crypto/openssl-0.9/crypto/rsa/rsa_oaep.c

   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
  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
  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
 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
 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