wpa_supplicant
==============
Copyright (c) 2003-2019, Jouni Malinen <j@w1.fi> and contributors
All Rights Reserved.
This program is licensed under the BSD license (the one with
advertisement clause removed).
If you are submitting changes to the project, please see CONTRIBUTIONS
file for more instructions.
License
-------
This software may be distributed, used, and modified under the terms of
BSD license:
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. Neither the name(s) of the above-listed copyright holder(s) nor the
names of its contributors may be used to endorse or promote products
derived from this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Features
--------
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-TLS
* 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)
* EAP-TTLS/EAP-MD5-Challenge
* EAP-TTLS/EAP-GTC
* EAP-TTLS/EAP-OTP
* EAP-TTLS/EAP-MSCHAPv2
* EAP-TTLS/EAP-TLS
* EAP-TTLS/MSCHAPv2
* EAP-TTLS/MSCHAP
* EAP-TTLS/PAP
* EAP-TTLS/CHAP
* EAP-SIM
* EAP-AKA
* EAP-AKA'
* EAP-PSK
* EAP-PAX
* EAP-SAKE
* EAP-IKEv2
* EAP-GPSK
* EAP-pwd
* 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 keying)
* EAP-MD5-Challenge
* EAP-MSCHAPv2
* EAP-GTC
* EAP-OTP
- key management for CCMP, TKIP, WEP104, WEP40
- RSN/WPA2 (IEEE 802.11i)
* pre-authentication
* PMKSA caching
Supported TLS/crypto libraries:
- OpenSSL (default)
- GnuTLS
Internal TLS/crypto implementation (optional):
- can be used in place of an external TLS/crypto library
- TLSv1
- X.509 certificate processing
- PKCS #1
- ASN.1
- RSA
- bignum
- minimal size (ca. 50 kB binary, parts of which are already needed for WPA;
TLSv1/X.509/ASN.1/RSA/bignum parts are about 25 kB on x86)
Requirements
------------
Current hardware/software requirements:
- Linux kernel 2.4.x or 2.6.x with Linux Wireless Extensions v15 or newer
- FreeBSD 6-CURRENT
- NetBSD-current
- Microsoft Windows with WinPcap (at least WinXP, may work with other versions)
- drivers:
Linux drivers that support cfg80211/nl80211. Even though there are
number of driver specific interface included in wpa_supplicant, please
note that Linux drivers are moving to use generic wireless configuration
interface driver_nl80211 (-Dnl80211 on wpa_supplicant command line)
should be the default option to start with before falling back to driver
specific interface.
Linux drivers that support WPA/WPA2 configuration with the generic
Linux wireless extensions (WE-18 or newer). Obsoleted by nl80211.
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 (with ap_scan=0)
BSD net80211 layer (e.g., Atheros driver)
At the moment, this is for FreeBSD 6-CURRENT branch and NetBSD-current.
Windows NDIS
The current Windows port requires WinPcap (http://winpcap.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's documentation
(http://hostap.epitest.fi/wpa_supplicant/devel/) 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.
Optional libraries for layer2 packet processing:
- libpcap (tested with 0.7.2, most relatively recent versions assumed to work,
this is likely to be available with most distributions,
http://tcpdump.org/)
- libdnet (tested with v1.4, most versions assumed to work,
http://libdnet.sourceforge.net/)
These libraries are _not_ used in the default Linux build. Instead,
internal Linux specific implementation is used. libpcap/libdnet are
more portable and they can be used by adding CONFIG_L2_PACKET=pcap into
.config. They may also be selected automatically for other operating
systems. In case of Windows builds, WinPcap is used by default
(CONFIG_L2_PACKET=winpcap).
Optional libraries for EAP-TLS, EAP-PEAP, and EAP-TTLS:
- OpenSSL (tested with 1.0.1 and 1.0.2 versions; assumed to
work with most relatively recent versions; this is likely to be
available with most distributions, http://www.openssl.org/)
- GnuTLS
- internal TLSv1 implementation
One of these libraries is needed when EAP-TLS, EAP-PEAP, EAP-TTLS, or
EAP-FAST support is enabled. WPA-PSK mode does not require this or EAPOL/EAP
implementation. A configuration file, .config, for compilation is
needed to enable IEEE 802.1X/EAPOL and EAP methods. Note that EAP-MD5,
EAP-GTC, EAP-OTP, and EAP-MSCHAPV2 cannot be used alone with WPA, so
they should only be enabled if testing the EAPOL/EAP state
machines. However, there can be used as inner authentication
algorithms with EAP-PEAP and EAP-TTLS.
See Building and installing section below for more detailed
information about the wpa_supplicant build time configuration.
WPA
---
The original security mechanism of IEEE 802.11 standard was not
designed to be strong and has proven to be insufficient for most
networks that require some kind of security. Task group I (Security)
of IEEE 802.11 working group (http://www.ieee802.org/11/) has worked
to address the flaws of the base standard and has in practice
completed its work in May 2004. The IEEE 802.11i amendment to the IEEE
802.11 standard was approved in June 2004 and published in July 2004.
Wi-Fi Alliance (http://www.wi-fi.org/) used a draft version of the
IEEE 802.11i work (draft 3.0) to define a subset of the security
enhancements that can be implemented with existing wlan hardware. This
is called Wi-Fi Protected Access<TM> (WPA). This has now become a
mandatory component of interoperability testing and certification done
by Wi-Fi Alliance. Wi-Fi provides information about WPA at its web
site (http://www.wi-fi.org/OpenSection/protected_access.asp).
IEEE 802.11 standard defined wired equivalent privacy (WEP) algorithm
for protecting wireless networks. WEP uses RC4 with 40-bit keys,
24-bit initialization vector (IV), and CRC32 to protect against packet
forgery. All these choices have proven to be insufficient: key space is
too small against current attacks, RC4 key scheduling is insufficient
(beginning of the pseudorandom stream should be skipped), IV space is
too small and IV reuse makes attacks easier, there is no replay
protection, and non-keyed authentication does not protect against bit
flipping packet data.
WPA is an intermediate solution for the security issues. It uses
Temporal Key Integrity Protocol (TKIP) to replace WEP. TKIP is a
compromise on strong security and possibility to use existing
hardware. It still uses RC4 for the encryption like WEP, but with
per-packet RC4 keys. In addition, it implements replay protection,
keyed packet authentication mechanism (Michael MIC).
Keys can be managed using two different mechanisms. WPA can either use
an external authentication server (e.g., RADIUS) and EAP just like
IEEE 802.1X is using or pre-shared keys without need for additional
servers. Wi-Fi calls these "WPA-Enterprise" and "WPA-Personal",
respectively. Both mechanisms will generate a master session key for
the Authenticator (AP) and Supplicant (client station).
WPA implements a new key handshake (4-Way Handshake and Group Key
Handshake) for generating and exchanging data encryption keys between
the Authenticator and Supplicant. This handshake is also used to
verify that both Authenticator and Supplicant know the master session
key. These handshakes are identical regardless of the selected key
management mechanism (only the method for generating master session
key changes).
IEEE 802.11i / WPA2
-------------------
The design for parts of IEEE 802.11i that were not included in WPA has
finished (May 2004) and this amendment to IEEE 802.11 was approved in
June 2004. Wi-Fi Alliance is using the final IEEE 802.11i as a new
version of WPA called WPA2. This includes, e.g., support for more
robust encryption algorithm (CCMP: AES in Counter mode with CBC-MAC)
to replace TKIP and optimizations for handoff (reduced number of
messages in initial key handshake, pre-authentication, and PMKSA caching).
wpa_supplicant
--------------
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 wlan 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.
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 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 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
Building and installing
-----------------------
In order to be able to build wpa_supplicant, you will first need to
select which parts of it will be included. This is done by creating a
build time configuration file, .config, in the wpa_supplicant root
directory. Configuration options are text lines using following
format: CONFIG_<option>=y. Lines starting with # are considered
comments and are ignored. See defconfig file for an example configuration
and a list of available options and additional notes.
The build time configuration can be used to select only the needed
features and limit the binary size and requirements for external
libraries. The main configuration parts are the selection of which
driver interfaces (e.g., nl80211, wext, ..) and which authentication
methods (e.g., EAP-TLS, EAP-PEAP, ..) are included.
Following build time configuration options are used to control IEEE
802.1X/EAPOL and EAP state machines and all EAP methods. Including
TLS, PEAP, or TTLS will require linking wpa_supplicant with OpenSSL
library for TLS implementation. Alternatively, GnuTLS or the internal
TLSv1 implementation can be used for TLS functionality.
CONFIG_IEEE8021X_EAPOL=y
CONFIG_EAP_MD5=y
CONFIG_EAP_MSCHAPV2=y
CONFIG_EAP_TLS=y
CONFIG_EAP_PEAP=y
CONFIG_EAP_TTLS=y
CONFIG_EAP_GTC=y
CONFIG_EAP_OTP=y
CONFIG_EAP_SIM=y
CONFIG_EAP_AKA=y
CONFIG_EAP_AKA_PRIME=y
CONFIG_EAP_PSK=y
CONFIG_EAP_SAKE=y
CONFIG_EAP_GPSK=y
CONFIG_EAP_PAX=y
CONFIG_EAP_LEAP=y
CONFIG_EAP_IKEV2=y
CONFIG_EAP_PWD=y
Following option can be used to include GSM SIM/USIM interface for GSM/UMTS
authentication algorithm (for EAP-SIM/EAP-AKA/EAP-AKA'). This requires pcsc-lite
(http://www.linuxnet.com/) for smart card access.
CONFIG_PCSC=y
Following options can be added to .config to select which driver
interfaces are included.
CONFIG_DRIVER_NL80211=y
CONFIG_DRIVER_WEXT=y
CONFIG_DRIVER_BSD=y
CONFIG_DRIVER_NDIS=y
Following example includes some more features and driver interfaces that
are included in the wpa_supplicant package:
CONFIG_DRIVER_NL80211=y
CONFIG_DRIVER_WEXT=y
CONFIG_DRIVER_BSD=y
CONFIG_DRIVER_NDIS=y
CONFIG_IEEE8021X_EAPOL=y
CONFIG_EAP_MD5=y
CONFIG_EAP_MSCHAPV2=y
CONFIG_EAP_TLS=y
CONFIG_EAP_PEAP=y
CONFIG_EAP_TTLS=y
CONFIG_EAP_GTC=y
CONFIG_EAP_OTP=y
CONFIG_EAP_SIM=y
CONFIG_EAP_AKA=y
CONFIG_EAP_PSK=y
CONFIG_EAP_SAKE=y
CONFIG_EAP_GPSK=y
CONFIG_EAP_PAX=y
CONFIG_EAP_LEAP=y
CONFIG_EAP_IKEV2=y
CONFIG_PCSC=y
EAP-PEAP and EAP-TTLS will automatically include configured EAP
methods (MD5, OTP, GTC, MSCHAPV2) for inner authentication selection.
After you have created a configuration file, you can build
wpa_supplicant and wpa_cli with 'make' command. You may then install
the binaries to a suitable system directory, e.g., /usr/local/bin.
Example commands:
# build wpa_supplicant and wpa_cli
make
# install binaries (this may need root privileges)
cp wpa_cli wpa_supplicant /usr/local/bin
You will need to make a configuration file, e.g.,
/etc/wpa_supplicant.conf, with network configuration for the networks
you are going to use. Configuration file section below includes
explanation fo the configuration file format and includes various
examples. Once the configuration is ready, you can test whether the
configuration work by first 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
line. See following section for more details on command line options
for wpa_supplicant.
Command line options
--------------------
usage:
wpa_supplicant [-BddfhKLqqtuvW] [-P<pid file>] [-g<global ctrl>] \
[-G<group>] \
-i<ifname> -c<config file> [-C<ctrl>] [-D<driver>] [-p<driver_param>] \
[-b<br_ifname> [-MN -i<ifname> -c<conf> [-C<ctrl>] [-D<driver>] \
[-p<driver_param>] [-b<br_ifname>] [-m<P2P Device config file>] ...
options:
-b = optional bridge interface name
-B = run daemon in the background
-c = Configuration file
-C = ctrl_interface parameter (only used if -c is not)
-i = interface name
-d = increase debugging verbosity (-dd even more)
-D = driver name (can be multiple drivers: nl80211,wext)
-f = Log output to default log location (normally /tmp)
-g = global ctrl_interface
-G = global ctrl_interface group
-K = include keys (passwords, etc.) in debug output
-t = include timestamp in debug messages
-h = show this help text
-L = show license (BSD)
-p = driver parameters
-P = PID file
-q = decrease debugging verbosity (-qq even less)
-u = enable DBus control interface
-v = show version
-W = wait for a control interface monitor before starting
-M = start describing matching interface
-N = start describing new interface
-m = Configuration file for the P2P Device
drivers:
nl80211 = Linux nl80211/cfg80211
wext = Linux wireless extensions (generic)
wired = wpa_supplicant wired Ethernet driver
roboswitch = wpa_supplicant Broadcom switch driver
bsd = BSD 802.11 support (Atheros, etc.)
ndis = Windows NDIS driver
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
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. 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
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:
wpa_supplicant \
-c wpa1.conf -i wlan0 -D nl80211 -N \
-c wpa2.conf -i wlan1 -D wext
If the interfaces on which wpa_supplicant is to run are not known or do
not exist, wpa_supplicant can match an interface when it arrives. Each
matched interface is separated with -M argument and the -i argument now
allows for pattern matching.
As an example, the following command would start wpa_supplicant for a
specific wired interface called lan0, any interface starting with wlan
and lastly any other interface. Each match has its own configuration
file, and for the wired interface a specific driver has also been given.
wpa_supplicant \
-M -c wpa_wired.conf -ilan0 -D wired \
-M -c wpa1.conf -iwlan* \
-M -c wpa2.conf
If the interface is added in a Linux bridge (e.g., br0), the bridge
interface needs to be configured to wpa_supplicant in addition to the
main interface:
wpa_supplicant -cw.conf -Dnl80211 -iwlan0 -bbr0
Configuration file
------------------
wpa_supplicant is configured using a text file that lists all accepted
networks and security policies, including pre-shared keys. See
example configuration file, wpa_supplicant.conf, for detailed
information about the configuration format and supported fields.
Changes to configuration file can be reloaded be sending SIGHUP signal
to wpa_supplicant ('killall -HUP wpa_supplicant'). Similarly,
reloading can be triggered with 'wpa_cli reconfigure' command.
Configuration file can include one or more network blocks, e.g., one
for each used SSID. wpa_supplicant will automatically select the best
network based on the order of network blocks in the configuration
file, network security level (WPA/WPA2 is preferred), and signal
strength.
Example configuration files for some common configurations:
1) WPA-Personal (PSK) as home network and WPA-Enterprise with EAP-TLS as work
network
# allow frontend (e.g., wpa_cli) to be used by all users in 'wheel' group
ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=wheel
#
# home network; allow all valid ciphers
network={
ssid="home"
scan_ssid=1
key_mgmt=WPA-PSK
psk="very secret passphrase"
}
#
# work network; use EAP-TLS with WPA; allow only CCMP and TKIP ciphers
network={
ssid="work"
scan_ssid=1
key_mgmt=WPA-EAP
pairwise=CCMP TKIP
group=CCMP TKIP
eap=TLS
identity="user@example.com"
ca_cert="/etc/cert/ca.pem"
client_cert="/etc/cert/user.pem"
private_key="/etc/cert/user.prv"
private_key_passwd="password"
}
2) WPA-RADIUS/EAP-PEAP/MSCHAPv2 with RADIUS servers that use old peaplabel
(e.g., Funk Odyssey and SBR, Meetinghouse Aegis, Interlink RAD-Series)
ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=wheel
network={
ssid="example"
scan_ssid=1
key_mgmt=WPA-EAP
eap=PEAP
identity="user@example.com"
password="foobar"
ca_cert="/etc/cert/ca.pem"
phase1="peaplabel=0"
phase2="auth=MSCHAPV2"
}
3) EAP-TTLS/EAP-MD5-Challenge configuration with anonymous identity for the
unencrypted use. Real identity is sent only within an encrypted TLS tunnel.
ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=wheel
network={
ssid="example"
scan_ssid=1
key_mgmt=WPA-EAP
eap=TTLS
identity="user@example.com"
anonymous_identity="anonymous@example.com"
password="foobar"
ca_cert="/etc/cert/ca.pem"
phase2="auth=MD5"
}
4) IEEE 802.1X (i.e., no WPA) with dynamic WEP keys (require both unicast and
broadcast); use EAP-TLS for authentication
ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=wheel
network={
ssid="1x-test"
scan_ssid=1
key_mgmt=IEEE8021X
eap=TLS
identity="user@example.com"
ca_cert="/etc/cert/ca.pem"
client_cert="/etc/cert/user.pem"
private_key="/etc/cert/user.prv"
private_key_passwd="password"
eapol_flags=3
}
5) Catch all example that allows more or less all configuration modes. The
configuration options are used based on what security policy is used in the
selected SSID. This is mostly for testing and is not recommended for normal
use.
ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=wheel
network={
ssid="example"
scan_ssid=1
key_mgmt=WPA-EAP WPA-PSK IEEE8021X NONE
pairwise=CCMP TKIP
group=CCMP TKIP WEP104 WEP40
psk="very secret passphrase"
eap=TTLS PEAP TLS
identity="user@example.com"
password="foobar"
ca_cert="/etc/cert/ca.pem"
client_cert="/etc/cert/user.pem"
private_key="/etc/cert/user.prv"
private_key_passwd="password"
phase1="peaplabel=0"
ca_cert2="/etc/cert/ca2.pem"
client_cert2="/etc/cer/user.pem"
private_key2="/etc/cer/user.prv"
private_key2_passwd="password"
}
6) Authentication for wired Ethernet. This can be used with 'wired' or
'roboswitch' interface (-Dwired or -Droboswitch on command line).
ctrl_interface=/var/run/wpa_supplicant
ctrl_interface_group=wheel
ap_scan=0
network={
key_mgmt=IEEE8021X
eap=MD5
identity="user"
password="password"
eapol_flags=0
}
Certificates
------------
Some EAP authentication methods require use of certificates. EAP-TLS
uses both server side and client certificates whereas EAP-PEAP and
EAP-TTLS only require the server side certificate. When client
certificate is used, a matching private key file has to also be
included in configuration. If the private key uses a passphrase, this
has to be configured in wpa_supplicant.conf ("private_key_passwd").
wpa_supplicant supports X.509 certificates in PEM and DER
formats. User certificate and private key can be included in the same
file.
If the user certificate and private key is received in PKCS#12/PFX
format, they need to be converted to suitable PEM/DER format for
wpa_supplicant. This can be done, e.g., with following commands:
# convert client certificate and private key to PEM format
openssl pkcs12 -in example.pfx -out user.pem -clcerts
# convert CA certificate (if included in PFX file) to PEM format
openssl pkcs12 -in example.pfx -out ca.pem -cacerts -nokeys
wpa_cli
-------
wpa_cli is a text-based frontend program for interacting with
wpa_supplicant. It is used to query current status, change
configuration, trigger events, and request interactive user input.
wpa_cli can show the current authentication status, selected security
mode, dot11 and dot1x MIBs, etc. In addition, it can configure some
variables like EAPOL state machine parameters and trigger events like
reassociation and IEEE 802.1X logoff/logon. wpa_cli provides a user
interface to request authentication information, like username and
password, if these are not included in the configuration. This can be
used to implement, e.g., one-time-passwords or generic token card
authentication where the authentication is based on a
challenge-response that uses an external device for generating the
response.
The control interface of wpa_supplicant can be configured to allow
non-root user access (ctrl_interface_group in the configuration
file). This makes it possible to run wpa_cli with a normal user
account.
wpa_cli supports two modes: interactive and command line. Both modes
share the same command set and the main difference is in interactive
mode providing access to unsolicited messages (event messages,
username/password requests).
Interactive mode is started when wpa_cli is executed without including
the command as a command line parameter. Commands are then entered on
the wpa_cli prompt. In command line mode, the same commands are
entered as command line arguments for wpa_cli.
Interactive authentication parameters request
When wpa_supplicant need authentication parameters, like username and
password, which are not present in the configuration file, it sends a
request message to all attached frontend programs, e.g., wpa_cli in
interactive mode. wpa_cli shows these requests with
"CTRL-REQ-<type>-<id>:<text>" prefix. <type> is IDENTITY, PASSWORD, or
OTP (one-time-password). <id> is a unique identifier for the current
network. <text> is description of the request. In case of OTP request,
it includes the challenge from the authentication server.
The reply to these requests can be given with 'identity', 'password',
and 'otp' commands. <id> needs to be copied from the the matching
request. 'password' and 'otp' commands can be used regardless of
whether the request was for PASSWORD or OTP. The main difference
between these two commands is that values given with 'password' are
remembered as long as wpa_supplicant is running whereas values given
with 'otp' are used only once and then forgotten, i.e., wpa_supplicant
will ask frontend for a new value for every use. This can be used to
implement one-time-password lists and generic token card -based
authentication.
Example request for password and a matching reply:
CTRL-REQ-PASSWORD-1:Password needed for SSID foobar
> password 1 mysecretpassword
Example request for generic token card challenge-response:
CTRL-REQ-OTP-2:Challenge 1235663 needed for SSID foobar
> otp 2 9876
wpa_cli commands
status = get current WPA/EAPOL/EAP status
mib = get MIB variables (dot1x, dot11)
help = show this usage help
interface [ifname] = show interfaces/select interface
level <debug level> = change debug level
license = show full wpa_cli license
logoff = IEEE 802.1X EAPOL state machine logoff
logon = IEEE 802.1X EAPOL state machine logon
set = set variables (shows list of variables when run without arguments)
pmksa = show PMKSA cache
reassociate = force reassociation
reconfigure = force wpa_supplicant to re-read its configuration file
preauthenticate <BSSID> = force preauthentication
identity <network id> <identity> = configure identity for an SSID
password <network id> <password> = configure password for an SSID
pin <network id> <pin> = configure pin for an SSID
otp <network id> <password> = configure one-time-password for an SSID
passphrase <network id> <passphrase> = configure private key passphrase
for an SSID
bssid <network id> <BSSID> = set preferred BSSID for an SSID
list_networks = list configured networks
select_network <network id> = select a network (disable others)
enable_network <network id> = enable a network
disable_network <network id> = disable a network
add_network = add a network
remove_network <network id> = remove a network
set_network <network id> <variable> <value> = set network variables (shows
list of variables when run without arguments)
get_network <network id> <variable> = get network variables
save_config = save the current configuration
disconnect = disconnect and wait for reassociate command before connecting
scan = request new BSS scan
scan_results = get latest scan results
get_capability <eap/pairwise/group/key_mgmt/proto/auth_alg> = get capabilies
terminate = terminate wpa_supplicant
quit = exit wpa_cli
wpa_cli command line options
wpa_cli [-p<path to ctrl sockets>] [-i<ifname>] [-hvB] [-a<action file>] \
[-P<pid file>] [-g<global ctrl>] [command..]
-h = help (show this usage text)
-v = shown version information
-a = run in daemon mode executing the action file based on events from
wpa_supplicant
-B = run a daemon in the background
default path: /var/run/wpa_supplicant
default interface: first interface found in socket path
Using wpa_cli to run external program on connect/disconnect
-----------------------------------------------------------
wpa_cli can used to run external programs whenever wpa_supplicant
connects or disconnects from a network. This can be used, e.g., to
update network configuration and/or trigget DHCP client to update IP
addresses, etc.
One wpa_cli process in "action" mode needs to be started for each
interface. For example, the following command starts wpa_cli for the
default interface (-i can be used to select the interface in case of
more than one interface being used at the same time):
wpa_cli -a/sbin/wpa_action.sh -B
The action file (-a option, /sbin/wpa_action.sh in this example) will
be executed whenever wpa_supplicant completes authentication (connect
event) or detects disconnection). The action script will be called
with two command line arguments: interface name and event (CONNECTED
or DISCONNECTED). If the action script needs to get more information
about the current network, it can use 'wpa_cli status' to query
wpa_supplicant for more information.
Following example can be used as a simple template for an action
script:
#!/bin/sh
IFNAME=$1
CMD=$2
if [ "$CMD" = "CONNECTED" ]; then
SSID=`wpa_cli -i$IFNAME status | grep ^ssid= | cut -f2- -d=`
# configure network, signal DHCP client, etc.
fi
if [ "$CMD" = "DISCONNECTED" ]; then
# remove network configuration, if needed
SSID=
fi
Integrating with pcmcia-cs/cardmgr scripts
------------------------------------------
wpa_supplicant needs to be running when using a wireless network with
WPA. It can be started either from system startup scripts or from
pcmcia-cs/cardmgr scripts (when using PC Cards). WPA handshake must be
completed before data frames can be exchanged, so wpa_supplicant
should be started before DHCP client.
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/pcmcia/wireless.opts.
Add the following block to the end of 'start' action handler in
/etc/pcmcia/wireless:
if [ "$WPA" = "y" -a -x /usr/local/bin/wpa_supplicant ]; then
/usr/local/bin/wpa_supplicant -B -c/etc/wpa_supplicant.conf \
-i$DEVICE
fi
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
killall wpa_supplicant
fi
This will make cardmgr start wpa_supplicant when the card is plugged
in.
Dynamic interface add and operation without configuration files
---------------------------------------------------------------
wpa_supplicant can be started without any configuration files or
network interfaces. When used in this way, a global (i.e., per
wpa_supplicant process) control interface is used to add and remove
network interfaces. Each network interface can then be configured
through a per-network interface control interface. For example,
following commands show how to start wpa_supplicant without any
network interfaces and then add a network interface and configure a
network (SSID):
# Start wpa_supplicant in the background
wpa_supplicant -g/var/run/wpa_supplicant-global -B
# Add a new interface (wlan0, no configuration file, driver=nl80211, and
# enable control interface)
wpa_cli -g/var/run/wpa_supplicant-global interface_add wlan0 \
"" nl80211 /var/run/wpa_supplicant
# Configure a network using the newly added network interface:
wpa_cli -iwlan0 add_network
wpa_cli -iwlan0 set_network 0 ssid '"test"'
wpa_cli -iwlan0 set_network 0 key_mgmt WPA-PSK
wpa_cli -iwlan0 set_network 0 psk '"12345678"'
wpa_cli -iwlan0 set_network 0 pairwise TKIP
wpa_cli -iwlan0 set_network 0 group TKIP
wpa_cli -iwlan0 set_network 0 proto WPA
wpa_cli -iwlan0 enable_network 0
# At this point, the new network interface should start trying to associate
# with the WPA-PSK network using SSID test.
# Remove network interface
wpa_cli -g/var/run/wpa_supplicant-global interface_remove wlan0
Privilege separation
--------------------
To minimize the size of code that needs to be run with root privileges
(e.g., to control wireless interface operation), wpa_supplicant
supports optional privilege separation. If enabled, this separates the
privileged operations into a separate process (wpa_priv) while leaving
rest of the code (e.g., EAP authentication and WPA handshakes) into an
unprivileged process (wpa_supplicant) that can be run as non-root
user. Privilege separation restricts the effects of potential software
errors by containing the majority of the code in an unprivileged
process to avoid full system compromise.
Privilege separation is not enabled by default and it can be enabled
by adding CONFIG_PRIVSEP=y to the build configuration (.config). When
enabled, the privileged operations (driver wrapper and l2_packet) are
linked into a separate daemon program, wpa_priv. The unprivileged
program, wpa_supplicant, will be built with a special driver/l2_packet
wrappers that communicate with the privileged wpa_priv process to
perform the needed operations. wpa_priv can control what privileged
are allowed.
wpa_priv needs to be run with network admin privileges (usually, root
user). It opens a UNIX domain socket for each interface that is
included on the command line; any other interface will be off limits
for wpa_supplicant in this kind of configuration. After this,
wpa_supplicant can be run as a non-root user (e.g., all standard users
on a laptop or as a special non-privileged user account created just
for this purpose to limit access to user files even further).
Example configuration:
- create user group for users that are allowed to use wpa_supplicant
('wpapriv' in this example) and assign users that should be able to
use wpa_supplicant into that group
- create /var/run/wpa_priv directory for UNIX domain sockets and control
user access by setting it accessible only for the wpapriv group:
mkdir /var/run/wpa_priv
chown root:wpapriv /var/run/wpa_priv
chmod 0750 /var/run/wpa_priv
- start wpa_priv as root (e.g., from system startup scripts) with the
enabled interfaces configured on the command line:
wpa_priv -B -P /var/run/wpa_priv.pid nl80211:wlan0
- run wpa_supplicant as non-root with a user that is in wpapriv group:
wpa_supplicant -i ath0 -c wpa_supplicant.conf
wpa_priv does not use the network interface before wpa_supplicant is
started, so it is fine to include network interfaces that are not
available at the time wpa_priv is started. As an alternative, wpa_priv
can be started when an interface is added (hotplug/udev/etc. scripts).
wpa_priv can control multiple interface with one process, but it is
also possible to run multiple wpa_priv processes at the same time, if
desired.
It should be noted that the interface used between wpa_supplicant and
wpa_priv does not include all the capabilities of the wpa_supplicant
driver interface and at times, this interface lacks update especially
for recent addition. Consequently, use of wpa_priv does come with the
price of somewhat reduced available functionality. The next section
describing how wpa_supplicant can be used with reduced privileges
without having to handle the complexity of separate wpa_priv. While that
approve does not provide separation for network admin capabilities, it
does allow other root privileges to be dropped without the drawbacks of
the wpa_priv process.
Linux capabilities instead of privileged process
------------------------------------------------
wpa_supplicant performs operations that need special permissions, e.g.,
to control the network connection. Traditionally this has been achieved
by running wpa_supplicant as a privileged process with effective user id
0 (root). Linux capabilities can be used to provide restricted set of
capabilities to match the functions needed by wpa_supplicant. The
minimum set of capabilities needed for the operations is CAP_NET_ADMIN
and CAP_NET_RAW.
setcap(8) can be used to set file capabilities. For example:
sudo setcap cap_net_raw,cap_net_admin+ep wpa_supplicant
Please note that this would give anyone being able to run that
wpa_supplicant binary access to the additional capabilities. This can
further be limited by file owner/group and mode bits. For example:
sudo chown wpas wpa_supplicant
sudo chmod 0100 wpa_supplicant
This combination of setcap, chown, and chmod commands would allow wpas
user to execute wpa_supplicant with additional network admin/raw
capabilities.
Common way style of creating a control interface socket in
/var/run/wpa_supplicant could not be done by this user, but this
directory could be created before starting the wpa_supplicant and set to
suitable mode to allow wpa_supplicant to create sockets
there. Alternatively, other directory or abstract socket namespace could
be used for the control interface.
External requests for radio control
-----------------------------------
External programs can request wpa_supplicant to not start offchannel
operations during other tasks that may need exclusive control of the
radio. The RADIO_WORK control interface command can be used for this.
"RADIO_WORK add <name> [freq=<MHz>] [timeout=<seconds>]" command can be
used to reserve a slot for radio access. If freq is specified, other
radio work items on the same channel may be completed in
parallel. Otherwise, all other radio work items are blocked during
execution. Timeout is set to 10 seconds by default to avoid blocking
wpa_supplicant operations for excessive time. If a longer (or shorter)
safety timeout is needed, that can be specified with the optional
timeout parameter. This command returns an identifier for the radio work
item.
Once the radio work item has been started, "EXT-RADIO-WORK-START <id>"
event message is indicated that the external processing can start. Once
the operation has been completed, "RADIO_WORK done <id>" is used to
indicate that to wpa_supplicant. This allows other radio works to be
performed. If this command is forgotten (e.g., due to the external
program terminating), wpa_supplicant will time out the radio work item
and send "EXT-RADIO-WORK-TIMEOUT <id>" event to indicate that this has
happened. "RADIO_WORK done <id>" can also be used to cancel items that
have not yet been started.
For example, in wpa_cli interactive mode:
> radio_work add test
1
<3>EXT-RADIO-WORK-START 1
> radio_work show
ext:test@wlan0:0:1:2.487797
> radio_work done 1
OK
> radio_work show
> radio_work done 3
OK
> radio_work show
ext:test freq=2412 timeout=30@wlan0:2412:1:28.583483
<3>EXT-RADIO-WORK-TIMEOUT 2
> radio_work add test2 freq=2412 timeout=60
5
<3>EXT-RADIO-WORK-START 5
> radio_work add test3
6
> radio_work add test4
7
> radio_work show
ext:test2 freq=2412 timeout=60@wlan0:2412:1:9.751844
ext:test3@wlan0:0:0:5.071812
ext:test4@wlan0:0:0:3.143870
> radio_work done 6
OK
> radio_work show
ext:test2 freq=2412 timeout=60@wlan0:2412:1:16.287869
ext:test4@wlan0:0:0:9.679895
> radio_work done 5
OK
<3>EXT-RADIO-WORK-START 7
<3>EXT-RADIO-WORK-TIMEOUT 7