xref: /freebsd/crypto/openssh/sshd-session.c (revision 3d9fd9fcb432750f3716b28f6ccb0104cd9d351a)
1 /* $OpenBSD: sshd-session.c,v 1.9 2024/09/09 02:39:57 djm Exp $ */
2 /*
3  * SSH2 implementation:
4  * Privilege Separation:
5  *
6  * Copyright (c) 2000, 2001, 2002 Markus Friedl.  All rights reserved.
7  * Copyright (c) 2002 Niels Provos.  All rights reserved.
8  *
9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
12  * 1. Redistributions of source code must retain the above copyright
13  *    notice, this list of conditions and the following disclaimer.
14  * 2. Redistributions in binary form must reproduce the above copyright
15  *    notice, this list of conditions and the following disclaimer in the
16  *    documentation and/or other materials provided with the distribution.
17  *
18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28  */
29 
30 #include "includes.h"
31 
32 #include <sys/types.h>
33 #include <sys/ioctl.h>
34 #include <sys/socket.h>
35 #ifdef HAVE_SYS_STAT_H
36 # include <sys/stat.h>
37 #endif
38 #ifdef HAVE_SYS_TIME_H
39 # include <sys/time.h>
40 #endif
41 #include "openbsd-compat/sys-tree.h"
42 #include "openbsd-compat/sys-queue.h"
43 #include <sys/wait.h>
44 
45 #include <errno.h>
46 #include <fcntl.h>
47 #include <netdb.h>
48 #ifdef HAVE_PATHS_H
49 # include <paths.h>
50 #endif
51 #include <pwd.h>
52 #include <grp.h>
53 #include <signal.h>
54 #include <stdio.h>
55 #include <stdlib.h>
56 #include <string.h>
57 #include <stdarg.h>
58 #include <unistd.h>
59 #include <limits.h>
60 
61 #ifdef WITH_OPENSSL
62 #include <openssl/bn.h>
63 #include <openssl/evp.h>
64 #include <openssl/rand.h>
65 #include "openbsd-compat/openssl-compat.h"
66 #endif
67 
68 #ifdef HAVE_SECUREWARE
69 #include <sys/security.h>
70 #include <prot.h>
71 #endif
72 
73 #include "xmalloc.h"
74 #include "ssh.h"
75 #include "ssh2.h"
76 #include "sshpty.h"
77 #include "packet.h"
78 #include "log.h"
79 #include "sshbuf.h"
80 #include "misc.h"
81 #include "match.h"
82 #include "servconf.h"
83 #include "uidswap.h"
84 #include "compat.h"
85 #include "cipher.h"
86 #include "digest.h"
87 #include "sshkey.h"
88 #include "kex.h"
89 #include "authfile.h"
90 #include "pathnames.h"
91 #include "atomicio.h"
92 #include "canohost.h"
93 #include "hostfile.h"
94 #include "auth.h"
95 #include "authfd.h"
96 #include "msg.h"
97 #include "dispatch.h"
98 #include "channels.h"
99 #include "session.h"
100 #include "monitor.h"
101 #ifdef GSSAPI
102 #include "ssh-gss.h"
103 #endif
104 #include "monitor_wrap.h"
105 #include "ssh-sandbox.h"
106 #include "auth-options.h"
107 #include "version.h"
108 #include "ssherr.h"
109 #include "sk-api.h"
110 #include "srclimit.h"
111 #include "dh.h"
112 
113 /* Re-exec fds */
114 #define REEXEC_DEVCRYPTO_RESERVED_FD	(STDERR_FILENO + 1)
115 #define REEXEC_STARTUP_PIPE_FD		(STDERR_FILENO + 2)
116 #define REEXEC_CONFIG_PASS_FD		(STDERR_FILENO + 3)
117 #define REEXEC_MIN_FREE_FD		(STDERR_FILENO + 4)
118 
119 extern char *__progname;
120 
121 /* Server configuration options. */
122 ServerOptions options;
123 
124 /* Name of the server configuration file. */
125 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
126 
127 /*
128  * Debug mode flag.  This can be set on the command line.  If debug
129  * mode is enabled, extra debugging output will be sent to the system
130  * log, the daemon will not go to background, and will exit after processing
131  * the first connection.
132  */
133 int debug_flag = 0;
134 
135 /* Flag indicating that the daemon is being started from inetd. */
136 static int inetd_flag = 0;
137 
138 /* debug goes to stderr unless inetd_flag is set */
139 static int log_stderr = 0;
140 
141 /* Saved arguments to main(). */
142 static char **saved_argv;
143 static int saved_argc;
144 
145 /* Daemon's agent connection */
146 int auth_sock = -1;
147 static int have_agent = 0;
148 
149 /*
150  * Any really sensitive data in the application is contained in this
151  * structure. The idea is that this structure could be locked into memory so
152  * that the pages do not get written into swap.  However, there are some
153  * problems. The private key contains BIGNUMs, and we do not (in principle)
154  * have access to the internals of them, and locking just the structure is
155  * not very useful.  Currently, memory locking is not implemented.
156  */
157 struct {
158 	u_int		num_hostkeys;
159 	struct sshkey	**host_keys;		/* all private host keys */
160 	struct sshkey	**host_pubkeys;		/* all public host keys */
161 	struct sshkey	**host_certificates;	/* all public host certificates */
162 } sensitive_data;
163 
164 /* record remote hostname or ip */
165 u_int utmp_len = HOST_NAME_MAX+1;
166 
167 static int startup_pipe = -1;		/* in child */
168 
169 /* variables used for privilege separation */
170 struct monitor *pmonitor = NULL;
171 int privsep_is_preauth = 1;
172 static int privsep_chroot = 1;
173 
174 /* Unprivileged user */
175 struct passwd *privsep_pw = NULL;
176 
177 /* global connection state and authentication contexts */
178 Authctxt *the_authctxt = NULL;
179 struct ssh *the_active_state;
180 
181 /* global key/cert auth options. XXX move to permanent ssh->authctxt? */
182 struct sshauthopt *auth_opts = NULL;
183 
184 /* sshd_config buffer */
185 struct sshbuf *cfg;
186 
187 /* Included files from the configuration file */
188 struct include_list includes = TAILQ_HEAD_INITIALIZER(includes);
189 
190 /* message to be displayed after login */
191 struct sshbuf *loginmsg;
192 
193 /* Prototypes for various functions defined later in this file. */
194 void destroy_sensitive_data(void);
195 void demote_sensitive_data(void);
196 static void do_ssh2_kex(struct ssh *);
197 
198 /*
199  * Signal handler for the alarm after the login grace period has expired.
200  * As usual, this may only take signal-safe actions, even though it is
201  * terminal.
202  */
203 static void
grace_alarm_handler(int sig)204 grace_alarm_handler(int sig)
205 {
206 	/*
207 	 * Try to kill any processes that we have spawned, E.g. authorized
208 	 * keys command helpers or privsep children.
209 	 */
210 	if (getpgid(0) == getpid()) {
211 		struct sigaction sa;
212 
213 		/* mask all other signals while in handler */
214 		memset(&sa, 0, sizeof(sa));
215 		sa.sa_handler = SIG_IGN;
216 		sigfillset(&sa.sa_mask);
217 #if defined(SA_RESTART)
218 		sa.sa_flags = SA_RESTART;
219 #endif
220 		(void)sigaction(SIGTERM, &sa, NULL);
221 		kill(0, SIGTERM);
222 	}
223 	_exit(EXIT_LOGIN_GRACE);
224 }
225 
226 /* Destroy the host and server keys.  They will no longer be needed. */
227 void
destroy_sensitive_data(void)228 destroy_sensitive_data(void)
229 {
230 	u_int i;
231 
232 	for (i = 0; i < options.num_host_key_files; i++) {
233 		if (sensitive_data.host_keys[i]) {
234 			sshkey_free(sensitive_data.host_keys[i]);
235 			sensitive_data.host_keys[i] = NULL;
236 		}
237 		if (sensitive_data.host_certificates[i]) {
238 			sshkey_free(sensitive_data.host_certificates[i]);
239 			sensitive_data.host_certificates[i] = NULL;
240 		}
241 	}
242 }
243 
244 /* Demote private to public keys for network child */
245 void
demote_sensitive_data(void)246 demote_sensitive_data(void)
247 {
248 	struct sshkey *tmp;
249 	u_int i;
250 	int r;
251 
252 	for (i = 0; i < options.num_host_key_files; i++) {
253 		if (sensitive_data.host_keys[i]) {
254 			if ((r = sshkey_from_private(
255 			    sensitive_data.host_keys[i], &tmp)) != 0)
256 				fatal_r(r, "could not demote host %s key",
257 				    sshkey_type(sensitive_data.host_keys[i]));
258 			sshkey_free(sensitive_data.host_keys[i]);
259 			sensitive_data.host_keys[i] = tmp;
260 		}
261 		/* Certs do not need demotion */
262 	}
263 }
264 
265 static void
reseed_prngs(void)266 reseed_prngs(void)
267 {
268 	u_int32_t rnd[256];
269 
270 #ifdef WITH_OPENSSL
271 	RAND_poll();
272 #endif
273 	arc4random_stir(); /* noop on recent arc4random() implementations */
274 	arc4random_buf(rnd, sizeof(rnd)); /* let arc4random notice PID change */
275 
276 #ifdef WITH_OPENSSL
277 	RAND_seed(rnd, sizeof(rnd));
278 	/* give libcrypto a chance to notice the PID change */
279 	if ((RAND_bytes((u_char *)rnd, 1)) != 1)
280 		fatal("%s: RAND_bytes failed", __func__);
281 #endif
282 
283 	explicit_bzero(rnd, sizeof(rnd));
284 }
285 
286 static void
privsep_preauth_child(void)287 privsep_preauth_child(void)
288 {
289 	gid_t gidset[1];
290 
291 	/* Enable challenge-response authentication for privilege separation */
292 	privsep_challenge_enable();
293 
294 #ifdef GSSAPI
295 	/* Cache supported mechanism OIDs for later use */
296 	ssh_gssapi_prepare_supported_oids();
297 #endif
298 
299 	reseed_prngs();
300 
301 	/* Demote the private keys to public keys. */
302 	demote_sensitive_data();
303 
304 	/* Demote the child */
305 	if (privsep_chroot) {
306 		/* Change our root directory */
307 		if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
308 			fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
309 			    strerror(errno));
310 		if (chdir("/") == -1)
311 			fatal("chdir(\"/\"): %s", strerror(errno));
312 
313 		/* Drop our privileges */
314 		debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid,
315 		    (u_int)privsep_pw->pw_gid);
316 		gidset[0] = privsep_pw->pw_gid;
317 		if (setgroups(1, gidset) == -1)
318 			fatal("setgroups: %.100s", strerror(errno));
319 		permanently_set_uid(privsep_pw);
320 	}
321 }
322 
323 static int
privsep_preauth(struct ssh * ssh)324 privsep_preauth(struct ssh *ssh)
325 {
326 	int status, r;
327 	pid_t pid;
328 	struct ssh_sandbox *box = NULL;
329 
330 	/* Set up unprivileged child process to deal with network data */
331 	pmonitor = monitor_init();
332 	/* Store a pointer to the kex for later rekeying */
333 	pmonitor->m_pkex = &ssh->kex;
334 
335 	box = ssh_sandbox_init(pmonitor);
336 	pid = fork();
337 	if (pid == -1) {
338 		fatal("fork of unprivileged child failed");
339 	} else if (pid != 0) {
340 		debug2("Network child is on pid %ld", (long)pid);
341 
342 		pmonitor->m_pid = pid;
343 		if (have_agent) {
344 			r = ssh_get_authentication_socket(&auth_sock);
345 			if (r != 0) {
346 				error_r(r, "Could not get agent socket");
347 				have_agent = 0;
348 			}
349 		}
350 		if (box != NULL)
351 			ssh_sandbox_parent_preauth(box, pid);
352 		monitor_child_preauth(ssh, pmonitor);
353 
354 		/* Wait for the child's exit status */
355 		while (waitpid(pid, &status, 0) == -1) {
356 			if (errno == EINTR)
357 				continue;
358 			pmonitor->m_pid = -1;
359 			fatal_f("waitpid: %s", strerror(errno));
360 		}
361 		privsep_is_preauth = 0;
362 		pmonitor->m_pid = -1;
363 		if (WIFEXITED(status)) {
364 			if (WEXITSTATUS(status) != 0)
365 				fatal_f("preauth child exited with status %d",
366 				    WEXITSTATUS(status));
367 		} else if (WIFSIGNALED(status))
368 			fatal_f("preauth child terminated by signal %d",
369 			    WTERMSIG(status));
370 		if (box != NULL)
371 			ssh_sandbox_parent_finish(box);
372 		return 1;
373 	} else {
374 		/* child */
375 		close(pmonitor->m_sendfd);
376 		close(pmonitor->m_log_recvfd);
377 
378 		/* Arrange for logging to be sent to the monitor */
379 		set_log_handler(mm_log_handler, pmonitor);
380 
381 		privsep_preauth_child();
382 		setproctitle("%s", "[net]");
383 		if (box != NULL)
384 			ssh_sandbox_child(box);
385 
386 		return 0;
387 	}
388 }
389 
390 static void
privsep_postauth(struct ssh * ssh,Authctxt * authctxt)391 privsep_postauth(struct ssh *ssh, Authctxt *authctxt)
392 {
393 	int skip_privdrop = 0;
394 
395 	/*
396 	 * Hack for systems that don't support FD passing: retain privileges
397 	 * in the post-auth privsep process so it can allocate PTYs directly.
398 	 * This is basically equivalent to what we did <= 9.7, which was to
399 	 * disable post-auth privsep entriely.
400 	 * Cygwin doesn't need to drop privs here although it doesn't support
401 	 * fd passing, as AFAIK PTY allocation on this platform doesn't require
402 	 * special privileges to begin with.
403 	 */
404 #if defined(DISABLE_FD_PASSING) && !defined(HAVE_CYGWIN)
405 	skip_privdrop = 1;
406 #endif
407 
408 	/* New socket pair */
409 	monitor_reinit(pmonitor);
410 
411 	pmonitor->m_pid = fork();
412 	if (pmonitor->m_pid == -1)
413 		fatal("fork of unprivileged child failed");
414 	else if (pmonitor->m_pid != 0) {
415 		verbose("User child is on pid %ld", (long)pmonitor->m_pid);
416 		sshbuf_reset(loginmsg);
417 		monitor_clear_keystate(ssh, pmonitor);
418 		monitor_child_postauth(ssh, pmonitor);
419 
420 		/* NEVERREACHED */
421 		exit(0);
422 	}
423 
424 	/* child */
425 
426 	close(pmonitor->m_sendfd);
427 	pmonitor->m_sendfd = -1;
428 
429 	/* Demote the private keys to public keys. */
430 	demote_sensitive_data();
431 
432 	reseed_prngs();
433 
434 	/* Drop privileges */
435 	if (!skip_privdrop)
436 		do_setusercontext(authctxt->pw);
437 
438 	/* It is safe now to apply the key state */
439 	monitor_apply_keystate(ssh, pmonitor);
440 
441 	/*
442 	 * Tell the packet layer that authentication was successful, since
443 	 * this information is not part of the key state.
444 	 */
445 	ssh_packet_set_authenticated(ssh);
446 }
447 
448 static void
append_hostkey_type(struct sshbuf * b,const char * s)449 append_hostkey_type(struct sshbuf *b, const char *s)
450 {
451 	int r;
452 
453 	if (match_pattern_list(s, options.hostkeyalgorithms, 0) != 1) {
454 		debug3_f("%s key not permitted by HostkeyAlgorithms", s);
455 		return;
456 	}
457 	if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) > 0 ? "," : "", s)) != 0)
458 		fatal_fr(r, "sshbuf_putf");
459 }
460 
461 static char *
list_hostkey_types(void)462 list_hostkey_types(void)
463 {
464 	struct sshbuf *b;
465 	struct sshkey *key;
466 	char *ret;
467 	u_int i;
468 
469 	if ((b = sshbuf_new()) == NULL)
470 		fatal_f("sshbuf_new failed");
471 	for (i = 0; i < options.num_host_key_files; i++) {
472 		key = sensitive_data.host_keys[i];
473 		if (key == NULL)
474 			key = sensitive_data.host_pubkeys[i];
475 		if (key == NULL)
476 			continue;
477 		switch (key->type) {
478 		case KEY_RSA:
479 			/* for RSA we also support SHA2 signatures */
480 			append_hostkey_type(b, "rsa-sha2-512");
481 			append_hostkey_type(b, "rsa-sha2-256");
482 			/* FALLTHROUGH */
483 		case KEY_DSA:
484 		case KEY_ECDSA:
485 		case KEY_ED25519:
486 		case KEY_ECDSA_SK:
487 		case KEY_ED25519_SK:
488 		case KEY_XMSS:
489 			append_hostkey_type(b, sshkey_ssh_name(key));
490 			break;
491 		}
492 		/* If the private key has a cert peer, then list that too */
493 		key = sensitive_data.host_certificates[i];
494 		if (key == NULL)
495 			continue;
496 		switch (key->type) {
497 		case KEY_RSA_CERT:
498 			/* for RSA we also support SHA2 signatures */
499 			append_hostkey_type(b,
500 			    "rsa-sha2-512-cert-v01@openssh.com");
501 			append_hostkey_type(b,
502 			    "rsa-sha2-256-cert-v01@openssh.com");
503 			/* FALLTHROUGH */
504 		case KEY_DSA_CERT:
505 		case KEY_ECDSA_CERT:
506 		case KEY_ED25519_CERT:
507 		case KEY_ECDSA_SK_CERT:
508 		case KEY_ED25519_SK_CERT:
509 		case KEY_XMSS_CERT:
510 			append_hostkey_type(b, sshkey_ssh_name(key));
511 			break;
512 		}
513 	}
514 	if ((ret = sshbuf_dup_string(b)) == NULL)
515 		fatal_f("sshbuf_dup_string failed");
516 	sshbuf_free(b);
517 	debug_f("%s", ret);
518 	return ret;
519 }
520 
521 static struct sshkey *
get_hostkey_by_type(int type,int nid,int need_private,struct ssh * ssh)522 get_hostkey_by_type(int type, int nid, int need_private, struct ssh *ssh)
523 {
524 	u_int i;
525 	struct sshkey *key;
526 
527 	for (i = 0; i < options.num_host_key_files; i++) {
528 		switch (type) {
529 		case KEY_RSA_CERT:
530 		case KEY_DSA_CERT:
531 		case KEY_ECDSA_CERT:
532 		case KEY_ED25519_CERT:
533 		case KEY_ECDSA_SK_CERT:
534 		case KEY_ED25519_SK_CERT:
535 		case KEY_XMSS_CERT:
536 			key = sensitive_data.host_certificates[i];
537 			break;
538 		default:
539 			key = sensitive_data.host_keys[i];
540 			if (key == NULL && !need_private)
541 				key = sensitive_data.host_pubkeys[i];
542 			break;
543 		}
544 		if (key == NULL || key->type != type)
545 			continue;
546 		switch (type) {
547 		case KEY_ECDSA:
548 		case KEY_ECDSA_SK:
549 		case KEY_ECDSA_CERT:
550 		case KEY_ECDSA_SK_CERT:
551 			if (key->ecdsa_nid != nid)
552 				continue;
553 			/* FALLTHROUGH */
554 		default:
555 			return need_private ?
556 			    sensitive_data.host_keys[i] : key;
557 		}
558 	}
559 	return NULL;
560 }
561 
562 struct sshkey *
get_hostkey_public_by_type(int type,int nid,struct ssh * ssh)563 get_hostkey_public_by_type(int type, int nid, struct ssh *ssh)
564 {
565 	return get_hostkey_by_type(type, nid, 0, ssh);
566 }
567 
568 struct sshkey *
get_hostkey_private_by_type(int type,int nid,struct ssh * ssh)569 get_hostkey_private_by_type(int type, int nid, struct ssh *ssh)
570 {
571 	return get_hostkey_by_type(type, nid, 1, ssh);
572 }
573 
574 struct sshkey *
get_hostkey_by_index(int ind)575 get_hostkey_by_index(int ind)
576 {
577 	if (ind < 0 || (u_int)ind >= options.num_host_key_files)
578 		return (NULL);
579 	return (sensitive_data.host_keys[ind]);
580 }
581 
582 struct sshkey *
get_hostkey_public_by_index(int ind,struct ssh * ssh)583 get_hostkey_public_by_index(int ind, struct ssh *ssh)
584 {
585 	if (ind < 0 || (u_int)ind >= options.num_host_key_files)
586 		return (NULL);
587 	return (sensitive_data.host_pubkeys[ind]);
588 }
589 
590 int
get_hostkey_index(struct sshkey * key,int compare,struct ssh * ssh)591 get_hostkey_index(struct sshkey *key, int compare, struct ssh *ssh)
592 {
593 	u_int i;
594 
595 	for (i = 0; i < options.num_host_key_files; i++) {
596 		if (sshkey_is_cert(key)) {
597 			if (key == sensitive_data.host_certificates[i] ||
598 			    (compare && sensitive_data.host_certificates[i] &&
599 			    sshkey_equal(key,
600 			    sensitive_data.host_certificates[i])))
601 				return (i);
602 		} else {
603 			if (key == sensitive_data.host_keys[i] ||
604 			    (compare && sensitive_data.host_keys[i] &&
605 			    sshkey_equal(key, sensitive_data.host_keys[i])))
606 				return (i);
607 			if (key == sensitive_data.host_pubkeys[i] ||
608 			    (compare && sensitive_data.host_pubkeys[i] &&
609 			    sshkey_equal(key, sensitive_data.host_pubkeys[i])))
610 				return (i);
611 		}
612 	}
613 	return (-1);
614 }
615 
616 /* Inform the client of all hostkeys */
617 static void
notify_hostkeys(struct ssh * ssh)618 notify_hostkeys(struct ssh *ssh)
619 {
620 	struct sshbuf *buf;
621 	struct sshkey *key;
622 	u_int i, nkeys;
623 	int r;
624 	char *fp;
625 
626 	/* Some clients cannot cope with the hostkeys message, skip those. */
627 	if (ssh->compat & SSH_BUG_HOSTKEYS)
628 		return;
629 
630 	if ((buf = sshbuf_new()) == NULL)
631 		fatal_f("sshbuf_new");
632 	for (i = nkeys = 0; i < options.num_host_key_files; i++) {
633 		key = get_hostkey_public_by_index(i, ssh);
634 		if (key == NULL || key->type == KEY_UNSPEC ||
635 		    sshkey_is_cert(key))
636 			continue;
637 		fp = sshkey_fingerprint(key, options.fingerprint_hash,
638 		    SSH_FP_DEFAULT);
639 		debug3_f("key %d: %s %s", i, sshkey_ssh_name(key), fp);
640 		free(fp);
641 		if (nkeys == 0) {
642 			/*
643 			 * Start building the request when we find the
644 			 * first usable key.
645 			 */
646 			if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 ||
647 			    (r = sshpkt_put_cstring(ssh, "hostkeys-00@openssh.com")) != 0 ||
648 			    (r = sshpkt_put_u8(ssh, 0)) != 0) /* want reply */
649 				sshpkt_fatal(ssh, r, "%s: start request", __func__);
650 		}
651 		/* Append the key to the request */
652 		sshbuf_reset(buf);
653 		if ((r = sshkey_putb(key, buf)) != 0)
654 			fatal_fr(r, "couldn't put hostkey %d", i);
655 		if ((r = sshpkt_put_stringb(ssh, buf)) != 0)
656 			sshpkt_fatal(ssh, r, "%s: append key", __func__);
657 		nkeys++;
658 	}
659 	debug3_f("sent %u hostkeys", nkeys);
660 	if (nkeys == 0)
661 		fatal_f("no hostkeys");
662 	if ((r = sshpkt_send(ssh)) != 0)
663 		sshpkt_fatal(ssh, r, "%s: send", __func__);
664 	sshbuf_free(buf);
665 }
666 
667 static void
usage(void)668 usage(void)
669 {
670 	fprintf(stderr, "%s, %s\n", SSH_RELEASE, SSH_OPENSSL_VERSION);
671 	fprintf(stderr,
672 "usage: sshd [-46DdeGiqTtV] [-C connection_spec] [-c host_cert_file]\n"
673 "            [-E log_file] [-f config_file] [-g login_grace_time]\n"
674 "            [-h host_key_file] [-o option] [-p port] [-u len]\n"
675 	);
676 	exit(1);
677 }
678 
679 static void
parse_hostkeys(struct sshbuf * hostkeys)680 parse_hostkeys(struct sshbuf *hostkeys)
681 {
682 	int r;
683 	u_int num_keys = 0;
684 	struct sshkey *k;
685 	struct sshbuf *kbuf;
686 	const u_char *cp;
687 	size_t len;
688 
689 	while (sshbuf_len(hostkeys) != 0) {
690 		if (num_keys > 2048)
691 			fatal_f("too many hostkeys");
692 		sensitive_data.host_keys = xrecallocarray(
693 		    sensitive_data.host_keys, num_keys, num_keys + 1,
694 		    sizeof(*sensitive_data.host_pubkeys));
695 		sensitive_data.host_pubkeys = xrecallocarray(
696 		    sensitive_data.host_pubkeys, num_keys, num_keys + 1,
697 		    sizeof(*sensitive_data.host_pubkeys));
698 		sensitive_data.host_certificates = xrecallocarray(
699 		    sensitive_data.host_certificates, num_keys, num_keys + 1,
700 		    sizeof(*sensitive_data.host_certificates));
701 		/* private key */
702 		k = NULL;
703 		if ((r = sshbuf_froms(hostkeys, &kbuf)) != 0)
704 			fatal_fr(r, "extract privkey");
705 		if (sshbuf_len(kbuf) != 0 &&
706 		    (r = sshkey_private_deserialize(kbuf, &k)) != 0)
707 			fatal_fr(r, "parse pubkey");
708 		sensitive_data.host_keys[num_keys] = k;
709 		sshbuf_free(kbuf);
710 		if (k)
711 			debug2_f("privkey %u: %s", num_keys, sshkey_ssh_name(k));
712 		/* public key */
713 		k = NULL;
714 		if ((r = sshbuf_get_string_direct(hostkeys, &cp, &len)) != 0)
715 			fatal_fr(r, "extract pubkey");
716 		if (len != 0 && (r = sshkey_from_blob(cp, len, &k)) != 0)
717 			fatal_fr(r, "parse pubkey");
718 		sensitive_data.host_pubkeys[num_keys] = k;
719 		if (k)
720 			debug2_f("pubkey %u: %s", num_keys, sshkey_ssh_name(k));
721 		/* certificate */
722 		k = NULL;
723 		if ((r = sshbuf_get_string_direct(hostkeys, &cp, &len)) != 0)
724 			fatal_fr(r, "extract pubkey");
725 		if (len != 0 && (r = sshkey_from_blob(cp, len, &k)) != 0)
726 			fatal_fr(r, "parse pubkey");
727 		sensitive_data.host_certificates[num_keys] = k;
728 		if (k)
729 			debug2_f("cert %u: %s", num_keys, sshkey_ssh_name(k));
730 		num_keys++;
731 	}
732 	sensitive_data.num_hostkeys = num_keys;
733 }
734 
735 static void
recv_rexec_state(int fd,struct sshbuf * conf,uint64_t * timing_secretp)736 recv_rexec_state(int fd, struct sshbuf *conf, uint64_t *timing_secretp)
737 {
738 	struct sshbuf *m, *inc, *hostkeys;
739 	u_char *cp, ver;
740 	size_t len;
741 	int r;
742 	struct include_item *item;
743 
744 	debug3_f("entering fd = %d", fd);
745 
746 	if ((m = sshbuf_new()) == NULL || (inc = sshbuf_new()) == NULL)
747 		fatal_f("sshbuf_new failed");
748 	if (ssh_msg_recv(fd, m) == -1)
749 		fatal_f("ssh_msg_recv failed");
750 	if ((r = sshbuf_get_u8(m, &ver)) != 0)
751 		fatal_fr(r, "parse version");
752 	if (ver != 0)
753 		fatal_f("rexec version mismatch");
754 	if ((r = sshbuf_get_string(m, &cp, &len)) != 0 || /* XXX _direct */
755 	    (r = sshbuf_get_u64(m, timing_secretp)) != 0 ||
756 	    (r = sshbuf_froms(m, &hostkeys)) != 0 ||
757 	    (r = sshbuf_get_stringb(m, inc)) != 0)
758 		fatal_fr(r, "parse config");
759 
760 	if (conf != NULL && (r = sshbuf_put(conf, cp, len)))
761 		fatal_fr(r, "sshbuf_put");
762 
763 	while (sshbuf_len(inc) != 0) {
764 		item = xcalloc(1, sizeof(*item));
765 		if ((item->contents = sshbuf_new()) == NULL)
766 			fatal_f("sshbuf_new failed");
767 		if ((r = sshbuf_get_cstring(inc, &item->selector, NULL)) != 0 ||
768 		    (r = sshbuf_get_cstring(inc, &item->filename, NULL)) != 0 ||
769 		    (r = sshbuf_get_stringb(inc, item->contents)) != 0)
770 			fatal_fr(r, "parse includes");
771 		TAILQ_INSERT_TAIL(&includes, item, entry);
772 	}
773 
774 	parse_hostkeys(hostkeys);
775 
776 	free(cp);
777 	sshbuf_free(m);
778 	sshbuf_free(hostkeys);
779 	sshbuf_free(inc);
780 
781 	debug3_f("done");
782 }
783 
784 /*
785  * If IP options are supported, make sure there are none (log and
786  * return an error if any are found).  Basically we are worried about
787  * source routing; it can be used to pretend you are somebody
788  * (ip-address) you are not. That itself may be "almost acceptable"
789  * under certain circumstances, but rhosts authentication is useless
790  * if source routing is accepted. Notice also that if we just dropped
791  * source routing here, the other side could use IP spoofing to do
792  * rest of the interaction and could still bypass security.  So we
793  * exit here if we detect any IP options.
794  */
795 static void
check_ip_options(struct ssh * ssh)796 check_ip_options(struct ssh *ssh)
797 {
798 #ifdef IP_OPTIONS
799 	int sock_in = ssh_packet_get_connection_in(ssh);
800 	struct sockaddr_storage from;
801 	u_char opts[200];
802 	socklen_t i, option_size = sizeof(opts), fromlen = sizeof(from);
803 	char text[sizeof(opts) * 3 + 1];
804 
805 	memset(&from, 0, sizeof(from));
806 	if (getpeername(sock_in, (struct sockaddr *)&from,
807 	    &fromlen) == -1)
808 		return;
809 	if (from.ss_family != AF_INET)
810 		return;
811 	/* XXX IPv6 options? */
812 
813 	if (getsockopt(sock_in, IPPROTO_IP, IP_OPTIONS, opts,
814 	    &option_size) >= 0 && option_size != 0) {
815 		text[0] = '\0';
816 		for (i = 0; i < option_size; i++)
817 			snprintf(text + i*3, sizeof(text) - i*3,
818 			    " %2.2x", opts[i]);
819 		fatal("Connection from %.100s port %d with IP opts: %.800s",
820 		    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), text);
821 	}
822 #endif /* IP_OPTIONS */
823 }
824 
825 /* Set the routing domain for this process */
826 static void
set_process_rdomain(struct ssh * ssh,const char * name)827 set_process_rdomain(struct ssh *ssh, const char *name)
828 {
829 #if defined(HAVE_SYS_SET_PROCESS_RDOMAIN)
830 	if (name == NULL)
831 		return; /* default */
832 
833 	if (strcmp(name, "%D") == 0) {
834 		/* "expands" to routing domain of connection */
835 		if ((name = ssh_packet_rdomain_in(ssh)) == NULL)
836 			return;
837 	}
838 	/* NB. We don't pass 'ssh' to sys_set_process_rdomain() */
839 	return sys_set_process_rdomain(name);
840 #elif defined(__OpenBSD__)
841 	int rtable, ortable = getrtable();
842 	const char *errstr;
843 
844 	if (name == NULL)
845 		return; /* default */
846 
847 	if (strcmp(name, "%D") == 0) {
848 		/* "expands" to routing domain of connection */
849 		if ((name = ssh_packet_rdomain_in(ssh)) == NULL)
850 			return;
851 	}
852 
853 	rtable = (int)strtonum(name, 0, 255, &errstr);
854 	if (errstr != NULL) /* Shouldn't happen */
855 		fatal("Invalid routing domain \"%s\": %s", name, errstr);
856 	if (rtable != ortable && setrtable(rtable) != 0)
857 		fatal("Unable to set routing domain %d: %s",
858 		    rtable, strerror(errno));
859 	debug_f("set routing domain %d (was %d)", rtable, ortable);
860 #else /* defined(__OpenBSD__) */
861 	fatal("Unable to set routing domain: not supported in this platform");
862 #endif
863 }
864 
865 /*
866  * Main program for the daemon.
867  */
868 int
main(int ac,char ** av)869 main(int ac, char **av)
870 {
871 	struct ssh *ssh = NULL;
872 	extern char *optarg;
873 	extern int optind;
874 	int r, opt, on = 1, remote_port;
875 	int sock_in = -1, sock_out = -1, rexeced_flag = 0, have_key = 0;
876 	const char *remote_ip, *rdomain;
877 	char *line, *laddr, *logfile = NULL;
878 	u_int i;
879 	u_int64_t ibytes, obytes;
880 	mode_t new_umask;
881 	Authctxt *authctxt;
882 	struct connection_info *connection_info = NULL;
883 	sigset_t sigmask;
884 	uint64_t timing_secret = 0;
885 	struct itimerval itv;
886 
887 	sigemptyset(&sigmask);
888 	sigprocmask(SIG_SETMASK, &sigmask, NULL);
889 
890 #ifdef HAVE_SECUREWARE
891 	(void)set_auth_parameters(ac, av);
892 #endif
893 	__progname = ssh_get_progname(av[0]);
894 
895 	/* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
896 	saved_argc = ac;
897 	saved_argv = xcalloc(ac + 1, sizeof(*saved_argv));
898 	for (i = 0; (int)i < ac; i++)
899 		saved_argv[i] = xstrdup(av[i]);
900 	saved_argv[i] = NULL;
901 
902 #ifndef HAVE_SETPROCTITLE
903 	/* Prepare for later setproctitle emulation */
904 	compat_init_setproctitle(ac, av);
905 	av = saved_argv;
906 #endif
907 
908 	/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
909 	sanitise_stdfd();
910 
911 	/* Initialize configuration options to their default values. */
912 	initialize_server_options(&options);
913 
914 	/* Parse command-line arguments. */
915 	while ((opt = getopt(ac, av,
916 	    "C:E:b:c:f:g:h:k:o:p:u:46DGQRTdeiqrtV")) != -1) {
917 		switch (opt) {
918 		case '4':
919 			options.address_family = AF_INET;
920 			break;
921 		case '6':
922 			options.address_family = AF_INET6;
923 			break;
924 		case 'f':
925 			config_file_name = optarg;
926 			break;
927 		case 'c':
928 			servconf_add_hostcert("[command-line]", 0,
929 			    &options, optarg);
930 			break;
931 		case 'd':
932 			if (debug_flag == 0) {
933 				debug_flag = 1;
934 				options.log_level = SYSLOG_LEVEL_DEBUG1;
935 			} else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
936 				options.log_level++;
937 			break;
938 		case 'D':
939 			/* ignore */
940 			break;
941 		case 'E':
942 			logfile = optarg;
943 			/* FALLTHROUGH */
944 		case 'e':
945 			log_stderr = 1;
946 			break;
947 		case 'i':
948 			inetd_flag = 1;
949 			break;
950 		case 'r':
951 			/* ignore */
952 			break;
953 		case 'R':
954 			rexeced_flag = 1;
955 			break;
956 		case 'Q':
957 			/* ignored */
958 			break;
959 		case 'q':
960 			options.log_level = SYSLOG_LEVEL_QUIET;
961 			break;
962 		case 'b':
963 			/* protocol 1, ignored */
964 			break;
965 		case 'p':
966 			options.ports_from_cmdline = 1;
967 			if (options.num_ports >= MAX_PORTS) {
968 				fprintf(stderr, "too many ports.\n");
969 				exit(1);
970 			}
971 			options.ports[options.num_ports++] = a2port(optarg);
972 			if (options.ports[options.num_ports-1] <= 0) {
973 				fprintf(stderr, "Bad port number.\n");
974 				exit(1);
975 			}
976 			break;
977 		case 'g':
978 			if ((options.login_grace_time = convtime(optarg)) == -1) {
979 				fprintf(stderr, "Invalid login grace time.\n");
980 				exit(1);
981 			}
982 			break;
983 		case 'k':
984 			/* protocol 1, ignored */
985 			break;
986 		case 'h':
987 			servconf_add_hostkey("[command-line]", 0,
988 			    &options, optarg, 1);
989 			break;
990 		case 't':
991 		case 'T':
992 		case 'G':
993 			fatal("test/dump modes not supported");
994 			break;
995 		case 'C':
996 			connection_info = server_get_connection_info(ssh, 0, 0);
997 			if (parse_server_match_testspec(connection_info,
998 			    optarg) == -1)
999 				exit(1);
1000 			break;
1001 		case 'u':
1002 			utmp_len = (u_int)strtonum(optarg, 0, HOST_NAME_MAX+1+1, NULL);
1003 			if (utmp_len > HOST_NAME_MAX+1) {
1004 				fprintf(stderr, "Invalid utmp length.\n");
1005 				exit(1);
1006 			}
1007 			break;
1008 		case 'o':
1009 			line = xstrdup(optarg);
1010 			if (process_server_config_line(&options, line,
1011 			    "command-line", 0, NULL, NULL, &includes) != 0)
1012 				exit(1);
1013 			free(line);
1014 			break;
1015 		case 'V':
1016 			fprintf(stderr, "%s, %s\n",
1017 			    SSH_RELEASE, SSH_OPENSSL_VERSION);
1018 			exit(0);
1019 		default:
1020 			usage();
1021 			break;
1022 		}
1023 	}
1024 
1025 	/* Check that there are no remaining arguments. */
1026 	if (optind < ac) {
1027 		fprintf(stderr, "Extra argument %s.\n", av[optind]);
1028 		exit(1);
1029 	}
1030 
1031 	debug("sshd version %s, %s", SSH_VERSION, SSH_OPENSSL_VERSION);
1032 
1033 	if (!rexeced_flag)
1034 		fatal("sshd-session should not be executed directly");
1035 
1036 	closefrom(REEXEC_MIN_FREE_FD);
1037 
1038 	seed_rng();
1039 
1040 	/* If requested, redirect the logs to the specified logfile. */
1041 	if (logfile != NULL) {
1042 		char *cp, pid_s[32];
1043 
1044 		snprintf(pid_s, sizeof(pid_s), "%ld", (unsigned long)getpid());
1045 		cp = percent_expand(logfile,
1046 		    "p", pid_s,
1047 		    "P", "sshd-session",
1048 		    (char *)NULL);
1049 		log_redirect_stderr_to(cp);
1050 		free(cp);
1051 	}
1052 
1053 	/*
1054 	 * Force logging to stderr until we have loaded the private host
1055 	 * key (unless started from inetd)
1056 	 */
1057 	log_init(__progname,
1058 	    options.log_level == SYSLOG_LEVEL_NOT_SET ?
1059 	    SYSLOG_LEVEL_INFO : options.log_level,
1060 	    options.log_facility == SYSLOG_FACILITY_NOT_SET ?
1061 	    SYSLOG_FACILITY_AUTH : options.log_facility,
1062 	    log_stderr || !inetd_flag || debug_flag);
1063 
1064 	debug("sshd version %s, %s", SSH_VERSION, SSH_OPENSSL_VERSION);
1065 
1066 	/* Fetch our configuration */
1067 	if ((cfg = sshbuf_new()) == NULL)
1068 		fatal("sshbuf_new config buf failed");
1069 	setproctitle("%s", "[rexeced]");
1070 	recv_rexec_state(REEXEC_CONFIG_PASS_FD, cfg, &timing_secret);
1071 	close(REEXEC_CONFIG_PASS_FD);
1072 	parse_server_config(&options, "rexec", cfg, &includes, NULL, 1);
1073 	/* Fill in default values for those options not explicitly set. */
1074 	fill_default_server_options(&options);
1075 	options.timing_secret = timing_secret;
1076 
1077 	/* Store privilege separation user for later use if required. */
1078 	privsep_chroot = (getuid() == 0 || geteuid() == 0);
1079 	if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) {
1080 		if (privsep_chroot || options.kerberos_authentication)
1081 			fatal("Privilege separation user %s does not exist",
1082 			    SSH_PRIVSEP_USER);
1083 	} else {
1084 		privsep_pw = pwcopy(privsep_pw);
1085 		freezero(privsep_pw->pw_passwd, strlen(privsep_pw->pw_passwd));
1086 		privsep_pw->pw_passwd = xstrdup("*");
1087 	}
1088 	endpwent();
1089 
1090 	if (!debug_flag) {
1091 		startup_pipe = dup(REEXEC_STARTUP_PIPE_FD);
1092 		close(REEXEC_STARTUP_PIPE_FD);
1093 		/*
1094 		 * Signal parent that this child is at a point where
1095 		 * they can go away if they have a SIGHUP pending.
1096 		 */
1097 		(void)atomicio(vwrite, startup_pipe, "\0", 1);
1098 	}
1099 
1100 	/* Check that options are sensible */
1101 	if (options.authorized_keys_command_user == NULL &&
1102 	    (options.authorized_keys_command != NULL &&
1103 	    strcasecmp(options.authorized_keys_command, "none") != 0))
1104 		fatal("AuthorizedKeysCommand set without "
1105 		    "AuthorizedKeysCommandUser");
1106 	if (options.authorized_principals_command_user == NULL &&
1107 	    (options.authorized_principals_command != NULL &&
1108 	    strcasecmp(options.authorized_principals_command, "none") != 0))
1109 		fatal("AuthorizedPrincipalsCommand set without "
1110 		    "AuthorizedPrincipalsCommandUser");
1111 
1112 	/*
1113 	 * Check whether there is any path through configured auth methods.
1114 	 * Unfortunately it is not possible to verify this generally before
1115 	 * daemonisation in the presence of Match block, but this catches
1116 	 * and warns for trivial misconfigurations that could break login.
1117 	 */
1118 	if (options.num_auth_methods != 0) {
1119 		for (i = 0; i < options.num_auth_methods; i++) {
1120 			if (auth2_methods_valid(options.auth_methods[i],
1121 			    1) == 0)
1122 				break;
1123 		}
1124 		if (i >= options.num_auth_methods)
1125 			fatal("AuthenticationMethods cannot be satisfied by "
1126 			    "enabled authentication methods");
1127 	}
1128 
1129 #ifdef WITH_OPENSSL
1130 	if (options.moduli_file != NULL)
1131 		dh_set_moduli_file(options.moduli_file);
1132 #endif
1133 
1134 	if (options.host_key_agent) {
1135 		if (strcmp(options.host_key_agent, SSH_AUTHSOCKET_ENV_NAME))
1136 			setenv(SSH_AUTHSOCKET_ENV_NAME,
1137 			    options.host_key_agent, 1);
1138 		if ((r = ssh_get_authentication_socket(NULL)) == 0)
1139 			have_agent = 1;
1140 		else
1141 			error_r(r, "Could not connect to agent \"%s\"",
1142 			    options.host_key_agent);
1143 	}
1144 
1145 	if (options.num_host_key_files != sensitive_data.num_hostkeys) {
1146 		fatal("internal error: hostkeys confused (config %u recvd %u)",
1147 		    options.num_host_key_files, sensitive_data.num_hostkeys);
1148 	}
1149 
1150 	for (i = 0; i < options.num_host_key_files; i++) {
1151 		if (sensitive_data.host_keys[i] != NULL ||
1152 		    (have_agent && sensitive_data.host_pubkeys[i] != NULL)) {
1153 			have_key = 1;
1154 			break;
1155 		}
1156 	}
1157 	if (!have_key)
1158 		fatal("internal error: monitor received no hostkeys");
1159 
1160 	/* Ensure that umask disallows at least group and world write */
1161 	new_umask = umask(0077) | 0022;
1162 	(void) umask(new_umask);
1163 
1164 	/* Initialize the log (it is reinitialized below in case we forked). */
1165 	if (debug_flag)
1166 		log_stderr = 1;
1167 	log_init(__progname, options.log_level,
1168 	    options.log_facility, log_stderr);
1169 	for (i = 0; i < options.num_log_verbose; i++)
1170 		log_verbose_add(options.log_verbose[i]);
1171 
1172 	/* Reinitialize the log (because of the fork above). */
1173 	log_init(__progname, options.log_level, options.log_facility, log_stderr);
1174 
1175 	/*
1176 	 * Chdir to the root directory so that the current disk can be
1177 	 * unmounted if desired.
1178 	 */
1179 	if (chdir("/") == -1)
1180 		error("chdir(\"/\"): %s", strerror(errno));
1181 
1182 	/* ignore SIGPIPE */
1183 	ssh_signal(SIGPIPE, SIG_IGN);
1184 
1185 	/* Get a connection, either from inetd or rexec */
1186 	if (inetd_flag) {
1187 		/*
1188 		 * NB. must be different fd numbers for the !socket case,
1189 		 * as packet_connection_is_on_socket() depends on this.
1190 		 */
1191 		sock_in = dup(STDIN_FILENO);
1192 		sock_out = dup(STDOUT_FILENO);
1193 	} else {
1194 		/* rexec case; accept()ed socket in ancestor listener */
1195 		sock_in = sock_out = dup(STDIN_FILENO);
1196 	}
1197 
1198 	/*
1199 	 * We intentionally do not close the descriptors 0, 1, and 2
1200 	 * as our code for setting the descriptors won't work if
1201 	 * ttyfd happens to be one of those.
1202 	 */
1203 	if (stdfd_devnull(1, 1, !log_stderr) == -1)
1204 		error("stdfd_devnull failed");
1205 	debug("network sockets: %d, %d", sock_in, sock_out);
1206 
1207 	/* This is the child processing a new connection. */
1208 	setproctitle("%s", "[accepted]");
1209 
1210 	/* Executed child processes don't need these. */
1211 	fcntl(sock_out, F_SETFD, FD_CLOEXEC);
1212 	fcntl(sock_in, F_SETFD, FD_CLOEXEC);
1213 
1214 	/* We will not restart on SIGHUP since it no longer makes sense. */
1215 	ssh_signal(SIGALRM, SIG_DFL);
1216 	ssh_signal(SIGHUP, SIG_DFL);
1217 	ssh_signal(SIGTERM, SIG_DFL);
1218 	ssh_signal(SIGQUIT, SIG_DFL);
1219 	ssh_signal(SIGCHLD, SIG_DFL);
1220 	ssh_signal(SIGINT, SIG_DFL);
1221 
1222 	/*
1223 	 * Register our connection.  This turns encryption off because we do
1224 	 * not have a key.
1225 	 */
1226 	if ((ssh = ssh_packet_set_connection(NULL, sock_in, sock_out)) == NULL)
1227 		fatal("Unable to create connection");
1228 	the_active_state = ssh;
1229 	ssh_packet_set_server(ssh);
1230 
1231 	check_ip_options(ssh);
1232 
1233 	/* Prepare the channels layer */
1234 	channel_init_channels(ssh);
1235 	channel_set_af(ssh, options.address_family);
1236 	server_process_channel_timeouts(ssh);
1237 	server_process_permitopen(ssh);
1238 
1239 	/* Set SO_KEEPALIVE if requested. */
1240 	if (options.tcp_keep_alive && ssh_packet_connection_is_on_socket(ssh) &&
1241 	    setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) == -1)
1242 		error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1243 
1244 	if ((remote_port = ssh_remote_port(ssh)) < 0) {
1245 		debug("ssh_remote_port failed");
1246 		cleanup_exit(255);
1247 	}
1248 
1249 #ifdef HAVE_LOGIN_CAP
1250 	/* Also caches remote hostname for sandboxed child. */
1251 	auth_get_canonical_hostname(ssh, options.use_dns);
1252 #endif
1253 
1254 	/*
1255 	 * The rest of the code depends on the fact that
1256 	 * ssh_remote_ipaddr() caches the remote ip, even if
1257 	 * the socket goes away.
1258 	 */
1259 	remote_ip = ssh_remote_ipaddr(ssh);
1260 
1261 #ifdef SSH_AUDIT_EVENTS
1262 	audit_connection_from(remote_ip, remote_port);
1263 #endif
1264 
1265 	rdomain = ssh_packet_rdomain_in(ssh);
1266 
1267 	/* Log the connection. */
1268 	laddr = get_local_ipaddr(sock_in);
1269 	verbose("Connection from %s port %d on %s port %d%s%s%s",
1270 	    remote_ip, remote_port, laddr,  ssh_local_port(ssh),
1271 	    rdomain == NULL ? "" : " rdomain \"",
1272 	    rdomain == NULL ? "" : rdomain,
1273 	    rdomain == NULL ? "" : "\"");
1274 	free(laddr);
1275 
1276 	/*
1277 	 * We don't want to listen forever unless the other side
1278 	 * successfully authenticates itself.  So we set up an alarm which is
1279 	 * cleared after successful authentication.  A limit of zero
1280 	 * indicates no limit. Note that we don't set the alarm in debugging
1281 	 * mode; it is just annoying to have the server exit just when you
1282 	 * are about to discover the bug.
1283 	 */
1284 	ssh_signal(SIGALRM, grace_alarm_handler);
1285 	if (!debug_flag && options.login_grace_time > 0) {
1286 		int ujitter = arc4random_uniform(4 * 1000000);
1287 
1288 		timerclear(&itv.it_interval);
1289 		itv.it_value.tv_sec = options.login_grace_time;
1290 		itv.it_value.tv_sec += ujitter / 1000000;
1291 		itv.it_value.tv_usec = ujitter % 1000000;
1292 
1293 		if (setitimer(ITIMER_REAL, &itv, NULL) == -1)
1294 			fatal("login grace time setitimer failed");
1295 	}
1296 
1297 	if ((r = kex_exchange_identification(ssh, -1,
1298 	    options.version_addendum)) != 0)
1299 		sshpkt_fatal(ssh, r, "banner exchange");
1300 
1301 	ssh_packet_set_nonblocking(ssh);
1302 
1303 	/* allocate authentication context */
1304 	authctxt = xcalloc(1, sizeof(*authctxt));
1305 	ssh->authctxt = authctxt;
1306 
1307 	/* XXX global for cleanup, access from other modules */
1308 	the_authctxt = authctxt;
1309 
1310 	/* Set default key authentication options */
1311 	if ((auth_opts = sshauthopt_new_with_keys_defaults()) == NULL)
1312 		fatal("allocation failed");
1313 
1314 	/* prepare buffer to collect messages to display to user after login */
1315 	if ((loginmsg = sshbuf_new()) == NULL)
1316 		fatal("sshbuf_new loginmsg failed");
1317 	auth_debug_reset();
1318 
1319 	if (privsep_preauth(ssh) == 1)
1320 		goto authenticated;
1321 
1322 	/* perform the key exchange */
1323 	/* authenticate user and start session */
1324 	do_ssh2_kex(ssh);
1325 	do_authentication2(ssh);
1326 
1327 	/*
1328 	 * The unprivileged child now transfers the current keystate and exits.
1329 	 */
1330 	mm_send_keystate(ssh, pmonitor);
1331 	ssh_packet_clear_keys(ssh);
1332 	exit(0);
1333 
1334  authenticated:
1335 	/*
1336 	 * Cancel the alarm we set to limit the time taken for
1337 	 * authentication.
1338 	 */
1339 	timerclear(&itv.it_interval);
1340 	timerclear(&itv.it_value);
1341 	if (setitimer(ITIMER_REAL, &itv, NULL) == -1)
1342 		fatal("login grace time clear failed");
1343 	ssh_signal(SIGALRM, SIG_DFL);
1344 	authctxt->authenticated = 1;
1345 	if (startup_pipe != -1) {
1346 		/* signal listener that authentication completed successfully */
1347 		(void)atomicio(vwrite, startup_pipe, "\001", 1);
1348 		close(startup_pipe);
1349 		startup_pipe = -1;
1350 	}
1351 
1352 	if (options.routing_domain != NULL)
1353 		set_process_rdomain(ssh, options.routing_domain);
1354 
1355 #ifdef SSH_AUDIT_EVENTS
1356 	audit_event(ssh, SSH_AUTH_SUCCESS);
1357 #endif
1358 
1359 #ifdef GSSAPI
1360 	if (options.gss_authentication) {
1361 		temporarily_use_uid(authctxt->pw);
1362 		ssh_gssapi_storecreds();
1363 		restore_uid();
1364 	}
1365 #endif
1366 #ifdef USE_PAM
1367 	if (options.use_pam) {
1368 		do_pam_setcred();
1369 		do_pam_session(ssh);
1370 	}
1371 #endif
1372 
1373 	/*
1374 	 * In privilege separation, we fork another child and prepare
1375 	 * file descriptor passing.
1376 	 */
1377 	privsep_postauth(ssh, authctxt);
1378 	/* the monitor process [priv] will not return */
1379 
1380 	ssh_packet_set_timeout(ssh, options.client_alive_interval,
1381 	    options.client_alive_count_max);
1382 
1383 	/* Try to send all our hostkeys to the client */
1384 	notify_hostkeys(ssh);
1385 
1386 	/* Start session. */
1387 	do_authenticated(ssh, authctxt);
1388 
1389 	/* The connection has been terminated. */
1390 	ssh_packet_get_bytes(ssh, &ibytes, &obytes);
1391 	verbose("Transferred: sent %llu, received %llu bytes",
1392 	    (unsigned long long)obytes, (unsigned long long)ibytes);
1393 
1394 	verbose("Closing connection to %.500s port %d", remote_ip, remote_port);
1395 
1396 #ifdef USE_PAM
1397 	if (options.use_pam)
1398 		finish_pam();
1399 #endif /* USE_PAM */
1400 
1401 #ifdef SSH_AUDIT_EVENTS
1402 	mm_audit_event(ssh, SSH_CONNECTION_CLOSE);
1403 #endif
1404 
1405 	ssh_packet_close(ssh);
1406 
1407 	mm_terminate();
1408 
1409 	exit(0);
1410 }
1411 
1412 int
sshd_hostkey_sign(struct ssh * ssh,struct sshkey * privkey,struct sshkey * pubkey,u_char ** signature,size_t * slenp,const u_char * data,size_t dlen,const char * alg)1413 sshd_hostkey_sign(struct ssh *ssh, struct sshkey *privkey,
1414     struct sshkey *pubkey, u_char **signature, size_t *slenp,
1415     const u_char *data, size_t dlen, const char *alg)
1416 {
1417 	if (privkey) {
1418 		if (mm_sshkey_sign(ssh, privkey, signature, slenp,
1419 		    data, dlen, alg, options.sk_provider, NULL,
1420 		    ssh->compat) < 0)
1421 			fatal_f("privkey sign failed");
1422 	} else {
1423 		if (mm_sshkey_sign(ssh, pubkey, signature, slenp,
1424 		    data, dlen, alg, options.sk_provider, NULL,
1425 		    ssh->compat) < 0)
1426 			fatal_f("pubkey sign failed");
1427 	}
1428 	return 0;
1429 }
1430 
1431 /* SSH2 key exchange */
1432 static void
do_ssh2_kex(struct ssh * ssh)1433 do_ssh2_kex(struct ssh *ssh)
1434 {
1435 	char *hkalgs = NULL, *myproposal[PROPOSAL_MAX];
1436 	const char *compression = NULL;
1437 	struct kex *kex;
1438 	int r;
1439 
1440 	if (options.rekey_limit || options.rekey_interval)
1441 		ssh_packet_set_rekey_limits(ssh, options.rekey_limit,
1442 		    options.rekey_interval);
1443 
1444 	if (options.compression == COMP_NONE)
1445 		compression = "none";
1446 	hkalgs = list_hostkey_types();
1447 
1448 	kex_proposal_populate_entries(ssh, myproposal, options.kex_algorithms,
1449 	    options.ciphers, options.macs, compression, hkalgs);
1450 
1451 	free(hkalgs);
1452 
1453 	/* start key exchange */
1454 	if ((r = kex_setup(ssh, myproposal)) != 0)
1455 		fatal_r(r, "kex_setup");
1456 	kex_set_server_sig_algs(ssh, options.pubkey_accepted_algos);
1457 	kex = ssh->kex;
1458 
1459 #ifdef WITH_OPENSSL
1460 	kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server;
1461 	kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server;
1462 	kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server;
1463 	kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server;
1464 	kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server;
1465 	kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
1466 	kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
1467  #ifdef OPENSSL_HAS_ECC
1468 	kex->kex[KEX_ECDH_SHA2] = kex_gen_server;
1469  #endif
1470 #endif
1471 	kex->kex[KEX_C25519_SHA256] = kex_gen_server;
1472 	kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server;
1473  	kex->kex[KEX_KEM_MLKEM768X25519_SHA256] = kex_gen_server;
1474 	kex->load_host_public_key=&get_hostkey_public_by_type;
1475 	kex->load_host_private_key=&get_hostkey_private_by_type;
1476 	kex->host_key_index=&get_hostkey_index;
1477 	kex->sign = sshd_hostkey_sign;
1478 
1479 	ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &kex->done);
1480 	kex_proposal_free_entries(myproposal);
1481 
1482 #ifdef DEBUG_KEXDH
1483 	/* send 1st encrypted/maced/compressed message */
1484 	if ((r = sshpkt_start(ssh, SSH2_MSG_IGNORE)) != 0 ||
1485 	    (r = sshpkt_put_cstring(ssh, "markus")) != 0 ||
1486 	    (r = sshpkt_send(ssh)) != 0 ||
1487 	    (r = ssh_packet_write_wait(ssh)) != 0)
1488 		fatal_fr(r, "send test");
1489 #endif
1490 	debug("KEX done");
1491 }
1492 
1493 /* server specific fatal cleanup */
1494 void
cleanup_exit(int i)1495 cleanup_exit(int i)
1496 {
1497 	extern int auth_attempted; /* monitor.c */
1498 
1499 	if (the_active_state != NULL && the_authctxt != NULL) {
1500 		do_cleanup(the_active_state, the_authctxt);
1501 		if (privsep_is_preauth &&
1502 		    pmonitor != NULL && pmonitor->m_pid > 1) {
1503 			debug("Killing privsep child %d", pmonitor->m_pid);
1504 			if (kill(pmonitor->m_pid, SIGKILL) != 0 &&
1505 			    errno != ESRCH) {
1506 				error_f("kill(%d): %s", pmonitor->m_pid,
1507 				    strerror(errno));
1508 			}
1509 		}
1510 	}
1511 #ifdef SSH_AUDIT_EVENTS
1512 	/* done after do_cleanup so it can cancel the PAM auth 'thread' */
1513 	if (the_active_state != NULL && mm_is_monitor())
1514 		audit_event(the_active_state, SSH_CONNECTION_ABANDON);
1515 #endif
1516 	/* Override default fatal exit value when auth was attempted */
1517 	if (i == 255 && auth_attempted)
1518 		_exit(EXIT_AUTH_ATTEMPTED);
1519 	_exit(i);
1520 }
1521