Alexandre Savard | 1b09e31 | 2012-08-07 20:33:29 -0400 | [diff] [blame] | 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 | |
| 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 | |
Alexandre Savard | 7541067 | 2012-08-08 09:50:01 -0400 | [diff] [blame] | 59 | EVP_Digest((void *)param, plen, db, NULL, EVP_sha1(), NULL); |
Alexandre Savard | 1b09e31 | 2012-08-07 20:33:29 -0400 | [diff] [blame] | 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 | |
| 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 | |
Alexandre Savard | 7541067 | 2012-08-08 09:50:01 -0400 | [diff] [blame] | 148 | EVP_Digest((void *)param, plen, phash, NULL, EVP_sha1(), NULL); |
Alexandre Savard | 1b09e31 | 2012-08-07 20:33:29 -0400 | [diff] [blame] | 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 | |
| 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 | |
| 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 |