Merge lp:~mfisch/lightdm/lightdm-lp999713 into lp:lightdm

[Matt Fischer]

Fixes 999713: setresgid and setresuid not portable

The patch includes logging which I verified and tested using a VM.

=== modified file 'configure.ac'
--- configure.ac	2012-04-19 04:30:45 +0000
+++ configure.ac	2012-06-06 03:33:20 +0000
@@ -21,6 +21,8 @@
 
 AC_CHECK_HEADERS(security/pam_appl.h, [], AC_MSG_ERROR(PAM not found))
 
+AC_CHECK_FUNCS(setresgid setresuid)
+
 PKG_CHECK_MODULES(LIGHTDM, [
     glib-2.0 >= 2.24
     gio-2.0 >= 2.26
 
=== modified file 'src/privileges.c'
--- src/privileges.c	2011-09-15 07:29:25 +0000
+++ src/privileges.c	2012-06-06 03:33:20 +0000
@@ -12,6 +12,7 @@
 /* for setres*id() */
 #define _GNU_SOURCE
 
+#include <config.h>
 #include "privileges.h"
 
 void
@@ -20,14 +21,38 @@
     g_return_if_fail (user != NULL);
 
     g_debug ("Dropping privileges to uid %i", user_get_uid (user));
+#ifdef HAVE_SETRESGID
+    g_debug ("Calling setresgid");
     g_assert (setresgid (user_get_gid (user), user_get_gid (user), -1) == 0);
+#else
+    g_assert (setgid (user_get_gid (user)) == 0);
+    g_assert (setegid (user_get_gid (user)) == 0);
+#endif
+#ifdef HAVE_SETRESUID
+    g_debug ("Calling setresuid");
     g_assert (setresuid (user_get_uid (user), user_get_uid (user), -1) == 0);
+#else
+    g_assert (setuid (user_get_uid (user)) == 0);
+    g_assert (seteuid (user_get_uid (user)) == 0);
+#endif
 }
 
 void
 privileges_reclaim (void)
 {
     g_debug ("Restoring privileges");
+#ifdef HAVE_SETRESUID
+    g_debug ("Calling setresuid");
     g_assert (setresuid (0, 0, -1) == 0);
-    g_assert (setresgid (0, 0, -1) == 0);  
+#else
+    g_assert (setuid (0) == 0);
+    g_assert (seteuid (0) == 0);
+#endif
+#ifdef HAVE_SETRESGID
+    g_debug ("Calling setresgid");
+    g_assert (setresgid (0, 0, -1) == 0);
+#else
+    g_assert (setgid (0) == 0);
+    g_assert (setegid (0) == 0);
+#endif
 }