1 /* $OpenBSD: serverloop.c,v 1.170 2014/02/02 03:44:31 djm Exp $ */
2 /* $FreeBSD: stable/9/crypto/openssh/serverloop.c 263970 2014-03-31 14:39:56Z des $ */
3 /*
4 * Author: Tatu Ylonen <ylo@cs.hut.fi>
5 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 * All rights reserved
7 * Server main loop for handling the interactive session.
8 *
9 * As far as I am concerned, the code I have written for this software
10 * can be used freely for any purpose. Any derived versions of this
11 * software must be clearly marked as such, and if the derived work is
12 * incompatible with the protocol description in the RFC file, it must be
13 * called by a name other than "ssh" or "Secure Shell".
14 *
15 * SSH2 support by Markus Friedl.
16 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
17 *
18 * Redistribution and use in source and binary forms, with or without
19 * modification, are permitted provided that the following conditions
20 * are met:
21 * 1. Redistributions of source code must retain the above copyright
22 * notice, this list of conditions and the following disclaimer.
23 * 2. Redistributions in binary form must reproduce the above copyright
24 * notice, this list of conditions and the following disclaimer in the
25 * documentation and/or other materials provided with the distribution.
26 *
27 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
28 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
29 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
30 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
31 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
32 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
33 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
34 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
36 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37 */
38
39 #include "includes.h"
40 __RCSID("$FreeBSD: stable/9/crypto/openssh/serverloop.c 263970 2014-03-31 14:39:56Z des $");
41
42 #include <sys/types.h>
43 #include <sys/param.h>
44 #include <sys/wait.h>
45 #include <sys/socket.h>
46 #ifdef HAVE_SYS_TIME_H
47 # include <sys/time.h>
48 #endif
49
50 #include <netinet/in.h>
51
52 #include <errno.h>
53 #include <fcntl.h>
54 #include <pwd.h>
55 #include <signal.h>
56 #include <string.h>
57 #include <termios.h>
58 #include <unistd.h>
59 #include <stdarg.h>
60
61 #include "openbsd-compat/sys-queue.h"
62 #include "xmalloc.h"
63 #include "packet.h"
64 #include "buffer.h"
65 #include "log.h"
66 #include "servconf.h"
67 #include "canohost.h"
68 #include "sshpty.h"
69 #include "channels.h"
70 #include "compat.h"
71 #include "ssh1.h"
72 #include "ssh2.h"
73 #include "key.h"
74 #include "cipher.h"
75 #include "kex.h"
76 #include "hostfile.h"
77 #include "auth.h"
78 #include "session.h"
79 #include "dispatch.h"
80 #include "auth-options.h"
81 #include "serverloop.h"
82 #include "misc.h"
83 #include "roaming.h"
84
85 extern ServerOptions options;
86
87 /* XXX */
88 extern Kex *xxx_kex;
89 extern Authctxt *the_authctxt;
90 extern int use_privsep;
91
92 static Buffer stdin_buffer; /* Buffer for stdin data. */
93 static Buffer stdout_buffer; /* Buffer for stdout data. */
94 static Buffer stderr_buffer; /* Buffer for stderr data. */
95 static int fdin; /* Descriptor for stdin (for writing) */
96 static int fdout; /* Descriptor for stdout (for reading);
97 May be same number as fdin. */
98 static int fderr; /* Descriptor for stderr. May be -1. */
99 static long stdin_bytes = 0; /* Number of bytes written to stdin. */
100 static long stdout_bytes = 0; /* Number of stdout bytes sent to client. */
101 static long stderr_bytes = 0; /* Number of stderr bytes sent to client. */
102 static long fdout_bytes = 0; /* Number of stdout bytes read from program. */
103 static int stdin_eof = 0; /* EOF message received from client. */
104 static int fdout_eof = 0; /* EOF encountered reading from fdout. */
105 static int fderr_eof = 0; /* EOF encountered readung from fderr. */
106 static int fdin_is_tty = 0; /* fdin points to a tty. */
107 static int connection_in; /* Connection to client (input). */
108 static int connection_out; /* Connection to client (output). */
109 static int connection_closed = 0; /* Connection to client closed. */
110 static u_int buffer_high; /* "Soft" max buffer size. */
111 static int no_more_sessions = 0; /* Disallow further sessions. */
112
113 /*
114 * This SIGCHLD kludge is used to detect when the child exits. The server
115 * will exit after that, as soon as forwarded connections have terminated.
116 */
117
118 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */
119
120 /* Cleanup on signals (!use_privsep case only) */
121 static volatile sig_atomic_t received_sigterm = 0;
122
123 /* prototypes */
124 static void server_init_dispatch(void);
125
126 /*
127 * we write to this pipe if a SIGCHLD is caught in order to avoid
128 * the race between select() and child_terminated
129 */
130 static int notify_pipe[2];
131 static void
notify_setup(void)132 notify_setup(void)
133 {
134 if (pipe(notify_pipe) < 0) {
135 error("pipe(notify_pipe) failed %s", strerror(errno));
136 } else if ((fcntl(notify_pipe[0], F_SETFD, FD_CLOEXEC) == -1) ||
137 (fcntl(notify_pipe[1], F_SETFD, FD_CLOEXEC) == -1)) {
138 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
139 close(notify_pipe[0]);
140 close(notify_pipe[1]);
141 } else {
142 set_nonblock(notify_pipe[0]);
143 set_nonblock(notify_pipe[1]);
144 return;
145 }
146 notify_pipe[0] = -1; /* read end */
147 notify_pipe[1] = -1; /* write end */
148 }
149 static void
notify_parent(void)150 notify_parent(void)
151 {
152 if (notify_pipe[1] != -1)
153 (void)write(notify_pipe[1], "", 1);
154 }
155 static void
notify_prepare(fd_set * readset)156 notify_prepare(fd_set *readset)
157 {
158 if (notify_pipe[0] != -1)
159 FD_SET(notify_pipe[0], readset);
160 }
161 static void
notify_done(fd_set * readset)162 notify_done(fd_set *readset)
163 {
164 char c;
165
166 if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
167 while (read(notify_pipe[0], &c, 1) != -1)
168 debug2("notify_done: reading");
169 }
170
171 /*ARGSUSED*/
172 static void
sigchld_handler(int sig)173 sigchld_handler(int sig)
174 {
175 int save_errno = errno;
176 child_terminated = 1;
177 #ifndef _UNICOS
178 mysignal(SIGCHLD, sigchld_handler);
179 #endif
180 notify_parent();
181 errno = save_errno;
182 }
183
184 /*ARGSUSED*/
185 static void
sigterm_handler(int sig)186 sigterm_handler(int sig)
187 {
188 received_sigterm = sig;
189 }
190
191 /*
192 * Make packets from buffered stderr data, and buffer it for sending
193 * to the client.
194 */
195 static void
make_packets_from_stderr_data(void)196 make_packets_from_stderr_data(void)
197 {
198 u_int len;
199
200 /* Send buffered stderr data to the client. */
201 while (buffer_len(&stderr_buffer) > 0 &&
202 packet_not_very_much_data_to_write()) {
203 len = buffer_len(&stderr_buffer);
204 if (packet_is_interactive()) {
205 if (len > 512)
206 len = 512;
207 } else {
208 /* Keep the packets at reasonable size. */
209 if (len > packet_get_maxsize())
210 len = packet_get_maxsize();
211 }
212 packet_start(SSH_SMSG_STDERR_DATA);
213 packet_put_string(buffer_ptr(&stderr_buffer), len);
214 packet_send();
215 buffer_consume(&stderr_buffer, len);
216 stderr_bytes += len;
217 }
218 }
219
220 /*
221 * Make packets from buffered stdout data, and buffer it for sending to the
222 * client.
223 */
224 static void
make_packets_from_stdout_data(void)225 make_packets_from_stdout_data(void)
226 {
227 u_int len;
228
229 /* Send buffered stdout data to the client. */
230 while (buffer_len(&stdout_buffer) > 0 &&
231 packet_not_very_much_data_to_write()) {
232 len = buffer_len(&stdout_buffer);
233 if (packet_is_interactive()) {
234 if (len > 512)
235 len = 512;
236 } else {
237 /* Keep the packets at reasonable size. */
238 if (len > packet_get_maxsize())
239 len = packet_get_maxsize();
240 }
241 packet_start(SSH_SMSG_STDOUT_DATA);
242 packet_put_string(buffer_ptr(&stdout_buffer), len);
243 packet_send();
244 buffer_consume(&stdout_buffer, len);
245 stdout_bytes += len;
246 }
247 }
248
249 static void
client_alive_check(void)250 client_alive_check(void)
251 {
252 int channel_id;
253
254 /* timeout, check to see how many we have had */
255 if (packet_inc_alive_timeouts() > options.client_alive_count_max) {
256 logit("Timeout, client not responding.");
257 cleanup_exit(255);
258 }
259
260 /*
261 * send a bogus global/channel request with "wantreply",
262 * we should get back a failure
263 */
264 if ((channel_id = channel_find_open()) == -1) {
265 packet_start(SSH2_MSG_GLOBAL_REQUEST);
266 packet_put_cstring("keepalive@openssh.com");
267 packet_put_char(1); /* boolean: want reply */
268 } else {
269 channel_request_start(channel_id, "keepalive@openssh.com", 1);
270 }
271 packet_send();
272 }
273
274 /*
275 * Sleep in select() until we can do something. This will initialize the
276 * select masks. Upon return, the masks will indicate which descriptors
277 * have data or can accept data. Optionally, a maximum time can be specified
278 * for the duration of the wait (0 = infinite).
279 */
280 static void
wait_until_can_do_something(fd_set ** readsetp,fd_set ** writesetp,int * maxfdp,u_int * nallocp,u_int64_t max_time_milliseconds)281 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
282 u_int *nallocp, u_int64_t max_time_milliseconds)
283 {
284 struct timeval tv, *tvp;
285 int ret;
286 time_t minwait_secs = 0;
287 int client_alive_scheduled = 0;
288 int program_alive_scheduled = 0;
289
290 /* Allocate and update select() masks for channel descriptors. */
291 channel_prepare_select(readsetp, writesetp, maxfdp, nallocp,
292 &minwait_secs, 0);
293
294 if (minwait_secs != 0)
295 max_time_milliseconds = MIN(max_time_milliseconds,
296 (u_int)minwait_secs * 1000);
297
298 /*
299 * if using client_alive, set the max timeout accordingly,
300 * and indicate that this particular timeout was for client
301 * alive by setting the client_alive_scheduled flag.
302 *
303 * this could be randomized somewhat to make traffic
304 * analysis more difficult, but we're not doing it yet.
305 */
306 if (compat20 &&
307 max_time_milliseconds == 0 && options.client_alive_interval) {
308 client_alive_scheduled = 1;
309 max_time_milliseconds =
310 (u_int64_t)options.client_alive_interval * 1000;
311 }
312
313 if (compat20) {
314 #if 0
315 /* wrong: bad condition XXX */
316 if (channel_not_very_much_buffered_data())
317 #endif
318 FD_SET(connection_in, *readsetp);
319 } else {
320 /*
321 * Read packets from the client unless we have too much
322 * buffered stdin or channel data.
323 */
324 if (buffer_len(&stdin_buffer) < buffer_high &&
325 channel_not_very_much_buffered_data())
326 FD_SET(connection_in, *readsetp);
327 /*
328 * If there is not too much data already buffered going to
329 * the client, try to get some more data from the program.
330 */
331 if (packet_not_very_much_data_to_write()) {
332 program_alive_scheduled = child_terminated;
333 if (!fdout_eof)
334 FD_SET(fdout, *readsetp);
335 if (!fderr_eof)
336 FD_SET(fderr, *readsetp);
337 }
338 /*
339 * If we have buffered data, try to write some of that data
340 * to the program.
341 */
342 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
343 FD_SET(fdin, *writesetp);
344 }
345 notify_prepare(*readsetp);
346
347 /*
348 * If we have buffered packet data going to the client, mark that
349 * descriptor.
350 */
351 if (packet_have_data_to_write())
352 FD_SET(connection_out, *writesetp);
353
354 /*
355 * If child has terminated and there is enough buffer space to read
356 * from it, then read as much as is available and exit.
357 */
358 if (child_terminated && packet_not_very_much_data_to_write())
359 if (max_time_milliseconds == 0 || client_alive_scheduled)
360 max_time_milliseconds = 100;
361
362 if (max_time_milliseconds == 0)
363 tvp = NULL;
364 else {
365 tv.tv_sec = max_time_milliseconds / 1000;
366 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
367 tvp = &tv;
368 }
369
370 /* Wait for something to happen, or the timeout to expire. */
371 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
372
373 if (ret == -1) {
374 memset(*readsetp, 0, *nallocp);
375 memset(*writesetp, 0, *nallocp);
376 if (errno != EINTR)
377 error("select: %.100s", strerror(errno));
378 } else {
379 if (ret == 0 && client_alive_scheduled)
380 client_alive_check();
381 if (!compat20 && program_alive_scheduled && fdin_is_tty) {
382 if (!fdout_eof)
383 FD_SET(fdout, *readsetp);
384 if (!fderr_eof)
385 FD_SET(fderr, *readsetp);
386 }
387 }
388
389 notify_done(*readsetp);
390 }
391
392 /*
393 * Processes input from the client and the program. Input data is stored
394 * in buffers and processed later.
395 */
396 static void
process_input(fd_set * readset)397 process_input(fd_set *readset)
398 {
399 int len;
400 char buf[16384];
401
402 /* Read and buffer any input data from the client. */
403 if (FD_ISSET(connection_in, readset)) {
404 int cont = 0;
405 len = roaming_read(connection_in, buf, sizeof(buf), &cont);
406 if (len == 0) {
407 if (cont)
408 return;
409 verbose("Connection closed by %.100s",
410 get_remote_ipaddr());
411 connection_closed = 1;
412 if (compat20)
413 return;
414 cleanup_exit(255);
415 } else if (len < 0) {
416 if (errno != EINTR && errno != EAGAIN &&
417 errno != EWOULDBLOCK) {
418 verbose("Read error from remote host "
419 "%.100s: %.100s",
420 get_remote_ipaddr(), strerror(errno));
421 cleanup_exit(255);
422 }
423 } else {
424 /* Buffer any received data. */
425 packet_process_incoming(buf, len);
426 }
427 }
428 if (compat20)
429 return;
430
431 /* Read and buffer any available stdout data from the program. */
432 if (!fdout_eof && FD_ISSET(fdout, readset)) {
433 errno = 0;
434 len = read(fdout, buf, sizeof(buf));
435 if (len < 0 && (errno == EINTR || ((errno == EAGAIN ||
436 errno == EWOULDBLOCK) && !child_terminated))) {
437 /* do nothing */
438 #ifndef PTY_ZEROREAD
439 } else if (len <= 0) {
440 #else
441 } else if ((!isatty(fdout) && len <= 0) ||
442 (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) {
443 #endif
444 fdout_eof = 1;
445 } else {
446 buffer_append(&stdout_buffer, buf, len);
447 fdout_bytes += len;
448 }
449 }
450 /* Read and buffer any available stderr data from the program. */
451 if (!fderr_eof && FD_ISSET(fderr, readset)) {
452 errno = 0;
453 len = read(fderr, buf, sizeof(buf));
454 if (len < 0 && (errno == EINTR || ((errno == EAGAIN ||
455 errno == EWOULDBLOCK) && !child_terminated))) {
456 /* do nothing */
457 #ifndef PTY_ZEROREAD
458 } else if (len <= 0) {
459 #else
460 } else if ((!isatty(fderr) && len <= 0) ||
461 (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) {
462 #endif
463 fderr_eof = 1;
464 } else {
465 buffer_append(&stderr_buffer, buf, len);
466 }
467 }
468 }
469
470 /*
471 * Sends data from internal buffers to client program stdin.
472 */
473 static void
process_output(fd_set * writeset)474 process_output(fd_set *writeset)
475 {
476 struct termios tio;
477 u_char *data;
478 u_int dlen;
479 int len;
480
481 /* Write buffered data to program stdin. */
482 if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
483 data = buffer_ptr(&stdin_buffer);
484 dlen = buffer_len(&stdin_buffer);
485 len = write(fdin, data, dlen);
486 if (len < 0 &&
487 (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)) {
488 /* do nothing */
489 } else if (len <= 0) {
490 if (fdin != fdout)
491 close(fdin);
492 else
493 shutdown(fdin, SHUT_WR); /* We will no longer send. */
494 fdin = -1;
495 } else {
496 /* Successful write. */
497 if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
498 tcgetattr(fdin, &tio) == 0 &&
499 !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
500 /*
501 * Simulate echo to reduce the impact of
502 * traffic analysis
503 */
504 packet_send_ignore(len);
505 packet_send();
506 }
507 /* Consume the data from the buffer. */
508 buffer_consume(&stdin_buffer, len);
509 /* Update the count of bytes written to the program. */
510 stdin_bytes += len;
511 }
512 }
513 /* Send any buffered packet data to the client. */
514 if (FD_ISSET(connection_out, writeset))
515 packet_write_poll();
516 }
517
518 /*
519 * Wait until all buffered output has been sent to the client.
520 * This is used when the program terminates.
521 */
522 static void
drain_output(void)523 drain_output(void)
524 {
525 /* Send any buffered stdout data to the client. */
526 if (buffer_len(&stdout_buffer) > 0) {
527 packet_start(SSH_SMSG_STDOUT_DATA);
528 packet_put_string(buffer_ptr(&stdout_buffer),
529 buffer_len(&stdout_buffer));
530 packet_send();
531 /* Update the count of sent bytes. */
532 stdout_bytes += buffer_len(&stdout_buffer);
533 }
534 /* Send any buffered stderr data to the client. */
535 if (buffer_len(&stderr_buffer) > 0) {
536 packet_start(SSH_SMSG_STDERR_DATA);
537 packet_put_string(buffer_ptr(&stderr_buffer),
538 buffer_len(&stderr_buffer));
539 packet_send();
540 /* Update the count of sent bytes. */
541 stderr_bytes += buffer_len(&stderr_buffer);
542 }
543 /* Wait until all buffered data has been written to the client. */
544 packet_write_wait();
545 }
546
547 static void
process_buffered_input_packets(void)548 process_buffered_input_packets(void)
549 {
550 dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
551 }
552
553 /*
554 * Performs the interactive session. This handles data transmission between
555 * the client and the program. Note that the notion of stdin, stdout, and
556 * stderr in this function is sort of reversed: this function writes to
557 * stdin (of the child program), and reads from stdout and stderr (of the
558 * child program).
559 */
560 void
server_loop(pid_t pid,int fdin_arg,int fdout_arg,int fderr_arg)561 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
562 {
563 fd_set *readset = NULL, *writeset = NULL;
564 int max_fd = 0;
565 u_int nalloc = 0;
566 int wait_status; /* Status returned by wait(). */
567 pid_t wait_pid; /* pid returned by wait(). */
568 int waiting_termination = 0; /* Have displayed waiting close message. */
569 u_int64_t max_time_milliseconds;
570 u_int previous_stdout_buffer_bytes;
571 u_int stdout_buffer_bytes;
572 int type;
573
574 debug("Entering interactive session.");
575
576 /* Initialize the SIGCHLD kludge. */
577 child_terminated = 0;
578 mysignal(SIGCHLD, sigchld_handler);
579
580 if (!use_privsep) {
581 signal(SIGTERM, sigterm_handler);
582 signal(SIGINT, sigterm_handler);
583 signal(SIGQUIT, sigterm_handler);
584 }
585
586 /* Initialize our global variables. */
587 fdin = fdin_arg;
588 fdout = fdout_arg;
589 fderr = fderr_arg;
590
591 /* nonblocking IO */
592 set_nonblock(fdin);
593 set_nonblock(fdout);
594 /* we don't have stderr for interactive terminal sessions, see below */
595 if (fderr != -1)
596 set_nonblock(fderr);
597
598 if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
599 fdin_is_tty = 1;
600
601 connection_in = packet_get_connection_in();
602 connection_out = packet_get_connection_out();
603
604 notify_setup();
605
606 previous_stdout_buffer_bytes = 0;
607
608 /* Set approximate I/O buffer size. */
609 if (packet_is_interactive())
610 buffer_high = 4096;
611 else
612 buffer_high = 64 * 1024;
613
614 #if 0
615 /* Initialize max_fd to the maximum of the known file descriptors. */
616 max_fd = MAX(connection_in, connection_out);
617 max_fd = MAX(max_fd, fdin);
618 max_fd = MAX(max_fd, fdout);
619 if (fderr != -1)
620 max_fd = MAX(max_fd, fderr);
621 #endif
622
623 /* Initialize Initialize buffers. */
624 buffer_init(&stdin_buffer);
625 buffer_init(&stdout_buffer);
626 buffer_init(&stderr_buffer);
627
628 /*
629 * If we have no separate fderr (which is the case when we have a pty
630 * - there we cannot make difference between data sent to stdout and
631 * stderr), indicate that we have seen an EOF from stderr. This way
632 * we don't need to check the descriptor everywhere.
633 */
634 if (fderr == -1)
635 fderr_eof = 1;
636
637 server_init_dispatch();
638
639 /* Main loop of the server for the interactive session mode. */
640 for (;;) {
641
642 /* Process buffered packets from the client. */
643 process_buffered_input_packets();
644
645 /*
646 * If we have received eof, and there is no more pending
647 * input data, cause a real eof by closing fdin.
648 */
649 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
650 if (fdin != fdout)
651 close(fdin);
652 else
653 shutdown(fdin, SHUT_WR); /* We will no longer send. */
654 fdin = -1;
655 }
656 /* Make packets from buffered stderr data to send to the client. */
657 make_packets_from_stderr_data();
658
659 /*
660 * Make packets from buffered stdout data to send to the
661 * client. If there is very little to send, this arranges to
662 * not send them now, but to wait a short while to see if we
663 * are getting more data. This is necessary, as some systems
664 * wake up readers from a pty after each separate character.
665 */
666 max_time_milliseconds = 0;
667 stdout_buffer_bytes = buffer_len(&stdout_buffer);
668 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
669 stdout_buffer_bytes != previous_stdout_buffer_bytes) {
670 /* try again after a while */
671 max_time_milliseconds = 10;
672 } else {
673 /* Send it now. */
674 make_packets_from_stdout_data();
675 }
676 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
677
678 /* Send channel data to the client. */
679 if (packet_not_very_much_data_to_write())
680 channel_output_poll();
681
682 /*
683 * Bail out of the loop if the program has closed its output
684 * descriptors, and we have no more data to send to the
685 * client, and there is no pending buffered data.
686 */
687 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
688 buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
689 if (!channel_still_open())
690 break;
691 if (!waiting_termination) {
692 const char *s = "Waiting for forwarded connections to terminate...\r\n";
693 char *cp;
694 waiting_termination = 1;
695 buffer_append(&stderr_buffer, s, strlen(s));
696
697 /* Display list of open channels. */
698 cp = channel_open_message();
699 buffer_append(&stderr_buffer, cp, strlen(cp));
700 free(cp);
701 }
702 }
703 max_fd = MAX(connection_in, connection_out);
704 max_fd = MAX(max_fd, fdin);
705 max_fd = MAX(max_fd, fdout);
706 max_fd = MAX(max_fd, fderr);
707 max_fd = MAX(max_fd, notify_pipe[0]);
708
709 /* Sleep in select() until we can do something. */
710 wait_until_can_do_something(&readset, &writeset, &max_fd,
711 &nalloc, max_time_milliseconds);
712
713 if (received_sigterm) {
714 logit("Exiting on signal %d", (int)received_sigterm);
715 /* Clean up sessions, utmp, etc. */
716 cleanup_exit(255);
717 }
718
719 /* Process any channel events. */
720 channel_after_select(readset, writeset);
721
722 /* Process input from the client and from program stdout/stderr. */
723 process_input(readset);
724
725 /* Process output to the client and to program stdin. */
726 process_output(writeset);
727 }
728 free(readset);
729 free(writeset);
730
731 /* Cleanup and termination code. */
732
733 /* Wait until all output has been sent to the client. */
734 drain_output();
735
736 debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
737 stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
738
739 /* Free and clear the buffers. */
740 buffer_free(&stdin_buffer);
741 buffer_free(&stdout_buffer);
742 buffer_free(&stderr_buffer);
743
744 /* Close the file descriptors. */
745 if (fdout != -1)
746 close(fdout);
747 fdout = -1;
748 fdout_eof = 1;
749 if (fderr != -1)
750 close(fderr);
751 fderr = -1;
752 fderr_eof = 1;
753 if (fdin != -1)
754 close(fdin);
755 fdin = -1;
756
757 channel_free_all();
758
759 /* We no longer want our SIGCHLD handler to be called. */
760 mysignal(SIGCHLD, SIG_DFL);
761
762 while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
763 if (errno != EINTR)
764 packet_disconnect("wait: %.100s", strerror(errno));
765 if (wait_pid != pid)
766 error("Strange, wait returned pid %ld, expected %ld",
767 (long)wait_pid, (long)pid);
768
769 /* Check if it exited normally. */
770 if (WIFEXITED(wait_status)) {
771 /* Yes, normal exit. Get exit status and send it to the client. */
772 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
773 packet_start(SSH_SMSG_EXITSTATUS);
774 packet_put_int(WEXITSTATUS(wait_status));
775 packet_send();
776 packet_write_wait();
777
778 /*
779 * Wait for exit confirmation. Note that there might be
780 * other packets coming before it; however, the program has
781 * already died so we just ignore them. The client is
782 * supposed to respond with the confirmation when it receives
783 * the exit status.
784 */
785 do {
786 type = packet_read();
787 }
788 while (type != SSH_CMSG_EXIT_CONFIRMATION);
789
790 debug("Received exit confirmation.");
791 return;
792 }
793 /* Check if the program terminated due to a signal. */
794 if (WIFSIGNALED(wait_status))
795 packet_disconnect("Command terminated on signal %d.",
796 WTERMSIG(wait_status));
797
798 /* Some weird exit cause. Just exit. */
799 packet_disconnect("wait returned status %04x.", wait_status);
800 /* NOTREACHED */
801 }
802
803 static void
collect_children(void)804 collect_children(void)
805 {
806 pid_t pid;
807 sigset_t oset, nset;
808 int status;
809
810 /* block SIGCHLD while we check for dead children */
811 sigemptyset(&nset);
812 sigaddset(&nset, SIGCHLD);
813 sigprocmask(SIG_BLOCK, &nset, &oset);
814 if (child_terminated) {
815 debug("Received SIGCHLD.");
816 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
817 (pid < 0 && errno == EINTR))
818 if (pid > 0)
819 session_close_by_pid(pid, status);
820 child_terminated = 0;
821 }
822 sigprocmask(SIG_SETMASK, &oset, NULL);
823 }
824
825 void
server_loop2(Authctxt * authctxt)826 server_loop2(Authctxt *authctxt)
827 {
828 fd_set *readset = NULL, *writeset = NULL;
829 int rekeying = 0, max_fd;
830 u_int nalloc = 0;
831 u_int64_t rekey_timeout_ms = 0;
832
833 debug("Entering interactive session for SSH2.");
834
835 mysignal(SIGCHLD, sigchld_handler);
836 child_terminated = 0;
837 connection_in = packet_get_connection_in();
838 connection_out = packet_get_connection_out();
839
840 if (!use_privsep) {
841 signal(SIGTERM, sigterm_handler);
842 signal(SIGINT, sigterm_handler);
843 signal(SIGQUIT, sigterm_handler);
844 }
845
846 notify_setup();
847
848 max_fd = MAX(connection_in, connection_out);
849 max_fd = MAX(max_fd, notify_pipe[0]);
850
851 server_init_dispatch();
852
853 for (;;) {
854 process_buffered_input_packets();
855
856 rekeying = (xxx_kex != NULL && !xxx_kex->done);
857
858 if (!rekeying && packet_not_very_much_data_to_write())
859 channel_output_poll();
860 if (options.rekey_interval > 0 && compat20 && !rekeying)
861 rekey_timeout_ms = packet_get_rekey_timeout() * 1000;
862 else
863 rekey_timeout_ms = 0;
864
865 wait_until_can_do_something(&readset, &writeset, &max_fd,
866 &nalloc, rekey_timeout_ms);
867
868 if (received_sigterm) {
869 logit("Exiting on signal %d", (int)received_sigterm);
870 /* Clean up sessions, utmp, etc. */
871 cleanup_exit(255);
872 }
873
874 collect_children();
875 if (!rekeying) {
876 channel_after_select(readset, writeset);
877 if (packet_need_rekeying()) {
878 debug("need rekeying");
879 xxx_kex->done = 0;
880 kex_send_kexinit(xxx_kex);
881 }
882 }
883 process_input(readset);
884 if (connection_closed)
885 break;
886 process_output(writeset);
887 }
888 collect_children();
889
890 free(readset);
891 free(writeset);
892
893 /* free all channels, no more reads and writes */
894 channel_free_all();
895
896 /* free remaining sessions, e.g. remove wtmp entries */
897 session_destroy_all(NULL);
898 }
899
900 static void
server_input_keep_alive(int type,u_int32_t seq,void * ctxt)901 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
902 {
903 debug("Got %d/%u for keepalive", type, seq);
904 /*
905 * reset timeout, since we got a sane answer from the client.
906 * even if this was generated by something other than
907 * the bogus CHANNEL_REQUEST we send for keepalives.
908 */
909 packet_set_alive_timeouts(0);
910 }
911
912 static void
server_input_stdin_data(int type,u_int32_t seq,void * ctxt)913 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
914 {
915 char *data;
916 u_int data_len;
917
918 /* Stdin data from the client. Append it to the buffer. */
919 /* Ignore any data if the client has closed stdin. */
920 if (fdin == -1)
921 return;
922 data = packet_get_string(&data_len);
923 packet_check_eom();
924 buffer_append(&stdin_buffer, data, data_len);
925 explicit_bzero(data, data_len);
926 free(data);
927 }
928
929 static void
server_input_eof(int type,u_int32_t seq,void * ctxt)930 server_input_eof(int type, u_int32_t seq, void *ctxt)
931 {
932 /*
933 * Eof from the client. The stdin descriptor to the
934 * program will be closed when all buffered data has
935 * drained.
936 */
937 debug("EOF received for stdin.");
938 packet_check_eom();
939 stdin_eof = 1;
940 }
941
942 static void
server_input_window_size(int type,u_int32_t seq,void * ctxt)943 server_input_window_size(int type, u_int32_t seq, void *ctxt)
944 {
945 u_int row = packet_get_int();
946 u_int col = packet_get_int();
947 u_int xpixel = packet_get_int();
948 u_int ypixel = packet_get_int();
949
950 debug("Window change received.");
951 packet_check_eom();
952 if (fdin != -1)
953 pty_change_window_size(fdin, row, col, xpixel, ypixel);
954 }
955
956 static Channel *
server_request_direct_tcpip(void)957 server_request_direct_tcpip(void)
958 {
959 Channel *c = NULL;
960 char *target, *originator;
961 u_short target_port, originator_port;
962
963 target = packet_get_string(NULL);
964 target_port = packet_get_int();
965 originator = packet_get_string(NULL);
966 originator_port = packet_get_int();
967 packet_check_eom();
968
969 debug("server_request_direct_tcpip: originator %s port %d, target %s "
970 "port %d", originator, originator_port, target, target_port);
971
972 /* XXX fine grained permissions */
973 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 &&
974 !no_port_forwarding_flag) {
975 c = channel_connect_to(target, target_port,
976 "direct-tcpip", "direct-tcpip");
977 } else {
978 logit("refused local port forward: "
979 "originator %s port %d, target %s port %d",
980 originator, originator_port, target, target_port);
981 }
982
983 free(originator);
984 free(target);
985
986 return c;
987 }
988
989 static Channel *
server_request_tun(void)990 server_request_tun(void)
991 {
992 Channel *c = NULL;
993 int mode, tun;
994 int sock;
995
996 mode = packet_get_int();
997 switch (mode) {
998 case SSH_TUNMODE_POINTOPOINT:
999 case SSH_TUNMODE_ETHERNET:
1000 break;
1001 default:
1002 packet_send_debug("Unsupported tunnel device mode.");
1003 return NULL;
1004 }
1005 if ((options.permit_tun & mode) == 0) {
1006 packet_send_debug("Server has rejected tunnel device "
1007 "forwarding");
1008 return NULL;
1009 }
1010
1011 tun = packet_get_int();
1012 if (forced_tun_device != -1) {
1013 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
1014 goto done;
1015 tun = forced_tun_device;
1016 }
1017 sock = tun_open(tun, mode);
1018 if (sock < 0)
1019 goto done;
1020 if (options.hpn_disabled)
1021 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
1022 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0,
1023 "tun", 1);
1024 else
1025 c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
1026 options.hpn_buffer_size, CHAN_TCP_PACKET_DEFAULT, 0,
1027 "tun", 1);
1028 c->datagram = 1;
1029 #if defined(SSH_TUN_FILTER)
1030 if (mode == SSH_TUNMODE_POINTOPOINT)
1031 channel_register_filter(c->self, sys_tun_infilter,
1032 sys_tun_outfilter, NULL, NULL);
1033 #endif
1034
1035 done:
1036 if (c == NULL)
1037 packet_send_debug("Failed to open the tunnel device.");
1038 return c;
1039 }
1040
1041 static Channel *
server_request_session(void)1042 server_request_session(void)
1043 {
1044 Channel *c;
1045
1046 debug("input_session_request");
1047 packet_check_eom();
1048
1049 if (no_more_sessions) {
1050 packet_disconnect("Possible attack: attempt to open a session "
1051 "after additional sessions disabled");
1052 }
1053
1054 /*
1055 * A server session has no fd to read or write until a
1056 * CHANNEL_REQUEST for a shell is made, so we set the type to
1057 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all
1058 * CHANNEL_REQUEST messages is registered.
1059 */
1060 c = channel_new("session", SSH_CHANNEL_LARVAL,
1061 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
1062 0, "server-session", 1);
1063 if (!options.hpn_disabled && options.tcp_rcv_buf_poll)
1064 c->dynamic_window = 1;
1065 if (session_open(the_authctxt, c->self) != 1) {
1066 debug("session open failed, free channel %d", c->self);
1067 channel_free(c);
1068 return NULL;
1069 }
1070 channel_register_cleanup(c->self, session_close_by_channel, 0);
1071 return c;
1072 }
1073
1074 static void
server_input_channel_open(int type,u_int32_t seq,void * ctxt)1075 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
1076 {
1077 Channel *c = NULL;
1078 char *ctype;
1079 int rchan;
1080 u_int rmaxpack, rwindow, len;
1081
1082 ctype = packet_get_string(&len);
1083 rchan = packet_get_int();
1084 rwindow = packet_get_int();
1085 rmaxpack = packet_get_int();
1086
1087 debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1088 ctype, rchan, rwindow, rmaxpack);
1089
1090 if (strcmp(ctype, "session") == 0) {
1091 c = server_request_session();
1092 } else if (strcmp(ctype, "direct-tcpip") == 0) {
1093 c = server_request_direct_tcpip();
1094 } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1095 c = server_request_tun();
1096 }
1097 if (c != NULL) {
1098 debug("server_input_channel_open: confirm %s", ctype);
1099 c->remote_id = rchan;
1100 c->remote_window = rwindow;
1101 c->remote_maxpacket = rmaxpack;
1102 if (c->type != SSH_CHANNEL_CONNECTING) {
1103 packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1104 packet_put_int(c->remote_id);
1105 packet_put_int(c->self);
1106 packet_put_int(c->local_window);
1107 packet_put_int(c->local_maxpacket);
1108 packet_send();
1109 }
1110 } else {
1111 debug("server_input_channel_open: failure %s", ctype);
1112 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1113 packet_put_int(rchan);
1114 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1115 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1116 packet_put_cstring("open failed");
1117 packet_put_cstring("");
1118 }
1119 packet_send();
1120 }
1121 free(ctype);
1122 }
1123
1124 static void
server_input_global_request(int type,u_int32_t seq,void * ctxt)1125 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1126 {
1127 char *rtype;
1128 int want_reply;
1129 int success = 0, allocated_listen_port = 0;
1130
1131 rtype = packet_get_string(NULL);
1132 want_reply = packet_get_char();
1133 debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1134
1135 /* -R style forwarding */
1136 if (strcmp(rtype, "tcpip-forward") == 0) {
1137 struct passwd *pw;
1138 char *listen_address;
1139 u_short listen_port;
1140
1141 pw = the_authctxt->pw;
1142 if (pw == NULL || !the_authctxt->valid)
1143 fatal("server_input_global_request: no/invalid user");
1144 listen_address = packet_get_string(NULL);
1145 listen_port = (u_short)packet_get_int();
1146 debug("server_input_global_request: tcpip-forward listen %s port %d",
1147 listen_address, listen_port);
1148
1149 /* check permissions */
1150 if ((options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 ||
1151 no_port_forwarding_flag ||
1152 (!want_reply && listen_port == 0)
1153 #ifndef NO_IPPORT_RESERVED_CONCEPT
1154 || (listen_port != 0 && listen_port < IPPORT_RESERVED &&
1155 pw->pw_uid != 0)
1156 #endif
1157 ) {
1158 success = 0;
1159 packet_send_debug("Server has disabled port forwarding.");
1160 } else {
1161 /* Start listening on the port */
1162 success = channel_setup_remote_fwd_listener(
1163 listen_address, listen_port,
1164 &allocated_listen_port, options.gateway_ports);
1165 }
1166 free(listen_address);
1167 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1168 char *cancel_address;
1169 u_short cancel_port;
1170
1171 cancel_address = packet_get_string(NULL);
1172 cancel_port = (u_short)packet_get_int();
1173 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1174 cancel_address, cancel_port);
1175
1176 success = channel_cancel_rport_listener(cancel_address,
1177 cancel_port);
1178 free(cancel_address);
1179 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
1180 no_more_sessions = 1;
1181 success = 1;
1182 }
1183 if (want_reply) {
1184 packet_start(success ?
1185 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1186 if (success && allocated_listen_port > 0)
1187 packet_put_int(allocated_listen_port);
1188 packet_send();
1189 packet_write_wait();
1190 }
1191 free(rtype);
1192 }
1193
1194 static void
server_input_channel_req(int type,u_int32_t seq,void * ctxt)1195 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1196 {
1197 Channel *c;
1198 int id, reply, success = 0;
1199 char *rtype;
1200
1201 id = packet_get_int();
1202 rtype = packet_get_string(NULL);
1203 reply = packet_get_char();
1204
1205 debug("server_input_channel_req: channel %d request %s reply %d",
1206 id, rtype, reply);
1207
1208 if ((c = channel_lookup(id)) == NULL)
1209 packet_disconnect("server_input_channel_req: "
1210 "unknown channel %d", id);
1211 if (!strcmp(rtype, "eow@openssh.com")) {
1212 packet_check_eom();
1213 chan_rcvd_eow(c);
1214 } else if ((c->type == SSH_CHANNEL_LARVAL ||
1215 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
1216 success = session_input_channel_req(c, rtype);
1217 if (reply) {
1218 packet_start(success ?
1219 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1220 packet_put_int(c->remote_id);
1221 packet_send();
1222 }
1223 free(rtype);
1224 }
1225
1226 static void
server_init_dispatch_20(void)1227 server_init_dispatch_20(void)
1228 {
1229 debug("server_init_dispatch_20");
1230 dispatch_init(&dispatch_protocol_error);
1231 dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1232 dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1233 dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1234 dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1235 dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1236 dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1237 dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1238 dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1239 dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1240 dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1241 /* client_alive */
1242 dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive);
1243 dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
1244 dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1245 dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1246 /* rekeying */
1247 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1248 }
1249 static void
server_init_dispatch_13(void)1250 server_init_dispatch_13(void)
1251 {
1252 debug("server_init_dispatch_13");
1253 dispatch_init(NULL);
1254 dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1255 dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1256 dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1257 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1258 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1259 dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1260 dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1261 dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1262 dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1263 }
1264 static void
server_init_dispatch_15(void)1265 server_init_dispatch_15(void)
1266 {
1267 server_init_dispatch_13();
1268 debug("server_init_dispatch_15");
1269 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1270 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1271 }
1272 static void
server_init_dispatch(void)1273 server_init_dispatch(void)
1274 {
1275 if (compat20)
1276 server_init_dispatch_20();
1277 else if (compat13)
1278 server_init_dispatch_13();
1279 else
1280 server_init_dispatch_15();
1281 }
1282