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| 1 /* ssl/s3_cbc.c */ | |
| 2 /* ==================================================================== | |
| 3 * Copyright (c) 2012 The OpenSSL Project. All rights reserved. | |
| 4 * | |
| 5 * Redistribution and use in source and binary forms, with or without | |
| 6 * modification, are permitted provided that the following conditions | |
| 7 * are met: | |
| 8 * | |
| 9 * 1. Redistributions of source code must retain the above copyright | |
| 10 * notice, this list of conditions and the following disclaimer. | |
| 11 * | |
| 12 * 2. Redistributions in binary form must reproduce the above copyright | |
| 13 * notice, this list of conditions and the following disclaimer in | |
| 14 * the documentation and/or other materials provided with the | |
| 15 * distribution. | |
| 16 * | |
| 17 * 3. All advertising materials mentioning features or use of this | |
| 18 * software must display the following acknowledgment: | |
| 19 * "This product includes software developed by the OpenSSL Project | |
| 20 * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" | |
| 21 * | |
| 22 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to | |
| 23 * endorse or promote products derived from this software without | |
| 24 * prior written permission. For written permission, please contact | |
| 25 * openssl-core@openssl.org. | |
| 26 * | |
| 27 * 5. Products derived from this software may not be called "OpenSSL" | |
| 28 * nor may "OpenSSL" appear in their names without prior written | |
| 29 * permission of the OpenSSL Project. | |
| 30 * | |
| 31 * 6. Redistributions of any form whatsoever must retain the following | |
| 32 * acknowledgment: | |
| 33 * "This product includes software developed by the OpenSSL Project | |
| 34 * for use in the OpenSSL Toolkit (http://www.openssl.org/)" | |
| 35 * | |
| 36 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY | |
| 37 * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
| 38 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR | |
| 39 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR | |
| 40 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |
| 41 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
| 42 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; | |
| 43 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
| 44 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, | |
| 45 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) | |
| 46 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED | |
| 47 * OF THE POSSIBILITY OF SUCH DAMAGE. | |
| 48 * ==================================================================== | |
| 49 * | |
| 50 * This product includes cryptographic software written by Eric Young | |
| 51 * (eay@cryptsoft.com). This product includes software written by Tim | |
| 52 * Hudson (tjh@cryptsoft.com). | |
| 53 * | |
| 54 */ | |
| 55 | |
| 56 #include "ssl_locl.h" | |
| 57 | |
| 58 #include <openssl/md5.h> | |
| 59 #include <openssl/sha.h> | |
| 60 | |
| 61 /* MAX_HASH_BIT_COUNT_BYTES is the maximum number of bytes in the hash's length | |
| 62 * field. (SHA-384/512 have 128-bit length.) */ | |
| 63 #define MAX_HASH_BIT_COUNT_BYTES 16 | |
| 64 | |
| 65 /* MAX_HASH_BLOCK_SIZE is the maximum hash block size that we'll support. | |
| 66 * Currently SHA-384/512 has a 128-byte block size and that's the largest | |
| 67 * supported by TLS.) */ | |
| 68 #define MAX_HASH_BLOCK_SIZE 128 | |
| 69 | |
| 70 /* Some utility functions are needed: | |
| 71 * | |
| 72 * These macros return the given value with the MSB copied to all the other | |
| 73 * bits. They use the fact that arithmetic shift shifts-in the sign bit. | |
| 74 * However, this is not ensured by the C standard so you may need to replace | |
| 75 * them with something else on odd CPUs. */ | |
| 76 #define DUPLICATE_MSB_TO_ALL(x) ( (unsigned)( (int)(x) >> (sizeof(int)*8-1) ) ) | |
| 77 #define DUPLICATE_MSB_TO_ALL_8(x) ((unsigned char)(DUPLICATE_MSB_TO_ALL(x))) | |
| 78 | |
| 79 /* constant_time_lt returns 0xff if a<b and 0x00 otherwise. */ | |
| 80 static unsigned constant_time_lt(unsigned a, unsigned b) | |
| 81 { | |
| 82 a -= b; | |
| 83 return DUPLICATE_MSB_TO_ALL(a); | |
| 84 } | |
| 85 | |
| 86 /* constant_time_ge returns 0xff if a>=b and 0x00 otherwise. */ | |
| 87 static unsigned constant_time_ge(unsigned a, unsigned b) | |
| 88 { | |
| 89 a -= b; | |
| 90 return DUPLICATE_MSB_TO_ALL(~a); | |
| 91 } | |
| 92 | |
| 93 /* constant_time_eq_8 returns 0xff if a==b and 0x00 otherwise. */ | |
| 94 static unsigned char constant_time_eq_8(unsigned a, unsigned b) | |
| 95 { | |
| 96 unsigned c = a ^ b; | |
| 97 c--; | |
| 98 return DUPLICATE_MSB_TO_ALL_8(c); | |
| 99 } | |
| 100 | |
| 101 /* ssl3_cbc_remove_padding removes padding from the decrypted, SSLv3, CBC | |
| 102 * record in |rec| by updating |rec->length| in constant time. | |
| 103 * | |
| 104 * block_size: the block size of the cipher used to encrypt the record. | |
| 105 * returns: | |
| 106 * 0: (in non-constant time) if the record is publicly invalid. | |
| 107 * 1: if the padding was valid | |
| 108 * -1: otherwise. */ | |
| 109 int ssl3_cbc_remove_padding(const SSL* s, | |
| 110 SSL3_RECORD *rec, | |
| 111 unsigned block_size, | |
| 112 unsigned mac_size) | |
| 113 { | |
| 114 unsigned padding_length, good; | |
| 115 const unsigned overhead = 1 /* padding length byte */ + mac_size; | |
| 116 | |
| 117 /* These lengths are all public so we can test them in non-constant | |
| 118 * time. */ | |
| 119 if (overhead > rec->length) | |
| 120 return 0; | |
| 121 | |
| 122 padding_length = rec->data[rec->length-1]; | |
| 123 good = constant_time_ge(rec->length, padding_length+overhead); | |
| 124 /* SSLv3 requires that the padding is minimal. */ | |
| 125 good &= constant_time_ge(block_size, padding_length+1); | |
| 126 padding_length = good & (padding_length+1); | |
| 127 rec->length -= padding_length; | |
| 128 rec->type |= padding_length<<8; /* kludge: pass padding length */ | |
| 129 return (int)((good & 1) | (~good & -1)); | |
| 130 } | |
| 131 | |
| 132 /* tls1_cbc_remove_padding removes the CBC padding from the decrypted, TLS, CBC | |
| 133 * record in |rec| in constant time and returns 1 if the padding is valid and | |
| 134 * -1 otherwise. It also removes any explicit IV from the start of the record | |
| 135 * without leaking any timing about whether there was enough space after the | |
| 136 * padding was removed. | |
| 137 * | |
| 138 * block_size: the block size of the cipher used to encrypt the record. | |
| 139 * returns: | |
| 140 * 0: (in non-constant time) if the record is publicly invalid. | |
| 141 * 1: if the padding was valid | |
| 142 * -1: otherwise. */ | |
| 143 int tls1_cbc_remove_padding(const SSL* s, | |
| 144 SSL3_RECORD *rec, | |
| 145 unsigned block_size, | |
| 146 unsigned mac_size) | |
| 147 { | |
| 148 unsigned padding_length, good, to_check, i; | |
| 149 const unsigned overhead = 1 /* padding length byte */ + mac_size; | |
| 150 /* Check if version requires explicit IV */ | |
| 151 if (s->version >= TLS1_1_VERSION || s->version == DTLS1_VERSION) | |
| 152 { | |
| 153 /* These lengths are all public so we can test them in | |
| 154 * non-constant time. | |
| 155 */ | |
| 156 if (overhead + block_size > rec->length) | |
| 157 return 0; | |
| 158 /* We can now safely skip explicit IV */ | |
| 159 rec->data += block_size; | |
| 160 rec->input += block_size; | |
| 161 rec->length -= block_size; | |
| 162 } | |
| 163 else if (overhead > rec->length) | |
| 164 return 0; | |
| 165 | |
| 166 padding_length = rec->data[rec->length-1]; | |
| 167 | |
| 168 /* NB: if compression is in operation the first packet may not be of | |
| 169 * even length so the padding bug check cannot be performed. This bug | |
| 170 * workaround has been around since SSLeay so hopefully it is either | |
| 171 * fixed now or no buggy implementation supports compression [steve] | |
| 172 */ | |
| 173 if ( (s->options&SSL_OP_TLS_BLOCK_PADDING_BUG) && !s->expand) | |
| 174 { | |
| 175 /* First packet is even in size, so check */ | |
| 176 if ((memcmp(s->s3->read_sequence, "\0\0\0\0\0\0\0\0",8) == 0) && | |
| 177 !(padding_length & 1)) | |
| 178 { | |
| 179 s->s3->flags|=TLS1_FLAGS_TLS_PADDING_BUG; | |
| 180 } | |
| 181 if ((s->s3->flags & TLS1_FLAGS_TLS_PADDING_BUG) && | |
| 182 padding_length > 0) | |
| 183 { | |
| 184 padding_length--; | |
| 185 } | |
| 186 } | |
| 187 | |
| 188 if (EVP_CIPHER_flags(s->enc_read_ctx->cipher)&EVP_CIPH_FLAG_AEAD_CIPHER) | |
| 189 { | |
| 190 /* padding is already verified */ | |
| 191 rec->length -= padding_length + 1; | |
| 192 return 1; | |
| 193 } | |
| 194 | |
| 195 good = constant_time_ge(rec->length, overhead+padding_length); | |
| 196 /* The padding consists of a length byte at the end of the record and | |
| 197 * then that many bytes of padding, all with the same value as the | |
| 198 * length byte. Thus, with the length byte included, there are i+1 | |
| 199 * bytes of padding. | |
| 200 * | |
| 201 * We can't check just |padding_length+1| bytes because that leaks | |
| 202 * decrypted information. Therefore we always have to check the maximum | |
| 203 * amount of padding possible. (Again, the length of the record is | |
| 204 * public information so we can use it.) */ | |
| 205 to_check = 255; /* maximum amount of padding. */ | |
| 206 if (to_check > rec->length-1) | |
| 207 to_check = rec->length-1; | |
| 208 | |
| 209 for (i = 0; i < to_check; i++) | |
| 210 { | |
| 211 unsigned char mask = constant_time_ge(padding_length, i); | |
| 212 unsigned char b = rec->data[rec->length-1-i]; | |
| 213 /* The final |padding_length+1| bytes should all have the value | |
| 214 * |padding_length|. Therefore the XOR should be zero. */ | |
| 215 good &= ~(mask&(padding_length ^ b)); | |
| 216 } | |
| 217 | |
| 218 /* If any of the final |padding_length+1| bytes had the wrong value, | |
| 219 * one or more of the lower eight bits of |good| will be cleared. We | |
| 220 * AND the bottom 8 bits together and duplicate the result to all the | |
| 221 * bits. */ | |
| 222 good &= good >> 4; | |
| 223 good &= good >> 2; | |
| 224 good &= good >> 1; | |
| 225 good <<= sizeof(good)*8-1; | |
| 226 good = DUPLICATE_MSB_TO_ALL(good); | |
| 227 | |
| 228 padding_length = good & (padding_length+1); | |
| 229 rec->length -= padding_length; | |
| 230 rec->type |= padding_length<<8; /* kludge: pass padding length */ | |
| 231 | |
| 232 return (int)((good & 1) | (~good & -1)); | |
| 233 } | |
| 234 | |
| 235 /* ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in | |
| 236 * constant time (independent of the concrete value of rec->length, which may | |
| 237 * vary within a 256-byte window). | |
| 238 * | |
| 239 * ssl3_cbc_remove_padding or tls1_cbc_remove_padding must be called prior to | |
| 240 * this function. | |
| 241 * | |
| 242 * On entry: | |
| 243 * rec->orig_len >= md_size | |
| 244 * md_size <= EVP_MAX_MD_SIZE | |
| 245 * | |
| 246 * If CBC_MAC_ROTATE_IN_PLACE is defined then the rotation is performed with | |
| 247 * variable accesses in a 64-byte-aligned buffer. Assuming that this fits into | |
| 248 * a single or pair of cache-lines, then the variable memory accesses don't | |
| 249 * actually affect the timing. CPUs with smaller cache-lines [if any] are | |
| 250 * not multi-core and are not considered vulnerable to cache-timing attacks. | |
| 251 */ | |
| 252 #define CBC_MAC_ROTATE_IN_PLACE | |
| 253 | |
| 254 void ssl3_cbc_copy_mac(unsigned char* out, | |
| 255 const SSL3_RECORD *rec, | |
| 256 unsigned md_size,unsigned orig_len) | |
| 257 { | |
| 258 #if defined(CBC_MAC_ROTATE_IN_PLACE) | |
| 259 unsigned char rotated_mac_buf[64+EVP_MAX_MD_SIZE]; | |
| 260 unsigned char *rotated_mac; | |
| 261 #else | |
| 262 unsigned char rotated_mac[EVP_MAX_MD_SIZE]; | |
| 263 #endif | |
| 264 | |
| 265 /* mac_end is the index of |rec->data| just after the end of the MAC. */ | |
| 266 unsigned mac_end = rec->length; | |
| 267 unsigned mac_start = mac_end - md_size; | |
| 268 /* scan_start contains the number of bytes that we can ignore because | |
| 269 * the MAC's position can only vary by 255 bytes. */ | |
| 270 unsigned scan_start = 0; | |
| 271 unsigned i, j; | |
| 272 unsigned div_spoiler; | |
| 273 unsigned rotate_offset; | |
| 274 | |
| 275 OPENSSL_assert(orig_len >= md_size); | |
| 276 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE); | |
| 277 | |
| 278 #if defined(CBC_MAC_ROTATE_IN_PLACE) | |
| 279 rotated_mac = rotated_mac_buf + ((0-(size_t)rotated_mac_buf)&63); | |
| 280 #endif | |
| 281 | |
| 282 /* This information is public so it's safe to branch based on it. */ | |
| 283 if (orig_len > md_size + 255 + 1) | |
| 284 scan_start = orig_len - (md_size + 255 + 1); | |
| 285 /* div_spoiler contains a multiple of md_size that is used to cause the | |
| 286 * modulo operation to be constant time. Without this, the time varies | |
| 287 * based on the amount of padding when running on Intel chips at least. | |
| 288 * | |
| 289 * The aim of right-shifting md_size is so that the compiler doesn't | |
| 290 * figure out that it can remove div_spoiler as that would require it | |
| 291 * to prove that md_size is always even, which I hope is beyond it. */ | |
| 292 div_spoiler = md_size >> 1; | |
| 293 div_spoiler <<= (sizeof(div_spoiler)-1)*8; | |
| 294 rotate_offset = (div_spoiler + mac_start - scan_start) % md_size; | |
| 295 | |
| 296 memset(rotated_mac, 0, md_size); | |
| 297 for (i = scan_start, j = 0; i < orig_len; i++) | |
| 298 { | |
| 299 unsigned char mac_started = constant_time_ge(i, mac_start); | |
| 300 unsigned char mac_ended = constant_time_ge(i, mac_end); | |
| 301 unsigned char b = rec->data[i]; | |
| 302 rotated_mac[j++] |= b & mac_started & ~mac_ended; | |
| 303 j &= constant_time_lt(j,md_size); | |
| 304 } | |
| 305 | |
| 306 /* Now rotate the MAC */ | |
| 307 #if defined(CBC_MAC_ROTATE_IN_PLACE) | |
| 308 j = 0; | |
| 309 for (i = 0; i < md_size; i++) | |
| 310 { | |
| 311 /* in case cache-line is 32 bytes, touch second line */ | |
| 312 ((volatile unsigned char *)rotated_mac)[rotate_offset^32]; | |
| 313 out[j++] = rotated_mac[rotate_offset++]; | |
| 314 rotate_offset &= constant_time_lt(rotate_offset,md_size); | |
| 315 } | |
| 316 #else | |
| 317 memset(out, 0, md_size); | |
| 318 rotate_offset = md_size - rotate_offset; | |
| 319 rotate_offset &= constant_time_lt(rotate_offset,md_size); | |
| 320 for (i = 0; i < md_size; i++) | |
| 321 { | |
| 322 for (j = 0; j < md_size; j++) | |
| 323 out[j] |= rotated_mac[i] & constant_time_eq_8(j, rotate_
offset); | |
| 324 rotate_offset++; | |
| 325 rotate_offset &= constant_time_lt(rotate_offset,md_size); | |
| 326 } | |
| 327 #endif | |
| 328 } | |
| 329 | |
| 330 /* u32toLE serialises an unsigned, 32-bit number (n) as four bytes at (p) in | |
| 331 * little-endian order. The value of p is advanced by four. */ | |
| 332 #define u32toLE(n, p) \ | |
| 333 (*((p)++)=(unsigned char)(n), \ | |
| 334 *((p)++)=(unsigned char)(n>>8), \ | |
| 335 *((p)++)=(unsigned char)(n>>16), \ | |
| 336 *((p)++)=(unsigned char)(n>>24)) | |
| 337 | |
| 338 /* These functions serialize the state of a hash and thus perform the standard | |
| 339 * "final" operation without adding the padding and length that such a function | |
| 340 * typically does. */ | |
| 341 static void tls1_md5_final_raw(void* ctx, unsigned char *md_out) | |
| 342 { | |
| 343 MD5_CTX *md5 = ctx; | |
| 344 u32toLE(md5->A, md_out); | |
| 345 u32toLE(md5->B, md_out); | |
| 346 u32toLE(md5->C, md_out); | |
| 347 u32toLE(md5->D, md_out); | |
| 348 } | |
| 349 | |
| 350 static void tls1_sha1_final_raw(void* ctx, unsigned char *md_out) | |
| 351 { | |
| 352 SHA_CTX *sha1 = ctx; | |
| 353 l2n(sha1->h0, md_out); | |
| 354 l2n(sha1->h1, md_out); | |
| 355 l2n(sha1->h2, md_out); | |
| 356 l2n(sha1->h3, md_out); | |
| 357 l2n(sha1->h4, md_out); | |
| 358 } | |
| 359 #define LARGEST_DIGEST_CTX SHA_CTX | |
| 360 | |
| 361 #ifndef OPENSSL_NO_SHA256 | |
| 362 static void tls1_sha256_final_raw(void* ctx, unsigned char *md_out) | |
| 363 { | |
| 364 SHA256_CTX *sha256 = ctx; | |
| 365 unsigned i; | |
| 366 | |
| 367 for (i = 0; i < 8; i++) | |
| 368 { | |
| 369 l2n(sha256->h[i], md_out); | |
| 370 } | |
| 371 } | |
| 372 #undef LARGEST_DIGEST_CTX | |
| 373 #define LARGEST_DIGEST_CTX SHA256_CTX | |
| 374 #endif | |
| 375 | |
| 376 #ifndef OPENSSL_NO_SHA512 | |
| 377 static void tls1_sha512_final_raw(void* ctx, unsigned char *md_out) | |
| 378 { | |
| 379 SHA512_CTX *sha512 = ctx; | |
| 380 unsigned i; | |
| 381 | |
| 382 for (i = 0; i < 8; i++) | |
| 383 { | |
| 384 l2n8(sha512->h[i], md_out); | |
| 385 } | |
| 386 } | |
| 387 #undef LARGEST_DIGEST_CTX | |
| 388 #define LARGEST_DIGEST_CTX SHA512_CTX | |
| 389 #endif | |
| 390 | |
| 391 /* ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function | |
| 392 * which ssl3_cbc_digest_record supports. */ | |
| 393 char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx) | |
| 394 { | |
| 395 #ifdef OPENSSL_FIPS | |
| 396 if (FIPS_mode()) | |
| 397 return 0; | |
| 398 #endif | |
| 399 switch (EVP_MD_CTX_type(ctx)) | |
| 400 { | |
| 401 case NID_md5: | |
| 402 case NID_sha1: | |
| 403 #ifndef OPENSSL_NO_SHA256 | |
| 404 case NID_sha224: | |
| 405 case NID_sha256: | |
| 406 #endif | |
| 407 #ifndef OPENSSL_NO_SHA512 | |
| 408 case NID_sha384: | |
| 409 case NID_sha512: | |
| 410 #endif | |
| 411 return 1; | |
| 412 default: | |
| 413 return 0; | |
| 414 } | |
| 415 } | |
| 416 | |
| 417 /* ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS | |
| 418 * record. | |
| 419 * | |
| 420 * ctx: the EVP_MD_CTX from which we take the hash function. | |
| 421 * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX. | |
| 422 * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written. | |
| 423 * md_out_size: if non-NULL, the number of output bytes is written here. | |
| 424 * header: the 13-byte, TLS record header. | |
| 425 * data: the record data itself, less any preceeding explicit IV. | |
| 426 * data_plus_mac_size: the secret, reported length of the data and MAC | |
| 427 * once the padding has been removed. | |
| 428 * data_plus_mac_plus_padding_size: the public length of the whole | |
| 429 * record, including padding. | |
| 430 * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS. | |
| 431 * | |
| 432 * On entry: by virtue of having been through one of the remove_padding | |
| 433 * functions, above, we know that data_plus_mac_size is large enough to contain | |
| 434 * a padding byte and MAC. (If the padding was invalid, it might contain the | |
| 435 * padding too. ) */ | |
| 436 void ssl3_cbc_digest_record( | |
| 437 const EVP_MD_CTX *ctx, | |
| 438 unsigned char* md_out, | |
| 439 size_t* md_out_size, | |
| 440 const unsigned char header[13], | |
| 441 const unsigned char *data, | |
| 442 size_t data_plus_mac_size, | |
| 443 size_t data_plus_mac_plus_padding_size, | |
| 444 const unsigned char *mac_secret, | |
| 445 unsigned mac_secret_length, | |
| 446 char is_sslv3) | |
| 447 { | |
| 448 union { double align; | |
| 449 unsigned char c[sizeof(LARGEST_DIGEST_CTX)]; } md_state; | |
| 450 void (*md_final_raw)(void *ctx, unsigned char *md_out); | |
| 451 void (*md_transform)(void *ctx, const unsigned char *block); | |
| 452 unsigned md_size, md_block_size = 64; | |
| 453 unsigned sslv3_pad_length = 40, header_length, variance_blocks, | |
| 454 len, max_mac_bytes, num_blocks, | |
| 455 num_starting_blocks, k, mac_end_offset, c, index_a, index_b; | |
| 456 unsigned int bits; /* at most 18 bits */ | |
| 457 unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES]; | |
| 458 /* hmac_pad is the masked HMAC key. */ | |
| 459 unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE]; | |
| 460 unsigned char first_block[MAX_HASH_BLOCK_SIZE]; | |
| 461 unsigned char mac_out[EVP_MAX_MD_SIZE]; | |
| 462 unsigned i, j, md_out_size_u; | |
| 463 EVP_MD_CTX md_ctx; | |
| 464 /* mdLengthSize is the number of bytes in the length field that terminat
es | |
| 465 * the hash. */ | |
| 466 unsigned md_length_size = 8; | |
| 467 char length_is_big_endian = 1; | |
| 468 | |
| 469 /* This is a, hopefully redundant, check that allows us to forget about | |
| 470 * many possible overflows later in this function. */ | |
| 471 OPENSSL_assert(data_plus_mac_plus_padding_size < 1024*1024); | |
| 472 | |
| 473 switch (EVP_MD_CTX_type(ctx)) | |
| 474 { | |
| 475 case NID_md5: | |
| 476 MD5_Init((MD5_CTX*)md_state.c); | |
| 477 md_final_raw = tls1_md5_final_raw; | |
| 478 md_transform = (void(*)(void *ctx, const unsigned char *
block)) MD5_Transform; | |
| 479 md_size = 16; | |
| 480 sslv3_pad_length = 48; | |
| 481 length_is_big_endian = 0; | |
| 482 break; | |
| 483 case NID_sha1: | |
| 484 SHA1_Init((SHA_CTX*)md_state.c); | |
| 485 md_final_raw = tls1_sha1_final_raw; | |
| 486 md_transform = (void(*)(void *ctx, const unsigned char *
block)) SHA1_Transform; | |
| 487 md_size = 20; | |
| 488 break; | |
| 489 #ifndef OPENSSL_NO_SHA256 | |
| 490 case NID_sha224: | |
| 491 SHA224_Init((SHA256_CTX*)md_state.c); | |
| 492 md_final_raw = tls1_sha256_final_raw; | |
| 493 md_transform = (void(*)(void *ctx, const unsigned char *
block)) SHA256_Transform; | |
| 494 md_size = 224/8; | |
| 495 break; | |
| 496 case NID_sha256: | |
| 497 SHA256_Init((SHA256_CTX*)md_state.c); | |
| 498 md_final_raw = tls1_sha256_final_raw; | |
| 499 md_transform = (void(*)(void *ctx, const unsigned char *
block)) SHA256_Transform; | |
| 500 md_size = 32; | |
| 501 break; | |
| 502 #endif | |
| 503 #ifndef OPENSSL_NO_SHA512 | |
| 504 case NID_sha384: | |
| 505 SHA384_Init((SHA512_CTX*)md_state.c); | |
| 506 md_final_raw = tls1_sha512_final_raw; | |
| 507 md_transform = (void(*)(void *ctx, const unsigned char *
block)) SHA512_Transform; | |
| 508 md_size = 384/8; | |
| 509 md_block_size = 128; | |
| 510 md_length_size = 16; | |
| 511 break; | |
| 512 case NID_sha512: | |
| 513 SHA512_Init((SHA512_CTX*)md_state.c); | |
| 514 md_final_raw = tls1_sha512_final_raw; | |
| 515 md_transform = (void(*)(void *ctx, const unsigned char *
block)) SHA512_Transform; | |
| 516 md_size = 64; | |
| 517 md_block_size = 128; | |
| 518 md_length_size = 16; | |
| 519 break; | |
| 520 #endif | |
| 521 default: | |
| 522 /* ssl3_cbc_record_digest_supported should have been | |
| 523 * called first to check that the hash function is | |
| 524 * supported. */ | |
| 525 OPENSSL_assert(0); | |
| 526 if (md_out_size) | |
| 527 *md_out_size = -1; | |
| 528 return; | |
| 529 } | |
| 530 | |
| 531 OPENSSL_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES); | |
| 532 OPENSSL_assert(md_block_size <= MAX_HASH_BLOCK_SIZE); | |
| 533 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE); | |
| 534 | |
| 535 header_length = 13; | |
| 536 if (is_sslv3) | |
| 537 { | |
| 538 header_length = | |
| 539 mac_secret_length + | |
| 540 sslv3_pad_length + | |
| 541 8 /* sequence number */ + | |
| 542 1 /* record type */ + | |
| 543 2 /* record length */; | |
| 544 } | |
| 545 | |
| 546 /* variance_blocks is the number of blocks of the hash that we have to | |
| 547 * calculate in constant time because they could be altered by the | |
| 548 * padding value. | |
| 549 * | |
| 550 * In SSLv3, the padding must be minimal so the end of the plaintext | |
| 551 * varies by, at most, 15+20 = 35 bytes. (We conservatively assume that | |
| 552 * the MAC size varies from 0..20 bytes.) In case the 9 bytes of hash | |
| 553 * termination (0x80 + 64-bit length) don't fit in the final block, we | |
| 554 * say that the final two blocks can vary based on the padding. | |
| 555 * | |
| 556 * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not | |
| 557 * required to be minimal. Therefore we say that the final six blocks | |
| 558 * can vary based on the padding. | |
| 559 * | |
| 560 * Later in the function, if the message is short and there obviously | |
| 561 * cannot be this many blocks then variance_blocks can be reduced. */ | |
| 562 variance_blocks = is_sslv3 ? 2 : 6; | |
| 563 /* From now on we're dealing with the MAC, which conceptually has 13 | |
| 564 * bytes of `header' before the start of the data (TLS) or 71/75 bytes | |
| 565 * (SSLv3) */ | |
| 566 len = data_plus_mac_plus_padding_size + header_length; | |
| 567 /* max_mac_bytes contains the maximum bytes of bytes in the MAC, includi
ng | |
| 568 * |header|, assuming that there's no padding. */ | |
| 569 max_mac_bytes = len - md_size - 1; | |
| 570 /* num_blocks is the maximum number of hash blocks. */ | |
| 571 num_blocks = (max_mac_bytes + 1 + md_length_size + md_block_size - 1) /
md_block_size; | |
| 572 /* In order to calculate the MAC in constant time we have to handle | |
| 573 * the final blocks specially because the padding value could cause the | |
| 574 * end to appear somewhere in the final |variance_blocks| blocks and we | |
| 575 * can't leak where. However, |num_starting_blocks| worth of data can | |
| 576 * be hashed right away because no padding value can affect whether | |
| 577 * they are plaintext. */ | |
| 578 num_starting_blocks = 0; | |
| 579 /* k is the starting byte offset into the conceptual header||data where | |
| 580 * we start processing. */ | |
| 581 k = 0; | |
| 582 /* mac_end_offset is the index just past the end of the data to be | |
| 583 * MACed. */ | |
| 584 mac_end_offset = data_plus_mac_size + header_length - md_size; | |
| 585 /* c is the index of the 0x80 byte in the final hash block that | |
| 586 * contains application data. */ | |
| 587 c = mac_end_offset % md_block_size; | |
| 588 /* index_a is the hash block number that contains the 0x80 terminating | |
| 589 * value. */ | |
| 590 index_a = mac_end_offset / md_block_size; | |
| 591 /* index_b is the hash block number that contains the 64-bit hash | |
| 592 * length, in bits. */ | |
| 593 index_b = (mac_end_offset + md_length_size) / md_block_size; | |
| 594 /* bits is the hash-length in bits. It includes the additional hash | |
| 595 * block for the masked HMAC key, or whole of |header| in the case of | |
| 596 * SSLv3. */ | |
| 597 | |
| 598 /* For SSLv3, if we're going to have any starting blocks then we need | |
| 599 * at least two because the header is larger than a single block. */ | |
| 600 if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0)) | |
| 601 { | |
| 602 num_starting_blocks = num_blocks - variance_blocks; | |
| 603 k = md_block_size*num_starting_blocks; | |
| 604 } | |
| 605 | |
| 606 bits = 8*mac_end_offset; | |
| 607 if (!is_sslv3) | |
| 608 { | |
| 609 /* Compute the initial HMAC block. For SSLv3, the padding and | |
| 610 * secret bytes are included in |header| because they take more | |
| 611 * than a single block. */ | |
| 612 bits += 8*md_block_size; | |
| 613 memset(hmac_pad, 0, md_block_size); | |
| 614 OPENSSL_assert(mac_secret_length <= sizeof(hmac_pad)); | |
| 615 memcpy(hmac_pad, mac_secret, mac_secret_length); | |
| 616 for (i = 0; i < md_block_size; i++) | |
| 617 hmac_pad[i] ^= 0x36; | |
| 618 | |
| 619 md_transform(md_state.c, hmac_pad); | |
| 620 } | |
| 621 | |
| 622 if (length_is_big_endian) | |
| 623 { | |
| 624 memset(length_bytes,0,md_length_size-4); | |
| 625 length_bytes[md_length_size-4] = (unsigned char)(bits>>24); | |
| 626 length_bytes[md_length_size-3] = (unsigned char)(bits>>16); | |
| 627 length_bytes[md_length_size-2] = (unsigned char)(bits>>8); | |
| 628 length_bytes[md_length_size-1] = (unsigned char)bits; | |
| 629 } | |
| 630 else | |
| 631 { | |
| 632 memset(length_bytes,0,md_length_size); | |
| 633 length_bytes[md_length_size-5] = (unsigned char)(bits>>24); | |
| 634 length_bytes[md_length_size-6] = (unsigned char)(bits>>16); | |
| 635 length_bytes[md_length_size-7] = (unsigned char)(bits>>8); | |
| 636 length_bytes[md_length_size-8] = (unsigned char)bits; | |
| 637 } | |
| 638 | |
| 639 if (k > 0) | |
| 640 { | |
| 641 if (is_sslv3) | |
| 642 { | |
| 643 /* The SSLv3 header is larger than a single block. | |
| 644 * overhang is the number of bytes beyond a single | |
| 645 * block that the header consumes: either 7 bytes | |
| 646 * (SHA1) or 11 bytes (MD5). */ | |
| 647 unsigned overhang = header_length-md_block_size; | |
| 648 md_transform(md_state.c, header); | |
| 649 memcpy(first_block, header + md_block_size, overhang); | |
| 650 memcpy(first_block + overhang, data, md_block_size-overh
ang); | |
| 651 md_transform(md_state.c, first_block); | |
| 652 for (i = 1; i < k/md_block_size - 1; i++) | |
| 653 md_transform(md_state.c, data + md_block_size*i
- overhang); | |
| 654 } | |
| 655 else | |
| 656 { | |
| 657 /* k is a multiple of md_block_size. */ | |
| 658 memcpy(first_block, header, 13); | |
| 659 memcpy(first_block+13, data, md_block_size-13); | |
| 660 md_transform(md_state.c, first_block); | |
| 661 for (i = 1; i < k/md_block_size; i++) | |
| 662 md_transform(md_state.c, data + md_block_size*i
- 13); | |
| 663 } | |
| 664 } | |
| 665 | |
| 666 memset(mac_out, 0, sizeof(mac_out)); | |
| 667 | |
| 668 /* We now process the final hash blocks. For each block, we construct | |
| 669 * it in constant time. If the |i==index_a| then we'll include the 0x80 | |
| 670 * bytes and zero pad etc. For each block we selectively copy it, in | |
| 671 * constant time, to |mac_out|. */ | |
| 672 for (i = num_starting_blocks; i <= num_starting_blocks+variance_blocks;
i++) | |
| 673 { | |
| 674 unsigned char block[MAX_HASH_BLOCK_SIZE]; | |
| 675 unsigned char is_block_a = constant_time_eq_8(i, index_a); | |
| 676 unsigned char is_block_b = constant_time_eq_8(i, index_b); | |
| 677 for (j = 0; j < md_block_size; j++) | |
| 678 { | |
| 679 unsigned char b = 0, is_past_c, is_past_cp1; | |
| 680 if (k < header_length) | |
| 681 b = header[k]; | |
| 682 else if (k < data_plus_mac_plus_padding_size + header_le
ngth) | |
| 683 b = data[k-header_length]; | |
| 684 k++; | |
| 685 | |
| 686 is_past_c = is_block_a & constant_time_ge(j, c); | |
| 687 is_past_cp1 = is_block_a & constant_time_ge(j, c+1); | |
| 688 /* If this is the block containing the end of the | |
| 689 * application data, and we are at the offset for the | |
| 690 * 0x80 value, then overwrite b with 0x80. */ | |
| 691 b = (b&~is_past_c) | (0x80&is_past_c); | |
| 692 /* If this the the block containing the end of the | |
| 693 * application data and we're past the 0x80 value then | |
| 694 * just write zero. */ | |
| 695 b = b&~is_past_cp1; | |
| 696 /* If this is index_b (the final block), but not | |
| 697 * index_a (the end of the data), then the 64-bit | |
| 698 * length didn't fit into index_a and we're having to | |
| 699 * add an extra block of zeros. */ | |
| 700 b &= ~is_block_b | is_block_a; | |
| 701 | |
| 702 /* The final bytes of one of the blocks contains the | |
| 703 * length. */ | |
| 704 if (j >= md_block_size - md_length_size) | |
| 705 { | |
| 706 /* If this is index_b, write a length byte. */ | |
| 707 b = (b&~is_block_b) | (is_block_b&length_bytes[j
-(md_block_size-md_length_size)]); | |
| 708 } | |
| 709 block[j] = b; | |
| 710 } | |
| 711 | |
| 712 md_transform(md_state.c, block); | |
| 713 md_final_raw(md_state.c, block); | |
| 714 /* If this is index_b, copy the hash value to |mac_out|. */ | |
| 715 for (j = 0; j < md_size; j++) | |
| 716 mac_out[j] |= block[j]&is_block_b; | |
| 717 } | |
| 718 | |
| 719 EVP_MD_CTX_init(&md_ctx); | |
| 720 EVP_DigestInit_ex(&md_ctx, ctx->digest, NULL /* engine */); | |
| 721 if (is_sslv3) | |
| 722 { | |
| 723 /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */ | |
| 724 memset(hmac_pad, 0x5c, sslv3_pad_length); | |
| 725 | |
| 726 EVP_DigestUpdate(&md_ctx, mac_secret, mac_secret_length); | |
| 727 EVP_DigestUpdate(&md_ctx, hmac_pad, sslv3_pad_length); | |
| 728 EVP_DigestUpdate(&md_ctx, mac_out, md_size); | |
| 729 } | |
| 730 else | |
| 731 { | |
| 732 /* Complete the HMAC in the standard manner. */ | |
| 733 for (i = 0; i < md_block_size; i++) | |
| 734 hmac_pad[i] ^= 0x6a; | |
| 735 | |
| 736 EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size); | |
| 737 EVP_DigestUpdate(&md_ctx, mac_out, md_size); | |
| 738 } | |
| 739 EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u); | |
| 740 if (md_out_size) | |
| 741 *md_out_size = md_out_size_u; | |
| 742 EVP_MD_CTX_cleanup(&md_ctx); | |
| 743 } | |
| 744 | |
| 745 #ifdef OPENSSL_FIPS | |
| 746 | |
| 747 /* Due to the need to use EVP in FIPS mode we can't reimplement digests but | |
| 748 * we can ensure the number of blocks processed is equal for all cases | |
| 749 * by digesting additional data. | |
| 750 */ | |
| 751 | |
| 752 void tls_fips_digest_extra( | |
| 753 const EVP_CIPHER_CTX *cipher_ctx, EVP_MD_CTX *mac_ctx, | |
| 754 const unsigned char *data, size_t data_len, size_t orig_len) | |
| 755 { | |
| 756 size_t block_size, digest_pad, blocks_data, blocks_orig; | |
| 757 if (EVP_CIPHER_CTX_mode(cipher_ctx) != EVP_CIPH_CBC_MODE) | |
| 758 return; | |
| 759 block_size = EVP_MD_CTX_block_size(mac_ctx); | |
| 760 /* We are in FIPS mode if we get this far so we know we have only SHA* | |
| 761 * digests and TLS to deal with. | |
| 762 * Minimum digest padding length is 17 for SHA384/SHA512 and 9 | |
| 763 * otherwise. | |
| 764 * Additional header is 13 bytes. To get the number of digest blocks | |
| 765 * processed round up the amount of data plus padding to the nearest | |
| 766 * block length. Block length is 128 for SHA384/SHA512 and 64 otherwise. | |
| 767 * So we have: | |
| 768 * blocks = (payload_len + digest_pad + 13 + block_size - 1)/block_size | |
| 769 * equivalently: | |
| 770 * blocks = (payload_len + digest_pad + 12)/block_size + 1 | |
| 771 * HMAC adds a constant overhead. | |
| 772 * We're ultimately only interested in differences so this becomes | |
| 773 * blocks = (payload_len + 29)/128 | |
| 774 * for SHA384/SHA512 and | |
| 775 * blocks = (payload_len + 21)/64 | |
| 776 * otherwise. | |
| 777 */ | |
| 778 digest_pad = block_size == 64 ? 21 : 29; | |
| 779 blocks_orig = (orig_len + digest_pad)/block_size; | |
| 780 blocks_data = (data_len + digest_pad)/block_size; | |
| 781 /* MAC enough blocks to make up the difference between the original | |
| 782 * and actual lengths plus one extra block to ensure this is never a | |
| 783 * no op. The "data" pointer should always have enough space to | |
| 784 * perform this operation as it is large enough for a maximum | |
| 785 * length TLS buffer. | |
| 786 */ | |
| 787 EVP_DigestSignUpdate(mac_ctx, data, | |
| 788 (blocks_orig - blocks_data + 1) * block_size); | |
| 789 } | |
| 790 #endif | |
| OLD | NEW |
|---|
Chromium Code Reviews
Issue 2072073002:
Delete bundled copy of OpenSSL and replace with README. (Closed)
Base URL: https://chromium.googlesource.com/chromium/deps/openssl@master