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1 /* $OpenBSD: serverloop.c,v 1.153 2008/06/30 12:15:39 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
82 extern ServerOptions options;
83
84 /* XXX */
85 extern Kex *xxx_kex;
86 extern Authctxt *the_authctxt;
87 extern int use_privsep;
88
89 static Buffer stdin_buffer;     /* Buffer for stdin data. */
90 static Buffer stdout_buffer;    /* Buffer for stdout data. */
91 static Buffer stderr_buffer;    /* Buffer for stderr data. */
92 static int fdin;                /* Descriptor for stdin (for writing) */
93 static int fdout;               /* Descriptor for stdout (for reading);
94                                    May be same number as fdin. */
95 static int fderr;               /* Descriptor for stderr.  May be -1. */
96 static long stdin_bytes = 0;    /* Number of bytes written to stdin. */
97 static long stdout_bytes = 0;   /* Number of stdout bytes sent to client. */
98 static long stderr_bytes = 0;   /* Number of stderr bytes sent to client. */
99 static long fdout_bytes = 0;    /* Number of stdout bytes read from program. */
100 static int stdin_eof = 0;       /* EOF message received from client. */
101 static int fdout_eof = 0;       /* EOF encountered reading from fdout. */
102 static int fderr_eof = 0;       /* EOF encountered readung from fderr. */
103 static int fdin_is_tty = 0;     /* fdin points to a tty. */
104 static int connection_in;       /* Connection to client (input). */
105 static int connection_out;      /* Connection to client (output). */
106 static int connection_closed = 0;       /* Connection to client closed. */
107 static u_int buffer_high;       /* "Soft" max buffer size. */
108 static int no_more_sessions = 0; /* Disallow further sessions. */
109
110 /*
111  * This SIGCHLD kludge is used to detect when the child exits.  The server
112  * will exit after that, as soon as forwarded connections have terminated.
113  */
114
115 static volatile sig_atomic_t child_terminated = 0;      /* The child has terminated. */
116
117 /* Cleanup on signals (!use_privsep case only) */
118 static volatile sig_atomic_t received_sigterm = 0;
119
120 /* prototypes */
121 static void server_init_dispatch(void);
122
123 /*
124  * we write to this pipe if a SIGCHLD is caught in order to avoid
125  * the race between select() and child_terminated
126  */
127 static int notify_pipe[2];
128 static void
129 notify_setup(void)
130 {
131         if (pipe(notify_pipe) < 0) {
132                 error("pipe(notify_pipe) failed %s", strerror(errno));
133         } else if ((fcntl(notify_pipe[0], F_SETFD, 1) == -1) ||
134             (fcntl(notify_pipe[1], F_SETFD, 1) == -1)) {
135                 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
136                 close(notify_pipe[0]);
137                 close(notify_pipe[1]);
138         } else {
139                 set_nonblock(notify_pipe[0]);
140                 set_nonblock(notify_pipe[1]);
141                 return;
142         }
143         notify_pipe[0] = -1;    /* read end */
144         notify_pipe[1] = -1;    /* write end */
145 }
146 static void
147 notify_parent(void)
148 {
149         if (notify_pipe[1] != -1)
150                 write(notify_pipe[1], "", 1);
151 }
152 static void
153 notify_prepare(fd_set *readset)
154 {
155         if (notify_pipe[0] != -1)
156                 FD_SET(notify_pipe[0], readset);
157 }
158 static void
159 notify_done(fd_set *readset)
160 {
161         char c;
162
163         if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
164                 while (read(notify_pipe[0], &c, 1) != -1)
165                         debug2("notify_done: reading");
166 }
167
168 /*ARGSUSED*/
169 static void
170 sigchld_handler(int sig)
171 {
172         int save_errno = errno;
173         child_terminated = 1;
174 #ifndef _UNICOS
175         mysignal(SIGCHLD, sigchld_handler);
176 #endif
177         notify_parent();
178         errno = save_errno;
179 }
180
181 /*ARGSUSED*/
182 static void
183 sigterm_handler(int sig)
184 {
185         received_sigterm = sig;
186 }
187
188 /*
189  * Make packets from buffered stderr data, and buffer it for sending
190  * to the client.
191  */
192 static void
193 make_packets_from_stderr_data(void)
194 {
195         u_int len;
196
197         /* Send buffered stderr data to the client. */
198         while (buffer_len(&stderr_buffer) > 0 &&
199             packet_not_very_much_data_to_write()) {
200                 len = buffer_len(&stderr_buffer);
201                 if (packet_is_interactive()) {
202                         if (len > 512)
203                                 len = 512;
204                 } else {
205                         /* Keep the packets at reasonable size. */
206                         if (len > packet_get_maxsize())
207                                 len = packet_get_maxsize();
208                 }
209                 packet_start(SSH_SMSG_STDERR_DATA);
210                 packet_put_string(buffer_ptr(&stderr_buffer), len);
211                 packet_send();
212                 buffer_consume(&stderr_buffer, len);
213                 stderr_bytes += len;
214         }
215 }
216
217 /*
218  * Make packets from buffered stdout data, and buffer it for sending to the
219  * client.
220  */
221 static void
222 make_packets_from_stdout_data(void)
223 {
224         u_int len;
225
226         /* Send buffered stdout data to the client. */
227         while (buffer_len(&stdout_buffer) > 0 &&
228             packet_not_very_much_data_to_write()) {
229                 len = buffer_len(&stdout_buffer);
230                 if (packet_is_interactive()) {
231                         if (len > 512)
232                                 len = 512;
233                 } else {
234                         /* Keep the packets at reasonable size. */
235                         if (len > packet_get_maxsize())
236                                 len = packet_get_maxsize();
237                 }
238                 packet_start(SSH_SMSG_STDOUT_DATA);
239                 packet_put_string(buffer_ptr(&stdout_buffer), len);
240                 packet_send();
241                 buffer_consume(&stdout_buffer, len);
242                 stdout_bytes += len;
243         }
244 }
245
246 static void
247 client_alive_check(void)
248 {
249         int channel_id;
250
251         /* timeout, check to see how many we have had */
252         if (++keep_alive_timeouts > options.client_alive_count_max) {
253                 logit("Timeout, client not responding.");
254                 cleanup_exit(255);
255         }
256
257         /*
258          * send a bogus global/channel request with "wantreply",
259          * we should get back a failure
260          */
261         if ((channel_id = channel_find_open()) == -1) {
262                 packet_start(SSH2_MSG_GLOBAL_REQUEST);
263                 packet_put_cstring("keepalive@openssh.com");
264                 packet_put_char(1);     /* boolean: want reply */
265         } else {
266                 channel_request_start(channel_id, "keepalive@openssh.com", 1);
267         }
268         packet_send();
269 }
270
271 /*
272  * Sleep in select() until we can do something.  This will initialize the
273  * select masks.  Upon return, the masks will indicate which descriptors
274  * have data or can accept data.  Optionally, a maximum time can be specified
275  * for the duration of the wait (0 = infinite).
276  */
277 static void
278 wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
279     u_int *nallocp, u_int max_time_milliseconds)
280 {
281         struct timeval tv, *tvp;
282         int ret;
283         int client_alive_scheduled = 0;
284         int program_alive_scheduled = 0;
285
286         /*
287          * if using client_alive, set the max timeout accordingly,
288          * and indicate that this particular timeout was for client
289          * alive by setting the client_alive_scheduled flag.
290          *
291          * this could be randomized somewhat to make traffic
292          * analysis more difficult, but we're not doing it yet.
293          */
294         if (compat20 &&
295             max_time_milliseconds == 0 && options.client_alive_interval) {
296                 client_alive_scheduled = 1;
297                 max_time_milliseconds = options.client_alive_interval * 1000;
298         }
299
300         /* Allocate and update select() masks for channel descriptors. */
301         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, 0);
302
303         if (compat20) {
304 #if 0
305                 /* wrong: bad condition XXX */
306                 if (channel_not_very_much_buffered_data())
307 #endif
308                 FD_SET(connection_in, *readsetp);
309         } else {
310                 /*
311                  * Read packets from the client unless we have too much
312                  * buffered stdin or channel data.
313                  */
314                 if (buffer_len(&stdin_buffer) < buffer_high &&
315                     channel_not_very_much_buffered_data())
316                         FD_SET(connection_in, *readsetp);
317                 /*
318                  * If there is not too much data already buffered going to
319                  * the client, try to get some more data from the program.
320                  */
321                 if (packet_not_very_much_data_to_write()) {
322                         program_alive_scheduled = child_terminated;
323                         if (!fdout_eof)
324                                 FD_SET(fdout, *readsetp);
325                         if (!fderr_eof)
326                                 FD_SET(fderr, *readsetp);
327                 }
328                 /*
329                  * If we have buffered data, try to write some of that data
330                  * to the program.
331                  */
332                 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
333                         FD_SET(fdin, *writesetp);
334         }
335         notify_prepare(*readsetp);
336
337         /*
338          * If we have buffered packet data going to the client, mark that
339          * descriptor.
340          */
341         if (packet_have_data_to_write())
342                 FD_SET(connection_out, *writesetp);
343
344         /*
345          * If child has terminated and there is enough buffer space to read
346          * from it, then read as much as is available and exit.
347          */
348         if (child_terminated && packet_not_very_much_data_to_write())
349                 if (max_time_milliseconds == 0 || client_alive_scheduled)
350                         max_time_milliseconds = 100;
351
352         if (max_time_milliseconds == 0)
353                 tvp = NULL;
354         else {
355                 tv.tv_sec = max_time_milliseconds / 1000;
356                 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
357                 tvp = &tv;
358         }
359
360         /* Wait for something to happen, or the timeout to expire. */
361         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
362
363         if (ret == -1) {
364                 memset(*readsetp, 0, *nallocp);
365                 memset(*writesetp, 0, *nallocp);
366                 if (errno != EINTR)
367                         error("select: %.100s", strerror(errno));
368         } else {
369                 if (ret == 0 && client_alive_scheduled)
370                         client_alive_check();
371                 if (!compat20 && program_alive_scheduled && fdin_is_tty) {
372                         if (!fdout_eof)
373                                 FD_SET(fdout, *readsetp);
374                         if (!fderr_eof)
375                                 FD_SET(fderr, *readsetp);
376                 }
377         }
378
379         notify_done(*readsetp);
380 }
381
382 /*
383  * Processes input from the client and the program.  Input data is stored
384  * in buffers and processed later.
385  */
386 static void
387 process_input(fd_set *readset)
388 {
389         int len;
390         char buf[16384];
391
392         /* Read and buffer any input data from the client. */
393         if (FD_ISSET(connection_in, readset)) {
394                 len = read(connection_in, buf, sizeof(buf));
395                 if (len == 0) {
396                         verbose("Connection closed by %.100s",
397                             get_remote_ipaddr());
398                         connection_closed = 1;
399                         if (compat20)
400                                 return;
401                         cleanup_exit(255);
402                 } else if (len < 0) {
403                         if (errno != EINTR && errno != EAGAIN) {
404                                 verbose("Read error from remote host "
405                                     "%.100s: %.100s",
406                                     get_remote_ipaddr(), strerror(errno));
407                                 cleanup_exit(255);
408                         }
409                 } else {
410                         /* Buffer any received data. */
411                         packet_process_incoming(buf, len);
412                 }
413         }
414         if (compat20)
415                 return;
416
417         /* Read and buffer any available stdout data from the program. */
418         if (!fdout_eof && FD_ISSET(fdout, readset)) {
419                 errno = 0;
420                 len = read(fdout, buf, sizeof(buf));
421                 if (len < 0 && (errno == EINTR ||
422                     (errno == EAGAIN && !child_terminated))) {
423                         /* do nothing */
424 #ifndef PTY_ZEROREAD
425                 } else if (len <= 0) {
426 #else
427                 } else if ((!isatty(fdout) && len <= 0) ||
428                     (isatty(fdout) && (len < 0 || (len == 0 && errno != 0)))) {
429 #endif
430                         fdout_eof = 1;
431                 } else {
432                         buffer_append(&stdout_buffer, buf, len);
433                         fdout_bytes += len;
434                 }
435         }
436         /* Read and buffer any available stderr data from the program. */
437         if (!fderr_eof && FD_ISSET(fderr, readset)) {
438                 errno = 0;
439                 len = read(fderr, buf, sizeof(buf));
440                 if (len < 0 && (errno == EINTR ||
441                     (errno == EAGAIN && !child_terminated))) {
442                         /* do nothing */
443 #ifndef PTY_ZEROREAD
444                 } else if (len <= 0) {
445 #else
446                 } else if ((!isatty(fderr) && len <= 0) ||
447                     (isatty(fderr) && (len < 0 || (len == 0 && errno != 0)))) {
448 #endif
449                         fderr_eof = 1;
450                 } else {
451                         buffer_append(&stderr_buffer, buf, len);
452                 }
453         }
454 }
455
456 /*
457  * Sends data from internal buffers to client program stdin.
458  */
459 static void
460 process_output(fd_set *writeset)
461 {
462         struct termios tio;
463         u_char *data;
464         u_int dlen;
465         int len;
466
467         /* Write buffered data to program stdin. */
468         if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
469                 data = buffer_ptr(&stdin_buffer);
470                 dlen = buffer_len(&stdin_buffer);
471                 len = write(fdin, data, dlen);
472                 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
473                         /* do nothing */
474                 } else if (len <= 0) {
475                         if (fdin != fdout)
476                                 close(fdin);
477                         else
478                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
479                         fdin = -1;
480                 } else {
481                         /* Successful write. */
482                         if (fdin_is_tty && dlen >= 1 && data[0] != '\r' &&
483                             tcgetattr(fdin, &tio) == 0 &&
484                             !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
485                                 /*
486                                  * Simulate echo to reduce the impact of
487                                  * traffic analysis
488                                  */
489                                 packet_send_ignore(len);
490                                 packet_send();
491                         }
492                         /* Consume the data from the buffer. */
493                         buffer_consume(&stdin_buffer, len);
494                         /* Update the count of bytes written to the program. */
495                         stdin_bytes += len;
496                 }
497         }
498         /* Send any buffered packet data to the client. */
499         if (FD_ISSET(connection_out, writeset))
500                 packet_write_poll();
501 }
502
503 /*
504  * Wait until all buffered output has been sent to the client.
505  * This is used when the program terminates.
506  */
507 static void
508 drain_output(void)
509 {
510         /* Send any buffered stdout data to the client. */
511         if (buffer_len(&stdout_buffer) > 0) {
512                 packet_start(SSH_SMSG_STDOUT_DATA);
513                 packet_put_string(buffer_ptr(&stdout_buffer),
514                                   buffer_len(&stdout_buffer));
515                 packet_send();
516                 /* Update the count of sent bytes. */
517                 stdout_bytes += buffer_len(&stdout_buffer);
518         }
519         /* Send any buffered stderr data to the client. */
520         if (buffer_len(&stderr_buffer) > 0) {
521                 packet_start(SSH_SMSG_STDERR_DATA);
522                 packet_put_string(buffer_ptr(&stderr_buffer),
523                                   buffer_len(&stderr_buffer));
524                 packet_send();
525                 /* Update the count of sent bytes. */
526                 stderr_bytes += buffer_len(&stderr_buffer);
527         }
528         /* Wait until all buffered data has been written to the client. */
529         packet_write_wait();
530 }
531
532 static void
533 process_buffered_input_packets(void)
534 {
535         dispatch_run(DISPATCH_NONBLOCK, NULL, compat20 ? xxx_kex : NULL);
536 }
537
538 /*
539  * Performs the interactive session.  This handles data transmission between
540  * the client and the program.  Note that the notion of stdin, stdout, and
541  * stderr in this function is sort of reversed: this function writes to
542  * stdin (of the child program), and reads from stdout and stderr (of the
543  * child program).
544  */
545 void
546 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
547 {
548         fd_set *readset = NULL, *writeset = NULL;
549         int max_fd = 0;
550         u_int nalloc = 0;
551         int wait_status;        /* Status returned by wait(). */
552         pid_t wait_pid;         /* pid returned by wait(). */
553         int waiting_termination = 0;    /* Have displayed waiting close message. */
554         u_int max_time_milliseconds;
555         u_int previous_stdout_buffer_bytes;
556         u_int stdout_buffer_bytes;
557         int type;
558
559         debug("Entering interactive session.");
560
561         /* Initialize the SIGCHLD kludge. */
562         child_terminated = 0;
563         mysignal(SIGCHLD, sigchld_handler);
564
565         if (!use_privsep) {
566                 signal(SIGTERM, sigterm_handler);
567                 signal(SIGINT, sigterm_handler);
568                 signal(SIGQUIT, sigterm_handler);
569         }
570
571         /* Initialize our global variables. */
572         fdin = fdin_arg;
573         fdout = fdout_arg;
574         fderr = fderr_arg;
575
576         /* nonblocking IO */
577         set_nonblock(fdin);
578         set_nonblock(fdout);
579         /* we don't have stderr for interactive terminal sessions, see below */
580         if (fderr != -1)
581                 set_nonblock(fderr);
582
583         if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
584                 fdin_is_tty = 1;
585
586         connection_in = packet_get_connection_in();
587         connection_out = packet_get_connection_out();
588
589         notify_setup();
590
591         previous_stdout_buffer_bytes = 0;
592
593         /* Set approximate I/O buffer size. */
594         if (packet_is_interactive())
595                 buffer_high = 4096;
596         else
597                 buffer_high = 64 * 1024;
598
599 #if 0
600         /* Initialize max_fd to the maximum of the known file descriptors. */
601         max_fd = MAX(connection_in, connection_out);
602         max_fd = MAX(max_fd, fdin);
603         max_fd = MAX(max_fd, fdout);
604         if (fderr != -1)
605                 max_fd = MAX(max_fd, fderr);
606 #endif
607
608         /* Initialize Initialize buffers. */
609         buffer_init(&stdin_buffer);
610         buffer_init(&stdout_buffer);
611         buffer_init(&stderr_buffer);
612
613         /*
614          * If we have no separate fderr (which is the case when we have a pty
615          * - there we cannot make difference between data sent to stdout and
616          * stderr), indicate that we have seen an EOF from stderr.  This way
617          * we don't need to check the descriptor everywhere.
618          */
619         if (fderr == -1)
620                 fderr_eof = 1;
621
622         server_init_dispatch();
623
624         /* Main loop of the server for the interactive session mode. */
625         for (;;) {
626
627                 /* Process buffered packets from the client. */
628                 process_buffered_input_packets();
629
630                 /*
631                  * If we have received eof, and there is no more pending
632                  * input data, cause a real eof by closing fdin.
633                  */
634                 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
635                         if (fdin != fdout)
636                                 close(fdin);
637                         else
638                                 shutdown(fdin, SHUT_WR); /* We will no longer send. */
639                         fdin = -1;
640                 }
641                 /* Make packets from buffered stderr data to send to the client. */
642                 make_packets_from_stderr_data();
643
644                 /*
645                  * Make packets from buffered stdout data to send to the
646                  * client. If there is very little to send, this arranges to
647                  * not send them now, but to wait a short while to see if we
648                  * are getting more data. This is necessary, as some systems
649                  * wake up readers from a pty after each separate character.
650                  */
651                 max_time_milliseconds = 0;
652                 stdout_buffer_bytes = buffer_len(&stdout_buffer);
653                 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
654                     stdout_buffer_bytes != previous_stdout_buffer_bytes) {
655                         /* try again after a while */
656                         max_time_milliseconds = 10;
657                 } else {
658                         /* Send it now. */
659                         make_packets_from_stdout_data();
660                 }
661                 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
662
663                 /* Send channel data to the client. */
664                 if (packet_not_very_much_data_to_write())
665                         channel_output_poll();
666
667                 /*
668                  * Bail out of the loop if the program has closed its output
669                  * descriptors, and we have no more data to send to the
670                  * client, and there is no pending buffered data.
671                  */
672                 if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
673                     buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
674                         if (!channel_still_open())
675                                 break;
676                         if (!waiting_termination) {
677                                 const char *s = "Waiting for forwarded connections to terminate...\r\n";
678                                 char *cp;
679                                 waiting_termination = 1;
680                                 buffer_append(&stderr_buffer, s, strlen(s));
681
682                                 /* Display list of open channels. */
683                                 cp = channel_open_message();
684                                 buffer_append(&stderr_buffer, cp, strlen(cp));
685                                 xfree(cp);
686                         }
687                 }
688                 max_fd = MAX(connection_in, connection_out);
689                 max_fd = MAX(max_fd, fdin);
690                 max_fd = MAX(max_fd, fdout);
691                 max_fd = MAX(max_fd, fderr);
692                 max_fd = MAX(max_fd, notify_pipe[0]);
693
694                 /* Sleep in select() until we can do something. */
695                 wait_until_can_do_something(&readset, &writeset, &max_fd,
696                     &nalloc, max_time_milliseconds);
697
698                 if (received_sigterm) {
699                         logit("Exiting on signal %d", received_sigterm);
700                         /* Clean up sessions, utmp, etc. */
701                         cleanup_exit(255);
702                 }
703
704                 /* Process any channel events. */
705                 channel_after_select(readset, writeset);
706
707                 /* Process input from the client and from program stdout/stderr. */
708                 process_input(readset);
709
710                 /* Process output to the client and to program stdin. */
711                 process_output(writeset);
712         }
713         if (readset)
714                 xfree(readset);
715         if (writeset)
716                 xfree(writeset);
717
718         /* Cleanup and termination code. */
719
720         /* Wait until all output has been sent to the client. */
721         drain_output();
722
723         debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
724             stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
725
726         /* Free and clear the buffers. */
727         buffer_free(&stdin_buffer);
728         buffer_free(&stdout_buffer);
729         buffer_free(&stderr_buffer);
730
731         /* Close the file descriptors. */
732         if (fdout != -1)
733                 close(fdout);
734         fdout = -1;
735         fdout_eof = 1;
736         if (fderr != -1)
737                 close(fderr);
738         fderr = -1;
739         fderr_eof = 1;
740         if (fdin != -1)
741                 close(fdin);
742         fdin = -1;
743
744         channel_free_all();
745
746         /* We no longer want our SIGCHLD handler to be called. */
747         mysignal(SIGCHLD, SIG_DFL);
748
749         while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
750                 if (errno != EINTR)
751                         packet_disconnect("wait: %.100s", strerror(errno));
752         if (wait_pid != pid)
753                 error("Strange, wait returned pid %ld, expected %ld",
754                     (long)wait_pid, (long)pid);
755
756         /* Check if it exited normally. */
757         if (WIFEXITED(wait_status)) {
758                 /* Yes, normal exit.  Get exit status and send it to the client. */
759                 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
760                 packet_start(SSH_SMSG_EXITSTATUS);
761                 packet_put_int(WEXITSTATUS(wait_status));
762                 packet_send();
763                 packet_write_wait();
764
765                 /*
766                  * Wait for exit confirmation.  Note that there might be
767                  * other packets coming before it; however, the program has
768                  * already died so we just ignore them.  The client is
769                  * supposed to respond with the confirmation when it receives
770                  * the exit status.
771                  */
772                 do {
773                         type = packet_read();
774                 }
775                 while (type != SSH_CMSG_EXIT_CONFIRMATION);
776
777                 debug("Received exit confirmation.");
778                 return;
779         }
780         /* Check if the program terminated due to a signal. */
781         if (WIFSIGNALED(wait_status))
782                 packet_disconnect("Command terminated on signal %d.",
783                                   WTERMSIG(wait_status));
784
785         /* Some weird exit cause.  Just exit. */
786         packet_disconnect("wait returned status %04x.", wait_status);
787         /* NOTREACHED */
788 }
789
790 static void
791 collect_children(void)
792 {
793         pid_t pid;
794         sigset_t oset, nset;
795         int status;
796
797         /* block SIGCHLD while we check for dead children */
798         sigemptyset(&nset);
799         sigaddset(&nset, SIGCHLD);
800         sigprocmask(SIG_BLOCK, &nset, &oset);
801         if (child_terminated) {
802                 debug("Received SIGCHLD.");
803                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
804                     (pid < 0 && errno == EINTR))
805                         if (pid > 0)
806                                 session_close_by_pid(pid, status);
807                 child_terminated = 0;
808         }
809         sigprocmask(SIG_SETMASK, &oset, NULL);
810 }
811
812 void
813 server_loop2(Authctxt *authctxt)
814 {
815         fd_set *readset = NULL, *writeset = NULL;
816         int rekeying = 0, max_fd, nalloc = 0;
817
818         debug("Entering interactive session for SSH2.");
819
820         mysignal(SIGCHLD, sigchld_handler);
821         child_terminated = 0;
822         connection_in = packet_get_connection_in();
823         connection_out = packet_get_connection_out();
824
825         if (!use_privsep) {
826                 signal(SIGTERM, sigterm_handler);
827                 signal(SIGINT, sigterm_handler);
828                 signal(SIGQUIT, sigterm_handler);
829         }
830
831         notify_setup();
832
833         max_fd = MAX(connection_in, connection_out);
834         max_fd = MAX(max_fd, notify_pipe[0]);
835
836         server_init_dispatch();
837
838         for (;;) {
839                 process_buffered_input_packets();
840
841                 rekeying = (xxx_kex != NULL && !xxx_kex->done);
842
843                 if (!rekeying && packet_not_very_much_data_to_write())
844                         channel_output_poll();
845                 wait_until_can_do_something(&readset, &writeset, &max_fd,
846                     &nalloc, 0);
847
848                 if (received_sigterm) {
849                         logit("Exiting on signal %d", received_sigterm);
850                         /* Clean up sessions, utmp, etc. */
851                         cleanup_exit(255);
852                 }
853
854                 collect_children();
855                 if (!rekeying) {
856                         channel_after_select(readset, writeset);
857                         if (packet_need_rekeying()) {
858                                 debug("need rekeying");
859                                 xxx_kex->done = 0;
860                                 kex_send_kexinit(xxx_kex);
861                         }
862                 }
863                 process_input(readset);
864                 if (connection_closed)
865                         break;
866                 process_output(writeset);
867         }
868         collect_children();
869
870         if (readset)
871                 xfree(readset);
872         if (writeset)
873                 xfree(writeset);
874
875         /* free all channels, no more reads and writes */
876         channel_free_all();
877
878         /* free remaining sessions, e.g. remove wtmp entries */
879         session_destroy_all(NULL);
880 }
881
882 static void
883 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
884 {
885         debug("Got %d/%u for keepalive", type, seq);
886         /*
887          * reset timeout, since we got a sane answer from the client.
888          * even if this was generated by something other than
889          * the bogus CHANNEL_REQUEST we send for keepalives.
890          */
891         keep_alive_timeouts = 0;
892 }
893
894 static void
895 server_input_stdin_data(int type, u_int32_t seq, void *ctxt)
896 {
897         char *data;
898         u_int data_len;
899
900         /* Stdin data from the client.  Append it to the buffer. */
901         /* Ignore any data if the client has closed stdin. */
902         if (fdin == -1)
903                 return;
904         data = packet_get_string(&data_len);
905         packet_check_eom();
906         buffer_append(&stdin_buffer, data, data_len);
907         memset(data, 0, data_len);
908         xfree(data);
909 }
910
911 static void
912 server_input_eof(int type, u_int32_t seq, void *ctxt)
913 {
914         /*
915          * Eof from the client.  The stdin descriptor to the
916          * program will be closed when all buffered data has
917          * drained.
918          */
919         debug("EOF received for stdin.");
920         packet_check_eom();
921         stdin_eof = 1;
922 }
923
924 static void
925 server_input_window_size(int type, u_int32_t seq, void *ctxt)
926 {
927         u_int row = packet_get_int();
928         u_int col = packet_get_int();
929         u_int xpixel = packet_get_int();
930         u_int ypixel = packet_get_int();
931
932         debug("Window change received.");
933         packet_check_eom();
934         if (fdin != -1)
935                 pty_change_window_size(fdin, row, col, xpixel, ypixel);
936 }
937
938 static Channel *
939 server_request_direct_tcpip(void)
940 {
941         Channel *c;
942         char *target, *originator;
943         int target_port, originator_port;
944
945         target = packet_get_string(NULL);
946         target_port = packet_get_int();
947         originator = packet_get_string(NULL);
948         originator_port = packet_get_int();
949         packet_check_eom();
950
951         debug("server_request_direct_tcpip: originator %s port %d, target %s "
952             "port %d", originator, originator_port, target, target_port);
953
954         /* XXX check permission */
955         c = channel_connect_to(target, target_port,
956             "direct-tcpip", "direct-tcpip");
957
958         xfree(originator);
959         xfree(target);
960
961         return c;
962 }
963
964 static Channel *
965 server_request_tun(void)
966 {
967         Channel *c = NULL;
968         int mode, tun;
969         int sock;
970
971         mode = packet_get_int();
972         switch (mode) {
973         case SSH_TUNMODE_POINTOPOINT:
974         case SSH_TUNMODE_ETHERNET:
975                 break;
976         default:
977                 packet_send_debug("Unsupported tunnel device mode.");
978                 return NULL;
979         }
980         if ((options.permit_tun & mode) == 0) {
981                 packet_send_debug("Server has rejected tunnel device "
982                     "forwarding");
983                 return NULL;
984         }
985
986         tun = packet_get_int();
987         if (forced_tun_device != -1) {
988                 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
989                         goto done;
990                 tun = forced_tun_device;
991         }
992         sock = tun_open(tun, mode);
993         if (sock < 0)
994                 goto done;
995         c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
996             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
997         c->datagram = 1;
998 #if defined(SSH_TUN_FILTER)
999         if (mode == SSH_TUNMODE_POINTOPOINT)
1000                 channel_register_filter(c->self, sys_tun_infilter,
1001                     sys_tun_outfilter, NULL, NULL);
1002 #endif
1003
1004  done:
1005         if (c == NULL)
1006                 packet_send_debug("Failed to open the tunnel device.");
1007         return c;
1008 }
1009
1010 static Channel *
1011 server_request_session(void)
1012 {
1013         Channel *c;
1014
1015         debug("input_session_request");
1016         packet_check_eom();
1017
1018         if (no_more_sessions) {
1019                 packet_disconnect("Possible attack: attempt to open a session "
1020                     "after additional sessions disabled");
1021         }
1022
1023         /*
1024          * A server session has no fd to read or write until a
1025          * CHANNEL_REQUEST for a shell is made, so we set the type to
1026          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
1027          * CHANNEL_REQUEST messages is registered.
1028          */
1029         c = channel_new("session", SSH_CHANNEL_LARVAL,
1030             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
1031             0, "server-session", 1);
1032         if (session_open(the_authctxt, c->self) != 1) {
1033                 debug("session open failed, free channel %d", c->self);
1034                 channel_free(c);
1035                 return NULL;
1036         }
1037         channel_register_cleanup(c->self, session_close_by_channel, 0);
1038         return c;
1039 }
1040
1041 static void
1042 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
1043 {
1044         Channel *c = NULL;
1045         char *ctype;
1046         int rchan;
1047         u_int rmaxpack, rwindow, len;
1048
1049         ctype = packet_get_string(&len);
1050         rchan = packet_get_int();
1051         rwindow = packet_get_int();
1052         rmaxpack = packet_get_int();
1053
1054         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
1055             ctype, rchan, rwindow, rmaxpack);
1056
1057         if (strcmp(ctype, "session") == 0) {
1058                 c = server_request_session();
1059         } else if (strcmp(ctype, "direct-tcpip") == 0) {
1060                 c = server_request_direct_tcpip();
1061         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
1062                 c = server_request_tun();
1063         }
1064         if (c != NULL) {
1065                 debug("server_input_channel_open: confirm %s", ctype);
1066                 c->remote_id = rchan;
1067                 c->remote_window = rwindow;
1068                 c->remote_maxpacket = rmaxpack;
1069                 if (c->type != SSH_CHANNEL_CONNECTING) {
1070                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
1071                         packet_put_int(c->remote_id);
1072                         packet_put_int(c->self);
1073                         packet_put_int(c->local_window);
1074                         packet_put_int(c->local_maxpacket);
1075                         packet_send();
1076                 }
1077         } else {
1078                 debug("server_input_channel_open: failure %s", ctype);
1079                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
1080                 packet_put_int(rchan);
1081                 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
1082                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
1083                         packet_put_cstring("open failed");
1084                         packet_put_cstring("");
1085                 }
1086                 packet_send();
1087         }
1088         xfree(ctype);
1089 }
1090
1091 static void
1092 server_input_global_request(int type, u_int32_t seq, void *ctxt)
1093 {
1094         char *rtype;
1095         int want_reply;
1096         int success = 0;
1097
1098         rtype = packet_get_string(NULL);
1099         want_reply = packet_get_char();
1100         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
1101
1102         /* -R style forwarding */
1103         if (strcmp(rtype, "tcpip-forward") == 0) {
1104                 struct passwd *pw;
1105                 char *listen_address;
1106                 u_short listen_port;
1107
1108                 pw = the_authctxt->pw;
1109                 if (pw == NULL || !the_authctxt->valid)
1110                         fatal("server_input_global_request: no/invalid user");
1111                 listen_address = packet_get_string(NULL);
1112                 listen_port = (u_short)packet_get_int();
1113                 debug("server_input_global_request: tcpip-forward listen %s port %d",
1114                     listen_address, listen_port);
1115
1116                 /* check permissions */
1117                 if (!options.allow_tcp_forwarding ||
1118                     no_port_forwarding_flag
1119 #ifndef NO_IPPORT_RESERVED_CONCEPT
1120                     || (listen_port < IPPORT_RESERVED && pw->pw_uid != 0)
1121 #endif
1122                     ) {
1123                         success = 0;
1124                         packet_send_debug("Server has disabled port forwarding.");
1125                 } else {
1126                         /* Start listening on the port */
1127                         success = channel_setup_remote_fwd_listener(
1128                             listen_address, listen_port, options.gateway_ports);
1129                 }
1130                 xfree(listen_address);
1131         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
1132                 char *cancel_address;
1133                 u_short cancel_port;
1134
1135                 cancel_address = packet_get_string(NULL);
1136                 cancel_port = (u_short)packet_get_int();
1137                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
1138                     cancel_address, cancel_port);
1139
1140                 success = channel_cancel_rport_listener(cancel_address,
1141                     cancel_port);
1142                 xfree(cancel_address);
1143         } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
1144                 no_more_sessions = 1;
1145                 success = 1;
1146         }
1147         if (want_reply) {
1148                 packet_start(success ?
1149                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
1150                 packet_send();
1151                 packet_write_wait();
1152         }
1153         xfree(rtype);
1154 }
1155
1156 static void
1157 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
1158 {
1159         Channel *c;
1160         int id, reply, success = 0;
1161         char *rtype;
1162
1163         id = packet_get_int();
1164         rtype = packet_get_string(NULL);
1165         reply = packet_get_char();
1166
1167         debug("server_input_channel_req: channel %d request %s reply %d",
1168             id, rtype, reply);
1169
1170         if ((c = channel_lookup(id)) == NULL)
1171                 packet_disconnect("server_input_channel_req: "
1172                     "unknown channel %d", id);
1173         if (!strcmp(rtype, "eow@openssh.com")) {
1174                 packet_check_eom();
1175                 chan_rcvd_eow(c);
1176         } else if ((c->type == SSH_CHANNEL_LARVAL ||
1177             c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
1178                 success = session_input_channel_req(c, rtype);
1179         if (reply) {
1180                 packet_start(success ?
1181                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
1182                 packet_put_int(c->remote_id);
1183                 packet_send();
1184         }
1185         xfree(rtype);
1186 }
1187
1188 static void
1189 server_init_dispatch_20(void)
1190 {
1191         debug("server_init_dispatch_20");
1192         dispatch_init(&dispatch_protocol_error);
1193         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
1194         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
1195         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
1196         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
1197         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
1198         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1199         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1200         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
1201         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
1202         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
1203         dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &channel_input_status_confirm);
1204         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &channel_input_status_confirm);
1205         /* client_alive */
1206         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
1207         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
1208         /* rekeying */
1209         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
1210 }
1211 static void
1212 server_init_dispatch_13(void)
1213 {
1214         debug("server_init_dispatch_13");
1215         dispatch_init(NULL);
1216         dispatch_set(SSH_CMSG_EOF, &server_input_eof);
1217         dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
1218         dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
1219         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
1220         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
1221         dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
1222         dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
1223         dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
1224         dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
1225 }
1226 static void
1227 server_init_dispatch_15(void)
1228 {
1229         server_init_dispatch_13();
1230         debug("server_init_dispatch_15");
1231         dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
1232         dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
1233 }
1234 static void
1235 server_init_dispatch(void)
1236 {
1237         if (compat20)
1238                 server_init_dispatch_20();
1239         else if (compat13)
1240                 server_init_dispatch_13();
1241         else
1242                 server_init_dispatch_15();
1243 }
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