24 June 2013
Protect yourself against future threats.
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2013.0858.2 Privilege escalation via mmap 24 June 2013 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: mmap Publisher: FreeBSD Operating System: FreeBSD Impact/Access: Modify Arbitrary Files -- Existing Account Resolution: Patch/Upgrade CVE Names: CVE-2013-2171 Original Bulletin: http://security.FreeBSD.org/advisories/FreeBSD-SA-13:06.mmap.asc Revision History: June 24 2013: Added workaround information June 19 2013: Initial Release - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 ============================================================================= FreeBSD-SA-13:06.mmap Security Advisory The FreeBSD Project Topic: Privilege escalation via mmap Category: core Module: kernel Announced: 2013-06-18 Credits: Konstantin Belousov Alan Cox Affects: FreeBSD 9.0 and later Corrected: 2013-06-18 07:04:19 UTC (stable/9, 9.1-STABLE) 2013-06-18 07:05:51 UTC (releng/9.1, 9.1-RELEASE-p4) CVE Name: CVE-2013-2171 For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit <URL:http://security.FreeBSD.org/>. 0. Revision History v1.0 2013-06-18 Initial release. v1.1 2013-06-21 Corrected correction date. Added workaround information. I. Background The FreeBSD virtual memory system allows files to be memory-mapped. All or parts of a file can be made available to a process via its address space. The process can then access the file using memory operations rather than filesystem I/O calls. The ptrace(2) system call provides tracing and debugging facilities by allowing one process (the tracing process) to watch and control another (the traced process). II. Problem Description Due to insufficient permission checks in the virtual memory system, a tracing process (such as a debugger) may be able to modify portions of the traced process's address space to which the traced process itself does not have write access. III. Impact This error can be exploited to allow unauthorized modification of an arbitrary file to which the attacker has read access, but not write access. Depending on the file and the nature of the modifications, this can result in privilege escalation. To exploit this vulnerability, an attacker must be able to run arbitrary code with user privileges on the target system. IV. Workaround Systems that do not allow unprivileged users to use the ptrace(2) system call are not vulnerable, this can be accomplished by setting the sysctl variable security.bsd.unprivileged_proc_debug to zero. Please note that this will also prevent debugging tools, for instance gdb, truss, procstat, as well as some built-in debugging facilities in certain scripting language like PHP, etc., from working for unprivileged users. The following command will set the sysctl accordingly and works until the next reboot of the system: sysctl security.bsd.unprivileged_proc_debug=0 To make this change persistent across reboot, the system administrator should also add the setting into /etc/sysctl.conf: echo 'security.bsd.unprivileged_proc_debug=0' >> /etc/sysctl.conf V. Solution Perform one of the following: 1) Upgrade your vulnerable system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date. 2) To update your vulnerable system via a source code patch: The following patches have been verified to apply to the applicable FreeBSD release branches. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. # fetch http://security.FreeBSD.org/patches/SA-13:06/mmap.patch # fetch http://security.FreeBSD.org/patches/SA-13:06/mmap.patch.asc # gpg --verify mmap.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. 3) To update your vulnerable system via a binary patch: Systems running a RELEASE version of FreeBSD on the i386 or amd64 platforms can be updated via the freebsd-update(8) utility: # freebsd-update fetch # freebsd-update install VI. Correction details The following list contains the correction revision numbers for each affected branch. Branch/path Revision - - ------------------------------------------------------------------------- stable/9/ r251902 releng/9.1/ r251903 - - ------------------------------------------------------------------------- To see which files were modified by a particular revision, run the following command, replacing XXXXXX with the revision number, on a machine with Subversion installed: # svn diff -cXXXXXX --summarize svn://svn.freebsd.org/base Or visit the following URL, replacing XXXXXX with the revision number: <URL:http://svnweb.freebsd.org/base?view=revision&revision=XXXXXX> VII. References <URL:http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2013-2171> The latest revision of this advisory is available at <URL:http://security.FreeBSD.org/advisories/FreeBSD-SA-13:06.mmap.asc> - -----BEGIN PGP SIGNATURE----- iEYEARECAAYFAlHExy0ACgkQFdaIBMps37L8PwCdGXatzPm7OWjZu+GmbbXQC16/ 8sgAoJ0LEmREO8Mp7f4YcLHAEwgnJtjT =WRZD - -----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 email@example.com and we will forward your request to the appropriate person. NOTE: Third Party Rights 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 =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: firstname.lastname@example.org 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 iQIVAwUBUcfRQhLndAQH1ShLAQJZOxAAocU79ctlY273E/clDZbBr1dmqW2lqk3z XfZP2nWrnW4zYePt8Kkp7ydsIaBeaE1ZlPhSZ6UTrWp9L+7To5DMabzwQx2QF5dL Te0MnrgrhkSEnQSXcaqzYGy2OIL/MCWAoFADHCsimUyJMTIYd7iSm8Ve8rcdHnm+ 9uCl2ygyEflWFgFvSS5eZxtDQ9KyN/FYR5qhAjh+VJ5bbl/zieeFpzK22kn63/C4 GJpN2fV0ktwE4Cm5PnfaurGLaa++Xe1WmwgIv6nF2aN9un/tiAd9vu6d27/9grIk IwM1ckuxjD0/e+rfOc6KoUOPlUFKC1VPIRkaHQWg9o4q89wyW2BbH3Yu2Nlrf0Dn RGYdm4LgxI9nw0+7PiCCVBPfSvSt56uieoO9xUv73JSOhjiI9XLGsQ/4EKi4vkes WlyouWf/kuhQGrQqi5UF9ViaK0KELVJkB+6U1xUdMWTj78LyLldmFOoYDIofhG/9 PKVmpOUVoU6wmflJ7qC/8x0xk4KcLihbiAR6bTIPYyCQVtQ5zKbm1Nw7TlumuexY NVALvPCoRvVBq9dhc2INu0ukxrWO0pvkrRC+oeg0GP7FD45PDBX7w5tw+L+WzrGf WoGFoVPDt8OroSz3+z9ckxfTYbk1HOm6TYML3cTAG3gULLfF10/qSVYP3Ts5OQHk AL5F42WleFg= =Gcx8 -----END PGP SIGNATURE-----