Popular Home Automation System Backdoored Via Unpatched Flaw

[UPDATED 4/17/15 at 9:00am with comments from Vera]

Billy Rios plans to demonstrate with a game of Pac-Man an attack on a long-known vulnerability in a popular home automation controller.

The security researcher, next week at the RSA Conference in San Francisco, will show an exploit he created that replaces the device's firmware with malicious code that means game over for the device -- literally, in this case, with a Pac-Man application.

The exploit demonstrates how an attacker could abuse a cross-site request forgery (CSRF) flaw first reported in 2013 by TrustWave SpiderLabs, CVE-2013-4861, in the Vera Smart Home Controller and completely own the smart home device, as well as infiltrate the home network and attached computers.

Rios, founder of Laconicly LLC, says the bug would allow an attacker to update his own firmware to the device. The attack begins when a user on the home network visits a website infected with a malvertising exploit, for example, which then redirects the Vera device to the attacker's server, silently installing the malicious code. It turns off the legitimate firmware update mechanisms for the home automation controller, with the consumer being none the wiser.

The home automation controller is a hub of sorts for home automation functions, such as controlling lights, HVAC systems, and garage-door openers.

"Firmware is the brains of the device. What we can do is remotely point it [the device] to an update from us" representing the attacker, says Rios, who tested the product in its default settings mode. "Once they're compromised, there's no way to tell they've been compromised … It's pretty much 'game over' for the device."

When TrustWave reported this and other vulnerabilities to Vera some 18 months ago, the company responded that it had no plans to fix the issue, which was "deliberate" in its design:  "...the 'vulnerabilities' you referred to were deliberate design decisions because that's what the customers in this particular channel (ie Vera retail) want. As you can see, we have an open forum to discuss this, and very people object to leaving Vera open. So we are not able to lock down the gateway, and effectively break the systems of many customers who rely on the open system to run their own scripts and plugins."

Vera's response echoes a similar theme with other Internet of Things (IoT) vendors whose products have been exposed carrying security bugs. Cesar Cerrudo, CTO at IOActive, ran into the same response last year when he reported firmware update flaws in Sensys Networks wireless smart traffic system sensors. In that case, the issue was unencrypted updates that could be hijacked with malware:  Sensys maintained that it had removed encryption because its customers had requested it.

Vera, which is based in Hong Kong, says a new feature in the newer version of the firmware called "secure to click" would mitigate such an attack. 

Rios' research was on the newest version of the software, which contains the CSRF flaw, he says. He says he tested it with the default settings in place because that's how most customers would typically run it out of the box.

Meanwhile, Rios says his firmware backdoor exploit demonstrates just how "punishing" the CSRF vulnerability in Vera's firmware update process really is. Plus the device itself doesn't validate firmware, leaving it vulnerable to malicious code. "Firmware integrity isn't validated anywhere," he says.

The Pac-Man application is mainly a lighthearted way for Rios to demonstrate that the Vera firmware has been replaced. "And I'm going to play one round of Pac-Man for the crowd," he says.

Once in control of the home automation controller, an attacker basically becomes an access point on the home network. "Having a foothold into the home network is pretty bad. They can attack you and other devices on the network," Rios says.

An attacker would need some knowledge of the device, Rios notes, such that his rogue firmware wouldn't merely break the device rather than backdoor it.

Other home automation controllers harbor similar weaknesses, Rios says, and he's demonstrating Vera's because it's a publicly reported bug.

"I think one of the things we're seeing is many of these vendors in IoT don't really understand the classes of attacks we're dealing with," he says. "They have to fix these bugs; they are pretty trivial to exploit."

Adding firmware- and application code verification would prevent this type of an attack, akin to how Apple only allows signed apps or firmware to download and run on an iPhone, he says. "It's not magic."

Rios also has built a Metasploit module for the attack. "All it does is push the backdoor firmware update. It allows us to specify the server where your firmware updates come from," he says.