[at-spi2-atk] Fix accessibility of root apps on Linux

[Mike Gorse <mgorse src gnome org>]

commit 3e6cf48cd7a24303324f10039b63bd916a8aa49e
Author: Mike Gorse <mgorse novell com>
Date:   Tue Mar 8 15:45:09 2011 -0600

    Fix accessibility of root apps on Linux
    
    For an application running as root, check the uid of its parent, and, if
    necessary, the parent's parent and so on, to find the user that initially
    launched the application, and permit dbus connections from this uid.  Note
    that this will likely only work under Linux.

 atk-adaptor/bridge.c |   44 ++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 44 insertions(+), 0 deletions(-)
---
diff --git a/atk-adaptor/bridge.c b/atk-adaptor/bridge.c
index da844d8..940d244 100644
--- a/atk-adaptor/bridge.c
+++ b/atk-adaptor/bridge.c
@@ -22,6 +22,7 @@
  * Boston, MA 02111-1307, USA.
  */
 
+#define _GNU_SOURCE
 #include "config.h"
 #include "dbus/dbus-glib-lowlevel.h"
 
@@ -509,11 +510,54 @@ install_plug_hooks ()
   socket_class->embed = socket_embed_hook;
 }
 
+static uint
+get_ancestral_uid (uint pid)
+{
+  FILE *fp;
+  char buf [80];
+  int ppid = 0;
+  int uid = 0;
+  gboolean got_ppid = 0;
+  gboolean got_uid = 0;
+
+  sprintf (buf, "/proc/%d/status", pid);
+  fp = fopen (buf, "r");
+  if (!fp)
+    return 0;
+  while ((!got_ppid || !got_uid) && fgets (buf, sizeof (buf), fp))
+  {
+    if (sscanf (buf, "PPid:\t%d", &ppid) == 1)
+      got_ppid = TRUE;
+    else if (sscanf (buf, "Uid:\t%d", &uid) == 1)
+      got_uid = TRUE;
+  }
+  fclose (fp);
+
+  if (!got_ppid || !got_uid)
+    return 0;
+  if (uid != 0)
+    return uid;
+  if (ppid == 0 || ppid == 1)
+    return 0;
+  return get_ancestral_uid (ppid);
+}
+
+static dbus_bool_t
+user_check (DBusConnection *bus, unsigned long uid)
+{
+  if (uid == getuid () || uid == geteuid ())
+    return TRUE;
+  if (getuid () == 0)
+    return get_ancestral_uid (getpid ()) == uid;
+  return FALSE;
+}
+
 static void
 new_connection_cb (DBusServer *server, DBusConnection *con, void *data)
 {
   GList *new_list;
 
+  dbus_connection_set_unix_user_function (con, user_check, NULL, NULL);
   dbus_connection_ref(con);
   dbus_connection_setup_with_g_main(con, NULL);
   droute_intercept_dbus (con);