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 63CONFIG_WPS2=y 64 65If you want to enable WPS external registrar (ER) functionality, you 66will also need to add following line: 67 68CONFIG_WPS_ER=y 69 70Following parameter can be used to enable support for NFC config method: 71 72CONFIG_WPS_NFC=y 73 74 75WPS needs the Universally Unique IDentifier (UUID; see RFC 4122) for 76the device. This is configured in the runtime configuration for 77wpa_supplicant (if not set, UUID will be generated based on local MAC 78address): 79 80# example UUID for WPS 81uuid=12345678-9abc-def0-1234-56789abcdef0 82 83The network configuration blocks needed for WPS are added 84automatically based on control interface commands, so they do not need 85to be added explicitly in the configuration file. 86 87WPS registration will generate new network blocks for the acquired 88credentials. If these are to be stored for future use (after 89restarting wpa_supplicant), wpa_supplicant will need to be configured 90to allow configuration file updates: 91 92update_config=1 93 94 95 96External operations 97------------------- 98 99WPS requires either a device PIN code (usually, 8-digit number) or a 100pushbutton event (for PBC) to allow a new WPS Enrollee to join the 101network. wpa_supplicant uses the control interface as an input channel 102for these events. 103 104The PIN value used in the commands must be processed by an UI to 105remove non-digit characters and potentially, to verify the checksum 106digit. "wpa_cli wps_check_pin <PIN>" can be used to do such processing. 107It returns FAIL if the PIN is invalid, or FAIL-CHECKSUM if the checksum 108digit is incorrect, or the processed PIN (non-digit characters removed) 109if the PIN is valid. 110 111If the client device has a display, a random PIN has to be generated 112for each WPS registration session. wpa_supplicant can do this with a 113control interface request, e.g., by calling wpa_cli: 114 115wpa_cli wps_pin any 116 117This will return the generated 8-digit PIN which will then need to be 118entered at the Registrar to complete WPS registration. At that point, 119the client will be enrolled with credentials needed to connect to the 120AP to access the network. 121 122 123If the client device does not have a display that could show the 124random PIN, a hardcoded PIN that is printed on a label can be 125used. wpa_supplicant is notified this with a control interface 126request, e.g., by calling wpa_cli: 127 128wpa_cli wps_pin any 12345670 129 130This starts the WPS negotiation in the same way as above with the 131generated PIN. 132 133 134If a random PIN is needed for a user interface, "wpa_cli wps_pin get" 135can be used to generate a new PIN without starting WPS negotiation. 136This random PIN can then be passed as an argument to another wps_pin 137call when the actual operation should be started. 138 139If the client design wants to support optional WPS PBC mode, this can 140be enabled by either a physical button in the client device or a 141virtual button in the user interface. The PBC operation requires that 142a button is also pressed at the AP/Registrar at about the same time (2 143minute window). wpa_supplicant is notified of the local button event 144over the control interface, e.g., by calling wpa_cli: 145 146wpa_cli wps_pbc 147 148At this point, the AP/Registrar has two minutes to complete WPS 149negotiation which will generate a new WPA PSK in the same way as the 150PIN method described above. 151 152 153If the client wants to operate in the Registrar role to learn the 154current AP configuration and optionally, to configure an AP, 155wpa_supplicant is notified over the control interface, e.g., with 156wpa_cli: 157 158wpa_cli wps_reg <AP BSSID> <AP PIN> 159(example: wpa_cli wps_reg 02:34:56:78:9a:bc 12345670) 160 161This is used to fetch the current AP settings instead of actually 162changing them. The main difference with the wps_pin command is that 163wps_reg uses the AP PIN (e.g., from a label on the AP) instead of a 164PIN generated at the client. 165 166In order to change the AP configuration, the new configuration 167parameters are given to the wps_reg command: 168 169wpa_cli wps_reg <AP BSSID> <AP PIN> <new SSID> <auth> <encr> <new key> 170examples: 171 wpa_cli wps_reg 02:34:56:78:9a:bc 12345670 testing WPA2PSK CCMP 12345678 172 wpa_cli wps_reg 02:34:56:78:9a:bc 12345670 clear OPEN NONE "" 173 174<auth> must be one of the following: OPEN WPAPSK WPA2PSK 175<encr> must be one of the following: NONE WEP TKIP CCMP 176 177 178Scanning 179-------- 180 181Scan results ('wpa_cli scan_results' or 'wpa_cli bss <idx>') include a 182flags field that is used to indicate whether the BSS support WPS. If 183the AP support WPS, but has not recently activated a Registrar, [WPS] 184flag will be included. If PIN method has been recently selected, 185[WPS-PIN] is shown instead. Similarly, [WPS-PBC] is shown if PBC mode 186is in progress. GUI programs can use these as triggers for suggesting 187a guided WPS configuration to the user. In addition, control interface 188monitor events WPS-AP-AVAILABLE{,-PBC,-PIN} can be used to find out if 189there are WPS enabled APs in scan results without having to go through 190all the details in the GUI. These notification could be used, e.g., to 191suggest possible WPS connection to the user. 192 193 194wpa_gui 195------- 196 197wpa_gui-qt4 directory contains a sample GUI that shows an example of 198how WPS support can be integrated into the GUI. Its main window has a 199WPS tab that guides user through WPS registration with automatic AP 200selection. In addition, it shows how WPS can be started manually by 201selecting an AP from scan results. 202 203 204Credential processing 205--------------------- 206 207By default, wpa_supplicant processes received credentials and updates 208its configuration internally. However, it is possible to 209control these operations from external programs, if desired. 210 211This internal processing can be disabled with wps_cred_processing=1 212option. When this is used, an external program is responsible for 213processing the credential attributes and updating wpa_supplicant 214configuration based on them. 215 216Following control interface messages are sent out for external programs: 217 218WPS-CRED-RECEIVED <hexdump of Credential attribute(s)> 219For example: 220<2>WPS-CRED-RECEIVED 100e006f10260001011045000c6a6b6d2d7770732d74657374100300020020100f000200081027004030653462303435366332363666653064333961643135353461316634626637313234333761636664623766333939653534663166316230323061643434386235102000060266a0ee1727 221 222 223wpa_supplicant as WPS External Registrar (ER) 224--------------------------------------------- 225 226wpa_supplicant can be used as a WPS ER to configure an AP or enroll 227new Enrollee to join the network. This functionality uses UPnP and 228requires that a working IP connectivity is available with the AP (this 229can be either over a wired or wireless connection). 230 231Separate wpa_supplicant process can be started for WPS ER 232operations. A special "none" driver can be used in such a case to 233indicate that no local network interface is actually controlled. For 234example, following command could be used to start the ER: 235 236wpa_supplicant -Dnone -c er.conf -ieth0 237 238Sample er.conf: 239 240ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=admin 241device_name=WPS External Registrar 242 243 244wpa_cli commands for ER functionality: 245 246wps_er_start [IP address] 247- start WPS ER functionality 248- the optional IP address parameter can be used to filter operations only 249 to include a single AP 250- if run again while ER is active, the stored information (discovered APs 251 and Enrollees) are shown again 252 253wps_er_stop 254- stop WPS ER functionality 255 256wps_er_learn <UUID> <AP PIN> 257- learn AP configuration 258 259wps_er_set_config <UUID> <network id> 260- use AP configuration from a locally configured network (e.g., from 261 wps_reg command); this does not change the AP's configuration, but 262 only prepares a configuration to be used when enrolling a new device 263 to the AP 264 265wps_er_config <UUID> <AP PIN> <new SSID> <auth> <encr> <new key> 266- examples: 267 wps_er_config 87654321-9abc-def0-1234-56789abc0002 12345670 testing WPA2PSK CCMP 12345678 268 wpa_er_config 87654321-9abc-def0-1234-56789abc0002 12345670 clear OPEN NONE "" 269 270<auth> must be one of the following: OPEN WPAPSK WPA2PSK 271<encr> must be one of the following: NONE WEP TKIP CCMP 272 273 274wps_er_pbc <Enrollee UUID> 275- accept an Enrollee PBC using External Registrar 276 277wps_er_pin <Enrollee UUID> <PIN> [Enrollee MAC address] 278- add an Enrollee PIN to External Registrar 279- if Enrollee UUID is not known, "any" can be used to add a wildcard PIN 280- if the MAC address of the enrollee is known, it should be configured 281 to allow the AP to advertise list of authorized enrollees 282 283 284WPS ER events: 285 286WPS_EVENT_ER_AP_ADD 287- WPS ER discovered an AP 288 289WPS-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/ 290 291WPS_EVENT_ER_AP_REMOVE 292- WPS ER removed an AP entry 293 294WPS-ER-AP-REMOVE 87654321-9abc-def0-1234-56789abc0002 295 296WPS_EVENT_ER_ENROLLEE_ADD 297- WPS ER discovered a new Enrollee 298 299WPS-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| 300 301WPS_EVENT_ER_ENROLLEE_REMOVE 302- WPS ER removed an Enrollee entry 303 304WPS-ER-ENROLLEE-REMOVE 2b7093f1-d6fb-5108-adbb-bea66bb87333 02:66:a0:ee:17:27 305 306WPS-ER-AP-SETTINGS 307- WPS ER learned AP settings 308 309WPS-ER-AP-SETTINGS uuid=fd91b4ec-e3fa-5891-a57d-8c59efeed1d2 ssid=test-wps auth_type=0x0020 encr_type=0x0008 key=12345678 310 311 312WPS with NFC 313------------ 314 315WPS can be used with NFC-based configuration method. An NFC tag 316containing a password token from the Enrollee can be used to 317authenticate the connection instead of the PIN. In addition, an NFC tag 318with a configuration token can be used to transfer AP settings without 319going through the WPS protocol. 320 321When the station acts as an Enrollee, a local NFC tag with a password 322token can be used by touching the NFC interface of a Registrar. 323 324"wps_nfc [BSSID]" command starts WPS protocol run with the local end as 325the Enrollee using the NFC password token that is either pre-configured 326in the configuration file (wps_nfc_dev_pw_id, wps_nfc_dh_pubkey, 327wps_nfc_dh_privkey, wps_nfc_dev_pw) or generated dynamically with 328"wps_nfc_token <WPS|NDEF>" command. The included nfc_pw_token tool 329(build with "make nfc_pw_token") can be used to generate NFC password 330tokens during manufacturing (each station needs to have its own random 331keys). 332 333If the station includes NFC interface and reads an NFC tag with a MIME 334media type "application/vnd.wfa.wsc", the NDEF message payload (with or 335without NDEF encapsulation) can be delivered to wpa_supplicant using the 336following wpa_cli command: 337 338wps_nfc_tag_read <hexdump of payload> 339 340If the NFC tag contains a configuration token, the network is added to 341wpa_supplicant configuration. If the NFC tag contains a password token, 342the token is added to the WPS Registrar component. This information can 343then be used with wps_reg command (when the NFC password token was from 344an AP) using a special value "nfc-pw" in place of the PIN parameter. If 345the ER functionality has been started (wps_er_start), the NFC password 346token is used to enable enrollment of a new station (that was the source 347of the NFC password token). 348