/* Copyright 1998 by the Massachusetts Institute of Technology.

 * Copyright (C) 2009 by Jakub Hrozek <jhrozek@redhat.com>

 *

 * Permission to use, copy, modify, and distribute this

 * software and its documentation for any purpose and without

 * fee is hereby granted, provided that the above copyright

 * notice appear in all copies and that both that copyright

 * notice and this permission notice appear in supporting

 * documentation, and that the name of M.I.T. not be used in

 * advertising or publicity pertaining to distribution of the

 * software without specific, written prior permission.

 * M.I.T. makes no representations about the suitability of

 * this software for any purpose.  It is provided "as is"

 * without express or implied warranty.

 *

 * SPDX-License-Identifier: MIT

 */

#include "ares_setup.h"

#ifdef HAVE_NETINET_IN_H

#  include <netinet/in.h>

#endif

#ifdef HAVE_NETDB_H

#  include <netdb.h>

#endif

#ifdef HAVE_ARPA_INET_H

#  include <arpa/inet.h>

#endif

#include "ares_nameser.h"

#ifdef HAVE_STRINGS_H

#  include <strings.h>

#endif

#include "ares.h"

#include "ares_dns.h"

#include "ares_data.h"

#include "ares_private.h"

static int

ares__parse_txt_reply (const unsigned char *abuf, int alen,

                       int ex, void **txt_out)

{

  size_t substr_len;

  unsigned int qdcount, ancount, i;

  const unsigned char *aptr;

  const unsigned char *strptr;

  int status, rr_type, rr_class, rr_len;

  long len;

  char *hostname = NULL, *rr_name = NULL;

  struct ares_txt_ext *txt_head = NULL;

  struct ares_txt_ext *txt_last = NULL;

  struct ares_txt_ext *txt_curr;

  /* Set *txt_out to NULL for all failure cases. */

  *txt_out = NULL;

  /* Give up if abuf doesn't have room for a header. */

  if (alen < HFIXEDSZ)

    return ARES_EBADRESP;

  /* Fetch the question and answer count from the header. */

  qdcount = DNS_HEADER_QDCOUNT (abuf);

  ancount = DNS_HEADER_ANCOUNT (abuf);

  if (qdcount != 1)

    return ARES_EBADRESP;

  if (ancount == 0)

    return ARES_ENODATA;

  /* Expand the name from the question, and skip past the question. */

  aptr = abuf + HFIXEDSZ;

  status = ares_expand_name (aptr, abuf, alen, &hostname, &len);

  if (status != ARES_SUCCESS)

    return status;

  if (aptr + len + QFIXEDSZ > abuf + alen)

    {

      ares_free (hostname);

      return ARES_EBADRESP;

    }

  aptr += len + QFIXEDSZ;

  /* Examine each answer resource record (RR) in turn. */

  for (i = 0; i < ancount; i++)

    {

      /* Decode the RR up to the data field. */

      status = ares_expand_name (aptr, abuf, alen, &rr_name, &len);

      if (status != ARES_SUCCESS)

        {

          break;

        }

      aptr += len;

      if (aptr + RRFIXEDSZ > abuf + alen)

        {

          status = ARES_EBADRESP;

          break;

        }

      rr_type = DNS_RR_TYPE (aptr);

      rr_class = DNS_RR_CLASS (aptr);

      rr_len = DNS_RR_LEN (aptr);

      aptr += RRFIXEDSZ;

      if (aptr + rr_len > abuf + alen)

        {

          status = ARES_EBADRESP;

          break;

        }

      /* Check if we are really looking at a TXT record */

      if ((rr_class == C_IN || rr_class == C_CHAOS) && rr_type == T_TXT)

        {

          /*

           * There may be multiple substrings in a single TXT record. Each

           * substring may be up to 255 characters in length, with a

           * "length byte" indicating the size of the substring payload.

           * RDATA contains both the length-bytes and payloads of all

           * substrings contained therein.

           */

          strptr = aptr;

          while (strptr < (aptr + rr_len))

            {

              substr_len = (unsigned char)*strptr;

              if (strptr + substr_len + 1 > aptr + rr_len)

                {

                  status = ARES_EBADRESP;

                  break;

                }

              /* Allocate storage for this TXT answer appending it to the list */

              txt_curr = ares_malloc_data(ex ? ARES_DATATYPE_TXT_EXT :

                                               ARES_DATATYPE_TXT_REPLY);

              if (!txt_curr)

                {

                  status = ARES_ENOMEM;

                  break;

                }

              if (txt_last)

                {

                  txt_last->next = txt_curr;

                }

              else

                {

                  txt_head = txt_curr;

                }

              txt_last = txt_curr;

              if (ex)

                txt_curr->record_start = (strptr == aptr);

              txt_curr->length = substr_len;

              txt_curr->txt = ares_malloc (substr_len + 1/* Including null byte */);

              if (txt_curr->txt == NULL)

                {

                  status = ARES_ENOMEM;

                  break;

                }

              ++strptr;

              memcpy ((char *) txt_curr->txt, strptr, substr_len);

              /* Make sure we NULL-terminate */

              txt_curr->txt[substr_len] = 0;

              strptr += substr_len;

            }

        }

      /* Propagate any failures */

      if (status != ARES_SUCCESS)

        {

          break;

        }

      /* Don't lose memory in the next iteration */

      ares_free (rr_name);

      rr_name = NULL;

      /* Move on to the next record */

      aptr += rr_len;

    }

  if (hostname)

    ares_free (hostname);

  if (rr_name)

    ares_free (rr_name);

  /* clean up on error */

  if (status != ARES_SUCCESS)

    {

      if (txt_head)

        ares_free_data (txt_head);

      return status;

    }

  /* everything looks fine, return the data */

  *txt_out = txt_head;

  return ARES_SUCCESS;

}

int

ares_parse_txt_reply (const unsigned char *abuf, int alen,

                      struct ares_txt_reply **txt_out)

{

  return ares__parse_txt_reply(abuf, alen, 0, (void **) txt_out);

}

int

ares_parse_txt_reply_ext (const unsigned char *abuf, int alen,

                          struct ares_txt_ext **txt_out)

{

  return ares__parse_txt_reply(abuf, alen, 1, (void **) txt_out);

}