Fix a bug that allows NFS clients to issue READDIR on files.
PR: kern/178016 Security: CVE-2013-3266 Security: FreeBSD-SA-13:05.nfsserver Approved by: so
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Dag-Erling Smørgrav
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svn2git
2020-12-08 03:00:23 +00:00
svn path=/head/; revision=41519
4 changed files with 166 additions and 0 deletions
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share/security/advisories/FreeBSD-SA-13:05.nfsserver.asc
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share/security/advisories/FreeBSD-SA-13:05.nfsserver.asc
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-----BEGIN PGP SIGNED MESSAGE-----
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Hash: SHA1
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=============================================================================
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FreeBSD-SA-13:05.nfsserver Security Advisory
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The FreeBSD Project
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Topic: Insufficient input validation in the NFS server
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Category: core
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Module: nfsserver
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Announced: 2013-04-29
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Credits: Adam Nowacki
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Affects: All supported versions of FreeBSD.
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Corrected: 2013-04-29 20:15:43 UTC (stable/8, 8.4-PRERELEASE)
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2013-04-29 20:15:47 UTC (releng/8.3, 8.3-RELEASE-p8)
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2013-04-29 20:16:25 UTC (releng/8.4, 8.4-RC1-p1)
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2013-04-29 20:16:25 UTC (releng/8.4, 8.4-RC2-p1)
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2013-04-29 20:15:55 UTC (stable/9, 9.1-STABLE)
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2013-04-29 20:16:00 UTC (releng/9.1, 9.1-RELEASE-p3)
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CVE Name: CVE-2013-3266
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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 Network File System (NFS) allows a host to export some or all of its
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file systems so that other hosts can access them over the network and mount
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them as if they were on local disks. FreeBSD includes server and client
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implementations of NFS.
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FreeBSD 8.0 and onward has two NFS implementations: the original CSRG
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NFSv2 and NFSv3 implementation and a new implementation which also
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supports NFSv4.
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FreeBSD 9.0 and onward uses the new NFS implementation by default.
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II. Problem Description
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When processing READDIR requests, the NFS server does not check that
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it is in fact operating on a directory node. An attacker can use a
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specially modified NFS client to submit a READDIR request on a file,
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causing the underlying filesystem to interpret that file as a
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directory.
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III. Impact
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The exact consequences of an attack depend on the amount of input
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validation in the underlying filesystem:
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- If the file resides on a UFS filesystem on a little-endian server,
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an attacker can cause random heap corruption with completely
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unpredictable consequences.
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- If the file resides on a ZFS filesystem, an attacker can write
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arbitrary data on the stack. It is believed, but has not been
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confirmed, that this can be exploited to run arbitrary code in
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kernel context.
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Other filesystems may also be vulnerable.
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IV. Workaround
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Systems that do not provide NFS service are not vulnerable. Neither
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are systems that do but use the old NFS implementation, which is the
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default in FreeBSD 8.x.
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To determine which implementation an NFS server is running, run the
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following command:
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# kldstat -v | grep -cw nfsd
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This will print 1 if the system is running the new NFS implementation,
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and 0 otherwise.
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V. Solution
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Perform one of the following:
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1) Upgrade your vulnerable system to a supported FreeBSD stable or
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release / security branch (releng) dated after the correction date.
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2) To update your vulnerable system via a source code patch:
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The following patches have been verified to apply to the applicable
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FreeBSD release branches.
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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-03:15/nfsserver.patch
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# fetch http://security.FreeBSD.org/patches/SA-03:15/nfsserver.patch.asc
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# gpg --verify nfsserver.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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3) To update your vulnerable system via a binary patch:
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Systems running a RELEASE version of FreeBSD on the i386 or amd64
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platforms can be updated via the freebsd-update(8) utility:
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# freebsd-update fetch
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# freebsd-update install
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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/path Revision
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- -------------------------------------------------------------------------
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stable/8/ r250058
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releng/8.3/ r250059
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releng/8.4/ r250062
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stable/9/ r250060
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releng/9.1/ r250061
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- -------------------------------------------------------------------------
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VII. References
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http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2013-3266
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The latest revision of this advisory is available at
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http://security.FreeBSD.org/advisories/FreeBSD-SA-13:05.nfsserver.asc
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-----BEGIN PGP SIGNATURE-----
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=polM
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-----END PGP SIGNATURE-----
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13
share/security/patches/SA-13:05/nfsserver.patch
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13
share/security/patches/SA-13:05/nfsserver.patch
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@ -0,0 +1,13 @@
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Index: sys/fs/nfsserver/nfs_nfsdport.c
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===================================================================
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--- sys/fs/nfsserver/nfs_nfsdport.c (revision 249651)
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+++ sys/fs/nfsserver/nfs_nfsdport.c (working copy)
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@@ -1568,6 +1568,8 @@ nfsrvd_readdir(struct nfsrv_descript *nd, int isdg
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nd->nd_repstat = NFSERR_BAD_COOKIE;
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#endif
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}
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+ if (!nd->nd_repstat && vp->v_type != VDIR)
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+ nd->nd_repstat = NFSERR_NOTDIR;
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if (nd->nd_repstat == 0 && cnt == 0) {
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if (nd->nd_flag & ND_NFSV2)
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/* NFSv2 does not have NFSERR_TOOSMALL */
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6
share/security/patches/SA-13:05/nfsserver.patch.asc
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6
share/security/patches/SA-13:05/nfsserver.patch.asc
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-----END PGP SIGNATURE-----
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@ -13,6 +13,14 @@
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<day>
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<day>
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<name>2</name>
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<name>2</name>
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<advisory>
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<name>FreeBSD-SA-13:05.bind</name>
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</advisory>
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<advisory>
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<name>FreeBSD-SA-13:04.bind</name>
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</advisory>
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<advisory>
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<advisory>
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<name>FreeBSD-SA-13:04.bind</name>
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<name>FreeBSD-SA-13:04.bind</name>
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</advisory>
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</advisory>
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