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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 <assert.h>
- #include <limits.h>
- #include <string.h>
-
- #if defined(BORINGSSL_FIPS)
- #include <unistd.h>
- #endif
-
- #include <openssl/chacha.h>
- #include <openssl/cpu.h>
- #include <openssl/mem.h>
-
- #include "internal.h"
- #include "../../internal.h"
- #include "../delocate.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 use it
- // as an additional-data input to CTR-DRBG.
- //
- // (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.)
-
- // kReseedInterval is the number of generate calls made to CTR-DRBG before
- // reseeding.
- static const unsigned kReseedInterval = 4096;
-
- // CRNGT_BLOCK_SIZE is the number of bytes in a “block” for the purposes of the
- // continuous random number generator test in FIPS 140-2, section 4.9.2.
- #define CRNGT_BLOCK_SIZE 16
-
- // rand_thread_state contains the per-thread state for the RNG.
- struct rand_thread_state {
- CTR_DRBG_STATE drbg;
- // calls is the number of generate calls made on |drbg| since it was last
- // (re)seeded. This is bound by |kReseedInterval|.
- unsigned calls;
- // last_block_valid is non-zero iff |last_block| contains data from
- // |CRYPTO_sysrand|.
- int last_block_valid;
-
- #if defined(BORINGSSL_FIPS)
- // last_block contains the previous block from |CRYPTO_sysrand|.
- uint8_t last_block[CRNGT_BLOCK_SIZE];
- // next and prev form a NULL-terminated, double-linked list of all states in
- // a process.
- struct rand_thread_state *next, *prev;
- #endif
- };
-
- #if defined(BORINGSSL_FIPS)
- // thread_states_list is the head of a linked-list of all |rand_thread_state|
- // objects in the process, one per thread. This is needed because FIPS requires
- // that they be zeroed on process exit, but thread-local destructors aren't
- // called when the whole process is exiting.
- DEFINE_BSS_GET(struct rand_thread_state *, thread_states_list);
- DEFINE_STATIC_MUTEX(thread_states_list_lock);
-
- static void rand_thread_state_clear_all(void) __attribute__((destructor));
- static void rand_thread_state_clear_all(void) {
- CRYPTO_STATIC_MUTEX_lock_write(thread_states_list_lock_bss_get());
- for (struct rand_thread_state *cur = *thread_states_list_bss_get();
- cur != NULL; cur = cur->next) {
- CTR_DRBG_clear(&cur->drbg);
- }
- // |thread_states_list_lock is deliberately left locked so that any threads
- // that are still running will hang if they try to call |RAND_bytes|.
- }
- #endif
-
- // rand_thread_state_free frees a |rand_thread_state|. This is called when a
- // thread exits.
- static void rand_thread_state_free(void *state_in) {
- struct rand_thread_state *state = state_in;
-
- if (state_in == NULL) {
- return;
- }
-
- #if defined(BORINGSSL_FIPS)
- CRYPTO_STATIC_MUTEX_lock_write(thread_states_list_lock_bss_get());
-
- if (state->prev != NULL) {
- state->prev->next = state->next;
- } else {
- *thread_states_list_bss_get() = state->next;
- }
-
- if (state->next != NULL) {
- state->next->prev = state->prev;
- }
-
- CRYPTO_STATIC_MUTEX_unlock_write(thread_states_list_lock_bss_get());
-
- CTR_DRBG_clear(&state->drbg);
- #endif
-
- OPENSSL_free(state);
- }
-
- #if defined(OPENSSL_X86_64) && !defined(OPENSSL_NO_ASM) && \
- !defined(BORINGSSL_UNSAFE_DETERMINISTIC_MODE)
-
- // These functions are defined in asm/rdrand-x86_64.pl
- extern int CRYPTO_rdrand(uint8_t out[8]);
- extern int CRYPTO_rdrand_multiple8_buf(uint8_t *buf, size_t len);
-
- static int have_rdrand(void) {
- return (OPENSSL_ia32cap_get()[1] & (1u << 30)) != 0;
- }
-
- static int hwrand(uint8_t *buf, const size_t len) {
- if (!have_rdrand()) {
- return 0;
- }
-
- const size_t len_multiple8 = len & ~7;
- if (!CRYPTO_rdrand_multiple8_buf(buf, len_multiple8)) {
- return 0;
- }
- const size_t remainder = len - len_multiple8;
-
- if (remainder != 0) {
- assert(remainder < 8);
-
- uint8_t rand_buf[8];
- if (!CRYPTO_rdrand(rand_buf)) {
- return 0;
- }
- OPENSSL_memcpy(buf + len_multiple8, rand_buf, remainder);
- }
-
- #if defined(BORINGSSL_FIPS_BREAK_CRNG)
- // This breaks the "continuous random number generator test" defined in FIPS
- // 140-2, section 4.9.2, and implemented in rand_get_seed().
- OPENSSL_memset(buf, 0, len);
- #endif
-
- return 1;
- }
-
- #else
-
- static int hwrand(uint8_t *buf, size_t len) {
- return 0;
- }
-
- #endif
-
- #if defined(BORINGSSL_FIPS)
-
- static void rand_get_seed(struct rand_thread_state *state,
- uint8_t seed[CTR_DRBG_ENTROPY_LEN]) {
- if (!state->last_block_valid) {
- if (!hwrand(state->last_block, sizeof(state->last_block))) {
- CRYPTO_sysrand(state->last_block, sizeof(state->last_block));
- }
- state->last_block_valid = 1;
- }
-
- // We overread from /dev/urandom or RDRAND by a factor of 10 and XOR to
- // whiten.
- #define FIPS_OVERREAD 10
- uint8_t entropy[CTR_DRBG_ENTROPY_LEN * FIPS_OVERREAD];
-
- if (!hwrand(entropy, sizeof(entropy))) {
- CRYPTO_sysrand(entropy, sizeof(entropy));
- }
-
- // See FIPS 140-2, section 4.9.2. This is the “continuous random number
- // generator test” which causes the program to randomly abort. Hopefully the
- // rate of failure is small enough not to be a problem in practice.
- if (CRYPTO_memcmp(state->last_block, entropy, CRNGT_BLOCK_SIZE) == 0) {
- printf("CRNGT failed.\n");
- BORINGSSL_FIPS_abort();
- }
-
- for (size_t i = CRNGT_BLOCK_SIZE; i < sizeof(entropy);
- i += CRNGT_BLOCK_SIZE) {
- if (CRYPTO_memcmp(entropy + i - CRNGT_BLOCK_SIZE, entropy + i,
- CRNGT_BLOCK_SIZE) == 0) {
- printf("CRNGT failed.\n");
- BORINGSSL_FIPS_abort();
- }
- }
- OPENSSL_memcpy(state->last_block,
- entropy + sizeof(entropy) - CRNGT_BLOCK_SIZE,
- CRNGT_BLOCK_SIZE);
-
- OPENSSL_memcpy(seed, entropy, CTR_DRBG_ENTROPY_LEN);
-
- for (size_t i = 1; i < FIPS_OVERREAD; i++) {
- for (size_t j = 0; j < CTR_DRBG_ENTROPY_LEN; j++) {
- seed[j] ^= entropy[CTR_DRBG_ENTROPY_LEN * i + j];
- }
- }
- }
-
- #else
-
- static void rand_get_seed(struct rand_thread_state *state,
- uint8_t seed[CTR_DRBG_ENTROPY_LEN]) {
- // If not in FIPS mode, we don't overread from the system entropy source and
- // we don't depend only on the hardware RDRAND.
- CRYPTO_sysrand(seed, CTR_DRBG_ENTROPY_LEN);
- }
-
- #endif
-
- void RAND_bytes_with_additional_data(uint8_t *out, size_t out_len,
- const uint8_t user_additional_data[32]) {
- if (out_len == 0) {
- return;
- }
-
- // Additional data is mixed into every CTR-DRBG call to protect, as best we
- // can, against forks & VM clones. We do not over-read this information and
- // don't reseed with it so, from the point of view of FIPS, this doesn't
- // provide “prediction resistance”. But, in practice, it does.
- uint8_t additional_data[32];
- if (!hwrand(additional_data, sizeof(additional_data))) {
- // Without a hardware RNG to save us from address-space duplication, the OS
- // entropy is used. This can be expensive (one read per |RAND_bytes| call)
- // and so can be disabled by applications that we have ensured don't fork
- // and aren't at risk of VM cloning.
- if (!rand_fork_unsafe_buffering_enabled()) {
- CRYPTO_sysrand(additional_data, sizeof(additional_data));
- } else {
- OPENSSL_memset(additional_data, 0, sizeof(additional_data));
- }
- }
-
- for (size_t i = 0; i < sizeof(additional_data); i++) {
- additional_data[i] ^= user_additional_data[i];
- }
-
- struct rand_thread_state stack_state;
- 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)) {
- // If the system is out of memory, use an ephemeral state on the
- // stack.
- state = &stack_state;
- }
-
- state->last_block_valid = 0;
- uint8_t seed[CTR_DRBG_ENTROPY_LEN];
- rand_get_seed(state, seed);
- if (!CTR_DRBG_init(&state->drbg, seed, NULL, 0)) {
- abort();
- }
- state->calls = 0;
-
- #if defined(BORINGSSL_FIPS)
- if (state != &stack_state) {
- CRYPTO_STATIC_MUTEX_lock_write(thread_states_list_lock_bss_get());
- struct rand_thread_state **states_list = thread_states_list_bss_get();
- state->next = *states_list;
- if (state->next != NULL) {
- state->next->prev = state;
- }
- state->prev = NULL;
- *states_list = state;
- CRYPTO_STATIC_MUTEX_unlock_write(thread_states_list_lock_bss_get());
- }
- #endif
- }
-
- if (state->calls >= kReseedInterval) {
- uint8_t seed[CTR_DRBG_ENTROPY_LEN];
- rand_get_seed(state, seed);
- #if defined(BORINGSSL_FIPS)
- // Take a read lock around accesses to |state->drbg|. This is needed to
- // avoid returning bad entropy if we race with
- // |rand_thread_state_clear_all|.
- //
- // This lock must be taken after any calls to |CRYPTO_sysrand| to avoid a
- // bug on ppc64le. glibc may implement pthread locks by wrapping user code
- // in a hardware transaction, but, on some older versions of glibc and the
- // kernel, syscalls made with |syscall| did not abort the transaction.
- CRYPTO_STATIC_MUTEX_lock_read(thread_states_list_lock_bss_get());
- #endif
- if (!CTR_DRBG_reseed(&state->drbg, seed, NULL, 0)) {
- abort();
- }
- state->calls = 0;
- } else {
- #if defined(BORINGSSL_FIPS)
- CRYPTO_STATIC_MUTEX_lock_read(thread_states_list_lock_bss_get());
- #endif
- }
-
- int first_call = 1;
- while (out_len > 0) {
- size_t todo = out_len;
- if (todo > CTR_DRBG_MAX_GENERATE_LENGTH) {
- todo = CTR_DRBG_MAX_GENERATE_LENGTH;
- }
-
- if (!CTR_DRBG_generate(&state->drbg, out, todo, additional_data,
- first_call ? sizeof(additional_data) : 0)) {
- abort();
- }
-
- out += todo;
- out_len -= todo;
- state->calls++;
- first_call = 0;
- }
-
- if (state == &stack_state) {
- CTR_DRBG_clear(&state->drbg);
- }
-
- #if defined(BORINGSSL_FIPS)
- CRYPTO_STATIC_MUTEX_unlock_read(thread_states_list_lock_bss_get());
- #endif
- }
-
- int RAND_bytes(uint8_t *out, size_t out_len) {
- 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);
- }
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