/*
 * rlm_eap_mschapv2.c    Handles that are called from eap
 *
 * Version:     $Id: e1f1ff4ef3c0a3afac84d90177c00c041f747597 $
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program 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 General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 *
 * Copyright 2003,2006  The FreeRADIUS server project
 */

RCSID("$Id: e1f1ff4ef3c0a3afac84d90177c00c041f747597 $")

#include <stdio.h>
#include <stdlib.h>

#include "eap_mschapv2.h"

#include <freeradius-devel/rad_assert.h>

typedef struct rlm_eap_mschapv2_t {
	bool with_ntdomain_hack;
	bool send_error;
} rlm_eap_mschapv2_t;

static CONF_PARSER module_config[] = {
	{ "with_ntdomain_hack",     PW_TYPE_BOOLEAN,
	  offsetof(rlm_eap_mschapv2_t,with_ntdomain_hack), NULL, "no" },

	{ "send_error",     PW_TYPE_BOOLEAN,
	  offsetof(rlm_eap_mschapv2_t,send_error), NULL, "no" },

	{ NULL, -1, 0, NULL, NULL }		/* end the list */
};


static void fix_mppe_keys(eap_handler_t *handler, mschapv2_opaque_t *data)
{
	pairfilter(data, &data->mppe_keys, &handler->request->reply->vps, 7, VENDORPEC_MICROSOFT, TAG_ANY);
	pairfilter(data, &data->mppe_keys, &handler->request->reply->vps, 8, VENDORPEC_MICROSOFT, TAG_ANY);
	pairfilter(data, &data->mppe_keys, &handler->request->reply->vps, 16, VENDORPEC_MICROSOFT, TAG_ANY);
	pairfilter(data, &data->mppe_keys, &handler->request->reply->vps, 17, VENDORPEC_MICROSOFT, TAG_ANY);
}

static void free_data(void *ptr)
{
	mschapv2_opaque_t *data = ptr;

	pairfree(&data->mppe_keys);
	pairfree(&data->reply);
	talloc_free(data);
}


/*
 *	Attach the module.
 */
static int mschapv2_attach(CONF_SECTION *cs, void **instance)
{
	rlm_eap_mschapv2_t *inst;

	*instance = inst = talloc_zero(cs, rlm_eap_mschapv2_t);
	if (!inst) return -1;

	/*
	 *	Parse the configuration attributes.
	 */
	if (cf_section_parse(cs, inst, module_config) < 0) {
		return -1;
	}

	return 0;
}


/*
 *	Compose the response.
 */
static int eapmschapv2_compose(eap_handler_t *handler, VALUE_PAIR *reply)
{
	uint8_t *ptr;
	int16_t length;
	mschapv2_header_t *hdr;
	EAP_DS *eap_ds = handler->eap_ds;

	eap_ds->request->code = PW_EAP_REQUEST;
	eap_ds->request->type.num = PW_EAP_MSCHAPV2;

	/*
	 *	Always called with vendor Microsoft
	 */
	switch (reply->da->attr) {
	case PW_MSCHAP_CHALLENGE:
		/*
		 *   0		   1		   2		   3
		 *   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
		 *  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
		 *  |     Code      |   Identifier  |	    Length	     |
		 *  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
		 *  |     Type      |   OpCode      |  MS-CHAPv2-ID |  MS-Length...
		 *  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
		 *  |   MS-Length   |  Value-Size   |  Challenge...
		 *  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
		 *  |			     Challenge...
		 *  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
		 *  |			     Name...
		 *  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
		 */
		length = MSCHAPV2_HEADER_LEN + MSCHAPV2_CHALLENGE_LEN + strlen(handler->identity);
		eap_ds->request->type.data = talloc_array(eap_ds->request,
							  uint8_t, length);
		/*
		 *	Allocate room for the EAP-MS-CHAPv2 data.
		 */
		if (!eap_ds->request->type.data) {
			return 0;
		}
		eap_ds->request->type.length = length;

		ptr = eap_ds->request->type.data;
		hdr = (mschapv2_header_t *) ptr;

		hdr->opcode = PW_EAP_MSCHAPV2_CHALLENGE;
		hdr->mschapv2_id = eap_ds->response->id + 1;
		length = htons(length);
		memcpy(hdr->ms_length, &length, sizeof(uint16_t));
		hdr->value_size = MSCHAPV2_CHALLENGE_LEN;

		ptr += MSCHAPV2_HEADER_LEN;

		/*
		 *	Copy the Challenge, success, or error over.
		 */
		memcpy(ptr, reply->vp_strvalue, reply->length);
		memcpy((ptr + reply->length), handler->identity, strlen(handler->identity));
		break;

	case PW_MSCHAP2_SUCCESS:
		/*
		 *   0		   1		   2		   3
		 *   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
		 *  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
		 *  |     Code      |   Identifier  |	    Length	     |
		 *  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
		 *  |     Type      |   OpCode      |  MS-CHAPv2-ID |  MS-Length...
		 *  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
		 *  |   MS-Length   |		    Message...
		 *  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
		 */
		DEBUG2("MSCHAP Success\n");
		length = 46;
		eap_ds->request->type.data = talloc_array(eap_ds->request,
							  uint8_t, length);
		/*
		 *	Allocate room for the EAP-MS-CHAPv2 data.
		 */
		if (!eap_ds->request->type.data) {
			return 0;
		}
		memset(eap_ds->request->type.data, 0, length);
		eap_ds->request->type.length = length;

		eap_ds->request->type.data[0] = PW_EAP_MSCHAPV2_SUCCESS;
		eap_ds->request->type.data[1] = eap_ds->response->id;
		length = htons(length);
		memcpy((eap_ds->request->type.data + 2), &length, sizeof(uint16_t));
		memcpy((eap_ds->request->type.data + 4), reply->vp_strvalue + 1, 42);
		break;

	case PW_MSCHAP_ERROR:
		DEBUG2("MSCHAP Failure\n");
		length = 4 + reply->length - 1;
		eap_ds->request->type.data = talloc_array(eap_ds->request,
							  uint8_t, length);

		/*
		 *	Allocate room for the EAP-MS-CHAPv2 data.
		 */
		if (!eap_ds->request->type.data) {
			return 0;
		}
		memset(eap_ds->request->type.data, 0, length);
		eap_ds->request->type.length = length;

		eap_ds->request->type.data[0] = PW_EAP_MSCHAPV2_FAILURE;
		eap_ds->request->type.data[1] = eap_ds->response->id;
		length = htons(length);
		memcpy((eap_ds->request->type.data + 2), &length, sizeof(uint16_t));
		/*
		 *	Copy the entire failure message.
		 */
		memcpy((eap_ds->request->type.data + 4),
		       reply->vp_strvalue + 1, reply->length - 1);
		break;

	default:
		ERROR("rlm_eap_mschapv2: Internal sanity check failed");
		return 0;
		break;
	}

	return 1;
}


/*
 *	Initiate the EAP-MSCHAPV2 session by sending a challenge to the peer.
 */
static int mschapv2_initiate(UNUSED void *instance, eap_handler_t *handler)
{
	int		i;
	VALUE_PAIR	*challenge;
	mschapv2_opaque_t *data;
	REQUEST		*request = handler->request;
	uint8_t 	*p;

	challenge = pairmake(handler, NULL,
			     "MS-CHAP-Challenge", NULL, T_OP_EQ);

	/*
	 *	Get a random challenge.
	 */
	challenge->length = MSCHAPV2_CHALLENGE_LEN;
	challenge->vp_octets = p = talloc_array(challenge, uint8_t, challenge->length);
	for (i = 0; i < MSCHAPV2_CHALLENGE_LEN; i++) {
		p[i] = fr_rand();
	}
	RDEBUG2("Issuing Challenge");

	/*
	 *	Keep track of the challenge.
	 */
	data = talloc_zero(handler, mschapv2_opaque_t);
	rad_assert(data != NULL);

	/*
	 *	We're at the stage where we're challenging the user.
	 */
	data->code = PW_EAP_MSCHAPV2_CHALLENGE;
	memcpy(data->challenge, challenge->vp_strvalue, MSCHAPV2_CHALLENGE_LEN);
	data->mppe_keys = NULL;
	data->reply = NULL;

	handler->opaque = data;
	handler->free_opaque = free_data;

	/*
	 *	Compose the EAP-MSCHAPV2 packet out of the data structure,
	 *	and free it.
	 */
	eapmschapv2_compose(handler, challenge);
	pairfree(&challenge);

#ifdef WITH_PROXY
	/*
	 *	The EAP session doesn't have enough information to
	 *	proxy the "inside EAP" protocol.  Disable EAP proxying.
	 */
	handler->request->options &= ~RAD_REQUEST_OPTION_PROXY_EAP;
#endif

	/*
	 *	We don't need to authorize the user at this point.
	 *
	 *	We also don't need to keep the challenge, as it's
	 *	stored in 'handler->eap_ds', which will be given back
	 *	to us...
	 */
	handler->stage = AUTHENTICATE;

	return 1;
}

#ifdef WITH_PROXY
/*
 *	Do post-proxy processing,
 *	0 = fail
 *	1 = OK.
 *
 *	Called from rlm_eap.c, eap_postproxy().
 */
static int mschap_postproxy(eap_handler_t *handler, UNUSED void *tunnel_data)
{
	VALUE_PAIR *response = NULL;
	mschapv2_opaque_t *data;
	REQUEST *request = handler->request;

	data = (mschapv2_opaque_t *) handler->opaque;
	rad_assert(data != NULL);
	rad_assert(request != NULL);

	RDEBUG2("Passing reply from proxy back into the tunnel %d.",
		request->reply->code);

	/*
	 *	There is only a limited number of possibilities.
	 */
	switch (request->reply->code) {
	case PW_AUTHENTICATION_ACK:
		RDEBUG2("Proxied authentication succeeded.");

		/*
		 *	Move the attribute, so it doesn't go into
		 *	the reply.
		 */
		pairfilter(data, &response,
			  &request->reply->vps,
			  PW_MSCHAP2_SUCCESS, VENDORPEC_MICROSOFT, TAG_ANY);
		break;

	default:
	case PW_AUTHENTICATION_REJECT:
		RDEBUG("Proxied authentication did not succeed.");
		return 0;
	}

	/*
	 *	No response, die.
	 */
	if (!response) {
		REDEBUG("Proxied reply contained no MS-CHAP-Success or MS-CHAP-Error");
		return 0;
	}

	/*
	 *	Done doing EAP proxy stuff.
	 */
	request->options &= ~RAD_REQUEST_OPTION_PROXY_EAP;
	eapmschapv2_compose(handler, response);
	data->code = PW_EAP_MSCHAPV2_SUCCESS;

	/*
	 *	Delete MPPE keys & encryption policy
	 *
	 *	FIXME: Use intelligent names...
	 */
	fix_mppe_keys(handler, data);

	/*
	 * save any other attributes for re-use in the final
	 * access-accept e.g. vlan, etc. This lets the PEAP
	 * use_tunneled_reply code work
	 */
	data->reply = paircopy(data, request->reply->vps);

	/*
	 *	And we need to challenge the user, not ack/reject them,
	 *	so we re-write the ACK to a challenge.  Yuck.
	 */
	request->reply->code = PW_ACCESS_CHALLENGE;
	pairfree(&response);

	return 1;
}
#endif

/*
 *	Authenticate a previously sent challenge.
 */
static int mschapv2_authenticate(void *arg, eap_handler_t *handler)
{
	int rcode, ccode;
	uint8_t *p;
	mschapv2_opaque_t *data;
	EAP_DS *eap_ds = handler->eap_ds;
	VALUE_PAIR *challenge, *response, *name;
	rlm_eap_mschapv2_t *inst = (rlm_eap_mschapv2_t *) arg;
	REQUEST *request = handler->request;

	rad_assert(request != NULL);
	rad_assert(handler->stage == AUTHENTICATE);

	data = (mschapv2_opaque_t *) handler->opaque;

	/*
	 *	Sanity check the response.
	 */
	if (eap_ds->response->length <= 5) {
		REDEBUG("corrupted data");
		return 0;
	}

	ccode = eap_ds->response->type.data[0];

	switch (data->code) {
		case PW_EAP_MSCHAPV2_FAILURE:
			if (ccode == PW_EAP_MSCHAPV2_RESPONSE) {
				RDEBUG2("authentication re-try from client after we sent a failure");
				break;
			}

			/*
			 * if we sent error 648 (password expired) to the client
			 * we might get an MSCHAP-CPW packet here; turn it into a
			 * regular MS-CHAP2-CPW packet and pass it to rlm_mschap
			 * (or proxy it, I guess)
			 */
			if (ccode == PW_EAP_MSCHAPV2_CHGPASSWD) {
				VALUE_PAIR *cpw;
				int mschap_id = eap_ds->response->type.data[1];
				int copied=0,seq=1;

				RDEBUG2("password change packet received");

				challenge = pairmake_packet("MS-CHAP-Challenge", NULL, T_OP_EQ);
				if (!challenge) {
					return 0;
				}
				pairmemcpy(challenge, data->challenge, MSCHAPV2_CHALLENGE_LEN);

				cpw = pairmake_packet("MS-CHAP2-CPW", NULL, T_OP_EQ);
				cpw->length = 68;

				cpw->vp_octets = p = talloc_array(cpw, uint8_t, cpw->length);
				p[0] = 7;
				p[1] = mschap_id;
				memcpy(p + 2, eap_ds->response->type.data + 520, 66);

				/*
				 * break the encoded password into VPs (3 of them)
				 */
				while (copied < 516) {
					VALUE_PAIR *nt_enc;

					int to_copy = 516 - copied;
					if (to_copy > 243)
						to_copy = 243;

					nt_enc = pairmake_packet("MS-CHAP-NT-Enc-PW", NULL, T_OP_ADD);
					nt_enc->length = 4 + to_copy;

					nt_enc->vp_octets = p = talloc_array(nt_enc, uint8_t, nt_enc->length);

					p[0] = 6;
					p[1] = mschap_id;
					p[2] = 0;
					p[3] = seq++;

					memcpy(p + 4, eap_ds->response->type.data + 4 + copied, to_copy);
					copied += to_copy;
				}

				RDEBUG2("built change password packet");
				debug_pair_list(request->packet->vps);

				/*
				 * jump to "authentication"
				 */
				goto packet_ready;
			}

			/*
			 * we sent a failure and are expecting a failure back
			 */
			if (ccode != PW_EAP_MSCHAPV2_FAILURE) {
				REDEBUG("Sent FAILURE expecting FAILURE but got %d", ccode);
				return 0;
			}

	failure:
			request->options &= ~RAD_REQUEST_OPTION_PROXY_EAP;
			eap_ds->request->code = PW_EAP_FAILURE;
			return 1;

		case PW_EAP_MSCHAPV2_SUCCESS:
			/*
			 * we sent a success to the client; some clients send a
			 * success back as-per the RFC, some send an ACK. Permit
			 * both, I guess...
			 */

			switch (ccode) {
				case PW_EAP_MSCHAPV2_SUCCESS:
					eap_ds->request->code = PW_EAP_SUCCESS;

					pairfilter(request->reply,
						  &request->reply->vps,
						  &data->mppe_keys, 0, 0, TAG_ANY);
					/* fall through... */

				case PW_EAP_MSCHAPV2_ACK:
#ifdef WITH_PROXY
					/*
					 *	It's a success.  Don't proxy it.
					 */
					request->options &= ~RAD_REQUEST_OPTION_PROXY_EAP;
#endif
					pairfilter(request->reply,
						  &request->reply->vps,
						  &data->reply, 0, 0, TAG_ANY);
					return 1;
			}
			REDEBUG("Sent SUCCESS expecting SUCCESS (or ACK) but got %d", ccode);
			return 0;

		case PW_EAP_MSCHAPV2_CHALLENGE:
			if (ccode == PW_EAP_MSCHAPV2_FAILURE) goto failure;

			/*
			 * we sent a challenge, expecting a response
			 */
			if (ccode != PW_EAP_MSCHAPV2_RESPONSE) {
				REDEBUG("Sent CHALLENGE expecting RESPONSE but got %d", ccode);
				return 0;
			}
			/* authentication happens below */
			break;


		default:
			/* should never happen */
			REDEBUG("unknown state %d", data->code);
			return 0;
	}


	/*
	 *	Ensure that we have at least enough data
	 *	to do the following checks.
	 *
	 *	EAP header (4), EAP type, MS-CHAP opcode,
	 *	MS-CHAP ident, MS-CHAP data length (2),
	 *	MS-CHAP value length.
	 */
	if (eap_ds->response->length < (4 + 1 + 1 + 1 + 2 + 1)) {
		REDEBUG("Response is too short");
		return 0;
	}

	/*
	 *	The 'value_size' is the size of the response,
	 *	which is supposed to be the response (48
	 *	bytes) plus 1 byte of flags at the end.
	 */
	if (eap_ds->response->type.data[4] != 49) {
		REDEBUG("Response is of incorrect length %d", eap_ds->response->type.data[4]);
		return 0;
	}

	/*
	 *	The MS-Length field is 5 + value_size + length
	 *	of name, which is put after the response.
	 */
	if (((eap_ds->response->type.data[2] << 8) |
	     eap_ds->response->type.data[3]) < (5 + 49)) {
		REDEBUG("Response contains contradictory length %d %d",
			(eap_ds->response->type.data[2] << 8) |
		       eap_ds->response->type.data[3], 5 + 49);
		return 0;
	}

	/*
	 *	We now know that the user has sent us a response
	 *	to the challenge.  Let's try to authenticate it.
	 *
	 *	We do this by taking the challenge from 'data',
	 *	the response from the EAP packet, and creating VALUE_PAIR's
	 *	to pass to the 'mschap' module.  This is a little wonky,
	 *	but it works.
	 */
	challenge = pairmake_packet("MS-CHAP-Challenge", NULL, T_OP_EQ);
	if (!challenge) {
		return 0;
	}
	pairmemcpy(challenge, data->challenge, MSCHAPV2_CHALLENGE_LEN);

	response = pairmake_packet("MS-CHAP2-Response", NULL, T_OP_EQ);
	if (!response) {
		return 0;
	}

	response->length = MSCHAPV2_RESPONSE_LEN;
	response->vp_octets = p = talloc_array(response, uint8_t, response->length);

	p[0] = eap_ds->response->type.data[1];
	p[1] = eap_ds->response->type.data[5 + MSCHAPV2_RESPONSE_LEN];
	memcpy(p + 2, &eap_ds->response->type.data[5],
	       MSCHAPV2_RESPONSE_LEN - 2);

	name = pairmake_packet("MS-CHAP-User-Name", NULL, T_OP_EQ);
	if (!name) {
		return 0;
	}

	/*
	 *	MS-Length - MS-Value - 5.
	 */
	name->length = (((eap_ds->response->type.data[2] << 8) |
			 eap_ds->response->type.data[3]) -
			eap_ds->response->type.data[4] - 5);
	name->vp_octets = p = talloc_array(name, uint8_t, name->length + 1);
	memcpy(p,
	       &eap_ds->response->type.data[4 + MSCHAPV2_RESPONSE_LEN],
	       name->length);
	p[name->length] = '\0';

packet_ready:

#ifdef WITH_PROXY
	/*
	 *	If this options is set, then we do NOT authenticate the
	 *	user here.  Instead, now that we've added the MS-CHAP
	 *	attributes to the request, we STOP, and let the outer
	 *	tunnel code handle it.
	 *
	 *	This means that the outer tunnel code will DELETE the
	 *	EAP attributes, and proxy the MS-CHAP attributes to a
	 *	home server.
	 */
	if (request->options & RAD_REQUEST_OPTION_PROXY_EAP) {
		char *username = NULL;
		eap_tunnel_data_t *tunnel;

		RDEBUG2("cancelling authentication and letting it be proxied");

		/*
		 *	Set up the callbacks for the tunnel
		 */
		tunnel = talloc_zero(request, eap_tunnel_data_t);

		tunnel->tls_session = arg;
		tunnel->callback = mschap_postproxy;

		/*
		 *	Associate the callback with the request.
		 */
		rcode = request_data_add(request,
					 request->proxy,
					 REQUEST_DATA_EAP_TUNNEL_CALLBACK,
					 tunnel, false);
		rad_assert(rcode == 0);

		/*
		 *	The State attribute is NOT supposed to
		 *	go into the proxied packet, it will confuse
		 *	other RADIUS servers, and they will discard
		 *	the request.
		 *
		 *	The PEAP module will take care of adding
		 *	the State attribute back, before passing
		 *	the handler & request back into the tunnel.
		 */
		pairdelete(&request->packet->vps, PW_STATE, 0, TAG_ANY);

		/*
		 *	Fix the User-Name when proxying, to strip off
		 *	the NT Domain, if we're told to, and a User-Name
		 *	exists, and there's a \\, meaning an NT-Domain
		 *	in the user name, THEN discard the user name.
		 */
		if (inst->with_ntdomain_hack &&
		    ((challenge = pairfind(request->packet->vps, PW_USER_NAME, 0, TAG_ANY)) != NULL) &&
		    ((username = strchr(challenge->vp_strvalue, '\\')) != NULL)) {
			/*
			 *	Wipe out the NT domain.
			 *
			 *	FIXME: Put it into MS-CHAP-Domain?
			 */
			username++; /* skip the \\ */
			pairstrcpy(challenge, username);
		}

		/*
		 *	Remember that in the post-proxy stage, we've got
		 *	to do the work below, AFTER the call to MS-CHAP
		 *	authentication...
		 */
		return 1;
	}
#endif

	/*
	 *	This is a wild & crazy hack.
	 */
	rcode = process_authenticate(PW_AUTHTYPE_MS_CHAP, request);

	/*
	 *	Delete MPPE keys & encryption policy.  We don't
	 *	want these here.
	 */
	fix_mppe_keys(handler, data);

	/*
	 *	Take the response from the mschap module, and
	 *	return success or failure, depending on the result.
	 */
	response = NULL;
	if (rcode == RLM_MODULE_OK) {
		pairfilter(data, &response, &request->reply->vps,
			 PW_MSCHAP2_SUCCESS, VENDORPEC_MICROSOFT, TAG_ANY);
		data->code = PW_EAP_MSCHAPV2_SUCCESS;

	} else if (inst->send_error) {
		pairfilter(data, &response, &request->reply->vps,
			  PW_MSCHAP_ERROR, VENDORPEC_MICROSOFT, TAG_ANY);
		if (response) {
			int n,err,retry;
			char buf[34];

			RDEBUG2("MSCHAP-Error: %s", response->vp_strvalue);

			/*
			 *	Pxarse the new challenge out of the
			 *	MS-CHAP-Error, so that if the client
			 *	issues a re-try, we will know which
			 *	challenge value that they used.
			 */
			n = sscanf(response->vp_strvalue, "%*cE=%d R=%d C=%32s", &err, &retry, &buf[0]);
			if (n == 3) {
				DEBUG2("Found new challenge from MS-CHAP-Error: err=%d retry=%d challenge=%s", err, retry, buf);
				fr_hex2bin(data->challenge, buf, 16);
			} else {
				DEBUG2("Could not parse new challenge from MS-CHAP-Error: %d", n);
			}
		}
		data->code = PW_EAP_MSCHAPV2_FAILURE;
	} else {
		eap_ds->request->code = PW_EAP_FAILURE;
		return 1;
	}

	/*
	 *	No response, die.
	 */
	if (!response) {
		REDEBUG("No MS-CHAP-Success or MS-CHAP-Error was found.");
		return 0;
	}

	/*
	 *	Compose the response (whatever it is),
	 *	and return it to the over-lying EAP module.
	 */
	eapmschapv2_compose(handler, response);
	pairfree(&response);

	return 1;
}

/*
 *	The module name should be the only globally exported symbol.
 *	That is, everything else should be 'static'.
 */
rlm_eap_module_t rlm_eap_mschapv2 = {
	"eap_mschapv2",
	mschapv2_attach,		/* attach */
	mschapv2_initiate,		/* Start the initial request */
	NULL,				/* authorization */
	mschapv2_authenticate,		/* authentication */
	NULL				/* detach */
};
