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a693ead6 BL |
1 | /* ssl/s3_cbc.c */ |
2 | /* ==================================================================== | |
3 | * Copyright (c) 2012 The OpenSSL Project. All rights reserved. | |
4 | * | |
5 | * Redistribution and use in source and binary forms, with or without | |
6 | * modification, are permitted provided that the following conditions | |
7 | * are met: | |
8 | * | |
9 | * 1. Redistributions of source code must retain the above copyright | |
10 | * notice, this list of conditions and the following disclaimer. | |
11 | * | |
12 | * 2. Redistributions in binary form must reproduce the above copyright | |
13 | * notice, this list of conditions and the following disclaimer in | |
14 | * the documentation and/or other materials provided with the | |
15 | * distribution. | |
16 | * | |
17 | * 3. All advertising materials mentioning features or use of this | |
18 | * software must display the following acknowledgment: | |
19 | * "This product includes software developed by the OpenSSL Project | |
20 | * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" | |
21 | * | |
22 | * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to | |
23 | * endorse or promote products derived from this software without | |
24 | * prior written permission. For written permission, please contact | |
25 | * openssl-core@openssl.org. | |
26 | * | |
27 | * 5. Products derived from this software may not be called "OpenSSL" | |
28 | * nor may "OpenSSL" appear in their names without prior written | |
29 | * permission of the OpenSSL Project. | |
30 | * | |
31 | * 6. Redistributions of any form whatsoever must retain the following | |
32 | * acknowledgment: | |
33 | * "This product includes software developed by the OpenSSL Project | |
34 | * for use in the OpenSSL Toolkit (http://www.openssl.org/)" | |
35 | * | |
36 | * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY | |
37 | * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
38 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR | |
39 | * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR | |
40 | * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |
41 | * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
42 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; | |
43 | * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
44 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, | |
45 | * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) | |
46 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED | |
47 | * OF THE POSSIBILITY OF SUCH DAMAGE. | |
48 | * ==================================================================== | |
49 | * | |
50 | * This product includes cryptographic software written by Eric Young | |
51 | * (eay@cryptsoft.com). This product includes software written by Tim | |
52 | * Hudson (tjh@cryptsoft.com). | |
53 | * | |
54 | */ | |
55 | ||
5a3d21c0 | 56 | #include "../crypto/constant_time_locl.h" |
a693ead6 BL |
57 | #include "ssl_locl.h" |
58 | ||
59 | #include <openssl/md5.h> | |
60 | #include <openssl/sha.h> | |
61 | ||
0f113f3e MC |
62 | /* |
63 | * MAX_HASH_BIT_COUNT_BYTES is the maximum number of bytes in the hash's | |
64 | * length field. (SHA-384/512 have 128-bit length.) | |
65 | */ | |
a693ead6 BL |
66 | #define MAX_HASH_BIT_COUNT_BYTES 16 |
67 | ||
0f113f3e MC |
68 | /* |
69 | * MAX_HASH_BLOCK_SIZE is the maximum hash block size that we'll support. | |
a693ead6 | 70 | * Currently SHA-384/512 has a 128-byte block size and that's the largest |
0f113f3e MC |
71 | * supported by TLS.) |
72 | */ | |
a693ead6 BL |
73 | #define MAX_HASH_BLOCK_SIZE 128 |
74 | ||
1d97c843 TH |
75 | /*- |
76 | * ssl3_cbc_remove_padding removes padding from the decrypted, SSLv3, CBC | |
a693ead6 BL |
77 | * record in |rec| by updating |rec->length| in constant time. |
78 | * | |
79 | * block_size: the block size of the cipher used to encrypt the record. | |
80 | * returns: | |
81 | * 0: (in non-constant time) if the record is publicly invalid. | |
82 | * 1: if the padding was valid | |
0f113f3e | 83 | * -1: otherwise. |
1d97c843 | 84 | */ |
0f113f3e MC |
85 | int ssl3_cbc_remove_padding(const SSL *s, |
86 | SSL3_RECORD *rec, | |
87 | unsigned block_size, unsigned mac_size) | |
88 | { | |
89 | unsigned padding_length, good; | |
90 | const unsigned overhead = 1 /* padding length byte */ + mac_size; | |
91 | ||
92 | /* | |
93 | * These lengths are all public so we can test them in non-constant time. | |
94 | */ | |
95 | if (overhead > rec->length) | |
96 | return 0; | |
97 | ||
98 | padding_length = rec->data[rec->length - 1]; | |
99 | good = constant_time_ge(rec->length, padding_length + overhead); | |
100 | /* SSLv3 requires that the padding is minimal. */ | |
101 | good &= constant_time_ge(block_size, padding_length + 1); | |
102 | rec->length -= good & (padding_length + 1); | |
103 | return constant_time_select_int(good, 1, -1); | |
104 | } | |
105 | ||
106 | /*- | |
1d97c843 | 107 | * tls1_cbc_remove_padding removes the CBC padding from the decrypted, TLS, CBC |
a693ead6 BL |
108 | * record in |rec| in constant time and returns 1 if the padding is valid and |
109 | * -1 otherwise. It also removes any explicit IV from the start of the record | |
110 | * without leaking any timing about whether there was enough space after the | |
111 | * padding was removed. | |
112 | * | |
113 | * block_size: the block size of the cipher used to encrypt the record. | |
114 | * returns: | |
115 | * 0: (in non-constant time) if the record is publicly invalid. | |
116 | * 1: if the padding was valid | |
0f113f3e | 117 | * -1: otherwise. |
1d97c843 | 118 | */ |
0f113f3e MC |
119 | int tls1_cbc_remove_padding(const SSL *s, |
120 | SSL3_RECORD *rec, | |
121 | unsigned block_size, unsigned mac_size) | |
122 | { | |
123 | unsigned padding_length, good, to_check, i; | |
124 | const unsigned overhead = 1 /* padding length byte */ + mac_size; | |
125 | /* Check if version requires explicit IV */ | |
126 | if (SSL_USE_EXPLICIT_IV(s)) { | |
127 | /* | |
128 | * These lengths are all public so we can test them in non-constant | |
129 | * time. | |
130 | */ | |
131 | if (overhead + block_size > rec->length) | |
132 | return 0; | |
133 | /* We can now safely skip explicit IV */ | |
134 | rec->data += block_size; | |
135 | rec->input += block_size; | |
136 | rec->length -= block_size; | |
137 | rec->orig_len -= block_size; | |
138 | } else if (overhead > rec->length) | |
139 | return 0; | |
140 | ||
141 | padding_length = rec->data[rec->length - 1]; | |
142 | ||
143 | /* | |
144 | * NB: if compression is in operation the first packet may not be of even | |
145 | * length so the padding bug check cannot be performed. This bug | |
146 | * workaround has been around since SSLeay so hopefully it is either | |
147 | * fixed now or no buggy implementation supports compression [steve] | |
148 | */ | |
149 | if ((s->options & SSL_OP_TLS_BLOCK_PADDING_BUG) && !s->expand) { | |
150 | /* First packet is even in size, so check */ | |
151 | if ((memcmp(s->s3->read_sequence, "\0\0\0\0\0\0\0\0", 8) == 0) && | |
152 | !(padding_length & 1)) { | |
153 | s->s3->flags |= TLS1_FLAGS_TLS_PADDING_BUG; | |
154 | } | |
155 | if ((s->s3->flags & TLS1_FLAGS_TLS_PADDING_BUG) && padding_length > 0) { | |
156 | padding_length--; | |
157 | } | |
158 | } | |
159 | ||
160 | if (EVP_CIPHER_flags(s->enc_read_ctx->cipher) & EVP_CIPH_FLAG_AEAD_CIPHER) { | |
161 | /* padding is already verified */ | |
162 | rec->length -= padding_length + 1; | |
163 | return 1; | |
164 | } | |
165 | ||
166 | good = constant_time_ge(rec->length, overhead + padding_length); | |
167 | /* | |
168 | * The padding consists of a length byte at the end of the record and | |
169 | * then that many bytes of padding, all with the same value as the length | |
170 | * byte. Thus, with the length byte included, there are i+1 bytes of | |
171 | * padding. We can't check just |padding_length+1| bytes because that | |
172 | * leaks decrypted information. Therefore we always have to check the | |
173 | * maximum amount of padding possible. (Again, the length of the record | |
174 | * is public information so we can use it.) | |
175 | */ | |
176 | to_check = 255; /* maximum amount of padding. */ | |
177 | if (to_check > rec->length - 1) | |
178 | to_check = rec->length - 1; | |
179 | ||
180 | for (i = 0; i < to_check; i++) { | |
181 | unsigned char mask = constant_time_ge_8(padding_length, i); | |
182 | unsigned char b = rec->data[rec->length - 1 - i]; | |
183 | /* | |
184 | * The final |padding_length+1| bytes should all have the value | |
185 | * |padding_length|. Therefore the XOR should be zero. | |
186 | */ | |
187 | good &= ~(mask & (padding_length ^ b)); | |
188 | } | |
189 | ||
190 | /* | |
191 | * If any of the final |padding_length+1| bytes had the wrong value, one | |
192 | * or more of the lower eight bits of |good| will be cleared. | |
193 | */ | |
194 | good = constant_time_eq(0xff, good & 0xff); | |
195 | rec->length -= good & (padding_length + 1); | |
196 | ||
197 | return constant_time_select_int(good, 1, -1); | |
198 | } | |
a693ead6 | 199 | |
1d97c843 TH |
200 | /*- |
201 | * ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in | |
a693ead6 BL |
202 | * constant time (independent of the concrete value of rec->length, which may |
203 | * vary within a 256-byte window). | |
204 | * | |
205 | * ssl3_cbc_remove_padding or tls1_cbc_remove_padding must be called prior to | |
206 | * this function. | |
207 | * | |
208 | * On entry: | |
209 | * rec->orig_len >= md_size | |
210 | * md_size <= EVP_MAX_MD_SIZE | |
211 | * | |
212 | * If CBC_MAC_ROTATE_IN_PLACE is defined then the rotation is performed with | |
213 | * variable accesses in a 64-byte-aligned buffer. Assuming that this fits into | |
f93a4187 AP |
214 | * a single or pair of cache-lines, then the variable memory accesses don't |
215 | * actually affect the timing. CPUs with smaller cache-lines [if any] are | |
216 | * not multi-core and are not considered vulnerable to cache-timing attacks. | |
a693ead6 | 217 | */ |
f93a4187 AP |
218 | #define CBC_MAC_ROTATE_IN_PLACE |
219 | ||
0f113f3e MC |
220 | void ssl3_cbc_copy_mac(unsigned char *out, |
221 | const SSL3_RECORD *rec, unsigned md_size) | |
222 | { | |
a693ead6 | 223 | #if defined(CBC_MAC_ROTATE_IN_PLACE) |
0f113f3e MC |
224 | unsigned char rotated_mac_buf[64 + EVP_MAX_MD_SIZE]; |
225 | unsigned char *rotated_mac; | |
a693ead6 | 226 | #else |
0f113f3e | 227 | unsigned char rotated_mac[EVP_MAX_MD_SIZE]; |
a693ead6 BL |
228 | #endif |
229 | ||
0f113f3e MC |
230 | /* |
231 | * mac_end is the index of |rec->data| just after the end of the MAC. | |
232 | */ | |
233 | unsigned mac_end = rec->length; | |
234 | unsigned mac_start = mac_end - md_size; | |
235 | /* | |
236 | * scan_start contains the number of bytes that we can ignore because the | |
237 | * MAC's position can only vary by 255 bytes. | |
238 | */ | |
239 | unsigned scan_start = 0; | |
240 | unsigned i, j; | |
241 | unsigned div_spoiler; | |
242 | unsigned rotate_offset; | |
243 | ||
244 | OPENSSL_assert(rec->orig_len >= md_size); | |
245 | OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE); | |
a693ead6 BL |
246 | |
247 | #if defined(CBC_MAC_ROTATE_IN_PLACE) | |
0f113f3e | 248 | rotated_mac = rotated_mac_buf + ((0 - (size_t)rotated_mac_buf) & 63); |
a693ead6 BL |
249 | #endif |
250 | ||
0f113f3e MC |
251 | /* This information is public so it's safe to branch based on it. */ |
252 | if (rec->orig_len > md_size + 255 + 1) | |
253 | scan_start = rec->orig_len - (md_size + 255 + 1); | |
254 | /* | |
255 | * div_spoiler contains a multiple of md_size that is used to cause the | |
256 | * modulo operation to be constant time. Without this, the time varies | |
257 | * based on the amount of padding when running on Intel chips at least. | |
258 | * The aim of right-shifting md_size is so that the compiler doesn't | |
259 | * figure out that it can remove div_spoiler as that would require it to | |
260 | * prove that md_size is always even, which I hope is beyond it. | |
261 | */ | |
262 | div_spoiler = md_size >> 1; | |
263 | div_spoiler <<= (sizeof(div_spoiler) - 1) * 8; | |
264 | rotate_offset = (div_spoiler + mac_start - scan_start) % md_size; | |
265 | ||
266 | memset(rotated_mac, 0, md_size); | |
267 | for (i = scan_start, j = 0; i < rec->orig_len; i++) { | |
268 | unsigned char mac_started = constant_time_ge_8(i, mac_start); | |
269 | unsigned char mac_ended = constant_time_ge_8(i, mac_end); | |
270 | unsigned char b = rec->data[i]; | |
271 | rotated_mac[j++] |= b & mac_started & ~mac_ended; | |
272 | j &= constant_time_lt(j, md_size); | |
273 | } | |
274 | ||
275 | /* Now rotate the MAC */ | |
a693ead6 | 276 | #if defined(CBC_MAC_ROTATE_IN_PLACE) |
0f113f3e MC |
277 | j = 0; |
278 | for (i = 0; i < md_size; i++) { | |
279 | /* in case cache-line is 32 bytes, touch second line */ | |
280 | ((volatile unsigned char *)rotated_mac)[rotate_offset ^ 32]; | |
281 | out[j++] = rotated_mac[rotate_offset++]; | |
282 | rotate_offset &= constant_time_lt(rotate_offset, md_size); | |
283 | } | |
a693ead6 | 284 | #else |
0f113f3e MC |
285 | memset(out, 0, md_size); |
286 | rotate_offset = md_size - rotate_offset; | |
287 | rotate_offset &= constant_time_lt(rotate_offset, md_size); | |
288 | for (i = 0; i < md_size; i++) { | |
289 | for (j = 0; j < md_size; j++) | |
290 | out[j] |= rotated_mac[i] & constant_time_eq_8(j, rotate_offset); | |
291 | rotate_offset++; | |
292 | rotate_offset &= constant_time_lt(rotate_offset, md_size); | |
293 | } | |
a693ead6 | 294 | #endif |
0f113f3e | 295 | } |
a693ead6 | 296 | |
0f113f3e MC |
297 | /* |
298 | * u32toLE serialises an unsigned, 32-bit number (n) as four bytes at (p) in | |
299 | * little-endian order. The value of p is advanced by four. | |
300 | */ | |
32620fe9 | 301 | #define u32toLE(n, p) \ |
0f113f3e MC |
302 | (*((p)++)=(unsigned char)(n), \ |
303 | *((p)++)=(unsigned char)(n>>8), \ | |
304 | *((p)++)=(unsigned char)(n>>16), \ | |
305 | *((p)++)=(unsigned char)(n>>24)) | |
306 | ||
307 | /* | |
308 | * These functions serialize the state of a hash and thus perform the | |
309 | * standard "final" operation without adding the padding and length that such | |
310 | * a function typically does. | |
311 | */ | |
312 | static void tls1_md5_final_raw(void *ctx, unsigned char *md_out) | |
313 | { | |
314 | MD5_CTX *md5 = ctx; | |
315 | u32toLE(md5->A, md_out); | |
316 | u32toLE(md5->B, md_out); | |
317 | u32toLE(md5->C, md_out); | |
318 | u32toLE(md5->D, md_out); | |
319 | } | |
320 | ||
321 | static void tls1_sha1_final_raw(void *ctx, unsigned char *md_out) | |
322 | { | |
323 | SHA_CTX *sha1 = ctx; | |
324 | l2n(sha1->h0, md_out); | |
325 | l2n(sha1->h1, md_out); | |
326 | l2n(sha1->h2, md_out); | |
327 | l2n(sha1->h3, md_out); | |
328 | l2n(sha1->h4, md_out); | |
329 | } | |
330 | ||
bbb4ee85 | 331 | #define LARGEST_DIGEST_CTX SHA_CTX |
a693ead6 | 332 | |
bbb4ee85 | 333 | #ifndef OPENSSL_NO_SHA256 |
0f113f3e MC |
334 | static void tls1_sha256_final_raw(void *ctx, unsigned char *md_out) |
335 | { | |
336 | SHA256_CTX *sha256 = ctx; | |
337 | unsigned i; | |
338 | ||
339 | for (i = 0; i < 8; i++) { | |
340 | l2n(sha256->h[i], md_out); | |
341 | } | |
342 | } | |
343 | ||
344 | # undef LARGEST_DIGEST_CTX | |
345 | # define LARGEST_DIGEST_CTX SHA256_CTX | |
bbb4ee85 | 346 | #endif |
a693ead6 | 347 | |
bbb4ee85 | 348 | #ifndef OPENSSL_NO_SHA512 |
0f113f3e MC |
349 | static void tls1_sha512_final_raw(void *ctx, unsigned char *md_out) |
350 | { | |
351 | SHA512_CTX *sha512 = ctx; | |
352 | unsigned i; | |
353 | ||
354 | for (i = 0; i < 8; i++) { | |
355 | l2n8(sha512->h[i], md_out); | |
356 | } | |
357 | } | |
358 | ||
359 | # undef LARGEST_DIGEST_CTX | |
360 | # define LARGEST_DIGEST_CTX SHA512_CTX | |
bbb4ee85 | 361 | #endif |
a693ead6 | 362 | |
0f113f3e MC |
363 | /* |
364 | * ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function | |
365 | * which ssl3_cbc_digest_record supports. | |
366 | */ | |
a693ead6 | 367 | char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx) |
0f113f3e MC |
368 | { |
369 | if (FIPS_mode()) | |
370 | return 0; | |
371 | switch (EVP_MD_CTX_type(ctx)) { | |
372 | case NID_md5: | |
373 | case NID_sha1: | |
bbb4ee85 | 374 | #ifndef OPENSSL_NO_SHA256 |
0f113f3e MC |
375 | case NID_sha224: |
376 | case NID_sha256: | |
bbb4ee85 AP |
377 | #endif |
378 | #ifndef OPENSSL_NO_SHA512 | |
0f113f3e MC |
379 | case NID_sha384: |
380 | case NID_sha512: | |
bbb4ee85 | 381 | #endif |
0f113f3e MC |
382 | return 1; |
383 | default: | |
384 | return 0; | |
385 | } | |
386 | } | |
a693ead6 | 387 | |
1d97c843 TH |
388 | /*- |
389 | * ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS | |
a693ead6 BL |
390 | * record. |
391 | * | |
392 | * ctx: the EVP_MD_CTX from which we take the hash function. | |
393 | * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX. | |
394 | * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written. | |
395 | * md_out_size: if non-NULL, the number of output bytes is written here. | |
396 | * header: the 13-byte, TLS record header. | |
478b50cf | 397 | * data: the record data itself, less any preceding explicit IV. |
a693ead6 BL |
398 | * data_plus_mac_size: the secret, reported length of the data and MAC |
399 | * once the padding has been removed. | |
400 | * data_plus_mac_plus_padding_size: the public length of the whole | |
401 | * record, including padding. | |
402 | * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS. | |
403 | * | |
404 | * On entry: by virtue of having been through one of the remove_padding | |
405 | * functions, above, we know that data_plus_mac_size is large enough to contain | |
406 | * a padding byte and MAC. (If the padding was invalid, it might contain the | |
0f113f3e | 407 | * padding too. ) |
1d97c843 | 408 | */ |
0f113f3e MC |
409 | void ssl3_cbc_digest_record(const EVP_MD_CTX *ctx, |
410 | unsigned char *md_out, | |
411 | size_t *md_out_size, | |
412 | const unsigned char header[13], | |
413 | const unsigned char *data, | |
414 | size_t data_plus_mac_size, | |
415 | size_t data_plus_mac_plus_padding_size, | |
416 | const unsigned char *mac_secret, | |
417 | unsigned mac_secret_length, char is_sslv3) | |
418 | { | |
419 | union { | |
420 | double align; | |
421 | unsigned char c[sizeof(LARGEST_DIGEST_CTX)]; | |
422 | } md_state; | |
423 | void (*md_final_raw) (void *ctx, unsigned char *md_out); | |
424 | void (*md_transform) (void *ctx, const unsigned char *block); | |
425 | unsigned md_size, md_block_size = 64; | |
426 | unsigned sslv3_pad_length = 40, header_length, variance_blocks, | |
427 | len, max_mac_bytes, num_blocks, | |
428 | num_starting_blocks, k, mac_end_offset, c, index_a, index_b; | |
429 | unsigned int bits; /* at most 18 bits */ | |
430 | unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES]; | |
431 | /* hmac_pad is the masked HMAC key. */ | |
432 | unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE]; | |
433 | unsigned char first_block[MAX_HASH_BLOCK_SIZE]; | |
434 | unsigned char mac_out[EVP_MAX_MD_SIZE]; | |
435 | unsigned i, j, md_out_size_u; | |
436 | EVP_MD_CTX md_ctx; | |
437 | /* | |
438 | * mdLengthSize is the number of bytes in the length field that | |
439 | * terminates * the hash. | |
440 | */ | |
441 | unsigned md_length_size = 8; | |
442 | char length_is_big_endian = 1; | |
443 | int ret; | |
444 | ||
445 | /* | |
446 | * This is a, hopefully redundant, check that allows us to forget about | |
447 | * many possible overflows later in this function. | |
448 | */ | |
449 | OPENSSL_assert(data_plus_mac_plus_padding_size < 1024 * 1024); | |
450 | ||
451 | switch (EVP_MD_CTX_type(ctx)) { | |
452 | case NID_md5: | |
453 | MD5_Init((MD5_CTX *)md_state.c); | |
454 | md_final_raw = tls1_md5_final_raw; | |
455 | md_transform = | |
456 | (void (*)(void *ctx, const unsigned char *block))MD5_Transform; | |
457 | md_size = 16; | |
458 | sslv3_pad_length = 48; | |
459 | length_is_big_endian = 0; | |
460 | break; | |
461 | case NID_sha1: | |
462 | SHA1_Init((SHA_CTX *)md_state.c); | |
463 | md_final_raw = tls1_sha1_final_raw; | |
464 | md_transform = | |
465 | (void (*)(void *ctx, const unsigned char *block))SHA1_Transform; | |
466 | md_size = 20; | |
467 | break; | |
bbb4ee85 | 468 | #ifndef OPENSSL_NO_SHA256 |
0f113f3e MC |
469 | case NID_sha224: |
470 | SHA224_Init((SHA256_CTX *)md_state.c); | |
471 | md_final_raw = tls1_sha256_final_raw; | |
472 | md_transform = | |
473 | (void (*)(void *ctx, const unsigned char *block))SHA256_Transform; | |
474 | md_size = 224 / 8; | |
475 | break; | |
476 | case NID_sha256: | |
477 | SHA256_Init((SHA256_CTX *)md_state.c); | |
478 | md_final_raw = tls1_sha256_final_raw; | |
479 | md_transform = | |
480 | (void (*)(void *ctx, const unsigned char *block))SHA256_Transform; | |
481 | md_size = 32; | |
482 | break; | |
bbb4ee85 AP |
483 | #endif |
484 | #ifndef OPENSSL_NO_SHA512 | |
0f113f3e MC |
485 | case NID_sha384: |
486 | SHA384_Init((SHA512_CTX *)md_state.c); | |
487 | md_final_raw = tls1_sha512_final_raw; | |
488 | md_transform = | |
489 | (void (*)(void *ctx, const unsigned char *block))SHA512_Transform; | |
490 | md_size = 384 / 8; | |
491 | md_block_size = 128; | |
492 | md_length_size = 16; | |
493 | break; | |
494 | case NID_sha512: | |
495 | SHA512_Init((SHA512_CTX *)md_state.c); | |
496 | md_final_raw = tls1_sha512_final_raw; | |
497 | md_transform = | |
498 | (void (*)(void *ctx, const unsigned char *block))SHA512_Transform; | |
499 | md_size = 64; | |
500 | md_block_size = 128; | |
501 | md_length_size = 16; | |
502 | break; | |
bbb4ee85 | 503 | #endif |
0f113f3e MC |
504 | default: |
505 | /* | |
506 | * ssl3_cbc_record_digest_supported should have been called first to | |
507 | * check that the hash function is supported. | |
508 | */ | |
509 | OPENSSL_assert(0); | |
510 | if (md_out_size) | |
511 | *md_out_size = -1; | |
512 | return; | |
513 | } | |
514 | ||
515 | OPENSSL_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES); | |
516 | OPENSSL_assert(md_block_size <= MAX_HASH_BLOCK_SIZE); | |
517 | OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE); | |
518 | ||
519 | header_length = 13; | |
520 | if (is_sslv3) { | |
521 | header_length = mac_secret_length + sslv3_pad_length + 8 /* sequence | |
522 | * number */ + | |
523 | 1 /* record type */ + | |
524 | 2 /* record length */ ; | |
525 | } | |
526 | ||
527 | /* | |
528 | * variance_blocks is the number of blocks of the hash that we have to | |
529 | * calculate in constant time because they could be altered by the | |
530 | * padding value. In SSLv3, the padding must be minimal so the end of | |
531 | * the plaintext varies by, at most, 15+20 = 35 bytes. (We conservatively | |
532 | * assume that the MAC size varies from 0..20 bytes.) In case the 9 bytes | |
533 | * of hash termination (0x80 + 64-bit length) don't fit in the final | |
534 | * block, we say that the final two blocks can vary based on the padding. | |
535 | * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not | |
536 | * required to be minimal. Therefore we say that the final six blocks can | |
537 | * vary based on the padding. Later in the function, if the message is | |
538 | * short and there obviously cannot be this many blocks then | |
539 | * variance_blocks can be reduced. | |
540 | */ | |
541 | variance_blocks = is_sslv3 ? 2 : 6; | |
542 | /* | |
543 | * From now on we're dealing with the MAC, which conceptually has 13 | |
544 | * bytes of `header' before the start of the data (TLS) or 71/75 bytes | |
545 | * (SSLv3) | |
546 | */ | |
547 | len = data_plus_mac_plus_padding_size + header_length; | |
548 | /* | |
549 | * max_mac_bytes contains the maximum bytes of bytes in the MAC, | |
550 | * including * |header|, assuming that there's no padding. | |
551 | */ | |
552 | max_mac_bytes = len - md_size - 1; | |
553 | /* num_blocks is the maximum number of hash blocks. */ | |
554 | num_blocks = | |
555 | (max_mac_bytes + 1 + md_length_size + md_block_size - | |
556 | 1) / md_block_size; | |
557 | /* | |
558 | * In order to calculate the MAC in constant time we have to handle the | |
559 | * final blocks specially because the padding value could cause the end | |
560 | * to appear somewhere in the final |variance_blocks| blocks and we can't | |
561 | * leak where. However, |num_starting_blocks| worth of data can be hashed | |
562 | * right away because no padding value can affect whether they are | |
563 | * plaintext. | |
564 | */ | |
565 | num_starting_blocks = 0; | |
566 | /* | |
567 | * k is the starting byte offset into the conceptual header||data where | |
568 | * we start processing. | |
569 | */ | |
570 | k = 0; | |
571 | /* | |
572 | * mac_end_offset is the index just past the end of the data to be MACed. | |
573 | */ | |
574 | mac_end_offset = data_plus_mac_size + header_length - md_size; | |
575 | /* | |
576 | * c is the index of the 0x80 byte in the final hash block that contains | |
577 | * application data. | |
578 | */ | |
579 | c = mac_end_offset % md_block_size; | |
580 | /* | |
581 | * index_a is the hash block number that contains the 0x80 terminating | |
582 | * value. | |
583 | */ | |
584 | index_a = mac_end_offset / md_block_size; | |
585 | /* | |
586 | * index_b is the hash block number that contains the 64-bit hash length, | |
587 | * in bits. | |
588 | */ | |
589 | index_b = (mac_end_offset + md_length_size) / md_block_size; | |
590 | /* | |
591 | * bits is the hash-length in bits. It includes the additional hash block | |
592 | * for the masked HMAC key, or whole of |header| in the case of SSLv3. | |
593 | */ | |
594 | ||
595 | /* | |
596 | * For SSLv3, if we're going to have any starting blocks then we need at | |
597 | * least two because the header is larger than a single block. | |
598 | */ | |
599 | if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0)) { | |
600 | num_starting_blocks = num_blocks - variance_blocks; | |
601 | k = md_block_size * num_starting_blocks; | |
602 | } | |
603 | ||
604 | bits = 8 * mac_end_offset; | |
605 | if (!is_sslv3) { | |
606 | /* | |
607 | * Compute the initial HMAC block. For SSLv3, the padding and secret | |
608 | * bytes are included in |header| because they take more than a | |
609 | * single block. | |
610 | */ | |
611 | bits += 8 * md_block_size; | |
612 | memset(hmac_pad, 0, md_block_size); | |
613 | OPENSSL_assert(mac_secret_length <= sizeof(hmac_pad)); | |
614 | memcpy(hmac_pad, mac_secret, mac_secret_length); | |
615 | for (i = 0; i < md_block_size; i++) | |
616 | hmac_pad[i] ^= 0x36; | |
617 | ||
618 | md_transform(md_state.c, hmac_pad); | |
619 | } | |
620 | ||
621 | if (length_is_big_endian) { | |
622 | memset(length_bytes, 0, md_length_size - 4); | |
623 | length_bytes[md_length_size - 4] = (unsigned char)(bits >> 24); | |
624 | length_bytes[md_length_size - 3] = (unsigned char)(bits >> 16); | |
625 | length_bytes[md_length_size - 2] = (unsigned char)(bits >> 8); | |
626 | length_bytes[md_length_size - 1] = (unsigned char)bits; | |
627 | } else { | |
628 | memset(length_bytes, 0, md_length_size); | |
629 | length_bytes[md_length_size - 5] = (unsigned char)(bits >> 24); | |
630 | length_bytes[md_length_size - 6] = (unsigned char)(bits >> 16); | |
631 | length_bytes[md_length_size - 7] = (unsigned char)(bits >> 8); | |
632 | length_bytes[md_length_size - 8] = (unsigned char)bits; | |
633 | } | |
634 | ||
635 | if (k > 0) { | |
636 | if (is_sslv3) { | |
637 | /* | |
638 | * The SSLv3 header is larger than a single block. overhang is | |
639 | * the number of bytes beyond a single block that the header | |
640 | * consumes: either 7 bytes (SHA1) or 11 bytes (MD5). | |
641 | */ | |
642 | unsigned overhang = header_length - md_block_size; | |
643 | md_transform(md_state.c, header); | |
644 | memcpy(first_block, header + md_block_size, overhang); | |
645 | memcpy(first_block + overhang, data, md_block_size - overhang); | |
646 | md_transform(md_state.c, first_block); | |
647 | for (i = 1; i < k / md_block_size - 1; i++) | |
648 | md_transform(md_state.c, data + md_block_size * i - overhang); | |
649 | } else { | |
650 | /* k is a multiple of md_block_size. */ | |
651 | memcpy(first_block, header, 13); | |
652 | memcpy(first_block + 13, data, md_block_size - 13); | |
653 | md_transform(md_state.c, first_block); | |
654 | for (i = 1; i < k / md_block_size; i++) | |
655 | md_transform(md_state.c, data + md_block_size * i - 13); | |
656 | } | |
657 | } | |
658 | ||
659 | memset(mac_out, 0, sizeof(mac_out)); | |
660 | ||
661 | /* | |
662 | * We now process the final hash blocks. For each block, we construct it | |
663 | * in constant time. If the |i==index_a| then we'll include the 0x80 | |
664 | * bytes and zero pad etc. For each block we selectively copy it, in | |
665 | * constant time, to |mac_out|. | |
666 | */ | |
667 | for (i = num_starting_blocks; i <= num_starting_blocks + variance_blocks; | |
668 | i++) { | |
669 | unsigned char block[MAX_HASH_BLOCK_SIZE]; | |
670 | unsigned char is_block_a = constant_time_eq_8(i, index_a); | |
671 | unsigned char is_block_b = constant_time_eq_8(i, index_b); | |
672 | for (j = 0; j < md_block_size; j++) { | |
673 | unsigned char b = 0, is_past_c, is_past_cp1; | |
674 | if (k < header_length) | |
675 | b = header[k]; | |
676 | else if (k < data_plus_mac_plus_padding_size + header_length) | |
677 | b = data[k - header_length]; | |
678 | k++; | |
679 | ||
680 | is_past_c = is_block_a & constant_time_ge_8(j, c); | |
681 | is_past_cp1 = is_block_a & constant_time_ge_8(j, c + 1); | |
682 | /* | |
683 | * If this is the block containing the end of the application | |
684 | * data, and we are at the offset for the 0x80 value, then | |
685 | * overwrite b with 0x80. | |
686 | */ | |
687 | b = constant_time_select_8(is_past_c, 0x80, b); | |
688 | /* | |
689 | * If this the the block containing the end of the application | |
690 | * data and we're past the 0x80 value then just write zero. | |
691 | */ | |
692 | b = b & ~is_past_cp1; | |
693 | /* | |
694 | * If this is index_b (the final block), but not index_a (the end | |
695 | * of the data), then the 64-bit length didn't fit into index_a | |
696 | * and we're having to add an extra block of zeros. | |
697 | */ | |
698 | b &= ~is_block_b | is_block_a; | |
699 | ||
700 | /* | |
701 | * The final bytes of one of the blocks contains the length. | |
702 | */ | |
703 | if (j >= md_block_size - md_length_size) { | |
704 | /* If this is index_b, write a length byte. */ | |
705 | b = constant_time_select_8(is_block_b, | |
706 | length_bytes[j - | |
707 | (md_block_size - | |
708 | md_length_size)], b); | |
709 | } | |
710 | block[j] = b; | |
711 | } | |
712 | ||
713 | md_transform(md_state.c, block); | |
714 | md_final_raw(md_state.c, block); | |
715 | /* If this is index_b, copy the hash value to |mac_out|. */ | |
716 | for (j = 0; j < md_size; j++) | |
717 | mac_out[j] |= block[j] & is_block_b; | |
718 | } | |
719 | ||
720 | EVP_MD_CTX_init(&md_ctx); | |
721 | EVP_DigestInit_ex(&md_ctx, ctx->digest, NULL /* engine */ ); | |
722 | if (is_sslv3) { | |
723 | /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */ | |
724 | memset(hmac_pad, 0x5c, sslv3_pad_length); | |
725 | ||
726 | EVP_DigestUpdate(&md_ctx, mac_secret, mac_secret_length); | |
727 | EVP_DigestUpdate(&md_ctx, hmac_pad, sslv3_pad_length); | |
728 | EVP_DigestUpdate(&md_ctx, mac_out, md_size); | |
729 | } else { | |
730 | /* Complete the HMAC in the standard manner. */ | |
731 | for (i = 0; i < md_block_size; i++) | |
732 | hmac_pad[i] ^= 0x6a; | |
733 | ||
734 | EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size); | |
735 | EVP_DigestUpdate(&md_ctx, mac_out, md_size); | |
736 | } | |
737 | ret = EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u); | |
738 | if (ret && md_out_size) | |
739 | *md_out_size = md_out_size_u; | |
740 | EVP_MD_CTX_cleanup(&md_ctx); | |
741 | } | |
742 | ||
743 | /* | |
744 | * Due to the need to use EVP in FIPS mode we can't reimplement digests but | |
745 | * we can ensure the number of blocks processed is equal for all cases by | |
746 | * digesting additional data. | |
c4e6fb15 DSH |
747 | */ |
748 | ||
0f113f3e MC |
749 | void tls_fips_digest_extra(const EVP_CIPHER_CTX *cipher_ctx, |
750 | EVP_MD_CTX *mac_ctx, const unsigned char *data, | |
751 | size_t data_len, size_t orig_len) | |
752 | { | |
753 | size_t block_size, digest_pad, blocks_data, blocks_orig; | |
754 | if (EVP_CIPHER_CTX_mode(cipher_ctx) != EVP_CIPH_CBC_MODE) | |
755 | return; | |
756 | block_size = EVP_MD_CTX_block_size(mac_ctx); | |
757 | /*- | |
758 | * We are in FIPS mode if we get this far so we know we have only SHA* | |
759 | * digests and TLS to deal with. | |
760 | * Minimum digest padding length is 17 for SHA384/SHA512 and 9 | |
761 | * otherwise. | |
762 | * Additional header is 13 bytes. To get the number of digest blocks | |
763 | * processed round up the amount of data plus padding to the nearest | |
764 | * block length. Block length is 128 for SHA384/SHA512 and 64 otherwise. | |
765 | * So we have: | |
766 | * blocks = (payload_len + digest_pad + 13 + block_size - 1)/block_size | |
767 | * equivalently: | |
768 | * blocks = (payload_len + digest_pad + 12)/block_size + 1 | |
769 | * HMAC adds a constant overhead. | |
770 | * We're ultimately only interested in differences so this becomes | |
771 | * blocks = (payload_len + 29)/128 | |
772 | * for SHA384/SHA512 and | |
773 | * blocks = (payload_len + 21)/64 | |
774 | * otherwise. | |
775 | */ | |
776 | digest_pad = block_size == 64 ? 21 : 29; | |
777 | blocks_orig = (orig_len + digest_pad) / block_size; | |
778 | blocks_data = (data_len + digest_pad) / block_size; | |
779 | /* | |
780 | * MAC enough blocks to make up the difference between the original and | |
781 | * actual lengths plus one extra block to ensure this is never a no op. | |
782 | * The "data" pointer should always have enough space to perform this | |
783 | * operation as it is large enough for a maximum length TLS buffer. | |
784 | */ | |
785 | EVP_DigestSignUpdate(mac_ctx, data, | |
786 | (blocks_orig - blocks_data + 1) * block_size); | |
787 | } |