3571e53040
patches for easier mirroring, to eliminate a special copy, to make www.freebsd.org/security a full copy of security.freebsd.org and be eventually be the same. For now files are just sitting there. The symlinks are missing. Discussed on: www (repository location) Discussed with: simon (so)
113 lines
3.9 KiB
Text
113 lines
3.9 KiB
Text
-----BEGIN PGP SIGNED MESSAGE-----
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Hash: SHA1
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=============================================================================
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FreeBSD-SA-08:08.nmount Security Advisory
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The FreeBSD Project
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Topic: nmount(2) local arbitrary code execution
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Category: core
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Module: sys_kern
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Announced: 2008-09-03
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Credits: James Gritton
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Affects: FreeBSD 7.0-RELEASE, FreeBSD 7.0-STABLE
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Corrected: 2008-09-03 19:09:47 UTC (RELENG_7, 7.1-PRERELEASE)
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2008-09-03 19:09:47 UTC (RELENG_7_0, 7.0-RELEASE-p4)
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CVE Name: CVE-2008-3531
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For general information regarding FreeBSD Security Advisories,
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including descriptions of the fields above, security branches, and the
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following sections, please visit <URL:http://security.FreeBSD.org/>.
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I. Background
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The mount(2) and nmount(2) system calls are used by various utilities
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in the base system to graft a file system object on to the file system
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tree to a given mount point. It is possible to allow unprivileged
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users to utililize these system calls by setting the vfs.usermount
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sysctl(8) variable.
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II. Problem Description
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Various user defined input such as mount points, devices, and mount
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options are prepared and passed as arguments to nmount(2) into the
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kernel. Under certain error conditions, user defined data will be
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copied into a stack allocated buffer stored in the kernel without
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sufficient bounds checking.
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III. Impact
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If the system is configured to allow unprivileged users to mount file
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systems, it is possible for a local adversary to exploit this
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vulnerability and execute code in the context of the kernel.
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IV. Workaround
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It is possible to work around this issue by allowing only privileged
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users to mount file systems by running the following sysctl(8)
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command:
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# sysctl vfs.usermount=0
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V. Solution
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NOTE WELL: Even with this fix allowing users to mount arbitrary media
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should not be considered safe. Most of the file systems in FreeBSD
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was not built to protect safeguard against malicious devices. While
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such bugs in file systems are fixed when found, a complete audit has
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not been perfomed on the file system code.
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Perform one of the following:
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1) Upgrade your vulnerable system to 7-STABLE, or to the RELENG_7_0
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security branch dated after the correction date.
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2) To patch your present system:
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The following patches have been verified to apply to FreeBSD 7.0 systems.
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a) Download the relevant patch from the location below, and verify the
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detached PGP signature using your PGP utility.
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# fetch http://security.FreeBSD.org/patches/SA-08:08/nmount.patch
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# fetch http://security.FreeBSD.org/patches/SA-08:08/nmount.patch.asc
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b) Apply the patch.
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# cd /usr/src
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# patch < /path/to/patch
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c) Recompile your kernel as described in
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<URL:http://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
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system.
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VI. Correction details
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The following list contains the revision numbers of each file that was
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corrected in FreeBSD.
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Branch Revision
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Path
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- -------------------------------------------------------------------------
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RELENG_7
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src/sys/kern/vfs_mount.c 1.265.2.10
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RELENG_7_0
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src/UPDATING 1.507.2.3.2.8
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src/sys/conf/newvers.sh 1.72.2.5.2.8
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src/sys/kern/vfs_mount.c 1.265.2.1.2.2
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- -------------------------------------------------------------------------
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VII. References
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http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2008-3531
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The latest revision of this advisory is available at
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http://security.FreeBSD.org/advisories/FreeBSD-SA-08:08.nmount.asc
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