From 72fd713962ca2c2450e23b01d9e22017a7e28fd4 Mon Sep 17 00:00:00 2001

From: Colin Walters <walters@verbum.org>

Date: Thu, 22 Aug 2013 13:55:21 -0400

Subject: [PATCH] polkit: Avoid race condition in scraping /proc

If a calling process execve()s a setuid program, it can appear to be

uid 0.  Since we're receiving requests over DBus, avoid this by simply

passing system-bus-name as a subject.

---

 src/shared/polkit.c | 31 +++++--------------------------

 1 file changed, 5 insertions(+), 26 deletions(-)

diff --git a/src/shared/polkit.c b/src/shared/polkit.c

index cea7074..1c5e9e3 100644

--- a/src/shared/polkit.c

+++ b/src/shared/polkit.c

@@ -38,12 +38,8 @@ int verify_polkit(

 #ifdef ENABLE_POLKIT

         DBusMessage *m = NULL, *reply = NULL;

-        const char *unix_process = "unix-process", *pid = "pid", *starttime = "start-time", *cancel_id = "";

+        const char *system_bus_name = "system-bus-name", *name = "name", *cancel_id = "";

         uint32_t flags = interactive ? 1 : 0;

-        pid_t pid_raw;

-        uint32_t pid_u32;

-        unsigned long long starttime_raw;

-        uint64_t starttime_u64;

         DBusMessageIter iter_msg, iter_struct, iter_array, iter_dict, iter_variant;

         int r;

         dbus_bool_t authorized = FALSE, challenge = FALSE;

@@ -68,14 +64,6 @@ int verify_polkit(

 #ifdef ENABLE_POLKIT

-        pid_raw = bus_get_unix_process_id(c, sender, error);

-        if (pid_raw == 0)

-                return -EINVAL;

-

-        r = get_starttime_of_pid(pid_raw, &starttime_raw);

-        if (r < 0)

-                return r;

-

         m = dbus_message_new_method_call(

                         "org.freedesktop.PolicyKit1",

                         "/org/freedesktop/PolicyKit1/Authority",

@@ -86,22 +74,13 @@ int verify_polkit(

         dbus_message_iter_init_append(m, &iter_msg);

-        pid_u32 = (uint32_t) pid_raw;

-        starttime_u64 = (uint64_t) starttime_raw;

-

         if (!dbus_message_iter_open_container(&iter_msg, DBUS_TYPE_STRUCT, NULL, &iter_struct) ||

-            !dbus_message_iter_append_basic(&iter_struct, DBUS_TYPE_STRING, &unix_process) ||

+            !dbus_message_iter_append_basic(&iter_struct, DBUS_TYPE_STRING, &system_bus_name) ||

             !dbus_message_iter_open_container(&iter_struct, DBUS_TYPE_ARRAY, "{sv}", &iter_array) ||

             !dbus_message_iter_open_container(&iter_array, DBUS_TYPE_DICT_ENTRY, NULL, &iter_dict) ||

-            !dbus_message_iter_append_basic(&iter_dict, DBUS_TYPE_STRING, &pid) ||

-            !dbus_message_iter_open_container(&iter_dict, DBUS_TYPE_VARIANT, "u", &iter_variant) ||

-            !dbus_message_iter_append_basic(&iter_variant, DBUS_TYPE_UINT32, &pid_u32) ||

-            !dbus_message_iter_close_container(&iter_dict, &iter_variant) ||

-            !dbus_message_iter_close_container(&iter_array, &iter_dict) ||

-            !dbus_message_iter_open_container(&iter_array, DBUS_TYPE_DICT_ENTRY, NULL, &iter_dict) ||

-            !dbus_message_iter_append_basic(&iter_dict, DBUS_TYPE_STRING, &starttime) ||

-            !dbus_message_iter_open_container(&iter_dict, DBUS_TYPE_VARIANT, "t", &iter_variant) ||

-            !dbus_message_iter_append_basic(&iter_variant, DBUS_TYPE_UINT64, &starttime_u64) ||

+            !dbus_message_iter_append_basic(&iter_dict, DBUS_TYPE_STRING, &name) ||

+            !dbus_message_iter_open_container(&iter_dict, DBUS_TYPE_VARIANT, "s", &iter_variant) ||

+            !dbus_message_iter_append_basic(&iter_variant, DBUS_TYPE_STRING, &sender) ||

             !dbus_message_iter_close_container(&iter_dict, &iter_variant) ||

             !dbus_message_iter_close_container(&iter_array, &iter_dict) ||

             !dbus_message_iter_close_container(&iter_struct, &iter_array) ||

-- 

1.8.3.1