Add FailOnAnonymousAction for SAML auth to get redirect

src/main/java/com/amazon/dlic/auth/http/saml/HTTPSamlAuthenticator.java

@@ -173,6 +173,12 @@ public AuthCredentials extractCredentials(final SecurityRequest request, final T
         return authCredentials;
     }
 
+    public static boolean isAuthTokenEndpoint(final SecurityRequest request) {
+        Matcher matcher = PATTERN_PATH_PREFIX.matcher(request.path());
+        final String suffix = matcher.matches() ? matcher.group(2) : null;
+        return API_AUTHTOKEN_SUFFIX.equals(suffix);
+    }
+
     @Override
     public String getType() {
         return "saml";
@@ -181,10 +187,7 @@ public String getType() {
     @Override
     public Optional<SecurityResponse> reRequestAuthentication(final SecurityRequest request, final AuthCredentials authCredentials) {
         try {
-            Matcher matcher = PATTERN_PATH_PREFIX.matcher(request.path());
-            final String suffix = matcher.matches() ? matcher.group(2) : null;
-
-            if (API_AUTHTOKEN_SUFFIX.equals(suffix)) {
+            if (isAuthTokenEndpoint(request)) {
                 // Verficiation of SAML ASC endpoint only works with RestRequests
                 if (!(request instanceof OpenSearchRequest)) {
                     throw new SecurityRequestChannelUnsupported(

src/main/java/org/opensearch/security/OpenSearchSecurityPlugin.java

@@ -159,6 +159,7 @@
 import org.opensearch.security.privileges.RestLayerPrivilegesEvaluator;
 import org.opensearch.security.resolver.IndexResolverReplacer;
 import org.opensearch.security.rest.DashboardsInfoAction;
+import org.opensearch.security.rest.FailOnAnonymousAction;
 import org.opensearch.security.rest.SecurityConfigUpdateAction;
 import org.opensearch.security.rest.SecurityHealthAction;
 import org.opensearch.security.rest.SecurityInfoAction;
@@ -562,6 +563,7 @@ public List<RestHandler> getRestHandlers(
                 handlers.add(
                     new SecurityInfoAction(settings, restController, Objects.requireNonNull(evaluator), Objects.requireNonNull(threadPool))
                 );
+                handlers.add(new FailOnAnonymousAction());
                 handlers.add(new SecurityHealthAction(settings, restController, Objects.requireNonNull(backendRegistry)));
                 handlers.add(
                     new DashboardsInfoAction(

src/main/java/org/opensearch/security/auth/BackendRegistry.java

@@ -71,6 +71,8 @@
 import static org.apache.http.HttpStatus.SC_FORBIDDEN;
 import static org.apache.http.HttpStatus.SC_SERVICE_UNAVAILABLE;
 import static org.apache.http.HttpStatus.SC_UNAUTHORIZED;
+import static org.opensearch.security.rest.FailOnAnonymousAction.isFailOnAnonymousEndpoint;
+import static com.amazon.dlic.auth.http.saml.HTTPSamlAuthenticator.isAuthTokenEndpoint;
 
 public class BackendRegistry {
 
@@ -286,7 +288,7 @@ public boolean authenticate(final SecurityRequestChannel request) {
 
             if (ac == null) {
                 // no credentials found in request
-                if (anonymousAuthEnabled) {
+                if (anonymousAuthEnabled && !(isFailOnAnonymousEndpoint(request) || isAuthTokenEndpoint(request))) {
                     continue;
                 }
 
@@ -386,7 +388,7 @@ public boolean authenticate(final SecurityRequestChannel request) {
                 log.debug("User still not authenticated after checking {} auth domains", restAuthDomains.size());
             }
 
-            if (authCredentials == null && anonymousAuthEnabled) {
+            if (authCredentials == null && anonymousAuthEnabled && !(isFailOnAnonymousEndpoint(request) || isAuthTokenEndpoint(request))) {
                 final String tenant = resolveTenantFrom(request);
                 User anonymousUser = new User(User.ANONYMOUS.getName(), new HashSet<String>(User.ANONYMOUS.getRoles()), null);
                 anonymousUser.setRequestedTenant(tenant);

src/main/java/org/opensearch/security/rest/FailOnAnonymousAction.java

@@ -0,0 +1,90 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ *
+ * Modifications Copyright OpenSearch Contributors. See
+ * GitHub history for details.
+ */
+
+package org.opensearch.security.rest;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import com.google.common.collect.ImmutableList;
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+
+import org.opensearch.client.node.NodeClient;
+import org.opensearch.core.rest.RestStatus;
+import org.opensearch.core.xcontent.XContentBuilder;
+import org.opensearch.rest.BaseRestHandler;
+import org.opensearch.rest.BytesRestResponse;
+import org.opensearch.rest.RestChannel;
+import org.opensearch.rest.RestRequest;
+import org.opensearch.security.filter.SecurityRequest;
+
+import static org.opensearch.rest.RestRequest.Method.GET;
+import static org.opensearch.security.OpenSearchSecurityPlugin.LEGACY_OPENDISTRO_PREFIX;
+import static org.opensearch.security.OpenSearchSecurityPlugin.PLUGINS_PREFIX;
+import static org.opensearch.security.dlic.rest.support.Utils.addRoutesPrefix;
+
+public class FailOnAnonymousAction extends BaseRestHandler {
+    private static final List<Route> routes = addRoutesPrefix(
+        ImmutableList.of(new Route(GET, "/failonanonymous")),
+        "/_opendistro/_security",
+        "/_plugins/_security"
+    );
+
+    private static final String FAILONANONYMOUS_SUFFIX = "failonanonymous";
+    private static final String REGEX_PATH_PREFIX = "/(" + LEGACY_OPENDISTRO_PREFIX + "|" + PLUGINS_PREFIX + ")/" + "(.*)";
+    private static final Pattern PATTERN_PATH_PREFIX = Pattern.compile(REGEX_PATH_PREFIX);
+
+    public static boolean isFailOnAnonymousEndpoint(final SecurityRequest request) {
+        Matcher matcher = PATTERN_PATH_PREFIX.matcher(request.path());
+        final String suffix = matcher.matches() ? matcher.group(2) : null;
+        return FAILONANONYMOUS_SUFFIX.equals(suffix);
+    }
+
+    private final Logger log = LogManager.getLogger(this.getClass());
+
+    public FailOnAnonymousAction() {
+        super();
+    }
+
+    @Override
+    public List<Route> routes() {
+        return routes;
+    }
+
+    @Override
+    protected RestChannelConsumer prepareRequest(RestRequest request, NodeClient client) throws IOException {
+        return new RestChannelConsumer() {
+
+            @Override
+            public void accept(RestChannel channel) throws Exception {
+                XContentBuilder builder = channel.newBuilder(); // NOSONAR
+                BytesRestResponse response = null;
+
+                builder.startObject();
+                builder.field("success", "true");
+
+                builder.endObject();
+
+                response = new BytesRestResponse(RestStatus.OK, builder);
+
+                channel.sendResponse(response);
+            }
+        };
+    }
+
+    @Override
+    public String getName() {
+        return "OpenSearch Security Fail on Anonymous Action";
+    }
+}