- stevesk@cvs.openbsd.org 2006/08/01 23:36:12

[openssh-git.git] / clientloop.c

/* $OpenBSD: clientloop.c,v 1.174 2006/08/01 23:22:47 stevesk Exp $ */
/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, 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"

#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/param.h>
#ifdef HAVE_SYS_STAT_H
# include <sys/stat.h>
#endif
#ifdef HAVE_SYS_TIME_H
# include <sys/time.h>
#endif
#include <sys/socket.h>

#include <ctype.h>
#include <errno.h>
#ifdef HAVE_PATHS_H
#include <paths.h>
#endif
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>

#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 "sshconnect.h"
#include "authfd.h"
#include "atomicio.h"
#include "sshpty.h"
#include "misc.h"
#include "monitor_fdpass.h"
#include "match.h"
#include "msg.h"

/* import options */
extern Options options;

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

/* Flag indicating that no shell has been requested */
extern int no_shell_flag;

/* Control socket */
extern int control_fd;

/*
 * 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 volatile sig_atomic_t quit_pending; /* Set non-zero to quit the 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 int server_alive_timeouts = 0;

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

struct confirm_ctx {
        int want_tty;
        int want_subsys;
        int want_x_fwd;
        int want_agent_fwd;
        Buffer cmd;
        char *term;
        struct termios tio;
        char **env;
};

/*XXX*/
extern Kex *xxx_kex;

void ssh_process_session2_setup(int, int, int, Buffer *);

/* Restores stdin to blocking mode. */

static void
leave_non_blocking(void)
{
        if (in_non_blocking_mode) {
                unset_nonblock(fileno(stdin));
                in_non_blocking_mode = 0;
        }
}

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

static void
enter_non_blocking(void)
{
        in_non_blocking_mode = 1;
        set_nonblock(fileno(stdin));
}

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

#define SSH_X11_PROTO "MIT-MAGIC-COOKIE-1"
void
client_x11_get_proto(const char *display, const char *xauth_path,
    u_int trusted, char **_proto, char **_data)
{
        char cmd[1024];
        char line[512];
        char xdisplay[512];
        static char proto[512], data[512];
        FILE *f;
        int got_data = 0, generated = 0, do_unlink = 0, i;
        char *xauthdir, *xauthfile;
        struct stat st;

        xauthdir = xauthfile = NULL;
        *_proto = proto;
        *_data = data;
        proto[0] = data[0] = '\0';

        if (xauth_path == NULL ||(stat(xauth_path, &st) == -1)) {
                debug("No xauth program.");
        } else {
                if (display == NULL) {
                        debug("x11_get_proto: DISPLAY not set");
                        return;
                }
                /*
                 * Handle FamilyLocal case where $DISPLAY does
                 * not match an authorization entry.  For this we
                 * just try "xauth list unix:displaynum.screennum".
                 * XXX: "localhost" match to determine FamilyLocal
                 *      is not perfect.
                 */
                if (strncmp(display, "localhost:", 10) == 0) {
                        snprintf(xdisplay, sizeof(xdisplay), "unix:%s",
                            display + 10);
                        display = xdisplay;
                }
                if (trusted == 0) {
                        xauthdir = xmalloc(MAXPATHLEN);
                        xauthfile = xmalloc(MAXPATHLEN);
                        strlcpy(xauthdir, "/tmp/ssh-XXXXXXXXXX", MAXPATHLEN);
                        if (mkdtemp(xauthdir) != NULL) {
                                do_unlink = 1;
                                snprintf(xauthfile, MAXPATHLEN, "%s/xauthfile",
                                    xauthdir);
                                snprintf(cmd, sizeof(cmd),
                                    "%s -f %s generate %s " SSH_X11_PROTO
                                    " untrusted timeout 1200 2>" _PATH_DEVNULL,
                                    xauth_path, xauthfile, display);
                                debug2("x11_get_proto: %s", cmd);
                                if (system(cmd) == 0)
                                        generated = 1;
                        }
                }
                snprintf(cmd, sizeof(cmd),
                    "%s %s%s list %s 2>" _PATH_DEVNULL,
                    xauth_path,
                    generated ? "-f " : "" ,
                    generated ? xauthfile : "",
                    display);
                debug2("x11_get_proto: %s", cmd);
                f = popen(cmd, "r");
                if (f && fgets(line, sizeof(line), f) &&
                    sscanf(line, "%*s %511s %511s", proto, data) == 2)
                        got_data = 1;
                if (f)
                        pclose(f);
        }

        if (do_unlink) {
                unlink(xauthfile);
                rmdir(xauthdir);
        }
        if (xauthdir)
                xfree(xauthdir);
        if (xauthfile)
                xfree(xauthfile);

        /*
         * If we didn't get authentication data, just make up some
         * data.  The forwarding code will check the validity of the
         * response anyway, and substitute this data.  The X11
         * server, however, will ignore this fake data and use
         * whatever authentication mechanisms it was using otherwise
         * for the local connection.
         */
        if (!got_data) {
                u_int32_t rnd = 0;

                logit("Warning: No xauth data; "
                    "using fake authentication data for X11 forwarding.");
                strlcpy(proto, SSH_X11_PROTO, sizeof proto);
                for (i = 0; i < 16; i++) {
                        if (i % 4 == 0)
                                rnd = arc4random();
                        snprintf(data + 2 * i, sizeof data - 2 * i, "%02x",
                            rnd & 0xff);
                        rnd >>= 8;
                }
        }
}

/*
 * 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;

        debug2("client_check_window_change: changed");

        if (compat20) {
                channel_send_window_changes();
        } else {
                if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0)
                        return;
                packet_start(SSH_CMSG_WINDOW_SIZE);
                packet_put_int((u_int)ws.ws_row);
                packet_put_int((u_int)ws.ws_col);
                packet_put_int((u_int)ws.ws_xpixel);
                packet_put_int((u_int)ws.ws_ypixel);
                packet_send();
        }
}

static void
client_global_request_reply(int type, u_int32_t seq, void *ctxt)
{
        server_alive_timeouts = 0;
        client_global_request_reply_fwd(type, seq, ctxt);
}

static void
server_alive_check(void)
{
        if (++server_alive_timeouts > options.server_alive_count_max)
                packet_disconnect("Timeout, server not responding.");
        packet_start(SSH2_MSG_GLOBAL_REQUEST);
        packet_put_cstring("keepalive@openssh.com");
        packet_put_char(1);     /* boolean: want reply */
        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, u_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);

        if (control_fd != -1)
                FD_SET(control_fd, *readsetp);

        /*
         * 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();
}

static void
client_suspend_self(Buffer *bin, Buffer *bout, Buffer *berr)
{
        /* Flush stdout and stderr buffers. */
        if (buffer_len(bout) > 0)
                atomicio(vwrite, fileno(stdout), buffer_ptr(bout), buffer_len(bout));
        if (buffer_len(berr) > 0)
                atomicio(vwrite, 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);

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

        /* Reset window sizes in case they have changed */
        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.
                 */
                if (len < 0 && (errno == EAGAIN || errno == EINTR))
                        len = 0;

                if (len < 0) {
                        /* An error has encountered.  Perhaps there is a network problem. */
                        snprintf(buf, sizeof buf, "Read from remote host %.300s: %.100s\r\n",
                                 host, strerror(errno));
                        buffer_append(&stderr_buffer, buf, strlen(buf));
                        quit_pending = 1;
                        return;
                }
                packet_process_incoming(buf, len);
        }
}

static void
client_subsystem_reply(int type, u_int32_t seq, void *ctxt)
{
        int id;
        Channel *c;

        id = packet_get_int();
        packet_check_eom();

        if ((c = channel_lookup(id)) == NULL) {
                error("%s: no channel for id %d", __func__, id);
                return;
        }

        if (type == SSH2_MSG_CHANNEL_SUCCESS)
                debug2("Request suceeded on channel %d", id);
        else if (type == SSH2_MSG_CHANNEL_FAILURE) {
                error("Request failed on channel %d", id);
                channel_free(c);
        }
}

static void
client_extra_session2_setup(int id, void *arg)
{
        struct confirm_ctx *cctx = arg;
        const char *display;
        Channel *c;
        int i;

        if (cctx == NULL)
                fatal("%s: cctx == NULL", __func__);
        if ((c = channel_lookup(id)) == NULL)
                fatal("%s: no channel for id %d", __func__, id);

        display = getenv("DISPLAY");
        if (cctx->want_x_fwd && options.forward_x11 && display != NULL) {
                char *proto, *data;
                /* Get reasonable local authentication information. */
                client_x11_get_proto(display, options.xauth_location,
                    options.forward_x11_trusted, &proto, &data);
                /* Request forwarding with authentication spoofing. */
                debug("Requesting X11 forwarding with authentication spoofing.");
                x11_request_forwarding_with_spoofing(id, display, proto, data);
                /* XXX wait for reply */
        }

        if (cctx->want_agent_fwd && options.forward_agent) {
                debug("Requesting authentication agent forwarding.");
                channel_request_start(id, "auth-agent-req@openssh.com", 0);
                packet_send();
        }

        client_session2_setup(id, cctx->want_tty, cctx->want_subsys,
            cctx->term, &cctx->tio, c->rfd, &cctx->cmd, cctx->env,
            client_subsystem_reply);

        c->confirm_ctx = NULL;
        buffer_free(&cctx->cmd);
        xfree(cctx->term);
        if (cctx->env != NULL) {
                for (i = 0; cctx->env[i] != NULL; i++)
                        xfree(cctx->env[i]);
                xfree(cctx->env);
        }
        xfree(cctx);
}

static void
client_process_control(fd_set *readset)
{
        Buffer m;
        Channel *c;
        int client_fd, new_fd[3], ver, allowed;
        socklen_t addrlen;
        struct sockaddr_storage addr;
        struct confirm_ctx *cctx;
        char *cmd;
        u_int i, len, env_len, command, flags;
        uid_t euid;
        gid_t egid;

        /*
         * Accept connection on control socket
         */
        if (control_fd == -1 || !FD_ISSET(control_fd, readset))
                return;

        memset(&addr, 0, sizeof(addr));
        addrlen = sizeof(addr);
        if ((client_fd = accept(control_fd,
            (struct sockaddr*)&addr, &addrlen)) == -1) {
                error("%s accept: %s", __func__, strerror(errno));
                return;
        }

        if (getpeereid(client_fd, &euid, &egid) < 0) {
                error("%s getpeereid failed: %s", __func__, strerror(errno));
                close(client_fd);
                return;
        }
        if ((euid != 0) && (getuid() != euid)) {
                error("control mode uid mismatch: peer euid %u != uid %u",
                    (u_int) euid, (u_int) getuid());
                close(client_fd);
                return;
        }

        unset_nonblock(client_fd);

        /* Read command */
        buffer_init(&m);
        if (ssh_msg_recv(client_fd, &m) == -1) {
                error("%s: client msg_recv failed", __func__);
                close(client_fd);
                buffer_free(&m);
                return;
        }
        if ((ver = buffer_get_char(&m)) != SSHMUX_VER) {
                error("%s: wrong client version %d", __func__, ver);
                buffer_free(&m);
                close(client_fd);
                return;
        }

        allowed = 1;
        command = buffer_get_int(&m);
        flags = buffer_get_int(&m);

        buffer_clear(&m);

        switch (command) {
        case SSHMUX_COMMAND_OPEN:
                if (options.control_master == SSHCTL_MASTER_ASK ||
                    options.control_master == SSHCTL_MASTER_AUTO_ASK)
                        allowed = ask_permission("Allow shared connection "
                            "to %s? ", host);
                /* continue below */
                break;
        case SSHMUX_COMMAND_TERMINATE:
                if (options.control_master == SSHCTL_MASTER_ASK ||
                    options.control_master == SSHCTL_MASTER_AUTO_ASK)
                        allowed = ask_permission("Terminate shared connection "
                            "to %s? ", host);
                if (allowed)
                        quit_pending = 1;
                /* FALLTHROUGH */
        case SSHMUX_COMMAND_ALIVE_CHECK:
                /* Reply for SSHMUX_COMMAND_TERMINATE and ALIVE_CHECK */
                buffer_clear(&m);
                buffer_put_int(&m, allowed);
                buffer_put_int(&m, getpid());
                if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
                        error("%s: client msg_send failed", __func__);
                        close(client_fd);
                        buffer_free(&m);
                        return;
                }
                buffer_free(&m);
                close(client_fd);
                return;
        default:
                error("Unsupported command %d", command);
                buffer_free(&m);
                close(client_fd);
                return;
        }

        /* Reply for SSHMUX_COMMAND_OPEN */
        buffer_clear(&m);
        buffer_put_int(&m, allowed);
        buffer_put_int(&m, getpid());
        if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
                error("%s: client msg_send failed", __func__);
                close(client_fd);
                buffer_free(&m);
                return;
        }

        if (!allowed) {
                error("Refused control connection");
                close(client_fd);
                buffer_free(&m);
                return;
        }

        buffer_clear(&m);
        if (ssh_msg_recv(client_fd, &m) == -1) {
                error("%s: client msg_recv failed", __func__);
                close(client_fd);
                buffer_free(&m);
                return;
        }
        if ((ver = buffer_get_char(&m)) != SSHMUX_VER) {
                error("%s: wrong client version %d", __func__, ver);
                buffer_free(&m);
                close(client_fd);
                return;
        }

        cctx = xcalloc(1, sizeof(*cctx));
        cctx->want_tty = (flags & SSHMUX_FLAG_TTY) != 0;
        cctx->want_subsys = (flags & SSHMUX_FLAG_SUBSYS) != 0;
        cctx->want_x_fwd = (flags & SSHMUX_FLAG_X11_FWD) != 0;
        cctx->want_agent_fwd = (flags & SSHMUX_FLAG_AGENT_FWD) != 0;
        cctx->term = buffer_get_string(&m, &len);

        cmd = buffer_get_string(&m, &len);
        buffer_init(&cctx->cmd);
        buffer_append(&cctx->cmd, cmd, strlen(cmd));

        env_len = buffer_get_int(&m);
        env_len = MIN(env_len, 4096);
        debug3("%s: receiving %d env vars", __func__, env_len);
        if (env_len != 0) {
                cctx->env = xcalloc(env_len + 1, sizeof(*cctx->env));
                for (i = 0; i < env_len; i++)
                        cctx->env[i] = buffer_get_string(&m, &len);
                cctx->env[i] = NULL;
        }

        debug2("%s: accepted tty %d, subsys %d, cmd %s", __func__,
            cctx->want_tty, cctx->want_subsys, cmd);
        xfree(cmd);

        /* Gather fds from client */
        new_fd[0] = mm_receive_fd(client_fd);
        new_fd[1] = mm_receive_fd(client_fd);
        new_fd[2] = mm_receive_fd(client_fd);

        debug2("%s: got fds stdin %d, stdout %d, stderr %d", __func__,
            new_fd[0], new_fd[1], new_fd[2]);

        /* Try to pick up ttymodes from client before it goes raw */
        if (cctx->want_tty && tcgetattr(new_fd[0], &cctx->tio) == -1)
                error("%s: tcgetattr: %s", __func__, strerror(errno));

        /* This roundtrip is just for synchronisation of ttymodes */
        buffer_clear(&m);
        if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
                error("%s: client msg_send failed", __func__);
                close(client_fd);
                close(new_fd[0]);
                close(new_fd[1]);
                close(new_fd[2]);
                buffer_free(&m);
                xfree(cctx->term);
                if (env_len != 0) {
                        for (i = 0; i < env_len; i++)
                                xfree(cctx->env[i]);
                        xfree(cctx->env);
                }
                return;
        }
        buffer_free(&m);

        /* enable nonblocking unless tty */
        if (!isatty(new_fd[0]))
                set_nonblock(new_fd[0]);
        if (!isatty(new_fd[1]))
                set_nonblock(new_fd[1]);
        if (!isatty(new_fd[2]))
                set_nonblock(new_fd[2]);

        set_nonblock(client_fd);

        c = channel_new("session", SSH_CHANNEL_OPENING,
            new_fd[0], new_fd[1], new_fd[2],
            CHAN_SES_WINDOW_DEFAULT, CHAN_SES_PACKET_DEFAULT,
            CHAN_EXTENDED_WRITE, "client-session", /*nonblock*/0);

        /* XXX */
        c->ctl_fd = client_fd;

        debug3("%s: channel_new: %d", __func__, c->self);

        channel_send_open(c->self);
        channel_register_confirm(c->self, client_extra_session2_setup, cctx);
}

static void
process_cmdline(void)
{
        void (*handler)(int);
        char *s, *cmd, *cancel_host;
        int delete = 0;
        int local = 0;
        u_short cancel_port;
        Forward fwd;

        leave_raw_mode();
        handler = signal(SIGINT, SIG_IGN);
        cmd = s = read_passphrase("\r\nssh> ", RP_ECHO);
        if (s == NULL)
                goto out;
        while (*s && isspace(*s))
                s++;
        if (*s == '-')
                s++;    /* Skip cmdline '-', if any */
        if (*s == '\0')
                goto out;

        if (*s == 'h' || *s == 'H' || *s == '?') {
                logit("Commands:");
                logit("      -L[bind_address:]port:host:hostport    "
                    "Request local forward");
                logit("      -R[bind_address:]port:host:hostport    "
                    "Request remote forward");
                logit("      -KR[bind_address:]port                 "
                    "Cancel remote forward");
                if (!options.permit_local_command)
                        goto out;
                logit("      !args                                  "
                    "Execute local command");
                goto out;
        }

        if (*s == '!' && options.permit_local_command) {
                s++;
                ssh_local_cmd(s);
                goto out;
        }

        if (*s == 'K') {
                delete = 1;
                s++;
        }
        if (*s != 'L' && *s != 'R') {
                logit("Invalid command.");
                goto out;
        }
        if (*s == 'L')
                local = 1;
        if (local && delete) {
                logit("Not supported.");
                goto out;
        }
        if ((!local || delete) && !compat20) {
                logit("Not supported for SSH protocol version 1.");
                goto out;
        }

        s++;
        while (*s && isspace(*s))
                s++;

        if (delete) {
                cancel_port = 0;
                cancel_host = hpdelim(&s);      /* may be NULL */
                if (s != NULL) {
                        cancel_port = a2port(s);
                        cancel_host = cleanhostname(cancel_host);
                } else {
                        cancel_port = a2port(cancel_host);
                        cancel_host = NULL;
                }
                if (cancel_port == 0) {
                        logit("Bad forwarding close port");
                        goto out;
                }
                channel_request_rforward_cancel(cancel_host, cancel_port);
        } else {
                if (!parse_forward(&fwd, s)) {
                        logit("Bad forwarding specification.");
                        goto out;
                }
                if (local) {
                        if (channel_setup_local_fwd_listener(fwd.listen_host,
                            fwd.listen_port, fwd.connect_host,
                            fwd.connect_port, options.gateway_ports) < 0) {
                                logit("Port forwarding failed.");
                                goto out;
                        }
                } else {
                        if (channel_request_remote_forwarding(fwd.listen_host,
                            fwd.listen_port, fwd.connect_host,
                            fwd.connect_port) < 0) {
                                logit("Port forwarding failed.");
                                goto out;
                        }
                }

                logit("Forwarding port.");
        }

out:
        signal(SIGINT, handler);
        enter_raw_mode();
        if (cmd)
                xfree(cmd);
}

/* process the characters one by one */
static int
process_escapes(Buffer *bin, Buffer *bout, Buffer *berr, char *buf, int len)
{
        char string[1024];
        pid_t pid;
        int bytes = 0;
        u_int i;
        u_char ch;
        char *s;

        if (len <= 0)
                return (0);

        for (i = 0; i < (u_int)len; i++) {
                /* Get one character at a time. */
                ch = buf[i];

                if (escape_pending) {
                        /* We have previously seen an escape character. */
                        /* Clear the flag now. */
                        escape_pending = 0;

                        /* Process the escaped character. */
                        switch (ch) {
                        case '.':
                                /* Terminate the connection. */
                                snprintf(string, sizeof string, "%c.\r\n", escape_char);
                                buffer_append(berr, string, strlen(string));

                                quit_pending = 1;
                                return -1;

                        case 'Z' - 64:
                                /* Suspend the program. */
                                /* Print a message to that effect to the user. */
                                snprintf(string, sizeof string, "%c^Z [suspend ssh]\r\n", escape_char);
                                buffer_append(berr, string, strlen(string));

                                /* Restore terminal modes and suspend. */
                                client_suspend_self(bin, bout, berr);

                                /* We have been continued. */
                                continue;

                        case 'B':
                                if (compat20) {
                                        snprintf(string, sizeof string,
                                            "%cB\r\n", escape_char);
                                        buffer_append(berr, string,
                                            strlen(string));
                                        channel_request_start(session_ident,
                                            "break", 0);
                                        packet_put_int(1000);
                                        packet_send();
                                }
                                continue;

                        case 'R':
                                if (compat20) {
                                        if (datafellows & SSH_BUG_NOREKEY)
                                                logit("Server does not support re-keying");
                                        else
                                                need_rekeying = 1;
                                }
                                continue;

                        case '&':
                                /*
                                 * Detach the program (continue to serve connections,
                                 * but put in background and no more new connections).
                                 */
                                /* Restore tty modes. */
                                leave_raw_mode();

                                /* Stop listening for new connections. */
                                channel_stop_listening();

                                snprintf(string, sizeof string,
                                    "%c& [backgrounded]\n", escape_char);
                                buffer_append(berr, string, strlen(string));

                                /* Fork into background. */
                                pid = fork();
                                if (pid < 0) {
                                        error("fork: %.100s", strerror(errno));
                                        continue;
                                }
                                if (pid != 0) { /* This is the parent. */
                                        /* The parent just exits. */
                                        exit(0);
                                }
                                /* The child continues serving connections. */
                                if (compat20) {
                                        buffer_append(bin, "\004", 1);
                                        /* fake EOF on stdin */
                                        return -1;
                                } else if (!stdin_eof) {
                                        /*
                                         * Sending SSH_CMSG_EOF alone does not always appear
                                         * to be enough.  So we try to send an EOF character
                                         * first.
                                         */
                                        packet_start(SSH_CMSG_STDIN_DATA);
                                        packet_put_string("\004", 1);
                                        packet_send();
                                        /* Close stdin. */
                                        stdin_eof = 1;
                                        if (buffer_len(bin) == 0) {
                                                packet_start(SSH_CMSG_EOF);
                                                packet_send();
                                        }
                                }
                                continue;

                        case '?':
                                snprintf(string, sizeof string,
"%c?\r\n\
Supported escape sequences:\r\n\
%c.  - terminate connection\r\n\
%cB  - send a BREAK to the remote system\r\n\
%cC  - open a command line\r\n\
%cR  - Request rekey (SSH protocol 2 only)\r\n\
%c^Z - suspend ssh\r\n\
%c#  - list forwarded connections\r\n\
%c&  - background ssh (when waiting for connections to terminate)\r\n\
%c?  - this message\r\n\
%c%c  - send the escape character by typing it twice\r\n\
(Note that escapes are only recognized immediately after newline.)\r\n",
                                    escape_char, escape_char, escape_char, escape_char,
                                    escape_char, escape_char, escape_char, escape_char,
                                    escape_char, escape_char, escape_char);
                                buffer_append(berr, string, strlen(string));
                                continue;

                        case '#':
                                snprintf(string, sizeof string, "%c#\r\n", escape_char);
                                buffer_append(berr, string, strlen(string));
                                s = channel_open_message();
                                buffer_append(berr, s, strlen(s));
                                xfree(s);
                                continue;

                        case 'C':
                                process_cmdline();
                                continue;

                        default:
                                if (ch != escape_char) {
                                        buffer_put_char(bin, escape_char);
                                        bytes++;
                                }
                                /* Escaped characters fall through here */
                                break;
                        }
                } else {
                        /*
                         * The previous character was not an escape char. Check if this
                         * is an escape.
                         */
                        if (last_was_cr && ch == escape_char) {
                                /* It is. Set the flag and continue to next character. */
                                escape_pending = 1;
                                continue;
                        }
                }

                /*
                 * Normal character.  Record whether it was a newline,
                 * and append it to the buffer.
                 */
                last_was_cr = (ch == '\r' || ch == '\n');
                buffer_put_char(bin, ch);
                bytes++;
        }
        return bytes;
}

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

        /* Read input from stdin. */
        if (FD_ISSET(fileno(stdin), readset)) {
                /* Read as much as possible. */
                len = read(fileno(stdin), buf, sizeof(buf));
                if (len < 0 && (errno == EAGAIN || errno == EINTR))
                        return;         /* we'll try again later */
                if (len <= 0) {
                        /*
                         * Received EOF or error.  They are treated
                         * similarly, except that an error message is printed
                         * if it was an error condition.
                         */
                        if (len < 0) {
                                snprintf(buf, sizeof buf, "read: %.100s\r\n", strerror(errno));
                                buffer_append(&stderr_buffer, buf, strlen(buf));
                        }
                        /* Mark that we have seen EOF. */
                        stdin_eof = 1;
                        /*
                         * Send an EOF message to the server unless there is
                         * data in the buffer.  If there is data in the
                         * buffer, no message will be sent now.  Code
                         * elsewhere will send the EOF when the buffer
                         * becomes empty if stdin_eof is set.
                         */
                        if (buffer_len(&stdin_buffer) == 0) {
                                packet_start(SSH_CMSG_EOF);
                                packet_send();
                        }
                } else if (escape_char == SSH_ESCAPECHAR_NONE) {
                        /*
                         * Normal successful read, and no escape character.
                         * Just append the data to buffer.
                         */
                        buffer_append(&stdin_buffer, buf, len);
                } else {
                        /*
                         * Normal, successful read.  But we have an escape character
                         * and have to process the characters one by one.
                         */
                        if (process_escapes(&stdin_buffer, &stdout_buffer,
                            &stderr_buffer, buf, len) == -1)
                                return;
                }
        }
}

static void
client_process_output(fd_set *writeset)
{
        int len;
        char buf[100];

        /* Write buffered output to stdout. */
        if (FD_ISSET(fileno(stdout), writeset)) {
                /* Write as much data as possible. */
                len = write(fileno(stdout), buffer_ptr(&stdout_buffer),
                    buffer_len(&stdout_buffer));
                if (len <= 0) {
                        if (errno == EINTR || errno == EAGAIN)
                                len = 0;
                        else {
                                /*
                                 * An error or EOF was encountered.  Put an
                                 * error message to stderr buffer.
                                 */
                                snprintf(buf, sizeof buf, "write stdout: %.50s\r\n", strerror(errno));
                                buffer_append(&stderr_buffer, buf, strlen(buf));
                                quit_pending = 1;
                                return;
                        }
                }
                /* Consume printed data from the buffer. */
                buffer_consume(&stdout_buffer, len);
                stdout_bytes += len;
        }
        /* Write buffered output to stderr. */
        if (FD_ISSET(fileno(stderr), writeset)) {
                /* Write as much data as possible. */
                len = write(fileno(stderr), buffer_ptr(&stderr_buffer),
                    buffer_len(&stderr_buffer));
                if (len <= 0) {
                        if (errno == EINTR || errno == EAGAIN)
                                len = 0;
                        else {
                                /* EOF or error, but can't even print error message. */
                                quit_pending = 1;
                                return;
                        }
                }
                /* Consume printed characters from the buffer. */
                buffer_consume(&stderr_buffer, len);
                stderr_bytes += len;
        }
}

/*
 * Get packets from the connection input buffer, and process them as long as
 * there are packets available.
 *
 * Any unknown packets received during the actual
 * session cause the session to terminate.  This is
 * intended to make debugging easier since no
 * confirmations are sent.  Any compatible protocol
 * extensions must be negotiated during the
 * preparatory phase.
 */

static void
client_process_buffered_input_packets(void)
{
        dispatch_run(DISPATCH_NONBLOCK, &quit_pending, compat20 ? xxx_kex : NULL);
}

/* scan buf[] for '~' before sending data to the peer */

static int
simple_escape_filter(Channel *c, char *buf, int len)
{
        /* XXX we assume c->extended is writeable */
        return process_escapes(&c->input, &c->output, &c->extended, buf, len);
}

static void
client_channel_closed(int id, void *arg)
{
        channel_cancel_cleanup(id);
        session_closed = 1;
        leave_raw_mode();
}

/*
 * Implements the interactive session with the server.  This is called after
 * the user has been authenticated, and a command has been started on the
 * remote host.  If escape_char != SSH_ESCAPECHAR_NONE, it is the character
 * used as an escape character for terminating or suspending the session.
 */

int
client_loop(int have_pty, int escape_char_arg, int ssh2_chan_id)
{
        fd_set *readset = NULL, *writeset = NULL;
        double start_time, total_time;
        int max_fd = 0, max_fd2 = 0, len, rekeying = 0;
        u_int nalloc = 0;
        char buf[100];

        debug("Entering interactive session.");

        start_time = get_current_time();

        /* Initialize variables. */
        escape_pending = 0;
        last_was_cr = 1;
        exit_status = -1;
        stdin_eof = 0;
        buffer_high = 64 * 1024;
        connection_in = packet_get_connection_in();
        connection_out = packet_get_connection_out();
        max_fd = MAX(connection_in, connection_out);
        if (control_fd != -1)
                max_fd = MAX(max_fd, control_fd);

        if (!compat20) {
                /* enable nonblocking unless tty */
                if (!isatty(fileno(stdin)))
                        set_nonblock(fileno(stdin));
                if (!isatty(fileno(stdout)))
                        set_nonblock(fileno(stdout));
                if (!isatty(fileno(stderr)))
                        set_nonblock(fileno(stderr));
                max_fd = MAX(max_fd, fileno(stdin));
                max_fd = MAX(max_fd, fileno(stdout));
                max_fd = MAX(max_fd, fileno(stderr));
        }
        stdin_bytes = 0;
        stdout_bytes = 0;
        stderr_bytes = 0;
        quit_pending = 0;
        escape_char = escape_char_arg;

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

        client_init_dispatch();

        /*
         * Set signal handlers, (e.g. to restore non-blocking mode)
         * but don't overwrite SIG_IGN, matches behaviour from rsh(1)
         */
        if (signal(SIGHUP, SIG_IGN) != SIG_IGN)
                signal(SIGHUP, signal_handler);
        if (signal(SIGINT, SIG_IGN) != SIG_IGN)
                signal(SIGINT, signal_handler);
        if (signal(SIGQUIT, SIG_IGN) != SIG_IGN)
                signal(SIGQUIT, signal_handler);
        if (signal(SIGTERM, SIG_IGN) != SIG_IGN)
                signal(SIGTERM, signal_handler);
        signal(SIGWINCH, window_change_handler);

        if (have_pty)
                enter_raw_mode();

        if (compat20) {
                session_ident = ssh2_chan_id;
                if (escape_char != SSH_ESCAPECHAR_NONE)
                        channel_register_filter(session_ident,
                            simple_escape_filter, NULL);
                if (session_ident != -1)
                        channel_register_cleanup(session_ident,
                            client_channel_closed, 0);
        } else {
                /* Check if we should immediately send eof on stdin. */
                client_check_initial_eof_on_stdin();
        }

        /* Main loop of the client for the interactive session mode. */
        while (!quit_pending) {

                /* Process buffered packets sent by the server. */
                client_process_buffered_input_packets();

                if (compat20 && session_closed && !channel_still_open())
                        break;

                rekeying = (xxx_kex != NULL && !xxx_kex->done);

                if (rekeying) {
                        debug("rekeying in progress");
                } else {
                        /*
                         * Make packets of buffered stdin data, and buffer
                         * them for sending to the server.
                         */
                        if (!compat20)
                                client_make_packets_from_stdin_data();

                        /*
                         * Make packets from buffered channel data, and
                         * enqueue them for sending to the server.
                         */
                        if (packet_not_very_much_data_to_write())
                                channel_output_poll();

                        /*
                         * Check if the window size has changed, and buffer a
                         * message about it to the server if so.
                         */
                        client_check_window_change();

                        if (quit_pending)
                                break;
                }
                /*
                 * Wait until we have something to do (something becomes
                 * available on one of the descriptors).
                 */
                max_fd2 = max_fd;
                client_wait_until_can_do_something(&readset, &writeset,
                    &max_fd2, &nalloc, rekeying);

                if (quit_pending)
                        break;

                /* Do channel operations unless rekeying in progress. */
                if (!rekeying) {
                        channel_after_select(readset, writeset);
                        if (need_rekeying || packet_need_rekeying()) {
                                debug("need rekeying");
                                xxx_kex->done = 0;
                                kex_send_kexinit(xxx_kex);
                                need_rekeying = 0;
                        }
                }

                /* Buffer input from the connection.  */
                client_process_net_input(readset);

                /* Accept control connections.  */
                client_process_control(readset);

                if (quit_pending)
                        break;

                if (!compat20) {
                        /* Buffer data from stdin */
                        client_process_input(readset);
                        /*
                         * Process output to stdout and stderr.  Output to
                         * the connection is processed elsewhere (above).
                         */
                        client_process_output(writeset);
                }

                /* Send as much buffered packet data as possible to the sender. */
                if (FD_ISSET(connection_out, writeset))
                        packet_write_poll();
        }
        if (readset)
                xfree(readset);
        if (writeset)
                xfree(writeset);

        /* Terminate the session. */

        /* Stop watching for window change. */
        signal(SIGWINCH, SIG_DFL);

        channel_free_all();

        if (have_pty)
                leave_raw_mode();

        /* restore blocking io */
        if (!isatty(fileno(stdin)))
                unset_nonblock(fileno(stdin));
        if (!isatty(fileno(stdout)))
                unset_nonblock(fileno(stdout));
        if (!isatty(fileno(stderr)))
                unset_nonblock(fileno(stderr));

        /*
         * If there was no shell or command requested, there will be no remote
         * exit status to be returned.  In that case, clear error code if the
         * connection was deliberately terminated at this end.
         */
        if (no_shell_flag && received_signal == SIGTERM) {
                received_signal = 0;
                exit_status = 0;
        }

        if (received_signal)
                fatal("Killed by signal %d.", (int) received_signal);

        /*
         * In interactive mode (with pseudo tty) display a message indicating
         * that the connection has been closed.
         */
        if (have_pty && options.log_level != SYSLOG_LEVEL_QUIET) {
                snprintf(buf, sizeof buf, "Connection to %.64s closed.\r\n", host);
                buffer_append(&stderr_buffer, buf, strlen(buf));
        }

        /* Output any buffered data for stdout. */
        while (buffer_len(&stdout_buffer) > 0) {
                len = write(fileno(stdout), buffer_ptr(&stdout_buffer),
                    buffer_len(&stdout_buffer));
                if (len <= 0) {
                        error("Write failed flushing stdout buffer.");
                        break;
                }
                buffer_consume(&stdout_buffer, len);
                stdout_bytes += len;
        }

        /* Output any buffered data for stderr. */
        while (buffer_len(&stderr_buffer) > 0) {
                len = write(fileno(stderr), buffer_ptr(&stderr_buffer),
                    buffer_len(&stderr_buffer));
                if (len <= 0) {
                        error("Write failed flushing stderr buffer.");
                        break;
                }
                buffer_consume(&stderr_buffer, len);
                stderr_bytes += len;
        }

        /* Clear and free any buffers. */
        memset(buf, 0, sizeof(buf));
        buffer_free(&stdin_buffer);
        buffer_free(&stdout_buffer);
        buffer_free(&stderr_buffer);

        /* Report bytes transferred, and transfer rates. */
        total_time = get_current_time() - start_time;
        debug("Transferred: stdin %lu, stdout %lu, stderr %lu bytes in %.1f seconds",
            stdin_bytes, stdout_bytes, stderr_bytes, total_time);
        if (total_time > 0)
                debug("Bytes per second: stdin %.1f, stdout %.1f, stderr %.1f",
                    stdin_bytes / total_time, stdout_bytes / total_time,
                    stderr_bytes / total_time);

        /* Return the exit status of the program. */
        debug("Exit status %d", exit_status);
        return exit_status;
}

/*********/

static void
client_input_stdout_data(int type, u_int32_t seq, void *ctxt)
{
        u_int data_len;
        char *data = packet_get_string(&data_len);
        packet_check_eom();
        buffer_append(&stdout_buffer, data, data_len);
        memset(data, 0, data_len);
        xfree(data);
}
static void
client_input_stderr_data(int type, u_int32_t seq, void *ctxt)
{
        u_int data_len;
        char *data = packet_get_string(&data_len);
        packet_check_eom();
        buffer_append(&stderr_buffer, data, data_len);
        memset(data, 0, data_len);
        xfree(data);
}
static void
client_input_exit_status(int type, u_int32_t seq, void *ctxt)
{
        exit_status = packet_get_int();
        packet_check_eom();
        /* Acknowledge the exit. */
        packet_start(SSH_CMSG_EXIT_CONFIRMATION);
        packet_send();
        /*
         * Must wait for packet to be sent since we are
         * exiting the loop.
         */
        packet_write_wait();
        /* Flag that we want to exit. */
        quit_pending = 1;
}
static void
client_input_agent_open(int type, u_int32_t seq, void *ctxt)
{
        Channel *c = NULL;
        int remote_id, sock;

        /* Read the remote channel number from the message. */
        remote_id = packet_get_int();
        packet_check_eom();

        /*
         * Get a connection to the local authentication agent (this may again
         * get forwarded).
         */
        sock = ssh_get_authentication_socket();

        /*
         * If we could not connect the agent, send an error message back to
         * the server. This should never happen unless the agent dies,
         * because authentication forwarding is only enabled if we have an
         * agent.
         */
        if (sock >= 0) {
                c = channel_new("", SSH_CHANNEL_OPEN, sock, sock,
                    -1, 0, 0, 0, "authentication agent connection", 1);
                c->remote_id = remote_id;
                c->force_drain = 1;
        }
        if (c == NULL) {
                packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
                packet_put_int(remote_id);
        } else {
                /* Send a confirmation to the remote host. */
                debug("Forwarding authentication connection.");
                packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
                packet_put_int(remote_id);
                packet_put_int(c->self);
        }
        packet_send();
}

static Channel *
client_request_forwarded_tcpip(const char *request_type, int rchan)
{
        Channel *c = NULL;
        char *listen_address, *originator_address;
        int listen_port, originator_port;
        int sock;

        /* Get rest of the packet */
        listen_address = packet_get_string(NULL);
        listen_port = packet_get_int();
        originator_address = packet_get_string(NULL);
        originator_port = packet_get_int();
        packet_check_eom();

        debug("client_request_forwarded_tcpip: listen %s port %d, originator %s port %d",
            listen_address, listen_port, originator_address, originator_port);

        sock = channel_connect_by_listen_address(listen_port);
        if (sock < 0) {
                xfree(originator_address);
                xfree(listen_address);
                return NULL;
        }
        c = channel_new("forwarded-tcpip",
            SSH_CHANNEL_CONNECTING, sock, sock, -1,
            CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_WINDOW_DEFAULT, 0,
            originator_address, 1);
        xfree(originator_address);
        xfree(listen_address);
        return c;
}

static Channel *
client_request_x11(const char *request_type, int rchan)
{
        Channel *c = NULL;
        char *originator;
        int originator_port;
        int sock;

        if (!options.forward_x11) {
                error("Warning: ssh server tried X11 forwarding.");
                error("Warning: this is probably a break-in attempt by a malicious server.");
                return NULL;
        }
        originator = packet_get_string(NULL);
        if (datafellows & SSH_BUG_X11FWD) {
                debug2("buggy server: x11 request w/o originator_port");
                originator_port = 0;
        } else {
                originator_port = packet_get_int();
        }
        packet_check_eom();
        /* XXX check permission */
        debug("client_request_x11: request from %s %d", originator,
            originator_port);
        xfree(originator);
        sock = x11_connect_display();
        if (sock < 0)
                return NULL;
        c = channel_new("x11",
            SSH_CHANNEL_X11_OPEN, sock, sock, -1,
            CHAN_TCP_WINDOW_DEFAULT, CHAN_X11_PACKET_DEFAULT, 0, "x11", 1);
        c->force_drain = 1;
        return c;
}

static Channel *
client_request_agent(const char *request_type, int rchan)
{
        Channel *c = NULL;
        int sock;

        if (!options.forward_agent) {
                error("Warning: ssh server tried agent forwarding.");
                error("Warning: this is probably a break-in attempt by a malicious server.");
                return NULL;
        }
        sock =  ssh_get_authentication_socket();
        if (sock < 0)
                return NULL;
        c = channel_new("authentication agent connection",
            SSH_CHANNEL_OPEN, sock, sock, -1,
            CHAN_X11_WINDOW_DEFAULT, CHAN_TCP_WINDOW_DEFAULT, 0,
            "authentication agent connection", 1);
        c->force_drain = 1;
        return c;
}

/* XXXX move to generic input handler */
static void
client_input_channel_open(int type, u_int32_t seq, void *ctxt)
{
        Channel *c = NULL;
        char *ctype;
        int rchan;
        u_int rmaxpack, rwindow, len;

        ctype = packet_get_string(&len);
        rchan = packet_get_int();
        rwindow = packet_get_int();
        rmaxpack = packet_get_int();

        debug("client_input_channel_open: ctype %s rchan %d win %d max %d",
            ctype, rchan, rwindow, rmaxpack);

        if (strcmp(ctype, "forwarded-tcpip") == 0) {
                c = client_request_forwarded_tcpip(ctype, rchan);
        } else if (strcmp(ctype, "x11") == 0) {
                c = client_request_x11(ctype, rchan);
        } else if (strcmp(ctype, "auth-agent@openssh.com") == 0) {
                c = client_request_agent(ctype, rchan);
        }
/* XXX duplicate : */
        if (c != NULL) {
                debug("confirm %s", ctype);
                c->remote_id = rchan;
                c->remote_window = rwindow;
                c->remote_maxpacket = rmaxpack;
                if (c->type != SSH_CHANNEL_CONNECTING) {
                        packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
                        packet_put_int(c->remote_id);
                        packet_put_int(c->self);
                        packet_put_int(c->local_window);
                        packet_put_int(c->local_maxpacket);
                        packet_send();
                }
        } else {
                debug("failure %s", ctype);
                packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
                packet_put_int(rchan);
                packet_put_int(SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED);
                if (!(datafellows & SSH_BUG_OPENFAILURE)) {
                        packet_put_cstring("open failed");
                        packet_put_cstring("");
                }
                packet_send();
        }
        xfree(ctype);
}
static void
client_input_channel_req(int type, u_int32_t seq, void *ctxt)
{
        Channel *c = NULL;
        int exitval, id, reply, success = 0;
        char *rtype;

        id = packet_get_int();
        rtype = packet_get_string(NULL);
        reply = packet_get_char();

        debug("client_input_channel_req: channel %d rtype %s reply %d",
            id, rtype, reply);

        if (id == -1) {
                error("client_input_channel_req: request for channel -1");
        } else if ((c = channel_lookup(id)) == NULL) {
                error("client_input_channel_req: channel %d: unknown channel", id);
        } else if (strcmp(rtype, "exit-status") == 0) {
                exitval = packet_get_int();
                if (id == session_ident) {
                        success = 1;
                        exit_status = exitval;
                } else if (c->ctl_fd == -1) {
                        error("client_input_channel_req: unexpected channel %d",
                            session_ident);
                } else {
                        atomicio(vwrite, c->ctl_fd, &exitval, sizeof(exitval));
                        success = 1;
                }
                packet_check_eom();
        }
        if (reply) {
                packet_start(success ?
                    SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
                packet_put_int(id);
                packet_send();
        }
        xfree(rtype);
}
static void
client_input_global_request(int type, u_int32_t seq, void *ctxt)
{
        char *rtype;
        int want_reply;
        int success = 0;

        rtype = packet_get_string(NULL);
        want_reply = packet_get_char();
        debug("client_input_global_request: rtype %s want_reply %d",
            rtype, want_reply);
        if (want_reply) {
                packet_start(success ?
                    SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
                packet_send();
                packet_write_wait();
        }
        xfree(rtype);
}

void
client_session2_setup(int id, int want_tty, int want_subsystem,
    const char *term, struct termios *tiop, int in_fd, Buffer *cmd, char **env,
    dispatch_fn *subsys_repl)
{
        int len;
        Channel *c = NULL;

        debug2("%s: id %d", __func__, id);

        if ((c = channel_lookup(id)) == NULL)
                fatal("client_session2_setup: channel %d: unknown channel", id);

        if (want_tty) {
                struct winsize ws;
                struct termios tio;

                /* Store window size in the packet. */
                if (ioctl(in_fd, TIOCGWINSZ, &ws) < 0)
                        memset(&ws, 0, sizeof(ws));

                channel_request_start(id, "pty-req", 0);
                packet_put_cstring(term != NULL ? term : "");
                packet_put_int((u_int)ws.ws_col);
                packet_put_int((u_int)ws.ws_row);
                packet_put_int((u_int)ws.ws_xpixel);
                packet_put_int((u_int)ws.ws_ypixel);
                tio = get_saved_tio();
                tty_make_modes(-1, tiop != NULL ? tiop : &tio);
                packet_send();
                /* XXX wait for reply */
                c->client_tty = 1;
        }

        /* Transfer any environment variables from client to server */
        if (options.num_send_env != 0 && env != NULL) {
                int i, j, matched;
                char *name, *val;

                debug("Sending environment.");
                for (i = 0; env[i] != NULL; i++) {
                        /* Split */
                        name = xstrdup(env[i]);
                        if ((val = strchr(name, '=')) == NULL) {
                                xfree(name);
                                continue;
                        }
                        *val++ = '\0';

                        matched = 0;
                        for (j = 0; j < options.num_send_env; j++) {
                                if (match_pattern(name, options.send_env[j])) {
                                        matched = 1;
                                        break;
                                }
                        }
                        if (!matched) {
                                debug3("Ignored env %s", name);
                                xfree(name);
                                continue;
                        }

                        debug("Sending env %s = %s", name, val);
                        channel_request_start(id, "env", 0);
                        packet_put_cstring(name);
                        packet_put_cstring(val);
                        packet_send();
                        xfree(name);
                }
        }

        len = buffer_len(cmd);
        if (len > 0) {
                if (len > 900)
                        len = 900;
                if (want_subsystem) {
                        debug("Sending subsystem: %.*s", len, (u_char*)buffer_ptr(cmd));
                        channel_request_start(id, "subsystem", subsys_repl != NULL);
                        if (subsys_repl != NULL) {
                                /* register callback for reply */
                                /* XXX we assume that client_loop has already been called */
                                dispatch_set(SSH2_MSG_CHANNEL_FAILURE, subsys_repl);
                                dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, subsys_repl);
                        }
                } else {
                        debug("Sending command: %.*s", len, (u_char*)buffer_ptr(cmd));
                        channel_request_start(id, "exec", 0);
                }
                packet_put_string(buffer_ptr(cmd), buffer_len(cmd));
                packet_send();
        } else {
                channel_request_start(id, "shell", 0);
                packet_send();
        }
}

static void
client_init_dispatch_20(void)
{
        dispatch_init(&dispatch_protocol_error);

        dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
        dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
        dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
        dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
        dispatch_set(SSH2_MSG_CHANNEL_OPEN, &client_input_channel_open);
        dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
        dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
        dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &client_input_channel_req);
        dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
        dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &client_input_global_request);

        /* rekeying */
        dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);

        /* global request reply messages */
        dispatch_set(SSH2_MSG_REQUEST_FAILURE, &client_global_request_reply);
        dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &client_global_request_reply);
}
static void
client_init_dispatch_13(void)
{
        dispatch_init(NULL);
        dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_close);
        dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, &channel_input_close_confirmation);
        dispatch_set(SSH_MSG_CHANNEL_DATA, &channel_input_data);
        dispatch_set(SSH_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
        dispatch_set(SSH_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
        dispatch_set(SSH_MSG_PORT_OPEN, &channel_input_port_open);
        dispatch_set(SSH_SMSG_EXITSTATUS, &client_input_exit_status);
        dispatch_set(SSH_SMSG_STDERR_DATA, &client_input_stderr_data);
        dispatch_set(SSH_SMSG_STDOUT_DATA, &client_input_stdout_data);

        dispatch_set(SSH_SMSG_AGENT_OPEN, options.forward_agent ?
            &client_input_agent_open : &deny_input_open);
        dispatch_set(SSH_SMSG_X11_OPEN, options.forward_x11 ?
            &x11_input_open : &deny_input_open);
}
static void
client_init_dispatch_15(void)
{
        client_init_dispatch_13();
        dispatch_set(SSH_MSG_CHANNEL_CLOSE, &channel_input_ieof);
        dispatch_set(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION, & channel_input_oclose);
}
static void
client_init_dispatch(void)
{
        if (compat20)
                client_init_dispatch_20();
        else if (compat13)
                client_init_dispatch_13();
        else
                client_init_dispatch_15();
}

/* client specific fatal cleanup */
void
cleanup_exit(int i)
{
        leave_raw_mode();
        leave_non_blocking();
        if (options.control_path != NULL && control_fd != -1)
                unlink(options.control_path);
        _exit(i);
}