summaryrefslogtreecommitdiff
path: root/networking/nc.c
blob: c771374805e9a0235e03a8a4a15ba4762ed7754b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
/* vi: set sw=4 ts=4: */
/*  nc: mini-netcat - built from the ground up for LRP
 *
 *  Copyright (C) 1998, 1999  Charles P. Wright
 *  Copyright (C) 1998  Dave Cinege
 *
 *  Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

#include "libbb.h"

//config:config NC
//config:	bool "nc"
//config:	default y
//config:	help
//config:	  A simple Unix utility which reads and writes data across network
//config:	  connections.
//config:
//config:config NC_SERVER
//config:	bool "Netcat server options (-l)"
//config:	default y
//config:	depends on NC
//config:	help
//config:	  Allow netcat to act as a server.
//config:
//config:config NC_EXTRA
//config:	bool "Netcat extensions (-eiw and filename)"
//config:	default y
//config:	depends on NC
//config:	help
//config:	  Add -e (support for executing the rest of the command line after
//config:	  making or receiving a successful connection), -i (delay interval for
//config:	  lines sent), -w (timeout for initial connection).
//config:
//config:config NC_110_COMPAT
//config:	bool "Netcat 1.10 compatibility (+2.5k)"
//config:	default n  # off specially for Rob
//config:	depends on NC
//config:	help
//config:	  This option makes nc closely follow original nc-1.10.
//config:	  The code is about 2.5k bigger. It enables
//config:	  -s ADDR, -n, -u, -v, -o FILE, -z options, but loses
//config:	  busybox-specific extensions: -f FILE and -ll.

#if ENABLE_NC_110_COMPAT
# include "nc_bloaty.c"
#else

//usage:#if !ENABLE_NC_110_COMPAT
//usage:
//usage:#if ENABLE_NC_SERVER || ENABLE_NC_EXTRA
//usage:#define NC_OPTIONS_STR "\n\nOptions:"
//usage:#else
//usage:#define NC_OPTIONS_STR
//usage:#endif
//usage:
//usage:#define nc_trivial_usage
//usage:	IF_NC_EXTRA("[-iN] [-wN] ")IF_NC_SERVER("[-l] [-p PORT] ")
//usage:       "["IF_NC_EXTRA("-f FILE|")"IPADDR PORT]"IF_NC_EXTRA(" [-e PROG]")
//usage:#define nc_full_usage "\n\n"
//usage:       "Open a pipe to IP:PORT" IF_NC_EXTRA(" or FILE")
//usage:	NC_OPTIONS_STR
//usage:	IF_NC_EXTRA(
//usage:     "\n	-e PROG	Run PROG after connect"
//usage:	IF_NC_SERVER(
//usage:     "\n	-l	Listen mode, for inbound connects"
//usage:	IF_NC_EXTRA(
//usage:     "\n		(use -l twice with -e for persistent server)")
//usage:     "\n	-p PORT	Local port"
//usage:	)
//usage:     "\n	-w SEC	Timeout for connect"
//usage:     "\n	-i SEC	Delay interval for lines sent"
//usage:     "\n	-f FILE	Use file (ala /dev/ttyS0) instead of network"
//usage:	)
//usage:
//usage:#define nc_notes_usage ""
//usage:	IF_NC_EXTRA(
//usage:       "To use netcat as a terminal emulator on a serial port:\n\n"
//usage:       "$ stty 115200 -F /dev/ttyS0\n"
//usage:       "$ stty raw -echo -ctlecho && nc -f /dev/ttyS0\n"
//usage:	)
//usage:
//usage:#define nc_example_usage
//usage:       "$ nc foobar.somedomain.com 25\n"
//usage:       "220 foobar ESMTP Exim 3.12 #1 Sat, 15 Apr 2000 00:03:02 -0600\n"
//usage:       "help\n"
//usage:       "214-Commands supported:\n"
//usage:       "214-    HELO EHLO MAIL RCPT DATA AUTH\n"
//usage:       "214     NOOP QUIT RSET HELP\n"
//usage:       "quit\n"
//usage:       "221 foobar closing connection\n"
//usage:
//usage:#endif

/* Lots of small differences in features
 * when compared to "standard" nc
 */

static void timeout(int signum UNUSED_PARAM)
{
	bb_error_msg_and_die("timed out");
}

int nc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int nc_main(int argc, char **argv)
{
	/* sfd sits _here_ only because of "repeat" option (-l -l). */
	int sfd = sfd; /* for gcc */
	int cfd = 0;
	unsigned lport = 0;
	IF_NOT_NC_SERVER(const) unsigned do_listen = 0;
	IF_NOT_NC_EXTRA (const) unsigned wsecs = 0;
	IF_NOT_NC_EXTRA (const) unsigned delay = 0;
	IF_NOT_NC_EXTRA (const int execparam = 0;)
	IF_NC_EXTRA     (char **execparam = NULL;)
	fd_set readfds, testfds;
	int opt; /* must be signed (getopt returns -1) */

	if (ENABLE_NC_SERVER || ENABLE_NC_EXTRA) {
		/* getopt32 is _almost_ usable:
		** it cannot handle "... -e PROG -prog-opt" */
		while ((opt = getopt(argc, argv,
		        "" IF_NC_SERVER("lp:") IF_NC_EXTRA("w:i:f:e:") )) > 0
		) {
			if (ENABLE_NC_SERVER && opt == 'l')
				IF_NC_SERVER(do_listen++);
			else if (ENABLE_NC_SERVER && opt == 'p')
				IF_NC_SERVER(lport = bb_lookup_port(optarg, "tcp", 0));
			else if (ENABLE_NC_EXTRA && opt == 'w')
				IF_NC_EXTRA( wsecs = xatou(optarg));
			else if (ENABLE_NC_EXTRA && opt == 'i')
				IF_NC_EXTRA( delay = xatou(optarg));
			else if (ENABLE_NC_EXTRA && opt == 'f')
				IF_NC_EXTRA( cfd = xopen(optarg, O_RDWR));
			else if (ENABLE_NC_EXTRA && opt == 'e' && optind <= argc) {
				/* We cannot just 'break'. We should let getopt finish.
				** Or else we won't be able to find where
				** 'host' and 'port' params are
				** (think "nc -w 60 host port -e PROG"). */
				IF_NC_EXTRA(
					char **p;
					// +2: one for progname (optarg) and one for NULL
					execparam = xzalloc(sizeof(char*) * (argc - optind + 2));
					p = execparam;
					*p++ = optarg;
					while (optind < argc) {
						*p++ = argv[optind++];
					}
				)
				/* optind points to argv[arvc] (NULL) now.
				** FIXME: we assume that getopt will not count options
				** possibly present on "-e PROG ARGS" and will not
				** include them into final value of optind
				** which is to be used ...  */
			} else bb_show_usage();
		}
		argv += optind; /* ... here! */
		argc -= optind;
		// -l and -f don't mix
		if (do_listen && cfd) bb_show_usage();
		// File mode needs need zero arguments, listen mode needs zero or one,
		// client mode needs one or two
		if (cfd) {
			if (argc) bb_show_usage();
		} else if (do_listen) {
			if (argc > 1) bb_show_usage();
		} else {
			if (!argc || argc > 2) bb_show_usage();
		}
	} else {
		if (argc != 3) bb_show_usage();
		argc--;
		argv++;
	}

	if (wsecs) {
		signal(SIGALRM, timeout);
		alarm(wsecs);
	}

	if (!cfd) {
		if (do_listen) {
			sfd = create_and_bind_stream_or_die(argv[0], lport);
			xlisten(sfd, do_listen); /* can be > 1 */
#if 0  /* nc-1.10 does not do this (without -v) */
			/* If we didn't specify a port number,
			 * query and print it after listen() */
			if (!lport) {
				len_and_sockaddr lsa;
				lsa.len = LSA_SIZEOF_SA;
				getsockname(sfd, &lsa.u.sa, &lsa.len);
				lport = get_nport(&lsa.u.sa);
				fdprintf(2, "%d\n", ntohs(lport));
			}
#endif
			close_on_exec_on(sfd);
 accept_again:
			cfd = accept(sfd, NULL, 0);
			if (cfd < 0)
				bb_perror_msg_and_die("accept");
			if (!execparam)
				close(sfd);
		} else {
			cfd = create_and_connect_stream_or_die(argv[0],
				argv[1] ? bb_lookup_port(argv[1], "tcp", 0) : 0);
		}
	}

	if (wsecs) {
		alarm(0);
		/* Non-ignored signals revert to SIG_DFL on exec anyway */
		/*signal(SIGALRM, SIG_DFL);*/
	}

	/* -e given? */
	if (execparam) {
		pid_t pid;
		/* With more than one -l, repeatedly act as server */
		if (do_listen > 1 && (pid = xvfork()) != 0) {
			/* parent */
			/* prevent zombies */
			signal(SIGCHLD, SIG_IGN);
			close(cfd);
			goto accept_again;
		}
		/* child, or main thread if only one -l */
		xmove_fd(cfd, 0);
		xdup2(0, 1);
		xdup2(0, 2);
		IF_NC_EXTRA(BB_EXECVP(execparam[0], execparam);)
		/* Don't print stuff or it will go over the wire... */
		_exit(127);
	}

	/* Select loop copying stdin to cfd, and cfd to stdout */

	FD_ZERO(&readfds);
	FD_SET(cfd, &readfds);
	FD_SET(STDIN_FILENO, &readfds);

	for (;;) {
		int fd;
		int ofd;
		int nread;

		testfds = readfds;

		if (select(cfd + 1, &testfds, NULL, NULL, NULL) < 0)
			bb_perror_msg_and_die("select");

#define iobuf bb_common_bufsiz1
		fd = STDIN_FILENO;
		while (1) {
			if (FD_ISSET(fd, &testfds)) {
				nread = safe_read(fd, iobuf, sizeof(iobuf));
				if (fd == cfd) {
					if (nread < 1)
						exit(EXIT_SUCCESS);
					ofd = STDOUT_FILENO;
				} else {
					if (nread < 1) {
						/* Close outgoing half-connection so they get EOF,
						 * but leave incoming alone so we can see response */
						shutdown(cfd, 1);
						FD_CLR(STDIN_FILENO, &readfds);
					}
					ofd = cfd;
				}
				xwrite(ofd, iobuf, nread);
				if (delay > 0)
					sleep(delay);
			}
			if (fd == cfd)
				break;
			fd = cfd;
		}
	}
}
#endif