src/eap_server/eap_server_pwd.c

/*
 * hostapd / EAP-pwd (RFC 5931) server
 * Copyright (c) 2010, Dan Harkins <dharkins@lounge.org>
 *
 * This software may be distributed under the terms of the BSD license.
 * See README for more details.
 */

#include "includes.h"

#include "common.h"
#include "crypto/sha256.h"
#include "crypto/ms_funcs.h"
#include "crypto/crypto.h"
#include "eap_server/eap_i.h"
#include "eap_common/eap_pwd_common.h"


struct eap_pwd_data {
	enum {
		PWD_ID_Req, PWD_Commit_Req, PWD_Confirm_Req, SUCCESS, FAILURE
	} state;
	u8 *id_peer;
	size_t id_peer_len;
	u8 *id_server;
	size_t id_server_len;
	u8 *password;
	size_t password_len;
	int password_hash;
	u8 *salt;
	size_t salt_len;
	u32 token;
	u16 group_num;
	u8 password_prep;
	EAP_PWD_group *grp;

	struct wpabuf *inbuf;
	size_t in_frag_pos;
	struct wpabuf *outbuf;
	size_t out_frag_pos;
	size_t mtu;

	struct crypto_bignum *k;
	struct crypto_bignum *private_value;
	struct crypto_bignum *peer_scalar;
	struct crypto_bignum *my_scalar;
	struct crypto_ec_point *my_element;
	struct crypto_ec_point *peer_element;

	u8 my_confirm[SHA256_MAC_LEN];

	u8 msk[EAP_MSK_LEN];
	u8 emsk[EAP_EMSK_LEN];
	u8 session_id[1 + SHA256_MAC_LEN];
};


static const char * eap_pwd_state_txt(int state)
{
	switch (state) {
        case PWD_ID_Req:
		return "PWD-ID-Req";
        case PWD_Commit_Req:
		return "PWD-Commit-Req";
        case PWD_Confirm_Req:
		return "PWD-Confirm-Req";
        case SUCCESS:
		return "SUCCESS";
        case FAILURE:
		return "FAILURE";
        default:
		return "PWD-Unk";
	}
}


static void eap_pwd_state(struct eap_pwd_data *data, int state)
{
	wpa_printf(MSG_DEBUG, "EAP-pwd: %s -> %s",
		   eap_pwd_state_txt(data->state), eap_pwd_state_txt(state));
	data->state = state;
}


static void * eap_pwd_init(struct eap_sm *sm)
{
	struct eap_pwd_data *data;

	if (sm->user == NULL || sm->user->password == NULL ||
	    sm->user->password_len == 0) {
		wpa_printf(MSG_INFO, "EAP-PWD (server): Password is not "
			   "configured");
		return NULL;
	}

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

	data->group_num = sm->cfg->pwd_group;
	wpa_printf(MSG_DEBUG, "EAP-pwd: Selected group number %d",
		   data->group_num);
	data->state = PWD_ID_Req;

	data->id_server = (u8 *) os_strdup("server");
	if (data->id_server)
		data->id_server_len = os_strlen((char *) data->id_server);

	data->password = os_malloc(sm->user->password_len);
	if (data->password == NULL) {
		wpa_printf(MSG_INFO, "EAP-PWD: Memory allocation password "
			   "fail");
		bin_clear_free(data->id_server, data->id_server_len);
		os_free(data);
		return NULL;
	}
	data->password_len = sm->user->password_len;
	os_memcpy(data->password, sm->user->password, data->password_len);
	data->password_hash = sm->user->password_hash;

	data->salt_len = sm->user->salt_len;
	if (data->salt_len) {
		data->salt = os_memdup(sm->user->salt, sm->user->salt_len);
		if (!data->salt) {
			wpa_printf(MSG_INFO,
				   "EAP-pwd: Memory allocation of salt failed");
			bin_clear_free(data->id_server, data->id_server_len);
			bin_clear_free(data->password, data->password_len);
			os_free(data);
			return NULL;
		}
	}

	data->in_frag_pos = data->out_frag_pos = 0;
	data->inbuf = data->outbuf = NULL;
	/* use default MTU from RFC 5931 if not configured otherwise */
	data->mtu = sm->cfg->fragment_size > 0 ? sm->cfg->fragment_size : 1020;

	return data;
}


static void eap_pwd_reset(struct eap_sm *sm, void *priv)
{
	struct eap_pwd_data *data = priv;

	crypto_bignum_deinit(data->private_value, 1);
	crypto_bignum_deinit(data->peer_scalar, 1);
	crypto_bignum_deinit(data->my_scalar, 1);
	crypto_bignum_deinit(data->k, 1);
	crypto_ec_point_deinit(data->my_element, 1);
	crypto_ec_point_deinit(data->peer_element, 1);
	bin_clear_free(data->id_peer, data->id_peer_len);
	bin_clear_free(data->id_server, data->id_server_len);
	bin_clear_free(data->password, data->password_len);
	bin_clear_free(data->salt, data->salt_len);
	if (data->grp) {
		crypto_ec_deinit(data->grp->group);
		crypto_ec_point_deinit(data->grp->pwe, 1);
		os_free(data->grp);
	}
	wpabuf_free(data->inbuf);
	wpabuf_free(data->outbuf);
	bin_clear_free(data, sizeof(*data));
}


static void eap_pwd_build_id_req(struct eap_sm *sm, struct eap_pwd_data *data,
				 u8 id)
{
	wpa_printf(MSG_DEBUG, "EAP-pwd: ID/Request");
	/*
	 * if we're fragmenting then we already have an id request, just return
	 */
	if (data->out_frag_pos)
		return;

	data->outbuf = wpabuf_alloc(sizeof(struct eap_pwd_id) +
				    data->id_server_len);
	if (data->outbuf == NULL) {
		eap_pwd_state(data, FAILURE);
		return;
	}

	if (os_get_random((u8 *) &data->token, sizeof(data->token)) < 0) {
		wpabuf_free(data->outbuf);
		data->outbuf = NULL;
		eap_pwd_state(data, FAILURE);
		return;
	}

	wpa_hexdump_key(MSG_DEBUG, "EAP-pwd (server): password",
			data->password, data->password_len);
	if (data->salt_len)
		wpa_hexdump(MSG_DEBUG, "EAP-pwd (server): salt",
			    data->salt, data->salt_len);

	/*
	 * If this is a salted password then figure out how it was hashed
	 * based on the length.
	 */
	if (data->salt_len) {
		switch (data->password_len) {
		case 20:
			data->password_prep = EAP_PWD_PREP_SSHA1;
			break;
		case 32:
			data->password_prep = EAP_PWD_PREP_SSHA256;
			break;
		case 64:
			data->password_prep = EAP_PWD_PREP_SSHA512;
			break;
		default:
			wpa_printf(MSG_INFO,
				   "EAP-pwd (server): bad size %d for salted password",
				   (int) data->password_len);
			eap_pwd_state(data, FAILURE);
			return;
		}
	} else {
		/* Otherwise, figure out whether it's MS hashed or plain */
		data->password_prep = data->password_hash ? EAP_PWD_PREP_MS :
			EAP_PWD_PREP_NONE;
	}

	wpabuf_put_be16(data->outbuf, data->group_num);
	wpabuf_put_u8(data->outbuf, EAP_PWD_DEFAULT_RAND_FUNC);
	wpabuf_put_u8(data->outbuf, EAP_PWD_DEFAULT_PRF);
	wpabuf_put_data(data->outbuf, &data->token, sizeof(data->token));
	wpabuf_put_u8(data->outbuf, data->password_prep);
	wpabuf_put_data(data->outbuf, data->id_server, data->id_server_len);
}


static void eap_pwd_build_commit_req(struct eap_sm *sm,
				     struct eap_pwd_data *data, u8 id)
{
	struct crypto_bignum *mask = NULL;
	u8 *scalar, *element;
	size_t prime_len, order_len;

	wpa_printf(MSG_DEBUG, "EAP-pwd: Commit/Request");
	/*
	 * if we're fragmenting then we already have an commit request, just
	 * return
	 */
	if (data->out_frag_pos)
		return;

	prime_len = crypto_ec_prime_len(data->grp->group);
	order_len = crypto_ec_order_len(data->grp->group);

	data->private_value = crypto_bignum_init();
	data->my_element = crypto_ec_point_init(data->grp->group);
	data->my_scalar = crypto_bignum_init();
	mask = crypto_bignum_init();
	if (!data->private_value || !data->my_element || !data->my_scalar ||
	    !mask) {
		wpa_printf(MSG_INFO, "EAP-PWD (server): scalar allocation "
			   "fail");
		goto fin;
	}

	if (eap_pwd_get_rand_mask(data->grp, data->private_value, mask,
				  data->my_scalar) < 0)
		goto fin;

	if (crypto_ec_point_mul(data->grp->group, data->grp->pwe, mask,
				data->my_element) < 0) {
		wpa_printf(MSG_INFO, "EAP-PWD (server): element allocation "
			   "fail");
		eap_pwd_state(data, FAILURE);
		goto fin;
	}

	if (crypto_ec_point_invert(data->grp->group, data->my_element) < 0) {
		wpa_printf(MSG_INFO, "EAP-PWD (server): element inversion "
			   "fail");
		goto fin;
	}

	data->outbuf = wpabuf_alloc(2 * prime_len + order_len +
				    (data->salt ? 1 + data->salt_len : 0));
	if (data->outbuf == NULL)
		goto fin;

	/* If we're doing salted password prep, add the salt */
	if (data->salt_len) {
		wpabuf_put_u8(data->outbuf, data->salt_len);
		wpabuf_put_data(data->outbuf, data->salt, data->salt_len);
	}

	/* We send the element as (x,y) followed by the scalar */
	element = wpabuf_put(data->outbuf, 2 * prime_len);
	scalar = wpabuf_put(data->outbuf, order_len);
	crypto_bignum_to_bin(data->my_scalar, scalar, order_len, order_len);
	if (crypto_ec_point_to_bin(data->grp->group, data->my_element, element,
				   element + prime_len) < 0) {
		wpa_printf(MSG_INFO, "EAP-PWD (server): point assignment "
			   "fail");
		goto fin;
	}

fin:
	crypto_bignum_deinit(mask, 1);
	if (data->outbuf == NULL)
		eap_pwd_state(data, FAILURE);
}


static void eap_pwd_build_confirm_req(struct eap_sm *sm,
				      struct eap_pwd_data *data, u8 id)
{
	struct crypto_hash *hash = NULL;
	u8 conf[SHA256_MAC_LEN], *cruft = NULL, *ptr;
	u16 grp;
	size_t prime_len, order_len;

	wpa_printf(MSG_DEBUG, "EAP-pwd: Confirm/Request");
	/*
	 * if we're fragmenting then we already have an confirm request, just
	 * return
	 */
	if (data->out_frag_pos)
		return;

	prime_len = crypto_ec_prime_len(data->grp->group);
	order_len = crypto_ec_order_len(data->grp->group);

	/* Each component of the cruft will be at most as big as the prime */
	cruft = os_malloc(prime_len * 2);
	if (!cruft) {
		wpa_printf(MSG_INFO, "EAP-PWD (server): debug allocation "
			   "fail");
		goto fin;
	}

	/*
	 * commit is H(k | server_element | server_scalar | peer_element |
	 *	       peer_scalar | ciphersuite)
	 */
	hash = eap_pwd_h_init();
	if (hash == NULL)
		goto fin;

	/*
	 * Zero the memory each time because this is mod prime math and some
	 * value may start with a few zeros and the previous one did not.
	 *
	 * First is k
	 */
	crypto_bignum_to_bin(data->k, cruft, prime_len, prime_len);
	eap_pwd_h_update(hash, cruft, prime_len);

	/* server element: x, y */
	if (crypto_ec_point_to_bin(data->grp->group, data->my_element, cruft,
				   cruft + prime_len) < 0) {
		wpa_printf(MSG_INFO, "EAP-PWD (server): confirm point "
			   "assignment fail");
		goto fin;
	}
	eap_pwd_h_update(hash, cruft, prime_len * 2);

	/* server scalar */
	crypto_bignum_to_bin(data->my_scalar, cruft, order_len, order_len);
	eap_pwd_h_update(hash, cruft, order_len);

	/* peer element: x, y */
	if (crypto_ec_point_to_bin(data->grp->group, data->peer_element, cruft,
				   cruft + prime_len) < 0) {
		wpa_printf(MSG_INFO, "EAP-PWD (server): confirm point "
			   "assignment fail");
		goto fin;
	}
	eap_pwd_h_update(hash, cruft, prime_len * 2);

	/* peer scalar */
	crypto_bignum_to_bin(data->peer_scalar, cruft, order_len, order_len);
	eap_pwd_h_update(hash, cruft, order_len);

	/* ciphersuite */
	grp = htons(data->group_num);
	os_memset(cruft, 0, prime_len);
	ptr = cruft;
	os_memcpy(ptr, &grp, sizeof(u16));
	ptr += sizeof(u16);
	*ptr = EAP_PWD_DEFAULT_RAND_FUNC;
	ptr += sizeof(u8);
	*ptr = EAP_PWD_DEFAULT_PRF;
	ptr += sizeof(u8);
	eap_pwd_h_update(hash, cruft, ptr - cruft);

	/* all done with the random function */
	eap_pwd_h_final(hash, conf);
	hash = NULL;
	os_memcpy(data->my_confirm, conf, SHA256_MAC_LEN);

	data->outbuf = wpabuf_alloc(SHA256_MAC_LEN);
	if (data->outbuf == NULL)
		goto fin;

	wpabuf_put_data(data->outbuf, conf, SHA256_MAC_LEN);

fin:
	bin_clear_free(cruft, prime_len * 2);
	if (data->outbuf == NULL)
		eap_pwd_state(data, FAILURE);
	eap_pwd_h_final(hash, NULL);
}


static struct wpabuf *
eap_pwd_build_req(struct eap_sm *sm, void *priv, u8 id)
{
	struct eap_pwd_data *data = priv;
	struct wpabuf *req;
	u8 lm_exch;
	const u8 *buf;
	u16 totlen = 0;
	size_t len;

	/*
	 * if we're buffering response fragments then just ACK
	 */
	if (data->in_frag_pos) {
		wpa_printf(MSG_DEBUG, "EAP-pwd: ACKing a fragment!!");
		req = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PWD,
				    EAP_PWD_HDR_SIZE, EAP_CODE_REQUEST, id);
		if (req == NULL) {
			eap_pwd_state(data, FAILURE);
			return NULL;
		}
		switch (data->state) {
		case PWD_ID_Req:
			wpabuf_put_u8(req, EAP_PWD_OPCODE_ID_EXCH);
			break;
		case PWD_Commit_Req:
			wpabuf_put_u8(req, EAP_PWD_OPCODE_COMMIT_EXCH);
			break;
		case PWD_Confirm_Req:
			wpabuf_put_u8(req, EAP_PWD_OPCODE_CONFIRM_EXCH);
			break;
		default:
			eap_pwd_state(data, FAILURE);   /* just to be sure */
			wpabuf_free(req);
			return NULL;
		}
		return req;
	}

	/*
	 * build the data portion of a request
	 */
	switch (data->state) {
	case PWD_ID_Req:
		eap_pwd_build_id_req(sm, data, id);
		lm_exch = EAP_PWD_OPCODE_ID_EXCH;
		break;
	case PWD_Commit_Req:
		eap_pwd_build_commit_req(sm, data, id);
		lm_exch = EAP_PWD_OPCODE_COMMIT_EXCH;
		break;
	case PWD_Confirm_Req:
		eap_pwd_build_confirm_req(sm, data, id);
		lm_exch = EAP_PWD_OPCODE_CONFIRM_EXCH;
		break;
	default:
		wpa_printf(MSG_INFO, "EAP-pwd: Unknown state %d in build_req",
			   data->state);
		eap_pwd_state(data, FAILURE);
		lm_exch = 0;    /* hush now, sweet compiler */
		break;
	}

	if (data->state == FAILURE)
		return NULL;

	/*
	 * determine whether that data needs to be fragmented
	 */
	len = wpabuf_len(data->outbuf) - data->out_frag_pos;
	if ((len + EAP_PWD_HDR_SIZE) > data->mtu) {
		len = data->mtu - EAP_PWD_HDR_SIZE;
		EAP_PWD_SET_MORE_BIT(lm_exch);
		/*
		 * if this is the first fragment, need to set the M bit
		 * and add the total length to the eap_pwd_hdr
		 */
		if (data->out_frag_pos == 0) {
			EAP_PWD_SET_LENGTH_BIT(lm_exch);
			totlen = wpabuf_len(data->outbuf) +
				EAP_PWD_HDR_SIZE + sizeof(u16);
			len -= sizeof(u16);
			wpa_printf(MSG_DEBUG, "EAP-pwd: Fragmenting output, "
				   "total length = %d", totlen);
		}
		wpa_printf(MSG_DEBUG, "EAP-pwd: Send a %d byte fragment",
			   (int) len);
	}

	/*
	 * alloc an eap request and populate it with the data
	 */
	req = eap_msg_alloc(EAP_VENDOR_IETF, EAP_TYPE_PWD,
			    EAP_PWD_HDR_SIZE + len +
			    (totlen ? sizeof(u16) : 0),
			    EAP_CODE_REQUEST, id);
	if (req == NULL) {
		eap_pwd_state(data, FAILURE);
		return NULL;
	}

	wpabuf_put_u8(req, lm_exch);
	if (EAP_PWD_GET_LENGTH_BIT(lm_exch))
		wpabuf_put_be16(req, totlen);

	buf = wpabuf_head_u8(data->outbuf);
	wpabuf_put_data(req, buf + data->out_frag_pos, len);
	data->out_frag_pos += len;
	/*
	 * either not fragged or last fragment, either way free up the data
	 */
	if (data->out_frag_pos >= wpabuf_len(data->outbuf)) {
		wpabuf_free(data->outbuf);
		data->outbuf = NULL;
		data->out_frag_pos = 0;
	}

	return req;
}


static bool eap_pwd_check(struct eap_sm *sm, void *priv,
			  struct wpabuf *respData)
{
	struct eap_pwd_data *data = priv;
	const u8 *pos;
	size_t len;

	pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PWD, respData, &len);
	if (pos == NULL || len < 1) {
		wpa_printf(MSG_INFO, "EAP-pwd: Invalid frame");
		return true;
	}

	wpa_printf(MSG_DEBUG, "EAP-pwd: Received frame: exch = %d, len = %d",
		   EAP_PWD_GET_EXCHANGE(*pos), (int) len);

	if (data->state == PWD_ID_Req &&
	    ((EAP_PWD_GET_EXCHANGE(*pos)) == EAP_PWD_OPCODE_ID_EXCH))
		return false;

	if (data->state == PWD_Commit_Req &&
	    ((EAP_PWD_GET_EXCHANGE(*pos)) == EAP_PWD_OPCODE_COMMIT_EXCH))
		return false;

	if (data->state == PWD_Confirm_Req &&
	    ((EAP_PWD_GET_EXCHANGE(*pos)) == EAP_PWD_OPCODE_CONFIRM_EXCH))
		return false;

	wpa_printf(MSG_INFO, "EAP-pwd: Unexpected opcode=%d in state=%d",
		   *pos, data->state);

	return true;
}


static void eap_pwd_process_id_resp(struct eap_sm *sm,
				    struct eap_pwd_data *data,
				    const u8 *payload, size_t payload_len)
{
	struct eap_pwd_id *id;
	const u8 *password;
	size_t password_len;
	u8 pwhashhash[16];
	int res;

	if (payload_len < sizeof(struct eap_pwd_id)) {
		wpa_printf(MSG_INFO, "EAP-pwd: Invalid ID response");
		return;
	}

	id = (struct eap_pwd_id *) payload;
	if ((data->group_num != be_to_host16(id->group_num)) ||
	    (id->random_function != EAP_PWD_DEFAULT_RAND_FUNC) ||
	    (os_memcmp(id->token, (u8 *)&data->token, sizeof(data->token))) ||
	    (id->prf != EAP_PWD_DEFAULT_PRF) ||
	    (id->prep != data->password_prep)) {
		wpa_printf(MSG_INFO, "EAP-pwd: peer changed parameters");
		eap_pwd_state(data, FAILURE);
		return;
	}
	if (data->id_peer || data->grp) {
		wpa_printf(MSG_INFO, "EAP-pwd: data was already allocated");
		return;
	}
	data->id_peer = os_malloc(payload_len - sizeof(struct eap_pwd_id));
	if (data->id_peer == NULL) {
		wpa_printf(MSG_INFO, "EAP-PWD: memory allocation id fail");
		return;
	}
	data->id_peer_len = payload_len - sizeof(struct eap_pwd_id);
	os_memcpy(data->id_peer, id->identity, data->id_peer_len);
	wpa_hexdump_ascii(MSG_DEBUG, "EAP-PWD (server): peer sent id of",
			  data->id_peer, data->id_peer_len);

	data->grp = get_eap_pwd_group(data->group_num);
	if (data->grp == NULL) {
		wpa_printf(MSG_INFO, "EAP-PWD: failed to allocate memory for "
			   "group");
		return;
	}

	/*
	 * If it's PREP_MS then hash the password again, otherwise regardless
	 * of the prep the client is doing, the password we have is the one to
	 * use to generate the password element.
	 */
	if (data->password_prep == EAP_PWD_PREP_MS) {
		res = hash_nt_password_hash(data->password, pwhashhash);
		if (res)
			return;
		password = pwhashhash;
		password_len = sizeof(pwhashhash);
	} else {
		password = data->password;
		password_len = data->password_len;
	}

	res = compute_password_element(data->grp, data->group_num,
				       password, password_len,
				       data->id_server, data->id_server_len,
				       data->id_peer, data->id_peer_len,
				       (u8 *) &data->token);
	forced_memzero(pwhashhash, sizeof(pwhashhash));
	if (res) {
		wpa_printf(MSG_INFO, "EAP-PWD (server): unable to compute "
			   "PWE");
		return;
	}
	wpa_printf(MSG_DEBUG, "EAP-PWD (server): computed %d bit PWE...",
		   (int) crypto_ec_prime_len_bits(data->grp->group));

	eap_pwd_state(data, PWD_Commit_Req);
}


static void
eap_pwd_process_commit_resp(struct eap_sm *sm, struct eap_pwd_data *data,
			    const u8 *payload, size_t payload_len)
{
	const u8 *ptr;
	struct crypto_ec_point *K = NULL;
	int res = 0;
	size_t prime_len, order_len;

	wpa_printf(MSG_DEBUG, "EAP-pwd: Received commit response");

	prime_len = crypto_ec_prime_len(data->grp->group);
	order_len = crypto_ec_order_len(data->grp->group);

	if (payload_len != 2 * prime_len + order_len) {
		wpa_printf(MSG_INFO,
			   "EAP-pwd: Unexpected Commit payload length %u (expected %u)",
			   (unsigned int) payload_len,
			   (unsigned int) (2 * prime_len + order_len));
		goto fin;
	}

	data->k = crypto_bignum_init();
	K = crypto_ec_point_init(data->grp->group);
	if (!data->k || !K) {
		wpa_printf(MSG_INFO, "EAP-PWD (server): peer data allocation "
			   "fail");
		goto fin;
	}

	/* element, x then y, followed by scalar */
	ptr = payload;
	data->peer_element = eap_pwd_get_element(data->grp, ptr);
	if (!data->peer_element) {
		wpa_printf(MSG_INFO, "EAP-PWD (server): setting peer element "
			   "fail");
		goto fin;
	}
	ptr += prime_len * 2;
	data->peer_scalar = eap_pwd_get_scalar(data->grp, ptr);
	if (!data->peer_scalar) {
		wpa_printf(MSG_INFO, "EAP-PWD (server): peer data allocation "
			   "fail");
		goto fin;
	}

	/* detect reflection attacks */
	if (crypto_bignum_cmp(data->my_scalar, data->peer_scalar) == 0 ||
	    crypto_ec_point_cmp(data->grp->group, data->my_element,
				data->peer_element) == 0) {
		wpa_printf(MSG_INFO,
			   "EAP-PWD (server): detected reflection attack!");
		goto fin;
	}

	/* compute the shared key, k */
	if ((crypto_ec_point_mul(data->grp->group, data->grp->pwe,
				 data->peer_scalar, K) < 0) ||
	    (crypto_ec_point_add(data->grp->group, K, data->peer_element,
				 K) < 0) ||
	    (crypto_ec_point_mul(data->grp->group, K, data->private_value,
				 K) < 0)) {
		wpa_printf(MSG_INFO, "EAP-PWD (server): computing shared key "
			   "fail");
		goto fin;
	}

	/*
	 * This check is strictly speaking just for the case where
	 * co-factor > 1 but it was suggested that even though this is probably
	 * never going to happen it is a simple and safe check "just to be
	 * sure" so let's be safe.
	 */
	if (crypto_ec_point_is_at_infinity(data->grp->group, K)) {
		wpa_printf(MSG_INFO, "EAP-PWD (server): shared key point is "
			   "at infinity");
		goto fin;
	}
	if (crypto_ec_point_x(data->grp->group, K, data->k)) {
		wpa_printf(MSG_INFO, "EAP-PWD (server): unable to extract "
			   "shared secret from secret point");
		goto fin;
	}
	res = 1;

fin:
	crypto_ec_point_deinit(K, 1);

	if (res)
		eap_pwd_state(data, PWD_Confirm_Req);
	else
		eap_pwd_state(data, FAILURE);
}


static void
eap_pwd_process_confirm_resp(struct eap_sm *sm, struct eap_pwd_data *data,
			     const u8 *payload, size_t payload_len)
{
	struct crypto_hash *hash = NULL;
	u32 cs;
	u16 grp;
	u8 conf[SHA256_MAC_LEN], *cruft = NULL, *ptr;
	size_t prime_len, order_len;

	prime_len = crypto_ec_prime_len(data->grp->group);
	order_len = crypto_ec_order_len(data->grp->group);

	if (payload_len != SHA256_MAC_LEN) {
		wpa_printf(MSG_INFO,
			   "EAP-pwd: Unexpected Confirm payload length %u (expected %u)",
			   (unsigned int) payload_len, SHA256_MAC_LEN);
		goto fin;
	}

	/* build up the ciphersuite: group | random_function | prf */
	grp = htons(data->group_num);
	ptr = (u8 *) &cs;
	os_memcpy(ptr, &grp, sizeof(u16));
	ptr += sizeof(u16);
	*ptr = EAP_PWD_DEFAULT_RAND_FUNC;
	ptr += sizeof(u8);
	*ptr = EAP_PWD_DEFAULT_PRF;

	/* each component of the cruft will be at most as big as the prime */
	cruft = os_malloc(prime_len * 2);
	if (!cruft) {
		wpa_printf(MSG_INFO, "EAP-PWD (peer): allocation fail");
		goto fin;
	}

	/*
	 * commit is H(k | peer_element | peer_scalar | server_element |
	 *	       server_scalar | ciphersuite)
	 */
	hash = eap_pwd_h_init();
	if (hash == NULL)
		goto fin;

	/* k */
	crypto_bignum_to_bin(data->k, cruft, prime_len, prime_len);
	eap_pwd_h_update(hash, cruft, prime_len);

	/* peer element: x, y */
	if (crypto_ec_point_to_bin(data->grp->group, data->peer_element, cruft,
				   cruft + prime_len) < 0) {
		wpa_printf(MSG_INFO, "EAP-PWD (server): confirm point "
			   "assignment fail");
		goto fin;
	}
	eap_pwd_h_update(hash, cruft, prime_len * 2);

	/* peer scalar */
	crypto_bignum_to_bin(data->peer_scalar, cruft, order_len, order_len);
	eap_pwd_h_update(hash, cruft, order_len);

	/* server element: x, y */
	if (crypto_ec_point_to_bin(data->grp->group, data->my_element, cruft,
				   cruft + prime_len) < 0) {
		wpa_printf(MSG_INFO, "EAP-PWD (server): confirm point "
			   "assignment fail");
		goto fin;
	}
	eap_pwd_h_update(hash, cruft, prime_len * 2);

	/* server scalar */
	crypto_bignum_to_bin(data->my_scalar, cruft, order_len, order_len);
	eap_pwd_h_update(hash, cruft, order_len);

	/* ciphersuite */
	eap_pwd_h_update(hash, (u8 *) &cs, sizeof(u32));

	/* all done */
	eap_pwd_h_final(hash, conf);
	hash = NULL;

	ptr = (u8 *) payload;
	if (os_memcmp_const(conf, ptr, SHA256_MAC_LEN)) {
		wpa_printf(MSG_INFO, "EAP-PWD (server): confirm did not "
			   "verify");
		goto fin;
	}

	wpa_printf(MSG_DEBUG, "EAP-pwd (server): confirm verified");
	if (compute_keys(data->grp, data->k,
			 data->peer_scalar, data->my_scalar, conf,
			 data->my_confirm, &cs, data->msk, data->emsk,
			 data->session_id) < 0)
		eap_pwd_state(data, FAILURE);
	else
		eap_pwd_state(data, SUCCESS);

fin:
	bin_clear_free(cruft, prime_len * 2);
	eap_pwd_h_final(hash, NULL);
}


static void eap_pwd_process(struct eap_sm *sm, void *priv,
			    struct wpabuf *respData)
{
	struct eap_pwd_data *data = priv;
	const u8 *pos;
	size_t len;
	u8 lm_exch;
	u16 tot_len;

	pos = eap_hdr_validate(EAP_VENDOR_IETF, EAP_TYPE_PWD, respData, &len);
	if ((pos == NULL) || (len < 1)) {
		wpa_printf(MSG_INFO, "Bad EAP header! pos %s and len = %d",
			   (pos == NULL) ? "is NULL" : "is not NULL",
			   (int) len);
		return;
	}

	lm_exch = *pos;
	pos++;            /* skip over the bits and the exch */
	len--;

	/*
	 * if we're fragmenting then this should be an ACK with no data,
	 * just return and continue fragmenting in the "build" section above
	 */
	if (data->out_frag_pos) {
		if (len > 1)
			wpa_printf(MSG_INFO, "EAP-pwd: Bad response! "
				   "Fragmenting but not an ACK");
		else
			wpa_printf(MSG_DEBUG, "EAP-pwd: received ACK from "
				   "peer");
		return;
	}
	/*
	 * if we're receiving fragmented packets then we need to buffer...
	 *
	 * the first fragment has a total length
	 */
	if (EAP_PWD_GET_LENGTH_BIT(lm_exch)) {
		if (len < 2) {
			wpa_printf(MSG_DEBUG,
				   "EAP-pwd: Frame too short to contain Total-Length field");
			return;
		}
		tot_len = WPA_GET_BE16(pos);
		wpa_printf(MSG_DEBUG, "EAP-pwd: Incoming fragments, total "
			   "length = %d", tot_len);
		if (tot_len > 15000)
			return;
		if (data->inbuf) {
			wpa_printf(MSG_DEBUG,
				   "EAP-pwd: Unexpected new fragment start when previous fragment is still in use");
			return;
		}
		data->inbuf = wpabuf_alloc(tot_len);
		if (data->inbuf == NULL) {
			wpa_printf(MSG_INFO, "EAP-pwd: Out of memory to "
				   "buffer fragments!");
			return;
		}
		data->in_frag_pos = 0;
		pos += sizeof(u16);
		len -= sizeof(u16);
	}
	/*
	 * the first and all intermediate fragments have the M bit set
	 */
	if (EAP_PWD_GET_MORE_BIT(lm_exch) || data->in_frag_pos) {
		if (!data->inbuf) {
			wpa_printf(MSG_DEBUG,
				   "EAP-pwd: No buffer for reassembly");
			eap_pwd_state(data, FAILURE);
			return;
		}
		if ((data->in_frag_pos + len) > wpabuf_size(data->inbuf)) {
			wpa_printf(MSG_DEBUG, "EAP-pwd: Buffer overflow "
				   "attack detected! (%d+%d > %d)",
				   (int) data->in_frag_pos, (int) len,
				   (int) wpabuf_size(data->inbuf));
			eap_pwd_state(data, FAILURE);
			return;
		}
		wpabuf_put_data(data->inbuf, pos, len);
		data->in_frag_pos += len;
	}
	if (EAP_PWD_GET_MORE_BIT(lm_exch)) {
		wpa_printf(MSG_DEBUG, "EAP-pwd: Got a %d byte fragment",
			   (int) len);
		return;
	}
	/*
	 * last fragment won't have the M bit set (but we're obviously
	 * buffering fragments so that's how we know it's the last)
	 */
	if (data->in_frag_pos && data->inbuf) {
		pos = wpabuf_head_u8(data->inbuf);
		len = data->in_frag_pos;
		wpa_printf(MSG_DEBUG, "EAP-pwd: Last fragment, %d bytes",
			   (int) len);
	}
	switch (EAP_PWD_GET_EXCHANGE(lm_exch)) {
	case EAP_PWD_OPCODE_ID_EXCH:
		eap_pwd_process_id_resp(sm, data, pos, len);
		break;
	case EAP_PWD_OPCODE_COMMIT_EXCH:
		eap_pwd_process_commit_resp(sm, data, pos, len);
		break;
	case EAP_PWD_OPCODE_CONFIRM_EXCH:
		eap_pwd_process_confirm_resp(sm, data, pos, len);
		break;
	}
	/*
	 * if we had been buffering fragments, here's a great place
	 * to clean up
	 */
	if (data->in_frag_pos) {
		wpabuf_free(data->inbuf);
		data->inbuf = NULL;
		data->in_frag_pos = 0;
	}
}


static u8 * eap_pwd_getkey(struct eap_sm *sm, void *priv, size_t *len)
{
	struct eap_pwd_data *data = priv;
	u8 *key;

	if (data->state != SUCCESS)
		return NULL;

	key = os_memdup(data->msk, EAP_MSK_LEN);
	if (key == NULL)
		return NULL;

	*len = EAP_MSK_LEN;

	return key;
}


static u8 * eap_pwd_get_emsk(struct eap_sm *sm, void *priv, size_t *len)
{
	struct eap_pwd_data *data = priv;
	u8 *key;

	if (data->state != SUCCESS)
		return NULL;

	key = os_memdup(data->emsk, EAP_EMSK_LEN);
	if (key == NULL)
		return NULL;

	*len = EAP_EMSK_LEN;

	return key;
}


static bool eap_pwd_is_success(struct eap_sm *sm, void *priv)
{
	struct eap_pwd_data *data = priv;
	return data->state == SUCCESS;
}


static bool eap_pwd_is_done(struct eap_sm *sm, void *priv)
{
	struct eap_pwd_data *data = priv;
	return (data->state == SUCCESS) || (data->state == FAILURE);
}


static u8 * eap_pwd_get_session_id(struct eap_sm *sm, void *priv, size_t *len)
{
	struct eap_pwd_data *data = priv;
	u8 *id;

	if (data->state != SUCCESS)
		return NULL;

	id = os_memdup(data->session_id, 1 + SHA256_MAC_LEN);
	if (id == NULL)
		return NULL;

	*len = 1 + SHA256_MAC_LEN;

	return id;
}


int eap_server_pwd_register(void)
{
	struct eap_method *eap;

	eap = eap_server_method_alloc(EAP_SERVER_METHOD_INTERFACE_VERSION,
				      EAP_VENDOR_IETF, EAP_TYPE_PWD,
				      "PWD");
	if (eap == NULL)
		return -1;

	eap->init = eap_pwd_init;
	eap->reset = eap_pwd_reset;
	eap->buildReq = eap_pwd_build_req;
	eap->check = eap_pwd_check;
	eap->process = eap_pwd_process;
	eap->isDone = eap_pwd_is_done;
	eap->getKey = eap_pwd_getkey;
	eap->get_emsk = eap_pwd_get_emsk;
	eap->isSuccess = eap_pwd_is_success;
	eap->getSessionId = eap_pwd_get_session_id;

	return eap_server_method_register(eap);
}