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_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
33 #include "ares_nameser.h"
34
35 #include "ares.h"
36 #include "ares_dns.h"
37 #include "ares_private.h"
38
ares_parse_ns_reply(const unsigned char * abuf,int alen,struct hostent ** host)39 int ares_parse_ns_reply( const unsigned char* abuf, int alen,
40 struct hostent** host )
41 {
42 unsigned int qdcount, ancount;
43 int status, i, rr_type, rr_class, rr_len;
44 int nameservers_num;
45 long len;
46 const unsigned char *aptr;
47 char* hostname, *rr_name, *rr_data, **nameservers;
48 struct hostent *hostent;
49
50 /* Set *host to NULL for all failure cases. */
51 *host = NULL;
52
53 /* Give up if abuf doesn't have room for a header. */
54 if ( alen < HFIXEDSZ )
55 return ARES_EBADRESP;
56
57 /* Fetch the question and answer count from the header. */
58 qdcount = DNS_HEADER_QDCOUNT( abuf );
59 ancount = DNS_HEADER_ANCOUNT( abuf );
60 if ( qdcount != 1 )
61 return ARES_EBADRESP;
62
63 /* Expand the name from the question, and skip past the question. */
64 aptr = abuf + HFIXEDSZ;
65 status = ares__expand_name_for_response( aptr, abuf, alen, &hostname, &len, 0);
66 if ( status != ARES_SUCCESS )
67 return status;
68 if ( aptr + len + QFIXEDSZ > abuf + alen )
69 {
70 ares_free( hostname );
71 return ARES_EBADRESP;
72 }
73 aptr += len + QFIXEDSZ;
74
75 /* Allocate nameservers array; ancount gives an upper bound */
76 nameservers = ares_malloc( ( ancount + 1 ) * sizeof( char * ) );
77 if ( !nameservers )
78 {
79 ares_free( hostname );
80 return ARES_ENOMEM;
81 }
82 nameservers_num = 0;
83
84 /* Examine each answer resource record (RR) in turn. */
85 for ( i = 0; i < ( int ) ancount; i++ )
86 {
87 /* Decode the RR up to the data field. */
88 status = ares__expand_name_for_response( aptr, abuf, alen, &rr_name, &len, 0);
89 if ( status != ARES_SUCCESS )
90 break;
91 aptr += len;
92 if ( aptr + RRFIXEDSZ > abuf + alen )
93 {
94 status = ARES_EBADRESP;
95 ares_free(rr_name);
96 break;
97 }
98 rr_type = DNS_RR_TYPE( aptr );
99 rr_class = DNS_RR_CLASS( aptr );
100 rr_len = DNS_RR_LEN( aptr );
101 aptr += RRFIXEDSZ;
102 if (aptr + rr_len > abuf + alen)
103 {
104 ares_free(rr_name);
105 status = ARES_EBADRESP;
106 break;
107 }
108
109 if ( rr_class == C_IN && rr_type == T_NS )
110 {
111 /* Decode the RR data and add it to the nameservers list */
112 status = ares__expand_name_for_response( aptr, abuf, alen, &rr_data,
113 &len, 1);
114 if ( status != ARES_SUCCESS )
115 {
116 ares_free(rr_name);
117 break;
118 }
119
120 nameservers[nameservers_num] = ares_malloc(strlen(rr_data)+1);
121
122 if (nameservers[nameservers_num]==NULL)
123 {
124 ares_free(rr_name);
125 ares_free(rr_data);
126 status=ARES_ENOMEM;
127 break;
128 }
129 strcpy(nameservers[nameservers_num],rr_data);
130 ares_free(rr_data);
131
132 nameservers_num++;
133 }
134
135 ares_free( rr_name );
136
137 aptr += rr_len;
138 if ( aptr > abuf + alen )
139 { /* LCOV_EXCL_START: already checked above */
140 status = ARES_EBADRESP;
141 break;
142 } /* LCOV_EXCL_STOP */
143 }
144
145 if ( status == ARES_SUCCESS && nameservers_num == 0 )
146 {
147 status = ARES_ENODATA;
148 }
149 if ( status == ARES_SUCCESS )
150 {
151 /* We got our answer. Allocate memory to build the host entry. */
152 nameservers[nameservers_num] = NULL;
153 hostent = ares_malloc( sizeof( struct hostent ) );
154 if ( hostent )
155 {
156 hostent->h_addr_list = ares_malloc( 1 * sizeof( char * ) );
157 if ( hostent->h_addr_list )
158 {
159 /* Fill in the hostent and return successfully. */
160 hostent->h_name = hostname;
161 hostent->h_aliases = nameservers;
162 hostent->h_addrtype = AF_INET;
163 hostent->h_length = sizeof( struct in_addr );
164 hostent->h_addr_list[0] = NULL;
165 *host = hostent;
166 return ARES_SUCCESS;
167 }
168 ares_free( hostent );
169 }
170 status = ARES_ENOMEM;
171 }
172 for ( i = 0; i < nameservers_num; i++ )
173 ares_free( nameservers[i] );
174 ares_free( nameservers );
175 ares_free( hostname );
176 return status;
177 }
178