Entries Tagged "Wi-Fi"

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How Apple's "Find My" Feature Works

Matthew Green intelligently speculates about how Apple’s new “Find My” feature works.

If you haven’t already been inspired by the description above, let me phrase the question you ought to be asking: how is this system going to avoid being a massive privacy nightmare?

Let me count the concerns:

  • If your device is constantly emitting a BLE signal that uniquely identifies it, the whole world is going to have (yet another) way to track you. Marketers already use WiFi and Bluetooth MAC addresses to do this: Find My could create yet another tracking channel.
  • It also exposes the phones who are doing the tracking. These people are now going to be sending their current location to Apple (which they may or may not already be doing). Now they’ll also be potentially sharing this information with strangers who “lose” their devices. That could go badly.
  • Scammers might also run active attacks in which they fake the location of your device. While this seems unlikely, people will always surprise you.

The good news is that Apple claims that their system actually does provide strong privacy, and that it accomplishes this using clever cryptography. But as is typical, they’ve declined to give out the details how they’re going to do it. Andy Greenberg talked me through an incomplete technical description that Apple provided to Wired, so that provides many hints. Unfortunately, what Apple provided still leaves huge gaps. It’s into those gaps that I’m going to fill in my best guess for what Apple is actually doing.

Posted on June 20, 2019 at 12:27 PM • View Comments

Vulnerabilities in the WPA3 Wi-Fi Security Protocol

Researchers have found several vulnerabilities in the WPA3 Wi-Fi security protocol:

The design flaws we discovered can be divided in two categories. The first category consists of downgrade attacks against WPA3-capable devices, and the second category consists of weaknesses in the Dragonfly handshake of WPA3, which in the Wi-Fi standard is better known as the Simultaneous Authentication of Equals (SAE) handshake. The discovered flaws can be abused to recover the password of the Wi-Fi network, launch resource consumption attacks, and force devices into using weaker security groups. All attacks are against home networks (i.e. WPA3-Personal), where one password is shared among all users.

News article. Research paper: “Dragonblood: A Security Analysis of WPA3’s SAE Handshake“:

Abstract: The WPA3 certification aims to secure Wi-Fi networks, and provides several advantages over its predecessor WPA2, such as protection against offline dictionary attacks and forward secrecy. Unfortunately, we show that WPA3 is affected by several design flaws,and analyze these flaws both theoretically and practically. Most prominently, we show that WPA3’s Simultaneous Authentication of Equals (SAE) handshake, commonly known as Dragonfly, is affected by password partitioning attacks. These attacks resemble dictionary attacks and allow an adversary to recover the password by abusing timing or cache-based side-channel leaks. Our side-channel attacks target the protocol’s password encoding method. For instance, our cache-based attack exploits SAE’s hash-to-curve algorithm. The resulting attacks are efficient and low cost: brute-forcing all 8-character lowercase password requires less than 125$in Amazon EC2 instances. In light of ongoing standardization efforts on hash-to-curve, Password-Authenticated Key Exchanges (PAKEs), and Dragonfly as a TLS handshake, our findings are also of more general interest. Finally, we discuss how to mitigate our attacks in a backwards-compatible manner, and explain how minor changes to the protocol could have prevented most of our attack

Posted on April 15, 2019 at 2:00 PM • View Comments

Security Analysis of the LIFX Smart Light Bulb

The security is terrible:

In a very short limited amount of time, three vulnerabilities have been discovered:

  • Wifi credentials of the user have been recovered (stored in plaintext into the flash memory).
  • No security settings. The device is completely open (no secure boot, no debug interface disabled, no flash encryption).
  • Root certificate and RSA private key have been extracted.

Boing Boing post.

Posted on January 30, 2019 at 10:00 AM • View Comments

Counting People through a Wall with Wi-Fi

Interesting research:

In the team’s experiments, one WiFi transmitter and one WiFi receiver are behind walls, outside a room in which a number of people are present. The room can get very crowded with as many as 20 people zigzagging each other. The transmitter sends a wireless signal whose received signal strength (RSSI) is measured by the receiver. Using only such received signal power measurements, the receiver estimates how many people are inside the room ­ an estimate that closely matches the actual number. It is noteworthy that the researchers do not do any prior measurements or calibration in the area of interest; their approach has only a very short calibration phase that need not be done in the same area.

Academic paper.

Posted on September 27, 2018 at 7:43 AM • View Comments

Major Bluetooth Vulnerability

Bluetooth has a serious security vulnerability:

In some implementations, the elliptic curve parameters are not all validated by the cryptographic algorithm implementation, which may allow a remote attacker within wireless range to inject an invalid public key to determine the session key with high probability. Such an attacker can then passively intercept and decrypt all device messages, and/or forge and inject malicious messages.

Paper. Website. Three news articles.

This is serious. Update your software now, and try not to think about all of the Bluetooth applications that can’t be updated.

Posted on July 25, 2018 at 2:08 PM • View Comments

WPA3

Everyone is writing about the new WPA3 Wi-Fi security standard, and how it improves security over the current WPA2 standard.

This summary is as good as any other:

The first big new feature in WPA3 is protection against offline, password-guessing attacks. This is where an attacker captures data from your Wi-Fi stream, brings it back to a private computer, and guesses passwords over and over again until they find a match. With WPA3, attackers are only supposed to be able to make a single guess against that offline data before it becomes useless; they’ll instead have to interact with the live Wi-Fi device every time they want to make a guess. (And that’s harder since they need to be physically present, and devices can be set up to protect against repeat guesses.)

WPA3’s other major addition, as highlighted by the Alliance, is forward secrecy. This is a privacy feature that prevents older data from being compromised by a later attack. So if an attacker captures an encrypted Wi-Fi transmission, then cracks the password, they still won’t be able to read the older data—they’d only be able to see new information currently flowing over the network.

Note that we’re just getting the new standard this week. Actual devices that implement the standard are still months away.

Posted on July 12, 2018 at 6:11 AM • View Comments

Needless Panic Over a Wi-FI Network Name

A Turkish Airlines flight made an emergency landing because someone named his wireless network (presumably from his smartphone) “bomb on board.”

In 2006, I wrote an essay titled “Refuse to be Terrorized.” (I am also reminded of my 2007 essay, “The War on the Unexpected.” A decade later, it seems that the frequency of incidents like the one above is less, although not zero. Progress, I suppose.

Posted on December 1, 2017 at 9:56 AM • View Comments

New KRACK Attack Against Wi-Fi Encryption

Mathy Vanhoef has just published a devastating attack against WPA2, the 14-year-old encryption protocol used by pretty much all Wi-Fi systems. It’s an interesting attack, where the attacker forces the protocol to reuse a key. The authors call this attack KRACK, for Key Reinstallation Attacks.

This is yet another of a series of marketed attacks; with a cool name, a website, and a logo. The Q&A on the website answers a lot of questions about the attack and its implications. And lots of good information in this ArsTechnica article.

There is an academic paper, too:

“Key Reinstallation Attacks: Forcing Nonce Reuse in WPA2,” by Mathy Vanhoef and Frank Piessens.

Abstract: We introduce the key reinstallation attack. This attack abuses design or implementation flaws in cryptographic protocols to reinstall an already-in-use key. This resets the key’s associated parameters such as transmit nonces and receive replay counters. Several types of cryptographic Wi-Fi handshakes are affected by the attack. All protected Wi-Fi networks use the 4-way handshake to generate a fresh session key. So far, this 14-year-old handshake has remained free from attacks, and is even proven secure. However, we show that the 4-way handshake is vulnerable to a key reinstallation attack. Here, the adversary tricks a victim into reinstalling an already-in-use key. This is achieved by manipulating and replaying handshake messages. When reinstalling the key, associated parameters such as the incremental transmit packet number (nonce) and receive packet number (replay counter) are reset to their initial value. Our key reinstallation attack also breaks the PeerKey, group key, and Fast BSS Transition (FT) handshake. The impact depends on the handshake being attacked, and the data-confidentiality protocol in use. Simplified, against AES-CCMP an adversary can replay and decrypt (but not forge) packets. This makes it possible to hijack TCP streams and inject malicious data into them. Against WPA-TKIP and GCMP the impact is catastrophic: packets can be replayed, decrypted, and forged. Because GCMP uses the same authentication key in both communication directions, it is especially affected.

Finally, we confirmed our findings in practice, and found that every Wi-Fi device is vulnerable to some variant of our attacks. Notably, our attack is exceptionally devastating against Android 6.0: it forces the client into using a predictable all-zero encryption key.

I’m just reading about this now, and will post more information as I learn it.

EDITED TO ADD: More news.

EDITED TO ADD: This meets my definition of brilliant. The attack is blindingly obvious once it’s pointed out, but for over a decade no one noticed it.

EDITED TO ADD: Matthew Green has a blog post on what went wrong. The vulnerability is in the interaction between two protocols. At a meta level, he blames the opaque IEEE standards process:

One of the problems with IEEE is that the standards are highly complex and get made via a closed-door process of private meetings. More importantly, even after the fact, they’re hard for ordinary security researchers to access. Go ahead and google for the IETF TLS or IPSec specifications—you’ll find detailed protocol documentation at the top of your Google results. Now go try to Google for the 802.11i standards. I wish you luck.

The IEEE has been making a few small steps to ease this problem, but they’re hyper-timid incrementalist bullshit. There’s an IEEE program called GET that allows researchers to access certain standards (including 802.11) for free, but only after they’ve been public for six months—coincidentally, about the same time it takes for vendors to bake them irrevocably into their hardware and software.

This whole process is dumb and—in this specific case—probably just cost industry tens of millions of dollars. It should stop.

Nicholas Weaver explains why most people shouldn’t worry about this:

So unless your Wi-Fi password looks something like a cat’s hairball (e.g. “:SNEIufeli7rc”—which is not guessable with a few million tries by a computer), a local attacker had the capability to determine the password, decrypt all the traffic, and join the network before KRACK.

KRACK is, however, relevant for enterprise Wi-Fi networks: networks where you needed to accept a cryptographic certificate to join initially and have to provide both a username and password. KRACK represents a new vulnerability for these networks. Depending on some esoteric details, the attacker can decrypt encrypted traffic and, in some cases, inject traffic onto the network.

But in none of these cases can the attacker join the network completely. And the most significant of these attacks affects Linux devices and Android phones, they don’t affect Macs, iPhones, or Windows systems. Even when feasible, these attacks require physical proximity: An attacker on the other side of the planet can’t exploit KRACK, only an attacker in the parking lot can.

EDITED TO ADD (11/13): The official link to the paper blocks anonymous users. Here’s an alternate.

Posted on October 16, 2017 at 8:39 AM • View Comments

Amazon Patents Measures to Prevent In-Store Comparison Shopping

Amazon has been issued a patent on security measures that prevents people from comparison shopping while in the store. It’s not a particularly sophisticated patent—it basically detects when you’re using the in-store Wi-Fi to visit a competitor’s site and then blocks access—but it is an indication of how retail has changed in recent years.

What’s interesting is that Amazon is on the other side of this arms race. As an on-line retailer, it wants people to walk into stores and then comparison shop on its site. Yes, I know it’s buying Whole Foods, but it’s still predominantly an online retailer. Maybe it patented this to prevent stores from implementing the technology.

It’s probably not nearly that strategic. It’s hard to build a business strategy around a security measure that can be defeated with cellular access.

Posted on June 23, 2017 at 6:26 AM • View Comments

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Sidebar photo of Bruce Schneier by Joe MacInnis.