hostapd - user space IEEE 802.11 AP and IEEE 802.1X/WPA/WPA2/EAP
	  Authenticator and RADIUS authentication server
================================================================

Copyright (c) 2002-2022, Jouni Malinen <j@w1.fi> and contributors
All Rights Reserved.

This program is licensed under the BSD license (the one with
advertisement clause removed).

If you are submitting changes to the project, please see CONTRIBUTIONS
file for more instructions.



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-------

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Introduction
============

Originally, hostapd was an optional user space component for Host AP
driver. It adds more features to the basic IEEE 802.11 management
included in the kernel driver: using external RADIUS authentication
server for MAC address based access control, IEEE 802.1X Authenticator
and dynamic WEP keying, RADIUS accounting, WPA/WPA2 (IEEE 802.11i/RSN)
Authenticator and dynamic TKIP/CCMP keying.

The current version includes support for other drivers, an integrated
EAP server (i.e., allow full authentication without requiring
an external RADIUS authentication server), and RADIUS authentication
server for EAP authentication.


Requirements
------------

Current hardware/software requirements:
- drivers:
	Host AP driver for Prism2/2.5/3.
	(http://w1.fi/hostap-driver.html)
	Please note that station firmware version needs to be 1.7.0 or newer
	to work in WPA mode.

	mac80211-based drivers that support AP mode (with driver=nl80211).
	This includes drivers for Atheros (ath9k) and Broadcom (b43)
	chipsets.

	Any wired Ethernet driver for wired IEEE 802.1X authentication
	(experimental code)

	FreeBSD -current
	BSD net80211 layer (e.g., Atheros driver)


Build configuration
-------------------

In order to be able to build hostapd, you will need to create a build
time configuration file, .config that selects which optional
components are included. See defconfig file for example configuration
and list of available options.



IEEE 802.1X
===========

IEEE Std 802.1X-2001 is a standard for port-based network access
control. In case of IEEE 802.11 networks, a "virtual port" is used
between each associated station and the AP. IEEE 802.11 specifies
minimal authentication mechanism for stations, whereas IEEE 802.1X
introduces a extensible mechanism for authenticating and authorizing
users.

IEEE 802.1X uses elements called Supplicant, Authenticator, Port
Access Entity, and Authentication Server. Supplicant is a component in
a station and it performs the authentication with the Authentication
Server. An access point includes an Authenticator that relays the packets
between a Supplicant and an Authentication Server. In addition, it has a
Port Access Entity (PAE) with Authenticator functionality for
controlling the virtual port authorization, i.e., whether to accept
packets from or to the station.

IEEE 802.1X uses Extensible Authentication Protocol (EAP). The frames
between a Supplicant and an Authenticator are sent using EAP over LAN
(EAPOL) and the Authenticator relays these frames to the Authentication
Server (and similarly, relays the messages from the Authentication
Server to the Supplicant). The Authentication Server can be colocated with the
Authenticator, in which case there is no need for additional protocol
for EAP frame transmission. However, a more common configuration is to
use an external Authentication Server and encapsulate EAP frame in the
frames used by that server. RADIUS is suitable for this, but IEEE
802.1X would also allow other mechanisms.

Host AP driver includes PAE functionality in the kernel driver. It
is a relatively simple mechanism for denying normal frames going to
or coming from an unauthorized port. PAE allows IEEE 802.1X related
frames to be passed between the Supplicant and the Authenticator even
on an unauthorized port.

User space daemon, hostapd, includes Authenticator functionality. It
receives 802.1X (EAPOL) frames from the Supplicant using the wlan#ap
device that is also used with IEEE 802.11 management frames. The
frames to the Supplicant are sent using the same device.

The normal configuration of the Authenticator would use an external
Authentication Server. hostapd supports RADIUS encapsulation of EAP
packets, so the Authentication Server should be a RADIUS server, like
FreeRADIUS (http://www.freeradius.org/). The Authenticator in hostapd
relays the frames between the Supplicant and the Authentication
Server. It also controls the PAE functionality in the kernel driver by
controlling virtual port authorization, i.e., station-AP
connection, based on the IEEE 802.1X state.

When a station would like to use the services of an access point, it
will first perform IEEE 802.11 authentication. This is normally done
with open systems authentication, so there is no security. After
this, IEEE 802.11 association is performed. If IEEE 802.1X is
configured to be used, the virtual port for the station is set in
Unauthorized state and only IEEE 802.1X frames are accepted at this
point. The Authenticator will then ask the Supplicant to authenticate
with the Authentication Server. After this is completed successfully,
the virtual port is set to Authorized state and frames from and to the
station are accepted.

Host AP configuration for IEEE 802.1X
-------------------------------------

The user space daemon has its own configuration file that can be used to
define AP options. Distribution package contains an example
configuration file (hostapd/hostapd.conf) that can be used as a basis
for configuration. It includes examples of all supported configuration
options and short description of each option. hostapd should be started
with full path to the configuration file as the command line argument,
e.g., './hostapd /etc/hostapd.conf'. If you have more that one wireless
LAN card, you can use one hostapd process for multiple interfaces by
giving a list of configuration files (one per interface) in the command
line.

hostapd includes a minimal co-located IEEE 802.1X server which can be
used to test IEEE 802.1X authentication. However, it should not be
used in normal use since it does not provide any security. This can be
configured by setting ieee8021x and minimal_eap options in the
configuration file.

An external Authentication Server (RADIUS) is configured with
auth_server_{addr,port,shared_secret} options. In addition,
ieee8021x and own_ip_addr must be set for this mode. With such
configuration, the co-located Authentication Server is not used and EAP
frames will be relayed using EAPOL between the Supplicant and the
Authenticator and RADIUS encapsulation between the Authenticator and
the Authentication Server. Other than this, the functionality is similar
to the case with the co-located Authentication Server.

Authentication Server
---------------------

Any RADIUS server supporting EAP should be usable as an IEEE 802.1X
Authentication Server with hostapd Authenticator. FreeRADIUS
(http://www.freeradius.org/) has been successfully tested with hostapd
Authenticator.

Automatic WEP key configuration
-------------------------------

EAP/TLS generates a session key that can be used to send WEP keys from
an AP to authenticated stations. The Authenticator in hostapd can be
configured to automatically select a random default/broadcast key
(shared by all authenticated stations) with wep_key_len_broadcast
option (5 for 40-bit WEP or 13 for 104-bit WEP). In addition,
wep_key_len_unicast option can be used to configure individual unicast
keys for stations. This requires support for individual keys in the
station driver.

WEP keys can be automatically updated by configuring rekeying. This
will improve security of the network since same WEP key will only be
used for a limited period of time. wep_rekey_period option sets the
interval for rekeying in seconds.


WPA/WPA2
========

Features
--------

Supported WPA/IEEE 802.11i features:
- WPA-PSK ("WPA-Personal")
- WPA with EAP (e.g., with RADIUS authentication server) ("WPA-Enterprise")
- key management for CCMP, TKIP, WEP104, WEP40
- RSN/WPA2 (IEEE 802.11i), including PMKSA caching and pre-authentication

WPA
---

The original security mechanism of IEEE 802.11 standard was not
designed to be strong and has proved to be insufficient for most
networks that require some kind of security. Task group I (Security)
of IEEE 802.11 working group (http://www.ieee802.org/11/) has worked
to address the flaws of the base standard and has in practice
completed its work in May 2004. The IEEE 802.11i amendment to the IEEE
802.11 standard was approved in June 2004 and this amendment was
published in July 2004.

Wi-Fi Alliance (http://www.wi-fi.org/) used a draft version of the
IEEE 802.11i work (draft 3.0) to define a subset of the security
enhancements that can be implemented with existing wlan hardware. This
is called Wi-Fi Protected Access<TM> (WPA). This has now become a
mandatory component of interoperability testing and certification done
by Wi-Fi Alliance.

IEEE 802.11 standard defined wired equivalent privacy (WEP) algorithm
for protecting wireless networks. WEP uses RC4 with 40-bit keys,
24-bit initialization vector (IV), and CRC32 to protect against packet
forgery. All these choices have proven to be insufficient: key space is
too small against current attacks, RC4 key scheduling is insufficient
(beginning of the pseudorandom stream should be skipped), IV space is
too small and IV reuse makes attacks easier, there is no replay
protection, and non-keyed authentication does not protect against bit
flipping packet data.

WPA is an intermediate solution for the security issues. It uses
Temporal Key Integrity Protocol (TKIP) to replace WEP. TKIP is a
compromise on strong security and possibility to use existing
hardware. It still uses RC4 for the encryption like WEP, but with
per-packet RC4 keys. In addition, it implements replay protection,
keyed packet authentication mechanism (Michael MIC).

Keys can be managed using two different mechanisms. WPA can either use
an external authentication server (e.g., RADIUS) and EAP just like
IEEE 802.1X is using or pre-shared keys without need for additional
servers. Wi-Fi calls these "WPA-Enterprise" and "WPA-Personal",
respectively. Both mechanisms will generate a master session key for
the Authenticator (AP) and Supplicant (client station).

WPA implements a new key handshake (4-Way Handshake and Group Key
Handshake) for generating and exchanging data encryption keys between
the Authenticator and Supplicant. This handshake is also used to
verify that both Authenticator and Supplicant know the master session
key. These handshakes are identical regardless of the selected key
management mechanism (only the method for generating master session
key changes).


IEEE 802.11i / WPA2
-------------------

The design for parts of IEEE 802.11i that were not included in WPA has
finished (May 2004) and this amendment to IEEE 802.11 was approved in
June 2004. Wi-Fi Alliance is using the final IEEE 802.11i as a new
version of WPA called WPA2. This includes, e.g., support for more
robust encryption algorithm (CCMP: AES in Counter mode with CBC-MAC)
to replace TKIP and optimizations for handoff (reduced number of
messages in initial key handshake, pre-authentication, and PMKSA caching).

Some wireless LAN vendors are already providing support for CCMP in
their WPA products. There is no "official" interoperability
certification for CCMP and/or mixed modes using both TKIP and CCMP, so
some interoperability issues can be expected even though many
combinations seem to be working with equipment from different vendors.
Testing for WPA2 is likely to start during the second half of 2004.

hostapd configuration for WPA/WPA2
----------------------------------

TODO

# Enable WPA. Setting this variable configures the AP to require WPA (either
# WPA-PSK or WPA-RADIUS/EAP based on other configuration). For WPA-PSK, either
# wpa_psk or wpa_passphrase must be set and wpa_key_mgmt must include WPA-PSK.
# For WPA-RADIUS/EAP, ieee8021x must be set (but without dynamic WEP keys),
# RADIUS authentication server must be configured, and WPA-EAP must be included
# in wpa_key_mgmt.
# This field is a bit field that can be used to enable WPA (IEEE 802.11i/D3.0)
# and/or WPA2 (full IEEE 802.11i/RSN):
# bit0 = WPA
# bit1 = IEEE 802.11i/RSN (WPA2)
#wpa=1

# WPA pre-shared keys for WPA-PSK. This can be either entered as a 256-bit
# secret in hex format (64 hex digits), wpa_psk, or as an ASCII passphrase
# (8..63 characters) that will be converted to PSK. This conversion uses SSID
# so the PSK changes when ASCII passphrase is used and the SSID is changed.
#wpa_psk=0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef
#wpa_passphrase=secret passphrase

# Set of accepted key management algorithms (WPA-PSK, WPA-EAP, or both). The
# entries are separated with a space.
#wpa_key_mgmt=WPA-PSK WPA-EAP

# Set of accepted cipher suites (encryption algorithms) for pairwise keys
# (unicast packets). This is a space separated list of algorithms:
# CCMP = AES in Counter mode with CBC-MAC [RFC 3610, IEEE 802.11i]
# TKIP = Temporal Key Integrity Protocol [IEEE 802.11i]
# Group cipher suite (encryption algorithm for broadcast and multicast frames)
# is automatically selected based on this configuration. If only CCMP is
# allowed as the pairwise cipher, group cipher will also be CCMP. Otherwise,
# TKIP will be used as the group cipher.
#wpa_pairwise=TKIP CCMP

# Time interval for rekeying GTK (broadcast/multicast encryption keys) in
# seconds.
#wpa_group_rekey=600

# Time interval for rekeying GMK (master key used internally to generate GTKs
# (in seconds).
#wpa_gmk_rekey=86400

# Enable IEEE 802.11i/RSN/WPA2 pre-authentication. This is used to speed up
# roaming be pre-authenticating IEEE 802.1X/EAP part of the full RSN
# authentication and key handshake before actually associating with a new AP.
#rsn_preauth=1
#
# Space separated list of interfaces from which pre-authentication frames are
# accepted (e.g., 'eth0' or 'eth0 wlan0wds0'. This list should include all
# interface that are used for connections to other APs. This could include
# wired interfaces and WDS links. The normal wireless data interface towards
# associated stations (e.g., wlan0) should not be added, since
# pre-authentication is only used with APs other than the currently associated
# one.
#rsn_preauth_interfaces=eth0

hostapd, wpa_supplicant and the Multi-AP Specification
======================================================

This document describes how hostapd and wpa_supplicant can be configured to
support the Multi-AP Specification.

Introduction to Multi-AP
------------------------

The Wi-Fi Alliance Multi-AP Specification is the technical specification for
Wi-Fi CERTIFIED EasyMesh(TM) [1], the Wi-Fi Alliance® certification program for
Multi-AP. It defines control protocols between Wi-Fi® access points (APs) to
join them into a network with centralized control and operation. It is targeted
only at routers (repeaters, gateways, ...), not at clients. Clients are not
involved at all in the protocols.

Most of the Multi-AP specification falls outside of the scope of
hostapd/wpa_supplicant. hostapd/wpa_supplicant is only involved for the items
summarized below. The rest of the protocol must be implemented by a separate
daemon, e.g., prplMesh [2]. That daemon also needs to communicate with hostapd,
e.g., to get a list of associated clients, but this can be done using the normal
hostapd interfaces.

hostapd/wpa_supplicant needs to be configured specifically to support:
- the WPS onboarding process;
- configuring backhaul links.

The text below refers to "Multi-AP Specification v1.0" [3].


Fronthaul and backhaul links
----------------------------

In a Multi-AP network, the central controller can configure the BSSs on the
devices that are joined into the network. These are called fronthaul BSSs.
From the point of view of hostapd, there is nothing special about these
fronthaul BSSs.

In addition to fronthaul BSSs, the controller can also configure backhaul
links. A backhaul link is a link between two access point devices, giving
internet access to access point devices that don't have a wired link. The
Multi-AP specification doesn't dictate this, but typically the backhaul link
will be bridged into a LAN together with (one of) the fronthaul BSS(s) and the
wired Ethernet ports.

A backhaul link must be treated specially by hostapd and wpa_supplicant. One
side of the backhaul link is configured through the Multi-AP protocol as the
"backhaul STA", i.e., the client side of the link. A backhaul STA is like any
station and is handled appropriately by wpa_supplicant, but two additional
features are required. It must send an additional information element in each
(Re)Association Request frame ([3], section 5.2, paragraph 4). In addition, it
must use 4-address mode for all frames sent over this link ([3], section 14).
Therefore, wpa_supplicant must be configured explicitly as the backhaul STA
role, by setting 'multi_ap_backhaul_sta=1' in the network configuration block
or when configuring the network profile through the control interface. When
'multi_ap_backhaul_sta=1', wpa_supplicant includes the Multi-AP IE in
(Re)Association Request frame and verifies that it is included in the
(Re)Association Response frame. If it is not, association fails. If it is,
wpa_supplicant sets 4-address mode for this interface through a driver
callback.

The AP side of the backhaul link is called a "backhaul BSS". Such a BSS must
be handled specially by hostapd, because it must add an additional information
element in each (Re)Association Response frame, but only to stations that have
identified themselves as backhaul stations ([3], section 5.2, paragraph 5-6).
This is important because it is possible to use the same BSS and SSID for
fronthaul and backhaul at the same time. The additional information element must
only be used for frames sent to a backhaul STA, not to a normal STA. Also,
frames sent to a backhaul STA must use 4-address mode, while frames sent to a
normal STA (fronthaul, when it's a fronthaul and backhaul BSS) must use
3-address mode.

A BSS is configured in Multi-AP mode in hostapd by setting the 'multi_ap'
configuration option to 1 (backhaul BSS), 2 (fronthaul BSS), or 3
(simultaneous backhaul and fronthaul BSS). If this option is set, hostapd
parses the Multi-AP information element in the Association Request frame. If the
station is a backhaul STA and the BSS is configured as a backhaul BSS,
hostapd sets up 4-address mode. Since there may be multiple stations connected
simultaneously, and each of them has a different RA (receiver address), a VLAN
is created for each backhaul STA and it is automatically added to a bridge.
This is the same behavior as for WDS, and the relevant option ('bridge' or
'wds_bridge') applies here as well.

If 'multi_ap' is 1 (backhaul BSS only), any station that tries to associate
without the Multi-AP information element will be denied.

If 'multi_ap' is 2 (fronthaul BSS only), any station that tries to associate
with the Multi-AP information element will be denied. That is also the only
difference with 'multi_ap' set to 0: in the latter case, the Multi-AP
information element is simply ignored.

In summary, this is the end-to-end behavior for a backhaul BSS (i.e.,
multi_ap_backhaul_sta=1 in wpa_supplicant on STA, and multi_ap=1 or 3 in
hostapd on AP). Note that point 1 means that hostapd must not be configured
with WPS support on the backhaul BSS (multi_ap=1). hostapd does not check for
that.

1. Backhaul BSS beacons do not advertise WPS support (other than that, nothing
   Multi-AP specific).
2. STA sends Authentication frame (nothing Multi-AP specific).
3. AP sends Authentication frame (nothing Multi-AP specific).
4. STA sends Association Request frame with Multi-AP IE.
5. AP sends Association Response frame with Multi-AP IE.
6. STA and AP both use 4-address mode for Data frames.


WPS support
-----------

WPS requires more special handling. WPS must only be advertised on fronthaul
BSSs, not on backhaul BSSs, so WPS should not be enabled on a backhaul-only
BSS in hostapd.conf. The WPS configuration purely works on the fronthaul BSS.
When a WPS M1 message has an additional subelement that indicates a request for
a Multi-AP backhaul link, hostapd must not respond with the normal fronthaul
BSS credentials; instead, it should respond with the (potentially different)
backhaul BSS credentials.

To support this, hostapd has the 'multi_ap_backhaul_ssid',
'multi_ap_backhaul_wpa_psk' and 'multi_ap_backhaul_wpa_passphrase' options.
When these are set on an BSS with WPS, they are used instead of the normal
credentials when hostapd receives a WPS M1 message with the Multi-AP IE. Only
WPA2-Personal is supported in the Multi-AP specification, so there is no need
to specify authentication or encryption options. For the backhaul credentials,
per-device PSK is not supported.

If the BSS is a simultaneous backhaul and fronthaul BSS, there is no need to
specify the backhaul credentials, since the backhaul and fronthaul credentials
are identical.

To enable the Multi-AP backhaul STA feature when it performs WPS, a new
parameter has been introduced to the WPS_PBC control interface call. When this
"multi_ap=1" option is set, it adds the Multi-AP backhaul subelement to the
Association Request frame and the M1 message. It then configures the new network
profile with 'multi_ap_backhaul_sta=1'. Note that this means that if the AP does
not follow the Multi-AP specification, wpa_supplicant will fail to associate.

In summary, this is the end-to-end behavior for WPS of a backhaul link (i.e.,
multi_ap=1 option is given in the wps_pbc call on the STA side, and multi_ap=2
and multi_ap_backhaul_ssid and either multi_ap_backhaul_wpa_psk or
multi_ap_backhaul_wpa_passphrase are set to the credentials of a backhaul BSS
in hostapd on Registrar AP).

1. Fronthaul BSS Beacon frames advertise WPS support (nothing Multi-AP
   specific).
2. Enrollee sends Authentication frame (nothing Multi-AP specific).
3. AP sends Authentication frame (nothing Multi-AP specific).
4. Enrollee sends Association Request frame with Multi-AP IE.
5. AP sends Association Response frame with Multi-AP IE.
6. Enrollee sends M1 with additional Multi-AP subelement.
7. AP sends M8 with backhaul instead of fronthaul credentials.
8. Enrollee sends Deauthentication frame.


References
----------

[1] https://www.wi-fi.org/discover-wi-fi/wi-fi-easymesh
[2] https://github.com/prplfoundation/prplMesh
[3] https://www.wi-fi.org/file/multi-ap-specification-v10
    (requires registration)

hostapd and Wi-Fi Protected Setup (WPS)
=======================================

This document describes how the WPS implementation in hostapd can be
configured and how an external component on an AP (e.g., web UI) is
used to enable enrollment of client devices.


Introduction to WPS
-------------------

Wi-Fi Protected Setup (WPS) is a mechanism for easy configuration of a
wireless network. It allows automated generation of random keys (WPA
passphrase/PSK) and configuration of an access point and client
devices. WPS includes number of methods for setting up connections
with PIN method and push-button configuration (PBC) being the most
commonly deployed options.

While WPS can enable more home networks to use encryption in the
wireless network, it should be noted that the use of the PIN and
especially PBC mechanisms for authenticating the initial key setup is
not very secure. As such, use of WPS may not be suitable for
environments that require secure network access without chance for
allowing outsiders to gain access during the setup phase.

WPS uses following terms to describe the entities participating in the
network setup:
- access point: the WLAN access point
- Registrar: a device that control a network and can authorize
  addition of new devices); this may be either in the AP ("internal
  Registrar") or in an external device, e.g., a laptop, ("external
  Registrar")
- Enrollee: a device that is being authorized to use the network

It should also be noted that the AP and a client device may change
roles (i.e., AP acts as an Enrollee and client device as a Registrar)
when WPS is used to configure the access point.


More information about WPS is available from Wi-Fi Alliance:
http://www.wi-fi.org/wifi-protected-setup


hostapd implementation
----------------------

hostapd includes an optional WPS component that can be used as an
internal WPS Registrar to manage addition of new WPS enabled clients
to the network. In addition, WPS Enrollee functionality in hostapd can
be used to allow external WPS Registrars to configure the access
point, e.g., for initial network setup. In addition, hostapd can proxy a
WPS registration between a wireless Enrollee and an external Registrar
(e.g., Microsoft Vista or Atheros JumpStart) with UPnP.


hostapd configuration
---------------------

WPS is an optional component that needs to be enabled in hostapd build
configuration (.config). Here is an example configuration that
includes WPS support and uses nl80211 driver interface:

CONFIG_DRIVER_NL80211=y
CONFIG_WPS=y
CONFIG_WPS_UPNP=y

Following parameter can be used to enable support for NFC config method:

CONFIG_WPS_NFC=y


Following section shows an example runtime configuration
(hostapd.conf) that enables WPS:

# Configure the driver and network interface
driver=nl80211
interface=wlan0

# WPA2-Personal configuration for the AP
ssid=wps-test
wpa=2
wpa_key_mgmt=WPA-PSK
wpa_pairwise=CCMP
# Default WPA passphrase for legacy (non-WPS) clients
wpa_passphrase=12345678
# Enable random per-device PSK generation for WPS clients
# Please note that the file has to exists for hostapd to start (i.e., create an
# empty file as a starting point).
wpa_psk_file=/etc/hostapd.psk

# Enable control interface for PBC/PIN entry
ctrl_interface=/var/run/hostapd

# Enable internal EAP server for EAP-WSC (part of Wi-Fi Protected Setup)
eap_server=1

# WPS configuration (AP configured, do not allow external WPS Registrars)
wps_state=2
ap_setup_locked=1
# If UUID is not configured, it will be generated based on local MAC address.
uuid=87654321-9abc-def0-1234-56789abc0000
wps_pin_requests=/var/run/hostapd.pin-req
device_name=Wireless AP
manufacturer=Company
model_name=WAP
model_number=123
serial_number=12345
device_type=6-0050F204-1
os_version=01020300
config_methods=label display push_button keypad

# if external Registrars are allowed, UPnP support could be added:
#upnp_iface=br0
#friendly_name=WPS Access Point


External operations
-------------------

WPS requires either a device PIN code (usually, 8-digit number) or a
pushbutton event (for PBC) to allow a new WPS Enrollee to join the
network. hostapd uses the control interface as an input channel for
these events.

The PIN value used in the commands must be processed by an UI to
remove non-digit characters and potentially, to verify the checksum
digit. "hostapd_cli wps_check_pin <PIN>" can be used to do such
processing. It returns FAIL if the PIN is invalid, or FAIL-CHECKSUM if
the checksum digit is incorrect, or the processed PIN (non-digit
characters removed) if the PIN is valid.

When a client device (WPS Enrollee) connects to hostapd (WPS
Registrar) in order to start PIN mode negotiation for WPS, an
identifier (Enrollee UUID) is sent. hostapd will need to be configured
with a device password (PIN) for this Enrollee. This is an operation
that requires user interaction (assuming there are no pre-configured
PINs on the AP for a set of Enrollee).

The PIN request with information about the device is appended to the
wps_pin_requests file (/var/run/hostapd.pin-req in this example). In
addition, hostapd control interface event is sent as a notification of
a new device. The AP could use, e.g., a web UI for showing active
Enrollees to the user and request a PIN for an Enrollee.

The PIN request file has one line for every Enrollee that connected to
the AP, but for which there was no PIN. Following information is
provided for each Enrollee (separated with tabulators):
- timestamp (seconds from 1970-01-01)
- Enrollee UUID
- MAC address
- Device name
- Manufacturer
- Model Name
- Model Number
- Serial Number
- Device category

Example line in the /var/run/hostapd.pin-req file:
1200188391	53b63a98-d29e-4457-a2ed-094d7e6a669c	Intel(R) Centrino(R)	Intel Corporation	Intel(R) Centrino(R)	-	-	1-0050F204-1

Control interface data:
WPS-PIN-NEEDED [UUID-E|MAC Address|Device Name|Manufacturer|Model Name|Model Number|Serial Number|Device Category]
For example:
<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]

When the user enters a PIN for a pending Enrollee, e.g., on the web
UI), hostapd needs to be notified of the new PIN over the control
interface. This can be done either by using the UNIX domain socket
-based control interface directly (src/common/wpa_ctrl.c provides
helper functions for using the interface) or by calling hostapd_cli.

Example command to add a PIN (12345670) for an Enrollee:

hostapd_cli wps_pin 53b63a98-d29e-4457-a2ed-094d7e6a669c 12345670

If the UUID-E is not available (e.g., Enrollee waits for the Registrar
to be selected before connecting), wildcard UUID may be used to allow
the PIN to be used once with any UUID:

hostapd_cli wps_pin any 12345670

To reduce likelihood of PIN being used with other devices or of
forgetting an active PIN available for potential attackers, expiration
time in seconds can be set for the new PIN (value 0 indicates no
expiration):

hostapd_cli wps_pin any 12345670 300

If the MAC address of the enrollee is known, it should be configured
to allow the AP to advertise list of authorized enrollees:

hostapd_cli wps_pin 53b63a98-d29e-4457-a2ed-094d7e6a669c \
	12345670 300 00:11:22:33:44:55


After this, the Enrollee can connect to the AP again and complete WPS
negotiation. At that point, a new, random WPA PSK is generated for the
client device and the client can then use that key to connect to the
AP to access the network.


If the AP includes a pushbutton, WPS PBC mode can be used. It is
enabled by pushing a button on both the AP and the client at about the
same time (2 minute window). hostapd needs to be notified about the AP
button pushed event over the control interface, e.g., by calling
hostapd_cli:

hostapd_cli wps_pbc

At this point, the client has two minutes to complete WPS negotiation
which will generate a new WPA PSK in the same way as the PIN method
described above.


When an external Registrar is used, the AP can act as an Enrollee and
use its AP PIN. A static AP PIN (e.g., one one a label in the AP
device) can be configured in hostapd.conf (ap_pin parameter). A more
secure option is to use hostapd_cli wps_ap_pin command to enable the
AP PIN only based on user action (and even better security by using a
random AP PIN for each session, i.e., by using "wps_ap_pin random"
command with a timeout value). Following commands are available for
managing the dynamic AP PIN operations:

hostapd_cli wps_ap_pin disable
- disable AP PIN (i.e., do not allow external Registrars to use it to
  learn the current AP settings or to reconfigure the AP)

hostapd_cli wps_ap_pin random [timeout]
- generate a random AP PIN and enable it
- if the optional timeout parameter is given, the AP PIN will be enabled
  for the specified number of seconds

hostapd_cli wps_ap_pin get
- fetch the current AP PIN

hostapd_cli wps_ap_pin set <PIN> [timeout]
- set the AP PIN and enable it
- if the optional timeout parameter is given, the AP PIN will be enabled
  for the specified number of seconds

hostapd_cli get_config
- display the current configuration

hostapd_cli wps_config <new SSID> <auth> <encr> <new key>
examples:
  hostapd_cli wps_config testing WPA2PSK CCMP 12345678
  hostapd_cli wps_config "no security" OPEN NONE ""

<auth> must be one of the following: OPEN WPAPSK WPA2PSK
<encr> must be one of the following: NONE WEP TKIP CCMP


Credential generation and configuration changes
-----------------------------------------------

By default, hostapd generates credentials for Enrollees and processing
AP configuration updates internally. However, it is possible to
control these operations from external programs, if desired.

The internal credential generation can be disabled with
skip_cred_build=1 option in the configuration. extra_cred option will
then need to be used to provide pre-configured Credential attribute(s)
for hostapd to use. The exact data from this binary file will be sent,
i.e., it will have to include valid WPS attributes. extra_cred can
also be used to add additional networks if the Registrar is used to
configure credentials for multiple networks.

Processing of received configuration updates can be disabled with
wps_cred_processing=1 option. When this is used, an external program
is responsible for creating hostapd configuration files and processing
configuration updates based on messages received from hostapd over
control interface. This will also include the initial configuration on
first successful registration if the AP is initially set in
unconfigured state.

Following control interface messages are sent out for external programs:

WPS-REG-SUCCESS <Enrollee MAC address <UUID-E>
For example:
<2>WPS-REG-SUCCESS 02:66:a0:ee:17:27 2b7093f1-d6fb-5108-adbb-bea66bb87333

This can be used to trigger change from unconfigured to configured
state (random configuration based on the first successful WPS
registration). In addition, this can be used to update AP UI about the
status of WPS registration progress.


WPS-NEW-AP-SETTINGS <hexdump of AP Setup attributes>
For example:
<2>WPS-NEW-AP-SETTINGS 10260001011045000c6a6b6d2d7770732d74657374100300020020100f00020008102700403065346230343536633236366665306433396164313535346131663462663731323433376163666462376633393965353466316631623032306164343438623510200006024231cede15101e000844

This can be used to update the externally stored AP configuration and
then update hostapd configuration (followed by restarting of hostapd).


WPS with NFC
------------

WPS can be used with NFC-based configuration method. An NFC tag
containing a password token from the Enrollee can be used to
authenticate the connection instead of the PIN. In addition, an NFC tag
with a configuration token can be used to transfer AP settings without
going through the WPS protocol.

When the AP acts as an Enrollee, a local NFC tag with a password token
can be used by touching the NFC interface of an external Registrar. The
wps_nfc_token command is used to manage use of the NFC password token
from the AP. "wps_nfc_token enable" enables the use of the AP's NFC
password token (in place of AP PIN) and "wps_nfc_token disable" disables
the NFC password token.

The NFC password token that is either pre-configured in the
configuration file (wps_nfc_dev_pw_id, wps_nfc_dh_pubkey,
wps_nfc_dh_privkey, wps_nfc_dev_pw) or generated dynamically with
"wps_nfc_token <WPS|NDEF>" command. The nfc_pw_token tool from
wpa_supplicant can be used to generate NFC password tokens during
manufacturing (each AP needs to have its own random keys).

The "wps_nfc_config_token <WPS/NDEF>" command can be used to build an
NFC configuration token. The output value from this command is a hexdump
of the current AP configuration (WPS parameter requests this to include
only the WPS attributes; NDEF parameter requests additional NDEF
encapsulation to be included). This data needs to be written to an NFC
tag with an external program. Once written, the NFC configuration token
can be used to touch an NFC interface on a station to provision the
credentials needed to access the network.

When the NFC device on the AP reads an NFC tag with a MIME media type
"application/vnd.wfa.wsc", the NDEF message payload (with or without
NDEF encapsulation) can be delivered to hostapd using the
following hostapd_cli command:

wps_nfc_tag_read <hexdump of payload>

If the NFC tag contains a password token, the token is added to the
internal Registrar. This allows station Enrollee from which the password
token was received to run through WPS protocol to provision the
credential.

"nfc_get_handover_sel <NDEF> <WPS>" command can be used to build the
contents of a Handover Select Message for connection handover when this
does not depend on the contents of the Handover Request Message. The
first argument selects the format of the output data and the second
argument selects which type of connection handover is requested (WPS =
Wi-Fi handover as specified in WSC 2.0).

"nfc_report_handover <INIT/RESP> WPS <carrier from handover request>
<carrier from handover select>" is used to report completed NFC
connection handover. The first parameter indicates whether the local
device initiated or responded to the connection handover and the carrier
records are the selected carrier from the handover request and select
messages as a hexdump.