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).
56 #include "../crypto/constant_time_locl.h"
59 #include <openssl/md5.h>
60 #include <openssl/sha.h>
62 /* MAX_HASH_BIT_COUNT_BYTES is the maximum number of bytes in the hash's length
63 * field. (SHA-384/512 have 128-bit length.) */
64 #define MAX_HASH_BIT_COUNT_BYTES 16
66 /* MAX_HASH_BLOCK_SIZE is the maximum hash block size that we'll support.
67 * Currently SHA-384/512 has a 128-byte block size and that's the largest
68 * supported by TLS.) */
69 #define MAX_HASH_BLOCK_SIZE 128
72 * ssl3_cbc_remove_padding removes padding from the decrypted, SSLv3, CBC
73 * record in |rec| by updating |rec->length| in constant time.
75 * block_size: the block size of the cipher used to encrypt the record.
77 * 0: (in non-constant time) if the record is publicly invalid.
78 * 1: if the padding was valid
81 int ssl3_cbc_remove_padding(const SSL
* s
,
86 unsigned padding_length
, good
;
87 const unsigned overhead
= 1 /* padding length byte */ + mac_size
;
89 /* These lengths are all public so we can test them in non-constant
91 if (overhead
> rec
->length
)
94 padding_length
= rec
->data
[rec
->length
-1];
95 good
= constant_time_ge(rec
->length
, padding_length
+overhead
);
96 /* SSLv3 requires that the padding is minimal. */
97 good
&= constant_time_ge(block_size
, padding_length
+1);
98 padding_length
= good
& (padding_length
+1);
99 rec
->length
-= padding_length
;
100 rec
->type
|= padding_length
<<8; /* kludge: pass padding length */
101 return constant_time_select_int(good
, 1, -1);
105 * tls1_cbc_remove_padding removes the CBC padding from the decrypted, TLS, CBC
106 * record in |rec| in constant time and returns 1 if the padding is valid and
107 * -1 otherwise. It also removes any explicit IV from the start of the record
108 * without leaking any timing about whether there was enough space after the
109 * padding was removed.
111 * block_size: the block size of the cipher used to encrypt the record.
113 * 0: (in non-constant time) if the record is publicly invalid.
114 * 1: if the padding was valid
117 int tls1_cbc_remove_padding(const SSL
* s
,
122 unsigned padding_length
, good
, to_check
, i
;
123 const unsigned overhead
= 1 /* padding length byte */ + mac_size
;
124 /* Check if version requires explicit IV */
125 if (SSL_USE_EXPLICIT_IV(s
))
127 /* These lengths are all public so we can test them in
130 if (overhead
+ block_size
> rec
->length
)
132 /* We can now safely skip explicit IV */
133 rec
->data
+= block_size
;
134 rec
->input
+= block_size
;
135 rec
->length
-= block_size
;
137 else if (overhead
> rec
->length
)
140 padding_length
= rec
->data
[rec
->length
-1];
142 /* NB: if compression is in operation the first packet may not be of
143 * even length so the padding bug check cannot be performed. This bug
144 * workaround has been around since SSLeay so hopefully it is either
145 * fixed now or no buggy implementation supports compression [steve]
147 if ( (s
->options
&SSL_OP_TLS_BLOCK_PADDING_BUG
) && !s
->expand
)
149 /* First packet is even in size, so check */
150 if ((memcmp(s
->s3
->read_sequence
, "\0\0\0\0\0\0\0\0",8) == 0) &&
151 !(padding_length
& 1))
153 s
->s3
->flags
|=TLS1_FLAGS_TLS_PADDING_BUG
;
155 if ((s
->s3
->flags
& TLS1_FLAGS_TLS_PADDING_BUG
) &&
162 if (EVP_CIPHER_flags(s
->enc_read_ctx
->cipher
)&EVP_CIPH_FLAG_AEAD_CIPHER
)
164 /* padding is already verified */
165 rec
->length
-= padding_length
+ 1;
169 good
= constant_time_ge(rec
->length
, overhead
+padding_length
);
170 /* The padding consists of a length byte at the end of the record and
171 * then that many bytes of padding, all with the same value as the
172 * length byte. Thus, with the length byte included, there are i+1
175 * We can't check just |padding_length+1| bytes because that leaks
176 * decrypted information. Therefore we always have to check the maximum
177 * amount of padding possible. (Again, the length of the record is
178 * public information so we can use it.) */
179 to_check
= 255; /* maximum amount of padding. */
180 if (to_check
> rec
->length
-1)
181 to_check
= rec
->length
-1;
183 for (i
= 0; i
< to_check
; i
++)
185 unsigned char mask
= constant_time_ge_8(padding_length
, i
);
186 unsigned char b
= rec
->data
[rec
->length
-1-i
];
187 /* The final |padding_length+1| bytes should all have the value
188 * |padding_length|. Therefore the XOR should be zero. */
189 good
&= ~(mask
&(padding_length
^ b
));
192 /* If any of the final |padding_length+1| bytes had the wrong value,
193 * one or more of the lower eight bits of |good| will be cleared.
195 good
= constant_time_eq(0xff, good
& 0xff);
196 padding_length
= good
& (padding_length
+1);
197 rec
->length
-= padding_length
;
198 rec
->type
|= padding_length
<<8; /* kludge: pass padding length */
200 return constant_time_select_int(good
, 1, -1);
204 * ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in
205 * constant time (independent of the concrete value of rec->length, which may
206 * vary within a 256-byte window).
208 * ssl3_cbc_remove_padding or tls1_cbc_remove_padding must be called prior to
212 * rec->orig_len >= md_size
213 * md_size <= EVP_MAX_MD_SIZE
215 * If CBC_MAC_ROTATE_IN_PLACE is defined then the rotation is performed with
216 * variable accesses in a 64-byte-aligned buffer. Assuming that this fits into
217 * a single or pair of cache-lines, then the variable memory accesses don't
218 * actually affect the timing. CPUs with smaller cache-lines [if any] are
219 * not multi-core and are not considered vulnerable to cache-timing attacks.
221 #define CBC_MAC_ROTATE_IN_PLACE
223 void ssl3_cbc_copy_mac(unsigned char* out
,
224 const SSL3_RECORD
*rec
,
225 unsigned md_size
,unsigned orig_len
)
227 #if defined(CBC_MAC_ROTATE_IN_PLACE)
228 unsigned char rotated_mac_buf
[64+EVP_MAX_MD_SIZE
];
229 unsigned char *rotated_mac
;
231 unsigned char rotated_mac
[EVP_MAX_MD_SIZE
];
234 /* mac_end is the index of |rec->data| just after the end of the MAC. */
235 unsigned mac_end
= rec
->length
;
236 unsigned mac_start
= mac_end
- md_size
;
237 /* scan_start contains the number of bytes that we can ignore because
238 * the MAC's position can only vary by 255 bytes. */
239 unsigned scan_start
= 0;
241 unsigned div_spoiler
;
242 unsigned rotate_offset
;
244 OPENSSL_assert(orig_len
>= md_size
);
245 OPENSSL_assert(md_size
<= EVP_MAX_MD_SIZE
);
247 #if defined(CBC_MAC_ROTATE_IN_PLACE)
248 rotated_mac
= rotated_mac_buf
+ ((0-(size_t)rotated_mac_buf
)&63);
251 /* This information is public so it's safe to branch based on it. */
252 if (orig_len
> md_size
+ 255 + 1)
253 scan_start
= orig_len
- (md_size
+ 255 + 1);
254 /* div_spoiler contains a multiple of md_size that is used to cause the
255 * modulo operation to be constant time. Without this, the time varies
256 * based on the amount of padding when running on Intel chips at least.
258 * The aim of right-shifting md_size is so that the compiler doesn't
259 * figure out that it can remove div_spoiler as that would require it
260 * to prove that md_size is always even, which I hope is beyond it. */
261 div_spoiler
= md_size
>> 1;
262 div_spoiler
<<= (sizeof(div_spoiler
)-1)*8;
263 rotate_offset
= (div_spoiler
+ mac_start
- scan_start
) % md_size
;
265 memset(rotated_mac
, 0, md_size
);
266 for (i
= scan_start
, j
= 0; i
< orig_len
; i
++)
268 unsigned char mac_started
= constant_time_ge_8(i
, mac_start
);
269 unsigned char mac_ended
= constant_time_ge_8(i
, mac_end
);
270 unsigned char b
= rec
->data
[i
];
271 rotated_mac
[j
++] |= b
& mac_started
& ~mac_ended
;
272 j
&= constant_time_lt(j
,md_size
);
275 /* Now rotate the MAC */
276 #if defined(CBC_MAC_ROTATE_IN_PLACE)
278 for (i
= 0; i
< md_size
; i
++)
280 /* in case cache-line is 32 bytes, touch second line */
281 ((volatile unsigned char *)rotated_mac
)[rotate_offset
^32];
282 out
[j
++] = rotated_mac
[rotate_offset
++];
283 rotate_offset
&= constant_time_lt(rotate_offset
,md_size
);
286 memset(out
, 0, md_size
);
287 rotate_offset
= md_size
- rotate_offset
;
288 rotate_offset
&= constant_time_lt(rotate_offset
,md_size
);
289 for (i
= 0; i
< md_size
; i
++)
291 for (j
= 0; j
< md_size
; j
++)
292 out
[j
] |= rotated_mac
[i
] & constant_time_eq_8(j
, rotate_offset
);
294 rotate_offset
&= constant_time_lt(rotate_offset
,md_size
);
299 /* u32toLE serialises an unsigned, 32-bit number (n) as four bytes at (p) in
300 * little-endian order. The value of p is advanced by four. */
301 #define u32toLE(n, p) \
302 (*((p)++)=(unsigned char)(n), \
303 *((p)++)=(unsigned char)(n>>8), \
304 *((p)++)=(unsigned char)(n>>16), \
305 *((p)++)=(unsigned char)(n>>24))
307 /* These functions serialize the state of a hash and thus perform the standard
308 * "final" operation without adding the padding and length that such a function
310 static void tls1_md5_final_raw(void* ctx
, unsigned char *md_out
)
313 u32toLE(md5
->A
, md_out
);
314 u32toLE(md5
->B
, md_out
);
315 u32toLE(md5
->C
, md_out
);
316 u32toLE(md5
->D
, md_out
);
319 static void tls1_sha1_final_raw(void* ctx
, unsigned char *md_out
)
322 l2n(sha1
->h0
, md_out
);
323 l2n(sha1
->h1
, md_out
);
324 l2n(sha1
->h2
, md_out
);
325 l2n(sha1
->h3
, md_out
);
326 l2n(sha1
->h4
, md_out
);
328 #define LARGEST_DIGEST_CTX SHA_CTX
330 #ifndef OPENSSL_NO_SHA256
331 static void tls1_sha256_final_raw(void* ctx
, unsigned char *md_out
)
333 SHA256_CTX
*sha256
= ctx
;
336 for (i
= 0; i
< 8; i
++)
338 l2n(sha256
->h
[i
], md_out
);
341 #undef LARGEST_DIGEST_CTX
342 #define LARGEST_DIGEST_CTX SHA256_CTX
345 #ifndef OPENSSL_NO_SHA512
346 static void tls1_sha512_final_raw(void* ctx
, unsigned char *md_out
)
348 SHA512_CTX
*sha512
= ctx
;
351 for (i
= 0; i
< 8; i
++)
353 l2n8(sha512
->h
[i
], md_out
);
356 #undef LARGEST_DIGEST_CTX
357 #define LARGEST_DIGEST_CTX SHA512_CTX
360 /* ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
361 * which ssl3_cbc_digest_record supports. */
362 char ssl3_cbc_record_digest_supported(const EVP_MD_CTX
*ctx
)
368 switch (EVP_MD_CTX_type(ctx
))
372 #ifndef OPENSSL_NO_SHA256
376 #ifndef OPENSSL_NO_SHA512
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
407 void ssl3_cbc_digest_record(
408 const EVP_MD_CTX
*ctx
,
409 unsigned char* md_out
,
411 const unsigned char header
[13],
412 const unsigned char *data
,
413 size_t data_plus_mac_size
,
414 size_t data_plus_mac_plus_padding_size
,
415 const unsigned char *mac_secret
,
416 unsigned mac_secret_length
,
419 union { double align
;
420 unsigned char c
[sizeof(LARGEST_DIGEST_CTX
)]; } md_state
;
421 void (*md_final_raw
)(void *ctx
, unsigned char *md_out
);
422 void (*md_transform
)(void *ctx
, const unsigned char *block
);
423 unsigned md_size
, md_block_size
= 64;
424 unsigned sslv3_pad_length
= 40, header_length
, variance_blocks
,
425 len
, max_mac_bytes
, num_blocks
,
426 num_starting_blocks
, k
, mac_end_offset
, c
, index_a
, index_b
;
427 unsigned int bits
; /* at most 18 bits */
428 unsigned char length_bytes
[MAX_HASH_BIT_COUNT_BYTES
];
429 /* hmac_pad is the masked HMAC key. */
430 unsigned char hmac_pad
[MAX_HASH_BLOCK_SIZE
];
431 unsigned char first_block
[MAX_HASH_BLOCK_SIZE
];
432 unsigned char mac_out
[EVP_MAX_MD_SIZE
];
433 unsigned i
, j
, md_out_size_u
;
435 /* mdLengthSize is the number of bytes in the length field that terminates
437 unsigned md_length_size
= 8;
438 char length_is_big_endian
= 1;
440 /* This is a, hopefully redundant, check that allows us to forget about
441 * many possible overflows later in this function. */
442 OPENSSL_assert(data_plus_mac_plus_padding_size
< 1024*1024);
444 switch (EVP_MD_CTX_type(ctx
))
447 MD5_Init((MD5_CTX
*)md_state
.c
);
448 md_final_raw
= tls1_md5_final_raw
;
449 md_transform
= (void(*)(void *ctx
, const unsigned char *block
)) MD5_Transform
;
451 sslv3_pad_length
= 48;
452 length_is_big_endian
= 0;
455 SHA1_Init((SHA_CTX
*)md_state
.c
);
456 md_final_raw
= tls1_sha1_final_raw
;
457 md_transform
= (void(*)(void *ctx
, const unsigned char *block
)) SHA1_Transform
;
460 #ifndef OPENSSL_NO_SHA256
462 SHA224_Init((SHA256_CTX
*)md_state
.c
);
463 md_final_raw
= tls1_sha256_final_raw
;
464 md_transform
= (void(*)(void *ctx
, const unsigned char *block
)) SHA256_Transform
;
468 SHA256_Init((SHA256_CTX
*)md_state
.c
);
469 md_final_raw
= tls1_sha256_final_raw
;
470 md_transform
= (void(*)(void *ctx
, const unsigned char *block
)) SHA256_Transform
;
474 #ifndef OPENSSL_NO_SHA512
476 SHA384_Init((SHA512_CTX
*)md_state
.c
);
477 md_final_raw
= tls1_sha512_final_raw
;
478 md_transform
= (void(*)(void *ctx
, const unsigned char *block
)) SHA512_Transform
;
484 SHA512_Init((SHA512_CTX
*)md_state
.c
);
485 md_final_raw
= tls1_sha512_final_raw
;
486 md_transform
= (void(*)(void *ctx
, const unsigned char *block
)) SHA512_Transform
;
493 /* ssl3_cbc_record_digest_supported should have been
494 * called first to check that the hash function is
502 OPENSSL_assert(md_length_size
<= MAX_HASH_BIT_COUNT_BYTES
);
503 OPENSSL_assert(md_block_size
<= MAX_HASH_BLOCK_SIZE
);
504 OPENSSL_assert(md_size
<= EVP_MAX_MD_SIZE
);
512 8 /* sequence number */ +
513 1 /* record type */ +
514 2 /* record length */;
517 /* variance_blocks is the number of blocks of the hash that we have to
518 * calculate in constant time because they could be altered by the
521 * In SSLv3, the padding must be minimal so the end of the plaintext
522 * varies by, at most, 15+20 = 35 bytes. (We conservatively assume that
523 * the MAC size varies from 0..20 bytes.) In case the 9 bytes of hash
524 * termination (0x80 + 64-bit length) don't fit in the final block, we
525 * say that the final two blocks can vary based on the padding.
527 * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
528 * required to be minimal. Therefore we say that the final six blocks
529 * can vary based on the padding.
531 * Later in the function, if the message is short and there obviously
532 * cannot be this many blocks then variance_blocks can be reduced. */
533 variance_blocks
= is_sslv3
? 2 : 6;
534 /* From now on we're dealing with the MAC, which conceptually has 13
535 * bytes of `header' before the start of the data (TLS) or 71/75 bytes
537 len
= data_plus_mac_plus_padding_size
+ header_length
;
538 /* max_mac_bytes contains the maximum bytes of bytes in the MAC, including
539 * |header|, assuming that there's no padding. */
540 max_mac_bytes
= len
- md_size
- 1;
541 /* num_blocks is the maximum number of hash blocks. */
542 num_blocks
= (max_mac_bytes
+ 1 + md_length_size
+ md_block_size
- 1) / md_block_size
;
543 /* In order to calculate the MAC in constant time we have to handle
544 * the final blocks specially because the padding value could cause the
545 * end to appear somewhere in the final |variance_blocks| blocks and we
546 * can't leak where. However, |num_starting_blocks| worth of data can
547 * be hashed right away because no padding value can affect whether
548 * they are plaintext. */
549 num_starting_blocks
= 0;
550 /* k is the starting byte offset into the conceptual header||data where
551 * we start processing. */
553 /* mac_end_offset is the index just past the end of the data to be
555 mac_end_offset
= data_plus_mac_size
+ header_length
- md_size
;
556 /* c is the index of the 0x80 byte in the final hash block that
557 * contains application data. */
558 c
= mac_end_offset
% md_block_size
;
559 /* index_a is the hash block number that contains the 0x80 terminating
561 index_a
= mac_end_offset
/ md_block_size
;
562 /* index_b is the hash block number that contains the 64-bit hash
563 * length, in bits. */
564 index_b
= (mac_end_offset
+ md_length_size
) / md_block_size
;
565 /* bits is the hash-length in bits. It includes the additional hash
566 * block for the masked HMAC key, or whole of |header| in the case of
569 /* For SSLv3, if we're going to have any starting blocks then we need
570 * at least two because the header is larger than a single block. */
571 if (num_blocks
> variance_blocks
+ (is_sslv3
? 1 : 0))
573 num_starting_blocks
= num_blocks
- variance_blocks
;
574 k
= md_block_size
*num_starting_blocks
;
577 bits
= 8*mac_end_offset
;
580 /* Compute the initial HMAC block. For SSLv3, the padding and
581 * secret bytes are included in |header| because they take more
582 * than a single block. */
583 bits
+= 8*md_block_size
;
584 memset(hmac_pad
, 0, md_block_size
);
585 OPENSSL_assert(mac_secret_length
<= sizeof(hmac_pad
));
586 memcpy(hmac_pad
, mac_secret
, mac_secret_length
);
587 for (i
= 0; i
< md_block_size
; i
++)
590 md_transform(md_state
.c
, hmac_pad
);
593 if (length_is_big_endian
)
595 memset(length_bytes
,0,md_length_size
-4);
596 length_bytes
[md_length_size
-4] = (unsigned char)(bits
>>24);
597 length_bytes
[md_length_size
-3] = (unsigned char)(bits
>>16);
598 length_bytes
[md_length_size
-2] = (unsigned char)(bits
>>8);
599 length_bytes
[md_length_size
-1] = (unsigned char)bits
;
603 memset(length_bytes
,0,md_length_size
);
604 length_bytes
[md_length_size
-5] = (unsigned char)(bits
>>24);
605 length_bytes
[md_length_size
-6] = (unsigned char)(bits
>>16);
606 length_bytes
[md_length_size
-7] = (unsigned char)(bits
>>8);
607 length_bytes
[md_length_size
-8] = (unsigned char)bits
;
614 /* The SSLv3 header is larger than a single block.
615 * overhang is the number of bytes beyond a single
616 * block that the header consumes: either 7 bytes
617 * (SHA1) or 11 bytes (MD5). */
618 unsigned overhang
= header_length
-md_block_size
;
619 md_transform(md_state
.c
, header
);
620 memcpy(first_block
, header
+ md_block_size
, overhang
);
621 memcpy(first_block
+ overhang
, data
, md_block_size
-overhang
);
622 md_transform(md_state
.c
, first_block
);
623 for (i
= 1; i
< k
/md_block_size
- 1; i
++)
624 md_transform(md_state
.c
, data
+ md_block_size
*i
- overhang
);
628 /* k is a multiple of md_block_size. */
629 memcpy(first_block
, header
, 13);
630 memcpy(first_block
+13, data
, md_block_size
-13);
631 md_transform(md_state
.c
, first_block
);
632 for (i
= 1; i
< k
/md_block_size
; i
++)
633 md_transform(md_state
.c
, data
+ md_block_size
*i
- 13);
637 memset(mac_out
, 0, sizeof(mac_out
));
639 /* We now process the final hash blocks. For each block, we construct
640 * it in constant time. If the |i==index_a| then we'll include the 0x80
641 * bytes and zero pad etc. For each block we selectively copy it, in
642 * constant time, to |mac_out|. */
643 for (i
= num_starting_blocks
; i
<= num_starting_blocks
+variance_blocks
; i
++)
645 unsigned char block
[MAX_HASH_BLOCK_SIZE
];
646 unsigned char is_block_a
= constant_time_eq_8(i
, index_a
);
647 unsigned char is_block_b
= constant_time_eq_8(i
, index_b
);
648 for (j
= 0; j
< md_block_size
; j
++)
650 unsigned char b
= 0, is_past_c
, is_past_cp1
;
651 if (k
< header_length
)
653 else if (k
< data_plus_mac_plus_padding_size
+ header_length
)
654 b
= data
[k
-header_length
];
657 is_past_c
= is_block_a
& constant_time_ge_8(j
, c
);
658 is_past_cp1
= is_block_a
& constant_time_ge_8(j
, c
+1);
659 /* If this is the block containing the end of the
660 * application data, and we are at the offset for the
661 * 0x80 value, then overwrite b with 0x80. */
662 b
= constant_time_select_8(is_past_c
, 0x80, b
);
663 /* If this the the block containing the end of the
664 * application data and we're past the 0x80 value then
665 * just write zero. */
667 /* If this is index_b (the final block), but not
668 * index_a (the end of the data), then the 64-bit
669 * length didn't fit into index_a and we're having to
670 * add an extra block of zeros. */
671 b
&= ~is_block_b
| is_block_a
;
673 /* The final bytes of one of the blocks contains the
675 if (j
>= md_block_size
- md_length_size
)
677 /* If this is index_b, write a length byte. */
678 b
= constant_time_select_8(
679 is_block_b
, length_bytes
[j
-(md_block_size
-md_length_size
)], b
);
684 md_transform(md_state
.c
, block
);
685 md_final_raw(md_state
.c
, block
);
686 /* If this is index_b, copy the hash value to |mac_out|. */
687 for (j
= 0; j
< md_size
; j
++)
688 mac_out
[j
] |= block
[j
]&is_block_b
;
691 EVP_MD_CTX_init(&md_ctx
);
692 EVP_DigestInit_ex(&md_ctx
, ctx
->digest
, NULL
/* engine */);
695 /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
696 memset(hmac_pad
, 0x5c, sslv3_pad_length
);
698 EVP_DigestUpdate(&md_ctx
, mac_secret
, mac_secret_length
);
699 EVP_DigestUpdate(&md_ctx
, hmac_pad
, sslv3_pad_length
);
700 EVP_DigestUpdate(&md_ctx
, mac_out
, md_size
);
704 /* Complete the HMAC in the standard manner. */
705 for (i
= 0; i
< md_block_size
; i
++)
708 EVP_DigestUpdate(&md_ctx
, hmac_pad
, md_block_size
);
709 EVP_DigestUpdate(&md_ctx
, mac_out
, md_size
);
711 EVP_DigestFinal(&md_ctx
, md_out
, &md_out_size_u
);
713 *md_out_size
= md_out_size_u
;
714 EVP_MD_CTX_cleanup(&md_ctx
);
719 /* Due to the need to use EVP in FIPS mode we can't reimplement digests but
720 * we can ensure the number of blocks processed is equal for all cases
721 * by digesting additional data.
724 void tls_fips_digest_extra(
725 const EVP_CIPHER_CTX
*cipher_ctx
, EVP_MD_CTX
*mac_ctx
,
726 const unsigned char *data
, size_t data_len
, size_t orig_len
)
728 size_t block_size
, digest_pad
, blocks_data
, blocks_orig
;
729 if (EVP_CIPHER_CTX_mode(cipher_ctx
) != EVP_CIPH_CBC_MODE
)
731 block_size
= EVP_MD_CTX_block_size(mac_ctx
);
732 /* We are in FIPS mode if we get this far so we know we have only SHA*
733 * digests and TLS to deal with.
734 * Minimum digest padding length is 17 for SHA384/SHA512 and 9
736 * Additional header is 13 bytes. To get the number of digest blocks
737 * processed round up the amount of data plus padding to the nearest
738 * block length. Block length is 128 for SHA384/SHA512 and 64 otherwise.
740 * blocks = (payload_len + digest_pad + 13 + block_size - 1)/block_size
742 * blocks = (payload_len + digest_pad + 12)/block_size + 1
743 * HMAC adds a constant overhead.
744 * We're ultimately only interested in differences so this becomes
745 * blocks = (payload_len + 29)/128
746 * for SHA384/SHA512 and
747 * blocks = (payload_len + 21)/64
750 digest_pad
= block_size
== 64 ? 21 : 29;
751 blocks_orig
= (orig_len
+ digest_pad
)/block_size
;
752 blocks_data
= (data_len
+ digest_pad
)/block_size
;
753 /* MAC enough blocks to make up the difference between the original
754 * and actual lengths plus one extra block to ensure this is never a
755 * no op. The "data" pointer should always have enough space to
756 * perform this operation as it is large enough for a maximum
759 EVP_DigestSignUpdate(mac_ctx
, data
,
760 (blocks_orig
- blocks_data
+ 1) * block_size
);