Updated: October 26, 2022

Wi-Fi Protected Access (WPA) client and IEEE 802.1X supplicant


wpa_supplicant-version [-BhKLNptuvWw] [-b br_ifname]
    [-C ctrl_interface] [-c filename] [-D driver] [-d[d]]
    [-f output_file] [-G group] [-g global_ctrl_interface] [-i ifname]
    [-m P2P_device_config_file] [-P file] [-q[q]] [-Z num]

Runs on:

QNX Neutrino


Most command-line options have global scope. Some are given per interface, and are valid only if you've specified at least one -i option; otherwise they're ignored. Option groups for different interfaces must be separated by an -N option.

Run as a daemon in the background.
-b br_ifname
Optional bridge interface name. (Per interface)
-C ctrl_interface
Path to the ctrl_interface socket. (Per interface; used only if -c is not)
-c filename
Path to the configuration file. (Per interface)
-D driver
Name of the driver. You can list more than one driver, separated by commas; for example, n180211,wext.
Increase debugging verbosity (specify -dd for even more).
-f output_file
Send the debug output to the specified file, instead of to standard output.
-G group
Name of the global_ctrl_interface group.
-g global_ctrl_interface
Path to the global_ctrl_interface socket. If you specify this option, you can omit the interface definitions.
Help; display a usage message.
-i ifname
Interface to listen on. Multiple instances of this option can be present, one per interface, separated by an -N option (see below).
Include keys (passwords, etc.) in the debugging output.
Show the license (GPL and BSD).
-m P2P_device_config_file
Name of the P2P device configuration file.
Start describing a new interface. The options that follow on the command-line will apply to that new interface.
-P file
Specify the location of the PID file.
Driver parameters. (Per interface)
Decrease debugging verbosity (specify -qq for even less).
Include the timestamp in debugging messages.
Enable the DBus control interface. If you specify this option, you can omit the interface definitions.
Show version information.
Wait for a control interface monitor before starting.
If needed, wait for an interface to be added.
-Z num
(QNX Neutrino extension; QNX Neutrino 7.0 or later) Specify the number of 4 KB pages for the slog2 buffer. The minimum is 5, the default is 10, and the maximum is 500.


Wireless networks don't 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 the user's explicit knowledge, because 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. But that proved to be flawed in many areas, and networks protected with WEP cannot be considered to be secure.

IEEE 802.1X authentication and frequently-changed dynamic WEP keys can be used to improve the network security, but even that has inherent security issues, due to the use of WEP for encryption. Wi-Fi Protected Access and the IEEE 802.11i amendment to the wireless LAN standard introduce a much-improved mechanism for securing wireless networks. IEEE 802.11i-enabled networks that are using CCMP (an encryption mechanism based on the strong cryptographic algorithm AES) can finally be called secure and used for applications that require efficient protection against unauthorized access.

The wpa_supplicant utility is an implementation of the WPA Supplicant component (i.e., the part that runs in 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.

The number in the wpa_supplicant utility name indicates the supported WPA version. For example, wpa_supplicant-2.9 supports version 2.9. The utility is designed to be a daemon that runs in the background and acts as the backend component controlling the wireless connection. It supports separate front-end programs such as the text-based wpa_cli.

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 have been loaded. The daemon exits immediately if the device isn't already available.

This program uses the OpenSSL library for cryptography services.

Configuring the wpa_supplicant utility

The wpa_supplicant utility is configured using a text file that lists all accepted networks and security policies, including pre-shared keys. See the sample configuration file, wpa_supplicant.conf, for detailed information about the configuration format and supported fields. Simpler sample configurations are available for plain text, static WEP, IEEE 802.1X with dynamic WEP (EAP-PEAP/MSCHAPv2), WPA-PSK/TKIP, and WPA2-EAP/CCMP (EAP-TLS). In addition, the utility can use the OpenSSL engine to avoid exposing private keys in the filesystem.

Integrating the wpa_supplicant utility

After wpa_supplicant has configured the network device, higher-level configuration such as DHCP may proceed. There are many ways to integrate wpa_supplicant into a machine's networking scripts, a few of which are described in the sections below.

The following steps are used when associating with an Access Point (AP) using WPA:

  1. wpa_supplicant requests the driver to scan neighboring BSSs.
  2. wpa_supplicant selects a BSS based on its configuration.
  3. wpa_supplicant requests the driver to associate with the chosen BSS.
  4. If WPA-EAP: the integrated IEEE 802.1X Supplicant or external Xsupplicant completes EAP authentication with the authentication server (proxied by the Authenticator in the AP).
  5. If WPA-EAP: the master key is received from the IEEE 802.1X Supplicant.
  6. If WPA-PSK: wpa_supplicant uses PSK as the master session key.
  7. wpa_supplicant completes WPA 4-Way Handshake and Group Key Handshake with the Authenticator in the AP.
  8. wpa_supplicant configures encryption keys for unicast and broadcast.
  9. Normal data packets can be transmitted and received.

Supported WPA/IEEE 802.11i features


The wpa_supplicant requires the following libraries and binaries be present:

The wpa_supplicant also needs a read/write filesystem for creating a ctrl_interface directory (see the sample wpa_supplicant.conf configuration file).

Note: You can't use /dev/shmem because it isn't possible to create a directory there.