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_BAD_VER)
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 /* 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 or pair of cache-lines, then the variable memory accesses don't
246 * actually affect the timing. CPUs with smaller cache-lines [if any] are
247 * not multi-core and are not considered vulnerable to cache-timing attacks.
249 #define CBC_MAC_ROTATE_IN_PLACE
251 void ssl3_cbc_copy_mac(unsigned char* out,
252 const SSL3_RECORD *rec,
255 #if defined(CBC_MAC_ROTATE_IN_PLACE)
256 unsigned char rotated_mac_buf[64+EVP_MAX_MD_SIZE];
257 unsigned char *rotated_mac;
259 unsigned char rotated_mac[EVP_MAX_MD_SIZE];
262 /* mac_end is the index of |rec->data| just after the end of the MAC. */
263 unsigned mac_end = rec->length;
264 unsigned mac_start = mac_end - md_size;
265 /* scan_start contains the number of bytes that we can ignore because
266 * the MAC's position can only vary by 255 bytes. */
267 unsigned scan_start = 0;
269 unsigned div_spoiler;
270 unsigned rotate_offset;
272 OPENSSL_assert(rec->orig_len >= md_size);
273 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
275 #if defined(CBC_MAC_ROTATE_IN_PLACE)
276 rotated_mac = rotated_mac_buf + ((0-(size_t)rotated_mac_buf)&63);
279 /* This information is public so it's safe to branch based on it. */
280 if (rec->orig_len > md_size + 255 + 1)
281 scan_start = rec->orig_len - (md_size + 255 + 1);
282 /* div_spoiler contains a multiple of md_size that is used to cause the
283 * modulo operation to be constant time. Without this, the time varies
284 * based on the amount of padding when running on Intel chips at least.
286 * The aim of right-shifting md_size is so that the compiler doesn't
287 * figure out that it can remove div_spoiler as that would require it
288 * to prove that md_size is always even, which I hope is beyond it. */
289 div_spoiler = md_size >> 1;
290 div_spoiler <<= (sizeof(div_spoiler)-1)*8;
291 rotate_offset = (div_spoiler + mac_start - scan_start) % md_size;
293 memset(rotated_mac, 0, md_size);
294 for (i = scan_start, j = 0; i < rec->orig_len; i++)
296 unsigned char mac_started = constant_time_ge(i, mac_start);
297 unsigned char mac_ended = constant_time_ge(i, mac_end);
298 unsigned char b = rec->data[i];
299 rotated_mac[j++] |= b & mac_started & ~mac_ended;
300 j &= constant_time_lt(j,md_size);
303 /* Now rotate the MAC */
304 #if defined(CBC_MAC_ROTATE_IN_PLACE)
306 for (i = 0; i < md_size; i++)
308 /* in case cache-line is 32 bytes, touch second line */
309 ((volatile unsigned char *)rotated_mac)[rotate_offset^32];
310 out[j++] = rotated_mac[rotate_offset++];
311 rotate_offset &= constant_time_lt(rotate_offset,md_size);
314 memset(out, 0, md_size);
315 rotate_offset = md_size - rotate_offset;
316 rotate_offset &= constant_time_lt(rotate_offset,md_size);
317 for (i = 0; i < md_size; i++)
319 for (j = 0; j < md_size; j++)
320 out[j] |= rotated_mac[i] & constant_time_eq_8(j, rotate_offset);
322 rotate_offset &= constant_time_lt(rotate_offset,md_size);
327 /* u32toLE serialises an unsigned, 32-bit number (n) as four bytes at (p) in
328 * little-endian order. The value of p is advanced by four. */
329 #define u32toLE(n, p) \
330 (*((p)++)=(unsigned char)(n), \
331 *((p)++)=(unsigned char)(n>>8), \
332 *((p)++)=(unsigned char)(n>>16), \
333 *((p)++)=(unsigned char)(n>>24))
335 /* These functions serialize the state of a hash and thus perform the standard
336 * "final" operation without adding the padding and length that such a function
338 static void tls1_md5_final_raw(void* ctx, unsigned char *md_out)
341 u32toLE(md5->A, md_out);
342 u32toLE(md5->B, md_out);
343 u32toLE(md5->C, md_out);
344 u32toLE(md5->D, md_out);
347 static void tls1_sha1_final_raw(void* ctx, unsigned char *md_out)
350 l2n(sha1->h0, md_out);
351 l2n(sha1->h1, md_out);
352 l2n(sha1->h2, md_out);
353 l2n(sha1->h3, md_out);
354 l2n(sha1->h4, md_out);
356 #define LARGEST_DIGEST_CTX SHA_CTX
358 #ifndef OPENSSL_NO_SHA256
359 static void tls1_sha256_final_raw(void* ctx, unsigned char *md_out)
361 SHA256_CTX *sha256 = ctx;
364 for (i = 0; i < 8; i++)
366 l2n(sha256->h[i], md_out);
369 #undef LARGEST_DIGEST_CTX
370 #define LARGEST_DIGEST_CTX SHA256_CTX
373 #ifndef OPENSSL_NO_SHA512
374 static void tls1_sha512_final_raw(void* ctx, unsigned char *md_out)
376 SHA512_CTX *sha512 = ctx;
379 for (i = 0; i < 8; i++)
381 l2n8(sha512->h[i], md_out);
384 #undef LARGEST_DIGEST_CTX
385 #define LARGEST_DIGEST_CTX SHA512_CTX
388 /* ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
389 * which ssl3_cbc_digest_record supports. */
390 char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx)
396 switch (EVP_MD_CTX_type(ctx))
400 #ifndef OPENSSL_NO_SHA256
404 #ifndef OPENSSL_NO_SHA512
414 /* ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS
417 * ctx: the EVP_MD_CTX from which we take the hash function.
418 * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX.
419 * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written.
420 * md_out_size: if non-NULL, the number of output bytes is written here.
421 * header: the 13-byte, TLS record header.
422 * data: the record data itself, less any preceeding explicit IV.
423 * data_plus_mac_size: the secret, reported length of the data and MAC
424 * once the padding has been removed.
425 * data_plus_mac_plus_padding_size: the public length of the whole
426 * record, including padding.
427 * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
429 * On entry: by virtue of having been through one of the remove_padding
430 * functions, above, we know that data_plus_mac_size is large enough to contain
431 * a padding byte and MAC. (If the padding was invalid, it might contain the
433 void ssl3_cbc_digest_record(
434 const EVP_MD_CTX *ctx,
435 unsigned char* md_out,
437 const unsigned char header[13],
438 const unsigned char *data,
439 size_t data_plus_mac_size,
440 size_t data_plus_mac_plus_padding_size,
441 const unsigned char *mac_secret,
442 unsigned mac_secret_length,
445 union { double align;
446 unsigned char c[sizeof(LARGEST_DIGEST_CTX)]; } md_state;
447 void (*md_final_raw)(void *ctx, unsigned char *md_out);
448 void (*md_transform)(void *ctx, const unsigned char *block);
449 unsigned md_size, md_block_size = 64;
450 unsigned sslv3_pad_length = 40, header_length, variance_blocks,
451 len, max_mac_bytes, num_blocks,
452 num_starting_blocks, k, mac_end_offset, c, index_a, index_b;
453 unsigned int bits; /* at most 18 bits */
454 unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES];
455 /* hmac_pad is the masked HMAC key. */
456 unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE];
457 unsigned char first_block[MAX_HASH_BLOCK_SIZE];
458 unsigned char mac_out[EVP_MAX_MD_SIZE];
459 unsigned i, j, md_out_size_u;
461 /* mdLengthSize is the number of bytes in the length field that terminates
463 unsigned md_length_size = 8;
464 char length_is_big_endian = 1;
466 /* This is a, hopefully redundant, check that allows us to forget about
467 * many possible overflows later in this function. */
468 OPENSSL_assert(data_plus_mac_plus_padding_size < 1024*1024);
470 switch (EVP_MD_CTX_type(ctx))
473 MD5_Init((MD5_CTX*)md_state.c);
474 md_final_raw = tls1_md5_final_raw;
475 md_transform = (void(*)(void *ctx, const unsigned char *block)) MD5_Transform;
477 sslv3_pad_length = 48;
478 length_is_big_endian = 0;
481 SHA1_Init((SHA_CTX*)md_state.c);
482 md_final_raw = tls1_sha1_final_raw;
483 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA1_Transform;
486 #ifndef OPENSSL_NO_SHA256
488 SHA224_Init((SHA256_CTX*)md_state.c);
489 md_final_raw = tls1_sha256_final_raw;
490 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;
494 SHA256_Init((SHA256_CTX*)md_state.c);
495 md_final_raw = tls1_sha256_final_raw;
496 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;
500 #ifndef OPENSSL_NO_SHA512
502 SHA384_Init((SHA512_CTX*)md_state.c);
503 md_final_raw = tls1_sha512_final_raw;
504 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA512_Transform;
510 SHA512_Init((SHA512_CTX*)md_state.c);
511 md_final_raw = tls1_sha512_final_raw;
512 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA512_Transform;
519 /* ssl3_cbc_record_digest_supported should have been
520 * called first to check that the hash function is
528 OPENSSL_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES);
529 OPENSSL_assert(md_block_size <= MAX_HASH_BLOCK_SIZE);
530 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
538 8 /* sequence number */ +
539 1 /* record type */ +
540 2 /* record length */;
543 /* variance_blocks is the number of blocks of the hash that we have to
544 * calculate in constant time because they could be altered by the
547 * In SSLv3, the padding must be minimal so the end of the plaintext
548 * varies by, at most, 15+20 = 35 bytes. (We conservatively assume that
549 * the MAC size varies from 0..20 bytes.) In case the 9 bytes of hash
550 * termination (0x80 + 64-bit length) don't fit in the final block, we
551 * say that the final two blocks can vary based on the padding.
553 * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
554 * required to be minimal. Therefore we say that the final six blocks
555 * can vary based on the padding.
557 * Later in the function, if the message is short and there obviously
558 * cannot be this many blocks then variance_blocks can be reduced. */
559 variance_blocks = is_sslv3 ? 2 : 6;
560 /* From now on we're dealing with the MAC, which conceptually has 13
561 * bytes of `header' before the start of the data (TLS) or 71/75 bytes
563 len = data_plus_mac_plus_padding_size + header_length;
564 /* max_mac_bytes contains the maximum bytes of bytes in the MAC, including
565 * |header|, assuming that there's no padding. */
566 max_mac_bytes = len - md_size - 1;
567 /* num_blocks is the maximum number of hash blocks. */
568 num_blocks = (max_mac_bytes + 1 + md_length_size + md_block_size - 1) / md_block_size;
569 /* In order to calculate the MAC in constant time we have to handle
570 * the final blocks specially because the padding value could cause the
571 * end to appear somewhere in the final |variance_blocks| blocks and we
572 * can't leak where. However, |num_starting_blocks| worth of data can
573 * be hashed right away because no padding value can affect whether
574 * they are plaintext. */
575 num_starting_blocks = 0;
576 /* k is the starting byte offset into the conceptual header||data where
577 * we start processing. */
579 /* mac_end_offset is the index just past the end of the data to be
581 mac_end_offset = data_plus_mac_size + header_length - md_size;
582 /* c is the index of the 0x80 byte in the final hash block that
583 * contains application data. */
584 c = mac_end_offset % md_block_size;
585 /* index_a is the hash block number that contains the 0x80 terminating
587 index_a = mac_end_offset / md_block_size;
588 /* index_b is the hash block number that contains the 64-bit hash
589 * length, in bits. */
590 index_b = (mac_end_offset + md_length_size) / md_block_size;
591 /* bits is the hash-length in bits. It includes the additional hash
592 * block for the masked HMAC key, or whole of |header| in the case of
595 /* For SSLv3, if we're going to have any starting blocks then we need
596 * at least two because the header is larger than a single block. */
597 if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0))
599 num_starting_blocks = num_blocks - variance_blocks;
600 k = md_block_size*num_starting_blocks;
603 bits = 8*mac_end_offset;
606 /* Compute the initial HMAC block. For SSLv3, the padding and
607 * secret bytes are included in |header| because they take more
608 * than a single block. */
609 bits += 8*md_block_size;
610 memset(hmac_pad, 0, md_block_size);
611 OPENSSL_assert(mac_secret_length <= sizeof(hmac_pad));
612 memcpy(hmac_pad, mac_secret, mac_secret_length);
613 for (i = 0; i < md_block_size; i++)
616 md_transform(md_state.c, hmac_pad);
619 if (length_is_big_endian)
621 memset(length_bytes,0,md_length_size-4);
622 length_bytes[md_length_size-4] = (unsigned char)(bits>>24);
623 length_bytes[md_length_size-3] = (unsigned char)(bits>>16);
624 length_bytes[md_length_size-2] = (unsigned char)(bits>>8);
625 length_bytes[md_length_size-1] = (unsigned char)bits;
629 memset(length_bytes,0,md_length_size);
630 length_bytes[md_length_size-5] = (unsigned char)(bits>>24);
631 length_bytes[md_length_size-6] = (unsigned char)(bits>>16);
632 length_bytes[md_length_size-7] = (unsigned char)(bits>>8);
633 length_bytes[md_length_size-8] = (unsigned char)bits;
640 /* The SSLv3 header is larger than a single block.
641 * overhang is the number of bytes beyond a single
642 * block that the header consumes: either 7 bytes
643 * (SHA1) or 11 bytes (MD5). */
644 unsigned overhang = header_length-md_block_size;
645 md_transform(md_state.c, header);
646 memcpy(first_block, header + md_block_size, overhang);
647 memcpy(first_block + overhang, data, md_block_size-overhang);
648 md_transform(md_state.c, first_block);
649 for (i = 1; i < k/md_block_size - 1; i++)
650 md_transform(md_state.c, data + md_block_size*i - overhang);
654 /* k is a multiple of md_block_size. */
655 memcpy(first_block, header, 13);
656 memcpy(first_block+13, data, md_block_size-13);
657 md_transform(md_state.c, first_block);
658 for (i = 1; i < k/md_block_size; i++)
659 md_transform(md_state.c, data + md_block_size*i - 13);
663 memset(mac_out, 0, sizeof(mac_out));
665 /* We now process the final hash blocks. For each block, we construct
666 * it in constant time. If the |i==index_a| then we'll include the 0x80
667 * bytes and zero pad etc. For each block we selectively copy it, in
668 * constant time, to |mac_out|. */
669 for (i = num_starting_blocks; i <= num_starting_blocks+variance_blocks; i++)
671 unsigned char block[MAX_HASH_BLOCK_SIZE];
672 unsigned char is_block_a = constant_time_eq_8(i, index_a);
673 unsigned char is_block_b = constant_time_eq_8(i, index_b);
674 for (j = 0; j < md_block_size; j++)
676 unsigned char b = 0, is_past_c, is_past_cp1;
677 if (k < header_length)
679 else if (k < data_plus_mac_plus_padding_size + header_length)
680 b = data[k-header_length];
683 is_past_c = is_block_a & constant_time_ge(j, c);
684 is_past_cp1 = is_block_a & constant_time_ge(j, c+1);
685 /* If this is the block containing the end of the
686 * application data, and we are at the offset for the
687 * 0x80 value, then overwrite b with 0x80. */
688 b = (b&~is_past_c) | (0x80&is_past_c);
689 /* If this the the block containing the end of the
690 * application data and we're past the 0x80 value then
691 * just write zero. */
693 /* If this is index_b (the final block), but not
694 * index_a (the end of the data), then the 64-bit
695 * length didn't fit into index_a and we're having to
696 * add an extra block of zeros. */
697 b &= ~is_block_b | is_block_a;
699 /* The final bytes of one of the blocks contains the
701 if (j >= md_block_size - md_length_size)
703 /* If this is index_b, write a length byte. */
704 b = (b&~is_block_b) | (is_block_b&length_bytes[j-(md_block_size-md_length_size)]);
709 md_transform(md_state.c, block);
710 md_final_raw(md_state.c, block);
711 /* If this is index_b, copy the hash value to |mac_out|. */
712 for (j = 0; j < md_size; j++)
713 mac_out[j] |= block[j]&is_block_b;
716 EVP_MD_CTX_init(&md_ctx);
717 EVP_DigestInit_ex(&md_ctx, ctx->digest, NULL /* engine */);
720 /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
721 memset(hmac_pad, 0x5c, sslv3_pad_length);
723 EVP_DigestUpdate(&md_ctx, mac_secret, mac_secret_length);
724 EVP_DigestUpdate(&md_ctx, hmac_pad, sslv3_pad_length);
725 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
729 /* Complete the HMAC in the standard manner. */
730 for (i = 0; i < md_block_size; i++)
733 EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size);
734 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
736 EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u);
738 *md_out_size = md_out_size_u;
739 EVP_MD_CTX_cleanup(&md_ctx);
744 /* Due to the need to use EVP in FIPS mode we can't reimplement digests but
745 * we can ensure the number of blocks processed is equal for all cases
746 * by digesting additional data.
749 void tls_fips_digest_extra(
750 const EVP_CIPHER_CTX *cipher_ctx, EVP_MD_CTX *mac_ctx,
751 const unsigned char *data, size_t data_len, size_t orig_len)
753 size_t block_size, digest_pad, blocks_data, blocks_orig;
754 if (EVP_CIPHER_CTX_mode(cipher_ctx) != EVP_CIPH_CBC_MODE)
756 block_size = EVP_MD_CTX_block_size(mac_ctx);
757 /* We are in FIPS mode if we get this far so we know we have only SHA*
758 * digests and TLS to deal with.
759 * Minimum digest padding length is 17 for SHA384/SHA512 and 9
761 * Additional header is 13 bytes. To get the number of digest blocks
762 * processed round up the amount of data plus padding to the nearest
763 * block length. Block length is 128 for SHA384/SHA512 and 64 otherwise.
765 * blocks = (payload_len + digest_pad + 13 + block_size - 1)/block_size
767 * blocks = (payload_len + digest_pad + 12)/block_size + 1
768 * HMAC adds a constant overhead.
769 * We're ultimately only interested in differences so this becomes
770 * blocks = (payload_len + 29)/128
771 * for SHA384/SHA512 and
772 * blocks = (payload_len + 21)/64
775 digest_pad = block_size == 64 ? 21 : 29;
776 blocks_orig = (orig_len + digest_pad)/block_size;
777 blocks_data = (data_len + digest_pad)/block_size;
778 /* MAC enough blocks to make up the difference between the original
779 * and actual lengths plus one extra block to ensure this is never a
780 * no op. The "data" pointer should always have enough space to
781 * perform this operation as it is large enough for a maximum
784 EVP_DigestSignUpdate(mac_ctx, data,
785 (blocks_orig - blocks_data + 1) * block_size);