internal static EncryptionInstructions BuildInstructionsFromObjectMetadata()

in src/EncryptionUtils.cs [394:442]
42 lines of code
5 McCabe index (conditional complexity)

        internal static EncryptionInstructions BuildInstructionsFromObjectMetadata(
            GetObjectResponse response, EncryptionMaterialsBase materials, byte[] decryptedEnvelopeKeyKMS)
        {
            MetadataCollection metadata = response.Metadata;

            var materialDescription = GetMaterialDescriptionFromMetaData(response.Metadata);

            if (metadata[XAmzKeyV2] != null)
            {
                EnsureSupportedAlgorithms(metadata);

                var base64EncodedEncryptedEnvelopeKey = metadata[XAmzKeyV2];
                var encryptedEnvelopeKey = Convert.FromBase64String(base64EncodedEncryptedEnvelopeKey);

                var base64EncodedIV = metadata[XAmzIV];
                var IV = Convert.FromBase64String(base64EncodedIV);
                var cekAlgorithm = metadata[XAmzCekAlg];
                var wrapAlgorithm = metadata[XAmzWrapAlg];

                if (decryptedEnvelopeKeyKMS != null)
                {
                    return new EncryptionInstructions(materialDescription, decryptedEnvelopeKeyKMS, encryptedEnvelopeKey, IV, wrapAlgorithm, cekAlgorithm);
                }
                else
                {
                    byte[] decryptedEnvelopeKey;
                    if (XAmzWrapAlgRsaOaepSha1.Equals(wrapAlgorithm) || XAmzWrapAlgAesGcmValue.Equals(wrapAlgorithm))
                    {
                        decryptedEnvelopeKey = DecryptNonKmsEnvelopeKeyV2(encryptedEnvelopeKey, materials);
                    }
                    else
                    {
                        decryptedEnvelopeKey = DecryptNonKMSEnvelopeKey(encryptedEnvelopeKey, materials);
                    }
                    return new EncryptionInstructions(materialDescription, decryptedEnvelopeKey, encryptedEnvelopeKey, IV, wrapAlgorithm, cekAlgorithm);
                }
            }
            else
            {
                string base64EncodedEncryptedEnvelopeKey = metadata[XAmzKey];
                byte[] encryptedEnvelopeKey = Convert.FromBase64String(base64EncodedEncryptedEnvelopeKey);
                byte[] decryptedEnvelopeKey = DecryptNonKMSEnvelopeKey(encryptedEnvelopeKey, materials);

                string base64EncodedIV = metadata[XAmzIV];
                byte[] IV = Convert.FromBase64String(base64EncodedIV);

                return new EncryptionInstructions(materialDescription, decryptedEnvelopeKey, encryptedEnvelopeKey, IV);
            }
        }