you know what? this sort of thing makes me laugh. hmm, what functions

have we got.  and what data do we have.  hmm.. i wonder what the NTLMv2
user session key can be... hmmm... weell.... there's some hidden data
here, generated from the user password that doesn't go over-the-wire,
so that's _got_ to be involved.  and... that bit of data took a lot of
computation to produce, so it's probably _also_ involved... and md4 no, md5?
no, how about hmac_md5 yes let's try that one (the other's didn't work)
oh goodie, it worked!

i love it when this sort of thing happens.  took all of fifteen minutes to
guess it.  tried concatenating client and server challenges.  tried
concatenating _random_ bits of client and server challenges.  tried
md5 of the above.  tried hmac_md5 of the above.  eventually, it boils down
to this:

kr = MD4(NT#,username,domainname)
hmacntchal=hmac_md5(kr, nt server challenge)
sess_key = hmac_md5(kr, hmacntchal);

source/include/client.h

@@ -74,6 +74,8 @@ struct pwd_info
 	uchar lm_cli_chal[8];
 	uchar nt_cli_chal[128];
 	size_t nt_cli_chal_len;
+
+	uchar sess_key[16];
 };
 
 struct cli_state {