FreeBSD Security Advisory FreeBSD-SA-11:08.telnetd

Fabricante: FreeBSD
Fecha: 23/12/2011
Identificador: FreeBSD-SA-11:08.telnetd
FreeBSD Security Advisory FreeBSD-SA-11:08.telnetd
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 ============================================================================= FreeBSD-SA-11:08.telnetd Security Advisory The FreeBSD Project Topic: telnetd code execution vulnerability Category: core Module: contrib Announced: 2011-12-23 Affects: All supported versions of FreeBSD. Corrected: 2011-12-23 15:00:37 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) 2011-12-23 15:00:37 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) 2011-12-23 15:00:37 UTC (RELENG_9, 9.0-STABLE) 2011-12-23 15:00:37 UTC (RELENG_9_0, 9.0-RELEASE) CVE Name: CVE-2011-4862 For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit . I. Background The FreeBSD telnet daemon, telnetd(8), implements the server side of the TELNET virtual terminal protocol. It has been disabled by default in FreeBSD since August 2001, and due to the lack of cryptographic security in the TELNET protocol, it is strongly recommended that the SSH protocol be used instead. The FreeBSD telnet daemon can be enabled via the /etc/inetd.conf configuration file and the inetd(8) daemon. The TELNET protocol has a mechanism for encryption of the data stream (but it is not cryptographically strong and should not be relied upon in any security-critical applications). II. Problem Description When an encryption key is supplied via the TELNET protocol, its length is not validated before the key is copied into a fixed-size buffer. III. Impact An attacker who can connect to the telnetd daemon can execute arbitrary code with the privileges of the daemon (which is usually the "root" superuser). IV. Workaround No workaround is available, but systems not running the telnet daemon are not vulnerable. Note that the telnet daemon is usually run via inetd, and consequently will not show up in a process listing unless a connection is currently active; to determine if it is enabled, run $ ps ax | grep telnetd | grep -v grep $ grep telnetd /etc/inetd.conf | grep -vE '^#' If any output is produced, your system may be vulnerable. V. Solution Perform one of the following: 1) Upgrade your vulnerable system to 7-STABLE or 8-STABLE, or to the RELENG_8_2, RELENG_8_1, RELENG_7_4, or RELENG_7_3 security branch dated after the correction date. 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, 8.2, and 8.1 systems. a) Download the patch from the location below, and verify the detached PGP signature using your PGP utility. # fetch http://security.FreeBSD.org/patches/SA-11:08/telnetd.patch # fetch http://security.FreeBSD.org/patches/SA-11:08/telnetd.patch.asc b) Execute the following commands as root: # cd /usr/src # patch < /path/to/patch # cd /usr/src/lib/libtelnet # make obj && make depend && make && make install # cd /usr/src/libexec/telnetd # make obj && make depend && make && make install 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 the i386 or amd64 platforms can be updated via the freebsd-update(8) utility: # freebsd-update fetch # freebsd-update install VI. Correction details The following list contains the revision numbers of each file that was corrected in FreeBSD. CVS: Branch Revision Path - ------------------------------------------------------------------------- RELENG_7 src/crypto/heimdal/appl/telnet/libtelnet/encrypt.c 1.1.1.2.24.1 src/contrib/telnet/libtelnet/encrypt.c 1.9.24.1 RELENG_7_4 src/UPDATING 1.507.2.36.2.7 src/sys/conf/newvers.sh 1.72.2.18.2.10 src/crypto/heimdal/appl/telnet/libtelnet/encrypt.c 1.1.1.2.38.1 src/contrib/telnet/libtelnet/encrypt.c 1.9.40.2 RELENG_7_3 src/UPDATING 1.507.2.34.2.11 src/sys/conf/newvers.sh 1.72.2.16.2.13 src/crypto/heimdal/appl/telnet/libtelnet/encrypt.c 1.1.1.2.36.1 src/contrib/telnet/libtelnet/encrypt.c 1.9.38.2 RELENG_8 src/crypto/heimdal/appl/telnet/libtelnet/encrypt.c 1.1.1.3.2.1 src/contrib/telnet/libtelnet/encrypt.c 1.9.36.2 RELENG_8_2 src/UPDATING 1.632.2.19.2.7 src/sys/conf/newvers.sh 1.83.2.12.2.10 src/crypto/heimdal/appl/telnet/libtelnet/encrypt.c 1.1.1.3.8.1 src/contrib/telnet/libtelnet/encrypt.c 1.9.36.1.6.2 RELENG_8_1 src/UPDATING 1.632.2.14.2.10 src/sys/conf/newvers.sh 1.83.2.10.2.11 src/crypto/heimdal/appl/telnet/libtelnet/encrypt.c 1.1.1.3.6.1 src/contrib/telnet/libtelnet/encrypt.c 1.9.36.1.4.2 RELENG_9 src/crypto/heimdal/appl/telnet/libtelnet/encrypt.c 1.1.1.3.10.1 src/contrib/telnet/libtelnet/encrypt.c 1.9.42.2 RELENG_9_0 src/crypto/heimdal/appl/telnet/libtelnet/encrypt.c 1.1.1.3.12.1 src/contrib/telnet/libtelnet/encrypt.c 1.9.42.1.2.2 - ------------------------------------------------------------------------- Subversion: Branch/path Revision - ------------------------------------------------------------------------- stable/7/ r228843 releng/7.4/ r228843 releng/7.3/ r228843 stable/8/ r228843 releng/8.2/ r228843 releng/8.1/ r228843 stable/9/ r228843 releng/9.0/ r228843 - ------------------------------------------------------------------------- VII. References http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-4862 The latest revision of this advisory is available at http://security.FreeBSD.org/advisories/FreeBSD-SA-11:08.telnetd.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (FreeBSD) iEYEARECAAYFAk70nOoACgkQFdaIBMps37IYcwCfXn5aQTfQDe/AnS31JBg+BB1m HJMAmgOE5pUKTlFqLw5UBouMNFfUmu2u =dcyj -----END PGP SIGNATURE-----