eap_aka.c

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/*
 * hostapd / EAP-AKA (RFC 4187) and EAP-AKA' (draft-arkko-eap-aka-kdf)
 * Copyright (c) 2005-2008, 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.
 */

#include "includes.h"

#include "common.h"
#include "eap_server/eap_i.h"
#include "eap_common/eap_sim_common.h"
#include "eap_server/eap_sim_db.h"
#include "sha1.h"
#include "sha256.h"
#include "crypto.h"


struct eap_aka_data {
	u8 mk[EAP_SIM_MK_LEN];
	u8 nonce_s[EAP_SIM_NONCE_S_LEN];
	u8 k_aut[EAP_AKA_PRIME_K_AUT_LEN];
	u8 k_encr[EAP_SIM_K_ENCR_LEN];
	u8 k_re[EAP_AKA_PRIME_K_RE_LEN]; /* EAP-AKA' only */
	u8 msk[EAP_SIM_KEYING_DATA_LEN];
	u8 emsk[EAP_EMSK_LEN];
	u8 rand[EAP_AKA_RAND_LEN];
	u8 autn[EAP_AKA_AUTN_LEN];
	u8 ck[EAP_AKA_CK_LEN];
	u8 ik[EAP_AKA_IK_LEN];
	u8 res[EAP_AKA_RES_MAX_LEN];
	size_t res_len;
	enum {
		IDENTITY, CHALLENGE, REAUTH, NOTIFICATION, SUCCESS, FAILURE
	} state;
	char *next_pseudonym;
	char *next_reauth_id;
	u16 counter;
	struct eap_sim_reauth *reauth;
	int auts_reported; /* whether the current AUTS has been reported to the
			    * eap_sim_db */
	u16 notification;
	int use_result_ind;

	struct wpabuf *id_msgs;
	int pending_id;
	u8 eap_method;
	u8 *network_name;
	size_t network_name_len;
	u16 kdf;
};


static void eap_aka_determine_identity(struct eap_sm *sm,
				       struct eap_aka_data *data,
				       int before_identity, int after_reauth);


static const char * eap_aka_state_txt(int state)
{
	switch (state) {
	case IDENTITY:
		return "IDENTITY";
	case CHALLENGE:
		return "CHALLENGE";
	case REAUTH:
		return "REAUTH";
	case SUCCESS:
		return "SUCCESS";
	case FAILURE:
		return "FAILURE";
	case NOTIFICATION:
		return "NOTIFICATION";
	default:
		return "Unknown?!";
	}
}


static void eap_aka_state(struct eap_aka_data *data, int state)
{
	wpa_printf(MSG_DEBUG, "EAP-AKA: %s -> %s",
		   eap_aka_state_txt(data->state),
		   eap_aka_state_txt(state));
	data->state = state;
}


static void * eap_aka_init(struct eap_sm *sm)
{
	struct eap_aka_data *data;

	if (sm->eap_sim_db_priv == NULL) {
		wpa_printf(MSG_WARNING, "EAP-AKA: eap_sim_db not configured");
		return NULL;
	}

	data = os_zalloc(sizeof(*data));
	if (data == NULL)
		return NULL;

	data->eap_method = EAP_TYPE_AKA;

	data->state = IDENTITY;
	eap_aka_determine_identity(sm, data, 1, 0);
	data->pending_id = -1;

	return data;
}


#ifdef EAP_AKA_PRIME
static void * eap_aka_prime_init(struct eap_sm *sm)
{
	struct eap_aka_data *data;
	/* TODO: make ANID configurable; see 3GPP TS 24.302 */
	char *network_name = "WLAN";

	if (sm->eap_sim_db_priv == NULL) {
		wpa_printf(MSG_WARNING, "EAP-AKA: eap_sim_db not configured");
		return NULL;
	}

	data = os_zalloc(sizeof(*data));
	if (data == NULL)
		return NULL;

	data->eap_method = EAP_TYPE_AKA_PRIME;
	data->network_name = os_malloc(os_strlen(network_name));
	if (data->network_name == NULL) {
		os_free(data);
		return NULL;
	}

	data->network_name_len = os_strlen(network_name);
	os_memcpy(data->network_name, network_name, data->network_name_len);

	data->state = IDENTITY;
	eap_aka_determine_identity(sm, data, 1, 0);
	data->pending_id = -1;

	return data;
}
#endif /* EAP_AKA_PRIME */


static void eap_aka_reset(struct eap_sm *sm, void *priv)
{
	struct eap_aka_data *data = priv;
	os_free(data->next_pseudonym);
	os_free(data->next_reauth_id);
	wpabuf_free(data->id_msgs);
	os_free(data->network_name);
	os_free(data);
}


static int eap_aka_add_id_msg(struct eap_aka_data *data,
			      const struct wpabuf *msg)
{
	if (msg == NULL)
		return -1;

	if (data->id_msgs == NULL) {
		data->id_msgs = wpabuf_dup(msg);
		return data->id_msgs == NULL ? -1 : 0;
	}

	if (wpabuf_resize(&data->id_msgs, wpabuf_len(msg)) < 0)
		return -1;
	wpabuf_put_buf(data->id_msgs, msg);

	return 0;
}


static void eap_aka_add_checkcode(struct eap_aka_data *data,
				  struct eap_sim_msg *msg)
{
	const u8 *addr;
	size_t len;
	u8 hash[SHA256_MAC_LEN];

	wpa_printf(MSG_DEBUG, "   AT_CHECKCODE");

	if (data->id_msgs == NULL) {
		/*
		 * No EAP-AKA/Identity packets were exchanged - send empty
		 * checkcode.
		 */
		eap_sim_msg_add(msg, EAP_SIM_AT_CHECKCODE, 0, NULL, 0);
		return;
	}

	/* Checkcode is SHA1 hash over all EAP-AKA/Identity packets. */
	addr = wpabuf_head(data->id_msgs);
	len = wpabuf_len(data->id_msgs);
	wpa_hexdump(MSG_MSGDUMP, "EAP-AKA: AT_CHECKCODE data", addr, len);
	if (data->eap_method == EAP_TYPE_AKA_PRIME)
		sha256_vector(1, &addr, &len, hash);
	else
		sha1_vector(1, &addr, &len, hash);

	eap_sim_msg_add(msg, EAP_SIM_AT_CHECKCODE, 0, hash,
			data->eap_method == EAP_TYPE_AKA_PRIME ?
			EAP_AKA_PRIME_CHECKCODE_LEN : EAP_AKA_CHECKCODE_LEN);
}


static int eap_aka_verify_checkcode(struct eap_aka_data *data,
				    const u8 *checkcode, size_t checkcode_len)
{
	const u8 *addr;
	size_t len;
	u8 hash[SHA256_MAC_LEN];
	size_t hash_len;

	if (checkcode == NULL)
		return -1;

	if (data->id_msgs == NULL) {
		if (checkcode_len != 0) {
			wpa_printf(MSG_DEBUG, "EAP-AKA: Checkcode from peer "
				   "indicates that AKA/Identity messages were "
				   "used, but they were not");
			return -1;
		}
		return 0;
	}

	hash_len = data->eap_method == EAP_TYPE_AKA_PRIME ?
		EAP_AKA_PRIME_CHECKCODE_LEN : EAP_AKA_CHECKCODE_LEN;

	if (checkcode_len != hash_len) {
		wpa_printf(MSG_DEBUG, "EAP-AKA: Checkcode from peer indicates "
			   "that AKA/Identity message were not used, but they "
			   "were");
		return -1;
	}

	/* Checkcode is SHA1 hash over all EAP-AKA/Identity packets. */
	addr = wpabuf_head(data->id_msgs);
	len = wpabuf_len(data->id_msgs);
	if (data->eap_method == EAP_TYPE_AKA_PRIME)
		sha256_vector(1, &addr, &len, hash);
	else
		sha1_vector(1, &addr, &len, hash);

	if (os_memcmp(hash, checkcode, hash_len) != 0) {
		wpa_printf(MSG_DEBUG, "EAP-AKA: Mismatch in AT_CHECKCODE");
		return -1;
	}

	return 0;
}


static struct wpabuf * eap_aka_build_identity(struct eap_sm *sm,
					      struct eap_aka_data *data, u8 id)
{
	struct eap_sim_msg *msg;
	struct wpabuf *buf;

	wpa_printf(MSG_DEBUG, "EAP-AKA: Generating Identity");
	msg = eap_sim_msg_init(EAP_CODE_REQUEST, id, data->eap_method,
			       EAP_AKA_SUBTYPE_IDENTITY);
	if (eap_sim_db_identity_known(sm->eap_sim_db_priv, sm->identity,
				      sm->identity_len)) {
		wpa_printf(MSG_DEBUG, "   AT_PERMANENT_ID_REQ");
		eap_sim_msg_add(msg, EAP_SIM_AT_PERMANENT_ID_REQ, 0, NULL, 0);
	} else {
		/*
		 * RFC 4187, Chap. 4.1.4 recommends that identity from EAP is
		 * ignored and the AKA/Identity is used to request the
		 * identity.
		 */
		wpa_printf(MSG_DEBUG, "   AT_ANY_ID_REQ");
		eap_sim_msg_add(msg, EAP_SIM_AT_ANY_ID_REQ, 0, NULL, 0);
	}
	buf = eap_sim_msg_finish(msg, NULL, NULL, 0);
	if (eap_aka_add_id_msg(data, buf) < 0) {
		wpabuf_free(buf);
		return NULL;
	}
	data->pending_id = id;
	return buf;
}


static int eap_aka_build_encr(struct eap_sm *sm, struct eap_aka_data *data,
			      struct eap_sim_msg *msg, u16 counter,
			      const u8 *nonce_s)
{
	os_free(data->next_pseudonym);
	data->next_pseudonym =
		eap_sim_db_get_next_pseudonym(sm->eap_sim_db_priv, 1);
	os_free(data->next_reauth_id);
	if (data->counter <= EAP_AKA_MAX_FAST_REAUTHS) {
		data->next_reauth_id =
			eap_sim_db_get_next_reauth_id(sm->eap_sim_db_priv, 1);
	} else {
		wpa_printf(MSG_DEBUG, "EAP-AKA: Max fast re-authentication "
			   "count exceeded - force full authentication");
		data->next_reauth_id = NULL;
	}

	if (data->next_pseudonym == NULL && data->next_reauth_id == NULL &&
	    counter == 0 && nonce_s == NULL)
		return 0;

	wpa_printf(MSG_DEBUG, "   AT_IV");
	wpa_printf(MSG_DEBUG, "   AT_ENCR_DATA");
	eap_sim_msg_add_encr_start(msg, EAP_SIM_AT_IV, EAP_SIM_AT_ENCR_DATA);

	if (counter > 0) {
		wpa_printf(MSG_DEBUG, "   *AT_COUNTER (%u)", counter);
		eap_sim_msg_add(msg, EAP_SIM_AT_COUNTER, counter, NULL, 0);
	}

	if (nonce_s) {
		wpa_printf(MSG_DEBUG, "   *AT_NONCE_S");
		eap_sim_msg_add(msg, EAP_SIM_AT_NONCE_S, 0, nonce_s,
				EAP_SIM_NONCE_S_LEN);
	}

	if (data->next_pseudonym) {
		wpa_printf(MSG_DEBUG, "   *AT_NEXT_PSEUDONYM (%s)",
			   data->next_pseudonym);
		eap_sim_msg_add(msg, EAP_SIM_AT_NEXT_PSEUDONYM,
				os_strlen(data->next_pseudonym),
				(u8 *) data->next_pseudonym,
				os_strlen(data->next_pseudonym));
	}

	if (data->next_reauth_id) {
		wpa_printf(MSG_DEBUG, "   *AT_NEXT_REAUTH_ID (%s)",
			   data->next_reauth_id);
		eap_sim_msg_add(msg, EAP_SIM_AT_NEXT_REAUTH_ID,
				os_strlen(data->next_reauth_id),
				(u8 *) data->next_reauth_id,
				os_strlen(data->next_reauth_id));
	}

	if (eap_sim_msg_add_encr_end(msg, data->k_encr, EAP_SIM_AT_PADDING)) {
		wpa_printf(MSG_WARNING, "EAP-AKA: Failed to encrypt "
			   "AT_ENCR_DATA");
		return -1;
	}

	return 0;
}


static struct wpabuf * eap_aka_build_challenge(struct eap_sm *sm,
					       struct eap_aka_data *data,
					       u8 id)
{
	struct eap_sim_msg *msg;

	wpa_printf(MSG_DEBUG, "EAP-AKA: Generating Challenge");
	msg = eap_sim_msg_init(EAP_CODE_REQUEST, id, data->eap_method,
			       EAP_AKA_SUBTYPE_CHALLENGE);
	wpa_printf(MSG_DEBUG, "   AT_RAND");
	eap_sim_msg_add(msg, EAP_SIM_AT_RAND, 0, data->rand, EAP_AKA_RAND_LEN);
	wpa_printf(MSG_DEBUG, "   AT_AUTN");
	eap_sim_msg_add(msg, EAP_SIM_AT_AUTN, 0, data->autn, EAP_AKA_AUTN_LEN);
	if (data->eap_method == EAP_TYPE_AKA_PRIME) {
		if (data->kdf) {
			/* Add the selected KDF into the beginning */
			wpa_printf(MSG_DEBUG, "   AT_KDF");
			eap_sim_msg_add(msg, EAP_SIM_AT_KDF, data->kdf,
					NULL, 0);
		}
		wpa_printf(MSG_DEBUG, "   AT_KDF");
		eap_sim_msg_add(msg, EAP_SIM_AT_KDF, EAP_AKA_PRIME_KDF,
				NULL, 0);
		wpa_printf(MSG_DEBUG, "   AT_KDF_INPUT");
		eap_sim_msg_add(msg, EAP_SIM_AT_KDF_INPUT,
				data->network_name_len,
				data->network_name, data->network_name_len);
	}

	if (eap_aka_build_encr(sm, data, msg, 0, NULL)) {
		eap_sim_msg_free(msg);
		return NULL;
	}

	eap_aka_add_checkcode(data, msg);

	if (sm->eap_sim_aka_result_ind) {
		wpa_printf(MSG_DEBUG, "   AT_RESULT_IND");
		eap_sim_msg_add(msg, EAP_SIM_AT_RESULT_IND, 0, NULL, 0);
	}

#ifdef EAP_AKA_PRIME
	if (data->eap_method == EAP_TYPE_AKA) {
		u16 flags = 0;
		int i;
		int aka_prime_preferred = 0;

		i = 0;
		while (sm->user && i < EAP_MAX_METHODS &&
		       (sm->user->methods[i].vendor != EAP_VENDOR_IETF ||
			sm->user->methods[i].method != EAP_TYPE_NONE)) {
			if (sm->user->methods[i].vendor == EAP_VENDOR_IETF) {
				if (sm->user->methods[i].method ==
				    EAP_TYPE_AKA)
					break;
				if (sm->user->methods[i].method ==
				    EAP_TYPE_AKA_PRIME) {
					aka_prime_preferred = 1;
					break;
				}
			}
			i++;
		}

		if (aka_prime_preferred)
			flags |= EAP_AKA_BIDDING_FLAG_D;
		eap_sim_msg_add(msg, EAP_SIM_AT_BIDDING, flags, NULL, 0);