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Date: Sat, 19 May 2018 15:37:56 +0200
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re: Re: Unable to crack the password of a test rar file.

On Sat, May 19, 2018 at 01:20:51PM +0100, Eric Watson wrote:
> pi@...pberrypi:/var/share/temp/JohnTheRipper-bleeding-jumbo/run $ ./john 
> test_pswd.txt
> Using default input encoding: UTF-8
> No password hashes loaded (see FAQ)
> pi@...pberrypi:/var/share/temp/JohnTheRipper-bleeding-jumbo/run $
> 
> Same outcome.
> 
> Content of hash file check:
> 
> nano test_pswd.txt
> test_file.txt.rar:$RAR3$*0*bd7549acfcdaf98f*391e8bdf3598de12b55063b6a5584bc3:0::::test_file.txt.rar

Oh, it looks like this JtR format is only enabled on some CPU
architectures, specifically when we define ARCH_ALLOWS_UNALIGNED, which
we probably don't when building for ARM.  Dhiru or magnum (JtR jumbo
developers who worked on this) might want to look into that and possibly
correct whatever it is in this format that requires unaligned access.
Meanwhile, you can try removing the "#if ARCH_ALLOWS_UNALIGNED" and
"#endif" pair from rar_fmt_plug.c, rebuild, and see what happens for you
(it might work or it might crash depending on whether unaligned access
is in fact required by this format, whether such accesses happen in your
specific case, whether your specific CPU possibly supports them in
hardware, or whether your Linux kernel build possibly emulates them).

On x86, your test_pswd.txt is loaded by JtR just fine.

Also, attacks on RAR file passwords are rather slow, and are better done
on GPUs - for example, GTX Titan X Maxwell tests 17k candidate passwords
per second against your file, whereas 2x E5-2670 (16 cores, 32 logical)
test only 800.  Your Raspberry Pi will probably do less than 100 even if
you get past the unaligned access hurdle.

Alexander

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