[thirdparty/hostap.git] / doc / eap_server.doxygen

/**
\page eap_server_module EAP server implementation

Extensible Authentication Protocol (EAP) is an authentication framework
defined in RFC 3748. hostapd uses a separate code module for EAP server
implementation. This module was designed to use only a minimal set of
direct function calls (mainly, to debug/event functions) in order for
it to be usable in other programs. The design of the EAP
implementation is based loosely on RFC 4137. The state machine is
defined in this RFC and so is the interface between the server state
machine and methods. As such, this RFC provides useful information for
understanding the EAP server implementation in hostapd.

Some of the terminology used in EAP state machine is referring to
EAPOL (IEEE 802.1X), but there is no strict requirement on the lower
layer being IEEE 802.1X if EAP module is built for other programs than
%wpa_supplicant. These terms should be understood to refer to the
lower layer as defined in RFC 4137.


\section adding_eap_methods Adding EAP methods

Each EAP method is implemented as a separate module, usually as one C
file named eap_<name of the method>.c, e.g., eap_md5.c. All EAP
methods use the same interface between the server state machine and
method specific functions. This allows new EAP methods to be added
without modifying the core EAP state machine implementation.

New EAP methods need to be registered by adding them into the build
(Makefile) and the EAP method registration list in the
eap_server_register_methods() function of eap_methods.c. Each EAP
method should use a build-time configuration option, e.g., EAP_TLS, in
order to make it possible to select which of the methods are included
in the build.

EAP methods must implement the interface defined in eap_i.h. struct
eap_method defines the needed function pointers that each EAP method
must provide. In addition, the EAP type and name are registered using
this structure. This interface is based on section 4.4 of RFC 4137.

It is recommended that the EAP methods would use generic helper
functions, eap_msg_alloc() and eap_hdr_validate() when processing
messages. This allows code sharing and can avoid missing some of the
needed validation steps for received packets. In addition, these
functions make it easier to change between expanded and legacy EAP
header, if needed.

When adding an EAP method that uses a vendor specific EAP type
(Expanded Type as defined in RFC 3748, Chapter 5.7), the new method
must be registered by passing vendor id instead of EAP_VENDOR_IETF to
eap_server_method_alloc(). These methods must not try to emulate
expanded types by registering a legacy EAP method for type 254. See
eap_vendor_test.c for an example of an EAP method implementation that
is implemented as an expanded type.

*/
Commit	Line	Data
30c28971 JM	1	/**
	2	\page eap_server_module EAP server implementation
	3
	4	Extensible Authentication Protocol (EAP) is an authentication framework
	5	defined in RFC 3748. hostapd uses a separate code module for EAP server
	6	implementation. This module was designed to use only a minimal set of
	7	direct function calls (mainly, to debug/event functions) in order for
	8	it to be usable in other programs. The design of the EAP
	9	implementation is based loosely on RFC 4137. The state machine is
	10	defined in this RFC and so is the interface between the server state
	11	machine and methods. As such, this RFC provides useful information for
	12	understanding the EAP server implementation in hostapd.
	13
	14	Some of the terminology used in EAP state machine is referring to
	15	EAPOL (IEEE 802.1X), but there is no strict requirement on the lower
	16	layer being IEEE 802.1X if EAP module is built for other programs than
	17	%wpa_supplicant. These terms should be understood to refer to the
	18	lower layer as defined in RFC 4137.
	19
	20
	21	\section adding_eap_methods Adding EAP methods
	22
	23	Each EAP method is implemented as a separate module, usually as one C
	24	file named eap_<name of the method>.c, e.g., eap_md5.c. All EAP
	25	methods use the same interface between the server state machine and
	26	method specific functions. This allows new EAP methods to be added
	27	without modifying the core EAP state machine implementation.
	28
	29	New EAP methods need to be registered by adding them into the build
	30	(Makefile) and the EAP method registration list in the
	31	eap_server_register_methods() function of eap_methods.c. Each EAP
	32	method should use a build-time configuration option, e.g., EAP_TLS, in
	33	order to make it possible to select which of the methods are included
	34	in the build.
	35
	36	EAP methods must implement the interface defined in eap_i.h. struct
	37	eap_method defines the needed function pointers that each EAP method
	38	must provide. In addition, the EAP type and name are registered using
	39	this structure. This interface is based on section 4.4 of RFC 4137.
	40
	41	It is recommended that the EAP methods would use generic helper
	42	functions, eap_msg_alloc() and eap_hdr_validate() when processing
	43	messages. This allows code sharing and can avoid missing some of the
	44	needed validation steps for received packets. In addition, these
	45	functions make it easier to change between expanded and legacy EAP
	46	header, if needed.
	47
	48	When adding an EAP method that uses a vendor specific EAP type
	49	(Expanded Type as defined in RFC 3748, Chapter 5.7), the new method
	50	must be registered by passing vendor id instead of EAP_VENDOR_IETF to
	51	eap_server_method_alloc(). These methods must not try to emulate
	52	expanded types by registering a legacy EAP method for type 254. See
	53	eap_vendor_test.c for an example of an EAP method implementation that
	54	is implemented as an expanded type.
	55
	56	*/