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SubjectRe: [PATCH] (0/4) Entropy accounting fixes
On Sat, Aug 17, 2002 at 09:01:20PM -0700, Linus Torvalds wrote:
>
> On 17 Aug 2002, Robert Love wrote:
> >
> > [1] this is why I wrote my netdev-random patches. some machines just
> > have to take the entropy from the network card... there is nothing
> > else.
>
> I suspect that Oliver is 100% correct in that the current code is just
> _too_ trusting. And parts of his patches seem to be in the "obviously
> good" category (ie the xor'ing of the buffers instead of overwriting).

Make sure you don't miss this bit, I should have sent it
separately. This is a longstanding bug that manufactures about a
thousand bits out of thin air when the pool runs dry.

Ironically, any confidence anyone had in /dev/random vs /dev/urandom
up until now has been misplaced.

--- a/drivers/char/random.c 2002-07-20 14:11:07.000000000 -0500
+++ b/drivers/char/random.c 2002-08-17 19:47:54.000000000 -0500
@@ -1239,18 +1184,18 @@

if (r->entropy_count < nbytes * 8 &&
r->entropy_count < r->poolinfo.POOLBITS) {
- int nwords = min_t(int,
- r->poolinfo.poolwords - r->entropy_count/32,
- sizeof(tmp) / 4);
+ int bytes = min_t(int,
+ nbytes - r->entropy_count/8,
+ sizeof(tmp));

- DEBUG_ENT("xfer %d from primary to %s (have %d, need %d)\n",
- nwords * 32,
+ DEBUG_ENT("xfer %d to %s (have %d, need %d)\n",
+ bytes * 8,
r == sec_random_state ? "secondary" : "unknown",
r->entropy_count, nbytes * 8);

- extract_entropy(random_state, tmp, nwords * 4, 0);
- add_entropy_words(r, tmp, nwords);
- credit_entropy_store(r, nwords * 32);
+ extract_entropy(random_state, tmp, bytes, 0);
+ add_entropy_words(r, tmp, (bytes+3)/4);
+ credit_entropy_store(r, bytes*8);
}
if (r->extract_count > 1024) {
DEBUG_ENT("reseeding %s with %d from primary\n",
--
"Love the dolphins," she advised him. "Write by W.A.S.T.E.."
-
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