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/* Copyright (C) 2009 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.
*/
#include "setup.h"
#if defined(WIN32) && !defined(WATT32)
#include "nameser.h"
#else
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <arpa/nameser.h>
#ifdef HAVE_ARPA_NAMESER_COMPAT_H
#include <arpa/nameser_compat.h>
#endif
#endif
#include <stdlib.h>
#include <string.h>
#include "ares.h"
#include "ares_dns.h"
#include "ares_private.h"
int
ares_parse_txt_reply (const unsigned char *abuf, int alen,
struct ares_txt_reply **txt_out, int *ntxtreply)
{
unsigned char substr_len = 0;
unsigned char str_len = 0;
unsigned int qdcount, ancount;
const unsigned char *aptr;
const unsigned char *strptr;
int status, i, rr_type, rr_class, rr_len;
long len;
char *hostname = NULL, *rr_name = NULL;
struct ares_txt_reply *txt = NULL;
*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)
{
free (hostname);
return ARES_EBADRESP;
}
aptr += len + QFIXEDSZ;
/* Allocate ares_txt_reply array; ancount gives an upper bound */
txt = malloc ((ancount) * sizeof (struct ares_txt_reply));
if (!txt)
{
free (hostname);
return ARES_ENOMEM;
}
/* Zero out so we can safely free txt.txt even if NULL */
memset(txt, 0, ancount * sizeof (struct ares_txt_reply));
/* Examine each answer resource record (RR) in turn. */
for (i = 0; i < (int) 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;
/* Check if we are really looking at a TXT record */
if (rr_class == C_IN && 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.
*/
/* Realloc would be expensive, compute the total length */
txt[i].length = 0;
strptr = aptr;
while (strptr < (aptr + rr_len))
{
memcpy ((void *) &substr_len, strptr, sizeof (unsigned char));
txt[i].length += substr_len;
strptr += substr_len + 1;
}
/* Including null byte */
txt[i].txt = malloc (sizeof (unsigned char) * (txt[i].length + 1));
if (txt[i].txt == NULL)
{
status = ARES_ENOMEM;
break;
}
/* Step through the list of substrings, concatenating them */
substr_len = 0;
str_len = 0;
strptr = aptr;
while (strptr < (aptr + rr_len))
{
memcpy ((void *) &substr_len, strptr, sizeof (unsigned char));
strptr++;
memcpy ((void *) txt[i].txt + str_len, strptr,
sizeof (unsigned char) * substr_len);
str_len += substr_len;
strptr += substr_len;
}
/* Make sure we NULL-terminate */
txt[i].txt[txt[i].length] = '\0';
/* Move on to the next record */
aptr += rr_len;
}
/* Don't lose memory in the next iteration */
free (rr_name);
rr_name = NULL;
}
free (hostname);
free (rr_name);
/* clean up on error */
if (status != ARES_SUCCESS)
{
ares_free_txt_reply(txt, ancount);
return status;
}
/* everything looks fine, return the data */
*txt_out = txt;
*ntxtreply = ancount;
return 0;
}
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