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Revision 8880 - (show annotations)
Sun Apr 14 16:02:11 2019 UTC (14 months, 3 weeks ago) by michael
File MIME type: text/x-chdr
File size: 18705 byte(s)
- Add address_compare() and make use of it in some places

1 /*
2 * ircd-hybrid: an advanced, lightweight Internet Relay Chat Daemon (ircd)
3 *
4 * Copyright (c) 1997-2019 ircd-hybrid development team
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301
19 * USA
20 */
21
22 /*! \file res.c
23 * \brief ircd resolver functions
24 * \version $Id$
25 */
26
27 /*
28 * A rewrite of Darren Reed's original res.c As there is nothing
29 * left of Darren's original code, this is now licensed by the hybrid group.
30 * (Well, some of the function names are the same, and bits of the structs..)
31 * You can use it where it is useful, free even. Buy us a beer and stuff.
32 *
33 * The authors takes no responsibility for any damage or loss
34 * of property which results from the use of this software.
35 *
36 * July 1999 - Rewrote a bunch of stuff here. Change hostent builder code,
37 * added callbacks and reference counting of returned hostents.
38 * --Bleep (Thomas Helvey <tomh@inxpress.net>)
39 *
40 * This was all needlessly complicated for irc. Simplified. No more hostent
41 * All we really care about is the IP -> hostname mappings. That's all.
42 *
43 * Apr 28, 2003 --cryogen and Dianora
44 */
45
46 #include "stdinc.h"
47 #include "list.h"
48 #include "event.h"
49 #include "irc_string.h"
50 #include "ircd.h"
51 #include "rng_mt.h"
52 #include "fdlist.h"
53 #include "s_bsd.h"
54 #include "misc.h"
55 #include "res.h"
56 #include "reslib.h"
57 #include "memory.h"
58
59 #if (CHAR_BIT != 8)
60 #error this code needs to be able to address individual octets
61 #endif
62
63 static void res_readreply(fde_t *, void *);
64
65 #define MAXPACKET 1024 /**< rfc says 512 but we expand names so ... */
66 #define AR_TTL 600 /**< TTL in seconds for dns cache entries */
67
68 /*
69 * RFC 1104/1105 wasn't very helpful about what these fields
70 * should be named, so for now, we'll just name them this way.
71 * We probably should look at what named calls them or something.
72 */
73 #define TYPE_SIZE (size_t)2
74 #define CLASS_SIZE (size_t)2
75 #define TTL_SIZE (size_t)4
76 #define RDLENGTH_SIZE (size_t)2
77 #define ANSWER_FIXED_SIZE (TYPE_SIZE + CLASS_SIZE + TTL_SIZE + RDLENGTH_SIZE)
78
79 struct reslist
80 {
81 dlink_node node; /**< Doubly linked list node. */
82 unsigned int id; /**< Request ID (from request header). */
83 char type; /**< Current request type. */
84 char retries; /**< Retry counter */
85 unsigned int sends; /**< Number of sends (>1 means resent). */
86 uintmax_t sentat; /**< Timestamp we last sent this request. */
87 uintmax_t timeout; /**< When this request times out. */
88 struct irc_ssaddr addr; /**< Address for this request. */
89 char name[RFC1035_MAX_DOMAIN_LENGTH + 1]; /**< Hostname for this request. */
90 size_t namelength; /**< Actual hostname length. */
91 dns_callback_fnc callback; /**< Callback function on completion. */
92 void *callback_ctx; /**< Context pointer for callback. */
93 };
94
95 static fde_t *ResolverFileDescriptor;
96 static dlink_list request_list;
97
98
99 /*
100 * rem_request - remove a request from the list.
101 * This must also free any memory that has been allocated for
102 * temporary storage of DNS results.
103 */
104 static void
105 rem_request(struct reslist *request)
106 {
107 dlinkDelete(&request->node, &request_list);
108 xfree(request);
109 }
110
111 /*
112 * make_request - Create a DNS request record for the server.
113 */
114 static struct reslist *
115 make_request(dns_callback_fnc callback, void *ctx)
116 {
117 struct reslist *request = xcalloc(sizeof(*request));
118
119 request->sentat = CurrentTime;
120 request->retries = 2;
121 request->timeout = 4; /* Start at 4 and exponential inc. */
122 request->callback = callback;
123 request->callback_ctx = ctx;
124
125 dlinkAdd(request, &request->node, &request_list);
126 return request;
127 }
128
129 /*
130 * int
131 * res_ourserver(inp)
132 * looks up "inp" in irc_nsaddr_list[]
133 * returns:
134 * 0 : not found
135 * >0 : found
136 * author:
137 * paul vixie, 29may94
138 * revised for ircd, cryogen(stu) may03
139 */
140 static bool
141 res_ourserver(const struct irc_ssaddr *inp)
142 {
143 for (unsigned int i = 0; i < irc_nscount; ++i)
144 if (address_compare(inp, &irc_nsaddr_list[i], true) == true)
145 return true;
146
147 return false;
148 }
149
150 /*
151 * start_resolver - do everything we need to read the resolv.conf file
152 * and initialize the resolver file descriptor if needed
153 */
154 static void
155 start_resolver(void)
156 {
157 irc_res_init();
158
159 if (ResolverFileDescriptor == NULL)
160 {
161 int fd = comm_socket(irc_nsaddr_list[0].ss.ss_family, SOCK_DGRAM, 0);
162 if (fd == -1)
163 return;
164
165 ResolverFileDescriptor = fd_open(fd, true, "UDP resolver socket");
166
167 /* At the moment, the resolver FD data is global .. */
168 comm_setselect(ResolverFileDescriptor, COMM_SELECT_READ, res_readreply, NULL, 0);
169 }
170 }
171
172 /*
173 * restart_resolver - reread resolv.conf, reopen socket
174 */
175 void
176 restart_resolver(void)
177 {
178 if (ResolverFileDescriptor)
179 {
180 fd_close(ResolverFileDescriptor);
181 ResolverFileDescriptor = NULL;
182 }
183
184 start_resolver();
185 }
186
187 /*
188 * delete_resolver_queries - cleanup outstanding queries
189 * for which there no longer exist clients or conf lines.
190 */
191 void
192 delete_resolver_queries(const void *vptr)
193 {
194 dlink_node *node, *node_next;
195
196 DLINK_FOREACH_SAFE(node, node_next, request_list.head)
197 {
198 struct reslist *request = node->data;
199
200 if (request->callback_ctx == vptr)
201 rem_request(request);
202 }
203 }
204
205 /*
206 * send_res_msg - sends msg to all nameservers found in the "_res" structure.
207 * This should reflect /etc/resolv.conf. We will get responses
208 * which arent needed but is easier than checking to see if nameserver
209 * isn't present. Returns number of messages successfully sent to
210 * nameservers or -1 if no successful sends.
211 */
212 static void
213 send_res_msg(const unsigned char *msg, int len, unsigned int rcount)
214 {
215 unsigned int max_queries = IRCD_MIN(irc_nscount, rcount);
216
217 /* RES_PRIMARY option is not implemented
218 * if (res.options & RES_PRIMARY || 0 == max_queries)
219 */
220 if (max_queries == 0)
221 max_queries = 1;
222
223 for (unsigned int i = 0; i < max_queries; ++i)
224 sendto(ResolverFileDescriptor->fd, msg, len, 0,
225 (struct sockaddr *)&irc_nsaddr_list[i], irc_nsaddr_list[i].ss_len);
226 }
227
228 /*
229 * find_id - find a dns request id (id is determined by dn_mkquery)
230 */
231 static struct reslist *
232 find_id(unsigned int id)
233 {
234 dlink_node *node;
235
236 DLINK_FOREACH(node, request_list.head)
237 {
238 struct reslist *request = node->data;
239
240 if (request->id == id)
241 return request;
242 }
243
244 return NULL;
245 }
246
247 /*
248 * query_name - generate a query based on class, type and name.
249 */
250 static void
251 query_name(const char *name, int query_class, int type, struct reslist *request)
252 {
253 unsigned char buf[MAXPACKET];
254 int request_len = 0;
255
256 memset(buf, 0, sizeof(buf));
257
258 if ((request_len = irc_res_mkquery(name, query_class, type, buf, sizeof(buf))) > 0)
259 {
260 HEADER *header = (HEADER *)buf;
261
262 /*
263 * Generate an unique id.
264 * NOTE: we don't have to worry about converting this to and from
265 * network byte order, the nameserver does not interpret this value
266 * and returns it unchanged.
267 */
268 do
269 header->id = (header->id + genrand_int32()) & 0xFFFF;
270 while (find_id(header->id));
271
272 request->id = header->id;
273 ++request->sends;
274
275 send_res_msg(buf, request_len, request->sends);
276 }
277 }
278
279 /*
280 * do_query_name - nameserver lookup name
281 */
282 static void
283 do_query_name(dns_callback_fnc callback, void *ctx, const char *name,
284 struct reslist *request, int type)
285 {
286 char host_name[RFC1035_MAX_DOMAIN_LENGTH + 1];
287
288 strlcpy(host_name, name, sizeof(host_name));
289
290 if (request == NULL)
291 {
292 request = make_request(callback, ctx);
293 request->type = type;
294 request->namelength = strlcpy(request->name, host_name, sizeof(request->name));
295 }
296
297 request->type = type;
298 query_name(host_name, C_IN, type, request);
299 }
300
301 /*
302 * do_query_number - Use this to do reverse IP# lookups.
303 */
304 static void
305 do_query_number(dns_callback_fnc callback, void *ctx,
306 const struct irc_ssaddr *addr,
307 struct reslist *request)
308 {
309 char ipbuf[128] = "";
310
311 if (addr->ss.ss_family == AF_INET)
312 {
313 const struct sockaddr_in *v4 = (const struct sockaddr_in *)addr;
314 const unsigned char *cp = (const unsigned char *)&v4->sin_addr.s_addr;
315
316 snprintf(ipbuf, sizeof(ipbuf), "%u.%u.%u.%u.in-addr.arpa.",
317 (unsigned int)(cp[3]), (unsigned int)(cp[2]),
318 (unsigned int)(cp[1]), (unsigned int)(cp[0]));
319 }
320 else if (addr->ss.ss_family == AF_INET6)
321 {
322 const struct sockaddr_in6 *v6 = (const struct sockaddr_in6 *)addr;
323 const unsigned char *cp = (const unsigned char *)&v6->sin6_addr.s6_addr;
324
325 snprintf(ipbuf, sizeof(ipbuf),
326 "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x."
327 "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.ip6.arpa.",
328 (unsigned int)(cp[15] & 0xf), (unsigned int)(cp[15] >> 4),
329 (unsigned int)(cp[14] & 0xf), (unsigned int)(cp[14] >> 4),
330 (unsigned int)(cp[13] & 0xf), (unsigned int)(cp[13] >> 4),
331 (unsigned int)(cp[12] & 0xf), (unsigned int)(cp[12] >> 4),
332 (unsigned int)(cp[11] & 0xf), (unsigned int)(cp[11] >> 4),
333 (unsigned int)(cp[10] & 0xf), (unsigned int)(cp[10] >> 4),
334 (unsigned int)(cp[9] & 0xf), (unsigned int)(cp[9] >> 4),
335 (unsigned int)(cp[8] & 0xf), (unsigned int)(cp[8] >> 4),
336 (unsigned int)(cp[7] & 0xf), (unsigned int)(cp[7] >> 4),
337 (unsigned int)(cp[6] & 0xf), (unsigned int)(cp[6] >> 4),
338 (unsigned int)(cp[5] & 0xf), (unsigned int)(cp[5] >> 4),
339 (unsigned int)(cp[4] & 0xf), (unsigned int)(cp[4] >> 4),
340 (unsigned int)(cp[3] & 0xf), (unsigned int)(cp[3] >> 4),
341 (unsigned int)(cp[2] & 0xf), (unsigned int)(cp[2] >> 4),
342 (unsigned int)(cp[1] & 0xf), (unsigned int)(cp[1] >> 4),
343 (unsigned int)(cp[0] & 0xf), (unsigned int)(cp[0] >> 4));
344 }
345
346 if (request == NULL)
347 {
348 request = make_request(callback, ctx);
349 request->type = T_PTR;
350 memcpy(&request->addr, addr, sizeof(struct irc_ssaddr));
351 }
352
353 query_name(ipbuf, C_IN, T_PTR, request);
354 }
355
356 /*
357 * gethost_byname_type - get host address from name
358 *
359 */
360 void
361 gethost_byname_type(dns_callback_fnc callback, void *ctx, const char *name, int type)
362 {
363 assert(name);
364 do_query_name(callback, ctx, name, NULL, type);
365 }
366
367 /*
368 * gethost_byaddr - get host name from address
369 */
370 void
371 gethost_byaddr(dns_callback_fnc callback, void *ctx, const struct irc_ssaddr *addr)
372 {
373 do_query_number(callback, ctx, addr, NULL);
374 }
375
376 static void
377 resend_query(struct reslist *request)
378 {
379 switch (request->type)
380 {
381 case T_PTR:
382 do_query_number(NULL, NULL, &request->addr, request);
383 break;
384 case T_A:
385 case T_AAAA:
386 do_query_name(NULL, NULL, request->name, request, request->type);
387 break;
388 default:
389 break;
390 }
391 }
392
393 /*
394 * proc_answer - process name server reply
395 */
396 static bool
397 proc_answer(struct reslist *request, HEADER *header, unsigned char *buf, unsigned char *eob)
398 {
399 char hostbuf[RFC1035_MAX_DOMAIN_LENGTH + 100]; /* working buffer */
400 unsigned char *current = buf + sizeof(HEADER); /* current position in buf */
401 unsigned int type = 0; /* answer type */
402 unsigned int rd_length = 0;
403 int n; /* temp count */
404 struct sockaddr_in *v4; /* conversion */
405 struct sockaddr_in6 *v6;
406
407 for (; header->qdcount > 0; --header->qdcount)
408 {
409 if ((n = irc_dn_skipname(current, eob)) < 0)
410 break;
411
412 current += (size_t)n + QFIXEDSZ;
413 }
414
415 /*
416 * Process each answer sent to us blech.
417 */
418 while (header->ancount > 0 && current < eob)
419 {
420 --header->ancount;
421
422 n = irc_dn_expand(buf, eob, current, hostbuf, sizeof(hostbuf));
423
424 if (n < 0 /* Broken message */ || n == 0 /* No more answers left */)
425 return false;
426
427 hostbuf[RFC1035_MAX_DOMAIN_LENGTH] = '\0';
428
429 /*
430 * With Address arithmetic you have to be very anal
431 * this code was not working on alpha due to that
432 * (spotted by rodder/jailbird/dianora)
433 */
434 current += (size_t)n;
435
436 if (!((current + ANSWER_FIXED_SIZE) < eob))
437 break;
438
439 type = irc_ns_get16(current);
440 current += TYPE_SIZE;
441 current += CLASS_SIZE;
442 current += TTL_SIZE;
443 rd_length = irc_ns_get16(current);
444 current += RDLENGTH_SIZE;
445
446 /*
447 * Wait to set request->type until we verify this structure
448 */
449 switch (type)
450 {
451 case T_A:
452 if (request->type != T_A)
453 return false;
454
455 /*
456 * Check for invalid rd_length or too many addresses
457 */
458 if (rd_length != sizeof(struct in_addr))
459 return false;
460
461 request->addr.ss_len = sizeof(struct sockaddr_in);
462 v4 = (struct sockaddr_in *)&request->addr;
463 v4->sin_family = AF_INET;
464 memcpy(&v4->sin_addr, current, sizeof(struct in_addr));
465 return true;
466 break;
467
468 case T_AAAA:
469 if (request->type != T_AAAA)
470 return false;
471
472 if (rd_length != sizeof(struct in6_addr))
473 return false;
474
475 request->addr.ss_len = sizeof(struct sockaddr_in6);
476 v6 = (struct sockaddr_in6 *)&request->addr;
477 v6->sin6_family = AF_INET6;
478 memcpy(&v6->sin6_addr, current, sizeof(struct in6_addr));
479 return true;
480 break;
481
482 case T_PTR:
483 if (request->type != T_PTR)
484 return false;
485
486 n = irc_dn_expand(buf, eob, current, hostbuf, sizeof(hostbuf));
487 if (n < 0 /* Broken message */ || n == 0 /* No more answers left */)
488 return false;
489
490 request->namelength = strlcpy(request->name, hostbuf, sizeof(request->name));
491 return true;
492 break;
493
494 case T_CNAME:
495 current += rd_length;
496 break;
497
498 default:
499 return false;
500 break;
501 }
502 }
503
504 return false;
505 }
506
507 /*
508 * res_readreply - read a dns reply from the nameserver and process it.
509 */
510 static void
511 res_readreply(fde_t *F, void *data)
512 {
513 unsigned char buf[sizeof(HEADER) + MAXPACKET];
514 ssize_t rc = 0;
515 socklen_t len = sizeof(struct irc_ssaddr);
516 struct irc_ssaddr lsin;
517
518 while ((rc = recvfrom(F->fd, buf, sizeof(buf), 0, (struct sockaddr *)&lsin, &len)) != -1)
519 {
520 if (rc <= (ssize_t)sizeof(HEADER))
521 continue;
522
523 /*
524 * Check against possibly fake replies
525 */
526 if (res_ourserver(&lsin) == false)
527 continue;
528
529 /*
530 * Convert DNS reply reader from Network byte order to CPU byte order.
531 */
532 HEADER *header = (HEADER *)buf;
533 header->ancount = ntohs(header->ancount);
534 header->qdcount = ntohs(header->qdcount);
535 header->nscount = ntohs(header->nscount);
536 header->arcount = ntohs(header->arcount);
537
538 /*
539 * Response for an id which we have already received an answer for
540 * just ignore this response.
541 */
542 struct reslist *request;
543 if ((request = find_id(header->id)) == NULL)
544 continue;
545
546 if (header->rcode != NO_ERRORS || header->ancount == 0)
547 {
548 /*
549 * If a bad error was returned, stop here and don't send
550 * any more (no retries granted).
551 */
552 (*request->callback)(request->callback_ctx, NULL, NULL, 0);
553 rem_request(request);
554 continue;
555 }
556
557 /*
558 * If this fails there was an error decoding the received packet.
559 * We only give it one shot. If it fails, just leave the client
560 * unresolved.
561 */
562 if (proc_answer(request, header, buf, buf + rc) == false)
563 {
564 (*request->callback)(request->callback_ctx, NULL, NULL, 0);
565 rem_request(request);
566 continue;
567 }
568
569 if (request->type == T_PTR)
570 {
571 if (request->namelength == 0)
572 {
573 /*
574 * Got a PTR response with no name, something bogus is happening
575 * don't bother trying again, the client address doesn't resolve
576 */
577 (*request->callback)(request->callback_ctx, NULL, NULL, 0);
578 rem_request(request);
579 continue;
580 }
581
582 /*
583 * Lookup the 'authoritative' name that we were given for the ip#.
584 */
585 if (request->addr.ss.ss_family == AF_INET6)
586 gethost_byname_type(request->callback, request->callback_ctx, request->name, T_AAAA);
587 else
588 gethost_byname_type(request->callback, request->callback_ctx, request->name, T_A);
589
590 rem_request(request);
591 }
592 else
593 {
594 /*
595 * Got a name and address response, client resolved
596 */
597 (*request->callback)(request->callback_ctx, &request->addr, request->name, request->namelength);
598 rem_request(request);
599 }
600
601 continue;
602 }
603
604 comm_setselect(F, COMM_SELECT_READ, res_readreply, NULL, 0);
605 }
606
607 /*
608 * timeout_query_list - Remove queries from the list which have been
609 * there too long without being resolved.
610 */
611 static uintmax_t
612 timeout_query_list(void)
613 {
614 dlink_node *node, *node_next;
615 uintmax_t next_time = 0;
616
617 DLINK_FOREACH_SAFE(node, node_next, request_list.head)
618 {
619 struct reslist *request = node->data;
620 uintmax_t timeout = request->sentat + request->timeout;
621
622 if (CurrentTime >= timeout)
623 {
624 if (--request->retries <= 0)
625 {
626 (*request->callback)(request->callback_ctx, NULL, NULL, 0);
627 rem_request(request);
628 continue;
629 }
630 else
631 {
632 request->sentat = CurrentTime;
633 request->timeout += request->timeout;
634 resend_query(request);
635 }
636 }
637
638 if (next_time == 0 || timeout < next_time)
639 next_time = timeout;
640 }
641
642 return (next_time > CurrentTime) ? next_time : (CurrentTime + AR_TTL);
643 }
644
645 /*
646 * timeout_resolver - check request list
647 */
648 static void
649 timeout_resolver(void *unused)
650 {
651 timeout_query_list();
652 }
653
654 /*
655 * resolver_init - initialize resolver and resolver library
656 */
657 void
658 resolver_init(void)
659 {
660 static struct event event_timeout_resolver =
661 {
662 .name = "timeout_resolver",
663 .handler = timeout_resolver,
664 .when = 1
665 };
666
667 start_resolver();
668 event_add(&event_timeout_resolver, NULL);
669 }

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