1 /* $OpenBSD: sshd.c,v 1.617 2025/04/07 08:12:22 dtucker Exp $ */
2 /*
3 * Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved.
4 * Copyright (c) 2002 Niels Provos. All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27 #include "includes.h"
28
29 #include <sys/types.h>
30 #include <sys/ioctl.h>
31 #include <sys/mman.h>
32 #include <sys/socket.h>
33 #ifdef HAVE_SYS_STAT_H
34 # include <sys/stat.h>
35 #endif
36 #ifdef HAVE_SYS_TIME_H
37 # include <sys/time.h>
38 #endif
39 #include "openbsd-compat/sys-tree.h"
40 #include "openbsd-compat/sys-queue.h"
41 #include <sys/wait.h>
42 #include <sys/utsname.h>
43
44 #include <errno.h>
45 #include <fcntl.h>
46 #include <netdb.h>
47 #ifdef HAVE_PATHS_H
48 #include <paths.h>
49 #endif
50 #include <grp.h>
51 #ifdef HAVE_POLL_H
52 #include <poll.h>
53 #endif
54 #include <pwd.h>
55 #include <signal.h>
56 #include <stdarg.h>
57 #include <time.h>
58 #include <stdio.h>
59 #include <stdlib.h>
60 #include <string.h>
61 #include <unistd.h>
62 #include <limits.h>
63
64 #ifdef WITH_OPENSSL
65 #include <openssl/evp.h>
66 #include <openssl/rand.h>
67 #include "openbsd-compat/openssl-compat.h"
68 #endif
69
70 #ifdef HAVE_SECUREWARE
71 #include <sys/security.h>
72 #include <prot.h>
73 #endif
74
75 #ifdef __FreeBSD__
76 #include <resolv.h>
77 #if defined(GSSAPI) && defined(HAVE_GSSAPI_GSSAPI_H)
78 #include <gssapi/gssapi.h>
79 #elif defined(GSSAPI) && defined(HAVE_GSSAPI_H)
80 #include <gssapi.h>
81 #endif
82 #endif
83
84 #include "xmalloc.h"
85 #include "ssh.h"
86 #include "sshpty.h"
87 #include "log.h"
88 #include "sshbuf.h"
89 #include "misc.h"
90 #include "servconf.h"
91 #include "compat.h"
92 #include "digest.h"
93 #include "sshkey.h"
94 #include "authfile.h"
95 #include "pathnames.h"
96 #include "canohost.h"
97 #include "hostfile.h"
98 #include "auth.h"
99 #include "authfd.h"
100 #include "msg.h"
101 #include "version.h"
102 #include "ssherr.h"
103 #include "sk-api.h"
104 #include "addr.h"
105 #include "srclimit.h"
106 #include "atomicio.h"
107
108 #ifdef LIBWRAP
109 #include <tcpd.h>
110 #include <syslog.h>
111 #endif /* LIBWRAP */
112
113 /* Re-exec fds */
114 #define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1)
115 #define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 2)
116 #define REEXEC_MIN_FREE_FD (STDERR_FILENO + 3)
117
118 extern char *__progname;
119
120 /* Server configuration options. */
121 ServerOptions options;
122
123 /*
124 * Debug mode flag. This can be set on the command line. If debug
125 * mode is enabled, extra debugging output will be sent to the system
126 * log, the daemon will not go to background, and will exit after processing
127 * the first connection.
128 */
129 int debug_flag = 0;
130
131 /* Saved arguments to main(). */
132 static char **saved_argv;
133 static int saved_argc;
134
135 /*
136 * The sockets that the server is listening; this is used in the SIGHUP
137 * signal handler.
138 */
139 #define MAX_LISTEN_SOCKS 16
140 static int listen_socks[MAX_LISTEN_SOCKS];
141 static int num_listen_socks = 0;
142
143 /*
144 * Any really sensitive data in the application is contained in this
145 * structure. The idea is that this structure could be locked into memory so
146 * that the pages do not get written into swap. However, there are some
147 * problems. The private key contains BIGNUMs, and we do not (in principle)
148 * have access to the internals of them, and locking just the structure is
149 * not very useful. Currently, memory locking is not implemented.
150 */
151 struct {
152 struct sshkey **host_keys; /* all private host keys */
153 struct sshkey **host_pubkeys; /* all public host keys */
154 struct sshkey **host_certificates; /* all public host certificates */
155 int have_ssh2_key;
156 } sensitive_data;
157
158 /* This is set to true when a signal is received. */
159 static volatile sig_atomic_t received_siginfo = 0;
160 static volatile sig_atomic_t received_sigchld = 0;
161 static volatile sig_atomic_t received_sighup = 0;
162 static volatile sig_atomic_t received_sigterm = 0;
163
164 /* record remote hostname or ip */
165 u_int utmp_len = HOST_NAME_MAX+1;
166
167 /*
168 * The early_child/children array below is used for tracking children of the
169 * listening sshd process early in their lifespans, before they have
170 * completed authentication. This tracking is needed for four things:
171 *
172 * 1) Implementing the MaxStartups limit of concurrent unauthenticated
173 * connections.
174 * 2) Avoiding a race condition for SIGHUP processing, where child processes
175 * may have listen_socks open that could collide with main listener process
176 * after it restarts.
177 * 3) Ensuring that rexec'd sshd processes have received their initial state
178 * from the parent listen process before handling SIGHUP.
179 * 4) Tracking and logging unsuccessful exits from the preauth sshd monitor,
180 * including and especially those for LoginGraceTime timeouts.
181 *
182 * Child processes signal that they have completed closure of the listen_socks
183 * and (if applicable) received their rexec state by sending a char over their
184 * sock.
185 *
186 * Child processes signal that authentication has completed by sending a
187 * second char over the socket before closing it, otherwise the listener will
188 * continue tracking the child (and using up a MaxStartups slot) until the
189 * preauth subprocess exits, whereupon the listener will log its exit status.
190 * preauth processes will exit with a status of EXIT_LOGIN_GRACE to indicate
191 * they did not authenticate before the LoginGraceTime alarm fired.
192 */
193 struct early_child {
194 int pipefd;
195 int early; /* Indicates child closed listener */
196 char *id; /* human readable connection identifier */
197 pid_t pid;
198 struct xaddr addr;
199 int have_addr;
200 int status, have_status;
201 struct sshbuf *config;
202 struct sshbuf *keys;
203 };
204 static struct early_child *children;
205 static int children_active;
206
207 /* sshd_config buffer */
208 struct sshbuf *cfg;
209 struct sshbuf *config; /* packed */
210
211 /* Included files from the configuration file */
212 struct include_list includes = TAILQ_HEAD_INITIALIZER(includes);
213
214 /* message to be displayed after login */
215 struct sshbuf *loginmsg;
216
217 /* Unprivileged user */
218 struct passwd *privsep_pw = NULL;
219
220 static char *listener_proctitle;
221
222 /*
223 * Close all listening sockets
224 */
225 static void
close_listen_socks(void)226 close_listen_socks(void)
227 {
228 int i;
229
230 for (i = 0; i < num_listen_socks; i++)
231 close(listen_socks[i]);
232 num_listen_socks = 0;
233 }
234
235 /* Allocate and initialise the children array */
236 static void
child_alloc(void)237 child_alloc(void)
238 {
239 int i;
240
241 children = xcalloc(options.max_startups, sizeof(*children));
242 for (i = 0; i < options.max_startups; i++) {
243 children[i].pipefd = -1;
244 children[i].pid = -1;
245 }
246 }
247
248 /* Register a new connection in the children array; child pid comes later */
249 static struct early_child *
child_register(int pipefd,int sockfd)250 child_register(int pipefd, int sockfd)
251 {
252 int i, lport, rport;
253 char *laddr = NULL, *raddr = NULL;
254 struct early_child *child = NULL;
255 struct sockaddr_storage addr;
256 socklen_t addrlen = sizeof(addr);
257 struct sockaddr *sa = (struct sockaddr *)&addr;
258
259 for (i = 0; i < options.max_startups; i++) {
260 if (children[i].pipefd != -1 ||
261 children[i].config != NULL ||
262 children[i].keys != NULL ||
263 children[i].pid > 0)
264 continue;
265 child = &(children[i]);
266 break;
267 }
268 if (child == NULL) {
269 fatal_f("error: accepted connection when all %d child "
270 " slots full", options.max_startups);
271 }
272 child->pipefd = pipefd;
273 child->early = 1;
274 if ((child->config = sshbuf_fromb(config)) == NULL)
275 fatal_f("sshbuf_fromb failed");
276 /* record peer address, if available */
277 if (getpeername(sockfd, sa, &addrlen) == 0 &&
278 addr_sa_to_xaddr(sa, addrlen, &child->addr) == 0)
279 child->have_addr = 1;
280 /* format peer address string for logs */
281 if ((lport = get_local_port(sockfd)) == 0 ||
282 (rport = get_peer_port(sockfd)) == 0) {
283 /* Not a TCP socket */
284 raddr = get_peer_ipaddr(sockfd);
285 xasprintf(&child->id, "connection from %s", raddr);
286 } else {
287 laddr = get_local_ipaddr(sockfd);
288 raddr = get_peer_ipaddr(sockfd);
289 xasprintf(&child->id, "connection from %s to %s", raddr, laddr);
290 }
291 free(laddr);
292 free(raddr);
293 if (++children_active > options.max_startups)
294 fatal_f("internal error: more children than max_startups");
295
296 return child;
297 }
298
299 /*
300 * Finally free a child entry. Don't call this directly.
301 */
302 static void
child_finish(struct early_child * child)303 child_finish(struct early_child *child)
304 {
305 if (children_active == 0)
306 fatal_f("internal error: children_active underflow");
307 if (child->pipefd != -1)
308 close(child->pipefd);
309 sshbuf_free(child->config);
310 sshbuf_free(child->keys);
311 free(child->id);
312 memset(child, '\0', sizeof(*child));
313 child->pipefd = -1;
314 child->pid = -1;
315 children_active--;
316 }
317
318 /*
319 * Close a child's pipe. This will not stop tracking the child immediately
320 * (it will still be tracked for waitpid()) unless force_final is set, or
321 * child has already exited.
322 */
323 static void
child_close(struct early_child * child,int force_final,int quiet)324 child_close(struct early_child *child, int force_final, int quiet)
325 {
326 if (!quiet)
327 debug_f("enter%s", force_final ? " (forcing)" : "");
328 if (child->pipefd != -1) {
329 close(child->pipefd);
330 child->pipefd = -1;
331 }
332 if (child->pid == -1 || force_final)
333 child_finish(child);
334 }
335
336 /* Record a child exit. Safe to call from signal handlers */
337 static void
child_exit(pid_t pid,int status)338 child_exit(pid_t pid, int status)
339 {
340 int i;
341
342 if (children == NULL || pid <= 0)
343 return;
344 for (i = 0; i < options.max_startups; i++) {
345 if (children[i].pid == pid) {
346 children[i].have_status = 1;
347 children[i].status = status;
348 break;
349 }
350 }
351 }
352
353 /*
354 * Reap a child entry that has exited, as previously flagged
355 * using child_exit().
356 * Handles logging of exit condition and will finalise the child if its pipe
357 * had already been closed.
358 */
359 static void
child_reap(struct early_child * child)360 child_reap(struct early_child *child)
361 {
362 LogLevel level = SYSLOG_LEVEL_DEBUG1;
363 int was_crash, penalty_type = SRCLIMIT_PENALTY_NONE;
364 const char *child_status;
365
366 if (child->config)
367 child_status = " (sending config)";
368 else if (child->keys)
369 child_status = " (sending keys)";
370 else if (child->early)
371 child_status = " (early)";
372 else
373 child_status = "";
374
375 /* Log exit information */
376 if (WIFSIGNALED(child->status)) {
377 /*
378 * Increase logging for signals potentially associated
379 * with serious conditions.
380 */
381 if ((was_crash = signal_is_crash(WTERMSIG(child->status))))
382 level = SYSLOG_LEVEL_ERROR;
383 do_log2(level, "session process %ld for %s killed by "
384 "signal %d%s", (long)child->pid, child->id,
385 WTERMSIG(child->status), child_status);
386 if (was_crash)
387 penalty_type = SRCLIMIT_PENALTY_CRASH;
388 } else if (!WIFEXITED(child->status)) {
389 penalty_type = SRCLIMIT_PENALTY_CRASH;
390 error("session process %ld for %s terminated abnormally, "
391 "status=0x%x%s", (long)child->pid, child->id, child->status,
392 child_status);
393 } else {
394 /* Normal exit. We care about the status */
395 switch (WEXITSTATUS(child->status)) {
396 case 0:
397 debug3_f("preauth child %ld for %s completed "
398 "normally%s", (long)child->pid, child->id,
399 child_status);
400 break;
401 case EXIT_LOGIN_GRACE:
402 penalty_type = SRCLIMIT_PENALTY_GRACE_EXCEEDED;
403 logit("Timeout before authentication for %s, "
404 "pid = %ld%s", child->id, (long)child->pid,
405 child_status);
406 break;
407 case EXIT_CHILD_CRASH:
408 penalty_type = SRCLIMIT_PENALTY_CRASH;
409 logit("Session process %ld unpriv child crash for %s%s",
410 (long)child->pid, child->id, child_status);
411 break;
412 case EXIT_AUTH_ATTEMPTED:
413 penalty_type = SRCLIMIT_PENALTY_AUTHFAIL;
414 debug_f("preauth child %ld for %s exited "
415 "after unsuccessful auth attempt%s",
416 (long)child->pid, child->id, child_status);
417 break;
418 case EXIT_CONFIG_REFUSED:
419 penalty_type = SRCLIMIT_PENALTY_REFUSECONNECTION;
420 debug_f("preauth child %ld for %s prohibited by"
421 "RefuseConnection%s",
422 (long)child->pid, child->id, child_status);
423 break;
424 default:
425 penalty_type = SRCLIMIT_PENALTY_NOAUTH;
426 debug_f("preauth child %ld for %s exited "
427 "with status %d%s", (long)child->pid, child->id,
428 WEXITSTATUS(child->status), child_status);
429 break;
430 }
431 }
432
433 if (child->have_addr)
434 srclimit_penalise(&child->addr, penalty_type);
435
436 child->pid = -1;
437 child->have_status = 0;
438 if (child->pipefd == -1)
439 child_finish(child);
440 }
441
442 /* Reap all children that have exited; called after SIGCHLD */
443 static void
child_reap_all_exited(void)444 child_reap_all_exited(void)
445 {
446 int i;
447 pid_t pid;
448 int status;
449
450 if (children == NULL)
451 return;
452
453 for (;;) {
454 if ((pid = waitpid(-1, &status, WNOHANG)) == 0)
455 break;
456 else if (pid == -1) {
457 if (errno == EINTR || errno == EAGAIN)
458 continue;
459 if (errno != ECHILD)
460 error_f("waitpid: %s", strerror(errno));
461 break;
462 }
463 child_exit(pid, status);
464 }
465
466 for (i = 0; i < options.max_startups; i++) {
467 if (!children[i].have_status)
468 continue;
469 child_reap(&(children[i]));
470 }
471 }
472
473 static void
close_startup_pipes(void)474 close_startup_pipes(void)
475 {
476 int i;
477
478 if (children == NULL)
479 return;
480 for (i = 0; i < options.max_startups; i++) {
481 if (children[i].pipefd != -1)
482 child_close(&(children[i]), 1, 1);
483 }
484 }
485
486 /* Called after SIGINFO */
487 static void
show_info(void)488 show_info(void)
489 {
490 int i;
491 const char *child_status;
492
493 /* XXX print listening sockets here too */
494 if (children == NULL)
495 return;
496 logit("%d active startups", children_active);
497 for (i = 0; i < options.max_startups; i++) {
498 if (children[i].pipefd == -1 && children[i].pid <= 0)
499 continue;
500 if (children[i].config)
501 child_status = " (sending config)";
502 else if (children[i].keys)
503 child_status = " (sending keys)";
504 else if (children[i].early)
505 child_status = " (early)";
506 else
507 child_status = "";
508 logit("child %d: fd=%d pid=%ld %s%s", i, children[i].pipefd,
509 (long)children[i].pid, children[i].id, child_status);
510 }
511 srclimit_penalty_info();
512 }
513
514 /*
515 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
516 * the effect is to reread the configuration file (and to regenerate
517 * the server key).
518 */
519
520 static void
sighup_handler(int sig)521 sighup_handler(int sig)
522 {
523 received_sighup = 1;
524 }
525
526 /*
527 * Called from the main program after receiving SIGHUP.
528 * Restarts the server.
529 */
530 static void
sighup_restart(void)531 sighup_restart(void)
532 {
533 logit("Received SIGHUP; restarting.");
534 if (options.pid_file != NULL)
535 unlink(options.pid_file);
536 platform_pre_restart();
537 close_listen_socks();
538 close_startup_pipes();
539 ssh_signal(SIGHUP, SIG_IGN); /* will be restored after exec */
540 execv(saved_argv[0], saved_argv);
541 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
542 strerror(errno));
543 exit(1);
544 }
545
546 /*
547 * Generic signal handler for terminating signals in the master daemon.
548 */
549 static void
sigterm_handler(int sig)550 sigterm_handler(int sig)
551 {
552 received_sigterm = sig;
553 }
554
555 #ifdef SIGINFO
556 static void
siginfo_handler(int sig)557 siginfo_handler(int sig)
558 {
559 received_siginfo = 1;
560 }
561 #endif
562
563 static void
main_sigchld_handler(int sig)564 main_sigchld_handler(int sig)
565 {
566 received_sigchld = 1;
567 }
568
569 /*
570 * returns 1 if connection should be dropped, 0 otherwise.
571 * dropping starts at connection #max_startups_begin with a probability
572 * of (max_startups_rate/100). the probability increases linearly until
573 * all connections are dropped for startups > max_startups
574 */
575 static int
should_drop_connection(int startups)576 should_drop_connection(int startups)
577 {
578 int p, r;
579
580 if (startups < options.max_startups_begin)
581 return 0;
582 if (startups >= options.max_startups)
583 return 1;
584 if (options.max_startups_rate == 100)
585 return 1;
586
587 p = 100 - options.max_startups_rate;
588 p *= startups - options.max_startups_begin;
589 p /= options.max_startups - options.max_startups_begin;
590 p += options.max_startups_rate;
591 r = arc4random_uniform(100);
592
593 debug_f("p %d, r %d", p, r);
594 return (r < p) ? 1 : 0;
595 }
596
597 /*
598 * Check whether connection should be accepted by MaxStartups or for penalty.
599 * Returns 0 if the connection is accepted. If the connection is refused,
600 * returns 1 and attempts to send notification to client.
601 * Logs when the MaxStartups condition is entered or exited, and periodically
602 * while in that state.
603 */
604 static int
drop_connection(int sock,int startups,int notify_pipe)605 drop_connection(int sock, int startups, int notify_pipe)
606 {
607 static struct log_ratelimit_ctx ratelimit_maxstartups;
608 static struct log_ratelimit_ctx ratelimit_penalty;
609 static int init_done;
610 char *laddr, *raddr;
611 const char *reason = NULL, *subreason = NULL;
612 const char msg[] = "Not allowed at this time\r\n";
613 struct log_ratelimit_ctx *rl = NULL;
614 int ratelimited;
615 u_int ndropped;
616
617 if (!init_done) {
618 init_done = 1;
619 log_ratelimit_init(&ratelimit_maxstartups, 4, 60, 20, 5*60);
620 log_ratelimit_init(&ratelimit_penalty, 8, 60, 30, 2*60);
621 }
622
623 /* PerSourcePenalties */
624 if (!srclimit_penalty_check_allow(sock, &subreason)) {
625 reason = "PerSourcePenalties";
626 rl = &ratelimit_penalty;
627 } else {
628 /* MaxStartups */
629 if (!should_drop_connection(startups) &&
630 srclimit_check_allow(sock, notify_pipe) == 1)
631 return 0;
632 reason = "Maxstartups";
633 rl = &ratelimit_maxstartups;
634 }
635
636 laddr = get_local_ipaddr(sock);
637 raddr = get_peer_ipaddr(sock);
638 ratelimited = log_ratelimit(rl, time(NULL), NULL, &ndropped);
639 do_log2(ratelimited ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO,
640 "drop connection #%d from [%s]:%d on [%s]:%d %s",
641 startups,
642 raddr, get_peer_port(sock),
643 laddr, get_local_port(sock),
644 subreason != NULL ? subreason : reason);
645 free(laddr);
646 free(raddr);
647 if (ndropped != 0) {
648 logit("%s logging rate-limited: additional %u connections "
649 "dropped", reason, ndropped);
650 }
651
652 /* best-effort notification to client */
653 (void)write(sock, msg, sizeof(msg) - 1);
654 return 1;
655 }
656
657 static void
usage(void)658 usage(void)
659 {
660 if (options.version_addendum != NULL &&
661 *options.version_addendum != '\0')
662 fprintf(stderr, "%s %s, %s\n",
663 SSH_RELEASE,
664 options.version_addendum, SSH_OPENSSL_VERSION);
665 else
666 fprintf(stderr, "%s, %s\n",
667 SSH_RELEASE, SSH_OPENSSL_VERSION);
668 fprintf(stderr,
669 "usage: sshd [-46DdeGiqTtV] [-C connection_spec] [-c host_cert_file]\n"
670 " [-E log_file] [-f config_file] [-g login_grace_time]\n"
671 " [-h host_key_file] [-o option] [-p port] [-u len]\n"
672 );
673 exit(1);
674 }
675
676 static struct sshbuf *
pack_hostkeys(void)677 pack_hostkeys(void)
678 {
679 struct sshbuf *m = NULL, *keybuf = NULL, *hostkeys = NULL;
680 int r;
681 u_int i;
682 size_t len;
683
684 if ((m = sshbuf_new()) == NULL ||
685 (keybuf = sshbuf_new()) == NULL ||
686 (hostkeys = sshbuf_new()) == NULL)
687 fatal_f("sshbuf_new failed");
688
689 /* pack hostkeys into a string. Empty key slots get empty strings */
690 for (i = 0; i < options.num_host_key_files; i++) {
691 /* private key */
692 sshbuf_reset(keybuf);
693 if (sensitive_data.host_keys[i] != NULL &&
694 (r = sshkey_private_serialize(sensitive_data.host_keys[i],
695 keybuf)) != 0)
696 fatal_fr(r, "serialize hostkey private");
697 if ((r = sshbuf_put_stringb(hostkeys, keybuf)) != 0)
698 fatal_fr(r, "compose hostkey private");
699 /* public key */
700 if (sensitive_data.host_pubkeys[i] != NULL) {
701 if ((r = sshkey_puts(sensitive_data.host_pubkeys[i],
702 hostkeys)) != 0)
703 fatal_fr(r, "compose hostkey public");
704 } else {
705 if ((r = sshbuf_put_string(hostkeys, NULL, 0)) != 0)
706 fatal_fr(r, "compose hostkey empty public");
707 }
708 /* cert */
709 if (sensitive_data.host_certificates[i] != NULL) {
710 if ((r = sshkey_puts(
711 sensitive_data.host_certificates[i],
712 hostkeys)) != 0)
713 fatal_fr(r, "compose host cert");
714 } else {
715 if ((r = sshbuf_put_string(hostkeys, NULL, 0)) != 0)
716 fatal_fr(r, "compose host cert empty");
717 }
718 }
719
720 if ((r = sshbuf_put_u32(m, 0)) != 0 ||
721 (r = sshbuf_put_u8(m, 0)) != 0 ||
722 (r = sshbuf_put_stringb(m, hostkeys)) != 0)
723 fatal_fr(r, "compose message");
724 if ((len = sshbuf_len(m)) < 5 || len > 0xffffffff)
725 fatal_f("bad length %zu", len);
726 POKE_U32(sshbuf_mutable_ptr(m), len - 4);
727
728 sshbuf_free(keybuf);
729 sshbuf_free(hostkeys);
730 return m;
731 }
732
733 static struct sshbuf *
pack_config(struct sshbuf * conf)734 pack_config(struct sshbuf *conf)
735 {
736 struct sshbuf *m = NULL, *inc = NULL;
737 struct include_item *item = NULL;
738 size_t len;
739 int r;
740
741 debug3_f("d config len %zu", sshbuf_len(conf));
742
743 if ((m = sshbuf_new()) == NULL ||
744 (inc = sshbuf_new()) == NULL)
745 fatal_f("sshbuf_new failed");
746
747 /* pack includes into a string */
748 TAILQ_FOREACH(item, &includes, entry) {
749 if ((r = sshbuf_put_cstring(inc, item->selector)) != 0 ||
750 (r = sshbuf_put_cstring(inc, item->filename)) != 0 ||
751 (r = sshbuf_put_stringb(inc, item->contents)) != 0)
752 fatal_fr(r, "compose includes");
753 }
754
755 if ((r = sshbuf_put_u32(m, 0)) != 0 ||
756 (r = sshbuf_put_u8(m, 0)) != 0 ||
757 (r = sshbuf_put_stringb(m, conf)) != 0 ||
758 (r = sshbuf_put_u64(m, options.timing_secret)) != 0 ||
759 (r = sshbuf_put_stringb(m, inc)) != 0)
760 fatal_fr(r, "compose config");
761
762 if ((len = sshbuf_len(m)) < 5 || len > 0xffffffff)
763 fatal_f("bad length %zu", len);
764 POKE_U32(sshbuf_mutable_ptr(m), len - 4);
765
766 sshbuf_free(inc);
767
768 debug3_f("done");
769 return m;
770 }
771
772 /*
773 * Protocol from reexec master to child:
774 * uint32 size
775 * uint8 type (ignored)
776 * string configuration
777 * uint64 timing_secret
778 * string included_files[] {
779 * string selector
780 * string filename
781 * string contents
782 * }
783 * Second message
784 * uint32 size
785 * uint8 type (ignored)
786 * string host_keys[] {
787 * string private_key
788 * string public_key
789 * string certificate
790 * }
791 */
792 /*
793 * This function is used only if inet_flag or debug_flag is set,
794 * otherwise the data is sent from the main poll loop.
795 * It sends the config from a child process back to the parent.
796 * The parent will read the config after exec.
797 */
798 static void
send_rexec_state(int fd)799 send_rexec_state(int fd)
800 {
801 struct sshbuf *keys;
802 u_int mlen;
803 pid_t pid;
804
805 if ((pid = fork()) == -1)
806 fatal_f("fork failed: %s", strerror(errno));
807 if (pid != 0)
808 return;
809
810 debug3_f("entering fd = %d config len %zu", fd,
811 sshbuf_len(config));
812
813 mlen = sshbuf_len(config);
814 if (atomicio(vwrite, fd, sshbuf_mutable_ptr(config), mlen) != mlen)
815 error_f("write: %s", strerror(errno));
816
817 keys = pack_hostkeys();
818 mlen = sshbuf_len(keys);
819 if (atomicio(vwrite, fd, sshbuf_mutable_ptr(keys), mlen) != mlen)
820 error_f("write: %s", strerror(errno));
821
822 sshbuf_free(keys);
823 debug3_f("done");
824 exit(0);
825 }
826
827 /*
828 * Listen for TCP connections
829 */
830 static void
listen_on_addrs(struct listenaddr * la)831 listen_on_addrs(struct listenaddr *la)
832 {
833 int ret, listen_sock;
834 struct addrinfo *ai;
835 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
836
837 for (ai = la->addrs; ai; ai = ai->ai_next) {
838 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
839 continue;
840 if (num_listen_socks >= MAX_LISTEN_SOCKS)
841 fatal("Too many listen sockets. "
842 "Enlarge MAX_LISTEN_SOCKS");
843 if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen,
844 ntop, sizeof(ntop), strport, sizeof(strport),
845 NI_NUMERICHOST|NI_NUMERICSERV)) != 0) {
846 error("getnameinfo failed: %.100s",
847 ssh_gai_strerror(ret));
848 continue;
849 }
850 /* Create socket for listening. */
851 listen_sock = socket(ai->ai_family, ai->ai_socktype,
852 ai->ai_protocol);
853 if (listen_sock == -1) {
854 /* kernel may not support ipv6 */
855 verbose("socket: %.100s", strerror(errno));
856 continue;
857 }
858 if (set_nonblock(listen_sock) == -1) {
859 close(listen_sock);
860 continue;
861 }
862 if (fcntl(listen_sock, F_SETFD, FD_CLOEXEC) == -1) {
863 verbose("socket: CLOEXEC: %s", strerror(errno));
864 close(listen_sock);
865 continue;
866 }
867 /* Socket options */
868 set_reuseaddr(listen_sock);
869 if (la->rdomain != NULL &&
870 set_rdomain(listen_sock, la->rdomain) == -1) {
871 close(listen_sock);
872 continue;
873 }
874
875 /* Only communicate in IPv6 over AF_INET6 sockets. */
876 if (ai->ai_family == AF_INET6)
877 sock_set_v6only(listen_sock);
878
879 debug("Bind to port %s on %s.", strport, ntop);
880
881 /* Bind the socket to the desired port. */
882 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) == -1) {
883 error("Bind to port %s on %s failed: %.200s.",
884 strport, ntop, strerror(errno));
885 close(listen_sock);
886 continue;
887 }
888 listen_socks[num_listen_socks] = listen_sock;
889 num_listen_socks++;
890
891 /* Start listening on the port. */
892 if (listen(listen_sock, SSH_LISTEN_BACKLOG) == -1)
893 fatal("listen on [%s]:%s: %.100s",
894 ntop, strport, strerror(errno));
895 logit("Server listening on %s port %s%s%s.",
896 ntop, strport,
897 la->rdomain == NULL ? "" : " rdomain ",
898 la->rdomain == NULL ? "" : la->rdomain);
899 }
900 }
901
902 static void
server_listen(void)903 server_listen(void)
904 {
905 u_int i;
906
907 /* Initialise per-source limit tracking. */
908 srclimit_init(options.max_startups,
909 options.per_source_max_startups,
910 options.per_source_masklen_ipv4,
911 options.per_source_masklen_ipv6,
912 &options.per_source_penalty,
913 options.per_source_penalty_exempt);
914
915 for (i = 0; i < options.num_listen_addrs; i++) {
916 listen_on_addrs(&options.listen_addrs[i]);
917 freeaddrinfo(options.listen_addrs[i].addrs);
918 free(options.listen_addrs[i].rdomain);
919 memset(&options.listen_addrs[i], 0,
920 sizeof(options.listen_addrs[i]));
921 }
922 free(options.listen_addrs);
923 options.listen_addrs = NULL;
924 options.num_listen_addrs = 0;
925
926 if (!num_listen_socks)
927 fatal("Cannot bind any address.");
928 }
929
930 /*
931 * The main TCP accept loop. Note that, for the non-debug case, returns
932 * from this function are in a forked subprocess.
933 */
934 static void
server_accept_loop(int * sock_in,int * sock_out,int * newsock,int * config_s,int log_stderr)935 server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s,
936 int log_stderr)
937 {
938 struct pollfd *pfd = NULL;
939 int i, ret, npfd, r;
940 int oactive = -1, listening = 0, lameduck = 0;
941 int *startup_pollfd;
942 ssize_t len;
943 const u_char *ptr;
944 char c = 0;
945 struct sockaddr_storage from;
946 struct early_child *child;
947 struct sshbuf *buf;
948 socklen_t fromlen;
949 u_char rnd[256];
950 sigset_t nsigset, osigset;
951 #ifdef LIBWRAP
952 struct request_info req;
953
954 request_init(&req, RQ_DAEMON, __progname, 0);
955 #endif
956
957 /* pipes connected to unauthenticated child sshd processes */
958 child_alloc();
959 startup_pollfd = xcalloc(options.max_startups, sizeof(int));
960
961 /*
962 * Prepare signal mask that we use to block signals that might set
963 * received_sigterm/hup/chld/info, so that we are guaranteed
964 * to immediately wake up the ppoll if a signal is received after
965 * the flag is checked.
966 */
967 sigemptyset(&nsigset);
968 sigaddset(&nsigset, SIGHUP);
969 sigaddset(&nsigset, SIGCHLD);
970 #ifdef SIGINFO
971 sigaddset(&nsigset, SIGINFO);
972 #endif
973 sigaddset(&nsigset, SIGTERM);
974 sigaddset(&nsigset, SIGQUIT);
975
976 /* sized for worst-case */
977 pfd = xcalloc(num_listen_socks + options.max_startups,
978 sizeof(struct pollfd));
979
980 /*
981 * Stay listening for connections until the system crashes or
982 * the daemon is killed with a signal.
983 */
984 for (;;) {
985 sigprocmask(SIG_BLOCK, &nsigset, &osigset);
986 if (received_sigterm) {
987 logit("Received signal %d; terminating.",
988 (int) received_sigterm);
989 close_listen_socks();
990 if (options.pid_file != NULL)
991 unlink(options.pid_file);
992 exit(received_sigterm == SIGTERM ? 0 : 255);
993 }
994 if (received_sigchld) {
995 child_reap_all_exited();
996 received_sigchld = 0;
997 }
998 if (received_siginfo) {
999 show_info();
1000 received_siginfo = 0;
1001 }
1002 if (oactive != children_active) {
1003 setproctitle("%s [listener] %d of %d-%d startups",
1004 listener_proctitle, children_active,
1005 options.max_startups_begin, options.max_startups);
1006 oactive = children_active;
1007 }
1008 if (received_sighup) {
1009 if (!lameduck) {
1010 debug("Received SIGHUP; waiting for children");
1011 close_listen_socks();
1012 lameduck = 1;
1013 }
1014 if (listening <= 0) {
1015 sigprocmask(SIG_SETMASK, &osigset, NULL);
1016 sighup_restart();
1017 }
1018 }
1019
1020 for (i = 0; i < num_listen_socks; i++) {
1021 pfd[i].fd = listen_socks[i];
1022 pfd[i].events = POLLIN;
1023 }
1024 npfd = num_listen_socks;
1025 for (i = 0; i < options.max_startups; i++) {
1026 startup_pollfd[i] = -1;
1027 if (children[i].pipefd != -1) {
1028 pfd[npfd].fd = children[i].pipefd;
1029 pfd[npfd].events = POLLIN;
1030 if (children[i].config != NULL ||
1031 children[i].keys != NULL)
1032 pfd[npfd].events |= POLLOUT;
1033 startup_pollfd[i] = npfd++;
1034 }
1035 }
1036
1037 /* Wait until a connection arrives or a child exits. */
1038 ret = ppoll(pfd, npfd, NULL, &osigset);
1039 if (ret == -1 && errno != EINTR) {
1040 error("ppoll: %.100s", strerror(errno));
1041 if (errno == EINVAL)
1042 cleanup_exit(1); /* can't recover */
1043 }
1044 sigprocmask(SIG_SETMASK, &osigset, NULL);
1045 if (ret == -1)
1046 continue;
1047
1048 for (i = 0; i < options.max_startups; i++) {
1049 if (children[i].pipefd == -1 ||
1050 startup_pollfd[i] == -1 ||
1051 !(pfd[startup_pollfd[i]].revents & POLLOUT))
1052 continue;
1053 if (children[i].config)
1054 buf = children[i].config;
1055 else if (children[i].keys)
1056 buf = children[i].keys;
1057 else {
1058 error_f("no buffer to send");
1059 continue;
1060 }
1061 ptr = sshbuf_ptr(buf);
1062 len = sshbuf_len(buf);
1063 ret = write(children[i].pipefd, ptr, len);
1064 if (ret == -1 && (errno == EINTR || errno == EAGAIN))
1065 continue;
1066 if (ret <= 0) {
1067 if (children[i].early)
1068 listening--;
1069 srclimit_done(children[i].pipefd);
1070 child_close(&(children[i]), 0, 0);
1071 continue;
1072 }
1073 if (ret == len) {
1074 /* finished sending buffer */
1075 sshbuf_free(buf);
1076 if (children[i].config == buf) {
1077 /* sent config, now send keys */
1078 children[i].config = NULL;
1079 children[i].keys = pack_hostkeys();
1080 } else if (children[i].keys == buf) {
1081 /* sent both config and keys */
1082 children[i].keys = NULL;
1083 } else {
1084 fatal("config buf not set");
1085 }
1086
1087 } else {
1088 if ((r = sshbuf_consume(buf, ret)) != 0)
1089 fatal_fr(r, "config buf inconsistent");
1090 }
1091 }
1092 for (i = 0; i < options.max_startups; i++) {
1093 if (children[i].pipefd == -1 ||
1094 startup_pollfd[i] == -1 ||
1095 !(pfd[startup_pollfd[i]].revents & (POLLIN|POLLHUP)))
1096 continue;
1097 switch (read(children[i].pipefd, &c, sizeof(c))) {
1098 case -1:
1099 if (errno == EINTR || errno == EAGAIN)
1100 continue;
1101 if (errno != EPIPE) {
1102 error_f("startup pipe %d (fd=%d): "
1103 "read %s", i, children[i].pipefd,
1104 strerror(errno));
1105 }
1106 /* FALLTHROUGH */
1107 case 0:
1108 /* child exited preauth */
1109 if (children[i].early)
1110 listening--;
1111 srclimit_done(children[i].pipefd);
1112 child_close(&(children[i]), 0, 0);
1113 break;
1114 case 1:
1115 if (children[i].config) {
1116 error_f("startup pipe %d (fd=%d)"
1117 " early read", i, children[i].pipefd);
1118 if (children[i].early)
1119 listening--;
1120 if (children[i].pid > 0)
1121 kill(children[i].pid, SIGTERM);
1122 srclimit_done(children[i].pipefd);
1123 child_close(&(children[i]), 0, 0);
1124 break;
1125 }
1126 if (children[i].early && c == '\0') {
1127 /* child has finished preliminaries */
1128 listening--;
1129 children[i].early = 0;
1130 debug2_f("child %lu for %s received "
1131 "config", (long)children[i].pid,
1132 children[i].id);
1133 } else if (!children[i].early && c == '\001') {
1134 /* child has completed auth */
1135 debug2_f("child %lu for %s auth done",
1136 (long)children[i].pid,
1137 children[i].id);
1138 child_close(&(children[i]), 1, 0);
1139 } else {
1140 error_f("unexpected message 0x%02x "
1141 "child %ld for %s in state %d",
1142 (int)c, (long)children[i].pid,
1143 children[i].id, children[i].early);
1144 }
1145 break;
1146 }
1147 }
1148 for (i = 0; i < num_listen_socks; i++) {
1149 if (!(pfd[i].revents & POLLIN))
1150 continue;
1151 fromlen = sizeof(from);
1152 *newsock = accept(listen_socks[i],
1153 (struct sockaddr *)&from, &fromlen);
1154 if (*newsock == -1) {
1155 if (errno != EINTR && errno != EWOULDBLOCK &&
1156 errno != ECONNABORTED && errno != EAGAIN)
1157 error("accept: %.100s",
1158 strerror(errno));
1159 if (errno == EMFILE || errno == ENFILE)
1160 usleep(100 * 1000);
1161 continue;
1162 }
1163 #ifdef LIBWRAP
1164 /* Check whether logins are denied from this host. */
1165 request_set(&req, RQ_FILE, *newsock,
1166 RQ_CLIENT_NAME, "", RQ_CLIENT_ADDR, "", 0);
1167 sock_host(&req);
1168 if (!hosts_access(&req)) {
1169 const struct linger l = { .l_onoff = 1,
1170 .l_linger = 0 };
1171
1172 (void )setsockopt(*newsock, SOL_SOCKET,
1173 SO_LINGER, &l, sizeof(l));
1174 (void )close(*newsock);
1175 /*
1176 * Mimic message from libwrap's refuse() as
1177 * precisely as we can afford. The authentic
1178 * message prints the IP address and the
1179 * hostname it resolves to in parentheses. If
1180 * the IP address cannot be resolved to a
1181 * hostname, the IP address will be repeated
1182 * in parentheses. As name resolution in the
1183 * main server loop could stall, and logging
1184 * resolved names adds little or no value to
1185 * incident investigation, this implementation
1186 * only repeats the IP address in parentheses.
1187 * This should resemble librwap's refuse()
1188 * closely enough not to break auditing
1189 * software like sshguard or custom scripts.
1190 */
1191 syslog(LOG_WARNING,
1192 "refused connect from %s (%s)",
1193 eval_hostaddr(req.client),
1194 eval_hostaddr(req.client));
1195 debug("Connection refused by tcp wrapper");
1196 continue;
1197 }
1198 #endif /* LIBWRAP */
1199 if (unset_nonblock(*newsock) == -1) {
1200 close(*newsock);
1201 continue;
1202 }
1203 if (socketpair(AF_UNIX,
1204 SOCK_STREAM, 0, config_s) == -1) {
1205 error("reexec socketpair: %s",
1206 strerror(errno));
1207 close(*newsock);
1208 continue;
1209 }
1210 if (drop_connection(*newsock,
1211 children_active, config_s[0])) {
1212 close(*newsock);
1213 close(config_s[0]);
1214 close(config_s[1]);
1215 continue;
1216 }
1217
1218 /*
1219 * Got connection. Fork a child to handle it, unless
1220 * we are in debugging mode.
1221 */
1222 if (debug_flag) {
1223 /*
1224 * In debugging mode. Close the listening
1225 * socket, and start processing the
1226 * connection without forking.
1227 */
1228 debug("Server will not fork when running in debugging mode.");
1229 close_listen_socks();
1230 *sock_in = *newsock;
1231 *sock_out = *newsock;
1232 send_rexec_state(config_s[0]);
1233 close(config_s[0]);
1234 free(pfd);
1235 return;
1236 }
1237
1238 /*
1239 * Normal production daemon. Fork, and have
1240 * the child process the connection. The
1241 * parent continues listening.
1242 */
1243 platform_pre_fork();
1244 set_nonblock(config_s[0]);
1245 listening++;
1246 child = child_register(config_s[0], *newsock);
1247 if ((child->pid = fork()) == 0) {
1248 /*
1249 * Child. Close the listening and
1250 * max_startup sockets. Start using
1251 * the accepted socket. Reinitialize
1252 * logging (since our pid has changed).
1253 * We return from this function to handle
1254 * the connection.
1255 */
1256 platform_post_fork_child();
1257 close_startup_pipes();
1258 close_listen_socks();
1259 *sock_in = *newsock;
1260 *sock_out = *newsock;
1261 log_init(__progname,
1262 options.log_level,
1263 options.log_facility,
1264 log_stderr);
1265 close(config_s[0]);
1266 free(pfd);
1267 return;
1268 }
1269
1270 /* Parent. Stay in the loop. */
1271 platform_post_fork_parent(child->pid);
1272 if (child->pid == -1)
1273 error("fork: %.100s", strerror(errno));
1274 else
1275 debug("Forked child %ld.", (long)child->pid);
1276
1277 close(config_s[1]);
1278 close(*newsock);
1279
1280 /*
1281 * Ensure that our random state differs
1282 * from that of the child
1283 */
1284 arc4random_stir();
1285 arc4random_buf(rnd, sizeof(rnd));
1286 #ifdef WITH_OPENSSL
1287 RAND_seed(rnd, sizeof(rnd));
1288 if ((RAND_bytes((u_char *)rnd, 1)) != 1)
1289 fatal("%s: RAND_bytes failed", __func__);
1290 #endif
1291 explicit_bzero(rnd, sizeof(rnd));
1292 }
1293 }
1294 }
1295
1296 static void
accumulate_host_timing_secret(struct sshbuf * server_cfg,struct sshkey * key)1297 accumulate_host_timing_secret(struct sshbuf *server_cfg,
1298 struct sshkey *key)
1299 {
1300 static struct ssh_digest_ctx *ctx;
1301 u_char *hash;
1302 size_t len;
1303 struct sshbuf *buf;
1304 int r;
1305
1306 if (ctx == NULL && (ctx = ssh_digest_start(SSH_DIGEST_SHA512)) == NULL)
1307 fatal_f("ssh_digest_start");
1308 if (key == NULL) { /* finalize */
1309 /* add server config in case we are using agent for host keys */
1310 if (ssh_digest_update(ctx, sshbuf_ptr(server_cfg),
1311 sshbuf_len(server_cfg)) != 0)
1312 fatal_f("ssh_digest_update");
1313 len = ssh_digest_bytes(SSH_DIGEST_SHA512);
1314 hash = xmalloc(len);
1315 if (ssh_digest_final(ctx, hash, len) != 0)
1316 fatal_f("ssh_digest_final");
1317 options.timing_secret = PEEK_U64(hash);
1318 freezero(hash, len);
1319 ssh_digest_free(ctx);
1320 ctx = NULL;
1321 return;
1322 }
1323 if ((buf = sshbuf_new()) == NULL)
1324 fatal_f("could not allocate buffer");
1325 if ((r = sshkey_private_serialize(key, buf)) != 0)
1326 fatal_fr(r, "encode %s key", sshkey_ssh_name(key));
1327 if (ssh_digest_update(ctx, sshbuf_ptr(buf), sshbuf_len(buf)) != 0)
1328 fatal_f("ssh_digest_update");
1329 sshbuf_reset(buf);
1330 sshbuf_free(buf);
1331 }
1332
1333 static char *
prepare_proctitle(int ac,char ** av)1334 prepare_proctitle(int ac, char **av)
1335 {
1336 char *ret = NULL;
1337 int i;
1338
1339 for (i = 0; i < ac; i++)
1340 xextendf(&ret, " ", "%s", av[i]);
1341 return ret;
1342 }
1343
1344 static void
print_config(struct connection_info * connection_info)1345 print_config(struct connection_info *connection_info)
1346 {
1347 connection_info->test = 1;
1348 parse_server_match_config(&options, &includes, connection_info);
1349 dump_config(&options);
1350 exit(0);
1351 }
1352
1353 /*
1354 * Main program for the daemon.
1355 */
1356 int
main(int ac,char ** av)1357 main(int ac, char **av)
1358 {
1359 extern char *optarg;
1360 extern int optind;
1361 int log_stderr = 0, inetd_flag = 0, test_flag = 0, no_daemon_flag = 0;
1362 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
1363 int r, opt, do_dump_cfg = 0, keytype, already_daemon, have_agent = 0;
1364 int sock_in = -1, sock_out = -1, newsock = -1, rexec_argc = 0;
1365 int devnull, config_s[2] = { -1 , -1 }, have_connection_info = 0;
1366 int need_chroot = 1;
1367 char *args, *fp, *line, *logfile = NULL, **rexec_argv = NULL;
1368 struct stat sb;
1369 u_int i, j;
1370 mode_t new_umask;
1371 struct sshkey *key;
1372 struct sshkey *pubkey;
1373 struct connection_info connection_info;
1374 struct utsname utsname;
1375 sigset_t sigmask;
1376
1377 memset(&connection_info, 0, sizeof(connection_info));
1378 #ifdef HAVE_SECUREWARE
1379 (void)set_auth_parameters(ac, av);
1380 #endif
1381 __progname = ssh_get_progname(av[0]);
1382
1383 sigemptyset(&sigmask);
1384 sigprocmask(SIG_SETMASK, &sigmask, NULL);
1385
1386 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
1387 saved_argc = ac;
1388 rexec_argc = ac;
1389 saved_argv = xcalloc(ac + 1, sizeof(*saved_argv));
1390 for (i = 0; (int)i < ac; i++)
1391 saved_argv[i] = xstrdup(av[i]);
1392 saved_argv[i] = NULL;
1393
1394 #ifndef HAVE_SETPROCTITLE
1395 /* Prepare for later setproctitle emulation */
1396 compat_init_setproctitle(ac, av);
1397 av = saved_argv;
1398 #endif
1399
1400 if (geteuid() == 0 && setgroups(0, NULL) == -1)
1401 debug("setgroups(): %.200s", strerror(errno));
1402
1403 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
1404 sanitise_stdfd();
1405
1406 /* Initialize configuration options to their default values. */
1407 initialize_server_options(&options);
1408
1409 /* Parse command-line arguments. */
1410 args = argv_assemble(ac, av); /* logged later */
1411 while ((opt = getopt(ac, av,
1412 "C:E:b:c:f:g:h:k:o:p:u:46DGQRTdeiqrtV")) != -1) {
1413 switch (opt) {
1414 case '4':
1415 options.address_family = AF_INET;
1416 break;
1417 case '6':
1418 options.address_family = AF_INET6;
1419 break;
1420 case 'f':
1421 config_file_name = optarg;
1422 break;
1423 case 'c':
1424 servconf_add_hostcert("[command-line]", 0,
1425 &options, optarg);
1426 break;
1427 case 'd':
1428 if (debug_flag == 0) {
1429 debug_flag = 1;
1430 options.log_level = SYSLOG_LEVEL_DEBUG1;
1431 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
1432 options.log_level++;
1433 break;
1434 case 'D':
1435 no_daemon_flag = 1;
1436 break;
1437 case 'G':
1438 do_dump_cfg = 1;
1439 break;
1440 case 'E':
1441 logfile = optarg;
1442 /* FALLTHROUGH */
1443 case 'e':
1444 log_stderr = 1;
1445 break;
1446 case 'i':
1447 inetd_flag = 1;
1448 break;
1449 case 'r':
1450 logit("-r option is deprecated");
1451 break;
1452 case 'R':
1453 fatal("-R not supported here");
1454 break;
1455 case 'Q':
1456 /* ignored */
1457 break;
1458 case 'q':
1459 options.log_level = SYSLOG_LEVEL_QUIET;
1460 break;
1461 case 'b':
1462 /* protocol 1, ignored */
1463 break;
1464 case 'p':
1465 options.ports_from_cmdline = 1;
1466 if (options.num_ports >= MAX_PORTS) {
1467 fprintf(stderr, "too many ports.\n");
1468 exit(1);
1469 }
1470 options.ports[options.num_ports++] = a2port(optarg);
1471 if (options.ports[options.num_ports-1] <= 0) {
1472 fprintf(stderr, "Bad port number.\n");
1473 exit(1);
1474 }
1475 break;
1476 case 'g':
1477 if ((options.login_grace_time = convtime(optarg)) == -1) {
1478 fprintf(stderr, "Invalid login grace time.\n");
1479 exit(1);
1480 }
1481 break;
1482 case 'k':
1483 /* protocol 1, ignored */
1484 break;
1485 case 'h':
1486 servconf_add_hostkey("[command-line]", 0,
1487 &options, optarg, 1);
1488 break;
1489 case 't':
1490 test_flag = 1;
1491 break;
1492 case 'T':
1493 test_flag = 2;
1494 break;
1495 case 'C':
1496 if (parse_server_match_testspec(&connection_info,
1497 optarg) == -1)
1498 exit(1);
1499 have_connection_info = 1;
1500 break;
1501 case 'u':
1502 utmp_len = (u_int)strtonum(optarg, 0, HOST_NAME_MAX+1+1, NULL);
1503 if (utmp_len > HOST_NAME_MAX+1) {
1504 fprintf(stderr, "Invalid utmp length.\n");
1505 exit(1);
1506 }
1507 break;
1508 case 'o':
1509 line = xstrdup(optarg);
1510 if (process_server_config_line(&options, line,
1511 "command-line", 0, NULL, NULL, &includes) != 0)
1512 exit(1);
1513 free(line);
1514 break;
1515 case 'V':
1516 fprintf(stderr, "%s, %s\n",
1517 SSH_RELEASE, SSH_OPENSSL_VERSION);
1518 exit(0);
1519 default:
1520 usage();
1521 break;
1522 }
1523 }
1524 if (!test_flag && !inetd_flag && !do_dump_cfg && !path_absolute(av[0]))
1525 fatal("sshd requires execution with an absolute path");
1526
1527 closefrom(STDERR_FILENO + 1);
1528
1529 /* Reserve fds we'll need later for reexec things */
1530 if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1)
1531 fatal("open %s: %s", _PATH_DEVNULL, strerror(errno));
1532 while (devnull < REEXEC_MIN_FREE_FD) {
1533 if ((devnull = dup(devnull)) == -1)
1534 fatal("dup %s: %s", _PATH_DEVNULL, strerror(errno));
1535 }
1536
1537 seed_rng();
1538
1539 /* If requested, redirect the logs to the specified logfile. */
1540 if (logfile != NULL) {
1541 char *cp, pid_s[32];
1542
1543 snprintf(pid_s, sizeof(pid_s), "%ld", (unsigned long)getpid());
1544 cp = percent_expand(logfile,
1545 "p", pid_s,
1546 "P", "sshd",
1547 (char *)NULL);
1548 log_redirect_stderr_to(cp);
1549 free(cp);
1550 }
1551
1552 /*
1553 * Force logging to stderr until we have loaded the private host
1554 * key (unless started from inetd)
1555 */
1556 log_init(__progname,
1557 options.log_level == SYSLOG_LEVEL_NOT_SET ?
1558 SYSLOG_LEVEL_INFO : options.log_level,
1559 options.log_facility == SYSLOG_FACILITY_NOT_SET ?
1560 SYSLOG_FACILITY_AUTH : options.log_facility,
1561 log_stderr || !inetd_flag || debug_flag);
1562
1563 /*
1564 * Unset KRB5CCNAME, otherwise the user's session may inherit it from
1565 * root's environment
1566 */
1567 if (getenv("KRB5CCNAME") != NULL)
1568 (void) unsetenv("KRB5CCNAME");
1569
1570 sensitive_data.have_ssh2_key = 0;
1571
1572 /*
1573 * If we're not doing an extended test do not silently ignore connection
1574 * test params.
1575 */
1576 if (test_flag < 2 && have_connection_info)
1577 fatal("Config test connection parameter (-C) provided without "
1578 "test mode (-T)");
1579
1580 debug("sshd version %s, %s", SSH_VERSION, SSH_OPENSSL_VERSION);
1581 if (uname(&utsname) != 0) {
1582 memset(&utsname, 0, sizeof(utsname));
1583 strlcpy(utsname.sysname, "UNKNOWN", sizeof(utsname.sysname));
1584 }
1585 debug3("Running on %s %s %s %s", utsname.sysname, utsname.release,
1586 utsname.version, utsname.machine);
1587 debug3("Started with: %s", args);
1588 free(args);
1589
1590 /* Fetch our configuration */
1591 if ((cfg = sshbuf_new()) == NULL)
1592 fatal("sshbuf_new config failed");
1593 if (strcasecmp(config_file_name, "none") != 0)
1594 load_server_config(config_file_name, cfg);
1595
1596 parse_server_config(&options, config_file_name, cfg,
1597 &includes, NULL, 0);
1598
1599 /* Fill in default values for those options not explicitly set. */
1600 fill_default_server_options(&options);
1601
1602 /* Check that options are sensible */
1603 if (options.authorized_keys_command_user == NULL &&
1604 (options.authorized_keys_command != NULL &&
1605 strcasecmp(options.authorized_keys_command, "none") != 0))
1606 fatal("AuthorizedKeysCommand set without "
1607 "AuthorizedKeysCommandUser");
1608 if (options.authorized_principals_command_user == NULL &&
1609 (options.authorized_principals_command != NULL &&
1610 strcasecmp(options.authorized_principals_command, "none") != 0))
1611 fatal("AuthorizedPrincipalsCommand set without "
1612 "AuthorizedPrincipalsCommandUser");
1613
1614 /*
1615 * Check whether there is any path through configured auth methods.
1616 * Unfortunately it is not possible to verify this generally before
1617 * daemonisation in the presence of Match blocks, but this catches
1618 * and warns for trivial misconfigurations that could break login.
1619 */
1620 if (options.num_auth_methods != 0) {
1621 for (i = 0; i < options.num_auth_methods; i++) {
1622 if (auth2_methods_valid(options.auth_methods[i],
1623 1) == 0)
1624 break;
1625 }
1626 if (i >= options.num_auth_methods)
1627 fatal("AuthenticationMethods cannot be satisfied by "
1628 "enabled authentication methods");
1629 }
1630
1631 /* Check that there are no remaining arguments. */
1632 if (optind < ac) {
1633 fprintf(stderr, "Extra argument %s.\n", av[optind]);
1634 exit(1);
1635 }
1636
1637 if (do_dump_cfg)
1638 print_config(&connection_info);
1639
1640 /* load host keys */
1641 sensitive_data.host_keys = xcalloc(options.num_host_key_files,
1642 sizeof(struct sshkey *));
1643 sensitive_data.host_pubkeys = xcalloc(options.num_host_key_files,
1644 sizeof(struct sshkey *));
1645
1646 if (options.host_key_agent) {
1647 if (strcmp(options.host_key_agent, SSH_AUTHSOCKET_ENV_NAME))
1648 setenv(SSH_AUTHSOCKET_ENV_NAME,
1649 options.host_key_agent, 1);
1650 if ((r = ssh_get_authentication_socket(NULL)) == 0)
1651 have_agent = 1;
1652 else
1653 error_r(r, "Could not connect to agent \"%s\"",
1654 options.host_key_agent);
1655 }
1656
1657 for (i = 0; i < options.num_host_key_files; i++) {
1658 int ll = options.host_key_file_userprovided[i] ?
1659 SYSLOG_LEVEL_ERROR : SYSLOG_LEVEL_DEBUG1;
1660
1661 if (options.host_key_files[i] == NULL)
1662 continue;
1663 if ((r = sshkey_load_private(options.host_key_files[i], "",
1664 &key, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR)
1665 do_log2_r(r, ll, "Unable to load host key \"%s\"",
1666 options.host_key_files[i]);
1667 if (sshkey_is_sk(key) &&
1668 key->sk_flags & SSH_SK_USER_PRESENCE_REQD) {
1669 debug("host key %s requires user presence, ignoring",
1670 options.host_key_files[i]);
1671 key->sk_flags &= ~SSH_SK_USER_PRESENCE_REQD;
1672 }
1673 if (r == 0 && key != NULL &&
1674 (r = sshkey_shield_private(key)) != 0) {
1675 do_log2_r(r, ll, "Unable to shield host key \"%s\"",
1676 options.host_key_files[i]);
1677 sshkey_free(key);
1678 key = NULL;
1679 }
1680 if ((r = sshkey_load_public(options.host_key_files[i],
1681 &pubkey, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR)
1682 do_log2_r(r, ll, "Unable to load host key \"%s\"",
1683 options.host_key_files[i]);
1684 if (pubkey != NULL && key != NULL) {
1685 if (!sshkey_equal(pubkey, key)) {
1686 error("Public key for %s does not match "
1687 "private key", options.host_key_files[i]);
1688 sshkey_free(pubkey);
1689 pubkey = NULL;
1690 }
1691 }
1692 if (pubkey == NULL && key != NULL) {
1693 if ((r = sshkey_from_private(key, &pubkey)) != 0)
1694 fatal_r(r, "Could not demote key: \"%s\"",
1695 options.host_key_files[i]);
1696 }
1697 if (pubkey != NULL && (r = sshkey_check_rsa_length(pubkey,
1698 options.required_rsa_size)) != 0) {
1699 error_fr(r, "Host key %s", options.host_key_files[i]);
1700 sshkey_free(pubkey);
1701 sshkey_free(key);
1702 continue;
1703 }
1704 sensitive_data.host_keys[i] = key;
1705 sensitive_data.host_pubkeys[i] = pubkey;
1706
1707 if (key == NULL && pubkey != NULL && have_agent) {
1708 debug("will rely on agent for hostkey %s",
1709 options.host_key_files[i]);
1710 keytype = pubkey->type;
1711 } else if (key != NULL) {
1712 keytype = key->type;
1713 accumulate_host_timing_secret(cfg, key);
1714 } else {
1715 do_log2(ll, "Unable to load host key: %s",
1716 options.host_key_files[i]);
1717 sensitive_data.host_keys[i] = NULL;
1718 sensitive_data.host_pubkeys[i] = NULL;
1719 continue;
1720 }
1721
1722 switch (keytype) {
1723 case KEY_RSA:
1724 case KEY_DSA:
1725 case KEY_ECDSA:
1726 case KEY_ED25519:
1727 case KEY_ECDSA_SK:
1728 case KEY_ED25519_SK:
1729 case KEY_XMSS:
1730 if (have_agent || key != NULL)
1731 sensitive_data.have_ssh2_key = 1;
1732 break;
1733 }
1734 if ((fp = sshkey_fingerprint(pubkey, options.fingerprint_hash,
1735 SSH_FP_DEFAULT)) == NULL)
1736 fatal("sshkey_fingerprint failed");
1737 debug("%s host key #%d: %s %s",
1738 key ? "private" : "agent", i, sshkey_ssh_name(pubkey), fp);
1739 free(fp);
1740 }
1741 accumulate_host_timing_secret(cfg, NULL);
1742 if (!sensitive_data.have_ssh2_key) {
1743 logit("sshd: no hostkeys available -- exiting.");
1744 exit(1);
1745 }
1746
1747 /*
1748 * Load certificates. They are stored in an array at identical
1749 * indices to the public keys that they relate to.
1750 */
1751 sensitive_data.host_certificates = xcalloc(options.num_host_key_files,
1752 sizeof(struct sshkey *));
1753 for (i = 0; i < options.num_host_key_files; i++)
1754 sensitive_data.host_certificates[i] = NULL;
1755
1756 for (i = 0; i < options.num_host_cert_files; i++) {
1757 if (options.host_cert_files[i] == NULL)
1758 continue;
1759 if ((r = sshkey_load_public(options.host_cert_files[i],
1760 &key, NULL)) != 0) {
1761 error_r(r, "Could not load host certificate \"%s\"",
1762 options.host_cert_files[i]);
1763 continue;
1764 }
1765 if (!sshkey_is_cert(key)) {
1766 error("Certificate file is not a certificate: %s",
1767 options.host_cert_files[i]);
1768 sshkey_free(key);
1769 continue;
1770 }
1771 /* Find matching private key */
1772 for (j = 0; j < options.num_host_key_files; j++) {
1773 if (sshkey_equal_public(key,
1774 sensitive_data.host_pubkeys[j])) {
1775 sensitive_data.host_certificates[j] = key;
1776 break;
1777 }
1778 }
1779 if (j >= options.num_host_key_files) {
1780 error("No matching private key for certificate: %s",
1781 options.host_cert_files[i]);
1782 sshkey_free(key);
1783 continue;
1784 }
1785 sensitive_data.host_certificates[j] = key;
1786 debug("host certificate: #%u type %d %s", j, key->type,
1787 sshkey_type(key));
1788 }
1789
1790 /* Ensure privsep directory is correctly configured. */
1791 need_chroot = ((getuid() == 0 || geteuid() == 0) ||
1792 options.kerberos_authentication);
1793 if ((getpwnam(SSH_PRIVSEP_USER)) == NULL && need_chroot) {
1794 fatal("Privilege separation user %s does not exist",
1795 SSH_PRIVSEP_USER);
1796 }
1797 endpwent();
1798
1799 if (need_chroot) {
1800 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &sb) == -1) ||
1801 (S_ISDIR(sb.st_mode) == 0))
1802 fatal("Missing privilege separation directory: %s",
1803 _PATH_PRIVSEP_CHROOT_DIR);
1804 #ifdef HAVE_CYGWIN
1805 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
1806 (sb.st_uid != getuid () ||
1807 (sb.st_mode & (S_IWGRP|S_IWOTH)) != 0))
1808 #else
1809 if (sb.st_uid != 0 || (sb.st_mode & (S_IWGRP|S_IWOTH)) != 0)
1810 #endif
1811 fatal("%s must be owned by root and not group or "
1812 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR);
1813 }
1814
1815 if (test_flag > 1)
1816 print_config(&connection_info);
1817
1818 /* Configuration looks good, so exit if in test mode. */
1819 if (test_flag)
1820 exit(0);
1821
1822 /*
1823 * Clear out any supplemental groups we may have inherited. This
1824 * prevents inadvertent creation of files with bad modes (in the
1825 * portable version at least, it's certainly possible for PAM
1826 * to create a file, and we can't control the code in every
1827 * module which might be used).
1828 */
1829 if (setgroups(0, NULL) < 0)
1830 debug("setgroups() failed: %.200s", strerror(errno));
1831
1832 /* Prepare arguments for sshd-session */
1833 if (rexec_argc < 0)
1834 fatal("rexec_argc %d < 0", rexec_argc);
1835 rexec_argv = xcalloc(rexec_argc + 3, sizeof(char *));
1836 /* Point to the sshd-session binary instead of sshd */
1837 rexec_argv[0] = options.sshd_session_path;
1838 for (i = 1; i < (u_int)rexec_argc; i++) {
1839 debug("rexec_argv[%d]='%s'", i, saved_argv[i]);
1840 rexec_argv[i] = saved_argv[i];
1841 }
1842 rexec_argv[rexec_argc++] = "-R";
1843 rexec_argv[rexec_argc] = NULL;
1844 if (stat(rexec_argv[0], &sb) != 0 || !(sb.st_mode & (S_IXOTH|S_IXUSR)))
1845 fatal("%s does not exist or is not executable", rexec_argv[0]);
1846 debug3("using %s for re-exec", rexec_argv[0]);
1847
1848 /* Ensure that the privsep binary exists now too. */
1849 if (stat(options.sshd_auth_path, &sb) != 0 ||
1850 !(sb.st_mode & (S_IXOTH|S_IXUSR))) {
1851 fatal("%s does not exist or is not executable",
1852 options.sshd_auth_path);
1853 }
1854
1855 listener_proctitle = prepare_proctitle(ac, av);
1856
1857 /* Ensure that umask disallows at least group and world write */
1858 new_umask = umask(0077) | 0022;
1859 (void) umask(new_umask);
1860
1861 /* Initialize the log (it is reinitialized below in case we forked). */
1862 if (debug_flag && !inetd_flag)
1863 log_stderr = 1;
1864 log_init(__progname, options.log_level,
1865 options.log_facility, log_stderr);
1866 for (i = 0; i < options.num_log_verbose; i++)
1867 log_verbose_add(options.log_verbose[i]);
1868
1869 /*
1870 * If not in debugging mode, not started from inetd and not already
1871 * daemonized (eg re-exec via SIGHUP), disconnect from the controlling
1872 * terminal, and fork. The original process exits.
1873 */
1874 already_daemon = daemonized();
1875 if (!(debug_flag || inetd_flag || no_daemon_flag || already_daemon)) {
1876
1877 if (daemon(0, 0) == -1)
1878 fatal("daemon() failed: %.200s", strerror(errno));
1879
1880 disconnect_controlling_tty();
1881 }
1882 /* Reinitialize the log (because of the fork above). */
1883 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1884
1885 /* Avoid killing the process in high-pressure swapping environments. */
1886 if (!inetd_flag && madvise(NULL, 0, MADV_PROTECT) != 0)
1887 debug("madvise(): %.200s", strerror(errno));
1888
1889 /*
1890 * Chdir to the root directory so that the current disk can be
1891 * unmounted if desired.
1892 */
1893 if (chdir("/") == -1)
1894 error("chdir(\"/\"): %s", strerror(errno));
1895
1896 /* ignore SIGPIPE */
1897 ssh_signal(SIGPIPE, SIG_IGN);
1898
1899 config = pack_config(cfg);
1900
1901 /* Get a connection, either from inetd or a listening TCP socket */
1902 if (inetd_flag) {
1903 /* Send configuration to ancestor sshd-session process */
1904 if (socketpair(AF_UNIX, SOCK_STREAM, 0, config_s) == -1)
1905 fatal("socketpair: %s", strerror(errno));
1906 send_rexec_state(config_s[0]);
1907 close(config_s[0]);
1908 } else {
1909 platform_pre_listen();
1910 server_listen();
1911
1912 ssh_signal(SIGHUP, sighup_handler);
1913 ssh_signal(SIGCHLD, main_sigchld_handler);
1914 ssh_signal(SIGTERM, sigterm_handler);
1915 ssh_signal(SIGQUIT, sigterm_handler);
1916 #ifdef SIGINFO
1917 ssh_signal(SIGINFO, siginfo_handler);
1918 #endif
1919
1920 platform_post_listen();
1921
1922 /*
1923 * Write out the pid file after the sigterm handler
1924 * is setup and the listen sockets are bound
1925 */
1926 if (options.pid_file != NULL && !debug_flag) {
1927 FILE *f = fopen(options.pid_file, "w");
1928
1929 if (f == NULL) {
1930 error("Couldn't create pid file \"%s\": %s",
1931 options.pid_file, strerror(errno));
1932 } else {
1933 fprintf(f, "%ld\n", (long) getpid());
1934 fclose(f);
1935 }
1936 }
1937
1938 /* Accept a connection and return in a forked child */
1939 server_accept_loop(&sock_in, &sock_out,
1940 &newsock, config_s, log_stderr);
1941 }
1942
1943 /* This is the child processing a new connection. */
1944 setproctitle("%s", "[accepted]");
1945
1946 /*
1947 * Create a new session and process group since the 4.4BSD
1948 * setlogin() affects the entire process group. We don't
1949 * want the child to be able to affect the parent.
1950 */
1951 if (!debug_flag && !inetd_flag && setsid() == -1)
1952 error("setsid: %.100s", strerror(errno));
1953
1954 debug("rexec start in %d out %d newsock %d config_s %d/%d",
1955 sock_in, sock_out, newsock, config_s[0], config_s[1]);
1956 if (!inetd_flag) {
1957 if (dup2(newsock, STDIN_FILENO) == -1)
1958 fatal("dup2 stdin: %s", strerror(errno));
1959 if (dup2(STDIN_FILENO, STDOUT_FILENO) == -1)
1960 fatal("dup2 stdout: %s", strerror(errno));
1961 if (newsock > STDOUT_FILENO)
1962 close(newsock);
1963 }
1964 if (config_s[1] != REEXEC_CONFIG_PASS_FD) {
1965 if (dup2(config_s[1], REEXEC_CONFIG_PASS_FD) == -1)
1966 fatal("dup2 config_s: %s", strerror(errno));
1967 close(config_s[1]);
1968 }
1969 log_redirect_stderr_to(NULL);
1970 closefrom(REEXEC_MIN_FREE_FD);
1971
1972 ssh_signal(SIGHUP, SIG_IGN); /* avoid reset to SIG_DFL */
1973 execv(rexec_argv[0], rexec_argv);
1974
1975 fatal("rexec of %s failed: %s", rexec_argv[0], strerror(errno));
1976 #ifdef __FreeBSD__
1977 /*
1978 * Initialize the resolver. This may not happen automatically
1979 * before privsep chroot().
1980 */
1981 if ((_res.options & RES_INIT) == 0) {
1982 debug("res_init()");
1983 res_init();
1984 }
1985 #ifdef GSSAPI
1986 /*
1987 * Force GSS-API to parse its configuration and load any
1988 * mechanism plugins.
1989 */
1990 {
1991 gss_OID_set mechs;
1992 OM_uint32 minor_status;
1993 gss_indicate_mechs(&minor_status, &mechs);
1994 gss_release_oid_set(&minor_status, &mechs);
1995 }
1996 #endif
1997 #endif
1998 }
1999
2000 /* server specific fatal cleanup */
2001 void
cleanup_exit(int i)2002 cleanup_exit(int i)
2003 {
2004 _exit(i);
2005 }
2006