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 1.111 2000/04/27 08:01:28 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();
197 * SIGCHLD handler. This is called whenever a child dies. This will then
198 * reap any zombies left by exited c.
201 main_sigchld_handler(int sig)
203 int save_errno = errno;
206 while (waitpid(-1, &status, WNOHANG) > 0)
209 signal(SIGCHLD, main_sigchld_handler);
214 * Signal handler for the alarm after the login grace period has expired.
217 grace_alarm_handler(int sig)
219 /* Close the connection. */
222 /* Log error and exit. */
223 fatal("Timeout before authentication for %s.", get_remote_ipaddr());
227 * Signal handler for the key regeneration alarm. Note that this
228 * alarm only occurs in the daemon waiting for connections, and it does not
229 * do anything with the private key or random state before forking.
230 * Thus there should be no concurrency control/asynchronous execution
233 /* XXX do we really want this work to be done in a signal handler ? -m */
235 key_regeneration_alarm(int sig)
237 int save_errno = errno;
239 /* Check if we should generate a new key. */
241 /* This should really be done in the background. */
242 log("Generating new %d bit RSA key.", options.server_key_bits);
244 if (sensitive_data.private_key != NULL)
245 RSA_free(sensitive_data.private_key);
246 sensitive_data.private_key = RSA_new();
248 if (public_key != NULL)
249 RSA_free(public_key);
250 public_key = RSA_new();
252 rsa_generate_key(sensitive_data.private_key, public_key,
253 options.server_key_bits);
256 log("RSA key generation complete.");
258 /* Reschedule the alarm. */
259 signal(SIGALRM, key_regeneration_alarm);
260 alarm(options.key_regeneration_time);
269 if(*t == '\n' || *t == '\r') {
280 sshd_exchange_identification(int sock_in, int sock_out)
283 int remote_major, remote_minor;
286 char buf[256]; /* Must not be larger than remote_version. */
287 char remote_version[256]; /* Must be at least as big as buf. */
289 if ((options.protocol & SSH_PROTO_1) &&
290 (options.protocol & SSH_PROTO_2)) {
291 major = PROTOCOL_MAJOR_1;
293 } else if (options.protocol & SSH_PROTO_2) {
294 major = PROTOCOL_MAJOR_2;
295 minor = PROTOCOL_MINOR_2;
297 major = PROTOCOL_MAJOR_1;
298 minor = PROTOCOL_MINOR_1;
300 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
301 server_version_string = xstrdup(buf);
303 if (client_version_string == NULL) {
304 /* Send our protocol version identification. */
305 if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
306 != strlen(server_version_string)) {
307 log("Could not write ident string to %s.", get_remote_ipaddr());
311 /* Read other side\'s version identification. */
312 for (i = 0; i < sizeof(buf) - 1; i++) {
313 if (read(sock_in, &buf[i], 1) != 1) {
314 log("Did not receive ident string from %s.", get_remote_ipaddr());
317 if (buf[i] == '\r') {
322 if (buf[i] == '\n') {
328 buf[sizeof(buf) - 1] = 0;
329 client_version_string = xstrdup(buf);
333 * Check that the versions match. In future this might accept
334 * several versions and set appropriate flags to handle them.
336 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
337 &remote_major, &remote_minor, remote_version) != 3) {
338 s = "Protocol mismatch.\n";
339 (void) atomicio(write, sock_out, s, strlen(s));
342 log("Bad protocol version identification '%.100s' from %s",
343 client_version_string, get_remote_ipaddr());
346 debug("Client protocol version %d.%d; client software version %.100s",
347 remote_major, remote_minor, remote_version);
349 compat_datafellows(remote_version);
352 switch(remote_major) {
354 if (remote_minor == 99) {
355 if (options.protocol & SSH_PROTO_2)
361 if (!(options.protocol & SSH_PROTO_1)) {
365 if (remote_minor < 3) {
366 packet_disconnect("Your ssh version is too old and"
367 "is no longer supported. Please install a newer version.");
368 } else if (remote_minor == 3) {
369 /* note that this disables agent-forwarding */
374 if (options.protocol & SSH_PROTO_2) {
383 chop(server_version_string);
384 chop(client_version_string);
385 debug("Local version string %.200s", server_version_string);
388 s = "Protocol major versions differ.\n";
389 (void) atomicio(write, sock_out, s, strlen(s));
392 log("Protocol major versions differ for %s: %.200s vs. %.200s",
394 server_version_string, client_version_string);
398 packet_set_ssh2_format();
403 destroy_sensitive_data(void)
405 /* Destroy the private and public keys. They will no longer be needed. */
406 RSA_free(public_key);
407 RSA_free(sensitive_data.private_key);
408 RSA_free(sensitive_data.host_key);
409 if (sensitive_data.dsa_host_key != NULL)
410 key_free(sensitive_data.dsa_host_key);
414 * Main program for the daemon.
417 main(int ac, char **av)
421 int opt, sock_in = 0, sock_out = 0, newsock, i, fdsetsz, on = 1;
426 struct sockaddr_storage from;
427 const char *remote_ip;
430 struct linger linger;
432 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
433 int listen_sock, maxfd;
437 if (strchr(av[0], '/'))
438 av0 = strrchr(av[0], '/') + 1;
442 /* Initialize configuration options to their default values. */
443 initialize_server_options(&options);
445 /* Parse command-line arguments. */
446 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:diqQ46")) != EOF) {
455 config_file_name = optarg;
459 options.log_level = SYSLOG_LEVEL_DEBUG;
468 options.log_level = SYSLOG_LEVEL_QUIET;
471 options.server_key_bits = atoi(optarg);
474 options.ports_from_cmdline = 1;
475 if (options.num_ports >= MAX_PORTS)
476 fatal("too many ports.\n");
477 options.ports[options.num_ports++] = atoi(optarg);
480 options.login_grace_time = atoi(optarg);
483 options.key_regeneration_time = atoi(optarg);
486 options.host_key_file = optarg;
489 client_version_string = optarg;
490 /* only makes sense with inetd_flag, i.e. no listen() */
495 fprintf(stderr, "sshd version %s\n", SSH_VERSION);
496 fprintf(stderr, "Usage: %s [options]\n", av0);
497 fprintf(stderr, "Options:\n");
498 fprintf(stderr, " -f file Configuration file (default %s)\n", SERVER_CONFIG_FILE);
499 fprintf(stderr, " -d Debugging mode\n");
500 fprintf(stderr, " -i Started from inetd\n");
501 fprintf(stderr, " -q Quiet (no logging)\n");
502 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
503 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
504 fprintf(stderr, " -g seconds Grace period for authentication (default: 300)\n");
505 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
506 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
508 fprintf(stderr, " -4 Use IPv4 only\n");
509 fprintf(stderr, " -6 Use IPv6 only\n");
515 * Force logging to stderr until we have loaded the private host
516 * key (unless started from inetd)
519 options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
520 options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
521 !silent && !inetd_flag);
523 /* Read server configuration options from the configuration file. */
524 read_server_config(&options, config_file_name);
526 /* Fill in default values for those options not explicitly set. */
527 fill_default_server_options(&options);
529 /* Check that there are no remaining arguments. */
531 fprintf(stderr, "Extra argument %s.\n", av[optind]);
535 debug("sshd version %.100s", SSH_VERSION);
537 sensitive_data.dsa_host_key = NULL;
538 sensitive_data.host_key = NULL;
540 /* check if RSA support exists */
541 if ((options.protocol & SSH_PROTO_1) &&
543 log("no RSA support in libssl and libcrypto. See ssl(8)");
544 log("Disabling protocol version 1");
545 options.protocol &= ~SSH_PROTO_1;
547 /* Load the RSA/DSA host key. It must have empty passphrase. */
548 if (options.protocol & SSH_PROTO_1) {
550 sensitive_data.host_key = RSA_new();
552 k.rsa = sensitive_data.host_key;
554 if (!load_private_key(options.host_key_file, "", &k, NULL)) {
555 error("Could not load host key: %.200s: %.100s",
556 options.host_key_file, strerror(errno));
557 log("Disabling protocol version 1");
558 options.protocol &= ~SSH_PROTO_1;
562 if (options.protocol & SSH_PROTO_2) {
563 sensitive_data.dsa_host_key = key_new(KEY_DSA);
564 if (!load_private_key(options.dsa_key_file, "", sensitive_data.dsa_host_key, NULL)) {
565 error("Could not load DSA host key: %.200s", options.dsa_key_file);
566 log("Disabling protocol version 2");
567 options.protocol &= ~SSH_PROTO_2;
570 if (! options.protocol & (SSH_PROTO_1|SSH_PROTO_2)) {
572 fprintf(stderr, "sshd: no hostkeys available -- exiting.\n");
573 log("sshd: no hostkeys available -- exiting.\n");
577 /* Check certain values for sanity. */
578 if (options.protocol & SSH_PROTO_1) {
579 if (options.server_key_bits < 512 ||
580 options.server_key_bits > 32768) {
581 fprintf(stderr, "Bad server key size.\n");
585 * Check that server and host key lengths differ sufficiently. This
586 * is necessary to make double encryption work with rsaref. Oh, I
587 * hate software patents. I dont know if this can go? Niels
589 if (options.server_key_bits >
590 BN_num_bits(sensitive_data.host_key->n) - SSH_KEY_BITS_RESERVED &&
591 options.server_key_bits <
592 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
593 options.server_key_bits =
594 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED;
595 debug("Forcing server key to %d bits to make it differ from host key.",
596 options.server_key_bits);
600 /* Initialize the log (it is reinitialized below in case we forked). */
601 if (debug_flag && !inetd_flag)
603 log_init(av0, options.log_level, options.log_facility, log_stderr);
606 * If not in debugging mode, and not started from inetd, disconnect
607 * from the controlling terminal, and fork. The original process
610 if (!debug_flag && !inetd_flag) {
613 #endif /* TIOCNOTTY */
614 if (daemon(0, 0) < 0)
615 fatal("daemon() failed: %.200s", strerror(errno));
617 /* Disconnect from the controlling tty. */
619 fd = open("/dev/tty", O_RDWR | O_NOCTTY);
621 (void) ioctl(fd, TIOCNOTTY, NULL);
624 #endif /* TIOCNOTTY */
626 /* Reinitialize the log (because of the fork above). */
627 log_init(av0, options.log_level, options.log_facility, log_stderr);
629 /* Do not display messages to stdout in RSA code. */
632 /* Initialize the random number generator. */
635 /* Chdir to the root directory so that the current disk can be
636 unmounted if desired. */
639 /* Start listening for a socket, unless started from inetd. */
642 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
647 * We intentionally do not close the descriptors 0, 1, and 2
648 * as our code for setting the descriptors won\'t work if
649 * ttyfd happens to be one of those.
651 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
653 if (options.protocol & SSH_PROTO_1) {
654 public_key = RSA_new();
655 sensitive_data.private_key = RSA_new();
656 log("Generating %d bit RSA key.", options.server_key_bits);
657 rsa_generate_key(sensitive_data.private_key, public_key,
658 options.server_key_bits);
660 log("RSA key generation complete.");
663 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
664 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
666 if (num_listen_socks >= MAX_LISTEN_SOCKS)
667 fatal("Too many listen sockets. "
668 "Enlarge MAX_LISTEN_SOCKS");
669 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
670 ntop, sizeof(ntop), strport, sizeof(strport),
671 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
672 error("getnameinfo failed");
675 /* Create socket for listening. */
676 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
677 if (listen_sock < 0) {
678 /* kernel may not support ipv6 */
679 verbose("socket: %.100s", strerror(errno));
682 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
683 error("listen_sock O_NONBLOCK: %s", strerror(errno));
688 * Set socket options. We try to make the port
689 * reusable and have it close as fast as possible
690 * without waiting in unnecessary wait states on
693 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
694 (void *) &on, sizeof(on));
697 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
698 (void *) &linger, sizeof(linger));
700 debug("Bind to port %s on %s.", strport, ntop);
702 /* Bind the socket to the desired port. */
703 if ((bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) &&
705 error("Bind to port %s on %s failed: %.200s.",
706 strport, ntop, strerror(errno));
710 listen_socks[num_listen_socks] = listen_sock;
713 /* Start listening on the port. */
714 log("Server listening on %s port %s.", ntop, strport);
715 if (listen(listen_sock, 5) < 0)
716 fatal("listen: %.100s", strerror(errno));
719 freeaddrinfo(options.listen_addrs);
721 if (!num_listen_socks)
722 fatal("Cannot bind any address.");
726 * Record our pid in /etc/sshd_pid to make it easier
727 * to kill the correct sshd. We don\'t want to do
728 * this before the bind above because the bind will
729 * fail if there already is a daemon, and this will
730 * overwrite any old pid in the file.
732 f = fopen(SSH_DAEMON_PID_FILE, "w");
734 fprintf(f, "%u\n", (unsigned int) getpid());
738 if (options.protocol & SSH_PROTO_1) {
739 public_key = RSA_new();
740 sensitive_data.private_key = RSA_new();
742 log("Generating %d bit RSA key.", options.server_key_bits);
743 rsa_generate_key(sensitive_data.private_key, public_key,
744 options.server_key_bits);
746 log("RSA key generation complete.");
748 /* Schedule server key regeneration alarm. */
749 signal(SIGALRM, key_regeneration_alarm);
750 alarm(options.key_regeneration_time);
753 /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
754 signal(SIGHUP, sighup_handler);
755 signal(SIGTERM, sigterm_handler);
756 signal(SIGQUIT, sigterm_handler);
758 /* Arrange SIGCHLD to be caught. */
759 signal(SIGCHLD, main_sigchld_handler);
761 /* setup fd set for listen */
763 for (i = 0; i < num_listen_socks; i++)
764 if (listen_socks[i] > maxfd)
765 maxfd = listen_socks[i];
766 fdsetsz = howmany(maxfd, NFDBITS) * sizeof(fd_mask);
767 fdset = (fd_set *)xmalloc(fdsetsz);
770 * Stay listening for connections until the system crashes or
771 * the daemon is killed with a signal.
776 /* Wait in select until there is a connection. */
777 memset(fdset, 0, fdsetsz);
778 for (i = 0; i < num_listen_socks; i++)
779 FD_SET(listen_socks[i], fdset);
780 if (select(maxfd + 1, fdset, NULL, NULL, NULL) < 0) {
782 error("select: %.100s", strerror(errno));
785 for (i = 0; i < num_listen_socks; i++) {
786 if (!FD_ISSET(listen_socks[i], fdset))
788 fromlen = sizeof(from);
789 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
792 if (errno != EINTR && errno != EWOULDBLOCK)
793 error("accept: %.100s", strerror(errno));
796 if (fcntl(newsock, F_SETFL, 0) < 0) {
797 error("newsock del O_NONBLOCK: %s", strerror(errno));
801 * Got connection. Fork a child to handle it, unless
802 * we are in debugging mode.
806 * In debugging mode. Close the listening
807 * socket, and start processing the
808 * connection without forking.
810 debug("Server will not fork when running in debugging mode.");
811 close_listen_socks();
818 * Normal production daemon. Fork, and have
819 * the child process the connection. The
820 * parent continues listening.
822 if ((pid = fork()) == 0) {
824 * Child. Close the listening socket, and start using the
825 * accepted socket. Reinitialize logging (since our pid has
826 * changed). We break out of the loop to handle the connection.
828 close_listen_socks();
831 log_init(av0, options.log_level, options.log_facility, log_stderr);
836 /* Parent. Stay in the loop. */
838 error("fork: %.100s", strerror(errno));
840 debug("Forked child %d.", pid);
842 /* Mark that the key has been used (it was "given" to the child). */
847 /* Close the new socket (the child is now taking care of it). */
849 } /* for (i = 0; i < num_listen_socks; i++) */
850 /* child process check (or debug mode) */
851 if (num_listen_socks < 0)
856 /* This is the child processing a new connection. */
859 * Disable the key regeneration alarm. We will not regenerate the
860 * key since we are no longer in a position to give it to anyone. We
861 * will not restart on SIGHUP since it no longer makes sense.
864 signal(SIGALRM, SIG_DFL);
865 signal(SIGHUP, SIG_DFL);
866 signal(SIGTERM, SIG_DFL);
867 signal(SIGQUIT, SIG_DFL);
868 signal(SIGCHLD, SIG_DFL);
871 * Set socket options for the connection. We want the socket to
872 * close as fast as possible without waiting for anything. If the
873 * connection is not a socket, these will do nothing.
875 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
878 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
881 * Register our connection. This turns encryption off because we do
884 packet_set_connection(sock_in, sock_out);
886 remote_port = get_remote_port();
887 remote_ip = get_remote_ipaddr();
889 /* Check whether logins are denied from this host. */
891 /* XXX LIBWRAP noes not know about IPv6 */
893 struct request_info req;
895 request_init(&req, RQ_DAEMON, av0, RQ_FILE, sock_in, NULL);
898 if (!hosts_access(&req)) {
903 /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
906 /* Log the connection. */
907 verbose("Connection from %.500s port %d", remote_ip, remote_port);
910 * We don\'t want to listen forever unless the other side
911 * successfully authenticates itself. So we set up an alarm which is
912 * cleared after successful authentication. A limit of zero
913 * indicates no limit. Note that we don\'t set the alarm in debugging
914 * mode; it is just annoying to have the server exit just when you
915 * are about to discover the bug.
917 signal(SIGALRM, grace_alarm_handler);
919 alarm(options.login_grace_time);
921 sshd_exchange_identification(sock_in, sock_out);
923 * Check that the connection comes from a privileged port. Rhosts-
924 * and Rhosts-RSA-Authentication only make sense from priviledged
925 * programs. Of course, if the intruder has root access on his local
926 * machine, he can connect from any port. So do not use these
927 * authentication methods from machines that you do not trust.
929 if (remote_port >= IPPORT_RESERVED ||
930 remote_port < IPPORT_RESERVED / 2) {
931 options.rhosts_authentication = 0;
932 options.rhosts_rsa_authentication = 0;
935 if (!packet_connection_is_ipv4() &&
936 options.kerberos_authentication) {
937 debug("Kerberos Authentication disabled, only available for IPv4.");
938 options.kerberos_authentication = 0;
942 packet_set_nonblocking();
944 /* perform the key exchange */
945 /* authenticate user and start session */
948 do_authentication2();
955 /* Cleanup user's ticket cache file. */
956 if (options.kerberos_ticket_cleanup)
960 /* The connection has been terminated. */
961 verbose("Closing connection to %.100s", remote_ip);
979 BIGNUM *session_key_int;
980 unsigned char session_key[SSH_SESSION_KEY_LENGTH];
981 unsigned char cookie[8];
982 unsigned int cipher_type, auth_mask, protocol_flags;
986 * Generate check bytes that the client must send back in the user
987 * packet in order for it to be accepted; this is used to defy ip
988 * spoofing attacks. Note that this only works against somebody
989 * doing IP spoofing from a remote machine; any machine on the local
990 * network can still see outgoing packets and catch the random
991 * cookie. This only affects rhosts authentication, and this is one
992 * of the reasons why it is inherently insecure.
994 for (i = 0; i < 8; i++) {
997 cookie[i] = rand & 0xff;
1002 * Send our public key. We include in the packet 64 bits of random
1003 * data that must be matched in the reply in order to prevent IP
1006 packet_start(SSH_SMSG_PUBLIC_KEY);
1007 for (i = 0; i < 8; i++)
1008 packet_put_char(cookie[i]);
1010 /* Store our public server RSA key. */
1011 packet_put_int(BN_num_bits(public_key->n));
1012 packet_put_bignum(public_key->e);
1013 packet_put_bignum(public_key->n);
1015 /* Store our public host RSA key. */
1016 packet_put_int(BN_num_bits(sensitive_data.host_key->n));
1017 packet_put_bignum(sensitive_data.host_key->e);
1018 packet_put_bignum(sensitive_data.host_key->n);
1020 /* Put protocol flags. */
1021 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1023 /* Declare which ciphers we support. */
1024 packet_put_int(cipher_mask1());
1026 /* Declare supported authentication types. */
1028 if (options.rhosts_authentication)
1029 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1030 if (options.rhosts_rsa_authentication)
1031 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1032 if (options.rsa_authentication)
1033 auth_mask |= 1 << SSH_AUTH_RSA;
1035 if (options.kerberos_authentication)
1036 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1039 if (options.kerberos_tgt_passing)
1040 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1041 if (options.afs_token_passing)
1042 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1045 if (options.skey_authentication == 1)
1046 auth_mask |= 1 << SSH_AUTH_TIS;
1048 if (options.password_authentication)
1049 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1050 packet_put_int(auth_mask);
1052 /* Send the packet and wait for it to be sent. */
1054 packet_write_wait();
1056 debug("Sent %d bit public key and %d bit host key.",
1057 BN_num_bits(public_key->n), BN_num_bits(sensitive_data.host_key->n));
1059 /* Read clients reply (cipher type and session key). */
1060 packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1062 /* Get cipher type and check whether we accept this. */
1063 cipher_type = packet_get_char();
1065 if (!(cipher_mask() & (1 << cipher_type)))
1066 packet_disconnect("Warning: client selects unsupported cipher.");
1068 /* Get check bytes from the packet. These must match those we
1069 sent earlier with the public key packet. */
1070 for (i = 0; i < 8; i++)
1071 if (cookie[i] != packet_get_char())
1072 packet_disconnect("IP Spoofing check bytes do not match.");
1074 debug("Encryption type: %.200s", cipher_name(cipher_type));
1076 /* Get the encrypted integer. */
1077 session_key_int = BN_new();
1078 packet_get_bignum(session_key_int, &slen);
1080 protocol_flags = packet_get_int();
1081 packet_set_protocol_flags(protocol_flags);
1083 packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1086 * Decrypt it using our private server key and private host key (key
1087 * with larger modulus first).
1089 if (BN_cmp(sensitive_data.private_key->n, sensitive_data.host_key->n) > 0) {
1090 /* Private key has bigger modulus. */
1091 if (BN_num_bits(sensitive_data.private_key->n) <
1092 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
1093 fatal("do_connection: %s: private_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1094 get_remote_ipaddr(),
1095 BN_num_bits(sensitive_data.private_key->n),
1096 BN_num_bits(sensitive_data.host_key->n),
1097 SSH_KEY_BITS_RESERVED);
1099 rsa_private_decrypt(session_key_int, session_key_int,
1100 sensitive_data.private_key);
1101 rsa_private_decrypt(session_key_int, session_key_int,
1102 sensitive_data.host_key);
1104 /* Host key has bigger modulus (or they are equal). */
1105 if (BN_num_bits(sensitive_data.host_key->n) <
1106 BN_num_bits(sensitive_data.private_key->n) + SSH_KEY_BITS_RESERVED) {
1107 fatal("do_connection: %s: host_key %d < private_key %d + SSH_KEY_BITS_RESERVED %d",
1108 get_remote_ipaddr(),
1109 BN_num_bits(sensitive_data.host_key->n),
1110 BN_num_bits(sensitive_data.private_key->n),
1111 SSH_KEY_BITS_RESERVED);
1113 rsa_private_decrypt(session_key_int, session_key_int,
1114 sensitive_data.host_key);
1115 rsa_private_decrypt(session_key_int, session_key_int,
1116 sensitive_data.private_key);
1119 compute_session_id(session_id, cookie,
1120 sensitive_data.host_key->n,
1121 sensitive_data.private_key->n);
1123 /* Destroy the private and public keys. They will no longer be needed. */
1124 destroy_sensitive_data();
1127 * Extract session key from the decrypted integer. The key is in the
1128 * least significant 256 bits of the integer; the first byte of the
1129 * key is in the highest bits.
1131 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1132 len = BN_num_bytes(session_key_int);
1133 if (len < 0 || len > sizeof(session_key))
1134 fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d",
1135 get_remote_ipaddr(),
1136 len, sizeof(session_key));
1137 memset(session_key, 0, sizeof(session_key));
1138 BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len);
1140 /* Destroy the decrypted integer. It is no longer needed. */
1141 BN_clear_free(session_key_int);
1143 /* Xor the first 16 bytes of the session key with the session id. */
1144 for (i = 0; i < 16; i++)
1145 session_key[i] ^= session_id[i];
1147 /* Set the session key. From this on all communications will be encrypted. */
1148 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1150 /* Destroy our copy of the session key. It is no longer needed. */
1151 memset(session_key, 0, sizeof(session_key));
1153 debug("Received session key; encryption turned on.");
1155 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1156 packet_start(SSH_SMSG_SUCCESS);
1158 packet_write_wait();
1162 * SSH2 key exchange: diffie-hellman-group1-sha1
1167 Buffer *server_kexinit;
1168 Buffer *client_kexinit;
1169 int payload_len, dlen;
1171 unsigned int klen, kout;
1173 unsigned char *signature = NULL;
1174 unsigned char *server_host_key_blob = NULL;
1175 unsigned int sbloblen;
1177 BIGNUM *dh_client_pub = 0;
1178 BIGNUM *shared_secret = 0;
1180 unsigned char *kbuf;
1181 unsigned char *hash;
1183 char *cprop[PROPOSAL_MAX];
1184 char *sprop[PROPOSAL_MAX];
1188 if (options.ciphers != NULL) {
1189 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1190 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1193 debug("Sending KEX init.");
1195 for (i = 0; i < PROPOSAL_MAX; i++)
1196 sprop[i] = xstrdup(myproposal[i]);
1197 server_kexinit = kex_init(sprop);
1198 packet_start(SSH2_MSG_KEXINIT);
1199 packet_put_raw(buffer_ptr(server_kexinit), buffer_len(server_kexinit));
1201 packet_write_wait();
1205 packet_read_expect(&payload_len, SSH2_MSG_KEXINIT);
1208 * save raw KEXINIT payload in buffer. this is used during
1209 * computation of the session_id and the session keys.
1211 client_kexinit = xmalloc(sizeof(*client_kexinit));
1212 buffer_init(client_kexinit);
1213 ptr = packet_get_raw(&payload_len);
1214 buffer_append(client_kexinit, ptr, payload_len);
1217 for (i = 0; i < 16; i++)
1218 (void) packet_get_char();
1219 /* save kex init proposal strings */
1220 for (i = 0; i < PROPOSAL_MAX; i++) {
1221 cprop[i] = packet_get_string(NULL);
1222 debug("got kexinit string: %s", cprop[i]);
1225 i = (int) packet_get_char();
1226 debug("first kex follow == %d", i);
1227 i = packet_get_int();
1228 debug("reserved == %d", i);
1230 debug("done read kexinit");
1231 kex = kex_choose_conf(cprop, sprop, 1);
1235 debug("Wait SSH2_MSG_KEXDH_INIT.");
1236 packet_read_expect(&payload_len, SSH2_MSG_KEXDH_INIT);
1239 dh_client_pub = BN_new();
1240 if (dh_client_pub == NULL)
1241 fatal("dh_client_pub == NULL");
1242 packet_get_bignum2(dh_client_pub, &dlen);
1245 fprintf(stderr, "\ndh_client_pub= ");
1246 bignum_print(dh_client_pub);
1247 fprintf(stderr, "\n");
1248 debug("bits %d", BN_num_bits(dh_client_pub));
1251 /* generate DH key */
1252 dh = dh_new_group1(); /* XXX depends on 'kex' */
1255 fprintf(stderr, "\np= ");
1256 bignum_print(dh->p);
1257 fprintf(stderr, "\ng= ");
1258 bignum_print(dh->g);
1259 fprintf(stderr, "\npub= ");
1260 bignum_print(dh->pub_key);
1261 fprintf(stderr, "\n");
1263 if (!dh_pub_is_valid(dh, dh_client_pub))
1264 packet_disconnect("bad client public DH value");
1267 kbuf = xmalloc(klen);
1268 kout = DH_compute_key(kbuf, dh_client_pub, dh);
1271 debug("shared secret: len %d/%d", klen, kout);
1272 fprintf(stderr, "shared secret == ");
1273 for (i = 0; i< kout; i++)
1274 fprintf(stderr, "%02x", (kbuf[i])&0xff);
1275 fprintf(stderr, "\n");
1277 shared_secret = BN_new();
1279 BN_bin2bn(kbuf, kout, shared_secret);
1280 memset(kbuf, 0, klen);
1283 /* XXX precompute? */
1284 dsa_make_key_blob(sensitive_data.dsa_host_key, &server_host_key_blob, &sbloblen);
1286 /* calc H */ /* XXX depends on 'kex' */
1288 client_version_string,
1289 server_version_string,
1290 buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1291 buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1292 (char *)server_host_key_blob, sbloblen,
1297 buffer_free(client_kexinit);
1298 buffer_free(server_kexinit);
1299 xfree(client_kexinit);
1300 xfree(server_kexinit);
1302 fprintf(stderr, "hash == ");
1303 for (i = 0; i< 20; i++)
1304 fprintf(stderr, "%02x", (hash[i])&0xff);
1305 fprintf(stderr, "\n");
1307 /* save session id := H */
1308 /* XXX hashlen depends on KEX */
1309 session_id2_len = 20;
1310 session_id2 = xmalloc(session_id2_len);
1311 memcpy(session_id2, hash, session_id2_len);
1314 /* XXX hashlen depends on KEX */
1315 dsa_sign(sensitive_data.dsa_host_key, &signature, &slen, hash, 20);
1317 destroy_sensitive_data();
1319 /* send server hostkey, DH pubkey 'f' and singed H */
1320 packet_start(SSH2_MSG_KEXDH_REPLY);
1321 packet_put_string((char *)server_host_key_blob, sbloblen);
1322 packet_put_bignum2(dh->pub_key); // f
1323 packet_put_string((char *)signature, slen);
1326 xfree(server_host_key_blob);
1327 packet_write_wait();
1329 kex_derive_keys(kex, hash, shared_secret);
1330 packet_set_kex(kex);
1332 /* have keys, free DH */
1335 debug("send SSH2_MSG_NEWKEYS.");
1336 packet_start(SSH2_MSG_NEWKEYS);
1338 packet_write_wait();
1339 debug("done: send SSH2_MSG_NEWKEYS.");
1341 debug("Wait SSH2_MSG_NEWKEYS.");
1342 packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS);
1343 debug("GOT SSH2_MSG_NEWKEYS.");
1346 /* send 1st encrypted/maced/compressed message */
1347 packet_start(SSH2_MSG_IGNORE);
1348 packet_put_cstring("markus");
1350 packet_write_wait();
1352 debug("done: KEX2.");