Part 6 – Permissions

[embedyt]https://www.youtube.com/watch?v=prueLyTvOwI[/embedyt]

Watch the next part

In part 6 of the BroadcastReceiver tutorial, we will learn how to keep our broadcasts and receivers secure and avoid that malicious apps intercept them.
One way to achieve this, is by limiting the scope of apps and components that are allowed to communicate with our BroadcastReceivers or listen to our broadcasts. We have learned about these techniques in earlier parts already. We can limit a statically (manifest) registered BroadcastReceiver to our own app by setting android:exported=”false”. A dynamically registered BroadcastReceiver is always exported. When sending a broadcast, we can make the broadcast explicit, either by targeting a single app with setPackage, or a single component with a ComponentName.
If we want to keep our broadcasts and receivers open to other apps but still add a security layer, we can specify permissions that then the other app has to request with uses-permission in order to receive our broadcasts or trigger our receivers.
We can add permissions to the sendBroadcast and sendOrderedBroadcast method, to the receiver tag in the manifest file, or to the registerReceiver method. Those can be either pre-defined system permissions (like android.permission.INTERNET) or we can create our own custom permissions. Instead of normal permissions, we can also use ones with a protectionLevel of “dangerous”, which means that they have to be requested at runtime and are more visible to the user.

Show more
Show less

Broadcast receiving app:

MainActivity.javaOrderedReceiver1.javaOrderedReceiver2.javaOrderedReceiver3.javaAndroidManifest.xml
package com.codinginflow.broadcastexample;

import android.Manifest;
import android.content.IntentFilter;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

public class MainActivity extends AppCompatActivity {
    OrderedReceiver1 orderedReceiver1 = new OrderedReceiver1();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        IntentFilter filter = new IntentFilter("com.codinginflow.EXAMPLE_ACTION");
        filter.setPriority(1);
        registerReceiver(orderedReceiver1, filter, Manifest.permission.VIBRATE, null);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        unregisterReceiver(orderedReceiver1);
    }
}
package com.codinginflow.broadcastexample;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.widget.Toast;

public class OrderedReceiver1 extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        int resultCode = getResultCode();
        String resultData = getResultData();
        Bundle resultExtras = getResultExtras(true);
        String stringExtra = resultExtras.getString("stringExtra");

        resultCode++;
        stringExtra += "->OR1";

        String toastText = "OR1\n" +
                "resultCode: " + resultCode + "\n" +
                "resultData: " + resultData + "\n" +
                "stringExtra: " + stringExtra;

        Toast.makeText(context, toastText, Toast.LENGTH_LONG).show();

        resultData = "OR1";
        resultExtras.putString("stringExtra", stringExtra);

        setResult(resultCode, resultData, resultExtras);
    }
}
package com.codinginflow.broadcastexample;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.widget.Toast;

public class OrderedReceiver2 extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        int resultCode = getResultCode();
        String resultData = getResultData();
        Bundle resultExtras = getResultExtras(true);
        String stringExtra = resultExtras.getString("stringExtra");

        resultCode++;
        stringExtra += "->OR2";

        String toastText = "OR2\n" +
                "resultCode: " + resultCode + "\n" +
                "resultData: " + resultData + "\n" +
                "stringExtra: " + stringExtra;

        Toast.makeText(context, toastText, Toast.LENGTH_LONG).show();

        resultData = "OR2";
        resultExtras.putString("stringExtra", stringExtra);

        setResult(resultCode, resultData, resultExtras);

        //abortBroadcast();
    }
}
package com.codinginflow.broadcastexample;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.widget.Toast;

public class OrderedReceiver3 extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        int resultCode = getResultCode();
        String resultData = getResultData();
        Bundle resultExtras = getResultExtras(true);
        String stringExtra = resultExtras.getString("stringExtra");

        resultCode++;
        stringExtra += "->OR3";

        String toastText = "OR3\n" +
                "resultCode: " + resultCode + "\n" +
                "resultData: " + resultData + "\n" +
                "stringExtra: " + stringExtra;

        Toast.makeText(context, toastText, Toast.LENGTH_LONG).show();

        resultData = "OR3";
        resultExtras.putString("stringExtra", stringExtra);

        setResult(resultCode, resultData, resultExtras);
    }
}
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.codinginflow.broadcastexample">

    <permission android:name="com.codinginflow.CUSTOM_PERMISSION" />
    
    <uses-permission android:name="android.permission.WAKE_LOCK" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <receiver
            android:name=".OrderedReceiver2"
            android:permission="android.permission.INTERNET">
            <intent-filter android:priority="2">
                <action android:name="com.codinginflow.EXAMPLE_ACTION" />
            </intent-filter>
        </receiver>
        <receiver
            android:name=".OrderedReceiver3"
            android:permission="com.codinginflow.CUSTOM_PERMISSION">
            <intent-filter android:priority="3">
                <action android:name="com.codinginflow.EXAMPLE_ACTION" />
            </intent-filter>
        </receiver>
    </application>

</manifest>

Broadcast sending app (BroadcastSender):

SenderReceiver.javaAndroidManifest.xmlactivity_main.xmlMainActivity.java
package com.codinginflow.broadcastsender;

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.widget.Toast;

public class SenderReceiver extends BroadcastReceiver {

    @Override
    public void onReceive(Context context, Intent intent) {
        int resultCode = getResultCode();
        String resultData = getResultData();
        Bundle resultExtras = getResultExtras(true);
        String stringExtra = resultExtras.getString("stringExtra");

        resultCode++;
        stringExtra += "->SenderReceiver";

        String toastText = "SenderReceiver\n" +
                "resultCode: " + resultCode + "\n" +
                "resultData: " + resultData + "\n" +
                "stringExtra: " + stringExtra;

        Toast.makeText(context, toastText, Toast.LENGTH_LONG).show();

        resultData = "SenderReceiver";
        resultExtras.putString("stringExtra", stringExtra);

        setResult(resultCode, resultData, resultExtras);
    }
}
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.codinginflow.broadcastsender">

    <uses-permission android:name="android.permission.VIBRATE" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="com.codinginflow.CUSTOM_PERMISSION" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <receiver android:name=".SenderReceiver" />
    </application>

</manifest>
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:gravity="center"
    android:orientation="vertical"
    android:padding="16dp"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/text_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Message"
        android:textSize="20sp" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="sendBroadcast"
        android:text="Send Broadcast" />

</LinearLayout>
package com.codinginflow.broadcastsender;

import android.Manifest;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    private TextView textView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        textView = findViewById(R.id.text_view);
    }

    public void sendBroadcast(View v) {
        Intent intent = new Intent("com.codinginflow.EXAMPLE_ACTION");

        intent.setPackage("com.codinginflow.broadcastexample");

        Bundle extras = new Bundle();
        extras.putString("stringExtra", "Start");

        sendOrderedBroadcast(intent, Manifest.permission.WAKE_LOCK, new SenderReceiver(),
                null, 0, "Start", extras);
    }
}