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 padding_length = good & (padding_length+1);
127 rec->length -= padding_length;
128 rec->type |= padding_length<<8; /* kludge: pass padding length */
129 return (int)((good & 1) | (~good & -1));
132 /* tls1_cbc_remove_padding removes the CBC padding from the decrypted, TLS, CBC
133 * record in |rec| in constant time and returns 1 if the padding is valid and
134 * -1 otherwise. It also removes any explicit IV from the start of the record
135 * without leaking any timing about whether there was enough space after the
136 * padding was removed.
138 * block_size: the block size of the cipher used to encrypt the record.
140 * 0: (in non-constant time) if the record is publicly invalid.
141 * 1: if the padding was valid
143 int tls1_cbc_remove_padding(const SSL* s,
148 unsigned padding_length, good, to_check, i;
149 const unsigned overhead = 1 /* padding length byte */ + mac_size;
150 /* Check if version requires explicit IV */
151 if (s->version >= TLS1_1_VERSION || s->version == DTLS1_VERSION)
153 /* These lengths are all public so we can test them in
156 if (overhead + block_size > rec->length)
158 /* We can now safely skip explicit IV */
159 rec->data += block_size;
160 rec->input += block_size;
161 rec->length -= block_size;
163 else if (overhead > rec->length)
166 padding_length = rec->data[rec->length-1];
168 /* NB: if compression is in operation the first packet may not be of
169 * even length so the padding bug check cannot be performed. This bug
170 * workaround has been around since SSLeay so hopefully it is either
171 * fixed now or no buggy implementation supports compression [steve]
173 if ( (s->options&SSL_OP_TLS_BLOCK_PADDING_BUG) && !s->expand)
175 /* First packet is even in size, so check */
176 if ((memcmp(s->s3->read_sequence, "\0\0\0\0\0\0\0\0",8) == 0) &&
177 !(padding_length & 1))
179 s->s3->flags|=TLS1_FLAGS_TLS_PADDING_BUG;
181 if ((s->s3->flags & TLS1_FLAGS_TLS_PADDING_BUG) &&
188 if (EVP_CIPHER_flags(s->enc_read_ctx->cipher)&EVP_CIPH_FLAG_AEAD_CIPHER)
190 /* padding is already verified */
191 rec->length -= padding_length + 1;
195 good = constant_time_ge(rec->length, overhead+padding_length);
196 /* The padding consists of a length byte at the end of the record and
197 * then that many bytes of padding, all with the same value as the
198 * length byte. Thus, with the length byte included, there are i+1
201 * We can't check just |padding_length+1| bytes because that leaks
202 * decrypted information. Therefore we always have to check the maximum
203 * amount of padding possible. (Again, the length of the record is
204 * public information so we can use it.) */
205 to_check = 255; /* maximum amount of padding. */
206 if (to_check > rec->length-1)
207 to_check = rec->length-1;
209 for (i = 0; i < to_check; i++)
211 unsigned char mask = constant_time_ge(padding_length, i);
212 unsigned char b = rec->data[rec->length-1-i];
213 /* The final |padding_length+1| bytes should all have the value
214 * |padding_length|. Therefore the XOR should be zero. */
215 good &= ~(mask&(padding_length ^ b));
218 /* If any of the final |padding_length+1| bytes had the wrong value,
219 * one or more of the lower eight bits of |good| will be cleared. We
220 * AND the bottom 8 bits together and duplicate the result to all the
225 good <<= sizeof(good)*8-1;
226 good = DUPLICATE_MSB_TO_ALL(good);
228 padding_length = good & (padding_length+1);
229 rec->length -= padding_length;
230 rec->type |= padding_length<<8; /* kludge: pass padding length */
232 return (int)((good & 1) | (~good & -1));
235 #if defined(_M_AMD64) || defined(__x86_64__)
236 #define CBC_MAC_ROTATE_IN_PLACE
239 /* ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in
240 * constant time (independent of the concrete value of rec->length, which may
241 * vary within a 256-byte window).
243 * ssl3_cbc_remove_padding or tls1_cbc_remove_padding must be called prior to
247 * rec->orig_len >= md_size
248 * md_size <= EVP_MAX_MD_SIZE
250 * If CBC_MAC_ROTATE_IN_PLACE is defined then the rotation is performed with
251 * variable accesses in a 64-byte-aligned buffer. Assuming that this fits into
252 * a single cache-line, then the variable memory accesses don't actually affect
253 * the timing. This has been tested to be true on Intel amd64 chips.
255 void ssl3_cbc_copy_mac(unsigned char* out,
256 const SSL3_RECORD *rec,
257 unsigned md_size,unsigned orig_len)
259 #if defined(CBC_MAC_ROTATE_IN_PLACE)
260 unsigned char rotated_mac_buf[EVP_MAX_MD_SIZE*2];
261 unsigned char *rotated_mac;
263 unsigned char rotated_mac[EVP_MAX_MD_SIZE];
266 /* mac_end is the index of |rec->data| just after the end of the MAC. */
267 unsigned mac_end = rec->length;
268 unsigned mac_start = mac_end - md_size;
269 /* scan_start contains the number of bytes that we can ignore because
270 * the MAC's position can only vary by 255 bytes. */
271 unsigned scan_start = 0;
273 unsigned div_spoiler;
274 unsigned rotate_offset;
276 OPENSSL_assert(orig_len >= md_size);
277 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
279 #if defined(CBC_MAC_ROTATE_IN_PLACE)
280 rotated_mac = (unsigned char*) (((intptr_t)(rotated_mac_buf + 64)) & ~63);
283 /* This information is public so it's safe to branch based on it. */
284 if (orig_len > md_size + 255 + 1)
285 scan_start = orig_len - (md_size + 255 + 1);
286 /* div_spoiler contains a multiple of md_size that is used to cause the
287 * modulo operation to be constant time. Without this, the time varies
288 * based on the amount of padding when running on Intel chips at least.
290 * The aim of right-shifting md_size is so that the compiler doesn't
291 * figure out that it can remove div_spoiler as that would require it
292 * to prove that md_size is always even, which I hope is beyond it. */
293 div_spoiler = md_size >> 1;
294 div_spoiler <<= (sizeof(div_spoiler)-1)*8;
295 rotate_offset = (div_spoiler + mac_start - scan_start) % md_size;
297 memset(rotated_mac, 0, md_size);
298 for (i = scan_start, j = 0; i < orig_len; i++)
300 unsigned char mac_started = constant_time_ge(i, mac_start);
301 unsigned char mac_ended = constant_time_ge(i, mac_end);
302 unsigned char b = rec->data[i];
303 rotated_mac[j++] |= b & mac_started & ~mac_ended;
304 j &= constant_time_lt(j,md_size);
307 /* Now rotate the MAC */
308 #if defined(CBC_MAC_ROTATE_IN_PLACE)
310 for (i = 0; i < md_size; i++)
312 out[j++] = rotated_mac[rotate_offset++];
313 rotate_offset &= constant_time_lt(rotate_offset,md_size);
316 memset(out, 0, md_size);
317 rotate_offset = md_size - rotate_offset;
318 rotate_offset &= constant_time_lt(rotate_offset,md_size);
319 for (i = 0; i < md_size; i++)
321 for (j = 0; j < md_size; j++)
322 out[j] |= rotated_mac[i] & constant_time_eq_8(j, rotate_offset);
324 rotate_offset &= constant_time_lt(rotate_offset,md_size);
329 /* u32toLE serialises an unsigned, 32-bit number (n) as four bytes at (p) in
330 * little-endian order. The value of p is advanced by four. */
331 #define u32toLE(n, p) \
332 (*((p)++)=(unsigned char)(n), \
333 *((p)++)=(unsigned char)(n>>8), \
334 *((p)++)=(unsigned char)(n>>16), \
335 *((p)++)=(unsigned char)(n>>24))
337 /* These functions serialize the state of a hash and thus perform the standard
338 * "final" operation without adding the padding and length that such a function
340 static void tls1_md5_final_raw(void* ctx, unsigned char *md_out)
343 u32toLE(md5->A, md_out);
344 u32toLE(md5->B, md_out);
345 u32toLE(md5->C, md_out);
346 u32toLE(md5->D, md_out);
349 static void tls1_sha1_final_raw(void* ctx, unsigned char *md_out)
352 l2n(sha1->h0, md_out);
353 l2n(sha1->h1, md_out);
354 l2n(sha1->h2, md_out);
355 l2n(sha1->h3, md_out);
356 l2n(sha1->h4, md_out);
358 #define LARGEST_DIGEST_CTX SHA_CTX
360 #ifndef OPENSSL_NO_SHA256
361 static void tls1_sha256_final_raw(void* ctx, unsigned char *md_out)
363 SHA256_CTX *sha256 = ctx;
366 for (i = 0; i < 8; i++)
368 l2n(sha256->h[i], md_out);
371 #undef LARGEST_DIGEST_CTX
372 #define LARGEST_DIGEST_CTX SHA256_CTX
375 #ifndef OPENSSL_NO_SHA512
376 static void tls1_sha512_final_raw(void* ctx, unsigned char *md_out)
378 SHA512_CTX *sha512 = ctx;
381 for (i = 0; i < 8; i++)
383 l2n8(sha512->h[i], md_out);
386 #undef LARGEST_DIGEST_CTX
387 #define LARGEST_DIGEST_CTX SHA512_CTX
390 /* ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
391 * which ssl3_cbc_digest_record supports. */
392 char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx)
398 switch (EVP_MD_CTX_type(ctx))
402 #ifndef OPENSSL_NO_SHA256
406 #ifndef OPENSSL_NO_SHA512
416 /* ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS
419 * ctx: the EVP_MD_CTX from which we take the hash function.
420 * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX.
421 * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written.
422 * md_out_size: if non-NULL, the number of output bytes is written here.
423 * header: the 13-byte, TLS record header.
424 * data: the record data itself, less any preceeding explicit IV.
425 * data_plus_mac_size: the secret, reported length of the data and MAC
426 * once the padding has been removed.
427 * data_plus_mac_plus_padding_size: the public length of the whole
428 * record, including padding.
429 * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
431 * On entry: by virtue of having been through one of the remove_padding
432 * functions, above, we know that data_plus_mac_size is large enough to contain
433 * a padding byte and MAC. (If the padding was invalid, it might contain the
435 void ssl3_cbc_digest_record(
436 const EVP_MD_CTX *ctx,
437 unsigned char* md_out,
439 const unsigned char header[13],
440 const unsigned char *data,
441 size_t data_plus_mac_size,
442 size_t data_plus_mac_plus_padding_size,
443 const unsigned char *mac_secret,
444 unsigned mac_secret_length,
447 union { double align;
448 unsigned char c[sizeof(LARGEST_DIGEST_CTX)]; } md_state;
449 void (*md_final_raw)(void *ctx, unsigned char *md_out);
450 void (*md_transform)(void *ctx, const unsigned char *block);
451 unsigned md_size, md_block_size = 64;
452 unsigned sslv3_pad_length = 40, header_length, variance_blocks,
453 len, max_mac_bytes, num_blocks,
454 num_starting_blocks, k, mac_end_offset, c, index_a, index_b;
455 unsigned int bits; /* at most 18 bits */
456 unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES];
457 /* hmac_pad is the masked HMAC key. */
458 unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE];
459 unsigned char first_block[MAX_HASH_BLOCK_SIZE];
460 unsigned char mac_out[EVP_MAX_MD_SIZE];
461 unsigned i, j, md_out_size_u;
463 /* mdLengthSize is the number of bytes in the length field that terminates
465 unsigned md_length_size = 8;
466 char length_is_big_endian = 1;
468 /* This is a, hopefully redundant, check that allows us to forget about
469 * many possible overflows later in this function. */
470 OPENSSL_assert(data_plus_mac_plus_padding_size < 1024*1024);
472 switch (EVP_MD_CTX_type(ctx))
475 MD5_Init((MD5_CTX*)md_state.c);
476 md_final_raw = tls1_md5_final_raw;
477 md_transform = (void(*)(void *ctx, const unsigned char *block)) MD5_Transform;
479 sslv3_pad_length = 48;
480 length_is_big_endian = 0;
483 SHA1_Init((SHA_CTX*)md_state.c);
484 md_final_raw = tls1_sha1_final_raw;
485 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA1_Transform;
488 #ifndef OPENSSL_NO_SHA256
490 SHA224_Init((SHA256_CTX*)md_state.c);
491 md_final_raw = tls1_sha256_final_raw;
492 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;
496 SHA256_Init((SHA256_CTX*)md_state.c);
497 md_final_raw = tls1_sha256_final_raw;
498 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;
502 #ifndef OPENSSL_NO_SHA512
504 SHA384_Init((SHA512_CTX*)md_state.c);
505 md_final_raw = tls1_sha512_final_raw;
506 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA512_Transform;
512 SHA512_Init((SHA512_CTX*)md_state.c);
513 md_final_raw = tls1_sha512_final_raw;
514 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA512_Transform;
521 /* ssl3_cbc_record_digest_supported should have been
522 * called first to check that the hash function is
530 OPENSSL_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES);
531 OPENSSL_assert(md_block_size <= MAX_HASH_BLOCK_SIZE);
532 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
540 8 /* sequence number */ +
541 1 /* record type */ +
542 2 /* record length */;
545 /* variance_blocks is the number of blocks of the hash that we have to
546 * calculate in constant time because they could be altered by the
549 * In SSLv3, the padding must be minimal so the end of the plaintext
550 * varies by, at most, 15+20 = 35 bytes. (We conservatively assume that
551 * the MAC size varies from 0..20 bytes.) In case the 9 bytes of hash
552 * termination (0x80 + 64-bit length) don't fit in the final block, we
553 * say that the final two blocks can vary based on the padding.
555 * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
556 * required to be minimal. Therefore we say that the final six blocks
557 * can vary based on the padding.
559 * Later in the function, if the message is short and there obviously
560 * cannot be this many blocks then variance_blocks can be reduced. */
561 variance_blocks = is_sslv3 ? 2 : 6;
562 /* From now on we're dealing with the MAC, which conceptually has 13
563 * bytes of `header' before the start of the data (TLS) or 71/75 bytes
565 len = data_plus_mac_plus_padding_size + header_length;
566 /* max_mac_bytes contains the maximum bytes of bytes in the MAC, including
567 * |header|, assuming that there's no padding. */
568 max_mac_bytes = len - md_size - 1;
569 /* num_blocks is the maximum number of hash blocks. */
570 num_blocks = (max_mac_bytes + 1 + md_length_size + md_block_size - 1) / md_block_size;
571 /* In order to calculate the MAC in constant time we have to handle
572 * the final blocks specially because the padding value could cause the
573 * end to appear somewhere in the final |variance_blocks| blocks and we
574 * can't leak where. However, |num_starting_blocks| worth of data can
575 * be hashed right away because no padding value can affect whether
576 * they are plaintext. */
577 num_starting_blocks = 0;
578 /* k is the starting byte offset into the conceptual header||data where
579 * we start processing. */
581 /* mac_end_offset is the index just past the end of the data to be
583 mac_end_offset = data_plus_mac_size + header_length - md_size;
584 /* c is the index of the 0x80 byte in the final hash block that
585 * contains application data. */
586 c = mac_end_offset % md_block_size;
587 /* index_a is the hash block number that contains the 0x80 terminating
589 index_a = mac_end_offset / md_block_size;
590 /* index_b is the hash block number that contains the 64-bit hash
591 * length, in bits. */
592 index_b = (mac_end_offset + md_length_size) / md_block_size;
593 /* bits is the hash-length in bits. It includes the additional hash
594 * block for the masked HMAC key, or whole of |header| in the case of
597 /* For SSLv3, if we're going to have any starting blocks then we need
598 * at least two because the header is larger than a single block. */
599 if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0))
601 num_starting_blocks = num_blocks - variance_blocks;
602 k = md_block_size*num_starting_blocks;
605 bits = 8*mac_end_offset;
608 /* Compute the initial HMAC block. For SSLv3, the padding and
609 * secret bytes are included in |header| because they take more
610 * than a single block. */
611 bits += 8*md_block_size;
612 memset(hmac_pad, 0, md_block_size);
613 OPENSSL_assert(mac_secret_length <= sizeof(hmac_pad));
614 memcpy(hmac_pad, mac_secret, mac_secret_length);
615 for (i = 0; i < md_block_size; i++)
618 md_transform(md_state.c, hmac_pad);
621 if (length_is_big_endian)
623 memset(length_bytes,0,md_length_size-4);
624 length_bytes[md_length_size-4] = (unsigned char)(bits>>24);
625 length_bytes[md_length_size-3] = (unsigned char)(bits>>16);
626 length_bytes[md_length_size-2] = (unsigned char)(bits>>8);
627 length_bytes[md_length_size-1] = (unsigned char)bits;
631 memset(length_bytes,0,md_length_size);
632 length_bytes[md_length_size-5] = (unsigned char)(bits>>24);
633 length_bytes[md_length_size-6] = (unsigned char)(bits>>16);
634 length_bytes[md_length_size-7] = (unsigned char)(bits>>8);
635 length_bytes[md_length_size-8] = (unsigned char)bits;
642 /* The SSLv3 header is larger than a single block.
643 * overhang is the number of bytes beyond a single
644 * block that the header consumes: either 7 bytes
645 * (SHA1) or 11 bytes (MD5). */
646 unsigned overhang = header_length-md_block_size;
647 md_transform(md_state.c, header);
648 memcpy(first_block, header + md_block_size, overhang);
649 memcpy(first_block + overhang, data, md_block_size-overhang);
650 md_transform(md_state.c, first_block);
651 for (i = 1; i < k/md_block_size - 1; i++)
652 md_transform(md_state.c, data + md_block_size*i - overhang);
656 /* k is a multiple of md_block_size. */
657 memcpy(first_block, header, 13);
658 memcpy(first_block+13, data, md_block_size-13);
659 md_transform(md_state.c, first_block);
660 for (i = 1; i < k/md_block_size; i++)
661 md_transform(md_state.c, data + md_block_size*i - 13);
665 memset(mac_out, 0, sizeof(mac_out));
667 /* We now process the final hash blocks. For each block, we construct
668 * it 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|. */
671 for (i = num_starting_blocks; i <= num_starting_blocks+variance_blocks; i++)
673 unsigned char block[MAX_HASH_BLOCK_SIZE];
674 unsigned char is_block_a = constant_time_eq_8(i, index_a);
675 unsigned char is_block_b = constant_time_eq_8(i, index_b);
676 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(j, c);
686 is_past_cp1 = is_block_a & constant_time_ge(j, c+1);
687 /* If this is the block containing the end of the
688 * application data, and we are at the offset for the
689 * 0x80 value, then overwrite b with 0x80. */
690 b = (b&~is_past_c) | (0x80&is_past_c);
691 /* If this the the block containing the end of the
692 * application data and we're past the 0x80 value then
693 * just write zero. */
695 /* If this is index_b (the final block), but not
696 * index_a (the end of the data), then the 64-bit
697 * length didn't fit into index_a and we're having to
698 * add an extra block of zeros. */
699 b &= ~is_block_b | is_block_a;
701 /* The final bytes of one of the blocks contains the
703 if (j >= md_block_size - md_length_size)
705 /* If this is index_b, write a length byte. */
706 b = (b&~is_block_b) | (is_block_b&length_bytes[j-(md_block_size-md_length_size)]);
711 md_transform(md_state.c, block);
712 md_final_raw(md_state.c, block);
713 /* If this is index_b, copy the hash value to |mac_out|. */
714 for (j = 0; j < md_size; j++)
715 mac_out[j] |= block[j]&is_block_b;
718 EVP_MD_CTX_init(&md_ctx);
719 EVP_DigestInit_ex(&md_ctx, ctx->digest, NULL /* engine */);
722 /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
723 memset(hmac_pad, 0x5c, sslv3_pad_length);
725 EVP_DigestUpdate(&md_ctx, mac_secret, mac_secret_length);
726 EVP_DigestUpdate(&md_ctx, hmac_pad, sslv3_pad_length);
727 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
731 /* Complete the HMAC in the standard manner. */
732 for (i = 0; i < md_block_size; i++)
735 EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size);
736 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
738 EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u);
740 *md_out_size = md_out_size_u;
741 EVP_MD_CTX_cleanup(&md_ctx);
746 /* Due to the need to use EVP in FIPS mode we can't reimplement digests but
747 * we can ensure the number of blocks processed is equal for all cases
748 * by digesting additional data.
751 void tls_fips_digest_extra(
752 const EVP_CIPHER_CTX *cipher_ctx, EVP_MD_CTX *mac_ctx,
753 const unsigned char *data, size_t data_len, size_t orig_len)
755 size_t block_size, digest_pad, blocks_data, blocks_orig;
756 if (EVP_CIPHER_CTX_mode(cipher_ctx) != EVP_CIPH_CBC_MODE)
758 block_size = EVP_MD_CTX_block_size(mac_ctx);
759 /* We are in FIPS mode if we get this far so we know we have only SHA*
760 * digests and TLS to deal with.
761 * Minimum digest padding length is 17 for SHA384/SHA512 and 9
763 * Additional header is 13 bytes. To get the number of digest blocks
764 * processed round up the amount of data plus padding to the nearest
765 * block length. Block length is 128 for SHA384/SHA512 and 64 otherwise.
767 * blocks = (payload_len + digest_pad + 13 + block_size - 1)/block_size
769 * blocks = (payload_len + digest_pad + 12)/block_size + 1
770 * HMAC adds a constant overhead.
771 * We're ultimately only interested in differences so this becomes
772 * blocks = (payload_len + 29)/128
773 * for SHA384/SHA512 and
774 * blocks = (payload_len + 21)/64
777 digest_pad = block_size == 64 ? 21 : 29;
778 blocks_orig = (orig_len + digest_pad)/block_size;
779 blocks_data = (data_len + digest_pad)/block_size;
780 /* MAC enough blocks to make up the difference between the original
781 * and actual lengths plus one extra block to ensure this is never a
782 * no op. The "data" pointer should always have enough space to
783 * perform this operation as it is large enough for a maximum
786 EVP_DigestSignUpdate(mac_ctx, data,
787 (blocks_orig - blocks_data + 1) * block_size);