1/* Copyright 2017 The BoringSSL Authors 2 * 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. 6 * 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. */ 14 15#include <openssl/ctrdrbg.h> 16 17#include <assert.h> 18 19#include <openssl/mem.h> 20 21#include "../aes/internal.h" 22#include "../service_indicator/internal.h" 23#include "internal.h" 24 25 26// Section references in this file refer to SP 800-90Ar1: 27// http://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-90Ar1.pdf 28 29// See table 3. 30static const uint64_t kMaxReseedCount = UINT64_C(1) << 48; 31 32CTR_DRBG_STATE *CTR_DRBG_new(const uint8_t entropy[CTR_DRBG_ENTROPY_LEN], 33 const uint8_t *personalization, 34 size_t personalization_len) { 35 CTR_DRBG_STATE *drbg = reinterpret_cast<CTR_DRBG_STATE *>( 36 OPENSSL_malloc(sizeof(CTR_DRBG_STATE))); 37 if (drbg == NULL || 38 !CTR_DRBG_init(drbg, entropy, personalization, personalization_len)) { 39 CTR_DRBG_free(drbg); 40 return NULL; 41 } 42 43 return drbg; 44} 45 46void CTR_DRBG_free(CTR_DRBG_STATE *state) { OPENSSL_free(state); } 47 48int CTR_DRBG_init(CTR_DRBG_STATE *drbg, 49 const uint8_t entropy[CTR_DRBG_ENTROPY_LEN], 50 const uint8_t *personalization, size_t personalization_len) { 51 // Section 10.2.1.3.1 52 if (personalization_len > CTR_DRBG_ENTROPY_LEN) { 53 return 0; 54 } 55 56 uint8_t seed_material[CTR_DRBG_ENTROPY_LEN]; 57 OPENSSL_memcpy(seed_material, entropy, CTR_DRBG_ENTROPY_LEN); 58 59 for (size_t i = 0; i < personalization_len; i++) { 60 seed_material[i] ^= personalization[i]; 61 } 62 63 // Section 10.2.1.2 64 65 // kInitMask is the result of encrypting blocks with big-endian value 1, 2 66 // and 3 with the all-zero AES-256 key. 67 static const uint8_t kInitMask[CTR_DRBG_ENTROPY_LEN] = { 68 0x53, 0x0f, 0x8a, 0xfb, 0xc7, 0x45, 0x36, 0xb9, 0xa9, 0x63, 0xb4, 0xf1, 69 0xc4, 0xcb, 0x73, 0x8b, 0xce, 0xa7, 0x40, 0x3d, 0x4d, 0x60, 0x6b, 0x6e, 70 0x07, 0x4e, 0xc5, 0xd3, 0xba, 0xf3, 0x9d, 0x18, 0x72, 0x60, 0x03, 0xca, 71 0x37, 0xa6, 0x2a, 0x74, 0xd1, 0xa2, 0xf5, 0x8e, 0x75, 0x06, 0x35, 0x8e, 72 }; 73 74 for (size_t i = 0; i < sizeof(kInitMask); i++) { 75 seed_material[i] ^= kInitMask[i]; 76 } 77 78 drbg->ctr = aes_ctr_set_key(&drbg->ks, NULL, &drbg->block, seed_material, 32); 79 OPENSSL_memcpy(drbg->counter, seed_material + 32, 16); 80 drbg->reseed_counter = 1; 81 82 return 1; 83} 84 85static_assert(CTR_DRBG_ENTROPY_LEN % AES_BLOCK_SIZE == 0, 86 "not a multiple of AES block size"); 87 88// ctr_inc adds |n| to the last four bytes of |drbg->counter|, treated as a 89// big-endian number. 90static void ctr32_add(CTR_DRBG_STATE *drbg, uint32_t n) { 91 uint32_t ctr = CRYPTO_load_u32_be(drbg->counter + 12); 92 CRYPTO_store_u32_be(drbg->counter + 12, ctr + n); 93} 94 95static int ctr_drbg_update(CTR_DRBG_STATE *drbg, const uint8_t *data, 96 size_t data_len) { 97 // Per section 10.2.1.2, |data_len| must be |CTR_DRBG_ENTROPY_LEN|. Here, we 98 // allow shorter inputs and right-pad them with zeros. This is equivalent to 99 // the specified algorithm but saves a copy in |CTR_DRBG_generate|. 100 if (data_len > CTR_DRBG_ENTROPY_LEN) { 101 return 0; 102 } 103 104 uint8_t temp[CTR_DRBG_ENTROPY_LEN]; 105 for (size_t i = 0; i < CTR_DRBG_ENTROPY_LEN; i += AES_BLOCK_SIZE) { 106 ctr32_add(drbg, 1); 107 drbg->block(drbg->counter, temp + i, &drbg->ks); 108 } 109 110 for (size_t i = 0; i < data_len; i++) { 111 temp[i] ^= data[i]; 112 } 113 114 drbg->ctr = aes_ctr_set_key(&drbg->ks, NULL, &drbg->block, temp, 32); 115 OPENSSL_memcpy(drbg->counter, temp + 32, 16); 116 117 return 1; 118} 119 120int CTR_DRBG_reseed(CTR_DRBG_STATE *drbg, 121 const uint8_t entropy[CTR_DRBG_ENTROPY_LEN], 122 const uint8_t *additional_data, 123 size_t additional_data_len) { 124 // Section 10.2.1.4 125 uint8_t entropy_copy[CTR_DRBG_ENTROPY_LEN]; 126 127 if (additional_data_len > 0) { 128 if (additional_data_len > CTR_DRBG_ENTROPY_LEN) { 129 return 0; 130 } 131 132 OPENSSL_memcpy(entropy_copy, entropy, CTR_DRBG_ENTROPY_LEN); 133 for (size_t i = 0; i < additional_data_len; i++) { 134 entropy_copy[i] ^= additional_data[i]; 135 } 136 137 entropy = entropy_copy; 138 } 139 140 if (!ctr_drbg_update(drbg, entropy, CTR_DRBG_ENTROPY_LEN)) { 141 return 0; 142 } 143 144 drbg->reseed_counter = 1; 145 146 return 1; 147} 148 149int CTR_DRBG_generate(CTR_DRBG_STATE *drbg, uint8_t *out, size_t out_len, 150 const uint8_t *additional_data, 151 size_t additional_data_len) { 152 // See 9.3.1 153 if (out_len > CTR_DRBG_MAX_GENERATE_LENGTH) { 154 return 0; 155 } 156 157 // See 10.2.1.5.1 158 if (drbg->reseed_counter > kMaxReseedCount) { 159 return 0; 160 } 161 162 if (additional_data_len != 0 && 163 !ctr_drbg_update(drbg, additional_data, additional_data_len)) { 164 return 0; 165 } 166 167 // kChunkSize is used to interact better with the cache. Since the AES-CTR 168 // code assumes that it's encrypting rather than just writing keystream, the 169 // buffer has to be zeroed first. Without chunking, large reads would zero 170 // the whole buffer, flushing the L1 cache, and then do another pass (missing 171 // the cache every time) to “encrypt” it. The code can avoid this by 172 // chunking. 173 static const size_t kChunkSize = 8 * 1024; 174 175 while (out_len >= AES_BLOCK_SIZE) { 176 size_t todo = kChunkSize; 177 if (todo > out_len) { 178 todo = out_len; 179 } 180 181 todo &= ~(AES_BLOCK_SIZE - 1); 182 const size_t num_blocks = todo / AES_BLOCK_SIZE; 183 184 OPENSSL_memset(out, 0, todo); 185 ctr32_add(drbg, 1); 186 drbg->ctr(out, out, num_blocks, &drbg->ks, drbg->counter); 187 ctr32_add(drbg, (uint32_t)(num_blocks - 1)); 188 189 out += todo; 190 out_len -= todo; 191 } 192 193 if (out_len > 0) { 194 uint8_t block[AES_BLOCK_SIZE]; 195 ctr32_add(drbg, 1); 196 drbg->block(drbg->counter, block, &drbg->ks); 197 198 OPENSSL_memcpy(out, block, out_len); 199 } 200 201 // Right-padding |additional_data| in step 2.2 is handled implicitly by 202 // |ctr_drbg_update|, to save a copy. 203 if (!ctr_drbg_update(drbg, additional_data, additional_data_len)) { 204 return 0; 205 } 206 207 drbg->reseed_counter++; 208 FIPS_service_indicator_update_state(); 209 return 1; 210} 211 212void CTR_DRBG_clear(CTR_DRBG_STATE *drbg) { 213 OPENSSL_cleanse(drbg, sizeof(CTR_DRBG_STATE)); 214} 215