[PATCH] keys: restrict contents of /proc/keys to Viewable keys

Restrict /proc/keys such that only those keys to which the current task is
granted View permission are presented.

The documentation is also updated to reflect these changes.

Signed-off-by: Michael LeMay <mdlemay@epoch.ncsc.mil>
Signed-off-by: James Morris <jmorris@namei.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 32 insertions, 11 deletions

diff --git a/Documentation/keys.txt b/Documentation/keys.txt
index 3bbe157b45e4..70e83cf664ae 100644
--- a/Documentation/keys.txt
+++ b/Documentation/keys.txt
@@ -270,9 +270,17 @@ about the status of the key service:
 
  (*) /proc/keys
 
-     This lists all the keys on the system, giving information about their
-     type, description and permissions. The payload of the key is not available
-     this way:
+     This lists the keys that are currently viewable by the task reading the
+     file, giving information about their type, description and permissions.
+     It is not possible to view the payload of the key this way, though some
+     information about it may be given.
+
+     The only keys included in the list are those that grant View permission to
+     the reading process whether or not it possesses them.  Note that LSM
+     security checks are still performed, and may further filter out keys that
+     the current process is not authorised to view.
+
+     The contents of the file look like this:
 
         SERIAL   FLAGS  USAGE EXPY PERM     UID   GID   TYPE      DESCRIPTION: SUMMARY
         00000001 I-----    39 perm 1f3f0000     0     0 keyring   _uid_ses.0: 1/4
@@ -300,7 +308,7 @@ about the status of the key service:
  (*) /proc/key-users
 
      This file lists the tracking data for each user that has at least one key
-     on the system. Such data includes quota information and statistics:
+     on the system.  Such data includes quota information and statistics:
 
         [root@andromeda root]# cat /proc/key-users
         0:     46 45/45 1/100 13/10000
diff --git a/security/Kconfig b/security/Kconfig
index 34f593410d57..67785df264e5 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -22,16 +22,22 @@ config KEYS
           If you are unsure as to whether this is required, answer N.
 
 config KEYS_DEBUG_PROC_KEYS
-        bool "Enable the /proc/keys file by which all keys may be viewed"
+        bool "Enable the /proc/keys file by which keys may be viewed"
         depends on KEYS
         help
-          This option turns on support for the /proc/keys file through which
-          all the keys on the system can be listed.
+          This option turns on support for the /proc/keys file - through which
+          can be listed all the keys on the system that are viewable by the
+          reading process.
 
-          This option is a slight security risk in that it makes it possible
-          for anyone to see all the keys on the system. Normally the manager
-          pretends keys that are inaccessible to a process don't exist as far
-          as that process is concerned.
+          The only keys included in the list are those that grant View
+          permission to the reading process whether or not it possesses them.
+          Note that LSM security checks are still performed, and may further
+          filter out keys that the current process is not authorised to view.
+
+          Only key attributes are listed here; key payloads are not included in
+          the resulting table.
+
+          If you are unsure as to whether this is required, answer N.
 
 config SECURITY
         bool "Enable different security models"
diff --git a/security/keys/proc.c b/security/keys/proc.c
index 12b750e51fbf..686a9ee0c5de 100644
--- a/security/keys/proc.c
+++ b/security/keys/proc.c
@@ -137,6 +137,13 @@ static int proc_keys_show(struct seq_file *m, void *v)
         struct timespec now;
         unsigned long timo;
         char xbuf[12];
+        int rc;
+
+        /* check whether the current task is allowed to view the key (assuming
+         * non-possession) */
+        rc = key_task_permission(make_key_ref(key, 0), current, KEY_VIEW);
+        if (rc < 0)
+                return 0;
 
         now = current_kernel_time();