[gnutls-dev] bug in _gnutls_pkcs1_rsa_encrypt

[Robey Pointer]

Matthias Urlichs wrote:

>Hi,
>
>Werner Koch:
>  
>
>>>This line doesn't make sense, IMHO.
>>>      
>>>
>>The idea is that when requesting K new random bytes to replace zero
>>bytes of the initial random string, we request a few bytes more so
>>that we have some spare random bytes in case the K new bytes contain
>>zero bytes.
>>
>>    
>>
>I thought so.
>
>However, it would help a great deal if you'd actually skip zero bytes in
>the new string when you replace the zeroes in the old string.  ;-)
>
>  
>
>>Agreed, requesting just one extra byte for replacing 128 zero bytes is
>>too less. 
>>    
>>
>
>s/is too less/isn't enough/.  (OK, OK, I'll shut up now.)
>
>To be reasonably safe, add three more bytes.
>  
>

IMHO, best to just leave the loop as-is and not bother to fetch the 
extra k/128 byte(s).  The simplicity outweighs the very very small 
chance that you might avoid an extra loop iteration by obsessively 
checking for (and skipping) zeros in the replacement buffer.

robey