1 /* crypto/rsa/rsa_oaep.c */
2 /* Written by Ulf Moeller. This software is distributed on an "AS IS"
3 basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. */
4
5 /* EME-OAEP as defined in RFC 2437 (PKCS #1 v2.0) */
6
7 /* See Victor Shoup, "OAEP reconsidered," Nov. 2000,
8 * <URL: http://www.shoup.net/papers/oaep.ps.Z>
9 * for problems with the security proof for the
10 * original OAEP scheme, which EME-OAEP is based on.
11 *
12 * A new proof can be found in E. Fujisaki, T. Okamoto,
13 * D. Pointcheval, J. Stern, "RSA-OEAP is Still Alive!",
14 * Dec. 2000, <URL: http://eprint.iacr.org/2000/061/>.
15 * The new proof has stronger requirements for the
16 * underlying permutation: "partial-one-wayness" instead
17 * of one-wayness. For the RSA function, this is
18 * an equivalent notion.
19 */
20
21
22 #if !defined(OPENSSL_NO_SHA) && !defined(OPENSSL_NO_SHA1)
23 #include <stdio.h>
24 #include "cryptlib.h"
25 #include <openssl/bn.h>
26 #include <openssl/rsa.h>
27 #include <openssl/evp.h>
28 #include <openssl/rand.h>
29 #include <openssl/sha.h>
30
31 int MGF1(unsigned char *mask, long len,
32 const unsigned char *seed, long seedlen);
33
RSA_padding_add_PKCS1_OAEP(unsigned char * to,int tlen,const unsigned char * from,int flen,const unsigned char * param,int plen)34 int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
35 const unsigned char *from, int flen,
36 const unsigned char *param, int plen)
37 {
38 int i, emlen = tlen - 1;
39 unsigned char *db, *seed;
40 unsigned char *dbmask, seedmask[SHA_DIGEST_LENGTH];
41
42 if (flen > emlen - 2 * SHA_DIGEST_LENGTH - 1)
43 {
44 RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP,
45 RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
46 return 0;
47 }
48
49 if (emlen < 2 * SHA_DIGEST_LENGTH + 1)
50 {
51 RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, RSA_R_KEY_SIZE_TOO_SMALL);
52 return 0;
53 }
54
55 dbmask = OPENSSL_malloc(emlen - SHA_DIGEST_LENGTH);
56 if (dbmask == NULL)
57 {
58 RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
59 return 0;
60 }
61
62 to[0] = 0;
63 seed = to + 1;
64 db = to + SHA_DIGEST_LENGTH + 1;
65
66 EVP_Digest((void *)param, plen, db, NULL, EVP_sha1(), NULL);
67 memset(db + SHA_DIGEST_LENGTH, 0,
68 emlen - flen - 2 * SHA_DIGEST_LENGTH - 1);
69 db[emlen - flen - SHA_DIGEST_LENGTH - 1] = 0x01;
70 memcpy(db + emlen - flen - SHA_DIGEST_LENGTH, from, (unsigned int) flen);
71 if (RAND_bytes(seed, SHA_DIGEST_LENGTH) <= 0)
72 return 0;
73 #ifdef PKCS_TESTVECT
74 memcpy(seed,
75 "\xaa\xfd\x12\xf6\x59\xca\xe6\x34\x89\xb4\x79\xe5\x07\x6d\xde\xc2\xf0\x6c\xb5\x8f",
76 20);
77 #endif
78
79 MGF1(dbmask, emlen - SHA_DIGEST_LENGTH, seed, SHA_DIGEST_LENGTH);
80 for (i = 0; i < emlen - SHA_DIGEST_LENGTH; i++)
81 db[i] ^= dbmask[i];
82
83 MGF1(seedmask, SHA_DIGEST_LENGTH, db, emlen - SHA_DIGEST_LENGTH);
84 for (i = 0; i < SHA_DIGEST_LENGTH; i++)
85 seed[i] ^= seedmask[i];
86
87 OPENSSL_free(dbmask);
88 return 1;
89 }
90
RSA_padding_check_PKCS1_OAEP(unsigned char * to,int tlen,const unsigned char * from,int flen,int num,const unsigned char * param,int plen)91 int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
92 const unsigned char *from, int flen, int num,
93 const unsigned char *param, int plen)
94 {
95 int i, dblen, mlen = -1;
96 const unsigned char *maskeddb;
97 int lzero;
98 unsigned char *db = NULL, seed[SHA_DIGEST_LENGTH], phash[SHA_DIGEST_LENGTH];
99 unsigned char *padded_from;
100 int bad = 0;
101
102 if (--num < 2 * SHA_DIGEST_LENGTH + 1)
103 /* 'num' is the length of the modulus, i.e. does not depend on the
104 * particular ciphertext. */
105 goto decoding_err;
106
107 lzero = num - flen;
108 if (lzero < 0)
109 {
110 /* signalling this error immediately after detection might allow
111 * for side-channel attacks (e.g. timing if 'plen' is huge
112 * -- cf. James H. Manger, "A Chosen Ciphertext Attack on RSA Optimal
113 * Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001),
114 * so we use a 'bad' flag */
115 bad = 1;
116 lzero = 0;
117 flen = num; /* don't overflow the memcpy to padded_from */
118 }
119
120 dblen = num - SHA_DIGEST_LENGTH;
121 db = OPENSSL_malloc(dblen + num);
122 if (db == NULL)
123 {
124 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
125 return -1;
126 }
127
128 /* Always do this zero-padding copy (even when lzero == 0)
129 * to avoid leaking timing info about the value of lzero. */
130 padded_from = db + dblen;
131 memset(padded_from, 0, lzero);
132 memcpy(padded_from + lzero, from, flen);
133
134 maskeddb = padded_from + SHA_DIGEST_LENGTH;
135
136 MGF1(seed, SHA_DIGEST_LENGTH, maskeddb, dblen);
137 for (i = 0; i < SHA_DIGEST_LENGTH; i++)
138 seed[i] ^= padded_from[i];
139
140 MGF1(db, dblen, seed, SHA_DIGEST_LENGTH);
141 for (i = 0; i < dblen; i++)
142 db[i] ^= maskeddb[i];
143
144 EVP_Digest((void *)param, plen, phash, NULL, EVP_sha1(), NULL);
145
146 if (memcmp(db, phash, SHA_DIGEST_LENGTH) != 0 || bad)
147 goto decoding_err;
148 else
149 {
150 for (i = SHA_DIGEST_LENGTH; i < dblen; i++)
151 if (db[i] != 0x00)
152 break;
153 if (i == dblen || db[i] != 0x01)
154 goto decoding_err;
155 else
156 {
157 /* everything looks OK */
158
159 mlen = dblen - ++i;
160 if (tlen < mlen)
161 {
162 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_DATA_TOO_LARGE);
163 mlen = -1;
164 }
165 else
166 memcpy(to, db + i, mlen);
167 }
168 }
169 OPENSSL_free(db);
170 return mlen;
171
172 decoding_err:
173 /* to avoid chosen ciphertext attacks, the error message should not reveal
174 * which kind of decoding error happened */
175 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_OAEP_DECODING_ERROR);
176 if (db != NULL) OPENSSL_free(db);
177 return -1;
178 }
179
PKCS1_MGF1(unsigned char * mask,long len,const unsigned char * seed,long seedlen,const EVP_MD * dgst)180 int PKCS1_MGF1(unsigned char *mask, long len,
181 const unsigned char *seed, long seedlen, const EVP_MD *dgst)
182 {
183 long i, outlen = 0;
184 unsigned char cnt[4];
185 EVP_MD_CTX c;
186 unsigned char md[EVP_MAX_MD_SIZE];
187 int mdlen;
188
189 EVP_MD_CTX_init(&c);
190 mdlen = EVP_MD_size(dgst);
191 for (i = 0; outlen < len; i++)
192 {
193 cnt[0] = (unsigned char)((i >> 24) & 255);
194 cnt[1] = (unsigned char)((i >> 16) & 255);
195 cnt[2] = (unsigned char)((i >> 8)) & 255;
196 cnt[3] = (unsigned char)(i & 255);
197 EVP_DigestInit_ex(&c,dgst, NULL);
198 EVP_DigestUpdate(&c, seed, seedlen);
199 EVP_DigestUpdate(&c, cnt, 4);
200 if (outlen + mdlen <= len)
201 {
202 EVP_DigestFinal_ex(&c, mask + outlen, NULL);
203 outlen += mdlen;
204 }
205 else
206 {
207 EVP_DigestFinal_ex(&c, md, NULL);
208 memcpy(mask + outlen, md, len - outlen);
209 outlen = len;
210 }
211 }
212 EVP_MD_CTX_cleanup(&c);
213 return 0;
214 }
215
MGF1(unsigned char * mask,long len,const unsigned char * seed,long seedlen)216 int MGF1(unsigned char *mask, long len, const unsigned char *seed, long seedlen)
217 {
218 return PKCS1_MGF1(mask, len, seed, seedlen, EVP_sha1());
219 }
220 #endif
221