1 /* Copyright (c) 2017, 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>
17 #include <openssl/type_check.h>
18 #include <openssl/mem.h>
21 #include "../cipher/internal.h"
24 // Section references in this file refer to SP 800-90Ar1:
25 // http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-90Ar1.pdf
28 static const uint64_t kMaxReseedCount = UINT64_C(1) << 48;
30 int CTR_DRBG_init(CTR_DRBG_STATE *drbg,
31 const uint8_t entropy[CTR_DRBG_ENTROPY_LEN],
32 const uint8_t *personalization, size_t personalization_len) {
34 if (personalization_len > CTR_DRBG_ENTROPY_LEN) {
38 uint8_t seed_material[CTR_DRBG_ENTROPY_LEN];
39 OPENSSL_memcpy(seed_material, entropy, CTR_DRBG_ENTROPY_LEN);
41 for (size_t i = 0; i < personalization_len; i++) {
42 seed_material[i] ^= personalization[i];
47 // kInitMask is the result of encrypting blocks with big-endian value 1, 2
48 // and 3 with the all-zero AES-256 key.
49 static const uint8_t kInitMask[CTR_DRBG_ENTROPY_LEN] = {
50 0x53, 0x0f, 0x8a, 0xfb, 0xc7, 0x45, 0x36, 0xb9, 0xa9, 0x63, 0xb4, 0xf1,
51 0xc4, 0xcb, 0x73, 0x8b, 0xce, 0xa7, 0x40, 0x3d, 0x4d, 0x60, 0x6b, 0x6e,
52 0x07, 0x4e, 0xc5, 0xd3, 0xba, 0xf3, 0x9d, 0x18, 0x72, 0x60, 0x03, 0xca,
53 0x37, 0xa6, 0x2a, 0x74, 0xd1, 0xa2, 0xf5, 0x8e, 0x75, 0x06, 0x35, 0x8e,
56 for (size_t i = 0; i < sizeof(kInitMask); i++) {
57 seed_material[i] ^= kInitMask[i];
60 drbg->ctr = aes_ctr_set_key(&drbg->ks, NULL, &drbg->block, seed_material, 32);
61 OPENSSL_memcpy(drbg->counter.bytes, seed_material + 32, 16);
62 drbg->reseed_counter = 1;
67 OPENSSL_COMPILE_ASSERT(CTR_DRBG_ENTROPY_LEN % AES_BLOCK_SIZE == 0,
68 not_a_multiple_of_block_size);
70 // ctr_inc adds |n| to the last four bytes of |drbg->counter|, treated as a
72 static void ctr32_add(CTR_DRBG_STATE *drbg, uint32_t n) {
73 drbg->counter.words[3] =
74 CRYPTO_bswap4(CRYPTO_bswap4(drbg->counter.words[3]) + n);
77 static int ctr_drbg_update(CTR_DRBG_STATE *drbg, const uint8_t *data,
79 // Per section 10.2.1.2, |data_len| must be |CTR_DRBG_ENTROPY_LEN|. Here, we
80 // allow shorter inputs and right-pad them with zeros. This is equivalent to
81 // the specified algorithm but saves a copy in |CTR_DRBG_generate|.
82 if (data_len > CTR_DRBG_ENTROPY_LEN) {
86 uint8_t temp[CTR_DRBG_ENTROPY_LEN];
87 for (size_t i = 0; i < CTR_DRBG_ENTROPY_LEN; i += AES_BLOCK_SIZE) {
89 drbg->block(drbg->counter.bytes, temp + i, &drbg->ks);
92 for (size_t i = 0; i < data_len; i++) {
96 drbg->ctr = aes_ctr_set_key(&drbg->ks, NULL, &drbg->block, temp, 32);
97 OPENSSL_memcpy(drbg->counter.bytes, temp + 32, 16);
102 int CTR_DRBG_reseed(CTR_DRBG_STATE *drbg,
103 const uint8_t entropy[CTR_DRBG_ENTROPY_LEN],
104 const uint8_t *additional_data,
105 size_t additional_data_len) {
107 uint8_t entropy_copy[CTR_DRBG_ENTROPY_LEN];
109 if (additional_data_len > 0) {
110 if (additional_data_len > CTR_DRBG_ENTROPY_LEN) {
114 OPENSSL_memcpy(entropy_copy, entropy, CTR_DRBG_ENTROPY_LEN);
115 for (size_t i = 0; i < additional_data_len; i++) {
116 entropy_copy[i] ^= additional_data[i];
119 entropy = entropy_copy;
122 if (!ctr_drbg_update(drbg, entropy, CTR_DRBG_ENTROPY_LEN)) {
126 drbg->reseed_counter = 1;
131 int CTR_DRBG_generate(CTR_DRBG_STATE *drbg, uint8_t *out, size_t out_len,
132 const uint8_t *additional_data,
133 size_t additional_data_len) {
135 if (out_len > CTR_DRBG_MAX_GENERATE_LENGTH) {
140 if (drbg->reseed_counter > kMaxReseedCount) {
144 if (additional_data_len != 0 &&
145 !ctr_drbg_update(drbg, additional_data, additional_data_len)) {
149 // kChunkSize is used to interact better with the cache. Since the AES-CTR
150 // code assumes that it's encrypting rather than just writing keystream, the
151 // buffer has to be zeroed first. Without chunking, large reads would zero
152 // the whole buffer, flushing the L1 cache, and then do another pass (missing
153 // the cache every time) to “encrypt” it. The code can avoid this by
155 static const size_t kChunkSize = 8 * 1024;
157 while (out_len >= AES_BLOCK_SIZE) {
158 size_t todo = kChunkSize;
159 if (todo > out_len) {
163 todo &= ~(AES_BLOCK_SIZE-1);
164 const size_t num_blocks = todo / AES_BLOCK_SIZE;
167 OPENSSL_memset(out, 0, todo);
169 drbg->ctr(out, out, num_blocks, &drbg->ks, drbg->counter.bytes);
170 ctr32_add(drbg, num_blocks - 1);
172 for (size_t i = 0; i < todo; i += AES_BLOCK_SIZE) {
174 drbg->block(drbg->counter.bytes, out + i, &drbg->ks);
183 uint8_t block[AES_BLOCK_SIZE];
185 drbg->block(drbg->counter.bytes, block, &drbg->ks);
187 OPENSSL_memcpy(out, block, out_len);
190 // Right-padding |additional_data| in step 2.2 is handled implicitly by
191 // |ctr_drbg_update|, to save a copy.
192 if (!ctr_drbg_update(drbg, additional_data, additional_data_len)) {
196 drbg->reseed_counter++;
200 void CTR_DRBG_clear(CTR_DRBG_STATE *drbg) {
201 OPENSSL_cleanse(drbg, sizeof(CTR_DRBG_STATE));