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a4949896 | 1 | /* crypto/rsa/rsa_oaep.c */ |
0f113f3e MC |
2 | /* |
3 | * Written by Ulf Moeller. This software is distributed on an "AS IS" basis, | |
4 | * WITHOUT WARRANTY OF ANY KIND, either express or implied. | |
5 | */ | |
a4949896 | 6 | |
9347ba48 BM |
7 | /* EME-OAEP as defined in RFC 2437 (PKCS #1 v2.0) */ |
8 | ||
0f113f3e MC |
9 | /* |
10 | * See Victor Shoup, "OAEP reconsidered," Nov. 2000, <URL: | |
11 | * http://www.shoup.net/papers/oaep.ps.Z> for problems with the security | |
12 | * proof for the original OAEP scheme, which EME-OAEP is based on. A new | |
13 | * proof can be found in E. Fujisaki, T. Okamoto, D. Pointcheval, J. Stern, | |
14 | * "RSA-OEAP is Still Alive!", Dec. 2000, <URL: | |
15 | * http://eprint.iacr.org/2000/061/>. The new proof has stronger requirements | |
16 | * for the underlying permutation: "partial-one-wayness" instead of | |
17 | * one-wayness. For the RSA function, this is an equivalent notion. | |
9347ba48 BM |
18 | */ |
19 | ||
68570797 | 20 | #include "internal/constant_time_locl.h" |
a4949896 | 21 | |
474e469b | 22 | #include <stdio.h> |
b39fc560 | 23 | #include "internal/cryptlib.h" |
474e469b RS |
24 | #include <openssl/bn.h> |
25 | #include <openssl/rsa.h> | |
26 | #include <openssl/evp.h> | |
27 | #include <openssl/rand.h> | |
28 | #include <openssl/sha.h> | |
a4949896 | 29 | |
6b691a5c | 30 | int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen, |
0f113f3e MC |
31 | const unsigned char *from, int flen, |
32 | const unsigned char *param, int plen) | |
33 | { | |
34 | return RSA_padding_add_PKCS1_OAEP_mgf1(to, tlen, from, flen, | |
35 | param, plen, NULL, NULL); | |
36 | } | |
271fef0e DSH |
37 | |
38 | int RSA_padding_add_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, | |
0f113f3e MC |
39 | const unsigned char *from, int flen, |
40 | const unsigned char *param, int plen, | |
41 | const EVP_MD *md, const EVP_MD *mgf1md) | |
42 | { | |
43 | int i, emlen = tlen - 1; | |
44 | unsigned char *db, *seed; | |
45 | unsigned char *dbmask, seedmask[EVP_MAX_MD_SIZE]; | |
46 | int mdlen; | |
47 | ||
48 | if (md == NULL) | |
49 | md = EVP_sha1(); | |
50 | if (mgf1md == NULL) | |
51 | mgf1md = md; | |
52 | ||
53 | mdlen = EVP_MD_size(md); | |
54 | ||
55 | if (flen > emlen - 2 * mdlen - 1) { | |
56 | RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP_MGF1, | |
57 | RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE); | |
58 | return 0; | |
59 | } | |
60 | ||
61 | if (emlen < 2 * mdlen + 1) { | |
62 | RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP_MGF1, | |
63 | RSA_R_KEY_SIZE_TOO_SMALL); | |
64 | return 0; | |
65 | } | |
66 | ||
67 | to[0] = 0; | |
68 | seed = to + 1; | |
69 | db = to + mdlen + 1; | |
70 | ||
71 | if (!EVP_Digest((void *)param, plen, db, NULL, md, NULL)) | |
72 | return 0; | |
73 | memset(db + mdlen, 0, emlen - flen - 2 * mdlen - 1); | |
74 | db[emlen - flen - mdlen - 1] = 0x01; | |
75 | memcpy(db + emlen - flen - mdlen, from, (unsigned int)flen); | |
76 | if (RAND_bytes(seed, mdlen) <= 0) | |
77 | return 0; | |
474e469b | 78 | #ifdef PKCS_TESTVECT |
0f113f3e MC |
79 | memcpy(seed, |
80 | "\xaa\xfd\x12\xf6\x59\xca\xe6\x34\x89\xb4\x79\xe5\x07\x6d\xde\xc2\xf0\x6c\xb5\x8f", | |
81 | 20); | |
474e469b | 82 | #endif |
0f113f3e MC |
83 | |
84 | dbmask = OPENSSL_malloc(emlen - mdlen); | |
85 | if (dbmask == NULL) { | |
86 | RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP_MGF1, ERR_R_MALLOC_FAILURE); | |
87 | return 0; | |
88 | } | |
89 | ||
90 | if (PKCS1_MGF1(dbmask, emlen - mdlen, seed, mdlen, mgf1md) < 0) | |
91 | return 0; | |
92 | for (i = 0; i < emlen - mdlen; i++) | |
93 | db[i] ^= dbmask[i]; | |
94 | ||
95 | if (PKCS1_MGF1(seedmask, mdlen, db, emlen - mdlen, mgf1md) < 0) | |
96 | return 0; | |
97 | for (i = 0; i < mdlen; i++) | |
98 | seed[i] ^= seedmask[i]; | |
99 | ||
100 | OPENSSL_free(dbmask); | |
101 | return 1; | |
102 | } | |
a4949896 | 103 | |
6b691a5c | 104 | int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen, |
0f113f3e MC |
105 | const unsigned char *from, int flen, int num, |
106 | const unsigned char *param, int plen) | |
107 | { | |
108 | return RSA_padding_check_PKCS1_OAEP_mgf1(to, tlen, from, flen, num, | |
109 | param, plen, NULL, NULL); | |
110 | } | |
271fef0e DSH |
111 | |
112 | int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, | |
0f113f3e MC |
113 | const unsigned char *from, int flen, |
114 | int num, const unsigned char *param, | |
115 | int plen, const EVP_MD *md, | |
116 | const EVP_MD *mgf1md) | |
117 | { | |
118 | int i, dblen, mlen = -1, one_index = 0, msg_index; | |
119 | unsigned int good, found_one_byte; | |
120 | const unsigned char *maskedseed, *maskeddb; | |
121 | /* | |
122 | * |em| is the encoded message, zero-padded to exactly |num| bytes: em = | |
123 | * Y || maskedSeed || maskedDB | |
124 | */ | |
125 | unsigned char *db = NULL, *em = NULL, seed[EVP_MAX_MD_SIZE], | |
126 | phash[EVP_MAX_MD_SIZE]; | |
127 | int mdlen; | |
128 | ||
129 | if (md == NULL) | |
130 | md = EVP_sha1(); | |
131 | if (mgf1md == NULL) | |
132 | mgf1md = md; | |
133 | ||
134 | mdlen = EVP_MD_size(md); | |
135 | ||
136 | if (tlen <= 0 || flen <= 0) | |
137 | return -1; | |
138 | /* | |
139 | * |num| is the length of the modulus; |flen| is the length of the | |
140 | * encoded message. Therefore, for any |from| that was obtained by | |
141 | * decrypting a ciphertext, we must have |flen| <= |num|. Similarly, | |
142 | * num < 2 * mdlen + 2 must hold for the modulus irrespective of | |
143 | * the ciphertext, see PKCS #1 v2.2, section 7.1.2. | |
144 | * This does not leak any side-channel information. | |
145 | */ | |
146 | if (num < flen || num < 2 * mdlen + 2) | |
147 | goto decoding_err; | |
148 | ||
149 | dblen = num - mdlen - 1; | |
150 | db = OPENSSL_malloc(dblen); | |
151 | em = OPENSSL_malloc(num); | |
152 | if (db == NULL || em == NULL) { | |
153 | RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, ERR_R_MALLOC_FAILURE); | |
154 | goto cleanup; | |
155 | } | |
156 | ||
157 | /* | |
158 | * Always do this zero-padding copy (even when num == flen) to avoid | |
159 | * leaking that information. The copy still leaks some side-channel | |
160 | * information, but it's impossible to have a fixed memory access | |
161 | * pattern since we can't read out of the bounds of |from|. | |
162 | * | |
163 | * TODO(emilia): Consider porting BN_bn2bin_padded from BoringSSL. | |
164 | */ | |
165 | memset(em, 0, num); | |
166 | memcpy(em + num - flen, from, flen); | |
167 | ||
168 | /* | |
169 | * The first byte must be zero, however we must not leak if this is | |
170 | * true. See James H. Manger, "A Chosen Ciphertext Attack on RSA | |
171 | * Optimal Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001). | |
172 | */ | |
173 | good = constant_time_is_zero(em[0]); | |
174 | ||
175 | maskedseed = em + 1; | |
176 | maskeddb = em + 1 + mdlen; | |
177 | ||
178 | if (PKCS1_MGF1(seed, mdlen, maskeddb, dblen, mgf1md)) | |
179 | goto cleanup; | |
180 | for (i = 0; i < mdlen; i++) | |
181 | seed[i] ^= maskedseed[i]; | |
182 | ||
183 | if (PKCS1_MGF1(db, dblen, seed, mdlen, mgf1md)) | |
184 | goto cleanup; | |
185 | for (i = 0; i < dblen; i++) | |
186 | db[i] ^= maskeddb[i]; | |
187 | ||
188 | if (!EVP_Digest((void *)param, plen, phash, NULL, md, NULL)) | |
189 | goto cleanup; | |
190 | ||
191 | good &= constant_time_is_zero(CRYPTO_memcmp(db, phash, mdlen)); | |
192 | ||
193 | found_one_byte = 0; | |
194 | for (i = mdlen; i < dblen; i++) { | |
195 | /* | |
196 | * Padding consists of a number of 0-bytes, followed by a 1. | |
197 | */ | |
198 | unsigned int equals1 = constant_time_eq(db[i], 1); | |
199 | unsigned int equals0 = constant_time_is_zero(db[i]); | |
200 | one_index = constant_time_select_int(~found_one_byte & equals1, | |
201 | i, one_index); | |
202 | found_one_byte |= equals1; | |
203 | good &= (found_one_byte | equals0); | |
204 | } | |
205 | ||
206 | good &= found_one_byte; | |
207 | ||
208 | /* | |
209 | * At this point |good| is zero unless the plaintext was valid, | |
210 | * so plaintext-awareness ensures timing side-channels are no longer a | |
211 | * concern. | |
212 | */ | |
213 | if (!good) | |
214 | goto decoding_err; | |
215 | ||
216 | msg_index = one_index + 1; | |
217 | mlen = dblen - msg_index; | |
218 | ||
219 | if (tlen < mlen) { | |
220 | RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, RSA_R_DATA_TOO_LARGE); | |
221 | mlen = -1; | |
222 | } else { | |
223 | memcpy(to, db + msg_index, mlen); | |
224 | goto cleanup; | |
225 | } | |
226 | ||
227 | decoding_err: | |
228 | /* | |
229 | * To avoid chosen ciphertext attacks, the error message should not | |
230 | * reveal which kind of decoding error happened. | |
231 | */ | |
232 | RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, | |
233 | RSA_R_OAEP_DECODING_ERROR); | |
234 | cleanup: | |
b548a1f1 RS |
235 | OPENSSL_free(db); |
236 | OPENSSL_free(em); | |
0f113f3e MC |
237 | return mlen; |
238 | } | |
a4949896 | 239 | |
499fca2d | 240 | int PKCS1_MGF1(unsigned char *mask, long len, |
0f113f3e MC |
241 | const unsigned char *seed, long seedlen, const EVP_MD *dgst) |
242 | { | |
243 | long i, outlen = 0; | |
244 | unsigned char cnt[4]; | |
6e59a892 | 245 | EVP_MD_CTX *c = EVP_MD_CTX_create(); |
0f113f3e MC |
246 | unsigned char md[EVP_MAX_MD_SIZE]; |
247 | int mdlen; | |
248 | int rv = -1; | |
249 | ||
6e59a892 RL |
250 | if (c == NULL) |
251 | goto err; | |
252 | mdlen = EVP_MD_size(dgst); | |
0f113f3e MC |
253 | if (mdlen < 0) |
254 | goto err; | |
255 | for (i = 0; outlen < len; i++) { | |
256 | cnt[0] = (unsigned char)((i >> 24) & 255); | |
257 | cnt[1] = (unsigned char)((i >> 16) & 255); | |
258 | cnt[2] = (unsigned char)((i >> 8)) & 255; | |
259 | cnt[3] = (unsigned char)(i & 255); | |
6e59a892 RL |
260 | if (!EVP_DigestInit_ex(c, dgst, NULL) |
261 | || !EVP_DigestUpdate(c, seed, seedlen) | |
262 | || !EVP_DigestUpdate(c, cnt, 4)) | |
0f113f3e MC |
263 | goto err; |
264 | if (outlen + mdlen <= len) { | |
6e59a892 | 265 | if (!EVP_DigestFinal_ex(c, mask + outlen, NULL)) |
0f113f3e MC |
266 | goto err; |
267 | outlen += mdlen; | |
268 | } else { | |
6e59a892 | 269 | if (!EVP_DigestFinal_ex(c, md, NULL)) |
0f113f3e MC |
270 | goto err; |
271 | memcpy(mask + outlen, md, len - outlen); | |
272 | outlen = len; | |
273 | } | |
274 | } | |
275 | rv = 0; | |
276 | err: | |
6e59a892 | 277 | EVP_MD_CTX_destroy(c); |
0f113f3e MC |
278 | return rv; |
279 | } |