1 /* Copyright 1998 by the Massachusetts Institute of Technology.
2 *
3 * Permission to use, copy, modify, and distribute this
4 * software and its documentation for any purpose and without
5 * fee is hereby granted, provided that the above copyright
6 * notice appear in all copies and that both that copyright
7 * notice and this permission notice appear in supporting
8 * documentation, and that the name of M.I.T. not be used in
9 * advertising or publicity pertaining to distribution of the
10 * software without specific, written prior permission.
11 * M.I.T. makes no representations about the suitability of
12 * this software for any purpose. It is provided "as is"
13 * without express or implied warranty.
14 */
15
16 /*
17 * ares_parse_ns_reply created by Vlad Dinulescu <vlad.dinulescu@avira.com>
18 * on behalf of AVIRA Gmbh - http://www.avira.com
19 */
20
21 #include "ares_setup.h"
22
23 #ifdef HAVE_SYS_SOCKET_H
24 # include <sys/socket.h>
25 #endif
26 #ifdef HAVE_NETINET_IN_H
27 # include <netinet/in.h>
28 #endif
29 #ifdef HAVE_NETDB_H
30 # include <netdb.h>
31 #endif
32 #ifdef HAVE_ARPA_INET_H
33 # include <arpa/inet.h>
34 #endif
35 #ifdef HAVE_ARPA_NAMESER_H
36 # include <arpa/nameser.h>
37 #else
38 # include "nameser.h"
39 #endif
40 #ifdef HAVE_ARPA_NAMESER_COMPAT_H
41 # include <arpa/nameser_compat.h>
42 #endif
43
44 #include <stdlib.h>
45 #include <string.h>
46 #include "ares.h"
47 #include "ares_dns.h"
48 #include "ares_private.h"
49
ares_parse_ns_reply(const unsigned char * abuf,int alen,struct hostent ** host)50 int ares_parse_ns_reply( const unsigned char* abuf, int alen,
51 struct hostent** host )
52 {
53 unsigned int qdcount, ancount;
54 int status, i, rr_type, rr_class, rr_len;
55 int nameservers_num;
56 long len;
57 const unsigned char *aptr;
58 char* hostname, *rr_name, *rr_data, **nameservers;
59 struct hostent *hostent;
60
61 /* Set *host to NULL for all failure cases. */
62 *host = 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
74 /* Expand the name from the question, and skip past the question. */
75 aptr = abuf + HFIXEDSZ;
76 status = ares__expand_name_for_response( aptr, abuf, alen, &hostname, &len);
77 if ( status != ARES_SUCCESS )
78 return status;
79 if ( aptr + len + QFIXEDSZ > abuf + alen )
80 {
81 free( hostname );
82 return ARES_EBADRESP;
83 }
84 aptr += len + QFIXEDSZ;
85
86 /* Allocate nameservers array; ancount gives an upper bound */
87 nameservers = malloc( ( ancount + 1 ) * sizeof( char * ) );
88 if ( !nameservers )
89 {
90 free( hostname );
91 return ARES_ENOMEM;
92 }
93 nameservers_num = 0;
94
95 /* Examine each answer resource record (RR) in turn. */
96 for ( i = 0; i < ( int ) ancount; i++ )
97 {
98 /* Decode the RR up to the data field. */
99 status = ares__expand_name_for_response( aptr, abuf, alen, &rr_name, &len );
100 if ( status != ARES_SUCCESS )
101 break;
102 aptr += len;
103 if ( aptr + RRFIXEDSZ > abuf + alen )
104 {
105 status = ARES_EBADRESP;
106 free(rr_name);
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 if ( rr_class == C_IN && rr_type == T_NS )
115 {
116 /* Decode the RR data and add it to the nameservers list */
117 status = ares__expand_name_for_response( aptr, abuf, alen, &rr_data,
118 &len);
119 if ( status != ARES_SUCCESS )
120 {
121 free(rr_name);
122 break;
123 }
124
125 nameservers[nameservers_num] = malloc(strlen(rr_data)+1);
126
127 if (nameservers[nameservers_num]==NULL)
128 {
129 free(rr_name);
130 free(rr_data);
131 status=ARES_ENOMEM;
132 break;
133 }
134 strcpy(nameservers[nameservers_num],rr_data);
135 free(rr_data);
136
137 nameservers_num++;
138 }
139
140 free( rr_name );
141
142 aptr += rr_len;
143 if ( aptr > abuf + alen )
144 {
145 status = ARES_EBADRESP;
146 break;
147 }
148 }
149
150 if ( status == ARES_SUCCESS && nameservers_num == 0 )
151 {
152 status = ARES_ENODATA;
153 }
154 if ( status == ARES_SUCCESS )
155 {
156 /* We got our answer. Allocate memory to build the host entry. */
157 nameservers[nameservers_num] = NULL;
158 hostent = malloc( sizeof( struct hostent ) );
159 if ( hostent )
160 {
161 hostent->h_addr_list = malloc( 1 * sizeof( char * ) );
162 if ( hostent->h_addr_list )
163 {
164 /* Fill in the hostent and return successfully. */
165 hostent->h_name = hostname;
166 hostent->h_aliases = nameservers;
167 hostent->h_addrtype = AF_INET;
168 hostent->h_length = sizeof( struct in_addr );
169 hostent->h_addr_list[0] = NULL;
170 *host = hostent;
171 return ARES_SUCCESS;
172 }
173 free( hostent );
174 }
175 status = ARES_ENOMEM;
176 }
177 for ( i = 0; i < nameservers_num; i++ )
178 free( nameservers[i] );
179 free( nameservers );
180 free( hostname );
181 return status;
182 }
183