1
2 /* Copyright 1998 by the Massachusetts Institute of Technology.
3 * Copyright (C) 2010 Jeremy Lal <kapouer@melix.org>
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 int
ares_parse_mx_reply(const unsigned char * abuf,int alen,struct ares_mx_reply ** mx_out)49 ares_parse_mx_reply (const unsigned char *abuf, int alen,
50 struct ares_mx_reply **mx_out)
51 {
52 unsigned int qdcount, ancount, i;
53 const unsigned char *aptr, *vptr;
54 int status, rr_type, rr_class, rr_len;
55 long len;
56 char *hostname = NULL, *rr_name = NULL;
57 struct ares_mx_reply *mx_head = NULL;
58 struct ares_mx_reply *mx_last = NULL;
59 struct ares_mx_reply *mx_curr;
60
61 /* Set *mx_out to NULL for all failure cases. */
62 *mx_out = 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 if (ancount == 0)
74 return ARES_ENODATA;
75
76 /* Expand the name from the question, and skip past the question. */
77 aptr = abuf + HFIXEDSZ;
78 status = ares_expand_name (aptr, abuf, alen, &hostname, &len);
79 if (status != ARES_SUCCESS)
80 return status;
81
82 if (aptr + len + QFIXEDSZ > abuf + alen)
83 {
84 free (hostname);
85 return ARES_EBADRESP;
86 }
87 aptr += len + QFIXEDSZ;
88
89 /* Examine each answer resource record (RR) in turn. */
90 for (i = 0; i < ancount; i++)
91 {
92 /* Decode the RR up to the data field. */
93 status = ares_expand_name (aptr, abuf, alen, &rr_name, &len);
94 if (status != ARES_SUCCESS)
95 {
96 break;
97 }
98 aptr += len;
99 if (aptr + RRFIXEDSZ > abuf + alen)
100 {
101 status = ARES_EBADRESP;
102 break;
103 }
104 rr_type = DNS_RR_TYPE (aptr);
105 rr_class = DNS_RR_CLASS (aptr);
106 rr_len = DNS_RR_LEN (aptr);
107 aptr += RRFIXEDSZ;
108
109 /* Check if we are really looking at a MX record */
110 if (rr_class == C_IN && rr_type == T_MX)
111 {
112 /* parse the MX record itself */
113 if (rr_len < 2)
114 {
115 status = ARES_EBADRESP;
116 break;
117 }
118
119 /* Allocate storage for this MX answer appending it to the list */
120 mx_curr = ares_malloc_data(ARES_DATATYPE_MX_REPLY);
121 if (!mx_curr)
122 {
123 status = ARES_ENOMEM;
124 break;
125 }
126 if (mx_last)
127 {
128 mx_last->next = mx_curr;
129 }
130 else
131 {
132 mx_head = mx_curr;
133 }
134 mx_last = mx_curr;
135
136 vptr = aptr;
137 mx_curr->priority = DNS__16BIT(vptr);
138 vptr += sizeof(unsigned short);
139
140 status = ares_expand_name (vptr, abuf, alen, &mx_curr->host, &len);
141 if (status != ARES_SUCCESS)
142 break;
143 }
144
145 /* Don't lose memory in the next iteration */
146 free (rr_name);
147 rr_name = NULL;
148
149 /* Move on to the next record */
150 aptr += rr_len;
151 }
152
153 if (hostname)
154 free (hostname);
155 if (rr_name)
156 free (rr_name);
157
158 /* clean up on error */
159 if (status != ARES_SUCCESS)
160 {
161 if (mx_head)
162 ares_free_data (mx_head);
163 return status;
164 }
165
166 /* everything looks fine, return the data */
167 *mx_out = mx_head;
168
169 return ARES_SUCCESS;
170 }
171