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Extract add-entropy code from crypto_fast_rng to a new function

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This commit is contained in:
Nick Mathewson 2019-03-18 11:54:37 -04:00 committed by David Goulet
parent c6a93beed8
commit e66b5153bd
1 changed files with 22 additions and 14 deletions
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36
src/lib/crypt_ops/crypto_rand_fast.c
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@ -192,6 +192,26 @@ cipher_from_seed(const uint8_t *seed)
return crypto_cipher_new_with_iv_and_bits(seed, seed+KEY_LEN, KEY_BITS);
}
/**
* Helper: mix additional entropy into <b>rng</b> by using our XOF to mix the
* old value for the seed with some additional bytes from
* crypto_strongest_rand().
**/
static void
crypto_fast_rng_add_entopy(crypto_fast_rng_t *rng)
{
crypto_xof_t *xof = crypto_xof_new();
crypto_xof_add_bytes(xof, rng->buf.seed, SEED_LEN);
{
uint8_t seedbuf[SEED_LEN];
crypto_strongest_rand(seedbuf, SEED_LEN);
crypto_xof_add_bytes(xof, seedbuf, SEED_LEN);
memwipe(seedbuf, 0, SEED_LEN);
}
crypto_xof_squeeze_bytes(xof, rng->buf.seed, SEED_LEN);
crypto_xof_free(xof);
}
/**
* Helper: refill the seed bytes and output buffer of <b>rng</b>, using
* the input seed bytes as input (key and IV) for the stream cipher.
@ -203,20 +223,8 @@ static void
crypto_fast_rng_refill(crypto_fast_rng_t *rng)
{
if (rng->n_till_reseed-- == 0) {
/* It's time to reseed the RNG. We'll do this by using our XOF to mix the
* old value for the seed with some additional bytes from
* crypto_strongest_rand(). */
crypto_xof_t *xof = crypto_xof_new();
crypto_xof_add_bytes(xof, rng->buf.seed, SEED_LEN);
{
uint8_t seedbuf[SEED_LEN];
crypto_strongest_rand(seedbuf, SEED_LEN);
crypto_xof_add_bytes(xof, seedbuf, SEED_LEN);
memwipe(seedbuf, 0, SEED_LEN);
}
crypto_xof_squeeze_bytes(xof, rng->buf.seed, SEED_LEN);
crypto_xof_free(xof);
/* It's time to reseed the RNG. */
crypto_fast_rng_add_entopy(rng);
rng->n_till_reseed = RESEED_AFTER;
}
/* Now fill rng->buf with output from our stream cipher, initialized from