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_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 #ifdef HAVE_STRINGS_H
42 # include <strings.h>
43 #endif
44
45 #include <stdlib.h>
46 #include <string.h>
47
48 #include "ares.h"
49 #include "ares_dns.h"
50 #include "ares_data.h"
51 #include "ares_private.h"
52
53 int
ares_parse_txt_reply(const unsigned char * abuf,int alen,struct ares_txt_reply ** txt_out)54 ares_parse_txt_reply (const unsigned char *abuf, int alen,
55 struct ares_txt_reply **txt_out)
56 {
57 size_t substr_len, str_len;
58 unsigned int qdcount, ancount, i;
59 const unsigned char *aptr;
60 const unsigned char *strptr;
61 int status, rr_type, rr_class, rr_len;
62 long len;
63 char *hostname = NULL, *rr_name = NULL;
64 struct ares_txt_reply *txt_head = NULL;
65 struct ares_txt_reply *txt_last = NULL;
66 struct ares_txt_reply *txt_curr;
67
68 /* Set *txt_out to NULL for all failure cases. */
69 *txt_out = NULL;
70
71 /* Give up if abuf doesn't have room for a header. */
72 if (alen < HFIXEDSZ)
73 return ARES_EBADRESP;
74
75 /* Fetch the question and answer count from the header. */
76 qdcount = DNS_HEADER_QDCOUNT (abuf);
77 ancount = DNS_HEADER_ANCOUNT (abuf);
78 if (qdcount != 1)
79 return ARES_EBADRESP;
80 if (ancount == 0)
81 return ARES_ENODATA;
82
83 /* Expand the name from the question, and skip past the question. */
84 aptr = abuf + HFIXEDSZ;
85 status = ares_expand_name (aptr, abuf, alen, &hostname, &len);
86 if (status != ARES_SUCCESS)
87 return status;
88
89 if (aptr + len + QFIXEDSZ > abuf + alen)
90 {
91 free (hostname);
92 return ARES_EBADRESP;
93 }
94 aptr += len + QFIXEDSZ;
95
96 /* Examine each answer resource record (RR) in turn. */
97 for (i = 0; i < ancount; i++)
98 {
99 /* Decode the RR up to the data field. */
100 status = ares_expand_name (aptr, abuf, alen, &rr_name, &len);
101 if (status != ARES_SUCCESS)
102 {
103 break;
104 }
105 aptr += len;
106 if (aptr + RRFIXEDSZ > abuf + alen)
107 {
108 status = ARES_EBADRESP;
109 break;
110 }
111 rr_type = DNS_RR_TYPE (aptr);
112 rr_class = DNS_RR_CLASS (aptr);
113 rr_len = DNS_RR_LEN (aptr);
114 aptr += RRFIXEDSZ;
115
116 /* Check if we are really looking at a TXT record */
117 if (rr_class == C_IN && rr_type == T_TXT)
118 {
119 /* Allocate storage for this TXT answer appending it to the list */
120 txt_curr = ares_malloc_data(ARES_DATATYPE_TXT_REPLY);
121 if (!txt_curr)
122 {
123 status = ARES_ENOMEM;
124 break;
125 }
126 if (txt_last)
127 {
128 txt_last->next = txt_curr;
129 }
130 else
131 {
132 txt_head = txt_curr;
133 }
134 txt_last = txt_curr;
135
136 /*
137 * There may be multiple substrings in a single TXT record. Each
138 * substring may be up to 255 characters in length, with a
139 * "length byte" indicating the size of the substring payload.
140 * RDATA contains both the length-bytes and payloads of all
141 * substrings contained therein.
142 */
143
144 /* Compute total length to allow a single memory allocation */
145 strptr = aptr;
146 while (strptr < (aptr + rr_len))
147 {
148 substr_len = (unsigned char)*strptr;
149 txt_curr->length += substr_len;
150 strptr += substr_len + 1;
151 }
152
153 /* Including null byte */
154 txt_curr->txt = malloc (txt_curr->length + 1);
155 if (txt_curr->txt == NULL)
156 {
157 status = ARES_ENOMEM;
158 break;
159 }
160
161 /* Step through the list of substrings, concatenating them */
162 str_len = 0;
163 strptr = aptr;
164 while (strptr < (aptr + rr_len))
165 {
166 substr_len = (unsigned char)*strptr;
167 strptr++;
168 memcpy ((char *) txt_curr->txt + str_len, strptr, substr_len);
169 str_len += substr_len;
170 strptr += substr_len;
171 }
172 /* Make sure we NULL-terminate */
173 *((char *) txt_curr->txt + txt_curr->length) = '\0';
174 }
175
176 /* Don't lose memory in the next iteration */
177 free (rr_name);
178 rr_name = NULL;
179
180 /* Move on to the next record */
181 aptr += rr_len;
182 }
183
184 if (hostname)
185 free (hostname);
186 if (rr_name)
187 free (rr_name);
188
189 /* clean up on error */
190 if (status != ARES_SUCCESS)
191 {
192 if (txt_head)
193 ares_free_data (txt_head);
194 return status;
195 }
196
197 /* everything looks fine, return the data */
198 *txt_out = txt_head;
199
200 return ARES_SUCCESS;
201 }
202