This protocol is the reason users are encouraged to use private or credential-protected Wi-Fi rather than public connections. KRACK affects the third step of the handshake, allowing the attacker to manipulate and replay the WPA2 encryption key to trick it into installing a key already in use.
When the key is reinstalled, other parameters associated with it — the incremental transmit packet number called the nonce and the replay counter — are set to their original values. Rather than move to the fourth step in the four-way handshake, nonce resets continue to replay transmissions of the third step.
This sets up the encryption protocol for attack, and depending on how the attackers replay the third-step transmissions, they can take down Wi-Fi security. Think of all the devices you use that rely on Wi-Fi. It's not just about laptops and smartphones; numerous smart devices now make up the Internet of Things IoT. Because of the vulnerability in WPA2, everything connected to Wi-Fi is at risk of being hacked or hijacked.
Hackers can read emails and view photos of transmitted data and then use that information to blackmail users or sell it on the Dark Web. Theft of stored data requires more steps, such as an HTTP content injection to load malware into the system.
Hackers could conceivably take control of any device used on that Wi-Fi connection. Because the attacks require hackers to be close to the target, these internet security threats could also lead to physical security threats. On the other hand, the need to be in close proximity is the only good news related to KRACK, as that means a widespread attack would be extremely difficult.
Note that for all tests, once the script is running, you must let the device being tested connect to the SSID testnetwork using the password abcdefgh. This tests whether the client accepts replayed broadcast frames.
If the client accepts replayed broadcast frames, this must be patched first. If you do not patch the client, our script will not be able to determine if the group key is being reinstalled because then the script will always say the group key is being reinstalled.
This tests whether the client installs the group key in the group key handshake with the given receive sequence counter RSC. See section 6. This tests whether the client reinstalls the group key in the group key handshake. In other words, it tests if the client is vulnerable to CVE Note that if the client always accepts replayed broadcast frames see --replay-broadcast , this test might incorrectly conclude the group key is being reinstalled.
This tests for key reinstallations in the 4-way handshake by repeatedly sending encrypted message 3's to the client. The script monitors traffic sent by the client to see if the pairwise key is being reinstalled.
Note that this effectively performs two tests: whether the pairwise key is reinstalled, and whether the group key is reinstalled. To assure the client is sending enough unicast frames, you can optionally ping the AP: ping Identical to test 4, except that a forged message 1 is injected before sending the encrypted message 3. This variant of the test is important because some clients e.
Same as the above test, except that the forged message 1 contains a random ANonce. This tests whether the client installs the group key in the 4-way handshake with the given receive sequence counter RSC. The script will continously execute new 4-way handshakes to test this. Unfortunately, this test can be rather unreliable, because any missed handshake messages cause synchronization issues, making the test unreliable.
You should only execute this test in environments with little background noise, and execute it several times. The most important test is. Perform these tests in a room with little interference.
A high amount of packet loss will make this script less reliable! Optionally you can manually inspect network traffic to confirm the output of the script some Wi-Fi NICs may interfere with our scripts :. In particular, check whether replayed broadcast frames indeed are sent using an already used packet number IV. Capture traffic on the client to see if the replayed broadcast ARP requests are accepted or not. All unrecognized parameters are passed on to hostapd, so you can include something like -dd -K to make hostapd output all debug info.
The Wi-Fi Alliance created a custom vulnerability detection tool based on our scripts. At the time of writing, this tool is only accessible to Wi-Fi Alliance members.
Their tools supports several different tests, and these tests correspond to the functionality in our script as follows:. We currently do not support this test. This test is not necessary anyway. Make sure the device being tested passes test 4. We currently do not suppor this test. Again, make sure the device being tested passes test 4. This corresponds to. The following Common Vulnerabilities and Exposures CVE identifiers were assigned to track which products are affected by specific instantiations of our key reinstallation attack:.
Note that each CVE identifier represents a specific instantiation of a key reinstallation attack. Although this paper is made public now, it was already submitted for review on 19 May After this, only minor changes were made. As a result, the findings in the paper are already several months old. In the meantime, we have found easier techniques to carry out our key reinstallation attack against the 4-way handshake. With our novel attack technique, it is now trivial to exploit implementations that only accept encrypted retransmissions of message 3 of the 4-way handshake.
This was discovered by John A. Van Boxtel. As a result, all Android versions higher than 6. The new attack works by injecting a forged message 1, with the same ANonce as used in the original message 1, before forwarding the retransmitted message 3 to the victim. Please cite our research paper and not this website or cite both. You can use the following example citation or bibtex entry:.
Mathy Vanhoef and Frank Piessens. We have made scripts to detect whether an implementation of the 4-way handshake, group key handshake, or Fast BSS Transition FT handshake is vulnerable to key reinstallation attacks. These scripts are available on github , and contain detailed instructions on how to use them.
We also made a proof-of-concept script that exploits the all-zero key re installation present in certain Android and Linux devices. This script is the one that we used in the demonstration video. It will be released once everyone has had a reasonable chance to update their devices and we have had a chance to prepare the code repository for release.
We remark that the reliability of our proof-of-concept script may depend on how close the victim is to the real network. If the victim is very close to the real network, the script may fail because the victim will always directly communicate with the real network, even if the victim is forced onto a different Wi-Fi channel than this network.
Yes there is. And a big thank you goes to Darlee Urbiztondo for conceptualizing and designing the logo! No, luckily implementations can be patched in a backwards-compatible manner. This means a patched client can still communicate with an unpatched access point AP , and vice versa.
In other words, a patched client or access point sends exactly the same handshake messages as before, and at exactly the same moment in time. However, the security updates will assure a key is only installed once, preventing our attack. So again, update all your devices once security updates are available. Finally, although an unpatched client can still connect to a patched AP, and vice versa, both the client and AP must be patched to defend against all attacks! Changing the password of your Wi-Fi network does not prevent or mitigate the attack.
So you do not have to update the password of your Wi-Fi network. Instead, you should make sure all your devices are updated, and you should also update the firmware of your router. Nevertheless, after updating both your client devices and your router, it's never a bad idea to change the Wi-Fi password.
Yes, that network configuration is also vulnerable. So everyone should update their devices to prevent the attack! I use the word "we" because that's what I'm used to writing in papers. In practice, all the work is done by me, with me being Mathy Vanhoef. My awesome supervisor is added under an honorary authorship to the research paper for his excellent general guidance.
But all the real work was done on my own. So the author list of academic papers does not represent division of work :. Any device that uses Wi-Fi is likely vulnerable. Contact your vendor for more information, or consult this community maintained list on GitHub. First, the FT handshake is part of Additionally, most home routers or APs do not support or will not use client functionality. In other words, your home router or AP likely does not require security updates. Instead, it are mainly enterprise networks that will have to update their network infrastructure i.
That said, some vendors discovered implementation-specific security issues while investigating our attack. For example, it was discovered that hostapd reuses the ANonce value in the 4-way handshake during rekeys.
Concretely this means that, even if your router or AP does not support Contact your vendor for more details. Finally, we remark that you can try to mitigate attacks against routers and APs by disabling client functionality which is for example used in repeater modes and disabling Additionally, update all your other client devices such as laptops and smartphones.
If one or more of your client devices is not receiving updates, you can also try to contact your router's vendor and ask if they have an update that prevents attacks against connected devices.
Currently, all vulnerable devices should be patched. In other words, patching the AP will not prevent attacks against vulnerable clients. Similarly, patching all clients will not prevent attacks against vulnerable access points.
That said, it is possible to modify the access point such that vulnerable clients when connected to this AP cannot be attacked. However, these modifications are different from the normal security patches that are being released for vulnerable access points!
So unless your access point vendor explicitly mentions that their patches prevent attacks against clients, you must also patch clients. It's possible to modify the access point router such that connected clients are not vulnerable to attacks against the 4-way handshake and group key handshake. Note that we consider these two attacks the most serious and widespread security issues we discovered.
However, these modifications only prevent attacks when a vulnerable client is connected to such a modified access point. When a vulnerable client connects to a different access point, it can still be attacked.
Technically, this is accomplished by modifying the access point such that it does not retransmit message 3 of the 4-way handshake. Additionally, the access point is modified to not retransmit message 1 of the group key handshake. The hostapd project has such a modification available. They are currently evaluating to which extend this impacts the reliability of these handshakes. We remark that the client-side attacks against the 4-way handshake and group key handshake can also be prevented by retransmitting the above handshake messages using the same previous EAPOL-Key replay counter.
The attack against the group key handshake can also be prevented by letting the access point install the group key in a delayed fashion, and by assuring the access point only accepts the latest replay counter see section 4. On some products, variants or generalizations of the above mitigations can be enabled without having to update products.
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