netcat.c revision 235037 
1/* $OpenBSD: netcat.c,v 1.105 2012/02/09 06:25:35 lum 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: head/contrib/netcat/netcat.c 235037 2012-05-04 21:03:39Z 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/un.h>
42
43#include <netinet/in.h>
44#include <netinet/in_systm.h>
45#ifdef IPSEC
46#include <netipsec/ipsec.h>
47#endif
48#include <netinet/tcp.h>
49#include <netinet/ip.h>
50#include <arpa/telnet.h>
51
52#include <err.h>
53#include <errno.h>
54#include <getopt.h>
55#include <netdb.h>
56#include <poll.h>
57#include <stdarg.h>
58#include <stdio.h>
59#include <stdlib.h>
60#include <string.h>
61#include <unistd.h>
62#include <fcntl.h>
63#include <limits.h>
64#include "atomicio.h"
65
66#ifndef SUN_LEN
67#define SUN_LEN(su) \
68	(sizeof(*(su)) - sizeof((su)->sun_path) + strlen((su)->sun_path))
69#endif
70
71#define PORT_MAX	65535
72#define PORT_MAX_LEN	6
73#define UNIX_DG_TMP_SOCKET_SIZE	19
74
75/* Command Line Options */
76int	dflag;					/* detached, no stdin */
77unsigned int iflag;				/* Interval Flag */
78int	jflag;					/* use jumbo frames if we can */
79int	kflag;					/* More than one connect */
80int	lflag;					/* Bind to local port */
81int	nflag;					/* Don't do name look up */
82int	FreeBSD_Oflag;				/* Do not use TCP options */
83char   *Pflag;					/* Proxy username */
84char   *pflag;					/* Localport flag */
85int	rflag;					/* Random ports flag */
86char   *sflag;					/* Source Address */
87int	tflag;					/* Telnet Emulation */
88int	uflag;					/* UDP - Default to TCP */
89int	vflag;					/* Verbosity */
90int	xflag;					/* Socks proxy */
91int	zflag;					/* Port Scan Flag */
92int	Dflag;					/* sodebug */
93int	Iflag;					/* TCP receive buffer size */
94int	Oflag;					/* TCP send buffer size */
95int	Sflag;					/* TCP MD5 signature option */
96int	Tflag = -1;				/* IP Type of Service */
97u_int	rtableid;
98
99int timeout = -1;
100int family = AF_UNSPEC;
101char *portlist[PORT_MAX+1];
102char *unix_dg_tmp_socket;
103
104void	atelnet(int, unsigned char *, unsigned int);
105void	build_ports(char *);
106void	help(void);
107int	local_listen(char *, char *, struct addrinfo);
108void	readwrite(int);
109int	remote_connect(const char *, const char *, struct addrinfo);
110int	timeout_connect(int, const struct sockaddr *, socklen_t);
111int	socks_connect(const char *, const char *, struct addrinfo,
112	    const char *, const char *, struct addrinfo, int, const char *);
113int	udptest(int);
114int	unix_bind(char *);
115int	unix_connect(char *);
116int	unix_listen(char *);
117void	set_common_sockopts(int);
118int	map_tos(char *, int *);
119void	usage(int);
120
121#ifdef IPSEC
122void	add_ipsec_policy(int, char *);
123
124char	*ipsec_policy[2];
125#endif
126
127int
128main(int argc, char *argv[])
129{
130	int ch, s, ret, socksv, ipsec_count;
131	int numfibs;
132	size_t intsize = sizeof(int);
133	char *host, *uport;
134	struct addrinfo hints;
135	struct servent *sv;
136	socklen_t len;
137	struct sockaddr_storage cliaddr;
138	char *proxy;
139	const char *errstr, *proxyhost = "", *proxyport = NULL;
140	struct addrinfo proxyhints;
141	char unix_dg_tmp_socket_buf[UNIX_DG_TMP_SOCKET_SIZE];
142	struct option longopts[] = {
143		{ "no-tcpopt",	no_argument,	&FreeBSD_Oflag,	1 },
144		{ NULL,		0,		NULL,		0 }
145	};
146
147	ret = 1;
148	ipsec_count = 0;
149	s = 0;
150	socksv = 5;
151	host = NULL;
152	uport = NULL;
153	sv = NULL;
154
155	while ((ch = getopt_long(argc, argv,
156	    "46DdEe:hI:i:jklnoO:P:p:rSs:tT:UuV:vw:X:x:z",
157	    longopts, NULL)) != -1) {
158		switch (ch) {
159		case '4':
160			family = AF_INET;
161			break;
162		case '6':
163			family = AF_INET6;
164			break;
165		case 'U':
166			family = AF_UNIX;
167			break;
168		case 'X':
169			if (strcasecmp(optarg, "connect") == 0)
170				socksv = -1; /* HTTP proxy CONNECT */
171			else if (strcmp(optarg, "4") == 0)
172				socksv = 4; /* SOCKS v.4 */
173			else if (strcmp(optarg, "5") == 0)
174				socksv = 5; /* SOCKS v.5 */
175			else
176				errx(1, "unsupported proxy protocol");
177			break;
178		case 'd':
179			dflag = 1;
180			break;
181		case 'e':
182#ifdef IPSEC
183			ipsec_policy[ipsec_count++ % 2] = optarg;
184#else
185			errx(1, "IPsec support unavailable.");
186#endif
187			break;
188		case 'E':
189#ifdef IPSEC
190			ipsec_policy[0] = "in  ipsec esp/transport//require";
191			ipsec_policy[1] = "out ipsec esp/transport//require";
192#else
193			errx(1, "IPsec support unavailable.");
194#endif
195			break;
196		case 'h':
197			help();
198			break;
199		case 'i':
200			iflag = strtonum(optarg, 0, UINT_MAX, &errstr);
201			if (errstr)
202				errx(1, "interval %s: %s", errstr, optarg);
203			break;
204#ifdef SO_JUMBO
205		case 'j':
206			jflag = 1;
207			break;
208#endif
209		case 'k':
210			kflag = 1;
211			break;
212		case 'l':
213			lflag = 1;
214			break;
215		case 'n':
216			nflag = 1;
217			break;
218		case 'o':
219			fprintf(stderr, "option -o is deprecated.\n");
220			break;
221		case 'P':
222			Pflag = optarg;
223			break;
224		case 'p':
225			pflag = optarg;
226			break;
227		case 'r':
228			rflag = 1;
229			break;
230		case 's':
231			sflag = optarg;
232			break;
233		case 't':
234			tflag = 1;
235			break;
236		case 'u':
237			uflag = 1;
238			break;
239		case 'V':
240			if (sysctlbyname("net.fibs", &numfibs, &intsize, NULL, 0) == -1)
241				errx(1, "Multiple FIBS not supported");
242			rtableid = (unsigned int)strtonum(optarg, 0,
243			    numfibs - 1, &errstr);
244			if (errstr)
245				errx(1, "rtable %s: %s", errstr, optarg);
246			break;
247		case 'v':
248			vflag = 1;
249			break;
250		case 'w':
251			timeout = strtonum(optarg, 0, INT_MAX / 1000, &errstr);
252			if (errstr)
253				errx(1, "timeout %s: %s", errstr, optarg);
254			timeout *= 1000;
255			break;
256		case 'x':
257			xflag = 1;
258			if ((proxy = strdup(optarg)) == NULL)
259				err(1, NULL);
260			break;
261		case 'z':
262			zflag = 1;
263			break;
264		case 'D':
265			Dflag = 1;
266			break;
267		case 'I':
268			Iflag = strtonum(optarg, 1, 65536 << 14, &errstr);
269			if (errstr != NULL)
270				errx(1, "TCP receive window %s: %s",
271				    errstr, optarg);
272			break;
273		case 'O':
274			Oflag = strtonum(optarg, 1, 65536 << 14, &errstr);
275			if (errstr != NULL) {
276			    if (strcmp(errstr, "invalid") != 0)
277				errx(1, "TCP send window %s: %s",
278				    errstr, optarg);
279			}
280			break;
281		case 'S':
282			Sflag = 1;
283			break;
284		case 'T':
285			errstr = NULL;
286			errno = 0;
287			if (map_tos(optarg, &Tflag))
288				break;
289			if (strlen(optarg) > 1 && optarg[0] == '0' &&
290			    optarg[1] == 'x')
291				Tflag = (int)strtol(optarg, NULL, 16);
292			else
293				Tflag = (int)strtonum(optarg, 0, 255,
294				    &errstr);
295			if (Tflag < 0 || Tflag > 255 || errstr || errno)
296				errx(1, "illegal tos value %s", optarg);
297			break;
298		default:
299			usage(1);
300		}
301	}
302	argc -= optind;
303	argv += optind;
304
305	/* Cruft to make sure options are clean, and used properly. */
306	if (argv[0] && !argv[1] && family == AF_UNIX) {
307		host = argv[0];
308		uport = NULL;
309	} else if (argv[0] && !argv[1]) {
310		if  (!lflag)
311			usage(1);
312		uport = argv[0];
313		host = NULL;
314	} else if (argv[0] && argv[1]) {
315		host = argv[0];
316		uport = argv[1];
317	} else
318		usage(1);
319
320	if (lflag && sflag)
321		errx(1, "cannot use -s and -l");
322	if (lflag && pflag)
323		errx(1, "cannot use -p and -l");
324	if (lflag && zflag)
325		errx(1, "cannot use -z and -l");
326	if (!lflag && kflag)
327		errx(1, "must use -l with -k");
328
329	/* Get name of temporary socket for unix datagram client */
330	if ((family == AF_UNIX) && uflag && !lflag) {
331		if (sflag) {
332			unix_dg_tmp_socket = sflag;
333		} else {
334			strlcpy(unix_dg_tmp_socket_buf, "/tmp/nc.XXXXXXXXXX",
335				UNIX_DG_TMP_SOCKET_SIZE);
336			if (mktemp(unix_dg_tmp_socket_buf) == NULL)
337				err(1, "mktemp");
338			unix_dg_tmp_socket = unix_dg_tmp_socket_buf;
339		}
340	}
341
342	/* Initialize addrinfo structure. */
343	if (family != AF_UNIX) {
344		memset(&hints, 0, sizeof(struct addrinfo));
345		hints.ai_family = family;
346		hints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM;
347		hints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP;
348		if (nflag)
349			hints.ai_flags |= AI_NUMERICHOST;
350	}
351
352	if (xflag) {
353		if (uflag)
354			errx(1, "no proxy support for UDP mode");
355
356		if (lflag)
357			errx(1, "no proxy support for listen");
358
359		if (family == AF_UNIX)
360			errx(1, "no proxy support for unix sockets");
361
362		/* XXX IPv6 transport to proxy would probably work */
363		if (family == AF_INET6)
364			errx(1, "no proxy support for IPv6");
365
366		if (sflag)
367			errx(1, "no proxy support for local source address");
368
369		proxyhost = strsep(&proxy, ":");
370		proxyport = proxy;
371
372		memset(&proxyhints, 0, sizeof(struct addrinfo));
373		proxyhints.ai_family = family;
374		proxyhints.ai_socktype = SOCK_STREAM;
375		proxyhints.ai_protocol = IPPROTO_TCP;
376		if (nflag)
377			proxyhints.ai_flags |= AI_NUMERICHOST;
378	}
379
380	if (lflag) {
381		int connfd;
382		ret = 0;
383
384		if (family == AF_UNIX) {
385			if (uflag)
386				s = unix_bind(host);
387			else
388				s = unix_listen(host);
389		}
390
391		/* Allow only one connection at a time, but stay alive. */
392		for (;;) {
393			if (family != AF_UNIX)
394				s = local_listen(host, uport, hints);
395			if (s < 0)
396				err(1, NULL);
397			/*
398			 * For UDP, we will use recvfrom() initially
399			 * to wait for a caller, then use the regular
400			 * functions to talk to the caller.
401			 */
402			if (uflag) {
403				int rv, plen;
404				char buf[16384];
405				struct sockaddr_storage z;
406
407				len = sizeof(z);
408				plen = jflag ? 16384 : 2048;
409				rv = recvfrom(s, buf, plen, MSG_PEEK,
410				    (struct sockaddr *)&z, &len);
411				if (rv < 0)
412					err(1, "recvfrom");
413
414				rv = connect(s, (struct sockaddr *)&z, len);
415				if (rv < 0)
416					err(1, "connect");
417
418				readwrite(s);
419			} else {
420				len = sizeof(cliaddr);
421				connfd = accept(s, (struct sockaddr *)&cliaddr,
422				    &len);
423				readwrite(connfd);
424				close(connfd);
425			}
426
427			if (family != AF_UNIX)
428				close(s);
429			else if (uflag) {
430				if (connect(s, NULL, 0) < 0)
431					err(1, "connect");
432			}
433
434			if (!kflag)
435				break;
436		}
437	} else if (family == AF_UNIX) {
438		ret = 0;
439
440		if ((s = unix_connect(host)) > 0 && !zflag) {
441			readwrite(s);
442			close(s);
443		} else
444			ret = 1;
445
446		if (uflag)
447			unlink(unix_dg_tmp_socket);
448		exit(ret);
449
450	} else {
451		int i = 0;
452
453		/* Construct the portlist[] array. */
454		build_ports(uport);
455
456		/* Cycle through portlist, connecting to each port. */
457		for (i = 0; portlist[i] != NULL; i++) {
458			if (s)
459				close(s);
460
461			if (xflag)
462				s = socks_connect(host, portlist[i], hints,
463				    proxyhost, proxyport, proxyhints, socksv,
464				    Pflag);
465			else
466				s = remote_connect(host, portlist[i], hints);
467
468			if (s < 0)
469				continue;
470
471			ret = 0;
472			if (vflag || zflag) {
473				/* For UDP, make sure we are connected. */
474				if (uflag) {
475					if (udptest(s) == -1) {
476						ret = 1;
477						continue;
478					}
479				}
480
481				/* Don't look up port if -n. */
482				if (nflag)
483					sv = NULL;
484				else {
485					sv = getservbyport(
486					    ntohs(atoi(portlist[i])),
487					    uflag ? "udp" : "tcp");
488				}
489
490				fprintf(stderr,
491				    "Connection to %s %s port [%s/%s] "
492				    "succeeded!\n", host, portlist[i],
493				    uflag ? "udp" : "tcp",
494				    sv ? sv->s_name : "*");
495			}
496			if (!zflag)
497				readwrite(s);
498		}
499	}
500
501	if (s)
502		close(s);
503
504	exit(ret);
505}
506
507/*
508 * unix_bind()
509 * Returns a unix socket bound to the given path
510 */
511int
512unix_bind(char *path)
513{
514	struct sockaddr_un sun;
515	int s;
516
517	/* Create unix domain socket. */
518	if ((s = socket(AF_UNIX, uflag ? SOCK_DGRAM : SOCK_STREAM,
519	     0)) < 0)
520		return (-1);
521
522	memset(&sun, 0, sizeof(struct sockaddr_un));
523	sun.sun_family = AF_UNIX;
524
525	if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
526	    sizeof(sun.sun_path)) {
527		close(s);
528		errno = ENAMETOOLONG;
529		return (-1);
530	}
531
532	if (bind(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
533		close(s);
534		return (-1);
535	}
536	return (s);
537}
538
539/*
540 * unix_connect()
541 * Returns a socket connected to a local unix socket. Returns -1 on failure.
542 */
543int
544unix_connect(char *path)
545{
546	struct sockaddr_un sun;
547	int s;
548
549	if (uflag) {
550		if ((s = unix_bind(unix_dg_tmp_socket)) < 0)
551			return (-1);
552	} else {
553		if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
554			return (-1);
555	}
556	(void)fcntl(s, F_SETFD, 1);
557
558	memset(&sun, 0, sizeof(struct sockaddr_un));
559	sun.sun_family = AF_UNIX;
560
561	if (strlcpy(sun.sun_path, path, sizeof(sun.sun_path)) >=
562	    sizeof(sun.sun_path)) {
563		close(s);
564		errno = ENAMETOOLONG;
565		return (-1);
566	}
567	if (connect(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
568		close(s);
569		return (-1);
570	}
571	return (s);
572
573}
574
575/*
576 * unix_listen()
577 * Create a unix domain socket, and listen on it.
578 */
579int
580unix_listen(char *path)
581{
582	int s;
583	if ((s = unix_bind(path)) < 0)
584		return (-1);
585
586	if (listen(s, 5) < 0) {
587		close(s);
588		return (-1);
589	}
590	return (s);
591}
592
593/*
594 * remote_connect()
595 * Returns a socket connected to a remote host. Properly binds to a local
596 * port or source address if needed. Returns -1 on failure.
597 */
598int
599remote_connect(const char *host, const char *port, struct addrinfo hints)
600{
601	struct addrinfo *res, *res0;
602	int s, error, on = 1;
603
604	if ((error = getaddrinfo(host, port, &hints, &res)))
605		errx(1, "getaddrinfo: %s", gai_strerror(error));
606
607	res0 = res;
608	do {
609		if ((s = socket(res0->ai_family, res0->ai_socktype,
610		    res0->ai_protocol)) < 0)
611			continue;
612#ifdef IPSEC
613		if (ipsec_policy[0] != NULL)
614			add_ipsec_policy(s, ipsec_policy[0]);
615		if (ipsec_policy[1] != NULL)
616			add_ipsec_policy(s, ipsec_policy[1]);
617#endif
618
619		if (rtableid) {
620			if (setsockopt(s, SOL_SOCKET, SO_SETFIB, &rtableid,
621			    sizeof(rtableid)) == -1)
622				err(1, "setsockopt(.., SO_SETFIB, %u, ..)",
623				    rtableid);
624		}
625
626		/* Bind to a local port or source address if specified. */
627		if (sflag || pflag) {
628			struct addrinfo ahints, *ares;
629
630			/* try IP_BINDANY, but don't insist */
631			setsockopt(s, IPPROTO_IP, IP_BINDANY, &on, sizeof(on));
632			memset(&ahints, 0, sizeof(struct addrinfo));
633			ahints.ai_family = res0->ai_family;
634			ahints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM;
635			ahints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP;
636			ahints.ai_flags = AI_PASSIVE;
637			if ((error = getaddrinfo(sflag, pflag, &ahints, &ares)))
638				errx(1, "getaddrinfo: %s", gai_strerror(error));
639
640			if (bind(s, (struct sockaddr *)ares->ai_addr,
641			    ares->ai_addrlen) < 0)
642				errx(1, "bind failed: %s", strerror(errno));
643			freeaddrinfo(ares);
644		}
645
646		set_common_sockopts(s);
647
648		if (timeout_connect(s, res0->ai_addr, res0->ai_addrlen) == 0)
649			break;
650		else if (vflag)
651			warn("connect to %s port %s (%s) failed", host, port,
652			    uflag ? "udp" : "tcp");
653
654		close(s);
655		s = -1;
656	} while ((res0 = res0->ai_next) != NULL);
657
658	freeaddrinfo(res);
659
660	return (s);
661}
662
663int
664timeout_connect(int s, const struct sockaddr *name, socklen_t namelen)
665{
666	struct pollfd pfd;
667	socklen_t optlen;
668	int flags, optval;
669	int ret;
670
671	if (timeout != -1) {
672		flags = fcntl(s, F_GETFL, 0);
673		if (fcntl(s, F_SETFL, flags | O_NONBLOCK) == -1)
674			err(1, "set non-blocking mode");
675	}
676
677	if ((ret = connect(s, name, namelen)) != 0 && errno == EINPROGRESS) {
678		pfd.fd = s;
679		pfd.events = POLLOUT;
680		if ((ret = poll(&pfd, 1, timeout)) == 1) {
681			optlen = sizeof(optval);
682			if ((ret = getsockopt(s, SOL_SOCKET, SO_ERROR,
683			    &optval, &optlen)) == 0) {
684				errno = optval;
685				ret = optval == 0 ? 0 : -1;
686			}
687		} else if (ret == 0) {
688			errno = ETIMEDOUT;
689			ret = -1;
690		} else
691			err(1, "poll failed");
692	}
693
694	if (timeout != -1 && fcntl(s, F_SETFL, flags) == -1)
695		err(1, "restoring flags");
696
697	return (ret);
698}
699
700/*
701 * local_listen()
702 * Returns a socket listening on a local port, binds to specified source
703 * address. Returns -1 on failure.
704 */
705int
706local_listen(char *host, char *port, struct addrinfo hints)
707{
708	struct addrinfo *res, *res0;
709	int s, ret, x = 1;
710	int error;
711
712	/* Allow nodename to be null. */
713	hints.ai_flags |= AI_PASSIVE;
714
715	/*
716	 * In the case of binding to a wildcard address
717	 * default to binding to an ipv4 address.
718	 */
719	if (host == NULL && hints.ai_family == AF_UNSPEC)
720		hints.ai_family = AF_INET;
721
722	if ((error = getaddrinfo(host, port, &hints, &res)))
723		errx(1, "getaddrinfo: %s", gai_strerror(error));
724
725	res0 = res;
726	do {
727		if ((s = socket(res0->ai_family, res0->ai_socktype,
728		    res0->ai_protocol)) < 0)
729			continue;
730
731		if (rtableid) {
732			ret = setsockopt(s, SOL_SOCKET, SO_SETFIB, &rtableid,
733			    sizeof(rtableid));
734			if (ret == -1)
735				err(1, "setsockopt(.., SO_SETFIB, %u, ..)",
736				    rtableid);
737		}
738
739		ret = setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &x, sizeof(x));
740		if (ret == -1)
741			err(1, NULL);
742#ifdef IPSEC
743		if (ipsec_policy[0] != NULL)
744			add_ipsec_policy(s, ipsec_policy[0]);
745		if (ipsec_policy[1] != NULL)
746			add_ipsec_policy(s, ipsec_policy[1]);
747#endif
748		if (FreeBSD_Oflag) {
749			if (setsockopt(s, IPPROTO_TCP, TCP_NOOPT,
750			    &FreeBSD_Oflag, sizeof(FreeBSD_Oflag)) == -1)
751				err(1, "disable TCP options");
752		}
753
754		if (bind(s, (struct sockaddr *)res0->ai_addr,
755		    res0->ai_addrlen) == 0)
756			break;
757
758		close(s);
759		s = -1;
760	} while ((res0 = res0->ai_next) != NULL);
761
762	if (!uflag && s != -1) {
763		if (listen(s, 1) < 0)
764			err(1, "listen");
765	}
766
767	freeaddrinfo(res);
768
769	return (s);
770}
771
772/*
773 * readwrite()
774 * Loop that polls on the network file descriptor and stdin.
775 */
776void
777readwrite(int nfd)
778{
779	struct pollfd pfd[2];
780	unsigned char buf[16384];
781	int n, wfd = fileno(stdin);
782	int lfd = fileno(stdout);
783	int plen;
784
785	plen = jflag ? 16384 : 2048;
786
787	/* Setup Network FD */
788	pfd[0].fd = nfd;
789	pfd[0].events = POLLIN;
790
791	/* Set up STDIN FD. */
792	pfd[1].fd = wfd;
793	pfd[1].events = POLLIN;
794
795	while (pfd[0].fd != -1) {
796		if (iflag)
797			sleep(iflag);
798
799		if ((n = poll(pfd, 2 - dflag, timeout)) < 0) {
800			close(nfd);
801			err(1, "Polling Error");
802		}
803
804		if (n == 0)
805			return;
806
807		if (pfd[0].revents & POLLIN) {
808			if ((n = read(nfd, buf, plen)) < 0)
809				return;
810			else if (n == 0) {
811				shutdown(nfd, SHUT_RD);
812				pfd[0].fd = -1;
813				pfd[0].events = 0;
814			} else {
815				if (tflag)
816					atelnet(nfd, buf, n);
817				if (atomicio(vwrite, lfd, buf, n) != n)
818					return;
819			}
820		}
821
822		if (!dflag && pfd[1].revents & POLLIN) {
823			if ((n = read(wfd, buf, plen)) < 0)
824				return;
825			else if (n == 0) {
826				shutdown(nfd, SHUT_WR);
827				pfd[1].fd = -1;
828				pfd[1].events = 0;
829			} else {
830				if (atomicio(vwrite, nfd, buf, n) != n)
831					return;
832			}
833		}
834	}
835}
836
837/* Deal with RFC 854 WILL/WONT DO/DONT negotiation. */
838void
839atelnet(int nfd, unsigned char *buf, unsigned int size)
840{
841	unsigned char *p, *end;
842	unsigned char obuf[4];
843
844	if (size < 3)
845		return;
846	end = buf + size - 2;
847
848	for (p = buf; p < end; p++) {
849		if (*p != IAC)
850			continue;
851
852		obuf[0] = IAC;
853		p++;
854		if ((*p == WILL) || (*p == WONT))
855			obuf[1] = DONT;
856		else if ((*p == DO) || (*p == DONT))
857			obuf[1] = WONT;
858		else
859			continue;
860
861		p++;
862		obuf[2] = *p;
863		if (atomicio(vwrite, nfd, obuf, 3) != 3)
864			warn("Write Error!");
865	}
866}
867
868/*
869 * build_ports()
870 * Build an array of ports in portlist[], listing each port
871 * that we should try to connect to.
872 */
873void
874build_ports(char *p)
875{
876	const char *errstr;
877	char *n;
878	int hi, lo, cp;
879	int x = 0;
880
881	if ((n = strchr(p, '-')) != NULL) {
882		*n = '\0';
883		n++;
884
885		/* Make sure the ports are in order: lowest->highest. */
886		hi = strtonum(n, 1, PORT_MAX, &errstr);
887		if (errstr)
888			errx(1, "port number %s: %s", errstr, n);
889		lo = strtonum(p, 1, PORT_MAX, &errstr);
890		if (errstr)
891			errx(1, "port number %s: %s", errstr, p);
892
893		if (lo > hi) {
894			cp = hi;
895			hi = lo;
896			lo = cp;
897		}
898
899		/* Load ports sequentially. */
900		for (cp = lo; cp <= hi; cp++) {
901			portlist[x] = calloc(1, PORT_MAX_LEN);
902			if (portlist[x] == NULL)
903				err(1, NULL);
904			snprintf(portlist[x], PORT_MAX_LEN, "%d", cp);
905			x++;
906		}
907
908		/* Randomly swap ports. */
909		if (rflag) {
910			int y;
911			char *c;
912
913			for (x = 0; x <= (hi - lo); x++) {
914				y = (arc4random() & 0xFFFF) % (hi - lo);
915				c = portlist[x];
916				portlist[x] = portlist[y];
917				portlist[y] = c;
918			}
919		}
920	} else {
921		hi = strtonum(p, 1, PORT_MAX, &errstr);
922		if (errstr)
923			errx(1, "port number %s: %s", errstr, p);
924		portlist[0] = strdup(p);
925		if (portlist[0] == NULL)
926			err(1, NULL);
927	}
928}
929
930/*
931 * udptest()
932 * Do a few writes to see if the UDP port is there.
933 * Fails once PF state table is full.
934 */
935int
936udptest(int s)
937{
938	int i, ret;
939
940	for (i = 0; i <= 3; i++) {
941		if (write(s, "X", 1) == 1)
942			ret = 1;
943		else
944			ret = -1;
945	}
946	return (ret);
947}
948
949void
950set_common_sockopts(int s)
951{
952	int x = 1;
953
954	if (Sflag) {
955		if (setsockopt(s, IPPROTO_TCP, TCP_MD5SIG,
956			&x, sizeof(x)) == -1)
957			err(1, NULL);
958	}
959	if (Dflag) {
960		if (setsockopt(s, SOL_SOCKET, SO_DEBUG,
961			&x, sizeof(x)) == -1)
962			err(1, NULL);
963	}
964#ifdef SO_JUMBO
965	if (jflag) {
966		if (setsockopt(s, SOL_SOCKET, SO_JUMBO,
967			&x, sizeof(x)) == -1)
968			err(1, NULL);
969	}
970#endif
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	if (Iflag) {
977		if (setsockopt(s, SOL_SOCKET, SO_RCVBUF,
978		    &Iflag, sizeof(Iflag)) == -1)
979			err(1, "set TCP receive buffer size");
980	}
981	if (Oflag) {
982		if (setsockopt(s, SOL_SOCKET, SO_SNDBUF,
983		    &Oflag, sizeof(Oflag)) == -1)
984			err(1, "set TCP send buffer size");
985	}
986	if (FreeBSD_Oflag) {
987		if (setsockopt(s, IPPROTO_TCP, TCP_NOOPT,
988		    &FreeBSD_Oflag, sizeof(FreeBSD_Oflag)) == -1)
989			err(1, "disable TCP options");
990	}
991}
992
993int
994map_tos(char *s, int *val)
995{
996	/* DiffServ Codepoints and other TOS mappings */
997	const struct toskeywords {
998		const char	*keyword;
999		int		 val;
1000	} *t, toskeywords[] = {
1001		{ "af11",		IPTOS_DSCP_AF11 },
1002		{ "af12",		IPTOS_DSCP_AF12 },
1003		{ "af13",		IPTOS_DSCP_AF13 },
1004		{ "af21",		IPTOS_DSCP_AF21 },
1005		{ "af22",		IPTOS_DSCP_AF22 },
1006		{ "af23",		IPTOS_DSCP_AF23 },
1007		{ "af31",		IPTOS_DSCP_AF31 },
1008		{ "af32",		IPTOS_DSCP_AF32 },
1009		{ "af33",		IPTOS_DSCP_AF33 },
1010		{ "af41",		IPTOS_DSCP_AF41 },
1011		{ "af42",		IPTOS_DSCP_AF42 },
1012		{ "af43",		IPTOS_DSCP_AF43 },
1013		{ "critical",		IPTOS_PREC_CRITIC_ECP },
1014		{ "cs0",		IPTOS_DSCP_CS0 },
1015		{ "cs1",		IPTOS_DSCP_CS1 },
1016		{ "cs2",		IPTOS_DSCP_CS2 },
1017		{ "cs3",		IPTOS_DSCP_CS3 },
1018		{ "cs4",		IPTOS_DSCP_CS4 },
1019		{ "cs5",		IPTOS_DSCP_CS5 },
1020		{ "cs6",		IPTOS_DSCP_CS6 },
1021		{ "cs7",		IPTOS_DSCP_CS7 },
1022		{ "ef",			IPTOS_DSCP_EF },
1023		{ "inetcontrol",	IPTOS_PREC_INTERNETCONTROL },
1024		{ "lowdelay",		IPTOS_LOWDELAY },
1025		{ "netcontrol",		IPTOS_PREC_NETCONTROL },
1026		{ "reliability",	IPTOS_RELIABILITY },
1027		{ "throughput",		IPTOS_THROUGHPUT },
1028		{ NULL, 		-1 },
1029	};
1030
1031	for (t = toskeywords; t->keyword != NULL; t++) {
1032		if (strcmp(s, t->keyword) == 0) {
1033			*val = t->val;
1034			return (1);
1035		}
1036	}
1037
1038	return (0);
1039}
1040
1041void
1042help(void)
1043{
1044	usage(0);
1045	fprintf(stderr, "\tCommand Summary:\n\
1046	\t-4		Use IPv4\n\
1047	\t-6		Use IPv6\n\
1048	\t-D		Enable the debug socket option\n\
1049	\t-d		Detach from stdin\n");
1050#ifdef IPSEC
1051	fprintf(stderr, "\
1052	\t-E		Use IPsec ESP\n\
1053	\t-e policy	Use specified IPsec policy\n");
1054#endif
1055	fprintf(stderr, "\
1056	\t-h		This help text\n\
1057	\t-I length	TCP receive buffer length\n\
1058	\t-i secs\t	Delay interval for lines sent, ports scanned\n\
1059	\t-k		Keep inbound sockets open for multiple connects\n\
1060	\t-l		Listen mode, for inbound connects\n\
1061	\t-n		Suppress name/port resolutions\n\
1062	\t--no-tcpopt	Disable TCP options\n\
1063	\t-O length	TCP send buffer length\n\
1064	\t-P proxyuser\tUsername for proxy authentication\n\
1065	\t-p port\t	Specify local port for remote connects\n\
1066	\t-r		Randomize remote ports\n\
1067	\t-S		Enable the TCP MD5 signature option\n\
1068	\t-s addr\t	Local source address\n\
1069	\t-T toskeyword\tSet IP Type of Service\n\
1070	\t-t		Answer TELNET negotiation\n\
1071	\t-U		Use UNIX domain socket\n\
1072	\t-u		UDP mode\n\
1073	\t-V rtable	Specify alternate routing table\n\
1074	\t-v		Verbose\n\
1075	\t-w secs\t	Timeout for connects and final net reads\n\
1076	\t-X proto	Proxy protocol: \"4\", \"5\" (SOCKS) or \"connect\"\n\
1077	\t-x addr[:port]\tSpecify proxy address and port\n\
1078	\t-z		Zero-I/O mode [used for scanning]\n\
1079	Port numbers can be individual or ranges: lo-hi [inclusive]\n");
1080#ifdef IPSEC
1081	fprintf(stderr, "See ipsec_set_policy(3) for -e argument format\n");
1082#endif
1083	exit(1);
1084}
1085
1086#ifdef IPSEC
1087void
1088add_ipsec_policy(int s, char *policy)
1089{
1090	char *raw;
1091	int e;
1092
1093	raw = ipsec_set_policy(policy, strlen(policy));
1094	if (raw == NULL)
1095		errx(1, "ipsec_set_policy `%s': %s", policy,
1096		     ipsec_strerror());
1097	e = setsockopt(s, IPPROTO_IP, IP_IPSEC_POLICY, raw,
1098			ipsec_get_policylen(raw));
1099	if (e < 0)
1100		err(1, "ipsec policy cannot be configured");
1101	free(raw);
1102	if (vflag)
1103		fprintf(stderr, "ipsec policy configured: `%s'\n", policy);
1104	return;
1105}
1106#endif /* IPSEC */
1107
1108void
1109usage(int ret)
1110{
1111	fprintf(stderr,
1112#ifdef IPSEC
1113	    "usage: nc [-46DdEhklnrStUuvz] [-e policy] [-I length] [-i interval] [-O length]\n"
1114#else
1115	    "usage: nc [-46DdhklnrStUuvz] [-I length] [-i interval] [-O length]\n"
1116#endif
1117	    "\t  [-P proxy_username] [-p source_port] [-s source] [-T ToS]\n"
1118	    "\t  [-V rtable] [-w timeout] [-X proxy_protocol]\n"
1119	    "\t  [-x proxy_address[:port]] [destination] [port]\n");
1120	if (ret)
1121		exit(1);
1122}
1123