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 1.231 2002/03/18 17:50:31 provos Exp $");
47 #include <openssl/dh.h>
48 #include <openssl/bn.h>
49 #include <openssl/md5.h>
50 #include <openssl/rand.h>
69 #include "myproposal.h"
71 #include "pathnames.h"
79 #include "monitor_mm.h"
81 #include "monitor_wrap.h"
82 #include "monitor_fdpass.h"
87 int allow_severity = LOG_INFO;
88 int deny_severity = LOG_WARNING;
95 #ifdef HAVE___PROGNAME
96 extern char *__progname;
101 /* Server configuration options. */
102 ServerOptions options;
104 /* Name of the server configuration file. */
105 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
108 * Flag indicating whether IPv4 or IPv6. This can be set on the command line.
109 * Default value is AF_UNSPEC means both IPv4 and IPv6.
112 int IPv4or6 = AF_INET;
114 int IPv4or6 = AF_UNSPEC;
118 * Debug mode flag. This can be set on the command line. If debug
119 * mode is enabled, extra debugging output will be sent to the system
120 * log, the daemon will not go to background, and will exit after processing
121 * the first connection.
125 /* Flag indicating that the daemon should only test the configuration and keys. */
128 /* Flag indicating that the daemon is being started from inetd. */
131 /* Flag indicating that sshd should not detach and become a daemon. */
132 int no_daemon_flag = 0;
134 /* debug goes to stderr unless inetd_flag is set */
137 /* Saved arguments to main(). */
142 * The sockets that the server is listening; this is used in the SIGHUP
145 #define MAX_LISTEN_SOCKS 16
146 int listen_socks[MAX_LISTEN_SOCKS];
147 int num_listen_socks = 0;
150 * the client's version string, passed by sshd2 in compat mode. if != NULL,
151 * sshd will skip the version-number exchange
153 char *client_version_string = NULL;
154 char *server_version_string = NULL;
156 /* for rekeying XXX fixme */
160 * Any really sensitive data in the application is contained in this
161 * structure. The idea is that this structure could be locked into memory so
162 * that the pages do not get written into swap. However, there are some
163 * problems. The private key contains BIGNUMs, and we do not (in principle)
164 * have access to the internals of them, and locking just the structure is
165 * not very useful. Currently, memory locking is not implemented.
168 Key *server_key; /* ephemeral server key */
169 Key *ssh1_host_key; /* ssh1 host key */
170 Key **host_keys; /* all private host keys */
173 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
177 * Flag indicating whether the RSA server key needs to be regenerated.
178 * Is set in the SIGALRM handler and cleared when the key is regenerated.
180 static volatile sig_atomic_t key_do_regen = 0;
182 /* This is set to true when a signal is received. */
183 static volatile sig_atomic_t received_sighup = 0;
184 static volatile sig_atomic_t received_sigterm = 0;
186 /* session identifier, used by RSA-auth */
187 u_char session_id[16];
190 u_char *session_id2 = NULL;
191 int session_id2_len = 0;
193 /* record remote hostname or ip */
194 u_int utmp_len = MAXHOSTNAMELEN;
196 /* options.max_startup sized array of fd ints */
197 int *startup_pipes = NULL;
198 int startup_pipe; /* in child */
200 /* variables used for privilege separation */
201 extern struct monitor *monitor;
202 extern int use_privsep;
204 /* Prototypes for various functions defined later in this file. */
205 void destroy_sensitive_data(void);
206 void demote_sensitive_data(void);
208 static void do_ssh1_kex(void);
209 static void do_ssh2_kex(void);
212 * Close all listening sockets
215 close_listen_socks(void)
218 for (i = 0; i < num_listen_socks; i++)
219 close(listen_socks[i]);
220 num_listen_socks = -1;
224 close_startup_pipes(void)
228 for (i = 0; i < options.max_startups; i++)
229 if (startup_pipes[i] != -1)
230 close(startup_pipes[i]);
234 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
235 * the effect is to reread the configuration file (and to regenerate
239 sighup_handler(int sig)
241 int save_errno = errno;
244 signal(SIGHUP, sighup_handler);
249 * Called from the main program after receiving SIGHUP.
250 * Restarts the server.
255 log("Received SIGHUP; restarting.");
256 close_listen_socks();
257 close_startup_pipes();
258 execv(saved_argv[0], saved_argv);
259 log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], strerror(errno));
264 * Generic signal handler for terminating signals in the master daemon.
267 sigterm_handler(int sig)
269 received_sigterm = sig;
273 * SIGCHLD handler. This is called whenever a child dies. This will then
274 * reap any zombies left by exited children.
277 main_sigchld_handler(int sig)
279 int save_errno = errno;
282 while (waitpid(-1, &status, WNOHANG) > 0)
285 signal(SIGCHLD, main_sigchld_handler);
290 * Signal handler for the alarm after the login grace period has expired.
293 grace_alarm_handler(int sig)
295 /* XXX no idea how fix this signal handler */
297 /* Close the connection. */
300 /* Log error and exit. */
301 fatal("Timeout before authentication for %s.", get_remote_ipaddr());
305 * Signal handler for the key regeneration alarm. Note that this
306 * alarm only occurs in the daemon waiting for connections, and it does not
307 * do anything with the private key or random state before forking.
308 * Thus there should be no concurrency control/asynchronous execution
312 generate_ephemeral_server_key(void)
317 verbose("Generating %s%d bit RSA key.",
318 sensitive_data.server_key ? "new " : "", options.server_key_bits);
319 if (sensitive_data.server_key != NULL)
320 key_free(sensitive_data.server_key);
321 sensitive_data.server_key = key_generate(KEY_RSA1,
322 options.server_key_bits);
323 verbose("RSA key generation complete.");
325 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
328 sensitive_data.ssh1_cookie[i] = rand & 0xff;
335 key_regeneration_alarm(int sig)
337 int save_errno = errno;
338 signal(SIGALRM, SIG_DFL);
344 sshd_exchange_identification(int sock_in, int sock_out)
347 int remote_major, remote_minor;
350 char buf[256]; /* Must not be larger than remote_version. */
351 char remote_version[256]; /* Must be at least as big as buf. */
353 if ((options.protocol & SSH_PROTO_1) &&
354 (options.protocol & SSH_PROTO_2)) {
355 major = PROTOCOL_MAJOR_1;
357 } else if (options.protocol & SSH_PROTO_2) {
358 major = PROTOCOL_MAJOR_2;
359 minor = PROTOCOL_MINOR_2;
361 major = PROTOCOL_MAJOR_1;
362 minor = PROTOCOL_MINOR_1;
364 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
365 server_version_string = xstrdup(buf);
367 if (client_version_string == NULL) {
368 /* Send our protocol version identification. */
369 if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
370 != strlen(server_version_string)) {
371 log("Could not write ident string to %s", get_remote_ipaddr());
375 /* Read other side's version identification. */
376 memset(buf, 0, sizeof(buf));
377 for (i = 0; i < sizeof(buf) - 1; i++) {
378 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
379 log("Did not receive identification string from %s",
380 get_remote_ipaddr());
383 if (buf[i] == '\r') {
385 /* Kludge for F-Secure Macintosh < 1.0.2 */
387 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
391 if (buf[i] == '\n') {
396 buf[sizeof(buf) - 1] = 0;
397 client_version_string = xstrdup(buf);
401 * Check that the versions match. In future this might accept
402 * several versions and set appropriate flags to handle them.
404 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
405 &remote_major, &remote_minor, remote_version) != 3) {
406 s = "Protocol mismatch.\n";
407 (void) atomicio(write, sock_out, s, strlen(s));
410 log("Bad protocol version identification '%.100s' from %s",
411 client_version_string, get_remote_ipaddr());
414 debug("Client protocol version %d.%d; client software version %.100s",
415 remote_major, remote_minor, remote_version);
417 compat_datafellows(remote_version);
419 if (datafellows & SSH_BUG_SCANNER) {
420 log("scanned from %s with %s. Don't panic.",
421 get_remote_ipaddr(), client_version_string);
426 switch (remote_major) {
428 if (remote_minor == 99) {
429 if (options.protocol & SSH_PROTO_2)
435 if (!(options.protocol & SSH_PROTO_1)) {
439 if (remote_minor < 3) {
440 packet_disconnect("Your ssh version is too old and "
441 "is no longer supported. Please install a newer version.");
442 } else if (remote_minor == 3) {
443 /* note that this disables agent-forwarding */
448 if (options.protocol & SSH_PROTO_2) {
457 chop(server_version_string);
458 debug("Local version string %.200s", server_version_string);
461 s = "Protocol major versions differ.\n";
462 (void) atomicio(write, sock_out, s, strlen(s));
465 log("Protocol major versions differ for %s: %.200s vs. %.200s",
467 server_version_string, client_version_string);
473 /* Destroy the host and server keys. They will no longer be needed. */
475 destroy_sensitive_data(void)
479 if (sensitive_data.server_key) {
480 key_free(sensitive_data.server_key);
481 sensitive_data.server_key = NULL;
483 for (i = 0; i < options.num_host_key_files; i++) {
484 if (sensitive_data.host_keys[i]) {
485 key_free(sensitive_data.host_keys[i]);
486 sensitive_data.host_keys[i] = NULL;
489 sensitive_data.ssh1_host_key = NULL;
490 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
493 /* Demote private to public keys for network child */
495 demote_sensitive_data(void)
500 if (sensitive_data.server_key) {
501 tmp = key_demote(sensitive_data.server_key);
502 key_free(sensitive_data.server_key);
503 sensitive_data.server_key = tmp;
506 for (i = 0; i < options.num_host_key_files; i++) {
507 if (sensitive_data.host_keys[i]) {
508 tmp = key_demote(sensitive_data.host_keys[i]);
509 key_free(sensitive_data.host_keys[i]);
510 sensitive_data.host_keys[i] = tmp;
511 if (tmp->type == KEY_RSA1)
512 sensitive_data.ssh1_host_key = tmp;
516 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */
520 privsep_preauth_child(void)
525 /* Enable challenge-response authentication for privilege separation */
526 privsep_challenge_enable();
528 for (i = 0; i < 256; i++)
529 rand[i] = arc4random();
530 RAND_seed(rand, sizeof(rand));
532 /* Demote the private keys to public keys. */
533 demote_sensitive_data();
535 /* Change our root directory*/
536 if (chroot(options.unprivileged_dir) == -1)
537 fatal("chroot(/var/empty)");
538 if (chdir("/") == -1)
541 /* Drop our privileges */
542 setegid(options.unprivileged_group);
543 setgid(options.unprivileged_group);
544 seteuid(options.unprivileged_user);
545 setuid(options.unprivileged_user);
549 privsep_postauth(Authctxt *authctxt, pid_t pid)
551 extern Authctxt *x_authctxt;
554 /* Wait for the child's exit status */
555 waitpid(pid, &status, 0);
557 /* XXX - Remote port forwarding */
558 x_authctxt = authctxt;
560 if (authctxt->pw->pw_uid == 0 || options.use_login) {
561 /* File descriptor passing is broken or root login */
562 monitor_apply_keystate(monitor);
567 /* Authentication complete */
569 if (startup_pipe != -1) {
574 /* New socket pair */
575 monitor_reinit(monitor);
577 monitor->m_pid = fork();
578 if (monitor->m_pid == -1)
579 fatal("fork of unprivileged child failed");
580 else if (monitor->m_pid != 0) {
581 debug2("User child is on pid %d", pid);
582 close(monitor->m_recvfd);
583 monitor_child_postauth(monitor);
589 close(monitor->m_sendfd);
591 /* Demote the private keys to public keys. */
592 demote_sensitive_data();
594 /* Drop privileges */
595 do_setusercontext(authctxt->pw);
597 /* It is safe now to apply the key state */
598 monitor_apply_keystate(monitor);
603 list_hostkey_types(void)
610 for (i = 0; i < options.num_host_key_files; i++) {
611 Key *key = sensitive_data.host_keys[i];
617 if (buffer_len(&b) > 0)
618 buffer_append(&b, ",", 1);
619 p = key_ssh_name(key);
620 buffer_append(&b, p, strlen(p));
624 buffer_append(&b, "\0", 1);
625 p = xstrdup(buffer_ptr(&b));
627 debug("list_hostkey_types: %s", p);
632 get_hostkey_by_type(int type)
635 for (i = 0; i < options.num_host_key_files; i++) {
636 Key *key = sensitive_data.host_keys[i];
637 if (key != NULL && key->type == type)
644 get_hostkey_by_index(int ind)
646 if (ind < 0 || ind >= options.num_host_key_files)
648 return (sensitive_data.host_keys[ind]);
652 get_hostkey_index(Key *key)
655 for (i = 0; i < options.num_host_key_files; i++) {
656 if (key == sensitive_data.host_keys[i])
663 * returns 1 if connection should be dropped, 0 otherwise.
664 * dropping starts at connection #max_startups_begin with a probability
665 * of (max_startups_rate/100). the probability increases linearly until
666 * all connections are dropped for startups > max_startups
669 drop_connection(int startups)
673 if (startups < options.max_startups_begin)
675 if (startups >= options.max_startups)
677 if (options.max_startups_rate == 100)
680 p = 100 - options.max_startups_rate;
681 p *= startups - options.max_startups_begin;
682 p /= (double) (options.max_startups - options.max_startups_begin);
683 p += options.max_startups_rate;
685 r = arc4random() / (double) UINT_MAX;
687 debug("drop_connection: p %g, r %g", p, r);
688 return (r < p) ? 1 : 0;
694 fprintf(stderr, "sshd version %s\n", SSH_VERSION);
695 fprintf(stderr, "Usage: %s [options]\n", __progname);
696 fprintf(stderr, "Options:\n");
697 fprintf(stderr, " -f file Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE);
698 fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n");
699 fprintf(stderr, " -i Started from inetd\n");
700 fprintf(stderr, " -D Do not fork into daemon mode\n");
701 fprintf(stderr, " -t Only test configuration file and keys\n");
702 fprintf(stderr, " -q Quiet (no logging)\n");
703 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
704 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
705 fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n");
706 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
707 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
708 _PATH_HOST_KEY_FILE);
709 fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
710 fprintf(stderr, " -4 Use IPv4 only\n");
711 fprintf(stderr, " -6 Use IPv6 only\n");
712 fprintf(stderr, " -o option Process the option as if it was read from a configuration file.\n");
717 * Main program for the daemon.
720 main(int ac, char **av)
724 int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
728 struct sockaddr_storage from;
729 const char *remote_ip;
732 struct linger linger;
734 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
735 int listen_sock, maxfd;
740 int ret, key_used = 0;
742 __progname = get_progname(av[0]);
749 /* Initialize configuration options to their default values. */
750 initialize_server_options(&options);
752 /* Parse command-line arguments. */
753 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:o:dDeiqtQ46")) != -1) {
762 config_file_name = optarg;
765 if (0 == debug_flag) {
767 options.log_level = SYSLOG_LEVEL_DEBUG1;
768 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
771 fprintf(stderr, "Too high debugging level.\n");
788 options.log_level = SYSLOG_LEVEL_QUIET;
791 options.server_key_bits = atoi(optarg);
794 options.ports_from_cmdline = 1;
795 if (options.num_ports >= MAX_PORTS) {
796 fprintf(stderr, "too many ports.\n");
799 options.ports[options.num_ports++] = a2port(optarg);
800 if (options.ports[options.num_ports-1] == 0) {
801 fprintf(stderr, "Bad port number.\n");
806 if ((options.login_grace_time = convtime(optarg)) == -1) {
807 fprintf(stderr, "Invalid login grace time.\n");
812 if ((options.key_regeneration_time = convtime(optarg)) == -1) {
813 fprintf(stderr, "Invalid key regeneration interval.\n");
818 if (options.num_host_key_files >= MAX_HOSTKEYS) {
819 fprintf(stderr, "too many host keys.\n");
822 options.host_key_files[options.num_host_key_files++] = optarg;
825 client_version_string = optarg;
826 /* only makes sense with inetd_flag, i.e. no listen() */
833 utmp_len = atoi(optarg);
836 if (process_server_config_line(&options, optarg,
837 "command-line", 0) != 0)
846 SSLeay_add_all_algorithms();
847 channel_set_af(IPv4or6);
850 * Force logging to stderr until we have loaded the private host
851 * key (unless started from inetd)
854 options.log_level == SYSLOG_LEVEL_NOT_SET ?
855 SYSLOG_LEVEL_INFO : options.log_level,
856 options.log_facility == SYSLOG_FACILITY_NOT_SET ?
857 SYSLOG_FACILITY_AUTH : options.log_facility,
861 /* Cray can define user privs drop all prives now!
862 * Not needed on PRIV_SU systems!
869 /* Read server configuration options from the configuration file. */
870 read_server_config(&options, config_file_name);
872 /* Fill in default values for those options not explicitly set. */
873 fill_default_server_options(&options);
875 /* Check that there are no remaining arguments. */
877 fprintf(stderr, "Extra argument %s.\n", av[optind]);
881 debug("sshd version %.100s", SSH_VERSION);
883 /* load private host keys */
884 sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*));
885 for (i = 0; i < options.num_host_key_files; i++)
886 sensitive_data.host_keys[i] = NULL;
887 sensitive_data.server_key = NULL;
888 sensitive_data.ssh1_host_key = NULL;
889 sensitive_data.have_ssh1_key = 0;
890 sensitive_data.have_ssh2_key = 0;
892 for (i = 0; i < options.num_host_key_files; i++) {
893 key = key_load_private(options.host_key_files[i], "", NULL);
894 sensitive_data.host_keys[i] = key;
896 error("Could not load host key: %s",
897 options.host_key_files[i]);
898 sensitive_data.host_keys[i] = NULL;
903 sensitive_data.ssh1_host_key = key;
904 sensitive_data.have_ssh1_key = 1;
908 sensitive_data.have_ssh2_key = 1;
911 debug("private host key: #%d type %d %s", i, key->type,
914 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
915 log("Disabling protocol version 1. Could not load host key");
916 options.protocol &= ~SSH_PROTO_1;
918 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
919 log("Disabling protocol version 2. Could not load host key");
920 options.protocol &= ~SSH_PROTO_2;
922 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
923 log("sshd: no hostkeys available -- exiting.");
927 /* Check certain values for sanity. */
928 if (options.protocol & SSH_PROTO_1) {
929 if (options.server_key_bits < 512 ||
930 options.server_key_bits > 32768) {
931 fprintf(stderr, "Bad server key size.\n");
935 * Check that server and host key lengths differ sufficiently. This
936 * is necessary to make double encryption work with rsaref. Oh, I
937 * hate software patents. I dont know if this can go? Niels
939 if (options.server_key_bits >
940 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - SSH_KEY_BITS_RESERVED &&
941 options.server_key_bits <
942 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
943 options.server_key_bits =
944 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED;
945 debug("Forcing server key to %d bits to make it differ from host key.",
946 options.server_key_bits);
950 /* Configuration looks good, so exit if in test mode. */
954 #ifdef HAVE_SCO_PROTECTED_PW
955 (void) set_auth_parameters(ac, av);
958 /* Initialize the log (it is reinitialized below in case we forked). */
959 if (debug_flag && !inetd_flag)
961 log_init(__progname, options.log_level, options.log_facility, log_stderr);
964 * If not in debugging mode, and not started from inetd, disconnect
965 * from the controlling terminal, and fork. The original process
968 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
971 #endif /* TIOCNOTTY */
972 if (daemon(0, 0) < 0)
973 fatal("daemon() failed: %.200s", strerror(errno));
975 /* Disconnect from the controlling tty. */
977 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
979 (void) ioctl(fd, TIOCNOTTY, NULL);
982 #endif /* TIOCNOTTY */
984 /* Reinitialize the log (because of the fork above). */
985 log_init(__progname, options.log_level, options.log_facility, log_stderr);
987 /* Initialize the random number generator. */
990 /* Chdir to the root directory so that the current disk can be
991 unmounted if desired. */
995 signal(SIGPIPE, SIG_IGN);
997 /* Start listening for a socket, unless started from inetd. */
1000 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
1006 * We intentionally do not close the descriptors 0, 1, and 2
1007 * as our code for setting the descriptors won\'t work if
1008 * ttyfd happens to be one of those.
1010 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
1011 if (options.protocol & SSH_PROTO_1)
1012 generate_ephemeral_server_key();
1014 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
1015 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
1017 if (num_listen_socks >= MAX_LISTEN_SOCKS)
1018 fatal("Too many listen sockets. "
1019 "Enlarge MAX_LISTEN_SOCKS");
1020 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
1021 ntop, sizeof(ntop), strport, sizeof(strport),
1022 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
1023 error("getnameinfo failed");
1026 /* Create socket for listening. */
1027 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
1028 if (listen_sock < 0) {
1029 /* kernel may not support ipv6 */
1030 verbose("socket: %.100s", strerror(errno));
1033 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
1034 error("listen_sock O_NONBLOCK: %s", strerror(errno));
1039 * Set socket options. We try to make the port
1040 * reusable and have it close as fast as possible
1041 * without waiting in unnecessary wait states on
1044 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
1047 linger.l_linger = 5;
1048 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
1049 &linger, sizeof(linger));
1051 debug("Bind to port %s on %s.", strport, ntop);
1053 /* Bind the socket to the desired port. */
1054 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1056 error("Bind to port %s on %s failed: %.200s.",
1057 strport, ntop, strerror(errno));
1061 listen_socks[num_listen_socks] = listen_sock;
1064 /* Start listening on the port. */
1065 log("Server listening on %s port %s.", ntop, strport);
1066 if (listen(listen_sock, 5) < 0)
1067 fatal("listen: %.100s", strerror(errno));
1070 freeaddrinfo(options.listen_addrs);
1072 if (!num_listen_socks)
1073 fatal("Cannot bind any address.");
1075 if (options.protocol & SSH_PROTO_1)
1076 generate_ephemeral_server_key();
1079 * Arrange to restart on SIGHUP. The handler needs
1082 signal(SIGHUP, sighup_handler);
1084 signal(SIGTERM, sigterm_handler);
1085 signal(SIGQUIT, sigterm_handler);
1087 /* Arrange SIGCHLD to be caught. */
1088 signal(SIGCHLD, main_sigchld_handler);
1090 /* Write out the pid file after the sigterm handler is setup */
1093 * Record our pid in /var/run/sshd.pid to make it
1094 * easier to kill the correct sshd. We don't want to
1095 * do this before the bind above because the bind will
1096 * fail if there already is a daemon, and this will
1097 * overwrite any old pid in the file.
1099 f = fopen(options.pid_file, "wb");
1101 fprintf(f, "%u\n", (u_int) getpid());
1106 /* setup fd set for listen */
1109 for (i = 0; i < num_listen_socks; i++)
1110 if (listen_socks[i] > maxfd)
1111 maxfd = listen_socks[i];
1112 /* pipes connected to unauthenticated childs */
1113 startup_pipes = xmalloc(options.max_startups * sizeof(int));
1114 for (i = 0; i < options.max_startups; i++)
1115 startup_pipes[i] = -1;
1118 * Stay listening for connections until the system crashes or
1119 * the daemon is killed with a signal.
1122 if (received_sighup)
1126 fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
1127 fdset = (fd_set *)xmalloc(fdsetsz);
1128 memset(fdset, 0, fdsetsz);
1130 for (i = 0; i < num_listen_socks; i++)
1131 FD_SET(listen_socks[i], fdset);
1132 for (i = 0; i < options.max_startups; i++)
1133 if (startup_pipes[i] != -1)
1134 FD_SET(startup_pipes[i], fdset);
1136 /* Wait in select until there is a connection. */
1137 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
1138 if (ret < 0 && errno != EINTR)
1139 error("select: %.100s", strerror(errno));
1140 if (received_sigterm) {
1141 log("Received signal %d; terminating.",
1142 (int) received_sigterm);
1143 close_listen_socks();
1144 unlink(options.pid_file);
1147 if (key_used && key_do_regen) {
1148 generate_ephemeral_server_key();
1155 for (i = 0; i < options.max_startups; i++)
1156 if (startup_pipes[i] != -1 &&
1157 FD_ISSET(startup_pipes[i], fdset)) {
1159 * the read end of the pipe is ready
1160 * if the child has closed the pipe
1161 * after successful authentication
1162 * or if the child has died
1164 close(startup_pipes[i]);
1165 startup_pipes[i] = -1;
1168 for (i = 0; i < num_listen_socks; i++) {
1169 if (!FD_ISSET(listen_socks[i], fdset))
1171 fromlen = sizeof(from);
1172 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
1175 if (errno != EINTR && errno != EWOULDBLOCK)
1176 error("accept: %.100s", strerror(errno));
1179 if (fcntl(newsock, F_SETFL, 0) < 0) {
1180 error("newsock del O_NONBLOCK: %s", strerror(errno));
1184 if (drop_connection(startups) == 1) {
1185 debug("drop connection #%d", startups);
1189 if (pipe(startup_p) == -1) {
1194 for (j = 0; j < options.max_startups; j++)
1195 if (startup_pipes[j] == -1) {
1196 startup_pipes[j] = startup_p[0];
1197 if (maxfd < startup_p[0])
1198 maxfd = startup_p[0];
1204 * Got connection. Fork a child to handle it, unless
1205 * we are in debugging mode.
1209 * In debugging mode. Close the listening
1210 * socket, and start processing the
1211 * connection without forking.
1213 debug("Server will not fork when running in debugging mode.");
1214 close_listen_socks();
1222 * Normal production daemon. Fork, and have
1223 * the child process the connection. The
1224 * parent continues listening.
1226 if ((pid = fork()) == 0) {
1228 * Child. Close the listening and max_startup
1229 * sockets. Start using the accepted socket.
1230 * Reinitialize logging (since our pid has
1231 * changed). We break out of the loop to handle
1234 startup_pipe = startup_p[1];
1235 close_startup_pipes();
1236 close_listen_socks();
1239 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1244 /* Parent. Stay in the loop. */
1246 error("fork: %.100s", strerror(errno));
1248 debug("Forked child %d.", pid);
1250 close(startup_p[1]);
1252 /* Mark that the key has been used (it was "given" to the child). */
1253 if ((options.protocol & SSH_PROTO_1) &&
1255 /* Schedule server key regeneration alarm. */
1256 signal(SIGALRM, key_regeneration_alarm);
1257 alarm(options.key_regeneration_time);
1263 /* Close the new socket (the child is now taking care of it). */
1266 /* child process check (or debug mode) */
1267 if (num_listen_socks < 0)
1272 /* This is the child processing a new connection. */
1275 * Disable the key regeneration alarm. We will not regenerate the
1276 * key since we are no longer in a position to give it to anyone. We
1277 * will not restart on SIGHUP since it no longer makes sense.
1280 signal(SIGALRM, SIG_DFL);
1281 signal(SIGHUP, SIG_DFL);
1282 signal(SIGTERM, SIG_DFL);
1283 signal(SIGQUIT, SIG_DFL);
1284 signal(SIGCHLD, SIG_DFL);
1285 signal(SIGINT, SIG_DFL);
1288 * Set socket options for the connection. We want the socket to
1289 * close as fast as possible without waiting for anything. If the
1290 * connection is not a socket, these will do nothing.
1292 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1294 linger.l_linger = 5;
1295 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, &linger, sizeof(linger));
1297 /* Set keepalives if requested. */
1298 if (options.keepalives &&
1299 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on,
1301 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1304 * Register our connection. This turns encryption off because we do
1307 packet_set_connection(sock_in, sock_out);
1309 remote_port = get_remote_port();
1310 remote_ip = get_remote_ipaddr();
1313 /* Check whether logins are denied from this host. */
1315 struct request_info req;
1317 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
1320 if (!hosts_access(&req)) {
1321 debug("Connection refused by tcp wrapper");
1324 fatal("libwrap refuse returns");
1327 #endif /* LIBWRAP */
1329 /* Log the connection. */
1330 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1333 * We don\'t want to listen forever unless the other side
1334 * successfully authenticates itself. So we set up an alarm which is
1335 * cleared after successful authentication. A limit of zero
1336 * indicates no limit. Note that we don\'t set the alarm in debugging
1337 * mode; it is just annoying to have the server exit just when you
1338 * are about to discover the bug.
1340 signal(SIGALRM, grace_alarm_handler);
1342 alarm(options.login_grace_time);
1344 sshd_exchange_identification(sock_in, sock_out);
1346 * Check that the connection comes from a privileged port.
1347 * Rhosts-Authentication only makes sense from priviledged
1348 * programs. Of course, if the intruder has root access on his local
1349 * machine, he can connect from any port. So do not use these
1350 * authentication methods from machines that you do not trust.
1352 if (options.rhosts_authentication &&
1353 (remote_port >= IPPORT_RESERVED ||
1354 remote_port < IPPORT_RESERVED / 2)) {
1355 debug("Rhosts Authentication disabled, "
1356 "originating port %d not trusted.", remote_port);
1357 options.rhosts_authentication = 0;
1359 #if defined(KRB4) && !defined(KRB5)
1360 if (!packet_connection_is_ipv4() &&
1361 options.kerberos_authentication) {
1362 debug("Kerberos Authentication disabled, only available for IPv4.");
1363 options.kerberos_authentication = 0;
1365 #endif /* KRB4 && !KRB5 */
1367 /* If machine has AFS, set process authentication group. */
1374 packet_set_nonblocking();
1377 goto skip_privilegeseparation;
1379 /* Set up unprivileged child process to deal with network data */
1380 monitor = monitor_init();
1381 /* Store a pointer to the kex for later rekeying */
1382 monitor->m_pkex = &xxx_kex;
1386 fatal("fork of unprivileged child failed");
1387 else if (pid != 0) {
1388 debug2("Network child is on pid %d", pid);
1390 close(monitor->m_recvfd);
1391 authctxt = monitor_child_preauth(monitor);
1392 close(monitor->m_sendfd);
1395 monitor_sync(monitor);
1398 close(monitor->m_sendfd);
1400 /* Demote the child */
1401 if (getuid() == 0 || geteuid() == 0)
1402 privsep_preauth_child();
1405 skip_privilegeseparation:
1407 /* perform the key exchange */
1408 /* authenticate user and start session */
1411 authctxt = do_authentication2();
1414 authctxt = do_authentication();
1417 mm_send_keystate(monitor);
1419 /* If we use privilege separation, the unprivileged child exits */
1425 * In privilege separation, we fork another child and prepare
1426 * file descriptor passing.
1429 privsep_postauth(authctxt, pid);
1431 destroy_sensitive_data();
1434 /* Perform session preparation. */
1435 do_authenticated(authctxt);
1437 /* The connection has been terminated. */
1438 verbose("Closing connection to %.100s", remote_ip);
1442 #endif /* USE_PAM */
1453 * Decrypt session_key_int using our private server key and private host key
1454 * (key with larger modulus first).
1457 ssh1_session_key(BIGNUM *session_key_int)
1461 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1462 /* Server key has bigger modulus. */
1463 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1464 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1465 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1466 get_remote_ipaddr(),
1467 BN_num_bits(sensitive_data.server_key->rsa->n),
1468 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1469 SSH_KEY_BITS_RESERVED);
1471 if (rsa_private_decrypt(session_key_int, session_key_int,
1472 sensitive_data.server_key->rsa) <= 0)
1474 if (rsa_private_decrypt(session_key_int, session_key_int,
1475 sensitive_data.ssh1_host_key->rsa) <= 0)
1478 /* Host key has bigger modulus (or they are equal). */
1479 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1480 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1481 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1482 get_remote_ipaddr(),
1483 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1484 BN_num_bits(sensitive_data.server_key->rsa->n),
1485 SSH_KEY_BITS_RESERVED);
1487 if (rsa_private_decrypt(session_key_int, session_key_int,
1488 sensitive_data.ssh1_host_key->rsa) < 0)
1490 if (rsa_private_decrypt(session_key_int, session_key_int,
1491 sensitive_data.server_key->rsa) < 0)
1504 BIGNUM *session_key_int;
1505 u_char session_key[SSH_SESSION_KEY_LENGTH];
1507 u_int cipher_type, auth_mask, protocol_flags;
1511 * Generate check bytes that the client must send back in the user
1512 * packet in order for it to be accepted; this is used to defy ip
1513 * spoofing attacks. Note that this only works against somebody
1514 * doing IP spoofing from a remote machine; any machine on the local
1515 * network can still see outgoing packets and catch the random
1516 * cookie. This only affects rhosts authentication, and this is one
1517 * of the reasons why it is inherently insecure.
1519 for (i = 0; i < 8; i++) {
1521 rand = arc4random();
1522 cookie[i] = rand & 0xff;
1527 * Send our public key. We include in the packet 64 bits of random
1528 * data that must be matched in the reply in order to prevent IP
1531 packet_start(SSH_SMSG_PUBLIC_KEY);
1532 for (i = 0; i < 8; i++)
1533 packet_put_char(cookie[i]);
1535 /* Store our public server RSA key. */
1536 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1537 packet_put_bignum(sensitive_data.server_key->rsa->e);
1538 packet_put_bignum(sensitive_data.server_key->rsa->n);
1540 /* Store our public host RSA key. */
1541 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1542 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1543 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1545 /* Put protocol flags. */
1546 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1548 /* Declare which ciphers we support. */
1549 packet_put_int(cipher_mask_ssh1(0));
1551 /* Declare supported authentication types. */
1553 if (options.rhosts_authentication)
1554 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1555 if (options.rhosts_rsa_authentication)
1556 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1557 if (options.rsa_authentication)
1558 auth_mask |= 1 << SSH_AUTH_RSA;
1559 #if defined(KRB4) || defined(KRB5)
1560 if (options.kerberos_authentication)
1561 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1563 #if defined(AFS) || defined(KRB5)
1564 if (options.kerberos_tgt_passing)
1565 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1568 if (options.afs_token_passing)
1569 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1571 if (options.challenge_response_authentication == 1)
1572 auth_mask |= 1 << SSH_AUTH_TIS;
1573 if (options.password_authentication)
1574 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1575 packet_put_int(auth_mask);
1577 /* Send the packet and wait for it to be sent. */
1579 packet_write_wait();
1581 debug("Sent %d bit server key and %d bit host key.",
1582 BN_num_bits(sensitive_data.server_key->rsa->n),
1583 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1585 /* Read clients reply (cipher type and session key). */
1586 packet_read_expect(SSH_CMSG_SESSION_KEY);
1588 /* Get cipher type and check whether we accept this. */
1589 cipher_type = packet_get_char();
1591 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1592 packet_disconnect("Warning: client selects unsupported cipher.");
1594 /* Get check bytes from the packet. These must match those we
1595 sent earlier with the public key packet. */
1596 for (i = 0; i < 8; i++)
1597 if (cookie[i] != packet_get_char())
1598 packet_disconnect("IP Spoofing check bytes do not match.");
1600 debug("Encryption type: %.200s", cipher_name(cipher_type));
1602 /* Get the encrypted integer. */
1603 if ((session_key_int = BN_new()) == NULL)
1604 fatal("do_ssh1_kex: BN_new failed");
1605 packet_get_bignum(session_key_int);
1607 protocol_flags = packet_get_int();
1608 packet_set_protocol_flags(protocol_flags);
1611 /* Decrypt session_key_int using host/server keys */
1612 rsafail = PRIVSEP(ssh1_session_key(session_key_int));
1615 * Extract session key from the decrypted integer. The key is in the
1616 * least significant 256 bits of the integer; the first byte of the
1617 * key is in the highest bits.
1620 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1621 len = BN_num_bytes(session_key_int);
1622 if (len < 0 || len > sizeof(session_key)) {
1623 error("do_connection: bad session key len from %s: "
1624 "session_key_int %d > sizeof(session_key) %lu",
1625 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
1628 memset(session_key, 0, sizeof(session_key));
1629 BN_bn2bin(session_key_int,
1630 session_key + sizeof(session_key) - len);
1632 compute_session_id(session_id, cookie,
1633 sensitive_data.ssh1_host_key->rsa->n,
1634 sensitive_data.server_key->rsa->n);
1636 * Xor the first 16 bytes of the session key with the
1639 for (i = 0; i < 16; i++)
1640 session_key[i] ^= session_id[i];
1644 int bytes = BN_num_bytes(session_key_int);
1645 u_char *buf = xmalloc(bytes);
1648 log("do_connection: generating a fake encryption key");
1649 BN_bn2bin(session_key_int, buf);
1651 MD5_Update(&md, buf, bytes);
1652 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1653 MD5_Final(session_key, &md);
1655 MD5_Update(&md, session_key, 16);
1656 MD5_Update(&md, buf, bytes);
1657 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1658 MD5_Final(session_key + 16, &md);
1659 memset(buf, 0, bytes);
1661 for (i = 0; i < 16; i++)
1662 session_id[i] = session_key[i] ^ session_key[i + 16];
1664 /* Destroy the private and public keys. No longer. */
1665 destroy_sensitive_data();
1668 mm_ssh1_session_id(session_id);
1670 /* Destroy the decrypted integer. It is no longer needed. */
1671 BN_clear_free(session_key_int);
1673 /* Set the session key. From this on all communications will be encrypted. */
1674 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1676 /* Destroy our copy of the session key. It is no longer needed. */
1677 memset(session_key, 0, sizeof(session_key));
1679 debug("Received session key; encryption turned on.");
1681 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1682 packet_start(SSH_SMSG_SUCCESS);
1684 packet_write_wait();
1688 * SSH2 key exchange: diffie-hellman-group1-sha1
1695 if (options.ciphers != NULL) {
1696 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1697 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1699 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1700 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
1701 myproposal[PROPOSAL_ENC_ALGS_STOC] =
1702 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
1704 if (options.macs != NULL) {
1705 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
1706 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
1708 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
1710 /* start key exchange */
1711 kex = kex_setup(myproposal);
1713 kex->client_version_string=client_version_string;
1714 kex->server_version_string=server_version_string;
1715 kex->load_host_key=&get_hostkey_by_type;
1716 kex->host_key_index=&get_hostkey_index;
1720 dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
1722 session_id2 = kex->session_id;
1723 session_id2_len = kex->session_id_len;
1726 /* send 1st encrypted/maced/compressed message */
1727 packet_start(SSH2_MSG_IGNORE);
1728 packet_put_cstring("markus");
1730 packet_write_wait();