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Date: Thu, 12 Mar 2020 03:10:16 +0100
From: magnum <john.magnum@...hmail.com>
To: john-users@...ts.openwall.com
Subject: Re: What format is used to crack a vBulletin hash with a
fixed 30 byte salt?
On 2020-03-11 15:23, Ian Onthax wrote:
> I am trying to use john to crack a vBulletin > 3.8.5 hash, which has a fixed 30 byte salt.
>
> I've been searching and searching, and have seen tried using format types dynamic_6 and dynamic_7, also dynamic_1007
$ ./john -list=subformats | grep -i vbulletin
UserFormat = dynamic_1007 type = dynamic_1007: md5(md5($p).$s) (vBulletin)
Yeah, should be 1007 but I'm not sure about versions.
> An example of the salt+hash I am trying to crack (changed of course):
> 50cff86a9fe4a3ccbc67e95272321dbe:_j&+jx^uzJ"S*gFn$k*s)&b=&0-~#7
>
> I've tried replacing the colon with a percent sign and specifying the percent sign as the field separator, and keeping the colin as is.
Did you read doc/DYNAMIC? In dynamic format, the salt delimiter is $ so
you should probably use:
50cff86a9fe4a3ccbc67e95272321dbe$_j&+jx^uzJ"S*gFn$k*s)&b=&0-~#7
Note that the above is the *ciphertext* and within it the $ is the salt
delimiter. We also have a : field delimiter for other fields, like
username:50cff86a9fe4a3ccbc67e95272321dbe$_j&+jx^uzJ"S*gFn$k*s)&b=&0-~#7:::username@...mple.com
(...)
If you can preserve at least the login and gecos fields from whatever
data you have, your chance of cracking them is a whole lot better. But I
digress...
The salt might contain nasty characters like ":" or "$" or even tabs or
vertical spaces, so it's safest to convert to hex like so:
echo '_j&+jx^uzJ"S*gFn$k*s)&b=&0-~#7' | perl -ne 'chomp; print "HEX\$",
unpack("H*", $_), "\n"'
HEX$5f6a262b6a785e757a4a22532a67466e246b2a732926623d26302d7e2337
And the full ciphertext becomes:
50cff86a9fe4a3ccbc67e95272321dbe$HEX$5f6a262b6a785e757a4a22532a67466e246b2a732926623d26302d7e2337
Now, for some reason john doesn't accept that (even with
-bare-always-valid=yes which you should read about in doc/OPTIONS).
Let's check out what Dynamic 1007 can handle:
$ ./john -form:dynamic_1007 --list=format-all-details | grep " size\b"
Binary size 16
Salt size 23
Apparently that format can only take up to 23 characters of salt. Maybe
we have some other dynamic with better capacity?
$ ./john --list=subformats | grep -F 'md5(md5($p).$s)'
Format = dynamic_6 type = dynamic_6: md5(md5($p).$s)
Format = dynamic_16 type = dynamic_16: md5(md5(md5($p).$s).$s2)
UserFormat = dynamic_1007 type = dynamic_1007: md5(md5($p).$s) (vBulletin)
UserFormat = dynamic_2006 type = dynamic_2006: md5(md5($p).$s) (PW > 55
bytes)
$ ./john -form:dynamic_2006 --list=format-all-details | grep "Salt size"
Salt size 64
Bingo!
$ ./john test.in -format:dynamic_2006
Using default input encoding: UTF-8
Loaded 1 password hash (dynamic_2006 [md5(md5($p).$s) (PW > 55 bytes)
256/256 AVX2 8x3])
Proceeding with single, rules:Single
Press 'q' or Ctrl-C to abort, almost any other key for status
(...)
Cheers,
magnum
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