Am Samstag, 12. November 2016, 09:55:19 CET schrieb Herbert Xu:

Hi Herbert,

> On Thu, Nov 10, 2016 at 04:32:03AM +0100, Stephan Mueller wrote:
> > The kernel crypto API AEAD cipher operation generates output such that
> > space for the AAD is reserved in the output buffer without being
> > touched. The processed ciphertext/plaintext is appended to the reserved
> > AAD buffer.
> > 
> > The user space interface followed that approach. However, this is a
> > violation of the POSIX read definition which requires that any read data
> > is placed at the beginning of the caller-provided buffer. As the kernel
> > crypto API would leave room for the AAD, the old approach did not fully
> > comply with the POSIX specification.
> 
> Nack.  The kernel AEAD API will copy the AD as is, it definitely
> does not leave the output untouched unless of course when it is
> an in-place operation.  The user-space operation should operate
> in the same manner.

When you have separate buffers, the kernel does not seem to copy the AD over 
to the target buffer.
> 
> Cheers,


Ciao
Stephan
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