private static CBORObject encodeEncryptMessageInternal()

in java/remoteprovisioning/CborUtil.java [88:128]
32 lines of code
1 McCabe index (conditional complexity)

  private static CBORObject encodeEncryptMessageInternal(
      byte[] plaintext, byte[] aesKey, CBORObject ephemeralPubKey, byte[] keyId)
      throws CborException, CryptoException {
    SecureRandom rand = new SecureRandom();
    byte[] iv = new byte[16];
    rand.nextBytes(iv);

    // A COSE_Encrypt message is a CBOR array with 4 entries
    CBORObject encMsg = CBORObject.NewArray();
    CBORObject protectedHeaders = CBORObject.NewMap();
    protectedHeaders.Add(HeaderKeys.Algorithm.AsCBOR(), AlgorithmID.AES_GCM_256.AsCBOR());
    byte[] aad = buildEncStructure(protectedHeaders.EncodeToBytes(), null);

    CBORObject unprotectedHeaders = CBORObject.NewMap();
    unprotectedHeaders.Add(HeaderKeys.IV.AsCBOR(), CBORObject.FromObject(iv));

    CBORObject content = CBORObject.FromObject(CryptoUtil.encrypt(plaintext, aad, aesKey, iv));

    CBORObject recipients = CBORObject.NewArray();
    // Build a COSE_Recipient object containing the public keys needed for ECDH
    CBORObject recipient = CBORObject.NewArray();
    CBORObject protectedHeadersRecip = CBORObject.NewMap();
    protectedHeadersRecip.Add(HeaderKeys.Algorithm.AsCBOR(), AlgorithmID.ECDH_ES_HKDF_256.AsCBOR());

    CBORObject unprotectedHeadersRecip = CBORObject.NewMap();
    // This adds the kid too, which is not specified for this Key in the spec
    unprotectedHeadersRecip.Add(
        HeaderKeys.ECDH_EPK.AsCBOR(),
        ephemeralPubKey);
    unprotectedHeadersRecip.Add(HeaderKeys.KID.AsCBOR(), keyId);
    recipient.Add(protectedHeadersRecip.EncodeToBytes());
    recipient.Add(unprotectedHeadersRecip);
    recipient.Add(CBORObject.Null); // ciphertext field, nil if no key

    encMsg.Add(protectedHeaders.EncodeToBytes());
    encMsg.Add(unprotectedHeaders);
    encMsg.Add(content);
    recipients.Add(recipient);
    encMsg.Add(recipients);
    return encMsg;
  }