2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * Created: Sun Sep 10 00:30:37 1995 ylo
6 * Server main loop for handling the interactive session.
9 * SSH2 support by Markus Friedl.
10 * Copyright (c) 2000 Markus Friedl. All rights reserved.
26 #include "auth-options.h"
28 static Buffer stdin_buffer; /* Buffer for stdin data. */
29 static Buffer stdout_buffer; /* Buffer for stdout data. */
30 static Buffer stderr_buffer; /* Buffer for stderr data. */
31 static int fdin; /* Descriptor for stdin (for writing) */
32 static int fdout; /* Descriptor for stdout (for reading);
33 May be same number as fdin. */
34 static int fderr; /* Descriptor for stderr. May be -1. */
35 static long stdin_bytes = 0; /* Number of bytes written to stdin. */
36 static long stdout_bytes = 0; /* Number of stdout bytes sent to client. */
37 static long stderr_bytes = 0; /* Number of stderr bytes sent to client. */
38 static long fdout_bytes = 0; /* Number of stdout bytes read from program. */
39 static int stdin_eof = 0; /* EOF message received from client. */
40 static int fdout_eof = 0; /* EOF encountered reading from fdout. */
41 static int fderr_eof = 0; /* EOF encountered readung from fderr. */
42 static int connection_in; /* Connection to client (input). */
43 static int connection_out; /* Connection to client (output). */
44 static unsigned int buffer_high;/* "Soft" max buffer size. */
45 static int max_fd; /* Max file descriptor number for select(). */
48 * This SIGCHLD kludge is used to detect when the child exits. The server
49 * will exit after that, as soon as forwarded connections have terminated.
51 * After SIGCHLD child_has_selected is set to 1 after the first pass
52 * through the wait_until_can_do_something() select(). This ensures
53 * that the child's output gets a chance to drain before it is yanked.
56 static pid_t child_pid; /* Pid of the child. */
57 static volatile int child_terminated; /* The child has terminated. */
58 static volatile int child_has_selected; /* Child has had chance to drain. */
59 static volatile int child_wait_status; /* Status from wait(). */
61 void server_init_dispatch(void);
64 sigchld_handler(int sig)
66 int save_errno = errno;
69 debug("Received SIGCHLD.");
70 wait_pid = wait((int *) &child_wait_status);
72 if (wait_pid != child_pid)
73 error("Strange, got SIGCHLD and wait returned pid %d but child is %d",
75 if (WIFEXITED(child_wait_status) ||
76 WIFSIGNALED(child_wait_status))
78 child_has_selected = 0;
80 signal(SIGCHLD, sigchld_handler);
84 sigchld_handler2(int sig)
86 int save_errno = errno;
87 debug("Received SIGCHLD.");
93 * Make packets from buffered stderr data, and buffer it for sending
97 make_packets_from_stderr_data()
101 /* Send buffered stderr data to the client. */
102 while (buffer_len(&stderr_buffer) > 0 &&
103 packet_not_very_much_data_to_write()) {
104 len = buffer_len(&stderr_buffer);
105 if (packet_is_interactive()) {
109 /* Keep the packets at reasonable size. */
110 if (len > packet_get_maxsize())
111 len = packet_get_maxsize();
113 packet_start(SSH_SMSG_STDERR_DATA);
114 packet_put_string(buffer_ptr(&stderr_buffer), len);
116 buffer_consume(&stderr_buffer, len);
122 * Make packets from buffered stdout data, and buffer it for sending to the
126 make_packets_from_stdout_data()
130 /* Send buffered stdout data to the client. */
131 while (buffer_len(&stdout_buffer) > 0 &&
132 packet_not_very_much_data_to_write()) {
133 len = buffer_len(&stdout_buffer);
134 if (packet_is_interactive()) {
138 /* Keep the packets at reasonable size. */
139 if (len > packet_get_maxsize())
140 len = packet_get_maxsize();
142 packet_start(SSH_SMSG_STDOUT_DATA);
143 packet_put_string(buffer_ptr(&stdout_buffer), len);
145 buffer_consume(&stdout_buffer, len);
151 * Sleep in select() until we can do something. This will initialize the
152 * select masks. Upon return, the masks will indicate which descriptors
153 * have data or can accept data. Optionally, a maximum time can be specified
154 * for the duration of the wait (0 = infinite).
157 wait_until_can_do_something(fd_set * readset, fd_set * writeset,
158 unsigned int max_time_milliseconds)
160 struct timeval tv, *tvp;
163 /* When select fails we restart from here. */
166 /* Initialize select() masks. */
171 /* wrong: bad condition XXX */
172 if (channel_not_very_much_buffered_data())
173 FD_SET(connection_in, readset);
176 * Read packets from the client unless we have too much
177 * buffered stdin or channel data.
179 if (buffer_len(&stdin_buffer) < buffer_high &&
180 channel_not_very_much_buffered_data())
181 FD_SET(connection_in, readset);
183 * If there is not too much data already buffered going to
184 * the client, try to get some more data from the program.
186 if (packet_not_very_much_data_to_write()) {
188 FD_SET(fdout, readset);
190 FD_SET(fderr, readset);
193 * If we have buffered data, try to write some of that data
196 if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
197 FD_SET(fdin, writeset);
199 /* Set masks for channel descriptors. */
200 channel_prepare_select(readset, writeset);
203 * If we have buffered packet data going to the client, mark that
206 if (packet_have_data_to_write())
207 FD_SET(connection_out, writeset);
209 /* Update the maximum descriptor number if appropriate. */
210 if (channel_max_fd() > max_fd)
211 max_fd = channel_max_fd();
214 * If child has terminated and there is enough buffer space to read
215 * from it, then read as much as is available and exit.
217 if (child_terminated && packet_not_very_much_data_to_write())
218 if (max_time_milliseconds == 0)
219 max_time_milliseconds = 100;
221 if (max_time_milliseconds == 0)
224 tv.tv_sec = max_time_milliseconds / 1000;
225 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
229 debug("tvp!=NULL kid %d mili %d", child_terminated, max_time_milliseconds);
231 /* Wait for something to happen, or the timeout to expire. */
232 ret = select(max_fd + 1, readset, writeset, NULL, tvp);
236 error("select: %.100s", strerror(errno));
241 if (child_terminated)
242 child_has_selected = 1;
246 * Processes input from the client and the program. Input data is stored
247 * in buffers and processed later.
250 process_input(fd_set * readset)
255 /* Read and buffer any input data from the client. */
256 if (FD_ISSET(connection_in, readset)) {
257 len = read(connection_in, buf, sizeof(buf));
259 verbose("Connection closed by remote host.");
261 } else if (len < 0) {
262 if (errno != EINTR && errno != EAGAIN) {
263 verbose("Read error from remote host: %.100s", strerror(errno));
267 /* Buffer any received data. */
268 packet_process_incoming(buf, len);
274 /* Read and buffer any available stdout data from the program. */
275 if (!fdout_eof && FD_ISSET(fdout, readset)) {
276 len = read(fdout, buf, sizeof(buf));
277 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
279 } else if (len <= 0) {
282 buffer_append(&stdout_buffer, buf, len);
286 /* Read and buffer any available stderr data from the program. */
287 if (!fderr_eof && FD_ISSET(fderr, readset)) {
288 len = read(fderr, buf, sizeof(buf));
289 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
291 } else if (len <= 0) {
294 buffer_append(&stderr_buffer, buf, len);
300 * Sends data from internal buffers to client program stdin.
303 process_output(fd_set * writeset)
307 /* Write buffered data to program stdin. */
308 if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
309 len = write(fdin, buffer_ptr(&stdin_buffer),
310 buffer_len(&stdin_buffer));
311 if (len < 0 && (errno == EINTR || errno == EAGAIN)) {
313 } else if (len <= 0) {
320 shutdown(fdin, SHUT_WR); /* We will no longer send. */
324 /* Successful write. Consume the data from the buffer. */
325 buffer_consume(&stdin_buffer, len);
326 /* Update the count of bytes written to the program. */
330 /* Send any buffered packet data to the client. */
331 if (FD_ISSET(connection_out, writeset))
336 * Wait until all buffered output has been sent to the client.
337 * This is used when the program terminates.
342 /* Send any buffered stdout data to the client. */
343 if (buffer_len(&stdout_buffer) > 0) {
344 packet_start(SSH_SMSG_STDOUT_DATA);
345 packet_put_string(buffer_ptr(&stdout_buffer),
346 buffer_len(&stdout_buffer));
348 /* Update the count of sent bytes. */
349 stdout_bytes += buffer_len(&stdout_buffer);
351 /* Send any buffered stderr data to the client. */
352 if (buffer_len(&stderr_buffer) > 0) {
353 packet_start(SSH_SMSG_STDERR_DATA);
354 packet_put_string(buffer_ptr(&stderr_buffer),
355 buffer_len(&stderr_buffer));
357 /* Update the count of sent bytes. */
358 stderr_bytes += buffer_len(&stderr_buffer);
360 /* Wait until all buffered data has been written to the client. */
365 process_buffered_input_packets()
367 dispatch_run(DISPATCH_NONBLOCK, NULL);
371 * Performs the interactive session. This handles data transmission between
372 * the client and the program. Note that the notion of stdin, stdout, and
373 * stderr in this function is sort of reversed: this function writes to
374 * stdin (of the child program), and reads from stdout and stderr (of the
378 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
380 fd_set readset, writeset;
381 int wait_status; /* Status returned by wait(). */
382 pid_t wait_pid; /* pid returned by wait(). */
383 int waiting_termination = 0; /* Have displayed waiting close message. */
384 unsigned int max_time_milliseconds;
385 unsigned int previous_stdout_buffer_bytes;
386 unsigned int stdout_buffer_bytes;
389 debug("Entering interactive session.");
391 /* Initialize the SIGCHLD kludge. */
393 child_terminated = 0;
394 child_has_selected = 0;
395 signal(SIGCHLD, sigchld_handler);
397 /* Initialize our global variables. */
405 /* we don't have stderr for interactive terminal sessions, see below */
409 connection_in = packet_get_connection_in();
410 connection_out = packet_get_connection_out();
412 previous_stdout_buffer_bytes = 0;
414 /* Set approximate I/O buffer size. */
415 if (packet_is_interactive())
418 buffer_high = 64 * 1024;
420 /* Initialize max_fd to the maximum of the known file descriptors. */
424 if (fderr != -1 && fderr > max_fd)
426 if (connection_in > max_fd)
427 max_fd = connection_in;
428 if (connection_out > max_fd)
429 max_fd = connection_out;
431 /* Initialize Initialize buffers. */
432 buffer_init(&stdin_buffer);
433 buffer_init(&stdout_buffer);
434 buffer_init(&stderr_buffer);
437 * If we have no separate fderr (which is the case when we have a pty
438 * - there we cannot make difference between data sent to stdout and
439 * stderr), indicate that we have seen an EOF from stderr. This way
440 * we don\'t need to check the descriptor everywhere.
445 server_init_dispatch();
447 /* Main loop of the server for the interactive session mode. */
450 /* Process buffered packets from the client. */
451 process_buffered_input_packets();
454 * If we have received eof, and there is no more pending
455 * input data, cause a real eof by closing fdin.
457 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
464 shutdown(fdin, SHUT_WR); /* We will no longer send. */
468 /* Make packets from buffered stderr data to send to the client. */
469 make_packets_from_stderr_data();
472 * Make packets from buffered stdout data to send to the
473 * client. If there is very little to send, this arranges to
474 * not send them now, but to wait a short while to see if we
475 * are getting more data. This is necessary, as some systems
476 * wake up readers from a pty after each separate character.
478 max_time_milliseconds = 0;
479 stdout_buffer_bytes = buffer_len(&stdout_buffer);
480 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
481 stdout_buffer_bytes != previous_stdout_buffer_bytes) {
482 /* try again after a while */
483 max_time_milliseconds = 10;
486 make_packets_from_stdout_data();
488 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
490 /* Send channel data to the client. */
491 if (packet_not_very_much_data_to_write())
492 channel_output_poll();
495 * Bail out of the loop if the program has closed its output
496 * descriptors, and we have no more data to send to the
497 * client, and there is no pending buffered data.
499 if (((fdout_eof && fderr_eof) ||
500 (child_terminated && child_has_selected)) &&
501 !packet_have_data_to_write() &&
502 (buffer_len(&stdout_buffer) == 0) &&
503 (buffer_len(&stderr_buffer) == 0)) {
504 if (!channel_still_open())
506 if (!waiting_termination) {
507 const char *s = "Waiting for forwarded connections to terminate...\r\n";
509 waiting_termination = 1;
510 buffer_append(&stderr_buffer, s, strlen(s));
512 /* Display list of open channels. */
513 cp = channel_open_message();
514 buffer_append(&stderr_buffer, cp, strlen(cp));
518 /* Sleep in select() until we can do something. */
519 wait_until_can_do_something(&readset, &writeset,
520 max_time_milliseconds);
522 /* Process any channel events. */
523 channel_after_select(&readset, &writeset);
525 /* Process input from the client and from program stdout/stderr. */
526 process_input(&readset);
528 /* Process output to the client and to program stdin. */
529 process_output(&writeset);
532 /* Cleanup and termination code. */
534 /* Wait until all output has been sent to the client. */
537 debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
538 stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
540 /* Free and clear the buffers. */
541 buffer_free(&stdin_buffer);
542 buffer_free(&stdout_buffer);
543 buffer_free(&stderr_buffer);
545 /* Close the file descriptors. */
558 /* Stop listening for channels; this removes unix domain sockets. */
559 channel_stop_listening();
561 /* Wait for the child to exit. Get its exit status. */
562 wait_pid = wait(&wait_status);
565 * It is possible that the wait was handled by SIGCHLD
566 * handler. This may result in either: this call
567 * returning with EINTR, or: this call returning ECHILD.
569 if (child_terminated)
570 wait_status = child_wait_status;
572 packet_disconnect("wait: %.100s", strerror(errno));
574 /* Check if it matches the process we forked. */
576 error("Strange, wait returned pid %d, expected %d",
580 /* We no longer want our SIGCHLD handler to be called. */
581 signal(SIGCHLD, SIG_DFL);
583 /* Check if it exited normally. */
584 if (WIFEXITED(wait_status)) {
585 /* Yes, normal exit. Get exit status and send it to the client. */
586 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
587 packet_start(SSH_SMSG_EXITSTATUS);
588 packet_put_int(WEXITSTATUS(wait_status));
593 * Wait for exit confirmation. Note that there might be
594 * other packets coming before it; however, the program has
595 * already died so we just ignore them. The client is
596 * supposed to respond with the confirmation when it receives
601 type = packet_read(&plen);
603 while (type != SSH_CMSG_EXIT_CONFIRMATION);
605 debug("Received exit confirmation.");
608 /* Check if the program terminated due to a signal. */
609 if (WIFSIGNALED(wait_status))
610 packet_disconnect("Command terminated on signal %d.",
611 WTERMSIG(wait_status));
613 /* Some weird exit cause. Just exit. */
614 packet_disconnect("wait returned status %04x.", wait_status);
621 fd_set readset, writeset;
626 debug("Entering interactive session for SSH2.");
628 signal(SIGCHLD, sigchld_handler2);
629 child_terminated = 0;
630 connection_in = packet_get_connection_in();
631 connection_out = packet_get_connection_out();
632 max_fd = connection_in;
633 if (connection_out > max_fd)
634 max_fd = connection_out;
635 server_init_dispatch();
638 process_buffered_input_packets();
639 if (!had_channel && channel_still_open())
641 if (had_channel && !channel_still_open()) {
642 debug("!channel_still_open.");
645 if (packet_not_very_much_data_to_write())
646 channel_output_poll();
647 wait_until_can_do_something(&readset, &writeset, 0);
648 if (child_terminated) {
649 while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
650 session_close_by_pid(pid, status);
651 child_terminated = 0;
652 signal(SIGCHLD, sigchld_handler2);
654 channel_after_select(&readset, &writeset);
655 process_input(&readset);
656 process_output(&writeset);
658 signal(SIGCHLD, SIG_DFL);
659 while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
660 session_close_by_pid(pid, status);
661 channel_stop_listening();
665 server_input_stdin_data(int type, int plen)
668 unsigned int data_len;
670 /* Stdin data from the client. Append it to the buffer. */
671 /* Ignore any data if the client has closed stdin. */
674 data = packet_get_string(&data_len);
675 packet_integrity_check(plen, (4 + data_len), type);
676 buffer_append(&stdin_buffer, data, data_len);
677 memset(data, 0, data_len);
682 server_input_eof(int type, int plen)
685 * Eof from the client. The stdin descriptor to the
686 * program will be closed when all buffered data has
689 debug("EOF received for stdin.");
690 packet_integrity_check(plen, 0, type);
695 server_input_window_size(int type, int plen)
697 int row = packet_get_int();
698 int col = packet_get_int();
699 int xpixel = packet_get_int();
700 int ypixel = packet_get_int();
702 debug("Window change received.");
703 packet_integrity_check(plen, 4 * 4, type);
705 pty_change_window_size(fdin, row, col, xpixel, ypixel);
709 input_direct_tcpip(void)
712 char *target, *originator;
713 int target_port, originator_port;
715 target = packet_get_string(NULL);
716 target_port = packet_get_int();
717 originator = packet_get_string(NULL);
718 originator_port = packet_get_int();
721 debug("open direct-tcpip: from %s port %d to %s port %d",
722 originator, originator_port, target, target_port);
724 /* XXX check permission */
725 if (no_port_forwarding_flag) {
730 sock = channel_connect_to(target, target_port);
735 return channel_new("direct-tcpip", SSH_CHANNEL_OPEN,
736 sock, sock, -1, 4*1024, 32*1024, 0, xstrdup("direct-tcpip"));
740 server_input_channel_open(int type, int plen)
750 ctype = packet_get_string(&len);
751 rchan = packet_get_int();
752 rwindow = packet_get_int();
753 rmaxpack = packet_get_int();
755 debug("channel_input_open: ctype %s rchan %d win %d max %d",
756 ctype, rchan, rwindow, rmaxpack);
758 if (strcmp(ctype, "session") == 0) {
759 debug("open session");
762 * A server session has no fd to read or write
763 * until a CHANNEL_REQUEST for a shell is made,
764 * so we set the type to SSH_CHANNEL_LARVAL.
765 * Additionally, a callback for handling all
766 * CHANNEL_REQUEST messages is registered.
768 id = channel_new(ctype, SSH_CHANNEL_LARVAL,
769 -1, -1, -1, 0, 32*1024, 0, xstrdup("server-session"));
770 if (session_open(id) == 1) {
771 channel_register_callback(id, SSH2_MSG_CHANNEL_REQUEST,
772 session_input_channel_req, (void *)0);
773 channel_register_cleanup(id, session_close_by_channel);
774 c = channel_lookup(id);
776 debug("session open failed, free channel %d", id);
779 } else if (strcmp(ctype, "direct-tcpip") == 0) {
780 id = input_direct_tcpip();
782 c = channel_lookup(id);
785 debug("confirm %s", ctype);
786 c->remote_id = rchan;
787 c->remote_window = rwindow;
788 c->remote_maxpacket = rmaxpack;
790 packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
791 packet_put_int(c->remote_id);
792 packet_put_int(c->self);
793 packet_put_int(c->local_window);
794 packet_put_int(c->local_maxpacket);
797 debug("failure %s", ctype);
798 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
799 packet_put_int(rchan);
800 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
801 packet_put_cstring("bla bla");
802 packet_put_cstring("");
809 server_init_dispatch_20()
811 debug("server_init_dispatch_20");
812 dispatch_init(&dispatch_protocol_error);
813 dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
814 dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
815 dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
816 dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
817 dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
818 dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
819 dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
820 dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &channel_input_channel_request);
821 dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
824 server_init_dispatch_13()
826 debug("server_init_dispatch_13");
828 dispatch_set(SSH_CMSG_EOF, &server_input_eof);
829 dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
830 dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
831 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
832 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
833 dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
834 dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
835 dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
836 dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
839 server_init_dispatch_15()
841 server_init_dispatch_13();
842 debug("server_init_dispatch_15");
843 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
844 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
847 server_init_dispatch()
850 server_init_dispatch_20();
852 server_init_dispatch_13();
854 server_init_dispatch_15();