Hash mismatch when SSHing to dropbear server

[Hans-Christian Egtvedt]

Matt Johnston wrote:
> On Fri, Aug 04, 2006 at 10:09:08AM +0200, Hans-Christian Egtvedt wrote:
> 
>> So the error corrects it self when I ssh localhost, but external targets
>> is a no-go.
>>
>> Could this be an alligment error?
> 
> Possibly? To try and figure what's going on, I've put a
> version with some copius debugging of the RSA bits at
> http://matt.ucc.asn.au/dropbear/testing/db-unrandom1.tar.gz
> The random number generator has been made totally
> deterministic, so subsequent runs on different hosts can be
> compared.
> 
> Compile the server binary for your workstation and compile
> the client for both the avr32 and the workstation. Run the
> server on your workstation using the included "constant_rsa"
> key - then I can compare what I'm seeing. You might want to
> run it with "2> /dev/null" as it'll print a lot of junk.

Done

> Then run the debugging client both on the avr32 and your
> workstation, as "./dbclient -v workstation 2> logfile".
> If it's working correctly, you should see mostly the same
> output on each host (I've put a copy of what I see in that
> website dir). If it seems to hang for ages before showing a
> password prompt, you might need to press "y" for the hidden
> key confirmation prompt.

You were right about the confirmation prompt

> I'm guessing that you'll probably see different big-number
> output on the avr32, which might help narrow things down.
> I'm not entirely sure what to be looking for, but with some
> extra dropbear_trace() and print_mp_int() calls in
> libtommath/bn_mp_exptmod_fast.c it should be possible to
> narrow down the differences to a particular bit of code.

I put the logs here:
http://www.egtvedt.no/dropbear/

> Hopefully that might be of use.

I'm not quite seeing what I should be looking for, if anybody have a
pointer to what I should see (correct calculations etc) then I can start
my debugging :)

-- 
With kind regards,
Med vennlig hilsen,

Hans-Christian Egtvedt
Applications Engineer - AVR Applications Lab
Atmel Norway