eap.c

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/*
 * EAP peer state machines (RFC 4137)
 * Copyright (c) 2004-2006, Jouni Malinen <[e-mail]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Alternatively, this software may be distributed under the terms of BSD
 * license.
 *
 * See README and COPYING for more details.
 *
 * This file implements the Peer State Machine as defined in RFC 4137. The used
 * states and state transitions match mostly with the RFC. However, there are
 * couple of additional transitions for working around small issues noticed
 * during testing. These exceptions are explained in comments within the
 * functions in this file. The method functions, m.func(), are similar to the
 * ones used in RFC 4137, but some small changes have used here to optimize
 * operations and to add functionality needed for fast re-authentication
 * (session resumption).
 */

#include "includes.h"

#include "common.h"
#include "eap_i.h"
#include "config_ssid.h"
#include "tls.h"
#include "crypto.h"
#include "pcsc_funcs.h"
#include "wpa_ctrl.h"
#include "state_machine.h"

#define STATE_MACHINE_DATA struct eap_sm
#define STATE_MACHINE_DEBUG_PREFIX "EAP"

#define EAP_MAX_AUTH_ROUNDS 50


static Boolean eap_sm_allowMethod(struct eap_sm *sm, int vendor,
				  EapType method);
static u8 * eap_sm_buildNak(struct eap_sm *sm, int id, size_t *len);
static void eap_sm_processIdentity(struct eap_sm *sm, const u8 *req);
static void eap_sm_processNotify(struct eap_sm *sm, const u8 *req);
static u8 * eap_sm_buildNotify(int id, size_t *len);
static void eap_sm_parseEapReq(struct eap_sm *sm, const u8 *req, size_t len);
#if defined(CONFIG_CTRL_IFACE) || !defined(CONFIG_NO_STDOUT_DEBUG)
static const char * eap_sm_method_state_txt(EapMethodState state);
static const char * eap_sm_decision_txt(EapDecision decision);
#endif /* CONFIG_CTRL_IFACE || !CONFIG_NO_STDOUT_DEBUG */



static Boolean eapol_get_bool(struct eap_sm *sm, enum eapol_bool_var var)
{
	return sm->eapol_cb->get_bool(sm->eapol_ctx, var);
}


static void eapol_set_bool(struct eap_sm *sm, enum eapol_bool_var var,
			   Boolean value)
{
	sm->eapol_cb->set_bool(sm->eapol_ctx, var, value);
}


static unsigned int eapol_get_int(struct eap_sm *sm, enum eapol_int_var var)
{
	return sm->eapol_cb->get_int(sm->eapol_ctx, var);
}


static void eapol_set_int(struct eap_sm *sm, enum eapol_int_var var,
			  unsigned int value)
{
	sm->eapol_cb->set_int(sm->eapol_ctx, var, value);
}


static u8 * eapol_get_eapReqData(struct eap_sm *sm, size_t *len)
{
	return sm->eapol_cb->get_eapReqData(sm->eapol_ctx, len);
}


static void eap_deinit_prev_method(struct eap_sm *sm, const char *txt)
{
	if (sm->m == NULL || sm->eap_method_priv == NULL)
		return;

	wpa_printf(MSG_DEBUG, "EAP: deinitialize previously used EAP method "
		   "(%d, %s) at %s", sm->selectedMethod, sm->m->name, txt);
	sm->m->deinit(sm, sm->eap_method_priv);
	sm->eap_method_priv = NULL;
	sm->m = NULL;
}


/*
 * This state initializes state machine variables when the machine is
 * activated (portEnabled = TRUE). This is also used when re-starting
 * authentication (eapRestart == TRUE).
 */
SM_STATE(EAP, INITIALIZE)
{
	SM_ENTRY(EAP, INITIALIZE);
	if (sm->fast_reauth && sm->m && sm->m->has_reauth_data &&
	    sm->m->has_reauth_data(sm, sm->eap_method_priv)) {
		wpa_printf(MSG_DEBUG, "EAP: maintaining EAP method data for "
			   "fast reauthentication");
		sm->m->deinit_for_reauth(sm, sm->eap_method_priv);
	} else {
		eap_deinit_prev_method(sm, "INITIALIZE");
	}
	sm->selectedMethod = EAP_TYPE_NONE;
	sm->methodState = METHOD_NONE;
	sm->allowNotifications = TRUE;
	sm->decision = DECISION_FAIL;
	eapol_set_int(sm, EAPOL_idleWhile, sm->ClientTimeout);
	eapol_set_bool(sm, EAPOL_eapSuccess, FALSE);
	eapol_set_bool(sm, EAPOL_eapFail, FALSE);
	os_free(sm->eapKeyData);
	sm->eapKeyData = NULL;
	sm->eapKeyAvailable = FALSE;
	eapol_set_bool(sm, EAPOL_eapRestart, FALSE);
	sm->lastId = -1; /* new session - make sure this does not match with
			  * the first EAP-Packet */
	/*
	 * RFC 4137 does not reset eapResp and eapNoResp here. However, this
	 * seemed to be able to trigger cases where both were set and if EAPOL
	 * state machine uses eapNoResp first, it may end up not sending a real
	 * reply correctly. This occurred when the workaround in FAIL state set
	 * eapNoResp = TRUE.. Maybe that workaround needs to be fixed to do
	 * something else(?)
	 */
	eapol_set_bool(sm, EAPOL_eapResp, FALSE);
	eapol_set_bool(sm, EAPOL_eapNoResp, FALSE);
	sm->num_rounds = 0;
}


/*
 * This state is reached whenever service from the lower layer is interrupted
 * or unavailable (portEnabled == FALSE). Immediate transition to INITIALIZE
 * occurs when the port becomes enabled.
 */
SM_STATE(EAP, DISABLED)
{
	SM_ENTRY(EAP, DISABLED);
	sm->num_rounds = 0;
}


/*
 * The state machine spends most of its time here, waiting for something to
 * happen. This state is entered unconditionally from INITIALIZE, DISCARD, and
 * SEND_RESPONSE states.
 */
SM_STATE(EAP, IDLE)
{
	SM_ENTRY(EAP, IDLE);
}


/*
 * This state is entered when an EAP packet is received (eapReq == TRUE) to
 * parse the packet header.
 */
SM_STATE(EAP, RECEIVED)
{
	const u8 *eapReqData;
	size_t eapReqDataLen;

	SM_ENTRY(EAP, RECEIVED);
	eapReqData = eapol_get_eapReqData(sm, &eapReqDataLen);
	/* parse rxReq, rxSuccess, rxFailure, reqId, reqMethod */
	eap_sm_parseEapReq(sm, eapReqData, eapReqDataLen);
	sm->num_rounds++;
}


/*
 * This state is entered when a request for a new type comes in. Either the
 * correct method is started, or a Nak response is built.
 */
SM_STATE(EAP, GET_METHOD)
{
	int reinit;
	EapType method;

	SM_ENTRY(EAP, GET_METHOD);

	if (sm->reqMethod == EAP_TYPE_EXPANDED)
		method = sm->reqVendorMethod;
	else
		method = sm->reqMethod;

	if (!eap_sm_allowMethod(sm, sm->reqVendor, method)) {
		wpa_printf(MSG_DEBUG, "EAP: vendor %u method %u not allowed",
			   sm->reqVendor, method);
		goto nak;
	}

	/*
	 * RFC 4137 does not define specific operation for fast
	 * re-authentication (session resumption). The design here is to allow
	 * the previously used method data to be maintained for
	 * re-authentication if the method support session resumption.
	 * Otherwise, the previously used method data is freed and a new method
	 * is allocated here.
	 */
	if (sm->fast_reauth &&
	    sm->m && sm->m->vendor == sm->reqVendor &&
	    sm->m->method == method &&
	    sm->m->has_reauth_data &&
	    sm->m->has_reauth_data(sm, sm->eap_method_priv)) {
		wpa_printf(MSG_DEBUG, "EAP: Using previous method data"
			   " for fast re-authentication");
		reinit = 1;
	} else {
		eap_deinit_prev_method(sm, "GET_METHOD");
		reinit = 0;
	}

	sm->selectedMethod = sm->reqMethod;
	if (sm->m == NULL)
		sm->m = eap_sm_get_eap_methods(sm->reqVendor, method);
	if (!sm->m) {
		wpa_printf(MSG_DEBUG, "EAP: Could not find selected method: "
			   "vendor %d method %d",
			   sm->reqVendor, method);
		goto nak;
	}

	wpa_printf(MSG_DEBUG, "EAP: Initialize selected EAP method: "
		   "vendor %u method %u (%s)",
		   sm->reqVendor, method, sm->m->name);
	if (reinit)
		sm->eap_method_priv = sm->m->init_for_reauth(
			sm, sm->eap_method_priv);
	else
		sm->eap_method_priv = sm->m->init(sm);

	if (sm->eap_method_priv == NULL) {
		struct wpa_ssid *config = eap_get_config(sm);
		wpa_msg(sm->msg_ctx, MSG_INFO,
			"EAP: Failed to initialize EAP method: vendor %u "
			"method %u (%s)",
			sm->reqVendor, method, sm->m->name);
		sm->m = NULL;
		sm->methodState = METHOD_NONE;
		sm->selectedMethod = EAP_TYPE_NONE;
		if (sm->reqMethod == EAP_TYPE_TLS && config &&
		    (config->pending_req_pin ||
		     config->pending_req_passphrase)) {
			/*
			 * Return without generating Nak in order to allow
			 * entering of PIN code or passphrase to retry the
			 * current EAP packet.
			 */
			wpa_printf(MSG_DEBUG, "EAP: Pending PIN/passphrase "
				   "request - skip Nak");
			return;
		}

		goto nak;
	}

	sm->methodState = METHOD_INIT;
	wpa_msg(sm->msg_ctx, MSG_INFO, WPA_EVENT_EAP_METHOD
		"EAP vendor %u method %u (%s) selected",
		sm->reqVendor, method, sm->m->name);
	return;

nak:
	os_free(sm->eapRespData);
	sm->eapRespData = NULL;
	sm->eapRespData = eap_sm_buildNak(sm, sm->reqId, &sm->eapRespDataLen);
}


/*
 * The method processing happens here. The request from the authenticator is
 * processed, and an appropriate response packet is built.
 */
SM_STATE(EAP, METHOD)
{
	u8 *eapReqData;
	size_t eapReqDataLen;
	struct eap_method_ret ret;

	SM_ENTRY(EAP, METHOD);
	if (sm->m == NULL) {
		wpa_printf(MSG_WARNING, "EAP::METHOD - method not selected");
		return;
	}

	eapReqData = eapol_get_eapReqData(sm, &eapReqDataLen);

	/*
	 * Get ignore, methodState, decision, allowNotifications, and
	 * eapRespData. RFC 4137 uses three separate method procedure (check,
	 * process, and buildResp) in this state. These have been combined into
	 * a single function call to m->process() in order to optimize EAP
	 * method implementation interface a bit. These procedures are only
	 * used from within this METHOD state, so there is no need to keep
	 * these as separate C functions.
	 *
	 * The RFC 4137 procedures return values as follows:
	 * ignore = m.check(eapReqData)
	 * (methodState, decision, allowNotifications) = m.process(eapReqData)
	 * eapRespData = m.buildResp(reqId)
	 */
	os_memset(&ret, 0, sizeof(ret));
	ret.ignore = sm->ignore;
	ret.methodState = sm->methodState;
	ret.decision = sm->decision;
	ret.allowNotifications = sm->allowNotifications;
	os_free(sm->eapRespData);
	sm->eapRespData = NULL;
	sm->eapRespData = sm->m->process(sm, sm->eap_method_priv, &ret,
					 eapReqData, eapReqDataLen,
					 &sm->eapRespDataLen);
	wpa_printf(MSG_DEBUG, "EAP: method process -> ignore=%s "
		   "methodState=%s decision=%s",
		   ret.ignore ? "TRUE" : "FALSE",
		   eap_sm_method_state_txt(ret.methodState),
		   eap_sm_decision_txt(ret.decision));

	sm->ignore = ret.ignore;
	if (sm->ignore)
		return;
	sm->methodState = ret.methodState;
	sm->decision = ret.decision;
	sm->allowNotifications = ret.allowNotifications;

	if (sm->m->isKeyAvailable && sm->m->getKey &&
	    sm->m->isKeyAvailable(sm, sm->eap_method_priv)) {
		os_free(sm->eapKeyData);
		sm->eapKeyData = sm->m->getKey(sm, sm->eap_method_priv,
					       &sm->eapKeyDataLen);
	}
}


/*
 * This state signals the lower layer that a response packet is ready to be
 * sent.
 */
SM_STATE(EAP, SEND_RESPONSE)
{
	SM_ENTRY(EAP, SEND_RESPONSE);
	os_free(sm->lastRespData);
	if (sm->eapRespData) {
		if (sm->workaround)
			os_memcpy(sm->last_md5, sm->req_md5, 16);
		sm->lastId = sm->reqId;
		sm->lastRespData = os_malloc(sm->eapRespDataLen);
		if (sm->lastRespData) {
			os_memcpy(sm->lastRespData, sm->eapRespData,
				  sm->eapRespDataLen);
			sm->lastRespDataLen = sm->eapRespDataLen;
		}
		eapol_set_bool(sm, EAPOL_eapResp, TRUE);
	} else
		sm->lastRespData = NULL;
	eapol_set_bool(sm, EAPOL_eapReq, FALSE);
	eapol_set_int(sm, EAPOL_idleWhile, sm->ClientTimeout);
}


/*
 * This state signals the lower layer that the request was discarded, and no
 * response packet will be sent at this time.
 */
SM_STATE(EAP, DISCARD)
{
	SM_ENTRY(EAP, DISCARD);
	eapol_set_bool(sm, EAPOL_eapReq, FALSE);
	eapol_set_bool(sm, EAPOL_eapNoResp, TRUE);
}


/*
 * Handles requests for Identity method and builds a response.
 */
SM_STATE(EAP, IDENTITY)
{
	const u8 *eapReqData;
	size_t eapReqDataLen;

	SM_ENTRY(EAP, IDENTITY);
	eapReqData = eapol_get_eapReqData(sm, &eapReqDataLen);
	eap_sm_processIdentity(sm, eapReqData);
	os_free(sm->eapRespData);
	sm->eapRespData = NULL;
	sm->eapRespData = eap_sm_buildIdentity(sm, sm->reqId,
					       &sm->eapRespDataLen, 0);
}


/*
 * Handles requests for Notification method and builds a response.
 */
SM_STATE(EAP, NOTIFICATION)
{
	const u8 *eapReqData;
	size_t eapReqDataLen;

	SM_ENTRY(EAP, NOTIFICATION);
	eapReqData = eapol_get_eapReqData(sm, &eapReqDataLen);
	eap_sm_processNotify(sm, eapReqData);
	os_free(sm->eapRespData);
	sm->eapRespData = NULL;
	sm->eapRespData = eap_sm_buildNotify(sm->reqId, &sm->eapRespDataLen);
}


/*
 * This state retransmits the previous response packet.
 */
SM_STATE(EAP, RETRANSMIT)
{
	SM_ENTRY(EAP, RETRANSMIT);
	os_free(sm->eapRespData);
	if (sm->lastRespData) {
		sm->eapRespData = os_malloc(sm->lastRespDataLen);
		if (sm->eapRespData) {
			os_memcpy(sm->eapRespData, sm->lastRespData,
				  sm->lastRespDataLen);
			sm->eapRespDataLen = sm->lastRespDataLen;
		}
	} else
		sm->eapRespData = NULL;
}


/*
 * This state is entered in case of a successful completion of authentication
 * and state machine waits here until port is disabled or EAP authentication is
 * restarted.
 */
SM_STATE(EAP, SUCCESS)
{
	SM_ENTRY(EAP, SUCCESS);
	if (sm->eapKeyData != NULL)
		sm->eapKeyAvailable = TRUE;
	eapol_set_bool(sm, EAPOL_eapSuccess, TRUE);

	/*
	 * RFC 4137 does not clear eapReq here, but this seems to be required
	 * to avoid processing the same request twice when state machine is
	 * initialized.
	 */
	eapol_set_bool(sm, EAPOL_eapReq, FALSE);

	/*
	 * RFC 4137 does not set eapNoResp here, but this seems to be required
	 * to get EAPOL Supplicant backend state machine into SUCCESS state. In
	 * addition, either eapResp or eapNoResp is required to be set after
	 * processing the received EAP frame.
	 */
	eapol_set_bool(sm, EAPOL_eapNoResp, TRUE);

	wpa_msg(sm->msg_ctx, MSG_INFO, WPA_EVENT_EAP_SUCCESS
		"EAP authentication completed successfully");
}


/*
 * This state is entered in case of a failure and state machine waits here
 * until port is disabled or EAP authentication is restarted.
 */
SM_STATE(EAP, FAILURE)
{
	SM_ENTRY(EAP, FAILURE);
	eapol_set_bool(sm, EAPOL_eapFail, TRUE);

	/*
	 * RFC 4137 does not clear eapReq here, but this seems to be required
	 * to avoid processing the same request twice when state machine is
	 * initialized.
	 */
	eapol_set_bool(sm, EAPOL_eapReq, FALSE);

	/*
	 * RFC 4137 does not set eapNoResp here. However, either eapResp or
	 * eapNoResp is required to be set after processing the received EAP
	 * frame.
	 */
	eapol_set_bool(sm, EAPOL_eapNoResp, TRUE);

	wpa_msg(sm->msg_ctx, MSG_INFO, WPA_EVENT_EAP_FAILURE
		"EAP authentication failed");
}


static int eap_success_workaround(struct eap_sm *sm, int reqId, int lastId)
{
	/*
	 * At least Microsoft IAS and Meetinghouse Aegis seem to be sending
	 * EAP-Success/Failure with lastId + 1 even though RFC 3748 and
	 * RFC 4137 require that reqId == lastId. In addition, it looks like
	 * Ringmaster v2.1.2.0 would be using lastId + 2 in EAP-Success.
	 *
	 * Accept this kind of Id if EAP workarounds are enabled. These are
	 * unauthenticated plaintext messages, so this should have minimal
	 * security implications (bit easier to fake EAP-Success/Failure).
	 */
	if (sm->workaround && (reqId == ((lastId + 1) & 0xff) ||
			       reqId == ((lastId + 2) & 0xff))) {
		wpa_printf(MSG_DEBUG, "EAP: Workaround for unexpected "
			   "identifier field in EAP Success: "
			   "reqId=%d lastId=%d (these are supposed to be "
			   "same)", reqId, lastId);
		return 1;
	}
	wpa_printf(MSG_DEBUG, "EAP: EAP-Success Id mismatch - reqId=%d "
		   "lastId=%d", reqId, lastId);
	return 0;
}


/*
 * RFC 4137 - Appendix A.1: EAP Peer State Machine - State transitions
 */
SM_STEP(EAP)
{
	int duplicate;