rsa_oaep.c revision 98d58bb80c64b02a33662f0ea80351d4a1535267
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 31int MGF1(unsigned char *mask, long len, 32 const unsigned char *seed, long seedlen); 33 34int 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 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 91int 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 172decoding_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 180int 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 = M_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 216int 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