1hostapd - user space IEEE 802.11 AP and IEEE 802.1X/WPA/WPA2/EAP 2 Authenticator and RADIUS authentication server 3================================================================ 4 5Copyright (c) 2002-2012, Jouni Malinen <j@w1.fi> and contributors 6All Rights Reserved. 7 8This program is licensed under the BSD license (the one with 9advertisement clause removed). 10 11If you are submitting changes to the project, please see CONTRIBUTIONS 12file for more instructions. 13 14 15 16License 17------- 18 19This software may be distributed, used, and modified under the terms of 20BSD license: 21 22Redistribution and use in source and binary forms, with or without 23modification, are permitted provided that the following conditions are 24met: 25 261. Redistributions of source code must retain the above copyright 27 notice, this list of conditions and the following disclaimer. 28 292. Redistributions in binary form must reproduce the above copyright 30 notice, this list of conditions and the following disclaimer in the 31 documentation and/or other materials provided with the distribution. 32 333. Neither the name(s) of the above-listed copyright holder(s) nor the 34 names of its contributors may be used to endorse or promote products 35 derived from this software without specific prior written permission. 36 37THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 38"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 39LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 40A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 41OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 42SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 43LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 44DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 45THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 46(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 47OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 48 49 50 51Introduction 52============ 53 54Originally, hostapd was an optional user space component for Host AP 55driver. It adds more features to the basic IEEE 802.11 management 56included in the kernel driver: using external RADIUS authentication 57server for MAC address based access control, IEEE 802.1X Authenticator 58and dynamic WEP keying, RADIUS accounting, WPA/WPA2 (IEEE 802.11i/RSN) 59Authenticator and dynamic TKIP/CCMP keying. 60 61The current version includes support for other drivers, an integrated 62EAP server (i.e., allow full authentication without requiring 63an external RADIUS authentication server), and RADIUS authentication 64server for EAP authentication. 65 66 67Requirements 68------------ 69 70Current hardware/software requirements: 71- drivers: 72 Host AP driver for Prism2/2.5/3. 73 (http://hostap.epitest.fi/) 74 Please note that station firmware version needs to be 1.7.0 or newer 75 to work in WPA mode. 76 77 madwifi driver for cards based on Atheros chip set (ar521x) 78 (http://sourceforge.net/projects/madwifi/) 79 Please note that you will need to add the correct path for 80 madwifi driver root directory in .config (see defconfig file for 81 an example: CFLAGS += -I<path>) 82 83 mac80211-based drivers that support AP mode (with driver=nl80211). 84 This includes drivers for Atheros (ath9k) and Broadcom (b43) 85 chipsets. 86 87 Any wired Ethernet driver for wired IEEE 802.1X authentication 88 (experimental code) 89 90 FreeBSD -current (with some kernel mods that have not yet been 91 committed when hostapd v0.3.0 was released) 92 BSD net80211 layer (e.g., Atheros driver) 93 94 95Build configuration 96------------------- 97 98In order to be able to build hostapd, you will need to create a build 99time configuration file, .config that selects which optional 100components are included. See defconfig file for example configuration 101and list of available options. 102 103 104 105IEEE 802.1X 106=========== 107 108IEEE Std 802.1X-2001 is a standard for port-based network access 109control. In case of IEEE 802.11 networks, a "virtual port" is used 110between each associated station and the AP. IEEE 802.11 specifies 111minimal authentication mechanism for stations, whereas IEEE 802.1X 112introduces a extensible mechanism for authenticating and authorizing 113users. 114 115IEEE 802.1X uses elements called Supplicant, Authenticator, Port 116Access Entity, and Authentication Server. Supplicant is a component in 117a station and it performs the authentication with the Authentication 118Server. An access point includes an Authenticator that relays the packets 119between a Supplicant and an Authentication Server. In addition, it has a 120Port Access Entity (PAE) with Authenticator functionality for 121controlling the virtual port authorization, i.e., whether to accept 122packets from or to the station. 123 124IEEE 802.1X uses Extensible Authentication Protocol (EAP). The frames 125between a Supplicant and an Authenticator are sent using EAP over LAN 126(EAPOL) and the Authenticator relays these frames to the Authentication 127Server (and similarly, relays the messages from the Authentication 128Server to the Supplicant). The Authentication Server can be colocated with the 129Authenticator, in which case there is no need for additional protocol 130for EAP frame transmission. However, a more common configuration is to 131use an external Authentication Server and encapsulate EAP frame in the 132frames used by that server. RADIUS is suitable for this, but IEEE 133802.1X would also allow other mechanisms. 134 135Host AP driver includes PAE functionality in the kernel driver. It 136is a relatively simple mechanism for denying normal frames going to 137or coming from an unauthorized port. PAE allows IEEE 802.1X related 138frames to be passed between the Supplicant and the Authenticator even 139on an unauthorized port. 140 141User space daemon, hostapd, includes Authenticator functionality. It 142receives 802.1X (EAPOL) frames from the Supplicant using the wlan#ap 143device that is also used with IEEE 802.11 management frames. The 144frames to the Supplicant are sent using the same device. 145 146The normal configuration of the Authenticator would use an external 147Authentication Server. hostapd supports RADIUS encapsulation of EAP 148packets, so the Authentication Server should be a RADIUS server, like 149FreeRADIUS (http://www.freeradius.org/). The Authenticator in hostapd 150relays the frames between the Supplicant and the Authentication 151Server. It also controls the PAE functionality in the kernel driver by 152controlling virtual port authorization, i.e., station-AP 153connection, based on the IEEE 802.1X state. 154 155When a station would like to use the services of an access point, it 156will first perform IEEE 802.11 authentication. This is normally done 157with open systems authentication, so there is no security. After 158this, IEEE 802.11 association is performed. If IEEE 802.1X is 159configured to be used, the virtual port for the station is set in 160Unauthorized state and only IEEE 802.1X frames are accepted at this 161point. The Authenticator will then ask the Supplicant to authenticate 162with the Authentication Server. After this is completed successfully, 163the virtual port is set to Authorized state and frames from and to the 164station are accepted. 165 166Host AP configuration for IEEE 802.1X 167------------------------------------- 168 169The user space daemon has its own configuration file that can be used to 170define AP options. Distribution package contains an example 171configuration file (hostapd/hostapd.conf) that can be used as a basis 172for configuration. It includes examples of all supported configuration 173options and short description of each option. hostapd should be started 174with full path to the configuration file as the command line argument, 175e.g., './hostapd /etc/hostapd.conf'. If you have more that one wireless 176LAN card, you can use one hostapd process for multiple interfaces by 177giving a list of configuration files (one per interface) in the command 178line. 179 180hostapd includes a minimal co-located IEEE 802.1X server which can be 181used to test IEEE 802.1X authentication. However, it should not be 182used in normal use since it does not provide any security. This can be 183configured by setting ieee8021x and minimal_eap options in the 184configuration file. 185 186An external Authentication Server (RADIUS) is configured with 187auth_server_{addr,port,shared_secret} options. In addition, 188ieee8021x and own_ip_addr must be set for this mode. With such 189configuration, the co-located Authentication Server is not used and EAP 190frames will be relayed using EAPOL between the Supplicant and the 191Authenticator and RADIUS encapsulation between the Authenticator and 192the Authentication Server. Other than this, the functionality is similar 193to the case with the co-located Authentication Server. 194 195Authentication Server and Supplicant 196------------------------------------ 197 198Any RADIUS server supporting EAP should be usable as an IEEE 802.1X 199Authentication Server with hostapd Authenticator. FreeRADIUS 200(http://www.freeradius.org/) has been successfully tested with hostapd 201Authenticator and both Xsupplicant (http://www.open1x.org) and Windows 202XP Supplicants. EAP/TLS was used with Xsupplicant and 203EAP/MD5-Challenge with Windows XP. 204 205http://www.missl.cs.umd.edu/wireless/eaptls/ has useful information 206about using EAP/TLS with FreeRADIUS and Xsupplicant (just replace 207Cisco access point with Host AP driver, hostapd daemon, and a Prism2 208card ;-). http://www.freeradius.org/doc/EAP-MD5.html has information 209about using EAP/MD5 with FreeRADIUS, including instructions for WinXP 210configuration. http://www.denobula.com/EAPTLS.pdf has a HOWTO on 211EAP/TLS use with WinXP Supplicant. 212 213Automatic WEP key configuration 214------------------------------- 215 216EAP/TLS generates a session key that can be used to send WEP keys from 217an AP to authenticated stations. The Authenticator in hostapd can be 218configured to automatically select a random default/broadcast key 219(shared by all authenticated stations) with wep_key_len_broadcast 220option (5 for 40-bit WEP or 13 for 104-bit WEP). In addition, 221wep_key_len_unicast option can be used to configure individual unicast 222keys for stations. This requires support for individual keys in the 223station driver. 224 225WEP keys can be automatically updated by configuring rekeying. This 226will improve security of the network since same WEP key will only be 227used for a limited period of time. wep_rekey_period option sets the 228interval for rekeying in seconds. 229 230 231WPA/WPA2 232======== 233 234Features 235-------- 236 237Supported WPA/IEEE 802.11i features: 238- WPA-PSK ("WPA-Personal") 239- WPA with EAP (e.g., with RADIUS authentication server) ("WPA-Enterprise") 240- key management for CCMP, TKIP, WEP104, WEP40 241- RSN/WPA2 (IEEE 802.11i), including PMKSA caching and pre-authentication 242 243WPA 244--- 245 246The original security mechanism of IEEE 802.11 standard was not 247designed to be strong and has proved to be insufficient for most 248networks that require some kind of security. Task group I (Security) 249of IEEE 802.11 working group (http://www.ieee802.org/11/) has worked 250to address the flaws of the base standard and has in practice 251completed its work in May 2004. The IEEE 802.11i amendment to the IEEE 252802.11 standard was approved in June 2004 and this amendment is likely 253to be published in July 2004. 254 255Wi-Fi Alliance (http://www.wi-fi.org/) used a draft version of the 256IEEE 802.11i work (draft 3.0) to define a subset of the security 257enhancements that can be implemented with existing wlan hardware. This 258is called Wi-Fi Protected Access<TM> (WPA). This has now become a 259mandatory component of interoperability testing and certification done 260by Wi-Fi Alliance. Wi-Fi provides information about WPA at its web 261site (http://www.wi-fi.org/OpenSection/protected_access.asp). 262 263IEEE 802.11 standard defined wired equivalent privacy (WEP) algorithm 264for protecting wireless networks. WEP uses RC4 with 40-bit keys, 26524-bit initialization vector (IV), and CRC32 to protect against packet 266forgery. All these choices have proven to be insufficient: key space is 267too small against current attacks, RC4 key scheduling is insufficient 268(beginning of the pseudorandom stream should be skipped), IV space is 269too small and IV reuse makes attacks easier, there is no replay 270protection, and non-keyed authentication does not protect against bit 271flipping packet data. 272 273WPA is an intermediate solution for the security issues. It uses 274Temporal Key Integrity Protocol (TKIP) to replace WEP. TKIP is a 275compromise on strong security and possibility to use existing 276hardware. It still uses RC4 for the encryption like WEP, but with 277per-packet RC4 keys. In addition, it implements replay protection, 278keyed packet authentication mechanism (Michael MIC). 279 280Keys can be managed using two different mechanisms. WPA can either use 281an external authentication server (e.g., RADIUS) and EAP just like 282IEEE 802.1X is using or pre-shared keys without need for additional 283servers. Wi-Fi calls these "WPA-Enterprise" and "WPA-Personal", 284respectively. Both mechanisms will generate a master session key for 285the Authenticator (AP) and Supplicant (client station). 286 287WPA implements a new key handshake (4-Way Handshake and Group Key 288Handshake) for generating and exchanging data encryption keys between 289the Authenticator and Supplicant. This handshake is also used to 290verify that both Authenticator and Supplicant know the master session 291key. These handshakes are identical regardless of the selected key 292management mechanism (only the method for generating master session 293key changes). 294 295 296IEEE 802.11i / WPA2 297------------------- 298 299The design for parts of IEEE 802.11i that were not included in WPA has 300finished (May 2004) and this amendment to IEEE 802.11 was approved in 301June 2004. Wi-Fi Alliance is using the final IEEE 802.11i as a new 302version of WPA called WPA2. This includes, e.g., support for more 303robust encryption algorithm (CCMP: AES in Counter mode with CBC-MAC) 304to replace TKIP and optimizations for handoff (reduced number of 305messages in initial key handshake, pre-authentication, and PMKSA caching). 306 307Some wireless LAN vendors are already providing support for CCMP in 308their WPA products. There is no "official" interoperability 309certification for CCMP and/or mixed modes using both TKIP and CCMP, so 310some interoperability issues can be expected even though many 311combinations seem to be working with equipment from different vendors. 312Testing for WPA2 is likely to start during the second half of 2004. 313 314hostapd configuration for WPA/WPA2 315---------------------------------- 316 317TODO 318 319# Enable WPA. Setting this variable configures the AP to require WPA (either 320# WPA-PSK or WPA-RADIUS/EAP based on other configuration). For WPA-PSK, either 321# wpa_psk or wpa_passphrase must be set and wpa_key_mgmt must include WPA-PSK. 322# For WPA-RADIUS/EAP, ieee8021x must be set (but without dynamic WEP keys), 323# RADIUS authentication server must be configured, and WPA-EAP must be included 324# in wpa_key_mgmt. 325# This field is a bit field that can be used to enable WPA (IEEE 802.11i/D3.0) 326# and/or WPA2 (full IEEE 802.11i/RSN): 327# bit0 = WPA 328# bit1 = IEEE 802.11i/RSN (WPA2) 329#wpa=1 330 331# WPA pre-shared keys for WPA-PSK. This can be either entered as a 256-bit 332# secret in hex format (64 hex digits), wpa_psk, or as an ASCII passphrase 333# (8..63 characters) that will be converted to PSK. This conversion uses SSID 334# so the PSK changes when ASCII passphrase is used and the SSID is changed. 335#wpa_psk=0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef 336#wpa_passphrase=secret passphrase 337 338# Set of accepted key management algorithms (WPA-PSK, WPA-EAP, or both). The 339# entries are separated with a space. 340#wpa_key_mgmt=WPA-PSK WPA-EAP 341 342# Set of accepted cipher suites (encryption algorithms) for pairwise keys 343# (unicast packets). This is a space separated list of algorithms: 344# CCMP = AES in Counter mode with CBC-MAC [RFC 3610, IEEE 802.11i] 345# TKIP = Temporal Key Integrity Protocol [IEEE 802.11i] 346# Group cipher suite (encryption algorithm for broadcast and multicast frames) 347# is automatically selected based on this configuration. If only CCMP is 348# allowed as the pairwise cipher, group cipher will also be CCMP. Otherwise, 349# TKIP will be used as the group cipher. 350#wpa_pairwise=TKIP CCMP 351 352# Time interval for rekeying GTK (broadcast/multicast encryption keys) in 353# seconds. 354#wpa_group_rekey=600 355 356# Time interval for rekeying GMK (master key used internally to generate GTKs 357# (in seconds). 358#wpa_gmk_rekey=86400 359 360# Enable IEEE 802.11i/RSN/WPA2 pre-authentication. This is used to speed up 361# roaming be pre-authenticating IEEE 802.1X/EAP part of the full RSN 362# authentication and key handshake before actually associating with a new AP. 363#rsn_preauth=1 364# 365# Space separated list of interfaces from which pre-authentication frames are 366# accepted (e.g., 'eth0' or 'eth0 wlan0wds0'. This list should include all 367# interface that are used for connections to other APs. This could include 368# wired interfaces and WDS links. The normal wireless data interface towards 369# associated stations (e.g., wlan0) should not be added, since 370# pre-authentication is only used with APs other than the currently associated 371# one. 372#rsn_preauth_interfaces=eth0 373