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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2008.0167 -- [UNIX/Linux][FreeBSD] sendfile(2) write-only file permission bypass 15 February 2008 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: sendfile Publisher: FreeBSD Operating System: UNIX variants (UNIX, Linux, OSX) FreeBSD Impact: Access Confidential Data Access: Existing Account CVE Names: CVE-2008-0777 Original Bulletin: http://security.freebsd.org/advisories/FreeBSD-SA-08:03.sendfile.asc Comment: This advisory references vulnerabilities in products which run on platforms other than FreeBSD. It is recommended that administrators running sendfile check for an updated version of the software for their operating system. Revision History: February 15 2008: Corrected Origional Bulletin February 15 2008: Initial Release - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 ============================================================================= FreeBSD-SA-08:03.sendfile Security Advisory The FreeBSD Project Topic: sendfile(2) write-only file permission bypass Category: core Module: sys_kern Announced: 2008-02-14 Credits: Kostik Belousov Affects: All supported versions of FreeBSD Corrected: 2008-02-14 11:45:00 UTC (RELENG_7, 7.0-PRERELEASE) 2008-02-14 11:45:41 UTC (RELENG_7_0, 7.0-RELEASE) 2008-02-14 11:46:08 UTC (RELENG_6, 6.3-STABLE) 2008-02-14 11:46:41 UTC (RELENG_6_3, 6.3-RELEASE-p1) 2008-02-14 11:47:06 UTC (RELENG_6_2, 6.2-RELEASE-p11) 2008-02-14 11:47:39 UTC (RELENG_6_1, 6.1-RELEASE-p23) 2008-02-14 11:49:39 UTC (RELENG_5, 5.5-STABLE) 2008-02-14 11:50:28 UTC (RELENG_5_5, 5.5-RELEASE-p19) CVE Name: CVE-2008-0777 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/>. I. Background The sendfile(2) system call allows a server application (such as a HTTP or FTP server) to transmit the contents of a file over a network connection without first copying it to application memory. High performance servers such as the Apache HTTP Server and ftpd use sendfile. II. Problem Description When a process opens a file (and other file system objects, such as directories), it specifies access flags indicating its intent to read, write, or perform other operations. These flags are checked against file system permissions, and then stored in the resulting file descriptor to validate future operations against. The sendfile(2) system call does not check the file descriptor access flags before sending data from a file. III. Impact If a file is write-only, a user process can open the file and use sendfile to send the content of the file over a socket, even though the user does not have read access to the file, resulting in possible disclosure of sensitive information. IV. Workaround No workaround is available, but systems are only vulnerable if write-only files exist, which are not widely used. V. Solution Perform one of the following: 1) Upgrade your vulnerable system to 5-STABLE, 6-STABLE, or 7.0-PRERELEASE, or to the RELENG_7_0, RELENG_6_3, RELENG_6_2, RELENG_6_1, or RELENG_5_5 security branch dated after the correction date. 2) To patch your present system: The following patches have been verified to apply to FreeBSD 5.5, 6.1, 6.2, 6.3, and 7.0 systems. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. [FreeBSD 6.2, 6.3, and 7.0] # fetch http://security.FreeBSD.org/patches/SA-08:03/sendfile.patch # fetch http://security.FreeBSD.org/patches/SA-08:03/sendfile.patch.asc [FreeBSD 6.1] # fetch http://security.FreeBSD.org/patches/SA-08:03/sendfile61.patch # fetch http://security.FreeBSD.org/patches/SA-08:03/sendfile61.patch.asc [FreeBSD 5.5] # fetch http://security.FreeBSD.org/patches/SA-08:03/sendfile55.patch # fetch http://security.FreeBSD.org/patches/SA-08:03/sendfile55.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 src/sys/kern/kern_descrip.c 1.243.2.11 RELENG_5_5 src/UPDATING 1.342.2.35.2.20 src/sys/conf/newvers.sh 1.62.2.21.2.21 src/sys/kern/kern_descrip.c 1.243.2.9.2.1 RELENG_6 src/sys/kern/kern_descrip.c 1.279.2.16 src/sys/kern/uipc_syscalls.c 1.221.2.5 RELENG_6_3 src/UPDATING 1.416.2.37.2.5 src/sys/conf/newvers.sh 1.69.2.15.2.4 src/sys/kern/kern_descrip.c 1.279.2.15.2.1 src/sys/kern/uipc_syscalls.c 1.221.2.4.4.1 RELENG_6_2 src/UPDATING 1.416.2.29.2.15 src/sys/conf/newvers.sh 1.69.2.13.2.14 src/sys/kern/kern_descrip.c 1.279.2.9.2.1 src/sys/kern/uipc_syscalls.c 1.221.2.4.2.1 RELENG_6_1 src/UPDATING 1.416.2.22.2.26 src/sys/conf/newvers.sh 1.69.2.11.2.25 src/sys/kern/kern_descrip.c 1.279.2.6.2.1 src/sys/kern/uipc_syscalls.c 1.221.2.1.2.1 RELENG_7 src/sys/kern/kern_descrip.c 1.313.2.1 src/sys/kern/uipc_syscalls.c 1.259.2.2 RELENG_7_0 src/UPDATING 1.507.2.3.2.3 src/sys/kern/kern_descrip.c 1.313.4.1 src/sys/kern/uipc_syscalls.c 1.259.4.2 - - ------------------------------------------------------------------------- VII. References http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-0777 The latest revision of this advisory is available at http://security.FreeBSD.org/advisories/FreeBSD-SA-08:03.sendfile.asc - -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.8 (FreeBSD) iD8DBQFHtC0DFdaIBMps37IRAqp8AJ91+flnCIUSvKoFQyXfD1YTnPnuqgCcDiPJ SR4X1dNFENsHMq9ROrQhr1c= =TX1R - -----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. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. 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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 =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 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 iQCVAwUBR7TiwCh9+71yA2DNAQKHDgP/etlaOuXKQ6tLHJ8Xq655spmX4e+kn/95 lyVMGg7BhCa9mybh+uNLlHe4d56Ht8JN5nSUNC3zlm8YkgxJL5cAxWAB3UDUl+Q9 WJvuihC3SOo+FVBBNY9VHFl/J9LOv2CDFdbwOObaHk5UOi/kQnu7ZQX3YVfKFeSB M57OmR/U40k= =ge1P -----END PGP SIGNATURE-----