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 static 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 to[0] = 0;
56 seed = to + 1;
57 db = to + SHA_DIGEST_LENGTH + 1;
58
59 EVP_Digest((void *)param, plen, db, NULL, EVP_sha1(), NULL);
60 memset(db + SHA_DIGEST_LENGTH, 0,
61 emlen - flen - 2 * SHA_DIGEST_LENGTH - 1);
62 db[emlen - flen - SHA_DIGEST_LENGTH - 1] = 0x01;
63 memcpy(db + emlen - flen - SHA_DIGEST_LENGTH, from, (unsigned int) flen);
64 if (RAND_bytes(seed, SHA_DIGEST_LENGTH) <= 0)
65 return 0;
66 #ifdef PKCS_TESTVECT
67 memcpy(seed,
68 "\xaa\xfd\x12\xf6\x59\xca\xe6\x34\x89\xb4\x79\xe5\x07\x6d\xde\xc2\xf0\x6c\xb5\x8f",
69 20);
70 #endif
71
72 dbmask = OPENSSL_malloc(emlen - SHA_DIGEST_LENGTH);
73 if (dbmask == NULL)
74 {
75 RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
76 return 0;
77 }
78
79 if (MGF1(dbmask, emlen - SHA_DIGEST_LENGTH, seed, SHA_DIGEST_LENGTH) < 0)
80 return 0;
81 for (i = 0; i < emlen - SHA_DIGEST_LENGTH; i++)
82 db[i] ^= dbmask[i];
83
84 if (MGF1(seedmask, SHA_DIGEST_LENGTH, db, emlen - SHA_DIGEST_LENGTH) < 0)
85 return 0;
86 for (i = 0; i < SHA_DIGEST_LENGTH; i++)
87 seed[i] ^= seedmask[i];
88
89 OPENSSL_free(dbmask);
90 return 1;
91 }
92
RSA_padding_check_PKCS1_OAEP(unsigned char * to,int tlen,const unsigned char * from,int flen,int num,const unsigned char * param,int plen)93 int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
94 const unsigned char *from, int flen, int num,
95 const unsigned char *param, int plen)
96 {
97 int i, dblen, mlen = -1;
98 const unsigned char *maskeddb;
99 int lzero;
100 unsigned char *db = NULL, seed[SHA_DIGEST_LENGTH], phash[SHA_DIGEST_LENGTH];
101 unsigned char *padded_from;
102 int bad = 0;
103
104 if (--num < 2 * SHA_DIGEST_LENGTH + 1)
105 /* 'num' is the length of the modulus, i.e. does not depend on the
106 * particular ciphertext. */
107 goto decoding_err;
108
109 lzero = num - flen;
110 if (lzero < 0)
111 {
112 /* signalling this error immediately after detection might allow
113 * for side-channel attacks (e.g. timing if 'plen' is huge
114 * -- cf. James H. Manger, "A Chosen Ciphertext Attack on RSA Optimal
115 * Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001),
116 * so we use a 'bad' flag */
117 bad = 1;
118 lzero = 0;
119 flen = num; /* don't overflow the memcpy to padded_from */
120 }
121
122 dblen = num - SHA_DIGEST_LENGTH;
123 db = OPENSSL_malloc(dblen + num);
124 if (db == NULL)
125 {
126 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
127 return -1;
128 }
129
130 /* Always do this zero-padding copy (even when lzero == 0)
131 * to avoid leaking timing info about the value of lzero. */
132 padded_from = db + dblen;
133 memset(padded_from, 0, lzero);
134 memcpy(padded_from + lzero, from, flen);
135
136 maskeddb = padded_from + SHA_DIGEST_LENGTH;
137
138 if (MGF1(seed, SHA_DIGEST_LENGTH, maskeddb, dblen))
139 return -1;
140 for (i = 0; i < SHA_DIGEST_LENGTH; i++)
141 seed[i] ^= padded_from[i];
142
143 if (MGF1(db, dblen, seed, SHA_DIGEST_LENGTH))
144 return -1;
145 for (i = 0; i < dblen; i++)
146 db[i] ^= maskeddb[i];
147
148 EVP_Digest((void *)param, plen, phash, NULL, EVP_sha1(), NULL);
149
150 if (memcmp(db, phash, SHA_DIGEST_LENGTH) != 0 || bad)
151 goto decoding_err;
152 else
153 {
154 for (i = SHA_DIGEST_LENGTH; i < dblen; i++)
155 if (db[i] != 0x00)
156 break;
157 if (i == dblen || db[i] != 0x01)
158 goto decoding_err;
159 else
160 {
161 /* everything looks OK */
162
163 mlen = dblen - ++i;
164 if (tlen < mlen)
165 {
166 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_DATA_TOO_LARGE);
167 mlen = -1;
168 }
169 else
170 memcpy(to, db + i, mlen);
171 }
172 }
173 OPENSSL_free(db);
174 return mlen;
175
176 decoding_err:
177 /* to avoid chosen ciphertext attacks, the error message should not reveal
178 * which kind of decoding error happened */
179 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_OAEP_DECODING_ERROR);
180 if (db != NULL) OPENSSL_free(db);
181 return -1;
182 }
183
PKCS1_MGF1(unsigned char * mask,long len,const unsigned char * seed,long seedlen,const EVP_MD * dgst)184 int PKCS1_MGF1(unsigned char *mask, long len,
185 const unsigned char *seed, long seedlen, const EVP_MD *dgst)
186 {
187 long i, outlen = 0;
188 unsigned char cnt[4];
189 EVP_MD_CTX c;
190 unsigned char md[EVP_MAX_MD_SIZE];
191 int mdlen;
192 int rv = -1;
193
194 EVP_MD_CTX_init(&c);
195 mdlen = EVP_MD_size(dgst);
196 if (mdlen < 0)
197 goto err;
198 for (i = 0; outlen < len; i++)
199 {
200 cnt[0] = (unsigned char)((i >> 24) & 255);
201 cnt[1] = (unsigned char)((i >> 16) & 255);
202 cnt[2] = (unsigned char)((i >> 8)) & 255;
203 cnt[3] = (unsigned char)(i & 255);
204 if (!EVP_DigestInit_ex(&c,dgst, NULL)
205 || !EVP_DigestUpdate(&c, seed, seedlen)
206 || !EVP_DigestUpdate(&c, cnt, 4))
207 goto err;
208 if (outlen + mdlen <= len)
209 {
210 if (!EVP_DigestFinal_ex(&c, mask + outlen, NULL))
211 goto err;
212 outlen += mdlen;
213 }
214 else
215 {
216 if (!EVP_DigestFinal_ex(&c, md, NULL))
217 goto err;
218 memcpy(mask + outlen, md, len - outlen);
219 outlen = len;
220 }
221 }
222 rv = 0;
223 err:
224 EVP_MD_CTX_cleanup(&c);
225 return rv;
226 }
227
MGF1(unsigned char * mask,long len,const unsigned char * seed,long seedlen)228 static int MGF1(unsigned char *mask, long len, const unsigned char *seed,
229 long seedlen)
230 {
231 return PKCS1_MGF1(mask, len, seed, seedlen, EVP_sha1());
232 }
233 #endif
234