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domain.c @ 19204

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Revision 19204, 28.0 KB checked in by zacheiss, 21 years ago (diff)
This commit was generated by cvs2svn to compensate for changes in r19203, which included commits to RCS files with non-trunk default branches.

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1	/*
2	* Copyright (c) 1998-2003 Sendmail, Inc. and its suppliers.
3	* All rights reserved.
4	* Copyright (c) 1986, 1995-1997 Eric P. Allman. All rights reserved.
5	* Copyright (c) 1988, 1993
6	* The Regents of the University of California. All rights reserved.
7	*
8	* By using this file, you agree to the terms and conditions set
9	* forth in the LICENSE file which can be found at the top level of
10	* the sendmail distribution.
11	*
12	*/
13
14	#include <sendmail.h>
15
16	#if NAMED_BIND
17	SM_RCSID("@(#)$Id: domain.c,v 1.1.1.1 2003-04-08 15:08:48 zacheiss Exp $ (with name server)")
18	#else /* NAMED_BIND */
19	SM_RCSID("@(#)$Id: domain.c,v 1.1.1.1 2003-04-08 15:08:48 zacheiss Exp $ (without name server)")
20	#endif /* NAMED_BIND */
21
22	#if NAMED_BIND
23
24	# include <arpa/inet.h>
25
26
27	/*
28	** The standard udp packet size PACKETSZ (512) is not sufficient for some
29	** nameserver answers containing very many resource records. The resolver
30	** may switch to tcp and retry if it detects udp packet overflow.
31	** Also note that the resolver routines res_query and res_search return
32	** the size of the untruncated answer in case the supplied answer buffer
33	** it not big enough to accommodate the entire answer.
34	*/
35
36	# ifndef MAXPACKET
37	# define MAXPACKET 8192 /* max packet size used internally by BIND */
38	# endif /* ! MAXPACKET */
39
40	typedef union
41	{
42	HEADER qb1;
43	unsigned char qb2[MAXPACKET];
44	} querybuf;
45
46	# ifndef MXHOSTBUFSIZE
47	# define MXHOSTBUFSIZE (128 * MAXMXHOSTS)
48	# endif /* ! MXHOSTBUFSIZE */
49
50	static char MXHostBuf[MXHOSTBUFSIZE];
51	#if (MXHOSTBUFSIZE < 2) \|\| (MXHOSTBUFSIZE >= INT_MAX/2)
52	ERROR: _MXHOSTBUFSIZE is out of range
53	#endif /* (MXHOSTBUFSIZE < 2) \|\| (MXHOSTBUFSIZE >= INT_MAX/2) */
54
55	# ifndef MAXDNSRCH
56	# define MAXDNSRCH 6 /* number of possible domains to search */
57	# endif /* ! MAXDNSRCH */
58
59	# ifndef RES_DNSRCH_VARIABLE
60	# define RES_DNSRCH_VARIABLE _res.dnsrch
61	# endif /* ! RES_DNSRCH_VARIABLE */
62
63	# ifndef NO_DATA
64	# define NO_DATA NO_ADDRESS
65	# endif /* ! NO_DATA */
66
67	# ifndef HFIXEDSZ
68	# define HFIXEDSZ 12 /* sizeof(HEADER) */
69	# endif /* ! HFIXEDSZ */
70
71	# define MAXCNAMEDEPTH 10 /* maximum depth of CNAME recursion */
72
73	# if defined(__RES) && (__RES >= 19940415)
74	# define RES_UNC_T char *
75	# else /* defined(__RES) && (__RES >= 19940415) */
76	# define RES_UNC_T unsigned char *
77	# endif /* defined(__RES) && (__RES >= 19940415) */
78
79	static char gethostalias __P((char ));
80	static int mxrand __P((char *));
81	static int fallbackmxrr __P((int, unsigned short , char *));
82
83	/*
84	** GETFALLBACKMXRR -- get MX resource records for fallback MX host.
85	**
86	** We have to initialize this once before doing anything else.
87	** Moreover, we have to repeat this from time to time to avoid
88	** stale data, e.g., in persistent queue runners.
89	** This should be done in a parent process so the child
90	** processes have the right data.
91	**
92	** Parameters:
93	** host -- the name of the fallback MX host.
94	**
95	** Returns:
96	** number of MX records.
97	**
98	** Side Effects:
99	** Populates NumFallBackMXHosts and fbhosts.
100	** Sets renewal time (based on TTL).
101	*/
102
103	int NumFallBackMXHosts = 0; /* Number of fallback MX hosts (after MX expansion) */
104	static char *fbhosts[MAXMXHOSTS + 1];
105
106	int
107	getfallbackmxrr(host)
108	char *host;
109	{
110	int i, rcode;
111	int ttl;
112	static time_t renew = 0;
113
114	#if 0
115	/* This is currently done before this function is called. */
116	if (host == NULL \|\| *host == '\0')
117	return 0;
118	#endif /* 0 */
119	if (NumFallBackMXHosts > 0 && renew > curtime())
120	return NumFallBackMXHosts;
121	if (host[0] == '[')
122	{
123	fbhosts[0] = host;
124	NumFallBackMXHosts = 1;
125	}
126	else
127	{
128	/* free old data */
129	for (i = 0; i < NumFallBackMXHosts; i++)
130	sm_free(fbhosts[i]);
131
132	/* get new data */
133	NumFallBackMXHosts = getmxrr(host, fbhosts, NULL, false,
134	&rcode, false, &ttl);
135	renew = curtime() + ttl;
136	for (i = 0; i < NumFallBackMXHosts; i++)
137	fbhosts[i] = newstr(fbhosts[i]);
138	}
139	return NumFallBackMXHosts;
140	}
141
142	/*
143	** FALLBACKMXRR -- add MX resource records for fallback MX host to list.
144	**
145	** Parameters:
146	** nmx -- current number of MX records.
147	** prefs -- array of preferences.
148	** mxhosts -- array of MX hosts (maximum size: MAXMXHOSTS)
149	**
150	** Returns:
151	** new number of MX records.
152	**
153	** Side Effects:
154	** If FallBackMX was set, it appends the MX records for
155	** that host to mxhosts (and modifies prefs accordingly).
156	*/
157
158	static int
159	fallbackmxrr(nmx, prefs, mxhosts)
160	int nmx;
161	unsigned short *prefs;
162	char **mxhosts;
163	{
164	int i;
165
166	for (i = 0; i < NumFallBackMXHosts && nmx < MAXMXHOSTS; i++)
167	{
168	if (nmx > 0)
169	prefs[nmx] = prefs[nmx - 1] + 1;
170	else
171	prefs[nmx] = 0;
172	mxhosts[nmx++] = fbhosts[i];
173	}
174	return nmx;
175	}
176
177	/*
178	** GETMXRR -- get MX resource records for a domain
179	**
180	** Parameters:
181	** host -- the name of the host to MX.
182	** mxhosts -- a pointer to a return buffer of MX records.
183	** mxprefs -- a pointer to a return buffer of MX preferences.
184	** If NULL, don't try to populate.
185	** droplocalhost -- If true, all MX records less preferred
186	** than the local host (as determined by $=w) will
187	** be discarded.
188	** rcode -- a pointer to an EX_ status code.
189	** tryfallback -- add also fallback MX host?
190	** pttl -- pointer to return TTL (can be NULL).
191	**
192	** Returns:
193	** The number of MX records found.
194	** -1 if there is an internal failure.
195	** If no MX records are found, mxhosts[0] is set to host
196	** and 1 is returned.
197	**
198	** Side Effects:
199	** The entries made for mxhosts point to a static array
200	** MXHostBuf[MXHOSTBUFSIZE], so the data needs to be copied,
201	** if it must be preserved across calls to this function.
202	*/
203
204	int
205	getmxrr(host, mxhosts, mxprefs, droplocalhost, rcode, tryfallback, pttl)
206	char *host;
207	char **mxhosts;
208	unsigned short *mxprefs;
209	bool droplocalhost;
210	int *rcode;
211	bool tryfallback;
212	int *pttl;
213	{
214	register unsigned char eom, cp;
215	register int i, j, n;
216	int nmx = 0;
217	register char *bp;
218	HEADER *hp;
219	querybuf answer;
220	int ancount, qdcount, buflen;
221	bool seenlocal = false;
222	unsigned short pref, type;
223	unsigned short localpref = 256;
224	char *fallbackMX = FallBackMX;
225	bool trycanon = false;
226	unsigned short *prefs;
227	int (*resfunc)();
228	unsigned short prefer[MAXMXHOSTS];
229	int weight[MAXMXHOSTS];
230	int ttl = 0;
231	extern int res_query(), res_search();
232
233	if (tTd(8, 2))
234	sm_dprintf("getmxrr(%s, droplocalhost=%d)\n",
235	host, droplocalhost);
236
237	if ((fallbackMX != NULL && droplocalhost &&
238	wordinclass(fallbackMX, 'w')) \|\| !tryfallback)
239	{
240	/* don't use fallback for this pass */
241	fallbackMX = NULL;
242	}
243
244	*rcode = EX_OK;
245
246	if (mxprefs != NULL)
247	prefs = mxprefs;
248	else
249	prefs = prefer;
250
251	/* efficiency hack -- numeric or non-MX lookups */
252	if (host[0] == '[')
253	goto punt;
254
255	/*
256	** If we don't have MX records in our host switch, don't
257	** try for MX records. Note that this really isn't "right",
258	** since we might be set up to try NIS first and then DNS;
259	** if the host is found in NIS we really shouldn't be doing
260	** MX lookups. However, that should be a degenerate case.
261	*/
262
263	if (!UseNameServer)
264	goto punt;
265	if (HasWildcardMX && ConfigLevel >= 6)
266	resfunc = res_query;
267	else
268	resfunc = res_search;
269
270	errno = 0;
271	n = (resfunc)(host, C_IN, T_MX, (unsigned char ) &answer,
272	sizeof(answer));
273	if (n < 0)
274	{
275	if (tTd(8, 1))
276	sm_dprintf("getmxrr: res_search(%s) failed (errno=%d, h_errno=%d)\n",
277	host == NULL ? "<NULL>" : host, errno, h_errno);
278	switch (h_errno)
279	{
280	case NO_DATA:
281	trycanon = true;
282	/* FALLTHROUGH */
283
284	case NO_RECOVERY:
285	/* no MX data on this host */
286	goto punt;
287
288	case HOST_NOT_FOUND:
289	# if BROKEN_RES_SEARCH
290	case 0: /* Ultrix resolver retns failure w/ h_errno=0 */
291	# endif /* BROKEN_RES_SEARCH */
292	/* host doesn't exist in DNS; might be in /etc/hosts */
293	trycanon = true;
294	*rcode = EX_NOHOST;
295	goto punt;
296
297	case TRY_AGAIN:
298	case -1:
299	/* couldn't connect to the name server */
300	if (fallbackMX != NULL)
301	{
302	/* name server is hosed -- push to fallback */
303	return fallbackmxrr(nmx, prefs, mxhosts);
304	}
305	/* it might come up later; better queue it up */
306	*rcode = EX_TEMPFAIL;
307	break;
308
309	default:
310	syserr("getmxrr: res_search (%s) failed with impossible h_errno (%d)",
311	host, h_errno);
312	*rcode = EX_OSERR;
313	break;
314	}
315
316	/* irreconcilable differences */
317	return -1;
318	}
319
320	/* avoid problems after truncation in tcp packets */
321	if (n > sizeof(answer))
322	n = sizeof(answer);
323
324	/* find first satisfactory answer */
325	hp = (HEADER *)&answer;
326	cp = (unsigned char *)&answer + HFIXEDSZ;
327	eom = (unsigned char *)&answer + n;
328	for (qdcount = ntohs((unsigned short) hp->qdcount);
329	qdcount--;
330	cp += n + QFIXEDSZ)
331	{
332	if ((n = dn_skipname(cp, eom)) < 0)
333	goto punt;
334	}
335
336	/* NOTE: see definition of MXHostBuf! */
337	buflen = sizeof(MXHostBuf) - 1;
338	SM_ASSERT(buflen > 0);
339	bp = MXHostBuf;
340	ancount = ntohs((unsigned short) hp->ancount);
341
342	/* See RFC 1035 for layout of RRs. */
343	/* XXX leave room for FallBackMX ? */
344	while (--ancount >= 0 && cp < eom && nmx < MAXMXHOSTS - 1)
345	{
346	if ((n = dn_expand((unsigned char *)&answer, eom, cp,
347	(RES_UNC_T) bp, buflen)) < 0)
348	break;
349	cp += n;
350	GETSHORT(type, cp);
351	cp += INT16SZ; /* skip over class */
352	GETLONG(ttl, cp);
353	GETSHORT(n, cp); /* rdlength */
354	if (type != T_MX)
355	{
356	if (tTd(8, 8) \|\| _res.options & RES_DEBUG)
357	sm_dprintf("unexpected answer type %d, size %d\n",
358	type, n);
359	cp += n;
360	continue;
361	}
362	GETSHORT(pref, cp);
363	if ((n = dn_expand((unsigned char *)&answer, eom, cp,
364	(RES_UNC_T) bp, buflen)) < 0)
365	break;
366	cp += n;
367	n = strlen(bp);
368	# if 0
369	/* Can this happen? */
370	if (n == 0)
371	{
372	if (LogLevel > 4)
373	sm_syslog(LOG_ERR, NOQID,
374	"MX records for %s contain empty string",
375	host);
376	continue;
377	}
378	# endif /* 0 */
379	if (wordinclass(bp, 'w'))
380	{
381	if (tTd(8, 3))
382	sm_dprintf("found localhost (%s) in MX list, pref=%d\n",
383	bp, pref);
384	if (droplocalhost)
385	{
386	if (!seenlocal \|\| pref < localpref)
387	localpref = pref;
388	seenlocal = true;
389	continue;
390	}
391	weight[nmx] = 0;
392	}
393	else
394	weight[nmx] = mxrand(bp);
395	prefs[nmx] = pref;
396	mxhosts[nmx++] = bp;
397	bp += n;
398	if (bp[-1] != '.')
399	{
400	*bp++ = '.';
401	n++;
402	}
403	*bp++ = '\0';
404	if (buflen < n + 1)
405	{
406	/* don't want to wrap buflen */
407	break;
408	}
409	buflen -= n + 1;
410	}
411
412	/* return only one TTL entry, that should be sufficient */
413	if (ttl > 0 && pttl != NULL)
414	*pttl = ttl;
415
416	/* sort the records */
417	for (i = 0; i < nmx; i++)
418	{
419	for (j = i + 1; j < nmx; j++)
420	{
421	if (prefs[i] > prefs[j] \|\|
422	(prefs[i] == prefs[j] && weight[i] > weight[j]))
423	{
424	register int temp;
425	register char *temp1;
426
427	temp = prefs[i];
428	prefs[i] = prefs[j];
429	prefs[j] = temp;
430	temp1 = mxhosts[i];
431	mxhosts[i] = mxhosts[j];
432	mxhosts[j] = temp1;
433	temp = weight[i];
434	weight[i] = weight[j];
435	weight[j] = temp;
436	}
437	}
438	if (seenlocal && prefs[i] >= localpref)
439	{
440	/* truncate higher preference part of list */
441	nmx = i;
442	}
443	}
444
445	/* delete duplicates from list (yes, some bozos have duplicates) */
446	for (i = 0; i < nmx - 1; )
447	{
448	if (sm_strcasecmp(mxhosts[i], mxhosts[i + 1]) != 0)
449	i++;
450	else
451	{
452	/* compress out duplicate */
453	for (j = i + 1; j < nmx; j++)
454	{
455	mxhosts[j] = mxhosts[j + 1];
456	prefs[j] = prefs[j + 1];
457	}
458	nmx--;
459	}
460	}
461
462	if (nmx == 0)
463	{
464	punt:
465	if (seenlocal)
466	{
467	struct hostent *h = NULL;
468
469	/*
470	** If we have deleted all MX entries, this is
471	** an error -- we should NEVER send to a host that
472	** has an MX, and this should have been caught
473	** earlier in the config file.
474	**
475	** Some sites prefer to go ahead and try the
476	** A record anyway; that case is handled by
477	** setting TryNullMXList. I believe this is a
478	** bad idea, but it's up to you....
479	*/
480
481	if (TryNullMXList)
482	{
483	SM_SET_H_ERRNO(0);
484	errno = 0;
485	h = sm_gethostbyname(host, AF_INET);
486	if (h == NULL)
487	{
488	if (errno == ETIMEDOUT \|\|
489	h_errno == TRY_AGAIN \|\|
490	(errno == ECONNREFUSED &&
491	UseNameServer))
492	{
493	*rcode = EX_TEMPFAIL;
494	return -1;
495	}
496	# if NETINET6
497	SM_SET_H_ERRNO(0);
498	errno = 0;
499	h = sm_gethostbyname(host, AF_INET6);
500	if (h == NULL &&
501	(errno == ETIMEDOUT \|\|
502	h_errno == TRY_AGAIN \|\|
503	(errno == ECONNREFUSED &&
504	UseNameServer)))
505	{
506	*rcode = EX_TEMPFAIL;
507	return -1;
508	}
509	# endif /* NETINET6 */
510	}
511	}
512
513	if (h == NULL)
514	{
515	*rcode = EX_CONFIG;
516	syserr("MX list for %s points back to %s",
517	host, MyHostName);
518	return -1;
519	}
520	# if NETINET6
521	freehostent(h);
522	hp = NULL;
523	# endif /* NETINET6 */
524	}
525	if (strlen(host) >= sizeof MXHostBuf)
526	{
527	*rcode = EX_CONFIG;
528	syserr("Host name %s too long",
529	shortenstring(host, MAXSHORTSTR));
530	return -1;
531	}
532	(void) sm_strlcpy(MXHostBuf, host, sizeof MXHostBuf);
533	mxhosts[0] = MXHostBuf;
534	prefs[0] = 0;
535	if (host[0] == '[')
536	{
537	register char *p;
538	# if NETINET6
539	struct sockaddr_in6 tmp6;
540	# endif /* NETINET6 */
541
542	/* this may be an MX suppression-style address */
543	p = strchr(MXHostBuf, ']');
544	if (p != NULL)
545	{
546	*p = '\0';
547
548	if (inet_addr(&MXHostBuf[1]) != INADDR_NONE)
549	{
550	nmx++;
551	*p = ']';
552	}
553	# if NETINET6
554	else if (anynet_pton(AF_INET6, &MXHostBuf[1],
555	&tmp6.sin6_addr) == 1)
556	{
557	nmx++;
558	*p = ']';
559	}
560	# endif /* NETINET6 */
561	else
562	{
563	trycanon = true;
564	mxhosts[0]++;
565	}
566	}
567	}
568	if (trycanon &&
569	getcanonname(mxhosts[0], sizeof MXHostBuf - 2, false, pttl))
570	{
571	/* XXX MXHostBuf == "" ? is that possible? */
572	bp = &MXHostBuf[strlen(MXHostBuf)];
573	if (bp[-1] != '.')
574	{
575	*bp++ = '.';
576	*bp = '\0';
577	}
578	nmx = 1;
579	}
580	}
581
582	/* if we have a default lowest preference, include that */
583	if (fallbackMX != NULL && !seenlocal)
584	{
585	nmx = fallbackmxrr(nmx, prefs, mxhosts);
586	}
587	return nmx;
588	}
589	/*
590	** MXRAND -- create a randomizer for equal MX preferences
591	**
592	** If two MX hosts have equal preferences we want to randomize
593	** the selection. But in order for signatures to be the same,
594	** we need to randomize the same way each time. This function
595	** computes a pseudo-random hash function from the host name.
596	**
597	** Parameters:
598	** host -- the name of the host.
599	**
600	** Returns:
601	** A random but repeatable value based on the host name.
602	*/
603
604	static int
605	mxrand(host)
606	register char *host;
607	{
608	int hfunc;
609	static unsigned int seed;
610
611	if (seed == 0)
612	{
613	seed = (int) curtime() & 0xffff;
614	if (seed == 0)
615	seed++;
616	}
617
618	if (tTd(17, 9))
619	sm_dprintf("mxrand(%s)", host);
620
621	hfunc = seed;
622	while (*host != '\0')
623	{
624	int c = *host++;
625
626	if (isascii(c) && isupper(c))
627	c = tolower(c);
628	hfunc = ((hfunc << 1) ^ c) % 2003;
629	}
630
631	hfunc &= 0xff;
632	hfunc++;
633
634	if (tTd(17, 9))
635	sm_dprintf(" = %d\n", hfunc);
636	return hfunc;
637	}
638	/*
639	** BESTMX -- find the best MX for a name
640	**
641	** This is really a hack, but I don't see any obvious way
642	** to generalize it at the moment.
643	*/
644
645	/* ARGSUSED3 */
646	char *
647	bestmx_map_lookup(map, name, av, statp)
648	MAP *map;
649	char *name;
650	char **av;
651	int *statp;
652	{
653	int nmx;
654	int saveopts = _res.options;
655	int i;
656	ssize_t len = 0;
657	char *result;
658	char *mxhosts[MAXMXHOSTS + 1];
659	#if _FFR_BESTMX_BETTER_TRUNCATION
660	char *buf;
661	#else /* _FFR_BESTMX_BETTER_TRUNCATION */
662	char *p;
663	char buf[PSBUFSIZE / 2];
664	#endif /* _FFR_BESTMX_BETTER_TRUNCATION */
665
666	_res.options &= ~(RES_DNSRCH\|RES_DEFNAMES);
667	nmx = getmxrr(name, mxhosts, NULL, false, statp, false, NULL);
668	_res.options = saveopts;
669	if (nmx <= 0)
670	return NULL;
671	if (bitset(MF_MATCHONLY, map->map_mflags))
672	return map_rewrite(map, name, strlen(name), NULL);
673	if ((map->map_coldelim == '\0') \|\| (nmx == 1))
674	return map_rewrite(map, mxhosts[0], strlen(mxhosts[0]), av);
675
676	/*
677	** We were given a -z flag (return all MXs) and there are multiple
678	** ones. We need to build them all into a list.
679	*/
680
681	#if _FFR_BESTMX_BETTER_TRUNCATION
682	for (i = 0; i < nmx; i++)
683	{
684	if (strchr(mxhosts[i], map->map_coldelim) != NULL)
685	{
686	syserr("bestmx_map_lookup: MX host %.64s includes map delimiter character 0x%02X",
687	mxhosts[i], map->map_coldelim);
688	return NULL;
689	}
690	len += strlen(mxhosts[i]) + 1;
691	if (len < 0)
692	{
693	len -= strlen(mxhosts[i]) + 1;
694	break;
695	}
696	}
697	buf = (char *) sm_malloc(len);
698	if (buf == NULL)
699	{
700	*statp = EX_UNAVAILABLE;
701	return NULL;
702	}
703	*buf = '\0';
704	for (i = 0; i < nmx; i++)
705	{
706	int end;
707
708	end = sm_strlcat(buf, mxhosts[i], len);
709	if (i != nmx && end + 1 < len)
710	{
711	buf[end] = map->map_coldelim;
712	buf[end + 1] = '\0';
713	}
714	}
715
716	/* Cleanly truncate for rulesets */
717	truncate_at_delim(buf, PSBUFSIZE / 2, map->map_coldelim);
718	#else /* _FFR_BESTMX_BETTER_TRUNCATION */
719	p = buf;
720	for (i = 0; i < nmx; i++)
721	{
722	size_t slen;
723
724	if (strchr(mxhosts[i], map->map_coldelim) != NULL)
725	{
726	syserr("bestmx_map_lookup: MX host %.64s includes map delimiter character 0x%02X",
727	mxhosts[i], map->map_coldelim);
728	return NULL;
729	}
730	slen = strlen(mxhosts[i]);
731	if (len + slen + 2 > sizeof buf)
732	break;
733	if (i > 0)
734	{
735	*p++ = map->map_coldelim;
736	len++;
737	}
738	(void) sm_strlcpy(p, mxhosts[i], sizeof buf - len);
739	p += slen;
740	len += slen;
741	}
742	#endif /* _FFR_BESTMX_BETTER_TRUNCATION */
743
744	result = map_rewrite(map, buf, len, av);
745	#if _FFR_BESTMX_BETTER_TRUNCATION
746	sm_free(buf);
747	#endif /* _FFR_BESTMX_BETTER_TRUNCATION */
748	return result;
749	}
750	/*
751	** DNS_GETCANONNAME -- get the canonical name for named host using DNS
752	**
753	** This algorithm tries to be smart about wildcard MX records.
754	** This is hard to do because DNS doesn't tell is if we matched
755	** against a wildcard or a specific MX.
756	**
757	** We always prefer A & CNAME records, since these are presumed
758	** to be specific.
759	**
760	** If we match an MX in one pass and lose it in the next, we use
761	** the old one. For example, consider an MX matching *.FOO.BAR.COM.
762	** A hostname bletch.foo.bar.com will match against this MX, but
763	** will stop matching when we try bletch.bar.com -- so we know
764	** that bletch.foo.bar.com must have been right. This fails if
765	** there was also an MX record matching *.BAR.COM, but there are
766	** some things that just can't be fixed.
767	**
768	** Parameters:
769	** host -- a buffer containing the name of the host.
770	** This is a value-result parameter.
771	** hbsize -- the size of the host buffer.
772	** trymx -- if set, try MX records as well as A and CNAME.
773	** statp -- pointer to place to store status.
774	** pttl -- pointer to return TTL (can be NULL).
775	**
776	** Returns:
777	** true -- if the host matched.
778	** false -- otherwise.
779	*/
780
781	# if NETINET6
782	# define SM_T_INITIAL T_AAAA
783	# else /* NETINET6 */
784	# define SM_T_INITIAL T_A
785	# endif /* NETINET6 */
786
787	bool
788	dns_getcanonname(host, hbsize, trymx, statp, pttl)
789	char *host;
790	int hbsize;
791	bool trymx;
792	int *statp;
793	int *pttl;
794	{
795	register unsigned char eom, ap;
796	register char *cp;
797	register int n;
798	HEADER *hp;
799	querybuf answer;
800	int ancount, qdcount;
801	int ret;
802	char **domain;
803	int type;
804	int ttl = 0;
805	char **dp;
806	char *mxmatch;
807	bool amatch;
808	bool gotmx = false;
809	int qtype;
810	int loopcnt;
811	char *xp;
812	char nbuf[SM_MAX(MAXPACKET, MAXDNAME*2+2)];
813	char *searchlist[MAXDNSRCH + 2];
814
815	if (tTd(8, 2))
816	sm_dprintf("dns_getcanonname(%s, trymx=%d)\n", host, trymx);
817
818	if ((_res.options & RES_INIT) == 0 && res_init() == -1)
819	{
820	*statp = EX_UNAVAILABLE;
821	return false;
822	}
823
824	*statp = EX_OK;
825
826	/*
827	** Initialize domain search list. If there is at least one
828	** dot in the name, search the unmodified name first so we
829	** find "vse.CS" in Czechoslovakia instead of in the local
830	** domain (e.g., vse.CS.Berkeley.EDU). Note that there is no
831	** longer a country named Czechoslovakia but this type of problem
832	** is still present.
833	**
834	** Older versions of the resolver could create this
835	** list by tearing apart the host name.
836	*/
837
838	loopcnt = 0;
839	cnameloop:
840	/* Check for dots in the name */
841	for (cp = host, n = 0; *cp != '\0'; cp++)
842	if (*cp == '.')
843	n++;
844
845	/*
846	** If this is a simple name, determine whether it matches an
847	** alias in the file defined by the environment variable HOSTALIASES.
848	*/
849
850	if (n == 0 && (xp = gethostalias(host)) != NULL)
851	{
852	if (loopcnt++ > MAXCNAMEDEPTH)
853	{
854	syserr("loop in ${HOSTALIASES} file");
855	}
856	else
857	{
858	(void) sm_strlcpy(host, xp, hbsize);
859	goto cnameloop;
860	}
861	}
862
863	/*
864	** Build the search list.
865	** If there is at least one dot in name, start with a null
866	** domain to search the unmodified name first.
867	** If name does not end with a dot and search up local domain
868	** tree desired, append each local domain component to the
869	** search list; if name contains no dots and default domain
870	** name is desired, append default domain name to search list;
871	** else if name ends in a dot, remove that dot.
872	*/
873
874	dp = searchlist;
875	if (n > 0)
876	*dp++ = "";
877	if (n >= 0 && *--cp != '.' && bitset(RES_DNSRCH, _res.options))
878	{
879	/* make sure there are less than MAXDNSRCH domains */
880	for (domain = RES_DNSRCH_VARIABLE, ret = 0;
881	*domain != NULL && ret < MAXDNSRCH;
882	ret++)
883	dp++ = domain++;
884	}
885	else if (n == 0 && bitset(RES_DEFNAMES, _res.options))
886	{
887	*dp++ = _res.defdname;
888	}
889	else if (*cp == '.')
890	{
891	*cp = '\0';
892	}
893	*dp = NULL;
894
895	/*
896	** Now loop through the search list, appending each domain in turn
897	** name and searching for a match.
898	*/
899
900	mxmatch = NULL;
901	qtype = SM_T_INITIAL;
902
903	for (dp = searchlist; *dp != NULL; )
904	{
905	if (qtype == SM_T_INITIAL)
906	gotmx = false;
907	if (tTd(8, 5))
908	sm_dprintf("dns_getcanonname: trying %s.%s (%s)\n",
909	host, *dp,
910	# if NETINET6
911	qtype == T_AAAA ? "AAAA" :
912	# endif /* NETINET6 */
913	qtype == T_A ? "A" :
914	qtype == T_MX ? "MX" :
915	"???");
916	errno = 0;
917	ret = res_querydomain(host, *dp, C_IN, qtype,
918	answer.qb2, sizeof(answer.qb2));
919	if (ret <= 0)
920	{
921	int save_errno = errno;
922
923	if (tTd(8, 7))
924	sm_dprintf("\tNO: errno=%d, h_errno=%d\n",
925	save_errno, h_errno);
926
927	if (save_errno == ECONNREFUSED \|\| h_errno == TRY_AGAIN)
928	{
929	/*
930	** the name server seems to be down or broken.
931	*/
932
933	SM_SET_H_ERRNO(TRY_AGAIN);
934	# if _FFR_DONT_STOP_LOOKING
935	if (**dp == '\0')
936	{
937	if (*statp == EX_OK)
938	*statp = EX_TEMPFAIL;
939	goto nexttype;
940	}
941	# endif /* _FFR_DONT_STOP_LOOKING */
942	*statp = EX_TEMPFAIL;
943
944	if (WorkAroundBrokenAAAA)
945	{
946	/*
947	** Only return if not TRY_AGAIN as an
948	** attempt with a different qtype may
949	** succeed (res_querydomain() calls
950	** res_query() calls res_send() which
951	** sets errno to ETIMEDOUT if the
952	** nameservers could be contacted but
953	** didn't give an answer).
954	*/
955
956	if (save_errno != ETIMEDOUT)
957	return false;
958	}
959	else
960	return false;
961	}
962
963	# if _FFR_DONT_STOP_LOOKING
964	nexttype:
965	# endif /* _FFR_DONT_STOP_LOOKING */
966	if (h_errno != HOST_NOT_FOUND)
967	{
968	/* might have another type of interest */
969	# if NETINET6
970	if (qtype == T_AAAA)
971	{
972	qtype = T_A;
973	continue;
974	}
975	else
976	# endif /* NETINET6 */
977	if (qtype == T_A && !gotmx &&
978	(trymx \|\| **dp == '\0'))
979	{
980	qtype = T_MX;
981	continue;
982	}
983	}
984
985	/* definite no -- try the next domain */
986	dp++;
987	qtype = SM_T_INITIAL;
988	continue;
989	}
990	else if (tTd(8, 7))
991	sm_dprintf("\tYES\n");
992
993	/* avoid problems after truncation in tcp packets */
994	if (ret > sizeof(answer))
995	ret = sizeof(answer);
996	if (ret < 0)
997	{
998	*statp = EX_SOFTWARE;
999	return false;
1000	}
1001
1002	/*
1003	** Appear to have a match. Confirm it by searching for A or
1004	** CNAME records. If we don't have a local domain
1005	** wild card MX record, we will accept MX as well.
1006	*/
1007
1008	hp = (HEADER *) &answer;
1009	ap = (unsigned char *) &answer + HFIXEDSZ;
1010	eom = (unsigned char *) &answer + ret;
1011
1012	/* skip question part of response -- we know what we asked */
1013	for (qdcount = ntohs((unsigned short) hp->qdcount);
1014	qdcount--;
1015	ap += ret + QFIXEDSZ)
1016	{
1017	if ((ret = dn_skipname(ap, eom)) < 0)
1018	{
1019	if (tTd(8, 20))
1020	sm_dprintf("qdcount failure (%d)\n",
1021	ntohs((unsigned short) hp->qdcount));
1022	*statp = EX_SOFTWARE;
1023	return false; /* ???XXX??? */
1024	}
1025	}
1026
1027	amatch = false;
1028	for (ancount = ntohs((unsigned short) hp->ancount);
1029	--ancount >= 0 && ap < eom;
1030	ap += n)
1031	{
1032	n = dn_expand((unsigned char *) &answer, eom, ap,
1033	(RES_UNC_T) nbuf, sizeof nbuf);
1034	if (n < 0)
1035	break;
1036	ap += n;
1037	GETSHORT(type, ap);
1038	ap += INT16SZ; /* skip over class */
1039	GETLONG(ttl, ap);
1040	GETSHORT(n, ap); /* rdlength */
1041	switch (type)
1042	{
1043	case T_MX:
1044	gotmx = true;
1045	if (**dp != '\0' && HasWildcardMX)
1046	{
1047	/*
1048	** If we are using MX matches and have
1049	** not yet gotten one, save this one
1050	** but keep searching for an A or
1051	** CNAME match.
1052	*/
1053
1054	if (trymx && mxmatch == NULL)
1055	mxmatch = *dp;
1056	continue;
1057	}
1058
1059	/*
1060	** If we did not append a domain name, this
1061	** must have been a canonical name to start
1062	** with. Even if we did append a domain name,
1063	** in the absence of a wildcard MX this must
1064	** still be a real MX match.
1065	** Such MX matches are as good as an A match,
1066	** fall through.
1067	*/
1068	/* FALLTHROUGH */
1069
1070	# if NETINET6
1071	case T_AAAA:
1072	/* Flag that a good match was found */
1073	amatch = true;
1074
1075	/* continue in case a CNAME also exists */
1076	continue;
1077	# endif /* NETINET6 */
1078
1079	case T_A:
1080	/* Flag that a good match was found */
1081	amatch = true;
1082
1083	/* continue in case a CNAME also exists */
1084	continue;
1085
1086	case T_CNAME:
1087	if (DontExpandCnames)
1088	{
1089	/* got CNAME -- guaranteed canonical */
1090	amatch = true;
1091	break;
1092	}
1093
1094	if (loopcnt++ > MAXCNAMEDEPTH)
1095	{
1096	/XXX should notify postmaster XXX/
1097	message("DNS failure: CNAME loop for %s",
1098	host);
1099	if (CurEnv->e_message == NULL)
1100	{
1101	char ebuf[MAXLINE];
1102
1103	(void) sm_snprintf(ebuf,
1104	sizeof ebuf,
1105	"Deferred: DNS failure: CNAME loop for %.100s",
1106	host);
1107	CurEnv->e_message =
1108	sm_rpool_strdup_x(
1109	CurEnv->e_rpool, ebuf);
1110	}
1111	SM_SET_H_ERRNO(NO_RECOVERY);
1112	*statp = EX_CONFIG;
1113	return false;
1114	}
1115
1116	/* value points at name */
1117	if ((ret = dn_expand((unsigned char *)&answer,
1118	eom, ap, (RES_UNC_T) nbuf,
1119	sizeof(nbuf))) < 0)
1120	break;
1121	(void) sm_strlcpy(host, nbuf, hbsize);
1122
1123	/*
1124	** RFC 1034 section 3.6 specifies that CNAME
1125	** should point at the canonical name -- but
1126	** urges software to try again anyway.
1127	*/
1128
1129	goto cnameloop;
1130
1131	default:
1132	/* not a record of interest */
1133	continue;
1134	}
1135	}
1136
1137	if (amatch)
1138	{
1139	/*
1140	** Got a good match -- either an A, CNAME, or an
1141	** exact MX record. Save it and get out of here.
1142	*/
1143
1144	mxmatch = *dp;
1145	break;
1146	}
1147
1148	/*
1149	** Nothing definitive yet.
1150	** If this was a T_A query and we haven't yet found a MX
1151	** match, try T_MX if allowed to do so.
1152	** Otherwise, try the next domain.
1153	*/
1154
1155	# if NETINET6
1156	if (qtype == T_AAAA)
1157	qtype = T_A;
1158	else
1159	# endif /* NETINET6 */
1160	if (qtype == T_A && !gotmx && (trymx \|\| **dp == '\0'))
1161	qtype = T_MX;
1162	else
1163	{
1164	qtype = SM_T_INITIAL;
1165	dp++;
1166	}
1167	}
1168
1169	/* if nothing was found, we are done */
1170	if (mxmatch == NULL)
1171	{
1172	if (*statp == EX_OK)
1173	*statp = EX_NOHOST;
1174	return false;
1175	}
1176
1177	/*
1178	** Create canonical name and return.
1179	** If saved domain name is null, name was already canonical.
1180	** Otherwise append the saved domain name.
1181	*/
1182
1183	(void) sm_snprintf(nbuf, sizeof nbuf, "%.s%s%.s", MAXDNAME, host,
1184	*mxmatch == '\0' ? "" : ".",
1185	MAXDNAME, mxmatch);
1186	(void) sm_strlcpy(host, nbuf, hbsize);
1187	if (tTd(8, 5))
1188	sm_dprintf("dns_getcanonname: %s\n", host);
1189	*statp = EX_OK;
1190
1191	/* return only one TTL entry, that should be sufficient */
1192	if (ttl > 0 && pttl != NULL)
1193	*pttl = ttl;
1194	return true;
1195	}
1196
1197	static char *
1198	gethostalias(host)
1199	char *host;
1200	{
1201	char *fname;
1202	SM_FILE_T *fp;
1203	register char *p = NULL;
1204	long sff = SFF_REGONLY;
1205	char buf[MAXLINE];
1206	static char hbuf[MAXDNAME];
1207
1208	if (ResNoAliases)
1209	return NULL;
1210	if (DontLockReadFiles)
1211	sff \|= SFF_NOLOCK;
1212	fname = getenv("HOSTALIASES");
1213	if (fname == NULL \|\|
1214	(fp = safefopen(fname, O_RDONLY, 0, sff)) == NULL)
1215	return NULL;
1216	while (sm_io_fgets(fp, SM_TIME_DEFAULT, buf, sizeof buf) != NULL)
1217	{
1218	for (p = buf; p != '\0' && !(isascii(p) && isspace(p)); p++)
1219	continue;
1220	if (*p == 0)
1221	{
1222	/* syntax error */
1223	continue;
1224	}
1225	*p++ = '\0';
1226	if (sm_strcasecmp(buf, host) == 0)
1227	break;
1228	}
1229
1230	if (sm_io_eof(fp))
1231	{
1232	/* no match */
1233	(void) sm_io_close(fp, SM_TIME_DEFAULT);
1234	return NULL;
1235	}
1236	(void) sm_io_close(fp, SM_TIME_DEFAULT);
1237
1238	/* got a match; extract the equivalent name */
1239	while (p != '\0' && isascii(p) && isspace(*p))
1240	p++;
1241	host = p;
1242	while (p != '\0' && !(isascii(p) && isspace(*p)))
1243	p++;
1244	*p = '\0';
1245	(void) sm_strlcpy(hbuf, host, sizeof hbuf);
1246	return hbuf;
1247	}
1248	#endif /* NAMED_BIND */

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source: trunk/third/sendmail/sendmail/domain.c @ 19204

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