linux-kernel - Re: [PATCH] crypto: add optional continuous repetition test to entropy store based rngs

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Date:	Thu, 4 Jun 2009 20:04:56 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Matt Mackall <mpm@...enic.com>
Cc:	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
	herbert@...dor.apana.org.au, davem@...emloft.net
Subject: Re: [PATCH] crypto: add optional continuous repetition test to
	entropy store based rngs

On Thu, Jun 04, 2009 at 03:14:10PM -0500, Matt Mackall wrote:
> On Thu, 2009-06-04 at 15:50 -0400, Neil Horman wrote:
> > FIPS-140 requires that all random number generators implement continuous self
> > tests in which each extracted block of data is compared against the last block
> > for repetition.  The ansi_cprng implements such a test, but it would be nice if
> > the hw rng's did the same thing.  Obviously its not something thats always
> > needed, but it seems like it would be a nice feature to have on occasion.  I've
> > written the below patch which allows individual entropy stores to be flagged as
> > desiring a continuous test to be run on them as is extracted.  By default this
> > option is off, but is enabled in the event that fips mode is selected during
> > bootup.
> > 
> > Neil
> > 
> > Signed-off-by: Neil Horman <nhorman@...driver.com>
> > 
> > diff --git a/crypto/internal.h b/crypto/internal.h
> > index fc76e1f..150d389 100644
> > --- a/crypto/internal.h
> > +++ b/crypto/internal.h
> > @@ -26,12 +26,6 @@
> >  #include <linux/rwsem.h>
> >  #include <linux/slab.h>
> >  
> > -#ifdef CONFIG_CRYPTO_FIPS
> > -extern int fips_enabled;
> > -#else
> > -#define fips_enabled 0
> > -#endif
> > -
> >  /* Crypto notification events. */
> >  enum {
> >  	CRYPTO_MSG_ALG_REQUEST,
> > diff --git a/drivers/char/random.c b/drivers/char/random.c
> > index 8c74448..fbdfc70 100644
> > --- a/drivers/char/random.c
> > +++ b/drivers/char/random.c
> > @@ -250,6 +250,8 @@
> >  #include <asm/irq.h>
> >  #include <asm/io.h>
> >  
> > +#include <crypto/algapi.h>
> > +
> 
> I think we'd rather not make random.c incestuous with crypto/.
> 
Not sure what to do about this.  The intent is to provide the external reference
to the fips_enabled flag (which is either defined as an extern in or #defined to
0 dependent on CONFIG_CRYPTO_FIPS).  I can cut'n'paste the code block from the
include file and put it in here, but that seems like a worse solution to me.
Let me know your thoughts, and I can change this accordingly.

As for the other comments, they all seem good to me, let me know what you want
to do about the above, and I'll respin/repost the patch for you

Thanks!
Neil

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