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doc/share/security/advisories/FreeBSD-SA-96:15.ppp.asc
Bjoern A. Zeeb 3571e53040 Import FreeBSD Security Advisories and Errata Notices, as well as their 
patches for easier mirroring, to eliminate a special copy, to make
www.freebsd.org/security a full copy of security.freebsd.org and be
eventually be the same.

For now files are just sitting there.   The symlinks are missing.

Discussed on:	www (repository location)
Discussed with:	simon (so)
2012-08-15 06:19:40 +00:00

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-----BEGIN PGP SIGNED MESSAGE-----
=============================================================================
FreeBSD-SA-96:15 Security Advisory
FreeBSD, Inc.
Topic: security compromise from ppp
Category: core
Module: ppp
Announced: 1996-07-04
Affects: FreeBSD 2.0.5, 2.1, 2.1-stable, and 2.2-current
Corrected: 2.1-stable and 2.2-current as of 1996-06-10
FreeBSD only: unknown
Patches: ftp://freebsd.org/pub/CERT/patches/SA-96:15/
=============================================================================
I. Background
FreeBSD ships a userland ppp program that can be used by users
to set up ppp connections.
This program is also known as ijppp.
The ppp program has a vulnerability that allows any user to run
commands under root privileges.
II. Problem Description
The ppp program does not properly manage user privileges, allowing
users to run any program with root privileges.
III. Impact
This vulnerability can only be exploited by users with a valid
account on the local system to easily obtain superuser access.
IV. Workaround
One may simply disable the setuid bit on all copies of the ppp
program. This will close the vulnerability but will only allow
the superuser to set up ppp connections.
As root, execute the commands:
# chmod 555 /usr/sbin/ppp
then verify that the setuid permissions of the files have been
removed. The permissions array should read "-r-xr-xr-x" as
shown here:
# ls -l /usr/sbin/ppp
-r-xr-xr-x 1 root bin 86016 Nov 16 1995 /usr/sbin/ppp
V. Solution
Patches are available which eliminate this vulnerability.
The following patch should be applied to the system sources and
ppp should be rebuilt and reinstalled. The first patch is against
the FreeBSD 2.1 and FreeBSD-stable source tree. The second patch
is for FreeBSD-current (version before 1996-06-10).
Apply the patch, then (being superuser):
# cd /usr/src/usr.sbin/ppp
# make depend
# make all
# make install
Index: command.c
===================================================================
RCS file: /home/ncvs/src/usr.sbin/ppp/command.c,v
retrieving revision 1.5.4.3
retrieving revision 1.5.4.4
diff -u -r1.5.4.3 -r1.5.4.4
--- command.c 1996/02/05 17:02:52 1.5.4.3
+++ command.c 1996/06/10 09:41:49 1.5.4.4
@@ -17,7 +17,7 @@
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*
- * $Id: FreeBSD-SA-96:15.ppp.asc,v 1.1 2001/09/02 00:04:38 kris Exp $
+ * $Id: FreeBSD-SA-96:15.ppp.asc,v 1.1 2001/09/02 00:04:38 kris Exp $
*
*/
#include <sys/types.h>
@@ -187,9 +187,14 @@
* We are running setuid, we should change to
* real user for avoiding security problems.
*/
- setgid( getgid() );
- setuid( getuid() );
-
+ if (setgid(getgid()) < 0) {
+ perror("setgid");
+ exit(1);
+ }
+ if (setuid(getuid()) < 0) {
+ perror("setuid");
+ exit(1);
+ }
TtyOldMode();
if(argc > 0)
execvp(argv[0], argv);
Index: chat.c
===================================================================
RCS file: /home/ncvs/src/usr.sbin/ppp/chat.c,v
retrieving revision 1.4.4.1
retrieving revision 1.4.4.2
diff -u -r1.4.4.1 -r1.4.4.2
--- chat.c 1995/10/06 11:24:31 1.4.4.1
+++ chat.c 1996/06/10 09:41:45 1.4.4.2
@@ -18,7 +18,7 @@
* Columbus, OH 43221
* (614)451-1883
*
- * $Id: FreeBSD-SA-96:15.ppp.asc,v 1.1 2001/09/02 00:04:38 kris Exp $
+ * $Id: FreeBSD-SA-96:15.ppp.asc,v 1.1 2001/09/02 00:04:38 kris Exp $
*
* TODO:
* o Support more UUCP compatible control sequences.
@@ -331,6 +331,15 @@
nb = open("/dev/tty", O_RDWR);
dup2(nb, 0);
LogPrintf(LOG_CHAT, "exec: %s\n", command);
+ /* switch back to original privileges */
+ if (setgid(getgid()) < 0) {
+ LogPrintf(LOG_CHAT, "setgid: %s\n", strerror(errno));
+ exit(1);
+ }
+ if (setuid(getuid()) < 0) {
+ LogPrintf(LOG_CHAT, "setuid: %s\n", strerror(errno));
+ exit(1);
+ }
pid = execvp(command, vector);
LogPrintf(LOG_CHAT, "execvp failed for (%d/%d): %s\n", pid, errno, command);
exit(127);
Patch for FreeBSd-current before 1996-06-10:
Index: command.c
===================================================================
RCS file: /home/ncvs/src/usr.sbin/ppp/command.c,v
retrieving revision 1.17
retrieving revision 1.18
diff -u -r1.17 -r1.18
--- command.c 1996/05/11 20:48:22 1.17
+++ command.c 1996/06/09 20:40:58 1.18
@@ -17,7 +17,7 @@
* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
* WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*
- * $Id: FreeBSD-SA-96:15.ppp.asc,v 1.1 2001/09/02 00:04:38 kris Exp $
+ * $Id: FreeBSD-SA-96:15.ppp.asc,v 1.1 2001/09/02 00:04:38 kris Exp $
*
*/
#include <sys/types.h>
@@ -190,9 +190,14 @@
* We are running setuid, we should change to
* real user for avoiding security problems.
*/
- setgid( getgid() );
- setuid( getuid() );
-
+ if (setgid(getgid()) < 0) {
+ perror("setgid");
+ exit(1);
+ }
+ if (setuid(getuid()) < 0) {
+ perror("setuid");
+ exit(1);
+ }
TtyOldMode();
if(argc > 0)
execvp(argv[0], argv);
Index: chat.c
===================================================================
RCS file: /home/ncvs/src/usr.sbin/ppp/chat.c,v
retrieving revision 1.10
retrieving revision 1.11
diff -u -r1.10 -r1.11
--- chat.c 1996/05/11 20:48:20 1.10
+++ chat.c 1996/06/09 20:40:56 1.11
@@ -18,7 +18,7 @@
* Columbus, OH 43221
* (614)451-1883
*
- * $Id: FreeBSD-SA-96:15.ppp.asc,v 1.1 2001/09/02 00:04:38 kris Exp $
+ * $Id: FreeBSD-SA-96:15.ppp.asc,v 1.1 2001/09/02 00:04:38 kris Exp $
*
* TODO:
* o Support more UUCP compatible control sequences.
@@ -393,6 +393,15 @@
nb = open("/dev/tty", O_RDWR);
dup2(nb, 0);
LogPrintf(LOG_CHAT_BIT, "exec: %s\n", command);
+ /* switch back to original privileges */
+ if (setgid(getgid()) < 0) {
+ LogPrintf(LOG_CHAT_BIT, "setgid: %s\n", strerror(errno));
+ exit(1);
+ }
+ if (setuid(getuid()) < 0) {
+ LogPrintf(LOG_CHAT_BIT, "setuid: %s\n", strerror(errno));
+ exit(1);
+ }
pid = execvp(command, vector);
LogPrintf(LOG_CHAT_BIT, "execvp failed for (%d/%d): %s\n", pid, errno, command);
exit(127);
=============================================================================
FreeBSD, Inc.
Web Site: http://www.freebsd.org/
Confidential contacts: security-officer@freebsd.org
PGP Key: ftp://freebsd.org/pub/CERT/public_key.asc
Security notifications: security-notifications@freebsd.org
Security public discussion: security@freebsd.org
Notice: Any patches in this document may not apply cleanly due to
modifications caused by digital signature or mailer software.
Please reference the URL listed at the top of this document
for original copies of all patches if necessary.
=============================================================================
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