xref: /dragonfly/usr.sbin/sliplogin/sliplogin.c (revision 0de61e28)
1 /*-
2  * Copyright (c) 1990, 1993
3  *	The Regents of the University of California.  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. Neither the name of the University nor the names of its contributors
14  *    may be used to endorse or promote products derived from this software
15  *    without specific prior written permission.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  *
29  * @(#) Copyright (c) 1990, 1993 The Regents of the University of California.  All rights reserved.
30  * @(#)sliplogin.c        8.2 (Berkeley) 2/1/94
31  * $FreeBSD: src/usr.sbin/sliplogin/sliplogin.c,v 1.9.6.2 2001/07/19 05:21:28 kris Exp $
32  */
33 
34 /*
35  * sliplogin.c
36  * [MUST BE RUN SUID, SLOPEN DOES A SUSER()!]
37  *
38  * This program initializes its own tty port to be an async TCP/IP interface.
39  * It sets the line discipline to slip, invokes a shell script to initialize
40  * the network interface, then pauses forever waiting for hangup.
41  *
42  * It is a remote descendant of several similar programs with incestuous ties:
43  * - Kirk Smith's slipconf, modified by Richard Johnsson @ DEC WRL.
44  * - slattach, probably by Rick Adams but touched by countless hordes.
45  * - the original sliplogin for 4.2bsd, Doug Kingston the mover behind it.
46  *
47  * There are two forms of usage:
48  *
49  * "sliplogin"
50  * Invoked simply as "sliplogin", the program looks up the username
51  * in the file /etc/slip.hosts.
52  * If an entry is found, the line on fd0 is configured for SLIP operation
53  * as specified in the file.
54  *
55  * "sliplogin IPhostlogin </dev/ttyb"
56  * Invoked by root with a username, the name is looked up in the
57  * /etc/slip.hosts file and if found fd0 is configured as in case 1.
58  */
59 
60 #include <sys/param.h>
61 #include <sys/socket.h>
62 #include <sys/stat.h>
63 #include <syslog.h>
64 #include <netdb.h>
65 
66 #include <termios.h>
67 #include <sys/ioctl.h>
68 #include <net/slip.h>
69 #include <net/if.h>
70 
71 #include <fcntl.h>
72 #include <stdio.h>
73 #include <errno.h>
74 #include <ctype.h>
75 #include <paths.h>
76 #include <string.h>
77 #include <unistd.h>
78 #include <stdlib.h>
79 #include <signal.h>
80 #include "pathnames.h"
81 
82 extern char **environ;
83 
84 static char *restricted_environ[] = {
85 	"PATH=" _PATH_STDPATH,
86 	NULL
87 };
88 
89 static int	unit;
90 static int	slip_mode;
91 static speed_t	speed;
92 static int	uid;
93 static int	keepal;
94 static int	outfill;
95 static int	slunit;
96 static char	loginargs[BUFSIZ];
97 static char	loginfile[MAXPATHLEN];
98 static char	loginname[BUFSIZ];
99 static char	raddr[32];			/* remote address */
100 static char	ifname[IFNAMSIZ];		/* interface name */
101 static char	pidfilename[MAXPATHLEN];	/* name of pid file */
102 static char	iffilename[MAXPATHLEN];		/* name of if file */
103 static pid_t	pid;				/* our pid */
104 
105 static char *
106 make_ipaddr(void)
107 {
108 	static char address[20] ="";
109 	struct hostent *he;
110 	unsigned long ipaddr;
111 
112 	address[0] = '\0';
113 	if ((he = gethostbyname(raddr)) != NULL) {
114 		ipaddr = ntohl(*(long *)he->h_addr_list[0]);
115 		sprintf(address, "%hu.%hu.%hu.%hu",
116 		    (ushort)(ipaddr >> 24),
117 		    (ushort)((ipaddr & 0x00ff0000) >> 16),
118 		    (ushort)((ipaddr & 0x0000ff00) >> 8),
119 		    (ushort)((ipaddr & 0x000000ff)));
120 	}
121 
122 	return address;
123 }
124 
125 static struct slip_modes {
126 	const char	*sm_name;
127 	int		sm_or_flag;
128 	int		sm_and_flag;
129 } modes[] = {
130 	{ "normal",	0,		0	  },
131 	{ "compress",	IFF_LINK0,	IFF_LINK2 },
132 	{ "noicmp",	IFF_LINK1,	0	  },
133 	{ "autocomp",	IFF_LINK2,	IFF_LINK0 }
134 };
135 
136 static void
137 findid(char *name)
138 {
139 	FILE *fp;
140 	static char slopt[5][16];
141 	static char laddr[16];
142 	static char mask[16];
143 	char   slparmsfile[MAXPATHLEN];
144 	char user[16];
145 	char buf[128];
146 	int i, j, n;
147 
148 	environ = restricted_environ; /* minimal protection for system() */
149 
150 	strncpy(loginname, name, sizeof(loginname)-1);
151 	loginname[sizeof(loginname)-1] = '\0';
152 
153 	if ((fp = fopen(_PATH_ACCESS, "r")) == NULL) {
154 	accfile_err:
155 		syslog(LOG_ERR, "%s: %m\n", _PATH_ACCESS);
156 		exit(1);
157 	}
158 	while (fgets(loginargs, sizeof(loginargs) - 1, fp)) {
159 		if (ferror(fp))
160 			goto accfile_err;
161 		if (loginargs[0] == '#' || isspace(loginargs[0]))
162 			continue;
163 		n = sscanf(loginargs, "%15s%*[ \t]%15s%*[ \t]%15s%*[ \t]%15s%*[ \t]%15s%*[ \t]%15s%*[ \t]%15s%*[ \t]%15s%*[ \t]%15s\n",
164                         user, laddr, raddr, mask, slopt[0], slopt[1],
165 			slopt[2], slopt[3], slopt[4]);
166 		if (n < 4) {
167 			syslog(LOG_ERR, "%s: wrong format\n", _PATH_ACCESS);
168 			exit(1);
169 		}
170 		if (strcmp(user, name) != 0)
171 			continue;
172 
173 		fclose(fp);
174 
175 		slip_mode = 0;
176 		for (i = 0; i < n - 4; i++) {
177 			for (j = 0; j < (int)NELEM(modes); j++) {
178 				if (strcmp(modes[j].sm_name, slopt[i]) == 0) {
179 					slip_mode |= (modes[j].sm_or_flag);
180 					slip_mode &= ~(modes[j].sm_and_flag);
181 					break;
182 				}
183 			}
184 		}
185 
186 		/*
187 		 * we've found the guy we're looking for -- see if
188 		 * there's a login file we can use.  First check for
189 		 * one specific to this host.  If none found, try for
190 		 * a generic one.
191 		 */
192 		snprintf(loginfile, sizeof(loginfile), "%s.%s", _PATH_SLOGIN, name);
193 		if (access(loginfile, R_OK|X_OK) != 0) {
194 			strncpy(loginfile, _PATH_SLOGIN, sizeof(loginfile)-1);
195 			loginfile[sizeof(loginfile)-1] = '\0';
196 			if (access(loginfile, R_OK|X_OK)) {
197 				syslog(LOG_ERR,
198 				       "access denied for %s - no %s\n",
199 				       name, _PATH_SLOGIN);
200 				exit(5);
201 			}
202 		}
203 		snprintf(slparmsfile, sizeof(slparmsfile), "%s.%s", _PATH_SLPARMS, name);
204 		if (access(slparmsfile, R_OK|X_OK) != 0) {
205 			strncpy(slparmsfile, _PATH_SLPARMS, sizeof(slparmsfile)-1);
206 			slparmsfile[sizeof(slparmsfile)-1] = '\0';
207 			if (access(slparmsfile, R_OK|X_OK))
208 				*slparmsfile = '\0';
209 		}
210 		keepal = outfill = 0;
211 		slunit = -1;
212 		if (*slparmsfile) {
213 			if ((fp = fopen(slparmsfile, "r")) == NULL) {
214 			slfile_err:
215 				syslog(LOG_ERR, "%s: %m\n", slparmsfile);
216 				exit(1);
217 			}
218 			n = 0;
219 			while (fgets(buf, sizeof(buf) - 1, fp) != NULL) {
220 				if (ferror(fp))
221 					goto slfile_err;
222 				if (buf[0] == '#' || isspace(buf[0]))
223 					continue;
224 				n = sscanf(buf, "%d %d %d", &keepal, &outfill, &slunit);
225 				if (n < 1) {
226 				slwrong_fmt:
227 					syslog(LOG_ERR, "%s: wrong format\n", slparmsfile);
228 					exit(1);
229 				}
230 				fclose(fp);
231 				break;
232 			}
233 			if (n == 0)
234 				goto slwrong_fmt;
235 		}
236 
237 		return;
238 	}
239 	syslog(LOG_ERR, "SLIP access denied for %s\n", name);
240 	exit(4);
241 	/* NOTREACHED */
242 }
243 
244 static const char *
245 sigstr(int s)
246 {
247 	static char buf[32];
248 
249 	switch (s) {
250 	case SIGHUP:	return("HUP");
251 	case SIGINT:	return("INT");
252 	case SIGQUIT:	return("QUIT");
253 	case SIGILL:	return("ILL");
254 	case SIGTRAP:	return("TRAP");
255 	case SIGIOT:	return("IOT");
256 	case SIGEMT:	return("EMT");
257 	case SIGFPE:	return("FPE");
258 	case SIGKILL:	return("KILL");
259 	case SIGBUS:	return("BUS");
260 	case SIGSEGV:	return("SEGV");
261 	case SIGSYS:	return("SYS");
262 	case SIGPIPE:	return("PIPE");
263 	case SIGALRM:	return("ALRM");
264 	case SIGTERM:	return("TERM");
265 	case SIGURG:	return("URG");
266 	case SIGSTOP:	return("STOP");
267 	case SIGTSTP:	return("TSTP");
268 	case SIGCONT:	return("CONT");
269 	case SIGCHLD:	return("CHLD");
270 	case SIGTTIN:	return("TTIN");
271 	case SIGTTOU:	return("TTOU");
272 	case SIGIO:	return("IO");
273 	case SIGXCPU:	return("XCPU");
274 	case SIGXFSZ:	return("XFSZ");
275 	case SIGVTALRM:	return("VTALRM");
276 	case SIGPROF:	return("PROF");
277 	case SIGWINCH:	return("WINCH");
278 #ifdef SIGLOST
279 	case SIGLOST:	return("LOST");
280 #endif
281 	case SIGUSR1:	return("USR1");
282 	case SIGUSR2:	return("USR2");
283 	}
284 	snprintf(buf, sizeof(buf), "sig %d", s);
285 	return(buf);
286 }
287 
288 static void
289 hup_handler(int s)
290 {
291 	char logoutfile[MAXPATHLEN];
292 
293 	close(0);
294 	seteuid(0);
295 	snprintf(logoutfile, sizeof(logoutfile), "%s.%.990s", _PATH_SLOGOUT, loginname);
296 	if (access(logoutfile, R_OK|X_OK) != 0) {
297 		strncpy(logoutfile, _PATH_SLOGOUT, sizeof(logoutfile)-1);
298 		logoutfile[sizeof(logoutfile)-1] = '\0';
299 	}
300 	if (access(logoutfile, R_OK|X_OK) == 0) {
301 		char logincmd[2*MAXPATHLEN+32];
302 
303 		snprintf(logincmd, sizeof(logincmd), "%s %d %u %s", logoutfile, unit, speed, loginargs);
304 		system(logincmd);
305 	}
306 	syslog(LOG_INFO, "closed %s slip unit %d (%s)\n", loginname, unit,
307 	       sigstr(s));
308 	if (unlink(pidfilename) < 0 && errno != ENOENT)
309 		syslog(LOG_WARNING, "unable to delete pid file: %m");
310 	if (unlink(iffilename) < 0 && errno != ENOENT)
311 		syslog(LOG_WARNING, "unable to delete if file: %m");
312 	exit(1);
313 	/* NOTREACHED */
314 }
315 
316 
317 /* Modify the slip line mode and add any compression or no-icmp flags. */
318 static void
319 line_flags(int _unit)
320 {
321 	struct ifreq ifr;
322 	int s;
323 
324 	/* open a socket as the handle to the interface */
325 	s = socket(AF_INET, SOCK_DGRAM, 0);
326 	if (s < 0) {
327 		syslog(LOG_ERR, "socket: %m");
328 		exit(1);
329 	}
330 	sprintf(ifr.ifr_name, "sl%d", _unit);
331 
332 	/* get the flags for the interface */
333 	if (ioctl(s, SIOCGIFFLAGS, (caddr_t)&ifr) < 0) {
334 		syslog(LOG_ERR, "ioctl (SIOCGIFFLAGS): %m");
335 		exit(1);
336         }
337 
338 	/* Assert any compression or no-icmp flags. */
339 #define SLMASK (~(IFF_LINK0 | IFF_LINK1 | IFF_LINK2))
340 	ifr.ifr_flags &= SLMASK;
341 	ifr.ifr_flags |= slip_mode;
342 	if (ioctl(s, SIOCSIFFLAGS, (caddr_t)&ifr) < 0) {
343 		syslog(LOG_ERR, "ioctl (SIOCSIFFLAGS): %m");
344 		exit(1);
345 	}
346         close(s);
347 }
348 
349 int
350 main(int argc, char *argv[])
351 {
352 	int fd, s, ldisc;
353 	char *name;
354 	struct termios tios;
355 	char logincmd[2*BUFSIZ+32];
356 
357 	FILE *pidfile;				/* pid file */
358 	FILE *iffile;				/* interfaces file */
359 	char *p;
360 	int n;
361 	char devnam[MAXPATHLEN] = _PATH_TTY;   /* Device name */
362 
363 	if ((name = strrchr(argv[0], '/')) == NULL)
364 		name = argv[0];
365 	s = getdtablesize();
366 	for (fd = 3 ; fd < s ; fd++)
367 		close(fd);
368 	openlog(name, LOG_PID|LOG_PERROR, LOG_DAEMON);
369 	uid = getuid();
370 	if (argc > 1) {
371 		findid(argv[1]);
372 
373 		/*
374 		 * Disassociate from current controlling terminal, if any,
375 		 * and ensure that the slip line is our controlling terminal.
376 		 */
377 		if (daemon(1, 1)) {
378 			syslog(LOG_ERR, "daemon(1, 1): %m");
379 			exit(1);
380 		}
381 		if (argc > 2) {
382 			if ((fd = open(argv[2], O_RDWR)) == -1) {
383 				syslog(LOG_ERR, "open %s: %m", argv[2]);
384 				exit(2);
385 			}
386 			dup2(fd, 0);
387 			if (fd > 2)
388 				close(fd);
389 		}
390 		if (ioctl(0, TIOCSCTTY, 0) == -1) {
391 			syslog(LOG_ERR, "ioctl (TIOCSCTTY): %m");
392 			exit(1);
393 		}
394 		if (tcsetpgrp(0, getpid()) < 0) {
395 			syslog(LOG_ERR, "tcsetpgrp failed: %m");
396 			exit(1);
397 		}
398 	} else {
399 		if ((name = getlogin()) == NULL) {
400 			syslog(LOG_ERR, "access denied - login name not found\n");
401 			exit(1);
402 		}
403 		findid(name);
404 	}
405 	fchmod(0, 0600);
406 	fprintf(stderr, "starting slip login for %s\n", loginname);
407         fprintf(stderr, "your address is %s\n\n", make_ipaddr());
408 
409 	fflush(stderr);
410 	sleep(1);
411 
412 	/* set up the line parameters */
413 	if (tcgetattr(0, &tios) < 0) {
414 		syslog(LOG_ERR, "tcgetattr: %m");
415 		exit(1);
416 	}
417 	cfmakeraw(&tios);
418 	if (tcsetattr(0, TCSAFLUSH, &tios) < 0) {
419 		syslog(LOG_ERR, "tcsetattr: %m");
420 		exit(1);
421 	}
422 	speed = cfgetispeed(&tios);
423 
424 	ldisc = SLIPDISC;
425 	if (ioctl(0, TIOCSETD, &ldisc) < 0) {
426 		syslog(LOG_ERR, "ioctl(TIOCSETD): %m");
427 		exit(1);
428 	}
429 	if (slunit >= 0 && ioctl(0, SLIOCSUNIT, &slunit) < 0) {
430 		syslog(LOG_ERR, "ioctl (SLIOCSUNIT): %m");
431 		exit(1);
432 	}
433 	/* find out what unit number we were assigned */
434 	if (ioctl(0, SLIOCGUNIT, &unit) < 0) {
435 		syslog(LOG_ERR, "ioctl (SLIOCGUNIT): %m");
436 		exit(1);
437 	}
438 	signal(SIGHUP, hup_handler);
439 	signal(SIGTERM, hup_handler);
440 
441 	if (keepal > 0) {
442 		signal(SIGURG, hup_handler);
443 		if (ioctl(0, SLIOCSKEEPAL, &keepal) < 0) {
444 			syslog(LOG_ERR, "ioctl(SLIOCSKEEPAL): %m");
445 			exit(1);
446 		}
447 	}
448 	if (outfill > 0 && ioctl(0, SLIOCSOUTFILL, &outfill) < 0) {
449 		syslog(LOG_ERR, "ioctl(SLIOCSOUTFILL): %m");
450 		exit(1);
451 	}
452 
453         /* write pid to file */
454 	pid = getpid();
455 	sprintf(ifname, "sl%d", unit);
456 	sprintf(pidfilename, "%s%s.pid", _PATH_VARRUN, ifname);
457 	if ((pidfile = fopen(pidfilename, "w")) != NULL) {
458 		fprintf(pidfile, "%d\n", pid);
459 		fclose(pidfile);
460 	} else {
461 		syslog(LOG_ERR, "Failed to create pid file %s: %m",
462 				pidfilename);
463 		pidfilename[0] = 0;
464 	}
465 
466         /* write interface unit number to file */
467 	p = ttyname(0);
468 	if (p)
469 		strcpy(devnam, p);
470 	for (n = strlen(devnam); n > 0; n--)
471 		if (devnam[n] == '/') {
472 			n++;
473 			break;
474 		}
475 	sprintf(iffilename, "%s%s.if", _PATH_VARRUN, &devnam[n]);
476 	if ((iffile = fopen(iffilename, "w")) != NULL) {
477 		fprintf(iffile, "sl%d\n", unit);
478 		fclose(iffile);
479 	} else {
480 		syslog(LOG_ERR, "Failed to create if file %s: %m", iffilename);
481 		iffilename[0] = 0;
482 	}
483 
484 
485 	syslog(LOG_INFO, "attaching slip unit %d for %s\n", unit, loginname);
486 	snprintf(logincmd, sizeof(logincmd), "%s %d %u %s", loginfile, unit, speed,
487 		 loginargs);
488 	/*
489 	 * aim stdout and errout at /dev/null so logincmd output won't
490 	 * babble into the slip tty line.
491 	 */
492 	close(1);
493 	if ((fd = open(_PATH_DEVNULL, O_WRONLY)) != 1) {
494 		if (fd < 0) {
495 			syslog(LOG_ERR, "open %s: %m", _PATH_DEVNULL);
496 			exit(1);
497 		}
498 		dup2(fd, 1);
499 		close(fd);
500 	}
501 	dup2(1, 2);
502 
503 	/*
504 	 * Run login and logout scripts as root (real and effective);
505 	 * current route(8) is setuid root, and checks the real uid
506 	 * to see whether changes are allowed (or just "route get").
507 	 */
508 	setuid(0);
509 	if ((s = system(logincmd)) == -1) {
510 		syslog(LOG_ERR, "%s login failed: exit status %d from %s",
511 		       loginname, s, loginfile);
512 		exit(6);
513 	}
514 
515 	/* Handle any compression or no-icmp flags. */
516 	line_flags(unit);
517 
518 	/* reset uid to users' to allow the user to give a signal. */
519 	seteuid(uid);
520 	/* twiddle thumbs until we get a signal */
521 	while (1)
522 		sigpause(0);
523 
524 	/* NOTREACHED */
525 }
526