135 lines
5.2 KiB
Text
135 lines
5.2 KiB
Text
-----BEGIN PGP SIGNED MESSAGE-----
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Hash: SHA512
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=============================================================================
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FreeBSD-SA-16:07.openssh Security Advisory
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The FreeBSD Project
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Topic: OpenSSH client information leak
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Category: contrib
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Module: openssh
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Announced: 2016-01-14
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Credits: Qualys Security Advisory Team
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Affects: All supported versions of FreeBSD.
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Corrected: 2016-01-14 22:42:43 UTC (stable/10, 10.2-STABLE)
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2016-01-14 22:45:33 UTC (releng/10.2, 10.2-RELEASE-p10)
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2016-01-14 22:47:54 UTC (releng/10.1, 10.1-RELEASE-p27)
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2016-01-14 22:50:35 UTC (stable/9, 9.3-STABLE)
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2016-01-14 22:53:07 UTC (releng/9.3, 9.3-RELEASE-p34)
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CVE Name: CVE-2016-0777
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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:https://security.FreeBSD.org/>.
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I. Background
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OpenSSH is an implementation of the SSH protocol suite, providing an
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encrypted and authenticated transport for a variety of services,
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including remote shell access. The ssh(1) is client side utility used
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to login to remote servers.
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II. Problem Description
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The OpenSSH client code contains experimental support for resuming SSH
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connections (roaming). The matching server code has never been shipped, but
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the client code was enabled by default and could be tricked by a malicious
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server into leaking client memory to the server, including private client
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user keys.
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III. Impact
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A user that authenticates to a malicious or compromised server may reveal
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private data, including the private SSH key of the user.
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IV. Workaround
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The vulnerable code in the client can be completely disabled by adding
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'UseRoaming no' to the global ssh_config(5) file, or to user configuration
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in ~/.ssh/config, or by passing -oUseRoaming=no on the command line.
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All current remote ssh(1) sessions need to be restared after changing
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the configuration file.
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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 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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3) 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 https://security.FreeBSD.org/patches/SA-16:07/openssh.patch
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# fetch https://security.FreeBSD.org/patches/SA-16:07/openssh.patch.asc
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# gpg --verify openssh.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:https://www.FreeBSD.org/handbook/makeworld.html>.
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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/ r294053
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releng/9.3/ r294054
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stable/10/ r294049
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releng/10.1/ r294051
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releng/10.2/ r294052
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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:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>
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VII. References
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<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-0777>
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The latest revision of this advisory is available at
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<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-16:07.openssh.asc>
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