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Date: Thu, 10 May 2007 02:42:34 +0400
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re:  Re: Potfile size limitation?

On Wed, May 09, 2007 at 10:09:54PM +0000, -. -PhanTom-. - wrote:
> I am gonna need a little more help to get this working...
> I installed gdb under cygwin, and added "-g" to the flags in the JTR
> makefile:
> 
> CFLAGS = -c -Wall -O2 -fomit-frame-pointer -g
> ASFLAGS = -c
> LDFLAGS = -g

This is almost right.   You should also remove -fomit-frame-pointer in
order to get backtrace ("bt") working.  Sorry, I forgot to mention that.

> "while running under gdb, then type "bt", "i r", "disass $pc-20 $pc+20"
>  in gdb (and post the output of these commands in here"
> 
> (gdb) bt
> No stack.
> (gdb) i r
> The program has no registers now.
> (gdb) disass $pc-20 $pc+20
> No registers.
> (gdb)
> 
> Doesn't look right...?

Of course it doesn't.  You need to actually "run" John under gdb and
have it crash first.  In John's "run" directory, you invoke gdb as:

	gdb ./john

Then in gdb you type:

	run --show passwd

(or whatever command-line options make John crash).  When it crashes
(you should be back to a gdb prompt), you type "bt" and so on.

> Maybe you could try to create a "fake" potfile at aprox 500MB and see
> if the problem also exists under Unix or if it's "just" some windows
> or 32bit overflow thing?

I seriously doubt that the problem is related to file size alone and at
the same time is not OS-specific.  It is far more likely that the
problem is either not directly related to file size or it is specific to
32-bit Windows or Cygwin.  In the former case, I'd need your pot file
rather than just a large file in order to reproduce the problem.  So I'd
rather wait for your gdb outputs before spending more of my time on it.

How many entries do you have in your john.pot, though?  (You can find
out with "wc -l john.pot".)

If you like to experiment, you can try Cygwin's "sort -S 1G" on a large
file (your john.pot or an even larger file) and see if that crashes in a
similar way (indicating that there is a memory size limitation imposed
by Cygwin or Windows' address space layout).

> Btw, a friend tested versions 1.6.31 - 1.6.37 - same error.

That's somewhat inconsistent with your previous report that 1.6.39
doesn't crash.  It is unlikely that I accidentally fixed a bug between
1.6.37 and 1.6.39, but then introduced a similar one in 1.6.40.

> Tried to compile 1.7.2 under ubuntu-7.04-desktop-amd64 - can't get
> it to compile, not even using "generic"....

Most likely you can't compile any other C program on that system as
well.  Please make sure that you have "development" packages installed -
including gcc, binutils, and perhaps libc6-dev and libc6-dev-amd64, as
well as their dependencies.  (Sorry, I am not familiar with Ubuntu to
provide you with an exact list of package names.)

-- 
Alexander Peslyak <solar at openwall.com>
GPG key ID: 5B341F15  fp: B3FB 63F4 D7A3 BCCC 6F6E  FC55 A2FC 027C 5B34 1F15
http://www.openwall.com - bringing security into open computing environments

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