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source: trunk/third/openssh/sshd.c @ 18763

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Revision 18763, 50.8 KB checked in by zacheiss, 22 years ago (diff)
Merge openssh 3.5p1.

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1	/*
2	* Author: Tatu Ylonen <ylo@cs.hut.fi>
3	* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4	* All rights reserved
5	* This program is the ssh daemon. It listens for connections from clients,
6	* and performs authentication, executes use commands or shell, and forwards
7	* information to/from the application to the user client over an encrypted
8	* connection. This can also handle forwarding of X11, TCP/IP, and
9	* authentication agent connections.
10	*
11	* As far as I am concerned, the code I have written for this software
12	* can be used freely for any purpose. Any derived versions of this
13	* software must be clearly marked as such, and if the derived work is
14	* incompatible with the protocol description in the RFC file, it must be
15	* called by a name other than "ssh" or "Secure Shell".
16	*
17	* SSH2 implementation:
18	* Privilege Separation:
19	*
20	* Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved.
21	* Copyright (c) 2002 Niels Provos. All rights reserved.
22	*
23	* Redistribution and use in source and binary forms, with or without
24	* modification, are permitted provided that the following conditions
25	* are met:
26	* 1. Redistributions of source code must retain the above copyright
27	* notice, this list of conditions and the following disclaimer.
28	* 2. Redistributions in binary form must reproduce the above copyright
29	* notice, this list of conditions and the following disclaimer in the
30	* documentation and/or other materials provided with the distribution.
31	*
32	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
33	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
34	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
35	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
36	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
37	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
38	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
39	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
40	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
41	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
42	*/
43
44	#include "includes.h"
45	RCSID("$OpenBSD: sshd.c,v 1.260 2002/09/27 10:42:09 mickey Exp $");
46
47	#include <openssl/dh.h>
48	#include <openssl/bn.h>
49	#include <openssl/md5.h>
50	#include <openssl/rand.h>
51	#ifdef HAVE_SECUREWARE
52	#include <sys/security.h>
53	#include <prot.h>
54	#endif
55
56	#include "ssh.h"
57	#include "ssh1.h"
58	#include "ssh2.h"
59	#include "xmalloc.h"
60	#include "rsa.h"
61	#include "sshpty.h"
62	#include "packet.h"
63	#include "mpaux.h"
64	#include "log.h"
65	#include "servconf.h"
66	#include "uidswap.h"
67	#include "compat.h"
68	#include "buffer.h"
69	#include "cipher.h"
70	#include "kex.h"
71	#include "key.h"
72	#include "dh.h"
73	#include "myproposal.h"
74	#include "authfile.h"
75	#include "pathnames.h"
76	#include "atomicio.h"
77	#include "canohost.h"
78	#include "auth.h"
79	#include "misc.h"
80	#include "dispatch.h"
81	#include "channels.h"
82	#include "session.h"
83	#include "monitor_mm.h"
84	#include "monitor.h"
85	#include "monitor_wrap.h"
86	#include "monitor_fdpass.h"
87
88	#ifdef GSSAPI
89	#include "ssh-gss.h"
90	#endif
91
92	#ifdef LIBWRAP
93	#include <tcpd.h>
94	#include <syslog.h>
95	int allow_severity = LOG_INFO;
96	int deny_severity = LOG_WARNING;
97	#endif /* LIBWRAP */
98
99	#ifndef O_NOCTTY
100	#define O_NOCTTY 0
101	#endif
102
103	#ifdef HAVE___PROGNAME
104	extern char *__progname;
105	#else
106	char *__progname;
107	#endif
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	* Flag indicating whether IPv4 or IPv6. This can be set on the command line.
117	* Default value is AF_UNSPEC means both IPv4 and IPv6.
118	*/
119	#ifdef IPV4_DEFAULT
120	int IPv4or6 = AF_INET;
121	#else
122	int IPv4or6 = AF_UNSPEC;
123	#endif
124
125	/*
126	* Debug mode flag. This can be set on the command line. If debug
127	* mode is enabled, extra debugging output will be sent to the system
128	* log, the daemon will not go to background, and will exit after processing
129	* the first connection.
130	*/
131	int debug_flag = 0;
132
133	/* Flag indicating that the daemon should only test the configuration and keys. */
134	int test_flag = 0;
135
136	/* Flag indicating that the daemon is being started from inetd. */
137	int inetd_flag = 0;
138
139	/* Flag indicating that sshd should not detach and become a daemon. */
140	int no_daemon_flag = 0;
141
142	/* debug goes to stderr unless inetd_flag is set */
143	int log_stderr = 0;
144
145	/* Saved arguments to main(). */
146	char **saved_argv;
147	int saved_argc;
148
149	/*
150	* The sockets that the server is listening; this is used in the SIGHUP
151	* signal handler.
152	*/
153	#define MAX_LISTEN_SOCKS 16
154	int listen_socks[MAX_LISTEN_SOCKS];
155	int num_listen_socks = 0;
156
157	/*
158	* the client's version string, passed by sshd2 in compat mode. if != NULL,
159	* sshd will skip the version-number exchange
160	*/
161	char *client_version_string = NULL;
162	char *server_version_string = NULL;
163
164	/* for rekeying XXX fixme */
165	Kex *xxx_kex;
166
167	/*
168	* Any really sensitive data in the application is contained in this
169	* structure. The idea is that this structure could be locked into memory so
170	* that the pages do not get written into swap. However, there are some
171	* problems. The private key contains BIGNUMs, and we do not (in principle)
172	* have access to the internals of them, and locking just the structure is
173	* not very useful. Currently, memory locking is not implemented.
174	*/
175	struct {
176	Key server_key; / ephemeral server key */
177	Key ssh1_host_key; / ssh1 host key */
178	Key *host_keys; / all private host keys */
179	int have_ssh1_key;
180	int have_ssh2_key;
181	u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
182	} sensitive_data;
183
184	/*
185	* Flag indicating whether the RSA server key needs to be regenerated.
186	* Is set in the SIGALRM handler and cleared when the key is regenerated.
187	*/
188	static volatile sig_atomic_t key_do_regen = 0;
189
190	/* This is set to true when a signal is received. */
191	static volatile sig_atomic_t received_sighup = 0;
192	static volatile sig_atomic_t received_sigterm = 0;
193
194	/* session identifier, used by RSA-auth */
195	u_char session_id[16];
196
197	/* same for ssh2 */
198	u_char *session_id2 = NULL;
199	int session_id2_len = 0;
200
201	/* record remote hostname or ip */
202	u_int utmp_len = MAXHOSTNAMELEN;
203
204	/* Whether the server should accept connections. */
205	static int switched = 0;
206	static int enabled = 1;
207
208	/* options.max_startup sized array of fd ints */
209	int *startup_pipes = NULL;
210	int startup_pipe; /* in child */
211
212	/* variables used for privilege separation */
213	extern struct monitor *pmonitor;
214	extern int use_privsep;
215
216	/* Prototypes for various functions defined later in this file. */
217	void destroy_sensitive_data(void);
218	void demote_sensitive_data(void);
219
220	static void do_ssh1_kex(void);
221	static void do_ssh2_kex(void);
222
223	static void
224	sigusr1_handler(int sig)
225	{
226	enabled = 1;
227	signal(SIGUSR1, sigusr1_handler);
228	}
229
230	static void
231	sigusr2_handler(int sig)
232	{
233	if (switched)
234	enabled = 0;
235	signal(SIGUSR2, sigusr2_handler);
236	}
237
238	/*
239	* Close all listening sockets
240	*/
241	static void
242	close_listen_socks(void)
243	{
244	int i;
245
246	for (i = 0; i < num_listen_socks; i++)
247	close(listen_socks[i]);
248	num_listen_socks = -1;
249	}
250
251	static void
252	close_startup_pipes(void)
253	{
254	int i;
255
256	if (startup_pipes)
257	for (i = 0; i < options.max_startups; i++)
258	if (startup_pipes[i] != -1)
259	close(startup_pipes[i]);
260	}
261
262	/*
263	* Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
264	* the effect is to reread the configuration file (and to regenerate
265	* the server key).
266	*/
267	static void
268	sighup_handler(int sig)
269	{
270	int save_errno = errno;
271
272	received_sighup = 1;
273	signal(SIGHUP, sighup_handler);
274	errno = save_errno;
275	}
276
277	/*
278	* Called from the main program after receiving SIGHUP.
279	* Restarts the server.
280	*/
281	static void
282	sighup_restart(void)
283	{
284	log("Received SIGHUP; restarting.");
285	close_listen_socks();
286	close_startup_pipes();
287	execvp(saved_argv[0], saved_argv);
288	log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
289	strerror(errno));
290	exit(1);
291	}
292
293	/*
294	* Generic signal handler for terminating signals in the master daemon.
295	*/
296	static void
297	sigterm_handler(int sig)
298	{
299	received_sigterm = sig;
300	}
301
302	/*
303	* SIGCHLD handler. This is called whenever a child dies. This will then
304	* reap any zombies left by exited children.
305	*/
306	static void
307	main_sigchld_handler(int sig)
308	{
309	int save_errno = errno;
310	pid_t pid;
311	int status;
312
313	while ((pid = waitpid(-1, &status, WNOHANG)) > 0 \|\|
314	(pid < 0 && errno == EINTR))
315	;
316
317	signal(SIGCHLD, main_sigchld_handler);
318	errno = save_errno;
319	}
320
321	/*
322	* Signal handler for the alarm after the login grace period has expired.
323	*/
324	static void
325	grace_alarm_handler(int sig)
326	{
327	/* XXX no idea how fix this signal handler */
328
329	/* Log error and exit. */
330	fatal("Timeout before authentication for %s", get_remote_ipaddr());
331	}
332
333	/*
334	* Signal handler for the key regeneration alarm. Note that this
335	* alarm only occurs in the daemon waiting for connections, and it does not
336	* do anything with the private key or random state before forking.
337	* Thus there should be no concurrency control/asynchronous execution
338	* problems.
339	*/
340	static void
341	generate_ephemeral_server_key(void)
342	{
343	u_int32_t rnd = 0;
344	int i;
345
346	verbose("Generating %s%d bit RSA key.",
347	sensitive_data.server_key ? "new " : "", options.server_key_bits);
348	if (sensitive_data.server_key != NULL)
349	key_free(sensitive_data.server_key);
350	sensitive_data.server_key = key_generate(KEY_RSA1,
351	options.server_key_bits);
352	verbose("RSA key generation complete.");
353
354	for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
355	if (i % 4 == 0)
356	rnd = arc4random();
357	sensitive_data.ssh1_cookie[i] = rnd & 0xff;
358	rnd >>= 8;
359	}
360	arc4random_stir();
361	}
362
363	static void
364	key_regeneration_alarm(int sig)
365	{
366	int save_errno = errno;
367
368	signal(SIGALRM, SIG_DFL);
369	errno = save_errno;
370	key_do_regen = 1;
371	}
372
373	static void
374	sshd_exchange_identification(int sock_in, int sock_out)
375	{
376	int i, mismatch;
377	int remote_major, remote_minor;
378	int major, minor;
379	char *s;
380	char buf[256]; /* Must not be larger than remote_version. */
381	char remote_version[256]; /* Must be at least as big as buf. */
382
383	if ((options.protocol & SSH_PROTO_1) &&
384	(options.protocol & SSH_PROTO_2)) {
385	major = PROTOCOL_MAJOR_1;
386	minor = 99;
387	} else if (options.protocol & SSH_PROTO_2) {
388	major = PROTOCOL_MAJOR_2;
389	minor = PROTOCOL_MINOR_2;
390	} else {
391	major = PROTOCOL_MAJOR_1;
392	minor = PROTOCOL_MINOR_1;
393	}
394	snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
395	server_version_string = xstrdup(buf);
396
397	if (client_version_string == NULL) {
398	/* Send our protocol version identification. */
399	if (atomicio(write, sock_out, server_version_string,
400	strlen(server_version_string))
401	!= strlen(server_version_string)) {
402	log("Could not write ident string to %s", get_remote_ipaddr());
403	fatal_cleanup();
404	}
405
406	/* Read other sides version identification. */
407	memset(buf, 0, sizeof(buf));
408	for (i = 0; i < sizeof(buf) - 1; i++) {
409	if (atomicio(read, sock_in, &buf[i], 1) != 1) {
410	log("Did not receive identification string from %s",
411	get_remote_ipaddr());
412	fatal_cleanup();
413	}
414	if (buf[i] == '\r') {
415	buf[i] = 0;
416	/* Kludge for F-Secure Macintosh < 1.0.2 */
417	if (i == 12 &&
418	strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
419	break;
420	continue;
421	}
422	if (buf[i] == '\n') {
423	buf[i] = 0;
424	break;
425	}
426	}
427	buf[sizeof(buf) - 1] = 0;
428	client_version_string = xstrdup(buf);
429	}
430
431	/*
432	* Check that the versions match. In future this might accept
433	* several versions and set appropriate flags to handle them.
434	*/
435	if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
436	&remote_major, &remote_minor, remote_version) != 3) {
437	s = "Protocol mismatch.\n";
438	(void) atomicio(write, sock_out, s, strlen(s));
439	close(sock_in);
440	close(sock_out);
441	log("Bad protocol version identification '%.100s' from %s",
442	client_version_string, get_remote_ipaddr());
443	fatal_cleanup();
444	}
445	debug("Client protocol version %d.%d; client software version %.100s",
446	remote_major, remote_minor, remote_version);
447
448	compat_datafellows(remote_version);
449
450	if (datafellows & SSH_BUG_PROBE) {
451	log("probed from %s with %s. Don't panic.",
452	get_remote_ipaddr(), client_version_string);
453	fatal_cleanup();
454	}
455
456	if (datafellows & SSH_BUG_SCANNER) {
457	log("scanned from %s with %s. Don't panic.",
458	get_remote_ipaddr(), client_version_string);
459	fatal_cleanup();
460	}
461
462	mismatch = 0;
463	switch (remote_major) {
464	case 1:
465	if (remote_minor == 99) {
466	if (options.protocol & SSH_PROTO_2)
467	enable_compat20();
468	else
469	mismatch = 1;
470	break;
471	}
472	if (!(options.protocol & SSH_PROTO_1)) {
473	mismatch = 1;
474	break;
475	}
476	if (remote_minor < 3) {
477	packet_disconnect("Your ssh version is too old and "
478	"is no longer supported. Please install a newer version.");
479	} else if (remote_minor == 3) {
480	/* note that this disables agent-forwarding */
481	enable_compat13();
482	}
483	break;
484	case 2:
485	if (options.protocol & SSH_PROTO_2) {
486	enable_compat20();
487	break;
488	}
489	/* FALLTHROUGH */
490	default:
491	mismatch = 1;
492	break;
493	}
494	chop(server_version_string);
495	debug("Local version string %.200s", server_version_string);
496
497	if (mismatch) {
498	s = "Protocol major versions differ.\n";
499	(void) atomicio(write, sock_out, s, strlen(s));
500	close(sock_in);
501	close(sock_out);
502	log("Protocol major versions differ for %s: %.200s vs. %.200s",
503	get_remote_ipaddr(),
504	server_version_string, client_version_string);
505	fatal_cleanup();
506	}
507	}
508
509	/* Destroy the host and server keys. They will no longer be needed. */
510	void
511	destroy_sensitive_data(void)
512	{
513	int i;
514
515	if (sensitive_data.server_key) {
516	key_free(sensitive_data.server_key);
517	sensitive_data.server_key = NULL;
518	}
519	for (i = 0; i < options.num_host_key_files; i++) {
520	if (sensitive_data.host_keys[i]) {
521	key_free(sensitive_data.host_keys[i]);
522	sensitive_data.host_keys[i] = NULL;
523	}
524	}
525	sensitive_data.ssh1_host_key = NULL;
526	memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
527	}
528
529	/* Demote private to public keys for network child */
530	void
531	demote_sensitive_data(void)
532	{
533	Key *tmp;
534	int i;
535
536	if (sensitive_data.server_key) {
537	tmp = key_demote(sensitive_data.server_key);
538	key_free(sensitive_data.server_key);
539	sensitive_data.server_key = tmp;
540	}
541
542	for (i = 0; i < options.num_host_key_files; i++) {
543	if (sensitive_data.host_keys[i]) {
544	tmp = key_demote(sensitive_data.host_keys[i]);
545	key_free(sensitive_data.host_keys[i]);
546	sensitive_data.host_keys[i] = tmp;
547	if (tmp->type == KEY_RSA1)
548	sensitive_data.ssh1_host_key = tmp;
549	}
550	}
551
552	/* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */
553	}
554
555	static void
556	privsep_preauth_child(void)
557	{
558	u_int32_t rnd[256];
559	gid_t gidset[1];
560	struct passwd *pw;
561	int i;
562
563	/* Enable challenge-response authentication for privilege separation */
564	privsep_challenge_enable();
565
566	for (i = 0; i < 256; i++)
567	rnd[i] = arc4random();
568	RAND_seed(rnd, sizeof(rnd));
569
570	/* Demote the private keys to public keys. */
571	demote_sensitive_data();
572
573	if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
574	fatal("Privilege separation user %s does not exist",
575	SSH_PRIVSEP_USER);
576	memset(pw->pw_passwd, 0, strlen(pw->pw_passwd));
577	endpwent();
578
579	/* Change our root directory */
580	if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
581	fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
582	strerror(errno));
583	if (chdir("/") == -1)
584	fatal("chdir(\"/\"): %s", strerror(errno));
585
586	/* Drop our privileges */
587	debug3("privsep user:group %u:%u", (u_int)pw->pw_uid,
588	(u_int)pw->pw_gid);
589	#if 0
590	/* XXX not ready, to heavy after chroot */
591	do_setusercontext(pw);
592	#else
593	gidset[0] = pw->pw_gid;
594	if (setgid(pw->pw_gid) < 0)
595	fatal("setgid failed for %u", pw->pw_gid );
596	if (setgroups(1, gidset) < 0)
597	fatal("setgroups: %.100s", strerror(errno));
598	permanently_set_uid(pw);
599	#endif
600	}
601
602	static Authctxt *
603	privsep_preauth(void)
604	{
605	Authctxt *authctxt = NULL;
606	int status;
607	pid_t pid;
608
609	/* Set up unprivileged child process to deal with network data */
610	pmonitor = monitor_init();
611	/* Store a pointer to the kex for later rekeying */
612	pmonitor->m_pkex = &xxx_kex;
613
614	pid = fork();
615	if (pid == -1) {
616	fatal("fork of unprivileged child failed");
617	} else if (pid != 0) {
618	fatal_remove_cleanup((void () (void )) packet_close, NULL);
619
620	debug2("Network child is on pid %ld", (long)pid);
621
622	close(pmonitor->m_recvfd);
623	authctxt = monitor_child_preauth(pmonitor);
624	close(pmonitor->m_sendfd);
625
626	/* Sync memory */
627	monitor_sync(pmonitor);
628
629	/* Wait for the child's exit status */
630	while (waitpid(pid, &status, 0) < 0)
631	if (errno != EINTR)
632	break;
633
634	/* Reinstall, since the child has finished */
635	fatal_add_cleanup((void () (void )) packet_close, NULL);
636
637	return (authctxt);
638	} else {
639	/* child */
640
641	close(pmonitor->m_sendfd);
642
643	/* Demote the child */
644	if (getuid() == 0 \|\| geteuid() == 0)
645	privsep_preauth_child();
646	setproctitle("%s", "[net]");
647	}
648	return (NULL);
649	}
650
651	static void
652	privsep_postauth(Authctxt *authctxt)
653	{
654	extern Authctxt *x_authctxt;
655
656	/* XXX - Remote port forwarding */
657	x_authctxt = authctxt;
658
659	#ifdef DISABLE_FD_PASSING
660	if (1) {
661	#else
662	if (authctxt->pw->pw_uid == 0 \|\| options.use_login) {
663	#endif
664	/* File descriptor passing is broken or root login */
665	monitor_apply_keystate(pmonitor);
666	use_privsep = 0;
667	return;
668	}
669
670	/* Authentication complete */
671	alarm(0);
672	if (startup_pipe != -1) {
673	close(startup_pipe);
674	startup_pipe = -1;
675	}
676
677	/* New socket pair */
678	monitor_reinit(pmonitor);
679
680	pmonitor->m_pid = fork();
681	if (pmonitor->m_pid == -1)
682	fatal("fork of unprivileged child failed");
683	else if (pmonitor->m_pid != 0) {
684	fatal_remove_cleanup((void () (void )) packet_close, NULL);
685
686	debug2("User child is on pid %ld", (long)pmonitor->m_pid);
687	close(pmonitor->m_recvfd);
688	monitor_child_postauth(pmonitor);
689
690	/* NEVERREACHED */
691	exit(0);
692	}
693
694	close(pmonitor->m_sendfd);
695
696	/* Demote the private keys to public keys. */
697	demote_sensitive_data();
698
699	/* Drop privileges */
700	do_setusercontext(authctxt->pw);
701
702	/* It is safe now to apply the key state */
703	monitor_apply_keystate(pmonitor);
704	}
705
706	static char *
707	list_hostkey_types(void)
708	{
709	Buffer b;
710	char *p;
711	int i;
712
713	buffer_init(&b);
714	for (i = 0; i < options.num_host_key_files; i++) {
715	Key *key = sensitive_data.host_keys[i];
716	if (key == NULL)
717	continue;
718	switch (key->type) {
719	case KEY_RSA:
720	case KEY_DSA:
721	if (buffer_len(&b) > 0)
722	buffer_append(&b, ",", 1);
723	p = key_ssh_name(key);
724	buffer_append(&b, p, strlen(p));
725	break;
726	}
727	}
728	buffer_append(&b, "\0", 1);
729	p = xstrdup(buffer_ptr(&b));
730	buffer_free(&b);
731	debug("list_hostkey_types: %s", p);
732	return p;
733	}
734
735	Key *
736	get_hostkey_by_type(int type)
737	{
738	int i;
739
740	for (i = 0; i < options.num_host_key_files; i++) {
741	Key *key = sensitive_data.host_keys[i];
742	if (key != NULL && key->type == type)
743	return key;
744	}
745	return NULL;
746	}
747
748	Key *
749	get_hostkey_by_index(int ind)
750	{
751	if (ind < 0 \|\| ind >= options.num_host_key_files)
752	return (NULL);
753	return (sensitive_data.host_keys[ind]);
754	}
755
756	int
757	get_hostkey_index(Key *key)
758	{
759	int i;
760
761	for (i = 0; i < options.num_host_key_files; i++) {
762	if (key == sensitive_data.host_keys[i])
763	return (i);
764	}
765	return (-1);
766	}
767
768	/*
769	* returns 1 if connection should be dropped, 0 otherwise.
770	* dropping starts at connection #max_startups_begin with a probability
771	* of (max_startups_rate/100). the probability increases linearly until
772	* all connections are dropped for startups > max_startups
773	*/
774	static int
775	drop_connection(int startups)
776	{
777	double p, r;
778
779	if (startups < options.max_startups_begin)
780	return 0;
781	if (startups >= options.max_startups)
782	return 1;
783	if (options.max_startups_rate == 100)
784	return 1;
785
786	p = 100 - options.max_startups_rate;
787	p *= startups - options.max_startups_begin;
788	p /= (double) (options.max_startups - options.max_startups_begin);
789	p += options.max_startups_rate;
790	p /= 100.0;
791	r = arc4random() / (double) UINT_MAX;
792
793	debug("drop_connection: p %g, r %g", p, r);
794	return (r < p) ? 1 : 0;
795	}
796
797	static void
798	usage(void)
799	{
800	fprintf(stderr, "sshd version %s\n", SSH_VERSION);
801	fprintf(stderr, "Usage: %s [options]\n", __progname);
802	fprintf(stderr, "Options:\n");
803	fprintf(stderr, " -f file Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE);
804	fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n");
805	fprintf(stderr, " -i Started from inetd\n");
806	fprintf(stderr, " -D Do not fork into daemon mode\n");
807	fprintf(stderr, " -t Only test configuration file and keys\n");
808	fprintf(stderr, " -q Quiet (no logging)\n");
809	fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
810	fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
811	fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n");
812	fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
813	fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
814	_PATH_HOST_KEY_FILE);
815	fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
816	fprintf(stderr, " -4 Use IPv4 only\n");
817	fprintf(stderr, " -6 Use IPv6 only\n");
818	fprintf(stderr, " -o option Process the option as if it was read from a configuration file.\n");
819	exit(1);
820	}
821
822	/*
823	* Main program for the daemon.
824	*/
825	int
826	main(int ac, char **av)
827	{
828	extern char *optarg;
829	extern int optind;
830	int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
831	pid_t pid;
832	socklen_t fromlen;
833	fd_set *fdset;
834	struct sockaddr_storage from;
835	const char *remote_ip;
836	int remote_port;
837	FILE *f;
838	struct addrinfo *ai;
839	char ntop[NI_MAXHOST], strport[NI_MAXSERV];
840	int listen_sock, maxfd;
841	int startup_p[2];
842	int startups = 0;
843	Authctxt *authctxt;
844	Key *key;
845	int ret, key_used = 0;
846
847	#ifdef HAVE_SECUREWARE
848	(void)set_auth_parameters(ac, av);
849	#endif
850	__progname = get_progname(av[0]);
851	init_rng();
852
853	/* Save argv. */
854	saved_argc = ac;
855	saved_argv = av;
856
857	/* Initialize configuration options to their default values. */
858	initialize_server_options(&options);
859
860	/* Parse command-line arguments. */
861	while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:o:dDeiqtQ46sS")) != -1) {
862	switch (opt) {
863	case '4':
864	IPv4or6 = AF_INET;
865	break;
866	case '6':
867	IPv4or6 = AF_INET6;
868	break;
869	case 'f':
870	config_file_name = optarg;
871	break;
872	case 'd':
873	if (0 == debug_flag) {
874	debug_flag = 1;
875	options.log_level = SYSLOG_LEVEL_DEBUG1;
876	} else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
877	options.log_level++;
878	} else {
879	fprintf(stderr, "Too high debugging level.\n");
880	exit(1);
881	}
882	break;
883	case 'D':
884	no_daemon_flag = 1;
885	break;
886	case 'e':
887	log_stderr = 1;
888	break;
889	case 'i':
890	inetd_flag = 1;
891	break;
892	case 'Q':
893	/* ignored */
894	break;
895	case 'q':
896	options.log_level = SYSLOG_LEVEL_QUIET;
897	break;
898	case 'b':
899	options.server_key_bits = atoi(optarg);
900	break;
901	case 'p':
902	options.ports_from_cmdline = 1;
903	if (options.num_ports >= MAX_PORTS) {
904	fprintf(stderr, "too many ports.\n");
905	exit(1);
906	}
907	options.ports[options.num_ports++] = a2port(optarg);
908	if (options.ports[options.num_ports-1] == 0) {
909	fprintf(stderr, "Bad port number.\n");
910	exit(1);
911	}
912	break;
913	case 'g':
914	if ((options.login_grace_time = convtime(optarg)) == -1) {
915	fprintf(stderr, "Invalid login grace time.\n");
916	exit(1);
917	}
918	break;
919	case 'k':
920	if ((options.key_regeneration_time = convtime(optarg)) == -1) {
921	fprintf(stderr, "Invalid key regeneration interval.\n");
922	exit(1);
923	}
924	break;
925	case 'h':
926	if (options.num_host_key_files >= MAX_HOSTKEYS) {
927	fprintf(stderr, "too many host keys.\n");
928	exit(1);
929	}
930	options.host_key_files[options.num_host_key_files++] = optarg;
931	break;
932	case 's':
933	switched = 1;
934	break;
935	case 'S':
936	switched = 1;
937	enabled = 0;
938	break;
939	case 'V':
940	client_version_string = optarg;
941	/* only makes sense with inetd_flag, i.e. no listen() */
942	inetd_flag = 1;
943	break;
944	case 't':
945	test_flag = 1;
946	break;
947	case 'u':
948	utmp_len = atoi(optarg);
949	if (utmp_len > MAXHOSTNAMELEN) {
950	fprintf(stderr, "Invalid utmp length.\n");
951	exit(1);
952	}
953	break;
954	case 'o':
955	if (process_server_config_line(&options, optarg,
956	"command-line", 0) != 0)
957	exit(1);
958	break;
959	case '?':
960	default:
961	usage();
962	break;
963	}
964	}
965	SSLeay_add_all_algorithms();
966	channel_set_af(IPv4or6);
967
968	/*
969	* Force logging to stderr until we have loaded the private host
970	* key (unless started from inetd)
971	*/
972	log_init(__progname,
973	options.log_level == SYSLOG_LEVEL_NOT_SET ?
974	SYSLOG_LEVEL_INFO : options.log_level,
975	options.log_facility == SYSLOG_FACILITY_NOT_SET ?
976	SYSLOG_FACILITY_AUTH : options.log_facility,
977	!inetd_flag);
978
979	#ifdef _UNICOS
980	/* Cray can define user privs drop all prives now!
981	* Not needed on PRIV_SU systems!
982	*/
983	drop_cray_privs();
984	#endif
985
986	seed_rng();
987
988	/* Read server configuration options from the configuration file. */
989	read_server_config(&options, config_file_name);
990
991	/* Fill in default values for those options not explicitly set. */
992	fill_default_server_options(&options);
993
994	/* Check that there are no remaining arguments. */
995	if (optind < ac) {
996	fprintf(stderr, "Extra argument %s.\n", av[optind]);
997	exit(1);
998	}
999
1000	debug("sshd version %.100s", SSH_VERSION);
1001
1002	/* load private host keys */
1003	sensitive_data.host_keys = xmalloc(options.num_host_key_files *
1004	sizeof(Key *));
1005	for (i = 0; i < options.num_host_key_files; i++)
1006	sensitive_data.host_keys[i] = NULL;
1007	sensitive_data.server_key = NULL;
1008	sensitive_data.ssh1_host_key = NULL;
1009	sensitive_data.have_ssh1_key = 0;
1010	sensitive_data.have_ssh2_key = 0;
1011
1012	for (i = 0; i < options.num_host_key_files; i++) {
1013	key = key_load_private(options.host_key_files[i], "", NULL);
1014	sensitive_data.host_keys[i] = key;
1015	if (key == NULL) {
1016	error("Could not load host key: %s",
1017	options.host_key_files[i]);
1018	sensitive_data.host_keys[i] = NULL;
1019	continue;
1020	}
1021	switch (key->type) {
1022	case KEY_RSA1:
1023	sensitive_data.ssh1_host_key = key;
1024	sensitive_data.have_ssh1_key = 1;
1025	break;
1026	case KEY_RSA:
1027	case KEY_DSA:
1028	sensitive_data.have_ssh2_key = 1;
1029	break;
1030	}
1031	debug("private host key: #%d type %d %s", i, key->type,
1032	key_type(key));
1033	}
1034	if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
1035	log("Disabling protocol version 1. Could not load host key");
1036	options.protocol &= ~SSH_PROTO_1;
1037	}
1038	#ifndef GSSAPI
1039	/* The GSSAPI key exchange can run without a host key */
1040	if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
1041	log("Disabling protocol version 2. Could not load host key");
1042	options.protocol &= ~SSH_PROTO_2;
1043	}
1044	#endif
1045	if (!(options.protocol & (SSH_PROTO_1\|SSH_PROTO_2))) {
1046	log("sshd: no hostkeys available -- exiting.");
1047	exit(1);
1048	}
1049
1050	/* Check certain values for sanity. */
1051	if (options.protocol & SSH_PROTO_1) {
1052	if (options.server_key_bits < 512 \|\|
1053	options.server_key_bits > 32768) {
1054	fprintf(stderr, "Bad server key size.\n");
1055	exit(1);
1056	}
1057	/*
1058	* Check that server and host key lengths differ sufficiently. This
1059	* is necessary to make double encryption work with rsaref. Oh, I
1060	* hate software patents. I dont know if this can go? Niels
1061	*/
1062	if (options.server_key_bits >
1063	BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) -
1064	SSH_KEY_BITS_RESERVED && options.server_key_bits <
1065	BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1066	SSH_KEY_BITS_RESERVED) {
1067	options.server_key_bits =
1068	BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1069	SSH_KEY_BITS_RESERVED;
1070	debug("Forcing server key to %d bits to make it differ from host key.",
1071	options.server_key_bits);
1072	}
1073	}
1074
1075	if (use_privsep) {
1076	struct passwd *pw;
1077	struct stat st;
1078
1079	if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
1080	fatal("Privilege separation user %s does not exist",
1081	SSH_PRIVSEP_USER);
1082	if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) \|\|
1083	(S_ISDIR(st.st_mode) == 0))
1084	fatal("Missing privilege separation directory: %s",
1085	_PATH_PRIVSEP_CHROOT_DIR);
1086
1087	#ifdef HAVE_CYGWIN
1088	if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
1089	(st.st_uid != getuid () \|\|
1090	(st.st_mode & (S_IWGRP\|S_IWOTH)) != 0))
1091	#else
1092	if (st.st_uid != 0 \|\| (st.st_mode & (S_IWGRP\|S_IWOTH)) != 0)
1093	#endif
1094	fatal("Bad owner or mode for %s",
1095	_PATH_PRIVSEP_CHROOT_DIR);
1096	}
1097
1098	/* Configuration looks good, so exit if in test mode. */
1099	if (test_flag)
1100	exit(0);
1101
1102	/*
1103	* Clear out any supplemental groups we may have inherited. This
1104	* prevents inadvertent creation of files with bad modes (in the
1105	* portable version at least, it's certainly possible for PAM
1106	* to create a file, and we can't control the code in every
1107	* module which might be used).
1108	*/
1109	if (setgroups(0, NULL) < 0)
1110	debug("setgroups() failed: %.200s", strerror(errno));
1111
1112	/* Initialize the log (it is reinitialized below in case we forked). */
1113	if (debug_flag && !inetd_flag)
1114	log_stderr = 1;
1115	log_init(__progname, options.log_level, options.log_facility, log_stderr);
1116
1117	/*
1118	* If not in debugging mode, and not started from inetd, disconnect
1119	* from the controlling terminal, and fork. The original process
1120	* exits.
1121	*/
1122	if (!(debug_flag \|\| inetd_flag \|\| no_daemon_flag)) {
1123	#ifdef TIOCNOTTY
1124	int fd;
1125	#endif /* TIOCNOTTY */
1126	if (daemon(0, 0) < 0)
1127	fatal("daemon() failed: %.200s", strerror(errno));
1128
1129	/* Disconnect from the controlling tty. */
1130	#ifdef TIOCNOTTY
1131	fd = open(_PATH_TTY, O_RDWR \| O_NOCTTY);
1132	if (fd >= 0) {
1133	(void) ioctl(fd, TIOCNOTTY, NULL);
1134	close(fd);
1135	}
1136	#endif /* TIOCNOTTY */
1137	}
1138	/* Reinitialize the log (because of the fork above). */
1139	log_init(__progname, options.log_level, options.log_facility, log_stderr);
1140
1141	/* Initialize the random number generator. */
1142	arc4random_stir();
1143
1144	/* Chdir to the root directory so that the current disk can be
1145	unmounted if desired. */
1146	chdir("/");
1147
1148	/* ignore SIGPIPE */
1149	signal(SIGPIPE, SIG_IGN);
1150
1151	/* Start listening for a socket, unless started from inetd. */
1152	if (inetd_flag) {
1153	int s1;
1154	s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
1155	dup(s1);
1156	sock_in = dup(0);
1157	sock_out = dup(1);
1158	startup_pipe = -1;
1159	/*
1160	* We intentionally do not close the descriptors 0, 1, and 2
1161	* as our code for setting the descriptors won\'t work if
1162	* ttyfd happens to be one of those.
1163	*/
1164	debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
1165	if (options.protocol & SSH_PROTO_1)
1166	generate_ephemeral_server_key();
1167	} else {
1168	for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
1169	if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
1170	continue;
1171	if (num_listen_socks >= MAX_LISTEN_SOCKS)
1172	fatal("Too many listen sockets. "
1173	"Enlarge MAX_LISTEN_SOCKS");
1174	if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
1175	ntop, sizeof(ntop), strport, sizeof(strport),
1176	NI_NUMERICHOST\|NI_NUMERICSERV) != 0) {
1177	error("getnameinfo failed");
1178	continue;
1179	}
1180	/* Create socket for listening. */
1181	listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
1182	if (listen_sock < 0) {
1183	/* kernel may not support ipv6 */
1184	verbose("socket: %.100s", strerror(errno));
1185	continue;
1186	}
1187	if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
1188	error("listen_sock O_NONBLOCK: %s", strerror(errno));
1189	close(listen_sock);
1190	continue;
1191	}
1192	/*
1193	* Set socket options.
1194	* Allow local port reuse in TIME_WAIT.
1195	*/
1196	if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
1197	&on, sizeof(on)) == -1)
1198	error("setsockopt SO_REUSEADDR: %s", strerror(errno));
1199
1200	debug("Bind to port %s on %s.", strport, ntop);
1201
1202	/* Bind the socket to the desired port. */
1203	if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1204	if (!ai->ai_next)
1205	error("Bind to port %s on %s failed: %.200s.",
1206	strport, ntop, strerror(errno));
1207	close(listen_sock);
1208	continue;
1209	}
1210	listen_socks[num_listen_socks] = listen_sock;
1211	num_listen_socks++;
1212
1213	/* Start listening on the port. */
1214	log("Server listening on %s port %s.", ntop, strport);
1215	if (listen(listen_sock, 5) < 0)
1216	fatal("listen: %.100s", strerror(errno));
1217
1218	}
1219	freeaddrinfo(options.listen_addrs);
1220
1221	if (!num_listen_socks)
1222	fatal("Cannot bind any address.");
1223
1224	if (options.protocol & SSH_PROTO_1)
1225	generate_ephemeral_server_key();
1226
1227	/*
1228	* Arrange to restart on SIGHUP. The handler needs
1229	* listen_sock.
1230	*/
1231	signal(SIGHUP, sighup_handler);
1232
1233	signal(SIGTERM, sigterm_handler);
1234	signal(SIGQUIT, sigterm_handler);
1235
1236	/* Switch on and off on SIGUSR1 and SIGUSR2 (conditional on
1237	switched). */
1238	signal(SIGUSR1, sigusr1_handler);
1239	signal(SIGUSR2, sigusr2_handler);
1240
1241	/* Arrange SIGCHLD to be caught. */
1242	signal(SIGCHLD, main_sigchld_handler);
1243
1244	/* Write out the pid file after the sigterm handler is setup */
1245	if (!debug_flag) {
1246	/*
1247	* Record our pid in /var/run/sshd.pid to make it
1248	* easier to kill the correct sshd. We don't want to
1249	* do this before the bind above because the bind will
1250	* fail if there already is a daemon, and this will
1251	* overwrite any old pid in the file.
1252	*/
1253	f = fopen(options.pid_file, "wb");
1254	if (f) {
1255	fprintf(f, "%ld\n", (long) getpid());
1256	fclose(f);
1257	}
1258	}
1259
1260	/* setup fd set for listen */
1261	fdset = NULL;
1262	maxfd = 0;
1263	for (i = 0; i < num_listen_socks; i++)
1264	if (listen_socks[i] > maxfd)
1265	maxfd = listen_socks[i];
1266	/* pipes connected to unauthenticated childs */
1267	startup_pipes = xmalloc(options.max_startups * sizeof(int));
1268	for (i = 0; i < options.max_startups; i++)
1269	startup_pipes[i] = -1;
1270
1271	/*
1272	* Stay listening for connections until the system crashes or
1273	* the daemon is killed with a signal.
1274	*/
1275	for (;;) {
1276	if (received_sighup)
1277	sighup_restart();
1278	if (fdset != NULL)
1279	xfree(fdset);
1280	fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
1281	fdset = (fd_set *)xmalloc(fdsetsz);
1282	memset(fdset, 0, fdsetsz);
1283
1284	for (i = 0; i < num_listen_socks; i++)
1285	FD_SET(listen_socks[i], fdset);
1286	for (i = 0; i < options.max_startups; i++)
1287	if (startup_pipes[i] != -1)
1288	FD_SET(startup_pipes[i], fdset);
1289
1290	/* Wait in select until there is a connection. */
1291	ret = select(maxfd+1, fdset, NULL, NULL, NULL);
1292	if (ret < 0 && errno != EINTR)
1293	error("select: %.100s", strerror(errno));
1294	if (received_sigterm) {
1295	log("Received signal %d; terminating.",
1296	(int) received_sigterm);
1297	close_listen_socks();
1298	unlink(options.pid_file);
1299	exit(255);
1300	}
1301	if (key_used && key_do_regen) {
1302	generate_ephemeral_server_key();
1303	key_used = 0;
1304	key_do_regen = 0;
1305	}
1306	if (ret < 0)
1307	continue;
1308
1309	for (i = 0; i < options.max_startups; i++)
1310	if (startup_pipes[i] != -1 &&
1311	FD_ISSET(startup_pipes[i], fdset)) {
1312	/*
1313	* the read end of the pipe is ready
1314	* if the child has closed the pipe
1315	* after successful authentication
1316	* or if the child has died
1317	*/
1318	close(startup_pipes[i]);
1319	startup_pipes[i] = -1;
1320	startups--;
1321	}
1322	for (i = 0; i < num_listen_socks; i++) {
1323	if (!FD_ISSET(listen_socks[i], fdset))
1324	continue;
1325	fromlen = sizeof(from);
1326	newsock = accept(listen_socks[i], (struct sockaddr *)&from,
1327	&fromlen);
1328	if (newsock < 0) {
1329	if (errno != EINTR && errno != EWOULDBLOCK)
1330	error("accept: %.100s", strerror(errno));
1331	continue;
1332	}
1333	if (fcntl(newsock, F_SETFL, 0) < 0) {
1334	error("newsock del O_NONBLOCK: %s", strerror(errno));
1335	close(newsock);
1336	continue;
1337	}
1338	if (pipe(startup_p) == -1) {
1339	close(newsock);
1340	continue;
1341	}
1342
1343	for (j = 0; j < options.max_startups; j++)
1344	if (startup_pipes[j] == -1) {
1345	startup_pipes[j] = startup_p[0];
1346	if (maxfd < startup_p[0])
1347	maxfd = startup_p[0];
1348	startups++;
1349	break;
1350	}
1351
1352	/*
1353	* Got connection. Fork a child to handle it, unless
1354	* we are in debugging mode.
1355	*/
1356	if (debug_flag) {
1357	/*
1358	* In debugging mode. Close the listening
1359	* socket, and start processing the
1360	* connection without forking.
1361	*/
1362	debug("Server will not fork when running in debugging mode.");
1363	close_listen_socks();
1364	sock_in = newsock;
1365	sock_out = newsock;
1366	startup_pipe = -1;
1367	pid = getpid();
1368	break;
1369	} else {
1370	/*
1371	* Normal production daemon. Fork, and have
1372	* the child process the connection. The
1373	* parent continues listening.
1374	*/
1375	if ((pid = fork()) == 0) {
1376	/*
1377	* Child. Close the listening and max_startup
1378	* sockets. Start using the accepted socket.
1379	* Reinitialize logging (since our pid has
1380	* changed). We break out of the loop to handle
1381	* the connection.
1382	*/
1383	startup_pipe = startup_p[1];
1384	close_startup_pipes();
1385	close_listen_socks();
1386	sock_in = newsock;
1387	sock_out = newsock;
1388	log_init(__progname, options.log_level, options.log_facility, log_stderr);
1389	break;
1390	}
1391	}
1392
1393	/* Parent. Stay in the loop. */
1394	if (pid < 0)
1395	error("fork: %.100s", strerror(errno));
1396	else
1397	debug("Forked child %ld.", (long)pid);
1398
1399	close(startup_p[1]);
1400
1401	/* Mark that the key has been used (it was "given" to the child). */
1402	if ((options.protocol & SSH_PROTO_1) &&
1403	key_used == 0) {
1404	/* Schedule server key regeneration alarm. */
1405	signal(SIGALRM, key_regeneration_alarm);
1406	alarm(options.key_regeneration_time);
1407	key_used = 1;
1408	}
1409
1410	arc4random_stir();
1411
1412	/* Close the new socket (the child is now taking care of it). */
1413	close(newsock);
1414	}
1415	/* child process check (or debug mode) */
1416	if (num_listen_socks < 0)
1417	break;
1418	}
1419	}
1420
1421	/* This is the child processing a new connection. */
1422
1423	/*
1424	* Create a new session and process group since the 4.4BSD
1425	* setlogin() affects the entire process group. We don't
1426	* want the child to be able to affect the parent.
1427	*/
1428	#if 0
1429	/* XXX: this breaks Solaris */
1430	if (!debug_flag && !inetd_flag && setsid() < 0)
1431	error("setsid: %.100s", strerror(errno));
1432	#endif
1433
1434	/*
1435	* Disable the key regeneration alarm. We will not regenerate the
1436	* key since we are no longer in a position to give it to anyone. We
1437	* will not restart on SIGHUP since it no longer makes sense.
1438	*/
1439	alarm(0);
1440	signal(SIGALRM, SIG_DFL);
1441	signal(SIGHUP, SIG_DFL);
1442	signal(SIGTERM, SIG_DFL);
1443	signal(SIGQUIT, SIG_DFL);
1444	signal(SIGCHLD, SIG_DFL);
1445	signal(SIGINT, SIG_DFL);
1446
1447	/* Set keepalives if requested. */
1448	if (options.keepalives &&
1449	setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on,
1450	sizeof(on)) < 0)
1451	error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1452
1453	/*
1454	* Register our connection. This turns encryption off because we do
1455	* not have a key.
1456	*/
1457	packet_set_connection(sock_in, sock_out);
1458
1459	remote_port = get_remote_port();
1460	remote_ip = get_remote_ipaddr();
1461
1462	#ifdef LIBWRAP
1463	/* Check whether logins are denied from this host. */
1464	{
1465	struct request_info req;
1466
1467	request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
1468	fromhost(&req);
1469
1470	if (!hosts_access(&req) \|\| !enabled) {
1471	debug("Connection refused by tcp wrapper");
1472	refuse(&req);
1473	/* NOTREACHED */
1474	fatal("libwrap refuse returns");
1475	}
1476	}
1477	#endif /* LIBWRAP */
1478
1479	/* Log the connection. */
1480	verbose("Connection from %.500s port %d", remote_ip, remote_port);
1481
1482	/*
1483	* We don\'t want to listen forever unless the other side
1484	* successfully authenticates itself. So we set up an alarm which is
1485	* cleared after successful authentication. A limit of zero
1486	* indicates no limit. Note that we don\'t set the alarm in debugging
1487	* mode; it is just annoying to have the server exit just when you
1488	* are about to discover the bug.
1489	*/
1490	signal(SIGALRM, grace_alarm_handler);
1491	if (!debug_flag)
1492	alarm(options.login_grace_time);
1493
1494	sshd_exchange_identification(sock_in, sock_out);
1495	/*
1496	* Check that the connection comes from a privileged port.
1497	* Rhosts-Authentication only makes sense from privileged
1498	* programs. Of course, if the intruder has root access on his local
1499	* machine, he can connect from any port. So do not use these
1500	* authentication methods from machines that you do not trust.
1501	*/
1502	if (options.rhosts_authentication &&
1503	(remote_port >= IPPORT_RESERVED \|\|
1504	remote_port < IPPORT_RESERVED / 2)) {
1505	debug("Rhosts Authentication disabled, "
1506	"originating port %d not trusted.", remote_port);
1507	options.rhosts_authentication = 0;
1508	}
1509	#if defined(KRB4) && !defined(KRB5)
1510	if (!packet_connection_is_ipv4() &&
1511	options.kerberos_authentication) {
1512	debug("Kerberos Authentication disabled, only available for IPv4.");
1513	options.kerberos_authentication = 0;
1514	}
1515	#endif /* KRB4 && !KRB5 */
1516	#ifdef AFS
1517	/* If machine has AFS, set process authentication group. */
1518	if (k_hasafs()) {
1519	k_setpag();
1520	k_unlog();
1521	}
1522	#endif /* AFS */
1523
1524	packet_set_nonblocking();
1525
1526	if (use_privsep)
1527	if ((authctxt = privsep_preauth()) != NULL)
1528	goto authenticated;
1529
1530	/* perform the key exchange */
1531	/* authenticate user and start session */
1532	if (compat20) {
1533	do_ssh2_kex();
1534	authctxt = do_authentication2();
1535	} else {
1536	do_ssh1_kex();
1537	authctxt = do_authentication();
1538	}
1539	/*
1540	* If we use privilege separation, the unprivileged child transfers
1541	* the current keystate and exits
1542	*/
1543	if (use_privsep) {
1544	mm_send_keystate(pmonitor);
1545	exit(0);
1546	}
1547
1548	authenticated:
1549	/*
1550	* In privilege separation, we fork another child and prepare
1551	* file descriptor passing.
1552	*/
1553	if (use_privsep) {
1554	privsep_postauth(authctxt);
1555	/* the monitor process [priv] will not return */
1556	if (!compat20)
1557	destroy_sensitive_data();
1558	}
1559
1560	/* Perform session preparation. */
1561	do_authenticated(authctxt);
1562
1563	/* The connection has been terminated. */
1564	verbose("Closing connection to %.100s", remote_ip);
1565
1566	#ifdef USE_PAM
1567	finish_pam();
1568	#endif /* USE_PAM */
1569
1570	packet_close();
1571
1572	if (use_privsep)
1573	mm_terminate();
1574
1575	exit(0);
1576	}
1577
1578	/*
1579	* Decrypt session_key_int using our private server key and private host key
1580	* (key with larger modulus first).
1581	*/
1582	int
1583	ssh1_session_key(BIGNUM *session_key_int)
1584	{
1585	int rsafail = 0;
1586
1587	if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1588	/* Server key has bigger modulus. */
1589	if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1590	BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1591	fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1592	get_remote_ipaddr(),
1593	BN_num_bits(sensitive_data.server_key->rsa->n),
1594	BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1595	SSH_KEY_BITS_RESERVED);
1596	}
1597	if (rsa_private_decrypt(session_key_int, session_key_int,
1598	sensitive_data.server_key->rsa) <= 0)
1599	rsafail++;
1600	if (rsa_private_decrypt(session_key_int, session_key_int,
1601	sensitive_data.ssh1_host_key->rsa) <= 0)
1602	rsafail++;
1603	} else {
1604	/* Host key has bigger modulus (or they are equal). */
1605	if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1606	BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1607	fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1608	get_remote_ipaddr(),
1609	BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1610	BN_num_bits(sensitive_data.server_key->rsa->n),
1611	SSH_KEY_BITS_RESERVED);
1612	}
1613	if (rsa_private_decrypt(session_key_int, session_key_int,
1614	sensitive_data.ssh1_host_key->rsa) < 0)
1615	rsafail++;
1616	if (rsa_private_decrypt(session_key_int, session_key_int,
1617	sensitive_data.server_key->rsa) < 0)
1618	rsafail++;
1619	}
1620	return (rsafail);
1621	}
1622	/*
1623	* SSH1 key exchange
1624	*/
1625	static void
1626	do_ssh1_kex(void)
1627	{
1628	int i, len;
1629	int rsafail = 0;
1630	BIGNUM *session_key_int;
1631	u_char session_key[SSH_SESSION_KEY_LENGTH];
1632	u_char cookie[8];
1633	u_int cipher_type, auth_mask, protocol_flags;
1634	u_int32_t rnd = 0;
1635
1636	/*
1637	* Generate check bytes that the client must send back in the user
1638	* packet in order for it to be accepted; this is used to defy ip
1639	* spoofing attacks. Note that this only works against somebody
1640	* doing IP spoofing from a remote machine; any machine on the local
1641	* network can still see outgoing packets and catch the random
1642	* cookie. This only affects rhosts authentication, and this is one
1643	* of the reasons why it is inherently insecure.
1644	*/
1645	for (i = 0; i < 8; i++) {
1646	if (i % 4 == 0)
1647	rnd = arc4random();
1648	cookie[i] = rnd & 0xff;
1649	rnd >>= 8;
1650	}
1651
1652	/*
1653	* Send our public key. We include in the packet 64 bits of random
1654	* data that must be matched in the reply in order to prevent IP
1655	* spoofing.
1656	*/
1657	packet_start(SSH_SMSG_PUBLIC_KEY);
1658	for (i = 0; i < 8; i++)
1659	packet_put_char(cookie[i]);
1660
1661	/* Store our public server RSA key. */
1662	packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1663	packet_put_bignum(sensitive_data.server_key->rsa->e);
1664	packet_put_bignum(sensitive_data.server_key->rsa->n);
1665
1666	/* Store our public host RSA key. */
1667	packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1668	packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1669	packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1670
1671	/* Put protocol flags. */
1672	packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1673
1674	/* Declare which ciphers we support. */
1675	packet_put_int(cipher_mask_ssh1(0));
1676
1677	/* Declare supported authentication types. */
1678	auth_mask = 0;
1679	if (options.rhosts_authentication)
1680	auth_mask \|= 1 << SSH_AUTH_RHOSTS;
1681	if (options.rhosts_rsa_authentication)
1682	auth_mask \|= 1 << SSH_AUTH_RHOSTS_RSA;
1683	if (options.rsa_authentication)
1684	auth_mask \|= 1 << SSH_AUTH_RSA;
1685	#if defined(KRB4) \|\| defined(KRB5)
1686	if (options.kerberos_authentication)
1687	auth_mask \|= 1 << SSH_AUTH_KERBEROS;
1688	#endif
1689	#if defined(AFS) \|\| defined(KRB5)
1690	if (options.kerberos_tgt_passing)
1691	auth_mask \|= 1 << SSH_PASS_KERBEROS_TGT;
1692	#endif
1693	#ifdef AFS
1694	if (options.afs_token_passing)
1695	auth_mask \|= 1 << SSH_PASS_AFS_TOKEN;
1696	#endif
1697	if (options.challenge_response_authentication == 1)
1698	auth_mask \|= 1 << SSH_AUTH_TIS;
1699	if (options.password_authentication)
1700	auth_mask \|= 1 << SSH_AUTH_PASSWORD;
1701	packet_put_int(auth_mask);
1702
1703	/* Send the packet and wait for it to be sent. */
1704	packet_send();
1705	packet_write_wait();
1706
1707	debug("Sent %d bit server key and %d bit host key.",
1708	BN_num_bits(sensitive_data.server_key->rsa->n),
1709	BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1710
1711	/* Read clients reply (cipher type and session key). */
1712	packet_read_expect(SSH_CMSG_SESSION_KEY);
1713
1714	/* Get cipher type and check whether we accept this. */
1715	cipher_type = packet_get_char();
1716
1717	if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1718	packet_disconnect("Warning: client selects unsupported cipher.");
1719
1720	/* Get check bytes from the packet. These must match those we
1721	sent earlier with the public key packet. */
1722	for (i = 0; i < 8; i++)
1723	if (cookie[i] != packet_get_char())
1724	packet_disconnect("IP Spoofing check bytes do not match.");
1725
1726	debug("Encryption type: %.200s", cipher_name(cipher_type));
1727
1728	/* Get the encrypted integer. */
1729	if ((session_key_int = BN_new()) == NULL)
1730	fatal("do_ssh1_kex: BN_new failed");
1731	packet_get_bignum(session_key_int);
1732
1733	protocol_flags = packet_get_int();
1734	packet_set_protocol_flags(protocol_flags);
1735	packet_check_eom();
1736
1737	/* Decrypt session_key_int using host/server keys */
1738	rsafail = PRIVSEP(ssh1_session_key(session_key_int));
1739
1740	/*
1741	* Extract session key from the decrypted integer. The key is in the
1742	* least significant 256 bits of the integer; the first byte of the
1743	* key is in the highest bits.
1744	*/
1745	if (!rsafail) {
1746	BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1747	len = BN_num_bytes(session_key_int);
1748	if (len < 0 \|\| len > sizeof(session_key)) {
1749	error("do_connection: bad session key len from %s: "
1750	"session_key_int %d > sizeof(session_key) %lu",
1751	get_remote_ipaddr(), len, (u_long)sizeof(session_key));
1752	rsafail++;
1753	} else {
1754	memset(session_key, 0, sizeof(session_key));
1755	BN_bn2bin(session_key_int,
1756	session_key + sizeof(session_key) - len);
1757
1758	compute_session_id(session_id, cookie,
1759	sensitive_data.ssh1_host_key->rsa->n,
1760	sensitive_data.server_key->rsa->n);
1761	/*
1762	* Xor the first 16 bytes of the session key with the
1763	* session id.
1764	*/
1765	for (i = 0; i < 16; i++)
1766	session_key[i] ^= session_id[i];
1767	}
1768	}
1769	if (rsafail) {
1770	int bytes = BN_num_bytes(session_key_int);
1771	u_char *buf = xmalloc(bytes);
1772	MD5_CTX md;
1773
1774	log("do_connection: generating a fake encryption key");
1775	BN_bn2bin(session_key_int, buf);
1776	MD5_Init(&md);
1777	MD5_Update(&md, buf, bytes);
1778	MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1779	MD5_Final(session_key, &md);
1780	MD5_Init(&md);
1781	MD5_Update(&md, session_key, 16);
1782	MD5_Update(&md, buf, bytes);
1783	MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1784	MD5_Final(session_key + 16, &md);
1785	memset(buf, 0, bytes);
1786	xfree(buf);
1787	for (i = 0; i < 16; i++)
1788	session_id[i] = session_key[i] ^ session_key[i + 16];
1789	}
1790	/* Destroy the private and public keys. No longer. */
1791	destroy_sensitive_data();
1792
1793	if (use_privsep)
1794	mm_ssh1_session_id(session_id);
1795
1796	/* Destroy the decrypted integer. It is no longer needed. */
1797	BN_clear_free(session_key_int);
1798
1799	/* Set the session key. From this on all communications will be encrypted. */
1800	packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1801
1802	/* Destroy our copy of the session key. It is no longer needed. */
1803	memset(session_key, 0, sizeof(session_key));
1804
1805	debug("Received session key; encryption turned on.");
1806
1807	/* Send an acknowledgment packet. Note that this packet is sent encrypted. */
1808	packet_start(SSH_SMSG_SUCCESS);
1809	packet_send();
1810	packet_write_wait();
1811	}
1812
1813	/*
1814	* SSH2 key exchange: diffie-hellman-group1-sha1
1815	*/
1816	static void
1817	do_ssh2_kex(void)
1818	{
1819	Kex *kex;
1820
1821	if (options.ciphers != NULL) {
1822	myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1823	myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1824	}
1825	myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1826	compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
1827	myproposal[PROPOSAL_ENC_ALGS_STOC] =
1828	compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
1829
1830	if (options.macs != NULL) {
1831	myproposal[PROPOSAL_MAC_ALGS_CTOS] =
1832	myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
1833	}
1834	if (!options.compression) {
1835	myproposal[PROPOSAL_COMP_ALGS_CTOS] =
1836	myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
1837	}
1838	myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
1839
1840	#ifdef GSSAPI
1841	{
1842	char *orig;
1843	char *gss = NULL;
1844	char *newstr = NULL;
1845	orig = myproposal[PROPOSAL_KEX_ALGS];
1846
1847	/* If we don't have a host key, then all of the algorithms
1848	* currently in myproposal are useless */
1849	if (strlen(myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS])==0)
1850	orig= NULL;
1851
1852	if (options.gss_keyex)
1853	gss = ssh_gssapi_mechanisms(1,NULL);
1854	else
1855	gss = NULL;
1856
1857	if (gss && orig) {
1858	int len = strlen(orig) + strlen(gss) +2;
1859	newstr=xmalloc(len);
1860	snprintf(newstr,len,"%s,%s",gss,orig);
1861	} else if (gss) {
1862	newstr=gss;
1863	} else if (orig) {
1864	newstr=orig;
1865	}
1866	/* If we've got GSSAPI mechanisms, then we've also got the 'null'
1867	host key algorithm, but we're not allowed to advertise it, unless
1868	its the only host key algorithm we're supporting */
1869	if (gss && (strlen(myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS])) == 0) {
1870	myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS]="null";
1871	}
1872	if (newstr)
1873	myproposal[PROPOSAL_KEX_ALGS]=newstr;
1874	else
1875	fatal("No supported key exchange algorithms");
1876	}
1877	#endif
1878
1879	/* start key exchange */
1880	kex = kex_setup(myproposal);
1881	kex->server = 1;
1882	kex->client_version_string=client_version_string;
1883	kex->server_version_string=server_version_string;
1884	kex->load_host_key=&get_hostkey_by_type;
1885	kex->host_key_index=&get_hostkey_index;
1886
1887	xxx_kex = kex;
1888
1889	dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
1890
1891	session_id2 = kex->session_id;
1892	session_id2_len = kex->session_id_len;
1893
1894	#ifdef DEBUG_KEXDH
1895	/* send 1st encrypted/maced/compressed message */
1896	packet_start(SSH2_MSG_IGNORE);
1897	packet_put_cstring("markus");
1898	packet_send();
1899	packet_write_wait();
1900	#endif
1901	debug("KEX done");
1902	}

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