Security Review: HomeLink Universal Transceiver

By vincez at 10:45 pm on February 13, 2009Comments Off on Security Review: HomeLink Universal Transceiver

The HomeLink Universal Transceiver is a device that, like a universal remote, can record the output of a wide variety of garage door openers and home automation control systems and emulate the output for future use. When used as advertised, the HomeLink system simply replays signals that you could have produced anyway, but from a central source. However, since the HomeLink device basically allows replay attacks, there are security implications if the device is to be used by someone with sinister intentions.

Community gate openers and garage door openers are, by their very design, long-range communication devices. If the signal the opener emits cannot be detected a good distance away, the devuce is not doing its job. Therefore, it follows that the HomeLink device could record garage door opener signals while passing by a car that is using a garage door opener. With access to many types of garage doors after being in the proximity of the door opening, a world of possibilities opens up.

Assets / Security Goals
– Gated communities. Many high-rent communities are protected by outside gates that, in theory, prevent any unauthorized people from even getting close to the homes in the communities. Although gates can be bypassed, for example by tailgating in, this requires a witness.
– Garage doors. Garage doors are ubiquitous throughout Americana. Opening them often leads to the nicest cars a family owns, unlocked interior doors, and many expensive shop tools and other items.
– Home automation systems. These systems can turn on and off music, lights, and other household appliances. Controlling advanced home automation systems can give someone — legitimate or otherwise — nearly full control over the systems inside of a house.
– Home and family security. A home is a trusted place where people and their belongings are thought to be generally safe and secure.

Potential Adversaries / Threats
– Burglars / Larceny. An obvious threat is being robbed. The HomeLink system can be used to gain access to garages, which often house expensive items, and often include unlocked doors to the interior of the rest of the house.
– Kidnappers / Hostage taking. In addition to being robbed, people within the home may be taken hostage or kidnapped.
– Home automation denial of service / attack. An attacker could prevent control or gain control of a home automation system, causing it to be unusable or go haywire, or activate unwanted systems (such as very loud music), or deactivate wanted systems (such as lights).

Potential Weaknesses
– Universal transceiver with insider knowledge of encrypted protocols. The Homelink system advertises that due to their relationships with manufacturers, the HomeLink device can be programmed with “encrypted” garage door systems. This makes it an attractive tool to use for a potential attacker of these types of systems.
– Necessarily a long-range device where the attacker does not have to be visible. As discussed in the introduction, these devices by their very nature are long distance. The attacker could record an open signal while driving by, or while hidden in a nearby place (behind bushes, around a corner, etc).

Potential Defenses
– Use an unsupported system (may become supported in future)
While using a system that is not supported by HomeLink works for the present, HomeLink will likely support more systems in the future, as this increases their potential customer base.
– Require second authentication factor (HomeLink may support both already, or may change to support both)
Going along with the idea of defense in depth, requiring a second authentication factor (ie, a PIN number) may increase security. However, depending on the sophistication of the original device and of HomeLink’s system, even this may not be sufficient.
– Design system with only limited trust (ie, lock door inside garage)
Trusting anyone who can gain access to the gated community or your garage is probably not the best security solution. Instead, trust such people only with access to the garage, and place additional security measures to prevent access to more sensitive/private parts of the home. This is once again defense in depth.

Evaluation of Risks

The risks associated with this technology are quite serious. In fact, they are very different from typical risks of other technologies. In regard to privacy and security in the general technology product sense, a successful breach often means an adversary can gain personal information about the victim or can deny them correct service from some sort of device. A security breach with the HomeLink typically means an adversary has free access to the victim’s residence, and their physical well-being is jeopardized. This is (arguably) the most important asset to any human being. This puts the risks of this technology in the highest category, and it’s quite clear that the accompanying defenses are not up to par with the seriousness of these risks.

Another factor dramatically increasing the risks with this technology is the ease of which the above-described attacks could be mounted. Again, speaking comparatively to other technologies, an attacker almost always is limited to someone with a high level of expertise in some part of the field of computing. With the HomeLink, virtually anybody would be able to use it to gain access to a victim’s physical premises. Increasing the pool of people with the ability to launch an attack inevitably increases the total number of attacks, and with the pool of able attackers being nearly the entire population, the assessed threats come with significantly higher associated risk.

One avenue of the vulnerability of the HomeLink that lowers the security risk is the way in which attacks must be carried out. When a security vulnerability is exploitable by computer experts working in the comfort of their living room (or their parents’ basement), the adversary has their own sense of security and anonymity. Also, they are typically attacking a nameless, faceless individual that they will never have to actually see. Attackers using the HomeLink to gain access to people’s homes put themselves in a great deal more exposure and risk, and in a situation many otherwise would-be attackers are not comfortable. This eliminates the attacker who has nothing better to do with their computer and is simply bored. Unfortunately, this also means that the attacks that are launched are deliberate and well thought-through, and are most likely of the very dangerous variety. In a sense, the attacks using the HomeLink are likely to come from the least ethical people, lowering the number of potential attackers, but increasing the risk of the attack being more malicious.

Conclusion

In summary, the HomeLink is a potentially dangerous device. It is a seemingly innocuous piece of technology, but the risks associated with its assets are of the highest magnitude. Nothing is more important for a product to protect than personal physical safety, and the HomeLink can be used to directly jeopardize victims’ well-being.  What’s more, this device poses a threat to the privacy and security of users who don’t own it and don’t use it. Without using the defenses described above, every person with an automatic garage door or gate is vulnerable just because of the existence of the HomeLink. The set of people with the ability to use the device maliciously is extraordinarily large, as is the set of potential victims. These potential threats and vulnerabilities are something the manufacturer will hopefully take into serious consideration.

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