Geico Android App Vulnerability

Summary

Geico'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.

Geico 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, I installed the genuine App from the Google Play Store.

I pulled the APK file from the device with adb, and decoded the APK file with apktool, as shown below.

Finding Vulnerable Code

Since the strings were not effectively obfuscated, it was easy to find vulnerable code using grep.

I modified the AceLoginFragment$AceLoginRulesFactory$2.smali file as shown below.

I rebuilt the APK and signed it, as shown below.

Installing the Modified App

I dragged the APK file from the dist/ directory and dropped it on the emulator to install it.

I entered a test username and password into the login form.

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

Timeline

I notified Geico on Mar. 6, 2015, as shown below. Wow, they actually have an intelligent form to use to report security vulnerabilties!

On 3-10-15, a Geico security officer called me and said they wanted more time to fix it, and preferred that I never disclose details about the security problem at all.

I said I was impressed that they spoke to me at all, and that I would consider his request. He said he'd email me more in a week.

On 4-8-15, I got this message, appearing to say the problem would be fixed in the May update:

I got a voicemail, summarized below:

May Update

I checked on 5-12-15, and saw that the Geico app had been updated: on 5-9-15

Now decompiling the app results in a lot of errors:

However, those errors don't make any difference in the Trojaning process. I just added these Smali Trojans:

Recompiling worked fine:

The Trojaned app leaks credentials into the log, just as before:

June Update

There was another update on 6-20-15:

It's still vulnerable to a similar code modification:

Originally written on 3-6-15
Revised 3-10-15 with phone call from Geico
Revised 5-12-15 with May update
Revised 7-12-15 with June update