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_ge returns 0xff if a>=b and 0x00 otherwise. */
80 static unsigned constant_time_ge(unsigned a, unsigned b)
83 return DUPLICATE_MSB_TO_ALL(~a);
86 /* constant_time_eq_8 returns 0xff if a==b and 0x00 otherwise. */
87 static unsigned char constant_time_eq_8(unsigned char a, unsigned char b)
91 return DUPLICATE_MSB_TO_ALL_8(c);
94 /* ssl3_cbc_remove_padding removes padding from the decrypted, SSLv3, CBC
95 * record in |rec| by updating |rec->length| in constant time.
97 * block_size: the block size of the cipher used to encrypt the record.
99 * 0: (in non-constant time) if the record is publicly invalid.
100 * 1: if the padding was valid
102 int ssl3_cbc_remove_padding(const SSL* s,
107 unsigned padding_length, good;
108 const unsigned overhead = 1 /* padding length byte */ + mac_size;
110 /* These lengths are all public so we can test them in non-constant
112 if (overhead > rec->length)
115 padding_length = rec->data[rec->length-1];
116 good = constant_time_ge(rec->length, padding_length+overhead);
117 /* SSLv3 requires that the padding is minimal. */
118 good &= constant_time_ge(block_size, padding_length+1);
119 padding_length = good & (padding_length+1);
120 rec->length -= padding_length;
121 rec->type |= padding_length<<8; /* kludge: pass padding length */
122 return (int)((good & 1) | (~good & -1));
125 /* tls1_cbc_remove_padding removes the CBC padding from the decrypted, TLS, CBC
126 * record in |rec| in constant time and returns 1 if the padding is valid and
127 * -1 otherwise. It also removes any explicit IV from the start of the record
128 * without leaking any timing about whether there was enough space after the
129 * padding was removed.
131 * block_size: the block size of the cipher used to encrypt the record.
133 * 0: (in non-constant time) if the record is publicly invalid.
134 * 1: if the padding was valid
136 int tls1_cbc_remove_padding(const SSL* s,
141 unsigned padding_length, good, to_check, i;
142 const char has_explicit_iv =
143 s->version >= TLS1_1_VERSION || s->version == DTLS1_VERSION;
144 const unsigned overhead = 1 /* padding length byte */ +
146 (has_explicit_iv ? block_size : 0);
148 /* These lengths are all public so we can test them in non-constant
150 if (overhead > rec->length)
153 padding_length = rec->data[rec->length-1];
155 /* NB: if compression is in operation the first packet may not be of
156 * even length so the padding bug check cannot be performed. This bug
157 * workaround has been around since SSLeay so hopefully it is either
158 * fixed now or no buggy implementation supports compression [steve]
160 if ( (s->options&SSL_OP_TLS_BLOCK_PADDING_BUG) && !s->expand)
162 /* First packet is even in size, so check */
163 if ((memcmp(s->s3->read_sequence, "\0\0\0\0\0\0\0\0",8) == 0) &&
164 !(padding_length & 1))
166 s->s3->flags|=TLS1_FLAGS_TLS_PADDING_BUG;
168 if ((s->s3->flags & TLS1_FLAGS_TLS_PADDING_BUG) &&
175 good = constant_time_ge(rec->length, overhead+padding_length);
176 /* The padding consists of a length byte at the end of the record and
177 * then that many bytes of padding, all with the same value as the
178 * length byte. Thus, with the length byte included, there are i+1
181 * We can't check just |padding_length+1| bytes because that leaks
182 * decrypted information. Therefore we always have to check the maximum
183 * amount of padding possible. (Again, the length of the record is
184 * public information so we can use it.) */
185 to_check = 255; /* maximum amount of padding. */
186 if (to_check > rec->length-1)
187 to_check = rec->length-1;
189 for (i = 0; i < to_check; i++)
191 unsigned char mask = constant_time_ge(padding_length, i);
192 unsigned char b = rec->data[rec->length-1-i];
193 /* The final |padding_length+1| bytes should all have the value
194 * |padding_length|. Therefore the XOR should be zero. */
195 good &= ~(mask&(padding_length ^ b));
198 /* If any of the final |padding_length+1| bytes had the wrong value,
199 * one or more of the lower eight bits of |good| will be cleared. We
200 * AND the bottom 8 bits together and duplicate the result to all the
205 good <<= sizeof(good)*8-1;
206 good = DUPLICATE_MSB_TO_ALL(good);
208 padding_length = good & (padding_length+1);
209 rec->length -= padding_length;
210 rec->type |= padding_length<<8; /* kludge: pass padding length */
212 /* We can always safely skip the explicit IV. We check at the beginning
213 * of this function that the record has at least enough space for the
214 * IV, MAC and padding length byte. (These can be checked in
215 * non-constant time because it's all public information.) So, if the
216 * padding was invalid, then we didn't change |rec->length| and this is
217 * safe. If the padding was valid then we know that we have at least
218 * overhead+padding_length bytes of space and so this is still safe
219 * because overhead accounts for the explicit IV. */
222 rec->data += block_size;
223 rec->input += block_size;
224 rec->length -= block_size;
227 return (int)((good & 1) | (~good & -1));
230 #if defined(_M_AMD64) || defined(__x86_64__)
231 #define CBC_MAC_ROTATE_IN_PLACE
234 /* ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in
235 * constant time (independent of the concrete value of rec->length, which may
236 * vary within a 256-byte window).
238 * ssl3_cbc_remove_padding or tls1_cbc_remove_padding must be called prior to
242 * rec->orig_len >= md_size
243 * md_size <= EVP_MAX_MD_SIZE
245 * If CBC_MAC_ROTATE_IN_PLACE is defined then the rotation is performed with
246 * variable accesses in a 64-byte-aligned buffer. Assuming that this fits into
247 * a single cache-line, then the variable memory accesses don't actually affect
248 * the timing. This has been tested to be true on Intel amd64 chips.
250 void ssl3_cbc_copy_mac(unsigned char* out,
251 const SSL3_RECORD *rec,
252 unsigned md_size,unsigned orig_len)
254 #if defined(CBC_MAC_ROTATE_IN_PLACE)
255 unsigned char rotated_mac_buf[EVP_MAX_MD_SIZE*2];
256 unsigned char *rotated_mac;
258 unsigned char rotated_mac[EVP_MAX_MD_SIZE];
261 /* mac_end is the index of |rec->data| just after the end of the MAC. */
262 unsigned mac_end = rec->length;
263 unsigned mac_start = mac_end - md_size;
264 /* scan_start contains the number of bytes that we can ignore because
265 * the MAC's position can only vary by 255 bytes. */
266 unsigned scan_start = 0;
268 unsigned div_spoiler;
269 unsigned rotate_offset;
271 OPENSSL_assert(orig_len >= md_size);
272 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
274 #if defined(CBC_MAC_ROTATE_IN_PLACE)
275 rotated_mac = (unsigned char*) (((intptr_t)(rotated_mac_buf + 64)) & ~63);
278 /* This information is public so it's safe to branch based on it. */
279 if (orig_len > md_size + 255 + 1)
280 scan_start = orig_len - (md_size + 255 + 1);
281 /* div_spoiler contains a multiple of md_size that is used to cause the
282 * modulo operation to be constant time. Without this, the time varies
283 * based on the amount of padding when running on Intel chips at least.
285 * The aim of right-shifting md_size is so that the compiler doesn't
286 * figure out that it can remove div_spoiler as that would require it
287 * to prove that md_size is always even, which I hope is beyond it. */
288 div_spoiler = md_size >> 1;
289 div_spoiler <<= (sizeof(div_spoiler)-1)*8;
290 rotate_offset = (div_spoiler + mac_start - scan_start) % md_size;
292 memset(rotated_mac, 0, md_size);
293 for (i = scan_start; i < orig_len;)
295 for (j = 0; j < md_size && i < orig_len; i++, j++)
297 unsigned char mac_started = constant_time_ge(i, mac_start);
298 unsigned char mac_ended = constant_time_ge(i, mac_end);
301 rotated_mac[j] |= b & mac_started & ~mac_ended;
305 /* Now rotate the MAC */
306 #if defined(CBC_MAC_ROTATE_IN_PLACE)
308 for (i = 0; i < md_size; i++)
310 unsigned char offset = (div_spoiler + rotate_offset + i) % md_size;
311 out[j++] = rotated_mac[offset];
314 memset(out, 0, md_size);
315 for (i = 0; i < md_size; i++)
317 unsigned char offset = (div_spoiler + md_size - rotate_offset + i) % md_size;
318 for (j = 0; j < md_size; j++)
319 out[j] |= rotated_mac[i] & constant_time_eq_8(j, offset);
324 /* These functions serialize the state of a hash and thus perform the standard
325 * "final" operation without adding the padding and length that such a function
327 static void tls1_md5_final_raw(void* ctx, unsigned char *md_out)
336 static void tls1_sha1_final_raw(void* ctx, unsigned char *md_out)
339 l2n(sha1->h0, md_out);
340 l2n(sha1->h1, md_out);
341 l2n(sha1->h2, md_out);
342 l2n(sha1->h3, md_out);
343 l2n(sha1->h4, md_out);
345 #define LARGEST_DIGEST_CTX SHA_CTX
347 #ifndef OPENSSL_NO_SHA256
348 static void tls1_sha256_final_raw(void* ctx, unsigned char *md_out)
350 SHA256_CTX *sha256 = ctx;
353 for (i = 0; i < 8; i++)
355 l2n(sha256->h[i], md_out);
358 #undef LARGEST_DIGEST_CTX
359 #define LARGEST_DIGEST_CTX SHA256_CTX
362 #ifndef OPENSSL_NO_SHA512
363 static void tls1_sha512_final_raw(void* ctx, unsigned char *md_out)
365 SHA512_CTX *sha512 = ctx;
368 for (i = 0; i < 8; i++)
370 l2n8(sha512->h[i], md_out);
373 #undef LARGEST_DIGEST_CTX
374 #define LARGEST_DIGEST_CTX SHA512_CTX
377 /* ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
378 * which ssl3_cbc_digest_record supports. */
379 char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx)
385 switch (EVP_MD_CTX_type(ctx))
389 #ifndef OPENSSL_NO_SHA256
393 #ifndef OPENSSL_NO_SHA512
403 /* ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS
406 * ctx: the EVP_MD_CTX from which we take the hash function.
407 * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX.
408 * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written.
409 * md_out_size: if non-NULL, the number of output bytes is written here.
410 * header: the 13-byte, TLS record header.
411 * data: the record data itself, less any preceeding explicit IV.
412 * data_plus_mac_size: the secret, reported length of the data and MAC
413 * once the padding has been removed.
414 * data_plus_mac_plus_padding_size: the public length of the whole
415 * record, including padding.
416 * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
418 * On entry: by virtue of having been through one of the remove_padding
419 * functions, above, we know that data_plus_mac_size is large enough to contain
420 * a padding byte and MAC. (If the padding was invalid, it might contain the
422 void ssl3_cbc_digest_record(
423 const EVP_MD_CTX *ctx,
424 unsigned char* md_out,
426 const unsigned char header[13],
427 const unsigned char *data,
428 size_t data_plus_mac_size,
429 size_t data_plus_mac_plus_padding_size,
430 const unsigned char *mac_secret,
431 unsigned mac_secret_length,
434 union { double align;
435 unsigned char c[sizeof(LARGEST_DIGEST_CTX)]; } md_state;
436 void (*md_final_raw)(void *ctx, unsigned char *md_out);
437 void (*md_transform)(void *ctx, const unsigned char *block);
438 unsigned md_size, md_block_size = 64;
439 unsigned sslv3_pad_length = 40, header_length, variance_blocks,
440 len, max_mac_bytes, num_blocks,
441 num_starting_blocks, k, mac_end_offset, c, index_a, index_b;
442 unsigned int bits; /* at most 18 bits */
443 unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES];
444 /* hmac_pad is the masked HMAC key. */
445 unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE];
446 unsigned char first_block[MAX_HASH_BLOCK_SIZE];
447 unsigned char mac_out[EVP_MAX_MD_SIZE];
448 unsigned i, j, md_out_size_u;
450 /* mdLengthSize is the number of bytes in the length field that terminates
452 unsigned md_length_size = 8;
454 /* This is a, hopefully redundant, check that allows us to forget about
455 * many possible overflows later in this function. */
456 OPENSSL_assert(data_plus_mac_plus_padding_size < 1024*1024);
458 switch (EVP_MD_CTX_type(ctx))
461 MD5_Init((MD5_CTX*)md_state.c);
462 md_final_raw = tls1_md5_final_raw;
463 md_transform = (void(*)(void *ctx, const unsigned char *block)) MD5_Transform;
465 sslv3_pad_length = 48;
468 SHA1_Init((SHA_CTX*)md_state.c);
469 md_final_raw = tls1_sha1_final_raw;
470 md_transform = (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;
477 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;
481 SHA256_Init((SHA256_CTX*)md_state.c);
482 md_final_raw = tls1_sha256_final_raw;
483 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform;
487 #ifndef OPENSSL_NO_SHA512
489 SHA384_Init((SHA512_CTX*)md_state.c);
490 md_final_raw = tls1_sha512_final_raw;
491 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA512_Transform;
497 SHA512_Init((SHA512_CTX*)md_state.c);
498 md_final_raw = tls1_sha512_final_raw;
499 md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA512_Transform;
506 /* ssl3_cbc_record_digest_supported should have been
507 * called first to check that the hash function is
515 OPENSSL_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES);
516 OPENSSL_assert(md_block_size <= MAX_HASH_BLOCK_SIZE);
517 OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
525 8 /* sequence number */ +
526 1 /* record type */ +
527 2 /* record length */;
530 /* variance_blocks is the number of blocks of the hash that we have to
531 * calculate in constant time because they could be altered by the
534 * In SSLv3, the padding must be minimal so the end of the plaintext
535 * varies by, at most, 15+20 = 35 bytes. (We conservatively assume that
536 * the MAC size varies from 0..20 bytes.) In case the 9 bytes of hash
537 * termination (0x80 + 64-bit length) don't fit in the final block, we
538 * 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
542 * can vary based on the padding.
544 * Later in the function, if the message is short and there obviously
545 * cannot be this many blocks then variance_blocks can be reduced. */
546 variance_blocks = is_sslv3 ? 2 : 6;
547 /* From now on we're dealing with the MAC, which conceptually has 13
548 * bytes of `header' before the start of the data (TLS) or 71/75 bytes
550 len = data_plus_mac_plus_padding_size + header_length;
551 /* max_mac_bytes contains the maximum bytes of bytes in the MAC, including
552 * |header|, assuming that there's no padding. */
553 max_mac_bytes = len - md_size - 1;
554 /* num_blocks is the maximum number of hash blocks. */
555 num_blocks = (max_mac_bytes + 1 + md_length_size + md_block_size - 1) / md_block_size;
556 /* In order to calculate the MAC in constant time we have to handle
557 * the final blocks specially because the padding value could cause the
558 * end to appear somewhere in the final |variance_blocks| blocks and we
559 * can't leak where. However, |num_starting_blocks| worth of data can
560 * be hashed right away because no padding value can affect whether
561 * they are plaintext. */
562 num_starting_blocks = 0;
563 /* k is the starting byte offset into the conceptual header||data where
564 * we start processing. */
566 /* mac_end_offset is the index just past the end of the data to be
568 mac_end_offset = data_plus_mac_size + header_length - md_size;
569 /* c is the index of the 0x80 byte in the final hash block that
570 * contains application data. */
571 c = mac_end_offset % md_block_size;
572 /* index_a is the hash block number that contains the 0x80 terminating
574 index_a = mac_end_offset / md_block_size;
575 /* index_b is the hash block number that contains the 64-bit hash
576 * length, in bits. */
577 index_b = (mac_end_offset + md_length_size) / md_block_size;
578 /* bits is the hash-length in bits. It includes the additional hash
579 * block for the masked HMAC key, or whole of |header| in the case of
582 /* For SSLv3, if we're going to have any starting blocks then we need
583 * at least two because the header is larger than a single block. */
584 if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0))
586 num_starting_blocks = num_blocks - variance_blocks;
587 k = md_block_size*num_starting_blocks;
590 bits = 8*mac_end_offset;
593 /* Compute the initial HMAC block. For SSLv3, the padding and
594 * secret bytes are included in |header| because they take more
595 * than a single block. */
596 bits += 8*md_block_size;
597 memset(hmac_pad, 0, md_block_size);
598 OPENSSL_assert(mac_secret_length <= sizeof(hmac_pad));
599 memcpy(hmac_pad, mac_secret, mac_secret_length);
600 for (i = 0; i < md_block_size; i++)
603 md_transform(md_state.c, hmac_pad);
606 memset(length_bytes,0,md_length_size-4);
607 length_bytes[md_length_size-4] = (unsigned char)(bits>>24);
608 length_bytes[md_length_size-3] = (unsigned char)(bits>>16);
609 length_bytes[md_length_size-2] = (unsigned char)(bits>>8);
610 length_bytes[md_length_size-1] = (unsigned char)bits;
616 /* The SSLv3 header is larger than a single block.
617 * overhang is the number of bytes beyond a single
618 * block that the header consumes: either 7 bytes
619 * (SHA1) or 11 bytes (MD5). */
620 unsigned overhang = header_length-md_block_size;
621 md_transform(md_state.c, header);
622 memcpy(first_block, header + md_block_size, overhang);
623 memcpy(first_block + overhang, data, md_block_size-overhang);
624 md_transform(md_state.c, first_block);
625 for (i = 1; i < k/md_block_size - 1; i++)
626 md_transform(md_state.c, data + md_block_size*i - overhang);
630 /* k is a multiple of md_block_size. */
631 memcpy(first_block, header, 13);
632 memcpy(first_block+13, data, md_block_size-13);
633 md_transform(md_state.c, first_block);
634 for (i = 1; i < k/md_block_size; i++)
635 md_transform(md_state.c, data + md_block_size*i - 13);
639 memset(mac_out, 0, sizeof(mac_out));
641 /* We now process the final hash blocks. For each block, we construct
642 * it in constant time. If the |i==index_a| then we'll include the 0x80
643 * bytes and zero pad etc. For each block we selectively copy it, in
644 * constant time, to |mac_out|. */
645 for (i = num_starting_blocks; i <= num_starting_blocks+variance_blocks; i++)
647 unsigned char block[MAX_HASH_BLOCK_SIZE];
648 unsigned char is_block_a = constant_time_eq_8(i, index_a);
649 unsigned char is_block_b = constant_time_eq_8(i, index_b);
650 for (j = 0; j < md_block_size; j++)
652 unsigned char b = 0, is_past_c, is_past_cp1;
653 if (k < header_length)
655 else if (k < data_plus_mac_plus_padding_size + header_length)
656 b = data[k-header_length];
659 is_past_c = is_block_a & constant_time_ge(j, c);
660 is_past_cp1 = is_block_a & constant_time_ge(j, c+1);
661 /* If this is the block containing the end of the
662 * application data, and we are at the offset for the
663 * 0x80 value, then overwrite b with 0x80. */
664 b = (b&~is_past_c) | (0x80&is_past_c);
665 /* If this the the block containing the end of the
666 * application data and we're past the 0x80 value then
667 * just write zero. */
669 /* If this is index_b (the final block), but not
670 * index_a (the end of the data), then the 64-bit
671 * length didn't fit into index_a and we're having to
672 * add an extra block of zeros. */
673 b &= ~is_block_b | is_block_a;
675 /* The final bytes of one of the blocks contains the
677 if (j >= md_block_size - md_length_size)
679 /* If this is index_b, write a length byte. */
680 b = (b&~is_block_b) | (is_block_b&length_bytes[j-(md_block_size-md_length_size)]);
685 md_transform(md_state.c, block);
686 md_final_raw(md_state.c, block);
687 /* If this is index_b, copy the hash value to |mac_out|. */
688 for (j = 0; j < md_size; j++)
689 mac_out[j] |= block[j]&is_block_b;
692 EVP_MD_CTX_init(&md_ctx);
693 EVP_DigestInit_ex(&md_ctx, ctx->digest, NULL /* engine */);
696 /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
697 memset(hmac_pad, 0x5c, sslv3_pad_length);
699 EVP_DigestUpdate(&md_ctx, mac_secret, mac_secret_length);
700 EVP_DigestUpdate(&md_ctx, hmac_pad, sslv3_pad_length);
701 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
705 /* Complete the HMAC in the standard manner. */
706 for (i = 0; i < md_block_size; i++)
709 EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size);
710 EVP_DigestUpdate(&md_ctx, mac_out, md_size);
712 EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u);
714 *md_out_size = md_out_size_u;
715 EVP_MD_CTX_cleanup(&md_ctx);
720 /* Due to the need to use EVP in FIPS mode we can't reimplement digests but
721 * we can ensure the number of blocks processed is equal for all cases
722 * by digesting additional data.
725 void tls_fips_digest_extra(
726 const EVP_CIPHER_CTX *cipher_ctx, EVP_MD_CTX *mac_ctx,
727 const unsigned char *data, size_t data_len, size_t orig_len)
729 size_t block_size, digest_pad, blocks_data, blocks_orig;
730 if (EVP_CIPHER_CTX_mode(cipher_ctx) != EVP_CIPH_CBC_MODE)
732 block_size = EVP_MD_CTX_block_size(mac_ctx);
733 /* We are in FIPS mode if we get this far so we know we have only SHA*
734 * digests and TLS to deal with.
735 * Minimum digest padding length is 17 for SHA384/SHA512 and 9
737 * Additional header is 13 bytes. To get the number of digest blocks
738 * processed round up the amount of data plus padding to the nearest
739 * block length. Block length is 128 for SHA384/SHA512 and 64 otherwise.
741 * blocks = (payload_len + digest_pad + 13 + block_size - 1)/block_size
743 * blocks = (payload_len + digest_pad + 12)/block_size + 1
744 * HMAC adds a constant overhead.
745 * We're ultimately only interested in differences so this becomes
746 * blocks = (payload_len + 29)/128
747 * for SHA384/SHA512 and
748 * blocks = (payload_len + 21)/64
751 digest_pad = block_size == 64 ? 21 : 29;
752 blocks_orig = (orig_len + digest_pad)/block_size;
753 blocks_data = (data_len + digest_pad)/block_size;
754 /* MAC enough blocks to make up the difference between the original
755 * and actual lengths plus one extra block to ensure this is never a
756 * no op. The "data" pointer should always have enough space to
757 * perform this operation as it is large enough for a maximum
760 EVP_DigestSignUpdate(mac_ctx, data,
761 (blocks_orig - blocks_data + 1) * block_size);