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polkit: Avoid race condition in scraping /proc

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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.
This commit is contained in:
Colin Walters
2013-08-22 13:55:21 -04:00
committed by Zbigniew Jędrzejewski-Szmek
parent 00f117a599
commit 72fd713962
Notes: Lennart Poettering 2013-10-04 17:11:46 +02:00 
Backport: security
1 changed files with 5 additions and 26 deletions
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31
src/shared/polkit.c
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@@ -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) ||