compose.c

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/*
 * eap.c    rfc2284 & rfc2869 implementation
 *
 * Version:     $Id: 908b87943621688589c6f80cd66c11121d1db4e0 $
 *
 *   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 2000-2003,2006 The FreeRADIUS server project
 * @copyright 2001 hereUare Communications, Inc. (raghud@hereuare.com)
 * @copyright 2003 Alan DeKok (aland@freeradius.org)
 */
/*
 *  EAP PACKET FORMAT
 *  --- ------ ------
 *  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           |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |    Data ...
 * +-+-+-+-+
 *
 *
 * EAP Request and Response Packet Format
 * --- ------- --- -------- ------ ------
 *  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      |  Type-Data ...
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
 *
 *
 * EAP Success and Failure Packet Format
 * --- ------- --- ------- ------ ------
 *  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           |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 *
 */
#define LOG_PREFIX "eap"
#include <freeradius-devel/server/modpriv.h>
#include <freeradius-devel/server/pair.h>
#include <freeradius-devel/radius/radius.h>
#include <ctype.h>
 
#include "attrs.h"
#include "compose.h"
 
RCSID("$Id: 908b87943621688589c6f80cd66c11121d1db4e0 $")
 
static char const *eap_codes[] = {
         "",                            /* 0 is invalid */
        "Request",
        "Response",
        "Success",
        "Failure"
};
 
/*
 *      EAP packet format to be sent over the wire
 *
 *      i.e. code+id+length+data where data = null/type+typedata
 *      based on code.
 *
 * INPUT to function is reply->code
 *                    reply->id
 *                    reply->type   - setup with data
 *
 * OUTPUT reply->packet is setup with wire format, and will
 *                    be allocated to the right size.
 *
 */
static int eap_wireformat(eap_packet_t *reply)
{
        eap_packet_raw_t        *header;
        uint16_t                total_length = 0;
 
        if (!reply) return 0;
 
        /*
         *      If reply->packet is set, then the wire format
         *      has already been calculated, just succeed.
         */
        if(reply->packet != NULL) return 0;
 
        total_length = EAP_HEADER_LEN;
        if (reply->code == FR_EAP_CODE_REQUEST) {
                total_length += 1/* EAP Method */;
                if (reply->type.data && (reply->type.length > 0)) {
                        if (reply->type.length > (size_t) (UINT16_MAX - total_length)) {
                                fr_strerror_const("EAP type data too large for wire format");
                                return -1;
                        }
                        total_length += reply->type.length;
                }
        }
 
        reply->packet = talloc_array(reply, uint8_t, total_length);
        if (!reply->packet) {
                return -1;
        }
 
        header = (eap_packet_raw_t *)reply->packet;
        header->code = (reply->code & 0xFF);
        header->id = (reply->id & 0xFF);
 
        total_length = htons(total_length);
        memcpy(header->length, &total_length, sizeof(total_length));
 
        /*
         *      Request and Response packets are special.
         */
        if ((reply->code == FR_EAP_CODE_REQUEST) ||
            (reply->code == FR_EAP_CODE_RESPONSE)) {
                header->data[0] = (reply->type.num & 0xFF);
 
                /*
                 * Here since we cannot know the typedata format and length
                 *
                 * Type_data is expected to be wired by each EAP-Type
                 *
                 * Zero length/No typedata is supported as long as
                 * type is defined
                 */
                if (reply->type.data && reply->type.length > 0) {
                        memcpy(&header->data[1], reply->type.data, reply->type.length);
                        talloc_free(reply->type.data);
                        reply->type.data = reply->packet + EAP_HEADER_LEN + 1/*EAPtype*/;
                }
        }
 
        return 0;
}
 
/*
 *      compose EAP reply packet in EAP-Message attr of RADIUS.
 *
 *      Set the RADIUS reply codes based on EAP request codes.  Append
 *      any additional VPs to RADIUS reply
 */
rlm_rcode_t eap_compose(eap_session_t *eap_session)
{
        fr_pair_t *vp;
        eap_packet_raw_t *eap_packet;
        request_t *request;
        eap_round_t *eap_round;
        eap_packet_t *reply;
        int rcode;
 
        eap_session = talloc_get_type_abort(eap_session, eap_session_t);
        request = talloc_get_type_abort(eap_session->request, request_t);
        eap_round = talloc_get_type_abort(eap_session->this_round, eap_round_t);
        reply = talloc_get_type_abort(eap_round->request, eap_packet_t);
 
        /*
         *      The Id for the EAP packet to the NAS wasn't set.
         *      Do so now.
         */
        if (!eap_round->set_request_id) {
                /*
                 *      Id serves to support request/response
                 *      retransmission in the EAP layer and as such
                 *      must be different for 'adjacent' packets
                 *      except in case of success/failure-replies.
                 *
                 *      RFC2716 (EAP-TLS) requires this to be
                 *      incremented, RFC2284 only makes the above-
                 *      mentioned restriction.
                 */
                reply->id = eap_session->this_round->response->id;
 
                switch (reply->code) {
                /*
                 *      The Id is a simple "ack" for success
                 *      and failure.
                 *
                 *      RFC 3748 section 4.2 says
                 *
                 *      ... The Identifier field MUST match
                 *      the Identifier field of the Response
                 *      packet that it is sent in response
                 *      to.
                 */
                case FR_EAP_CODE_SUCCESS:
                case FR_EAP_CODE_FAILURE:
                        break;
 
                /*
                 *      We've sent a response to their
                 *      request, the Id is incremented.
                 */
                default:
                        ++reply->id;
                }
        }
 
        /*
         *      For Request & Response packets, set the EAP sub-type,
         *      if the EAP sub-module didn't already set it.
         *
         *      This allows the TLS module to be "morphic", and means
         *      that the TTLS and PEAP modules can call it to do most
         *      of their dirty work.
         */
        if (((eap_round->request->code == FR_EAP_CODE_REQUEST) ||
             (eap_round->request->code == FR_EAP_CODE_RESPONSE)) &&
            (eap_round->request->type.num == 0)) {
                fr_assert(eap_session->type >= FR_EAP_METHOD_MD5);
                fr_assert(eap_session->type < FR_EAP_METHOD_MAX);
 
                eap_round->request->type.num = eap_session->type;
        }
 
        if (eap_wireformat(reply) < 0) return RLM_MODULE_INVALID;
 
        eap_packet = (eap_packet_raw_t *)reply->packet;
 
        MEM(pair_append_reply(&vp, attr_eap_message) >= 0);
        fr_pair_value_memdup_shallow(vp, talloc_steal(vp, reply->packet),
                                     eap_packet->length[0] * 256 + eap_packet->length[1], false);
        reply->packet = NULL;
 
        /*
         *      EAP-Message is always associated with
         *      Message-Authenticator but not vice-versa.
         *
         *      Don't add a Message-Authenticator if
         *      it's already there.
         */
        vp = fr_pair_find_by_da(&request->reply_pairs, NULL, attr_message_authenticator);
        if (!vp) {
                static uint8_t auth_vector[RADIUS_AUTH_VECTOR_LENGTH] = { 0x00 };
 
                MEM(pair_append_reply(&vp, attr_message_authenticator) >= 0);
                fr_pair_value_memdup(vp, auth_vector, sizeof(auth_vector), false);
        }
 
        switch (reply->code) {
        case FR_EAP_CODE_RESPONSE:
                request->reply->code = FR_RADIUS_CODE_ACCESS_ACCEPT;
                rcode = RLM_MODULE_HANDLED;
                break;
 
        case FR_EAP_CODE_SUCCESS:
                request->reply->code = FR_RADIUS_CODE_ACCESS_ACCEPT;
                rcode = RLM_MODULE_OK;
                break;
 
        case FR_EAP_CODE_FAILURE:
                request->reply->code = FR_RADIUS_CODE_ACCESS_REJECT;
                rcode = RLM_MODULE_REJECT;
                break;
 
        case FR_EAP_CODE_REQUEST:
                request->reply->code = FR_RADIUS_CODE_ACCESS_CHALLENGE;
                rcode = RLM_MODULE_HANDLED;
                break;
 
        default:
                /* Should never enter here */
                REDEBUG("Reply code %u is unknown, rejecting the request", reply->code);
                request->reply->code = FR_RADIUS_CODE_ACCESS_REJECT;
                eap_packet->code = reply->code = FR_EAP_CODE_FAILURE;
                rcode = RLM_MODULE_REJECT;
                break;
        }
 
        RDEBUG2("Sending EAP %s (code %d) ID %d length %i",
                eap_codes[reply->code], reply->code, reply->id,
                eap_packet->length[0] * 256 + eap_packet->length[1]);
 
        return rcode;
}
 
/*
 *      Code to return when we either ignore unknown EAP types (so that they can be proxied), or else we fail,
 *      so that we reject them.
 */
static const rlm_rcode_t rcode_ignore[2] = {
        RLM_MODULE_FAIL, RLM_MODULE_NOOP,
};
 
/*
 *      Start or continue an EAP session.
 */
rlm_rcode_t eap_start(request_t *request, rlm_eap_method_t const methods[], bool ignore_unknown_types)
{
        fr_pair_t *vp;
        fr_pair_t *eap_msg;
 
        eap_msg = fr_pair_find_by_da(&request->request_pairs, NULL, attr_eap_message);
        if (!eap_msg) {
                RDEBUG2("No EAP-Message, not doing EAP");
                return RLM_MODULE_NOOP;
        }
 
        /*
         *      Look for EAP-Type = None (FreeRADIUS specific attribute)
         *      this allows you to NOT do EAP for some users.
         */
        vp = fr_pair_find_by_da(&request->request_pairs, NULL, attr_eap_type);
        if (vp && vp->vp_uint32 == 0) {
                RDEBUG2("Found EAP-Message, but EAP-Type = None, so we're not doing EAP");
                return RLM_MODULE_NOOP;
        }
 
        /*
         *      Check the length before dereferencing the contents.
         *
         *      Lengths of zero are required by the RFC for EAP-Start,
         *      but we've never seen them in practice.
         *
         *      Lengths of two are what we see in practice as
         *      EAP-Starts.
         */
        if ((eap_msg->vp_length == 0) || (eap_msg->vp_length == 2)) {
                uint8_t *p;
 
                RDEBUG2("Got EAP_START message");
 
                MEM(pair_append_reply(&vp, attr_eap_message) >= 0);
 
                /*
                 *      Manually create an EAP Identity request
                 */
                MEM(fr_pair_value_mem_alloc(vp, &p, 5, false) == 0);
                p[0] = FR_EAP_CODE_REQUEST;
                p[1] = 0; /* ID */
                p[2] = 0;
                p[3] = 5; /* length */
                p[4] = FR_EAP_METHOD_IDENTITY;
 
                return RLM_MODULE_HANDLED;
        } /* end of handling EAP-Start */
 
        /*
         *      Supplicants don't usually send EAP-Failures to the server, but they're not forbidden from
         *      doing so.
         *
         *      This behaviour was observed with a Spirent Avalanche test server.
         */
        if ((eap_msg->vp_octets[0] == FR_EAP_CODE_FAILURE) &&
            (eap_msg->vp_length >= EAP_HEADER_LEN)) {
                REDEBUG("Peer sent EAP %s (code %i) ID %d length %zu",
                        eap_codes[eap_msg->vp_octets[0]],
                        eap_msg->vp_octets[0],
                        eap_msg->vp_octets[1],
                        eap_msg->vp_length);
                return RLM_MODULE_FAIL;
        }
 
        /*
         *      The EAP packet header is 4 bytes, plus one byte of EAP sub-type.  Short packets are invalid,
         *      and are discarded.
         */
        if (eap_msg->vp_length < (EAP_HEADER_LEN + 1)) {
                RDEBUG2("Ignoring EAP-Message which is too short to be meaningful");
                return RLM_MODULE_INVALID;
        }
 
        /*
         *      We only get EAP RESPONSE from the supplicant.
         *
         *      LEAP sent requests from the supplicant, but that has been removed for years.
         */
        if (eap_msg->vp_octets[0] != FR_EAP_CODE_RESPONSE) {
                RDEBUG2("Ignoring unexpected EAP code %d", eap_msg->vp_octets[0]);
                return RLM_MODULE_INVALID;
        }
 
        if ((eap_msg->vp_octets[4] == 0) ||
            (eap_msg->vp_octets[4] == FR_EAP_METHOD_NOTIFICATION)) {
                RDEBUG2("Ignoring invalid EAP type %d", eap_msg->vp_octets[4]);
                return RLM_MODULE_INVALID;
        }
 
        /*
         *      Create an EAP-Type containing the EAP-type
         *      from the packet.
         */
        MEM(pair_append_request(&vp, attr_eap_type) >= 0);
        vp->vp_uint32 = eap_msg->vp_octets[4];
 
        /*
         *      From now on, we're supposed to be handling the
         *      EAP packet.  We better understand it...
         */
 
        RDEBUG2("Peer sent EAP %s (code %i) ID %d length %zu Type %d",
                eap_codes[eap_msg->vp_octets[0]],
                eap_msg->vp_octets[0],
                eap_msg->vp_octets[1],
                eap_msg->vp_length,
                eap_msg->vp_octets[4]);
 
        /*
         *      We return ok in response to EAP identity This means we can write:
         *
         *              eap {
         *                      ok = return
         *              }
         *              ldap
         *              sql
         *
         *      ...in the inner-tunnel, to avoid expensive and unnecessary SQL/LDAP lookups.
         */
        if (eap_msg->vp_octets[4] == FR_EAP_METHOD_IDENTITY) {
                RDEBUG2("Peer sent EAP-Identity.  Returning 'ok' so we can short-circuit the rest of authorize");
                return RLM_MODULE_OK;
        }
 
        /*
         *      They're NAKing the EAP type that we proposed.
         *
         *      NAK is code + id + length[2] + NAK + requested EAP type(s).
         */
        if (eap_msg->vp_octets[4] == FR_EAP_METHOD_NAK) {
                uint8_t type;
 
                /*
                 *      Empty NAK means we just fail.
                 */
                if (eap_msg->vp_length == (EAP_HEADER_LEN + 1)) {
                        RDEBUG2("Received NAK with no proposed EAP types");
                        return RLM_MODULE_FAIL;
                }
 
                /*
                 *      @todo - walk over the EAP types to be sure that there is at least one which we
                 *      support.
                 */
                type = eap_msg->vp_octets[5];
 
                /*
                 *      Can't NAK,and ask for Invalid, Identity, Notification, or NAK.
                 */
                if (type < FR_EAP_METHOD_MD5) {
                        RDEBUG2("Ignoring NAK for invalid EAP type %d", type);
                        return RLM_MODULE_FAIL;
                }
 
                if (type >= FR_EAP_METHOD_MAX) {
                        RDEBUG2("Ignoring NAK for unknown EAP type %d", type);
                        return rcode_ignore[ignore_unknown_types];
                }
 
                if (!methods[type].submodule) {
                        RDEBUG2("Ignoring NAK for unsupported EAP type %d", eap_msg->vp_octets[4]);
                        return rcode_ignore[ignore_unknown_types];
                }
 
                /*
                 *      Else the NAK is for a method that we support.
                 */
                return RLM_MODULE_OK;
        }
 
        /*
         *      Valid, but something we don't implement at all.
         */
        if (eap_msg->vp_octets[4] >= FR_EAP_METHOD_MAX) {
                RDEBUG2("Ignoring unknown EAP type %d", eap_msg->vp_octets[4]);
                return rcode_ignore[ignore_unknown_types];
        }
 
        /*
         *      Known (potentially), but not currently configured.
         */
        if (!methods[eap_msg->vp_octets[4]].submodule) {
                RDEBUG2("Ignoring unsupported EAP type %d", eap_msg->vp_octets[4]);
                return rcode_ignore[ignore_unknown_types];
        }
 
        /*
         *      Later EAP messages are longer than the 'start'
         *      message, so if everything is OK, this function returns
         *      'no start found', so that the rest of the EAP code can
         *      use the State attribute to match this EAP-Message to
         *      an ongoing conversation.
         */
        RDEBUG2("Continuing on-going EAP conversation");
 
        return RLM_MODULE_NOTFOUND;
}
 
rlm_rcode_t eap_continue(eap_session_t *eap_session)
{
        eap_session->this_round->request->code = FR_EAP_CODE_REQUEST;
        eap_session->finished = false;
 
        return eap_compose(eap_session);
}
 
/*
 *      compose EAP FAILURE packet in EAP-Message
 */
rlm_rcode_t eap_fail(eap_session_t *eap_session)
{
        /*
         *      Delete any previous replies.
         */
        fr_pair_delete_by_da(&eap_session->request->reply_pairs, attr_eap_message);
        fr_pair_delete_by_da(&eap_session->request->reply_pairs, attr_state);
 
        talloc_free(eap_session->this_round->request);
        eap_session->this_round->request = talloc_zero(eap_session->this_round, eap_packet_t);
        eap_session->this_round->request->code = FR_EAP_CODE_FAILURE;
        eap_session->finished = true;
 
        return eap_compose(eap_session);
}
 
/*
 *      compose EAP SUCCESS packet in EAP-Message
 */
rlm_rcode_t eap_success(eap_session_t *eap_session)
{
        eap_session->this_round->request->code = FR_EAP_CODE_SUCCESS;
        eap_session->finished = true;
 
        return eap_compose(eap_session);
}
 
/*
 * Allocate a new eap_packet_t
 */
static eap_round_t *eap_round_alloc(eap_session_t *eap_session)
{
        eap_round_t     *eap_round;
 
        eap_round = talloc_zero(eap_session, eap_round_t);
        if (!eap_round) return NULL;
 
        eap_round->response = talloc_zero(eap_round, eap_packet_t);
        if (!eap_round->response) {
                talloc_free(eap_round);
                return NULL;
        }
        eap_round->request = talloc_zero(eap_round, eap_packet_t);
        if (!eap_round->request) {
                talloc_free(eap_round);
                return NULL;
        }
 
        return eap_round;
}
 
/*
 *      Create our Request-Response data structure with the eap packet
 */
eap_round_t *eap_round_build(eap_session_t *eap_session, eap_packet_raw_t **eap_packet_p)
{
        eap_round_t             *eap_round = NULL;
        int                     typelen;
        eap_packet_raw_t        *eap_packet = *eap_packet_p;
        uint16_t                len;
 
        eap_round = eap_round_alloc(eap_session);
        if (eap_round == NULL) return NULL;
 
        eap_round->response->packet = (uint8_t *)eap_packet;
        (void) talloc_steal(eap_round, eap_packet);
        eap_round->response->code = eap_packet->code;
        eap_round->response->id = eap_packet->id;
        eap_round->response->type.num = eap_packet->data[0];
 
        memcpy(&len, eap_packet->length, sizeof(uint16_t));
        len = ntohs(len);
        eap_round->response->length = len;
 
        /*
         *      We've eaten the eap packet into the eap_round.
         */
        *eap_packet_p = NULL;
 
        /*
         *      First 5 bytes in eap, are code + id + length(2) + type.
         *
         *      The rest is type-specific data.  We skip type while
         *      getting typedata from data.
         */
        typelen = len - 5/*code + id + length + type */;
        if (typelen > 0) {
                /*
                 *      Since the packet contains the complete
                 *      eap_packet, typedata will be a ptr in packet
                 *      to its typedata
                 */
                eap_round->response->type.data = eap_round->response->packet + 5/*code+id+length+type*/;
                eap_round->response->type.length = typelen;
        } else {
                eap_round->response->type.length = 0;
                eap_round->response->type.data = NULL;
        }
 
        return eap_round;
}