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_lt returns 0xff if a<b and 0x00 otherwise. */
80 static unsigned constant_time_lt(unsigned a, unsigned b)
83 return DUPLICATE_MSB_TO_ALL(a);
86 /* constant_time_ge returns 0xff if a>=b and 0x00 otherwise. */
87 static unsigned constant_time_ge(unsigned a, unsigned b)
90 return DUPLICATE_MSB_TO_ALL(~a);
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)
98 return DUPLICATE_MSB_TO_ALL_8(c);
101 /* ssl3_cbc_remove_padding removes padding from the decrypted, SSLv3, CBC
102 * record in |rec| by updating |rec->length| in constant time.
104 * block_size: the block size of the cipher used to encrypt the record.
106 * 0: (in non-constant time) if the record is publicly invalid.
107 * 1: if the padding was valid
109 int ssl3_cbc_remove_padding(const SSL* s,
114 unsigned padding_length, good;
115 const unsigned overhead = 1 /* padding length byte */ + mac_size;
117 /* These lengths are all public so we can test them in non-constant
119 if (overhead > rec->length)
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));
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.
138 * block_size: the block size of the cipher used to encrypt the record.
140 * 0: (in non-constant time) if the record is publicly invalid.
141 * 1: if the padding was valid
143 int tls1_cbc_remove_padding(const SSL* s,
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 == DTLS1_VERSION)
153 /* These lengths are all public so we can test them in
156 if (overhead + block_size > rec->length)
158 /* We can now safely skip explicit IV */
159 rec->data += block_size;
160 rec->input += block_size;
161 rec->length -= block_size;
163 else if (overhead > rec->length)
166 padding_length = rec->data[rec->length-1];
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]
173 if ( (s->options&SSL_OP_TLS_BLOCK_PADDING_BUG) && !s->expand)
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))
179 s->s3->flags|=TLS1_FLAGS_TLS_PADDING_BUG;
181 if ((s->s3->flags & TLS1_FLAGS_TLS_PADDING_BUG) &&
188 good = constant_time_ge(rec->length, overhead+padding_length);
189 /* The padding consists of a length byte at the end of the record and
190 * then that many bytes of padding, all with the same value as the
191 * length byte. Thus, with the length byte included, there are i+1
194 * We can't check just |padding_length+1| bytes because that leaks
195 * decrypted information. Therefore we always have to check the maximum
196 * amount of padding possible. (Again, the length of the record is
197 * public information so we can use it.) */
198 to_check = 255; /* maximum amount of padding. */
199 if (to_check > rec->length-1)
200 to_check = rec->length-1;
202 for (i = 0; i < to_check; i++)
204 unsigned char mask = constant_time_ge(padding_length, i);
205 unsigned char b = rec->data[rec->length-1-i];
206 /* The final |padding_length+1| bytes should all have the value
207 * |padding_length|. Therefore the XOR should be zero. */
208 good &= ~(mask&(padding_length ^ b));
211 /* If any of the final |padding_length+1| bytes had the wrong value,
212 * one or more of the lower eight bits of |good| will be cleared. We
213 * AND the bottom 8 bits together and duplicate the result to all the
218 good <<= sizeof(good)*8-1;
219 good = DUPLICATE_MSB_TO_ALL(good);
221 padding_length = good & (padding_length+1);
222 rec->length -= padding_length;
223 rec->type |= padding_length<<8; /* kludge: pass padding length */
225 return (int)((good & 1) | (~good & -1));
228 #if defined(_M_AMD64) || defined(__x86_64__)
229 #define CBC_MAC_ROTATE_IN_PLACE
232 /* ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in
233 * constant time (independent of the concrete value of rec->length, which may
234 * vary within a 256-byte window).
236 * ssl3_cbc_remove_padding or tls1_cbc_remove_padding must be called prior to
240 * rec->orig_len >= md_size
241 * md_size <= EVP_MAX_MD_SIZE
243 * If CBC_MAC_ROTATE_IN_PLACE is defined then the rotation is performed with
244 * variable accesses in a 64-byte-aligned buffer. Assuming that this fits into
245 * a single cache-line, then the variable memory accesses don't actually affect
246 * the timing. This has been tested to be true on Intel amd64 chips.
248 void ssl3_cbc_copy_mac(unsigned char* out,
249 const SSL3_RECORD *rec,
250 unsigned md_size,unsigned orig_len)
252 #if defined(CBC_MAC_ROTATE_IN_PLACE)
253 unsigned char rotated_mac_buf[EVP_MAX_MD_SIZE*2];
254 unsigned char *rotated_mac;
256 unsigned char rotated_mac[EVP_MAX_MD_SIZE];
259 /* mac_end is the index of |rec->data| just after the end of the MAC. */
260 unsigned mac_end = rec->length;
261 unsigned mac_start = mac_end - md_size;
262 /* scan_start contains the number of bytes that we can ignore because
263 * the MAC's position can only vary by 255 bytes. */
264 unsigned scan_start = 0;
266 unsigned div_spoiler;
267 unsigned rotate_offset;
269 OPENSSL_assert(orig_len >= md_size);
270 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
272 #if defined(CBC_MAC_ROTATE_IN_PLACE)
273 rotated_mac = (unsigned char*) (((intptr_t)(rotated_mac_buf + 64)) & ~63);
276 /* This information is public so it's safe to branch based on it. */
277 if (orig_len > md_size + 255 + 1)
278 scan_start = orig_len - (md_size + 255 + 1);
279 /* div_spoiler contains a multiple of md_size that is used to cause the
280 * modulo operation to be constant time. Without this, the time varies
281 * based on the amount of padding when running on Intel chips at least.
283 * The aim of right-shifting md_size is so that the compiler doesn't
284 * figure out that it can remove div_spoiler as that would require it
285 * to prove that md_size is always even, which I hope is beyond it. */
286 div_spoiler = md_size >> 1;
287 div_spoiler <<= (sizeof(div_spoiler)-1)*8;
288 rotate_offset = (div_spoiler + mac_start - scan_start) % md_size;
290 memset(rotated_mac, 0, md_size);
291 for (i = scan_start, j = 0; i < orig_len; i++)
293 unsigned char mac_started = constant_time_ge(i, mac_start);
294 unsigned char mac_ended = constant_time_ge(i, mac_end);
295 unsigned char b = rec->data[i];
296 rotated_mac[j++] |= b & mac_started & ~mac_ended;
297 j &= constant_time_lt(j,md_size);
300 /* Now rotate the MAC */
301 #if defined(CBC_MAC_ROTATE_IN_PLACE)
303 for (i = 0; i < md_size; i++)
305 out[j++] = rotated_mac[rotate_offset++];
306 rotate_offset &= constant_time_lt(rotate_offset,md_size);
309 memset(out, 0, md_size);
310 rotate_offset = md_size - rotate_offset;
311 rotate_offset &= constant_time_lt(rotate_offset,md_size);
312 for (i = 0; i < md_size; i++)
314 for (j = 0; j < md_size; j++)
315 out[j] |= rotated_mac[i] & constant_time_eq_8(j, rotate_offset);
317 rotate_offset &= constant_time_lt(rotate_offset,md_size);
322 /* u32toLE serialises an unsigned, 32-bit number (n) as four bytes at (p) in
323 * little-endian order. The value of p is advanced by four. */
324 #define u32toLE(n, p) \
325 (*((p)++)=(unsigned char)(n), \
326 *((p)++)=(unsigned char)(n>>8), \
327 *((p)++)=(unsigned char)(n>>16), \
328 *((p)++)=(unsigned char)(n>>24))
330 /* These functions serialize the state of a hash and thus perform the standard
331 * "final" operation without adding the padding and length that such a function
333 static void tls1_md5_final_raw(void* ctx, unsigned char *md_out)
336 u32toLE(md5->A, md_out);
337 u32toLE(md5->B, md_out);
338 u32toLE(md5->C, md_out);
339 u32toLE(md5->D, md_out);
342 static void tls1_sha1_final_raw(void* ctx, unsigned char *md_out)
345 l2n(sha1->h0, md_out);
346 l2n(sha1->h1, md_out);
347 l2n(sha1->h2, md_out);
348 l2n(sha1->h3, md_out);
349 l2n(sha1->h4, md_out);
351 #define LARGEST_DIGEST_CTX SHA_CTX
353 #ifndef OPENSSL_NO_SHA256
354 static void tls1_sha256_final_raw(void* ctx, unsigned char *md_out)
356 SHA256_CTX *sha256 = ctx;
359 for (i = 0; i < 8; i++)
361 l2n(sha256->h[i], md_out);
364 #undef LARGEST_DIGEST_CTX
365 #define LARGEST_DIGEST_CTX SHA256_CTX
368 #ifndef OPENSSL_NO_SHA512
369 static void tls1_sha512_final_raw(void* ctx, unsigned char *md_out)
371 SHA512_CTX *sha512 = ctx;
374 for (i = 0; i < 8; i++)
376 l2n8(sha512->h[i], md_out);
379 #undef LARGEST_DIGEST_CTX
380 #define LARGEST_DIGEST_CTX SHA512_CTX
383 /* ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
384 * which ssl3_cbc_digest_record supports. */
385 char ssl3_cbc_record_digest_supported(const EVP_MD *digest)
391 switch (EVP_MD_type(digest))
395 #ifndef OPENSSL_NO_SHA256
399 #ifndef OPENSSL_NO_SHA512
409 /* ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS
412 * ctx: the EVP_MD_CTX from which we take the hash function.
413 * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX.
414 * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written.
415 * md_out_size: if non-NULL, the number of output bytes is written here.
416 * header: the 13-byte, TLS record header.
417 * data: the record data itself, less any preceeding explicit IV.
418 * data_plus_mac_size: the secret, reported length of the data and MAC
419 * once the padding has been removed.
420 * data_plus_mac_plus_padding_size: the public length of the whole
421 * record, including padding.
422 * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
424 * On entry: by virtue of having been through one of the remove_padding
425 * functions, above, we know that data_plus_mac_size is large enough to contain
426 * a padding byte and MAC. (If the padding was invalid, it might contain the
428 void ssl3_cbc_digest_record(
429 const EVP_MD *digest,
430 unsigned char* md_out,
432 const unsigned char header[13],
433 const unsigned char *data,
434 size_t data_plus_mac_size,
435 size_t data_plus_mac_plus_padding_size,
436 const unsigned char *mac_secret,
437 unsigned mac_secret_length,
440 union { double align;
441 unsigned char c[sizeof(LARGEST_DIGEST_CTX)]; } md_state;
442 void (*md_final_raw)(void *ctx, unsigned char *md_out);
443 void (*md_transform)(void *ctx, const unsigned char *block);
444 unsigned md_size, md_block_size = 64;
445 unsigned sslv3_pad_length = 40, header_length, variance_blocks,
446 len, max_mac_bytes, num_blocks,
447 num_starting_blocks, k, mac_end_offset, c, index_a, index_b;
448 unsigned int bits; /* at most 18 bits */
449 unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES];
450 /* hmac_pad is the masked HMAC key. */
451 unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE];
452 unsigned char first_block[MAX_HASH_BLOCK_SIZE];
453 unsigned char mac_out[EVP_MAX_MD_SIZE];
454 unsigned i, j, md_out_size_u;
456 /* mdLengthSize is the number of bytes in the length field that terminates
458 unsigned md_length_size = 8;
459 char length_is_big_endian = 1;
461 /* This is a, hopefully redundant, check that allows us to forget about
462 * many possible overflows later in this function. */
463 OPENSSL_assert(data_plus_mac_plus_padding_size < 1024*1024);
465 switch (EVP_MD_type(digest))
468 MD5_Init((MD5_CTX*)md_state.c);
469 md_final_raw = tls1_md5_final_raw;
470 md_transform = (void(*)(void *ctx, const unsigned char *block)) MD5_Transform;
472 sslv3_pad_length = 48;
473 length_is_big_endian = 0;
476 SHA1_Init((SHA_CTX*)md_state.c);
477 md_final_raw = tls1_sha1_final_raw;
478 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA1_Transform;
481 #ifndef OPENSSL_NO_SHA256
483 SHA224_Init((SHA256_CTX*)md_state.c);
484 md_final_raw = tls1_sha256_final_raw;
485 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;
489 SHA256_Init((SHA256_CTX*)md_state.c);
490 md_final_raw = tls1_sha256_final_raw;
491 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;
495 #ifndef OPENSSL_NO_SHA512
497 SHA384_Init((SHA512_CTX*)md_state.c);
498 md_final_raw = tls1_sha512_final_raw;
499 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA512_Transform;
505 SHA512_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;
514 /* ssl3_cbc_record_digest_supported should have been
515 * called first to check that the hash function is
523 OPENSSL_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES);
524 OPENSSL_assert(md_block_size <= MAX_HASH_BLOCK_SIZE);
525 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
533 8 /* sequence number */ +
534 1 /* record type */ +
535 2 /* record length */;
538 /* variance_blocks is the number of blocks of the hash that we have to
539 * calculate in constant time because they could be altered by the
542 * In SSLv3, the padding must be minimal so the end of the plaintext
543 * varies by, at most, 15+20 = 35 bytes. (We conservatively assume that
544 * the MAC size varies from 0..20 bytes.) In case the 9 bytes of hash
545 * termination (0x80 + 64-bit length) don't fit in the final block, we
546 * say that the final two blocks can vary based on the padding.
548 * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
549 * required to be minimal. Therefore we say that the final six blocks
550 * can vary based on the padding.
552 * Later in the function, if the message is short and there obviously
553 * cannot be this many blocks then variance_blocks can be reduced. */
554 variance_blocks = is_sslv3 ? 2 : 6;
555 /* From now on we're dealing with the MAC, which conceptually has 13
556 * bytes of `header' before the start of the data (TLS) or 71/75 bytes
558 len = data_plus_mac_plus_padding_size + header_length;
559 /* max_mac_bytes contains the maximum bytes of bytes in the MAC, including
560 * |header|, assuming that there's no padding. */
561 max_mac_bytes = len - md_size - 1;
562 /* num_blocks is the maximum number of hash blocks. */
563 num_blocks = (max_mac_bytes + 1 + md_length_size + md_block_size - 1) / md_block_size;
564 /* In order to calculate the MAC in constant time we have to handle
565 * the final blocks specially because the padding value could cause the
566 * end to appear somewhere in the final |variance_blocks| blocks and we
567 * can't leak where. However, |num_starting_blocks| worth of data can
568 * be hashed right away because no padding value can affect whether
569 * they are plaintext. */
570 num_starting_blocks = 0;
571 /* k is the starting byte offset into the conceptual header||data where
572 * we start processing. */
574 /* mac_end_offset is the index just past the end of the data to be
576 mac_end_offset = data_plus_mac_size + header_length - md_size;
577 /* c is the index of the 0x80 byte in the final hash block that
578 * contains application data. */
579 c = mac_end_offset % md_block_size;
580 /* index_a is the hash block number that contains the 0x80 terminating
582 index_a = mac_end_offset / md_block_size;
583 /* index_b is the hash block number that contains the 64-bit hash
584 * length, in bits. */
585 index_b = (mac_end_offset + md_length_size) / md_block_size;
586 /* bits is the hash-length in bits. It includes the additional hash
587 * block for the masked HMAC key, or whole of |header| in the case of
590 /* For SSLv3, if we're going to have any starting blocks then we need
591 * at least two because the header is larger than a single block. */
592 if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0))
594 num_starting_blocks = num_blocks - variance_blocks;
595 k = md_block_size*num_starting_blocks;
598 bits = 8*mac_end_offset;
601 /* Compute the initial HMAC block. For SSLv3, the padding and
602 * secret bytes are included in |header| because they take more
603 * than a single block. */
604 bits += 8*md_block_size;
605 memset(hmac_pad, 0, md_block_size);
606 OPENSSL_assert(mac_secret_length <= sizeof(hmac_pad));
607 memcpy(hmac_pad, mac_secret, mac_secret_length);
608 for (i = 0; i < md_block_size; i++)
611 md_transform(md_state.c, hmac_pad);
614 if (length_is_big_endian)
616 memset(length_bytes,0,md_length_size-4);
617 length_bytes[md_length_size-4] = (unsigned char)(bits>>24);
618 length_bytes[md_length_size-3] = (unsigned char)(bits>>16);
619 length_bytes[md_length_size-2] = (unsigned char)(bits>>8);
620 length_bytes[md_length_size-1] = (unsigned char)bits;
624 memset(length_bytes,0,md_length_size);
625 length_bytes[md_length_size-5] = (unsigned char)(bits>>24);
626 length_bytes[md_length_size-6] = (unsigned char)(bits>>16);
627 length_bytes[md_length_size-7] = (unsigned char)(bits>>8);
628 length_bytes[md_length_size-8] = (unsigned char)bits;
635 /* The SSLv3 header is larger than a single block.
636 * overhang is the number of bytes beyond a single
637 * block that the header consumes: either 7 bytes
638 * (SHA1) or 11 bytes (MD5). */
639 unsigned overhang = header_length-md_block_size;
640 md_transform(md_state.c, header);
641 memcpy(first_block, header + md_block_size, overhang);
642 memcpy(first_block + overhang, data, md_block_size-overhang);
643 md_transform(md_state.c, first_block);
644 for (i = 1; i < k/md_block_size - 1; i++)
645 md_transform(md_state.c, data + md_block_size*i - overhang);
649 /* k is a multiple of md_block_size. */
650 memcpy(first_block, header, 13);
651 memcpy(first_block+13, data, md_block_size-13);
652 md_transform(md_state.c, first_block);
653 for (i = 1; i < k/md_block_size; i++)
654 md_transform(md_state.c, data + md_block_size*i - 13);
658 memset(mac_out, 0, sizeof(mac_out));
660 /* We now process the final hash blocks. For each block, we construct
661 * it in constant time. If the |i==index_a| then we'll include the 0x80
662 * bytes and zero pad etc. For each block we selectively copy it, in
663 * constant time, to |mac_out|. */
664 for (i = num_starting_blocks; i <= num_starting_blocks+variance_blocks; i++)
666 unsigned char block[MAX_HASH_BLOCK_SIZE];
667 unsigned char is_block_a = constant_time_eq_8(i, index_a);
668 unsigned char is_block_b = constant_time_eq_8(i, index_b);
669 for (j = 0; j < md_block_size; j++)
671 unsigned char b = 0, is_past_c, is_past_cp1;
672 if (k < header_length)
674 else if (k < data_plus_mac_plus_padding_size + header_length)
675 b = data[k-header_length];
678 is_past_c = is_block_a & constant_time_ge(j, c);
679 is_past_cp1 = is_block_a & constant_time_ge(j, c+1);
680 /* If this is the block containing the end of the
681 * application data, and we are at the offset for the
682 * 0x80 value, then overwrite b with 0x80. */
683 b = (b&~is_past_c) | (0x80&is_past_c);
684 /* If this the the block containing the end of the
685 * application data and we're past the 0x80 value then
686 * just write zero. */
688 /* If this is index_b (the final block), but not
689 * index_a (the end of the data), then the 64-bit
690 * length didn't fit into index_a and we're having to
691 * add an extra block of zeros. */
692 b &= ~is_block_b | is_block_a;
694 /* The final bytes of one of the blocks contains the
696 if (j >= md_block_size - md_length_size)
698 /* If this is index_b, write a length byte. */
699 b = (b&~is_block_b) | (is_block_b&length_bytes[j-(md_block_size-md_length_size)]);
704 md_transform(md_state.c, block);
705 md_final_raw(md_state.c, block);
706 /* If this is index_b, copy the hash value to |mac_out|. */
707 for (j = 0; j < md_size; j++)
708 mac_out[j] |= block[j]&is_block_b;
711 EVP_MD_CTX_init(&md_ctx);
712 EVP_DigestInit_ex(&md_ctx, digest, NULL /* engine */);
715 /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
716 memset(hmac_pad, 0x5c, sslv3_pad_length);
718 EVP_DigestUpdate(&md_ctx, mac_secret, mac_secret_length);
719 EVP_DigestUpdate(&md_ctx, hmac_pad, sslv3_pad_length);
720 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
724 /* Complete the HMAC in the standard manner. */
725 for (i = 0; i < md_block_size; i++)
728 EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size);
729 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
731 EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u);
733 *md_out_size = md_out_size_u;
734 EVP_MD_CTX_cleanup(&md_ctx);
739 /* Due to the need to use EVP in FIPS mode we can't reimplement digests but
740 * we can ensure the number of blocks processed is equal for all cases
741 * by digesting additional data.
744 void tls_fips_digest_extra(
745 const EVP_CIPHER_CTX *cipher_ctx, const EVP_MD *hash, HMAC_CTX *hctx,
746 const unsigned char *data, size_t data_len, size_t orig_len)
748 size_t block_size, digest_pad, blocks_data, blocks_orig;
749 if (EVP_CIPHER_CTX_mode(cipher_ctx) != EVP_CIPH_CBC_MODE)
751 block_size = EVP_MD_block_size(hash);
752 /* We are in FIPS mode if we get this far so we know we have only SHA*
753 * digests and TLS to deal with.
754 * Minimum digest padding length is 17 for SHA384/SHA512 and 9
756 * Additional header is 13 bytes. To get the number of digest blocks
757 * processed round up the amount of data plus padding to the nearest
758 * block length. Block length is 128 for SHA384/SHA512 and 64 otherwise.
760 * blocks = (payload_len + digest_pad + 13 + block_size - 1)/block_size
762 * blocks = (payload_len + digest_pad + 12)/block_size + 1
763 * HMAC adds a constant overhead.
764 * We're ultimately only interested in differences so this becomes
765 * blocks = (payload_len + 29)/128
766 * for SHA384/SHA512 and
767 * blocks = (payload_len + 21)/64
770 digest_pad = block_size == 64 ? 21 : 29;
771 blocks_orig = (orig_len + digest_pad)/block_size;
772 blocks_data = (data_len + digest_pad)/block_size;
773 /* MAC enough blocks to make up the difference between the original
774 * and actual lengths plus one extra block to ensure this is never a
775 * no op. The "data" pointer should always have enough space to
776 * perform this operation as it is large enough for a maximum
779 HMAC_Update(hctx, data,
780 (blocks_orig - blocks_data + 1) * block_size);