188.8.131.52 Principal Name Validation
Digest-Uri indicates the principal name of the service that the client is attempting to connect with, as specified in [RFC2831] section 2.1.2. Servers SHOULD<16> check that the supplied value is correct.
The digest implementation does not do any validation of the digest-uri value. The application that calls the digest authentication validates the principal name specified by the digest-uri. The digest authentication implementation returns the principal name to the calling application.