1 /* vi: set sw=4 ts=4: */
4 * Bjorn Wesen, Axis Communications AB (bjornw@axis.com)
6 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
8 * ---------------------------------------------------------------------------
9 * (C) Copyright 2000, Axis Communications AB, LUND, SWEDEN
10 ****************************************************************************
12 * The telnetd manpage says it all:
14 * Telnetd operates by allocating a pseudo-terminal device (see pty(4)) for
15 * a client, then creating a login process which has the slave side of the
16 * pseudo-terminal as stdin, stdout, and stderr. Telnetd manipulates the
17 * master side of the pseudo-terminal, implementing the telnet protocol and
18 * passing characters between the remote client and the login process.
20 * Vladimir Oleynik <dzo@simtreas.ru> 2001
21 * Set process group corrections, initial busybox port
33 #include <arpa/telnet.h>
34 #include <sys/syslog.h>
39 #ifdef CONFIG_FEATURE_IPV6
40 #define SOCKET_TYPE AF_INET6
41 typedef struct sockaddr_in6 sockaddr_type;
43 #define SOCKET_TYPE AF_INET
44 typedef struct sockaddr_in sockaddr_type;
49 static const char *loginpath = "/bin/login";
51 static const char *loginpath;
53 static const char *issuefile = "/etc/issue.net";
55 /* shell name and arguments */
57 static const char *argv_init[] = {NULL, NULL};
59 /* structure that describes a session */
62 #ifdef CONFIG_FEATURE_TELNETD_INETD
63 int sockfd_read, sockfd_write, ptyfd;
64 #else /* CONFIG_FEATURE_TELNETD_INETD */
65 struct tsession *next;
67 #endif /* CONFIG_FEATURE_TELNETD_INETD */
69 /* two circular buffers */
71 int rdidx1, wridx1, size1;
72 int rdidx2, wridx2, size2;
77 This is how the buffers are used. The arrows indicate the movement
80 +-------+ wridx1++ +------+ rdidx1++ +----------+
81 | | <-------------- | buf1 | <-------------- | |
82 | | size1-- +------+ size1++ | |
84 | | rdidx2++ +------+ wridx2++ | |
85 | | --------------> | buf2 | --------------> | |
86 +-------+ size2++ +------+ size2-- +----------+
88 Each session has got two buffers.
94 static struct tsession *sessions;
99 Remove all IAC's from the buffer pointed to by bf (received IACs are ignored
100 and must be removed so as to not be interpreted by the terminal). Make an
101 uninterrupted string of characters fit for the terminal. Do this by packing
102 all characters meant for the terminal sequentially towards the end of bf.
104 Return a pointer to the beginning of the characters meant for the terminal.
105 and make *num_totty the number of characters that should be sent to
108 Note - If an IAC (3 byte quantity) starts before (bf + len) but extends
109 past (bf + len) then that IAC will be left unprocessed and *processed will be
112 FIXME - if we mean to send 0xFF to the terminal then it will be escaped,
113 what is the escape character? We aren't handling that situation here.
115 CR-LF ->'s CR mapping is also done here, for convenience
119 remove_iacs(struct tsession *ts, int *pnum_totty) {
120 unsigned char *ptr0 = (unsigned char *)ts->buf1 + ts->wridx1;
121 unsigned char *ptr = ptr0;
122 unsigned char *totty = ptr;
123 unsigned char *end = ptr + MIN(BUFSIZE - ts->wridx1, ts->size1);
131 /* We now map \r\n ==> \r for pragmatic reasons.
132 * Many client implementations send \r\n when
133 * the user hits the CarriageReturn key.
135 if (c == '\r' && (*ptr == '\n' || *ptr == 0) && ptr < end)
140 * TELOPT_NAWS support!
142 if ((ptr+2) >= end) {
143 /* only the beginning of the IAC is in the
144 buffer we were asked to process, we can't
145 process this char. */
150 * IAC -> SB -> TELOPT_NAWS -> 4-byte -> IAC -> SE
152 else if (ptr[1] == SB && ptr[2] == TELOPT_NAWS) {
155 break; /* incomplete, can't process */
156 ws.ws_col = (ptr[3] << 8) | ptr[4];
157 ws.ws_row = (ptr[5] << 8) | ptr[6];
158 (void) ioctl(ts->ptyfd, TIOCSWINSZ, (char *)&ws);
162 /* skip 3-byte IAC non-SB cmd */
164 fprintf(stderr, "Ignoring IAC %s,%s\n",
165 TELCMD(*(ptr+1)), TELOPT(*(ptr+2)));
172 processed = ptr - ptr0;
173 num_totty = totty - ptr0;
174 /* the difference between processed and num_to tty
175 is all the iacs we removed from the stream.
176 Adjust buf1 accordingly. */
177 ts->wridx1 += processed - num_totty;
178 ts->size1 -= processed - num_totty;
179 *pnum_totty = num_totty;
180 /* move the chars meant for the terminal towards the end of the
182 return memmove(ptr - num_totty, ptr0, num_totty);
190 #ifdef CONFIG_FEATURE_DEVPTS
191 p = open("/dev/ptmx", 2);
195 strcpy(line, ptsname(p));
203 strcpy(line, "/dev/ptyXX");
205 for (i = 0; i < 16; i++) {
206 line[8] = "pqrstuvwxyzabcde"[i];
208 if (stat(line, &stb) < 0) {
211 for (j = 0; j < 16; j++) {
212 line[9] = j < 10 ? j + '0' : j - 10 + 'a';
214 fprintf(stderr, "Trying to open device: %s\n", line);
216 if ((p = open(line, O_RDWR | O_NOCTTY)) >= 0) {
222 #endif /* CONFIG_FEATURE_DEVPTS */
228 send_iac(struct tsession *ts, unsigned char command, int option)
230 /* We rely on that there is space in the buffer for now. */
231 char *b = ts->buf2 + ts->rdidx2;
240 static struct tsession *
241 #ifdef CONFIG_FEATURE_TELNETD_INETD
242 make_new_session(void)
243 #else /* CONFIG_FEATURE_TELNETD_INETD */
244 make_new_session(int sockfd)
245 #endif /* CONFIG_FEATURE_TELNETD_INETD */
247 struct termios termbuf;
250 struct tsession *ts = xzalloc(sizeof(struct tsession) + BUFSIZE * 2);
252 ts->buf1 = (char *)(&ts[1]);
253 ts->buf2 = ts->buf1 + BUFSIZE;
255 #ifdef CONFIG_FEATURE_TELNETD_INETD
256 ts->sockfd_write = 1;
257 #else /* CONFIG_FEATURE_TELNETD_INETD */
259 #endif /* CONFIG_FEATURE_TELNETD_INETD */
261 /* Got a new connection, set up a tty and spawn a shell. */
263 pty = getpty(tty_name);
266 bb_error_msg("all terminals in use");
275 /* Make the telnet client understand we will echo characters so it
276 * should not do it locally. We don't tell the client to run linemode,
277 * because we want to handle line editing and tab completion and other
278 * stuff that requires char-by-char support.
281 send_iac(ts, DO, TELOPT_ECHO);
282 send_iac(ts, DO, TELOPT_NAWS);
283 send_iac(ts, DO, TELOPT_LFLOW);
284 send_iac(ts, WILL, TELOPT_ECHO);
285 send_iac(ts, WILL, TELOPT_SGA);
287 if ((pid = fork()) < 0) {
288 bb_perror_msg("fork");
291 /* In child, open the child's side of the tty. */
294 for(i = 0; i <= maxfd; i++)
296 /* make new process group */
299 xopen(tty_name, O_RDWR /*| O_NOCTTY*/);
303 tcsetpgrp(0, getpid());
305 /* The pseudo-terminal allocated to the client is configured to operate in
306 * cooked mode, and with XTABS CRMOD enabled (see tty(4)).
309 tcgetattr(0, &termbuf);
310 termbuf.c_lflag |= ECHO; /* if we use readline we dont want this */
311 termbuf.c_oflag |= ONLCR|XTABS;
312 termbuf.c_iflag |= ICRNL;
313 termbuf.c_iflag &= ~IXOFF;
314 /*termbuf.c_lflag &= ~ICANON;*/
315 tcsetattr(0, TCSANOW, &termbuf);
317 print_login_issue(issuefile, NULL);
319 /* exec shell, with correct argv and env */
320 execv(loginpath, (char *const *)argv_init);
323 bb_perror_msg_and_die("execv");
331 #ifndef CONFIG_FEATURE_TELNETD_INETD
333 free_session(struct tsession *ts)
335 struct tsession *t = sessions;
337 /* Unlink this telnet session from the session list. */
346 kill(ts->shell_pid, SIGKILL);
348 wait4(ts->shell_pid, NULL, 0, NULL);
353 if (ts->ptyfd == maxfd || ts->sockfd == maxfd)
355 if (ts->ptyfd == maxfd || ts->sockfd == maxfd)
360 #endif /* CONFIG_FEATURE_TELNETD_INETD */
363 telnetd_main(int argc, char **argv)
366 fd_set rdfdset, wrfdset;
368 #ifndef CONFIG_FEATURE_TELNETD_INETD
373 struct in_addr bind_addr = { .s_addr = 0x0 };
374 char *opt_portnbr, *opt_bindaddr;
375 #endif /* CONFIG_FEATURE_TELNETD_INETD */
379 loginpath = DEFAULT_SHELL;
382 /* We use inetd-style operation unconditionally
383 * (no --foreground option), user most likely will
384 * look into syslog for all errors, even early ones.
385 * Direct all output to syslog at once.
387 openlog(applet_name, 0, LOG_USER);
388 logmode = LOGMODE_SYSLOG;
390 opt = getopt32(argc, argv, "f:l:" USE_FEATURE_TELNETD_INETD("p:b:"),
391 &issuefile, &loginpath
392 SKIP_FEATURE_TELNETD_INETD(, &opt_portnbr, &opt_bindaddr));
395 #ifndef CONFIG_FEATURE_TELNETD_INETD
396 if (opt & 4) portnbr = atoi(opt_portnbr); // -p
398 if (inet_aton(opt_bindaddr, &bind_addr) == 0) bb_show_usage();
399 #endif /* CONFIG_FEATURE_TELNETD_INETD */
401 if (access(loginpath, X_OK) < 0) {
402 bb_error_msg_and_die("'%s' unavailable", loginpath);
405 argv_init[0] = loginpath;
407 #ifdef CONFIG_FEATURE_TELNETD_INETD
409 sessions = make_new_session();
410 #else /* CONFIG_EATURE_TELNETD_INETD */
413 /* Grab a TCP socket. */
415 master_fd = xsocket(SOCKET_TYPE, SOCK_STREAM, 0);
416 (void)setsockopt(master_fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));
418 /* Set it to listen to specified port. */
420 memset((void *)&sa, 0, sizeof(sa));
421 #ifdef CONFIG_FEATURE_IPV6
422 sa.sin6_family = AF_INET6;
423 sa.sin6_port = htons(portnbr);
424 /* sa.sin6_addr = bind_addr6; */
426 sa.sin_family = AF_INET;
427 sa.sin_port = htons(portnbr);
428 sa.sin_addr = bind_addr;
431 xbind(master_fd, (struct sockaddr *) &sa, sizeof(sa));
432 xlisten(master_fd, 1);
436 #endif /* CONFIG_FEATURE_TELNETD_INETD */
444 /* select on the master socket, all telnet sockets and their
445 * ptys if there is room in their respective session buffers.
448 #ifndef CONFIG_FEATURE_TELNETD_INETD
449 FD_SET(master_fd, &rdfdset);
450 #endif /* CONFIG_FEATURE_TELNETD_INETD */
453 #ifndef CONFIG_FEATURE_TELNETD_INETD
455 #endif /* CONFIG_FEATURE_TELNETD_INETD */
456 /* buf1 is used from socket to pty
457 * buf2 is used from pty to socket
460 FD_SET(ts->ptyfd, &wrfdset); /* can write to pty */
462 if (ts->size1 < BUFSIZE) {
463 #ifdef CONFIG_FEATURE_TELNETD_INETD
464 FD_SET(ts->sockfd_read, &rdfdset); /* can read from socket */
465 #else /* CONFIG_FEATURE_TELNETD_INETD */
466 FD_SET(ts->sockfd, &rdfdset); /* can read from socket */
467 #endif /* CONFIG_FEATURE_TELNETD_INETD */
470 #ifdef CONFIG_FEATURE_TELNETD_INETD
471 FD_SET(ts->sockfd_write, &wrfdset); /* can write to socket */
472 #else /* CONFIG_FEATURE_TELNETD_INETD */
473 FD_SET(ts->sockfd, &wrfdset); /* can write to socket */
474 #endif /* CONFIG_FEATURE_TELNETD_INETD */
476 if (ts->size2 < BUFSIZE) {
477 FD_SET(ts->ptyfd, &rdfdset); /* can read from pty */
479 #ifndef CONFIG_FEATURE_TELNETD_INETD
482 #endif /* CONFIG_FEATURE_TELNETD_INETD */
484 selret = select(maxfd + 1, &rdfdset, &wrfdset, 0, 0);
489 #ifndef CONFIG_FEATURE_TELNETD_INETD
490 /* First check for and accept new sessions. */
491 if (FD_ISSET(master_fd, &rdfdset)) {
496 if ((fd = accept(master_fd, (struct sockaddr *)&sa,
500 /* Create a new session and link it into
502 struct tsession *new_ts = make_new_session(fd);
504 new_ts->next = sessions;
514 /* Then check for data tunneling. */
517 while (ts) { /* For all sessions... */
518 #endif /* CONFIG_FEATURE_TELNETD_INETD */
519 #ifndef CONFIG_FEATURE_TELNETD_INETD
520 struct tsession *next = ts->next; /* in case we free ts. */
521 #endif /* CONFIG_FEATURE_TELNETD_INETD */
523 if (ts->size1 && FD_ISSET(ts->ptyfd, &wrfdset)) {
526 /* Write to pty from buffer 1. */
528 ptr = remove_iacs(ts, &num_totty);
530 w = write(ts->ptyfd, ptr, num_totty);
532 #ifdef CONFIG_FEATURE_TELNETD_INETD
534 #else /* CONFIG_FEATURE_TELNETD_INETD */
538 #endif /* CONFIG_FEATURE_TELNETD_INETD */
542 if (ts->wridx1 == BUFSIZE)
546 #ifdef CONFIG_FEATURE_TELNETD_INETD
547 if (ts->size2 && FD_ISSET(ts->sockfd_write, &wrfdset)) {
548 #else /* CONFIG_FEATURE_TELNETD_INETD */
549 if (ts->size2 && FD_ISSET(ts->sockfd, &wrfdset)) {
550 #endif /* CONFIG_FEATURE_TELNETD_INETD */
551 /* Write to socket from buffer 2. */
552 maxlen = MIN(BUFSIZE - ts->wridx2, ts->size2);
553 #ifdef CONFIG_FEATURE_TELNETD_INETD
554 w = write(ts->sockfd_write, ts->buf2 + ts->wridx2, maxlen);
557 #else /* CONFIG_FEATURE_TELNETD_INETD */
558 w = write(ts->sockfd, ts->buf2 + ts->wridx2, maxlen);
564 #endif /* CONFIG_FEATURE_TELNETD_INETD */
567 if (ts->wridx2 == BUFSIZE)
571 #ifdef CONFIG_FEATURE_TELNETD_INETD
572 if (ts->size1 < BUFSIZE && FD_ISSET(ts->sockfd_read, &rdfdset)) {
573 #else /* CONFIG_FEATURE_TELNETD_INETD */
574 if (ts->size1 < BUFSIZE && FD_ISSET(ts->sockfd, &rdfdset)) {
575 #endif /* CONFIG_FEATURE_TELNETD_INETD */
576 /* Read from socket to buffer 1. */
577 maxlen = MIN(BUFSIZE - ts->rdidx1,
578 BUFSIZE - ts->size1);
579 #ifdef CONFIG_FEATURE_TELNETD_INETD
580 r = read(ts->sockfd_read, ts->buf1 + ts->rdidx1, maxlen);
581 if (!r || (r < 0 && errno != EINTR))
583 #else /* CONFIG_FEATURE_TELNETD_INETD */
584 r = read(ts->sockfd, ts->buf1 + ts->rdidx1, maxlen);
585 if (!r || (r < 0 && errno != EINTR)) {
590 #endif /* CONFIG_FEATURE_TELNETD_INETD */
591 if (!*(ts->buf1 + ts->rdidx1 + r - 1)) {
598 if (ts->rdidx1 == BUFSIZE)
602 if (ts->size2 < BUFSIZE && FD_ISSET(ts->ptyfd, &rdfdset)) {
603 /* Read from pty to buffer 2. */
604 maxlen = MIN(BUFSIZE - ts->rdidx2,
605 BUFSIZE - ts->size2);
606 r = read(ts->ptyfd, ts->buf2 + ts->rdidx2, maxlen);
607 if (!r || (r < 0 && errno != EINTR)) {
608 #ifdef CONFIG_FEATURE_TELNETD_INETD
610 #else /* CONFIG_FEATURE_TELNETD_INETD */
614 #endif /* CONFIG_FEATURE_TELNETD_INETD */
618 if (ts->rdidx2 == BUFSIZE)
622 if (ts->size1 == 0) {
626 if (ts->size2 == 0) {
630 #ifndef CONFIG_FEATURE_TELNETD_INETD
633 #endif /* CONFIG_FEATURE_TELNETD_INETD */