rshd.c revision 262435 
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/10/libexec/rshd/rshd.c 262435 2014-02-24 08:21:49Z brueffer $");
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
91static struct pam_conv pamc = { openpam_nullconv, NULL };
92static pam_handle_t *pamh;
93static int pam_err;
94
95#define PAM_END { \
96	if ((pam_err = pam_setcred(pamh, PAM_DELETE_CRED)) != PAM_SUCCESS) \
97		syslog(LOG_ERR|LOG_AUTH, "pam_setcred(): %s", pam_strerror(pamh, pam_err)); \
98	if ((pam_err = pam_close_session(pamh,0)) != PAM_SUCCESS) \
99		syslog(LOG_ERR|LOG_AUTH, "pam_close_session(): %s", pam_strerror(pamh, pam_err)); \
100	if ((pam_err = pam_end(pamh, pam_err)) != PAM_SUCCESS) \
101		syslog(LOG_ERR|LOG_AUTH, "pam_end(): %s", pam_strerror(pamh, pam_err)); \
102}
103
104int	keepalive = 1;
105int	log_success;		/* If TRUE, log all successful accesses */
106int	sent_null;
107int	no_delay;
108
109void	 doit(struct sockaddr *);
110static void	 rshd_errx(int, const char *, ...) __printf0like(2, 3);
111void	 getstr(char *, int, const char *);
112int	 local_domain(char *);
113char	*topdomain(char *);
114void	 usage(void);
115
116char	 slash[] = "/";
117char	 bshell[] = _PATH_BSHELL;
118
119#define	OPTIONS	"aDLln"
120
121int
122main(int argc, char *argv[])
123{
124	extern int __check_rhosts_file;
125	struct linger linger;
126	socklen_t fromlen;
127	int ch, on = 1;
128	struct sockaddr_storage from;
129
130	openlog("rshd", LOG_PID | LOG_ODELAY, LOG_DAEMON);
131
132	opterr = 0;
133	while ((ch = getopt(argc, argv, OPTIONS)) != -1)
134		switch (ch) {
135		case 'a':
136			/* ignored for compatibility */
137			break;
138		case 'l':
139			__check_rhosts_file = 0;
140			break;
141		case 'n':
142			keepalive = 0;
143			break;
144		case 'D':
145			no_delay = 1;
146			break;
147		case 'L':
148			log_success = 1;
149			break;
150		case '?':
151		default:
152			usage();
153			break;
154		}
155
156	argc -= optind;
157	argv += optind;
158
159	fromlen = sizeof (from);
160	if (getpeername(0, (struct sockaddr *)&from, &fromlen) < 0) {
161		syslog(LOG_ERR, "getpeername: %m");
162		exit(1);
163	}
164	if (keepalive &&
165	    setsockopt(0, SOL_SOCKET, SO_KEEPALIVE, (char *)&on,
166	    sizeof(on)) < 0)
167		syslog(LOG_WARNING, "setsockopt (SO_KEEPALIVE): %m");
168	linger.l_onoff = 1;
169	linger.l_linger = 60;			/* XXX */
170	if (setsockopt(0, SOL_SOCKET, SO_LINGER, (char *)&linger,
171	    sizeof (linger)) < 0)
172		syslog(LOG_WARNING, "setsockopt (SO_LINGER): %m");
173	if (no_delay &&
174	    setsockopt(0, IPPROTO_TCP, TCP_NODELAY, &on, sizeof(on)) < 0)
175		syslog(LOG_WARNING, "setsockopt (TCP_NODELAY): %m");
176	doit((struct sockaddr *)&from);
177	/* NOTREACHED */
178	return(0);
179}
180
181extern char **environ;
182
183void
184doit(struct sockaddr *fromp)
185{
186	extern char *__rcmd_errstr;	/* syslog hook from libc/net/rcmd.c. */
187	struct passwd *pwd;
188	u_short port;
189	fd_set ready, readfrom;
190	int cc, fd, nfd, pv[2], pid, s;
191	int one = 1;
192	const char *cp, *errorstr;
193	char sig, buf[BUFSIZ];
194	char *cmdbuf, luser[16], ruser[16];
195	char rhost[2 * MAXHOSTNAMELEN + 1];
196	char numericname[INET6_ADDRSTRLEN];
197	int af, srcport;
198	int maxcmdlen;
199	login_cap_t *lc;
200
201	maxcmdlen = (int)sysconf(_SC_ARG_MAX);
202	if (maxcmdlen <= 0 || (cmdbuf = malloc(maxcmdlen)) == NULL)
203		exit(1);
204
205	(void) signal(SIGINT, SIG_DFL);
206	(void) signal(SIGQUIT, SIG_DFL);
207	(void) signal(SIGTERM, SIG_DFL);
208	af = fromp->sa_family;
209	srcport = ntohs(*((in_port_t *)&fromp->sa_data));
210	if (af == AF_INET) {
211		inet_ntop(af, &((struct sockaddr_in *)fromp)->sin_addr,
212		    numericname, sizeof numericname);
213	} else if (af == AF_INET6) {
214		inet_ntop(af, &((struct sockaddr_in6 *)fromp)->sin6_addr,
215		    numericname, sizeof numericname);
216	} else {
217		syslog(LOG_ERR, "malformed \"from\" address (af %d)", af);
218		exit(1);
219	}
220#ifdef IP_OPTIONS
221	if (af == AF_INET) {
222		u_char optbuf[BUFSIZ/3];
223		socklen_t optsize = sizeof(optbuf), ipproto, i;
224		struct protoent *ip;
225
226		if ((ip = getprotobyname("ip")) != NULL)
227			ipproto = ip->p_proto;
228		else
229			ipproto = IPPROTO_IP;
230		if (!getsockopt(0, ipproto, IP_OPTIONS, optbuf, &optsize) &&
231		    optsize != 0) {
232			for (i = 0; i < optsize; ) {
233				u_char c = optbuf[i];
234				if (c == IPOPT_LSRR || c == IPOPT_SSRR) {
235					syslog(LOG_NOTICE,
236					    "connection refused from %s with IP option %s",
237					    numericname,
238					    c == IPOPT_LSRR ? "LSRR" : "SSRR");
239					exit(1);
240				}
241				if (c == IPOPT_EOL)
242					break;
243				i += (c == IPOPT_NOP) ? 1 : optbuf[i+1];
244			}
245		}
246	}
247#endif
248
249	if (srcport >= IPPORT_RESERVED ||
250	    srcport < IPPORT_RESERVED/2) {
251		syslog(LOG_NOTICE|LOG_AUTH,
252		    "connection from %s on illegal port %u",
253		    numericname,
254		    srcport);
255		exit(1);
256	}
257
258	(void) alarm(60);
259	port = 0;
260	s = 0;		/* not set or used if port == 0 */
261	for (;;) {
262		char c;
263		if ((cc = read(STDIN_FILENO, &c, 1)) != 1) {
264			if (cc < 0)
265				syslog(LOG_NOTICE, "read: %m");
266			shutdown(0, SHUT_RDWR);
267			exit(1);
268		}
269		if (c == 0)
270			break;
271		port = port * 10 + c - '0';
272	}
273
274	(void) alarm(0);
275	if (port != 0) {
276		int lport = IPPORT_RESERVED - 1;
277		s = rresvport_af(&lport, af);
278		if (s < 0) {
279			syslog(LOG_ERR, "can't get stderr port: %m");
280			exit(1);
281		}
282		if (port >= IPPORT_RESERVED ||
283		    port < IPPORT_RESERVED/2) {
284			syslog(LOG_NOTICE|LOG_AUTH,
285			    "2nd socket from %s on unreserved port %u",
286			    numericname,
287			    port);
288			exit(1);
289		}
290		*((in_port_t *)&fromp->sa_data) = htons(port);
291		if (connect(s, fromp, fromp->sa_len) < 0) {
292			syslog(LOG_INFO, "connect second port %d: %m", port);
293			exit(1);
294		}
295	}
296
297	errorstr = NULL;
298	realhostname_sa(rhost, sizeof(rhost) - 1, fromp, fromp->sa_len);
299	rhost[sizeof(rhost) - 1] = '\0';
300	/* XXX truncation! */
301
302	(void) alarm(60);
303	getstr(ruser, sizeof(ruser), "ruser");
304	getstr(luser, sizeof(luser), "luser");
305	getstr(cmdbuf, maxcmdlen, "command");
306	(void) alarm(0);
307
308	pam_err = pam_start("rsh", luser, &pamc, &pamh);
309	if (pam_err != PAM_SUCCESS) {
310		syslog(LOG_ERR|LOG_AUTH, "pam_start(): %s",
311		    pam_strerror(pamh, pam_err));
312		rshd_errx(1, "Login incorrect.");
313	}
314
315	if ((pam_err = pam_set_item(pamh, PAM_RUSER, ruser)) != PAM_SUCCESS ||
316	    (pam_err = pam_set_item(pamh, PAM_RHOST, rhost)) != PAM_SUCCESS) {
317		syslog(LOG_ERR|LOG_AUTH, "pam_set_item(): %s",
318		    pam_strerror(pamh, pam_err));
319		rshd_errx(1, "Login incorrect.");
320	}
321
322	pam_err = pam_authenticate(pamh, 0);
323	if (pam_err == PAM_SUCCESS) {
324		if ((pam_err = pam_get_user(pamh, &cp, NULL)) == PAM_SUCCESS) {
325			strncpy(luser, cp, sizeof(luser));
326			luser[sizeof(luser) - 1] = '\0';
327			/* XXX truncation! */
328		}
329		pam_err = pam_acct_mgmt(pamh, 0);
330	}
331	if (pam_err != PAM_SUCCESS) {
332		syslog(LOG_INFO|LOG_AUTH,
333		    "%s@%s as %s: permission denied (%s). cmd='%.80s'",
334		    ruser, rhost, luser, pam_strerror(pamh, pam_err), cmdbuf);
335		rshd_errx(1, "Login incorrect.");
336	}
337
338	setpwent();
339	pwd = getpwnam(luser);
340	if (pwd == NULL) {
341		syslog(LOG_INFO|LOG_AUTH,
342		    "%s@%s as %s: unknown login. cmd='%.80s'",
343		    ruser, rhost, luser, cmdbuf);
344		if (errorstr == NULL)
345			errorstr = "Login incorrect.";
346		rshd_errx(1, errorstr, rhost);
347	}
348
349	lc = login_getpwclass(pwd);
350	if (pwd->pw_uid)
351		auth_checknologin(lc);
352
353	if (chdir(pwd->pw_dir) < 0) {
354		if (chdir("/") < 0 ||
355		    login_getcapbool(lc, "requirehome", !!pwd->pw_uid)) {
356			syslog(LOG_INFO|LOG_AUTH,
357			"%s@%s as %s: no home directory. cmd='%.80s'",
358			ruser, rhost, luser, cmdbuf);
359			rshd_errx(0, "No remote home directory.");
360		}
361		pwd->pw_dir = slash;
362	}
363
364	if (lc != NULL && fromp->sa_family == AF_INET) {	/*XXX*/
365		char	remote_ip[MAXHOSTNAMELEN];
366
367		strncpy(remote_ip, numericname,
368			sizeof(remote_ip) - 1);
369		remote_ip[sizeof(remote_ip) - 1] = 0;
370		/* XXX truncation! */
371		if (!auth_hostok(lc, rhost, remote_ip)) {
372			syslog(LOG_INFO|LOG_AUTH,
373			    "%s@%s as %s: permission denied (%s). cmd='%.80s'",
374			    ruser, rhost, luser, __rcmd_errstr,
375			    cmdbuf);
376			rshd_errx(1, "Login incorrect.");
377		}
378		if (!auth_timeok(lc, time(NULL)))
379			rshd_errx(1, "Logins not available right now");
380	}
381
382	/*
383	 * PAM modules might add supplementary groups in
384	 * pam_setcred(), so initialize them first.
385	 * But we need to open the session as root.
386	 */
387	if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) != 0) {
388		syslog(LOG_ERR, "setusercontext: %m");
389		exit(1);
390	}
391
392	if ((pam_err = pam_open_session(pamh, 0)) != PAM_SUCCESS) {
393		syslog(LOG_ERR, "pam_open_session: %s", pam_strerror(pamh, pam_err));
394	} else if ((pam_err = pam_setcred(pamh, PAM_ESTABLISH_CRED)) != PAM_SUCCESS) {
395		syslog(LOG_ERR, "pam_setcred: %s", pam_strerror(pamh, pam_err));
396	}
397
398	(void) write(STDERR_FILENO, "\0", 1);
399	sent_null = 1;
400
401	if (port) {
402		if (pipe(pv) < 0)
403			rshd_errx(1, "Can't make pipe.");
404		pid = fork();
405		if (pid == -1)
406			rshd_errx(1, "Can't fork; try again.");
407		if (pid) {
408			(void) close(0);
409			(void) close(1);
410			(void) close(2);
411			(void) close(pv[1]);
412
413			FD_ZERO(&readfrom);
414			FD_SET(s, &readfrom);
415			FD_SET(pv[0], &readfrom);
416			if (pv[0] > s)
417				nfd = pv[0];
418			else
419				nfd = s;
420				ioctl(pv[0], FIONBIO, (char *)&one);
421
422			/* should set s nbio! */
423			nfd++;
424			do {
425				ready = readfrom;
426				if (select(nfd, &ready, (fd_set *)0,
427				  (fd_set *)0, (struct timeval *)0) < 0)
428					break;
429				if (FD_ISSET(s, &ready)) {
430					int	ret;
431						ret = read(s, &sig, 1);
432				if (ret <= 0)
433					FD_CLR(s, &readfrom);
434				else
435					killpg(pid, sig);
436				}
437				if (FD_ISSET(pv[0], &ready)) {
438					errno = 0;
439					cc = read(pv[0], buf, sizeof(buf));
440					if (cc <= 0) {
441						shutdown(s, SHUT_RDWR);
442						FD_CLR(pv[0], &readfrom);
443					} else {
444						(void)write(s, buf, cc);
445					}
446				}
447
448			} while (FD_ISSET(s, &readfrom) ||
449			    FD_ISSET(pv[0], &readfrom));
450			PAM_END;
451			exit(0);
452		}
453		(void) close(s);
454		(void) close(pv[0]);
455		dup2(pv[1], 2);
456		close(pv[1]);
457	}
458	else {
459		pid = fork();
460		if (pid == -1)
461			rshd_errx(1, "Can't fork; try again.");
462		if (pid) {
463			/* Parent. */
464			while (wait(NULL) > 0 || errno == EINTR)
465				/* nothing */ ;
466			PAM_END;
467			exit(0);
468		}
469	}
470
471	for (fd = getdtablesize(); fd > 2; fd--)
472		(void) close(fd);
473	if (setsid() == -1)
474		syslog(LOG_ERR, "setsid() failed: %m");
475	if (setlogin(pwd->pw_name) < 0)
476		syslog(LOG_ERR, "setlogin() failed: %m");
477
478	if (*pwd->pw_shell == '\0')
479		pwd->pw_shell = bshell;
480	(void) pam_setenv(pamh, "HOME", pwd->pw_dir, 1);
481	(void) pam_setenv(pamh, "SHELL", pwd->pw_shell, 1);
482	(void) pam_setenv(pamh, "USER", pwd->pw_name, 1);
483	(void) pam_setenv(pamh, "PATH", _PATH_DEFPATH, 1);
484	environ = pam_getenvlist(pamh);
485	(void) pam_end(pamh, pam_err);
486	cp = strrchr(pwd->pw_shell, '/');
487	if (cp)
488		cp++;
489	else
490		cp = pwd->pw_shell;
491
492	if (setusercontext(lc, pwd, pwd->pw_uid,
493		LOGIN_SETALL & ~LOGIN_SETGROUP) < 0) {
494		syslog(LOG_ERR, "setusercontext(): %m");
495		exit(1);
496	}
497	login_close(lc);
498	endpwent();
499	if (log_success || pwd->pw_uid == 0) {
500		    syslog(LOG_INFO|LOG_AUTH, "%s@%s as %s: cmd='%.80s'",
501			ruser, rhost, luser, cmdbuf);
502	}
503	execl(pwd->pw_shell, cp, "-c", cmdbuf, (char *)NULL);
504	err(1, "%s", pwd->pw_shell);
505	exit(1);
506}
507
508/*
509 * Report error to client.  Note: can't be used until second socket has
510 * connected to client, or older clients will hang waiting for that
511 * connection first.
512 */
513
514static void
515rshd_errx(int errcode, const char *fmt, ...)
516{
517	va_list ap;
518
519	va_start(ap, fmt);
520
521	if (sent_null == 0)
522		write(STDERR_FILENO, "\1", 1);
523
524	verrx(errcode, fmt, ap);
525	/* NOTREACHED */
526}
527
528void
529getstr(char *buf, int cnt, const char *error)
530{
531	char c;
532
533	do {
534		if (read(STDIN_FILENO, &c, 1) != 1)
535			exit(1);
536		*buf++ = c;
537		if (--cnt == 0)
538			rshd_errx(1, "%s too long", error);
539	} while (c != 0);
540}
541
542/*
543 * Check whether host h is in our local domain,
544 * defined as sharing the last two components of the domain part,
545 * or the entire domain part if the local domain has only one component.
546 * If either name is unqualified (contains no '.'),
547 * assume that the host is local, as it will be
548 * interpreted as such.
549 */
550int
551local_domain(char *h)
552{
553	char localhost[MAXHOSTNAMELEN];
554	char *p1, *p2;
555
556	localhost[0] = 0;
557	(void) gethostname(localhost, sizeof(localhost) - 1);
558	localhost[sizeof(localhost) - 1] = '\0';
559	/* XXX truncation! */
560	p1 = topdomain(localhost);
561	p2 = topdomain(h);
562	if (p1 == NULL || p2 == NULL || !strcasecmp(p1, p2))
563		return (1);
564	return (0);
565}
566
567char *
568topdomain(char *h)
569{
570	char *p, *maybe = NULL;
571	int dots = 0;
572
573	for (p = h + strlen(h); p >= h; p--) {
574		if (*p == '.') {
575			if (++dots == 2)
576				return (p);
577			maybe = p;
578		}
579	}
580	return (maybe);
581}
582
583void
584usage(void)
585{
586
587	syslog(LOG_ERR, "usage: rshd [-%s]", OPTIONS);
588	exit(2);
589}
590