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0f113f3e | 1 | /* |
82eba370 | 2 | * Copyright 1999-2018 The OpenSSL Project Authors. All Rights Reserved. |
2039c421 | 3 | * |
2a7b6f39 | 4 | * Licensed under the Apache License 2.0 (the "License"). You may not use |
2039c421 RS |
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 | |
0f113f3e | 8 | */ |
a4949896 | 9 | |
9347ba48 BM |
10 | /* EME-OAEP as defined in RFC 2437 (PKCS #1 v2.0) */ |
11 | ||
0f113f3e MC |
12 | /* |
13 | * See Victor Shoup, "OAEP reconsidered," Nov. 2000, <URL: | |
14 | * http://www.shoup.net/papers/oaep.ps.Z> for problems with the security | |
15 | * proof for the original OAEP scheme, which EME-OAEP is based on. A new | |
16 | * proof can be found in E. Fujisaki, T. Okamoto, D. Pointcheval, J. Stern, | |
17 | * "RSA-OEAP is Still Alive!", Dec. 2000, <URL: | |
18 | * http://eprint.iacr.org/2000/061/>. The new proof has stronger requirements | |
19 | * for the underlying permutation: "partial-one-wayness" instead of | |
20 | * one-wayness. For the RSA function, this is an equivalent notion. | |
9347ba48 BM |
21 | */ |
22 | ||
68570797 | 23 | #include "internal/constant_time_locl.h" |
a4949896 | 24 | |
474e469b | 25 | #include <stdio.h> |
b39fc560 | 26 | #include "internal/cryptlib.h" |
474e469b | 27 | #include <openssl/bn.h> |
474e469b RS |
28 | #include <openssl/evp.h> |
29 | #include <openssl/rand.h> | |
30 | #include <openssl/sha.h> | |
9862e9aa | 31 | #include "rsa_locl.h" |
a4949896 | 32 | |
6b691a5c | 33 | int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen, |
0f113f3e MC |
34 | const unsigned char *from, int flen, |
35 | const unsigned char *param, int plen) | |
36 | { | |
37 | return RSA_padding_add_PKCS1_OAEP_mgf1(to, tlen, from, flen, | |
38 | param, plen, NULL, NULL); | |
39 | } | |
271fef0e DSH |
40 | |
41 | int RSA_padding_add_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, | |
0f113f3e MC |
42 | const unsigned char *from, int flen, |
43 | const unsigned char *param, int plen, | |
44 | const EVP_MD *md, const EVP_MD *mgf1md) | |
45 | { | |
82eba370 | 46 | int rv = 0; |
0f113f3e MC |
47 | int i, emlen = tlen - 1; |
48 | unsigned char *db, *seed; | |
82eba370 SL |
49 | unsigned char *dbmask = NULL; |
50 | unsigned char seedmask[EVP_MAX_MD_SIZE]; | |
51 | int mdlen, dbmask_len = 0; | |
0f113f3e MC |
52 | |
53 | if (md == NULL) | |
54 | md = EVP_sha1(); | |
55 | if (mgf1md == NULL) | |
56 | mgf1md = md; | |
57 | ||
58 | mdlen = EVP_MD_size(md); | |
59 | ||
60 | if (flen > emlen - 2 * mdlen - 1) { | |
61 | RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP_MGF1, | |
62 | RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE); | |
63 | return 0; | |
64 | } | |
65 | ||
66 | if (emlen < 2 * mdlen + 1) { | |
67 | RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP_MGF1, | |
68 | RSA_R_KEY_SIZE_TOO_SMALL); | |
69 | return 0; | |
70 | } | |
71 | ||
72 | to[0] = 0; | |
73 | seed = to + 1; | |
74 | db = to + mdlen + 1; | |
75 | ||
76 | if (!EVP_Digest((void *)param, plen, db, NULL, md, NULL)) | |
82eba370 | 77 | goto err; |
0f113f3e MC |
78 | memset(db + mdlen, 0, emlen - flen - 2 * mdlen - 1); |
79 | db[emlen - flen - mdlen - 1] = 0x01; | |
80 | memcpy(db + emlen - flen - mdlen, from, (unsigned int)flen); | |
81 | if (RAND_bytes(seed, mdlen) <= 0) | |
82eba370 | 82 | goto err; |
0f113f3e | 83 | |
82eba370 SL |
84 | dbmask_len = emlen - mdlen; |
85 | dbmask = OPENSSL_malloc(dbmask_len); | |
0f113f3e MC |
86 | if (dbmask == NULL) { |
87 | RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP_MGF1, ERR_R_MALLOC_FAILURE); | |
82eba370 | 88 | goto err; |
0f113f3e MC |
89 | } |
90 | ||
82eba370 | 91 | if (PKCS1_MGF1(dbmask, dbmask_len, seed, mdlen, mgf1md) < 0) |
c6d215e0 | 92 | goto err; |
82eba370 | 93 | for (i = 0; i < dbmask_len; i++) |
0f113f3e MC |
94 | db[i] ^= dbmask[i]; |
95 | ||
82eba370 | 96 | if (PKCS1_MGF1(seedmask, mdlen, db, dbmask_len, mgf1md) < 0) |
c6d215e0 | 97 | goto err; |
0f113f3e MC |
98 | for (i = 0; i < mdlen; i++) |
99 | seed[i] ^= seedmask[i]; | |
82eba370 | 100 | rv = 1; |
c6d215e0 BE |
101 | |
102 | err: | |
82eba370 SL |
103 | OPENSSL_cleanse(seedmask, sizeof(seedmask)); |
104 | OPENSSL_clear_free(dbmask, dbmask_len); | |
105 | return rv; | |
0f113f3e | 106 | } |
a4949896 | 107 | |
6b691a5c | 108 | int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen, |
0f113f3e MC |
109 | const unsigned char *from, int flen, int num, |
110 | const unsigned char *param, int plen) | |
111 | { | |
112 | return RSA_padding_check_PKCS1_OAEP_mgf1(to, tlen, from, flen, num, | |
113 | param, plen, NULL, NULL); | |
114 | } | |
271fef0e DSH |
115 | |
116 | int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, | |
0f113f3e MC |
117 | const unsigned char *from, int flen, |
118 | int num, const unsigned char *param, | |
119 | int plen, const EVP_MD *md, | |
120 | const EVP_MD *mgf1md) | |
121 | { | |
e670db01 | 122 | int i, dblen = 0, mlen = -1, one_index = 0, msg_index; |
75f5e944 | 123 | unsigned int good = 0, found_one_byte, mask; |
0f113f3e MC |
124 | const unsigned char *maskedseed, *maskeddb; |
125 | /* | |
126 | * |em| is the encoded message, zero-padded to exactly |num| bytes: em = | |
127 | * Y || maskedSeed || maskedDB | |
128 | */ | |
129 | unsigned char *db = NULL, *em = NULL, seed[EVP_MAX_MD_SIZE], | |
130 | phash[EVP_MAX_MD_SIZE]; | |
131 | int mdlen; | |
132 | ||
133 | if (md == NULL) | |
134 | md = EVP_sha1(); | |
135 | if (mgf1md == NULL) | |
136 | mgf1md = md; | |
137 | ||
138 | mdlen = EVP_MD_size(md); | |
139 | ||
140 | if (tlen <= 0 || flen <= 0) | |
141 | return -1; | |
142 | /* | |
143 | * |num| is the length of the modulus; |flen| is the length of the | |
144 | * encoded message. Therefore, for any |from| that was obtained by | |
145 | * decrypting a ciphertext, we must have |flen| <= |num|. Similarly, | |
146 | * num < 2 * mdlen + 2 must hold for the modulus irrespective of | |
147 | * the ciphertext, see PKCS #1 v2.2, section 7.1.2. | |
148 | * This does not leak any side-channel information. | |
149 | */ | |
75f5e944 AP |
150 | if (num < flen || num < 2 * mdlen + 2) { |
151 | RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, | |
152 | RSA_R_OAEP_DECODING_ERROR); | |
153 | return -1; | |
154 | } | |
0f113f3e MC |
155 | |
156 | dblen = num - mdlen - 1; | |
157 | db = OPENSSL_malloc(dblen); | |
582ad5d4 | 158 | if (db == NULL) { |
0f113f3e MC |
159 | RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, ERR_R_MALLOC_FAILURE); |
160 | goto cleanup; | |
161 | } | |
162 | ||
75f5e944 AP |
163 | em = OPENSSL_malloc(num); |
164 | if (em == NULL) { | |
165 | RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, | |
166 | ERR_R_MALLOC_FAILURE); | |
167 | goto cleanup; | |
168 | } | |
582ad5d4 | 169 | |
75f5e944 AP |
170 | /* |
171 | * Caller is encouraged to pass zero-padded message created with | |
172 | * BN_bn2binpad. Trouble is that since we can't read out of |from|'s | |
173 | * bounds, it's impossible to have an invariant memory access pattern | |
174 | * in case |from| was not zero-padded in advance. | |
175 | */ | |
176 | for (from += flen, em += num, i = 0; i < num; i++) { | |
177 | mask = ~constant_time_is_zero(flen); | |
178 | flen -= 1 & mask; | |
179 | from -= 1 & mask; | |
180 | *--em = *from & mask; | |
582ad5d4 | 181 | } |
75f5e944 | 182 | from = em; |
0f113f3e MC |
183 | |
184 | /* | |
185 | * The first byte must be zero, however we must not leak if this is | |
186 | * true. See James H. Manger, "A Chosen Ciphertext Attack on RSA | |
187 | * Optimal Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001). | |
188 | */ | |
582ad5d4 | 189 | good = constant_time_is_zero(from[0]); |
0f113f3e | 190 | |
582ad5d4 AP |
191 | maskedseed = from + 1; |
192 | maskeddb = from + 1 + mdlen; | |
0f113f3e MC |
193 | |
194 | if (PKCS1_MGF1(seed, mdlen, maskeddb, dblen, mgf1md)) | |
195 | goto cleanup; | |
196 | for (i = 0; i < mdlen; i++) | |
197 | seed[i] ^= maskedseed[i]; | |
198 | ||
199 | if (PKCS1_MGF1(db, dblen, seed, mdlen, mgf1md)) | |
200 | goto cleanup; | |
201 | for (i = 0; i < dblen; i++) | |
202 | db[i] ^= maskeddb[i]; | |
203 | ||
204 | if (!EVP_Digest((void *)param, plen, phash, NULL, md, NULL)) | |
205 | goto cleanup; | |
206 | ||
207 | good &= constant_time_is_zero(CRYPTO_memcmp(db, phash, mdlen)); | |
208 | ||
209 | found_one_byte = 0; | |
210 | for (i = mdlen; i < dblen; i++) { | |
211 | /* | |
212 | * Padding consists of a number of 0-bytes, followed by a 1. | |
213 | */ | |
214 | unsigned int equals1 = constant_time_eq(db[i], 1); | |
215 | unsigned int equals0 = constant_time_is_zero(db[i]); | |
216 | one_index = constant_time_select_int(~found_one_byte & equals1, | |
217 | i, one_index); | |
218 | found_one_byte |= equals1; | |
219 | good &= (found_one_byte | equals0); | |
220 | } | |
221 | ||
222 | good &= found_one_byte; | |
223 | ||
224 | /* | |
225 | * At this point |good| is zero unless the plaintext was valid, | |
226 | * so plaintext-awareness ensures timing side-channels are no longer a | |
227 | * concern. | |
228 | */ | |
0f113f3e MC |
229 | msg_index = one_index + 1; |
230 | mlen = dblen - msg_index; | |
231 | ||
75f5e944 AP |
232 | /* |
233 | * For good measure, do this check in constant tine as well. | |
234 | */ | |
235 | good &= constant_time_ge(tlen, mlen); | |
236 | ||
237 | /* | |
238 | * Even though we can't fake result's length, we can pretend copying | |
239 | * |tlen| bytes where |mlen| bytes would be real. Last |tlen| of |dblen| | |
240 | * bytes are viewed as circular buffer with start at |tlen|-|mlen'|, | |
241 | * where |mlen'| is "saturated" |mlen| value. Deducing information | |
242 | * about failure or |mlen| would take attacker's ability to observe | |
243 | * memory access pattern with byte granularity *as it occurs*. It | |
244 | * should be noted that failure is indistinguishable from normal | |
245 | * operation if |tlen| is fixed by protocol. | |
246 | */ | |
247 | tlen = constant_time_select_int(constant_time_lt(dblen, tlen), dblen, tlen); | |
248 | msg_index = constant_time_select_int(good, msg_index, dblen - tlen); | |
249 | mlen = dblen - msg_index; | |
250 | for (from = db + msg_index, mask = good, i = 0; i < tlen; i++) { | |
251 | unsigned int equals = constant_time_eq(i, mlen); | |
252 | ||
253 | from -= dblen & equals; /* if (i == dblen) rewind */ | |
254 | mask &= mask ^ equals; /* if (i == dblen) mask = 0 */ | |
255 | to[i] = constant_time_select_8(mask, from[i], to[i]); | |
0f113f3e MC |
256 | } |
257 | ||
0f113f3e MC |
258 | /* |
259 | * To avoid chosen ciphertext attacks, the error message should not | |
260 | * reveal which kind of decoding error happened. | |
261 | */ | |
262 | RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, | |
263 | RSA_R_OAEP_DECODING_ERROR); | |
75f5e944 | 264 | err_clear_last_constant_time(1 & good); |
0f113f3e | 265 | cleanup: |
82eba370 | 266 | OPENSSL_cleanse(seed, sizeof(seed)); |
e670db01 BE |
267 | OPENSSL_clear_free(db, dblen); |
268 | OPENSSL_clear_free(em, num); | |
75f5e944 AP |
269 | |
270 | return constant_time_select_int(good, mlen, -1); | |
0f113f3e | 271 | } |
a4949896 | 272 | |
499fca2d | 273 | int PKCS1_MGF1(unsigned char *mask, long len, |
0f113f3e MC |
274 | const unsigned char *seed, long seedlen, const EVP_MD *dgst) |
275 | { | |
276 | long i, outlen = 0; | |
277 | unsigned char cnt[4]; | |
bfb0641f | 278 | EVP_MD_CTX *c = EVP_MD_CTX_new(); |
0f113f3e MC |
279 | unsigned char md[EVP_MAX_MD_SIZE]; |
280 | int mdlen; | |
281 | int rv = -1; | |
282 | ||
6e59a892 RL |
283 | if (c == NULL) |
284 | goto err; | |
285 | mdlen = EVP_MD_size(dgst); | |
0f113f3e MC |
286 | if (mdlen < 0) |
287 | goto err; | |
288 | for (i = 0; outlen < len; i++) { | |
289 | cnt[0] = (unsigned char)((i >> 24) & 255); | |
290 | cnt[1] = (unsigned char)((i >> 16) & 255); | |
291 | cnt[2] = (unsigned char)((i >> 8)) & 255; | |
292 | cnt[3] = (unsigned char)(i & 255); | |
6e59a892 RL |
293 | if (!EVP_DigestInit_ex(c, dgst, NULL) |
294 | || !EVP_DigestUpdate(c, seed, seedlen) | |
295 | || !EVP_DigestUpdate(c, cnt, 4)) | |
0f113f3e MC |
296 | goto err; |
297 | if (outlen + mdlen <= len) { | |
6e59a892 | 298 | if (!EVP_DigestFinal_ex(c, mask + outlen, NULL)) |
0f113f3e MC |
299 | goto err; |
300 | outlen += mdlen; | |
301 | } else { | |
6e59a892 | 302 | if (!EVP_DigestFinal_ex(c, md, NULL)) |
0f113f3e MC |
303 | goto err; |
304 | memcpy(mask + outlen, md, len - outlen); | |
305 | outlen = len; | |
306 | } | |
307 | } | |
308 | rv = 0; | |
309 | err: | |
82eba370 | 310 | OPENSSL_cleanse(md, sizeof(md)); |
bfb0641f | 311 | EVP_MD_CTX_free(c); |
0f113f3e MC |
312 | return rv; |
313 | } |