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
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_size: the secret, reported length of the data once the MAC and padding
166 * data_plus_mac_plus_padding_size: the public length of the whole
167 * record, including MAC and padding.
168 * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
170 * On entry: we know that data is data_plus_mac_plus_padding_size in length
171 * Returns 1 on success or 0 on error
173 int ssl3_cbc_digest_record(const EVP_MD *md,
174 unsigned char *md_out,
176 const unsigned char header[13],
177 const unsigned char *data,
179 size_t data_plus_mac_plus_padding_size,
180 const unsigned char *mac_secret,
181 size_t mac_secret_length, char is_sslv3)
185 unsigned char c[sizeof(LARGEST_DIGEST_CTX)];
187 void (*md_final_raw) (void *ctx, unsigned char *md_out);
188 void (*md_transform) (void *ctx, const unsigned char *block);
189 size_t md_size, md_block_size = 64;
190 size_t sslv3_pad_length = 40, header_length, variance_blocks,
191 len, max_mac_bytes, num_blocks,
192 num_starting_blocks, k, mac_end_offset, c, index_a, index_b;
193 size_t bits; /* at most 18 bits */
194 unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES];
195 /* hmac_pad is the masked HMAC key. */
196 unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE];
197 unsigned char first_block[MAX_HASH_BLOCK_SIZE];
198 unsigned char mac_out[EVP_MAX_MD_SIZE];
200 unsigned md_out_size_u;
201 EVP_MD_CTX *md_ctx = NULL;
203 * mdLengthSize is the number of bytes in the length field that
204 * terminates * the hash.
206 size_t md_length_size = 8;
207 char length_is_big_endian = 1;
211 * This is a, hopefully redundant, check that allows us to forget about
212 * many possible overflows later in this function.
214 if (!ossl_assert(data_plus_mac_plus_padding_size < 1024 * 1024))
217 if (EVP_MD_is_a(md, "MD5")) {
218 if (MD5_Init((MD5_CTX *)md_state.c) <= 0)
220 md_final_raw = tls1_md5_final_raw;
222 (void (*)(void *ctx, const unsigned char *block))MD5_Transform;
224 sslv3_pad_length = 48;
225 length_is_big_endian = 0;
226 } else if (EVP_MD_is_a(md, "SHA1")) {
227 if (SHA1_Init((SHA_CTX *)md_state.c) <= 0)
229 md_final_raw = tls1_sha1_final_raw;
231 (void (*)(void *ctx, const unsigned char *block))SHA1_Transform;
233 } else if (EVP_MD_is_a(md, "SHA2-224")) {
234 if (SHA224_Init((SHA256_CTX *)md_state.c) <= 0)
236 md_final_raw = tls1_sha256_final_raw;
238 (void (*)(void *ctx, const unsigned char *block))SHA256_Transform;
240 } else if (EVP_MD_is_a(md, "SHA2-256")) {
241 if (SHA256_Init((SHA256_CTX *)md_state.c) <= 0)
243 md_final_raw = tls1_sha256_final_raw;
245 (void (*)(void *ctx, const unsigned char *block))SHA256_Transform;
247 } else if (EVP_MD_is_a(md, "SHA2-384")) {
248 if (SHA384_Init((SHA512_CTX *)md_state.c) <= 0)
250 md_final_raw = tls1_sha512_final_raw;
252 (void (*)(void *ctx, const unsigned char *block))SHA512_Transform;
256 } else if (EVP_MD_is_a(md, "SHA2-512")) {
257 if (SHA512_Init((SHA512_CTX *)md_state.c) <= 0)
259 md_final_raw = tls1_sha512_final_raw;
261 (void (*)(void *ctx, const unsigned char *block))SHA512_Transform;
267 * ssl3_cbc_record_digest_supported should have been called first to
268 * check that the hash function is supported.
270 if (md_out_size != NULL)
272 return ossl_assert(0);
275 if (!ossl_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES)
276 || !ossl_assert(md_block_size <= MAX_HASH_BLOCK_SIZE)
277 || !ossl_assert(md_size <= EVP_MAX_MD_SIZE))
282 header_length = mac_secret_length + sslv3_pad_length + 8 /* sequence
284 1 /* record type */ +
285 2 /* record length */ ;
289 * variance_blocks is the number of blocks of the hash that we have to
290 * calculate in constant time because they could be altered by the
291 * padding value. In SSLv3, the padding must be minimal so the end of
292 * the plaintext varies by, at most, 15+20 = 35 bytes. (We conservatively
293 * assume that the MAC size varies from 0..20 bytes.) In case the 9 bytes
294 * of hash termination (0x80 + 64-bit length) don't fit in the final
295 * block, we say that the final two blocks can vary based on the padding.
296 * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
297 * required to be minimal. Therefore we say that the final |variance_blocks|
299 * vary based on the padding. Later in the function, if the message is
300 * short and there obviously cannot be this many blocks then
301 * variance_blocks can be reduced.
303 variance_blocks = is_sslv3 ? 2 : ( ((255 + 1 + md_size + md_block_size - 1) / md_block_size) + 1);
305 * From now on we're dealing with the MAC, which conceptually has 13
306 * bytes of `header' before the start of the data (TLS) or 71/75 bytes
309 len = data_plus_mac_plus_padding_size + header_length;
311 * max_mac_bytes contains the maximum bytes of bytes in the MAC,
312 * including * |header|, assuming that there's no padding.
314 max_mac_bytes = len - md_size - 1;
315 /* num_blocks is the maximum number of hash blocks. */
317 (max_mac_bytes + 1 + md_length_size + md_block_size -
320 * In order to calculate the MAC in constant time we have to handle the
321 * final blocks specially because the padding value could cause the end
322 * to appear somewhere in the final |variance_blocks| blocks and we can't
323 * leak where. However, |num_starting_blocks| worth of data can be hashed
324 * right away because no padding value can affect whether they are
327 num_starting_blocks = 0;
329 * k is the starting byte offset into the conceptual header||data where
330 * we start processing.
334 * mac_end_offset is the index just past the end of the data to be MACed.
336 mac_end_offset = data_size + header_length;
338 * c is the index of the 0x80 byte in the final hash block that contains
341 c = mac_end_offset % md_block_size;
343 * index_a is the hash block number that contains the 0x80 terminating
346 index_a = mac_end_offset / md_block_size;
348 * index_b is the hash block number that contains the 64-bit hash length,
351 index_b = (mac_end_offset + md_length_size) / md_block_size;
353 * bits is the hash-length in bits. It includes the additional hash block
354 * for the masked HMAC key, or whole of |header| in the case of SSLv3.
358 * For SSLv3, if we're going to have any starting blocks then we need at
359 * least two because the header is larger than a single block.
361 if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0)) {
362 num_starting_blocks = num_blocks - variance_blocks;
363 k = md_block_size * num_starting_blocks;
366 bits = 8 * mac_end_offset;
369 * Compute the initial HMAC block. For SSLv3, the padding and secret
370 * bytes are included in |header| because they take more than a
373 bits += 8 * md_block_size;
374 memset(hmac_pad, 0, md_block_size);
375 if (!ossl_assert(mac_secret_length <= sizeof(hmac_pad)))
377 memcpy(hmac_pad, mac_secret, mac_secret_length);
378 for (i = 0; i < md_block_size; i++)
381 md_transform(md_state.c, hmac_pad);
384 if (length_is_big_endian) {
385 memset(length_bytes, 0, md_length_size - 4);
386 length_bytes[md_length_size - 4] = (unsigned char)(bits >> 24);
387 length_bytes[md_length_size - 3] = (unsigned char)(bits >> 16);
388 length_bytes[md_length_size - 2] = (unsigned char)(bits >> 8);
389 length_bytes[md_length_size - 1] = (unsigned char)bits;
391 memset(length_bytes, 0, md_length_size);
392 length_bytes[md_length_size - 5] = (unsigned char)(bits >> 24);
393 length_bytes[md_length_size - 6] = (unsigned char)(bits >> 16);
394 length_bytes[md_length_size - 7] = (unsigned char)(bits >> 8);
395 length_bytes[md_length_size - 8] = (unsigned char)bits;
403 * The SSLv3 header is larger than a single block. overhang is
404 * the number of bytes beyond a single block that the header
405 * consumes: either 7 bytes (SHA1) or 11 bytes (MD5). There are no
406 * ciphersuites in SSLv3 that are not SHA1 or MD5 based and
407 * therefore we can be confident that the header_length will be
408 * greater than |md_block_size|. However we add a sanity check just
411 if (header_length <= md_block_size) {
412 /* Should never happen */
415 overhang = header_length - md_block_size;
416 md_transform(md_state.c, header);
417 memcpy(first_block, header + md_block_size, overhang);
418 memcpy(first_block + overhang, data, md_block_size - overhang);
419 md_transform(md_state.c, first_block);
420 for (i = 1; i < k / md_block_size - 1; i++)
421 md_transform(md_state.c, data + md_block_size * i - overhang);
423 /* k is a multiple of md_block_size. */
424 memcpy(first_block, header, 13);
425 memcpy(first_block + 13, data, md_block_size - 13);
426 md_transform(md_state.c, first_block);
427 for (i = 1; i < k / md_block_size; i++)
428 md_transform(md_state.c, data + md_block_size * i - 13);
432 memset(mac_out, 0, sizeof(mac_out));
435 * We now process the final hash blocks. For each block, we construct it
436 * in constant time. If the |i==index_a| then we'll include the 0x80
437 * bytes and zero pad etc. For each block we selectively copy it, in
438 * constant time, to |mac_out|.
440 for (i = num_starting_blocks; i <= num_starting_blocks + variance_blocks;
442 unsigned char block[MAX_HASH_BLOCK_SIZE];
443 unsigned char is_block_a = constant_time_eq_8_s(i, index_a);
444 unsigned char is_block_b = constant_time_eq_8_s(i, index_b);
445 for (j = 0; j < md_block_size; j++) {
446 unsigned char b = 0, is_past_c, is_past_cp1;
447 if (k < header_length)
449 else if (k < data_plus_mac_plus_padding_size + header_length)
450 b = data[k - header_length];
453 is_past_c = is_block_a & constant_time_ge_8_s(j, c);
454 is_past_cp1 = is_block_a & constant_time_ge_8_s(j, c + 1);
456 * If this is the block containing the end of the application
457 * data, and we are at the offset for the 0x80 value, then
458 * overwrite b with 0x80.
460 b = constant_time_select_8(is_past_c, 0x80, b);
462 * If this block contains the end of the application data
463 * and we're past the 0x80 value then just write zero.
465 b = b & ~is_past_cp1;
467 * If this is index_b (the final block), but not index_a (the end
468 * of the data), then the 64-bit length didn't fit into index_a
469 * and we're having to add an extra block of zeros.
471 b &= ~is_block_b | is_block_a;
474 * The final bytes of one of the blocks contains the length.
476 if (j >= md_block_size - md_length_size) {
477 /* If this is index_b, write a length byte. */
478 b = constant_time_select_8(is_block_b,
481 md_length_size)], b);
486 md_transform(md_state.c, block);
487 md_final_raw(md_state.c, block);
488 /* If this is index_b, copy the hash value to |mac_out|. */
489 for (j = 0; j < md_size; j++)
490 mac_out[j] |= block[j] & is_block_b;
493 md_ctx = EVP_MD_CTX_new();
497 if (EVP_DigestInit_ex(md_ctx, md, NULL /* engine */ ) <= 0)
500 /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
501 memset(hmac_pad, 0x5c, sslv3_pad_length);
503 if (EVP_DigestUpdate(md_ctx, mac_secret, mac_secret_length) <= 0
504 || EVP_DigestUpdate(md_ctx, hmac_pad, sslv3_pad_length) <= 0
505 || EVP_DigestUpdate(md_ctx, mac_out, md_size) <= 0)
508 /* Complete the HMAC in the standard manner. */
509 for (i = 0; i < md_block_size; i++)
512 if (EVP_DigestUpdate(md_ctx, hmac_pad, md_block_size) <= 0
513 || EVP_DigestUpdate(md_ctx, mac_out, md_size) <= 0)
516 /* TODO(size_t): Convert me */
517 ret = EVP_DigestFinal(md_ctx, md_out, &md_out_size_u);
518 if (ret && md_out_size)
519 *md_out_size = md_out_size_u;
523 EVP_MD_CTX_free(md_ctx);