netcat.c revision 274263 
1/* $OpenBSD: netcat.c,v 1.122 2014/07/20 01:38:40 guenther 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 * $FreeBSD: stable/10/contrib/netcat/netcat.c 274263 2014-11-08 00:55:06Z delphij $
29 */
30
31/*
32 * Re-written nc(1) for OpenBSD. Original implementation by
33 * *Hobbit* <hobbit@avian.org>.
34 */
35
36#include <sys/limits.h>
37#include <sys/types.h>
38#include <sys/socket.h>
39#include <sys/sysctl.h>
40#include <sys/time.h>
41#include <sys/uio.h>
42#include <sys/un.h>
43
44#include <netinet/in.h>
45#include <netinet/in_systm.h>
46#ifdef IPSEC
47#include <netipsec/ipsec.h>
48#endif
49#include <netinet/tcp.h>
50#include <netinet/ip.h>
51#include <arpa/telnet.h>
52
53#include <err.h>
54#include <errno.h>
55#include <getopt.h>
56#include <netdb.h>
57#include <poll.h>
58#include <stdarg.h>
59#include <stdio.h>
60#include <stdlib.h>
61#include <string.h>
62#include <unistd.h>
63#include <fcntl.h>
64#include <limits.h>
65#include "atomicio.h"
66
67#ifndef SUN_LEN
68#define SUN_LEN(su) \
69	(sizeof(*(su)) - sizeof((su)->sun_path) + strlen((su)->sun_path))
70#endif
71
72#define PORT_MAX	65535
73#define PORT_MAX_LEN	6
74#define UNIX_DG_TMP_SOCKET_SIZE	19
75
76/* Command Line Options */
77int	dflag;					/* detached, no stdin */
78int	Fflag;					/* fdpass sock to stdout */
79unsigned int iflag;				/* Interval Flag */
80int	kflag;					/* More than one connect */
81int	lflag;					/* Bind to local port */
82int	Nflag;					/* shutdown() network socket */
83int	nflag;					/* Don't do name look up */
84int	FreeBSD_Oflag;				/* Do not use TCP options */
85char   *Pflag;					/* Proxy username */
86char   *pflag;					/* Localport flag */
87int	rflag;					/* Random ports flag */
88char   *sflag;					/* Source Address */
89int	tflag;					/* Telnet Emulation */
90int	uflag;					/* UDP - Default to TCP */
91int	vflag;					/* Verbosity */
92int	xflag;					/* Socks proxy */
93int	zflag;					/* Port Scan Flag */
94int	Dflag;					/* sodebug */
95int	Iflag;					/* TCP receive buffer size */
96int	Oflag;					/* TCP send buffer size */
97int	Sflag;					/* TCP MD5 signature option */
98int	Tflag = -1;				/* IP Type of Service */
99int	rtableid = -1;
100
101int timeout = -1;
102int family = AF_UNSPEC;
103char *portlist[PORT_MAX+1];
104char *unix_dg_tmp_socket;
105
106void	atelnet(int, unsigned char *, unsigned int);
107void	build_ports(char *);
108void	help(void);
109int	local_listen(char *, char *, struct addrinfo);
110void	readwrite(int);
111void	fdpass(int nfd) __attribute__((noreturn));
112int	remote_connect(const char *, const char *, struct addrinfo);
113int	timeout_connect(int, const struct sockaddr *, socklen_t);
114int	socks_connect(const char *, const char *, struct addrinfo,
115	    const char *, const char *, struct addrinfo, int, const char *);
116int	udptest(int);
117int	unix_bind(char *);
118int	unix_connect(char *);
119int	unix_listen(char *);
120void	set_common_sockopts(int);
121int	map_tos(char *, int *);
122void	report_connect(const struct sockaddr *, socklen_t);
123void	usage(int);
124
125#ifdef IPSEC
126void	add_ipsec_policy(int, char *);
127
128char	*ipsec_policy[2];
129#endif
130
131int
132main(int argc, char *argv[])
133{
134	int ch, s, ret, socksv, ipsec_count;
135	int numfibs;
136	size_t intsize = sizeof(int);
137	char *host, *uport;
138	struct addrinfo hints;
139	struct servent *sv;
140	socklen_t len;
141	struct sockaddr_storage cliaddr;
142	char *proxy;
143	const char *errstr, *proxyhost = "", *proxyport = NULL;
144	struct addrinfo proxyhints;
145	char unix_dg_tmp_socket_buf[UNIX_DG_TMP_SOCKET_SIZE];
146	struct option longopts[] = {
147		{ "no-tcpopt",	no_argument,	&FreeBSD_Oflag,	1 },
148		{ NULL,		0,		NULL,		0 }
149	};
150
151	ret = 1;
152	ipsec_count = 0;
153	s = 0;
154	socksv = 5;
155	host = NULL;
156	uport = NULL;
157	sv = NULL;
158
159	while ((ch = getopt_long(argc, argv,
160	    "46DdEe:FhI:i:klNnoO:P:p:rSs:tT:UuV:vw:X:x:z",
161	    longopts, NULL)) != -1) {
162		switch (ch) {
163		case '4':
164			family = AF_INET;
165			break;
166		case '6':
167			family = AF_INET6;
168			break;
169		case 'U':
170			family = AF_UNIX;
171			break;
172		case 'X':
173			if (strcasecmp(optarg, "connect") == 0)
174				socksv = -1; /* HTTP proxy CONNECT */
175			else if (strcmp(optarg, "4") == 0)
176				socksv = 4; /* SOCKS v.4 */
177			else if (strcmp(optarg, "5") == 0)
178				socksv = 5; /* SOCKS v.5 */
179			else
180				errx(1, "unsupported proxy protocol");
181			break;
182		case 'd':
183			dflag = 1;
184			break;
185		case 'e':
186#ifdef IPSEC
187			ipsec_policy[ipsec_count++ % 2] = optarg;
188#else
189			errx(1, "IPsec support unavailable.");
190#endif
191			break;
192		case 'E':
193#ifdef IPSEC
194			ipsec_policy[0] = "in  ipsec esp/transport//require";
195			ipsec_policy[1] = "out ipsec esp/transport//require";
196#else
197			errx(1, "IPsec support unavailable.");
198#endif
199			break;
200		case 'F':
201			Fflag = 1;
202			break;
203		case 'h':
204			help();
205			break;
206		case 'i':
207			iflag = strtonum(optarg, 0, UINT_MAX, &errstr);
208			if (errstr)
209				errx(1, "interval %s: %s", errstr, optarg);
210			break;
211		case 'k':
212			kflag = 1;
213			break;
214		case 'l':
215			lflag = 1;
216			break;
217		case 'N':
218			Nflag = 1;
219			break;
220		case 'n':
221			nflag = 1;
222			break;
223		case 'o':
224			fprintf(stderr, "option -o is deprecated.\n");
225			break;
226		case 'P':
227			Pflag = optarg;
228			break;
229		case 'p':
230			pflag = optarg;
231			break;
232		case 'r':
233			rflag = 1;
234			break;
235		case 's':
236			sflag = optarg;
237			break;
238		case 't':
239			tflag = 1;
240			break;
241		case 'u':
242			uflag = 1;
243			break;
244		case 'V':
245			if (sysctlbyname("net.fibs", &numfibs, &intsize, NULL, 0) == -1)
246				errx(1, "Multiple FIBS not supported");
247			rtableid = (int)strtonum(optarg, 0,
248			    numfibs - 1, &errstr);
249			if (errstr)
250				errx(1, "rtable %s: %s", errstr, optarg);
251			break;
252		case 'v':
253			vflag = 1;
254			break;
255		case 'w':
256			timeout = strtonum(optarg, 0, INT_MAX / 1000, &errstr);
257			if (errstr)
258				errx(1, "timeout %s: %s", errstr, optarg);
259			timeout *= 1000;
260			break;
261		case 'x':
262			xflag = 1;
263			if ((proxy = strdup(optarg)) == NULL)
264				err(1, NULL);
265			break;
266		case 'z':
267			zflag = 1;
268			break;
269		case 'D':
270			Dflag = 1;
271			break;
272		case 'I':
273			Iflag = strtonum(optarg, 1, 65536 << 14, &errstr);
274			if (errstr != NULL)
275				errx(1, "TCP receive window %s: %s",
276				    errstr, optarg);
277			break;
278		case 'O':
279			Oflag = strtonum(optarg, 1, 65536 << 14, &errstr);
280			if (errstr != NULL) {
281			    if (strcmp(errstr, "invalid") != 0)
282				errx(1, "TCP send window %s: %s",
283				    errstr, optarg);
284			}
285			break;
286		case 'S':
287			Sflag = 1;
288			break;
289		case 'T':
290			errstr = NULL;
291			errno = 0;
292			if (map_tos(optarg, &Tflag))
293				break;
294			if (strlen(optarg) > 1 && optarg[0] == '0' &&
295			    optarg[1] == 'x')
296				Tflag = (int)strtol(optarg, NULL, 16);
297			else
298				Tflag = (int)strtonum(optarg, 0, 255,
299				    &errstr);
300			if (Tflag < 0 || Tflag > 255 || errstr || errno)
301				errx(1, "illegal tos value %s", optarg);
302			break;
303		default:
304			usage(1);
305		}
306	}
307	argc -= optind;
308	argv += optind;
309
310	/* Cruft to make sure options are clean, and used properly. */
311	if (argv[0] && !argv[1] && family == AF_UNIX) {
312		host = argv[0];
313		uport = NULL;
314	} else if (argv[0] && !argv[1]) {
315		if  (!lflag)
316			usage(1);
317		uport = argv[0];
318		host = NULL;
319	} else if (argv[0] && argv[1]) {
320		host = argv[0];
321		uport = argv[1];
322	} else
323		usage(1);
324
325	if (lflag && sflag)
326		errx(1, "cannot use -s and -l");
327	if (lflag && pflag)
328		errx(1, "cannot use -p and -l");
329	if (lflag && zflag)
330		errx(1, "cannot use -z and -l");
331	if (!lflag && kflag)
332		errx(1, "must use -l with -k");
333
334	/* Get name of temporary socket for unix datagram client */
335	if ((family == AF_UNIX) && uflag && !lflag) {
336		if (sflag) {
337			unix_dg_tmp_socket = sflag;
338		} else {
339			strlcpy(unix_dg_tmp_socket_buf, "/tmp/nc.XXXXXXXXXX",
340				UNIX_DG_TMP_SOCKET_SIZE);
341			if (mktemp(unix_dg_tmp_socket_buf) == NULL)
342				err(1, "mktemp");
343			unix_dg_tmp_socket = unix_dg_tmp_socket_buf;
344		}
345	}
346
347	/* Initialize addrinfo structure. */
348	if (family != AF_UNIX) {
349		memset(&hints, 0, sizeof(struct addrinfo));
350		hints.ai_family = family;
351		hints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM;
352		hints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP;
353		if (nflag)
354			hints.ai_flags |= AI_NUMERICHOST;
355	}
356
357	if (xflag) {
358		if (uflag)
359			errx(1, "no proxy support for UDP mode");
360
361		if (lflag)
362			errx(1, "no proxy support for listen");
363
364		if (family == AF_UNIX)
365			errx(1, "no proxy support for unix sockets");
366
367		/* XXX IPv6 transport to proxy would probably work */
368		if (family == AF_INET6)
369			errx(1, "no proxy support for IPv6");
370
371		if (sflag)
372			errx(1, "no proxy support for local source address");
373
374		proxyhost = strsep(&proxy, ":");
375		proxyport = proxy;
376
377		memset(&proxyhints, 0, sizeof(struct addrinfo));
378		proxyhints.ai_family = family;
379		proxyhints.ai_socktype = SOCK_STREAM;
380		proxyhints.ai_protocol = IPPROTO_TCP;
381		if (nflag)
382			proxyhints.ai_flags |= AI_NUMERICHOST;
383	}
384
385	if (lflag) {
386		int connfd;
387		ret = 0;
388
389		if (family == AF_UNIX) {
390			if (uflag)
391				s = unix_bind(host);
392			else
393				s = unix_listen(host);
394		}
395
396		/* Allow only one connection at a time, but stay alive. */
397		for (;;) {
398			if (family != AF_UNIX)
399				s = local_listen(host, uport, hints);
400			if (s < 0)
401				err(1, NULL);
402			/*
403			 * For UDP and -k, don't connect the socket, let it
404			 * receive datagrams from multiple socket pairs.
405			 */
406			if (uflag && kflag)
407				readwrite(s);
408			/*
409			 * For UDP and not -k, we will use recvfrom() initially
410			 * to wait for a caller, then use the regular functions
411			 * to talk to the caller.
412			 */
413			else if (uflag && !kflag) {
414				int rv, plen;
415				char buf[16384];
416				struct sockaddr_storage z;
417
418				len = sizeof(z);
419				plen = 2048;
420				rv = recvfrom(s, buf, plen, MSG_PEEK,
421				    (struct sockaddr *)&z, &len);
422				if (rv < 0)
423					err(1, "recvfrom");
424
425				rv = connect(s, (struct sockaddr *)&z, len);
426				if (rv < 0)
427					err(1, "connect");
428
429				if (vflag)
430					report_connect((struct sockaddr *)&z, len);
431
432				readwrite(s);
433			} else {
434				len = sizeof(cliaddr);
435				connfd = accept(s, (struct sockaddr *)&cliaddr,
436				    &len);
437				if (connfd == -1) {
438					/* For now, all errnos are fatal */
439   					err(1, "accept");
440				}
441				if (vflag)
442					report_connect((struct sockaddr *)&cliaddr, len);
443
444				readwrite(connfd);
445				close(connfd);
446			}
447
448			if (family != AF_UNIX)
449				close(s);
450			else if (uflag) {
451				if (connect(s, NULL, 0) < 0)
452					err(1, "connect");
453			}
454
455			if (!kflag)
456				break;
457		}
458	} else if (family == AF_UNIX) {
459		ret = 0;
460
461		if ((s = unix_connect(host)) > 0 && !zflag) {
462			readwrite(s);
463			close(s);
464		} else
465			ret = 1;
466
467		if (uflag)
468			unlink(unix_dg_tmp_socket);
469		exit(ret);
470
471	} else {
472		int i = 0;
473
474		/* Construct the portlist[] array. */
475		build_ports(uport);
476
477		/* Cycle through portlist, connecting to each port. */
478		for (i = 0; portlist[i] != NULL; i++) {
479			if (s)
480				close(s);
481
482			if (xflag)
483				s = socks_connect(host, portlist[i], hints,
484				    proxyhost, proxyport, proxyhints, socksv,
485				    Pflag);
486			else
487				s = remote_connect(host, portlist[i], hints);
488
489			if (s < 0)
490				continue;
491
492			ret = 0;
493			if (vflag || zflag) {
494				/* For UDP, make sure we are connected. */
495				if (uflag) {
496					if (udptest(s) == -1) {
497						ret = 1;
498						continue;
499					}
500				}
501
502				/* Don't look up port if -n. */
503				if (nflag)
504					sv = NULL;
505				else {
506					sv = getservbyport(
507					    ntohs(atoi(portlist[i])),
508					    uflag ? "udp" : "tcp");
509				}
510
511				fprintf(stderr,
512				    "Connection to %s %s port [%s/%s] "
513				    "succeeded!\n", host, portlist[i],
514				    uflag ? "udp" : "tcp",
515				    sv ? sv->s_name : "*");
516			}
517			if (Fflag)
518				fdpass(s);
519			else if (!zflag)
520				readwrite(s);
521		}
522	}
523
524	if (s)
525		close(s);
526
527	exit(ret);
528}
529
530/*
531 * unix_bind()
532 * Returns a unix socket bound to the given path
533 */
534int
535unix_bind(char *path)
536{
537	struct sockaddr_un sun;
538	int s;
539
540	/* Create unix domain socket. */
541	if ((s = socket(AF_UNIX, uflag ? SOCK_DGRAM : SOCK_STREAM,
542	     0)) < 0)
543		return (-1);
544
545	memset(&sun, 0, sizeof(struct sockaddr_un));
546	sun.sun_family = AF_UNIX;
547
548	if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
549	    sizeof(sun.sun_path)) {
550		close(s);
551		errno = ENAMETOOLONG;
552		return (-1);
553	}
554
555	if (bind(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
556		close(s);
557		return (-1);
558	}
559	return (s);
560}
561
562/*
563 * unix_connect()
564 * Returns a socket connected to a local unix socket. Returns -1 on failure.
565 */
566int
567unix_connect(char *path)
568{
569	struct sockaddr_un sun;
570	int s;
571
572	if (uflag) {
573		if ((s = unix_bind(unix_dg_tmp_socket)) < 0)
574			return (-1);
575	} else {
576		if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
577			return (-1);
578	}
579	(void)fcntl(s, F_SETFD, FD_CLOEXEC);
580
581	memset(&sun, 0, sizeof(struct sockaddr_un));
582	sun.sun_family = AF_UNIX;
583
584	if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
585	    sizeof(sun.sun_path)) {
586		close(s);
587		errno = ENAMETOOLONG;
588		return (-1);
589	}
590	if (connect(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
591		close(s);
592		return (-1);
593	}
594	return (s);
595
596}
597
598/*
599 * unix_listen()
600 * Create a unix domain socket, and listen on it.
601 */
602int
603unix_listen(char *path)
604{
605	int s;
606	if ((s = unix_bind(path)) < 0)
607		return (-1);
608
609	if (listen(s, 5) < 0) {
610		close(s);
611		return (-1);
612	}
613	return (s);
614}
615
616/*
617 * remote_connect()
618 * Returns a socket connected to a remote host. Properly binds to a local
619 * port or source address if needed. Returns -1 on failure.
620 */
621int
622remote_connect(const char *host, const char *port, struct addrinfo hints)
623{
624	struct addrinfo *res, *res0;
625	int s, error, on = 1;
626
627	if ((error = getaddrinfo(host, port, &hints, &res)))
628		errx(1, "getaddrinfo: %s", gai_strerror(error));
629
630	res0 = res;
631	do {
632		if ((s = socket(res0->ai_family, res0->ai_socktype,
633		    res0->ai_protocol)) < 0)
634			continue;
635#ifdef IPSEC
636		if (ipsec_policy[0] != NULL)
637			add_ipsec_policy(s, ipsec_policy[0]);
638		if (ipsec_policy[1] != NULL)
639			add_ipsec_policy(s, ipsec_policy[1]);
640#endif
641
642		if (rtableid >= 0 && (setsockopt(s, SOL_SOCKET, SO_SETFIB,
643		    &rtableid, sizeof(rtableid)) == -1))
644			err(1, "setsockopt SO_SETFIB");
645
646		/* Bind to a local port or source address if specified. */
647		if (sflag || pflag) {
648			struct addrinfo ahints, *ares;
649
650			/* try IP_BINDANY, but don't insist */
651			setsockopt(s, IPPROTO_IP, IP_BINDANY, &on, sizeof(on));
652			memset(&ahints, 0, sizeof(struct addrinfo));
653			ahints.ai_family = res0->ai_family;
654			ahints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM;
655			ahints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP;
656			ahints.ai_flags = AI_PASSIVE;
657			if ((error = getaddrinfo(sflag, pflag, &ahints, &ares)))
658				errx(1, "getaddrinfo: %s", gai_strerror(error));
659
660			if (bind(s, (struct sockaddr *)ares->ai_addr,
661			    ares->ai_addrlen) < 0)
662				err(1, "bind failed");
663			freeaddrinfo(ares);
664		}
665
666		set_common_sockopts(s);
667
668		if (timeout_connect(s, res0->ai_addr, res0->ai_addrlen) == 0)
669			break;
670		else if (vflag)
671			warn("connect to %s port %s (%s) failed", host, port,
672			    uflag ? "udp" : "tcp");
673
674		close(s);
675		s = -1;
676	} while ((res0 = res0->ai_next) != NULL);
677
678	freeaddrinfo(res);
679
680	return (s);
681}
682
683int
684timeout_connect(int s, const struct sockaddr *name, socklen_t namelen)
685{
686	struct pollfd pfd;
687	socklen_t optlen;
688	int flags, optval;
689	int ret;
690
691	if (timeout != -1) {
692		flags = fcntl(s, F_GETFL, 0);
693		if (fcntl(s, F_SETFL, flags | O_NONBLOCK) == -1)
694			err(1, "set non-blocking mode");
695	}
696
697	if ((ret = connect(s, name, namelen)) != 0 && errno == EINPROGRESS) {
698		pfd.fd = s;
699		pfd.events = POLLOUT;
700		if ((ret = poll(&pfd, 1, timeout)) == 1) {
701			optlen = sizeof(optval);
702			if ((ret = getsockopt(s, SOL_SOCKET, SO_ERROR,
703			    &optval, &optlen)) == 0) {
704				errno = optval;
705				ret = optval == 0 ? 0 : -1;
706			}
707		} else if (ret == 0) {
708			errno = ETIMEDOUT;
709			ret = -1;
710		} else
711			err(1, "poll failed");
712	}
713
714	if (timeout != -1 && fcntl(s, F_SETFL, flags) == -1)
715		err(1, "restoring flags");
716
717	return (ret);
718}
719
720/*
721 * local_listen()
722 * Returns a socket listening on a local port, binds to specified source
723 * address. Returns -1 on failure.
724 */
725int
726local_listen(char *host, char *port, struct addrinfo hints)
727{
728	struct addrinfo *res, *res0;
729	int s, ret, x = 1;
730	int error;
731
732	/* Allow nodename to be null. */
733	hints.ai_flags |= AI_PASSIVE;
734
735	/*
736	 * In the case of binding to a wildcard address
737	 * default to binding to an ipv4 address.
738	 */
739	if (host == NULL && hints.ai_family == AF_UNSPEC)
740		hints.ai_family = AF_INET;
741
742	if ((error = getaddrinfo(host, port, &hints, &res)))
743		errx(1, "getaddrinfo: %s", gai_strerror(error));
744
745	res0 = res;
746	do {
747		if ((s = socket(res0->ai_family, res0->ai_socktype,
748		    res0->ai_protocol)) < 0)
749			continue;
750
751		if (rtableid >= 0 && (setsockopt(s, SOL_SOCKET, SO_SETFIB,
752		    &rtableid, sizeof(rtableid)) == -1))
753			err(1, "setsockopt SO_SETFIB");
754
755		ret = setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &x, sizeof(x));
756		if (ret == -1)
757			err(1, NULL);
758#ifdef IPSEC
759		if (ipsec_policy[0] != NULL)
760			add_ipsec_policy(s, ipsec_policy[0]);
761		if (ipsec_policy[1] != NULL)
762			add_ipsec_policy(s, ipsec_policy[1]);
763#endif
764		if (FreeBSD_Oflag) {
765			if (setsockopt(s, IPPROTO_TCP, TCP_NOOPT,
766			    &FreeBSD_Oflag, sizeof(FreeBSD_Oflag)) == -1)
767				err(1, "disable TCP options");
768		}
769
770		if (bind(s, (struct sockaddr *)res0->ai_addr,
771		    res0->ai_addrlen) == 0)
772			break;
773
774		close(s);
775		s = -1;
776	} while ((res0 = res0->ai_next) != NULL);
777
778	if (!uflag && s != -1) {
779		if (listen(s, 1) < 0)
780			err(1, "listen");
781	}
782
783	freeaddrinfo(res);
784
785	return (s);
786}
787
788/*
789 * readwrite()
790 * Loop that polls on the network file descriptor and stdin.
791 */
792void
793readwrite(int nfd)
794{
795	struct pollfd pfd[2];
796	unsigned char buf[16 * 1024];
797	int n, wfd = fileno(stdin);
798	int lfd = fileno(stdout);
799	int plen;
800
801	plen = sizeof(buf);
802
803	/* Setup Network FD */
804	pfd[0].fd = nfd;
805	pfd[0].events = POLLIN;
806
807	/* Set up STDIN FD. */
808	pfd[1].fd = wfd;
809	pfd[1].events = POLLIN;
810
811	while (pfd[0].fd != -1) {
812		if (iflag)
813			sleep(iflag);
814
815		if ((n = poll(pfd, 2 - dflag, timeout)) < 0) {
816			int saved_errno = errno;
817			close(nfd);
818			errc(1, saved_errno, "Polling Error");
819		}
820
821		if (n == 0)
822			return;
823
824		if (pfd[0].revents & POLLIN) {
825			if ((n = read(nfd, buf, plen)) < 0)
826				return;
827			else if (n == 0) {
828				shutdown(nfd, SHUT_RD);
829				pfd[0].fd = -1;
830				pfd[0].events = 0;
831			} else {
832				if (tflag)
833					atelnet(nfd, buf, n);
834				if (atomicio(vwrite, lfd, buf, n) != n)
835					return;
836			}
837		}
838
839		if (!dflag && pfd[1].revents & POLLIN) {
840			if ((n = read(wfd, buf, plen)) < 0)
841				return;
842			else if (n == 0) {
843				if (Nflag)
844					shutdown(nfd, SHUT_WR);
845				pfd[1].fd = -1;
846				pfd[1].events = 0;
847			} else {
848				if (atomicio(vwrite, nfd, buf, n) != n)
849					return;
850			}
851		}
852	}
853}
854
855/*
856 * fdpass()
857 * Pass the connected file descriptor to stdout and exit.
858 */
859void
860fdpass(int nfd)
861{
862	struct msghdr mh;
863	union {
864		struct cmsghdr hdr;
865		char buf[CMSG_SPACE(sizeof(int))];
866	} cmsgbuf;
867	struct cmsghdr *cmsg;
868	struct iovec iov;
869	char c = '\0';
870	ssize_t r;
871	struct pollfd pfd;
872
873	/* Avoid obvious stupidity */
874	if (isatty(STDOUT_FILENO))
875		errx(1, "Cannot pass file descriptor to tty");
876
877	bzero(&mh, sizeof(mh));
878	bzero(&cmsgbuf, sizeof(cmsgbuf));
879	bzero(&iov, sizeof(iov));
880	bzero(&pfd, sizeof(pfd));
881
882	mh.msg_control = (caddr_t)&cmsgbuf.buf;
883	mh.msg_controllen = sizeof(cmsgbuf.buf);
884	cmsg = CMSG_FIRSTHDR(&mh);
885	cmsg->cmsg_len = CMSG_LEN(sizeof(int));
886	cmsg->cmsg_level = SOL_SOCKET;
887	cmsg->cmsg_type = SCM_RIGHTS;
888	*(int *)CMSG_DATA(cmsg) = nfd;
889
890	iov.iov_base = &c;
891	iov.iov_len = 1;
892	mh.msg_iov = &iov;
893	mh.msg_iovlen = 1;
894
895	bzero(&pfd, sizeof(pfd));
896	pfd.fd = STDOUT_FILENO;
897	for (;;) {
898		r = sendmsg(STDOUT_FILENO, &mh, 0);
899		if (r == -1) {
900			if (errno == EAGAIN || errno == EINTR) {
901				pfd.events = POLLOUT;
902				if (poll(&pfd, 1, -1) == -1)
903					err(1, "poll");
904				continue;
905			}
906			err(1, "sendmsg");
907		} else if (r == -1)
908			errx(1, "sendmsg: unexpected return value %zd", r);
909		else
910			break;
911	}
912	exit(0);
913}
914
915/* Deal with RFC 854 WILL/WONT DO/DONT negotiation. */
916void
917atelnet(int nfd, unsigned char *buf, unsigned int size)
918{
919	unsigned char *p, *end;
920	unsigned char obuf[4];
921
922	if (size < 3)
923		return;
924	end = buf + size - 2;
925
926	for (p = buf; p < end; p++) {
927		if (*p != IAC)
928			continue;
929
930		obuf[0] = IAC;
931		p++;
932		if ((*p == WILL) || (*p == WONT))
933			obuf[1] = DONT;
934		else if ((*p == DO) || (*p == DONT))
935			obuf[1] = WONT;
936		else
937			continue;
938
939		p++;
940		obuf[2] = *p;
941		if (atomicio(vwrite, nfd, obuf, 3) != 3)
942			warn("Write Error!");
943	}
944}
945
946/*
947 * build_ports()
948 * Build an array of ports in portlist[], listing each port
949 * that we should try to connect to.
950 */
951void
952build_ports(char *p)
953{
954	const char *errstr;
955	char *n;
956	int hi, lo, cp;
957	int x = 0;
958
959	if ((n = strchr(p, '-')) != NULL) {
960		*n = '\0';
961		n++;
962
963		/* Make sure the ports are in order: lowest->highest. */
964		hi = strtonum(n, 1, PORT_MAX, &errstr);
965		if (errstr)
966			errx(1, "port number %s: %s", errstr, n);
967		lo = strtonum(p, 1, PORT_MAX, &errstr);
968		if (errstr)
969			errx(1, "port number %s: %s", errstr, p);
970
971		if (lo > hi) {
972			cp = hi;
973			hi = lo;
974			lo = cp;
975		}
976
977		/* Load ports sequentially. */
978		for (cp = lo; cp <= hi; cp++) {
979			portlist[x] = calloc(1, PORT_MAX_LEN);
980			if (portlist[x] == NULL)
981				err(1, NULL);
982			snprintf(portlist[x], PORT_MAX_LEN, "%d", cp);
983			x++;
984		}
985
986		/* Randomly swap ports. */
987		if (rflag) {
988			int y;
989			char *c;
990
991			for (x = 0; x <= (hi - lo); x++) {
992				y = (arc4random() & 0xFFFF) % (hi - lo);
993				c = portlist[x];
994				portlist[x] = portlist[y];
995				portlist[y] = c;
996			}
997		}
998	} else {
999		hi = strtonum(p, 1, PORT_MAX, &errstr);
1000		if (errstr)
1001			errx(1, "port number %s: %s", errstr, p);
1002		portlist[0] = strdup(p);
1003		if (portlist[0] == NULL)
1004			err(1, NULL);
1005	}
1006}
1007
1008/*
1009 * udptest()
1010 * Do a few writes to see if the UDP port is there.
1011 * Fails once PF state table is full.
1012 */
1013int
1014udptest(int s)
1015{
1016	int i, ret;
1017
1018	for (i = 0; i <= 3; i++) {
1019		if (write(s, "X", 1) == 1)
1020			ret = 1;
1021		else
1022			ret = -1;
1023	}
1024	return (ret);
1025}
1026
1027void
1028set_common_sockopts(int s)
1029{
1030	int x = 1;
1031
1032	if (Sflag) {
1033		if (setsockopt(s, IPPROTO_TCP, TCP_MD5SIG,
1034			&x, sizeof(x)) == -1)
1035			err(1, NULL);
1036	}
1037	if (Dflag) {
1038		if (setsockopt(s, SOL_SOCKET, SO_DEBUG,
1039			&x, sizeof(x)) == -1)
1040			err(1, NULL);
1041	}
1042	if (Tflag != -1) {
1043		if (setsockopt(s, IPPROTO_IP, IP_TOS,
1044		    &Tflag, sizeof(Tflag)) == -1)
1045			err(1, "set IP ToS");
1046	}
1047	if (Iflag) {
1048		if (setsockopt(s, SOL_SOCKET, SO_RCVBUF,
1049		    &Iflag, sizeof(Iflag)) == -1)
1050			err(1, "set TCP receive buffer size");
1051	}
1052	if (Oflag) {
1053		if (setsockopt(s, SOL_SOCKET, SO_SNDBUF,
1054		    &Oflag, sizeof(Oflag)) == -1)
1055			err(1, "set TCP send buffer size");
1056	}
1057	if (FreeBSD_Oflag) {
1058		if (setsockopt(s, IPPROTO_TCP, TCP_NOOPT,
1059		    &FreeBSD_Oflag, sizeof(FreeBSD_Oflag)) == -1)
1060			err(1, "disable TCP options");
1061	}
1062}
1063
1064int
1065map_tos(char *s, int *val)
1066{
1067	/* DiffServ Codepoints and other TOS mappings */
1068	const struct toskeywords {
1069		const char	*keyword;
1070		int		 val;
1071	} *t, toskeywords[] = {
1072		{ "af11",		IPTOS_DSCP_AF11 },
1073		{ "af12",		IPTOS_DSCP_AF12 },
1074		{ "af13",		IPTOS_DSCP_AF13 },
1075		{ "af21",		IPTOS_DSCP_AF21 },
1076		{ "af22",		IPTOS_DSCP_AF22 },
1077		{ "af23",		IPTOS_DSCP_AF23 },
1078		{ "af31",		IPTOS_DSCP_AF31 },
1079		{ "af32",		IPTOS_DSCP_AF32 },
1080		{ "af33",		IPTOS_DSCP_AF33 },
1081		{ "af41",		IPTOS_DSCP_AF41 },
1082		{ "af42",		IPTOS_DSCP_AF42 },
1083		{ "af43",		IPTOS_DSCP_AF43 },
1084		{ "critical",		IPTOS_PREC_CRITIC_ECP },
1085		{ "cs0",		IPTOS_DSCP_CS0 },
1086		{ "cs1",		IPTOS_DSCP_CS1 },
1087		{ "cs2",		IPTOS_DSCP_CS2 },
1088		{ "cs3",		IPTOS_DSCP_CS3 },
1089		{ "cs4",		IPTOS_DSCP_CS4 },
1090		{ "cs5",		IPTOS_DSCP_CS5 },
1091		{ "cs6",		IPTOS_DSCP_CS6 },
1092		{ "cs7",		IPTOS_DSCP_CS7 },
1093		{ "ef",			IPTOS_DSCP_EF },
1094		{ "inetcontrol",	IPTOS_PREC_INTERNETCONTROL },
1095		{ "lowdelay",		IPTOS_LOWDELAY },
1096		{ "netcontrol",		IPTOS_PREC_NETCONTROL },
1097		{ "reliability",	IPTOS_RELIABILITY },
1098		{ "throughput",		IPTOS_THROUGHPUT },
1099		{ NULL, 		-1 },
1100	};
1101
1102	for (t = toskeywords; t->keyword != NULL; t++) {
1103		if (strcmp(s, t->keyword) == 0) {
1104			*val = t->val;
1105			return (1);
1106		}
1107	}
1108
1109	return (0);
1110}
1111
1112void
1113report_connect(const struct sockaddr *sa, socklen_t salen)
1114{
1115	char remote_host[NI_MAXHOST];
1116	char remote_port[NI_MAXSERV];
1117	int herr;
1118	int flags = NI_NUMERICSERV;
1119
1120	if (nflag)
1121		flags |= NI_NUMERICHOST;
1122
1123	if ((herr = getnameinfo(sa, salen,
1124	    remote_host, sizeof(remote_host),
1125	    remote_port, sizeof(remote_port),
1126	    flags)) != 0) {
1127		if (herr == EAI_SYSTEM)
1128			err(1, "getnameinfo");
1129		else
1130			errx(1, "getnameinfo: %s", gai_strerror(herr));
1131	}
1132
1133	fprintf(stderr,
1134	    "Connection from %s %s "
1135	    "received!\n", remote_host, remote_port);
1136}
1137
1138void
1139help(void)
1140{
1141	usage(0);
1142	fprintf(stderr, "\tCommand Summary:\n\
1143	\t-4		Use IPv4\n\
1144	\t-6		Use IPv6\n\
1145	\t-D		Enable the debug socket option\n\
1146	\t-d		Detach from stdin\n");
1147#ifdef IPSEC
1148	fprintf(stderr, "\
1149	\t-E		Use IPsec ESP\n\
1150	\t-e policy	Use specified IPsec policy\n");
1151#endif
1152	fprintf(stderr, "\
1153	\t-F		Pass socket fd\n\
1154	\t-h		This help text\n\
1155	\t-I length	TCP receive buffer length\n\
1156	\t-i secs\t	Delay interval for lines sent, ports scanned\n\
1157	\t-k		Keep inbound sockets open for multiple connects\n\
1158	\t-l		Listen mode, for inbound connects\n\
1159	\t-N		Shutdown the network socket after EOF on stdin\n\
1160	\t-n		Suppress name/port resolutions\n\
1161	\t--no-tcpopt	Disable TCP options\n\
1162	\t-O length	TCP send buffer length\n\
1163	\t-P proxyuser\tUsername for proxy authentication\n\
1164	\t-p port\t	Specify local port for remote connects\n\
1165	\t-r		Randomize remote ports\n\
1166	\t-S		Enable the TCP MD5 signature option\n\
1167	\t-s addr\t	Local source address\n\
1168	\t-T toskeyword\tSet IP Type of Service\n\
1169	\t-t		Answer TELNET negotiation\n\
1170	\t-U		Use UNIX domain socket\n\
1171	\t-u		UDP mode\n\
1172	\t-V rtable	Specify alternate routing table\n\
1173	\t-v		Verbose\n\
1174	\t-w secs\t	Timeout for connects and final net reads\n\
1175	\t-X proto	Proxy protocol: \"4\", \"5\" (SOCKS) or \"connect\"\n\
1176	\t-x addr[:port]\tSpecify proxy address and port\n\
1177	\t-z		Zero-I/O mode [used for scanning]\n\
1178	Port numbers can be individual or ranges: lo-hi [inclusive]\n");
1179#ifdef IPSEC
1180	fprintf(stderr, "See ipsec_set_policy(3) for -e argument format\n");
1181#endif
1182	exit(1);
1183}
1184
1185#ifdef IPSEC
1186void
1187add_ipsec_policy(int s, char *policy)
1188{
1189	char *raw;
1190	int e;
1191
1192	raw = ipsec_set_policy(policy, strlen(policy));
1193	if (raw == NULL)
1194		errx(1, "ipsec_set_policy `%s': %s", policy,
1195		     ipsec_strerror());
1196	e = setsockopt(s, IPPROTO_IP, IP_IPSEC_POLICY, raw,
1197			ipsec_get_policylen(raw));
1198	if (e < 0)
1199		err(1, "ipsec policy cannot be configured");
1200	free(raw);
1201	if (vflag)
1202		fprintf(stderr, "ipsec policy configured: `%s'\n", policy);
1203	return;
1204}
1205#endif /* IPSEC */
1206
1207void
1208usage(int ret)
1209{
1210	fprintf(stderr,
1211#ifdef IPSEC
1212	    "usage: nc [-46DdEFhklNnrStUuvz] [-e policy] [-I length] [-i interval] [-O length]\n"
1213#else
1214	    "usage: nc [-46DdFhklNnrStUuvz] [-I length] [-i interval] [-O length]\n"
1215#endif
1216	    "\t  [-P proxy_username] [-p source_port] [-s source] [-T ToS]\n"
1217	    "\t  [-V rtable] [-w timeout] [-X proxy_protocol]\n"
1218	    "\t  [-x proxy_address[:port]] [destination] [port]\n");
1219	if (ret)
1220		exit(1);
1221}
1222