wpa_supplicant - Wi-Fi Protected Access client and IEEE 802.1X suppli-
wpa_supplicant [ -BddfhKLqqsTtuvW ] [ -iifname ] [ -cconfig file ] [
-Ddriver ] [ -PPID_file ] [ -foutput file ]
Wireless networks do not require physical access to the network equip-
ment in the same way as wired networks. This makes it easier for unau-
thorized users to passively monitor a network and capture all transmit-
ted frames. In addition, unauthorized use of the network is much eas-
ier. In many cases, this can happen even without user's explicit knowl-
edge since the wireless LAN adapter may have been configured to auto-
matically 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 stan-
dard introduce a much improvement mechanism for securing wireless net-
works. 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:
o wpa_supplicant requests the kernel driver to scan neighboring BSSes
o wpa_supplicant selects a BSS based on its configuration
o wpa_supplicant requests the kernel driver to associate with the cho-
o If WPA-EAP: integrated IEEE 802.1X Supplicant completes EAP authenti-
cation with the authentication server (proxied by the Authenticator
in the AP)
o If WPA-EAP: master key is received from the IEEE 802.1X Supplicant
o If WPA-PSK: wpa_supplicant uses PSK as the master session key
o wpa_supplicant completes WPA 4-Way Handshake and Group Key Handshake
with the Authenticator (AP)
o wpa_supplicant configures encryption keys for unicast and broadcast
o normal data packets can be transmitted and received
Supported WPA/IEEE 802.11i features:
o WPA-PSK ("WPA-Personal")
o WPA with EAP (e.g., with RADIUS authentication server) ("WPA-Enter-
prise") Following authentication methods are supported with an inte-
grate IEEE 802.1X Supplicant:
o EAP-PEAP/MSCHAPv2 (both PEAPv0 and PEAPv1)
o EAP-PEAP/TLS (both PEAPv0 and PEAPv1)
o EAP-PEAP/GTC (both PEAPv0 and PEAPv1)
o EAP-PEAP/OTP (both PEAPv0 and PEAPv1)
o EAP-PEAP/MD5-Challenge (both PEAPv0 and PEAPv1)
o LEAP (note: requires special support from the driver for IEEE
o (following methods are supported, but since they do not generate
keying material, they cannot be used with WPA or IEEE 802.1X WEP
o key management for CCMP, TKIP, WEP104, WEP40
o RSN/WPA2 (IEEE 802.11i)
o 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 (wpa_suppli-
wext Linux wireless extensions (generic).
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 inter-
face, and are only valid if at least one -i option is specified, other-
wise 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 (can be multiple drivers: nl80211,wext). (Per
interface, see the available options below.)
-e entropy file
File for wpa_supplicant to use to maintain its internal entropy
store in over restarts.
-f output file
Log output to specified file instead of stdout. (This is only
available if wpa_supplicant was built with the CONFIG_DEBUG_FILE
-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 (BSD).
-o override driver
Override the driver parameter for new interfaces.
-O override ctrl_interface
Override the ctrl_interface parameter for new interfaces.
-p Driver parameters. (Per interface)
Path to PID file.
-q Decrease debugging verbosity (-qq even less).
-s Log output to syslog instead of stdout. (This is only available
if wpa_supplicant was built with the CONFIG_DEBUG_SYSLOG
-T Log output to Linux tracing in addition to any other destina-
tions. (This is only available if wpa_supplicant was built with
the CONFIG_DEBUG_LINUX_TRACING option.)
-t Include timestamp in debug messages.
-u Enable DBus control interface. If enabled, interface definitions
may be omitted. (This is only available if wpa_supplicant was
built with the CONFIG_DBUS option.)
-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
If the specific driver wrapper is not known beforehand, it is possible
to specify multiple comma separated driver wrappers on the command
line. wpa_supplicant will use the first driver wrapper that is able to
initialize the interface.
wpa_supplicant -Dnl80211,wext -c/etc/wpa_supplicant.conf -iwlan0
wpa_supplicant can control multiple interfaces (radios) either by run-
ning one process for each interface separately or by running just one
process and list of options at command line. Each interface is sepa-
rated with -N argument. As an example, following command would start
wpa_supplicant for two interfaces:
-c wpa1.conf -i wlan0 -D nl80211 -N \
-c wpa2.conf -i ath0 -D wext
Current hardware/software requirements:
o Linux kernel 2.4.x or 2.6.x with Linux Wireless Extensions v15 or
o FreeBSD 6-CURRENT
o Microsoft Windows with WinPcap (at least WinXP, may work with other
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://win-
pcap.polito.it/). See README-Windows.txt for more information.
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_suppli-
cant.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 /etc/pcm-
Add the following block to the end of start action handler in /etc/pcm-
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) 2003-2015, Jouni Malinen <firstname.lastname@example.org> and
contributors. All Rights Reserved.
This program is licensed under the BSD license (the one with advertise-
ment clause removed).
01 March 2021 WPA_SUPPLICANT(8)
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