2 * Copyright 2012-2019 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 * MD5 and SHA-1 low level APIs are deprecated for public use, but still ok for
14 #include "internal/deprecated.h"
16 #include "internal/constant_time.h"
17 #include "ssl_local.h"
18 #include "internal/cryptlib.h"
20 #include <openssl/md5.h>
21 #include <openssl/sha.h>
24 * MAX_HASH_BIT_COUNT_BYTES is the maximum number of bytes in the hash's
25 * length field. (SHA-384/512 have 128-bit length.)
27 #define MAX_HASH_BIT_COUNT_BYTES 16
30 * MAX_HASH_BLOCK_SIZE is the maximum hash block size that we'll support.
31 * Currently SHA-384/512 has a 128-byte block size and that's the largest
34 #define MAX_HASH_BLOCK_SIZE 128
37 * u32toLE serialises an unsigned, 32-bit number (n) as four bytes at (p) in
38 * little-endian order. The value of p is advanced by four.
40 #define u32toLE(n, p) \
41 (*((p)++)=(unsigned char)(n), \
42 *((p)++)=(unsigned char)(n>>8), \
43 *((p)++)=(unsigned char)(n>>16), \
44 *((p)++)=(unsigned char)(n>>24))
47 * These functions serialize the state of a hash and thus perform the
48 * standard "final" operation without adding the padding and length that such
49 * a function typically does.
51 static void tls1_md5_final_raw(void *ctx, unsigned char *md_out)
54 u32toLE(md5->A, md_out);
55 u32toLE(md5->B, md_out);
56 u32toLE(md5->C, md_out);
57 u32toLE(md5->D, md_out);
60 static void tls1_sha1_final_raw(void *ctx, unsigned char *md_out)
63 l2n(sha1->h0, md_out);
64 l2n(sha1->h1, md_out);
65 l2n(sha1->h2, md_out);
66 l2n(sha1->h3, md_out);
67 l2n(sha1->h4, md_out);
70 static void tls1_sha256_final_raw(void *ctx, unsigned char *md_out)
72 SHA256_CTX *sha256 = ctx;
75 for (i = 0; i < 8; i++) {
76 l2n(sha256->h[i], md_out);
80 static void tls1_sha512_final_raw(void *ctx, unsigned char *md_out)
82 SHA512_CTX *sha512 = ctx;
85 for (i = 0; i < 8; i++) {
86 l2n8(sha512->h[i], md_out);
90 #undef LARGEST_DIGEST_CTX
91 #define LARGEST_DIGEST_CTX SHA512_CTX
94 * ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
95 * which ssl3_cbc_digest_record supports.
97 char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx)
99 switch (EVP_MD_CTX_type(ctx)) {
113 * ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS
116 * ctx: the EVP_MD_CTX from which we take the hash function.
117 * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX.
118 * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written.
119 * md_out_size: if non-NULL, the number of output bytes is written here.
120 * header: the 13-byte, TLS record header.
121 * data: the record data itself, less any preceding explicit IV.
122 * data_plus_mac_size: the secret, reported length of the data and MAC
123 * once the padding has been removed.
124 * data_plus_mac_plus_padding_size: the public length of the whole
125 * record, including padding.
126 * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
128 * On entry: by virtue of having been through one of the remove_padding
129 * functions, above, we know that data_plus_mac_size is large enough to contain
130 * a padding byte and MAC. (If the padding was invalid, it might contain the
132 * Returns 1 on success or 0 on error
134 int ssl3_cbc_digest_record(const EVP_MD_CTX *ctx,
135 unsigned char *md_out,
137 const unsigned char header[13],
138 const unsigned char *data,
139 size_t data_plus_mac_size,
140 size_t data_plus_mac_plus_padding_size,
141 const unsigned char *mac_secret,
142 size_t mac_secret_length, char is_sslv3)
146 unsigned char c[sizeof(LARGEST_DIGEST_CTX)];
148 void (*md_final_raw) (void *ctx, unsigned char *md_out);
149 void (*md_transform) (void *ctx, const unsigned char *block);
150 size_t md_size, md_block_size = 64;
151 size_t sslv3_pad_length = 40, header_length, variance_blocks,
152 len, max_mac_bytes, num_blocks,
153 num_starting_blocks, k, mac_end_offset, c, index_a, index_b;
154 size_t bits; /* at most 18 bits */
155 unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES];
156 /* hmac_pad is the masked HMAC key. */
157 unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE];
158 unsigned char first_block[MAX_HASH_BLOCK_SIZE];
159 unsigned char mac_out[EVP_MAX_MD_SIZE];
161 unsigned md_out_size_u;
162 EVP_MD_CTX *md_ctx = NULL;
164 * mdLengthSize is the number of bytes in the length field that
165 * terminates * the hash.
167 size_t md_length_size = 8;
168 char length_is_big_endian = 1;
172 * This is a, hopefully redundant, check that allows us to forget about
173 * many possible overflows later in this function.
175 if (!ossl_assert(data_plus_mac_plus_padding_size < 1024 * 1024))
178 switch (EVP_MD_CTX_type(ctx)) {
180 if (MD5_Init((MD5_CTX *)md_state.c) <= 0)
182 md_final_raw = tls1_md5_final_raw;
184 (void (*)(void *ctx, const unsigned char *block))MD5_Transform;
186 sslv3_pad_length = 48;
187 length_is_big_endian = 0;
190 if (SHA1_Init((SHA_CTX *)md_state.c) <= 0)
192 md_final_raw = tls1_sha1_final_raw;
194 (void (*)(void *ctx, const unsigned char *block))SHA1_Transform;
198 if (SHA224_Init((SHA256_CTX *)md_state.c) <= 0)
200 md_final_raw = tls1_sha256_final_raw;
202 (void (*)(void *ctx, const unsigned char *block))SHA256_Transform;
206 if (SHA256_Init((SHA256_CTX *)md_state.c) <= 0)
208 md_final_raw = tls1_sha256_final_raw;
210 (void (*)(void *ctx, const unsigned char *block))SHA256_Transform;
214 if (SHA384_Init((SHA512_CTX *)md_state.c) <= 0)
216 md_final_raw = tls1_sha512_final_raw;
218 (void (*)(void *ctx, const unsigned char *block))SHA512_Transform;
224 if (SHA512_Init((SHA512_CTX *)md_state.c) <= 0)
226 md_final_raw = tls1_sha512_final_raw;
228 (void (*)(void *ctx, const unsigned char *block))SHA512_Transform;
235 * ssl3_cbc_record_digest_supported should have been called first to
236 * check that the hash function is supported.
238 if (md_out_size != NULL)
240 return ossl_assert(0);
243 if (!ossl_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES)
244 || !ossl_assert(md_block_size <= MAX_HASH_BLOCK_SIZE)
245 || !ossl_assert(md_size <= EVP_MAX_MD_SIZE))
250 header_length = mac_secret_length + sslv3_pad_length + 8 /* sequence
252 1 /* record type */ +
253 2 /* record length */ ;
257 * variance_blocks is the number of blocks of the hash that we have to
258 * calculate in constant time because they could be altered by the
259 * padding value. In SSLv3, the padding must be minimal so the end of
260 * the plaintext varies by, at most, 15+20 = 35 bytes. (We conservatively
261 * assume that the MAC size varies from 0..20 bytes.) In case the 9 bytes
262 * of hash termination (0x80 + 64-bit length) don't fit in the final
263 * block, we say that the final two blocks can vary based on the padding.
264 * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
265 * required to be minimal. Therefore we say that the final |variance_blocks|
267 * vary based on the padding. Later in the function, if the message is
268 * short and there obviously cannot be this many blocks then
269 * variance_blocks can be reduced.
271 variance_blocks = is_sslv3 ? 2 : ( ((255 + 1 + md_size + md_block_size - 1) / md_block_size) + 1);
273 * From now on we're dealing with the MAC, which conceptually has 13
274 * bytes of `header' before the start of the data (TLS) or 71/75 bytes
277 len = data_plus_mac_plus_padding_size + header_length;
279 * max_mac_bytes contains the maximum bytes of bytes in the MAC,
280 * including * |header|, assuming that there's no padding.
282 max_mac_bytes = len - md_size - 1;
283 /* num_blocks is the maximum number of hash blocks. */
285 (max_mac_bytes + 1 + md_length_size + md_block_size -
288 * In order to calculate the MAC in constant time we have to handle the
289 * final blocks specially because the padding value could cause the end
290 * to appear somewhere in the final |variance_blocks| blocks and we can't
291 * leak where. However, |num_starting_blocks| worth of data can be hashed
292 * right away because no padding value can affect whether they are
295 num_starting_blocks = 0;
297 * k is the starting byte offset into the conceptual header||data where
298 * we start processing.
302 * mac_end_offset is the index just past the end of the data to be MACed.
304 mac_end_offset = data_plus_mac_size + header_length - md_size;
306 * c is the index of the 0x80 byte in the final hash block that contains
309 c = mac_end_offset % md_block_size;
311 * index_a is the hash block number that contains the 0x80 terminating
314 index_a = mac_end_offset / md_block_size;
316 * index_b is the hash block number that contains the 64-bit hash length,
319 index_b = (mac_end_offset + md_length_size) / md_block_size;
321 * bits is the hash-length in bits. It includes the additional hash block
322 * for the masked HMAC key, or whole of |header| in the case of SSLv3.
326 * For SSLv3, if we're going to have any starting blocks then we need at
327 * least two because the header is larger than a single block.
329 if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0)) {
330 num_starting_blocks = num_blocks - variance_blocks;
331 k = md_block_size * num_starting_blocks;
334 bits = 8 * mac_end_offset;
337 * Compute the initial HMAC block. For SSLv3, the padding and secret
338 * bytes are included in |header| because they take more than a
341 bits += 8 * md_block_size;
342 memset(hmac_pad, 0, md_block_size);
343 if (!ossl_assert(mac_secret_length <= sizeof(hmac_pad)))
345 memcpy(hmac_pad, mac_secret, mac_secret_length);
346 for (i = 0; i < md_block_size; i++)
349 md_transform(md_state.c, hmac_pad);
352 if (length_is_big_endian) {
353 memset(length_bytes, 0, md_length_size - 4);
354 length_bytes[md_length_size - 4] = (unsigned char)(bits >> 24);
355 length_bytes[md_length_size - 3] = (unsigned char)(bits >> 16);
356 length_bytes[md_length_size - 2] = (unsigned char)(bits >> 8);
357 length_bytes[md_length_size - 1] = (unsigned char)bits;
359 memset(length_bytes, 0, md_length_size);
360 length_bytes[md_length_size - 5] = (unsigned char)(bits >> 24);
361 length_bytes[md_length_size - 6] = (unsigned char)(bits >> 16);
362 length_bytes[md_length_size - 7] = (unsigned char)(bits >> 8);
363 length_bytes[md_length_size - 8] = (unsigned char)bits;
371 * The SSLv3 header is larger than a single block. overhang is
372 * the number of bytes beyond a single block that the header
373 * consumes: either 7 bytes (SHA1) or 11 bytes (MD5). There are no
374 * ciphersuites in SSLv3 that are not SHA1 or MD5 based and
375 * therefore we can be confident that the header_length will be
376 * greater than |md_block_size|. However we add a sanity check just
379 if (header_length <= md_block_size) {
380 /* Should never happen */
383 overhang = header_length - md_block_size;
384 md_transform(md_state.c, header);
385 memcpy(first_block, header + md_block_size, overhang);
386 memcpy(first_block + overhang, data, md_block_size - overhang);
387 md_transform(md_state.c, first_block);
388 for (i = 1; i < k / md_block_size - 1; i++)
389 md_transform(md_state.c, data + md_block_size * i - overhang);
391 /* k is a multiple of md_block_size. */
392 memcpy(first_block, header, 13);
393 memcpy(first_block + 13, data, md_block_size - 13);
394 md_transform(md_state.c, first_block);
395 for (i = 1; i < k / md_block_size; i++)
396 md_transform(md_state.c, data + md_block_size * i - 13);
400 memset(mac_out, 0, sizeof(mac_out));
403 * We now process the final hash blocks. For each block, we construct it
404 * in constant time. If the |i==index_a| then we'll include the 0x80
405 * bytes and zero pad etc. For each block we selectively copy it, in
406 * constant time, to |mac_out|.
408 for (i = num_starting_blocks; i <= num_starting_blocks + variance_blocks;
410 unsigned char block[MAX_HASH_BLOCK_SIZE];
411 unsigned char is_block_a = constant_time_eq_8_s(i, index_a);
412 unsigned char is_block_b = constant_time_eq_8_s(i, index_b);
413 for (j = 0; j < md_block_size; j++) {
414 unsigned char b = 0, is_past_c, is_past_cp1;
415 if (k < header_length)
417 else if (k < data_plus_mac_plus_padding_size + header_length)
418 b = data[k - header_length];
421 is_past_c = is_block_a & constant_time_ge_8_s(j, c);
422 is_past_cp1 = is_block_a & constant_time_ge_8_s(j, c + 1);
424 * If this is the block containing the end of the application
425 * data, and we are at the offset for the 0x80 value, then
426 * overwrite b with 0x80.
428 b = constant_time_select_8(is_past_c, 0x80, b);
430 * If this block contains the end of the application data
431 * and we're past the 0x80 value then just write zero.
433 b = b & ~is_past_cp1;
435 * If this is index_b (the final block), but not index_a (the end
436 * of the data), then the 64-bit length didn't fit into index_a
437 * and we're having to add an extra block of zeros.
439 b &= ~is_block_b | is_block_a;
442 * The final bytes of one of the blocks contains the length.
444 if (j >= md_block_size - md_length_size) {
445 /* If this is index_b, write a length byte. */
446 b = constant_time_select_8(is_block_b,
449 md_length_size)], b);
454 md_transform(md_state.c, block);
455 md_final_raw(md_state.c, block);
456 /* If this is index_b, copy the hash value to |mac_out|. */
457 for (j = 0; j < md_size; j++)
458 mac_out[j] |= block[j] & is_block_b;
461 md_ctx = EVP_MD_CTX_new();
464 if (EVP_DigestInit_ex(md_ctx, EVP_MD_CTX_md(ctx), NULL /* engine */ ) <= 0)
467 /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
468 memset(hmac_pad, 0x5c, sslv3_pad_length);
470 if (EVP_DigestUpdate(md_ctx, mac_secret, mac_secret_length) <= 0
471 || EVP_DigestUpdate(md_ctx, hmac_pad, sslv3_pad_length) <= 0
472 || EVP_DigestUpdate(md_ctx, mac_out, md_size) <= 0)
475 /* Complete the HMAC in the standard manner. */
476 for (i = 0; i < md_block_size; i++)
479 if (EVP_DigestUpdate(md_ctx, hmac_pad, md_block_size) <= 0
480 || EVP_DigestUpdate(md_ctx, mac_out, md_size) <= 0)
483 /* TODO(size_t): Convert me */
484 ret = EVP_DigestFinal(md_ctx, md_out, &md_out_size_u);
485 if (ret && md_out_size)
486 *md_out_size = md_out_size_u;
487 EVP_MD_CTX_free(md_ctx);
491 EVP_MD_CTX_free(md_ctx);