2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * Created: Fri Mar 17 17:09:28 1995 ylo
6 * This program is the ssh daemon. It listens for connections from clients, and
7 * performs authentication, executes use commands or shell, and forwards
8 * information to/from the application to the user client over an encrypted
9 * connection. This can also handle forwarding of X11, TCP/IP, and authentication
12 * SSH2 implementation,
13 * Copyright (c) 2000 Markus Friedl. All rights reserved.
17 RCSID("$OpenBSD: sshd.c,v 1.125 2000/08/17 20:06:34 markus Exp $");
32 #include <openssl/dh.h>
33 #include <openssl/bn.h>
34 #include <openssl/hmac.h>
36 #include <openssl/dsa.h>
37 #include <openssl/rsa.h>
42 #include "myproposal.h"
48 int allow_severity = LOG_INFO;
49 int deny_severity = LOG_WARNING;
56 /* Server configuration options. */
57 ServerOptions options;
59 /* Name of the server configuration file. */
60 char *config_file_name = SERVER_CONFIG_FILE;
63 * Flag indicating whether IPv4 or IPv6. This can be set on the command line.
64 * Default value is AF_UNSPEC means both IPv4 and IPv6.
67 int IPv4or6 = AF_INET;
69 int IPv4or6 = AF_UNSPEC;
73 * Debug mode flag. This can be set on the command line. If debug
74 * mode is enabled, extra debugging output will be sent to the system
75 * log, the daemon will not go to background, and will exit after processing
76 * the first connection.
80 /* Flag indicating that the daemon is being started from inetd. */
83 /* debug goes to stderr unless inetd_flag is set */
86 /* argv[0] without path. */
89 /* Saved arguments to main(). */
94 * The sockets that the server is listening; this is used in the SIGHUP
97 #define MAX_LISTEN_SOCKS 16
98 int listen_socks[MAX_LISTEN_SOCKS];
99 int num_listen_socks = 0;
102 * the client's version string, passed by sshd2 in compat mode. if != NULL,
103 * sshd will skip the version-number exchange
105 char *client_version_string = NULL;
106 char *server_version_string = NULL;
109 * Any really sensitive data in the application is contained in this
110 * structure. The idea is that this structure could be locked into memory so
111 * that the pages do not get written into swap. However, there are some
112 * problems. The private key contains BIGNUMs, and we do not (in principle)
113 * have access to the internals of them, and locking just the structure is
114 * not very useful. Currently, memory locking is not implemented.
117 RSA *private_key; /* Private part of empheral server key. */
118 RSA *host_key; /* Private part of host key. */
119 Key *dsa_host_key; /* Private DSA host key. */
123 * Flag indicating whether the current session key has been used. This flag
124 * is set whenever the key is used, and cleared when the key is regenerated.
128 /* This is set to true when SIGHUP is received. */
129 int received_sighup = 0;
131 /* Public side of the server key. This value is regenerated regularly with
135 /* session identifier, used by RSA-auth */
136 unsigned char session_id[16];
139 unsigned char *session_id2 = NULL;
140 int session_id2_len = 0;
142 /* record remote hostname or ip */
143 unsigned int utmp_len = MAXHOSTNAMELEN;
145 /* Prototypes for various functions defined later in this file. */
150 * Close all listening sockets
153 close_listen_socks(void)
156 for (i = 0; i < num_listen_socks; i++)
157 close(listen_socks[i]);
158 num_listen_socks = -1;
162 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
163 * the effect is to reread the configuration file (and to regenerate
167 sighup_handler(int sig)
170 signal(SIGHUP, sighup_handler);
174 * Called from the main program after receiving SIGHUP.
175 * Restarts the server.
180 log("Received SIGHUP; restarting.");
181 close_listen_socks();
182 execv(saved_argv[0], saved_argv);
183 log("RESTART FAILED: av0='%s', error: %s.", av0, strerror(errno));
188 * Generic signal handler for terminating signals in the master daemon.
189 * These close the listen socket; not closing it seems to cause "Address
190 * already in use" problems on some machines, which is inconvenient.
193 sigterm_handler(int sig)
195 log("Received signal %d; terminating.", sig);
196 close_listen_socks();
197 unlink(options.pid_file);
202 * SIGCHLD handler. This is called whenever a child dies. This will then
203 * reap any zombies left by exited c.
206 main_sigchld_handler(int sig)
208 int save_errno = errno;
211 while (waitpid(-1, &status, WNOHANG) > 0)
214 signal(SIGCHLD, main_sigchld_handler);
219 * Signal handler for the alarm after the login grace period has expired.
222 grace_alarm_handler(int sig)
224 /* Close the connection. */
227 /* Log error and exit. */
228 fatal("Timeout before authentication for %s.", get_remote_ipaddr());
232 * Signal handler for the key regeneration alarm. Note that this
233 * alarm only occurs in the daemon waiting for connections, and it does not
234 * do anything with the private key or random state before forking.
235 * Thus there should be no concurrency control/asynchronous execution
238 /* XXX do we really want this work to be done in a signal handler ? -m */
240 key_regeneration_alarm(int sig)
242 int save_errno = errno;
244 /* Check if we should generate a new key. */
246 /* This should really be done in the background. */
247 log("Generating new %d bit RSA key.", options.server_key_bits);
249 if (sensitive_data.private_key != NULL)
250 RSA_free(sensitive_data.private_key);
251 sensitive_data.private_key = RSA_new();
253 if (public_key != NULL)
254 RSA_free(public_key);
255 public_key = RSA_new();
257 rsa_generate_key(sensitive_data.private_key, public_key,
258 options.server_key_bits);
261 log("RSA key generation complete.");
263 /* Reschedule the alarm. */
264 signal(SIGALRM, key_regeneration_alarm);
265 alarm(options.key_regeneration_time);
270 sshd_exchange_identification(int sock_in, int sock_out)
273 int remote_major, remote_minor;
276 char buf[256]; /* Must not be larger than remote_version. */
277 char remote_version[256]; /* Must be at least as big as buf. */
279 if ((options.protocol & SSH_PROTO_1) &&
280 (options.protocol & SSH_PROTO_2)) {
281 major = PROTOCOL_MAJOR_1;
283 } else if (options.protocol & SSH_PROTO_2) {
284 major = PROTOCOL_MAJOR_2;
285 minor = PROTOCOL_MINOR_2;
287 major = PROTOCOL_MAJOR_1;
288 minor = PROTOCOL_MINOR_1;
290 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
291 server_version_string = xstrdup(buf);
293 if (client_version_string == NULL) {
294 /* Send our protocol version identification. */
295 if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
296 != strlen(server_version_string)) {
297 log("Could not write ident string to %s.", get_remote_ipaddr());
301 /* Read other side\'s version identification. */
302 for (i = 0; i < sizeof(buf) - 1; i++) {
303 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
304 log("Did not receive ident string from %s.", get_remote_ipaddr());
307 if (buf[i] == '\r') {
312 if (buf[i] == '\n') {
318 buf[sizeof(buf) - 1] = 0;
319 client_version_string = xstrdup(buf);
323 * Check that the versions match. In future this might accept
324 * several versions and set appropriate flags to handle them.
326 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
327 &remote_major, &remote_minor, remote_version) != 3) {
328 s = "Protocol mismatch.\n";
329 (void) atomicio(write, sock_out, s, strlen(s));
332 log("Bad protocol version identification '%.100s' from %s",
333 client_version_string, get_remote_ipaddr());
336 debug("Client protocol version %d.%d; client software version %.100s",
337 remote_major, remote_minor, remote_version);
339 compat_datafellows(remote_version);
342 switch(remote_major) {
344 if (remote_minor == 99) {
345 if (options.protocol & SSH_PROTO_2)
351 if (!(options.protocol & SSH_PROTO_1)) {
355 if (remote_minor < 3) {
356 packet_disconnect("Your ssh version is too old and "
357 "is no longer supported. Please install a newer version.");
358 } else if (remote_minor == 3) {
359 /* note that this disables agent-forwarding */
364 if (options.protocol & SSH_PROTO_2) {
373 chop(server_version_string);
374 chop(client_version_string);
375 debug("Local version string %.200s", server_version_string);
378 s = "Protocol major versions differ.\n";
379 (void) atomicio(write, sock_out, s, strlen(s));
382 log("Protocol major versions differ for %s: %.200s vs. %.200s",
384 server_version_string, client_version_string);
388 packet_set_ssh2_format();
393 destroy_sensitive_data(void)
395 /* Destroy the private and public keys. They will no longer be needed. */
397 RSA_free(public_key);
398 if (sensitive_data.private_key)
399 RSA_free(sensitive_data.private_key);
400 if (sensitive_data.host_key)
401 RSA_free(sensitive_data.host_key);
402 if (sensitive_data.dsa_host_key != NULL)
403 key_free(sensitive_data.dsa_host_key);
407 * returns 1 if connection should be dropped, 0 otherwise.
408 * dropping starts at connection #max_startups_begin with a probability
409 * of (max_startups_rate/100). the probability increases linearly until
410 * all connections are dropped for startups > max_startups
413 drop_connection(int startups)
417 if (startups < options.max_startups_begin)
419 if (startups >= options.max_startups)
421 if (options.max_startups_rate == 100)
424 p = 100 - options.max_startups_rate;
425 p *= startups - options.max_startups_begin;
426 p /= (double) (options.max_startups - options.max_startups_begin);
427 p += options.max_startups_rate;
429 r = arc4random() / (double) UINT_MAX;
431 debug("drop_connection: p %g, r %g", p, r);
432 return (r < p) ? 1 : 0;
435 int *startup_pipes = NULL; /* options.max_startup sized array of fd ints */
436 int startup_pipe; /* in child */
439 * Main program for the daemon.
442 main(int ac, char **av)
446 int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
451 struct sockaddr_storage from;
452 const char *remote_ip;
455 struct linger linger;
457 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
458 int listen_sock, maxfd;
467 if (strchr(av[0], '/'))
468 av0 = strrchr(av[0], '/') + 1;
472 /* Initialize configuration options to their default values. */
473 initialize_server_options(&options);
475 /* Parse command-line arguments. */
476 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:diqQ46")) != EOF) {
485 config_file_name = optarg;
489 options.log_level = SYSLOG_LEVEL_DEBUG;
498 options.log_level = SYSLOG_LEVEL_QUIET;
501 options.server_key_bits = atoi(optarg);
504 options.ports_from_cmdline = 1;
505 if (options.num_ports >= MAX_PORTS)
506 fatal("too many ports.\n");
507 options.ports[options.num_ports++] = atoi(optarg);
510 options.login_grace_time = atoi(optarg);
513 options.key_regeneration_time = atoi(optarg);
516 options.host_key_file = optarg;
519 client_version_string = optarg;
520 /* only makes sense with inetd_flag, i.e. no listen() */
524 utmp_len = atoi(optarg);
528 fprintf(stderr, "sshd version %s\n", SSH_VERSION);
529 fprintf(stderr, "Usage: %s [options]\n", av0);
530 fprintf(stderr, "Options:\n");
531 fprintf(stderr, " -f file Configuration file (default %s)\n", SERVER_CONFIG_FILE);
532 fprintf(stderr, " -d Debugging mode\n");
533 fprintf(stderr, " -i Started from inetd\n");
534 fprintf(stderr, " -q Quiet (no logging)\n");
535 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
536 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
537 fprintf(stderr, " -g seconds Grace period for authentication (default: 300)\n");
538 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
539 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
541 fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
542 fprintf(stderr, " -4 Use IPv4 only\n");
543 fprintf(stderr, " -6 Use IPv6 only\n");
549 * Force logging to stderr until we have loaded the private host
550 * key (unless started from inetd)
553 options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
554 options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
555 !silent && !inetd_flag);
557 /* Read server configuration options from the configuration file. */
558 read_server_config(&options, config_file_name);
560 /* Fill in default values for those options not explicitly set. */
561 fill_default_server_options(&options);
563 /* Check that there are no remaining arguments. */
565 fprintf(stderr, "Extra argument %s.\n", av[optind]);
569 debug("sshd version %.100s", SSH_VERSION);
571 sensitive_data.dsa_host_key = NULL;
572 sensitive_data.host_key = NULL;
574 /* check if RSA support exists */
575 if ((options.protocol & SSH_PROTO_1) &&
577 log("no RSA support in libssl and libcrypto. See ssl(8)");
578 log("Disabling protocol version 1");
579 options.protocol &= ~SSH_PROTO_1;
581 /* Load the RSA/DSA host key. It must have empty passphrase. */
582 if (options.protocol & SSH_PROTO_1) {
584 sensitive_data.host_key = RSA_new();
586 k.rsa = sensitive_data.host_key;
588 if (!load_private_key(options.host_key_file, "", &k, NULL)) {
589 error("Could not load host key: %.200s: %.100s",
590 options.host_key_file, strerror(errno));
591 log("Disabling protocol version 1");
592 options.protocol &= ~SSH_PROTO_1;
596 if (options.protocol & SSH_PROTO_2) {
597 sensitive_data.dsa_host_key = key_new(KEY_DSA);
598 if (!load_private_key(options.host_dsa_key_file, "", sensitive_data.dsa_host_key, NULL)) {
600 error("Could not load DSA host key: %.200s", options.host_dsa_key_file);
601 log("Disabling protocol version 2");
602 options.protocol &= ~SSH_PROTO_2;
605 if (! options.protocol & (SSH_PROTO_1|SSH_PROTO_2)) {
607 fprintf(stderr, "sshd: no hostkeys available -- exiting.\n");
608 log("sshd: no hostkeys available -- exiting.\n");
612 /* Check certain values for sanity. */
613 if (options.protocol & SSH_PROTO_1) {
614 if (options.server_key_bits < 512 ||
615 options.server_key_bits > 32768) {
616 fprintf(stderr, "Bad server key size.\n");
620 * Check that server and host key lengths differ sufficiently. This
621 * is necessary to make double encryption work with rsaref. Oh, I
622 * hate software patents. I dont know if this can go? Niels
624 if (options.server_key_bits >
625 BN_num_bits(sensitive_data.host_key->n) - SSH_KEY_BITS_RESERVED &&
626 options.server_key_bits <
627 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
628 options.server_key_bits =
629 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED;
630 debug("Forcing server key to %d bits to make it differ from host key.",
631 options.server_key_bits);
635 /* Initialize the log (it is reinitialized below in case we forked). */
636 if (debug_flag && !inetd_flag)
638 log_init(av0, options.log_level, options.log_facility, log_stderr);
641 * If not in debugging mode, and not started from inetd, disconnect
642 * from the controlling terminal, and fork. The original process
645 if (!debug_flag && !inetd_flag) {
648 #endif /* TIOCNOTTY */
649 if (daemon(0, 0) < 0)
650 fatal("daemon() failed: %.200s", strerror(errno));
652 /* Disconnect from the controlling tty. */
654 fd = open("/dev/tty", O_RDWR | O_NOCTTY);
656 (void) ioctl(fd, TIOCNOTTY, NULL);
659 #endif /* TIOCNOTTY */
661 /* Reinitialize the log (because of the fork above). */
662 log_init(av0, options.log_level, options.log_facility, log_stderr);
664 /* Do not display messages to stdout in RSA code. */
667 /* Initialize the random number generator. */
670 /* Chdir to the root directory so that the current disk can be
671 unmounted if desired. */
674 /* Start listening for a socket, unless started from inetd. */
677 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
683 * We intentionally do not close the descriptors 0, 1, and 2
684 * as our code for setting the descriptors won\'t work if
685 * ttyfd happens to be one of those.
687 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
689 if (options.protocol & SSH_PROTO_1) {
690 public_key = RSA_new();
691 sensitive_data.private_key = RSA_new();
692 log("Generating %d bit RSA key.", options.server_key_bits);
693 rsa_generate_key(sensitive_data.private_key, public_key,
694 options.server_key_bits);
696 log("RSA key generation complete.");
699 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
700 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
702 if (num_listen_socks >= MAX_LISTEN_SOCKS)
703 fatal("Too many listen sockets. "
704 "Enlarge MAX_LISTEN_SOCKS");
705 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
706 ntop, sizeof(ntop), strport, sizeof(strport),
707 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
708 error("getnameinfo failed");
711 /* Create socket for listening. */
712 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
713 if (listen_sock < 0) {
714 /* kernel may not support ipv6 */
715 verbose("socket: %.100s", strerror(errno));
718 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
719 error("listen_sock O_NONBLOCK: %s", strerror(errno));
724 * Set socket options. We try to make the port
725 * reusable and have it close as fast as possible
726 * without waiting in unnecessary wait states on
729 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
730 (void *) &on, sizeof(on));
733 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
734 (void *) &linger, sizeof(linger));
736 debug("Bind to port %s on %s.", strport, ntop);
738 /* Bind the socket to the desired port. */
739 if ((bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) &&
741 error("Bind to port %s on %s failed: %.200s.",
742 strport, ntop, strerror(errno));
746 listen_socks[num_listen_socks] = listen_sock;
749 /* Start listening on the port. */
750 log("Server listening on %s port %s.", ntop, strport);
751 if (listen(listen_sock, 5) < 0)
752 fatal("listen: %.100s", strerror(errno));
755 freeaddrinfo(options.listen_addrs);
757 if (!num_listen_socks)
758 fatal("Cannot bind any address.");
762 * Record our pid in /etc/sshd_pid to make it easier
763 * to kill the correct sshd. We don\'t want to do
764 * this before the bind above because the bind will
765 * fail if there already is a daemon, and this will
766 * overwrite any old pid in the file.
768 f = fopen(options.pid_file, "wb");
770 fprintf(f, "%u\n", (unsigned int) getpid());
774 if (options.protocol & SSH_PROTO_1) {
775 public_key = RSA_new();
776 sensitive_data.private_key = RSA_new();
778 log("Generating %d bit RSA key.", options.server_key_bits);
779 rsa_generate_key(sensitive_data.private_key, public_key,
780 options.server_key_bits);
782 log("RSA key generation complete.");
784 /* Schedule server key regeneration alarm. */
785 signal(SIGALRM, key_regeneration_alarm);
786 alarm(options.key_regeneration_time);
789 /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
790 signal(SIGHUP, sighup_handler);
792 signal(SIGTERM, sigterm_handler);
793 signal(SIGQUIT, sigterm_handler);
795 /* Arrange SIGCHLD to be caught. */
796 signal(SIGCHLD, main_sigchld_handler);
798 /* setup fd set for listen */
801 for (i = 0; i < num_listen_socks; i++)
802 if (listen_socks[i] > maxfd)
803 maxfd = listen_socks[i];
804 /* pipes connected to unauthenticated childs */
805 startup_pipes = xmalloc(options.max_startups * sizeof(int));
806 for (i = 0; i < options.max_startups; i++)
807 startup_pipes[i] = -1;
810 * Stay listening for connections until the system crashes or
811 * the daemon is killed with a signal.
818 fdsetsz = howmany(maxfd, NFDBITS) * sizeof(fd_mask);
819 fdset = (fd_set *)xmalloc(fdsetsz);
820 memset(fdset, 0, fdsetsz);
822 for (i = 0; i < num_listen_socks; i++)
823 FD_SET(listen_socks[i], fdset);
824 for (i = 0; i < options.max_startups; i++)
825 if (startup_pipes[i] != -1)
826 FD_SET(startup_pipes[i], fdset);
828 /* Wait in select until there is a connection. */
829 if (select(maxfd + 1, fdset, NULL, NULL, NULL) < 0) {
831 error("select: %.100s", strerror(errno));
834 for (i = 0; i < options.max_startups; i++)
835 if (startup_pipes[i] != -1 &&
836 FD_ISSET(startup_pipes[i], fdset)) {
838 * the read end of the pipe is ready
839 * if the child has closed the pipe
840 * after successfull authentication
841 * or if the child has died
843 close(startup_pipes[i]);
844 startup_pipes[i] = -1;
847 for (i = 0; i < num_listen_socks; i++) {
848 if (!FD_ISSET(listen_socks[i], fdset))
850 fromlen = sizeof(from);
851 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
854 if (errno != EINTR && errno != EWOULDBLOCK)
855 error("accept: %.100s", strerror(errno));
858 if (fcntl(newsock, F_SETFL, 0) < 0) {
859 error("newsock del O_NONBLOCK: %s", strerror(errno));
862 if (drop_connection(startups) == 1) {
863 debug("drop connection #%d", startups);
867 if (pipe(startup_p) == -1) {
872 for (j = 0; j < options.max_startups; j++)
873 if (startup_pipes[j] == -1) {
874 startup_pipes[j] = startup_p[0];
875 if (maxfd < startup_p[0])
876 maxfd = startup_p[0];
882 * Got connection. Fork a child to handle it, unless
883 * we are in debugging mode.
887 * In debugging mode. Close the listening
888 * socket, and start processing the
889 * connection without forking.
891 debug("Server will not fork when running in debugging mode.");
892 close_listen_socks();
900 * Normal production daemon. Fork, and have
901 * the child process the connection. The
902 * parent continues listening.
904 if ((pid = fork()) == 0) {
906 * Child. Close the listening and max_startup
907 * sockets. Start using the accepted socket.
908 * Reinitialize logging (since our pid has
909 * changed). We break out of the loop to handle
912 startup_pipe = startup_p[1];
913 for (j = 0; j < options.max_startups; j++)
914 if (startup_pipes[j] != -1)
915 close(startup_pipes[j]);
916 close_listen_socks();
919 log_init(av0, options.log_level, options.log_facility, log_stderr);
924 /* Parent. Stay in the loop. */
926 error("fork: %.100s", strerror(errno));
928 debug("Forked child %d.", pid);
932 /* Mark that the key has been used (it was "given" to the child). */
937 /* Close the new socket (the child is now taking care of it). */
940 /* child process check (or debug mode) */
941 if (num_listen_socks < 0)
946 /* This is the child processing a new connection. */
949 * Disable the key regeneration alarm. We will not regenerate the
950 * key since we are no longer in a position to give it to anyone. We
951 * will not restart on SIGHUP since it no longer makes sense.
954 signal(SIGALRM, SIG_DFL);
955 signal(SIGHUP, SIG_DFL);
956 signal(SIGTERM, SIG_DFL);
957 signal(SIGQUIT, SIG_DFL);
958 signal(SIGCHLD, SIG_DFL);
959 signal(SIGINT, SIG_DFL);
962 * Set socket options for the connection. We want the socket to
963 * close as fast as possible without waiting for anything. If the
964 * connection is not a socket, these will do nothing.
966 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
969 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
972 * Register our connection. This turns encryption off because we do
975 packet_set_connection(sock_in, sock_out);
977 remote_port = get_remote_port();
978 remote_ip = get_remote_ipaddr();
980 /* Check whether logins are denied from this host. */
982 /* XXX LIBWRAP noes not know about IPv6 */
984 struct request_info req;
986 request_init(&req, RQ_DAEMON, av0, RQ_FILE, sock_in, NULL);
989 if (!hosts_access(&req)) {
994 /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
997 /* Log the connection. */
998 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1001 * We don\'t want to listen forever unless the other side
1002 * successfully authenticates itself. So we set up an alarm which is
1003 * cleared after successful authentication. A limit of zero
1004 * indicates no limit. Note that we don\'t set the alarm in debugging
1005 * mode; it is just annoying to have the server exit just when you
1006 * are about to discover the bug.
1008 signal(SIGALRM, grace_alarm_handler);
1010 alarm(options.login_grace_time);
1012 sshd_exchange_identification(sock_in, sock_out);
1014 * Check that the connection comes from a privileged port. Rhosts-
1015 * and Rhosts-RSA-Authentication only make sense from priviledged
1016 * programs. Of course, if the intruder has root access on his local
1017 * machine, he can connect from any port. So do not use these
1018 * authentication methods from machines that you do not trust.
1020 if (remote_port >= IPPORT_RESERVED ||
1021 remote_port < IPPORT_RESERVED / 2) {
1022 options.rhosts_authentication = 0;
1023 options.rhosts_rsa_authentication = 0;
1026 if (!packet_connection_is_ipv4() &&
1027 options.kerberos_authentication) {
1028 debug("Kerberos Authentication disabled, only available for IPv4.");
1029 options.kerberos_authentication = 0;
1033 packet_set_nonblocking();
1035 /* perform the key exchange */
1036 /* authenticate user and start session */
1039 do_authentication2();
1042 do_authentication();
1046 /* Cleanup user's ticket cache file. */
1047 if (options.kerberos_ticket_cleanup)
1051 /* The connection has been terminated. */
1052 verbose("Closing connection to %.100s", remote_ip);
1056 #endif /* USE_PAM */
1070 BIGNUM *session_key_int;
1071 unsigned char session_key[SSH_SESSION_KEY_LENGTH];
1072 unsigned char cookie[8];
1073 unsigned int cipher_type, auth_mask, protocol_flags;
1077 * Generate check bytes that the client must send back in the user
1078 * packet in order for it to be accepted; this is used to defy ip
1079 * spoofing attacks. Note that this only works against somebody
1080 * doing IP spoofing from a remote machine; any machine on the local
1081 * network can still see outgoing packets and catch the random
1082 * cookie. This only affects rhosts authentication, and this is one
1083 * of the reasons why it is inherently insecure.
1085 for (i = 0; i < 8; i++) {
1087 rand = arc4random();
1088 cookie[i] = rand & 0xff;
1093 * Send our public key. We include in the packet 64 bits of random
1094 * data that must be matched in the reply in order to prevent IP
1097 packet_start(SSH_SMSG_PUBLIC_KEY);
1098 for (i = 0; i < 8; i++)
1099 packet_put_char(cookie[i]);
1101 /* Store our public server RSA key. */
1102 packet_put_int(BN_num_bits(public_key->n));
1103 packet_put_bignum(public_key->e);
1104 packet_put_bignum(public_key->n);
1106 /* Store our public host RSA key. */
1107 packet_put_int(BN_num_bits(sensitive_data.host_key->n));
1108 packet_put_bignum(sensitive_data.host_key->e);
1109 packet_put_bignum(sensitive_data.host_key->n);
1111 /* Put protocol flags. */
1112 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1114 /* Declare which ciphers we support. */
1115 packet_put_int(cipher_mask1());
1117 /* Declare supported authentication types. */
1119 if (options.rhosts_authentication)
1120 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1121 if (options.rhosts_rsa_authentication)
1122 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1123 if (options.rsa_authentication)
1124 auth_mask |= 1 << SSH_AUTH_RSA;
1126 if (options.kerberos_authentication)
1127 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1130 if (options.kerberos_tgt_passing)
1131 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1132 if (options.afs_token_passing)
1133 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1136 if (options.skey_authentication == 1)
1137 auth_mask |= 1 << SSH_AUTH_TIS;
1139 if (options.password_authentication)
1140 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1141 packet_put_int(auth_mask);
1143 /* Send the packet and wait for it to be sent. */
1145 packet_write_wait();
1147 debug("Sent %d bit public key and %d bit host key.",
1148 BN_num_bits(public_key->n), BN_num_bits(sensitive_data.host_key->n));
1150 /* Read clients reply (cipher type and session key). */
1151 packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1153 /* Get cipher type and check whether we accept this. */
1154 cipher_type = packet_get_char();
1156 if (!(cipher_mask() & (1 << cipher_type)))
1157 packet_disconnect("Warning: client selects unsupported cipher.");
1159 /* Get check bytes from the packet. These must match those we
1160 sent earlier with the public key packet. */
1161 for (i = 0; i < 8; i++)
1162 if (cookie[i] != packet_get_char())
1163 packet_disconnect("IP Spoofing check bytes do not match.");
1165 debug("Encryption type: %.200s", cipher_name(cipher_type));
1167 /* Get the encrypted integer. */
1168 session_key_int = BN_new();
1169 packet_get_bignum(session_key_int, &slen);
1171 protocol_flags = packet_get_int();
1172 packet_set_protocol_flags(protocol_flags);
1174 packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1177 * Decrypt it using our private server key and private host key (key
1178 * with larger modulus first).
1180 if (BN_cmp(sensitive_data.private_key->n, sensitive_data.host_key->n) > 0) {
1181 /* Private key has bigger modulus. */
1182 if (BN_num_bits(sensitive_data.private_key->n) <
1183 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
1184 fatal("do_connection: %s: private_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1185 get_remote_ipaddr(),
1186 BN_num_bits(sensitive_data.private_key->n),
1187 BN_num_bits(sensitive_data.host_key->n),
1188 SSH_KEY_BITS_RESERVED);
1190 rsa_private_decrypt(session_key_int, session_key_int,
1191 sensitive_data.private_key);
1192 rsa_private_decrypt(session_key_int, session_key_int,
1193 sensitive_data.host_key);
1195 /* Host key has bigger modulus (or they are equal). */
1196 if (BN_num_bits(sensitive_data.host_key->n) <
1197 BN_num_bits(sensitive_data.private_key->n) + SSH_KEY_BITS_RESERVED) {
1198 fatal("do_connection: %s: host_key %d < private_key %d + SSH_KEY_BITS_RESERVED %d",
1199 get_remote_ipaddr(),
1200 BN_num_bits(sensitive_data.host_key->n),
1201 BN_num_bits(sensitive_data.private_key->n),
1202 SSH_KEY_BITS_RESERVED);
1204 rsa_private_decrypt(session_key_int, session_key_int,
1205 sensitive_data.host_key);
1206 rsa_private_decrypt(session_key_int, session_key_int,
1207 sensitive_data.private_key);
1210 compute_session_id(session_id, cookie,
1211 sensitive_data.host_key->n,
1212 sensitive_data.private_key->n);
1214 /* Destroy the private and public keys. They will no longer be needed. */
1215 destroy_sensitive_data();
1218 * Extract session key from the decrypted integer. The key is in the
1219 * least significant 256 bits of the integer; the first byte of the
1220 * key is in the highest bits.
1222 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1223 len = BN_num_bytes(session_key_int);
1224 if (len < 0 || len > sizeof(session_key))
1225 fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d",
1226 get_remote_ipaddr(),
1227 len, sizeof(session_key));
1228 memset(session_key, 0, sizeof(session_key));
1229 BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len);
1231 /* Destroy the decrypted integer. It is no longer needed. */
1232 BN_clear_free(session_key_int);
1234 /* Xor the first 16 bytes of the session key with the session id. */
1235 for (i = 0; i < 16; i++)
1236 session_key[i] ^= session_id[i];
1238 /* Set the session key. From this on all communications will be encrypted. */
1239 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1241 /* Destroy our copy of the session key. It is no longer needed. */
1242 memset(session_key, 0, sizeof(session_key));
1244 debug("Received session key; encryption turned on.");
1246 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1247 packet_start(SSH_SMSG_SUCCESS);
1249 packet_write_wait();
1253 * SSH2 key exchange: diffie-hellman-group1-sha1
1258 Buffer *server_kexinit;
1259 Buffer *client_kexinit;
1260 int payload_len, dlen;
1262 unsigned int klen, kout;
1263 unsigned char *signature = NULL;
1264 unsigned char *server_host_key_blob = NULL;
1265 unsigned int sbloblen;
1267 BIGNUM *dh_client_pub = 0;
1268 BIGNUM *shared_secret = 0;
1270 unsigned char *kbuf;
1271 unsigned char *hash;
1273 char *cprop[PROPOSAL_MAX];
1277 if (options.ciphers != NULL) {
1278 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1279 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1281 server_kexinit = kex_init(myproposal);
1282 client_kexinit = xmalloc(sizeof(*client_kexinit));
1283 buffer_init(client_kexinit);
1285 /* algorithm negotiation */
1286 kex_exchange_kexinit(server_kexinit, client_kexinit, cprop);
1287 kex = kex_choose_conf(cprop, myproposal, 1);
1288 for (i = 0; i < PROPOSAL_MAX; i++)
1293 debug("Wait SSH2_MSG_KEXDH_INIT.");
1294 packet_read_expect(&payload_len, SSH2_MSG_KEXDH_INIT);
1297 dh_client_pub = BN_new();
1298 if (dh_client_pub == NULL)
1299 fatal("dh_client_pub == NULL");
1300 packet_get_bignum2(dh_client_pub, &dlen);
1303 fprintf(stderr, "\ndh_client_pub= ");
1304 bignum_print(dh_client_pub);
1305 fprintf(stderr, "\n");
1306 debug("bits %d", BN_num_bits(dh_client_pub));
1309 /* generate DH key */
1310 dh = dh_new_group1(); /* XXX depends on 'kex' */
1313 fprintf(stderr, "\np= ");
1314 bignum_print(dh->p);
1315 fprintf(stderr, "\ng= ");
1316 bignum_print(dh->g);
1317 fprintf(stderr, "\npub= ");
1318 bignum_print(dh->pub_key);
1319 fprintf(stderr, "\n");
1321 if (!dh_pub_is_valid(dh, dh_client_pub))
1322 packet_disconnect("bad client public DH value");
1325 kbuf = xmalloc(klen);
1326 kout = DH_compute_key(kbuf, dh_client_pub, dh);
1329 debug("shared secret: len %d/%d", klen, kout);
1330 fprintf(stderr, "shared secret == ");
1331 for (i = 0; i< kout; i++)
1332 fprintf(stderr, "%02x", (kbuf[i])&0xff);
1333 fprintf(stderr, "\n");
1335 shared_secret = BN_new();
1337 BN_bin2bn(kbuf, kout, shared_secret);
1338 memset(kbuf, 0, klen);
1341 /* XXX precompute? */
1342 dsa_make_key_blob(sensitive_data.dsa_host_key, &server_host_key_blob, &sbloblen);
1344 /* calc H */ /* XXX depends on 'kex' */
1346 client_version_string,
1347 server_version_string,
1348 buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1349 buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1350 (char *)server_host_key_blob, sbloblen,
1355 buffer_free(client_kexinit);
1356 buffer_free(server_kexinit);
1357 xfree(client_kexinit);
1358 xfree(server_kexinit);
1360 fprintf(stderr, "hash == ");
1361 for (i = 0; i< 20; i++)
1362 fprintf(stderr, "%02x", (hash[i])&0xff);
1363 fprintf(stderr, "\n");
1365 /* save session id := H */
1366 /* XXX hashlen depends on KEX */
1367 session_id2_len = 20;
1368 session_id2 = xmalloc(session_id2_len);
1369 memcpy(session_id2, hash, session_id2_len);
1372 /* XXX hashlen depends on KEX */
1373 dsa_sign(sensitive_data.dsa_host_key, &signature, &slen, hash, 20);
1375 destroy_sensitive_data();
1377 /* send server hostkey, DH pubkey 'f' and singed H */
1378 packet_start(SSH2_MSG_KEXDH_REPLY);
1379 packet_put_string((char *)server_host_key_blob, sbloblen);
1380 packet_put_bignum2(dh->pub_key); /* f */
1381 packet_put_string((char *)signature, slen);
1384 xfree(server_host_key_blob);
1385 packet_write_wait();
1387 kex_derive_keys(kex, hash, shared_secret);
1388 packet_set_kex(kex);
1390 /* have keys, free DH */
1393 debug("send SSH2_MSG_NEWKEYS.");
1394 packet_start(SSH2_MSG_NEWKEYS);
1396 packet_write_wait();
1397 debug("done: send SSH2_MSG_NEWKEYS.");
1399 debug("Wait SSH2_MSG_NEWKEYS.");
1400 packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS);
1401 debug("GOT SSH2_MSG_NEWKEYS.");
1404 /* send 1st encrypted/maced/compressed message */
1405 packet_start(SSH2_MSG_IGNORE);
1406 packet_put_cstring("markus");
1408 packet_write_wait();
1410 debug("done: KEX2.");