public static X25519PublicKeyParameters getX25519PublicKeyFromCert()

in java/remoteprovisioning/CryptoUtil.java [526:576]
51 lines of code
8 McCabe index (conditional complexity)

  public static X25519PublicKeyParameters getX25519PublicKeyFromCert(CBORObject certObj)
      throws CborException, CryptoException {
    try {
      Sign1Message cert =
          (Sign1Message) Message.DecodeFromBytes(certObj.EncodeToBytes(), MessageTag.Sign1);
      CBORObject content = CBORObject.DecodeFromBytes(cert.GetContent());
      if (content.get(KeyKeys.OKP_Curve.AsCBOR()).getType() != CBORType.Integer) {
        throw new CborException(
            "Curve field does not have expected type",
            CBORType.Integer,
            content.get(KeyKeys.OKP_Curve.AsCBOR()).getType(),
            CborException.TYPE_MISMATCH);
      }
      CBORObject keyType = content.get(KeyKeys.KeyType.AsCBOR());
      if (keyType.getType() != CBORType.Integer) {
        throw new CborException(
            "Key type field does not have expected type",
            CBORType.Integer,
            keyType.getType(),
            CborException.TYPE_MISMATCH);
      }
      if (keyType.AsInt32() != KeyKeys.KeyType_OKP.AsInt32()) {
        throw new CborException(
            "Key has unexpected key type (kty)",
            KeyKeys.KeyType_OKP.AsInt32(),
            keyType.AsInt32(),
            CborException.INCORRECT_COSE_TYPE);
      }
      int curve = content.get(KeyKeys.OKP_Curve.AsCBOR()).AsInt32();
      CBORObject algorithm = content.get(KeyKeys.Algorithm.AsCBOR());
      if (algorithm.getType() != CBORType.Integer) {
        throw new CborException(
            "Algorithm has unexpected CBOR type",
            CBORType.Integer,
            algorithm.getType(),
            CborException.TYPE_MISMATCH);
      }
      if (curve != X25519
          || algorithm.AsInt32() != AlgorithmID.ECDH_ES_HKDF_256.AsCBOR().AsInt32()) {
        throw new CborException(
            "Algorithm does not match the curve",
            AlgorithmID.ECDH_ES_HKDF_256.AsCBOR().AsInt32(),
            algorithm.AsInt32(),
            CborException.INCORRECT_COSE_TYPE);
      }
      return getX25519PublicKeyFromCert(cert);
    } catch (CoseException e) {
      throw new CborException(
          "Failed to decode certificate", e, CborException.DESERIALIZATION_ERROR);
    }
  }