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freetds - Re: [freetds] Backporting NTLMv2 (was: NTLMv2 support for domain logins using freetds)

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  • From: Peter Deacon <peterd AT iea-software.com>
  • To: FreeTDS Development Group <freetds AT lists.ibiblio.org>
  • Subject: Re: [freetds] Backporting NTLMv2 (was: NTLMv2 support for domain logins using freetds)
  • Date: Fri, 1 Aug 2008 10:59:27 -0700 (Pacific Daylight Time)

On Fri, 1 Aug 2008, Frediano Ziglio wrote:

Il giorno gio, 31/07/2008 alle 18.25 -0400, Sergey Sikorskiy ha scritto:
Hi,

I've just checked with Microsoft web-site and found detailed
documentation for NTLM.
http://msdn.microsoft.com/en-us/library/cc207842.aspx

This documentation clearly says that "(1.7) "The NTLM authentication
version is not negotiated by the protocol. It must be configured on
both the client and the server prior to authentication. The version is
selected by the client, and requested during the protocol negotiation.
If the server does not support the version selected by the client,
authentication fails."

The rest is negotiable, including sending of LMv2 hash, which won't be
sent in my implementation.

yes, but I think that client should say: I support all these and server
reply, you can use such... If we support all versions we should be
always able to negotiate the correct (most secure) authentication.
I think that is NTLM2 is negotiated either NTLMv2 or NTLM2 should be
used. At this point I think that if we have valid Target Info NTLMv2
should be negotiated...

IMHO with these sorts of things where there is no serious machinary to perform secure protocol negotiation both client and server side configuration is required to prevent attacks which can cause less secure protocols being negotiated in order to take advantage of a weakness.

For example v2 supports mutual authentication, earlier protocols did not. If your able to MITM the connection and negotiate a protocol without mutual auth ... there is little point remaining in having v2 as its enhanced security properties can simply be bypassed.

take care,
Peter




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