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.
27 static Buffer stdin_buffer; /* Buffer for stdin data. */
28 static Buffer stdout_buffer; /* Buffer for stdout data. */
29 static Buffer stderr_buffer; /* Buffer for stderr data. */
30 static int fdin; /* Descriptor for stdin (for writing) */
31 static int fdout; /* Descriptor for stdout (for reading);
32 May be same number as fdin. */
33 static int fderr; /* Descriptor for stderr. May be -1. */
34 static long stdin_bytes = 0; /* Number of bytes written to stdin. */
35 static long stdout_bytes = 0; /* Number of stdout bytes sent to client. */
36 static long stderr_bytes = 0; /* Number of stderr bytes sent to client. */
37 static long fdout_bytes = 0; /* Number of stdout bytes read from program. */
38 static int stdin_eof = 0; /* EOF message received from client. */
39 static int fdout_eof = 0; /* EOF encountered reading from fdout. */
40 static int fderr_eof = 0; /* EOF encountered readung from fderr. */
41 static int connection_in; /* Connection to client (input). */
42 static int connection_out; /* Connection to client (output). */
43 static unsigned int buffer_high;/* "Soft" max buffer size. */
44 static int max_fd; /* Max file descriptor number for select(). */
47 * This SIGCHLD kludge is used to detect when the child exits. The server
48 * will exit after that, as soon as forwarded connections have terminated.
50 * After SIGCHLD child_has_selected is set to 1 after the first pass
51 * through the wait_until_can_do_something() select(). This ensures
52 * that the child's output gets a chance to drain before it is yanked.
55 static pid_t child_pid; /* Pid of the child. */
56 static volatile int child_terminated; /* The child has terminated. */
57 static volatile int child_has_selected; /* Child has had chance to drain. */
58 static volatile int child_wait_status; /* Status from wait(). */
60 void server_init_dispatch(void);
63 sigchld_handler(int sig)
65 int save_errno = errno;
68 debug("Received SIGCHLD.");
69 wait_pid = wait((int *) &child_wait_status);
71 if (wait_pid != child_pid)
72 error("Strange, got SIGCHLD and wait returned pid %d but child is %d",
74 if (WIFEXITED(child_wait_status) ||
75 WIFSIGNALED(child_wait_status))
77 child_has_selected = 0;
79 signal(SIGCHLD, sigchld_handler);
83 sigchld_handler2(int sig)
85 int save_errno = errno;
86 debug("Received SIGCHLD.");
88 signal(SIGCHLD, sigchld_handler2);
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. */
170 * Read packets from the client unless we have too much buffered
171 * stdin or channel data.
174 // wrong: bad conditionXXX
175 if (channel_not_very_much_buffered_data())
176 FD_SET(connection_in, readset);
178 if (buffer_len(&stdin_buffer) < 4096 &&
179 channel_not_very_much_buffered_data())
180 FD_SET(connection_in, readset);
184 * If there is not too much data already buffered going to the
185 * client, try to get some more data from the program.
187 if (!compat20 && packet_not_very_much_data_to_write()) {
189 FD_SET(fdout, readset);
191 FD_SET(fderr, readset);
195 /* Set masks for channel descriptors. */
196 channel_prepare_select(readset, writeset);
199 * If we have buffered packet data going to the client, mark that
202 if (packet_have_data_to_write())
203 FD_SET(connection_out, writeset);
205 /* If we have buffered data, try to write some of that data to the
207 if (!compat20 && fdin != -1 && buffer_len(&stdin_buffer) > 0)
208 FD_SET(fdin, writeset);
210 /* Update the maximum descriptor number if appropriate. */
211 if (channel_max_fd() > max_fd)
212 max_fd = channel_max_fd();
215 * If child has terminated and there is enough buffer space to read
216 * from it, then read as much as is available and exit.
218 if (child_terminated && packet_not_very_much_data_to_write())
219 if (max_time_milliseconds == 0)
220 max_time_milliseconds = 100;
222 if (max_time_milliseconds == 0)
225 tv.tv_sec = max_time_milliseconds / 1000;
226 tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
230 debug("tvp!=NULL kid %d mili %d", child_terminated, max_time_milliseconds);
232 /* Wait for something to happen, or the timeout to expire. */
233 ret = select(max_fd + 1, readset, writeset, NULL, tvp);
237 error("select: %.100s", strerror(errno));
242 if (child_terminated)
243 child_has_selected = 1;
247 * Processes input from the client and the program. Input data is stored
248 * in buffers and processed later.
251 process_input(fd_set * readset)
256 /* Read and buffer any input data from the client. */
257 if (FD_ISSET(connection_in, readset)) {
258 len = read(connection_in, buf, sizeof(buf));
260 verbose("Connection closed by remote host.");
264 * There is a kernel bug on Solaris that causes select to
265 * sometimes wake up even though there is no data available.
267 if (len < 0 && errno == EAGAIN)
271 verbose("Read error from remote host: %.100s", strerror(errno));
274 /* Buffer any received data. */
275 packet_process_incoming(buf, len);
280 /* Read and buffer any available stdout data from the program. */
281 if (!fdout_eof && FD_ISSET(fdout, readset)) {
282 len = read(fdout, buf, sizeof(buf));
286 buffer_append(&stdout_buffer, buf, len);
290 /* Read and buffer any available stderr data from the program. */
291 if (!fderr_eof && FD_ISSET(fderr, readset)) {
292 len = read(fderr, buf, sizeof(buf));
296 buffer_append(&stderr_buffer, buf, len);
301 * Sends data from internal buffers to client program stdin.
304 process_output(fd_set * writeset)
308 /* Write buffered data to program stdin. */
309 if (!compat20 && fdin != -1 && FD_ISSET(fdin, writeset)) {
310 len = write(fdin, buffer_ptr(&stdin_buffer),
311 buffer_len(&stdin_buffer));
319 shutdown(fdin, SHUT_WR); /* We will no longer send. */
323 /* Successful write. Consume the data from the buffer. */
324 buffer_consume(&stdin_buffer, len);
325 /* Update the count of bytes written to the program. */
329 /* Send any buffered packet data to the client. */
330 if (FD_ISSET(connection_out, writeset))
335 * Wait until all buffered output has been sent to the client.
336 * This is used when the program terminates.
341 /* Send any buffered stdout data to the client. */
342 if (buffer_len(&stdout_buffer) > 0) {
343 packet_start(SSH_SMSG_STDOUT_DATA);
344 packet_put_string(buffer_ptr(&stdout_buffer),
345 buffer_len(&stdout_buffer));
347 /* Update the count of sent bytes. */
348 stdout_bytes += buffer_len(&stdout_buffer);
350 /* Send any buffered stderr data to the client. */
351 if (buffer_len(&stderr_buffer) > 0) {
352 packet_start(SSH_SMSG_STDERR_DATA);
353 packet_put_string(buffer_ptr(&stderr_buffer),
354 buffer_len(&stderr_buffer));
356 /* Update the count of sent bytes. */
357 stderr_bytes += buffer_len(&stderr_buffer);
359 /* Wait until all buffered data has been written to the client. */
364 process_buffered_input_packets()
366 dispatch_run(DISPATCH_NONBLOCK, NULL);
370 * Performs the interactive session. This handles data transmission between
371 * the client and the program. Note that the notion of stdin, stdout, and
372 * stderr in this function is sort of reversed: this function writes to
373 * stdin (of the child program), and reads from stdout and stderr (of the
377 server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
379 int wait_status; /* Status returned by wait(). */
380 pid_t wait_pid; /* pid returned by wait(). */
381 int waiting_termination = 0; /* Have displayed waiting close message. */
382 unsigned int max_time_milliseconds;
383 unsigned int previous_stdout_buffer_bytes;
384 unsigned int stdout_buffer_bytes;
387 debug("Entering interactive session.");
389 /* Initialize the SIGCHLD kludge. */
391 child_terminated = 0;
392 child_has_selected = 0;
393 signal(SIGCHLD, sigchld_handler);
395 /* Initialize our global variables. */
399 connection_in = packet_get_connection_in();
400 connection_out = packet_get_connection_out();
402 previous_stdout_buffer_bytes = 0;
404 /* Set approximate I/O buffer size. */
405 if (packet_is_interactive())
408 buffer_high = 64 * 1024;
410 /* Initialize max_fd to the maximum of the known file descriptors. */
414 if (fderr != -1 && fderr > max_fd)
416 if (connection_in > max_fd)
417 max_fd = connection_in;
418 if (connection_out > max_fd)
419 max_fd = connection_out;
421 /* Initialize Initialize buffers. */
422 buffer_init(&stdin_buffer);
423 buffer_init(&stdout_buffer);
424 buffer_init(&stderr_buffer);
427 * If we have no separate fderr (which is the case when we have a pty
428 * - there we cannot make difference between data sent to stdout and
429 * stderr), indicate that we have seen an EOF from stderr. This way
430 * we don\'t need to check the descriptor everywhere.
435 server_init_dispatch();
437 /* Main loop of the server for the interactive session mode. */
439 fd_set readset, writeset;
441 /* Process buffered packets from the client. */
442 process_buffered_input_packets();
445 * If we have received eof, and there is no more pending
446 * input data, cause a real eof by closing fdin.
448 if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
455 shutdown(fdin, SHUT_WR); /* We will no longer send. */
459 /* Make packets from buffered stderr data to send to the client. */
460 make_packets_from_stderr_data();
463 * Make packets from buffered stdout data to send to the
464 * client. If there is very little to send, this arranges to
465 * not send them now, but to wait a short while to see if we
466 * are getting more data. This is necessary, as some systems
467 * wake up readers from a pty after each separate character.
469 max_time_milliseconds = 0;
470 stdout_buffer_bytes = buffer_len(&stdout_buffer);
471 if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
472 stdout_buffer_bytes != previous_stdout_buffer_bytes) {
473 /* try again after a while */
474 max_time_milliseconds = 10;
477 make_packets_from_stdout_data();
479 previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);
481 /* Send channel data to the client. */
482 if (packet_not_very_much_data_to_write())
483 channel_output_poll();
486 * Bail out of the loop if the program has closed its output
487 * descriptors, and we have no more data to send to the
488 * client, and there is no pending buffered data.
490 if (((fdout_eof && fderr_eof) ||
491 (child_terminated && child_has_selected)) &&
492 !packet_have_data_to_write() &&
493 (buffer_len(&stdout_buffer) == 0) &&
494 (buffer_len(&stderr_buffer) == 0)) {
495 if (!channel_still_open())
497 if (!waiting_termination) {
498 const char *s = "Waiting for forwarded connections to terminate...\r\n";
500 waiting_termination = 1;
501 buffer_append(&stderr_buffer, s, strlen(s));
503 /* Display list of open channels. */
504 cp = channel_open_message();
505 buffer_append(&stderr_buffer, cp, strlen(cp));
509 /* Sleep in select() until we can do something. */
510 wait_until_can_do_something(&readset, &writeset,
511 max_time_milliseconds);
513 /* Process any channel events. */
514 channel_after_select(&readset, &writeset);
516 /* Process input from the client and from program stdout/stderr. */
517 process_input(&readset);
519 /* Process output to the client and to program stdin. */
520 process_output(&writeset);
523 /* Cleanup and termination code. */
525 /* Wait until all output has been sent to the client. */
528 debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
529 stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);
531 /* Free and clear the buffers. */
532 buffer_free(&stdin_buffer);
533 buffer_free(&stdout_buffer);
534 buffer_free(&stderr_buffer);
536 /* Close the file descriptors. */
549 /* Stop listening for channels; this removes unix domain sockets. */
550 channel_stop_listening();
552 /* Wait for the child to exit. Get its exit status. */
553 wait_pid = wait(&wait_status);
556 * It is possible that the wait was handled by SIGCHLD
557 * handler. This may result in either: this call
558 * returning with EINTR, or: this call returning ECHILD.
560 if (child_terminated)
561 wait_status = child_wait_status;
563 packet_disconnect("wait: %.100s", strerror(errno));
565 /* Check if it matches the process we forked. */
567 error("Strange, wait returned pid %d, expected %d",
571 /* We no longer want our SIGCHLD handler to be called. */
572 signal(SIGCHLD, SIG_DFL);
574 /* Check if it exited normally. */
575 if (WIFEXITED(wait_status)) {
576 /* Yes, normal exit. Get exit status and send it to the client. */
577 debug("Command exited with status %d.", WEXITSTATUS(wait_status));
578 packet_start(SSH_SMSG_EXITSTATUS);
579 packet_put_int(WEXITSTATUS(wait_status));
584 * Wait for exit confirmation. Note that there might be
585 * other packets coming before it; however, the program has
586 * already died so we just ignore them. The client is
587 * supposed to respond with the confirmation when it receives
592 type = packet_read(&plen);
594 while (type != SSH_CMSG_EXIT_CONFIRMATION);
596 debug("Received exit confirmation.");
599 /* Check if the program terminated due to a signal. */
600 if (WIFSIGNALED(wait_status))
601 packet_disconnect("Command terminated on signal %d.",
602 WTERMSIG(wait_status));
604 /* Some weird exit cause. Just exit. */
605 packet_disconnect("wait returned status %04x.", wait_status);
612 fd_set readset, writeset;
617 debug("Entering interactive session for SSH2.");
619 signal(SIGCHLD, sigchld_handler2);
620 child_terminated = 0;
621 connection_in = packet_get_connection_in();
622 connection_out = packet_get_connection_out();
623 max_fd = connection_in;
624 if (connection_out > max_fd)
625 max_fd = connection_out;
626 server_init_dispatch();
629 process_buffered_input_packets();
630 if (!had_channel && channel_still_open())
632 if (had_channel && !channel_still_open()) {
633 debug("!channel_still_open.");
636 if (packet_not_very_much_data_to_write())
637 channel_output_poll();
638 wait_until_can_do_something(&readset, &writeset, 0);
639 if (child_terminated) {
640 while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
641 session_close_by_pid(pid, status);
642 child_terminated = 0;
644 channel_after_select(&readset, &writeset);
645 process_input(&readset);
646 process_output(&writeset);
648 signal(SIGCHLD, SIG_DFL);
649 while ((pid = waitpid(-1, &status, WNOHANG)) > 0)
650 session_close_by_pid(pid, status);
651 channel_stop_listening();
655 server_input_stdin_data(int type, int plen)
658 unsigned int data_len;
660 /* Stdin data from the client. Append it to the buffer. */
661 /* Ignore any data if the client has closed stdin. */
664 data = packet_get_string(&data_len);
665 packet_integrity_check(plen, (4 + data_len), type);
666 buffer_append(&stdin_buffer, data, data_len);
667 memset(data, 0, data_len);
672 server_input_eof(int type, int plen)
675 * Eof from the client. The stdin descriptor to the
676 * program will be closed when all buffered data has
679 debug("EOF received for stdin.");
680 packet_integrity_check(plen, 0, type);
685 server_input_window_size(int type, int plen)
687 int row = packet_get_int();
688 int col = packet_get_int();
689 int xpixel = packet_get_int();
690 int ypixel = packet_get_int();
692 debug("Window change received.");
693 packet_integrity_check(plen, 4 * 4, type);
695 pty_change_window_size(fdin, row, col, xpixel, ypixel);
699 input_direct_tcpip(void)
702 char *target, *originator;
703 int target_port, originator_port;
705 target = packet_get_string(NULL);
706 target_port = packet_get_int();
707 originator = packet_get_string(NULL);
708 originator_port = packet_get_int();
710 /* XXX check permission */
711 sock = channel_connect_to(target, target_port);
716 return channel_new("direct-tcpip", SSH_CHANNEL_OPEN,
717 sock, sock, -1, 4*1024, 32*1024, 0, xstrdup("direct-tcpip"));
721 server_input_channel_open(int type, int plen)
731 ctype = packet_get_string(&len);
732 rchan = packet_get_int();
733 rwindow = packet_get_int();
734 rmaxpack = packet_get_int();
736 debug("channel_input_open: ctype %s rchan %d win %d max %d",
737 ctype, rchan, rwindow, rmaxpack);
739 if (strcmp(ctype, "session") == 0) {
740 debug("open session");
743 * A server session has no fd to read or write
744 * until a CHANNEL_REQUEST for a shell is made,
745 * so we set the type to SSH_CHANNEL_LARVAL.
746 * Additionally, a callback for handling all
747 * CHANNEL_REQUEST messages is registered.
749 id = channel_new(ctype, SSH_CHANNEL_LARVAL,
750 -1, -1, -1, 0, 32*1024, 0, xstrdup("server-session"));
751 if (session_open(id) == 1) {
752 channel_register_callback(id, SSH2_MSG_CHANNEL_REQUEST,
753 session_input_channel_req, (void *)0);
754 channel_register_cleanup(id, session_close_by_channel);
755 c = channel_lookup(id);
757 debug("session open failed, free channel %d", id);
760 } else if (strcmp(ctype, "direct-tcpip") == 0) {
761 debug("open direct-tcpip");
762 id = input_direct_tcpip();
764 c = channel_lookup(id);
767 debug("confirm %s", ctype);
768 c->remote_id = rchan;
769 c->remote_window = rwindow;
770 c->remote_maxpacket = rmaxpack;
772 packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
773 packet_put_int(c->remote_id);
774 packet_put_int(c->self);
775 packet_put_int(c->local_window);
776 packet_put_int(c->local_maxpacket);
779 debug("failure %s", ctype);
780 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
781 packet_put_int(rchan);
782 packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
783 packet_put_cstring("bla bla");
784 packet_put_cstring("");
791 server_init_dispatch_20()
793 debug("server_init_dispatch_20");
794 dispatch_init(&dispatch_protocol_error);
795 dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
796 dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
797 dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
798 dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
799 dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
800 dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
801 dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
802 dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &channel_input_channel_request);
803 dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
806 server_init_dispatch_13()
808 debug("server_init_dispatch_13");
810 dispatch_set(SSH_CMSG_EOF, &server_input_eof);
811 dispatch_set(SSH_CMSG_STDIN_DATA, &server_input_stdin_data);
812 dispatch_set(SSH_CMSG_WINDOW_SIZE, &server_input_window_size);
813 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
814 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
815 dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
816 dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
817 dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
818 dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
821 server_init_dispatch_15()
823 server_init_dispatch_13();
824 debug("server_init_dispatch_15");
825 dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
826 dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_oclose);
829 server_init_dispatch()
832 server_init_dispatch_20();
834 server_init_dispatch_13();
836 server_init_dispatch_15();