Date: Tue, 16 Jul 1996 21:52:09 -0700 From: "FreeBSD Security Officer" <security-officer@freebsd.org> To: freebsd-security-notification@freebsd.org Cc: freebsd-announce@freebsd.org, security-officer@freebsd.org Subject: FreeBSD Security Advisory 96:16 - rdist Message-ID: <199607170456.VAA01645@precipice.shockwave.com> Resent-Message-ID: <199607170456.VAA01645@precipice.shockwave.com>
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-----BEGIN PGP SIGNED MESSAGE----- ============================================================================= FreeBSD-SA-96:16 Security Advisory Revised: Fri Jul 12 09:32:53 PDT 1996 FreeBSD, Inc. Topic: security vulnerability in rdist Category: core Module: rdist Announced: 1996-07-12 Affects: FreeBSD 2.0, 2.0.5, 2.1, 2.1-stable, and 2.2-current Corrected: 2.1-stable and 2.2-current as of 1996-07-11 Source: 4.4BSD (lite) FreeBSD only: no Patches: ftp://freebsd.org/pub/CERT/patches/SA-96:16/ Reference: [8lgm]-Advisory-26.UNIX.rdist.20-3-1996 ============================================================================= I. Background A bug was found in the BSD rdist utility which can allow an unprivileged local user to gain unauthorized access. This problem is present in all source code and binary distributions of FreeBSD version 2.x released before 1996-07-12. rdist has been the subject of security vulnerabilities in the past. This is a newly discovered vulnerability not related to previous race conditions fixed in rdist. II. Problem Description rdist creates an error message based on a user provided string, without checking bounds on the buffer used. This buffer is on the stack, and can therefore be used to execute arbitrary instructions. III. Impact This vulnerability can allow a local user to obtain superuser privileges. It may only be exploited by users with a valid account on the local system. It is present in almost all BSD derived operating systems with a "setuid" rdist program. IV. Workaround The rdist program must be setuid root to function properly. This vulnerability can be eliminated by making rdist not executable by unprivileged users. Since this limits the usefulness of the program, a software update is advised. This workaround will work for all versions of FreeBSD affected by this problem. As root, execute the commands: # chflags noschg /usr/bin/rdist # chmod u-s,go-rx /usr/bin/rdist then verify that the setuid permissions of the files have been removed. The permissions array should read "-r-x------" as shown here: # ls -l /usr/bin/rdist -r-x------ 1 root bin 49152 Jun 16 10:46 rdist V. Solution(s) Apply the available via FTP from the patch directory noted at the top of this message. Recompile, and reinstall the rdist program. This patch is known to apply to all FreeBSD 2.x systems, it has not been tested with FreeBSD 1.x. The [8lgm] organization correctly points out that this program does not have a particularly good security "history." While the patch for this vulnerability does solve this particular problem, it's not clear if other security issues involving rdist will appear in the future. Administrators should consider whether it is appropriate to remove the standard rdist program and upgrade to rdist version 6, which is available as a FreeBSD port. FreeBSD, Inc. has not replaced the standard BSD rdist with the newer code because the new rdist is not protocol-compatible with the original version. ============================================================================= 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. ============================================================================= -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBMeaC1FUuHi5z0oilAQHtzQP/U1f9y0R+upwCs5IFeBCUBVkFWUeJ/Wwb CJPFmsBr54quI6Aie/LXa/Qw8EdrL54GIiNDZYkAzb9XvWOehOsmtoYN4oj0JAbJ lesq746xOEfNMtpL866T8dxJRTsK98VMSaZK5IU8fVpVYUURcVDv+y+bqfL72Mst 3ajof2ieNxE= =j2z5 -----END PGP SIGNATURE-----
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