Android webview tries to switch to CE context

android_webview/glue/java/src/com/android/webview/chromium/WebViewChromiumFactoryProvider.java

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package com.android.webview.chromium;
 
 import android.Manifest;
 import android.app.ActivityManager;
 import android.content.ComponentCallbacks2;
 import android.content.Context;
 import android.content.Intent;
 import android.content.SharedPreferences;
+import android.content.pm.ApplicationInfo;
 import android.content.pm.PackageInfo;
 import android.content.pm.PackageManager;
 import android.content.pm.PackageManager.NameNotFoundException;
 import android.net.Uri;
 import android.os.Build;
 import android.os.Looper;
 import android.os.Process;
 import android.os.StrictMode;
 import android.provider.Settings;
 import android.util.Log;
@@ skipping 36 matching lines @@
 import org.chromium.base.TraceEvent;
 import org.chromium.base.annotations.SuppressFBWarnings;
 import org.chromium.base.library_loader.LibraryLoader;
 import org.chromium.base.library_loader.LibraryProcessType;
 import org.chromium.base.library_loader.ProcessInitException;
 import org.chromium.content.browser.ContentViewStatics;
 import org.chromium.net.NetworkChangeNotifier;
 import org.chromium.ui.base.ResourceBundle;
 
 import java.io.File;
+import java.lang.reflect.InvocationTargetException;
 import java.util.Queue;
 import java.util.concurrent.Callable;
 import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.FutureTask;
 import java.util.concurrent.TimeUnit;
 
 /**
  * Entry point to the WebView. The system framework talks to this class to get instances of the
  * implementation classes.
  */
@@ skipping 113 matching lines @@
      * Constructor called by the API 22 version of {@link WebViewFactory} and later.
      */
     public WebViewChromiumFactoryProvider(android.webkit.WebViewDelegate delegate) {
         initialize(WebViewDelegateFactory.createProxyDelegate(delegate));
     }
 
     @SuppressFBWarnings("DMI_HARDCODED_ABSOLUTE_FILENAME")
     private void initialize(WebViewDelegate webViewDelegate) {
         mWebViewDelegate = webViewDelegate;
 
-        checkStorageIsNotDeviceProtected(mWebViewDelegate.getApplication());
+        Context ctx = switchToCredentialProtectedStorage(
+                mWebViewDelegate.getApplication().getApplicationContext());
 
         // WebView needs to make sure to always use the wrapped application context.
-        ContextUtils.initApplicationContext(
-                ResourcesContextWrapperFactory.get(
-                        mWebViewDelegate.getApplication().getApplicationContext()));
+        ContextUtils.initApplicationContext(ResourcesContextWrapperFactory.get(ctx));
 
         if (isBuildDebuggable()) {
             // Suppress the StrictMode violation as this codepath is only hit on debuggable builds.
             StrictMode.ThreadPolicy oldPolicy = StrictMode.allowThreadDiskReads();
             CommandLine.initFromFile(COMMAND_LINE_FILE);
             StrictMode.setThreadPolicy(oldPolicy);
         } else {
             CommandLine.init(null);
         }
 
@@ skipping 28 matching lines @@
         }
         if (lastVersion != currentVersion) {
             mWebViewPrefs.edit().putInt(VERSION_CODE_PREF, currentVersion).apply();
         }
 
         mShouldDisableThreadChecking =
                 shouldDisableThreadChecking(ContextUtils.getApplicationContext());
         // Now safe to use WebView data directory.
     }
 
-    static void checkStorageIsNotDeviceProtected(Context context) {
+    // Webview must use a CredentialEncrypted Context. If context is a CE context, then simply
+    // return it without modification. Otherwise, create a new CE context and return that instead.
+    static Context switchToCredentialProtectedStorage(Context context) {
+        // For versions N+, android webview must use a CredentialEncrypted Context
         if ((Build.VERSION.CODENAME.equals("N") || Build.VERSION.SDK_INT > Build.VERSION_CODES.M)
                 && context.isDeviceProtectedStorage()) {
-            throw new IllegalArgumentException(
-                    "WebView cannot be used with device protected storage");
+            ApplicationInfo appInfo = context.getApplicationInfo();
+            try {
+                // Check the manifest flag android:defaultToDeviceProtectedStorage

[Torne, 2016/09/21 12:04:18]

I'm not sure there's any point in actually checking this. The only time the
application context is going to be device-protected storage is when it's
defaulting to it.

[Nate Fischer, 2016/09/22 04:21:12]

Ok, I misunderstood the bug report. I've removed the check.

+                boolean defaultsToDeviceProtection =
+                        (Boolean) appInfo.getClass()
+                                .getMethod("isDefaultToDeviceProtectedStorage")
+                                .invoke(appInfo);
+                // For system applications using the flag, attempt to use a CE context if it's
+                // available
+                if (defaultsToDeviceProtection) {
+                    context = context.createCredentialProtectedStorageContext();
+                }
+
+                // If this application does not default to DE storage, or we were unable to create a
+                // CE context
+                if (context.isDeviceProtectedStorage()) {
+                    throw new IllegalArgumentException(
+                            "WebView cannot be used with device protected storage");
+                }
+            } catch (NoSuchMethodException | InvocationTargetException | IllegalAccessException
+                    | IllegalArgumentException e) {
+                throw new IllegalArgumentException(
+                        "WebView cannot be used with device protected storage");
+            }
         }
+        return context;
     }
 
     private static boolean isBuildDebuggable() {
         return !Build.TYPE.equals("user");
     }
 
     /**
      * Both versionCodes should be from a WebView provider package implemented by Chromium.
      * VersionCodes from other kinds of packages won't make any sense in this method.
      *
@@ skipping 374 matching lines @@
                 mWebViewDatabase = new WebViewDatabaseAdapter(this, awDatabase);
             }
         }
         return mWebViewDatabase;
     }
 
     WebViewDelegate getWebViewDelegate() {
         return mWebViewDelegate;
     }
 }