AP mode PMF disconnection protection bypass
Published: September 11, 2019
Identifiers:
- CVE-2019-16275
Latest version available from: https://w1.fi/security/2019-7/
Vulnerability
hostapd (and wpa_supplicant when controlling AP mode) did not perform
sufficient source address validation for some received Management frames
and this could result in ending up sending a frame that caused
associated stations to incorrectly believe they were disconnected from
the network even if management frame protection (also known as PMF) was
negotiated for the association. This could be considered to be a denial
of service vulnerability since PMF is supposed to protect from this type
of issues. It should be noted that if PMF is not enabled, there would be
no protocol level protection against this type of denial service
attacks.
An attacker in radio range of the access point could inject a specially
constructed unauthenticated IEEE 802.11 frame to the access point to
cause associated stations to be disconnected and require a reconnection
to the network.
Vulnerable versions/configurations
All hostapd and wpa_supplicants versions with PMF support
(CONFIG_IEEE80211W=y) and a runtime configuration enabled AP mode with
PMF being enabled (optional or required). In addition, this would be
applicable only when using user space based MLME/SME in AP mode, i.e.,
when hostapd (or wpa_supplicant when controlling AP mode) would process
authentication and association management frames. This condition would
be applicable mainly with drivers that use mac80211.
Possible mitigation steps
- Merge the following commit to wpa_supplicant/hostapd and rebuild:
AP: Silently ignore management frame from unexpected source address
This patch is available from https://w1.fi/security/2019-7/
- Update to wpa_supplicant/hostapd v2.10 or newer, once available
Applies OpenWRT's noscan patch to hostapd and the relevant option to
the hostapd module.
This noscan patch adds a new `noscan` option allowing us to create
some overlapping BSSs in HT40+/- mode.
Note: this option is disabled by default, we leave this up to the end
user whether it should be enabled or not.
Not being able to create those overlapping BSSs is basically
preventing us to use 802.11n in any urban area where chances to
overlap with another SSID are extremely high.
The patch we are using is a courtesy of the openwrt team and is
applied to the defaul hostapd package in both OpenWRT and Archlinux.
He prefers to contribute to his own nixpkgs fork triton.
Since he is still marked as maintainer in many packages
this leaves the wrong impression he still maintains those.
CVE-2017-13077: Reinstallation of the pairwise encryption key (PTK-TK) in the 4-way handshake.
CVE-2017-13078: Reinstallation of the group key (GTK) in the 4-way handshake.
CVE-2017-13079: Reinstallation of the integrity group key (IGTK) in the 4-way handshake.
CVE-2017-13080: Reinstallation of the group key (GTK) in the group key handshake.
CVE-2017-13081: Reinstallation of the integrity group key (IGTK) in the group key handshake.
CVE-2017-13082: Accepting a retransmitted Fast BSS Transition (FT) Reassociation Request and reinstalling the pairwise encryption key (PTK-TK) while processing it.
CVE-2017-13084: Reinstallation of the STK key in the PeerKey handshake.
CVE-2017-13086: reinstallation of the Tunneled Direct-Link Setup (TDLS) PeerKey (TPK) key in the TDLS handshake.
CVE-2017-13087: reinstallation of the group key (GTK) when processing a Wireless Network Management (WNM) Sleep Mode Response frame.
CVE-2017-13088: reinstallation of the integrity group key (IGTK) when processing a Wireless Network Management (WNM) Sleep Mode Response frame.
