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Filename : Authentication.Mechanisms.NTLM.txt
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NTLM
====

There are four authentication submethods inside the NTLM:

 1. LM: server nonce only, highly vulnerable to MITM and rogue server attacks.
 2. NTLM: different algorithm, almost equally vulnerable as LM today.
 3. NTLM2: server and client nonce, but MITM can force downgrade to NTLM/LM.
 4. NTLMv2: server and client nonce, MITM can't force downgrade.

NTLM <password scheme> [Authentication.PasswordSchemes.txt] is required for
NTLM, NTLM2 and NTLMv2.

NTLMv2 can not be negotiated. It must be explicitly enabled on the client side
by setting registry key below to at least 3:

 * Win9x:
   'HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\LSA\LMCompatibility'
 * WinNT:
   'HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\LSA\LMCompatibilityLevel'

Dovecot's NTLM logic is:

 1. If we have only LM password scheme, try LM authentication;
 2. If client sends LM response only (some very old clients do it), try LM too;

 3. If NTLMv2 is guessed (using client response length), try NTLMv2;
 4. If NTLM2 was negotiated, try it;
 5. Otherwise try NTLM.

For more information about NTLM internals, see http://ubiqx.org/cifs/ and
http://davenport.sourceforge.net/ntlm.html

(This file was created from the wiki on 2019-06-19 12:42)