Though Flutter apps have become immensely popular in recent years, certain security risks pose a threat to app security. Flutter apps can expose sensitive data in the absence of adequate security measures. Reverse engineering is among the most common threats faced by Flutter apps as Dart code (the programming language used in Flutter apps) generates metadata that can easily give insights into the application’s workings. Hackers conduct static analysis that can compromise the security of Flutter apps and encourage tampering attempts. This article will shed light on Flutter apps and ways to ensure Flutter app security.

Flutter Security Philosophy

Flutter facilitates the development of natively compiled, multi-platform applications from a single codebase. The Flutter team offers robust measures to tackle security flaws in apps created with the Flutter framework. Let’s understand the security philosophy that forms the foundation of Flutter’s security strategy.

1. Identify: Identify core assets, threats, and vulnerabilities to track and prioritize key security risks
2. Detect: Employ techniques and tools like vulnerability scanning, static application security testing, and fuzzing to pinpoint vulnerabilities
3. Protect: Mitigate known vulnerabilities and safeguard critical assets against source threats to prevent security risks
4. Respond: Define processes to report, triage, and respond to vulnerabilities or attacks
5. Recover: Equip apps with capabilities to contain damage and recover from the incident with minimal impact

How to Secure Your Flutter Applications?

Developers rely on Flutter to minimize development efforts and maintain native performance. Intellectual property theft, cloning, and tampering are among the security concerns to be addressed when developing Flutter apps. Here are the top 10 ways to secure your Flutter application:

1. Use code obfuscation

Hackers can reverse engineer app code. Strings, methods, class names, and API keys can be leaked if hackers launch attacks on the application. Hackers can easily misuse the code if data is stored in plain text. Obfuscation is a process that makes it difficult for hackers to read the code. It hides functions and class names in compiled Dart code. You can secure Flutter apps using code obfuscation techniques that modify an app’s binary. Use the -obfuscate parameter from the Dart side to obfuscate data.

2. Secure API keys

API keys that are not protected using obfuscation or encryption can be taken advantage of by hackers. You can apply application restriction controls to control which applications, websites, or IP addresses can access your API keys. Encrypting/decrypting API keys on runtime is yet another effective way to secure API keys and prevent hackers from deciphering the data. You should avoid tracking API keys on the repository to minimize the risk of exposing values. Using Firebase Remote Config is not recommended for storing sensitive data.

3. Use Flutter jailbreak detection

Flutter_jailbreak_detection package in Flutter helps safeguard apps against security threats from a jailbroken or rooted device. This package can be used to detect whether the app is running on a compromised device. Jailbroken or rooted devices have more privileges and enable easy installation of malware and viruses. Flutter apps with jailbreak detection use RootBeer on Android and DTTJailbreakDetection on iOS to detect if the app is running on a jailbroken or rooted device.

4. Ensure secure network connections

A secure network connection between mobile apps and servers is a prerequisite to ensure the protection of apps. Using a Transport Secure Layer (TSL) facilitates the secure exchange of information. Whitelisting your domain can help restrict traffic that is not secure. Implementing certificate pinning is another security best practice that will ensure all connections are secure. This prevents hackers from tampering with data in transit using illegitimate certificates.

5. Use only necessary permissions

Applications can access hardware and native APIs through app permissions. Avoid adding plugins that contain unnecessary permission requests.

6. Secure user data

Applications sometimes may have to store sensitive data such as PII. Use the Flutter_secure_storage package when there is a need to store PII, auth token, or other sensitive data. This package uses Keystore for Android and Keychains for iOS. You can use Hive which is a Dart package to store data locally and prevent tampering.

7. Background snapshots protection

Mobile devices have a task-switcher feature that displays a snapshot of the last state of the app. This snapshot, however, can expose sensitive information. The secure_application package is designed to protect application content from view on demand.

8. Implement local authentication

Local_auth is a Flutter plugin that enables local authentication for Flutter apps. Biometric authentication is useful to protect apps that store payment information or other critical information. Local authentication also helps provide an extra layer of protection in case the device is stolen.

9. Secure developer identity

Any data that may expose developer identity needs to be encrypted. Encrypt sensitive files like key.jks & keystore.properties with GPG. Avoid keeping track of unencrypted sensitive data in your repository.

10. Secure CI infrastructure

CI infrastructure refers to developers integrating code into a shared repository frequently. Developers should constantly monitor vulnerabilities and keep Virtual Machines updated to ensure apps are running in a protected environment. API keys and other sensitive data should not be added to the code. They should instead be included in the secret settings of the project.

Important Security Best Practices to Bear in Mind

• Stay up-to-date: Staying updated about the latest Flutter SDK, plugins, and packages is critical to enhancing the security of Flutter apps. The Flutter team regularly releases updates to address security flaws detected in previous versions.
• Update your application’s dependencies: You need to upgrade your package dependencies on time. Pinning to specific versions of dependencies is not recommended. If you decide to pin, make sure you do timely checks to ensure dependencies are updated properly.
• Keep your Flutter version up to date: You may miss out on important security updates if you are using customized versions of Flutter. Such versions may not include security fixes usually found in the current versions. Hence, it is mandatory to update your copy of Flutter from time to time.

Final Thoughts

Flutter is a cost-effective way to build multi-platform native applications. Flutter apps are compiled directly into the native code which leads developers to think that security is not a major concern in Flutter apps. But Flutter apps, like every other traditional mobile app, are at risk of getting hacked. Flutter apps running in hostile environments are vulnerable to tampering and dynamic attacks. Hackers that know how to reverse engineer binaries can easily exploit security loopholes in Flutter apps. Robust security measures that include runtime detections to identify modifications or tampering are imperative to secure Flutter apps. Though Flutter has emerged to be a prominent framework among developers, building apps without appropriate security measures will have disastrous consequences for the enterprise. The security measures discussed in this article will help safeguard your Flutter mobile apps from a wide range of threats.