1 /* Copyright (c) 2017, Google Inc. 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/aead.h> 16 #include <openssl/cipher.h> 17 #include <openssl/crypto.h> 18 #include <openssl/err.h> 19 #include <openssl/sha.h> 20 21 #include "../fipsmodule/cipher/internal.h" 22 23 24 #define EVP_AEAD_AES_CTR_HMAC_SHA256_TAG_LEN SHA256_DIGEST_LENGTH 25 #define EVP_AEAD_AES_CTR_HMAC_SHA256_NONCE_LEN 12 26 27 struct aead_aes_ctr_hmac_sha256_ctx { 28 union { 29 double align; 30 AES_KEY ks; 31 } ks; 32 ctr128_f ctr; 33 block128_f block; 34 SHA256_CTX inner_init_state; 35 SHA256_CTX outer_init_state; 36 }; 37 38 static void hmac_init(SHA256_CTX *out_inner, SHA256_CTX *out_outer, 39 const uint8_t hmac_key[32]) { 40 static const size_t hmac_key_len = 32; 41 uint8_t block[SHA256_CBLOCK]; 42 OPENSSL_memcpy(block, hmac_key, hmac_key_len); 43 OPENSSL_memset(block + hmac_key_len, 0x36, sizeof(block) - hmac_key_len); 44 45 unsigned i; 46 for (i = 0; i < hmac_key_len; i++) { 47 block[i] ^= 0x36; 48 } 49 50 SHA256_Init(out_inner); 51 SHA256_Update(out_inner, block, sizeof(block)); 52 53 OPENSSL_memset(block + hmac_key_len, 0x5c, sizeof(block) - hmac_key_len); 54 for (i = 0; i < hmac_key_len; i++) { 55 block[i] ^= (0x36 ^ 0x5c); 56 } 57 58 SHA256_Init(out_outer); 59 SHA256_Update(out_outer, block, sizeof(block)); 60 } 61 62 static int aead_aes_ctr_hmac_sha256_init(EVP_AEAD_CTX *ctx, const uint8_t *key, 63 size_t key_len, size_t tag_len) { 64 struct aead_aes_ctr_hmac_sha256_ctx *aes_ctx; 65 static const size_t hmac_key_len = 32; 66 67 if (key_len < hmac_key_len) { 68 OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_KEY_LENGTH); 69 return 0; // EVP_AEAD_CTX_init should catch this. 70 } 71 72 const size_t aes_key_len = key_len - hmac_key_len; 73 if (aes_key_len != 16 && aes_key_len != 32) { 74 OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_KEY_LENGTH); 75 return 0; // EVP_AEAD_CTX_init should catch this. 76 } 77 78 if (tag_len == EVP_AEAD_DEFAULT_TAG_LENGTH) { 79 tag_len = EVP_AEAD_AES_CTR_HMAC_SHA256_TAG_LEN; 80 } 81 82 if (tag_len > EVP_AEAD_AES_CTR_HMAC_SHA256_TAG_LEN) { 83 OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TAG_TOO_LARGE); 84 return 0; 85 } 86 87 aes_ctx = OPENSSL_malloc(sizeof(struct aead_aes_ctr_hmac_sha256_ctx)); 88 if (aes_ctx == NULL) { 89 OPENSSL_PUT_ERROR(CIPHER, ERR_R_MALLOC_FAILURE); 90 return 0; 91 } 92 93 aes_ctx->ctr = 94 aes_ctr_set_key(&aes_ctx->ks.ks, NULL, &aes_ctx->block, key, aes_key_len); 95 ctx->tag_len = tag_len; 96 hmac_init(&aes_ctx->inner_init_state, &aes_ctx->outer_init_state, 97 key + aes_key_len); 98 99 ctx->aead_state = aes_ctx; 100 101 return 1; 102 } 103 104 static void aead_aes_ctr_hmac_sha256_cleanup(EVP_AEAD_CTX *ctx) { 105 OPENSSL_free(ctx->aead_state); 106 } 107 108 static void hmac_update_uint64(SHA256_CTX *sha256, uint64_t value) { 109 unsigned i; 110 uint8_t bytes[8]; 111 112 for (i = 0; i < sizeof(bytes); i++) { 113 bytes[i] = value & 0xff; 114 value >>= 8; 115 } 116 SHA256_Update(sha256, bytes, sizeof(bytes)); 117 } 118 119 static void hmac_calculate(uint8_t out[SHA256_DIGEST_LENGTH], 120 const SHA256_CTX *inner_init_state, 121 const SHA256_CTX *outer_init_state, 122 const uint8_t *ad, size_t ad_len, 123 const uint8_t *nonce, const uint8_t *ciphertext, 124 size_t ciphertext_len) { 125 SHA256_CTX sha256; 126 OPENSSL_memcpy(&sha256, inner_init_state, sizeof(sha256)); 127 hmac_update_uint64(&sha256, ad_len); 128 hmac_update_uint64(&sha256, ciphertext_len); 129 SHA256_Update(&sha256, nonce, EVP_AEAD_AES_CTR_HMAC_SHA256_NONCE_LEN); 130 SHA256_Update(&sha256, ad, ad_len); 131 132 // Pad with zeros to the end of the SHA-256 block. 133 const unsigned num_padding = 134 (SHA256_CBLOCK - ((sizeof(uint64_t)*2 + 135 EVP_AEAD_AES_CTR_HMAC_SHA256_NONCE_LEN + ad_len) % 136 SHA256_CBLOCK)) % 137 SHA256_CBLOCK; 138 uint8_t padding[SHA256_CBLOCK]; 139 OPENSSL_memset(padding, 0, num_padding); 140 SHA256_Update(&sha256, padding, num_padding); 141 142 SHA256_Update(&sha256, ciphertext, ciphertext_len); 143 144 uint8_t inner_digest[SHA256_DIGEST_LENGTH]; 145 SHA256_Final(inner_digest, &sha256); 146 147 OPENSSL_memcpy(&sha256, outer_init_state, sizeof(sha256)); 148 SHA256_Update(&sha256, inner_digest, sizeof(inner_digest)); 149 SHA256_Final(out, &sha256); 150 } 151 152 static void aead_aes_ctr_hmac_sha256_crypt( 153 const struct aead_aes_ctr_hmac_sha256_ctx *aes_ctx, uint8_t *out, 154 const uint8_t *in, size_t len, const uint8_t *nonce) { 155 // Since the AEAD operation is one-shot, keeping a buffer of unused keystream 156 // bytes is pointless. However, |CRYPTO_ctr128_encrypt| requires it. 157 uint8_t partial_block_buffer[AES_BLOCK_SIZE]; 158 unsigned partial_block_offset = 0; 159 OPENSSL_memset(partial_block_buffer, 0, sizeof(partial_block_buffer)); 160 161 uint8_t counter[AES_BLOCK_SIZE]; 162 OPENSSL_memcpy(counter, nonce, EVP_AEAD_AES_CTR_HMAC_SHA256_NONCE_LEN); 163 OPENSSL_memset(counter + EVP_AEAD_AES_CTR_HMAC_SHA256_NONCE_LEN, 0, 4); 164 165 if (aes_ctx->ctr) { 166 CRYPTO_ctr128_encrypt_ctr32(in, out, len, &aes_ctx->ks.ks, counter, 167 partial_block_buffer, &partial_block_offset, 168 aes_ctx->ctr); 169 } else { 170 CRYPTO_ctr128_encrypt(in, out, len, &aes_ctx->ks.ks, counter, 171 partial_block_buffer, &partial_block_offset, 172 aes_ctx->block); 173 } 174 } 175 176 static int aead_aes_ctr_hmac_sha256_seal_scatter( 177 const EVP_AEAD_CTX *ctx, uint8_t *out, uint8_t *out_tag, 178 size_t *out_tag_len, size_t max_out_tag_len, const uint8_t *nonce, 179 size_t nonce_len, const uint8_t *in, size_t in_len, const uint8_t *extra_in, 180 size_t extra_in_len, const uint8_t *ad, size_t ad_len) { 181 const struct aead_aes_ctr_hmac_sha256_ctx *aes_ctx = ctx->aead_state; 182 const uint64_t in_len_64 = in_len; 183 184 if (in_len_64 >= (UINT64_C(1) << 32) * AES_BLOCK_SIZE) { 185 // This input is so large it would overflow the 32-bit block counter. 186 OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE); 187 return 0; 188 } 189 190 if (max_out_tag_len < ctx->tag_len) { 191 OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL); 192 return 0; 193 } 194 195 if (nonce_len != EVP_AEAD_AES_CTR_HMAC_SHA256_NONCE_LEN) { 196 OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_NONCE_SIZE); 197 return 0; 198 } 199 200 aead_aes_ctr_hmac_sha256_crypt(aes_ctx, out, in, in_len, nonce); 201 202 uint8_t hmac_result[SHA256_DIGEST_LENGTH]; 203 hmac_calculate(hmac_result, &aes_ctx->inner_init_state, 204 &aes_ctx->outer_init_state, ad, ad_len, nonce, out, in_len); 205 OPENSSL_memcpy(out_tag, hmac_result, ctx->tag_len); 206 *out_tag_len = ctx->tag_len; 207 208 return 1; 209 } 210 211 static int aead_aes_ctr_hmac_sha256_open_gather( 212 const EVP_AEAD_CTX *ctx, uint8_t *out, const uint8_t *nonce, 213 size_t nonce_len, const uint8_t *in, size_t in_len, const uint8_t *in_tag, 214 size_t in_tag_len, const uint8_t *ad, size_t ad_len) { 215 const struct aead_aes_ctr_hmac_sha256_ctx *aes_ctx = ctx->aead_state; 216 217 if (in_tag_len != ctx->tag_len) { 218 OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT); 219 return 0; 220 } 221 222 if (nonce_len != EVP_AEAD_AES_CTR_HMAC_SHA256_NONCE_LEN) { 223 OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_NONCE_SIZE); 224 return 0; 225 } 226 227 uint8_t hmac_result[SHA256_DIGEST_LENGTH]; 228 hmac_calculate(hmac_result, &aes_ctx->inner_init_state, 229 &aes_ctx->outer_init_state, ad, ad_len, nonce, in, 230 in_len); 231 if (CRYPTO_memcmp(hmac_result, in_tag, ctx->tag_len) != 0) { 232 OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT); 233 return 0; 234 } 235 236 aead_aes_ctr_hmac_sha256_crypt(aes_ctx, out, in, in_len, nonce); 237 238 return 1; 239 } 240 241 static const EVP_AEAD aead_aes_128_ctr_hmac_sha256 = { 242 16 /* AES key */ + 32 /* HMAC key */, 243 12, // nonce length 244 EVP_AEAD_AES_CTR_HMAC_SHA256_TAG_LEN, // overhead 245 EVP_AEAD_AES_CTR_HMAC_SHA256_TAG_LEN, // max tag length 246 0, // seal_scatter_supports_extra_in 247 248 aead_aes_ctr_hmac_sha256_init, 249 NULL /* init_with_direction */, 250 aead_aes_ctr_hmac_sha256_cleanup, 251 NULL /* open */, 252 aead_aes_ctr_hmac_sha256_seal_scatter, 253 aead_aes_ctr_hmac_sha256_open_gather, 254 NULL /* get_iv */, 255 NULL /* tag_len */, 256 }; 257 258 static const EVP_AEAD aead_aes_256_ctr_hmac_sha256 = { 259 32 /* AES key */ + 32 /* HMAC key */, 260 12, // nonce length 261 EVP_AEAD_AES_CTR_HMAC_SHA256_TAG_LEN, // overhead 262 EVP_AEAD_AES_CTR_HMAC_SHA256_TAG_LEN, // max tag length 263 0, // seal_scatter_supports_extra_in 264 265 aead_aes_ctr_hmac_sha256_init, 266 NULL /* init_with_direction */, 267 aead_aes_ctr_hmac_sha256_cleanup, 268 NULL /* open */, 269 aead_aes_ctr_hmac_sha256_seal_scatter, 270 aead_aes_ctr_hmac_sha256_open_gather, 271 NULL /* get_iv */, 272 NULL /* tag_len */, 273 }; 274 275 const EVP_AEAD *EVP_aead_aes_128_ctr_hmac_sha256(void) { 276 return &aead_aes_128_ctr_hmac_sha256; 277 } 278 279 const EVP_AEAD *EVP_aead_aes_256_ctr_hmac_sha256(void) { 280 return &aead_aes_256_ctr_hmac_sha256; 281 } 282
