Date: Wed, 8 Aug 2018 17:33:00 +0200 From: Jens Timmerman <jens.timmerman@...il.com> To: oss-security@...ts.openwall.com Subject: Re: Unauthenticated EAPOL-Key decryption in wpa_supplicant I have to ask since this was only published 4 days ago and also describes an attack on the EAPOL frames Is this in any way related to atom's new attack on WPA/WPA2 using PMKID, https://hashcat.net/forum/thread-7717.html As far as I can see these are 2 different attacks? Regards, Jens Timmerman On 8 August 2018 at 16:22, Jouni Malinen <j@...fi> wrote: > Published: August 8, 2018 > Identifiers: > - CVE-2018-14526 > Latest version available from: https://w1.fi/security/2018-1/ > > Vulnerability > > A vulnerability was found in how wpa_supplicant processes EAPOL-Key > frames. It is possible for an attacker to modify the frame in a way that > makes wpa_supplicant decrypt the Key Data field without requiring a > valid MIC value in the frame, i.e., without the frame being > authenticated. This has a potential issue in the case where WPA2/RSN > style of EAPOL-Key construction is used with TKIP negotiated as the > pairwise cipher. It should be noted that WPA2 is not supposed to be used > with TKIP as the pairwise cipher. Instead, CCMP is expected to be used > and with that pairwise cipher, this vulnerability is not applicable in > practice. > > When TKIP is negotiated as the pairwise cipher, the EAPOL-Key Key Data > field is encrypted using RC4. This vulnerability allows unauthenticated > EAPOL-Key frames to be processed and due to the RC4 design, this makes > it possible for an attacker to modify the plaintext version of the Key > Data field with bitwise XOR operations without knowing the contents. > This can be used to cause a denial of service attack by modifying > GTK/IGTK on the station (without the attacker learning any of the keys) > which would prevent the station from accepting received group-addressed > frames. Furthermore, this might be abused by making wpa_supplicant act > as a decryption oracle to try to recover some of the Key Data payload > (GTK/IGTK) to get knowledge of the group encryption keys. > > Full recovery of the group encryption keys requires multiple attempts > (128 connection attempts per octet) and each attempt results in > disconnection due to a failure to complete the 4-way handshake. These > failures can result in the AP/network getting disabled temporarily or > even permanently (requiring user action to re-enable) which may make it > impractical to perform the attack to recover the keys before the AP has > already changes the group keys. By default, wpa_supplicant is enforcing > at minimum a ten second wait time between each failed connection > attempt, i.e., over 20 minutes waiting to recover each octet while > hostapd AP implementation uses 10 minute default for GTK rekeying when > using TKIP. With such timing behavior, practical attack would need large > number of impacted stations to be trying to connect to the same AP to be > able to recover sufficient information from the GTK to be able to > determine the key before it gets changed. > > > Vulnerable versions/configurations > > All wpa_supplicant versions. > > > Acknowledgments > > Thanks to Mathy Vanhoef of the imec-DistriNet research group of KU > Leuven for discovering and reporting this issue. > > > Possible mitigation steps > > - Remove TKIP as an allowed pairwise cipher in RSN/WPA2 networks. This > can be done also on the AP side. > > - Merge the following commits to wpa_supplicant and rebuild: > > WPA: Ignore unauthenticated encrypted EAPOL-Key data > > This patch is available from https://w1.fi/security/2018-1/ > > - Update to wpa_supplicant v2.7 or newer, once available > > -- > Jouni Malinen PGP id EFC895FA >
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