Retry authentication with all remaining auth methods after partial success

Signed-off-by: Jeroen van Erp <jeroen@hierynomus.com>

src/main/java/net/schmizz/sshj/SSHClient.java

@@ -40,6 +40,7 @@ import net.schmizz.sshj.transport.verification.AlgorithmsVerifier;
 import net.schmizz.sshj.transport.verification.FingerprintVerifier;
 import net.schmizz.sshj.transport.verification.HostKeyVerifier;
 import net.schmizz.sshj.transport.verification.OpenSSHKnownHosts;
+import net.schmizz.sshj.userauth.AuthResult;
 import net.schmizz.sshj.userauth.UserAuth;
 import net.schmizz.sshj.userauth.UserAuthException;
 import net.schmizz.sshj.userauth.UserAuthImpl;
@@ -218,13 +219,30 @@ public class SSHClient
             throws UserAuthException, TransportException {
         checkConnected();
         final Deque<UserAuthException> savedEx = new LinkedList<UserAuthException>();
-        for (AuthMethod method: methods) {
+        final List<AuthMethod> tried = new LinkedList<AuthMethod>();
+
+        for (Iterator<AuthMethod> it = methods.iterator(); it.hasNext();) {
+            AuthMethod method = it.next();
             method.setLoggerFactory(loggerFactory);
+
             try {
-                if (auth.authenticate(username, (Service) conn, method, trans.getTimeoutMs()))
+                AuthResult result = auth.authenticate(username, (Service) conn, method, trans.getTimeoutMs());
+
+                if (result == AuthResult.SUCCESS) {
                     return;
+                } else if (result == AuthResult.PARTIAL) {
+                    // Put all remaining methods in the tried list, so that we can try them for the second round of authentication
+                    while (it.hasNext()) {
+                        tried.add(it.next());
+                    }
+
+                    auth(username, tried);
+                    return;
+                }
+                tried.add(method);
             } catch (UserAuthException e) {
                 savedEx.push(e);
+                tried.add(method);
             }
         }
         throw new UserAuthException("Exhausted available authentication methods", savedEx.peek());

src/main/java/net/schmizz/sshj/userauth/AuthResult.java

@@ -0,0 +1,22 @@
+/*
+ * Copyright (C)2009 - SSHJ Contributors
+ *
+ * Licensed 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 net.schmizz.sshj.userauth;
+
+public enum AuthResult {
+    SUCCESS,
+    FAILURE,
+    PARTIAL
+}

src/main/java/net/schmizz/sshj/userauth/UserAuth.java

@@ -37,12 +37,12 @@ public interface UserAuth {
      * @param nextService the service to set on successful authentication
      * @param methods     the {@link AuthMethod}'s to try
      *
-     * @return whether authentication was successful
+     * @return whether authentication was successful, failed, or partially successful
      *
      * @throws UserAuthException  in case of authentication failure
      * @throws TransportException if there was a transport-layer error
      */
-    boolean authenticate(String username, Service nextService, AuthMethod methods, int timeoutMs)
+    AuthResult authenticate(String username, Service nextService, AuthMethod methods, int timeoutMs)
             throws UserAuthException, TransportException;
 
     /**

src/main/java/net/schmizz/sshj/userauth/UserAuthImpl.java

@@ -40,7 +40,7 @@ public class UserAuthImpl
         extends AbstractService
         implements UserAuth {
 
-    private final Promise<Boolean, UserAuthException> authenticated;
+    private final Promise<AuthResult, UserAuthException> authenticated;
 
     // Externally available
     private volatile String banner = "";
@@ -53,13 +53,13 @@ public class UserAuthImpl
 
     public UserAuthImpl(Transport trans) {
         super("ssh-userauth", trans);
-        authenticated = new Promise<Boolean, UserAuthException>("authenticated", UserAuthException.chainer, trans.getConfig().getLoggerFactory());
+        authenticated = new Promise<AuthResult, UserAuthException>("authenticated", UserAuthException.chainer, trans.getConfig().getLoggerFactory());
     }
 
     @Override
-    public boolean authenticate(String username, Service nextService, AuthMethod method, int timeoutMs)
+    public AuthResult authenticate(String username, Service nextService, AuthMethod method, int timeoutMs)
             throws UserAuthException, TransportException {
-        final boolean outcome;
+        final AuthResult outcome;
 
         authenticated.lock();
         try {
@@ -73,8 +73,10 @@ public class UserAuthImpl
             currentMethod.request();
             outcome = authenticated.retrieve(timeoutMs, TimeUnit.MILLISECONDS);
 
-            if (outcome) {
+            if (outcome == AuthResult.SUCCESS) {
                 log.debug("`{}` auth successful", method.getName());
+            }  else if (outcome == AuthResult.PARTIAL) {
+                log.debug("`{}` auth partially successful", method.getName());
             } else {
                 log.debug("`{}` auth failed", method.getName());
             }
@@ -124,7 +126,7 @@ public class UserAuthImpl
                     // Should fix https://github.com/hierynomus/sshj/issues/237
                     trans.setAuthenticated(); // So it can put delayed compression into force if applicable
                     trans.setService(nextService); // We aren't in charge anymore, next service is
-                    authenticated.deliver(true);
+                    authenticated.deliver(AuthResult.SUCCESS);
                     break;
 
                 case USERAUTH_FAILURE:
@@ -133,7 +135,7 @@ public class UserAuthImpl
                     if (allowedMethods.contains(currentMethod.getName()) && currentMethod.shouldRetry()) {
                         currentMethod.request();
                     } else {
-                        authenticated.deliver(false);
+                        authenticated.deliver(partialSuccess ? AuthResult.PARTIAL : AuthResult.FAILURE);
                     }
                     break;