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1 | /* SPDX-License-Identifier: LGPL-2.1+ */ | |
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 "string-util.h" | |
14 | #include "strv.h" | |
15 | #include "time-util.h" | |
16 | ||
17 | /* Recheck /etc/hosts at most once every 2s */ | |
18 | #define ETC_HOSTS_RECHECK_USEC (2*USEC_PER_SEC) | |
19 | ||
20 | static void etc_hosts_item_free(EtcHostsItem *item) { | |
21 | strv_free(item->names); | |
22 | free(item); | |
23 | } | |
24 | ||
25 | static void etc_hosts_item_by_name_free(EtcHostsItemByName *item) { | |
26 | free(item->name); | |
27 | free(item->addresses); | |
28 | free(item); | |
29 | } | |
30 | ||
31 | void etc_hosts_free(EtcHosts *hosts) { | |
32 | hosts->by_address = hashmap_free_with_destructor(hosts->by_address, etc_hosts_item_free); | |
33 | hosts->by_name = hashmap_free_with_destructor(hosts->by_name, etc_hosts_item_by_name_free); | |
34 | hosts->no_address = set_free_free(hosts->no_address); | |
35 | } | |
36 | ||
37 | void manager_etc_hosts_flush(Manager *m) { | |
38 | etc_hosts_free(&m->etc_hosts); | |
39 | m->etc_hosts_mtime = USEC_INFINITY; | |
40 | m->etc_hosts_ino = 0; | |
41 | m->etc_hosts_dev = 0; | |
42 | } | |
43 | ||
44 | static int parse_line(EtcHosts *hosts, unsigned nr, const char *line) { | |
45 | _cleanup_free_ char *address_str = NULL; | |
46 | struct in_addr_data address = {}; | |
47 | bool found = false; | |
48 | EtcHostsItem *item; | |
49 | int r; | |
50 | ||
51 | assert(hosts); | |
52 | assert(line); | |
53 | ||
54 | r = extract_first_word(&line, &address_str, NULL, EXTRACT_RELAX); | |
55 | if (r < 0) | |
56 | return log_error_errno(r, "/etc/hosts:%u: failed to extract address: %m", nr); | |
57 | assert(r > 0); /* We already checked that the line is not empty, so it should contain *something* */ | |
58 | ||
59 | r = in_addr_ifindex_from_string_auto(address_str, &address.family, &address.address, NULL); | |
60 | if (r < 0) { | |
61 | log_warning_errno(r, "/etc/hosts:%u: address '%s' is invalid, ignoring: %m", nr, address_str); | |
62 | return 0; | |
63 | } | |
64 | ||
65 | r = in_addr_is_null(address.family, &address.address); | |
66 | if (r < 0) { | |
67 | log_warning_errno(r, "/etc/hosts:%u: address '%s' is invalid, ignoring: %m", nr, address_str); | |
68 | return 0; | |
69 | } | |
70 | if (r > 0) | |
71 | /* This is an 0.0.0.0 or :: item, which we assume means that we shall map the specified hostname to | |
72 | * nothing. */ | |
73 | item = NULL; | |
74 | else { | |
75 | /* If this is a normal address, then simply add entry mapping it to the specified names */ | |
76 | ||
77 | item = hashmap_get(hosts->by_address, &address); | |
78 | if (!item) { | |
79 | r = hashmap_ensure_allocated(&hosts->by_address, &in_addr_data_hash_ops); | |
80 | if (r < 0) | |
81 | return log_oom(); | |
82 | ||
83 | item = new0(EtcHostsItem, 1); | |
84 | if (!item) | |
85 | return log_oom(); | |
86 | ||
87 | item->address = address; | |
88 | ||
89 | r = hashmap_put(hosts->by_address, &item->address, item); | |
90 | if (r < 0) { | |
91 | free(item); | |
92 | return log_oom(); | |
93 | } | |
94 | } | |
95 | } | |
96 | ||
97 | for (;;) { | |
98 | _cleanup_free_ char *name = NULL; | |
99 | EtcHostsItemByName *bn; | |
100 | ||
101 | r = extract_first_word(&line, &name, NULL, EXTRACT_RELAX); | |
102 | if (r < 0) | |
103 | return log_error_errno(r, "/etc/hosts:%u: couldn't extract hostname: %m", nr); | |
104 | if (r == 0) | |
105 | break; | |
106 | ||
107 | found = true; | |
108 | ||
109 | r = dns_name_is_valid_ldh(name); | |
110 | if (r <= 0) { | |
111 | log_warning_errno(r, "/etc/hosts:%u: hostname \"%s\" is not valid, ignoring.", nr, name); | |
112 | continue; | |
113 | } | |
114 | ||
115 | if (is_localhost(name)) | |
116 | /* Suppress the "localhost" line that is often seen */ | |
117 | continue; | |
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_put(&hosts->no_address, &dns_name_hash_ops, name); | |
124 | if (r < 0) | |
125 | return r; | |
126 | ||
127 | TAKE_PTR(name); | |
128 | continue; | |
129 | } | |
130 | ||
131 | r = strv_extend(&item->names, name); | |
132 | if (r < 0) | |
133 | return log_oom(); | |
134 | ||
135 | bn = hashmap_get(hosts->by_name, name); | |
136 | if (!bn) { | |
137 | r = hashmap_ensure_allocated(&hosts->by_name, &dns_name_hash_ops); | |
138 | if (r < 0) | |
139 | return log_oom(); | |
140 | ||
141 | bn = new0(EtcHostsItemByName, 1); | |
142 | if (!bn) | |
143 | return log_oom(); | |
144 | ||
145 | r = hashmap_put(hosts->by_name, name, bn); | |
146 | if (r < 0) { | |
147 | free(bn); | |
148 | return log_oom(); | |
149 | } | |
150 | ||
151 | bn->name = TAKE_PTR(name); | |
152 | } | |
153 | ||
154 | if (!GREEDY_REALLOC(bn->addresses, bn->n_allocated, bn->n_addresses + 1)) | |
155 | return log_oom(); | |
156 | ||
157 | bn->addresses[bn->n_addresses++] = &item->address; | |
158 | } | |
159 | ||
160 | if (!found) | |
161 | log_warning("/etc/hosts:%u: line is missing any hostnames", nr); | |
162 | ||
163 | return 0; | |
164 | } | |
165 | ||
166 | int etc_hosts_parse(EtcHosts *hosts, FILE *f) { | |
167 | _cleanup_(etc_hosts_free) EtcHosts t = {}; | |
168 | unsigned nr = 0; | |
169 | int r; | |
170 | ||
171 | for (;;) { | |
172 | _cleanup_free_ char *line = NULL; | |
173 | char *l; | |
174 | ||
175 | r = read_line(f, LONG_LINE_MAX, &line); | |
176 | if (r < 0) | |
177 | return log_error_errno(r, "Failed to read /etc/hosts: %m"); | |
178 | if (r == 0) | |
179 | break; | |
180 | ||
181 | nr++; | |
182 | ||
183 | l = strchr(line, '#'); | |
184 | if (l) | |
185 | *l = '\0'; | |
186 | ||
187 | l = strstrip(line); | |
188 | if (isempty(l)) | |
189 | continue; | |
190 | ||
191 | r = parse_line(&t, nr, l); | |
192 | if (r < 0) | |
193 | return r; | |
194 | } | |
195 | ||
196 | etc_hosts_free(hosts); | |
197 | *hosts = t; | |
198 | t = (EtcHosts) {}; /* prevent cleanup */ | |
199 | return 0; | |
200 | } | |
201 | ||
202 | static int manager_etc_hosts_read(Manager *m) { | |
203 | _cleanup_fclose_ FILE *f = NULL; | |
204 | struct stat st; | |
205 | usec_t ts; | |
206 | int r; | |
207 | ||
208 | assert_se(sd_event_now(m->event, clock_boottime_or_monotonic(), &ts) >= 0); | |
209 | ||
210 | /* See if we checked /etc/hosts recently already */ | |
211 | if (m->etc_hosts_last != USEC_INFINITY && m->etc_hosts_last + ETC_HOSTS_RECHECK_USEC > ts) | |
212 | return 0; | |
213 | ||
214 | m->etc_hosts_last = ts; | |
215 | ||
216 | if (m->etc_hosts_mtime != USEC_INFINITY) { | |
217 | if (stat("/etc/hosts", &st) < 0) { | |
218 | if (errno != ENOENT) | |
219 | return log_error_errno(errno, "Failed to stat /etc/hosts: %m"); | |
220 | ||
221 | manager_etc_hosts_flush(m); | |
222 | return 0; | |
223 | } | |
224 | ||
225 | /* Did the mtime or ino/dev change? If not, there's no point in re-reading the file. */ | |
226 | if (timespec_load(&st.st_mtim) == m->etc_hosts_mtime && | |
227 | st.st_ino == m->etc_hosts_ino && st.st_dev == m->etc_hosts_dev) | |
228 | return 0; | |
229 | } | |
230 | ||
231 | f = fopen("/etc/hosts", "re"); | |
232 | if (!f) { | |
233 | if (errno != ENOENT) | |
234 | return log_error_errno(errno, "Failed to open /etc/hosts: %m"); | |
235 | ||
236 | manager_etc_hosts_flush(m); | |
237 | return 0; | |
238 | } | |
239 | ||
240 | /* Take the timestamp at the beginning of processing, so that any changes made later are read on the next | |
241 | * invocation */ | |
242 | r = fstat(fileno(f), &st); | |
243 | if (r < 0) | |
244 | return log_error_errno(errno, "Failed to fstat() /etc/hosts: %m"); | |
245 | ||
246 | r = etc_hosts_parse(&m->etc_hosts, f); | |
247 | if (r < 0) | |
248 | return r; | |
249 | ||
250 | m->etc_hosts_mtime = timespec_load(&st.st_mtim); | |
251 | m->etc_hosts_ino = st.st_ino; | |
252 | m->etc_hosts_dev = st.st_dev; | |
253 | m->etc_hosts_last = ts; | |
254 | ||
255 | return 1; | |
256 | } | |
257 | ||
258 | int manager_etc_hosts_lookup(Manager *m, DnsQuestion* q, DnsAnswer **answer) { | |
259 | bool found_a = false, found_aaaa = false; | |
260 | struct in_addr_data k = {}; | |
261 | EtcHostsItemByName *bn; | |
262 | DnsResourceKey *t; | |
263 | const char *name; | |
264 | unsigned i; | |
265 | int r; | |
266 | ||
267 | assert(m); | |
268 | assert(q); | |
269 | assert(answer); | |
270 | ||
271 | if (!m->read_etc_hosts) | |
272 | return 0; | |
273 | ||
274 | (void) manager_etc_hosts_read(m); | |
275 | ||
276 | name = dns_question_first_name(q); | |
277 | if (!name) | |
278 | return 0; | |
279 | ||
280 | r = dns_name_address(name, &k.family, &k.address); | |
281 | if (r > 0) { | |
282 | EtcHostsItem *item; | |
283 | DnsResourceKey *found_ptr = NULL; | |
284 | ||
285 | item = hashmap_get(m->etc_hosts.by_address, &k); | |
286 | if (!item) | |
287 | return 0; | |
288 | ||
289 | /* We have an address in /etc/hosts that matches the queried name. Let's return successful. Actual data | |
290 | * we'll only return if the request was for PTR. */ | |
291 | ||
292 | DNS_QUESTION_FOREACH(t, q) { | |
293 | if (!IN_SET(t->type, DNS_TYPE_PTR, DNS_TYPE_ANY)) | |
294 | continue; | |
295 | if (!IN_SET(t->class, DNS_CLASS_IN, DNS_CLASS_ANY)) | |
296 | continue; | |
297 | ||
298 | r = dns_name_equal(dns_resource_key_name(t), name); | |
299 | if (r < 0) | |
300 | return r; | |
301 | if (r > 0) { | |
302 | found_ptr = t; | |
303 | break; | |
304 | } | |
305 | } | |
306 | ||
307 | if (found_ptr) { | |
308 | char **n; | |
309 | ||
310 | r = dns_answer_reserve(answer, strv_length(item->names)); | |
311 | if (r < 0) | |
312 | return r; | |
313 | ||
314 | STRV_FOREACH(n, item->names) { | |
315 | _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL; | |
316 | ||
317 | rr = dns_resource_record_new(found_ptr); | |
318 | if (!rr) | |
319 | return -ENOMEM; | |
320 | ||
321 | rr->ptr.name = strdup(*n); | |
322 | if (!rr->ptr.name) | |
323 | return -ENOMEM; | |
324 | ||
325 | r = dns_answer_add(*answer, rr, 0, DNS_ANSWER_AUTHENTICATED); | |
326 | if (r < 0) | |
327 | return r; | |
328 | } | |
329 | } | |
330 | ||
331 | return 1; | |
332 | } | |
333 | ||
334 | bn = hashmap_get(m->etc_hosts.by_name, name); | |
335 | if (bn) { | |
336 | r = dns_answer_reserve(answer, bn->n_addresses); | |
337 | if (r < 0) | |
338 | return r; | |
339 | } else { | |
340 | /* Check if name was listed with no address. If yes, continue to return an answer. */ | |
341 | if (!set_contains(m->etc_hosts.no_address, name)) | |
342 | return 0; | |
343 | } | |
344 | ||
345 | DNS_QUESTION_FOREACH(t, q) { | |
346 | if (!IN_SET(t->type, DNS_TYPE_A, DNS_TYPE_AAAA, DNS_TYPE_ANY)) | |
347 | continue; | |
348 | if (!IN_SET(t->class, DNS_CLASS_IN, DNS_CLASS_ANY)) | |
349 | continue; | |
350 | ||
351 | r = dns_name_equal(dns_resource_key_name(t), name); | |
352 | if (r < 0) | |
353 | return r; | |
354 | if (r == 0) | |
355 | continue; | |
356 | ||
357 | if (IN_SET(t->type, DNS_TYPE_A, DNS_TYPE_ANY)) | |
358 | found_a = true; | |
359 | if (IN_SET(t->type, DNS_TYPE_AAAA, DNS_TYPE_ANY)) | |
360 | found_aaaa = true; | |
361 | ||
362 | if (found_a && found_aaaa) | |
363 | break; | |
364 | } | |
365 | ||
366 | for (i = 0; bn && i < bn->n_addresses; i++) { | |
367 | _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL; | |
368 | ||
369 | if ((!found_a && bn->addresses[i]->family == AF_INET) || | |
370 | (!found_aaaa && bn->addresses[i]->family == AF_INET6)) | |
371 | continue; | |
372 | ||
373 | r = dns_resource_record_new_address(&rr, bn->addresses[i]->family, &bn->addresses[i]->address, bn->name); | |
374 | if (r < 0) | |
375 | return r; | |
376 | ||
377 | r = dns_answer_add(*answer, rr, 0, DNS_ANSWER_AUTHENTICATED); | |
378 | if (r < 0) | |
379 | return r; | |
380 | } | |
381 | ||
382 | return found_a || found_aaaa; | |
383 | } |