From owner-freebsd-announce Mon Apr 22 11:53:18 2002 Delivered-To: freebsd-announce@freebsd.org Received: from freefall.freebsd.org (freefall.FreeBSD.org [216.136.204.21]) by hub.freebsd.org (Postfix) with ESMTP id 932E337B43C; Mon, 22 Apr 2002 11:52:07 -0700 (PDT) Received: (from nectar@localhost) by freefall.freebsd.org (8.11.6/8.11.6) id g3MI1Z996493; Mon, 22 Apr 2002 11:01:35 -0700 (PDT) (envelope-from security-advisories@freebsd.org) Date: Mon, 22 Apr 2002 11:01:35 -0700 (PDT) Message-Id: <200204221801.g3MI1Z996493@freefall.freebsd.org> X-Authentication-Warning: freefall.freebsd.org: nectar set sender to security-advisories@freebsd.org using -f From: FreeBSD Security Advisories To: FreeBSD Security Advisories Subject: FreeBSD Security Advisory FreeBSD-SA-02:23.stdio Reply-To: security-advisories@freebsd.org Sender: owner-freebsd-announce@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org -----BEGIN PGP SIGNED MESSAGE----- ============================================================================= FreeBSD-SA-02:23.stdio Security Advisory The FreeBSD Project Topic: insecure handling of stdio file descriptors Category: core Module: kernel Announced: 2002-04-22 Credits: Joost Pol Affects: All releases of FreeBSD up to and including 4.5-RELEASE 4.5-STABLE prior to the correction date Corrected: 2002-04-21 13:06:45 UTC (RELENG_4) 2002-04-21 13:08:57 UTC (RELENG_4_5) 2002-04-21 13:10:51 UTC (RELENG_4_4) FreeBSD only: NO I. Background By convention, POSIX systems associate file descriptors 0, 1, and 2 with standard input, standard output, and standard error, respectively. Almost all applications give these stdio file descriptors special significance, such as writing error messages to standard error (file descriptor 2). In new processes, all file descriptors are duplicated from the parent process. Unless these descriptors are marked close-on-exec, they retain their state during an exec. All POSIX systems assign file descriptors in sequential order, starting with the lowest unused file descriptor. For example, if a newly exec'd process has file descriptors 0 and 1 open, but file descriptor 2 closed, and then opens a file, the new file descriptor is guaranteed to be 2 (standard error). II. Problem Description Some programs are set-user-id or set-group-id, and therefore run with increased privileges. If such a program is started with some of the stdio file descriptors closed, the program may open a file and inadvertently associate it with standard input, standard output, or standard error. The program may then read data from or write data to the file inappropriately. If the file is one that the user would normally not have privileges to open, this may result in an opportunity for privilege escalation. III. Impact Local users may gain superuser privileges. It is known that the `keyinit' set-user-id program is exploitable using this method. There may be other programs that are exploitable. IV. Workaround None. The set-user-id bit may be removed from `keyinit' using the following command, but note that there may be other programs that can be exploited. # chmod 0555 /usr/bin/keyinit V. Solution 1) Upgrade your vulnerable system to 4.5-STABLE; or to either of the RELENG_4_5 (4.5-RELEASE-p4) or RELENG_4_4 (4.4-RELEASE-p11) security branches dated after the respective correction dates. 2) To patch your present system: a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-02:23/stdio.patch # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-02:23/stdio.patch.asc b) Execute the following commands as root: # cd /usr/src # patch < /path/to/patch c) Recompile your kernel as described in http://www.freebsd.org/handbook/kernelconfig.html and reboot the system. VI. Correction details The following list contains the revision numbers of each file that was corrected in FreeBSD. Path Revision Branch - ------------------------------------------------------------------------- sys/sys/filedesc.h RELENG_4 1.19.2.4 RELENG_4_5 1.19.2.3.6.1 RELENG_4_4 1.19.2.3.4.1 sys/kern/kern_exec.c RELENG_4 1.107.2.14 RELENG_4_5 1.107.2.13.2.1 RELENG_4_4 1.107.2.8.2.2 sys/kern/kern_descrip.c RELENG_4 1.81.2.11 RELENG_4_5 1.81.2.9.2.1 RELENG_4_4 1.81.2.8.2.1 sys/conf/newvers.sh RELENG_4_5 1.44.2.20.2.5 RELENG_4_4 1.44.2.17.2.10 - ------------------------------------------------------------------------- VII. References PINE-CERT-20020401 -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (FreeBSD) Comment: For info see http://www.gnupg.org iQCVAwUBPMRPoFUuHi5z0oilAQE0/AP/R2qPI5bI2XIFgQ6FL+m4rUZ7M6VQzZqY yzGskbEkG2LKTYPFQ/FF+Tx6ffbMicnyrTTvDcJ3F9lmKRNvPBVaOuiNBjkrLdQc rerg2aHSJunQCkcd7f/+RjxtWO8wbjTM9TXmc8X1G9kJGaglCwEfHkZJzmsyGDyD qjkDToXu9a8= =oXDh -----END PGP SIGNATURE----- This is the moderated mailing list freebsd-announce. 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