From owner-freebsd-security Wed Nov 1 15: 0:21 2000 Delivered-To: freebsd-security@freebsd.org Received: by hub.freebsd.org (Postfix, from userid 758) id E5B2C37B479; Wed, 1 Nov 2000 14:59:54 -0800 (PST) From: FreeBSD Security Advisories To: FreeBSD Security Advisories Subject: FreeBSD Security Advisory: FreeBSD-SA-00:62.top Reply-To: security-advisories@freebsd.org Message-Id: <20001101225954.E5B2C37B479@hub.freebsd.org> Date: Wed, 1 Nov 2000 14:59:54 -0800 (PST) Sender: owner-freebsd-security@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org -----BEGIN PGP SIGNED MESSAGE----- ============================================================================= FreeBSD-SA-00:62 Security Advisory FreeBSD, Inc. Topic: top allows reading of kernel memory Category: core Module: top Announced: 2000-11-01 Credits: vort@wiretapped.net via OpenBSD Affects: FreeBSD 3.x (all releases), FreeBSD 4.x (all releases prior to 4.2), FreeBSD 3.5.1-STABLE and 4.1.1-STABLE prior to the correction date. Corrected: 2000/10/04 (FreeBSD 4.1.1-STABLE) 2000/10/04 (FreeBSD 3.5.1-STABLE) FreeBSD only: NO I. Background top is a utility for displaying current system resource statistics such as process CPU and memory use. It is externally-maintained, contributed software which is included in FreeBSD by default. II. Problem Description A "format string vulnerability" was discovered in the top(1) utility which allows unprivileged local users to cause the top process to execute arbitrary code. The top utility runs with increased privileges as a member of the kmem group, which allows it to read from kernel memory (but not write to it). A process with the ability to read from kernel memory can monitor privileged data such as network traffic, disk buffers and terminal activity, and may be able to leverage this to obtain further privileges on the local system or on other systems, including root privileges. All released versions of FreeBSD prior to the correction date including 4.0, 4.1, 4.1.1 and 3.5.1 are vulnerable to this problem, but it was fixed in the 4.1.1-STABLE branch prior to the release of FreeBSD 4.2-RELEASE. III. Impact Local users can read privileged data from kernel memory which may provide information allowing them to further increase their local or remote system access privileges. IV. Workaround Remove the setgid bit on the top utilities. This has the side-effect that users who are not a member of the kmem group or who are not the superuser cannot use the top utility. # chmod g-s /usr/bin/top V. Solution One of the following: 1) Upgrade your vulnerable FreeBSD system to 4.1.1-STABLE or 3.5.1-STABLE after the respective correction dates. 2) Apply the patch below and recompile the relevant files: Either save this advisory to a file, or download the patch and detached PGP signature from the following locations, and verify the signature using your PGP utility. ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-00:62/top.patch ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-00:62/top.patch.asc Execute the following commands as root: # cd /usr/src/contrib/top # patch -p < /path/to/patch_or_advisory # cd /usr/src/usr.bin/top # make depend && make all install Patch for vulnerable systems: Index: display.c =================================================================== RCS file: /mnt/ncvs/src/contrib/top/display.c,v retrieving revision 1.4 retrieving revision 1.5 diff -u -r1.4 -r1.5 --- display.c 1999/01/09 20:20:33 1.4 +++ display.c 2000/10/04 23:34:16 1.5 @@ -829,7 +831,7 @@ register int i; /* first, format the message */ - (void) sprintf(next_msg, msgfmt, a1, a2, a3); + (void) snprintf(next_msg, sizeof(next_msg), msgfmt, a1, a2, a3); if (msglen > 0) { Index: top.c =================================================================== RCS file: /mnt/ncvs/src/contrib/top/top.c,v retrieving revision 1.4 retrieving revision 1.5 diff -u -r1.4 -r1.5 --- top.c 1999/01/09 20:20:34 1.4 +++ top.c 2000/10/04 23:34:16 1.5 @@ -807,7 +809,7 @@ { if ((errmsg = kill_procs(tempbuf2)) != NULL) { - new_message(MT_standout, errmsg); + new_message(MT_standout, "%s", errmsg); putchar('\r'); no_command = Yes; } -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.4 (FreeBSD) Comment: For info see http://www.gnupg.org iQCVAwUBOgCfWFUuHi5z0oilAQECnwP8CCL5roxtZIfgV7yEfNGW3u61+NNfFK7V bEsygpUlT0/KGLM1gBWkMhn7oTlrYk4xJ01SdXenlBJg05ScS6qd8MhJ2TgqsS2l f5w7ZIvZhSu+V+mLKmjmc52aHM+9Jth2ejyRwlcxWa+tE1XXCUK0KO6oaXod0TR9 g0TXn2UfHJ4= =eU0t -----END PGP SIGNATURE----- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message