eap_tls.c

使用最广泛的radius的linux的源码

/*
 * eap_tls.c
 *
 * Version:     $Id: eap_tls.c,v 1.10 2007/12/15 14:56:10 aland Exp $
 *
 *   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 2001  hereUare Communications, Inc. <[e-mail]>
 * Copyright 2003  Alan DeKok <[e-mail]>
 * Copyright 2006  The FreeRADIUS server project
 */

/*
 *
 *  TLS Packet Format in EAP
 *  --- ------ ------ -- ---
 * 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      |     Flags     |      TLS Message Length
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |     TLS Message Length        |       TLS Data...
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 */

#include <freeradius-devel/ident.h>
RCSID("$Id: eap_tls.c,v 1.10 2007/12/15 14:56:10 aland Exp $")

#include <freeradius-devel/autoconf.h>
#include <assert.h>
#include "eap_tls.h"

/*
 *      Allocate a new TLS_PACKET
 */
EAPTLS_PACKET *eaptls_alloc(void)
{
	EAPTLS_PACKET   *rp;

	if ((rp = malloc(sizeof(EAPTLS_PACKET))) == NULL) {
		radlog(L_ERR, "rlm_eap_tls: out of memory");
		return NULL;
	}
	memset(rp, 0, sizeof(EAPTLS_PACKET));
	return rp;
}

/*
 *      Free EAPTLS_PACKET
 */
void eaptls_free(EAPTLS_PACKET **eaptls_packet_ptr)
{
	EAPTLS_PACKET *eaptls_packet;

	if (!eaptls_packet_ptr) return;
	eaptls_packet = *eaptls_packet_ptr;
	if (eaptls_packet == NULL) return;

	if (eaptls_packet->data) {
		free(eaptls_packet->data);
		eaptls_packet->data = NULL;
	}

	free(eaptls_packet);
	*eaptls_packet_ptr = NULL;
}

/*
   The S flag is set only within the EAP-TLS start message
   sent from the EAP server to the peer.
*/
int eaptls_start(EAP_DS *eap_ds, int peap_flag)
{
	EAPTLS_PACKET 	reply;

	reply.code = EAPTLS_START;
	reply.length = TLS_HEADER_LEN + 1/*flags*/;

	reply.flags = peap_flag;
	reply.flags = SET_START(reply.flags);

	reply.data = NULL;
	reply.dlen = 0;

	eaptls_compose(eap_ds, &reply);

	return 1;
}

int eaptls_success(EAP_DS *eap_ds, int peap_flag)
{
	EAPTLS_PACKET	reply;

	reply.code = EAPTLS_SUCCESS;
	reply.length = TLS_HEADER_LEN;
	reply.flags = peap_flag;
	reply.data = NULL;
	reply.dlen = 0;

	eaptls_compose(eap_ds, &reply);

	return 1;
}

int eaptls_fail(EAP_DS *eap_ds, int peap_flag)
{
	EAPTLS_PACKET	reply;

	reply.code = EAPTLS_FAIL;
	reply.length = TLS_HEADER_LEN;
	reply.flags = peap_flag;
	reply.data = NULL;
	reply.dlen = 0;

	eaptls_compose(eap_ds, &reply);

	return 1;
}

/*
   A single TLS record may be up to 16384 octets in length, but a TLS
   message may span multiple TLS records, and a TLS certificate message
   may in principle be as long as 16MB.
*/

/*
 *	Frame the Dirty data that needs to be send to the client in an
 *	EAP-Request.  We always embed the TLS-length in all EAP-TLS
 *	packets that we send, for easy reference purpose.  Handle
 *	fragmentation and sending the next fragment etc.
 */
int eaptls_request(EAP_DS *eap_ds, tls_session_t *ssn)
{
	EAPTLS_PACKET	reply;
	unsigned int	size;
	unsigned int 	nlen;
	unsigned int 	lbit = 0;

	/* This value determines whether we set (L)ength flag for
		EVERY packet we send and add corresponding
		"TLS Message Length" field.

	length_flag = TRUE;
		This means we include L flag and "TLS Msg Len" in EVERY
		packet we send out.

	length_flag = FALSE;
		This means we include L flag and "TLS Msg Len" **ONLY**
		in First packet of a fragment series. We do not use
		it anywhere else.

		Having L flag in every packet is prefered.

	*/
	if (ssn->length_flag) {
		lbit = 4;
	}
	if (ssn->fragment == 0) {
		ssn->tls_msg_len = ssn->dirty_out.used;
	}

	reply.code = EAPTLS_REQUEST;
	reply.flags = ssn->peap_flag;

	/* Send data, NOT more than the FRAGMENT size */
	if (ssn->dirty_out.used > ssn->offset) {
		size = ssn->offset;
		reply.flags = SET_MORE_FRAGMENTS(reply.flags);
		/* Length MUST be included if it is the First Fragment */
		if (ssn->fragment == 0) {
			lbit = 4;
		}
		ssn->fragment = 1;
	} else {
		size = ssn->dirty_out.used;
		ssn->fragment = 0;
	}

	reply.dlen = lbit + size;
	reply.length = TLS_HEADER_LEN + 1/*flags*/ + reply.dlen;

	reply.data = malloc(reply.dlen);
	if (lbit) {
		nlen = htonl(ssn->tls_msg_len);
		memcpy(reply.data, &nlen, lbit);
		reply.flags = SET_LENGTH_INCLUDED(reply.flags);
	}
	(ssn->record_minus)(&ssn->dirty_out, reply.data + lbit, size);

	eaptls_compose(eap_ds, &reply);
	free(reply.data);
	reply.data = NULL;

	return 1;
}

/*
 * Acknowledge received is for one of the following messages sent earlier
 * 1. Handshake completed Message, so now send, EAP-Success
 * 2. Alert Message, now send, EAP-Failure
 * 3. Fragment Message, now send, next Fragment
 */
static eaptls_status_t eaptls_ack_handler(EAP_HANDLER *handler)
{
	tls_session_t *tls_session;

	tls_session = (tls_session_t *)handler->opaque;
	if (tls_session == NULL){
		radlog(L_ERR, "rlm_eap_tls: Unexpected ACK received");
		return EAPTLS_FAIL;
	}
	if (tls_session->info.initialized == 0) {
		DEBUG("  rlm_eap_tls: No SSL info available. Waiting for more SSL data.");
		return EAPTLS_REQUEST;
	}
	if (tls_session->info.origin == 0) {
		radlog(L_ERR, "rlm_eap_tls: Unexpected ACK received");
		return EAPTLS_FAIL;
	}

	switch (tls_session->info.content_type) {
	case alert:
		DEBUG2("  rlm_eap_tls: ack alert");
		eaptls_fail(handler->eap_ds, tls_session->peap_flag);
		return EAPTLS_FAIL;

	case handshake:
		if ((tls_session->info.handshake_type == finished) &&
		    (tls_session->dirty_out.used == 0)) {
			DEBUG2("  rlm_eap_tls: ack handshake is finished");
			return EAPTLS_SUCCESS;
		} /* else more data to send */

		DEBUG2("  rlm_eap_tls: ack handshake fragment handler");
		/* Fragmentation handler, send next fragment */
		return EAPTLS_REQUEST;

		/*
		 *	For the rest of the conditions, switch over
		 *	to the default section below.
		 */
	default:
		DEBUG2("  rlm_eap_tls: ack default");
		radlog(L_ERR, "rlm_eap_tls: Invalid ACK received: %d",
		       tls_session->info.content_type);
		return EAPTLS_FAIL;
	}
}

/*
 *	Similarly, when the EAP server receives an EAP-Response with
 *	the M bit set, it MUST respond with an EAP-Request with
 *	EAP-Type=EAP-TLS and no data. This serves as a fragment ACK.
 *
 *	In order to prevent errors in the processing of fragments, the
 *	EAP server MUST use increment the Identifier value for each
 *	fragment ACK contained within an EAP-Request, and the peer
 *	MUST include this Identifier value in the subsequent fragment
 *	contained within an EAP- Reponse.
 *
 *	EAP server sends an ACK when it determines there are More
 *	fragments to receive to make the complete
 *	TLS-record/TLS-Message
 */
static int eaptls_send_ack(EAP_DS *eap_ds, int peap_flag)
{
	EAPTLS_PACKET 	reply;

	reply.code = EAPTLS_ACK;
	reply.length = TLS_HEADER_LEN + 1/*flags*/;
	reply.flags = peap_flag;
	reply.data = NULL;
	reply.dlen = 0;

	eaptls_compose(eap_ds, &reply);

	return 1;
}

/*
 *	The S flag is set only within the EAP-TLS start message sent
 *	from the EAP server to the peer.
 *
 *	Similarly, when the EAP server receives an EAP-Response with
 *	the M bit set, it MUST respond with an EAP-Request with
 *	EAP-Type=EAP-TLS and no data. This serves as a fragment
 *	ACK. The EAP peer MUST wait.
 */
static eaptls_status_t eaptls_verify(EAP_HANDLER *handler)
{
	EAP_DS *eap_ds = handler->eap_ds;
	EAP_DS *prev_eap_ds = handler->prev_eapds;
	eaptls_packet_t	*eaptls_packet, *eaptls_prev = NULL;

	/*
	 *	We don't check ANY of the input parameters.  It's all
	 *	code which works together, so if something is wrong,
	 *	we SHOULD core dump.
	 *
	 *	e.g. if eap_ds is NULL, of if eap_ds->response is
	 *	NULL, of if it's NOT an EAP-Response, or if the packet
	 *	is too short.  See eap_validation()., in ../../eap.c
	 *
	 *	Also, eaptype_select() takes care of selecting the
	 *	appropriate type, so we don't need to check
	 *	eap_ds->response->type.type == PW_EAP_TLS, or anything
	 *	else.
	 */
	eaptls_packet = (eaptls_packet_t *)eap_ds->response->type.data;
	if (prev_eap_ds && prev_eap_ds->response)
		eaptls_prev = (eaptls_packet_t *)prev_eap_ds->response->type.data;

	/*
	 *	check for ACK
	 *
	 *	If there's no TLS data, or there's 1 byte of TLS data,
	 *	with the flags set to zero, then it's an ACK.
	 *
	 *	Find if this is a reply to the previous request sent
	 */
	if ((eaptls_packet == NULL) ||
	    ((eap_ds->response->length == EAP_HEADER_LEN + 2) &&
	     ((eaptls_packet->flags & 0xc0) == 0x00))) {

#if 0
		/*
		 *	Un-comment this for TLS inside of TTLS/PEAP
		 */
		DEBUG2("rlm_eap_tls: Received EAP-TLS ACK message");
		return eaptls_ack_handler(handler);
#else
		if (prev_eap_ds->request->id == eap_ds->response->id) {
			/*
			 *	Run the ACK handler directly from here.
			 */
			DEBUG2("rlm_eap_tls: Received EAP-TLS ACK message");
			return eaptls_ack_handler(handler);
		} else {
			radlog(L_ERR, "rlm_eap_tls: Received Invalid EAP-TLS ACK message");
			return EAPTLS_INVALID;
		}
#endif
	}

	/*
	 *	We send TLS_START, but do not receive it.
	 */
	if (TLS_START(eaptls_packet->flags)) {
		radlog(L_ERR, "rlm_eap_tls:  Received unexpected EAP-TLS Start message");
		return EAPTLS_INVALID;
	}

	/*
	 *	The L bit (length included) is set to indicate the
	 *	presence of the four octet TLS Message Length field,
	 *	and MUST be set for the first fragment of a fragmented
	 *	TLS message or set of messages.
	 *
	 *	The M bit (more fragments) is set on all but the last
	 *	fragment.
	 *
	 *	The S bit (EAP-TLS start) is set in an EAP-TLS Start
	 *	message. This differentiates the EAP-TLS Start message
	 *	from a fragment acknowledgement.
	 */
	if (TLS_LENGTH_INCLUDED(eaptls_packet->flags)) {
		DEBUG2("  TLS Length %d",
		       eaptls_packet->data[2] * 256 | eaptls_packet->data[3]);
		if (TLS_MORE_FRAGMENTS(eaptls_packet->flags)) {
			/*
			 * FIRST_FRAGMENT is identified
			 * 1. If there is no previous EAP-response received.
			 * 2. If EAP-response received, then its M bit not set.
			 * 	(It is because Last fragment will not have M bit set)
			 */
			if (!prev_eap_ds ||
			    (prev_eap_ds->response == NULL) ||
			    (eaptls_prev == NULL) ||
			    !TLS_MORE_FRAGMENTS(eaptls_prev->flags)) {

				DEBUG2("rlm_eap_tls:  Received EAP-TLS First Fragment of the message");
				return EAPTLS_FIRST_FRAGMENT;
			} else {

				DEBUG2("rlm_eap_tls:  More Fragments with length included");
				return EAPTLS_MORE_FRAGMENTS_WITH_LENGTH;
			}
		} else {
			DEBUG2("rlm_eap_tls:  Length Included");
			return EAPTLS_LENGTH_INCLUDED;
		}
	}

	if (TLS_MORE_FRAGMENTS(eaptls_packet->flags)) {
		DEBUG2("rlm_eap_tls:  More fragments to follow");
		return EAPTLS_MORE_FRAGMENTS;
	}

	/*
	 *	None of the flags are set, but it's still a valid
	 *	EAPTLS packet.
	 */
	return EAPTLS_OK;
}

/*
 * EAPTLS_PACKET
 * code   =  EAP-code
 * id     =  EAP-id
 * length = code + id + length + flags + tlsdata
 *        =  1   +  1 +   2    +  1    +  X
 * length = EAP-length - 1(EAP-Type = 1 octet)
 * flags  = EAP-typedata[0] (1 octet)
 * dlen   = EAP-typedata[1-4] (4 octets), if L flag set
 *        = length - 5(code+id+length+flags), otherwise
 * data   = EAP-typedata[5-n], if L flag set
 *        = EAP-typedata[1-n], otherwise
 * packet = EAP-typedata (complete typedata)
 *
 * Points to consider during EAP-TLS data extraction
 * 1. In the received packet, No data will be present incase of ACK-NAK
 * 2. Incase if more fragments need to be received then ACK after retreiving this fragment.
 *