165 lines
6.4 KiB
Text
165 lines
6.4 KiB
Text
-----BEGIN PGP SIGNED MESSAGE-----
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Hash: SHA512
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=============================================================================
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FreeBSD-EN-15:08.sendmail Errata Notice
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The FreeBSD Project
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Topic: sendmail TLS/DH Interoperability Improvement
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Category: contrib
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Module: sendmail
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Announced: 2015-06-18; Last revised on 2015-06-30.
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Credits: Frank Seltzer, Gregory Shapiro
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Affects: All supported versions of FreeBSD.
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Corrected: 2015-06-25 01:49:44 UTC (stable/10, 10.1-STABLE)
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2015-06-30 23:21:37 UTC (releng/10.1, 10.1-RELEASE-p14)
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2015-06-25 01:53:45 UTC (stable/9, 9.3-STABLE)
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2015-06-30 23:21:48 UTC (releng/9.3, 9.3-RELEASE-p18)
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2015-06-25 01:56:36 UTC (stable/8, 8.4-STABLE)
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2015-06-30 23:21:59 UTC (releng/8.4, 8.4-RELEASE-p32)
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For general information regarding FreeBSD Errata Notices and Security
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Advisories, including descriptions of the fields above, security
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branches, and the following sections, please visit
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<URL:https://security.freebsd.org/>.
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0. Revision history
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v1.0 2015-06-18 Initial release.
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v1.1 2015-06-30 Revised patch for non-existent DH parameter file.
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I. Background
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Sendmail supports STARTTLS encrypted connections using DHE_EXPORT
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ciphers. As part of that support, by default, Sendmail employs 1024-bit
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DH parameters for server connections but 512-bit DH parameters if
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configured to use a DH parameter file that does not exist.
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II. Problem Description
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In response to CVE-2015-4000 ("Logjam TLS vulnerability"), OpenSSL and
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other encryption packages have begun rejecting 512-bit and lower DH
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parameters during negotiation, thereby reducing interoperability.
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III. Impact
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In its default FreeBSD configuration, client connections from Sendmail
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to other SMTP servers will not be able to negotiate a STARTTLS encrypted
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session with SMTP servers that reject 512-bit DH parameters. This may
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cause mail deliverability issues for outbound mail.
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IV. Workaround
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Systems that do not use Sendmail are not affected.
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To work around this interoperability, Sendmail can be configured to use
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a 1024 or 2048 bit DH parameter using these steps:
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1. Edit /etc/mail/`hostname`.mc
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2. If a setting for confDH_PARAMETERS does not exist or
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exists and is set to a string beginning with '5',
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replace it with '1' for 1024-bit or '2' for 2048-bit.
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3. If a setting for confDH_PARAMETERS exists and is set to
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a file path, create a new file with:
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openssl dhparam -out /path/to/file 2048
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for 2048-bit or:
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openssl dhparam -out /path/to/file 1024
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for 1024-bit.
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4. Rebuild the .cf file:
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cd /etc/mail/; make; make install
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5. Restart sendmail:
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cd /etc/mail/; make restart
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V. Solution
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A change to the raise the default for Sendmail connections to use
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1024-bit DH parameters if the configured DH parameters file does not
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exist has been committed.
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Perform one of the following:
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1) Upgrade your system to a supported FreeBSD stable or release / security
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branch (releng) dated after the correction date.
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2) To update your present 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 present 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/EN-15:08/sendmail.patch
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# fetch https://security.FreeBSD.org/patches/EN-15:08/sendmail.patch.asc
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# gpg --verify sendmail.patch.asc
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# fetch https://security.FreeBSD.org/patches/EN-15:08/sendmail-01.patch
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# fetch https://security.FreeBSD.org/patches/EN-15:08/sendmail-01.patch.asc
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# gpg --verify sendmail.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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Restart the Sendmail daemon(s), or reboot the system.
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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/8/ r284790
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releng/8.4/ r284987
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stable/9/ r284788
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releng/9.3/ r284986
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stable/10/ r284786
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releng/10.1/ r284985
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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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The latest revision of this Errata Notice is available at
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https://security.FreeBSD.org/advisories/FreeBSD-EN-15:08.sendmail.asc
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