Mobile Application Testing

Technology is evolving faster by the day. Today, we see mobiles are no longer mobiles, they are small computers. The smartphones run powerful applications, providing everything to users at their fingertips. Users can use their mobiles for:

• Logging in to banks in order to transfer funds
• Purchasing or selling shares via trading portals
• Booking travel or movie tickets
• Tweeting or social networking
• Donating to charity

As money transactions move to mobiles, hackers also move their attention to it. Hence, as a precautionary measure, securing mobile applications becomes important. This article introduces you to the three key aspects of securing mobile applications.

Mobile applications may be a -

• web application accessed via a WAP browser.
• thick client application sending out an HTTP request or an SMS.

Security testers should broadly focus on the following categories while analyzing their test cases -

• Local Storage of Data
• Hard-coded Sensitive Data in the Source Code
• Data in Transition

Let us further discuss these categories in detail from a security tester’s perspective.

Local Storage of Data

The local storage of data can also be referred to as a “Handset Memory Analysis” for mobiles.

Mobile applications store data in the local memory of a handset. This data is stored by developers in files locally and is used by the application.

• The Android OS stores data in files at runtime, but due to its native sand-boxing mechanism, obtaining access to this data is difficult. It also stores some data in the SQLite database.
• The Apple iOS stores sensitive information like keystrokes, snapshots and other cached information in the iPhone local memory in the form of client-side SQLite databases or .plist files.
• The Java application in Nokia phones stores it in the form of RMS files. These RMS (Record Management System) files get stored permanently and are easily accessible. Sometimes, they are easily readable when connected to a PC via a data cable. These files have a history of containing sensitive information like bank account numbers, beneficiary details or registered biller(s) auto-pay details.

A security tester needs to conduct a Handset Memory Analysis to detect sensitive information stored in the device.

A mobile application should not store sensitive data in user handsets. If at all it is necessary to store some data, it should be stored in a secure manner using strong encryption algorithms. It can further be stored at non-reachable locations with strict permissions.

Hard-coded Sensitive Data in the Source Code

Applications are also known to comprise hard-coded data in the source code. We may come across various types of sensitive data like –

• payment gateways hard-coding the credentials
• applications hard-coding the server and application-specific details
• developer names & comments explaining the code pieces

Reverse-engineer the source code to obtain readable code files. This would ultimately help discover hard-coded data. It would also help reveal the application logic.

• Android packages the application in .apk files, which have to be reverse-engineered to .dex files and then to readable class files.
• Other .jar files can be simply renamed to .rar and extracted by WinRAR software. This results in decompiled class files that can be read using text editors.

A security tester has to decompile the application code in order to detect sensitive data or hard-coded information.

A mobile application should not hard-code sensitive data in the client-side code.

Data in Transition

Another aspect of mobile usage is the communication channel. Data in transit may be vulnerable to sniffing or manipulation. The data in transit can be tampered or stolen to –

• obtain access to other user accounts.
• transfer funds from other accounts.
• sell shares of other users in order to create a nuisance.
• conduct social engineering.

During a security test, the tester should analyze the data in transition. The HTTP traffic in mobile networks can be intercepted via a proxy editor tool. Here, the security tester can execute targeted manipulation attacks in order to test the application’s resilience against such attacks.

Mobile applications should thus implement server-side validation to prevent data manipulation in transit. Strong SSL encryption should also be implemented to protect data in transit.

Conclusion

There may be various dimensions to mobile application attacks. This article attempts to focus on three key aspects of the mobile security testing domain. Most of the tests revolve around these three aspects. OWASP and other known security forums periodically release guidelines for securing mobile applications. All these guidelines should be diligently followed by developers and included in the detection armory by a security tester.

Originally written by me for Palizine Magazine in 2011