FreeBSD Security Advisories
2020-May-12 19:44 UTC
FreeBSD Security Advisory FreeBSD-SA-20:13.libalias
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================FreeBSD-SA-20:13.libalias Security Advisory The FreeBSD Project Topic: Memory disclosure vulnerability in libalias Category: core Module: libalias Announced: 2020-05-12 Credits: Vishnu Dev TJ working with Trend Micro Zero Day Initiative Affects: All supported versions of FreeBSD Corrected: 2020-05-12 16:52:08 UTC (stable/12, 12.1-STABLE) 2020-05-12 16:54:39 UTC (releng/12.1, 12.1-RELEASE-p5) 2020-05-12 16:52:08 UTC (stable/11, 11.4-STABLE) 2020-05-12 16:54:39 UTC (releng/11.4, 11.4-BETA1-p1) 2020-05-12 16:54:39 UTC (releng/11.3, 11.3-RELEASE-p9) CVE Name: CVE-2020-7455 For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit <URL:https://security.FreeBSD.org/>. I. Background The ipfw(4) system facility allows IP packet filtering, redirecting, and traffic accounting. The ipfw(4) packet filter also contains two different methods of accomplishing network address translation (NAT): in-kernel and userspace. Both implementations use the same functions provided by libalias. The libalias(3) library is a collection of functions for aliasing and dealiasing of IP packets, intended for masquerading and NAT. Additionally, libalias(3) includes modules to support protocols that require additional logic to support address translation. Note: libalias(3) is not used by either the pf(4) or ipf(4) firewalls. II. Problem Description The FTP packet handler in libalias incorrectly calculates some packet lengths. This may result in disclosing small amounts of memory from the kernel (for the in-kernel NAT implementation) or from the process space for natd (for the userspace implementation). III. Impact A malicious attacker could send specially constructed packets that exploit the erroneous calculation allowing the attacker to disclose small amount of memory either from the kernel (for the in-kernel NAT implementation) or from the process space for natd (for the userspace implementation). IV. Workaround No workaround is available. Only systems using NAT and ipfw together are affected. Systems using ipfw without NAT, or systems leveraging pf(4) or ipf(4) are not affected. V. Solution Upgrade your vulnerable system to a supported FreeBSD stable or release / security branch (releng) dated after the correction date, and reboot. Perform one of the following: 1) 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 # shutdown -r +10min "Rebooting for a security update" 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. # fetch https://security.FreeBSD.org/patches/SA-20:13/libalias.patch # fetch https://security.FreeBSD.org/patches/SA-20:13/libalias.patch.asc # gpg --verify libalias.patch.asc b) Apply the patch. Execute the following commands as root: # cd /usr/src # patch < /path/to/patch c) Recompile your kernel as described in <URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the system. VI. Correction details The following list contains the correction revision numbers for each affected branch. Branch/path Revision - ------------------------------------------------------------------------- stable/12/ r360973 releng/12.1/ r360974 stable/11/ r360973 releng/11.4/ r360974 releng/11.3/ r360974 - ------------------------------------------------------------------------- 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:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN> VII. References <URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-7455> The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-20:13.libalias.asc> -----BEGIN PGP SIGNATURE----- iQKTBAEBCgB9FiEE/A6HiuWv54gCjWNV05eS9J6n5cIFAl663tdfFIAAAAAALgAo aXNzdWVyLWZwckBub3RhdGlvbnMub3BlbnBncC5maWZ0aGhvcnNlbWFuLm5ldEZD MEU4NzhBRTVBRkU3ODgwMjhENjM1NUQzOTc5MkY0OUVBN0U1QzIACgkQ05eS9J6n 5cK3hhAAlkHMjDluGni1AaDicw5jZuyrdGLEMfgH2OdxcrTQvrBN6ZEkfLsiFvLV KWgUS+rx3GJApz4rZ6DFwsb+DG+kMCwYGevbT5zH5IUwe1HklyMLmjw48z47DVhx 8tpjCKNb4ttqBzb6RMURoJgo+2NAUQOZLnFGLSGOkquqeW9AhA97ZIGv7TyOPC1p rJD/ic1IxTUXniNu4soexsRqVoMqv1nA1DLrN4TTooFVCQTHaBUBxSTFlaAsBXyb 7L5GIEydZ2429spQACnFGW4RDveOGB/6Jbt2yHEuu+ASOrwl9sRSu79PYijcz28v yXjI0zG4A+78qmeCMbGHIySrLjc8XaWgr13Kp4S+40MWQhoGHJ2ZZVdLX010WTvm nbGs9NQ60sytxdJn1QRTleiBIKjJiVqNEADfS4DhXa/0HouN3L8dVR/+jPfLMFmT /7GZjhdbn4u0a1ZlgUZ62oHoo8NLop49KY4LHtHd7VpJZ8OfK0qkCN0DL4Ep+Wrg oZWJL5HGhFOEA4TDYuypJ58yIPsTDVa9MuLMx/SBF30jVZcS1LtbiMXXuZs6clig oOk4ZE0hpSRdA69xgX459kcTjU6XVJRnTPWyepG3sNljktwk8jyfwKHXOUpJONos 0jWu0ngj60djS8qCrxdkMn3t26fk0IhbA4leBEM+wAKmWsARt/M=woOx -----END PGP SIGNATURE-----