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Date: Tue, 4 Jul 2006 02:46:28 +0400
From: Solar Designer <>
Subject: Re: tcb and friends with shadow-utils 4.0.12

On Mon, Jul 03, 2006 at 09:27:59AM -0600, Vincent Danen wrote:
> I'd been debugging for most of the night, but still came up with nothing
> concrete.  I wish I had, but I didn't, so I'm still suspecting things
> until I can actually find the culprit.

Oh, I was implying that you would run the passwd program (or whatever
else segfaults) under gdb and see just where the segfault occurs.  It
would not take that long to do.

> >      FreeBSD-style MD5-based
> > [...]
> >        Iteration count
> >               1000
> Interesting.  I must have missed that when I was reading the manpage,
> thanks.  I didn't think that the count would have been the problem... is
> "count" only useful for bcrypt then (in a real-world scenario)?

Currently, variable iteration counts are supported for bcrypt and for
the BSDI-style DES-based hashes ("prefix=_").  The latter are supported
for compatibility with weird systems only, so you would most likely not
use them in practice.

> Ie if someone wants to use md5 passwords, crypt should just be removed,
> correct?

(I assume that you meant "count", not "crypt".)  Yes, that's correct.

> [vdanen@...ld SOURCES]$ perl -e 'print crypt("foo", "\$2a\$05\$abcdefghijklmnopqrstuu"), "\n"'
> Segmentation fault

OK, this suggests that the problem is in fact with crypt_blowfish or the
way it is integrated or compiled.  And I think that I know what it is -
most likely, you need to increase BF_FRAME in x86.S:;r2=1.5

Sorry it did not occur to me to mention this to you before.

BTW, if this is indeed the problem, gdb would make it obvious immediately.
You would see that the program crashes on a "hlt" - and there's only one
such instruction in our stuff that you're integrating.

Alexander Peslyak <solar at>
GPG key ID: B35D3598  fp: 6429 0D7E F130 C13E C929  6447 73C3 A290 B35D 3598 - bringing security into open computing environments

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