Four Secure Coding Best Practices for Mobile Apps

Mobile apps have become the primary point of innovation for many companies, and skilled mobile developers are in high demand. The business asks developers to innovate fast using the latest smartphone features and capabilities to drive high download rates, wow their users, capture customers and grow their business. Dev teams facing constant pressure to move faster may push security to the back burner, focusing on required features and delivery dates the business demands. However, many dev teams have figured out how to innovate faster with security built in by ensuring that devs understand key security requirements and coding best practices. Working with hundreds of development teams on securing thousands of mobile apps, we found four common areas of security failure that can be addressed easily.

Use SSL via HTTPS

Mobile app devs may instinctually use Hypertext Transfer Protocol (HTTP) for network communications. However, HTTP puts private user information out in the open for threat actors to intercept. Developers can fix this common mistake by using HTTPS instead, which encrypts data sent to and from servers via industry-standard SSL. Android developers can use the available NetworkSecurityConfig file to set up a predetermined configuration for all network connections made within the app or manually incorporate HTTPS. iOS developers can use App Transport Security (ATS) as the default feature that enforces secure communications in iOS apps and prevents any insecure connections between the mobile app and the server from being completed.

Validate the Contents of the Certificate

Certificates add an additional layer of security to HTTPS connections by enforcing additional validations when performing a connection. Certificates include the certificate authority (CA) that signed it and the list of hostnames known or accepted by the application. Apps that validate these components when performing connections with the server significantly reduce the risk of a man-in-the-middle (MITM) attack that can steal credentials and sensitive data.

To verify a certificate has been issued by a valid CA, Android developers can reference the preconfigured list of CAs included on devices running the mobile operating system. Android developers can implement native classes such as HostnameVerifier to achieve proper hostname verification within their app.

iOS developers can leverage ATS that provides built-in validation, or use methods in the NSURLSession class to manually code these instead.

Avoid Hardcoding Resources of a Mobile App

Attackers often use hardcoded info within the source code of a mobile app to take advantage of users. For instance, attackers can use credentials stored within app files to gain access to a user account. Attackers can also find hardcoded API keys or URLs to gather private data or take over an app entirely. Mobile app developers can prevent these areas from being compromised by not hardcoding keys, passwords and URLs into the source code. Encrypting transport and decrypting data on the backend also adds an extra layer of security.

Use the Latest Cryptography to Protect Mobile Users

Outdated cryptography algorithms like SHA-2, RC4 and DES allow attackers to easily break a seemingly secure mobile app. Using older algorithms may also make a mobile app non-compliant with industry regulations leaving an organization at risk of fines or legal jeopardy. Devs can avoid this problem for Android and iOS mobile apps by using the latest cryptography algorithms available, selecting those that are suitable for a specific app scenario. When signing your binary before publishing it to the store, use keys with a length of at least 2048 bits (preferably 4096 bits), and on Android use SecureRandom or SecRandomCopyBytes on iOS when generating random values for cryptographic implementations. Android devs can leverage the Keystore class and iOS devs can leverage Keychain services to store highly sensitive data. Devs should avoid insecure modes of operation, improperly generated cryptographic keys and initialization vectors (IVs) to guarantee that the information that is encrypted cannot be decrypted by a malicious actor.

Today’s mobile app users need confidence that mobile apps are built with security in mind. While building innovative mobile apps, developers have a responsibility to learn a practical set of secure coding best practices to protect their users (and their businesses).