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 1.113 2000/05/01 20:34:51 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.dsa_key_file, "", sensitive_data.dsa_host_key, NULL)) {
566 error("Could not load DSA host key: %.200s", options.dsa_key_file);
567 log("Disabling protocol version 2");
568 options.protocol &= ~SSH_PROTO_2;
571 if (! options.protocol & (SSH_PROTO_1|SSH_PROTO_2)) {
573 fprintf(stderr, "sshd: no hostkeys available -- exiting.\n");
574 log("sshd: no hostkeys available -- exiting.\n");
578 /* Check certain values for sanity. */
579 if (options.protocol & SSH_PROTO_1) {
580 if (options.server_key_bits < 512 ||
581 options.server_key_bits > 32768) {
582 fprintf(stderr, "Bad server key size.\n");
586 * Check that server and host key lengths differ sufficiently. This
587 * is necessary to make double encryption work with rsaref. Oh, I
588 * hate software patents. I dont know if this can go? Niels
590 if (options.server_key_bits >
591 BN_num_bits(sensitive_data.host_key->n) - SSH_KEY_BITS_RESERVED &&
592 options.server_key_bits <
593 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
594 options.server_key_bits =
595 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED;
596 debug("Forcing server key to %d bits to make it differ from host key.",
597 options.server_key_bits);
601 /* Initialize the log (it is reinitialized below in case we forked). */
602 if (debug_flag && !inetd_flag)
604 log_init(av0, options.log_level, options.log_facility, log_stderr);
607 * If not in debugging mode, and not started from inetd, disconnect
608 * from the controlling terminal, and fork. The original process
611 if (!debug_flag && !inetd_flag) {
614 #endif /* TIOCNOTTY */
615 if (daemon(0, 0) < 0)
616 fatal("daemon() failed: %.200s", strerror(errno));
618 /* Disconnect from the controlling tty. */
620 fd = open("/dev/tty", O_RDWR | O_NOCTTY);
622 (void) ioctl(fd, TIOCNOTTY, NULL);
625 #endif /* TIOCNOTTY */
627 /* Reinitialize the log (because of the fork above). */
628 log_init(av0, options.log_level, options.log_facility, log_stderr);
630 /* Do not display messages to stdout in RSA code. */
633 /* Initialize the random number generator. */
636 /* Chdir to the root directory so that the current disk can be
637 unmounted if desired. */
640 /* Start listening for a socket, unless started from inetd. */
643 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
648 * We intentionally do not close the descriptors 0, 1, and 2
649 * as our code for setting the descriptors won\'t work if
650 * ttyfd happens to be one of those.
652 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
654 if (options.protocol & SSH_PROTO_1) {
655 public_key = RSA_new();
656 sensitive_data.private_key = RSA_new();
657 log("Generating %d bit RSA key.", options.server_key_bits);
658 rsa_generate_key(sensitive_data.private_key, public_key,
659 options.server_key_bits);
661 log("RSA key generation complete.");
664 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
665 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
667 if (num_listen_socks >= MAX_LISTEN_SOCKS)
668 fatal("Too many listen sockets. "
669 "Enlarge MAX_LISTEN_SOCKS");
670 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
671 ntop, sizeof(ntop), strport, sizeof(strport),
672 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
673 error("getnameinfo failed");
676 /* Create socket for listening. */
677 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
678 if (listen_sock < 0) {
679 /* kernel may not support ipv6 */
680 verbose("socket: %.100s", strerror(errno));
683 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
684 error("listen_sock O_NONBLOCK: %s", strerror(errno));
689 * Set socket options. We try to make the port
690 * reusable and have it close as fast as possible
691 * without waiting in unnecessary wait states on
694 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
695 (void *) &on, sizeof(on));
698 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
699 (void *) &linger, sizeof(linger));
701 debug("Bind to port %s on %s.", strport, ntop);
703 /* Bind the socket to the desired port. */
704 if ((bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) &&
706 error("Bind to port %s on %s failed: %.200s.",
707 strport, ntop, strerror(errno));
711 listen_socks[num_listen_socks] = listen_sock;
714 /* Start listening on the port. */
715 log("Server listening on %s port %s.", ntop, strport);
716 if (listen(listen_sock, 5) < 0)
717 fatal("listen: %.100s", strerror(errno));
720 freeaddrinfo(options.listen_addrs);
722 if (!num_listen_socks)
723 fatal("Cannot bind any address.");
727 * Record our pid in /etc/sshd_pid to make it easier
728 * to kill the correct sshd. We don\'t want to do
729 * this before the bind above because the bind will
730 * fail if there already is a daemon, and this will
731 * overwrite any old pid in the file.
733 f = fopen(options.pid_file, "w");
735 fprintf(f, "%u\n", (unsigned int) getpid());
739 if (options.protocol & SSH_PROTO_1) {
740 public_key = RSA_new();
741 sensitive_data.private_key = RSA_new();
743 log("Generating %d bit RSA key.", options.server_key_bits);
744 rsa_generate_key(sensitive_data.private_key, public_key,
745 options.server_key_bits);
747 log("RSA key generation complete.");
749 /* Schedule server key regeneration alarm. */
750 signal(SIGALRM, key_regeneration_alarm);
751 alarm(options.key_regeneration_time);
754 /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
755 signal(SIGHUP, sighup_handler);
756 signal(SIGTERM, sigterm_handler);
757 signal(SIGQUIT, sigterm_handler);
759 /* Arrange SIGCHLD to be caught. */
760 signal(SIGCHLD, main_sigchld_handler);
762 /* setup fd set for listen */
764 for (i = 0; i < num_listen_socks; i++)
765 if (listen_socks[i] > maxfd)
766 maxfd = listen_socks[i];
767 fdsetsz = howmany(maxfd, NFDBITS) * sizeof(fd_mask);
768 fdset = (fd_set *)xmalloc(fdsetsz);
771 * Stay listening for connections until the system crashes or
772 * the daemon is killed with a signal.
777 /* Wait in select until there is a connection. */
778 memset(fdset, 0, fdsetsz);
779 for (i = 0; i < num_listen_socks; i++)
780 FD_SET(listen_socks[i], fdset);
781 if (select(maxfd + 1, fdset, NULL, NULL, NULL) < 0) {
783 error("select: %.100s", strerror(errno));
786 for (i = 0; i < num_listen_socks; i++) {
787 if (!FD_ISSET(listen_socks[i], fdset))
789 fromlen = sizeof(from);
790 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
793 if (errno != EINTR && errno != EWOULDBLOCK)
794 error("accept: %.100s", strerror(errno));
797 if (fcntl(newsock, F_SETFL, 0) < 0) {
798 error("newsock del O_NONBLOCK: %s", strerror(errno));
802 * Got connection. Fork a child to handle it, unless
803 * we are in debugging mode.
807 * In debugging mode. Close the listening
808 * socket, and start processing the
809 * connection without forking.
811 debug("Server will not fork when running in debugging mode.");
812 close_listen_socks();
819 * Normal production daemon. Fork, and have
820 * the child process the connection. The
821 * parent continues listening.
823 if ((pid = fork()) == 0) {
825 * Child. Close the listening socket, and start using the
826 * accepted socket. Reinitialize logging (since our pid has
827 * changed). We break out of the loop to handle the connection.
829 close_listen_socks();
832 log_init(av0, options.log_level, options.log_facility, log_stderr);
837 /* Parent. Stay in the loop. */
839 error("fork: %.100s", strerror(errno));
841 debug("Forked child %d.", pid);
843 /* Mark that the key has been used (it was "given" to the child). */
848 /* Close the new socket (the child is now taking care of it). */
850 } /* for (i = 0; i < num_listen_socks; i++) */
851 /* child process check (or debug mode) */
852 if (num_listen_socks < 0)
857 /* This is the child processing a new connection. */
860 * Disable the key regeneration alarm. We will not regenerate the
861 * key since we are no longer in a position to give it to anyone. We
862 * will not restart on SIGHUP since it no longer makes sense.
865 signal(SIGALRM, SIG_DFL);
866 signal(SIGHUP, SIG_DFL);
867 signal(SIGTERM, SIG_DFL);
868 signal(SIGQUIT, SIG_DFL);
869 signal(SIGCHLD, SIG_DFL);
872 * Set socket options for the connection. We want the socket to
873 * close as fast as possible without waiting for anything. If the
874 * connection is not a socket, these will do nothing.
876 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
879 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
882 * Register our connection. This turns encryption off because we do
885 packet_set_connection(sock_in, sock_out);
887 remote_port = get_remote_port();
888 remote_ip = get_remote_ipaddr();
890 /* Check whether logins are denied from this host. */
892 /* XXX LIBWRAP noes not know about IPv6 */
894 struct request_info req;
896 request_init(&req, RQ_DAEMON, av0, RQ_FILE, sock_in, NULL);
899 if (!hosts_access(&req)) {
904 /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
907 /* Log the connection. */
908 verbose("Connection from %.500s port %d", remote_ip, remote_port);
911 * We don\'t want to listen forever unless the other side
912 * successfully authenticates itself. So we set up an alarm which is
913 * cleared after successful authentication. A limit of zero
914 * indicates no limit. Note that we don\'t set the alarm in debugging
915 * mode; it is just annoying to have the server exit just when you
916 * are about to discover the bug.
918 signal(SIGALRM, grace_alarm_handler);
920 alarm(options.login_grace_time);
922 sshd_exchange_identification(sock_in, sock_out);
924 * Check that the connection comes from a privileged port. Rhosts-
925 * and Rhosts-RSA-Authentication only make sense from priviledged
926 * programs. Of course, if the intruder has root access on his local
927 * machine, he can connect from any port. So do not use these
928 * authentication methods from machines that you do not trust.
930 if (remote_port >= IPPORT_RESERVED ||
931 remote_port < IPPORT_RESERVED / 2) {
932 options.rhosts_authentication = 0;
933 options.rhosts_rsa_authentication = 0;
936 if (!packet_connection_is_ipv4() &&
937 options.kerberos_authentication) {
938 debug("Kerberos Authentication disabled, only available for IPv4.");
939 options.kerberos_authentication = 0;
943 packet_set_nonblocking();
945 /* perform the key exchange */
946 /* authenticate user and start session */
949 do_authentication2();
956 /* Cleanup user's ticket cache file. */
957 if (options.kerberos_ticket_cleanup)
961 /* The connection has been terminated. */
962 verbose("Closing connection to %.100s", remote_ip);
980 BIGNUM *session_key_int;
981 unsigned char session_key[SSH_SESSION_KEY_LENGTH];
982 unsigned char cookie[8];
983 unsigned int cipher_type, auth_mask, protocol_flags;
987 * Generate check bytes that the client must send back in the user
988 * packet in order for it to be accepted; this is used to defy ip
989 * spoofing attacks. Note that this only works against somebody
990 * doing IP spoofing from a remote machine; any machine on the local
991 * network can still see outgoing packets and catch the random
992 * cookie. This only affects rhosts authentication, and this is one
993 * of the reasons why it is inherently insecure.
995 for (i = 0; i < 8; i++) {
998 cookie[i] = rand & 0xff;
1003 * Send our public key. We include in the packet 64 bits of random
1004 * data that must be matched in the reply in order to prevent IP
1007 packet_start(SSH_SMSG_PUBLIC_KEY);
1008 for (i = 0; i < 8; i++)
1009 packet_put_char(cookie[i]);
1011 /* Store our public server RSA key. */
1012 packet_put_int(BN_num_bits(public_key->n));
1013 packet_put_bignum(public_key->e);
1014 packet_put_bignum(public_key->n);
1016 /* Store our public host RSA key. */
1017 packet_put_int(BN_num_bits(sensitive_data.host_key->n));
1018 packet_put_bignum(sensitive_data.host_key->e);
1019 packet_put_bignum(sensitive_data.host_key->n);
1021 /* Put protocol flags. */
1022 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1024 /* Declare which ciphers we support. */
1025 packet_put_int(cipher_mask1());
1027 /* Declare supported authentication types. */
1029 if (options.rhosts_authentication)
1030 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1031 if (options.rhosts_rsa_authentication)
1032 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1033 if (options.rsa_authentication)
1034 auth_mask |= 1 << SSH_AUTH_RSA;
1036 if (options.kerberos_authentication)
1037 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1040 if (options.kerberos_tgt_passing)
1041 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1042 if (options.afs_token_passing)
1043 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1046 if (options.skey_authentication == 1)
1047 auth_mask |= 1 << SSH_AUTH_TIS;
1049 if (options.password_authentication)
1050 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1051 packet_put_int(auth_mask);
1053 /* Send the packet and wait for it to be sent. */
1055 packet_write_wait();
1057 debug("Sent %d bit public key and %d bit host key.",
1058 BN_num_bits(public_key->n), BN_num_bits(sensitive_data.host_key->n));
1060 /* Read clients reply (cipher type and session key). */
1061 packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1063 /* Get cipher type and check whether we accept this. */
1064 cipher_type = packet_get_char();
1066 if (!(cipher_mask() & (1 << cipher_type)))
1067 packet_disconnect("Warning: client selects unsupported cipher.");
1069 /* Get check bytes from the packet. These must match those we
1070 sent earlier with the public key packet. */
1071 for (i = 0; i < 8; i++)
1072 if (cookie[i] != packet_get_char())
1073 packet_disconnect("IP Spoofing check bytes do not match.");
1075 debug("Encryption type: %.200s", cipher_name(cipher_type));
1077 /* Get the encrypted integer. */
1078 session_key_int = BN_new();
1079 packet_get_bignum(session_key_int, &slen);
1081 protocol_flags = packet_get_int();
1082 packet_set_protocol_flags(protocol_flags);
1084 packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1087 * Decrypt it using our private server key and private host key (key
1088 * with larger modulus first).
1090 if (BN_cmp(sensitive_data.private_key->n, sensitive_data.host_key->n) > 0) {
1091 /* Private key has bigger modulus. */
1092 if (BN_num_bits(sensitive_data.private_key->n) <
1093 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
1094 fatal("do_connection: %s: private_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1095 get_remote_ipaddr(),
1096 BN_num_bits(sensitive_data.private_key->n),
1097 BN_num_bits(sensitive_data.host_key->n),
1098 SSH_KEY_BITS_RESERVED);
1100 rsa_private_decrypt(session_key_int, session_key_int,
1101 sensitive_data.private_key);
1102 rsa_private_decrypt(session_key_int, session_key_int,
1103 sensitive_data.host_key);
1105 /* Host key has bigger modulus (or they are equal). */
1106 if (BN_num_bits(sensitive_data.host_key->n) <
1107 BN_num_bits(sensitive_data.private_key->n) + SSH_KEY_BITS_RESERVED) {
1108 fatal("do_connection: %s: host_key %d < private_key %d + SSH_KEY_BITS_RESERVED %d",
1109 get_remote_ipaddr(),
1110 BN_num_bits(sensitive_data.host_key->n),
1111 BN_num_bits(sensitive_data.private_key->n),
1112 SSH_KEY_BITS_RESERVED);
1114 rsa_private_decrypt(session_key_int, session_key_int,
1115 sensitive_data.host_key);
1116 rsa_private_decrypt(session_key_int, session_key_int,
1117 sensitive_data.private_key);
1120 compute_session_id(session_id, cookie,
1121 sensitive_data.host_key->n,
1122 sensitive_data.private_key->n);
1124 /* Destroy the private and public keys. They will no longer be needed. */
1125 destroy_sensitive_data();
1128 * Extract session key from the decrypted integer. The key is in the
1129 * least significant 256 bits of the integer; the first byte of the
1130 * key is in the highest bits.
1132 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1133 len = BN_num_bytes(session_key_int);
1134 if (len < 0 || len > sizeof(session_key))
1135 fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d",
1136 get_remote_ipaddr(),
1137 len, sizeof(session_key));
1138 memset(session_key, 0, sizeof(session_key));
1139 BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len);
1141 /* Destroy the decrypted integer. It is no longer needed. */
1142 BN_clear_free(session_key_int);
1144 /* Xor the first 16 bytes of the session key with the session id. */
1145 for (i = 0; i < 16; i++)
1146 session_key[i] ^= session_id[i];
1148 /* Set the session key. From this on all communications will be encrypted. */
1149 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1151 /* Destroy our copy of the session key. It is no longer needed. */
1152 memset(session_key, 0, sizeof(session_key));
1154 debug("Received session key; encryption turned on.");
1156 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1157 packet_start(SSH_SMSG_SUCCESS);
1159 packet_write_wait();
1163 * SSH2 key exchange: diffie-hellman-group1-sha1
1168 Buffer *server_kexinit;
1169 Buffer *client_kexinit;
1170 int payload_len, dlen;
1172 unsigned int klen, kout;
1174 unsigned char *signature = NULL;
1175 unsigned char *server_host_key_blob = NULL;
1176 unsigned int sbloblen;
1178 BIGNUM *dh_client_pub = 0;
1179 BIGNUM *shared_secret = 0;
1181 unsigned char *kbuf;
1182 unsigned char *hash;
1184 char *cprop[PROPOSAL_MAX];
1185 char *sprop[PROPOSAL_MAX];
1189 if (options.ciphers != NULL) {
1190 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1191 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1194 debug("Sending KEX init.");
1196 for (i = 0; i < PROPOSAL_MAX; i++)
1197 sprop[i] = xstrdup(myproposal[i]);
1198 server_kexinit = kex_init(sprop);
1199 packet_start(SSH2_MSG_KEXINIT);
1200 packet_put_raw(buffer_ptr(server_kexinit), buffer_len(server_kexinit));
1202 packet_write_wait();
1206 packet_read_expect(&payload_len, SSH2_MSG_KEXINIT);
1209 * save raw KEXINIT payload in buffer. this is used during
1210 * computation of the session_id and the session keys.
1212 client_kexinit = xmalloc(sizeof(*client_kexinit));
1213 buffer_init(client_kexinit);
1214 ptr = packet_get_raw(&payload_len);
1215 buffer_append(client_kexinit, ptr, payload_len);
1218 for (i = 0; i < 16; i++)
1219 (void) packet_get_char();
1220 /* save kex init proposal strings */
1221 for (i = 0; i < PROPOSAL_MAX; i++) {
1222 cprop[i] = packet_get_string(NULL);
1223 debug("got kexinit string: %s", cprop[i]);
1226 i = (int) packet_get_char();
1227 debug("first kex follow == %d", i);
1228 i = packet_get_int();
1229 debug("reserved == %d", i);
1231 debug("done read kexinit");
1232 kex = kex_choose_conf(cprop, sprop, 1);
1236 debug("Wait SSH2_MSG_KEXDH_INIT.");
1237 packet_read_expect(&payload_len, SSH2_MSG_KEXDH_INIT);
1240 dh_client_pub = BN_new();
1241 if (dh_client_pub == NULL)
1242 fatal("dh_client_pub == NULL");
1243 packet_get_bignum2(dh_client_pub, &dlen);
1246 fprintf(stderr, "\ndh_client_pub= ");
1247 bignum_print(dh_client_pub);
1248 fprintf(stderr, "\n");
1249 debug("bits %d", BN_num_bits(dh_client_pub));
1252 /* generate DH key */
1253 dh = dh_new_group1(); /* XXX depends on 'kex' */
1256 fprintf(stderr, "\np= ");
1257 bignum_print(dh->p);
1258 fprintf(stderr, "\ng= ");
1259 bignum_print(dh->g);
1260 fprintf(stderr, "\npub= ");
1261 bignum_print(dh->pub_key);
1262 fprintf(stderr, "\n");
1264 if (!dh_pub_is_valid(dh, dh_client_pub))
1265 packet_disconnect("bad client public DH value");
1268 kbuf = xmalloc(klen);
1269 kout = DH_compute_key(kbuf, dh_client_pub, dh);
1272 debug("shared secret: len %d/%d", klen, kout);
1273 fprintf(stderr, "shared secret == ");
1274 for (i = 0; i< kout; i++)
1275 fprintf(stderr, "%02x", (kbuf[i])&0xff);
1276 fprintf(stderr, "\n");
1278 shared_secret = BN_new();
1280 BN_bin2bn(kbuf, kout, shared_secret);
1281 memset(kbuf, 0, klen);
1284 /* XXX precompute? */
1285 dsa_make_key_blob(sensitive_data.dsa_host_key, &server_host_key_blob, &sbloblen);
1287 /* calc H */ /* XXX depends on 'kex' */
1289 client_version_string,
1290 server_version_string,
1291 buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1292 buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1293 (char *)server_host_key_blob, sbloblen,
1298 buffer_free(client_kexinit);
1299 buffer_free(server_kexinit);
1300 xfree(client_kexinit);
1301 xfree(server_kexinit);
1303 fprintf(stderr, "hash == ");
1304 for (i = 0; i< 20; i++)
1305 fprintf(stderr, "%02x", (hash[i])&0xff);
1306 fprintf(stderr, "\n");
1308 /* save session id := H */
1309 /* XXX hashlen depends on KEX */
1310 session_id2_len = 20;
1311 session_id2 = xmalloc(session_id2_len);
1312 memcpy(session_id2, hash, session_id2_len);
1315 /* XXX hashlen depends on KEX */
1316 dsa_sign(sensitive_data.dsa_host_key, &signature, &slen, hash, 20);
1318 destroy_sensitive_data();
1320 /* send server hostkey, DH pubkey 'f' and singed H */
1321 packet_start(SSH2_MSG_KEXDH_REPLY);
1322 packet_put_string((char *)server_host_key_blob, sbloblen);
1323 packet_put_bignum2(dh->pub_key); // f
1324 packet_put_string((char *)signature, slen);
1327 xfree(server_host_key_blob);
1328 packet_write_wait();
1330 kex_derive_keys(kex, hash, shared_secret);
1331 packet_set_kex(kex);
1333 /* have keys, free DH */
1336 debug("send SSH2_MSG_NEWKEYS.");
1337 packet_start(SSH2_MSG_NEWKEYS);
1339 packet_write_wait();
1340 debug("done: send SSH2_MSG_NEWKEYS.");
1342 debug("Wait SSH2_MSG_NEWKEYS.");
1343 packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS);
1344 debug("GOT SSH2_MSG_NEWKEYS.");
1347 /* send 1st encrypted/maced/compressed message */
1348 packet_start(SSH2_MSG_IGNORE);
1349 packet_put_cstring("markus");
1351 packet_write_wait();
1353 debug("done: KEX2.");