[openssl-users] CBC ciphers + TLS 1.0 protocol does not work in OpenSSL 1.0.2d

[Jayalakshmi bhat]

Hi All,



Thanks for all the responses. As mentioned by Matt in the discussion
thread,constant_time_msb performs the copy the msb of the input to all of
the other bits so the return value should either be one of 0x00000000 or
0xffffffff.



I found another interesting thing,constant_time_msb worked as it is without
any changes, after I added a printf in constant_time_is_zero_8 test routine
to print the return value. I added the printf just before comparing the
return value with the expected value.



I have confirmed the failures by removing the printf and printing any thing
else other than the returned value.



Now based on the discussions here and print results I am thinking, after
constant_time_msb operation probably overflow bit is set in case of
0xffffffff. And it is not cleared before comparing, hence compare fails.
When I add a printf to print the return value probably overflow flag got
cleared and things worked.



I am planning to attach the debugger to check the flags. I will get back
with debugger results.



I have attached the test file.



Regards

Jaya



On Fri, Dec 11, 2015 at 11:30 AM, Jeffrey Walton <noloader at gmail.com> wrote:

> > 3. The compiler wasn't written by a fanatic who put
> >   the "right shift of negative signed values is
> >   undefined" rule above common sense.
> >
> > This is only implementation-defined behavior, not undefined behavior.
> It is
> > not permitted to crash the system or launch the missiles.  (n1256.pdf
> 6.5.7
> > paragraph 5.)
>
> The potential problem with implementation defined is its not
> guaranteed to produce consistent results. Different compilers or
> different versions of the same compiler may arrive at different
> results.
>
> In this light, the crash might be welcomed to make it easy to find the
> trouble spot :)
> _______________________________________________
> openssl-users mailing list
> To unsubscribe: https://mta.openssl.org/mailman/listinfo/openssl-users
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mta.openssl.org/pipermail/openssl-users/attachments/20151213/a3d791af/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: constant_time_test.7z
Type: application/octet-stream
Size: 1661 bytes
Desc: not available
URL: <http://mta.openssl.org/pipermail/openssl-users/attachments/20151213/a3d791af/attachment.obj>