-----BEGIN PGP SIGNED MESSAGE----- ============================================================================= FreeBSD-SA-02:34.rpc Security Advisory The FreeBSD Project Topic: Sun RPC XDR decoder contains buffer overflow Category: core Module: libc Announced: 2002-08-01 Credits: ISS X-Force Affects: All releases of FreeBSD up to and including 4.6.1-RELEASE-p5 Corrected: 2002-08-01 12:23:20 UTC (RELENG_4) 2002-08-01 12:23:40 UTC (RELENG_4_6) 2002-08-01 12:23:58 UTC (RELENG_4_5) 2002-08-01 12:24:20 UTC (RELENG_4_4) FreeBSD only: NO 0. Revision History v1.0 2002-07-31 Initial release v1.1 2002-08-01 Corrected patch I. Background Sun RPC is a remote procedure call framework which allows clients to invoke procedures in a server process over a network somewhat transparently. XDR is a mechanism for encoding data structures for use with RPC. NFS, NIS, and many other network services are built upon Sun RPC. The FreeBSD C runtime library (libc) contains an XDR encoder/decoder derived from Sun's RPC implementation. II. Problem Description An error in the calculation of memory needed for unpacking arrays in the XDR decoder can result in a heap buffer overflow. III. Impact Any application using Sun RPC may be vulnerable to the heap buffer overflow. Depending upon the application, this vulnerability may be exploitable and lead to arbitrary code execution. Though no exploits are known to exist currently, many RPC-based services run as the superuser (such as NFS, the NIS server, rpc.statd, and others) and thus this vulnerability should be considered high-risk. No RPC-based services are enabled by default in FreeBSD installations. IV. Workaround Do not run any RPC-based services. The RPC-based services running on a machine may be determined by: # rpcinfo -p To disable any RPC-based services at next boot, add (or change if it is already present) the following lines in /etc/rc.conf: portmap_enable="NO" nfs_client_enable="NO" nfs_server_enable="NO" nis_client_enable="NO" nis_server_enable="NO" V. Solution Do one of the following: 1) Upgrade your vulnerable system to 4.6-STABLE; or to the RELENG_4_6, RELENG_4_5, or RELENG_4_4 security branch dated after the correction date (4.6.1-RELEASE-p6, 4.5-RELEASE-p15, or 4.4-RELEASE-p22). 2) To patch your present system: The following patch has been verified to apply to FreeBSD 4.4, 4.5, and 4.6 systems. a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility. # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-02:34/rpc.patch # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-02:34/rpc.patch.asc b) Execute the following commands as root: # cd /usr/src # patch < /path/to/patch c) Recompile the operating system as described in . Note that any statically linked applications that are not part of the base system (i.e. from the Ports Collection or other 3rd-party sources) must be recompiled if they use Sun RPC. All affected applications must be restarted in order to use the corrected library. Though it is not required, rebooting may be the easiest way to accomplish this. VI. Correction details The following list contains the revision numbers of each file that was corrected in FreeBSD. Path Revision Branch - ------------------------------------------------------------------------- src/lib/libc/xdr/xdr_array.c RELENG_4 1.8.2.3 RELENG_4_6 1.8.10.4 RELENG_4_5 1.8.8.3 RELENG_4_4 1.8.6.3 src/sys/conf/newvers.sh RELENG_4_6 1.44.2.23.2.11 RELENG_4_5 1.44.2.20.2.16 RELENG_4_4 1.44.2.17.2.21 - ------------------------------------------------------------------------- VII. References -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.7 (FreeBSD) iQCVAwUBPUkpkFUuHi5z0oilAQF7TQP9H50V3qUsZcWC5nemnMO9CL+QBmIuuGkE C7p3mBxcH6mS5EmUU4zFOum4QSaEh9J47I7CGcS+sNg7JN5lfK1oSwsE9JidbZz4 kx9cQrx+rppQuQyK9tK4TXVXz0PiUdZMs3vgytJDuAOu38bg3ttUd4jhTIKHnLGh NMjQMH2vNUk= =yP62 -----END PGP SIGNATURE-----