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,
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
80 * u32toLE serializes an unsigned, 32-bit number (n) as four bytes at (p) in
81 * little-endian order. The value of p is advanced by four.
83 # define u32toLE(n, p) \
84 (*((p)++)=(unsigned char)(n), \
85 *((p)++)=(unsigned char)(n>>8), \
86 *((p)++)=(unsigned char)(n>>16), \
87 *((p)++)=(unsigned char)(n>>24))
90 * These functions serialize the state of a hash and thus perform the
91 * standard "final" operation without adding the padding and length that such
92 * a function typically does.
94 static void tls1_md5_final_raw(void *ctx, unsigned char *md_out)
97 u32toLE(md5->A, md_out);
98 u32toLE(md5->B, md_out);
99 u32toLE(md5->C, md_out);
100 u32toLE(md5->D, md_out);
102 #endif /* FIPS_MODULE */
104 static void tls1_sha1_final_raw(void *ctx, unsigned char *md_out)
107 l2n(sha1->h0, md_out);
108 l2n(sha1->h1, md_out);
109 l2n(sha1->h2, md_out);
110 l2n(sha1->h3, md_out);
111 l2n(sha1->h4, md_out);
114 static void tls1_sha256_final_raw(void *ctx, unsigned char *md_out)
116 SHA256_CTX *sha256 = ctx;
119 for (i = 0; i < 8; i++) {
120 l2n(sha256->h[i], md_out);
124 static void tls1_sha512_final_raw(void *ctx, unsigned char *md_out)
126 SHA512_CTX *sha512 = ctx;
129 for (i = 0; i < 8; i++) {
130 l2n8(sha512->h[i], md_out);
134 #undef LARGEST_DIGEST_CTX
135 #define LARGEST_DIGEST_CTX SHA512_CTX
138 * ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS
141 * ctx: the EVP_MD_CTX from which we take the hash function.
142 * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX.
143 * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written.
144 * md_out_size: if non-NULL, the number of output bytes is written here.
145 * header: the 13-byte, TLS record header.
146 * data: the record data itself, less any preceding explicit IV.
147 * data_size: the secret, reported length of the data once the MAC and padding
149 * data_plus_mac_plus_padding_size: the public length of the whole
150 * record, including MAC and padding.
151 * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
153 * On entry: we know that data is data_plus_mac_plus_padding_size in length
154 * Returns 1 on success or 0 on error
156 int ssl3_cbc_digest_record(const EVP_MD *md,
157 unsigned char *md_out,
159 const unsigned char header[13],
160 const unsigned char *data,
162 size_t data_plus_mac_plus_padding_size,
163 const unsigned char *mac_secret,
164 size_t mac_secret_length, char is_sslv3)
168 unsigned char c[sizeof(LARGEST_DIGEST_CTX)];
170 void (*md_final_raw) (void *ctx, unsigned char *md_out);
171 void (*md_transform) (void *ctx, const unsigned char *block);
172 size_t md_size, md_block_size = 64;
173 size_t sslv3_pad_length = 40, header_length, variance_blocks,
174 len, max_mac_bytes, num_blocks,
175 num_starting_blocks, k, mac_end_offset, c, index_a, index_b;
176 size_t bits; /* at most 18 bits */
177 unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES];
178 /* hmac_pad is the masked HMAC key. */
179 unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE];
180 unsigned char first_block[MAX_HASH_BLOCK_SIZE];
181 unsigned char mac_out[EVP_MAX_MD_SIZE];
183 unsigned md_out_size_u;
184 EVP_MD_CTX *md_ctx = NULL;
186 * mdLengthSize is the number of bytes in the length field that
187 * terminates * the hash.
189 size_t md_length_size = 8;
190 char length_is_big_endian = 1;
194 * This is a, hopefully redundant, check that allows us to forget about
195 * many possible overflows later in this function.
197 if (!ossl_assert(data_plus_mac_plus_padding_size < 1024 * 1024))
200 if (EVP_MD_is_a(md, "MD5")) {
204 if (MD5_Init((MD5_CTX *)md_state.c) <= 0)
206 md_final_raw = tls1_md5_final_raw;
208 (void (*)(void *ctx, const unsigned char *block))MD5_Transform;
210 sslv3_pad_length = 48;
211 length_is_big_endian = 0;
213 } else if (EVP_MD_is_a(md, "SHA1")) {
214 if (SHA1_Init((SHA_CTX *)md_state.c) <= 0)
216 md_final_raw = tls1_sha1_final_raw;
218 (void (*)(void *ctx, const unsigned char *block))SHA1_Transform;
220 } else if (EVP_MD_is_a(md, "SHA2-224")) {
221 if (SHA224_Init((SHA256_CTX *)md_state.c) <= 0)
223 md_final_raw = tls1_sha256_final_raw;
225 (void (*)(void *ctx, const unsigned char *block))SHA256_Transform;
227 } else if (EVP_MD_is_a(md, "SHA2-256")) {
228 if (SHA256_Init((SHA256_CTX *)md_state.c) <= 0)
230 md_final_raw = tls1_sha256_final_raw;
232 (void (*)(void *ctx, const unsigned char *block))SHA256_Transform;
234 } else if (EVP_MD_is_a(md, "SHA2-384")) {
235 if (SHA384_Init((SHA512_CTX *)md_state.c) <= 0)
237 md_final_raw = tls1_sha512_final_raw;
239 (void (*)(void *ctx, const unsigned char *block))SHA512_Transform;
243 } else if (EVP_MD_is_a(md, "SHA2-512")) {
244 if (SHA512_Init((SHA512_CTX *)md_state.c) <= 0)
246 md_final_raw = tls1_sha512_final_raw;
248 (void (*)(void *ctx, const unsigned char *block))SHA512_Transform;
254 * ssl3_cbc_record_digest_supported should have been called first to
255 * check that the hash function is supported.
257 if (md_out_size != NULL)
259 return ossl_assert(0);
262 if (!ossl_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES)
263 || !ossl_assert(md_block_size <= MAX_HASH_BLOCK_SIZE)
264 || !ossl_assert(md_size <= EVP_MAX_MD_SIZE))
269 header_length = mac_secret_length + sslv3_pad_length + 8 /* sequence
271 1 /* record type */ +
272 2 /* record length */ ;
276 * variance_blocks is the number of blocks of the hash that we have to
277 * calculate in constant time because they could be altered by the
278 * padding value. In SSLv3, the padding must be minimal so the end of
279 * the plaintext varies by, at most, 15+20 = 35 bytes. (We conservatively
280 * assume that the MAC size varies from 0..20 bytes.) In case the 9 bytes
281 * of hash termination (0x80 + 64-bit length) don't fit in the final
282 * block, we say that the final two blocks can vary based on the padding.
283 * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
284 * required to be minimal. Therefore we say that the final |variance_blocks|
286 * vary based on the padding. Later in the function, if the message is
287 * short and there obviously cannot be this many blocks then
288 * variance_blocks can be reduced.
290 variance_blocks = is_sslv3 ? 2 : ( ((255 + 1 + md_size + md_block_size - 1) / md_block_size) + 1);
292 * From now on we're dealing with the MAC, which conceptually has 13
293 * bytes of `header' before the start of the data (TLS) or 71/75 bytes
296 len = data_plus_mac_plus_padding_size + header_length;
298 * max_mac_bytes contains the maximum bytes of bytes in the MAC,
299 * including * |header|, assuming that there's no padding.
301 max_mac_bytes = len - md_size - 1;
302 /* num_blocks is the maximum number of hash blocks. */
304 (max_mac_bytes + 1 + md_length_size + md_block_size -
307 * In order to calculate the MAC in constant time we have to handle the
308 * final blocks specially because the padding value could cause the end
309 * to appear somewhere in the final |variance_blocks| blocks and we can't
310 * leak where. However, |num_starting_blocks| worth of data can be hashed
311 * right away because no padding value can affect whether they are
314 num_starting_blocks = 0;
316 * k is the starting byte offset into the conceptual header||data where
317 * we start processing.
321 * mac_end_offset is the index just past the end of the data to be MACed.
323 mac_end_offset = data_size + header_length;
325 * c is the index of the 0x80 byte in the final hash block that contains
328 c = mac_end_offset % md_block_size;
330 * index_a is the hash block number that contains the 0x80 terminating
333 index_a = mac_end_offset / md_block_size;
335 * index_b is the hash block number that contains the 64-bit hash length,
338 index_b = (mac_end_offset + md_length_size) / md_block_size;
340 * bits is the hash-length in bits. It includes the additional hash block
341 * for the masked HMAC key, or whole of |header| in the case of SSLv3.
345 * For SSLv3, if we're going to have any starting blocks then we need at
346 * least two because the header is larger than a single block.
348 if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0)) {
349 num_starting_blocks = num_blocks - variance_blocks;
350 k = md_block_size * num_starting_blocks;
353 bits = 8 * mac_end_offset;
356 * Compute the initial HMAC block. For SSLv3, the padding and secret
357 * bytes are included in |header| because they take more than a
360 bits += 8 * md_block_size;
361 memset(hmac_pad, 0, md_block_size);
362 if (!ossl_assert(mac_secret_length <= sizeof(hmac_pad)))
364 memcpy(hmac_pad, mac_secret, mac_secret_length);
365 for (i = 0; i < md_block_size; i++)
368 md_transform(md_state.c, hmac_pad);
371 if (length_is_big_endian) {
372 memset(length_bytes, 0, md_length_size - 4);
373 length_bytes[md_length_size - 4] = (unsigned char)(bits >> 24);
374 length_bytes[md_length_size - 3] = (unsigned char)(bits >> 16);
375 length_bytes[md_length_size - 2] = (unsigned char)(bits >> 8);
376 length_bytes[md_length_size - 1] = (unsigned char)bits;
378 memset(length_bytes, 0, md_length_size);
379 length_bytes[md_length_size - 5] = (unsigned char)(bits >> 24);
380 length_bytes[md_length_size - 6] = (unsigned char)(bits >> 16);
381 length_bytes[md_length_size - 7] = (unsigned char)(bits >> 8);
382 length_bytes[md_length_size - 8] = (unsigned char)bits;
390 * The SSLv3 header is larger than a single block. overhang is
391 * the number of bytes beyond a single block that the header
392 * consumes: either 7 bytes (SHA1) or 11 bytes (MD5). There are no
393 * ciphersuites in SSLv3 that are not SHA1 or MD5 based and
394 * therefore we can be confident that the header_length will be
395 * greater than |md_block_size|. However we add a sanity check just
398 if (header_length <= md_block_size) {
399 /* Should never happen */
402 overhang = header_length - md_block_size;
403 md_transform(md_state.c, header);
404 memcpy(first_block, header + md_block_size, overhang);
405 memcpy(first_block + overhang, data, md_block_size - overhang);
406 md_transform(md_state.c, first_block);
407 for (i = 1; i < k / md_block_size - 1; i++)
408 md_transform(md_state.c, data + md_block_size * i - overhang);
410 /* k is a multiple of md_block_size. */
411 memcpy(first_block, header, 13);
412 memcpy(first_block + 13, data, md_block_size - 13);
413 md_transform(md_state.c, first_block);
414 for (i = 1; i < k / md_block_size; i++)
415 md_transform(md_state.c, data + md_block_size * i - 13);
419 memset(mac_out, 0, sizeof(mac_out));
422 * We now process the final hash blocks. For each block, we construct it
423 * in constant time. If the |i==index_a| then we'll include the 0x80
424 * bytes and zero pad etc. For each block we selectively copy it, in
425 * constant time, to |mac_out|.
427 for (i = num_starting_blocks; i <= num_starting_blocks + variance_blocks;
429 unsigned char block[MAX_HASH_BLOCK_SIZE];
430 unsigned char is_block_a = constant_time_eq_8_s(i, index_a);
431 unsigned char is_block_b = constant_time_eq_8_s(i, index_b);
432 for (j = 0; j < md_block_size; j++) {
433 unsigned char b = 0, is_past_c, is_past_cp1;
434 if (k < header_length)
436 else if (k < data_plus_mac_plus_padding_size + header_length)
437 b = data[k - header_length];
440 is_past_c = is_block_a & constant_time_ge_8_s(j, c);
441 is_past_cp1 = is_block_a & constant_time_ge_8_s(j, c + 1);
443 * If this is the block containing the end of the application
444 * data, and we are at the offset for the 0x80 value, then
445 * overwrite b with 0x80.
447 b = constant_time_select_8(is_past_c, 0x80, b);
449 * If this block contains the end of the application data
450 * and we're past the 0x80 value then just write zero.
452 b = b & ~is_past_cp1;
454 * If this is index_b (the final block), but not index_a (the end
455 * of the data), then the 64-bit length didn't fit into index_a
456 * and we're having to add an extra block of zeros.
458 b &= ~is_block_b | is_block_a;
461 * The final bytes of one of the blocks contains the length.
463 if (j >= md_block_size - md_length_size) {
464 /* If this is index_b, write a length byte. */
465 b = constant_time_select_8(is_block_b,
468 md_length_size)], b);
473 md_transform(md_state.c, block);
474 md_final_raw(md_state.c, block);
475 /* If this is index_b, copy the hash value to |mac_out|. */
476 for (j = 0; j < md_size; j++)
477 mac_out[j] |= block[j] & is_block_b;
480 md_ctx = EVP_MD_CTX_new();
484 if (EVP_DigestInit_ex(md_ctx, md, NULL /* engine */ ) <= 0)
487 /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
488 memset(hmac_pad, 0x5c, sslv3_pad_length);
490 if (EVP_DigestUpdate(md_ctx, mac_secret, mac_secret_length) <= 0
491 || EVP_DigestUpdate(md_ctx, hmac_pad, sslv3_pad_length) <= 0
492 || EVP_DigestUpdate(md_ctx, mac_out, md_size) <= 0)
495 /* Complete the HMAC in the standard manner. */
496 for (i = 0; i < md_block_size; i++)
499 if (EVP_DigestUpdate(md_ctx, hmac_pad, md_block_size) <= 0
500 || EVP_DigestUpdate(md_ctx, mac_out, md_size) <= 0)
503 /* TODO(size_t): Convert me */
504 ret = EVP_DigestFinal(md_ctx, md_out, &md_out_size_u);
505 if (ret && md_out_size)
506 *md_out_size = md_out_size_u;
510 EVP_MD_CTX_free(md_ctx);