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 1.119 2000/06/22 16:32:27 markus Exp $");
32 #include <openssl/dh.h>
33 #include <openssl/bn.h>
34 #include <openssl/hmac.h>
36 #include <openssl/dsa.h>
37 #include <openssl/rsa.h>
42 #include "myproposal.h"
48 int allow_severity = LOG_INFO;
49 int deny_severity = LOG_WARNING;
56 /* Server configuration options. */
57 ServerOptions options;
59 /* Name of the server configuration file. */
60 char *config_file_name = SERVER_CONFIG_FILE;
63 * Flag indicating whether IPv4 or IPv6. This can be set on the command line.
64 * Default value is AF_UNSPEC means both IPv4 and IPv6.
67 int IPv4or6 = AF_INET;
69 int IPv4or6 = AF_UNSPEC;
73 * Debug mode flag. This can be set on the command line. If debug
74 * mode is enabled, extra debugging output will be sent to the system
75 * log, the daemon will not go to background, and will exit after processing
76 * the first connection.
80 /* Flag indicating that the daemon is being started from inetd. */
83 /* debug goes to stderr unless inetd_flag is set */
86 /* argv[0] without path. */
89 /* Saved arguments to main(). */
94 * The sockets that the server is listening; this is used in the SIGHUP
97 #define MAX_LISTEN_SOCKS 16
98 int listen_socks[MAX_LISTEN_SOCKS];
99 int num_listen_socks = 0;
102 * the client's version string, passed by sshd2 in compat mode. if != NULL,
103 * sshd will skip the version-number exchange
105 char *client_version_string = NULL;
106 char *server_version_string = NULL;
109 * Any really sensitive data in the application is contained in this
110 * structure. The idea is that this structure could be locked into memory so
111 * that the pages do not get written into swap. However, there are some
112 * problems. The private key contains BIGNUMs, and we do not (in principle)
113 * have access to the internals of them, and locking just the structure is
114 * not very useful. Currently, memory locking is not implemented.
117 RSA *private_key; /* Private part of empheral server key. */
118 RSA *host_key; /* Private part of host key. */
119 Key *dsa_host_key; /* Private DSA host key. */
123 * Flag indicating whether the current session key has been used. This flag
124 * is set whenever the key is used, and cleared when the key is regenerated.
128 /* This is set to true when SIGHUP is received. */
129 int received_sighup = 0;
131 /* Public side of the server key. This value is regenerated regularly with
135 /* session identifier, used by RSA-auth */
136 unsigned char session_id[16];
139 unsigned char *session_id2 = NULL;
140 int session_id2_len = 0;
142 /* Prototypes for various functions defined later in this file. */
147 * Close all listening sockets
150 close_listen_socks(void)
153 for (i = 0; i < num_listen_socks; i++)
154 close(listen_socks[i]);
155 num_listen_socks = -1;
159 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
160 * the effect is to reread the configuration file (and to regenerate
164 sighup_handler(int sig)
167 signal(SIGHUP, sighup_handler);
171 * Called from the main program after receiving SIGHUP.
172 * Restarts the server.
177 log("Received SIGHUP; restarting.");
178 close_listen_socks();
179 execv(saved_argv[0], saved_argv);
180 log("RESTART FAILED: av0='%s', error: %s.", av0, strerror(errno));
185 * Generic signal handler for terminating signals in the master daemon.
186 * These close the listen socket; not closing it seems to cause "Address
187 * already in use" problems on some machines, which is inconvenient.
190 sigterm_handler(int sig)
192 log("Received signal %d; terminating.", sig);
193 close_listen_socks();
194 unlink(options.pid_file);
199 * SIGCHLD handler. This is called whenever a child dies. This will then
200 * reap any zombies left by exited c.
203 main_sigchld_handler(int sig)
205 int save_errno = errno;
208 while (waitpid(-1, &status, WNOHANG) > 0)
211 signal(SIGCHLD, main_sigchld_handler);
216 * Signal handler for the alarm after the login grace period has expired.
219 grace_alarm_handler(int sig)
221 /* Close the connection. */
224 /* Log error and exit. */
225 fatal("Timeout before authentication for %s.", get_remote_ipaddr());
229 * Signal handler for the key regeneration alarm. Note that this
230 * alarm only occurs in the daemon waiting for connections, and it does not
231 * do anything with the private key or random state before forking.
232 * Thus there should be no concurrency control/asynchronous execution
235 /* XXX do we really want this work to be done in a signal handler ? -m */
237 key_regeneration_alarm(int sig)
239 int save_errno = errno;
241 /* Check if we should generate a new key. */
243 /* This should really be done in the background. */
244 log("Generating new %d bit RSA key.", options.server_key_bits);
246 if (sensitive_data.private_key != NULL)
247 RSA_free(sensitive_data.private_key);
248 sensitive_data.private_key = RSA_new();
250 if (public_key != NULL)
251 RSA_free(public_key);
252 public_key = RSA_new();
254 rsa_generate_key(sensitive_data.private_key, public_key,
255 options.server_key_bits);
258 log("RSA key generation complete.");
260 /* Reschedule the alarm. */
261 signal(SIGALRM, key_regeneration_alarm);
262 alarm(options.key_regeneration_time);
267 sshd_exchange_identification(int sock_in, int sock_out)
270 int remote_major, remote_minor;
273 char buf[256]; /* Must not be larger than remote_version. */
274 char remote_version[256]; /* Must be at least as big as buf. */
276 if ((options.protocol & SSH_PROTO_1) &&
277 (options.protocol & SSH_PROTO_2)) {
278 major = PROTOCOL_MAJOR_1;
280 } else if (options.protocol & SSH_PROTO_2) {
281 major = PROTOCOL_MAJOR_2;
282 minor = PROTOCOL_MINOR_2;
284 major = PROTOCOL_MAJOR_1;
285 minor = PROTOCOL_MINOR_1;
287 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
288 server_version_string = xstrdup(buf);
290 if (client_version_string == NULL) {
291 /* Send our protocol version identification. */
292 if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
293 != strlen(server_version_string)) {
294 log("Could not write ident string to %s.", get_remote_ipaddr());
298 /* Read other side\'s version identification. */
299 for (i = 0; i < sizeof(buf) - 1; i++) {
300 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
301 log("Did not receive ident string from %s.", get_remote_ipaddr());
304 if (buf[i] == '\r') {
309 if (buf[i] == '\n') {
315 buf[sizeof(buf) - 1] = 0;
316 client_version_string = xstrdup(buf);
320 * Check that the versions match. In future this might accept
321 * several versions and set appropriate flags to handle them.
323 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
324 &remote_major, &remote_minor, remote_version) != 3) {
325 s = "Protocol mismatch.\n";
326 (void) atomicio(write, sock_out, s, strlen(s));
329 log("Bad protocol version identification '%.100s' from %s",
330 client_version_string, get_remote_ipaddr());
333 debug("Client protocol version %d.%d; client software version %.100s",
334 remote_major, remote_minor, remote_version);
336 compat_datafellows(remote_version);
339 switch(remote_major) {
341 if (remote_minor == 99) {
342 if (options.protocol & SSH_PROTO_2)
348 if (!(options.protocol & SSH_PROTO_1)) {
352 if (remote_minor < 3) {
353 packet_disconnect("Your ssh version is too old and"
354 "is no longer supported. Please install a newer version.");
355 } else if (remote_minor == 3) {
356 /* note that this disables agent-forwarding */
361 if (options.protocol & SSH_PROTO_2) {
370 chop(server_version_string);
371 chop(client_version_string);
372 debug("Local version string %.200s", server_version_string);
375 s = "Protocol major versions differ.\n";
376 (void) atomicio(write, sock_out, s, strlen(s));
379 log("Protocol major versions differ for %s: %.200s vs. %.200s",
381 server_version_string, client_version_string);
385 packet_set_ssh2_format();
390 destroy_sensitive_data(void)
392 /* Destroy the private and public keys. They will no longer be needed. */
394 RSA_free(public_key);
395 if (sensitive_data.private_key)
396 RSA_free(sensitive_data.private_key);
397 if (sensitive_data.host_key)
398 RSA_free(sensitive_data.host_key);
399 if (sensitive_data.dsa_host_key != NULL)
400 key_free(sensitive_data.dsa_host_key);
404 * Main program for the daemon.
407 main(int ac, char **av)
411 int opt, sock_in = 0, sock_out = 0, newsock, i, fdsetsz, on = 1;
416 struct sockaddr_storage from;
417 const char *remote_ip;
420 struct linger linger;
422 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
423 int listen_sock, maxfd;
428 if (strchr(av[0], '/'))
429 av0 = strrchr(av[0], '/') + 1;
433 /* Initialize configuration options to their default values. */
434 initialize_server_options(&options);
436 /* Parse command-line arguments. */
437 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:diqQ46")) != EOF) {
446 config_file_name = optarg;
450 options.log_level = SYSLOG_LEVEL_DEBUG;
459 options.log_level = SYSLOG_LEVEL_QUIET;
462 options.server_key_bits = atoi(optarg);
465 options.ports_from_cmdline = 1;
466 if (options.num_ports >= MAX_PORTS)
467 fatal("too many ports.\n");
468 options.ports[options.num_ports++] = atoi(optarg);
471 options.login_grace_time = atoi(optarg);
474 options.key_regeneration_time = atoi(optarg);
477 options.host_key_file = optarg;
480 client_version_string = optarg;
481 /* only makes sense with inetd_flag, i.e. no listen() */
486 fprintf(stderr, "sshd version %s\n", SSH_VERSION);
487 fprintf(stderr, "Usage: %s [options]\n", av0);
488 fprintf(stderr, "Options:\n");
489 fprintf(stderr, " -f file Configuration file (default %s)\n", SERVER_CONFIG_FILE);
490 fprintf(stderr, " -d Debugging mode\n");
491 fprintf(stderr, " -i Started from inetd\n");
492 fprintf(stderr, " -q Quiet (no logging)\n");
493 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
494 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
495 fprintf(stderr, " -g seconds Grace period for authentication (default: 300)\n");
496 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
497 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
499 fprintf(stderr, " -4 Use IPv4 only\n");
500 fprintf(stderr, " -6 Use IPv6 only\n");
506 * Force logging to stderr until we have loaded the private host
507 * key (unless started from inetd)
510 options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
511 options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
512 !silent && !inetd_flag);
514 /* Read server configuration options from the configuration file. */
515 read_server_config(&options, config_file_name);
517 /* Fill in default values for those options not explicitly set. */
518 fill_default_server_options(&options);
520 /* Check that there are no remaining arguments. */
522 fprintf(stderr, "Extra argument %s.\n", av[optind]);
526 debug("sshd version %.100s", SSH_VERSION);
528 sensitive_data.dsa_host_key = NULL;
529 sensitive_data.host_key = NULL;
531 /* check if RSA support exists */
532 if ((options.protocol & SSH_PROTO_1) &&
534 log("no RSA support in libssl and libcrypto. See ssl(8)");
535 log("Disabling protocol version 1");
536 options.protocol &= ~SSH_PROTO_1;
538 /* Load the RSA/DSA host key. It must have empty passphrase. */
539 if (options.protocol & SSH_PROTO_1) {
541 sensitive_data.host_key = RSA_new();
543 k.rsa = sensitive_data.host_key;
545 if (!load_private_key(options.host_key_file, "", &k, NULL)) {
546 error("Could not load host key: %.200s: %.100s",
547 options.host_key_file, strerror(errno));
548 log("Disabling protocol version 1");
549 options.protocol &= ~SSH_PROTO_1;
553 if (options.protocol & SSH_PROTO_2) {
554 sensitive_data.dsa_host_key = key_new(KEY_DSA);
555 if (!load_private_key(options.host_dsa_key_file, "", sensitive_data.dsa_host_key, NULL)) {
557 error("Could not load DSA host key: %.200s", options.host_dsa_key_file);
558 log("Disabling protocol version 2");
559 options.protocol &= ~SSH_PROTO_2;
562 if (! options.protocol & (SSH_PROTO_1|SSH_PROTO_2)) {
564 fprintf(stderr, "sshd: no hostkeys available -- exiting.\n");
565 log("sshd: no hostkeys available -- exiting.\n");
569 /* Check certain values for sanity. */
570 if (options.protocol & SSH_PROTO_1) {
571 if (options.server_key_bits < 512 ||
572 options.server_key_bits > 32768) {
573 fprintf(stderr, "Bad server key size.\n");
577 * Check that server and host key lengths differ sufficiently. This
578 * is necessary to make double encryption work with rsaref. Oh, I
579 * hate software patents. I dont know if this can go? Niels
581 if (options.server_key_bits >
582 BN_num_bits(sensitive_data.host_key->n) - SSH_KEY_BITS_RESERVED &&
583 options.server_key_bits <
584 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
585 options.server_key_bits =
586 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED;
587 debug("Forcing server key to %d bits to make it differ from host key.",
588 options.server_key_bits);
592 /* Initialize the log (it is reinitialized below in case we forked). */
593 if (debug_flag && !inetd_flag)
595 log_init(av0, options.log_level, options.log_facility, log_stderr);
598 * If not in debugging mode, and not started from inetd, disconnect
599 * from the controlling terminal, and fork. The original process
602 if (!debug_flag && !inetd_flag) {
605 #endif /* TIOCNOTTY */
606 if (daemon(0, 0) < 0)
607 fatal("daemon() failed: %.200s", strerror(errno));
609 /* Disconnect from the controlling tty. */
611 fd = open("/dev/tty", O_RDWR | O_NOCTTY);
613 (void) ioctl(fd, TIOCNOTTY, NULL);
616 #endif /* TIOCNOTTY */
618 /* Reinitialize the log (because of the fork above). */
619 log_init(av0, options.log_level, options.log_facility, log_stderr);
621 /* Do not display messages to stdout in RSA code. */
624 /* Initialize the random number generator. */
627 /* Chdir to the root directory so that the current disk can be
628 unmounted if desired. */
631 /* Start listening for a socket, unless started from inetd. */
634 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
639 * We intentionally do not close the descriptors 0, 1, and 2
640 * as our code for setting the descriptors won\'t work if
641 * ttyfd happens to be one of those.
643 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
645 if (options.protocol & SSH_PROTO_1) {
646 public_key = RSA_new();
647 sensitive_data.private_key = RSA_new();
648 log("Generating %d bit RSA key.", options.server_key_bits);
649 rsa_generate_key(sensitive_data.private_key, public_key,
650 options.server_key_bits);
652 log("RSA key generation complete.");
655 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
656 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
658 if (num_listen_socks >= MAX_LISTEN_SOCKS)
659 fatal("Too many listen sockets. "
660 "Enlarge MAX_LISTEN_SOCKS");
661 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
662 ntop, sizeof(ntop), strport, sizeof(strport),
663 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
664 error("getnameinfo failed");
667 /* Create socket for listening. */
668 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
669 if (listen_sock < 0) {
670 /* kernel may not support ipv6 */
671 verbose("socket: %.100s", strerror(errno));
674 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
675 error("listen_sock O_NONBLOCK: %s", strerror(errno));
680 * Set socket options. We try to make the port
681 * reusable and have it close as fast as possible
682 * without waiting in unnecessary wait states on
685 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
686 (void *) &on, sizeof(on));
689 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
690 (void *) &linger, sizeof(linger));
692 debug("Bind to port %s on %s.", strport, ntop);
694 /* Bind the socket to the desired port. */
695 if ((bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) &&
697 error("Bind to port %s on %s failed: %.200s.",
698 strport, ntop, strerror(errno));
702 listen_socks[num_listen_socks] = listen_sock;
705 /* Start listening on the port. */
706 log("Server listening on %s port %s.", ntop, strport);
707 if (listen(listen_sock, 5) < 0)
708 fatal("listen: %.100s", strerror(errno));
711 freeaddrinfo(options.listen_addrs);
713 if (!num_listen_socks)
714 fatal("Cannot bind any address.");
718 * Record our pid in /etc/sshd_pid to make it easier
719 * to kill the correct sshd. We don\'t want to do
720 * this before the bind above because the bind will
721 * fail if there already is a daemon, and this will
722 * overwrite any old pid in the file.
724 f = fopen(options.pid_file, "w");
726 fprintf(f, "%u\n", (unsigned int) getpid());
730 if (options.protocol & SSH_PROTO_1) {
731 public_key = RSA_new();
732 sensitive_data.private_key = RSA_new();
734 log("Generating %d bit RSA key.", options.server_key_bits);
735 rsa_generate_key(sensitive_data.private_key, public_key,
736 options.server_key_bits);
738 log("RSA key generation complete.");
740 /* Schedule server key regeneration alarm. */
741 signal(SIGALRM, key_regeneration_alarm);
742 alarm(options.key_regeneration_time);
745 /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
746 signal(SIGHUP, sighup_handler);
747 signal(SIGTERM, sigterm_handler);
748 signal(SIGQUIT, sigterm_handler);
750 /* Arrange SIGCHLD to be caught. */
751 signal(SIGCHLD, main_sigchld_handler);
753 /* setup fd set for listen */
755 for (i = 0; i < num_listen_socks; i++)
756 if (listen_socks[i] > maxfd)
757 maxfd = listen_socks[i];
758 fdsetsz = howmany(maxfd, NFDBITS) * sizeof(fd_mask);
759 fdset = (fd_set *)xmalloc(fdsetsz);
762 * Stay listening for connections until the system crashes or
763 * the daemon is killed with a signal.
768 /* Wait in select until there is a connection. */
769 memset(fdset, 0, fdsetsz);
770 for (i = 0; i < num_listen_socks; i++)
771 FD_SET(listen_socks[i], fdset);
772 if (select(maxfd + 1, fdset, NULL, NULL, NULL) < 0) {
774 error("select: %.100s", strerror(errno));
777 for (i = 0; i < num_listen_socks; i++) {
778 if (!FD_ISSET(listen_socks[i], fdset))
780 fromlen = sizeof(from);
781 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
784 if (errno != EINTR && errno != EWOULDBLOCK)
785 error("accept: %.100s", strerror(errno));
788 if (fcntl(newsock, F_SETFL, 0) < 0) {
789 error("newsock del O_NONBLOCK: %s", strerror(errno));
793 * Got connection. Fork a child to handle it, unless
794 * we are in debugging mode.
798 * In debugging mode. Close the listening
799 * socket, and start processing the
800 * connection without forking.
802 debug("Server will not fork when running in debugging mode.");
803 close_listen_socks();
810 * Normal production daemon. Fork, and have
811 * the child process the connection. The
812 * parent continues listening.
814 if ((pid = fork()) == 0) {
816 * Child. Close the listening socket, and start using the
817 * accepted socket. Reinitialize logging (since our pid has
818 * changed). We break out of the loop to handle the connection.
820 close_listen_socks();
823 log_init(av0, options.log_level, options.log_facility, log_stderr);
828 /* Parent. Stay in the loop. */
830 error("fork: %.100s", strerror(errno));
832 debug("Forked child %d.", pid);
834 /* Mark that the key has been used (it was "given" to the child). */
839 /* Close the new socket (the child is now taking care of it). */
841 } /* for (i = 0; i < num_listen_socks; i++) */
842 /* child process check (or debug mode) */
843 if (num_listen_socks < 0)
848 /* This is the child processing a new connection. */
851 * Disable the key regeneration alarm. We will not regenerate the
852 * key since we are no longer in a position to give it to anyone. We
853 * will not restart on SIGHUP since it no longer makes sense.
856 signal(SIGALRM, SIG_DFL);
857 signal(SIGHUP, SIG_DFL);
858 signal(SIGTERM, SIG_DFL);
859 signal(SIGQUIT, SIG_DFL);
860 signal(SIGCHLD, SIG_DFL);
863 * Set socket options for the connection. We want the socket to
864 * close as fast as possible without waiting for anything. If the
865 * connection is not a socket, these will do nothing.
867 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
870 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
873 * Register our connection. This turns encryption off because we do
876 packet_set_connection(sock_in, sock_out);
878 remote_port = get_remote_port();
879 remote_ip = get_remote_ipaddr();
881 /* Check whether logins are denied from this host. */
883 /* XXX LIBWRAP noes not know about IPv6 */
885 struct request_info req;
887 request_init(&req, RQ_DAEMON, av0, RQ_FILE, sock_in, NULL);
890 if (!hosts_access(&req)) {
895 /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
898 /* Log the connection. */
899 verbose("Connection from %.500s port %d", remote_ip, remote_port);
902 * We don\'t want to listen forever unless the other side
903 * successfully authenticates itself. So we set up an alarm which is
904 * cleared after successful authentication. A limit of zero
905 * indicates no limit. Note that we don\'t set the alarm in debugging
906 * mode; it is just annoying to have the server exit just when you
907 * are about to discover the bug.
909 signal(SIGALRM, grace_alarm_handler);
911 alarm(options.login_grace_time);
913 sshd_exchange_identification(sock_in, sock_out);
915 * Check that the connection comes from a privileged port. Rhosts-
916 * and Rhosts-RSA-Authentication only make sense from priviledged
917 * programs. Of course, if the intruder has root access on his local
918 * machine, he can connect from any port. So do not use these
919 * authentication methods from machines that you do not trust.
921 if (remote_port >= IPPORT_RESERVED ||
922 remote_port < IPPORT_RESERVED / 2) {
923 options.rhosts_authentication = 0;
924 options.rhosts_rsa_authentication = 0;
927 if (!packet_connection_is_ipv4() &&
928 options.kerberos_authentication) {
929 debug("Kerberos Authentication disabled, only available for IPv4.");
930 options.kerberos_authentication = 0;
934 packet_set_nonblocking();
936 /* perform the key exchange */
937 /* authenticate user and start session */
940 do_authentication2();
947 /* Cleanup user's ticket cache file. */
948 if (options.kerberos_ticket_cleanup)
952 /* The connection has been terminated. */
953 verbose("Closing connection to %.100s", remote_ip);
971 BIGNUM *session_key_int;
972 unsigned char session_key[SSH_SESSION_KEY_LENGTH];
973 unsigned char cookie[8];
974 unsigned int cipher_type, auth_mask, protocol_flags;
978 * Generate check bytes that the client must send back in the user
979 * packet in order for it to be accepted; this is used to defy ip
980 * spoofing attacks. Note that this only works against somebody
981 * doing IP spoofing from a remote machine; any machine on the local
982 * network can still see outgoing packets and catch the random
983 * cookie. This only affects rhosts authentication, and this is one
984 * of the reasons why it is inherently insecure.
986 for (i = 0; i < 8; i++) {
989 cookie[i] = rand & 0xff;
994 * Send our public key. We include in the packet 64 bits of random
995 * data that must be matched in the reply in order to prevent IP
998 packet_start(SSH_SMSG_PUBLIC_KEY);
999 for (i = 0; i < 8; i++)
1000 packet_put_char(cookie[i]);
1002 /* Store our public server RSA key. */
1003 packet_put_int(BN_num_bits(public_key->n));
1004 packet_put_bignum(public_key->e);
1005 packet_put_bignum(public_key->n);
1007 /* Store our public host RSA key. */
1008 packet_put_int(BN_num_bits(sensitive_data.host_key->n));
1009 packet_put_bignum(sensitive_data.host_key->e);
1010 packet_put_bignum(sensitive_data.host_key->n);
1012 /* Put protocol flags. */
1013 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1015 /* Declare which ciphers we support. */
1016 packet_put_int(cipher_mask1());
1018 /* Declare supported authentication types. */
1020 if (options.rhosts_authentication)
1021 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1022 if (options.rhosts_rsa_authentication)
1023 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1024 if (options.rsa_authentication)
1025 auth_mask |= 1 << SSH_AUTH_RSA;
1027 if (options.kerberos_authentication)
1028 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1031 if (options.kerberos_tgt_passing)
1032 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1033 if (options.afs_token_passing)
1034 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1037 if (options.skey_authentication == 1)
1038 auth_mask |= 1 << SSH_AUTH_TIS;
1040 if (options.password_authentication)
1041 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1042 packet_put_int(auth_mask);
1044 /* Send the packet and wait for it to be sent. */
1046 packet_write_wait();
1048 debug("Sent %d bit public key and %d bit host key.",
1049 BN_num_bits(public_key->n), BN_num_bits(sensitive_data.host_key->n));
1051 /* Read clients reply (cipher type and session key). */
1052 packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1054 /* Get cipher type and check whether we accept this. */
1055 cipher_type = packet_get_char();
1057 if (!(cipher_mask() & (1 << cipher_type)))
1058 packet_disconnect("Warning: client selects unsupported cipher.");
1060 /* Get check bytes from the packet. These must match those we
1061 sent earlier with the public key packet. */
1062 for (i = 0; i < 8; i++)
1063 if (cookie[i] != packet_get_char())
1064 packet_disconnect("IP Spoofing check bytes do not match.");
1066 debug("Encryption type: %.200s", cipher_name(cipher_type));
1068 /* Get the encrypted integer. */
1069 session_key_int = BN_new();
1070 packet_get_bignum(session_key_int, &slen);
1072 protocol_flags = packet_get_int();
1073 packet_set_protocol_flags(protocol_flags);
1075 packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1078 * Decrypt it using our private server key and private host key (key
1079 * with larger modulus first).
1081 if (BN_cmp(sensitive_data.private_key->n, sensitive_data.host_key->n) > 0) {
1082 /* Private key has bigger modulus. */
1083 if (BN_num_bits(sensitive_data.private_key->n) <
1084 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
1085 fatal("do_connection: %s: private_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1086 get_remote_ipaddr(),
1087 BN_num_bits(sensitive_data.private_key->n),
1088 BN_num_bits(sensitive_data.host_key->n),
1089 SSH_KEY_BITS_RESERVED);
1091 rsa_private_decrypt(session_key_int, session_key_int,
1092 sensitive_data.private_key);
1093 rsa_private_decrypt(session_key_int, session_key_int,
1094 sensitive_data.host_key);
1096 /* Host key has bigger modulus (or they are equal). */
1097 if (BN_num_bits(sensitive_data.host_key->n) <
1098 BN_num_bits(sensitive_data.private_key->n) + SSH_KEY_BITS_RESERVED) {
1099 fatal("do_connection: %s: host_key %d < private_key %d + SSH_KEY_BITS_RESERVED %d",
1100 get_remote_ipaddr(),
1101 BN_num_bits(sensitive_data.host_key->n),
1102 BN_num_bits(sensitive_data.private_key->n),
1103 SSH_KEY_BITS_RESERVED);
1105 rsa_private_decrypt(session_key_int, session_key_int,
1106 sensitive_data.host_key);
1107 rsa_private_decrypt(session_key_int, session_key_int,
1108 sensitive_data.private_key);
1111 compute_session_id(session_id, cookie,
1112 sensitive_data.host_key->n,
1113 sensitive_data.private_key->n);
1115 /* Destroy the private and public keys. They will no longer be needed. */
1116 destroy_sensitive_data();
1119 * Extract session key from the decrypted integer. The key is in the
1120 * least significant 256 bits of the integer; the first byte of the
1121 * key is in the highest bits.
1123 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1124 len = BN_num_bytes(session_key_int);
1125 if (len < 0 || len > sizeof(session_key))
1126 fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d",
1127 get_remote_ipaddr(),
1128 len, sizeof(session_key));
1129 memset(session_key, 0, sizeof(session_key));
1130 BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len);
1132 /* Destroy the decrypted integer. It is no longer needed. */
1133 BN_clear_free(session_key_int);
1135 /* Xor the first 16 bytes of the session key with the session id. */
1136 for (i = 0; i < 16; i++)
1137 session_key[i] ^= session_id[i];
1139 /* Set the session key. From this on all communications will be encrypted. */
1140 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1142 /* Destroy our copy of the session key. It is no longer needed. */
1143 memset(session_key, 0, sizeof(session_key));
1145 debug("Received session key; encryption turned on.");
1147 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1148 packet_start(SSH_SMSG_SUCCESS);
1150 packet_write_wait();
1154 * SSH2 key exchange: diffie-hellman-group1-sha1
1159 Buffer *server_kexinit;
1160 Buffer *client_kexinit;
1161 int payload_len, dlen;
1163 unsigned int klen, kout;
1164 unsigned char *signature = NULL;
1165 unsigned char *server_host_key_blob = NULL;
1166 unsigned int sbloblen;
1168 BIGNUM *dh_client_pub = 0;
1169 BIGNUM *shared_secret = 0;
1171 unsigned char *kbuf;
1172 unsigned char *hash;
1174 char *cprop[PROPOSAL_MAX];
1178 if (options.ciphers != NULL) {
1179 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1180 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1182 server_kexinit = kex_init(myproposal);
1183 client_kexinit = xmalloc(sizeof(*client_kexinit));
1184 buffer_init(client_kexinit);
1186 /* algorithm negotiation */
1187 kex_exchange_kexinit(server_kexinit, client_kexinit, cprop);
1188 kex = kex_choose_conf(cprop, myproposal, 1);
1189 for (i = 0; i < PROPOSAL_MAX; i++)
1194 debug("Wait SSH2_MSG_KEXDH_INIT.");
1195 packet_read_expect(&payload_len, SSH2_MSG_KEXDH_INIT);
1198 dh_client_pub = BN_new();
1199 if (dh_client_pub == NULL)
1200 fatal("dh_client_pub == NULL");
1201 packet_get_bignum2(dh_client_pub, &dlen);
1204 fprintf(stderr, "\ndh_client_pub= ");
1205 bignum_print(dh_client_pub);
1206 fprintf(stderr, "\n");
1207 debug("bits %d", BN_num_bits(dh_client_pub));
1210 /* generate DH key */
1211 dh = dh_new_group1(); /* XXX depends on 'kex' */
1214 fprintf(stderr, "\np= ");
1215 bignum_print(dh->p);
1216 fprintf(stderr, "\ng= ");
1217 bignum_print(dh->g);
1218 fprintf(stderr, "\npub= ");
1219 bignum_print(dh->pub_key);
1220 fprintf(stderr, "\n");
1222 if (!dh_pub_is_valid(dh, dh_client_pub))
1223 packet_disconnect("bad client public DH value");
1226 kbuf = xmalloc(klen);
1227 kout = DH_compute_key(kbuf, dh_client_pub, dh);
1230 debug("shared secret: len %d/%d", klen, kout);
1231 fprintf(stderr, "shared secret == ");
1232 for (i = 0; i< kout; i++)
1233 fprintf(stderr, "%02x", (kbuf[i])&0xff);
1234 fprintf(stderr, "\n");
1236 shared_secret = BN_new();
1238 BN_bin2bn(kbuf, kout, shared_secret);
1239 memset(kbuf, 0, klen);
1242 /* XXX precompute? */
1243 dsa_make_key_blob(sensitive_data.dsa_host_key, &server_host_key_blob, &sbloblen);
1245 /* calc H */ /* XXX depends on 'kex' */
1247 client_version_string,
1248 server_version_string,
1249 buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1250 buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1251 (char *)server_host_key_blob, sbloblen,
1256 buffer_free(client_kexinit);
1257 buffer_free(server_kexinit);
1258 xfree(client_kexinit);
1259 xfree(server_kexinit);
1261 fprintf(stderr, "hash == ");
1262 for (i = 0; i< 20; i++)
1263 fprintf(stderr, "%02x", (hash[i])&0xff);
1264 fprintf(stderr, "\n");
1266 /* save session id := H */
1267 /* XXX hashlen depends on KEX */
1268 session_id2_len = 20;
1269 session_id2 = xmalloc(session_id2_len);
1270 memcpy(session_id2, hash, session_id2_len);
1273 /* XXX hashlen depends on KEX */
1274 dsa_sign(sensitive_data.dsa_host_key, &signature, &slen, hash, 20);
1276 destroy_sensitive_data();
1278 /* send server hostkey, DH pubkey 'f' and singed H */
1279 packet_start(SSH2_MSG_KEXDH_REPLY);
1280 packet_put_string((char *)server_host_key_blob, sbloblen);
1281 packet_put_bignum2(dh->pub_key); /* f */
1282 packet_put_string((char *)signature, slen);
1285 xfree(server_host_key_blob);
1286 packet_write_wait();
1288 kex_derive_keys(kex, hash, shared_secret);
1289 packet_set_kex(kex);
1291 /* have keys, free DH */
1294 debug("send SSH2_MSG_NEWKEYS.");
1295 packet_start(SSH2_MSG_NEWKEYS);
1297 packet_write_wait();
1298 debug("done: send SSH2_MSG_NEWKEYS.");
1300 debug("Wait SSH2_MSG_NEWKEYS.");
1301 packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS);
1302 debug("GOT SSH2_MSG_NEWKEYS.");
1305 /* send 1st encrypted/maced/compressed message */
1306 packet_start(SSH2_MSG_IGNORE);
1307 packet_put_cstring("markus");
1309 packet_write_wait();
1311 debug("done: KEX2.");