README-WPS revision 8d520ff1dc2da35cdca849e982051b86468016d8
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. The current version of wpa_supplicant does not 51support operation as an external WLAN Management Registrar for adding 52new client devices or configuring the AP over UPnP. 53 54 55wpa_supplicant configuration 56---------------------------- 57 58WPS is an optional component that needs to be enabled in 59wpa_supplicant build configuration (.config). Here is an example 60configuration that includes WPS support and Linux wireless extensions 61-based driver interface: 62 63CONFIG_DRIVER_WEXT=y 64CONFIG_WPS=y 65CONFIG_WPS2=y 66 67 68WPS needs the Universally Unique IDentifier (UUID; see RFC 4122) for 69the device. This is configured in the runtime configuration for 70wpa_supplicant (if not set, UUID will be generated based on local MAC 71address): 72 73# example UUID for WPS 74uuid=12345678-9abc-def0-1234-56789abcdef0 75 76The network configuration blocks needed for WPS are added 77automatically based on control interface commands, so they do not need 78to be added explicitly in the configuration file. 79 80WPS registration will generate new network blocks for the acquired 81credentials. If these are to be stored for future use (after 82restarting wpa_supplicant), wpa_supplicant will need to be configured 83to allow configuration file updates: 84 85update_config=1 86 87 88 89External operations 90------------------- 91 92WPS requires either a device PIN code (usually, 8-digit number) or a 93pushbutton event (for PBC) to allow a new WPS Enrollee to join the 94network. wpa_supplicant uses the control interface as an input channel 95for these events. 96 97The PIN value used in the commands must be processed by an UI to 98remove non-digit characters and potentially, to verify the checksum 99digit. "wpa_cli wps_check_pin <PIN>" can be used to do such processing. 100It returns FAIL if the PIN is invalid, or FAIL-CHECKSUM if the checksum 101digit is incorrect, or the processed PIN (non-digit characters removed) 102if the PIN is valid. 103 104If the client device has a display, a random PIN has to be generated 105for each WPS registration session. wpa_supplicant can do this with a 106control interface request, e.g., by calling wpa_cli: 107 108wpa_cli wps_pin any 109 110This will return the generated 8-digit PIN which will then need to be 111entered at the Registrar to complete WPS registration. At that point, 112the client will be enrolled with credentials needed to connect to the 113AP to access the network. 114 115 116If the client device does not have a display that could show the 117random PIN, a hardcoded PIN that is printed on a label can be 118used. wpa_supplicant is notified this with a control interface 119request, e.g., by calling wpa_cli: 120 121wpa_cli wps_pin any 12345670 122 123This starts the WPS negotiation in the same way as above with the 124generated PIN. 125 126 127If the client design wants to support optional WPS PBC mode, this can 128be enabled by either a physical button in the client device or a 129virtual button in the user interface. The PBC operation requires that 130a button is also pressed at the AP/Registrar at about the same time (2 131minute window). wpa_supplicant is notified of the local button event 132over the control interface, e.g., by calling wpa_cli: 133 134wpa_cli wps_pbc 135 136At this point, the AP/Registrar has two minutes to complete WPS 137negotiation which will generate a new WPA PSK in the same way as the 138PIN method described above. 139 140 141If the client wants to operate in the Registrar role to learn the 142current AP configuration and optionally, to configure an AP, 143wpa_supplicant is notified over the control interface, e.g., with 144wpa_cli: 145 146wpa_cli wps_reg <AP BSSID> <AP PIN> 147(example: wpa_cli wps_reg 02:34:56:78:9a:bc 12345670) 148 149This is used to fetch the current AP settings instead of actually 150changing them. The main difference with the wps_pin command is that 151wps_reg uses the AP PIN (e.g., from a label on the AP) instead of a 152PIN generated at the client. 153 154In order to change the AP configuration, the new configuration 155parameters are given to the wps_reg command: 156 157wpa_cli wps_reg <AP BSSID> <AP PIN> <new SSID> <auth> <encr> <new key> 158examples: 159 wpa_cli wps_reg 02:34:56:78:9a:bc 12345670 testing WPA2PSK CCMP 12345678 160 wpa_cli wps_reg 02:34:56:78:9a:bc 12345670 clear OPEN NONE "" 161 162<auth> must be one of the following: OPEN WPAPSK WPA2PSK 163<encr> must be one of the following: NONE WEP TKIP CCMP 164 165 166Scanning 167-------- 168 169Scan results ('wpa_cli scan_results' or 'wpa_cli bss <idx>') include a 170flags field that is used to indicate whether the BSS support WPS. If 171the AP support WPS, but has not recently activated a Registrar, [WPS] 172flag will be included. If PIN method has been recently selected, 173[WPS-PIN] is shown instead. Similarly, [WPS-PBC] is shown if PBC mode 174is in progress. GUI programs can use these as triggers for suggesting 175a guided WPS configuration to the user. In addition, control interface 176monitor events WPS-AP-AVAILABLE{,-PBC,-PIN} can be used to find out if 177there are WPS enabled APs in scan results without having to go through 178all the details in the GUI. These notification could be used, e.g., to 179suggest possible WPS connection to the user. 180 181 182wpa_gui 183------- 184 185wpa_gui-qt4 directory contains a sample GUI that shows an example of 186how WPS support can be integrated into the GUI. Its main window has a 187WPS tab that guides user through WPS registration with automatic AP 188selection. In addition, it shows how WPS can be started manually by 189selecting an AP from scan results. 190 191 192Credential processing 193--------------------- 194 195By default, wpa_supplicant processes received credentials and updates 196its configuration internally. However, it is possible to 197control these operations from external programs, if desired. 198 199This internal processing can be disabled with wps_cred_processing=1 200option. When this is used, an external program is responsible for 201processing the credential attributes and updating wpa_supplicant 202configuration based on them. 203 204Following control interface messages are sent out for external programs: 205 206WPS-CRED-RECEIVED <hexdump of Credential attribute(s)> 207For example: 208<2>WPS-CRED-RECEIVED 100e006f10260001011045000c6a6b6d2d7770732d74657374100300020020100f000200081027004030653462303435366332363666653064333961643135353461316634626637313234333761636664623766333939653534663166316230323061643434386235102000060266a0ee1727 209 210 211wpa_supplicant as WPS External Registrar (ER) 212--------------------------------------------- 213 214wpa_supplicant can be used as a WPS ER to configure an AP or enroll 215new Enrollee to join the network. This functionality uses UPnP and 216requires that a working IP connectivity is available with the AP (this 217can be either over a wired or wireless connection). 218 219Separate wpa_supplicant process can be started for WPS ER 220operations. A special "none" driver can be used in such a case to 221indicate that no local network interface is actually controlled. For 222example, following command could be used to start the ER: 223 224wpa_supplicant -Dnone -c er.conf -ieth0 225 226Sample er.conf: 227 228ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=admin 229device_name=WPS External Registrar 230 231 232wpa_cli commands for ER functionality: 233 234wps_er_start [IP address] 235- start WPS ER functionality 236- the optional IP address parameter can be used to filter operations only 237 to include a single AP 238- if run again while ER is active, the stored information (discovered APs 239 and Enrollees) are shown again 240 241wps_er_stop 242- stop WPS ER functionality 243 244wps_er_learn <UUID> <AP PIN> 245- learn AP configuration 246 247wps_er_set_config <UUID> <network id> 248- use AP configuration from a locally configured network (e.g., from 249 wps_reg command); this does not change the AP's configuration, but 250 only prepares a configuration to be used when enrolling a new device 251 to the AP 252 253wps_er_config <UUID> <AP PIN> <new SSID> <auth> <encr> <new key> 254- examples: 255 wps_er_config 87654321-9abc-def0-1234-56789abc0002 12345670 testing WPA2PSK CCMP 12345678 256 wpa_er_config 87654321-9abc-def0-1234-56789abc0002 12345670 clear OPEN NONE "" 257 258<auth> must be one of the following: OPEN WPAPSK WPA2PSK 259<encr> must be one of the following: NONE WEP TKIP CCMP 260 261 262wps_er_pbc <Enrollee UUID> 263- accept an Enrollee PBC using External Registrar 264 265wps_er_pin <Enrollee UUID> <PIN> [Enrollee MAC address] 266- add an Enrollee PIN to External Registrar 267- if Enrollee UUID is not known, "any" can be used to add a wildcard PIN 268- if the MAC address of the enrollee is known, it should be configured 269 to allow the AP to advertise list of authorized enrollees 270 271 272WPS ER events: 273 274WPS_EVENT_ER_AP_ADD 275- WPS ER discovered an AP 276 277WPS-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/ 278 279WPS_EVENT_ER_AP_REMOVE 280- WPS ER removed an AP entry 281 282WPS-ER-AP-REMOVE 87654321-9abc-def0-1234-56789abc0002 283 284WPS_EVENT_ER_ENROLLEE_ADD 285- WPS ER discovered a new Enrollee 286 287WPS-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| 288 289WPS_EVENT_ER_ENROLLEE_REMOVE 290- WPS ER removed an Enrollee entry 291 292WPS-ER-ENROLLEE-REMOVE 2b7093f1-d6fb-5108-adbb-bea66bb87333 02:66:a0:ee:17:27 293 294WPS-ER-AP-SETTINGS 295- WPS ER learned AP settings 296 297WPS-ER-AP-SETTINGS uuid=fd91b4ec-e3fa-5891-a57d-8c59efeed1d2 ssid=test-wps auth_type=0x0020 encr_type=0x0008 key=12345678 298