1 /* $OpenBSD: serverloop.c,v 1.170 2014/02/02 03:44:31 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 __RCSID("$FreeBSD$");
40
41 #include <sys/types.h>
42 #include <sys/param.h>
43 #include <sys/wait.h>
44 #include <sys/socket.h>
45 #ifdef HAVE_SYS_TIME_H
46 # include <sys/time.h>
47 #endif
48
49 #include <netinet/in.h>
50
51 #include <errno.h>
52 #include <fcntl.h>
53 #include <pwd.h>
54 #include <signal.h>
55 #include <string.h>
56 #include <termios.h>
57 #include <unistd.h>
58 #include <stdarg.h>
59
60 #include "openbsd-compat/sys-queue.h"
61 #include "xmalloc.h"
62 #include "packet.h"
63 #include "buffer.h"
64 #include "log.h"
65 #include "servconf.h"
66 #include "canohost.h"
67 #include "sshpty.h"
68 #include "channels.h"
69 #include "compat.h"
70 #include "ssh1.h"
71 #include "ssh2.h"
72 #include "key.h"
73 #include "cipher.h"
74 #include "kex.h"
75 #include "hostfile.h"
76 #include "auth.h"
77 #include "session.h"
78 #include "dispatch.h"
79 #include "auth-options.h"
80 #include "serverloop.h"
81 #include "misc.h"
82 #include "roaming.h"
83
84 extern ServerOptions options;
85
86 /* XXX */
87 extern Kex *xxx_kex;
88 extern Authctxt *the_authctxt;
89 extern int use_privsep;
90
91 static Buffer stdin_buffer; /* Buffer for stdin data. */
92 static Buffer stdout_buffer; /* Buffer for stdout data. */
93 static Buffer stderr_buffer; /* Buffer for stderr data. */
94 static int fdin; /* Descriptor for stdin (for writing) */
95 static int fdout; /* Descriptor for stdout (for reading);
96 May be same number as fdin. */
97 static int fderr; /* Descriptor for stderr. May be -1. */
98 static long stdin_bytes = 0; /* Number of bytes written to stdin. */
99 static long stdout_bytes = 0; /* Number of stdout bytes sent to client. */
100 static long stderr_bytes = 0; /* Number of stderr bytes sent to client. */
101 static long fdout_bytes = 0; /* Number of stdout bytes read from program. */
102 static int stdin_eof = 0; /* EOF message received from client. */
103 static int fdout_eof = 0; /* EOF encountered reading from fdout. */
104 static int fderr_eof = 0; /* EOF encountered readung from fderr. */
105 static int fdin_is_tty = 0; /* fdin points to a tty. */
106 static int connection_in; /* Connection to client (input). */
107 static int connection_out; /* Connection to client (output). */
108 static int connection_closed = 0; /* Connection to client closed. */
109 static u_int buffer_high; /* "Soft" max buffer size. */
110 static int no_more_sessions = 0; /* Disallow further sessions. */
111
112 /*
113 * This SIGCHLD kludge is used to detect when the child exits. The server
114 * will exit after that, as soon as forwarded connections have terminated.
115 */
116
117 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */
118
119 /* Cleanup on signals (!use_privsep case only) */
120 static volatile sig_atomic_t received_sigterm = 0;
121
122 /* prototypes */
123 static void server_init_dispatch(void);
124
125 /*
126 * we write to this pipe if a SIGCHLD is caught in order to avoid
127 * the race between select() and child_terminated
128 */
129 static int notify_pipe[2];
130 static void
notify_setup(void)131 notify_setup(void)
132 {
133 if (pipe(notify_pipe) < 0) {
134 error("pipe(notify_pipe) failed %s", strerror(errno));
135 } else if ((fcntl(notify_pipe[0], F_SETFD, FD_CLOEXEC) == -1) ||
136 (fcntl(notify_pipe[1], F_SETFD, FD_CLOEXEC) == -1)) {
137 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
138 close(notify_pipe[0]);
139 close(notify_pipe[1]);
140 } else {
141 set_nonblock(notify_pipe[0]);
142 set_nonblock(notify_pipe[1]);
143 return;
144 }
145 notify_pipe[0] = -1; /* read end */
146 notify_pipe[1] = -1; /* write end */
147 }
148 static void
notify_parent(void)149 notify_parent(void)
150 {
151 if (notify_pipe[1] != -1)
152 (void)write(notify_pipe[1], "", 1);
153 }
154 static void
notify_prepare(fd_set * readset)155 notify_prepare(fd_set *readset)
156 {
157 if (notify_pipe[0] != -1)
158 FD_SET(notify_pipe[0], readset);
159 }
160 static void
notify_done(fd_set * readset)161 notify_done(fd_set *readset)
162 {
163 char c;
164
165 if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
166 while (read(notify_pipe[0], &c, 1) != -1)
167 debug2("notify_done: reading");
168 }
169
170 /*ARGSUSED*/
171 static void
sigchld_handler(int sig)172 sigchld_handler(int sig)
173 {
174 int save_errno = errno;
175 child_terminated = 1;
176 #ifndef _UNICOS
177 mysignal(SIGCHLD, sigchld_handler);
178 #endif
179 notify_parent();
180 errno = save_errno;
181 }
182
183 /*ARGSUSED*/
184 static void
sigterm_handler(int sig)185 sigterm_handler(int sig)
186 {
187 received_sigterm = sig;
188 }
189
190 /*
191 * Make packets from buffered stderr data, and buffer it for sending
192 * to the client.
193 */
194 static void
make_packets_from_stderr_data(void)195 make_packets_from_stderr_data(void)
196 {
197 u_int len;
198
199 /* Send buffered stderr data to the client. */
200 while (buffer_len(&stderr_buffer) > 0 &&
201 packet_not_very_much_data_to_write()) {
202 len = buffer_len(&stderr_buffer);
203 if (packet_is_interactive()) {
204 if (len > 512)
205 len = 512;
206 } else {
207 /* Keep the packets at reasonable size. */
208 if (len > packet_get_maxsize())
209 len = packet_get_maxsize();
210 }
211 packet_start(SSH_SMSG_STDERR_DATA);
212 packet_put_string(buffer_ptr(&stderr_buffer), len);
213 packet_send();
214 buffer_consume(&stderr_buffer, len);
215 stderr_bytes += len;
216 }
217 }
218
219 /*
220 * Make packets from buffered stdout data, and buffer it for sending to the
221 * client.
222 */
223 static void
make_packets_from_stdout_data(void)224 make_packets_from_stdout_data(void)
225 {
226 u_int len;
227
228 /* Send buffered stdout data to the client. */
229 while (buffer_len(&stdout_buffer) > 0 &&
230 packet_not_very_much_data_to_write()) {
231 len = buffer_len(&stdout_buffer);
232 if (packet_is_interactive()) {
233 if (len > 512)
234 len = 512;
235 } else {
236 /* Keep the packets at reasonable size. */
237 if (len > packet_get_maxsize())
238 len = packet_get_maxsize();
239 }
240 packet_start(SSH_SMSG_STDOUT_DATA);
241 packet_put_string(buffer_ptr(&stdout_buffer), len);
242 packet_send();
243 buffer_consume(&stdout_buffer, len);
244 stdout_bytes += len;
245 }
246 }
247
248 static void
client_alive_check(void)249 client_alive_check(void)
250 {
251 int channel_id;
252
253 /* timeout, check to see how many we have had */
254 if (packet_inc_alive_timeouts() > options.client_alive_count_max) {
255 logit("Timeout, client not responding.");
256 cleanup_exit(255);
257 }
258
259 /*
260 * send a bogus global/channel request with "wantreply",
261 * we should get back a failure
262 */
263 if ((channel_id = channel_find_open()) == -1) {
264 packet_start(SSH2_MSG_GLOBAL_REQUEST);
265 packet_put_cstring("keepalive@openssh.com");
266 packet_put_char(1); /* boolean: want reply */
267 } else {
268 channel_request_start(channel_id, "keepalive@openssh.com", 1);
269 }
270 packet_send();
271 }
272
273 /*
274 * Sleep in select() until we can do something. This will initialize the
275 * select masks. Upon return, the masks will indicate which descriptors
276 * have data or can accept data. Optionally, a maximum time can be specified
277 * for the duration of the wait (0 = infinite).
278 */
279 static void
wait_until_can_do_something(fd_set ** readsetp,fd_set ** writesetp,int * maxfdp,u_int * nallocp,u_int64_t max_time_milliseconds)280 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
281 u_int *nallocp, u_int64_t max_time_milliseconds)
282 {
283 struct timeval tv, *tvp;
284 int ret;
285 time_t minwait_secs = 0;
286 int client_alive_scheduled = 0;
287 int program_alive_scheduled = 0;
288
289 /* Allocate and update select() masks for channel descriptors. */
290 channel_prepare_select(readsetp, writesetp, maxfdp, nallocp,
291 &minwait_secs, 0);
292
293 if (minwait_secs != 0)
294 max_time_milliseconds = MIN(max_time_milliseconds,
295 (u_int)minwait_secs * 1000);
296
297 /*
298 * if using client_alive, set the max timeout accordingly,
299 * and indicate that this particular timeout was for client
300 * alive by setting the client_alive_scheduled flag.
301 *
302 * this could be randomized somewhat to make traffic
303 * analysis more difficult, but we're not doing it yet.
304 */
305 if (compat20 &&
306 max_time_milliseconds == 0 && options.client_alive_interval) {
307 client_alive_scheduled = 1;
308 max_time_milliseconds =
309 (u_int64_t)options.client_alive_interval * 1000;
310 }
311
312 if (compat20) {
313 #if 0
314 /* wrong: bad condition XXX */
315 if (channel_not_very_much_buffered_data())
316 #endif
317 FD_SET(connection_in, *readsetp);
318 } else {
319 /*
320 * Read packets from the client unless we have too much
321 * buffered stdin or channel data.
322 */
323 if (buffer_len(&stdin_buffer) < buffer_high &&
324 channel_not_very_much_buffered_data())
325 FD_SET(connection_in, *readsetp);
326 /*
327 * If there is not too much data already buffered going to
328 * the client, try to get some more data from the program.
329 */
330 if (packet_not_very_much_data_to_write()) {
331 program_alive_scheduled = child_terminated;
332 if (!fdout_eof)
333 FD_SET(fdout, *readsetp);
334 if (!fderr_eof)
335 FD_SET(fderr, *readsetp);
336 }
337 /*
338 * If we have buffered data, try to write some of that data
339 * to the program.
340 */
341 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
342 FD_SET(fdin, *writesetp);
343 }
344 notify_prepare(*readsetp);
345
346 /*
347 * If we have buffered packet data going to the client, mark that
348 * descriptor.
349 */
350 if (packet_have_data_to_write())
351 FD_SET(connection_out, *writesetp);
352
353 /*
354 * If child has terminated and there is enough buffer space to read
355 * from it, then read as much as is available and exit.
356 */
357 if (child_terminated && packet_not_very_much_data_to_write())
358 if (max_time_milliseconds == 0 || client_alive_scheduled)
359 max_time_milliseconds = 100;
360
361 if (max_time_milliseconds == 0)
362 tvp = NULL;
363 else {
364 tv.tv_sec = max_time_milliseconds / 1000;
365 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
366 tvp = &tv;
367 }
368
369 /* Wait for something to happen, or the timeout to expire. */
370 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
371
372 if (ret == -1) {
373 memset(*readsetp, 0, *nallocp);
374 memset(*writesetp, 0, *nallocp);
375 if (errno != EINTR)
376 error("select: %.100s", strerror(errno));
377 } else {
378 if (ret == 0 && client_alive_scheduled)
379 client_alive_check();
380 if (!compat20 && program_alive_scheduled && fdin_is_tty) {
381 if (!fdout_eof)
382 FD_SET(fdout, *readsetp);
383 if (!fderr_eof)
384 FD_SET(fderr, *readsetp);
385 }
386 }
387
388 notify_done(*readsetp);
389 }
390
391 /*
392 * Processes input from the client and the program. Input data is stored
393 * in buffers and processed later.
394 */
395 static void
process_input(fd_set * readset)396 process_input(fd_set *readset)
397 {
398 int len;
399 char buf[16384];
400
401 /* Read and buffer any input data from the client. */
402 if (FD_ISSET(connection_in, readset)) {
403 int cont = 0;
404 len = roaming_read(connection_in, buf, sizeof(buf), &cont);
405 if (len == 0) {
406 if (cont)
407 return;
408 verbose("Connection closed by %.100s",
409 get_remote_ipaddr());
410 connection_closed = 1;
411 if (compat20)
412 return;
413 cleanup_exit(255);
414 } else if (len < 0) {
415 if (errno != EINTR && errno != EAGAIN &&
416 errno != EWOULDBLOCK) {
417 verbose("Read error from remote host "
418 "%.100s: %.100s",
419 get_remote_ipaddr(), strerror(errno));
420 cleanup_exit(255);
421 }
422 } else {
423 /* Buffer any received data. */
424 packet_process_incoming(buf, len);
425 }
426 }
427 if (compat20)
428 return;
429
430 /* Read and buffer any available stdout data from the program. */
431 if (!fdout_eof && FD_ISSET(fdout, readset)) {
432 errno = 0;
433 len = read(fdout, buf, sizeof(buf));
434 if (len < 0 && (errno == EINTR || ((errno == EAGAIN ||
435 errno == EWOULDBLOCK) && !child_terminated))) {
436 /* do nothing */
437 #ifndef PTY_ZEROREAD
438 } else if (len <= 0) {
439 #else
440 } else if ((!isatty(fdout) && len <= 0) ||
441 (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) {
442 #endif
443 fdout_eof = 1;
444 } else {
445 buffer_append(&stdout_buffer, buf, len);
446 fdout_bytes += len;
447 }
448 }
449 /* Read and buffer any available stderr data from the program. */
450 if (!fderr_eof && FD_ISSET(fderr, readset)) {
451 errno = 0;
452 len = read(fderr, buf, sizeof(buf));
453 if (len < 0 && (errno == EINTR || ((errno == EAGAIN ||
454 errno == EWOULDBLOCK) && !child_terminated))) {
455 /* do nothing */
456 #ifndef PTY_ZEROREAD
457 } else if (len <= 0) {
458 #else
459 } else if ((!isatty(fderr) && len <= 0) ||
460 (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) {
461 #endif
462 fderr_eof = 1;
463 } else {
464 buffer_append(&stderr_buffer, buf, len);
465 }
466 }
467 }
468
469 /*
470 * Sends data from internal buffers to client program stdin.
471 */
472 static void
process_output(fd_set * writeset)473 process_output(fd_set *writeset)
474 {
475 struct termios tio;
476 u_char *data;
477 u_int dlen;
478 int len;
479
480 /* Write buffered data to program stdin. */
481 if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
482 data = buffer_ptr(&stdin_buffer);
483 dlen = buffer_len(&stdin_buffer);
484 len = write(fdin, data, dlen);
485 if (len < 0 &&
486 (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)) {
487 /* do nothing */
488 } else if (len <= 0) {
489 if (fdin != fdout)
490 close(fdin);
491 else
492 shutdown(fdin, SHUT_WR); /* We will no longer send. */
493 fdin = -1;
494 } else {
495 /* Successful write. */
496 if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
497 tcgetattr(fdin, &tio) == 0 &&
498 !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
499 /*
500 * Simulate echo to reduce the impact of
501 * traffic analysis
502 */
503 packet_send_ignore(len);
504 packet_send();
505 }
506 /* Consume the data from the buffer. */
507 buffer_consume(&stdin_buffer, len);
508 /* Update the count of bytes written to the program. */
509 stdin_bytes += len;
510 }
511 }
512 /* Send any buffered packet data to the client. */
513 if (FD_ISSET(connection_out, writeset))
514 packet_write_poll();
515 }
516
517 /*
518 * Wait until all buffered output has been sent to the client.
519 * This is used when the program terminates.
520 */
521 static void
drain_output(void)522 drain_output(void)
523 {
524 /* Send any buffered stdout data to the client. */
525 if (buffer_len(&stdout_buffer) > 0) {
526 packet_start(SSH_SMSG_STDOUT_DATA);
527 packet_put_string(buffer_ptr(&stdout_buffer),
528 buffer_len(&stdout_buffer));
529 packet_send();
530 /* Update the count of sent bytes. */
531 stdout_bytes += buffer_len(&stdout_buffer);
532 }
533 /* Send any buffered stderr data to the client. */
534 if (buffer_len(&stderr_buffer) > 0) {
535 packet_start(SSH_SMSG_STDERR_DATA);
536 packet_put_string(buffer_ptr(&stderr_buffer),
537 buffer_len(&stderr_buffer));
538 packet_send();
539 /* Update the count of sent bytes. */
540 stderr_bytes += buffer_len(&stderr_buffer);
541 }
542 /* Wait until all buffered data has been written to the client. */
543 packet_write_wait();
544 }
545
546 static void
process_buffered_input_packets(void)547 process_buffered_input_packets(void)
548 {
549 dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
550 }
551
552 /*
553 * Performs the interactive session. This handles data transmission between
554 * the client and the program. Note that the notion of stdin, stdout, and
555 * stderr in this function is sort of reversed: this function writes to
556 * stdin (of the child program), and reads from stdout and stderr (of the
557 * child program).
558 */
559 void
server_loop(pid_t pid,int fdin_arg,int fdout_arg,int fderr_arg)560 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
561 {
562 fd_set *readset = NULL, *writeset = NULL;
563 int max_fd = 0;
564 u_int nalloc = 0;
565 int wait_status; /* Status returned by wait(). */
566 pid_t wait_pid; /* pid returned by wait(). */
567 int waiting_termination = 0; /* Have displayed waiting close message. */
568 u_int64_t max_time_milliseconds;
569 u_int previous_stdout_buffer_bytes;
570 u_int stdout_buffer_bytes;
571 int type;
572
573 debug("Entering interactive session.");
574
575 /* Initialize the SIGCHLD kludge. */
576 child_terminated = 0;
577 mysignal(SIGCHLD, sigchld_handler);
578
579 if (!use_privsep) {
580 signal(SIGTERM, sigterm_handler);
581 signal(SIGINT, sigterm_handler);
582 signal(SIGQUIT, sigterm_handler);
583 }
584
585 /* Initialize our global variables. */
586 fdin = fdin_arg;
587 fdout = fdout_arg;
588 fderr = fderr_arg;
589
590 /* nonblocking IO */
591 set_nonblock(fdin);
592 set_nonblock(fdout);
593 /* we don't have stderr for interactive terminal sessions, see below */
594 if (fderr != -1)
595 set_nonblock(fderr);
596
597 if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
598 fdin_is_tty = 1;
599
600 connection_in = packet_get_connection_in();
601 connection_out = packet_get_connection_out();
602
603 notify_setup();
604
605 previous_stdout_buffer_bytes = 0;
606
607 /* Set approximate I/O buffer size. */
608 if (packet_is_interactive())
609 buffer_high = 4096;
610 else
611 buffer_high = 64 * 1024;
612
613 #if 0
614 /* Initialize max_fd to the maximum of the known file descriptors. */
615 max_fd = MAX(connection_in, connection_out);
616 max_fd = MAX(max_fd, fdin);
617 max_fd = MAX(max_fd, fdout);
618 if (fderr != -1)
619 max_fd = MAX(max_fd, fderr);
620 #endif
621
622 /* Initialize Initialize buffers. */
623 buffer_init(&stdin_buffer);
624 buffer_init(&stdout_buffer);
625 buffer_init(&stderr_buffer);
626
627 /*
628 * If we have no separate fderr (which is the case when we have a pty
629 * - there we cannot make difference between data sent to stdout and
630 * stderr), indicate that we have seen an EOF from stderr. This way
631 * we don't need to check the descriptor everywhere.
632 */
633 if (fderr == -1)
634 fderr_eof = 1;
635
636 server_init_dispatch();
637
638 /* Main loop of the server for the interactive session mode. */
639 for (;;) {
640
641 /* Process buffered packets from the client. */
642 process_buffered_input_packets();
643
644 /*
645 * If we have received eof, and there is no more pending
646 * input data, cause a real eof by closing fdin.
647 */
648 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
649 if (fdin != fdout)
650 close(fdin);
651 else
652 shutdown(fdin, SHUT_WR); /* We will no longer send. */
653 fdin = -1;
654 }
655 /* Make packets from buffered stderr data to send to the client. */
656 make_packets_from_stderr_data();
657
658 /*
659 * Make packets from buffered stdout data to send to the
660 * client. If there is very little to send, this arranges to
661 * not send them now, but to wait a short while to see if we
662 * are getting more data. This is necessary, as some systems
663 * wake up readers from a pty after each separate character.
664 */
665 max_time_milliseconds = 0;
666 stdout_buffer_bytes = buffer_len(&stdout_buffer);
667 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
668 stdout_buffer_bytes != previous_stdout_buffer_bytes) {
669 /* try again after a while */
670 max_time_milliseconds = 10;
671 } else {
672 /* Send it now. */
673 make_packets_from_stdout_data();
674 }
675 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
676
677 /* Send channel data to the client. */
678 if (packet_not_very_much_data_to_write())
679 channel_output_poll();
680
681 /*
682 * Bail out of the loop if the program has closed its output
683 * descriptors, and we have no more data to send to the
684 * client, and there is no pending buffered data.
685 */
686 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
687 buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
688 if (!channel_still_open())
689 break;
690 if (!waiting_termination) {
691 const char *s = "Waiting for forwarded connections to terminate...\r\n";
692 char *cp;
693 waiting_termination = 1;
694 buffer_append(&stderr_buffer, s, strlen(s));
695
696 /* Display list of open channels. */
697 cp = channel_open_message();
698 buffer_append(&stderr_buffer, cp, strlen(cp));
699 free(cp);
700 }
701 }
702 max_fd = MAX(connection_in, connection_out);
703 max_fd = MAX(max_fd, fdin);
704 max_fd = MAX(max_fd, fdout);
705 max_fd = MAX(max_fd, fderr);
706 max_fd = MAX(max_fd, notify_pipe[0]);
707
708 /* Sleep in select() until we can do something. */
709 wait_until_can_do_something(&readset, &writeset, &max_fd,
710 &nalloc, max_time_milliseconds);
711
712 if (received_sigterm) {
713 logit("Exiting on signal %d", (int)received_sigterm);
714 /* Clean up sessions, utmp, etc. */
715 cleanup_exit(255);
716 }
717
718 /* Process any channel events. */
719 channel_after_select(readset, writeset);
720
721 /* Process input from the client and from program stdout/stderr. */
722 process_input(readset);
723
724 /* Process output to the client and to program stdin. */
725 process_output(writeset);
726 }
727 free(readset);
728 free(writeset);
729
730 /* Cleanup and termination code. */
731
732 /* Wait until all output has been sent to the client. */
733 drain_output();
734
735 debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
736 stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
737
738 /* Free and clear the buffers. */
739 buffer_free(&stdin_buffer);
740 buffer_free(&stdout_buffer);
741 buffer_free(&stderr_buffer);
742
743 /* Close the file descriptors. */
744 if (fdout != -1)
745 close(fdout);
746 fdout = -1;
747 fdout_eof = 1;
748 if (fderr != -1)
749 close(fderr);
750 fderr = -1;
751 fderr_eof = 1;
752 if (fdin != -1)
753 close(fdin);
754 fdin = -1;
755
756 channel_free_all();
757
758 /* We no longer want our SIGCHLD handler to be called. */
759 mysignal(SIGCHLD, SIG_DFL);
760
761 while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
762 if (errno != EINTR)
763 packet_disconnect("wait: %.100s", strerror(errno));
764 if (wait_pid != pid)
765 error("Strange, wait returned pid %ld, expected %ld",
766 (long)wait_pid, (long)pid);
767
768 /* Check if it exited normally. */
769 if (WIFEXITED(wait_status)) {
770 /* Yes, normal exit. Get exit status and send it to the client. */
771 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
772 packet_start(SSH_SMSG_EXITSTATUS);
773 packet_put_int(WEXITSTATUS(wait_status));
774 packet_send();
775 packet_write_wait();
776
777 /*
778 * Wait for exit confirmation. Note that there might be
779 * other packets coming before it; however, the program has
780 * already died so we just ignore them. The client is
781 * supposed to respond with the confirmation when it receives
782 * the exit status.
783 */
784 do {
785 type = packet_read();
786 }
787 while (type != SSH_CMSG_EXIT_CONFIRMATION);
788
789 debug("Received exit confirmation.");
790 return;
791 }
792 /* Check if the program terminated due to a signal. */
793 if (WIFSIGNALED(wait_status))
794 packet_disconnect("Command terminated on signal %d.",
795 WTERMSIG(wait_status));
796
797 /* Some weird exit cause. Just exit. */
798 packet_disconnect("wait returned status %04x.", wait_status);
799 /* NOTREACHED */
800 }
801
802 static void
collect_children(void)803 collect_children(void)
804 {
805 pid_t pid;
806 sigset_t oset, nset;
807 int status;
808
809 /* block SIGCHLD while we check for dead children */
810 sigemptyset(&nset);
811 sigaddset(&nset, SIGCHLD);
812 sigprocmask(SIG_BLOCK, &nset, &oset);
813 if (child_terminated) {
814 debug("Received SIGCHLD.");
815 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
816 (pid < 0 && errno == EINTR))
817 if (pid > 0)
818 session_close_by_pid(pid, status);
819 child_terminated = 0;
820 }
821 sigprocmask(SIG_SETMASK, &oset, NULL);
822 }
823
824 void
server_loop2(Authctxt * authctxt)825 server_loop2(Authctxt *authctxt)
826 {
827 fd_set *readset = NULL, *writeset = NULL;
828 int rekeying = 0, max_fd;
829 u_int nalloc = 0;
830 u_int64_t rekey_timeout_ms = 0;
831
832 debug("Entering interactive session for SSH2.");
833
834 mysignal(SIGCHLD, sigchld_handler);
835 child_terminated = 0;
836 connection_in = packet_get_connection_in();
837 connection_out = packet_get_connection_out();
838
839 if (!use_privsep) {
840 signal(SIGTERM, sigterm_handler);
841 signal(SIGINT, sigterm_handler);
842 signal(SIGQUIT, sigterm_handler);
843 }
844
845 notify_setup();
846
847 max_fd = MAX(connection_in, connection_out);
848 max_fd = MAX(max_fd, notify_pipe[0]);
849
850 server_init_dispatch();
851
852 for (;;) {
853 process_buffered_input_packets();
854
855 rekeying = (xxx_kex != NULL && !xxx_kex->done);
856
857 if (!rekeying && packet_not_very_much_data_to_write())
858 channel_output_poll();
859 if (options.rekey_interval > 0 && compat20 && !rekeying)
860 rekey_timeout_ms = packet_get_rekey_timeout() * 1000;
861 else
862 rekey_timeout_ms = 0;
863
864 wait_until_can_do_something(&readset, &writeset, &max_fd,
865 &nalloc, rekey_timeout_ms);
866
867 if (received_sigterm) {
868 logit("Exiting on signal %d", (int)received_sigterm);
869 /* Clean up sessions, utmp, etc. */
870 cleanup_exit(255);
871 }
872
873 collect_children();
874 if (!rekeying) {
875 channel_after_select(readset, writeset);
876 if (packet_need_rekeying()) {
877 debug("need rekeying");
878 xxx_kex->done = 0;
879 kex_send_kexinit(xxx_kex);
880 }
881 }
882 process_input(readset);
883 if (connection_closed)
884 break;
885 process_output(writeset);
886 }
887 collect_children();
888
889 free(readset);
890 free(writeset);
891
892 /* free all channels, no more reads and writes */
893 channel_free_all();
894
895 /* free remaining sessions, e.g. remove wtmp entries */
896 session_destroy_all(NULL);
897 }
898
899 static void
server_input_keep_alive(int type,u_int32_t seq,void * ctxt)900 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
901 {
902 debug("Got %d/%u for keepalive", type, seq);
903 /*
904 * reset timeout, since we got a sane answer from the client.
905 * even if this was generated by something other than
906 * the bogus CHANNEL_REQUEST we send for keepalives.
907 */
908 packet_set_alive_timeouts(0);
909 }
910
911 static void
server_input_stdin_data(int type,u_int32_t seq,void * ctxt)912 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
913 {
914 char *data;
915 u_int data_len;
916
917 /* Stdin data from the client. Append it to the buffer. */
918 /* Ignore any data if the client has closed stdin. */
919 if (fdin == -1)
920 return;
921 data = packet_get_string(&data_len);
922 packet_check_eom();
923 buffer_append(&stdin_buffer, data, data_len);
924 explicit_bzero(data, data_len);
925 free(data);
926 }
927
928 static void
server_input_eof(int type,u_int32_t seq,void * ctxt)929 server_input_eof(int type, u_int32_t seq, void *ctxt)
930 {
931 /*
932 * Eof from the client. The stdin descriptor to the
933 * program will be closed when all buffered data has
934 * drained.
935 */
936 debug("EOF received for stdin.");
937 packet_check_eom();
938 stdin_eof = 1;
939 }
940
941 static void
server_input_window_size(int type,u_int32_t seq,void * ctxt)942 server_input_window_size(int type, u_int32_t seq, void *ctxt)
943 {
944 u_int row = packet_get_int();
945 u_int col = packet_get_int();
946 u_int xpixel = packet_get_int();
947 u_int ypixel = packet_get_int();
948
949 debug("Window change received.");
950 packet_check_eom();
951 if (fdin != -1)
952 pty_change_window_size(fdin, row, col, xpixel, ypixel);
953 }
954
955 static Channel *
server_request_direct_tcpip(void)956 server_request_direct_tcpip(void)
957 {
958 Channel *c = NULL;
959 char *target, *originator;
960 u_short target_port, originator_port;
961
962 target = packet_get_string(NULL);
963 target_port = packet_get_int();
964 originator = packet_get_string(NULL);
965 originator_port = packet_get_int();
966 packet_check_eom();
967
968 debug("server_request_direct_tcpip: originator %s port %d, target %s "
969 "port %d", originator, originator_port, target, target_port);
970
971 /* XXX fine grained permissions */
972 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 &&
973 !no_port_forwarding_flag) {
974 c = channel_connect_to(target, target_port,
975 "direct-tcpip", "direct-tcpip");
976 } else {
977 logit("refused local port forward: "
978 "originator %s port %d, target %s port %d",
979 originator, originator_port, target, target_port);
980 }
981
982 free(originator);
983 free(target);
984
985 return c;
986 }
987
988 static Channel *
server_request_tun(void)989 server_request_tun(void)
990 {
991 Channel *c = NULL;
992 int mode, tun;
993 int sock;
994
995 mode = packet_get_int();
996 switch (mode) {
997 case SSH_TUNMODE_POINTOPOINT:
998 case SSH_TUNMODE_ETHERNET:
999 break;
1000 default:
1001 packet_send_debug("Unsupported tunnel device mode.");
1002 return NULL;
1003 }
1004 if ((options.permit_tun & mode) == 0) {
1005 packet_send_debug("Server has rejected tunnel device "
1006 "forwarding");
1007 return NULL;
1008 }
1009
1010 tun = packet_get_int();
1011 if (forced_tun_device != -1) {
1012 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
1013 goto done;
1014 tun = forced_tun_device;
1015 }
1016 sock = tun_open(tun, mode);
1017 if (sock < 0)
1018 goto done;
1019 if (options.hpn_disabled)
1020 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
1021 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0,
1022 "tun", 1);
1023 else
1024 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
1025 options.hpn_buffer_size, CHAN_TCP_PACKET_DEFAULT, 0,
1026 "tun", 1);
1027 c->datagram = 1;
1028 #if defined(SSH_TUN_FILTER)
1029 if (mode == SSH_TUNMODE_POINTOPOINT)
1030 channel_register_filter(c->self, sys_tun_infilter,
1031 sys_tun_outfilter, NULL, NULL);
1032 #endif
1033
1034 done:
1035 if (c == NULL)
1036 packet_send_debug("Failed to open the tunnel device.");
1037 return c;
1038 }
1039
1040 static Channel *
server_request_session(void)1041 server_request_session(void)
1042 {
1043 Channel *c;
1044
1045 debug("input_session_request");
1046 packet_check_eom();
1047
1048 if (no_more_sessions) {
1049 packet_disconnect("Possible attack: attempt to open a session "
1050 "after additional sessions disabled");
1051 }
1052
1053 /*
1054 * A server session has no fd to read or write until a
1055 * CHANNEL_REQUEST for a shell is made, so we set the type to
1056 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all
1057 * CHANNEL_REQUEST messages is registered.
1058 */
1059 c = channel_new("session", SSH_CHANNEL_LARVAL,
1060 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
1061 0, "server-session", 1);
1062 if (!options.hpn_disabled && options.tcp_rcv_buf_poll)
1063 c->dynamic_window = 1;
1064 if (session_open(the_authctxt, c->self) != 1) {
1065 debug("session open failed, free channel %d", c->self);
1066 channel_free(c);
1067 return NULL;
1068 }
1069 channel_register_cleanup(c->self, session_close_by_channel, 0);
1070 return c;
1071 }
1072
1073 static void
server_input_channel_open(int type,u_int32_t seq,void * ctxt)1074 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
1075 {
1076 Channel *c = NULL;
1077 char *ctype;
1078 int rchan;
1079 u_int rmaxpack, rwindow, len;
1080
1081 ctype = packet_get_string(&len);
1082 rchan = packet_get_int();
1083 rwindow = packet_get_int();
1084 rmaxpack = packet_get_int();
1085
1086 debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1087 ctype, rchan, rwindow, rmaxpack);
1088
1089 if (strcmp(ctype, "session") == 0) {
1090 c = server_request_session();
1091 } else if (strcmp(ctype, "direct-tcpip") == 0) {
1092 c = server_request_direct_tcpip();
1093 } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1094 c = server_request_tun();
1095 }
1096 if (c != NULL) {
1097 debug("server_input_channel_open: confirm %s", ctype);
1098 c->remote_id = rchan;
1099 c->remote_window = rwindow;
1100 c->remote_maxpacket = rmaxpack;
1101 if (c->type != SSH_CHANNEL_CONNECTING) {
1102 packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1103 packet_put_int(c->remote_id);
1104 packet_put_int(c->self);
1105 packet_put_int(c->local_window);
1106 packet_put_int(c->local_maxpacket);
1107 packet_send();
1108 }
1109 } else {
1110 debug("server_input_channel_open: failure %s", ctype);
1111 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1112 packet_put_int(rchan);
1113 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1114 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1115 packet_put_cstring("open failed");
1116 packet_put_cstring("");
1117 }
1118 packet_send();
1119 }
1120 free(ctype);
1121 }
1122
1123 static void
server_input_global_request(int type,u_int32_t seq,void * ctxt)1124 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1125 {
1126 char *rtype;
1127 int want_reply;
1128 int success = 0, allocated_listen_port = 0;
1129
1130 rtype = packet_get_string(NULL);
1131 want_reply = packet_get_char();
1132 debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1133
1134 /* -R style forwarding */
1135 if (strcmp(rtype, "tcpip-forward") == 0) {
1136 struct passwd *pw;
1137 char *listen_address;
1138 u_short listen_port;
1139
1140 pw = the_authctxt->pw;
1141 if (pw == NULL || !the_authctxt->valid)
1142 fatal("server_input_global_request: no/invalid user");
1143 listen_address = packet_get_string(NULL);
1144 listen_port = (u_short)packet_get_int();
1145 debug("server_input_global_request: tcpip-forward listen %s port %d",
1146 listen_address, listen_port);
1147
1148 /* check permissions */
1149 if ((options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 ||
1150 no_port_forwarding_flag ||
1151 (!want_reply && listen_port == 0)
1152 #ifndef NO_IPPORT_RESERVED_CONCEPT
1153 || (listen_port != 0 && listen_port < IPPORT_RESERVED &&
1154 pw->pw_uid != 0)
1155 #endif
1156 ) {
1157 success = 0;
1158 packet_send_debug("Server has disabled port forwarding.");
1159 } else {
1160 /* Start listening on the port */
1161 success = channel_setup_remote_fwd_listener(
1162 listen_address, listen_port,
1163 &allocated_listen_port, options.gateway_ports);
1164 }
1165 free(listen_address);
1166 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1167 char *cancel_address;
1168 u_short cancel_port;
1169
1170 cancel_address = packet_get_string(NULL);
1171 cancel_port = (u_short)packet_get_int();
1172 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1173 cancel_address, cancel_port);
1174
1175 success = channel_cancel_rport_listener(cancel_address,
1176 cancel_port);
1177 free(cancel_address);
1178 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
1179 no_more_sessions = 1;
1180 success = 1;
1181 }
1182 if (want_reply) {
1183 packet_start(success ?
1184 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1185 if (success && allocated_listen_port > 0)
1186 packet_put_int(allocated_listen_port);
1187 packet_send();
1188 packet_write_wait();
1189 }
1190 free(rtype);
1191 }
1192
1193 static void
server_input_channel_req(int type,u_int32_t seq,void * ctxt)1194 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1195 {
1196 Channel *c;
1197 int id, reply, success = 0;
1198 char *rtype;
1199
1200 id = packet_get_int();
1201 rtype = packet_get_string(NULL);
1202 reply = packet_get_char();
1203
1204 debug("server_input_channel_req: channel %d request %s reply %d",
1205 id, rtype, reply);
1206
1207 if ((c = channel_lookup(id)) == NULL)
1208 packet_disconnect("server_input_channel_req: "
1209 "unknown channel %d", id);
1210 if (!strcmp(rtype, "eow@openssh.com")) {
1211 packet_check_eom();
1212 chan_rcvd_eow(c);
1213 } else if ((c->type == SSH_CHANNEL_LARVAL ||
1214 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
1215 success = session_input_channel_req(c, rtype);
1216 if (reply) {
1217 packet_start(success ?
1218 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1219 packet_put_int(c->remote_id);
1220 packet_send();
1221 }
1222 free(rtype);
1223 }
1224
1225 static void
server_init_dispatch_20(void)1226 server_init_dispatch_20(void)
1227 {
1228 debug("server_init_dispatch_20");
1229 dispatch_init(&dispatch_protocol_error);
1230 dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1231 dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1232 dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1233 dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1234 dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1235 dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1236 dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1237 dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1238 dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1239 dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1240 /* client_alive */
1241 dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive);
1242 dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
1243 dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1244 dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1245 /* rekeying */
1246 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1247 }
1248 static void
server_init_dispatch_13(void)1249 server_init_dispatch_13(void)
1250 {
1251 debug("server_init_dispatch_13");
1252 dispatch_init(NULL);
1253 dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1254 dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1255 dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1256 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1257 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1258 dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1259 dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1260 dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1261 dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1262 }
1263 static void
server_init_dispatch_15(void)1264 server_init_dispatch_15(void)
1265 {
1266 server_init_dispatch_13();
1267 debug("server_init_dispatch_15");
1268 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1269 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1270 }
1271 static void
server_init_dispatch(void)1272 server_init_dispatch(void)
1273 {
1274 if (compat20)
1275 server_init_dispatch_20();
1276 else if (compat13)
1277 server_init_dispatch_13();
1278 else
1279 server_init_dispatch_15();
1280 }
1281