e6520ef815
Fix sendmail improper close-on-exec flag handling. [SA-14:11] Fix ktrace memory disclosure. [SA-14:12] Fix incorrect error handling in PAM policy parser. [SA-14:13] Fix triple-fault when executing from a threaded process. [EN-14:06]
171 lines
6.8 KiB
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171 lines
6.8 KiB
Text
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=============================================================================
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FreeBSD-SA-14:13.pam Security Advisory
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The FreeBSD Project
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Topic: Incorrect error handling in PAM policy parser
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Category: contrib
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Module: pam
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Announced: 2014-06-03
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Credits: Peter Wemm, Dag-Erling Smørgrav
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Affects: FreeBSD 9.2 and later.
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Corrected: 2014-06-03 19:02:33 UTC (stable/9, 9.3-BETA1)
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2014-06-03 19:02:33 UTC (stable/9, 9.3-BETA1-p1)
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2014-06-03 19:03:11 UTC (releng/9.2, 9.2-RELEASE-p7)
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2014-06-03 19:02:18 UTC (stable/10, 10.0-STABLE)
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2014-06-03 19:02:52 UTC (releng/10.0, 10.0-RELEASE-p4)
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CVE Name: CVE-2014-3879
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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 PAM (Pluggable Authentication Modules) library provides a flexible
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framework for user authentication and session setup / teardown. It is
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used not only in the base system, but also by a large number of
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third-party applications.
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Various authentication methods (UNIX, LDAP, Kerberos etc.) are
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implemented in modules which are loaded and executed according to
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predefined, named policies. These policies are defined in
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/etc/pam.conf, /etc/pam.d/<policy name>, /usr/local/etc/pam.conf or
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/usr/local/etc/pam.d/<policy name>.
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The PAM API is a de facto industry standard which has been implemented
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by several parties. FreeBSD uses the OpenPAM implementation.
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II. Problem Description
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The OpenPAM library searches for policy definitions in several
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locations. While doing so, the absence of a policy file is a soft
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failure (handled by searching in the next location) while the presence
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of an invalid file is a hard failure (handled by returning an error to
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the caller).
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The policy parser returns the same error code (ENOENT) when a
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syntactically valid policy references a non-existent module as when
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the requested policy file does not exist. The search loop regards
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this as a soft failure and looks for the next similarly-named policy,
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without discarding the partially-loaded configuration.
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A similar issue can arise if a policy contains an include directive
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that refers to a non-existent policy.
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III. Impact
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If a module is removed, or the name of a module is misspelled in the
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policy file, the PAM library will proceed with a partially loaded
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configuration. Depending on the exact circumstances, this may result
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in a fail-open scenario where users are allowed to log in without a
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password, or with an incorrect password.
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In particular, if a policy references a module installed by a package
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or port, and that package or port is being reinstalled or upgraded,
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there is a brief window of time during which the module is absent and
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policies that use it may fail open. This can be especially damaging
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to Internet-facing SSH servers, which are regularly subjected to
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brute-force scans.
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IV. Workaround
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If your system uses customized PAM policies, carefully review your
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policies to ensure that all module names are spelled correctly.
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If your system uses third-party authentication modules, either refrain
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from upgrading those modules until you have patched your system, or
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shut down the affected services before upgrading.
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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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[FreeBSD 9.2]
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# fetch http://security.FreeBSD.org/patches/SA-14:13/pam-freebsd9.patch
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# fetch http://security.FreeBSD.org/patches/SA-14:13/pam-freebsd9.patch.asc
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# gpg --verify pam-freebsd9.patch.asc
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[FreeBSD 9.3 and 10.0]
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# fetch http://security.FreeBSD.org/patches/SA-14:13/pam-freebsd10.patch
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# fetch http://security.FreeBSD.org/patches/SA-14:13/pam-freebsd10.patch.asc
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# gpg --verify pam-freebsd10.patch.asc
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b) Apply the patch. Execute the following commands as root:
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# cd /usr/src
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# patch < /path/to/patch
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c) Recompile the operating system using buildworld and installworld as
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described in <URL:http://www.FreeBSD.org/handbook/makeworld.html>.
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Restart all deamons using the library, or reboot the 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 correction revision numbers for each
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affected branch.
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Branch/path Revision
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- -------------------------------------------------------------------------
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stable/9/ r267015
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releng/9.2/ r267018
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stable/10/ r267014
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releng/10.0/ r267017
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- -------------------------------------------------------------------------
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To see which files were modified by a particular revision, run the
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following command, replacing NNNNNN with the revision number, on a
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machine with Subversion installed:
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# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base
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Or visit the following URL, replacing NNNNNN with the revision number:
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<URL:http://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>
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VII. References
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<URL:http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-3879>
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The latest revision of this advisory is available at
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<URL:http://security.FreeBSD.org/advisories/FreeBSD-SA-14:13.pam.asc>
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