chbind.c

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/*
 *   This program is 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
 */
 
/**
 * $Id: fb2881fd45834f51bea41c3655c3c0f028c539ff $
 * @file lib/eap/chbind.c
 * @brief Channel binding
 *
 * @copyright 2014 Network RADIUS SAS
 * @copyright 2014 The FreeRADIUS server project
 */
 
RCSID("$Id: fb2881fd45834f51bea41c3655c3c0f028c539ff $")
 
#include <freeradius-devel/radius/defs.h>
#include <freeradius-devel/radius/radius.h>
#include <freeradius-devel/server/auth.h>
 
#include <freeradius-devel/io/pair.h>
#include "chbind.h"
#include "attrs.h"
 
static bool chbind_build_response(request_t *request, CHBIND_REQ *chbind)
{
        ssize_t                 slen;
        size_t                  total;
        uint8_t                 *ptr, *start, *end;
        fr_pair_t               const *vp;
        fr_dcursor_t            cursor;
 
        total = 0;
        for (vp = fr_pair_list_head(&request->reply_pairs);
             vp != NULL;
             vp = fr_pair_list_next(&request->reply_pairs, vp)) {
                /*
                 *      Skip things which shouldn't be in channel bindings.
                 */
                if (vp->da->flags.internal || (!vp->da->flags.extra && vp->da->flags.subtype)) continue;
                if (vp->da == attr_message_authenticator) continue;
 
                total += 2 + vp->vp_length;
        }
 
        /*
         *      No attributes: just send a 1-byte response code.
         */
        if (!total) {
                ptr = start = talloc_zero_array(chbind, uint8_t, 1);
        } else {
                ptr = start = 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_da(&request->control_pairs, NULL, attr_chbind_response_code);
        if (vp) {
                ptr[0] = vp->vp_uint32;
        } 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;
 
        RDEBUG2("Sending chbind response: code %i", (int )(ptr[0]));
        log_request_pair_list(L_DBG_LVL_1, request, NULL, &request->reply_pairs, NULL);
 
        /* Encode the chbind attributes into the response */
        ptr += 4;
        end = ptr + total;
 
        fr_pair_dcursor_init(&cursor, &request->reply_pairs);
        while ((vp = fr_dcursor_current(&cursor)) && (ptr < end)) {
                /*
                 *      Skip things which shouldn't be in channel bindings.
                 */
                if (vp->da->flags.internal || (!vp->da->flags.extra && vp->da->flags.subtype) ||
                    (vp->da == attr_message_authenticator)) {
                next:
                        fr_dcursor_next(&cursor);
                        continue;
                }
 
                if (vp->da == attr_message_authenticator) goto next;
 
                slen = fr_radius_encode_pair(&FR_DBUFF_TMP(ptr, end), &cursor, NULL);
                if (slen < 0) {
                        RPERROR("Failed encoding chbind response");
                        chbind->response = NULL;
                        talloc_free(start);
                        return false;
                }
 
                ptr += slen;
        }
 
        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((uint8_t const *) 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 = fr_nbo_to_uint16(ptr);
                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;
}
 
 
fr_radius_packet_code_t chbind_process(request_t *request, CHBIND_REQ *chbind)
{
        fr_radius_packet_code_t         code;
        unlang_result_t result;
        request_t       *fake = NULL;
        uint8_t const   *attr_data;
        size_t          data_len = 0;
        fr_pair_t       *vp;
        fr_radius_ctx_t common_ctx = {};
        fr_radius_decode_ctx_t packet_ctx = {};
 
        /* check input parameters */
        fr_assert((request != NULL) &&
                   (chbind != NULL) &&
                   (chbind->request != NULL) &&
                   (chbind->response == NULL));
 
        /* Set-up the fake request */
        fake = request_local_alloc_internal(request, &(request_init_args_t){ .parent = request });
        MEM(fr_pair_prepend_by_da(fake->request_ctx, &vp, &fake->request_pairs, attr_freeradius_proxied_to) >= 0);
        (void) fr_pair_value_from_str(vp, "127.0.0.1", sizeof("127.0.0.1") - 1, NULL, false);
 
        /* Add the username to the fake request */
        if (chbind->username) {
                MEM(vp = fr_pair_copy(fake->request_ctx, chbind->username));
                fr_pair_append(&fake->request_pairs, vp);
        }
 
        /*
         *      Maybe copy the State over, too?
         */
        packet_ctx.common = &common_ctx;
        packet_ctx.tmp_ctx = talloc_init_const("tmp");
 
        /* Add the channel binding attributes to the fake packet */
        data_len = chbind_get_data(chbind->request, CHBIND_NSID_RADIUS, &attr_data);
        if (data_len) {
                fr_assert(data_len <= talloc_array_length((uint8_t const *) chbind->request));
 
                packet_ctx.end = attr_data + data_len;
 
                while (data_len > 0) {
                        ssize_t attr_len;
 
                        attr_len = fr_radius_decode_pair(fake->request_ctx, &fake->request_pairs,
                                                         attr_data, data_len, &packet_ctx);
                        if (attr_len <= 0) {
                                /*
                                 *      If fr_radius_decode_pair fails, return NULL string for
                                 *      channel binding response.
                                 */
                                talloc_free(fake);
                                talloc_free(packet_ctx.tmp_ctx);
                                talloc_free(packet_ctx.tags);
 
                                return FR_RADIUS_CODE_ACCESS_ACCEPT;
                        }
                        attr_data += attr_len;
                        data_len -= attr_len;
                }
 
                talloc_free_children(packet_ctx.tmp_ctx);
        }
        talloc_free(packet_ctx.tmp_ctx);
        talloc_free(packet_ctx.tags);
 
        /*
         *      Set virtual server based on configuration for channel
         *      bindings, this is hard-coded for now.
         */
//      fake->server_cs = virtual_server_find("channel_bindings");
        fake->packet->code = FR_RADIUS_CODE_ACCESS_REQUEST;
 
        rad_virtual_server(&result, fake);
        switch (result.rcode) {
                /* If the virtual server succeeded, build a reply */
        case RLM_MODULE_OK:
        case RLM_MODULE_HANDLED:
                if (chbind_build_response(fake, chbind)) {
                        code = FR_RADIUS_CODE_ACCESS_ACCEPT;
                        break;
                }
                FALL_THROUGH;
 
                /* If we got any other response from the virtual server, it maps to a reject */
        default:
                code = FR_RADIUS_CODE_ACCESS_REJECT;
                break;
        }
 
        talloc_free(fake);
 
        return code;
}
 
/*
 *      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, fr_pair_list_t *vps)
{
        size_t                  length;
        uint8_t                 *ptr;
        fr_pair_t               *vp;
        chbind_packet_t         *packet;
        fr_dcursor_t            cursor;
 
        if (!fr_pair_dcursor_by_da_init(&cursor, vps, attr_eap_channel_binding_message)) return NULL;
 
        /*
         *      Compute the total length of the channel binding data.
         */
        length = 0;
        for (vp = fr_dcursor_current(&cursor);
             vp;
             vp = fr_dcursor_next(&cursor)) {
                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_dcursor_head(&cursor);
             vp != NULL;
             vp = fr_dcursor_next(&cursor)) {
                memcpy(ptr, vp->vp_octets, vp->vp_length);
                ptr += vp->vp_length;
        }
 
        return packet;
}
 
fr_pair_t *eap_chbind_packet2vp(TALLOC_CTX *ctx, chbind_packet_t *chbind)
{
        fr_pair_t       *vp;
 
        if (!chbind) return NULL; /* don't produce garbage */
 
        MEM(vp = fr_pair_afrom_da(ctx, attr_eap_channel_binding_message));
        fr_pair_value_memdup(vp, (uint8_t *) chbind, talloc_array_length((uint8_t *)chbind), false);
 
        return vp;
}