rshd.c revision 302408 
1/*-
2 * Copyright (c) 1988, 1989, 1992, 1993, 1994
3 *	The Regents of the University of California.  All rights reserved.
4 * Copyright (c) 2002 Networks Associates Technology, Inc.
5 * All rights reserved.
6 *
7 * Portions of this software were developed for the FreeBSD Project by
8 * ThinkSec AS and NAI Labs, the Security Research Division of Network
9 * Associates, Inc.  under DARPA/SPAWAR contract N66001-01-C-8035
10 * ("CBOSS"), as part of the DARPA CHATS research program.
11 *
12 * Redistribution and use in source and binary forms, with or without
13 * modification, are permitted provided that the following conditions
14 * are met:
15 * 1. Redistributions of source code must retain the above copyright
16 *    notice, this list of conditions and the following disclaimer.
17 * 2. Redistributions in binary form must reproduce the above copyright
18 *    notice, this list of conditions and the following disclaimer in the
19 *    documentation and/or other materials provided with the distribution.
20 * 3. Neither the name of the University nor the names of its contributors
21 *    may be used to endorse or promote products derived from this software
22 *    without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37#ifndef lint
38static const char copyright[] =
39"@(#) Copyright (c) 1988, 1989, 1992, 1993, 1994\n\
40	The Regents of the University of California.  All rights reserved.\n";
41#endif /* not lint */
42
43#ifndef lint
44#if 0
45static const char sccsid[] = "@(#)rshd.c	8.2 (Berkeley) 4/6/94";
46#endif
47#endif /* not lint */
48
49#include <sys/cdefs.h>
50__FBSDID("$FreeBSD: stable/11/libexec/rshd/rshd.c 301242 2016-06-03 06:58:20Z lidl $");
51
52/*
53 * remote shell server:
54 *	[port]\0
55 *	ruser\0
56 *	luser\0
57 *	command\0
58 *	data
59 */
60#include <sys/param.h>
61#include <sys/ioctl.h>
62#include <sys/time.h>
63#include <sys/socket.h>
64
65#include <netinet/in_systm.h>
66#include <netinet/in.h>
67#include <netinet/ip.h>
68#include <netinet/tcp.h>
69#include <arpa/inet.h>
70#include <netdb.h>
71
72#include <err.h>
73#include <errno.h>
74#include <fcntl.h>
75#include <libutil.h>
76#include <paths.h>
77#include <pwd.h>
78#include <signal.h>
79#include <stdarg.h>
80#include <stdio.h>
81#include <stdlib.h>
82#include <string.h>
83#include <syslog.h>
84#include <unistd.h>
85#include <login_cap.h>
86
87#include <security/pam_appl.h>
88#include <security/openpam.h>
89#include <sys/wait.h>
90
91#ifdef USE_BLACKLIST
92#include <blacklist.h>
93#endif
94
95static struct pam_conv pamc = { openpam_nullconv, NULL };
96static pam_handle_t *pamh;
97static int pam_err;
98
99#define PAM_END { \
100	if ((pam_err = pam_setcred(pamh, PAM_DELETE_CRED)) != PAM_SUCCESS) \
101		syslog(LOG_ERR|LOG_AUTH, "pam_setcred(): %s", pam_strerror(pamh, pam_err)); \
102	if ((pam_err = pam_close_session(pamh,0)) != PAM_SUCCESS) \
103		syslog(LOG_ERR|LOG_AUTH, "pam_close_session(): %s", pam_strerror(pamh, pam_err)); \
104	if ((pam_err = pam_end(pamh, pam_err)) != PAM_SUCCESS) \
105		syslog(LOG_ERR|LOG_AUTH, "pam_end(): %s", pam_strerror(pamh, pam_err)); \
106}
107
108int	keepalive = 1;
109int	log_success;		/* If TRUE, log all successful accesses */
110int	sent_null;
111int	no_delay;
112
113void	 doit(struct sockaddr *);
114static void	 rshd_errx(int, const char *, ...) __printf0like(2, 3);
115void	 getstr(char *, int, const char *);
116int	 local_domain(char *);
117char	*topdomain(char *);
118void	 usage(void);
119
120char	 slash[] = "/";
121char	 bshell[] = _PATH_BSHELL;
122
123#define	OPTIONS	"aDLln"
124
125int
126main(int argc, char *argv[])
127{
128	extern int __check_rhosts_file;
129	struct linger linger;
130	socklen_t fromlen;
131	int ch, on = 1;
132	struct sockaddr_storage from;
133
134	openlog("rshd", LOG_PID, LOG_DAEMON);
135
136	opterr = 0;
137	while ((ch = getopt(argc, argv, OPTIONS)) != -1)
138		switch (ch) {
139		case 'a':
140			/* ignored for compatibility */
141			break;
142		case 'l':
143			__check_rhosts_file = 0;
144			break;
145		case 'n':
146			keepalive = 0;
147			break;
148		case 'D':
149			no_delay = 1;
150			break;
151		case 'L':
152			log_success = 1;
153			break;
154		case '?':
155		default:
156			usage();
157			break;
158		}
159
160	argc -= optind;
161	argv += optind;
162
163	fromlen = sizeof (from);
164	if (getpeername(0, (struct sockaddr *)&from, &fromlen) < 0) {
165		syslog(LOG_ERR, "getpeername: %m");
166		exit(1);
167	}
168	if (keepalive &&
169	    setsockopt(0, SOL_SOCKET, SO_KEEPALIVE, (char *)&on,
170	    sizeof(on)) < 0)
171		syslog(LOG_WARNING, "setsockopt (SO_KEEPALIVE): %m");
172	linger.l_onoff = 1;
173	linger.l_linger = 60;			/* XXX */
174	if (setsockopt(0, SOL_SOCKET, SO_LINGER, (char *)&linger,
175	    sizeof (linger)) < 0)
176		syslog(LOG_WARNING, "setsockopt (SO_LINGER): %m");
177	if (no_delay &&
178	    setsockopt(0, IPPROTO_TCP, TCP_NODELAY, &on, sizeof(on)) < 0)
179		syslog(LOG_WARNING, "setsockopt (TCP_NODELAY): %m");
180	doit((struct sockaddr *)&from);
181	/* NOTREACHED */
182	return(0);
183}
184
185extern char **environ;
186
187void
188doit(struct sockaddr *fromp)
189{
190	extern char *__rcmd_errstr;	/* syslog hook from libc/net/rcmd.c. */
191	struct passwd *pwd;
192	u_short port;
193	fd_set ready, readfrom;
194	int cc, fd, nfd, pv[2], pid, s;
195	int one = 1;
196	const char *cp, *errorstr;
197	char sig, buf[BUFSIZ];
198	char *cmdbuf, luser[16], ruser[16];
199	char rhost[2 * MAXHOSTNAMELEN + 1];
200	char numericname[INET6_ADDRSTRLEN];
201	int af, srcport;
202	int maxcmdlen;
203	login_cap_t *lc;
204
205	maxcmdlen = (int)sysconf(_SC_ARG_MAX);
206	if (maxcmdlen <= 0 || (cmdbuf = malloc(maxcmdlen)) == NULL)
207		exit(1);
208
209	(void) signal(SIGINT, SIG_DFL);
210	(void) signal(SIGQUIT, SIG_DFL);
211	(void) signal(SIGTERM, SIG_DFL);
212	af = fromp->sa_family;
213	srcport = ntohs(*((in_port_t *)&fromp->sa_data));
214	if (af == AF_INET) {
215		inet_ntop(af, &((struct sockaddr_in *)fromp)->sin_addr,
216		    numericname, sizeof numericname);
217	} else if (af == AF_INET6) {
218		inet_ntop(af, &((struct sockaddr_in6 *)fromp)->sin6_addr,
219		    numericname, sizeof numericname);
220	} else {
221		syslog(LOG_ERR, "malformed \"from\" address (af %d)", af);
222		exit(1);
223	}
224#ifdef IP_OPTIONS
225	if (af == AF_INET) {
226		u_char optbuf[BUFSIZ/3];
227		socklen_t optsize = sizeof(optbuf), ipproto, i;
228		struct protoent *ip;
229
230		if ((ip = getprotobyname("ip")) != NULL)
231			ipproto = ip->p_proto;
232		else
233			ipproto = IPPROTO_IP;
234		if (!getsockopt(0, ipproto, IP_OPTIONS, optbuf, &optsize) &&
235		    optsize != 0) {
236			for (i = 0; i < optsize; ) {
237				u_char c = optbuf[i];
238				if (c == IPOPT_LSRR || c == IPOPT_SSRR) {
239					syslog(LOG_NOTICE,
240					    "connection refused from %s with IP option %s",
241					    numericname,
242					    c == IPOPT_LSRR ? "LSRR" : "SSRR");
243					exit(1);
244				}
245				if (c == IPOPT_EOL)
246					break;
247				i += (c == IPOPT_NOP) ? 1 : optbuf[i+1];
248			}
249		}
250	}
251#endif
252
253	if (srcport >= IPPORT_RESERVED ||
254	    srcport < IPPORT_RESERVED/2) {
255		syslog(LOG_NOTICE|LOG_AUTH,
256		    "connection from %s on illegal port %u",
257		    numericname,
258		    srcport);
259#ifdef USE_BLACKLIST
260		blacklist(1, STDIN_FILENO, "illegal port");
261#endif
262		exit(1);
263	}
264
265	(void) alarm(60);
266	port = 0;
267	s = 0;		/* not set or used if port == 0 */
268	for (;;) {
269		char c;
270		if ((cc = read(STDIN_FILENO, &c, 1)) != 1) {
271			if (cc < 0)
272				syslog(LOG_NOTICE, "read: %m");
273			shutdown(0, SHUT_RDWR);
274			exit(1);
275		}
276		if (c == 0)
277			break;
278		port = port * 10 + c - '0';
279	}
280
281	(void) alarm(0);
282	if (port != 0) {
283		int lport = IPPORT_RESERVED - 1;
284		s = rresvport_af(&lport, af);
285		if (s < 0) {
286			syslog(LOG_ERR, "can't get stderr port: %m");
287			exit(1);
288		}
289		if (port >= IPPORT_RESERVED ||
290		    port < IPPORT_RESERVED/2) {
291			syslog(LOG_NOTICE|LOG_AUTH,
292			    "2nd socket from %s on unreserved port %u",
293			    numericname,
294			    port);
295#ifdef USE_BLACKLIST
296			blacklist(1, STDIN_FILENO, "unreserved port");
297#endif
298			exit(1);
299		}
300		*((in_port_t *)&fromp->sa_data) = htons(port);
301		if (connect(s, fromp, fromp->sa_len) < 0) {
302			syslog(LOG_INFO, "connect second port %d: %m", port);
303			exit(1);
304		}
305	}
306
307	errorstr = NULL;
308	realhostname_sa(rhost, sizeof(rhost) - 1, fromp, fromp->sa_len);
309	rhost[sizeof(rhost) - 1] = '\0';
310	/* XXX truncation! */
311
312	(void) alarm(60);
313	getstr(ruser, sizeof(ruser), "ruser");
314	getstr(luser, sizeof(luser), "luser");
315	getstr(cmdbuf, maxcmdlen, "command");
316	(void) alarm(0);
317
318	pam_err = pam_start("rsh", luser, &pamc, &pamh);
319	if (pam_err != PAM_SUCCESS) {
320		syslog(LOG_ERR|LOG_AUTH, "pam_start(): %s",
321		    pam_strerror(pamh, pam_err));
322#ifdef USE_BLACKLIST
323		blacklist(1, STDIN_FILENO, "login incorrect");
324#endif
325		rshd_errx(1, "Login incorrect.");
326	}
327
328	if ((pam_err = pam_set_item(pamh, PAM_RUSER, ruser)) != PAM_SUCCESS ||
329	    (pam_err = pam_set_item(pamh, PAM_RHOST, rhost)) != PAM_SUCCESS) {
330		syslog(LOG_ERR|LOG_AUTH, "pam_set_item(): %s",
331		    pam_strerror(pamh, pam_err));
332#ifdef USE_BLACKLIST
333		blacklist(1, STDIN_FILENO, "login incorrect");
334#endif
335		rshd_errx(1, "Login incorrect.");
336	}
337
338	pam_err = pam_authenticate(pamh, 0);
339	if (pam_err == PAM_SUCCESS) {
340		if ((pam_err = pam_get_user(pamh, &cp, NULL)) == PAM_SUCCESS) {
341			strncpy(luser, cp, sizeof(luser));
342			luser[sizeof(luser) - 1] = '\0';
343			/* XXX truncation! */
344		}
345		pam_err = pam_acct_mgmt(pamh, 0);
346	}
347	if (pam_err != PAM_SUCCESS) {
348		syslog(LOG_INFO|LOG_AUTH,
349		    "%s@%s as %s: permission denied (%s). cmd='%.80s'",
350		    ruser, rhost, luser, pam_strerror(pamh, pam_err), cmdbuf);
351#ifdef USE_BLACKLIST
352		blacklist(1, STDIN_FILENO, "permission denied");
353#endif
354		rshd_errx(1, "Login incorrect.");
355	}
356
357	setpwent();
358	pwd = getpwnam(luser);
359	if (pwd == NULL) {
360		syslog(LOG_INFO|LOG_AUTH,
361		    "%s@%s as %s: unknown login. cmd='%.80s'",
362		    ruser, rhost, luser, cmdbuf);
363#ifdef USE_BLACKLIST
364		blacklist(1, STDIN_FILENO, "unknown login");
365#endif
366		if (errorstr == NULL)
367			errorstr = "Login incorrect.";
368		rshd_errx(1, errorstr, rhost);
369	}
370
371	lc = login_getpwclass(pwd);
372	if (pwd->pw_uid)
373		auth_checknologin(lc);
374
375	if (chdir(pwd->pw_dir) < 0) {
376		if (chdir("/") < 0 ||
377		    login_getcapbool(lc, "requirehome", !!pwd->pw_uid)) {
378			syslog(LOG_INFO|LOG_AUTH,
379			"%s@%s as %s: no home directory. cmd='%.80s'",
380			ruser, rhost, luser, cmdbuf);
381			rshd_errx(0, "No remote home directory.");
382		}
383		pwd->pw_dir = slash;
384	}
385
386	if (lc != NULL && fromp->sa_family == AF_INET) {	/*XXX*/
387		char	remote_ip[MAXHOSTNAMELEN];
388
389		strncpy(remote_ip, numericname,
390			sizeof(remote_ip) - 1);
391		remote_ip[sizeof(remote_ip) - 1] = 0;
392		/* XXX truncation! */
393		if (!auth_hostok(lc, rhost, remote_ip)) {
394			syslog(LOG_INFO|LOG_AUTH,
395			    "%s@%s as %s: permission denied (%s). cmd='%.80s'",
396			    ruser, rhost, luser, __rcmd_errstr,
397			    cmdbuf);
398#ifdef USE_BLACKLIST
399			blacklist(1, STDIN_FILENO, "permission denied");
400#endif
401			rshd_errx(1, "Login incorrect.");
402		}
403		if (!auth_timeok(lc, time(NULL)))
404			rshd_errx(1, "Logins not available right now");
405	}
406
407	/*
408	 * PAM modules might add supplementary groups in
409	 * pam_setcred(), so initialize them first.
410	 * But we need to open the session as root.
411	 */
412	if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) != 0) {
413		syslog(LOG_ERR, "setusercontext: %m");
414		exit(1);
415	}
416
417	if ((pam_err = pam_open_session(pamh, 0)) != PAM_SUCCESS) {
418		syslog(LOG_ERR, "pam_open_session: %s", pam_strerror(pamh, pam_err));
419	} else if ((pam_err = pam_setcred(pamh, PAM_ESTABLISH_CRED)) != PAM_SUCCESS) {
420		syslog(LOG_ERR, "pam_setcred: %s", pam_strerror(pamh, pam_err));
421	}
422
423	(void) write(STDERR_FILENO, "\0", 1);
424	sent_null = 1;
425
426	if (port) {
427		if (pipe(pv) < 0)
428			rshd_errx(1, "Can't make pipe.");
429		pid = fork();
430		if (pid == -1)
431			rshd_errx(1, "Can't fork; try again.");
432		if (pid) {
433			(void) close(0);
434			(void) close(1);
435			(void) close(2);
436			(void) close(pv[1]);
437
438			FD_ZERO(&readfrom);
439			FD_SET(s, &readfrom);
440			FD_SET(pv[0], &readfrom);
441			if (pv[0] > s)
442				nfd = pv[0];
443			else
444				nfd = s;
445				ioctl(pv[0], FIONBIO, (char *)&one);
446
447			/* should set s nbio! */
448			nfd++;
449			do {
450				ready = readfrom;
451				if (select(nfd, &ready, (fd_set *)0,
452				  (fd_set *)0, (struct timeval *)0) < 0)
453					break;
454				if (FD_ISSET(s, &ready)) {
455					int	ret;
456						ret = read(s, &sig, 1);
457				if (ret <= 0)
458					FD_CLR(s, &readfrom);
459				else
460					killpg(pid, sig);
461				}
462				if (FD_ISSET(pv[0], &ready)) {
463					errno = 0;
464					cc = read(pv[0], buf, sizeof(buf));
465					if (cc <= 0) {
466						shutdown(s, SHUT_RDWR);
467						FD_CLR(pv[0], &readfrom);
468					} else {
469						(void)write(s, buf, cc);
470					}
471				}
472
473			} while (FD_ISSET(s, &readfrom) ||
474			    FD_ISSET(pv[0], &readfrom));
475			PAM_END;
476			exit(0);
477		}
478		(void) close(s);
479		(void) close(pv[0]);
480		dup2(pv[1], 2);
481		close(pv[1]);
482	}
483	else {
484		pid = fork();
485		if (pid == -1)
486			rshd_errx(1, "Can't fork; try again.");
487		if (pid) {
488			/* Parent. */
489			while (wait(NULL) > 0 || errno == EINTR)
490				/* nothing */ ;
491			PAM_END;
492			exit(0);
493		}
494	}
495
496#ifdef USE_BLACKLIST
497	blacklist(0, STDIN_FILENO, "success");
498#endif
499	for (fd = getdtablesize(); fd > 2; fd--)
500		(void) close(fd);
501	if (setsid() == -1)
502		syslog(LOG_ERR, "setsid() failed: %m");
503	if (setlogin(pwd->pw_name) < 0)
504		syslog(LOG_ERR, "setlogin() failed: %m");
505
506	if (*pwd->pw_shell == '\0')
507		pwd->pw_shell = bshell;
508	(void) pam_setenv(pamh, "HOME", pwd->pw_dir, 1);
509	(void) pam_setenv(pamh, "SHELL", pwd->pw_shell, 1);
510	(void) pam_setenv(pamh, "USER", pwd->pw_name, 1);
511	(void) pam_setenv(pamh, "PATH", _PATH_DEFPATH, 1);
512	environ = pam_getenvlist(pamh);
513	(void) pam_end(pamh, pam_err);
514	cp = strrchr(pwd->pw_shell, '/');
515	if (cp)
516		cp++;
517	else
518		cp = pwd->pw_shell;
519
520	if (setusercontext(lc, pwd, pwd->pw_uid,
521		LOGIN_SETALL & ~LOGIN_SETGROUP) < 0) {
522		syslog(LOG_ERR, "setusercontext(): %m");
523		exit(1);
524	}
525	login_close(lc);
526	endpwent();
527	if (log_success || pwd->pw_uid == 0) {
528		    syslog(LOG_INFO|LOG_AUTH, "%s@%s as %s: cmd='%.80s'",
529			ruser, rhost, luser, cmdbuf);
530	}
531	execl(pwd->pw_shell, cp, "-c", cmdbuf, (char *)NULL);
532	err(1, "%s", pwd->pw_shell);
533	exit(1);
534}
535
536/*
537 * Report error to client.  Note: can't be used until second socket has
538 * connected to client, or older clients will hang waiting for that
539 * connection first.
540 */
541
542static void
543rshd_errx(int errcode, const char *fmt, ...)
544{
545	va_list ap;
546
547	va_start(ap, fmt);
548
549	if (sent_null == 0)
550		write(STDERR_FILENO, "\1", 1);
551
552	verrx(errcode, fmt, ap);
553	/* NOTREACHED */
554}
555
556void
557getstr(char *buf, int cnt, const char *error)
558{
559	char c;
560
561	do {
562		if (read(STDIN_FILENO, &c, 1) != 1)
563			exit(1);
564		*buf++ = c;
565		if (--cnt == 0) {
566#ifdef USE_BLACKLIST
567			blacklist(1, STDIN_FILENO, "buffer overflow");
568#endif
569			rshd_errx(1, "%s too long", error);
570		}
571	} while (c != 0);
572}
573
574/*
575 * Check whether host h is in our local domain,
576 * defined as sharing the last two components of the domain part,
577 * or the entire domain part if the local domain has only one component.
578 * If either name is unqualified (contains no '.'),
579 * assume that the host is local, as it will be
580 * interpreted as such.
581 */
582int
583local_domain(char *h)
584{
585	char localhost[MAXHOSTNAMELEN];
586	char *p1, *p2;
587
588	localhost[0] = 0;
589	(void) gethostname(localhost, sizeof(localhost) - 1);
590	localhost[sizeof(localhost) - 1] = '\0';
591	/* XXX truncation! */
592	p1 = topdomain(localhost);
593	p2 = topdomain(h);
594	if (p1 == NULL || p2 == NULL || !strcasecmp(p1, p2))
595		return (1);
596	return (0);
597}
598
599char *
600topdomain(char *h)
601{
602	char *p, *maybe = NULL;
603	int dots = 0;
604
605	for (p = h + strlen(h); p >= h; p--) {
606		if (*p == '.') {
607			if (++dots == 2)
608				return (p);
609			maybe = p;
610		}
611	}
612	return (maybe);
613}
614
615void
616usage(void)
617{
618
619	syslog(LOG_ERR, "usage: rshd [-%s]", OPTIONS);
620	exit(2);
621}
622