FreeBSD Security Advisories
2007-Nov-29 08:31 UTC
FreeBSD Security Advisory FreeBSD-SA-07:09.random
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 ============================================================================FreeBSD-SA-07:09.random Security Advisory The FreeBSD Project Topic: Random value disclosure Category: core Module: sys_dev_random Announced: 2007-11-29 Credits: Robert Woolley Affects: All supported versions of FreeBSD Corrected: 2007-11-29 16:05:38 UTC (RELENG_7, 7.0-BETA4) 2007-11-29 16:06:12 UTC (RELENG_6, 6.3-PRERELEASE) 2007-11-29 16:06:54 UTC (RELENG_6_3, 6.3-RC2) 2007-11-29 16:07:30 UTC (RELENG_6_2, 6.2-RELEASE-p9) 2007-11-29 16:07:54 UTC (RELENG_6_1, 6.1-RELEASE-p21) 2007-11-29 16:08:54 UTC (RELENG_5, 5.5-STABLE) 2007-11-29 16:09:26 UTC (RELENG_5_5, 5.5-RELEASE-p17) CVE Name: CVE-2007-6150 For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit <URL:http://security.FreeBSD.org/>. I. Background The random(4) and urandom(4) devices return an endless supply of pseudo-random bytes when read. Cryptographic algorithms often depend on the secrecy of these pseudo-random values for security. II. Problem Description Under certain circumstances, a bug in the internal state tracking on the random(4) and urandom(4) devices can be exploited to allow replaying of data distributed during subsequent reads. III. Impact This could enable an adversary to determine fragments of random values previously read, allowing them to defeat certain security mechanisms. Note that the attacker has to be in close proximity to the source of the pseudo-randomness, which typically means local access to the system. IV. Workaround No workaround is available. V. Solution Perform one of the following: 1) Upgrade your vulnerable system to 5-STABLE, or 6-STABLE, or to the RELENG_6_2, RELENG_6_1, or RELENG_5_5 security branch dated after the correction date. 2) To patch your present system: The following patches have been verified to apply to FreeBSD 5.5, 6.1, and 6.2 systems. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. # fetch http://security.FreeBSD.org/patches/SA-07:09/random.patch # fetch http://security.FreeBSD.org/patches/SA-07:09/random.patch.asc b) Apply the patch. # cd /usr/src # patch < /path/to/patch c) Recompile your kernel as described in <URL:http://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the system. VI. Correction details The following list contains the revision numbers of each file that was corrected in FreeBSD. Branch Revision Path - ------------------------------------------------------------------------- RELENG_5 src/sys/dev/random/yarrow.c 1.44.2.1 RELENG_5_5 src/UPDATING 1.342.2.35.2.17 src/sys/conf/newvers.sh 1.62.2.21.2.19 src/sys/dev/random/yarrow.c 1.44.8.1 RELENG_6 src/sys/dev/random/yarrow.c 1.45.2.2 RELENG_6_3 src/UPDATING 1.416.2.37.2.2 src/sys/dev/random/yarrow.c 1.45.2.1.6.1 RELENG_6_2 src/UPDATING 1.416.2.29.2.12 src/sys/conf/newvers.sh 1.69.2.13.2.12 src/sys/dev/random/yarrow.c 1.45.2.1.4.1 RELENG_6_1 src/UPDATING 1.416.2.22.2.23 src/sys/conf/newvers.sh 1.69.2.11.2.23 src/sys/dev/random/yarrow.c 1.45.2.1.2.1 RELENG_7 src/sys/dev/random/yarrow.c 1.47.2.1 - ------------------------------------------------------------------------- VII. References http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2007-6150 The latest revision of this advisory is available at http://security.FreeBSD.org/advisories/FreeBSD-SA-07:09.random.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (FreeBSD) iD8DBQFHTuezFdaIBMps37IRAhp3AJ0UHJiYycOQCEai3Aid2uT6Jf3WZwCfdR65 Ozmn0Qn6Ru54NRriBJG1o4g=95t9 -----END PGP SIGNATURE-----