XFOR: Chat Service Fails DPA Authentication with 9-Character User Names

• Microsoft Exchange Server, version 5.5
• Microsoft Commercial Internet System version 2.0

SYMPTOMS

Chat clients with nine character user names get "Login Failures" when they try to connect to Chat servers using DPA authentication.

CAUSE

The problem occurs because chat clients encode the length of a nine character username as a '\t' per the IRCX spec; the IRCX specifies that all TAB (ASCII TAB = 0x09) characters are to be escaped as a backslash followed by a 't'. In this case when the Chat service decoded the authentication message from the client, it incorrectly decoded '\t' as 0x07 (the ASCII BEL code). The resulting decoded string length of 0x07 resulted in the nine character user name being truncated to seven characters long, thus failing DPA authentication.

RESOLUTION

To resolve this problem, obtain the latest service pack for Exchange Server version 5.5. For additional information, please see the following article in the Microsoft Knowledge Base:

Q191014 XGEN: How to Obtain the latest Exchange Server 5.5 Service Pack

STATUS

Microsoft has confirmed this to be a problem in the Chat Service that is included with the Microsoft products listed at the beginning of this article. This problem was first corrected in Exchange Server 5.5 Service Pack 3.

Additional query words:

Keywords : prodmcis2 prodICS MCIS_MSG exc55 EXC55SP3Fix
Version : winnt:2.0,5.5
Platform : winnt
Issue type : kbbug