From: Craig Wright (cwright@bdosyd.com.au)
Date: Thu Sep 22 2005 - 02:41:17 EDT
First "You can't precompile that data into a rainbow, you know?". Please
explain why not. HMAC-MD5 message authentication and MD4 are used to
create the challenge. There are rainbow tables for both of these - yes
they take more time to search the challenges but they exist. Publicly
available MD4 rainbow tables are still in early development and mostly
only cover "alpha numeric"...but they exist.
Yes (before you state that this does not supply an attacker with the
password itself) I do understand that using a rainbow table against the
challenge hash does not give you the password itself. But it can give
you access to the system. Personally what I care about is if the system
is accessed not if the password is known by the attacker. If I have
access to the system I can do damage. Install a keylogger for example if
all I wanted was the password.
"Well, that's an issue with the client"...well we are talking a client
server environment. Both are necessary. Yes IBM created Lanman, I read
the RFC when they first submitted it, but MS implemented it, not IBM. PS
to this, MSFT are dropping NTLMv2 at the expense of causing issues with
backward compatibility... Please explain why if "NTLMv2 is tight". This
is a BIG step for MSFT and one I do really applaud.
***---***---*** Gratuitous MSFT Quote ***---***---***
"All three algorithms (MD4, MD5 and DES - my my... NTLMv2) show signs of
"extreme weakness" and have been banned", Michael Howard - Microsoft.
***---***---*** Gratuitous MSFT Quote ***---***---***
As I said earlier "Kerberos support with IPsec" And by this yes
certificates are the best. I still stick by IPsec based auth as I did
state in an earlier post "Kerberos support with IPsec" which is a valid
option as I originally stated it, the alternative being Kerberos without
IPsec. IPsec is used in this case to protect the traffic between the
systems.
Why authentication as a term for IPsec. Because AH is used to negotiate
between the client and the server. (and I also know that the domain
controllers do not use IPsec to send encrypted Kerberos info to each
other and that this needs to be taken into account in the design and
placement of AD domain systems).
Though preshared keys are supported - certificates are better. These are
used to setup the IPsec session which is used to protect the Kerberos
key exchange.
Thus the first stage - before the initial "TGS request for a ticket" is
to have encryption between the client and the AD server thus further
protecting the process. AN IPsec session is later used from the Kerberos
client to the application server (and yes I have not gone into the
stages used by the TGS and AS, have just passed over the TGT, not even
mentioned the 3 subprotocols used etc) protecting the ticket exchange.
Craig
PS - I know that this is simplified and that I could expand this further
(into a few hundred page paper) to cover all the stages and miss
nothing.
PPS I have not even gone into collision analysis against MD5 or MD4 both
of which are viable options
-----Original Message-----
From: Thor (Hammer of God) [mailto:thor@hammerofgod.com]
Sent: 22 September 2005 3:46
To: Craig Wright; pand0ra.usa@gmail.com; pen-test@securityfocus.com
Subject: Re: Passwords with Lan Manager (LM) under Windows
Well, that's an issue with the client, not NTLMv2. NTLMv2 is tight. LM
sucks- that's obvious (and it was IBM, not MS that gave us that one.)
And yes, you can use precomputed tables against NTLM hashes, but not
against NTLMv2... The NTLM hash is keyed off of the password, but NTLMv2
hashes up the password with the user's domain/user data when generating
the key...
You can't precompile that data into a rainbow, you know?
Regarding the "IPsec based auth" reference (here I go again), I'd have
to say that there is no such thing... IPSec negotiation in Windows can
be based on one of three mechanisms: A pre-shared key, Kerberos, or a
cert-- it is not an authentication protocol in itself... (the cert being
the strongest IMO).
t
----- Original Message -----
From: "Craig Wright" <cwright@bdosyd.com.au>
To: "Thor (Hammer of God)" <thor@hammerofgod.com>;
<pand0ra.usa@gmail.com>; <pen-test@securityfocus.com>
Sent: Wednesday, September 21, 2005 10:05 PM
Subject: RE: Passwords with Lan Manager (LM) under Windows
Further to the last post
There are a number of issues with NTLMv2 and legacy applications such as
Windows RAS that cause lower levels of authentication
I still say that Kerberos or IPsec based auth is the best policy in
windows. LanMan, NTLMv1 or V2 are vulnerable.
Precomputed tables may have been uncommon 12 months ago - but that was
then and this is now.
Cain & Abel will use sorted Rainbow Tables for Cryptanalysis attacks
Craig
-----Original Message-----
From: Thor (Hammer of God) [mailto:thor@hammerofgod.com]
Sent: 22 September 2005 12:00
To: Craig Wright; pand0ra.usa@gmail.com; pen-test@securityfocus.com
Subject: Re: Passwords with Lan Manager (LM) under Windows
----- Original Message -----
From: "Craig Wright" <cwright@bdosyd.com.au>
To: <pand0ra.usa@gmail.com>; <pen-test@securityfocus.com>
Sent: Wednesday, September 21, 2005 12:32 PM
Subject: RE: Passwords with Lan Manager (LM) under Windows
> Even NTLMv2 will break the hashing into chunks which are able to be
> individually broken down.
I'm not sure what you mean... NTLMv2 uses a single 128bit key for the
hash, challenge and response... Or are you referring to the NTLM2
session response key (56+56+16)? If so, that is not the same thing as
NTLMv2...
Can
you elaborate please ?
t
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