2 * Copyright 2012-2020 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the Apache License 2.0 (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
11 * This file has no dependencies on the rest of libssl because it is shared
12 * with the providers. It contains functions for low level MAC calculations.
13 * Responsibility for this lies with the HMAC implementation in the
14 * providers. However there are legacy code paths in libssl which also need to
15 * do this. In time those legacy code paths can be removed and this file can be
16 * moved out of libssl.
21 * MD5 and SHA-1 low level APIs are deprecated for public use, but still ok for
24 #include "internal/deprecated.h"
26 #include "internal/constant_time.h"
27 #include "internal/cryptlib.h"
29 #include <openssl/evp.h>
30 #include <openssl/md5.h>
31 #include <openssl/sha.h>
33 char ssl3_cbc_record_digest_supported(const EVP_MD_CTX
*ctx
);
34 int ssl3_cbc_digest_record(const EVP_MD
*md
,
35 unsigned char *md_out
,
37 const unsigned char header
[13],
38 const unsigned char *data
,
39 size_t data_plus_mac_size
,
40 size_t data_plus_mac_plus_padding_size
,
41 const unsigned char *mac_secret
,
42 size_t mac_secret_length
, char is_sslv3
);
44 # define l2n(l,c) (*((c)++)=(unsigned char)(((l)>>24)&0xff), \
45 *((c)++)=(unsigned char)(((l)>>16)&0xff), \
46 *((c)++)=(unsigned char)(((l)>> 8)&0xff), \
47 *((c)++)=(unsigned char)(((l) )&0xff))
49 # define l2n6(l,c) (*((c)++)=(unsigned char)(((l)>>40)&0xff), \
50 *((c)++)=(unsigned char)(((l)>>32)&0xff), \
51 *((c)++)=(unsigned char)(((l)>>24)&0xff), \
52 *((c)++)=(unsigned char)(((l)>>16)&0xff), \
53 *((c)++)=(unsigned char)(((l)>> 8)&0xff), \
54 *((c)++)=(unsigned char)(((l) )&0xff))
56 # define l2n8(l,c) (*((c)++)=(unsigned char)(((l)>>56)&0xff), \
57 *((c)++)=(unsigned char)(((l)>>48)&0xff), \
58 *((c)++)=(unsigned char)(((l)>>40)&0xff), \
59 *((c)++)=(unsigned char)(((l)>>32)&0xff), \
60 *((c)++)=(unsigned char)(((l)>>24)&0xff), \
61 *((c)++)=(unsigned char)(((l)>>16)&0xff), \
62 *((c)++)=(unsigned char)(((l)>> 8)&0xff), \
63 *((c)++)=(unsigned char)(((l) )&0xff))
66 * MAX_HASH_BIT_COUNT_BYTES is the maximum number of bytes in the hash's
67 * length field. (SHA-384/512 have 128-bit length.)
69 #define MAX_HASH_BIT_COUNT_BYTES 16
72 * MAX_HASH_BLOCK_SIZE is the maximum hash block size that we'll support.
73 * Currently SHA-384/512 has a 128-byte block size and that's the largest
76 #define MAX_HASH_BLOCK_SIZE 128
79 * u32toLE serializes an unsigned, 32-bit number (n) as four bytes at (p) in
80 * little-endian order. The value of p is advanced by four.
82 #define u32toLE(n, p) \
83 (*((p)++)=(unsigned char)(n), \
84 *((p)++)=(unsigned char)(n>>8), \
85 *((p)++)=(unsigned char)(n>>16), \
86 *((p)++)=(unsigned char)(n>>24))
89 * These functions serialize the state of a hash and thus perform the
90 * standard "final" operation without adding the padding and length that such
91 * a function typically does.
93 static void tls1_md5_final_raw(void *ctx
, unsigned char *md_out
)
96 u32toLE(md5
->A
, md_out
);
97 u32toLE(md5
->B
, md_out
);
98 u32toLE(md5
->C
, md_out
);
99 u32toLE(md5
->D
, md_out
);
102 static void tls1_sha1_final_raw(void *ctx
, unsigned char *md_out
)
105 l2n(sha1
->h0
, md_out
);
106 l2n(sha1
->h1
, md_out
);
107 l2n(sha1
->h2
, md_out
);
108 l2n(sha1
->h3
, md_out
);
109 l2n(sha1
->h4
, md_out
);
112 static void tls1_sha256_final_raw(void *ctx
, unsigned char *md_out
)
114 SHA256_CTX
*sha256
= ctx
;
117 for (i
= 0; i
< 8; i
++) {
118 l2n(sha256
->h
[i
], md_out
);
122 static void tls1_sha512_final_raw(void *ctx
, unsigned char *md_out
)
124 SHA512_CTX
*sha512
= ctx
;
127 for (i
= 0; i
< 8; i
++) {
128 l2n8(sha512
->h
[i
], md_out
);
132 #undef LARGEST_DIGEST_CTX
133 #define LARGEST_DIGEST_CTX SHA512_CTX
136 * ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
137 * which ssl3_cbc_digest_record supports.
139 char ssl3_cbc_record_digest_supported(const EVP_MD_CTX
*ctx
)
141 switch (EVP_MD_CTX_type(ctx
)) {
155 * ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS
158 * ctx: the EVP_MD_CTX from which we take the hash function.
159 * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX.
160 * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written.
161 * md_out_size: if non-NULL, the number of output bytes is written here.
162 * header: the 13-byte, TLS record header.
163 * data: the record data itself, less any preceding explicit IV.
164 * data_plus_mac_size: the secret, reported length of the data and MAC
165 * once the padding has been removed.
166 * data_plus_mac_plus_padding_size: the public length of the whole
167 * record, including padding.
168 * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
170 * On entry: by virtue of having been through one of the remove_padding
171 * functions, above, we know that data_plus_mac_size is large enough to contain
172 * a padding byte and MAC. (If the padding was invalid, it might contain the
174 * Returns 1 on success or 0 on error
176 int ssl3_cbc_digest_record(const EVP_MD
*md
,
177 unsigned char *md_out
,
179 const unsigned char header
[13],
180 const unsigned char *data
,
181 size_t data_plus_mac_size
,
182 size_t data_plus_mac_plus_padding_size
,
183 const unsigned char *mac_secret
,
184 size_t mac_secret_length
, char is_sslv3
)
188 unsigned char c
[sizeof(LARGEST_DIGEST_CTX
)];
190 void (*md_final_raw
) (void *ctx
, unsigned char *md_out
);
191 void (*md_transform
) (void *ctx
, const unsigned char *block
);
192 size_t md_size
, md_block_size
= 64;
193 size_t sslv3_pad_length
= 40, header_length
, variance_blocks
,
194 len
, max_mac_bytes
, num_blocks
,
195 num_starting_blocks
, k
, mac_end_offset
, c
, index_a
, index_b
;
196 size_t bits
; /* at most 18 bits */
197 unsigned char length_bytes
[MAX_HASH_BIT_COUNT_BYTES
];
198 /* hmac_pad is the masked HMAC key. */
199 unsigned char hmac_pad
[MAX_HASH_BLOCK_SIZE
];
200 unsigned char first_block
[MAX_HASH_BLOCK_SIZE
];
201 unsigned char mac_out
[EVP_MAX_MD_SIZE
];
203 unsigned md_out_size_u
;
204 EVP_MD_CTX
*md_ctx
= NULL
;
206 * mdLengthSize is the number of bytes in the length field that
207 * terminates * the hash.
209 size_t md_length_size
= 8;
210 char length_is_big_endian
= 1;
214 * This is a, hopefully redundant, check that allows us to forget about
215 * many possible overflows later in this function.
217 if (!ossl_assert(data_plus_mac_plus_padding_size
< 1024 * 1024))
220 switch (EVP_MD_type(md
)) {
222 if (MD5_Init((MD5_CTX
*)md_state
.c
) <= 0)
224 md_final_raw
= tls1_md5_final_raw
;
226 (void (*)(void *ctx
, const unsigned char *block
))MD5_Transform
;
228 sslv3_pad_length
= 48;
229 length_is_big_endian
= 0;
232 if (SHA1_Init((SHA_CTX
*)md_state
.c
) <= 0)
234 md_final_raw
= tls1_sha1_final_raw
;
236 (void (*)(void *ctx
, const unsigned char *block
))SHA1_Transform
;
240 if (SHA224_Init((SHA256_CTX
*)md_state
.c
) <= 0)
242 md_final_raw
= tls1_sha256_final_raw
;
244 (void (*)(void *ctx
, const unsigned char *block
))SHA256_Transform
;
248 if (SHA256_Init((SHA256_CTX
*)md_state
.c
) <= 0)
250 md_final_raw
= tls1_sha256_final_raw
;
252 (void (*)(void *ctx
, const unsigned char *block
))SHA256_Transform
;
256 if (SHA384_Init((SHA512_CTX
*)md_state
.c
) <= 0)
258 md_final_raw
= tls1_sha512_final_raw
;
260 (void (*)(void *ctx
, const unsigned char *block
))SHA512_Transform
;
266 if (SHA512_Init((SHA512_CTX
*)md_state
.c
) <= 0)
268 md_final_raw
= tls1_sha512_final_raw
;
270 (void (*)(void *ctx
, const unsigned char *block
))SHA512_Transform
;
277 * ssl3_cbc_record_digest_supported should have been called first to
278 * check that the hash function is supported.
280 if (md_out_size
!= NULL
)
282 return ossl_assert(0);
285 if (!ossl_assert(md_length_size
<= MAX_HASH_BIT_COUNT_BYTES
)
286 || !ossl_assert(md_block_size
<= MAX_HASH_BLOCK_SIZE
)
287 || !ossl_assert(md_size
<= EVP_MAX_MD_SIZE
))
292 header_length
= mac_secret_length
+ sslv3_pad_length
+ 8 /* sequence
294 1 /* record type */ +
295 2 /* record length */ ;
299 * variance_blocks is the number of blocks of the hash that we have to
300 * calculate in constant time because they could be altered by the
301 * padding value. In SSLv3, the padding must be minimal so the end of
302 * the plaintext varies by, at most, 15+20 = 35 bytes. (We conservatively
303 * assume that the MAC size varies from 0..20 bytes.) In case the 9 bytes
304 * of hash termination (0x80 + 64-bit length) don't fit in the final
305 * block, we say that the final two blocks can vary based on the padding.
306 * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
307 * required to be minimal. Therefore we say that the final |variance_blocks|
309 * vary based on the padding. Later in the function, if the message is
310 * short and there obviously cannot be this many blocks then
311 * variance_blocks can be reduced.
313 variance_blocks
= is_sslv3
? 2 : ( ((255 + 1 + md_size
+ md_block_size
- 1) / md_block_size
) + 1);
315 * From now on we're dealing with the MAC, which conceptually has 13
316 * bytes of `header' before the start of the data (TLS) or 71/75 bytes
319 len
= data_plus_mac_plus_padding_size
+ header_length
;
321 * max_mac_bytes contains the maximum bytes of bytes in the MAC,
322 * including * |header|, assuming that there's no padding.
324 max_mac_bytes
= len
- md_size
- 1;
325 /* num_blocks is the maximum number of hash blocks. */
327 (max_mac_bytes
+ 1 + md_length_size
+ md_block_size
-
330 * In order to calculate the MAC in constant time we have to handle the
331 * final blocks specially because the padding value could cause the end
332 * to appear somewhere in the final |variance_blocks| blocks and we can't
333 * leak where. However, |num_starting_blocks| worth of data can be hashed
334 * right away because no padding value can affect whether they are
337 num_starting_blocks
= 0;
339 * k is the starting byte offset into the conceptual header||data where
340 * we start processing.
344 * mac_end_offset is the index just past the end of the data to be MACed.
346 mac_end_offset
= data_plus_mac_size
+ header_length
- md_size
;
348 * c is the index of the 0x80 byte in the final hash block that contains
351 c
= mac_end_offset
% md_block_size
;
353 * index_a is the hash block number that contains the 0x80 terminating
356 index_a
= mac_end_offset
/ md_block_size
;
358 * index_b is the hash block number that contains the 64-bit hash length,
361 index_b
= (mac_end_offset
+ md_length_size
) / md_block_size
;
363 * bits is the hash-length in bits. It includes the additional hash block
364 * for the masked HMAC key, or whole of |header| in the case of SSLv3.
368 * For SSLv3, if we're going to have any starting blocks then we need at
369 * least two because the header is larger than a single block.
371 if (num_blocks
> variance_blocks
+ (is_sslv3
? 1 : 0)) {
372 num_starting_blocks
= num_blocks
- variance_blocks
;
373 k
= md_block_size
* num_starting_blocks
;
376 bits
= 8 * mac_end_offset
;
379 * Compute the initial HMAC block. For SSLv3, the padding and secret
380 * bytes are included in |header| because they take more than a
383 bits
+= 8 * md_block_size
;
384 memset(hmac_pad
, 0, md_block_size
);
385 if (!ossl_assert(mac_secret_length
<= sizeof(hmac_pad
)))
387 memcpy(hmac_pad
, mac_secret
, mac_secret_length
);
388 for (i
= 0; i
< md_block_size
; i
++)
391 md_transform(md_state
.c
, hmac_pad
);
394 if (length_is_big_endian
) {
395 memset(length_bytes
, 0, md_length_size
- 4);
396 length_bytes
[md_length_size
- 4] = (unsigned char)(bits
>> 24);
397 length_bytes
[md_length_size
- 3] = (unsigned char)(bits
>> 16);
398 length_bytes
[md_length_size
- 2] = (unsigned char)(bits
>> 8);
399 length_bytes
[md_length_size
- 1] = (unsigned char)bits
;
401 memset(length_bytes
, 0, md_length_size
);
402 length_bytes
[md_length_size
- 5] = (unsigned char)(bits
>> 24);
403 length_bytes
[md_length_size
- 6] = (unsigned char)(bits
>> 16);
404 length_bytes
[md_length_size
- 7] = (unsigned char)(bits
>> 8);
405 length_bytes
[md_length_size
- 8] = (unsigned char)bits
;
413 * The SSLv3 header is larger than a single block. overhang is
414 * the number of bytes beyond a single block that the header
415 * consumes: either 7 bytes (SHA1) or 11 bytes (MD5). There are no
416 * ciphersuites in SSLv3 that are not SHA1 or MD5 based and
417 * therefore we can be confident that the header_length will be
418 * greater than |md_block_size|. However we add a sanity check just
421 if (header_length
<= md_block_size
) {
422 /* Should never happen */
425 overhang
= header_length
- md_block_size
;
426 md_transform(md_state
.c
, header
);
427 memcpy(first_block
, header
+ md_block_size
, overhang
);
428 memcpy(first_block
+ overhang
, data
, md_block_size
- overhang
);
429 md_transform(md_state
.c
, first_block
);
430 for (i
= 1; i
< k
/ md_block_size
- 1; i
++)
431 md_transform(md_state
.c
, data
+ md_block_size
* i
- overhang
);
433 /* k is a multiple of md_block_size. */
434 memcpy(first_block
, header
, 13);
435 memcpy(first_block
+ 13, data
, md_block_size
- 13);
436 md_transform(md_state
.c
, first_block
);
437 for (i
= 1; i
< k
/ md_block_size
; i
++)
438 md_transform(md_state
.c
, data
+ md_block_size
* i
- 13);
442 memset(mac_out
, 0, sizeof(mac_out
));
445 * We now process the final hash blocks. For each block, we construct it
446 * in constant time. If the |i==index_a| then we'll include the 0x80
447 * bytes and zero pad etc. For each block we selectively copy it, in
448 * constant time, to |mac_out|.
450 for (i
= num_starting_blocks
; i
<= num_starting_blocks
+ variance_blocks
;
452 unsigned char block
[MAX_HASH_BLOCK_SIZE
];
453 unsigned char is_block_a
= constant_time_eq_8_s(i
, index_a
);
454 unsigned char is_block_b
= constant_time_eq_8_s(i
, index_b
);
455 for (j
= 0; j
< md_block_size
; j
++) {
456 unsigned char b
= 0, is_past_c
, is_past_cp1
;
457 if (k
< header_length
)
459 else if (k
< data_plus_mac_plus_padding_size
+ header_length
)
460 b
= data
[k
- header_length
];
463 is_past_c
= is_block_a
& constant_time_ge_8_s(j
, c
);
464 is_past_cp1
= is_block_a
& constant_time_ge_8_s(j
, c
+ 1);
466 * If this is the block containing the end of the application
467 * data, and we are at the offset for the 0x80 value, then
468 * overwrite b with 0x80.
470 b
= constant_time_select_8(is_past_c
, 0x80, b
);
472 * If this block contains the end of the application data
473 * and we're past the 0x80 value then just write zero.
475 b
= b
& ~is_past_cp1
;
477 * If this is index_b (the final block), but not index_a (the end
478 * of the data), then the 64-bit length didn't fit into index_a
479 * and we're having to add an extra block of zeros.
481 b
&= ~is_block_b
| is_block_a
;
484 * The final bytes of one of the blocks contains the length.
486 if (j
>= md_block_size
- md_length_size
) {
487 /* If this is index_b, write a length byte. */
488 b
= constant_time_select_8(is_block_b
,
491 md_length_size
)], b
);
496 md_transform(md_state
.c
, block
);
497 md_final_raw(md_state
.c
, block
);
498 /* If this is index_b, copy the hash value to |mac_out|. */
499 for (j
= 0; j
< md_size
; j
++)
500 mac_out
[j
] |= block
[j
] & is_block_b
;
503 md_ctx
= EVP_MD_CTX_new();
507 if (EVP_DigestInit_ex(md_ctx
, md
, NULL
/* engine */ ) <= 0)
510 /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
511 memset(hmac_pad
, 0x5c, sslv3_pad_length
);
513 if (EVP_DigestUpdate(md_ctx
, mac_secret
, mac_secret_length
) <= 0
514 || EVP_DigestUpdate(md_ctx
, hmac_pad
, sslv3_pad_length
) <= 0
515 || EVP_DigestUpdate(md_ctx
, mac_out
, md_size
) <= 0)
518 /* Complete the HMAC in the standard manner. */
519 for (i
= 0; i
< md_block_size
; i
++)
522 if (EVP_DigestUpdate(md_ctx
, hmac_pad
, md_block_size
) <= 0
523 || EVP_DigestUpdate(md_ctx
, mac_out
, md_size
) <= 0)
526 /* TODO(size_t): Convert me */
527 ret
= EVP_DigestFinal(md_ctx
, md_out
, &md_out_size_u
);
528 if (ret
&& md_out_size
)
529 *md_out_size
= md_out_size_u
;
533 EVP_MD_CTX_free(md_ctx
);