TL;DR
Yes, an attacker can potentially recover a WPA2 passphrase if they have access to the WPA key data (PMKID) and the WPA MIC. This is because these pieces of information can be used in offline cracking attempts using tools like Hashcat or Aircrack-ng.
Understanding the Problem
WPA2 security relies on a four-way handshake to establish a secure connection between a client and an access point. The core secret is the Pairwise Master Key (PMK). The PMKID is derived from this key, and the MIC (Message Integrity Check) verifies the integrity of the handshake. If an attacker captures enough information during this process – specifically the PMKID and MIC – they can attempt to crack the passphrase offline.
Steps to Recover the Passphrase
- Capture the WPA2 Handshake: This is usually done using tools like Aircrack-ng. You need to deauthenticate a client connected to the target network to force it to re-establish the connection, capturing the handshake data in the process.
- Extract PMKID and MIC: Once you have the capture file (.cap), use tools like Wireshark or tshark to extract the PMKID and MIC from the 4-way handshake packets. The exact method depends on the network configuration, but generally involves filtering for WPA2 traffic and examining the EAPOL frames.
tshark -r capture.cap -Y "wpa2" | grep "PMKID" - Offline Cracking with Hashcat: Hashcat is a powerful password cracking tool that supports various hash types, including those used in WPA/WPA2 security.
- Convert the PMKID to a Hashcat-compatible format: Use tools like pmkid_to_hashcat.py (often included with Aircrack-ng) or similar scripts to convert the captured PMKID into a hash that Hashcat can understand.
- Run Hashcat with a Wordlist: Provide Hashcat with a wordlist containing potential passphrases. The larger and more comprehensive the wordlist, the higher the chance of success.
hashcat -m 32000 --attack-mode 0 - Consider using a Mask Attack: If you have some knowledge about the passphrase structure (e.g., length, character types), use a mask attack to reduce the search space.
hashcat -m 32000 --attack-mode 1 ?d?d?d?d?d?d
- Offline Cracking with Aircrack-ng (aircrack-ng wpa2-psk): While Hashcat is generally more efficient, aircrack-ng can also be used for offline cracking.
aircrack-ng -w - Analyze Results: If Hashcat or Aircrack-ng finds a match, it will display the recovered passphrase.
Mitigation Strategies
- Use Strong Passphrases: Employ long and complex passphrases that are difficult to guess.
- Enable WPA3: If your hardware supports it, switch to WPA3 for improved security features.
- Regularly Change Passphrases: Periodically update your Wi-Fi passphrase to reduce the risk of compromise.
- Monitor Network Traffic: Use intrusion detection systems (IDS) to detect and prevent unauthorized access attempts.