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Lotus Notes Protocol Authentication Buffer Overflow
Date: 2003-03-14

Author : Rapid 7 Security Advisories - advisory@rapid7.com

1. Affected system(s):

KNOWN VULNERABLE:
o Lotus Notes R4
o Lotus Notes R5 up to and including R5.0.11
o Lotus Notes R6 betas and pre-releases

NOT VULNERABLE:
o Lotus Notes R5.0.12
o Lotus Notes R6.0 Gold
o Lotus Notes R6.0.1

UNKNOWN / NOT TESTED:
o Lotus Notes R3 and earlier

2. Summary

Lotus Notes and Domino servers support a proprietary protocol called
NotesRPC, commonly known as the Notes protocol. This protocol is
usually bound to TCP port 1352, but can also use NetBIOS, Netware
SPX, Banyan Vines, and modem dialup for transport.

When a Notes client connects to a Notes server, it authenticates with
the server to establish a session. This authentication consists of a
series of exchanges in which the client and server present each other
with challenges to verify each other's identity.

It is possible for an unauthenticated client to manipulate the data
during this exchange to trigger a buffer overflow on the Notes
server. This allows an attacker to overwrite large sections of the
heap with arbitrary data. While our testing only covered TCP/IP, we
believe it is possible for this overflow to be triggered via other
protocols, including dialup. It is theoretically possible for an
attacker to supply the data in such a way as to compromise the
Notes server's security.

3. Vendor status and information

Lotus
http://www.lotus.com/
http://www.ibm.com/

Lotus was notified and they have fixed this vulnerability. Lotus is
tracking this issue with SPR #DBAR5CJJJS. [1] IBM has also prepared
Technote #1105101, which discusses this vulnerability. [2]

See the References section for more information.

4. Solution

This vulnerability is fixed in R5.0.12 and R6.0 Gold. Customers
running R5.0.11 or earlier (or Notes R6 beta) are advised to upgrade.
R6.0 Gold is not affected, but due to other vulnerabilities
discovered in R6.0 Gold, you should consider upgrading to R6.0.1,
which was released in February 2003.

Domino incremental installers may be downloaded from the following
URL (which has been wrapped):

http://www14.software.ibm.com
/webapp/download/search.jsp?go=y&rs=ESD-DMNTSRVRi&sb=r

For more information on partial mitigation strategies for this
and other Notes vulnerabilities (including best practices for
Internet-facing Domino servers), please see Rapid7's FAQ for
these vulnerabilities at:

http://www.rapid7.com/advisories/R7-0010-info.html

5. Detailed analysis

During NotesRPC authentication, the client sends the server its
distinguished name (DN). The distinguished name is a string that
looks like "CN=John Smith/O=Acme/C=US". The DN string is prefixed
by a 16-bit word that specifies its length. The outer packet
structure contains a header field that refers to the DN field's
length (which is the length of the prefix plus the length of the
DN itself).

If the length specified in the outer header field is less than or
equal to the length specified in the DN field, an error occurs in
the data offset arithmetic such that a total of 65534 bytes are
copied onto the Notes heap (a proprietary structure managed by
Notes API calls such as OSMemoryAllocate). An attacker can supply
all of the bytes to be copied by specifying additional data in the
packet after the DN.

6. References

[1] Lotus SPR #DBAR5CJJJS (URL wrapped)
http://www-10.lotus.com
/ldd/r5fixlist.nsf/Search?SearchView&Query=DBAR5CJJJS

[2] IBM Technote #1105101 (URL wrapped)
http://www-1.ibm.com
/support/docview.wss?rs=482&q=Domino&uid=swg21105101

7. Contact Information

Rapid7 Security Advisories
Email: advisory@rapid7.com
Web: http://www.rapid7.com/
Phone: +1 (212) 558-8700

8. Disclaimer and Copyright

Rapid7, Inc. is not responsible for the misuse of the information
provided in our security advisories. These advisories are a service
to the professional security community. There are NO WARRANTIES
with regard to this information. Any application or distribution of
this information constitutes acceptance AS IS, at the user's own
risk. This information is subject to change without notice.

This advisory Copyright (C) 2003 Rapid7, Inc. Permission is
hereby granted to redistribute this advisory, providing that no
changes are made and that the copyright notices and disclaimers
remain intact.



 

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