1 /* $OpenBSD: sshd-session.c,v 1.11 2025/01/16 06:37:10 dtucker Exp $ */
2 /*
3 * SSH2 implementation:
4 * Privilege Separation:
5 *
6 * Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved.
7 * Copyright (c) 2002 Niels Provos. All rights reserved.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 * notice, this list of conditions and the following disclaimer in the
16 * documentation and/or other materials provided with the distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 */
29
30 #include <sys/types.h>
31 #include <sys/ioctl.h>
32 #include <sys/wait.h>
33 #include <sys/tree.h>
34 #include <sys/stat.h>
35 #include <sys/socket.h>
36 #include <sys/time.h>
37 #include <sys/queue.h>
38
39 #include <errno.h>
40 #include <fcntl.h>
41 #include <netdb.h>
42 #include <paths.h>
43 #include <pwd.h>
44 #include <signal.h>
45 #include <stdio.h>
46 #include <stdlib.h>
47 #include <string.h>
48 #include <stdarg.h>
49 #include <unistd.h>
50 #include <limits.h>
51
52 #ifdef WITH_OPENSSL
53 #include <openssl/bn.h>
54 #include <openssl/evp.h>
55 #endif
56
57 #include "xmalloc.h"
58 #include "ssh.h"
59 #include "ssh2.h"
60 #include "sshpty.h"
61 #include "packet.h"
62 #include "log.h"
63 #include "sshbuf.h"
64 #include "misc.h"
65 #include "match.h"
66 #include "servconf.h"
67 #include "uidswap.h"
68 #include "compat.h"
69 #include "cipher.h"
70 #include "digest.h"
71 #include "sshkey.h"
72 #include "kex.h"
73 #include "authfile.h"
74 #include "pathnames.h"
75 #include "atomicio.h"
76 #include "canohost.h"
77 #include "hostfile.h"
78 #include "auth.h"
79 #include "authfd.h"
80 #include "msg.h"
81 #include "dispatch.h"
82 #include "channels.h"
83 #include "session.h"
84 #include "monitor.h"
85 #ifdef GSSAPI
86 #include "ssh-gss.h"
87 #endif
88 #include "monitor_wrap.h"
89 #include "auth-options.h"
90 #include "version.h"
91 #include "ssherr.h"
92 #include "sk-api.h"
93 #include "srclimit.h"
94 #include "dh.h"
95
96 /* Re-exec fds */
97 #define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1)
98 #define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2)
99 #define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3)
100 #define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4)
101
102 /* Privsep fds */
103 #define PRIVSEP_MONITOR_FD (STDERR_FILENO + 1)
104 #define PRIVSEP_LOG_FD (STDERR_FILENO + 2)
105 #define PRIVSEP_MIN_FREE_FD (STDERR_FILENO + 3)
106
107 extern char *__progname;
108
109 /* Server configuration options. */
110 ServerOptions options;
111
112 /* Name of the server configuration file. */
113 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
114
115 /*
116 * Debug mode flag. This can be set on the command line. If debug
117 * mode is enabled, extra debugging output will be sent to the system
118 * log, the daemon will not go to background, and will exit after processing
119 * the first connection.
120 */
121 int debug_flag = 0;
122
123 /* Flag indicating that the daemon is being started from inetd. */
124 static int inetd_flag = 0;
125
126 /* debug goes to stderr unless inetd_flag is set */
127 static int log_stderr = 0;
128
129 /* Saved arguments to main(). */
130 static char **saved_argv;
131
132 /* Daemon's agent connection */
133 int auth_sock = -1;
134 static int have_agent = 0;
135
136 /*
137 * Any really sensitive data in the application is contained in this
138 * structure. The idea is that this structure could be locked into memory so
139 * that the pages do not get written into swap. However, there are some
140 * problems. The private key contains BIGNUMs, and we do not (in principle)
141 * have access to the internals of them, and locking just the structure is
142 * not very useful. Currently, memory locking is not implemented.
143 */
144 struct {
145 u_int num_hostkeys;
146 struct sshkey **host_keys; /* all private host keys */
147 struct sshkey **host_pubkeys; /* all public host keys */
148 struct sshkey **host_certificates; /* all public host certificates */
149 } sensitive_data;
150
151 /* record remote hostname or ip */
152 u_int utmp_len = HOST_NAME_MAX+1;
153
154 static int startup_pipe = -1; /* in child */
155
156 /* variables used for privilege separation */
157 struct monitor *pmonitor = NULL;
158 int privsep_is_preauth = 1;
159
160 /* global connection state and authentication contexts */
161 Authctxt *the_authctxt = NULL;
162 struct ssh *the_active_state;
163
164 /* global key/cert auth options. XXX move to permanent ssh->authctxt? */
165 struct sshauthopt *auth_opts = NULL;
166
167 /* sshd_config buffer */
168 struct sshbuf *cfg;
169
170 /* Included files from the configuration file */
171 struct include_list includes = TAILQ_HEAD_INITIALIZER(includes);
172
173 /* message to be displayed after login */
174 struct sshbuf *loginmsg;
175
176 /* Prototypes for various functions defined later in this file. */
177 void destroy_sensitive_data(void);
178 void demote_sensitive_data(void);
179
180 /* XXX reduce to stub once postauth split */
181 int
mm_is_monitor(void)182 mm_is_monitor(void)
183 {
184 /*
185 * m_pid is only set in the privileged part, and
186 * points to the unprivileged child.
187 */
188 return (pmonitor && pmonitor->m_pid > 0);
189 }
190
191 /*
192 * Signal handler for the alarm after the login grace period has expired.
193 * As usual, this may only take signal-safe actions, even though it is
194 * terminal.
195 */
196 static void
grace_alarm_handler(int sig)197 grace_alarm_handler(int sig)
198 {
199 /*
200 * Try to kill any processes that we have spawned, E.g. authorized
201 * keys command helpers or privsep children.
202 */
203 if (getpgid(0) == getpid()) {
204 struct sigaction sa;
205
206 /* mask all other signals while in handler */
207 memset(&sa, 0, sizeof(sa));
208 sa.sa_handler = SIG_IGN;
209 sigfillset(&sa.sa_mask);
210 sa.sa_flags = SA_RESTART;
211 (void)sigaction(SIGTERM, &sa, NULL);
212 kill(0, SIGTERM);
213 }
214 _exit(EXIT_LOGIN_GRACE);
215 }
216
217 /* Destroy the host and server keys. They will no longer be needed. */
218 void
destroy_sensitive_data(void)219 destroy_sensitive_data(void)
220 {
221 u_int i;
222
223 for (i = 0; i < options.num_host_key_files; i++) {
224 if (sensitive_data.host_keys[i]) {
225 sshkey_free(sensitive_data.host_keys[i]);
226 sensitive_data.host_keys[i] = NULL;
227 }
228 if (sensitive_data.host_certificates[i]) {
229 sshkey_free(sensitive_data.host_certificates[i]);
230 sensitive_data.host_certificates[i] = NULL;
231 }
232 }
233 }
234
235 /* Demote private to public keys for network child */
236 void
demote_sensitive_data(void)237 demote_sensitive_data(void)
238 {
239 struct sshkey *tmp;
240 u_int i;
241 int r;
242
243 for (i = 0; i < options.num_host_key_files; i++) {
244 if (sensitive_data.host_keys[i]) {
245 if ((r = sshkey_from_private(
246 sensitive_data.host_keys[i], &tmp)) != 0)
247 fatal_r(r, "could not demote host %s key",
248 sshkey_type(sensitive_data.host_keys[i]));
249 sshkey_free(sensitive_data.host_keys[i]);
250 sensitive_data.host_keys[i] = tmp;
251 }
252 /* Certs do not need demotion */
253 }
254 }
255
256 struct sshbuf *
pack_hostkeys(void)257 pack_hostkeys(void)
258 {
259 struct sshbuf *keybuf = NULL, *hostkeys = NULL;
260 int r;
261 u_int i;
262
263 if ((hostkeys = sshbuf_new()) == NULL)
264 fatal_f("sshbuf_new failed");
265
266 /* pack hostkeys into a string. Empty key slots get empty strings */
267 for (i = 0; i < options.num_host_key_files; i++) {
268 /* public key */
269 if (sensitive_data.host_pubkeys[i] != NULL) {
270 if ((r = sshkey_puts(sensitive_data.host_pubkeys[i],
271 hostkeys)) != 0)
272 fatal_fr(r, "compose hostkey public");
273 } else {
274 if ((r = sshbuf_put_string(hostkeys, NULL, 0)) != 0)
275 fatal_fr(r, "compose hostkey empty public");
276 }
277 /* cert */
278 if (sensitive_data.host_certificates[i] != NULL) {
279 if ((r = sshkey_puts(
280 sensitive_data.host_certificates[i],
281 hostkeys)) != 0)
282 fatal_fr(r, "compose host cert");
283 } else {
284 if ((r = sshbuf_put_string(hostkeys, NULL, 0)) != 0)
285 fatal_fr(r, "compose host cert empty");
286 }
287 }
288
289 sshbuf_free(keybuf);
290 return hostkeys;
291 }
292
293 static int
privsep_preauth(struct ssh * ssh)294 privsep_preauth(struct ssh *ssh)
295 {
296 int status, r;
297 pid_t pid;
298
299 /* Set up unprivileged child process to deal with network data */
300 pmonitor = monitor_init();
301 /* Store a pointer to the kex for later rekeying */
302 pmonitor->m_pkex = &ssh->kex;
303
304 if ((pid = fork()) == -1)
305 fatal("fork of unprivileged child failed");
306 else if (pid != 0) {
307 debug2("Network child is on pid %ld", (long)pid);
308 pmonitor->m_pid = pid;
309 if (have_agent) {
310 r = ssh_get_authentication_socket(&auth_sock);
311 if (r != 0) {
312 error_r(r, "Could not get agent socket");
313 have_agent = 0;
314 }
315 }
316 monitor_child_preauth(ssh, pmonitor);
317
318 /* Wait for the child's exit status */
319 while (waitpid(pid, &status, 0) == -1) {
320 if (errno == EINTR)
321 continue;
322 pmonitor->m_pid = -1;
323 fatal_f("waitpid: %s", strerror(errno));
324 }
325 privsep_is_preauth = 0;
326 pmonitor->m_pid = -1;
327 if (WIFEXITED(status)) {
328 if (WEXITSTATUS(status) != 0)
329 fatal_f("preauth child exited with status %d",
330 WEXITSTATUS(status));
331 } else if (WIFSIGNALED(status))
332 fatal_f("preauth child terminated by signal %d",
333 WTERMSIG(status));
334 return 1;
335 } else {
336 /* child */
337 close(pmonitor->m_sendfd);
338 close(pmonitor->m_log_recvfd);
339
340 /*
341 * Arrange unpriv-preauth child process fds:
342 * 0, 1 network socket
343 * 2 optional stderr
344 * 3 reserved
345 * 4 monitor message socket
346 * 5 monitor logging socket
347 *
348 * We know that the monitor sockets will have fds > 4 because
349 * of the reserved fds in main()
350 */
351
352 if (ssh_packet_get_connection_in(ssh) != STDIN_FILENO &&
353 dup2(ssh_packet_get_connection_in(ssh), STDIN_FILENO) == -1)
354 fatal("dup2 stdin failed: %s", strerror(errno));
355 if (ssh_packet_get_connection_out(ssh) != STDOUT_FILENO &&
356 dup2(ssh_packet_get_connection_out(ssh),
357 STDOUT_FILENO) == -1)
358 fatal("dup2 stdout failed: %s", strerror(errno));
359 /* leave stderr as-is */
360 log_redirect_stderr_to(NULL); /* dup can clobber log fd */
361 if (pmonitor->m_recvfd != PRIVSEP_MONITOR_FD &&
362 dup2(pmonitor->m_recvfd, PRIVSEP_MONITOR_FD) == -1)
363 fatal("dup2 monitor fd: %s", strerror(errno));
364 if (pmonitor->m_log_sendfd != PRIVSEP_LOG_FD &&
365 dup2(pmonitor->m_log_sendfd, PRIVSEP_LOG_FD) == -1)
366 fatal("dup2 log fd: %s", strerror(errno));
367 closefrom(PRIVSEP_MIN_FREE_FD);
368
369 saved_argv[0] = options.sshd_auth_path;
370 execv(options.sshd_auth_path, saved_argv);
371
372 fatal_f("exec of %s failed: %s",
373 options.sshd_auth_path, strerror(errno));
374 }
375 }
376
377 static void
privsep_postauth(struct ssh * ssh,Authctxt * authctxt)378 privsep_postauth(struct ssh *ssh, Authctxt *authctxt)
379 {
380 /* New socket pair */
381 monitor_reinit(pmonitor);
382
383 pmonitor->m_pid = fork();
384 if (pmonitor->m_pid == -1)
385 fatal("fork of unprivileged child failed");
386 else if (pmonitor->m_pid != 0) {
387 verbose("User child is on pid %ld", (long)pmonitor->m_pid);
388 sshbuf_reset(loginmsg);
389 monitor_clear_keystate(ssh, pmonitor);
390 monitor_child_postauth(ssh, pmonitor);
391
392 /* NEVERREACHED */
393 exit(0);
394 }
395
396 /* child */
397
398 close(pmonitor->m_sendfd);
399 pmonitor->m_sendfd = -1;
400
401 /* Demote the private keys to public keys. */
402 demote_sensitive_data();
403
404 /* Drop privileges */
405 do_setusercontext(authctxt->pw);
406
407 /* It is safe now to apply the key state */
408 monitor_apply_keystate(ssh, pmonitor);
409
410 /*
411 * Tell the packet layer that authentication was successful, since
412 * this information is not part of the key state.
413 */
414 ssh_packet_set_authenticated(ssh);
415 }
416
417 static struct sshkey *
get_hostkey_by_type(int type,int nid,int need_private,struct ssh * ssh)418 get_hostkey_by_type(int type, int nid, int need_private, struct ssh *ssh)
419 {
420 u_int i;
421 struct sshkey *key;
422
423 for (i = 0; i < options.num_host_key_files; i++) {
424 switch (type) {
425 case KEY_RSA_CERT:
426 case KEY_DSA_CERT:
427 case KEY_ECDSA_CERT:
428 case KEY_ED25519_CERT:
429 case KEY_ECDSA_SK_CERT:
430 case KEY_ED25519_SK_CERT:
431 case KEY_XMSS_CERT:
432 key = sensitive_data.host_certificates[i];
433 break;
434 default:
435 key = sensitive_data.host_keys[i];
436 if (key == NULL && !need_private)
437 key = sensitive_data.host_pubkeys[i];
438 break;
439 }
440 if (key == NULL || key->type != type)
441 continue;
442 switch (type) {
443 case KEY_ECDSA:
444 case KEY_ECDSA_SK:
445 case KEY_ECDSA_CERT:
446 case KEY_ECDSA_SK_CERT:
447 if (key->ecdsa_nid != nid)
448 continue;
449 /* FALLTHROUGH */
450 default:
451 return need_private ?
452 sensitive_data.host_keys[i] : key;
453 }
454 }
455 return NULL;
456 }
457
458 struct sshkey *
get_hostkey_public_by_type(int type,int nid,struct ssh * ssh)459 get_hostkey_public_by_type(int type, int nid, struct ssh *ssh)
460 {
461 return get_hostkey_by_type(type, nid, 0, ssh);
462 }
463
464 struct sshkey *
get_hostkey_private_by_type(int type,int nid,struct ssh * ssh)465 get_hostkey_private_by_type(int type, int nid, struct ssh *ssh)
466 {
467 return get_hostkey_by_type(type, nid, 1, ssh);
468 }
469
470 struct sshkey *
get_hostkey_by_index(int ind)471 get_hostkey_by_index(int ind)
472 {
473 if (ind < 0 || (u_int)ind >= options.num_host_key_files)
474 return (NULL);
475 return (sensitive_data.host_keys[ind]);
476 }
477
478 struct sshkey *
get_hostkey_public_by_index(int ind,struct ssh * ssh)479 get_hostkey_public_by_index(int ind, struct ssh *ssh)
480 {
481 if (ind < 0 || (u_int)ind >= options.num_host_key_files)
482 return (NULL);
483 return (sensitive_data.host_pubkeys[ind]);
484 }
485
486 int
get_hostkey_index(struct sshkey * key,int compare,struct ssh * ssh)487 get_hostkey_index(struct sshkey *key, int compare, struct ssh *ssh)
488 {
489 u_int i;
490
491 for (i = 0; i < options.num_host_key_files; i++) {
492 if (sshkey_is_cert(key)) {
493 if (key == sensitive_data.host_certificates[i] ||
494 (compare && sensitive_data.host_certificates[i] &&
495 sshkey_equal(key,
496 sensitive_data.host_certificates[i])))
497 return (i);
498 } else {
499 if (key == sensitive_data.host_keys[i] ||
500 (compare && sensitive_data.host_keys[i] &&
501 sshkey_equal(key, sensitive_data.host_keys[i])))
502 return (i);
503 if (key == sensitive_data.host_pubkeys[i] ||
504 (compare && sensitive_data.host_pubkeys[i] &&
505 sshkey_equal(key, sensitive_data.host_pubkeys[i])))
506 return (i);
507 }
508 }
509 return (-1);
510 }
511
512 /* Inform the client of all hostkeys */
513 static void
notify_hostkeys(struct ssh * ssh)514 notify_hostkeys(struct ssh *ssh)
515 {
516 struct sshbuf *buf;
517 struct sshkey *key;
518 u_int i, nkeys;
519 int r;
520 char *fp;
521
522 /* Some clients cannot cope with the hostkeys message, skip those. */
523 if (ssh->compat & SSH_BUG_HOSTKEYS)
524 return;
525
526 if ((buf = sshbuf_new()) == NULL)
527 fatal_f("sshbuf_new");
528 for (i = nkeys = 0; i < options.num_host_key_files; i++) {
529 key = get_hostkey_public_by_index(i, ssh);
530 if (key == NULL || key->type == KEY_UNSPEC ||
531 sshkey_is_cert(key))
532 continue;
533 fp = sshkey_fingerprint(key, options.fingerprint_hash,
534 SSH_FP_DEFAULT);
535 debug3_f("key %d: %s %s", i, sshkey_ssh_name(key), fp);
536 free(fp);
537 if (nkeys == 0) {
538 /*
539 * Start building the request when we find the
540 * first usable key.
541 */
542 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 ||
543 (r = sshpkt_put_cstring(ssh, "hostkeys-00@openssh.com")) != 0 ||
544 (r = sshpkt_put_u8(ssh, 0)) != 0) /* want reply */
545 sshpkt_fatal(ssh, r, "%s: start request", __func__);
546 }
547 /* Append the key to the request */
548 sshbuf_reset(buf);
549 if ((r = sshkey_putb(key, buf)) != 0)
550 fatal_fr(r, "couldn't put hostkey %d", i);
551 if ((r = sshpkt_put_stringb(ssh, buf)) != 0)
552 sshpkt_fatal(ssh, r, "%s: append key", __func__);
553 nkeys++;
554 }
555 debug3_f("sent %u hostkeys", nkeys);
556 if (nkeys == 0)
557 fatal_f("no hostkeys");
558 if ((r = sshpkt_send(ssh)) != 0)
559 sshpkt_fatal(ssh, r, "%s: send", __func__);
560 sshbuf_free(buf);
561 }
562
563 static void
usage(void)564 usage(void)
565 {
566 fprintf(stderr, "%s, %s\n", SSH_VERSION, SSH_OPENSSL_VERSION);
567 fprintf(stderr,
568 "usage: sshd [-46DdeGiqTtV] [-C connection_spec] [-c host_cert_file]\n"
569 " [-E log_file] [-f config_file] [-g login_grace_time]\n"
570 " [-h host_key_file] [-o option] [-p port] [-u len]\n"
571 );
572 exit(1);
573 }
574
575 static void
parse_hostkeys(struct sshbuf * hostkeys)576 parse_hostkeys(struct sshbuf *hostkeys)
577 {
578 int r;
579 u_int num_keys = 0;
580 struct sshkey *k;
581 struct sshbuf *kbuf;
582 const u_char *cp;
583 size_t len;
584
585 while (sshbuf_len(hostkeys) != 0) {
586 if (num_keys > 2048)
587 fatal_f("too many hostkeys");
588 sensitive_data.host_keys = xrecallocarray(
589 sensitive_data.host_keys, num_keys, num_keys + 1,
590 sizeof(*sensitive_data.host_pubkeys));
591 sensitive_data.host_pubkeys = xrecallocarray(
592 sensitive_data.host_pubkeys, num_keys, num_keys + 1,
593 sizeof(*sensitive_data.host_pubkeys));
594 sensitive_data.host_certificates = xrecallocarray(
595 sensitive_data.host_certificates, num_keys, num_keys + 1,
596 sizeof(*sensitive_data.host_certificates));
597 /* private key */
598 k = NULL;
599 if ((r = sshbuf_froms(hostkeys, &kbuf)) != 0)
600 fatal_fr(r, "extract privkey");
601 if (sshbuf_len(kbuf) != 0 &&
602 (r = sshkey_private_deserialize(kbuf, &k)) != 0)
603 fatal_fr(r, "parse pubkey");
604 sensitive_data.host_keys[num_keys] = k;
605 sshbuf_free(kbuf);
606 if (k)
607 debug2_f("privkey %u: %s", num_keys, sshkey_ssh_name(k));
608 /* public key */
609 k = NULL;
610 if ((r = sshbuf_get_string_direct(hostkeys, &cp, &len)) != 0)
611 fatal_fr(r, "extract pubkey");
612 if (len != 0 && (r = sshkey_from_blob(cp, len, &k)) != 0)
613 fatal_fr(r, "parse pubkey");
614 sensitive_data.host_pubkeys[num_keys] = k;
615 if (k)
616 debug2_f("pubkey %u: %s", num_keys, sshkey_ssh_name(k));
617 /* certificate */
618 k = NULL;
619 if ((r = sshbuf_get_string_direct(hostkeys, &cp, &len)) != 0)
620 fatal_fr(r, "extract pubkey");
621 if (len != 0 && (r = sshkey_from_blob(cp, len, &k)) != 0)
622 fatal_fr(r, "parse pubkey");
623 sensitive_data.host_certificates[num_keys] = k;
624 if (k)
625 debug2_f("cert %u: %s", num_keys, sshkey_ssh_name(k));
626 num_keys++;
627 }
628 sensitive_data.num_hostkeys = num_keys;
629 }
630
631 static void
recv_rexec_state(int fd,struct sshbuf * conf,uint64_t * timing_secretp)632 recv_rexec_state(int fd, struct sshbuf *conf, uint64_t *timing_secretp)
633 {
634 struct sshbuf *m, *inc, *hostkeys;
635 u_char *cp, ver;
636 size_t len;
637 int r;
638 struct include_item *item;
639
640 debug3_f("entering fd = %d", fd);
641
642 if ((m = sshbuf_new()) == NULL || (inc = sshbuf_new()) == NULL)
643 fatal_f("sshbuf_new failed");
644 if (ssh_msg_recv(fd, m) == -1)
645 fatal_f("ssh_msg_recv failed");
646 if ((r = sshbuf_get_u8(m, &ver)) != 0)
647 fatal_fr(r, "parse version");
648 if (ver != 0)
649 fatal_f("rexec version mismatch");
650 if ((r = sshbuf_get_string(m, &cp, &len)) != 0 || /* XXX _direct */
651 (r = sshbuf_get_u64(m, timing_secretp)) != 0 ||
652 (r = sshbuf_froms(m, &hostkeys)) != 0 ||
653 (r = sshbuf_get_stringb(m, inc)) != 0)
654 fatal_fr(r, "parse config");
655
656 if (conf != NULL && (r = sshbuf_put(conf, cp, len)))
657 fatal_fr(r, "sshbuf_put");
658
659 while (sshbuf_len(inc) != 0) {
660 item = xcalloc(1, sizeof(*item));
661 if ((item->contents = sshbuf_new()) == NULL)
662 fatal_f("sshbuf_new failed");
663 if ((r = sshbuf_get_cstring(inc, &item->selector, NULL)) != 0 ||
664 (r = sshbuf_get_cstring(inc, &item->filename, NULL)) != 0 ||
665 (r = sshbuf_get_stringb(inc, item->contents)) != 0)
666 fatal_fr(r, "parse includes");
667 TAILQ_INSERT_TAIL(&includes, item, entry);
668 }
669
670 parse_hostkeys(hostkeys);
671
672 free(cp);
673 sshbuf_free(m);
674 sshbuf_free(hostkeys);
675 sshbuf_free(inc);
676
677 debug3_f("done");
678 }
679
680 /*
681 * If IP options are supported, make sure there are none (log and
682 * return an error if any are found). Basically we are worried about
683 * source routing; it can be used to pretend you are somebody
684 * (ip-address) you are not. That itself may be "almost acceptable"
685 * under certain circumstances, but rhosts authentication is useless
686 * if source routing is accepted. Notice also that if we just dropped
687 * source routing here, the other side could use IP spoofing to do
688 * rest of the interaction and could still bypass security. So we
689 * exit here if we detect any IP options.
690 */
691 static void
check_ip_options(struct ssh * ssh)692 check_ip_options(struct ssh *ssh)
693 {
694 int sock_in = ssh_packet_get_connection_in(ssh);
695 struct sockaddr_storage from;
696 u_char opts[200];
697 socklen_t i, option_size = sizeof(opts), fromlen = sizeof(from);
698 char text[sizeof(opts) * 3 + 1];
699
700 memset(&from, 0, sizeof(from));
701 if (getpeername(sock_in, (struct sockaddr *)&from,
702 &fromlen) == -1)
703 return;
704 if (from.ss_family != AF_INET)
705 return;
706 /* XXX IPv6 options? */
707
708 if (getsockopt(sock_in, IPPROTO_IP, IP_OPTIONS, opts,
709 &option_size) >= 0 && option_size != 0) {
710 text[0] = '\0';
711 for (i = 0; i < option_size; i++)
712 snprintf(text + i*3, sizeof(text) - i*3,
713 " %2.2x", opts[i]);
714 fatal("Connection from %.100s port %d with IP opts: %.800s",
715 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), text);
716 }
717 }
718
719 /* Set the routing domain for this process */
720 static void
set_process_rdomain(struct ssh * ssh,const char * name)721 set_process_rdomain(struct ssh *ssh, const char *name)
722 {
723 int rtable, ortable = getrtable();
724 const char *errstr;
725
726 if (name == NULL)
727 return; /* default */
728
729 if (strcmp(name, "%D") == 0) {
730 /* "expands" to routing domain of connection */
731 if ((name = ssh_packet_rdomain_in(ssh)) == NULL)
732 return;
733 }
734
735 rtable = (int)strtonum(name, 0, 255, &errstr);
736 if (errstr != NULL) /* Shouldn't happen */
737 fatal("Invalid routing domain \"%s\": %s", name, errstr);
738 if (rtable != ortable && setrtable(rtable) != 0)
739 fatal("Unable to set routing domain %d: %s",
740 rtable, strerror(errno));
741 debug_f("set routing domain %d (was %d)", rtable, ortable);
742 }
743
744 /*
745 * Main program for the daemon.
746 */
747 int
main(int ac,char ** av)748 main(int ac, char **av)
749 {
750 struct ssh *ssh = NULL;
751 extern char *optarg;
752 extern int optind;
753 int devnull, r, opt, on = 1, remote_port;
754 int sock_in = -1, sock_out = -1, rexeced_flag = 0, have_key = 0;
755 const char *remote_ip, *rdomain;
756 char *line, *laddr, *logfile = NULL;
757 u_int i;
758 u_int64_t ibytes, obytes;
759 mode_t new_umask;
760 Authctxt *authctxt;
761 struct connection_info *connection_info = NULL;
762 sigset_t sigmask;
763 uint64_t timing_secret = 0;
764 struct itimerval itv;
765
766 sigemptyset(&sigmask);
767 sigprocmask(SIG_SETMASK, &sigmask, NULL);
768
769 /* Save argv. */
770 saved_argv = av;
771
772 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
773 sanitise_stdfd();
774
775 /* Initialize configuration options to their default values. */
776 initialize_server_options(&options);
777
778 /* Parse command-line arguments. */
779 while ((opt = getopt(ac, av,
780 "C:E:b:c:f:g:h:k:o:p:u:46DGQRTdeiqrtV")) != -1) {
781 switch (opt) {
782 case '4':
783 options.address_family = AF_INET;
784 break;
785 case '6':
786 options.address_family = AF_INET6;
787 break;
788 case 'f':
789 config_file_name = optarg;
790 break;
791 case 'c':
792 servconf_add_hostcert("[command-line]", 0,
793 &options, optarg);
794 break;
795 case 'd':
796 if (debug_flag == 0) {
797 debug_flag = 1;
798 options.log_level = SYSLOG_LEVEL_DEBUG1;
799 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
800 options.log_level++;
801 break;
802 case 'D':
803 /* ignore */
804 break;
805 case 'E':
806 logfile = optarg;
807 /* FALLTHROUGH */
808 case 'e':
809 log_stderr = 1;
810 break;
811 case 'i':
812 inetd_flag = 1;
813 break;
814 case 'r':
815 /* ignore */
816 break;
817 case 'R':
818 rexeced_flag = 1;
819 break;
820 case 'Q':
821 /* ignored */
822 break;
823 case 'q':
824 options.log_level = SYSLOG_LEVEL_QUIET;
825 break;
826 case 'b':
827 /* protocol 1, ignored */
828 break;
829 case 'p':
830 options.ports_from_cmdline = 1;
831 if (options.num_ports >= MAX_PORTS) {
832 fprintf(stderr, "too many ports.\n");
833 exit(1);
834 }
835 options.ports[options.num_ports++] = a2port(optarg);
836 if (options.ports[options.num_ports-1] <= 0) {
837 fprintf(stderr, "Bad port number.\n");
838 exit(1);
839 }
840 break;
841 case 'g':
842 if ((options.login_grace_time = convtime(optarg)) == -1) {
843 fprintf(stderr, "Invalid login grace time.\n");
844 exit(1);
845 }
846 break;
847 case 'k':
848 /* protocol 1, ignored */
849 break;
850 case 'h':
851 servconf_add_hostkey("[command-line]", 0,
852 &options, optarg, 1);
853 break;
854 case 't':
855 case 'T':
856 case 'G':
857 fatal("test/dump modes not supported");
858 break;
859 case 'C':
860 connection_info = server_get_connection_info(ssh, 0, 0);
861 if (parse_server_match_testspec(connection_info,
862 optarg) == -1)
863 exit(1);
864 break;
865 case 'u':
866 utmp_len = (u_int)strtonum(optarg, 0, HOST_NAME_MAX+1+1, NULL);
867 if (utmp_len > HOST_NAME_MAX+1) {
868 fprintf(stderr, "Invalid utmp length.\n");
869 exit(1);
870 }
871 break;
872 case 'o':
873 line = xstrdup(optarg);
874 if (process_server_config_line(&options, line,
875 "command-line", 0, NULL, NULL, &includes) != 0)
876 exit(1);
877 free(line);
878 break;
879 case 'V':
880 fprintf(stderr, "%s, %s\n",
881 SSH_VERSION, SSH_OPENSSL_VERSION);
882 exit(0);
883 default:
884 usage();
885 break;
886 }
887 }
888
889 /* Check that there are no remaining arguments. */
890 if (optind < ac) {
891 fprintf(stderr, "Extra argument %s.\n", av[optind]);
892 exit(1);
893 }
894
895 if (!rexeced_flag)
896 fatal("sshd-session should not be executed directly");
897
898 closefrom(REEXEC_MIN_FREE_FD);
899
900 /* Reserve fds we'll need later for reexec things */
901 if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1)
902 fatal("open %s: %s", _PATH_DEVNULL, strerror(errno));
903 while (devnull < PRIVSEP_MIN_FREE_FD) {
904 if ((devnull = dup(devnull)) == -1)
905 fatal("dup %s: %s", _PATH_DEVNULL, strerror(errno));
906 }
907
908 #ifdef WITH_OPENSSL
909 OpenSSL_add_all_algorithms();
910 #endif
911
912 /* If requested, redirect the logs to the specified logfile. */
913 if (logfile != NULL) {
914 char *cp, pid_s[32];
915
916 snprintf(pid_s, sizeof(pid_s), "%ld", (unsigned long)getpid());
917 cp = percent_expand(logfile,
918 "p", pid_s,
919 "P", "sshd-session",
920 (char *)NULL);
921 log_redirect_stderr_to(cp);
922 free(cp);
923 }
924
925 /*
926 * Force logging to stderr until we have loaded the private host
927 * key (unless started from inetd)
928 */
929 log_init(__progname,
930 options.log_level == SYSLOG_LEVEL_NOT_SET ?
931 SYSLOG_LEVEL_INFO : options.log_level,
932 options.log_facility == SYSLOG_FACILITY_NOT_SET ?
933 SYSLOG_FACILITY_AUTH : options.log_facility,
934 log_stderr || !inetd_flag || debug_flag);
935
936 /* Fetch our configuration */
937 if ((cfg = sshbuf_new()) == NULL)
938 fatal("sshbuf_new config buf failed");
939 setproctitle("%s", "[rexeced]");
940 recv_rexec_state(REEXEC_CONFIG_PASS_FD, cfg, &timing_secret);
941 /* close the fd, but keep the slot reserved */
942 if (dup2(devnull, REEXEC_CONFIG_PASS_FD) == -1)
943 fatal("dup2 devnull->config fd: %s", strerror(errno));
944 parse_server_config(&options, "rexec", cfg, &includes, NULL, 1);
945 /* Fill in default values for those options not explicitly set. */
946 fill_default_server_options(&options);
947 options.timing_secret = timing_secret;
948
949 /* Reinit logging in case config set Level, Facility or Verbose. */
950 log_init(__progname, options.log_level, options.log_facility,
951 log_stderr || !inetd_flag || debug_flag);
952
953 debug("sshd-session version %s, %s", SSH_VERSION, SSH_OPENSSL_VERSION);
954
955 if (!debug_flag && !inetd_flag) {
956 if ((startup_pipe = dup(REEXEC_STARTUP_PIPE_FD)) == -1)
957 fatal("internal error: no startup pipe");
958 /* close the fd, but keep the slot reserved */
959 if (dup2(devnull, REEXEC_STARTUP_PIPE_FD) == -1)
960 fatal("dup2 devnull->startup fd: %s", strerror(errno));
961
962 /*
963 * Signal parent that this child is at a point where
964 * they can go away if they have a SIGHUP pending.
965 */
966 (void)atomicio(vwrite, startup_pipe, "\0", 1);
967 }
968
969 /* Check that options are sensible */
970 if (options.authorized_keys_command_user == NULL &&
971 (options.authorized_keys_command != NULL &&
972 strcasecmp(options.authorized_keys_command, "none") != 0))
973 fatal("AuthorizedKeysCommand set without "
974 "AuthorizedKeysCommandUser");
975 if (options.authorized_principals_command_user == NULL &&
976 (options.authorized_principals_command != NULL &&
977 strcasecmp(options.authorized_principals_command, "none") != 0))
978 fatal("AuthorizedPrincipalsCommand set without "
979 "AuthorizedPrincipalsCommandUser");
980
981 /*
982 * Check whether there is any path through configured auth methods.
983 * Unfortunately it is not possible to verify this generally before
984 * daemonisation in the presence of Match block, but this catches
985 * and warns for trivial misconfigurations that could break login.
986 */
987 if (options.num_auth_methods != 0) {
988 for (i = 0; i < options.num_auth_methods; i++) {
989 if (auth2_methods_valid(options.auth_methods[i],
990 1) == 0)
991 break;
992 }
993 if (i >= options.num_auth_methods)
994 fatal("AuthenticationMethods cannot be satisfied by "
995 "enabled authentication methods");
996 }
997
998 #ifdef WITH_OPENSSL
999 if (options.moduli_file != NULL)
1000 dh_set_moduli_file(options.moduli_file);
1001 #endif
1002
1003 if (options.host_key_agent) {
1004 if (strcmp(options.host_key_agent, SSH_AUTHSOCKET_ENV_NAME))
1005 setenv(SSH_AUTHSOCKET_ENV_NAME,
1006 options.host_key_agent, 1);
1007 if ((r = ssh_get_authentication_socket(NULL)) == 0)
1008 have_agent = 1;
1009 else
1010 error_r(r, "Could not connect to agent \"%s\"",
1011 options.host_key_agent);
1012 }
1013
1014 if (options.num_host_key_files != sensitive_data.num_hostkeys) {
1015 fatal("internal error: hostkeys confused (config %u recvd %u)",
1016 options.num_host_key_files, sensitive_data.num_hostkeys);
1017 }
1018
1019 for (i = 0; i < options.num_host_key_files; i++) {
1020 if (sensitive_data.host_keys[i] != NULL ||
1021 (have_agent && sensitive_data.host_pubkeys[i] != NULL)) {
1022 have_key = 1;
1023 break;
1024 }
1025 }
1026 if (!have_key)
1027 fatal("internal error: monitor received no hostkeys");
1028
1029 /* Ensure that umask disallows at least group and world write */
1030 new_umask = umask(0077) | 0022;
1031 (void) umask(new_umask);
1032
1033 /* Initialize the log (it is reinitialized below in case we forked). */
1034 if (debug_flag)
1035 log_stderr = 1;
1036 log_init(__progname, options.log_level,
1037 options.log_facility, log_stderr);
1038 for (i = 0; i < options.num_log_verbose; i++)
1039 log_verbose_add(options.log_verbose[i]);
1040
1041 /* Reinitialize the log (because of the fork above). */
1042 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1043
1044 /*
1045 * Chdir to the root directory so that the current disk can be
1046 * unmounted if desired.
1047 */
1048 if (chdir("/") == -1)
1049 error("chdir(\"/\"): %s", strerror(errno));
1050
1051 /* ignore SIGPIPE */
1052 ssh_signal(SIGPIPE, SIG_IGN);
1053
1054 /* Get a connection, either from inetd or rexec */
1055 if (inetd_flag) {
1056 /*
1057 * NB. must be different fd numbers for the !socket case,
1058 * as packet_connection_is_on_socket() depends on this.
1059 */
1060 sock_in = dup(STDIN_FILENO);
1061 sock_out = dup(STDOUT_FILENO);
1062 } else {
1063 /* rexec case; accept()ed socket in ancestor listener */
1064 sock_in = sock_out = dup(STDIN_FILENO);
1065 }
1066
1067 /*
1068 * We intentionally do not close the descriptors 0, 1, and 2
1069 * as our code for setting the descriptors won't work if
1070 * ttyfd happens to be one of those.
1071 */
1072 if (stdfd_devnull(1, 1, !log_stderr) == -1)
1073 error("stdfd_devnull failed");
1074 debug("network sockets: %d, %d", sock_in, sock_out);
1075
1076 /* This is the child processing a new connection. */
1077 setproctitle("%s", "[accepted]");
1078
1079 /* Executed child processes don't need these. */
1080 fcntl(sock_out, F_SETFD, FD_CLOEXEC);
1081 fcntl(sock_in, F_SETFD, FD_CLOEXEC);
1082
1083 /* We will not restart on SIGHUP since it no longer makes sense. */
1084 ssh_signal(SIGALRM, SIG_DFL);
1085 ssh_signal(SIGHUP, SIG_DFL);
1086 ssh_signal(SIGTERM, SIG_DFL);
1087 ssh_signal(SIGQUIT, SIG_DFL);
1088 ssh_signal(SIGCHLD, SIG_DFL);
1089
1090 /*
1091 * Register our connection. This turns encryption off because we do
1092 * not have a key.
1093 */
1094 if ((ssh = ssh_packet_set_connection(NULL, sock_in, sock_out)) == NULL)
1095 fatal("Unable to create connection");
1096 the_active_state = ssh;
1097 ssh_packet_set_server(ssh);
1098
1099 check_ip_options(ssh);
1100
1101 /* Prepare the channels layer */
1102 channel_init_channels(ssh);
1103 channel_set_af(ssh, options.address_family);
1104 server_process_channel_timeouts(ssh);
1105 server_process_permitopen(ssh);
1106
1107 /* Set SO_KEEPALIVE if requested. */
1108 if (options.tcp_keep_alive && ssh_packet_connection_is_on_socket(ssh) &&
1109 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) == -1)
1110 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1111
1112 if ((remote_port = ssh_remote_port(ssh)) < 0) {
1113 debug("ssh_remote_port failed");
1114 cleanup_exit(255);
1115 }
1116
1117 /*
1118 * The rest of the code depends on the fact that
1119 * ssh_remote_ipaddr() caches the remote ip, even if
1120 * the socket goes away.
1121 */
1122 remote_ip = ssh_remote_ipaddr(ssh);
1123
1124 rdomain = ssh_packet_rdomain_in(ssh);
1125
1126 /* Log the connection. */
1127 laddr = get_local_ipaddr(sock_in);
1128 verbose("Connection from %s port %d on %s port %d%s%s%s",
1129 remote_ip, remote_port, laddr, ssh_local_port(ssh),
1130 rdomain == NULL ? "" : " rdomain \"",
1131 rdomain == NULL ? "" : rdomain,
1132 rdomain == NULL ? "" : "\"");
1133 free(laddr);
1134
1135 /*
1136 * We don't want to listen forever unless the other side
1137 * successfully authenticates itself. So we set up an alarm which is
1138 * cleared after successful authentication. A limit of zero
1139 * indicates no limit. Note that we don't set the alarm in debugging
1140 * mode; it is just annoying to have the server exit just when you
1141 * are about to discover the bug.
1142 */
1143 ssh_signal(SIGALRM, grace_alarm_handler);
1144 if (!debug_flag && options.login_grace_time > 0) {
1145 int ujitter = arc4random_uniform(4 * 1000000);
1146
1147 timerclear(&itv.it_interval);
1148 itv.it_value.tv_sec = options.login_grace_time;
1149 itv.it_value.tv_sec += ujitter / 1000000;
1150 itv.it_value.tv_usec = ujitter % 1000000;
1151
1152 if (setitimer(ITIMER_REAL, &itv, NULL) == -1)
1153 fatal("login grace time setitimer failed");
1154 }
1155
1156 if ((r = kex_exchange_identification(ssh, -1,
1157 options.version_addendum)) != 0)
1158 sshpkt_fatal(ssh, r, "banner exchange");
1159
1160 ssh_packet_set_nonblocking(ssh);
1161
1162 /* allocate authentication context */
1163 authctxt = xcalloc(1, sizeof(*authctxt));
1164 ssh->authctxt = authctxt;
1165
1166 /* XXX global for cleanup, access from other modules */
1167 the_authctxt = authctxt;
1168
1169 /* Set default key authentication options */
1170 if ((auth_opts = sshauthopt_new_with_keys_defaults()) == NULL)
1171 fatal("allocation failed");
1172
1173 /* prepare buffer to collect messages to display to user after login */
1174 if ((loginmsg = sshbuf_new()) == NULL)
1175 fatal("sshbuf_new loginmsg failed");
1176 auth_debug_reset();
1177
1178 if (privsep_preauth(ssh) != 1)
1179 fatal("privsep_preauth failed");
1180
1181 /* Now user is authenticated */
1182
1183 /*
1184 * Cancel the alarm we set to limit the time taken for
1185 * authentication.
1186 */
1187 timerclear(&itv.it_interval);
1188 timerclear(&itv.it_value);
1189 if (setitimer(ITIMER_REAL, &itv, NULL) == -1)
1190 fatal("login grace time clear failed");
1191 ssh_signal(SIGALRM, SIG_DFL);
1192 authctxt->authenticated = 1;
1193 if (startup_pipe != -1) {
1194 /* signal listener that authentication completed successfully */
1195 (void)atomicio(vwrite, startup_pipe, "\001", 1);
1196 close(startup_pipe);
1197 startup_pipe = -1;
1198 }
1199
1200 if (options.routing_domain != NULL)
1201 set_process_rdomain(ssh, options.routing_domain);
1202
1203 /*
1204 * In privilege separation, we fork another child and prepare
1205 * file descriptor passing.
1206 */
1207 privsep_postauth(ssh, authctxt);
1208 /* the monitor process [priv] will not return */
1209
1210 ssh_packet_set_timeout(ssh, options.client_alive_interval,
1211 options.client_alive_count_max);
1212
1213 /* Try to send all our hostkeys to the client */
1214 notify_hostkeys(ssh);
1215
1216 /* Start session. */
1217 do_authenticated(ssh, authctxt);
1218
1219 /* The connection has been terminated. */
1220 ssh_packet_get_bytes(ssh, &ibytes, &obytes);
1221 verbose("Transferred: sent %llu, received %llu bytes",
1222 (unsigned long long)obytes, (unsigned long long)ibytes);
1223
1224 verbose("Closing connection to %.500s port %d", remote_ip, remote_port);
1225 ssh_packet_close(ssh);
1226
1227 mm_terminate();
1228
1229 exit(0);
1230 }
1231
1232 int
sshd_hostkey_sign(struct ssh * ssh,struct sshkey * privkey,struct sshkey * pubkey,u_char ** signature,size_t * slenp,const u_char * data,size_t dlen,const char * alg)1233 sshd_hostkey_sign(struct ssh *ssh, struct sshkey *privkey,
1234 struct sshkey *pubkey, u_char **signature, size_t *slenp,
1235 const u_char *data, size_t dlen, const char *alg)
1236 {
1237 if (privkey) {
1238 if (mm_sshkey_sign(ssh, privkey, signature, slenp,
1239 data, dlen, alg, options.sk_provider, NULL,
1240 ssh->compat) < 0)
1241 fatal_f("privkey sign failed");
1242 } else {
1243 if (mm_sshkey_sign(ssh, pubkey, signature, slenp,
1244 data, dlen, alg, options.sk_provider, NULL,
1245 ssh->compat) < 0)
1246 fatal_f("pubkey sign failed");
1247 }
1248 return 0;
1249 }
1250
1251 /* server specific fatal cleanup */
1252 void
cleanup_exit(int i)1253 cleanup_exit(int i)
1254 {
1255 extern int auth_attempted; /* monitor.c */
1256
1257 if (the_active_state != NULL && the_authctxt != NULL) {
1258 do_cleanup(the_active_state, the_authctxt);
1259 if (privsep_is_preauth &&
1260 pmonitor != NULL && pmonitor->m_pid > 1) {
1261 debug("Killing privsep child %d", pmonitor->m_pid);
1262 if (kill(pmonitor->m_pid, SIGKILL) != 0 &&
1263 errno != ESRCH) {
1264 error_f("kill(%d): %s", pmonitor->m_pid,
1265 strerror(errno));
1266 }
1267 }
1268 }
1269 /* Override default fatal exit value when auth was attempted */
1270 if (i == 255 && auth_attempted)
1271 _exit(EXIT_AUTH_ATTEMPTED);
1272 _exit(i);
1273 }
1274