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 rec->length -= good & (padding_length+1);
127 return (int)((good & 1) | (~good & -1));
130 /* tls1_cbc_remove_padding removes the CBC padding from the decrypted, TLS, CBC
131 * record in |rec| in constant time and returns 1 if the padding is valid and
132 * -1 otherwise. It also removes any explicit IV from the start of the record
133 * without leaking any timing about whether there was enough space after the
134 * padding was removed.
136 * block_size: the block size of the cipher used to encrypt the record.
138 * 0: (in non-constant time) if the record is publicly invalid.
139 * 1: if the padding was valid
141 int tls1_cbc_remove_padding(const SSL* s,
146 unsigned padding_length, good, to_check, i;
147 const unsigned overhead = 1 /* padding length byte */ + mac_size;
148 /* Check if version requires explicit IV */
149 if (s->version >= TLS1_1_VERSION || s->version == DTLS1_VERSION)
151 /* These lengths are all public so we can test them in
154 if (overhead + block_size > rec->length)
156 /* We can now safely skip explicit IV */
157 rec->data += block_size;
158 rec->input += block_size;
159 rec->length -= block_size;
160 rec->orig_len -= block_size;
162 else if (overhead > rec->length)
165 padding_length = rec->data[rec->length-1];
167 /* NB: if compression is in operation the first packet may not be of
168 * even length so the padding bug check cannot be performed. This bug
169 * workaround has been around since SSLeay so hopefully it is either
170 * fixed now or no buggy implementation supports compression [steve]
172 if ( (s->options&SSL_OP_TLS_BLOCK_PADDING_BUG) && !s->expand)
174 /* First packet is even in size, so check */
175 if ((memcmp(s->s3->read_sequence, "\0\0\0\0\0\0\0\0",8) == 0) &&
176 !(padding_length & 1))
178 s->s3->flags|=TLS1_FLAGS_TLS_PADDING_BUG;
180 if ((s->s3->flags & TLS1_FLAGS_TLS_PADDING_BUG) &&
187 if (EVP_CIPHER_flags(s->enc_read_ctx->cipher)&EVP_CIPH_FLAG_AEAD_CIPHER)
189 /* padding is already verified */
190 rec->length -= padding_length + 1;
194 good = constant_time_ge(rec->length, overhead+padding_length);
195 /* The padding consists of a length byte at the end of the record and
196 * then that many bytes of padding, all with the same value as the
197 * length byte. Thus, with the length byte included, there are i+1
200 * We can't check just |padding_length+1| bytes because that leaks
201 * decrypted information. Therefore we always have to check the maximum
202 * amount of padding possible. (Again, the length of the record is
203 * public information so we can use it.) */
204 to_check = 255; /* maximum amount of padding. */
205 if (to_check > rec->length-1)
206 to_check = rec->length-1;
208 for (i = 0; i < to_check; i++)
210 unsigned char mask = constant_time_ge(padding_length, i);
211 unsigned char b = rec->data[rec->length-1-i];
212 /* The final |padding_length+1| bytes should all have the value
213 * |padding_length|. Therefore the XOR should be zero. */
214 good &= ~(mask&(padding_length ^ b));
217 /* If any of the final |padding_length+1| bytes had the wrong value,
218 * one or more of the lower eight bits of |good| will be cleared. We
219 * AND the bottom 8 bits together and duplicate the result to all the
224 good <<= sizeof(good)*8-1;
225 good = DUPLICATE_MSB_TO_ALL(good);
227 rec->length -= good & (padding_length+1);
229 return (int)((good & 1) | (~good & -1));
232 #if defined(_M_AMD64) || defined(__x86_64__)
233 #define CBC_MAC_ROTATE_IN_PLACE
236 /* ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in
237 * constant time (independent of the concrete value of rec->length, which may
238 * vary within a 256-byte window).
240 * ssl3_cbc_remove_padding or tls1_cbc_remove_padding must be called prior to
244 * rec->orig_len >= md_size
245 * md_size <= EVP_MAX_MD_SIZE
247 * If CBC_MAC_ROTATE_IN_PLACE is defined then the rotation is performed with
248 * variable accesses in a 64-byte-aligned buffer. Assuming that this fits into
249 * a single cache-line, then the variable memory accesses don't actually affect
250 * the timing. This has been tested to be true on Intel amd64 chips.
252 void ssl3_cbc_copy_mac(unsigned char* out,
253 const SSL3_RECORD *rec,
256 #if defined(CBC_MAC_ROTATE_IN_PLACE)
257 unsigned char rotated_mac_buf[EVP_MAX_MD_SIZE*2];
258 unsigned char *rotated_mac;
260 unsigned char rotated_mac[EVP_MAX_MD_SIZE];
263 /* mac_end is the index of |rec->data| just after the end of the MAC. */
264 unsigned mac_end = rec->length;
265 unsigned mac_start = mac_end - md_size;
266 /* scan_start contains the number of bytes that we can ignore because
267 * the MAC's position can only vary by 255 bytes. */
268 unsigned scan_start = 0;
270 unsigned div_spoiler;
271 unsigned rotate_offset;
273 OPENSSL_assert(rec->orig_len >= md_size);
274 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
276 #if defined(CBC_MAC_ROTATE_IN_PLACE)
277 rotated_mac = (unsigned char*) (((intptr_t)(rotated_mac_buf + 64)) & ~63);
280 /* This information is public so it's safe to branch based on it. */
281 if (rec->orig_len > md_size + 255 + 1)
282 scan_start = rec->orig_len - (md_size + 255 + 1);
283 /* div_spoiler contains a multiple of md_size that is used to cause the
284 * modulo operation to be constant time. Without this, the time varies
285 * based on the amount of padding when running on Intel chips at least.
287 * The aim of right-shifting md_size is so that the compiler doesn't
288 * figure out that it can remove div_spoiler as that would require it
289 * to prove that md_size is always even, which I hope is beyond it. */
290 div_spoiler = md_size >> 1;
291 div_spoiler <<= (sizeof(div_spoiler)-1)*8;
292 rotate_offset = (div_spoiler + mac_start - scan_start) % md_size;
294 memset(rotated_mac, 0, md_size);
295 for (i = scan_start, j = 0; i < rec->orig_len; i++)
297 unsigned char mac_started = constant_time_ge(i, mac_start);
298 unsigned char mac_ended = constant_time_ge(i, mac_end);
299 unsigned char b = rec->data[i];
300 rotated_mac[j++] |= b & mac_started & ~mac_ended;
301 j &= constant_time_lt(j,md_size);
304 /* Now rotate the MAC */
305 #if defined(CBC_MAC_ROTATE_IN_PLACE)
307 for (i = 0; i < md_size; i++)
309 out[j++] = rotated_mac[rotate_offset++];
310 rotate_offset &= constant_time_lt(rotate_offset,md_size);
313 memset(out, 0, md_size);
314 rotate_offset = md_size - rotate_offset;
315 rotate_offset &= constant_time_lt(rotate_offset,md_size);
316 for (i = 0; i < md_size; i++)
318 for (j = 0; j < md_size; j++)
319 out[j] |= rotated_mac[i] & constant_time_eq_8(j, rotate_offset);
321 rotate_offset &= constant_time_lt(rotate_offset,md_size);
326 /* u32toLE serialises an unsigned, 32-bit number (n) as four bytes at (p) in
327 * little-endian order. The value of p is advanced by four. */
328 #define u32toLE(n, p) \
329 (*((p)++)=(unsigned char)(n), \
330 *((p)++)=(unsigned char)(n>>8), \
331 *((p)++)=(unsigned char)(n>>16), \
332 *((p)++)=(unsigned char)(n>>24))
334 /* These functions serialize the state of a hash and thus perform the standard
335 * "final" operation without adding the padding and length that such a function
337 static void tls1_md5_final_raw(void* ctx, unsigned char *md_out)
340 u32toLE(md5->A, md_out);
341 u32toLE(md5->B, md_out);
342 u32toLE(md5->C, md_out);
343 u32toLE(md5->D, md_out);
346 static void tls1_sha1_final_raw(void* ctx, unsigned char *md_out)
349 l2n(sha1->h0, md_out);
350 l2n(sha1->h1, md_out);
351 l2n(sha1->h2, md_out);
352 l2n(sha1->h3, md_out);
353 l2n(sha1->h4, md_out);
355 #define LARGEST_DIGEST_CTX SHA_CTX
357 #ifndef OPENSSL_NO_SHA256
358 static void tls1_sha256_final_raw(void* ctx, unsigned char *md_out)
360 SHA256_CTX *sha256 = ctx;
363 for (i = 0; i < 8; i++)
365 l2n(sha256->h[i], md_out);
368 #undef LARGEST_DIGEST_CTX
369 #define LARGEST_DIGEST_CTX SHA256_CTX
372 #ifndef OPENSSL_NO_SHA512
373 static void tls1_sha512_final_raw(void* ctx, unsigned char *md_out)
375 SHA512_CTX *sha512 = ctx;
378 for (i = 0; i < 8; i++)
380 l2n8(sha512->h[i], md_out);
383 #undef LARGEST_DIGEST_CTX
384 #define LARGEST_DIGEST_CTX SHA512_CTX
387 /* ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
388 * which ssl3_cbc_digest_record supports. */
389 char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx)
395 switch (EVP_MD_CTX_type(ctx))
399 #ifndef OPENSSL_NO_SHA256
403 #ifndef OPENSSL_NO_SHA512
413 /* ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS
416 * ctx: the EVP_MD_CTX from which we take the hash function.
417 * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX.
418 * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written.
419 * md_out_size: if non-NULL, the number of output bytes is written here.
420 * header: the 13-byte, TLS record header.
421 * data: the record data itself, less any preceeding explicit IV.
422 * data_plus_mac_size: the secret, reported length of the data and MAC
423 * once the padding has been removed.
424 * data_plus_mac_plus_padding_size: the public length of the whole
425 * record, including padding.
426 * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
428 * On entry: by virtue of having been through one of the remove_padding
429 * functions, above, we know that data_plus_mac_size is large enough to contain
430 * a padding byte and MAC. (If the padding was invalid, it might contain the
432 void ssl3_cbc_digest_record(
433 const EVP_MD_CTX *ctx,
434 unsigned char* md_out,
436 const unsigned char header[13],
437 const unsigned char *data,
438 size_t data_plus_mac_size,
439 size_t data_plus_mac_plus_padding_size,
440 const unsigned char *mac_secret,
441 unsigned mac_secret_length,
444 union { double align;
445 unsigned char c[sizeof(LARGEST_DIGEST_CTX)]; } md_state;
446 void (*md_final_raw)(void *ctx, unsigned char *md_out);
447 void (*md_transform)(void *ctx, const unsigned char *block);
448 unsigned md_size, md_block_size = 64;
449 unsigned sslv3_pad_length = 40, header_length, variance_blocks,
450 len, max_mac_bytes, num_blocks,
451 num_starting_blocks, k, mac_end_offset, c, index_a, index_b;
452 unsigned int bits; /* at most 18 bits */
453 unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES];
454 /* hmac_pad is the masked HMAC key. */
455 unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE];
456 unsigned char first_block[MAX_HASH_BLOCK_SIZE];
457 unsigned char mac_out[EVP_MAX_MD_SIZE];
458 unsigned i, j, md_out_size_u;
460 /* mdLengthSize is the number of bytes in the length field that terminates
462 unsigned md_length_size = 8;
463 char length_is_big_endian = 1;
465 /* This is a, hopefully redundant, check that allows us to forget about
466 * many possible overflows later in this function. */
467 OPENSSL_assert(data_plus_mac_plus_padding_size < 1024*1024);
469 switch (EVP_MD_CTX_type(ctx))
472 MD5_Init((MD5_CTX*)md_state.c);
473 md_final_raw = tls1_md5_final_raw;
474 md_transform = (void(*)(void *ctx, const unsigned char *block)) MD5_Transform;
476 sslv3_pad_length = 48;
477 length_is_big_endian = 0;
480 SHA1_Init((SHA_CTX*)md_state.c);
481 md_final_raw = tls1_sha1_final_raw;
482 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA1_Transform;
485 #ifndef OPENSSL_NO_SHA256
487 SHA224_Init((SHA256_CTX*)md_state.c);
488 md_final_raw = tls1_sha256_final_raw;
489 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;
493 SHA256_Init((SHA256_CTX*)md_state.c);
494 md_final_raw = tls1_sha256_final_raw;
495 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;
499 #ifndef OPENSSL_NO_SHA512
501 SHA384_Init((SHA512_CTX*)md_state.c);
502 md_final_raw = tls1_sha512_final_raw;
503 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA512_Transform;
509 SHA512_Init((SHA512_CTX*)md_state.c);
510 md_final_raw = tls1_sha512_final_raw;
511 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA512_Transform;
518 /* ssl3_cbc_record_digest_supported should have been
519 * called first to check that the hash function is
527 OPENSSL_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES);
528 OPENSSL_assert(md_block_size <= MAX_HASH_BLOCK_SIZE);
529 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
537 8 /* sequence number */ +
538 1 /* record type */ +
539 2 /* record length */;
542 /* variance_blocks is the number of blocks of the hash that we have to
543 * calculate in constant time because they could be altered by the
546 * In SSLv3, the padding must be minimal so the end of the plaintext
547 * varies by, at most, 15+20 = 35 bytes. (We conservatively assume that
548 * the MAC size varies from 0..20 bytes.) In case the 9 bytes of hash
549 * termination (0x80 + 64-bit length) don't fit in the final block, we
550 * say that the final two blocks can vary based on the padding.
552 * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
553 * required to be minimal. Therefore we say that the final six blocks
554 * can vary based on the padding.
556 * Later in the function, if the message is short and there obviously
557 * cannot be this many blocks then variance_blocks can be reduced. */
558 variance_blocks = is_sslv3 ? 2 : 6;
559 /* From now on we're dealing with the MAC, which conceptually has 13
560 * bytes of `header' before the start of the data (TLS) or 71/75 bytes
562 len = data_plus_mac_plus_padding_size + header_length;
563 /* max_mac_bytes contains the maximum bytes of bytes in the MAC, including
564 * |header|, assuming that there's no padding. */
565 max_mac_bytes = len - md_size - 1;
566 /* num_blocks is the maximum number of hash blocks. */
567 num_blocks = (max_mac_bytes + 1 + md_length_size + md_block_size - 1) / md_block_size;
568 /* In order to calculate the MAC in constant time we have to handle
569 * the final blocks specially because the padding value could cause the
570 * end to appear somewhere in the final |variance_blocks| blocks and we
571 * can't leak where. However, |num_starting_blocks| worth of data can
572 * be hashed right away because no padding value can affect whether
573 * they are plaintext. */
574 num_starting_blocks = 0;
575 /* k is the starting byte offset into the conceptual header||data where
576 * we start processing. */
578 /* mac_end_offset is the index just past the end of the data to be
580 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
582 * contains application data. */
583 c = mac_end_offset % md_block_size;
584 /* index_a is the hash block number that contains the 0x80 terminating
586 index_a = mac_end_offset / md_block_size;
587 /* index_b is the hash block number that contains the 64-bit hash
588 * length, in bits. */
589 index_b = (mac_end_offset + md_length_size) / md_block_size;
590 /* bits is the hash-length in bits. It includes the additional hash
591 * block for the masked HMAC key, or whole of |header| in the case of
594 /* For SSLv3, if we're going to have any starting blocks then we need
595 * at least two because the header is larger than a single block. */
596 if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0))
598 num_starting_blocks = num_blocks - variance_blocks;
599 k = md_block_size*num_starting_blocks;
602 bits = 8*mac_end_offset;
605 /* Compute the initial HMAC block. For SSLv3, the padding and
606 * secret bytes are included in |header| because they take more
607 * than a single block. */
608 bits += 8*md_block_size;
609 memset(hmac_pad, 0, md_block_size);
610 OPENSSL_assert(mac_secret_length <= sizeof(hmac_pad));
611 memcpy(hmac_pad, mac_secret, mac_secret_length);
612 for (i = 0; i < md_block_size; i++)
615 md_transform(md_state.c, hmac_pad);
618 if (length_is_big_endian)
620 memset(length_bytes,0,md_length_size-4);
621 length_bytes[md_length_size-4] = (unsigned char)(bits>>24);
622 length_bytes[md_length_size-3] = (unsigned char)(bits>>16);
623 length_bytes[md_length_size-2] = (unsigned char)(bits>>8);
624 length_bytes[md_length_size-1] = (unsigned char)bits;
628 memset(length_bytes,0,md_length_size);
629 length_bytes[md_length_size-5] = (unsigned char)(bits>>24);
630 length_bytes[md_length_size-6] = (unsigned char)(bits>>16);
631 length_bytes[md_length_size-7] = (unsigned char)(bits>>8);
632 length_bytes[md_length_size-8] = (unsigned char)bits;
639 /* The SSLv3 header is larger than a single block.
640 * overhang is the number of bytes beyond a single
641 * block that the header consumes: either 7 bytes
642 * (SHA1) or 11 bytes (MD5). */
643 unsigned overhang = header_length-md_block_size;
644 md_transform(md_state.c, header);
645 memcpy(first_block, header + md_block_size, overhang);
646 memcpy(first_block + overhang, data, md_block_size-overhang);
647 md_transform(md_state.c, first_block);
648 for (i = 1; i < k/md_block_size - 1; i++)
649 md_transform(md_state.c, data + md_block_size*i - overhang);
653 /* k is a multiple of md_block_size. */
654 memcpy(first_block, header, 13);
655 memcpy(first_block+13, data, md_block_size-13);
656 md_transform(md_state.c, first_block);
657 for (i = 1; i < k/md_block_size; i++)
658 md_transform(md_state.c, data + md_block_size*i - 13);
662 memset(mac_out, 0, sizeof(mac_out));
664 /* We now process the final hash blocks. For each block, we construct
665 * it in constant time. If the |i==index_a| then we'll include the 0x80
666 * bytes and zero pad etc. For each block we selectively copy it, in
667 * constant time, to |mac_out|. */
668 for (i = num_starting_blocks; i <= num_starting_blocks+variance_blocks; i++)
670 unsigned char block[MAX_HASH_BLOCK_SIZE];
671 unsigned char is_block_a = constant_time_eq_8(i, index_a);
672 unsigned char is_block_b = constant_time_eq_8(i, index_b);
673 for (j = 0; j < md_block_size; j++)
675 unsigned char b = 0, is_past_c, is_past_cp1;
676 if (k < header_length)
678 else if (k < data_plus_mac_plus_padding_size + header_length)
679 b = data[k-header_length];
682 is_past_c = is_block_a & constant_time_ge(j, c);
683 is_past_cp1 = is_block_a & constant_time_ge(j, c+1);
684 /* If this is the block containing the end of the
685 * application data, and we are at the offset for the
686 * 0x80 value, then overwrite b with 0x80. */
687 b = (b&~is_past_c) | (0x80&is_past_c);
688 /* If this the the block containing the end of the
689 * application data and we're past the 0x80 value then
690 * just write zero. */
692 /* If this is index_b (the final block), but not
693 * index_a (the end of the data), then the 64-bit
694 * length didn't fit into index_a and we're having to
695 * add an extra block of zeros. */
696 b &= ~is_block_b | is_block_a;
698 /* The final bytes of one of the blocks contains the
700 if (j >= md_block_size - md_length_size)
702 /* If this is index_b, write a length byte. */
703 b = (b&~is_block_b) | (is_block_b&length_bytes[j-(md_block_size-md_length_size)]);
708 md_transform(md_state.c, block);
709 md_final_raw(md_state.c, block);
710 /* If this is index_b, copy the hash value to |mac_out|. */
711 for (j = 0; j < md_size; j++)
712 mac_out[j] |= block[j]&is_block_b;
715 EVP_MD_CTX_init(&md_ctx);
716 EVP_DigestInit_ex(&md_ctx, ctx->digest, NULL /* engine */);
719 /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
720 memset(hmac_pad, 0x5c, sslv3_pad_length);
722 EVP_DigestUpdate(&md_ctx, mac_secret, mac_secret_length);
723 EVP_DigestUpdate(&md_ctx, hmac_pad, sslv3_pad_length);
724 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
728 /* Complete the HMAC in the standard manner. */
729 for (i = 0; i < md_block_size; i++)
732 EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size);
733 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
735 EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u);
737 *md_out_size = md_out_size_u;
738 EVP_MD_CTX_cleanup(&md_ctx);
743 /* Due to the need to use EVP in FIPS mode we can't reimplement digests but
744 * we can ensure the number of blocks processed is equal for all cases
745 * by digesting additional data.
748 void tls_fips_digest_extra(
749 const EVP_CIPHER_CTX *cipher_ctx, EVP_MD_CTX *mac_ctx,
750 const unsigned char *data, size_t data_len, size_t orig_len)
752 size_t block_size, digest_pad, blocks_data, blocks_orig;
753 if (EVP_CIPHER_CTX_mode(cipher_ctx) != EVP_CIPH_CBC_MODE)
755 block_size = EVP_MD_CTX_block_size(mac_ctx);
756 /* We are in FIPS mode if we get this far so we know we have only SHA*
757 * digests and TLS to deal with.
758 * Minimum digest padding length is 17 for SHA384/SHA512 and 9
760 * Additional header is 13 bytes. To get the number of digest blocks
761 * processed round up the amount of data plus padding to the nearest
762 * block length. Block length is 128 for SHA384/SHA512 and 64 otherwise.
764 * blocks = (payload_len + digest_pad + 13 + block_size - 1)/block_size
766 * blocks = (payload_len + digest_pad + 12)/block_size + 1
767 * HMAC adds a constant overhead.
768 * We're ultimately only interested in differences so this becomes
769 * blocks = (payload_len + 29)/128
770 * for SHA384/SHA512 and
771 * blocks = (payload_len + 21)/64
774 digest_pad = block_size == 64 ? 21 : 29;
775 blocks_orig = (orig_len + digest_pad)/block_size;
776 blocks_data = (data_len + digest_pad)/block_size;
777 /* MAC enough blocks to make up the difference between the original
778 * and actual lengths plus one extra block to ensure this is never a
779 * no op. The "data" pointer should always have enough space to
780 * perform this operation as it is large enough for a maximum
783 EVP_DigestSignUpdate(mac_ctx, data,
784 (blocks_orig - blocks_data + 1) * block_size);