https://bugs.winehq.org/show_bug.cgi?id=37063
--- Comment #7 from dwmw2@infradead.org dwmw2@infradead.org --- Regarding the buffer layout for DecryptMessage, these are quite enlightening:
http://rc.quest.com/viewvc/authtest/trunk/sspi/wrap.c?r1=57&r2=67&pa... (which links to http://msdn.microsoft.com/en-us/magazine/cc301890.aspx )
"When you receive a GSSAPI encrypted or signed message, you'll describe it with a buffer of type SECBUFFER_STREAM, as shown in Figure 3, and provide that buffer along with a second buffer of type SECBUFFER_DATA that will receive the decrypted message."