예제 #1
0
static int test_eq_int(int a, int b)
{
    unsigned int equal = constant_time_eq_int(a, b);
    if (a == b && equal != CONSTTIME_TRUE) {
        fprintf(stderr, "Test failed for constant_time_eq_int(%d, %d): "
                "expected %du(TRUE), got %du\n", a, b, CONSTTIME_TRUE, equal);
        return 1;
    } else if (a != b && equal != CONSTTIME_FALSE) {
        fprintf(stderr, "Test failed for constant_time_eq_int(%d, %d): "
                "expected %du(FALSE), got %du\n",
                a, b, CONSTTIME_FALSE, equal);
        return 1;
    }
    return 0;
}
예제 #2
0
파일: err.c 프로젝트: dgalaxy/openssl
void err_clear_last_constant_time(int clear)
{
    ERR_STATE *es;
    int top;

    es = ERR_get_state();
    if (es == NULL)
        return;

    top = es->top;

    /*
     * Flag error as cleared but remove it elsewhere to avoid two errors
     * accessing the same error stack location, revealing timing information.
     */
    clear = constant_time_select_int(constant_time_eq_int(clear, 0),
                                     0, ERR_FLAG_CLEAR);
    es->err_flags[top] |= clear;
}
예제 #3
0
static int aead_tls_open(const EVP_AEAD_CTX *ctx, uint8_t *out,
                         size_t *out_len, size_t max_out_len,
                         const uint8_t *nonce, size_t nonce_len,
                         const uint8_t *in, size_t in_len,
                         const uint8_t *ad, size_t ad_len) {
  AEAD_TLS_CTX *tls_ctx = (AEAD_TLS_CTX *)ctx->aead_state;

  if (tls_ctx->cipher_ctx.encrypt) {
    /* Unlike a normal AEAD, a TLS AEAD may only be used in one direction. */
    OPENSSL_PUT_ERROR(CIPHER, aead_tls_open, CIPHER_R_INVALID_OPERATION);
    return 0;

  }

  if (in_len < HMAC_size(&tls_ctx->hmac_ctx)) {
    OPENSSL_PUT_ERROR(CIPHER, aead_tls_open, CIPHER_R_BAD_DECRYPT);
    return 0;
  }

  if (max_out_len < in_len) {
    /* This requires that the caller provide space for the MAC, even though it
     * will always be removed on return. */
    OPENSSL_PUT_ERROR(CIPHER, aead_tls_open, CIPHER_R_BUFFER_TOO_SMALL);
    return 0;
  }

  if (nonce_len != EVP_AEAD_nonce_length(ctx->aead)) {
    OPENSSL_PUT_ERROR(CIPHER, aead_tls_open, CIPHER_R_INVALID_NONCE_SIZE);
    return 0;
  }

  if (ad_len != 13 - 2 /* length bytes */) {
    OPENSSL_PUT_ERROR(CIPHER, aead_tls_open, CIPHER_R_INVALID_AD_SIZE);
    return 0;
  }

  if (in_len > INT_MAX) {
    /* EVP_CIPHER takes int as input. */
    OPENSSL_PUT_ERROR(CIPHER, aead_tls_open, CIPHER_R_TOO_LARGE);
    return 0;
  }

  /* Configure the explicit IV. */
  if (EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) == EVP_CIPH_CBC_MODE &&
      !tls_ctx->implicit_iv &&
      !EVP_DecryptInit_ex(&tls_ctx->cipher_ctx, NULL, NULL, NULL, nonce)) {
    return 0;
  }

  /* Decrypt to get the plaintext + MAC + padding. */
  size_t total = 0;
  int len;
  if (!EVP_DecryptUpdate(&tls_ctx->cipher_ctx, out, &len, in, (int)in_len)) {
    return 0;
  }
  total += len;
  if (!EVP_DecryptFinal_ex(&tls_ctx->cipher_ctx, out + total, &len)) {
    return 0;
  }
  total += len;
  assert(total == in_len);

  /* Remove CBC padding. Code from here on is timing-sensitive with respect to
   * |padding_ok| and |data_plus_mac_len| for CBC ciphers. */
  int padding_ok;
  unsigned data_plus_mac_len, data_len;
  if (EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) == EVP_CIPH_CBC_MODE) {
    padding_ok = EVP_tls_cbc_remove_padding(
        &data_plus_mac_len, out, total,
        EVP_CIPHER_CTX_block_size(&tls_ctx->cipher_ctx),
        (unsigned)HMAC_size(&tls_ctx->hmac_ctx));
    /* Publicly invalid. This can be rejected in non-constant time. */
    if (padding_ok == 0) {
      OPENSSL_PUT_ERROR(CIPHER, aead_tls_open, CIPHER_R_BAD_DECRYPT);
      return 0;
    }
  } else {
    padding_ok = 1;
    data_plus_mac_len = total;
    /* |data_plus_mac_len| = |total| = |in_len| at this point. |in_len| has
     * already been checked against the MAC size at the top of the function. */
    assert(data_plus_mac_len >= HMAC_size(&tls_ctx->hmac_ctx));
  }
  data_len = data_plus_mac_len - HMAC_size(&tls_ctx->hmac_ctx);

  /* At this point, |padding_ok| is 1 or -1. If 1, the padding is valid and the
   * first |data_plus_mac_size| bytes after |out| are the plaintext and
   * MAC. Either way, |data_plus_mac_size| is large enough to extract a MAC. */

  /* To allow for CBC mode which changes cipher length, |ad| doesn't include the
   * length for legacy ciphers. */
  uint8_t ad_fixed[13];
  memcpy(ad_fixed, ad, 11);
  ad_fixed[11] = (uint8_t)(data_len >> 8);
  ad_fixed[12] = (uint8_t)(data_len & 0xff);
  ad_len += 2;

  /* Compute the MAC and extract the one in the record. */
  uint8_t mac[EVP_MAX_MD_SIZE];
  size_t mac_len;
  uint8_t record_mac_tmp[EVP_MAX_MD_SIZE];
  uint8_t *record_mac;
  if (EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) == EVP_CIPH_CBC_MODE &&
      EVP_tls_cbc_record_digest_supported(tls_ctx->hmac_ctx.md)) {
    if (!EVP_tls_cbc_digest_record(tls_ctx->hmac_ctx.md, mac, &mac_len,
                                   ad_fixed, out, data_plus_mac_len, total,
                                   tls_ctx->mac_key, tls_ctx->mac_key_len)) {
      OPENSSL_PUT_ERROR(CIPHER, aead_tls_open, CIPHER_R_BAD_DECRYPT);
      return 0;
    }
    assert(mac_len == HMAC_size(&tls_ctx->hmac_ctx));

    record_mac = record_mac_tmp;
    EVP_tls_cbc_copy_mac(record_mac, mac_len, out, data_plus_mac_len, total);
  } else {
    /* We should support the constant-time path for all CBC-mode ciphers
     * implemented. */
    assert(EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) != EVP_CIPH_CBC_MODE);

    HMAC_CTX hmac_ctx;
    HMAC_CTX_init(&hmac_ctx);
    unsigned mac_len_u;
    if (!HMAC_CTX_copy_ex(&hmac_ctx, &tls_ctx->hmac_ctx) ||
        !HMAC_Update(&hmac_ctx, ad_fixed, ad_len) ||
        !HMAC_Update(&hmac_ctx, out, data_len) ||
        !HMAC_Final(&hmac_ctx, mac, &mac_len_u)) {
      HMAC_CTX_cleanup(&hmac_ctx);
      return 0;
    }
    mac_len = mac_len_u;
    HMAC_CTX_cleanup(&hmac_ctx);

    assert(mac_len == HMAC_size(&tls_ctx->hmac_ctx));
    record_mac = &out[data_len];
  }

  /* Perform the MAC check and the padding check in constant-time. It should be
   * safe to simply perform the padding check first, but it would not be under a
   * different choice of MAC location on padding failure. See
   * EVP_tls_cbc_remove_padding. */
  unsigned good = constant_time_eq_int(CRYPTO_memcmp(record_mac, mac, mac_len),
                                       0);
  good &= constant_time_eq_int(padding_ok, 1);
  if (!good) {
    OPENSSL_PUT_ERROR(CIPHER, aead_tls_open, CIPHER_R_BAD_DECRYPT);
    return 0;
  }

  /* End of timing-sensitive code. */

  *out_len = data_len;
  return 1;
}
예제 #4
0
static int aead_tls_open(const EVP_AEAD_CTX *ctx, uint8_t *out, size_t *out_len,
                         size_t max_out_len, const uint8_t *nonce,
                         size_t nonce_len, const uint8_t *in, size_t in_len,
                         const uint8_t *ad, size_t ad_len) {
  AEAD_TLS_CTX *tls_ctx = (AEAD_TLS_CTX *)ctx->aead_state;

  if (tls_ctx->cipher_ctx.encrypt) {
    // Unlike a normal AEAD, a TLS AEAD may only be used in one direction.
    OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_INVALID_OPERATION);
    return 0;
  }

  if (in_len < HMAC_size(&tls_ctx->hmac_ctx)) {
    OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
    return 0;
  }

  if (max_out_len < in_len) {
    // This requires that the caller provide space for the MAC, even though it
    // will always be removed on return.
    OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);
    return 0;
  }

  if (nonce_len != EVP_AEAD_nonce_length(ctx->aead)) {
    OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_INVALID_NONCE_SIZE);
    return 0;
  }

  if (ad_len != 13 - 2 /* length bytes */) {
    OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_INVALID_AD_SIZE);
    return 0;
  }

  if (in_len > INT_MAX) {
    // EVP_CIPHER takes int as input.
    OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
    return 0;
  }

  // Configure the explicit IV.
  if (EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) == EVP_CIPH_CBC_MODE &&
      !tls_ctx->implicit_iv &&
      !EVP_DecryptInit_ex(&tls_ctx->cipher_ctx, NULL, NULL, NULL, nonce)) {
    return 0;
  }

  // Decrypt to get the plaintext + MAC + padding.
  size_t total = 0;
  int len;
  if (!EVP_DecryptUpdate(&tls_ctx->cipher_ctx, out, &len, in, (int)in_len)) {
    return 0;
  }
  total += len;
  if (!EVP_DecryptFinal_ex(&tls_ctx->cipher_ctx, out + total, &len)) {
    return 0;
  }
  total += len;
  assert(total == in_len);

  // Remove CBC padding. Code from here on is timing-sensitive with respect to
  // |padding_ok| and |data_plus_mac_len| for CBC ciphers.
  size_t data_plus_mac_len;
  crypto_word_t padding_ok;
  if (EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) == EVP_CIPH_CBC_MODE) {
    if (!EVP_tls_cbc_remove_padding(
            &padding_ok, &data_plus_mac_len, out, total,
            EVP_CIPHER_CTX_block_size(&tls_ctx->cipher_ctx),
            HMAC_size(&tls_ctx->hmac_ctx))) {
      // Publicly invalid. This can be rejected in non-constant time.
      OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
      return 0;
    }
  } else {
    padding_ok = CONSTTIME_TRUE_W;
    data_plus_mac_len = total;
    // |data_plus_mac_len| = |total| = |in_len| at this point. |in_len| has
    // already been checked against the MAC size at the top of the function.
    assert(data_plus_mac_len >= HMAC_size(&tls_ctx->hmac_ctx));
  }
  size_t data_len = data_plus_mac_len - HMAC_size(&tls_ctx->hmac_ctx);

  // At this point, if the padding is valid, the first |data_plus_mac_len| bytes
  // after |out| are the plaintext and MAC. Otherwise, |data_plus_mac_len| is
  // still large enough to extract a MAC, but it will be irrelevant.

  // To allow for CBC mode which changes cipher length, |ad| doesn't include the
  // length for legacy ciphers.
  uint8_t ad_fixed[13];
  OPENSSL_memcpy(ad_fixed, ad, 11);
  ad_fixed[11] = (uint8_t)(data_len >> 8);
  ad_fixed[12] = (uint8_t)(data_len & 0xff);
  ad_len += 2;

  // Compute the MAC and extract the one in the record.
  uint8_t mac[EVP_MAX_MD_SIZE];
  size_t mac_len;
  uint8_t record_mac_tmp[EVP_MAX_MD_SIZE];
  uint8_t *record_mac;
  if (EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) == EVP_CIPH_CBC_MODE &&
      EVP_tls_cbc_record_digest_supported(tls_ctx->hmac_ctx.md)) {
    if (!EVP_tls_cbc_digest_record(tls_ctx->hmac_ctx.md, mac, &mac_len,
                                   ad_fixed, out, data_plus_mac_len, total,
                                   tls_ctx->mac_key, tls_ctx->mac_key_len)) {
      OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
      return 0;
    }
    assert(mac_len == HMAC_size(&tls_ctx->hmac_ctx));

    record_mac = record_mac_tmp;
    EVP_tls_cbc_copy_mac(record_mac, mac_len, out, data_plus_mac_len, total);
  } else {
    // We should support the constant-time path for all CBC-mode ciphers
    // implemented.
    assert(EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) != EVP_CIPH_CBC_MODE);

    unsigned mac_len_u;
    if (!HMAC_Init_ex(&tls_ctx->hmac_ctx, NULL, 0, NULL, NULL) ||
        !HMAC_Update(&tls_ctx->hmac_ctx, ad_fixed, ad_len) ||
        !HMAC_Update(&tls_ctx->hmac_ctx, out, data_len) ||
        !HMAC_Final(&tls_ctx->hmac_ctx, mac, &mac_len_u)) {
      return 0;
    }
    mac_len = mac_len_u;

    assert(mac_len == HMAC_size(&tls_ctx->hmac_ctx));
    record_mac = &out[data_len];
  }

  // Perform the MAC check and the padding check in constant-time. It should be
  // safe to simply perform the padding check first, but it would not be under a
  // different choice of MAC location on padding failure. See
  // EVP_tls_cbc_remove_padding.
  crypto_word_t good =
      constant_time_eq_int(CRYPTO_memcmp(record_mac, mac, mac_len), 0);
  good &= padding_ok;
  if (!good) {
    OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
    return 0;
  }

  // End of timing-sensitive code.

  *out_len = data_len;
  return 1;
}