RESTRICT AUTOMERGE Fix exported broadcast receiver vulnerabilityandroid-security-8.1.0_r93android-security-8.1.0_r92android-security-8.1.0_r91android-security-8.1.0_r90android-security-8.1.0_r89android-security-8.1.0_r88android-security-8.1.0_r87android-security-8.1.0_r86android-security-8.1.0_r85android-security-8.1.0_r84android-security-8.1.0_r83android-security-8.1.0_r82oreo-mr1-security-release

CellBroadcastReceiver was declared as exported in the manifest and
therefore allowed any app to send a MARK_AS_READ intent, even though
it's only supposed to be called from an internal PendingIntent. Fix this
by creating a new non-exported receiver and using that to handle the
mark-as-read intent instead.

Fixes: 162741784
Test: atest GoogleCellBroadcastReceiverUnitTests
Change-Id: I03c8163c22a6fbc92613ca2ccd2ac191fc0084a4
(cherry picked from commit e514bc6a01fdd36a519fd4fefffa45f166911c97)
(cherry picked from commit c41e7acd2c289b3dcef42d2e88d21dcac61b2f86)

4 files changed, 71 insertions, 13 deletions

diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 4972533ff..cb6bacf71 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -128,6 +128,11 @@
             </intent-filter>
         </receiver>
 
+        <receiver android:name="com.android.cellbroadcastreceiver.CellBroadcastInternalReceiver"
+                  android:exported="false">
+            <!-- No intent filter on purpose: this should only receive explicit intents -->
+        </receiver>
+
         <provider
                 android:name="CellBroadcastSearchIndexableProvider"
                 android:authorities="com.android.cellbroadcastreceiver"
diff --git a/src/com/android/cellbroadcastreceiver/CellBroadcastAlertService.java b/src/com/android/cellbroadcastreceiver/CellBroadcastAlertService.java
index d80bff7ea..6694987b7 100644
--- a/src/com/android/cellbroadcastreceiver/CellBroadcastAlertService.java
+++ b/src/com/android/cellbroadcastreceiver/CellBroadcastAlertService.java
@@ -603,9 +603,11 @@ public class CellBroadcastAlertService extends Service {
         final NotificationManager notificationManager = NotificationManager.from(context);
         createNotificationChannels(context);
 
+        boolean isWatch = context.getPackageManager()
+                .hasSystemFeature(PackageManager.FEATURE_WATCH);
         // Create intent to show the new messages when user selects the notification.
         Intent intent;
-        if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_WATCH)) {
+        if (isWatch) {
             // For FEATURE_WATCH we want to mark as read
             intent = createMarkAsReadIntent(context, message.getDeliveryTime());
         } else {
@@ -618,7 +620,7 @@ public class CellBroadcastAlertService extends Service {
         intent.putExtra(CellBroadcastAlertDialog.FROM_SAVE_STATE_NOTIFICATION_EXTRA, fromSaveState);
 
         PendingIntent pi;
-        if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_WATCH)) {
+        if (isWatch) {
             pi = PendingIntent.getBroadcast(context, 0, intent, 0);
         } else {
             pi = PendingIntent.getActivity(context, NOTIFICATION_ID, intent,
@@ -639,7 +641,7 @@ public class CellBroadcastAlertService extends Service {
 
         builder.setDefaults(Notification.DEFAULT_ALL);
 
-        if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_WATCH)) {
+        if (isWatch) {
             builder.setDeleteIntent(pi);
         } else {
             builder.setContentIntent(pi);
@@ -687,7 +689,7 @@ public class CellBroadcastAlertService extends Service {
      * @return delete intent to add to the pending intent
      */
     static Intent createMarkAsReadIntent(Context context, long deliveryTime) {
-        Intent deleteIntent = new Intent(context, CellBroadcastReceiver.class);
+        Intent deleteIntent = new Intent(context, CellBroadcastInternalReceiver.class);
         deleteIntent.setAction(CellBroadcastReceiver.ACTION_MARK_AS_READ);
         deleteIntent.putExtra(CellBroadcastReceiver.EXTRA_DELIVERY_TIME, deliveryTime);
         return deleteIntent;
diff --git a/src/com/android/cellbroadcastreceiver/CellBroadcastInternalReceiver.java b/src/com/android/cellbroadcastreceiver/CellBroadcastInternalReceiver.java
new file mode 100644
index 000000000..455c5b68c
--- /dev/null
+++ b/src/com/android/cellbroadcastreceiver/CellBroadcastInternalReceiver.java
@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.cellbroadcastreceiver;
+
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.provider.Telephony;
+
+import com.android.internal.annotations.VisibleForTesting;
+
+/**
+ * {@link BroadcastReceiver} used for handling internal broadcasts (e.g. generated from
+ * {@link android.app.PendingIntent}s).
+ */
+public class CellBroadcastInternalReceiver extends BroadcastReceiver {
+
+    /**
+     * helper method for easier testing. To generate a new CellBroadcastTask
+     * @param deliveryTime message delivery time
+     */
+    @VisibleForTesting
+    public void getCellBroadcastTask(Context context, long deliveryTime) {
+        new CellBroadcastContentProvider.AsyncCellBroadcastTask(context.getContentResolver())
+                .execute(new CellBroadcastContentProvider.CellBroadcastOperation() {
+                    @Override
+                    public boolean execute(CellBroadcastContentProvider provider) {
+                        return provider.markBroadcastRead(Telephony.CellBroadcasts.DELIVERY_TIME,
+                                deliveryTime);
+                    }
+                });
+    }
+
+    @Override
+    public void onReceive(Context context, Intent intent) {
+        if (CellBroadcastReceiver.ACTION_MARK_AS_READ.equals(intent.getAction())) {
+            final long deliveryTime = intent.getLongExtra(
+                    CellBroadcastReceiver.EXTRA_DELIVERY_TIME, -1);
+            getCellBroadcastTask(context, deliveryTime);
+        }
+    }
+}
diff --git a/src/com/android/cellbroadcastreceiver/CellBroadcastReceiver.java b/src/com/android/cellbroadcastreceiver/CellBroadcastReceiver.java
index 012089946..67588e7ce 100644
--- a/src/com/android/cellbroadcastreceiver/CellBroadcastReceiver.java
+++ b/src/com/android/cellbroadcastreceiver/CellBroadcastReceiver.java
@@ -27,6 +27,7 @@ import android.provider.Telephony;
 import android.provider.Telephony.CellBroadcasts;
 import android.telephony.CarrierConfigManager;
 import android.telephony.cdma.CdmaSmsCbProgramData;
+import android.util.EventLog;
 import android.util.Log;
 
 import com.android.internal.telephony.TelephonyIntents;
@@ -59,15 +60,9 @@ public class CellBroadcastReceiver extends BroadcastReceiver {
         String action = intent.getAction();
 
         if (ACTION_MARK_AS_READ.equals(action)) {
-            final long deliveryTime = intent.getLongExtra(EXTRA_DELIVERY_TIME, -1);
-            new CellBroadcastContentProvider.AsyncCellBroadcastTask(context.getContentResolver())
-                    .execute(new CellBroadcastContentProvider.CellBroadcastOperation() {
-                        @Override
-                        public boolean execute(CellBroadcastContentProvider provider) {
-                            return provider.markBroadcastRead(CellBroadcasts.DELIVERY_TIME,
-                                    deliveryTime);
-                        }
-                    });
+            // The only way this'll be called is if someone tries to maliciously set something as
+            // read. Log an event.
+            EventLog.writeEvent(0x534e4554, "162741784", -1, null);
         } else if (TelephonyIntents.ACTION_DEFAULT_SMS_SUBSCRIPTION_CHANGED.equals(action)
                 || CarrierConfigManager.ACTION_CARRIER_CONFIG_CHANGED.equals(action)
                 || Intent.ACTION_BOOT_COMPLETED.equals(action)