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_NETINET_IN_H
21 # include <netinet/in.h>
22 #endif
23 #ifdef HAVE_NETDB_H
24 # include <netdb.h>
25 #endif
26 #ifdef HAVE_ARPA_INET_H
27 # include <arpa/inet.h>
28 #endif
29 #ifdef HAVE_ARPA_NAMESER_H
30 # include <arpa/nameser.h>
31 #else
32 # include "nameser.h"
33 #endif
34 #ifdef HAVE_ARPA_NAMESER_COMPAT_H
35 # include <arpa/nameser_compat.h>
36 #endif
37
38 #include "ares.h"
39 #include "ares_dns.h"
40 #include "ares_data.h"
41 #include "ares_private.h"
42
43 int
ares_parse_mx_reply(const unsigned char * abuf,int alen,struct ares_mx_reply ** mx_out)44 ares_parse_mx_reply (const unsigned char *abuf, int alen,
45 struct ares_mx_reply **mx_out)
46 {
47 unsigned int qdcount, ancount, i;
48 const unsigned char *aptr, *vptr;
49 int status, rr_type, rr_class, rr_len;
50 long len;
51 char *hostname = NULL, *rr_name = NULL;
52 struct ares_mx_reply *mx_head = NULL;
53 struct ares_mx_reply *mx_last = NULL;
54 struct ares_mx_reply *mx_curr;
55
56 /* Set *mx_out to NULL for all failure cases. */
57 *mx_out = NULL;
58
59 /* Give up if abuf doesn't have room for a header. */
60 if (alen < HFIXEDSZ)
61 return ARES_EBADRESP;
62
63 /* Fetch the question and answer count from the header. */
64 qdcount = DNS_HEADER_QDCOUNT (abuf);
65 ancount = DNS_HEADER_ANCOUNT (abuf);
66 if (qdcount != 1)
67 return ARES_EBADRESP;
68 if (ancount == 0)
69 return ARES_ENODATA;
70
71 /* Expand the name from the question, and skip past the question. */
72 aptr = abuf + HFIXEDSZ;
73 status = ares_expand_name (aptr, abuf, alen, &hostname, &len);
74 if (status != ARES_SUCCESS)
75 return status;
76
77 if (aptr + len + QFIXEDSZ > abuf + alen)
78 {
79 ares_free (hostname);
80 return ARES_EBADRESP;
81 }
82 aptr += len + QFIXEDSZ;
83
84 /* Examine each answer resource record (RR) in turn. */
85 for (i = 0; i < ancount; i++)
86 {
87 /* Decode the RR up to the data field. */
88 status = ares_expand_name (aptr, abuf, alen, &rr_name, &len);
89 if (status != ARES_SUCCESS)
90 {
91 break;
92 }
93 aptr += len;
94 if (aptr + RRFIXEDSZ > abuf + alen)
95 {
96 status = ARES_EBADRESP;
97 break;
98 }
99 rr_type = DNS_RR_TYPE (aptr);
100 rr_class = DNS_RR_CLASS (aptr);
101 rr_len = DNS_RR_LEN (aptr);
102 aptr += RRFIXEDSZ;
103 if (aptr + rr_len > abuf + alen)
104 {
105 status = ARES_EBADRESP;
106 break;
107 }
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 ares_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 ares_free (hostname);
155 if (rr_name)
156 ares_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