2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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.
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".
17 * SSH2 implementation:
18 * Privilege Separation:
20 * Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved.
21 * Copyright (c) 2002 Niels Provos. All rights reserved.
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
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.
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.
45 RCSID("$OpenBSD: sshd.c,v 1.240 2002/04/23 22:16:29 djm Exp $");
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>
73 #include "myproposal.h"
75 #include "pathnames.h"
83 #include "monitor_mm.h"
85 #include "monitor_wrap.h"
86 #include "monitor_fdpass.h"
91 int allow_severity = LOG_INFO;
92 int deny_severity = LOG_WARNING;
99 #ifdef HAVE___PROGNAME
100 extern char *__progname;
105 /* Server configuration options. */
106 ServerOptions options;
108 /* Name of the server configuration file. */
109 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
112 * Flag indicating whether IPv4 or IPv6. This can be set on the command line.
113 * Default value is AF_UNSPEC means both IPv4 and IPv6.
116 int IPv4or6 = AF_INET;
118 int IPv4or6 = AF_UNSPEC;
122 * Debug mode flag. This can be set on the command line. If debug
123 * mode is enabled, extra debugging output will be sent to the system
124 * log, the daemon will not go to background, and will exit after processing
125 * the first connection.
129 /* Flag indicating that the daemon should only test the configuration and keys. */
132 /* Flag indicating that the daemon is being started from inetd. */
135 /* Flag indicating that sshd should not detach and become a daemon. */
136 int no_daemon_flag = 0;
138 /* debug goes to stderr unless inetd_flag is set */
141 /* Saved arguments to main(). */
146 * The sockets that the server is listening; this is used in the SIGHUP
149 #define MAX_LISTEN_SOCKS 16
150 int listen_socks[MAX_LISTEN_SOCKS];
151 int num_listen_socks = 0;
154 * the client's version string, passed by sshd2 in compat mode. if != NULL,
155 * sshd will skip the version-number exchange
157 char *client_version_string = NULL;
158 char *server_version_string = NULL;
160 /* for rekeying XXX fixme */
164 * Any really sensitive data in the application is contained in this
165 * structure. The idea is that this structure could be locked into memory so
166 * that the pages do not get written into swap. However, there are some
167 * problems. The private key contains BIGNUMs, and we do not (in principle)
168 * have access to the internals of them, and locking just the structure is
169 * not very useful. Currently, memory locking is not implemented.
172 Key *server_key; /* ephemeral server key */
173 Key *ssh1_host_key; /* ssh1 host key */
174 Key **host_keys; /* all private host keys */
177 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
181 * Flag indicating whether the RSA server key needs to be regenerated.
182 * Is set in the SIGALRM handler and cleared when the key is regenerated.
184 static volatile sig_atomic_t key_do_regen = 0;
186 /* This is set to true when a signal is received. */
187 static volatile sig_atomic_t received_sighup = 0;
188 static volatile sig_atomic_t received_sigterm = 0;
190 /* session identifier, used by RSA-auth */
191 u_char session_id[16];
194 u_char *session_id2 = NULL;
195 int session_id2_len = 0;
197 /* record remote hostname or ip */
198 u_int utmp_len = MAXHOSTNAMELEN;
200 /* options.max_startup sized array of fd ints */
201 int *startup_pipes = NULL;
202 int startup_pipe; /* in child */
204 /* variables used for privilege separation */
205 extern struct monitor *monitor;
206 extern int use_privsep;
208 /* Prototypes for various functions defined later in this file. */
209 void destroy_sensitive_data(void);
210 void demote_sensitive_data(void);
212 static void do_ssh1_kex(void);
213 static void do_ssh2_kex(void);
216 * Close all listening sockets
219 close_listen_socks(void)
222 for (i = 0; i < num_listen_socks; i++)
223 close(listen_socks[i]);
224 num_listen_socks = -1;
228 close_startup_pipes(void)
232 for (i = 0; i < options.max_startups; i++)
233 if (startup_pipes[i] != -1)
234 close(startup_pipes[i]);
238 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
239 * the effect is to reread the configuration file (and to regenerate
243 sighup_handler(int sig)
245 int save_errno = errno;
248 signal(SIGHUP, sighup_handler);
253 * Called from the main program after receiving SIGHUP.
254 * Restarts the server.
259 log("Received SIGHUP; restarting.");
260 close_listen_socks();
261 close_startup_pipes();
262 execv(saved_argv[0], saved_argv);
263 log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], strerror(errno));
268 * Generic signal handler for terminating signals in the master daemon.
271 sigterm_handler(int sig)
273 received_sigterm = sig;
277 * SIGCHLD handler. This is called whenever a child dies. This will then
278 * reap any zombies left by exited children.
281 main_sigchld_handler(int sig)
284 int save_errno = errno;
287 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
288 (pid < 0 && errno == EINTR))
291 signal(SIGCHLD, main_sigchld_handler);
296 * Signal handler for the alarm after the login grace period has expired.
299 grace_alarm_handler(int sig)
301 /* XXX no idea how fix this signal handler */
303 /* Close the connection. */
306 /* Log error and exit. */
307 fatal("Timeout before authentication for %s.", get_remote_ipaddr());
311 * Signal handler for the key regeneration alarm. Note that this
312 * alarm only occurs in the daemon waiting for connections, and it does not
313 * do anything with the private key or random state before forking.
314 * Thus there should be no concurrency control/asynchronous execution
318 generate_ephemeral_server_key(void)
323 verbose("Generating %s%d bit RSA key.",
324 sensitive_data.server_key ? "new " : "", options.server_key_bits);
325 if (sensitive_data.server_key != NULL)
326 key_free(sensitive_data.server_key);
327 sensitive_data.server_key = key_generate(KEY_RSA1,
328 options.server_key_bits);
329 verbose("RSA key generation complete.");
331 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
334 sensitive_data.ssh1_cookie[i] = rand & 0xff;
341 key_regeneration_alarm(int sig)
343 int save_errno = errno;
344 signal(SIGALRM, SIG_DFL);
350 sshd_exchange_identification(int sock_in, int sock_out)
353 int remote_major, remote_minor;
356 char buf[256]; /* Must not be larger than remote_version. */
357 char remote_version[256]; /* Must be at least as big as buf. */
359 if ((options.protocol & SSH_PROTO_1) &&
360 (options.protocol & SSH_PROTO_2)) {
361 major = PROTOCOL_MAJOR_1;
363 } else if (options.protocol & SSH_PROTO_2) {
364 major = PROTOCOL_MAJOR_2;
365 minor = PROTOCOL_MINOR_2;
367 major = PROTOCOL_MAJOR_1;
368 minor = PROTOCOL_MINOR_1;
370 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
371 server_version_string = xstrdup(buf);
373 if (client_version_string == NULL) {
374 /* Send our protocol version identification. */
375 if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
376 != strlen(server_version_string)) {
377 log("Could not write ident string to %s", get_remote_ipaddr());
381 /* Read other side's version identification. */
382 memset(buf, 0, sizeof(buf));
383 for (i = 0; i < sizeof(buf) - 1; i++) {
384 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
385 log("Did not receive identification string from %s",
386 get_remote_ipaddr());
389 if (buf[i] == '\r') {
391 /* Kludge for F-Secure Macintosh < 1.0.2 */
393 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
397 if (buf[i] == '\n') {
402 buf[sizeof(buf) - 1] = 0;
403 client_version_string = xstrdup(buf);
407 * Check that the versions match. In future this might accept
408 * several versions and set appropriate flags to handle them.
410 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
411 &remote_major, &remote_minor, remote_version) != 3) {
412 s = "Protocol mismatch.\n";
413 (void) atomicio(write, sock_out, s, strlen(s));
416 log("Bad protocol version identification '%.100s' from %s",
417 client_version_string, get_remote_ipaddr());
420 debug("Client protocol version %d.%d; client software version %.100s",
421 remote_major, remote_minor, remote_version);
423 compat_datafellows(remote_version);
425 if (datafellows & SSH_BUG_SCANNER) {
426 log("scanned from %s with %s. Don't panic.",
427 get_remote_ipaddr(), client_version_string);
432 switch (remote_major) {
434 if (remote_minor == 99) {
435 if (options.protocol & SSH_PROTO_2)
441 if (!(options.protocol & SSH_PROTO_1)) {
445 if (remote_minor < 3) {
446 packet_disconnect("Your ssh version is too old and "
447 "is no longer supported. Please install a newer version.");
448 } else if (remote_minor == 3) {
449 /* note that this disables agent-forwarding */
454 if (options.protocol & SSH_PROTO_2) {
463 chop(server_version_string);
464 debug("Local version string %.200s", server_version_string);
467 s = "Protocol major versions differ.\n";
468 (void) atomicio(write, sock_out, s, strlen(s));
471 log("Protocol major versions differ for %s: %.200s vs. %.200s",
473 server_version_string, client_version_string);
479 /* Destroy the host and server keys. They will no longer be needed. */
481 destroy_sensitive_data(void)
485 if (sensitive_data.server_key) {
486 key_free(sensitive_data.server_key);
487 sensitive_data.server_key = NULL;
489 for (i = 0; i < options.num_host_key_files; i++) {
490 if (sensitive_data.host_keys[i]) {
491 key_free(sensitive_data.host_keys[i]);
492 sensitive_data.host_keys[i] = NULL;
495 sensitive_data.ssh1_host_key = NULL;
496 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
499 /* Demote private to public keys for network child */
501 demote_sensitive_data(void)
506 if (sensitive_data.server_key) {
507 tmp = key_demote(sensitive_data.server_key);
508 key_free(sensitive_data.server_key);
509 sensitive_data.server_key = tmp;
512 for (i = 0; i < options.num_host_key_files; i++) {
513 if (sensitive_data.host_keys[i]) {
514 tmp = key_demote(sensitive_data.host_keys[i]);
515 key_free(sensitive_data.host_keys[i]);
516 sensitive_data.host_keys[i] = tmp;
517 if (tmp->type == KEY_RSA1)
518 sensitive_data.ssh1_host_key = tmp;
522 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */
526 privsep_preauth_child(void)
532 /* Enable challenge-response authentication for privilege separation */
533 privsep_challenge_enable();
535 for (i = 0; i < 256; i++)
536 rand[i] = arc4random();
537 RAND_seed(rand, sizeof(rand));
539 /* Demote the private keys to public keys. */
540 demote_sensitive_data();
542 if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
543 fatal("Privilege separation user %s does not exist",
545 memset(pw->pw_passwd, 0, strlen(pw->pw_passwd));
548 /* Change our root directory*/
549 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
550 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
552 if (chdir("/") == -1)
553 fatal("chdir(\"/\"): %s", strerror(errno));
555 /* Drop our privileges */
556 debug3("privsep user:group %u:%u", (u_int)pw->pw_uid,
558 do_setusercontext(pw);
562 privsep_preauth(void)
564 Authctxt *authctxt = NULL;
568 /* Set up unprivileged child process to deal with network data */
569 monitor = monitor_init();
570 /* Store a pointer to the kex for later rekeying */
571 monitor->m_pkex = &xxx_kex;
575 fatal("fork of unprivileged child failed");
576 } else if (pid != 0) {
577 debug2("Network child is on pid %d", pid);
579 close(monitor->m_recvfd);
580 authctxt = monitor_child_preauth(monitor);
581 close(monitor->m_sendfd);
584 monitor_sync(monitor);
586 /* Wait for the child's exit status */
587 while (waitpid(pid, &status, 0) < 0)
594 close(monitor->m_sendfd);
596 /* Demote the child */
597 if (getuid() == 0 || geteuid() == 0)
598 privsep_preauth_child();
599 setproctitle("%s", "[net]");
605 privsep_postauth(Authctxt *authctxt)
607 extern Authctxt *x_authctxt;
609 /* XXX - Remote port forwarding */
610 x_authctxt = authctxt;
612 if (authctxt->pw->pw_uid == 0 || options.use_login) {
613 /* File descriptor passing is broken or root login */
614 monitor_apply_keystate(monitor);
619 /* Authentication complete */
621 if (startup_pipe != -1) {
626 /* New socket pair */
627 monitor_reinit(monitor);
629 monitor->m_pid = fork();
630 if (monitor->m_pid == -1)
631 fatal("fork of unprivileged child failed");
632 else if (monitor->m_pid != 0) {
633 debug2("User child is on pid %d", monitor->m_pid);
634 close(monitor->m_recvfd);
635 monitor_child_postauth(monitor);
641 close(monitor->m_sendfd);
643 /* Demote the private keys to public keys. */
644 demote_sensitive_data();
646 /* Drop privileges */
647 do_setusercontext(authctxt->pw);
649 /* It is safe now to apply the key state */
650 monitor_apply_keystate(monitor);
654 list_hostkey_types(void)
661 for (i = 0; i < options.num_host_key_files; i++) {
662 Key *key = sensitive_data.host_keys[i];
668 if (buffer_len(&b) > 0)
669 buffer_append(&b, ",", 1);
670 p = key_ssh_name(key);
671 buffer_append(&b, p, strlen(p));
675 buffer_append(&b, "\0", 1);
676 p = xstrdup(buffer_ptr(&b));
678 debug("list_hostkey_types: %s", p);
683 get_hostkey_by_type(int type)
686 for (i = 0; i < options.num_host_key_files; i++) {
687 Key *key = sensitive_data.host_keys[i];
688 if (key != NULL && key->type == type)
695 get_hostkey_by_index(int ind)
697 if (ind < 0 || ind >= options.num_host_key_files)
699 return (sensitive_data.host_keys[ind]);
703 get_hostkey_index(Key *key)
706 for (i = 0; i < options.num_host_key_files; i++) {
707 if (key == sensitive_data.host_keys[i])
714 * returns 1 if connection should be dropped, 0 otherwise.
715 * dropping starts at connection #max_startups_begin with a probability
716 * of (max_startups_rate/100). the probability increases linearly until
717 * all connections are dropped for startups > max_startups
720 drop_connection(int startups)
724 if (startups < options.max_startups_begin)
726 if (startups >= options.max_startups)
728 if (options.max_startups_rate == 100)
731 p = 100 - options.max_startups_rate;
732 p *= startups - options.max_startups_begin;
733 p /= (double) (options.max_startups - options.max_startups_begin);
734 p += options.max_startups_rate;
736 r = arc4random() / (double) UINT_MAX;
738 debug("drop_connection: p %g, r %g", p, r);
739 return (r < p) ? 1 : 0;
745 fprintf(stderr, "sshd version %s\n", SSH_VERSION);
746 fprintf(stderr, "Usage: %s [options]\n", __progname);
747 fprintf(stderr, "Options:\n");
748 fprintf(stderr, " -f file Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE);
749 fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n");
750 fprintf(stderr, " -i Started from inetd\n");
751 fprintf(stderr, " -D Do not fork into daemon mode\n");
752 fprintf(stderr, " -t Only test configuration file and keys\n");
753 fprintf(stderr, " -q Quiet (no logging)\n");
754 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
755 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
756 fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n");
757 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
758 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
759 _PATH_HOST_KEY_FILE);
760 fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
761 fprintf(stderr, " -4 Use IPv4 only\n");
762 fprintf(stderr, " -6 Use IPv6 only\n");
763 fprintf(stderr, " -o option Process the option as if it was read from a configuration file.\n");
768 * Main program for the daemon.
771 main(int ac, char **av)
775 int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
779 struct sockaddr_storage from;
780 const char *remote_ip;
783 struct linger linger;
785 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
786 int listen_sock, maxfd;
791 int ret, key_used = 0;
793 #ifdef HAVE_SECUREWARE
794 (void)set_auth_parameters(ac, av);
796 __progname = get_progname(av[0]);
803 /* Initialize configuration options to their default values. */
804 initialize_server_options(&options);
806 /* Parse command-line arguments. */
807 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:o:dDeiqtQ46")) != -1) {
816 config_file_name = optarg;
819 if (0 == debug_flag) {
821 options.log_level = SYSLOG_LEVEL_DEBUG1;
822 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
825 fprintf(stderr, "Too high debugging level.\n");
842 options.log_level = SYSLOG_LEVEL_QUIET;
845 options.server_key_bits = atoi(optarg);
848 options.ports_from_cmdline = 1;
849 if (options.num_ports >= MAX_PORTS) {
850 fprintf(stderr, "too many ports.\n");
853 options.ports[options.num_ports++] = a2port(optarg);
854 if (options.ports[options.num_ports-1] == 0) {
855 fprintf(stderr, "Bad port number.\n");
860 if ((options.login_grace_time = convtime(optarg)) == -1) {
861 fprintf(stderr, "Invalid login grace time.\n");
866 if ((options.key_regeneration_time = convtime(optarg)) == -1) {
867 fprintf(stderr, "Invalid key regeneration interval.\n");
872 if (options.num_host_key_files >= MAX_HOSTKEYS) {
873 fprintf(stderr, "too many host keys.\n");
876 options.host_key_files[options.num_host_key_files++] = optarg;
879 client_version_string = optarg;
880 /* only makes sense with inetd_flag, i.e. no listen() */
887 utmp_len = atoi(optarg);
890 if (process_server_config_line(&options, optarg,
891 "command-line", 0) != 0)
900 SSLeay_add_all_algorithms();
901 channel_set_af(IPv4or6);
904 * Force logging to stderr until we have loaded the private host
905 * key (unless started from inetd)
908 options.log_level == SYSLOG_LEVEL_NOT_SET ?
909 SYSLOG_LEVEL_INFO : options.log_level,
910 options.log_facility == SYSLOG_FACILITY_NOT_SET ?
911 SYSLOG_FACILITY_AUTH : options.log_facility,
915 /* Cray can define user privs drop all prives now!
916 * Not needed on PRIV_SU systems!
923 /* Read server configuration options from the configuration file. */
924 read_server_config(&options, config_file_name);
926 /* Fill in default values for those options not explicitly set. */
927 fill_default_server_options(&options);
929 /* Check that there are no remaining arguments. */
931 fprintf(stderr, "Extra argument %s.\n", av[optind]);
935 debug("sshd version %.100s", SSH_VERSION);
937 /* load private host keys */
938 sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*));
939 for (i = 0; i < options.num_host_key_files; i++)
940 sensitive_data.host_keys[i] = NULL;
941 sensitive_data.server_key = NULL;
942 sensitive_data.ssh1_host_key = NULL;
943 sensitive_data.have_ssh1_key = 0;
944 sensitive_data.have_ssh2_key = 0;
946 for (i = 0; i < options.num_host_key_files; i++) {
947 key = key_load_private(options.host_key_files[i], "", NULL);
948 sensitive_data.host_keys[i] = key;
950 error("Could not load host key: %s",
951 options.host_key_files[i]);
952 sensitive_data.host_keys[i] = NULL;
957 sensitive_data.ssh1_host_key = key;
958 sensitive_data.have_ssh1_key = 1;
962 sensitive_data.have_ssh2_key = 1;
965 debug("private host key: #%d type %d %s", i, key->type,
968 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
969 log("Disabling protocol version 1. Could not load host key");
970 options.protocol &= ~SSH_PROTO_1;
972 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
973 log("Disabling protocol version 2. Could not load host key");
974 options.protocol &= ~SSH_PROTO_2;
976 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
977 log("sshd: no hostkeys available -- exiting.");
981 /* Check certain values for sanity. */
982 if (options.protocol & SSH_PROTO_1) {
983 if (options.server_key_bits < 512 ||
984 options.server_key_bits > 32768) {
985 fprintf(stderr, "Bad server key size.\n");
989 * Check that server and host key lengths differ sufficiently. This
990 * is necessary to make double encryption work with rsaref. Oh, I
991 * hate software patents. I dont know if this can go? Niels
993 if (options.server_key_bits >
994 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - SSH_KEY_BITS_RESERVED &&
995 options.server_key_bits <
996 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
997 options.server_key_bits =
998 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED;
999 debug("Forcing server key to %d bits to make it differ from host key.",
1000 options.server_key_bits);
1004 /* Configuration looks good, so exit if in test mode. */
1008 /* Initialize the log (it is reinitialized below in case we forked). */
1009 if (debug_flag && !inetd_flag)
1011 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1014 * If not in debugging mode, and not started from inetd, disconnect
1015 * from the controlling terminal, and fork. The original process
1018 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
1021 #endif /* TIOCNOTTY */
1022 if (daemon(0, 0) < 0)
1023 fatal("daemon() failed: %.200s", strerror(errno));
1025 /* Disconnect from the controlling tty. */
1027 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
1029 (void) ioctl(fd, TIOCNOTTY, NULL);
1032 #endif /* TIOCNOTTY */
1034 /* Reinitialize the log (because of the fork above). */
1035 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1037 /* Initialize the random number generator. */
1040 /* Chdir to the root directory so that the current disk can be
1041 unmounted if desired. */
1044 /* ignore SIGPIPE */
1045 signal(SIGPIPE, SIG_IGN);
1047 /* Start listening for a socket, unless started from inetd. */
1050 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
1056 * We intentionally do not close the descriptors 0, 1, and 2
1057 * as our code for setting the descriptors won\'t work if
1058 * ttyfd happens to be one of those.
1060 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
1061 if (options.protocol & SSH_PROTO_1)
1062 generate_ephemeral_server_key();
1064 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
1065 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
1067 if (num_listen_socks >= MAX_LISTEN_SOCKS)
1068 fatal("Too many listen sockets. "
1069 "Enlarge MAX_LISTEN_SOCKS");
1070 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
1071 ntop, sizeof(ntop), strport, sizeof(strport),
1072 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
1073 error("getnameinfo failed");
1076 /* Create socket for listening. */
1077 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
1078 if (listen_sock < 0) {
1079 /* kernel may not support ipv6 */
1080 verbose("socket: %.100s", strerror(errno));
1083 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
1084 error("listen_sock O_NONBLOCK: %s", strerror(errno));
1089 * Set socket options. We try to make the port
1090 * reusable and have it close as fast as possible
1091 * without waiting in unnecessary wait states on
1094 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
1097 linger.l_linger = 5;
1098 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
1099 &linger, sizeof(linger));
1101 debug("Bind to port %s on %s.", strport, ntop);
1103 /* Bind the socket to the desired port. */
1104 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1106 error("Bind to port %s on %s failed: %.200s.",
1107 strport, ntop, strerror(errno));
1111 listen_socks[num_listen_socks] = listen_sock;
1114 /* Start listening on the port. */
1115 log("Server listening on %s port %s.", ntop, strport);
1116 if (listen(listen_sock, 5) < 0)
1117 fatal("listen: %.100s", strerror(errno));
1120 freeaddrinfo(options.listen_addrs);
1122 if (!num_listen_socks)
1123 fatal("Cannot bind any address.");
1125 if (options.protocol & SSH_PROTO_1)
1126 generate_ephemeral_server_key();
1129 * Arrange to restart on SIGHUP. The handler needs
1132 signal(SIGHUP, sighup_handler);
1134 signal(SIGTERM, sigterm_handler);
1135 signal(SIGQUIT, sigterm_handler);
1137 /* Arrange SIGCHLD to be caught. */
1138 signal(SIGCHLD, main_sigchld_handler);
1140 /* Write out the pid file after the sigterm handler is setup */
1143 * Record our pid in /var/run/sshd.pid to make it
1144 * easier to kill the correct sshd. We don't want to
1145 * do this before the bind above because the bind will
1146 * fail if there already is a daemon, and this will
1147 * overwrite any old pid in the file.
1149 f = fopen(options.pid_file, "wb");
1151 fprintf(f, "%u\n", (u_int) getpid());
1156 /* setup fd set for listen */
1159 for (i = 0; i < num_listen_socks; i++)
1160 if (listen_socks[i] > maxfd)
1161 maxfd = listen_socks[i];
1162 /* pipes connected to unauthenticated childs */
1163 startup_pipes = xmalloc(options.max_startups * sizeof(int));
1164 for (i = 0; i < options.max_startups; i++)
1165 startup_pipes[i] = -1;
1168 * Stay listening for connections until the system crashes or
1169 * the daemon is killed with a signal.
1172 if (received_sighup)
1176 fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
1177 fdset = (fd_set *)xmalloc(fdsetsz);
1178 memset(fdset, 0, fdsetsz);
1180 for (i = 0; i < num_listen_socks; i++)
1181 FD_SET(listen_socks[i], fdset);
1182 for (i = 0; i < options.max_startups; i++)
1183 if (startup_pipes[i] != -1)
1184 FD_SET(startup_pipes[i], fdset);
1186 /* Wait in select until there is a connection. */
1187 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
1188 if (ret < 0 && errno != EINTR)
1189 error("select: %.100s", strerror(errno));
1190 if (received_sigterm) {
1191 log("Received signal %d; terminating.",
1192 (int) received_sigterm);
1193 close_listen_socks();
1194 unlink(options.pid_file);
1197 if (key_used && key_do_regen) {
1198 generate_ephemeral_server_key();
1205 for (i = 0; i < options.max_startups; i++)
1206 if (startup_pipes[i] != -1 &&
1207 FD_ISSET(startup_pipes[i], fdset)) {
1209 * the read end of the pipe is ready
1210 * if the child has closed the pipe
1211 * after successful authentication
1212 * or if the child has died
1214 close(startup_pipes[i]);
1215 startup_pipes[i] = -1;
1218 for (i = 0; i < num_listen_socks; i++) {
1219 if (!FD_ISSET(listen_socks[i], fdset))
1221 fromlen = sizeof(from);
1222 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
1225 if (errno != EINTR && errno != EWOULDBLOCK)
1226 error("accept: %.100s", strerror(errno));
1229 if (fcntl(newsock, F_SETFL, 0) < 0) {
1230 error("newsock del O_NONBLOCK: %s", strerror(errno));
1234 if (drop_connection(startups) == 1) {
1235 debug("drop connection #%d", startups);
1239 if (pipe(startup_p) == -1) {
1244 for (j = 0; j < options.max_startups; j++)
1245 if (startup_pipes[j] == -1) {
1246 startup_pipes[j] = startup_p[0];
1247 if (maxfd < startup_p[0])
1248 maxfd = startup_p[0];
1254 * Got connection. Fork a child to handle it, unless
1255 * we are in debugging mode.
1259 * In debugging mode. Close the listening
1260 * socket, and start processing the
1261 * connection without forking.
1263 debug("Server will not fork when running in debugging mode.");
1264 close_listen_socks();
1272 * Normal production daemon. Fork, and have
1273 * the child process the connection. The
1274 * parent continues listening.
1276 if ((pid = fork()) == 0) {
1278 * Child. Close the listening and max_startup
1279 * sockets. Start using the accepted socket.
1280 * Reinitialize logging (since our pid has
1281 * changed). We break out of the loop to handle
1284 startup_pipe = startup_p[1];
1285 close_startup_pipes();
1286 close_listen_socks();
1289 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1294 /* Parent. Stay in the loop. */
1296 error("fork: %.100s", strerror(errno));
1298 debug("Forked child %d.", pid);
1300 close(startup_p[1]);
1302 /* Mark that the key has been used (it was "given" to the child). */
1303 if ((options.protocol & SSH_PROTO_1) &&
1305 /* Schedule server key regeneration alarm. */
1306 signal(SIGALRM, key_regeneration_alarm);
1307 alarm(options.key_regeneration_time);
1313 /* Close the new socket (the child is now taking care of it). */
1316 /* child process check (or debug mode) */
1317 if (num_listen_socks < 0)
1322 /* This is the child processing a new connection. */
1325 * Disable the key regeneration alarm. We will not regenerate the
1326 * key since we are no longer in a position to give it to anyone. We
1327 * will not restart on SIGHUP since it no longer makes sense.
1330 signal(SIGALRM, SIG_DFL);
1331 signal(SIGHUP, SIG_DFL);
1332 signal(SIGTERM, SIG_DFL);
1333 signal(SIGQUIT, SIG_DFL);
1334 signal(SIGCHLD, SIG_DFL);
1335 signal(SIGINT, SIG_DFL);
1338 * Set socket options for the connection. We want the socket to
1339 * close as fast as possible without waiting for anything. If the
1340 * connection is not a socket, these will do nothing.
1342 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1344 linger.l_linger = 5;
1345 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, &linger, sizeof(linger));
1347 /* Set keepalives if requested. */
1348 if (options.keepalives &&
1349 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on,
1351 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1354 * Register our connection. This turns encryption off because we do
1357 packet_set_connection(sock_in, sock_out);
1359 remote_port = get_remote_port();
1360 remote_ip = get_remote_ipaddr();
1363 /* Check whether logins are denied from this host. */
1365 struct request_info req;
1367 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
1370 if (!hosts_access(&req)) {
1371 debug("Connection refused by tcp wrapper");
1374 fatal("libwrap refuse returns");
1377 #endif /* LIBWRAP */
1379 /* Log the connection. */
1380 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1383 * We don\'t want to listen forever unless the other side
1384 * successfully authenticates itself. So we set up an alarm which is
1385 * cleared after successful authentication. A limit of zero
1386 * indicates no limit. Note that we don\'t set the alarm in debugging
1387 * mode; it is just annoying to have the server exit just when you
1388 * are about to discover the bug.
1390 signal(SIGALRM, grace_alarm_handler);
1392 alarm(options.login_grace_time);
1394 sshd_exchange_identification(sock_in, sock_out);
1396 * Check that the connection comes from a privileged port.
1397 * Rhosts-Authentication only makes sense from priviledged
1398 * programs. Of course, if the intruder has root access on his local
1399 * machine, he can connect from any port. So do not use these
1400 * authentication methods from machines that you do not trust.
1402 if (options.rhosts_authentication &&
1403 (remote_port >= IPPORT_RESERVED ||
1404 remote_port < IPPORT_RESERVED / 2)) {
1405 debug("Rhosts Authentication disabled, "
1406 "originating port %d not trusted.", remote_port);
1407 options.rhosts_authentication = 0;
1409 #if defined(KRB4) && !defined(KRB5)
1410 if (!packet_connection_is_ipv4() &&
1411 options.kerberos_authentication) {
1412 debug("Kerberos Authentication disabled, only available for IPv4.");
1413 options.kerberos_authentication = 0;
1415 #endif /* KRB4 && !KRB5 */
1417 /* If machine has AFS, set process authentication group. */
1424 packet_set_nonblocking();
1427 if ((authctxt = privsep_preauth()) != NULL)
1430 /* perform the key exchange */
1431 /* authenticate user and start session */
1434 authctxt = do_authentication2();
1437 authctxt = do_authentication();
1440 * If we use privilege separation, the unprivileged child transfers
1441 * the current keystate and exits
1444 mm_send_keystate(monitor);
1450 * In privilege separation, we fork another child and prepare
1451 * file descriptor passing.
1454 privsep_postauth(authctxt);
1455 /* the monitor process [priv] will not return */
1457 destroy_sensitive_data();
1460 /* Perform session preparation. */
1461 do_authenticated(authctxt);
1463 /* The connection has been terminated. */
1464 verbose("Closing connection to %.100s", remote_ip);
1468 #endif /* USE_PAM */
1479 * Decrypt session_key_int using our private server key and private host key
1480 * (key with larger modulus first).
1483 ssh1_session_key(BIGNUM *session_key_int)
1487 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1488 /* Server key has bigger modulus. */
1489 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1490 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1491 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1492 get_remote_ipaddr(),
1493 BN_num_bits(sensitive_data.server_key->rsa->n),
1494 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1495 SSH_KEY_BITS_RESERVED);
1497 if (rsa_private_decrypt(session_key_int, session_key_int,
1498 sensitive_data.server_key->rsa) <= 0)
1500 if (rsa_private_decrypt(session_key_int, session_key_int,
1501 sensitive_data.ssh1_host_key->rsa) <= 0)
1504 /* Host key has bigger modulus (or they are equal). */
1505 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1506 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1507 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1508 get_remote_ipaddr(),
1509 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1510 BN_num_bits(sensitive_data.server_key->rsa->n),
1511 SSH_KEY_BITS_RESERVED);
1513 if (rsa_private_decrypt(session_key_int, session_key_int,
1514 sensitive_data.ssh1_host_key->rsa) < 0)
1516 if (rsa_private_decrypt(session_key_int, session_key_int,
1517 sensitive_data.server_key->rsa) < 0)
1530 BIGNUM *session_key_int;
1531 u_char session_key[SSH_SESSION_KEY_LENGTH];
1533 u_int cipher_type, auth_mask, protocol_flags;
1537 * Generate check bytes that the client must send back in the user
1538 * packet in order for it to be accepted; this is used to defy ip
1539 * spoofing attacks. Note that this only works against somebody
1540 * doing IP spoofing from a remote machine; any machine on the local
1541 * network can still see outgoing packets and catch the random
1542 * cookie. This only affects rhosts authentication, and this is one
1543 * of the reasons why it is inherently insecure.
1545 for (i = 0; i < 8; i++) {
1547 rand = arc4random();
1548 cookie[i] = rand & 0xff;
1553 * Send our public key. We include in the packet 64 bits of random
1554 * data that must be matched in the reply in order to prevent IP
1557 packet_start(SSH_SMSG_PUBLIC_KEY);
1558 for (i = 0; i < 8; i++)
1559 packet_put_char(cookie[i]);
1561 /* Store our public server RSA key. */
1562 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1563 packet_put_bignum(sensitive_data.server_key->rsa->e);
1564 packet_put_bignum(sensitive_data.server_key->rsa->n);
1566 /* Store our public host RSA key. */
1567 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1568 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1569 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1571 /* Put protocol flags. */
1572 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1574 /* Declare which ciphers we support. */
1575 packet_put_int(cipher_mask_ssh1(0));
1577 /* Declare supported authentication types. */
1579 if (options.rhosts_authentication)
1580 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1581 if (options.rhosts_rsa_authentication)
1582 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1583 if (options.rsa_authentication)
1584 auth_mask |= 1 << SSH_AUTH_RSA;
1585 #if defined(KRB4) || defined(KRB5)
1586 if (options.kerberos_authentication)
1587 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1589 #if defined(AFS) || defined(KRB5)
1590 if (options.kerberos_tgt_passing)
1591 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1594 if (options.afs_token_passing)
1595 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1597 if (options.challenge_response_authentication == 1)
1598 auth_mask |= 1 << SSH_AUTH_TIS;
1599 if (options.password_authentication)
1600 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1601 packet_put_int(auth_mask);
1603 /* Send the packet and wait for it to be sent. */
1605 packet_write_wait();
1607 debug("Sent %d bit server key and %d bit host key.",
1608 BN_num_bits(sensitive_data.server_key->rsa->n),
1609 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1611 /* Read clients reply (cipher type and session key). */
1612 packet_read_expect(SSH_CMSG_SESSION_KEY);
1614 /* Get cipher type and check whether we accept this. */
1615 cipher_type = packet_get_char();
1617 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1618 packet_disconnect("Warning: client selects unsupported cipher.");
1620 /* Get check bytes from the packet. These must match those we
1621 sent earlier with the public key packet. */
1622 for (i = 0; i < 8; i++)
1623 if (cookie[i] != packet_get_char())
1624 packet_disconnect("IP Spoofing check bytes do not match.");
1626 debug("Encryption type: %.200s", cipher_name(cipher_type));
1628 /* Get the encrypted integer. */
1629 if ((session_key_int = BN_new()) == NULL)
1630 fatal("do_ssh1_kex: BN_new failed");
1631 packet_get_bignum(session_key_int);
1633 protocol_flags = packet_get_int();
1634 packet_set_protocol_flags(protocol_flags);
1637 /* Decrypt session_key_int using host/server keys */
1638 rsafail = PRIVSEP(ssh1_session_key(session_key_int));
1641 * Extract session key from the decrypted integer. The key is in the
1642 * least significant 256 bits of the integer; the first byte of the
1643 * key is in the highest bits.
1646 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1647 len = BN_num_bytes(session_key_int);
1648 if (len < 0 || len > sizeof(session_key)) {
1649 error("do_connection: bad session key len from %s: "
1650 "session_key_int %d > sizeof(session_key) %lu",
1651 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
1654 memset(session_key, 0, sizeof(session_key));
1655 BN_bn2bin(session_key_int,
1656 session_key + sizeof(session_key) - len);
1658 compute_session_id(session_id, cookie,
1659 sensitive_data.ssh1_host_key->rsa->n,
1660 sensitive_data.server_key->rsa->n);
1662 * Xor the first 16 bytes of the session key with the
1665 for (i = 0; i < 16; i++)
1666 session_key[i] ^= session_id[i];
1670 int bytes = BN_num_bytes(session_key_int);
1671 u_char *buf = xmalloc(bytes);
1674 log("do_connection: generating a fake encryption key");
1675 BN_bn2bin(session_key_int, buf);
1677 MD5_Update(&md, buf, bytes);
1678 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1679 MD5_Final(session_key, &md);
1681 MD5_Update(&md, session_key, 16);
1682 MD5_Update(&md, buf, bytes);
1683 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1684 MD5_Final(session_key + 16, &md);
1685 memset(buf, 0, bytes);
1687 for (i = 0; i < 16; i++)
1688 session_id[i] = session_key[i] ^ session_key[i + 16];
1690 /* Destroy the private and public keys. No longer. */
1691 destroy_sensitive_data();
1694 mm_ssh1_session_id(session_id);
1696 /* Destroy the decrypted integer. It is no longer needed. */
1697 BN_clear_free(session_key_int);
1699 /* Set the session key. From this on all communications will be encrypted. */
1700 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1702 /* Destroy our copy of the session key. It is no longer needed. */
1703 memset(session_key, 0, sizeof(session_key));
1705 debug("Received session key; encryption turned on.");
1707 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1708 packet_start(SSH_SMSG_SUCCESS);
1710 packet_write_wait();
1714 * SSH2 key exchange: diffie-hellman-group1-sha1
1721 if (options.ciphers != NULL) {
1722 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1723 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1725 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1726 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
1727 myproposal[PROPOSAL_ENC_ALGS_STOC] =
1728 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
1730 if (options.macs != NULL) {
1731 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
1732 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
1734 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
1736 /* start key exchange */
1737 kex = kex_setup(myproposal);
1739 kex->client_version_string=client_version_string;
1740 kex->server_version_string=server_version_string;
1741 kex->load_host_key=&get_hostkey_by_type;
1742 kex->host_key_index=&get_hostkey_index;
1746 dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
1748 session_id2 = kex->session_id;
1749 session_id2_len = kex->session_id_len;
1752 /* send 1st encrypted/maced/compressed message */
1753 packet_start(SSH2_MSG_IGNORE);
1754 packet_put_cstring("markus");
1756 packet_write_wait();