Refactors ClientHelper to combine header logic (#30620)

* Refactors ClientHelper to combine header logic

This change removes all the `*ClientHelper` classes which were
repeating logic between plugins and instead adds
`ClientHelper.executeWithHeaders()` and
`ClientHelper.executeWithHeadersAsync()` methods to centralise the
logic for executing requests with stored security headers.

* Removes Watcher headers constant

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ClientHelper.java

@@ -14,16 +14,28 @@
 import org.elasticsearch.client.Client;
 import org.elasticsearch.client.FilterClient;
 import org.elasticsearch.common.util.concurrent.ThreadContext;
+import org.elasticsearch.common.util.set.Sets;
+import org.elasticsearch.xpack.core.security.authc.AuthenticationField;
+import org.elasticsearch.xpack.core.security.authc.AuthenticationServiceField;
 
+import java.util.Map;
+import java.util.Set;
 import java.util.function.BiConsumer;
 import java.util.function.Supplier;
+import java.util.stream.Collectors;
 
 /**
  * Utility class to help with the execution of requests made using a {@link Client} such that they
  * have the origin as a transient and listeners have the appropriate context upon invocation
  */
 public final class ClientHelper {
 
+    /**
+     * List of headers that are related to security
+     */
+    public static final Set<String> SECURITY_HEADER_FILTERS = Sets.newHashSet(AuthenticationServiceField.RUN_AS_USER_HEADER,
+            AuthenticationField.AUTHENTICATION_KEY);
+
     public static final String ACTION_ORIGIN_TRANSIENT_NAME = "action.origin";
     public static final String SECURITY_ORIGIN = "security";
     public static final String WATCHER_ORIGIN = "watcher";
@@ -78,6 +90,82 @@ RequestBuilder extends ActionRequestBuilder<Request, Response, RequestBuilder>>
         }
     }
 
+    /**
+     * Execute a client operation and return the response, try to run an action
+     * with least privileges, when headers exist
+     *
+     * @param headers
+     *            Request headers, ideally including security headers
+     * @param origin
+     *            The origin to fall back to if there are no security headers
+     * @param client
+     *            The client used to query
+     * @param supplier
+     *            The action to run
+     * @return An instance of the response class
+     */
+    public static <T extends ActionResponse> T executeWithHeaders(Map<String, String> headers, String origin, Client client,
+            Supplier<T> supplier) {
+        Map<String, String> filteredHeaders = headers.entrySet().stream().filter(e -> SECURITY_HEADER_FILTERS.contains(e.getKey()))
+                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
+
+        // no security headers, we will have to use the xpack internal user for
+        // our execution by specifying the origin
+        if (filteredHeaders.isEmpty()) {
+            try (ThreadContext.StoredContext ignore = stashWithOrigin(client.threadPool().getThreadContext(), origin)) {
+                return supplier.get();
+            }
+        } else {
+            try (ThreadContext.StoredContext ignore = client.threadPool().getThreadContext().stashContext()) {
+                client.threadPool().getThreadContext().copyHeaders(filteredHeaders.entrySet());
+                return supplier.get();
+            }
+        }
+    }
+
+    /**
+     * Execute a client operation asynchronously, try to run an action with
+     * least privileges, when headers exist
+     *
+     * @param headers
+     *            Request headers, ideally including security headers
+     * @param origin
+     *            The origin to fall back to if there are no security headers
+     * @param action
+     *            The action to execute
+     * @param request
+     *            The request object for the action
+     * @param listener
+     *            The listener to call when the action is complete
+     */
+    public static <Request extends ActionRequest, Response extends ActionResponse, 
+            RequestBuilder extends ActionRequestBuilder<Request, Response, RequestBuilder>> void executeWithHeadersAsync(
+            Map<String, String> headers, String origin, Client client, Action<Request, Response, RequestBuilder> action, Request request,
+            ActionListener<Response> listener) {
+
+        Map<String, String> filteredHeaders = headers.entrySet().stream().filter(e -> SECURITY_HEADER_FILTERS.contains(e.getKey()))
+                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
+
+        final ThreadContext threadContext = client.threadPool().getThreadContext();
+
+        // No headers (e.g. security not installed/in use) so execute as origin
+        if (filteredHeaders.isEmpty()) {
+            ClientHelper.executeAsyncWithOrigin(client, origin, action, request, listener);
+        } else {
+            // Otherwise stash the context and copy in the saved headers before executing
+            final Supplier<ThreadContext.StoredContext> supplier = threadContext.newRestorableContext(false);
+            try (ThreadContext.StoredContext ignore = stashWithHeaders(threadContext, filteredHeaders)) {
+                client.execute(action, request, new ContextPreservingActionListener<>(supplier, listener));
+            }
+        }
+    }
+
+    private static ThreadContext.StoredContext stashWithHeaders(ThreadContext threadContext, Map<String, String> headers) {
+        final ThreadContext.StoredContext storedContext = threadContext.stashContext();
+        threadContext.copyHeaders(headers.entrySet());
+        return storedContext;
+    }
+
     private static final class ClientWithOrigin extends FilterClient {
 
         private final String origin;
@@ -98,5 +186,4 @@ RequestBuilder extends ActionRequestBuilder<Request, Response, RequestBuilder>>
             }
         }
     }
-
 }

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/MlMetadata.java

@@ -23,6 +23,9 @@
 import org.elasticsearch.common.xcontent.ObjectParser;
 import org.elasticsearch.common.xcontent.ToXContent;
 import org.elasticsearch.common.xcontent.XContentBuilder;
+import org.elasticsearch.persistent.PersistentTasksCustomMetaData;
+import org.elasticsearch.persistent.PersistentTasksCustomMetaData.PersistentTask;
+import org.elasticsearch.xpack.core.ClientHelper;
 import org.elasticsearch.xpack.core.ml.datafeed.DatafeedConfig;
 import org.elasticsearch.xpack.core.ml.datafeed.DatafeedJobValidator;
 import org.elasticsearch.xpack.core.ml.datafeed.DatafeedState;
@@ -35,8 +38,6 @@
 import org.elasticsearch.xpack.core.ml.utils.ExceptionsHelper;
 import org.elasticsearch.xpack.core.ml.utils.NameResolver;
 import org.elasticsearch.xpack.core.ml.utils.ToXContentParams;
-import org.elasticsearch.persistent.PersistentTasksCustomMetaData;
-import org.elasticsearch.persistent.PersistentTasksCustomMetaData.PersistentTask;
 
 import java.io.IOException;
 import java.util.Collection;
@@ -303,7 +304,7 @@ public Builder putDatafeed(DatafeedConfig datafeedConfig, ThreadContext threadCo
                 // Adjust the request, adding security headers from the current thread context
                 DatafeedConfig.Builder builder = new DatafeedConfig.Builder(datafeedConfig);
                 Map<String, String> headers = threadContext.getHeaders().entrySet().stream()
-                        .filter(e -> MlClientHelper.SECURITY_HEADER_FILTERS.contains(e.getKey()))
+                        .filter(e -> ClientHelper.SECURITY_HEADER_FILTERS.contains(e.getKey()))
                         .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
                 builder.setHeaders(headers);
                 datafeedConfig = builder.build();

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/datafeed/DatafeedUpdate.java

@@ -21,7 +21,7 @@
 import org.elasticsearch.index.query.QueryBuilder;
 import org.elasticsearch.search.aggregations.AggregatorFactories;
 import org.elasticsearch.search.builder.SearchSourceBuilder;
-import org.elasticsearch.xpack.core.ml.MlClientHelper;
+import org.elasticsearch.xpack.core.ClientHelper;
 import org.elasticsearch.xpack.core.ml.datafeed.extractor.ExtractorUtils;
 import org.elasticsearch.xpack.core.ml.job.config.Job;
 import org.elasticsearch.xpack.core.ml.utils.ExceptionsHelper;
@@ -304,7 +304,7 @@ public DatafeedConfig apply(DatafeedConfig datafeedConfig, ThreadContext threadC
         if (threadContext != null) {
             // Adjust the request, adding security headers from the current thread context
             Map<String, String> headers = threadContext.getHeaders().entrySet().stream()
-                    .filter(e -> MlClientHelper.SECURITY_HEADER_FILTERS.contains(e.getKey()))
+                    .filter(e -> ClientHelper.SECURITY_HEADER_FILTERS.contains(e.getKey()))
                     .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));
             builder.setHeaders(headers);
         }