base.c

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/*
 *   This library is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU Lesser General Public
 *   License as published by the Free Software Foundation; either
 *   version 2.1 of the License, or (at your option) any later version.
 *
 *   This library 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
 *   Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public
 *   License along with this library; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/**
 * $Id: 1147d41d3af04d286891788b82baca5f2106cd0c $
 *
 * @file protocols/bfd/base.c
 * @brief Functions to send/receive BFD packets.
 *
 * @copyright 2023 Network RADIUS SAS (legal@networkradius.com)
 */
 
RCSID("$Id: 1147d41d3af04d286891788b82baca5f2106cd0c $")
 
#include <fcntl.h>
#include <ctype.h>
 
#include "attrs.h"
 
#include <freeradius-devel/io/pair.h>
#include <freeradius-devel/util/net.h>
#include <freeradius-devel/util/proto.h>
#include <freeradius-devel/util/udp.h>
 
static uint32_t instance_count = 0;
static bool     instantiated = false;
 
fr_dict_t const *dict_freeradius;
fr_dict_t const *dict_bfd;
 
extern fr_dict_autoload_t libfreeradius_bfd_dict[];
fr_dict_autoload_t libfreeradius_bfd_dict[] = {
        { .out = &dict_freeradius, .proto = "freeradius" },
        { .out = &dict_bfd, .proto = "bfd" },
        DICT_AUTOLOAD_TERMINATOR
};
 
fr_dict_attr_t const *attr_packet_type;
fr_dict_attr_t const *attr_bfd_packet;
fr_dict_attr_t const *attr_bfd_additional_data;
 
extern fr_dict_attr_autoload_t libfreeradius_bfd_dict_attr[];
fr_dict_attr_autoload_t libfreeradius_bfd_dict_attr[] = {
        { .out = &attr_packet_type, .name = "Packet-Type", .type = FR_TYPE_UINT32, .dict = &dict_bfd },
        { .out = &attr_bfd_packet, .name = "Packet", .type = FR_TYPE_STRUCT, .dict = &dict_bfd },
        { .out = &attr_bfd_additional_data, .name = "Additional-Data", .type = FR_TYPE_GROUP, .dict = &dict_bfd },
 
        DICT_AUTOLOAD_TERMINATOR
};
 
char const *fr_bfd_packet_names[FR_BFD_CODE_MAX] = {
        "Admin-Down",
        "Down",
        "Init",
        "Up",
};
 
fr_table_num_ordered_t const bfd_auth_type_table[] = {
        { L("none"),            BFD_AUTH_RESERVED               },
        { L("simple"),          BFD_AUTH_SIMPLE                 },
        { L("keyed-md5"),       BFD_AUTH_KEYED_MD5              },
        { L("met-keyed-md5"),   BFD_AUTH_MET_KEYED_MD5          },
        { L("keyed-sha1"),      BFD_AUTH_KEYED_SHA1             },
        { L("met-keyed-sha1"),  BFD_AUTH_MET_KEYED_SHA1         },
};
size_t const bfd_auth_type_table_len = NUM_ELEMENTS(bfd_auth_type_table);
 
/*
 *      Perform basic packet checks as per the first part of RFC 5880 Section 6.8.6.
 */
bool fr_bfd_packet_ok(char const **err, uint8_t const *packet, size_t packet_len)
{
        bfd_packet_t const *bfd;
        char const *msg = NULL;
 
        if (packet_len < FR_BFD_HEADER_LENGTH) {
                msg = "Packet is too short to be BFD";
        fail:
                if (err) *err = msg;
                return false;
        }
 
        bfd = (bfd_packet_t const *) packet;
 
        /*
         *      If the version number is not correct (1), the packet MUST be
         *      discarded.
         */
        if (bfd->version != 1) {
                msg = "Packet has wrong version - should be 1";
                goto fail;
        }
 
        /*
         *      If the Length field is less than the minimum correct value (24 if
         *      the A bit is clear, or 26 if the A bit is set), the packet MUST be
         *      discarded.
         */
        if (bfd->length < FR_BFD_HEADER_LENGTH) {
                msg = "Header length is too small";
                goto fail;
        }
 
        /*
         *      If the Length field is greater than the payload of the
         *      encapsulating protocol, the packet MUST be discarded.
         *
         *      Addendum: if the Length field is smaller than the
         *      received data, that's bad, too.
         */
        if (bfd->length > packet_len) {
                msg = "Header length is not the same as the amount of data we read";
                goto fail;
        }
 
        /*
         *      If the Length field is less than the minimum correct value (24 if
         *      the A bit is clear, or 26 if the A bit is set), the packet MUST be
         *      discarded.
         *
         *      Addendum: if the Length field is not equal to 24 plus Auth-Len field,
         *      then the packet is discarded.
         */
        if (bfd->auth_present) {
                if (bfd->length < (FR_BFD_HEADER_LENGTH + 2)) { /* auth-type and auth-len */
                        msg = "Header length is not enough for auth-type and auth-len";
                        goto fail;
                }
 
                if (bfd->length != FR_BFD_HEADER_LENGTH + bfd->auth.basic.auth_len) {
                        msg = "Header length mismatch with auth-len and amount of received data";
                        goto fail;
 
                }
 
                switch (bfd->auth.basic.auth_type) {
                case BFD_AUTH_SIMPLE:
                        if ((bfd->auth.basic.auth_len < (3 + 1)) || (bfd->auth.basic.auth_len > (3 + 16))) {
                                msg = "Auth-Type Simple has invalid value for password length";
                                goto fail;
                        }
                        break;
 
                case BFD_AUTH_KEYED_MD5:
                case BFD_AUTH_MET_KEYED_MD5:
                        if (bfd->auth.basic.auth_len != 24) {
                                msg = "Auth-Type MD5 has invalid value for digest length";
                                goto fail;
                        }
                        break;
 
                case BFD_AUTH_KEYED_SHA1:
                case BFD_AUTH_MET_KEYED_SHA1:
                        if (bfd->auth.basic.auth_len != 28) {
                                msg = "Auth-Type SHA1 has invalid value for digest length";
                                goto fail;
                        }
                        break;
 
                default:
                        msg = "Invalid Auth-Type";
                        goto fail;
                }
        }
 
        /*
         *      If the Detect Mult field is zero, the packet MUST be discarded.
         */
        if (bfd->detect_multi == 0) {
                msg = "Packet has invalid detect-multi == 0";
                goto fail;
        }
 
        /*
         *      If the Multipoint (M) bit is nonzero, the packet MUST be
         *      discarded.
         */
        if (bfd->multipoint != 0) {
                msg = "Packet has invalid multipoint != 0";
                goto fail;
        }
 
        /*
         *      If the My Discriminator field is zero, the packet MUST be
         *      discarded.
         */
        if (bfd->my_disc == 0) {
                msg = "Packet has invalid my-discriminator == 0";
                goto fail;
        }
 
        /*
         *      If the Your Discriminator field is zero and the State field is not
         *      Down or AdminDown, the packet MUST be discarded.
         */
        if ((bfd->your_disc == 0) &&
            !((bfd->state == BFD_STATE_DOWN) ||
              (bfd->state == BFD_STATE_ADMIN_DOWN))) {
                msg = "Packet has your-discrimator==0, but state is not down or admin-down";
                goto fail;
        }
 
        if (err) *err = NULL;
        return true;
}
 
 
 
int fr_bfd_global_init(void)
{
        if (instance_count > 0) {
                instance_count++;
                return 0;
        }
 
        instance_count++;
 
        if (fr_dict_autoload(libfreeradius_bfd_dict) < 0) {
        fail:
                instance_count--;
                return -1;
        }
 
        if (fr_dict_attr_autoload(libfreeradius_bfd_dict_attr) < 0) {
                fr_dict_autofree(libfreeradius_bfd_dict);
                goto fail;
        }
 
        instantiated = true;    
 
        return 0;
}
 
void fr_bfd_global_free(void)
{
        if (!instantiated) return;
 
        if (--instance_count > 0) return;
 
        fr_dict_autofree(libfreeradius_bfd_dict);
 
        instantiated = false;
}
 
extern fr_dict_protocol_t libfreeradius_bfd_dict_protocol;
fr_dict_protocol_t libfreeradius_bfd_dict_protocol = {
        .name = "bfd",
        .default_type_size = 1,
        .default_type_length = 1,
 
        .init = fr_bfd_global_init,
        .free = fr_bfd_global_free,
};