1/* $OpenBSD: netcat.c,v 1.103 2011/10/04 08:34:34 fgsch Exp $ */
2/*
3 * Copyright (c) 2001 Eric Jackson <ericj@monkey.org>
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 *
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. The name of the author may not be used to endorse or promote products
15 *   derived from this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29/*
30 * Re-written nc(1) for OpenBSD. Original implementation by
31 * *Hobbit* <hobbit@avian.org>.
32 */
33
34#include <sys/types.h>
35#include <sys/socket.h>
36#include <sys/time.h>
37#include <sys/un.h>
38
39#include <netinet/in.h>
40#include <netinet/in_systm.h>
41#include <netinet/tcp.h>
42#include <netinet/ip.h>
43#include <arpa/telnet.h>
44
45#include <err.h>
46#include <errno.h>
47#include <netdb.h>
48#include <poll.h>
49#include <stdarg.h>
50#include <stdio.h>
51#include <stdlib.h>
52#include <string.h>
53#include <unistd.h>
54#include <fcntl.h>
55#include <limits.h>
56#include "atomicio.h"
57
58#ifndef SUN_LEN
59#define SUN_LEN(su) \
60	(sizeof(*(su)) - sizeof((su)->sun_path) + strlen((su)->sun_path))
61#endif
62
63#define PORT_MAX	65535
64#define PORT_MAX_LEN	6
65#define UNIX_DG_TMP_SOCKET_SIZE	19
66
67/* Command Line Options */
68int	dflag;					/* detached, no stdin */
69unsigned int iflag;				/* Interval Flag */
70#ifdef ANDROID
71int	jflag = 0;
72#else
73int	jflag;					/* use jumbo frames if we can */
74#endif /* !ANDROID */
75int	kflag;					/* More than one connect */
76int	lflag;					/* Bind to local port */
77int	nflag;					/* Don't do name look up */
78char   *Pflag;					/* Proxy username */
79char   *pflag;					/* Localport flag */
80int	rflag;					/* Random ports flag */
81char   *sflag;					/* Source Address */
82int	tflag;					/* Telnet Emulation */
83int	uflag;					/* UDP - Default to TCP */
84int	vflag;					/* Verbosity */
85#ifndef ANDROID
86int	xflag;					/* Socks proxy */
87#endif /* !ANDROID */
88int	zflag;					/* Port Scan Flag */
89int	Dflag;					/* sodebug */
90int	Iflag;					/* TCP receive buffer size */
91int	Oflag;					/* TCP send buffer size */
92#ifndef ANDROID
93int	Sflag;					/* TCP MD5 signature option */
94int	Tflag = -1;				/* IP Type of Service */
95u_int	rtableid;
96#endif /* !ANDROID */
97
98int timeout = -1;
99int family = AF_UNSPEC;
100char *portlist[PORT_MAX+1];
101char *unix_dg_tmp_socket;
102
103void	atelnet(int, unsigned char *, unsigned int);
104void	build_ports(char *);
105void	help(void);
106int	local_listen(char *, char *, struct addrinfo);
107void	readwrite(int);
108int	remote_connect(const char *, const char *, struct addrinfo);
109int	timeout_connect(int, const struct sockaddr *, socklen_t);
110#ifndef ANDROID
111int	socks_connect(const char *, const char *, struct addrinfo,
112	    const char *, const char *, struct addrinfo, int, const char *);
113#endif /* !ANDROID */
114int	udptest(int);
115int	unix_bind(char *);
116int	unix_connect(char *);
117int	unix_listen(char *);
118void	set_common_sockopts(int);
119int	map_tos(char *, int *);
120void	usage(int);
121
122int
123main(int argc, char *argv[])
124{
125	int ch, s, ret, socksv;
126	char *host, *uport;
127	struct addrinfo hints;
128	struct servent *sv;
129	socklen_t len;
130	struct sockaddr_storage cliaddr;
131	char *proxy;
132	const char *errstr, *proxyhost = "", *proxyport = NULL;
133	struct addrinfo proxyhints;
134	char unix_dg_tmp_socket_buf[UNIX_DG_TMP_SOCKET_SIZE];
135
136	ret = 1;
137	s = 0;
138	socksv = 5;
139	host = NULL;
140	uport = NULL;
141	sv = NULL;
142
143	while ((ch = getopt(argc, argv,
144	    "46DdhI:i:jklnO:P:p:rSs:tT:UuV:vw:X:x:z")) != -1) {
145		switch (ch) {
146		case '4':
147			family = AF_INET;
148			break;
149		case '6':
150			family = AF_INET6;
151			break;
152		case 'U':
153			family = AF_UNIX;
154			break;
155		case 'X':
156			if (strcasecmp(optarg, "connect") == 0)
157				socksv = -1; /* HTTP proxy CONNECT */
158			else if (strcmp(optarg, "4") == 0)
159				socksv = 4; /* SOCKS v.4 */
160			else if (strcmp(optarg, "5") == 0)
161				socksv = 5; /* SOCKS v.5 */
162			else
163				errx(1, "unsupported proxy protocol");
164			break;
165		case 'd':
166			dflag = 1;
167			break;
168		case 'h':
169			help();
170			break;
171		case 'i':
172#ifdef ANDROID
173			iflag = atoi(optarg);
174#else
175			iflag = strtonum(optarg, 0, UINT_MAX, &errstr);
176			if (errstr)
177				errx(1, "interval %s: %s", errstr, optarg);
178#endif /* ANDROID */
179			break;
180#ifndef ANDROID
181		case 'j':
182			jflag = 1;
183			break;
184#endif /* !ANDROID */
185		case 'k':
186			kflag = 1;
187			break;
188		case 'l':
189			lflag = 1;
190			break;
191		case 'n':
192			nflag = 1;
193			break;
194		case 'P':
195			Pflag = optarg;
196			break;
197		case 'p':
198			pflag = optarg;
199			break;
200		case 'r':
201			rflag = 1;
202			break;
203		case 's':
204			sflag = optarg;
205			break;
206		case 't':
207			tflag = 1;
208			break;
209		case 'u':
210			uflag = 1;
211			break;
212#ifndef ANDROID
213		case 'V':
214			rtableid = (unsigned int)strtonum(optarg, 0,
215			    RT_TABLEID_MAX, &errstr);
216			if (errstr)
217				errx(1, "rtable %s: %s", errstr, optarg);
218			break;
219#endif /* !ANDROID */
220		case 'v':
221			vflag = 1;
222			break;
223		case 'w':
224#ifdef ANDROID
225			timeout = atoi(optarg);
226#else
227			timeout = strtonum(optarg, 0, INT_MAX / 1000, &errstr);
228			if (errstr)
229				errx(1, "timeout %s: %s", errstr, optarg);
230#endif
231			timeout *= 1000;
232			break;
233#ifndef ANDROID
234		case 'x':
235			xflag = 1;
236			if ((proxy = strdup(optarg)) == NULL)
237				err(1, NULL);
238			break;
239#endif /* !ANDROID */
240		case 'z':
241			zflag = 1;
242			break;
243		case 'D':
244			Dflag = 1;
245			break;
246		case 'I':
247#ifdef ANDROID
248			Iflag = atoi(optarg);
249#else
250			Iflag = strtonum(optarg, 1, 65536 << 14, &errstr);
251			if (errstr != NULL)
252				errx(1, "TCP receive window %s: %s",
253				    errstr, optarg);
254#endif
255			break;
256		case 'O':
257#ifdef ANDROID
258			Oflag = atoi(optarg);
259#else
260			Oflag = strtonum(optarg, 1, 65536 << 14, &errstr);
261			if (errstr != NULL)
262				errx(1, "TCP send window %s: %s",
263				    errstr, optarg);
264#endif
265			break;
266#ifndef ANDROID
267		case 'S':
268			Sflag = 1;
269			break;
270		case 'T':
271			errstr = NULL;
272			errno = 0;
273			if (map_tos(optarg, &Tflag))
274				break;
275			if (strlen(optarg) > 1 && optarg[0] == '0' &&
276			    optarg[1] == 'x')
277				Tflag = (int)strtol(optarg, NULL, 16);
278			else
279				Tflag = (int)strtonum(optarg, 0, 255,
280				    &errstr);
281			if (Tflag < 0 || Tflag > 255 || errstr || errno)
282				errx(1, "illegal tos value %s", optarg);
283			break;
284#endif /* !ANDROID */
285		default:
286			usage(1);
287		}
288	}
289	argc -= optind;
290	argv += optind;
291
292	/* Cruft to make sure options are clean, and used properly. */
293	if (argv[0] && !argv[1] && family == AF_UNIX) {
294		host = argv[0];
295		uport = NULL;
296	} else if (argv[0] && !argv[1]) {
297		if  (!lflag)
298			usage(1);
299		uport = argv[0];
300		host = NULL;
301	} else if (argv[0] && argv[1]) {
302		host = argv[0];
303		uport = argv[1];
304	} else
305		usage(1);
306
307	if (lflag && sflag)
308		errx(1, "cannot use -s and -l");
309	if (lflag && pflag)
310		errx(1, "cannot use -p and -l");
311	if (lflag && zflag)
312		errx(1, "cannot use -z and -l");
313	if (!lflag && kflag)
314		errx(1, "must use -l with -k");
315
316	/* Get name of temporary socket for unix datagram client */
317	if ((family == AF_UNIX) && uflag && !lflag) {
318		if (sflag) {
319			unix_dg_tmp_socket = sflag;
320		} else {
321			strlcpy(unix_dg_tmp_socket_buf, "/tmp/nc.XXXXXXXXXX",
322				UNIX_DG_TMP_SOCKET_SIZE);
323			if (mktemp(unix_dg_tmp_socket_buf) == NULL)
324				err(1, "mktemp");
325			unix_dg_tmp_socket = unix_dg_tmp_socket_buf;
326		}
327	}
328
329	/* Initialize addrinfo structure. */
330	if (family != AF_UNIX) {
331		memset(&hints, 0, sizeof(struct addrinfo));
332		hints.ai_family = family;
333		hints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM;
334		hints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP;
335		if (nflag)
336			hints.ai_flags |= AI_NUMERICHOST;
337	}
338
339#ifndef ANDROID
340	if (xflag) {
341		if (uflag)
342			errx(1, "no proxy support for UDP mode");
343
344		if (lflag)
345			errx(1, "no proxy support for listen");
346
347		if (family == AF_UNIX)
348			errx(1, "no proxy support for unix sockets");
349
350		/* XXX IPv6 transport to proxy would probably work */
351		if (family == AF_INET6)
352			errx(1, "no proxy support for IPv6");
353
354		if (sflag)
355			errx(1, "no proxy support for local source address");
356
357		proxyhost = strsep(&proxy, ":");
358		proxyport = proxy;
359
360		memset(&proxyhints, 0, sizeof(struct addrinfo));
361		proxyhints.ai_family = family;
362		proxyhints.ai_socktype = SOCK_STREAM;
363		proxyhints.ai_protocol = IPPROTO_TCP;
364		if (nflag)
365			proxyhints.ai_flags |= AI_NUMERICHOST;
366	}
367#endif /* !ANDROID */
368
369	if (lflag) {
370		int connfd;
371		ret = 0;
372
373		if (family == AF_UNIX) {
374			if (uflag)
375				s = unix_bind(host);
376			else
377				s = unix_listen(host);
378		}
379
380		/* Allow only one connection at a time, but stay alive. */
381		for (;;) {
382			if (family != AF_UNIX)
383				s = local_listen(host, uport, hints);
384			if (s < 0)
385				err(1, NULL);
386			/*
387			 * For UDP, we will use recvfrom() initially
388			 * to wait for a caller, then use the regular
389			 * functions to talk to the caller.
390			 */
391			if (uflag) {
392				int rv, plen;
393				char buf[16384];
394				struct sockaddr_storage z;
395
396				len = sizeof(z);
397				plen = jflag ? 16384 : 2048;
398				rv = recvfrom(s, buf, plen, MSG_PEEK,
399				    (struct sockaddr *)&z, &len);
400				if (rv < 0)
401					err(1, "recvfrom");
402
403				rv = connect(s, (struct sockaddr *)&z, len);
404				if (rv < 0)
405					err(1, "connect");
406
407				readwrite(s);
408			} else {
409				len = sizeof(cliaddr);
410				connfd = accept(s, (struct sockaddr *)&cliaddr,
411				    &len);
412				readwrite(connfd);
413				close(connfd);
414			}
415
416			if (family != AF_UNIX)
417				close(s);
418			else if (uflag) {
419				if (connect(s, NULL, 0) < 0)
420					err(1, "connect");
421			}
422
423			if (!kflag)
424				break;
425		}
426	} else if (family == AF_UNIX) {
427		ret = 0;
428
429		if ((s = unix_connect(host)) > 0 && !zflag) {
430			readwrite(s);
431			close(s);
432		} else
433			ret = 1;
434
435		if (uflag)
436			unlink(unix_dg_tmp_socket);
437		exit(ret);
438
439	} else {
440		int i = 0;
441
442		/* Construct the portlist[] array. */
443		build_ports(uport);
444
445		/* Cycle through portlist, connecting to each port. */
446		for (i = 0; portlist[i] != NULL; i++) {
447			if (s)
448				close(s);
449
450#ifndef ANDROID
451			if (xflag)
452				s = socks_connect(host, portlist[i], hints,
453				    proxyhost, proxyport, proxyhints, socksv,
454				    Pflag);
455			else
456#endif /* !ANDROID */
457				s = remote_connect(host, portlist[i], hints);
458
459			if (s < 0)
460				continue;
461
462			ret = 0;
463			if (vflag || zflag) {
464				/* For UDP, make sure we are connected. */
465				if (uflag) {
466					if (udptest(s) == -1) {
467						ret = 1;
468						continue;
469					}
470				}
471
472				/* Don't look up port if -n. */
473				if (nflag)
474					sv = NULL;
475				else {
476					sv = getservbyport(
477					    ntohs(atoi(portlist[i])),
478					    uflag ? "udp" : "tcp");
479				}
480
481				fprintf(stderr,
482				    "Connection to %s %s port [%s/%s] "
483				    "succeeded!\n", host, portlist[i],
484				    uflag ? "udp" : "tcp",
485				    sv ? sv->s_name : "*");
486			}
487			if (!zflag)
488				readwrite(s);
489		}
490	}
491
492	if (s)
493		close(s);
494
495	exit(ret);
496}
497
498/*
499 * unix_bind()
500 * Returns a unix socket bound to the given path
501 */
502int
503unix_bind(char *path)
504{
505	struct sockaddr_un sun;
506	int s;
507
508	/* Create unix domain socket. */
509	if ((s = socket(AF_UNIX, uflag ? SOCK_DGRAM : SOCK_STREAM,
510	     0)) < 0)
511		return (-1);
512
513	memset(&sun, 0, sizeof(struct sockaddr_un));
514	sun.sun_family = AF_UNIX;
515
516	if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
517	    sizeof(sun.sun_path)) {
518		close(s);
519		errno = ENAMETOOLONG;
520		return (-1);
521	}
522
523	if (bind(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
524		close(s);
525		return (-1);
526	}
527	return (s);
528}
529
530/*
531 * unix_connect()
532 * Returns a socket connected to a local unix socket. Returns -1 on failure.
533 */
534int
535unix_connect(char *path)
536{
537	struct sockaddr_un sun;
538	int s;
539
540	if (uflag) {
541		if ((s = unix_bind(unix_dg_tmp_socket)) < 0)
542			return (-1);
543	} else {
544		if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
545			return (-1);
546	}
547	(void)fcntl(s, F_SETFD, 1);
548
549	memset(&sun, 0, sizeof(struct sockaddr_un));
550	sun.sun_family = AF_UNIX;
551
552	if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
553	    sizeof(sun.sun_path)) {
554		close(s);
555		errno = ENAMETOOLONG;
556		return (-1);
557	}
558	if (connect(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
559		close(s);
560		return (-1);
561	}
562	return (s);
563
564}
565
566/*
567 * unix_listen()
568 * Create a unix domain socket, and listen on it.
569 */
570int
571unix_listen(char *path)
572{
573	int s;
574	if ((s = unix_bind(path)) < 0)
575		return (-1);
576
577	if (listen(s, 5) < 0) {
578		close(s);
579		return (-1);
580	}
581	return (s);
582}
583
584/*
585 * remote_connect()
586 * Returns a socket connected to a remote host. Properly binds to a local
587 * port or source address if needed. Returns -1 on failure.
588 */
589int
590remote_connect(const char *host, const char *port, struct addrinfo hints)
591{
592	struct addrinfo *res, *res0;
593	int s, error, on = 1;
594
595	if ((error = getaddrinfo(host, port, &hints, &res)))
596		errx(1, "getaddrinfo: %s", gai_strerror(error));
597
598	res0 = res;
599	do {
600		if ((s = socket(res0->ai_family, res0->ai_socktype,
601		    res0->ai_protocol)) < 0)
602			continue;
603
604#ifndef ANDROID
605		if (rtableid) {
606			if (setsockopt(s, SOL_SOCKET, SO_RTABLE, &rtableid,
607			    sizeof(rtableid)) == -1)
608				err(1, "setsockopt SO_RTABLE");
609		}
610#endif /* !ANDROID */
611
612		/* Bind to a local port or source address if specified. */
613		if (sflag || pflag) {
614			struct addrinfo ahints, *ares;
615
616#ifndef ANDROID
617			/* try SO_BINDANY, but don't insist */
618			setsockopt(s, SOL_SOCKET, SO_BINDANY, &on, sizeof(on));
619#endif /* !ANDROID */
620			memset(&ahints, 0, sizeof(struct addrinfo));
621			ahints.ai_family = res0->ai_family;
622			ahints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM;
623			ahints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP;
624			ahints.ai_flags = AI_PASSIVE;
625			if ((error = getaddrinfo(sflag, pflag, &ahints, &ares)))
626				errx(1, "getaddrinfo: %s", gai_strerror(error));
627
628			if (bind(s, (struct sockaddr *)ares->ai_addr,
629			    ares->ai_addrlen) < 0)
630				errx(1, "bind failed: %s", strerror(errno));
631			freeaddrinfo(ares);
632		}
633
634		set_common_sockopts(s);
635
636		if (timeout_connect(s, res0->ai_addr, res0->ai_addrlen) == 0)
637			break;
638		else if (vflag)
639			warn("connect to %s port %s (%s) failed", host, port,
640			    uflag ? "udp" : "tcp");
641
642		close(s);
643		s = -1;
644	} while ((res0 = res0->ai_next) != NULL);
645
646	freeaddrinfo(res);
647
648	return (s);
649}
650
651int
652timeout_connect(int s, const struct sockaddr *name, socklen_t namelen)
653{
654	struct pollfd pfd;
655	socklen_t optlen;
656	int flags, optval;
657	int ret;
658
659	if (timeout != -1) {
660		flags = fcntl(s, F_GETFL, 0);
661		if (fcntl(s, F_SETFL, flags | O_NONBLOCK) == -1)
662			err(1, "set non-blocking mode");
663	}
664
665	if ((ret = connect(s, name, namelen)) != 0 && errno == EINPROGRESS) {
666		pfd.fd = s;
667		pfd.events = POLLOUT;
668		if ((ret = poll(&pfd, 1, timeout)) == 1) {
669			optlen = sizeof(optval);
670			if ((ret = getsockopt(s, SOL_SOCKET, SO_ERROR,
671			    &optval, &optlen)) == 0) {
672				errno = optval;
673				ret = optval == 0 ? 0 : -1;
674			}
675		} else if (ret == 0) {
676			errno = ETIMEDOUT;
677			ret = -1;
678		} else
679			err(1, "poll failed");
680	}
681
682	if (timeout != -1 && fcntl(s, F_SETFL, flags) == -1)
683		err(1, "restoring flags");
684
685	return (ret);
686}
687
688/*
689 * local_listen()
690 * Returns a socket listening on a local port, binds to specified source
691 * address. Returns -1 on failure.
692 */
693int
694local_listen(char *host, char *port, struct addrinfo hints)
695{
696	struct addrinfo *res, *res0;
697	int s, ret, x = 1;
698	int error;
699
700	/* Allow nodename to be null. */
701	hints.ai_flags |= AI_PASSIVE;
702
703	/*
704	 * In the case of binding to a wildcard address
705	 * default to binding to an ipv4 address.
706	 */
707	if (host == NULL && hints.ai_family == AF_UNSPEC)
708		hints.ai_family = AF_INET;
709
710	if ((error = getaddrinfo(host, port, &hints, &res)))
711		errx(1, "getaddrinfo: %s", gai_strerror(error));
712
713	res0 = res;
714	do {
715		if ((s = socket(res0->ai_family, res0->ai_socktype,
716		    res0->ai_protocol)) < 0)
717			continue;
718
719#ifndef ANDROID
720		if (rtableid) {
721			if (setsockopt(s, IPPROTO_IP, SO_RTABLE, &rtableid,
722			    sizeof(rtableid)) == -1)
723				err(1, "setsockopt SO_RTABLE");
724		}
725#endif /* !ANDROID */
726
727#ifdef ANDROID
728		ret = setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &x, sizeof(x));
729#else
730		ret = setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &x, sizeof(x));
731#endif
732		if (ret == -1)
733			err(1, NULL);
734
735		set_common_sockopts(s);
736
737		if (bind(s, (struct sockaddr *)res0->ai_addr,
738		    res0->ai_addrlen) == 0)
739			break;
740
741		close(s);
742		s = -1;
743	} while ((res0 = res0->ai_next) != NULL);
744
745	if (!uflag && s != -1) {
746		if (listen(s, 1) < 0)
747			err(1, "listen");
748	}
749
750	freeaddrinfo(res);
751
752	return (s);
753}
754
755/*
756 * readwrite()
757 * Loop that polls on the network file descriptor and stdin.
758 */
759void
760readwrite(int nfd)
761{
762	struct pollfd pfd[2];
763	unsigned char buf[16384];
764	int n, wfd = fileno(stdin);
765	int lfd = fileno(stdout);
766	int plen;
767
768	plen = jflag ? 16384 : 2048;
769
770	/* Setup Network FD */
771	pfd[0].fd = nfd;
772	pfd[0].events = POLLIN;
773
774	/* Set up STDIN FD. */
775	pfd[1].fd = wfd;
776	pfd[1].events = POLLIN;
777
778	while (pfd[0].fd != -1) {
779		if (iflag)
780			sleep(iflag);
781
782		if ((n = poll(pfd, 2 - dflag, timeout)) < 0) {
783			close(nfd);
784			err(1, "Polling Error");
785		}
786
787		if (n == 0)
788			return;
789
790		if (pfd[0].revents & POLLIN) {
791			if ((n = read(nfd, buf, plen)) < 0)
792				return;
793			else if (n == 0) {
794				shutdown(nfd, SHUT_RD);
795				pfd[0].fd = -1;
796				pfd[0].events = 0;
797			} else {
798				if (tflag)
799					atelnet(nfd, buf, n);
800				if (atomicio(vwrite, lfd, buf, n) != n)
801					return;
802			}
803		}
804
805		if (!dflag && pfd[1].revents & POLLIN) {
806			if ((n = read(wfd, buf, plen)) < 0)
807				return;
808			else if (n == 0) {
809				shutdown(nfd, SHUT_WR);
810				pfd[1].fd = -1;
811				pfd[1].events = 0;
812			} else {
813				if (atomicio(vwrite, nfd, buf, n) != n)
814					return;
815			}
816		}
817	}
818}
819
820/* Deal with RFC 854 WILL/WONT DO/DONT negotiation. */
821void
822atelnet(int nfd, unsigned char *buf, unsigned int size)
823{
824	unsigned char *p, *end;
825	unsigned char obuf[4];
826
827	if (size < 3)
828		return;
829	end = buf + size - 2;
830
831	for (p = buf; p < end; p++) {
832		if (*p != IAC)
833			continue;
834
835		obuf[0] = IAC;
836		p++;
837		if ((*p == WILL) || (*p == WONT))
838			obuf[1] = DONT;
839		else if ((*p == DO) || (*p == DONT))
840			obuf[1] = WONT;
841		else
842			continue;
843
844		p++;
845		obuf[2] = *p;
846		if (atomicio(vwrite, nfd, obuf, 3) != 3)
847			warn("Write Error!");
848	}
849}
850
851/*
852 * build_ports()
853 * Build an array or ports in portlist[], listing each port
854 * that we should try to connect to.
855 */
856void
857build_ports(char *p)
858{
859	const char *errstr;
860	char *n;
861	int hi, lo, cp;
862	int x = 0;
863
864	if ((n = strchr(p, '-')) != NULL) {
865		if (lflag)
866			errx(1, "Cannot use -l with multiple ports!");
867
868		*n = '\0';
869		n++;
870
871		/* Make sure the ports are in order: lowest->highest. */
872#ifdef ANDROID
873		hi = atoi(n);
874#else
875		hi = strtonum(n, 1, PORT_MAX, &errstr);
876		if (errstr)
877			errx(1, "port number %s: %s", errstr, n);
878#endif
879#ifdef ANDROID
880		lo = atoi(p);
881#else
882		lo = strtonum(p, 1, PORT_MAX, &errstr);
883		if (errstr)
884			errx(1, "port number %s: %s", errstr, p);
885#endif
886
887		if (lo > hi) {
888			cp = hi;
889			hi = lo;
890			lo = cp;
891		}
892
893		/* Load ports sequentially. */
894		for (cp = lo; cp <= hi; cp++) {
895			portlist[x] = calloc(1, PORT_MAX_LEN);
896			if (portlist[x] == NULL)
897				err(1, NULL);
898			snprintf(portlist[x], PORT_MAX_LEN, "%d", cp);
899			x++;
900		}
901
902		/* Randomly swap ports. */
903		if (rflag) {
904			int y;
905			char *c;
906
907			for (x = 0; x <= (hi - lo); x++) {
908				y = (arc4random() & 0xFFFF) % (hi - lo);
909				c = portlist[x];
910				portlist[x] = portlist[y];
911				portlist[y] = c;
912			}
913		}
914	} else {
915#ifdef ANDROID
916		hi = atoi(p);
917#else
918		hi = strtonum(p, 1, PORT_MAX, &errstr);
919		if (errstr)
920			errx(1, "port number %s: %s", errstr, p);
921#endif
922		portlist[0] = strdup(p);
923		if (portlist[0] == NULL)
924			err(1, NULL);
925	}
926}
927
928/*
929 * udptest()
930 * Do a few writes to see if the UDP port is there.
931 * XXX - Better way of doing this? Doesn't work for IPv6.
932 * Also fails after around 100 ports checked.
933 */
934int
935udptest(int s)
936{
937	int i, ret;
938
939	for (i = 0; i <= 3; i++) {
940		if (write(s, "X", 1) == 1)
941			ret = 1;
942		else
943			ret = -1;
944	}
945	return (ret);
946}
947
948void
949set_common_sockopts(int s)
950{
951	int x = 1;
952
953#ifndef ANDROID
954	if (Sflag) {
955		if (setsockopt(s, IPPROTO_TCP, TCP_MD5SIG,
956			&x, sizeof(x)) == -1)
957			err(1, NULL);
958	}
959#endif
960	if (Dflag) {
961		if (setsockopt(s, SOL_SOCKET, SO_DEBUG,
962			&x, sizeof(x)) == -1)
963			err(1, NULL);
964	}
965#ifndef ANDROID
966	if (jflag) {
967		if (setsockopt(s, SOL_SOCKET, SO_JUMBO,
968			&x, sizeof(x)) == -1)
969			err(1, NULL);
970	}
971	if (Tflag != -1) {
972		if (setsockopt(s, IPPROTO_IP, IP_TOS,
973		    &Tflag, sizeof(Tflag)) == -1)
974			err(1, "set IP ToS");
975	}
976#endif
977	if (Iflag) {
978		if (setsockopt(s, SOL_SOCKET, SO_RCVBUF,
979		    &Iflag, sizeof(Iflag)) == -1)
980			err(1, "set TCP receive buffer size");
981	}
982	if (Oflag) {
983		if (setsockopt(s, SOL_SOCKET, SO_SNDBUF,
984		    &Oflag, sizeof(Oflag)) == -1)
985			err(1, "set TCP send buffer size");
986	}
987}
988
989#ifndef ANDROID
990int
991map_tos(char *s, int *val)
992{
993	/* DiffServ Codepoints and other TOS mappings */
994	const struct toskeywords {
995		const char	*keyword;
996		int		 val;
997	} *t, toskeywords[] = {
998		{ "af11",		IPTOS_DSCP_AF11 },
999		{ "af12",		IPTOS_DSCP_AF12 },
1000		{ "af13",		IPTOS_DSCP_AF13 },
1001		{ "af21",		IPTOS_DSCP_AF21 },
1002		{ "af22",		IPTOS_DSCP_AF22 },
1003		{ "af23",		IPTOS_DSCP_AF23 },
1004		{ "af31",		IPTOS_DSCP_AF31 },
1005		{ "af32",		IPTOS_DSCP_AF32 },
1006		{ "af33",		IPTOS_DSCP_AF33 },
1007		{ "af41",		IPTOS_DSCP_AF41 },
1008		{ "af42",		IPTOS_DSCP_AF42 },
1009		{ "af43",		IPTOS_DSCP_AF43 },
1010		{ "critical",		IPTOS_PREC_CRITIC_ECP },
1011		{ "cs0",		IPTOS_DSCP_CS0 },
1012		{ "cs1",		IPTOS_DSCP_CS1 },
1013		{ "cs2",		IPTOS_DSCP_CS2 },
1014		{ "cs3",		IPTOS_DSCP_CS3 },
1015		{ "cs4",		IPTOS_DSCP_CS4 },
1016		{ "cs5",		IPTOS_DSCP_CS5 },
1017		{ "cs6",		IPTOS_DSCP_CS6 },
1018		{ "cs7",		IPTOS_DSCP_CS7 },
1019		{ "ef",			IPTOS_DSCP_EF },
1020		{ "inetcontrol",	IPTOS_PREC_INTERNETCONTROL },
1021		{ "lowdelay",		IPTOS_LOWDELAY },
1022		{ "netcontrol",		IPTOS_PREC_NETCONTROL },
1023		{ "reliability",	IPTOS_RELIABILITY },
1024		{ "throughput",		IPTOS_THROUGHPUT },
1025		{ NULL, 		-1 },
1026	};
1027
1028	for (t = toskeywords; t->keyword != NULL; t++) {
1029		if (strcmp(s, t->keyword) == 0) {
1030			*val = t->val;
1031			return (1);
1032		}
1033	}
1034
1035	return (0);
1036}
1037#endif
1038
1039void
1040help(void)
1041{
1042	usage(0);
1043	fprintf(stderr, "\tCommand Summary:\n\
1044	\t-4		Use IPv4\n\
1045	\t-6		Use IPv6\n\
1046	\t-D		Enable the debug socket option\n\
1047	\t-d		Detach from stdin\n\
1048	\t-h		This help text\n\
1049	\t-I length	TCP receive buffer length\n\
1050	\t-i secs\t	Delay interval for lines sent, ports scanned\n\
1051	\t-k		Keep inbound sockets open for multiple connects\n\
1052	\t-l		Listen mode, for inbound connects\n\
1053	\t-n		Suppress name/port resolutions\n\
1054	\t-O length	TCP send buffer length\n\
1055	\t-P proxyuser\tUsername for proxy authentication\n\
1056	\t-p port\t	Specify local port for remote connects\n\
1057	\t-r		Randomize remote ports\n\
1058	\t-S		Enable the TCP MD5 signature option\n\
1059	\t-s addr\t	Local source address\n\
1060	\t-T toskeyword\tSet IP Type of Service\n\
1061	\t-t		Answer TELNET negotiation\n\
1062	\t-U		Use UNIX domain socket\n\
1063	\t-u		UDP mode\n\
1064	\t-V rtable	Specify alternate routing table\n\
1065	\t-v		Verbose\n\
1066	\t-w secs\t	Timeout for connects and final net reads\n\
1067	\t-X proto	Proxy protocol: \"4\", \"5\" (SOCKS) or \"connect\"\n\
1068	\t-x addr[:port]\tSpecify proxy address and port\n\
1069	\t-z		Zero-I/O mode [used for scanning]\n\
1070	Port numbers can be individual or ranges: lo-hi [inclusive]\n");
1071	exit(1);
1072}
1073
1074void
1075usage(int ret)
1076{
1077	fprintf(stderr,
1078	    "usage: nc [-46DdhklnrStUuvz] [-I length] [-i interval] [-O length]\n"
1079	    "\t  [-P proxy_username] [-p source_port] [-s source] [-T ToS]\n"
1080	    "\t  [-V rtable] [-w timeout] [-X proxy_protocol]\n"
1081	    "\t  [-x proxy_address[:port]] [destination] [port]\n");
1082	if (ret)
1083		exit(1);
1084}
1085