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 1.115 2000/05/03 10:21:49 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);
270 if(*t == '\n' || *t == '\r') {
281 sshd_exchange_identification(int sock_in, int sock_out)
284 int remote_major, remote_minor;
287 char buf[256]; /* Must not be larger than remote_version. */
288 char remote_version[256]; /* Must be at least as big as buf. */
290 if ((options.protocol & SSH_PROTO_1) &&
291 (options.protocol & SSH_PROTO_2)) {
292 major = PROTOCOL_MAJOR_1;
294 } else if (options.protocol & SSH_PROTO_2) {
295 major = PROTOCOL_MAJOR_2;
296 minor = PROTOCOL_MINOR_2;
298 major = PROTOCOL_MAJOR_1;
299 minor = PROTOCOL_MINOR_1;
301 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
302 server_version_string = xstrdup(buf);
304 if (client_version_string == NULL) {
305 /* Send our protocol version identification. */
306 if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
307 != strlen(server_version_string)) {
308 log("Could not write ident string to %s.", get_remote_ipaddr());
312 /* Read other side\'s version identification. */
313 for (i = 0; i < sizeof(buf) - 1; i++) {
314 if (read(sock_in, &buf[i], 1) != 1) {
315 log("Did not receive ident string from %s.", get_remote_ipaddr());
318 if (buf[i] == '\r') {
323 if (buf[i] == '\n') {
329 buf[sizeof(buf) - 1] = 0;
330 client_version_string = xstrdup(buf);
334 * Check that the versions match. In future this might accept
335 * several versions and set appropriate flags to handle them.
337 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
338 &remote_major, &remote_minor, remote_version) != 3) {
339 s = "Protocol mismatch.\n";
340 (void) atomicio(write, sock_out, s, strlen(s));
343 log("Bad protocol version identification '%.100s' from %s",
344 client_version_string, get_remote_ipaddr());
347 debug("Client protocol version %d.%d; client software version %.100s",
348 remote_major, remote_minor, remote_version);
350 compat_datafellows(remote_version);
353 switch(remote_major) {
355 if (remote_minor == 99) {
356 if (options.protocol & SSH_PROTO_2)
362 if (!(options.protocol & SSH_PROTO_1)) {
366 if (remote_minor < 3) {
367 packet_disconnect("Your ssh version is too old and"
368 "is no longer supported. Please install a newer version.");
369 } else if (remote_minor == 3) {
370 /* note that this disables agent-forwarding */
375 if (options.protocol & SSH_PROTO_2) {
384 chop(server_version_string);
385 chop(client_version_string);
386 debug("Local version string %.200s", server_version_string);
389 s = "Protocol major versions differ.\n";
390 (void) atomicio(write, sock_out, s, strlen(s));
393 log("Protocol major versions differ for %s: %.200s vs. %.200s",
395 server_version_string, client_version_string);
399 packet_set_ssh2_format();
404 destroy_sensitive_data(void)
406 /* Destroy the private and public keys. They will no longer be needed. */
407 RSA_free(public_key);
408 RSA_free(sensitive_data.private_key);
409 RSA_free(sensitive_data.host_key);
410 if (sensitive_data.dsa_host_key != NULL)
411 key_free(sensitive_data.dsa_host_key);
415 * Main program for the daemon.
418 main(int ac, char **av)
422 int opt, sock_in = 0, sock_out = 0, newsock, i, fdsetsz, on = 1;
427 struct sockaddr_storage from;
428 const char *remote_ip;
431 struct linger linger;
433 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
434 int listen_sock, maxfd;
438 if (strchr(av[0], '/'))
439 av0 = strrchr(av[0], '/') + 1;
443 /* Initialize configuration options to their default values. */
444 initialize_server_options(&options);
446 /* Parse command-line arguments. */
447 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:diqQ46")) != EOF) {
456 config_file_name = optarg;
460 options.log_level = SYSLOG_LEVEL_DEBUG;
469 options.log_level = SYSLOG_LEVEL_QUIET;
472 options.server_key_bits = atoi(optarg);
475 options.ports_from_cmdline = 1;
476 if (options.num_ports >= MAX_PORTS)
477 fatal("too many ports.\n");
478 options.ports[options.num_ports++] = atoi(optarg);
481 options.login_grace_time = atoi(optarg);
484 options.key_regeneration_time = atoi(optarg);
487 options.host_key_file = optarg;
490 client_version_string = optarg;
491 /* only makes sense with inetd_flag, i.e. no listen() */
496 fprintf(stderr, "sshd version %s\n", SSH_VERSION);
497 fprintf(stderr, "Usage: %s [options]\n", av0);
498 fprintf(stderr, "Options:\n");
499 fprintf(stderr, " -f file Configuration file (default %s)\n", SERVER_CONFIG_FILE);
500 fprintf(stderr, " -d Debugging mode\n");
501 fprintf(stderr, " -i Started from inetd\n");
502 fprintf(stderr, " -q Quiet (no logging)\n");
503 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
504 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
505 fprintf(stderr, " -g seconds Grace period for authentication (default: 300)\n");
506 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
507 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
509 fprintf(stderr, " -4 Use IPv4 only\n");
510 fprintf(stderr, " -6 Use IPv6 only\n");
516 * Force logging to stderr until we have loaded the private host
517 * key (unless started from inetd)
520 options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
521 options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
522 !silent && !inetd_flag);
524 /* Read server configuration options from the configuration file. */
525 read_server_config(&options, config_file_name);
527 /* Fill in default values for those options not explicitly set. */
528 fill_default_server_options(&options);
530 /* Check that there are no remaining arguments. */
532 fprintf(stderr, "Extra argument %s.\n", av[optind]);
536 debug("sshd version %.100s", SSH_VERSION);
538 sensitive_data.dsa_host_key = NULL;
539 sensitive_data.host_key = NULL;
541 /* check if RSA support exists */
542 if ((options.protocol & SSH_PROTO_1) &&
544 log("no RSA support in libssl and libcrypto. See ssl(8)");
545 log("Disabling protocol version 1");
546 options.protocol &= ~SSH_PROTO_1;
548 /* Load the RSA/DSA host key. It must have empty passphrase. */
549 if (options.protocol & SSH_PROTO_1) {
551 sensitive_data.host_key = RSA_new();
553 k.rsa = sensitive_data.host_key;
555 if (!load_private_key(options.host_key_file, "", &k, NULL)) {
556 error("Could not load host key: %.200s: %.100s",
557 options.host_key_file, strerror(errno));
558 log("Disabling protocol version 1");
559 options.protocol &= ~SSH_PROTO_1;
563 if (options.protocol & SSH_PROTO_2) {
564 sensitive_data.dsa_host_key = key_new(KEY_DSA);
565 if (!load_private_key(options.host_dsa_key_file, "", sensitive_data.dsa_host_key, NULL)) {
567 error("Could not load DSA host key: %.200s", options.host_dsa_key_file);
568 log("Disabling protocol version 2");
569 options.protocol &= ~SSH_PROTO_2;
572 if (! options.protocol & (SSH_PROTO_1|SSH_PROTO_2)) {
574 fprintf(stderr, "sshd: no hostkeys available -- exiting.\n");
575 log("sshd: no hostkeys available -- exiting.\n");
579 /* Check certain values for sanity. */
580 if (options.protocol & SSH_PROTO_1) {
581 if (options.server_key_bits < 512 ||
582 options.server_key_bits > 32768) {
583 fprintf(stderr, "Bad server key size.\n");
587 * Check that server and host key lengths differ sufficiently. This
588 * is necessary to make double encryption work with rsaref. Oh, I
589 * hate software patents. I dont know if this can go? Niels
591 if (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 options.server_key_bits =
596 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED;
597 debug("Forcing server key to %d bits to make it differ from host key.",
598 options.server_key_bits);
602 /* Initialize the log (it is reinitialized below in case we forked). */
603 if (debug_flag && !inetd_flag)
605 log_init(av0, options.log_level, options.log_facility, log_stderr);
608 * If not in debugging mode, and not started from inetd, disconnect
609 * from the controlling terminal, and fork. The original process
612 if (!debug_flag && !inetd_flag) {
615 #endif /* TIOCNOTTY */
616 if (daemon(0, 0) < 0)
617 fatal("daemon() failed: %.200s", strerror(errno));
619 /* Disconnect from the controlling tty. */
621 fd = open("/dev/tty", O_RDWR | O_NOCTTY);
623 (void) ioctl(fd, TIOCNOTTY, NULL);
626 #endif /* TIOCNOTTY */
628 /* Reinitialize the log (because of the fork above). */
629 log_init(av0, options.log_level, options.log_facility, log_stderr);
631 /* Do not display messages to stdout in RSA code. */
634 /* Initialize the random number generator. */
637 /* Chdir to the root directory so that the current disk can be
638 unmounted if desired. */
641 /* Start listening for a socket, unless started from inetd. */
644 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
649 * We intentionally do not close the descriptors 0, 1, and 2
650 * as our code for setting the descriptors won\'t work if
651 * ttyfd happens to be one of those.
653 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
655 if (options.protocol & SSH_PROTO_1) {
656 public_key = RSA_new();
657 sensitive_data.private_key = RSA_new();
658 log("Generating %d bit RSA key.", options.server_key_bits);
659 rsa_generate_key(sensitive_data.private_key, public_key,
660 options.server_key_bits);
662 log("RSA key generation complete.");
665 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
666 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
668 if (num_listen_socks >= MAX_LISTEN_SOCKS)
669 fatal("Too many listen sockets. "
670 "Enlarge MAX_LISTEN_SOCKS");
671 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
672 ntop, sizeof(ntop), strport, sizeof(strport),
673 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
674 error("getnameinfo failed");
677 /* Create socket for listening. */
678 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
679 if (listen_sock < 0) {
680 /* kernel may not support ipv6 */
681 verbose("socket: %.100s", strerror(errno));
684 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
685 error("listen_sock O_NONBLOCK: %s", strerror(errno));
690 * Set socket options. We try to make the port
691 * reusable and have it close as fast as possible
692 * without waiting in unnecessary wait states on
695 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
696 (void *) &on, sizeof(on));
699 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
700 (void *) &linger, sizeof(linger));
702 debug("Bind to port %s on %s.", strport, ntop);
704 /* Bind the socket to the desired port. */
705 if ((bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) &&
707 error("Bind to port %s on %s failed: %.200s.",
708 strport, ntop, strerror(errno));
712 listen_socks[num_listen_socks] = listen_sock;
715 /* Start listening on the port. */
716 log("Server listening on %s port %s.", ntop, strport);
717 if (listen(listen_sock, 5) < 0)
718 fatal("listen: %.100s", strerror(errno));
721 freeaddrinfo(options.listen_addrs);
723 if (!num_listen_socks)
724 fatal("Cannot bind any address.");
728 * Record our pid in /etc/sshd_pid to make it easier
729 * to kill the correct sshd. We don\'t want to do
730 * this before the bind above because the bind will
731 * fail if there already is a daemon, and this will
732 * overwrite any old pid in the file.
734 f = fopen(options.pid_file, "w");
736 fprintf(f, "%u\n", (unsigned int) getpid());
740 if (options.protocol & SSH_PROTO_1) {
741 public_key = RSA_new();
742 sensitive_data.private_key = RSA_new();
744 log("Generating %d bit RSA key.", options.server_key_bits);
745 rsa_generate_key(sensitive_data.private_key, public_key,
746 options.server_key_bits);
748 log("RSA key generation complete.");
750 /* Schedule server key regeneration alarm. */
751 signal(SIGALRM, key_regeneration_alarm);
752 alarm(options.key_regeneration_time);
755 /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
756 signal(SIGHUP, sighup_handler);
757 signal(SIGTERM, sigterm_handler);
758 signal(SIGQUIT, sigterm_handler);
760 /* Arrange SIGCHLD to be caught. */
761 signal(SIGCHLD, main_sigchld_handler);
763 /* setup fd set for listen */
765 for (i = 0; i < num_listen_socks; i++)
766 if (listen_socks[i] > maxfd)
767 maxfd = listen_socks[i];
768 fdsetsz = howmany(maxfd, NFDBITS) * sizeof(fd_mask);
769 fdset = (fd_set *)xmalloc(fdsetsz);
772 * Stay listening for connections until the system crashes or
773 * the daemon is killed with a signal.
778 /* Wait in select until there is a connection. */
779 memset(fdset, 0, fdsetsz);
780 for (i = 0; i < num_listen_socks; i++)
781 FD_SET(listen_socks[i], fdset);
782 if (select(maxfd + 1, fdset, NULL, NULL, NULL) < 0) {
784 error("select: %.100s", strerror(errno));
787 for (i = 0; i < num_listen_socks; i++) {
788 if (!FD_ISSET(listen_socks[i], fdset))
790 fromlen = sizeof(from);
791 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
794 if (errno != EINTR && errno != EWOULDBLOCK)
795 error("accept: %.100s", strerror(errno));
798 if (fcntl(newsock, F_SETFL, 0) < 0) {
799 error("newsock del O_NONBLOCK: %s", strerror(errno));
803 * Got connection. Fork a child to handle it, unless
804 * we are in debugging mode.
808 * In debugging mode. Close the listening
809 * socket, and start processing the
810 * connection without forking.
812 debug("Server will not fork when running in debugging mode.");
813 close_listen_socks();
820 * Normal production daemon. Fork, and have
821 * the child process the connection. The
822 * parent continues listening.
824 if ((pid = fork()) == 0) {
826 * Child. Close the listening socket, and start using the
827 * accepted socket. Reinitialize logging (since our pid has
828 * changed). We break out of the loop to handle the connection.
830 close_listen_socks();
833 log_init(av0, options.log_level, options.log_facility, log_stderr);
838 /* Parent. Stay in the loop. */
840 error("fork: %.100s", strerror(errno));
842 debug("Forked child %d.", pid);
844 /* Mark that the key has been used (it was "given" to the child). */
849 /* Close the new socket (the child is now taking care of it). */
851 } /* for (i = 0; i < num_listen_socks; i++) */
852 /* child process check (or debug mode) */
853 if (num_listen_socks < 0)
858 /* This is the child processing a new connection. */
861 * Disable the key regeneration alarm. We will not regenerate the
862 * key since we are no longer in a position to give it to anyone. We
863 * will not restart on SIGHUP since it no longer makes sense.
866 signal(SIGALRM, SIG_DFL);
867 signal(SIGHUP, SIG_DFL);
868 signal(SIGTERM, SIG_DFL);
869 signal(SIGQUIT, SIG_DFL);
870 signal(SIGCHLD, SIG_DFL);
873 * Set socket options for the connection. We want the socket to
874 * close as fast as possible without waiting for anything. If the
875 * connection is not a socket, these will do nothing.
877 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
880 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
883 * Register our connection. This turns encryption off because we do
886 packet_set_connection(sock_in, sock_out);
888 remote_port = get_remote_port();
889 remote_ip = get_remote_ipaddr();
891 /* Check whether logins are denied from this host. */
893 /* XXX LIBWRAP noes not know about IPv6 */
895 struct request_info req;
897 request_init(&req, RQ_DAEMON, av0, RQ_FILE, sock_in, NULL);
900 if (!hosts_access(&req)) {
905 /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
908 /* Log the connection. */
909 verbose("Connection from %.500s port %d", remote_ip, remote_port);
912 * We don\'t want to listen forever unless the other side
913 * successfully authenticates itself. So we set up an alarm which is
914 * cleared after successful authentication. A limit of zero
915 * indicates no limit. Note that we don\'t set the alarm in debugging
916 * mode; it is just annoying to have the server exit just when you
917 * are about to discover the bug.
919 signal(SIGALRM, grace_alarm_handler);
921 alarm(options.login_grace_time);
923 sshd_exchange_identification(sock_in, sock_out);
925 * Check that the connection comes from a privileged port. Rhosts-
926 * and Rhosts-RSA-Authentication only make sense from priviledged
927 * programs. Of course, if the intruder has root access on his local
928 * machine, he can connect from any port. So do not use these
929 * authentication methods from machines that you do not trust.
931 if (remote_port >= IPPORT_RESERVED ||
932 remote_port < IPPORT_RESERVED / 2) {
933 options.rhosts_authentication = 0;
934 options.rhosts_rsa_authentication = 0;
937 if (!packet_connection_is_ipv4() &&
938 options.kerberos_authentication) {
939 debug("Kerberos Authentication disabled, only available for IPv4.");
940 options.kerberos_authentication = 0;
944 packet_set_nonblocking();
946 /* perform the key exchange */
947 /* authenticate user and start session */
950 do_authentication2();
957 /* Cleanup user's ticket cache file. */
958 if (options.kerberos_ticket_cleanup)
962 /* The connection has been terminated. */
963 verbose("Closing connection to %.100s", remote_ip);
981 BIGNUM *session_key_int;
982 unsigned char session_key[SSH_SESSION_KEY_LENGTH];
983 unsigned char cookie[8];
984 unsigned int cipher_type, auth_mask, protocol_flags;
988 * Generate check bytes that the client must send back in the user
989 * packet in order for it to be accepted; this is used to defy ip
990 * spoofing attacks. Note that this only works against somebody
991 * doing IP spoofing from a remote machine; any machine on the local
992 * network can still see outgoing packets and catch the random
993 * cookie. This only affects rhosts authentication, and this is one
994 * of the reasons why it is inherently insecure.
996 for (i = 0; i < 8; i++) {
999 cookie[i] = rand & 0xff;
1004 * Send our public key. We include in the packet 64 bits of random
1005 * data that must be matched in the reply in order to prevent IP
1008 packet_start(SSH_SMSG_PUBLIC_KEY);
1009 for (i = 0; i < 8; i++)
1010 packet_put_char(cookie[i]);
1012 /* Store our public server RSA key. */
1013 packet_put_int(BN_num_bits(public_key->n));
1014 packet_put_bignum(public_key->e);
1015 packet_put_bignum(public_key->n);
1017 /* Store our public host RSA key. */
1018 packet_put_int(BN_num_bits(sensitive_data.host_key->n));
1019 packet_put_bignum(sensitive_data.host_key->e);
1020 packet_put_bignum(sensitive_data.host_key->n);
1022 /* Put protocol flags. */
1023 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1025 /* Declare which ciphers we support. */
1026 packet_put_int(cipher_mask1());
1028 /* Declare supported authentication types. */
1030 if (options.rhosts_authentication)
1031 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1032 if (options.rhosts_rsa_authentication)
1033 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1034 if (options.rsa_authentication)
1035 auth_mask |= 1 << SSH_AUTH_RSA;
1037 if (options.kerberos_authentication)
1038 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1041 if (options.kerberos_tgt_passing)
1042 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1043 if (options.afs_token_passing)
1044 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1047 if (options.skey_authentication == 1)
1048 auth_mask |= 1 << SSH_AUTH_TIS;
1050 if (options.password_authentication)
1051 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1052 packet_put_int(auth_mask);
1054 /* Send the packet and wait for it to be sent. */
1056 packet_write_wait();
1058 debug("Sent %d bit public key and %d bit host key.",
1059 BN_num_bits(public_key->n), BN_num_bits(sensitive_data.host_key->n));
1061 /* Read clients reply (cipher type and session key). */
1062 packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1064 /* Get cipher type and check whether we accept this. */
1065 cipher_type = packet_get_char();
1067 if (!(cipher_mask() & (1 << cipher_type)))
1068 packet_disconnect("Warning: client selects unsupported cipher.");
1070 /* Get check bytes from the packet. These must match those we
1071 sent earlier with the public key packet. */
1072 for (i = 0; i < 8; i++)
1073 if (cookie[i] != packet_get_char())
1074 packet_disconnect("IP Spoofing check bytes do not match.");
1076 debug("Encryption type: %.200s", cipher_name(cipher_type));
1078 /* Get the encrypted integer. */
1079 session_key_int = BN_new();
1080 packet_get_bignum(session_key_int, &slen);
1082 protocol_flags = packet_get_int();
1083 packet_set_protocol_flags(protocol_flags);
1085 packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1088 * Decrypt it using our private server key and private host key (key
1089 * with larger modulus first).
1091 if (BN_cmp(sensitive_data.private_key->n, sensitive_data.host_key->n) > 0) {
1092 /* Private key has bigger modulus. */
1093 if (BN_num_bits(sensitive_data.private_key->n) <
1094 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
1095 fatal("do_connection: %s: private_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1096 get_remote_ipaddr(),
1097 BN_num_bits(sensitive_data.private_key->n),
1098 BN_num_bits(sensitive_data.host_key->n),
1099 SSH_KEY_BITS_RESERVED);
1101 rsa_private_decrypt(session_key_int, session_key_int,
1102 sensitive_data.private_key);
1103 rsa_private_decrypt(session_key_int, session_key_int,
1104 sensitive_data.host_key);
1106 /* Host key has bigger modulus (or they are equal). */
1107 if (BN_num_bits(sensitive_data.host_key->n) <
1108 BN_num_bits(sensitive_data.private_key->n) + SSH_KEY_BITS_RESERVED) {
1109 fatal("do_connection: %s: host_key %d < private_key %d + SSH_KEY_BITS_RESERVED %d",
1110 get_remote_ipaddr(),
1111 BN_num_bits(sensitive_data.host_key->n),
1112 BN_num_bits(sensitive_data.private_key->n),
1113 SSH_KEY_BITS_RESERVED);
1115 rsa_private_decrypt(session_key_int, session_key_int,
1116 sensitive_data.host_key);
1117 rsa_private_decrypt(session_key_int, session_key_int,
1118 sensitive_data.private_key);
1121 compute_session_id(session_id, cookie,
1122 sensitive_data.host_key->n,
1123 sensitive_data.private_key->n);
1125 /* Destroy the private and public keys. They will no longer be needed. */
1126 destroy_sensitive_data();
1129 * Extract session key from the decrypted integer. The key is in the
1130 * least significant 256 bits of the integer; the first byte of the
1131 * key is in the highest bits.
1133 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1134 len = BN_num_bytes(session_key_int);
1135 if (len < 0 || len > sizeof(session_key))
1136 fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d",
1137 get_remote_ipaddr(),
1138 len, sizeof(session_key));
1139 memset(session_key, 0, sizeof(session_key));
1140 BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len);
1142 /* Destroy the decrypted integer. It is no longer needed. */
1143 BN_clear_free(session_key_int);
1145 /* Xor the first 16 bytes of the session key with the session id. */
1146 for (i = 0; i < 16; i++)
1147 session_key[i] ^= session_id[i];
1149 /* Set the session key. From this on all communications will be encrypted. */
1150 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1152 /* Destroy our copy of the session key. It is no longer needed. */
1153 memset(session_key, 0, sizeof(session_key));
1155 debug("Received session key; encryption turned on.");
1157 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1158 packet_start(SSH_SMSG_SUCCESS);
1160 packet_write_wait();
1164 * SSH2 key exchange: diffie-hellman-group1-sha1
1169 Buffer *server_kexinit;
1170 Buffer *client_kexinit;
1171 int payload_len, dlen;
1173 unsigned int klen, kout;
1175 unsigned char *signature = NULL;
1176 unsigned char *server_host_key_blob = NULL;
1177 unsigned int sbloblen;
1179 BIGNUM *dh_client_pub = 0;
1180 BIGNUM *shared_secret = 0;
1182 unsigned char *kbuf;
1183 unsigned char *hash;
1185 char *cprop[PROPOSAL_MAX];
1186 char *sprop[PROPOSAL_MAX];
1190 if (options.ciphers != NULL) {
1191 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1192 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1195 debug("Sending KEX init.");
1197 for (i = 0; i < PROPOSAL_MAX; i++)
1198 sprop[i] = xstrdup(myproposal[i]);
1199 server_kexinit = kex_init(sprop);
1200 packet_start(SSH2_MSG_KEXINIT);
1201 packet_put_raw(buffer_ptr(server_kexinit), buffer_len(server_kexinit));
1203 packet_write_wait();
1207 packet_read_expect(&payload_len, SSH2_MSG_KEXINIT);
1210 * save raw KEXINIT payload in buffer. this is used during
1211 * computation of the session_id and the session keys.
1213 client_kexinit = xmalloc(sizeof(*client_kexinit));
1214 buffer_init(client_kexinit);
1215 ptr = packet_get_raw(&payload_len);
1216 buffer_append(client_kexinit, ptr, payload_len);
1219 for (i = 0; i < 16; i++)
1220 (void) packet_get_char();
1221 /* save kex init proposal strings */
1222 for (i = 0; i < PROPOSAL_MAX; i++) {
1223 cprop[i] = packet_get_string(NULL);
1224 debug("got kexinit string: %s", cprop[i]);
1227 i = (int) packet_get_char();
1228 debug("first kex follow == %d", i);
1229 i = packet_get_int();
1230 debug("reserved == %d", i);
1232 debug("done read kexinit");
1233 kex = kex_choose_conf(cprop, sprop, 1);
1237 debug("Wait SSH2_MSG_KEXDH_INIT.");
1238 packet_read_expect(&payload_len, SSH2_MSG_KEXDH_INIT);
1241 dh_client_pub = BN_new();
1242 if (dh_client_pub == NULL)
1243 fatal("dh_client_pub == NULL");
1244 packet_get_bignum2(dh_client_pub, &dlen);
1247 fprintf(stderr, "\ndh_client_pub= ");
1248 bignum_print(dh_client_pub);
1249 fprintf(stderr, "\n");
1250 debug("bits %d", BN_num_bits(dh_client_pub));
1253 /* generate DH key */
1254 dh = dh_new_group1(); /* XXX depends on 'kex' */
1257 fprintf(stderr, "\np= ");
1258 bignum_print(dh->p);
1259 fprintf(stderr, "\ng= ");
1260 bignum_print(dh->g);
1261 fprintf(stderr, "\npub= ");
1262 bignum_print(dh->pub_key);
1263 fprintf(stderr, "\n");
1265 if (!dh_pub_is_valid(dh, dh_client_pub))
1266 packet_disconnect("bad client public DH value");
1269 kbuf = xmalloc(klen);
1270 kout = DH_compute_key(kbuf, dh_client_pub, dh);
1273 debug("shared secret: len %d/%d", klen, kout);
1274 fprintf(stderr, "shared secret == ");
1275 for (i = 0; i< kout; i++)
1276 fprintf(stderr, "%02x", (kbuf[i])&0xff);
1277 fprintf(stderr, "\n");
1279 shared_secret = BN_new();
1281 BN_bin2bn(kbuf, kout, shared_secret);
1282 memset(kbuf, 0, klen);
1285 /* XXX precompute? */
1286 dsa_make_key_blob(sensitive_data.dsa_host_key, &server_host_key_blob, &sbloblen);
1288 /* calc H */ /* XXX depends on 'kex' */
1290 client_version_string,
1291 server_version_string,
1292 buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1293 buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1294 (char *)server_host_key_blob, sbloblen,
1299 buffer_free(client_kexinit);
1300 buffer_free(server_kexinit);
1301 xfree(client_kexinit);
1302 xfree(server_kexinit);
1304 fprintf(stderr, "hash == ");
1305 for (i = 0; i< 20; i++)
1306 fprintf(stderr, "%02x", (hash[i])&0xff);
1307 fprintf(stderr, "\n");
1309 /* save session id := H */
1310 /* XXX hashlen depends on KEX */
1311 session_id2_len = 20;
1312 session_id2 = xmalloc(session_id2_len);
1313 memcpy(session_id2, hash, session_id2_len);
1316 /* XXX hashlen depends on KEX */
1317 dsa_sign(sensitive_data.dsa_host_key, &signature, &slen, hash, 20);
1319 destroy_sensitive_data();
1321 /* send server hostkey, DH pubkey 'f' and singed H */
1322 packet_start(SSH2_MSG_KEXDH_REPLY);
1323 packet_put_string((char *)server_host_key_blob, sbloblen);
1324 packet_put_bignum2(dh->pub_key); /* f */
1325 packet_put_string((char *)signature, slen);
1328 xfree(server_host_key_blob);
1329 packet_write_wait();
1331 kex_derive_keys(kex, hash, shared_secret);
1332 packet_set_kex(kex);
1334 /* have keys, free DH */
1337 debug("send SSH2_MSG_NEWKEYS.");
1338 packet_start(SSH2_MSG_NEWKEYS);
1340 packet_write_wait();
1341 debug("done: send SSH2_MSG_NEWKEYS.");
1343 debug("Wait SSH2_MSG_NEWKEYS.");
1344 packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS);
1345 debug("GOT SSH2_MSG_NEWKEYS.");
1348 /* send 1st encrypted/maced/compressed message */
1349 packet_start(SSH2_MSG_IGNORE);
1350 packet_put_cstring("markus");
1352 packet_write_wait();
1354 debug("done: KEX2.");