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- /* Copyright (c) 2014, Google Inc.
- *
- * Permission to use, copy, modify, and/or distribute this software for any
- * purpose with or without fee is hereby granted, provided that the above
- * copyright notice and this permission notice appear in all copies.
- *
- * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
- * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
- * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
- * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
- * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
- * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
- * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
-
- #include <openssl/rand.h>
-
- #include <string.h>
-
- #include <openssl/mem.h>
-
- #include "internal.h"
- #include "../internal.h"
-
-
- /* It's assumed that the operating system always has an unfailing source of
- * entropy which is accessed via |CRYPTO_sysrand|. (If the operating system
- * entropy source fails, it's up to |CRYPTO_sysrand| to abort the process—we
- * don't try to handle it.)
- *
- * In addition, the hardware may provide a low-latency RNG. Intel's rdrand
- * instruction is the canonical example of this. When a hardware RNG is
- * available we don't need to worry about an RNG failure arising from fork()ing
- * the process or moving a VM, so we can keep thread-local RNG state and XOR
- * the hardware entropy in.
- *
- * (We assume that the OS entropy is safe from fork()ing and VM duplication.
- * This might be a bit of a leap of faith, esp on Windows, but there's nothing
- * that we can do about it.) */
-
- /* rand_thread_state contains the per-thread state for the RNG. This is only
- * used if the system has support for a hardware RNG. */
- struct rand_thread_state {
- uint8_t key[32];
- uint64_t calls_used;
- size_t bytes_used;
- uint8_t partial_block[64];
- unsigned partial_block_used;
- };
-
- /* kMaxCallsPerRefresh is the maximum number of |RAND_bytes| calls that we'll
- * serve before reading a new key from the operating system. This only applies
- * if we have a hardware RNG. */
- static const unsigned kMaxCallsPerRefresh = 1024;
-
- /* kMaxBytesPerRefresh is the maximum number of bytes that we'll return from
- * |RAND_bytes| before reading a new key from the operating system. This only
- * applies if we have a hardware RNG. */
- static const uint64_t kMaxBytesPerRefresh = 1024 * 1024;
-
- /* rand_thread_state_free frees a |rand_thread_state|. This is called when a
- * thread exits. */
- static void rand_thread_state_free(void *state) {
- if (state == NULL) {
- return;
- }
-
- OPENSSL_cleanse(state, sizeof(struct rand_thread_state));
- OPENSSL_free(state);
- }
-
- extern void CRYPTO_chacha_20(uint8_t *out, const uint8_t *in, size_t in_len,
- const uint8_t key[32], const uint8_t nonce[8],
- size_t counter);
-
- int RAND_bytes(uint8_t *buf, size_t len) {
- if (len == 0) {
- return 1;
- }
-
- if (!CRYPTO_have_hwrand()) {
- /* Without a hardware RNG to save us from address-space duplication, the OS
- * entropy is used directly. */
- CRYPTO_sysrand(buf, len);
- return 1;
- }
-
- struct rand_thread_state *state =
- CRYPTO_get_thread_local(OPENSSL_THREAD_LOCAL_RAND);
- if (state == NULL) {
- state = OPENSSL_malloc(sizeof(struct rand_thread_state));
- if (state == NULL ||
- !CRYPTO_set_thread_local(OPENSSL_THREAD_LOCAL_RAND, state,
- rand_thread_state_free)) {
- CRYPTO_sysrand(buf, len);
- return 1;
- }
-
- state->calls_used = kMaxCallsPerRefresh;
- }
-
- if (state->calls_used >= kMaxCallsPerRefresh ||
- state->bytes_used >= kMaxBytesPerRefresh) {
- CRYPTO_sysrand(state->key, sizeof(state->key));
- state->calls_used = 0;
- state->bytes_used = 0;
- state->partial_block_used = sizeof(state->partial_block);
- }
-
- CRYPTO_hwrand(buf, len);
-
- if (len >= sizeof(state->partial_block)) {
- size_t remaining = len;
- while (remaining > 0) {
- // kMaxBytesPerCall is only 2GB, while ChaCha can handle 256GB. But this
- // is sufficient and easier on 32-bit.
- static const size_t kMaxBytesPerCall = 0x80000000;
- size_t todo = remaining;
- if (todo > kMaxBytesPerCall) {
- todo = kMaxBytesPerCall;
- }
- CRYPTO_chacha_20(buf, buf, todo, state->key,
- (uint8_t *)&state->calls_used, 0);
- buf += todo;
- remaining -= todo;
- state->calls_used++;
- }
- } else {
- if (sizeof(state->partial_block) - state->partial_block_used < len) {
- CRYPTO_chacha_20(state->partial_block, state->partial_block,
- sizeof(state->partial_block), state->key,
- (uint8_t *)&state->calls_used, 0);
- state->partial_block_used = 0;
- }
-
- unsigned i;
- for (i = 0; i < len; i++) {
- buf[i] ^= state->partial_block[state->partial_block_used++];
- }
- state->calls_used++;
- }
- state->bytes_used += len;
-
- return 1;
- }
-
- int RAND_pseudo_bytes(uint8_t *buf, size_t len) {
- return RAND_bytes(buf, len);
- }
-
- void RAND_seed(const void *buf, int num) {}
-
- void RAND_add(const void *buf, int num, double entropy) {}
-
- int RAND_poll(void) {
- return 1;
- }
-
- int RAND_status(void) {
- return 1;
- }
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