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diff --git a/doc/modules/rlm_eap b/doc/modules/rlm_eap new file mode 100644 index 0000000..4f903af --- /dev/null +++ b/doc/modules/rlm_eap @@ -0,0 +1,395 @@ + + + Extensible Authentication Protocol (EAP) + + +INTRODUCTION + + Extensible Authentication Protocol(EAP), rfc2284, is a general protocol + that allows network access points to support multiple authentication + methods. Each EAP-Type indicates a specific authentication mechanism. + 802.1x standard authenticates wireless LAN users trying to access + enterprise networks. + + RADIUS attribute used for EAP is EAP-Message, 79(rfc2869). RADIUS + communicates all EAP messages by embedding them in this attribute. + + General Terminology + Supplicant/EAP Client - is the software on the end-user/client machine + (machine with the wireless card). + Authenticator/NAS/Access Point(AP) - A network device providing users + with a point of entry into the network. + EAPOL - EAP over LAN as defined in 802.1x standard. + EAPOW - EAP over Wireless. + + + +----------+ +----------+ +----------+ + | | EAPOL | | RADIUS | | + | EAP |<------>| Access |<------>| RADIUS | + | Client | EAPOW | Point | (EAP) | Server | + | | | | | | + +----------+ +----------+ +----------+ + + + The sequence of events, for EAP-MD5, runs as follows: + 1. The end-user associates with the Access Point(AP). + 2. The supplicant specifies AP to use EAP by sending EAP-Start. + 3. AP requests the supplicant to Identify itself (EAP-Identity). + 4. Supplicant then sends its Identity (username) to the AP. + 5. AP forwards this EAP-response AS-IS to the RADIUS server. + (The supplicant and the RADIUS server mutually authenticate via AP. + AP just acts as a passthru till authentication is finished.) + 6. The server sends a challenge to the supplicant. + 7. The supplicant carries out a hash on the password and sends + this hashed password to the RADIUS server as its response. + 8. The RADIUS server performs a hash on the password for that supplicant + in its user database and compares the two hashed values and + authenticates the client if the two values match(EAP-Success/EAP-Failure) + 9. AP now opens a port to accept data from the end-user. + + Currently, EAP is widely used in wireless networks than in wired networks. + In 802.11/wireless based networking, following sequence of events happen in + addition to the above EAP events. + + 10. RADIUS server and the supplicant agree to a specific WEP key. + 11. The supplicant loads the key ready for logging on. + 12. The RADIUS server sends the key for this session (Session key) to the AP. + 13. The AP encrypts its Broadcast key with the Session key + 14. The AP sends the encypted key to the supplicant + 15. The supplicant decrypts the Broadcast key with the Session key and + the session continues using the Broadcast and Session keys until + the session ends. + + References: + The Implementation of EAP over RADIUS is based on the following RFCs + rfc2869 -- RADIUS Extensions + rfc2284 -- PPP Extensible Authentication Protocol (EAP) + rfc2716 -- PPP EAP TLS Authentication Protocol + + Following links help to understand HOW EAP works + www.ieee802.org/1/mirror/8021/docs2000/ieee_plenary.PDF + + +EAP CODE ORGANIZATION + + EAP is implemented as a module in freeradius + and the code is placed in src/modules/rlm_eap. + All EAP-Types are organized as subdirectories in rlm_eap/types/. + + Each EAP-Type, like types/rlm_eap_md5, contains a chunk of code that + knows how to deal with a particular kind of authentication mechanism. + + To add a new EAP-Type then a new directory should be created as + rlm_eap/types/rlm_eap_XXXX, where XXXX is EAP-Type name + ie for EAP-Type like ONE TIME PASSWORD (OTP) it would be rlm_eap_otp + + src/modules/rlm_eap -- contains the basic EAP and generalized interfaces + to all the EAP-Types. + rlm_eap/types -- contains all the supported EAP-Types + rlm_eap/types/rlm_eap_md5 -- EAP-MD5 authentication. + rlm_eap/types/rlm_eap_tls -- EAP-TLS based authentication. + rlm_eap/types/rlm_eap_ttls -- TTLS based authentication. + rlm_eap/types/rlm_eap_peap -- Windows PEAP based authentication. + rlm_eap/types/rlm_eap_sim -- EAP-SIM (GSM) based authentication + +CONFIGURATION + + Add the eap configuration stanza to the modules section in radiusd.conf + to load and control rlm_eap and all the supported EAP-Types: + + For example: + modules { + ... + eap { + default_eap_type = md5 + + md5 { + } + ... + } + ... + } + + NOTE: You cannot have empty eap stanza. At least one EAP-Type sub-stanza + should be defined as above, otherwise the server will not know what type + of eap authentication mechanism to be used and the server will exit + with error. + + All the various options and their associated default values for each + EAP-Type are documented in the sample radiusd.conf that is provided + with the distribution. + + Since the EAP requests may not contain a requested EAP type, the + 'default_eap_type' configuration options is used by the EAP module + to determine which EAP type to choose for authentication. + + NOTE: EAP cannot authorize a user. It can only authenticate. + Other Freeradius modules authorize the user. + + +EAP SIM server + + To configure EAP-SIM authentication, the following attributes must be + set in the server. This can be done in the users file, but in many cases + will be taken from a database server, via one of the SQL interface. + + If one has SIM cards that one controls (i.e. whose share secret you know), + one should be able to write a module to generate these attributes + (the triplets) in the server. + + If one has access to the SS7 based settlement network, then a module to + fetch appropriate triplets could be written. This module would act as + an authorization only module. + + The attributes are: + EAP-Sim-Rand1 16 bytes + EAP-Sim-SRES1 4 bytes + EAP-Sim-KC1 8 bytes + EAP-Sim-Rand2 16 bytes + EAP-Sim-SRES2 4 bytes + EAP-Sim-KC2 8 bytes + EAP-Sim-Rand3 16 bytes + EAP-Sim-SRES3 4 bytes + EAP-Sim-KC3 8 bytes + + EAP-SIM will send WEP attributes to the resquestor. + +EAP CLIENTS + + 1. eapol_test, from wpa_supplicant. + + 2. Freeradius has an "radeapclient" that can do EAP-MD5 (passwords), + as well as EAP-SIM. It is in modules/rlm_eap/radeapclient. + +TESTING + + You will find several test cases in src/tests/ for the EAP-SIM code. + + +HOW DO I USE IT (FAQ/Examples) + + 1. How can I enable EAP-MD5 authentication ? + + In radiusd.conf + + modules { + ... + eap { + default_eap_type = md5 + md5 { + } + ... + } + ... + } + + # eap sets the authenticate type as EAP + authorize { + ... + eap + } + + # eap authentication takes place. + authenticate { + eap + } + + # If you are proxying EAP-LEAP requests + # This is required to make LEAP work. + post-proxy { + eap + } + + 2. My Userbase is in LDAP and I want to use EAP-MD5 authentication + + In radiusd.conf + + modules { + ... + eap { + default_eap_type = md5 + md5 { + } + ... + } + ... + } + + # ldap gets the Configured password. + # eap sets the authenticate type as EAP + authorize { + ... + ldap + eap + ... + } + + # eap authentication takes place. + authenticate { + ... + eap + ... + } + + 3. How can I Proxy EAP messages, with/without User-Name attribute + in the Access-Request packets + + With User-Name attribute in Access-Request packet, + EAP-proxying is just same as RADIUS-proxying. + + If User-Name attribute is not present in Access-Request packet, + Freeradius can proxy the request with the following configuration + in radiusd.conf + + # eap module should be configured as the First module in + # the authorize stanza + + authorize { + eap + ... other modules. + } + + With this configuration, eap_authorize creates User-Name attribute + from EAP-Identity response, if it is not present. + Once User-Name attribute is created, RADIUS proxying takes care + of EAP proxying. + + 4. How Freeradius can handle EAP-START messages ? + + In most of the cases this is handled by the Authenticator. + + Only if it is required then, in radiusd.conf + + authorize { + eap + ... other modules. + } + + With the above configuration, RADIUS server immediately responds with + EAP-Identity request. + + NOTE: EAP does not check for any Identity or maintains any state in case + of EAP-START. It blindly responds with EAP-Identity request. + Proxying is handled only after EAP-Identity response is received. + + 5. I want to enable multiple EAP-Types, how can I configure ? + + In radiusd.conf + + modules { + ... + eap { + default_eap_type = tls + md5 { + } + tls { + ... + } + ... + } + ... + } + + The above configuration will let the server load all the EAP-Types, + but the server can have only one default EAP-Type, as above. + + Once EAP-Identity response is received by the server, based on the + default_eap_type, the server will send a new request (MD5-Challenge + request incase of md5, TLS-START request incase of tls) to the supplicant. + If the supplicant is rfc2284 compliant and does not support the + EAP-Type sent by the server then it sends EAP-Acknowledge with the + supported EAP-Type. If this EAP-Type is supported by the server then it + will send the respective EAP-request. + + Example: If the supplicant supports only EAP-MD5 but the server + default_eap_type is configured as EAP-TLS, as above, then the server + will send TLS-START after EAP-Identity is received. Supplicant will + respond with EAP-Acknowledge(EAP-MD5). Server now responds with + MD5-Challenge. + + +INSTALLATION + EAP, EAP-MD5, and Cisco LEAP do not require any additional packages. + Freeradius contains all the required packages. + + For EAP-TLS, EAP-TTLS, and PEAP, OPENSSL, <http://www.openssl.org/>, + is required to be installed. + Any version from 0.9.7, should fairly work with this module. + + EAP-SIM should not require any additional packages. + + +IMPLEMENTATION (For Developers) + + The rlm_eap module only deals with EAP specific authentication mechanism + and the generic interface to interact with all the EAP-Types. + + Currently, these are the existing interfaces, + int attach(CONF_SECTION *conf, void **type_arg); + int initiate(void *type_arg, EAP_HANDLER *handler); + int authenticate(void *type_arg, EAP_HANDLER *handler); + int detach(void **type_arg); + + attach() and detach() functions allocate and deallocate all the + required resources. + + initiate() function begins the conversation when EAP-Identity response + is received. Incase of EAP-MD5, initiate() function sends the challenge. + + authenticate() function uses specific EAP-Type authentication mechanism + to authenticate the user. During authentication many EAP-Requests and + EAP-Responses takes place for each authentication. Hence authenticate() + function may be called many times. EAP_HANDLER contains the complete + state information required. + + +HOW EAP WORKS + as posted to the list, by John Lindsay <jlindsay@internode.com.au> + + To make it clear for everyone, the supplicant is the software on the + client (machine with the wireless card). + + The EAP process doesn't start until the client has associated with + the Access Point using Open authentication. If this process isn't + crystal clear you need to go away and gain understanding. + + Once the association is made the AP blocks all traffic that is not + 802.1x so although associated the connection only has value for EAP. + Any EAP traffic is passed to the radius server and any radius traffic + is passed back to the client. + + So, after the client has associated to the Access Point, the + supplicant starts the process for using EAP over LAN by asking the + user for their logon and password. + + Using 802.1x and EAP the supplicant sends the username and a one-way + hash of the password to the AP. + + The AP encapsulates the request and sends it to the RADIUS server. + + The radius server needs a plaintext password so that it can perform + the same one-way hash to determine that the password is correct. If + it is, the radius server issues an access challenge which goes back + via to the AP to the client. (my study guide says client but my + brain says 'supplicant') + + The client sends the EAP response to the challenge via the AP to the + RADIUS server. + + If the response is valid the RADIUS server sends a success message + and the session WEP key (EAP over wireless) to the client via the + AP. The same session WEP key is also sent to the AP in the success + packet. + + The client and the AP then begin using session WEP keys. The WEP key + used for multicasts is then sent from the AP to the client. It is + encrypted using the session WEP key. + +ACKNOWLEDGEMENTS + Primary author - Raghu <raghud@mail.com> + + EAP-SIM - Michael Richardson <mcr@sandelman.ottawa.on.ca> + The development of the EAP/SIM support was funded by + Internet Foundation Austria (http://www.nic.at/ipa). + + |