mirror of
https://github.com/lwfinger/rtl8188eu.git
synced 2024-11-22 12:33:40 +00:00
291 lines
11 KiB
Text
291 lines
11 KiB
Text
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 madwifi driver interface:
|
|
|
|
CONFIG_DRIVER_MADWIFI=y
|
|
CFLAGS += -I/usr/src/madwifi-0.9.3
|
|
CONFIG_WPS=y
|
|
CONFIG_WPS2=y
|
|
CONFIG_WPS_UPNP=y
|
|
|
|
|
|
Following section shows an example runtime configuration
|
|
(hostapd.conf) that enables WPS:
|
|
|
|
# Configure the driver and network interface
|
|
driver=madwifi
|
|
interface=ath0
|
|
|
|
# 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).
|