3 Extensible Authentication Protocol (EAP)
8 Extensible Authentication Protocol(EAP), rfc2284, is a general protocol
9 that allows network access points to support multiple authentication
10 methods. Each EAP-Type indicates a specific authentication mechanism.
11 802.1x standard authenticates wireless LAN users trying to access
14 RADIUS attribute used for EAP is EAP-Message, 79(rfc2869). RADIUS
15 communicates all EAP messages by embedding them in this attribute.
18 Supplicant/EAP Client - is the software on the end-user/client machine
19 (machine with the wireless card).
20 Authenticator/NAS/Access Point(AP) - A network device providing users
21 with a point of entry into the network.
22 EAPOL - EAP over LAN as defined in 802.1x standard.
23 EAPOW - EAP over Wireless.
26 +----------+ +----------+ +----------+
27 | | EAPOL | | RADIUS | |
28 | EAP |<------>| Access |<------>| RADIUS |
29 | Client | EAPOW | Point | (EAP) | Server |
31 +----------+ +----------+ +----------+
34 The sequence of events, for EAP-MD5, runs as follows:
35 1. The end-user associates with the Access Point(AP).
36 2. The supplicant specifies AP to use EAP by sending EAP-Start.
37 3. AP requests the supplicant to Identify itself (EAP-Identity).
38 4. Supplicant then sends its Identity (username) to the AP.
39 5. AP forwards this EAP-response AS-IS to the RADIUS server.
40 (The supplicant and the RADIUS server mutually authenticate via AP.
41 AP just acts as a passthru till authentication is finished.)
42 6. The server sends a challenge to the supplicant.
43 7. The supplicant carries out a hash on the password and sends
44 this hashed password to the RADIUS server as its response.
45 8. The RADIUS server performs a hash on the password for that supplicant
46 in its user database and compares the two hashed values and
47 authenticates the client if the two values match(EAP-Success/EAP-Failure)
48 9. AP now opens a port to accept data from the end-user.
50 Currently, EAP is widely used in wireless networks than in wired networks.
51 In 802.11/wireless based networking, following sequence of events happen in
52 addition to the above EAP events.
54 10. RADIUS server and the supplicant agree to a specific WEP key.
55 11. The supplicant loads the key ready for logging on.
56 12. The RADIUS server sends the key for this session (Session key) to the AP.
57 13. The AP encrypts its Broadcast key with the Session key
58 14. The AP sends the encypted key to the supplicant
59 15. The supplicant decrypts the Broadcast key with the Session key and
60 the session continues using the Broadcast and Session keys until
64 The Implementation of EAP over RADIUS is based on the following RFCs
65 rfc2869 -- RADIUS Extensions
66 rfc2284 -- PPP Extensible Authentication Protocol (EAP)
67 rfc2716 -- PPP EAP TLS Authentication Protocol
69 Following links help to understand HOW EAP works
70 www.ieee802.org/1/mirror/8021/docs2000/ieee_plenary.PDF
75 EAP is implemented as a module in freeradius
76 and the code is placed in src/modules/rlm_eap.
77 All EAP-Types are organized as subdirectories in rlm_eap/types/.
78 Currently Freeradius supports only 2 EAP-Types (EAP-MD5, EAP-TLS).
80 Each EAP-Type, like types/rlm_eap_md5, contains a chunk of code that
81 knows how to deal with a particular kind of authentication mechanism.
83 To add a new EAP-Type then a new directory should be created as
84 rlm_eap/types/rlm_eap_XXXX, where XXXX is EAP-Type name
85 ie for EAP-Type like ONE TIME PASSWORD (OTP) it would be rlm_eap_otp
87 src/modules/rlm_eap -- contains the basic EAP and generalized interfaces
89 rlm_eap/types -- contains all the supported EAP-Types
90 rlm_eap/types/rlm_eap_md5 -- EAP-MD5 authentication.
91 rlm_eap/types/rlm_eap_tls -- EAP-TLS based authentication.
92 rlm_eap/types/rlm_eap_ttls -- TTLS based authentication.
93 rlm_eap/types/rlm_eap_peap -- Windows PEAP based authentication.
94 rlm_eap/types/rlm_eap_leap -- Cisco LEAP authentication.
95 rlm_eap/types/rlm_eap_sim -- EAP-SIM (GSM) based authentication
99 Add the eap configuration stanza to the modules section in radiusd.conf
100 to load and control rlm_eap and all the supported EAP-Types:
106 default_eap_type = md5
115 NOTE: You cannot have empty eap stanza. At least one EAP-Type sub-stanza
116 should be defined as above, otherwise the server will not know what type
117 of eap authentication mechanism to be used and the server will exit
120 All the various options and their associated default values for each
121 EAP-Type are documented in the sample radiusd.conf that is provided
122 with the distribution.
124 Since the EAP requests may not contain a requested EAP type, the
125 'default_eap_type' configuration options is used by the EAP module
126 to determine which EAP type to choose for authentication.
128 NOTE: EAP cannot authorize a user. It can only authenticate.
129 Other Freeradius modules authorize the user.
134 To configure EAP-SIM authentication, the following attributes must be
135 set in the server. This can be done in the users file, but in many cases
136 will be taken from a database server, via one of the SQL interface.
138 If one has SIM cards that one controls (i.e. whose share secret you know),
139 one should be able to write a module to generate these attributes
140 (the triplets) in the server.
142 If one has access to the SS7 based settlement network, then a module to
143 fetch appropriate triplets could be written. This module would act as
144 an authorization only module.
147 EAP-Sim-Rand1 16 bytes
148 EAP-Sim-SRES1 4 bytes
150 EAP-Sim-Rand2 16 bytes
151 EAP-Sim-SRES2 4 bytes
153 EAP-Sim-Rand3 16 bytes
154 EAP-Sim-SRES3 4 bytes
157 EAP-SIM will send WEP attributes to the resquestor.
161 1. XSupplicant - freeradius (EAP/TLS) notes may be found at:
163 http://www.eax.com/802/
164 or http://www.missl.cs.umd.edu/wireless/eaptls/
166 XSupplicant is hosted by:
168 http://www.open1x.org/
170 2. XP - freeradius (EAP/TLS) notes may be found at:
172 http://www.denobula.com/EAPTLS.pdf
174 3. Freeradius has an "radeapclient" that can do EAP-MD5 (passwords),
175 as well as EAP-SIM. It is in modules/rlm_eap/radeapclient.
179 You will find several test cases in src/tests/ for the EAP-SIM code.
182 HOW DO I USE IT (FAQ/Examples)
184 1. How can I enable EAP-MD5 authentication ?
191 default_eap_type = md5
199 # eap sets the authenticate type as EAP
205 # eap authentication takes place.
210 # If you are proxying EAP-LEAP requests
211 # This is required to make LEAP work.
216 2. My Userbase is in LDAP and I want to use EAP-MD5 authentication
223 default_eap_type = md5
231 # ldap gets the Configured password.
232 # eap sets the authenticate type as EAP
240 # eap authentication takes place.
247 3. How can I Proxy EAP messages, with/without User-Name attribute
248 in the Access-Request packets
250 With User-Name attribute in Access-Request packet,
251 EAP-proxying is just same as RADIUS-proxying.
253 If User-Name attribute is not present in Access-Request packet,
254 Freeradius can proxy the request with the following configuration
257 # eap module should be configured as the First module in
258 # the authorize stanza
265 With this configuration, eap_authorize creates User-Name attribute
266 from EAP-Identity response, if it is not present.
267 Once User-Name attribute is created, RADIUS proxying takes care
270 4. How Freeradius can handle EAP-START messages ?
272 In most of the cases this is handled by the Authenticator.
274 Only if it is required then, in radiusd.conf
281 With the above configuration, RADIUS server immediately responds with
282 EAP-Identity request.
284 NOTE: EAP does not check for any Identity or maintains any state in case
285 of EAP-START. It blindly responds with EAP-Identity request.
286 Proxying is handled only after EAP-Identity response is received.
288 5. I want to enable multiple EAP-Types, how can I configure ?
295 default_eap_type = tls
306 The above configuration will let the server load all the EAP-Types,
307 but the server can have only one default EAP-Type, as above.
309 Once EAP-Identity response is received by the server, based on the
310 default_eap_type, the server will send a new request (MD5-Challenge
311 request incase of md5, TLS-START request incase of tls) to the supplicant.
312 If the supplicant is rfc2284 compliant and doesnot support the
313 EAP-Type sent by the server then it sends EAP-Acknowledge with the
314 supported EAP-Type. If this EAP-Type is supported by the server then it
315 will send the respective EAP-request.
317 Example: If the supplicant supports only EAP-MD5 but the server
318 default_eap_type is configured as EAP-TLS, as above, then the server
319 will send TLS-START after EAP-Identity is received. Supplicant will
320 respond with EAP-Acknowledge(EAP-MD5). Server now responds with
325 EAP, EAP-MD5, and Cisco LEAP do not require any additional packages.
326 Freeradius contains all the required packages.
328 For EAP-TLS, EAP-TTLS, and PEAP, OPENSSL, <http://www.openssl.org/>,
329 is required to be installed.
330 Any version from 0.9.7, should fairly work with this module.
332 EAP-SIM should not require any additional packages.
335 IMPLEMENTATION (For Developers)
337 The rlm_eap module only deals with EAP specific authentication mechanism
338 and the generic interface to interact with all the EAP-Types.
340 Currently, these are the existing interfaces,
341 int attach(CONF_SECTION *conf, void **type_arg);
342 int initiate(void *type_arg, EAP_HANDLER *handler);
343 int authenticate(void *type_arg, EAP_HANDLER *handler);
344 int detach(void **type_arg);
346 attach() and detach() functions allocate and deallocate all the
349 initiate() function begins the conversation when EAP-Identity response
350 is received. Incase of EAP-MD5, initiate() function sends the challenge.
352 authenticate() function uses specific EAP-Type authentication mechanism
353 to authenticate the user. During authentication many EAP-Requests and
354 EAP-Responses takes place for each authentication. Hence authenticate()
355 function may be called many times. EAP_HANDLER contains the complete
356 state information required.
360 as posted to the list, by John Lindsay <jlindsay@internode.com.au>
362 To make it clear for everyone, the supplicant is the software on the
363 client (machine with the wireless card).
365 The EAP process doesn't start until the client has associated with
366 the Access Point using Open authentication. If this process isn't
367 crystal clear you need to go away and gain understanding.
369 Once the association is made the AP blocks all traffic that is not
370 802.1x so although associated the connection only has value for EAP.
371 Any EAP traffic is passed to the radius server and any radius traffic
372 is passed back to the client.
374 So, after the client has associated to the Access Point, the
375 supplicant starts the process for using EAP over LAN by asking the
376 user for their logon and password.
378 Using 802.1x and EAP the supplicant sends the username and a one-way
379 hash of the password to the AP.
381 The AP encapsulates the request and sends it to the RADIUS server.
383 The radius server needs a plaintext password so that it can perform
384 the same one-way hash to determine that the password is correct. If
385 it is, the radius server issues an access challenge which goes back
386 via to the AP to the client. (my study guide says client but my
387 brain says 'supplicant')
389 The client sends the EAP response to the challenge via the AP to the
392 If the response is valid the RADIUS server sends a success message
393 and the session WEP key (EAP over wireless) to the client via the
394 AP. The same session WEP key is also sent to the AP in the success
397 The client and the AP then begin using session WEP keys. The WEP key
398 used for multicasts is then sent from the AP to the client. It is
399 encrypted using the session WEP key.
402 Primary author - Raghu <raghud@mail.com>
404 EAP-SIM - Michael Richardson <mcr@sandelman.ottawa.on.ca>
405 The development of the EAP/SIM support was funded by
406 Internet Foundation Austria (http://www.nic.at/ipa).