[gdm] common: Also set GROUP in scripts

[Ray Strode <halfline src gnome org>]

commit bf0a66405dae3fadef187e72e41406f816f1d2e1
Author: Sam Spilsbury <sam endlessm com>
Date:   Wed Sep 27 20:51:47 2017 +0800

    common: Also set GROUP in scripts
    
    https://bugzilla.gnome.org/show_bug.cgi?id=787287

 common/gdm-common.c |   26 ++++++++++++++++++++++++++
 1 files changed, 26 insertions(+), 0 deletions(-)
---
diff --git a/common/gdm-common.c b/common/gdm-common.c
index c4fc707..c44fa99 100644
--- a/common/gdm-common.c
+++ b/common/gdm-common.c
@@ -26,6 +26,7 @@
 #include <locale.h>
 #include <fcntl.h>
 #include <sys/wait.h>
+#include <grp.h>
 #include <pwd.h>
 
 #include <glib.h>
@@ -97,6 +98,24 @@ gdm_get_pwent_for_name (const char     *name,
         return (pwent != NULL);
 }
 
+static gboolean
+gdm_get_grent_for_gid (gint           gid,
+                       struct group **grentp)
+{
+        struct group *grent;
+
+        do {
+                errno = 0;
+                grent = getgrgid (gid);
+        } while (grent == NULL && errno == EINTR);
+
+        if (grentp != NULL) {
+                *grentp = grent;
+        }
+
+        return (grent != NULL);
+}
+
 int
 gdm_wait_on_and_disown_pid (int pid,
                             int timeout)
@@ -586,6 +605,13 @@ gdm_get_script_environment (const char *username,
 
                         g_hash_table_insert (hash, g_strdup ("SHELL"),
                                              g_strdup (pwent->pw_shell));
+
+                        /* Also get group name and propagate down */
+                        struct group *grent;
+
+                        if (gdm_get_grent_for_gid (pwent->pw_gid, &grent)) {
+                                g_hash_table_insert (hash, g_strdup ("GROUP"), g_strdup (grent->gr_name));
+                        }
                 }
         }