/*

 *   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

 */

/**

 * $Id: 3ade5916865e76eedd14e69087b1fd0885d1d486 $

 * @file src/protocols/tftp/encode.c

 * @brief Functions to encode TFTP packets.

 * @author Jorge Pereira <jpereira@freeradius.org>

 *

 * @copyright 2021 The FreeRADIUS server project.

 * @copyright 2021 Network RADIUS SAS (legal@networkradius.com)

 */

RCSID("$Id: 3ade5916865e76eedd14e69087b1fd0885d1d486 $")

#include <freeradius-devel/util/dbuff.h>

#include <freeradius-devel/util/udp.h>

#include <freeradius-devel/io/test_point.h>

#include "tftp.h"

#include "attrs.h"

/*

 *  https://tools.ietf.org/html/rfc1350

 *

 *  Order of Headers

 *

 *                                                 2 bytes

 *   ----------------------------------------------------------

 *  |  Local Medium  |  Internet  |  Datagram  |  TFTP Opcode  |

 *   ----------------------------------------------------------

 *

 *  TFTP Formats

 *

 *  Type   Op #     Format without header

 *

 *         2 bytes    string   1 byte     string   1 byte

 *         -----------------------------------------------

 *  RRQ/  | 01/02 |  Filename  |   0  |    Mode    |   0  |

 *  WRQ    -----------------------------------------------

 *          2 bytes    2 bytes       n bytes

 *         ---------------------------------

 *  DATA  | 03    |   Block #  |    Data    |

 *         ---------------------------------

 *          2 bytes    2 bytes

 *         -------------------

 *  ACK   | 04    |   Block #  |

 *         --------------------

 *         2 bytes  2 bytes        string    1 byte

 *         ----------------------------------------

 *  ERROR | 05    |  ErrorCode |   ErrMsg   |   0  |

 *         ----------------------------------------

 *

 *  Initial Connection Protocol for reading a file

 *

 *  1. Host  A  sends  a  "RRQ"  to  host  B  with  source= A's TID,

 *     destination= 69.

 *

 *  2. Host B sends a "DATA" (with block number= 1) to host  A  with

 *     source= B's TID, destination= A's TID.

 */

ssize_t fr_tftp_encode(fr_dbuff_t *dbuff, fr_pair_list_t *vps)

{

  fr_dbuff_t  work_dbuff = FR_DBUFF_MAX(dbuff, FR_TFTP_BLOCK_MAX_SIZE);

  fr_pair_t   *vp;

  uint16_t  opcode;

  char const  *buf;

  vp = fr_pair_find_by_da(vps, NULL, attr_tftp_opcode);

  if (!vp) {

    fr_strerror_printf("Cannot send TFTP packet without %s", attr_tftp_opcode->name);

    return -1;

  }

  opcode = vp->vp_uint16;

  fr_dbuff_in(&work_dbuff, opcode);

  switch (opcode) {

  case FR_OPCODE_VALUE_READ_REQUEST:

  case FR_OPCODE_VALUE_WRITE_REQUEST:

    /*

     *  2 bytes     string    1 byte     string   1 byte   string    1 byte   string   1 byte

     *  +------------------------------------------------------------------------------------+

     *  | Opcode |  Filename  |   0  |    Mode    |   0  |  blksize  |  0  |  #blksize |  0  |

     *  +------------------------------------------------------------------------------------+

     *  Figure 5-1: RRQ/WRQ packet

     */

    /* <Filename> */

    vp = fr_pair_find_by_da(vps, NULL, attr_tftp_filename);

    if (!vp) {

      fr_strerror_printf("Invalid TFTP packet without %s", attr_tftp_filename->name);

      return -1;

    }

    FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff, vp->vp_strvalue, vp->vp_length);

    fr_dbuff_in_bytes(&work_dbuff, '\0');

    /* <mode> */

    vp = fr_pair_find_by_da(vps, NULL, attr_tftp_mode);

    if (!vp) {

      fr_strerror_printf("Invalid TFTP packet without %s", attr_tftp_mode->name);

      return -1;

    }

    switch(vp->vp_uint16) {

    case FR_MODE_VALUE_ASCII: buf = "ascii"; break;

    case FR_MODE_VALUE_OCTET: buf = "octet"; break;

    default:

      fr_strerror_printf("Invalid %s value", attr_tftp_mode->name);

      return -1;

    }

    FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff, buf, 5);

    fr_dbuff_in_bytes(&work_dbuff, '\0');

    /* <blksize> is optional */

    vp = fr_pair_find_by_da(vps, NULL, attr_tftp_block_size);

    if (vp) {

      char tmp[5+1];                                   /* max: 65535 */

      FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff, "blksize", 7);

      fr_dbuff_in_bytes(&work_dbuff, '\0');

      snprintf(tmp, sizeof(tmp), "%d", vp->vp_uint16); /* #blksize */

      FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff, tmp, strlen(tmp));

      fr_dbuff_in_bytes(&work_dbuff, '\0');

    }

    break;

  case FR_OPCODE_VALUE_ACKNOWLEDGEMENT:

  case FR_OPCODE_VALUE_DATA:

    /**

     * 2 bytes     2 bytes

     * ---------------------

     * | Opcode |   Block #  |

     * ---------------------

     * Figure 5-3: ACK packet

     */

    /* <Block> */

    vp = fr_pair_find_by_da(vps, NULL, attr_tftp_block);

    if (!vp) {

      fr_strerror_printf("Invalid TFTP packet without %s", attr_tftp_block->name);

      return -1;

    }

    fr_dbuff_in(&work_dbuff, vp->vp_uint16);

    /*

     *  From that point...

     *

     *  2 bytes     2 bytes      n bytes

     *  ----------------------------------

     *  | Opcode |   Block #  |   Data     |

     *  ----------------------------------

     *  Figure 5-2: DATA packet

     */

    if (opcode != FR_OPCODE_VALUE_DATA) goto done;

    /* <Data> */

    vp = fr_pair_find_by_da(vps, NULL, attr_tftp_data);

    if (!vp) {

      fr_strerror_printf("Invalid TFTP packet without %s", attr_tftp_data->name);

      return -1;

    }

    FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff, vp->vp_octets, vp->vp_length);

    break;

  case FR_OPCODE_VALUE_ERROR:

  {

    /**

     * 2 bytes     2 bytes      string    1 byte

     * -----------------------------------------

     * | Opcode |  ErrorCode |   ErrMsg   |   0  |

     * -----------------------------------------

     *

     * Figure 5-4: ERROR packet

     */

    uint16_t  error_code;

    char const  *error_msg;

    size_t    error_msg_len;

    /* <ErroCode> */

    vp = fr_pair_find_by_da(vps, NULL, attr_tftp_error_code);

    if (!vp) {

      fr_strerror_printf("Invalid TFTP packet without %s", attr_tftp_error_code->name);

      return -1;

    }

    error_code = vp->vp_uint16;

    fr_dbuff_in(&work_dbuff, error_code);

    /* <ErrMsg> */

    vp = fr_pair_find_by_da(vps, NULL, attr_tftp_error_message);

    if (vp) {

      error_msg = vp->vp_strvalue;

      error_msg_len = vp->vp_length;

    } else {

      error_msg = fr_tftp_error_codes[error_code] ? fr_tftp_error_codes[error_code] : "Invalid ErrorCode";

      error_msg_len = strlen(error_msg);

    }

    FR_DBUFF_IN_MEMCPY_RETURN(&work_dbuff, error_msg, error_msg_len);

    fr_dbuff_in_bytes(&work_dbuff, '\0');

    break;

  }

  default:

    fr_strerror_printf("Invalid TFTP opcode %#04x", opcode);

    return -1;

  }

done:

  fr_dbuff_set(dbuff, &work_dbuff);

  return fr_dbuff_used(dbuff);

}

/**

 *  Used as the encoder ctx.

 */

typedef struct {

  int   nothing;

} fr_tftp_ctx_t;

/*

 *  Test points for protocol encode

 */

static ssize_t fr_tftp_encode_proto(UNUSED TALLOC_CTX *ctx, fr_pair_list_t *vps, uint8_t *data, size_t data_len, UNUSED void *proto_ctx)

{

  return fr_tftp_encode(&FR_DBUFF_TMP(data, data_len), vps);

}

static int _encode_test_ctx(UNUSED fr_tftp_ctx_t *proto_ctx)

{

  fr_tftp_global_free();

  return 0;

}

static int encode_test_ctx(void **out, TALLOC_CTX *ctx)

{

  fr_tftp_ctx_t *test_ctx;

  if (fr_tftp_global_init() < 0) return -1;

  test_ctx = talloc_zero(ctx, fr_tftp_ctx_t);

  if (!test_ctx) return -1;

  talloc_set_destructor(test_ctx, _encode_test_ctx);

  *out = test_ctx;

  return 0;

}

/*

 *  Test points

 */

extern fr_test_point_proto_encode_t tftp_tp_encode_proto;

fr_test_point_proto_encode_t tftp_tp_encode_proto = {

  .test_ctx = encode_test_ctx,

  .func   = fr_tftp_encode_proto

};