DSSync encryption notes

[Andrew Bartlett]

I just wanted to put some observations to the list about the encryptped
blobs in the DRSUAPI replication.

Firstly, this is the command I've been running:

bin/smbtorture ncacn_ip_tcp:win2k3dc.win2k3.abartlet.net RPC-DSSYNC
-Uadministrator%penguin --option=dssync:print_pwd_blobs=true
--option=realm=win2k3.abartlet.net --option=workgroup=win2k3ab
--option=ntlmssp_client:ntlm2=false
--option=ntlmssp_client:keyexchange=false

This particular setup ensures that the base encryption keys for NTLMSSP
remain constant, which is an important for the crypt-analysis of this
problem.

Interestingly, the output (in terms of encrypted blobs) varies between
runs.  I also note that attributes appear 20 bytes longer than I would
have expected.  My suspicion is that each value is encrypted with the
hash of a 16 or 20 byte 'confounder' and the session key, much like the
samr_set_password_ex call. 

I'm yet to figure out what algorithms are used for the hash, but I
strongly suspect that the actual data encryption is RC4 (due to
irregular length data blobs, which discount a block cipher).

At some point I'll write up a 'challenge' to narrow this down further.

Andrew Bartlett
-- 
Andrew Bartlett                                http://samba.org/~abartlet/
Authentication Developer, Samba Team           http://samba.org
Student Network Administrator, Hawker College  http://hawkerc.net
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: This is a digitally signed message part
Url : http://lists.samba.org/archive/samba-technical/attachments/20051223/d6d8f6af/attachment.bin