Support authentication without anonymous user (#53528)

This change adds a new parameter to the authenticate methods in the
AuthenticationService to optionally exclude support for the anonymous
user (if an anonymous user exists).

Backport of: #52094

Author: tvernum

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/AuthenticationService.java

@@ -118,11 +118,27 @@ public AuthenticationService(Settings settings, Realms realms, AuditTrailService
      * Authenticates the user that is associated with the given request. If the user was authenticated successfully (i.e.
      * a user was indeed associated with the request and the credentials were verified to be valid), the method returns
      * the user and that user is then "attached" to the request's context.
+     * This method will authenticate as the anonymous user if the service is configured to allow anonymous access.
      *
      * @param request The request to be authenticated
      */
     public void authenticate(RestRequest request, ActionListener<Authentication> authenticationListener) {
-        createAuthenticator(request, authenticationListener).authenticateAsync();
+        authenticate(request, true, authenticationListener);
+    }
+
+    /**
+     * Authenticates the user that is associated with the given request. If the user was authenticated successfully (i.e.
+     * a user was indeed associated with the request and the credentials were verified to be valid), the method returns
+     * the user and that user is then "attached" to the request's context.
+     * This method will optionally, authenticate as the anonymous user if the service is configured to allow anonymous access.
+     *
+     * @param request The request to be authenticated
+     * @param allowAnonymous If {@code false}, then authentication will <em>not</em> fallback to anonymous.
+     *                               If {@code true}, then authentication <em>will</em> fallback to anonymous, if this service is
+     *                               configured to allow anonymous access (see {@link #isAnonymousUserEnabled}).
+     */
+    public void authenticate(RestRequest request, boolean allowAnonymous, ActionListener<Authentication> authenticationListener) {
+        createAuthenticator(request, allowAnonymous, authenticationListener).authenticateAsync();
     }
 
     /**
@@ -133,15 +149,31 @@ public void authenticate(RestRequest request, ActionListener<Authentication> aut
      *
      * @param action       The action of the message
      * @param message      The message to be authenticated
-     * @param fallbackUser The default user that will be assumed if no other user is attached to the message. Can be
-     *                     {@code null}, in which case there will be no fallback user and the success/failure of the
-     *                     authentication will be based on the whether there's an attached user to in the message and
-     *                     if there is, whether its credentials are valid.
+     * @param fallbackUser The default user that will be assumed if no other user is attached to the message. May not
+     *                      be {@code null}.
      */
     public void authenticate(String action, TransportMessage message, User fallbackUser, ActionListener<Authentication> listener) {
+        Objects.requireNonNull(fallbackUser, "fallback user may not be null");
         createAuthenticator(action, message, fallbackUser, listener).authenticateAsync();
     }
 
+    /**
+     * Authenticates the user that is associated with the given message. If the user was authenticated successfully (i.e.
+     * a user was indeed associated with the request and the credentials were verified to be valid), the method returns
+     * the user and that user is then "attached" to the message's context.
+     * If no user or credentials are found to be attached to the given message, and the caller allows anonymous access
+     * ({@code allowAnonymous} parameter), and this service is configured for anonymous access (see {@link #isAnonymousUserEnabled} and
+     * {@link #anonymousUser}), then the anonymous user will be returned instead.
+     *
+     * @param action       The action of the message
+     * @param message      The message to be authenticated
+     * @param allowAnonymous Whether to permit anonymous access for this request (this only relevant if the service is
+     *                       {@link #isAnonymousUserEnabled configured for anonymous access}).
+     */
+    public void authenticate(String action, TransportMessage message, boolean allowAnonymous, ActionListener<Authentication> listener) {
+        createAuthenticator(action, message, allowAnonymous, listener).authenticateAsync();
+    }
+
     /**
      * Authenticates the user based on the contents of the token that is provided as parameter. This will not look at the values in the
      * ThreadContext for Authentication.
@@ -152,7 +184,7 @@ public void authenticate(String action, TransportMessage message, User fallbackU
      */
     public void authenticate(String action, TransportMessage message,
                              AuthenticationToken token, ActionListener<Authentication> listener) {
-        new Authenticator(action, message, null, listener).authenticateToken(token);
+        new Authenticator(action, message, shouldFallbackToAnonymous(true), listener).authenticateToken(token);
     }
 
     public void expire(String principal) {
@@ -178,12 +210,19 @@ public void onSecurityIndexStateChange(SecurityIndexManager.State previousState,
     }
 
     // pkg private method for testing
-    Authenticator createAuthenticator(RestRequest request, ActionListener<Authentication> listener) {
-        return new Authenticator(request, listener);
+    Authenticator createAuthenticator(RestRequest request, boolean fallbackToAnonymous, ActionListener<Authentication> listener) {
+        return new Authenticator(request, shouldFallbackToAnonymous(fallbackToAnonymous), listener);
     }
 
     // pkg private method for testing
-    Authenticator createAuthenticator(String action, TransportMessage message, User fallbackUser, ActionListener<Authentication> listener) {
+    Authenticator createAuthenticator(String action, TransportMessage message, boolean fallbackToAnonymous,
+                                      ActionListener<Authentication> listener) {
+        return new Authenticator(action, message, shouldFallbackToAnonymous(fallbackToAnonymous), listener);
+    }
+
+    // pkg private method for testing
+    Authenticator createAuthenticator(String action, TransportMessage message, User fallbackUser,
+                                      ActionListener<Authentication> listener) {
         return new Authenticator(action, message, fallbackUser, listener);
     }
 
@@ -192,6 +231,31 @@ long getNumInvalidation() {
         return numInvalidation.get();
     }
 
+    /**
+     * Determines whether to support anonymous access for the current request. Returns {@code true} if all of the following are true
+     * <ul>
+     *     <li>The service has anonymous authentication enabled (see {@link #isAnonymousUserEnabled})</li>
+     *     <li>Anonymous access is accepted for this request ({@code allowAnonymousOnThisRequest} parameter)
+     *     <li>The {@link ThreadContext} does not provide API Key or Bearer Token credentials. If these are present, we
+     *     treat the request as though it attempted to authenticate (even if that failed), and will not fall back to anonymous.</li>
+     * </ul>
+     */
+    boolean shouldFallbackToAnonymous(boolean allowAnonymousOnThisRequest) {
+        if (isAnonymousUserEnabled == false) {
+            return false;
+        }
+        if (allowAnonymousOnThisRequest == false) {
+            return false;
+        }
+        String header = threadContext.getHeader("Authorization");
+        if (Strings.hasText(header) &&
+            ((header.regionMatches(true, 0, "Bearer ", 0, "Bearer ".length()) && header.length() > "Bearer ".length()) ||
+                (header.regionMatches(true, 0, "ApiKey ", 0, "ApiKey ".length()) && header.length() > "ApiKey ".length()))) {
+            return false;
+        }
+        return true;
+    }
+
     /**
      * This class is responsible for taking a request and executing the authentication. The authentication is executed in an asynchronous
      * fashion in order to avoid blocking calls on a network thread. This class also performs the auditing necessary around authentication
@@ -200,6 +264,7 @@ class Authenticator {
 
         private final AuditableRequest request;
         private final User fallbackUser;
+        private final boolean fallbackToAnonymous;
         private final List<Realm> defaultOrderedRealmList;
         private final ActionListener<Authentication> listener;
 
@@ -208,18 +273,25 @@ class Authenticator {
         private AuthenticationToken authenticationToken = null;
         private AuthenticationResult authenticationResult = null;
 
-        Authenticator(RestRequest request, ActionListener<Authentication> listener) {
-            this(new AuditableRestRequest(auditTrail, failureHandler, threadContext, request), null, listener);
+        Authenticator(RestRequest request, boolean fallbackToAnonymous, ActionListener<Authentication> listener) {
+            this(new AuditableRestRequest(auditTrail, failureHandler, threadContext, request), null, fallbackToAnonymous, listener);
+        }
+
+        Authenticator(String action, TransportMessage message, boolean fallbackToAnonymous, ActionListener<Authentication> listener) {
+            this(new AuditableTransportRequest(auditTrail, failureHandler, threadContext, action, message),
+                null, fallbackToAnonymous, listener);
         }
 
         Authenticator(String action, TransportMessage message, User fallbackUser, ActionListener<Authentication> listener) {
-            this(new AuditableTransportRequest(auditTrail, failureHandler, threadContext, action, message
-            ), fallbackUser, listener);
+            this(new AuditableTransportRequest(auditTrail, failureHandler, threadContext, action, message),
+                Objects.requireNonNull(fallbackUser, "Fallback user cannot be null"), false, listener);
         }
 
-        private Authenticator(AuditableRequest auditableRequest, User fallbackUser, ActionListener<Authentication> listener) {
+        private Authenticator(AuditableRequest auditableRequest, User fallbackUser, boolean fallbackToAnonymous,
+                              ActionListener<Authentication> listener) {
             this.request = auditableRequest;
             this.fallbackUser = fallbackUser;
+            this.fallbackToAnonymous = fallbackToAnonymous;
             this.defaultOrderedRealmList = realms.asList();
             this.listener = listener;
         }
@@ -479,7 +551,7 @@ void handleNullToken() {
                 RealmRef authenticatedBy = new RealmRef("__fallback", "__fallback", nodeName);
                 authentication = new Authentication(fallbackUser, authenticatedBy, null, Version.CURRENT, AuthenticationType.INTERNAL,
                     Collections.emptyMap());
-            } else if (isAnonymousUserEnabled && shouldFallbackToAnonymous()) {
+            } else if (fallbackToAnonymous) {
                 logger.trace("No valid credentials found in request [{}], using anonymous [{}]", request, anonymousUser.principal());
                 RealmRef authenticatedBy = new RealmRef("__anonymous", "__anonymous", nodeName);
                 authentication = new Authentication(anonymousUser, authenticatedBy, null, Version.CURRENT, AuthenticationType.ANONYMOUS,
@@ -503,20 +575,6 @@ void handleNullToken() {
             action.run();
         }
 
-        /**
-         * When an API Key or an Elasticsearch Token Service token is used for authentication and authentication fails (as indicated by
-         * a null AuthenticationToken) we should not fallback to the anonymous user.
-         */
-        boolean shouldFallbackToAnonymous(){
-            String header = threadContext.getHeader("Authorization");
-            if (Strings.hasText(header) &&
-                ((header.regionMatches(true, 0, "Bearer ", 0, "Bearer ".length()) && header.length() > "Bearer ".length()) ||
-                (header.regionMatches(true, 0, "ApiKey ", 0, "ApiKey ".length()) && header.length() > "ApiKey ".length()))) {
-                return false;
-            }
-            return true;
-        }
-
         /**
          * Consumes the {@link User} that resulted from attempting to authenticate a token against the {@link Realms}. When the user is
          * {@code null}, authentication fails and does not proceed. When there is a user, the request is inspected to see if the run as

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/transport/ServerTransportFilter.java

@@ -27,7 +27,6 @@
 import org.elasticsearch.xpack.core.security.SecurityContext;
 import org.elasticsearch.xpack.core.security.authc.Authentication;
 import org.elasticsearch.xpack.core.security.user.SystemUser;
-import org.elasticsearch.xpack.core.security.user.User;
 import org.elasticsearch.xpack.security.action.SecurityActionMapper;
 import org.elasticsearch.xpack.security.authc.AuthenticationService;
 import org.elasticsearch.xpack.security.authz.AuthorizationService;
@@ -118,7 +117,7 @@ requests from all the nodes are attached with a user (either a serialize
             }
 
             final Version version = transportChannel.getVersion();
-            authcService.authenticate(securityAction, request, (User)null, ActionListener.wrap((authentication) -> {
+            authcService.authenticate(securityAction, request, true, ActionListener.wrap((authentication) -> {
                 if (authentication != null) {
                     if (securityAction.equals(TransportService.HANDSHAKE_ACTION_NAME) &&
                         SystemUser.is(authentication.getUser()) == false) {

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/action/filter/SecurityActionFilterTests.java

@@ -40,6 +40,7 @@
 
 import java.util.Collections;
 
+import static org.hamcrest.Matchers.arrayWithSize;
 import static org.mockito.Matchers.any;
 import static org.mockito.Matchers.eq;
 import static org.mockito.Matchers.isA;
@@ -92,14 +93,17 @@ public void testApply() throws Exception {
         Task task = mock(Task.class);
         User user = new User("username", "r1", "r2");
         Authentication authentication = new Authentication(user, new RealmRef("test", "test", "foo"), null);
-        doAnswer((i) -> {
-            ActionListener callback =
-                    (ActionListener) i.getArguments()[3];
+        doAnswer(i -> {
+            final Object[] args = i.getArguments();
+            assertThat(args, arrayWithSize(4));
+            ActionListener callback = (ActionListener) args[args.length - 1];
             callback.onResponse(authentication);
             return Void.TYPE;
         }).when(authcService).authenticate(eq("_action"), eq(request), eq(SystemUser.INSTANCE), any(ActionListener.class));
-        doAnswer((i) -> {
-            ActionListener<Void> callback = (ActionListener<Void>) i.getArguments()[3];
+        doAnswer(i -> {
+            final Object[] args = i.getArguments();
+            assertThat(args, arrayWithSize(4));
+            ActionListener callback = (ActionListener) args[args.length - 1];
             callback.onResponse(null);
             return Void.TYPE;
         }).when(authzService)
@@ -116,16 +120,19 @@ public void testApplyRestoresThreadContext() throws Exception {
         Task task = mock(Task.class);
         User user = new User("username", "r1", "r2");
         Authentication authentication = new Authentication(user, new RealmRef("test", "test", "foo"), null);
-        doAnswer((i) -> {
-            ActionListener callback =
-                    (ActionListener) i.getArguments()[3];
+        doAnswer(i -> {
+            final Object[] args = i.getArguments();
+            assertThat(args, arrayWithSize(4));
+            ActionListener callback = (ActionListener) args[args.length - 1];
             assertNull(threadContext.getTransient(AuthenticationField.AUTHENTICATION_KEY));
             threadContext.putTransient(AuthenticationField.AUTHENTICATION_KEY, authentication);
             callback.onResponse(authentication);
             return Void.TYPE;
         }).when(authcService).authenticate(eq("_action"), eq(request), eq(SystemUser.INSTANCE), any(ActionListener.class));
-        doAnswer((i) -> {
-            ActionListener<Void> callback = (ActionListener<Void>) i.getArguments()[3];
+        doAnswer(i -> {
+            final Object[] args = i.getArguments();
+            assertThat(args, arrayWithSize(4));
+            ActionListener callback = (ActionListener) args[args.length - 1];
             callback.onResponse(null);
             return Void.TYPE;
         }).when(authzService)
@@ -158,9 +165,10 @@ public void testApplyAsSystemUser() throws Exception {
         } else {
             assertNull(threadContext.getTransient(AuthenticationField.AUTHENTICATION_KEY));
         }
-        doAnswer((i) -> {
-            ActionListener callback =
-                    (ActionListener) i.getArguments()[3];
+        doAnswer(i -> {
+            final Object[] args = i.getArguments();
+            assertThat(args, arrayWithSize(4));
+            ActionListener callback = (ActionListener) args[args.length - 1];
             callback.onResponse(threadContext.getTransient(AuthenticationField.AUTHENTICATION_KEY));
             return Void.TYPE;
         }).when(authcService).authenticate(eq(action), eq(request), eq(SystemUser.INSTANCE), any(ActionListener.class));
@@ -193,9 +201,10 @@ public void testApplyDestructiveOperations() throws Exception {
         Task task = mock(Task.class);
         User user = new User("username", "r1", "r2");
         Authentication authentication = new Authentication(user, new RealmRef("test", "test", "foo"), null);
-        doAnswer((i) -> {
-            ActionListener callback =
-                    (ActionListener) i.getArguments()[3];
+        doAnswer(i -> {
+            final Object[] args = i.getArguments();
+            assertThat(args, arrayWithSize(4));
+            ActionListener callback = (ActionListener) args[args.length - 1];
             callback.onResponse(authentication);
             return Void.TYPE;
         }).when(authcService).authenticate(eq(action), eq(request), eq(SystemUser.INSTANCE), any(ActionListener.class));
@@ -223,9 +232,10 @@ public void testActionProcessException() throws Exception {
         Task task = mock(Task.class);
         User user = new User("username", "r1", "r2");
         Authentication authentication = new Authentication(user, new RealmRef("test", "test", "foo"), null);
-        doAnswer((i) -> {
-            ActionListener callback =
-                    (ActionListener) i.getArguments()[3];
+        doAnswer(i -> {
+            final Object[] args = i.getArguments();
+            assertThat(args, arrayWithSize(4));
+            ActionListener callback = (ActionListener) args[args.length - 1];
             callback.onResponse(authentication);
             return Void.TYPE;
         }).when(authcService).authenticate(eq("_action"), eq(request), eq(SystemUser.INSTANCE), any(ActionListener.class));