5-improve-encrypted-storage (#6)

Added the use of DEK's for encryption of secrets. Both the KEK's and DEK's are stored in a way that you can have multiple key of which one is active. But the others are still available for decrypting. This allows for implementing key rotation.

Co-authored-by: eelke <eelke@eelkeklein.nl>
Co-authored-by: Eelke76 <31384324+Eelke76@users.noreply.github.com>
Reviewed-on: #6

IdentityShroud.Core/Services/KeyService.cs

@@ -0,0 +1,46 @@
+using IdentityShroud.Core.Contracts;
+using IdentityShroud.Core.Messages;
+using IdentityShroud.Core.Model;
+using IdentityShroud.Core.Security.Keys;
+
+namespace IdentityShroud.Core.Services;
+
+public class KeyService(
+    IDekEncryptionService cryptor,
+    IKeyProviderFactory keyProviderFactory,
+    IClock clock) : IKeyService
+{
+    public RealmKey CreateKey(KeyPolicy policy)
+    {
+        IKeyProvider provider = keyProviderFactory.CreateProvider(policy.KeyType);
+        var plainKey = provider.CreateKey(policy);
+
+        return CreateKey(policy.KeyType, plainKey);
+    }
+
+    public JsonWebKey? CreateJsonWebKey(RealmKey realmKey)
+    {
+        JsonWebKey jwk = new()
+        {
+            KeyId = realmKey.Id.ToString(),
+            KeyType = realmKey.KeyType,
+            Use = "sig",
+        };
+        
+        IKeyProvider provider = keyProviderFactory.CreateProvider(realmKey.KeyType);
+        provider.SetJwkParameters(
+            cryptor.Decrypt(realmKey.Key),
+            jwk);
+
+        return jwk;
+    }
+
+    private RealmKey CreateKey(string keyType, byte[] plainKey) =>
+        new RealmKey()
+            {
+                Id = Guid.NewGuid(),
+                KeyType = keyType,
+                Key = cryptor.Encrypt(plainKey),
+                CreatedAt = clock.UtcNow(),
+            };
+}