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_SYS_SOCKET_H
20#  include <sys/socket.h>
21#endif
22#ifdef HAVE_NETINET_IN_H
23#  include <netinet/in.h>
24#endif
25#ifdef HAVE_NETDB_H
26#  include <netdb.h>
27#endif
28#ifdef HAVE_ARPA_INET_H
29#  include <arpa/inet.h>
30#endif
31#ifdef HAVE_ARPA_NAMESER_H
32#  include <arpa/nameser.h>
33#else
34#  include "nameser.h"
35#endif
36#ifdef HAVE_ARPA_NAMESER_COMPAT_H
37#  include <arpa/nameser_compat.h>
38#endif
39
40#include <stdio.h>
41#include <stdlib.h>
42#include <string.h>
43#include <ctype.h>
44#ifdef HAVE_STRINGS_H
45#include <strings.h>
46#endif
47
48#include "ares.h"
49#include "inet_net_pton.h"
50#include "bitncmp.h"
51#include "ares_platform.h"
52#include "ares_private.h"
53
54#ifdef WATT32
55#undef WIN32
56#endif
57
58struct host_query {
59  /* Arguments passed to ares_gethostbyname() */
60  ares_channel channel;
61  char *name;
62  ares_host_callback callback;
63  void *arg;
64  int sent_family; /* this family is what was is being used */
65  int want_family; /* this family is what is asked for in the API */
66  const char *remaining_lookups;
67  int timeouts;
68};
69
70static void next_lookup(struct host_query *hquery, int status_code);
71static void host_callback(void *arg, int status, int timeouts,
72                          unsigned char *abuf, int alen);
73static void end_hquery(struct host_query *hquery, int status,
74                       struct hostent *host);
75static int fake_hostent(const char *name, int family,
76                        ares_host_callback callback, void *arg);
77static int file_lookup(const char *name, int family, struct hostent **host);
78static void sort_addresses(struct hostent *host,
79                           const struct apattern *sortlist, int nsort);
80static void sort6_addresses(struct hostent *host,
81                            const struct apattern *sortlist, int nsort);
82static int get_address_index(const struct in_addr *addr,
83                             const struct apattern *sortlist, int nsort);
84static int get6_address_index(const struct ares_in6_addr *addr,
85                              const struct apattern *sortlist, int nsort);
86
87void ares_gethostbyname(ares_channel channel, const char *name, int family,
88                        ares_host_callback callback, void *arg)
89{
90  struct host_query *hquery;
91
92  /* Right now we only know how to look up Internet addresses - and unspec
93     means try both basically. */
94  switch (family) {
95  case AF_INET:
96  case AF_INET6:
97  case AF_UNSPEC:
98    break;
99  default:
100    callback(arg, ARES_ENOTIMP, 0, NULL);
101    return;
102  }
103
104  if (fake_hostent(name, family, callback, arg))
105    return;
106
107  /* Allocate and fill in the host query structure. */
108  hquery = malloc(sizeof(struct host_query));
109  if (!hquery)
110    {
111      callback(arg, ARES_ENOMEM, 0, NULL);
112      return;
113    }
114  hquery->channel = channel;
115  hquery->name = strdup(name);
116  hquery->want_family = family;
117  hquery->sent_family = -1; /* nothing is sent yet */
118  if (!hquery->name) {
119    free(hquery);
120    callback(arg, ARES_ENOMEM, 0, NULL);
121    return;
122  }
123  hquery->callback = callback;
124  hquery->arg = arg;
125  hquery->remaining_lookups = channel->lookups;
126  hquery->timeouts = 0;
127
128  /* Start performing lookups according to channel->lookups. */
129  next_lookup(hquery, ARES_ECONNREFUSED /* initial error code */);
130}
131
132static void next_lookup(struct host_query *hquery, int status_code)
133{
134  const char *p;
135  struct hostent *host;
136  int status = status_code;
137
138  for (p = hquery->remaining_lookups; *p; p++)
139    {
140      switch (*p)
141        {
142        case 'b':
143          /* DNS lookup */
144          hquery->remaining_lookups = p + 1;
145          if ((hquery->want_family == AF_INET6) ||
146              (hquery->want_family == AF_UNSPEC)) {
147            /* if inet6 or unspec, start out with AAAA */
148            hquery->sent_family = AF_INET6;
149            ares_search(hquery->channel, hquery->name, C_IN, T_AAAA,
150                        host_callback, hquery);
151          }
152          else {
153            hquery->sent_family = AF_INET;
154            ares_search(hquery->channel, hquery->name, C_IN, T_A,
155                        host_callback, hquery);
156          }
157          return;
158
159        case 'f':
160          /* Host file lookup */
161          status = file_lookup(hquery->name, hquery->want_family, &host);
162
163          /* this status check below previously checked for !ARES_ENOTFOUND,
164             but we should not assume that this single error code is the one
165             that can occur, as that is in fact no longer the case */
166          if (status == ARES_SUCCESS)
167            {
168              end_hquery(hquery, status, host);
169              return;
170            }
171          status = status_code;   /* Use original status code */
172          break;
173        }
174    }
175  end_hquery(hquery, status, NULL);
176}
177
178static void host_callback(void *arg, int status, int timeouts,
179                          unsigned char *abuf, int alen)
180{
181  struct host_query *hquery = (struct host_query *) arg;
182  ares_channel channel = hquery->channel;
183  struct hostent *host = NULL;
184
185  hquery->timeouts += timeouts;
186  if (status == ARES_SUCCESS)
187    {
188      if (hquery->sent_family == AF_INET)
189        {
190          status = ares_parse_a_reply(abuf, alen, &host, NULL, NULL);
191          if (host && channel->nsort)
192            sort_addresses(host, channel->sortlist, channel->nsort);
193        }
194      else if (hquery->sent_family == AF_INET6)
195        {
196          status = ares_parse_aaaa_reply(abuf, alen, &host, NULL, NULL);
197          if ((status == ARES_ENODATA || status == ARES_EBADRESP) &&
198               hquery->want_family == AF_UNSPEC) {
199            /* The query returned something but either there were no AAAA
200               records (e.g. just CNAME) or the response was malformed.  Try
201               looking up A instead. */
202            hquery->sent_family = AF_INET;
203            ares_search(hquery->channel, hquery->name, C_IN, T_A,
204                        host_callback, hquery);
205            return;
206          }
207          if (host && channel->nsort)
208            sort6_addresses(host, channel->sortlist, channel->nsort);
209        }
210      end_hquery(hquery, status, host);
211    }
212  else if ((status == ARES_ENODATA || status == ARES_EBADRESP ||
213            status == ARES_ETIMEOUT) && (hquery->sent_family == AF_INET6 &&
214            hquery->want_family == AF_UNSPEC))
215    {
216      /* The AAAA query yielded no useful result.  Now look up an A instead. */
217      hquery->sent_family = AF_INET;
218      ares_search(hquery->channel, hquery->name, C_IN, T_A, host_callback,
219                  hquery);
220    }
221  else if (status == ARES_EDESTRUCTION)
222    end_hquery(hquery, status, NULL);
223  else
224    next_lookup(hquery, status);
225}
226
227static void end_hquery(struct host_query *hquery, int status,
228                       struct hostent *host)
229{
230  hquery->callback(hquery->arg, status, hquery->timeouts, host);
231  if (host)
232    ares_free_hostent(host);
233  free(hquery->name);
234  free(hquery);
235}
236
237/* If the name looks like an IP address, fake up a host entry, end the
238 * query immediately, and return true.  Otherwise return false.
239 */
240static int fake_hostent(const char *name, int family,
241                        ares_host_callback callback, void *arg)
242{
243  struct hostent hostent;
244  char *aliases[1] = { NULL };
245  char *addrs[2];
246  int result = 0;
247  struct in_addr in;
248  struct ares_in6_addr in6;
249
250  if (family == AF_INET || family == AF_INET6)
251    {
252      /* It only looks like an IP address if it's all numbers and dots. */
253      int numdots = 0, valid = 1;
254      const char *p;
255      for (p = name; *p; p++)
256        {
257          if (!ISDIGIT(*p) && *p != '.') {
258            valid = 0;
259            break;
260          } else if (*p == '.') {
261            numdots++;
262          }
263        }
264
265      /* if we don't have 3 dots, it is illegal
266       * (although inet_addr doesn't think so).
267       */
268      if (numdots != 3 || !valid)
269        result = 0;
270      else
271        result = ((in.s_addr = inet_addr(name)) == INADDR_NONE ? 0 : 1);
272
273      if (result)
274        family = AF_INET;
275    }
276  if (family == AF_INET6)
277    result = (ares_inet_pton(AF_INET6, name, &in6) < 1 ? 0 : 1);
278
279  if (!result)
280    return 0;
281
282  if (family == AF_INET)
283    {
284      hostent.h_length = (int)sizeof(struct in_addr);
285      addrs[0] = (char *)&in;
286    }
287  else if (family == AF_INET6)
288    {
289      hostent.h_length = (int)sizeof(struct ares_in6_addr);
290      addrs[0] = (char *)&in6;
291    }
292  /* Duplicate the name, to avoid a constness violation. */
293  hostent.h_name = strdup(name);
294  if (!hostent.h_name)
295    {
296      callback(arg, ARES_ENOMEM, 0, NULL);
297      return 1;
298    }
299
300  /* Fill in the rest of the host structure and terminate the query. */
301  addrs[1] = NULL;
302  hostent.h_aliases = aliases;
303  hostent.h_addrtype = family;
304  hostent.h_addr_list = addrs;
305  callback(arg, ARES_SUCCESS, 0, &hostent);
306
307  free((char *)(hostent.h_name));
308  return 1;
309}
310
311/* This is an API method */
312int ares_gethostbyname_file(ares_channel channel, const char *name,
313                            int family, struct hostent **host)
314{
315  int result;
316
317  /* We only take the channel to ensure that ares_init() been called. */
318  if(channel == NULL)
319    {
320      /* Anything will do, really.  This seems fine, and is consistent with
321         other error cases. */
322      *host = NULL;
323      return ARES_ENOTFOUND;
324    }
325
326  /* Just chain to the internal implementation we use here; it's exactly
327   * what we want.
328   */
329  result = file_lookup(name, family, host);
330  if(result != ARES_SUCCESS)
331    {
332      /* We guarantee a NULL hostent on failure. */
333      *host = NULL;
334    }
335  return result;
336}
337
338static int file_lookup(const char *name, int family, struct hostent **host)
339{
340  FILE *fp;
341  char **alias;
342  int status;
343  int error;
344
345#ifdef WIN32
346  char PATH_HOSTS[MAX_PATH];
347  win_platform platform;
348
349  PATH_HOSTS[0] = '\0';
350
351  platform = ares__getplatform();
352
353  if (platform == WIN_NT) {
354    char tmp[MAX_PATH];
355    HKEY hkeyHosts;
356
357    if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0, KEY_READ,
358                     &hkeyHosts) == ERROR_SUCCESS)
359    {
360      DWORD dwLength = MAX_PATH;
361      RegQueryValueEx(hkeyHosts, DATABASEPATH, NULL, NULL, (LPBYTE)tmp,
362                      &dwLength);
363      ExpandEnvironmentStrings(tmp, PATH_HOSTS, MAX_PATH);
364      RegCloseKey(hkeyHosts);
365    }
366  }
367  else if (platform == WIN_9X)
368    GetWindowsDirectory(PATH_HOSTS, MAX_PATH);
369  else
370    return ARES_ENOTFOUND;
371
372  strcat(PATH_HOSTS, WIN_PATH_HOSTS);
373
374#elif defined(WATT32)
375  extern const char *_w32_GetHostsFile (void);
376  const char *PATH_HOSTS = _w32_GetHostsFile();
377
378  if (!PATH_HOSTS)
379    return ARES_ENOTFOUND;
380#endif
381
382  fp = fopen(PATH_HOSTS, "r");
383  if (!fp)
384    {
385      error = ERRNO;
386      switch(error)
387        {
388        case ENOENT:
389        case ESRCH:
390          return ARES_ENOTFOUND;
391        default:
392          DEBUGF(fprintf(stderr, "fopen() failed with error: %d %s\n",
393                         error, strerror(error)));
394          DEBUGF(fprintf(stderr, "Error opening file: %s\n",
395                         PATH_HOSTS));
396          *host = NULL;
397          return ARES_EFILE;
398        }
399    }
400  while ((status = ares__get_hostent(fp, family, host)) == ARES_SUCCESS)
401    {
402      if (strcasecmp((*host)->h_name, name) == 0)
403        break;
404      for (alias = (*host)->h_aliases; *alias; alias++)
405        {
406          if (strcasecmp(*alias, name) == 0)
407            break;
408        }
409      if (*alias)
410        break;
411      ares_free_hostent(*host);
412    }
413  fclose(fp);
414  if (status == ARES_EOF)
415    status = ARES_ENOTFOUND;
416  if (status != ARES_SUCCESS)
417    *host = NULL;
418  return status;
419}
420
421static void sort_addresses(struct hostent *host,
422                           const struct apattern *sortlist, int nsort)
423{
424  struct in_addr a1, a2;
425  int i1, i2, ind1, ind2;
426
427  /* This is a simple insertion sort, not optimized at all.  i1 walks
428   * through the address list, with the loop invariant that everything
429   * to the left of i1 is sorted.  In the loop body, the value at i1 is moved
430   * back through the list (via i2) until it is in sorted order.
431   */
432  for (i1 = 0; host->h_addr_list[i1]; i1++)
433    {
434      memcpy(&a1, host->h_addr_list[i1], sizeof(struct in_addr));
435      ind1 = get_address_index(&a1, sortlist, nsort);
436      for (i2 = i1 - 1; i2 >= 0; i2--)
437        {
438          memcpy(&a2, host->h_addr_list[i2], sizeof(struct in_addr));
439          ind2 = get_address_index(&a2, sortlist, nsort);
440          if (ind2 <= ind1)
441            break;
442          memcpy(host->h_addr_list[i2 + 1], &a2, sizeof(struct in_addr));
443        }
444      memcpy(host->h_addr_list[i2 + 1], &a1, sizeof(struct in_addr));
445    }
446}
447
448/* Find the first entry in sortlist which matches addr.  Return nsort
449 * if none of them match.
450 */
451static int get_address_index(const struct in_addr *addr,
452                             const struct apattern *sortlist,
453                             int nsort)
454{
455  int i;
456
457  for (i = 0; i < nsort; i++)
458    {
459      if (sortlist[i].family != AF_INET)
460        continue;
461      if (sortlist[i].type == PATTERN_MASK)
462        {
463          if ((addr->s_addr & sortlist[i].mask.addr4.s_addr)
464              == sortlist[i].addrV4.s_addr)
465            break;
466        }
467      else
468        {
469          if (!ares_bitncmp(&addr->s_addr, &sortlist[i].addrV4.s_addr,
470                            sortlist[i].mask.bits))
471            break;
472        }
473    }
474  return i;
475}
476
477static void sort6_addresses(struct hostent *host,
478                            const struct apattern *sortlist, int nsort)
479{
480  struct ares_in6_addr a1, a2;
481  int i1, i2, ind1, ind2;
482
483  /* This is a simple insertion sort, not optimized at all.  i1 walks
484   * through the address list, with the loop invariant that everything
485   * to the left of i1 is sorted.  In the loop body, the value at i1 is moved
486   * back through the list (via i2) until it is in sorted order.
487   */
488  for (i1 = 0; host->h_addr_list[i1]; i1++)
489    {
490      memcpy(&a1, host->h_addr_list[i1], sizeof(struct ares_in6_addr));
491      ind1 = get6_address_index(&a1, sortlist, nsort);
492      for (i2 = i1 - 1; i2 >= 0; i2--)
493        {
494          memcpy(&a2, host->h_addr_list[i2], sizeof(struct ares_in6_addr));
495          ind2 = get6_address_index(&a2, sortlist, nsort);
496          if (ind2 <= ind1)
497            break;
498          memcpy(host->h_addr_list[i2 + 1], &a2, sizeof(struct ares_in6_addr));
499        }
500      memcpy(host->h_addr_list[i2 + 1], &a1, sizeof(struct ares_in6_addr));
501    }
502}
503
504/* Find the first entry in sortlist which matches addr.  Return nsort
505 * if none of them match.
506 */
507static int get6_address_index(const struct ares_in6_addr *addr,
508                              const struct apattern *sortlist,
509                              int nsort)
510{
511  int i;
512
513  for (i = 0; i < nsort; i++)
514    {
515      if (sortlist[i].family != AF_INET6)
516        continue;
517        if (!ares_bitncmp(addr,
518                          &sortlist[i].addrV6,
519                          sortlist[i].mask.bits))
520          break;
521    }
522  return i;
523}
524