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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 #include "ares_setup.h"
17 
18 #ifdef HAVE_SYS_SOCKET_H
19 #  include <sys/socket.h>
20 #endif
21 #ifdef HAVE_NETINET_IN_H
22 #  include <netinet/in.h>
23 #endif
24 #ifdef HAVE_NETDB_H
25 #  include <netdb.h>
26 #endif
27 #ifdef HAVE_ARPA_INET_H
28 #  include <arpa/inet.h>
29 #endif
30 #ifdef HAVE_ARPA_NAMESER_H
31 #  include <arpa/nameser.h>
32 #else
33 #  include "nameser.h"
34 #endif
35 #ifdef HAVE_ARPA_NAMESER_COMPAT_H
36 #  include <arpa/nameser_compat.h>
37 #endif
38 
39 #include <stdio.h>
40 #include <stdlib.h>
41 #include <string.h>
42 
43 #include "ares.h"
44 #include "inet_net_pton.h"
45 #include "ares_platform.h"
46 #include "ares_private.h"
47 
48 #ifdef WATT32
49 #undef WIN32
50 #endif
51 
52 struct addr_query {
53   /* Arguments passed to ares_gethostbyaddr() */
54   ares_channel channel;
55   struct ares_addr addr;
56   ares_host_callback callback;
57   void *arg;
58 
59   const char *remaining_lookups;
60   int timeouts;
61 };
62 
63 static void next_lookup(struct addr_query *aquery);
64 static void addr_callback(void *arg, int status, int timeouts,
65                           unsigned char *abuf, int alen);
66 static void end_aquery(struct addr_query *aquery, int status,
67                        struct hostent *host);
68 static int file_lookup(struct ares_addr *addr, struct hostent **host);
69 static void ptr_rr_name(char *name, const struct ares_addr *addr);
70 
ares_gethostbyaddr(ares_channel channel,const void * addr,int addrlen,int family,ares_host_callback callback,void * arg)71 void ares_gethostbyaddr(ares_channel channel, const void *addr, int addrlen,
72                         int family, ares_host_callback callback, void *arg)
73 {
74   struct addr_query *aquery;
75 
76   if (family != AF_INET && family != AF_INET6)
77     {
78       callback(arg, ARES_ENOTIMP, 0, NULL);
79       return;
80     }
81 
82   if ((family == AF_INET && addrlen != sizeof(aquery->addr.addrV4)) ||
83       (family == AF_INET6 && addrlen != sizeof(aquery->addr.addrV6)))
84     {
85       callback(arg, ARES_ENOTIMP, 0, NULL);
86       return;
87     }
88 
89   aquery = malloc(sizeof(struct addr_query));
90   if (!aquery)
91     {
92       callback(arg, ARES_ENOMEM, 0, NULL);
93       return;
94     }
95   aquery->channel = channel;
96   if (family == AF_INET)
97     memcpy(&aquery->addr.addrV4, addr, sizeof(aquery->addr.addrV4));
98   else
99     memcpy(&aquery->addr.addrV6, addr, sizeof(aquery->addr.addrV6));
100   aquery->addr.family = family;
101   aquery->callback = callback;
102   aquery->arg = arg;
103   aquery->remaining_lookups = channel->lookups;
104   aquery->timeouts = 0;
105 
106   next_lookup(aquery);
107 }
108 
next_lookup(struct addr_query * aquery)109 static void next_lookup(struct addr_query *aquery)
110 {
111   const char *p;
112   char name[128];
113   int status;
114   struct hostent *host;
115 
116   for (p = aquery->remaining_lookups; *p; p++)
117     {
118       switch (*p)
119         {
120         case 'b':
121           ptr_rr_name(name, &aquery->addr);
122           aquery->remaining_lookups = p + 1;
123           ares_query(aquery->channel, name, C_IN, T_PTR, addr_callback,
124                      aquery);
125           return;
126         case 'f':
127           status = file_lookup(&aquery->addr, &host);
128 
129           /* this status check below previously checked for !ARES_ENOTFOUND,
130              but we should not assume that this single error code is the one
131              that can occur, as that is in fact no longer the case */
132           if (status == ARES_SUCCESS)
133             {
134               end_aquery(aquery, status, host);
135               return;
136             }
137           break;
138         }
139     }
140   end_aquery(aquery, ARES_ENOTFOUND, NULL);
141 }
142 
addr_callback(void * arg,int status,int timeouts,unsigned char * abuf,int alen)143 static void addr_callback(void *arg, int status, int timeouts,
144                           unsigned char *abuf, int alen)
145 {
146   struct addr_query *aquery = (struct addr_query *) arg;
147   struct hostent *host;
148   size_t addrlen;
149 
150   aquery->timeouts += timeouts;
151   if (status == ARES_SUCCESS)
152     {
153       if (aquery->addr.family == AF_INET)
154         {
155           addrlen = sizeof(aquery->addr.addrV4);
156           status = ares_parse_ptr_reply(abuf, alen, &aquery->addr.addrV4,
157                                         (int)addrlen, AF_INET, &host);
158         }
159       else
160         {
161           addrlen = sizeof(aquery->addr.addrV6);
162           status = ares_parse_ptr_reply(abuf, alen, &aquery->addr.addrV6,
163                                         (int)addrlen, AF_INET6, &host);
164         }
165       end_aquery(aquery, status, host);
166     }
167   else if (status == ARES_EDESTRUCTION)
168     end_aquery(aquery, status, NULL);
169   else
170     next_lookup(aquery);
171 }
172 
end_aquery(struct addr_query * aquery,int status,struct hostent * host)173 static void end_aquery(struct addr_query *aquery, int status,
174                        struct hostent *host)
175 {
176   aquery->callback(aquery->arg, status, aquery->timeouts, host);
177   if (host)
178     ares_free_hostent(host);
179   free(aquery);
180 }
181 
file_lookup(struct ares_addr * addr,struct hostent ** host)182 static int file_lookup(struct ares_addr *addr, struct hostent **host)
183 {
184   FILE *fp;
185   int status;
186   int error;
187 
188 #ifdef WIN32
189   char PATH_HOSTS[MAX_PATH];
190   win_platform platform;
191 
192   PATH_HOSTS[0] = '\0';
193 
194   platform = ares__getplatform();
195 
196   if (platform == WIN_NT) {
197     char tmp[MAX_PATH];
198     HKEY hkeyHosts;
199 
200     if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0, KEY_READ,
201                      &hkeyHosts) == ERROR_SUCCESS)
202     {
203       DWORD dwLength = MAX_PATH;
204       RegQueryValueEx(hkeyHosts, DATABASEPATH, NULL, NULL, (LPBYTE)tmp,
205                       &dwLength);
206       ExpandEnvironmentStrings(tmp, PATH_HOSTS, MAX_PATH);
207       RegCloseKey(hkeyHosts);
208     }
209   }
210   else if (platform == WIN_9X)
211     GetWindowsDirectory(PATH_HOSTS, MAX_PATH);
212   else
213     return ARES_ENOTFOUND;
214 
215   strcat(PATH_HOSTS, WIN_PATH_HOSTS);
216 
217 #elif defined(WATT32)
218   extern const char *_w32_GetHostsFile (void);
219   const char *PATH_HOSTS = _w32_GetHostsFile();
220 
221   if (!PATH_HOSTS)
222     return ARES_ENOTFOUND;
223 #endif
224 
225   fp = fopen(PATH_HOSTS, "r");
226   if (!fp)
227     {
228       error = ERRNO;
229       switch(error)
230         {
231         case ENOENT:
232         case ESRCH:
233           return ARES_ENOTFOUND;
234         default:
235           DEBUGF(fprintf(stderr, "fopen() failed with error: %d %s\n",
236                          error, strerror(error)));
237           DEBUGF(fprintf(stderr, "Error opening file: %s\n",
238                          PATH_HOSTS));
239           *host = NULL;
240           return ARES_EFILE;
241         }
242     }
243   while ((status = ares__get_hostent(fp, addr->family, host)) == ARES_SUCCESS)
244     {
245       if (addr->family != (*host)->h_addrtype)
246         {
247           ares_free_hostent(*host);
248           continue;
249         }
250       if (addr->family == AF_INET)
251         {
252           if (memcmp((*host)->h_addr, &addr->addrV4,
253                      sizeof(addr->addrV4)) == 0)
254             break;
255         }
256       else if (addr->family == AF_INET6)
257         {
258           if (memcmp((*host)->h_addr, &addr->addrV6,
259                      sizeof(addr->addrV6)) == 0)
260             break;
261         }
262       ares_free_hostent(*host);
263     }
264   fclose(fp);
265   if (status == ARES_EOF)
266     status = ARES_ENOTFOUND;
267   if (status != ARES_SUCCESS)
268     *host = NULL;
269   return status;
270 }
271 
ptr_rr_name(char * name,const struct ares_addr * addr)272 static void ptr_rr_name(char *name, const struct ares_addr *addr)
273 {
274   if (addr->family == AF_INET)
275     {
276        unsigned long laddr = ntohl(addr->addrV4.s_addr);
277        unsigned long a1 = (laddr >> 24UL) & 0xFFUL;
278        unsigned long a2 = (laddr >> 16UL) & 0xFFUL;
279        unsigned long a3 = (laddr >>  8UL) & 0xFFUL;
280        unsigned long a4 = laddr & 0xFFUL;
281        sprintf(name, "%lu.%lu.%lu.%lu.in-addr.arpa", a4, a3, a2, a1);
282     }
283   else
284     {
285        unsigned char *bytes = (unsigned char *)&addr->addrV6;
286        /* There are too many arguments to do this in one line using
287         * minimally C89-compliant compilers */
288        sprintf(name,
289                 "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.",
290                 bytes[15]&0xf, bytes[15] >> 4, bytes[14]&0xf, bytes[14] >> 4,
291                 bytes[13]&0xf, bytes[13] >> 4, bytes[12]&0xf, bytes[12] >> 4,
292                 bytes[11]&0xf, bytes[11] >> 4, bytes[10]&0xf, bytes[10] >> 4,
293                 bytes[9]&0xf, bytes[9] >> 4, bytes[8]&0xf, bytes[8] >> 4);
294        sprintf(name+strlen(name),
295                 "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.ip6.arpa",
296                 bytes[7]&0xf, bytes[7] >> 4, bytes[6]&0xf, bytes[6] >> 4,
297                 bytes[5]&0xf, bytes[5] >> 4, bytes[4]&0xf, bytes[4] >> 4,
298                 bytes[3]&0xf, bytes[3] >> 4, bytes[2]&0xf, bytes[2] >> 4,
299                 bytes[1]&0xf, bytes[1] >> 4, bytes[0]&0xf, bytes[0] >> 4);
300     }
301 }
302