/*

 *   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,

};