Authentication improvements/fixes

app/src/main/java/eu/faircode/email/ActivityBase.java

@@ -20,8 +20,10 @@ package eu.faircode.email;
 */
 
 import android.Manifest;
+import android.content.BroadcastReceiver;
 import android.content.Context;
 import android.content.Intent;
+import android.content.IntentFilter;
 import android.content.SharedPreferences;
 import android.content.res.Configuration;
 import android.os.Bundle;
@@ -84,6 +86,8 @@ abstract class ActivityBase extends AppCompatActivity implements SharedPreferenc
 
         prefs.registerOnSharedPreferenceChangeListener(this);
 
+        registerReceiver(onScreenOff, new IntentFilter(Intent.ACTION_SCREEN_OFF));
+
         super.onCreate(savedInstanceState);
     }
 
@@ -139,6 +143,7 @@ abstract class ActivityBase extends AppCompatActivity implements SharedPreferenc
     @Override
     protected void onDestroy() {
         Log.i("Destroy " + this.getClass().getName());
+        unregisterReceiver(onScreenOff);
         PreferenceManager.getDefaultSharedPreferences(this).unregisterOnSharedPreferenceChangeListener(this);
         super.onDestroy();
     }
@@ -163,6 +168,17 @@ abstract class ActivityBase extends AppCompatActivity implements SharedPreferenc
             finish();
     }
 
+    private BroadcastReceiver onScreenOff = new BroadcastReceiver() {
+        @Override
+        public void onReceive(Context context, Intent intent) {
+            Log.i(intent.toString());
+            Log.logExtras(intent);
+
+            SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(ActivityBase.this);
+            prefs.edit().remove("last_authentication").apply();
+        }
+    };
+
     public boolean hasPermission(String name) {
         return Helper.hasPermission(this, name);
     }

app/src/main/java/eu/faircode/email/Helper.java

@@ -658,18 +658,23 @@ public class Helper {
     static boolean shouldAuthenticate(Context context) {
         SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
         boolean biometrics = prefs.getBoolean("biometrics", false);
-        if (!biometrics)
-            return false;
 
-        ContentResolver resolver = context.getContentResolver();
-        int screen_timeout = Settings.System.getInt(resolver, Settings.System.SCREEN_OFF_TIMEOUT, -1);
-        Log.i("Screen timeout=" + screen_timeout);
+        if (biometrics) {
+            ContentResolver resolver = context.getContentResolver();
+            int screen_timeout = Settings.System.getInt(resolver, Settings.System.SCREEN_OFF_TIMEOUT, -1);
+            Log.i("Screen timeout=" + screen_timeout);
+
+            long now = new Date().getTime();
+            long last_authentication = prefs.getLong("last_authentication", 0);
+            Log.i("Authentication valid until=" + new Date(last_authentication + screen_timeout));
+
+            if (last_authentication + screen_timeout < now)
+                return true;
 
-        long now = new Date().getTime();
-        long last_authentication = prefs.getLong("last_authentication", 0);
-        prefs.edit().putLong("last_authentication", now).apply();
+            prefs.edit().putLong("last_authentication", now).apply();
+        }
 
-        return (last_authentication + screen_timeout < now);
+        return false;
     }
 
     static void authenticate(final FragmentActivity activity,