xref: /openbsd-src/lib/libc/net/rcmd.c (revision 23deffcede86a89a2e6bd6e90fd8115dc08a0b80)
1 /*
2  * Copyright (c) 1995, 1996 Theo de Raadt.  All rights reserved.
3  * Copyright (c) 1983, 1993, 1994
4  *	The Regents of the University of California.  All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  * 3. All advertising materials mentioning features or use of this software
15  *    must display the following acknowledgement:
16  *	This product includes software developed by the University of
17  *	California, Berkeley and its contributors.
18  *	This product includes software developed by Theo de Raadt.
19  * 4. Neither the name of the University nor the names of its contributors
20  *    may be used to endorse or promote products derived from this software
21  *    without specific prior written permission.
22  *
23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33  * SUCH DAMAGE.
34  */
35 
36 #if defined(LIBC_SCCS) && !defined(lint)
37 static char *rcsid = "$OpenBSD: rcmd.c,v 1.27 1998/02/11 02:26:15 deraadt Exp $";
38 #endif /* LIBC_SCCS and not lint */
39 
40 #include <sys/param.h>
41 #include <sys/socket.h>
42 #include <sys/stat.h>
43 
44 #include <netinet/in.h>
45 #include <arpa/inet.h>
46 
47 #include <signal.h>
48 #include <fcntl.h>
49 #include <netdb.h>
50 #include <unistd.h>
51 #include <pwd.h>
52 #include <errno.h>
53 #include <stdio.h>
54 #include <ctype.h>
55 #include <string.h>
56 #include <syslog.h>
57 #include <stdlib.h>
58 #include <netgroup.h>
59 
60 int	__ivaliduser __P((FILE *, in_addr_t, const char *, const char *));
61 static int __icheckhost __P((u_int32_t, const char *));
62 static char *__gethostloop __P((u_int32_t));
63 
64 int
65 rcmd(ahost, rport, locuser, remuser, cmd, fd2p)
66 	char **ahost;
67 	in_port_t rport;
68 	const char *locuser, *remuser, *cmd;
69 	int *fd2p;
70 {
71 	struct hostent *hp;
72 	struct sockaddr_in sin, from;
73 	fd_set *readsp = NULL;
74 	int oldmask;
75 	pid_t pid;
76 	int s, lport, timo;
77 	char c, *p;
78 
79 	/* call rcmdsh() with specified remote shell if appropriate. */
80 	if (!issetugid() && (p = getenv("RSH"))) {
81 		struct servent *sp = getservbyname("shell", "tcp");
82 
83 		if (sp && sp->s_port == rport)
84 			return (rcmdsh(ahost, rport, locuser, remuser,
85 			    cmd, p));
86 	}
87 
88 	/* use rsh(1) if non-root and remote port is shell. */
89 	if (geteuid()) {
90 		struct servent *sp = getservbyname("shell", "tcp");
91 
92 		if (sp && sp->s_port == rport)
93 			return (rcmdsh(ahost, rport, locuser, remuser,
94 			    cmd, NULL));
95 	}
96 
97 	pid = getpid();
98 	hp = gethostbyname(*ahost);
99 	if (hp == NULL) {
100 		herror(*ahost);
101 		return (-1);
102 	}
103 	*ahost = hp->h_name;
104 
105 	oldmask = sigblock(sigmask(SIGURG));
106 	for (timo = 1, lport = IPPORT_RESERVED - 1;;) {
107 		s = rresvport(&lport);
108 		if (s < 0) {
109 			if (errno == EAGAIN)
110 				(void)fprintf(stderr,
111 				    "rcmd: socket: All ports in use\n");
112 			else
113 				(void)fprintf(stderr, "rcmd: socket: %s\n",
114 				    strerror(errno));
115 			sigsetmask(oldmask);
116 			return (-1);
117 		}
118 		fcntl(s, F_SETOWN, pid);
119 		bzero(&sin, sizeof sin);
120 		sin.sin_len = sizeof(struct sockaddr_in);
121 		sin.sin_family = hp->h_addrtype;
122 		sin.sin_port = rport;
123 		bcopy(hp->h_addr_list[0], &sin.sin_addr, hp->h_length);
124 		if (connect(s, (struct sockaddr *)&sin, sizeof(sin)) >= 0)
125 			break;
126 		(void)close(s);
127 		if (errno == EADDRINUSE) {
128 			lport--;
129 			continue;
130 		}
131 		if (errno == ECONNREFUSED && timo <= 16) {
132 			(void)sleep(timo);
133 			timo *= 2;
134 			continue;
135 		}
136 		if (hp->h_addr_list[1] != NULL) {
137 			int oerrno = errno;
138 
139 			(void)fprintf(stderr, "connect to address %s: ",
140 			    inet_ntoa(sin.sin_addr));
141 			errno = oerrno;
142 			perror(0);
143 			hp->h_addr_list++;
144 			bcopy(hp->h_addr_list[0], &sin.sin_addr, hp->h_length);
145 			(void)fprintf(stderr, "Trying %s...\n",
146 			    inet_ntoa(sin.sin_addr));
147 			continue;
148 		}
149 		(void)fprintf(stderr, "%s: %s\n", hp->h_name, strerror(errno));
150 		sigsetmask(oldmask);
151 		return (-1);
152 	}
153 #if 0
154 	/*
155 	 * try to rresvport() to the same port. This will make rresvport()
156 	 * fail it's first bind, resulting in it choosing a random port.
157 	 */
158 	lport--;
159 #endif
160 	if (fd2p == 0) {
161 		write(s, "", 1);
162 		lport = 0;
163 	} else {
164 		char num[8];
165 		int s2 = rresvport(&lport), s3;
166 		int len = sizeof(from);
167 		int fdssize = howmany(MAX(s, s2)+1, NFDBITS) * sizeof(fd_mask);
168 
169 		if (s2 < 0)
170 			goto bad;
171 		readsp = (fd_set *)malloc(fdssize);
172 		if (readsp == NULL)
173 			goto bad;
174 		listen(s2, 1);
175 		(void)snprintf(num, sizeof(num), "%d", lport);
176 		if (write(s, num, strlen(num)+1) != strlen(num)+1) {
177 			(void)fprintf(stderr,
178 			    "rcmd: write (setting up stderr): %s\n",
179 			    strerror(errno));
180 			(void)close(s2);
181 			goto bad;
182 		}
183 again:
184 		bzero(readsp, fdssize);
185 		FD_SET(s, readsp);
186 		FD_SET(s2, readsp);
187 		errno = 0;
188 		if (select(MAX(s, s2) + 1, readsp, 0, 0, 0) < 1 ||
189 		    !FD_ISSET(s2, readsp)) {
190 			if (errno != 0)
191 				(void)fprintf(stderr,
192 				    "rcmd: select (setting up stderr): %s\n",
193 				    strerror(errno));
194 			else
195 				(void)fprintf(stderr,
196 				"select: protocol failure in circuit setup\n");
197 			(void)close(s2);
198 			goto bad;
199 		}
200 		s3 = accept(s2, (struct sockaddr *)&from, &len);
201 		/*
202 		 * XXX careful for ftp bounce attacks. If discovered, shut them
203 		 * down and check for the real auxiliary channel to connect.
204 		 */
205 		if (from.sin_family == AF_INET && from.sin_port == htons(20)) {
206 			close(s3);
207 			goto again;
208 		}
209 		(void)close(s2);
210 		if (s3 < 0) {
211 			(void)fprintf(stderr,
212 			    "rcmd: accept: %s\n", strerror(errno));
213 			lport = 0;
214 			goto bad;
215 		}
216 		*fd2p = s3;
217 		from.sin_port = ntohs(from.sin_port);
218 		if (from.sin_family != AF_INET ||
219 		    from.sin_port >= IPPORT_RESERVED ||
220 		    from.sin_port < IPPORT_RESERVED / 2) {
221 			(void)fprintf(stderr,
222 			    "socket: protocol failure in circuit setup.\n");
223 			goto bad2;
224 		}
225 	}
226 	(void)write(s, locuser, strlen(locuser)+1);
227 	(void)write(s, remuser, strlen(remuser)+1);
228 	(void)write(s, cmd, strlen(cmd)+1);
229 	if (read(s, &c, 1) != 1) {
230 		(void)fprintf(stderr,
231 		    "rcmd: %s: %s\n", *ahost, strerror(errno));
232 		goto bad2;
233 	}
234 	if (c != 0) {
235 		while (read(s, &c, 1) == 1) {
236 			(void)write(STDERR_FILENO, &c, 1);
237 			if (c == '\n')
238 				break;
239 		}
240 		goto bad2;
241 	}
242 	sigsetmask(oldmask);
243 	free(readsp);
244 	return (s);
245 bad2:
246 	if (lport)
247 		(void)close(*fd2p);
248 bad:
249 	if (readsp)
250 		free(readsp);
251 	(void)close(s);
252 	sigsetmask(oldmask);
253 	return (-1);
254 }
255 
256 int
257 rresvport(alport)
258 	int *alport;
259 {
260 	struct sockaddr_in sin;
261 	int s;
262 
263 	bzero(&sin, sizeof sin);
264 	sin.sin_len = sizeof(struct sockaddr_in);
265 	sin.sin_family = AF_INET;
266 	sin.sin_addr.s_addr = INADDR_ANY;
267 	s = socket(AF_INET, SOCK_STREAM, 0);
268 	if (s < 0)
269 		return (-1);
270 	sin.sin_port = htons((in_port_t)*alport);
271 	if (*alport < IPPORT_RESERVED - 1) {
272 		if (bind(s, (struct sockaddr *)&sin, sizeof(sin)) >= 0)
273 			return (s);
274 		if (errno != EADDRINUSE) {
275 			(void)close(s);
276 			return (-1);
277 		}
278 	}
279 	sin.sin_port = 0;
280 	if (bindresvport(s, &sin) == -1) {
281 		(void)close(s);
282 		return (-1);
283 	}
284 	*alport = (int)ntohs(sin.sin_port);
285 	return (s);
286 }
287 
288 int	__check_rhosts_file = 1;
289 char	*__rcmd_errstr;
290 
291 int
292 ruserok(rhost, superuser, ruser, luser)
293 	const char *rhost, *ruser, *luser;
294 	int superuser;
295 {
296 	struct hostent *hp;
297 	char **ap;
298 	int i;
299 #define MAXADDRS	35
300 	u_int32_t addrs[MAXADDRS + 1];
301 
302 	if ((hp = gethostbyname(rhost)) == NULL)
303 		return (-1);
304 	for (i = 0, ap = hp->h_addr_list; *ap && i < MAXADDRS; ++ap, ++i)
305 		bcopy(*ap, &addrs[i], sizeof(addrs[i]));
306 	addrs[i] = 0;
307 
308 	for (i = 0; i < MAXADDRS && addrs[i]; i++)
309 		if (iruserok((in_addr_t)addrs[i], superuser, ruser, luser) == 0)
310 			return (0);
311 	return (-1);
312 }
313 
314 /*
315  * New .rhosts strategy: We are passed an ip address. We spin through
316  * hosts.equiv and .rhosts looking for a match. When the .rhosts only
317  * has ip addresses, we don't have to trust a nameserver.  When it
318  * contains hostnames, we spin through the list of addresses the nameserver
319  * gives us and look for a match.
320  *
321  * Returns 0 if ok, -1 if not ok.
322  */
323 int
324 iruserok(raddr, superuser, ruser, luser)
325 	u_int32_t raddr;
326 	int superuser;
327 	const char *ruser, *luser;
328 {
329 	register char *cp;
330 	struct stat sbuf;
331 	struct passwd *pwd;
332 	FILE *hostf;
333 	uid_t uid;
334 	int first;
335 	char pbuf[MAXPATHLEN];
336 
337 	first = 1;
338 	hostf = superuser ? NULL : fopen(_PATH_HEQUIV, "r");
339 again:
340 	if (hostf) {
341 		if (__ivaliduser(hostf, raddr, luser, ruser) == 0) {
342 			(void)fclose(hostf);
343 			return (0);
344 		}
345 		(void)fclose(hostf);
346 	}
347 	if (first == 1 && (__check_rhosts_file || superuser)) {
348 		first = 0;
349 		if ((pwd = getpwnam(luser)) == NULL)
350 			return (-1);
351 		(void)strcpy(pbuf, pwd->pw_dir);
352 		(void)strcat(pbuf, "/.rhosts");
353 
354 		/*
355 		 * Change effective uid while opening .rhosts.  If root and
356 		 * reading an NFS mounted file system, can't read files that
357 		 * are protected read/write owner only.
358 		 */
359 		uid = geteuid();
360 		(void)seteuid(pwd->pw_uid);
361 		hostf = fopen(pbuf, "r");
362 		(void)seteuid(uid);
363 
364 		if (hostf == NULL)
365 			return (-1);
366 		/*
367 		 * If not a regular file, or is owned by someone other than
368 		 * user or root or if writeable by anyone but the owner, quit.
369 		 */
370 		cp = NULL;
371 		if (lstat(pbuf, &sbuf) < 0)
372 			cp = ".rhosts lstat failed";
373 		else if (!S_ISREG(sbuf.st_mode))
374 			cp = ".rhosts not regular file";
375 		else if (fstat(fileno(hostf), &sbuf) < 0)
376 			cp = ".rhosts fstat failed";
377 		else if (sbuf.st_uid && sbuf.st_uid != pwd->pw_uid)
378 			cp = "bad .rhosts owner";
379 		else if (sbuf.st_mode & (S_IWGRP|S_IWOTH))
380 			cp = ".rhosts writeable by other than owner";
381 		/* If there were any problems, quit. */
382 		if (cp) {
383 			__rcmd_errstr = cp;
384 			(void)fclose(hostf);
385 			return (-1);
386 		}
387 		goto again;
388 	}
389 	return (-1);
390 }
391 
392 /*
393  * XXX
394  * Don't make static, used by lpd(8).
395  *
396  * Returns 0 if ok, -1 if not ok.
397  */
398 int
399 __ivaliduser(hostf, raddrl, luser, ruser)
400 	FILE *hostf;
401 	in_addr_t raddrl;
402 	const char *luser, *ruser;
403 {
404 	register char *user, *p;
405 	int ch;
406 	char buf[MAXHOSTNAMELEN + 128];		/* host + login */
407 	const char *auser, *ahost;
408 	int hostok, userok;
409 	char *rhost = (char *)-1;
410 	char domain[MAXHOSTNAMELEN];
411 	u_int32_t raddr = (u_int32_t)raddrl;
412 
413 	getdomainname(domain, sizeof(domain));
414 
415 	while (fgets(buf, sizeof(buf), hostf)) {
416 		p = buf;
417 		/* Skip lines that are too long. */
418 		if (strchr(p, '\n') == NULL) {
419 			while ((ch = getc(hostf)) != '\n' && ch != EOF)
420 				if (!isprint(ch))
421 					goto bail;
422 			continue;
423 		}
424 		if (*p == '#')
425 			continue;
426 		while (*p != '\n' && *p != ' ' && *p != '\t' && *p != '\0') {
427 			if (!isprint(*p))
428 				goto bail;
429 			*p = isupper(*p) ? tolower(*p) : *p;
430 			p++;
431 		}
432 		if (*p == ' ' || *p == '\t') {
433 			*p++ = '\0';
434 			while (*p == ' ' || *p == '\t')
435 				p++;
436 			user = p;
437 			while (*p != '\n' && *p != ' ' &&
438 			    *p != '\t' && *p != '\0') {
439 				if (!isprint(*p))
440 					goto bail;
441 				p++;
442 			}
443 		} else
444 			user = p;
445 		*p = '\0';
446 
447 		if (p == buf)
448 			continue;
449 
450 		auser = *user ? user : luser;
451 		ahost = buf;
452 
453 		/*
454 		 * innetgr() must lookup a hostname (we do not attempt
455 		 * to change the semantics so that netgroups may have
456 		 * #.#.#.# addresses in the list.)
457 		 */
458 		if (ahost[0] == '+')
459 			switch (ahost[1]) {
460 			case '\0':
461 				hostok = 1;
462 				break;
463 			case '@':
464 				if (rhost == (char *)-1)
465 					rhost = __gethostloop(raddr);
466 				hostok = 0;
467 				if (rhost)
468 					hostok = innetgr(&ahost[2], rhost,
469 					    NULL, domain);
470 				break;
471 			default:
472 				hostok = __icheckhost(raddr, &ahost[1]);
473 				break;
474 			}
475 		else if (ahost[0] == '-')
476 			switch (ahost[1]) {
477 			case '\0':
478 				hostok = -1;
479 				break;
480 			case '@':
481 				if (rhost == (char *)-1)
482 					rhost = __gethostloop(raddr);
483 				hostok = 0;
484 				if (rhost)
485 					hostok = -innetgr(&ahost[2], rhost,
486 					    NULL, domain);
487 				break;
488 			default:
489 				hostok = -__icheckhost(raddr, &ahost[1]);
490 				break;
491 			}
492 		else
493 			hostok = __icheckhost(raddr, ahost);
494 
495 
496 		if (auser[0] == '+')
497 			switch (auser[1]) {
498 			case '\0':
499 				userok = 1;
500 				break;
501 			case '@':
502 				userok = innetgr(&auser[2], NULL, ruser,
503 				    domain);
504 				break;
505 			default:
506 				userok = strcmp(ruser, &auser[1]) ? 0 : 1;
507 				break;
508 			}
509 		else if (auser[0] == '-')
510 			switch (auser[1]) {
511 			case '\0':
512 				userok = -1;
513 				break;
514 			case '@':
515 				userok = -innetgr(&auser[2], NULL, ruser,
516 				    domain);
517 				break;
518 			default:
519 				userok = strcmp(ruser, &auser[1]) ? 0 : -1;
520 				break;
521 			}
522 		else
523 			userok = strcmp(ruser, auser) ? 0 : 1;
524 
525 		/* Check if one component did not match */
526 		if (hostok == 0 || userok == 0)
527 			continue;
528 
529 		/* Check if we got a forbidden pair */
530 		if (userok <= -1 || hostok <= -1)
531 			return (-1);
532 
533 		/* Check if we got a valid pair */
534 		if (hostok >= 1 && userok >= 1)
535 			return (0);
536 	}
537 bail:
538 	return (-1);
539 }
540 
541 /*
542  * Returns "true" if match, 0 if no match.  If we do not find any
543  * semblance of an A->PTR->A loop, allow a simple #.#.#.# match to work.
544  */
545 static int
546 __icheckhost(raddr, lhost)
547 	u_int32_t raddr;
548 	const char *lhost;
549 {
550 	register struct hostent *hp;
551 	register char **pp;
552 	struct in_addr in;
553 
554 	hp = gethostbyname(lhost);
555 	if (hp != NULL) {
556 		/* Spin through ip addresses. */
557 		for (pp = hp->h_addr_list; *pp; ++pp)
558 			if (!bcmp(&raddr, *pp, sizeof(raddr)))
559 				return (1);
560 	}
561 
562 	in.s_addr = raddr;
563 	if (strcmp(lhost, inet_ntoa(in)) == 0)
564 		return (1);
565 	return (0);
566 }
567 
568 /*
569  * Return the hostname associated with the supplied address.
570  * Do a reverse lookup as well for security. If a loop cannot
571  * be found, pack the result of inet_ntoa() into the string.
572  */
573 static char *
574 __gethostloop(raddr)
575 	u_int32_t raddr;
576 {
577 	static char remotehost[MAXHOSTNAMELEN];
578 	struct hostent *hp;
579 	struct in_addr in;
580 
581 	hp = gethostbyaddr((char *) &raddr, sizeof(raddr), AF_INET);
582 	if (hp == NULL)
583 		return (NULL);
584 
585 	/*
586 	 * Look up the name and check that the supplied
587 	 * address is in the list
588 	 */
589 	strncpy(remotehost, hp->h_name, sizeof(remotehost) - 1);
590 	remotehost[sizeof(remotehost) - 1] = '\0';
591 	hp = gethostbyname(remotehost);
592 	if (hp == NULL)
593 		return (NULL);
594 
595 	for (; hp->h_addr_list[0] != NULL; hp->h_addr_list++)
596 		if (!bcmp(hp->h_addr_list[0], (caddr_t)&raddr, sizeof(raddr)))
597 			return (remotehost);
598 
599 	/*
600 	 * either the DNS adminstrator has made a configuration
601 	 * mistake, or someone has attempted to spoof us
602 	 */
603 	in.s_addr = raddr;
604 	syslog(LOG_NOTICE, "rcmd: address %s not listed for host %s",
605 	    inet_ntoa(in), hp->h_name);
606 	return (NULL);
607 }
608