iwd/src/eap-peap.c

/*
 *
 *  Wireless daemon for Linux
 *
 *  Copyright (C) 2018  Intel Corporation. All rights reserved.
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <ell/ell.h>

#include "src/missing.h"
#include "src/eap.h"
#include "src/eap-private.h"
#include "src/eap-tls-common.h"

/*
 * Protected EAP Protocol (PEAP): EAP type 25 as described in:
 *
 * PEAPv0: draft-kamath-pppext-peapv0-00
 * PEAPv1: draft-josefsson-pppext-eap-tls-eap-05
 */

static void eap_peap_phase2_send_response(const uint8_t *pdu, size_t pdu_len,
								void *user_data)
{
	struct eap_state *eap = user_data;

	if (eap_tls_common_get_negotiated_version(eap) == EAP_TLS_VERSION_0) {
		if (pdu_len < 5)
			return;

		if (pdu[4] != EAP_TYPE_EXTENSIONS) {
			pdu += 4;
			pdu_len -= 4;
		}
	}

	eap_tls_common_tunnel_send(eap, pdu, pdu_len);
}

static void eap_peap_phase2_complete(enum eap_result result, void *user_data)
{
	struct eap_state *eap = user_data;

	l_debug("result: %d", result);

	/*
	 * PEAPv1: draft-josefsson-pppext-eap-tls-eap-05, Section 2.2
	 *
	 * The receipt of a EAP-Failure or EAP-Success within the TLS protected
	 * channel results in a shutdown of the TLS channel by the peer.
	 */
	if (result == EAP_RESULT_SUCCESS)
		/*
		 * Some of the EAP-PEAP server implementations seem to require a
		 * cleartext ACK for the tunneled EAP-Success messages instead
		 * of simply closing the tunnel.
		 */
		eap_tls_common_send_empty_response(eap);
	else
		eap_tls_common_tunnel_close(eap);

	eap_discard_success_and_failure(eap, false);
	eap_tls_common_set_completed(eap);

	if (result != EAP_RESULT_SUCCESS) {
		eap_tls_common_set_phase2_failed(eap);

		return;
	}

	eap_method_success(eap);
}

/*
 * PEAPv0: draft-kamath-pppext-peapv0-00, Section 2
 */
#define EAP_EXTENSIONS_HEADER_LEN 5
#define EAP_EXTENSIONS_AVP_HEADER_LEN 4

enum eap_extensions_avp_type {
	/* Reserved = 0x0000, */
	/* Reserved = 0x0001, */
	/* Reserved = 0x0002, */
	EAP_EXTENSIONS_AVP_TYPE_RESULT = 0x8003,
};

enum eap_extensions_result {
	EAP_EXTENSIONS_RESULT_SUCCCESS = 1,
	EAP_EXTENSIONS_RESULT_FAILURE  = 2,
};

static int eap_extensions_handle_result_avp(struct eap_state *eap,
						const uint8_t *data,
						size_t data_len,
						uint8_t *response)
{
	uint16_t type;
	uint16_t len;
	uint16_t result;

	if (data_len < EAP_EXTENSIONS_AVP_HEADER_LEN + 2)
		return -ENOENT;

	type = l_get_be16(data);

	if (type != EAP_EXTENSIONS_AVP_TYPE_RESULT)
		return -ENOENT;

	data += 2;

	len = l_get_be16(data);

	if (len != 2)
		return -ENOENT;

	data += 2;

	result = l_get_be16(data);

	l_debug("result: %d", result);

	switch (result) {
	case EAP_EXTENSIONS_RESULT_SUCCCESS:
		result = eap_method_is_success(
				eap_tls_common_get_variant_data(eap)) ?
					EAP_EXTENSIONS_RESULT_SUCCCESS :
					EAP_EXTENSIONS_RESULT_FAILURE;
		/* fall through */
	case EAP_EXTENSIONS_RESULT_FAILURE:
		break;
	default:
		return -ENOENT;
	}

	l_put_be16(EAP_EXTENSIONS_AVP_TYPE_RESULT,
					&response[EAP_EXTENSIONS_HEADER_LEN]);
	l_put_be16(2, &response[EAP_EXTENSIONS_HEADER_LEN + 2]);
	l_put_be16(result, &response[EAP_EXTENSIONS_HEADER_LEN +
						EAP_EXTENSIONS_AVP_HEADER_LEN]);

	return result;
}

static void eap_extensions_handle_request(struct eap_state *eap,
							uint8_t id,
							const uint8_t *pkt,
							size_t len)
{
	uint8_t response[EAP_EXTENSIONS_HEADER_LEN +
					EAP_EXTENSIONS_AVP_HEADER_LEN + 2];
	int r = eap_extensions_handle_result_avp(eap, pkt, len, response);

	if (r < 0)
		return;

	response[0] = EAP_CODE_RESPONSE;
	response[1] = id;
	l_put_be16(sizeof(response), &response[2]);
	response[4] = EAP_TYPE_EXTENSIONS;

	eap_peap_phase2_send_response(response, sizeof(response), eap);

	eap_tls_common_tunnel_close(eap);

	eap_discard_success_and_failure(eap, false);
	eap_tls_common_set_completed(eap);

	if (r != EAP_EXTENSIONS_RESULT_SUCCCESS) {
		eap_tls_common_set_phase2_failed(eap);

		return;
	}

	eap_method_success(eap);
}

static bool eap_peap_tunnel_ready(struct eap_state *eap,
						const char *peer_identity)
{
	uint8_t msk_emsk[128];

	/*
	* PEAPv1: draft-josefsson-pppext-eap-tls-eap-05, Section 2.1.1
	*
	* Cleartext Success/Failure packets MUST be silently discarded once TLS
	* tunnel has been brought up.
	*/
	eap_discard_success_and_failure(eap, true);

	/* MSK, EMSK and challenge derivation */
	eap_tls_common_tunnel_prf_get_bytes(eap, true, "client EAP encryption",
								msk_emsk, 128);

	eap_set_key_material(eap, msk_emsk + 0, 64, NULL, 0, NULL, 0, NULL, 0);
	explicit_bzero(msk_emsk, sizeof(msk_emsk));

	eap_tls_common_send_empty_response(eap);

	return true;
}

static bool eap_peap_tunnel_handle_request(struct eap_state *eap,
							const uint8_t *pkt,
								size_t len)
{
	uint8_t id;

	if (len > 4 && pkt[4] == EAP_TYPE_EXTENSIONS) {
		uint16_t pkt_len;
		uint8_t code = pkt[0];

		if (code != EAP_CODE_REQUEST)
			return false;

		pkt_len = l_get_be16(pkt + 2);
		if (pkt_len != len)
			return false;

		id = pkt[1];

		eap_extensions_handle_request(eap, id,
					pkt + EAP_EXTENSIONS_HEADER_LEN,
					len - EAP_EXTENSIONS_HEADER_LEN);

		return true;
	}

	if (eap_tls_common_get_negotiated_version(eap) == EAP_TLS_VERSION_0) {
		if (len < 1)
			return false;

		/*
		 * The PEAPv0 phase2 packets are headerless. Our implementation
		 * of the EAP methods requires packet identifier. Therefore,
		 * PEAP packet identifier is used for the headerless
		 * phase2 packets.
		 */
		eap_save_last_id(eap, &id);

		__eap_handle_request(eap_tls_common_get_variant_data(eap), id,
								pkt, len);

		return true;
	}

	eap_rx_packet(eap_tls_common_get_variant_data(eap), pkt, len);

	return true;
}

static void eap_peap_state_reset(void *phase2)
{
	if (!phase2)
		return;

	eap_reset(phase2);
}

static void eap_peap_state_destroy(void *phase2)
{
	if (!phase2)
		return;

	eap_reset(phase2);
	eap_free(phase2);
}

static int eap_peap_settings_check(struct l_settings *settings,
						struct l_queue *secrets,
						const char *prefix,
						struct l_queue **out_missing)
{
	char setting_key_prefix[72];
	int r;

	snprintf(setting_key_prefix, sizeof(setting_key_prefix),
						"%sPEAP-Phase2-", prefix);

	r = __eap_check_settings(settings, secrets, setting_key_prefix, false,
								out_missing);
	if (r)
		return r;

	snprintf(setting_key_prefix, sizeof(setting_key_prefix), "%sPEAP-",
									prefix);
	return eap_tls_common_settings_check(settings, secrets,
							setting_key_prefix,
							out_missing);
}

static const struct eap_tls_variant_ops eap_ttls_ops = {
	.version_max_supported = EAP_TLS_VERSION_1,
	.tunnel_ready = eap_peap_tunnel_ready,
	.tunnel_handle_request = eap_peap_tunnel_handle_request,
	.reset = eap_peap_state_reset,
	.destroy = eap_peap_state_destroy,
};

static bool eap_peap_settings_load(struct eap_state *eap,
						struct l_settings *settings,
						const char *prefix)
{
	char setting_key_prefix[72];
	void *phase2;

	phase2 = eap_new(eap_peap_phase2_send_response,
						eap_peap_phase2_complete, eap);

	if (!phase2) {
		l_error("Could not create the PEAP phase two EAP instance");

		return false;
	}

	snprintf(setting_key_prefix, sizeof(setting_key_prefix),
						"%sPEAP-Phase2-", prefix);

	if (!eap_load_settings(phase2, settings, setting_key_prefix)) {
		eap_free(phase2);

		return false;
	}

	snprintf(setting_key_prefix, sizeof(setting_key_prefix), "%sPEAP-",
									prefix);

	if (!eap_tls_common_settings_load(eap, settings, setting_key_prefix,
							&eap_ttls_ops, phase2))
		return false;

	return true;
}

static struct eap_method eap_peap = {
	.request_type = EAP_TYPE_PEAP,
	.name = "PEAP",
	.exports_msk = true,

	.handle_request = eap_tls_common_handle_request,
	.handle_retransmit = eap_tls_common_handle_retransmit,
	.free = eap_tls_common_state_free,
	.reset_state = eap_tls_common_state_reset,

	.check_settings = eap_peap_settings_check,
	.load_settings = eap_peap_settings_load,
};

static int eap_peap_init(void)
{
	l_debug("");
	return eap_register_method(&eap_peap);
}

static void eap_peap_exit(void)
{
	l_debug("");
	eap_unregister_method(&eap_peap);
}

EAP_METHOD_BUILTIN(eap_peap, eap_peap_init, eap_peap_exit)