1/* Copyright 1998 by the Massachusetts Institute of Technology.
2 *
3 * Permission to use, copy, modify, and distribute this
4 * software and its documentation for any purpose and without
5 * fee is hereby granted, provided that the above copyright
6 * notice appear in all copies and that both that copyright
7 * notice and this permission notice appear in supporting
8 * documentation, and that the name of M.I.T. not be used in
9 * advertising or publicity pertaining to distribution of the
10 * software without specific, written prior permission.
11 * M.I.T. makes no representations about the suitability of
12 * this software for any purpose.  It is provided "as is"
13 * without express or implied warranty.
14 */
15
16/*
17 * ares_parse_ns_reply created by Vlad Dinulescu <vlad.dinulescu@avira.com>
18 *      on behalf of AVIRA Gmbh - http://www.avira.com
19 */
20
21#include "ares_setup.h"
22
23#ifdef HAVE_SYS_SOCKET_H
24#  include <sys/socket.h>
25#endif
26#ifdef HAVE_NETINET_IN_H
27#  include <netinet/in.h>
28#endif
29#ifdef HAVE_NETDB_H
30#  include <netdb.h>
31#endif
32#ifdef HAVE_ARPA_INET_H
33#  include <arpa/inet.h>
34#endif
35#ifdef HAVE_ARPA_NAMESER_H
36#  include <arpa/nameser.h>
37#else
38#  include "nameser.h"
39#endif
40#ifdef HAVE_ARPA_NAMESER_COMPAT_H
41#  include <arpa/nameser_compat.h>
42#endif
43
44#include <stdlib.h>
45#include <string.h>
46#include "ares.h"
47#include "ares_dns.h"
48#include "ares_private.h"
49
50int ares_parse_ns_reply( const unsigned char* abuf, int alen,
51                         struct hostent** host )
52{
53  unsigned int qdcount, ancount;
54  int status, i, rr_type, rr_class, rr_len;
55  int nameservers_num;
56  long len;
57  const unsigned char *aptr;
58  char* hostname, *rr_name, *rr_data, **nameservers;
59  struct hostent *hostent;
60
61  /* Set *host to NULL for all failure cases. */
62  *host = NULL;
63
64  /* Give up if abuf doesn't have room for a header. */
65  if ( alen < HFIXEDSZ )
66    return ARES_EBADRESP;
67
68  /* Fetch the question and answer count from the header. */
69  qdcount = DNS_HEADER_QDCOUNT( abuf );
70  ancount = DNS_HEADER_ANCOUNT( abuf );
71  if ( qdcount != 1 )
72    return ARES_EBADRESP;
73
74  /* Expand the name from the question, and skip past the question. */
75  aptr = abuf + HFIXEDSZ;
76  status = ares__expand_name_for_response( aptr, abuf, alen, &hostname, &len);
77  if ( status != ARES_SUCCESS )
78    return status;
79  if ( aptr + len + QFIXEDSZ > abuf + alen )
80  {
81    free( hostname );
82    return ARES_EBADRESP;
83  }
84  aptr += len + QFIXEDSZ;
85
86  /* Allocate nameservers array; ancount gives an upper bound */
87  nameservers = malloc( ( ancount + 1 ) * sizeof( char * ) );
88  if ( !nameservers )
89  {
90    free( hostname );
91    return ARES_ENOMEM;
92  }
93  nameservers_num = 0;
94
95  /* Examine each answer resource record (RR) in turn. */
96  for ( i = 0; i < ( int ) ancount; i++ )
97  {
98    /* Decode the RR up to the data field. */
99    status = ares__expand_name_for_response( aptr, abuf, alen, &rr_name, &len );
100    if ( status != ARES_SUCCESS )
101      break;
102    aptr += len;
103    if ( aptr + RRFIXEDSZ > abuf + alen )
104    {
105      status = ARES_EBADRESP;
106      free(rr_name);
107      break;
108    }
109    rr_type = DNS_RR_TYPE( aptr );
110    rr_class = DNS_RR_CLASS( aptr );
111    rr_len = DNS_RR_LEN( aptr );
112    aptr += RRFIXEDSZ;
113
114    if ( rr_class == C_IN && rr_type == T_NS )
115    {
116      /* Decode the RR data and add it to the nameservers list */
117      status = ares__expand_name_for_response( aptr, abuf, alen, &rr_data,
118                                               &len);
119      if ( status != ARES_SUCCESS )
120      {
121        free(rr_name);
122        break;
123      }
124
125      nameservers[nameservers_num] = malloc(strlen(rr_data)+1);
126
127      if (nameservers[nameservers_num]==NULL)
128      {
129        free(rr_name);
130        free(rr_data);
131        status=ARES_ENOMEM;
132        break;
133      }
134      strcpy(nameservers[nameservers_num],rr_data);
135      free(rr_data);
136
137      nameservers_num++;
138    }
139
140    free( rr_name );
141
142    aptr += rr_len;
143    if ( aptr > abuf + alen )
144    {
145      status = ARES_EBADRESP;
146      break;
147    }
148  }
149
150  if ( status == ARES_SUCCESS && nameservers_num == 0 )
151  {
152    status = ARES_ENODATA;
153  }
154  if ( status == ARES_SUCCESS )
155  {
156    /* We got our answer.  Allocate memory to build the host entry. */
157    nameservers[nameservers_num] = NULL;
158    hostent = malloc( sizeof( struct hostent ) );
159    if ( hostent )
160    {
161      hostent->h_addr_list = malloc( 1 * sizeof( char * ) );
162      if ( hostent->h_addr_list )
163      {
164        /* Fill in the hostent and return successfully. */
165        hostent->h_name = hostname;
166        hostent->h_aliases = nameservers;
167        hostent->h_addrtype = AF_INET;
168        hostent->h_length = sizeof( struct in_addr );
169        hostent->h_addr_list[0] = NULL;
170        *host = hostent;
171        return ARES_SUCCESS;
172      }
173      free( hostent );
174    }
175    status = ARES_ENOMEM;
176  }
177  for ( i = 0; i < nameservers_num; i++ )
178    free( nameservers[i] );
179  free( nameservers );
180  free( hostname );
181  return status;
182}
183