release/src/router/openssl/crypto/rsa/rsa_oaep.c

   1 /* crypto/rsa/rsa_oaep.c */
   2 /*
   3  * Written by Ulf Moeller. This software is distributed on an "AS IS" basis,
   4  * WITHOUT WARRANTY OF ANY KIND, either express or implied.
   5  */
   6
   7 /* EME-OAEP as defined in RFC 2437 (PKCS #1 v2.0) */
   8
   9 /*
  10  * See Victor Shoup, "OAEP reconsidered," Nov. 2000, <URL:
  11  * http://www.shoup.net/papers/oaep.ps.Z> for problems with the security
  12  * proof for the original OAEP scheme, which EME-OAEP is based on. A new
  13  * proof can be found in E. Fujisaki, T. Okamoto, D. Pointcheval, J. Stern,
  14  * "RSA-OEAP is Still Alive!", Dec. 2000, <URL:
  15  * http://eprint.iacr.org/2000/061/>. The new proof has stronger requirements
  16  * for the underlying permutation: "partial-one-wayness" instead of
  17  * one-wayness.  For the RSA function, this is an equivalent notion.
  18  */
  19
  20 #include "constant_time_locl.h"
  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         RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP,
  44                RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
  45         return 0;
  46     }
  47
  48     if (emlen < 2 * SHA_DIGEST_LENGTH + 1) {
  49         RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, RSA_R_KEY_SIZE_TOO_SMALL);
  50         return 0;
  51     }
  52
  53     to[0] = 0;
  54     seed = to + 1;
  55     db = to + SHA_DIGEST_LENGTH + 1;
  56
  57     if (!EVP_Digest((void *)param, plen, db, NULL, EVP_sha1(), NULL))
  58         return 0;
  59     memset(db + SHA_DIGEST_LENGTH, 0,
  60            emlen - flen - 2 * SHA_DIGEST_LENGTH - 1);
  61     db[emlen - flen - SHA_DIGEST_LENGTH - 1] = 0x01;
  62     memcpy(db + emlen - flen - SHA_DIGEST_LENGTH, from, (unsigned int)flen);
  63     if (RAND_bytes(seed, SHA_DIGEST_LENGTH) <= 0)
  64         return 0;
  65 # ifdef PKCS_TESTVECT
  66     memcpy(seed,
  67            "\xaa\xfd\x12\xf6\x59\xca\xe6\x34\x89\xb4\x79\xe5\x07\x6d\xde\xc2\xf0\x6c\xb5\x8f",
  68            20);
  69 # endif
  70
  71     dbmask = OPENSSL_malloc(emlen - SHA_DIGEST_LENGTH);
  72     if (dbmask == NULL) {
  73         RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
  74         return 0;
  75     }
  76
  77     if (MGF1(dbmask, emlen - SHA_DIGEST_LENGTH, seed, SHA_DIGEST_LENGTH) < 0)
  78         return 0;
  79     for (i = 0; i < emlen - SHA_DIGEST_LENGTH; i++)
  80         db[i] ^= dbmask[i];
  81
  82     if (MGF1(seedmask, SHA_DIGEST_LENGTH, db, emlen - SHA_DIGEST_LENGTH) < 0)
  83         return 0;
  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, one_index = 0, msg_index;
  96     unsigned int good, found_one_byte;
  97     const unsigned char *maskedseed, *maskeddb;
  98     /*
  99      * |em| is the encoded message, zero-padded to exactly |num| bytes: em =
 100      * Y || maskedSeed || maskedDB
 101      */
 102     unsigned char *db = NULL, *em = NULL, seed[EVP_MAX_MD_SIZE],
 103         phash[EVP_MAX_MD_SIZE];
 104
 105     if (tlen <= 0 || flen <= 0)
 106         return -1;
 107
 108     /*
 109      * |num| is the length of the modulus; |flen| is the length of the
 110      * encoded message. Therefore, for any |from| that was obtained by
 111      * decrypting a ciphertext, we must have |flen| <= |num|. Similarly,
 112      * num < 2 * SHA_DIGEST_LENGTH + 2 must hold for the modulus
 113      * irrespective of the ciphertext, see PKCS #1 v2.2, section 7.1.2.
 114      * This does not leak any side-channel information.
 115      */
 116     if (num < flen || num < 2 * SHA_DIGEST_LENGTH + 2)
 117         goto decoding_err;
 118
 119     dblen = num - SHA_DIGEST_LENGTH - 1;
 120     db = OPENSSL_malloc(dblen);
 121     em = OPENSSL_malloc(num);
 122     if (db == NULL || em == NULL) {
 123         RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
 124         goto cleanup;
 125     }
 126
 127     /*
 128      * Always do this zero-padding copy (even when num == flen) to avoid
 129      * leaking that information. The copy still leaks some side-channel
 130      * information, but it's impossible to have a fixed  memory access
 131      * pattern since we can't read out of the bounds of |from|.
 132      *
 133      * TODO(emilia): Consider porting BN_bn2bin_padded from BoringSSL.
 134      */
 135     memset(em, 0, num);
 136     memcpy(em + num - flen, from, flen);
 137
 138     /*
 139      * The first byte must be zero, however we must not leak if this is
 140      * true. See James H. Manger, "A Chosen Ciphertext  Attack on RSA
 141      * Optimal Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001).
 142      */
 143     good = constant_time_is_zero(em[0]);
 144
 145     maskedseed = em + 1;
 146     maskeddb = em + 1 + SHA_DIGEST_LENGTH;
 147
 148     if (MGF1(seed, SHA_DIGEST_LENGTH, maskeddb, dblen))
 149         goto cleanup;
 150     for (i = 0; i < SHA_DIGEST_LENGTH; i++)
 151         seed[i] ^= maskedseed[i];
 152
 153     if (MGF1(db, dblen, seed, SHA_DIGEST_LENGTH))
 154         goto cleanup;
 155     for (i = 0; i < dblen; i++)
 156         db[i] ^= maskeddb[i];
 157
 158     if (!EVP_Digest((void *)param, plen, phash, NULL, EVP_sha1(), NULL))
 159         goto cleanup;
 160
 161     good &=
 162         constant_time_is_zero(CRYPTO_memcmp(db, phash, SHA_DIGEST_LENGTH));
 163
 164     found_one_byte = 0;
 165     for (i = SHA_DIGEST_LENGTH; i < dblen; i++) {
 166         /*
 167          * Padding consists of a number of 0-bytes, followed by a 1.
 168          */
 169         unsigned int equals1 = constant_time_eq(db[i], 1);
 170         unsigned int equals0 = constant_time_is_zero(db[i]);
 171         one_index = constant_time_select_int(~found_one_byte & equals1,
 172                                              i, one_index);
 173         found_one_byte |= equals1;
 174         good &= (found_one_byte | equals0);
 175     }
 176
 177     good &= found_one_byte;
 178
 179     /*
 180      * At this point |good| is zero unless the plaintext was valid,
 181      * so plaintext-awareness ensures timing side-channels are no longer a
 182      * concern.
 183      */
 184     if (!good)
 185         goto decoding_err;
 186
 187     msg_index = one_index + 1;
 188     mlen = dblen - msg_index;
 189
 190     if (tlen < mlen) {
 191         RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_DATA_TOO_LARGE);
 192         mlen = -1;
 193     } else {
 194         memcpy(to, db + msg_index, mlen);
 195         goto cleanup;
 196     }
 197
 198  decoding_err:
 199     /*
 200      * To avoid chosen ciphertext attacks, the error message should not
 201      * reveal which kind of decoding error happened.
 202      */
 203     RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_OAEP_DECODING_ERROR);
 204  cleanup:
 205     if (db != NULL)
 206         OPENSSL_free(db);
 207     if (em != NULL)
 208         OPENSSL_free(em);
 209     return mlen;
 210 }
 211
 212 int PKCS1_MGF1(unsigned char *mask, long len,
 213                const unsigned char *seed, long seedlen, const EVP_MD *dgst)
 214 {
 215     long i, outlen = 0;
 216     unsigned char cnt[4];
 217     EVP_MD_CTX c;
 218     unsigned char md[EVP_MAX_MD_SIZE];
 219     int mdlen;
 220     int rv = -1;
 221
 222     EVP_MD_CTX_init(&c);
 223     mdlen = EVP_MD_size(dgst);
 224     if (mdlen < 0)
 225         goto err;
 226     for (i = 0; outlen < len; i++) {
 227         cnt[0] = (unsigned char)((i >> 24) & 255);
 228         cnt[1] = (unsigned char)((i >> 16) & 255);
 229         cnt[2] = (unsigned char)((i >> 8)) & 255;
 230         cnt[3] = (unsigned char)(i & 255);
 231         if (!EVP_DigestInit_ex(&c, dgst, NULL)
 232             || !EVP_DigestUpdate(&c, seed, seedlen)
 233             || !EVP_DigestUpdate(&c, cnt, 4))
 234             goto err;
 235         if (outlen + mdlen <= len) {
 236             if (!EVP_DigestFinal_ex(&c, mask + outlen, NULL))
 237                 goto err;
 238             outlen += mdlen;
 239         } else {
 240             if (!EVP_DigestFinal_ex(&c, md, NULL))
 241                 goto err;
 242             memcpy(mask + outlen, md, len - outlen);
 243             outlen = len;
 244         }
 245     }
 246     rv = 0;
 247  err:
 248     EVP_MD_CTX_cleanup(&c);
 249     return rv;
 250 }
 251
 252 static int MGF1(unsigned char *mask, long len, const unsigned char *seed,
 253                 long seedlen)
 254 {
 255     return PKCS1_MGF1(mask, len, seed, seedlen, EVP_sha1());
 256 }
 257 #endif