xref: /freebsd/contrib/wpa/hostapd/README-WPS (revision 7aa383846770374466b1dcb2cefd71bde9acf463)
1hostapd and Wi-Fi Protected Setup (WPS)
2=======================================
3
4This document describes how the WPS implementation in hostapd can be
5configured and how an external component on an AP (e.g., web UI) is
6used to enable enrollment of client devices.
7
8
9Introduction to WPS
10-------------------
11
12Wi-Fi Protected Setup (WPS) is a mechanism for easy configuration of a
13wireless network. It allows automated generation of random keys (WPA
14passphrase/PSK) and configuration of an access point and client
15devices. WPS includes number of methods for setting up connections
16with PIN method and push-button configuration (PBC) being the most
17commonly deployed options.
18
19While WPS can enable more home networks to use encryption in the
20wireless network, it should be noted that the use of the PIN and
21especially PBC mechanisms for authenticating the initial key setup is
22not very secure. As such, use of WPS may not be suitable for
23environments that require secure network access without chance for
24allowing outsiders to gain access during the setup phase.
25
26WPS uses following terms to describe the entities participating in the
27network setup:
28- access point: the WLAN access point
29- Registrar: a device that control a network and can authorize
30  addition of new devices); this may be either in the AP ("internal
31  Registrar") or in an external device, e.g., a laptop, ("external
32  Registrar")
33- Enrollee: a device that is being authorized to use the network
34
35It should also be noted that the AP and a client device may change
36roles (i.e., AP acts as an Enrollee and client device as a Registrar)
37when WPS is used to configure the access point.
38
39
40More information about WPS is available from Wi-Fi Alliance:
41http://www.wi-fi.org/wifi-protected-setup
42
43
44hostapd implementation
45----------------------
46
47hostapd includes an optional WPS component that can be used as an
48internal WPS Registrar to manage addition of new WPS enabled clients
49to the network. In addition, WPS Enrollee functionality in hostapd can
50be used to allow external WPS Registrars to configure the access
51point, e.g., for initial network setup. In addition, hostapd can proxy a
52WPS registration between a wireless Enrollee and an external Registrar
53(e.g., Microsoft Vista or Atheros JumpStart) with UPnP.
54
55
56hostapd configuration
57---------------------
58
59WPS is an optional component that needs to be enabled in hostapd build
60configuration (.config). Here is an example configuration that
61includes WPS support and uses madwifi driver interface:
62
63CONFIG_DRIVER_MADWIFI=y
64CFLAGS += -I/usr/src/madwifi-0.9.3
65CONFIG_EAP=y
66CONFIG_WPS=y
67CONFIG_WPS_UPNP=y
68
69
70Following section shows an example runtime configuration
71(hostapd.conf) that enables WPS:
72
73# Configure the driver and network interface
74driver=madwifi
75interface=ath0
76
77# WPA2-Personal configuration for the AP
78ssid=wps-test
79wpa=2
80wpa_key_mgmt=WPA-PSK
81wpa_pairwise=CCMP
82# Default WPA passphrase for legacy (non-WPS) clients
83wpa_passphrase=12345678
84# Enable random per-device PSK generation for WPS clients
85# Please note that the file has to exists for hostapd to start (i.e., create an
86# empty file as a starting point).
87wpa_psk_file=/etc/hostapd.psk
88
89# Enable control interface for PBC/PIN entry
90ctrl_interface=/var/run/hostapd
91
92# Enable internal EAP server for EAP-WSC (part of Wi-Fi Protected Setup)
93eap_server=1
94
95# WPS configuration (AP configured, do not allow external WPS Registrars)
96wps_state=2
97ap_setup_locked=1
98# If UUID is not configured, it will be generated based on local MAC address.
99uuid=87654321-9abc-def0-1234-56789abc0000
100wps_pin_requests=/var/run/hostapd.pin-req
101device_name=Wireless AP
102manufacturer=Company
103model_name=WAP
104model_number=123
105serial_number=12345
106device_type=6-0050F204-1
107os_version=01020300
108config_methods=label display push_button keypad
109
110# if external Registrars are allowed, UPnP support could be added:
111#upnp_iface=br0
112#friendly_name=WPS Access Point
113
114
115External operations
116-------------------
117
118WPS requires either a device PIN code (usually, 8-digit number) or a
119pushbutton event (for PBC) to allow a new WPS Enrollee to join the
120network. hostapd uses the control interface as an input channel for
121these events.
122
123When a client device (WPS Enrollee) connects to hostapd (WPS
124Registrar) in order to start PIN mode negotiation for WPS, an
125identifier (Enrollee UUID) is sent. hostapd will need to be configured
126with a device password (PIN) for this Enrollee. This is an operation
127that requires user interaction (assuming there are no pre-configured
128PINs on the AP for a set of Enrollee).
129
130The PIN request with information about the device is appended to the
131wps_pin_requests file (/var/run/hostapd.pin-req in this example). In
132addition, hostapd control interface event is sent as a notification of
133a new device. The AP could use, e.g., a web UI for showing active
134Enrollees to the user and request a PIN for an Enrollee.
135
136The PIN request file has one line for every Enrollee that connected to
137the AP, but for which there was no PIN. Following information is
138provided for each Enrollee (separated with tabulators):
139- timestamp (seconds from 1970-01-01)
140- Enrollee UUID
141- MAC address
142- Device name
143- Manufacturer
144- Model Name
145- Model Number
146- Serial Number
147- Device category
148
149Example line in the /var/run/hostapd.pin-req file:
1501200188391	53b63a98-d29e-4457-a2ed-094d7e6a669c	Intel(R) Centrino(R)	Intel Corporation	Intel(R) Centrino(R)	-	-	1-0050F204-1
151
152Control interface data:
153WPS-PIN-NEEDED [UUID-E|MAC Address|Device Name|Manufacturer|Model Name|Model Number|Serial Number|Device Category]
154For example:
155<2>WPS-PIN-NEEDED [53b63a98-d29e-4457-a2ed-094d7e6a669c|02:12:34:56:78:9a|Device|Manuf|Model|Model Number|Serial Number|1-0050F204-1]
156
157When the user enters a PIN for a pending Enrollee, e.g., on the web
158UI), hostapd needs to be notified of the new PIN over the control
159interface. This can be done either by using the UNIX domain socket
160-based control interface directly (src/common/wpa_ctrl.c provides
161helper functions for using the interface) or by calling hostapd_cli.
162
163Example command to add a PIN (12345670) for an Enrollee:
164
165hostapd_cli wps_pin 53b63a98-d29e-4457-a2ed-094d7e6a669c 12345670
166
167If the UUID-E is not available (e.g., Enrollee waits for the Registrar
168to be selected before connecting), wildcard UUID may be used to allow
169the PIN to be used once with any UUID:
170
171hostapd_cli wps_pin any 12345670
172
173To reduce likelihood of PIN being used with other devices or of
174forgetting an active PIN available for potential attackers, expiration
175time can be set for the new PIN:
176
177hostapd_cli wps_pin any 12345670 300
178
179
180After this, the Enrollee can connect to the AP again and complete WPS
181negotiation. At that point, a new, random WPA PSK is generated for the
182client device and the client can then use that key to connect to the
183AP to access the network.
184
185
186If the AP includes a pushbutton, WPS PBC mode can be used. It is
187enabled by pushing a button on both the AP and the client at about the
188same time (2 minute window). hostapd needs to be notified about the AP
189button pushed event over the control interface, e.g., by calling
190hostapd_cli:
191
192hostapd_cli wps_pbc
193
194At this point, the client has two minutes to complete WPS negotiation
195which will generate a new WPA PSK in the same way as the PIN method
196described above.
197
198
199Credential generation and configuration changes
200-----------------------------------------------
201
202By default, hostapd generates credentials for Enrollees and processing
203AP configuration updates internally. However, it is possible to
204control these operations from external programs, if desired.
205
206The internal credential generation can be disabled with
207skip_cred_build=1 option in the configuration. extra_cred option will
208then need to be used to provide pre-configured Credential attribute(s)
209for hostapd to use. The exact data from this binary file will be sent,
210i.e., it will have to include valid WPS attributes. extra_cred can
211also be used to add additional networks if the Registrar is used to
212configure credentials for multiple networks.
213
214Processing of received configuration updates can be disabled with
215wps_cred_processing=1 option. When this is used, an external program
216is responsible for creating hostapd configuration files and processing
217configuration updates based on messages received from hostapd over
218control interface. This will also include the initial configuration on
219first successful registration if the AP is initially set in
220unconfigured state.
221
222Following control interface messages are sent out for external programs:
223
224WPS-REG-SUCCESS <Enrollee MAC address <UUID-E>
225For example:
226<2>WPS-REG-SUCCESS 02:66:a0:ee:17:27 2b7093f1-d6fb-5108-adbb-bea66bb87333
227
228This can be used to tricker change from unconfigured to configured
229state (random configuration based on the first successful WPS
230registration). In addition, this can be used to update AP UI about the
231status of WPS registration progress.
232
233
234WPS-NEW-AP-SETTINGS <hexdump of AP Setup attributes>
235For example:
236<2>WPS-NEW-AP-SETTINGS 10260001011045000c6a6b6d2d7770732d74657374100300020020100f00020008102700403065346230343536633236366665306433396164313535346131663462663731323433376163666462376633393965353466316631623032306164343438623510200006024231cede15101e000844
237
238This can be used to update the externally stored AP configuration and
239then update hostapd configuration (followed by restarting of hostapd).
240