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. */
5 /* EME-OAEP as defined in RFC 2437 (PKCS #1 v2.0) */
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.
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.
22 #if !defined(OPENSSL_NO_SHA) && !defined(OPENSSL_NO_SHA1)
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>
31 int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
32 const unsigned char *from, int flen,
33 const unsigned char *param, int plen)
35 return RSA_padding_add_PKCS1_OAEP_mgf1(to, tlen, from, flen,
36 param, plen, NULL, NULL);
39 int RSA_padding_add_PKCS1_OAEP_mgf1(unsigned char *to, int tlen,
40 const unsigned char *from, int flen,
41 const unsigned char *param, int plen,
42 const EVP_MD *md, const EVP_MD *mgf1md)
44 int i, emlen = tlen - 1;
45 unsigned char *db, *seed;
46 unsigned char *dbmask, seedmask[EVP_MAX_MD_SIZE];
54 mdlen = EVP_MD_size(md);
56 if (flen > emlen - 2 * mdlen - 1)
58 RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP_MGF1,
59 RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
63 if (emlen < 2 * mdlen + 1)
65 RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP_MGF1, RSA_R_KEY_SIZE_TOO_SMALL);
73 if (!EVP_Digest((void *)param, plen, db, NULL, md, NULL))
76 emlen - flen - 2 * mdlen - 1);
77 db[emlen - flen - mdlen - 1] = 0x01;
78 memcpy(db + emlen - flen - mdlen, from, (unsigned int) flen);
79 if (RAND_bytes(seed, mdlen) <= 0)
83 "\xaa\xfd\x12\xf6\x59\xca\xe6\x34\x89\xb4\x79\xe5\x07\x6d\xde\xc2\xf0\x6c\xb5\x8f",
87 dbmask = OPENSSL_malloc(emlen - mdlen);
90 RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP_MGF1, ERR_R_MALLOC_FAILURE);
94 if (PKCS1_MGF1(dbmask, emlen - mdlen, seed, mdlen, mgf1md) < 0)
96 for (i = 0; i < emlen - mdlen; i++)
99 if (PKCS1_MGF1(seedmask, mdlen, db, emlen - mdlen, mgf1md) < 0)
101 for (i = 0; i < mdlen; i++)
102 seed[i] ^= seedmask[i];
104 OPENSSL_free(dbmask);
108 int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
109 const unsigned char *from, int flen, int num,
110 const unsigned char *param, int plen)
112 return RSA_padding_check_PKCS1_OAEP_mgf1(to, tlen, from , flen, num,
117 int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen,
118 const unsigned char *from, int flen, int num,
119 const unsigned char *param, int plen,
120 const EVP_MD *md, const EVP_MD *mgf1md)
122 int i, dblen, mlen = -1;
123 const unsigned char *maskeddb;
125 unsigned char *db = NULL, seed[EVP_MAX_MD_SIZE], phash[EVP_MAX_MD_SIZE];
126 unsigned char *padded_from;
135 mdlen = EVP_MD_size(md);
137 if (--num < 2 * mdlen + 1)
138 /* 'num' is the length of the modulus, i.e. does not depend on the
139 * particular ciphertext. */
145 /* signalling this error immediately after detection might allow
146 * for side-channel attacks (e.g. timing if 'plen' is huge
147 * -- cf. James H. Manger, "A Chosen Ciphertext Attack on RSA Optimal
148 * Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001),
149 * so we use a 'bad' flag */
152 flen = num; /* don't overflow the memcpy to padded_from */
156 db = OPENSSL_malloc(dblen + num);
159 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, ERR_R_MALLOC_FAILURE);
163 /* Always do this zero-padding copy (even when lzero == 0)
164 * to avoid leaking timing info about the value of lzero. */
165 padded_from = db + dblen;
166 memset(padded_from, 0, lzero);
167 memcpy(padded_from + lzero, from, flen);
169 maskeddb = padded_from + mdlen;
171 if (PKCS1_MGF1(seed, mdlen, maskeddb, dblen, mgf1md))
173 for (i = 0; i < mdlen; i++)
174 seed[i] ^= padded_from[i];
176 if (PKCS1_MGF1(db, dblen, seed, mdlen, mgf1md))
178 for (i = 0; i < dblen; i++)
179 db[i] ^= maskeddb[i];
181 if (!EVP_Digest((void *)param, plen, phash, NULL, md, NULL))
184 if (CRYPTO_memcmp(db, phash, mdlen) != 0 || bad)
188 for (i = mdlen; i < dblen; i++)
191 if (i == dblen || db[i] != 0x01)
195 /* everything looks OK */
200 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, RSA_R_DATA_TOO_LARGE);
204 memcpy(to, db + i, mlen);
211 /* to avoid chosen ciphertext attacks, the error message should not reveal
212 * which kind of decoding error happened */
213 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP_MGF1, RSA_R_OAEP_DECODING_ERROR);
214 if (db != NULL) OPENSSL_free(db);
218 int PKCS1_MGF1(unsigned char *mask, long len,
219 const unsigned char *seed, long seedlen, const EVP_MD *dgst)
222 unsigned char cnt[4];
224 unsigned char md[EVP_MAX_MD_SIZE];
229 mdlen = EVP_MD_size(dgst);
232 for (i = 0; outlen < len; i++)
234 cnt[0] = (unsigned char)((i >> 24) & 255);
235 cnt[1] = (unsigned char)((i >> 16) & 255);
236 cnt[2] = (unsigned char)((i >> 8)) & 255;
237 cnt[3] = (unsigned char)(i & 255);
238 if (!EVP_DigestInit_ex(&c,dgst, NULL)
239 || !EVP_DigestUpdate(&c, seed, seedlen)
240 || !EVP_DigestUpdate(&c, cnt, 4))
242 if (outlen + mdlen <= len)
244 if (!EVP_DigestFinal_ex(&c, mask + outlen, NULL))
250 if (!EVP_DigestFinal_ex(&c, md, NULL))
252 memcpy(mask + outlen, md, len - outlen);
258 EVP_MD_CTX_cleanup(&c);