Пример #1
0
/*
 * Sleep in select() until we can do something.  This will initialize the
 * select masks.  Upon return, the masks will indicate which descriptors
 * have data or can accept data.  Optionally, a maximum time can be specified
 * for the duration of the wait (0 = infinite).
 */
static void
wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp, int *maxfdp,
    u_int *nallocp, u_int64_t max_time_milliseconds)
{
	struct timeval tv, *tvp;
	int ret;
	time_t minwait_secs = 0;
	int client_alive_scheduled = 0;
	int program_alive_scheduled = 0;

	/* Allocate and update select() masks for channel descriptors. */
	channel_prepare_select(readsetp, writesetp, maxfdp, nallocp,
	    &minwait_secs, 0);

	if (minwait_secs != 0)
		max_time_milliseconds = MIN(max_time_milliseconds,
		    (u_int)minwait_secs * 1000);

	/*
	 * if using client_alive, set the max timeout accordingly,
	 * and indicate that this particular timeout was for client
	 * alive by setting the client_alive_scheduled flag.
	 *
	 * this could be randomized somewhat to make traffic
	 * analysis more difficult, but we're not doing it yet.
	 */
	if (compat20 &&
	    max_time_milliseconds == 0 && options.client_alive_interval) {
		client_alive_scheduled = 1;
		max_time_milliseconds =
		    (u_int64_t)options.client_alive_interval * 1000;
	}

	if (compat20) {
#if 0
		/* wrong: bad condition XXX */
		if (channel_not_very_much_buffered_data())
#endif
		FD_SET(connection_in, *readsetp);
	} else {
		/*
		 * Read packets from the client unless we have too much
		 * buffered stdin or channel data.
		 */
		if (buffer_len(&stdin_buffer) < buffer_high &&
		    channel_not_very_much_buffered_data())
			FD_SET(connection_in, *readsetp);
		/*
		 * If there is not too much data already buffered going to
		 * the client, try to get some more data from the program.
		 */
		if (packet_not_very_much_data_to_write()) {
			program_alive_scheduled = child_terminated;
			if (!fdout_eof)
				FD_SET(fdout, *readsetp);
			if (!fderr_eof)
				FD_SET(fderr, *readsetp);
		}
		/*
		 * If we have buffered data, try to write some of that data
		 * to the program.
		 */
		if (fdin != -1 && buffer_len(&stdin_buffer) > 0)
			FD_SET(fdin, *writesetp);
	}
	notify_prepare(*readsetp);

	/*
	 * If we have buffered packet data going to the client, mark that
	 * descriptor.
	 */
	if (packet_have_data_to_write())
		FD_SET(connection_out, *writesetp);

	/*
	 * If child has terminated and there is enough buffer space to read
	 * from it, then read as much as is available and exit.
	 */
	if (child_terminated && packet_not_very_much_data_to_write())
		if (max_time_milliseconds == 0 || client_alive_scheduled)
			max_time_milliseconds = 100;

	if (max_time_milliseconds == 0)
		tvp = NULL;
	else {
		tv.tv_sec = max_time_milliseconds / 1000;
		tv.tv_usec = 1000 * (max_time_milliseconds % 1000);
		tvp = &tv;
	}

	/* Wait for something to happen, or the timeout to expire. */
	ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);

	if (ret == -1) {
		memset(*readsetp, 0, *nallocp);
		memset(*writesetp, 0, *nallocp);
		if (errno != EINTR)
			error("select: %.100s", strerror(errno));
	} else {
		if (ret == 0 && client_alive_scheduled)
			client_alive_check();
		if (!compat20 && program_alive_scheduled && fdin_is_tty) {
			if (!fdout_eof)
				FD_SET(fdout, *readsetp);
			if (!fderr_eof)
				FD_SET(fderr, *readsetp);
		}
	}

	notify_done(*readsetp);
}
Пример #2
0
/*
 * Performs the interactive session.  This handles data transmission between
 * the client and the program.  Note that the notion of stdin, stdout, and
 * stderr in this function is sort of reversed: this function writes to
 * stdin (of the child program), and reads from stdout and stderr (of the
 * child program).
 */
void
server_loop(pid_t pid, int fdin_arg, int fdout_arg, int fderr_arg)
{
	fd_set *readset = NULL, *writeset = NULL;
	int max_fd = 0;
	u_int nalloc = 0;
	int wait_status;	/* Status returned by wait(). */
	pid_t wait_pid;		/* pid returned by wait(). */
	int waiting_termination = 0;	/* Have displayed waiting close message. */
	u_int64_t max_time_milliseconds;
	u_int previous_stdout_buffer_bytes;
	u_int stdout_buffer_bytes;
	int type;

	debug("Entering interactive session.");

	/* Initialize the SIGCHLD kludge. */
	child_terminated = 0;
	mysignal(SIGCHLD, sigchld_handler);

	if (!use_privsep) {
		signal(SIGTERM, sigterm_handler);
		signal(SIGINT, sigterm_handler);
		signal(SIGQUIT, sigterm_handler);
	}

	/* Initialize our global variables. */
	fdin = fdin_arg;
	fdout = fdout_arg;
	fderr = fderr_arg;

	/* nonblocking IO */
	set_nonblock(fdin);
	set_nonblock(fdout);
	/* we don't have stderr for interactive terminal sessions, see below */
	if (fderr != -1)
		set_nonblock(fderr);

	if (!(datafellows & SSH_BUG_IGNOREMSG) && isatty(fdin))
		fdin_is_tty = 1;

	connection_in = packet_get_connection_in();
	connection_out = packet_get_connection_out();

	notify_setup();

	previous_stdout_buffer_bytes = 0;

	/* Set approximate I/O buffer size. */
	if (packet_is_interactive())
		buffer_high = 4096;
	else
		buffer_high = 64 * 1024;

#if 0
	/* Initialize max_fd to the maximum of the known file descriptors. */
	max_fd = MAX(connection_in, connection_out);
	max_fd = MAX(max_fd, fdin);
	max_fd = MAX(max_fd, fdout);
	if (fderr != -1)
		max_fd = MAX(max_fd, fderr);
#endif

	/* Initialize Initialize buffers. */
	buffer_init(&stdin_buffer);
	buffer_init(&stdout_buffer);
	buffer_init(&stderr_buffer);

	/*
	 * If we have no separate fderr (which is the case when we have a pty
	 * - there we cannot make difference between data sent to stdout and
	 * stderr), indicate that we have seen an EOF from stderr.  This way
	 * we don't need to check the descriptor everywhere.
	 */
	if (fderr == -1)
		fderr_eof = 1;

	server_init_dispatch();

	/* Main loop of the server for the interactive session mode. */
	for (;;) {

		/* Process buffered packets from the client. */
		process_buffered_input_packets();

		/*
		 * If we have received eof, and there is no more pending
		 * input data, cause a real eof by closing fdin.
		 */
		if (stdin_eof && fdin != -1 && buffer_len(&stdin_buffer) == 0) {
			if (fdin != fdout)
				close(fdin);
			else
				shutdown(fdin, SHUT_WR); /* We will no longer send. */
			fdin = -1;
		}
		/* Make packets from buffered stderr data to send to the client. */
		make_packets_from_stderr_data();

		/*
		 * Make packets from buffered stdout data to send to the
		 * client. If there is very little to send, this arranges to
		 * not send them now, but to wait a short while to see if we
		 * are getting more data. This is necessary, as some systems
		 * wake up readers from a pty after each separate character.
		 */
		max_time_milliseconds = 0;
		stdout_buffer_bytes = buffer_len(&stdout_buffer);
		if (stdout_buffer_bytes != 0 && stdout_buffer_bytes < 256 &&
		    stdout_buffer_bytes != previous_stdout_buffer_bytes) {
			/* try again after a while */
			max_time_milliseconds = 10;
		} else {
			/* Send it now. */
			make_packets_from_stdout_data();
		}
		previous_stdout_buffer_bytes = buffer_len(&stdout_buffer);

		/* Send channel data to the client. */
		if (packet_not_very_much_data_to_write())
			channel_output_poll();

		/*
		 * Bail out of the loop if the program has closed its output
		 * descriptors, and we have no more data to send to the
		 * client, and there is no pending buffered data.
		 */
		if (fdout_eof && fderr_eof && !packet_have_data_to_write() &&
		    buffer_len(&stdout_buffer) == 0 && buffer_len(&stderr_buffer) == 0) {
			if (!channel_still_open())
				break;
			if (!waiting_termination) {
				const char *s = "Waiting for forwarded connections to terminate... (press ~& to background)\r\n";
				char *cp;
				waiting_termination = 1;
				buffer_append(&stderr_buffer, s, strlen(s));

				/* Display list of open channels. */
				cp = channel_open_message();
				buffer_append(&stderr_buffer, cp, strlen(cp));
				free(cp);
			}
		}
		max_fd = MAX(connection_in, connection_out);
		max_fd = MAX(max_fd, fdin);
		max_fd = MAX(max_fd, fdout);
		max_fd = MAX(max_fd, fderr);
		max_fd = MAX(max_fd, notify_pipe[0]);

		/* Sleep in select() until we can do something. */
		wait_until_can_do_something(&readset, &writeset, &max_fd,
		    &nalloc, max_time_milliseconds);

		if (received_sigterm) {
			logit("Exiting on signal %d", (int)received_sigterm);
			/* Clean up sessions, utmp, etc. */
			cleanup_exit(255);
		}

		/* Process any channel events. */
		channel_after_select(readset, writeset);

		/* Process input from the client and from program stdout/stderr. */
		process_input(readset);

		/* Process output to the client and to program stdin. */
		process_output(writeset);
	}
	free(readset);
	free(writeset);

	/* Cleanup and termination code. */

	/* Wait until all output has been sent to the client. */
	drain_output();

	debug("End of interactive session; stdin %ld, stdout (read %ld, sent %ld), stderr %ld bytes.",
	    stdin_bytes, fdout_bytes, stdout_bytes, stderr_bytes);

	/* Free and clear the buffers. */
	buffer_free(&stdin_buffer);
	buffer_free(&stdout_buffer);
	buffer_free(&stderr_buffer);

	/* Close the file descriptors. */
	if (fdout != -1)
		close(fdout);
	fdout = -1;
	fdout_eof = 1;
	if (fderr != -1)
		close(fderr);
	fderr = -1;
	fderr_eof = 1;
	if (fdin != -1)
		close(fdin);
	fdin = -1;

	channel_free_all();

	/* We no longer want our SIGCHLD handler to be called. */
	mysignal(SIGCHLD, SIG_DFL);

	while ((wait_pid = waitpid(-1, &wait_status, 0)) < 0)
		if (errno != EINTR)
			packet_disconnect("wait: %.100s", strerror(errno));
	if (wait_pid != pid)
		error("Strange, wait returned pid %ld, expected %ld",
		    (long)wait_pid, (long)pid);

	/* Check if it exited normally. */
	if (WIFEXITED(wait_status)) {
		/* Yes, normal exit.  Get exit status and send it to the client. */
		debug("Command exited with status %d.", WEXITSTATUS(wait_status));
		packet_start(SSH_SMSG_EXITSTATUS);
		packet_put_int(WEXITSTATUS(wait_status));
		packet_send();
		packet_write_wait();

		/*
		 * Wait for exit confirmation.  Note that there might be
		 * other packets coming before it; however, the program has
		 * already died so we just ignore them.  The client is
		 * supposed to respond with the confirmation when it receives
		 * the exit status.
		 */
		do {
			type = packet_read();
		}
		while (type != SSH_CMSG_EXIT_CONFIRMATION);

		debug("Received exit confirmation.");
		return;
	}
	/* Check if the program terminated due to a signal. */
	if (WIFSIGNALED(wait_status))
		packet_disconnect("Command terminated on signal %d.",
				  WTERMSIG(wait_status));

	/* Some weird exit cause.  Just exit. */
	packet_disconnect("wait returned status %04x.", wait_status);
	/* NOTREACHED */
}
Пример #3
0
static void
client_wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp,
    int *maxfdp, int *nallocp, int rekeying)
{
	struct timeval tv, *tvp;
	int ret;

	/* Add any selections by the channel mechanism. */
	channel_prepare_select(readsetp, writesetp, maxfdp, nallocp, rekeying);

	if (!compat20) {
		/* Read from the connection, unless our buffers are full. */
		if (buffer_len(&stdout_buffer) < buffer_high &&
		    buffer_len(&stderr_buffer) < buffer_high &&
		    channel_not_very_much_buffered_data())
			FD_SET(connection_in, *readsetp);
		/*
		 * Read from stdin, unless we have seen EOF or have very much
		 * buffered data to send to the server.
		 */
		if (!stdin_eof && packet_not_very_much_data_to_write())
			FD_SET(fileno(stdin), *readsetp);

		/* Select stdout/stderr if have data in buffer. */
		if (buffer_len(&stdout_buffer) > 0)
			FD_SET(fileno(stdout), *writesetp);
		if (buffer_len(&stderr_buffer) > 0)
			FD_SET(fileno(stderr), *writesetp);
	} else {
		/* channel_prepare_select could have closed the last channel */
		if (session_closed && !channel_still_open() &&
		    !packet_have_data_to_write()) {
			/* clear mask since we did not call select() */
			memset(*readsetp, 0, *nallocp);
			memset(*writesetp, 0, *nallocp);
			return;
		} else {
			FD_SET(connection_in, *readsetp);
		}
	}

	/* Select server connection if have data to write to the server. */
	if (packet_have_data_to_write())
		FD_SET(connection_out, *writesetp);

	/*
	 * Wait for something to happen.  This will suspend the process until
	 * some selected descriptor can be read, written, or has some other
	 * event pending.
	 */

	if (options.server_alive_interval == 0 || !compat20)
		tvp = NULL;
	else {  
		tv.tv_sec = options.server_alive_interval;
		tv.tv_usec = 0;
		tvp = &tv;
	}
	ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
	if (ret < 0) {
		char buf[100];

		/*
		 * We have to clear the select masks, because we return.
		 * We have to return, because the mainloop checks for the flags
		 * set by the signal handlers.
		 */
		memset(*readsetp, 0, *nallocp);
		memset(*writesetp, 0, *nallocp);

		if (errno == EINTR)
			return;
		/* Note: we might still have data in the buffers. */
		snprintf(buf, sizeof buf, "select: %s\r\n", strerror(errno));
		buffer_append(&stderr_buffer, buf, strlen(buf));
		quit_pending = 1;
	} else if (ret == 0)
		server_alive_check();
}