1 files changed, 205 insertions, 236 deletions

diff --git a/sshd.c b/sshd.c
index ba26287ba..cbd3bce91 100644
--- a/sshd.c
+++ b/sshd.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sshd.c,v 1.516 2018/09/21 12:23:17 djm Exp $ */
+/* $OpenBSD: sshd.c,v 1.533 2019/03/01 02:32:39 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -151,45 +151,38 @@ int debug_flag = 0;
  * configuration, optionally using connection information provided by the
  * "-C" flag.
  */
-int test_flag = 0;
+static int test_flag = 0;
 
 /* Flag indicating that the daemon is being started from inetd. */
-int inetd_flag = 0;
+static int inetd_flag = 0;
 
 /* Flag indicating that sshd should not detach and become a daemon. */
-int no_daemon_flag = 0;
+static int no_daemon_flag = 0;
 
 /* debug goes to stderr unless inetd_flag is set */
-int log_stderr = 0;
+static int log_stderr = 0;
 
 /* Saved arguments to main(). */
-char **saved_argv;
-int saved_argc;
+static char **saved_argv;
+static int saved_argc;
 
 /* re-exec */
-int rexeced_flag = 0;
-int rexec_flag = 1;
-int rexec_argc = 0;
-char **rexec_argv;
+static int rexeced_flag = 0;
+static int rexec_flag = 1;
+static int rexec_argc = 0;
+static char **rexec_argv;
 
 /*
  * The sockets that the server is listening; this is used in the SIGHUP
  * signal handler.
  */
 #define MAX_LISTEN_SOCKS        16
-int listen_socks[MAX_LISTEN_SOCKS];
-int num_listen_socks = 0;
-
-/*
- * the client's version string, passed by sshd2 in compat mode. if != NULL,
- * sshd will skip the version-number exchange
- */
-char *client_version_string = NULL;
-char *server_version_string = NULL;
+static int listen_socks[MAX_LISTEN_SOCKS];
+static int num_listen_socks = 0;
 
 /* Daemon's agent connection */
 int auth_sock = -1;
-int have_agent = 0;
+static int have_agent = 0;
 
 /*
  * Any really sensitive data in the application is contained in this
@@ -220,9 +213,26 @@ u_int session_id2_len = 0;
 /* record remote hostname or ip */
 u_int utmp_len = HOST_NAME_MAX+1;
 
-/* options.max_startup sized array of fd ints */
-int *startup_pipes = NULL;
-int startup_pipe;               /* in child */
+/*
+ * startup_pipes/flags are used for tracking children of the listening sshd
+ * process early in their lifespans. This tracking is needed for three things:
+ *
+ * 1) Implementing the MaxStartups limit of concurrent unauthenticated
+ *    connections.
+ * 2) Avoiding a race condition for SIGHUP processing, where child processes
+ *    may have listen_socks open that could collide with main listener process
+ *    after it restarts.
+ * 3) Ensuring that rexec'd sshd processes have received their initial state
+ *    from the parent listen process before handling SIGHUP.
+ *
+ * Child processes signal that they have completed closure of the listen_socks
+ * and (if applicable) received their rexec state by sending a char over their
+ * sock. Child processes signal that authentication has completed by closing
+ * the sock (or by exiting).
+ */
+static int *startup_pipes = NULL;
+static int *startup_flags = NULL;       /* Indicates child closed listener */
+static int startup_pipe = -1;           /* in child */
 
 /* variables used for privilege separation */
 int use_privsep = -1;
@@ -230,8 +240,9 @@ struct monitor *pmonitor = NULL;
 int privsep_is_preauth = 1;
 static int privsep_chroot = 1;
 
-/* global authentication context */
+/* 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;
@@ -248,7 +259,7 @@ struct passwd *privsep_pw = NULL;
 /* Prototypes for various functions defined later in this file. */
 void destroy_sensitive_data(void);
 void demote_sensitive_data(void);
-static void do_ssh2_kex(void);
+static void do_ssh2_kex(struct ssh *);
 
 /*
  * Close all listening sockets
@@ -358,111 +369,11 @@ grace_alarm_handler(int sig)
                 kill(0, SIGTERM);
         }
 
+        /* XXX pre-format ipaddr/port so we don't need to access active_state */
         /* Log error and exit. */
         sigdie("Timeout before authentication for %s port %d",
-            ssh_remote_ipaddr(active_state), ssh_remote_port(active_state));
-}
-
-static void
-sshd_exchange_identification(struct ssh *ssh, int sock_in, int sock_out)
-{
-        u_int i;
-        int remote_major, remote_minor;
-        char *s;
-        char buf[256];                  /* Must not be larger than remote_version. */
-        char remote_version[256];       /* Must be at least as big as buf. */
-
-        xasprintf(&server_version_string, "SSH-%d.%d-%.100s%s%s\r\n",
-            PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION,
-            *options.version_addendum == '\0' ? "" : " ",
-            options.version_addendum);
-
-        /* Send our protocol version identification. */
-        if (atomicio(vwrite, sock_out, server_version_string,
-            strlen(server_version_string))
-            != strlen(server_version_string)) {
-                logit("Could not write ident string to %s port %d",
-                    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
-                cleanup_exit(255);
-        }
-
-        /* Read other sides version identification. */
-        memset(buf, 0, sizeof(buf));
-        for (i = 0; i < sizeof(buf) - 1; i++) {
-                if (atomicio(read, sock_in, &buf[i], 1) != 1) {
-                        logit("Did not receive identification string "
-                            "from %s port %d",
-                            ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
-                        cleanup_exit(255);
-                }
-                if (buf[i] == '\r') {
-                        buf[i] = 0;
-                        /* Kludge for F-Secure Macintosh < 1.0.2 */
-                        if (i == 12 &&
-                            strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
-                                break;
-                        continue;
-                }
-                if (buf[i] == '\n') {
-                        buf[i] = 0;
-                        break;
-                }
-        }
-        buf[sizeof(buf) - 1] = 0;
-        client_version_string = xstrdup(buf);
-
-        /*
-         * Check that the versions match.  In future this might accept
-         * several versions and set appropriate flags to handle them.
-         */
-        if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
-            &remote_major, &remote_minor, remote_version) != 3) {
-                s = "Protocol mismatch.\n";
-                (void) atomicio(vwrite, sock_out, s, strlen(s));
-                logit("Bad protocol version identification '%.100s' "
-                    "from %s port %d", client_version_string,
-                    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
-                close(sock_in);
-                close(sock_out);
-                cleanup_exit(255);
-        }
-        debug("Client protocol version %d.%d; client software version %.100s",
-            remote_major, remote_minor, remote_version);
-
-        ssh->compat = compat_datafellows(remote_version);
-
-        if ((ssh->compat & SSH_BUG_PROBE) != 0) {
-                logit("probed from %s port %d with %s.  Don't panic.",
-                    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
-                    client_version_string);
-                cleanup_exit(255);
-        }
-        if ((ssh->compat & SSH_BUG_SCANNER) != 0) {
-                logit("scanned from %s port %d with %s.  Don't panic.",
-                    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
-                    client_version_string);
-                cleanup_exit(255);
-        }
-        if ((ssh->compat & SSH_BUG_RSASIGMD5) != 0) {
-                logit("Client version \"%.100s\" uses unsafe RSA signature "
-                    "scheme; disabling use of RSA keys", remote_version);
-        }
-
-        chop(server_version_string);
-        debug("Local version string %.200s", server_version_string);
-
-        if (remote_major != 2 &&
-            !(remote_major == 1 && remote_minor == 99)) {
-                s = "Protocol major versions differ.\n";
-                (void) atomicio(vwrite, sock_out, s, strlen(s));
-                close(sock_in);
-                close(sock_out);
-                logit("Protocol major versions differ for %s port %d: "
-                    "%.200s vs. %.200s",
-                    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
-                    server_version_string, client_version_string);
-                cleanup_exit(255);
-        }
+            ssh_remote_ipaddr(the_active_state),
+            ssh_remote_port(the_active_state));
 }
 
 /* Destroy the host and server keys.  They will no longer be needed. */
@@ -564,7 +475,7 @@ privsep_preauth_child(void)
 }
 
 static int
-privsep_preauth(Authctxt *authctxt)
+privsep_preauth(struct ssh *ssh)
 {
         int status, r;
         pid_t pid;
@@ -573,7 +484,7 @@ privsep_preauth(Authctxt *authctxt)
         /* 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 = &active_state->kex;
+        pmonitor->m_pkex = &ssh->kex;
 
         if (use_privsep == PRIVSEP_ON)
                 box = ssh_sandbox_init(pmonitor);
@@ -594,7 +505,7 @@ privsep_preauth(Authctxt *authctxt)
                 }
                 if (box != NULL)
                         ssh_sandbox_parent_preauth(box, pid);
-                monitor_child_preauth(authctxt, pmonitor);
+                monitor_child_preauth(ssh, pmonitor);
 
                 /* Wait for the child's exit status */
                 while (waitpid(pid, &status, 0) < 0) {
@@ -633,7 +544,7 @@ privsep_preauth(Authctxt *authctxt)
 }
 
 static void
-privsep_postauth(Authctxt *authctxt)
+privsep_postauth(struct ssh *ssh, Authctxt *authctxt)
 {
 #ifdef DISABLE_FD_PASSING
         if (1) {
@@ -654,8 +565,8 @@ privsep_postauth(Authctxt *authctxt)
         else if (pmonitor->m_pid != 0) {
                 verbose("User child is on pid %ld", (long)pmonitor->m_pid);
                 sshbuf_reset(loginmsg);
-                monitor_clear_keystate(pmonitor);
-                monitor_child_postauth(pmonitor);
+                monitor_clear_keystate(ssh, pmonitor);
+                monitor_child_postauth(ssh, pmonitor);
 
                 /* NEVERREACHED */
                 exit(0);
@@ -676,13 +587,13 @@ privsep_postauth(Authctxt *authctxt)
 
  skip:
         /* It is safe now to apply the key state */
-        monitor_apply_keystate(pmonitor);
+        monitor_apply_keystate(ssh, pmonitor);
 
         /*
          * Tell the packet layer that authentication was successful, since
          * this information is not part of the key state.
          */
-        packet_set_authenticated();
+        ssh_packet_set_authenticated(ssh);
 }
 
 static void
@@ -849,7 +760,7 @@ notify_hostkeys(struct ssh *ssh)
         char *fp;
 
         /* Some clients cannot cope with the hostkeys message, skip those. */
-        if (datafellows & SSH_BUG_HOSTKEYS)
+        if (ssh->compat & SSH_BUG_HOSTKEYS)
                 return;
 
         if ((buf = sshbuf_new()) == NULL)
@@ -865,21 +776,29 @@ notify_hostkeys(struct ssh *ssh)
                     sshkey_ssh_name(key), fp);
                 free(fp);
                 if (nkeys == 0) {
-                        packet_start(SSH2_MSG_GLOBAL_REQUEST);
-                        packet_put_cstring("hostkeys-00@openssh.com");
-                        packet_put_char(0); /* want-reply */
+                        /*
+                         * 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("%s: couldn't put hostkey %d: %s",
                             __func__, i, ssh_err(r));
-                packet_put_string(sshbuf_ptr(buf), sshbuf_len(buf));
+                if ((r = sshpkt_put_stringb(ssh, buf)) != 0)
+                        sshpkt_fatal(ssh, r, "%s: append key", __func__);
                 nkeys++;
         }
         debug3("%s: sent %u hostkeys", __func__, nkeys);
         if (nkeys == 0)
                 fatal("%s: no hostkeys", __func__);
-        packet_send();
+        if ((r = sshpkt_send(ssh)) != 0)
+                sshpkt_fatal(ssh, r, "%s: send", __func__);
         sshbuf_free(buf);
 }
 
@@ -917,7 +836,7 @@ usage(void)
         fprintf(stderr, "%s, %s\n",
             SSH_RELEASE,
 #ifdef WITH_OPENSSL
-            SSLeay_version(SSLEAY_VERSION)
+            OpenSSL_version(OPENSSL_VERSION)
 #else
             "without OpenSSL"
 #endif
@@ -999,14 +918,9 @@ server_accept_inetd(int *sock_in, int *sock_out)
 {
         int fd;
 
-        startup_pipe = -1;
         if (rexeced_flag) {
                 close(REEXEC_CONFIG_PASS_FD);
                 *sock_in = *sock_out = dup(STDIN_FILENO);
-                if (!debug_flag) {
-                        startup_pipe = dup(REEXEC_STARTUP_PIPE_FD);
-                        close(REEXEC_STARTUP_PIPE_FD);
-                }
         } else {
                 *sock_in = dup(STDIN_FILENO);
                 *sock_out = dup(STDOUT_FILENO);
@@ -1131,8 +1045,9 @@ server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
 {
         fd_set *fdset;
         int i, j, ret, maxfd;
-        int startups = 0;
+        int startups = 0, listening = 0, lameduck = 0;
         int startup_p[2] = { -1 , -1 };
+        char c = 0;
         struct sockaddr_storage from;
         socklen_t fromlen;
         pid_t pid;
@@ -1146,6 +1061,7 @@ server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
                         maxfd = listen_socks[i];
         /* pipes connected to unauthenticated childs */
         startup_pipes = xcalloc(options.max_startups, sizeof(int));
+        startup_flags = xcalloc(options.max_startups, sizeof(int));
         for (i = 0; i < options.max_startups; i++)
                 startup_pipes[i] = -1;
 
@@ -1154,8 +1070,15 @@ server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
          * the daemon is killed with a signal.
          */
         for (;;) {
-                if (received_sighup)
-                        sighup_restart();
+                if (received_sighup) {
+                        if (!lameduck) {
+                                debug("Received SIGHUP; waiting for children");
+                                close_listen_socks();
+                                lameduck = 1;
+                        }
+                        if (listening <= 0)
+                                sighup_restart();
+                }
                 free(fdset);
                 fdset = xcalloc(howmany(maxfd + 1, NFDBITS),
                     sizeof(fd_mask));
@@ -1181,19 +1104,37 @@ server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
                 if (ret < 0)
                         continue;
 
-                for (i = 0; i < options.max_startups; i++)
-                        if (startup_pipes[i] != -1 &&
-                            FD_ISSET(startup_pipes[i], fdset)) {
-                                /*
-                                 * the read end of the pipe is ready
-                                 * if the child has closed the pipe
-                                 * after successful authentication
-                                 * or if the child has died
-                                 */
+                for (i = 0; i < options.max_startups; i++) {
+                        if (startup_pipes[i] == -1 ||
+                            !FD_ISSET(startup_pipes[i], fdset))
+                                continue;
+                        switch (read(startup_pipes[i], &c, sizeof(c))) {
+                        case -1:
+                                if (errno == EINTR || errno == EAGAIN)
+                                        continue;
+                                if (errno != EPIPE) {
+                                        error("%s: startup pipe %d (fd=%d): "
+                                            "read %s", __func__, i,
+                                            startup_pipes[i], strerror(errno));
+                                }
+                                /* FALLTHROUGH */
+                        case 0:
+                                /* child exited or completed auth */
                                 close(startup_pipes[i]);
                                 startup_pipes[i] = -1;
                                 startups--;
+                                if (startup_flags[i])
+                                        listening--;
+                                break;
+                        case 1:
+                                /* child has finished preliminaries */
+                                if (startup_flags[i]) {
+                                        listening--;
+                                        startup_flags[i] = 0;
+                                }
+                                break;
                         }
+                }
                 for (i = 0; i < num_listen_socks; i++) {
                         if (!FD_ISSET(listen_socks[i], fdset))
                                 continue;
@@ -1247,6 +1188,7 @@ server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
                                         if (maxfd < startup_p[0])
                                                 maxfd = startup_p[0];
                                         startups++;
+                                        startup_flags[j] = 1;
                                         break;
                                 }
 
@@ -1272,7 +1214,7 @@ server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
                                         send_rexec_state(config_s[0], cfg);
                                         close(config_s[0]);
                                 }
-                                break;
+                                return;
                         }
 
                         /*
@@ -1281,13 +1223,14 @@ server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
                          * parent continues listening.
                          */
                         platform_pre_fork();
+                        listening++;
                         if ((pid = fork()) == 0) {
                                 /*
                                  * Child.  Close the listening and
                                  * max_startup sockets.  Start using
                                  * the accepted socket. Reinitialize
                                  * logging (since our pid has changed).
-                                 * We break out of the loop to handle
+                                 * We return from this function to handle
                                  * the connection.
                                  */
                                 platform_post_fork_child();
@@ -1302,7 +1245,18 @@ server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
                                     log_stderr);
                                 if (rexec_flag)
                                         close(config_s[0]);
-                                break;
+                                else {
+                                        /*
+                                         * Signal parent that the preliminaries
+                                         * for this child are complete. For the
+                                         * re-exec case, this happens after the
+                                         * child has received the rexec state
+                                         * from the server.
+                                         */
+                                        (void)atomicio(vwrite, startup_pipe,
+                                            "\0", 1);
+                                }
+                                return;
                         }
 
                         /* Parent.  Stay in the loop. */
@@ -1334,10 +1288,6 @@ server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
 #endif
                         explicit_bzero(rnd, sizeof(rnd));
                 }
-
-                /* child process check (or debug mode) */
-                if (num_listen_socks < 0)
-                        break;
         }
 }
 
@@ -1510,6 +1460,8 @@ main(int ac, char **av)
         /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
         sanitise_stdfd();
 
+        seed_rng();
+
         /* Initialize configuration options to their default values. */
         initialize_server_options(&options);
 
@@ -1588,7 +1540,7 @@ main(int ac, char **av)
                         break;
                 case 'h':
                         servconf_add_hostkey("[command-line]", 0,
-                            &options, optarg);
+                            &options, optarg, 1);
                         break;
                 case 't':
                         test_flag = 1;
@@ -1597,7 +1549,7 @@ main(int ac, char **av)
                         test_flag = 2;
                         break;
                 case 'C':
-                        connection_info = get_connection_info(0, 0);
+                        connection_info = get_connection_info(ssh, 0, 0);
                         if (parse_server_match_testspec(connection_info,
                             optarg) == -1)
                                 exit(1);
@@ -1624,17 +1576,13 @@ main(int ac, char **av)
         }
         if (rexeced_flag || inetd_flag)
                 rexec_flag = 0;
-        if (!test_flag && (rexec_flag && (av[0] == NULL || *av[0] != '/')))
+        if (!test_flag && rexec_flag && !path_absolute(av[0]))
                 fatal("sshd re-exec requires execution with an absolute path");
         if (rexeced_flag)
                 closefrom(REEXEC_MIN_FREE_FD);
         else
                 closefrom(REEXEC_DEVCRYPTO_RESERVED_FD);
 
-#ifdef WITH_OPENSSL
-        OpenSSL_add_all_algorithms();
-#endif
-
         /* If requested, redirect the logs to the specified logfile. */
         if (logfile != NULL)
                 log_redirect_stderr_to(logfile);
@@ -1669,16 +1617,24 @@ main(int ac, char **av)
         /* Fetch our configuration */
         if ((cfg = sshbuf_new()) == NULL)
                 fatal("%s: sshbuf_new failed", __func__);
-        if (rexeced_flag)
+        if (rexeced_flag) {
                 recv_rexec_state(REEXEC_CONFIG_PASS_FD, cfg);
+                if (!debug_flag) {
+                        startup_pipe = dup(REEXEC_STARTUP_PIPE_FD);
+                        close(REEXEC_STARTUP_PIPE_FD);
+                        /*
+                         * 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);
+                }
+        }
         else if (strcasecmp(config_file_name, "none") != 0)
                 load_server_config(config_file_name, cfg);
 
         parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name,
             cfg, NULL);
 
-        seed_rng();
-
         /* Fill in default values for those options not explicitly set. */
         fill_default_server_options(&options);
 
@@ -1723,7 +1679,7 @@ main(int ac, char **av)
 
         debug("sshd version %s, %s", SSH_VERSION,
 #ifdef WITH_OPENSSL
-            SSLeay_version(SSLEAY_VERSION)
+            OpenSSL_version(OPENSSL_VERSION)
 #else
             "without OpenSSL"
 #endif
@@ -1760,15 +1716,18 @@ main(int ac, char **av)
         }
 
         for (i = 0; i < options.num_host_key_files; i++) {
+                int ll = options.host_key_file_userprovided[i] ?
+                    SYSLOG_LEVEL_ERROR : SYSLOG_LEVEL_DEBUG1;
+
                 if (options.host_key_files[i] == NULL)
                         continue;
                 if ((r = sshkey_load_private(options.host_key_files[i], "",
                     &key, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR)
-                        error("Error loading host key \"%s\": %s",
+                        do_log2(ll, "Unable to load host key \"%s\": %s",
                             options.host_key_files[i], ssh_err(r));
                 if ((r = sshkey_load_public(options.host_key_files[i],
                     &pubkey, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR)
-                        error("Error loading host key \"%s\": %s",
+                        do_log2(ll, "Unable to load host key \"%s\": %s",
                             options.host_key_files[i], ssh_err(r));
                 if (pubkey == NULL && key != NULL)
                         if ((r = sshkey_from_private(key, &pubkey)) != 0)
@@ -1785,7 +1744,7 @@ main(int ac, char **av)
                         keytype = key->type;
                         accumulate_host_timing_secret(cfg, key);
                 } else {
-                        error("Could not load host key: %s",
+                        do_log2(ll, "Unable to load host key: %s",
                             options.host_key_files[i]);
                         sensitive_data.host_keys[i] = NULL;
                         sensitive_data.host_pubkeys[i] = NULL;
@@ -1883,7 +1842,7 @@ main(int ac, char **av)
                  * use a blank one that will cause no predicate to match.
                  */
                 if (connection_info == NULL)
-                        connection_info = get_connection_info(0, 0);
+                        connection_info = get_connection_info(ssh, 0, 0);
                 parse_server_match_config(&options, connection_info);
                 dump_config(&options);
         }
@@ -2058,9 +2017,10 @@ main(int ac, char **av)
          * Register our connection.  This turns encryption off because we do
          * not have a key.
          */
-        packet_set_connection(sock_in, sock_out);
-        packet_set_server();
-        ssh = active_state; /* XXX */
+        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);
 
         check_ip_options(ssh);
 
@@ -2070,7 +2030,7 @@ main(int ac, char **av)
         process_permitopen(ssh, &options);
 
         /* Set SO_KEEPALIVE if requested. */
-        if (options.tcp_keep_alive && packet_connection_is_on_socket() &&
+        if (options.tcp_keep_alive && ssh_packet_connection_is_on_socket(ssh) &&
             setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) < 0)
                 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
 
@@ -2116,11 +2076,14 @@ main(int ac, char **av)
         if (!debug_flag)
                 alarm(options.login_grace_time);
 
-        sshd_exchange_identification(ssh, sock_in, sock_out);
-        packet_set_nonblocking();
+        if (kex_exchange_identification(ssh, -1, options.version_addendum) != 0)
+                cleanup_exit(255); /* error already logged */
+
+        ssh_packet_set_nonblocking(ssh);
 
         /* allocate authentication context */
         authctxt = xcalloc(1, sizeof(*authctxt));
+        ssh->authctxt = authctxt;
 
         authctxt->loginmsg = loginmsg;
 
@@ -2137,7 +2100,7 @@ main(int ac, char **av)
         auth_debug_reset();
 
         if (use_privsep) {
-                if (privsep_preauth(authctxt) == 1)
+                if (privsep_preauth(ssh) == 1)
                         goto authenticated;
         } else if (have_agent) {
                 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) {
@@ -2148,16 +2111,16 @@ main(int ac, char **av)
 
         /* perform the key exchange */
         /* authenticate user and start session */
-        do_ssh2_kex();
-        do_authentication2(authctxt);
+        do_ssh2_kex(ssh);
+        do_authentication2(ssh);
 
         /*
          * If we use privilege separation, the unprivileged child transfers
          * the current keystate and exits
          */
         if (use_privsep) {
-                mm_send_keystate(pmonitor);
-                packet_clear_keys();
+                mm_send_keystate(ssh, pmonitor);
+                ssh_packet_clear_keys(ssh);
                 exit(0);
         }
 
@@ -2175,7 +2138,7 @@ main(int ac, char **av)
         }
 
 #ifdef SSH_AUDIT_EVENTS
-        audit_event(SSH_AUTH_SUCCESS);
+        audit_event(ssh, SSH_AUTH_SUCCESS);
 #endif
 
 #ifdef GSSAPI
@@ -2197,11 +2160,11 @@ main(int ac, char **av)
          * file descriptor passing.
          */
         if (use_privsep) {
-                privsep_postauth(authctxt);
+                privsep_postauth(ssh, authctxt);
                 /* the monitor process [priv] will not return */
         }
 
-        packet_set_timeout(options.client_alive_interval,
+        ssh_packet_set_timeout(ssh, options.client_alive_interval,
             options.client_alive_count_max);
 
         /* Try to send all our hostkeys to the client */
@@ -2211,7 +2174,7 @@ main(int ac, char **av)
         do_authenticated(ssh, authctxt);
 
         /* The connection has been terminated. */
-        packet_get_bytes(&ibytes, &obytes);
+        ssh_packet_get_bytes(ssh, &ibytes, &obytes);
         verbose("Transferred: sent %llu, received %llu bytes",
             (unsigned long long)obytes, (unsigned long long)ibytes);
 
@@ -2223,10 +2186,10 @@ main(int ac, char **av)
 #endif /* USE_PAM */
 
 #ifdef SSH_AUDIT_EVENTS
-        PRIVSEP(audit_event(SSH_CONNECTION_CLOSE));
+        PRIVSEP(audit_event(ssh, SSH_CONNECTION_CLOSE));
 #endif
 
-        packet_close();
+        ssh_packet_close(ssh);
 
         if (use_privsep)
                 mm_terminate();
@@ -2235,32 +2198,42 @@ main(int ac, char **av)
 }
 
 int
-sshd_hostkey_sign(struct sshkey *privkey, struct sshkey *pubkey,
-    u_char **signature, size_t *slenp, const u_char *data, size_t dlen,
-    const char *alg, u_int flag)
+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)
 {
         int r;
 
-        if (privkey) {
-                if (PRIVSEP(sshkey_sign(privkey, signature, slenp, data, dlen,
-                    alg, datafellows)) < 0)
-                        fatal("%s: key_sign failed", __func__);
-        } else if (use_privsep) {
-                if (mm_sshkey_sign(pubkey, signature, slenp, data, dlen,
-                    alg, datafellows) < 0)
-                        fatal("%s: pubkey_sign failed", __func__);
+        if (use_privsep) {
+                if (privkey) {
+                        if (mm_sshkey_sign(ssh, privkey, signature, slenp,
+                            data, dlen, alg, ssh->compat) < 0)
+                                fatal("%s: privkey sign failed", __func__);
+                } else {
+                        if (mm_sshkey_sign(ssh, pubkey, signature, slenp,
+                            data, dlen, alg, ssh->compat) < 0)
+                                fatal("%s: pubkey sign failed", __func__);
+                }
         } else {
-                if ((r = ssh_agent_sign(auth_sock, pubkey, signature, slenp,
-                    data, dlen, alg, datafellows)) != 0)
-                        fatal("%s: ssh_agent_sign failed: %s",
-                            __func__, ssh_err(r));
+                if (privkey) {
+                        if (sshkey_sign(privkey, signature, slenp, data, dlen,
+                            alg, ssh->compat) < 0)
+                                fatal("%s: privkey sign failed", __func__);
+                } else {
+                        if ((r = ssh_agent_sign(auth_sock, pubkey,
+                            signature, slenp, data, dlen, alg,
+                            ssh->compat)) != 0) {
+                                fatal("%s: agent sign failed: %s",
+                                    __func__, ssh_err(r));
+                        }
+                }
         }
         return 0;
 }
 
 /* SSH2 key exchange */
 static void
-do_ssh2_kex(void)
+do_ssh2_kex(struct ssh *ssh)
 {
         char *myproposal[PROPOSAL_MAX] = { KEX_SERVER };
         struct kex *kex;
@@ -2281,38 +2254,36 @@ do_ssh2_kex(void)
         }
 
         if (options.rekey_limit || options.rekey_interval)
-                packet_set_rekey_limits(options.rekey_limit,
+                ssh_packet_set_rekey_limits(ssh, options.rekey_limit,
                     options.rekey_interval);
 
         myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = compat_pkalg_proposal(
             list_hostkey_types());
 
         /* start key exchange */
-        if ((r = kex_setup(active_state, myproposal)) != 0)
+        if ((r = kex_setup(ssh, myproposal)) != 0)
                 fatal("kex_setup: %s", ssh_err(r));
-        kex = active_state->kex;
+        kex = ssh->kex;
 #ifdef WITH_OPENSSL
-        kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
-        kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
-        kex->kex[KEX_DH_GRP14_SHA256] = kexdh_server;
-        kex->kex[KEX_DH_GRP16_SHA512] = kexdh_server;
-        kex->kex[KEX_DH_GRP18_SHA512] = kexdh_server;
+        kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server;
+        kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server;
+        kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server;
+        kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server;
+        kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server;
         kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
         kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
 # ifdef OPENSSL_HAS_ECC
-        kex->kex[KEX_ECDH_SHA2] = kexecdh_server;
+        kex->kex[KEX_ECDH_SHA2] = kex_gen_server;
 # endif
 #endif
-        kex->kex[KEX_C25519_SHA256] = kexc25519_server;
-        kex->server = 1;
-        kex->client_version_string=client_version_string;
-        kex->server_version_string=server_version_string;
+        kex->kex[KEX_C25519_SHA256] = kex_gen_server;
+        kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_gen_server;
         kex->load_host_public_key=&get_hostkey_public_by_type;
         kex->load_host_private_key=&get_hostkey_private_by_type;
         kex->host_key_index=&get_hostkey_index;
         kex->sign = sshd_hostkey_sign;
 
-        ssh_dispatch_run_fatal(active_state, DISPATCH_BLOCK, &kex->done);
+        ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &kex->done);
 
         session_id2 = kex->session_id;
         session_id2_len = kex->session_id_len;
@@ -2331,10 +2302,8 @@ do_ssh2_kex(void)
 void
 cleanup_exit(int i)
 {
-        struct ssh *ssh = active_state; /* XXX */
-
-        if (the_authctxt) {
-                do_cleanup(ssh, the_authctxt);
+        if (the_active_state != NULL && the_authctxt != NULL) {
+                do_cleanup(the_active_state, the_authctxt);
                 if (use_privsep && privsep_is_preauth &&
                     pmonitor != NULL && pmonitor->m_pid > 1) {
                         debug("Killing privsep child %d", pmonitor->m_pid);
@@ -2346,8 +2315,8 @@ cleanup_exit(int i)
         }
 #ifdef SSH_AUDIT_EVENTS
         /* done after do_cleanup so it can cancel the PAM auth 'thread' */
-        if (!use_privsep || mm_is_monitor())
-                audit_event(SSH_CONNECTION_ABANDON);
+        if (the_active_state != NULL && (!use_privsep || mm_is_monitor()))
+                audit_event(the_active_state, SSH_CONNECTION_ABANDON);
 #endif
         _exit(i);
 }