Tools: Drozer, APKTool (en)

Drozer: A Versatile Tool for Android Security Testing

What is Drozer?

Drozer is an open-source framework designed to conduct in-depth security testing on Android applications. With Drozer, you can interact with other applications, the operating system, and other Android components as if you were an application itself. This capability allows you to uncover various vulnerabilities that may be missed by other testing methods. Drozer enables vulnerability testing on applications installed on Android devices, such as exploiting weaknesses in Intents, Content Providers, and other Android components.

Key Features of Drozer:

• Interacting with Other Apps: Drozer can interact with the IPC (Inter-Process Communication) endpoints of other applications, allowing you to send commands and receive responses.
• Data Manipulation: You can manipulate the data sent and received by applications to uncover vulnerabilities like injection, authentication bypass, and more.
• Traffic Analysis: Drozer can monitor network traffic generated by applications, allowing you to identify potential vulnerabilities related to encryption, data protection, and more.
• Exploiting Vulnerabilities: Drozer provides various exploitation modules that can be used to exploit identified vulnerabilities.

Examples of Use:

• Finding SQL Injection Vulnerabilities: Drozer can be used to send SQL-injected inputs to applications vulnerable to SQL injection attacks.
• Analyzing Access Protection: Drozer can be used to check if applications properly implement access protection like permissions and authentication.
• Detecting XML Vulnerabilities: Drozer can analyze XML configuration files used by applications to find vulnerabilities related to XML injection and more.

Why is Drozer Important for Ethical Hacking?

Drozer is an invaluable tool for Android pentesters as it enables comprehensive and efficient security testing. By understanding Drozer, you can discover and exploit vulnerabilities that other testing tools may overlook.

Steps:

• Installing Drozer:
  • In KALI Linux, install Drozer by running:

sudo apt install drozer

• Preparing the Android Device:
  • Enable *Developer Options* and *USB Debugging* on the Android device.
  • Connect the device to KALI Linux via USB, then ensure the device is detected by running:

adb devices

• Running Drozer:
  • In the terminal, run adb to set up port forwarding between the device and Drozer:

adb forward tcp:31415 tcp:31415

• • Launch Drozer with the command:

drozer console connect

• Exploiting Content Provider:

An example of exploiting this involves accessing data exposed by poorly protected Content Providers:

• • Type the following command to view available Content Providers:

run app.provider.finduri

• • Once a vulnerable URI is identified, perform a query to extract data:

run app.provider.query <content-uri>

Case Example:

In applications that inadequately protect Content Providers, user data like contacts or SMS can be extracted. If an application provides access to a specific URI without proper permissions, you may be able to read, write, or modify that data.

APKTool: A Tool for Reverse Engineering Android Apps

What is APKTool?

• APKTool* is a tool for reverse engineering Android applications. With APKTool, you can decompile APKs into source code, modify them, and rebuild them. This enables you to open APK files (Android Package) and extract resources like images, layouts, and source code (in the form of smali files).

Key Features of APKTool:

• Decompilation: APKTool can decompile DEX (Dalvik Executable) files into smali code, an assembly language for the Dalvik virtual machine.
• Reconstruction: APKTool can reconstruct application resources, allowing you to modify them.
• Disassembly: APKTool can disassemble the app structure so you can understand its functionality.

Examples of Use:

• Source Code Analysis: APKTool can be used to analyze an application's source code, allowing you to understand business logic and algorithms.
• Application Modification: APKTool can be used to modify apps by removing ads, changing layouts, or adding new features.
• Patch Creation: APKTool can be used to create patches to fix vulnerabilities in applications.

Why is APKTool Important for Ethical Hacking?

APKTool is highly useful for understanding how Android applications work. By examining an application’s source code, you can find vulnerabilities that may not be visible at the binary level. Additionally, APKTool can be used to create proof-of-concept (PoC) exploits.

Steps:

• Installing APKTool:
  • In KALI Linux, APKTool can be downloaded from the official repository:

sudo apt install apktool

• Decompiling an APK:
  • To decompile an APK file and view its source code, run:

apktool d <file.apk>

• • This will generate a directory containing the app’s file structure.

• Source Code Analysis:
  • Open the resulting decompiled directory and examine XML and *smali* files (the representation of Android bytecode) to find potential vulnerabilities such as hardcoded credentials, authentication logic flaws, or unsafe API functions.

• Modifying an APK:
  • After identifying weaknesses or making changes, rebuild the APK with the command:

apktool b <directory>

• • Once the APK is successfully built, sign it to enable installation:

jarsigner -verbose -keystore my-release-key.keystore <path/to/apk> alias_name

Case Example:

An attacker could use APKTool to extract and modify Android applications, such as by inserting a *backdoor*, removing license verification, or editing app logic to bypass security controls.

Conclusion:

Drozer and APKTool are two essential tools for Android pentesters. Drozer allows you to perform dynamic security testing, while APKTool allows for static analysis of applications. By combining these tools, you can conduct highly comprehensive Android security assessments.

• Drozer is used for security testing of Android applications, focusing on components like *Intents* and *Content Providers*.
• APKTool is used for *reverse engineering* APKs and modifying Android application code. This tool is valuable for exploiting weak APKs, such as inserting a backdoor or bypassing security verification.

Using these tools, students can explore Android application security both in penetration testing and in reverse engineering analysis.

Disclaimer:

Use of these tools should be responsible and for educational or authorized security testing purposes only. Using these tools for unlawful purposes may have legal consequences.

Additional Resources

• Ethical Hacking

Additional Tips:

• Learn Android Basics: Before using Drozer and APKTool, ensure you understand Android’s operating system basics, including architecture, components, and security mechanisms.
• Practice Regularly: The best way to master Drozer and APKTool is through consistent practice. Try analyzing different applications and look for potential vulnerabilities.
• Stay Updated: Technology evolves, as do security tools. Be sure to keep up with the latest updates for Drozer and APKTool.