Persist created keystore on startup unless keystore is present

We already added the functionality to create a new keystore on startup
in elastic#26126 but apparently missed to persist the keystore. This change adds
peristence and adds a test for the boostrap loading.

core/src/main/java/org/elasticsearch/bootstrap/Bootstrap.java

@@ -35,7 +35,6 @@
 import org.elasticsearch.common.PidFile;
 import org.elasticsearch.common.SuppressForbidden;
 import org.elasticsearch.common.inject.CreationException;
-import org.elasticsearch.common.logging.DeprecationLogger;
 import org.elasticsearch.common.logging.ESLoggerFactory;
 import org.elasticsearch.common.logging.LogConfigurator;
 import org.elasticsearch.common.logging.Loggers;
@@ -220,7 +219,7 @@ protected void validateNodeBeforeAcceptingRequests(
         };
     }
 
-    private static SecureSettings loadSecureSettings(Environment initialEnv) throws BootstrapException {
+    static SecureSettings loadSecureSettings(Environment initialEnv) throws BootstrapException {
         final KeyStoreWrapper keystore;
         try {
             keystore = KeyStoreWrapper.load(initialEnv.configFile());
@@ -231,7 +230,9 @@ private static SecureSettings loadSecureSettings(Environment initialEnv) throws
         try {
             if (keystore == null) {
                 // create it, we always want one! we use an empty passphrase, but a user can change this later if they want.
-                KeyStoreWrapper.create(new char[0]);
+                KeyStoreWrapper keyStoreWrapper = KeyStoreWrapper.create(new char[0]);
+                keyStoreWrapper.save(initialEnv.configFile());
+                return keyStoreWrapper;
             } else {
                 keystore.decrypt(new char[0] /* TODO: read password from stdin */);
             }

core/src/test/java/org/elasticsearch/bootstrap/BootstrapTests.java

@@ -0,0 +1,76 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you 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 org.elasticsearch.bootstrap;
+
+import org.apache.lucene.util.IOUtils;
+import org.elasticsearch.common.settings.KeyStoreCommandTestCase;
+import org.elasticsearch.common.settings.KeyStoreWrapper;
+import org.elasticsearch.common.settings.SecureSettings;
+import org.elasticsearch.common.settings.SecureString;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.env.Environment;
+import org.elasticsearch.test.ESTestCase;
+import org.junit.After;
+import org.junit.Before;
+
+import java.io.IOException;
+import java.nio.file.FileSystem;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+
+public class BootstrapTests extends ESTestCase {
+    Environment env;
+    List<FileSystem> fileSystems = new ArrayList<>();
+
+    @After
+    public void closeMockFileSystems() throws IOException {
+        IOUtils.close(fileSystems);
+    }
+
+    @Before
+    public void setupEnv() throws IOException {
+        env = KeyStoreCommandTestCase.setupEnv(true, fileSystems);
+    }
+
+    public void testLoadSecureSettingsCreatesKeystore() throws BootstrapException {
+        final Path configPath = env.configFile();
+        assertFalse(Files.exists(configPath.resolve("elasticsearch.keystore")));
+        Bootstrap.loadSecureSettings(env);
+        assertTrue(Files.exists(configPath.resolve("elasticsearch.keystore")));
+    }
+
+    public void testLoadSecureSettings() throws Exception {
+        final Path configPath = env.configFile();
+        final SecureString seed;
+        try (KeyStoreWrapper keyStoreWrapper = KeyStoreWrapper.create(new char[0])) {
+            seed = KeyStoreWrapper.SEED_SETTING.get(Settings.builder().setSecureSettings(keyStoreWrapper).build());
+            assertNotNull(seed);
+            assertTrue(seed.length() > 0);
+            keyStoreWrapper.save(configPath);
+        }
+        assertTrue(Files.exists(configPath.resolve("elasticsearch.keystore")));
+        try (SecureSettings secureSettings = Bootstrap.loadSecureSettings(env)) {
+            SecureString seedAfterLoad = KeyStoreWrapper.SEED_SETTING.get(Settings.builder().setSecureSettings(secureSettings).build());
+            assertEquals(seedAfterLoad.toString(), seed.toString());
+            assertTrue(Files.exists(configPath.resolve("elasticsearch.keystore")));
+        }
+    }
+}

core/src/test/java/org/elasticsearch/common/settings/KeyStoreCommandTestCase.java

@@ -58,7 +58,7 @@ public void setupEnv() throws IOException {
         env = setupEnv(true, fileSystems); // default to posix, but tests may call setupEnv(false) to overwrite
     }
 
-    static Environment setupEnv(boolean posix, List<FileSystem> fileSystems) throws IOException {
+    public static Environment setupEnv(boolean posix, List<FileSystem> fileSystems) throws IOException {
         final Configuration configuration;
         if (posix) {
             configuration = Configuration.unix().toBuilder().setAttributeViews("basic", "owner", "posix", "unix").build();