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Diffstat (limited to 'src/polkit/polkitunixprocess.c')
-rw-r--r--src/polkit/polkitunixprocess.c61
1 files changed, 51 insertions, 10 deletions
diff --git a/src/polkit/polkitunixprocess.c b/src/polkit/polkitunixprocess.c
index d4ebf50..972b777 100644
--- a/src/polkit/polkitunixprocess.c
+++ b/src/polkit/polkitunixprocess.c
@@ -56,6 +56,14 @@
* To uniquely identify processes, both the process id and the start
* time of the process (a monotonic increasing value representing the
* time since the kernel was started) is used.
+ *
+ * NOTE: This object stores, and provides access to, the real UID of the
+ * process. That value can change over time (with set*uid*(2) and exec*(2)).
+ * Checks whether an operation is allowed need to take care to use the UID
+ * value as of the time when the operation was made (or, following the open()
+ * privilege check model, when the connection making the operation possible
+ * was initiated). That is usually done by initializing this with
+ * polkit_unix_process_new_for_owner() with trusted data.
*/
/**
@@ -90,9 +98,6 @@ static void subject_iface_init (PolkitSubjectIface *subject_iface);
static guint64 get_start_time_for_pid (gint pid,
GError **error);
-static gint _polkit_unix_process_get_owner (PolkitUnixProcess *process,
- GError **error);
-
#if defined(HAVE_FREEBSD) || defined(HAVE_NETBSD) || defined(HAVE_OPENBSD)
static gboolean get_kinfo_proc (gint pid,
#if defined(HAVE_NETBSD)
@@ -182,7 +187,7 @@ polkit_unix_process_constructed (GObject *object)
{
GError *error;
error = NULL;
- process->uid = _polkit_unix_process_get_owner (process, &error);
+ process->uid = polkit_unix_process_get_racy_uid__ (process, &error);
if (error != NULL)
{
process->uid = -1;
@@ -271,6 +276,12 @@ polkit_unix_process_class_init (PolkitUnixProcessClass *klass)
* Gets the user id for @process. Note that this is the real user-id,
* not the effective user-id.
*
+ * NOTE: The UID may change over time, so the returned value may not match the
+ * current state of the underlying process; or the UID may have been set by
+ * polkit_unix_process_new_for_owner() or polkit_unix_process_set_uid(),
+ * in which case it may not correspond to the actual UID of the referenced
+ * process at all (at any point in time).
+ *
* Returns: The user id for @process or -1 if unknown.
*/
gint
@@ -708,13 +719,20 @@ out:
return start_time;
}
-static gint
-_polkit_unix_process_get_owner (PolkitUnixProcess *process,
- GError **error)
+/*
+ * Private: Return the "current" UID. Note that this is inherently racy,
+ * and the value may already be obsolete by the time this function returns;
+ * this function only guarantees that the UID was valid at some point during
+ * its execution.
+ */
+gint
+polkit_unix_process_get_racy_uid__ (PolkitUnixProcess *process,
+ GError **error)
{
gint result;
gchar *contents;
gchar **lines;
+ guint64 start_time;
#if defined(HAVE_FREEBSD) || defined(HAVE_OPENBSD)
struct kinfo_proc p;
#elif defined(HAVE_NETBSD)
@@ -722,6 +740,7 @@ _polkit_unix_process_get_owner (PolkitUnixProcess *process,
#else
gchar filename[64];
guint n;
+ GError *local_error;
#endif
g_return_val_if_fail (POLKIT_IS_UNIX_PROCESS (process), 0);
@@ -745,8 +764,10 @@ _polkit_unix_process_get_owner (PolkitUnixProcess *process,
#if defined(HAVE_FREEBSD)
result = p.ki_uid;
+ start_time = (guint64) p.ki_start.tv_sec;
#else
result = p.p_uid;
+ start_time = (guint64) p.p_ustart_sec;
#endif
#else
@@ -781,17 +802,37 @@ _polkit_unix_process_get_owner (PolkitUnixProcess *process,
else
{
result = real_uid;
- goto out;
+ goto found;
}
}
-
g_set_error (error,
POLKIT_ERROR,
POLKIT_ERROR_FAILED,
"Didn't find any line starting with `Uid:' in file %s",
filename);
+ goto out;
+
+found:
+ /* The UID and start time are, sadly, not available in a single file. So,
+ * read the UID first, and then the start time; if the start time is the same
+ * before and after reading the UID, it couldn't have changed.
+ */
+ local_error = NULL;
+ start_time = get_start_time_for_pid (process->pid, &local_error);
+ if (local_error != NULL)
+ {
+ g_propagate_error (error, local_error);
+ goto out;
+ }
#endif
+ if (process->start_time != start_time)
+ {
+ g_set_error (error, POLKIT_ERROR, POLKIT_ERROR_FAILED,
+ "process with PID %d has been replaced", process->pid);
+ goto out;
+ }
+
out:
g_strfreev (lines);
g_free (contents);
@@ -810,5 +851,5 @@ gint
polkit_unix_process_get_owner (PolkitUnixProcess *process,
GError **error)
{
- return _polkit_unix_process_get_owner (process, error);
+ return polkit_unix_process_get_racy_uid__ (process, error);
}