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 || s->version == DTLS1_BAD_VER)
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 /* ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in
229 * constant time (independent of the concrete value of rec->length, which may
230 * vary within a 256-byte window).
232 * ssl3_cbc_remove_padding or tls1_cbc_remove_padding must be called prior to
236 * rec->orig_len >= md_size
237 * md_size <= EVP_MAX_MD_SIZE
239 * If CBC_MAC_ROTATE_IN_PLACE is defined then the rotation is performed with
240 * variable accesses in a 64-byte-aligned buffer. Assuming that this fits into
241 * a single or pair of cache-lines, then the variable memory accesses don't
242 * actually affect the timing. CPUs with smaller cache-lines [if any] are
243 * not multi-core and are not considered vulnerable to cache-timing attacks.
245 #define CBC_MAC_ROTATE_IN_PLACE
247 void ssl3_cbc_copy_mac(unsigned char* out,
248 const SSL3_RECORD *rec,
249 unsigned md_size,unsigned orig_len)
251 #if defined(CBC_MAC_ROTATE_IN_PLACE)
252 unsigned char rotated_mac_buf[64+EVP_MAX_MD_SIZE];
253 unsigned char *rotated_mac;
255 unsigned char rotated_mac[EVP_MAX_MD_SIZE];
258 /* mac_end is the index of |rec->data| just after the end of the MAC. */
259 unsigned mac_end = rec->length;
260 unsigned mac_start = mac_end - md_size;
261 /* scan_start contains the number of bytes that we can ignore because
262 * the MAC's position can only vary by 255 bytes. */
263 unsigned scan_start = 0;
265 unsigned div_spoiler;
266 unsigned rotate_offset;
268 OPENSSL_assert(orig_len >= md_size);
269 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
271 #if defined(CBC_MAC_ROTATE_IN_PLACE)
272 rotated_mac = rotated_mac_buf + ((0-(size_t)rotated_mac_buf)&63);
275 /* This information is public so it's safe to branch based on it. */
276 if (orig_len > md_size + 255 + 1)
277 scan_start = orig_len - (md_size + 255 + 1);
278 /* div_spoiler contains a multiple of md_size that is used to cause the
279 * modulo operation to be constant time. Without this, the time varies
280 * based on the amount of padding when running on Intel chips at least.
282 * The aim of right-shifting md_size is so that the compiler doesn't
283 * figure out that it can remove div_spoiler as that would require it
284 * to prove that md_size is always even, which I hope is beyond it. */
285 div_spoiler = md_size >> 1;
286 div_spoiler <<= (sizeof(div_spoiler)-1)*8;
287 rotate_offset = (div_spoiler + mac_start - scan_start) % md_size;
289 memset(rotated_mac, 0, md_size);
290 for (i = scan_start, j = 0; i < orig_len; i++)
292 unsigned char mac_started = constant_time_ge(i, mac_start);
293 unsigned char mac_ended = constant_time_ge(i, mac_end);
294 unsigned char b = rec->data[i];
295 rotated_mac[j++] |= b & mac_started & ~mac_ended;
296 j &= constant_time_lt(j,md_size);
299 /* Now rotate the MAC */
300 #if defined(CBC_MAC_ROTATE_IN_PLACE)
302 for (i = 0; i < md_size; i++)
304 /* in case cache-line is 32 bytes, touch second line */
305 ((volatile unsigned char *)rotated_mac)[rotate_offset^32];
306 out[j++] = rotated_mac[rotate_offset++];
307 rotate_offset &= constant_time_lt(rotate_offset,md_size);
310 memset(out, 0, md_size);
311 rotate_offset = md_size - rotate_offset;
312 rotate_offset &= constant_time_lt(rotate_offset,md_size);
313 for (i = 0; i < md_size; i++)
315 for (j = 0; j < md_size; j++)
316 out[j] |= rotated_mac[i] & constant_time_eq_8(j, rotate_offset);
318 rotate_offset &= constant_time_lt(rotate_offset,md_size);
323 /* u32toLE serialises an unsigned, 32-bit number (n) as four bytes at (p) in
324 * little-endian order. The value of p is advanced by four. */
325 #define u32toLE(n, p) \
326 (*((p)++)=(unsigned char)(n), \
327 *((p)++)=(unsigned char)(n>>8), \
328 *((p)++)=(unsigned char)(n>>16), \
329 *((p)++)=(unsigned char)(n>>24))
331 /* These functions serialize the state of a hash and thus perform the standard
332 * "final" operation without adding the padding and length that such a function
334 static void tls1_md5_final_raw(void* ctx, unsigned char *md_out)
337 u32toLE(md5->A, md_out);
338 u32toLE(md5->B, md_out);
339 u32toLE(md5->C, md_out);
340 u32toLE(md5->D, md_out);
343 static void tls1_sha1_final_raw(void* ctx, unsigned char *md_out)
346 l2n(sha1->h0, md_out);
347 l2n(sha1->h1, md_out);
348 l2n(sha1->h2, md_out);
349 l2n(sha1->h3, md_out);
350 l2n(sha1->h4, md_out);
352 #define LARGEST_DIGEST_CTX SHA_CTX
354 #ifndef OPENSSL_NO_SHA256
355 static void tls1_sha256_final_raw(void* ctx, unsigned char *md_out)
357 SHA256_CTX *sha256 = ctx;
360 for (i = 0; i < 8; i++)
362 l2n(sha256->h[i], md_out);
365 #undef LARGEST_DIGEST_CTX
366 #define LARGEST_DIGEST_CTX SHA256_CTX
369 #ifndef OPENSSL_NO_SHA512
370 static void tls1_sha512_final_raw(void* ctx, unsigned char *md_out)
372 SHA512_CTX *sha512 = ctx;
375 for (i = 0; i < 8; i++)
377 l2n8(sha512->h[i], md_out);
380 #undef LARGEST_DIGEST_CTX
381 #define LARGEST_DIGEST_CTX SHA512_CTX
384 /* ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
385 * which ssl3_cbc_digest_record supports. */
386 char ssl3_cbc_record_digest_supported(const EVP_MD *digest)
392 switch (EVP_MD_type(digest))
396 #ifndef OPENSSL_NO_SHA256
400 #ifndef OPENSSL_NO_SHA512
410 /* ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS
413 * ctx: the EVP_MD_CTX from which we take the hash function.
414 * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX.
415 * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written.
416 * md_out_size: if non-NULL, the number of output bytes is written here.
417 * header: the 13-byte, TLS record header.
418 * data: the record data itself, less any preceeding explicit IV.
419 * data_plus_mac_size: the secret, reported length of the data and MAC
420 * once the padding has been removed.
421 * data_plus_mac_plus_padding_size: the public length of the whole
422 * record, including padding.
423 * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
425 * On entry: by virtue of having been through one of the remove_padding
426 * functions, above, we know that data_plus_mac_size is large enough to contain
427 * a padding byte and MAC. (If the padding was invalid, it might contain the
429 void ssl3_cbc_digest_record(
430 const EVP_MD *digest,
431 unsigned char* md_out,
433 const unsigned char header[13],
434 const unsigned char *data,
435 size_t data_plus_mac_size,
436 size_t data_plus_mac_plus_padding_size,
437 const unsigned char *mac_secret,
438 unsigned mac_secret_length,
441 union { double align;
442 unsigned char c[sizeof(LARGEST_DIGEST_CTX)]; } md_state;
443 void (*md_final_raw)(void *ctx, unsigned char *md_out);
444 void (*md_transform)(void *ctx, const unsigned char *block);
445 unsigned md_size, md_block_size = 64;
446 unsigned sslv3_pad_length = 40, header_length, variance_blocks,
447 len, max_mac_bytes, num_blocks,
448 num_starting_blocks, k, mac_end_offset, c, index_a, index_b;
449 unsigned int bits; /* at most 18 bits */
450 unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES];
451 /* hmac_pad is the masked HMAC key. */
452 unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE];
453 unsigned char first_block[MAX_HASH_BLOCK_SIZE];
454 unsigned char mac_out[EVP_MAX_MD_SIZE];
455 unsigned i, j, md_out_size_u;
457 /* mdLengthSize is the number of bytes in the length field that terminates
459 unsigned md_length_size = 8;
460 char length_is_big_endian = 1;
462 /* This is a, hopefully redundant, check that allows us to forget about
463 * many possible overflows later in this function. */
464 OPENSSL_assert(data_plus_mac_plus_padding_size < 1024*1024);
466 switch (EVP_MD_type(digest))
469 MD5_Init((MD5_CTX*)md_state.c);
470 md_final_raw = tls1_md5_final_raw;
471 md_transform = (void(*)(void *ctx, const unsigned char *block)) MD5_Transform;
473 sslv3_pad_length = 48;
474 length_is_big_endian = 0;
477 SHA1_Init((SHA_CTX*)md_state.c);
478 md_final_raw = tls1_sha1_final_raw;
479 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA1_Transform;
482 #ifndef OPENSSL_NO_SHA256
484 SHA224_Init((SHA256_CTX*)md_state.c);
485 md_final_raw = tls1_sha256_final_raw;
486 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;
490 SHA256_Init((SHA256_CTX*)md_state.c);
491 md_final_raw = tls1_sha256_final_raw;
492 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;
496 #ifndef OPENSSL_NO_SHA512
498 SHA384_Init((SHA512_CTX*)md_state.c);
499 md_final_raw = tls1_sha512_final_raw;
500 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA512_Transform;
506 SHA512_Init((SHA512_CTX*)md_state.c);
507 md_final_raw = tls1_sha512_final_raw;
508 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA512_Transform;
515 /* ssl3_cbc_record_digest_supported should have been
516 * called first to check that the hash function is
524 OPENSSL_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES);
525 OPENSSL_assert(md_block_size <= MAX_HASH_BLOCK_SIZE);
526 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
534 8 /* sequence number */ +
535 1 /* record type */ +
536 2 /* record length */;
539 /* variance_blocks is the number of blocks of the hash that we have to
540 * calculate in constant time because they could be altered by the
543 * In SSLv3, the padding must be minimal so the end of the plaintext
544 * varies by, at most, 15+20 = 35 bytes. (We conservatively assume that
545 * the MAC size varies from 0..20 bytes.) In case the 9 bytes of hash
546 * termination (0x80 + 64-bit length) don't fit in the final block, we
547 * say that the final two blocks can vary based on the padding.
549 * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
550 * required to be minimal. Therefore we say that the final six blocks
551 * can vary based on the padding.
553 * Later in the function, if the message is short and there obviously
554 * cannot be this many blocks then variance_blocks can be reduced. */
555 variance_blocks = is_sslv3 ? 2 : 6;
556 /* From now on we're dealing with the MAC, which conceptually has 13
557 * bytes of `header' before the start of the data (TLS) or 71/75 bytes
559 len = data_plus_mac_plus_padding_size + header_length;
560 /* max_mac_bytes contains the maximum bytes of bytes in the MAC, including
561 * |header|, assuming that there's no padding. */
562 max_mac_bytes = len - md_size - 1;
563 /* num_blocks is the maximum number of hash blocks. */
564 num_blocks = (max_mac_bytes + 1 + md_length_size + md_block_size - 1) / md_block_size;
565 /* In order to calculate the MAC in constant time we have to handle
566 * the final blocks specially because the padding value could cause the
567 * end to appear somewhere in the final |variance_blocks| blocks and we
568 * can't leak where. However, |num_starting_blocks| worth of data can
569 * be hashed right away because no padding value can affect whether
570 * they are plaintext. */
571 num_starting_blocks = 0;
572 /* k is the starting byte offset into the conceptual header||data where
573 * we start processing. */
575 /* mac_end_offset is the index just past the end of the data to be
577 mac_end_offset = data_plus_mac_size + header_length - md_size;
578 /* c is the index of the 0x80 byte in the final hash block that
579 * contains application data. */
580 c = mac_end_offset % md_block_size;
581 /* index_a is the hash block number that contains the 0x80 terminating
583 index_a = mac_end_offset / md_block_size;
584 /* index_b is the hash block number that contains the 64-bit hash
585 * length, in bits. */
586 index_b = (mac_end_offset + md_length_size) / md_block_size;
587 /* bits is the hash-length in bits. It includes the additional hash
588 * block for the masked HMAC key, or whole of |header| in the case of
591 /* For SSLv3, if we're going to have any starting blocks then we need
592 * at least two because the header is larger than a single block. */
593 if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0))
595 num_starting_blocks = num_blocks - variance_blocks;
596 k = md_block_size*num_starting_blocks;
599 bits = 8*mac_end_offset;
602 /* Compute the initial HMAC block. For SSLv3, the padding and
603 * secret bytes are included in |header| because they take more
604 * than a single block. */
605 bits += 8*md_block_size;
606 memset(hmac_pad, 0, md_block_size);
607 OPENSSL_assert(mac_secret_length <= sizeof(hmac_pad));
608 memcpy(hmac_pad, mac_secret, mac_secret_length);
609 for (i = 0; i < md_block_size; i++)
612 md_transform(md_state.c, hmac_pad);
615 if (length_is_big_endian)
617 memset(length_bytes,0,md_length_size-4);
618 length_bytes[md_length_size-4] = (unsigned char)(bits>>24);
619 length_bytes[md_length_size-3] = (unsigned char)(bits>>16);
620 length_bytes[md_length_size-2] = (unsigned char)(bits>>8);
621 length_bytes[md_length_size-1] = (unsigned char)bits;
625 memset(length_bytes,0,md_length_size);
626 length_bytes[md_length_size-5] = (unsigned char)(bits>>24);
627 length_bytes[md_length_size-6] = (unsigned char)(bits>>16);
628 length_bytes[md_length_size-7] = (unsigned char)(bits>>8);
629 length_bytes[md_length_size-8] = (unsigned char)bits;
636 /* The SSLv3 header is larger than a single block.
637 * overhang is the number of bytes beyond a single
638 * block that the header consumes: either 7 bytes
639 * (SHA1) or 11 bytes (MD5). */
640 unsigned overhang = header_length-md_block_size;
641 md_transform(md_state.c, header);
642 memcpy(first_block, header + md_block_size, overhang);
643 memcpy(first_block + overhang, data, md_block_size-overhang);
644 md_transform(md_state.c, first_block);
645 for (i = 1; i < k/md_block_size - 1; i++)
646 md_transform(md_state.c, data + md_block_size*i - overhang);
650 /* k is a multiple of md_block_size. */
651 memcpy(first_block, header, 13);
652 memcpy(first_block+13, data, md_block_size-13);
653 md_transform(md_state.c, first_block);
654 for (i = 1; i < k/md_block_size; i++)
655 md_transform(md_state.c, data + md_block_size*i - 13);
659 memset(mac_out, 0, sizeof(mac_out));
661 /* We now process the final hash blocks. For each block, we construct
662 * it in constant time. If the |i==index_a| then we'll include the 0x80
663 * bytes and zero pad etc. For each block we selectively copy it, in
664 * constant time, to |mac_out|. */
665 for (i = num_starting_blocks; i <= num_starting_blocks+variance_blocks; i++)
667 unsigned char block[MAX_HASH_BLOCK_SIZE];
668 unsigned char is_block_a = constant_time_eq_8(i, index_a);
669 unsigned char is_block_b = constant_time_eq_8(i, index_b);
670 for (j = 0; j < md_block_size; j++)
672 unsigned char b = 0, is_past_c, is_past_cp1;
673 if (k < header_length)
675 else if (k < data_plus_mac_plus_padding_size + header_length)
676 b = data[k-header_length];
679 is_past_c = is_block_a & constant_time_ge(j, c);
680 is_past_cp1 = is_block_a & constant_time_ge(j, c+1);
681 /* If this is the block containing the end of the
682 * application data, and we are at the offset for the
683 * 0x80 value, then overwrite b with 0x80. */
684 b = (b&~is_past_c) | (0x80&is_past_c);
685 /* If this the the block containing the end of the
686 * application data and we're past the 0x80 value then
687 * just write zero. */
689 /* If this is index_b (the final block), but not
690 * index_a (the end of the data), then the 64-bit
691 * length didn't fit into index_a and we're having to
692 * add an extra block of zeros. */
693 b &= ~is_block_b | is_block_a;
695 /* The final bytes of one of the blocks contains the
697 if (j >= md_block_size - md_length_size)
699 /* If this is index_b, write a length byte. */
700 b = (b&~is_block_b) | (is_block_b&length_bytes[j-(md_block_size-md_length_size)]);
705 md_transform(md_state.c, block);
706 md_final_raw(md_state.c, block);
707 /* If this is index_b, copy the hash value to |mac_out|. */
708 for (j = 0; j < md_size; j++)
709 mac_out[j] |= block[j]&is_block_b;
712 EVP_MD_CTX_init(&md_ctx);
713 EVP_DigestInit_ex(&md_ctx, digest, NULL /* engine */);
716 /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
717 memset(hmac_pad, 0x5c, sslv3_pad_length);
719 EVP_DigestUpdate(&md_ctx, mac_secret, mac_secret_length);
720 EVP_DigestUpdate(&md_ctx, hmac_pad, sslv3_pad_length);
721 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
725 /* Complete the HMAC in the standard manner. */
726 for (i = 0; i < md_block_size; i++)
729 EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size);
730 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
732 EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u);
734 *md_out_size = md_out_size_u;
735 EVP_MD_CTX_cleanup(&md_ctx);
740 /* Due to the need to use EVP in FIPS mode we can't reimplement digests but
741 * we can ensure the number of blocks processed is equal for all cases
742 * by digesting additional data.
745 void tls_fips_digest_extra(
746 const EVP_CIPHER_CTX *cipher_ctx, const EVP_MD *hash, HMAC_CTX *hctx,
747 const unsigned char *data, size_t data_len, size_t orig_len)
749 size_t block_size, digest_pad, blocks_data, blocks_orig;
750 if (EVP_CIPHER_CTX_mode(cipher_ctx) != EVP_CIPH_CBC_MODE)
752 block_size = EVP_MD_block_size(hash);
753 /* We are in FIPS mode if we get this far so we know we have only SHA*
754 * digests and TLS to deal with.
755 * Minimum digest padding length is 17 for SHA384/SHA512 and 9
757 * Additional header is 13 bytes. To get the number of digest blocks
758 * processed round up the amount of data plus padding to the nearest
759 * block length. Block length is 128 for SHA384/SHA512 and 64 otherwise.
761 * blocks = (payload_len + digest_pad + 13 + block_size - 1)/block_size
763 * blocks = (payload_len + digest_pad + 12)/block_size + 1
764 * HMAC adds a constant overhead.
765 * We're ultimately only interested in differences so this becomes
766 * blocks = (payload_len + 29)/128
767 * for SHA384/SHA512 and
768 * blocks = (payload_len + 21)/64
771 digest_pad = block_size == 64 ? 21 : 29;
772 blocks_orig = (orig_len + digest_pad)/block_size;
773 blocks_data = (data_len + digest_pad)/block_size;
774 /* MAC enough blocks to make up the difference between the original
775 * and actual lengths plus one extra block to ensure this is never a
776 * no op. The "data" pointer should always have enough space to
777 * perform this operation as it is large enough for a maximum
780 HMAC_Update(hctx, data,
781 (blocks_orig - blocks_data + 1) * block_size);