res_gethost.c revision 1219:f89f56c2d9ac 
1/*
2 * Copyright (c) 1985, 1988 Regents of the University of California.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms are permitted
6 * provided that this notice is preserved and that due credit is given
7 * to the University of California at Berkeley. The name of the University
8 * may not be used to endorse or promote products derived from this
9 * software without specific prior written permission. This software
10 * is provided ``as is'' without express or implied warranty.
11 *
12 */
13
14/*
15 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
16 * Use is subject to license terms.
17 */
18
19#pragma ident	"%Z%%M%	%I%	%E% SMI" /* SunOS 1.11; UCB 6.32 */
20
21#include "c_synonyms.h"
22#include <sys/param.h>
23#include <sys/socket.h>
24#include <netinet/in.h>
25#include <ctype.h>
26#include <netdb.h>
27#include <stdio.h>
28#include <errno.h>
29#include <arpa/inet.h>
30#include <arpa/nameser.h>
31#include <resolv.h>
32#include <syslog.h>
33
34/*
35 * When the name service switch calls libresolv, it doesn't want fallback
36 * to /etc/hosts, so we provide a method to turn it off.
37 */
38static int	no_hosts_fallback = 0;
39
40void
41__res_set_no_hosts_fallback(void) {
42	no_hosts_fallback = 1;
43}
44
45static int
46__res_no_hosts_fallback(void) {
47	return(no_hosts_fallback);
48}
49
50static char *h_addr_ptrs[MAXADDRS + 1];
51
52static struct hostent host;
53static char *host_aliases[MAXALIASES];
54static char hostbuf[BUFSIZ+1];
55static struct in_addr host_addr;
56static char HOSTDB[] = "/etc/hosts";
57static FILE *hostf = NULL;
58static char hostaddr[MAXADDRS];
59static char *host_addrs[2];
60static int stayopen = 0;
61static char *any();
62
63#if PACKETSZ > 1024
64#define	MAXPACKET	PACKETSZ
65#else
66#define	MAXPACKET	1024
67#endif
68
69typedef union {
70	HEADER hdr;
71	u_char buf[MAXPACKET];
72} querybuf;
73
74static union {
75	long al;
76	char ac;
77} align;
78
79
80int h_errno;
81
82static struct hostent *
83getanswer(answer, anslen, iquery)
84	querybuf *answer;
85	int anslen;
86	int iquery;
87{
88	register HEADER *hp;
89	register u_char *cp;
90	register int n;
91	u_char *eom;
92	char *bp, **ap;
93	int type, class, buflen, ancount, qdcount;
94	int haveanswer, getclass = C_ANY;
95	char **hap;
96
97	eom = answer->buf + anslen;
98	/*
99	 * find first satisfactory answer
100	 */
101	hp = &answer->hdr;
102	ancount = ntohs(hp->ancount);
103	qdcount = ntohs(hp->qdcount);
104	bp = hostbuf;
105	buflen = sizeof (hostbuf);
106	cp = answer->buf + sizeof (HEADER);
107	if (qdcount) {
108		if (iquery) {
109			if ((n = dn_expand((char *)answer->buf, eom,
110						cp, bp, buflen)) < 0) {
111				h_errno = NO_RECOVERY;
112				return ((struct hostent *) NULL);
113			}
114			cp += n + QFIXEDSZ;
115			host.h_name = bp;
116			n = strlen(bp) + 1;
117			bp += n;
118			buflen -= n;
119		} else
120			cp += dn_skipname(cp, eom) + QFIXEDSZ;
121		while (--qdcount > 0)
122			cp += dn_skipname(cp, eom) + QFIXEDSZ;
123	} else if (iquery) {
124		if (hp->aa)
125			h_errno = HOST_NOT_FOUND;
126		else
127			h_errno = TRY_AGAIN;
128		return ((struct hostent *) NULL);
129	}
130	ap = host_aliases;
131	host.h_aliases = host_aliases;
132	hap = h_addr_ptrs;
133#if BSD >= 43 || defined(h_addr)	/* new-style hostent structure */
134	host.h_addr_list = h_addr_ptrs;
135#endif
136	haveanswer = 0;
137	while (--ancount >= 0 && cp < eom && haveanswer < MAXADDRS) {
138		if ((n = dn_expand((char *)answer->buf, eom,
139						cp, bp, buflen)) < 0)
140			break;
141		cp += n;
142		type = _getshort(cp);
143		cp += sizeof (u_short);
144		class = _getshort(cp);
145		cp += sizeof (u_short) + sizeof (u_long);
146		n = _getshort(cp);
147		cp += sizeof (u_short);
148		if (type == T_CNAME) {
149			cp += n;
150			if (ap >= &host_aliases[MAXALIASES-1])
151				continue;
152			*ap++ = bp;
153			n = strlen(bp) + 1;
154			bp += n;
155			buflen -= n;
156			continue;
157		}
158		if (iquery && type == T_PTR) {
159			if ((n = dn_expand((char *)answer->buf, eom,
160					cp, bp, buflen)) < 0) {
161				cp += n;
162				continue;
163			}
164			cp += n;
165			host.h_name = bp;
166			return (&host);
167		}
168		if (iquery || type != T_A) {
169#ifdef DEBUG
170			if (_res.options & RES_DEBUG)
171				printf("unexpected answer type %d, size %d\n",
172					type, n);
173#endif
174			cp += n;
175			continue;
176		}
177		if (haveanswer) {
178			if (n != host.h_length) {
179				cp += n;
180				continue;
181			}
182			if (class != getclass) {
183				cp += n;
184				continue;
185			}
186		} else {
187			host.h_length = n;
188			getclass = class;
189			host.h_addrtype = (class == C_IN) ? AF_INET : AF_UNSPEC;
190			if (!iquery) {
191				host.h_name = bp;
192				bp += strlen(bp) + 1;
193			}
194		}
195
196		bp += sizeof (align) - ((u_long)bp % sizeof (align));
197
198		if (bp + n >= &hostbuf[sizeof (hostbuf)]) {
199#ifdef DEBUG
200			if (_res.options & RES_DEBUG)
201				printf("size (%d) too big\n", n);
202#endif
203			break;
204		}
205#ifdef SYSV
206		memcpy((void *)(*hap++ = bp), (void *)cp, n);
207#else
208		bcopy(cp, *hap++ = bp, n);
209#endif
210		bp += n;
211		cp += n;
212		haveanswer++;
213	}
214	if (haveanswer) {
215		*ap = NULL;
216#if BSD >= 43 || defined(h_addr)	/* new-style hostent structure */
217		*hap = NULL;
218#else
219		host.h_addr = h_addr_ptrs[0];
220#endif
221		return (&host);
222	} else {
223		h_errno = TRY_AGAIN;
224		return ((struct hostent *) NULL);
225	}
226}
227
228struct hostent *
229res_gethostbyname(name)
230	char *name;
231{
232	querybuf buf;
233	register char *cp;
234	int n;
235	struct hostent *hp, *gethostdomain();
236	static struct hostent *_gethtbyname();
237
238	/*
239	 * disallow names consisting only of digits/dots, unless
240	 * they end in a dot.
241	 */
242	if (isdigit(name[0]))
243		for (cp = name; /*EMPTY*/; ++cp) {
244			if (!*cp) {
245				if (*--cp == '.')
246					break;
247				h_errno = HOST_NOT_FOUND;
248				return ((struct hostent *) NULL);
249			}
250			if (!isdigit(*cp) && *cp != '.')
251				break;
252		}
253
254	if ((n = res_search(name, C_IN, T_A, buf.buf, sizeof (buf))) < 0) {
255#ifdef DEBUG
256		if (_res.options & RES_DEBUG)
257			printf("res_search failed\n");
258#endif
259		if (errno == ECONNREFUSED)
260			return (_gethtbyname(name));
261		else
262			return ((struct hostent *) NULL);
263	}
264	return (getanswer(&buf, n, 0));
265}
266
267static struct hostent *
268_getrhbyaddr(addr, len, type)
269	char *addr;
270	int len, type;
271{
272	int n;
273	querybuf buf;
274	register struct hostent *hp;
275	char qbuf[MAXDNAME];
276	static struct hostent *_gethtbyaddr();
277
278	if (type != AF_INET)
279		return ((struct hostent *) NULL);
280	(void) sprintf(qbuf, "%d.%d.%d.%d.in-addr.arpa",
281		((unsigned)addr[3] & 0xff),
282		((unsigned)addr[2] & 0xff),
283		((unsigned)addr[1] & 0xff),
284		((unsigned)addr[0] & 0xff));
285	n = res_query(qbuf, C_IN, T_PTR, (char *)&buf, sizeof (buf));
286	if (n < 0) {
287#ifdef DEBUG
288		if (_res.options & RES_DEBUG)
289			printf("res_query failed\n");
290#endif
291		if (errno == ECONNREFUSED)
292			return (_gethtbyaddr(addr, len, type));
293		return ((struct hostent *) NULL);
294	}
295	hp = getanswer(&buf, n, 1);
296	if (hp == NULL)
297		return ((struct hostent *) NULL);
298	hp->h_addrtype = type;
299	hp->h_length = len;
300	h_addr_ptrs[0] = (char *)&host_addr;
301	h_addr_ptrs[1] = (char *)0;
302	host_addr = *(struct in_addr *)addr;
303	return (hp);
304}
305
306/*
307 * First we get what the PTR record says, but do an extra call
308 * to gethostbyname() to make sure that someone is not trying to
309 * spoof us.  Hopefully this is not done that often, so good
310 * performance is not really an issue.
311 */
312struct hostent *
313res_gethostbyaddr(addr, len, type)
314	char	*addr;
315	int	len;
316	int	type;
317{
318	char		**a, hbuf[MAXHOSTNAMELEN];
319	struct hostent	*hp, *hp2;
320
321	if ((hp = _getrhbyaddr(addr, len, type)) == (struct hostent *)NULL)
322		return ((struct hostent *)NULL);
323
324	/* hang on to what we got as an answer */
325	(void) strcpy(hbuf, hp->h_name);
326
327	/* check to make sure by doing a forward query */
328	if ((hp2 = res_gethostbyname(hbuf)) != (struct hostent *)NULL)
329		for (a = hp2->h_addr_list; *a; a++)
330#ifdef SYSV
331			if (memcmp(*a, addr, hp2->h_length) == 0)
332#else
333			if (bcmp(*a, addr, hp2->h_length) == 0)
334#endif
335				return (hp2);
336
337	/*
338	 * we've been spoofed, make sure to log it.
339	 * XXX - syslog needs a security priority level.
340	 */
341	syslog(LOG_NOTICE, "gethostbyaddr: %s != %s", hbuf,
342		inet_ntoa(*(struct in_addr *)addr));
343	return ((struct hostent *)NULL);
344}
345
346static void
347_sethtent(int f)
348{
349	if (__res_no_hosts_fallback()) return;
350
351	if (hostf == NULL)
352		hostf = fopen(HOSTDB, "r");
353	else
354		rewind(hostf);
355	stayopen |= f;
356}
357
358static void
359_endhtent(void)
360{
361	if (__res_no_hosts_fallback()) return;
362
363	if (hostf && !stayopen) {
364		(void) fclose(hostf);
365		hostf = NULL;
366	}
367}
368
369static struct hostent *
370_gethtent()
371{
372	char *p;
373	register char *cp, **q;
374
375	if (__res_no_hosts_fallback()) return(NULL);
376
377	if (hostf == NULL && (hostf = fopen(HOSTDB, "r")) == NULL)
378		return (NULL);
379again:
380	if ((p = fgets(hostbuf, BUFSIZ, hostf)) == NULL)
381		return (NULL);
382	if (*p == '#')
383		goto again;
384	cp = any(p, "#\n");
385	if (cp == NULL)
386		goto again;
387	*cp = '\0';
388	cp = any(p, " \t");
389	if (cp == NULL)
390		goto again;
391	*cp++ = '\0';
392	/* THIS STUFF IS INTERNET SPECIFIC */
393#if BSD >= 43 || defined(h_addr)	/* new-style hostent structure */
394	host.h_addr_list = host_addrs;
395#endif
396	host.h_addr = hostaddr;
397	*((u_long *)host.h_addr) = inet_addr(p);
398	host.h_length = sizeof (u_long);
399	host.h_addrtype = AF_INET;
400	while (*cp == ' ' || *cp == '\t')
401		cp++;
402	host.h_name = cp;
403	q = host.h_aliases = host_aliases;
404	cp = any(cp, " \t");
405	if (cp != NULL)
406		*cp++ = '\0';
407	while (cp && *cp) {
408		if (*cp == ' ' || *cp == '\t') {
409			cp++;
410			continue;
411		}
412		if (q < &host_aliases[MAXALIASES - 1])
413			*q++ = cp;
414		cp = any(cp, " \t");
415		if (cp != NULL)
416			*cp++ = '\0';
417	}
418	*q = NULL;
419	return (&host);
420}
421
422static char *
423any(cp, match)
424	register char *cp;
425	char *match;
426{
427	register char *mp, c;
428
429	while (c = *cp) {
430		for (mp = match; *mp; mp++)
431			if (*mp == c)
432				return (cp);
433		cp++;
434	}
435	return ((char *)0);
436}
437
438static struct hostent *
439_gethtbyname(name)
440	char *name;
441{
442	register struct hostent *p;
443	register char **cp;
444
445	_sethtent(0);
446	while (p = _gethtent()) {
447		if (strcasecmp(p->h_name, name) == 0)
448			break;
449		for (cp = p->h_aliases; *cp != 0; cp++)
450			if (strcasecmp(*cp, name) == 0)
451				goto found;
452	}
453found:
454	_endhtent();
455	return (p);
456}
457
458static struct hostent *
459_gethtbyaddr(addr, len, type)
460	char *addr;
461	int len, type;
462{
463	register struct hostent *p;
464
465	_sethtent(0);
466	while (p = _gethtent())
467#ifdef SYSV
468		if (p->h_addrtype == type && !memcmp(p->h_addr, addr, len))
469#else
470		if (p->h_addrtype == type && !bcmp(p->h_addr, addr, len))
471#endif
472			break;
473	_endhtent();
474	return (p);
475}
476