xref: /netbsd-src/libexec/rshd/rshd.c (revision ce63d6c20fc4ec8ddc95c84bb229e3c4ecf82b69)
1 /*-
2  * Copyright (c) 1988, 1989 The Regents of the University of California.
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without
6  * modification, are permitted provided that the following conditions
7  * are met:
8  * 1. Redistributions of source code must retain the above copyright
9  *    notice, this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright
11  *    notice, this list of conditions and the following disclaimer in the
12  *    documentation and/or other materials provided with the distribution.
13  * 3. All advertising materials mentioning features or use of this software
14  *    must display the following acknowledgement:
15  *	This product includes software developed by the University of
16  *	California, Berkeley and its contributors.
17  * 4. Neither the name of the University nor the names of its contributors
18  *    may be used to endorse or promote products derived from this software
19  *    without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  */
33 
34 #ifndef lint
35 char copyright[] =
36 "@(#) Copyright (c) 1988, 1989 The Regents of the University of California.\n\
37  All rights reserved.\n";
38 #endif /* not lint */
39 
40 #ifndef lint
41 static char sccsid[] = "@(#)rshd.c	5.38 (Berkeley) 3/2/91";
42 #endif /* not lint */
43 
44 /*
45  * From:
46  *	$Source: /cvsroot/src/libexec/rshd/rshd.c,v $
47  *	$Header: /mit/kerberos/ucb/mit/rshd/RCS/rshd.c,v
48  *		5.2 89/07/31 19:30:04 kfall Exp $
49  */
50 
51 /*
52  * remote shell server:
53  *	[port]\0
54  *	remuser\0
55  *	locuser\0
56  *	command\0
57  *	data
58  */
59 #include <sys/param.h>
60 #include <sys/ioctl.h>
61 #include <sys/time.h>
62 #include <fcntl.h>
63 #include <signal.h>
64 
65 #include <sys/socket.h>
66 #include <netinet/in.h>
67 #include <arpa/inet.h>
68 #include <netdb.h>
69 
70 #include <pwd.h>
71 #include <syslog.h>
72 #include <arpa/nameser.h>
73 #include <resolv.h>
74 #include <unistd.h>
75 #include <errno.h>
76 #include <stdio.h>
77 #include <stdlib.h>
78 #include <string.h>
79 #include <paths.h>
80 
81 int	keepalive = 1;
82 int	check_all = 0;
83 char	*index(), *rindex(), *strncat();
84 /*VARARGS1*/
85 int	error();
86 int	sent_null;
87 
88 #ifdef	KERBEROS
89 #include <kerberosIV/des.h>
90 #include <kerberosIV/krb.h>
91 #define	VERSION_SIZE	9
92 #define SECURE_MESSAGE  "This rsh session is using DES encryption for all transmissions.\r\n"
93 #define	OPTIONS		"alknvx"
94 char	authbuf[sizeof(AUTH_DAT)];
95 char	tickbuf[sizeof(KTEXT_ST)];
96 int	doencrypt, use_kerberos, vacuous;
97 Key_schedule	schedule;
98 #else
99 #define	OPTIONS	"aln"
100 #endif
101 
102 /*ARGSUSED*/
103 main(argc, argv)
104 	int argc;
105 	char **argv;
106 {
107 	extern int opterr, optind;
108 	extern int _check_rhosts_file;
109 	struct linger linger;
110 	int ch, on = 1, fromlen;
111 	struct sockaddr_in from;
112 
113 	openlog("rshd", LOG_PID | LOG_ODELAY, LOG_DAEMON);
114 
115 	opterr = 0;
116 	while ((ch = getopt(argc, argv, OPTIONS)) != EOF)
117 		switch (ch) {
118 		case 'a':
119 			check_all = 1;
120 			break;
121 		case 'l':
122 			_check_rhosts_file = 0;
123 			break;
124 		case 'n':
125 			keepalive = 0;
126 			break;
127 #ifdef	KERBEROS
128 		case 'k':
129 			use_kerberos = 1;
130 			break;
131 
132 		case 'v':
133 			vacuous = 1;
134 			break;
135 
136 #ifdef CRYPT
137 		case 'x':
138 			doencrypt = 1;
139 			break;
140 #endif
141 #endif
142 		case '?':
143 		default:
144 			usage();
145 			exit(2);
146 		}
147 
148 	argc -= optind;
149 	argv += optind;
150 
151 #ifdef	KERBEROS
152 	if (use_kerberos && vacuous) {
153 		syslog(LOG_ERR, "only one of -k and -v allowed");
154 		exit(2);
155 	}
156 #ifdef CRYPT
157 	if (doencrypt && !use_kerberos) {
158 		syslog(LOG_ERR, "-k is required for -x");
159 		exit(2);
160 	}
161 #endif
162 #endif
163 
164 	fromlen = sizeof (from);
165 	if (getpeername(0, (struct sockaddr *)&from, &fromlen) < 0) {
166 		syslog(LOG_ERR, "getpeername: %m");
167 		_exit(1);
168 	}
169 	if (keepalive &&
170 	    setsockopt(0, SOL_SOCKET, SO_KEEPALIVE, (char *)&on,
171 	    sizeof(on)) < 0)
172 		syslog(LOG_WARNING, "setsockopt (SO_KEEPALIVE): %m");
173 	linger.l_onoff = 1;
174 	linger.l_linger = 60;			/* XXX */
175 	if (setsockopt(0, SOL_SOCKET, SO_LINGER, (char *)&linger,
176 	    sizeof (linger)) < 0)
177 		syslog(LOG_WARNING, "setsockopt (SO_LINGER): %m");
178 	doit(&from);
179 }
180 
181 char	username[20] = "USER=";
182 char	homedir[64] = "HOME=";
183 char	shell[64] = "SHELL=";
184 char	path[100] = "PATH=";
185 char	*envinit[] =
186 	    {homedir, shell, path, username, 0};
187 char	**environ;
188 
189 doit(fromp)
190 	struct sockaddr_in *fromp;
191 {
192 	char cmdbuf[NCARGS+1], *cp;
193 	char locuser[16], remuser[16];
194 	struct passwd *pwd;
195 	int s;
196 	struct hostent *hp;
197 	char *hostname, *errorstr = NULL, *errorhost;
198 	u_short port;
199 	int pv[2], pid, cc;
200 	int nfd;
201 	fd_set ready, readfrom;
202 	char buf[BUFSIZ], sig;
203 	int one = 1;
204 	char remotehost[2 * MAXHOSTNAMELEN + 1];
205 
206 #ifdef	KERBEROS
207 	AUTH_DAT	*kdata = (AUTH_DAT *) NULL;
208 	KTEXT		ticket = (KTEXT) NULL;
209 	char		instance[INST_SZ], version[VERSION_SIZE];
210 	struct		sockaddr_in	fromaddr;
211 	int		rc;
212 	long		authopts;
213 	int		pv1[2], pv2[2];
214 	fd_set		wready, writeto;
215 
216 	fromaddr = *fromp;
217 #endif
218 
219 	(void) signal(SIGINT, SIG_DFL);
220 	(void) signal(SIGQUIT, SIG_DFL);
221 	(void) signal(SIGTERM, SIG_DFL);
222 #ifdef DEBUG
223 	{ int t = open(_PATH_TTY, 2);
224 	  if (t >= 0) {
225 		ioctl(t, TIOCNOTTY, (char *)0);
226 		(void) close(t);
227 	  }
228 	}
229 #endif
230 	fromp->sin_port = ntohs((u_short)fromp->sin_port);
231 	if (fromp->sin_family != AF_INET) {
232 		syslog(LOG_ERR, "malformed \"from\" address (af %d)\n",
233 		    fromp->sin_family);
234 		exit(1);
235 	}
236 #ifdef IP_OPTIONS
237       {
238 	u_char optbuf[BUFSIZ/3], *cp;
239 	char lbuf[BUFSIZ], *lp;
240 	int optsize = sizeof(optbuf), ipproto;
241 	struct protoent *ip;
242 
243 	if ((ip = getprotobyname("ip")) != NULL)
244 		ipproto = ip->p_proto;
245 	else
246 		ipproto = IPPROTO_IP;
247 	if (!getsockopt(0, ipproto, IP_OPTIONS, (char *)optbuf, &optsize) &&
248 	    optsize != 0) {
249 		lp = lbuf;
250 		for (cp = optbuf; optsize > 0; cp++, optsize--, lp += 3)
251 			sprintf(lp, " %2.2x", *cp);
252 		syslog(LOG_NOTICE,
253 		    "Connection received from %s using IP options (ignored):%s",
254 		    inet_ntoa(fromp->sin_addr), lbuf);
255 		if (setsockopt(0, ipproto, IP_OPTIONS,
256 		    (char *)NULL, optsize) != 0) {
257 			syslog(LOG_ERR, "setsockopt IP_OPTIONS NULL: %m");
258 			exit(1);
259 		}
260 	}
261       }
262 #endif
263 
264 #ifdef	KERBEROS
265 	if (!use_kerberos)
266 #endif
267 		if (fromp->sin_port >= IPPORT_RESERVED ||
268 		    fromp->sin_port < IPPORT_RESERVED/2) {
269 			syslog(LOG_NOTICE|LOG_AUTH,
270 			    "Connection from %s on illegal port",
271 			    inet_ntoa(fromp->sin_addr));
272 			exit(1);
273 		}
274 
275 	(void) alarm(60);
276 	port = 0;
277 	for (;;) {
278 		char c;
279 		if ((cc = read(0, &c, 1)) != 1) {
280 			if (cc < 0)
281 				syslog(LOG_NOTICE, "read: %m");
282 			shutdown(0, 1+1);
283 			exit(1);
284 		}
285 		if (c== 0)
286 			break;
287 		port = port * 10 + c - '0';
288 	}
289 
290 	(void) alarm(0);
291 	if (port != 0) {
292 		int lport = IPPORT_RESERVED - 1;
293 		s = rresvport(&lport);
294 		if (s < 0) {
295 			syslog(LOG_ERR, "can't get stderr port: %m");
296 			exit(1);
297 		}
298 #ifdef	KERBEROS
299 		if (!use_kerberos)
300 #endif
301 			if (port >= IPPORT_RESERVED) {
302 				syslog(LOG_ERR, "2nd port not reserved\n");
303 				exit(1);
304 			}
305 		fromp->sin_port = htons(port);
306 		if (connect(s, (struct sockaddr *)fromp, sizeof (*fromp)) < 0) {
307 			syslog(LOG_INFO, "connect second port: %m");
308 			exit(1);
309 		}
310 	}
311 
312 #ifdef	KERBEROS
313 	if (vacuous) {
314 		error("rshd: remote host requires Kerberos authentication\n");
315 		exit(1);
316 	}
317 #endif
318 
319 #ifdef notdef
320 	/* from inetd, socket is already on 0, 1, 2 */
321 	dup2(f, 0);
322 	dup2(f, 1);
323 	dup2(f, 2);
324 #endif
325 	hp = gethostbyaddr((char *)&fromp->sin_addr, sizeof (struct in_addr),
326 		fromp->sin_family);
327 	if (hp) {
328 		/*
329 		 * If name returned by gethostbyaddr is in our domain,
330 		 * attempt to verify that we haven't been fooled by someone
331 		 * in a remote net; look up the name and check that this
332 		 * address corresponds to the name.
333 		 */
334 		hostname = hp->h_name;
335 #ifdef	KERBEROS
336 		if (!use_kerberos)
337 #endif
338 		if (check_all || local_domain(hp->h_name)) {
339 			strncpy(remotehost, hp->h_name, sizeof(remotehost) - 1);
340 			remotehost[sizeof(remotehost) - 1] = 0;
341 			errorhost = remotehost;
342 #ifdef	RES_DNSRCH
343 			_res.options &= ~RES_DNSRCH;
344 #endif
345 			hp = gethostbyname(remotehost);
346 			if (hp == NULL) {
347 				syslog(LOG_INFO,
348 				    "Couldn't look up address for %s",
349 				    remotehost);
350 				errorstr =
351 				"Couldn't look up address for your host (%s)\n";
352 				hostname = inet_ntoa(fromp->sin_addr);
353 			} else for (; ; hp->h_addr_list++) {
354 				if (hp->h_addr_list[0] == NULL) {
355 					syslog(LOG_NOTICE,
356 					  "Host addr %s not listed for host %s",
357 					    inet_ntoa(fromp->sin_addr),
358 					    hp->h_name);
359 					errorstr =
360 					    "Host address mismatch for %s\n";
361 					hostname = inet_ntoa(fromp->sin_addr);
362 					break;
363 				}
364 				if (!bcmp(hp->h_addr_list[0],
365 				    (caddr_t)&fromp->sin_addr,
366 				    sizeof(fromp->sin_addr))) {
367 					hostname = hp->h_name;
368 					break;
369 				}
370 			}
371 		}
372 	} else
373 		errorhost = hostname = inet_ntoa(fromp->sin_addr);
374 
375 #ifdef	KERBEROS
376 	if (use_kerberos) {
377 		kdata = (AUTH_DAT *) authbuf;
378 		ticket = (KTEXT) tickbuf;
379 		authopts = 0L;
380 		strcpy(instance, "*");
381 		version[VERSION_SIZE - 1] = '\0';
382 #ifdef CRYPT
383 		if (doencrypt) {
384 			struct sockaddr_in local_addr;
385 			rc = sizeof(local_addr);
386 			if (getsockname(0, (struct sockaddr *)&local_addr,
387 			    &rc) < 0) {
388 				syslog(LOG_ERR, "getsockname: %m");
389 				error("rlogind: getsockname: %m");
390 				exit(1);
391 			}
392 			authopts = KOPT_DO_MUTUAL;
393 			rc = krb_recvauth(authopts, 0, ticket,
394 				"rcmd", instance, &fromaddr,
395 				&local_addr, kdata, "", schedule,
396 				version);
397 			des_set_key(kdata->session, schedule);
398 		} else
399 #endif
400 			rc = krb_recvauth(authopts, 0, ticket, "rcmd",
401 				instance, &fromaddr,
402 				(struct sockaddr_in *) 0,
403 				kdata, "", (bit_64 *) 0, version);
404 		if (rc != KSUCCESS) {
405 			error("Kerberos authentication failure: %s\n",
406 				  krb_err_txt[rc]);
407 			exit(1);
408 		}
409 	} else
410 #endif
411 		getstr(remuser, sizeof(remuser), "remuser");
412 
413 	getstr(locuser, sizeof(locuser), "locuser");
414 	getstr(cmdbuf, sizeof(cmdbuf), "command");
415 	setpwent();
416 	pwd = getpwnam(locuser);
417 	if (pwd == NULL) {
418 		if (errorstr == NULL)
419 			errorstr = "Login incorrect.\n";
420 		goto fail;
421 	}
422 	if (chdir(pwd->pw_dir) < 0) {
423 		(void) chdir("/");
424 #ifdef notdef
425 		error("No remote directory.\n");
426 		exit(1);
427 #endif
428 	}
429 
430 #ifdef	KERBEROS
431 	if (use_kerberos) {
432 		if (pwd->pw_passwd != 0 && *pwd->pw_passwd != '\0') {
433 			if (kuserok(kdata, locuser) != 0) {
434 				syslog(LOG_NOTICE|LOG_AUTH,
435 				    "Kerberos rsh denied to %s.%s@%s",
436 				    kdata->pname, kdata->pinst, kdata->prealm);
437 				error("Permission denied.\n");
438 				exit(1);
439 			}
440 		}
441 	} else
442 #endif
443 
444 		if (errorstr ||
445 		    pwd->pw_passwd != 0 && *pwd->pw_passwd != '\0' &&
446 		    ruserok(hostname, pwd->pw_uid == 0, remuser, locuser) < 0) {
447 fail:
448 			if (errorstr == NULL)
449 				errorstr = "Permission denied.\n";
450 			error(errorstr, errorhost);
451 			exit(1);
452 		}
453 
454 	if (pwd->pw_uid && !access(_PATH_NOLOGIN, F_OK)) {
455 		error("Logins currently disabled.\n");
456 		exit(1);
457 	}
458 
459 	(void) write(2, "\0", 1);
460 	sent_null = 1;
461 
462 	if (port) {
463 		if (pipe(pv) < 0) {
464 			error("Can't make pipe.\n");
465 			exit(1);
466 		}
467 #ifdef CRYPT
468 #ifdef KERBEROS
469 		if (doencrypt) {
470 			if (pipe(pv1) < 0) {
471 				error("Can't make 2nd pipe.\n");
472 				exit(1);
473 			}
474 			if (pipe(pv2) < 0) {
475 				error("Can't make 3rd pipe.\n");
476 				exit(1);
477 			}
478 		}
479 #endif
480 #endif
481 		pid = fork();
482 		if (pid == -1)  {
483 			error("Can't fork; try again.\n");
484 			exit(1);
485 		}
486 		if (pid) {
487 #ifdef CRYPT
488 #ifdef KERBEROS
489 			if (doencrypt) {
490 				static char msg[] = SECURE_MESSAGE;
491 				(void) close(pv1[1]);
492 				(void) close(pv2[1]);
493 				des_write(s, msg, sizeof(msg));
494 
495 			} else
496 #endif
497 #endif
498 			{
499 				(void) close(0); (void) close(1);
500 			}
501 			(void) close(2); (void) close(pv[1]);
502 
503 			FD_ZERO(&readfrom);
504 			FD_SET(s, &readfrom);
505 			FD_SET(pv[0], &readfrom);
506 			if (pv[0] > s)
507 				nfd = pv[0];
508 			else
509 				nfd = s;
510 #ifdef CRYPT
511 #ifdef KERBEROS
512 			if (doencrypt) {
513 				FD_ZERO(&writeto);
514 				FD_SET(pv2[0], &writeto);
515 				FD_SET(pv1[0], &readfrom);
516 
517 				nfd = MAX(nfd, pv2[0]);
518 				nfd = MAX(nfd, pv1[0]);
519 			} else
520 #endif
521 #endif
522 				ioctl(pv[0], FIONBIO, (char *)&one);
523 
524 			/* should set s nbio! */
525 			nfd++;
526 			do {
527 				ready = readfrom;
528 #ifdef CRYPT
529 #ifdef KERBEROS
530 				if (doencrypt) {
531 					wready = writeto;
532 					if (select(nfd, &ready,
533 					    &wready, (fd_set *) 0,
534 					    (struct timeval *) 0) < 0)
535 						break;
536 				} else
537 #endif
538 #endif
539 					if (select(nfd, &ready, (fd_set *)0,
540 					  (fd_set *)0, (struct timeval *)0) < 0)
541 						break;
542 				if (FD_ISSET(s, &ready)) {
543 					int	ret;
544 #ifdef CRYPT
545 #ifdef KERBEROS
546 					if (doencrypt)
547 						ret = des_read(s, &sig, 1);
548 					else
549 #endif
550 #endif
551 						ret = read(s, &sig, 1);
552 					if (ret <= 0)
553 						FD_CLR(s, &readfrom);
554 					else
555 						killpg(pid, sig);
556 				}
557 				if (FD_ISSET(pv[0], &ready)) {
558 					errno = 0;
559 					cc = read(pv[0], buf, sizeof(buf));
560 					if (cc <= 0) {
561 						shutdown(s, 1+1);
562 						FD_CLR(pv[0], &readfrom);
563 					} else {
564 #ifdef CRYPT
565 #ifdef KERBEROS
566 						if (doencrypt)
567 							(void)
568 							  des_write(s, buf, cc);
569 						else
570 #endif
571 #endif
572 							(void)
573 							  write(s, buf, cc);
574 					}
575 				}
576 #ifdef CRYPT
577 #ifdef KERBEROS
578 				if (doencrypt && FD_ISSET(pv1[0], &ready)) {
579 					errno = 0;
580 					cc = read(pv1[0], buf, sizeof(buf));
581 					if (cc <= 0) {
582 						shutdown(pv1[0], 1+1);
583 						FD_CLR(pv1[0], &readfrom);
584 					} else
585 						(void) des_write(1, buf, cc);
586 				}
587 
588 				if (doencrypt && FD_ISSET(pv2[0], &wready)) {
589 					errno = 0;
590 					cc = des_read(0, buf, sizeof(buf));
591 					if (cc <= 0) {
592 						shutdown(pv2[0], 1+1);
593 						FD_CLR(pv2[0], &writeto);
594 					} else
595 						(void) write(pv2[0], buf, cc);
596 				}
597 #endif
598 #endif
599 
600 			} while (FD_ISSET(s, &readfrom) ||
601 #ifdef CRYPT
602 #ifdef KERBEROS
603 			    (doencrypt && FD_ISSET(pv1[0], &readfrom)) ||
604 #endif
605 #endif
606 			    FD_ISSET(pv[0], &readfrom));
607 			exit(0);
608 		}
609 		setpgrp(0, getpid());
610 		(void) close(s); (void) close(pv[0]);
611 #ifdef CRYPT
612 #ifdef KERBEROS
613 		if (doencrypt) {
614 			close(pv1[0]); close(pv2[0]);
615 			dup2(pv1[1], 1);
616 			dup2(pv2[1], 0);
617 			close(pv1[1]);
618 			close(pv2[1]);
619 		}
620 #endif
621 #endif
622 		dup2(pv[1], 2);
623 		close(pv[1]);
624 	}
625 	if (*pwd->pw_shell == '\0')
626 		pwd->pw_shell = _PATH_BSHELL;
627 #if	BSD > 43
628 	if (setlogin(pwd->pw_name) < 0)
629 		syslog(LOG_ERR, "setlogin() failed: %m");
630 #endif
631 	(void) setgid((gid_t)pwd->pw_gid);
632 	initgroups(pwd->pw_name, pwd->pw_gid);
633 	(void) setuid((uid_t)pwd->pw_uid);
634 	environ = envinit;
635 	strncat(homedir, pwd->pw_dir, sizeof(homedir)-6);
636 	strcat(path, _PATH_DEFPATH);
637 	strncat(shell, pwd->pw_shell, sizeof(shell)-7);
638 	strncat(username, pwd->pw_name, sizeof(username)-6);
639 	cp = rindex(pwd->pw_shell, '/');
640 	if (cp)
641 		cp++;
642 	else
643 		cp = pwd->pw_shell;
644 	endpwent();
645 	if (pwd->pw_uid == 0) {
646 #ifdef	KERBEROS
647 		if (use_kerberos)
648 			syslog(LOG_INFO|LOG_AUTH,
649 				"ROOT Kerberos shell from %s.%s@%s on %s, comm: %s\n",
650 				kdata->pname, kdata->pinst, kdata->prealm,
651 				hostname, cmdbuf);
652 		else
653 #endif
654 			syslog(LOG_INFO|LOG_AUTH,
655 				"ROOT shell from %s@%s, comm: %s\n",
656 				remuser, hostname, cmdbuf);
657 	}
658 	execl(pwd->pw_shell, cp, "-c", cmdbuf, 0);
659 	perror(pwd->pw_shell);
660 	exit(1);
661 }
662 
663 /*
664  * Report error to client.
665  * Note: can't be used until second socket has connected
666  * to client, or older clients will hang waiting
667  * for that connection first.
668  */
669 /*VARARGS1*/
670 error(fmt, a1, a2, a3)
671 	char *fmt;
672 	int a1, a2, a3;
673 {
674 	char buf[BUFSIZ], *bp = buf;
675 
676 	if (sent_null == 0)
677 		*bp++ = 1;
678 	(void) sprintf(bp, fmt, a1, a2, a3);
679 	(void) write(2, buf, strlen(buf));
680 }
681 
682 getstr(buf, cnt, err)
683 	char *buf;
684 	int cnt;
685 	char *err;
686 {
687 	char c;
688 
689 	do {
690 		if (read(0, &c, 1) != 1)
691 			exit(1);
692 		*buf++ = c;
693 		if (--cnt == 0) {
694 			error("%s too long\n", err);
695 			exit(1);
696 		}
697 	} while (c != 0);
698 }
699 
700 /*
701  * Check whether host h is in our local domain,
702  * defined as sharing the last two components of the domain part,
703  * or the entire domain part if the local domain has only one component.
704  * If either name is unqualified (contains no '.'),
705  * assume that the host is local, as it will be
706  * interpreted as such.
707  */
708 local_domain(h)
709 	char *h;
710 {
711 	char localhost[MAXHOSTNAMELEN];
712 	char *p1, *p2, *topdomain();
713 
714 	localhost[0] = 0;
715 	(void) gethostname(localhost, sizeof(localhost));
716 	p1 = topdomain(localhost);
717 	p2 = topdomain(h);
718 	if (p1 == NULL || p2 == NULL || !strcasecmp(p1, p2))
719 		return(1);
720 	return(0);
721 }
722 
723 char *
724 topdomain(h)
725 	char *h;
726 {
727 	register char *p;
728 	char *maybe = NULL;
729 	int dots = 0;
730 
731 	for (p = h + strlen(h); p >= h; p--) {
732 		if (*p == '.') {
733 			if (++dots == 2)
734 				return (p);
735 			maybe = p;
736 		}
737 	}
738 	return (maybe);
739 }
740 
741 usage()
742 {
743 	syslog(LOG_ERR, "usage: rshd [-%s]", OPTIONS);
744 }
745