release/src/router/openssl/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 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
  59         if (!EVP_Digest((void *)param, plen, db, NULL, EVP_sha1(), NULL))
  60                 return 0;
  61         memset(db + SHA_DIGEST_LENGTH, 0,
  62                 emlen - flen - 2 * SHA_DIGEST_LENGTH - 1);
  63         db[emlen - flen - SHA_DIGEST_LENGTH - 1] = 0x01;
  64         memcpy(db + emlen - flen - SHA_DIGEST_LENGTH, from, (unsigned int) flen);
  65         if (RAND_bytes(seed, SHA_DIGEST_LENGTH) <= 0)
  66                 return 0;
  67 #ifdef PKCS_TESTVECT
  68         memcpy(seed,
  69            "\xaa\xfd\x12\xf6\x59\xca\xe6\x34\x89\xb4\x79\xe5\x07\x6d\xde\xc2\xf0\x6c\xb5\x8f",
  70            20);
  71 #endif
  72
  73         dbmask = OPENSSL_malloc(emlen - SHA_DIGEST_LENGTH);
  74         if (dbmask == NULL)
  75                 {
  76                 RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
  77                 return 0;
  78                 }
  79
  80         if (MGF1(dbmask, emlen - SHA_DIGEST_LENGTH, seed, SHA_DIGEST_LENGTH) < 0)
  81                 return 0;
  82         for (i = 0; i < emlen - SHA_DIGEST_LENGTH; i++)
  83                 db[i] ^= dbmask[i];
  84
  85         if (MGF1(seedmask, SHA_DIGEST_LENGTH, db, emlen - SHA_DIGEST_LENGTH) < 0)
  86                 return 0;
  87         for (i = 0; i < SHA_DIGEST_LENGTH; i++)
  88                 seed[i] ^= seedmask[i];
  89
  90         OPENSSL_free(dbmask);
  91         return 1;
  92         }
  93
  94 int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
  95         const unsigned char *from, int flen, int num,
  96         const unsigned char *param, int plen)
  97         {
  98         int i, dblen, mlen = -1;
  99         const unsigned char *maskeddb;
 100         int lzero;
 101         unsigned char *db = NULL, seed[SHA_DIGEST_LENGTH], phash[SHA_DIGEST_LENGTH];
 102         unsigned char *padded_from;
 103         int bad = 0;
 104
 105         if (--num < 2 * SHA_DIGEST_LENGTH + 1)
 106                 /* 'num' is the length of the modulus, i.e. does not depend on the
 107                  * particular ciphertext. */
 108                 goto decoding_err;
 109
 110         lzero = num - flen;
 111         if (lzero < 0)
 112                 {
 113                 /* signalling this error immediately after detection might allow
 114                  * for side-channel attacks (e.g. timing if 'plen' is huge
 115                  * -- cf. James H. Manger, "A Chosen Ciphertext Attack on RSA Optimal
 116                  * Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001),
 117                  * so we use a 'bad' flag */
 118                 bad = 1;
 119                 lzero = 0;
 120                 flen = num; /* don't overflow the memcpy to padded_from */
 121                 }
 122
 123         dblen = num - SHA_DIGEST_LENGTH;
 124         db = OPENSSL_malloc(dblen + num);
 125         if (db == NULL)
 126                 {
 127                 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
 128                 return -1;
 129                 }
 130
 131         /* Always do this zero-padding copy (even when lzero == 0)
 132          * to avoid leaking timing info about the value of lzero. */
 133         padded_from = db + dblen;
 134         memset(padded_from, 0, lzero);
 135         memcpy(padded_from + lzero, from, flen);
 136
 137         maskeddb = padded_from + SHA_DIGEST_LENGTH;
 138
 139         if (MGF1(seed, SHA_DIGEST_LENGTH, maskeddb, dblen))
 140                 return -1;
 141         for (i = 0; i < SHA_DIGEST_LENGTH; i++)
 142                 seed[i] ^= padded_from[i];
 143
 144         if (MGF1(db, dblen, seed, SHA_DIGEST_LENGTH))
 145                 return -1;
 146         for (i = 0; i < dblen; i++)
 147                 db[i] ^= maskeddb[i];
 148
 149         if (!EVP_Digest((void *)param, plen, phash, NULL, EVP_sha1(), NULL))
 150                 return -1;
 151
 152         if (memcmp(db, phash, SHA_DIGEST_LENGTH) != 0 || bad)
 153                 goto decoding_err;
 154         else
 155                 {
 156                 for (i = SHA_DIGEST_LENGTH; i < dblen; i++)
 157                         if (db[i] != 0x00)
 158                                 break;
 159                 if (i == dblen || db[i] != 0x01)
 160                         goto decoding_err;
 161                 else
 162                         {
 163                         /* everything looks OK */
 164
 165                         mlen = dblen - ++i;
 166                         if (tlen < mlen)
 167                                 {
 168                                 RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_DATA_TOO_LARGE);
 169                                 mlen = -1;
 170                                 }
 171                         else
 172                                 memcpy(to, db + i, mlen);
 173                         }
 174                 }
 175         OPENSSL_free(db);
 176         return mlen;
 177
 178 decoding_err:
 179         /* to avoid chosen ciphertext attacks, the error message should not reveal
 180          * which kind of decoding error happened */
 181         RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_OAEP_DECODING_ERROR);
 182         if (db != NULL) OPENSSL_free(db);
 183         return -1;
 184         }
 185
 186 int PKCS1_MGF1(unsigned char *mask, long len,
 187         const unsigned char *seed, long seedlen, const EVP_MD *dgst)
 188         {
 189         long i, outlen = 0;
 190         unsigned char cnt[4];
 191         EVP_MD_CTX c;
 192         unsigned char md[EVP_MAX_MD_SIZE];
 193         int mdlen;
 194         int rv = -1;
 195
 196         EVP_MD_CTX_init(&c);
 197         mdlen = EVP_MD_size(dgst);
 198         if (mdlen < 0)
 199                 goto err;
 200         for (i = 0; outlen < len; i++)
 201                 {
 202                 cnt[0] = (unsigned char)((i >> 24) & 255);
 203                 cnt[1] = (unsigned char)((i >> 16) & 255);
 204                 cnt[2] = (unsigned char)((i >> 8)) & 255;
 205                 cnt[3] = (unsigned char)(i & 255);
 206                 if (!EVP_DigestInit_ex(&c,dgst, NULL)
 207                         || !EVP_DigestUpdate(&c, seed, seedlen)
 208                         || !EVP_DigestUpdate(&c, cnt, 4))
 209                         goto err;
 210                 if (outlen + mdlen <= len)
 211                         {
 212                         if (!EVP_DigestFinal_ex(&c, mask + outlen, NULL))
 213                                 goto err;
 214                         outlen += mdlen;
 215                         }
 216                 else
 217                         {
 218                         if (!EVP_DigestFinal_ex(&c, md, NULL))
 219                                 goto err;
 220                         memcpy(mask + outlen, md, len - outlen);
 221                         outlen = len;
 222                         }
 223                 }
 224         rv = 0;
 225         err:
 226         EVP_MD_CTX_cleanup(&c);
 227         return rv;
 228         }
 229
 230 static int MGF1(unsigned char *mask, long len, const unsigned char *seed,
 231                  long seedlen)
 232         {
 233         return PKCS1_MGF1(mask, len, seed, seedlen, EVP_sha1());
 234         }
 235 #endif