1
2/* Copyright 1998 by the Massachusetts Institute of Technology.
3 * Copyright (C) 2009 by Jakub Hrozek <jhrozek@redhat.com>
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#include <stdlib.h>
42#include <string.h>
43#include "ares.h"
44#include "ares_dns.h"
45#include "ares_data.h"
46#include "ares_private.h"
47
48/* AIX portability check */
49#ifndef T_SRV
50#  define T_SRV 33 /* server selection */
51#endif
52
53int
54ares_parse_srv_reply (const unsigned char *abuf, int alen,
55                      struct ares_srv_reply **srv_out)
56{
57  unsigned int qdcount, ancount, i;
58  const unsigned char *aptr, *vptr;
59  int status, rr_type, rr_class, rr_len;
60  long len;
61  char *hostname = NULL, *rr_name = NULL;
62  struct ares_srv_reply *srv_head = NULL;
63  struct ares_srv_reply *srv_last = NULL;
64  struct ares_srv_reply *srv_curr;
65
66  /* Set *srv_out to NULL for all failure cases. */
67  *srv_out = NULL;
68
69  /* Give up if abuf doesn't have room for a header. */
70  if (alen < HFIXEDSZ)
71    return ARES_EBADRESP;
72
73  /* Fetch the question and answer count from the header. */
74  qdcount = DNS_HEADER_QDCOUNT (abuf);
75  ancount = DNS_HEADER_ANCOUNT (abuf);
76  if (qdcount != 1)
77    return ARES_EBADRESP;
78  if (ancount == 0)
79    return ARES_ENODATA;
80
81  /* Expand the name from the question, and skip past the question. */
82  aptr = abuf + HFIXEDSZ;
83  status = ares_expand_name (aptr, abuf, alen, &hostname, &len);
84  if (status != ARES_SUCCESS)
85    return status;
86
87  if (aptr + len + QFIXEDSZ > abuf + alen)
88    {
89      free (hostname);
90      return ARES_EBADRESP;
91    }
92  aptr += len + QFIXEDSZ;
93
94  /* Examine each answer resource record (RR) in turn. */
95  for (i = 0; i < ancount; i++)
96    {
97      /* Decode the RR up to the data field. */
98      status = ares_expand_name (aptr, abuf, alen, &rr_name, &len);
99      if (status != ARES_SUCCESS)
100        {
101          break;
102        }
103      aptr += len;
104      if (aptr + RRFIXEDSZ > abuf + alen)
105        {
106          status = ARES_EBADRESP;
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      /* Check if we are really looking at a SRV record */
115      if (rr_class == C_IN && rr_type == T_SRV)
116        {
117          /* parse the SRV record itself */
118          if (rr_len < 6)
119            {
120              status = ARES_EBADRESP;
121              break;
122            }
123
124          /* Allocate storage for this SRV answer appending it to the list */
125          srv_curr = ares_malloc_data(ARES_DATATYPE_SRV_REPLY);
126          if (!srv_curr)
127            {
128              status = ARES_ENOMEM;
129              break;
130            }
131          if (srv_last)
132            {
133              srv_last->next = srv_curr;
134            }
135          else
136            {
137              srv_head = srv_curr;
138            }
139          srv_last = srv_curr;
140
141          vptr = aptr;
142          srv_curr->priority = DNS__16BIT(vptr);
143          vptr += sizeof(unsigned short);
144          srv_curr->weight = DNS__16BIT(vptr);
145          vptr += sizeof(unsigned short);
146          srv_curr->port = DNS__16BIT(vptr);
147          vptr += sizeof(unsigned short);
148
149          status = ares_expand_name (vptr, abuf, alen, &srv_curr->host, &len);
150          if (status != ARES_SUCCESS)
151            break;
152        }
153
154      /* Don't lose memory in the next iteration */
155      free (rr_name);
156      rr_name = NULL;
157
158      /* Move on to the next record */
159      aptr += rr_len;
160    }
161
162  if (hostname)
163    free (hostname);
164  if (rr_name)
165    free (rr_name);
166
167  /* clean up on error */
168  if (status != ARES_SUCCESS)
169    {
170      if (srv_head)
171        ares_free_data (srv_head);
172      return status;
173    }
174
175  /* everything looks fine, return the data */
176  *srv_out = srv_head;
177
178  return ARES_SUCCESS;
179}
180