PreferenceActivity Fragment security

Provides a way for PreferenceActivities to verify that they
aren't being launched with Fragments not meant to be attached to
them. Default implementation will fail verification for apps built
with KLP. This will not affect apps built for earlier targets.

Also, make sure that the class being instantiated is a Fragment and
not some random class.

Bug: 9901133

Change-Id: I564cd5168eabcadd7594ea8011e2081ebebfe063

1 files changed, 36 insertions, 2 deletions

diff --git a/core/java/android/preference/PreferenceActivity.java b/core/java/android/preference/PreferenceActivity.java
index ec97efb0df28..7a41f3cfa55b 100644
--- a/core/java/android/preference/PreferenceActivity.java
+++ b/core/java/android/preference/PreferenceActivity.java
@@ -33,6 +33,7 @@ import android.os.Parcel;
 import android.os.Parcelable;
 import android.text.TextUtils;
 import android.util.AttributeSet;
+import android.util.Log;
 import android.util.TypedValue;
 import android.util.Xml;
 import android.view.LayoutInflater;
@@ -124,6 +125,8 @@ public abstract class PreferenceActivity extends ListActivity implements
         PreferenceManager.OnPreferenceTreeClickListener,
         PreferenceFragment.OnPreferenceStartFragmentCallback {
 
+    private static final String TAG = "PreferenceActivity";
+
     // Constants for state save/restore
     private static final String HEADERS_TAG = ":android:headers";
     private static final String CUR_HEADER_TAG = ":android:cur_header";
@@ -132,6 +135,9 @@ public abstract class PreferenceActivity extends ListActivity implements
     /**
      * When starting this activity, the invoking Intent can contain this extra
      * string to specify which fragment should be initially displayed.
+     * <p/>Starting from Key Lime Pie, when this argument is passed in, the PreferenceActivity
+     * will call isValidFragment() to confirm that the fragment class name is valid for this
+     * activity.
      */
     public static final String EXTRA_SHOW_FRAGMENT = ":android:show_fragment";
 
@@ -299,7 +305,7 @@ public abstract class PreferenceActivity extends ListActivity implements
      * are valid.
      */
     public static final long HEADER_ID_UNDEFINED = -1;
-    
+
     /**
      * Description of a single Header item that the user can select.
      */
@@ -877,7 +883,27 @@ public abstract class PreferenceActivity extends ListActivity implements
         } finally {
             if (parser != null) parser.close();
         }
+    }
 
+    /**
+     * Subclasses should override this method and verify that the given fragment is a valid type
+     * to be attached to this activity. The default implementation returns <code>true</code> prior
+     * to Key Lime Pie, <code>false</code> otherwise.
+     * @param f the class name of the Fragment about to be attached to this activity.
+     * @return true if the fragment class name is valid for this Activity and false otherwise.
+     */
+    protected boolean isValidFragment(String fragmentName) {
+        if (getApplicationInfo().targetSdkVersion  >= android.os.Build.VERSION_CODES.KEY_LIME_PIE) {
+            Log.w(TAG, "Subclasses of PreferenceActivity must override isValidFragment(String)"
+                    + " to verify that the Fragment class is valid! " + this.getClass().getName()
+                    + " has not checked if fragment " + fragmentName + " is valid.");
+            // Return true for now, but will eventually return false when all bundled apps
+            // have been modified. TODO: change to return false
+            return true;
+        } else {
+            Log.i(TAG, "PreferenceActivity built on pre-KLP launching fragment: " + fragmentName);
+            return true;
+        }
     }
 
     /**
@@ -1146,6 +1172,10 @@ public abstract class PreferenceActivity extends ListActivity implements
     private void switchToHeaderInner(String fragmentName, Bundle args, int direction) {
         getFragmentManager().popBackStack(BACK_STACK_PREFS,
                 FragmentManager.POP_BACK_STACK_INCLUSIVE);
+        if (!isValidFragment(fragmentName)) {
+            throw new IllegalArgumentException("Invalid fragment for this activity: "
+                    + fragmentName);
+        }
         Fragment f = Fragment.instantiate(this, fragmentName, args);
         FragmentTransaction transaction = getFragmentManager().beginTransaction();
         transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
@@ -1275,6 +1305,10 @@ public abstract class PreferenceActivity extends ListActivity implements
         if (mSinglePane) {
             startWithFragment(fragmentClass, args, resultTo, resultRequestCode, titleRes, 0);
         } else {
+            if (!isValidFragment(fragmentClass)) {
+                throw new IllegalArgumentException("Invalid fragment for this activity: "
+                        + fragmentClass);
+            }
             Fragment f = Fragment.instantiate(this, fragmentClass, args);
             if (resultTo != null) {
                 f.setTargetFragment(resultTo, resultRequestCode);
@@ -1291,7 +1325,7 @@ public abstract class PreferenceActivity extends ListActivity implements
             transaction.commitAllowingStateLoss();
         }
     }
-    
+
     /**
      * Called by a preference panel fragment to finish itself.
      *