1
2/* Copyright 1998 by the Massachusetts Institute of Technology.
3 * Copyright 2005 Dominick Meglio
4 *
5 * Permission to use, copy, modify, and distribute this
6 * software and its documentation for any purpose and without
7 * fee is hereby granted, provided that the above copyright
8 * notice appear in all copies and that both that copyright
9 * notice and this permission notice appear in supporting
10 * documentation, and that the name of M.I.T. not be used in
11 * advertising or publicity pertaining to distribution of the
12 * software without specific, written prior permission.
13 * M.I.T. makes no representations about the suitability of
14 * this software for any purpose.  It is provided "as is"
15 * without express or implied warranty.
16 */
17
18#include "ares_setup.h"
19
20#ifdef HAVE_SYS_SOCKET_H
21#  include <sys/socket.h>
22#endif
23#ifdef HAVE_NETINET_IN_H
24#  include <netinet/in.h>
25#endif
26#ifdef HAVE_NETDB_H
27#  include <netdb.h>
28#endif
29#ifdef HAVE_ARPA_INET_H
30#  include <arpa/inet.h>
31#endif
32#ifdef HAVE_ARPA_NAMESER_H
33#  include <arpa/nameser.h>
34#else
35#  include "nameser.h"
36#endif
37#ifdef HAVE_ARPA_NAMESER_COMPAT_H
38#  include <arpa/nameser_compat.h>
39#endif
40
41#ifdef HAVE_STRINGS_H
42#  include <strings.h>
43#endif
44
45#include <stdlib.h>
46#include <string.h>
47#ifdef HAVE_LIMITS_H
48#  include <limits.h>
49#endif
50
51#include "ares.h"
52#include "ares_dns.h"
53#include "inet_net_pton.h"
54#include "ares_private.h"
55
56int ares_parse_aaaa_reply(const unsigned char *abuf, int alen,
57                          struct hostent **host, struct ares_addr6ttl *addrttls,
58                          int *naddrttls)
59{
60  unsigned int qdcount, ancount;
61  int status, i, rr_type, rr_class, rr_len, rr_ttl, naddrs;
62  int cname_ttl = INT_MAX;  /* the TTL imposed by the CNAME chain */
63  int naliases;
64  long len;
65  const unsigned char *aptr;
66  char *hostname, *rr_name, *rr_data, **aliases;
67  struct ares_in6_addr *addrs;
68  struct hostent *hostent;
69  const int max_addr_ttls = (addrttls && naddrttls) ? *naddrttls : 0;
70
71  /* Set *host to NULL for all failure cases. */
72  if (host)
73    *host = NULL;
74  /* Same with *naddrttls. */
75  if (naddrttls)
76    *naddrttls = 0;
77
78  /* Give up if abuf doesn't have room for a header. */
79  if (alen < HFIXEDSZ)
80    return ARES_EBADRESP;
81
82  /* Fetch the question and answer count from the header. */
83  qdcount = DNS_HEADER_QDCOUNT(abuf);
84  ancount = DNS_HEADER_ANCOUNT(abuf);
85  if (qdcount != 1)
86    return ARES_EBADRESP;
87
88  /* Expand the name from the question, and skip past the question. */
89  aptr = abuf + HFIXEDSZ;
90  status = ares__expand_name_for_response(aptr, abuf, alen, &hostname, &len);
91  if (status != ARES_SUCCESS)
92    return status;
93  if (aptr + len + QFIXEDSZ > abuf + alen)
94    {
95      free(hostname);
96      return ARES_EBADRESP;
97    }
98  aptr += len + QFIXEDSZ;
99
100  /* Allocate addresses and aliases; ancount gives an upper bound for both. */
101  if (host)
102    {
103      addrs = malloc(ancount * sizeof(struct ares_in6_addr));
104      if (!addrs)
105        {
106          free(hostname);
107          return ARES_ENOMEM;
108        }
109      aliases = malloc((ancount + 1) * sizeof(char *));
110      if (!aliases)
111        {
112          free(hostname);
113          free(addrs);
114          return ARES_ENOMEM;
115        }
116    }
117  else
118    {
119      addrs = NULL;
120      aliases = NULL;
121    }
122  naddrs = 0;
123  naliases = 0;
124
125  /* Examine each answer resource record (RR) in turn. */
126  for (i = 0; i < (int)ancount; i++)
127    {
128      /* Decode the RR up to the data field. */
129      status = ares__expand_name_for_response(aptr, abuf, alen, &rr_name, &len);
130      if (status != ARES_SUCCESS)
131        break;
132      aptr += len;
133      if (aptr + RRFIXEDSZ > abuf + alen)
134        {
135          free(rr_name);
136          status = ARES_EBADRESP;
137          break;
138        }
139      rr_type = DNS_RR_TYPE(aptr);
140      rr_class = DNS_RR_CLASS(aptr);
141      rr_len = DNS_RR_LEN(aptr);
142      rr_ttl = DNS_RR_TTL(aptr);
143      aptr += RRFIXEDSZ;
144
145      if (rr_class == C_IN && rr_type == T_AAAA
146          && rr_len == sizeof(struct ares_in6_addr)
147          && strcasecmp(rr_name, hostname) == 0)
148        {
149          if (addrs)
150            {
151              if (aptr + sizeof(struct ares_in6_addr) > abuf + alen)
152              {
153                free(rr_name);
154                status = ARES_EBADRESP;
155                break;
156              }
157              memcpy(&addrs[naddrs], aptr, sizeof(struct ares_in6_addr));
158            }
159          if (naddrs < max_addr_ttls)
160            {
161              struct ares_addr6ttl * const at = &addrttls[naddrs];
162              if (aptr + sizeof(struct ares_in6_addr) > abuf + alen)
163              {
164                free(rr_name);
165                status = ARES_EBADRESP;
166                break;
167              }
168              memcpy(&at->ip6addr, aptr,  sizeof(struct ares_in6_addr));
169              at->ttl = rr_ttl;
170            }
171          naddrs++;
172          status = ARES_SUCCESS;
173        }
174
175      if (rr_class == C_IN && rr_type == T_CNAME)
176        {
177          /* Record the RR name as an alias. */
178          if (aliases)
179            aliases[naliases] = rr_name;
180          else
181            free(rr_name);
182          naliases++;
183
184          /* Decode the RR data and replace the hostname with it. */
185          status = ares__expand_name_for_response(aptr, abuf, alen, &rr_data,
186                                                  &len);
187          if (status != ARES_SUCCESS)
188            break;
189          free(hostname);
190          hostname = rr_data;
191
192          /* Take the min of the TTLs we see in the CNAME chain. */
193          if (cname_ttl > rr_ttl)
194            cname_ttl = rr_ttl;
195        }
196      else
197        free(rr_name);
198
199      aptr += rr_len;
200      if (aptr > abuf + alen)
201        {
202          status = ARES_EBADRESP;
203          break;
204        }
205    }
206
207  if (status == ARES_SUCCESS && naddrs == 0)
208    status = ARES_ENODATA;
209  if (status == ARES_SUCCESS)
210    {
211      /* We got our answer. */
212      if (naddrttls)
213        {
214          const int n = naddrs < max_addr_ttls ? naddrs : max_addr_ttls;
215          for (i = 0; i < n; i++)
216            {
217              /* Ensure that each A TTL is no larger than the CNAME TTL. */
218              if (addrttls[i].ttl > cname_ttl)
219                addrttls[i].ttl = cname_ttl;
220            }
221          *naddrttls = n;
222        }
223      if (aliases)
224        aliases[naliases] = NULL;
225      if (host)
226        {
227          /* Allocate memory to build the host entry. */
228          hostent = malloc(sizeof(struct hostent));
229          if (hostent)
230            {
231              hostent->h_addr_list = malloc((naddrs + 1) * sizeof(char *));
232              if (hostent->h_addr_list)
233                {
234                  /* Fill in the hostent and return successfully. */
235                  hostent->h_name = hostname;
236                  hostent->h_aliases = aliases;
237                  hostent->h_addrtype = AF_INET6;
238                  hostent->h_length = sizeof(struct ares_in6_addr);
239                  for (i = 0; i < naddrs; i++)
240                    hostent->h_addr_list[i] = (char *) &addrs[i];
241                  hostent->h_addr_list[naddrs] = NULL;
242                  *host = hostent;
243                  return ARES_SUCCESS;
244                }
245              free(hostent);
246            }
247          status = ARES_ENOMEM;
248        }
249    }
250  if (aliases)
251    {
252      for (i = 0; i < naliases; i++)
253        free(aliases[i]);
254      free(aliases);
255    }
256  free(addrs);
257  free(hostname);
258  return status;
259}
260