From 357bbde5ca0942bb787b22cb83f6ae87fb298cb1 Mon Sep 17 00:00:00 2001
From: Matt McCutchen <matt@mattmccutchen.net>
Date: Thu, 8 Jan 2009 16:25:07 -0500
Subject: [PATCH] polkit_caller_new_from_pid: use the real uid, as documented

https://bugs.freedesktop.org/show_bug.cgi?id=19469
---
 src/polkit-dbus/polkit-dbus.c |   33 ++++++++++++++++++++++++++-------
 1 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/src/polkit-dbus/polkit-dbus.c b/src/polkit-dbus/polkit-dbus.c
index f7be03f..2efbf2a 100644
--- a/src/polkit-dbus/polkit-dbus.c
+++ b/src/polkit-dbus/polkit-dbus.c
@@ -603,8 +603,9 @@ polkit_caller_new_from_pid (DBusConnection *con, pid_t pid, DBusError *error)
         DBusMessage *reply;
         DBusMessageIter iter;
         char *str;
-        char *proc_path;
-        struct stat statbuf;
+        char *proc_status_path;
+        FILE *proc_status;
+        char proc_status_buf[128];
 #ifdef HAVE_SELINUX
         security_context_t secon;
 #endif
@@ -621,7 +622,7 @@ polkit_caller_new_from_pid (DBusConnection *con, pid_t pid, DBusError *error)
         uid = (uid_t) -1;
         caller = NULL;
         session = NULL;
-        proc_path = NULL;
+        proc_status_path = NULL;
 
 #ifdef POLKIT_BUILD_TESTS
         char *pretend;
@@ -642,12 +643,30 @@ polkit_caller_new_from_pid (DBusConnection *con, pid_t pid, DBusError *error)
 #endif
 
         if (uid == (uid_t) -1) {
-                proc_path = kit_strdup_printf ("/proc/%d", pid);
-                if (proc_path && stat (proc_path, &statbuf) != 0) {
+                /* Extract the real uid from /proc/pid/status . */
+                if ((proc_status_path = kit_strdup_printf ("/proc/%d/status", pid)) != NULL
+                        && (proc_status = fopen (proc_status_path, "r")) != NULL) {
+                        /* Successfully opened the file; now parse it. */
+                        while (fgets (proc_status_buf, sizeof (proc_status_buf), proc_status) != NULL) {
+                                /* Abort if line was longer than we planned for (shouldn't happen on Linux). */
+                                size_t len = strlen (proc_status_buf);
+                                if (len == 0 || proc_status_buf[len - 1] != '\n')
+                                        break;
+                                if (strncmp (proc_status_buf, "Uid:", 4) == 0) {
+                                        /* The real uid is the first of the four numbers on the line.
+                                         * On error, the uid simply won't be set. */
+                                        sscanf (proc_status_buf, "Uid: %d", &uid);
+                                        break;
+                                }
+                        }
+                        fclose (proc_status);
+                }
+                if (uid == (uid_t) -1) {
+                        /* For one reason or another, we didn't get the uid. */
                         kit_warning ("Cannot lookup information for pid %d: %s", pid, strerror (errno));
                         goto out;
                 }
-                uid = statbuf.st_uid;
+                polkit_debug ("Got real uid %d for pid %d", uid, pid);
         }
 
 #ifdef HAVE_SELINUX
@@ -769,7 +788,7 @@ not_in_session:
 out:
         kit_free (selinux_context);
         kit_free (ck_session_objpath);
-        kit_free (proc_path);
+        kit_free (proc_status_path);
         return caller;
 }
 
-- 
1.6.1.34.gf5a74