1 /*
2 * Copyright 2009 Sun Microsystems, Inc. All rights reserved.
3 * Use is subject to license terms.
4 */
5
6 /*
7 * Copyright (c) 1985, 1988 Regents of the University of California.
8 * All rights reserved.
9 *
10 * Redistribution and use in source and binary forms are permitted
11 * provided that this notice is preserved and that due credit is given
12 * to the University of California at Berkeley. The name of the University
13 * may not be used to endorse or promote products derived from this
14 * software without specific prior written permission. This software
15 * is provided ``as is'' without express or implied warranty.
16 *
17 */
18
19 #include <sys/param.h>
20 #include <sys/socket.h>
21 #include <netinet/in.h>
22 #include <ctype.h>
23 #include <netdb.h>
24 #include <stdio.h>
25 #include <errno.h>
26 #include <arpa/inet.h>
27 #include <arpa/nameser.h>
28 #include <resolv.h>
29 #include <syslog.h>
30
31 /*
32 * When the name service switch calls libresolv, it doesn't want fallback
33 * to /etc/hosts, so we provide a method to turn it off.
34 */
35 static int no_hosts_fallback = 0;
36
37 void
38 __res_set_no_hosts_fallback(void) {
39 no_hosts_fallback = 1;
40 }
41
42 static int
43 __res_no_hosts_fallback(void) {
44 return(no_hosts_fallback);
45 }
46
47 static char *h_addr_ptrs[MAXADDRS + 1];
48
49 static struct hostent host;
50 static char *host_aliases[MAXALIASES];
51 static char hostbuf[BUFSIZ+1];
52 static struct in_addr host_addr;
53 static char HOSTDB[] = "/etc/hosts";
54 static FILE *hostf = NULL;
55 static char hostaddr[MAXADDRS];
56 static char *host_addrs[2];
57 static int stayopen = 0;
58 static char *any();
59
60 #if PACKETSZ > 1024
61 #define MAXPACKET PACKETSZ
62 #else
63 #define MAXPACKET 1024
64 #endif
65
66 typedef union {
67 HEADER hdr;
68 u_char buf[MAXPACKET];
69 } querybuf;
70
71 static union {
72 long al;
73 char ac;
74 } align;
75
76
77 int h_errno;
78
79 static struct hostent *
80 getanswer(answer, anslen, iquery)
81 querybuf *answer;
82 int anslen;
83 int iquery;
84 {
85 register HEADER *hp;
86 register u_char *cp;
87 register int n;
88 u_char *eom;
89 char *bp, **ap;
90 int type, class, buflen, ancount, qdcount;
91 int haveanswer, getclass = C_ANY;
92 char **hap;
93
94 eom = answer->buf + anslen;
95 /*
96 * find first satisfactory answer
97 */
98 hp = &answer->hdr;
99 ancount = ntohs(hp->ancount);
100 qdcount = ntohs(hp->qdcount);
101 bp = hostbuf;
102 buflen = sizeof (hostbuf);
103 cp = answer->buf + sizeof (HEADER);
104 if (qdcount) {
105 if (iquery) {
106 if ((n = dn_expand((char *)answer->buf, eom,
107 cp, bp, buflen)) < 0) {
108 h_errno = NO_RECOVERY;
109 return ((struct hostent *) NULL);
110 }
111 cp += n + QFIXEDSZ;
112 host.h_name = bp;
113 n = strlen(bp) + 1;
114 bp += n;
115 buflen -= n;
116 } else
117 cp += dn_skipname(cp, eom) + QFIXEDSZ;
118 while (--qdcount > 0)
119 cp += dn_skipname(cp, eom) + QFIXEDSZ;
120 } else if (iquery) {
121 if (hp->aa)
122 h_errno = HOST_NOT_FOUND;
123 else
124 h_errno = TRY_AGAIN;
125 return ((struct hostent *) NULL);
126 }
127 ap = host_aliases;
128 host.h_aliases = host_aliases;
129 hap = h_addr_ptrs;
130 #if BSD >= 43 || defined(h_addr) /* new-style hostent structure */
131 host.h_addr_list = h_addr_ptrs;
132 #endif
133 haveanswer = 0;
134 while (--ancount >= 0 && cp < eom && haveanswer < MAXADDRS) {
135 if ((n = dn_expand((char *)answer->buf, eom,
136 cp, bp, buflen)) < 0)
137 break;
138 cp += n;
139 type = _getshort(cp);
140 cp += sizeof (u_short);
141 class = _getshort(cp);
142 cp += sizeof (u_short) + sizeof (u_long);
143 n = _getshort(cp);
144 cp += sizeof (u_short);
145 if (type == T_CNAME) {
146 cp += n;
147 if (ap >= &host_aliases[MAXALIASES-1])
148 continue;
149 *ap++ = bp;
150 n = strlen(bp) + 1;
151 bp += n;
152 buflen -= n;
153 continue;
154 }
155 if (iquery && type == T_PTR) {
156 if ((n = dn_expand((char *)answer->buf, eom,
157 cp, bp, buflen)) < 0) {
158 cp += n;
159 continue;
160 }
161 cp += n;
162 host.h_name = bp;
163 return (&host);
164 }
165 if (iquery || type != T_A) {
166 #ifdef DEBUG
167 if (_res.options & RES_DEBUG)
168 printf("unexpected answer type %d, size %d\n",
169 type, n);
170 #endif
171 cp += n;
172 continue;
173 }
174 if (haveanswer) {
175 if (n != host.h_length) {
176 cp += n;
177 continue;
178 }
179 if (class != getclass) {
180 cp += n;
181 continue;
182 }
183 } else {
184 host.h_length = n;
185 getclass = class;
186 host.h_addrtype = (class == C_IN) ? AF_INET : AF_UNSPEC;
187 if (!iquery) {
188 host.h_name = bp;
189 bp += strlen(bp) + 1;
190 }
191 }
192
193 bp += sizeof (align) - ((u_long)bp % sizeof (align));
194
195 if (bp + n >= &hostbuf[sizeof (hostbuf)]) {
196 #ifdef DEBUG
197 if (_res.options & RES_DEBUG)
198 printf("size (%d) too big\n", n);
199 #endif
200 break;
201 }
202 #ifdef SYSV
203 memcpy((void *)(*hap++ = bp), (void *)cp, n);
204 #else
205 bcopy(cp, *hap++ = bp, n);
206 #endif
207 bp += n;
208 cp += n;
209 haveanswer++;
210 }
211 if (haveanswer) {
212 *ap = NULL;
213 #if BSD >= 43 || defined(h_addr) /* new-style hostent structure */
214 *hap = NULL;
215 #else
216 host.h_addr = h_addr_ptrs[0];
217 #endif
218 return (&host);
219 } else {
220 h_errno = TRY_AGAIN;
221 return ((struct hostent *) NULL);
222 }
223 }
224
225 static struct hostent *_gethtbyname();
226
227 struct hostent *
228 res_gethostbyname(name)
229 char *name;
230 {
231 querybuf buf;
232 register char *cp;
233 int n;
234 struct hostent *hp, *gethostdomain();
235
236 /*
237 * disallow names consisting only of digits/dots, unless
238 * they end in a dot.
239 */
240 if (isdigit(name[0]))
241 for (cp = name; /*EMPTY*/; ++cp) {
242 if (!*cp) {
243 if (*--cp == '.')
244 break;
245 h_errno = HOST_NOT_FOUND;
246 return ((struct hostent *) NULL);
247 }
248 if (!isdigit(*cp) && *cp != '.')
249 break;
250 }
251
252 if ((n = res_search(name, C_IN, T_A, buf.buf, sizeof (buf))) < 0) {
253 #ifdef DEBUG
254 if (_res.options & RES_DEBUG)
255 printf("res_search failed\n");
256 #endif
257 if (errno == ECONNREFUSED)
258 return (_gethtbyname(name));
259 else
260 return ((struct hostent *) NULL);
261 }
262 return (getanswer(&buf, n, 0));
263 }
264
265 static struct hostent *_gethtbyaddr();
266
267 static 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
277 if (type != AF_INET)
278 return ((struct hostent *) NULL);
279 (void) sprintf(qbuf, "%d.%d.%d.%d.in-addr.arpa",
280 ((unsigned)addr[3] & 0xff),
281 ((unsigned)addr[2] & 0xff),
282 ((unsigned)addr[1] & 0xff),
283 ((unsigned)addr[0] & 0xff));
284 n = res_query(qbuf, C_IN, T_PTR, (char *)&buf, sizeof (buf));
285 if (n < 0) {
286 #ifdef DEBUG
287 if (_res.options & RES_DEBUG)
288 printf("res_query failed\n");
289 #endif
290 if (errno == ECONNREFUSED)
291 return (_gethtbyaddr(addr, len, type));
292 return ((struct hostent *) NULL);
293 }
294 hp = getanswer(&buf, n, 1);
295 if (hp == NULL)
296 return ((struct hostent *) NULL);
297 hp->h_addrtype = type;
298 hp->h_length = len;
299 h_addr_ptrs[0] = (char *)&host_addr;
300 h_addr_ptrs[1] = (char *)0;
301 host_addr = *(struct in_addr *)addr;
302 return (hp);
303 }
304
305 /*
306 * First we get what the PTR record says, but do an extra call
307 * to gethostbyname() to make sure that someone is not trying to
308 * spoof us. Hopefully this is not done that often, so good
309 * performance is not really an issue.
310 */
311 struct hostent *
312 res_gethostbyaddr(addr, len, type)
313 char *addr;
314 int len;
315 int type;
316 {
317 char **a, hbuf[MAXHOSTNAMELEN];
318 struct hostent *hp, *hp2;
319
320 if ((hp = _getrhbyaddr(addr, len, type)) == (struct hostent *)NULL)
321 return ((struct hostent *)NULL);
322
323 /* hang on to what we got as an answer */
324 (void) strcpy(hbuf, hp->h_name);
325
326 /* check to make sure by doing a forward query */
327 if ((hp2 = res_gethostbyname(hbuf)) != (struct hostent *)NULL)
328 for (a = hp2->h_addr_list; *a; a++)
329 #ifdef SYSV
330 if (memcmp(*a, addr, hp2->h_length) == 0)
331 #else
332 if (bcmp(*a, addr, hp2->h_length) == 0)
333 #endif
334 return (hp2);
335
336 /*
337 * we've been spoofed, make sure to log it.
338 * XXX - syslog needs a security priority level.
339 */
340 syslog(LOG_NOTICE, "gethostbyaddr: %s != %s", hbuf,
341 inet_ntoa(*(struct in_addr *)addr));
342 return ((struct hostent *)NULL);
343 }
344
345 static void
346 _sethtent(int f)
347 {
348 if (__res_no_hosts_fallback()) return;
349
350 if (hostf == NULL)
351 hostf = fopen(HOSTDB, "r");
352 else
353 rewind(hostf);
354 stayopen |= f;
355 }
356
357 static void
358 _endhtent(void)
359 {
360 if (__res_no_hosts_fallback()) return;
361
362 if (hostf && !stayopen) {
363 (void) fclose(hostf);
364 hostf = NULL;
365 }
366 }
367
368 static struct hostent *
369 _gethtent()
370 {
371 char *p;
372 register char *cp, **q;
373
374 if (__res_no_hosts_fallback()) return(NULL);
375
376 if (hostf == NULL && (hostf = fopen(HOSTDB, "r")) == NULL)
377 return (NULL);
378 again:
379 if ((p = fgets(hostbuf, BUFSIZ, hostf)) == NULL)
380 return (NULL);
381 if (*p == '#')
382 goto again;
383 cp = any(p, "#\n");
384 if (cp == NULL)
385 goto again;
386 *cp = '\0';
387 cp = any(p, " \t");
388 if (cp == NULL)
389 goto again;
390 *cp++ = '\0';
391 /* THIS STUFF IS INTERNET SPECIFIC */
392 #if BSD >= 43 || defined(h_addr) /* new-style hostent structure */
393 host.h_addr_list = host_addrs;
394 #endif
395 host.h_addr = hostaddr;
396 *((u_long *)host.h_addr) = inet_addr(p);
397 host.h_length = sizeof (u_long);
398 host.h_addrtype = AF_INET;
399 while (*cp == ' ' || *cp == '\t')
400 cp++;
401 host.h_name = cp;
402 q = host.h_aliases = host_aliases;
403 cp = any(cp, " \t");
404 if (cp != NULL)
405 *cp++ = '\0';
406 while (cp && *cp) {
407 if (*cp == ' ' || *cp == '\t') {
408 cp++;
409 continue;
410 }
411 if (q < &host_aliases[MAXALIASES - 1])
412 *q++ = cp;
413 cp = any(cp, " \t");
414 if (cp != NULL)
415 *cp++ = '\0';
416 }
417 *q = NULL;
418 return (&host);
419 }
420
421 static char *
422 any(cp, match)
423 register char *cp;
424 char *match;
425 {
426 register char *mp, c;
427
428 while (c = *cp) {
429 for (mp = match; *mp; mp++)
430 if (*mp == c)
431 return (cp);
432 cp++;
433 }
434 return ((char *)0);
435 }
436
437 static struct hostent *
438 _gethtbyname(name)
439 char *name;
440 {
441 register struct hostent *p;
442 register char **cp;
443
444 _sethtent(0);
445 while (p = _gethtent()) {
446 if (strcasecmp(p->h_name, name) == 0)
447 break;
448 for (cp = p->h_aliases; *cp != 0; cp++)
449 if (strcasecmp(*cp, name) == 0)
450 goto found;
451 }
452 found:
453 _endhtent();
454 return (p);
455 }
456
457 static struct hostent *
458 _gethtbyaddr(addr, len, type)
459 char *addr;
460 int len, type;
461 {
462 register struct hostent *p;
463
464 _sethtent(0);
465 while (p = _gethtent())
466 #ifdef SYSV
467 if (p->h_addrtype == type && !memcmp(p->h_addr, addr, len))
468 #else
469 if (p->h_addrtype == type && !bcmp(p->h_addr, addr, len))
470 #endif
471 break;
472 _endhtent();
473 return (p);
474 }