Last updated at Thu, 29 Aug 2024 20:44:12 GMT

Pokemon Go started it.

The crusty old house cell phone, which we had years ago ported from a genuine AT&T land line to a T-Mobile account, suddenly caught the attention of my middle son.

"Hey Dad, can I use that phone to catch Pokemon at the park?"

"Sure! Have fun, and don't come back until sundown!"

A few minutes later, he had hunted down his first Pikachu, which apparently required running around the block in Texas summer heat a few times. Sweat-soaked but proud, he happily presented his prize. I could get used to this! The kids were getting out of the house, exploring the neighborhood, having fun, and I was getting a little peace and quiet. Then one day, Pokemon Go stopped working, stating that it did not support 'rooted' phones.

First some back story. Our 'house phone' role is generally filled by the most-working last-gen reject device that is too old to be useful as a daily driver, but too new to throw away. In this case, it was a Google Nexus 4. I have always preferred the Google phones over other third parties for a number of reasons:

  • They're cheap if you get the last generation (and sometimes the current).
  • They usually lead the pack when it comes to software updates and hackability.

However, given the industry's appetite for quick turnarounds and obsolescence cycles, (and in spite of Google's generally good support) this phone is end-of-life, and has not received an official firmware update in over a year. In fact, this phone is the amalgamation of two Nexus 4's, combined into a frankenstein assemblage of the most-working screen, battery, and charging ports of the original pair.

Since it has been a year and a half since Google released a firmware for this phone, I had it running the next-best thing: Cyanogenmod 13, which backported Android 6 to this hardware. Now, this junker phone is up-to-date as much as the Android Open Source Project (AOSP) allows. But, there was now a show-stopper: you now can't run Pokemon Go on rooted phones using Cyanogenmod. Technically, there is a new set of hacks, but this is a cat-and-mouse game, but there comes a time in your life when you just want things to work. And they were already hooked.

Why did Niantic decide to impose this restriction after several months of unrestricted access? It comes down to cheaters. People were rooting their phones specifically to fake GPS coordinates to get rare Pokemon, grow eggs, etc. Since having root access is also required to install non-stock firmware, in this guilty-until-proven-innocent model, we basically get to choose between two possibilities: get up-to-date software but sacrifice the ability to run some applications, or run increasingly out-of-date 'official' software, for the sake of satisfying a DRM or anti-cheating scheme.

In the end, I decided that the stock firmware still allowed upgrading a lot of the key components via the Google's Play Store, the real core around which an increasing amount of the software in the Android ecosystem relies. Sure, I'm not getting the latest advances in encrypted filesystems, kernel hardening, or process isolation in the latest versions of Android, but it's a tradeoff. Maybe the phone will have died completely by the time the next exploitable bug in libstagefright rears its head.

But, maybe it already has.

It took over a year for enough of the moving parts for a reliable exploit for CVE-2015-3864, one of the 'StageFright' series of vulnerabilities, to come together within Metasploit. The exploit needed new payloads, new techniques, and a number of independent research projects to become useful outside of the proof-of-concept realm. In the end, it works very well, even better than the Metaphor exploit from earlier this year, and can be easily targeted to any vulnerable Nexus phone.

Ironically, the very openness of the Google Nexus ecosystem made porting the exploit to those firmware builds particularly easy. In contrast, Samsung firmware, which contains many proprietary additions to the base Android system, and is not open-source, is harder to target simply because it is harder to examine. In spite of this, it was still possible to target Samsung phones as well. Effectively, with enough effort, any firmware is exploitable. It is just a question of time.

When you think of exploits in the StageFright family, think of the vector: someone sends a special text message and take over a phone without anyone even reading it. You get an email, and without opening it, code is already executed on your device. It's a simple concept, but the fix is not nearly as straightforward.

Automatic parsing of metadata in media files is a commonly-researched and targeted vulnerability in many different products. Adobe flash has had nasty vulnerabilities in its MP3 metadata parsing code earlier this year. Apple iOS has been vulnerable a number of times to similar attacks. Just last month, similar vulnerabilities in Android's libutils library were found, which could be attacked in a similar way.

The exploit that we included in Metasploit for CVE-2015-3864 only targets one vector (web browser) and one file type (MP4 video files). However, there are many other vectors and file types that could also be exploited in the same family, that were discovered around the same time period as CVE-2015-3864. Not only that, but more vectors and file types have been found since the original round of StageFright branded vulnerabilities were hot in the news, and quietly patched.

Of course, none of these patches have made it into the official firmware for my Nexus 4. I even had to do a double-take in researching this article, since Wikipedia claimed Android 5.1.1 was last updated 2 months ago, while I knew the phone hadn't gotten an over-the-air update in some time. To really know if you're up-to-date, you have to look at the build number, Nexus 4 being on LMY48T while the latest is LMY49M. It's unlikely that the average consumer with a phone running Android '5.1.1' would be able to know difference between a vulnerable or up-to-date build number, much less the average business with a bring-your-own-device policy.

The choice between running the software you want, like Pokemon Go, and the quick road to obsolete devices in the Android ecosystem, at best forces users to make a choice between security and functionality. The theoretical exploit chains being patched this year can easily turn into next year's reliable Metasploit module.

Maybe it's time to bring back to a land line.