README-WPS 14 KB

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  1. hostapd and Wi-Fi Protected Setup (WPS)
  2. =======================================
  3. This document describes how the WPS implementation in hostapd can be
  4. configured and how an external component on an AP (e.g., web UI) is
  5. used to enable enrollment of client devices.
  6. Introduction to WPS
  7. -------------------
  8. Wi-Fi Protected Setup (WPS) is a mechanism for easy configuration of a
  9. wireless network. It allows automated generation of random keys (WPA
  10. passphrase/PSK) and configuration of an access point and client
  11. devices. WPS includes number of methods for setting up connections
  12. with PIN method and push-button configuration (PBC) being the most
  13. commonly deployed options.
  14. While WPS can enable more home networks to use encryption in the
  15. wireless network, it should be noted that the use of the PIN and
  16. especially PBC mechanisms for authenticating the initial key setup is
  17. not very secure. As such, use of WPS may not be suitable for
  18. environments that require secure network access without chance for
  19. allowing outsiders to gain access during the setup phase.
  20. WPS uses following terms to describe the entities participating in the
  21. network setup:
  22. - access point: the WLAN access point
  23. - Registrar: a device that control a network and can authorize
  24. addition of new devices); this may be either in the AP ("internal
  25. Registrar") or in an external device, e.g., a laptop, ("external
  26. Registrar")
  27. - Enrollee: a device that is being authorized to use the network
  28. It should also be noted that the AP and a client device may change
  29. roles (i.e., AP acts as an Enrollee and client device as a Registrar)
  30. when WPS is used to configure the access point.
  31. More information about WPS is available from Wi-Fi Alliance:
  32. http://www.wi-fi.org/wifi-protected-setup
  33. hostapd implementation
  34. ----------------------
  35. hostapd includes an optional WPS component that can be used as an
  36. internal WPS Registrar to manage addition of new WPS enabled clients
  37. to the network. In addition, WPS Enrollee functionality in hostapd can
  38. be used to allow external WPS Registrars to configure the access
  39. point, e.g., for initial network setup. In addition, hostapd can proxy a
  40. WPS registration between a wireless Enrollee and an external Registrar
  41. (e.g., Microsoft Vista or Atheros JumpStart) with UPnP.
  42. hostapd configuration
  43. ---------------------
  44. WPS is an optional component that needs to be enabled in hostapd build
  45. configuration (.config). Here is an example configuration that
  46. includes WPS support and uses nl80211 driver interface:
  47. CONFIG_DRIVER_NL80211=y
  48. CONFIG_WPS=y
  49. CONFIG_WPS_UPNP=y
  50. Following parameter can be used to enable support for NFC config method:
  51. CONFIG_WPS_NFC=y
  52. Following section shows an example runtime configuration
  53. (hostapd.conf) that enables WPS:
  54. # Configure the driver and network interface
  55. driver=nl80211
  56. interface=wlan0
  57. # WPA2-Personal configuration for the AP
  58. ssid=wps-test
  59. wpa=2
  60. wpa_key_mgmt=WPA-PSK
  61. wpa_pairwise=CCMP
  62. # Default WPA passphrase for legacy (non-WPS) clients
  63. wpa_passphrase=12345678
  64. # Enable random per-device PSK generation for WPS clients
  65. # Please note that the file has to exists for hostapd to start (i.e., create an
  66. # empty file as a starting point).
  67. wpa_psk_file=/etc/hostapd.psk
  68. # Enable control interface for PBC/PIN entry
  69. ctrl_interface=/var/run/hostapd
  70. # Enable internal EAP server for EAP-WSC (part of Wi-Fi Protected Setup)
  71. eap_server=1
  72. # WPS configuration (AP configured, do not allow external WPS Registrars)
  73. wps_state=2
  74. ap_setup_locked=1
  75. # If UUID is not configured, it will be generated based on local MAC address.
  76. uuid=87654321-9abc-def0-1234-56789abc0000
  77. wps_pin_requests=/var/run/hostapd.pin-req
  78. device_name=Wireless AP
  79. manufacturer=Company
  80. model_name=WAP
  81. model_number=123
  82. serial_number=12345
  83. device_type=6-0050F204-1
  84. os_version=01020300
  85. config_methods=label display push_button keypad
  86. # if external Registrars are allowed, UPnP support could be added:
  87. #upnp_iface=br0
  88. #friendly_name=WPS Access Point
  89. External operations
  90. -------------------
  91. WPS requires either a device PIN code (usually, 8-digit number) or a
  92. pushbutton event (for PBC) to allow a new WPS Enrollee to join the
  93. network. hostapd uses the control interface as an input channel for
  94. these events.
  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. "hostapd_cli wps_check_pin <PIN>" can be used to do such
  98. processing. It returns FAIL if the PIN is invalid, or FAIL-CHECKSUM if
  99. the checksum digit is incorrect, or the processed PIN (non-digit
  100. characters removed) if the PIN is valid.
  101. When a client device (WPS Enrollee) connects to hostapd (WPS
  102. Registrar) in order to start PIN mode negotiation for WPS, an
  103. identifier (Enrollee UUID) is sent. hostapd will need to be configured
  104. with a device password (PIN) for this Enrollee. This is an operation
  105. that requires user interaction (assuming there are no pre-configured
  106. PINs on the AP for a set of Enrollee).
  107. The PIN request with information about the device is appended to the
  108. wps_pin_requests file (/var/run/hostapd.pin-req in this example). In
  109. addition, hostapd control interface event is sent as a notification of
  110. a new device. The AP could use, e.g., a web UI for showing active
  111. Enrollees to the user and request a PIN for an Enrollee.
  112. The PIN request file has one line for every Enrollee that connected to
  113. the AP, but for which there was no PIN. Following information is
  114. provided for each Enrollee (separated with tabulators):
  115. - timestamp (seconds from 1970-01-01)
  116. - Enrollee UUID
  117. - MAC address
  118. - Device name
  119. - Manufacturer
  120. - Model Name
  121. - Model Number
  122. - Serial Number
  123. - Device category
  124. Example line in the /var/run/hostapd.pin-req file:
  125. 1200188391 53b63a98-d29e-4457-a2ed-094d7e6a669c Intel(R) Centrino(R) Intel Corporation Intel(R) Centrino(R) - - 1-0050F204-1
  126. Control interface data:
  127. WPS-PIN-NEEDED [UUID-E|MAC Address|Device Name|Manufacturer|Model Name|Model Number|Serial Number|Device Category]
  128. For example:
  129. <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]
  130. When the user enters a PIN for a pending Enrollee, e.g., on the web
  131. UI), hostapd needs to be notified of the new PIN over the control
  132. interface. This can be done either by using the UNIX domain socket
  133. -based control interface directly (src/common/wpa_ctrl.c provides
  134. helper functions for using the interface) or by calling hostapd_cli.
  135. Example command to add a PIN (12345670) for an Enrollee:
  136. hostapd_cli wps_pin 53b63a98-d29e-4457-a2ed-094d7e6a669c 12345670
  137. If the UUID-E is not available (e.g., Enrollee waits for the Registrar
  138. to be selected before connecting), wildcard UUID may be used to allow
  139. the PIN to be used once with any UUID:
  140. hostapd_cli wps_pin any 12345670
  141. To reduce likelihood of PIN being used with other devices or of
  142. forgetting an active PIN available for potential attackers, expiration
  143. time in seconds can be set for the new PIN (value 0 indicates no
  144. expiration):
  145. hostapd_cli wps_pin any 12345670 300
  146. If the MAC address of the enrollee is known, it should be configured
  147. to allow the AP to advertise list of authorized enrollees:
  148. hostapd_cli wps_pin 53b63a98-d29e-4457-a2ed-094d7e6a669c \
  149. 12345670 300 00:11:22:33:44:55
  150. After this, the Enrollee can connect to the AP again and complete WPS
  151. negotiation. At that point, a new, random WPA PSK is generated for the
  152. client device and the client can then use that key to connect to the
  153. AP to access the network.
  154. If the AP includes a pushbutton, WPS PBC mode can be used. It is
  155. enabled by pushing a button on both the AP and the client at about the
  156. same time (2 minute window). hostapd needs to be notified about the AP
  157. button pushed event over the control interface, e.g., by calling
  158. hostapd_cli:
  159. hostapd_cli wps_pbc
  160. At this point, the client has two minutes to complete WPS negotiation
  161. which will generate a new WPA PSK in the same way as the PIN method
  162. described above.
  163. When an external Registrar is used, the AP can act as an Enrollee and
  164. use its AP PIN. A static AP PIN (e.g., one one a label in the AP
  165. device) can be configured in hostapd.conf (ap_pin parameter). A more
  166. secure option is to use hostapd_cli wps_ap_pin command to enable the
  167. AP PIN only based on user action (and even better security by using a
  168. random AP PIN for each session, i.e., by using "wps_ap_pin random"
  169. command with a timeout value). Following commands are available for
  170. managing the dynamic AP PIN operations:
  171. hostapd_cli wps_ap_pin disable
  172. - disable AP PIN (i.e., do not allow external Registrars to use it to
  173. learn the current AP settings or to reconfigure the AP)
  174. hostapd_cli wps_ap_pin random [timeout]
  175. - generate a random AP PIN and enable it
  176. - if the optional timeout parameter is given, the AP PIN will be enabled
  177. for the specified number of seconds
  178. hostapd_cli wps_ap_pin get
  179. - fetch the current AP PIN
  180. hostapd_cli wps_ap_pin set <PIN> [timeout]
  181. - set the AP PIN and enable it
  182. - if the optional timeout parameter is given, the AP PIN will be enabled
  183. for the specified number of seconds
  184. hostapd_cli get_config
  185. - display the current configuration
  186. hostapd_cli wps_config <new SSID> <auth> <encr> <new key>
  187. examples:
  188. hostapd_cli wps_config testing WPA2PSK CCMP 12345678
  189. hostapd_cli wps_config "no security" OPEN NONE ""
  190. <auth> must be one of the following: OPEN WPAPSK WPA2PSK
  191. <encr> must be one of the following: NONE WEP TKIP CCMP
  192. Credential generation and configuration changes
  193. -----------------------------------------------
  194. By default, hostapd generates credentials for Enrollees and processing
  195. AP configuration updates internally. However, it is possible to
  196. control these operations from external programs, if desired.
  197. The internal credential generation can be disabled with
  198. skip_cred_build=1 option in the configuration. extra_cred option will
  199. then need to be used to provide pre-configured Credential attribute(s)
  200. for hostapd to use. The exact data from this binary file will be sent,
  201. i.e., it will have to include valid WPS attributes. extra_cred can
  202. also be used to add additional networks if the Registrar is used to
  203. configure credentials for multiple networks.
  204. Processing of received configuration updates can be disabled with
  205. wps_cred_processing=1 option. When this is used, an external program
  206. is responsible for creating hostapd configuration files and processing
  207. configuration updates based on messages received from hostapd over
  208. control interface. This will also include the initial configuration on
  209. first successful registration if the AP is initially set in
  210. unconfigured state.
  211. Following control interface messages are sent out for external programs:
  212. WPS-REG-SUCCESS <Enrollee MAC address <UUID-E>
  213. For example:
  214. <2>WPS-REG-SUCCESS 02:66:a0:ee:17:27 2b7093f1-d6fb-5108-adbb-bea66bb87333
  215. This can be used to trigger change from unconfigured to configured
  216. state (random configuration based on the first successful WPS
  217. registration). In addition, this can be used to update AP UI about the
  218. status of WPS registration progress.
  219. WPS-NEW-AP-SETTINGS <hexdump of AP Setup attributes>
  220. For example:
  221. <2>WPS-NEW-AP-SETTINGS 10260001011045000c6a6b6d2d7770732d74657374100300020020100f00020008102700403065346230343536633236366665306433396164313535346131663462663731323433376163666462376633393965353466316631623032306164343438623510200006024231cede15101e000844
  222. This can be used to update the externally stored AP configuration and
  223. then update hostapd configuration (followed by restarting of hostapd).
  224. WPS with NFC
  225. ------------
  226. WPS can be used with NFC-based configuration method. An NFC tag
  227. containing a password token from the Enrollee can be used to
  228. authenticate the connection instead of the PIN. In addition, an NFC tag
  229. with a configuration token can be used to transfer AP settings without
  230. going through the WPS protocol.
  231. When the AP acts as an Enrollee, a local NFC tag with a password token
  232. can be used by touching the NFC interface of an external Registrar. The
  233. wps_nfc_token command is used to manage use of the NFC password token
  234. from the AP. "wps_nfc_token enable" enables the use of the AP's NFC
  235. password token (in place of AP PIN) and "wps_nfc_token disable" disables
  236. the NFC password token.
  237. The NFC password token that is either pre-configured in the
  238. configuration file (wps_nfc_dev_pw_id, wps_nfc_dh_pubkey,
  239. wps_nfc_dh_privkey, wps_nfc_dev_pw) or generated dynamically with
  240. "wps_nfc_token <WPS|NDEF>" command. The nfc_pw_token tool from
  241. wpa_supplicant can be used to generate NFC password tokens during
  242. manufacturing (each AP needs to have its own random keys).
  243. The "wps_nfc_config_token <WPS/NDEF>" command can be used to build an
  244. NFC configuration token. The output value from this command is a hexdump
  245. of the current AP configuration (WPS parameter requests this to include
  246. only the WPS attributes; NDEF parameter requests additional NDEF
  247. encapsulation to be included). This data needs to be written to an NFC
  248. tag with an external program. Once written, the NFC configuration token
  249. can be used to touch an NFC interface on a station to provision the
  250. credentials needed to access the network.
  251. When the NFC device on the AP reads an NFC tag with a MIME media type
  252. "application/vnd.wfa.wsc", the NDEF message payload (with or without
  253. NDEF encapsulation) can be delivered to hostapd using the
  254. following hostapd_cli command:
  255. wps_nfc_tag_read <hexdump of payload>
  256. If the NFC tag contains a password token, the token is added to the
  257. internal Registrar. This allows station Enrollee from which the password
  258. token was received to run through WPS protocol to provision the
  259. credential.
  260. "nfc_get_handover_sel <NDEF> <WPS>" command can be used to build the
  261. contents of a Handover Select Message for connection handover when this
  262. does not depend on the contents of the Handover Request Message. The
  263. first argument selects the format of the output data and the second
  264. argument selects which type of connection handover is requested (WPS =
  265. Wi-Fi handover as specified in WSC 2.0).
  266. "nfc_report_handover <INIT/RESP> WPS <carrier from handover request>
  267. <carrier from handover select>" is used to report completed NFC
  268. connection handover. The first parameter indicates whether the local
  269. device initiated or responded to the connection handover and the carrier
  270. records are the selected carrier from the handover request and select
  271. messages as a hexdump.