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-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2004.0171 -- FreeBSD-SA-04:03.jail Jailed processes can attach to other jails 01 March 2004 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: jail_attach(2) Publisher: FreeBSD Operating System: FreeBSD 5.2-RELEASE FreeBSD 5.1-RELEASE Impact: Inappropriate Access Access Required: Existing Account CVE Names: CAN-2004-0126 - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 ============================================================================= 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----- - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. The decision to follow or act on information or advice contained in this security bulletin is the responsibility of each user or organisation, and should be considered in accordance with your organisation's site policies and procedures. AusCERT takes no responsibility for consequences which may arise from following or acting on information or advice contained in this security bulletin. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the author's website to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/render.html?cid=1980 If you believe that your computer system has been compromised or attacked in any way, we encourage you to let us know by completing the secure National IT Incident Reporting Form at: http://www.auscert.org.au/render.html?it=3192 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQCVAwUBQEKMiih9+71yA2DNAQEiZQP+IL6vS+M1nMNQqgpzThC/hZbwd4ORQXmV UMAM6tBNraNCnHebcEEzoaGhPBKroV6B66i9Dcvwr4VCp+Tr97n3HP6MDGw1PJAZ 1hDwWUgLM2UVfY07k4V5sh6Zr5c7OBA/j4a3wU/51F/IAqbq5HhgjXEFi9/0X0fy cYLbu/sbf4U= =uOjR -----END PGP SIGNATURE-----