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 padding_length = good & (padding_length + 1);
103 rec->length -= padding_length;
104 rec->type |= padding_length << 8; /* kludge: pass padding length */
105 return constant_time_select_int(good, 1, -1);
109 * tls1_cbc_remove_padding removes the CBC padding from the decrypted, TLS, CBC
110 * record in |rec| in constant time and returns 1 if the padding is valid and
111 * -1 otherwise. It also removes any explicit IV from the start of the record
112 * without leaking any timing about whether there was enough space after the
113 * padding was removed.
115 * block_size: the block size of the cipher used to encrypt the record.
117 * 0: (in non-constant time) if the record is publicly invalid.
118 * 1: if the padding was valid
121 int tls1_cbc_remove_padding(const SSL *s,
123 unsigned block_size, unsigned mac_size)
125 unsigned padding_length, good, to_check, i;
126 const unsigned overhead = 1 /* padding length byte */ + mac_size;
127 /* Check if version requires explicit IV */
128 if (SSL_USE_EXPLICIT_IV(s)) {
130 * These lengths are all public so we can test them in non-constant
133 if (overhead + block_size > rec->length)
135 /* We can now safely skip explicit IV */
136 rec->data += block_size;
137 rec->input += block_size;
138 rec->length -= block_size;
139 } else if (overhead > rec->length)
142 padding_length = rec->data[rec->length - 1];
145 * NB: if compression is in operation the first packet may not be of even
146 * length so the padding bug check cannot be performed. This bug
147 * workaround has been around since SSLeay so hopefully it is either
148 * fixed now or no buggy implementation supports compression [steve]
150 if ((s->options & SSL_OP_TLS_BLOCK_PADDING_BUG) && !s->expand) {
151 /* First packet is even in size, so check */
152 if ((memcmp(s->s3->read_sequence, "\0\0\0\0\0\0\0\0", 8) == 0) &&
153 !(padding_length & 1)) {
154 s->s3->flags |= TLS1_FLAGS_TLS_PADDING_BUG;
156 if ((s->s3->flags & TLS1_FLAGS_TLS_PADDING_BUG) && padding_length > 0) {
161 if (EVP_CIPHER_flags(s->enc_read_ctx->cipher) & EVP_CIPH_FLAG_AEAD_CIPHER) {
162 /* padding is already verified */
163 rec->length -= padding_length + 1;
167 good = constant_time_ge(rec->length, overhead + padding_length);
169 * The padding consists of a length byte at the end of the record and
170 * then that many bytes of padding, all with the same value as the length
171 * byte. Thus, with the length byte included, there are i+1 bytes of
172 * padding. We can't check just |padding_length+1| bytes because that
173 * leaks decrypted information. Therefore we always have to check the
174 * maximum amount of padding possible. (Again, the length of the record
175 * is public information so we can use it.)
177 to_check = 255; /* maximum amount of padding. */
178 if (to_check > rec->length - 1)
179 to_check = rec->length - 1;
181 for (i = 0; i < to_check; i++) {
182 unsigned char mask = constant_time_ge_8(padding_length, i);
183 unsigned char b = rec->data[rec->length - 1 - i];
185 * The final |padding_length+1| bytes should all have the value
186 * |padding_length|. Therefore the XOR should be zero.
188 good &= ~(mask & (padding_length ^ b));
192 * If any of the final |padding_length+1| bytes had the wrong value, one
193 * or more of the lower eight bits of |good| will be cleared.
195 good = constant_time_eq(0xff, good & 0xff);
196 padding_length = good & (padding_length + 1);
197 rec->length -= padding_length;
198 rec->type |= padding_length << 8; /* kludge: pass padding length */
200 return constant_time_select_int(good, 1, -1);
204 * ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in
205 * constant time (independent of the concrete value of rec->length, which may
206 * vary within a 256-byte window).
208 * ssl3_cbc_remove_padding or tls1_cbc_remove_padding must be called prior to
212 * rec->orig_len >= md_size
213 * md_size <= EVP_MAX_MD_SIZE
215 * If CBC_MAC_ROTATE_IN_PLACE is defined then the rotation is performed with
216 * variable accesses in a 64-byte-aligned buffer. Assuming that this fits into
217 * a single or pair of cache-lines, then the variable memory accesses don't
218 * actually affect the timing. CPUs with smaller cache-lines [if any] are
219 * not multi-core and are not considered vulnerable to cache-timing attacks.
221 #define CBC_MAC_ROTATE_IN_PLACE
223 void ssl3_cbc_copy_mac(unsigned char *out,
224 const SSL3_RECORD *rec,
225 unsigned md_size, unsigned orig_len)
227 #if defined(CBC_MAC_ROTATE_IN_PLACE)
228 unsigned char rotated_mac_buf[64 + EVP_MAX_MD_SIZE];
229 unsigned char *rotated_mac;
231 unsigned char rotated_mac[EVP_MAX_MD_SIZE];
235 * mac_end is the index of |rec->data| just after the end of the MAC.
237 unsigned mac_end = rec->length;
238 unsigned mac_start = mac_end - md_size;
240 * scan_start contains the number of bytes that we can ignore because the
241 * MAC's position can only vary by 255 bytes.
243 unsigned scan_start = 0;
245 unsigned div_spoiler;
246 unsigned rotate_offset;
248 OPENSSL_assert(orig_len >= md_size);
249 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
251 #if defined(CBC_MAC_ROTATE_IN_PLACE)
252 rotated_mac = rotated_mac_buf + ((0 - (size_t)rotated_mac_buf) & 63);
255 /* This information is public so it's safe to branch based on it. */
256 if (orig_len > md_size + 255 + 1)
257 scan_start = orig_len - (md_size + 255 + 1);
259 * div_spoiler contains a multiple of md_size that is used to cause the
260 * modulo operation to be constant time. Without this, the time varies
261 * based on the amount of padding when running on Intel chips at least.
262 * The aim of right-shifting md_size is so that the compiler doesn't
263 * figure out that it can remove div_spoiler as that would require it to
264 * prove that md_size is always even, which I hope is beyond it.
266 div_spoiler = md_size >> 1;
267 div_spoiler <<= (sizeof(div_spoiler) - 1) * 8;
268 rotate_offset = (div_spoiler + mac_start - scan_start) % md_size;
270 memset(rotated_mac, 0, md_size);
271 for (i = scan_start, j = 0; i < orig_len; i++) {
272 unsigned char mac_started = constant_time_ge_8(i, mac_start);
273 unsigned char mac_ended = constant_time_ge_8(i, mac_end);
274 unsigned char b = rec->data[i];
275 rotated_mac[j++] |= b & mac_started & ~mac_ended;
276 j &= constant_time_lt(j, md_size);
279 /* Now rotate the MAC */
280 #if defined(CBC_MAC_ROTATE_IN_PLACE)
282 for (i = 0; i < md_size; i++) {
283 /* in case cache-line is 32 bytes, touch second line */
284 ((volatile unsigned char *)rotated_mac)[rotate_offset ^ 32];
285 out[j++] = rotated_mac[rotate_offset++];
286 rotate_offset &= constant_time_lt(rotate_offset, md_size);
289 memset(out, 0, md_size);
290 rotate_offset = md_size - rotate_offset;
291 rotate_offset &= constant_time_lt(rotate_offset, md_size);
292 for (i = 0; i < md_size; i++) {
293 for (j = 0; j < md_size; j++)
294 out[j] |= rotated_mac[i] & constant_time_eq_8(j, rotate_offset);
296 rotate_offset &= constant_time_lt(rotate_offset, md_size);
302 * u32toLE serialises an unsigned, 32-bit number (n) as four bytes at (p) in
303 * little-endian order. The value of p is advanced by four.
305 #define u32toLE(n, p) \
306 (*((p)++)=(unsigned char)(n), \
307 *((p)++)=(unsigned char)(n>>8), \
308 *((p)++)=(unsigned char)(n>>16), \
309 *((p)++)=(unsigned char)(n>>24))
312 * These functions serialize the state of a hash and thus perform the
313 * standard "final" operation without adding the padding and length that such
314 * a function typically does.
316 static void tls1_md5_final_raw(void *ctx, unsigned char *md_out)
319 u32toLE(md5->A, md_out);
320 u32toLE(md5->B, md_out);
321 u32toLE(md5->C, md_out);
322 u32toLE(md5->D, md_out);
325 static void tls1_sha1_final_raw(void *ctx, unsigned char *md_out)
328 l2n(sha1->h0, md_out);
329 l2n(sha1->h1, md_out);
330 l2n(sha1->h2, md_out);
331 l2n(sha1->h3, md_out);
332 l2n(sha1->h4, md_out);
335 #define LARGEST_DIGEST_CTX SHA_CTX
337 #ifndef OPENSSL_NO_SHA256
338 static void tls1_sha256_final_raw(void *ctx, unsigned char *md_out)
340 SHA256_CTX *sha256 = ctx;
343 for (i = 0; i < 8; i++) {
344 l2n(sha256->h[i], md_out);
348 # undef LARGEST_DIGEST_CTX
349 # define LARGEST_DIGEST_CTX SHA256_CTX
352 #ifndef OPENSSL_NO_SHA512
353 static void tls1_sha512_final_raw(void *ctx, unsigned char *md_out)
355 SHA512_CTX *sha512 = ctx;
358 for (i = 0; i < 8; i++) {
359 l2n8(sha512->h[i], md_out);
363 # undef LARGEST_DIGEST_CTX
364 # define LARGEST_DIGEST_CTX SHA512_CTX
368 * ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
369 * which ssl3_cbc_digest_record supports.
371 char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx)
377 switch (EVP_MD_CTX_type(ctx)) {
380 #ifndef OPENSSL_NO_SHA256
384 #ifndef OPENSSL_NO_SHA512
395 * ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS
398 * ctx: the EVP_MD_CTX from which we take the hash function.
399 * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX.
400 * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written.
401 * md_out_size: if non-NULL, the number of output bytes is written here.
402 * header: the 13-byte, TLS record header.
403 * data: the record data itself, less any preceeding explicit IV.
404 * data_plus_mac_size: the secret, reported length of the data and MAC
405 * once the padding has been removed.
406 * data_plus_mac_plus_padding_size: the public length of the whole
407 * record, including padding.
408 * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
410 * On entry: by virtue of having been through one of the remove_padding
411 * functions, above, we know that data_plus_mac_size is large enough to contain
412 * a padding byte and MAC. (If the padding was invalid, it might contain the
415 void ssl3_cbc_digest_record(const EVP_MD_CTX *ctx,
416 unsigned char *md_out,
418 const unsigned char header[13],
419 const unsigned char *data,
420 size_t data_plus_mac_size,
421 size_t data_plus_mac_plus_padding_size,
422 const unsigned char *mac_secret,
423 unsigned mac_secret_length, char is_sslv3)
427 unsigned char c[sizeof(LARGEST_DIGEST_CTX)];
429 void (*md_final_raw) (void *ctx, unsigned char *md_out);
430 void (*md_transform) (void *ctx, const unsigned char *block);
431 unsigned md_size, md_block_size = 64;
432 unsigned sslv3_pad_length = 40, header_length, variance_blocks,
433 len, max_mac_bytes, num_blocks,
434 num_starting_blocks, k, mac_end_offset, c, index_a, index_b;
435 unsigned int bits; /* at most 18 bits */
436 unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES];
437 /* hmac_pad is the masked HMAC key. */
438 unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE];
439 unsigned char first_block[MAX_HASH_BLOCK_SIZE];
440 unsigned char mac_out[EVP_MAX_MD_SIZE];
441 unsigned i, j, md_out_size_u;
444 * mdLengthSize is the number of bytes in the length field that
445 * terminates * the hash.
447 unsigned md_length_size = 8;
448 char length_is_big_endian = 1;
451 * This is a, hopefully redundant, check that allows us to forget about
452 * many possible overflows later in this function.
454 OPENSSL_assert(data_plus_mac_plus_padding_size < 1024 * 1024);
456 switch (EVP_MD_CTX_type(ctx)) {
458 MD5_Init((MD5_CTX *)md_state.c);
459 md_final_raw = tls1_md5_final_raw;
461 (void (*)(void *ctx, const unsigned char *block))MD5_Transform;
463 sslv3_pad_length = 48;
464 length_is_big_endian = 0;
467 SHA1_Init((SHA_CTX *)md_state.c);
468 md_final_raw = tls1_sha1_final_raw;
470 (void (*)(void *ctx, const unsigned char *block))SHA1_Transform;
473 #ifndef OPENSSL_NO_SHA256
475 SHA224_Init((SHA256_CTX *)md_state.c);
476 md_final_raw = tls1_sha256_final_raw;
478 (void (*)(void *ctx, const unsigned char *block))SHA256_Transform;
482 SHA256_Init((SHA256_CTX *)md_state.c);
483 md_final_raw = tls1_sha256_final_raw;
485 (void (*)(void *ctx, const unsigned char *block))SHA256_Transform;
489 #ifndef OPENSSL_NO_SHA512
491 SHA384_Init((SHA512_CTX *)md_state.c);
492 md_final_raw = tls1_sha512_final_raw;
494 (void (*)(void *ctx, const unsigned char *block))SHA512_Transform;
500 SHA512_Init((SHA512_CTX *)md_state.c);
501 md_final_raw = tls1_sha512_final_raw;
503 (void (*)(void *ctx, const unsigned char *block))SHA512_Transform;
511 * ssl3_cbc_record_digest_supported should have been called first to
512 * check that the hash function is supported.
520 OPENSSL_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES);
521 OPENSSL_assert(md_block_size <= MAX_HASH_BLOCK_SIZE);
522 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
526 header_length = mac_secret_length + sslv3_pad_length + 8 /* sequence
528 1 /* record type */ +
529 2 /* record length */ ;
533 * variance_blocks is the number of blocks of the hash that we have to
534 * calculate in constant time because they could be altered by the
535 * padding value. In SSLv3, the padding must be minimal so the end of
536 * the plaintext varies by, at most, 15+20 = 35 bytes. (We conservatively
537 * assume that the MAC size varies from 0..20 bytes.) In case the 9 bytes
538 * of hash termination (0x80 + 64-bit length) don't fit in the final
539 * block, we say that the final two blocks can vary based on the padding.
540 * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
541 * required to be minimal. Therefore we say that the final six blocks can
542 * vary based on the padding. Later in the function, if the message is
543 * short and there obviously cannot be this many blocks then
544 * variance_blocks can be reduced.
546 variance_blocks = is_sslv3 ? 2 : 6;
548 * From now on we're dealing with the MAC, which conceptually has 13
549 * bytes of `header' before the start of the data (TLS) or 71/75 bytes
552 len = data_plus_mac_plus_padding_size + header_length;
554 * max_mac_bytes contains the maximum bytes of bytes in the MAC,
555 * including * |header|, assuming that there's no padding.
557 max_mac_bytes = len - md_size - 1;
558 /* num_blocks is the maximum number of hash blocks. */
560 (max_mac_bytes + 1 + md_length_size + md_block_size -
563 * In order to calculate the MAC in constant time we have to handle the
564 * final blocks specially because the padding value could cause the end
565 * to appear somewhere in the final |variance_blocks| blocks and we can't
566 * leak where. However, |num_starting_blocks| worth of data can be hashed
567 * right away because no padding value can affect whether they are
570 num_starting_blocks = 0;
572 * k is the starting byte offset into the conceptual header||data where
573 * we start processing.
577 * mac_end_offset is the index just past the end of the data to be MACed.
579 mac_end_offset = data_plus_mac_size + header_length - md_size;
581 * c is the index of the 0x80 byte in the final hash block that contains
584 c = mac_end_offset % md_block_size;
586 * index_a is the hash block number that contains the 0x80 terminating
589 index_a = mac_end_offset / md_block_size;
591 * index_b is the hash block number that contains the 64-bit hash length,
594 index_b = (mac_end_offset + md_length_size) / md_block_size;
596 * bits is the hash-length in bits. It includes the additional hash block
597 * for the masked HMAC key, or whole of |header| in the case of SSLv3.
601 * For SSLv3, if we're going to have any starting blocks then we need at
602 * least two because the header is larger than a single block.
604 if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0)) {
605 num_starting_blocks = num_blocks - variance_blocks;
606 k = md_block_size * num_starting_blocks;
609 bits = 8 * mac_end_offset;
612 * Compute the initial HMAC block. For SSLv3, the padding and secret
613 * bytes are included in |header| because they take more than a
616 bits += 8 * md_block_size;
617 memset(hmac_pad, 0, md_block_size);
618 OPENSSL_assert(mac_secret_length <= sizeof(hmac_pad));
619 memcpy(hmac_pad, mac_secret, mac_secret_length);
620 for (i = 0; i < md_block_size; i++)
623 md_transform(md_state.c, hmac_pad);
626 if (length_is_big_endian) {
627 memset(length_bytes, 0, md_length_size - 4);
628 length_bytes[md_length_size - 4] = (unsigned char)(bits >> 24);
629 length_bytes[md_length_size - 3] = (unsigned char)(bits >> 16);
630 length_bytes[md_length_size - 2] = (unsigned char)(bits >> 8);
631 length_bytes[md_length_size - 1] = (unsigned char)bits;
633 memset(length_bytes, 0, md_length_size);
634 length_bytes[md_length_size - 5] = (unsigned char)(bits >> 24);
635 length_bytes[md_length_size - 6] = (unsigned char)(bits >> 16);
636 length_bytes[md_length_size - 7] = (unsigned char)(bits >> 8);
637 length_bytes[md_length_size - 8] = (unsigned char)bits;
643 * The SSLv3 header is larger than a single block. overhang is
644 * the number of bytes beyond a single block that the header
645 * consumes: either 7 bytes (SHA1) or 11 bytes (MD5).
647 unsigned overhang = header_length - md_block_size;
648 md_transform(md_state.c, header);
649 memcpy(first_block, header + md_block_size, overhang);
650 memcpy(first_block + overhang, data, md_block_size - overhang);
651 md_transform(md_state.c, first_block);
652 for (i = 1; i < k / md_block_size - 1; i++)
653 md_transform(md_state.c, data + md_block_size * i - overhang);
655 /* k is a multiple of md_block_size. */
656 memcpy(first_block, header, 13);
657 memcpy(first_block + 13, data, md_block_size - 13);
658 md_transform(md_state.c, first_block);
659 for (i = 1; i < k / md_block_size; i++)
660 md_transform(md_state.c, data + md_block_size * i - 13);
664 memset(mac_out, 0, sizeof(mac_out));
667 * We now process the final hash blocks. For each block, we construct it
668 * in constant time. If the |i==index_a| then we'll include the 0x80
669 * bytes and zero pad etc. For each block we selectively copy it, in
670 * constant time, to |mac_out|.
672 for (i = num_starting_blocks; i <= num_starting_blocks + variance_blocks;
674 unsigned char block[MAX_HASH_BLOCK_SIZE];
675 unsigned char is_block_a = constant_time_eq_8(i, index_a);
676 unsigned char is_block_b = constant_time_eq_8(i, index_b);
677 for (j = 0; j < md_block_size; j++) {
678 unsigned char b = 0, is_past_c, is_past_cp1;
679 if (k < header_length)
681 else if (k < data_plus_mac_plus_padding_size + header_length)
682 b = data[k - header_length];
685 is_past_c = is_block_a & constant_time_ge_8(j, c);
686 is_past_cp1 = is_block_a & constant_time_ge_8(j, c + 1);
688 * If this is the block containing the end of the application
689 * data, and we are at the offset for the 0x80 value, then
690 * overwrite b with 0x80.
692 b = constant_time_select_8(is_past_c, 0x80, b);
694 * If this the the block containing the end of the application
695 * data and we're past the 0x80 value then just write zero.
697 b = b & ~is_past_cp1;
699 * If this is index_b (the final block), but not index_a (the end
700 * of the data), then the 64-bit length didn't fit into index_a
701 * and we're having to add an extra block of zeros.
703 b &= ~is_block_b | is_block_a;
706 * The final bytes of one of the blocks contains the length.
708 if (j >= md_block_size - md_length_size) {
709 /* If this is index_b, write a length byte. */
710 b = constant_time_select_8(is_block_b,
713 md_length_size)], b);
718 md_transform(md_state.c, block);
719 md_final_raw(md_state.c, block);
720 /* If this is index_b, copy the hash value to |mac_out|. */
721 for (j = 0; j < md_size; j++)
722 mac_out[j] |= block[j] & is_block_b;
725 EVP_MD_CTX_init(&md_ctx);
726 EVP_DigestInit_ex(&md_ctx, ctx->digest, NULL /* engine */ );
728 /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
729 memset(hmac_pad, 0x5c, sslv3_pad_length);
731 EVP_DigestUpdate(&md_ctx, mac_secret, mac_secret_length);
732 EVP_DigestUpdate(&md_ctx, hmac_pad, sslv3_pad_length);
733 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
735 /* Complete the HMAC in the standard manner. */
736 for (i = 0; i < md_block_size; i++)
739 EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size);
740 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
742 EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u);
744 *md_out_size = md_out_size_u;
745 EVP_MD_CTX_cleanup(&md_ctx);
751 * Due to the need to use EVP in FIPS mode we can't reimplement digests but
752 * we can ensure the number of blocks processed is equal for all cases by
753 * digesting additional data.
756 void tls_fips_digest_extra(const EVP_CIPHER_CTX *cipher_ctx,
757 EVP_MD_CTX *mac_ctx, const unsigned char *data,
758 size_t data_len, size_t orig_len)
760 size_t block_size, digest_pad, blocks_data, blocks_orig;
761 if (EVP_CIPHER_CTX_mode(cipher_ctx) != EVP_CIPH_CBC_MODE)
763 block_size = EVP_MD_CTX_block_size(mac_ctx);
765 * We are in FIPS mode if we get this far so we know we have only SHA*
766 * digests and TLS to deal with.
767 * Minimum digest padding length is 17 for SHA384/SHA512 and 9
769 * Additional header is 13 bytes. To get the number of digest blocks
770 * processed round up the amount of data plus padding to the nearest
771 * block length. Block length is 128 for SHA384/SHA512 and 64 otherwise.
773 * blocks = (payload_len + digest_pad + 13 + block_size - 1)/block_size
775 * blocks = (payload_len + digest_pad + 12)/block_size + 1
776 * HMAC adds a constant overhead.
777 * We're ultimately only interested in differences so this becomes
778 * blocks = (payload_len + 29)/128
779 * for SHA384/SHA512 and
780 * blocks = (payload_len + 21)/64
783 digest_pad = block_size == 64 ? 21 : 29;
784 blocks_orig = (orig_len + digest_pad) / block_size;
785 blocks_data = (data_len + digest_pad) / block_size;
787 * MAC enough blocks to make up the difference between the original and
788 * actual lengths plus one extra block to ensure this is never a no op.
789 * The "data" pointer should always have enough space to perform this
790 * operation as it is large enough for a maximum length TLS buffer.
792 EVP_DigestSignUpdate(mac_ctx, data,
793 (blocks_orig - blocks_data + 1) * block_size);