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FreeBSD Security Advisory - FreeBSD-SA-18:11.hostapd

FreeBSD Security Advisory - FreeBSD-SA-18:11.hostapd
Posted Aug 15, 2018
Authored by Mathy Vanhoef | Site security.freebsd.org

FreeBSD Security Advisory - When using WPA2, EAPOL-Key frames with the Encrypted flag and without the MIC flag set, the data field was decrypted first without verifying the MIC. When the dta field was encrypted using RC4, for example, when negotiating TKIP as a pairwise cipher, the unauthenticated but decrypted data was subsequently processed. This opened wpa_supplicant(8) to abuse by decryption and recovery of sensitive information contained in EAPOL-Key messages. All users of the WPA2 TKIP pairwise cipher are vulnerable to information, for example, the group key.

tags | advisory
systems | freebsd, bsd
advisories | CVE-2018-14526
MD5 | 6161d24d13a49c91a2677cc51cfcb2a2

FreeBSD Security Advisory - FreeBSD-SA-18:11.hostapd

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============================================================================
FreeBSD-SA-18:11.hostapd Security Advisory
The FreeBSD Project

Topic: Unauthenticated EAPOL-Key Decryption Vulnerability

Category: contrib
Module: wpa
Announced: 2018-08-14
Credits: Mathy Vanhoef of the imec-DistriNet research group of
KU Leuven
Affects: All supported versions of FreeBSD.
Corrected: 2018-08-15 05:03:54 UTC (stable/11, 11.1-STABLE)
2018-08-15 02:30:11 UTC (releng/11.2, 11.2-RELEASE-p2)
2018-08-15 02:30:11 UTC (releng/11.1, 11.1-RELEASE-p13)
2018-08-15 05:05:02 UTC (stable/10, 10.4-STABLE)
2018-08-15 02:31:10 UTC (releng/10.4, 10.4-RELEASE-p11)
CVE Name: CVE-2018-14526

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:https://security.FreeBSD.org/>.

I. Background

The wpa_supplicant(8) utility is a client (supplicant) with support for WPA
and WPA2 (IEEE 802.11i / RSN). It is suitable for both desktop and laptop
computers as well as embedded systems. Supplicant is the IEEE 802.1X/WPA
component that is used in the client stations. It implements key negotiation
with a WPA Authenticator and it controls the roaming and IEEE 802.11
authentication/association of the wlan(4) driver.

The wpa_supplicant(8) utility is designed to be a "daemon" program that runs
in the background and acts as the backend component controlling the wireless
connection. The wpa_supplicant(8) utility supports separate frontend programs
and a text-based frontend (wpa_cli(8)) and a GUI (wpa_gui) are included with
wpa_supplicant(8).

II. Problem Description

When using WPA2, EAPOL-Key frames with the Encrypted flag and without the MIC
flag set, the data field was decrypted first without verifying the MIC. When
the dta field was encrypted using RC4, for example, when negotiating TKIP as
a pairwise cipher, the unauthenticated but decrypted data was subsequently
processed. This opened wpa_supplicant(8) to abuse by decryption and recovery
of sensitive information contained in EAPOL-Key messages.

See https://w1.fi/security/2018-1/unauthenticated-eapol-key-decryption.txt
for a detailed description of the bug.

III. Impact

All users of the WPA2 TKIP pairwise cipher are vulnerable to information, for
example, the group key.

IV. Workaround

Remove TKIP as an allowed pairwise cipher in RSN/WPA2 networks in
wpa_supplicant.conf(5) by changing 'pairwiseIMP TKIP' to 'pariwiseIMP'.

This can also be mitigated by removing TKIP as a cipher on the AP.

Systems and users who do not use WPA2 TKIP are not affected.

V. Solution

Perform one of the following:

1) Upgrade your vulnerable system to a supported FreeBSD stable or
release / security branch (releng) dated after the correction date.

2) To update your vulnerable system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

3) To update your vulnerable system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

[FreeBSD 11.x]
# fetch https://security.FreeBSD.org/patches/SA-18:11/hostapd.patch
# fetch https://security.FreeBSD.org/patches/SA-18:11/hostapd.patch.asc
# gpg --verify hostapd.patch.asc

[FreeBSD 10.4]
# fetch https://security.FreeBSD.org/patches/SA-18:11/hostapd-10.patch
# fetch https://security.FreeBSD.org/patches/SA-18:11/hostapd-10.patch.asc
# gpg --verify hostapd-10.patch.asc

b) Apply the patch. Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile the operating system using buildworld and installworld as
described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>.

Restart the applicable daemons, or reboot the system.

VI. Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path Revision
- -------------------------------------------------------------------------
stable/10/ r337832
releng/10.4/ r337829
stable/11/ r337831
releng/11.1/ r337828
releng/11.2/ r337828
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://w1.fi/security/2018-1/unauthenticated-eapol-key-decryption.txt>

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-14526>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-18:09.hostapd.asc>
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