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Tweaks to RNG code

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This commit is contained in:
Bruce Hill 2024-12-12 14:01:58 -05:00
parent c5db5fef62
commit 10a0a16686
1 changed files with 8 additions and 4 deletions
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12
stdlib/rng.c
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@ -18,7 +18,7 @@
#include "chacha.h"
public _Thread_local RNG_t default_rng;
public _Thread_local RNG_t default_rng = NULL;
struct RNGState_t {
chacha_ctx chacha;
@ -69,22 +69,26 @@ static void rekey(RNG_t rng)
chacha_ivsetup(&rng->chacha, rng->random_bytes + KEYSZ);
explicit_bzero(rng->random_bytes, KEYSZ + IVSZ);
rng->unused_bytes = sizeof(rng->random_bytes) - KEYSZ - IVSZ;
assert(rng->unused_bytes <= sizeof(rng->random_bytes));
}
static void random_bytes(RNG_t rng, uint8_t *dest, size_t needed)
{
while (needed > 0) {
if (rng->unused_bytes > 0) {
assert(rng->unused_bytes <= sizeof(rng->random_bytes));
if (rng->unused_bytes == 0) {
rekey(rng);
} else {
size_t to_get = MIN(needed, rng->unused_bytes);
assert(to_get <= rng->unused_bytes);
uint8_t *keystream = rng->random_bytes + sizeof(rng->random_bytes) - rng->unused_bytes;
memcpy(dest, keystream, to_get);
memset(keystream, 0, to_get);
dest += to_get;
needed -= to_get;
rng->unused_bytes -= to_get;
assert(rng->unused_bytes <= sizeof(rng->random_bytes));
}
if (rng->unused_bytes == 0)
rekey(rng);
}
}