Add check for legality of the returned Matrix ID in Auth

- Helps troubleshoot reported issues that might not be obvious at first
- Add basic unit test for auth manager

src/main/java/io/kamax/mxisd/auth/AuthManager.java

@@ -64,6 +64,8 @@ import java.util.Objects;
 
 public class AuthManager {
 
+    private static final Logger log = LoggerFactory.getLogger(AuthManager.class);
+
     private static final String TypeKey = "type";
     private static final String UserKey = "user";
     private static final String IdentifierKey = "identifier";
@@ -72,7 +74,6 @@ public class AuthManager {
     private static final String UserIdTypeValue = "m.id.user";
     private static final String ThreepidTypeValue = "m.id.thirdparty";
 
-    private transient final Logger log = LoggerFactory.getLogger(AuthManager.class);
     private final Gson gson = GsonUtil.get(); // FIXME replace
 
     private List<AuthenticatorProvider> providers;
@@ -138,6 +139,12 @@ public class AuthManager {
                     invMgr.publishMappingIfInvited(new ThreePidMapping(pid, mxId));
                 }
 
+                try {
+                    MatrixID.asValid(mxId);
+                } catch (IllegalArgumentException e) {
+                    log.warn("The returned User ID {} is not a valid Matrix ID. Login might fail at the Homeserver level", mxId);
+                }
+
                 invMgr.lookupMappingsForInvites();
 
                 return authResult;

src/test/java/io/kamax/mxisd/test/auth/AuthManagerTest.java

@@ -0,0 +1,77 @@
+/*
+ * mxisd - Matrix Identity Server Daemon
+ * Copyright (C) 2019 Kamax Sarl
+ *
+ * https://www.kamax.io/
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package io.kamax.mxisd.test.auth;
+
+import io.kamax.mxisd.Mxisd;
+import io.kamax.mxisd.auth.AuthManager;
+import io.kamax.mxisd.auth.UserAuthResult;
+import io.kamax.mxisd.config.MxisdConfig;
+import io.kamax.mxisd.config.memory.MemoryIdentityConfig;
+import io.kamax.mxisd.config.memory.MemoryThreePid;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.junit.Assert.assertTrue;
+
+public class AuthManagerTest {
+
+    private static AuthManager mgr;
+
+    // FIXME we should be able to easily build the class ourselves
+    // FIXME use constants
+    @BeforeClass
+    public static void beforeClass() {
+        MxisdConfig cfg = new MxisdConfig();
+        cfg.getMatrix().setDomain("localhost");
+        cfg.getKey().setPath(":memory:");
+        cfg.getStorage().getProvider().getSqlite().setDatabase(":memory:");
+
+        MemoryThreePid mem3pid = new MemoryThreePid();
+        mem3pid.setMedium("email");
+        mem3pid.setAddress("john@localhost");
+        MemoryIdentityConfig validCfg = new MemoryIdentityConfig();
+        validCfg.setUsername("john");
+        validCfg.setPassword("doe");
+        validCfg.getThreepids().add(mem3pid);
+        MemoryIdentityConfig illegalUser = new MemoryIdentityConfig();
+        illegalUser.setUsername("JANE");
+        illegalUser.setPassword("doe");
+        cfg.getMemory().setEnabled(true);
+        cfg.getMemory().getIdentities().add(validCfg);
+        cfg.getMemory().getIdentities().add(illegalUser);
+
+        Mxisd m = new Mxisd(cfg);
+        m.start();
+        mgr = m.getAuth();
+    }
+
+    @Test
+    public void basic() {
+        UserAuthResult result = mgr.authenticate("@john:localhost", "doe");
+        assertTrue(result.isSuccess());
+
+        // For backward-compatibility as per instructed by the spec, we do not fail on an illegal username
+        // This makes sure we don't break it
+        result = mgr.authenticate("@JANE:localhost", "doe");
+        assertTrue(result.isSuccess());
+    }
+
+}