Re: Potential vulnerabilities of the Microsoft RVP-based Instant Messaging

From: 3APA3A (3APA3A@SECURITY.NNOV.RU)
Date: 03/22/02 

Date:         Fri, 22 Mar 2002 12:42:20 +0300
From: 3APA3A <3APA3A@SECURITY.NNOV.RU>
To: NTBUGTRAQ@LISTSERV.NTBUGTRAQ.COM

Dear Brown, Keith,

--Thursday, March 21, 2002, 9:51:21 PM, you wrote to NTBUGTRAQ@LISTSERV.NTBUGTRAQ.COM:

BK> NTLM does in fact offer integrity and confidentiality protection of
BK> messages after the initial handshake. The session key is a function of
BK> the OWF(password) and the challenge. In the case of pass-through
BK> authentication, the session key is passed from the authority to the
BK> server over a secure channel.

It's only true for secure channel, then encryption is used. And it's
only true for NTLMv2. NTLMv2 can only be used inside domain tree. For
NTLMv1 there is no mutual authentication and m-i-t-m can impersonate
server. If encryption is not used session may be intercepted by m-i-t-m
in any time after initial authentication for both NTLMv1 and NTLMv2.

IM doesn't use secure channel.

NTLM authentication should never be used to access servers outside
domain because it can lead to compromisation of domain account. An
example of such attack is given in SECURITY.NNOV paper on NTLM
authentication in Outlook Express,
http://www.security.nnov.ru/advisories/oespa.asp 

--
~/ZARAZA
Ну а теперь, Уильям, хорошенько поразмыслите над данным письмом. (Твен)

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