public DecryptionMaterials getDecryptionMaterials()

in DynamoDbEncryption/runtimes/java/src/main/sdkv1/com/amazonaws/services/dynamodbv2/datamodeling/encryption/providers/DirectKmsMaterialProvider.java [120:176]

49 lines of code
4 McCabe index (conditional complexity)


  public DecryptionMaterials getDecryptionMaterials(EncryptionContext context) {
    final Map<String, String> materialDescription =
      context.getMaterialDescription();

    final Map<String, String> ec = new HashMap<>();
    final String providedEncAlg = materialDescription.get(
      CONTENT_KEY_ALGORITHM
    );
    final String providedSigAlg = materialDescription.get(
      SIGNING_KEY_ALGORITHM
    );

    ec.put("*" + CONTENT_KEY_ALGORITHM + "*", providedEncAlg);
    ec.put("*" + SIGNING_KEY_ALGORITHM + "*", providedSigAlg);

    populateKmsEcFromEc(context, ec);

    DecryptRequest request = appendUserAgent(new DecryptRequest());
    request.setCiphertextBlob(
      ByteBuffer.wrap(Base64.decode(materialDescription.get(ENVELOPE_KEY)))
    );
    request.setEncryptionContext(ec);
    final DecryptResult decryptResult = decrypt(request, context);
    validateEncryptionKeyId(decryptResult.getKeyId(), context);

    final Hkdf kdf;
    try {
      kdf = Hkdf.getInstance(KDF_ALG);
    } catch (NoSuchAlgorithmException e) {
      throw new DynamoDBMappingException(e);
    }
    kdf.init(toArray(decryptResult.getPlaintext()));

    final String[] encAlgParts = providedEncAlg.split("/", 2);
    int encLength = encAlgParts.length == 2
      ? Integer.parseInt(encAlgParts[1])
      : 256;
    final String[] sigAlgParts = providedSigAlg.split("/", 2);
    int sigLength = sigAlgParts.length == 2
      ? Integer.parseInt(sigAlgParts[1])
      : 256;

    final SecretKey encryptionKey = new SecretKeySpec(
      kdf.deriveKey(KDF_ENC_INFO, encLength / 8),
      encAlgParts[0]
    );
    final SecretKey macKey = new SecretKeySpec(
      kdf.deriveKey(KDF_SIG_INFO, sigLength / 8),
      sigAlgParts[0]
    );

    return new SymmetricRawMaterials(
      encryptionKey,
      macKey,
      materialDescription
    );
  }