Am Donnerstag, 15. Februar 2018, 06:30:36 CET schrieb Harsh Jain:

Hi Harsh,

> On 14-02-2018 18:22, Stephan Mueller wrote:
> > Am Mittwoch, 14. Februar 2018, 06:43:53 CET schrieb Harsh Jain:
> > 
> > Hi Harsh,
> > 
> >> Patch set is working fine with chelsio Driver.
> > 
> > Thank you.
> > 
> >> Do we really need IV locking mechanism for AEAD algo because AEAD algo's
> >> don't support Partial mode operation and Driver are not updating(atleast
> >> Chelsio) IV's on AEAD request completions.
> > 
> > Yes, I think we would need it. It is technically possible to have multiple
> > IOCBs for AEAD ciphers. Even though your implementation may not write the
> > IV back, others may do that. At least I do not see a guarantee that the
> > IV is *not* written back by a driver.
> There is no  use of writing IV back in AEAD algo till Framework starts
> supporting Partial mode.

I agree.

> Even if Driver starts updating IV for AEAD,
> Multiple IOCB's in both cases will yield wrong results only.

This would only be the case if the driver would not implicitly or explicitly 
serialize the requests.
> Case 1 : If we have AEAD IV serialization  applied,  Encryption will be
> wrong if same IV gets used.


> Case 2: If we do not have IV serialization for
> AEAD. Encryption will be fine but user will have multiple Authentication 
> tag (that too with final block processed).  Its like 2nd Block encryption
> is based on IV received from 1st block  and Authentication Tag value is
> based on 2nd block content only.


But are we sure that all drivers behave correctly? Before you notified us of 
the issue, I was not even aware of the fact that this serialization may not be 
done in the driver. And we only have seen that issue with AF_ALG where we test 
for multiple concurrent AIO operations.

Besides, when we do not have the locking for AEAD, what would we gain: one 
less lock to take vs. guarantee that the AEAD operation is always properly 


Reply via email to