Reverse Engineering Flutter Apps: What You Need To Know?

Reverse engineering is one of the most notorious methods hackers use to exploit an application or software. If you're in the mobile app development industry and use Flutter for app development, you'd know the threat reverse engineering poses to apps.

While 100% protection from reverse engineering isn't possible, you can give the hackers a tough time trying to exploit your app. And this blog is there to help.

Below, we'll discuss reverse engineering, whether reverse engineering Flutter apps is possible, and how to protect Flutter apps from this threat. 

What is Flutter?

While most websites define Flutter as a framework for crafting cross-platform applications, it's much more than that. Flutter is a complete toolkit or SDK with everything (rendering engine, tools, UI library) a developer needs to create interactive cross-platform web, mobile, or desktop applications.

Developers need to use Dart, a highly functional, safe language created by Google, to craft cross-platform apps via Flutter. 

What is reverse engineering?

Reverse Engineering is the process of deconstructing software or a mobile app to access the source code and other crucial resources (API keys, URLs, etc.) of the application. Reverse engineering Flutter apps means deconstructing apps developed using the Flutter framework.

Organizations use reverse engineering techniques to learn more about their competitors and the features they're using and take inspiration from those features. This use case may sound okay. So, here's another one:

Hackers use reverse engineering to access source code, modify it, and create popular application replicas. Their motive is to bypass security, access premium features for free, and upload the app for mass adoption, which can be further used to capture and steal user data.

The above actions impact both the business and the users. For instance, companies might lose invaluable business logic, and customers might lose money. Also, if your app is exploitable, the customers won't trust your business, reducing retention and, thus, revenue.

Is reverse engineering Flutter apps possible?

Yes, it is. While the difficulty of deconstructing an application may vary from language to language and several other factors, almost all apps can be reverse-engineered. And apps built using Flutter are no exception.

Flutter apps can be reverse-engineered statically or dynamically using various open-source tools that simplify the job. For instance, MobSF is known for static reverse engineering, and Frida is known for dynamic reverse engineering. 

However, reverse engineering Flutter apps may be more challenging than it may seem. Here's why:

The Dart snapshot format changes a lot with every update

Dart is a new and evolving programming language. Because of this, the snapshot (containing data and compiled machine code) format changes each time an update is launched, making it hard to reverse-engineer the app.

So, if developers write a parser for data extraction, it'll become outdated with every Dart update, and the entire process will have to be repeated.

Dart frameworks are linked in the application library statically

Dart frameworks are linked into the Dart snapshots statically, which makes the reverse engineering process hard; here's how:

• A bigger size of the snapshot makes the reverse engineering process more extensive. 
• App code becomes hard to distinguish from framework code.
• Internal function calls make it hard for developers to determine what a function does.

The Dart code depends on the Dart virtual machine for execution

Because of this dependency, reverse engineering tools cannot locate the function of Dart objects, making reverse engineering quite a task. Also, Dart Virtual Machine uses a custom ABI and layout, which makes the Dart code appear complex and challenging to decipher.

While reverse engineering Flutter apps is tough, it's not impossible. Flutter apps are at as much risk of being reverse-engineered as other apps.

However, developers can take additional steps to make this process even harder and demotivate hackers from reverse engineering Flutter apps. Let's learn about that below.

Good Read: Why is Flutter the Ideal Framework for Optimum App Security?

How to protect your app’s code against reverse engineering?

1) Obfuscation

Reverse engineering involves using tools to access an application's source code. Hackers perform Flutter code analysis to understand how the code works and to manipulate it for their benefit. However, you can conceal your Flutter code using code obfuscation.

Obfuscation helps obfuscate or hide the class and function names. This way, even if the hackers access the source code, it won't make any sense, which will help enhance Flutter app security.

2) Secure the API keys

Securing your API is essential for reverse engineering protection for Flutter. If your APIs are not secure, hackers can access the data in transit and use it for illicit purposes.

To secure your APIs, you can implement restriction controls and restrict access to them. You can also encrypt and decrypt API keys on runtime.

3) Flutter jailbreak detection

Developers must integrate the Flutter_jailbreak_detection package while developing the mobile app to secure the app from threats posed by rooted or jailbroken devices. Such packages help detect if the app is running on a compromised device, enabling you to take appropriate measures to mitigate potential threats.

4) Protect network connections

Information or data on the move is always at risk of being intercepted. However, you can prevent this using Transport Layer Protection.

You can also whitelist your domain, restricting any insecure traffic. Furthermore, you can implement certificate pinning, preventing hackers from accessing data using illegitimate certificates.

5) Ask for necessary permissions only and secure user data

Ensure you're not adding any plugins or 3rd party components that ask for permissions from the user that aren't necessary. Otherwise, native APIs and hardware can be accessed.

While it's not ideal, certain apps store personally identifiable information (PII), auth tokens, and similar information. If left unprotected, this information can be manipulated.

However, you can use Flutter's Flutter_secure_storage package, which uses Keystore to store information.

In addition, you can opt for Hive, a dart-specific package that prevents tempering efforts and safely stores the data locally.

6) Protect background snapshots

A task switcher feature captures and displays the last app state. This snapshot can potentially expose sensitive information. However, by using the secure_application package, developers can prevent this from being viewed and thus protect sensitive data. 

7) Securing the CI infrastructure

The code is uploaded and integrated regularly into the CI infrastructure. This infrastructure should be constantly monitored to identify potential vulnerabilities. The virtual machine must also be updated to ensure the apps are running in a safe environment.

Wrapping Up

Flutter is one of the best, most secure, and most reliable cross-platform app development frameworks. But that doesn't make it immune to cybercriminals and attacks. So, developers must follow the steps before developing Flutter apps to protect against reverse engineering.

In addition to following the above steps, you can refer to Top Mobile App Security Best Practices to make your apps even more resilient to attacks.

FAQs

How to reverse engineer software?

While the actual reverse engineering process varies with the type of software you're using and other factors, here are the typical steps involved in reverse engineering:

1. Defining the objective
2. Acquiring the software, i.e., the binary of the application
3. Setting up the environment (gathering the required tools such as decompilers)
4. Static analysis (analyzing the app's code when it's static)
5. Dynamic analysis (running the app in VM and analyzing it)
6. Identifying the components (data structures, libraries, etc.)
7. Understanding the functionality or logic
8. Documenting the findings

Are Flutter apps secure?

Flutter is more robust in terms of security features than other cross-platform app development frameworks. From data loss prevention to code injection and user authentication, Flutter has some of the best security features.

While Flutter is innately secure, it's still possible to reverse engineer Flutter apps. However, you can follow the abovementioned steps and make your app more resilient against such efforts.