From owner-freebsd-announce Tue Jul 10 7: 2:34 2001 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 4907737B401; Tue, 10 Jul 2001 07:02:26 -0700 (PDT) (envelope-from security-advisories@FreeBSD.org) Received: (from jedgar@localhost) by freefall.freebsd.org (8.11.3/8.11.3) id f6AE2MU63568; Tue, 10 Jul 2001 07:02:22 -0700 (PDT) (envelope-from security-advisories@FreeBSD.org) Date: Tue, 10 Jul 2001 07:02:22 -0700 (PDT) Message-Id: <200107101402.f6AE2MU63568@freefall.freebsd.org> X-Authentication-Warning: freefall.freebsd.org: jedgar set sender to security-advisories@FreeBSD.org using -f From: FreeBSD Security Advisories To: FreeBSD Security Advisories Subject: FreeBSD Security Advisory FreeBSD-SA-01: 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-01:42 Security Advisory FreeBSD, Inc. Topic: signal handling during exec may allow local root compromise Category: core Module: kernel Announced: 2001-07-10 Credits: Georgi Guninski Affects: All released versions of FreeBSD 4.x, FreeBSD 4.3-STABLE prior to the correction date. Corrected: 2001-07-09 FreeBSD only: Yes I. Background When a process forks, it inherits the parent's signals. When the process execs, the kernel clears the signal handlers because they are not valid in the new address space. II. Problem Description A flaw exists in FreeBSD signal handler clearing that would allow for some signal handlers to remain in effect after the exec. Most of the signals were cleared, but some signal hanlders were not. This allowed an attacker to execute arbitrary code in the context of a setuid binary. All versions of 4.x prior to the correction date including and 4.3-RELEASE are vulnerable to this problem. The problem has been corrected by copying the inherited signal handlers and resetting the signals instead of sharing the signal handlers. III. Impact Local users may be able to gain increased privileges on the local system. IV. Workaround Do not allow untrusted users to gain access to the local system. V. Solution One of the following: 1) Upgrade your vulnerable FreeBSD system to 4.3-STABLE after the correction date. 2) To patch your present system: download the relevant patch from the below location, and execute the following commands as root: [FreeBSD 4.1, 4.2, and 4.3 base systems] This patch has been verified to apply to FreeBSD 4.1, 4.2, and 4.3 only. It may or may not apply to older releases. # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-01:42/signal-4.3.patch # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-01:42/signal-4.3.patch.asc Verify the detached PGP signature using your PGP utility. # cd /usr/src/sys/kern # patch -p < /path/to/patch [ Recompile your kernel as described in http://www.freebsd.org/handbook/kernelconfig.html and reboot the system ] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (FreeBSD) Comment: FreeBSD: The Power To Serve iQCVAwUBO0sBrlUuHi5z0oilAQF4nAP/Wi8RsYGjJQ7NgP/+FwMs8/lekAJ9iEan 3Ph7xpsFEhJFWhCfrhmM71fMnOwpZ5kijztSOEko7TMRzTtG+dZLKcCKmVg+a1dT SJmm2SJp3NE1nlYVqSH1vfVeVcJI5rtAQ33gTPhiL5U26AMr4wep/Elv1p/Shb/D CUpueXr6tEE= =n74Z -----END PGP SIGNATURE----- This is the moderated mailing list freebsd-announce. The list contains announcements of new FreeBSD capabilities, important events and project milestones. See also the FreeBSD Web pages at http://www.freebsd.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-announce" in the body of the message