1
2 /* Copyright 1998 by the Massachusetts Institute of Technology.
3 * Copyright 2005 Dominick Meglio
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 #ifdef HAVE_STRINGS_H
39 # include <strings.h>
40 #endif
41
42 #ifdef HAVE_LIMITS_H
43 # include <limits.h>
44 #endif
45
46 #include "ares.h"
47 #include "ares_dns.h"
48 #include "ares_inet_net_pton.h"
49 #include "ares_private.h"
50
ares_parse_aaaa_reply(const unsigned char * abuf,int alen,struct hostent ** host,struct ares_addr6ttl * addrttls,int * naddrttls)51 int ares_parse_aaaa_reply(const unsigned char *abuf, int alen,
52 struct hostent **host, struct ares_addr6ttl *addrttls,
53 int *naddrttls)
54 {
55 unsigned int qdcount, ancount;
56 int status, i, rr_type, rr_class, rr_len, rr_ttl, naddrs;
57 int cname_ttl = INT_MAX; /* the TTL imposed by the CNAME chain */
58 int naliases;
59 long len;
60 const unsigned char *aptr;
61 char *hostname, *rr_name, *rr_data, **aliases;
62 struct ares_in6_addr *addrs;
63 struct hostent *hostent;
64 const int max_addr_ttls = (addrttls && naddrttls) ? *naddrttls : 0;
65
66 /* Set *host to NULL for all failure cases. */
67 if (host)
68 *host = NULL;
69 /* Same with *naddrttls. */
70 if (naddrttls)
71 *naddrttls = 0;
72
73 /* Give up if abuf doesn't have room for a header. */
74 if (alen < HFIXEDSZ)
75 return ARES_EBADRESP;
76
77 /* Fetch the question and answer count from the header. */
78 qdcount = DNS_HEADER_QDCOUNT(abuf);
79 ancount = DNS_HEADER_ANCOUNT(abuf);
80 if (qdcount != 1)
81 return ARES_EBADRESP;
82
83 /* Expand the name from the question, and skip past the question. */
84 aptr = abuf + HFIXEDSZ;
85 status = ares__expand_name_for_response(aptr, abuf, alen, &hostname, &len);
86 if (status != ARES_SUCCESS)
87 return status;
88 if (aptr + len + QFIXEDSZ > abuf + alen)
89 {
90 ares_free(hostname);
91 return ARES_EBADRESP;
92 }
93 aptr += len + QFIXEDSZ;
94
95 /* Allocate addresses and aliases; ancount gives an upper bound for both. */
96 if (host)
97 {
98 addrs = ares_malloc(ancount * sizeof(struct ares_in6_addr));
99 if (!addrs)
100 {
101 ares_free(hostname);
102 return ARES_ENOMEM;
103 }
104 aliases = ares_malloc((ancount + 1) * sizeof(char *));
105 if (!aliases)
106 {
107 ares_free(hostname);
108 ares_free(addrs);
109 return ARES_ENOMEM;
110 }
111 }
112 else
113 {
114 addrs = NULL;
115 aliases = NULL;
116 }
117 naddrs = 0;
118 naliases = 0;
119
120 /* Examine each answer resource record (RR) in turn. */
121 for (i = 0; i < (int)ancount; i++)
122 {
123 /* Decode the RR up to the data field. */
124 status = ares__expand_name_for_response(aptr, abuf, alen, &rr_name, &len);
125 if (status != ARES_SUCCESS)
126 break;
127 aptr += len;
128 if (aptr + RRFIXEDSZ > abuf + alen)
129 {
130 ares_free(rr_name);
131 status = ARES_EBADRESP;
132 break;
133 }
134 rr_type = DNS_RR_TYPE(aptr);
135 rr_class = DNS_RR_CLASS(aptr);
136 rr_len = DNS_RR_LEN(aptr);
137 rr_ttl = DNS_RR_TTL(aptr);
138 aptr += RRFIXEDSZ;
139 if (aptr + rr_len > abuf + alen)
140 {
141 ares_free(rr_name);
142 status = ARES_EBADRESP;
143 break;
144 }
145
146 if (rr_class == C_IN && rr_type == T_AAAA
147 && rr_len == sizeof(struct ares_in6_addr)
148 && strcasecmp(rr_name, hostname) == 0)
149 {
150 if (addrs)
151 {
152 if (aptr + sizeof(struct ares_in6_addr) > abuf + alen)
153 { /* LCOV_EXCL_START: already checked above */
154 ares_free(rr_name);
155 status = ARES_EBADRESP;
156 break;
157 } /* LCOV_EXCL_STOP */
158 memcpy(&addrs[naddrs], aptr, sizeof(struct ares_in6_addr));
159 }
160 if (naddrs < max_addr_ttls)
161 {
162 struct ares_addr6ttl * const at = &addrttls[naddrs];
163 if (aptr + sizeof(struct ares_in6_addr) > abuf + alen)
164 { /* LCOV_EXCL_START: already checked above */
165 ares_free(rr_name);
166 status = ARES_EBADRESP;
167 break;
168 } /* LCOV_EXCL_STOP */
169 memcpy(&at->ip6addr, aptr, sizeof(struct ares_in6_addr));
170 at->ttl = rr_ttl;
171 }
172 naddrs++;
173 status = ARES_SUCCESS;
174 }
175
176 if (rr_class == C_IN && rr_type == T_CNAME)
177 {
178 /* Record the RR name as an alias. */
179 if (aliases)
180 aliases[naliases] = rr_name;
181 else
182 ares_free(rr_name);
183 naliases++;
184
185 /* Decode the RR data and replace the hostname with it. */
186 status = ares__expand_name_for_response(aptr, abuf, alen, &rr_data,
187 &len);
188 if (status != ARES_SUCCESS)
189 break;
190 ares_free(hostname);
191 hostname = rr_data;
192
193 /* Take the min of the TTLs we see in the CNAME chain. */
194 if (cname_ttl > rr_ttl)
195 cname_ttl = rr_ttl;
196 }
197 else
198 ares_free(rr_name);
199
200 aptr += rr_len;
201 if (aptr > abuf + alen)
202 { /* LCOV_EXCL_START: already checked above */
203 status = ARES_EBADRESP;
204 break;
205 } /* LCOV_EXCL_STOP */
206 }
207
208 /* the check for naliases to be zero is to make sure CNAME responses
209 don't get caught here */
210 if (status == ARES_SUCCESS && naddrs == 0 && naliases == 0)
211 status = ARES_ENODATA;
212 if (status == ARES_SUCCESS)
213 {
214 /* We got our answer. */
215 if (naddrttls)
216 {
217 const int n = naddrs < max_addr_ttls ? naddrs : max_addr_ttls;
218 for (i = 0; i < n; i++)
219 {
220 /* Ensure that each A TTL is no larger than the CNAME TTL. */
221 if (addrttls[i].ttl > cname_ttl)
222 addrttls[i].ttl = cname_ttl;
223 }
224 *naddrttls = n;
225 }
226 if (aliases)
227 aliases[naliases] = NULL;
228 if (host)
229 {
230 /* Allocate memory to build the host entry. */
231 hostent = ares_malloc(sizeof(struct hostent));
232 if (hostent)
233 {
234 hostent->h_addr_list = ares_malloc((naddrs + 1) * sizeof(char *));
235 if (hostent->h_addr_list)
236 {
237 /* Fill in the hostent and return successfully. */
238 hostent->h_name = hostname;
239 hostent->h_aliases = aliases;
240 hostent->h_addrtype = AF_INET6;
241 hostent->h_length = sizeof(struct ares_in6_addr);
242 for (i = 0; i < naddrs; i++)
243 hostent->h_addr_list[i] = (char *) &addrs[i];
244 hostent->h_addr_list[naddrs] = NULL;
245 if (!naddrs && addrs)
246 ares_free(addrs);
247 *host = hostent;
248 return ARES_SUCCESS;
249 }
250 ares_free(hostent);
251 }
252 status = ARES_ENOMEM;
253 }
254 }
255 if (aliases)
256 {
257 for (i = 0; i < naliases; i++)
258 ares_free(aliases[i]);
259 ares_free(aliases);
260 }
261 ares_free(addrs);
262 ares_free(hostname);
263 return status;
264 }
265