elastic · elasticsearchmachine · Dec 8, 2023 · Aug 2, 2023 · Aug 2, 2023 · Aug 2, 2023
diff --git a/docs/changelog/102798.yaml b/docs/changelog/102798.yaml
@@ -0,0 +1,5 @@
+pr: 102798
+summary: Hot-reloadable remote cluster credentials
+area: Security
+type: enhancement
+issues: []
diff --git a/server/src/main/java/org/elasticsearch/transport/ProxyConnectionStrategy.java b/server/src/main/java/org/elasticsearch/transport/ProxyConnectionStrategy.java
@@ -179,7 +179,7 @@ public class ProxyConnectionStrategy extends RemoteConnectionStrategy {
                 RemoteConnectionManager.wrapConnectionWithRemoteClusterInfo(
                     newConnection,
                     clusterAlias,
-                    actualProfile.getTransportProfile()
+                    connectionManager.getCredentialsManager()
                 ),
                 actualProfile.getHandshakeTimeout(),
                 cn -> true,

diff --git a/server/src/main/java/org/elasticsearch/transport/RemoteClusterConnection.java b/server/src/main/java/org/elasticsearch/transport/RemoteClusterConnection.java
@@ -57,15 +57,28 @@ final class RemoteClusterConnection implements Closeable {
      * @param settings the nodes settings object
      * @param clusterAlias the configured alias of the cluster to connect to
      * @param transportService the local nodes transport service
-     * @param credentialsProtected Whether the remote cluster is protected by a credentials, i.e. it has a credentials configured
-     *                             via secure setting. This means the remote cluster uses the new configurable access RCS model
-     *                             (as opposed to the basic model).
+     * @param credentialsManager object to lookup remote cluster credentials by cluster alias. If a cluster is protected by a credential,
+     *                           i.e. it has a credential configured via secure setting.
+     *                           This means the remote cluster uses the advances RCS model (as opposed to the basic model).
      */
-    RemoteClusterConnection(Settings settings, String clusterAlias, TransportService transportService, boolean credentialsProtected) {
+    RemoteClusterConnection(
+        Settings settings,
+        String clusterAlias,
+        TransportService transportService,
+        RemoteClusterCredentialsManager credentialsManager
+    ) {
         this.transportService = transportService;
         this.clusterAlias = clusterAlias;
-        ConnectionProfile profile = RemoteConnectionStrategy.buildConnectionProfile(clusterAlias, settings, credentialsProtected);
-        this.remoteConnectionManager = new RemoteConnectionManager(clusterAlias, createConnectionManager(profile, transportService));
+        ConnectionProfile profile = RemoteConnectionStrategy.buildConnectionProfile(
+            clusterAlias,
+            settings,
+            credentialsManager.hasCredentials(clusterAlias)
+        );
+        this.remoteConnectionManager = new RemoteConnectionManager(
+            clusterAlias,
+            credentialsManager,
+            createConnectionManager(profile, transportService)
+        );
         this.connectionStrategy = RemoteConnectionStrategy.buildStrategy(clusterAlias, transportService, remoteConnectionManager, settings);
         // we register the transport service here as a listener to make sure we notify handlers on disconnect etc.
         this.remoteConnectionManager.addListener(transportService);

diff --git a/server/src/main/java/org/elasticsearch/transport/RemoteClusterCredentialsManager.java b/server/src/main/java/org/elasticsearch/transport/RemoteClusterCredentialsManager.java
@@ -0,0 +1,52 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+package org.elasticsearch.transport;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.settings.SecureString;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.core.Nullable;
+
+import java.util.Map;
+
+import static org.elasticsearch.transport.RemoteClusterService.REMOTE_CLUSTER_CREDENTIALS;
+
+public class RemoteClusterCredentialsManager {
+
+    private static final Logger logger = LogManager.getLogger(RemoteClusterCredentialsManager.class);
+
+    private volatile Map<String, SecureString> clusterCredentials;
+
+    public RemoteClusterCredentialsManager(Settings settings) {
+        updateClusterCredentials(settings);
+    }
+
+    public void updateClusterCredentials(Settings settings) {
+        clusterCredentials = REMOTE_CLUSTER_CREDENTIALS.getAsMap(settings);
+        logger.debug(
+            () -> Strings.format(
+                "Updated remote cluster credentials for clusters: [%s]",
+                Strings.collectionToCommaDelimitedString(clusterCredentials.keySet())
+            )
+        );
+    }
+
+    @Nullable
+    public SecureString resolveCredentials(String clusterAlias) {
+        return clusterCredentials.get(clusterAlias);
+    }
+
+    public boolean hasCredentials(String clusterAlias) {
+        return clusterCredentials.containsKey(clusterAlias);
+    }
+
+    public static final RemoteClusterCredentialsManager EMPTY = new RemoteClusterCredentialsManager(Settings.EMPTY);
+}
diff --git a/server/src/main/java/org/elasticsearch/transport/RemoteClusterService.java b/server/src/main/java/org/elasticsearch/transport/RemoteClusterService.java
@@ -147,15 +147,14 @@ public boolean isRemoteClusterServerEnabled() {
 
     private final TransportService transportService;
     private final Map<String, RemoteClusterConnection> remoteClusters = ConcurrentCollections.newConcurrentMap();
-    private final Set<String> credentialsProtectedRemoteClusters;
+    private final RemoteClusterCredentialsManager remoteClusterCredentialsManager;
 
     RemoteClusterService(Settings settings, TransportService transportService) {
         super(settings);
         this.enabled = DiscoveryNode.isRemoteClusterClient(settings);
         this.remoteClusterServerEnabled = REMOTE_CLUSTER_SERVER_ENABLED.get(settings);
         this.transportService = transportService;
-        this.credentialsProtectedRemoteClusters = REMOTE_CLUSTER_CREDENTIALS.getAsMap(settings).keySet();
-
+        this.remoteClusterCredentialsManager = new RemoteClusterCredentialsManager(settings);
         if (remoteClusterServerEnabled) {
             registerRemoteClusterHandshakeRequestHandler(transportService);
         }
@@ -305,6 +304,14 @@ private synchronized void updateSkipUnavailable(String clusterAlias, Boolean ski
         }
     }
 
+    public void updateRemoteClusterCredentials(Settings settings) {
+        remoteClusterCredentialsManager.updateClusterCredentials(settings);
+    }
+
+    public RemoteClusterCredentialsManager getRemoteClusterCredentialsManager() {
+        return remoteClusterCredentialsManager;
+    }
+
     @Override
     protected void updateRemoteCluster(String clusterAlias, Settings settings) {
         CountDownLatch latch = new CountDownLatch(1);
@@ -363,12 +370,7 @@ synchronized void updateRemoteCluster(
         if (remote == null) {
             // this is a new cluster we have to add a new representation
             Settings finalSettings = Settings.builder().put(this.settings, false).put(newSettings, false).build();
-            remote = new RemoteClusterConnection(
-                finalSettings,
-                clusterAlias,
-                transportService,
-                credentialsProtectedRemoteClusters.contains(clusterAlias)
-            );
+            remote = new RemoteClusterConnection(finalSettings, clusterAlias, transportService, remoteClusterCredentialsManager);
             remoteClusters.put(clusterAlias, remote);
             remote.ensureConnected(listener.map(ignored -> RemoteClusterConnectionStatus.CONNECTED));
         } else if (remote.shouldRebuildConnection(newSettings)) {
@@ -380,12 +382,7 @@ synchronized void updateRemoteCluster(
             }
             remoteClusters.remove(clusterAlias);
             Settings finalSettings = Settings.builder().put(this.settings, false).put(newSettings, false).build();
-            remote = new RemoteClusterConnection(
-                finalSettings,
-                clusterAlias,
-                transportService,
-                credentialsProtectedRemoteClusters.contains(clusterAlias)
-            );
+            remote = new RemoteClusterConnection(finalSettings, clusterAlias, transportService, remoteClusterCredentialsManager);
             remoteClusters.put(clusterAlias, remote);
             remote.ensureConnected(listener.map(ignored -> RemoteClusterConnectionStatus.RECONNECTED));
         } else {

diff --git a/server/src/main/java/org/elasticsearch/transport/RemoteConnectionManager.java b/server/src/main/java/org/elasticsearch/transport/RemoteConnectionManager.java
@@ -12,6 +12,7 @@
 import org.elasticsearch.TransportVersion;
 import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.cluster.node.DiscoveryNode;
+import org.elasticsearch.common.settings.SecureString;
 import org.elasticsearch.common.util.CollectionUtils;
 import org.elasticsearch.core.Nullable;
 import org.elasticsearch.core.Releasable;
@@ -25,18 +26,19 @@
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicLong;
 
-import static org.elasticsearch.transport.RemoteClusterPortSettings.REMOTE_CLUSTER_PROFILE;
 import static org.elasticsearch.transport.RemoteClusterService.REMOTE_CLUSTER_HANDSHAKE_ACTION_NAME;
 
 public class RemoteConnectionManager implements ConnectionManager {
 
     private final String clusterAlias;
+    private final RemoteClusterCredentialsManager credentialsManager;
     private final ConnectionManager delegate;
     private final AtomicLong counter = new AtomicLong();
     private volatile List<DiscoveryNode> connectedNodes = Collections.emptyList();
 
-    RemoteConnectionManager(String clusterAlias, ConnectionManager delegate) {
+    RemoteConnectionManager(String clusterAlias, RemoteClusterCredentialsManager credentialsManager, ConnectionManager delegate) {
         this.clusterAlias = clusterAlias;
+        this.credentialsManager = credentialsManager;
         this.delegate = delegate;
         this.delegate.addListener(new TransportConnectionListener() {
             @Override
@@ -51,6 +53,10 @@ public void onNodeDisconnected(DiscoveryNode node, Transport.Connection connecti
         });
     }
 
+    public RemoteClusterCredentialsManager getCredentialsManager() {
+        return credentialsManager;
+    }
+
     /**
      * Remote cluster connections have a different lifecycle from intra-cluster connections. Use {@link #connectToRemoteClusterNode}
      * instead of this method.
@@ -95,13 +101,7 @@ public void openConnection(DiscoveryNode node, @Nullable ConnectionProfile profi
             node,
             profile,
             listener.delegateFailureAndWrap(
-                (l, connection) -> l.onResponse(
-                    new InternalRemoteConnection(
-                        connection,
-                        clusterAlias,
-                        profile != null ? profile.getTransportProfile() : getConnectionProfile().getTransportProfile()
-                    )
-                )
+                (l, connection) -> l.onResponse(wrapConnectionWithRemoteClusterInfo(connection, clusterAlias, credentialsManager))
             )
         );
     }
@@ -182,16 +182,35 @@ public void closeNoBlock() {
      * @return a cluster alias if the connection target a node in the remote cluster, otherwise an empty result
      */
     public static Optional<String> resolveRemoteClusterAlias(Transport.Connection connection) {
+        return resolveRemoteClusterAliasWithCredentials(connection).map(RemoteClusterAliasWithCredentials::clusterAlias);
+    }
+
+    public record RemoteClusterAliasWithCredentials(String clusterAlias, @Nullable SecureString credentials) {
+        @Override
+        public String toString() {
+            return "RemoteClusterAliasWithCredentials{clusterAlias='" + clusterAlias + "', credentials='::es_redacted::'}";
+        }
+    }
+
+    /**
+     * This method returns information (alias and credentials) for remote cluster for the given transport connection.
+     * Either or both of alias and credentials can be null depending on the connection.
+     *
+     * @param connection the transport connection for which to resolve a remote cluster alias
+     */
+    public static Optional<RemoteClusterAliasWithCredentials> resolveRemoteClusterAliasWithCredentials(Transport.Connection connection) {
         Transport.Connection unwrapped = TransportService.unwrapConnection(connection);
         if (unwrapped instanceof InternalRemoteConnection remoteConnection) {
-            return Optional.of(remoteConnection.getClusterAlias());
+            return Optional.of(
+                new RemoteClusterAliasWithCredentials(remoteConnection.getClusterAlias(), remoteConnection.getClusterCredentials())
+            );
         }
         return Optional.empty();
     }
 
     private Transport.Connection getConnectionInternal(DiscoveryNode node) throws NodeNotConnectedException {
         Transport.Connection connection = delegate.getConnection(node);
-        return new InternalRemoteConnection(connection, clusterAlias, getConnectionProfile().getTransportProfile());
+        return wrapConnectionWithRemoteClusterInfo(connection, clusterAlias, credentialsManager);
     }
 
     private synchronized void addConnectedNode(DiscoveryNode addedNode) {
@@ -297,21 +316,27 @@ private static final class InternalRemoteConnection implements Transport.Connect
         private static final Logger logger = LogManager.getLogger(InternalRemoteConnection.class);
         private final Transport.Connection connection;
         private final String clusterAlias;
-        private final boolean isRemoteClusterProfile;
+        @Nullable
+        private final SecureString clusterCredentials;
 
-        InternalRemoteConnection(Transport.Connection connection, String clusterAlias, String transportProfile) {
+        private InternalRemoteConnection(Transport.Connection connection, String clusterAlias, @Nullable SecureString clusterCredentials) {
             assert false == connection instanceof InternalRemoteConnection : "should not double wrap";
             assert false == connection instanceof ProxyConnection
                 : "proxy connection should wrap internal remote connection, not the other way around";
-            this.clusterAlias = Objects.requireNonNull(clusterAlias);
             this.connection = Objects.requireNonNull(connection);
-            this.isRemoteClusterProfile = REMOTE_CLUSTER_PROFILE.equals(Objects.requireNonNull(transportProfile));
+            this.clusterAlias = Objects.requireNonNull(clusterAlias);
+            this.clusterCredentials = clusterCredentials;
         }
 
         public String getClusterAlias() {
             return clusterAlias;
         }
 
+        @Nullable
+        public SecureString getClusterCredentials() {
+            return clusterCredentials;
+        }
+
         @Override
         public DiscoveryNode getNode() {
             return connection.getNode();
@@ -321,7 +346,7 @@ public DiscoveryNode getNode() {
         public void sendRequest(long requestId, String action, TransportRequest request, TransportRequestOptions options)
             throws IOException, TransportException {
             final String effectiveAction;
-            if (isRemoteClusterProfile && TransportService.HANDSHAKE_ACTION_NAME.equals(action)) {
+            if (clusterCredentials != null && TransportService.HANDSHAKE_ACTION_NAME.equals(action)) {
                 logger.trace("sending remote cluster specific handshake to node [{}] of remote cluster [{}]", getNode(), clusterAlias);
                 effectiveAction = REMOTE_CLUSTER_HANDSHAKE_ACTION_NAME;
             } else {
@@ -389,8 +414,8 @@ public boolean hasReferences() {
     static InternalRemoteConnection wrapConnectionWithRemoteClusterInfo(
         Transport.Connection connection,
         String clusterAlias,
-        String transportProfile
+        RemoteClusterCredentialsManager credentialsManager
     ) {
-        return new InternalRemoteConnection(connection, clusterAlias, transportProfile);
+        return new InternalRemoteConnection(connection, clusterAlias, credentialsManager.resolveCredentials(clusterAlias));
     }
 }
diff --git a/server/src/main/java/org/elasticsearch/transport/SniffConnectionStrategy.java b/server/src/main/java/org/elasticsearch/transport/SniffConnectionStrategy.java
@@ -357,7 +357,11 @@ private ConnectionManager.ConnectionValidator getConnectionValidator(DiscoveryNo
                 : "transport profile must be consistent between the connection manager and the actual profile";
             transportService.connectionValidator(node)
                 .validate(
-                    RemoteConnectionManager.wrapConnectionWithRemoteClusterInfo(connection, clusterAlias, profile.getTransportProfile()),
+                    RemoteConnectionManager.wrapConnectionWithRemoteClusterInfo(
+                        connection,
+                        clusterAlias,
+                        connectionManager.getCredentialsManager()
+                    ),
                     profile,
                     listener
                 );