Users login

Create an account »


Users login

Home » Hacking News » FreeBSD-SA-02:34.rpc


by Nikola Strahija on August 1st, 2002 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

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:


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
# fetch

b) Execute the following commands as root:

# cd /usr/src
# patch .

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
- -------------------------------------------------------------------------
- -------------------------------------------------------------------------

VII. References

Version: GnuPG v1.0.7 (FreeBSD)

Newsletter signup

Signup to our monthly newsletter and stay in touch with IT news!

Free E-books

We've got ebooks! But they're not online. :( Please give us a few days to bring downloads back.


Have something to say or just wanna drop us a line? Please keep this in mind: to spam, we reply with spam.

Contact us »