1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
2
3 #include <sys/stat.h>
4 #include <sys/types.h>
5 #include <unistd.h>
6
7 #include "fd-util.h"
8 #include "fileio.h"
9 #include "hostname-util.h"
10 #include "resolved-dns-synthesize.h"
11 #include "resolved-etc-hosts.h"
12 #include "socket-netlink.h"
13 #include "stat-util.h"
14 #include "string-util.h"
15 #include "strv.h"
16 #include "time-util.h"
17
18 /* Recheck /etc/hosts at most once every 2s */
19 #define ETC_HOSTS_RECHECK_USEC (2*USEC_PER_SEC)
20
etc_hosts_item_free(EtcHostsItem * item)21 static void etc_hosts_item_free(EtcHostsItem *item) {
22 strv_free(item->names);
23 free(item);
24 }
25
etc_hosts_item_by_name_free(EtcHostsItemByName * item)26 static void etc_hosts_item_by_name_free(EtcHostsItemByName *item) {
27 free(item->name);
28 free(item->addresses);
29 free(item);
30 }
31
etc_hosts_free(EtcHosts * hosts)32 void etc_hosts_free(EtcHosts *hosts) {
33 hosts->by_address = hashmap_free_with_destructor(hosts->by_address, etc_hosts_item_free);
34 hosts->by_name = hashmap_free_with_destructor(hosts->by_name, etc_hosts_item_by_name_free);
35 hosts->no_address = set_free_free(hosts->no_address);
36 }
37
manager_etc_hosts_flush(Manager * m)38 void manager_etc_hosts_flush(Manager *m) {
39 etc_hosts_free(&m->etc_hosts);
40 m->etc_hosts_stat = (struct stat) {};
41 }
42
parse_line(EtcHosts * hosts,unsigned nr,const char * line)43 static int parse_line(EtcHosts *hosts, unsigned nr, const char *line) {
44 _cleanup_free_ char *address_str = NULL;
45 struct in_addr_data address = {};
46 bool found = false;
47 EtcHostsItem *item;
48 int r;
49
50 assert(hosts);
51 assert(line);
52
53 r = extract_first_word(&line, &address_str, NULL, EXTRACT_RELAX);
54 if (r < 0)
55 return log_error_errno(r, "/etc/hosts:%u: failed to extract address: %m", nr);
56 assert(r > 0); /* We already checked that the line is not empty, so it should contain *something* */
57
58 r = in_addr_ifindex_from_string_auto(address_str, &address.family, &address.address, NULL);
59 if (r < 0) {
60 log_warning_errno(r, "/etc/hosts:%u: address '%s' is invalid, ignoring: %m", nr, address_str);
61 return 0;
62 }
63
64 r = in_addr_data_is_null(&address);
65 if (r < 0) {
66 log_warning_errno(r, "/etc/hosts:%u: address '%s' is invalid, ignoring: %m", nr, address_str);
67 return 0;
68 }
69 if (r > 0)
70 /* This is an 0.0.0.0 or :: item, which we assume means that we shall map the specified hostname to
71 * nothing. */
72 item = NULL;
73 else {
74 /* If this is a normal address, then simply add entry mapping it to the specified names */
75
76 item = hashmap_get(hosts->by_address, &address);
77 if (!item) {
78 r = hashmap_ensure_allocated(&hosts->by_address, &in_addr_data_hash_ops);
79 if (r < 0)
80 return log_oom();
81
82 item = new(EtcHostsItem, 1);
83 if (!item)
84 return log_oom();
85
86 *item = (EtcHostsItem) {
87 .address = address,
88 };
89
90 r = hashmap_put(hosts->by_address, &item->address, item);
91 if (r < 0) {
92 free(item);
93 return log_oom();
94 }
95 }
96 }
97
98 for (;;) {
99 _cleanup_free_ char *name = NULL;
100 EtcHostsItemByName *bn;
101
102 r = extract_first_word(&line, &name, NULL, EXTRACT_RELAX);
103 if (r < 0)
104 return log_error_errno(r, "/etc/hosts:%u: couldn't extract hostname: %m", nr);
105 if (r == 0)
106 break;
107
108 found = true;
109
110 r = dns_name_is_valid_ldh(name);
111 if (r <= 0) {
112 if (r < 0)
113 log_warning_errno(r, "/etc/hosts:%u: Failed to check the validity of hostname \"%s\", ignoring: %m", nr, name);
114 else
115 log_warning("/etc/hosts:%u: hostname \"%s\" is not valid, ignoring.", nr, name);
116 continue;
117 }
118
119 if (!item) {
120 /* Optimize the case where we don't need to store any addresses, by storing
121 * only the name in a dedicated Set instead of the hashmap */
122
123 r = set_ensure_consume(&hosts->no_address, &dns_name_hash_ops, TAKE_PTR(name));
124 if (r < 0)
125 return r;
126
127 continue;
128 }
129
130 r = strv_extend(&item->names, name);
131 if (r < 0)
132 return log_oom();
133
134 bn = hashmap_get(hosts->by_name, name);
135 if (!bn) {
136 r = hashmap_ensure_allocated(&hosts->by_name, &dns_name_hash_ops);
137 if (r < 0)
138 return log_oom();
139
140 bn = new0(EtcHostsItemByName, 1);
141 if (!bn)
142 return log_oom();
143
144 r = hashmap_put(hosts->by_name, name, bn);
145 if (r < 0) {
146 free(bn);
147 return log_oom();
148 }
149
150 bn->name = TAKE_PTR(name);
151 }
152
153 if (!GREEDY_REALLOC(bn->addresses, bn->n_addresses + 1))
154 return log_oom();
155
156 bn->addresses[bn->n_addresses++] = &item->address;
157 }
158
159 if (!found)
160 log_warning("/etc/hosts:%u: line is missing any hostnames", nr);
161
162 return 0;
163 }
164
strip_localhost(EtcHosts * hosts)165 static void strip_localhost(EtcHosts *hosts) {
166 static const struct in_addr_data local_in_addrs[] = {
167 {
168 .family = AF_INET,
169 #if __BYTE_ORDER == __LITTLE_ENDIAN
170 /* We want constant expressions here, that's why we don't use htole32() here */
171 .address.in.s_addr = UINT32_C(0x0100007F),
172 #else
173 .address.in.s_addr = UINT32_C(0x7F000001),
174 #endif
175 },
176 {
177 .family = AF_INET6,
178 .address.in6 = IN6ADDR_LOOPBACK_INIT,
179 },
180 };
181
182 EtcHostsItem *item;
183
184 assert(hosts);
185
186 /* Removes the 'localhost' entry from what we loaded. But only if the mapping is exclusively between
187 * 127.0.0.1 and localhost (or aliases to that we recognize). If there's any other name assigned to
188 * it, we leave the entry in.
189 *
190 * This way our regular synthesizing can take over, but only if it would result in the exact same
191 * mappings. */
192
193 for (size_t j = 0; j < ELEMENTSOF(local_in_addrs); j++) {
194 bool all_localhost, in_order;
195
196 item = hashmap_get(hosts->by_address, local_in_addrs + j);
197 if (!item)
198 continue;
199
200 /* Check whether all hostnames the loopback address points to are localhost ones */
201 all_localhost = true;
202 STRV_FOREACH(i, item->names)
203 if (!is_localhost(*i)) {
204 all_localhost = false;
205 break;
206 }
207
208 if (!all_localhost) /* Not all names are localhost, hence keep the entries for this address. */
209 continue;
210
211 /* Now check if the names listed for this address actually all point back just to this
212 * address (or the other loopback address). If not, let's stay away from this too. */
213 in_order = true;
214 STRV_FOREACH(i, item->names) {
215 EtcHostsItemByName *n;
216 bool all_local_address;
217
218 n = hashmap_get(hosts->by_name, *i);
219 if (!n) /* No reverse entry? Then almost certainly the entry already got deleted from
220 * the previous iteration of this loop, i.e. via the other protocol */
221 break;
222
223 /* Now check if the addresses of this item are all localhost addresses */
224 all_local_address = true;
225 for (size_t m = 0; m < n->n_addresses; m++)
226 if (!in_addr_is_localhost(n->addresses[m]->family, &n->addresses[m]->address)) {
227 all_local_address = false;
228 break;
229 }
230
231 if (!all_local_address) {
232 in_order = false;
233 break;
234 }
235 }
236
237 if (!in_order)
238 continue;
239
240 STRV_FOREACH(i, item->names) {
241 EtcHostsItemByName *n;
242
243 n = hashmap_remove(hosts->by_name, *i);
244 if (n)
245 etc_hosts_item_by_name_free(n);
246 }
247
248 assert_se(hashmap_remove(hosts->by_address, local_in_addrs + j) == item);
249 etc_hosts_item_free(item);
250 }
251 }
252
etc_hosts_parse(EtcHosts * hosts,FILE * f)253 int etc_hosts_parse(EtcHosts *hosts, FILE *f) {
254 _cleanup_(etc_hosts_free) EtcHosts t = {};
255 unsigned nr = 0;
256 int r;
257
258 for (;;) {
259 _cleanup_free_ char *line = NULL;
260 char *l;
261
262 r = read_line(f, LONG_LINE_MAX, &line);
263 if (r < 0)
264 return log_error_errno(r, "Failed to read /etc/hosts: %m");
265 if (r == 0)
266 break;
267
268 nr++;
269
270 l = strchr(line, '#');
271 if (l)
272 *l = '\0';
273
274 l = strstrip(line);
275 if (isempty(l))
276 continue;
277
278 r = parse_line(&t, nr, l);
279 if (r < 0)
280 return r;
281 }
282
283 strip_localhost(&t);
284
285 etc_hosts_free(hosts);
286 *hosts = t;
287 t = (EtcHosts) {}; /* prevent cleanup */
288 return 0;
289 }
290
manager_etc_hosts_read(Manager * m)291 static int manager_etc_hosts_read(Manager *m) {
292 _cleanup_fclose_ FILE *f = NULL;
293 struct stat st;
294 usec_t ts;
295 int r;
296
297 assert_se(sd_event_now(m->event, CLOCK_BOOTTIME, &ts) >= 0);
298
299 /* See if we checked /etc/hosts recently already */
300 if (m->etc_hosts_last != USEC_INFINITY && m->etc_hosts_last + ETC_HOSTS_RECHECK_USEC > ts)
301 return 0;
302
303 m->etc_hosts_last = ts;
304
305 if (m->etc_hosts_stat.st_mode != 0) {
306 if (stat("/etc/hosts", &st) < 0) {
307 if (errno != ENOENT)
308 return log_error_errno(errno, "Failed to stat /etc/hosts: %m");
309
310 manager_etc_hosts_flush(m);
311 return 0;
312 }
313
314 /* Did the mtime or ino/dev change? If not, there's no point in re-reading the file. */
315 if (stat_inode_unmodified(&m->etc_hosts_stat, &st))
316 return 0;
317 }
318
319 f = fopen("/etc/hosts", "re");
320 if (!f) {
321 if (errno != ENOENT)
322 return log_error_errno(errno, "Failed to open /etc/hosts: %m");
323
324 manager_etc_hosts_flush(m);
325 return 0;
326 }
327
328 /* Take the timestamp at the beginning of processing, so that any changes made later are read on the next
329 * invocation */
330 r = fstat(fileno(f), &st);
331 if (r < 0)
332 return log_error_errno(errno, "Failed to fstat() /etc/hosts: %m");
333
334 r = etc_hosts_parse(&m->etc_hosts, f);
335 if (r < 0)
336 return r;
337
338 m->etc_hosts_stat = st;
339 m->etc_hosts_last = ts;
340
341 return 1;
342 }
343
manager_etc_hosts_lookup(Manager * m,DnsQuestion * q,DnsAnswer ** answer)344 int manager_etc_hosts_lookup(Manager *m, DnsQuestion* q, DnsAnswer **answer) {
345 bool found_a = false, found_aaaa = false;
346 struct in_addr_data k = {};
347 EtcHostsItemByName *bn;
348 DnsResourceKey *t;
349 const char *name;
350 unsigned i;
351 int r;
352
353 assert(m);
354 assert(q);
355 assert(answer);
356
357 if (!m->read_etc_hosts)
358 return 0;
359
360 (void) manager_etc_hosts_read(m);
361
362 name = dns_question_first_name(q);
363 if (!name)
364 return 0;
365
366 r = dns_name_address(name, &k.family, &k.address);
367 if (r > 0) {
368 EtcHostsItem *item;
369 DnsResourceKey *found_ptr = NULL;
370
371 item = hashmap_get(m->etc_hosts.by_address, &k);
372 if (!item)
373 return 0;
374
375 /* We have an address in /etc/hosts that matches the queried name. Let's return successful. Actual data
376 * we'll only return if the request was for PTR. */
377
378 DNS_QUESTION_FOREACH(t, q) {
379 if (!IN_SET(t->type, DNS_TYPE_PTR, DNS_TYPE_ANY))
380 continue;
381 if (!IN_SET(t->class, DNS_CLASS_IN, DNS_CLASS_ANY))
382 continue;
383
384 r = dns_name_equal(dns_resource_key_name(t), name);
385 if (r < 0)
386 return r;
387 if (r > 0) {
388 found_ptr = t;
389 break;
390 }
391 }
392
393 if (found_ptr) {
394 r = dns_answer_reserve(answer, strv_length(item->names));
395 if (r < 0)
396 return r;
397
398 STRV_FOREACH(n, item->names) {
399 _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
400
401 rr = dns_resource_record_new(found_ptr);
402 if (!rr)
403 return -ENOMEM;
404
405 rr->ptr.name = strdup(*n);
406 if (!rr->ptr.name)
407 return -ENOMEM;
408
409 r = dns_answer_add(*answer, rr, 0, DNS_ANSWER_AUTHENTICATED, NULL);
410 if (r < 0)
411 return r;
412 }
413 }
414
415 return 1;
416 }
417
418 bn = hashmap_get(m->etc_hosts.by_name, name);
419 if (bn) {
420 r = dns_answer_reserve(answer, bn->n_addresses);
421 if (r < 0)
422 return r;
423 } else {
424 /* Check if name was listed with no address. If yes, continue to return an answer. */
425 if (!set_contains(m->etc_hosts.no_address, name))
426 return 0;
427 }
428
429 DNS_QUESTION_FOREACH(t, q) {
430 if (!IN_SET(t->type, DNS_TYPE_A, DNS_TYPE_AAAA, DNS_TYPE_ANY))
431 continue;
432 if (!IN_SET(t->class, DNS_CLASS_IN, DNS_CLASS_ANY))
433 continue;
434
435 r = dns_name_equal(dns_resource_key_name(t), name);
436 if (r < 0)
437 return r;
438 if (r == 0)
439 continue;
440
441 if (IN_SET(t->type, DNS_TYPE_A, DNS_TYPE_ANY))
442 found_a = true;
443 if (IN_SET(t->type, DNS_TYPE_AAAA, DNS_TYPE_ANY))
444 found_aaaa = true;
445
446 if (found_a && found_aaaa)
447 break;
448 }
449
450 for (i = 0; bn && i < bn->n_addresses; i++) {
451 _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL;
452
453 if ((!found_a && bn->addresses[i]->family == AF_INET) ||
454 (!found_aaaa && bn->addresses[i]->family == AF_INET6))
455 continue;
456
457 r = dns_resource_record_new_address(&rr, bn->addresses[i]->family, &bn->addresses[i]->address, bn->name);
458 if (r < 0)
459 return r;
460
461 r = dns_answer_add(*answer, rr, 0, DNS_ANSWER_AUTHENTICATED, NULL);
462 if (r < 0)
463 return r;
464 }
465
466 return found_a || found_aaaa;
467 }
468