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
30 #include "ares_nameser.h"
31
32 #ifdef HAVE_STRINGS_H
33 # include <strings.h>
34 #endif
35
36 #include "ares.h"
37 #include "ares_dns.h"
38 #include "ares_data.h"
39 #include "ares_private.h"
40
41 static int
ares__parse_txt_reply(const unsigned char * abuf,int alen,int ex,void ** txt_out)42 ares__parse_txt_reply (const unsigned char *abuf, int alen,
43 int ex, void **txt_out)
44 {
45 size_t substr_len;
46 unsigned int qdcount, ancount, i;
47 const unsigned char *aptr;
48 const unsigned char *strptr;
49 int status, rr_type, rr_class, rr_len;
50 long len;
51 char *hostname = NULL, *rr_name = NULL;
52 struct ares_txt_ext *txt_head = NULL;
53 struct ares_txt_ext *txt_last = NULL;
54 struct ares_txt_ext *txt_curr;
55
56 /* Set *txt_out to NULL for all failure cases. */
57 *txt_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 TXT record */
110 if ((rr_class == C_IN || rr_class == C_CHAOS) && rr_type == T_TXT)
111 {
112 /*
113 * There may be multiple substrings in a single TXT record. Each
114 * substring may be up to 255 characters in length, with a
115 * "length byte" indicating the size of the substring payload.
116 * RDATA contains both the length-bytes and payloads of all
117 * substrings contained therein.
118 */
119
120 strptr = aptr;
121 while (strptr < (aptr + rr_len))
122 {
123 substr_len = (unsigned char)*strptr;
124 if (strptr + substr_len + 1 > aptr + rr_len)
125 {
126 status = ARES_EBADRESP;
127 break;
128 }
129
130 /* Allocate storage for this TXT answer appending it to the list */
131 txt_curr = ares_malloc_data(ex ? ARES_DATATYPE_TXT_EXT :
132 ARES_DATATYPE_TXT_REPLY);
133 if (!txt_curr)
134 {
135 status = ARES_ENOMEM;
136 break;
137 }
138 if (txt_last)
139 {
140 txt_last->next = txt_curr;
141 }
142 else
143 {
144 txt_head = txt_curr;
145 }
146 txt_last = txt_curr;
147
148 if (ex)
149 txt_curr->record_start = (strptr == aptr);
150 txt_curr->length = substr_len;
151 txt_curr->txt = ares_malloc (substr_len + 1/* Including null byte */);
152 if (txt_curr->txt == NULL)
153 {
154 status = ARES_ENOMEM;
155 break;
156 }
157
158 ++strptr;
159 memcpy ((char *) txt_curr->txt, strptr, substr_len);
160
161 /* Make sure we NULL-terminate */
162 txt_curr->txt[substr_len] = 0;
163
164 strptr += substr_len;
165 }
166 }
167
168 /* Propagate any failures */
169 if (status != ARES_SUCCESS)
170 {
171 break;
172 }
173
174 /* Don't lose memory in the next iteration */
175 ares_free (rr_name);
176 rr_name = NULL;
177
178 /* Move on to the next record */
179 aptr += rr_len;
180 }
181
182 if (hostname)
183 ares_free (hostname);
184 if (rr_name)
185 ares_free (rr_name);
186
187 /* clean up on error */
188 if (status != ARES_SUCCESS)
189 {
190 if (txt_head)
191 ares_free_data (txt_head);
192 return status;
193 }
194
195 /* everything looks fine, return the data */
196 *txt_out = txt_head;
197
198 return ARES_SUCCESS;
199 }
200
201 int
ares_parse_txt_reply(const unsigned char * abuf,int alen,struct ares_txt_reply ** txt_out)202 ares_parse_txt_reply (const unsigned char *abuf, int alen,
203 struct ares_txt_reply **txt_out)
204 {
205 return ares__parse_txt_reply(abuf, alen, 0, (void **) txt_out);
206 }
207
208
209 int
ares_parse_txt_reply_ext(const unsigned char * abuf,int alen,struct ares_txt_ext ** txt_out)210 ares_parse_txt_reply_ext (const unsigned char *abuf, int alen,
211 struct ares_txt_ext **txt_out)
212 {
213 return ares__parse_txt_reply(abuf, alen, 1, (void **) txt_out);
214 }
215