From owner-freebsd-security-notifications@freebsd.org Tue Jul 28 20:30:26 2015 Return-Path: Delivered-To: freebsd-security-notifications@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 6624F9ADD36 for ; Tue, 28 Jul 2015 20:30:26 +0000 (UTC) (envelope-from security-advisories@freebsd.org) Received: from freefall.freebsd.org (freefall.freebsd.org [IPv6:2001:1900:2254:206c::16:87]) by mx1.freebsd.org (Postfix) with ESMTP id 5BA77B9E; Tue, 28 Jul 2015 20:30:26 +0000 (UTC) (envelope-from security-advisories@freebsd.org) Received: by freefall.freebsd.org (Postfix, from userid 1035) id 5B0E11760; Tue, 28 Jul 2015 20:30:26 +0000 (UTC) From: FreeBSD Security Advisories To: FreeBSD Security Advisories Subject: FreeBSD Security Advisory FreeBSD-SA-15:16.openssh Reply-To: freebsd-security@freebsd.org Precedence: bulk Message-Id: <20150728203026.5B0E11760@freefall.freebsd.org> Date: Tue, 28 Jul 2015 20:30:26 +0000 (UTC) X-BeenThere: freebsd-security-notifications@freebsd.org X-Mailman-Version: 2.1.20 List-Id: "Moderated Security Notifications \[moderated, low volume\]" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 28 Jul 2015 20:30:26 -0000 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-SA-15:16.openssh Security Advisory The FreeBSD Project Topic: OpenSSH multiple vulnerabilities Category: contrib Module: openssh Announced: 2015-07-28 Affects: All supported versions of FreeBSD. Corrected: 2015-07-28 19:58:44 UTC (stable/10, 10.2-PRERELEASE) 2015-07-28 19:58:44 UTC (stable/10, 10.2-BETA2-p2) 2015-07-28 19:59:04 UTC (releng/10.2, 10.2-RC1-p1) 2015-07-28 19:59:11 UTC (releng/10.1, 10.1-RELEASE-p16) 2015-07-28 19:58:54 UTC (stable/9, 9.3-STABLE) 2015-07-28 19:59:22 UTC (releng/9.3, 9.3-RELEASE-p21) 2015-07-28 19:58:54 UTC (stable/8, 8.4-STABLE) 2015-07-28 19:59:22 UTC (releng/8.4, 8.4-RELEASE-p35) CVE Name: CVE-2014-2653, CVE-2015-5600 For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit . I. Background OpenSSH is an implementation of the SSH protocol suite, providing an encrypted and authenticated transport for a variety of services, including remote shell access. The security of the SSH connection relies on the server authenticating itself to the client as well as the user authenticating itself to the server. SSH servers uses host keys to verify their identity. RFC 4255 has defined a method of verifying SSH host keys using Domain Name System Security (DNSSEC), by publishing the key fingerprint using DNS with "SSHFP" resource record. RFC 6187 has defined methods to use a signature by a trusted certification authority to bind a given public key to a given digital identity with X.509v3 certificates. The PAM (Pluggable Authentication Modules) library provides a flexible framework for user authentication and session setup / teardown. OpenSSH uses PAM for password authentication by default. II. Problem Description OpenSSH clients does not correctly verify DNS SSHFP records when a server offers a certificate. [CVE-2014-2653] OpenSSH servers which are configured to allow password authentication using PAM (default) would allow many password attempts. III. Impact A malicious server may be able to force a connecting client to skip DNS SSHFP record check and require the user to perform manual host verification of the host key fingerprint. This could allow man-in-the-middle attack if the user does not carefully check the fingerprint. [CVE-2014-2653] A remote attacker may effectively bypass MaxAuthTries settings, which would enable them to brute force passwords. [CVE-2015-5600] IV. Workaround Systems that do not use OpenSSH are not affected. There is no workaround for CVE-2014-2653, but the problem only affects networks where DNSsec and SSHFP is properly configured. Users who uses SSH should always check server host key fingerprints carefully when prompted. System administrators can set: UsePAM no In their /etc/ssh/sshd_config and restart sshd service to workaround the problem described as CVE-2015-5600 at expense of losing features provided by the PAM framework. We recommend system administrators to disable password based authentication completely, and use key based authentication exclusively in their SSH server configuration, when possible. This would eliminate the possibility of being ever exposed to password brute force attack. 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. SSH service has to be restarted after the update. A reboot is recommended but not required. 2) 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 SSH service has to be restarted after the update. A reboot is recommended but not required. 3) 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 9.3, 10.1, 10.2] # fetch https://security.FreeBSD.org/patches/SA-15:16/openssh.patch # fetch https://security.FreeBSD.org/patches/SA-15:16/openssh.patch.asc # gpg --verify openssh.patch.asc [FreeBSD 8.4] # fetch https://security.FreeBSD.org/patches/SA-15:16/openssh-8.patch # fetch https://security.FreeBSD.org/patches/SA-15:16/openssh-8.patch.asc # gpg --verify openssh-8.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 . Restart the SSH service, or reboot the system. VI. Correction details The following list contains the correction revision numbers for each affected branch. Branch/path Revision - ------------------------------------------------------------------------- stable/8/ r285977 releng/8.4/ r285980 stable/9/ r285977 releng/9.3/ r285980 stable/10/ r285976 releng/10.1/ r285979 releng/10.2/ r285978 - ------------------------------------------------------------------------- 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: VII. References The latest revision of this advisory is available at -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.1.6 (FreeBSD) iQIcBAEBCgAGBQJVt+FdAAoJEO1n7NZdz2rnPxEQAIFMhBzUuAEEeG3GoO6o6DQn 7ZVPdd+EdijDk0VAZbaa3NyeVGTNSEQhjpL/lSkIQUQT+yEAUUsUCVWu0T8OpCN0 UT6JlYhV+AwQVyWujlTjspQ3Ba3Kn3o76MCzvdIQWPTzD1yCZqRmpZ1eSjonmySZ ts+kVDCV2ZJyWACOdG2GXHSmTraIErn0J1YaLg++c8nHUvb+TNo2/8viBGJINhdP bvA6fzYPpAzgaq5EEKevySLUnUfUE2Nx5LGD2CUx/hMu7K8y2h4SR2fKmpyBauNS 4VHSssX6KjxZCYctCEsUgCokWYzt9fepyBsCiS9Vx4mTwat8Vuiz2zB1lCOwM97v iDbkcmR/ixElrXSBb5+wrhOpBLnYtHFTNPx8dRz39wdb1MxJQqyOOb8KtDSlFMmQ l5Lk1vTEcZQjWvmCV9XjVlPqcHnX4wNnV+IgUnQTnhQlbe0YgszdLAi5XZDGBmtA DHuLfBy1091KYBoP641GRuldsq6/r6DUzyZuQJ+p30BDUEfkUAptIEnQWA2l3Y8W /10eels29WJhV9N7WWo4pbADA54+DLvi0T/46R9WRbM9bA/dsqK9G5wmREaKCqmX ccQUFrruxJTn7TV4QbN69ABEkOFCyQjqecP2GqA2N/5AAUsV47WC/VtKgOPp4FZ6 E0SkAoNzIighyNk54U9p =6PBw -----END PGP SIGNATURE-----