Use Google Tink format for DEKs (confluentinc#3) (confluentinc#2277)

* Use Google Tink format for DEKs

* Fix test

Author: rayokota

src/Confluent.SchemaRegistry.Encryption/Confluent.SchemaRegistry.Encryption.csproj

@@ -28,6 +28,7 @@
     </ItemGroup>
 
     <ItemGroup>
+        <PackageReference Include="Google.Protobuf" Version="3.26.1" />
         <PackageReference Include="HKDF.Standard" Version="2.0.0" />
         <PackageReference Include="Miscreant" Version="0.3.3" />
     </ItemGroup>

src/Confluent.SchemaRegistry.Encryption/Cryptor.cs

@@ -1,6 +1,8 @@
 using System;
 using System.IO;
 using System.Security.Cryptography;
+using Google.Crypto.Tink;
+using Google.Protobuf;
 using Miscreant;
 
 namespace Confluent.SchemaRegistry.Encryption
@@ -40,32 +42,58 @@ public int KeySize()
 
         public byte[] GenerateKey()
         {
-            return Aead.GenerateNonce(KeySize());
+            byte[] rawKey = Aead.GenerateNonce(KeySize());
+            switch (DekFormat)
+            {
+                case DekFormat.AES256_SIV:
+                    AesSivKey aesSiv = new AesSivKey();
+                    aesSiv.Version = 0;
+                    aesSiv.KeyValue = ByteString.CopyFrom(rawKey);
+                    return aesSiv.ToByteArray();
+                case DekFormat.AES128_GCM:
+                case DekFormat.AES256_GCM:
+                    AesGcmKey aesGcm = new AesGcmKey();
+                    aesGcm.Version = 0;
+                    aesGcm.KeyValue = ByteString.CopyFrom(rawKey);
+                    return aesGcm.ToByteArray();
+                default:
+                    throw new ArgumentException();
+            }
         }
 
         public byte[] Encrypt(byte[] key, byte[] plaintext)
         {
+            byte[] rawKey;
             switch (DekFormat)
             {
                 case DekFormat.AES256_SIV:
-                    return EncryptWithAesSiv(key, plaintext);
+                    AesSivKey aesSiv = AesSivKey.Parser.ParseFrom(key);
+                    rawKey = aesSiv.KeyValue.ToByteArray();
+                    return EncryptWithAesSiv(rawKey, plaintext);
                 case DekFormat.AES128_GCM:
                 case DekFormat.AES256_GCM:
-                    return EncryptWithAesGcm(key, plaintext);
+                    AesGcmKey aesGcm = AesGcmKey.Parser.ParseFrom(key);
+                    rawKey = aesGcm.KeyValue.ToByteArray();
+                    return EncryptWithAesGcm(rawKey, plaintext);
                 default:
                     throw new ArgumentException();
             }
         }
 
         public byte[] Decrypt(byte[] key, byte[] ciphertext)
         {
+            byte[] rawKey;
             switch (DekFormat)
             {
                 case DekFormat.AES256_SIV:
-                    return DecryptWithAesSiv(key, ciphertext);
+                    AesSivKey aesSiv = AesSivKey.Parser.ParseFrom(key);
+                    rawKey = aesSiv.KeyValue.ToByteArray();
+                    return DecryptWithAesSiv(rawKey, ciphertext);
                 case DekFormat.AES128_GCM:
                 case DekFormat.AES256_GCM:
-                    return DecryptWithAesGcm(key, ciphertext);
+                    AesGcmKey aesGcm = AesGcmKey.Parser.ParseFrom(key);
+                    rawKey = aesGcm.KeyValue.ToByteArray();
+                    return DecryptWithAesGcm(rawKey, ciphertext);
                 default:
                     throw new ArgumentException();
             }

src/Confluent.SchemaRegistry.Encryption/LocalKmsClient.cs

@@ -3,6 +3,8 @@
 using System.Security.Cryptography;
 using System.Text;
 using System.Threading.Tasks;
+using Google.Crypto.Tink;
+using Google.Protobuf;
 
 namespace Confluent.SchemaRegistry.Encryption
 {
@@ -20,7 +22,12 @@ public LocalKmsClient(string secret)
             }
             Secret = secret;
             cryptor = new Cryptor(DekFormat.AES256_GCM);
-            key = Hkdf.DeriveKey(HashAlgorithmName.SHA256, Encoding.UTF8.GetBytes(secret), cryptor.KeySize());
+            byte[] rawKey = Hkdf.DeriveKey(
+                HashAlgorithmName.SHA256, Encoding.UTF8.GetBytes(secret), cryptor.KeySize());
+            AesGcmKey aesGcm = new AesGcmKey();
+            aesGcm.Version = 0;
+            aesGcm.KeyValue = ByteString.CopyFrom(rawKey);
+            key = aesGcm.ToByteArray();
         }
 
         public bool DoesSupport(string uri)