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Date: Wed, 06 May 2015 10:16:43 +0200
From: Frank Dittrich <frank.dittrich@...lbox.org>
To: john-dev@...ts.openwall.com
Subject: John core: --format=crypt rejecting descrypt hashes when it first
 found some bfegg hashes

Solar,

when john --format=crypt loads bfegg hashes first (length 13), it
doesn't recognize valid descrypt hashes anymore.

First, collect some test hashes for a few formats, using a
bleeding-jumbo binary:

(bleeding-jumbo)run $ ./john --list=format-tests --format=aix-smd5 |cut
-f 3 > hashes.aix-smd5
(bleeding-jumbo)run $ ./john --list=format-tests --format=descrypt |cut
-f 3 > hashes.descrypt
(bleeding-jumbo)run $ ./john --list=format-tests --format=bfegg |cut -f
3 > hashes.bfegg


Now, switch to master:

(bleeding-jumbo)run $ cd ../src/
(bleeding-jumbo)src $ git checkout master
Switched to branch 'master'
Your branch is up-to-date with 'origin/master'.
(master)src $ make -s clean ; make -s -j 16 linux-x86-64-avx
DES_std.c: In function ‘DES_std_set_key’:
DES_std.c:635:17: warning: array subscript is above array bounds
[-Warray-bounds]
   while (DES_key[i++]) k += 2;
                 ^
(master)src $ cd ../run/

Test with valid non-descrypt hashes and invalid bfegg hashes:

(master)run $ ./john hashes.aix-smd5 hashes.bfegg
--wordlist=password.lst --format=crypt
Warning: hash encoding string length 37, type id #0
appears to be unsupported on this system; will not load such hashes.
Warning: hash encoding string length 13, type id #1
appears to be unsupported on this system; will not load such hashes.
Loaded 3 password hashes with 3 different salts (crypt, generic crypt(3)
[?/64])
Self test failed (valid)

Test with invalid bfegg hashes and valid descrypt hashes:

(master)run $ ./john hashes.bfegg hashes.descrypt
--wordlist=password.lst --format=crypt
Warning: hash encoding string length 13, type id #1
appears to be unsupported on this system; will not load such hashes.
No password hashes loaded (see FAQ)


If you switch the sequence, i.e., load descrypt first, then bfegg, all
these hashes are considered valid, but later on you get a

Warning: crypt() returned NULL


In December, 2014, I found this problem in bleeding-jumbo, see
https://github.com/magnumripper/JohnTheRipper/issues/967

Soon we realized it is a core problem.

In January, I reported it to john-users:
http://openwall.com/lists/john-users/2015/01/04/1

In February, commit
https://github.com/magnumripper/JohnTheRipper/commit/8fb75ddcf9a66ce6553cff8852cc02ecd2daf59c
was applied to bleeding-jumbo, basically never rejecting hashes of
length 14 as invalid, but warning if someone uses --format=crypt trying
to crack descrypt hashes.


I think a fix in core would be better, so that magnum can get rid of a
deviation from core.

Frank

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