Cracking the password for WPA2 networks has been roughly the same for many years, but a new attack requires less interaction and information than previous techniques and has the added advantage of being able to target access points with no one connected. This new attack against the PMKID uses Hashcat to mod WPA passwords and allows hackers to find networks with weak passwords more easily.
The Old Way to Crack WPA2 Passwords
The old way of cracking WPA2 has been along quite some time and involves momentarily disconnecting a connected device from the access point we want to try to mod. This has two downsides which are important for Wi-Fi hackers to understand.
The first downside is the requirement that someone is connected to the network to attack it. The network password might be weak and very easy to break, but without a device connected to briefly kick off, there is no opportunity to capture a handshake, thus no chance to try cracking it.
The second downside of this tactic is that it’s noisy and legally troubling in that it forces you to send packets that deliberately disconnect an authorized user for a service they are paying to use. This kind of unauthorized interference is technically a denial-of-service attack and, if sustained, is equivalent to jamming a network. This can get you into trouble and is easily detectable by some of our previous guides.
A New Method of Password Cracking
Rather than relying on intercepting two-way communications between Wi-Fi devices to try cracking the password, an attacker can communicate directly with a vulnerable access point using the new method. On Aug. 4, 2018, a post on the Hashcat forum detailed a new technique leveraging an attack against the RSN IE (Robust Security Network Information Element) of a single EAPOL frame to capture the needed information to attempt a brute-force attack.
Similar to the previous attacks against WPA, the attacker must be in proximity to the network they wish to attack. The objective will be to use a Kali-compatible wireless network adapter to capture the information needed from the network to try brute-forcing the password. Rather than using Aireplay-ng or Aircrack-ng, we’ll be using a new wireless attack tool to do this called hcxtools.
Using Hcxtools & Hashcat
Hcxdumptool and hcxpcaptool are tools written for Wi-Fi auditing and penetration testing, and they allow us to interact with nearby Wi-Fi networks to capture WPA handshakes and PMKID hashes. It works similar to Besside-ng in that it requires minimal arguments to start an attack from the command line, can be run against either specific targets or targets of convenience, and can be executed easily over SSH on a Raspberry Pi or another device without a screen.
Once the PMKID is captured, the next step is to load the hash into Hashcat and attempt to mod the password. This is where hcxtools differs from Besside-ng, in that a conversion step is required in order to prepare the file for Hashcat to use. We’ll use hcxpcaptool to convert our PCAPNG file into one Hashcat can work with, leaving only the step of selecting a strong list of passwords for your brute-forcing attempts.
It’s worth mentioning that not every network is vulnerable to this attack. Because this is an optional field added by some manufacturers, you should not expect universal success with this technique. Whether you are able to capture the PMKID depends on if the manufacturer of the access point did you the favor of including an element that includes it, and whether you can mod the captured PMKID depends on if the underlying password is contained in your brute-force password list. If either condition is not met, this attack will fail.
To try this attack, you’ll need to be running Kali Linux and have access to a wireless network adapter that supports monitor mode and packet injection. We have several guides about selecting a compatible wireless network adapter below.
Aside from a Kali-compatible network adapter, make sure that you’ve fully updated and upgraded your system. If you don’t, some packages can be out of date and cause issues while capturing.
First, we’ll install the tools we need. To download , type the following into a terminal window.
git clone https://github.com/ZerBea/hcxdumptool.git cd hcxdumptool make make install
When this finishes installing, we’ll move onto installing hxctools. To do this, open a terminal window and paste the following line by line. If you get an error, try typing sudo before the command.
cd git clone https://github.com/ZerBea/hcxtools.git cd hxctools make make install
Finally, we’ll need to install Hashcat. This should be easy, as it’s included in the Kali Linux repo by default. Simply type the following to install the latest version of Hashcat.
apt install hashcat
With this complete, we can move on to setting up the wireless network adapter.
After plugging in your Kali-compatible wireless network adapter, you can find the name by typing ifconfig or ip a. Typically, it will be named something like wlan0. The first step will be to put the card into wireless monitor mode, allowing us to listen in on Wi-Fi traffic in the immediate area.
To do this, type the following command into a terminal window, substituting the name of your wireless network adapter for wlan0.
airmon-ng start wlan0 Found 3 processes that could cause trouble Kill them using ‘airmon-ng check kill’ before putting the card in monitor mode, they will interfere by changing channels and sometimes putting the interface back in managed mode PID Name 555 NetworkManager 611 wpa_supplicant 6636 dhclient PHY Interface Driver Chipset phy0 wlan0 ath9k Qualcomm Atheros QCA9565 / AR9565 Wireless Network Adapter (rev 01) (mac80211 monitor mode vif enabled for [phy0]wlan0 on [phy0]wlan0mon) (mac80211 station mode vif disabled for [phy0]wlan0) phy1 wlan1 ath9k_htc Atheros Communications, Inc. AR9271 802.11n
Now, your wireless network adapter should have a name like “wlan0mon” and be in monitor mode. You can confirm this by running ifconfig again.
Now we are ready to capture the PMKIDs of devices we want to try attacking. With our wireless network adapter in monitor mode as “wlan1mon,” we’ll execute the following command to begin the attack.
hcxdumptool -i wlan1mon -o galleria.pcapng –enable__status=1
Breaking this down, -i tells the program which interface we are using, in this case, wlan1mon. The file name we’ll be saving the results to can be specified with the -o flag argument. The channel we want to scan on can be indicated with the -c flag followed by the number of the channel to scan.
In our command above, we’re using wlan1mon to save captured PMKIDs to a file called “galleria.pcapng.” While you can specify another status value, I haven’t had success capturing with any value except 1.
warning: NetworkManager is running with pid 555 warning: wpa_supplicant is running with pid 611 warning: wlan1mon is probably a monitor interface start capturing (stop with ctrl+c) INTERFACE:……………: wlan1mon FILTERLIST……………: 0 entries MAC CLIENT……………: fcc233ca8bc5 MAC ACCESS POINT………: 10ae604b9e82 (incremented on every new client) EAPOL TIMEOUT…………: 150000 REPLAYCOUNT…………..: 62439 ANONCE……………….: d8dd2206c82ad030e843a39e8f99281e215492dbef56f693cd882d4dfcde9956 [22:17:32 – 001] c8b5adb615ea -> fcc233ca8bc5 [FOUND PMKID CLIENT-LESS] [22:17:32 – 001] c8b5adb615e9 -> fcc233ca8bc5 [FOUND PMKID CLIENT-LESS] [22:17:33 – 001] 2c95694f3ca0 -> fcc233ca8bc5 [FOUND PMKID CLIENT-LESS] [22:17:33 – 001] 2c95694f3ca0 -> b4b686abc81a [FOUND PMKID] [22:17:48 – 011] 14edbb9938ea -> fcc233ca8bc5 [FOUND PMKID CLIENT-LESS] [22:17:48 – 011] 88964e3a8ea0 -> fcc233ca8bc5 [FOUND PMKID CLIENT-LESS] [22:17:49 – 011] dc7fa425888a -> fcc233ca8bc5 [FOUND PMKID CLIENT-LESS] [22:17:51 – 011] 88964e801fa0 -> fcc233ca8bc5 [FOUND PMKID CLIENT-LESS] [22:17:57 – 001] 9822efc6fdff -> ba634d3eb80d [EAPOL 4/4 – M4 RETRY ATTACK] [22:17:57 – 001] 9822efc6fdff -> ba634d3eb80d [FOUND HANDSHAKE AP-LESS, EAPOL TIMEOUT 6696] [22:18:04 – 011] 803773defd01 -> fcc233ca8bc5 [FOUND PMKID CLIENT-LESS] [22:19:21 – 011] 14edbb9ba0e6 -> 803773defd01 [FOUND AUTHORIZED HANDSHAKE, EAPOL TIMEOUT 15247] [22:19:34 – 006] 0618d629465b -> 58fb8433aac2 [FOUND AUTHORIZED HANDSHAKE, EAPOL TIMEOUT 2832] [22:19:42 – 005] e0220203294e -> fcc233ca8bc5 [FOUND PMKID CLIENT-LESS] [22:19:57 – 011] 14edbb9ba0e6 -> fcc233ca8bc5 [FOUND PMKID CLIENT-LESS] [22:20:02 – 008] 14edbbd29326 -> fcc233ca8bc5 [FOUND PMKID CLIENT-LESS] [22:20:04 – 008] 1c872c707c60 -> 78e7d17791e7 [FOUND PMKID] [22:20:11 – 009] e0220453a576 -> fcc233ca8bc5 [FOUND PMKID CLIENT-LESS] [22:20:27 – 001] ace2d32602da -> c8665d5dd654 [FOUND HANDSHAKE AP-LESS, EAPOL TIMEOUT 5202] INFO: cha=2, rx=32752, rx(dropped)=2801, tx=2205, powned=18, err=0
When you’ve gathered enough, you can stop the program by typing Ctrl-C to end the attack. This should produce a PCAPNG file containing the information we need to attempt a brute-forcing attack, but we will need to convert it into a format Hashcat can understand.
To convert our PCAPNG file, we’ll use hcxpcaptool with a few arguments specified. In the same folder that your .PCAPNG file is saved, run the following command in a terminal window.
hcxpcaptool -E essidlist -I identitylist -U usernamelist -z galleriaHC.16800 galleria.pcapng
This command is telling hxcpcaptool to use the information included in the file to help Hashcat understand it with the -E, -I, and -U flags. The -Z flag is used for the name of the newly converted file for Hashcat to use, and the last part of the command is the PCAPNG file we want to convert.
Running the command should show us the following.
summary: ——– file name………………..: galleria.pcapng file type………………..: pcapng 1.0 file hardware information….: x86_64 file os information……….: Linux 4.18.0-kali2-amd64 file application information.: hcxdumptool 4.2.1 network type……………..: DLT_IEEE802_11_RADIO (127) endianess………………..: little endian read errors………………: flawless packets inside……………: 1089 skipped packets…………..: 0 packets with GPS data……..: 0 packets with FCS………….: 732 beacons (with ESSID inside)..: 49 probe requests……………: 26 probe responses…………..: 40 association requests………: 103 association responses……..: 204 reassociation requests…….: 2 reassocaition responses……: 7 authentications (OPEN SYSTEM): 346 authentications (BROADCOM)…: 114 authentications (APPLE)……: 1 EAPOL packets…………….: 304 EAPOL PMKIDs……………..: 21 best handshakes…………..: 4 (ap-less: 1) 21 PMKID(s) written to galleriahC.16800
Here, we can see we’ve gathered 21 PMKIDs in a short amount of time. Now we can use the “galleriaHC.16800” file in Hashcat to try cracking network passwords.
To start attacking the hashes we’ve captured, we’ll need to pick a good password list. You can find several good password lists to get started over at the SecList collection. Once you have a password list, put it in the same folder as the .16800 file you just converted, and then run the following command in a terminal window.
hashcat -m 16800 galleriaHC.16800 -a 0 –kernel-accel=1 -w 4 –force ‘topwifipass.txt’
In this command, we are starting Hashcat in 16800 mode, which is for attacking WPA-PMKID-PBKDF2 network protocols. Next, we’ll specify the name of the file we want to mod, in this case, “galleriaHC.16800.” The -a flag tells us which types of attack to use, in this case, a “straight” attack, and then the -w and –kernel-accel=1 flags specifies the highest performance workload profile. If your computer suffers performance issues, you can lower the number in the -w argument.
Next, the –force option ignores any warnings to proceed with the attack, and the last part of the command specifies the password list we’re using to try to brute force the PMKIDs in our file, in this case, called “topwifipass.txt.”
Depending on your hardware speed and the size of your password list, this can take quite some time to complete. To see the status at any time, you can press the S key for an update.
As Hashcat cracks away, you’ll be able to check in as it progresses to see if any keys have been recovered.
When the password list is getting close to the end, Hashcat will automatically adjust the workload and give you a final report when it’s complete.
Approaching final keyspace – workload adjusted. Session……….: hashcat Status………..: Exhausted Hash.Type……..: WPA-PMKID-PBKDF2 Hash.Target……: hotspotcap.16800 Time.Started…..: Sun Oct 28 18:05:57 2018 (3 mins, 49 secs) Time.Estimated…: Sun Oct 28 18:09:46 2018 (0 secs) Guess.Base…….: File (topwifipass.txt) Guess.Queue……: 1/1 (100.00%) Speed.Dev.#1…..: 42 H/s (15.56ms) @ Accel:1 Loops:1024 Thr:1 Vec:4 Recovered……..: 0/2 (0.00%) Digests, 0/2 (0.00%) Salts Progress………: 9602/9602 (100.0%) Rejected………: 2/9602 (0.02%) Restore.Point….: 4801/4801 (100.0%) Candidates.#1….: 159159159 -> 00001111 HWon.Dev.#1……: N/A Started: Sun Oct 28 18:05:56 2018 Stopped: Sun Oct 28 18:09:49 2018
If you’ve managed to mod any passwords, you’ll see them here. In our test run, none of the PMKIDs we gathered contained passwords in our password list, thus we were unable to mod any of the hashes. This will most likely be your result too against any networks with a strong password but expect to see results here for networks using a weak password.
The PMKID Hashcat Attack Makes Wi-Fi Attacks Easier
While the new attack against Wi-Fi passwords makes it easier for hackers to attempt an attack on a target, the same methods that were effective against previous types of WPA cracking remain effective. If your network doesn’t even support the robust security element containing the PMKID, this attack has no chance of success. You can audit your own network with hcxtools to see if it is susceptible to this attack.
Even if your network is vulnerable, a strong password is still the best defense against an attacker gaining access to your Wi-Fi network using this or another password cracking attack.
Because these attacks rely on guessing the password the Wi-Fi network is using, there are two common sources of guesses; The first is users picking default or outrageously bad passwords, such as “12345678” or “password.” These will be easily cracked. The second source of password guesses comes from data breaches that reveal millions of real user passwords. Because many users will reuse passwords between different types of accounts, these lists tend to be very effective at cracking Wi-Fi networks.
I hope you enjoyed this guide to the new PMKID-based Hashcat attack on WPA2 passwords!