "DESKTOP_SESSION",
+                                                    "DISPLAY",
+                                                    "GDMSESSION",
+                                                    "GDM_LANG",
+                                                    "GNOME_SHELL_SESSION_MODE",
+                                                    "LANG",
+                                                    "WAYLAND_DISPLAY",
+                                                    "WAYLAND_SOCKET",
+                                                    "WINDOWPATH",
+                                                    "XAUTHORITY",
+                                                    "XDG_CURRENT_DESKTOP",
+                                                    "XDG_SEAT",
+                                                    "XDG_SESSION_ID",
+                                                    "XDG_SESSION_CLASS",
+                                                    "XDG_SESSION_DESKTOP",
+                                                    "XDG_VTNR",
+                                                    NULL };
 
         g_debug ("Running X session");
 
@@ -641,8 +652,11 @@ spawn_session (State        *state,
                 /* Don't allow session specific environment variables from earlier sessions to
                  * leak through */
                 for (i = 0; session_variables[i] != NULL; i++) {
-                        if (g_getenv (session_variables[i]) == NULL) {
+                        const char *value = g_getenv (session_variables[i]);
+                        if (value == NULL) {
                                 g_subprocess_launcher_unsetenv (launcher, session_variables[i]);
+                        } else {
+                                g_subprocess_launcher_setenv (launcher, session_variables[i], value, TRUE);
                         }
                 }
         }