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handle entropy estimate correctly

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This commit is contained in:
Bodo Möller 2000-02-25 07:40:53 +00:00
parent fbb41ae0ad
commit c6709c6b0f
1 changed files with 17 additions and 4 deletions
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21
crypto/rand/md_rand.c
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@ -282,13 +282,13 @@ static void ssleay_rand_add(const void *buf, int num, double add)
{
md[k] ^= local_md[k];
}
if (entropy < ENTROPY_NEEDED) /* stop counting when we have enough */
entropy += add;
CRYPTO_w_unlock(CRYPTO_LOCK_RAND);
#ifndef THREADS
assert(md_c[1] == md_count[1]);
#endif
if (entropy < ENTROPY_NEEDED) /* stop counting when we have enough */
entropy += add;
}
static void ssleay_rand_seed(const void *buf, int num)
@ -318,8 +318,8 @@ static void ssleay_rand_initialize(void)
RAND_add(&l,sizeof(l),0);
#ifdef DEVRANDOM
/* Use a random entropy pool device. Linux and FreeBSD have
* this. Use /dev/urandom if you can as /dev/random will block
/* Use a random entropy pool device. Linux, FreeBSD and OpenBSD
* have this. Use /dev/urandom if you can as /dev/random may block
* if it runs out of random entries. */
if ((fh = fopen(DEVRANDOM, "r")) != NULL)
@ -388,6 +388,19 @@ static int ssleay_rand_bytes(unsigned char *buf, int num)
ssleay_rand_initialize();
ok = (entropy >= ENTROPY_NEEDED);
if (!ok)
{
/* If the PRNG state is not yet unpredictable, then seeing
* the PRNG output may help attackers to determine the new
* state; thus we have to decrease the entropy estimate.
* Once we've had enough initial seeding we don't bother to
* adjust the entropy count, though, because we're not ambitious
* to provide *information-theoretic* randomness.
*/
entropy -= num;
if (entropy < 0)
entropy = 0;
}
st_idx=state_index;
st_num=state_num;