Date: Wed, 4 Jun 2014 04:51:56 GMT From: FreeBSD Security Advisories <security-advisories@...ebsd.org> To: oss-security@...ts.openwall.com Subject: FreeBSD Security Advisory FreeBSD-SA-14:13.pam -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-SA-14:13.pam Security Advisory The FreeBSD Project Topic: Incorrect error handling in PAM policy parser Category: contrib Module: pam Announced: 2014-06-03 Credits: Peter Wemm, Dag-Erling Smørgrav Affects: FreeBSD 9.2 and later. Corrected: 2014-06-03 19:02:33 UTC (stable/9, 9.3-BETA1) 2014-06-03 19:02:33 UTC (stable/9, 9.3-BETA1-p1) 2014-06-03 19:03:11 UTC (releng/9.2, 9.2-RELEASE-p7) 2014-06-03 19:02:18 UTC (stable/10, 10.0-STABLE) 2014-06-03 19:02:52 UTC (releng/10.0, 10.0-RELEASE-p4) CVE Name: CVE-2014-3879 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 PAM (Pluggable Authentication Modules) library provides a flexible framework for user authentication and session setup / teardown. It is used not only in the base system, but also by a large number of third-party applications. Various authentication methods (UNIX, LDAP, Kerberos etc.) are implemented in modules which are loaded and executed according to predefined, named policies. These policies are defined in /etc/pam.conf, /etc/pam.d/<policy name>, /usr/local/etc/pam.conf or /usr/local/etc/pam.d/<policy name>. The PAM API is a de facto industry standard which has been implemented by several parties. FreeBSD uses the OpenPAM implementation. II. Problem Description The OpenPAM library searches for policy definitions in several locations. While doing so, the absence of a policy file is a soft failure (handled by searching in the next location) while the presence of an invalid file is a hard failure (handled by returning an error to the caller). The policy parser returns the same error code (ENOENT) when a syntactically valid policy references a non-existent module as when the requested policy file does not exist. The search loop regards this as a soft failure and looks for the next similarly-named policy, without discarding the partially-loaded configuration. A similar issue can arise if a policy contains an include directive that refers to a non-existent policy. III. Impact If a module is removed, or the name of a module is misspelled in the policy file, the PAM library will proceed with a partially loaded configuration. Depending on the exact circumstances, this may result in a fail-open scenario where users are allowed to log in without a password, or with an incorrect password. In particular, if a policy references a module installed by a package or port, and that package or port is being reinstalled or upgraded, there is a brief window of time during which the module is absent and policies that use it may fail open. This can be especially damaging to Internet-facing SSH servers, which are regularly subjected to brute-force scans. IV. Workaround If your system uses customized PAM policies, carefully review your policies to ensure that all module names are spelled correctly. If your system uses third-party authentication modules, either refrain from upgrading those modules until you have patched your system, or shut down the affected services before upgrading. 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. [FreeBSD 9.2] # fetch http://security.FreeBSD.org/patches/SA-14:13/pam-freebsd9.patch # fetch http://security.FreeBSD.org/patches/SA-14:13/pam-freebsd9.patch.asc # gpg --verify pam-freebsd9.patch.asc [FreeBSD 9.3 and 10.0] # fetch http://security.FreeBSD.org/patches/SA-14:13/pam-freebsd10.patch # fetch http://security.FreeBSD.org/patches/SA-14:13/pam-freebsd10.patch.asc # gpg --verify pam-freebsd10.patch.asc b) Apply the patch. Execute the following commands as root: # cd /usr/src # patch < /path/to/patch c) Recompile the operating system using buildworld and installworld as described in <URL:http://www.FreeBSD.org/handbook/makeworld.html>. Restart all deamons using the library, or 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/ r267015 releng/9.2/ r267018 stable/10/ r267014 releng/10.0/ r267017 - ------------------------------------------------------------------------- To see which files were modified by a particular revision, run the following command, replacing NNNNNN with the revision number, on a machine with Subversion installed: # svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base Or visit the following URL, replacing NNNNNN with the revision number: <URL:http://svnweb.freebsd.org/base?view=revision&revision=NNNNNN> VII. References <URL:http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-3879> The latest revision of this advisory is available at <URL:http://security.FreeBSD.org/advisories/FreeBSD-SA-14:13.pam.asc> -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (FreeBSD) iQIcBAEBCgAGBQJTjiDaAAoJEO1n7NZdz2rnx90P/je9ArC02N90sK//UauenbXV BJCNh1WRSVE3hoxgVyPC0R+6Ts6J9At42ANUHXHVxipA2Qpu2UKf+/c3JreSuSGs 6rgAj1TPZEideQInTs9qCJWr6f/M2aPlYCF8iHuuLMJTO35wfVYQENDaFJmebKoI fKkVvTh8ig2cgJWe7RZxd+Y4tPxKZb5ix5jV+xFjDPrmzVgSCUVpW0GrD7qWOg1W 25Ysx+LLBr03guDnFd9RodObWoNZ+aFxuvkKELmjUKva7xRSEw6PfwPCpLp9/83Q HDVlkw0jH+0sF1SY7V+GUvQriPNpwyGNEOfDvL47gnlN/Z7HOZ0hYlVuYw4QYGv5 l5PZOL5eFC6xl88fn+ypKQwGDdzpM4i+svBy//2CW17luU31L4F/cde+yCxsEJB5 JXNhVTYe2z+ACfSs+Oxzk5uGI1f9FhvTzIyoO26Coq6e2Nk2633451kRgdPNxoAP kMimT2Mle/1kqupLirGi44lEyUYV9As2AhnLBFFUXTnESlWVe6q0N0Rb8G6D2jcR 0m5hccsS2HcysUtSIP8ADB6LlSgH+bKP2FUFopdjQUx3J+/KQ5kl6L/UhOOr1Hag 4PdoCPpR15s2CaICmu5HkDtGNkZQV7xdN6TLcksJHXRshISlbzZjlaNyrbu6oJu9 nz3mhzGz1ZH6l7kuNYXD =qUxk -----END PGP SIGNATURE-----
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