Fix bypass CALL_PRIVILEGED permission in AppRestrictionsFragment

In onReceive of AppRestrictionsFragment.java, there is a possible way to
start a phone call without permissions due to a confused deputy.
This could lead to local escalation of privilege with no additional
execution privileges needed.

We should not allow the restrictionsIntent to startActivity simply
because it resolves to multiple activities.
Instead, we should call resolveActivity and check the result's package
name is same as current package name, then it is safe to startActivity.

Bug: 200688991
Test: manual verify
Change-Id: Iaa2d3a9497c3266babe0789961befc9776a4db7a

src/com/android/settings/users/AppRestrictionsFragment.java

@@ -18,6 +18,7 @@ package com.android.settings.users;
 
 import android.app.Activity;
 import android.app.settings.SettingsEnums;
+import android.content.ActivityNotFoundException;
 import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
@@ -37,6 +38,7 @@ import android.os.RemoteException;
 import android.os.ServiceManager;
 import android.os.UserHandle;
 import android.os.UserManager;
+import android.util.EventLog;
 import android.util.Log;
 import android.view.View;
 import android.view.View.OnClickListener;
@@ -641,7 +643,15 @@ public class AppRestrictionsFragment extends SettingsPreferenceFragment implemen
             } else if (restrictionsIntent != null) {
                 preference.setRestrictions(restrictions);
                 if (invokeIfCustom && AppRestrictionsFragment.this.isResumed()) {
-                    assertSafeToStartCustomActivity(restrictionsIntent);
+                    try {
+                        assertSafeToStartCustomActivity(restrictionsIntent);
+                    } catch (ActivityNotFoundException | SecurityException e) {
+                        // return without startActivity
+                        Log.e(TAG, "Cannot start restrictionsIntent " + e);
+                        EventLog.writeEvent(0x534e4554, "200688991", -1 /* UID */, "");
+                        return;
+                    }
+
                     int requestCode = generateCustomActivityRequestCode(
                             RestrictionsResultReceiver.this.preference);
                     AppRestrictionsFragment.this.startActivityForResult(
@@ -655,14 +665,14 @@ public class AppRestrictionsFragment extends SettingsPreferenceFragment implemen
             if (intent.getPackage() != null && intent.getPackage().equals(packageName)) {
                 return;
             }
-            // Activity can be started if intent resolves to multiple activities
-            List<ResolveInfo> resolveInfos = AppRestrictionsFragment.this.mPackageManager
-                    .queryIntentActivities(intent, 0 /* no flags */);
-            if (resolveInfos.size() != 1) {
-                return;
+            ResolveInfo resolveInfo = mPackageManager.resolveActivity(
+                    intent, PackageManager.MATCH_DEFAULT_ONLY);
+
+            if (resolveInfo == null) {
+                throw new ActivityNotFoundException("No result for resolving " + intent);
             }
             // Prevent potential privilege escalation
-            ActivityInfo activityInfo = resolveInfos.get(0).activityInfo;
+            ActivityInfo activityInfo = resolveInfo.activityInfo;
             if (!packageName.equals(activityInfo.packageName)) {
                 throw new SecurityException("Application " + packageName
                         + " is not allowed to start activity " + intent);