Linux cryptographic layer development
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From: Stephan Mueller <smueller@chronox.de>
To: Andrzej Zaborowski <andrew.zaborowski@intel.com>
Cc: tadeusz.struk@intel.com, linux-crypto@vger.kernel.org
Subject: Re: [RFC PATCH] crypto: RSA padding transform
Date: Sun, 06 Sep 2015 23:17:21 +0200	[thread overview]
Message-ID: <2234268.M7UZMy8YJa@tauon.atsec.com> (raw)
In-Reply-To: <CAOq732JmhBh7kqDH1mMhUz1MXz9zJSx1jaqdBMjgDVvtraSrrQ@mail.gmail.com>

Am Sonntag, 6. September 2015, 16:33:26 schrieb Andrzej Zaborowski:

Hi Andrzej,

>>> +     for (pos = 2; pos < child_req->dst_len; pos++)
>>> +             if (dst[pos] == 0x00)
>>> +                     break;
>> 
>> What happens if the padding has a 0x00 in its pseudo random data?
>
>The pseudo random bytes must all be non-zero for the padding to be
>unambiguous (RFC3447 iirc).  If there's a 0x00 in the first 8 bytes

I see, I did not know that detail. Now, you use prandom_u32_max to generate 
the padding in case of encryption/signing. I do not see any code that filters 
out any 0x00 that may be generated by this call. How would it prevented that 
this code does not generate 0x00?


Ciao
Stephan

  reply	other threads:[~2015-09-06 21:17 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-09-05 23:00 [RFC PATCH] crypto: RSA padding transform Andrew Zaborowski
2015-09-06  8:34 ` Stephan Mueller
2015-09-06 14:33   ` Andrzej Zaborowski
2015-09-06 21:17     ` Stephan Mueller [this message]
2015-09-07 14:42       ` Andrzej Zaborowski
2015-09-07 15:10         ` Stephan Mueller
2015-09-07 14:31     ` Tadeusz Struk
2015-09-07 17:54       ` Stephan Mueller
2015-09-08 16:09         ` Andrzej Zaborowski
2015-10-30  8:35           ` Marcel Holtmann
2015-09-08  1:07       ` Herbert Xu
2015-09-07 14:11   ` Tadeusz Struk
2015-09-07 15:07     ` Stephan Mueller
2015-09-07 14:06 ` Tadeusz Struk
2015-09-07 14:38   ` Andrzej Zaborowski

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