wpa_supplicant - Wi-Fi Protected Access client and IEEE 802.1X
wpa_supplicant [ -BddfhKLqqtuvW ] [ -iifname ] [ -cconfig file ] [
-Ddriver ] [ -PPID_file ] [ -foutput file ]
Wireless networks do not require physical access to the network
equipment in the same way as wired networks. This makes it easier for
unauthorized users to passively monitor a network and capture all
transmitted frames. In addition, unauthorized use of the network is
much easier. In many cases, this can happen even without user’s
explicit knowledge since the wireless LAN adapter may have been
configured to automatically join any available network.
Link-layer encryption can be used to provide a layer of security for
wireless networks. The original wireless LAN standard, IEEE 802.11,
included a simple encryption mechanism, WEP. However, that proved to be
flawed in many areas and network protected with WEP cannot be consider
secure. IEEE 802.1X authentication and frequently changed dynamic WEP
keys can be used to improve the network security, but even that has
inherited security issues due to the use of WEP for encryption. Wi-Fi
Protected Access and IEEE 802.11i amendment to the wireless LAN
standard introduce a much improvement mechanism for securing wireless
networks. IEEE 802.11i enabled networks that are using CCMP (encryption
mechanism based on strong cryptographic algorithm AES) can finally be
called secure used for applications which require efficient protection
against unauthorized access.
wpa_supplicant is an implementation of the WPA Supplicant component,
i.e., the part that runs in the client stations. It implements WPA key
negotiation with a WPA Authenticator and EAP authentication with
Authentication Server. In addition, it controls the roaming and IEEE
802.11 authentication/association of the wireless LAN driver.
wpa_supplicant is designed to be a "daemon" program that runs in the
background and acts as the backend component controlling the wireless
connection. wpa_supplicant supports separate frontend programs and an
example text-based frontend, wpa_cli, is included with wpa_supplicant.
Before wpa_supplicant can do its work, the network interface must be
available. That means that the physical device must be present and
enabled, and the driver for the device must be loaded. The daemon will
exit immediately if the device is not already available.
After wpa_supplicant has configured the network device, higher level
configuration such as DHCP may proceed. There are a variety of ways to
integrate wpa_supplicant into a machine’s networking scripts, a few of
which are described in sections below.
The following steps are used when associating with an AP using WPA:
· wpa_supplicant requests the kernel driver to scan neighboring BSSes
· wpa_supplicant selects a BSS based on its configuration
· wpa_supplicant requests the kernel driver to associate with the
· If WPA-EAP: integrated IEEE 802.1X Supplicant completes EAP
authentication with the authentication server (proxied by the
Authenticator in the AP)
· If WPA-EAP: master key is received from the IEEE 802.1X Supplicant
· If WPA-PSK: wpa_supplicant uses PSK as the master session key
· wpa_supplicant completes WPA 4-Way Handshake and Group Key Handshake
with the Authenticator (AP)
· wpa_supplicant configures encryption keys for unicast and broadcast
· normal data packets can be transmitted and received
Supported WPA/IEEE 802.11i features:
· WPA-PSK ("WPA-Personal")
· WPA with EAP (e.g., with RADIUS authentication server) ("WPA-
Enterprise") Following authentication methods are supported with an
integrate IEEE 802.1X Supplicant:
· EAP-PEAP/MSCHAPv2 (both PEAPv0 and PEAPv1)
· EAP-PEAP/TLS (both PEAPv0 and PEAPv1)
· EAP-PEAP/GTC (both PEAPv0 and PEAPv1)
· EAP-PEAP/OTP (both PEAPv0 and PEAPv1)
· EAP-PEAP/MD5-Challenge (both PEAPv0 and PEAPv1)
· LEAP (note: requires special support from the driver for IEEE
· (following methods are supported, but since they do not generate
keying material, they cannot be used with WPA or IEEE 802.1X WEP
· key management for CCMP, TKIP, WEP104, WEP40
· RSN/WPA2 (IEEE 802.11i)
· PMKSA caching
A summary of available driver backends is below. Support for each of
the driver backends is chosen at wpa_supplicant compile time. For a
list of supported driver backends that may be used with the -D option
on your system, refer to the help output of wpa_supplicant
hostap (default) Host AP driver (Intersil Prism2/2.5/3). (this can
also be used with Linuxant DriverLoader).
hermes Agere Systems Inc. driver (Hermes-I/Hermes-II).
MADWIFI 802.11 support (Atheros, etc.).
atmel ATMEL AT76C5XXx (USB, PCMCIA).
wext Linux wireless extensions (generic).
Broadcom wl.o driver.
ipw Intel ipw2100/2200 driver.
wired wpa_supplicant wired Ethernet driver
wpa_supplicant Broadcom switch driver
bsd BSD 802.11 support (Atheros, etc.).
ndis Windows NDIS driver.
COMMAND LINE OPTIONS
Most command line options have global scope. Some are given per
interface, and are only valid if at least one -i option is specified,
otherwise they’re ignored. Option groups for different interfaces must
be separated by -N option.
Optional bridge interface name. (Per interface)
-B Run daemon in the background.
Path to configuration file. (Per interface)
Path to ctrl_interface socket (Per interface. Only used if -c is
Interface to listen on. Multiple instances of this option can be
present, one per interface, separated by -N option (see below).
-d Increase debugging verbosity (-dd even more).
Driver to use. (Per interface, see the available options below.)
-f output file
Log output to specified file instead of stdout.
-g global ctrl_interface
Path to global ctrl_interface socket. If specified, interface
definitions may be omitted.
-K Include keys (passwords, etc.) in debug output.
-t Include timestamp in debug messages.
-h Help. Show a usage message.
-L Show license (GPL and BSD).
-p Driver parameters. (Per interface)
Path to PID file.
-q Decrease debugging verbosity (-qq even less).
-u Enabled DBus control interface. If enabled, interface
definitions may be omitted.
-v Show version.
-W Wait for a control interface monitor before starting.
-N Start describing new interface.
In most common cases, wpa_supplicant is started with:
wpa_supplicant -B -c/etc/wpa_supplicant.conf -iwlan0
This makes the process fork into background.
The easiest way to debug problems, and to get debug log for bug
reports, is to start wpa_supplicant on foreground with debugging
wpa_supplicant -c/etc/wpa_supplicant.conf -iwlan0 -d
wpa_supplicant can control multiple interfaces (radios) either by
running one process for each interface separately or by running just
one process and list of options at command line. Each interface is
separated with -N argument. As an example, following command would
start wpa_supplicant for two interfaces:
-c wpa1.conf -i wlan0 -D hostap -N \
-c wpa2.conf -i ath0 -D madwifi
Current hardware/software requirements:
· Linux kernel 2.4.x or 2.6.x with Linux Wireless Extensions v15 or
· FreeBSD 6-CURRENT
· Microsoft Windows with WinPcap (at least WinXP, may work with other
Host AP driver for Prism2/2.5/3 (development snapshot/v0.2.x)
(http://hostap.epitest.fi/) Driver needs to be set in Managed
mode (iwconfig wlan0 mode managed). Please note that station
firmware version needs to be 1.7.0 or newer to work in WPA mode.
(http://www.linuxant.com/driverloader/) with Windows NDIS driver
for your wlan card supporting WPA.
Agere Systems Inc. Linux Driver
(http://www.agere.com/support/drivers/) Please note that the
driver interface file (driver_hermes.c) and hardware specific
include files are not included in the wpa_supplicant
distribution. You will need to copy these from the source
package of the Agere driver.
madwifi driver for cards based on Atheros chip set (ar521x)
(http://sourceforge.net/projects/madwifi/) Please note that you
will need to modify the wpa_supplicant .config file to use the
correct path for the madwifi driver root directory (CFLAGS +=
-I../madwifi/wpa line in example defconfig).
ATMEL AT76C5XXx driver for USB and PCMCIA cards
(http://ndiswrapper.sourceforge.net/) with Windows NDIS driver.
Broadcom wl.o driver
This is a generic Linux driver for Broadcom IEEE 802.11a/g
cards. However, it is proprietary driver that is not publicly
available except for couple of exceptions, mainly Broadcom-based
APs/wireless routers that use Linux. The driver binary can be
downloaded, e.g., from Linksys support site
(http://www.linksys.com/support/gpl.asp) for Linksys WRT54G. The
GPL tarball includes cross-compiler and the needed header file,
wlioctl.h, for compiling wpa_supplicant. This driver support in
wpa_supplicant is expected to work also with other devices based
on Broadcom driver (assuming the driver includes client mode
Intel ipw2100 driver
Intel ipw2200 driver
Linux wireless extensions
In theory, any driver that supports Linux wireless extensions
can be used with IEEE 802.1X (i.e., not WPA) when using
ap_scan=0 option in configuration file.
Wired Ethernet drivers
BSD net80211 layer (e.g., Atheros driver)
At the moment, this is for FreeBSD 6-CURRENT branch.
The current Windows port requires WinPcap
(http://winpcap.polito.it/). See README-Windows.txt for more
wpa_supplicant was designed to be portable for different drivers and
operating systems. Hopefully, support for more wlan cards and OSes will
be added in the future. See developer.txt for more information about
the design of wpa_supplicant and porting to other drivers. One main
goal is to add full WPA/WPA2 support to Linux wireless extensions to
allow new drivers to be supported without having to implement new
driver-specific interface code in wpa_supplicant.
The wpa_supplicant system consists of the following components:
the configuration file describing all networks that the user
wants the computer to connect to.
the program that directly interacts with the network interface.
the client program that provides a high-level interface to the
functionality of the daemon.
a utility needed to construct wpa_supplicant.conf files that
include encrypted passwords.
First, make a configuration file, e.g. /etc/wpa_supplicant.conf, that
describes the networks you are interested in. See
wpa_supplicant.conf(5) for details.
Once the configuration is ready, you can test whether the configuration
works by running wpa_supplicant with following command to start it on
foreground with debugging enabled:
wpa_supplicant -iwlan0 -c/etc/wpa_supplicant.conf -d
Assuming everything goes fine, you can start using following command to
start wpa_supplicant on background without debugging:
wpa_supplicant -iwlan0 -c/etc/wpa_supplicant.conf -B
Please note that if you included more than one driver interface in the
build time configuration (.config), you may need to specify which
interface to use by including -D<driver name> option on the command
INTERFACE TO PCMCIA-CS/CARDMRG
For example, following small changes to pcmcia-cs scripts can be used
to enable WPA support:
Add MODE="Managed" and WPA="y" to the network scheme in
Add the following block to the end of start action handler in
if [ "$WPA" = "y" -a -x /usr/local/bin/wpa_supplicant ]; then
/usr/local/bin/wpa_supplicant -B -c/etc/wpa_supplicant.conf -i$DEVICE
Add the following block to the end of stop action handler (may need to
be separated from other actions) in /etc/pcmcia/wireless:
if [ "$WPA" = "y" -a -x /usr/local/bin/wpa_supplicant ]; then
This will make cardmgr start wpa_supplicant when the card is plugged
wpa_background(8) wpa_supplicant.conf(5) wpa_cli(8) wpa_passphrase(8)
wpa_supplicant is copyright (c) 2003-2007, Jouni Malinen <email@example.com> and
contributors. All Rights Reserved.
This program is dual-licensed under both the GPL version 2 and BSD
license. Either license may be used at your option.
12 January 2010