Hash: SHA1
=============================================================================
FreeBSD-SA-11:09.pam_ssh Security Advisory
The FreeBSD Project
Topic: pam_ssh improperly grants access when user account has
unencrypted SSH private keys
Category: contrib
Module: pam
Announced: 2011-12-23
Credits: Guy Helmer, Dag-Erling Smorgrav
Affects: All supported versions of FreeBSD.
Corrected: 2011-12-11 20:40:23 UTC (RELENG_7, 7.4-STABLE)
2011-12-23 15:00:37 UTC (RELENG_7_4, 7.4-RELEASE-p5)
2011-12-23 15:00:37 UTC (RELENG_7_3, 7.3-RELEASE-p9)
2011-12-11 20:38:36 UTC (RELENG_8, 8.2-STABLE)
2011-12-23 15:00:37 UTC (RELENG_8_2, 8.2-RELEASE-p5)
2011-12-23 15:00:37 UTC (RELENG_8_1, 8.1-RELEASE-p7)
2011-12-11 16:57:27 UTC (RELENG_9, 9.0-STABLE)
2011-12-11 17:32:37 UTC (RELENG_9_0, 9.0-RELEASE)
For general information regarding FreeBSD Security Advisories, I. Background The PAM (Pluggable Authentication Modules) library provides a flexible Various authentication methods (UNIX, LDAP, Kerberos etc.) are The base system includes a module named pam_ssh which, if enabled, By default, the pam_ssh module rejects SSH private keys with no II. Problem Description The OpenSSL library call used to decrypt private keys ignores the III. Impact If the pam_ssh module is enabled, attackers may be able to gain access IV. Workaround No workaround is available, but systems that do not have the pam_ssh module The system administrator can use the following procedure to inspect all # egrep -r '^[^#].*\ The following command will disable the pam_ssh module in all PAM # sed -i '' -e '/^[^#].*pam_ssh/s/^/#/' /etc/pam.conf /etc/pam.d/* \ V. Solution Perform one of the following: 1) Upgrade your vulnerable system to 7-STABLE or 8-STABLE, or to 2) To update your vulnerable system via a source code patch: The following patches have been verified to apply to FreeBSD 7.4, 7.3, a) Download the relevant patch from the location below, and verify the # fetch http://security.FreeBSD.org/patches/SA-11:09/pam_ssh.patch b) Execute the following commands as root: # cd /usr/src NOTE: On the amd64 platform, the above procedure will not update the 3) To update your vulnerable system via a binary patch: Systems running 7.4-RELEASE, 7.3-RELEASE, 8.2-RELEASE, or 8.1-RELEASE on # freebsd-update fetch VI. Correction details The following list contains the revision numbers of each file that was CVS: Branch Revision Subversion: Branch/path Revision VII. References The latest revision of this advisory is available at iEYEARECAAYFAk70nOoACgkQFdaIBMps37JTSwCfS+bmWBxv5hote7Hrcl7VZjjk
including descriptions of the fields above, security branches, and the
following sections, please visit
framework for user authentication and session setup / teardown. It is
used not only in the base system, but also by a large number of
third-party applications.
implemented in modules which are loaded and executed according to
predefined, named policies. These policies are defined in
/etc/pam.conf, /etc/pam.d/
/usr/local/etc/pam.d/
allows users to authenticate themselves by typing in the passphrase of
one of the SSH private keys which are stored in encrypted form in the
their .ssh directory. Authentication is considered successful if at
least one of these keys could be decrypted using the provided
passphrase.
passphrase. A "nullok" option exists to allow these keys.
passphrase argument if the key is not encrypted. Because the pam_ssh
module only checks whether the passphrase provided by the user is
null, users with unencrypted SSH private keys may successfully
authenticate themselves by providing a dummy passphrase.
to user accounts which have unencrypted SSH private keys.
enabled are not vulnerable. The pam_ssh module is not enabled in any
of the default policies provided in the base system.
PAM policy files to determine whether the pam_ssh module is enabled.
If the following command produces any output, the system may be
vulnerable:
policies present in the system:
/usr/local/etc/pam.conf /usr/local/etc/pam.d/*
the RELENG_8_2, RELENG_8_1, RELENG_7_4, or RELENG_7_3 security
branch dated after the correction date.
8.2 and 8.1 systems.
detached PGP signature using your PGP utility.
# fetch http://security.FreeBSD.org/patches/SA-11:09/pam_ssh.patch.asc
# patch < /path/to/patch
# cd /usr/src/lib/libpam/modules/pam_ssh
# make obj && make depend && make && make install
lib32 (i386 compatibility) libraries. On amd64 systems where the i386
compatibility libraries are used, the operating system should instead
be recompiled as described in
the i386 or amd64 platforms can be updated via the freebsd-update(8)
utility:
# freebsd-update install
corrected in FreeBSD.
Path
- -------------------------------------------------------------------------
RELENG_7
src/lib/libpam/modules/pam_ssh/pam_ssh.c 1.44.2.2
RELENG_7_4
src/UPDATING 1.507.2.36.2.7
src/sys/conf/newvers.sh 1.72.2.18.2.10
src/lib/libpam/modules/pam_ssh/pam_ssh.c 1.44.2.1.8.2
RELENG_7_3
src/UPDATING 1.507.2.34.2.11
src/sys/conf/newvers.sh 1.72.2.16.2.13
src/lib/libpam/modules/pam_ssh/pam_ssh.c 1.44.2.1.6.2
RELENG_8
src/lib/libpam/modules/pam_ssh/pam_ssh.c 1.45.2.3
RELENG_8_2
src/UPDATING 1.632.2.19.2.7
src/sys/conf/newvers.sh 1.83.2.12.2.10
src/lib/libpam/modules/pam_ssh/pam_ssh.c 1.45.2.2.4.2
RELENG_8_1
src/UPDATING 1.632.2.14.2.10
src/sys/conf/newvers.sh 1.83.2.10.2.11
src/lib/libpam/modules/pam_ssh/pam_ssh.c 1.45.2.2.2.2
RELENG_9
src/lib/libpam/modules/pam_ssh/pam_ssh.c 1.47.2.2
RELENG_9_0
src/lib/libpam/modules/pam_ssh/pam_ssh.c 1.47.2.1.2.2
- -------------------------------------------------------------------------
- -------------------------------------------------------------------------
stable/7/ r228421
releng/7.4/ r228843
releng/7.3/ r228843
stable/8/ r228420
releng/8.2/ r228843
releng/8.1/ r228843
stable/9/ r228410
releng/9.0/ r228414
- -------------------------------------------------------------------------
http://security.FreeBSD.org/advisories/FreeBSD-SA-11:09.pam_ssh.asc
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.18 (FreeBSD)
vKMAn116aLADxmdYsyZ5WdSrfFTRt3Xm
=Y+ar
-----END PGP SIGNATURE-----
_______________________________________________
freebsd-announce@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/freebsd-announce
To unsubscribe, send any mail to "freebsd-announce-unsubscribe@freebsd.org"
No comments:
Post a Comment