A digest in a Session Initiation Protocol (SIP) Referred-By header uses a non-standard base64 encoding in Communications Server 2007

In Microsoft Office Communications Server 2007, the Session Initiation Protocol (SIP) Referred-By header includes a signed digest. This digest guarantees that no intermediate party has altered the basic details of the referral.

The encoding scheme that is used to communicate the signed digest in the Referred-By header is incorrect. Standard base64 encoding should be used, according to the "Request for Comments: 4648" (RFC) document. However, a modified encoding is used that does not communicate the exact length of the data that was encoded. Therefore, a binary-signed binary large object (BLOB) is obtained after the digest in a Referred-By header is decoded. This binary large object may have trailing zero bytes that are appended to it, and these bytes should not be part of the binary large object.

To resolve this issue, install the update package for Communications Server 2007 that is dated August 2008. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

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