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
65 If you want to enable WPS external registrar (ER) functionality, you
66 will also need to add following line:
71 WPS needs the Universally Unique IDentifier (UUID; see RFC 4122) for
72 the device. This is configured in the runtime configuration for
73 wpa_supplicant (if not set, UUID will be generated based on local MAC
76 # example UUID for WPS
77 uuid=12345678-9abc-def0-1234-56789abcdef0
79 The network configuration blocks needed for WPS are added
80 automatically based on control interface commands, so they do not need
81 to be added explicitly in the configuration file.
83 WPS registration will generate new network blocks for the acquired
84 credentials. If these are to be stored for future use (after
85 restarting wpa_supplicant), wpa_supplicant will need to be configured
86 to allow configuration file updates:
95 WPS requires either a device PIN code (usually, 8-digit number) or a
96 pushbutton event (for PBC) to allow a new WPS Enrollee to join the
97 network. wpa_supplicant uses the control interface as an input channel
100 The PIN value used in the commands must be processed by an UI to
101 remove non-digit characters and potentially, to verify the checksum
102 digit. "wpa_cli wps_check_pin <PIN>" can be used to do such processing.
103 It returns FAIL if the PIN is invalid, or FAIL-CHECKSUM if the checksum
104 digit is incorrect, or the processed PIN (non-digit characters removed)
107 If the client device has a display, a random PIN has to be generated
108 for each WPS registration session. wpa_supplicant can do this with a
109 control interface request, e.g., by calling wpa_cli:
113 This will return the generated 8-digit PIN which will then need to be
114 entered at the Registrar to complete WPS registration. At that point,
115 the client will be enrolled with credentials needed to connect to the
116 AP to access the network.
119 If the client device does not have a display that could show the
120 random PIN, a hardcoded PIN that is printed on a label can be
121 used. wpa_supplicant is notified this with a control interface
122 request, e.g., by calling wpa_cli:
124 wpa_cli wps_pin any 12345670
126 This starts the WPS negotiation in the same way as above with the
130 If a random PIN is needed for a user interface, "wpa_cli wps_pin get"
131 can be used to generate a new PIN without starting WPS negotiation.
132 This random PIN can then be passed as an argument to another wps_pin
133 call when the actual operation should be started.
135 If the client design wants to support optional WPS PBC mode, this can
136 be enabled by either a physical button in the client device or a
137 virtual button in the user interface. The PBC operation requires that
138 a button is also pressed at the AP/Registrar at about the same time (2
139 minute window). wpa_supplicant is notified of the local button event
140 over the control interface, e.g., by calling wpa_cli:
144 At this point, the AP/Registrar has two minutes to complete WPS
145 negotiation which will generate a new WPA PSK in the same way as the
146 PIN method described above.
149 If the client wants to operate in the Registrar role to learn the
150 current AP configuration and optionally, to configure an AP,
151 wpa_supplicant is notified over the control interface, e.g., with
154 wpa_cli wps_reg <AP BSSID> <AP PIN>
155 (example: wpa_cli wps_reg 02:34:56:78:9a:bc 12345670)
157 This is used to fetch the current AP settings instead of actually
158 changing them. The main difference with the wps_pin command is that
159 wps_reg uses the AP PIN (e.g., from a label on the AP) instead of a
160 PIN generated at the client.
162 In order to change the AP configuration, the new configuration
163 parameters are given to the wps_reg command:
165 wpa_cli wps_reg <AP BSSID> <AP PIN> <new SSID> <auth> <encr> <new key>
167 wpa_cli wps_reg 02:34:56:78:9a:bc 12345670 testing WPA2PSK CCMP 12345678
168 wpa_cli wps_reg 02:34:56:78:9a:bc 12345670 clear OPEN NONE ""
170 <auth> must be one of the following: OPEN WPAPSK WPA2PSK
171 <encr> must be one of the following: NONE WEP TKIP CCMP
177 Scan results ('wpa_cli scan_results' or 'wpa_cli bss <idx>') include a
178 flags field that is used to indicate whether the BSS support WPS. If
179 the AP support WPS, but has not recently activated a Registrar, [WPS]
180 flag will be included. If PIN method has been recently selected,
181 [WPS-PIN] is shown instead. Similarly, [WPS-PBC] is shown if PBC mode
182 is in progress. GUI programs can use these as triggers for suggesting
183 a guided WPS configuration to the user. In addition, control interface
184 monitor events WPS-AP-AVAILABLE{,-PBC,-PIN} can be used to find out if
185 there are WPS enabled APs in scan results without having to go through
186 all the details in the GUI. These notification could be used, e.g., to
187 suggest possible WPS connection to the user.
193 wpa_gui-qt4 directory contains a sample GUI that shows an example of
194 how WPS support can be integrated into the GUI. Its main window has a
195 WPS tab that guides user through WPS registration with automatic AP
196 selection. In addition, it shows how WPS can be started manually by
197 selecting an AP from scan results.
200 Credential processing
201 ---------------------
203 By default, wpa_supplicant processes received credentials and updates
204 its configuration internally. However, it is possible to
205 control these operations from external programs, if desired.
207 This internal processing can be disabled with wps_cred_processing=1
208 option. When this is used, an external program is responsible for
209 processing the credential attributes and updating wpa_supplicant
210 configuration based on them.
212 Following control interface messages are sent out for external programs:
214 WPS-CRED-RECEIVED <hexdump of Credential attribute(s)>
216 <2>WPS-CRED-RECEIVED 100e006f10260001011045000c6a6b6d2d7770732d74657374100300020020100f000200081027004030653462303435366332363666653064333961643135353461316634626637313234333761636664623766333939653534663166316230323061643434386235102000060266a0ee1727
219 wpa_supplicant as WPS External Registrar (ER)
220 ---------------------------------------------
222 wpa_supplicant can be used as a WPS ER to configure an AP or enroll
223 new Enrollee to join the network. This functionality uses UPnP and
224 requires that a working IP connectivity is available with the AP (this
225 can be either over a wired or wireless connection).
227 Separate wpa_supplicant process can be started for WPS ER
228 operations. A special "none" driver can be used in such a case to
229 indicate that no local network interface is actually controlled. For
230 example, following command could be used to start the ER:
232 wpa_supplicant -Dnone -c er.conf -ieth0
236 ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=admin
237 device_name=WPS External Registrar
240 wpa_cli commands for ER functionality:
242 wps_er_start [IP address]
243 - start WPS ER functionality
244 - the optional IP address parameter can be used to filter operations only
245 to include a single AP
246 - if run again while ER is active, the stored information (discovered APs
247 and Enrollees) are shown again
250 - stop WPS ER functionality
252 wps_er_learn <UUID> <AP PIN>
253 - learn AP configuration
255 wps_er_set_config <UUID> <network id>
256 - use AP configuration from a locally configured network (e.g., from
257 wps_reg command); this does not change the AP's configuration, but
258 only prepares a configuration to be used when enrolling a new device
261 wps_er_config <UUID> <AP PIN> <new SSID> <auth> <encr> <new key>
263 wps_er_config 87654321-9abc-def0-1234-56789abc0002 12345670 testing WPA2PSK CCMP 12345678
264 wpa_er_config 87654321-9abc-def0-1234-56789abc0002 12345670 clear OPEN NONE ""
266 <auth> must be one of the following: OPEN WPAPSK WPA2PSK
267 <encr> must be one of the following: NONE WEP TKIP CCMP
270 wps_er_pbc <Enrollee UUID>
271 - accept an Enrollee PBC using External Registrar
273 wps_er_pin <Enrollee UUID> <PIN> [Enrollee MAC address]
274 - add an Enrollee PIN to External Registrar
275 - if Enrollee UUID is not known, "any" can be used to add a wildcard PIN
276 - if the MAC address of the enrollee is known, it should be configured
277 to allow the AP to advertise list of authorized enrollees
283 - WPS ER discovered an AP
285 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/
287 WPS_EVENT_ER_AP_REMOVE
288 - WPS ER removed an AP entry
290 WPS-ER-AP-REMOVE 87654321-9abc-def0-1234-56789abc0002
292 WPS_EVENT_ER_ENROLLEE_ADD
293 - WPS ER discovered a new Enrollee
295 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|
297 WPS_EVENT_ER_ENROLLEE_REMOVE
298 - WPS ER removed an Enrollee entry
300 WPS-ER-ENROLLEE-REMOVE 2b7093f1-d6fb-5108-adbb-bea66bb87333 02:66:a0:ee:17:27
303 - WPS ER learned AP settings
305 WPS-ER-AP-SETTINGS uuid=fd91b4ec-e3fa-5891-a57d-8c59efeed1d2 ssid=test-wps auth_type=0x0020 encr_type=0x0008 key=12345678