clientloop.c

OpenSSL Source code for SFTP, SSH, and many others

/*
 * Author: Tatu Ylonen <[e-mail]>
 * Copyright (c) 1995 Tatu Ylonen <[e-mail]>, Espoo, Finland
 *                    All rights reserved
 * The main loop for the interactive session (client side).
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 *
 *
 * Copyright (c) 1999 Theo de Raadt.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 *
 * SSH2 support added by Markus Friedl.
 * Copyright (c) 1999, 2000, 2001 Markus Friedl.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "includes.h"
RCSID("$OpenBSD: clientloop.c,v 1.101 2002/06/09 13:32:01 markus Exp $");

#include "ssh.h"
#include "ssh1.h"
#include "ssh2.h"
#include "xmalloc.h"
#include "packet.h"
#include "buffer.h"
#include "compat.h"
#include "channels.h"
#include "dispatch.h"
#include "buffer.h"
#include "bufaux.h"
#include "key.h"
#include "kex.h"
#include "log.h"
#include "readconf.h"
#include "clientloop.h"
#include "authfd.h"
#include "atomicio.h"
#include "sshtty.h"
#include "misc.h"
#include "readpass.h"

/* import options */
extern Options options;

/* Flag indicating that stdin should be redirected from /dev/null. */
extern int stdin_null_flag;

/*
 * Name of the host we are connecting to.  This is the name given on the
 * command line, or the HostName specified for the user-supplied name in a
 * configuration file.
 */
extern char *host;

/*
 * Flag to indicate that we have received a window change signal which has
 * not yet been processed.  This will cause a message indicating the new
 * window size to be sent to the server a little later.  This is volatile
 * because this is updated in a signal handler.
 */
static volatile sig_atomic_t received_window_change_signal = 0;
static volatile sig_atomic_t received_signal = 0;

/* Flag indicating whether the user\'s terminal is in non-blocking mode. */
static int in_non_blocking_mode = 0;

/* Common data for the client loop code. */
static int quit_pending;	/* Set to non-zero to quit the client loop. */
static int escape_char;		/* Escape character. */
static int escape_pending;	/* Last character was the escape character */
static int last_was_cr;		/* Last character was a newline. */
static int exit_status;		/* Used to store the exit status of the command. */
static int stdin_eof;		/* EOF has been encountered on standard error. */
static Buffer stdin_buffer;	/* Buffer for stdin data. */
static Buffer stdout_buffer;	/* Buffer for stdout data. */
static Buffer stderr_buffer;	/* Buffer for stderr data. */
static u_long stdin_bytes, stdout_bytes, stderr_bytes;
static u_int buffer_high;/* Soft max buffer size. */
static int connection_in;	/* Connection to server (input). */
static int connection_out;	/* Connection to server (output). */
static int need_rekeying;	/* Set to non-zero if rekeying is requested. */
static int session_closed = 0;	/* In SSH2: login session closed. */

static void client_init_dispatch(void);
int	session_ident = -1;

/*XXX*/
extern Kex *xxx_kex;

/* Restores stdin to blocking mode. */

static void
leave_non_blocking(void)
{
	if (in_non_blocking_mode) {
		(void) fcntl(fileno(stdin), F_SETFL, 0);
		in_non_blocking_mode = 0;
		fatal_remove_cleanup((void (*) (void *)) leave_non_blocking, NULL);
	}
}

/* Puts stdin terminal in non-blocking mode. */

static void
enter_non_blocking(void)
{
	in_non_blocking_mode = 1;
	(void) fcntl(fileno(stdin), F_SETFL, O_NONBLOCK);
	fatal_add_cleanup((void (*) (void *)) leave_non_blocking, NULL);
}

/*
 * Signal handler for the window change signal (SIGWINCH).  This just sets a
 * flag indicating that the window has changed.
 */

static void
window_change_handler(int sig)
{
	received_window_change_signal = 1;
	signal(SIGWINCH, window_change_handler);
}

/*
 * Signal handler for signals that cause the program to terminate.  These
 * signals must be trapped to restore terminal modes.
 */

static void
signal_handler(int sig)
{
	received_signal = sig;
	quit_pending = 1;
}

/*
 * Returns current time in seconds from Jan 1, 1970 with the maximum
 * available resolution.
 */

static double
get_current_time(void)
{
	struct timeval tv;
	gettimeofday(&tv, NULL);
	return (double) tv.tv_sec + (double) tv.tv_usec / 1000000.0;
}

/*
 * This is called when the interactive is entered.  This checks if there is
 * an EOF coming on stdin.  We must check this explicitly, as select() does
 * not appear to wake up when redirecting from /dev/null.
 */

static void
client_check_initial_eof_on_stdin(void)
{
	int len;
	char buf[1];

	/*
	 * If standard input is to be "redirected from /dev/null", we simply
	 * mark that we have seen an EOF and send an EOF message to the
	 * server. Otherwise, we try to read a single character; it appears
	 * that for some files, such /dev/null, select() never wakes up for
	 * read for this descriptor, which means that we never get EOF.  This
	 * way we will get the EOF if stdin comes from /dev/null or similar.
	 */
	if (stdin_null_flag) {
		/* Fake EOF on stdin. */
		debug("Sending eof.");
		stdin_eof = 1;
		packet_start(SSH_CMSG_EOF);
		packet_send();
	} else {
		enter_non_blocking();

		/* Check for immediate EOF on stdin. */
		len = read(fileno(stdin), buf, 1);
		if (len == 0) {
			/* EOF.  Record that we have seen it and send EOF to server. */
			debug("Sending eof.");
			stdin_eof = 1;
			packet_start(SSH_CMSG_EOF);
			packet_send();
		} else if (len > 0) {
			/*
			 * Got data.  We must store the data in the buffer,
			 * and also process it as an escape character if
			 * appropriate.
			 */
			if ((u_char) buf[0] == escape_char)
				escape_pending = 1;
			else
				buffer_append(&stdin_buffer, buf, 1);
		}
		leave_non_blocking();
	}
}


/*
 * Make packets from buffered stdin data, and buffer them for sending to the
 * connection.
 */

static void
client_make_packets_from_stdin_data(void)
{
	u_int len;

	/* Send buffered stdin data to the server. */
	while (buffer_len(&stdin_buffer) > 0 &&
	    packet_not_very_much_data_to_write()) {
		len = buffer_len(&stdin_buffer);
		/* Keep the packets at reasonable size. */
		if (len > packet_get_maxsize())
			len = packet_get_maxsize();
		packet_start(SSH_CMSG_STDIN_DATA);
		packet_put_string(buffer_ptr(&stdin_buffer), len);
		packet_send();
		buffer_consume(&stdin_buffer, len);
		stdin_bytes += len;
		/* If we have a pending EOF, send it now. */
		if (stdin_eof && buffer_len(&stdin_buffer) == 0) {
			packet_start(SSH_CMSG_EOF);
			packet_send();
		}
	}
}

/*
 * Checks if the client window has changed, and sends a packet about it to
 * the server if so.  The actual change is detected elsewhere (by a software
 * interrupt on Unix); this just checks the flag and sends a message if
 * appropriate.
 */

static void
client_check_window_change(void)
{
	struct winsize ws;

	if (! received_window_change_signal)
		return;
	/** XXX race */
	received_window_change_signal = 0;

	if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0)
		return;

	debug2("client_check_window_change: changed");

	if (compat20) {
		channel_request_start(session_ident, "window-change", 0);
		packet_put_int(ws.ws_col);
		packet_put_int(ws.ws_row);
		packet_put_int(ws.ws_xpixel);
		packet_put_int(ws.ws_ypixel);
		packet_send();
	} else {
		packet_start(SSH_CMSG_WINDOW_SIZE);
		packet_put_int(ws.ws_row);
		packet_put_int(ws.ws_col);
		packet_put_int(ws.ws_xpixel);
		packet_put_int(ws.ws_ypixel);
		packet_send();
	}
}

/*
 * Waits until the client can do something (some data becomes available on
 * one of the file descriptors).
 */

static void
client_wait_until_can_do_something(fd_set **readsetp, fd_set **writesetp,
    int *maxfdp, int *nallocp, int rekeying)
{
	/* 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. Note: if you want to implement SSH_MSG_IGNORE
	 * messages to fool traffic analysis, this might be the place to do
	 * it: just have a random timeout for the select, and send a random
	 * SSH_MSG_IGNORE packet when the timeout expires.
	 */

	if (select((*maxfdp)+1, *readsetp, *writesetp, NULL, NULL) < 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;
	}
}

static void
client_suspend_self(Buffer *bin, Buffer *bout, Buffer *berr)
{
	struct winsize oldws, newws;

	/* Flush stdout and stderr buffers. */
	if (buffer_len(bout) > 0)
		atomicio(write, fileno(stdout), buffer_ptr(bout), buffer_len(bout));
	if (buffer_len(berr) > 0)
		atomicio(write, fileno(stderr), buffer_ptr(berr), buffer_len(berr));

	leave_raw_mode();

	/*
	 * Free (and clear) the buffer to reduce the amount of data that gets
	 * written to swap.
	 */
	buffer_free(bin);
	buffer_free(bout);
	buffer_free(berr);

	/* Save old window size. */
	ioctl(fileno(stdin), TIOCGWINSZ, &oldws);

	/* Send the suspend signal to the program itself. */
	kill(getpid(), SIGTSTP);

	/* Check if the window size has changed. */
	if (ioctl(fileno(stdin), TIOCGWINSZ, &newws) >= 0 &&
	    (oldws.ws_row != newws.ws_row ||
	    oldws.ws_col != newws.ws_col ||
	    oldws.ws_xpixel != newws.ws_xpixel ||
	    oldws.ws_ypixel != newws.ws_ypixel))
		received_window_change_signal = 1;

	/* OK, we have been continued by the user. Reinitialize buffers. */
	buffer_init(bin);
	buffer_init(bout);
	buffer_init(berr);

	enter_raw_mode();
}

static void
client_process_net_input(fd_set * readset)
{
	int len;
	char buf[8192];

	/*
	 * Read input from the server, and add any such data to the buffer of
	 * the packet subsystem.
	 */
	if (FD_ISSET(connection_in, readset)) {
		/* Read as much as possible. */
		len = read(connection_in, buf, sizeof(buf));
		if (len == 0) {
			/* Received EOF.  The remote host has closed the connection. */
			snprintf(buf, sizeof buf, "Connection to %.300s closed by remote host.\r\n",
				 host);
			buffer_append(&stderr_buffer, buf, strlen(buf));
			quit_pending = 1;
			return;
		}
		/*
		 * There is a kernel bug on Solaris that causes select to
		 * sometimes wake up even though there is no data available.
		 */