7d6640a62c
wps_er_config can now be used to configure an AP. It is similar to wps_er_learn, but instead of only learning the current AP settings, it continues to send M8 with the new settings for the AP.
280 lines
10 KiB
Text
280 lines
10 KiB
Text
wpa_supplicant and Wi-Fi Protected Setup (WPS)
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==============================================
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This document describes how the WPS implementation in wpa_supplicant
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can be configured and how an external component on the client (e.g.,
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management GUI) is used to enable WPS enrollment and registrar
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registration.
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Introduction to WPS
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-------------------
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Wi-Fi Protected Setup (WPS) is a mechanism for easy configuration of a
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wireless network. It allows automated generation of random keys (WPA
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passphrase/PSK) and configuration of an access point and client
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devices. WPS includes number of methods for setting up connections
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with PIN method and push-button configuration (PBC) being the most
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commonly deployed options.
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While WPS can enable more home networks to use encryption in the
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wireless network, it should be noted that the use of the PIN and
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especially PBC mechanisms for authenticating the initial key setup is
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not very secure. As such, use of WPS may not be suitable for
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environments that require secure network access without chance for
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allowing outsiders to gain access during the setup phase.
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WPS uses following terms to describe the entities participating in the
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network setup:
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- access point: the WLAN access point
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- Registrar: a device that control a network and can authorize
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addition of new devices); this may be either in the AP ("internal
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Registrar") or in an external device, e.g., a laptop, ("external
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Registrar")
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- Enrollee: a device that is being authorized to use the network
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It should also be noted that the AP and a client device may change
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roles (i.e., AP acts as an Enrollee and client device as a Registrar)
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when WPS is used to configure the access point.
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More information about WPS is available from Wi-Fi Alliance:
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http://www.wi-fi.org/wifi-protected-setup
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wpa_supplicant implementation
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-----------------------------
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wpa_supplicant includes an optional WPS component that can be used as
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an Enrollee to enroll new network credential or as a Registrar to
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configure an AP. The current version of wpa_supplicant does not
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support operation as an external WLAN Management Registrar for adding
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new client devices or configuring the AP over UPnP.
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wpa_supplicant configuration
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----------------------------
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WPS is an optional component that needs to be enabled in
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wpa_supplicant build configuration (.config). Here is an example
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configuration that includes WPS support and Linux wireless extensions
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-based driver interface:
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CONFIG_DRIVER_WEXT=y
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CONFIG_WPS=y
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WPS needs the Universally Unique IDentifier (UUID; see RFC 4122) for
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the device. This is configured in the runtime configuration for
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wpa_supplicant (if not set, UUID will be generated based on local MAC
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address):
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# example UUID for WPS
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uuid=12345678-9abc-def0-1234-56789abcdef0
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The network configuration blocks needed for WPS are added
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automatically based on control interface commands, so they do not need
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to be added explicitly in the configuration file.
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WPS registration will generate new network blocks for the acquired
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credentials. If these are to be stored for future use (after
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restarting wpa_supplicant), wpa_supplicant will need to be configured
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to allow configuration file updates:
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update_config=1
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External operations
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-------------------
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WPS requires either a device PIN code (usually, 8-digit number) or a
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pushbutton event (for PBC) to allow a new WPS Enrollee to join the
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network. wpa_supplicant uses the control interface as an input channel
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for these events.
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If the client device has a display, a random PIN has to be generated
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for each WPS registration session. wpa_supplicant can do this with a
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control interface request, e.g., by calling wpa_cli:
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wpa_cli wps_pin any
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This will return the generated 8-digit PIN which will then need to be
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entered at the Registrar to complete WPS registration. At that point,
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the client will be enrolled with credentials needed to connect to the
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AP to access the network.
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If the client device does not have a display that could show the
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random PIN, a hardcoded PIN that is printed on a label can be
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used. wpa_supplicant is notified this with a control interface
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request, e.g., by calling wpa_cli:
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wpa_cli wps_pin any 12345670
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This starts the WPS negotiation in the same way as above with the
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generated PIN.
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If the client design wants to support optional WPS PBC mode, this can
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be enabled by either a physical button in the client device or a
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virtual button in the user interface. The PBC operation requires that
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a button is also pressed at the AP/Registrar at about the same time (2
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minute window). wpa_supplicant is notified of the local button event
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over the control interface, e.g., by calling wpa_cli:
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wpa_cli wps_pbc
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At this point, the AP/Registrar has two minutes to complete WPS
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negotiation which will generate a new WPA PSK in the same way as the
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PIN method described above.
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If the client wants to operate in the Registrar role to learn the
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current AP configuration and optionally, to configure an AP,
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wpa_supplicant is notified over the control interface, e.g., with
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wpa_cli:
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wpa_cli wps_reg <AP BSSID> <AP PIN>
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(example: wpa_cli wps_reg 02:34:56:78:9a:bc 12345670)
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This is used to fetch the current AP settings instead of actually
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changing them. The main difference with the wps_pin command is that
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wps_reg uses the AP PIN (e.g., from a label on the AP) instead of a
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PIN generated at the client.
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In order to change the AP configuration, the new configuration
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parameters are given to the wps_reg command:
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wpa_cli wps_reg <AP BSSID> <AP PIN> <new SSID> <auth> <encr> <new key>
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examples:
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wpa_cli wps_reg 02:34:56:78:9a:bc 12345670 testing WPA2PSK CCMP 12345678
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wpa_cli wps_reg 02:34:56:78:9a:bc 12345670 clear OPEN NONE ""
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<auth> must be one of the following: OPEN WPAPSK WPA2PSK
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<encr> must be one of the following: NONE WEP TKIP CCMP
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Scanning
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--------
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Scan results ('wpa_cli scan_results' or 'wpa_cli bss <idx>') include a
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flags field that is used to indicate whether the BSS support WPS. If
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the AP support WPS, but has not recently activated a Registrar, [WPS]
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flag will be included. If PIN method has been recently selected,
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[WPS-PIN] is shown instead. Similarly, [WPS-PBC] is shown if PBC mode
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is in progress. GUI programs can use these as triggers for suggesting
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a guided WPS configuration to the user. In addition, control interface
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monitor events WPS-AP-AVAILABLE{,-PBC,-PIN} can be used to find out if
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there are WPS enabled APs in scan results without having to go through
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all the details in the GUI. These notification could be used, e.g., to
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suggest possible WPS connection to the user.
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wpa_gui
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-------
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wpa_gui-qt4 directory contains a sample GUI that shows an example of
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how WPS support can be integrated into the GUI. Its main window has a
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WPS tab that guides user through WPS registration with automatic AP
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selection. In addition, it shows how WPS can be started manually by
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selecting an AP from scan results.
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Credential processing
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---------------------
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By default, wpa_supplicant processes received credentials and updates
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its configuration internally. However, it is possible to
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control these operations from external programs, if desired.
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This internal processing can be disabled with wps_cred_processing=1
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option. When this is used, an external program is responsible for
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processing the credential attributes and updating wpa_supplicant
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configuration based on them.
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Following control interface messages are sent out for external programs:
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WPS-CRED-RECEIVED <hexdump of Credential attribute(s)>
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For example:
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<2>WPS-CRED-RECEIVED 100e006f10260001011045000c6a6b6d2d7770732d74657374100300020020100f000200081027004030653462303435366332363666653064333961643135353461316634626637313234333761636664623766333939653534663166316230323061643434386235102000060266a0ee1727
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wpa_supplicant as WPS External Registrar (ER)
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---------------------------------------------
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wpa_supplicant can be used as a WPS ER to configure an AP or enroll
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new Enrollee to join the network. This functionality uses UPnP and
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requires that a working IP connectivity is available with the AP (this
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can be either over a wired or wireless connection).
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Separate wpa_supplicant process can be started for WPS ER
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operations. A special "none" driver can be used in such a case to
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indicate that no local network interface is actually controlled. For
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example, following command could be used to start the ER:
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wpa_supplicant -Dnone -c er.conf -ieth0
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Sample er.conf:
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ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=admin
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device_name=WPS External Registrar
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wpa_cli commands for ER functionality:
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wps_er_start [IP address]
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- start WPS ER functionality
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- the optional IP address parameter can be used to filter operations only
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to include a single AP
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- if run again while ER is active, the stored information (discovered APs
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and Enrollees) are shown again
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wps_er_stop
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- stop WPS ER functionality
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wps_er_learn <UUID> <AP PIN>
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- learn AP configuration
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wps_er_config <UUID> <AP PIN> <new SSID> <auth> <encr> <new key>
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- examples:
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wps_er_config 87654321-9abc-def0-1234-56789abc0002 12345670 testing WPA2PSK CCMP 12345678
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wpa_er_config 87654321-9abc-def0-1234-56789abc0002 12345670 clear OPEN NONE ""
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<auth> must be one of the following: OPEN WPAPSK WPA2PSK
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<encr> must be one of the following: NONE WEP TKIP CCMP
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wps_er_pbc <Enrollee UUID>
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- accept an Enrollee PBC using External Registrar
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wps_er_pin <Enrollee UUID> <PIN>
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- add an Enrollee PIN to External Registrar
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WPS ER events:
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WPS_EVENT_ER_AP_ADD
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- WPS ER discovered an AP
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WPS-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/
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WPS_EVENT_ER_AP_REMOVE
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- WPS ER removed an AP entry
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WPS-ER-AP-REMOVE 87654321-9abc-def0-1234-56789abc0002
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WPS_EVENT_ER_ENROLLEE_ADD
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- WPS ER discovered a new Enrollee
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WPS-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|
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WPS_EVENT_ER_ENROLLEE_REMOVE
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- WPS ER removed an Enrollee entry
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WPS-ER-ENROLLEE-REMOVE 2b7093f1-d6fb-5108-adbb-bea66bb87333 02:66:a0:ee:17:27
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WPS-ER-AP-SETTINGS
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- WPS ER learned AP settings
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WPS-ER-AP-SETTINGS uuid=fd91b4ec-e3fa-5891-a57d-8c59efeed1d2 ssid=test-wps auth_type=0x0020 encr_type=0x0008 key=12345678
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