Re: [PATCH 3/4] crypto: drbg - replace spinlock with mutex

[Stephan Mueller <smueller@chronox.de>]

Am Sonntag, 19. April 2015, 13:48:03 schrieb Herbert Xu:

Hi Herbert,

> On Sat, Apr 18, 2015 at 01:35:40PM +0200, Stephan Mueller wrote:
> > When you do that, may I ask you to also update the crypto_alloc_rng. This
> > function has one major drawback at the moment: we are wasting precious
> > entropy. The testmgr must allocate the RNG for performing its testing
> > using
> > crypto_alloc_rng. As the RNG implementation has no knowledge at allocation
> > time that it will be used for testing, it will seed itself for the real
> > work. Then comes testing: the seeded RNG is now reset with the test
> > "entropy" and thereby wasting the initial seed.
> 
> Yes the DRBG will be unusable when first allocated and you must
> seed it to actually draw entropy and be able to use it.

I am not sure I understand you correctly: shall the DRBG have these 
precautions? If so, wouldn't we break the requirements in SP800-90A where the 
DRBG is intended to seed itself?

Or would you want to update the crypto_alloc_rng routine?
> 
> Cheers,


-- 
Ciao
Stephan