1wpa_supplicant and Wi-Fi Protected Setup (WPS)
2==============================================
3
4This document describes how the WPS implementation in wpa_supplicant
5can be configured and how an external component on the client (e.g.,
6management GUI) is used to enable WPS enrollment and registrar
7registration.
8
9
10Introduction to WPS
11-------------------
12
13Wi-Fi Protected Setup (WPS) is a mechanism for easy configuration of a
14wireless network. It allows automated generation of random keys (WPA
15passphrase/PSK) and configuration of an access point and client
16devices. WPS includes number of methods for setting up connections
17with PIN method and push-button configuration (PBC) being the most
18commonly deployed options.
19
20While WPS can enable more home networks to use encryption in the
21wireless network, it should be noted that the use of the PIN and
22especially PBC mechanisms for authenticating the initial key setup is
23not very secure. As such, use of WPS may not be suitable for
24environments that require secure network access without chance for
25allowing outsiders to gain access during the setup phase.
26
27WPS uses following terms to describe the entities participating in the
28network setup:
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
33  Registrar")
34- Enrollee: a device that is being authorized to use the network
35
36It should also be noted that the AP and a client device may change
37roles (i.e., AP acts as an Enrollee and client device as a Registrar)
38when WPS is used to configure the access point.
39
40
41More information about WPS is available from Wi-Fi Alliance:
42http://www.wi-fi.org/wifi-protected-setup
43
44
45wpa_supplicant implementation
46-----------------------------
47
48wpa_supplicant includes an optional WPS component that can be used as
49an Enrollee to enroll new network credential or as a Registrar to
50configure an AP.
51
52
53wpa_supplicant configuration
54----------------------------
55
56WPS is an optional component that needs to be enabled in
57wpa_supplicant build configuration (.config). Here is an example
58configuration that includes WPS support and Linux nl80211 -based
59driver interface:
60
61CONFIG_DRIVER_NL80211=y
62CONFIG_WPS=y
63
64If you want to enable WPS external registrar (ER) functionality, you
65will also need to add following line:
66
67CONFIG_WPS_ER=y
68
69Following parameter can be used to enable support for NFC config method:
70
71CONFIG_WPS_NFC=y
72
73
74WPS needs the Universally Unique IDentifier (UUID; see RFC 4122) for
75the device. This is configured in the runtime configuration for
76wpa_supplicant (if not set, UUID will be generated based on local MAC
77address):
78
79# example UUID for WPS
80uuid=12345678-9abc-def0-1234-56789abcdef0
81
82The network configuration blocks needed for WPS are added
83automatically based on control interface commands, so they do not need
84to be added explicitly in the configuration file.
85
86WPS registration will generate new network blocks for the acquired
87credentials. If these are to be stored for future use (after
88restarting wpa_supplicant), wpa_supplicant will need to be configured
89to allow configuration file updates:
90
91update_config=1
92
93
94
95External operations
96-------------------
97
98WPS requires either a device PIN code (usually, 8-digit number) or a
99pushbutton event (for PBC) to allow a new WPS Enrollee to join the
100network. wpa_supplicant uses the control interface as an input channel
101for these events.
102
103The PIN value used in the commands must be processed by an UI to
104remove non-digit characters and potentially, to verify the checksum
105digit. "wpa_cli wps_check_pin <PIN>" can be used to do such processing.
106It returns FAIL if the PIN is invalid, or FAIL-CHECKSUM if the checksum
107digit is incorrect, or the processed PIN (non-digit characters removed)
108if the PIN is valid.
109
110If the client device has a display, a random PIN has to be generated
111for each WPS registration session. wpa_supplicant can do this with a
112control interface request, e.g., by calling wpa_cli:
113
114wpa_cli wps_pin any
115
116This will return the generated 8-digit PIN which will then need to be
117entered at the Registrar to complete WPS registration. At that point,
118the client will be enrolled with credentials needed to connect to the
119AP to access the network.
120
121
122If the client device does not have a display that could show the
123random PIN, a hardcoded PIN that is printed on a label can be
124used. wpa_supplicant is notified this with a control interface
125request, e.g., by calling wpa_cli:
126
127wpa_cli wps_pin any 12345670
128
129This starts the WPS negotiation in the same way as above with the
130generated PIN.
131
132When the wps_pin command is issued for an AP (including P2P GO) mode
133interface, an optional timeout parameter can be used to specify
134expiration timeout for the PIN in seconds. For example:
135
136wpa_cli wps_pin any 12345670 300
137
138
139If a random PIN is needed for a user interface, "wpa_cli wps_pin get"
140can be used to generate a new PIN without starting WPS negotiation.
141This random PIN can then be passed as an argument to another wps_pin
142call when the actual operation should be started.
143
144If the client design wants to support optional WPS PBC mode, this can
145be enabled by either a physical button in the client device or a
146virtual button in the user interface. The PBC operation requires that
147a button is also pressed at the AP/Registrar at about the same time (2
148minute window). wpa_supplicant is notified of the local button event
149over the control interface, e.g., by calling wpa_cli:
150
151wpa_cli wps_pbc
152
153At this point, the AP/Registrar has two minutes to complete WPS
154negotiation which will generate a new WPA PSK in the same way as the
155PIN method described above.
156
157
158If the client wants to operate in the Registrar role to learn the
159current AP configuration and optionally, to configure an AP,
160wpa_supplicant is notified over the control interface, e.g., with
161wpa_cli:
162
163wpa_cli wps_reg <AP BSSID> <AP PIN>
164(example: wpa_cli wps_reg 02:34:56:78:9a:bc 12345670)
165
166This is used to fetch the current AP settings instead of actually
167changing them. The main difference with the wps_pin command is that
168wps_reg uses the AP PIN (e.g., from a label on the AP) instead of a
169PIN generated at the client.
170
171In order to change the AP configuration, the new configuration
172parameters are given to the wps_reg command:
173
174wpa_cli wps_reg <AP BSSID> <AP PIN> <new SSID> <auth> <encr> <new key>
175examples:
176  wpa_cli wps_reg 02:34:56:78:9a:bc 12345670 testing WPA2PSK CCMP 12345678
177  wpa_cli wps_reg 02:34:56:78:9a:bc 12345670 clear OPEN NONE ""
178
179<auth> must be one of the following: OPEN WPAPSK WPA2PSK
180<encr> must be one of the following: NONE WEP TKIP CCMP
181
182
183Scanning
184--------
185
186Scan results ('wpa_cli scan_results' or 'wpa_cli bss <idx>') include a
187flags field that is used to indicate whether the BSS support WPS. If
188the AP support WPS, but has not recently activated a Registrar, [WPS]
189flag will be included. If PIN method has been recently selected,
190[WPS-PIN] is shown instead. Similarly, [WPS-PBC] is shown if PBC mode
191is in progress. GUI programs can use these as triggers for suggesting
192a guided WPS configuration to the user. In addition, control interface
193monitor events WPS-AP-AVAILABLE{,-PBC,-PIN} can be used to find out if
194there are WPS enabled APs in scan results without having to go through
195all the details in the GUI. These notification could be used, e.g., to
196suggest possible WPS connection to the user.
197
198
199wpa_gui
200-------
201
202wpa_gui-qt4 directory contains a sample GUI that shows an example of
203how WPS support can be integrated into the GUI. Its main window has a
204WPS tab that guides user through WPS registration with automatic AP
205selection. In addition, it shows how WPS can be started manually by
206selecting an AP from scan results.
207
208
209Credential processing
210---------------------
211
212By default, wpa_supplicant processes received credentials and updates
213its configuration internally. However, it is possible to
214control these operations from external programs, if desired.
215
216This internal processing can be disabled with wps_cred_processing=1
217option. When this is used, an external program is responsible for
218processing the credential attributes and updating wpa_supplicant
219configuration based on them.
220
221Following control interface messages are sent out for external programs:
222
223WPS-CRED-RECEIVED  <hexdump of Credential attribute(s)>
224For example:
225<2>WPS-CRED-RECEIVED 100e006f10260001011045000c6a6b6d2d7770732d74657374100300020020100f000200081027004030653462303435366332363666653064333961643135353461316634626637313234333761636664623766333939653534663166316230323061643434386235102000060266a0ee1727
226
227
228wpa_supplicant as WPS External Registrar (ER)
229---------------------------------------------
230
231wpa_supplicant can be used as a WPS ER to configure an AP or enroll
232new Enrollee to join the network. This functionality uses UPnP and
233requires that a working IP connectivity is available with the AP (this
234can be either over a wired or wireless connection).
235
236Separate wpa_supplicant process can be started for WPS ER
237operations. A special "none" driver can be used in such a case to
238indicate that no local network interface is actually controlled. For
239example, following command could be used to start the ER:
240
241wpa_supplicant -Dnone -c er.conf -ieth0
242
243Sample er.conf:
244
245ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=admin
246device_name=WPS External Registrar
247
248
249wpa_cli commands for ER functionality:
250
251wps_er_start [IP address]
252- start WPS ER functionality
253- the optional IP address parameter can be used to filter operations only
254  to include a single AP
255- if run again while ER is active, the stored information (discovered APs
256  and Enrollees) are shown again
257
258wps_er_stop
259- stop WPS ER functionality
260
261wps_er_learn <UUID|BSSID> <AP PIN>
262- learn AP configuration
263
264wps_er_set_config <UUID|BSSID> <network id>
265- use AP configuration from a locally configured network (e.g., from
266  wps_reg command); this does not change the AP's configuration, but
267  only prepares a configuration to be used when enrolling a new device
268  to the AP
269
270wps_er_config <UUID|BSSID> <AP PIN> <new SSID> <auth> <encr> <new key>
271- examples:
272  wps_er_config 87654321-9abc-def0-1234-56789abc0002 12345670 testing WPA2PSK CCMP 12345678
273  wpa_er_config 87654321-9abc-def0-1234-56789abc0002 12345670 clear OPEN NONE ""
274
275<auth> must be one of the following: OPEN WPAPSK WPA2PSK
276<encr> must be one of the following: NONE WEP TKIP CCMP
277
278
279wps_er_pbc <Enrollee UUID|MAC address>
280- accept an Enrollee PBC using External Registrar
281
282wps_er_pin <Enrollee UUID|"any"|MAC address> <PIN> [Enrollee MAC address]
283- add an Enrollee PIN to External Registrar
284- if Enrollee UUID is not known, "any" can be used to add a wildcard PIN
285- if the MAC address of the enrollee is known, it should be configured
286  to allow the AP to advertise list of authorized enrollees
287
288
289WPS ER events:
290
291WPS_EVENT_ER_AP_ADD
292- WPS ER discovered an AP
293
294WPS-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/
295
296WPS_EVENT_ER_AP_REMOVE
297- WPS ER removed an AP entry
298
299WPS-ER-AP-REMOVE 87654321-9abc-def0-1234-56789abc0002
300
301WPS_EVENT_ER_ENROLLEE_ADD
302- WPS ER discovered a new Enrollee
303
304WPS-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|
305
306WPS_EVENT_ER_ENROLLEE_REMOVE
307- WPS ER removed an Enrollee entry
308
309WPS-ER-ENROLLEE-REMOVE 2b7093f1-d6fb-5108-adbb-bea66bb87333 02:66:a0:ee:17:27
310
311WPS-ER-AP-SETTINGS
312- WPS ER learned AP settings
313
314WPS-ER-AP-SETTINGS uuid=fd91b4ec-e3fa-5891-a57d-8c59efeed1d2 ssid=test-wps auth_type=0x0020 encr_type=0x0008 key=12345678
315
316
317WPS with NFC
318------------
319
320WPS can be used with NFC-based configuration method. An NFC tag
321containing a password token from the Enrollee can be used to
322authenticate the connection instead of the PIN. In addition, an NFC tag
323with a configuration token can be used to transfer AP settings without
324going through the WPS protocol.
325
326When the station acts as an Enrollee, a local NFC tag with a password
327token can be used by touching the NFC interface of a Registrar.
328
329"wps_nfc [BSSID]" command starts WPS protocol run with the local end as
330the Enrollee using the NFC password token that is either pre-configured
331in the configuration file (wps_nfc_dev_pw_id, wps_nfc_dh_pubkey,
332wps_nfc_dh_privkey, wps_nfc_dev_pw) or generated dynamically with
333"wps_nfc_token <WPS|NDEF>" command. The included nfc_pw_token tool
334(build with "make nfc_pw_token") can be used to generate NFC password
335tokens during manufacturing (each station needs to have its own random
336keys).
337
338The "wps_nfc_config_token <WPS/NDEF>" command can be used to build an
339NFC configuration token when wpa_supplicant is controlling an AP
340interface (AP or P2P GO). The output value from this command is a
341hexdump of the current AP configuration (WPS parameter requests this to
342include only the WPS attributes; NDEF parameter requests additional NDEF
343encapsulation to be included). This data needs to be written to an NFC
344tag with an external program. Once written, the NFC configuration token
345can be used to touch an NFC interface on a station to provision the
346credentials needed to access the network.
347
348The "wps_nfc_config_token <WPS/NDEF> <network id>" command can be used
349to build an NFC configuration token based on a locally configured
350network.
351
352If the station includes NFC interface and reads an NFC tag with a MIME
353media type "application/vnd.wfa.wsc", the NDEF message payload (with or
354without NDEF encapsulation) can be delivered to wpa_supplicant using the
355following wpa_cli command:
356
357wps_nfc_tag_read <hexdump of payload>
358
359If the NFC tag contains a configuration token, the network is added to
360wpa_supplicant configuration. If the NFC tag contains a password token,
361the token is added to the WPS Registrar component. This information can
362then be used with wps_reg command (when the NFC password token was from
363an AP) using a special value "nfc-pw" in place of the PIN parameter. If
364the ER functionality has been started (wps_er_start), the NFC password
365token is used to enable enrollment of a new station (that was the source
366of the NFC password token).
367
368"nfc_get_handover_req <NDEF> <WPS-CR>" command can be used to build the
369WPS carrier record for a Handover Request Message for connection
370handover. The first argument selects the format of the output data and
371the second argument selects which type of connection handover is
372requested (WPS-CR = Wi-Fi handover as specified in WSC 2.0).
373
374"nfc_get_handover_sel <NDEF> <WPS> [UUID|BSSID]" command can be used to
375build the contents of a Handover Select Message for connection handover
376when this does not depend on the contents of the Handover Request
377Message. The first argument selects the format of the output data and
378the second argument selects which type of connection handover is
379requested (WPS = Wi-Fi handover as specified in WSC 2.0). If the options
380UUID|BSSID argument is included, this is a request to build the handover
381message for the specified AP when wpa_supplicant is operating as a WPS
382ER.
383
384"nfc_report_handover <INIT/RESP> WPS <carrier from handover request>
385<carrier from handover select>" can be used as an alternative way for
386reporting completed NFC connection handover. The first parameter
387indicates whether the local device initiated or responded to the
388connection handover and the carrier records are the selected carrier
389from the handover request and select messages as a hexdump.
390
391The "wps_er_nfc_config_token <WPS/NDEF> <UUID|BSSID>" command can be
392used to build an NFC configuration token for the specified AP when
393wpa_supplicant is operating as a WPS ER. The output value from this
394command is a hexdump of the selected AP configuration (WPS parameter
395requests this to include only the WPS attributes; NDEF parameter
396requests additional NDEF encapsulation to be included). This data needs
397to be written to an NFC tag with an external program. Once written, the
398NFC configuration token can be used to touch an NFC interface on a
399station to provision the credentials needed to access the network.
400