1 /* Hosts file parser in nss_files module.
2 Copyright (C) 1996-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19 #include <assert.h>
20 #include <netinet/in.h>
21 #include <arpa/inet.h>
22 #include <arpa/nameser.h>
23 #include <netdb.h>
24 #include <resolv/resolv-internal.h>
25 #include <scratch_buffer.h>
26 #include <alloc_buffer.h>
27 #include <nss.h>
28
29 /* Get implementation for some internal functions. */
30 #include "../resolv/mapv4v6addr.h"
31 #include "../resolv/res_hconf.h"
32
33
34 #define ENTNAME hostent
35 #define DATABASE "hosts"
36 #define NEED_H_ERRNO
37
38 #define EXTRA_ARGS , af, flags
39 #define EXTRA_ARGS_DECL , int af, int flags
40
41 #define ENTDATA hostent_data
42 struct hostent_data
43 {
44 unsigned char host_addr[16]; /* IPv4 or IPv6 address. */
45 char *h_addr_ptrs[2]; /* Points to that and null terminator. */
46 };
47
48 #define TRAILING_LIST_MEMBER h_aliases
49 #define TRAILING_LIST_SEPARATOR_P isspace
50 #include "files-parse.c"
51 LINE_PARSER
52 ("#",
53 {
54 char *addr;
55
56 STRING_FIELD (addr, isspace, 1);
57
58 /* Parse address. */
59 if (__inet_pton (af == AF_UNSPEC ? AF_INET : af, addr, entdata->host_addr)
60 > 0)
61 af = af == AF_UNSPEC ? AF_INET : af;
62 else
63 {
64 if (af == AF_INET6 && (flags & AI_V4MAPPED) != 0
65 && __inet_pton (AF_INET, addr, entdata->host_addr) > 0)
66 map_v4v6_address ((char *) entdata->host_addr,
67 (char *) entdata->host_addr);
68 else if (af == AF_INET
69 && __inet_pton (AF_INET6, addr, entdata->host_addr) > 0)
70 {
71 if (IN6_IS_ADDR_V4MAPPED (entdata->host_addr))
72 memcpy (entdata->host_addr, entdata->host_addr + 12, INADDRSZ);
73 else if (IN6_IS_ADDR_LOOPBACK (entdata->host_addr))
74 {
75 in_addr_t localhost = htonl (INADDR_LOOPBACK);
76 memcpy (entdata->host_addr, &localhost, sizeof (localhost));
77 }
78 else
79 /* Illegal address: ignore line. */
80 return 0;
81 }
82 else if (af == AF_UNSPEC
83 && __inet_pton (AF_INET6, addr, entdata->host_addr) > 0)
84 af = AF_INET6;
85 else
86 /* Illegal address: ignore line. */
87 return 0;
88 }
89
90 /* We always return entries of the requested form. */
91 result->h_addrtype = af;
92 result->h_length = af == AF_INET ? INADDRSZ : IN6ADDRSZ;
93
94 /* Store a pointer to the address in the expected form. */
95 entdata->h_addr_ptrs[0] = (char *) entdata->host_addr;
96 entdata->h_addr_ptrs[1] = NULL;
97 result->h_addr_list = entdata->h_addr_ptrs;
98
99 STRING_FIELD (result->h_name, isspace, 1);
100 })
101
102 #define EXTRA_ARGS_VALUE , AF_INET, 0
103 #include "files-XXX.c"
104 #undef EXTRA_ARGS_VALUE
105
106 /* We only need to consider IPv4 mapped addresses if the input to the
107 gethostbyaddr() function is an IPv6 address. */
108 #define EXTRA_ARGS_VALUE \
109 , af, (len == IN6ADDRSZ ? AI_V4MAPPED : 0)
110 DB_LOOKUP (hostbyaddr, ,,,
111 {
112 if (result->h_length == (int) len
113 && ! memcmp (addr, result->h_addr_list[0], len))
114 break;
115 }, const void *addr, socklen_t len, int af)
116 #undef EXTRA_ARGS_VALUE
117
118 /* Type of the address and alias arrays. */
119 #define DYNARRAY_STRUCT array
120 #define DYNARRAY_ELEMENT char *
121 #define DYNARRAY_PREFIX array_
122 #include <malloc/dynarray-skeleton.c>
123
124 static enum nss_status
125 gethostbyname3_multi (FILE * stream, const char *name, int af,
126 struct hostent *result, char *buffer, size_t buflen,
127 int *errnop, int *herrnop)
128 {
129 assert (af == AF_INET || af == AF_INET6);
130
131 /* We have to get all host entries from the file. */
132 struct scratch_buffer tmp_buffer;
133 scratch_buffer_init (&tmp_buffer);
134 struct hostent tmp_result_buf;
135 struct array addresses;
136 array_init (&addresses);
137 struct array aliases;
138 array_init (&aliases);
139 enum nss_status status;
140
141 /* Preserve the addresses and aliases encountered so far. */
142 for (size_t i = 0; result->h_addr_list[i] != NULL; ++i)
143 array_add (&addresses, result->h_addr_list[i]);
144 for (size_t i = 0; result->h_aliases[i] != NULL; ++i)
145 array_add (&aliases, result->h_aliases[i]);
146
147 /* The output buffer re-uses now-unused space at the end of the
148 buffer, starting with the aliases array. It comes last in the
149 data produced by internal_getent. (The alias names themselves
150 are still located in the line read in internal_getent, which is
151 stored at the beginning of the buffer.) */
152 struct alloc_buffer outbuf;
153 {
154 char *bufferend = (char *) result->h_aliases;
155 outbuf = alloc_buffer_create (bufferend, buffer + buflen - bufferend);
156 }
157
158 while (true)
159 {
160 status = internal_getent (stream, &tmp_result_buf, tmp_buffer.data,
161 tmp_buffer.length, errnop, herrnop, af, 0);
162 /* Enlarge the buffer if necessary. */
163 if (status == NSS_STATUS_TRYAGAIN && *herrnop == NETDB_INTERNAL
164 && *errnop == ERANGE)
165 {
166 if (!scratch_buffer_grow (&tmp_buffer))
167 {
168 *errnop = ENOMEM;
169 /* *herrnop and status already have the right value. */
170 break;
171 }
172 /* Loop around and retry with a larger buffer. */
173 }
174 else if (status == NSS_STATUS_SUCCESS)
175 {
176 /* A line was read. Check that it matches the search
177 criteria. */
178
179 int matches = 1;
180 struct hostent *old_result = result;
181 result = &tmp_result_buf;
182 /* The following piece is a bit clumsy but we want to use
183 the `LOOKUP_NAME_CASE' value. The optimizer should do
184 its job. */
185 do
186 {
187 LOOKUP_NAME_CASE (h_name, h_aliases)
188 result = old_result;
189 }
190 while ((matches = 0));
191
192 /* If the line matches, we need to copy the addresses and
193 aliases, so that we can reuse tmp_buffer for the next
194 line. */
195 if (matches)
196 {
197 /* Record the addresses. */
198 for (size_t i = 0; tmp_result_buf.h_addr_list[i] != NULL; ++i)
199 {
200 /* Allocate the target space in the output buffer,
201 depending on the address family. */
202 void *target;
203 if (af == AF_INET)
204 {
205 assert (tmp_result_buf.h_length == 4);
206 target = alloc_buffer_alloc (&outbuf, struct in_addr);
207 }
208 else if (af == AF_INET6)
209 {
210 assert (tmp_result_buf.h_length == 16);
211 target = alloc_buffer_alloc (&outbuf, struct in6_addr);
212 }
213 else
214 __builtin_unreachable ();
215
216 if (target == NULL)
217 {
218 /* Request a larger output buffer. */
219 *errnop = ERANGE;
220 *herrnop = NETDB_INTERNAL;
221 status = NSS_STATUS_TRYAGAIN;
222 break;
223 }
224 memcpy (target, tmp_result_buf.h_addr_list[i],
225 tmp_result_buf.h_length);
226 array_add (&addresses, target);
227 }
228
229 /* Record the aliases. */
230 for (size_t i = 0; tmp_result_buf.h_aliases[i] != NULL; ++i)
231 {
232 char *alias = tmp_result_buf.h_aliases[i];
233 array_add (&aliases,
234 alloc_buffer_copy_string (&outbuf, alias));
235 }
236
237 /* If the real name is different add, it also to the
238 aliases. This means that there is a duplication in
239 the alias list but this is really the user's
240 problem. */
241 {
242 char *new_name = tmp_result_buf.h_name;
243 if (strcmp (old_result->h_name, new_name) != 0)
244 array_add (&aliases,
245 alloc_buffer_copy_string (&outbuf, new_name));
246 }
247
248 /* Report memory allocation failures during the
249 expansion of the temporary arrays. */
250 if (array_has_failed (&addresses) || array_has_failed (&aliases))
251 {
252 *errnop = ENOMEM;
253 *herrnop = NETDB_INTERNAL;
254 status = NSS_STATUS_UNAVAIL;
255 break;
256 }
257
258 /* Request a larger output buffer if we ran out of room. */
259 if (alloc_buffer_has_failed (&outbuf))
260 {
261 *errnop = ERANGE;
262 *herrnop = NETDB_INTERNAL;
263 status = NSS_STATUS_TRYAGAIN;
264 break;
265 }
266
267 result = old_result;
268 } /* If match was found. */
269
270 /* If no match is found, loop around and fetch another
271 line. */
272
273 } /* status == NSS_STATUS_SUCCESS. */
274 else
275 /* internal_getent returned an error. */
276 break;
277 } /* while (true) */
278
279 /* Propagate the NSS_STATUS_TRYAGAIN error to the caller. It means
280 that we may not have loaded the complete result.
281 NSS_STATUS_NOTFOUND, however, means that we reached the end of
282 the file successfully. */
283 if (status != NSS_STATUS_TRYAGAIN)
284 status = NSS_STATUS_SUCCESS;
285
286 if (status == NSS_STATUS_SUCCESS)
287 {
288 /* Copy the address and alias arrays into the output buffer and
289 add NULL terminators. The pointed-to elements were directly
290 written into the output buffer above and do not need to be
291 copied again. */
292 size_t addresses_count = array_size (&addresses);
293 size_t aliases_count = array_size (&aliases);
294 char **out_addresses = alloc_buffer_alloc_array
295 (&outbuf, char *, addresses_count + 1);
296 char **out_aliases = alloc_buffer_alloc_array
297 (&outbuf, char *, aliases_count + 1);
298 if (out_addresses == NULL || out_aliases == NULL)
299 {
300 /* The output buffer is not large enough. */
301 *errnop = ERANGE;
302 *herrnop = NETDB_INTERNAL;
303 status = NSS_STATUS_TRYAGAIN;
304 /* Fall through to function exit. */
305 }
306 else
307 {
308 /* Everything is allocated in place. Make the copies and
309 adjust the array pointers. */
310 memcpy (out_addresses, array_begin (&addresses),
311 addresses_count * sizeof (char *));
312 out_addresses[addresses_count] = NULL;
313 memcpy (out_aliases, array_begin (&aliases),
314 aliases_count * sizeof (char *));
315 out_aliases[aliases_count] = NULL;
316
317 result->h_addr_list = out_addresses;
318 result->h_aliases = out_aliases;
319
320 status = NSS_STATUS_SUCCESS;
321 }
322 }
323
324 scratch_buffer_free (&tmp_buffer);
325 array_free (&addresses);
326 array_free (&aliases);
327 return status;
328 }
329
330 enum nss_status
331 _nss_files_gethostbyname3_r (const char *name, int af, struct hostent *result,
332 char *buffer, size_t buflen, int *errnop,
333 int *herrnop, int32_t *ttlp, char **canonp)
334 {
335 FILE *stream = NULL;
336 uintptr_t pad = -(uintptr_t) buffer % __alignof__ (struct hostent_data);
337 buffer += pad;
338 buflen = buflen > pad ? buflen - pad : 0;
339
340 /* Open file. */
341 enum nss_status status = internal_setent (&stream);
342
343 if (status == NSS_STATUS_SUCCESS)
344 {
345 while ((status = internal_getent (stream, result, buffer, buflen, errnop,
346 herrnop, af, 0))
347 == NSS_STATUS_SUCCESS)
348 {
349 LOOKUP_NAME_CASE (h_name, h_aliases)
350 }
351
352 if (status == NSS_STATUS_SUCCESS
353 && _res_hconf.flags & HCONF_FLAG_MULTI)
354 status = gethostbyname3_multi
355 (stream, name, af, result, buffer, buflen, errnop, herrnop);
356
357 fclose (stream);
358 }
359
360 if (canonp && status == NSS_STATUS_SUCCESS)
361 *canonp = result->h_name;
362
363 return status;
364 }
365 libc_hidden_def (_nss_files_gethostbyname3_r)
366
367 enum nss_status
368 _nss_files_gethostbyname_r (const char *name, struct hostent *result,
369 char *buffer, size_t buflen, int *errnop,
370 int *herrnop)
371 {
372 return _nss_files_gethostbyname3_r (name, AF_INET, result, buffer, buflen,
373 errnop, herrnop, NULL, NULL);
374 }
375 libc_hidden_def (_nss_files_gethostbyname_r)
376
377 enum nss_status
378 _nss_files_gethostbyname2_r (const char *name, int af, struct hostent *result,
379 char *buffer, size_t buflen, int *errnop,
380 int *herrnop)
381 {
382 return _nss_files_gethostbyname3_r (name, af, result, buffer, buflen,
383 errnop, herrnop, NULL, NULL);
384 }
385 libc_hidden_def (_nss_files_gethostbyname2_r)
386
387 enum nss_status
388 _nss_files_gethostbyname4_r (const char *name, struct gaih_addrtuple **pat,
389 char *buffer, size_t buflen, int *errnop,
390 int *herrnop, int32_t *ttlp)
391 {
392 FILE *stream = NULL;
393
394 /* Open file. */
395 enum nss_status status = internal_setent (&stream);
396
397 if (status == NSS_STATUS_SUCCESS)
398 {
399 bool any = false;
400 bool got_canon = false;
401 while (1)
402 {
403 /* Align the buffer for the next record. */
404 uintptr_t pad = (-(uintptr_t) buffer
405 % __alignof__ (struct hostent_data));
406 buffer += pad;
407 buflen = buflen > pad ? buflen - pad : 0;
408
409 struct hostent result;
410 status = internal_getent (stream, &result, buffer, buflen, errnop,
411 herrnop, AF_UNSPEC, 0);
412 if (status != NSS_STATUS_SUCCESS)
413 break;
414
415 int naliases = 0;
416 if (__strcasecmp (name, result.h_name) != 0)
417 {
418 for (; result.h_aliases[naliases] != NULL; ++naliases)
419 if (! __strcasecmp (name, result.h_aliases[naliases]))
420 break;
421 if (result.h_aliases[naliases] == NULL)
422 continue;
423
424 /* We know this alias exist. Count it. */
425 ++naliases;
426 }
427
428 /* Determine how much memory has been used so far. */
429 // XXX It is not necessary to preserve the aliases array
430 while (result.h_aliases[naliases] != NULL)
431 ++naliases;
432 char *bufferend = (char *) &result.h_aliases[naliases + 1];
433 assert (buflen >= bufferend - buffer);
434 buflen -= bufferend - buffer;
435 buffer = bufferend;
436
437 /* We found something. */
438 any = true;
439
440 /* Create the record the caller expects. There is only one
441 address. */
442 assert (result.h_addr_list[1] == NULL);
443 if (*pat == NULL)
444 {
445 uintptr_t pad = (-(uintptr_t) buffer
446 % __alignof__ (struct gaih_addrtuple));
447 buffer += pad;
448 buflen = buflen > pad ? buflen - pad : 0;
449
450 if (__builtin_expect (buflen < sizeof (struct gaih_addrtuple),
451 0))
452 {
453 *errnop = ERANGE;
454 *herrnop = NETDB_INTERNAL;
455 status = NSS_STATUS_TRYAGAIN;
456 break;
457 }
458
459 *pat = (struct gaih_addrtuple *) buffer;
460 buffer += sizeof (struct gaih_addrtuple);
461 buflen -= sizeof (struct gaih_addrtuple);
462 }
463
464 (*pat)->next = NULL;
465 (*pat)->name = got_canon ? NULL : result.h_name;
466 got_canon = true;
467 (*pat)->family = result.h_addrtype;
468 memcpy ((*pat)->addr, result.h_addr_list[0], result.h_length);
469 (*pat)->scopeid = 0;
470
471 pat = &((*pat)->next);
472
473 /* If we only look for the first matching entry we are done. */
474 if ((_res_hconf.flags & HCONF_FLAG_MULTI) == 0)
475 break;
476 }
477
478 /* If we have to look for multiple records and found one, this
479 is a success. */
480 if (status == NSS_STATUS_NOTFOUND && any)
481 {
482 assert ((_res_hconf.flags & HCONF_FLAG_MULTI) != 0);
483 status = NSS_STATUS_SUCCESS;
484 }
485
486 fclose (stream);
487 }
488 else if (status == NSS_STATUS_TRYAGAIN)
489 {
490 *errnop = errno;
491 *herrnop = TRY_AGAIN;
492 }
493 else
494 {
495 *errnop = errno;
496 *herrnop = NO_DATA;
497 }
498
499 return status;
500 }
501 libc_hidden_def (_nss_files_gethostbyname4_r)