Date: Thu, 12 Apr 2012 11:03:52 +0200 From: magnum <john.magnum@...hmail.com> To: john-dev@...ts.openwall.com Subject: Re: MSCash2 formats reliability & usability On 04/12/2012 12:17 AM, Solar Designer wrote: > 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: IMO we should not drop the iteration count support. Any admin can raise it with a change in the registry, and MS may bump the default at any time. > $DCC2$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): > > 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]) That's a bug. I or Jim should have a look at this. > 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. Assuming that this is the correct > value to use, we should specify SALT_SIZE as (11*4+4) right away. Yes, that sounds weird. > 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. This is clearly also a bug. Mscash should at least reject the $DCC2$ tag. > Yet another issue is that strings of the form something#32hexdigits are > valid for "hmac-md5", so that's what the above ones are autodetected as. > Perhaps we want to have mscash and mscash2 (as well as their CUDA and > OpenCL varieties) checked before hmac-md5. Maybe we should rename > hmacMD5_fmt_plug.c into non-plug and register it explicitly after other > stuff. For consistency, maybe we should do it for hmacSHA1_fmt_plug.c > as well. SHA-2 based HMACs are already non-plugins for another reason. I'll have a look at this. > Finally, as it relates to the CUDA and OpenCL formats for mscash2, these > recognize only a subset of inputs that the CPU mscash2 format does. > Can we please bring the three in sync, including maybe by dropping > support for weird inputs (not actually used by anyone) in the CPU format? > > BTW, the CUDA and OpenCL formats do not have the salts bug Unless there are specific reasons, prepare(), valid(), get_salt() and several other functions could/should be identical between the GPU and non-GPU formats (once bugs are gone), and then they will behave the same. At that point I think all three should use the same set of test vectors too. magnum
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