How to perform APK simple code injection

1. Foreword

The smail file is obtained by decompiling the apk without encryption. Just inject the code that needs to be injected. Then seal and sign it!

2. Make apk

Use android studio to generate a simple apk. Just use the default code.

package com.example.myapplication1;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

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

After generating the apk, run the apk.

3. Decompile

1. Open the androimanifest.xml file and find the android:name followed by the class under activity.

#2. Use np manager to decompile and obtain the smail file.

The content of the file is as above. We need to find the onCreate function, which is a function called to create the page. Then we can paste the code we want to inject before return-void. The injected code is a pop-up prompt. The prompt word is test. Its smail code is

const-string v0, "test"
const/4 v1, 0x0
invoke-static {p0, v0, v1}, Landroid/widget/Toast;->makeText(Landroid/content/Context;Ljava/lang/CharSequence;I)Landroid/widget/Toast;
move-result-object v0
invoke-virtual {v0}, Landroid/widget/Toast;->show()V

. After filling in the smail, the format is as follows:

The inserted method is a complete method. Need line plus 1. At the same time, the pop-up window is a component and needs to be registered

and change 3 to 4. After modification, just save the overall code

. Automatically compile signatures.

4. Test results

Compile, sign and install.

Successful pop-up window.

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