wpa_supplicant - Wi-Fi Protected Access client and IEEE 802.1X supplicant
] [ -cconfig file
] [ -PPID_file
-f output 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.
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.
is designed to be a "daemon" program that runs
in the background and acts as the backend component controlling the wireless
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.
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
- wpa_supplicant selects a BSS based on its
- wpa_supplicant requests the kernel driver to
associate with the chosen BSS
- 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
- If WPA-PSK: wpa_supplicant uses PSK as the master
- 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 802.11 authentication)
- (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 ( wpa_supplicant -h
- Linux wireless extensions (generic).
- wpa_supplicant wired Ethernet driver
- wpa_supplicant Broadcom switch driver
- BSD 802.11 support (Atheros, etc.).
- Windows NDIS driver.
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
- -b br_ifname
- Optional bridge interface name. (Per interface)
- Run daemon in the background.
- -c filename
- Path to configuration file. (Per interface)
- -C ctrl_interface
- Path to ctrl_interface socket (Per interface. Only used if
-c is not).
- -i ifname
- Interface to listen on. Multiple instances of this option
can be present, one per interface, separated by -N option (see
- Increase debugging verbosity (-dd even more).
- -D driver
- 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
- -g global ctrl_interface
- Path to global ctrl_interface socket. If specified,
interface definitions may be omitted.
- Include keys (passwords, etc.) in debug output.
- Help. Show a usage message.
- Show license (BSD).
- -o override driver
- Override the driver parameter for new interfaces.
- -O override ctrl_interface
- Override the ctrl_interface parameter for new
- Driver parameters. (Per interface)
- -P PID_file
- Path to PID file.
- Decrease debugging verbosity (-qq even less).
- Log output to syslog instead of stdout. (This is only
available if wpa_supplicant was built with the CONFIG_DEBUG_SYSLOG
- Log output to Linux tracing in addition to any other
destinations. (This is only available if wpa_supplicant was built
with the CONFIG_DEBUG_LINUX_TRACING option.)
- Include timestamp in debug messages.
- 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.)
- Show version.
- Wait for a control interface monitor before starting.
- 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
on foreground with debugging enabled:
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.
will use the first driver wrapper that is able to
initialize the interface.
wpa_supplicant -Dnl80211,wext -c/etc/wpa_supplicant.conf -iwlan0
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
-c wpa1.conf -i wlan0 -D nl80211 -N \
-c wpa2.conf -i ath0 -D wext
Current hardware/software requirements:
- Linux kernel 2.4.x or 2.6.x with Linux Wireless Extensions
v15 or newer
- FreeBSD 6-CURRENT
- Microsoft Windows with WinPcap (at least WinXP, may work
with other versions)
- 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
- Use ap_scan=0.
- BSD net80211 layer (e.g., Atheros driver)
- At the moment, this is for FreeBSD 6-CURRENT branch.
- Windows NDIS
- 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
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
- 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
describes the networks you are interested in. See
Once the configuration is ready, you can test whether the configuration works by
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
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 line.
For example, following small changes to pcmcia-cs scripts can be used to enable
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
when the card is
wpa_background(8) wpa_supplicant.conf(5) wpa_cli(8)
wpa_supplicant is copyright (c) 2003-2016, Jouni Malinen <email@example.com> and
contributors. All Rights Reserved.
This program is licensed under the BSD license (the one with advertisement