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0f113f3e | 1 | /* |
4333b89f | 2 | * Copyright 1999-2021 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 | ||
c5f87134 P |
23 | /* |
24 | * RSA low level APIs are deprecated for public use, but still ok for | |
25 | * internal use. | |
26 | */ | |
27 | #include "internal/deprecated.h" | |
28 | ||
706457b7 | 29 | #include "internal/constant_time.h" |
a4949896 | 30 | |
474e469b | 31 | #include <stdio.h> |
b39fc560 | 32 | #include "internal/cryptlib.h" |
474e469b | 33 | #include <openssl/bn.h> |
474e469b RS |
34 | #include <openssl/evp.h> |
35 | #include <openssl/rand.h> | |
36 | #include <openssl/sha.h> | |
706457b7 | 37 | #include "rsa_local.h" |
a4949896 | 38 | |
6b691a5c | 39 | int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen, |
0f113f3e MC |
40 | const unsigned char *from, int flen, |
41 | const unsigned char *param, int plen) | |
42 | { | |
23b2fc0b P |
43 | return ossl_rsa_padding_add_PKCS1_OAEP_mgf1_ex(NULL, to, tlen, from, flen, |
44 | param, plen, NULL, NULL); | |
0f113f3e | 45 | } |
271fef0e | 46 | |
ad7e17dd | 47 | /* |
0434f984 | 48 | * Perform the padding as per NIST 800-56B 7.2.2.3 |
ad7e17dd P |
49 | * from (K) is the key material. |
50 | * param (A) is the additional input. | |
51 | * Step numbers are included here but not in the constant time inverse below | |
52 | * to avoid complicating an already difficult enough function. | |
53 | */ | |
b4250010 | 54 | int ossl_rsa_padding_add_PKCS1_OAEP_mgf1_ex(OSSL_LIB_CTX *libctx, |
23b2fc0b P |
55 | unsigned char *to, int tlen, |
56 | const unsigned char *from, int flen, | |
57 | const unsigned char *param, | |
58 | int plen, const EVP_MD *md, | |
59 | const EVP_MD *mgf1md) | |
0f113f3e | 60 | { |
82eba370 | 61 | int rv = 0; |
0f113f3e MC |
62 | int i, emlen = tlen - 1; |
63 | unsigned char *db, *seed; | |
82eba370 SL |
64 | unsigned char *dbmask = NULL; |
65 | unsigned char seedmask[EVP_MAX_MD_SIZE]; | |
66 | int mdlen, dbmask_len = 0; | |
0f113f3e | 67 | |
e637d47c | 68 | if (md == NULL) { |
f844f9eb | 69 | #ifndef FIPS_MODULE |
0f113f3e | 70 | md = EVP_sha1(); |
afb638f1 | 71 | #else |
9311d0c4 | 72 | ERR_raise(ERR_LIB_RSA, ERR_R_PASSED_NULL_PARAMETER); |
afb638f1 MC |
73 | return 0; |
74 | #endif | |
e637d47c | 75 | } |
0f113f3e MC |
76 | if (mgf1md == NULL) |
77 | mgf1md = md; | |
78 | ||
ed576acd | 79 | mdlen = EVP_MD_get_size(md); |
28cab209 P |
80 | if (mdlen <= 0) { |
81 | ERR_raise(ERR_LIB_RSA, RSA_R_INVALID_LENGTH); | |
82 | return 0; | |
83 | } | |
0f113f3e | 84 | |
ad7e17dd | 85 | /* step 2b: check KLen > nLen - 2 HLen - 2 */ |
0f113f3e | 86 | if (flen > emlen - 2 * mdlen - 1) { |
9311d0c4 | 87 | ERR_raise(ERR_LIB_RSA, RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE); |
0f113f3e MC |
88 | return 0; |
89 | } | |
90 | ||
91 | if (emlen < 2 * mdlen + 1) { | |
9311d0c4 | 92 | ERR_raise(ERR_LIB_RSA, RSA_R_KEY_SIZE_TOO_SMALL); |
0f113f3e MC |
93 | return 0; |
94 | } | |
95 | ||
ad7e17dd | 96 | /* step 3i: EM = 00000000 || maskedMGF || maskedDB */ |
0f113f3e MC |
97 | to[0] = 0; |
98 | seed = to + 1; | |
99 | db = to + mdlen + 1; | |
100 | ||
ad7e17dd | 101 | /* step 3a: hash the additional input */ |
0f113f3e | 102 | if (!EVP_Digest((void *)param, plen, db, NULL, md, NULL)) |
82eba370 | 103 | goto err; |
ad7e17dd | 104 | /* step 3b: zero bytes array of length nLen - KLen - 2 HLen -2 */ |
0f113f3e | 105 | memset(db + mdlen, 0, emlen - flen - 2 * mdlen - 1); |
ad7e17dd | 106 | /* step 3c: DB = HA || PS || 00000001 || K */ |
0f113f3e MC |
107 | db[emlen - flen - mdlen - 1] = 0x01; |
108 | memcpy(db + emlen - flen - mdlen, from, (unsigned int)flen); | |
ad7e17dd | 109 | /* step 3d: generate random byte string */ |
5cbd2ea3 | 110 | if (RAND_bytes_ex(libctx, seed, mdlen, 0) <= 0) |
82eba370 | 111 | goto err; |
0f113f3e | 112 | |
82eba370 SL |
113 | dbmask_len = emlen - mdlen; |
114 | dbmask = OPENSSL_malloc(dbmask_len); | |
0f113f3e | 115 | if (dbmask == NULL) { |
9311d0c4 | 116 | ERR_raise(ERR_LIB_RSA, ERR_R_MALLOC_FAILURE); |
82eba370 | 117 | goto err; |
0f113f3e MC |
118 | } |
119 | ||
ad7e17dd | 120 | /* step 3e: dbMask = MGF(mgfSeed, nLen - HLen - 1) */ |
82eba370 | 121 | if (PKCS1_MGF1(dbmask, dbmask_len, seed, mdlen, mgf1md) < 0) |
c6d215e0 | 122 | goto err; |
ad7e17dd | 123 | /* step 3f: maskedDB = DB XOR dbMask */ |
82eba370 | 124 | for (i = 0; i < dbmask_len; i++) |
0f113f3e MC |
125 | db[i] ^= dbmask[i]; |
126 | ||
ad7e17dd | 127 | /* step 3g: mgfSeed = MGF(maskedDB, HLen) */ |
82eba370 | 128 | if (PKCS1_MGF1(seedmask, mdlen, db, dbmask_len, mgf1md) < 0) |
c6d215e0 | 129 | goto err; |
ad7e17dd | 130 | /* stepo 3h: maskedMGFSeed = mgfSeed XOR mgfSeedMask */ |
0f113f3e MC |
131 | for (i = 0; i < mdlen; i++) |
132 | seed[i] ^= seedmask[i]; | |
82eba370 | 133 | rv = 1; |
c6d215e0 BE |
134 | |
135 | err: | |
82eba370 SL |
136 | OPENSSL_cleanse(seedmask, sizeof(seedmask)); |
137 | OPENSSL_clear_free(dbmask, dbmask_len); | |
138 | return rv; | |
0f113f3e | 139 | } |
a4949896 | 140 | |
0f2deef5 MC |
141 | int RSA_padding_add_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, |
142 | const unsigned char *from, int flen, | |
143 | const unsigned char *param, int plen, | |
144 | const EVP_MD *md, const EVP_MD *mgf1md) | |
145 | { | |
23b2fc0b P |
146 | return ossl_rsa_padding_add_PKCS1_OAEP_mgf1_ex(NULL, to, tlen, from, flen, |
147 | param, plen, md, mgf1md); | |
0f2deef5 MC |
148 | } |
149 | ||
6b691a5c | 150 | int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen, |
0f113f3e MC |
151 | const unsigned char *from, int flen, int num, |
152 | const unsigned char *param, int plen) | |
153 | { | |
154 | return RSA_padding_check_PKCS1_OAEP_mgf1(to, tlen, from, flen, num, | |
155 | param, plen, NULL, NULL); | |
156 | } | |
271fef0e DSH |
157 | |
158 | int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, | |
0f113f3e MC |
159 | const unsigned char *from, int flen, |
160 | int num, const unsigned char *param, | |
161 | int plen, const EVP_MD *md, | |
162 | const EVP_MD *mgf1md) | |
163 | { | |
e670db01 | 164 | int i, dblen = 0, mlen = -1, one_index = 0, msg_index; |
75f5e944 | 165 | unsigned int good = 0, found_one_byte, mask; |
0f113f3e MC |
166 | const unsigned char *maskedseed, *maskeddb; |
167 | /* | |
168 | * |em| is the encoded message, zero-padded to exactly |num| bytes: em = | |
169 | * Y || maskedSeed || maskedDB | |
170 | */ | |
171 | unsigned char *db = NULL, *em = NULL, seed[EVP_MAX_MD_SIZE], | |
172 | phash[EVP_MAX_MD_SIZE]; | |
173 | int mdlen; | |
174 | ||
afb638f1 | 175 | if (md == NULL) { |
f844f9eb | 176 | #ifndef FIPS_MODULE |
0f113f3e | 177 | md = EVP_sha1(); |
afb638f1 | 178 | #else |
9311d0c4 | 179 | ERR_raise(ERR_LIB_RSA, ERR_R_PASSED_NULL_PARAMETER); |
afb638f1 MC |
180 | return -1; |
181 | #endif | |
182 | } | |
183 | ||
0f113f3e MC |
184 | if (mgf1md == NULL) |
185 | mgf1md = md; | |
186 | ||
ed576acd | 187 | mdlen = EVP_MD_get_size(md); |
0f113f3e MC |
188 | |
189 | if (tlen <= 0 || flen <= 0) | |
190 | return -1; | |
191 | /* | |
192 | * |num| is the length of the modulus; |flen| is the length of the | |
193 | * encoded message. Therefore, for any |from| that was obtained by | |
194 | * decrypting a ciphertext, we must have |flen| <= |num|. Similarly, | |
d7f5e5ae | 195 | * |num| >= 2 * |mdlen| + 2 must hold for the modulus irrespective of |
0f113f3e MC |
196 | * the ciphertext, see PKCS #1 v2.2, section 7.1.2. |
197 | * This does not leak any side-channel information. | |
198 | */ | |
75f5e944 | 199 | if (num < flen || num < 2 * mdlen + 2) { |
9311d0c4 | 200 | ERR_raise(ERR_LIB_RSA, RSA_R_OAEP_DECODING_ERROR); |
75f5e944 AP |
201 | return -1; |
202 | } | |
0f113f3e MC |
203 | |
204 | dblen = num - mdlen - 1; | |
205 | db = OPENSSL_malloc(dblen); | |
582ad5d4 | 206 | if (db == NULL) { |
9311d0c4 | 207 | ERR_raise(ERR_LIB_RSA, ERR_R_MALLOC_FAILURE); |
0f113f3e MC |
208 | goto cleanup; |
209 | } | |
210 | ||
75f5e944 AP |
211 | em = OPENSSL_malloc(num); |
212 | if (em == NULL) { | |
9311d0c4 | 213 | ERR_raise(ERR_LIB_RSA, ERR_R_MALLOC_FAILURE); |
75f5e944 AP |
214 | goto cleanup; |
215 | } | |
582ad5d4 | 216 | |
75f5e944 AP |
217 | /* |
218 | * Caller is encouraged to pass zero-padded message created with | |
219 | * BN_bn2binpad. Trouble is that since we can't read out of |from|'s | |
220 | * bounds, it's impossible to have an invariant memory access pattern | |
221 | * in case |from| was not zero-padded in advance. | |
222 | */ | |
223 | for (from += flen, em += num, i = 0; i < num; i++) { | |
224 | mask = ~constant_time_is_zero(flen); | |
225 | flen -= 1 & mask; | |
226 | from -= 1 & mask; | |
227 | *--em = *from & mask; | |
582ad5d4 | 228 | } |
0f113f3e MC |
229 | |
230 | /* | |
231 | * The first byte must be zero, however we must not leak if this is | |
232 | * true. See James H. Manger, "A Chosen Ciphertext Attack on RSA | |
233 | * Optimal Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001). | |
234 | */ | |
d7f5e5ae | 235 | good = constant_time_is_zero(em[0]); |
0f113f3e | 236 | |
d7f5e5ae BE |
237 | maskedseed = em + 1; |
238 | maskeddb = em + 1 + mdlen; | |
0f113f3e MC |
239 | |
240 | if (PKCS1_MGF1(seed, mdlen, maskeddb, dblen, mgf1md)) | |
241 | goto cleanup; | |
242 | for (i = 0; i < mdlen; i++) | |
243 | seed[i] ^= maskedseed[i]; | |
244 | ||
245 | if (PKCS1_MGF1(db, dblen, seed, mdlen, mgf1md)) | |
246 | goto cleanup; | |
247 | for (i = 0; i < dblen; i++) | |
248 | db[i] ^= maskeddb[i]; | |
249 | ||
250 | if (!EVP_Digest((void *)param, plen, phash, NULL, md, NULL)) | |
251 | goto cleanup; | |
252 | ||
253 | good &= constant_time_is_zero(CRYPTO_memcmp(db, phash, mdlen)); | |
254 | ||
255 | found_one_byte = 0; | |
256 | for (i = mdlen; i < dblen; i++) { | |
257 | /* | |
258 | * Padding consists of a number of 0-bytes, followed by a 1. | |
259 | */ | |
260 | unsigned int equals1 = constant_time_eq(db[i], 1); | |
261 | unsigned int equals0 = constant_time_is_zero(db[i]); | |
262 | one_index = constant_time_select_int(~found_one_byte & equals1, | |
263 | i, one_index); | |
264 | found_one_byte |= equals1; | |
265 | good &= (found_one_byte | equals0); | |
266 | } | |
267 | ||
268 | good &= found_one_byte; | |
269 | ||
270 | /* | |
271 | * At this point |good| is zero unless the plaintext was valid, | |
272 | * so plaintext-awareness ensures timing side-channels are no longer a | |
273 | * concern. | |
274 | */ | |
0f113f3e MC |
275 | msg_index = one_index + 1; |
276 | mlen = dblen - msg_index; | |
277 | ||
75f5e944 | 278 | /* |
d7f5e5ae | 279 | * For good measure, do this check in constant time as well. |
75f5e944 AP |
280 | */ |
281 | good &= constant_time_ge(tlen, mlen); | |
282 | ||
283 | /* | |
9c0cf214 BE |
284 | * Move the result in-place by |dblen|-|mdlen|-1-|mlen| bytes to the left. |
285 | * Then if |good| move |mlen| bytes from |db|+|mdlen|+1 to |to|. | |
286 | * Otherwise leave |to| unchanged. | |
287 | * Copy the memory back in a way that does not reveal the size of | |
288 | * the data being copied via a timing side channel. This requires copying | |
289 | * parts of the buffer multiple times based on the bits set in the real | |
290 | * length. Clear bits do a non-copy with identical access pattern. | |
291 | * The loop below has overall complexity of O(N*log(N)). | |
75f5e944 | 292 | */ |
d7f5e5ae BE |
293 | tlen = constant_time_select_int(constant_time_lt(dblen - mdlen - 1, tlen), |
294 | dblen - mdlen - 1, tlen); | |
9c0cf214 BE |
295 | for (msg_index = 1; msg_index < dblen - mdlen - 1; msg_index <<= 1) { |
296 | mask = ~constant_time_eq(msg_index & (dblen - mdlen - 1 - mlen), 0); | |
297 | for (i = mdlen + 1; i < dblen - msg_index; i++) | |
298 | db[i] = constant_time_select_8(mask, db[i + msg_index], db[i]); | |
299 | } | |
300 | for (i = 0; i < tlen; i++) { | |
301 | mask = good & constant_time_lt(i, mlen); | |
302 | to[i] = constant_time_select_8(mask, db[i + mdlen + 1], to[i]); | |
0f113f3e MC |
303 | } |
304 | ||
f844f9eb | 305 | #ifndef FIPS_MODULE |
0f113f3e MC |
306 | /* |
307 | * To avoid chosen ciphertext attacks, the error message should not | |
308 | * reveal which kind of decoding error happened. | |
afb638f1 MC |
309 | * |
310 | * This trick doesn't work in the FIPS provider because libcrypto manages | |
311 | * the error stack. Instead we opt not to put an error on the stack at all | |
312 | * in case of padding failure in the FIPS provider. | |
0f113f3e | 313 | */ |
9311d0c4 | 314 | ERR_raise(ERR_LIB_RSA, RSA_R_OAEP_DECODING_ERROR); |
75f5e944 | 315 | err_clear_last_constant_time(1 & good); |
afb638f1 | 316 | #endif |
0f113f3e | 317 | cleanup: |
82eba370 | 318 | OPENSSL_cleanse(seed, sizeof(seed)); |
e670db01 BE |
319 | OPENSSL_clear_free(db, dblen); |
320 | OPENSSL_clear_free(em, num); | |
75f5e944 AP |
321 | |
322 | return constant_time_select_int(good, mlen, -1); | |
0f113f3e | 323 | } |
a4949896 | 324 | |
ad7e17dd P |
325 | /* |
326 | * Mask Generation Function corresponding to section 7.2.2.2 of NIST SP 800-56B. | |
327 | * The variables are named differently to NIST: | |
328 | * mask (T) and len (maskLen)are the returned mask. | |
329 | * seed (mgfSeed). | |
330 | * The range checking steps inm the process are performed outside. | |
331 | */ | |
499fca2d | 332 | int PKCS1_MGF1(unsigned char *mask, long len, |
0f113f3e MC |
333 | const unsigned char *seed, long seedlen, const EVP_MD *dgst) |
334 | { | |
335 | long i, outlen = 0; | |
336 | unsigned char cnt[4]; | |
bfb0641f | 337 | EVP_MD_CTX *c = EVP_MD_CTX_new(); |
0f113f3e MC |
338 | unsigned char md[EVP_MAX_MD_SIZE]; |
339 | int mdlen; | |
340 | int rv = -1; | |
341 | ||
6e59a892 RL |
342 | if (c == NULL) |
343 | goto err; | |
ed576acd | 344 | mdlen = EVP_MD_get_size(dgst); |
0f113f3e MC |
345 | if (mdlen < 0) |
346 | goto err; | |
ad7e17dd | 347 | /* step 4 */ |
0f113f3e | 348 | for (i = 0; outlen < len; i++) { |
ad7e17dd | 349 | /* step 4a: D = I2BS(counter, 4) */ |
0f113f3e MC |
350 | cnt[0] = (unsigned char)((i >> 24) & 255); |
351 | cnt[1] = (unsigned char)((i >> 16) & 255); | |
352 | cnt[2] = (unsigned char)((i >> 8)) & 255; | |
353 | cnt[3] = (unsigned char)(i & 255); | |
ad7e17dd | 354 | /* step 4b: T =T || hash(mgfSeed || D) */ |
6e59a892 RL |
355 | if (!EVP_DigestInit_ex(c, dgst, NULL) |
356 | || !EVP_DigestUpdate(c, seed, seedlen) | |
357 | || !EVP_DigestUpdate(c, cnt, 4)) | |
0f113f3e MC |
358 | goto err; |
359 | if (outlen + mdlen <= len) { | |
6e59a892 | 360 | if (!EVP_DigestFinal_ex(c, mask + outlen, NULL)) |
0f113f3e MC |
361 | goto err; |
362 | outlen += mdlen; | |
363 | } else { | |
6e59a892 | 364 | if (!EVP_DigestFinal_ex(c, md, NULL)) |
0f113f3e MC |
365 | goto err; |
366 | memcpy(mask + outlen, md, len - outlen); | |
367 | outlen = len; | |
368 | } | |
369 | } | |
370 | rv = 0; | |
371 | err: | |
82eba370 | 372 | OPENSSL_cleanse(md, sizeof(md)); |
bfb0641f | 373 | EVP_MD_CTX_free(c); |
0f113f3e MC |
374 | return rv; |
375 | } |