text: /* $OpenBSD: serverloop.c,v 1.228 2021/07/16 09:00:23 djm Exp $ */
  /*
   * Author: Tatu Ylonen <ylo@cs.hut.fi>
   * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   *                    All rights reserved
   * Server main loop for handling the interactive session.
   *
   * 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".
   *
   * SSH2 support by Markus Friedl.
   * Copyright (c) 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/wait.h>
  #include <sys/socket.h>
  #ifdef HAVE_SYS_TIME_H
  # include <sys/time.h>
  #endif
  
  #include <netinet/in.h>
  
  #include <errno.h>
  #include <fcntl.h>
  #include <pwd.h>
  #include <limits.h>
  #include <signal.h>
  #include <string.h>
  #include <termios.h>
  #include <unistd.h>
  #include <stdarg.h>
  
  #include "openbsd-compat/sys-queue.h"
  #include "xmalloc.h"
  #include "packet.h"
  #include "sshbuf.h"
  #include "log.h"
  #include "misc.h"
  #include "servconf.h"
  #include "canohost.h"
  #include "sshpty.h"
  #include "channels.h"
  #include "compat.h"
  #include "ssh2.h"
  #include "sshkey.h"
  #include "cipher.h"
  #include "kex.h"
  #include "hostfile.h"
  #include "auth.h"
  #include "session.h"
  #include "dispatch.h"
  #include "auth-options.h"
  #include "serverloop.h"
  #include "ssherr.h"
  
  extern ServerOptions options;
  
  /* XXX */
  extern Authctxt *the_authctxt;
  extern struct sshauthopt *auth_opts;
  extern int use_privsep;
  
  static int no_more_sessions = 0; /* Disallow further sessions. */
  
  static volatile sig_atomic_t child_terminated = 0;	/* The child has terminated. */
  
  /* Cleanup on signals (!use_privsep case only) */
  static volatile sig_atomic_t received_sigterm = 0;
  
  /* prototypes */
  static void server_init_dispatch(struct ssh *);
  
  /* requested tunnel forwarding interface(s), shared with session.c */
  char *tun_fwd_ifnames = NULL;
  
  /* returns 1 if bind to specified port by specified user is permitted */
  static int
  bind_permitted(int port, uid_t uid)
  {
  	if (use_privsep)
  		return 1; /* allow system to decide */
  	if (port < IPPORT_RESERVED && uid != 0)
  		return 0;
  	return 1;
  }
  
  /*ARGSUSED*/
  static void
  sigchld_handler(int sig)
  {
  	child_terminated = 1;
  }
  
  /*ARGSUSED*/
  static void
  sigterm_handler(int sig)
  {
  	received_sigterm = sig;
  }
  
  static void
  client_alive_check(struct ssh *ssh)
  {
  	char remote_id[512];
  	int r, channel_id;
  
  	/* timeout, check to see how many we have had */
  	if (options.client_alive_count_max > 0 &&
  	    ssh_packet_inc_alive_timeouts(ssh) >
  	    options.client_alive_count_max) {
  		sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id));
  		logit("Timeout, client not responding from %s", remote_id);
  		cleanup_exit(255);
  	}
  
  	/*
  	 * send a bogus global/channel request with "wantreply",
  	 * we should get back a failure
  	 */
  	if ((channel_id = channel_find_open(ssh)) == -1) {
  		if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 ||
  		    (r = sshpkt_put_cstring(ssh, "keepalive@openssh.com"))
  		    != 0 ||
  		    (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */
  			fatal_fr(r, "compose");
  	} else {
  		channel_request_start(ssh, channel_id,
  		    "keepalive@openssh.com", 1);
  	}
  	if ((r = sshpkt_send(ssh)) != 0)
  		fatal_fr(r, "send");
  }
  
  /*
   * Sleep in pselect() until we can do something.  This will initialize the
   * pselect 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(struct ssh *ssh,
      int connection_in, int connection_out,
      fd_set **readsetp, fd_set **writesetp, int *maxfdp,
      u_int *nallocp, u_int64_t max_time_ms, sigset_t *sigsetp)
  {
  	struct timespec ts, *tsp;
  	int ret;
  	time_t minwait_secs = 0;
  	int client_alive_scheduled = 0;
  	/* time we last heard from the client OR sent a keepalive */
  	static time_t last_client_time;
  
  	/* Allocate and update pselect() masks for channel descriptors. */
  	channel_prepare_select(ssh, readsetp, writesetp, maxfdp,
  	    nallocp, &minwait_secs);
  
  	/* XXX need proper deadline system for rekey/client alive */
  	if (minwait_secs != 0)
  		max_time_ms = MINIMUM(max_time_ms, (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 (options.client_alive_interval) {
  		uint64_t keepalive_ms =
  		    (uint64_t)options.client_alive_interval * 1000;
  
  		if (max_time_ms == 0 || max_time_ms > keepalive_ms) {
  			max_time_ms = keepalive_ms;
  			client_alive_scheduled = 1;
  		}
  		if (last_client_time == 0)
  			last_client_time = monotime();
  	}
  
  #if 0
  	/* wrong: bad condition XXX */
  	if (channel_not_very_much_buffered_data())
  #endif
  	FD_SET(connection_in, *readsetp);
  
  	/*
  	 * If we have buffered packet data going to the client, mark that
  	 * descriptor.
  	 */
  	if (ssh_packet_have_data_to_write(ssh))
  		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 && ssh_packet_not_very_much_data_to_write(ssh))
  		if (max_time_ms == 0 || client_alive_scheduled)
  			max_time_ms = 100;
  
  	if (max_time_ms == 0)
  		tsp = NULL;
  	else {
  		ts.tv_sec = max_time_ms / 1000;
  		ts.tv_nsec = 1000000 * (max_time_ms % 1000);
  		tsp = &ts;
  	}
  
  	/* Wait for something to happen, or the timeout to expire. */
  	ret = pselect((*maxfdp)+1, *readsetp, *writesetp, NULL, tsp, sigsetp);
  
  	if (ret == -1) {
  		memset(*readsetp, 0, *nallocp);
  		memset(*writesetp, 0, *nallocp);
  		if (errno != EINTR)
  			error("pselect: %.100s", strerror(errno));
  	} else if (client_alive_scheduled) {
  		time_t now = monotime();
  
  		/*
  		 * If the pselect timed out, or returned for some other reason
  		 * but we haven't heard from the client in time, send keepalive.
  		 */
  		if (ret == 0 || (last_client_time != 0 && last_client_time +
  		    options.client_alive_interval <= now)) {
  			client_alive_check(ssh);
  			last_client_time = now;
  		} else if (FD_ISSET(connection_in, *readsetp)) {
  			last_client_time = now;
  		}
  	}
  }
  
  /*
   * Processes input from the client and the program.  Input data is stored
   * in buffers and processed later.
   */
  static int
  process_input(struct ssh *ssh, fd_set *readset, int connection_in)
  {
  	int r, len;
  	char buf[SSH_IOBUFSZ];
  
  	/* Read and buffer any input data from the client. */
  	if (FD_ISSET(connection_in, readset)) {
  		len = read(connection_in, buf, sizeof(buf));
  		if (len == 0) {
  			verbose("Connection closed by %.100s port %d",
  			    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
  			return -1;
  		} else if (len == -1) {
  			if (errno == EINTR || errno == EAGAIN ||
  			    errno == EWOULDBLOCK)
  				return 0;
  			verbose("Read error from remote host %s port %d: %s",
  			    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
  			    strerror(errno));
  			cleanup_exit(255);
  		}
  		/* Buffer any received data. */
  		if ((r = ssh_packet_process_incoming(ssh, buf, len)) != 0)
  			fatal_fr(r, "ssh_packet_process_incoming");
  		ssh->fdout_bytes += len;
  	}
  	return 0;
  }
  
  /*
   * Sends data from internal buffers to client program stdin.
   */
  static void
  process_output(struct ssh *ssh, fd_set *writeset, int connection_out)
  {
  	int r;
  
  	/* Send any buffered packet data to the client. */
  	if (FD_ISSET(connection_out, writeset)) {
  		if ((r = ssh_packet_write_poll(ssh)) != 0) {
  			sshpkt_fatal(ssh, r, "%s: ssh_packet_write_poll",
  			    __func__);
  		}
  	}
  }
  
  static void
  process_buffered_input_packets(struct ssh *ssh)
  {
  	ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL);
  }
  
  static void
  collect_children(struct ssh *ssh)
  {
  	pid_t pid;
  	int status;
  
  	if (child_terminated) {
  		debug("Received SIGCHLD.");
  		while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
  		    (pid == -1 && errno == EINTR))
  			if (pid > 0)
  				session_close_by_pid(ssh, pid, status);
  		child_terminated = 0;
  	}
  }
  
  void
  server_loop2(struct ssh *ssh, Authctxt *authctxt)
  {
  	fd_set *readset = NULL, *writeset = NULL;
  	int r, max_fd;
  	u_int nalloc = 0, connection_in, connection_out;
  	u_int64_t rekey_timeout_ms = 0;
  	sigset_t bsigset, osigset;
  
  	debug("Entering interactive session for SSH2.");
  	ssh->start_time = monotime_double();
  
  	if (sigemptyset(&bsigset) == -1 || sigaddset(&bsigset, SIGCHLD) == -1)
  		error_f("bsigset setup: %s", strerror(errno));
  	ssh_signal(SIGCHLD, sigchld_handler);
  	child_terminated = 0;
  	connection_in = ssh_packet_get_connection_in(ssh);
  	connection_out = ssh_packet_get_connection_out(ssh);
  
  	if (!use_privsep) {
  		ssh_signal(SIGTERM, sigterm_handler);
  		ssh_signal(SIGINT, sigterm_handler);
  		ssh_signal(SIGQUIT, sigterm_handler);
  	}
  
  	max_fd = MAXIMUM(connection_in, connection_out);
  
  	server_init_dispatch(ssh);
  
  	for (;;) {
  		process_buffered_input_packets(ssh);
  
  		if (!ssh_packet_is_rekeying(ssh) &&
  		    ssh_packet_not_very_much_data_to_write(ssh))
  			channel_output_poll(ssh);
  		if (options.rekey_interval > 0 &&
  		    !ssh_packet_is_rekeying(ssh)) {
  			rekey_timeout_ms = ssh_packet_get_rekey_timeout(ssh) *
  			    1000;
  		} else {
  			rekey_timeout_ms = 0;
  		}
  
  		/*
  		 * Block SIGCHLD while we check for dead children, then pass
  		 * the old signal mask through to pselect() so that it'll wake
  		 * up immediately if a child exits after we've called waitpid().
  		 */
  		if (sigprocmask(SIG_BLOCK, &bsigset, &osigset) == -1)
  			error_f("bsigset sigprocmask: %s", strerror(errno));
  		collect_children(ssh);
  		wait_until_can_do_something(ssh, connection_in, connection_out,
  		    &readset, &writeset, &max_fd, &nalloc, rekey_timeout_ms,
  		    &osigset);
  		if (sigprocmask(SIG_UNBLOCK, &bsigset, &osigset) == -1)
  			error_f("osigset sigprocmask: %s", strerror(errno));
  
  		if (received_sigterm) {
  			logit("Exiting on signal %d", (int)received_sigterm);
  			sshpkt_final_log_entry(ssh);
  			/* Clean up sessions, utmp, etc. */
  			cleanup_exit(255);
  		}
  
  		if (!ssh_packet_is_rekeying(ssh))
  			channel_after_select(ssh, readset, writeset);
  		if (process_input(ssh, readset, connection_in) < 0)
  			break;
  		/* A timeout may have triggered rekeying */
  		if ((r = ssh_packet_check_rekey(ssh)) != 0)
  			fatal_fr(r, "cannot start rekeying");
  		process_output(ssh, writeset, connection_out);
  	}
  	collect_children(ssh);
  
  	free(readset);
  	free(writeset);
  
  	/* free all channels, no more reads and writes */
  	channel_free_all(ssh);
  
  	/* final entry must come after channels close -cjr */
  	sshpkt_final_log_entry(ssh);
  
  	/* free remaining sessions, e.g. remove wtmp entries */
  	session_destroy_all(ssh, NULL);
  }
  
  static int
  server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh)
  {
  	debug("Got %d/%u for keepalive", type, seq);
  	/*
  	 * reset timeout, since we got a sane answer from the client.
  	 * even if this was generated by something other than
  	 * the bogus CHANNEL_REQUEST we send for keepalives.
  	 */
  	ssh_packet_set_alive_timeouts(ssh, 0);
  	return 0;
  }
  
  static Channel *
  server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg)
  {
  	Channel *c = NULL;
  	char *target = NULL, *originator = NULL;
  	u_int target_port = 0, originator_port = 0;
  	int r;
  
  	if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 ||
  	    (r = sshpkt_get_u32(ssh, &target_port)) != 0 ||
  	    (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 ||
  	    (r = sshpkt_get_u32(ssh, &originator_port)) != 0 ||
  	    (r = sshpkt_get_end(ssh)) != 0)
  		sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
  	if (target_port > 0xFFFF) {
  		error_f("invalid target port");
  		*reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
  		goto out;
  	}
  	if (originator_port > 0xFFFF) {
  		error_f("invalid originator port");
  		*reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
  		goto out;
  	}
  
  	debug_f("originator %s port %u, target %s port %u",
  	    originator, originator_port, target, target_port);
  
  	/* XXX fine grained permissions */
  	if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 &&
  	    auth_opts->permit_port_forwarding_flag &&
  	    !options.disable_forwarding) {
  		c = channel_connect_to_port(ssh, target, target_port,
  		    "direct-tcpip", "direct-tcpip", reason, errmsg);
  	} else {
  		logit("refused local port forward: "
  		    "originator %s port %d, target %s port %d",
  		    originator, originator_port, target, target_port);
  		if (reason != NULL)
  			*reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
  	}
  
   out:
  	free(originator);
  	free(target);
  	return c;
  }
  
  static Channel *
  server_request_direct_streamlocal(struct ssh *ssh)
  {
  	Channel *c = NULL;
  	char *target = NULL, *originator = NULL;
  	u_int originator_port = 0;
  	struct passwd *pw = the_authctxt->pw;
  	int r;
  
  	if (pw == NULL || !the_authctxt->valid)
  		fatal_f("no/invalid user");
  
  	if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 ||
  	    (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 ||
  	    (r = sshpkt_get_u32(ssh, &originator_port)) != 0 ||
  	    (r = sshpkt_get_end(ssh)) != 0)
  		sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
  	if (originator_port > 0xFFFF) {
  		error_f("invalid originator port");
  		goto out;
  	}
  
  	debug_f("originator %s port %d, target %s",
  	    originator, originator_port, target);
  
  	/* XXX fine grained permissions */
  	if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 &&
  	    auth_opts->permit_port_forwarding_flag &&
  	    !options.disable_forwarding && (pw->pw_uid == 0 || use_privsep)) {
  		c = channel_connect_to_path(ssh, target,
  		    "direct-streamlocal@openssh.com", "direct-streamlocal");
  	} else {
  		logit("refused streamlocal port forward: "
  		    "originator %s port %d, target %s",
  		    originator, originator_port, target);
  	}
  
  out:
  	free(originator);
  	free(target);
  	return c;
  }
  
  static Channel *
  server_request_tun(struct ssh *ssh)
  {
  	Channel *c = NULL;
  	u_int mode, tun;
  	int r, sock;
  	char *tmp, *ifname = NULL;
  
  	if ((r = sshpkt_get_u32(ssh, &mode)) != 0)
  		sshpkt_fatal(ssh, r, "%s: parse mode", __func__);
  	switch (mode) {
  	case SSH_TUNMODE_POINTOPOINT:
  	case SSH_TUNMODE_ETHERNET:
  		break;
  	default:
  		ssh_packet_send_debug(ssh, "Unsupported tunnel device mode.");
  		return NULL;
  	}
  	if ((options.permit_tun & mode) == 0) {
  		ssh_packet_send_debug(ssh, "Server has rejected tunnel device "
  		    "forwarding");
  		return NULL;
  	}
  
  	if ((r = sshpkt_get_u32(ssh, &tun)) != 0)
  		sshpkt_fatal(ssh, r, "%s: parse device", __func__);
  	if (tun > INT_MAX) {
  		debug_f("invalid tun");
  		goto done;
  	}
  	if (auth_opts->force_tun_device >= 0) {
  		if (tun != SSH_TUNID_ANY &&
  		    auth_opts->force_tun_device != (int)tun)
  			goto done;
  		tun = auth_opts->force_tun_device;
  	}
  	sock = tun_open(tun, mode, &ifname);
  	if (sock < 0)
  		goto done;
  	debug("Tunnel forwarding using interface %s", ifname);
  
  	c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1,
  	    options.hpn_disabled ? CHAN_TCP_WINDOW_DEFAULT : options.hpn_buffer_size,
  	    CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
  	c->datagram = 1;
  #if defined(SSH_TUN_FILTER)
  	if (mode == SSH_TUNMODE_POINTOPOINT)
  		channel_register_filter(ssh, c->self, sys_tun_infilter,
  		    sys_tun_outfilter, NULL, NULL);
  #endif
  
  	/*
  	 * Update the list of names exposed to the session
  	 * XXX remove these if the tunnels are closed (won't matter
  	 * much if they are already in the environment though)
  	 */
  	tmp = tun_fwd_ifnames;
  	xasprintf(&tun_fwd_ifnames, "%s%s%s",
  	    tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames,
  	    tun_fwd_ifnames == NULL ? "" : ",",
  	    ifname);
  	free(tmp);
  	free(ifname);
  
   done:
  	if (c == NULL)
  		ssh_packet_send_debug(ssh, "Failed to open the tunnel device.");
  	return c;
  }
  
  static Channel *
  server_request_session(struct ssh *ssh)
  {
  	Channel *c;
  	int r;
  
  	debug("input_session_request");
  	if ((r = sshpkt_get_end(ssh)) != 0)
  		sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
  
  	if (no_more_sessions) {
  		ssh_packet_disconnect(ssh, "Possible attack: attempt to open a "
  		    "session after additional sessions disabled");
  	}
  
  	/*
  	 * A server session has no fd to read or write until a
  	 * CHANNEL_REQUEST for a shell is made, so we set the type to
  	 * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
  	 * CHANNEL_REQUEST messages is registered.
  	 */
  	c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL,
  	    -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
  	    0, "server-session", 1);
  	if ((options.tcp_rcv_buf_poll) && (!options.hpn_disabled))
  		c->dynamic_window = 1;
  	if (session_open(the_authctxt, c->self) != 1) {
  		debug("session open failed, free channel %d", c->self);
  		channel_free(ssh, c);
  		return NULL;
  	}
  	channel_register_cleanup(ssh, c->self, session_close_by_channel, 0);
  	return c;
  }
  
  static int
  server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh)
  {
  	Channel *c = NULL;
  	char *ctype = NULL;
  	const char *errmsg = NULL;
  	int r, reason = SSH2_OPEN_CONNECT_FAILED;
  	u_int rchan = 0, rmaxpack = 0, rwindow = 0;
  
  	if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 ||
  	    (r = sshpkt_get_u32(ssh, &rchan)) != 0 ||
  	    (r = sshpkt_get_u32(ssh, &rwindow)) != 0 ||
  	    (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0)
  		sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
  	debug_f("ctype %s rchan %u win %u max %u",
  	    ctype, rchan, rwindow, rmaxpack);
  
  	if (strcmp(ctype, "session") == 0) {
  		c = server_request_session(ssh);
  	} else if (strcmp(ctype, "direct-tcpip") == 0) {
  		c = server_request_direct_tcpip(ssh, &reason, &errmsg);
  	} else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) {
  		c = server_request_direct_streamlocal(ssh);
  	} else if (strcmp(ctype, "tun@openssh.com") == 0) {
  		c = server_request_tun(ssh);
  	}
  	if (c != NULL) {
  		debug_f("confirm %s", ctype);
  		c->remote_id = rchan;
  		c->have_remote_id = 1;
  		c->remote_window = rwindow;
  		c->remote_maxpacket = rmaxpack;
  		if (c->type != SSH_CHANNEL_CONNECTING) {
  			if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 ||
  			    (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
  			    (r = sshpkt_put_u32(ssh, c->self)) != 0 ||
  			    (r = sshpkt_put_u32(ssh, c->local_window)) != 0 ||
  			    (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 ||
  			    (r = sshpkt_send(ssh)) != 0) {
  				sshpkt_fatal(ssh, r,
  				    "%s: send open confirm", __func__);
  			}
  		}
  	} else {
  		debug_f("failure %s", ctype);
  		if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 ||
  		    (r = sshpkt_put_u32(ssh, rchan)) != 0 ||
  		    (r = sshpkt_put_u32(ssh, reason)) != 0 ||
  		    (r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 ||
  		    (r = sshpkt_put_cstring(ssh, "")) != 0 ||
  		    (r = sshpkt_send(ssh)) != 0) {
  			sshpkt_fatal(ssh, r,
  			    "%s: send open failure", __func__);
  		}
  	}
  	free(ctype);
  	return 0;
  }
  
  static int
  server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp)
  {
  	struct sshbuf *resp = NULL;
  	struct sshbuf *sigbuf = NULL;
  	struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL;
  	int r, ndx, kexsigtype, use_kexsigtype, success = 0;
  	const u_char *blob;
  	u_char *sig = 0;
  	size_t blen, slen;
  
  	if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL)
  		fatal_f("sshbuf_new");
  
  	kexsigtype = sshkey_type_plain(
  	    sshkey_type_from_name(ssh->kex->hostkey_alg));
  	while (ssh_packet_remaining(ssh) > 0) {
  		sshkey_free(key);
  		key = NULL;
  		if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 ||
  		    (r = sshkey_from_blob(blob, blen, &key)) != 0) {
  			error_fr(r, "parse key");
  			goto out;
  		}
  		/*
  		 * Better check that this is actually one of our hostkeys
  		 * before attempting to sign anything with it.
  		 */
  		if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) {
  			error_f("unknown host %s key", sshkey_type(key));
  			goto out;
  		}
  		/*
  		 * XXX refactor: make kex->sign just use an index rather
  		 * than passing in public and private keys
  		 */
  		if ((key_prv = get_hostkey_by_index(ndx)) == NULL &&
  		    (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) {
  			error_f("can't retrieve hostkey %d", ndx);
  			goto out;
  		}
  		sshbuf_reset(sigbuf);
  		free(sig);
  		sig = NULL;
  		/*
  		 * For RSA keys, prefer to use the signature type negotiated
  		 * during KEX to the default (SHA1).
  		 */
  		use_kexsigtype = kexsigtype == KEY_RSA &&
  		    sshkey_type_plain(key->type) == KEY_RSA;
  		if ((r = sshbuf_put_cstring(sigbuf,
  		    "hostkeys-prove-00@openssh.com")) != 0 ||
  		    (r = sshbuf_put_stringb(sigbuf,
  		    ssh->kex->session_id)) != 0 ||
  		    (r = sshkey_puts(key, sigbuf)) != 0 ||
  		    (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen,
  		    sshbuf_ptr(sigbuf), sshbuf_len(sigbuf),
  		    use_kexsigtype ? ssh->kex->hostkey_alg : NULL)) != 0 ||
  		    (r = sshbuf_put_string(resp, sig, slen)) != 0) {
  			error_fr(r, "assemble signature");
  			goto out;
  		}
  	}
  	/* Success */
  	*respp = resp;
  	resp = NULL; /* don't free it */
  	success = 1;
   out:
  	free(sig);
  	sshbuf_free(resp);
  	sshbuf_free(sigbuf);
  	sshkey_free(key);
  	return success;
  }
  
  static int
  server_input_global_request(int type, u_int32_t seq, struct ssh *ssh)
  {
  	char *rtype = NULL;
  	u_char want_reply = 0;
  	int r, success = 0, allocated_listen_port = 0;
  	u_int port = 0;
  	struct sshbuf *resp = NULL;
  	struct passwd *pw = the_authctxt->pw;
  	struct Forward fwd;
  
  	memset(&fwd, 0, sizeof(fwd));
  	if (pw == NULL || !the_authctxt->valid)
  		fatal_f("no/invalid user");
  
  	if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 ||
  	    (r = sshpkt_get_u8(ssh, &want_reply)) != 0)
  		sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
  	debug_f("rtype %s want_reply %d", rtype, want_reply);
  
  	/* -R style forwarding */
  	if (strcmp(rtype, "tcpip-forward") == 0) {
  		if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 ||
  		    (r = sshpkt_get_u32(ssh, &port)) != 0)
  			sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__);
  		debug_f("tcpip-forward listen %s port %u",
  		    fwd.listen_host, port);
  		if (port <= INT_MAX)
  			fwd.listen_port = (int)port;
  		/* check permissions */
  		if (port > INT_MAX ||
  		    (options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 ||
  		    !auth_opts->permit_port_forwarding_flag ||
  		    options.disable_forwarding ||
  		    (!want_reply && fwd.listen_port == 0) ||
  		    (fwd.listen_port != 0 &&
  		    !bind_permitted(fwd.listen_port, pw->pw_uid))) {
  			success = 0;
  			ssh_packet_send_debug(ssh, "Server has disabled port forwarding.");
  		} else {
  			/* Start listening on the port */
  			success = channel_setup_remote_fwd_listener(ssh, &fwd,
  			    &allocated_listen_port, &options.fwd_opts);
  		}
  		if ((resp = sshbuf_new()) == NULL)
  			fatal_f("sshbuf_new");
  		if (allocated_listen_port != 0 &&
  		    (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0)
  			fatal_fr(r, "sshbuf_put_u32");
  	} else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
  		if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 ||
  		    (r = sshpkt_get_u32(ssh, &port)) != 0)
  			sshpkt_fatal(ssh, r, "%s: parse cancel-tcpip-forward", __func__);
  
  		debug_f("cancel-tcpip-forward addr %s port %d",
  		    fwd.listen_host, port);
  		if (port <= INT_MAX) {
  			fwd.listen_port = (int)port;
  			success = channel_cancel_rport_listener(ssh, &fwd);
  		}
  	} else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) {
  		if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0)
  			sshpkt_fatal(ssh, r, "%s: parse streamlocal-forward@openssh.com", __func__);
  		debug_f("streamlocal-forward listen path %s",
  		    fwd.listen_path);
  
  		/* check permissions */
  		if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0
  		    || !auth_opts->permit_port_forwarding_flag ||
  		    options.disable_forwarding ||
  		    (pw->pw_uid != 0 && !use_privsep)) {
  			success = 0;
  			ssh_packet_send_debug(ssh, "Server has disabled "
  			    "streamlocal forwarding.");
  		} else {
  			/* Start listening on the socket */
  			success = channel_setup_remote_fwd_listener(ssh,
  			    &fwd, NULL, &options.fwd_opts);
  		}
  	} else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) {
  		if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0)
  			sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward@openssh.com", __func__);
  		debug_f("cancel-streamlocal-forward path %s",
  		    fwd.listen_path);
  
  		success = channel_cancel_rport_listener(ssh, &fwd);
  	} else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
  		no_more_sessions = 1;
  		success = 1;
  	} else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) {
  		success = server_input_hostkeys_prove(ssh, &resp);
  	}
  	/* XXX sshpkt_get_end() */
  	if (want_reply) {
  		if ((r = sshpkt_start(ssh, success ?
  		    SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 ||
  		    (success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) ||
  		    (r = sshpkt_send(ssh)) != 0 ||
  		    (r = ssh_packet_write_wait(ssh)) != 0)
  			sshpkt_fatal(ssh, r, "%s: send reply", __func__);
  	}
  	free(fwd.listen_host);
  	free(fwd.listen_path);
  	free(rtype);
  	sshbuf_free(resp);
  	return 0;
  }
  
  static int
  server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh)
  {
  	Channel *c;
  	int r, success = 0;
  	char *rtype = NULL;
  	u_char want_reply = 0;
  	u_int id = 0;
  
  	if ((r = sshpkt_get_u32(ssh, &id)) != 0 ||
  	    (r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 ||
  	    (r = sshpkt_get_u8(ssh, &want_reply)) != 0)
  		sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
  
  	debug("server_input_channel_req: channel %u request %s reply %d",
  	    id, rtype, want_reply);
  
  	if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) {
  		ssh_packet_disconnect(ssh, "%s: unknown channel %d",
  		    __func__, id);
  	}
  	if (!strcmp(rtype, "eow@openssh.com")) {
  		if ((r = sshpkt_get_end(ssh)) != 0)
  			sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
  		chan_rcvd_eow(ssh, c);
  	} else if ((c->type == SSH_CHANNEL_LARVAL ||
  	    c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
  		success = session_input_channel_req(ssh, c, rtype);
  	if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) {
  		if (!c->have_remote_id)
  			fatal_f("channel %d: no remote_id", c->self);
  		if ((r = sshpkt_start(ssh, success ?
  		    SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 ||
  		    (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
  		    (r = sshpkt_send(ssh)) != 0)
  			sshpkt_fatal(ssh, r, "%s: send reply", __func__);
  	}
  	free(rtype);
  	return 0;
  }
  
  static void
  server_init_dispatch(struct ssh *ssh)
  {
  	debug("server_init_dispatch");
  	ssh_dispatch_init(ssh, &dispatch_protocol_error);
  	ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
  	ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data);
  	ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
  	ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
  	ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
  	ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
  	ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
  	ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
  	ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
  	ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
  	/* client_alive */
  	ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive);
  	ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
  	ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
  	ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
  	/* rekeying */
  	ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
  }
  