XSS protection in signin / signout.

XSRF protection for register / unregister.
Support only v3 and upwards.
Rev to version 4.

appengine/src/com/google/android/chrometophone/server/AuthServlet.java

@@ -18,6 +18,7 @@ package com.google.android.chrometophone.server;
 
 import java.io.IOException;
 import java.net.URLEncoder;
+import java.util.logging.Logger;
 
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
@@ -28,61 +29,46 @@ import com.google.appengine.api.users.UserServiceFactory;
 
 @SuppressWarnings("serial")
 public class AuthServlet extends HttpServlet {
+    private static final Logger log =
+        Logger.getLogger(SendServlet.class.getName());
     private static final String ERROR_STATUS = "ERROR";
+
     @Override
     public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
-        if (req.getRequestURI().startsWith("/signin")) {
+        resp.setContentType("text/html");
-            doSignIn(req, resp);
+        boolean signIn = req.getRequestURI().startsWith("/signin");
-        } else if (req.getRequestURI().startsWith("/signout")) {
-            doSignOut(req, resp);
-        }
-    }
 
-    private void doSignIn(HttpServletRequest req, HttpServletResponse resp) throws IOException {
         // Get the extension return URL
         String extRet = req.getParameter("extret");
         if (extRet == null) {
-            resp.setContentType("text/plain");
+            resp.setStatus(400);
             resp.getWriter().println(ERROR_STATUS + " (extret parameter missing)");
             return;
         }
 
-        // If login is complete, redirect to the extension page. Otherwise, send user to login,
+        // If login/logout is complete, redirect to the extension page. Otherwise, send user to
-        // setting the continue page back to this servlet (since UserService does not understand
+        // login/logout, setting the continue page back to this servlet (since UserService does
-        // chrome-extension:// URLs
+        // not understand chrome-extension:// URLs)
         if (req.getParameter("completed") != null) {
             // Server-side redirects don't work for chrome-extension:// URLs so we do a client-
             // side redirect instead
-            resp.getWriter().println("<meta http-equiv=\"refresh\" content=\"0;url=" + extRet + "\">");
+
+            // Sanitize the extRet URL for XSS protection
+            String regEx = "chrome-extension://[a-z]+" +
+                    (signIn ? "/signed_in\\.html" : "/signed_out\\.html");
+            if (extRet.matches(regEx)) {
+                resp.getWriter().println("<meta http-equiv=\"refresh\" content=\"0;url=" + extRet + "\">");
+            } else {
+                resp.setStatus(400);
+                resp.getWriter().println(ERROR_STATUS + " (invalid redirect)");
+                log.warning("Invalid redirect " + extRet);
+            }
         } else {
             String followOnURL = req.getRequestURI() + "?completed=true&extret=" +
                     URLEncoder.encode(extRet, "UTF-8");
             UserService userService = UserServiceFactory.getUserService();
-            resp.sendRedirect(userService.createLoginURL(followOnURL));
+            resp.sendRedirect(signIn ? userService.createLoginURL(followOnURL) :
-        }
+                    userService.createLogoutURL(followOnURL));
-    }
-
-    private void doSignOut(HttpServletRequest req, HttpServletResponse resp) throws IOException {
-        // Get the extension return URL
-        String extRet = req.getParameter("extret");
-        if (extRet == null) {
-            resp.setContentType("text/plain");
-            resp.getWriter().println(ERROR_STATUS + " (extret parameter missing)");
-            return;
-        }
-
-        // If logout is complete, redirect to the extension page. Otherwise, send user to login,
-        // setting the continue page back to this servlet (since UserService does not understand
-        // chrome-extension:// URLs
-        if (req.getParameter("completed") != null) {
-            // Server-side redirects don't work for chrome-extension:// URLs so we do a client-
-            // side redirect instead
-            resp.getWriter().println("<meta http-equiv=\"refresh\" content=\"0;url=" + extRet + "\">");
-        } else {
-            String followOnURL = req.getRequestURI() + "?completed=true&extret=" +
-                    URLEncoder.encode(extRet, "UTF-8");
-            UserService userService = UserServiceFactory.getUserService();
-            resp.sendRedirect(userService.createLogoutURL(followOnURL));
         }
     }
 }

appengine/src/com/google/android/chrometophone/server/RegisterServlet.java

@@ -77,6 +77,7 @@ public class RegisterServlet extends HttpServlet {
     /**
      * @deprecated will be removed in next rel.
      */
+    @Deprecated
     @Override
     public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
         doPost(req, resp);
@@ -86,6 +87,14 @@ public class RegisterServlet extends HttpServlet {
     public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
         resp.setContentType("text/plain");
 
+        // Basic XSRF protection
+        if (req.getHeader("X-Same-Domain") == null) {
+            // TODO: Enable at consumer launch
+            //resp.setStatus(400);
+            //resp.getWriter().println(ERROR_STATUS + " (Missing X-Same-Domain header)");
+            //return;
+        }
+
         String deviceRegistrationID = req.getParameter("devregid");
         if (deviceRegistrationID == null) {
             resp.setStatus(400);

appengine/src/com/google/android/chrometophone/server/SendServlet.java

@@ -17,7 +17,6 @@
 package com.google.android.chrometophone.server;
 
 import java.io.IOException;
-import java.net.URLEncoder;
 import java.util.logging.Logger;
 
 import javax.jdo.JDOObjectNotFoundException;
@@ -30,8 +29,6 @@ import com.google.android.c2dm.server.C2DMessaging;
 import com.google.appengine.api.datastore.Key;
 import com.google.appengine.api.datastore.KeyFactory;
 import com.google.appengine.api.users.User;
-import com.google.appengine.api.users.UserService;
-import com.google.appengine.api.users.UserServiceFactory;
 
 @SuppressWarnings("serial")
 public class SendServlet extends HttpServlet {
@@ -51,19 +48,25 @@ public class SendServlet extends HttpServlet {
     public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
         resp.setContentType("text/plain");
 
-        // Basic XSRF protection
+        // Check API version
-        if (req.getHeader("X-Extension") == null) {
-            resp.setStatus(400);
-            resp.getWriter().println(ERROR_STATUS + " - Please upgrade your extension");
-            log.warning("Missing X-Extension header");
-            resp.setStatus(400);
-            return;
-        }
-
         String apiVersionString = req.getParameter("ver");
         if (apiVersionString == null) apiVersionString = "1";
         int apiVersion = Integer.parseInt(apiVersionString);
         log.info("Extension version: " + apiVersion);
+        if (apiVersion < 3) {
+            resp.setStatus(400);
+            resp.getWriter().println(ERROR_STATUS +
+                    " (Please remove old Chrome extension and install latest)");
+            return;
+        }
+
+        // Basic XSRF protection (TODO: remove X-Extension in a future release for consistency)
+        if (req.getHeader("X-Same-Domain") == null && req.getHeader("X-Extension") == null) {
+            resp.setStatus(400);
+            resp.getWriter().println(ERROR_STATUS + " (Missing header)");
+            log.warning("Missing header");
+            return;
+        }
 
         String sel = req.getParameter("sel");
         if (sel == null) sel = "";  // optional
@@ -78,23 +81,14 @@ public class SendServlet extends HttpServlet {
 
         User user = RegisterServlet.checkUser(req, resp, false);
         if (user != null) {
-            doSendToPhone(url, title, sel, user.getEmail(), apiVersion, resp);
+            doSendToPhone(url, title, sel, user.getEmail(), resp);
         } else {
-            if (apiVersion >= 2) {  // TODO: Make this default code path on launch
+            resp.getWriter().println(LOGIN_REQUIRED_STATUS);
-              resp.getWriter().println(LOGIN_REQUIRED_STATUS);
-            } else {  // TODO: DEPRECATED code path. Delete on launch
-                String followOnURL = req.getRequestURI() + "?title="  +
-                        URLEncoder.encode(title, "UTF-8") +
-                        "&url=" + URLEncoder.encode(url, "UTF-8") +
-                        "&sel=" + URLEncoder.encode(sel, "UTF-8");
-                UserService userService = UserServiceFactory.getUserService();
-                resp.sendRedirect(userService.createLoginURL(followOnURL));
-            }
         }
     }
 
     private boolean doSendToPhone(String url, String title, String sel,
-            String userAccount, int apiVersion, HttpServletResponse resp) throws IOException {
+            String userAccount, HttpServletResponse resp) throws IOException {
         // Get device info
         DeviceInfo deviceInfo = null;
         // Shared PMF
@@ -106,12 +100,7 @@ public class SendServlet extends HttpServlet {
                 deviceInfo = pm.getObjectById(DeviceInfo.class, key);
             } catch (JDOObjectNotFoundException e) {
                 log.warning("Device not registered");
-                if (apiVersion >= 3) {  // TODO: Make this default code path on launch
+                resp.getWriter().println(DEVICE_NOT_REGISTERED_STATUS);
-                    resp.getWriter().println(DEVICE_NOT_REGISTERED_STATUS);
-                } else {  // TODO: DEPRECATED code path. Delete on launch
-                    resp.setStatus(400);
-                    resp.getWriter().println(ERROR_STATUS + " (Device not registered)");
-                }
                 return false;
             }
         } finally {

appengine/src/com/google/android/chrometophone/server/UnregisterServlet.java

@@ -42,6 +42,7 @@ public class UnregisterServlet extends HttpServlet {
     /**
      * @deprecated Will be removed in next rel cycle.
      */
+    @Deprecated
     @Override
     public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
         doPost(req, resp);
@@ -51,6 +52,14 @@ public class UnregisterServlet extends HttpServlet {
     public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
         resp.setContentType("text/plain");
 
+        // Basic XSRF protection
+        if (req.getHeader("X-Same-Domain") == null) {
+            // TODO: Enable at consumer launch
+            //resp.setStatus(400);
+            //resp.getWriter().println(ERROR_STATUS + " (Missing X-Same-Domain header)");
+            //return;
+        }
+
         String deviceRegistrationID = req.getParameter("devregid");
         if (deviceRegistrationID == null) {
             resp.setStatus(400);

appengine/war/WEB-INF/appengine-web.xml

@@ -16,7 +16,7 @@
 -->
 <appengine-web-app xmlns="http://appengine.google.com/ns/1.0">
     <application>chrometophone</application>
-    <version>3</version>
+    <version>4</version>
     <system-properties>
         <property name="java.util.logging.config.file" value="WEB-INF/logging.properties"/>
     </system-properties>