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Date: Thu, 12 Apr 2012 14:40:38 -0500
From: "jfoug" <jfoug@....net>
To: <john-dev@...ts.openwall.com>
Subject: RE: MSCash2 formats reliability & usability
>From: Solar Designer [mailto:solar@...nwall.com]
>
>Jim, magnum, Lukas, Sayantan -
>
>We have three JtR formats for MSCash2: CPU, CUDA, OpenCL.
>
>The CPU one supports many different representations of MSCash2 hashes
>and has many test vectors of different form ($DCC2$ prefix present vs.
>not, iteration count included vs. not, username included vs. separate).
>This is great, although the format's support for variable iteration
>counts is probably unneeded (there are no non-10240 MSCash2 hashes in
>the wild, as far as I'm aware). However, I think with all this
>complexity the format is also more prone to bugs than it has to be.
>For example, with this combination of hashes in the input file:
>
>$DCC2$Joe#e09b38f84ab0be586b730baf61781e30
>$DCC2$test#a86012faf7d88d1fc037a69764a92cac
>$DCC2$administrator#a150f71752b5d605ef0b2a1e98945611
>$DCC2$administrator#c14eb8279e4233ec14e9d393637b65e2
>$DCC2$administrator#8ce9c0279b4e6f226f52d559f9c2c5f3
>$DCC2$administrator#2fc788d09fad7e26a92d12356fa44bdf
>$DCC2$administrator#6aa19842ffea11f0f0c89f8ca8d245bd
>
>John does not recognize the different salts (should be 3 different):
I have tightened up prepare in mscash1 and mscash2.
>user@...l:~/john/magnum-jumbo/run$ ./john pw-bug -fo=mscash2 Loaded 7
>password hashes with no different salts (M$ Cache Hash 2 (DCC2) [SSE2i
>8x])
They were being loaded totally wrong. The string being loaded for the
first one, was:
$DCC2$10240#?#$dcc2$joe#e09b38f84ab0be586b730baf61781e30
Thus, in that form, ALL were getting the salt of ? as the salt.
>I guess there's a bug in prepare(), get_salt() or/and SALT_SIZE. By the
>way, it is weird how SALT_SIZE is defined as 11*4, but is actually put
>into the struct as SALT_SIZE+4.
Because I 'stole' the first 4 bytes (array of 2 2 byte values), to store the
iteration count, and the salt len, so they would be 'ready' to be used and
not have to be computed over and over again. I simply left the salt 'junk'
alone, and bumped up the size in bytes of the salt in the format structure
by 4.
Looking at it now, the SALT_LEN #define is only used within setting the
format
struct, so I have simply modified the #define.
>Assuming that this is the correct value
>to use, we should specify SALT_SIZE as (11*4+4) right away.
>
>Another issue is that strings of the above form are somehow also
>recognized as "mscash". I guess this has to do with
>mscash1_fmt_plug.c's prepare() being too willing to turn anything into
>what its valid() would recognize. It should probably perform some
>validation first.
Fixed in patch. It 'only' appends the M$ (or $DCC2$1024# for cash2),
IF the field 1 is 32 byte hex number (i.e. raw). So yes, it did get
some added validation.
Download attachment "jumbo_unstable_mscash_1_2_perpare_fixes-01.diff" of type "application/octet-stream" (2956 bytes)
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