TradeKing Android App Vulnerability


TradeKing's servers don't check the integrity of their Android app when it connects to their servers. It is therefore easy to modify the app, adding trojan code that does malicious things. An attacker who can trick people into using the trojaned app can exploit them.

This vulnerability does not affect people who are using the genuine app from the Google Play Store. It would only harm people who are tricked into installing a modified app from a Web site, email, etc.

The Proof of Concept code below merely logs the user id and password, where other apps on the phone can see it, but there's nothing preventing a better programmer from sending that data, and all the other data the app has, out over the Net.

TradeKing should add integrity-checking to their server-side code. Obfuscating their smali code would also be an improvement, with a powerful obfuscator like DashO, not the worthless ProGuard.

Proof of Concept: Step by Step

Using the GenyMotion Android emulator, install the genuine App from the Google Play Store.

Pull the APK file from the device with adb, and decode the APK file with apktool, as shown below.

Modify the Login.smali file as shown below.

Build the APK and sign it, as shown below.

Drag the APK file from the dist/ directory and drop it on the emulator to install it.

Launch the app and log in.

The user id and password are in the logs, as shown below.


I notified TradeKing on Feb. 22, 2015, as shown below.

Update: Fixed on 5-22-15!

On 5-22-15 I tested the app again, since there was a new version:

The app now crashes after modification=, and the log shows that they are now performing code verification!