1 /* Copyright (c) 2014, Google Inc.
3 * Permission to use, copy, modify, and/or distribute this software for any
4 * purpose with or without fee is hereby granted, provided that the above
5 * copyright notice and this permission notice appear in all copies.
7 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
8 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
10 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
15 #include <openssl/rand.h>
21 #if defined(BORINGSSL_FIPS)
25 #include <openssl/chacha.h>
26 #include <openssl/cpu.h>
27 #include <openssl/mem.h>
30 #include "../../internal.h"
31 #include "../delocate.h"
34 // It's assumed that the operating system always has an unfailing source of
35 // entropy which is accessed via |CRYPTO_sysrand|. (If the operating system
36 // entropy source fails, it's up to |CRYPTO_sysrand| to abort the process—we
37 // don't try to handle it.)
39 // In addition, the hardware may provide a low-latency RNG. Intel's rdrand
40 // instruction is the canonical example of this. When a hardware RNG is
41 // available we don't need to worry about an RNG failure arising from fork()ing
42 // the process or moving a VM, so we can keep thread-local RNG state and use it
43 // as an additional-data input to CTR-DRBG.
45 // (We assume that the OS entropy is safe from fork()ing and VM duplication.
46 // This might be a bit of a leap of faith, esp on Windows, but there's nothing
47 // that we can do about it.)
49 // kReseedInterval is the number of generate calls made to CTR-DRBG before
51 static const unsigned kReseedInterval = 4096;
53 // CRNGT_BLOCK_SIZE is the number of bytes in a “block” for the purposes of the
54 // continuous random number generator test in FIPS 140-2, section 4.9.2.
55 #define CRNGT_BLOCK_SIZE 16
57 // rand_thread_state contains the per-thread state for the RNG.
58 struct rand_thread_state {
60 // calls is the number of generate calls made on |drbg| since it was last
61 // (re)seeded. This is bound by |kReseedInterval|.
63 // last_block_valid is non-zero iff |last_block| contains data from
67 #if defined(BORINGSSL_FIPS)
68 // last_block contains the previous block from |CRYPTO_sysrand|.
69 uint8_t last_block[CRNGT_BLOCK_SIZE];
70 // next and prev form a NULL-terminated, double-linked list of all states in
72 struct rand_thread_state *next, *prev;
76 #if defined(BORINGSSL_FIPS)
77 // thread_states_list is the head of a linked-list of all |rand_thread_state|
78 // objects in the process, one per thread. This is needed because FIPS requires
79 // that they be zeroed on process exit, but thread-local destructors aren't
80 // called when the whole process is exiting.
81 DEFINE_BSS_GET(struct rand_thread_state *, thread_states_list);
82 DEFINE_STATIC_MUTEX(thread_states_list_lock);
84 static void rand_thread_state_clear_all(void) __attribute__((destructor));
85 static void rand_thread_state_clear_all(void) {
86 CRYPTO_STATIC_MUTEX_lock_write(thread_states_list_lock_bss_get());
87 for (struct rand_thread_state *cur = *thread_states_list_bss_get();
88 cur != NULL; cur = cur->next) {
89 CTR_DRBG_clear(&cur->drbg);
91 // |thread_states_list_lock is deliberately left locked so that any threads
92 // that are still running will hang if they try to call |RAND_bytes|.
96 // rand_thread_state_free frees a |rand_thread_state|. This is called when a
98 static void rand_thread_state_free(void *state_in) {
99 struct rand_thread_state *state = state_in;
101 if (state_in == NULL) {
105 #if defined(BORINGSSL_FIPS)
106 CRYPTO_STATIC_MUTEX_lock_write(thread_states_list_lock_bss_get());
108 if (state->prev != NULL) {
109 state->prev->next = state->next;
111 *thread_states_list_bss_get() = state->next;
114 if (state->next != NULL) {
115 state->next->prev = state->prev;
118 CRYPTO_STATIC_MUTEX_unlock_write(thread_states_list_lock_bss_get());
120 CTR_DRBG_clear(&state->drbg);
126 #if defined(OPENSSL_X86_64) && !defined(OPENSSL_NO_ASM) && \
127 !defined(BORINGSSL_UNSAFE_DETERMINISTIC_MODE)
129 // These functions are defined in asm/rdrand-x86_64.pl
130 extern int CRYPTO_rdrand(uint8_t out[8]);
131 extern int CRYPTO_rdrand_multiple8_buf(uint8_t *buf, size_t len);
133 static int have_rdrand(void) {
134 return (OPENSSL_ia32cap_get()[1] & (1u << 30)) != 0;
137 static int hwrand(uint8_t *buf, const size_t len) {
138 if (!have_rdrand()) {
142 const size_t len_multiple8 = len & ~7;
143 if (!CRYPTO_rdrand_multiple8_buf(buf, len_multiple8)) {
146 const size_t remainder = len - len_multiple8;
148 if (remainder != 0) {
149 assert(remainder < 8);
152 if (!CRYPTO_rdrand(rand_buf)) {
155 OPENSSL_memcpy(buf + len_multiple8, rand_buf, remainder);
158 #if defined(BORINGSSL_FIPS_BREAK_CRNG)
159 // This breaks the "continuous random number generator test" defined in FIPS
160 // 140-2, section 4.9.2, and implemented in rand_get_seed().
161 OPENSSL_memset(buf, 0, len);
169 static int hwrand(uint8_t *buf, size_t len) {
175 #if defined(BORINGSSL_FIPS)
177 static void rand_get_seed(struct rand_thread_state *state,
178 uint8_t seed[CTR_DRBG_ENTROPY_LEN]) {
179 if (!state->last_block_valid) {
180 if (!hwrand(state->last_block, sizeof(state->last_block))) {
181 CRYPTO_sysrand(state->last_block, sizeof(state->last_block));
183 state->last_block_valid = 1;
186 // We overread from /dev/urandom or RDRAND by a factor of 10 and XOR to
188 #define FIPS_OVERREAD 10
189 uint8_t entropy[CTR_DRBG_ENTROPY_LEN * FIPS_OVERREAD];
191 if (!hwrand(entropy, sizeof(entropy))) {
192 CRYPTO_sysrand(entropy, sizeof(entropy));
195 // See FIPS 140-2, section 4.9.2. This is the “continuous random number
196 // generator test” which causes the program to randomly abort. Hopefully the
197 // rate of failure is small enough not to be a problem in practice.
198 if (CRYPTO_memcmp(state->last_block, entropy, CRNGT_BLOCK_SIZE) == 0) {
199 printf("CRNGT failed.\n");
200 BORINGSSL_FIPS_abort();
203 for (size_t i = CRNGT_BLOCK_SIZE; i < sizeof(entropy);
204 i += CRNGT_BLOCK_SIZE) {
205 if (CRYPTO_memcmp(entropy + i - CRNGT_BLOCK_SIZE, entropy + i,
206 CRNGT_BLOCK_SIZE) == 0) {
207 printf("CRNGT failed.\n");
208 BORINGSSL_FIPS_abort();
211 OPENSSL_memcpy(state->last_block,
212 entropy + sizeof(entropy) - CRNGT_BLOCK_SIZE,
215 OPENSSL_memcpy(seed, entropy, CTR_DRBG_ENTROPY_LEN);
217 for (size_t i = 1; i < FIPS_OVERREAD; i++) {
218 for (size_t j = 0; j < CTR_DRBG_ENTROPY_LEN; j++) {
219 seed[j] ^= entropy[CTR_DRBG_ENTROPY_LEN * i + j];
226 static void rand_get_seed(struct rand_thread_state *state,
227 uint8_t seed[CTR_DRBG_ENTROPY_LEN]) {
228 // If not in FIPS mode, we don't overread from the system entropy source and
229 // we don't depend only on the hardware RDRAND.
230 CRYPTO_sysrand(seed, CTR_DRBG_ENTROPY_LEN);
235 void RAND_bytes_with_additional_data(uint8_t *out, size_t out_len,
236 const uint8_t user_additional_data[32]) {
241 // Additional data is mixed into every CTR-DRBG call to protect, as best we
242 // can, against forks & VM clones. We do not over-read this information and
243 // don't reseed with it so, from the point of view of FIPS, this doesn't
244 // provide “prediction resistance”. But, in practice, it does.
245 uint8_t additional_data[32];
246 if (!hwrand(additional_data, sizeof(additional_data))) {
247 // Without a hardware RNG to save us from address-space duplication, the OS
248 // entropy is used. This can be expensive (one read per |RAND_bytes| call)
249 // and so can be disabled by applications that we have ensured don't fork
250 // and aren't at risk of VM cloning.
251 if (!rand_fork_unsafe_buffering_enabled()) {
252 CRYPTO_sysrand(additional_data, sizeof(additional_data));
254 OPENSSL_memset(additional_data, 0, sizeof(additional_data));
258 for (size_t i = 0; i < sizeof(additional_data); i++) {
259 additional_data[i] ^= user_additional_data[i];
262 struct rand_thread_state stack_state;
263 struct rand_thread_state *state =
264 CRYPTO_get_thread_local(OPENSSL_THREAD_LOCAL_RAND);
267 state = OPENSSL_malloc(sizeof(struct rand_thread_state));
269 !CRYPTO_set_thread_local(OPENSSL_THREAD_LOCAL_RAND, state,
270 rand_thread_state_free)) {
271 // If the system is out of memory, use an ephemeral state on the
273 state = &stack_state;
276 state->last_block_valid = 0;
277 uint8_t seed[CTR_DRBG_ENTROPY_LEN];
278 rand_get_seed(state, seed);
279 if (!CTR_DRBG_init(&state->drbg, seed, NULL, 0)) {
284 #if defined(BORINGSSL_FIPS)
285 if (state != &stack_state) {
286 CRYPTO_STATIC_MUTEX_lock_write(thread_states_list_lock_bss_get());
287 struct rand_thread_state **states_list = thread_states_list_bss_get();
288 state->next = *states_list;
289 if (state->next != NULL) {
290 state->next->prev = state;
293 *states_list = state;
294 CRYPTO_STATIC_MUTEX_unlock_write(thread_states_list_lock_bss_get());
299 if (state->calls >= kReseedInterval) {
300 uint8_t seed[CTR_DRBG_ENTROPY_LEN];
301 rand_get_seed(state, seed);
302 #if defined(BORINGSSL_FIPS)
303 // Take a read lock around accesses to |state->drbg|. This is needed to
304 // avoid returning bad entropy if we race with
305 // |rand_thread_state_clear_all|.
307 // This lock must be taken after any calls to |CRYPTO_sysrand| to avoid a
308 // bug on ppc64le. glibc may implement pthread locks by wrapping user code
309 // in a hardware transaction, but, on some older versions of glibc and the
310 // kernel, syscalls made with |syscall| did not abort the transaction.
311 CRYPTO_STATIC_MUTEX_lock_read(thread_states_list_lock_bss_get());
313 if (!CTR_DRBG_reseed(&state->drbg, seed, NULL, 0)) {
318 #if defined(BORINGSSL_FIPS)
319 CRYPTO_STATIC_MUTEX_lock_read(thread_states_list_lock_bss_get());
324 while (out_len > 0) {
325 size_t todo = out_len;
326 if (todo > CTR_DRBG_MAX_GENERATE_LENGTH) {
327 todo = CTR_DRBG_MAX_GENERATE_LENGTH;
330 if (!CTR_DRBG_generate(&state->drbg, out, todo, additional_data,
331 first_call ? sizeof(additional_data) : 0)) {
341 if (state == &stack_state) {
342 CTR_DRBG_clear(&state->drbg);
345 #if defined(BORINGSSL_FIPS)
346 CRYPTO_STATIC_MUTEX_unlock_read(thread_states_list_lock_bss_get());
350 int RAND_bytes(uint8_t *out, size_t out_len) {
351 static const uint8_t kZeroAdditionalData[32] = {0};
352 RAND_bytes_with_additional_data(out, out_len, kZeroAdditionalData);
356 int RAND_pseudo_bytes(uint8_t *buf, size_t len) {
357 return RAND_bytes(buf, len);