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).
60 #include <openssl/md5.h>
61 #include <openssl/sha.h>
63 /* MAX_HASH_BIT_COUNT_BYTES is the maximum number of bytes in the hash's length
64 * field. (SHA-384/512 have 128-bit length.) */
65 #define MAX_HASH_BIT_COUNT_BYTES 16
67 /* MAX_HASH_BLOCK_SIZE is the maximum hash block size that we'll support.
68 * Currently SHA-384/512 has a 128-byte block size and that's the largest
69 * supported by TLS.) */
70 #define MAX_HASH_BLOCK_SIZE 128
72 /* Some utility functions are needed:
74 * These macros return the given value with the MSB copied to all the other
75 * bits. They use the fact that arithmetic shift shifts-in the sign bit.
76 * However, this is not ensured by the C standard so you may need to replace
77 * them with something else on odd CPUs. */
78 #define DUPLICATE_MSB_TO_ALL(x) ( (unsigned)( (int)(x) >> (sizeof(int)*8-1) ) )
79 #define DUPLICATE_MSB_TO_ALL_8(x) ((unsigned char)(DUPLICATE_MSB_TO_ALL(x)))
81 /* constant_time_ge returns 0xff if a>=b and 0x00 otherwise. */
82 static unsigned constant_time_ge(unsigned a, unsigned b)
85 return DUPLICATE_MSB_TO_ALL(~a);
88 /* constant_time_eq_8 returns 0xff if a==b and 0x00 otherwise. */
89 static unsigned char constant_time_eq_8(unsigned char a, unsigned char b)
93 return DUPLICATE_MSB_TO_ALL_8(c);
96 /* ssl3_cbc_remove_padding removes padding from the decrypted, SSLv3, CBC
97 * record in |rec| by updating |rec->length| in constant time.
99 * block_size: the block size of the cipher used to encrypt the record.
101 * 0: (in non-constant time) if the record is publicly invalid.
102 * 1: if the padding was valid
104 int ssl3_cbc_remove_padding(const SSL* s,
109 unsigned padding_length, good;
110 const unsigned overhead = 1 /* padding length byte */ + mac_size;
112 /* These lengths are all public so we can test them in non-constant
114 if (overhead > rec->length)
117 padding_length = rec->data[rec->length-1];
118 good = constant_time_ge(rec->length, padding_length+overhead);
119 /* SSLv3 requires that the padding is minimal. */
120 good &= constant_time_ge(block_size, padding_length+1);
121 rec->length -= good & (padding_length+1);
122 return (int)((good & 1) | (~good & -1));
125 /* tls1_cbc_remove_padding removes the CBC padding from the decrypted, TLS, CBC
126 * record in |rec| in constant time and returns 1 if the padding is valid and
127 * -1 otherwise. It also removes any explicit IV from the start of the record
128 * without leaking any timing about whether there was enough space after the
129 * padding was removed.
131 * block_size: the block size of the cipher used to encrypt the record.
133 * 0: (in non-constant time) if the record is publicly invalid.
134 * 1: if the padding was valid
136 int tls1_cbc_remove_padding(const SSL* s,
141 unsigned padding_length, good, to_check, i;
142 const char has_explicit_iv = s->version == DTLS1_VERSION;
143 const unsigned overhead = 1 /* padding length byte */ +
145 (has_explicit_iv ? block_size : 0);
147 /* These lengths are all public so we can test them in non-constant
149 if (overhead > rec->length)
152 padding_length = rec->data[rec->length-1];
154 /* NB: if compression is in operation the first packet may not be of
155 * even length so the padding bug check cannot be performed. This bug
156 * workaround has been around since SSLeay so hopefully it is either
157 * fixed now or no buggy implementation supports compression [steve]
159 if ( (s->options&SSL_OP_TLS_BLOCK_PADDING_BUG) && !s->expand)
161 /* First packet is even in size, so check */
162 if ((memcmp(s->s3->read_sequence, "\0\0\0\0\0\0\0\0",8) == 0) &&
163 !(padding_length & 1))
165 s->s3->flags|=TLS1_FLAGS_TLS_PADDING_BUG;
167 if ((s->s3->flags & TLS1_FLAGS_TLS_PADDING_BUG) &&
174 good = constant_time_ge(rec->length, overhead+padding_length);
175 /* The padding consists of a length byte at the end of the record and
176 * then that many bytes of padding, all with the same value as the
177 * length byte. Thus, with the length byte included, there are i+1
180 * We can't check just |padding_length+1| bytes because that leaks
181 * decrypted information. Therefore we always have to check the maximum
182 * amount of padding possible. (Again, the length of the record is
183 * public information so we can use it.) */
184 to_check = 255; /* maximum amount of padding. */
185 if (to_check > rec->length-1)
186 to_check = rec->length-1;
188 for (i = 0; i < to_check; i++)
190 unsigned char mask = constant_time_ge(padding_length, i);
191 unsigned char b = rec->data[rec->length-1-i];
192 /* The final |padding_length+1| bytes should all have the value
193 * |padding_length|. Therefore the XOR should be zero. */
194 good &= ~(mask&(padding_length ^ b));
197 /* If any of the final |padding_length+1| bytes had the wrong value,
198 * one or more of the lower eight bits of |good| will be cleared. We
199 * AND the bottom 8 bits together and duplicate the result to all the
204 good <<= sizeof(good)*8-1;
205 good = DUPLICATE_MSB_TO_ALL(good);
207 rec->length -= good & (padding_length+1);
209 /* We can always safely skip the explicit IV. We check at the beginning
210 * of this function that the record has at least enough space for the
211 * IV, MAC and padding length byte. (These can be checked in
212 * non-constant time because it's all public information.) So, if the
213 * padding was invalid, then we didn't change |rec->length| and this is
214 * safe. If the padding was valid then we know that we have at least
215 * overhead+padding_length bytes of space and so this is still safe
216 * because overhead accounts for the explicit IV. */
219 rec->data += block_size;
220 rec->input += block_size;
221 rec->length -= block_size;
222 rec->orig_len -= block_size;
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,
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(rec->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 (rec->orig_len > md_size + 255 + 1)
278 scan_start = rec->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; i < rec->orig_len;)
293 for (j = 0; j < md_size && i < rec->orig_len; i++, j++)
295 unsigned char mac_started = constant_time_ge(i, mac_start);
296 unsigned char mac_ended = constant_time_ge(i, mac_end);
299 rotated_mac[j] |= b & mac_started & ~mac_ended;
303 /* Now rotate the MAC */
304 #if defined(CBC_MAC_ROTATE_IN_PLACE)
306 for (i = 0; i < md_size; i++)
308 unsigned char offset = (div_spoiler + rotate_offset + i) % md_size;
309 out[j++] = rotated_mac[offset];
312 memset(out, 0, md_size);
313 for (i = 0; i < md_size; i++)
315 unsigned char offset = (div_spoiler + md_size - rotate_offset + i) % md_size;
316 for (j = 0; j < md_size; j++)
317 out[j] |= rotated_mac[i] & constant_time_eq_8(j, offset);
322 /* These functions serialize the state of a hash and thus perform the standard
323 * "final" operation without adding the padding and length that such a function
325 static void tls1_md5_final_raw(void* ctx, unsigned char *md_out)
334 static void tls1_sha1_final_raw(void* ctx, unsigned char *md_out)
337 l2n(sha1->h0, md_out);
338 l2n(sha1->h1, md_out);
339 l2n(sha1->h2, md_out);
340 l2n(sha1->h3, md_out);
341 l2n(sha1->h4, md_out);
344 static void tls1_sha256_final_raw(void* ctx, unsigned char *md_out)
346 SHA256_CTX *sha256 = ctx;
349 for (i = 0; i < 8; i++)
351 l2n(sha256->h[i], md_out);
355 static void tls1_sha512_final_raw(void* ctx, unsigned char *md_out)
357 SHA512_CTX *sha512 = ctx;
360 for (i = 0; i < 8; i++)
362 l2n8(sha512->h[i], md_out);
366 /* ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
367 * which ssl3_cbc_digest_record supports. */
368 char ssl3_cbc_record_digest_supported(const EVP_MD *digest)
374 switch (EVP_MD_type(digest))
388 /* ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS
391 * ctx: the EVP_MD_CTX from which we take the hash function.
392 * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX.
393 * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written.
394 * md_out_size: if non-NULL, the number of output bytes is written here.
395 * header: the 13-byte, TLS record header.
396 * data: the record data itself, less any preceeding explicit IV.
397 * data_plus_mac_size: the secret, reported length of the data and MAC
398 * once the padding has been removed.
399 * data_plus_mac_plus_padding_size: the public length of the whole
400 * record, including padding.
401 * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
403 * On entry: by virtue of having been through one of the remove_padding
404 * functions, above, we know that data_plus_mac_size is large enough to contain
405 * a padding byte and MAC. (If the padding was invalid, it might contain the
407 void ssl3_cbc_digest_record(
408 const EVP_MD *digest,
409 unsigned char* md_out,
411 const unsigned char header[13],
412 const unsigned char *data,
413 size_t data_plus_mac_size,
414 size_t data_plus_mac_plus_padding_size,
415 const unsigned char *mac_secret,
416 unsigned mac_secret_length,
419 unsigned char md_state[sizeof(SHA512_CTX)];
420 void (*md_final_raw)(void *ctx, unsigned char *md_out);
421 void (*md_transform)(void *ctx, const unsigned char *block);
422 unsigned md_size, md_block_size = 64;
423 unsigned sslv3_pad_length = 40, header_length, variance_blocks,
424 len, max_mac_bytes, num_blocks,
425 num_starting_blocks, k, mac_end_offset, c, index_a, index_b;
427 unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES];
428 /* hmac_pad is the masked HMAC key. */
429 unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE];
430 unsigned char first_block[MAX_HASH_BLOCK_SIZE];
431 unsigned char mac_out[EVP_MAX_MD_SIZE];
432 unsigned i, j, md_out_size_u;
434 /* mdLengthSize is the number of bytes in the length field that terminates
436 unsigned md_length_size = 8;
438 /* This is a, hopefully redundant, check that allows us to forget about
439 * many possible overflows later in this function. */
440 OPENSSL_assert(data_plus_mac_plus_padding_size < 1024*1024);
442 switch (EVP_MD_type(digest))
445 MD5_Init((MD5_CTX*)md_state);
446 md_final_raw = tls1_md5_final_raw;
447 md_transform = (void(*)(void *ctx, const unsigned char *block)) MD5_Transform;
449 sslv3_pad_length = 48;
452 SHA1_Init((SHA_CTX*)md_state);
453 md_final_raw = tls1_sha1_final_raw;
454 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA1_Transform;
458 SHA224_Init((SHA256_CTX*)md_state);
459 md_final_raw = tls1_sha256_final_raw;
460 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;
464 SHA256_Init((SHA256_CTX*)md_state);
465 md_final_raw = tls1_sha256_final_raw;
466 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;
470 SHA384_Init((SHA512_CTX*)md_state);
471 md_final_raw = tls1_sha512_final_raw;
472 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA512_Transform;
478 SHA512_Init((SHA512_CTX*)md_state);
479 md_final_raw = tls1_sha512_final_raw;
480 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA512_Transform;
486 /* ssl3_cbc_record_digest_supported should have been
487 * called first to check that the hash function is
495 OPENSSL_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES);
496 OPENSSL_assert(md_block_size <= MAX_HASH_BLOCK_SIZE);
497 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
505 8 /* sequence number */ +
506 1 /* record type */ +
507 2 /* record length */;
510 /* variance_blocks is the number of blocks of the hash that we have to
511 * calculate in constant time because they could be altered by the
514 * In SSLv3, the padding must be minimal so the end of the plaintext
515 * varies by, at most, 15+20 = 35 bytes. (We conservatively assume that
516 * the MAC size varies from 0..20 bytes.) In case the 9 bytes of hash
517 * termination (0x80 + 64-bit length) don't fit in the final block, we
518 * say that the final two blocks can vary based on the padding.
520 * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
521 * required to be minimal. Therefore we say that the final six blocks
522 * can vary based on the padding.
524 * Later in the function, if the message is short and there obviously
525 * cannot be this many blocks then variance_blocks can be reduced. */
526 variance_blocks = is_sslv3 ? 2 : 6;
527 /* From now on we're dealing with the MAC, which conceptually has 13
528 * bytes of `header' before the start of the data (TLS) or 71/75 bytes
530 len = data_plus_mac_plus_padding_size + header_length;
531 /* max_mac_bytes contains the maximum bytes of bytes in the MAC, including
532 * |header|, assuming that there's no padding. */
533 max_mac_bytes = len - md_size - 1;
534 /* num_blocks is the maximum number of hash blocks. */
535 num_blocks = (max_mac_bytes + 1 + md_length_size + md_block_size - 1) / md_block_size;
536 /* In order to calculate the MAC in constant time we have to handle
537 * the final blocks specially because the padding value could cause the
538 * end to appear somewhere in the final |variance_blocks| blocks and we
539 * can't leak where. However, |num_starting_blocks| worth of data can
540 * be hashed right away because no padding value can affect whether
541 * they are plaintext. */
542 num_starting_blocks = 0;
543 /* k is the starting byte offset into the conceptual header||data where
544 * we start processing. */
546 /* mac_end_offset is the index just past the end of the data to be
548 mac_end_offset = data_plus_mac_size + header_length - md_size;
549 /* c is the index of the 0x80 byte in the final hash block that
550 * contains application data. */
551 c = mac_end_offset % md_block_size;
552 /* index_a is the hash block number that contains the 0x80 terminating
554 index_a = mac_end_offset / md_block_size;
555 /* index_b is the hash block number that contains the 64-bit hash
556 * length, in bits. */
557 index_b = (mac_end_offset + md_length_size) / md_block_size;
558 /* bits is the hash-length in bits. It includes the additional hash
559 * block for the masked HMAC key, or whole of |header| in the case of
562 /* For SSLv3, if we're going to have any starting blocks then we need
563 * at least two because the header is larger than a single block. */
564 if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0))
566 num_starting_blocks = num_blocks - variance_blocks;
567 k = md_block_size*num_starting_blocks;
570 bits = 8*mac_end_offset;
573 /* Compute the initial HMAC block. For SSLv3, the padding and
574 * secret bytes are included in |header| because they take more
575 * than a single block. */
576 bits += 8*md_block_size;
577 memset(hmac_pad, 0, md_block_size);
578 OPENSSL_assert(mac_secret_length <= sizeof(hmac_pad));
579 memcpy(hmac_pad, mac_secret, mac_secret_length);
580 for (i = 0; i < md_block_size; i++)
583 md_transform(md_state, hmac_pad);
587 if (md_length_size == 16)
589 memset(length_bytes, 0, 8);
592 for (i = 0; i < 8; i++)
593 length_bytes[i+j] = bits >> (8*(7-i));
599 /* The SSLv3 header is larger than a single block.
600 * overhang is the number of bytes beyond a single
601 * block that the header consumes: either 7 bytes
602 * (SHA1) or 11 bytes (MD5). */
603 unsigned overhang = header_length-md_block_size;
604 md_transform(md_state, header);
605 memcpy(first_block, header + md_block_size, overhang);
606 memcpy(first_block + overhang, data, md_block_size-overhang);
607 md_transform(md_state, first_block);
608 for (i = 1; i < k/md_block_size - 1; i++)
609 md_transform(md_state, data + md_block_size*i - overhang);
613 /* k is a multiple of md_block_size. */
614 memcpy(first_block, header, 13);
615 memcpy(first_block+13, data, md_block_size-13);
616 md_transform(md_state, first_block);
617 for (i = 1; i < k/md_block_size; i++)
618 md_transform(md_state, data + md_block_size*i - 13);
622 memset(mac_out, 0, sizeof(mac_out));
624 /* We now process the final hash blocks. For each block, we construct
625 * it in constant time. If the |i==index_a| then we'll include the 0x80
626 * bytes and zero pad etc. For each block we selectively copy it, in
627 * constant time, to |mac_out|. */
628 for (i = num_starting_blocks; i <= num_starting_blocks+variance_blocks; i++)
630 unsigned char block[MAX_HASH_BLOCK_SIZE];
631 unsigned char is_block_a = constant_time_eq_8(i, index_a);
632 unsigned char is_block_b = constant_time_eq_8(i, index_b);
633 for (j = 0; j < md_block_size; j++)
635 unsigned char b = 0, is_past_c, is_past_cp1;
636 if (k < header_length)
638 else if (k < data_plus_mac_plus_padding_size + header_length)
639 b = data[k-header_length];
642 is_past_c = is_block_a & constant_time_ge(j, c);
643 is_past_cp1 = is_block_a & constant_time_ge(j, c+1);
644 /* If this is the block containing the end of the
645 * application data, and we are at the offset for the
646 * 0x80 value, then overwrite b with 0x80. */
647 b = (b&~is_past_c) | (0x80&is_past_c);
648 /* If this the the block containing the end of the
649 * application data and we're past the 0x80 value then
650 * just write zero. */
652 /* If this is index_b (the final block), but not
653 * index_a (the end of the data), then the 64-bit
654 * length didn't fit into index_a and we're having to
655 * add an extra block of zeros. */
656 b &= ~is_block_b | is_block_a;
658 /* The final bytes of one of the blocks contains the
660 if (j >= md_block_size - md_length_size)
662 /* If this is index_b, write a length byte. */
663 b = (b&~is_block_b) | (is_block_b&length_bytes[j-(md_block_size-md_length_size)]);
668 md_transform(md_state, block);
669 md_final_raw(md_state, block);
670 /* If this is index_b, copy the hash value to |mac_out|. */
671 for (j = 0; j < md_size; j++)
672 mac_out[j] |= block[j]&is_block_b;
675 EVP_MD_CTX_init(&md_ctx);
676 EVP_DigestInit_ex(&md_ctx, digest, NULL /* engine */);
679 /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
680 memset(hmac_pad, 0x5c, sslv3_pad_length);
682 EVP_DigestUpdate(&md_ctx, mac_secret, mac_secret_length);
683 EVP_DigestUpdate(&md_ctx, hmac_pad, sslv3_pad_length);
684 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
688 /* Complete the HMAC in the standard manner. */
689 for (i = 0; i < md_block_size; i++)
692 EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size);
693 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
695 EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u);
697 *md_out_size = md_out_size_u;
698 EVP_MD_CTX_cleanup(&md_ctx);
703 /* Due to the need to use EVP in FIPS mode we can't reimplement digests but
704 * we can ensure the number of blocks processed is equal for all cases
705 * by digesting additional data.
708 void tls_fips_digest_extra(
709 const EVP_CIPHER_CTX *cipher_ctx, const EVP_MD *hash, HMAC_CTX *hctx,
710 const unsigned char *data, size_t data_len, size_t orig_len)
712 size_t block_size, digest_pad, blocks_data, blocks_orig;
713 if (EVP_CIPHER_CTX_mode(cipher_ctx) != EVP_CIPH_CBC_MODE)
715 block_size = EVP_MD_block_size(hash);
716 /* We are in FIPS mode if we get this far so we know we have only SHA*
717 * digests and TLS to deal with.
718 * Minimum digest padding length is 17 for SHA384/SHA512 and 9
720 * Additional header is 13 bytes. To get the number of digest blocks
721 * processed round up the amount of data plus padding to the nearest
722 * block length. Block length is 128 for SHA384/SHA512 and 64 otherwise.
724 * blocks = (payload_len + digest_pad + 13 + block_size - 1)/block_size
726 * blocks = (payload_len + digest_pad + 12)/block_size + 1
727 * HMAC adds a constant overhead.
728 * We're ultimately only interested in differences so this becomes
729 * blocks = (payload_len + 29)/128
730 * for SHA384/SHA512 and
731 * blocks = (payload_len + 21)/64
734 digest_pad = block_size == 64 ? 21 : 29;
735 blocks_orig = (orig_len + digest_pad)/block_size;
736 blocks_data = (data_len + digest_pad)/block_size;
737 /* MAC enough blocks to make up the difference between the original
738 * and actual lengths plus one extra block to ensure this is never a
739 * no op. The "data" pointer should always have enough space to
740 * perform this operation as it is large enough for a maximum
743 HMAC_Update(hctx, data,
744 (blocks_orig - blocks_data + 1) * block_size);