xref: /freebsd/crypto/openssh/sshd.c (revision 38a52bd3b5cac3da6f7f6eef3dd050e6aa08ebb3)
1 /* $OpenBSD: sshd.c,v 1.591 2022/09/17 10:34:29 djm Exp $ */
2 /*
3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5  *                    All rights reserved
6  * This program is the ssh daemon.  It listens for connections from clients,
7  * and performs authentication, executes use commands or shell, and forwards
8  * information to/from the application to the user client over an encrypted
9  * connection.  This can also handle forwarding of X11, TCP/IP, and
10  * authentication agent connections.
11  *
12  * As far as I am concerned, the code I have written for this software
13  * can be used freely for any purpose.  Any derived versions of this
14  * software must be clearly marked as such, and if the derived work is
15  * incompatible with the protocol description in the RFC file, it must be
16  * called by a name other than "ssh" or "Secure Shell".
17  *
18  * SSH2 implementation:
19  * Privilege Separation:
20  *
21  * Copyright (c) 2000, 2001, 2002 Markus Friedl.  All rights reserved.
22  * Copyright (c) 2002 Niels Provos.  All rights reserved.
23  *
24  * Redistribution and use in source and binary forms, with or without
25  * modification, are permitted provided that the following conditions
26  * are met:
27  * 1. Redistributions of source code must retain the above copyright
28  *    notice, this list of conditions and the following disclaimer.
29  * 2. Redistributions in binary form must reproduce the above copyright
30  *    notice, this list of conditions and the following disclaimer in the
31  *    documentation and/or other materials provided with the distribution.
32  *
33  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
34  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
35  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
36  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
37  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
38  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
39  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
40  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
41  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
42  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
43  */
44 
45 #include "includes.h"
46 
47 #include <sys/types.h>
48 #include <sys/ioctl.h>
49 #include <sys/mman.h>
50 #include <sys/socket.h>
51 #ifdef HAVE_SYS_STAT_H
52 # include <sys/stat.h>
53 #endif
54 #ifdef HAVE_SYS_TIME_H
55 # include <sys/time.h>
56 #endif
57 #include "openbsd-compat/sys-tree.h"
58 #include "openbsd-compat/sys-queue.h"
59 #include <sys/wait.h>
60 
61 #include <errno.h>
62 #include <fcntl.h>
63 #include <netdb.h>
64 #ifdef HAVE_PATHS_H
65 #include <paths.h>
66 #endif
67 #include <grp.h>
68 #ifdef HAVE_POLL_H
69 #include <poll.h>
70 #endif
71 #include <pwd.h>
72 #include <signal.h>
73 #include <stdarg.h>
74 #include <stdio.h>
75 #include <stdlib.h>
76 #include <string.h>
77 #include <unistd.h>
78 #include <limits.h>
79 
80 #ifdef WITH_OPENSSL
81 #include <openssl/dh.h>
82 #include <openssl/bn.h>
83 #include <openssl/rand.h>
84 #include "openbsd-compat/openssl-compat.h"
85 #endif
86 
87 #ifdef HAVE_SECUREWARE
88 #include <sys/security.h>
89 #include <prot.h>
90 #endif
91 
92 #ifdef __FreeBSD__
93 #include <resolv.h>
94 #if defined(GSSAPI) && defined(HAVE_GSSAPI_GSSAPI_H)
95 #include <gssapi/gssapi.h>
96 #elif defined(GSSAPI) && defined(HAVE_GSSAPI_H)
97 #include <gssapi.h>
98 #endif
99 #endif
100 
101 #include "xmalloc.h"
102 #include "ssh.h"
103 #include "ssh2.h"
104 #include "sshpty.h"
105 #include "packet.h"
106 #include "log.h"
107 #include "sshbuf.h"
108 #include "misc.h"
109 #include "match.h"
110 #include "servconf.h"
111 #include "uidswap.h"
112 #include "compat.h"
113 #include "cipher.h"
114 #include "digest.h"
115 #include "sshkey.h"
116 #include "kex.h"
117 #include "myproposal.h"
118 #include "authfile.h"
119 #include "pathnames.h"
120 #include "atomicio.h"
121 #include "canohost.h"
122 #include "hostfile.h"
123 #include "auth.h"
124 #include "authfd.h"
125 #include "msg.h"
126 #include "dispatch.h"
127 #include "channels.h"
128 #include "session.h"
129 #include "monitor.h"
130 #ifdef GSSAPI
131 #include "ssh-gss.h"
132 #endif
133 #include "monitor_wrap.h"
134 #include "ssh-sandbox.h"
135 #include "auth-options.h"
136 #include "version.h"
137 #include "ssherr.h"
138 #include "sk-api.h"
139 #include "srclimit.h"
140 #include "dh.h"
141 #include "blacklist_client.h"
142 
143 #ifdef LIBWRAP
144 #include <tcpd.h>
145 #include <syslog.h>
146 extern int allow_severity;
147 extern int deny_severity;
148 #endif /* LIBWRAP */
149 
150 /* Re-exec fds */
151 #define REEXEC_DEVCRYPTO_RESERVED_FD	(STDERR_FILENO + 1)
152 #define REEXEC_STARTUP_PIPE_FD		(STDERR_FILENO + 2)
153 #define REEXEC_CONFIG_PASS_FD		(STDERR_FILENO + 3)
154 #define REEXEC_MIN_FREE_FD		(STDERR_FILENO + 4)
155 
156 extern char *__progname;
157 
158 /* Server configuration options. */
159 ServerOptions options;
160 
161 /* Name of the server configuration file. */
162 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
163 
164 /*
165  * Debug mode flag.  This can be set on the command line.  If debug
166  * mode is enabled, extra debugging output will be sent to the system
167  * log, the daemon will not go to background, and will exit after processing
168  * the first connection.
169  */
170 int debug_flag = 0;
171 
172 /*
173  * Indicating that the daemon should only test the configuration and keys.
174  * If test_flag > 1 ("-T" flag), then sshd will also dump the effective
175  * configuration, optionally using connection information provided by the
176  * "-C" flag.
177  */
178 static int test_flag = 0;
179 
180 /* Flag indicating that the daemon is being started from inetd. */
181 static int inetd_flag = 0;
182 
183 /* Flag indicating that sshd should not detach and become a daemon. */
184 static int no_daemon_flag = 0;
185 
186 /* debug goes to stderr unless inetd_flag is set */
187 static int log_stderr = 0;
188 
189 /* Saved arguments to main(). */
190 static char **saved_argv;
191 static int saved_argc;
192 
193 /* re-exec */
194 static int rexeced_flag = 0;
195 static int rexec_flag = 1;
196 static int rexec_argc = 0;
197 static char **rexec_argv;
198 
199 /*
200  * The sockets that the server is listening; this is used in the SIGHUP
201  * signal handler.
202  */
203 #define	MAX_LISTEN_SOCKS	16
204 static int listen_socks[MAX_LISTEN_SOCKS];
205 static int num_listen_socks = 0;
206 
207 /* Daemon's agent connection */
208 int auth_sock = -1;
209 static int have_agent = 0;
210 
211 /*
212  * Any really sensitive data in the application is contained in this
213  * structure. The idea is that this structure could be locked into memory so
214  * that the pages do not get written into swap.  However, there are some
215  * problems. The private key contains BIGNUMs, and we do not (in principle)
216  * have access to the internals of them, and locking just the structure is
217  * not very useful.  Currently, memory locking is not implemented.
218  */
219 struct {
220 	struct sshkey	**host_keys;		/* all private host keys */
221 	struct sshkey	**host_pubkeys;		/* all public host keys */
222 	struct sshkey	**host_certificates;	/* all public host certificates */
223 	int		have_ssh2_key;
224 } sensitive_data;
225 
226 /* This is set to true when a signal is received. */
227 static volatile sig_atomic_t received_sighup = 0;
228 static volatile sig_atomic_t received_sigterm = 0;
229 
230 /* record remote hostname or ip */
231 u_int utmp_len = HOST_NAME_MAX+1;
232 
233 /*
234  * startup_pipes/flags are used for tracking children of the listening sshd
235  * process early in their lifespans. This tracking is needed for three things:
236  *
237  * 1) Implementing the MaxStartups limit of concurrent unauthenticated
238  *    connections.
239  * 2) Avoiding a race condition for SIGHUP processing, where child processes
240  *    may have listen_socks open that could collide with main listener process
241  *    after it restarts.
242  * 3) Ensuring that rexec'd sshd processes have received their initial state
243  *    from the parent listen process before handling SIGHUP.
244  *
245  * Child processes signal that they have completed closure of the listen_socks
246  * and (if applicable) received their rexec state by sending a char over their
247  * sock. Child processes signal that authentication has completed by closing
248  * the sock (or by exiting).
249  */
250 static int *startup_pipes = NULL;
251 static int *startup_flags = NULL;	/* Indicates child closed listener */
252 static int startup_pipe = -1;		/* in child */
253 
254 /* variables used for privilege separation */
255 int use_privsep = -1;
256 struct monitor *pmonitor = NULL;
257 int privsep_is_preauth = 1;
258 static int privsep_chroot = 1;
259 
260 /* global connection state and authentication contexts */
261 Authctxt *the_authctxt = NULL;
262 struct ssh *the_active_state;
263 
264 /* global key/cert auth options. XXX move to permanent ssh->authctxt? */
265 struct sshauthopt *auth_opts = NULL;
266 
267 /* sshd_config buffer */
268 struct sshbuf *cfg;
269 
270 /* Included files from the configuration file */
271 struct include_list includes = TAILQ_HEAD_INITIALIZER(includes);
272 
273 /* message to be displayed after login */
274 struct sshbuf *loginmsg;
275 
276 /* Unprivileged user */
277 struct passwd *privsep_pw = NULL;
278 
279 /* Prototypes for various functions defined later in this file. */
280 void destroy_sensitive_data(void);
281 void demote_sensitive_data(void);
282 static void do_ssh2_kex(struct ssh *);
283 
284 static char *listener_proctitle;
285 
286 /*
287  * Close all listening sockets
288  */
289 static void
290 close_listen_socks(void)
291 {
292 	int i;
293 
294 	for (i = 0; i < num_listen_socks; i++)
295 		close(listen_socks[i]);
296 	num_listen_socks = 0;
297 }
298 
299 static void
300 close_startup_pipes(void)
301 {
302 	int i;
303 
304 	if (startup_pipes)
305 		for (i = 0; i < options.max_startups; i++)
306 			if (startup_pipes[i] != -1)
307 				close(startup_pipes[i]);
308 }
309 
310 /*
311  * Signal handler for SIGHUP.  Sshd execs itself when it receives SIGHUP;
312  * the effect is to reread the configuration file (and to regenerate
313  * the server key).
314  */
315 
316 /*ARGSUSED*/
317 static void
318 sighup_handler(int sig)
319 {
320 	received_sighup = 1;
321 }
322 
323 /*
324  * Called from the main program after receiving SIGHUP.
325  * Restarts the server.
326  */
327 static void
328 sighup_restart(void)
329 {
330 	logit("Received SIGHUP; restarting.");
331 	if (options.pid_file != NULL)
332 		unlink(options.pid_file);
333 	platform_pre_restart();
334 	close_listen_socks();
335 	close_startup_pipes();
336 	ssh_signal(SIGHUP, SIG_IGN); /* will be restored after exec */
337 	execv(saved_argv[0], saved_argv);
338 	logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
339 	    strerror(errno));
340 	exit(1);
341 }
342 
343 /*
344  * Generic signal handler for terminating signals in the master daemon.
345  */
346 /*ARGSUSED*/
347 static void
348 sigterm_handler(int sig)
349 {
350 	received_sigterm = sig;
351 }
352 
353 /*
354  * SIGCHLD handler.  This is called whenever a child dies.  This will then
355  * reap any zombies left by exited children.
356  */
357 /*ARGSUSED*/
358 static void
359 main_sigchld_handler(int sig)
360 {
361 	int save_errno = errno;
362 	pid_t pid;
363 	int status;
364 
365 	while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
366 	    (pid == -1 && errno == EINTR))
367 		;
368 	errno = save_errno;
369 }
370 
371 /*
372  * Signal handler for the alarm after the login grace period has expired.
373  */
374 /*ARGSUSED*/
375 static void
376 grace_alarm_handler(int sig)
377 {
378 	/*
379 	 * Try to kill any processes that we have spawned, E.g. authorized
380 	 * keys command helpers or privsep children.
381 	 */
382 	if (getpgid(0) == getpid()) {
383 		ssh_signal(SIGTERM, SIG_IGN);
384 		kill(0, SIGTERM);
385 	}
386 
387 	BLACKLIST_NOTIFY(the_active_state, BLACKLIST_AUTH_FAIL, "ssh");
388 
389 	/* Log error and exit. */
390 	sigdie("Timeout before authentication for %s port %d",
391 	    ssh_remote_ipaddr(the_active_state),
392 	    ssh_remote_port(the_active_state));
393 }
394 
395 /* Destroy the host and server keys.  They will no longer be needed. */
396 void
397 destroy_sensitive_data(void)
398 {
399 	u_int i;
400 
401 	for (i = 0; i < options.num_host_key_files; i++) {
402 		if (sensitive_data.host_keys[i]) {
403 			sshkey_free(sensitive_data.host_keys[i]);
404 			sensitive_data.host_keys[i] = NULL;
405 		}
406 		if (sensitive_data.host_certificates[i]) {
407 			sshkey_free(sensitive_data.host_certificates[i]);
408 			sensitive_data.host_certificates[i] = NULL;
409 		}
410 	}
411 }
412 
413 /* Demote private to public keys for network child */
414 void
415 demote_sensitive_data(void)
416 {
417 	struct sshkey *tmp;
418 	u_int i;
419 	int r;
420 
421 	for (i = 0; i < options.num_host_key_files; i++) {
422 		if (sensitive_data.host_keys[i]) {
423 			if ((r = sshkey_from_private(
424 			    sensitive_data.host_keys[i], &tmp)) != 0)
425 				fatal_r(r, "could not demote host %s key",
426 				    sshkey_type(sensitive_data.host_keys[i]));
427 			sshkey_free(sensitive_data.host_keys[i]);
428 			sensitive_data.host_keys[i] = tmp;
429 		}
430 		/* Certs do not need demotion */
431 	}
432 }
433 
434 static void
435 reseed_prngs(void)
436 {
437 	u_int32_t rnd[256];
438 
439 #ifdef WITH_OPENSSL
440 	RAND_poll();
441 #endif
442 	arc4random_stir(); /* noop on recent arc4random() implementations */
443 	arc4random_buf(rnd, sizeof(rnd)); /* let arc4random notice PID change */
444 
445 #ifdef WITH_OPENSSL
446 	RAND_seed(rnd, sizeof(rnd));
447 	/* give libcrypto a chance to notice the PID change */
448 	if ((RAND_bytes((u_char *)rnd, 1)) != 1)
449 		fatal("%s: RAND_bytes failed", __func__);
450 #endif
451 
452 	explicit_bzero(rnd, sizeof(rnd));
453 }
454 
455 static void
456 privsep_preauth_child(void)
457 {
458 	gid_t gidset[1];
459 
460 	/* Enable challenge-response authentication for privilege separation */
461 	privsep_challenge_enable();
462 
463 #ifdef GSSAPI
464 	/* Cache supported mechanism OIDs for later use */
465 	ssh_gssapi_prepare_supported_oids();
466 #endif
467 
468 	reseed_prngs();
469 
470 	/* Demote the private keys to public keys. */
471 	demote_sensitive_data();
472 
473 	/* Demote the child */
474 	if (privsep_chroot) {
475 		/* Change our root directory */
476 		if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
477 			fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
478 			    strerror(errno));
479 		if (chdir("/") == -1)
480 			fatal("chdir(\"/\"): %s", strerror(errno));
481 
482 		/* Drop our privileges */
483 		debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid,
484 		    (u_int)privsep_pw->pw_gid);
485 		gidset[0] = privsep_pw->pw_gid;
486 		if (setgroups(1, gidset) == -1)
487 			fatal("setgroups: %.100s", strerror(errno));
488 		permanently_set_uid(privsep_pw);
489 	}
490 }
491 
492 static int
493 privsep_preauth(struct ssh *ssh)
494 {
495 	int status, r;
496 	pid_t pid;
497 	struct ssh_sandbox *box = NULL;
498 
499 	/* Set up unprivileged child process to deal with network data */
500 	pmonitor = monitor_init();
501 	/* Store a pointer to the kex for later rekeying */
502 	pmonitor->m_pkex = &ssh->kex;
503 
504 	if (use_privsep == PRIVSEP_ON)
505 		box = ssh_sandbox_init(pmonitor);
506 	pid = fork();
507 	if (pid == -1) {
508 		fatal("fork of unprivileged child failed");
509 	} else if (pid != 0) {
510 		debug2("Network child is on pid %ld", (long)pid);
511 
512 		pmonitor->m_pid = pid;
513 		if (have_agent) {
514 			r = ssh_get_authentication_socket(&auth_sock);
515 			if (r != 0) {
516 				error_r(r, "Could not get agent socket");
517 				have_agent = 0;
518 			}
519 		}
520 		if (box != NULL)
521 			ssh_sandbox_parent_preauth(box, pid);
522 		monitor_child_preauth(ssh, pmonitor);
523 
524 		/* Wait for the child's exit status */
525 		while (waitpid(pid, &status, 0) == -1) {
526 			if (errno == EINTR)
527 				continue;
528 			pmonitor->m_pid = -1;
529 			fatal_f("waitpid: %s", strerror(errno));
530 		}
531 		privsep_is_preauth = 0;
532 		pmonitor->m_pid = -1;
533 		if (WIFEXITED(status)) {
534 			if (WEXITSTATUS(status) != 0)
535 				fatal_f("preauth child exited with status %d",
536 				    WEXITSTATUS(status));
537 		} else if (WIFSIGNALED(status))
538 			fatal_f("preauth child terminated by signal %d",
539 			    WTERMSIG(status));
540 		if (box != NULL)
541 			ssh_sandbox_parent_finish(box);
542 		return 1;
543 	} else {
544 		/* child */
545 		close(pmonitor->m_sendfd);
546 		close(pmonitor->m_log_recvfd);
547 
548 		/* Arrange for logging to be sent to the monitor */
549 		set_log_handler(mm_log_handler, pmonitor);
550 
551 		privsep_preauth_child();
552 		setproctitle("%s", "[net]");
553 		if (box != NULL)
554 			ssh_sandbox_child(box);
555 
556 		return 0;
557 	}
558 }
559 
560 static void
561 privsep_postauth(struct ssh *ssh, Authctxt *authctxt)
562 {
563 #ifdef DISABLE_FD_PASSING
564 	if (1) {
565 #else
566 	if (authctxt->pw->pw_uid == 0) {
567 #endif
568 		/* File descriptor passing is broken or root login */
569 		use_privsep = 0;
570 		goto skip;
571 	}
572 
573 	/* New socket pair */
574 	monitor_reinit(pmonitor);
575 
576 	pmonitor->m_pid = fork();
577 	if (pmonitor->m_pid == -1)
578 		fatal("fork of unprivileged child failed");
579 	else if (pmonitor->m_pid != 0) {
580 		verbose("User child is on pid %ld", (long)pmonitor->m_pid);
581 		sshbuf_reset(loginmsg);
582 		monitor_clear_keystate(ssh, pmonitor);
583 		monitor_child_postauth(ssh, pmonitor);
584 
585 		/* NEVERREACHED */
586 		exit(0);
587 	}
588 
589 	/* child */
590 
591 	close(pmonitor->m_sendfd);
592 	pmonitor->m_sendfd = -1;
593 
594 	/* Demote the private keys to public keys. */
595 	demote_sensitive_data();
596 
597 	reseed_prngs();
598 
599 	/* Drop privileges */
600 	do_setusercontext(authctxt->pw);
601 
602  skip:
603 	/* It is safe now to apply the key state */
604 	monitor_apply_keystate(ssh, pmonitor);
605 
606 	/*
607 	 * Tell the packet layer that authentication was successful, since
608 	 * this information is not part of the key state.
609 	 */
610 	ssh_packet_set_authenticated(ssh);
611 }
612 
613 static void
614 append_hostkey_type(struct sshbuf *b, const char *s)
615 {
616 	int r;
617 
618 	if (match_pattern_list(s, options.hostkeyalgorithms, 0) != 1) {
619 		debug3_f("%s key not permitted by HostkeyAlgorithms", s);
620 		return;
621 	}
622 	if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) > 0 ? "," : "", s)) != 0)
623 		fatal_fr(r, "sshbuf_putf");
624 }
625 
626 static char *
627 list_hostkey_types(void)
628 {
629 	struct sshbuf *b;
630 	struct sshkey *key;
631 	char *ret;
632 	u_int i;
633 
634 	if ((b = sshbuf_new()) == NULL)
635 		fatal_f("sshbuf_new failed");
636 	for (i = 0; i < options.num_host_key_files; i++) {
637 		key = sensitive_data.host_keys[i];
638 		if (key == NULL)
639 			key = sensitive_data.host_pubkeys[i];
640 		if (key == NULL)
641 			continue;
642 		switch (key->type) {
643 		case KEY_RSA:
644 			/* for RSA we also support SHA2 signatures */
645 			append_hostkey_type(b, "rsa-sha2-512");
646 			append_hostkey_type(b, "rsa-sha2-256");
647 			/* FALLTHROUGH */
648 		case KEY_DSA:
649 		case KEY_ECDSA:
650 		case KEY_ED25519:
651 		case KEY_ECDSA_SK:
652 		case KEY_ED25519_SK:
653 		case KEY_XMSS:
654 			append_hostkey_type(b, sshkey_ssh_name(key));
655 			break;
656 		}
657 		/* If the private key has a cert peer, then list that too */
658 		key = sensitive_data.host_certificates[i];
659 		if (key == NULL)
660 			continue;
661 		switch (key->type) {
662 		case KEY_RSA_CERT:
663 			/* for RSA we also support SHA2 signatures */
664 			append_hostkey_type(b,
665 			    "rsa-sha2-512-cert-v01@openssh.com");
666 			append_hostkey_type(b,
667 			    "rsa-sha2-256-cert-v01@openssh.com");
668 			/* FALLTHROUGH */
669 		case KEY_DSA_CERT:
670 		case KEY_ECDSA_CERT:
671 		case KEY_ED25519_CERT:
672 		case KEY_ECDSA_SK_CERT:
673 		case KEY_ED25519_SK_CERT:
674 		case KEY_XMSS_CERT:
675 			append_hostkey_type(b, sshkey_ssh_name(key));
676 			break;
677 		}
678 	}
679 	if ((ret = sshbuf_dup_string(b)) == NULL)
680 		fatal_f("sshbuf_dup_string failed");
681 	sshbuf_free(b);
682 	debug_f("%s", ret);
683 	return ret;
684 }
685 
686 static struct sshkey *
687 get_hostkey_by_type(int type, int nid, int need_private, struct ssh *ssh)
688 {
689 	u_int i;
690 	struct sshkey *key;
691 
692 	for (i = 0; i < options.num_host_key_files; i++) {
693 		switch (type) {
694 		case KEY_RSA_CERT:
695 		case KEY_DSA_CERT:
696 		case KEY_ECDSA_CERT:
697 		case KEY_ED25519_CERT:
698 		case KEY_ECDSA_SK_CERT:
699 		case KEY_ED25519_SK_CERT:
700 		case KEY_XMSS_CERT:
701 			key = sensitive_data.host_certificates[i];
702 			break;
703 		default:
704 			key = sensitive_data.host_keys[i];
705 			if (key == NULL && !need_private)
706 				key = sensitive_data.host_pubkeys[i];
707 			break;
708 		}
709 		if (key == NULL || key->type != type)
710 			continue;
711 		switch (type) {
712 		case KEY_ECDSA:
713 		case KEY_ECDSA_SK:
714 		case KEY_ECDSA_CERT:
715 		case KEY_ECDSA_SK_CERT:
716 			if (key->ecdsa_nid != nid)
717 				continue;
718 			/* FALLTHROUGH */
719 		default:
720 			return need_private ?
721 			    sensitive_data.host_keys[i] : key;
722 		}
723 	}
724 	return NULL;
725 }
726 
727 struct sshkey *
728 get_hostkey_public_by_type(int type, int nid, struct ssh *ssh)
729 {
730 	return get_hostkey_by_type(type, nid, 0, ssh);
731 }
732 
733 struct sshkey *
734 get_hostkey_private_by_type(int type, int nid, struct ssh *ssh)
735 {
736 	return get_hostkey_by_type(type, nid, 1, ssh);
737 }
738 
739 struct sshkey *
740 get_hostkey_by_index(int ind)
741 {
742 	if (ind < 0 || (u_int)ind >= options.num_host_key_files)
743 		return (NULL);
744 	return (sensitive_data.host_keys[ind]);
745 }
746 
747 struct sshkey *
748 get_hostkey_public_by_index(int ind, struct ssh *ssh)
749 {
750 	if (ind < 0 || (u_int)ind >= options.num_host_key_files)
751 		return (NULL);
752 	return (sensitive_data.host_pubkeys[ind]);
753 }
754 
755 int
756 get_hostkey_index(struct sshkey *key, int compare, struct ssh *ssh)
757 {
758 	u_int i;
759 
760 	for (i = 0; i < options.num_host_key_files; i++) {
761 		if (sshkey_is_cert(key)) {
762 			if (key == sensitive_data.host_certificates[i] ||
763 			    (compare && sensitive_data.host_certificates[i] &&
764 			    sshkey_equal(key,
765 			    sensitive_data.host_certificates[i])))
766 				return (i);
767 		} else {
768 			if (key == sensitive_data.host_keys[i] ||
769 			    (compare && sensitive_data.host_keys[i] &&
770 			    sshkey_equal(key, sensitive_data.host_keys[i])))
771 				return (i);
772 			if (key == sensitive_data.host_pubkeys[i] ||
773 			    (compare && sensitive_data.host_pubkeys[i] &&
774 			    sshkey_equal(key, sensitive_data.host_pubkeys[i])))
775 				return (i);
776 		}
777 	}
778 	return (-1);
779 }
780 
781 /* Inform the client of all hostkeys */
782 static void
783 notify_hostkeys(struct ssh *ssh)
784 {
785 	struct sshbuf *buf;
786 	struct sshkey *key;
787 	u_int i, nkeys;
788 	int r;
789 	char *fp;
790 
791 	/* Some clients cannot cope with the hostkeys message, skip those. */
792 	if (ssh->compat & SSH_BUG_HOSTKEYS)
793 		return;
794 
795 	if ((buf = sshbuf_new()) == NULL)
796 		fatal_f("sshbuf_new");
797 	for (i = nkeys = 0; i < options.num_host_key_files; i++) {
798 		key = get_hostkey_public_by_index(i, ssh);
799 		if (key == NULL || key->type == KEY_UNSPEC ||
800 		    sshkey_is_cert(key))
801 			continue;
802 		fp = sshkey_fingerprint(key, options.fingerprint_hash,
803 		    SSH_FP_DEFAULT);
804 		debug3_f("key %d: %s %s", i, sshkey_ssh_name(key), fp);
805 		free(fp);
806 		if (nkeys == 0) {
807 			/*
808 			 * Start building the request when we find the
809 			 * first usable key.
810 			 */
811 			if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 ||
812 			    (r = sshpkt_put_cstring(ssh, "hostkeys-00@openssh.com")) != 0 ||
813 			    (r = sshpkt_put_u8(ssh, 0)) != 0) /* want reply */
814 				sshpkt_fatal(ssh, r, "%s: start request", __func__);
815 		}
816 		/* Append the key to the request */
817 		sshbuf_reset(buf);
818 		if ((r = sshkey_putb(key, buf)) != 0)
819 			fatal_fr(r, "couldn't put hostkey %d", i);
820 		if ((r = sshpkt_put_stringb(ssh, buf)) != 0)
821 			sshpkt_fatal(ssh, r, "%s: append key", __func__);
822 		nkeys++;
823 	}
824 	debug3_f("sent %u hostkeys", nkeys);
825 	if (nkeys == 0)
826 		fatal_f("no hostkeys");
827 	if ((r = sshpkt_send(ssh)) != 0)
828 		sshpkt_fatal(ssh, r, "%s: send", __func__);
829 	sshbuf_free(buf);
830 }
831 
832 /*
833  * returns 1 if connection should be dropped, 0 otherwise.
834  * dropping starts at connection #max_startups_begin with a probability
835  * of (max_startups_rate/100). the probability increases linearly until
836  * all connections are dropped for startups > max_startups
837  */
838 static int
839 should_drop_connection(int startups)
840 {
841 	int p, r;
842 
843 	if (startups < options.max_startups_begin)
844 		return 0;
845 	if (startups >= options.max_startups)
846 		return 1;
847 	if (options.max_startups_rate == 100)
848 		return 1;
849 
850 	p  = 100 - options.max_startups_rate;
851 	p *= startups - options.max_startups_begin;
852 	p /= options.max_startups - options.max_startups_begin;
853 	p += options.max_startups_rate;
854 	r = arc4random_uniform(100);
855 
856 	debug_f("p %d, r %d", p, r);
857 	return (r < p) ? 1 : 0;
858 }
859 
860 /*
861  * Check whether connection should be accepted by MaxStartups.
862  * Returns 0 if the connection is accepted. If the connection is refused,
863  * returns 1 and attempts to send notification to client.
864  * Logs when the MaxStartups condition is entered or exited, and periodically
865  * while in that state.
866  */
867 static int
868 drop_connection(int sock, int startups, int notify_pipe)
869 {
870 	char *laddr, *raddr;
871 	const char msg[] = "Exceeded MaxStartups\r\n";
872 	static time_t last_drop, first_drop;
873 	static u_int ndropped;
874 	LogLevel drop_level = SYSLOG_LEVEL_VERBOSE;
875 	time_t now;
876 
877 	now = monotime();
878 	if (!should_drop_connection(startups) &&
879 	    srclimit_check_allow(sock, notify_pipe) == 1) {
880 		if (last_drop != 0 &&
881 		    startups < options.max_startups_begin - 1) {
882 			/* XXX maybe need better hysteresis here */
883 			logit("exited MaxStartups throttling after %s, "
884 			    "%u connections dropped",
885 			    fmt_timeframe(now - first_drop), ndropped);
886 			last_drop = 0;
887 		}
888 		return 0;
889 	}
890 
891 #define SSHD_MAXSTARTUPS_LOG_INTERVAL	(5 * 60)
892 	if (last_drop == 0) {
893 		error("beginning MaxStartups throttling");
894 		drop_level = SYSLOG_LEVEL_INFO;
895 		first_drop = now;
896 		ndropped = 0;
897 	} else if (last_drop + SSHD_MAXSTARTUPS_LOG_INTERVAL < now) {
898 		/* Periodic logs */
899 		error("in MaxStartups throttling for %s, "
900 		    "%u connections dropped",
901 		    fmt_timeframe(now - first_drop), ndropped + 1);
902 		drop_level = SYSLOG_LEVEL_INFO;
903 	}
904 	last_drop = now;
905 	ndropped++;
906 
907 	laddr = get_local_ipaddr(sock);
908 	raddr = get_peer_ipaddr(sock);
909 	do_log2(drop_level, "drop connection #%d from [%s]:%d on [%s]:%d "
910 	    "past MaxStartups", startups, raddr, get_peer_port(sock),
911 	    laddr, get_local_port(sock));
912 	free(laddr);
913 	free(raddr);
914 	/* best-effort notification to client */
915 	(void)write(sock, msg, sizeof(msg) - 1);
916 	return 1;
917 }
918 
919 static void
920 usage(void)
921 {
922 	if (options.version_addendum != NULL &&
923 	    *options.version_addendum != '\0')
924 		fprintf(stderr, "%s %s, %s\n",
925 		    SSH_RELEASE,
926 		    options.version_addendum, SSH_OPENSSL_VERSION);
927 	else
928 		fprintf(stderr, "%s, %s\n",
929 		    SSH_RELEASE, SSH_OPENSSL_VERSION);
930 	fprintf(stderr,
931 "usage: sshd [-46DdeiqTt] [-C connection_spec] [-c host_cert_file]\n"
932 "            [-E log_file] [-f config_file] [-g login_grace_time]\n"
933 "            [-h host_key_file] [-o option] [-p port] [-u len]\n"
934 	);
935 	exit(1);
936 }
937 
938 static void
939 send_rexec_state(int fd, struct sshbuf *conf)
940 {
941 	struct sshbuf *m = NULL, *inc = NULL;
942 	struct include_item *item = NULL;
943 	int r;
944 
945 	debug3_f("entering fd = %d config len %zu", fd,
946 	    sshbuf_len(conf));
947 
948 	if ((m = sshbuf_new()) == NULL || (inc = sshbuf_new()) == NULL)
949 		fatal_f("sshbuf_new failed");
950 
951 	/* pack includes into a string */
952 	TAILQ_FOREACH(item, &includes, entry) {
953 		if ((r = sshbuf_put_cstring(inc, item->selector)) != 0 ||
954 		    (r = sshbuf_put_cstring(inc, item->filename)) != 0 ||
955 		    (r = sshbuf_put_stringb(inc, item->contents)) != 0)
956 			fatal_fr(r, "compose includes");
957 	}
958 
959 	/*
960 	 * Protocol from reexec master to child:
961 	 *	string	configuration
962 	 *	string	included_files[] {
963 	 *		string	selector
964 	 *		string	filename
965 	 *		string	contents
966 	 *	}
967 	 *	string	rng_seed (if required)
968 	 */
969 	if ((r = sshbuf_put_stringb(m, conf)) != 0 ||
970 	    (r = sshbuf_put_stringb(m, inc)) != 0)
971 		fatal_fr(r, "compose config");
972 #if defined(WITH_OPENSSL) && !defined(OPENSSL_PRNG_ONLY)
973 	rexec_send_rng_seed(m);
974 #endif
975 	if (ssh_msg_send(fd, 0, m) == -1)
976 		error_f("ssh_msg_send failed");
977 
978 	sshbuf_free(m);
979 	sshbuf_free(inc);
980 
981 	debug3_f("done");
982 }
983 
984 static void
985 recv_rexec_state(int fd, struct sshbuf *conf)
986 {
987 	struct sshbuf *m, *inc;
988 	u_char *cp, ver;
989 	size_t len;
990 	int r;
991 	struct include_item *item;
992 
993 	debug3_f("entering fd = %d", fd);
994 
995 	if ((m = sshbuf_new()) == NULL || (inc = sshbuf_new()) == NULL)
996 		fatal_f("sshbuf_new failed");
997 	if (ssh_msg_recv(fd, m) == -1)
998 		fatal_f("ssh_msg_recv failed");
999 	if ((r = sshbuf_get_u8(m, &ver)) != 0)
1000 		fatal_fr(r, "parse version");
1001 	if (ver != 0)
1002 		fatal_f("rexec version mismatch");
1003 	if ((r = sshbuf_get_string(m, &cp, &len)) != 0 ||
1004 	    (r = sshbuf_get_stringb(m, inc)) != 0)
1005 		fatal_fr(r, "parse config");
1006 
1007 #if defined(WITH_OPENSSL) && !defined(OPENSSL_PRNG_ONLY)
1008 	rexec_recv_rng_seed(m);
1009 #endif
1010 
1011 	if (conf != NULL && (r = sshbuf_put(conf, cp, len)))
1012 		fatal_fr(r, "sshbuf_put");
1013 
1014 	while (sshbuf_len(inc) != 0) {
1015 		item = xcalloc(1, sizeof(*item));
1016 		if ((item->contents = sshbuf_new()) == NULL)
1017 			fatal_f("sshbuf_new failed");
1018 		if ((r = sshbuf_get_cstring(inc, &item->selector, NULL)) != 0 ||
1019 		    (r = sshbuf_get_cstring(inc, &item->filename, NULL)) != 0 ||
1020 		    (r = sshbuf_get_stringb(inc, item->contents)) != 0)
1021 			fatal_fr(r, "parse includes");
1022 		TAILQ_INSERT_TAIL(&includes, item, entry);
1023 	}
1024 
1025 	free(cp);
1026 	sshbuf_free(m);
1027 
1028 	debug3_f("done");
1029 }
1030 
1031 /* Accept a connection from inetd */
1032 static void
1033 server_accept_inetd(int *sock_in, int *sock_out)
1034 {
1035 	if (rexeced_flag) {
1036 		close(REEXEC_CONFIG_PASS_FD);
1037 		*sock_in = *sock_out = dup(STDIN_FILENO);
1038 	} else {
1039 		*sock_in = dup(STDIN_FILENO);
1040 		*sock_out = dup(STDOUT_FILENO);
1041 	}
1042 	/*
1043 	 * We intentionally do not close the descriptors 0, 1, and 2
1044 	 * as our code for setting the descriptors won't work if
1045 	 * ttyfd happens to be one of those.
1046 	 */
1047 	if (stdfd_devnull(1, 1, !log_stderr) == -1)
1048 		error_f("stdfd_devnull failed");
1049 	debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out);
1050 }
1051 
1052 /*
1053  * Listen for TCP connections
1054  */
1055 static void
1056 listen_on_addrs(struct listenaddr *la)
1057 {
1058 	int ret, listen_sock;
1059 	struct addrinfo *ai;
1060 	char ntop[NI_MAXHOST], strport[NI_MAXSERV];
1061 
1062 	for (ai = la->addrs; ai; ai = ai->ai_next) {
1063 		if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
1064 			continue;
1065 		if (num_listen_socks >= MAX_LISTEN_SOCKS)
1066 			fatal("Too many listen sockets. "
1067 			    "Enlarge MAX_LISTEN_SOCKS");
1068 		if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen,
1069 		    ntop, sizeof(ntop), strport, sizeof(strport),
1070 		    NI_NUMERICHOST|NI_NUMERICSERV)) != 0) {
1071 			error("getnameinfo failed: %.100s",
1072 			    ssh_gai_strerror(ret));
1073 			continue;
1074 		}
1075 		/* Create socket for listening. */
1076 		listen_sock = socket(ai->ai_family, ai->ai_socktype,
1077 		    ai->ai_protocol);
1078 		if (listen_sock == -1) {
1079 			/* kernel may not support ipv6 */
1080 			verbose("socket: %.100s", strerror(errno));
1081 			continue;
1082 		}
1083 		if (set_nonblock(listen_sock) == -1) {
1084 			close(listen_sock);
1085 			continue;
1086 		}
1087 		if (fcntl(listen_sock, F_SETFD, FD_CLOEXEC) == -1) {
1088 			verbose("socket: CLOEXEC: %s", strerror(errno));
1089 			close(listen_sock);
1090 			continue;
1091 		}
1092 		/* Socket options */
1093 		set_reuseaddr(listen_sock);
1094 		if (la->rdomain != NULL &&
1095 		    set_rdomain(listen_sock, la->rdomain) == -1) {
1096 			close(listen_sock);
1097 			continue;
1098 		}
1099 
1100 		/* Only communicate in IPv6 over AF_INET6 sockets. */
1101 		if (ai->ai_family == AF_INET6)
1102 			sock_set_v6only(listen_sock);
1103 
1104 		debug("Bind to port %s on %s.", strport, ntop);
1105 
1106 		/* Bind the socket to the desired port. */
1107 		if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) == -1) {
1108 			error("Bind to port %s on %s failed: %.200s.",
1109 			    strport, ntop, strerror(errno));
1110 			close(listen_sock);
1111 			continue;
1112 		}
1113 		listen_socks[num_listen_socks] = listen_sock;
1114 		num_listen_socks++;
1115 
1116 		/* Start listening on the port. */
1117 		if (listen(listen_sock, SSH_LISTEN_BACKLOG) == -1)
1118 			fatal("listen on [%s]:%s: %.100s",
1119 			    ntop, strport, strerror(errno));
1120 		logit("Server listening on %s port %s%s%s.",
1121 		    ntop, strport,
1122 		    la->rdomain == NULL ? "" : " rdomain ",
1123 		    la->rdomain == NULL ? "" : la->rdomain);
1124 	}
1125 }
1126 
1127 static void
1128 server_listen(void)
1129 {
1130 	u_int i;
1131 
1132 	/* Initialise per-source limit tracking. */
1133 	srclimit_init(options.max_startups, options.per_source_max_startups,
1134 	    options.per_source_masklen_ipv4, options.per_source_masklen_ipv6);
1135 
1136 	for (i = 0; i < options.num_listen_addrs; i++) {
1137 		listen_on_addrs(&options.listen_addrs[i]);
1138 		freeaddrinfo(options.listen_addrs[i].addrs);
1139 		free(options.listen_addrs[i].rdomain);
1140 		memset(&options.listen_addrs[i], 0,
1141 		    sizeof(options.listen_addrs[i]));
1142 	}
1143 	free(options.listen_addrs);
1144 	options.listen_addrs = NULL;
1145 	options.num_listen_addrs = 0;
1146 
1147 	if (!num_listen_socks)
1148 		fatal("Cannot bind any address.");
1149 }
1150 
1151 /*
1152  * The main TCP accept loop. Note that, for the non-debug case, returns
1153  * from this function are in a forked subprocess.
1154  */
1155 static void
1156 server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
1157 {
1158 	struct pollfd *pfd = NULL;
1159 	int i, j, ret, npfd;
1160 	int ostartups = -1, startups = 0, listening = 0, lameduck = 0;
1161 	int startup_p[2] = { -1 , -1 }, *startup_pollfd;
1162 	char c = 0;
1163 	struct sockaddr_storage from;
1164 	socklen_t fromlen;
1165 	pid_t pid;
1166 	u_char rnd[256];
1167 	sigset_t nsigset, osigset;
1168 #ifdef LIBWRAP
1169 	struct request_info req;
1170 
1171 	request_init(&req, RQ_DAEMON, __progname, 0);
1172 #endif
1173 
1174 	/* pipes connected to unauthenticated child sshd processes */
1175 	startup_pipes = xcalloc(options.max_startups, sizeof(int));
1176 	startup_flags = xcalloc(options.max_startups, sizeof(int));
1177 	startup_pollfd = xcalloc(options.max_startups, sizeof(int));
1178 	for (i = 0; i < options.max_startups; i++)
1179 		startup_pipes[i] = -1;
1180 
1181 	/*
1182 	 * Prepare signal mask that we use to block signals that might set
1183 	 * received_sigterm or received_sighup, so that we are guaranteed
1184 	 * to immediately wake up the ppoll if a signal is received after
1185 	 * the flag is checked.
1186 	 */
1187 	sigemptyset(&nsigset);
1188 	sigaddset(&nsigset, SIGHUP);
1189 	sigaddset(&nsigset, SIGCHLD);
1190 	sigaddset(&nsigset, SIGTERM);
1191 	sigaddset(&nsigset, SIGQUIT);
1192 
1193 	/* sized for worst-case */
1194 	pfd = xcalloc(num_listen_socks + options.max_startups,
1195 	    sizeof(struct pollfd));
1196 
1197 	/*
1198 	 * Stay listening for connections until the system crashes or
1199 	 * the daemon is killed with a signal.
1200 	 */
1201 	for (;;) {
1202 		sigprocmask(SIG_BLOCK, &nsigset, &osigset);
1203 		if (received_sigterm) {
1204 			logit("Received signal %d; terminating.",
1205 			    (int) received_sigterm);
1206 			close_listen_socks();
1207 			if (options.pid_file != NULL)
1208 				unlink(options.pid_file);
1209 			exit(received_sigterm == SIGTERM ? 0 : 255);
1210 		}
1211 		if (ostartups != startups) {
1212 			setproctitle("%s [listener] %d of %d-%d startups",
1213 			    listener_proctitle, startups,
1214 			    options.max_startups_begin, options.max_startups);
1215 			ostartups = startups;
1216 		}
1217 		if (received_sighup) {
1218 			if (!lameduck) {
1219 				debug("Received SIGHUP; waiting for children");
1220 				close_listen_socks();
1221 				lameduck = 1;
1222 			}
1223 			if (listening <= 0) {
1224 				sigprocmask(SIG_SETMASK, &osigset, NULL);
1225 				sighup_restart();
1226 			}
1227 		}
1228 
1229 		for (i = 0; i < num_listen_socks; i++) {
1230 			pfd[i].fd = listen_socks[i];
1231 			pfd[i].events = POLLIN;
1232 		}
1233 		npfd = num_listen_socks;
1234 		for (i = 0; i < options.max_startups; i++) {
1235 			startup_pollfd[i] = -1;
1236 			if (startup_pipes[i] != -1) {
1237 				pfd[npfd].fd = startup_pipes[i];
1238 				pfd[npfd].events = POLLIN;
1239 				startup_pollfd[i] = npfd++;
1240 			}
1241 		}
1242 
1243 		/* Wait until a connection arrives or a child exits. */
1244 		ret = ppoll(pfd, npfd, NULL, &osigset);
1245 		if (ret == -1 && errno != EINTR) {
1246 			error("ppoll: %.100s", strerror(errno));
1247 			if (errno == EINVAL)
1248 				cleanup_exit(1); /* can't recover */
1249 		}
1250 		sigprocmask(SIG_SETMASK, &osigset, NULL);
1251 		if (ret == -1)
1252 			continue;
1253 
1254 		for (i = 0; i < options.max_startups; i++) {
1255 			if (startup_pipes[i] == -1 ||
1256 			    startup_pollfd[i] == -1 ||
1257 			    !(pfd[startup_pollfd[i]].revents & (POLLIN|POLLHUP)))
1258 				continue;
1259 			switch (read(startup_pipes[i], &c, sizeof(c))) {
1260 			case -1:
1261 				if (errno == EINTR || errno == EAGAIN)
1262 					continue;
1263 				if (errno != EPIPE) {
1264 					error_f("startup pipe %d (fd=%d): "
1265 					    "read %s", i, startup_pipes[i],
1266 					    strerror(errno));
1267 				}
1268 				/* FALLTHROUGH */
1269 			case 0:
1270 				/* child exited or completed auth */
1271 				close(startup_pipes[i]);
1272 				srclimit_done(startup_pipes[i]);
1273 				startup_pipes[i] = -1;
1274 				startups--;
1275 				if (startup_flags[i])
1276 					listening--;
1277 				break;
1278 			case 1:
1279 				/* child has finished preliminaries */
1280 				if (startup_flags[i]) {
1281 					listening--;
1282 					startup_flags[i] = 0;
1283 				}
1284 				break;
1285 			}
1286 		}
1287 		for (i = 0; i < num_listen_socks; i++) {
1288 			if (!(pfd[i].revents & POLLIN))
1289 				continue;
1290 			fromlen = sizeof(from);
1291 			*newsock = accept(listen_socks[i],
1292 			    (struct sockaddr *)&from, &fromlen);
1293 			if (*newsock == -1) {
1294 				if (errno != EINTR && errno != EWOULDBLOCK &&
1295 				    errno != ECONNABORTED && errno != EAGAIN)
1296 					error("accept: %.100s",
1297 					    strerror(errno));
1298 				if (errno == EMFILE || errno == ENFILE)
1299 					usleep(100 * 1000);
1300 				continue;
1301 			}
1302 #ifdef LIBWRAP
1303 			/* Check whether logins are denied from this host. */
1304 			request_set(&req, RQ_FILE, *newsock,
1305 			    RQ_CLIENT_NAME, "", RQ_CLIENT_ADDR, "", 0);
1306 			sock_host(&req);
1307 			if (!hosts_access(&req)) {
1308 				const struct linger l = { .l_onoff = 1,
1309 				    .l_linger  = 0 };
1310 
1311 				(void )setsockopt(*newsock, SOL_SOCKET,
1312 				    SO_LINGER, &l, sizeof(l));
1313 				(void )close(*newsock);
1314 				/*
1315 				 * Mimic message from libwrap's refuse()
1316 				 * exactly.  sshguard, and supposedly lots
1317 				 * of custom made scripts rely on it.
1318 				 */
1319 				syslog(deny_severity,
1320 				    "refused connect from %s (%s)",
1321 				    eval_client(&req),
1322 				    eval_hostaddr(req.client));
1323 				debug("Connection refused by tcp wrapper");
1324 				continue;
1325 			}
1326 #endif /* LIBWRAP */
1327 			if (unset_nonblock(*newsock) == -1) {
1328 				close(*newsock);
1329 				continue;
1330 			}
1331 			if (pipe(startup_p) == -1) {
1332 				error_f("pipe(startup_p): %s", strerror(errno));
1333 				close(*newsock);
1334 				continue;
1335 			}
1336 			if (drop_connection(*newsock, startups, startup_p[0])) {
1337 				close(*newsock);
1338 				close(startup_p[0]);
1339 				close(startup_p[1]);
1340 				continue;
1341 			}
1342 
1343 			if (rexec_flag && socketpair(AF_UNIX,
1344 			    SOCK_STREAM, 0, config_s) == -1) {
1345 				error("reexec socketpair: %s",
1346 				    strerror(errno));
1347 				close(*newsock);
1348 				close(startup_p[0]);
1349 				close(startup_p[1]);
1350 				continue;
1351 			}
1352 
1353 			for (j = 0; j < options.max_startups; j++)
1354 				if (startup_pipes[j] == -1) {
1355 					startup_pipes[j] = startup_p[0];
1356 					startups++;
1357 					startup_flags[j] = 1;
1358 					break;
1359 				}
1360 
1361 			/*
1362 			 * Got connection.  Fork a child to handle it, unless
1363 			 * we are in debugging mode.
1364 			 */
1365 			if (debug_flag) {
1366 				/*
1367 				 * In debugging mode.  Close the listening
1368 				 * socket, and start processing the
1369 				 * connection without forking.
1370 				 */
1371 				debug("Server will not fork when running in debugging mode.");
1372 				close_listen_socks();
1373 				*sock_in = *newsock;
1374 				*sock_out = *newsock;
1375 				close(startup_p[0]);
1376 				close(startup_p[1]);
1377 				startup_pipe = -1;
1378 				pid = getpid();
1379 				if (rexec_flag) {
1380 					send_rexec_state(config_s[0], cfg);
1381 					close(config_s[0]);
1382 				}
1383 				free(pfd);
1384 				return;
1385 			}
1386 
1387 			/*
1388 			 * Normal production daemon.  Fork, and have
1389 			 * the child process the connection. The
1390 			 * parent continues listening.
1391 			 */
1392 			platform_pre_fork();
1393 			listening++;
1394 			if ((pid = fork()) == 0) {
1395 				/*
1396 				 * Child.  Close the listening and
1397 				 * max_startup sockets.  Start using
1398 				 * the accepted socket. Reinitialize
1399 				 * logging (since our pid has changed).
1400 				 * We return from this function to handle
1401 				 * the connection.
1402 				 */
1403 				platform_post_fork_child();
1404 				startup_pipe = startup_p[1];
1405 				close_startup_pipes();
1406 				close_listen_socks();
1407 				*sock_in = *newsock;
1408 				*sock_out = *newsock;
1409 				log_init(__progname,
1410 				    options.log_level,
1411 				    options.log_facility,
1412 				    log_stderr);
1413 				if (rexec_flag)
1414 					close(config_s[0]);
1415 				else {
1416 					/*
1417 					 * Signal parent that the preliminaries
1418 					 * for this child are complete. For the
1419 					 * re-exec case, this happens after the
1420 					 * child has received the rexec state
1421 					 * from the server.
1422 					 */
1423 					(void)atomicio(vwrite, startup_pipe,
1424 					    "\0", 1);
1425 				}
1426 				free(pfd);
1427 				return;
1428 			}
1429 
1430 			/* Parent.  Stay in the loop. */
1431 			platform_post_fork_parent(pid);
1432 			if (pid == -1)
1433 				error("fork: %.100s", strerror(errno));
1434 			else
1435 				debug("Forked child %ld.", (long)pid);
1436 
1437 			close(startup_p[1]);
1438 
1439 			if (rexec_flag) {
1440 				close(config_s[1]);
1441 				send_rexec_state(config_s[0], cfg);
1442 				close(config_s[0]);
1443 			}
1444 			close(*newsock);
1445 
1446 			/*
1447 			 * Ensure that our random state differs
1448 			 * from that of the child
1449 			 */
1450 			arc4random_stir();
1451 			arc4random_buf(rnd, sizeof(rnd));
1452 #ifdef WITH_OPENSSL
1453 			RAND_seed(rnd, sizeof(rnd));
1454 			if ((RAND_bytes((u_char *)rnd, 1)) != 1)
1455 				fatal("%s: RAND_bytes failed", __func__);
1456 #endif
1457 			explicit_bzero(rnd, sizeof(rnd));
1458 		}
1459 	}
1460 }
1461 
1462 /*
1463  * If IP options are supported, make sure there are none (log and
1464  * return an error if any are found).  Basically we are worried about
1465  * source routing; it can be used to pretend you are somebody
1466  * (ip-address) you are not. That itself may be "almost acceptable"
1467  * under certain circumstances, but rhosts authentication is useless
1468  * if source routing is accepted. Notice also that if we just dropped
1469  * source routing here, the other side could use IP spoofing to do
1470  * rest of the interaction and could still bypass security.  So we
1471  * exit here if we detect any IP options.
1472  */
1473 static void
1474 check_ip_options(struct ssh *ssh)
1475 {
1476 #ifdef IP_OPTIONS
1477 	int sock_in = ssh_packet_get_connection_in(ssh);
1478 	struct sockaddr_storage from;
1479 	u_char opts[200];
1480 	socklen_t i, option_size = sizeof(opts), fromlen = sizeof(from);
1481 	char text[sizeof(opts) * 3 + 1];
1482 
1483 	memset(&from, 0, sizeof(from));
1484 	if (getpeername(sock_in, (struct sockaddr *)&from,
1485 	    &fromlen) == -1)
1486 		return;
1487 	if (from.ss_family != AF_INET)
1488 		return;
1489 	/* XXX IPv6 options? */
1490 
1491 	if (getsockopt(sock_in, IPPROTO_IP, IP_OPTIONS, opts,
1492 	    &option_size) >= 0 && option_size != 0) {
1493 		text[0] = '\0';
1494 		for (i = 0; i < option_size; i++)
1495 			snprintf(text + i*3, sizeof(text) - i*3,
1496 			    " %2.2x", opts[i]);
1497 		fatal("Connection from %.100s port %d with IP opts: %.800s",
1498 		    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), text);
1499 	}
1500 	return;
1501 #endif /* IP_OPTIONS */
1502 }
1503 
1504 /* Set the routing domain for this process */
1505 static void
1506 set_process_rdomain(struct ssh *ssh, const char *name)
1507 {
1508 #if defined(HAVE_SYS_SET_PROCESS_RDOMAIN)
1509 	if (name == NULL)
1510 		return; /* default */
1511 
1512 	if (strcmp(name, "%D") == 0) {
1513 		/* "expands" to routing domain of connection */
1514 		if ((name = ssh_packet_rdomain_in(ssh)) == NULL)
1515 			return;
1516 	}
1517 	/* NB. We don't pass 'ssh' to sys_set_process_rdomain() */
1518 	return sys_set_process_rdomain(name);
1519 #elif defined(__OpenBSD__)
1520 	int rtable, ortable = getrtable();
1521 	const char *errstr;
1522 
1523 	if (name == NULL)
1524 		return; /* default */
1525 
1526 	if (strcmp(name, "%D") == 0) {
1527 		/* "expands" to routing domain of connection */
1528 		if ((name = ssh_packet_rdomain_in(ssh)) == NULL)
1529 			return;
1530 	}
1531 
1532 	rtable = (int)strtonum(name, 0, 255, &errstr);
1533 	if (errstr != NULL) /* Shouldn't happen */
1534 		fatal("Invalid routing domain \"%s\": %s", name, errstr);
1535 	if (rtable != ortable && setrtable(rtable) != 0)
1536 		fatal("Unable to set routing domain %d: %s",
1537 		    rtable, strerror(errno));
1538 	debug_f("set routing domain %d (was %d)", rtable, ortable);
1539 #else /* defined(__OpenBSD__) */
1540 	fatal("Unable to set routing domain: not supported in this platform");
1541 #endif
1542 }
1543 
1544 static void
1545 accumulate_host_timing_secret(struct sshbuf *server_cfg,
1546     struct sshkey *key)
1547 {
1548 	static struct ssh_digest_ctx *ctx;
1549 	u_char *hash;
1550 	size_t len;
1551 	struct sshbuf *buf;
1552 	int r;
1553 
1554 	if (ctx == NULL && (ctx = ssh_digest_start(SSH_DIGEST_SHA512)) == NULL)
1555 		fatal_f("ssh_digest_start");
1556 	if (key == NULL) { /* finalize */
1557 		/* add server config in case we are using agent for host keys */
1558 		if (ssh_digest_update(ctx, sshbuf_ptr(server_cfg),
1559 		    sshbuf_len(server_cfg)) != 0)
1560 			fatal_f("ssh_digest_update");
1561 		len = ssh_digest_bytes(SSH_DIGEST_SHA512);
1562 		hash = xmalloc(len);
1563 		if (ssh_digest_final(ctx, hash, len) != 0)
1564 			fatal_f("ssh_digest_final");
1565 		options.timing_secret = PEEK_U64(hash);
1566 		freezero(hash, len);
1567 		ssh_digest_free(ctx);
1568 		ctx = NULL;
1569 		return;
1570 	}
1571 	if ((buf = sshbuf_new()) == NULL)
1572 		fatal_f("could not allocate buffer");
1573 	if ((r = sshkey_private_serialize(key, buf)) != 0)
1574 		fatal_fr(r, "decode key");
1575 	if (ssh_digest_update(ctx, sshbuf_ptr(buf), sshbuf_len(buf)) != 0)
1576 		fatal_f("ssh_digest_update");
1577 	sshbuf_reset(buf);
1578 	sshbuf_free(buf);
1579 }
1580 
1581 static char *
1582 prepare_proctitle(int ac, char **av)
1583 {
1584 	char *ret = NULL;
1585 	int i;
1586 
1587 	for (i = 0; i < ac; i++)
1588 		xextendf(&ret, " ", "%s", av[i]);
1589 	return ret;
1590 }
1591 
1592 /*
1593  * Main program for the daemon.
1594  */
1595 int
1596 main(int ac, char **av)
1597 {
1598 	struct ssh *ssh = NULL;
1599 	extern char *optarg;
1600 	extern int optind;
1601 	int r, opt, on = 1, already_daemon, remote_port;
1602 	int sock_in = -1, sock_out = -1, newsock = -1;
1603 	const char *remote_ip, *rdomain;
1604 	char *fp, *line, *laddr, *logfile = NULL;
1605 	int config_s[2] = { -1 , -1 };
1606 	u_int i, j;
1607 	u_int64_t ibytes, obytes;
1608 	mode_t new_umask;
1609 	struct sshkey *key;
1610 	struct sshkey *pubkey;
1611 	int keytype;
1612 	Authctxt *authctxt;
1613 	struct connection_info *connection_info = NULL;
1614 
1615 #ifdef HAVE_SECUREWARE
1616 	(void)set_auth_parameters(ac, av);
1617 #endif
1618 	__progname = ssh_get_progname(av[0]);
1619 
1620 	/* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
1621 	saved_argc = ac;
1622 	rexec_argc = ac;
1623 	saved_argv = xcalloc(ac + 1, sizeof(*saved_argv));
1624 	for (i = 0; (int)i < ac; i++)
1625 		saved_argv[i] = xstrdup(av[i]);
1626 	saved_argv[i] = NULL;
1627 
1628 #ifndef HAVE_SETPROCTITLE
1629 	/* Prepare for later setproctitle emulation */
1630 	compat_init_setproctitle(ac, av);
1631 	av = saved_argv;
1632 #endif
1633 
1634 	if (geteuid() == 0 && setgroups(0, NULL) == -1)
1635 		debug("setgroups(): %.200s", strerror(errno));
1636 
1637 	/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
1638 	sanitise_stdfd();
1639 
1640 	seed_rng();
1641 
1642 	/* Initialize configuration options to their default values. */
1643 	initialize_server_options(&options);
1644 
1645 	/* Parse command-line arguments. */
1646 	while ((opt = getopt(ac, av,
1647 	    "C:E:b:c:f:g:h:k:o:p:u:46DQRTdeiqrt")) != -1) {
1648 		switch (opt) {
1649 		case '4':
1650 			options.address_family = AF_INET;
1651 			break;
1652 		case '6':
1653 			options.address_family = AF_INET6;
1654 			break;
1655 		case 'f':
1656 			config_file_name = optarg;
1657 			break;
1658 		case 'c':
1659 			servconf_add_hostcert("[command-line]", 0,
1660 			    &options, optarg);
1661 			break;
1662 		case 'd':
1663 			if (debug_flag == 0) {
1664 				debug_flag = 1;
1665 				options.log_level = SYSLOG_LEVEL_DEBUG1;
1666 			} else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
1667 				options.log_level++;
1668 			break;
1669 		case 'D':
1670 			no_daemon_flag = 1;
1671 			break;
1672 		case 'E':
1673 			logfile = optarg;
1674 			/* FALLTHROUGH */
1675 		case 'e':
1676 			log_stderr = 1;
1677 			break;
1678 		case 'i':
1679 			inetd_flag = 1;
1680 			break;
1681 		case 'r':
1682 			rexec_flag = 0;
1683 			break;
1684 		case 'R':
1685 			rexeced_flag = 1;
1686 			inetd_flag = 1;
1687 			break;
1688 		case 'Q':
1689 			/* ignored */
1690 			break;
1691 		case 'q':
1692 			options.log_level = SYSLOG_LEVEL_QUIET;
1693 			break;
1694 		case 'b':
1695 			/* protocol 1, ignored */
1696 			break;
1697 		case 'p':
1698 			options.ports_from_cmdline = 1;
1699 			if (options.num_ports >= MAX_PORTS) {
1700 				fprintf(stderr, "too many ports.\n");
1701 				exit(1);
1702 			}
1703 			options.ports[options.num_ports++] = a2port(optarg);
1704 			if (options.ports[options.num_ports-1] <= 0) {
1705 				fprintf(stderr, "Bad port number.\n");
1706 				exit(1);
1707 			}
1708 			break;
1709 		case 'g':
1710 			if ((options.login_grace_time = convtime(optarg)) == -1) {
1711 				fprintf(stderr, "Invalid login grace time.\n");
1712 				exit(1);
1713 			}
1714 			break;
1715 		case 'k':
1716 			/* protocol 1, ignored */
1717 			break;
1718 		case 'h':
1719 			servconf_add_hostkey("[command-line]", 0,
1720 			    &options, optarg, 1);
1721 			break;
1722 		case 't':
1723 			test_flag = 1;
1724 			break;
1725 		case 'T':
1726 			test_flag = 2;
1727 			break;
1728 		case 'C':
1729 			connection_info = get_connection_info(ssh, 0, 0);
1730 			if (parse_server_match_testspec(connection_info,
1731 			    optarg) == -1)
1732 				exit(1);
1733 			break;
1734 		case 'u':
1735 			utmp_len = (u_int)strtonum(optarg, 0, HOST_NAME_MAX+1+1, NULL);
1736 			if (utmp_len > HOST_NAME_MAX+1) {
1737 				fprintf(stderr, "Invalid utmp length.\n");
1738 				exit(1);
1739 			}
1740 			break;
1741 		case 'o':
1742 			line = xstrdup(optarg);
1743 			if (process_server_config_line(&options, line,
1744 			    "command-line", 0, NULL, NULL, &includes) != 0)
1745 				exit(1);
1746 			free(line);
1747 			break;
1748 		case '?':
1749 		default:
1750 			usage();
1751 			break;
1752 		}
1753 	}
1754 	if (rexeced_flag || inetd_flag)
1755 		rexec_flag = 0;
1756 	if (!test_flag && rexec_flag && !path_absolute(av[0]))
1757 		fatal("sshd re-exec requires execution with an absolute path");
1758 	if (rexeced_flag)
1759 		closefrom(REEXEC_MIN_FREE_FD);
1760 	else
1761 		closefrom(REEXEC_DEVCRYPTO_RESERVED_FD);
1762 
1763 	/* If requested, redirect the logs to the specified logfile. */
1764 	if (logfile != NULL)
1765 		log_redirect_stderr_to(logfile);
1766 	/*
1767 	 * Force logging to stderr until we have loaded the private host
1768 	 * key (unless started from inetd)
1769 	 */
1770 	log_init(__progname,
1771 	    options.log_level == SYSLOG_LEVEL_NOT_SET ?
1772 	    SYSLOG_LEVEL_INFO : options.log_level,
1773 	    options.log_facility == SYSLOG_FACILITY_NOT_SET ?
1774 	    SYSLOG_FACILITY_AUTH : options.log_facility,
1775 	    log_stderr || !inetd_flag || debug_flag);
1776 
1777 	/*
1778 	 * Unset KRB5CCNAME, otherwise the user's session may inherit it from
1779 	 * root's environment
1780 	 */
1781 	if (getenv("KRB5CCNAME") != NULL)
1782 		(void) unsetenv("KRB5CCNAME");
1783 
1784 	sensitive_data.have_ssh2_key = 0;
1785 
1786 	/*
1787 	 * If we're not doing an extended test do not silently ignore connection
1788 	 * test params.
1789 	 */
1790 	if (test_flag < 2 && connection_info != NULL)
1791 		fatal("Config test connection parameter (-C) provided without "
1792 		    "test mode (-T)");
1793 
1794 	/* Fetch our configuration */
1795 	if ((cfg = sshbuf_new()) == NULL)
1796 		fatal_f("sshbuf_new failed");
1797 	if (rexeced_flag) {
1798 		setproctitle("%s", "[rexeced]");
1799 		recv_rexec_state(REEXEC_CONFIG_PASS_FD, cfg);
1800 		if (!debug_flag) {
1801 			startup_pipe = dup(REEXEC_STARTUP_PIPE_FD);
1802 			close(REEXEC_STARTUP_PIPE_FD);
1803 			/*
1804 			 * Signal parent that this child is at a point where
1805 			 * they can go away if they have a SIGHUP pending.
1806 			 */
1807 			(void)atomicio(vwrite, startup_pipe, "\0", 1);
1808 		}
1809 	} else if (strcasecmp(config_file_name, "none") != 0)
1810 		load_server_config(config_file_name, cfg);
1811 
1812 	parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name,
1813 	    cfg, &includes, NULL, rexeced_flag);
1814 
1815 #ifdef WITH_OPENSSL
1816 	if (options.moduli_file != NULL)
1817 		dh_set_moduli_file(options.moduli_file);
1818 #endif
1819 
1820 	/* Fill in default values for those options not explicitly set. */
1821 	fill_default_server_options(&options);
1822 
1823 	/* Check that options are sensible */
1824 	if (options.authorized_keys_command_user == NULL &&
1825 	    (options.authorized_keys_command != NULL &&
1826 	    strcasecmp(options.authorized_keys_command, "none") != 0))
1827 		fatal("AuthorizedKeysCommand set without "
1828 		    "AuthorizedKeysCommandUser");
1829 	if (options.authorized_principals_command_user == NULL &&
1830 	    (options.authorized_principals_command != NULL &&
1831 	    strcasecmp(options.authorized_principals_command, "none") != 0))
1832 		fatal("AuthorizedPrincipalsCommand set without "
1833 		    "AuthorizedPrincipalsCommandUser");
1834 
1835 	/*
1836 	 * Check whether there is any path through configured auth methods.
1837 	 * Unfortunately it is not possible to verify this generally before
1838 	 * daemonisation in the presence of Match block, but this catches
1839 	 * and warns for trivial misconfigurations that could break login.
1840 	 */
1841 	if (options.num_auth_methods != 0) {
1842 		for (i = 0; i < options.num_auth_methods; i++) {
1843 			if (auth2_methods_valid(options.auth_methods[i],
1844 			    1) == 0)
1845 				break;
1846 		}
1847 		if (i >= options.num_auth_methods)
1848 			fatal("AuthenticationMethods cannot be satisfied by "
1849 			    "enabled authentication methods");
1850 	}
1851 
1852 	/* Check that there are no remaining arguments. */
1853 	if (optind < ac) {
1854 		fprintf(stderr, "Extra argument %s.\n", av[optind]);
1855 		exit(1);
1856 	}
1857 
1858 	debug("sshd version %s, %s", SSH_VERSION, SSH_OPENSSL_VERSION);
1859 
1860 	/* Store privilege separation user for later use if required. */
1861 	privsep_chroot = use_privsep && (getuid() == 0 || geteuid() == 0);
1862 	if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) {
1863 		if (privsep_chroot || options.kerberos_authentication)
1864 			fatal("Privilege separation user %s does not exist",
1865 			    SSH_PRIVSEP_USER);
1866 	} else {
1867 		privsep_pw = pwcopy(privsep_pw);
1868 		freezero(privsep_pw->pw_passwd, strlen(privsep_pw->pw_passwd));
1869 		privsep_pw->pw_passwd = xstrdup("*");
1870 	}
1871 	endpwent();
1872 
1873 	/* load host keys */
1874 	sensitive_data.host_keys = xcalloc(options.num_host_key_files,
1875 	    sizeof(struct sshkey *));
1876 	sensitive_data.host_pubkeys = xcalloc(options.num_host_key_files,
1877 	    sizeof(struct sshkey *));
1878 
1879 	if (options.host_key_agent) {
1880 		if (strcmp(options.host_key_agent, SSH_AUTHSOCKET_ENV_NAME))
1881 			setenv(SSH_AUTHSOCKET_ENV_NAME,
1882 			    options.host_key_agent, 1);
1883 		if ((r = ssh_get_authentication_socket(NULL)) == 0)
1884 			have_agent = 1;
1885 		else
1886 			error_r(r, "Could not connect to agent \"%s\"",
1887 			    options.host_key_agent);
1888 	}
1889 
1890 	for (i = 0; i < options.num_host_key_files; i++) {
1891 		int ll = options.host_key_file_userprovided[i] ?
1892 		    SYSLOG_LEVEL_ERROR : SYSLOG_LEVEL_DEBUG1;
1893 
1894 		if (options.host_key_files[i] == NULL)
1895 			continue;
1896 		if ((r = sshkey_load_private(options.host_key_files[i], "",
1897 		    &key, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR)
1898 			do_log2_r(r, ll, "Unable to load host key \"%s\"",
1899 			    options.host_key_files[i]);
1900 		if (sshkey_is_sk(key) &&
1901 		    key->sk_flags & SSH_SK_USER_PRESENCE_REQD) {
1902 			debug("host key %s requires user presence, ignoring",
1903 			    options.host_key_files[i]);
1904 			key->sk_flags &= ~SSH_SK_USER_PRESENCE_REQD;
1905 		}
1906 		if (r == 0 && key != NULL &&
1907 		    (r = sshkey_shield_private(key)) != 0) {
1908 			do_log2_r(r, ll, "Unable to shield host key \"%s\"",
1909 			    options.host_key_files[i]);
1910 			sshkey_free(key);
1911 			key = NULL;
1912 		}
1913 		if ((r = sshkey_load_public(options.host_key_files[i],
1914 		    &pubkey, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR)
1915 			do_log2_r(r, ll, "Unable to load host key \"%s\"",
1916 			    options.host_key_files[i]);
1917 		if (pubkey != NULL && key != NULL) {
1918 			if (!sshkey_equal(pubkey, key)) {
1919 				error("Public key for %s does not match "
1920 				    "private key", options.host_key_files[i]);
1921 				sshkey_free(pubkey);
1922 				pubkey = NULL;
1923 			}
1924 		}
1925 		if (pubkey == NULL && key != NULL) {
1926 			if ((r = sshkey_from_private(key, &pubkey)) != 0)
1927 				fatal_r(r, "Could not demote key: \"%s\"",
1928 				    options.host_key_files[i]);
1929 		}
1930 		if (pubkey != NULL && (r = sshkey_check_rsa_length(pubkey,
1931 		    options.required_rsa_size)) != 0) {
1932 			error_fr(r, "Host key %s", options.host_key_files[i]);
1933 			sshkey_free(pubkey);
1934 			sshkey_free(key);
1935 			continue;
1936 		}
1937 		sensitive_data.host_keys[i] = key;
1938 		sensitive_data.host_pubkeys[i] = pubkey;
1939 
1940 		if (key == NULL && pubkey != NULL && have_agent) {
1941 			debug("will rely on agent for hostkey %s",
1942 			    options.host_key_files[i]);
1943 			keytype = pubkey->type;
1944 		} else if (key != NULL) {
1945 			keytype = key->type;
1946 			accumulate_host_timing_secret(cfg, key);
1947 		} else {
1948 			do_log2(ll, "Unable to load host key: %s",
1949 			    options.host_key_files[i]);
1950 			sensitive_data.host_keys[i] = NULL;
1951 			sensitive_data.host_pubkeys[i] = NULL;
1952 			continue;
1953 		}
1954 
1955 		switch (keytype) {
1956 		case KEY_RSA:
1957 		case KEY_DSA:
1958 		case KEY_ECDSA:
1959 		case KEY_ED25519:
1960 		case KEY_ECDSA_SK:
1961 		case KEY_ED25519_SK:
1962 		case KEY_XMSS:
1963 			if (have_agent || key != NULL)
1964 				sensitive_data.have_ssh2_key = 1;
1965 			break;
1966 		}
1967 		if ((fp = sshkey_fingerprint(pubkey, options.fingerprint_hash,
1968 		    SSH_FP_DEFAULT)) == NULL)
1969 			fatal("sshkey_fingerprint failed");
1970 		debug("%s host key #%d: %s %s",
1971 		    key ? "private" : "agent", i, sshkey_ssh_name(pubkey), fp);
1972 		free(fp);
1973 	}
1974 	accumulate_host_timing_secret(cfg, NULL);
1975 	if (!sensitive_data.have_ssh2_key) {
1976 		logit("sshd: no hostkeys available -- exiting.");
1977 		exit(1);
1978 	}
1979 
1980 	/*
1981 	 * Load certificates. They are stored in an array at identical
1982 	 * indices to the public keys that they relate to.
1983 	 */
1984 	sensitive_data.host_certificates = xcalloc(options.num_host_key_files,
1985 	    sizeof(struct sshkey *));
1986 	for (i = 0; i < options.num_host_key_files; i++)
1987 		sensitive_data.host_certificates[i] = NULL;
1988 
1989 	for (i = 0; i < options.num_host_cert_files; i++) {
1990 		if (options.host_cert_files[i] == NULL)
1991 			continue;
1992 		if ((r = sshkey_load_public(options.host_cert_files[i],
1993 		    &key, NULL)) != 0) {
1994 			error_r(r, "Could not load host certificate \"%s\"",
1995 			    options.host_cert_files[i]);
1996 			continue;
1997 		}
1998 		if (!sshkey_is_cert(key)) {
1999 			error("Certificate file is not a certificate: %s",
2000 			    options.host_cert_files[i]);
2001 			sshkey_free(key);
2002 			continue;
2003 		}
2004 		/* Find matching private key */
2005 		for (j = 0; j < options.num_host_key_files; j++) {
2006 			if (sshkey_equal_public(key,
2007 			    sensitive_data.host_pubkeys[j])) {
2008 				sensitive_data.host_certificates[j] = key;
2009 				break;
2010 			}
2011 		}
2012 		if (j >= options.num_host_key_files) {
2013 			error("No matching private key for certificate: %s",
2014 			    options.host_cert_files[i]);
2015 			sshkey_free(key);
2016 			continue;
2017 		}
2018 		sensitive_data.host_certificates[j] = key;
2019 		debug("host certificate: #%u type %d %s", j, key->type,
2020 		    sshkey_type(key));
2021 	}
2022 
2023 	if (privsep_chroot) {
2024 		struct stat st;
2025 
2026 		if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) ||
2027 		    (S_ISDIR(st.st_mode) == 0))
2028 			fatal("Missing privilege separation directory: %s",
2029 			    _PATH_PRIVSEP_CHROOT_DIR);
2030 
2031 #ifdef HAVE_CYGWIN
2032 		if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
2033 		    (st.st_uid != getuid () ||
2034 		    (st.st_mode & (S_IWGRP|S_IWOTH)) != 0))
2035 #else
2036 		if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)
2037 #endif
2038 			fatal("%s must be owned by root and not group or "
2039 			    "world-writable.", _PATH_PRIVSEP_CHROOT_DIR);
2040 	}
2041 
2042 	if (test_flag > 1) {
2043 		/*
2044 		 * If no connection info was provided by -C then use
2045 		 * use a blank one that will cause no predicate to match.
2046 		 */
2047 		if (connection_info == NULL)
2048 			connection_info = get_connection_info(ssh, 0, 0);
2049 		connection_info->test = 1;
2050 		parse_server_match_config(&options, &includes, connection_info);
2051 		dump_config(&options);
2052 	}
2053 
2054 	/* Configuration looks good, so exit if in test mode. */
2055 	if (test_flag)
2056 		exit(0);
2057 
2058 	/*
2059 	 * Clear out any supplemental groups we may have inherited.  This
2060 	 * prevents inadvertent creation of files with bad modes (in the
2061 	 * portable version at least, it's certainly possible for PAM
2062 	 * to create a file, and we can't control the code in every
2063 	 * module which might be used).
2064 	 */
2065 	if (setgroups(0, NULL) < 0)
2066 		debug("setgroups() failed: %.200s", strerror(errno));
2067 
2068 	if (rexec_flag) {
2069 		if (rexec_argc < 0)
2070 			fatal("rexec_argc %d < 0", rexec_argc);
2071 		rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *));
2072 		for (i = 0; i < (u_int)rexec_argc; i++) {
2073 			debug("rexec_argv[%d]='%s'", i, saved_argv[i]);
2074 			rexec_argv[i] = saved_argv[i];
2075 		}
2076 		rexec_argv[rexec_argc] = "-R";
2077 		rexec_argv[rexec_argc + 1] = NULL;
2078 	}
2079 	listener_proctitle = prepare_proctitle(ac, av);
2080 
2081 	/* Ensure that umask disallows at least group and world write */
2082 	new_umask = umask(0077) | 0022;
2083 	(void) umask(new_umask);
2084 
2085 	/* Initialize the log (it is reinitialized below in case we forked). */
2086 	if (debug_flag && (!inetd_flag || rexeced_flag))
2087 		log_stderr = 1;
2088 	log_init(__progname, options.log_level,
2089 	    options.log_facility, log_stderr);
2090 	for (i = 0; i < options.num_log_verbose; i++)
2091 		log_verbose_add(options.log_verbose[i]);
2092 
2093 	/*
2094 	 * If not in debugging mode, not started from inetd and not already
2095 	 * daemonized (eg re-exec via SIGHUP), disconnect from the controlling
2096 	 * terminal, and fork.  The original process exits.
2097 	 */
2098 	already_daemon = daemonized();
2099 	if (!(debug_flag || inetd_flag || no_daemon_flag || already_daemon)) {
2100 
2101 		if (daemon(0, 0) == -1)
2102 			fatal("daemon() failed: %.200s", strerror(errno));
2103 
2104 		disconnect_controlling_tty();
2105 	}
2106 	/* Reinitialize the log (because of the fork above). */
2107 	log_init(__progname, options.log_level, options.log_facility, log_stderr);
2108 
2109 #ifdef LIBWRAP
2110 	/*
2111 	 * We log refusals ourselves.  However, libwrap will report
2112 	 * syntax errors in hosts.allow via syslog(3).
2113 	 */
2114 	allow_severity = options.log_facility|LOG_INFO;
2115 	deny_severity = options.log_facility|LOG_WARNING;
2116 #endif
2117 	/* Avoid killing the process in high-pressure swapping environments. */
2118 	if (!inetd_flag && madvise(NULL, 0, MADV_PROTECT) != 0)
2119 		debug("madvise(): %.200s", strerror(errno));
2120 
2121 	/*
2122 	 * Chdir to the root directory so that the current disk can be
2123 	 * unmounted if desired.
2124 	 */
2125 	if (chdir("/") == -1)
2126 		error("chdir(\"/\"): %s", strerror(errno));
2127 
2128 	/* ignore SIGPIPE */
2129 	ssh_signal(SIGPIPE, SIG_IGN);
2130 
2131 	/* Get a connection, either from inetd or a listening TCP socket */
2132 	if (inetd_flag) {
2133 		server_accept_inetd(&sock_in, &sock_out);
2134 	} else {
2135 		platform_pre_listen();
2136 		server_listen();
2137 
2138 		ssh_signal(SIGHUP, sighup_handler);
2139 		ssh_signal(SIGCHLD, main_sigchld_handler);
2140 		ssh_signal(SIGTERM, sigterm_handler);
2141 		ssh_signal(SIGQUIT, sigterm_handler);
2142 
2143 		/*
2144 		 * Write out the pid file after the sigterm handler
2145 		 * is setup and the listen sockets are bound
2146 		 */
2147 		if (options.pid_file != NULL && !debug_flag) {
2148 			FILE *f = fopen(options.pid_file, "w");
2149 
2150 			if (f == NULL) {
2151 				error("Couldn't create pid file \"%s\": %s",
2152 				    options.pid_file, strerror(errno));
2153 			} else {
2154 				fprintf(f, "%ld\n", (long) getpid());
2155 				fclose(f);
2156 			}
2157 		}
2158 
2159 		/* Accept a connection and return in a forked child */
2160 		server_accept_loop(&sock_in, &sock_out,
2161 		    &newsock, config_s);
2162 	}
2163 
2164 	/* This is the child processing a new connection. */
2165 	setproctitle("%s", "[accepted]");
2166 
2167 	/*
2168 	 * Create a new session and process group since the 4.4BSD
2169 	 * setlogin() affects the entire process group.  We don't
2170 	 * want the child to be able to affect the parent.
2171 	 */
2172 	if (!debug_flag && !inetd_flag && setsid() == -1)
2173 		error("setsid: %.100s", strerror(errno));
2174 
2175 	if (rexec_flag) {
2176 		debug("rexec start in %d out %d newsock %d pipe %d sock %d",
2177 		    sock_in, sock_out, newsock, startup_pipe, config_s[0]);
2178 		dup2(newsock, STDIN_FILENO);
2179 		dup2(STDIN_FILENO, STDOUT_FILENO);
2180 		if (startup_pipe == -1)
2181 			close(REEXEC_STARTUP_PIPE_FD);
2182 		else if (startup_pipe != REEXEC_STARTUP_PIPE_FD) {
2183 			dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD);
2184 			close(startup_pipe);
2185 			startup_pipe = REEXEC_STARTUP_PIPE_FD;
2186 		}
2187 
2188 		dup2(config_s[1], REEXEC_CONFIG_PASS_FD);
2189 		close(config_s[1]);
2190 
2191 		ssh_signal(SIGHUP, SIG_IGN); /* avoid reset to SIG_DFL */
2192 		execv(rexec_argv[0], rexec_argv);
2193 
2194 		/* Reexec has failed, fall back and continue */
2195 		error("rexec of %s failed: %s", rexec_argv[0], strerror(errno));
2196 		recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL);
2197 		log_init(__progname, options.log_level,
2198 		    options.log_facility, log_stderr);
2199 
2200 		/* Clean up fds */
2201 		close(REEXEC_CONFIG_PASS_FD);
2202 		newsock = sock_out = sock_in = dup(STDIN_FILENO);
2203 		if (stdfd_devnull(1, 1, 0) == -1)
2204 			error_f("stdfd_devnull failed");
2205 		debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d",
2206 		    sock_in, sock_out, newsock, startup_pipe, config_s[0]);
2207 	}
2208 
2209 	/* Executed child processes don't need these. */
2210 	fcntl(sock_out, F_SETFD, FD_CLOEXEC);
2211 	fcntl(sock_in, F_SETFD, FD_CLOEXEC);
2212 
2213 	/* We will not restart on SIGHUP since it no longer makes sense. */
2214 	ssh_signal(SIGALRM, SIG_DFL);
2215 	ssh_signal(SIGHUP, SIG_DFL);
2216 	ssh_signal(SIGTERM, SIG_DFL);
2217 	ssh_signal(SIGQUIT, SIG_DFL);
2218 	ssh_signal(SIGCHLD, SIG_DFL);
2219 	ssh_signal(SIGINT, SIG_DFL);
2220 
2221 #ifdef __FreeBSD__
2222 	/*
2223 	 * Initialize the resolver.  This may not happen automatically
2224 	 * before privsep chroot().
2225 	 */
2226 	if ((_res.options & RES_INIT) == 0) {
2227 		debug("res_init()");
2228 		res_init();
2229 	}
2230 #ifdef GSSAPI
2231 	/*
2232 	 * Force GSS-API to parse its configuration and load any
2233 	 * mechanism plugins.
2234 	 */
2235 	{
2236 		gss_OID_set mechs;
2237 		OM_uint32 minor_status;
2238 		gss_indicate_mechs(&minor_status, &mechs);
2239 		gss_release_oid_set(&minor_status, &mechs);
2240 	}
2241 #endif
2242 #endif
2243 
2244 	/*
2245 	 * Register our connection.  This turns encryption off because we do
2246 	 * not have a key.
2247 	 */
2248 	if ((ssh = ssh_packet_set_connection(NULL, sock_in, sock_out)) == NULL)
2249 		fatal("Unable to create connection");
2250 	the_active_state = ssh;
2251 	ssh_packet_set_server(ssh);
2252 
2253 	check_ip_options(ssh);
2254 
2255 	/* Prepare the channels layer */
2256 	channel_init_channels(ssh);
2257 	channel_set_af(ssh, options.address_family);
2258 	process_permitopen(ssh, &options);
2259 
2260 	/* Set SO_KEEPALIVE if requested. */
2261 	if (options.tcp_keep_alive && ssh_packet_connection_is_on_socket(ssh) &&
2262 	    setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) == -1)
2263 		error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
2264 
2265 	if ((remote_port = ssh_remote_port(ssh)) < 0) {
2266 		debug("ssh_remote_port failed");
2267 		cleanup_exit(255);
2268 	}
2269 
2270 	if (options.routing_domain != NULL)
2271 		set_process_rdomain(ssh, options.routing_domain);
2272 
2273 	/*
2274 	 * The rest of the code depends on the fact that
2275 	 * ssh_remote_ipaddr() caches the remote ip, even if
2276 	 * the socket goes away.
2277 	 */
2278 	remote_ip = ssh_remote_ipaddr(ssh);
2279 
2280 #ifdef HAVE_LOGIN_CAP
2281 	/* Also caches remote hostname for sandboxed child. */
2282 	auth_get_canonical_hostname(ssh, options.use_dns);
2283 #endif
2284 
2285 #ifdef SSH_AUDIT_EVENTS
2286 	audit_connection_from(remote_ip, remote_port);
2287 #endif
2288 
2289 	rdomain = ssh_packet_rdomain_in(ssh);
2290 
2291 	/* Log the connection. */
2292 	laddr = get_local_ipaddr(sock_in);
2293 	verbose("Connection from %s port %d on %s port %d%s%s%s",
2294 	    remote_ip, remote_port, laddr,  ssh_local_port(ssh),
2295 	    rdomain == NULL ? "" : " rdomain \"",
2296 	    rdomain == NULL ? "" : rdomain,
2297 	    rdomain == NULL ? "" : "\"");
2298 	free(laddr);
2299 
2300 	/*
2301 	 * We don't want to listen forever unless the other side
2302 	 * successfully authenticates itself.  So we set up an alarm which is
2303 	 * cleared after successful authentication.  A limit of zero
2304 	 * indicates no limit. Note that we don't set the alarm in debugging
2305 	 * mode; it is just annoying to have the server exit just when you
2306 	 * are about to discover the bug.
2307 	 */
2308 	ssh_signal(SIGALRM, grace_alarm_handler);
2309 	if (!debug_flag)
2310 		alarm(options.login_grace_time);
2311 
2312 	if ((r = kex_exchange_identification(ssh, -1,
2313 	    options.version_addendum)) != 0)
2314 		sshpkt_fatal(ssh, r, "banner exchange");
2315 
2316 	ssh_packet_set_nonblocking(ssh);
2317 
2318 	/* allocate authentication context */
2319 	authctxt = xcalloc(1, sizeof(*authctxt));
2320 	ssh->authctxt = authctxt;
2321 
2322 	authctxt->loginmsg = loginmsg;
2323 
2324 	/* XXX global for cleanup, access from other modules */
2325 	the_authctxt = authctxt;
2326 
2327 	/* Set default key authentication options */
2328 	if ((auth_opts = sshauthopt_new_with_keys_defaults()) == NULL)
2329 		fatal("allocation failed");
2330 
2331 	/* prepare buffer to collect messages to display to user after login */
2332 	if ((loginmsg = sshbuf_new()) == NULL)
2333 		fatal_f("sshbuf_new failed");
2334 	auth_debug_reset();
2335 
2336 	BLACKLIST_INIT();
2337 
2338 	if (use_privsep) {
2339 		if (privsep_preauth(ssh) == 1)
2340 			goto authenticated;
2341 	} else if (have_agent) {
2342 		if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) {
2343 			error_r(r, "Unable to get agent socket");
2344 			have_agent = 0;
2345 		}
2346 	}
2347 
2348 	/* perform the key exchange */
2349 	/* authenticate user and start session */
2350 	do_ssh2_kex(ssh);
2351 	do_authentication2(ssh);
2352 
2353 	/*
2354 	 * If we use privilege separation, the unprivileged child transfers
2355 	 * the current keystate and exits
2356 	 */
2357 	if (use_privsep) {
2358 		mm_send_keystate(ssh, pmonitor);
2359 		ssh_packet_clear_keys(ssh);
2360 		exit(0);
2361 	}
2362 
2363  authenticated:
2364 	/*
2365 	 * Cancel the alarm we set to limit the time taken for
2366 	 * authentication.
2367 	 */
2368 	alarm(0);
2369 	ssh_signal(SIGALRM, SIG_DFL);
2370 	authctxt->authenticated = 1;
2371 	if (startup_pipe != -1) {
2372 		close(startup_pipe);
2373 		startup_pipe = -1;
2374 	}
2375 
2376 #ifdef SSH_AUDIT_EVENTS
2377 	audit_event(ssh, SSH_AUTH_SUCCESS);
2378 #endif
2379 
2380 #ifdef GSSAPI
2381 	if (options.gss_authentication) {
2382 		temporarily_use_uid(authctxt->pw);
2383 		ssh_gssapi_storecreds();
2384 		restore_uid();
2385 	}
2386 #endif
2387 #ifdef USE_PAM
2388 	if (options.use_pam) {
2389 		do_pam_setcred(1);
2390 		do_pam_session(ssh);
2391 	}
2392 #endif
2393 
2394 	/*
2395 	 * In privilege separation, we fork another child and prepare
2396 	 * file descriptor passing.
2397 	 */
2398 	if (use_privsep) {
2399 		privsep_postauth(ssh, authctxt);
2400 		/* the monitor process [priv] will not return */
2401 	}
2402 
2403 	ssh_packet_set_timeout(ssh, options.client_alive_interval,
2404 	    options.client_alive_count_max);
2405 
2406 	/* Try to send all our hostkeys to the client */
2407 	notify_hostkeys(ssh);
2408 
2409 	/* Start session. */
2410 	do_authenticated(ssh, authctxt);
2411 
2412 	/* The connection has been terminated. */
2413 	ssh_packet_get_bytes(ssh, &ibytes, &obytes);
2414 	verbose("Transferred: sent %llu, received %llu bytes",
2415 	    (unsigned long long)obytes, (unsigned long long)ibytes);
2416 
2417 	verbose("Closing connection to %.500s port %d", remote_ip, remote_port);
2418 
2419 #ifdef USE_PAM
2420 	if (options.use_pam)
2421 		finish_pam();
2422 #endif /* USE_PAM */
2423 
2424 #ifdef SSH_AUDIT_EVENTS
2425 	PRIVSEP(audit_event(ssh, SSH_CONNECTION_CLOSE));
2426 #endif
2427 
2428 	ssh_packet_close(ssh);
2429 
2430 	if (use_privsep)
2431 		mm_terminate();
2432 
2433 	exit(0);
2434 }
2435 
2436 int
2437 sshd_hostkey_sign(struct ssh *ssh, struct sshkey *privkey,
2438     struct sshkey *pubkey, u_char **signature, size_t *slenp,
2439     const u_char *data, size_t dlen, const char *alg)
2440 {
2441 	int r;
2442 
2443 	if (use_privsep) {
2444 		if (privkey) {
2445 			if (mm_sshkey_sign(ssh, privkey, signature, slenp,
2446 			    data, dlen, alg, options.sk_provider, NULL,
2447 			    ssh->compat) < 0)
2448 				fatal_f("privkey sign failed");
2449 		} else {
2450 			if (mm_sshkey_sign(ssh, pubkey, signature, slenp,
2451 			    data, dlen, alg, options.sk_provider, NULL,
2452 			    ssh->compat) < 0)
2453 				fatal_f("pubkey sign failed");
2454 		}
2455 	} else {
2456 		if (privkey) {
2457 			if (sshkey_sign(privkey, signature, slenp, data, dlen,
2458 			    alg, options.sk_provider, NULL, ssh->compat) < 0)
2459 				fatal_f("privkey sign failed");
2460 		} else {
2461 			if ((r = ssh_agent_sign(auth_sock, pubkey,
2462 			    signature, slenp, data, dlen, alg,
2463 			    ssh->compat)) != 0) {
2464 				fatal_fr(r, "agent sign failed");
2465 			}
2466 		}
2467 	}
2468 	return 0;
2469 }
2470 
2471 /* SSH2 key exchange */
2472 static void
2473 do_ssh2_kex(struct ssh *ssh)
2474 {
2475 	char *myproposal[PROPOSAL_MAX] = { KEX_SERVER };
2476 	struct kex *kex;
2477 	char *prop_kex = NULL, *prop_enc = NULL, *prop_hostkey = NULL;
2478 	int r;
2479 
2480 	myproposal[PROPOSAL_KEX_ALGS] = prop_kex = compat_kex_proposal(ssh,
2481 	    options.kex_algorithms);
2482 	myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2483 	    myproposal[PROPOSAL_ENC_ALGS_STOC] = prop_enc =
2484 	    compat_cipher_proposal(ssh, options.ciphers);
2485 	myproposal[PROPOSAL_MAC_ALGS_CTOS] =
2486 	    myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
2487 
2488 	if (options.compression == COMP_NONE) {
2489 		myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2490 		    myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
2491 	}
2492 
2493 	if (options.rekey_limit || options.rekey_interval)
2494 		ssh_packet_set_rekey_limits(ssh, options.rekey_limit,
2495 		    options.rekey_interval);
2496 
2497 	myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = prop_hostkey =
2498 	   compat_pkalg_proposal(ssh, list_hostkey_types());
2499 
2500 	/* start key exchange */
2501 	if ((r = kex_setup(ssh, myproposal)) != 0)
2502 		fatal_r(r, "kex_setup");
2503 	kex = ssh->kex;
2504 #ifdef WITH_OPENSSL
2505 	kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server;
2506 	kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server;
2507 	kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server;
2508 	kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server;
2509 	kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server;
2510 	kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
2511 	kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
2512 # ifdef OPENSSL_HAS_ECC
2513 	kex->kex[KEX_ECDH_SHA2] = kex_gen_server;
2514 # endif
2515 #endif
2516 	kex->kex[KEX_C25519_SHA256] = kex_gen_server;
2517 	kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server;
2518 	kex->load_host_public_key=&get_hostkey_public_by_type;
2519 	kex->load_host_private_key=&get_hostkey_private_by_type;
2520 	kex->host_key_index=&get_hostkey_index;
2521 	kex->sign = sshd_hostkey_sign;
2522 
2523 	ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &kex->done);
2524 
2525 #ifdef DEBUG_KEXDH
2526 	/* send 1st encrypted/maced/compressed message */
2527 	if ((r = sshpkt_start(ssh, SSH2_MSG_IGNORE)) != 0 ||
2528 	    (r = sshpkt_put_cstring(ssh, "markus")) != 0 ||
2529 	    (r = sshpkt_send(ssh)) != 0 ||
2530 	    (r = ssh_packet_write_wait(ssh)) != 0)
2531 		fatal_fr(r, "send test");
2532 #endif
2533 	free(prop_kex);
2534 	free(prop_enc);
2535 	free(prop_hostkey);
2536 	debug("KEX done");
2537 }
2538 
2539 /* server specific fatal cleanup */
2540 void
2541 cleanup_exit(int i)
2542 {
2543 	if (the_active_state != NULL && the_authctxt != NULL) {
2544 		do_cleanup(the_active_state, the_authctxt);
2545 		if (use_privsep && privsep_is_preauth &&
2546 		    pmonitor != NULL && pmonitor->m_pid > 1) {
2547 			debug("Killing privsep child %d", pmonitor->m_pid);
2548 			if (kill(pmonitor->m_pid, SIGKILL) != 0 &&
2549 			    errno != ESRCH) {
2550 				error_f("kill(%d): %s", pmonitor->m_pid,
2551 				    strerror(errno));
2552 			}
2553 		}
2554 	}
2555 #ifdef SSH_AUDIT_EVENTS
2556 	/* done after do_cleanup so it can cancel the PAM auth 'thread' */
2557 	if (the_active_state != NULL && (!use_privsep || mm_is_monitor()))
2558 		audit_event(the_active_state, SSH_CONNECTION_ABANDON);
2559 #endif
2560 	_exit(i);
2561 }
2562