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).
56 #include "../crypto/constant_time_locl.h"
59 #include <openssl/md5.h>
60 #include <openssl/sha.h>
63 * MAX_HASH_BIT_COUNT_BYTES is the maximum number of bytes in the hash's
64 * length field. (SHA-384/512 have 128-bit length.)
66 #define MAX_HASH_BIT_COUNT_BYTES 16
69 * MAX_HASH_BLOCK_SIZE is the maximum hash block size that we'll support.
70 * Currently SHA-384/512 has a 128-byte block size and that's the largest
73 #define MAX_HASH_BLOCK_SIZE 128
76 * ssl3_cbc_remove_padding removes padding from the decrypted, SSLv3, CBC
77 * record in |rec| by updating |rec->length| in constant time.
79 * block_size: the block size of the cipher used to encrypt the record.
81 * 0: (in non-constant time) if the record is publicly invalid.
82 * 1: if the padding was valid
85 int ssl3_cbc_remove_padding(const SSL *s,
87 unsigned block_size, unsigned mac_size)
89 unsigned padding_length, good;
90 const unsigned overhead = 1 /* padding length byte */ + mac_size;
93 * These lengths are all public so we can test them in non-constant time.
95 if (overhead > rec->length)
98 padding_length = rec->data[rec->length - 1];
99 good = constant_time_ge(rec->length, padding_length + overhead);
100 /* SSLv3 requires that the padding is minimal. */
101 good &= constant_time_ge(block_size, padding_length + 1);
102 rec->length -= good & (padding_length + 1);
103 return constant_time_select_int(good, 1, -1);
107 * tls1_cbc_remove_padding removes the CBC padding from the decrypted, TLS, CBC
108 * record in |rec| in constant time and returns 1 if the padding is valid and
109 * -1 otherwise. It also removes any explicit IV from the start of the record
110 * without leaking any timing about whether there was enough space after the
111 * padding was removed.
113 * block_size: the block size of the cipher used to encrypt the record.
115 * 0: (in non-constant time) if the record is publicly invalid.
116 * 1: if the padding was valid
119 int tls1_cbc_remove_padding(const SSL *s,
121 unsigned block_size, unsigned mac_size)
123 unsigned padding_length, good, to_check, i;
124 const unsigned overhead = 1 /* padding length byte */ + mac_size;
125 /* Check if version requires explicit IV */
126 if (SSL_USE_EXPLICIT_IV(s)) {
128 * These lengths are all public so we can test them in non-constant
131 if (overhead + block_size > rec->length)
133 /* We can now safely skip explicit IV */
134 rec->data += block_size;
135 rec->input += block_size;
136 rec->length -= block_size;
137 rec->orig_len -= block_size;
138 } else if (overhead > rec->length)
141 padding_length = rec->data[rec->length - 1];
144 * NB: if compression is in operation the first packet may not be of even
145 * length so the padding bug check cannot be performed. This bug
146 * workaround has been around since SSLeay so hopefully it is either
147 * fixed now or no buggy implementation supports compression [steve]
149 if ((s->options & SSL_OP_TLS_BLOCK_PADDING_BUG) && !s->expand) {
150 /* First packet is even in size, so check */
151 if ((memcmp(s->s3->read_sequence, "\0\0\0\0\0\0\0\0", 8) == 0) &&
152 !(padding_length & 1)) {
153 s->s3->flags |= TLS1_FLAGS_TLS_PADDING_BUG;
155 if ((s->s3->flags & TLS1_FLAGS_TLS_PADDING_BUG) && padding_length > 0) {
160 if (EVP_CIPHER_flags(s->enc_read_ctx->cipher) & EVP_CIPH_FLAG_AEAD_CIPHER) {
161 /* padding is already verified */
162 rec->length -= padding_length + 1;
166 good = constant_time_ge(rec->length, overhead + padding_length);
168 * The padding consists of a length byte at the end of the record and
169 * then that many bytes of padding, all with the same value as the length
170 * byte. Thus, with the length byte included, there are i+1 bytes of
171 * padding. We can't check just |padding_length+1| bytes because that
172 * leaks decrypted information. Therefore we always have to check the
173 * maximum amount of padding possible. (Again, the length of the record
174 * is public information so we can use it.)
176 to_check = 255; /* maximum amount of padding. */
177 if (to_check > rec->length - 1)
178 to_check = rec->length - 1;
180 for (i = 0; i < to_check; i++) {
181 unsigned char mask = constant_time_ge_8(padding_length, i);
182 unsigned char b = rec->data[rec->length - 1 - i];
184 * The final |padding_length+1| bytes should all have the value
185 * |padding_length|. Therefore the XOR should be zero.
187 good &= ~(mask & (padding_length ^ b));
191 * If any of the final |padding_length+1| bytes had the wrong value, one
192 * or more of the lower eight bits of |good| will be cleared.
194 good = constant_time_eq(0xff, good & 0xff);
195 rec->length -= good & (padding_length + 1);
197 return constant_time_select_int(good, 1, -1);
201 * ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in
202 * constant time (independent of the concrete value of rec->length, which may
203 * vary within a 256-byte window).
205 * ssl3_cbc_remove_padding or tls1_cbc_remove_padding must be called prior to
209 * rec->orig_len >= md_size
210 * md_size <= EVP_MAX_MD_SIZE
212 * If CBC_MAC_ROTATE_IN_PLACE is defined then the rotation is performed with
213 * variable accesses in a 64-byte-aligned buffer. Assuming that this fits into
214 * a single or pair of cache-lines, then the variable memory accesses don't
215 * actually affect the timing. CPUs with smaller cache-lines [if any] are
216 * not multi-core and are not considered vulnerable to cache-timing attacks.
218 #define CBC_MAC_ROTATE_IN_PLACE
220 void ssl3_cbc_copy_mac(unsigned char *out,
221 const SSL3_RECORD *rec, unsigned md_size)
223 #if defined(CBC_MAC_ROTATE_IN_PLACE)
224 unsigned char rotated_mac_buf[64 + EVP_MAX_MD_SIZE];
225 unsigned char *rotated_mac;
227 unsigned char rotated_mac[EVP_MAX_MD_SIZE];
231 * mac_end is the index of |rec->data| just after the end of the MAC.
233 unsigned mac_end = rec->length;
234 unsigned mac_start = mac_end - md_size;
236 * scan_start contains the number of bytes that we can ignore because the
237 * MAC's position can only vary by 255 bytes.
239 unsigned scan_start = 0;
241 unsigned div_spoiler;
242 unsigned rotate_offset;
244 OPENSSL_assert(rec->orig_len >= md_size);
245 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
247 #if defined(CBC_MAC_ROTATE_IN_PLACE)
248 rotated_mac = rotated_mac_buf + ((0 - (size_t)rotated_mac_buf) & 63);
251 /* This information is public so it's safe to branch based on it. */
252 if (rec->orig_len > md_size + 255 + 1)
253 scan_start = rec->orig_len - (md_size + 255 + 1);
255 * div_spoiler contains a multiple of md_size that is used to cause the
256 * modulo operation to be constant time. Without this, the time varies
257 * based on the amount of padding when running on Intel chips at least.
258 * The aim of right-shifting md_size is so that the compiler doesn't
259 * figure out that it can remove div_spoiler as that would require it to
260 * prove that md_size is always even, which I hope is beyond it.
262 div_spoiler = md_size >> 1;
263 div_spoiler <<= (sizeof(div_spoiler) - 1) * 8;
264 rotate_offset = (div_spoiler + mac_start - scan_start) % md_size;
266 memset(rotated_mac, 0, md_size);
267 for (i = scan_start, j = 0; i < rec->orig_len; i++) {
268 unsigned char mac_started = constant_time_ge_8(i, mac_start);
269 unsigned char mac_ended = constant_time_ge_8(i, mac_end);
270 unsigned char b = rec->data[i];
271 rotated_mac[j++] |= b & mac_started & ~mac_ended;
272 j &= constant_time_lt(j, md_size);
275 /* Now rotate the MAC */
276 #if defined(CBC_MAC_ROTATE_IN_PLACE)
278 for (i = 0; i < md_size; i++) {
279 /* in case cache-line is 32 bytes, touch second line */
280 ((volatile unsigned char *)rotated_mac)[rotate_offset ^ 32];
281 out[j++] = rotated_mac[rotate_offset++];
282 rotate_offset &= constant_time_lt(rotate_offset, md_size);
285 memset(out, 0, md_size);
286 rotate_offset = md_size - rotate_offset;
287 rotate_offset &= constant_time_lt(rotate_offset, md_size);
288 for (i = 0; i < md_size; i++) {
289 for (j = 0; j < md_size; j++)
290 out[j] |= rotated_mac[i] & constant_time_eq_8(j, rotate_offset);
292 rotate_offset &= constant_time_lt(rotate_offset, md_size);
298 * u32toLE serialises an unsigned, 32-bit number (n) as four bytes at (p) in
299 * little-endian order. The value of p is advanced by four.
301 #define u32toLE(n, p) \
302 (*((p)++)=(unsigned char)(n), \
303 *((p)++)=(unsigned char)(n>>8), \
304 *((p)++)=(unsigned char)(n>>16), \
305 *((p)++)=(unsigned char)(n>>24))
308 * These functions serialize the state of a hash and thus perform the
309 * standard "final" operation without adding the padding and length that such
310 * a function typically does.
312 static void tls1_md5_final_raw(void *ctx, unsigned char *md_out)
315 u32toLE(md5->A, md_out);
316 u32toLE(md5->B, md_out);
317 u32toLE(md5->C, md_out);
318 u32toLE(md5->D, md_out);
321 static void tls1_sha1_final_raw(void *ctx, unsigned char *md_out)
324 l2n(sha1->h0, md_out);
325 l2n(sha1->h1, md_out);
326 l2n(sha1->h2, md_out);
327 l2n(sha1->h3, md_out);
328 l2n(sha1->h4, md_out);
331 static void tls1_sha256_final_raw(void *ctx, unsigned char *md_out)
333 SHA256_CTX *sha256 = ctx;
336 for (i = 0; i < 8; i++) {
337 l2n(sha256->h[i], md_out);
341 static void tls1_sha512_final_raw(void *ctx, unsigned char *md_out)
343 SHA512_CTX *sha512 = ctx;
346 for (i = 0; i < 8; i++) {
347 l2n8(sha512->h[i], md_out);
351 #undef LARGEST_DIGEST_CTX
352 #define LARGEST_DIGEST_CTX SHA512_CTX
355 * ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
356 * which ssl3_cbc_digest_record supports.
358 char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx)
362 switch (EVP_MD_CTX_type(ctx)) {
376 * ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS
379 * ctx: the EVP_MD_CTX from which we take the hash function.
380 * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX.
381 * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written.
382 * md_out_size: if non-NULL, the number of output bytes is written here.
383 * header: the 13-byte, TLS record header.
384 * data: the record data itself, less any preceding explicit IV.
385 * data_plus_mac_size: the secret, reported length of the data and MAC
386 * once the padding has been removed.
387 * data_plus_mac_plus_padding_size: the public length of the whole
388 * record, including padding.
389 * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
391 * On entry: by virtue of having been through one of the remove_padding
392 * functions, above, we know that data_plus_mac_size is large enough to contain
393 * a padding byte and MAC. (If the padding was invalid, it might contain the
396 void ssl3_cbc_digest_record(const EVP_MD_CTX *ctx,
397 unsigned char *md_out,
399 const unsigned char header[13],
400 const unsigned char *data,
401 size_t data_plus_mac_size,
402 size_t data_plus_mac_plus_padding_size,
403 const unsigned char *mac_secret,
404 unsigned mac_secret_length, char is_sslv3)
408 unsigned char c[sizeof(LARGEST_DIGEST_CTX)];
410 void (*md_final_raw) (void *ctx, unsigned char *md_out);
411 void (*md_transform) (void *ctx, const unsigned char *block);
412 unsigned md_size, md_block_size = 64;
413 unsigned sslv3_pad_length = 40, header_length, variance_blocks,
414 len, max_mac_bytes, num_blocks,
415 num_starting_blocks, k, mac_end_offset, c, index_a, index_b;
416 unsigned int bits; /* at most 18 bits */
417 unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES];
418 /* hmac_pad is the masked HMAC key. */
419 unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE];
420 unsigned char first_block[MAX_HASH_BLOCK_SIZE];
421 unsigned char mac_out[EVP_MAX_MD_SIZE];
422 unsigned i, j, md_out_size_u;
425 * mdLengthSize is the number of bytes in the length field that
426 * terminates * the hash.
428 unsigned md_length_size = 8;
429 char length_is_big_endian = 1;
433 * This is a, hopefully redundant, check that allows us to forget about
434 * many possible overflows later in this function.
436 OPENSSL_assert(data_plus_mac_plus_padding_size < 1024 * 1024);
438 switch (EVP_MD_CTX_type(ctx)) {
440 MD5_Init((MD5_CTX *)md_state.c);
441 md_final_raw = tls1_md5_final_raw;
443 (void (*)(void *ctx, const unsigned char *block))MD5_Transform;
445 sslv3_pad_length = 48;
446 length_is_big_endian = 0;
449 SHA1_Init((SHA_CTX *)md_state.c);
450 md_final_raw = tls1_sha1_final_raw;
452 (void (*)(void *ctx, const unsigned char *block))SHA1_Transform;
456 SHA224_Init((SHA256_CTX *)md_state.c);
457 md_final_raw = tls1_sha256_final_raw;
459 (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;
466 (void (*)(void *ctx, const unsigned char *block))SHA256_Transform;
470 SHA384_Init((SHA512_CTX *)md_state.c);
471 md_final_raw = tls1_sha512_final_raw;
473 (void (*)(void *ctx, const unsigned char *block))SHA512_Transform;
479 SHA512_Init((SHA512_CTX *)md_state.c);
480 md_final_raw = tls1_sha512_final_raw;
482 (void (*)(void *ctx, const unsigned char *block))SHA512_Transform;
489 * ssl3_cbc_record_digest_supported should have been called first to
490 * check that the hash function is supported.
498 OPENSSL_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES);
499 OPENSSL_assert(md_block_size <= MAX_HASH_BLOCK_SIZE);
500 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
504 header_length = mac_secret_length + sslv3_pad_length + 8 /* sequence
506 1 /* record type */ +
507 2 /* record length */ ;
511 * variance_blocks is the number of blocks of the hash that we have to
512 * calculate in constant time because they could be altered by the
513 * padding value. In SSLv3, the padding must be minimal so the end of
514 * the plaintext varies by, at most, 15+20 = 35 bytes. (We conservatively
515 * assume that the MAC size varies from 0..20 bytes.) In case the 9 bytes
516 * of hash termination (0x80 + 64-bit length) don't fit in the final
517 * block, we say that the final two blocks can vary based on the padding.
518 * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
519 * required to be minimal. Therefore we say that the final six blocks can
520 * vary based on the padding. Later in the function, if the message is
521 * short and there obviously cannot be this many blocks then
522 * variance_blocks can be reduced.
524 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
530 len = data_plus_mac_plus_padding_size + header_length;
532 * max_mac_bytes contains the maximum bytes of bytes in the MAC,
533 * including * |header|, assuming that there's no padding.
535 max_mac_bytes = len - md_size - 1;
536 /* num_blocks is the maximum number of hash blocks. */
538 (max_mac_bytes + 1 + md_length_size + md_block_size -
541 * In order to calculate the MAC in constant time we have to handle the
542 * final blocks specially because the padding value could cause the end
543 * to appear somewhere in the final |variance_blocks| blocks and we can't
544 * leak where. However, |num_starting_blocks| worth of data can be hashed
545 * right away because no padding value can affect whether they are
548 num_starting_blocks = 0;
550 * k is the starting byte offset into the conceptual header||data where
551 * we start processing.
555 * mac_end_offset is the index just past the end of the data to be MACed.
557 mac_end_offset = data_plus_mac_size + header_length - md_size;
559 * c is the index of the 0x80 byte in the final hash block that contains
562 c = mac_end_offset % md_block_size;
564 * index_a is the hash block number that contains the 0x80 terminating
567 index_a = mac_end_offset / md_block_size;
569 * index_b is the hash block number that contains the 64-bit hash length,
572 index_b = (mac_end_offset + md_length_size) / md_block_size;
574 * bits is the hash-length in bits. It includes the additional hash block
575 * for the masked HMAC key, or whole of |header| in the case of SSLv3.
579 * For SSLv3, if we're going to have any starting blocks then we need at
580 * least two because the header is larger than a single block.
582 if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0)) {
583 num_starting_blocks = num_blocks - variance_blocks;
584 k = md_block_size * num_starting_blocks;
587 bits = 8 * mac_end_offset;
590 * Compute the initial HMAC block. For SSLv3, the padding and secret
591 * bytes are included in |header| because they take more than a
594 bits += 8 * md_block_size;
595 memset(hmac_pad, 0, md_block_size);
596 OPENSSL_assert(mac_secret_length <= sizeof(hmac_pad));
597 memcpy(hmac_pad, mac_secret, mac_secret_length);
598 for (i = 0; i < md_block_size; i++)
601 md_transform(md_state.c, hmac_pad);
604 if (length_is_big_endian) {
605 memset(length_bytes, 0, md_length_size - 4);
606 length_bytes[md_length_size - 4] = (unsigned char)(bits >> 24);
607 length_bytes[md_length_size - 3] = (unsigned char)(bits >> 16);
608 length_bytes[md_length_size - 2] = (unsigned char)(bits >> 8);
609 length_bytes[md_length_size - 1] = (unsigned char)bits;
611 memset(length_bytes, 0, md_length_size);
612 length_bytes[md_length_size - 5] = (unsigned char)(bits >> 24);
613 length_bytes[md_length_size - 6] = (unsigned char)(bits >> 16);
614 length_bytes[md_length_size - 7] = (unsigned char)(bits >> 8);
615 length_bytes[md_length_size - 8] = (unsigned char)bits;
621 * The SSLv3 header is larger than a single block. overhang is
622 * the number of bytes beyond a single block that the header
623 * consumes: either 7 bytes (SHA1) or 11 bytes (MD5).
625 unsigned overhang = header_length - md_block_size;
626 md_transform(md_state.c, header);
627 memcpy(first_block, header + md_block_size, overhang);
628 memcpy(first_block + overhang, data, md_block_size - overhang);
629 md_transform(md_state.c, first_block);
630 for (i = 1; i < k / md_block_size - 1; i++)
631 md_transform(md_state.c, data + md_block_size * i - overhang);
633 /* k is a multiple of md_block_size. */
634 memcpy(first_block, header, 13);
635 memcpy(first_block + 13, data, md_block_size - 13);
636 md_transform(md_state.c, first_block);
637 for (i = 1; i < k / md_block_size; i++)
638 md_transform(md_state.c, data + md_block_size * i - 13);
642 memset(mac_out, 0, sizeof(mac_out));
645 * We now process the final hash blocks. For each block, we construct it
646 * in constant time. If the |i==index_a| then we'll include the 0x80
647 * bytes and zero pad etc. For each block we selectively copy it, in
648 * constant time, to |mac_out|.
650 for (i = num_starting_blocks; i <= num_starting_blocks + variance_blocks;
652 unsigned char block[MAX_HASH_BLOCK_SIZE];
653 unsigned char is_block_a = constant_time_eq_8(i, index_a);
654 unsigned char is_block_b = constant_time_eq_8(i, index_b);
655 for (j = 0; j < md_block_size; j++) {
656 unsigned char b = 0, is_past_c, is_past_cp1;
657 if (k < header_length)
659 else if (k < data_plus_mac_plus_padding_size + header_length)
660 b = data[k - header_length];
663 is_past_c = is_block_a & constant_time_ge_8(j, c);
664 is_past_cp1 = is_block_a & constant_time_ge_8(j, c + 1);
666 * If this is the block containing the end of the application
667 * data, and we are at the offset for the 0x80 value, then
668 * overwrite b with 0x80.
670 b = constant_time_select_8(is_past_c, 0x80, b);
672 * If this the the block containing the end of the application
673 * data and we're past the 0x80 value then just write zero.
675 b = b & ~is_past_cp1;
677 * If this is index_b (the final block), but not index_a (the end
678 * of the data), then the 64-bit length didn't fit into index_a
679 * and we're having to add an extra block of zeros.
681 b &= ~is_block_b | is_block_a;
684 * The final bytes of one of the blocks contains the length.
686 if (j >= md_block_size - md_length_size) {
687 /* If this is index_b, write a length byte. */
688 b = constant_time_select_8(is_block_b,
691 md_length_size)], b);
696 md_transform(md_state.c, block);
697 md_final_raw(md_state.c, block);
698 /* If this is index_b, copy the hash value to |mac_out|. */
699 for (j = 0; j < md_size; j++)
700 mac_out[j] |= block[j] & is_block_b;
703 EVP_MD_CTX_init(&md_ctx);
704 EVP_DigestInit_ex(&md_ctx, ctx->digest, NULL /* engine */ );
706 /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
707 memset(hmac_pad, 0x5c, sslv3_pad_length);
709 EVP_DigestUpdate(&md_ctx, mac_secret, mac_secret_length);
710 EVP_DigestUpdate(&md_ctx, hmac_pad, sslv3_pad_length);
711 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
713 /* Complete the HMAC in the standard manner. */
714 for (i = 0; i < md_block_size; i++)
717 EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size);
718 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
720 ret = EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u);
721 if (ret && md_out_size)
722 *md_out_size = md_out_size_u;
723 EVP_MD_CTX_cleanup(&md_ctx);
727 * Due to the need to use EVP in FIPS mode we can't reimplement digests but
728 * we can ensure the number of blocks processed is equal for all cases by
729 * digesting additional data.
732 void tls_fips_digest_extra(const EVP_CIPHER_CTX *cipher_ctx,
733 EVP_MD_CTX *mac_ctx, const unsigned char *data,
734 size_t data_len, size_t orig_len)
736 size_t block_size, digest_pad, blocks_data, blocks_orig;
737 if (EVP_CIPHER_CTX_mode(cipher_ctx) != EVP_CIPH_CBC_MODE)
739 block_size = EVP_MD_CTX_block_size(mac_ctx);
741 * We are in FIPS mode if we get this far so we know we have only SHA*
742 * digests and TLS to deal with.
743 * Minimum digest padding length is 17 for SHA384/SHA512 and 9
745 * Additional header is 13 bytes. To get the number of digest blocks
746 * processed round up the amount of data plus padding to the nearest
747 * block length. Block length is 128 for SHA384/SHA512 and 64 otherwise.
749 * blocks = (payload_len + digest_pad + 13 + block_size - 1)/block_size
751 * blocks = (payload_len + digest_pad + 12)/block_size + 1
752 * HMAC adds a constant overhead.
753 * We're ultimately only interested in differences so this becomes
754 * blocks = (payload_len + 29)/128
755 * for SHA384/SHA512 and
756 * blocks = (payload_len + 21)/64
759 digest_pad = block_size == 64 ? 21 : 29;
760 blocks_orig = (orig_len + digest_pad) / block_size;
761 blocks_data = (data_len + digest_pad) / block_size;
763 * MAC enough blocks to make up the difference between the original and
764 * actual lengths plus one extra block to ensure this is never a no op.
765 * The "data" pointer should always have enough space to perform this
766 * operation as it is large enough for a maximum length TLS buffer.
768 EVP_DigestSignUpdate(mac_ctx, data,
769 (blocks_orig - blocks_data + 1) * block_size);