2 /* ====================================================================
3 * Copyright (c) 2012 The OpenSSL Project. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
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
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/)"
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.
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.
31 * 6. Redistributions of any form whatsoever must retain the following
33 * "This product includes software developed by the OpenSSL Project
34 * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
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 * ====================================================================
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).
58 #include <openssl/md5.h>
59 #include <openssl/sha.h>
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
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
70 /* Some utility functions are needed:
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)))
79 /* constant_time_ge returns 0xff if a>=b and 0x00 otherwise. */
80 static unsigned constant_time_ge(unsigned a, unsigned b)
83 return DUPLICATE_MSB_TO_ALL(~a);
86 /* constant_time_eq_8 returns 0xff if a==b and 0x00 otherwise. */
87 static unsigned char constant_time_eq_8(unsigned char a, unsigned char b)
91 return DUPLICATE_MSB_TO_ALL_8(c);
94 /* ssl3_cbc_remove_padding removes padding from the decrypted, SSLv3, CBC
95 * record in |rec| by updating |rec->length| in constant time.
97 * block_size: the block size of the cipher used to encrypt the record.
99 * 0: (in non-constant time) if the record is publicly invalid.
100 * 1: if the padding was valid
102 int ssl3_cbc_remove_padding(const SSL* s,
107 unsigned padding_length, good;
108 const unsigned overhead = 1 /* padding length byte */ + mac_size;
110 /* These lengths are all public so we can test them in non-constant
112 if (overhead > rec->length)
115 padding_length = rec->data[rec->length-1];
116 good = constant_time_ge(rec->length, padding_length+overhead);
117 /* SSLv3 requires that the padding is minimal. */
118 good &= constant_time_ge(block_size, padding_length+1);
119 rec->length -= good & (padding_length+1);
120 return (int)((good & 1) | (~good & -1));
123 /* tls1_cbc_remove_padding removes the CBC padding from the decrypted, TLS, CBC
124 * record in |rec| in constant time and returns 1 if the padding is valid and
125 * -1 otherwise. It also removes any explicit IV from the start of the record
126 * without leaking any timing about whether there was enough space after the
127 * padding was removed.
129 * block_size: the block size of the cipher used to encrypt the record.
131 * 0: (in non-constant time) if the record is publicly invalid.
132 * 1: if the padding was valid
134 int tls1_cbc_remove_padding(const SSL* s,
139 unsigned padding_length, good, to_check, i;
140 const char has_explicit_iv = s->version == DTLS1_VERSION;
141 const unsigned overhead = 1 /* padding length byte */ +
143 (has_explicit_iv ? block_size : 0);
145 /* These lengths are all public so we can test them in non-constant
147 if (overhead > rec->length)
150 padding_length = rec->data[rec->length-1];
152 /* NB: if compression is in operation the first packet may not be of
153 * even length so the padding bug check cannot be performed. This bug
154 * workaround has been around since SSLeay so hopefully it is either
155 * fixed now or no buggy implementation supports compression [steve]
157 if ( (s->options&SSL_OP_TLS_BLOCK_PADDING_BUG) && !s->expand)
159 /* First packet is even in size, so check */
160 if ((memcmp(s->s3->read_sequence, "\0\0\0\0\0\0\0\0",8) == 0) &&
161 !(padding_length & 1))
163 s->s3->flags|=TLS1_FLAGS_TLS_PADDING_BUG;
165 if ((s->s3->flags & TLS1_FLAGS_TLS_PADDING_BUG) &&
172 good = constant_time_ge(rec->length, overhead+padding_length);
173 /* The padding consists of a length byte at the end of the record and
174 * then that many bytes of padding, all with the same value as the
175 * length byte. Thus, with the length byte included, there are i+1
178 * We can't check just |padding_length+1| bytes because that leaks
179 * decrypted information. Therefore we always have to check the maximum
180 * amount of padding possible. (Again, the length of the record is
181 * public information so we can use it.) */
182 to_check = 255; /* maximum amount of padding. */
183 if (to_check > rec->length-1)
184 to_check = rec->length-1;
186 for (i = 0; i < to_check; i++)
188 unsigned char mask = constant_time_ge(padding_length, i);
189 unsigned char b = rec->data[rec->length-1-i];
190 /* The final |padding_length+1| bytes should all have the value
191 * |padding_length|. Therefore the XOR should be zero. */
192 good &= ~(mask&(padding_length ^ b));
195 /* If any of the final |padding_length+1| bytes had the wrong value,
196 * one or more of the lower eight bits of |good| will be cleared. We
197 * AND the bottom 8 bits together and duplicate the result to all the
202 good <<= sizeof(good)*8-1;
203 good = DUPLICATE_MSB_TO_ALL(good);
205 rec->length -= good & (padding_length+1);
207 /* We can always safely skip the explicit IV. We check at the beginning
208 * of this function that the record has at least enough space for the
209 * IV, MAC and padding length byte. (These can be checked in
210 * non-constant time because it's all public information.) So, if the
211 * padding was invalid, then we didn't change |rec->length| and this is
212 * safe. If the padding was valid then we know that we have at least
213 * overhead+padding_length bytes of space and so this is still safe
214 * because overhead accounts for the explicit IV. */
217 rec->data += block_size;
218 rec->input += block_size;
219 rec->length -= block_size;
220 rec->orig_len -= block_size;
223 return (int)((good & 1) | (~good & -1));
226 #if defined(_M_AMD64) || defined(__x86_64__)
227 #define CBC_MAC_ROTATE_IN_PLACE
230 /* ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in
231 * constant time (independent of the concrete value of rec->length, which may
232 * vary within a 256-byte window).
234 * ssl3_cbc_remove_padding or tls1_cbc_remove_padding must be called prior to
238 * rec->orig_len >= md_size
239 * md_size <= EVP_MAX_MD_SIZE
241 * If CBC_MAC_ROTATE_IN_PLACE is defined then the rotation is performed with
242 * variable accesses in a 64-byte-aligned buffer. Assuming that this fits into
243 * a single cache-line, then the variable memory accesses don't actually affect
244 * the timing. This has been tested to be true on Intel amd64 chips.
246 void ssl3_cbc_copy_mac(unsigned char* out,
247 const SSL3_RECORD *rec,
250 #if defined(CBC_MAC_ROTATE_IN_PLACE)
251 unsigned char rotated_mac_buf[EVP_MAX_MD_SIZE*2];
252 unsigned char *rotated_mac;
254 unsigned char rotated_mac[EVP_MAX_MD_SIZE];
257 /* mac_end is the index of |rec->data| just after the end of the MAC. */
258 unsigned mac_end = rec->length;
259 unsigned mac_start = mac_end - md_size;
260 /* scan_start contains the number of bytes that we can ignore because
261 * the MAC's position can only vary by 255 bytes. */
262 unsigned scan_start = 0;
264 unsigned div_spoiler;
265 unsigned rotate_offset;
267 OPENSSL_assert(rec->orig_len >= md_size);
268 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
270 #if defined(CBC_MAC_ROTATE_IN_PLACE)
271 rotated_mac = (unsigned char*) (((intptr_t)(rotated_mac_buf + 64)) & ~63);
274 /* This information is public so it's safe to branch based on it. */
275 if (rec->orig_len > md_size + 255 + 1)
276 scan_start = rec->orig_len - (md_size + 255 + 1);
277 /* div_spoiler contains a multiple of md_size that is used to cause the
278 * modulo operation to be constant time. Without this, the time varies
279 * based on the amount of padding when running on Intel chips at least.
281 * The aim of right-shifting md_size is so that the compiler doesn't
282 * figure out that it can remove div_spoiler as that would require it
283 * to prove that md_size is always even, which I hope is beyond it. */
284 div_spoiler = md_size >> 1;
285 div_spoiler <<= (sizeof(div_spoiler)-1)*8;
286 rotate_offset = (div_spoiler + mac_start - scan_start) % md_size;
288 memset(rotated_mac, 0, md_size);
289 for (i = scan_start; i < rec->orig_len;)
291 for (j = 0; j < md_size && i < rec->orig_len; i++, j++)
293 unsigned char mac_started = constant_time_ge(i, mac_start);
294 unsigned char mac_ended = constant_time_ge(i, mac_end);
297 rotated_mac[j] |= b & mac_started & ~mac_ended;
301 /* Now rotate the MAC */
302 #if defined(CBC_MAC_ROTATE_IN_PLACE)
304 for (i = 0; i < md_size; i++)
306 unsigned char offset = (div_spoiler + rotate_offset + i) % md_size;
307 out[j++] = rotated_mac[offset];
310 memset(out, 0, md_size);
311 for (i = 0; i < md_size; i++)
313 unsigned char offset = (div_spoiler + md_size - rotate_offset + i) % md_size;
314 for (j = 0; j < md_size; j++)
315 out[j] |= rotated_mac[i] & constant_time_eq_8(j, offset);
320 /* These functions serialize the state of a hash and thus perform the standard
321 * "final" operation without adding the padding and length that such a function
323 static void tls1_md5_final_raw(void* ctx, unsigned char *md_out)
332 static void tls1_sha1_final_raw(void* ctx, unsigned char *md_out)
335 l2n(sha1->h0, md_out);
336 l2n(sha1->h1, md_out);
337 l2n(sha1->h2, md_out);
338 l2n(sha1->h3, md_out);
339 l2n(sha1->h4, md_out);
342 static void tls1_sha256_final_raw(void* ctx, unsigned char *md_out)
344 SHA256_CTX *sha256 = ctx;
347 for (i = 0; i < 8; i++)
349 l2n(sha256->h[i], md_out);
353 static void tls1_sha512_final_raw(void* ctx, unsigned char *md_out)
355 SHA512_CTX *sha512 = ctx;
358 for (i = 0; i < 8; i++)
360 l2n8(sha512->h[i], md_out);
364 /* ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
365 * which ssl3_cbc_digest_record supports. */
366 char ssl3_cbc_record_digest_supported(const EVP_MD *digest)
372 switch (EVP_MD_type(digest))
386 /* ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS
389 * ctx: the EVP_MD_CTX from which we take the hash function.
390 * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX.
391 * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written.
392 * md_out_size: if non-NULL, the number of output bytes is written here.
393 * header: the 13-byte, TLS record header.
394 * data: the record data itself, less any preceeding explicit IV.
395 * data_plus_mac_size: the secret, reported length of the data and MAC
396 * once the padding has been removed.
397 * data_plus_mac_plus_padding_size: the public length of the whole
398 * record, including padding.
399 * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
401 * On entry: by virtue of having been through one of the remove_padding
402 * functions, above, we know that data_plus_mac_size is large enough to contain
403 * a padding byte and MAC. (If the padding was invalid, it might contain the
405 void ssl3_cbc_digest_record(
406 const EVP_MD *digest,
407 unsigned char* md_out,
409 const unsigned char header[13],
410 const unsigned char *data,
411 size_t data_plus_mac_size,
412 size_t data_plus_mac_plus_padding_size,
413 const unsigned char *mac_secret,
414 unsigned mac_secret_length,
417 union { double align;
418 unsigned char c[sizeof(SHA512_CTX)]; } md_state;
419 void (*md_final_raw)(void *ctx, unsigned char *md_out);
420 void (*md_transform)(void *ctx, const unsigned char *block);
421 unsigned md_size, md_block_size = 64;
422 unsigned sslv3_pad_length = 40, header_length, variance_blocks,
423 len, max_mac_bytes, num_blocks,
424 num_starting_blocks, k, mac_end_offset, c, index_a, index_b;
425 unsigned int bits; /* at most 18 bits */
426 unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES];
427 /* hmac_pad is the masked HMAC key. */
428 unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE];
429 unsigned char first_block[MAX_HASH_BLOCK_SIZE];
430 unsigned char mac_out[EVP_MAX_MD_SIZE];
431 unsigned i, j, md_out_size_u;
433 /* mdLengthSize is the number of bytes in the length field that terminates
435 unsigned md_length_size = 8;
437 /* This is a, hopefully redundant, check that allows us to forget about
438 * many possible overflows later in this function. */
439 OPENSSL_assert(data_plus_mac_plus_padding_size < 1024*1024);
441 switch (EVP_MD_type(digest))
444 MD5_Init((MD5_CTX*)md_state.c);
445 md_final_raw = tls1_md5_final_raw;
446 md_transform = (void(*)(void *ctx, const unsigned char *block)) MD5_Transform;
448 sslv3_pad_length = 48;
451 SHA1_Init((SHA_CTX*)md_state.c);
452 md_final_raw = tls1_sha1_final_raw;
453 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA1_Transform;
457 SHA224_Init((SHA256_CTX*)md_state.c);
458 md_final_raw = tls1_sha256_final_raw;
459 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;
463 SHA256_Init((SHA256_CTX*)md_state.c);
464 md_final_raw = tls1_sha256_final_raw;
465 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;
469 SHA384_Init((SHA512_CTX*)md_state.c);
470 md_final_raw = tls1_sha512_final_raw;
471 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA512_Transform;
477 SHA512_Init((SHA512_CTX*)md_state.c);
478 md_final_raw = tls1_sha512_final_raw;
479 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA512_Transform;
485 /* ssl3_cbc_record_digest_supported should have been
486 * called first to check that the hash function is
494 OPENSSL_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES);
495 OPENSSL_assert(md_block_size <= MAX_HASH_BLOCK_SIZE);
496 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
504 8 /* sequence number */ +
505 1 /* record type */ +
506 2 /* record length */;
509 /* variance_blocks is the number of blocks of the hash that we have to
510 * calculate in constant time because they could be altered by the
513 * In SSLv3, the padding must be minimal so the end of the plaintext
514 * varies by, at most, 15+20 = 35 bytes. (We conservatively assume that
515 * the MAC size varies from 0..20 bytes.) In case the 9 bytes of hash
516 * termination (0x80 + 64-bit length) don't fit in the final block, we
517 * say that the final two blocks can vary based on the padding.
519 * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
520 * required to be minimal. Therefore we say that the final six blocks
521 * can vary based on the padding.
523 * Later in the function, if the message is short and there obviously
524 * cannot be this many blocks then variance_blocks can be reduced. */
525 variance_blocks = is_sslv3 ? 2 : 6;
526 /* From now on we're dealing with the MAC, which conceptually has 13
527 * bytes of `header' before the start of the data (TLS) or 71/75 bytes
529 len = data_plus_mac_plus_padding_size + header_length;
530 /* max_mac_bytes contains the maximum bytes of bytes in the MAC, including
531 * |header|, assuming that there's no padding. */
532 max_mac_bytes = len - md_size - 1;
533 /* num_blocks is the maximum number of hash blocks. */
534 num_blocks = (max_mac_bytes + 1 + md_length_size + md_block_size - 1) / md_block_size;
535 /* In order to calculate the MAC in constant time we have to handle
536 * the final blocks specially because the padding value could cause the
537 * end to appear somewhere in the final |variance_blocks| blocks and we
538 * can't leak where. However, |num_starting_blocks| worth of data can
539 * be hashed right away because no padding value can affect whether
540 * they are plaintext. */
541 num_starting_blocks = 0;
542 /* k is the starting byte offset into the conceptual header||data where
543 * we start processing. */
545 /* mac_end_offset is the index just past the end of the data to be
547 mac_end_offset = data_plus_mac_size + header_length - md_size;
548 /* c is the index of the 0x80 byte in the final hash block that
549 * contains application data. */
550 c = mac_end_offset % md_block_size;
551 /* index_a is the hash block number that contains the 0x80 terminating
553 index_a = mac_end_offset / md_block_size;
554 /* index_b is the hash block number that contains the 64-bit hash
555 * length, in bits. */
556 index_b = (mac_end_offset + md_length_size) / md_block_size;
557 /* bits is the hash-length in bits. It includes the additional hash
558 * block for the masked HMAC key, or whole of |header| in the case of
561 /* For SSLv3, if we're going to have any starting blocks then we need
562 * at least two because the header is larger than a single block. */
563 if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0))
565 num_starting_blocks = num_blocks - variance_blocks;
566 k = md_block_size*num_starting_blocks;
569 bits = 8*mac_end_offset;
572 /* Compute the initial HMAC block. For SSLv3, the padding and
573 * secret bytes are included in |header| because they take more
574 * than a single block. */
575 bits += 8*md_block_size;
576 memset(hmac_pad, 0, md_block_size);
577 OPENSSL_assert(mac_secret_length <= sizeof(hmac_pad));
578 memcpy(hmac_pad, mac_secret, mac_secret_length);
579 for (i = 0; i < md_block_size; i++)
582 md_transform(md_state.c, hmac_pad);
585 memset(length_bytes,0,md_length_size-4);
586 length_bytes[md_length_size-4] = (unsigned char)(bits>>24);
587 length_bytes[md_length_size-3] = (unsigned char)(bits>>16);
588 length_bytes[md_length_size-2] = (unsigned char)(bits>>8);
589 length_bytes[md_length_size-1] = (unsigned char)bits;
595 /* The SSLv3 header is larger than a single block.
596 * overhang is the number of bytes beyond a single
597 * block that the header consumes: either 7 bytes
598 * (SHA1) or 11 bytes (MD5). */
599 unsigned overhang = header_length-md_block_size;
600 md_transform(md_state.c, header);
601 memcpy(first_block, header + md_block_size, overhang);
602 memcpy(first_block + overhang, data, md_block_size-overhang);
603 md_transform(md_state.c, first_block);
604 for (i = 1; i < k/md_block_size - 1; i++)
605 md_transform(md_state.c, data + md_block_size*i - overhang);
609 /* k is a multiple of md_block_size. */
610 memcpy(first_block, header, 13);
611 memcpy(first_block+13, data, md_block_size-13);
612 md_transform(md_state.c, first_block);
613 for (i = 1; i < k/md_block_size; i++)
614 md_transform(md_state.c, data + md_block_size*i - 13);
618 memset(mac_out, 0, sizeof(mac_out));
620 /* We now process the final hash blocks. For each block, we construct
621 * it in constant time. If the |i==index_a| then we'll include the 0x80
622 * bytes and zero pad etc. For each block we selectively copy it, in
623 * constant time, to |mac_out|. */
624 for (i = num_starting_blocks; i <= num_starting_blocks+variance_blocks; i++)
626 unsigned char block[MAX_HASH_BLOCK_SIZE];
627 unsigned char is_block_a = constant_time_eq_8(i, index_a);
628 unsigned char is_block_b = constant_time_eq_8(i, index_b);
629 for (j = 0; j < md_block_size; j++)
631 unsigned char b = 0, is_past_c, is_past_cp1;
632 if (k < header_length)
634 else if (k < data_plus_mac_plus_padding_size + header_length)
635 b = data[k-header_length];
638 is_past_c = is_block_a & constant_time_ge(j, c);
639 is_past_cp1 = is_block_a & constant_time_ge(j, c+1);
640 /* If this is the block containing the end of the
641 * application data, and we are at the offset for the
642 * 0x80 value, then overwrite b with 0x80. */
643 b = (b&~is_past_c) | (0x80&is_past_c);
644 /* If this the the block containing the end of the
645 * application data and we're past the 0x80 value then
646 * just write zero. */
648 /* If this is index_b (the final block), but not
649 * index_a (the end of the data), then the 64-bit
650 * length didn't fit into index_a and we're having to
651 * add an extra block of zeros. */
652 b &= ~is_block_b | is_block_a;
654 /* The final bytes of one of the blocks contains the
656 if (j >= md_block_size - md_length_size)
658 /* If this is index_b, write a length byte. */
659 b = (b&~is_block_b) | (is_block_b&length_bytes[j-(md_block_size-md_length_size)]);
664 md_transform(md_state.c, block);
665 md_final_raw(md_state.c, block);
666 /* If this is index_b, copy the hash value to |mac_out|. */
667 for (j = 0; j < md_size; j++)
668 mac_out[j] |= block[j]&is_block_b;
671 EVP_MD_CTX_init(&md_ctx);
672 EVP_DigestInit_ex(&md_ctx, digest, NULL /* engine */);
675 /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
676 memset(hmac_pad, 0x5c, sslv3_pad_length);
678 EVP_DigestUpdate(&md_ctx, mac_secret, mac_secret_length);
679 EVP_DigestUpdate(&md_ctx, hmac_pad, sslv3_pad_length);
680 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
684 /* Complete the HMAC in the standard manner. */
685 for (i = 0; i < md_block_size; i++)
688 EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size);
689 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
691 EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u);
693 *md_out_size = md_out_size_u;
694 EVP_MD_CTX_cleanup(&md_ctx);
699 /* Due to the need to use EVP in FIPS mode we can't reimplement digests but
700 * we can ensure the number of blocks processed is equal for all cases
701 * by digesting additional data.
704 void tls_fips_digest_extra(
705 const EVP_CIPHER_CTX *cipher_ctx, const EVP_MD *hash, HMAC_CTX *hctx,
706 const unsigned char *data, size_t data_len, size_t orig_len)
708 size_t block_size, digest_pad, blocks_data, blocks_orig;
709 if (EVP_CIPHER_CTX_mode(cipher_ctx) != EVP_CIPH_CBC_MODE)
711 block_size = EVP_MD_block_size(hash);
712 /* We are in FIPS mode if we get this far so we know we have only SHA*
713 * digests and TLS to deal with.
714 * Minimum digest padding length is 17 for SHA384/SHA512 and 9
716 * Additional header is 13 bytes. To get the number of digest blocks
717 * processed round up the amount of data plus padding to the nearest
718 * block length. Block length is 128 for SHA384/SHA512 and 64 otherwise.
720 * blocks = (payload_len + digest_pad + 13 + block_size - 1)/block_size
722 * blocks = (payload_len + digest_pad + 12)/block_size + 1
723 * HMAC adds a constant overhead.
724 * We're ultimately only interested in differences so this becomes
725 * blocks = (payload_len + 29)/128
726 * for SHA384/SHA512 and
727 * blocks = (payload_len + 21)/64
730 digest_pad = block_size == 64 ? 21 : 29;
731 blocks_orig = (orig_len + digest_pad)/block_size;
732 blocks_data = (data_len + digest_pad)/block_size;
733 /* MAC enough blocks to make up the difference between the original
734 * and actual lengths plus one extra block to ensure this is never a
735 * no op. The "data" pointer should always have enough space to
736 * perform this operation as it is large enough for a maximum
739 HMAC_Update(hctx, data,
740 (blocks_orig - blocks_data + 1) * block_size);