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FreeBSD Security Advisory FreeBSD-SA-04:03.jail


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Date: Fri, 27 Feb 2004 10:32:01 -0800 (PST)
From: FreeBSD Security Advisories <security-advisories@freebsd.org.>
To: Bugtraq <bugtraq@securityfocus.com.>
Subject: FreeBSD Security Advisory FreeBSD-SA-04:03.jail

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FreeBSD-SA-04:03.jail Security Advisory The FreeBSD Project Topic: Jailed processes can attach to other jails Category: core Module: kernel Announced: 2004-02-25 Credits: JAS Group (http://www.cs.mu.oz.au/jas/) Affects: FreeBSD 5.1-RELEASE FreeBSD 5.2-RELEASE Corrected: 2004-02-19 23:26:39 UTC (RELENG_5_2, 5.2.1-RC2) 2004-02-25 20:03:35 UTC (RELENG_5_1, 5.1-RELEASE-p14) CVE Name: CAN-2004-0126 FreeBSD only: YES For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit <URL:http://www.freebsd.org/security/>;. I. Background The jail(2) system call allows a system administrator to lock up a process and all its descendants inside a closed environment with very limited ability to affect the system outside that environment, even for processes with superuser privileges. It is an extension of, but far more stringent than, the traditional Unix chroot(2) system call. The jail_attach(2) system call, which was introduced in FreeBSD 5 before 5.1-RELEASE, allows a non-jailed process to permanently move into an existing jail. II. Problem Description A programming error has been found in the jail_attach(2) system call which affects the way that system call verifies the privilege level of the calling process. Instead of failing immediately if the calling process was already jailed, the jail_attach(2) system call would fail only after changing the calling process's root directory. III. Impact A process with superuser privileges inside a jail could change its root directory to that of a different jail, and thus gain full read and write access to files and directories within the target jail. IV. Workaround No workaround is available. V. Solution Do one of the following: 1) Upgrade your vulnerable system to 5.2.1-RELEASE, or to the RELENG_5_2 or RELENG_5_1 security branch dated after the correction date. OR 2) Patch your present system: The following patch has been verified to apply to FreeBSD 5.1 and 5.2 systems. 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-04:03/jail.patch # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-04:03/jail.patch.asc b) Apply the patch. # cd /usr/src # patch < /path/to/patch c) Recompile your kernel as described in <URL: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. Branch Revision Path - ------------------------------------------------------------------------- RELENG_5_2 src/sys/kern/kern_jail.c 1.34.2.1 RELENG_5_1 src/UPDATING 1.251.2.16 src/sys/conf/newvers.sh 1.50.2.16 src/sys/kern/kern_jail.c 1.33.2.1 - ------------------------------------------------------------------------- VII. References <URL:http://www.cs.mu.oz.au/jas/>; -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFAP4xVFdaIBMps37IRArw1AJ9jNZIsJHYlKt+NEsOgp5cti/Cs+gCdFa0j 3cvPHMce6awUESculjC3Z/I= =LQo0 -----END PGP SIGNATURE-----

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