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Date: Mon, 22 Mar 2010 20:55:15 +0300
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re: raw-md5 from unicode string

On Mon, Mar 22, 2010 at 04:09:41PM +0100, drobik wrote:
> is possible to use JtR to get password from raw-md5 hash, when md5
> hash is computed from unicode string ?

What character encoding, specifically?  It sounds like you're trying to
represent your string in UCS-2, but is that what you really need?  As
W.A. has correctly pointed out, UTF-8 would work just fine - of course,
if that's what your hash was calculated from.

> I tried to solve this problem by using external rule (to insert \x00
> after every char), but it doesn't work.
> It looks like \x00 works as string terminator for JtR in this case.

Indeed.

> Is something wrong with my external rule

It's precisely what you suspected - you can't embed a NUL byte in a string.

> or is another way to solve this problem?

You need to start by defining the problem fully.  If you do need to
embed NUL bytes, then you'll have to modify the source code for JtR (or
for a specific "format").  Maybe do it the way NTLM hashes are
implemented in the jumbo patch (they have to expand the string to UCS-2
internally).

> I tried to use simplel perl script to insert \x00 char after every
> char from password, but it's little bit slow (probably perl script
> isn't too fast):
> john --incremental=lanman --external=myfilter --stdout | perl
> insert00.pl | john --stdin passwd.txt

This is not just slow, it also "does not work", for the same reason
(can't have embedded NUL bytes in wordlist entries).

Alexander

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