1 hostapd - user space IEEE 802.11 AP and IEEE 802.1X/WPA/WPA2/EAP
2 Authenticator and RADIUS authentication server
3 ================================================================
5 Copyright (c) 2002-2011, Jouni Malinen <j@w1.fi> and contributors
8 This program is dual-licensed under both the GPL version 2 and BSD
9 license. Either license may be used at your option.
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19 it under the terms of the GNU General Public License version 2 as
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69 Originally, hostapd was an optional user space component for Host AP
70 driver. It adds more features to the basic IEEE 802.11 management
71 included in the kernel driver: using external RADIUS authentication
72 server for MAC address based access control, IEEE 802.1X Authenticator
73 and dynamic WEP keying, RADIUS accounting, WPA/WPA2 (IEEE 802.11i/RSN)
74 Authenticator and dynamic TKIP/CCMP keying.
76 The current version includes support for other drivers, an integrated
77 EAP server (i.e., allow full authentication without requiring
78 an external RADIUS authentication server), and RADIUS authentication
79 server for EAP authentication.
85 Current hardware/software requirements:
87 Host AP driver for Prism2/2.5/3.
88 (http://hostap.epitest.fi/)
89 Please note that station firmware version needs to be 1.7.0 or newer
92 madwifi driver for cards based on Atheros chip set (ar521x)
93 (http://sourceforge.net/projects/madwifi/)
94 Please note that you will need to add the correct path for
95 madwifi driver root directory in .config (see defconfig file for
96 an example: CFLAGS += -I<path>)
98 mac80211-based drivers that support AP mode (with driver=nl80211).
99 This includes drivers for Atheros (ath9k) and Broadcom (b43)
102 Any wired Ethernet driver for wired IEEE 802.1X authentication
105 FreeBSD -current (with some kernel mods that have not yet been
106 committed when hostapd v0.3.0 was released)
107 BSD net80211 layer (e.g., Atheros driver)
113 In order to be able to build hostapd, you will need to create a build
114 time configuration file, .config that selects which optional
115 components are included. See defconfig file for example configuration
116 and list of available options.
123 IEEE Std 802.1X-2001 is a standard for port-based network access
124 control. In case of IEEE 802.11 networks, a "virtual port" is used
125 between each associated station and the AP. IEEE 802.11 specifies
126 minimal authentication mechanism for stations, whereas IEEE 802.1X
127 introduces a extensible mechanism for authenticating and authorizing
130 IEEE 802.1X uses elements called Supplicant, Authenticator, Port
131 Access Entity, and Authentication Server. Supplicant is a component in
132 a station and it performs the authentication with the Authentication
133 Server. An access point includes an Authenticator that relays the packets
134 between a Supplicant and an Authentication Server. In addition, it has a
135 Port Access Entity (PAE) with Authenticator functionality for
136 controlling the virtual port authorization, i.e., whether to accept
137 packets from or to the station.
139 IEEE 802.1X uses Extensible Authentication Protocol (EAP). The frames
140 between a Supplicant and an Authenticator are sent using EAP over LAN
141 (EAPOL) and the Authenticator relays these frames to the Authentication
142 Server (and similarly, relays the messages from the Authentication
143 Server to the Supplicant). The Authentication Server can be colocated with the
144 Authenticator, in which case there is no need for additional protocol
145 for EAP frame transmission. However, a more common configuration is to
146 use an external Authentication Server and encapsulate EAP frame in the
147 frames used by that server. RADIUS is suitable for this, but IEEE
148 802.1X would also allow other mechanisms.
150 Host AP driver includes PAE functionality in the kernel driver. It
151 is a relatively simple mechanism for denying normal frames going to
152 or coming from an unauthorized port. PAE allows IEEE 802.1X related
153 frames to be passed between the Supplicant and the Authenticator even
154 on an unauthorized port.
156 User space daemon, hostapd, includes Authenticator functionality. It
157 receives 802.1X (EAPOL) frames from the Supplicant using the wlan#ap
158 device that is also used with IEEE 802.11 management frames. The
159 frames to the Supplicant are sent using the same device.
161 The normal configuration of the Authenticator would use an external
162 Authentication Server. hostapd supports RADIUS encapsulation of EAP
163 packets, so the Authentication Server should be a RADIUS server, like
164 FreeRADIUS (http://www.freeradius.org/). The Authenticator in hostapd
165 relays the frames between the Supplicant and the Authentication
166 Server. It also controls the PAE functionality in the kernel driver by
167 controlling virtual port authorization, i.e., station-AP
168 connection, based on the IEEE 802.1X state.
170 When a station would like to use the services of an access point, it
171 will first perform IEEE 802.11 authentication. This is normally done
172 with open systems authentication, so there is no security. After
173 this, IEEE 802.11 association is performed. If IEEE 802.1X is
174 configured to be used, the virtual port for the station is set in
175 Unauthorized state and only IEEE 802.1X frames are accepted at this
176 point. The Authenticator will then ask the Supplicant to authenticate
177 with the Authentication Server. After this is completed successfully,
178 the virtual port is set to Authorized state and frames from and to the
179 station are accepted.
181 Host AP configuration for IEEE 802.1X
182 -------------------------------------
184 The user space daemon has its own configuration file that can be used to
185 define AP options. Distribution package contains an example
186 configuration file (hostapd/hostapd.conf) that can be used as a basis
187 for configuration. It includes examples of all supported configuration
188 options and short description of each option. hostapd should be started
189 with full path to the configuration file as the command line argument,
190 e.g., './hostapd /etc/hostapd.conf'. If you have more that one wireless
191 LAN card, you can use one hostapd process for multiple interfaces by
192 giving a list of configuration files (one per interface) in the command
195 hostapd includes a minimal co-located IEEE 802.1X server which can be
196 used to test IEEE 802.1X authentication. However, it should not be
197 used in normal use since it does not provide any security. This can be
198 configured by setting ieee8021x and minimal_eap options in the
201 An external Authentication Server (RADIUS) is configured with
202 auth_server_{addr,port,shared_secret} options. In addition,
203 ieee8021x and own_ip_addr must be set for this mode. With such
204 configuration, the co-located Authentication Server is not used and EAP
205 frames will be relayed using EAPOL between the Supplicant and the
206 Authenticator and RADIUS encapsulation between the Authenticator and
207 the Authentication Server. Other than this, the functionality is similar
208 to the case with the co-located Authentication Server.
210 Authentication Server and Supplicant
211 ------------------------------------
213 Any RADIUS server supporting EAP should be usable as an IEEE 802.1X
214 Authentication Server with hostapd Authenticator. FreeRADIUS
215 (http://www.freeradius.org/) has been successfully tested with hostapd
216 Authenticator and both Xsupplicant (http://www.open1x.org) and Windows
217 XP Supplicants. EAP/TLS was used with Xsupplicant and
218 EAP/MD5-Challenge with Windows XP.
220 http://www.missl.cs.umd.edu/wireless/eaptls/ has useful information
221 about using EAP/TLS with FreeRADIUS and Xsupplicant (just replace
222 Cisco access point with Host AP driver, hostapd daemon, and a Prism2
223 card ;-). http://www.freeradius.org/doc/EAP-MD5.html has information
224 about using EAP/MD5 with FreeRADIUS, including instructions for WinXP
225 configuration. http://www.denobula.com/EAPTLS.pdf has a HOWTO on
226 EAP/TLS use with WinXP Supplicant.
228 Automatic WEP key configuration
229 -------------------------------
231 EAP/TLS generates a session key that can be used to send WEP keys from
232 an AP to authenticated stations. The Authenticator in hostapd can be
233 configured to automatically select a random default/broadcast key
234 (shared by all authenticated stations) with wep_key_len_broadcast
235 option (5 for 40-bit WEP or 13 for 104-bit WEP). In addition,
236 wep_key_len_unicast option can be used to configure individual unicast
237 keys for stations. This requires support for individual keys in the
240 WEP keys can be automatically updated by configuring rekeying. This
241 will improve security of the network since same WEP key will only be
242 used for a limited period of time. wep_rekey_period option sets the
243 interval for rekeying in seconds.
252 Supported WPA/IEEE 802.11i features:
253 - WPA-PSK ("WPA-Personal")
254 - WPA with EAP (e.g., with RADIUS authentication server) ("WPA-Enterprise")
255 - key management for CCMP, TKIP, WEP104, WEP40
256 - RSN/WPA2 (IEEE 802.11i), including PMKSA caching and pre-authentication
261 The original security mechanism of IEEE 802.11 standard was not
262 designed to be strong and has proved to be insufficient for most
263 networks that require some kind of security. Task group I (Security)
264 of IEEE 802.11 working group (http://www.ieee802.org/11/) has worked
265 to address the flaws of the base standard and has in practice
266 completed its work in May 2004. The IEEE 802.11i amendment to the IEEE
267 802.11 standard was approved in June 2004 and this amendment is likely
268 to be published in July 2004.
270 Wi-Fi Alliance (http://www.wi-fi.org/) used a draft version of the
271 IEEE 802.11i work (draft 3.0) to define a subset of the security
272 enhancements that can be implemented with existing wlan hardware. This
273 is called Wi-Fi Protected Access<TM> (WPA). This has now become a
274 mandatory component of interoperability testing and certification done
275 by Wi-Fi Alliance. Wi-Fi provides information about WPA at its web
276 site (http://www.wi-fi.org/OpenSection/protected_access.asp).
278 IEEE 802.11 standard defined wired equivalent privacy (WEP) algorithm
279 for protecting wireless networks. WEP uses RC4 with 40-bit keys,
280 24-bit initialization vector (IV), and CRC32 to protect against packet
281 forgery. All these choices have proven to be insufficient: key space is
282 too small against current attacks, RC4 key scheduling is insufficient
283 (beginning of the pseudorandom stream should be skipped), IV space is
284 too small and IV reuse makes attacks easier, there is no replay
285 protection, and non-keyed authentication does not protect against bit
286 flipping packet data.
288 WPA is an intermediate solution for the security issues. It uses
289 Temporal Key Integrity Protocol (TKIP) to replace WEP. TKIP is a
290 compromise on strong security and possibility to use existing
291 hardware. It still uses RC4 for the encryption like WEP, but with
292 per-packet RC4 keys. In addition, it implements replay protection,
293 keyed packet authentication mechanism (Michael MIC).
295 Keys can be managed using two different mechanisms. WPA can either use
296 an external authentication server (e.g., RADIUS) and EAP just like
297 IEEE 802.1X is using or pre-shared keys without need for additional
298 servers. Wi-Fi calls these "WPA-Enterprise" and "WPA-Personal",
299 respectively. Both mechanisms will generate a master session key for
300 the Authenticator (AP) and Supplicant (client station).
302 WPA implements a new key handshake (4-Way Handshake and Group Key
303 Handshake) for generating and exchanging data encryption keys between
304 the Authenticator and Supplicant. This handshake is also used to
305 verify that both Authenticator and Supplicant know the master session
306 key. These handshakes are identical regardless of the selected key
307 management mechanism (only the method for generating master session
314 The design for parts of IEEE 802.11i that were not included in WPA has
315 finished (May 2004) and this amendment to IEEE 802.11 was approved in
316 June 2004. Wi-Fi Alliance is using the final IEEE 802.11i as a new
317 version of WPA called WPA2. This includes, e.g., support for more
318 robust encryption algorithm (CCMP: AES in Counter mode with CBC-MAC)
319 to replace TKIP and optimizations for handoff (reduced number of
320 messages in initial key handshake, pre-authentication, and PMKSA caching).
322 Some wireless LAN vendors are already providing support for CCMP in
323 their WPA products. There is no "official" interoperability
324 certification for CCMP and/or mixed modes using both TKIP and CCMP, so
325 some interoperability issues can be expected even though many
326 combinations seem to be working with equipment from different vendors.
327 Testing for WPA2 is likely to start during the second half of 2004.
329 hostapd configuration for WPA/WPA2
330 ----------------------------------
334 # Enable WPA. Setting this variable configures the AP to require WPA (either
335 # WPA-PSK or WPA-RADIUS/EAP based on other configuration). For WPA-PSK, either
336 # wpa_psk or wpa_passphrase must be set and wpa_key_mgmt must include WPA-PSK.
337 # For WPA-RADIUS/EAP, ieee8021x must be set (but without dynamic WEP keys),
338 # RADIUS authentication server must be configured, and WPA-EAP must be included
340 # This field is a bit field that can be used to enable WPA (IEEE 802.11i/D3.0)
341 # and/or WPA2 (full IEEE 802.11i/RSN):
343 # bit1 = IEEE 802.11i/RSN (WPA2)
346 # WPA pre-shared keys for WPA-PSK. This can be either entered as a 256-bit
347 # secret in hex format (64 hex digits), wpa_psk, or as an ASCII passphrase
348 # (8..63 characters) that will be converted to PSK. This conversion uses SSID
349 # so the PSK changes when ASCII passphrase is used and the SSID is changed.
350 #wpa_psk=0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef
351 #wpa_passphrase=secret passphrase
353 # Set of accepted key management algorithms (WPA-PSK, WPA-EAP, or both). The
354 # entries are separated with a space.
355 #wpa_key_mgmt=WPA-PSK WPA-EAP
357 # Set of accepted cipher suites (encryption algorithms) for pairwise keys
358 # (unicast packets). This is a space separated list of algorithms:
359 # CCMP = AES in Counter mode with CBC-MAC [RFC 3610, IEEE 802.11i]
360 # TKIP = Temporal Key Integrity Protocol [IEEE 802.11i]
361 # Group cipher suite (encryption algorithm for broadcast and multicast frames)
362 # is automatically selected based on this configuration. If only CCMP is
363 # allowed as the pairwise cipher, group cipher will also be CCMP. Otherwise,
364 # TKIP will be used as the group cipher.
365 #wpa_pairwise=TKIP CCMP
367 # Time interval for rekeying GTK (broadcast/multicast encryption keys) in
371 # Time interval for rekeying GMK (master key used internally to generate GTKs
375 # Enable IEEE 802.11i/RSN/WPA2 pre-authentication. This is used to speed up
376 # roaming be pre-authenticating IEEE 802.1X/EAP part of the full RSN
377 # authentication and key handshake before actually associating with a new AP.
380 # Space separated list of interfaces from which pre-authentication frames are
381 # accepted (e.g., 'eth0' or 'eth0 wlan0wds0'. This list should include all
382 # interface that are used for connections to other APs. This could include
383 # wired interfaces and WDS links. The normal wireless data interface towards
384 # associated stations (e.g., wlan0) should not be added, since
385 # pre-authentication is only used with APs other than the currently associated
387 #rsn_preauth_interfaces=eth0