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