1 wpa_supplicant and Wi-Fi Protected Setup (WPS)
2 ==============================================
4 This document describes how the WPS implementation in wpa_supplicant
5 can be configured and how an external component on the client (e.g.,
6 management GUI) is used to enable WPS enrollment and registrar
13 Wi-Fi Protected Setup (WPS) is a mechanism for easy configuration of a
14 wireless network. It allows automated generation of random keys (WPA
15 passphrase/PSK) and configuration of an access point and client
16 devices. WPS includes number of methods for setting up connections
17 with PIN method and push-button configuration (PBC) being the most
18 commonly deployed options.
20 While WPS can enable more home networks to use encryption in the
21 wireless network, it should be noted that the use of the PIN and
22 especially PBC mechanisms for authenticating the initial key setup is
23 not very secure. As such, use of WPS may not be suitable for
24 environments that require secure network access without chance for
25 allowing outsiders to gain access during the setup phase.
27 WPS uses following terms to describe the entities participating in the
29 - access point: the WLAN access point
30 - Registrar: a device that control a network and can authorize
31 addition of new devices); this may be either in the AP ("internal
32 Registrar") or in an external device, e.g., a laptop, ("external
34 - Enrollee: a device that is being authorized to use the network
36 It should also be noted that the AP and a client device may change
37 roles (i.e., AP acts as an Enrollee and client device as a Registrar)
38 when WPS is used to configure the access point.
41 More information about WPS is available from Wi-Fi Alliance:
42 http://www.wi-fi.org/wifi-protected-setup
45 wpa_supplicant implementation
46 -----------------------------
48 wpa_supplicant includes an optional WPS component that can be used as
49 an Enrollee to enroll new network credential or as a Registrar to
53 wpa_supplicant configuration
54 ----------------------------
56 WPS is an optional component that needs to be enabled in
57 wpa_supplicant build configuration (.config). Here is an example
58 configuration that includes WPS support and Linux nl80211 -based
61 CONFIG_DRIVER_NL80211=y
66 WPS needs the Universally Unique IDentifier (UUID; see RFC 4122) for
67 the device. This is configured in the runtime configuration for
68 wpa_supplicant (if not set, UUID will be generated based on local MAC
71 # example UUID for WPS
72 uuid=12345678-9abc-def0-1234-56789abcdef0
74 The network configuration blocks needed for WPS are added
75 automatically based on control interface commands, so they do not need
76 to be added explicitly in the configuration file.
78 WPS registration will generate new network blocks for the acquired
79 credentials. If these are to be stored for future use (after
80 restarting wpa_supplicant), wpa_supplicant will need to be configured
81 to allow configuration file updates:
90 WPS requires either a device PIN code (usually, 8-digit number) or a
91 pushbutton event (for PBC) to allow a new WPS Enrollee to join the
92 network. wpa_supplicant uses the control interface as an input channel
95 The PIN value used in the commands must be processed by an UI to
96 remove non-digit characters and potentially, to verify the checksum
97 digit. "wpa_cli wps_check_pin <PIN>" can be used to do such processing.
98 It returns FAIL if the PIN is invalid, or FAIL-CHECKSUM if the checksum
99 digit is incorrect, or the processed PIN (non-digit characters removed)
102 If the client device has a display, a random PIN has to be generated
103 for each WPS registration session. wpa_supplicant can do this with a
104 control interface request, e.g., by calling wpa_cli:
108 This will return the generated 8-digit PIN which will then need to be
109 entered at the Registrar to complete WPS registration. At that point,
110 the client will be enrolled with credentials needed to connect to the
111 AP to access the network.
114 If the client device does not have a display that could show the
115 random PIN, a hardcoded PIN that is printed on a label can be
116 used. wpa_supplicant is notified this with a control interface
117 request, e.g., by calling wpa_cli:
119 wpa_cli wps_pin any 12345670
121 This starts the WPS negotiation in the same way as above with the
125 If the client design wants to support optional WPS PBC mode, this can
126 be enabled by either a physical button in the client device or a
127 virtual button in the user interface. The PBC operation requires that
128 a button is also pressed at the AP/Registrar at about the same time (2
129 minute window). wpa_supplicant is notified of the local button event
130 over the control interface, e.g., by calling wpa_cli:
134 At this point, the AP/Registrar has two minutes to complete WPS
135 negotiation which will generate a new WPA PSK in the same way as the
136 PIN method described above.
139 If the client wants to operate in the Registrar role to learn the
140 current AP configuration and optionally, to configure an AP,
141 wpa_supplicant is notified over the control interface, e.g., with
144 wpa_cli wps_reg <AP BSSID> <AP PIN>
145 (example: wpa_cli wps_reg 02:34:56:78:9a:bc 12345670)
147 This is used to fetch the current AP settings instead of actually
148 changing them. The main difference with the wps_pin command is that
149 wps_reg uses the AP PIN (e.g., from a label on the AP) instead of a
150 PIN generated at the client.
152 In order to change the AP configuration, the new configuration
153 parameters are given to the wps_reg command:
155 wpa_cli wps_reg <AP BSSID> <AP PIN> <new SSID> <auth> <encr> <new key>
157 wpa_cli wps_reg 02:34:56:78:9a:bc 12345670 testing WPA2PSK CCMP 12345678
158 wpa_cli wps_reg 02:34:56:78:9a:bc 12345670 clear OPEN NONE ""
160 <auth> must be one of the following: OPEN WPAPSK WPA2PSK
161 <encr> must be one of the following: NONE WEP TKIP CCMP
167 Scan results ('wpa_cli scan_results' or 'wpa_cli bss <idx>') include a
168 flags field that is used to indicate whether the BSS support WPS. If
169 the AP support WPS, but has not recently activated a Registrar, [WPS]
170 flag will be included. If PIN method has been recently selected,
171 [WPS-PIN] is shown instead. Similarly, [WPS-PBC] is shown if PBC mode
172 is in progress. GUI programs can use these as triggers for suggesting
173 a guided WPS configuration to the user. In addition, control interface
174 monitor events WPS-AP-AVAILABLE{,-PBC,-PIN} can be used to find out if
175 there are WPS enabled APs in scan results without having to go through
176 all the details in the GUI. These notification could be used, e.g., to
177 suggest possible WPS connection to the user.
183 wpa_gui-qt4 directory contains a sample GUI that shows an example of
184 how WPS support can be integrated into the GUI. Its main window has a
185 WPS tab that guides user through WPS registration with automatic AP
186 selection. In addition, it shows how WPS can be started manually by
187 selecting an AP from scan results.
190 Credential processing
191 ---------------------
193 By default, wpa_supplicant processes received credentials and updates
194 its configuration internally. However, it is possible to
195 control these operations from external programs, if desired.
197 This internal processing can be disabled with wps_cred_processing=1
198 option. When this is used, an external program is responsible for
199 processing the credential attributes and updating wpa_supplicant
200 configuration based on them.
202 Following control interface messages are sent out for external programs:
204 WPS-CRED-RECEIVED <hexdump of Credential attribute(s)>
206 <2>WPS-CRED-RECEIVED 100e006f10260001011045000c6a6b6d2d7770732d74657374100300020020100f000200081027004030653462303435366332363666653064333961643135353461316634626637313234333761636664623766333939653534663166316230323061643434386235102000060266a0ee1727
209 wpa_supplicant as WPS External Registrar (ER)
210 ---------------------------------------------
212 wpa_supplicant can be used as a WPS ER to configure an AP or enroll
213 new Enrollee to join the network. This functionality uses UPnP and
214 requires that a working IP connectivity is available with the AP (this
215 can be either over a wired or wireless connection).
217 Separate wpa_supplicant process can be started for WPS ER
218 operations. A special "none" driver can be used in such a case to
219 indicate that no local network interface is actually controlled. For
220 example, following command could be used to start the ER:
222 wpa_supplicant -Dnone -c er.conf -ieth0
226 ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=admin
227 device_name=WPS External Registrar
230 wpa_cli commands for ER functionality:
232 wps_er_start [IP address]
233 - start WPS ER functionality
234 - the optional IP address parameter can be used to filter operations only
235 to include a single AP
236 - if run again while ER is active, the stored information (discovered APs
237 and Enrollees) are shown again
240 - stop WPS ER functionality
242 wps_er_learn <UUID> <AP PIN>
243 - learn AP configuration
245 wps_er_set_config <UUID> <network id>
246 - use AP configuration from a locally configured network (e.g., from
247 wps_reg command); this does not change the AP's configuration, but
248 only prepares a configuration to be used when enrolling a new device
251 wps_er_config <UUID> <AP PIN> <new SSID> <auth> <encr> <new key>
253 wps_er_config 87654321-9abc-def0-1234-56789abc0002 12345670 testing WPA2PSK CCMP 12345678
254 wpa_er_config 87654321-9abc-def0-1234-56789abc0002 12345670 clear OPEN NONE ""
256 <auth> must be one of the following: OPEN WPAPSK WPA2PSK
257 <encr> must be one of the following: NONE WEP TKIP CCMP
260 wps_er_pbc <Enrollee UUID>
261 - accept an Enrollee PBC using External Registrar
263 wps_er_pin <Enrollee UUID> <PIN> [Enrollee MAC address]
264 - add an Enrollee PIN to External Registrar
265 - if Enrollee UUID is not known, "any" can be used to add a wildcard PIN
266 - if the MAC address of the enrollee is known, it should be configured
267 to allow the AP to advertise list of authorized enrollees
273 - WPS ER discovered an AP
275 WPS-ER-AP-ADD 87654321-9abc-def0-1234-56789abc0002 02:11:22:33:44:55 pri_dev_type=6-0050F204-1 wps_state=1 |Very friendly name|Company|Long description of the model|WAP|http://w1.fi/|http://w1.fi/hostapd/
277 WPS_EVENT_ER_AP_REMOVE
278 - WPS ER removed an AP entry
280 WPS-ER-AP-REMOVE 87654321-9abc-def0-1234-56789abc0002
282 WPS_EVENT_ER_ENROLLEE_ADD
283 - WPS ER discovered a new Enrollee
285 WPS-ER-ENROLLEE-ADD 2b7093f1-d6fb-5108-adbb-bea66bb87333 02:66:a0:ee:17:27 M1=1 config_methods=0x14d dev_passwd_id=0 pri_dev_type=1-0050F204-1 |Wireless Client|Company|cmodel|123|12345|
287 WPS_EVENT_ER_ENROLLEE_REMOVE
288 - WPS ER removed an Enrollee entry
290 WPS-ER-ENROLLEE-REMOVE 2b7093f1-d6fb-5108-adbb-bea66bb87333 02:66:a0:ee:17:27
293 - WPS ER learned AP settings
295 WPS-ER-AP-SETTINGS uuid=fd91b4ec-e3fa-5891-a57d-8c59efeed1d2 ssid=test-wps auth_type=0x0020 encr_type=0x0008 key=12345678