/* $OpenBSD: sshd-session.c,v 1.23 2026/03/11 09:10:59 dtucker Exp $ */
/*
 * SSH2 implementation:
 * Privilege Separation:
 *
 * Copyright (c) 2000, 2001, 2002 Markus Friedl.  All rights reserved.
 * Copyright (c) 2002 Niels Provos.  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/ioctl.h>
#include <sys/wait.h>
#include <sys/tree.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/queue.h>

#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#include <paths.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <unistd.h>
#include <limits.h>

#include "xmalloc.h"
#include "ssh.h"
#include "ssh2.h"
#include "sshpty.h"
#include "packet.h"
#include "log.h"
#include "sshbuf.h"
#include "misc.h"
#include "match.h"
#include "servconf.h"
#include "uidswap.h"
#include "compat.h"
#include "cipher.h"
#include "digest.h"
#include "sshkey.h"
#include "kex.h"
#include "authfile.h"
#include "pathnames.h"
#include "atomicio.h"
#include "canohost.h"
#include "hostfile.h"
#include "auth.h"
#include "authfd.h"
#include "msg.h"
#include "dispatch.h"
#include "channels.h"
#include "session.h"
#include "monitor.h"
#ifdef GSSAPI
#include "ssh-gss.h"
#endif
#include "monitor_wrap.h"
#include "auth-options.h"
#include "version.h"
#include "ssherr.h"
#include "sk-api.h"
#include "srclimit.h"
#include "dh.h"

/* Re-exec fds */
#define REEXEC_DEVCRYPTO_RESERVED_FD    (STDERR_FILENO + 1)
#define REEXEC_CONFIG_PASS_FD           (STDERR_FILENO + 2)
#define REEXEC_MIN_FREE_FD              (STDERR_FILENO + 3)

/* Privsep fds */
#define PRIVSEP_MONITOR_FD              (STDERR_FILENO + 1)
#define PRIVSEP_LOG_FD                  (STDERR_FILENO + 2)
#define PRIVSEP_MIN_FREE_FD             (STDERR_FILENO + 3)

extern char *__progname;

/* Server configuration options. */
ServerOptions options;

/* Name of the server configuration file. */
char *config_file_name = _PATH_SERVER_CONFIG_FILE;

/*
 * Debug mode flag.  This can be set on the command line.  If debug
 * mode is enabled, extra debugging output will be sent to the system
 * log, the daemon will not go to background, and will exit after processing
 * the first connection.
 */
int debug_flag = 0;

/* Flag indicating that the daemon is being started from inetd. */
static int inetd_flag = 0;

/* debug goes to stderr unless inetd_flag is set */
static int log_stderr = 0;

/* Saved arguments to main(). */
static char **saved_argv;

/* Daemon's agent connection */
int auth_sock = -1;
static int have_agent = 0;

/*
 * Any really sensitive data in the application is contained in this
 * structure. The idea is that this structure could be locked into memory so
 * that the pages do not get written into swap.  However, there are some
 * problems. The private key contains BIGNUMs, and we do not (in principle)
 * have access to the internals of them, and locking just the structure is
 * not very useful.  Currently, memory locking is not implemented.
 */
struct {
        u_int           num_hostkeys;
        struct sshkey   **host_keys;            /* all private host keys */
        struct sshkey   **host_pubkeys;         /* all public host keys */
        struct sshkey   **host_certificates;    /* all public host certificates */
} sensitive_data;

/* record remote hostname or ip */
u_int utmp_len = HOST_NAME_MAX+1;

static int startup_pipe = -1;           /* in child */

/* variables used for privilege separation */
struct monitor *pmonitor = NULL;
int privsep_is_preauth = 1;

/* global connection state and authentication contexts */
Authctxt *the_authctxt = NULL;
struct ssh *the_active_state;

/* global key/cert auth options. XXX move to permanent ssh->authctxt? */
struct sshauthopt *auth_opts = NULL;

/* sshd_config buffer */
struct sshbuf *cfg;

/* Included files from the configuration file */
struct include_list includes = TAILQ_HEAD_INITIALIZER(includes);

/* message to be displayed after login */
struct sshbuf *loginmsg;

/* Prototypes for various functions defined later in this file. */
void destroy_sensitive_data(void);
void demote_sensitive_data(void);

/* XXX reduce to stub once postauth split */
int
mm_is_monitor(void)
{
        /*
         * m_pid is only set in the privileged part, and
         * points to the unprivileged child.
         */
        return (pmonitor && pmonitor->m_pid > 0);
}

/*
 * Signal handler for the alarm after the login grace period has expired.
 * As usual, this may only take signal-safe actions, even though it is
 * terminal.
 */
static void
grace_alarm_handler(int sig)
{
        /*
         * Try to kill any processes that we have spawned, E.g. authorized
         * keys command helpers or privsep children.
         */
        if (getpgid(0) == getpid()) {
                struct sigaction sa;

                /* mask all other signals while in handler */
                memset(&sa, 0, sizeof(sa));
                sa.sa_handler = SIG_IGN;
                sigfillset(&sa.sa_mask);
                sa.sa_flags = SA_RESTART;
                (void)sigaction(SIGTERM, &sa, NULL);
                kill(0, SIGTERM);
        }
        _exit(EXIT_LOGIN_GRACE);
}

/* Destroy the host and server keys.  They will no longer be needed. */
void
destroy_sensitive_data(void)
{
        u_int i;

        for (i = 0; i < options.num_host_key_files; i++) {
                if (sensitive_data.host_keys[i]) {
                        sshkey_free(sensitive_data.host_keys[i]);
                        sensitive_data.host_keys[i] = NULL;
                }
                if (sensitive_data.host_certificates[i]) {
                        sshkey_free(sensitive_data.host_certificates[i]);
                        sensitive_data.host_certificates[i] = NULL;
                }
        }
}

/* Demote private to public keys for network child */
void
demote_sensitive_data(void)
{
        struct sshkey *tmp;
        u_int i;
        int r;

        for (i = 0; i < options.num_host_key_files; i++) {
                if (sensitive_data.host_keys[i]) {
                        if ((r = sshkey_from_private(
                            sensitive_data.host_keys[i], &tmp)) != 0)
                                fatal_r(r, "could not demote host %s key",
                                    sshkey_type(sensitive_data.host_keys[i]));
                        sshkey_free(sensitive_data.host_keys[i]);
                        sensitive_data.host_keys[i] = tmp;
                }
                /* Certs do not need demotion */
        }
}

struct sshbuf *
pack_hostkeys(void)
{
        struct sshbuf *keybuf = NULL, *hostkeys = NULL;
        int r;
        u_int i;

        if ((hostkeys = sshbuf_new()) == NULL)
                fatal_f("sshbuf_new failed");

        /* pack hostkeys into a string. Empty key slots get empty strings */
        for (i = 0; i < options.num_host_key_files; i++) {
                /* public key */
                if (sensitive_data.host_pubkeys[i] != NULL) {
                        if ((r = sshkey_puts(sensitive_data.host_pubkeys[i],
                            hostkeys)) != 0)
                                fatal_fr(r, "compose hostkey public");
                } else {
                        if ((r = sshbuf_put_string(hostkeys, NULL, 0)) != 0)
                                fatal_fr(r, "compose hostkey empty public");
                }
                /* cert */
                if (sensitive_data.host_certificates[i] != NULL) {
                        if ((r = sshkey_puts(
                            sensitive_data.host_certificates[i],
                            hostkeys)) != 0)
                                fatal_fr(r, "compose host cert");
                } else {
                        if ((r = sshbuf_put_string(hostkeys, NULL, 0)) != 0)
                                fatal_fr(r, "compose host cert empty");
                }
        }

        sshbuf_free(keybuf);
        return hostkeys;
}

static int
privsep_preauth(struct ssh *ssh)
{
        int r;
        pid_t pid;

        /* Set up unprivileged child process to deal with network data */
        pmonitor = monitor_init();
        /* Store a pointer to the kex for later rekeying */
        pmonitor->m_pkex = &ssh->kex;

        if ((pid = fork()) == -1)
                fatal("fork of unprivileged child failed");
        else if (pid != 0) {
                debug2("Network child is on pid %ld", (long)pid);
                pmonitor->m_pid = pid;
                if (have_agent) {
                        r = ssh_get_authentication_socket(&auth_sock);
                        if (r != 0) {
                                error_r(r, "Could not get agent socket");
                                have_agent = 0;
                        }
                }
                monitor_child_preauth(ssh, pmonitor);
                privsep_is_preauth = 0;
                return 1;
        } else {
                /* child */
                close(pmonitor->m_sendfd);
                close(pmonitor->m_log_recvfd);

                /*
                 * Arrange unpriv-preauth child process fds:
                 * 0, 1 network socket
                 * 2 optional stderr
                 * 3 reserved
                 * 4 monitor message socket
                 * 5 monitor logging socket
                 *
                 * We know that the monitor sockets will have fds > 4 because
                 * of the reserved fds in main()
                 */

                if (ssh_packet_get_connection_in(ssh) != STDIN_FILENO &&
                    dup2(ssh_packet_get_connection_in(ssh), STDIN_FILENO) == -1)
                        fatal("dup2 stdin failed: %s", strerror(errno));
                if (ssh_packet_get_connection_out(ssh) != STDOUT_FILENO &&
                    dup2(ssh_packet_get_connection_out(ssh),
                    STDOUT_FILENO) == -1)
                        fatal("dup2 stdout failed: %s", strerror(errno));
                /* leave stderr as-is */
                log_redirect_stderr_to(NULL); /* dup can clobber log fd */
                if (pmonitor->m_recvfd != PRIVSEP_MONITOR_FD &&
                    dup2(pmonitor->m_recvfd, PRIVSEP_MONITOR_FD) == -1)
                        fatal("dup2 monitor fd: %s", strerror(errno));
                if (pmonitor->m_log_sendfd != PRIVSEP_LOG_FD &&
                    dup2(pmonitor->m_log_sendfd, PRIVSEP_LOG_FD) == -1)
                        fatal("dup2 log fd: %s", strerror(errno));
                closefrom(PRIVSEP_MIN_FREE_FD);

                saved_argv[0] = options.sshd_auth_path;
                execv(options.sshd_auth_path, saved_argv);

                fatal_f("exec of %s failed: %s",
                    options.sshd_auth_path, strerror(errno));
        }
}

static void
privsep_postauth(struct ssh *ssh, Authctxt *authctxt)
{
        /* New socket pair */
        monitor_reinit(pmonitor);

        pmonitor->m_pid = fork();
        if (pmonitor->m_pid == -1)
                fatal("fork of unprivileged child failed");
        else if (pmonitor->m_pid != 0) {
                verbose("User child is on pid %ld", (long)pmonitor->m_pid);
                sshbuf_reset(loginmsg);
                monitor_clear_keystate(ssh, pmonitor);
                monitor_child_postauth(ssh, pmonitor);

                /* NEVERREACHED */
                exit(0);
        }

        /* child */

        close(pmonitor->m_sendfd);
        pmonitor->m_sendfd = -1;

        /* Demote the private keys to public keys. */
        demote_sensitive_data();

        /* Drop privileges */
        do_setusercontext(authctxt->pw);

        /* It is safe now to apply the key state */
        monitor_apply_keystate(ssh, pmonitor);

        /*
         * Tell the packet layer that authentication was successful, since
         * this information is not part of the key state.
         */
        ssh_packet_set_authenticated(ssh);
}

static struct sshkey *
get_hostkey_by_type(int type, int nid, int need_private, struct ssh *ssh)
{
        u_int i;
        struct sshkey *key;

        for (i = 0; i < options.num_host_key_files; i++) {
                switch (type) {
                case KEY_RSA_CERT:
                case KEY_ECDSA_CERT:
                case KEY_ED25519_CERT:
                case KEY_ECDSA_SK_CERT:
                case KEY_ED25519_SK_CERT:
                        key = sensitive_data.host_certificates[i];
                        break;
                default:
                        key = sensitive_data.host_keys[i];
                        if (key == NULL && !need_private)
                                key = sensitive_data.host_pubkeys[i];
                        break;
                }
                if (key == NULL || key->type != type)
                        continue;
                switch (type) {
                case KEY_ECDSA:
                case KEY_ECDSA_SK:
                case KEY_ECDSA_CERT:
                case KEY_ECDSA_SK_CERT:
                        if (key->ecdsa_nid != nid)
                                continue;
                        /* FALLTHROUGH */
                default:
                        return need_private ?
                            sensitive_data.host_keys[i] : key;
                }
        }
        return NULL;
}

struct sshkey *
get_hostkey_public_by_type(int type, int nid, struct ssh *ssh)
{
        return get_hostkey_by_type(type, nid, 0, ssh);
}

struct sshkey *
get_hostkey_private_by_type(int type, int nid, struct ssh *ssh)
{
        return get_hostkey_by_type(type, nid, 1, ssh);
}

struct sshkey *
get_hostkey_by_index(int ind)
{
        if (ind < 0 || (u_int)ind >= options.num_host_key_files)
                return (NULL);
        return (sensitive_data.host_keys[ind]);
}

struct sshkey *
get_hostkey_public_by_index(int ind, struct ssh *ssh)
{
        if (ind < 0 || (u_int)ind >= options.num_host_key_files)
                return (NULL);
        return (sensitive_data.host_pubkeys[ind]);
}

int
get_hostkey_index(struct sshkey *key, int compare, struct ssh *ssh)
{
        u_int i;

        for (i = 0; i < options.num_host_key_files; i++) {
                if (sshkey_is_cert(key)) {
                        if (key == sensitive_data.host_certificates[i] ||
                            (compare && sensitive_data.host_certificates[i] &&
                            sshkey_equal(key,
                            sensitive_data.host_certificates[i])))
                                return (i);
                } else {
                        if (key == sensitive_data.host_keys[i] ||
                            (compare && sensitive_data.host_keys[i] &&
                            sshkey_equal(key, sensitive_data.host_keys[i])))
                                return (i);
                        if (key == sensitive_data.host_pubkeys[i] ||
                            (compare && sensitive_data.host_pubkeys[i] &&
                            sshkey_equal(key, sensitive_data.host_pubkeys[i])))
                                return (i);
                }
        }
        return (-1);
}

/* Inform the client of all hostkeys */
static void
notify_hostkeys(struct ssh *ssh)
{
        struct sshbuf *buf;
        struct sshkey *key;
        u_int i, nkeys;
        int r;
        char *fp;

        /* Some clients cannot cope with the hostkeys message, skip those. */
        if (ssh->compat & SSH_BUG_HOSTKEYS)
                return;

        if ((buf = sshbuf_new()) == NULL)
                fatal_f("sshbuf_new");
        for (i = nkeys = 0; i < options.num_host_key_files; i++) {
                key = get_hostkey_public_by_index(i, ssh);
                if (key == NULL || key->type == KEY_UNSPEC ||
                    sshkey_is_cert(key))
                        continue;
                fp = sshkey_fingerprint(key, options.fingerprint_hash,
                    SSH_FP_DEFAULT);
                debug3_f("key %d: %s %s", i, sshkey_ssh_name(key), fp);
                free(fp);
                if (nkeys == 0) {
                        /*
                         * Start building the request when we find the
                         * first usable key.
                         */
                        if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 ||
                            (r = sshpkt_put_cstring(ssh, "hostkeys-00@openssh.com")) != 0 ||
                            (r = sshpkt_put_u8(ssh, 0)) != 0) /* want reply */
                                sshpkt_fatal(ssh, r, "%s: start request", __func__);
                }
                /* Append the key to the request */
                sshbuf_reset(buf);
                if ((r = sshkey_putb(key, buf)) != 0)
                        fatal_fr(r, "couldn't put hostkey %d", i);
                if ((r = sshpkt_put_stringb(ssh, buf)) != 0)
                        sshpkt_fatal(ssh, r, "%s: append key", __func__);
                nkeys++;
        }
        debug3_f("sent %u hostkeys", nkeys);
        if (nkeys == 0)
                fatal_f("no hostkeys");
        if ((r = sshpkt_send(ssh)) != 0)
                sshpkt_fatal(ssh, r, "%s: send", __func__);
        sshbuf_free(buf);
}

static void
usage(void)
{
        fprintf(stderr, "%s, %s\n", SSH_VERSION, SSH_OPENSSL_VERSION);
        fprintf(stderr,
"usage: sshd [-46DdeGiqTtV] [-C connection_spec] [-c host_cert_file]\n"
"            [-E log_file] [-f config_file] [-g login_grace_time]\n"
"            [-h host_key_file] [-o option] [-p port] [-u len]\n"
        );
        exit(1);
}

static void
parse_hostkeys(struct sshbuf *hostkeys)
{
        int r;
        u_int num_keys = 0;
        struct sshkey *k;
        struct sshbuf *kbuf;
        const u_char *cp;
        size_t len;

        while (sshbuf_len(hostkeys) != 0) {
                if (num_keys > 2048)
                        fatal_f("too many hostkeys");
                sensitive_data.host_keys = xrecallocarray(
                    sensitive_data.host_keys, num_keys, num_keys + 1,
                    sizeof(*sensitive_data.host_pubkeys));
                sensitive_data.host_pubkeys = xrecallocarray(
                    sensitive_data.host_pubkeys, num_keys, num_keys + 1,
                    sizeof(*sensitive_data.host_pubkeys));
                sensitive_data.host_certificates = xrecallocarray(
                    sensitive_data.host_certificates, num_keys, num_keys + 1,
                    sizeof(*sensitive_data.host_certificates));
                /* private key */
                k = NULL;
                if ((r = sshbuf_froms(hostkeys, &kbuf)) != 0)
                        fatal_fr(r, "extract privkey");
                if (sshbuf_len(kbuf) != 0 &&
                    (r = sshkey_private_deserialize(kbuf, &k)) != 0)
                        fatal_fr(r, "parse pubkey");
                sensitive_data.host_keys[num_keys] = k;
                sshbuf_free(kbuf);
                if (k)
                        debug2_f("privkey %u: %s", num_keys, sshkey_ssh_name(k));
                /* public key */
                k = NULL;
                if ((r = sshbuf_get_string_direct(hostkeys, &cp, &len)) != 0)
                        fatal_fr(r, "extract pubkey");
                if (len != 0 && (r = sshkey_from_blob(cp, len, &k)) != 0)
                        fatal_fr(r, "parse pubkey");
                sensitive_data.host_pubkeys[num_keys] = k;
                if (k)
                        debug2_f("pubkey %u: %s", num_keys, sshkey_ssh_name(k));
                /* certificate */
                k = NULL;
                if ((r = sshbuf_get_string_direct(hostkeys, &cp, &len)) != 0)
                        fatal_fr(r, "extract pubkey");
                if (len != 0 && (r = sshkey_from_blob(cp, len, &k)) != 0)
                        fatal_fr(r, "parse pubkey");
                sensitive_data.host_certificates[num_keys] = k;
                if (k)
                        debug2_f("cert %u: %s", num_keys, sshkey_ssh_name(k));
                num_keys++;
        }
        sensitive_data.num_hostkeys = num_keys;
}

static void
recv_rexec_state(int fd, struct sshbuf *conf, uint64_t *timing_secretp)
{
        struct sshbuf *m, *inc, *hostkeys;
        u_char *cp, ver;
        size_t len;
        int r;
        struct include_item *item;

        debug3_f("entering fd = %d", fd);

        if ((m = sshbuf_new()) == NULL || (inc = sshbuf_new()) == NULL)
                fatal_f("sshbuf_new failed");

        /* receive config */
        if (ssh_msg_recv(fd, m) == -1)
                fatal_f("ssh_msg_recv failed");
        if ((r = sshbuf_get_u8(m, &ver)) != 0)
                fatal_fr(r, "parse version");
        if (ver != 0)
                fatal_f("rexec version mismatch");
        if ((r = sshbuf_get_string(m, &cp, &len)) != 0 || /* XXX _direct */
            (r = sshbuf_get_u64(m, timing_secretp)) != 0 ||
            (r = sshbuf_get_stringb(m, inc)) != 0)
                fatal_fr(r, "parse config");

        if (conf != NULL && (r = sshbuf_put(conf, cp, len)))
                fatal_fr(r, "sshbuf_put");

        while (sshbuf_len(inc) != 0) {
                item = xcalloc(1, sizeof(*item));
                if ((item->contents = sshbuf_new()) == NULL)
                        fatal_f("sshbuf_new failed");
                if ((r = sshbuf_get_cstring(inc, &item->selector, NULL)) != 0 ||
                    (r = sshbuf_get_cstring(inc, &item->filename, NULL)) != 0 ||
                    (r = sshbuf_get_stringb(inc, item->contents)) != 0)
                        fatal_fr(r, "parse includes");
                TAILQ_INSERT_TAIL(&includes, item, entry);
        }

        /* receive hostkeys */
        sshbuf_reset(m);
        if (ssh_msg_recv(fd, m) == -1)
                fatal_f("ssh_msg_recv failed");
        if ((r = sshbuf_get_u8(m, NULL)) != 0 ||
            (r = sshbuf_froms(m, &hostkeys)) != 0)
                fatal_fr(r, "parse config");
        parse_hostkeys(hostkeys);

        free(cp);
        sshbuf_free(m);
        sshbuf_free(hostkeys);
        sshbuf_free(inc);

        debug3_f("done");
}

/*
 * If IP options are supported, make sure there are none (log and
 * return an error if any are found).  Basically we are worried about
 * source routing; it can be used to pretend you are somebody
 * (ip-address) you are not. That itself may be "almost acceptable"
 * under certain circumstances, but rhosts authentication is useless
 * if source routing is accepted. Notice also that if we just dropped
 * source routing here, the other side could use IP spoofing to do
 * rest of the interaction and could still bypass security.  So we
 * exit here if we detect any IP options.
 */
static void
check_ip_options(struct ssh *ssh)
{
        int sock_in = ssh_packet_get_connection_in(ssh);
        struct sockaddr_storage from;
        u_char opts[200];
        socklen_t i, option_size = sizeof(opts), fromlen = sizeof(from);
        char text[sizeof(opts) * 3 + 1];

        memset(&from, 0, sizeof(from));
        if (getpeername(sock_in, (struct sockaddr *)&from,
            &fromlen) == -1)
                return;
        if (from.ss_family != AF_INET)
                return;
        /* XXX IPv6 options? */

        if (getsockopt(sock_in, IPPROTO_IP, IP_OPTIONS, opts,
            &option_size) >= 0 && option_size != 0) {
                text[0] = '\0';
                for (i = 0; i < option_size; i++)
                        snprintf(text + i*3, sizeof(text) - i*3,
                            " %2.2x", opts[i]);
                fatal("Connection from %.100s port %d with IP opts: %.800s",
                    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), text);
        }
}

/* Set the routing domain for this process */
static void
set_process_rdomain(struct ssh *ssh, const char *name)
{
        int rtable, ortable = getrtable();
        const char *errstr;

        if (name == NULL)
                return; /* default */

        if (strcmp(name, "%D") == 0) {
                /* "expands" to routing domain of connection */
                if ((name = ssh_packet_rdomain_in(ssh)) == NULL)
                        return;
        }

        rtable = (int)strtonum(name, 0, 255, &errstr);
        if (errstr != NULL) /* Shouldn't happen */
                fatal("Invalid routing domain \"%s\": %s", name, errstr);
        if (rtable != ortable && setrtable(rtable) != 0)
                fatal("Unable to set routing domain %d: %s",
                    rtable, strerror(errno));
        debug_f("set routing domain %d (was %d)", rtable, ortable);
}

/*
 * Main program for the daemon.
 */
int
main(int ac, char **av)
{
        struct ssh *ssh = NULL;
        extern char *optarg;
        extern int optind;
        int devnull, r, opt, on = 1, remote_port;
        int sock_in = -1, sock_out = -1, rexeced_flag = 0, have_key = 0;
        const char *remote_ip, *rdomain;
        char *line, *laddr, *logfile = NULL;
        u_int i;
        uint64_t ibytes, obytes;
        mode_t new_umask;
        Authctxt *authctxt;
        struct connection_info *connection_info = NULL;
        sigset_t sigmask;
        uint64_t timing_secret = 0;
        struct itimerval itv;

        sigemptyset(&sigmask);
        sigprocmask(SIG_SETMASK, &sigmask, NULL);

        /* Save argv. */
        saved_argv = av;

        /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
        sanitise_stdfd();

        /* Initialize configuration options to their default values. */
        initialize_server_options(&options);

        /* Parse command-line arguments. */
        while ((opt = getopt(ac, av,
            "C:E:b:c:f:g:h:k:o:p:u:46DGQRTdeiqrtV")) != -1) {
                switch (opt) {
                case '4':
                        options.address_family = AF_INET;
                        break;
                case '6':
                        options.address_family = AF_INET6;
                        break;
                case 'f':
                        config_file_name = optarg;
                        break;
                case 'c':
                        servconf_add_hostcert("[command-line]", 0,
                            &options, optarg);
                        break;
                case 'd':
                        if (debug_flag == 0) {
                                debug_flag = 1;
                                options.log_level = SYSLOG_LEVEL_DEBUG1;
                        } else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
                                options.log_level++;
                        break;
                case 'D':
                        /* ignore */
                        break;
                case 'E':
                        logfile = optarg;
                        /* FALLTHROUGH */
                case 'e':
                        log_stderr = 1;
                        break;
                case 'i':
                        inetd_flag = 1;
                        break;
                case 'r':
                        /* ignore */
                        break;
                case 'R':
                        rexeced_flag = 1;
                        break;
                case 'Q':
                        /* ignored */
                        break;
                case 'q':
                        options.log_level = SYSLOG_LEVEL_QUIET;
                        break;
                case 'b':
                        /* protocol 1, ignored */
                        break;
                case 'p':
                        options.ports_from_cmdline = 1;
                        if (options.num_ports >= MAX_PORTS) {
                                fprintf(stderr, "too many ports.\n");
                                exit(1);
                        }
                        options.ports[options.num_ports++] = a2port(optarg);
                        if (options.ports[options.num_ports-1] <= 0) {
                                fprintf(stderr, "Bad port number.\n");
                                exit(1);
                        }
                        break;
                case 'g':
                        if ((options.login_grace_time = convtime(optarg)) == -1) {
                                fprintf(stderr, "Invalid login grace time.\n");
                                exit(1);
                        }
                        break;
                case 'k':
                        /* protocol 1, ignored */
                        break;
                case 'h':
                        servconf_add_hostkey("[command-line]", 0,
                            &options, optarg, 1);
                        break;
                case 't':
                case 'T':
                case 'G':
                        fatal("test/dump modes not supported");
                        break;
                case 'C':
                        connection_info = server_get_connection_info(ssh, 0, 0);
                        if (parse_server_match_testspec(connection_info,
                            optarg) == -1)
                                exit(1);
                        break;
                case 'u':
                        utmp_len = (u_int)strtonum(optarg, 0, HOST_NAME_MAX+1+1, NULL);
                        if (utmp_len > HOST_NAME_MAX+1) {
                                fprintf(stderr, "Invalid utmp length.\n");
                                exit(1);
                        }
                        break;
                case 'o':
                        line = xstrdup(optarg);
                        if (process_server_config_line(&options, line,
                            "command-line", 0, NULL, NULL, &includes) != 0)
                                exit(1);
                        free(line);
                        break;
                case 'V':
                        fprintf(stderr, "%s, %s\n",
                            SSH_VERSION, SSH_OPENSSL_VERSION);
                        exit(0);
                default:
                        usage();
                        break;
                }
        }

        /* Check that there are no remaining arguments. */
        if (optind < ac) {
                fprintf(stderr, "Extra argument %s.\n", av[optind]);
                exit(1);
        }

        if (!rexeced_flag)
                fatal("sshd-session should not be executed directly");

        closefrom(REEXEC_MIN_FREE_FD);

        /* Reserve fds we'll need later for reexec things */
        if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1)
                fatal("open %s: %s", _PATH_DEVNULL, strerror(errno));
        while (devnull < PRIVSEP_MIN_FREE_FD) {
                if ((devnull = dup(devnull)) == -1)
                        fatal("dup %s: %s", _PATH_DEVNULL, strerror(errno));
        }

        /* If requested, redirect the logs to the specified logfile. */
        if (logfile != NULL) {
                char *cp, pid_s[32];

                snprintf(pid_s, sizeof(pid_s), "%ld", (unsigned long)getpid());
                cp = percent_expand(logfile,
                    "p", pid_s,
                    "P", "sshd-session",
                    (char *)NULL);
                log_redirect_stderr_to(cp);
                free(cp);
        }

        /*
         * Force logging to stderr until we have loaded the private host
         * key (unless started from inetd)
         */
        log_init(__progname,
            options.log_level == SYSLOG_LEVEL_NOT_SET ?
            SYSLOG_LEVEL_INFO : options.log_level,
            options.log_facility == SYSLOG_FACILITY_NOT_SET ?
            SYSLOG_FACILITY_AUTH : options.log_facility,
            log_stderr || !inetd_flag || debug_flag);

        /* Fetch our configuration */
        if ((cfg = sshbuf_new()) == NULL)
                fatal("sshbuf_new config buf failed");
        setproctitle("%s", "[rexeced]");
        recv_rexec_state(REEXEC_CONFIG_PASS_FD, cfg, &timing_secret);
        parse_server_config(&options, "rexec", cfg, &includes, NULL, 1);
        /* Fill in default values for those options not explicitly set. */
        fill_default_server_options(&options);
        options.timing_secret = timing_secret;

        /* Reinit logging in case config set Level, Facility or Verbose. */
        log_init(__progname, options.log_level, options.log_facility,
            log_stderr || !inetd_flag || debug_flag);

        debug("sshd-session version %s, %s", SSH_VERSION, SSH_OPENSSL_VERSION);

        if (!debug_flag && !inetd_flag) {
                if ((startup_pipe = dup(REEXEC_CONFIG_PASS_FD)) == -1)
                        fatal("internal error: no startup pipe");

                /*
                 * Signal parent that this child is at a point where
                 * they can go away if they have a SIGHUP pending.
                 */
                (void)atomicio(vwrite, startup_pipe, "\0", 1);
        }
        /* close the fd, but keep the slot reserved */
        if (dup2(devnull, REEXEC_CONFIG_PASS_FD) == -1)
                fatal("dup2 devnull->config fd: %s", strerror(errno));

        /* Check that options are sensible */
        if (options.authorized_keys_command_user == NULL &&
            (options.authorized_keys_command != NULL &&
            strcasecmp(options.authorized_keys_command, "none") != 0))
                fatal("AuthorizedKeysCommand set without "
                    "AuthorizedKeysCommandUser");
        if (options.authorized_principals_command_user == NULL &&
            (options.authorized_principals_command != NULL &&
            strcasecmp(options.authorized_principals_command, "none") != 0))
                fatal("AuthorizedPrincipalsCommand set without "
                    "AuthorizedPrincipalsCommandUser");

        /*
         * Check whether there is any path through configured auth methods.
         * Unfortunately it is not possible to verify this generally before
         * daemonisation in the presence of Match block, but this catches
         * and warns for trivial misconfigurations that could break login.
         */
        if (options.num_auth_methods != 0) {
                for (i = 0; i < options.num_auth_methods; i++) {
                        if (auth2_methods_valid(options.auth_methods[i],
                            1) == 0)
                                break;
                }
                if (i >= options.num_auth_methods)
                        fatal("AuthenticationMethods cannot be satisfied by "
                            "enabled authentication methods");
        }

#ifdef WITH_OPENSSL
        if (options.moduli_file != NULL)
                dh_set_moduli_file(options.moduli_file);
#endif

        if (options.host_key_agent) {
                if (strcmp(options.host_key_agent, SSH_AUTHSOCKET_ENV_NAME))
                        setenv(SSH_AUTHSOCKET_ENV_NAME,
                            options.host_key_agent, 1);
                if ((r = ssh_get_authentication_socket(NULL)) == 0)
                        have_agent = 1;
                else
                        error_r(r, "Could not connect to agent \"%s\"",
                            options.host_key_agent);
        }

        if (options.num_host_key_files != sensitive_data.num_hostkeys) {
                fatal("internal error: hostkeys confused (config %u recvd %u)",
                    options.num_host_key_files, sensitive_data.num_hostkeys);
        }

        for (i = 0; i < options.num_host_key_files; i++) {
                if (sensitive_data.host_keys[i] != NULL ||
                    (have_agent && sensitive_data.host_pubkeys[i] != NULL)) {
                        have_key = 1;
                        break;
                }
        }
        if (!have_key)
                fatal("internal error: monitor received no hostkeys");

        /* Ensure that umask disallows at least group and world write */
        new_umask = umask(0077) | 0022;
        (void) umask(new_umask);

        /* Initialize the log (it is reinitialized below in case we forked). */
        if (debug_flag)
                log_stderr = 1;
        log_init(__progname, options.log_level,
            options.log_facility, log_stderr);
        for (i = 0; i < options.num_log_verbose; i++)
                log_verbose_add(options.log_verbose[i]);

        /* Reinitialize the log (because of the fork above). */
        log_init(__progname, options.log_level, options.log_facility, log_stderr);

        /*
         * Chdir to the root directory so that the current disk can be
         * unmounted if desired.
         */
        if (chdir("/") == -1)
                error("chdir(\"/\"): %s", strerror(errno));

        /* ignore SIGPIPE */
        ssh_signal(SIGPIPE, SIG_IGN);

        /* Get a connection, either from inetd or rexec */
        if (inetd_flag) {
                /*
                 * NB. must be different fd numbers for the !socket case,
                 * as packet_connection_is_on_socket() depends on this.
                 */
                sock_in = dup(STDIN_FILENO);
                sock_out = dup(STDOUT_FILENO);
        } else {
                /* rexec case; accept()ed socket in ancestor listener */
                sock_in = sock_out = dup(STDIN_FILENO);
        }

        /*
         * We intentionally do not close the descriptors 0, 1, and 2
         * as our code for setting the descriptors won't work if
         * ttyfd happens to be one of those.
         */
        if (stdfd_devnull(1, 1, !log_stderr) == -1)
                error("stdfd_devnull failed");
        debug("network sockets: %d, %d", sock_in, sock_out);

        /* This is the child processing a new connection. */
        setproctitle("%s", "[accepted]");

        /* Executed child processes don't need these. */
        FD_CLOSEONEXEC(sock_out);
        FD_CLOSEONEXEC(sock_in);

        /* We will not restart on SIGHUP since it no longer makes sense. */
        ssh_signal(SIGALRM, SIG_DFL);
        ssh_signal(SIGHUP, SIG_DFL);
        ssh_signal(SIGTERM, SIG_DFL);
        ssh_signal(SIGQUIT, SIG_DFL);
        ssh_signal(SIGCHLD, SIG_DFL);

        /*
         * Register our connection.  This turns encryption off because we do
         * not have a key.
         */
        if ((ssh = ssh_packet_set_connection(NULL, sock_in, sock_out)) == NULL)
                fatal("Unable to create connection");
        the_active_state = ssh;
        ssh_packet_set_server(ssh);
        ssh_packet_set_qos(ssh, options.ip_qos_interactive,
            options.ip_qos_bulk);

        check_ip_options(ssh);

        /* Prepare the channels layer */
        channel_init_channels(ssh);
        channel_set_af(ssh, options.address_family);
        server_process_channel_timeouts(ssh);
        server_process_permitopen(ssh);

        /* Set SO_KEEPALIVE if requested. */
        if (options.tcp_keep_alive && ssh_packet_connection_is_on_socket(ssh) &&
            setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) == -1)
                error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));

        if ((remote_port = ssh_remote_port(ssh)) < 0) {
                debug("ssh_remote_port failed");
                cleanup_exit(255);
        }

        /*
         * The rest of the code depends on the fact that
         * ssh_remote_ipaddr() caches the remote ip, even if
         * the socket goes away.
         */
        remote_ip = ssh_remote_ipaddr(ssh);

        rdomain = ssh_packet_rdomain_in(ssh);

        /* Log the connection. */
        laddr = get_local_ipaddr(sock_in);
        verbose("Connection from %s port %d on %s port %d%s%s%s",
            remote_ip, remote_port, laddr,  ssh_local_port(ssh),
            rdomain == NULL ? "" : " rdomain \"",
            rdomain == NULL ? "" : rdomain,
            rdomain == NULL ? "" : "\"");
        free(laddr);

        /*
         * We don't want to listen forever unless the other side
         * successfully authenticates itself.  So we set up an alarm which is
         * cleared after successful authentication.  A limit of zero
         * indicates no limit. Note that we don't set the alarm in debugging
         * mode; it is just annoying to have the server exit just when you
         * are about to discover the bug.
         */
        ssh_signal(SIGALRM, grace_alarm_handler);
        if (!debug_flag && options.login_grace_time > 0) {
                int ujitter = arc4random_uniform(4 * 1000000);

                timerclear(&itv.it_interval);
                itv.it_value.tv_sec = options.login_grace_time;
                itv.it_value.tv_sec += ujitter / 1000000;
                itv.it_value.tv_usec = ujitter % 1000000; 

                if (setitimer(ITIMER_REAL, &itv, NULL) == -1)
                        fatal("login grace time setitimer failed");
        }

        ssh_packet_set_nonblocking(ssh);

        /* allocate authentication context */
        authctxt = xcalloc(1, sizeof(*authctxt));
        ssh->authctxt = authctxt;

        /* XXX global for cleanup, access from other modules */
        the_authctxt = authctxt;

        /* Set default key authentication options */
        if ((auth_opts = sshauthopt_new_with_keys_defaults()) == NULL)
                fatal("allocation failed");

        /* prepare buffer to collect messages to display to user after login */
        if ((loginmsg = sshbuf_new()) == NULL)
                fatal("sshbuf_new loginmsg failed");
        auth_debug_reset();

        if (privsep_preauth(ssh) != 1)
                fatal("privsep_preauth failed");

        /* Now user is authenticated */

        /*
         * Cancel the alarm we set to limit the time taken for
         * authentication.
         */
        timerclear(&itv.it_interval);
        timerclear(&itv.it_value);
        if (setitimer(ITIMER_REAL, &itv, NULL) == -1)
                fatal("login grace time clear failed");
        ssh_signal(SIGALRM, SIG_DFL);
        authctxt->authenticated = 1;
        if (startup_pipe != -1) {
                /* signal listener that authentication completed successfully */
                (void)atomicio(vwrite, startup_pipe, "\001", 1);
                close(startup_pipe);
                startup_pipe = -1;
        }

        if (options.routing_domain != NULL)
                set_process_rdomain(ssh, options.routing_domain);

        /*
         * In privilege separation, we fork another child and prepare
         * file descriptor passing.
         */
        privsep_postauth(ssh, authctxt);
        /* the monitor process [priv] will not return */

        ssh_packet_set_timeout(ssh, options.client_alive_interval,
            options.client_alive_count_max);

        /* Try to send all our hostkeys to the client */
        notify_hostkeys(ssh);

        /* Start session. */
        do_authenticated(ssh, authctxt);

        /* The connection has been terminated. */
        ssh_packet_get_bytes(ssh, &ibytes, &obytes);
        verbose("Transferred: sent %llu, received %llu bytes",
            (unsigned long long)obytes, (unsigned long long)ibytes);

        verbose("Closing connection to %.500s port %d", remote_ip, remote_port);
        ssh_packet_close(ssh);

        mm_terminate();

        exit(0);
}

int
sshd_hostkey_sign(struct ssh *ssh, struct sshkey *privkey,
    struct sshkey *pubkey, u_char **signature, size_t *slenp,
    const u_char *data, size_t dlen, const char *alg)
{
        if (privkey) {
                if (mm_sshkey_sign(ssh, privkey, signature, slenp,
                    data, dlen, alg, options.sk_provider, NULL,
                    ssh->compat) < 0)
                        fatal_f("privkey sign failed");
        } else {
                if (mm_sshkey_sign(ssh, pubkey, signature, slenp,
                    data, dlen, alg, options.sk_provider, NULL,
                    ssh->compat) < 0)
                        fatal_f("pubkey sign failed");
        }
        return 0;
}

/* server specific fatal cleanup */
void
cleanup_exit(int i)
{
        if (the_active_state != NULL && the_authctxt != NULL) {
                do_cleanup(the_active_state, the_authctxt);
                if (privsep_is_preauth &&
                    pmonitor != NULL && pmonitor->m_pid > 1) {
                        debug("Killing privsep child %d", pmonitor->m_pid);
                        if (kill(pmonitor->m_pid, SIGKILL) != 0 &&
                            errno != ESRCH) {
                                error_f("kill(%d): %s", pmonitor->m_pid,
                                    strerror(errno));
                        }
                }
        }
        /* Override default fatal exit value when auth was attempted */
        if (i == 255 && monitor_auth_attempted())
                _exit(EXIT_AUTH_ATTEMPTED);
        if (i == 255 && monitor_invalid_user())
                _exit(EXIT_INVALID_USER);
        _exit(i);
}