1 /* $OpenBSD: serverloop.c,v 1.160 2011/05/15 08:09:01 djm Exp $ */
2 /*
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * All rights reserved
6 * Server main loop for handling the interactive session.
7 *
8 * As far as I am concerned, the code I have written for this software
9 * can be used freely for any purpose. Any derived versions of this
10 * software must be clearly marked as such, and if the derived work is
11 * incompatible with the protocol description in the RFC file, it must be
12 * called by a name other than "ssh" or "Secure Shell".
13 *
14 * SSH2 support by Markus Friedl.
15 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions
19 * are met:
20 * 1. Redistributions of source code must retain the above copyright
21 * notice, this list of conditions and the following disclaimer.
22 * 2. Redistributions in binary form must reproduce the above copyright
23 * notice, this list of conditions and the following disclaimer in the
24 * documentation and/or other materials provided with the distribution.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
27 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
29 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
30 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
31 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 */
37
38 #include "includes.h"
39
40 #include <sys/types.h>
41 #include <sys/param.h>
42 #include <sys/wait.h>
43 #include <sys/socket.h>
44 #ifdef HAVE_SYS_TIME_H
45 # include <sys/time.h>
46 #endif
47
48 #include <netinet/in.h>
49
50 #include <errno.h>
51 #include <fcntl.h>
52 #include <pwd.h>
53 #include <signal.h>
54 #include <string.h>
55 #include <termios.h>
56 #include <unistd.h>
57 #include <stdarg.h>
58
59 #include "openbsd-compat/sys-queue.h"
60 #include "xmalloc.h"
61 #include "packet.h"
62 #include "buffer.h"
63 #include "log.h"
64 #include "servconf.h"
65 #include "canohost.h"
66 #include "sshpty.h"
67 #include "channels.h"
68 #include "compat.h"
69 #include "ssh1.h"
70 #include "ssh2.h"
71 #include "key.h"
72 #include "cipher.h"
73 #include "kex.h"
74 #include "hostfile.h"
75 #include "auth.h"
76 #include "session.h"
77 #include "dispatch.h"
78 #include "auth-options.h"
79 #include "serverloop.h"
80 #include "misc.h"
81 #include "roaming.h"
82
83 extern ServerOptions options;
84
85 /* XXX */
86 extern Kex *xxx_kex;
87 extern Authctxt *the_authctxt;
88 extern int use_privsep;
89
90 static Buffer stdin_buffer; /* Buffer for stdin data. */
91 static Buffer stdout_buffer; /* Buffer for stdout data. */
92 static Buffer stderr_buffer; /* Buffer for stderr data. */
93 static int fdin; /* Descriptor for stdin (for writing) */
94 static int fdout; /* Descriptor for stdout (for reading);
95 May be same number as fdin. */
96 static int fderr; /* Descriptor for stderr. May be -1. */
97 static long stdin_bytes = 0; /* Number of bytes written to stdin. */
98 static long stdout_bytes = 0; /* Number of stdout bytes sent to client. */
99 static long stderr_bytes = 0; /* Number of stderr bytes sent to client. */
100 static long fdout_bytes = 0; /* Number of stdout bytes read from program. */
101 static int stdin_eof = 0; /* EOF message received from client. */
102 static int fdout_eof = 0; /* EOF encountered reading from fdout. */
103 static int fderr_eof = 0; /* EOF encountered readung from fderr. */
104 static int fdin_is_tty = 0; /* fdin points to a tty. */
105 static int connection_in; /* Connection to client (input). */
106 static int connection_out; /* Connection to client (output). */
107 static int connection_closed = 0; /* Connection to client closed. */
108 static u_int buffer_high; /* "Soft" max buffer size. */
109 static int no_more_sessions = 0; /* Disallow further sessions. */
110
111 /*
112 * This SIGCHLD kludge is used to detect when the child exits. The server
113 * will exit after that, as soon as forwarded connections have terminated.
114 */
115
116 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */
117
118 /* Cleanup on signals (!use_privsep case only) */
119 static volatile sig_atomic_t received_sigterm = 0;
120
121 /* prototypes */
122 static void server_init_dispatch(void);
123
124 /*
125 * we write to this pipe if a SIGCHLD is caught in order to avoid
126 * the race between select() and child_terminated
127 */
128 static int notify_pipe[2];
129 static void
notify_setup(void)130 notify_setup(void)
131 {
132 if (pipe(notify_pipe) < 0) {
133 error("pipe(notify_pipe) failed %s", strerror(errno));
134 } else if ((fcntl(notify_pipe[0], F_SETFD, FD_CLOEXEC) == -1) ||
135 (fcntl(notify_pipe[1], F_SETFD, FD_CLOEXEC) == -1)) {
136 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
137 close(notify_pipe[0]);
138 close(notify_pipe[1]);
139 } else {
140 set_nonblock(notify_pipe[0]);
141 set_nonblock(notify_pipe[1]);
142 return;
143 }
144 notify_pipe[0] = -1; /* read end */
145 notify_pipe[1] = -1; /* write end */
146 }
147 static void
notify_parent(void)148 notify_parent(void)
149 {
150 if (notify_pipe[1] != -1)
151 write(notify_pipe[1], "", 1);
152 }
153 static void
notify_prepare(fd_set * readset)154 notify_prepare(fd_set *readset)
155 {
156 if (notify_pipe[0] != -1)
157 FD_SET(notify_pipe[0], readset);
158 }
159 static void
notify_done(fd_set * readset)160 notify_done(fd_set *readset)
161 {
162 char c;
163
164 if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
165 while (read(notify_pipe[0], &c, 1) != -1)
166 debug2("notify_done: reading");
167 }
168
169 /*ARGSUSED*/
170 static void
sigchld_handler(int sig)171 sigchld_handler(int sig)
172 {
173 int save_errno = errno;
174 child_terminated = 1;
175 #ifndef _UNICOS
176 mysignal(SIGCHLD, sigchld_handler);
177 #endif
178 notify_parent();
179 errno = save_errno;
180 }
181
182 /*ARGSUSED*/
183 static void
sigterm_handler(int sig)184 sigterm_handler(int sig)
185 {
186 received_sigterm = sig;
187 }
188
189 /*
190 * Make packets from buffered stderr data, and buffer it for sending
191 * to the client.
192 */
193 static void
make_packets_from_stderr_data(void)194 make_packets_from_stderr_data(void)
195 {
196 u_int len;
197
198 /* Send buffered stderr data to the client. */
199 while (buffer_len(&stderr_buffer) > 0 &&
200 packet_not_very_much_data_to_write()) {
201 len = buffer_len(&stderr_buffer);
202 if (packet_is_interactive()) {
203 if (len > 512)
204 len = 512;
205 } else {
206 /* Keep the packets at reasonable size. */
207 if (len > packet_get_maxsize())
208 len = packet_get_maxsize();
209 }
210 packet_start(SSH_SMSG_STDERR_DATA);
211 packet_put_string(buffer_ptr(&stderr_buffer), len);
212 packet_send();
213 buffer_consume(&stderr_buffer, len);
214 stderr_bytes += len;
215 }
216 }
217
218 /*
219 * Make packets from buffered stdout data, and buffer it for sending to the
220 * client.
221 */
222 static void
make_packets_from_stdout_data(void)223 make_packets_from_stdout_data(void)
224 {
225 u_int len;
226
227 /* Send buffered stdout data to the client. */
228 while (buffer_len(&stdout_buffer) > 0 &&
229 packet_not_very_much_data_to_write()) {
230 len = buffer_len(&stdout_buffer);
231 if (packet_is_interactive()) {
232 if (len > 512)
233 len = 512;
234 } else {
235 /* Keep the packets at reasonable size. */
236 if (len > packet_get_maxsize())
237 len = packet_get_maxsize();
238 }
239 packet_start(SSH_SMSG_STDOUT_DATA);
240 packet_put_string(buffer_ptr(&stdout_buffer), len);
241 packet_send();
242 buffer_consume(&stdout_buffer, len);
243 stdout_bytes += len;
244 }
245 }
246
247 static void
client_alive_check(void)248 client_alive_check(void)
249 {
250 int channel_id;
251
252 /* timeout, check to see how many we have had */
253 if (packet_inc_alive_timeouts() > options.client_alive_count_max) {
254 logit("Timeout, client not responding.");
255 cleanup_exit(255);
256 }
257
258 /*
259 * send a bogus global/channel request with "wantreply",
260 * we should get back a failure
261 */
262 if ((channel_id = channel_find_open()) == -1) {
263 packet_start(SSH2_MSG_GLOBAL_REQUEST);
264 packet_put_cstring("keepalive@openssh.com");
265 packet_put_char(1); /* boolean: want reply */
266 } else {
267 channel_request_start(channel_id, "keepalive@openssh.com", 1);
268 }
269 packet_send();
270 }
271
272 /*
273 * Sleep in select() until we can do something. This will initialize the
274 * select masks. Upon return, the masks will indicate which descriptors
275 * have data or can accept data. Optionally, a maximum time can be specified
276 * for the duration of the wait (0 = infinite).
277 */
278 static void
wait_until_can_do_something(fd_set ** readsetp,fd_set ** writesetp,int * maxfdp,u_int * nallocp,u_int max_time_milliseconds)279 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
280 u_int *nallocp, u_int max_time_milliseconds)
281 {
282 struct timeval tv, *tvp;
283 int ret;
284 int client_alive_scheduled = 0;
285 int program_alive_scheduled = 0;
286
287 /*
288 * if using client_alive, set the max timeout accordingly,
289 * and indicate that this particular timeout was for client
290 * alive by setting the client_alive_scheduled flag.
291 *
292 * this could be randomized somewhat to make traffic
293 * analysis more difficult, but we're not doing it yet.
294 */
295 if (compat20 &&
296 max_time_milliseconds == 0 && options.client_alive_interval) {
297 client_alive_scheduled = 1;
298 max_time_milliseconds = options.client_alive_interval * 1000;
299 }
300
301 /* Allocate and update select() masks for channel descriptors. */
302 channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0);
303
304 if (compat20) {
305 #if 0
306 /* wrong: bad condition XXX */
307 if (channel_not_very_much_buffered_data())
308 #endif
309 FD_SET(connection_in, *readsetp);
310 } else {
311 /*
312 * Read packets from the client unless we have too much
313 * buffered stdin or channel data.
314 */
315 if (buffer_len(&stdin_buffer) < buffer_high &&
316 channel_not_very_much_buffered_data())
317 FD_SET(connection_in, *readsetp);
318 /*
319 * If there is not too much data already buffered going to
320 * the client, try to get some more data from the program.
321 */
322 if (packet_not_very_much_data_to_write()) {
323 program_alive_scheduled = child_terminated;
324 if (!fdout_eof)
325 FD_SET(fdout, *readsetp);
326 if (!fderr_eof)
327 FD_SET(fderr, *readsetp);
328 }
329 /*
330 * If we have buffered data, try to write some of that data
331 * to the program.
332 */
333 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
334 FD_SET(fdin, *writesetp);
335 }
336 notify_prepare(*readsetp);
337
338 /*
339 * If we have buffered packet data going to the client, mark that
340 * descriptor.
341 */
342 if (packet_have_data_to_write())
343 FD_SET(connection_out, *writesetp);
344
345 /*
346 * If child has terminated and there is enough buffer space to read
347 * from it, then read as much as is available and exit.
348 */
349 if (child_terminated && packet_not_very_much_data_to_write())
350 if (max_time_milliseconds == 0 || client_alive_scheduled)
351 max_time_milliseconds = 100;
352
353 if (max_time_milliseconds == 0)
354 tvp = NULL;
355 else {
356 tv.tv_sec = max_time_milliseconds / 1000;
357 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
358 tvp = &tv;
359 }
360
361 /* Wait for something to happen, or the timeout to expire. */
362 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
363
364 if (ret == -1) {
365 memset(*readsetp, 0, *nallocp);
366 memset(*writesetp, 0, *nallocp);
367 if (errno != EINTR)
368 error("select: %.100s", strerror(errno));
369 } else {
370 if (ret == 0 && client_alive_scheduled)
371 client_alive_check();
372 if (!compat20 && program_alive_scheduled && fdin_is_tty) {
373 if (!fdout_eof)
374 FD_SET(fdout, *readsetp);
375 if (!fderr_eof)
376 FD_SET(fderr, *readsetp);
377 }
378 }
379
380 notify_done(*readsetp);
381 }
382
383 /*
384 * Processes input from the client and the program. Input data is stored
385 * in buffers and processed later.
386 */
387 static void
process_input(fd_set * readset)388 process_input(fd_set *readset)
389 {
390 int len;
391 char buf[16384];
392
393 /* Read and buffer any input data from the client. */
394 if (FD_ISSET(connection_in, readset)) {
395 int cont = 0;
396 len = roaming_read(connection_in, buf, sizeof(buf), &cont);
397 if (len == 0) {
398 if (cont)
399 return;
400 verbose("Connection closed by %.100s",
401 get_remote_ipaddr());
402 connection_closed = 1;
403 if (compat20)
404 return;
405 cleanup_exit(255);
406 } else if (len < 0) {
407 if (errno != EINTR && errno != EAGAIN &&
408 errno != EWOULDBLOCK) {
409 verbose("Read error from remote host "
410 "%.100s: %.100s",
411 get_remote_ipaddr(), strerror(errno));
412 cleanup_exit(255);
413 }
414 } else {
415 /* Buffer any received data. */
416 packet_process_incoming(buf, len);
417 }
418 }
419 if (compat20)
420 return;
421
422 /* Read and buffer any available stdout data from the program. */
423 if (!fdout_eof && FD_ISSET(fdout, readset)) {
424 errno = 0;
425 len = read(fdout, buf, sizeof(buf));
426 if (len < 0 && (errno == EINTR || ((errno == EAGAIN ||
427 errno == EWOULDBLOCK) && !child_terminated))) {
428 /* do nothing */
429 #ifndef PTY_ZEROREAD
430 } else if (len <= 0) {
431 #else
432 } else if ((!isatty(fdout) && len <= 0) ||
433 (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) {
434 #endif
435 fdout_eof = 1;
436 } else {
437 buffer_append(&stdout_buffer, buf, len);
438 fdout_bytes += len;
439 }
440 }
441 /* Read and buffer any available stderr data from the program. */
442 if (!fderr_eof && FD_ISSET(fderr, readset)) {
443 errno = 0;
444 len = read(fderr, buf, sizeof(buf));
445 if (len < 0 && (errno == EINTR || ((errno == EAGAIN ||
446 errno == EWOULDBLOCK) && !child_terminated))) {
447 /* do nothing */
448 #ifndef PTY_ZEROREAD
449 } else if (len <= 0) {
450 #else
451 } else if ((!isatty(fderr) && len <= 0) ||
452 (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) {
453 #endif
454 fderr_eof = 1;
455 } else {
456 buffer_append(&stderr_buffer, buf, len);
457 }
458 }
459 }
460
461 /*
462 * Sends data from internal buffers to client program stdin.
463 */
464 static void
process_output(fd_set * writeset)465 process_output(fd_set *writeset)
466 {
467 struct termios tio;
468 u_char *data;
469 u_int dlen;
470 int len;
471
472 /* Write buffered data to program stdin. */
473 if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
474 data = buffer_ptr(&stdin_buffer);
475 dlen = buffer_len(&stdin_buffer);
476 len = write(fdin, data, dlen);
477 if (len < 0 &&
478 (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)) {
479 /* do nothing */
480 } else if (len <= 0) {
481 if (fdin != fdout)
482 close(fdin);
483 else
484 shutdown(fdin, SHUT_WR); /* We will no longer send. */
485 fdin = -1;
486 } else {
487 /* Successful write. */
488 if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
489 tcgetattr(fdin, &tio) == 0 &&
490 !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
491 /*
492 * Simulate echo to reduce the impact of
493 * traffic analysis
494 */
495 packet_send_ignore(len);
496 packet_send();
497 }
498 /* Consume the data from the buffer. */
499 buffer_consume(&stdin_buffer, len);
500 /* Update the count of bytes written to the program. */
501 stdin_bytes += len;
502 }
503 }
504 /* Send any buffered packet data to the client. */
505 if (FD_ISSET(connection_out, writeset))
506 packet_write_poll();
507 }
508
509 /*
510 * Wait until all buffered output has been sent to the client.
511 * This is used when the program terminates.
512 */
513 static void
drain_output(void)514 drain_output(void)
515 {
516 /* Send any buffered stdout data to the client. */
517 if (buffer_len(&stdout_buffer) > 0) {
518 packet_start(SSH_SMSG_STDOUT_DATA);
519 packet_put_string(buffer_ptr(&stdout_buffer),
520 buffer_len(&stdout_buffer));
521 packet_send();
522 /* Update the count of sent bytes. */
523 stdout_bytes += buffer_len(&stdout_buffer);
524 }
525 /* Send any buffered stderr data to the client. */
526 if (buffer_len(&stderr_buffer) > 0) {
527 packet_start(SSH_SMSG_STDERR_DATA);
528 packet_put_string(buffer_ptr(&stderr_buffer),
529 buffer_len(&stderr_buffer));
530 packet_send();
531 /* Update the count of sent bytes. */
532 stderr_bytes += buffer_len(&stderr_buffer);
533 }
534 /* Wait until all buffered data has been written to the client. */
535 packet_write_wait();
536 }
537
538 static void
process_buffered_input_packets(void)539 process_buffered_input_packets(void)
540 {
541 dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
542 }
543
544 /*
545 * Performs the interactive session. This handles data transmission between
546 * the client and the program. Note that the notion of stdin, stdout, and
547 * stderr in this function is sort of reversed: this function writes to
548 * stdin (of the child program), and reads from stdout and stderr (of the
549 * child program).
550 */
551 void
server_loop(pid_t pid,int fdin_arg,int fdout_arg,int fderr_arg)552 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
553 {
554 fd_set *readset = NULL, *writeset = NULL;
555 int max_fd = 0;
556 u_int nalloc = 0;
557 int wait_status; /* Status returned by wait(). */
558 pid_t wait_pid; /* pid returned by wait(). */
559 int waiting_termination = 0; /* Have displayed waiting close message. */
560 u_int max_time_milliseconds;
561 u_int previous_stdout_buffer_bytes;
562 u_int stdout_buffer_bytes;
563 int type;
564
565 debug("Entering interactive session.");
566
567 /* Initialize the SIGCHLD kludge. */
568 child_terminated = 0;
569 mysignal(SIGCHLD, sigchld_handler);
570
571 if (!use_privsep) {
572 signal(SIGTERM, sigterm_handler);
573 signal(SIGINT, sigterm_handler);
574 signal(SIGQUIT, sigterm_handler);
575 }
576
577 /* Initialize our global variables. */
578 fdin = fdin_arg;
579 fdout = fdout_arg;
580 fderr = fderr_arg;
581
582 /* nonblocking IO */
583 set_nonblock(fdin);
584 set_nonblock(fdout);
585 /* we don't have stderr for interactive terminal sessions, see below */
586 if (fderr != -1)
587 set_nonblock(fderr);
588
589 if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
590 fdin_is_tty = 1;
591
592 connection_in = packet_get_connection_in();
593 connection_out = packet_get_connection_out();
594
595 notify_setup();
596
597 previous_stdout_buffer_bytes = 0;
598
599 /* Set approximate I/O buffer size. */
600 if (packet_is_interactive())
601 buffer_high = 4096;
602 else
603 buffer_high = 64 * 1024;
604
605 #if 0
606 /* Initialize max_fd to the maximum of the known file descriptors. */
607 max_fd = MAX(connection_in, connection_out);
608 max_fd = MAX(max_fd, fdin);
609 max_fd = MAX(max_fd, fdout);
610 if (fderr != -1)
611 max_fd = MAX(max_fd, fderr);
612 #endif
613
614 /* Initialize Initialize buffers. */
615 buffer_init(&stdin_buffer);
616 buffer_init(&stdout_buffer);
617 buffer_init(&stderr_buffer);
618
619 /*
620 * If we have no separate fderr (which is the case when we have a pty
621 * - there we cannot make difference between data sent to stdout and
622 * stderr), indicate that we have seen an EOF from stderr. This way
623 * we don't need to check the descriptor everywhere.
624 */
625 if (fderr == -1)
626 fderr_eof = 1;
627
628 server_init_dispatch();
629
630 /* Main loop of the server for the interactive session mode. */
631 for (;;) {
632
633 /* Process buffered packets from the client. */
634 process_buffered_input_packets();
635
636 /*
637 * If we have received eof, and there is no more pending
638 * input data, cause a real eof by closing fdin.
639 */
640 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
641 if (fdin != fdout)
642 close(fdin);
643 else
644 shutdown(fdin, SHUT_WR); /* We will no longer send. */
645 fdin = -1;
646 }
647 /* Make packets from buffered stderr data to send to the client. */
648 make_packets_from_stderr_data();
649
650 /*
651 * Make packets from buffered stdout data to send to the
652 * client. If there is very little to send, this arranges to
653 * not send them now, but to wait a short while to see if we
654 * are getting more data. This is necessary, as some systems
655 * wake up readers from a pty after each separate character.
656 */
657 max_time_milliseconds = 0;
658 stdout_buffer_bytes = buffer_len(&stdout_buffer);
659 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
660 stdout_buffer_bytes != previous_stdout_buffer_bytes) {
661 /* try again after a while */
662 max_time_milliseconds = 10;
663 } else {
664 /* Send it now. */
665 make_packets_from_stdout_data();
666 }
667 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
668
669 /* Send channel data to the client. */
670 if (packet_not_very_much_data_to_write())
671 channel_output_poll();
672
673 /*
674 * Bail out of the loop if the program has closed its output
675 * descriptors, and we have no more data to send to the
676 * client, and there is no pending buffered data.
677 */
678 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
679 buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
680 if (!channel_still_open())
681 break;
682 if (!waiting_termination) {
683 const char *s = "Waiting for forwarded connections to terminate...\r\n";
684 char *cp;
685 waiting_termination = 1;
686 buffer_append(&stderr_buffer, s, strlen(s));
687
688 /* Display list of open channels. */
689 cp = channel_open_message();
690 buffer_append(&stderr_buffer, cp, strlen(cp));
691 xfree(cp);
692 }
693 }
694 max_fd = MAX(connection_in, connection_out);
695 max_fd = MAX(max_fd, fdin);
696 max_fd = MAX(max_fd, fdout);
697 max_fd = MAX(max_fd, fderr);
698 max_fd = MAX(max_fd, notify_pipe[0]);
699
700 /* Sleep in select() until we can do something. */
701 wait_until_can_do_something(&readset, &writeset, &max_fd,
702 &nalloc, max_time_milliseconds);
703
704 if (received_sigterm) {
705 logit("Exiting on signal %d", received_sigterm);
706 /* Clean up sessions, utmp, etc. */
707 cleanup_exit(255);
708 }
709
710 /* Process any channel events. */
711 channel_after_select(readset, writeset);
712
713 /* Process input from the client and from program stdout/stderr. */
714 process_input(readset);
715
716 /* Process output to the client and to program stdin. */
717 process_output(writeset);
718 }
719 if (readset)
720 xfree(readset);
721 if (writeset)
722 xfree(writeset);
723
724 /* Cleanup and termination code. */
725
726 /* Wait until all output has been sent to the client. */
727 drain_output();
728
729 debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
730 stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
731
732 /* Free and clear the buffers. */
733 buffer_free(&stdin_buffer);
734 buffer_free(&stdout_buffer);
735 buffer_free(&stderr_buffer);
736
737 /* Close the file descriptors. */
738 if (fdout != -1)
739 close(fdout);
740 fdout = -1;
741 fdout_eof = 1;
742 if (fderr != -1)
743 close(fderr);
744 fderr = -1;
745 fderr_eof = 1;
746 if (fdin != -1)
747 close(fdin);
748 fdin = -1;
749
750 channel_free_all();
751
752 /* We no longer want our SIGCHLD handler to be called. */
753 mysignal(SIGCHLD, SIG_DFL);
754
755 while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
756 if (errno != EINTR)
757 packet_disconnect("wait: %.100s", strerror(errno));
758 if (wait_pid != pid)
759 error("Strange, wait returned pid %ld, expected %ld",
760 (long)wait_pid, (long)pid);
761
762 /* Check if it exited normally. */
763 if (WIFEXITED(wait_status)) {
764 /* Yes, normal exit. Get exit status and send it to the client. */
765 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
766 packet_start(SSH_SMSG_EXITSTATUS);
767 packet_put_int(WEXITSTATUS(wait_status));
768 packet_send();
769 packet_write_wait();
770
771 /*
772 * Wait for exit confirmation. Note that there might be
773 * other packets coming before it; however, the program has
774 * already died so we just ignore them. The client is
775 * supposed to respond with the confirmation when it receives
776 * the exit status.
777 */
778 do {
779 type = packet_read();
780 }
781 while (type != SSH_CMSG_EXIT_CONFIRMATION);
782
783 debug("Received exit confirmation.");
784 return;
785 }
786 /* Check if the program terminated due to a signal. */
787 if (WIFSIGNALED(wait_status))
788 packet_disconnect("Command terminated on signal %d.",
789 WTERMSIG(wait_status));
790
791 /* Some weird exit cause. Just exit. */
792 packet_disconnect("wait returned status %04x.", wait_status);
793 /* NOTREACHED */
794 }
795
796 static void
collect_children(void)797 collect_children(void)
798 {
799 pid_t pid;
800 sigset_t oset, nset;
801 int status;
802
803 /* block SIGCHLD while we check for dead children */
804 sigemptyset(&nset);
805 sigaddset(&nset, SIGCHLD);
806 sigprocmask(SIG_BLOCK, &nset, &oset);
807 if (child_terminated) {
808 debug("Received SIGCHLD.");
809 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
810 (pid < 0 && errno == EINTR))
811 if (pid > 0)
812 session_close_by_pid(pid, status);
813 child_terminated = 0;
814 }
815 sigprocmask(SIG_SETMASK, &oset, NULL);
816 }
817
818 void
server_loop2(Authctxt * authctxt)819 server_loop2(Authctxt *authctxt)
820 {
821 fd_set *readset = NULL, *writeset = NULL;
822 int rekeying = 0, max_fd, nalloc = 0;
823
824 debug("Entering interactive session for SSH2.");
825
826 mysignal(SIGCHLD, sigchld_handler);
827 child_terminated = 0;
828 connection_in = packet_get_connection_in();
829 connection_out = packet_get_connection_out();
830
831 if (!use_privsep) {
832 signal(SIGTERM, sigterm_handler);
833 signal(SIGINT, sigterm_handler);
834 signal(SIGQUIT, sigterm_handler);
835 }
836
837 notify_setup();
838
839 max_fd = MAX(connection_in, connection_out);
840 max_fd = MAX(max_fd, notify_pipe[0]);
841
842 server_init_dispatch();
843
844 for (;;) {
845 process_buffered_input_packets();
846
847 rekeying = (xxx_kex != NULL && !xxx_kex->done);
848
849 if (!rekeying && packet_not_very_much_data_to_write())
850 channel_output_poll();
851 wait_until_can_do_something(&readset, &writeset, &max_fd,
852 &nalloc, 0);
853
854 if (received_sigterm) {
855 logit("Exiting on signal %d", received_sigterm);
856 /* Clean up sessions, utmp, etc. */
857 cleanup_exit(255);
858 }
859
860 collect_children();
861 if (!rekeying) {
862 channel_after_select(readset, writeset);
863 if (packet_need_rekeying()) {
864 debug("need rekeying");
865 xxx_kex->done = 0;
866 kex_send_kexinit(xxx_kex);
867 }
868 }
869 process_input(readset);
870 if (connection_closed)
871 break;
872 process_output(writeset);
873 }
874 collect_children();
875
876 if (readset)
877 xfree(readset);
878 if (writeset)
879 xfree(writeset);
880
881 /* free all channels, no more reads and writes */
882 channel_free_all();
883
884 /* free remaining sessions, e.g. remove wtmp entries */
885 session_destroy_all(NULL);
886 }
887
888 static void
server_input_keep_alive(int type,u_int32_t seq,void * ctxt)889 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
890 {
891 debug("Got %d/%u for keepalive", type, seq);
892 /*
893 * reset timeout, since we got a sane answer from the client.
894 * even if this was generated by something other than
895 * the bogus CHANNEL_REQUEST we send for keepalives.
896 */
897 packet_set_alive_timeouts(0);
898 }
899
900 static void
server_input_stdin_data(int type,u_int32_t seq,void * ctxt)901 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
902 {
903 char *data;
904 u_int data_len;
905
906 /* Stdin data from the client. Append it to the buffer. */
907 /* Ignore any data if the client has closed stdin. */
908 if (fdin == -1)
909 return;
910 data = packet_get_string(&data_len);
911 packet_check_eom();
912 buffer_append(&stdin_buffer, data, data_len);
913 memset(data, 0, data_len);
914 xfree(data);
915 }
916
917 static void
server_input_eof(int type,u_int32_t seq,void * ctxt)918 server_input_eof(int type, u_int32_t seq, void *ctxt)
919 {
920 /*
921 * Eof from the client. The stdin descriptor to the
922 * program will be closed when all buffered data has
923 * drained.
924 */
925 debug("EOF received for stdin.");
926 packet_check_eom();
927 stdin_eof = 1;
928 }
929
930 static void
server_input_window_size(int type,u_int32_t seq,void * ctxt)931 server_input_window_size(int type, u_int32_t seq, void *ctxt)
932 {
933 u_int row = packet_get_int();
934 u_int col = packet_get_int();
935 u_int xpixel = packet_get_int();
936 u_int ypixel = packet_get_int();
937
938 debug("Window change received.");
939 packet_check_eom();
940 if (fdin != -1)
941 pty_change_window_size(fdin, row, col, xpixel, ypixel);
942 }
943
944 static Channel *
server_request_direct_tcpip(void)945 server_request_direct_tcpip(void)
946 {
947 Channel *c;
948 char *target, *originator;
949 u_short target_port, originator_port;
950
951 target = packet_get_string(NULL);
952 target_port = packet_get_int();
953 originator = packet_get_string(NULL);
954 originator_port = packet_get_int();
955 packet_check_eom();
956
957 debug("server_request_direct_tcpip: originator %s port %d, target %s "
958 "port %d", originator, originator_port, target, target_port);
959
960 /* XXX check permission */
961 c = channel_connect_to(target, target_port,
962 "direct-tcpip", "direct-tcpip");
963
964 xfree(originator);
965 xfree(target);
966
967 return c;
968 }
969
970 static Channel *
server_request_tun(void)971 server_request_tun(void)
972 {
973 Channel *c = NULL;
974 int mode, tun;
975 int sock;
976
977 mode = packet_get_int();
978 switch (mode) {
979 case SSH_TUNMODE_POINTOPOINT:
980 case SSH_TUNMODE_ETHERNET:
981 break;
982 default:
983 packet_send_debug("Unsupported tunnel device mode.");
984 return NULL;
985 }
986 if ((options.permit_tun & mode) == 0) {
987 packet_send_debug("Server has rejected tunnel device "
988 "forwarding");
989 return NULL;
990 }
991
992 tun = packet_get_int();
993 if (forced_tun_device != -1) {
994 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
995 goto done;
996 tun = forced_tun_device;
997 }
998 sock = tun_open(tun, mode);
999 if (sock < 0)
1000 goto done;
1001 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
1002 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
1003 c->datagram = 1;
1004 #if defined(SSH_TUN_FILTER)
1005 if (mode == SSH_TUNMODE_POINTOPOINT)
1006 channel_register_filter(c->self, sys_tun_infilter,
1007 sys_tun_outfilter, NULL, NULL);
1008 #endif
1009
1010 done:
1011 if (c == NULL)
1012 packet_send_debug("Failed to open the tunnel device.");
1013 return c;
1014 }
1015
1016 static Channel *
server_request_session(void)1017 server_request_session(void)
1018 {
1019 Channel *c;
1020
1021 debug("input_session_request");
1022 packet_check_eom();
1023
1024 if (no_more_sessions) {
1025 packet_disconnect("Possible attack: attempt to open a session "
1026 "after additional sessions disabled");
1027 }
1028
1029 /*
1030 * A server session has no fd to read or write until a
1031 * CHANNEL_REQUEST for a shell is made, so we set the type to
1032 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all
1033 * CHANNEL_REQUEST messages is registered.
1034 */
1035 c = channel_new("session", SSH_CHANNEL_LARVAL,
1036 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
1037 0, "server-session", 1);
1038 if (session_open(the_authctxt, c->self) != 1) {
1039 debug("session open failed, free channel %d", c->self);
1040 channel_free(c);
1041 return NULL;
1042 }
1043 channel_register_cleanup(c->self, session_close_by_channel, 0);
1044 return c;
1045 }
1046
1047 static void
server_input_channel_open(int type,u_int32_t seq,void * ctxt)1048 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
1049 {
1050 Channel *c = NULL;
1051 char *ctype;
1052 int rchan;
1053 u_int rmaxpack, rwindow, len;
1054
1055 ctype = packet_get_string(&len);
1056 rchan = packet_get_int();
1057 rwindow = packet_get_int();
1058 rmaxpack = packet_get_int();
1059
1060 debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1061 ctype, rchan, rwindow, rmaxpack);
1062
1063 if (strcmp(ctype, "session") == 0) {
1064 c = server_request_session();
1065 } else if (strcmp(ctype, "direct-tcpip") == 0) {
1066 c = server_request_direct_tcpip();
1067 } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1068 c = server_request_tun();
1069 }
1070 if (c != NULL) {
1071 debug("server_input_channel_open: confirm %s", ctype);
1072 c->remote_id = rchan;
1073 c->remote_window = rwindow;
1074 c->remote_maxpacket = rmaxpack;
1075 if (c->type != SSH_CHANNEL_CONNECTING) {
1076 packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1077 packet_put_int(c->remote_id);
1078 packet_put_int(c->self);
1079 packet_put_int(c->local_window);
1080 packet_put_int(c->local_maxpacket);
1081 packet_send();
1082 }
1083 } else {
1084 debug("server_input_channel_open: failure %s", ctype);
1085 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1086 packet_put_int(rchan);
1087 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1088 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1089 packet_put_cstring("open failed");
1090 packet_put_cstring("");
1091 }
1092 packet_send();
1093 }
1094 xfree(ctype);
1095 }
1096
1097 static void
server_input_global_request(int type,u_int32_t seq,void * ctxt)1098 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1099 {
1100 char *rtype;
1101 int want_reply;
1102 int success = 0, allocated_listen_port = 0;
1103
1104 rtype = packet_get_string(NULL);
1105 want_reply = packet_get_char();
1106 debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1107
1108 /* -R style forwarding */
1109 if (strcmp(rtype, "tcpip-forward") == 0) {
1110 struct passwd *pw;
1111 char *listen_address;
1112 u_short listen_port;
1113
1114 pw = the_authctxt->pw;
1115 if (pw == NULL || !the_authctxt->valid)
1116 fatal("server_input_global_request: no/invalid user");
1117 listen_address = packet_get_string(NULL);
1118 listen_port = (u_short)packet_get_int();
1119 debug("server_input_global_request: tcpip-forward listen %s port %d",
1120 listen_address, listen_port);
1121
1122 /* check permissions */
1123 if (!options.allow_tcp_forwarding ||
1124 no_port_forwarding_flag ||
1125 (!want_reply && listen_port == 0)
1126 #ifndef NO_IPPORT_RESERVED_CONCEPT
1127 || (listen_port != 0 && listen_port < IPPORT_RESERVED &&
1128 pw->pw_uid != 0)
1129 #endif
1130 ) {
1131 success = 0;
1132 packet_send_debug("Server has disabled port forwarding.");
1133 } else {
1134 /* Start listening on the port */
1135 success = channel_setup_remote_fwd_listener(
1136 listen_address, listen_port,
1137 &allocated_listen_port, options.gateway_ports);
1138 }
1139 xfree(listen_address);
1140 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1141 char *cancel_address;
1142 u_short cancel_port;
1143
1144 cancel_address = packet_get_string(NULL);
1145 cancel_port = (u_short)packet_get_int();
1146 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1147 cancel_address, cancel_port);
1148
1149 success = channel_cancel_rport_listener(cancel_address,
1150 cancel_port);
1151 xfree(cancel_address);
1152 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
1153 no_more_sessions = 1;
1154 success = 1;
1155 }
1156 if (want_reply) {
1157 packet_start(success ?
1158 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1159 if (success && allocated_listen_port > 0)
1160 packet_put_int(allocated_listen_port);
1161 packet_send();
1162 packet_write_wait();
1163 }
1164 xfree(rtype);
1165 }
1166
1167 static void
server_input_channel_req(int type,u_int32_t seq,void * ctxt)1168 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1169 {
1170 Channel *c;
1171 int id, reply, success = 0;
1172 char *rtype;
1173
1174 id = packet_get_int();
1175 rtype = packet_get_string(NULL);
1176 reply = packet_get_char();
1177
1178 debug("server_input_channel_req: channel %d request %s reply %d",
1179 id, rtype, reply);
1180
1181 if ((c = channel_lookup(id)) == NULL)
1182 packet_disconnect("server_input_channel_req: "
1183 "unknown channel %d", id);
1184 if (!strcmp(rtype, "eow@openssh.com")) {
1185 packet_check_eom();
1186 chan_rcvd_eow(c);
1187 } else if ((c->type == SSH_CHANNEL_LARVAL ||
1188 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
1189 success = session_input_channel_req(c, rtype);
1190 if (reply) {
1191 packet_start(success ?
1192 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1193 packet_put_int(c->remote_id);
1194 packet_send();
1195 }
1196 xfree(rtype);
1197 }
1198
1199 static void
server_init_dispatch_20(void)1200 server_init_dispatch_20(void)
1201 {
1202 debug("server_init_dispatch_20");
1203 dispatch_init(&dispatch_protocol_error);
1204 dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1205 dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1206 dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1207 dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1208 dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1209 dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1210 dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1211 dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1212 dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1213 dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1214 /* client_alive */
1215 dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive);
1216 dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
1217 dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1218 dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1219 /* rekeying */
1220 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1221 }
1222 static void
server_init_dispatch_13(void)1223 server_init_dispatch_13(void)
1224 {
1225 debug("server_init_dispatch_13");
1226 dispatch_init(NULL);
1227 dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1228 dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1229 dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1230 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1231 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1232 dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1233 dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1234 dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1235 dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1236 }
1237 static void
server_init_dispatch_15(void)1238 server_init_dispatch_15(void)
1239 {
1240 server_init_dispatch_13();
1241 debug("server_init_dispatch_15");
1242 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1243 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1244 }
1245 static void
server_init_dispatch(void)1246 server_init_dispatch(void)
1247 {
1248 if (compat20)
1249 server_init_dispatch_20();
1250 else if (compat13)
1251 server_init_dispatch_13();
1252 else
1253 server_init_dispatch_15();
1254 }
1255