Re: Imminent bugfix release (1.97.1)

[Vladimir 'phcoder' Serbinenko <phcoder@gmail.com>]

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Bean wrote:
> On Mon, Nov 9, 2009 at 9:50 PM, Vladimir 'phcoder' Serbinenko
> <phcoder@gmail.com> wrote:
>   
>> Bean wrote:
>>     
>>> On Mon, Nov 9, 2009 at 9:04 AM, Robert Millan <rmh@aybabtu.com> wrote:
>>>
>>>       
>>>> A security problem [1] was found in our password-checking routines,
>>>> which affects GRUB 1.97.  I'll be releasing 1.97.1 tomorrow.
>>>>
>>>> Additionally, I cherry-picked fixes for a few problems that should
>>>> have made it to the release, like GNU/Hurd support (see NEWS file
>>>> for details).  The release branch is available in:
>>>>
>>>>  sftp://bzr.savannah.gnu.org/srv/bzr/grub/branches/release_1_97/
>>>>
>>>> If you have time, please test this tree, specially password support,
>>>> to help find possible problems.
>>>>
>>>>         
>>> Hi,
>>>
>>> Actually, the function of grub_auth_strcmp puzzles me, why would it
>>> need to wait 100 ms to return the result ?
>>>       
>> 10 ms actually. The goal is to take same amount of time indpendently of
>> input values. But probably the delay should be around whole thing and
>> it's how I'll do but for this urgent release this will do it
>>     
>
> Hi,
>
> int
> grub_auth_strcmp (const char *s1, const char *s2)
> {
>   int ret;
>   grub_uint64_t end;
>
>   end = grub_get_time_ms () + 100;
>   ret = grub_strcmp (s1, s2);
>
>   /* This prevents an attacker from deriving information about the
>      password from the time it took to execute this function.  */
>   while (grub_get_time_ms () < end);
>
>   return ret;
> }
>
> Isn't this 100 ms ? Anyway, the longest supported string is 1024 long,
> I doubt there is any perceivable difference between them.
>
>   
If attacker is on fast serial connection he could possibly measure the
difference


-- 
Regards
Vladimir 'phcoder' Serbinenko



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