Add an action to download encrypted service account credentials

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=222902380

java/google/registry/tools/server/DownloadServiceAccountCredentialAction.java

@@ -0,0 +1,70 @@
+// Copyright 2018 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.tools.server;
+
+import static google.registry.request.Action.Method.GET;
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static javax.servlet.http.HttpServletResponse.SC_INTERNAL_SERVER_ERROR;
+
+import com.google.common.flogger.FluentLogger;
+import com.google.common.io.BaseEncoding;
+import com.google.common.net.MediaType;
+import google.registry.keyring.kms.KmsKeyring.StringKeyLabel;
+import google.registry.request.Action;
+import google.registry.request.Response;
+import google.registry.request.auth.Auth;
+import java.util.function.Function;
+import javax.inject.Inject;
+import javax.inject.Named;
+
+/**
+ * An action that returns KMS encrypted service account credential in its payload.
+ *
+ * <p>This credential can be stored locally, and a {@code RemoteApiOptions} can use it to initialize
+ * an {@code AppEngineConnection}.
+ */
+@Action(
+    path = DownloadServiceAccountCredentialAction.PATH,
+    method = {GET},
+    auth = Auth.AUTH_INTERNAL_OR_ADMIN)
+public class DownloadServiceAccountCredentialAction implements Runnable {
+
+  private static final FluentLogger logger = FluentLogger.forEnclosingClass();
+
+  public static final String PATH = "/_dr/admin/downloadCredential";
+
+  @Inject
+  @Named("encryptedDataRetriever")
+  Function<String, String> encryptedDataRetriever;
+
+  @Inject Response response;
+
+  @Inject
+  DownloadServiceAccountCredentialAction() {}
+
+  @Override
+  public void run() {
+    try {
+      String encryptedJsonCredential =
+          encryptedDataRetriever.apply(StringKeyLabel.JSON_CREDENTIAL_STRING.getLabel());
+      response.setContentType(MediaType.APPLICATION_BINARY);
+      response.setPayload(BaseEncoding.base64().encode(encryptedJsonCredential.getBytes(UTF_8)));
+    } catch (Exception e) {
+      logger.atSevere().withCause(e).log("Cannot retrieve encrypted service account credential.");
+      response.setPayload(e.getMessage());
+      response.setStatus(SC_INTERNAL_SERVER_ERROR);
+    }
+  }
+}