Cyrus IMSP remote root vulnerability Dec 15 2003 06:55PM
Felix Lindner (felix lindner nruns com)

n.runs GmbH
http://www.nruns.com/ security (at) nruns (dot) com [email concealed]
n.runs-SA-2003.001 15-Dec-2003

Vendor: Andrew Systems Group, Carnegie Mellon (cmu.edu)
Product: Cyrus IMSP
Vulnerability: Buffer overflow in address book handling
Affected Releases: 1.4, 1.5a6, 1.6a3, 1.7
NOT Affected Releases: -
Severty: HIGH
CERT tracking: VU#933878
CVE: n/a

Vendor communication:
08.12.2003 Initial notification
08.12.2003 Rob Siemborski answers
08.12.2003 Rob Siemborski sends a patch
09.12.2003 n.runs tests the patch and finds it to be correct
09.12.2003 CERT VU# assigned
12.12.2003 Rob Siemborski sends the new versions
15.12.2003 public release

Cyrus IMSP is a implementation of the IMSP protocol [2].

"The Internet Message Support Protocol (IMSP) is designed to support
the provision of mail in a medium to large scale operation. It is
intended to be used as a companion to the IMAP4 protocol [IMAP4],
providing services which are either outside the scope of mail access
or which pertain to environments which must run more than one IMAP4
server in the same mail domain. The services that IMSP provides are
extended mailbox management, configuration options, and address

There is a remotely exploitable buffer overflow in the Cyrus IMSPd.
The vulnerability can be triggered before authentication. The IMSP
daemon is required to run as root.

In the function abook_dbname, a sprintf() call takes place. The
function takes two char pointers (dbname and name), which are later
used in the sprintf() call:

sprintf(dbname, abookdb, ownerlen, name, name);

abookdb is defined as

static char abookdb[] = "user/%.*s/abook.%s";

Several functions in the code use abook_dbname() and supply a local
char buffer of 256 bytes as first argument to the function. Since the
second argument "name" is controlled by the user in serveral protocol
messages [2], a remotely exploitable buffer overflow is created.

n.runs has a prove of concept exploit for the issue discussed.

Andrew Systems Group has released new versions. Older versions are
no longer supported.



Bug found by Felix Lindner and Michael Guenther of n.runs GmbH.
Additional credits to Steffen Weinreich for support during research.

Greets to Halvar, Johnny Cyberpunk, Nicolas Fischbach, all@EEye


[1] http://asg.web.cmu.edu/cyrus/download/
[2] http://asg.web.cmu.edu/cyrus/rfc/imsp.html

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