1/* 2 * Copyright 2012-2021 The OpenSSL Project Authors. All Rights Reserved. 3 * 4 * Licensed under the Apache License 2.0 (the "License"). You may not use 5 * this file except in compliance with the License. You can obtain a copy 6 * in the file LICENSE in the source distribution or at 7 * https://www.openssl.org/source/license.html 8 */ 9 10/* 11 * This file has no dependencies on the rest of libssl because it is shared 12 * with the providers. It contains functions for low level MAC calculations. 13 * Responsibility for this lies with the HMAC implementation in the 14 * providers. However there are legacy code paths in libssl which also need to 15 * do this. In time those legacy code paths can be removed and this file can be 16 * moved out of libssl. 17 */ 18 19 20/* 21 * MD5 and SHA-1 low level APIs are deprecated for public use, but still ok for 22 * internal use. 23 */ 24#include "internal/deprecated.h" 25 26#include "internal/constant_time.h" 27#include "internal/cryptlib.h" 28 29#include <openssl/evp.h> 30#ifndef FIPS_MODULE 31# include <openssl/md5.h> 32#endif 33#include <openssl/sha.h> 34 35char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx); 36int ssl3_cbc_digest_record(const EVP_MD *md, 37 unsigned char *md_out, 38 size_t *md_out_size, 39 const unsigned char *header, 40 const unsigned char *data, 41 size_t data_size, 42 size_t data_plus_mac_plus_padding_size, 43 const unsigned char *mac_secret, 44 size_t mac_secret_length, char is_sslv3); 45 46# define l2n(l,c) (*((c)++)=(unsigned char)(((l)>>24)&0xff), \ 47 *((c)++)=(unsigned char)(((l)>>16)&0xff), \ 48 *((c)++)=(unsigned char)(((l)>> 8)&0xff), \ 49 *((c)++)=(unsigned char)(((l) )&0xff)) 50 51# define l2n6(l,c) (*((c)++)=(unsigned char)(((l)>>40)&0xff), \ 52 *((c)++)=(unsigned char)(((l)>>32)&0xff), \ 53 *((c)++)=(unsigned char)(((l)>>24)&0xff), \ 54 *((c)++)=(unsigned char)(((l)>>16)&0xff), \ 55 *((c)++)=(unsigned char)(((l)>> 8)&0xff), \ 56 *((c)++)=(unsigned char)(((l) )&0xff)) 57 58# define l2n8(l,c) (*((c)++)=(unsigned char)(((l)>>56)&0xff), \ 59 *((c)++)=(unsigned char)(((l)>>48)&0xff), \ 60 *((c)++)=(unsigned char)(((l)>>40)&0xff), \ 61 *((c)++)=(unsigned char)(((l)>>32)&0xff), \ 62 *((c)++)=(unsigned char)(((l)>>24)&0xff), \ 63 *((c)++)=(unsigned char)(((l)>>16)&0xff), \ 64 *((c)++)=(unsigned char)(((l)>> 8)&0xff), \ 65 *((c)++)=(unsigned char)(((l) )&0xff)) 66 67/* 68 * MAX_HASH_BIT_COUNT_BYTES is the maximum number of bytes in the hash's 69 * length field. (SHA-384/512 have 128-bit length.) 70 */ 71#define MAX_HASH_BIT_COUNT_BYTES 16 72 73/* 74 * MAX_HASH_BLOCK_SIZE is the maximum hash block size that we'll support. 75 * Currently SHA-384/512 has a 128-byte block size and that's the largest 76 * supported by TLS.) 77 */ 78#define MAX_HASH_BLOCK_SIZE 128 79 80#ifndef FIPS_MODULE 81/* 82 * u32toLE serializes an unsigned, 32-bit number (n) as four bytes at (p) in 83 * little-endian order. The value of p is advanced by four. 84 */ 85# define u32toLE(n, p) \ 86 (*((p)++)=(unsigned char)(n), \ 87 *((p)++)=(unsigned char)(n>>8), \ 88 *((p)++)=(unsigned char)(n>>16), \ 89 *((p)++)=(unsigned char)(n>>24)) 90 91/* 92 * These functions serialize the state of a hash and thus perform the 93 * standard "final" operation without adding the padding and length that such 94 * a function typically does. 95 */ 96static void tls1_md5_final_raw(void *ctx, unsigned char *md_out) 97{ 98 MD5_CTX *md5 = ctx; 99 u32toLE(md5->A, md_out); 100 u32toLE(md5->B, md_out); 101 u32toLE(md5->C, md_out); 102 u32toLE(md5->D, md_out); 103} 104#endif /* FIPS_MODULE */ 105 106static void tls1_sha1_final_raw(void *ctx, unsigned char *md_out) 107{ 108 SHA_CTX *sha1 = ctx; 109 l2n(sha1->h0, md_out); 110 l2n(sha1->h1, md_out); 111 l2n(sha1->h2, md_out); 112 l2n(sha1->h3, md_out); 113 l2n(sha1->h4, md_out); 114} 115 116static void tls1_sha256_final_raw(void *ctx, unsigned char *md_out) 117{ 118 SHA256_CTX *sha256 = ctx; 119 unsigned i; 120 121 for (i = 0; i < 8; i++) { 122 l2n(sha256->h[i], md_out); 123 } 124} 125 126static void tls1_sha512_final_raw(void *ctx, unsigned char *md_out) 127{ 128 SHA512_CTX *sha512 = ctx; 129 unsigned i; 130 131 for (i = 0; i < 8; i++) { 132 l2n8(sha512->h[i], md_out); 133 } 134} 135 136#undef LARGEST_DIGEST_CTX 137#define LARGEST_DIGEST_CTX SHA512_CTX 138 139/*- 140 * ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS 141 * record. 142 * 143 * ctx: the EVP_MD_CTX from which we take the hash function. 144 * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX. 145 * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written. 146 * md_out_size: if non-NULL, the number of output bytes is written here. 147 * header: the 13-byte, TLS record header. 148 * data: the record data itself, less any preceding explicit IV. 149 * data_size: the secret, reported length of the data once the MAC and padding 150 * has been removed. 151 * data_plus_mac_plus_padding_size: the public length of the whole 152 * record, including MAC and padding. 153 * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS. 154 * 155 * On entry: we know that data is data_plus_mac_plus_padding_size in length 156 * Returns 1 on success or 0 on error 157 */ 158int ssl3_cbc_digest_record(const EVP_MD *md, 159 unsigned char *md_out, 160 size_t *md_out_size, 161 const unsigned char *header, 162 const unsigned char *data, 163 size_t data_size, 164 size_t data_plus_mac_plus_padding_size, 165 const unsigned char *mac_secret, 166 size_t mac_secret_length, char is_sslv3) 167{ 168 union { 169 OSSL_UNION_ALIGN; 170 unsigned char c[sizeof(LARGEST_DIGEST_CTX)]; 171 } md_state; 172 void (*md_final_raw) (void *ctx, unsigned char *md_out); 173 void (*md_transform) (void *ctx, const unsigned char *block); 174 size_t md_size, md_block_size = 64; 175 size_t sslv3_pad_length = 40, header_length, variance_blocks, 176 len, max_mac_bytes, num_blocks, 177 num_starting_blocks, k, mac_end_offset, c, index_a, index_b; 178 size_t bits; /* at most 18 bits */ 179 unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES]; 180 /* hmac_pad is the masked HMAC key. */ 181 unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE]; 182 unsigned char first_block[MAX_HASH_BLOCK_SIZE]; 183 unsigned char mac_out[EVP_MAX_MD_SIZE]; 184 size_t i, j; 185 unsigned md_out_size_u; 186 EVP_MD_CTX *md_ctx = NULL; 187 /* 188 * mdLengthSize is the number of bytes in the length field that 189 * terminates * the hash. 190 */ 191 size_t md_length_size = 8; 192 char length_is_big_endian = 1; 193 int ret = 0; 194 195 /* 196 * This is a, hopefully redundant, check that allows us to forget about 197 * many possible overflows later in this function. 198 */ 199 if (!ossl_assert(data_plus_mac_plus_padding_size < 1024 * 1024)) 200 return 0; 201 202 if (EVP_MD_is_a(md, "MD5")) { 203#ifdef FIPS_MODULE 204 return 0; 205#else 206 if (MD5_Init((MD5_CTX *)md_state.c) <= 0) 207 return 0; 208 md_final_raw = tls1_md5_final_raw; 209 md_transform = 210 (void (*)(void *ctx, const unsigned char *block))MD5_Transform; 211 md_size = 16; 212 sslv3_pad_length = 48; 213 length_is_big_endian = 0; 214#endif 215 } else if (EVP_MD_is_a(md, "SHA1")) { 216 if (SHA1_Init((SHA_CTX *)md_state.c) <= 0) 217 return 0; 218 md_final_raw = tls1_sha1_final_raw; 219 md_transform = 220 (void (*)(void *ctx, const unsigned char *block))SHA1_Transform; 221 md_size = 20; 222 } else if (EVP_MD_is_a(md, "SHA2-224")) { 223 if (SHA224_Init((SHA256_CTX *)md_state.c) <= 0) 224 return 0; 225 md_final_raw = tls1_sha256_final_raw; 226 md_transform = 227 (void (*)(void *ctx, const unsigned char *block))SHA256_Transform; 228 md_size = 224 / 8; 229 } else if (EVP_MD_is_a(md, "SHA2-256")) { 230 if (SHA256_Init((SHA256_CTX *)md_state.c) <= 0) 231 return 0; 232 md_final_raw = tls1_sha256_final_raw; 233 md_transform = 234 (void (*)(void *ctx, const unsigned char *block))SHA256_Transform; 235 md_size = 32; 236 } else if (EVP_MD_is_a(md, "SHA2-384")) { 237 if (SHA384_Init((SHA512_CTX *)md_state.c) <= 0) 238 return 0; 239 md_final_raw = tls1_sha512_final_raw; 240 md_transform = 241 (void (*)(void *ctx, const unsigned char *block))SHA512_Transform; 242 md_size = 384 / 8; 243 md_block_size = 128; 244 md_length_size = 16; 245 } else if (EVP_MD_is_a(md, "SHA2-512")) { 246 if (SHA512_Init((SHA512_CTX *)md_state.c) <= 0) 247 return 0; 248 md_final_raw = tls1_sha512_final_raw; 249 md_transform = 250 (void (*)(void *ctx, const unsigned char *block))SHA512_Transform; 251 md_size = 64; 252 md_block_size = 128; 253 md_length_size = 16; 254 } else { 255 /* 256 * ssl3_cbc_record_digest_supported should have been called first to 257 * check that the hash function is supported. 258 */ 259 if (md_out_size != NULL) 260 *md_out_size = 0; 261 return ossl_assert(0); 262 } 263 264 if (!ossl_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES) 265 || !ossl_assert(md_block_size <= MAX_HASH_BLOCK_SIZE) 266 || !ossl_assert(md_size <= EVP_MAX_MD_SIZE)) 267 return 0; 268 269 header_length = 13; 270 if (is_sslv3) { 271 header_length = mac_secret_length + sslv3_pad_length + 8 /* sequence 272 * number */ + 273 1 /* record type */ + 274 2 /* record length */ ; 275 } 276 277 /* 278 * variance_blocks is the number of blocks of the hash that we have to 279 * calculate in constant time because they could be altered by the 280 * padding value. In SSLv3, the padding must be minimal so the end of 281 * the plaintext varies by, at most, 15+20 = 35 bytes. (We conservatively 282 * assume that the MAC size varies from 0..20 bytes.) In case the 9 bytes 283 * of hash termination (0x80 + 64-bit length) don't fit in the final 284 * block, we say that the final two blocks can vary based on the padding. 285 * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not 286 * required to be minimal. Therefore we say that the final |variance_blocks| 287 * blocks can 288 * vary based on the padding. Later in the function, if the message is 289 * short and there obviously cannot be this many blocks then 290 * variance_blocks can be reduced. 291 */ 292 variance_blocks = is_sslv3 ? 2 : ( ((255 + 1 + md_size + md_block_size - 1) / md_block_size) + 1); 293 /* 294 * From now on we're dealing with the MAC, which conceptually has 13 295 * bytes of `header' before the start of the data (TLS) or 71/75 bytes 296 * (SSLv3) 297 */ 298 len = data_plus_mac_plus_padding_size + header_length; 299 /* 300 * max_mac_bytes contains the maximum bytes of bytes in the MAC, 301 * including * |header|, assuming that there's no padding. 302 */ 303 max_mac_bytes = len - md_size - 1; 304 /* num_blocks is the maximum number of hash blocks. */ 305 num_blocks = 306 (max_mac_bytes + 1 + md_length_size + md_block_size - 307 1) / md_block_size; 308 /* 309 * In order to calculate the MAC in constant time we have to handle the 310 * final blocks specially because the padding value could cause the end 311 * to appear somewhere in the final |variance_blocks| blocks and we can't 312 * leak where. However, |num_starting_blocks| worth of data can be hashed 313 * right away because no padding value can affect whether they are 314 * plaintext. 315 */ 316 num_starting_blocks = 0; 317 /* 318 * k is the starting byte offset into the conceptual header||data where 319 * we start processing. 320 */ 321 k = 0; 322 /* 323 * mac_end_offset is the index just past the end of the data to be MACed. 324 */ 325 mac_end_offset = data_size + header_length; 326 /* 327 * c is the index of the 0x80 byte in the final hash block that contains 328 * application data. 329 */ 330 c = mac_end_offset % md_block_size; 331 /* 332 * index_a is the hash block number that contains the 0x80 terminating 333 * value. 334 */ 335 index_a = mac_end_offset / md_block_size; 336 /* 337 * index_b is the hash block number that contains the 64-bit hash length, 338 * in bits. 339 */ 340 index_b = (mac_end_offset + md_length_size) / md_block_size; 341 /* 342 * bits is the hash-length in bits. It includes the additional hash block 343 * for the masked HMAC key, or whole of |header| in the case of SSLv3. 344 */ 345 346 /* 347 * For SSLv3, if we're going to have any starting blocks then we need at 348 * least two because the header is larger than a single block. 349 */ 350 if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0)) { 351 num_starting_blocks = num_blocks - variance_blocks; 352 k = md_block_size * num_starting_blocks; 353 } 354 355 bits = 8 * mac_end_offset; 356 if (!is_sslv3) { 357 /* 358 * Compute the initial HMAC block. For SSLv3, the padding and secret 359 * bytes are included in |header| because they take more than a 360 * single block. 361 */ 362 bits += 8 * md_block_size; 363 memset(hmac_pad, 0, md_block_size); 364 if (!ossl_assert(mac_secret_length <= sizeof(hmac_pad))) 365 return 0; 366 memcpy(hmac_pad, mac_secret, mac_secret_length); 367 for (i = 0; i < md_block_size; i++) 368 hmac_pad[i] ^= 0x36; 369 370 md_transform(md_state.c, hmac_pad); 371 } 372 373 if (length_is_big_endian) { 374 memset(length_bytes, 0, md_length_size - 4); 375 length_bytes[md_length_size - 4] = (unsigned char)(bits >> 24); 376 length_bytes[md_length_size - 3] = (unsigned char)(bits >> 16); 377 length_bytes[md_length_size - 2] = (unsigned char)(bits >> 8); 378 length_bytes[md_length_size - 1] = (unsigned char)bits; 379 } else { 380 memset(length_bytes, 0, md_length_size); 381 length_bytes[md_length_size - 5] = (unsigned char)(bits >> 24); 382 length_bytes[md_length_size - 6] = (unsigned char)(bits >> 16); 383 length_bytes[md_length_size - 7] = (unsigned char)(bits >> 8); 384 length_bytes[md_length_size - 8] = (unsigned char)bits; 385 } 386 387 if (k > 0) { 388 if (is_sslv3) { 389 size_t overhang; 390 391 /* 392 * The SSLv3 header is larger than a single block. overhang is 393 * the number of bytes beyond a single block that the header 394 * consumes: either 7 bytes (SHA1) or 11 bytes (MD5). There are no 395 * ciphersuites in SSLv3 that are not SHA1 or MD5 based and 396 * therefore we can be confident that the header_length will be 397 * greater than |md_block_size|. However we add a sanity check just 398 * in case 399 */ 400 if (header_length <= md_block_size) { 401 /* Should never happen */ 402 return 0; 403 } 404 overhang = header_length - md_block_size; 405 md_transform(md_state.c, header); 406 memcpy(first_block, header + md_block_size, overhang); 407 memcpy(first_block + overhang, data, md_block_size - overhang); 408 md_transform(md_state.c, first_block); 409 for (i = 1; i < k / md_block_size - 1; i++) 410 md_transform(md_state.c, data + md_block_size * i - overhang); 411 } else { 412 /* k is a multiple of md_block_size. */ 413 memcpy(first_block, header, 13); 414 memcpy(first_block + 13, data, md_block_size - 13); 415 md_transform(md_state.c, first_block); 416 for (i = 1; i < k / md_block_size; i++) 417 md_transform(md_state.c, data + md_block_size * i - 13); 418 } 419 } 420 421 memset(mac_out, 0, sizeof(mac_out)); 422 423 /* 424 * We now process the final hash blocks. For each block, we construct it 425 * in constant time. If the |i==index_a| then we'll include the 0x80 426 * bytes and zero pad etc. For each block we selectively copy it, in 427 * constant time, to |mac_out|. 428 */ 429 for (i = num_starting_blocks; i <= num_starting_blocks + variance_blocks; 430 i++) { 431 unsigned char block[MAX_HASH_BLOCK_SIZE]; 432 unsigned char is_block_a = constant_time_eq_8_s(i, index_a); 433 unsigned char is_block_b = constant_time_eq_8_s(i, index_b); 434 for (j = 0; j < md_block_size; j++) { 435 unsigned char b = 0, is_past_c, is_past_cp1; 436 if (k < header_length) 437 b = header[k]; 438 else if (k < data_plus_mac_plus_padding_size + header_length) 439 b = data[k - header_length]; 440 k++; 441 442 is_past_c = is_block_a & constant_time_ge_8_s(j, c); 443 is_past_cp1 = is_block_a & constant_time_ge_8_s(j, c + 1); 444 /* 445 * If this is the block containing the end of the application 446 * data, and we are at the offset for the 0x80 value, then 447 * overwrite b with 0x80. 448 */ 449 b = constant_time_select_8(is_past_c, 0x80, b); 450 /* 451 * If this block contains the end of the application data 452 * and we're past the 0x80 value then just write zero. 453 */ 454 b = b & ~is_past_cp1; 455 /* 456 * If this is index_b (the final block), but not index_a (the end 457 * of the data), then the 64-bit length didn't fit into index_a 458 * and we're having to add an extra block of zeros. 459 */ 460 b &= ~is_block_b | is_block_a; 461 462 /* 463 * The final bytes of one of the blocks contains the length. 464 */ 465 if (j >= md_block_size - md_length_size) { 466 /* If this is index_b, write a length byte. */ 467 b = constant_time_select_8(is_block_b, 468 length_bytes[j - 469 (md_block_size - 470 md_length_size)], b); 471 } 472 block[j] = b; 473 } 474 475 md_transform(md_state.c, block); 476 md_final_raw(md_state.c, block); 477 /* If this is index_b, copy the hash value to |mac_out|. */ 478 for (j = 0; j < md_size; j++) 479 mac_out[j] |= block[j] & is_block_b; 480 } 481 482 md_ctx = EVP_MD_CTX_new(); 483 if (md_ctx == NULL) 484 goto err; 485 486 if (EVP_DigestInit_ex(md_ctx, md, NULL /* engine */ ) <= 0) 487 goto err; 488 if (is_sslv3) { 489 /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */ 490 memset(hmac_pad, 0x5c, sslv3_pad_length); 491 492 if (EVP_DigestUpdate(md_ctx, mac_secret, mac_secret_length) <= 0 493 || EVP_DigestUpdate(md_ctx, hmac_pad, sslv3_pad_length) <= 0 494 || EVP_DigestUpdate(md_ctx, mac_out, md_size) <= 0) 495 goto err; 496 } else { 497 /* Complete the HMAC in the standard manner. */ 498 for (i = 0; i < md_block_size; i++) 499 hmac_pad[i] ^= 0x6a; 500 501 if (EVP_DigestUpdate(md_ctx, hmac_pad, md_block_size) <= 0 502 || EVP_DigestUpdate(md_ctx, mac_out, md_size) <= 0) 503 goto err; 504 } 505 ret = EVP_DigestFinal(md_ctx, md_out, &md_out_size_u); 506 if (ret && md_out_size) 507 *md_out_size = md_out_size_u; 508 509 ret = 1; 510 err: 511 EVP_MD_CTX_free(md_ctx); 512 return ret; 513} 514