builtins.c revision 69532 
1/*-
2 * Copyright (c) 1983, 1991, 1993, 1994
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 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 *
26 * $FreeBSD: head/usr.sbin/inetd/builtins.c 69532 2000-12-02 21:18:11Z green $
27 *
28 */
29
30#include <sys/filio.h>
31#include <sys/ioccom.h>
32#include <sys/param.h>
33#include <sys/stat.h>
34#include <sys/socket.h>
35#include <sys/sysctl.h>
36#include <sys/ucred.h>
37#include <sys/uio.h>
38#include <sys/utsname.h>
39
40#include <ctype.h>
41#include <err.h>
42#include <errno.h>
43#include <fcntl.h>
44#include <limits.h>
45#include <pwd.h>
46#include <signal.h>
47#include <stdlib.h>
48#include <string.h>
49#include <sysexits.h>
50#include <syslog.h>
51#include <unistd.h>
52
53#include "inetd.h"
54
55extern int	 debug;
56extern struct servtab *servtab;
57
58char ring[128];
59char *endring;
60
61int check_loop __P((struct sockaddr *, struct servtab *sep));
62void inetd_setproctitle __P((char *, int));
63
64struct biltin biltins[] = {
65	/* Echo received data */
66	{ "echo",	SOCK_STREAM,	1, -1,	echo_stream },
67	{ "echo",	SOCK_DGRAM,	0, 1,	echo_dg },
68
69	/* Internet /dev/null */
70	{ "discard",	SOCK_STREAM,	1, -1,	discard_stream },
71	{ "discard",	SOCK_DGRAM,	0, 1,	discard_dg },
72
73	/* Return 32 bit time since 1970 */
74	{ "time",	SOCK_STREAM,	0, -1,	machtime_stream },
75	{ "time",	SOCK_DGRAM,	0, 1,	machtime_dg },
76
77	/* Return human-readable time */
78	{ "daytime",	SOCK_STREAM,	0, -1,	daytime_stream },
79	{ "daytime",	SOCK_DGRAM,	0, 1,	daytime_dg },
80
81	/* Familiar character generator */
82	{ "chargen",	SOCK_STREAM,	1, -1,	chargen_stream },
83	{ "chargen",	SOCK_DGRAM,	0, 1,	chargen_dg },
84
85	{ "tcpmux",	SOCK_STREAM,	1, -1,	(void (*)())tcpmux },
86
87	{ "auth",	SOCK_STREAM,	1, -1,	ident_stream },
88
89	{ NULL }
90};
91
92/*
93 * RFC864 Character Generator Protocol. Generates character data without
94 * any regard for input.
95 */
96
97void
98initring()
99{
100	int i;
101
102	endring = ring;
103
104	for (i = 0; i <= 128; ++i)
105		if (isprint(i))
106			*endring++ = i;
107}
108
109/* ARGSUSED */
110void
111chargen_dg(s, sep)		/* Character generator */
112	int s;
113	struct servtab *sep;
114{
115	struct sockaddr_storage ss;
116	static char *rs;
117	int len;
118	socklen_t size;
119	char text[LINESIZ+2];
120
121	if (endring == 0) {
122		initring();
123		rs = ring;
124	}
125
126	size = sizeof(ss);
127	if (recvfrom(s, text, sizeof(text), 0,
128		     (struct sockaddr *)&ss, &size) < 0)
129		return;
130
131	if (check_loop((struct sockaddr *)&ss, sep))
132		return;
133
134	if ((len = endring - rs) >= LINESIZ)
135		memmove(text, rs, LINESIZ);
136	else {
137		memmove(text, rs, len);
138		memmove(text + len, ring, LINESIZ - len);
139	}
140	if (++rs == endring)
141		rs = ring;
142	text[LINESIZ] = '\r';
143	text[LINESIZ + 1] = '\n';
144	(void) sendto(s, text, sizeof(text), 0, (struct sockaddr *)&ss, size);
145}
146
147/* ARGSUSED */
148void
149chargen_stream(s, sep)		/* Character generator */
150	int s;
151	struct servtab *sep;
152{
153	int len;
154	char *rs, text[LINESIZ+2];
155
156	inetd_setproctitle(sep->se_service, s);
157
158	if (!endring) {
159		initring();
160		rs = ring;
161	}
162
163	text[LINESIZ] = '\r';
164	text[LINESIZ + 1] = '\n';
165	for (rs = ring;;) {
166		if ((len = endring - rs) >= LINESIZ)
167			memmove(text, rs, LINESIZ);
168		else {
169			memmove(text, rs, len);
170			memmove(text + len, ring, LINESIZ - len);
171		}
172		if (++rs == endring)
173			rs = ring;
174		if (write(s, text, sizeof(text)) != sizeof(text))
175			break;
176	}
177	exit(0);
178}
179
180/*
181 * RFC867 Daytime Protocol. Sends the current date and time as an ascii
182 * character string without any regard for input.
183 */
184
185/* ARGSUSED */
186void
187daytime_dg(s, sep)		/* Return human-readable time of day */
188	int s;
189	struct servtab *sep;
190{
191	char buffer[256];
192	time_t clock;
193	struct sockaddr_storage ss;
194	socklen_t size;
195
196	clock = time((time_t *) 0);
197
198	size = sizeof(ss);
199	if (recvfrom(s, buffer, sizeof(buffer), 0,
200		     (struct sockaddr *)&ss, &size) < 0)
201		return;
202
203	if (check_loop((struct sockaddr *)&ss, sep))
204		return;
205
206	(void) sprintf(buffer, "%.24s\r\n", ctime(&clock));
207	(void) sendto(s, buffer, strlen(buffer), 0,
208		      (struct sockaddr *)&ss, size);
209}
210
211/* ARGSUSED */
212void
213daytime_stream(s, sep)		/* Return human-readable time of day */
214	int s;
215	struct servtab *sep;
216{
217	char buffer[256];
218	time_t clock;
219
220	clock = time((time_t *) 0);
221
222	(void) sprintf(buffer, "%.24s\r\n", ctime(&clock));
223	(void) send(s, buffer, strlen(buffer), MSG_EOF);
224}
225
226/*
227 * RFC863 Discard Protocol. Any data received is thrown away and no response
228 * is sent.
229 */
230
231/* ARGSUSED */
232void
233discard_dg(s, sep)		/* Discard service -- ignore data */
234	int s;
235	struct servtab *sep;
236{
237	char buffer[BUFSIZE];
238
239	(void) read(s, buffer, sizeof(buffer));
240}
241
242/* ARGSUSED */
243void
244discard_stream(s, sep)		/* Discard service -- ignore data */
245	int s;
246	struct servtab *sep;
247{
248	int ret;
249	char buffer[BUFSIZE];
250
251	inetd_setproctitle(sep->se_service, s);
252	while (1) {
253		while ((ret = read(s, buffer, sizeof(buffer))) > 0)
254			;
255		if (ret == 0 || errno != EINTR)
256			break;
257	}
258	exit(0);
259}
260
261/*
262 * RFC862 Echo Protocol. Any data received is sent back to the sender as
263 * received.
264 */
265
266/* ARGSUSED */
267void
268echo_dg(s, sep)			/* Echo service -- echo data back */
269	int s;
270	struct servtab *sep;
271{
272	char buffer[BUFSIZE];
273	int i;
274	socklen_t size;
275	struct sockaddr_storage ss;
276
277	size = sizeof(ss);
278	if ((i = recvfrom(s, buffer, sizeof(buffer), 0,
279			  (struct sockaddr *)&ss, &size)) < 0)
280		return;
281
282	if (check_loop((struct sockaddr *)&ss, sep))
283		return;
284
285	(void) sendto(s, buffer, i, 0, (struct sockaddr *)&ss, size);
286}
287
288/* ARGSUSED */
289void
290echo_stream(s, sep)		/* Echo service -- echo data back */
291	int s;
292	struct servtab *sep;
293{
294	char buffer[BUFSIZE];
295	int i;
296
297	inetd_setproctitle(sep->se_service, s);
298	while ((i = read(s, buffer, sizeof(buffer))) > 0 &&
299	    write(s, buffer, i) > 0)
300		;
301	exit(0);
302}
303
304/*
305 * RFC1413 Identification Protocol. Given a TCP port number pair, return a
306 * character string which identifies the owner of that connection on the
307 * server's system. Extended to allow for ~/.fakeid support and ~/.noident
308 * support.
309 */
310
311/* ARGSUSED */
312void
313iderror(lport, fport, s, er)	/* Generic ident_stream error-sending func */
314	int lport, fport, s, er;
315{
316	char *p;
317
318	asprintf(&p, "%d , %d : ERROR : %s\r\n", lport, fport,
319	    er == -1 ? "HIDDEN-USER" : er ? strerror(er) : "UNKNOWN-ERROR");
320	if (p == NULL) {
321		syslog(LOG_ERR, "asprintf: %m");
322		exit(EX_OSERR);
323	}
324	send(s, p, strlen(p), MSG_EOF);
325	free(p);
326
327	exit(0);
328}
329
330/* ARGSUSED */
331void
332ident_stream(s, sep)		/* Ident service (AKA "auth") */
333	int s;
334	struct servtab *sep;
335{
336	struct utsname un;
337	struct stat sb;
338	struct sockaddr_in sin[2];
339#ifdef INET6
340	struct sockaddr_in6 sin6[2];
341#endif
342	struct sockaddr_storage ss[2];
343	struct ucred uc;
344	struct timeval tv = {
345		10,
346		0
347	}, to;
348	struct passwd *pw = NULL;
349	fd_set fdset;
350	char buf[BUFSIZE], *cp = NULL, *p, **av, *osname = NULL, garbage[7], e;
351	char *fallback = NULL;
352	socklen_t socklen;
353	ssize_t ssize;
354	size_t size, bufsiz;
355	int c, fflag = 0, nflag = 0, rflag = 0, argc = 0, usedfallback = 0;
356	int gflag = 0, getcredfail = 0, onreadlen;
357	u_short lport, fport;
358
359	inetd_setproctitle(sep->se_service, s);
360	/*
361	 * Reset getopt() since we are a fork() but not an exec() from
362	 * a parent which used getopt() already.
363	 */
364	optind = 1;
365	optreset = 1;
366	/*
367	 * Take the internal argument vector and count it out to make an
368	 * argument count for getopt. This can be used for any internal
369	 * service to read arguments and use getopt() easily.
370	 */
371	for (av = sep->se_argv; *av; av++)
372		argc++;
373	if (argc) {
374		int sec, usec;
375		size_t i;
376		u_int32_t random;
377
378		while ((c = getopt(argc, sep->se_argv, "d:fgno:rt:")) != -1)
379			switch (c) {
380			case 'd':
381				fallback = optarg;
382				break;
383			case 'f':
384				fflag = 1;
385				break;
386			case 'g':
387				gflag = 1;
388				random = 0;	/* Shush, compiler. */
389				/*
390				 * The number of bits in "random" divided
391				 * by the number of bits needed per iteration
392				 * gives a more optimal way to reload the
393				 * random number only when necessary.
394				 *
395				 * I'm using base-36, so I need at least 6
396				 * bits; round it up to 8 bits to make it
397				 * easier.
398				 */
399				for (i = 0; i < sizeof(garbage) - 1; i++) {
400					const char *const base36 =
401					    "0123456789"
402					    "abcdefghijklmnopqrstuvwxyz";
403					if (i % (sizeof(random) * 8 / 8) == 0)
404						random = arc4random();
405					garbage[i] =
406					    base36[(random & 0xff) % 36];
407					random >>= 8;
408				}
409				garbage[i] = '\0';
410				break;
411			case 'n':
412				nflag = 1;
413				break;
414			case 'o':
415				osname = optarg;
416				break;
417			case 'r':
418				rflag = 1;
419				break;
420			case 't':
421				switch (sscanf(optarg, "%d.%d", &sec, &usec)) {
422				case 2:
423					tv.tv_usec = usec;
424				case 1:
425					tv.tv_sec = sec;
426					break;
427				default:
428					if (debug)
429						warnx("bad -t argument");
430					break;
431				}
432				break;
433			default:
434				break;
435			}
436	}
437	if (osname == NULL) {
438		if (uname(&un) == -1)
439			iderror(0, 0, s, errno);
440		osname = un.sysname;
441	}
442	socklen = sizeof(ss[0]);
443	if (getsockname(s, (struct sockaddr *)&ss[0], &socklen) == -1)
444		iderror(0, 0, s, errno);
445	socklen = sizeof(ss[1]);
446	if (getpeername(s, (struct sockaddr *)&ss[1], &socklen) == -1)
447		iderror(0, 0, s, errno);
448	/*
449	 * We're going to prepare for and execute reception of a
450	 * packet of data from the user. The data is in the format
451	 * "local_port , foreign_port\r\n" (with local being the
452	 * server's port and foreign being the client's.)
453	 */
454	gettimeofday(&to, NULL);
455	to.tv_sec += tv.tv_sec;
456	to.tv_usec += tv.tv_usec;
457	if (to.tv_usec >= 1000000) {
458		to.tv_usec -= 1000000;
459		to.tv_sec++;
460	}
461
462	size = 0;
463	bufsiz = sizeof(buf) - 1;
464	FD_ZERO(&fdset);
465 	while (bufsiz > 0 && (size == 0 || buf[size - 1] != '\n')) {
466		gettimeofday(&tv, NULL);
467		tv.tv_sec = to.tv_sec - tv.tv_sec;
468		tv.tv_usec = to.tv_usec - tv.tv_usec;
469		if (tv.tv_usec < 0) {
470			tv.tv_usec += 1000000;
471			tv.tv_sec--;
472		}
473		if (tv.tv_sec < 0)
474			break;
475		FD_SET(s, &fdset);
476		if (select(s + 1, &fdset, NULL, NULL, &tv) == -1)
477			iderror(0, 0, s, errno);
478		if (ioctl(s, FIONREAD, &onreadlen) == -1)
479			iderror(0, 0, s, errno);
480		if (onreadlen > bufsiz)
481			onreadlen = bufsiz;
482		ssize = read(s, &buf[size], (size_t)onreadlen);
483		if (ssize == -1)
484			iderror(0, 0, s, errno);
485		else if (ssize == 0)
486			break;
487		bufsiz -= ssize;
488		size += ssize;
489 	}
490	buf[size] = '\0';
491	/* Read two characters, and check for a delimiting character */
492	if (sscanf(buf, "%hu , %hu%c", &lport, &fport, &e) != 3 || isdigit(e))
493		iderror(0, 0, s, 0);
494	if (gflag) {
495		cp = garbage;
496		goto printit;
497	}
498
499	/*
500	 * If not "real" (-r), send a HIDDEN-USER error for everything.
501	 * If -d is used to set a fallback username, this is used to
502	 * override it, and the fallback is returned instead.
503	 */
504	if (!rflag) {
505		if (fallback == NULL)
506			iderror(lport, fport, s, -1);
507		else {
508			cp = fallback;
509			goto printit;
510		}
511	}
512
513	/*
514	 * We take the input and construct an array of two sockaddr_ins
515	 * which contain the local address information and foreign
516	 * address information, respectively, used to look up the
517	 * credentials for the socket (which are returned by the
518	 * sysctl "net.inet.tcp.getcred" when we call it.) The
519	 * arrays have been filled in above via get{peer,sock}name(),
520	 * so right here we are only setting the ports.
521	 */
522	if (ss[0].ss_family != ss[1].ss_family)
523		iderror(lport, fport, s, EINVAL);
524	size = sizeof(uc);
525	switch (ss[0].ss_family) {
526	case AF_INET:
527		sin[0] = *(struct sockaddr_in *)&ss[0];
528		sin[0].sin_port = htons(lport);
529		sin[1] = *(struct sockaddr_in *)&ss[1];
530		sin[1].sin_port = htons(fport);
531		if (sysctlbyname("net.inet.tcp.getcred", &uc, &size, sin,
532				 sizeof(sin)) == -1)
533			getcredfail = errno;
534		break;
535#ifdef INET6
536	case AF_INET6:
537		sin6[0] = *(struct sockaddr_in6 *)&ss[0];
538		sin6[0].sin6_port = htons(lport);
539		sin6[1] = *(struct sockaddr_in6 *)&ss[1];
540		sin6[1].sin6_port = htons(fport);
541		if (sysctlbyname("net.inet6.tcp6.getcred", &uc, &size, sin6,
542				 sizeof(sin6)) == -1)
543			getcredfail = errno;
544		break;
545#endif
546	default: /* should not reach here */
547		getcredfail = EAFNOSUPPORT;
548		break;
549	}
550	if (getcredfail != 0) {
551		if (fallback == NULL)		/* Use a default, if asked to */
552			iderror(lport, fport, s, getcredfail);
553		usedfallback = 1;
554	} else {
555		/* Look up the pw to get the username */
556		errno = 0;
557		pw = getpwuid(uc.cr_uid);
558	}
559	if (pw == NULL && !usedfallback)		/* No such user... */
560		iderror(lport, fport, s, errno != 0 ? errno : ENOENT);
561	/*
562	 * If enabled, we check for a file named ".noident" in the user's
563	 * home directory. If found, we return HIDDEN-USER.
564	 */
565	if (nflag && !usedfallback) {
566		if (asprintf(&p, "%s/.noident", pw->pw_dir) == -1)
567			iderror(lport, fport, s, errno);
568		if (lstat(p, &sb) == 0) {
569			free(p);
570			iderror(lport, fport, s, -1);
571		}
572		free(p);
573	}
574	/*
575	 * Here, if enabled, we read a user's ".fakeid" file in their
576	 * home directory. It consists of a line containing the name
577	 * they want.
578	 */
579	if (fflag && !usedfallback) {
580		FILE *fakeid = NULL;
581		int fakeid_fd;
582
583		if (asprintf(&p, "%s/.fakeid", pw->pw_dir) == -1)
584			iderror(lport, fport, s, errno);
585		/*
586		 * Here we set ourself to effectively be the user, so we don't
587		 * open any files we have no permission to open, especially
588		 * symbolic links to sensitive root-owned files or devices.
589		 */
590		if (initgroups(pw->pw_name, pw->pw_gid) == -1)
591			iderror(lport, fport, s, errno);
592		seteuid(pw->pw_uid);
593		/*
594		 * We can't stat() here since that would be a race
595		 * condition.
596		 * Therefore, we open the file we have permissions to open
597		 * and if it's not a regular file, we close it and end up
598		 * returning the user's real username.
599		 */
600		fakeid_fd = open(p, O_RDONLY | O_NONBLOCK);
601		free(p);
602		if (fakeid_fd != -1 && fstat(fakeid_fd, &sb) != -1 &&
603		    S_ISREG(sb.st_mode) &&
604		    (fakeid = fdopen(fakeid_fd, "r")) != NULL) {
605			buf[sizeof(buf) - 1] = '\0';
606			if (fgets(buf, sizeof(buf), fakeid) == NULL) {
607				cp = pw->pw_name;
608				fclose(fakeid);
609				goto printit;
610			}
611			/*
612			 * Usually, the file will have the desired identity
613			 * in the form "identity\n", so we use strcspn() to
614			 * end the string (which fgets() doesn't do.)
615			 */
616			buf[strcspn(buf, "\r\n")] = '\0';
617			cp = buf;
618			/* Allow for beginning white space... */
619			while (isspace(*cp))
620				cp++;
621			/* ...and ending white space. */
622			cp[strcspn(cp, " \t")] = '\0';
623			/* User names of >16 characters are invalid */
624			if (strlen(cp) > 16)
625				cp[16] = '\0';
626			/*
627			 * If the name is a zero-length string or matches
628			 * the name of another user, it's invalid, so
629			 * we will return their real identity instead.
630			 */
631
632			if (!*cp || getpwnam(cp)) {
633				errno = 0;
634				pw = getpwuid(uc.cr_uid);
635				if (pw == NULL)
636					iderror(lport, fport, s,
637					    errno != 0 ? errno : ENOENT);
638				cp = pw->pw_name;
639			}
640		} else
641			cp = pw->pw_name;
642		if (fakeid != NULL)
643			fclose(fakeid);
644		else if (fakeid_fd != -1)
645			close(fakeid_fd);
646	} else if (!usedfallback)
647		cp = pw->pw_name;
648	else
649		cp = fallback;
650printit:
651	/* Finally, we make and send the reply. */
652	if (asprintf(&p, "%d , %d : USERID : %s : %s\r\n", lport, fport, osname,
653	    cp) == -1) {
654		syslog(LOG_ERR, "asprintf: %m");
655		exit(EX_OSERR);
656	}
657	send(s, p, strlen(p), MSG_EOF);
658	free(p);
659
660	exit(0);
661}
662
663/*
664 * RFC738 Time Server.
665 * Return a machine readable date and time, in the form of the
666 * number of seconds since midnight, Jan 1, 1900.  Since gettimeofday
667 * returns the number of seconds since midnight, Jan 1, 1970,
668 * we must add 2208988800 seconds to this figure to make up for
669 * some seventy years Bell Labs was asleep.
670 */
671
672unsigned long
673machtime()
674{
675	struct timeval tv;
676
677	if (gettimeofday(&tv, (struct timezone *)NULL) < 0) {
678		if (debug)
679			warnx("unable to get time of day");
680		return (0L);
681	}
682#define	OFFSET ((u_long)25567 * 24*60*60)
683	return (htonl((long)(tv.tv_sec + OFFSET)));
684#undef OFFSET
685}
686
687/* ARGSUSED */
688void
689machtime_dg(s, sep)
690	int s;
691	struct servtab *sep;
692{
693	unsigned long result;
694	struct sockaddr_storage ss;
695	socklen_t size;
696
697	size = sizeof(ss);
698	if (recvfrom(s, (char *)&result, sizeof(result), 0,
699		     (struct sockaddr *)&ss, &size) < 0)
700		return;
701
702	if (check_loop((struct sockaddr *)&ss, sep))
703		return;
704
705	result = machtime();
706	(void) sendto(s, (char *) &result, sizeof(result), 0,
707		      (struct sockaddr *)&ss, size);
708}
709
710/* ARGSUSED */
711void
712machtime_stream(s, sep)
713	int s;
714	struct servtab *sep;
715{
716	unsigned long result;
717
718	result = machtime();
719	(void) send(s, (char *) &result, sizeof(result), MSG_EOF);
720}
721
722/*
723 * RFC1078 TCP Port Service Multiplexer (TCPMUX). Service connections to
724 * services based on the service name sent.
725 *
726 *  Based on TCPMUX.C by Mark K. Lottor November 1988
727 *  sri-nic::ps:<mkl>tcpmux.c
728 */
729
730#define MAX_SERV_LEN	(256+2)		/* 2 bytes for \r\n */
731#define strwrite(fd, buf)	(void) write(fd, buf, sizeof(buf)-1)
732
733static int		/* # of characters upto \r,\n or \0 */
734getline(fd, buf, len)
735	int fd;
736	char *buf;
737	int len;
738{
739	int count = 0, n;
740	struct sigaction sa;
741
742	sa.sa_flags = 0;
743	sigemptyset(&sa.sa_mask);
744	sa.sa_handler = SIG_DFL;
745	sigaction(SIGALRM, &sa, (struct sigaction *)0);
746	do {
747		alarm(10);
748		n = read(fd, buf, len-count);
749		alarm(0);
750		if (n == 0)
751			return (count);
752		if (n < 0)
753			return (-1);
754		while (--n >= 0) {
755			if (*buf == '\r' || *buf == '\n' || *buf == '\0')
756				return (count);
757			count++;
758			buf++;
759		}
760	} while (count < len);
761	return (count);
762}
763
764struct servtab *
765tcpmux(s)
766	int s;
767{
768	struct servtab *sep;
769	char service[MAX_SERV_LEN+1];
770	int len;
771
772	/* Get requested service name */
773	if ((len = getline(s, service, MAX_SERV_LEN)) < 0) {
774		strwrite(s, "-Error reading service name\r\n");
775		return (NULL);
776	}
777	service[len] = '\0';
778
779	if (debug)
780		warnx("tcpmux: someone wants %s", service);
781
782	/*
783	 * Help is a required command, and lists available services,
784	 * one per line.
785	 */
786	if (!strcasecmp(service, "help")) {
787		for (sep = servtab; sep; sep = sep->se_next) {
788			if (!ISMUX(sep))
789				continue;
790			(void)write(s,sep->se_service,strlen(sep->se_service));
791			strwrite(s, "\r\n");
792		}
793		return (NULL);
794	}
795
796	/* Try matching a service in inetd.conf with the request */
797	for (sep = servtab; sep; sep = sep->se_next) {
798		if (!ISMUX(sep))
799			continue;
800		if (!strcasecmp(service, sep->se_service)) {
801			if (ISMUXPLUS(sep)) {
802				strwrite(s, "+Go\r\n");
803			}
804			return (sep);
805		}
806	}
807	strwrite(s, "-Service not available\r\n");
808	return (NULL);
809}
810