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);