~ubuntu-branches/ubuntu/trusty/wpa/trusty

WPA Supplicant

==============

Copyright (c) 2003-2014, 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-PSK

  * EAP-PAX

  * EAP-SAKE

  * EAP-IKEv2

  * EAP-GPSK

  * 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 0.9.7c and 0.9.7d, and 0.9.8 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

TLS options for EAP-FAST:

- OpenSSL 0.9.8d _with_ openssl-0.9.8d-tls-extensions.patch applied

  (i.e., the default OpenSSL package does not include support for

  extensions needed for EAP-FAST)

- 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 functionaly.

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

Following option can be used to include GSM SIM/USIM interface for GSM/UMTS

authentication algorithm (for EAP-SIM/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 [-BddfhKLqqtuvwW] [-P<pid file>] [-g<global ctrl>] \

        [-G<group>] \

        -i<ifname> -c<config file> [-C<ctrl>] [-D<driver>] [-p<driver_param>] \

        [-b<br_ifname> [-N -i<ifname> -c<conf> [-C<ctrl>] [-D<driver>] \

        [-p<driver_param>] [-b<br_ifname>] ...]

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 interface to be added, if needed

  -W = wait for a control interface monitor before starting

  -N = start describing new interface

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 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

betwork 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 ingterface (-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.

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 owrk item

and send "EXT-RADIO-WORK-TIMEOUT <id>" event ot 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