1 /* $OpenBSD: sshd.c,v 1.602 2024/01/08 00:34:34 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 "authfile.h"
118 #include "pathnames.h"
119 #include "atomicio.h"
120 #include "canohost.h"
121 #include "hostfile.h"
122 #include "auth.h"
123 #include "authfd.h"
124 #include "msg.h"
125 #include "dispatch.h"
126 #include "channels.h"
127 #include "session.h"
128 #include "monitor.h"
129 #ifdef GSSAPI
130 #include "ssh-gss.h"
131 #endif
132 #include "monitor_wrap.h"
133 #include "ssh-sandbox.h"
134 #include "auth-options.h"
135 #include "version.h"
136 #include "ssherr.h"
137 #include "sk-api.h"
138 #include "srclimit.h"
139 #include "dh.h"
140 #include "blacklist_client.h"
141
142 #ifdef LIBWRAP
143 #include <tcpd.h>
144 #include <syslog.h>
145 #endif /* LIBWRAP */
146
147 /* Re-exec fds */
148 #define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1)
149 #define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2)
150 #define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3)
151 #define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4)
152
153 extern char *__progname;
154
155 /* Server configuration options. */
156 ServerOptions options;
157
158 /* Name of the server configuration file. */
159 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
160
161 /*
162 * Debug mode flag. This can be set on the command line. If debug
163 * mode is enabled, extra debugging output will be sent to the system
164 * log, the daemon will not go to background, and will exit after processing
165 * the first connection.
166 */
167 int debug_flag = 0;
168
169 /*
170 * Indicating that the daemon should only test the configuration and keys.
171 * If test_flag > 1 ("-T" flag), then sshd will also dump the effective
172 * configuration, optionally using connection information provided by the
173 * "-C" flag.
174 */
175 static int test_flag = 0;
176
177 /* Flag indicating that the daemon is being started from inetd. */
178 static int inetd_flag = 0;
179
180 /* Flag indicating that sshd should not detach and become a daemon. */
181 static int no_daemon_flag = 0;
182
183 /* debug goes to stderr unless inetd_flag is set */
184 static int log_stderr = 0;
185
186 /* Saved arguments to main(). */
187 static char **saved_argv;
188 static int saved_argc;
189
190 /* re-exec */
191 static int rexeced_flag = 0;
192 static int rexec_flag = 1;
193 static int rexec_argc = 0;
194 static char **rexec_argv;
195
196 /*
197 * The sockets that the server is listening; this is used in the SIGHUP
198 * signal handler.
199 */
200 #define MAX_LISTEN_SOCKS 16
201 static int listen_socks[MAX_LISTEN_SOCKS];
202 static int num_listen_socks = 0;
203
204 /* Daemon's agent connection */
205 int auth_sock = -1;
206 static int have_agent = 0;
207
208 /*
209 * Any really sensitive data in the application is contained in this
210 * structure. The idea is that this structure could be locked into memory so
211 * that the pages do not get written into swap. However, there are some
212 * problems. The private key contains BIGNUMs, and we do not (in principle)
213 * have access to the internals of them, and locking just the structure is
214 * not very useful. Currently, memory locking is not implemented.
215 */
216 struct {
217 struct sshkey **host_keys; /* all private host keys */
218 struct sshkey **host_pubkeys; /* all public host keys */
219 struct sshkey **host_certificates; /* all public host certificates */
220 int have_ssh2_key;
221 } sensitive_data;
222
223 /* This is set to true when a signal is received. */
224 static volatile sig_atomic_t received_sighup = 0;
225 static volatile sig_atomic_t received_sigterm = 0;
226
227 /* record remote hostname or ip */
228 u_int utmp_len = HOST_NAME_MAX+1;
229
230 /*
231 * startup_pipes/flags are used for tracking children of the listening sshd
232 * process early in their lifespans. This tracking is needed for three things:
233 *
234 * 1) Implementing the MaxStartups limit of concurrent unauthenticated
235 * connections.
236 * 2) Avoiding a race condition for SIGHUP processing, where child processes
237 * may have listen_socks open that could collide with main listener process
238 * after it restarts.
239 * 3) Ensuring that rexec'd sshd processes have received their initial state
240 * from the parent listen process before handling SIGHUP.
241 *
242 * Child processes signal that they have completed closure of the listen_socks
243 * and (if applicable) received their rexec state by sending a char over their
244 * sock. Child processes signal that authentication has completed by closing
245 * the sock (or by exiting).
246 */
247 static int *startup_pipes = NULL;
248 static int *startup_flags = NULL; /* Indicates child closed listener */
249 static int startup_pipe = -1; /* in child */
250
251 /* variables used for privilege separation */
252 int use_privsep = -1;
253 struct monitor *pmonitor = NULL;
254 int privsep_is_preauth = 1;
255 static int privsep_chroot = 1;
256
257 /* global connection state and authentication contexts */
258 Authctxt *the_authctxt = NULL;
259 struct ssh *the_active_state;
260
261 /* global key/cert auth options. XXX move to permanent ssh->authctxt? */
262 struct sshauthopt *auth_opts = NULL;
263
264 /* sshd_config buffer */
265 struct sshbuf *cfg;
266
267 /* Included files from the configuration file */
268 struct include_list includes = TAILQ_HEAD_INITIALIZER(includes);
269
270 /* message to be displayed after login */
271 struct sshbuf *loginmsg;
272
273 /* Unprivileged user */
274 struct passwd *privsep_pw = NULL;
275
276 /* Prototypes for various functions defined later in this file. */
277 void destroy_sensitive_data(void);
278 void demote_sensitive_data(void);
279 static void do_ssh2_kex(struct ssh *);
280
281 static char *listener_proctitle;
282
283 /*
284 * Close all listening sockets
285 */
286 static void
close_listen_socks(void)287 close_listen_socks(void)
288 {
289 int i;
290
291 for (i = 0; i < num_listen_socks; i++)
292 close(listen_socks[i]);
293 num_listen_socks = 0;
294 }
295
296 static void
close_startup_pipes(void)297 close_startup_pipes(void)
298 {
299 int i;
300
301 if (startup_pipes)
302 for (i = 0; i < options.max_startups; i++)
303 if (startup_pipes[i] != -1)
304 close(startup_pipes[i]);
305 }
306
307 /*
308 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
309 * the effect is to reread the configuration file (and to regenerate
310 * the server key).
311 */
312
313 static void
sighup_handler(int sig)314 sighup_handler(int sig)
315 {
316 received_sighup = 1;
317 }
318
319 /*
320 * Called from the main program after receiving SIGHUP.
321 * Restarts the server.
322 */
323 static void
sighup_restart(void)324 sighup_restart(void)
325 {
326 logit("Received SIGHUP; restarting.");
327 if (options.pid_file != NULL)
328 unlink(options.pid_file);
329 platform_pre_restart();
330 close_listen_socks();
331 close_startup_pipes();
332 ssh_signal(SIGHUP, SIG_IGN); /* will be restored after exec */
333 execv(saved_argv[0], saved_argv);
334 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
335 strerror(errno));
336 exit(1);
337 }
338
339 /*
340 * Generic signal handler for terminating signals in the master daemon.
341 */
342 static void
sigterm_handler(int sig)343 sigterm_handler(int sig)
344 {
345 received_sigterm = sig;
346 }
347
348 /*
349 * SIGCHLD handler. This is called whenever a child dies. This will then
350 * reap any zombies left by exited children.
351 */
352 static void
main_sigchld_handler(int sig)353 main_sigchld_handler(int sig)
354 {
355 int save_errno = errno;
356 pid_t pid;
357 int status;
358
359 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
360 (pid == -1 && errno == EINTR))
361 ;
362 errno = save_errno;
363 }
364
365 /*
366 * Signal handler for the alarm after the login grace period has expired.
367 */
368 static void
grace_alarm_handler(int sig)369 grace_alarm_handler(int sig)
370 {
371 /*
372 * Try to kill any processes that we have spawned, E.g. authorized
373 * keys command helpers or privsep children.
374 */
375 if (getpgid(0) == getpid()) {
376 ssh_signal(SIGTERM, SIG_IGN);
377 kill(0, SIGTERM);
378 }
379
380 /* Log error and exit. */
381 sigdie("Timeout before authentication for %s port %d",
382 ssh_remote_ipaddr(the_active_state),
383 ssh_remote_port(the_active_state));
384 }
385
386 /* Destroy the host and server keys. They will no longer be needed. */
387 void
destroy_sensitive_data(void)388 destroy_sensitive_data(void)
389 {
390 u_int i;
391
392 for (i = 0; i < options.num_host_key_files; i++) {
393 if (sensitive_data.host_keys[i]) {
394 sshkey_free(sensitive_data.host_keys[i]);
395 sensitive_data.host_keys[i] = NULL;
396 }
397 if (sensitive_data.host_certificates[i]) {
398 sshkey_free(sensitive_data.host_certificates[i]);
399 sensitive_data.host_certificates[i] = NULL;
400 }
401 }
402 }
403
404 /* Demote private to public keys for network child */
405 void
demote_sensitive_data(void)406 demote_sensitive_data(void)
407 {
408 struct sshkey *tmp;
409 u_int i;
410 int r;
411
412 for (i = 0; i < options.num_host_key_files; i++) {
413 if (sensitive_data.host_keys[i]) {
414 if ((r = sshkey_from_private(
415 sensitive_data.host_keys[i], &tmp)) != 0)
416 fatal_r(r, "could not demote host %s key",
417 sshkey_type(sensitive_data.host_keys[i]));
418 sshkey_free(sensitive_data.host_keys[i]);
419 sensitive_data.host_keys[i] = tmp;
420 }
421 /* Certs do not need demotion */
422 }
423 }
424
425 static void
reseed_prngs(void)426 reseed_prngs(void)
427 {
428 u_int32_t rnd[256];
429
430 #ifdef WITH_OPENSSL
431 RAND_poll();
432 #endif
433 arc4random_stir(); /* noop on recent arc4random() implementations */
434 arc4random_buf(rnd, sizeof(rnd)); /* let arc4random notice PID change */
435
436 #ifdef WITH_OPENSSL
437 RAND_seed(rnd, sizeof(rnd));
438 /* give libcrypto a chance to notice the PID change */
439 if ((RAND_bytes((u_char *)rnd, 1)) != 1)
440 fatal("%s: RAND_bytes failed", __func__);
441 #endif
442
443 explicit_bzero(rnd, sizeof(rnd));
444 }
445
446 static void
privsep_preauth_child(void)447 privsep_preauth_child(void)
448 {
449 gid_t gidset[1];
450
451 /* Enable challenge-response authentication for privilege separation */
452 privsep_challenge_enable();
453
454 #ifdef GSSAPI
455 /* Cache supported mechanism OIDs for later use */
456 ssh_gssapi_prepare_supported_oids();
457 #endif
458
459 reseed_prngs();
460
461 /* Demote the private keys to public keys. */
462 demote_sensitive_data();
463
464 /* Demote the child */
465 if (privsep_chroot) {
466 /* Change our root directory */
467 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
468 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
469 strerror(errno));
470 if (chdir("/") == -1)
471 fatal("chdir(\"/\"): %s", strerror(errno));
472
473 /* Drop our privileges */
474 debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid,
475 (u_int)privsep_pw->pw_gid);
476 gidset[0] = privsep_pw->pw_gid;
477 if (setgroups(1, gidset) == -1)
478 fatal("setgroups: %.100s", strerror(errno));
479 permanently_set_uid(privsep_pw);
480 }
481 }
482
483 static int
privsep_preauth(struct ssh * ssh)484 privsep_preauth(struct ssh *ssh)
485 {
486 int status, r;
487 pid_t pid;
488 struct ssh_sandbox *box = NULL;
489
490 /* Set up unprivileged child process to deal with network data */
491 pmonitor = monitor_init();
492 /* Store a pointer to the kex for later rekeying */
493 pmonitor->m_pkex = &ssh->kex;
494
495 if (use_privsep == PRIVSEP_ON)
496 box = ssh_sandbox_init(pmonitor);
497 pid = fork();
498 if (pid == -1) {
499 fatal("fork of unprivileged child failed");
500 } else if (pid != 0) {
501 debug2("Network child is on pid %ld", (long)pid);
502
503 pmonitor->m_pid = pid;
504 if (have_agent) {
505 r = ssh_get_authentication_socket(&auth_sock);
506 if (r != 0) {
507 error_r(r, "Could not get agent socket");
508 have_agent = 0;
509 }
510 }
511 if (box != NULL)
512 ssh_sandbox_parent_preauth(box, pid);
513 monitor_child_preauth(ssh, pmonitor);
514
515 /* Wait for the child's exit status */
516 while (waitpid(pid, &status, 0) == -1) {
517 if (errno == EINTR)
518 continue;
519 pmonitor->m_pid = -1;
520 fatal_f("waitpid: %s", strerror(errno));
521 }
522 privsep_is_preauth = 0;
523 pmonitor->m_pid = -1;
524 if (WIFEXITED(status)) {
525 if (WEXITSTATUS(status) != 0)
526 fatal_f("preauth child exited with status %d",
527 WEXITSTATUS(status));
528 } else if (WIFSIGNALED(status))
529 fatal_f("preauth child terminated by signal %d",
530 WTERMSIG(status));
531 if (box != NULL)
532 ssh_sandbox_parent_finish(box);
533 return 1;
534 } else {
535 /* child */
536 close(pmonitor->m_sendfd);
537 close(pmonitor->m_log_recvfd);
538
539 /* Arrange for logging to be sent to the monitor */
540 set_log_handler(mm_log_handler, pmonitor);
541
542 privsep_preauth_child();
543 setproctitle("%s", "[net]");
544 if (box != NULL)
545 ssh_sandbox_child(box);
546
547 return 0;
548 }
549 }
550
551 static void
privsep_postauth(struct ssh * ssh,Authctxt * authctxt)552 privsep_postauth(struct ssh *ssh, Authctxt *authctxt)
553 {
554 #ifdef DISABLE_FD_PASSING
555 if (1) {
556 #else
557 if (authctxt->pw->pw_uid == 0) {
558 #endif
559 /* File descriptor passing is broken or root login */
560 use_privsep = 0;
561 goto skip;
562 }
563
564 /* New socket pair */
565 monitor_reinit(pmonitor);
566
567 pmonitor->m_pid = fork();
568 if (pmonitor->m_pid == -1)
569 fatal("fork of unprivileged child failed");
570 else if (pmonitor->m_pid != 0) {
571 verbose("User child is on pid %ld", (long)pmonitor->m_pid);
572 sshbuf_reset(loginmsg);
573 monitor_clear_keystate(ssh, pmonitor);
574 monitor_child_postauth(ssh, pmonitor);
575
576 /* NEVERREACHED */
577 exit(0);
578 }
579
580 /* child */
581
582 close(pmonitor->m_sendfd);
583 pmonitor->m_sendfd = -1;
584
585 /* Demote the private keys to public keys. */
586 demote_sensitive_data();
587
588 reseed_prngs();
589
590 /* Drop privileges */
591 do_setusercontext(authctxt->pw);
592
593 skip:
594 /* It is safe now to apply the key state */
595 monitor_apply_keystate(ssh, pmonitor);
596
597 /*
598 * Tell the packet layer that authentication was successful, since
599 * this information is not part of the key state.
600 */
601 ssh_packet_set_authenticated(ssh);
602 }
603
604 static void
605 append_hostkey_type(struct sshbuf *b, const char *s)
606 {
607 int r;
608
609 if (match_pattern_list(s, options.hostkeyalgorithms, 0) != 1) {
610 debug3_f("%s key not permitted by HostkeyAlgorithms", s);
611 return;
612 }
613 if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) > 0 ? "," : "", s)) != 0)
614 fatal_fr(r, "sshbuf_putf");
615 }
616
617 static char *
618 list_hostkey_types(void)
619 {
620 struct sshbuf *b;
621 struct sshkey *key;
622 char *ret;
623 u_int i;
624
625 if ((b = sshbuf_new()) == NULL)
626 fatal_f("sshbuf_new failed");
627 for (i = 0; i < options.num_host_key_files; i++) {
628 key = sensitive_data.host_keys[i];
629 if (key == NULL)
630 key = sensitive_data.host_pubkeys[i];
631 if (key == NULL)
632 continue;
633 switch (key->type) {
634 case KEY_RSA:
635 /* for RSA we also support SHA2 signatures */
636 append_hostkey_type(b, "rsa-sha2-512");
637 append_hostkey_type(b, "rsa-sha2-256");
638 /* FALLTHROUGH */
639 case KEY_DSA:
640 case KEY_ECDSA:
641 case KEY_ED25519:
642 case KEY_ECDSA_SK:
643 case KEY_ED25519_SK:
644 case KEY_XMSS:
645 append_hostkey_type(b, sshkey_ssh_name(key));
646 break;
647 }
648 /* If the private key has a cert peer, then list that too */
649 key = sensitive_data.host_certificates[i];
650 if (key == NULL)
651 continue;
652 switch (key->type) {
653 case KEY_RSA_CERT:
654 /* for RSA we also support SHA2 signatures */
655 append_hostkey_type(b,
656 "rsa-sha2-512-cert-v01@openssh.com");
657 append_hostkey_type(b,
658 "rsa-sha2-256-cert-v01@openssh.com");
659 /* FALLTHROUGH */
660 case KEY_DSA_CERT:
661 case KEY_ECDSA_CERT:
662 case KEY_ED25519_CERT:
663 case KEY_ECDSA_SK_CERT:
664 case KEY_ED25519_SK_CERT:
665 case KEY_XMSS_CERT:
666 append_hostkey_type(b, sshkey_ssh_name(key));
667 break;
668 }
669 }
670 if ((ret = sshbuf_dup_string(b)) == NULL)
671 fatal_f("sshbuf_dup_string failed");
672 sshbuf_free(b);
673 debug_f("%s", ret);
674 return ret;
675 }
676
677 static struct sshkey *
678 get_hostkey_by_type(int type, int nid, int need_private, struct ssh *ssh)
679 {
680 u_int i;
681 struct sshkey *key;
682
683 for (i = 0; i < options.num_host_key_files; i++) {
684 switch (type) {
685 case KEY_RSA_CERT:
686 case KEY_DSA_CERT:
687 case KEY_ECDSA_CERT:
688 case KEY_ED25519_CERT:
689 case KEY_ECDSA_SK_CERT:
690 case KEY_ED25519_SK_CERT:
691 case KEY_XMSS_CERT:
692 key = sensitive_data.host_certificates[i];
693 break;
694 default:
695 key = sensitive_data.host_keys[i];
696 if (key == NULL && !need_private)
697 key = sensitive_data.host_pubkeys[i];
698 break;
699 }
700 if (key == NULL || key->type != type)
701 continue;
702 switch (type) {
703 case KEY_ECDSA:
704 case KEY_ECDSA_SK:
705 case KEY_ECDSA_CERT:
706 case KEY_ECDSA_SK_CERT:
707 if (key->ecdsa_nid != nid)
708 continue;
709 /* FALLTHROUGH */
710 default:
711 return need_private ?
712 sensitive_data.host_keys[i] : key;
713 }
714 }
715 return NULL;
716 }
717
718 struct sshkey *
719 get_hostkey_public_by_type(int type, int nid, struct ssh *ssh)
720 {
721 return get_hostkey_by_type(type, nid, 0, ssh);
722 }
723
724 struct sshkey *
725 get_hostkey_private_by_type(int type, int nid, struct ssh *ssh)
726 {
727 return get_hostkey_by_type(type, nid, 1, ssh);
728 }
729
730 struct sshkey *
731 get_hostkey_by_index(int ind)
732 {
733 if (ind < 0 || (u_int)ind >= options.num_host_key_files)
734 return (NULL);
735 return (sensitive_data.host_keys[ind]);
736 }
737
738 struct sshkey *
739 get_hostkey_public_by_index(int ind, struct ssh *ssh)
740 {
741 if (ind < 0 || (u_int)ind >= options.num_host_key_files)
742 return (NULL);
743 return (sensitive_data.host_pubkeys[ind]);
744 }
745
746 int
747 get_hostkey_index(struct sshkey *key, int compare, struct ssh *ssh)
748 {
749 u_int i;
750
751 for (i = 0; i < options.num_host_key_files; i++) {
752 if (sshkey_is_cert(key)) {
753 if (key == sensitive_data.host_certificates[i] ||
754 (compare && sensitive_data.host_certificates[i] &&
755 sshkey_equal(key,
756 sensitive_data.host_certificates[i])))
757 return (i);
758 } else {
759 if (key == sensitive_data.host_keys[i] ||
760 (compare && sensitive_data.host_keys[i] &&
761 sshkey_equal(key, sensitive_data.host_keys[i])))
762 return (i);
763 if (key == sensitive_data.host_pubkeys[i] ||
764 (compare && sensitive_data.host_pubkeys[i] &&
765 sshkey_equal(key, sensitive_data.host_pubkeys[i])))
766 return (i);
767 }
768 }
769 return (-1);
770 }
771
772 /* Inform the client of all hostkeys */
773 static void
774 notify_hostkeys(struct ssh *ssh)
775 {
776 struct sshbuf *buf;
777 struct sshkey *key;
778 u_int i, nkeys;
779 int r;
780 char *fp;
781
782 /* Some clients cannot cope with the hostkeys message, skip those. */
783 if (ssh->compat & SSH_BUG_HOSTKEYS)
784 return;
785
786 if ((buf = sshbuf_new()) == NULL)
787 fatal_f("sshbuf_new");
788 for (i = nkeys = 0; i < options.num_host_key_files; i++) {
789 key = get_hostkey_public_by_index(i, ssh);
790 if (key == NULL || key->type == KEY_UNSPEC ||
791 sshkey_is_cert(key))
792 continue;
793 fp = sshkey_fingerprint(key, options.fingerprint_hash,
794 SSH_FP_DEFAULT);
795 debug3_f("key %d: %s %s", i, sshkey_ssh_name(key), fp);
796 free(fp);
797 if (nkeys == 0) {
798 /*
799 * Start building the request when we find the
800 * first usable key.
801 */
802 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 ||
803 (r = sshpkt_put_cstring(ssh, "hostkeys-00@openssh.com")) != 0 ||
804 (r = sshpkt_put_u8(ssh, 0)) != 0) /* want reply */
805 sshpkt_fatal(ssh, r, "%s: start request", __func__);
806 }
807 /* Append the key to the request */
808 sshbuf_reset(buf);
809 if ((r = sshkey_putb(key, buf)) != 0)
810 fatal_fr(r, "couldn't put hostkey %d", i);
811 if ((r = sshpkt_put_stringb(ssh, buf)) != 0)
812 sshpkt_fatal(ssh, r, "%s: append key", __func__);
813 nkeys++;
814 }
815 debug3_f("sent %u hostkeys", nkeys);
816 if (nkeys == 0)
817 fatal_f("no hostkeys");
818 if ((r = sshpkt_send(ssh)) != 0)
819 sshpkt_fatal(ssh, r, "%s: send", __func__);
820 sshbuf_free(buf);
821 }
822
823 /*
824 * returns 1 if connection should be dropped, 0 otherwise.
825 * dropping starts at connection #max_startups_begin with a probability
826 * of (max_startups_rate/100). the probability increases linearly until
827 * all connections are dropped for startups > max_startups
828 */
829 static int
830 should_drop_connection(int startups)
831 {
832 int p, r;
833
834 if (startups < options.max_startups_begin)
835 return 0;
836 if (startups >= options.max_startups)
837 return 1;
838 if (options.max_startups_rate == 100)
839 return 1;
840
841 p = 100 - options.max_startups_rate;
842 p *= startups - options.max_startups_begin;
843 p /= options.max_startups - options.max_startups_begin;
844 p += options.max_startups_rate;
845 r = arc4random_uniform(100);
846
847 debug_f("p %d, r %d", p, r);
848 return (r < p) ? 1 : 0;
849 }
850
851 /*
852 * Check whether connection should be accepted by MaxStartups.
853 * Returns 0 if the connection is accepted. If the connection is refused,
854 * returns 1 and attempts to send notification to client.
855 * Logs when the MaxStartups condition is entered or exited, and periodically
856 * while in that state.
857 */
858 static int
859 drop_connection(int sock, int startups, int notify_pipe)
860 {
861 char *laddr, *raddr;
862 const char msg[] = "Exceeded MaxStartups\r\n";
863 static time_t last_drop, first_drop;
864 static u_int ndropped;
865 LogLevel drop_level = SYSLOG_LEVEL_VERBOSE;
866 time_t now;
867
868 now = monotime();
869 if (!should_drop_connection(startups) &&
870 srclimit_check_allow(sock, notify_pipe) == 1) {
871 if (last_drop != 0 &&
872 startups < options.max_startups_begin - 1) {
873 /* XXX maybe need better hysteresis here */
874 logit("exited MaxStartups throttling after %s, "
875 "%u connections dropped",
876 fmt_timeframe(now - first_drop), ndropped);
877 last_drop = 0;
878 }
879 return 0;
880 }
881
882 #define SSHD_MAXSTARTUPS_LOG_INTERVAL (5 * 60)
883 if (last_drop == 0) {
884 error("beginning MaxStartups throttling");
885 drop_level = SYSLOG_LEVEL_INFO;
886 first_drop = now;
887 ndropped = 0;
888 } else if (last_drop + SSHD_MAXSTARTUPS_LOG_INTERVAL < now) {
889 /* Periodic logs */
890 error("in MaxStartups throttling for %s, "
891 "%u connections dropped",
892 fmt_timeframe(now - first_drop), ndropped + 1);
893 drop_level = SYSLOG_LEVEL_INFO;
894 }
895 last_drop = now;
896 ndropped++;
897
898 laddr = get_local_ipaddr(sock);
899 raddr = get_peer_ipaddr(sock);
900 do_log2(drop_level, "drop connection #%d from [%s]:%d on [%s]:%d "
901 "past MaxStartups", startups, raddr, get_peer_port(sock),
902 laddr, get_local_port(sock));
903 free(laddr);
904 free(raddr);
905 /* best-effort notification to client */
906 (void)write(sock, msg, sizeof(msg) - 1);
907 return 1;
908 }
909
910 static void
911 usage(void)
912 {
913 if (options.version_addendum != NULL &&
914 *options.version_addendum != '\0')
915 fprintf(stderr, "%s %s, %s\n",
916 SSH_RELEASE,
917 options.version_addendum, SSH_OPENSSL_VERSION);
918 else
919 fprintf(stderr, "%s, %s\n",
920 SSH_RELEASE, SSH_OPENSSL_VERSION);
921 fprintf(stderr,
922 "usage: sshd [-46DdeGiqTtV] [-C connection_spec] [-c host_cert_file]\n"
923 " [-E log_file] [-f config_file] [-g login_grace_time]\n"
924 " [-h host_key_file] [-o option] [-p port] [-u len]\n"
925 );
926 exit(1);
927 }
928
929 static void
930 send_rexec_state(int fd, struct sshbuf *conf)
931 {
932 struct sshbuf *m = NULL, *inc = NULL;
933 struct include_item *item = NULL;
934 int r;
935
936 debug3_f("entering fd = %d config len %zu", fd,
937 sshbuf_len(conf));
938
939 if ((m = sshbuf_new()) == NULL || (inc = sshbuf_new()) == NULL)
940 fatal_f("sshbuf_new failed");
941
942 /* pack includes into a string */
943 TAILQ_FOREACH(item, &includes, entry) {
944 if ((r = sshbuf_put_cstring(inc, item->selector)) != 0 ||
945 (r = sshbuf_put_cstring(inc, item->filename)) != 0 ||
946 (r = sshbuf_put_stringb(inc, item->contents)) != 0)
947 fatal_fr(r, "compose includes");
948 }
949
950 /*
951 * Protocol from reexec master to child:
952 * string configuration
953 * string included_files[] {
954 * string selector
955 * string filename
956 * string contents
957 * }
958 */
959 if ((r = sshbuf_put_stringb(m, conf)) != 0 ||
960 (r = sshbuf_put_stringb(m, inc)) != 0)
961 fatal_fr(r, "compose config");
962 if (ssh_msg_send(fd, 0, m) == -1)
963 error_f("ssh_msg_send failed");
964
965 sshbuf_free(m);
966 sshbuf_free(inc);
967
968 debug3_f("done");
969 }
970
971 static void
972 recv_rexec_state(int fd, struct sshbuf *conf)
973 {
974 struct sshbuf *m, *inc;
975 u_char *cp, ver;
976 size_t len;
977 int r;
978 struct include_item *item;
979
980 debug3_f("entering fd = %d", fd);
981
982 if ((m = sshbuf_new()) == NULL || (inc = sshbuf_new()) == NULL)
983 fatal_f("sshbuf_new failed");
984 if (ssh_msg_recv(fd, m) == -1)
985 fatal_f("ssh_msg_recv failed");
986 if ((r = sshbuf_get_u8(m, &ver)) != 0)
987 fatal_fr(r, "parse version");
988 if (ver != 0)
989 fatal_f("rexec version mismatch");
990 if ((r = sshbuf_get_string(m, &cp, &len)) != 0 ||
991 (r = sshbuf_get_stringb(m, inc)) != 0)
992 fatal_fr(r, "parse config");
993
994 if (conf != NULL && (r = sshbuf_put(conf, cp, len)))
995 fatal_fr(r, "sshbuf_put");
996
997 while (sshbuf_len(inc) != 0) {
998 item = xcalloc(1, sizeof(*item));
999 if ((item->contents = sshbuf_new()) == NULL)
1000 fatal_f("sshbuf_new failed");
1001 if ((r = sshbuf_get_cstring(inc, &item->selector, NULL)) != 0 ||
1002 (r = sshbuf_get_cstring(inc, &item->filename, NULL)) != 0 ||
1003 (r = sshbuf_get_stringb(inc, item->contents)) != 0)
1004 fatal_fr(r, "parse includes");
1005 TAILQ_INSERT_TAIL(&includes, item, entry);
1006 }
1007
1008 free(cp);
1009 sshbuf_free(m);
1010
1011 debug3_f("done");
1012 }
1013
1014 /* Accept a connection from inetd */
1015 static void
1016 server_accept_inetd(int *sock_in, int *sock_out)
1017 {
1018 if (rexeced_flag) {
1019 close(REEXEC_CONFIG_PASS_FD);
1020 *sock_in = *sock_out = dup(STDIN_FILENO);
1021 } else {
1022 *sock_in = dup(STDIN_FILENO);
1023 *sock_out = dup(STDOUT_FILENO);
1024 }
1025 /*
1026 * We intentionally do not close the descriptors 0, 1, and 2
1027 * as our code for setting the descriptors won't work if
1028 * ttyfd happens to be one of those.
1029 */
1030 if (stdfd_devnull(1, 1, !log_stderr) == -1)
1031 error_f("stdfd_devnull failed");
1032 debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out);
1033 }
1034
1035 /*
1036 * Listen for TCP connections
1037 */
1038 static void
1039 listen_on_addrs(struct listenaddr *la)
1040 {
1041 int ret, listen_sock;
1042 struct addrinfo *ai;
1043 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
1044
1045 for (ai = la->addrs; ai; ai = ai->ai_next) {
1046 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
1047 continue;
1048 if (num_listen_socks >= MAX_LISTEN_SOCKS)
1049 fatal("Too many listen sockets. "
1050 "Enlarge MAX_LISTEN_SOCKS");
1051 if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen,
1052 ntop, sizeof(ntop), strport, sizeof(strport),
1053 NI_NUMERICHOST|NI_NUMERICSERV)) != 0) {
1054 error("getnameinfo failed: %.100s",
1055 ssh_gai_strerror(ret));
1056 continue;
1057 }
1058 /* Create socket for listening. */
1059 listen_sock = socket(ai->ai_family, ai->ai_socktype,
1060 ai->ai_protocol);
1061 if (listen_sock == -1) {
1062 /* kernel may not support ipv6 */
1063 verbose("socket: %.100s", strerror(errno));
1064 continue;
1065 }
1066 if (set_nonblock(listen_sock) == -1) {
1067 close(listen_sock);
1068 continue;
1069 }
1070 if (fcntl(listen_sock, F_SETFD, FD_CLOEXEC) == -1) {
1071 verbose("socket: CLOEXEC: %s", strerror(errno));
1072 close(listen_sock);
1073 continue;
1074 }
1075 /* Socket options */
1076 set_reuseaddr(listen_sock);
1077 if (la->rdomain != NULL &&
1078 set_rdomain(listen_sock, la->rdomain) == -1) {
1079 close(listen_sock);
1080 continue;
1081 }
1082
1083 /* Only communicate in IPv6 over AF_INET6 sockets. */
1084 if (ai->ai_family == AF_INET6)
1085 sock_set_v6only(listen_sock);
1086
1087 debug("Bind to port %s on %s.", strport, ntop);
1088
1089 /* Bind the socket to the desired port. */
1090 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) == -1) {
1091 error("Bind to port %s on %s failed: %.200s.",
1092 strport, ntop, strerror(errno));
1093 close(listen_sock);
1094 continue;
1095 }
1096 listen_socks[num_listen_socks] = listen_sock;
1097 num_listen_socks++;
1098
1099 /* Start listening on the port. */
1100 if (listen(listen_sock, SSH_LISTEN_BACKLOG) == -1)
1101 fatal("listen on [%s]:%s: %.100s",
1102 ntop, strport, strerror(errno));
1103 logit("Server listening on %s port %s%s%s.",
1104 ntop, strport,
1105 la->rdomain == NULL ? "" : " rdomain ",
1106 la->rdomain == NULL ? "" : la->rdomain);
1107 }
1108 }
1109
1110 static void
1111 server_listen(void)
1112 {
1113 u_int i;
1114
1115 /* Initialise per-source limit tracking. */
1116 srclimit_init(options.max_startups, options.per_source_max_startups,
1117 options.per_source_masklen_ipv4, options.per_source_masklen_ipv6);
1118
1119 for (i = 0; i < options.num_listen_addrs; i++) {
1120 listen_on_addrs(&options.listen_addrs[i]);
1121 freeaddrinfo(options.listen_addrs[i].addrs);
1122 free(options.listen_addrs[i].rdomain);
1123 memset(&options.listen_addrs[i], 0,
1124 sizeof(options.listen_addrs[i]));
1125 }
1126 free(options.listen_addrs);
1127 options.listen_addrs = NULL;
1128 options.num_listen_addrs = 0;
1129
1130 if (!num_listen_socks)
1131 fatal("Cannot bind any address.");
1132 }
1133
1134 /*
1135 * The main TCP accept loop. Note that, for the non-debug case, returns
1136 * from this function are in a forked subprocess.
1137 */
1138 static void
1139 server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
1140 {
1141 struct pollfd *pfd = NULL;
1142 int i, j, ret, npfd;
1143 int ostartups = -1, startups = 0, listening = 0, lameduck = 0;
1144 int startup_p[2] = { -1 , -1 }, *startup_pollfd;
1145 char c = 0;
1146 struct sockaddr_storage from;
1147 socklen_t fromlen;
1148 pid_t pid;
1149 u_char rnd[256];
1150 sigset_t nsigset, osigset;
1151 #ifdef LIBWRAP
1152 struct request_info req;
1153
1154 request_init(&req, RQ_DAEMON, __progname, 0);
1155 #endif
1156
1157 /* pipes connected to unauthenticated child sshd processes */
1158 startup_pipes = xcalloc(options.max_startups, sizeof(int));
1159 startup_flags = xcalloc(options.max_startups, sizeof(int));
1160 startup_pollfd = xcalloc(options.max_startups, sizeof(int));
1161 for (i = 0; i < options.max_startups; i++)
1162 startup_pipes[i] = -1;
1163
1164 /*
1165 * Prepare signal mask that we use to block signals that might set
1166 * received_sigterm or received_sighup, so that we are guaranteed
1167 * to immediately wake up the ppoll if a signal is received after
1168 * the flag is checked.
1169 */
1170 sigemptyset(&nsigset);
1171 sigaddset(&nsigset, SIGHUP);
1172 sigaddset(&nsigset, SIGCHLD);
1173 sigaddset(&nsigset, SIGTERM);
1174 sigaddset(&nsigset, SIGQUIT);
1175
1176 /* sized for worst-case */
1177 pfd = xcalloc(num_listen_socks + options.max_startups,
1178 sizeof(struct pollfd));
1179
1180 /*
1181 * Stay listening for connections until the system crashes or
1182 * the daemon is killed with a signal.
1183 */
1184 for (;;) {
1185 sigprocmask(SIG_BLOCK, &nsigset, &osigset);
1186 if (received_sigterm) {
1187 logit("Received signal %d; terminating.",
1188 (int) received_sigterm);
1189 close_listen_socks();
1190 if (options.pid_file != NULL)
1191 unlink(options.pid_file);
1192 exit(received_sigterm == SIGTERM ? 0 : 255);
1193 }
1194 if (ostartups != startups) {
1195 setproctitle("%s [listener] %d of %d-%d startups",
1196 listener_proctitle, startups,
1197 options.max_startups_begin, options.max_startups);
1198 ostartups = startups;
1199 }
1200 if (received_sighup) {
1201 if (!lameduck) {
1202 debug("Received SIGHUP; waiting for children");
1203 close_listen_socks();
1204 lameduck = 1;
1205 }
1206 if (listening <= 0) {
1207 sigprocmask(SIG_SETMASK, &osigset, NULL);
1208 sighup_restart();
1209 }
1210 }
1211
1212 for (i = 0; i < num_listen_socks; i++) {
1213 pfd[i].fd = listen_socks[i];
1214 pfd[i].events = POLLIN;
1215 }
1216 npfd = num_listen_socks;
1217 for (i = 0; i < options.max_startups; i++) {
1218 startup_pollfd[i] = -1;
1219 if (startup_pipes[i] != -1) {
1220 pfd[npfd].fd = startup_pipes[i];
1221 pfd[npfd].events = POLLIN;
1222 startup_pollfd[i] = npfd++;
1223 }
1224 }
1225
1226 /* Wait until a connection arrives or a child exits. */
1227 ret = ppoll(pfd, npfd, NULL, &osigset);
1228 if (ret == -1 && errno != EINTR) {
1229 error("ppoll: %.100s", strerror(errno));
1230 if (errno == EINVAL)
1231 cleanup_exit(1); /* can't recover */
1232 }
1233 sigprocmask(SIG_SETMASK, &osigset, NULL);
1234 if (ret == -1)
1235 continue;
1236
1237 for (i = 0; i < options.max_startups; i++) {
1238 if (startup_pipes[i] == -1 ||
1239 startup_pollfd[i] == -1 ||
1240 !(pfd[startup_pollfd[i]].revents & (POLLIN|POLLHUP)))
1241 continue;
1242 switch (read(startup_pipes[i], &c, sizeof(c))) {
1243 case -1:
1244 if (errno == EINTR || errno == EAGAIN)
1245 continue;
1246 if (errno != EPIPE) {
1247 error_f("startup pipe %d (fd=%d): "
1248 "read %s", i, startup_pipes[i],
1249 strerror(errno));
1250 }
1251 /* FALLTHROUGH */
1252 case 0:
1253 /* child exited or completed auth */
1254 close(startup_pipes[i]);
1255 srclimit_done(startup_pipes[i]);
1256 startup_pipes[i] = -1;
1257 startups--;
1258 if (startup_flags[i])
1259 listening--;
1260 break;
1261 case 1:
1262 /* child has finished preliminaries */
1263 if (startup_flags[i]) {
1264 listening--;
1265 startup_flags[i] = 0;
1266 }
1267 break;
1268 }
1269 }
1270 for (i = 0; i < num_listen_socks; i++) {
1271 if (!(pfd[i].revents & POLLIN))
1272 continue;
1273 fromlen = sizeof(from);
1274 *newsock = accept(listen_socks[i],
1275 (struct sockaddr *)&from, &fromlen);
1276 if (*newsock == -1) {
1277 if (errno != EINTR && errno != EWOULDBLOCK &&
1278 errno != ECONNABORTED && errno != EAGAIN)
1279 error("accept: %.100s",
1280 strerror(errno));
1281 if (errno == EMFILE || errno == ENFILE)
1282 usleep(100 * 1000);
1283 continue;
1284 }
1285 #ifdef LIBWRAP
1286 /* Check whether logins are denied from this host. */
1287 request_set(&req, RQ_FILE, *newsock,
1288 RQ_CLIENT_NAME, "", RQ_CLIENT_ADDR, "", 0);
1289 sock_host(&req);
1290 if (!hosts_access(&req)) {
1291 const struct linger l = { .l_onoff = 1,
1292 .l_linger = 0 };
1293
1294 (void )setsockopt(*newsock, SOL_SOCKET,
1295 SO_LINGER, &l, sizeof(l));
1296 (void )close(*newsock);
1297 /*
1298 * Mimic message from libwrap's refuse() as
1299 * precisely as we can afford. The authentic
1300 * message prints the IP address and the
1301 * hostname it resolves to in parentheses. If
1302 * the IP address cannot be resolved to a
1303 * hostname, the IP address will be repeated
1304 * in parentheses. As name resolution in the
1305 * main server loop could stall, and logging
1306 * resolved names adds little or no value to
1307 * incident investigation, this implementation
1308 * only repeats the IP address in parentheses.
1309 * This should resemble librwap's refuse()
1310 * closely enough not to break auditing
1311 * software like sshguard or custom scripts.
1312 */
1313 syslog(LOG_WARNING,
1314 "refused connect from %s (%s)",
1315 eval_hostaddr(req.client),
1316 eval_hostaddr(req.client));
1317 debug("Connection refused by tcp wrapper");
1318 continue;
1319 }
1320 #endif /* LIBWRAP */
1321 if (unset_nonblock(*newsock) == -1) {
1322 close(*newsock);
1323 continue;
1324 }
1325 if (pipe(startup_p) == -1) {
1326 error_f("pipe(startup_p): %s", strerror(errno));
1327 close(*newsock);
1328 continue;
1329 }
1330 if (drop_connection(*newsock, startups, startup_p[0])) {
1331 close(*newsock);
1332 close(startup_p[0]);
1333 close(startup_p[1]);
1334 continue;
1335 }
1336
1337 if (rexec_flag && socketpair(AF_UNIX,
1338 SOCK_STREAM, 0, config_s) == -1) {
1339 error("reexec socketpair: %s",
1340 strerror(errno));
1341 close(*newsock);
1342 close(startup_p[0]);
1343 close(startup_p[1]);
1344 continue;
1345 }
1346
1347 for (j = 0; j < options.max_startups; j++)
1348 if (startup_pipes[j] == -1) {
1349 startup_pipes[j] = startup_p[0];
1350 startups++;
1351 startup_flags[j] = 1;
1352 break;
1353 }
1354
1355 /*
1356 * Got connection. Fork a child to handle it, unless
1357 * we are in debugging mode.
1358 */
1359 if (debug_flag) {
1360 /*
1361 * In debugging mode. Close the listening
1362 * socket, and start processing the
1363 * connection without forking.
1364 */
1365 debug("Server will not fork when running in debugging mode.");
1366 close_listen_socks();
1367 *sock_in = *newsock;
1368 *sock_out = *newsock;
1369 close(startup_p[0]);
1370 close(startup_p[1]);
1371 startup_pipe = -1;
1372 pid = getpid();
1373 if (rexec_flag) {
1374 send_rexec_state(config_s[0], cfg);
1375 close(config_s[0]);
1376 }
1377 free(pfd);
1378 return;
1379 }
1380
1381 /*
1382 * Normal production daemon. Fork, and have
1383 * the child process the connection. The
1384 * parent continues listening.
1385 */
1386 platform_pre_fork();
1387 listening++;
1388 if ((pid = fork()) == 0) {
1389 /*
1390 * Child. Close the listening and
1391 * max_startup sockets. Start using
1392 * the accepted socket. Reinitialize
1393 * logging (since our pid has changed).
1394 * We return from this function to handle
1395 * the connection.
1396 */
1397 platform_post_fork_child();
1398 startup_pipe = startup_p[1];
1399 close_startup_pipes();
1400 close_listen_socks();
1401 *sock_in = *newsock;
1402 *sock_out = *newsock;
1403 log_init(__progname,
1404 options.log_level,
1405 options.log_facility,
1406 log_stderr);
1407 if (rexec_flag)
1408 close(config_s[0]);
1409 else {
1410 /*
1411 * Signal parent that the preliminaries
1412 * for this child are complete. For the
1413 * re-exec case, this happens after the
1414 * child has received the rexec state
1415 * from the server.
1416 */
1417 (void)atomicio(vwrite, startup_pipe,
1418 "\0", 1);
1419 }
1420 free(pfd);
1421 return;
1422 }
1423
1424 /* Parent. Stay in the loop. */
1425 platform_post_fork_parent(pid);
1426 if (pid == -1)
1427 error("fork: %.100s", strerror(errno));
1428 else
1429 debug("Forked child %ld.", (long)pid);
1430
1431 close(startup_p[1]);
1432
1433 if (rexec_flag) {
1434 close(config_s[1]);
1435 send_rexec_state(config_s[0], cfg);
1436 close(config_s[0]);
1437 }
1438 close(*newsock);
1439
1440 /*
1441 * Ensure that our random state differs
1442 * from that of the child
1443 */
1444 arc4random_stir();
1445 arc4random_buf(rnd, sizeof(rnd));
1446 #ifdef WITH_OPENSSL
1447 RAND_seed(rnd, sizeof(rnd));
1448 if ((RAND_bytes((u_char *)rnd, 1)) != 1)
1449 fatal("%s: RAND_bytes failed", __func__);
1450 #endif
1451 explicit_bzero(rnd, sizeof(rnd));
1452 }
1453 }
1454 }
1455
1456 /*
1457 * If IP options are supported, make sure there are none (log and
1458 * return an error if any are found). Basically we are worried about
1459 * source routing; it can be used to pretend you are somebody
1460 * (ip-address) you are not. That itself may be "almost acceptable"
1461 * under certain circumstances, but rhosts authentication is useless
1462 * if source routing is accepted. Notice also that if we just dropped
1463 * source routing here, the other side could use IP spoofing to do
1464 * rest of the interaction and could still bypass security. So we
1465 * exit here if we detect any IP options.
1466 */
1467 static void
1468 check_ip_options(struct ssh *ssh)
1469 {
1470 #ifdef IP_OPTIONS
1471 int sock_in = ssh_packet_get_connection_in(ssh);
1472 struct sockaddr_storage from;
1473 u_char opts[200];
1474 socklen_t i, option_size = sizeof(opts), fromlen = sizeof(from);
1475 char text[sizeof(opts) * 3 + 1];
1476
1477 memset(&from, 0, sizeof(from));
1478 if (getpeername(sock_in, (struct sockaddr *)&from,
1479 &fromlen) == -1)
1480 return;
1481 if (from.ss_family != AF_INET)
1482 return;
1483 /* XXX IPv6 options? */
1484
1485 if (getsockopt(sock_in, IPPROTO_IP, IP_OPTIONS, opts,
1486 &option_size) >= 0 && option_size != 0) {
1487 text[0] = '\0';
1488 for (i = 0; i < option_size; i++)
1489 snprintf(text + i*3, sizeof(text) - i*3,
1490 " %2.2x", opts[i]);
1491 fatal("Connection from %.100s port %d with IP opts: %.800s",
1492 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), text);
1493 }
1494 return;
1495 #endif /* IP_OPTIONS */
1496 }
1497
1498 /* Set the routing domain for this process */
1499 static void
1500 set_process_rdomain(struct ssh *ssh, const char *name)
1501 {
1502 #if defined(HAVE_SYS_SET_PROCESS_RDOMAIN)
1503 if (name == NULL)
1504 return; /* default */
1505
1506 if (strcmp(name, "%D") == 0) {
1507 /* "expands" to routing domain of connection */
1508 if ((name = ssh_packet_rdomain_in(ssh)) == NULL)
1509 return;
1510 }
1511 /* NB. We don't pass 'ssh' to sys_set_process_rdomain() */
1512 return sys_set_process_rdomain(name);
1513 #elif defined(__OpenBSD__)
1514 int rtable, ortable = getrtable();
1515 const char *errstr;
1516
1517 if (name == NULL)
1518 return; /* default */
1519
1520 if (strcmp(name, "%D") == 0) {
1521 /* "expands" to routing domain of connection */
1522 if ((name = ssh_packet_rdomain_in(ssh)) == NULL)
1523 return;
1524 }
1525
1526 rtable = (int)strtonum(name, 0, 255, &errstr);
1527 if (errstr != NULL) /* Shouldn't happen */
1528 fatal("Invalid routing domain \"%s\": %s", name, errstr);
1529 if (rtable != ortable && setrtable(rtable) != 0)
1530 fatal("Unable to set routing domain %d: %s",
1531 rtable, strerror(errno));
1532 debug_f("set routing domain %d (was %d)", rtable, ortable);
1533 #else /* defined(__OpenBSD__) */
1534 fatal("Unable to set routing domain: not supported in this platform");
1535 #endif
1536 }
1537
1538 static void
1539 accumulate_host_timing_secret(struct sshbuf *server_cfg,
1540 struct sshkey *key)
1541 {
1542 static struct ssh_digest_ctx *ctx;
1543 u_char *hash;
1544 size_t len;
1545 struct sshbuf *buf;
1546 int r;
1547
1548 if (ctx == NULL && (ctx = ssh_digest_start(SSH_DIGEST_SHA512)) == NULL)
1549 fatal_f("ssh_digest_start");
1550 if (key == NULL) { /* finalize */
1551 /* add server config in case we are using agent for host keys */
1552 if (ssh_digest_update(ctx, sshbuf_ptr(server_cfg),
1553 sshbuf_len(server_cfg)) != 0)
1554 fatal_f("ssh_digest_update");
1555 len = ssh_digest_bytes(SSH_DIGEST_SHA512);
1556 hash = xmalloc(len);
1557 if (ssh_digest_final(ctx, hash, len) != 0)
1558 fatal_f("ssh_digest_final");
1559 options.timing_secret = PEEK_U64(hash);
1560 freezero(hash, len);
1561 ssh_digest_free(ctx);
1562 ctx = NULL;
1563 return;
1564 }
1565 if ((buf = sshbuf_new()) == NULL)
1566 fatal_f("could not allocate buffer");
1567 if ((r = sshkey_private_serialize(key, buf)) != 0)
1568 fatal_fr(r, "encode %s key", sshkey_ssh_name(key));
1569 if (ssh_digest_update(ctx, sshbuf_ptr(buf), sshbuf_len(buf)) != 0)
1570 fatal_f("ssh_digest_update");
1571 sshbuf_reset(buf);
1572 sshbuf_free(buf);
1573 }
1574
1575 static char *
1576 prepare_proctitle(int ac, char **av)
1577 {
1578 char *ret = NULL;
1579 int i;
1580
1581 for (i = 0; i < ac; i++)
1582 xextendf(&ret, " ", "%s", av[i]);
1583 return ret;
1584 }
1585
1586 static void
1587 print_config(struct ssh *ssh, struct connection_info *connection_info)
1588 {
1589 /*
1590 * If no connection info was provided by -C then use
1591 * use a blank one that will cause no predicate to match.
1592 */
1593 if (connection_info == NULL)
1594 connection_info = get_connection_info(ssh, 0, 0);
1595 connection_info->test = 1;
1596 parse_server_match_config(&options, &includes, connection_info);
1597 dump_config(&options);
1598 exit(0);
1599 }
1600
1601 /*
1602 * Main program for the daemon.
1603 */
1604 int
1605 main(int ac, char **av)
1606 {
1607 struct ssh *ssh = NULL;
1608 extern char *optarg;
1609 extern int optind;
1610 int r, opt, on = 1, do_dump_cfg = 0, already_daemon, remote_port;
1611 int sock_in = -1, sock_out = -1, newsock = -1;
1612 const char *remote_ip, *rdomain;
1613 char *fp, *line, *laddr, *logfile = NULL;
1614 int config_s[2] = { -1 , -1 };
1615 u_int i, j;
1616 u_int64_t ibytes, obytes;
1617 mode_t new_umask;
1618 struct sshkey *key;
1619 struct sshkey *pubkey;
1620 int keytype;
1621 Authctxt *authctxt;
1622 struct connection_info *connection_info = NULL;
1623 sigset_t sigmask;
1624
1625 #ifdef HAVE_SECUREWARE
1626 (void)set_auth_parameters(ac, av);
1627 #endif
1628 __progname = ssh_get_progname(av[0]);
1629
1630 sigemptyset(&sigmask);
1631 sigprocmask(SIG_SETMASK, &sigmask, NULL);
1632
1633 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
1634 saved_argc = ac;
1635 rexec_argc = ac;
1636 saved_argv = xcalloc(ac + 1, sizeof(*saved_argv));
1637 for (i = 0; (int)i < ac; i++)
1638 saved_argv[i] = xstrdup(av[i]);
1639 saved_argv[i] = NULL;
1640
1641 #ifndef HAVE_SETPROCTITLE
1642 /* Prepare for later setproctitle emulation */
1643 compat_init_setproctitle(ac, av);
1644 av = saved_argv;
1645 #endif
1646
1647 if (geteuid() == 0 && setgroups(0, NULL) == -1)
1648 debug("setgroups(): %.200s", strerror(errno));
1649
1650 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
1651 sanitise_stdfd();
1652
1653 /* Initialize configuration options to their default values. */
1654 initialize_server_options(&options);
1655
1656 /* Parse command-line arguments. */
1657 while ((opt = getopt(ac, av,
1658 "C:E:b:c:f:g:h:k:o:p:u:46DGQRTdeiqrtV")) != -1) {
1659 switch (opt) {
1660 case '4':
1661 options.address_family = AF_INET;
1662 break;
1663 case '6':
1664 options.address_family = AF_INET6;
1665 break;
1666 case 'f':
1667 config_file_name = optarg;
1668 break;
1669 case 'c':
1670 servconf_add_hostcert("[command-line]", 0,
1671 &options, optarg);
1672 break;
1673 case 'd':
1674 if (debug_flag == 0) {
1675 debug_flag = 1;
1676 options.log_level = SYSLOG_LEVEL_DEBUG1;
1677 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
1678 options.log_level++;
1679 break;
1680 case 'D':
1681 no_daemon_flag = 1;
1682 break;
1683 case 'G':
1684 do_dump_cfg = 1;
1685 break;
1686 case 'E':
1687 logfile = optarg;
1688 /* FALLTHROUGH */
1689 case 'e':
1690 log_stderr = 1;
1691 break;
1692 case 'i':
1693 inetd_flag = 1;
1694 break;
1695 case 'r':
1696 rexec_flag = 0;
1697 break;
1698 case 'R':
1699 rexeced_flag = 1;
1700 inetd_flag = 1;
1701 break;
1702 case 'Q':
1703 /* ignored */
1704 break;
1705 case 'q':
1706 options.log_level = SYSLOG_LEVEL_QUIET;
1707 break;
1708 case 'b':
1709 /* protocol 1, ignored */
1710 break;
1711 case 'p':
1712 options.ports_from_cmdline = 1;
1713 if (options.num_ports >= MAX_PORTS) {
1714 fprintf(stderr, "too many ports.\n");
1715 exit(1);
1716 }
1717 options.ports[options.num_ports++] = a2port(optarg);
1718 if (options.ports[options.num_ports-1] <= 0) {
1719 fprintf(stderr, "Bad port number.\n");
1720 exit(1);
1721 }
1722 break;
1723 case 'g':
1724 if ((options.login_grace_time = convtime(optarg)) == -1) {
1725 fprintf(stderr, "Invalid login grace time.\n");
1726 exit(1);
1727 }
1728 break;
1729 case 'k':
1730 /* protocol 1, ignored */
1731 break;
1732 case 'h':
1733 servconf_add_hostkey("[command-line]", 0,
1734 &options, optarg, 1);
1735 break;
1736 case 't':
1737 test_flag = 1;
1738 break;
1739 case 'T':
1740 test_flag = 2;
1741 break;
1742 case 'C':
1743 connection_info = get_connection_info(ssh, 0, 0);
1744 if (parse_server_match_testspec(connection_info,
1745 optarg) == -1)
1746 exit(1);
1747 break;
1748 case 'u':
1749 utmp_len = (u_int)strtonum(optarg, 0, HOST_NAME_MAX+1+1, NULL);
1750 if (utmp_len > HOST_NAME_MAX+1) {
1751 fprintf(stderr, "Invalid utmp length.\n");
1752 exit(1);
1753 }
1754 break;
1755 case 'o':
1756 line = xstrdup(optarg);
1757 if (process_server_config_line(&options, line,
1758 "command-line", 0, NULL, NULL, &includes) != 0)
1759 exit(1);
1760 free(line);
1761 break;
1762 case 'V':
1763 fprintf(stderr, "%s, %s\n",
1764 SSH_RELEASE, SSH_OPENSSL_VERSION);
1765 exit(0);
1766 default:
1767 usage();
1768 break;
1769 }
1770 }
1771 if (rexeced_flag || inetd_flag)
1772 rexec_flag = 0;
1773 if (!test_flag && !do_dump_cfg && rexec_flag && !path_absolute(av[0]))
1774 fatal("sshd re-exec requires execution with an absolute path");
1775 if (rexeced_flag)
1776 closefrom(REEXEC_MIN_FREE_FD);
1777 else
1778 closefrom(REEXEC_DEVCRYPTO_RESERVED_FD);
1779
1780 seed_rng();
1781
1782 /* If requested, redirect the logs to the specified logfile. */
1783 if (logfile != NULL)
1784 log_redirect_stderr_to(logfile);
1785 /*
1786 * Force logging to stderr until we have loaded the private host
1787 * key (unless started from inetd)
1788 */
1789 log_init(__progname,
1790 options.log_level == SYSLOG_LEVEL_NOT_SET ?
1791 SYSLOG_LEVEL_INFO : options.log_level,
1792 options.log_facility == SYSLOG_FACILITY_NOT_SET ?
1793 SYSLOG_FACILITY_AUTH : options.log_facility,
1794 log_stderr || !inetd_flag || debug_flag);
1795
1796 /*
1797 * Unset KRB5CCNAME, otherwise the user's session may inherit it from
1798 * root's environment
1799 */
1800 if (getenv("KRB5CCNAME") != NULL)
1801 (void) unsetenv("KRB5CCNAME");
1802
1803 sensitive_data.have_ssh2_key = 0;
1804
1805 /*
1806 * If we're not doing an extended test do not silently ignore connection
1807 * test params.
1808 */
1809 if (test_flag < 2 && connection_info != NULL)
1810 fatal("Config test connection parameter (-C) provided without "
1811 "test mode (-T)");
1812
1813 /* Fetch our configuration */
1814 if ((cfg = sshbuf_new()) == NULL)
1815 fatal_f("sshbuf_new failed");
1816 if (rexeced_flag) {
1817 setproctitle("%s", "[rexeced]");
1818 recv_rexec_state(REEXEC_CONFIG_PASS_FD, cfg);
1819 if (!debug_flag) {
1820 startup_pipe = dup(REEXEC_STARTUP_PIPE_FD);
1821 close(REEXEC_STARTUP_PIPE_FD);
1822 /*
1823 * Signal parent that this child is at a point where
1824 * they can go away if they have a SIGHUP pending.
1825 */
1826 (void)atomicio(vwrite, startup_pipe, "\0", 1);
1827 }
1828 } else if (strcasecmp(config_file_name, "none") != 0)
1829 load_server_config(config_file_name, cfg);
1830
1831 parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name,
1832 cfg, &includes, NULL, rexeced_flag);
1833
1834 #ifdef WITH_OPENSSL
1835 if (options.moduli_file != NULL)
1836 dh_set_moduli_file(options.moduli_file);
1837 #endif
1838
1839 /* Fill in default values for those options not explicitly set. */
1840 fill_default_server_options(&options);
1841
1842 /* Check that options are sensible */
1843 if (options.authorized_keys_command_user == NULL &&
1844 (options.authorized_keys_command != NULL &&
1845 strcasecmp(options.authorized_keys_command, "none") != 0))
1846 fatal("AuthorizedKeysCommand set without "
1847 "AuthorizedKeysCommandUser");
1848 if (options.authorized_principals_command_user == NULL &&
1849 (options.authorized_principals_command != NULL &&
1850 strcasecmp(options.authorized_principals_command, "none") != 0))
1851 fatal("AuthorizedPrincipalsCommand set without "
1852 "AuthorizedPrincipalsCommandUser");
1853
1854 /*
1855 * Check whether there is any path through configured auth methods.
1856 * Unfortunately it is not possible to verify this generally before
1857 * daemonisation in the presence of Match block, but this catches
1858 * and warns for trivial misconfigurations that could break login.
1859 */
1860 if (options.num_auth_methods != 0) {
1861 for (i = 0; i < options.num_auth_methods; i++) {
1862 if (auth2_methods_valid(options.auth_methods[i],
1863 1) == 0)
1864 break;
1865 }
1866 if (i >= options.num_auth_methods)
1867 fatal("AuthenticationMethods cannot be satisfied by "
1868 "enabled authentication methods");
1869 }
1870
1871 /* Check that there are no remaining arguments. */
1872 if (optind < ac) {
1873 fprintf(stderr, "Extra argument %s.\n", av[optind]);
1874 exit(1);
1875 }
1876
1877 debug("sshd version %s, %s", SSH_VERSION, SSH_OPENSSL_VERSION);
1878
1879 if (do_dump_cfg)
1880 print_config(ssh, connection_info);
1881
1882 /* Store privilege separation user for later use if required. */
1883 privsep_chroot = use_privsep && (getuid() == 0 || geteuid() == 0);
1884 if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) {
1885 if (privsep_chroot || options.kerberos_authentication)
1886 fatal("Privilege separation user %s does not exist",
1887 SSH_PRIVSEP_USER);
1888 } else {
1889 privsep_pw = pwcopy(privsep_pw);
1890 freezero(privsep_pw->pw_passwd, strlen(privsep_pw->pw_passwd));
1891 privsep_pw->pw_passwd = xstrdup("*");
1892 }
1893 endpwent();
1894
1895 /* load host keys */
1896 sensitive_data.host_keys = xcalloc(options.num_host_key_files,
1897 sizeof(struct sshkey *));
1898 sensitive_data.host_pubkeys = xcalloc(options.num_host_key_files,
1899 sizeof(struct sshkey *));
1900
1901 if (options.host_key_agent) {
1902 if (strcmp(options.host_key_agent, SSH_AUTHSOCKET_ENV_NAME))
1903 setenv(SSH_AUTHSOCKET_ENV_NAME,
1904 options.host_key_agent, 1);
1905 if ((r = ssh_get_authentication_socket(NULL)) == 0)
1906 have_agent = 1;
1907 else
1908 error_r(r, "Could not connect to agent \"%s\"",
1909 options.host_key_agent);
1910 }
1911
1912 for (i = 0; i < options.num_host_key_files; i++) {
1913 int ll = options.host_key_file_userprovided[i] ?
1914 SYSLOG_LEVEL_ERROR : SYSLOG_LEVEL_DEBUG1;
1915
1916 if (options.host_key_files[i] == NULL)
1917 continue;
1918 if ((r = sshkey_load_private(options.host_key_files[i], "",
1919 &key, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR)
1920 do_log2_r(r, ll, "Unable to load host key \"%s\"",
1921 options.host_key_files[i]);
1922 if (sshkey_is_sk(key) &&
1923 key->sk_flags & SSH_SK_USER_PRESENCE_REQD) {
1924 debug("host key %s requires user presence, ignoring",
1925 options.host_key_files[i]);
1926 key->sk_flags &= ~SSH_SK_USER_PRESENCE_REQD;
1927 }
1928 if (r == 0 && key != NULL &&
1929 (r = sshkey_shield_private(key)) != 0) {
1930 do_log2_r(r, ll, "Unable to shield host key \"%s\"",
1931 options.host_key_files[i]);
1932 sshkey_free(key);
1933 key = NULL;
1934 }
1935 if ((r = sshkey_load_public(options.host_key_files[i],
1936 &pubkey, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR)
1937 do_log2_r(r, ll, "Unable to load host key \"%s\"",
1938 options.host_key_files[i]);
1939 if (pubkey != NULL && key != NULL) {
1940 if (!sshkey_equal(pubkey, key)) {
1941 error("Public key for %s does not match "
1942 "private key", options.host_key_files[i]);
1943 sshkey_free(pubkey);
1944 pubkey = NULL;
1945 }
1946 }
1947 if (pubkey == NULL && key != NULL) {
1948 if ((r = sshkey_from_private(key, &pubkey)) != 0)
1949 fatal_r(r, "Could not demote key: \"%s\"",
1950 options.host_key_files[i]);
1951 }
1952 if (pubkey != NULL && (r = sshkey_check_rsa_length(pubkey,
1953 options.required_rsa_size)) != 0) {
1954 error_fr(r, "Host key %s", options.host_key_files[i]);
1955 sshkey_free(pubkey);
1956 sshkey_free(key);
1957 continue;
1958 }
1959 sensitive_data.host_keys[i] = key;
1960 sensitive_data.host_pubkeys[i] = pubkey;
1961
1962 if (key == NULL && pubkey != NULL && have_agent) {
1963 debug("will rely on agent for hostkey %s",
1964 options.host_key_files[i]);
1965 keytype = pubkey->type;
1966 } else if (key != NULL) {
1967 keytype = key->type;
1968 accumulate_host_timing_secret(cfg, key);
1969 } else {
1970 do_log2(ll, "Unable to load host key: %s",
1971 options.host_key_files[i]);
1972 sensitive_data.host_keys[i] = NULL;
1973 sensitive_data.host_pubkeys[i] = NULL;
1974 continue;
1975 }
1976
1977 switch (keytype) {
1978 case KEY_RSA:
1979 case KEY_DSA:
1980 case KEY_ECDSA:
1981 case KEY_ED25519:
1982 case KEY_ECDSA_SK:
1983 case KEY_ED25519_SK:
1984 case KEY_XMSS:
1985 if (have_agent || key != NULL)
1986 sensitive_data.have_ssh2_key = 1;
1987 break;
1988 }
1989 if ((fp = sshkey_fingerprint(pubkey, options.fingerprint_hash,
1990 SSH_FP_DEFAULT)) == NULL)
1991 fatal("sshkey_fingerprint failed");
1992 debug("%s host key #%d: %s %s",
1993 key ? "private" : "agent", i, sshkey_ssh_name(pubkey), fp);
1994 free(fp);
1995 }
1996 accumulate_host_timing_secret(cfg, NULL);
1997 if (!sensitive_data.have_ssh2_key) {
1998 logit("sshd: no hostkeys available -- exiting.");
1999 exit(1);
2000 }
2001
2002 /*
2003 * Load certificates. They are stored in an array at identical
2004 * indices to the public keys that they relate to.
2005 */
2006 sensitive_data.host_certificates = xcalloc(options.num_host_key_files,
2007 sizeof(struct sshkey *));
2008 for (i = 0; i < options.num_host_key_files; i++)
2009 sensitive_data.host_certificates[i] = NULL;
2010
2011 for (i = 0; i < options.num_host_cert_files; i++) {
2012 if (options.host_cert_files[i] == NULL)
2013 continue;
2014 if ((r = sshkey_load_public(options.host_cert_files[i],
2015 &key, NULL)) != 0) {
2016 error_r(r, "Could not load host certificate \"%s\"",
2017 options.host_cert_files[i]);
2018 continue;
2019 }
2020 if (!sshkey_is_cert(key)) {
2021 error("Certificate file is not a certificate: %s",
2022 options.host_cert_files[i]);
2023 sshkey_free(key);
2024 continue;
2025 }
2026 /* Find matching private key */
2027 for (j = 0; j < options.num_host_key_files; j++) {
2028 if (sshkey_equal_public(key,
2029 sensitive_data.host_pubkeys[j])) {
2030 sensitive_data.host_certificates[j] = key;
2031 break;
2032 }
2033 }
2034 if (j >= options.num_host_key_files) {
2035 error("No matching private key for certificate: %s",
2036 options.host_cert_files[i]);
2037 sshkey_free(key);
2038 continue;
2039 }
2040 sensitive_data.host_certificates[j] = key;
2041 debug("host certificate: #%u type %d %s", j, key->type,
2042 sshkey_type(key));
2043 }
2044
2045 if (privsep_chroot) {
2046 struct stat st;
2047
2048 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) ||
2049 (S_ISDIR(st.st_mode) == 0))
2050 fatal("Missing privilege separation directory: %s",
2051 _PATH_PRIVSEP_CHROOT_DIR);
2052
2053 #ifdef HAVE_CYGWIN
2054 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
2055 (st.st_uid != getuid () ||
2056 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0))
2057 #else
2058 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)
2059 #endif
2060 fatal("%s must be owned by root and not group or "
2061 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR);
2062 }
2063
2064 if (test_flag > 1)
2065 print_config(ssh, connection_info);
2066
2067 /* Configuration looks good, so exit if in test mode. */
2068 if (test_flag)
2069 exit(0);
2070
2071 /*
2072 * Clear out any supplemental groups we may have inherited. This
2073 * prevents inadvertent creation of files with bad modes (in the
2074 * portable version at least, it's certainly possible for PAM
2075 * to create a file, and we can't control the code in every
2076 * module which might be used).
2077 */
2078 if (setgroups(0, NULL) < 0)
2079 debug("setgroups() failed: %.200s", strerror(errno));
2080
2081 if (rexec_flag) {
2082 if (rexec_argc < 0)
2083 fatal("rexec_argc %d < 0", rexec_argc);
2084 rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *));
2085 for (i = 0; i < (u_int)rexec_argc; i++) {
2086 debug("rexec_argv[%d]='%s'", i, saved_argv[i]);
2087 rexec_argv[i] = saved_argv[i];
2088 }
2089 rexec_argv[rexec_argc] = "-R";
2090 rexec_argv[rexec_argc + 1] = NULL;
2091 }
2092 listener_proctitle = prepare_proctitle(ac, av);
2093
2094 /* Ensure that umask disallows at least group and world write */
2095 new_umask = umask(0077) | 0022;
2096 (void) umask(new_umask);
2097
2098 /* Initialize the log (it is reinitialized below in case we forked). */
2099 if (debug_flag && (!inetd_flag || rexeced_flag))
2100 log_stderr = 1;
2101 log_init(__progname, options.log_level,
2102 options.log_facility, log_stderr);
2103 for (i = 0; i < options.num_log_verbose; i++)
2104 log_verbose_add(options.log_verbose[i]);
2105
2106 /*
2107 * If not in debugging mode, not started from inetd and not already
2108 * daemonized (eg re-exec via SIGHUP), disconnect from the controlling
2109 * terminal, and fork. The original process exits.
2110 */
2111 already_daemon = daemonized();
2112 if (!(debug_flag || inetd_flag || no_daemon_flag || already_daemon)) {
2113
2114 if (daemon(0, 0) == -1)
2115 fatal("daemon() failed: %.200s", strerror(errno));
2116
2117 disconnect_controlling_tty();
2118 }
2119 /* Reinitialize the log (because of the fork above). */
2120 log_init(__progname, options.log_level, options.log_facility, log_stderr);
2121
2122 /* Avoid killing the process in high-pressure swapping environments. */
2123 if (!inetd_flag && madvise(NULL, 0, MADV_PROTECT) != 0)
2124 debug("madvise(): %.200s", strerror(errno));
2125
2126 /*
2127 * Chdir to the root directory so that the current disk can be
2128 * unmounted if desired.
2129 */
2130 if (chdir("/") == -1)
2131 error("chdir(\"/\"): %s", strerror(errno));
2132
2133 /* ignore SIGPIPE */
2134 ssh_signal(SIGPIPE, SIG_IGN);
2135
2136 /* Get a connection, either from inetd or a listening TCP socket */
2137 if (inetd_flag) {
2138 server_accept_inetd(&sock_in, &sock_out);
2139 } else {
2140 platform_pre_listen();
2141 server_listen();
2142
2143 ssh_signal(SIGHUP, sighup_handler);
2144 ssh_signal(SIGCHLD, main_sigchld_handler);
2145 ssh_signal(SIGTERM, sigterm_handler);
2146 ssh_signal(SIGQUIT, sigterm_handler);
2147
2148 /*
2149 * Write out the pid file after the sigterm handler
2150 * is setup and the listen sockets are bound
2151 */
2152 if (options.pid_file != NULL && !debug_flag) {
2153 FILE *f = fopen(options.pid_file, "w");
2154
2155 if (f == NULL) {
2156 error("Couldn't create pid file \"%s\": %s",
2157 options.pid_file, strerror(errno));
2158 } else {
2159 fprintf(f, "%ld\n", (long) getpid());
2160 fclose(f);
2161 }
2162 }
2163
2164 /* Accept a connection and return in a forked child */
2165 server_accept_loop(&sock_in, &sock_out,
2166 &newsock, config_s);
2167 }
2168
2169 /* This is the child processing a new connection. */
2170 setproctitle("%s", "[accepted]");
2171
2172 /*
2173 * Create a new session and process group since the 4.4BSD
2174 * setlogin() affects the entire process group. We don't
2175 * want the child to be able to affect the parent.
2176 */
2177 if (!debug_flag && !inetd_flag && setsid() == -1)
2178 error("setsid: %.100s", strerror(errno));
2179
2180 if (rexec_flag) {
2181 debug("rexec start in %d out %d newsock %d pipe %d sock %d",
2182 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
2183 if (dup2(newsock, STDIN_FILENO) == -1)
2184 debug3_f("dup2 stdin: %s", strerror(errno));
2185 if (dup2(STDIN_FILENO, STDOUT_FILENO) == -1)
2186 debug3_f("dup2 stdout: %s", strerror(errno));
2187 if (startup_pipe == -1)
2188 close(REEXEC_STARTUP_PIPE_FD);
2189 else if (startup_pipe != REEXEC_STARTUP_PIPE_FD) {
2190 if (dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD) == -1)
2191 debug3_f("dup2 startup_p: %s", strerror(errno));
2192 close(startup_pipe);
2193 startup_pipe = REEXEC_STARTUP_PIPE_FD;
2194 }
2195
2196 if (dup2(config_s[1], REEXEC_CONFIG_PASS_FD) == -1)
2197 debug3_f("dup2 config_s: %s", strerror(errno));
2198 close(config_s[1]);
2199
2200 ssh_signal(SIGHUP, SIG_IGN); /* avoid reset to SIG_DFL */
2201 execv(rexec_argv[0], rexec_argv);
2202
2203 /* Reexec has failed, fall back and continue */
2204 error("rexec of %s failed: %s", rexec_argv[0], strerror(errno));
2205 recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL);
2206 log_init(__progname, options.log_level,
2207 options.log_facility, log_stderr);
2208
2209 /* Clean up fds */
2210 close(REEXEC_CONFIG_PASS_FD);
2211 newsock = sock_out = sock_in = dup(STDIN_FILENO);
2212 if (stdfd_devnull(1, 1, 0) == -1)
2213 error_f("stdfd_devnull failed");
2214 debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d",
2215 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
2216 }
2217
2218 /* Executed child processes don't need these. */
2219 fcntl(sock_out, F_SETFD, FD_CLOEXEC);
2220 fcntl(sock_in, F_SETFD, FD_CLOEXEC);
2221
2222 /* We will not restart on SIGHUP since it no longer makes sense. */
2223 ssh_signal(SIGALRM, SIG_DFL);
2224 ssh_signal(SIGHUP, SIG_DFL);
2225 ssh_signal(SIGTERM, SIG_DFL);
2226 ssh_signal(SIGQUIT, SIG_DFL);
2227 ssh_signal(SIGCHLD, SIG_DFL);
2228 ssh_signal(SIGINT, SIG_DFL);
2229
2230 #ifdef __FreeBSD__
2231 /*
2232 * Initialize the resolver. This may not happen automatically
2233 * before privsep chroot().
2234 */
2235 if ((_res.options & RES_INIT) == 0) {
2236 debug("res_init()");
2237 res_init();
2238 }
2239 #ifdef GSSAPI
2240 /*
2241 * Force GSS-API to parse its configuration and load any
2242 * mechanism plugins.
2243 */
2244 {
2245 gss_OID_set mechs;
2246 OM_uint32 minor_status;
2247 gss_indicate_mechs(&minor_status, &mechs);
2248 gss_release_oid_set(&minor_status, &mechs);
2249 }
2250 #endif
2251 #endif
2252
2253 /*
2254 * Register our connection. This turns encryption off because we do
2255 * not have a key.
2256 */
2257 if ((ssh = ssh_packet_set_connection(NULL, sock_in, sock_out)) == NULL)
2258 fatal("Unable to create connection");
2259 the_active_state = ssh;
2260 ssh_packet_set_server(ssh);
2261
2262 check_ip_options(ssh);
2263
2264 /* Prepare the channels layer */
2265 channel_init_channels(ssh);
2266 channel_set_af(ssh, options.address_family);
2267 process_channel_timeouts(ssh, &options);
2268 process_permitopen(ssh, &options);
2269
2270 /* Set SO_KEEPALIVE if requested. */
2271 if (options.tcp_keep_alive && ssh_packet_connection_is_on_socket(ssh) &&
2272 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) == -1)
2273 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
2274
2275 if ((remote_port = ssh_remote_port(ssh)) < 0) {
2276 debug("ssh_remote_port failed");
2277 cleanup_exit(255);
2278 }
2279
2280 if (options.routing_domain != NULL)
2281 set_process_rdomain(ssh, options.routing_domain);
2282
2283 /*
2284 * The rest of the code depends on the fact that
2285 * ssh_remote_ipaddr() caches the remote ip, even if
2286 * the socket goes away.
2287 */
2288 remote_ip = ssh_remote_ipaddr(ssh);
2289
2290 #ifdef HAVE_LOGIN_CAP
2291 /* Also caches remote hostname for sandboxed child. */
2292 auth_get_canonical_hostname(ssh, options.use_dns);
2293 #endif
2294
2295 #ifdef SSH_AUDIT_EVENTS
2296 audit_connection_from(remote_ip, remote_port);
2297 #endif
2298
2299 rdomain = ssh_packet_rdomain_in(ssh);
2300
2301 /* Log the connection. */
2302 laddr = get_local_ipaddr(sock_in);
2303 verbose("Connection from %s port %d on %s port %d%s%s%s",
2304 remote_ip, remote_port, laddr, ssh_local_port(ssh),
2305 rdomain == NULL ? "" : " rdomain \"",
2306 rdomain == NULL ? "" : rdomain,
2307 rdomain == NULL ? "" : "\"");
2308 free(laddr);
2309
2310 /*
2311 * We don't want to listen forever unless the other side
2312 * successfully authenticates itself. So we set up an alarm which is
2313 * cleared after successful authentication. A limit of zero
2314 * indicates no limit. Note that we don't set the alarm in debugging
2315 * mode; it is just annoying to have the server exit just when you
2316 * are about to discover the bug.
2317 */
2318 ssh_signal(SIGALRM, grace_alarm_handler);
2319 if (!debug_flag)
2320 alarm(options.login_grace_time);
2321
2322 if ((r = kex_exchange_identification(ssh, -1,
2323 options.version_addendum)) != 0)
2324 sshpkt_fatal(ssh, r, "banner exchange");
2325
2326 ssh_packet_set_nonblocking(ssh);
2327
2328 /* allocate authentication context */
2329 authctxt = xcalloc(1, sizeof(*authctxt));
2330 ssh->authctxt = authctxt;
2331
2332 authctxt->loginmsg = loginmsg;
2333
2334 /* XXX global for cleanup, access from other modules */
2335 the_authctxt = authctxt;
2336
2337 /* Set default key authentication options */
2338 if ((auth_opts = sshauthopt_new_with_keys_defaults()) == NULL)
2339 fatal("allocation failed");
2340
2341 /* prepare buffer to collect messages to display to user after login */
2342 if ((loginmsg = sshbuf_new()) == NULL)
2343 fatal_f("sshbuf_new failed");
2344 auth_debug_reset();
2345
2346 BLACKLIST_INIT();
2347
2348 if (use_privsep) {
2349 if (privsep_preauth(ssh) == 1)
2350 goto authenticated;
2351 } else if (have_agent) {
2352 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) {
2353 error_r(r, "Unable to get agent socket");
2354 have_agent = 0;
2355 }
2356 }
2357
2358 /* perform the key exchange */
2359 /* authenticate user and start session */
2360 do_ssh2_kex(ssh);
2361 do_authentication2(ssh);
2362
2363 /*
2364 * If we use privilege separation, the unprivileged child transfers
2365 * the current keystate and exits
2366 */
2367 if (use_privsep) {
2368 mm_send_keystate(ssh, pmonitor);
2369 ssh_packet_clear_keys(ssh);
2370 exit(0);
2371 }
2372
2373 authenticated:
2374 /*
2375 * Cancel the alarm we set to limit the time taken for
2376 * authentication.
2377 */
2378 alarm(0);
2379 ssh_signal(SIGALRM, SIG_DFL);
2380 authctxt->authenticated = 1;
2381 if (startup_pipe != -1) {
2382 close(startup_pipe);
2383 startup_pipe = -1;
2384 }
2385
2386 #ifdef SSH_AUDIT_EVENTS
2387 audit_event(ssh, SSH_AUTH_SUCCESS);
2388 #endif
2389
2390 #ifdef GSSAPI
2391 if (options.gss_authentication) {
2392 temporarily_use_uid(authctxt->pw);
2393 ssh_gssapi_storecreds();
2394 restore_uid();
2395 }
2396 #endif
2397 #ifdef USE_PAM
2398 if (options.use_pam) {
2399 do_pam_setcred(1);
2400 do_pam_session(ssh);
2401 }
2402 #endif
2403
2404 /*
2405 * In privilege separation, we fork another child and prepare
2406 * file descriptor passing.
2407 */
2408 if (use_privsep) {
2409 privsep_postauth(ssh, authctxt);
2410 /* the monitor process [priv] will not return */
2411 }
2412
2413 ssh_packet_set_timeout(ssh, options.client_alive_interval,
2414 options.client_alive_count_max);
2415
2416 /* Try to send all our hostkeys to the client */
2417 notify_hostkeys(ssh);
2418
2419 /* Start session. */
2420 do_authenticated(ssh, authctxt);
2421
2422 /* The connection has been terminated. */
2423 ssh_packet_get_bytes(ssh, &ibytes, &obytes);
2424 verbose("Transferred: sent %llu, received %llu bytes",
2425 (unsigned long long)obytes, (unsigned long long)ibytes);
2426
2427 verbose("Closing connection to %.500s port %d", remote_ip, remote_port);
2428
2429 #ifdef USE_PAM
2430 if (options.use_pam)
2431 finish_pam();
2432 #endif /* USE_PAM */
2433
2434 #ifdef SSH_AUDIT_EVENTS
2435 PRIVSEP(audit_event(ssh, SSH_CONNECTION_CLOSE));
2436 #endif
2437
2438 ssh_packet_close(ssh);
2439
2440 if (use_privsep)
2441 mm_terminate();
2442
2443 exit(0);
2444 }
2445
2446 int
2447 sshd_hostkey_sign(struct ssh *ssh, struct sshkey *privkey,
2448 struct sshkey *pubkey, u_char **signature, size_t *slenp,
2449 const u_char *data, size_t dlen, const char *alg)
2450 {
2451 int r;
2452
2453 if (use_privsep) {
2454 if (privkey) {
2455 if (mm_sshkey_sign(ssh, privkey, signature, slenp,
2456 data, dlen, alg, options.sk_provider, NULL,
2457 ssh->compat) < 0)
2458 fatal_f("privkey sign failed");
2459 } else {
2460 if (mm_sshkey_sign(ssh, pubkey, signature, slenp,
2461 data, dlen, alg, options.sk_provider, NULL,
2462 ssh->compat) < 0)
2463 fatal_f("pubkey sign failed");
2464 }
2465 } else {
2466 if (privkey) {
2467 if (sshkey_sign(privkey, signature, slenp, data, dlen,
2468 alg, options.sk_provider, NULL, ssh->compat) < 0)
2469 fatal_f("privkey sign failed");
2470 } else {
2471 if ((r = ssh_agent_sign(auth_sock, pubkey,
2472 signature, slenp, data, dlen, alg,
2473 ssh->compat)) != 0) {
2474 fatal_fr(r, "agent sign failed");
2475 }
2476 }
2477 }
2478 return 0;
2479 }
2480
2481 /* SSH2 key exchange */
2482 static void
2483 do_ssh2_kex(struct ssh *ssh)
2484 {
2485 char *hkalgs = NULL, *myproposal[PROPOSAL_MAX];
2486 const char *compression = NULL;
2487 struct kex *kex;
2488 int r;
2489
2490 if (options.rekey_limit || options.rekey_interval)
2491 ssh_packet_set_rekey_limits(ssh, options.rekey_limit,
2492 options.rekey_interval);
2493
2494 if (options.compression == COMP_NONE)
2495 compression = "none";
2496 hkalgs = list_hostkey_types();
2497
2498 kex_proposal_populate_entries(ssh, myproposal, options.kex_algorithms,
2499 options.ciphers, options.macs, compression, hkalgs);
2500
2501 free(hkalgs);
2502
2503 /* start key exchange */
2504 if ((r = kex_setup(ssh, myproposal)) != 0)
2505 fatal_r(r, "kex_setup");
2506 kex_set_server_sig_algs(ssh, options.pubkey_accepted_algos);
2507 kex = ssh->kex;
2508
2509 #ifdef WITH_OPENSSL
2510 kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server;
2511 kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server;
2512 kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server;
2513 kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server;
2514 kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server;
2515 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
2516 kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
2517 # ifdef OPENSSL_HAS_ECC
2518 kex->kex[KEX_ECDH_SHA2] = kex_gen_server;
2519 # endif
2520 #endif
2521 kex->kex[KEX_C25519_SHA256] = kex_gen_server;
2522 kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server;
2523 kex->load_host_public_key=&get_hostkey_public_by_type;
2524 kex->load_host_private_key=&get_hostkey_private_by_type;
2525 kex->host_key_index=&get_hostkey_index;
2526 kex->sign = sshd_hostkey_sign;
2527
2528 ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &kex->done);
2529 kex_proposal_free_entries(myproposal);
2530
2531 #ifdef DEBUG_KEXDH
2532 /* send 1st encrypted/maced/compressed message */
2533 if ((r = sshpkt_start(ssh, SSH2_MSG_IGNORE)) != 0 ||
2534 (r = sshpkt_put_cstring(ssh, "markus")) != 0 ||
2535 (r = sshpkt_send(ssh)) != 0 ||
2536 (r = ssh_packet_write_wait(ssh)) != 0)
2537 fatal_fr(r, "send test");
2538 #endif
2539 debug("KEX done");
2540 }
2541
2542 /* server specific fatal cleanup */
2543 void
2544 cleanup_exit(int i)
2545 {
2546 if (the_active_state != NULL && the_authctxt != NULL) {
2547 do_cleanup(the_active_state, the_authctxt);
2548 if (use_privsep && privsep_is_preauth &&
2549 pmonitor != NULL && pmonitor->m_pid > 1) {
2550 debug("Killing privsep child %d", pmonitor->m_pid);
2551 if (kill(pmonitor->m_pid, SIGKILL) != 0 &&
2552 errno != ESRCH) {
2553 error_f("kill(%d): %s", pmonitor->m_pid,
2554 strerror(errno));
2555 }
2556 }
2557 }
2558 #ifdef SSH_AUDIT_EVENTS
2559 /* done after do_cleanup so it can cancel the PAM auth 'thread' */
2560 if (the_active_state != NULL && (!use_privsep || mm_is_monitor()))
2561 audit_event(the_active_state, SSH_CONNECTION_ABANDON);
2562 #endif
2563 _exit(i);
2564 }
2565