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_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 /* AIX portability check */
44 #ifndef T_SRV
45 # define T_SRV 33 /* server selection */
46 #endif
47
48 int
ares_parse_srv_reply(const unsigned char * abuf,int alen,struct ares_srv_reply ** srv_out)49 ares_parse_srv_reply (const unsigned char *abuf, int alen,
50 struct ares_srv_reply **srv_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_srv_reply *srv_head = NULL;
58 struct ares_srv_reply *srv_last = NULL;
59 struct ares_srv_reply *srv_curr;
60
61 /* Set *srv_out to NULL for all failure cases. */
62 *srv_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 ares_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 if (aptr + rr_len > abuf + alen)
109 {
110 status = ARES_EBADRESP;
111 break;
112 }
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 ares_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 ares_free (hostname);
164 if (rr_name)
165 ares_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