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 rec
->length
-= good
& (padding_length
+1);
120 return (int)((good
& 1) | (~good
& -1));
123 /* tls1_cbc_remove_padding removes the CBC padding from the decrypted, TLS, CBC
124 * record in |rec| in constant time and returns 1 if the padding is valid and
125 * -1 otherwise. It also removes any explicit IV from the start of the record
126 * without leaking any timing about whether there was enough space after the
127 * padding was removed.
129 * block_size: the block size of the cipher used to encrypt the record.
131 * 0: (in non-constant time) if the record is publicly invalid.
132 * 1: if the padding was valid
134 int tls1_cbc_remove_padding(const SSL
* s
,
139 unsigned padding_length
, good
, to_check
, i
;
140 const char has_explicit_iv
=
141 s
->version
>= TLS1_1_VERSION
|| s
->version
== DTLS1_VERSION
;
142 const unsigned overhead
= 1 /* padding length byte */ +
144 (has_explicit_iv
? block_size
: 0);
146 /* These lengths are all public so we can test them in non-constant
148 if (overhead
> rec
->length
)
151 padding_length
= rec
->data
[rec
->length
-1];
153 /* NB: if compression is in operation the first packet may not be of
154 * even length so the padding bug check cannot be performed. This bug
155 * workaround has been around since SSLeay so hopefully it is either
156 * fixed now or no buggy implementation supports compression [steve]
158 if ( (s
->options
&SSL_OP_TLS_BLOCK_PADDING_BUG
) && !s
->expand
)
160 /* First packet is even in size, so check */
161 if ((memcmp(s
->s3
->read_sequence
, "\0\0\0\0\0\0\0\0",8) == 0) &&
162 !(padding_length
& 1))
164 s
->s3
->flags
|=TLS1_FLAGS_TLS_PADDING_BUG
;
166 if ((s
->s3
->flags
& TLS1_FLAGS_TLS_PADDING_BUG
) &&
173 good
= constant_time_ge(rec
->length
, overhead
+padding_length
);
174 /* The padding consists of a length byte at the end of the record and
175 * then that many bytes of padding, all with the same value as the
176 * length byte. Thus, with the length byte included, there are i+1
179 * We can't check just |padding_length+1| bytes because that leaks
180 * decrypted information. Therefore we always have to check the maximum
181 * amount of padding possible. (Again, the length of the record is
182 * public information so we can use it.) */
183 to_check
= 255; /* maximum amount of padding. */
184 if (to_check
> rec
->length
-1)
185 to_check
= rec
->length
-1;
187 for (i
= 0; i
< to_check
; i
++)
189 unsigned char mask
= constant_time_ge(padding_length
, i
);
190 unsigned char b
= rec
->data
[rec
->length
-1-i
];
191 /* The final |padding_length+1| bytes should all have the value
192 * |padding_length|. Therefore the XOR should be zero. */
193 good
&= ~(mask
&(padding_length
^ b
));
196 /* If any of the final |padding_length+1| bytes had the wrong value,
197 * one or more of the lower eight bits of |good| will be cleared. We
198 * AND the bottom 8 bits together and duplicate the result to all the
203 good
<<= sizeof(good
)*8-1;
204 good
= DUPLICATE_MSB_TO_ALL(good
);
206 rec
->length
-= good
& (padding_length
+1);
208 /* We can always safely skip the explicit IV. We check at the beginning
209 * of this function that the record has at least enough space for the
210 * IV, MAC and padding length byte. (These can be checked in
211 * non-constant time because it's all public information.) So, if the
212 * padding was invalid, then we didn't change |rec->length| and this is
213 * safe. If the padding was valid then we know that we have at least
214 * overhead+padding_length bytes of space and so this is still safe
215 * because overhead accounts for the explicit IV. */
218 rec
->data
+= block_size
;
219 rec
->input
+= block_size
;
220 rec
->length
-= block_size
;
221 rec
->orig_len
-= block_size
;
224 return (int)((good
& 1) | (~good
& -1));
227 #if defined(_M_AMD64) || defined(__x86_64__)
228 #define CBC_MAC_ROTATE_IN_PLACE
231 /* ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in
232 * constant time (independent of the concrete value of rec->length, which may
233 * vary within a 256-byte window).
235 * ssl3_cbc_remove_padding or tls1_cbc_remove_padding must be called prior to
239 * rec->orig_len >= md_size
240 * md_size <= EVP_MAX_MD_SIZE
242 * If CBC_MAC_ROTATE_IN_PLACE is defined then the rotation is performed with
243 * variable accesses in a 64-byte-aligned buffer. Assuming that this fits into
244 * a single cache-line, then the variable memory accesses don't actually affect
245 * the timing. This has been tested to be true on Intel amd64 chips.
247 void ssl3_cbc_copy_mac(unsigned char* out
,
248 const SSL3_RECORD
*rec
,
251 #if defined(CBC_MAC_ROTATE_IN_PLACE)
252 unsigned char rotated_mac_buf
[EVP_MAX_MD_SIZE
*2];
253 unsigned char *rotated_mac
;
255 unsigned char rotated_mac
[EVP_MAX_MD_SIZE
];
258 /* mac_end is the index of |rec->data| just after the end of the MAC. */
259 unsigned mac_end
= rec
->length
;
260 unsigned mac_start
= mac_end
- md_size
;
261 /* scan_start contains the number of bytes that we can ignore because
262 * the MAC's position can only vary by 255 bytes. */
263 unsigned scan_start
= 0;
265 unsigned div_spoiler
;
266 unsigned rotate_offset
;
268 OPENSSL_assert(rec
->orig_len
>= md_size
);
269 OPENSSL_assert(md_size
<= EVP_MAX_MD_SIZE
);
271 #if defined(CBC_MAC_ROTATE_IN_PLACE)
272 rotated_mac
= (unsigned char*) (((intptr_t)(rotated_mac_buf
+ 64)) & ~63);
275 /* This information is public so it's safe to branch based on it. */
276 if (rec
->orig_len
> md_size
+ 255 + 1)
277 scan_start
= rec
->orig_len
- (md_size
+ 255 + 1);
278 /* div_spoiler contains a multiple of md_size that is used to cause the
279 * modulo operation to be constant time. Without this, the time varies
280 * based on the amount of padding when running on Intel chips at least.
282 * The aim of right-shifting md_size is so that the compiler doesn't
283 * figure out that it can remove div_spoiler as that would require it
284 * to prove that md_size is always even, which I hope is beyond it. */
285 div_spoiler
= md_size
>> 1;
286 div_spoiler
<<= (sizeof(div_spoiler
)-1)*8;
287 rotate_offset
= (div_spoiler
+ mac_start
- scan_start
) % md_size
;
289 memset(rotated_mac
, 0, md_size
);
290 for (i
= scan_start
; i
< rec
->orig_len
;)
292 for (j
= 0; j
< md_size
&& i
< rec
->orig_len
; i
++, j
++)
294 unsigned char mac_started
= constant_time_ge(i
, mac_start
);
295 unsigned char mac_ended
= constant_time_ge(i
, mac_end
);
298 rotated_mac
[j
] |= b
& mac_started
& ~mac_ended
;
302 /* Now rotate the MAC */
303 #if defined(CBC_MAC_ROTATE_IN_PLACE)
305 for (i
= 0; i
< md_size
; i
++)
307 unsigned char offset
= (div_spoiler
+ rotate_offset
+ i
) % md_size
;
308 out
[j
++] = rotated_mac
[offset
];
311 memset(out
, 0, md_size
);
312 for (i
= 0; i
< md_size
; i
++)
314 unsigned char offset
= (div_spoiler
+ md_size
- rotate_offset
+ i
) % md_size
;
315 for (j
= 0; j
< md_size
; j
++)
316 out
[j
] |= rotated_mac
[i
] & constant_time_eq_8(j
, offset
);
321 /* These functions serialize the state of a hash and thus perform the standard
322 * "final" operation without adding the padding and length that such a function
324 static void tls1_md5_final_raw(void* ctx
, unsigned char *md_out
)
333 static void tls1_sha1_final_raw(void* ctx
, unsigned char *md_out
)
336 l2n(sha1
->h0
, md_out
);
337 l2n(sha1
->h1
, md_out
);
338 l2n(sha1
->h2
, md_out
);
339 l2n(sha1
->h3
, md_out
);
340 l2n(sha1
->h4
, md_out
);
343 static void tls1_sha256_final_raw(void* ctx
, unsigned char *md_out
)
345 SHA256_CTX
*sha256
= ctx
;
348 for (i
= 0; i
< 8; i
++)
350 l2n(sha256
->h
[i
], md_out
);
354 static void tls1_sha512_final_raw(void* ctx
, unsigned char *md_out
)
356 SHA512_CTX
*sha512
= ctx
;
359 for (i
= 0; i
< 8; i
++)
361 l2n8(sha512
->h
[i
], md_out
);
365 /* ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
366 * which ssl3_cbc_digest_record supports. */
367 char ssl3_cbc_record_digest_supported(const EVP_MD_CTX
*ctx
)
373 switch (ctx
->digest
->type
)
387 /* ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS
390 * ctx: the EVP_MD_CTX from which we take the hash function.
391 * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX.
392 * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written.
393 * md_out_size: if non-NULL, the number of output bytes is written here.
394 * header: the 13-byte, TLS record header.
395 * data: the record data itself, less any preceeding explicit IV.
396 * data_plus_mac_size: the secret, reported length of the data and MAC
397 * once the padding has been removed.
398 * data_plus_mac_plus_padding_size: the public length of the whole
399 * record, including padding.
400 * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
402 * On entry: by virtue of having been through one of the remove_padding
403 * functions, above, we know that data_plus_mac_size is large enough to contain
404 * a padding byte and MAC. (If the padding was invalid, it might contain the
406 void ssl3_cbc_digest_record(
407 const EVP_MD_CTX
*ctx
,
408 unsigned char* md_out
,
410 const unsigned char header
[13],
411 const unsigned char *data
,
412 size_t data_plus_mac_size
,
413 size_t data_plus_mac_plus_padding_size
,
414 const unsigned char *mac_secret
,
415 unsigned mac_secret_length
,
418 union { double align
;
419 unsigned char c
[sizeof(SHA512_CTX
)]; } md_state
;
420 void (*md_final_raw
)(void *ctx
, unsigned char *md_out
);
421 void (*md_transform
)(void *ctx
, const unsigned char *block
);
422 unsigned md_size
, md_block_size
= 64;
423 unsigned sslv3_pad_length
= 40, header_length
, variance_blocks
,
424 len
, max_mac_bytes
, num_blocks
,
425 num_starting_blocks
, k
, mac_end_offset
, c
, index_a
, index_b
;
426 unsigned int bits
; /* at most 18 bits */
427 unsigned char length_bytes
[MAX_HASH_BIT_COUNT_BYTES
];
428 /* hmac_pad is the masked HMAC key. */
429 unsigned char hmac_pad
[MAX_HASH_BLOCK_SIZE
];
430 unsigned char first_block
[MAX_HASH_BLOCK_SIZE
];
431 unsigned char mac_out
[EVP_MAX_MD_SIZE
];
432 unsigned i
, j
, md_out_size_u
;
434 /* mdLengthSize is the number of bytes in the length field that terminates
436 unsigned md_length_size
= 8;
438 /* This is a, hopefully redundant, check that allows us to forget about
439 * many possible overflows later in this function. */
440 OPENSSL_assert(data_plus_mac_plus_padding_size
< 1024*1024);
442 switch (ctx
->digest
->type
)
445 MD5_Init((MD5_CTX
*)md_state
.c
);
446 md_final_raw
= tls1_md5_final_raw
;
447 md_transform
= (void(*)(void *ctx
, const unsigned char *block
)) MD5_Transform
;
449 sslv3_pad_length
= 48;
452 SHA1_Init((SHA_CTX
*)md_state
.c
);
453 md_final_raw
= tls1_sha1_final_raw
;
454 md_transform
= (void(*)(void *ctx
, const unsigned char *block
)) SHA1_Transform
;
458 SHA224_Init((SHA256_CTX
*)md_state
.c
);
459 md_final_raw
= tls1_sha256_final_raw
;
460 md_transform
= (void(*)(void *ctx
, const unsigned char *block
)) SHA256_Transform
;
464 SHA256_Init((SHA256_CTX
*)md_state
.c
);
465 md_final_raw
= tls1_sha256_final_raw
;
466 md_transform
= (void(*)(void *ctx
, const unsigned char *block
)) SHA256_Transform
;
470 SHA384_Init((SHA512_CTX
*)md_state
.c
);
471 md_final_raw
= tls1_sha512_final_raw
;
472 md_transform
= (void(*)(void *ctx
, const unsigned char *block
)) SHA512_Transform
;
478 SHA512_Init((SHA512_CTX
*)md_state
.c
);
479 md_final_raw
= tls1_sha512_final_raw
;
480 md_transform
= (void(*)(void *ctx
, const unsigned char *block
)) SHA512_Transform
;
486 /* ssl3_cbc_record_digest_supported should have been
487 * called first to check that the hash function is
495 OPENSSL_assert(md_length_size
<= MAX_HASH_BIT_COUNT_BYTES
);
496 OPENSSL_assert(md_block_size
<= MAX_HASH_BLOCK_SIZE
);
497 OPENSSL_assert(md_size
<= EVP_MAX_MD_SIZE
);
505 8 /* sequence number */ +
506 1 /* record type */ +
507 2 /* record length */;
510 /* variance_blocks is the number of blocks of the hash that we have to
511 * calculate in constant time because they could be altered by the
514 * In SSLv3, the padding must be minimal so the end of the plaintext
515 * varies by, at most, 15+20 = 35 bytes. (We conservatively assume that
516 * the MAC size varies from 0..20 bytes.) In case the 9 bytes of hash
517 * termination (0x80 + 64-bit length) don't fit in the final block, we
518 * say that the final two blocks can vary based on the padding.
520 * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
521 * required to be minimal. Therefore we say that the final six blocks
522 * can vary based on the padding.
524 * Later in the function, if the message is short and there obviously
525 * cannot be this many blocks then variance_blocks can be reduced. */
526 variance_blocks
= is_sslv3
? 2 : 6;
527 /* From now on we're dealing with the MAC, which conceptually has 13
528 * bytes of `header' before the start of the data (TLS) or 71/75 bytes
530 len
= data_plus_mac_plus_padding_size
+ header_length
;
531 /* max_mac_bytes contains the maximum bytes of bytes in the MAC, including
532 * |header|, assuming that there's no padding. */
533 max_mac_bytes
= len
- md_size
- 1;
534 /* num_blocks is the maximum number of hash blocks. */
535 num_blocks
= (max_mac_bytes
+ 1 + md_length_size
+ md_block_size
- 1) / md_block_size
;
536 /* In order to calculate the MAC in constant time we have to handle
537 * the final blocks specially because the padding value could cause the
538 * end to appear somewhere in the final |variance_blocks| blocks and we
539 * can't leak where. However, |num_starting_blocks| worth of data can
540 * be hashed right away because no padding value can affect whether
541 * they are plaintext. */
542 num_starting_blocks
= 0;
543 /* k is the starting byte offset into the conceptual header||data where
544 * we start processing. */
546 /* mac_end_offset is the index just past the end of the data to be
548 mac_end_offset
= data_plus_mac_size
+ header_length
- md_size
;
549 /* c is the index of the 0x80 byte in the final hash block that
550 * contains application data. */
551 c
= mac_end_offset
% md_block_size
;
552 /* index_a is the hash block number that contains the 0x80 terminating
554 index_a
= mac_end_offset
/ md_block_size
;
555 /* index_b is the hash block number that contains the 64-bit hash
556 * length, in bits. */
557 index_b
= (mac_end_offset
+ md_length_size
) / md_block_size
;
558 /* bits is the hash-length in bits. It includes the additional hash
559 * block for the masked HMAC key, or whole of |header| in the case of
562 /* For SSLv3, if we're going to have any starting blocks then we need
563 * at least two because the header is larger than a single block. */
564 if (num_blocks
> variance_blocks
+ (is_sslv3
? 1 : 0))
566 num_starting_blocks
= num_blocks
- variance_blocks
;
567 k
= md_block_size
*num_starting_blocks
;
570 bits
= 8*mac_end_offset
;
573 /* Compute the initial HMAC block. For SSLv3, the padding and
574 * secret bytes are included in |header| because they take more
575 * than a single block. */
576 bits
+= 8*md_block_size
;
577 memset(hmac_pad
, 0, md_block_size
);
578 OPENSSL_assert(mac_secret_length
<= sizeof(hmac_pad
));
579 memcpy(hmac_pad
, mac_secret
, mac_secret_length
);
580 for (i
= 0; i
< md_block_size
; i
++)
583 md_transform(md_state
.c
, hmac_pad
);
586 memset(length_bytes
,0,md_length_size
-4);
587 length_bytes
[md_length_size
-4] = (unsigned char)(bits
>>24);
588 length_bytes
[md_length_size
-3] = (unsigned char)(bits
>>16);
589 length_bytes
[md_length_size
-2] = (unsigned char)(bits
>>8);
590 length_bytes
[md_length_size
-1] = (unsigned char)bits
;
596 /* The SSLv3 header is larger than a single block.
597 * overhang is the number of bytes beyond a single
598 * block that the header consumes: either 7 bytes
599 * (SHA1) or 11 bytes (MD5). */
600 unsigned overhang
= header_length
-md_block_size
;
601 md_transform(md_state
.c
, header
);
602 memcpy(first_block
, header
+ md_block_size
, overhang
);
603 memcpy(first_block
+ overhang
, data
, md_block_size
-overhang
);
604 md_transform(md_state
.c
, first_block
);
605 for (i
= 1; i
< k
/md_block_size
- 1; i
++)
606 md_transform(md_state
.c
, data
+ md_block_size
*i
- overhang
);
610 /* k is a multiple of md_block_size. */
611 memcpy(first_block
, header
, 13);
612 memcpy(first_block
+13, data
, md_block_size
-13);
613 md_transform(md_state
.c
, first_block
);
614 for (i
= 1; i
< k
/md_block_size
; i
++)
615 md_transform(md_state
.c
, data
+ md_block_size
*i
- 13);
619 memset(mac_out
, 0, sizeof(mac_out
));
621 /* We now process the final hash blocks. For each block, we construct
622 * it in constant time. If the |i==index_a| then we'll include the 0x80
623 * bytes and zero pad etc. For each block we selectively copy it, in
624 * constant time, to |mac_out|. */
625 for (i
= num_starting_blocks
; i
<= num_starting_blocks
+variance_blocks
; i
++)
627 unsigned char block
[MAX_HASH_BLOCK_SIZE
];
628 unsigned char is_block_a
= constant_time_eq_8(i
, index_a
);
629 unsigned char is_block_b
= constant_time_eq_8(i
, index_b
);
630 for (j
= 0; j
< md_block_size
; j
++)
632 unsigned char b
= 0, is_past_c
, is_past_cp1
;
633 if (k
< header_length
)
635 else if (k
< data_plus_mac_plus_padding_size
+ header_length
)
636 b
= data
[k
-header_length
];
639 is_past_c
= is_block_a
& constant_time_ge(j
, c
);
640 is_past_cp1
= is_block_a
& constant_time_ge(j
, c
+1);
641 /* If this is the block containing the end of the
642 * application data, and we are at the offset for the
643 * 0x80 value, then overwrite b with 0x80. */
644 b
= (b
&~is_past_c
) | (0x80&is_past_c
);
645 /* If this the the block containing the end of the
646 * application data and we're past the 0x80 value then
647 * just write zero. */
649 /* If this is index_b (the final block), but not
650 * index_a (the end of the data), then the 64-bit
651 * length didn't fit into index_a and we're having to
652 * add an extra block of zeros. */
653 b
&= ~is_block_b
| is_block_a
;
655 /* The final bytes of one of the blocks contains the
657 if (j
>= md_block_size
- md_length_size
)
659 /* If this is index_b, write a length byte. */
660 b
= (b
&~is_block_b
) | (is_block_b
&length_bytes
[j
-(md_block_size
-md_length_size
)]);
665 md_transform(md_state
.c
, block
);
666 md_final_raw(md_state
.c
, block
);
667 /* If this is index_b, copy the hash value to |mac_out|. */
668 for (j
= 0; j
< md_size
; j
++)
669 mac_out
[j
] |= block
[j
]&is_block_b
;
672 EVP_MD_CTX_init(&md_ctx
);
673 EVP_DigestInit_ex(&md_ctx
, ctx
->digest
, NULL
/* engine */);
676 /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
677 memset(hmac_pad
, 0x5c, sslv3_pad_length
);
679 EVP_DigestUpdate(&md_ctx
, mac_secret
, mac_secret_length
);
680 EVP_DigestUpdate(&md_ctx
, hmac_pad
, sslv3_pad_length
);
681 EVP_DigestUpdate(&md_ctx
, mac_out
, md_size
);
685 /* Complete the HMAC in the standard manner. */
686 for (i
= 0; i
< md_block_size
; i
++)
689 EVP_DigestUpdate(&md_ctx
, hmac_pad
, md_block_size
);
690 EVP_DigestUpdate(&md_ctx
, mac_out
, md_size
);
692 EVP_DigestFinal(&md_ctx
, md_out
, &md_out_size_u
);
694 *md_out_size
= md_out_size_u
;
695 EVP_MD_CTX_cleanup(&md_ctx
);
700 /* Due to the need to use EVP in FIPS mode we can't reimplement digests but
701 * we can ensure the number of blocks processed is equal for all cases
702 * by digesting additional data.
705 void tls_fips_digest_extra(
706 const EVP_CIPHER_CTX
*cipher_ctx
, EVP_MD_CTX
*mac_ctx
,
707 const unsigned char *data
, size_t data_len
, size_t orig_len
)
709 size_t block_size
, digest_pad
, blocks_data
, blocks_orig
;
710 if (EVP_CIPHER_CTX_mode(cipher_ctx
) != EVP_CIPH_CBC_MODE
)
712 block_size
= EVP_MD_CTX_block_size(mac_ctx
);
713 /* We are in FIPS mode if we get this far so we know we have only SHA*
714 * digests and TLS to deal with.
715 * Minimum digest padding length is 17 for SHA384/SHA512 and 9
717 * Additional header is 13 bytes. To get the number of digest blocks
718 * processed round up the amount of data plus padding to the nearest
719 * block length. Block length is 128 for SHA384/SHA512 and 64 otherwise.
721 * blocks = (payload_len + digest_pad + 13 + block_size - 1)/block_size
723 * blocks = (payload_len + digest_pad + 12)/block_size + 1
724 * HMAC adds a constant overhead.
725 * We're ultimately only interested in differences so this becomes
726 * blocks = (payload_len + 29)/128
727 * for SHA384/SHA512 and
728 * blocks = (payload_len + 21)/64
731 digest_pad
= block_size
== 64 ? 21 : 29;
732 blocks_orig
= (orig_len
+ digest_pad
)/block_size
;
733 blocks_data
= (data_len
+ digest_pad
)/block_size
;
734 /* MAC enough blocks to make up the difference between the original
735 * and actual lengths plus one extra block to ensure this is never a
736 * no op. The "data" pointer should always have enough space to
737 * perform this operation as it is large enough for a maximum
740 EVP_DigestSignUpdate(mac_ctx
, data
,
741 (blocks_orig
- blocks_data
+ 1) * block_size
);