146 lines
5.9 KiB
Text
146 lines
5.9 KiB
Text
-----BEGIN PGP SIGNED MESSAGE-----
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Hash: SHA512
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=============================================================================
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FreeBSD-SA-20:12.libalias Security Advisory
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The FreeBSD Project
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Topic: Insufficient packet length validation in libalias
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Category: core
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Module: libalias
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Announced: 2020-05-12
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Credits: Lucas Leong (@_wmliang_) of Trend Micro Zero Day Initiative
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Vishnu working with Trend Micro Zero Day Initiative
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Affects: All supported versions of FreeBSD.
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Corrected: 2020-05-12 16:49:04 UTC (stable/12, 12.1-STABLE)
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2020-05-12 16:51:11 UTC (releng/12.1, 12.1-RELEASE-p5)
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2020-05-12 16:49:04 UTC (stable/11, 11.4-STABLE)
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2020-05-12 16:51:11 UTC (releng/11.4, 11.4-BETA1-p1)
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2020-05-12 16:51:11 UTC (releng/11.3, 11.3-RELEASE-p9)
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CVE Name: CVE-2020-7454
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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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The ipfw(4) system facility allows IP packet filtering, redirecting, and
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traffic accounting. The ipfw(4) packet filter also contains two different
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methods of accomplishing network address translation (NAT): in-kernel and
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userspace. Both implementations use the same functions provided by libalias.
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The libalias(3) library is a collection of functions for aliasing and
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dealiasing of IP packets, intended for masquerading and NAT. Additionally,
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libalias(3) includes modules to support protocols that require additional
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logic to support address translation.
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Note: libalias(3) is not used by either the pf(4) or ipf(4) firewalls.
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II. Problem Description
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libalias(3) packet handlers do not properly validate the packet length before
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accessing the protocol headers. As a result, if a libalias(3) module does
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not properly validate the packet length before accessing the protocol header,
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it is possible for an out of bound read or write condition to occur.
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III. Impact
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A malicious attacker could send specially constructed packets that exploit
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the lack of validation allowing the attacker to read or write memory either
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from the kernel (for the in-kernel NAT implementation) or from the process
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space for natd (for the userspace implementation).
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IV. Workaround
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No workaround is available. Only systems using NAT and ipfw together are
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affected. Systems using ipfw(4) without NAT, or systems leveraging pf(4) or
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ipf(4) are not affected.
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V. Solution
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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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and reboot.
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Perform one of the following:
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1) 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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# shutdown -r +10min "Rebooting for a security update"
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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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# fetch https://security.FreeBSD.org/patches/SA-20:12/libalias.patch
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# fetch https://security.FreeBSD.org/patches/SA-20:12/libalias.patch.asc
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# gpg --verify libalias.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 your kernel as described in
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<URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
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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/12/ r360971
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releng/12.1/ r360972
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stable/11/ r360971
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releng/11.4/ r360972
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releng/11.3/ r360972
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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-2020-7454>
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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-20:12.libalias.asc>
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