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 1.116 2000/05/17 08:20:16 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(). */
93 * The sockets that the server is listening; this is used in the SIGHUP
96 #define MAX_LISTEN_SOCKS 16
97 int listen_socks[MAX_LISTEN_SOCKS];
98 int num_listen_socks = 0;
101 * the client's version string, passed by sshd2 in compat mode. if != NULL,
102 * sshd will skip the version-number exchange
104 char *client_version_string = NULL;
105 char *server_version_string = NULL;
108 * Any really sensitive data in the application is contained in this
109 * structure. The idea is that this structure could be locked into memory so
110 * that the pages do not get written into swap. However, there are some
111 * problems. The private key contains BIGNUMs, and we do not (in principle)
112 * have access to the internals of them, and locking just the structure is
113 * not very useful. Currently, memory locking is not implemented.
116 RSA *private_key; /* Private part of empheral server key. */
117 RSA *host_key; /* Private part of host key. */
118 Key *dsa_host_key; /* Private DSA host key. */
122 * Flag indicating whether the current session key has been used. This flag
123 * is set whenever the key is used, and cleared when the key is regenerated.
127 /* This is set to true when SIGHUP is received. */
128 int received_sighup = 0;
130 /* Public side of the server key. This value is regenerated regularly with
134 /* session identifier, used by RSA-auth */
135 unsigned char session_id[16];
138 unsigned char *session_id2 = NULL;
139 int session_id2_len = 0;
141 /* Prototypes for various functions defined later in this file. */
146 * Close all listening sockets
149 close_listen_socks(void)
152 for (i = 0; i < num_listen_socks; i++)
153 close(listen_socks[i]);
154 num_listen_socks = -1;
158 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
159 * the effect is to reread the configuration file (and to regenerate
163 sighup_handler(int sig)
166 signal(SIGHUP, sighup_handler);
170 * Called from the main program after receiving SIGHUP.
171 * Restarts the server.
176 log("Received SIGHUP; restarting.");
177 close_listen_socks();
178 execv(saved_argv[0], saved_argv);
179 log("RESTART FAILED: av0='%s', error: %s.", av0, strerror(errno));
184 * Generic signal handler for terminating signals in the master daemon.
185 * These close the listen socket; not closing it seems to cause "Address
186 * already in use" problems on some machines, which is inconvenient.
189 sigterm_handler(int sig)
191 log("Received signal %d; terminating.", sig);
192 close_listen_socks();
193 unlink(options.pid_file);
198 * SIGCHLD handler. This is called whenever a child dies. This will then
199 * reap any zombies left by exited c.
202 main_sigchld_handler(int sig)
204 int save_errno = errno;
207 while (waitpid(-1, &status, WNOHANG) > 0)
210 signal(SIGCHLD, main_sigchld_handler);
215 * Signal handler for the alarm after the login grace period has expired.
218 grace_alarm_handler(int sig)
220 /* Close the connection. */
223 /* Log error and exit. */
224 fatal("Timeout before authentication for %s.", get_remote_ipaddr());
228 * Signal handler for the key regeneration alarm. Note that this
229 * alarm only occurs in the daemon waiting for connections, and it does not
230 * do anything with the private key or random state before forking.
231 * Thus there should be no concurrency control/asynchronous execution
234 /* XXX do we really want this work to be done in a signal handler ? -m */
236 key_regeneration_alarm(int sig)
238 int save_errno = errno;
240 /* Check if we should generate a new key. */
242 /* This should really be done in the background. */
243 log("Generating new %d bit RSA key.", options.server_key_bits);
245 if (sensitive_data.private_key != NULL)
246 RSA_free(sensitive_data.private_key);
247 sensitive_data.private_key = RSA_new();
249 if (public_key != NULL)
250 RSA_free(public_key);
251 public_key = RSA_new();
253 rsa_generate_key(sensitive_data.private_key, public_key,
254 options.server_key_bits);
257 log("RSA key generation complete.");
259 /* Reschedule the alarm. */
260 signal(SIGALRM, key_regeneration_alarm);
261 alarm(options.key_regeneration_time);
266 sshd_exchange_identification(int sock_in, int sock_out)
269 int remote_major, remote_minor;
272 char buf[256]; /* Must not be larger than remote_version. */
273 char remote_version[256]; /* Must be at least as big as buf. */
275 if ((options.protocol & SSH_PROTO_1) &&
276 (options.protocol & SSH_PROTO_2)) {
277 major = PROTOCOL_MAJOR_1;
279 } else if (options.protocol & SSH_PROTO_2) {
280 major = PROTOCOL_MAJOR_2;
281 minor = PROTOCOL_MINOR_2;
283 major = PROTOCOL_MAJOR_1;
284 minor = PROTOCOL_MINOR_1;
286 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
287 server_version_string = xstrdup(buf);
289 if (client_version_string == NULL) {
290 /* Send our protocol version identification. */
291 if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
292 != strlen(server_version_string)) {
293 log("Could not write ident string to %s.", get_remote_ipaddr());
297 /* Read other side\'s version identification. */
298 for (i = 0; i < sizeof(buf) - 1; i++) {
299 if (read(sock_in, &buf[i], 1) != 1) {
300 log("Did not receive ident string from %s.", get_remote_ipaddr());
303 if (buf[i] == '\r') {
308 if (buf[i] == '\n') {
314 buf[sizeof(buf) - 1] = 0;
315 client_version_string = xstrdup(buf);
319 * Check that the versions match. In future this might accept
320 * several versions and set appropriate flags to handle them.
322 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
323 &remote_major, &remote_minor, remote_version) != 3) {
324 s = "Protocol mismatch.\n";
325 (void) atomicio(write, sock_out, s, strlen(s));
328 log("Bad protocol version identification '%.100s' from %s",
329 client_version_string, get_remote_ipaddr());
332 debug("Client protocol version %d.%d; client software version %.100s",
333 remote_major, remote_minor, remote_version);
335 compat_datafellows(remote_version);
338 switch(remote_major) {
340 if (remote_minor == 99) {
341 if (options.protocol & SSH_PROTO_2)
347 if (!(options.protocol & SSH_PROTO_1)) {
351 if (remote_minor < 3) {
352 packet_disconnect("Your ssh version is too old and"
353 "is no longer supported. Please install a newer version.");
354 } else if (remote_minor == 3) {
355 /* note that this disables agent-forwarding */
360 if (options.protocol & SSH_PROTO_2) {
369 chop(server_version_string);
370 chop(client_version_string);
371 debug("Local version string %.200s", server_version_string);
374 s = "Protocol major versions differ.\n";
375 (void) atomicio(write, sock_out, s, strlen(s));
378 log("Protocol major versions differ for %s: %.200s vs. %.200s",
380 server_version_string, client_version_string);
384 packet_set_ssh2_format();
389 destroy_sensitive_data(void)
391 /* Destroy the private and public keys. They will no longer be needed. */
392 RSA_free(public_key);
393 RSA_free(sensitive_data.private_key);
394 RSA_free(sensitive_data.host_key);
395 if (sensitive_data.dsa_host_key != NULL)
396 key_free(sensitive_data.dsa_host_key);
400 * Main program for the daemon.
403 main(int ac, char **av)
407 int opt, sock_in = 0, sock_out = 0, newsock, i, fdsetsz, on = 1;
412 struct sockaddr_storage from;
413 const char *remote_ip;
416 struct linger linger;
418 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
419 int listen_sock, maxfd;
423 if (strchr(av[0], '/'))
424 av0 = strrchr(av[0], '/') + 1;
428 /* Initialize configuration options to their default values. */
429 initialize_server_options(&options);
431 /* Parse command-line arguments. */
432 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:diqQ46")) != EOF) {
441 config_file_name = optarg;
445 options.log_level = SYSLOG_LEVEL_DEBUG;
454 options.log_level = SYSLOG_LEVEL_QUIET;
457 options.server_key_bits = atoi(optarg);
460 options.ports_from_cmdline = 1;
461 if (options.num_ports >= MAX_PORTS)
462 fatal("too many ports.\n");
463 options.ports[options.num_ports++] = atoi(optarg);
466 options.login_grace_time = atoi(optarg);
469 options.key_regeneration_time = atoi(optarg);
472 options.host_key_file = optarg;
475 client_version_string = optarg;
476 /* only makes sense with inetd_flag, i.e. no listen() */
481 fprintf(stderr, "sshd version %s\n", SSH_VERSION);
482 fprintf(stderr, "Usage: %s [options]\n", av0);
483 fprintf(stderr, "Options:\n");
484 fprintf(stderr, " -f file Configuration file (default %s)\n", SERVER_CONFIG_FILE);
485 fprintf(stderr, " -d Debugging mode\n");
486 fprintf(stderr, " -i Started from inetd\n");
487 fprintf(stderr, " -q Quiet (no logging)\n");
488 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
489 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
490 fprintf(stderr, " -g seconds Grace period for authentication (default: 300)\n");
491 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
492 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
494 fprintf(stderr, " -4 Use IPv4 only\n");
495 fprintf(stderr, " -6 Use IPv6 only\n");
501 * Force logging to stderr until we have loaded the private host
502 * key (unless started from inetd)
505 options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
506 options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
507 !silent && !inetd_flag);
509 /* Read server configuration options from the configuration file. */
510 read_server_config(&options, config_file_name);
512 /* Fill in default values for those options not explicitly set. */
513 fill_default_server_options(&options);
515 /* Check that there are no remaining arguments. */
517 fprintf(stderr, "Extra argument %s.\n", av[optind]);
521 debug("sshd version %.100s", SSH_VERSION);
523 sensitive_data.dsa_host_key = NULL;
524 sensitive_data.host_key = NULL;
526 /* check if RSA support exists */
527 if ((options.protocol & SSH_PROTO_1) &&
529 log("no RSA support in libssl and libcrypto. See ssl(8)");
530 log("Disabling protocol version 1");
531 options.protocol &= ~SSH_PROTO_1;
533 /* Load the RSA/DSA host key. It must have empty passphrase. */
534 if (options.protocol & SSH_PROTO_1) {
536 sensitive_data.host_key = RSA_new();
538 k.rsa = sensitive_data.host_key;
540 if (!load_private_key(options.host_key_file, "", &k, NULL)) {
541 error("Could not load host key: %.200s: %.100s",
542 options.host_key_file, strerror(errno));
543 log("Disabling protocol version 1");
544 options.protocol &= ~SSH_PROTO_1;
548 if (options.protocol & SSH_PROTO_2) {
549 sensitive_data.dsa_host_key = key_new(KEY_DSA);
550 if (!load_private_key(options.host_dsa_key_file, "", sensitive_data.dsa_host_key, NULL)) {
552 error("Could not load DSA host key: %.200s", options.host_dsa_key_file);
553 log("Disabling protocol version 2");
554 options.protocol &= ~SSH_PROTO_2;
557 if (! options.protocol & (SSH_PROTO_1|SSH_PROTO_2)) {
559 fprintf(stderr, "sshd: no hostkeys available -- exiting.\n");
560 log("sshd: no hostkeys available -- exiting.\n");
564 /* Check certain values for sanity. */
565 if (options.protocol & SSH_PROTO_1) {
566 if (options.server_key_bits < 512 ||
567 options.server_key_bits > 32768) {
568 fprintf(stderr, "Bad server key size.\n");
572 * Check that server and host key lengths differ sufficiently. This
573 * is necessary to make double encryption work with rsaref. Oh, I
574 * hate software patents. I dont know if this can go? Niels
576 if (options.server_key_bits >
577 BN_num_bits(sensitive_data.host_key->n) - SSH_KEY_BITS_RESERVED &&
578 options.server_key_bits <
579 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
580 options.server_key_bits =
581 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED;
582 debug("Forcing server key to %d bits to make it differ from host key.",
583 options.server_key_bits);
587 /* Initialize the log (it is reinitialized below in case we forked). */
588 if (debug_flag && !inetd_flag)
590 log_init(av0, options.log_level, options.log_facility, log_stderr);
593 * If not in debugging mode, and not started from inetd, disconnect
594 * from the controlling terminal, and fork. The original process
597 if (!debug_flag && !inetd_flag) {
600 #endif /* TIOCNOTTY */
601 if (daemon(0, 0) < 0)
602 fatal("daemon() failed: %.200s", strerror(errno));
604 /* Disconnect from the controlling tty. */
606 fd = open("/dev/tty", O_RDWR | O_NOCTTY);
608 (void) ioctl(fd, TIOCNOTTY, NULL);
611 #endif /* TIOCNOTTY */
613 /* Reinitialize the log (because of the fork above). */
614 log_init(av0, options.log_level, options.log_facility, log_stderr);
616 /* Do not display messages to stdout in RSA code. */
619 /* Initialize the random number generator. */
622 /* Chdir to the root directory so that the current disk can be
623 unmounted if desired. */
626 /* Start listening for a socket, unless started from inetd. */
629 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
634 * We intentionally do not close the descriptors 0, 1, and 2
635 * as our code for setting the descriptors won\'t work if
636 * ttyfd happens to be one of those.
638 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
640 if (options.protocol & SSH_PROTO_1) {
641 public_key = RSA_new();
642 sensitive_data.private_key = RSA_new();
643 log("Generating %d bit RSA key.", options.server_key_bits);
644 rsa_generate_key(sensitive_data.private_key, public_key,
645 options.server_key_bits);
647 log("RSA key generation complete.");
650 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
651 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
653 if (num_listen_socks >= MAX_LISTEN_SOCKS)
654 fatal("Too many listen sockets. "
655 "Enlarge MAX_LISTEN_SOCKS");
656 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
657 ntop, sizeof(ntop), strport, sizeof(strport),
658 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
659 error("getnameinfo failed");
662 /* Create socket for listening. */
663 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
664 if (listen_sock < 0) {
665 /* kernel may not support ipv6 */
666 verbose("socket: %.100s", strerror(errno));
669 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
670 error("listen_sock O_NONBLOCK: %s", strerror(errno));
675 * Set socket options. We try to make the port
676 * reusable and have it close as fast as possible
677 * without waiting in unnecessary wait states on
680 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
681 (void *) &on, sizeof(on));
684 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
685 (void *) &linger, sizeof(linger));
687 debug("Bind to port %s on %s.", strport, ntop);
689 /* Bind the socket to the desired port. */
690 if ((bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) &&
692 error("Bind to port %s on %s failed: %.200s.",
693 strport, ntop, strerror(errno));
697 listen_socks[num_listen_socks] = listen_sock;
700 /* Start listening on the port. */
701 log("Server listening on %s port %s.", ntop, strport);
702 if (listen(listen_sock, 5) < 0)
703 fatal("listen: %.100s", strerror(errno));
706 freeaddrinfo(options.listen_addrs);
708 if (!num_listen_socks)
709 fatal("Cannot bind any address.");
713 * Record our pid in /etc/sshd_pid to make it easier
714 * to kill the correct sshd. We don\'t want to do
715 * this before the bind above because the bind will
716 * fail if there already is a daemon, and this will
717 * overwrite any old pid in the file.
719 f = fopen(options.pid_file, "w");
721 fprintf(f, "%u\n", (unsigned int) getpid());
725 if (options.protocol & SSH_PROTO_1) {
726 public_key = RSA_new();
727 sensitive_data.private_key = RSA_new();
729 log("Generating %d bit RSA key.", options.server_key_bits);
730 rsa_generate_key(sensitive_data.private_key, public_key,
731 options.server_key_bits);
733 log("RSA key generation complete.");
735 /* Schedule server key regeneration alarm. */
736 signal(SIGALRM, key_regeneration_alarm);
737 alarm(options.key_regeneration_time);
740 /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
741 signal(SIGHUP, sighup_handler);
742 signal(SIGTERM, sigterm_handler);
743 signal(SIGQUIT, sigterm_handler);
745 /* Arrange SIGCHLD to be caught. */
746 signal(SIGCHLD, main_sigchld_handler);
748 /* setup fd set for listen */
750 for (i = 0; i < num_listen_socks; i++)
751 if (listen_socks[i] > maxfd)
752 maxfd = listen_socks[i];
753 fdsetsz = howmany(maxfd, NFDBITS) * sizeof(fd_mask);
754 fdset = (fd_set *)xmalloc(fdsetsz);
757 * Stay listening for connections until the system crashes or
758 * the daemon is killed with a signal.
763 /* Wait in select until there is a connection. */
764 memset(fdset, 0, fdsetsz);
765 for (i = 0; i < num_listen_socks; i++)
766 FD_SET(listen_socks[i], fdset);
767 if (select(maxfd + 1, fdset, NULL, NULL, NULL) < 0) {
769 error("select: %.100s", strerror(errno));
772 for (i = 0; i < num_listen_socks; i++) {
773 if (!FD_ISSET(listen_socks[i], fdset))
775 fromlen = sizeof(from);
776 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
779 if (errno != EINTR && errno != EWOULDBLOCK)
780 error("accept: %.100s", strerror(errno));
783 if (fcntl(newsock, F_SETFL, 0) < 0) {
784 error("newsock del O_NONBLOCK: %s", strerror(errno));
788 * Got connection. Fork a child to handle it, unless
789 * we are in debugging mode.
793 * In debugging mode. Close the listening
794 * socket, and start processing the
795 * connection without forking.
797 debug("Server will not fork when running in debugging mode.");
798 close_listen_socks();
805 * Normal production daemon. Fork, and have
806 * the child process the connection. The
807 * parent continues listening.
809 if ((pid = fork()) == 0) {
811 * Child. Close the listening socket, and start using the
812 * accepted socket. Reinitialize logging (since our pid has
813 * changed). We break out of the loop to handle the connection.
815 close_listen_socks();
818 log_init(av0, options.log_level, options.log_facility, log_stderr);
823 /* Parent. Stay in the loop. */
825 error("fork: %.100s", strerror(errno));
827 debug("Forked child %d.", pid);
829 /* Mark that the key has been used (it was "given" to the child). */
834 /* Close the new socket (the child is now taking care of it). */
836 } /* for (i = 0; i < num_listen_socks; i++) */
837 /* child process check (or debug mode) */
838 if (num_listen_socks < 0)
843 /* This is the child processing a new connection. */
846 * Disable the key regeneration alarm. We will not regenerate the
847 * key since we are no longer in a position to give it to anyone. We
848 * will not restart on SIGHUP since it no longer makes sense.
851 signal(SIGALRM, SIG_DFL);
852 signal(SIGHUP, SIG_DFL);
853 signal(SIGTERM, SIG_DFL);
854 signal(SIGQUIT, SIG_DFL);
855 signal(SIGCHLD, SIG_DFL);
858 * Set socket options for the connection. We want the socket to
859 * close as fast as possible without waiting for anything. If the
860 * connection is not a socket, these will do nothing.
862 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
865 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
868 * Register our connection. This turns encryption off because we do
871 packet_set_connection(sock_in, sock_out);
873 remote_port = get_remote_port();
874 remote_ip = get_remote_ipaddr();
876 /* Check whether logins are denied from this host. */
878 /* XXX LIBWRAP noes not know about IPv6 */
880 struct request_info req;
882 request_init(&req, RQ_DAEMON, av0, RQ_FILE, sock_in, NULL);
885 if (!hosts_access(&req)) {
890 /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
893 /* Log the connection. */
894 verbose("Connection from %.500s port %d", remote_ip, remote_port);
897 * We don\'t want to listen forever unless the other side
898 * successfully authenticates itself. So we set up an alarm which is
899 * cleared after successful authentication. A limit of zero
900 * indicates no limit. Note that we don\'t set the alarm in debugging
901 * mode; it is just annoying to have the server exit just when you
902 * are about to discover the bug.
904 signal(SIGALRM, grace_alarm_handler);
906 alarm(options.login_grace_time);
908 sshd_exchange_identification(sock_in, sock_out);
910 * Check that the connection comes from a privileged port. Rhosts-
911 * and Rhosts-RSA-Authentication only make sense from priviledged
912 * programs. Of course, if the intruder has root access on his local
913 * machine, he can connect from any port. So do not use these
914 * authentication methods from machines that you do not trust.
916 if (remote_port >= IPPORT_RESERVED ||
917 remote_port < IPPORT_RESERVED / 2) {
918 options.rhosts_authentication = 0;
919 options.rhosts_rsa_authentication = 0;
922 if (!packet_connection_is_ipv4() &&
923 options.kerberos_authentication) {
924 debug("Kerberos Authentication disabled, only available for IPv4.");
925 options.kerberos_authentication = 0;
929 packet_set_nonblocking();
931 /* perform the key exchange */
932 /* authenticate user and start session */
935 do_authentication2();
942 /* Cleanup user's ticket cache file. */
943 if (options.kerberos_ticket_cleanup)
947 /* The connection has been terminated. */
948 verbose("Closing connection to %.100s", remote_ip);
966 BIGNUM *session_key_int;
967 unsigned char session_key[SSH_SESSION_KEY_LENGTH];
968 unsigned char cookie[8];
969 unsigned int cipher_type, auth_mask, protocol_flags;
973 * Generate check bytes that the client must send back in the user
974 * packet in order for it to be accepted; this is used to defy ip
975 * spoofing attacks. Note that this only works against somebody
976 * doing IP spoofing from a remote machine; any machine on the local
977 * network can still see outgoing packets and catch the random
978 * cookie. This only affects rhosts authentication, and this is one
979 * of the reasons why it is inherently insecure.
981 for (i = 0; i < 8; i++) {
984 cookie[i] = rand & 0xff;
989 * Send our public key. We include in the packet 64 bits of random
990 * data that must be matched in the reply in order to prevent IP
993 packet_start(SSH_SMSG_PUBLIC_KEY);
994 for (i = 0; i < 8; i++)
995 packet_put_char(cookie[i]);
997 /* Store our public server RSA key. */
998 packet_put_int(BN_num_bits(public_key->n));
999 packet_put_bignum(public_key->e);
1000 packet_put_bignum(public_key->n);
1002 /* Store our public host RSA key. */
1003 packet_put_int(BN_num_bits(sensitive_data.host_key->n));
1004 packet_put_bignum(sensitive_data.host_key->e);
1005 packet_put_bignum(sensitive_data.host_key->n);
1007 /* Put protocol flags. */
1008 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1010 /* Declare which ciphers we support. */
1011 packet_put_int(cipher_mask1());
1013 /* Declare supported authentication types. */
1015 if (options.rhosts_authentication)
1016 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1017 if (options.rhosts_rsa_authentication)
1018 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1019 if (options.rsa_authentication)
1020 auth_mask |= 1 << SSH_AUTH_RSA;
1022 if (options.kerberos_authentication)
1023 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1026 if (options.kerberos_tgt_passing)
1027 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1028 if (options.afs_token_passing)
1029 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1032 if (options.skey_authentication == 1)
1033 auth_mask |= 1 << SSH_AUTH_TIS;
1035 if (options.password_authentication)
1036 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1037 packet_put_int(auth_mask);
1039 /* Send the packet and wait for it to be sent. */
1041 packet_write_wait();
1043 debug("Sent %d bit public key and %d bit host key.",
1044 BN_num_bits(public_key->n), BN_num_bits(sensitive_data.host_key->n));
1046 /* Read clients reply (cipher type and session key). */
1047 packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1049 /* Get cipher type and check whether we accept this. */
1050 cipher_type = packet_get_char();
1052 if (!(cipher_mask() & (1 << cipher_type)))
1053 packet_disconnect("Warning: client selects unsupported cipher.");
1055 /* Get check bytes from the packet. These must match those we
1056 sent earlier with the public key packet. */
1057 for (i = 0; i < 8; i++)
1058 if (cookie[i] != packet_get_char())
1059 packet_disconnect("IP Spoofing check bytes do not match.");
1061 debug("Encryption type: %.200s", cipher_name(cipher_type));
1063 /* Get the encrypted integer. */
1064 session_key_int = BN_new();
1065 packet_get_bignum(session_key_int, &slen);
1067 protocol_flags = packet_get_int();
1068 packet_set_protocol_flags(protocol_flags);
1070 packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1073 * Decrypt it using our private server key and private host key (key
1074 * with larger modulus first).
1076 if (BN_cmp(sensitive_data.private_key->n, sensitive_data.host_key->n) > 0) {
1077 /* Private key has bigger modulus. */
1078 if (BN_num_bits(sensitive_data.private_key->n) <
1079 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
1080 fatal("do_connection: %s: private_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1081 get_remote_ipaddr(),
1082 BN_num_bits(sensitive_data.private_key->n),
1083 BN_num_bits(sensitive_data.host_key->n),
1084 SSH_KEY_BITS_RESERVED);
1086 rsa_private_decrypt(session_key_int, session_key_int,
1087 sensitive_data.private_key);
1088 rsa_private_decrypt(session_key_int, session_key_int,
1089 sensitive_data.host_key);
1091 /* Host key has bigger modulus (or they are equal). */
1092 if (BN_num_bits(sensitive_data.host_key->n) <
1093 BN_num_bits(sensitive_data.private_key->n) + SSH_KEY_BITS_RESERVED) {
1094 fatal("do_connection: %s: host_key %d < private_key %d + SSH_KEY_BITS_RESERVED %d",
1095 get_remote_ipaddr(),
1096 BN_num_bits(sensitive_data.host_key->n),
1097 BN_num_bits(sensitive_data.private_key->n),
1098 SSH_KEY_BITS_RESERVED);
1100 rsa_private_decrypt(session_key_int, session_key_int,
1101 sensitive_data.host_key);
1102 rsa_private_decrypt(session_key_int, session_key_int,
1103 sensitive_data.private_key);
1106 compute_session_id(session_id, cookie,
1107 sensitive_data.host_key->n,
1108 sensitive_data.private_key->n);
1110 /* Destroy the private and public keys. They will no longer be needed. */
1111 destroy_sensitive_data();
1114 * Extract session key from the decrypted integer. The key is in the
1115 * least significant 256 bits of the integer; the first byte of the
1116 * key is in the highest bits.
1118 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1119 len = BN_num_bytes(session_key_int);
1120 if (len < 0 || len > sizeof(session_key))
1121 fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d",
1122 get_remote_ipaddr(),
1123 len, sizeof(session_key));
1124 memset(session_key, 0, sizeof(session_key));
1125 BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len);
1127 /* Destroy the decrypted integer. It is no longer needed. */
1128 BN_clear_free(session_key_int);
1130 /* Xor the first 16 bytes of the session key with the session id. */
1131 for (i = 0; i < 16; i++)
1132 session_key[i] ^= session_id[i];
1134 /* Set the session key. From this on all communications will be encrypted. */
1135 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1137 /* Destroy our copy of the session key. It is no longer needed. */
1138 memset(session_key, 0, sizeof(session_key));
1140 debug("Received session key; encryption turned on.");
1142 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1143 packet_start(SSH_SMSG_SUCCESS);
1145 packet_write_wait();
1149 * SSH2 key exchange: diffie-hellman-group1-sha1
1154 Buffer *server_kexinit;
1155 Buffer *client_kexinit;
1156 int payload_len, dlen;
1158 unsigned int klen, kout;
1160 unsigned char *signature = NULL;
1161 unsigned char *server_host_key_blob = NULL;
1162 unsigned int sbloblen;
1164 BIGNUM *dh_client_pub = 0;
1165 BIGNUM *shared_secret = 0;
1167 unsigned char *kbuf;
1168 unsigned char *hash;
1170 char *cprop[PROPOSAL_MAX];
1171 char *sprop[PROPOSAL_MAX];
1175 if (options.ciphers != NULL) {
1176 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1177 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1180 debug("Sending KEX init.");
1182 for (i = 0; i < PROPOSAL_MAX; i++)
1183 sprop[i] = xstrdup(myproposal[i]);
1184 server_kexinit = kex_init(sprop);
1185 packet_start(SSH2_MSG_KEXINIT);
1186 packet_put_raw(buffer_ptr(server_kexinit), buffer_len(server_kexinit));
1188 packet_write_wait();
1192 packet_read_expect(&payload_len, SSH2_MSG_KEXINIT);
1195 * save raw KEXINIT payload in buffer. this is used during
1196 * computation of the session_id and the session keys.
1198 client_kexinit = xmalloc(sizeof(*client_kexinit));
1199 buffer_init(client_kexinit);
1200 ptr = packet_get_raw(&payload_len);
1201 buffer_append(client_kexinit, ptr, payload_len);
1204 for (i = 0; i < 16; i++)
1205 (void) packet_get_char();
1206 /* save kex init proposal strings */
1207 for (i = 0; i < PROPOSAL_MAX; i++) {
1208 cprop[i] = packet_get_string(NULL);
1209 debug("got kexinit string: %s", cprop[i]);
1212 i = (int) packet_get_char();
1213 debug("first kex follow == %d", i);
1214 i = packet_get_int();
1215 debug("reserved == %d", i);
1217 debug("done read kexinit");
1218 kex = kex_choose_conf(cprop, sprop, 1);
1222 debug("Wait SSH2_MSG_KEXDH_INIT.");
1223 packet_read_expect(&payload_len, SSH2_MSG_KEXDH_INIT);
1226 dh_client_pub = BN_new();
1227 if (dh_client_pub == NULL)
1228 fatal("dh_client_pub == NULL");
1229 packet_get_bignum2(dh_client_pub, &dlen);
1232 fprintf(stderr, "\ndh_client_pub= ");
1233 bignum_print(dh_client_pub);
1234 fprintf(stderr, "\n");
1235 debug("bits %d", BN_num_bits(dh_client_pub));
1238 /* generate DH key */
1239 dh = dh_new_group1(); /* XXX depends on 'kex' */
1242 fprintf(stderr, "\np= ");
1243 bignum_print(dh->p);
1244 fprintf(stderr, "\ng= ");
1245 bignum_print(dh->g);
1246 fprintf(stderr, "\npub= ");
1247 bignum_print(dh->pub_key);
1248 fprintf(stderr, "\n");
1250 if (!dh_pub_is_valid(dh, dh_client_pub))
1251 packet_disconnect("bad client public DH value");
1254 kbuf = xmalloc(klen);
1255 kout = DH_compute_key(kbuf, dh_client_pub, dh);
1258 debug("shared secret: len %d/%d", klen, kout);
1259 fprintf(stderr, "shared secret == ");
1260 for (i = 0; i< kout; i++)
1261 fprintf(stderr, "%02x", (kbuf[i])&0xff);
1262 fprintf(stderr, "\n");
1264 shared_secret = BN_new();
1266 BN_bin2bn(kbuf, kout, shared_secret);
1267 memset(kbuf, 0, klen);
1270 /* XXX precompute? */
1271 dsa_make_key_blob(sensitive_data.dsa_host_key, &server_host_key_blob, &sbloblen);
1273 /* calc H */ /* XXX depends on 'kex' */
1275 client_version_string,
1276 server_version_string,
1277 buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1278 buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1279 (char *)server_host_key_blob, sbloblen,
1284 buffer_free(client_kexinit);
1285 buffer_free(server_kexinit);
1286 xfree(client_kexinit);
1287 xfree(server_kexinit);
1289 fprintf(stderr, "hash == ");
1290 for (i = 0; i< 20; i++)
1291 fprintf(stderr, "%02x", (hash[i])&0xff);
1292 fprintf(stderr, "\n");
1294 /* save session id := H */
1295 /* XXX hashlen depends on KEX */
1296 session_id2_len = 20;
1297 session_id2 = xmalloc(session_id2_len);
1298 memcpy(session_id2, hash, session_id2_len);
1301 /* XXX hashlen depends on KEX */
1302 dsa_sign(sensitive_data.dsa_host_key, &signature, &slen, hash, 20);
1304 destroy_sensitive_data();
1306 /* send server hostkey, DH pubkey 'f' and singed H */
1307 packet_start(SSH2_MSG_KEXDH_REPLY);
1308 packet_put_string((char *)server_host_key_blob, sbloblen);
1309 packet_put_bignum2(dh->pub_key); /* f */
1310 packet_put_string((char *)signature, slen);
1313 xfree(server_host_key_blob);
1314 packet_write_wait();
1316 kex_derive_keys(kex, hash, shared_secret);
1317 packet_set_kex(kex);
1319 /* have keys, free DH */
1322 debug("send SSH2_MSG_NEWKEYS.");
1323 packet_start(SSH2_MSG_NEWKEYS);
1325 packet_write_wait();
1326 debug("done: send SSH2_MSG_NEWKEYS.");
1328 debug("Wait SSH2_MSG_NEWKEYS.");
1329 packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS);
1330 debug("GOT SSH2_MSG_NEWKEYS.");
1333 /* send 1st encrypted/maced/compressed message */
1334 packet_start(SSH2_MSG_IGNORE);
1335 packet_put_cstring("markus");
1337 packet_write_wait();
1339 debug("done: KEX2.");