Question

Update:
I have spent more than 2 hours to google, but I can’t find the answer. I’ve add a main.java the handle the activity send from the Login Activity. Now the file tree looks like:

But still got error

E/AndroidRuntime(1282): android.content.ActivityNotFoundException: No
Activity found to handle Intent {
act=com.goodboy.loginIntent.action.main
cat=[android.intent.category.DEFAULT] (has extras) }

I know this question is simple, I am new to android, any help would be appreciated:)

Android allows for Intents that have specific recipients(the Activity or Service) as well as Intents that are broadcast throughout the system to any components that may be listening.

I want to make a PoC(Proof of Concept) that if we do not set setClassName, others can listen your private message.

This PoC is simple, suppose there is Login Activity for App Goodboy, when a user put his username and password in the login activity, and click the login button, the evil activity from App Badboy steal the this message.

However, failed:(

When I click the login button, failed:

And the evil intent got nothing:

The java source code of Login Activity

package com.goodboy.loginIntent;
import com.goodboy.loginIntent.R;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
public class GoodloginActivity extends Activity {
    private EditText et_user;
    private EditText et_pwd;
    private Button btn_login;
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login);
        et_user = (EditText) findViewById(R.id.et_user);
        et_pwd = (EditText) findViewById(R.id.et_pwd);
        btn_login = (Button) findViewById(R.id.btn_login);
        btn_login.setOnClickListener(new OnClickListener(){
        public void onClick(View v) {
                Intent m_intent = new Intent();
                m_intent.putExtra("username", et_user.getText().toString());
                m_intent.putExtra("password", et_pwd.getText().toString());
                m_intent.setAction("com.goodboy.loginIntent.action.main");
                m_intent.addCategory(Intent.CATEGORY_DEFAULT);
                startActivity(m_intent);
            }
        });
    }
}

The source code of main.java

package com.goodboy.loginIntent;
import android.app.Activity;
import android.os.Bundle;
import com.goodboy.loginIntent.R;
public class main  extends Activity {
@Override
 public void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     setContentView(R.layout.main);
  }
}

The login layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >


    <EditText
        android:id="@+id/et_user"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10" >

        <requestFocus />
    </EditText>


    <EditText
        android:id="@+id/et_pwd"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:inputType="textPassword" />


    <Button
        android:id="@+id/btn_login"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Button" />

</LinearLayout>

The java source code of evil activity:

package com.badboy.stealIntent;

import com.badboy.stealIntent.R;

import android.app.Activity;
import android.os.Bundle;
import android.widget.Toast;

public class BadIntentActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        Toast.makeText(getBaseContext(),
                "username: "+this.getIntent().getStringExtra("username")+
                "\npassword: "+this.getIntent().getStringExtra("password"),
                Toast.LENGTH_SHORT).show();
    }
}

Thanks @David Wasser, the manifest of login app(update):

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.goodboy.loginIntent"
    android:versionCode="1"
    android:versionName="1.0" >
    <uses-sdk android:minSdkVersion="15" />
    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:name=".GoodloginActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".main"
            android:label="@string/main" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>

The manifest of the badIntent:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.badboy.stealIntent"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="15" />

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:name=".BadIntentActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

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

</manifest>

Answer 1

You are probably getting an ActivityNotFoundException when you call startActivity() in GoodloginActivity because there is no Activity known to the system that responds to:

ACTION = "com.goodboy.loginIntent.action.main" and
CATEGORY = CATEGORY_DEFAULT

Have a look at your logcat output.