FreeBSD Security Advisory FreeBSD-SA-17:04.ipfilter
27 April, 2017 by firstname.lastname@example.org | freebsd
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-SA-17:04.ipfilter Security Advisory The FreeBSD Project Topic: ipfilter(4) fragment handling panic Category: contrib Module: ipfilter Announced: 2017-04-27 Credits: Cy Schubert Affects: All supported versions of FreeBSD. Corrected: 2017-04-21 01:51:49 UTC (stable/11, 11.0-STABLE) 2017-04-27 06:52:30 UTC (releng/11.0, 11.0-RELEASE-p10) 2017-04-21 01:51:49 UTC (stable/10, 10.3-STABLE) 2017-04-27 06:52:30 UTC (releng/10.3, 10.3-RELEASE-p19) CVE Name: CVE-2017-1081 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 IP Filter, also known as ipfilter(4), is a cross-platform, open source packet filter (firewall) originally written for BSD operating systems, including FreeBSD, NetBSD, and OpenBSD, and for Solaris. ipfilter(4) is one of three firewalls included in FreeBSD (the others being ipfw(4) and pf(4)). It performs firewall and NAT functions using the pfil(9) framework as do the other firewalls in FreeBSD in the kernel. II. Problem Description ipfilter(4), capable of stateful packet inspection, using the "keep state" or "keep frags" rule options, will not only maintain the state of connections, such as TCP streams or UDP communication, it also maintains the state of fragmented packets. When a packet fragments are received they are cached in a hash table (and linked list). When a fragment is received it is compared with fragments already cached in the hash table for a match. If it does not match the new entry is used to create a new entry in the hash table. If on the other hand it does match, unfortunately the wrong entry is freed, the entry in the hash table. This results in use after free panic (and for a brief moment prior to the panic a memory leak due to the wrong entry being freed). III. Impact Carefully feeding fragments that are allowed to pass by an ipfilter(4) firewall can be used to cause a panic followed by reboot loop denial of service attack. IV. Workaround No workaround is available, but systems not using ipfilter(4) are not vulnerable. A default installation doesn't enable ipfilter(4). ipfilter(4) configurations not using "keep state" pr "keep frags" are not vulnerable. Users may be able to temporarily replace stateful inspection with stateless rules however this is not as secure as stateful inspection. 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. Reload the ipl.ko kernel module or reboot the system. 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 Reload the ipl.ko kernel module or reboot the system. 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. # fetch https://security.FreeBSD.org/patches/SA-17:04/ipfilter.patch # fetch https://security.FreeBSD.org/patches/SA-17:04/ipfilter.patch.asc # gpg --verify ipfilter.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 or reload the ipl.ko kernel module. VI. Correction details The following list contains the correction revision numbers for each affected branch. Branch/path Revision - ------------------------------------------------------------------------- stable/10/ r317241 releng/10.3/ r317487 stable/11/ r317241 releng/11.0/ r317487 - ------------------------------------------------------------------------- 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-2017-1081> The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-17:04.ipfilter.asc> -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.1.20 (FreeBSD) iQIzBAEBCgAdFiEEHPf/b631yp++G4yy7Wfs1l3PaucFAlkBlbAACgkQ7Wfs1l3P auejpBAAtsITE8qn04H5gT8EGq/ntkN8DQydmVHn0OpmwDGg/XD4Wrwye8jqHhFb XdOj5aMb0QbEK3WjDZwbvHNqTkyzl5QXc3PPs7V5mHdYGHsMRWvSyXutRmopgmsp ee59qLeKxvWGss0gqkUWZQQcbdIVN8hTXnumBZ8ncrpjluaYZuO8DvyZQ1Cy4f+f sd6PCZHemjs4MtSriV4AKOtM1QPuBQEkrQ6clA5j55Txk6fkcy1CUoyP0KmW20Iu VFY/UyrfvbVDgbsFMMFsSn/F9DlKVLLtgjpXqztuOu1QhLbAs7spMnUjRnilfOE6 rsyOh26sjEIlQ3sNf7IrFsXdoqLWgn7CDToZEk5xfyv7MyEuEd5INfAkcLz9Mcp+ AymVRmC29CDt8dIJlEaXPyYXDLx5PGPB+SUR2VghzPQkHM9X9EOnJcVEbAn3QnQ1 sFkh4mlsh3cQ9iw2+RYzIybgBzv0OjxIasU3QtnbRNXgdNVnoV/yTeEUFSyVzvC2 6JcjJCq7WZ3U9EBKbPoVzRBsHAal/3EWMnXMprcdNPuxjd+9357K5OnMXiP9ab9G KthAVRN1y+bZ/SNEtqE/T1vrxH9JV/BEqQjtx+DMp7v7TzGgK8rqSJT8H/bIu2h3 IecRnQRkDipqITFQKSoPiqJZeuoVcXaYw8Cp5gUpL618m4DwZ3w= =C7OI -----END PGP SIGNATURE----- _______________________________________________ email@example.com mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-announce To unsubscribe, send any mail to "firstname.lastname@example.org"