crypto/openssl-0.9.7e/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         int bad = 0;
 100
 101         if (--num < 2 * SHA_DIGEST_LENGTH + 1)
 102                 /* 'num' is the length of the modulus, i.e. does not depend on the
 103                  * particular ciphertext. */
 104                 goto decoding_err;
 105
 106         lzero = num - flen;
 107         if (lzero < 0)
 108                 {
 109                 /* lzero == -1 */
 110
 111                 /* signalling this error immediately after detection might allow
 112                  * for side-channel attacks (e.g. timing if 'plen' is huge
 113                  * -- cf. James H. Manger, "A Chosen Ciphertext Attack on RSA Optimal
 114                  * Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001),
 115                  * so we use a 'bad' flag */
 116                 bad = 1;
 117                 lzero = 0;
 118                 }
 119         maskeddb = from - lzero + SHA_DIGEST_LENGTH;
 120
 121         dblen = num - SHA_DIGEST_LENGTH;
 122         db = OPENSSL_malloc(dblen);
 123         if (db == NULL)
 124                 {
 125                 RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
 126                 return -1;
 127                 }
 128
 129         MGF1(seed, SHA_DIGEST_LENGTH, maskeddb, dblen);
 130         for (i = lzero; i < SHA_DIGEST_LENGTH; i++)
 131                 seed[i] ^= from[i - lzero];
 132
 133         MGF1(db, dblen, seed, SHA_DIGEST_LENGTH);
 134         for (i = 0; i < dblen; i++)
 135                 db[i] ^= maskeddb[i];
 136
 137         EVP_Digest((void *)param, plen, phash, NULL, EVP_sha1(), NULL);
 138
 139         if (memcmp(db, phash, SHA_DIGEST_LENGTH) != 0 || bad)
 140                 goto decoding_err;
 141         else
 142                 {
 143                 for (i = SHA_DIGEST_LENGTH; i < dblen; i++)
 144                         if (db[i] != 0x00)
 145                                 break;
 146                 if (db[i] != 0x01 || i++ >= dblen)
 147                         goto decoding_err;
 148                 else
 149                         {
 150                         /* everything looks OK */
 151
 152                         mlen = dblen - i;
 153                         if (tlen < mlen)
 154                                 {
 155                                 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_DATA_TOO_LARGE);
 156                                 mlen = -1;
 157                                 }
 158                         else
 159                                 memcpy(to, db + i, mlen);
 160                         }
 161                 }
 162         OPENSSL_free(db);
 163         return mlen;
 164
 165 decoding_err:
 166         /* to avoid chosen ciphertext attacks, the error message should not reveal
 167          * which kind of decoding error happened */
 168         RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_OAEP_DECODING_ERROR);
 169         if (db != NULL) OPENSSL_free(db);
 170         return -1;
 171         }
 172
 173 int MGF1(unsigned char *mask, long len,
 174         const unsigned char *seed, long seedlen)
 175         {
 176         long i, outlen = 0;
 177         unsigned char cnt[4];
 178         EVP_MD_CTX c;
 179         unsigned char md[SHA_DIGEST_LENGTH];
 180
 181         EVP_MD_CTX_init(&c);
 182         for (i = 0; outlen < len; i++)
 183                 {
 184                 cnt[0] = (unsigned char)((i >> 24) & 255);
 185                 cnt[1] = (unsigned char)((i >> 16) & 255);
 186                 cnt[2] = (unsigned char)((i >> 8)) & 255;
 187                 cnt[3] = (unsigned char)(i & 255);
 188                 EVP_DigestInit_ex(&c,EVP_sha1(), NULL);
 189                 EVP_DigestUpdate(&c, seed, seedlen);
 190                 EVP_DigestUpdate(&c, cnt, 4);
 191                 if (outlen + SHA_DIGEST_LENGTH <= len)
 192                         {
 193                         EVP_DigestFinal_ex(&c, mask + outlen, NULL);
 194                         outlen += SHA_DIGEST_LENGTH;
 195                         }
 196                 else
 197                         {
 198                         EVP_DigestFinal_ex(&c, md, NULL);
 199                         memcpy(mask + outlen, md, len - outlen);
 200                         outlen = len;
 201                         }
 202                 }
 203         EVP_MD_CTX_cleanup(&c);
 204         return 0;
 205         }
 206 #endif