1
2 /* Copyright 1998 by the Massachusetts Institute of Technology.
3 *
4 * Permission to use, copy, modify, and distribute this
5 * software and its documentation for any purpose and without
6 * fee is hereby granted, provided that the above copyright
7 * notice appear in all copies and that both that copyright
8 * notice and this permission notice appear in supporting
9 * documentation, and that the name of M.I.T. not be used in
10 * advertising or publicity pertaining to distribution of the
11 * software without specific, written prior permission.
12 * M.I.T. makes no representations about the suitability of
13 * this software for any purpose. It is provided "as is"
14 * without express or implied warranty.
15 */
16
17 #include "ares_setup.h"
18
19 #ifdef HAVE_NETINET_IN_H
20 # include <netinet/in.h>
21 #endif
22 #ifdef HAVE_NETDB_H
23 # include <netdb.h>
24 #endif
25 #ifdef HAVE_ARPA_NAMESER_H
26 # include <arpa/nameser.h>
27 #else
28 # include "nameser.h"
29 #endif
30 #ifdef HAVE_ARPA_NAMESER_COMPAT_H
31 # include <arpa/nameser_compat.h>
32 #endif
33
34 #ifdef HAVE_STRINGS_H
35 # include <strings.h>
36 #endif
37
38 #include "ares.h"
39 #include "ares_dns.h"
40 #include "ares_nowarn.h"
41 #include "ares_private.h"
42
ares_parse_ptr_reply(const unsigned char * abuf,int alen,const void * addr,int addrlen,int family,struct hostent ** host)43 int ares_parse_ptr_reply(const unsigned char *abuf, int alen, const void *addr,
44 int addrlen, int family, struct hostent **host)
45 {
46 unsigned int qdcount, ancount;
47 int status, i, rr_type, rr_class, rr_len;
48 long len;
49 const unsigned char *aptr;
50 char *ptrname, *hostname, *rr_name, *rr_data;
51 struct hostent *hostent;
52 int aliascnt = 0;
53 int alias_alloc = 8;
54 char ** aliases;
55 size_t rr_data_len;
56
57 /* Set *host to NULL for all failure cases. */
58 *host = NULL;
59
60 /* Give up if abuf doesn't have room for a header. */
61 if (alen < HFIXEDSZ)
62 return ARES_EBADRESP;
63
64 /* Fetch the question and answer count from the header. */
65 qdcount = DNS_HEADER_QDCOUNT(abuf);
66 ancount = DNS_HEADER_ANCOUNT(abuf);
67 if (qdcount != 1)
68 return ARES_EBADRESP;
69
70 /* Expand the name from the question, and skip past the question. */
71 aptr = abuf + HFIXEDSZ;
72 status = ares__expand_name_for_response(aptr, abuf, alen, &ptrname, &len);
73 if (status != ARES_SUCCESS)
74 return status;
75 if (aptr + len + QFIXEDSZ > abuf + alen)
76 {
77 ares_free(ptrname);
78 return ARES_EBADRESP;
79 }
80 aptr += len + QFIXEDSZ;
81
82 /* Examine each answer resource record (RR) in turn. */
83 hostname = NULL;
84 aliases = ares_malloc(alias_alloc * sizeof(char *));
85 if (!aliases)
86 {
87 ares_free(ptrname);
88 return ARES_ENOMEM;
89 }
90 for (i = 0; i < (int)ancount; i++)
91 {
92 /* Decode the RR up to the data field. */
93 status = ares__expand_name_for_response(aptr, abuf, alen, &rr_name, &len);
94 if (status != ARES_SUCCESS)
95 break;
96 aptr += len;
97 if (aptr + RRFIXEDSZ > abuf + alen)
98 {
99 ares_free(rr_name);
100 status = ARES_EBADRESP;
101 break;
102 }
103 rr_type = DNS_RR_TYPE(aptr);
104 rr_class = DNS_RR_CLASS(aptr);
105 rr_len = DNS_RR_LEN(aptr);
106 aptr += RRFIXEDSZ;
107 if (aptr + rr_len > abuf + alen)
108 {
109 ares_free(rr_name);
110 status = ARES_EBADRESP;
111 break;
112 }
113
114 if (rr_class == C_IN && rr_type == T_PTR
115 && strcasecmp(rr_name, ptrname) == 0)
116 {
117 /* Decode the RR data and set hostname to it. */
118 status = ares__expand_name_for_response(aptr, abuf, alen, &rr_data,
119 &len);
120 if (status != ARES_SUCCESS)
121 {
122 ares_free(rr_name);
123 break;
124 }
125 if (hostname)
126 ares_free(hostname);
127 hostname = rr_data;
128 rr_data_len = strlen(rr_data)+1;
129 aliases[aliascnt] = ares_malloc(rr_data_len * sizeof(char));
130 if (!aliases[aliascnt])
131 {
132 ares_free(rr_name);
133 status = ARES_ENOMEM;
134 break;
135 }
136 strncpy(aliases[aliascnt], rr_data, rr_data_len);
137 aliascnt++;
138 if (aliascnt >= alias_alloc) {
139 char **ptr;
140 alias_alloc *= 2;
141 ptr = ares_realloc(aliases, alias_alloc * sizeof(char *));
142 if(!ptr) {
143 ares_free(rr_name);
144 status = ARES_ENOMEM;
145 break;
146 }
147 aliases = ptr;
148 }
149 }
150
151 if (rr_class == C_IN && rr_type == T_CNAME)
152 {
153 /* Decode the RR data and replace ptrname with it. */
154 status = ares__expand_name_for_response(aptr, abuf, alen, &rr_data,
155 &len);
156 if (status != ARES_SUCCESS)
157 {
158 ares_free(rr_name);
159 break;
160 }
161 ares_free(ptrname);
162 ptrname = rr_data;
163 }
164
165 ares_free(rr_name);
166 aptr += rr_len;
167 if (aptr > abuf + alen)
168 { /* LCOV_EXCL_START: already checked above */
169 status = ARES_EBADRESP;
170 break;
171 } /* LCOV_EXCL_STOP */
172 }
173
174 if (status == ARES_SUCCESS && !hostname)
175 status = ARES_ENODATA;
176 if (status == ARES_SUCCESS)
177 {
178 /* We got our answer. Allocate memory to build the host entry. */
179 hostent = ares_malloc(sizeof(struct hostent));
180 if (hostent)
181 {
182 hostent->h_addr_list = ares_malloc(2 * sizeof(char *));
183 if (hostent->h_addr_list)
184 {
185 hostent->h_addr_list[0] = ares_malloc(addrlen);
186 if (hostent->h_addr_list[0])
187 {
188 hostent->h_aliases = ares_malloc((aliascnt+1) * sizeof (char *));
189 if (hostent->h_aliases)
190 {
191 /* Fill in the hostent and return successfully. */
192 hostent->h_name = hostname;
193 for (i=0 ; i<aliascnt ; i++)
194 hostent->h_aliases[i] = aliases[i];
195 hostent->h_aliases[aliascnt] = NULL;
196 hostent->h_addrtype = aresx_sitoss(family);
197 hostent->h_length = aresx_sitoss(addrlen);
198 memcpy(hostent->h_addr_list[0], addr, addrlen);
199 hostent->h_addr_list[1] = NULL;
200 *host = hostent;
201 ares_free(aliases);
202 ares_free(ptrname);
203 return ARES_SUCCESS;
204 }
205 ares_free(hostent->h_addr_list[0]);
206 }
207 ares_free(hostent->h_addr_list);
208 }
209 ares_free(hostent);
210 }
211 status = ARES_ENOMEM;
212 }
213 for (i=0 ; i<aliascnt ; i++)
214 if (aliases[i])
215 ares_free(aliases[i]);
216 ares_free(aliases);
217 if (hostname)
218 ares_free(hostname);
219 ares_free(ptrname);
220 return status;
221 }
222