about summary refs log tree commit diff
path: root/resolv/res_hconf.c
blob: 3905360d50deb1e50284bc93bc8d9997ca77049c (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
/* Copyright (C) 1993, 95, 96, 97, 98, 99 Free Software Foundation, Inc.
   Contributed by David Mosberger (davidm@azstarnet.com).

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

/* This file provides a Linux /etc/host.conf compatible front end to
the various name resolvers (/etc/hosts, named, NIS server, etc.).
Though mostly compatibly, the following differences exist compared
to the original implementation:

	- new command "spoof" takes an arguments like RESOLV_SPOOF_CHECK
	  environment variable (i.e., `off', `nowarn', or `warn').

	- line comments can appear anywhere (not just at the beginning of
	  a line)
*/
#include <ctype.h>
#include <memory.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <net/if.h>

#include "res_hconf.h"

#define _PATH_HOSTCONF	"/etc/host.conf"

/* Environment vars that all user to override default behavior:  */
#define ENV_HOSTCONF	"RESOLV_HOST_CONF"
#define ENV_SERVORDER	"RESOLV_SERV_ORDER"
#define ENV_SPOOF	"RESOLV_SPOOF_CHECK"
#define ENV_TRIM_OVERR	"RESOLV_OVERRIDE_TRIM_DOMAINS"
#define ENV_TRIM_ADD	"RESOLV_ADD_TRIM_DOMAINS"
#define ENV_MULTI	"RESOLV_MULTI"
#define ENV_REORDER	"RESOLV_REORDER"

static const char *arg_service_list (const char *, int, const char *,
				     unsigned int);
static const char *arg_trimdomain_list (const char *, int, const char *,
					unsigned int);
static const char *arg_spoof (const char *, int, const char *, unsigned int);
static const char *arg_bool (const char *, int, const char *, unsigned int);

static struct cmd
{
  const char *name;
  const char *(*parse_args) (const char * filename, int line_num,
			     const char * args, unsigned int arg);
  unsigned int arg;
} cmd[] =
{
  {"order",		arg_service_list,	0},
  {"trim",		arg_trimdomain_list,	0},
  {"spoof",		arg_spoof,		0},
  {"multi",		arg_bool,		HCONF_FLAG_MULTI},
  {"nospoof",		arg_bool,		HCONF_FLAG_SPOOF},
  {"spoofalert",	arg_bool,		HCONF_FLAG_SPOOFALERT},
  {"reorder",		arg_bool,		HCONF_FLAG_REORDER}
};

/* Structure containing the state.  */
struct hconf _res_hconf;

/* Skip white space.  */
static const char *
skip_ws (const char *str)
{
  while (isspace (*str)) ++str;
  return str;
}


/* Skip until whitespace, comma, end of line, or comment character.  */
static const char *
skip_string (const char *str)
{
  while (*str && !isspace (*str) && *str != '#' && *str != ',')
    ++str;
  return str;
}


static const char *
arg_service_list (const char *fname, int line_num, const char *args,
		  unsigned int arg)
{
  enum Name_Service service;
  const char *start;
  size_t len;
  int i;
  static struct
  {
    const char * name;
    enum Name_Service service;
  } svcs[] =
    {
      {"bind",	SERVICE_BIND},
      {"hosts",	SERVICE_HOSTS},
      {"nis",	SERVICE_NIS},
    };

  do
    {
      start = args;
      args = skip_string (args);
      len = args - start;

      service = SERVICE_NONE;
      for (i = 0; i < sizeof (svcs) / sizeof (svcs[0]); ++i)
	{
	  if (__strncasecmp (start, svcs[i].name, len) == 0
	      && len == strlen (svcs[i].name))
	  {
	    service = svcs[i].service;
	    break;
	  }
      }
      if (service == SERVICE_NONE)
	{
	  fprintf (stderr, "%s: line %d: expected service, found `%s'\n",
		   fname, line_num, start);
	  return 0;
	}
      if (_res_hconf.num_services >= SERVICE_MAX)
	{
	  fprintf (stderr, "%s: line %d: cannot specify more than %d services",
		   fname, line_num, SERVICE_MAX);
	  return 0;
	}
      _res_hconf.service[_res_hconf.num_services++] = service;

      args = skip_ws (args);
      switch (*args)
	{
	case ',':
	case ';':
	case ':':
	  args = skip_ws (++args);
	  if (!*args || *args == '#')
	    {
	      fprintf (stderr,
		       "%s: line %d: list delimiter not followed by keyword",
		       fname, line_num);
	      return 0;
	    }
	default:
	  break;
	}
    }
  while (*args && *args != '#');
  return args;
}


static const char *
arg_trimdomain_list (const char *fname, int line_num, const char *args,
		     unsigned int flag)
{
  const char * start;
  size_t len;

  do
    {
      start = args;
      args = skip_string (args);
      len = args - start;

      if (_res_hconf.num_trimdomains >= TRIMDOMAINS_MAX)
	{
	  fprintf (stderr,
		   "%s: line %d: cannot specify more than %d trim domains",
		   fname, line_num, TRIMDOMAINS_MAX);
	  return 0;
	}
      _res_hconf.trimdomain[_res_hconf.num_trimdomains++] =
	__strndup (start, len);
      args = skip_ws (args);
      switch (*args)
	{
	case ',': case ';': case ':':
	  args = skip_ws (++args);
	  if (!*args || *args == '#')
	    {
	      fprintf (stderr,
		       "%s: line %d: list delimiter not followed by domain",
		       fname, line_num);
	      return 0;
	    }
	default:
	  break;
	}
    }
  while (*args && *args != '#');
  return args;
}


static const char *
arg_spoof (const char *fname, int line_num, const char *args, unsigned flag)
{
  const char *start = args;
  size_t len;

  args = skip_string (args);
  len = args - start;

  if (len == 3 && __strncasecmp (start, "off", len) == 0)
    _res_hconf.flags &= ~(HCONF_FLAG_SPOOF | HCONF_FLAG_SPOOFALERT);
  else
    {
      _res_hconf.flags |= (HCONF_FLAG_SPOOF | HCONF_FLAG_SPOOFALERT);
      if ((len == 6 && __strncasecmp (start, "nowarn", len) == 0)
	  || !(len == 4 && __strncasecmp (start, "warn", len) == 0))
	_res_hconf.flags &= ~HCONF_FLAG_SPOOFALERT;
    }
  return args;
}


static const char *
arg_bool (const char *fname, int line_num, const char *args, unsigned flag)
{
  if (__strncasecmp (args, "on", 2) == 0)
    {
      args += 2;
      _res_hconf.flags |= flag;
    }
  else if (__strncasecmp (args, "off", 3) == 0)
    {
      args += 3;
      _res_hconf.flags &= ~flag;
    }
  else
    {
      fprintf (stderr, "%s: line %d: expected `on' or `off', found `%s'\n",
	       fname, line_num, args);
      return 0;
    }
  return args;
}


static void
parse_line (const char *fname, int line_num, const char *str)
{
  const char *start;
  struct cmd *c = 0;
  size_t len;
  int i;

  str = skip_ws (str);

  if (*str == '#') return;		/* skip line comment */

  start = str;
  str = skip_string (str);
  len = str - start;

  for (i = 0; i < sizeof (cmd) / sizeof (cmd[0]); ++i)
    {
      if (strncasecmp (start, cmd[i].name, len) == 0
	  && strlen (cmd[i].name) == len)
	{
	  c = &cmd[i];
	  break;
	}
    }
  if (c == NULL)
    {
      fprintf (stderr, "%s: line %d: bad command `%s'\n",
	       fname, line_num, start);
      return;
    }

  /* process args: */
  str = skip_ws (str);
  str = (*c->parse_args) (fname, line_num, str, c->arg);
  if (!str)
    return;

  /* rest of line must contain white space or comment only: */
  while (*str)
    {
      if (!isspace (*str)) {
	if (*str != '#')
	  fprintf (stderr, "%s: line %d: ignoring trailing garbage `%s'\n",
		   fname, line_num, str);
	break;
      }
      ++str;
    }
}


/* Initialize hconf datastructure by reading host.conf file and
   environment variables.  */
void
_res_hconf_init (void)
{
  const char *hconf_name;
  int line_num = 0;
  char buf[256], *end, *envval;
  FILE *fp;

  if (_res_hconf.initialized)
    return;

  memset (&_res_hconf, '\0', sizeof (_res_hconf));

  hconf_name = __secure_getenv (ENV_HOSTCONF);
  if (hconf_name == NULL)
    hconf_name = _PATH_HOSTCONF;

  fp = fopen (hconf_name, "r");
  if (!fp)
    /* make up something reasonable: */
    _res_hconf.service[_res_hconf.num_services++] = SERVICE_BIND;
  else
    {
      while (fgets_unlocked (buf, sizeof (buf), fp))
	{
	  ++line_num;
	  end = strchr (buf, '\n');
	  if (end)
	    *end = '\0';
	  parse_line (hconf_name, line_num, buf);
	}
      fclose (fp);
    }

  envval = getenv (ENV_SERVORDER);
  if (envval)
    {
      _res_hconf.num_services = 0;
      arg_service_list (ENV_SERVORDER, 1, envval, 0);
    }

  envval = getenv (ENV_SPOOF);
  if (envval)
    arg_spoof (ENV_SPOOF, 1, envval, 0);

  envval = getenv (ENV_MULTI);
  if (envval)
    arg_bool (ENV_MULTI, 1, envval, HCONF_FLAG_MULTI);

  envval = getenv (ENV_REORDER);
  if (envval)
    arg_bool (ENV_REORDER, 1, envval, HCONF_FLAG_REORDER);

  envval = getenv (ENV_TRIM_ADD);
  if (envval)
    arg_trimdomain_list (ENV_TRIM_ADD, 1, envval, 0);

  envval = getenv (ENV_TRIM_OVERR);
  if (envval)
    {
      _res_hconf.num_trimdomains = 0;
      arg_trimdomain_list (ENV_TRIM_OVERR, 1, envval, 0);
    }

  _res_hconf.initialized = 1;
}


/* Reorder addresses returned in a hostent such that the first address
   is an address on the local subnet, if there is such an address.
   Otherwise, nothing is changed.  */

void
_res_hconf_reorder_addrs (struct hostent *hp)
{
#if defined SIOCGIFCONF && defined SIOCGIFNETMASK
  static int num_ifs = -1;	/* number of interfaces */
  static struct netaddr
  {
    int addrtype;
    union
    {
      struct
      {
	u_int32_t	addr;
	u_int32_t	mask;
      } ipv4
    } u;
  } *ifaddrs;

  if (hp->h_addrtype != AF_INET)
    return;	/* can't deal with anything but IPv4 for now... */

  if (num_ifs <= 0)
    {
      struct ifconf ifs;
      struct ifreq *ifr;
      size_t size, num;
      int sd;

      /* initialize interface table: */

      num_ifs = 0;

      sd = __socket (AF_INET, SOCK_DGRAM, 0);
      if (sd < 0)
	return;

      /* Now get list of interfaces.  Since we don't know how many
	 interfaces there are, we keep increasing the buffer size
	 until we have at least sizeof(struct ifreq) too many bytes.
	 That implies that the ioctl() return because it ran out of
	 interfaces, not memory */
      size = 0;
      ifs.ifc_buf = 0;
      do
	{
	  size += 4 * sizeof (struct ifreq);
	  ifs.ifc_buf = realloc (ifs.ifs_buf, size);
	  if (ifs.ifc_buf == NULL)
	    {
	      close (sd);
	      return;
	    }
	  ifs.ifc_len = size;
	  if (__ioctl (sd, SIOCGIFCONF, &ifs) < 0)
	    goto cleanup;
	}
      while (size - ifs.ifc_len < sizeof (struct ifreq));

      num = ifs.ifc_len / sizeof (struct ifreq);

      ifaddrs = malloc (num * sizeof (ifaddrs[0]));
      if (!ifaddrs)
	goto cleanup;

      ifr = ifs.ifc_req;
      for (i = 0; i < num; ++i)
	{
	  if (ifr->ifr_addr.sa_family != AF_INET)
	    continue;
	  ifaddrs[num_ifs].addrtype = AF_INET;

	  memcpy (&ifaddrs[num_ifs].u.ipv4.addr,
		  &((struct sockaddr_in *)ifr->ifr_addr)->sin_addr, 4);

	  if (__ioctl (sd, SIOCGIFNETMASK, if) < 0)
	    continue;
	  memcpy (&ifaddrs[num_ifs].u.ipv4.mask,
		  ((struct sockaddr_in *)ifr->ifr_mask)->sin_addr, 4);

	  ++num_ifs;	/* now we're committed to this entry */
	}
      /* just keep enough memory to hold all the interfaces we want: */
      ifaddrs = realloc (ifaddrs, num_ifs * sizeof (ifaddrs[0]));

    cleanup:
      close (sd);
      free (ifs.ifc_buf);
    }

  if (num_ifs == 0)
    return;

  /* find an address for which we have a direct connection: */
  for (i = 0; hp->h_addr_list[i]; ++i)
    {
      h_addr = (struct in_addr *) hp->h_addr_list[i];

      for (j = 0; j < num_ifs; ++j)
	{
	  if_addr    = ifaddrs[j].u.ipv4.addr;
	  if_netmask = ifaddrs[j].u.ipv4.mask;

	  if (((h_addr->s_addr ^ if_addr) & if_netmask) == 0)
	    {
	      void *tmp;

	      tmp = hp->h_addr_list[i];
	      hp->h_addr_list[i] = hp->h_addr_list[0];
	      hp->h_addr_list[0] = tmp;
	      return;
	    }
	}
    }
#endif /* defined(SIOCGIFCONF) && ... */
}


/* If HOSTNAME has a postfix matching any of the trimdomains, trim away
   that postfix.  Notice that HOSTNAME is modified inplace.  Also, the
   original code applied all trimdomains in order, meaning that the
   same domainname could be trimmed multiple times.  I believe this
   was unintentional.  */
void
_res_hconf_trim_domain (char *hostname)
{
  size_t hostname_len, trim_len;
  int i;

  hostname_len = strlen (hostname);

  for (i = 0; i < _res_hconf.num_trimdomains; ++i)
    {
      const char *trim = _res_hconf.trimdomain[i];

      trim_len = strlen (trim);
      if (hostname_len > trim_len
	  && __strcasecmp (&hostname[hostname_len - trim_len], trim) == 0)
	{
	  hostname[hostname_len - trim_len] = '\0';
	  break;
	}
    }
}


/* Trim all hostnames/aliases in HP according to the trimdomain list.
   Notice that HP is modified inplace!  */
void
_res_hconf_trim_domains (struct hostent *hp)
{
  int i;

  if (_res_hconf.num_trimdomains == 0)
    return;

  _res_hconf_trim_domain (hp->h_name);
  for (i = 0; hp->h_aliases[i]; ++i)
    _res_hconf_trim_domain (hp->h_aliases[i]);
}