eap_chbind.c

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/*
 * eap_chbind.c
 *
 * Version:     $Id: 67c2e0d67a8a23f032ffe67258f0a8f6641d2524 $
 *
 *   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 2014  Network RADIUS SARL
 * Copyright 2014  The FreeRADIUS server project
 */


RCSID("$Id: 67c2e0d67a8a23f032ffe67258f0a8f6641d2524 $")

#include "eap_chbind.h"

static bool chbind_build_response(REQUEST *request, CHBIND_REQ *chbind)
{
        int length;
        size_t total;
        uint8_t *ptr, *end;
        VALUE_PAIR const *vp;
        vp_cursor_t cursor;

        total = 0;
        for (vp = fr_cursor_init(&cursor, &request->reply->vps);
             vp != NULL;
             vp = fr_cursor_next(&cursor)) {
                /*
                 *      Skip things which shouldn't be in channel bindings.
                 */
                if (vp->da->flags.encrypt != FLAG_ENCRYPT_NONE) continue;
                if (!vp->da->vendor && (vp->da->attr == PW_MESSAGE_AUTHENTICATOR)) continue;

                total += 2 + vp->vp_length;
        }

        /*
         *      No attributes: just send a 1-byte response code.
         */
        if (!total) {
                ptr = talloc_zero_array(chbind, uint8_t, 1);
        } else {
                ptr = talloc_zero_array(chbind, uint8_t, total + 4);
        }
        if (!ptr) return false;
        chbind->response = (chbind_packet_t *) ptr;

        /*
         *      Set the response code.  Default to "fail" if none was
         *      specified.
         */
        vp = fr_pair_find_by_num(request->config, 0, PW_CHBIND_RESPONSE_CODE, TAG_ANY);
        if (vp) {
                ptr[0] = vp->vp_integer;
        } else {
                ptr[0] = CHBIND_CODE_FAILURE;
        }

        if (!total) return true; /* nothing to encode */

        /* Write the length field into the header */
        ptr[1] = (total >> 8) & 0xff;
        ptr[2] = total & 0xff;
        ptr[3] = CHBIND_NSID_RADIUS;

        RDEBUG("Sending chbind response: code %i", (int )(ptr[0]));
        rdebug_pair_list(L_DBG_LVL_1, request, request->reply->vps, NULL);

        /* Encode the chbind attributes into the response */
        ptr += 4;
        end = ptr + total;

        fr_cursor_init(&cursor, &request->reply->vps);
        while ((vp = fr_cursor_current(&cursor)) && (ptr < end)) {
                /*
                 *      Skip things which shouldn't be in channel bindings.
                 */
                if (vp->da->flags.encrypt != FLAG_ENCRYPT_NONE) {
                next:
                        fr_cursor_next(&cursor);
                        continue;
                }
                if (!vp->da->vendor && (vp->da->attr == PW_MESSAGE_AUTHENTICATOR)) goto next;

                length = fr_radius_encode_pair(ptr, end - ptr, &cursor, NULL);
                ptr += length;
        }

        return true;
}


/*
 *      Parse channel binding packet to obtain data for a specific
 *      NSID.
 *
 *      See:
 *      http://tools.ietf.org/html/draft-ietf-emu-chbind-13#section-5.3.2
 */
static size_t chbind_get_data(chbind_packet_t const *packet,
                              int desired_nsid,
                              uint8_t const **data)
{
        uint8_t const *ptr;
        uint8_t const *end;

        if (packet->code != CHBIND_CODE_REQUEST) {
                return 0;
        }

        ptr = (uint8_t const *) packet;
        end = ptr + talloc_array_length(packet);

        ptr++;                  /* skip the code at the start of the packet */
        while (ptr < end) {
                uint8_t nsid;
                size_t length;

                /*
                 *      Need room for length(2) + NSID + data.
                 */
                if ((end - ptr) < 4) return 0;

                length = (ptr[0] << 8) | ptr[1];
                if (length == 0) return 0;

                if ((ptr + length + 3) > end) return 0;

                nsid = ptr[2];
                if (nsid == desired_nsid) {
                        ptr += 3;
                        *data = ptr;
                        return length;
                }

                ptr += 3 + length;
        }

        return 0;
}


PW_CODE chbind_process(REQUEST *request, CHBIND_REQ *chbind)
{
        PW_CODE rcode;
        REQUEST *fake = NULL;
        VALUE_PAIR *vp = NULL;
        uint8_t const *attr_data;
        size_t data_len = 0;

        /* check input parameters */
        rad_assert((request != NULL) &&
                   (chbind != NULL) &&
                   (chbind->request != NULL) &&
                   (chbind->response == NULL));

        /* Set-up the fake request */
        fake = request_alloc_fake(request);
        pair_make_request("Freeradius-Proxied-To", "127.0.0.1", T_OP_EQ);

        /* Add the username to the fake request */
        if (chbind->username) {
                vp = fr_pair_copy(fake->packet, chbind->username);
                fr_pair_add(&fake->packet->vps, vp);
                fake->username = vp;
        }

        /*
         *      Maybe copy the State over, too?
         */

        /* Add the channel binding attributes to the fake packet */
        data_len = chbind_get_data(chbind->request, CHBIND_NSID_RADIUS, &attr_data);
        if (data_len) {
                vp_cursor_t cursor;
                rad_assert(data_len <= talloc_array_length(chbind->request));

                fr_cursor_init(&cursor, &vp);
                while (data_len > 0) {
                        ssize_t attr_len;

                        attr_len = fr_radius_decode_pair(fake->packet, &cursor, fr_dict_root(fr_dict_internal),
                                                         attr_data, data_len, NULL);
                        if (attr_len <= 0) {
                                /* If radaddr2vp fails, return NULL string for
                                   channel binding response */
                                talloc_free(fake);
                                return PW_CODE_ACCESS_ACCEPT;
                        }
                        if (vp) {
                                fr_pair_add(&fake->packet->vps, vp);
                        }
                        attr_data += attr_len;
                        data_len -= attr_len;
                }
        }

        /*
         *      Set virtual server based on configuration for channel
         *      bindings, this is hard-coded for now.
         */
        fake->server = "channel_bindings";
        fake->packet->code = PW_CODE_ACCESS_REQUEST;

        rcode = rad_virtual_server(fake);

        switch (rcode) {
                /* If rad_authenticate succeeded, build a reply */
        case RLM_MODULE_OK:
        case RLM_MODULE_HANDLED:
                if (chbind_build_response(fake, chbind)) {
                        rcode = PW_CODE_ACCESS_ACCEPT;
                        break;
                }
                /* FALL-THROUGH */

                /* If we got any other response from rad_authenticate, it maps to a reject */
        default:
                rcode = PW_CODE_ACCESS_REJECT;
                break;
        }

        talloc_free(fake);

        return rcode;
}

/*
 *      Handles multiple EAP-channel-binding Message attrs
 *      ie concatenates all to get the complete EAP-channel-binding packet.
 */
chbind_packet_t *eap_chbind_vp2packet(TALLOC_CTX *ctx, VALUE_PAIR *vps)
{
        size_t length;
        uint8_t *ptr;
        VALUE_PAIR *first, *vp;
        chbind_packet_t *packet;
        vp_cursor_t cursor;

        first = fr_pair_find_by_num(vps, VENDORPEC_UKERNA, PW_UKERNA_CHBIND, TAG_ANY);
        if (!first) return NULL;

        /*
         *      Compute the total length of the channel binding data.
         */
        length = 0;
        for (vp =fr_cursor_init(&cursor, &first);
             vp != NULL;
             vp = fr_cursor_next_by_num(&cursor, VENDORPEC_UKERNA, PW_UKERNA_CHBIND, TAG_ANY)) {
                length += vp->vp_length;
        }

        if (length < 4) {
                DEBUG("Invalid length %u for channel binding data", (unsigned int) length);
                return NULL;
        }

        /*
         *      Now that we know the length, allocate memory for the packet.
         */
        ptr = talloc_zero_array(ctx, uint8_t, length);
        if (!ptr) return NULL;

        /*
         *      Copy the data over to our packet.
         */
        packet = (chbind_packet_t *) ptr;
        for (vp = fr_cursor_init(&cursor, &first);
             vp != NULL;
             vp = fr_cursor_next_by_num(&cursor, VENDORPEC_UKERNA, PW_UKERNA_CHBIND, TAG_ANY)) {
                memcpy(ptr, vp->vp_octets, vp->vp_length);
                ptr += vp->vp_length;
        }

        return packet;
}

VALUE_PAIR *eap_chbind_packet2vp(REQUEST *request, chbind_packet_t *packet)
{
        VALUE_PAIR      *vp;

        if (!packet) return NULL; /* don't produce garbage */

        vp = fr_pair_afrom_num(request->packet, VENDORPEC_UKERNA, PW_UKERNA_CHBIND);
        if (!vp) return NULL;
        fr_pair_value_memcpy(vp, (uint8_t *) packet, talloc_array_length((uint8_t *)packet));

        return vp;
}