LatinIME: Fix Implicit PendingIntent Vulnerability

* checkTimeAndMaybeSetupUpdateAlarm method created an Implicit PendingIntent vulnerability, which may cause security threats in the form of denial-of-service, private data theft, and privilege escalation.

* PendingIntents are Intents delegated to another app to be delivered at some future time. Creating an implicit intent wrapped under a PendingIntent is a security vulnerability that might lead to denial-of-service, private data theft, and privilege escalation.

* We've used FLAG_IMMUTABLE (added in SDK 23) to create PendingIntents for SDK > 23, This prevents apps that receive the PendingIntent from filling in unpopulated properties & Ensures that PendingIntent is only delivered to trusted components.

Test: m
Change-Id: I68a1f3f2d81138e42092cc201d36e5d29853a86e
Signed-off-by: techyminati <[email protected]>

Author: techyminati

java/src/com/android/inputmethod/dictionarypack/DictionaryService.java

@@ -229,8 +229,14 @@ private static void checkTimeAndMaybeSetupUpdateAlarm(final Context context) {
         final long now = System.currentTimeMillis();
         final long alarmTime = now + new Random().nextInt(MAX_ALARM_DELAY_MILLIS);
         final Intent updateIntent = new Intent(DictionaryPackConstants.UPDATE_NOW_INTENT_ACTION);
+        // Set the package name to ensure the PendingIntent is only delivered to trusted components
+        updateIntent.setPackage(context.getPackageName());
+        int pendingIntentFlags = PendingIntent.FLAG_CANCEL_CURRENT;
+        if (android.os.Build.VERSION.SDK_INT >= 23) {
+            pendingIntentFlags |= PendingIntent.FLAG_IMMUTABLE;
+        }
         final PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0,
-                updateIntent, PendingIntent.FLAG_CANCEL_CURRENT);
+                updateIntent, pendingIntentFlags);
 
         // We set the alarm in the type that doesn't forcefully wake the device
         // from sleep, but fires the next time the device actually wakes for any