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#include "pseudorand.h"
#include <assert.h>
#include <ccan/crypto/sha256/sha256.h>
#include <ccan/crypto/siphash24/siphash24.h>
#include <ccan/err/err.h>
#include <ccan/isaac/isaac64.h>
#include <ccan/likely/likely.h>
#include <sodium/randombytes.h>
#include <stdbool.h>
#include <string.h>
static struct isaac64_ctx isaac64;
static struct siphash_seed siphashseed;
static bool pseudorand_initted = false;
static void init_if_needed(void)
{
if (unlikely(!pseudorand_initted)) {
unsigned char seedbuf[16];
struct sha256 sha;
randombytes_buf(seedbuf, sizeof(seedbuf));
memcpy(&siphashseed, seedbuf, sizeof(siphashseed));
/* In case isaac is reversible, don't leak seed. */
sha256(&sha, seedbuf, sizeof(seedbuf));
isaac64_init(&isaac64, sha.u.u8, sizeof(sha.u.u8));
pseudorand_initted = true;
}
}
uint64_t pseudorand(uint64_t max)
{
init_if_needed();
assert(max);
return isaac64_next_uint(&isaac64, max);
}
const struct siphash_seed *siphash_seed(void)
{
init_if_needed();
return &siphashseed;
}