/* $OpenBSD: serverloop.c,v 1.241 2024/11/26 22:01:37 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>
#ifdef HAVE_POLL_H
#include <poll.h>
#endif
#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 "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 || errno == EWOULDBLOCK)
                        return 0;
                if (errno == EPIPE) {
                        logit("Connection closed by %.100s port %d",
                            ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
                        return -1;
                }
                logit("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;
#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 (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 = sshkey_ssh_name(key);
                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);
}