Hi Stephan,
For those less perfect noise source, can't pass the FIPS test.
static int update_kernel_random(int random_step,
unsigned char *buf, fips_ctx_t *fipsctx_in)
{
unsigned char *p;
int fips;
fips = fips_run_rng_test(fipsctx_in, buf);
if (fips)
return 1;
for (p = buf; p + random_step <= &buf[FIPS_RNG_BUFFER_SIZE];
p += random_step) {
random_add_entropy(p, random_step);
random_sleep();
}
return 0;
}
--
Miaoqing
________________________________________
From: Stephan Mueller <smueller@xxxxxxxxxx>
Sent: Tuesday, August 9, 2016 5:37 PM
To: Herbert Xu
Cc: Pan, Miaoqing; Matt Mackall; miaoqing@xxxxxxxxxxxxxx; Valo, Kalle; linux-wireless@xxxxxxxxxxxxxxx; ath9k-devel; linux-crypto@xxxxxxxxxxxxxxx; jason@xxxxxxxxxxxxxx; Sepehrdad, Pouyan
Subject: Re: [PATCH 2/2] ath9k: disable RNG by default
Am Dienstag, 9. August 2016, 17:17:55 CEST schrieb Herbert Xu:
Hi Herbert,
> On Tue, Aug 09, 2016 at 11:02:58AM +0200, Stephan Mueller wrote:
> > But shouldn't the default of the rngd then be adjusted a bit?
>
> Please elaborate.
in rngd_linux.c:random_add_entropy(void *buf, size_t size):
entropy.ent_count = size * 8;
entropy.size = size;
memcpy(entropy.data, buf, size);
if (ioctl(random_fd, RNDADDENTROPY, &entropy) != 0) {
...
in rngd.c:do_loop():
retval = iter->xread(buf, sizeof buf, iter);
...
rc = update_kernel_random(random_step,
buf, iter->fipsctx);
where update_kernel_random simply invokes random_add_entropy in chunks.
Hence, the rngd reads some bytes from /dev/hwrand and injects it into /dev/
random with an entropy estimate that is equal to the read bytes.
With less than perfect noise sources, entropy.ent_count should be much
smaller.
>
> Thanks,
Ciao
Stephan
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