359 lines
11 KiB
C
359 lines
11 KiB
C
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/* Copyright (c) 2014, Google Inc.
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
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* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
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* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
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#include <openssl/rand.h>
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#include <assert.h>
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#include <limits.h>
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#include <string.h>
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#if defined(BORINGSSL_FIPS)
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#include <unistd.h>
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#endif
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#include <openssl/chacha.h>
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#include <openssl/cpu.h>
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#include <openssl/mem.h>
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#include "internal.h"
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#include "../../internal.h"
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#include "../delocate.h"
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// It's assumed that the operating system always has an unfailing source of
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// entropy which is accessed via |CRYPTO_sysrand|. (If the operating system
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// entropy source fails, it's up to |CRYPTO_sysrand| to abort the process—we
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// don't try to handle it.)
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//
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// In addition, the hardware may provide a low-latency RNG. Intel's rdrand
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// instruction is the canonical example of this. When a hardware RNG is
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// available we don't need to worry about an RNG failure arising from fork()ing
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// the process or moving a VM, so we can keep thread-local RNG state and use it
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// as an additional-data input to CTR-DRBG.
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//
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// (We assume that the OS entropy is safe from fork()ing and VM duplication.
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// This might be a bit of a leap of faith, esp on Windows, but there's nothing
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// that we can do about it.)
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// kReseedInterval is the number of generate calls made to CTR-DRBG before
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// reseeding.
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static const unsigned kReseedInterval = 4096;
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// CRNGT_BLOCK_SIZE is the number of bytes in a “block” for the purposes of the
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// continuous random number generator test in FIPS 140-2, section 4.9.2.
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#define CRNGT_BLOCK_SIZE 16
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// rand_thread_state contains the per-thread state for the RNG.
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struct rand_thread_state {
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CTR_DRBG_STATE drbg;
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// calls is the number of generate calls made on |drbg| since it was last
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// (re)seeded. This is bound by |kReseedInterval|.
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unsigned calls;
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// last_block_valid is non-zero iff |last_block| contains data from
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// |CRYPTO_sysrand|.
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int last_block_valid;
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#if defined(BORINGSSL_FIPS)
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// last_block contains the previous block from |CRYPTO_sysrand|.
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uint8_t last_block[CRNGT_BLOCK_SIZE];
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// next and prev form a NULL-terminated, double-linked list of all states in
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// a process.
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struct rand_thread_state *next, *prev;
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#endif
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};
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#if defined(BORINGSSL_FIPS)
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// thread_states_list is the head of a linked-list of all |rand_thread_state|
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// objects in the process, one per thread. This is needed because FIPS requires
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// that they be zeroed on process exit, but thread-local destructors aren't
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// called when the whole process is exiting.
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DEFINE_BSS_GET(struct rand_thread_state *, thread_states_list);
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DEFINE_STATIC_MUTEX(thread_states_list_lock);
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static void rand_thread_state_clear_all(void) __attribute__((destructor));
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static void rand_thread_state_clear_all(void) {
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CRYPTO_STATIC_MUTEX_lock_write(thread_states_list_lock_bss_get());
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for (struct rand_thread_state *cur = *thread_states_list_bss_get();
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cur != NULL; cur = cur->next) {
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CTR_DRBG_clear(&cur->drbg);
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}
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// |thread_states_list_lock is deliberately left locked so that any threads
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// that are still running will hang if they try to call |RAND_bytes|.
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}
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#endif
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// rand_thread_state_free frees a |rand_thread_state|. This is called when a
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// thread exits.
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static void rand_thread_state_free(void *state_in) {
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struct rand_thread_state *state = state_in;
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if (state_in == NULL) {
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return;
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}
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#if defined(BORINGSSL_FIPS)
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CRYPTO_STATIC_MUTEX_lock_write(thread_states_list_lock_bss_get());
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if (state->prev != NULL) {
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state->prev->next = state->next;
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} else {
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*thread_states_list_bss_get() = state->next;
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}
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if (state->next != NULL) {
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state->next->prev = state->prev;
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}
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CRYPTO_STATIC_MUTEX_unlock_write(thread_states_list_lock_bss_get());
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CTR_DRBG_clear(&state->drbg);
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#endif
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OPENSSL_free(state);
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}
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#if defined(OPENSSL_X86_64) && !defined(OPENSSL_NO_ASM) && \
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!defined(BORINGSSL_UNSAFE_DETERMINISTIC_MODE)
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// These functions are defined in asm/rdrand-x86_64.pl
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extern int CRYPTO_rdrand(uint8_t out[8]);
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extern int CRYPTO_rdrand_multiple8_buf(uint8_t *buf, size_t len);
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static int have_rdrand(void) {
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return (OPENSSL_ia32cap_get()[1] & (1u << 30)) != 0;
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}
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static int hwrand(uint8_t *buf, const size_t len) {
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if (!have_rdrand()) {
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return 0;
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}
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const size_t len_multiple8 = len & ~7;
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if (!CRYPTO_rdrand_multiple8_buf(buf, len_multiple8)) {
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return 0;
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}
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const size_t remainder = len - len_multiple8;
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if (remainder != 0) {
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assert(remainder < 8);
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uint8_t rand_buf[8];
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if (!CRYPTO_rdrand(rand_buf)) {
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return 0;
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}
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OPENSSL_memcpy(buf + len_multiple8, rand_buf, remainder);
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}
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#if defined(BORINGSSL_FIPS_BREAK_CRNG)
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// This breaks the "continuous random number generator test" defined in FIPS
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// 140-2, section 4.9.2, and implemented in rand_get_seed().
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OPENSSL_memset(buf, 0, len);
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#endif
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return 1;
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}
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#else
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static int hwrand(uint8_t *buf, size_t len) {
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return 0;
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}
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#endif
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#if defined(BORINGSSL_FIPS)
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static void rand_get_seed(struct rand_thread_state *state,
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uint8_t seed[CTR_DRBG_ENTROPY_LEN]) {
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if (!state->last_block_valid) {
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if (!hwrand(state->last_block, sizeof(state->last_block))) {
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CRYPTO_sysrand(state->last_block, sizeof(state->last_block));
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}
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state->last_block_valid = 1;
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}
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// We overread from /dev/urandom or RDRAND by a factor of 10 and XOR to
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// whiten.
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#define FIPS_OVERREAD 10
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uint8_t entropy[CTR_DRBG_ENTROPY_LEN * FIPS_OVERREAD];
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if (!hwrand(entropy, sizeof(entropy))) {
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CRYPTO_sysrand(entropy, sizeof(entropy));
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}
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// See FIPS 140-2, section 4.9.2. This is the “continuous random number
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// generator test” which causes the program to randomly abort. Hopefully the
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// rate of failure is small enough not to be a problem in practice.
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if (CRYPTO_memcmp(state->last_block, entropy, CRNGT_BLOCK_SIZE) == 0) {
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printf("CRNGT failed.\n");
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BORINGSSL_FIPS_abort();
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}
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for (size_t i = CRNGT_BLOCK_SIZE; i < sizeof(entropy);
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i += CRNGT_BLOCK_SIZE) {
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if (CRYPTO_memcmp(entropy + i - CRNGT_BLOCK_SIZE, entropy + i,
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CRNGT_BLOCK_SIZE) == 0) {
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printf("CRNGT failed.\n");
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BORINGSSL_FIPS_abort();
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}
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}
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OPENSSL_memcpy(state->last_block,
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entropy + sizeof(entropy) - CRNGT_BLOCK_SIZE,
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CRNGT_BLOCK_SIZE);
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OPENSSL_memcpy(seed, entropy, CTR_DRBG_ENTROPY_LEN);
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for (size_t i = 1; i < FIPS_OVERREAD; i++) {
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for (size_t j = 0; j < CTR_DRBG_ENTROPY_LEN; j++) {
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seed[j] ^= entropy[CTR_DRBG_ENTROPY_LEN * i + j];
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}
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}
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}
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#else
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static void rand_get_seed(struct rand_thread_state *state,
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uint8_t seed[CTR_DRBG_ENTROPY_LEN]) {
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// If not in FIPS mode, we don't overread from the system entropy source and
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// we don't depend only on the hardware RDRAND.
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CRYPTO_sysrand(seed, CTR_DRBG_ENTROPY_LEN);
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}
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#endif
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void RAND_bytes_with_additional_data(uint8_t *out, size_t out_len,
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const uint8_t user_additional_data[32]) {
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if (out_len == 0) {
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return;
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}
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// Additional data is mixed into every CTR-DRBG call to protect, as best we
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// can, against forks & VM clones. We do not over-read this information and
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// don't reseed with it so, from the point of view of FIPS, this doesn't
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// provide “prediction resistance”. But, in practice, it does.
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uint8_t additional_data[32];
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if (!hwrand(additional_data, sizeof(additional_data))) {
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// Without a hardware RNG to save us from address-space duplication, the OS
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// entropy is used. This can be expensive (one read per |RAND_bytes| call)
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// and so can be disabled by applications that we have ensured don't fork
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// and aren't at risk of VM cloning.
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if (!rand_fork_unsafe_buffering_enabled()) {
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CRYPTO_sysrand(additional_data, sizeof(additional_data));
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} else {
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OPENSSL_memset(additional_data, 0, sizeof(additional_data));
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}
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}
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for (size_t i = 0; i < sizeof(additional_data); i++) {
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additional_data[i] ^= user_additional_data[i];
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}
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struct rand_thread_state stack_state;
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struct rand_thread_state *state =
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CRYPTO_get_thread_local(OPENSSL_THREAD_LOCAL_RAND);
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if (state == NULL) {
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state = OPENSSL_malloc(sizeof(struct rand_thread_state));
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if (state == NULL ||
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!CRYPTO_set_thread_local(OPENSSL_THREAD_LOCAL_RAND, state,
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rand_thread_state_free)) {
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// If the system is out of memory, use an ephemeral state on the
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// stack.
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state = &stack_state;
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}
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state->last_block_valid = 0;
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uint8_t seed[CTR_DRBG_ENTROPY_LEN];
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rand_get_seed(state, seed);
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if (!CTR_DRBG_init(&state->drbg, seed, NULL, 0)) {
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abort();
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}
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state->calls = 0;
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#if defined(BORINGSSL_FIPS)
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if (state != &stack_state) {
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CRYPTO_STATIC_MUTEX_lock_write(thread_states_list_lock_bss_get());
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struct rand_thread_state **states_list = thread_states_list_bss_get();
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state->next = *states_list;
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if (state->next != NULL) {
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state->next->prev = state;
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}
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state->prev = NULL;
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*states_list = state;
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CRYPTO_STATIC_MUTEX_unlock_write(thread_states_list_lock_bss_get());
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}
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#endif
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}
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if (state->calls >= kReseedInterval) {
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uint8_t seed[CTR_DRBG_ENTROPY_LEN];
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rand_get_seed(state, seed);
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#if defined(BORINGSSL_FIPS)
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// Take a read lock around accesses to |state->drbg|. This is needed to
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// avoid returning bad entropy if we race with
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// |rand_thread_state_clear_all|.
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//
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// This lock must be taken after any calls to |CRYPTO_sysrand| to avoid a
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// bug on ppc64le. glibc may implement pthread locks by wrapping user code
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// in a hardware transaction, but, on some older versions of glibc and the
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// kernel, syscalls made with |syscall| did not abort the transaction.
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CRYPTO_STATIC_MUTEX_lock_read(thread_states_list_lock_bss_get());
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#endif
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if (!CTR_DRBG_reseed(&state->drbg, seed, NULL, 0)) {
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abort();
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}
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state->calls = 0;
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} else {
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#if defined(BORINGSSL_FIPS)
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CRYPTO_STATIC_MUTEX_lock_read(thread_states_list_lock_bss_get());
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#endif
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}
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int first_call = 1;
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while (out_len > 0) {
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size_t todo = out_len;
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if (todo > CTR_DRBG_MAX_GENERATE_LENGTH) {
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todo = CTR_DRBG_MAX_GENERATE_LENGTH;
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}
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if (!CTR_DRBG_generate(&state->drbg, out, todo, additional_data,
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first_call ? sizeof(additional_data) : 0)) {
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abort();
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}
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out += todo;
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out_len -= todo;
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state->calls++;
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first_call = 0;
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}
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if (state == &stack_state) {
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CTR_DRBG_clear(&state->drbg);
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}
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#if defined(BORINGSSL_FIPS)
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CRYPTO_STATIC_MUTEX_unlock_read(thread_states_list_lock_bss_get());
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#endif
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}
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int RAND_bytes(uint8_t *out, size_t out_len) {
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static const uint8_t kZeroAdditionalData[32] = {0};
|
||
|
|
RAND_bytes_with_additional_data(out, out_len, kZeroAdditionalData);
|
||
|
|
return 1;
|
||
|
|
}
|
||
|
|
|
||
|
|
int RAND_pseudo_bytes(uint8_t *buf, size_t len) {
|
||
|
|
return RAND_bytes(buf, len);
|
||
|
|
}
|