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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 <limits.h>
#include <string.h>
#include <openssl/chacha.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);
}
int RAND_bytes(uint8_t *buf, size_t len) {
if (len == 0) {
return 1;
}
if (!CRYPTO_hwrand(buf, len)) {
/* 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;
}
memset(state->partial_block, 0, sizeof(state->partial_block));
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);
}
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) {}
int RAND_load_file(const char *path, long num) {
if (num < 0) { /* read the "whole file" */
return 1;
} else if (num <= INT_MAX) {
return (int) num;
} else {
return INT_MAX;
}
}
void RAND_add(const void *buf, int num, double entropy) {}
int RAND_egd(const char *path) {
return 255;
}
int RAND_poll(void) {
return 1;
}
int RAND_status(void) {
return 1;
}
static const struct rand_meth_st kSSLeayMethod = {
RAND_seed,
RAND_bytes,
RAND_cleanup,
RAND_add,
RAND_pseudo_bytes,
RAND_status,
};
RAND_METHOD *RAND_SSLeay(void) {
return (RAND_METHOD*) &kSSLeayMethod;
}
void RAND_set_rand_method(const RAND_METHOD *method) {}
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