Return to serverloop.c CVS log

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Start the process of splitting sshd into separate binaries. This step
splits sshd into a listener and a session binary. More splits are
planned.

After this changes, the listener binary will validate the configuration,
load the hostkeys, listen on port 22 and manage MaxStartups only. All
session handling will be performed by a new sshd-session binary that the
listener fork+execs.

This reduces the listener process to the minimum necessary and sets us
up for future work on the sshd-session binary.

feedback/ok markus@ deraadt@

NB. if you're updating via source, please restart sshd after installing,
otherwise you run the risk of locking yourself out.

/* $OpenBSD: serverloop.c,v 1.239 2024/05/17 00:30:24 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 <sys/types.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/queue.h>

#include <netinet/in.h>

#include <errno.h>
#include <fcntl.h>
#include <pwd.h>
#include <limits.h>
#include <poll.h>
#include <signal.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>
#include <stdarg.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 "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;

static int no_more_sessions = 0; /* Disallow further sessions. */

static volatile sig_atomic_t child_terminated = 0;	/* The child has terminated. */

/* prototypes */
static void server_init_dispatch(struct ssh *);

/* requested tunnel forwarding interface(s), shared with session.c */
char *tun_fwd_ifnames = NULL;

static void
sigchld_handler(int sig)
{
	child_terminated = 1;
}

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 ppoll() until we can do something.
 * 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, struct pollfd **pfdp,
    u_int *npfd_allocp, u_int *npfd_activep, sigset_t *sigsetp,
    int *conn_in_readyp, int *conn_out_readyp)
{
	struct timespec timeout;
	char remote_id[512];
	int ret;
	int client_alive_scheduled = 0;
	u_int p;
	time_t now;
	static time_t last_client_time, unused_connection_expiry;

	*conn_in_readyp = *conn_out_readyp = 0;

	/* Prepare channel poll. First two pollfd entries are reserved */
	ptimeout_init(&timeout);
	channel_prepare_poll(ssh, pfdp, npfd_allocp, npfd_activep, 2, &timeout);
	now = monotime();
	if (*npfd_activep < 2)
		fatal_f("bad npfd %u", *npfd_activep); /* shouldn't happen */
	if (options.rekey_interval > 0 && !ssh_packet_is_rekeying(ssh)) {
		ptimeout_deadline_sec(&timeout,
		    ssh_packet_get_rekey_timeout(ssh));
	}

	/*
	 * If no channels are open and UnusedConnectionTimeout is set, then
	 * start the clock to terminate the connection.
	 */
	if (options.unused_connection_timeout != 0) {
		if (channel_still_open(ssh) || unused_connection_expiry == 0) {
			unused_connection_expiry = now +
			    options.unused_connection_timeout;
		}
		ptimeout_deadline_monotime(&timeout, unused_connection_expiry);
	}

	/*
	 * 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) {
		/* Time we last heard from the client OR sent a keepalive */
		if (last_client_time == 0)
			last_client_time = now;
		ptimeout_deadline_sec(&timeout, options.client_alive_interval);
		/* XXX ? deadline_monotime(last_client_time + alive_interval) */
		client_alive_scheduled = 1;
	}

#if 0
	/* wrong: bad condition XXX */
	if (channel_not_very_much_buffered_data())
#endif
	/* Monitor client connection on reserved pollfd entries */
	(*pfdp)[0].fd = connection_in;
	(*pfdp)[0].events = POLLIN;
	(*pfdp)[1].fd = connection_out;
	(*pfdp)[1].events = ssh_packet_have_data_to_write(ssh) ? POLLOUT : 0;

	/*
	 * 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))
		ptimeout_deadline_ms(&timeout, 100);

	/* Wait for something to happen, or the timeout to expire. */
	ret = ppoll(*pfdp, *npfd_activep, ptimeout_get_tsp(&timeout), sigsetp);

	if (ret == -1) {
		for (p = 0; p < *npfd_activep; p++)
			(*pfdp)[p].revents = 0;
		if (errno != EINTR)
			fatal_f("ppoll: %.100s", strerror(errno));
		return;
	}

	*conn_in_readyp = (*pfdp)[0].revents != 0;
	*conn_out_readyp = (*pfdp)[1].revents != 0;

	now = monotime(); /* need to reset after ppoll() */
	/* ClientAliveInterval probing */
	if (client_alive_scheduled) {
		if (ret == 0 &&
		    now >= last_client_time + options.client_alive_interval) {
			/* ppoll timed out and we're due to probe */
			client_alive_check(ssh);
			last_client_time = now;
		} else if (ret != 0 && *conn_in_readyp) {
			/* Data from peer; reset probe timer. */
			last_client_time = now;
		}
	}

	/* UnusedConnectionTimeout handling */
	if (unused_connection_expiry != 0 &&
	    now > unused_connection_expiry && !channel_still_open(ssh)) {
		sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id));
		logit("terminating inactive connection from %s", remote_id);
		cleanup_exit(255);
	}
}

/*
 * Processes input from the client and the program.  Input data is stored
 * in buffers and processed later.
 */
static int
process_input(struct ssh *ssh, int connection_in)
{
	int r;

	if ((r = ssh_packet_process_read(ssh, connection_in)) == 0)
		return 0; /* success */
	if (r == SSH_ERR_SYSTEM_ERROR) {
		if (errno == EAGAIN || errno == EINTR)
			return 0;
		if (errno == EPIPE) {
			verbose("Connection closed by %.100s port %d",
			    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
			return -1;
		}
		verbose("Read error from remote host %s port %d: %s",
		    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
		    strerror(errno));
		cleanup_exit(255);
	}
	return -1;
}

/*
 * Sends data from internal buffers to client program stdin.
 */
static void
process_output(struct ssh *ssh, int connection_out)
{
	int r;

	/* Send any buffered packet data to the client. */
	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)
{
	struct pollfd *pfd = NULL;
	u_int npfd_alloc = 0, npfd_active = 0;
	int r, conn_in_ready, conn_out_ready;
	u_int connection_in, connection_out;
	sigset_t bsigset, osigset;

	debug("Entering interactive session for SSH2.");

	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);

	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);

		/*
		 * Block SIGCHLD while we check for dead children, then pass
		 * the old signal mask through to ppoll() 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,
		    &pfd, &npfd_alloc, &npfd_active, &osigset,
		    &conn_in_ready, &conn_out_ready);
		if (sigprocmask(SIG_SETMASK, &osigset, NULL) == -1)
			error_f("osigset sigprocmask: %s", strerror(errno));

		channel_after_poll(ssh, pfd, npfd_active);
		if (conn_in_ready &&
		    process_input(ssh, connection_in) < 0)
			break;
		/* A timeout may have triggered rekeying */
		if ((r = ssh_packet_check_rekey(ssh)) != 0)
			fatal_fr(r, "cannot start rekeying");
		if (conn_out_ready)
			process_output(ssh, connection_out);
	}
	collect_children(ssh);
	free(pfd);

	/* free all channels, no more reads and writes */
	channel_free_all(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) {
		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 != -1) {
		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,
	    CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
	c->datagram = 1;

	/*
	 * 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 (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, success = 0;
	const u_char *blob;
	const char *sigalg, *kex_rsa_sigalg = NULL;
	u_char *sig = 0;
	size_t blen, slen;

	if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL)
		fatal_f("sshbuf_new");
	if (sshkey_type_plain(sshkey_type_from_name(
	    ssh->kex->hostkey_alg)) == KEY_RSA)
		kex_rsa_sigalg = 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).
		 */
		sigalg = NULL;
		if (sshkey_type_plain(key->type) == KEY_RSA) {
			if (kex_rsa_sigalg != NULL)
				sigalg = kex_rsa_sigalg;
			else if (ssh->kex->flags & KEX_RSA_SHA2_512_SUPPORTED)
				sigalg = "rsa-sha2-512";
			else if (ssh->kex->flags & KEX_RSA_SHA2_256_SUPPORTED)
				sigalg = "rsa-sha2-256";
		}
		debug3_f("sign %s key (index %d) using sigalg %s",
		    sshkey_type(key), ndx, sigalg == NULL ? "default" : sigalg);
		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), sigalg)) != 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)) {
			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) {
			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);
}