1 /* $OpenBSD: sshd.c,v 1.444 2015/02/20 22:17:21 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/socket.h>
50 #ifdef HAVE_SYS_STAT_H
51 # include <sys/stat.h>
52 #endif
53 #ifdef HAVE_SYS_TIME_H
54 # include <sys/time.h>
55 #endif
56 #include "openbsd-compat/sys-tree.h"
57 #include "openbsd-compat/sys-queue.h"
58 #include <sys/wait.h>
59
60 #include <errno.h>
61 #include <fcntl.h>
62 #include <netdb.h>
63 #ifdef HAVE_PATHS_H
64 #include <paths.h>
65 #endif
66 #include <grp.h>
67 #include <pwd.h>
68 #include <signal.h>
69 #include <stdarg.h>
70 #include <stdio.h>
71 #include <stdlib.h>
72 #include <string.h>
73 #include <unistd.h>
74 #include <limits.h>
75
76 #ifdef WITH_OPENSSL
77 #include <openssl/dh.h>
78 #include <openssl/bn.h>
79 #include <openssl/rand.h>
80 #include "openbsd-compat/openssl-compat.h"
81 #endif
82
83 #ifdef HAVE_SECUREWARE
84 #include <sys/security.h>
85 #include <prot.h>
86 #endif
87
88 #include "xmalloc.h"
89 #include "ssh.h"
90 #include "ssh1.h"
91 #include "ssh2.h"
92 #include "rsa.h"
93 #include "sshpty.h"
94 #include "packet.h"
95 #include "log.h"
96 #include "buffer.h"
97 #include "misc.h"
98 #include "servconf.h"
99 #include "uidswap.h"
100 #include "compat.h"
101 #include "cipher.h"
102 #include "digest.h"
103 #include "key.h"
104 #include "kex.h"
105 #include "myproposal.h"
106 #include "authfile.h"
107 #include "pathnames.h"
108 #include "atomicio.h"
109 #include "canohost.h"
110 #include "hostfile.h"
111 #include "auth.h"
112 #include "authfd.h"
113 #include "msg.h"
114 #include "dispatch.h"
115 #include "channels.h"
116 #include "session.h"
117 #include "monitor_mm.h"
118 #include "monitor.h"
119 #ifdef GSSAPI
120 #include "ssh-gss.h"
121 #endif
122 #include "monitor_wrap.h"
123 #include "roaming.h"
124 #include "ssh-sandbox.h"
125 #include "version.h"
126 #include "ssherr.h"
127
128 #ifndef O_NOCTTY
129 #define O_NOCTTY 0
130 #endif
131
132 /* Re-exec fds */
133 #define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1)
134 #define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2)
135 #define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3)
136 #define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4)
137
138 extern char *__progname;
139
140 /* Server configuration options. */
141 ServerOptions options;
142
143 /* Name of the server configuration file. */
144 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
145
146 /*
147 * Debug mode flag. This can be set on the command line. If debug
148 * mode is enabled, extra debugging output will be sent to the system
149 * log, the daemon will not go to background, and will exit after processing
150 * the first connection.
151 */
152 int debug_flag = 0;
153
154 /* Flag indicating that the daemon should only test the configuration and keys. */
155 int test_flag = 0;
156
157 /* Flag indicating that the daemon is being started from inetd. */
158 int inetd_flag = 0;
159
160 /* Flag indicating that sshd should not detach and become a daemon. */
161 int no_daemon_flag = 0;
162
163 /* debug goes to stderr unless inetd_flag is set */
164 int log_stderr = 0;
165
166 /* Saved arguments to main(). */
167 char **saved_argv;
168 int saved_argc;
169
170 /* re-exec */
171 int rexeced_flag = 0;
172 int rexec_flag = 1;
173 int rexec_argc = 0;
174 char **rexec_argv;
175
176 /*
177 * The sockets that the server is listening; this is used in the SIGHUP
178 * signal handler.
179 */
180 #define MAX_LISTEN_SOCKS 16
181 int listen_socks[MAX_LISTEN_SOCKS];
182 int num_listen_socks = 0;
183
184 /*
185 * the client's version string, passed by sshd2 in compat mode. if != NULL,
186 * sshd will skip the version-number exchange
187 */
188 char *client_version_string = NULL;
189 char *server_version_string = NULL;
190
191 /* Daemon's agent connection */
192 int auth_sock = -1;
193 int have_agent = 0;
194
195 /*
196 * Any really sensitive data in the application is contained in this
197 * structure. The idea is that this structure could be locked into memory so
198 * that the pages do not get written into swap. However, there are some
199 * problems. The private key contains BIGNUMs, and we do not (in principle)
200 * have access to the internals of them, and locking just the structure is
201 * not very useful. Currently, memory locking is not implemented.
202 */
203 struct {
204 Key *server_key; /* ephemeral server key */
205 Key *ssh1_host_key; /* ssh1 host key */
206 Key **host_keys; /* all private host keys */
207 Key **host_pubkeys; /* all public host keys */
208 Key **host_certificates; /* all public host certificates */
209 int have_ssh1_key;
210 int have_ssh2_key;
211 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
212 } sensitive_data;
213
214 /*
215 * Flag indicating whether the RSA server key needs to be regenerated.
216 * Is set in the SIGALRM handler and cleared when the key is regenerated.
217 */
218 static volatile sig_atomic_t key_do_regen = 0;
219
220 /* This is set to true when a signal is received. */
221 static volatile sig_atomic_t received_sighup = 0;
222 static volatile sig_atomic_t received_sigterm = 0;
223
224 /* session identifier, used by RSA-auth */
225 u_char session_id[16];
226
227 /* same for ssh2 */
228 u_char *session_id2 = NULL;
229 u_int session_id2_len = 0;
230
231 /* record remote hostname or ip */
232 u_int utmp_len = HOST_NAME_MAX+1;
233
234 /* options.max_startup sized array of fd ints */
235 int *startup_pipes = NULL;
236 int startup_pipe; /* in child */
237
238 /* variables used for privilege separation */
239 int use_privsep = -1;
240 struct monitor *pmonitor = NULL;
241 int privsep_is_preauth = 1;
242
243 /* global authentication context */
244 Authctxt *the_authctxt = NULL;
245
246 /* sshd_config buffer */
247 Buffer cfg;
248
249 /* message to be displayed after login */
250 Buffer loginmsg;
251
252 /* Unprivileged user */
253 struct passwd *privsep_pw = NULL;
254
255 /* Prototypes for various functions defined later in this file. */
256 void destroy_sensitive_data(void);
257 void demote_sensitive_data(void);
258
259 #ifdef WITH_SSH1
260 static void do_ssh1_kex(void);
261 #endif
262 static void do_ssh2_kex(void);
263
264 /*
265 * Close all listening sockets
266 */
267 static void
close_listen_socks(void)268 close_listen_socks(void)
269 {
270 int i;
271
272 for (i = 0; i < num_listen_socks; i++)
273 close(listen_socks[i]);
274 num_listen_socks = -1;
275 }
276
277 static void
close_startup_pipes(void)278 close_startup_pipes(void)
279 {
280 int i;
281
282 if (startup_pipes)
283 for (i = 0; i < options.max_startups; i++)
284 if (startup_pipes[i] != -1)
285 close(startup_pipes[i]);
286 }
287
288 /*
289 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
290 * the effect is to reread the configuration file (and to regenerate
291 * the server key).
292 */
293
294 /*ARGSUSED*/
295 static void
sighup_handler(int sig)296 sighup_handler(int sig)
297 {
298 int save_errno = errno;
299
300 received_sighup = 1;
301 signal(SIGHUP, sighup_handler);
302 errno = save_errno;
303 }
304
305 /*
306 * Called from the main program after receiving SIGHUP.
307 * Restarts the server.
308 */
309 static void
sighup_restart(void)310 sighup_restart(void)
311 {
312 logit("Received SIGHUP; restarting.");
313 platform_pre_restart();
314 close_listen_socks();
315 close_startup_pipes();
316 alarm(0); /* alarm timer persists across exec */
317 signal(SIGHUP, SIG_IGN); /* will be restored after exec */
318 execv(saved_argv[0], saved_argv);
319 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
320 strerror(errno));
321 exit(1);
322 }
323
324 /*
325 * Generic signal handler for terminating signals in the master daemon.
326 */
327 /*ARGSUSED*/
328 static void
sigterm_handler(int sig)329 sigterm_handler(int sig)
330 {
331 received_sigterm = sig;
332 }
333
334 /*
335 * SIGCHLD handler. This is called whenever a child dies. This will then
336 * reap any zombies left by exited children.
337 */
338 /*ARGSUSED*/
339 static void
main_sigchld_handler(int sig)340 main_sigchld_handler(int sig)
341 {
342 int save_errno = errno;
343 pid_t pid;
344 int status;
345
346 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
347 (pid < 0 && errno == EINTR))
348 ;
349
350 signal(SIGCHLD, main_sigchld_handler);
351 errno = save_errno;
352 }
353
354 /*
355 * Signal handler for the alarm after the login grace period has expired.
356 */
357 /*ARGSUSED*/
358 static void
grace_alarm_handler(int sig)359 grace_alarm_handler(int sig)
360 {
361 if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0)
362 kill(pmonitor->m_pid, SIGALRM);
363
364 /*
365 * Try to kill any processes that we have spawned, E.g. authorized
366 * keys command helpers.
367 */
368 if (getpgid(0) == getpid()) {
369 signal(SIGTERM, SIG_IGN);
370 kill(0, SIGTERM);
371 }
372
373 /* Log error and exit. */
374 sigdie("Timeout before authentication for %s", get_remote_ipaddr());
375 }
376
377 /*
378 * Signal handler for the key regeneration alarm. Note that this
379 * alarm only occurs in the daemon waiting for connections, and it does not
380 * do anything with the private key or random state before forking.
381 * Thus there should be no concurrency control/asynchronous execution
382 * problems.
383 */
384 static void
generate_ephemeral_server_key(void)385 generate_ephemeral_server_key(void)
386 {
387 verbose("Generating %s%d bit RSA key.",
388 sensitive_data.server_key ? "new " : "", options.server_key_bits);
389 if (sensitive_data.server_key != NULL)
390 key_free(sensitive_data.server_key);
391 sensitive_data.server_key = key_generate(KEY_RSA1,
392 options.server_key_bits);
393 verbose("RSA key generation complete.");
394
395 arc4random_buf(sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
396 }
397
398 /*ARGSUSED*/
399 static void
key_regeneration_alarm(int sig)400 key_regeneration_alarm(int sig)
401 {
402 int save_errno = errno;
403
404 signal(SIGALRM, SIG_DFL);
405 errno = save_errno;
406 key_do_regen = 1;
407 }
408
409 static void
sshd_exchange_identification(int sock_in,int sock_out)410 sshd_exchange_identification(int sock_in, int sock_out)
411 {
412 u_int i;
413 int mismatch;
414 int remote_major, remote_minor;
415 int major, minor;
416 char *s, *newline = "\n";
417 char buf[256]; /* Must not be larger than remote_version. */
418 char remote_version[256]; /* Must be at least as big as buf. */
419
420 if ((options.protocol & SSH_PROTO_1) &&
421 (options.protocol & SSH_PROTO_2)) {
422 major = PROTOCOL_MAJOR_1;
423 minor = 99;
424 } else if (options.protocol & SSH_PROTO_2) {
425 major = PROTOCOL_MAJOR_2;
426 minor = PROTOCOL_MINOR_2;
427 newline = "\r\n";
428 } else {
429 major = PROTOCOL_MAJOR_1;
430 minor = PROTOCOL_MINOR_1;
431 }
432
433 xasprintf(&server_version_string, "SSH-%d.%d-%.100s%s%s%s",
434 major, minor, SSH_VERSION,
435 *options.version_addendum == '\0' ? "" : " ",
436 options.version_addendum, newline);
437
438 /* Send our protocol version identification. */
439 if (roaming_atomicio(vwrite, sock_out, server_version_string,
440 strlen(server_version_string))
441 != strlen(server_version_string)) {
442 logit("Could not write ident string to %s", get_remote_ipaddr());
443 cleanup_exit(255);
444 }
445
446 /* Read other sides version identification. */
447 memset(buf, 0, sizeof(buf));
448 for (i = 0; i < sizeof(buf) - 1; i++) {
449 if (roaming_atomicio(read, sock_in, &buf[i], 1) != 1) {
450 logit("Did not receive identification string from %s",
451 get_remote_ipaddr());
452 cleanup_exit(255);
453 }
454 if (buf[i] == '\r') {
455 buf[i] = 0;
456 /* Kludge for F-Secure Macintosh < 1.0.2 */
457 if (i == 12 &&
458 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
459 break;
460 continue;
461 }
462 if (buf[i] == '\n') {
463 buf[i] = 0;
464 break;
465 }
466 }
467 buf[sizeof(buf) - 1] = 0;
468 client_version_string = xstrdup(buf);
469
470 /*
471 * Check that the versions match. In future this might accept
472 * several versions and set appropriate flags to handle them.
473 */
474 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
475 &remote_major, &remote_minor, remote_version) != 3) {
476 s = "Protocol mismatch.\n";
477 (void) atomicio(vwrite, sock_out, s, strlen(s));
478 logit("Bad protocol version identification '%.100s' "
479 "from %s port %d", client_version_string,
480 get_remote_ipaddr(), get_remote_port());
481 close(sock_in);
482 close(sock_out);
483 cleanup_exit(255);
484 }
485 debug("Client protocol version %d.%d; client software version %.100s",
486 remote_major, remote_minor, remote_version);
487
488 active_state->compat = compat_datafellows(remote_version);
489
490 if ((datafellows & SSH_BUG_PROBE) != 0) {
491 logit("probed from %s with %s. Don't panic.",
492 get_remote_ipaddr(), client_version_string);
493 cleanup_exit(255);
494 }
495 if ((datafellows & SSH_BUG_SCANNER) != 0) {
496 logit("scanned from %s with %s. Don't panic.",
497 get_remote_ipaddr(), client_version_string);
498 cleanup_exit(255);
499 }
500 if ((datafellows & SSH_BUG_RSASIGMD5) != 0) {
501 logit("Client version \"%.100s\" uses unsafe RSA signature "
502 "scheme; disabling use of RSA keys", remote_version);
503 }
504 if ((datafellows & SSH_BUG_DERIVEKEY) != 0) {
505 fatal("Client version \"%.100s\" uses unsafe key agreement; "
506 "refusing connection", remote_version);
507 }
508
509 mismatch = 0;
510 switch (remote_major) {
511 case 1:
512 if (remote_minor == 99) {
513 if (options.protocol & SSH_PROTO_2)
514 enable_compat20();
515 else
516 mismatch = 1;
517 break;
518 }
519 if (!(options.protocol & SSH_PROTO_1)) {
520 mismatch = 1;
521 break;
522 }
523 if (remote_minor < 3) {
524 packet_disconnect("Your ssh version is too old and "
525 "is no longer supported. Please install a newer version.");
526 } else if (remote_minor == 3) {
527 /* note that this disables agent-forwarding */
528 enable_compat13();
529 }
530 break;
531 case 2:
532 if (options.protocol & SSH_PROTO_2) {
533 enable_compat20();
534 break;
535 }
536 /* FALLTHROUGH */
537 default:
538 mismatch = 1;
539 break;
540 }
541 chop(server_version_string);
542 debug("Local version string %.200s", server_version_string);
543
544 if (mismatch) {
545 s = "Protocol major versions differ.\n";
546 (void) atomicio(vwrite, sock_out, s, strlen(s));
547 close(sock_in);
548 close(sock_out);
549 logit("Protocol major versions differ for %s: %.200s vs. %.200s",
550 get_remote_ipaddr(),
551 server_version_string, client_version_string);
552 cleanup_exit(255);
553 }
554 }
555
556 /* Destroy the host and server keys. They will no longer be needed. */
557 void
destroy_sensitive_data(void)558 destroy_sensitive_data(void)
559 {
560 int i;
561
562 if (sensitive_data.server_key) {
563 key_free(sensitive_data.server_key);
564 sensitive_data.server_key = NULL;
565 }
566 for (i = 0; i < options.num_host_key_files; i++) {
567 if (sensitive_data.host_keys[i]) {
568 key_free(sensitive_data.host_keys[i]);
569 sensitive_data.host_keys[i] = NULL;
570 }
571 if (sensitive_data.host_certificates[i]) {
572 key_free(sensitive_data.host_certificates[i]);
573 sensitive_data.host_certificates[i] = NULL;
574 }
575 }
576 sensitive_data.ssh1_host_key = NULL;
577 explicit_bzero(sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
578 }
579
580 /* Demote private to public keys for network child */
581 void
demote_sensitive_data(void)582 demote_sensitive_data(void)
583 {
584 Key *tmp;
585 int i;
586
587 if (sensitive_data.server_key) {
588 tmp = key_demote(sensitive_data.server_key);
589 key_free(sensitive_data.server_key);
590 sensitive_data.server_key = tmp;
591 }
592
593 for (i = 0; i < options.num_host_key_files; i++) {
594 if (sensitive_data.host_keys[i]) {
595 tmp = key_demote(sensitive_data.host_keys[i]);
596 key_free(sensitive_data.host_keys[i]);
597 sensitive_data.host_keys[i] = tmp;
598 if (tmp->type == KEY_RSA1)
599 sensitive_data.ssh1_host_key = tmp;
600 }
601 /* Certs do not need demotion */
602 }
603
604 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */
605 }
606
607 static void
privsep_preauth_child(void)608 privsep_preauth_child(void)
609 {
610 u_int32_t rnd[256];
611 gid_t gidset[1];
612
613 /* Enable challenge-response authentication for privilege separation */
614 privsep_challenge_enable();
615
616 #ifdef GSSAPI
617 /* Cache supported mechanism OIDs for later use */
618 if (options.gss_authentication)
619 ssh_gssapi_prepare_supported_oids();
620 #endif
621
622 arc4random_stir();
623 arc4random_buf(rnd, sizeof(rnd));
624 #ifdef WITH_OPENSSL
625 RAND_seed(rnd, sizeof(rnd));
626 #endif
627 explicit_bzero(rnd, sizeof(rnd));
628
629 /* Demote the private keys to public keys. */
630 demote_sensitive_data();
631
632 /* Change our root directory */
633 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
634 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
635 strerror(errno));
636 if (chdir("/") == -1)
637 fatal("chdir(\"/\"): %s", strerror(errno));
638
639 /* Drop our privileges */
640 debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid,
641 (u_int)privsep_pw->pw_gid);
642 #if 0
643 /* XXX not ready, too heavy after chroot */
644 do_setusercontext(privsep_pw);
645 #else
646 gidset[0] = privsep_pw->pw_gid;
647 if (setgroups(1, gidset) < 0)
648 fatal("setgroups: %.100s", strerror(errno));
649 permanently_set_uid(privsep_pw);
650 #endif
651 }
652
653 static int
privsep_preauth(Authctxt * authctxt)654 privsep_preauth(Authctxt *authctxt)
655 {
656 int status, r;
657 pid_t pid;
658 struct ssh_sandbox *box = NULL;
659
660 /* Set up unprivileged child process to deal with network data */
661 pmonitor = monitor_init();
662 /* Store a pointer to the kex for later rekeying */
663 pmonitor->m_pkex = &active_state->kex;
664
665 if (use_privsep == PRIVSEP_ON)
666 box = ssh_sandbox_init(pmonitor);
667 pid = fork();
668 if (pid == -1) {
669 fatal("fork of unprivileged child failed");
670 } else if (pid != 0) {
671 debug2("Network child is on pid %ld", (long)pid);
672
673 pmonitor->m_pid = pid;
674 if (have_agent) {
675 r = ssh_get_authentication_socket(&auth_sock);
676 if (r != 0) {
677 error("Could not get agent socket: %s",
678 ssh_err(r));
679 have_agent = 0;
680 }
681 }
682 if (box != NULL)
683 ssh_sandbox_parent_preauth(box, pid);
684 monitor_child_preauth(authctxt, pmonitor);
685
686 /* Sync memory */
687 monitor_sync(pmonitor);
688
689 /* Wait for the child's exit status */
690 while (waitpid(pid, &status, 0) < 0) {
691 if (errno == EINTR)
692 continue;
693 pmonitor->m_pid = -1;
694 fatal("%s: waitpid: %s", __func__, strerror(errno));
695 }
696 privsep_is_preauth = 0;
697 pmonitor->m_pid = -1;
698 if (WIFEXITED(status)) {
699 if (WEXITSTATUS(status) != 0)
700 fatal("%s: preauth child exited with status %d",
701 __func__, WEXITSTATUS(status));
702 } else if (WIFSIGNALED(status))
703 fatal("%s: preauth child terminated by signal %d",
704 __func__, WTERMSIG(status));
705 if (box != NULL)
706 ssh_sandbox_parent_finish(box);
707 return 1;
708 } else {
709 /* child */
710 close(pmonitor->m_sendfd);
711 close(pmonitor->m_log_recvfd);
712
713 /* Arrange for logging to be sent to the monitor */
714 set_log_handler(mm_log_handler, pmonitor);
715
716 /* Demote the child */
717 if (getuid() == 0 || geteuid() == 0)
718 privsep_preauth_child();
719 setproctitle("%s", "[net]");
720 if (box != NULL)
721 ssh_sandbox_child(box);
722
723 return 0;
724 }
725 }
726
727 static void
privsep_postauth(Authctxt * authctxt)728 privsep_postauth(Authctxt *authctxt)
729 {
730 u_int32_t rnd[256];
731
732 #ifdef DISABLE_FD_PASSING
733 if (1) {
734 #else
735 if (authctxt->pw->pw_uid == 0 || options.use_login) {
736 #endif
737 /* File descriptor passing is broken or root login */
738 use_privsep = 0;
739 goto skip;
740 }
741
742 /* New socket pair */
743 monitor_reinit(pmonitor);
744
745 pmonitor->m_pid = fork();
746 if (pmonitor->m_pid == -1)
747 fatal("fork of unprivileged child failed");
748 else if (pmonitor->m_pid != 0) {
749 verbose("User child is on pid %ld", (long)pmonitor->m_pid);
750 buffer_clear(&loginmsg);
751 monitor_child_postauth(pmonitor);
752
753 /* NEVERREACHED */
754 exit(0);
755 }
756
757 /* child */
758
759 close(pmonitor->m_sendfd);
760 pmonitor->m_sendfd = -1;
761
762 /* Demote the private keys to public keys. */
763 demote_sensitive_data();
764
765 arc4random_stir();
766 arc4random_buf(rnd, sizeof(rnd));
767 #ifdef WITH_OPENSSL
768 RAND_seed(rnd, sizeof(rnd));
769 #endif
770 explicit_bzero(rnd, sizeof(rnd));
771
772 /* Drop privileges */
773 do_setusercontext(authctxt->pw);
774
775 skip:
776 /* It is safe now to apply the key state */
777 monitor_apply_keystate(pmonitor);
778
779 /*
780 * Tell the packet layer that authentication was successful, since
781 * this information is not part of the key state.
782 */
783 packet_set_authenticated();
784 }
785
786 static char *
787 list_hostkey_types(void)
788 {
789 Buffer b;
790 const char *p;
791 char *ret;
792 int i;
793 Key *key;
794
795 buffer_init(&b);
796 for (i = 0; i < options.num_host_key_files; i++) {
797 key = sensitive_data.host_keys[i];
798 if (key == NULL)
799 key = sensitive_data.host_pubkeys[i];
800 if (key == NULL)
801 continue;
802 switch (key->type) {
803 case KEY_RSA:
804 case KEY_DSA:
805 case KEY_ECDSA:
806 case KEY_ED25519:
807 if (buffer_len(&b) > 0)
808 buffer_append(&b, ",", 1);
809 p = key_ssh_name(key);
810 buffer_append(&b, p, strlen(p));
811 break;
812 }
813 /* If the private key has a cert peer, then list that too */
814 key = sensitive_data.host_certificates[i];
815 if (key == NULL)
816 continue;
817 switch (key->type) {
818 case KEY_RSA_CERT_V00:
819 case KEY_DSA_CERT_V00:
820 case KEY_RSA_CERT:
821 case KEY_DSA_CERT:
822 case KEY_ECDSA_CERT:
823 case KEY_ED25519_CERT:
824 if (buffer_len(&b) > 0)
825 buffer_append(&b, ",", 1);
826 p = key_ssh_name(key);
827 buffer_append(&b, p, strlen(p));
828 break;
829 }
830 }
831 buffer_append(&b, "\0", 1);
832 ret = xstrdup(buffer_ptr(&b));
833 buffer_free(&b);
834 debug("list_hostkey_types: %s", ret);
835 return ret;
836 }
837
838 static Key *
839 get_hostkey_by_type(int type, int nid, int need_private, struct ssh *ssh)
840 {
841 int i;
842 Key *key;
843
844 for (i = 0; i < options.num_host_key_files; i++) {
845 switch (type) {
846 case KEY_RSA_CERT_V00:
847 case KEY_DSA_CERT_V00:
848 case KEY_RSA_CERT:
849 case KEY_DSA_CERT:
850 case KEY_ECDSA_CERT:
851 case KEY_ED25519_CERT:
852 key = sensitive_data.host_certificates[i];
853 break;
854 default:
855 key = sensitive_data.host_keys[i];
856 if (key == NULL && !need_private)
857 key = sensitive_data.host_pubkeys[i];
858 break;
859 }
860 if (key != NULL && key->type == type &&
861 (key->type != KEY_ECDSA || key->ecdsa_nid == nid))
862 return need_private ?
863 sensitive_data.host_keys[i] : key;
864 }
865 return NULL;
866 }
867
868 Key *
869 get_hostkey_public_by_type(int type, int nid, struct ssh *ssh)
870 {
871 return get_hostkey_by_type(type, nid, 0, ssh);
872 }
873
874 Key *
875 get_hostkey_private_by_type(int type, int nid, struct ssh *ssh)
876 {
877 return get_hostkey_by_type(type, nid, 1, ssh);
878 }
879
880 Key *
881 get_hostkey_by_index(int ind)
882 {
883 if (ind < 0 || ind >= options.num_host_key_files)
884 return (NULL);
885 return (sensitive_data.host_keys[ind]);
886 }
887
888 Key *
889 get_hostkey_public_by_index(int ind, struct ssh *ssh)
890 {
891 if (ind < 0 || ind >= options.num_host_key_files)
892 return (NULL);
893 return (sensitive_data.host_pubkeys[ind]);
894 }
895
896 int
897 get_hostkey_index(Key *key, int compare, struct ssh *ssh)
898 {
899 int i;
900
901 for (i = 0; i < options.num_host_key_files; i++) {
902 if (key_is_cert(key)) {
903 if (key == sensitive_data.host_certificates[i] ||
904 (compare && sensitive_data.host_certificates[i] &&
905 sshkey_equal(key,
906 sensitive_data.host_certificates[i])))
907 return (i);
908 } else {
909 if (key == sensitive_data.host_keys[i] ||
910 (compare && sensitive_data.host_keys[i] &&
911 sshkey_equal(key, sensitive_data.host_keys[i])))
912 return (i);
913 if (key == sensitive_data.host_pubkeys[i] ||
914 (compare && sensitive_data.host_pubkeys[i] &&
915 sshkey_equal(key, sensitive_data.host_pubkeys[i])))
916 return (i);
917 }
918 }
919 return (-1);
920 }
921
922 /* Inform the client of all hostkeys */
923 static void
924 notify_hostkeys(struct ssh *ssh)
925 {
926 struct sshbuf *buf;
927 struct sshkey *key;
928 int i, nkeys, r;
929 char *fp;
930
931 if ((buf = sshbuf_new()) == NULL)
932 fatal("%s: sshbuf_new", __func__);
933 for (i = nkeys = 0; i < options.num_host_key_files; i++) {
934 key = get_hostkey_public_by_index(i, ssh);
935 if (key == NULL || key->type == KEY_UNSPEC ||
936 key->type == KEY_RSA1 || sshkey_is_cert(key))
937 continue;
938 fp = sshkey_fingerprint(key, options.fingerprint_hash,
939 SSH_FP_DEFAULT);
940 debug3("%s: key %d: %s %s", __func__, i,
941 sshkey_ssh_name(key), fp);
942 free(fp);
943 if (nkeys == 0) {
944 packet_start(SSH2_MSG_GLOBAL_REQUEST);
945 packet_put_cstring("hostkeys-00@openssh.com");
946 packet_put_char(0); /* want-reply */
947 }
948 sshbuf_reset(buf);
949 if ((r = sshkey_putb(key, buf)) != 0)
950 fatal("%s: couldn't put hostkey %d: %s",
951 __func__, i, ssh_err(r));
952 packet_put_string(sshbuf_ptr(buf), sshbuf_len(buf));
953 nkeys++;
954 }
955 debug3("%s: sent %d hostkeys", __func__, nkeys);
956 if (nkeys == 0)
957 fatal("%s: no hostkeys", __func__);
958 packet_send();
959 sshbuf_free(buf);
960 }
961
962 /*
963 * returns 1 if connection should be dropped, 0 otherwise.
964 * dropping starts at connection #max_startups_begin with a probability
965 * of (max_startups_rate/100). the probability increases linearly until
966 * all connections are dropped for startups > max_startups
967 */
968 static int
969 drop_connection(int startups)
970 {
971 int p, r;
972
973 if (startups < options.max_startups_begin)
974 return 0;
975 if (startups >= options.max_startups)
976 return 1;
977 if (options.max_startups_rate == 100)
978 return 1;
979
980 p = 100 - options.max_startups_rate;
981 p *= startups - options.max_startups_begin;
982 p /= options.max_startups - options.max_startups_begin;
983 p += options.max_startups_rate;
984 r = arc4random_uniform(100);
985
986 debug("drop_connection: p %d, r %d", p, r);
987 return (r < p) ? 1 : 0;
988 }
989
990 static void
991 usage(void)
992 {
993 fprintf(stderr, "%s, %s\n",
994 SSH_RELEASE,
995 #ifdef WITH_OPENSSL
996 SSLeay_version(SSLEAY_VERSION)
997 #else
998 "without OpenSSL"
999 #endif
1000 );
1001 fprintf(stderr,
1002 "usage: sshd [-46DdeiqTt] [-b bits] [-C connection_spec] [-c host_cert_file]\n"
1003 " [-E log_file] [-f config_file] [-g login_grace_time]\n"
1004 " [-h host_key_file] [-k key_gen_time] [-o option] [-p port]\n"
1005 " [-u len]\n"
1006 );
1007 exit(1);
1008 }
1009
1010 static void
1011 send_rexec_state(int fd, Buffer *conf)
1012 {
1013 Buffer m;
1014
1015 debug3("%s: entering fd = %d config len %d", __func__, fd,
1016 buffer_len(conf));
1017
1018 /*
1019 * Protocol from reexec master to child:
1020 * string configuration
1021 * u_int ephemeral_key_follows
1022 * bignum e (only if ephemeral_key_follows == 1)
1023 * bignum n "
1024 * bignum d "
1025 * bignum iqmp "
1026 * bignum p "
1027 * bignum q "
1028 * string rngseed (only if OpenSSL is not self-seeded)
1029 */
1030 buffer_init(&m);
1031 buffer_put_cstring(&m, buffer_ptr(conf));
1032
1033 #ifdef WITH_SSH1
1034 if (sensitive_data.server_key != NULL &&
1035 sensitive_data.server_key->type == KEY_RSA1) {
1036 buffer_put_int(&m, 1);
1037 buffer_put_bignum(&m, sensitive_data.server_key->rsa->e);
1038 buffer_put_bignum(&m, sensitive_data.server_key->rsa->n);
1039 buffer_put_bignum(&m, sensitive_data.server_key->rsa->d);
1040 buffer_put_bignum(&m, sensitive_data.server_key->rsa->iqmp);
1041 buffer_put_bignum(&m, sensitive_data.server_key->rsa->p);
1042 buffer_put_bignum(&m, sensitive_data.server_key->rsa->q);
1043 } else
1044 #endif
1045 buffer_put_int(&m, 0);
1046
1047 #if defined(WITH_OPENSSL) && !defined(OPENSSL_PRNG_ONLY)
1048 rexec_send_rng_seed(&m);
1049 #endif
1050
1051 if (ssh_msg_send(fd, 0, &m) == -1)
1052 fatal("%s: ssh_msg_send failed", __func__);
1053
1054 buffer_free(&m);
1055
1056 debug3("%s: done", __func__);
1057 }
1058
1059 static void
1060 recv_rexec_state(int fd, Buffer *conf)
1061 {
1062 Buffer m;
1063 char *cp;
1064 u_int len;
1065
1066 debug3("%s: entering fd = %d", __func__, fd);
1067
1068 buffer_init(&m);
1069
1070 if (ssh_msg_recv(fd, &m) == -1)
1071 fatal("%s: ssh_msg_recv failed", __func__);
1072 if (buffer_get_char(&m) != 0)
1073 fatal("%s: rexec version mismatch", __func__);
1074
1075 cp = buffer_get_string(&m, &len);
1076 if (conf != NULL)
1077 buffer_append(conf, cp, len + 1);
1078 free(cp);
1079
1080 if (buffer_get_int(&m)) {
1081 #ifdef WITH_SSH1
1082 if (sensitive_data.server_key != NULL)
1083 key_free(sensitive_data.server_key);
1084 sensitive_data.server_key = key_new_private(KEY_RSA1);
1085 buffer_get_bignum(&m, sensitive_data.server_key->rsa->e);
1086 buffer_get_bignum(&m, sensitive_data.server_key->rsa->n);
1087 buffer_get_bignum(&m, sensitive_data.server_key->rsa->d);
1088 buffer_get_bignum(&m, sensitive_data.server_key->rsa->iqmp);
1089 buffer_get_bignum(&m, sensitive_data.server_key->rsa->p);
1090 buffer_get_bignum(&m, sensitive_data.server_key->rsa->q);
1091 if (rsa_generate_additional_parameters(
1092 sensitive_data.server_key->rsa) != 0)
1093 fatal("%s: rsa_generate_additional_parameters "
1094 "error", __func__);
1095 #else
1096 fatal("ssh1 not supported");
1097 #endif
1098 }
1099
1100 #if defined(WITH_OPENSSL) && !defined(OPENSSL_PRNG_ONLY)
1101 rexec_recv_rng_seed(&m);
1102 #endif
1103
1104 buffer_free(&m);
1105
1106 debug3("%s: done", __func__);
1107 }
1108
1109 /* Accept a connection from inetd */
1110 static void
1111 server_accept_inetd(int *sock_in, int *sock_out)
1112 {
1113 int fd;
1114
1115 startup_pipe = -1;
1116 if (rexeced_flag) {
1117 close(REEXEC_CONFIG_PASS_FD);
1118 *sock_in = *sock_out = dup(STDIN_FILENO);
1119 if (!debug_flag) {
1120 startup_pipe = dup(REEXEC_STARTUP_PIPE_FD);
1121 close(REEXEC_STARTUP_PIPE_FD);
1122 }
1123 } else {
1124 *sock_in = dup(STDIN_FILENO);
1125 *sock_out = dup(STDOUT_FILENO);
1126 }
1127 /*
1128 * We intentionally do not close the descriptors 0, 1, and 2
1129 * as our code for setting the descriptors won't work if
1130 * ttyfd happens to be one of those.
1131 */
1132 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
1133 dup2(fd, STDIN_FILENO);
1134 dup2(fd, STDOUT_FILENO);
1135 if (!log_stderr)
1136 dup2(fd, STDERR_FILENO);
1137 if (fd > (log_stderr ? STDERR_FILENO : STDOUT_FILENO))
1138 close(fd);
1139 }
1140 debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out);
1141 }
1142
1143 /*
1144 * Listen for TCP connections
1145 */
1146 static void
1147 server_listen(void)
1148 {
1149 int ret, listen_sock, on = 1;
1150 struct addrinfo *ai;
1151 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
1152
1153 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
1154 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
1155 continue;
1156 if (num_listen_socks >= MAX_LISTEN_SOCKS)
1157 fatal("Too many listen sockets. "
1158 "Enlarge MAX_LISTEN_SOCKS");
1159 if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen,
1160 ntop, sizeof(ntop), strport, sizeof(strport),
1161 NI_NUMERICHOST|NI_NUMERICSERV)) != 0) {
1162 error("getnameinfo failed: %.100s",
1163 ssh_gai_strerror(ret));
1164 continue;
1165 }
1166 /* Create socket for listening. */
1167 listen_sock = socket(ai->ai_family, ai->ai_socktype,
1168 ai->ai_protocol);
1169 if (listen_sock < 0) {
1170 /* kernel may not support ipv6 */
1171 verbose("socket: %.100s", strerror(errno));
1172 continue;
1173 }
1174 if (set_nonblock(listen_sock) == -1) {
1175 close(listen_sock);
1176 continue;
1177 }
1178 /*
1179 * Set socket options.
1180 * Allow local port reuse in TIME_WAIT.
1181 */
1182 if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
1183 &on, sizeof(on)) == -1)
1184 error("setsockopt SO_REUSEADDR: %s", strerror(errno));
1185
1186 /* Only communicate in IPv6 over AF_INET6 sockets. */
1187 if (ai->ai_family == AF_INET6)
1188 sock_set_v6only(listen_sock);
1189
1190 debug("Bind to port %s on %s.", strport, ntop);
1191
1192 /* Bind the socket to the desired port. */
1193 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1194 error("Bind to port %s on %s failed: %.200s.",
1195 strport, ntop, strerror(errno));
1196 close(listen_sock);
1197 continue;
1198 }
1199 listen_socks[num_listen_socks] = listen_sock;
1200 num_listen_socks++;
1201
1202 /* Start listening on the port. */
1203 if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0)
1204 fatal("listen on [%s]:%s: %.100s",
1205 ntop, strport, strerror(errno));
1206 logit("Server listening on %s port %s.", ntop, strport);
1207 }
1208 freeaddrinfo(options.listen_addrs);
1209
1210 if (!num_listen_socks)
1211 fatal("Cannot bind any address.");
1212 }
1213
1214 /*
1215 * The main TCP accept loop. Note that, for the non-debug case, returns
1216 * from this function are in a forked subprocess.
1217 */
1218 static void
1219 server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
1220 {
1221 fd_set *fdset;
1222 int i, j, ret, maxfd;
1223 int key_used = 0, startups = 0;
1224 int startup_p[2] = { -1 , -1 };
1225 struct sockaddr_storage from;
1226 socklen_t fromlen;
1227 pid_t pid;
1228 u_char rnd[256];
1229
1230 /* setup fd set for accept */
1231 fdset = NULL;
1232 maxfd = 0;
1233 for (i = 0; i < num_listen_socks; i++)
1234 if (listen_socks[i] > maxfd)
1235 maxfd = listen_socks[i];
1236 /* pipes connected to unauthenticated childs */
1237 startup_pipes = xcalloc(options.max_startups, sizeof(int));
1238 for (i = 0; i < options.max_startups; i++)
1239 startup_pipes[i] = -1;
1240
1241 /*
1242 * Stay listening for connections until the system crashes or
1243 * the daemon is killed with a signal.
1244 */
1245 for (;;) {
1246 if (received_sighup)
1247 sighup_restart();
1248 if (fdset != NULL)
1249 free(fdset);
1250 fdset = (fd_set *)xcalloc(howmany(maxfd + 1, NFDBITS),
1251 sizeof(fd_mask));
1252
1253 for (i = 0; i < num_listen_socks; i++)
1254 FD_SET(listen_socks[i], fdset);
1255 for (i = 0; i < options.max_startups; i++)
1256 if (startup_pipes[i] != -1)
1257 FD_SET(startup_pipes[i], fdset);
1258
1259 /* Wait in select until there is a connection. */
1260 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
1261 if (ret < 0 && errno != EINTR)
1262 error("select: %.100s", strerror(errno));
1263 if (received_sigterm) {
1264 logit("Received signal %d; terminating.",
1265 (int) received_sigterm);
1266 close_listen_socks();
1267 if (options.pid_file != NULL)
1268 unlink(options.pid_file);
1269 exit(received_sigterm == SIGTERM ? 0 : 255);
1270 }
1271 if (key_used && key_do_regen) {
1272 generate_ephemeral_server_key();
1273 key_used = 0;
1274 key_do_regen = 0;
1275 }
1276 if (ret < 0)
1277 continue;
1278
1279 for (i = 0; i < options.max_startups; i++)
1280 if (startup_pipes[i] != -1 &&
1281 FD_ISSET(startup_pipes[i], fdset)) {
1282 /*
1283 * the read end of the pipe is ready
1284 * if the child has closed the pipe
1285 * after successful authentication
1286 * or if the child has died
1287 */
1288 close(startup_pipes[i]);
1289 startup_pipes[i] = -1;
1290 startups--;
1291 }
1292 for (i = 0; i < num_listen_socks; i++) {
1293 if (!FD_ISSET(listen_socks[i], fdset))
1294 continue;
1295 fromlen = sizeof(from);
1296 *newsock = accept(listen_socks[i],
1297 (struct sockaddr *)&from, &fromlen);
1298 if (*newsock < 0) {
1299 if (errno != EINTR && errno != EWOULDBLOCK &&
1300 errno != ECONNABORTED && errno != EAGAIN)
1301 error("accept: %.100s",
1302 strerror(errno));
1303 if (errno == EMFILE || errno == ENFILE)
1304 usleep(100 * 1000);
1305 continue;
1306 }
1307 if (unset_nonblock(*newsock) == -1) {
1308 close(*newsock);
1309 continue;
1310 }
1311 if (drop_connection(startups) == 1) {
1312 debug("drop connection #%d", startups);
1313 close(*newsock);
1314 continue;
1315 }
1316 if (pipe(startup_p) == -1) {
1317 close(*newsock);
1318 continue;
1319 }
1320
1321 if (rexec_flag && socketpair(AF_UNIX,
1322 SOCK_STREAM, 0, config_s) == -1) {
1323 error("reexec socketpair: %s",
1324 strerror(errno));
1325 close(*newsock);
1326 close(startup_p[0]);
1327 close(startup_p[1]);
1328 continue;
1329 }
1330
1331 for (j = 0; j < options.max_startups; j++)
1332 if (startup_pipes[j] == -1) {
1333 startup_pipes[j] = startup_p[0];
1334 if (maxfd < startup_p[0])
1335 maxfd = startup_p[0];
1336 startups++;
1337 break;
1338 }
1339
1340 /*
1341 * Got connection. Fork a child to handle it, unless
1342 * we are in debugging mode.
1343 */
1344 if (debug_flag) {
1345 /*
1346 * In debugging mode. Close the listening
1347 * socket, and start processing the
1348 * connection without forking.
1349 */
1350 debug("Server will not fork when running in debugging mode.");
1351 close_listen_socks();
1352 *sock_in = *newsock;
1353 *sock_out = *newsock;
1354 close(startup_p[0]);
1355 close(startup_p[1]);
1356 startup_pipe = -1;
1357 pid = getpid();
1358 if (rexec_flag) {
1359 send_rexec_state(config_s[0],
1360 &cfg);
1361 close(config_s[0]);
1362 }
1363 break;
1364 }
1365
1366 /*
1367 * Normal production daemon. Fork, and have
1368 * the child process the connection. The
1369 * parent continues listening.
1370 */
1371 platform_pre_fork();
1372 if ((pid = fork()) == 0) {
1373 /*
1374 * Child. Close the listening and
1375 * max_startup sockets. Start using
1376 * the accepted socket. Reinitialize
1377 * logging (since our pid has changed).
1378 * We break out of the loop to handle
1379 * the connection.
1380 */
1381 platform_post_fork_child();
1382 startup_pipe = startup_p[1];
1383 close_startup_pipes();
1384 close_listen_socks();
1385 *sock_in = *newsock;
1386 *sock_out = *newsock;
1387 log_init(__progname,
1388 options.log_level,
1389 options.log_facility,
1390 log_stderr);
1391 if (rexec_flag)
1392 close(config_s[0]);
1393 break;
1394 }
1395
1396 /* Parent. Stay in the loop. */
1397 platform_post_fork_parent(pid);
1398 if (pid < 0)
1399 error("fork: %.100s", strerror(errno));
1400 else
1401 debug("Forked child %ld.", (long)pid);
1402
1403 close(startup_p[1]);
1404
1405 if (rexec_flag) {
1406 send_rexec_state(config_s[0], &cfg);
1407 close(config_s[0]);
1408 close(config_s[1]);
1409 }
1410
1411 /*
1412 * Mark that the key has been used (it
1413 * was "given" to the child).
1414 */
1415 if ((options.protocol & SSH_PROTO_1) &&
1416 key_used == 0) {
1417 /* Schedule server key regeneration alarm. */
1418 signal(SIGALRM, key_regeneration_alarm);
1419 alarm(options.key_regeneration_time);
1420 key_used = 1;
1421 }
1422
1423 close(*newsock);
1424
1425 /*
1426 * Ensure that our random state differs
1427 * from that of the child
1428 */
1429 arc4random_stir();
1430 arc4random_buf(rnd, sizeof(rnd));
1431 #ifdef WITH_OPENSSL
1432 RAND_seed(rnd, sizeof(rnd));
1433 #endif
1434 explicit_bzero(rnd, sizeof(rnd));
1435 }
1436
1437 /* child process check (or debug mode) */
1438 if (num_listen_socks < 0)
1439 break;
1440 }
1441 }
1442
1443
1444 /*
1445 * Main program for the daemon.
1446 */
1447 int
1448 main(int ac, char **av)
1449 {
1450 extern char *optarg;
1451 extern int optind;
1452 int r, opt, i, j, on = 1;
1453 int sock_in = -1, sock_out = -1, newsock = -1;
1454 const char *remote_ip;
1455 int remote_port;
1456 char *fp, *line, *logfile = NULL;
1457 int config_s[2] = { -1 , -1 };
1458 u_int n;
1459 u_int64_t ibytes, obytes;
1460 mode_t new_umask;
1461 Key *key;
1462 Key *pubkey;
1463 int keytype;
1464 Authctxt *authctxt;
1465 struct connection_info *connection_info = get_connection_info(0, 0);
1466
1467 #ifdef HAVE_SECUREWARE
1468 (void)set_auth_parameters(ac, av);
1469 #endif
1470 __progname = ssh_get_progname(av[0]);
1471
1472 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
1473 saved_argc = ac;
1474 rexec_argc = ac;
1475 saved_argv = xcalloc(ac + 1, sizeof(*saved_argv));
1476 for (i = 0; i < ac; i++)
1477 saved_argv[i] = xstrdup(av[i]);
1478 saved_argv[i] = NULL;
1479
1480 #ifndef HAVE_SETPROCTITLE
1481 /* Prepare for later setproctitle emulation */
1482 compat_init_setproctitle(ac, av);
1483 av = saved_argv;
1484 #endif
1485
1486 if (geteuid() == 0 && setgroups(0, NULL) == -1)
1487 debug("setgroups(): %.200s", strerror(errno));
1488
1489 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
1490 sanitise_stdfd();
1491
1492 /* Initialize configuration options to their default values. */
1493 initialize_server_options(&options);
1494
1495 /* Parse command-line arguments. */
1496 while ((opt = getopt(ac, av, "f:p:b:k:h:g:u:o:C:dDeE:iqrtQRT46")) != -1) {
1497 switch (opt) {
1498 case '4':
1499 options.address_family = AF_INET;
1500 break;
1501 case '6':
1502 options.address_family = AF_INET6;
1503 break;
1504 case 'f':
1505 config_file_name = optarg;
1506 break;
1507 case 'c':
1508 if (options.num_host_cert_files >= MAX_HOSTCERTS) {
1509 fprintf(stderr, "too many host certificates.\n");
1510 exit(1);
1511 }
1512 options.host_cert_files[options.num_host_cert_files++] =
1513 derelativise_path(optarg);
1514 break;
1515 case 'd':
1516 if (debug_flag == 0) {
1517 debug_flag = 1;
1518 options.log_level = SYSLOG_LEVEL_DEBUG1;
1519 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
1520 options.log_level++;
1521 break;
1522 case 'D':
1523 no_daemon_flag = 1;
1524 break;
1525 case 'E':
1526 logfile = xstrdup(optarg);
1527 /* FALLTHROUGH */
1528 case 'e':
1529 log_stderr = 1;
1530 break;
1531 case 'i':
1532 inetd_flag = 1;
1533 break;
1534 case 'r':
1535 rexec_flag = 0;
1536 break;
1537 case 'R':
1538 rexeced_flag = 1;
1539 inetd_flag = 1;
1540 break;
1541 case 'Q':
1542 /* ignored */
1543 break;
1544 case 'q':
1545 options.log_level = SYSLOG_LEVEL_QUIET;
1546 break;
1547 case 'b':
1548 options.server_key_bits = (int)strtonum(optarg, 256,
1549 32768, NULL);
1550 break;
1551 case 'p':
1552 options.ports_from_cmdline = 1;
1553 if (options.num_ports >= MAX_PORTS) {
1554 fprintf(stderr, "too many ports.\n");
1555 exit(1);
1556 }
1557 options.ports[options.num_ports++] = a2port(optarg);
1558 if (options.ports[options.num_ports-1] <= 0) {
1559 fprintf(stderr, "Bad port number.\n");
1560 exit(1);
1561 }
1562 break;
1563 case 'g':
1564 if ((options.login_grace_time = convtime(optarg)) == -1) {
1565 fprintf(stderr, "Invalid login grace time.\n");
1566 exit(1);
1567 }
1568 break;
1569 case 'k':
1570 if ((options.key_regeneration_time = convtime(optarg)) == -1) {
1571 fprintf(stderr, "Invalid key regeneration interval.\n");
1572 exit(1);
1573 }
1574 break;
1575 case 'h':
1576 if (options.num_host_key_files >= MAX_HOSTKEYS) {
1577 fprintf(stderr, "too many host keys.\n");
1578 exit(1);
1579 }
1580 options.host_key_files[options.num_host_key_files++] =
1581 derelativise_path(optarg);
1582 break;
1583 case 't':
1584 test_flag = 1;
1585 break;
1586 case 'T':
1587 test_flag = 2;
1588 break;
1589 case 'C':
1590 if (parse_server_match_testspec(connection_info,
1591 optarg) == -1)
1592 exit(1);
1593 break;
1594 case 'u':
1595 utmp_len = (u_int)strtonum(optarg, 0, HOST_NAME_MAX+1+1, NULL);
1596 if (utmp_len > HOST_NAME_MAX+1) {
1597 fprintf(stderr, "Invalid utmp length.\n");
1598 exit(1);
1599 }
1600 break;
1601 case 'o':
1602 line = xstrdup(optarg);
1603 if (process_server_config_line(&options, line,
1604 "command-line", 0, NULL, NULL) != 0)
1605 exit(1);
1606 free(line);
1607 break;
1608 case '?':
1609 default:
1610 usage();
1611 break;
1612 }
1613 }
1614 if (rexeced_flag || inetd_flag)
1615 rexec_flag = 0;
1616 if (!test_flag && (rexec_flag && (av[0] == NULL || *av[0] != '/')))
1617 fatal("sshd re-exec requires execution with an absolute path");
1618 if (rexeced_flag)
1619 closefrom(REEXEC_MIN_FREE_FD);
1620 else
1621 closefrom(REEXEC_DEVCRYPTO_RESERVED_FD);
1622
1623 #ifdef WITH_OPENSSL
1624 OpenSSL_add_all_algorithms();
1625 #endif
1626
1627 /* If requested, redirect the logs to the specified logfile. */
1628 if (logfile != NULL) {
1629 log_redirect_stderr_to(logfile);
1630 free(logfile);
1631 }
1632 /*
1633 * Force logging to stderr until we have loaded the private host
1634 * key (unless started from inetd)
1635 */
1636 log_init(__progname,
1637 options.log_level == SYSLOG_LEVEL_NOT_SET ?
1638 SYSLOG_LEVEL_INFO : options.log_level,
1639 options.log_facility == SYSLOG_FACILITY_NOT_SET ?
1640 SYSLOG_FACILITY_AUTH : options.log_facility,
1641 log_stderr || !inetd_flag);
1642
1643 /*
1644 * Unset KRB5CCNAME, otherwise the user's session may inherit it from
1645 * root's environment
1646 */
1647 if (getenv("KRB5CCNAME") != NULL)
1648 (void) unsetenv("KRB5CCNAME");
1649
1650 #ifdef _UNICOS
1651 /* Cray can define user privs drop all privs now!
1652 * Not needed on PRIV_SU systems!
1653 */
1654 drop_cray_privs();
1655 #endif
1656
1657 sensitive_data.server_key = NULL;
1658 sensitive_data.ssh1_host_key = NULL;
1659 sensitive_data.have_ssh1_key = 0;
1660 sensitive_data.have_ssh2_key = 0;
1661
1662 /*
1663 * If we're doing an extended config test, make sure we have all of
1664 * the parameters we need. If we're not doing an extended test,
1665 * do not silently ignore connection test params.
1666 */
1667 if (test_flag >= 2 && server_match_spec_complete(connection_info) == 0)
1668 fatal("user, host and addr are all required when testing "
1669 "Match configs");
1670 if (test_flag < 2 && server_match_spec_complete(connection_info) >= 0)
1671 fatal("Config test connection parameter (-C) provided without "
1672 "test mode (-T)");
1673
1674 /* Fetch our configuration */
1675 buffer_init(&cfg);
1676 if (rexeced_flag)
1677 recv_rexec_state(REEXEC_CONFIG_PASS_FD, &cfg);
1678 else
1679 load_server_config(config_file_name, &cfg);
1680
1681 parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name,
1682 &cfg, NULL);
1683
1684 seed_rng();
1685
1686 /* Fill in default values for those options not explicitly set. */
1687 fill_default_server_options(&options);
1688
1689 /* challenge-response is implemented via keyboard interactive */
1690 if (options.challenge_response_authentication)
1691 options.kbd_interactive_authentication = 1;
1692
1693 /* Check that options are sensible */
1694 if (options.authorized_keys_command_user == NULL &&
1695 (options.authorized_keys_command != NULL &&
1696 strcasecmp(options.authorized_keys_command, "none") != 0))
1697 fatal("AuthorizedKeysCommand set without "
1698 "AuthorizedKeysCommandUser");
1699
1700 /*
1701 * Check whether there is any path through configured auth methods.
1702 * Unfortunately it is not possible to verify this generally before
1703 * daemonisation in the presence of Match block, but this catches
1704 * and warns for trivial misconfigurations that could break login.
1705 */
1706 if (options.num_auth_methods != 0) {
1707 if ((options.protocol & SSH_PROTO_1))
1708 fatal("AuthenticationMethods is not supported with "
1709 "SSH protocol 1");
1710 for (n = 0; n < options.num_auth_methods; n++) {
1711 if (auth2_methods_valid(options.auth_methods[n],
1712 1) == 0)
1713 break;
1714 }
1715 if (n >= options.num_auth_methods)
1716 fatal("AuthenticationMethods cannot be satisfied by "
1717 "enabled authentication methods");
1718 }
1719
1720 /* set default channel AF */
1721 channel_set_af(options.address_family);
1722
1723 /* Check that there are no remaining arguments. */
1724 if (optind < ac) {
1725 fprintf(stderr, "Extra argument %s.\n", av[optind]);
1726 exit(1);
1727 }
1728
1729 debug("sshd version %s, %s", SSH_VERSION,
1730 #ifdef WITH_OPENSSL
1731 SSLeay_version(SSLEAY_VERSION)
1732 #else
1733 "without OpenSSL"
1734 #endif
1735 );
1736
1737 /* Store privilege separation user for later use if required. */
1738 if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) {
1739 if (use_privsep || options.kerberos_authentication)
1740 fatal("Privilege separation user %s does not exist",
1741 SSH_PRIVSEP_USER);
1742 } else {
1743 if (privsep_pw->pw_passwd != NULL) {
1744 explicit_bzero(privsep_pw->pw_passwd,
1745 strlen(privsep_pw->pw_passwd));
1746 }
1747 privsep_pw = pwcopy(privsep_pw);
1748 if (privsep_pw->pw_passwd != NULL) {
1749 free(privsep_pw->pw_passwd);
1750 }
1751 privsep_pw->pw_passwd = xstrdup("*");
1752 }
1753 #if !defined(ANDROID)
1754 endpwent();
1755 #endif
1756
1757 /* load host keys */
1758 sensitive_data.host_keys = xcalloc(options.num_host_key_files,
1759 sizeof(Key *));
1760 sensitive_data.host_pubkeys = xcalloc(options.num_host_key_files,
1761 sizeof(Key *));
1762
1763 if (options.host_key_agent) {
1764 if (strcmp(options.host_key_agent, SSH_AUTHSOCKET_ENV_NAME))
1765 setenv(SSH_AUTHSOCKET_ENV_NAME,
1766 options.host_key_agent, 1);
1767 if ((r = ssh_get_authentication_socket(NULL)) == 0)
1768 have_agent = 1;
1769 else
1770 error("Could not connect to agent \"%s\": %s",
1771 options.host_key_agent, ssh_err(r));
1772 }
1773
1774 for (i = 0; i < options.num_host_key_files; i++) {
1775 if (options.host_key_files[i] == NULL)
1776 continue;
1777 key = key_load_private(options.host_key_files[i], "", NULL);
1778 pubkey = key_load_public(options.host_key_files[i], NULL);
1779 if (pubkey == NULL && key != NULL)
1780 pubkey = key_demote(key);
1781 sensitive_data.host_keys[i] = key;
1782 sensitive_data.host_pubkeys[i] = pubkey;
1783
1784 if (key == NULL && pubkey != NULL && pubkey->type != KEY_RSA1 &&
1785 have_agent) {
1786 debug("will rely on agent for hostkey %s",
1787 options.host_key_files[i]);
1788 keytype = pubkey->type;
1789 } else if (key != NULL) {
1790 keytype = key->type;
1791 } else {
1792 error("Could not load host key: %s",
1793 options.host_key_files[i]);
1794 sensitive_data.host_keys[i] = NULL;
1795 sensitive_data.host_pubkeys[i] = NULL;
1796 continue;
1797 }
1798
1799 switch (keytype) {
1800 case KEY_RSA1:
1801 sensitive_data.ssh1_host_key = key;
1802 sensitive_data.have_ssh1_key = 1;
1803 break;
1804 case KEY_RSA:
1805 case KEY_DSA:
1806 case KEY_ECDSA:
1807 case KEY_ED25519:
1808 if (have_agent || key != NULL)
1809 sensitive_data.have_ssh2_key = 1;
1810 break;
1811 }
1812 if ((fp = sshkey_fingerprint(pubkey, options.fingerprint_hash,
1813 SSH_FP_DEFAULT)) == NULL)
1814 fatal("sshkey_fingerprint failed");
1815 debug("%s host key #%d: %s %s",
1816 key ? "private" : "agent", i, keytype == KEY_RSA1 ?
1817 sshkey_type(pubkey) : sshkey_ssh_name(pubkey), fp);
1818 free(fp);
1819 }
1820 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
1821 logit("Disabling protocol version 1. Could not load host key");
1822 options.protocol &= ~SSH_PROTO_1;
1823 }
1824 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
1825 logit("Disabling protocol version 2. Could not load host key");
1826 options.protocol &= ~SSH_PROTO_2;
1827 }
1828 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
1829 logit("sshd: no hostkeys available -- exiting.");
1830 exit(1);
1831 }
1832
1833 /*
1834 * Load certificates. They are stored in an array at identical
1835 * indices to the public keys that they relate to.
1836 */
1837 sensitive_data.host_certificates = xcalloc(options.num_host_key_files,
1838 sizeof(Key *));
1839 for (i = 0; i < options.num_host_key_files; i++)
1840 sensitive_data.host_certificates[i] = NULL;
1841
1842 for (i = 0; i < options.num_host_cert_files; i++) {
1843 if (options.host_cert_files[i] == NULL)
1844 continue;
1845 key = key_load_public(options.host_cert_files[i], NULL);
1846 if (key == NULL) {
1847 error("Could not load host certificate: %s",
1848 options.host_cert_files[i]);
1849 continue;
1850 }
1851 if (!key_is_cert(key)) {
1852 error("Certificate file is not a certificate: %s",
1853 options.host_cert_files[i]);
1854 key_free(key);
1855 continue;
1856 }
1857 /* Find matching private key */
1858 for (j = 0; j < options.num_host_key_files; j++) {
1859 if (key_equal_public(key,
1860 sensitive_data.host_keys[j])) {
1861 sensitive_data.host_certificates[j] = key;
1862 break;
1863 }
1864 }
1865 if (j >= options.num_host_key_files) {
1866 error("No matching private key for certificate: %s",
1867 options.host_cert_files[i]);
1868 key_free(key);
1869 continue;
1870 }
1871 sensitive_data.host_certificates[j] = key;
1872 debug("host certificate: #%d type %d %s", j, key->type,
1873 key_type(key));
1874 }
1875
1876 #ifdef WITH_SSH1
1877 /* Check certain values for sanity. */
1878 if (options.protocol & SSH_PROTO_1) {
1879 if (options.server_key_bits < 512 ||
1880 options.server_key_bits > 32768) {
1881 fprintf(stderr, "Bad server key size.\n");
1882 exit(1);
1883 }
1884 /*
1885 * Check that server and host key lengths differ sufficiently. This
1886 * is necessary to make double encryption work with rsaref. Oh, I
1887 * hate software patents. I dont know if this can go? Niels
1888 */
1889 if (options.server_key_bits >
1890 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) -
1891 SSH_KEY_BITS_RESERVED && options.server_key_bits <
1892 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1893 SSH_KEY_BITS_RESERVED) {
1894 options.server_key_bits =
1895 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1896 SSH_KEY_BITS_RESERVED;
1897 debug("Forcing server key to %d bits to make it differ from host key.",
1898 options.server_key_bits);
1899 }
1900 }
1901 #endif
1902
1903 if (use_privsep) {
1904 struct stat st;
1905
1906 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) ||
1907 (S_ISDIR(st.st_mode) == 0))
1908 fatal("Missing privilege separation directory: %s",
1909 _PATH_PRIVSEP_CHROOT_DIR);
1910
1911 #ifdef HAVE_CYGWIN
1912 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
1913 (st.st_uid != getuid () ||
1914 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0))
1915 #else
1916 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)
1917 #endif
1918 fatal("%s must be owned by root and not group or "
1919 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR);
1920 }
1921
1922 if (test_flag > 1) {
1923 if (server_match_spec_complete(connection_info) == 1)
1924 parse_server_match_config(&options, connection_info);
1925 dump_config(&options);
1926 }
1927
1928 /* Configuration looks good, so exit if in test mode. */
1929 if (test_flag)
1930 exit(0);
1931
1932 /*
1933 * Clear out any supplemental groups we may have inherited. This
1934 * prevents inadvertent creation of files with bad modes (in the
1935 * portable version at least, it's certainly possible for PAM
1936 * to create a file, and we can't control the code in every
1937 * module which might be used).
1938 */
1939 if (setgroups(0, NULL) < 0)
1940 debug("setgroups() failed: %.200s", strerror(errno));
1941
1942 if (rexec_flag) {
1943 rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *));
1944 for (i = 0; i < rexec_argc; i++) {
1945 debug("rexec_argv[%d]='%s'", i, saved_argv[i]);
1946 rexec_argv[i] = saved_argv[i];
1947 }
1948 rexec_argv[rexec_argc] = "-R";
1949 rexec_argv[rexec_argc + 1] = NULL;
1950 }
1951
1952 /* Ensure that umask disallows at least group and world write */
1953 new_umask = umask(0077) | 0022;
1954 (void) umask(new_umask);
1955
1956 /* Initialize the log (it is reinitialized below in case we forked). */
1957 if (debug_flag && (!inetd_flag || rexeced_flag))
1958 log_stderr = 1;
1959 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1960
1961 /*
1962 * If not in debugging mode, and not started from inetd, disconnect
1963 * from the controlling terminal, and fork. The original process
1964 * exits.
1965 */
1966 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
1967 #ifdef TIOCNOTTY
1968 int fd;
1969 #endif /* TIOCNOTTY */
1970 if (daemon(0, 0) < 0)
1971 fatal("daemon() failed: %.200s", strerror(errno));
1972
1973 /* Disconnect from the controlling tty. */
1974 #ifdef TIOCNOTTY
1975 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
1976 if (fd >= 0) {
1977 (void) ioctl(fd, TIOCNOTTY, NULL);
1978 close(fd);
1979 }
1980 #endif /* TIOCNOTTY */
1981 }
1982 /* Reinitialize the log (because of the fork above). */
1983 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1984
1985 /* Chdir to the root directory so that the current disk can be
1986 unmounted if desired. */
1987 if (chdir("/") == -1)
1988 error("chdir(\"/\"): %s", strerror(errno));
1989
1990 /* ignore SIGPIPE */
1991 signal(SIGPIPE, SIG_IGN);
1992
1993 /* Get a connection, either from inetd or a listening TCP socket */
1994 if (inetd_flag) {
1995 server_accept_inetd(&sock_in, &sock_out);
1996 } else {
1997 platform_pre_listen();
1998 server_listen();
1999
2000 if (options.protocol & SSH_PROTO_1)
2001 generate_ephemeral_server_key();
2002
2003 signal(SIGHUP, sighup_handler);
2004 signal(SIGCHLD, main_sigchld_handler);
2005 signal(SIGTERM, sigterm_handler);
2006 signal(SIGQUIT, sigterm_handler);
2007
2008 /*
2009 * Write out the pid file after the sigterm handler
2010 * is setup and the listen sockets are bound
2011 */
2012 if (options.pid_file != NULL && !debug_flag) {
2013 FILE *f = fopen(options.pid_file, "w");
2014
2015 if (f == NULL) {
2016 error("Couldn't create pid file \"%s\": %s",
2017 options.pid_file, strerror(errno));
2018 } else {
2019 fprintf(f, "%ld\n", (long) getpid());
2020 fclose(f);
2021 }
2022 }
2023
2024 /* Accept a connection and return in a forked child */
2025 server_accept_loop(&sock_in, &sock_out,
2026 &newsock, config_s);
2027 }
2028
2029 /* This is the child processing a new connection. */
2030 setproctitle("%s", "[accepted]");
2031
2032 /*
2033 * Create a new session and process group since the 4.4BSD
2034 * setlogin() affects the entire process group. We don't
2035 * want the child to be able to affect the parent.
2036 */
2037 #if !defined(SSHD_ACQUIRES_CTTY)
2038 /*
2039 * If setsid is called, on some platforms sshd will later acquire a
2040 * controlling terminal which will result in "could not set
2041 * controlling tty" errors.
2042 */
2043 if (!debug_flag && !inetd_flag && setsid() < 0)
2044 error("setsid: %.100s", strerror(errno));
2045 #endif
2046
2047 if (rexec_flag) {
2048 int fd;
2049
2050 debug("rexec start in %d out %d newsock %d pipe %d sock %d",
2051 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
2052 dup2(newsock, STDIN_FILENO);
2053 dup2(STDIN_FILENO, STDOUT_FILENO);
2054 if (startup_pipe == -1)
2055 close(REEXEC_STARTUP_PIPE_FD);
2056 else if (startup_pipe != REEXEC_STARTUP_PIPE_FD) {
2057 dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD);
2058 close(startup_pipe);
2059 startup_pipe = REEXEC_STARTUP_PIPE_FD;
2060 }
2061
2062 dup2(config_s[1], REEXEC_CONFIG_PASS_FD);
2063 close(config_s[1]);
2064
2065 execv(rexec_argv[0], rexec_argv);
2066
2067 /* Reexec has failed, fall back and continue */
2068 error("rexec of %s failed: %s", rexec_argv[0], strerror(errno));
2069 recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL);
2070 log_init(__progname, options.log_level,
2071 options.log_facility, log_stderr);
2072
2073 /* Clean up fds */
2074 close(REEXEC_CONFIG_PASS_FD);
2075 newsock = sock_out = sock_in = dup(STDIN_FILENO);
2076 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
2077 dup2(fd, STDIN_FILENO);
2078 dup2(fd, STDOUT_FILENO);
2079 if (fd > STDERR_FILENO)
2080 close(fd);
2081 }
2082 debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d",
2083 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
2084 }
2085
2086 /* Executed child processes don't need these. */
2087 fcntl(sock_out, F_SETFD, FD_CLOEXEC);
2088 fcntl(sock_in, F_SETFD, FD_CLOEXEC);
2089
2090 /*
2091 * Disable the key regeneration alarm. We will not regenerate the
2092 * key since we are no longer in a position to give it to anyone. We
2093 * will not restart on SIGHUP since it no longer makes sense.
2094 */
2095 alarm(0);
2096 signal(SIGALRM, SIG_DFL);
2097 signal(SIGHUP, SIG_DFL);
2098 signal(SIGTERM, SIG_DFL);
2099 signal(SIGQUIT, SIG_DFL);
2100 signal(SIGCHLD, SIG_DFL);
2101 signal(SIGINT, SIG_DFL);
2102
2103 /*
2104 * Register our connection. This turns encryption off because we do
2105 * not have a key.
2106 */
2107 packet_set_connection(sock_in, sock_out);
2108 packet_set_server();
2109
2110 /* Set SO_KEEPALIVE if requested. */
2111 if (options.tcp_keep_alive && packet_connection_is_on_socket() &&
2112 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) < 0)
2113 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
2114
2115 if ((remote_port = get_remote_port()) < 0) {
2116 debug("get_remote_port failed");
2117 cleanup_exit(255);
2118 }
2119
2120 /*
2121 * We use get_canonical_hostname with usedns = 0 instead of
2122 * get_remote_ipaddr here so IP options will be checked.
2123 */
2124 (void) get_canonical_hostname(0);
2125 /*
2126 * The rest of the code depends on the fact that
2127 * get_remote_ipaddr() caches the remote ip, even if
2128 * the socket goes away.
2129 */
2130 remote_ip = get_remote_ipaddr();
2131
2132 #ifdef SSH_AUDIT_EVENTS
2133 audit_connection_from(remote_ip, remote_port);
2134 #endif
2135
2136 /* Log the connection. */
2137 verbose("Connection from %s port %d on %s port %d",
2138 remote_ip, remote_port,
2139 get_local_ipaddr(sock_in), get_local_port());
2140
2141 /*
2142 * We don't want to listen forever unless the other side
2143 * successfully authenticates itself. So we set up an alarm which is
2144 * cleared after successful authentication. A limit of zero
2145 * indicates no limit. Note that we don't set the alarm in debugging
2146 * mode; it is just annoying to have the server exit just when you
2147 * are about to discover the bug.
2148 */
2149 signal(SIGALRM, grace_alarm_handler);
2150 if (!debug_flag)
2151 alarm(options.login_grace_time);
2152
2153 sshd_exchange_identification(sock_in, sock_out);
2154
2155 /* In inetd mode, generate ephemeral key only for proto 1 connections */
2156 if (!compat20 && inetd_flag && sensitive_data.server_key == NULL)
2157 generate_ephemeral_server_key();
2158
2159 packet_set_nonblocking();
2160
2161 /* allocate authentication context */
2162 authctxt = xcalloc(1, sizeof(*authctxt));
2163
2164 authctxt->loginmsg = &loginmsg;
2165
2166 /* XXX global for cleanup, access from other modules */
2167 the_authctxt = authctxt;
2168
2169 /* prepare buffer to collect messages to display to user after login */
2170 buffer_init(&loginmsg);
2171 auth_debug_reset();
2172
2173 if (use_privsep) {
2174 if (privsep_preauth(authctxt) == 1)
2175 goto authenticated;
2176 } else if (compat20 && have_agent) {
2177 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) {
2178 error("Unable to get agent socket: %s", ssh_err(r));
2179 have_agent = 0;
2180 }
2181 }
2182
2183 /* perform the key exchange */
2184 /* authenticate user and start session */
2185 if (compat20) {
2186 do_ssh2_kex();
2187 do_authentication2(authctxt);
2188 } else {
2189 #ifdef WITH_SSH1
2190 do_ssh1_kex();
2191 do_authentication(authctxt);
2192 #else
2193 fatal("ssh1 not supported");
2194 #endif
2195 }
2196 /*
2197 * If we use privilege separation, the unprivileged child transfers
2198 * the current keystate and exits
2199 */
2200 if (use_privsep) {
2201 mm_send_keystate(pmonitor);
2202 exit(0);
2203 }
2204
2205 authenticated:
2206 /*
2207 * Cancel the alarm we set to limit the time taken for
2208 * authentication.
2209 */
2210 alarm(0);
2211 signal(SIGALRM, SIG_DFL);
2212 authctxt->authenticated = 1;
2213 if (startup_pipe != -1) {
2214 close(startup_pipe);
2215 startup_pipe = -1;
2216 }
2217
2218 #ifdef SSH_AUDIT_EVENTS
2219 audit_event(SSH_AUTH_SUCCESS);
2220 #endif
2221
2222 #ifdef GSSAPI
2223 if (options.gss_authentication) {
2224 temporarily_use_uid(authctxt->pw);
2225 ssh_gssapi_storecreds();
2226 restore_uid();
2227 }
2228 #endif
2229 #ifdef USE_PAM
2230 if (options.use_pam) {
2231 do_pam_setcred(1);
2232 do_pam_session();
2233 }
2234 #endif
2235
2236 /*
2237 * In privilege separation, we fork another child and prepare
2238 * file descriptor passing.
2239 */
2240 if (use_privsep) {
2241 privsep_postauth(authctxt);
2242 /* the monitor process [priv] will not return */
2243 if (!compat20)
2244 destroy_sensitive_data();
2245 }
2246
2247 packet_set_timeout(options.client_alive_interval,
2248 options.client_alive_count_max);
2249
2250 /* Try to send all our hostkeys to the client */
2251 if (compat20)
2252 notify_hostkeys(active_state);
2253
2254 /* Start session. */
2255 do_authenticated(authctxt);
2256
2257 /* The connection has been terminated. */
2258 packet_get_bytes(&ibytes, &obytes);
2259 verbose("Transferred: sent %llu, received %llu bytes",
2260 (unsigned long long)obytes, (unsigned long long)ibytes);
2261
2262 verbose("Closing connection to %.500s port %d", remote_ip, remote_port);
2263
2264 #ifdef USE_PAM
2265 if (options.use_pam)
2266 finish_pam();
2267 #endif /* USE_PAM */
2268
2269 #ifdef SSH_AUDIT_EVENTS
2270 PRIVSEP(audit_event(SSH_CONNECTION_CLOSE));
2271 #endif
2272
2273 packet_close();
2274
2275 if (use_privsep)
2276 mm_terminate();
2277
2278 exit(0);
2279 }
2280
2281 #ifdef WITH_SSH1
2282 /*
2283 * Decrypt session_key_int using our private server key and private host key
2284 * (key with larger modulus first).
2285 */
2286 int
2287 ssh1_session_key(BIGNUM *session_key_int)
2288 {
2289 int rsafail = 0;
2290
2291 if (BN_cmp(sensitive_data.server_key->rsa->n,
2292 sensitive_data.ssh1_host_key->rsa->n) > 0) {
2293 /* Server key has bigger modulus. */
2294 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
2295 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
2296 SSH_KEY_BITS_RESERVED) {
2297 fatal("do_connection: %s: "
2298 "server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
2299 get_remote_ipaddr(),
2300 BN_num_bits(sensitive_data.server_key->rsa->n),
2301 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
2302 SSH_KEY_BITS_RESERVED);
2303 }
2304 if (rsa_private_decrypt(session_key_int, session_key_int,
2305 sensitive_data.server_key->rsa) != 0)
2306 rsafail++;
2307 if (rsa_private_decrypt(session_key_int, session_key_int,
2308 sensitive_data.ssh1_host_key->rsa) != 0)
2309 rsafail++;
2310 } else {
2311 /* Host key has bigger modulus (or they are equal). */
2312 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
2313 BN_num_bits(sensitive_data.server_key->rsa->n) +
2314 SSH_KEY_BITS_RESERVED) {
2315 fatal("do_connection: %s: "
2316 "host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
2317 get_remote_ipaddr(),
2318 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
2319 BN_num_bits(sensitive_data.server_key->rsa->n),
2320 SSH_KEY_BITS_RESERVED);
2321 }
2322 if (rsa_private_decrypt(session_key_int, session_key_int,
2323 sensitive_data.ssh1_host_key->rsa) != 0)
2324 rsafail++;
2325 if (rsa_private_decrypt(session_key_int, session_key_int,
2326 sensitive_data.server_key->rsa) != 0)
2327 rsafail++;
2328 }
2329 return (rsafail);
2330 }
2331
2332 /*
2333 * SSH1 key exchange
2334 */
2335 static void
2336 do_ssh1_kex(void)
2337 {
2338 int i, len;
2339 int rsafail = 0;
2340 BIGNUM *session_key_int, *fake_key_int, *real_key_int;
2341 u_char session_key[SSH_SESSION_KEY_LENGTH];
2342 u_char fake_key_bytes[4096 / 8];
2343 size_t fake_key_len;
2344 u_char cookie[8];
2345 u_int cipher_type, auth_mask, protocol_flags;
2346
2347 /*
2348 * Generate check bytes that the client must send back in the user
2349 * packet in order for it to be accepted; this is used to defy ip
2350 * spoofing attacks. Note that this only works against somebody
2351 * doing IP spoofing from a remote machine; any machine on the local
2352 * network can still see outgoing packets and catch the random
2353 * cookie. This only affects rhosts authentication, and this is one
2354 * of the reasons why it is inherently insecure.
2355 */
2356 arc4random_buf(cookie, sizeof(cookie));
2357
2358 /*
2359 * Send our public key. We include in the packet 64 bits of random
2360 * data that must be matched in the reply in order to prevent IP
2361 * spoofing.
2362 */
2363 packet_start(SSH_SMSG_PUBLIC_KEY);
2364 for (i = 0; i < 8; i++)
2365 packet_put_char(cookie[i]);
2366
2367 /* Store our public server RSA key. */
2368 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
2369 packet_put_bignum(sensitive_data.server_key->rsa->e);
2370 packet_put_bignum(sensitive_data.server_key->rsa->n);
2371
2372 /* Store our public host RSA key. */
2373 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
2374 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
2375 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
2376
2377 /* Put protocol flags. */
2378 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
2379
2380 /* Declare which ciphers we support. */
2381 packet_put_int(cipher_mask_ssh1(0));
2382
2383 /* Declare supported authentication types. */
2384 auth_mask = 0;
2385 if (options.rhosts_rsa_authentication)
2386 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
2387 if (options.rsa_authentication)
2388 auth_mask |= 1 << SSH_AUTH_RSA;
2389 if (options.challenge_response_authentication == 1)
2390 auth_mask |= 1 << SSH_AUTH_TIS;
2391 if (options.password_authentication)
2392 auth_mask |= 1 << SSH_AUTH_PASSWORD;
2393 packet_put_int(auth_mask);
2394
2395 /* Send the packet and wait for it to be sent. */
2396 packet_send();
2397 packet_write_wait();
2398
2399 debug("Sent %d bit server key and %d bit host key.",
2400 BN_num_bits(sensitive_data.server_key->rsa->n),
2401 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
2402
2403 /* Read clients reply (cipher type and session key). */
2404 packet_read_expect(SSH_CMSG_SESSION_KEY);
2405
2406 /* Get cipher type and check whether we accept this. */
2407 cipher_type = packet_get_char();
2408
2409 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
2410 packet_disconnect("Warning: client selects unsupported cipher.");
2411
2412 /* Get check bytes from the packet. These must match those we
2413 sent earlier with the public key packet. */
2414 for (i = 0; i < 8; i++)
2415 if (cookie[i] != packet_get_char())
2416 packet_disconnect("IP Spoofing check bytes do not match.");
2417
2418 debug("Encryption type: %.200s", cipher_name(cipher_type));
2419
2420 /* Get the encrypted integer. */
2421 if ((real_key_int = BN_new()) == NULL)
2422 fatal("do_ssh1_kex: BN_new failed");
2423 packet_get_bignum(real_key_int);
2424
2425 protocol_flags = packet_get_int();
2426 packet_set_protocol_flags(protocol_flags);
2427 packet_check_eom();
2428
2429 /* Setup a fake key in case RSA decryption fails */
2430 if ((fake_key_int = BN_new()) == NULL)
2431 fatal("do_ssh1_kex: BN_new failed");
2432 fake_key_len = BN_num_bytes(real_key_int);
2433 if (fake_key_len > sizeof(fake_key_bytes))
2434 fake_key_len = sizeof(fake_key_bytes);
2435 arc4random_buf(fake_key_bytes, fake_key_len);
2436 if (BN_bin2bn(fake_key_bytes, fake_key_len, fake_key_int) == NULL)
2437 fatal("do_ssh1_kex: BN_bin2bn failed");
2438
2439 /* Decrypt real_key_int using host/server keys */
2440 rsafail = PRIVSEP(ssh1_session_key(real_key_int));
2441 /* If decryption failed, use the fake key. Else, the real key. */
2442 if (rsafail)
2443 session_key_int = fake_key_int;
2444 else
2445 session_key_int = real_key_int;
2446
2447 /*
2448 * Extract session key from the decrypted integer. The key is in the
2449 * least significant 256 bits of the integer; the first byte of the
2450 * key is in the highest bits.
2451 */
2452 (void) BN_mask_bits(session_key_int, sizeof(session_key) * 8);
2453 len = BN_num_bytes(session_key_int);
2454 if (len < 0 || (u_int)len > sizeof(session_key)) {
2455 error("do_ssh1_kex: bad session key len from %s: "
2456 "session_key_int %d > sizeof(session_key) %lu",
2457 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
2458 rsafail++;
2459 } else {
2460 explicit_bzero(session_key, sizeof(session_key));
2461 BN_bn2bin(session_key_int,
2462 session_key + sizeof(session_key) - len);
2463
2464 derive_ssh1_session_id(
2465 sensitive_data.ssh1_host_key->rsa->n,
2466 sensitive_data.server_key->rsa->n,
2467 cookie, session_id);
2468 /*
2469 * Xor the first 16 bytes of the session key with the
2470 * session id.
2471 */
2472 for (i = 0; i < 16; i++)
2473 session_key[i] ^= session_id[i];
2474 }
2475
2476 /* Destroy the private and public keys. No longer. */
2477 destroy_sensitive_data();
2478
2479 if (use_privsep)
2480 mm_ssh1_session_id(session_id);
2481
2482 /* Destroy the decrypted integer. It is no longer needed. */
2483 BN_clear_free(real_key_int);
2484 BN_clear_free(fake_key_int);
2485
2486 /* Set the session key. From this on all communications will be encrypted. */
2487 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
2488
2489 /* Destroy our copy of the session key. It is no longer needed. */
2490 explicit_bzero(session_key, sizeof(session_key));
2491
2492 debug("Received session key; encryption turned on.");
2493
2494 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */
2495 packet_start(SSH_SMSG_SUCCESS);
2496 packet_send();
2497 packet_write_wait();
2498 }
2499 #endif
2500
2501 int
2502 sshd_hostkey_sign(Key *privkey, Key *pubkey, u_char **signature, size_t *slen,
2503 const u_char *data, size_t dlen, u_int flag)
2504 {
2505 int r;
2506 u_int xxx_slen, xxx_dlen = dlen;
2507
2508 if (privkey) {
2509 if (PRIVSEP(key_sign(privkey, signature, &xxx_slen, data, xxx_dlen) < 0))
2510 fatal("%s: key_sign failed", __func__);
2511 if (slen)
2512 *slen = xxx_slen;
2513 } else if (use_privsep) {
2514 if (mm_key_sign(pubkey, signature, &xxx_slen, data, xxx_dlen) < 0)
2515 fatal("%s: pubkey_sign failed", __func__);
2516 if (slen)
2517 *slen = xxx_slen;
2518 } else {
2519 if ((r = ssh_agent_sign(auth_sock, pubkey, signature, slen,
2520 data, dlen, datafellows)) != 0)
2521 fatal("%s: ssh_agent_sign failed: %s",
2522 __func__, ssh_err(r));
2523 }
2524 return 0;
2525 }
2526
2527 /*
2528 * SSH2 key exchange: diffie-hellman-group1-sha1
2529 */
2530 static void
2531 do_ssh2_kex(void)
2532 {
2533 char *myproposal[PROPOSAL_MAX] = { KEX_SERVER };
2534 struct kex *kex;
2535 int r;
2536
2537 if (options.ciphers != NULL) {
2538 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2539 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
2540 }
2541 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2542 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
2543 myproposal[PROPOSAL_ENC_ALGS_STOC] =
2544 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
2545
2546 if (options.macs != NULL) {
2547 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
2548 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
2549 }
2550 if (options.compression == COMP_NONE) {
2551 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2552 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
2553 } else if (options.compression == COMP_DELAYED) {
2554 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2555 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com";
2556 }
2557 if (options.kex_algorithms != NULL)
2558 myproposal[PROPOSAL_KEX_ALGS] = options.kex_algorithms;
2559
2560 myproposal[PROPOSAL_KEX_ALGS] = compat_kex_proposal(
2561 myproposal[PROPOSAL_KEX_ALGS]);
2562
2563 if (options.rekey_limit || options.rekey_interval)
2564 packet_set_rekey_limits((u_int32_t)options.rekey_limit,
2565 (time_t)options.rekey_interval);
2566
2567 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = compat_pkalg_proposal(
2568 list_hostkey_types());
2569
2570 /* start key exchange */
2571 if ((r = kex_setup(active_state, myproposal)) != 0)
2572 fatal("kex_setup: %s", ssh_err(r));
2573 kex = active_state->kex;
2574 #ifdef WITH_OPENSSL
2575 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
2576 kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
2577 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
2578 kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
2579 # ifdef OPENSSL_HAS_ECC
2580 kex->kex[KEX_ECDH_SHA2] = kexecdh_server;
2581 # endif
2582 #endif
2583 kex->kex[KEX_C25519_SHA256] = kexc25519_server;
2584 kex->server = 1;
2585 kex->client_version_string=client_version_string;
2586 kex->server_version_string=server_version_string;
2587 kex->load_host_public_key=&get_hostkey_public_by_type;
2588 kex->load_host_private_key=&get_hostkey_private_by_type;
2589 kex->host_key_index=&get_hostkey_index;
2590 kex->sign = sshd_hostkey_sign;
2591
2592 dispatch_run(DISPATCH_BLOCK, &kex->done, active_state);
2593
2594 session_id2 = kex->session_id;
2595 session_id2_len = kex->session_id_len;
2596
2597 #ifdef DEBUG_KEXDH
2598 /* send 1st encrypted/maced/compressed message */
2599 packet_start(SSH2_MSG_IGNORE);
2600 packet_put_cstring("markus");
2601 packet_send();
2602 packet_write_wait();
2603 #endif
2604 debug("KEX done");
2605 }
2606
2607 /* server specific fatal cleanup */
2608 void
2609 cleanup_exit(int i)
2610 {
2611 if (the_authctxt) {
2612 do_cleanup(the_authctxt);
2613 if (use_privsep && privsep_is_preauth &&
2614 pmonitor != NULL && pmonitor->m_pid > 1) {
2615 debug("Killing privsep child %d", pmonitor->m_pid);
2616 if (kill(pmonitor->m_pid, SIGKILL) != 0 &&
2617 errno != ESRCH)
2618 error("%s: kill(%d): %s", __func__,
2619 pmonitor->m_pid, strerror(errno));
2620 }
2621 }
2622 #ifdef SSH_AUDIT_EVENTS
2623 /* done after do_cleanup so it can cancel the PAM auth 'thread' */
2624 if (!use_privsep || mm_is_monitor())
2625 audit_event(SSH_CONNECTION_ABANDON);
2626 #endif
2627 _exit(i);
2628 }
2629