2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * This program is the ssh daemon. It listens for connections from clients,
6 * and performs authentication, executes use commands or shell, and forwards
7 * information to/from the application to the user client over an encrypted
8 * connection. This can also handle forwarding of X11, TCP/IP, and
9 * authentication agent connections.
11 * As far as I am concerned, the code I have written for this software
12 * can be used freely for any purpose. Any derived versions of this
13 * software must be clearly marked as such, and if the derived work is
14 * incompatible with the protocol description in the RFC file, it must be
15 * called by a name other than "ssh" or "Secure Shell".
17 * SSH2 implementation:
19 * Copyright (c) 2000 Markus Friedl. All rights reserved.
21 * Redistribution and use in source and binary forms, with or without
22 * modification, are permitted provided that the following conditions
24 * 1. Redistributions of source code must retain the above copyright
25 * notice, this list of conditions and the following disclaimer.
26 * 2. Redistributions in binary form must reproduce the above copyright
27 * notice, this list of conditions and the following disclaimer in the
28 * documentation and/or other materials provided with the distribution.
30 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
31 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
32 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
33 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
34 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
35 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
36 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
37 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
38 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
39 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
43 RCSID("$OpenBSD: sshd.c,v 1.209 2001/11/10 13:19:45 markus Exp $");
45 #include <openssl/dh.h>
46 #include <openssl/bn.h>
47 #include <openssl/hmac.h>
66 #include "myproposal.h"
68 #include "pathnames.h"
79 int allow_severity = LOG_INFO;
80 int deny_severity = LOG_WARNING;
87 #ifdef HAVE___PROGNAME
88 extern char *__progname;
93 /* Server configuration options. */
94 ServerOptions options;
96 /* Name of the server configuration file. */
97 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
100 * Flag indicating whether IPv4 or IPv6. This can be set on the command line.
101 * Default value is AF_UNSPEC means both IPv4 and IPv6.
104 int IPv4or6 = AF_INET;
106 int IPv4or6 = AF_UNSPEC;
110 * Debug mode flag. This can be set on the command line. If debug
111 * mode is enabled, extra debugging output will be sent to the system
112 * log, the daemon will not go to background, and will exit after processing
113 * the first connection.
117 /* Flag indicating that the daemon should only test the configuration and keys. */
120 /* Flag indicating that the daemon is being started from inetd. */
123 /* Flag indicating that sshd should not detach and become a daemon. */
124 int no_daemon_flag = 0;
126 /* debug goes to stderr unless inetd_flag is set */
129 /* Saved arguments to main(). */
134 * The sockets that the server is listening; this is used in the SIGHUP
137 #define MAX_LISTEN_SOCKS 16
138 int listen_socks[MAX_LISTEN_SOCKS];
139 int num_listen_socks = 0;
142 * the client's version string, passed by sshd2 in compat mode. if != NULL,
143 * sshd will skip the version-number exchange
145 char *client_version_string = NULL;
146 char *server_version_string = NULL;
148 /* for rekeying XXX fixme */
152 * Any really sensitive data in the application is contained in this
153 * structure. The idea is that this structure could be locked into memory so
154 * that the pages do not get written into swap. However, there are some
155 * problems. The private key contains BIGNUMs, and we do not (in principle)
156 * have access to the internals of them, and locking just the structure is
157 * not very useful. Currently, memory locking is not implemented.
160 Key *server_key; /* ephemeral server key */
161 Key *ssh1_host_key; /* ssh1 host key */
162 Key **host_keys; /* all private host keys */
165 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
169 * Flag indicating whether the RSA server key needs to be regenerated.
170 * Is set in the SIGALRM handler and cleared when the key is regenerated.
172 int key_do_regen = 0;
174 /* This is set to true when a signal is received. */
175 int received_sighup = 0;
176 int received_sigterm = 0;
178 /* session identifier, used by RSA-auth */
179 u_char session_id[16];
182 u_char *session_id2 = NULL;
183 int session_id2_len = 0;
185 /* record remote hostname or ip */
186 u_int utmp_len = MAXHOSTNAMELEN;
188 /* Prototypes for various functions defined later in this file. */
189 void destroy_sensitive_data(void);
191 static void do_ssh1_kex(void);
192 static void do_ssh2_kex(void);
195 * Close all listening sockets
198 close_listen_socks(void)
201 for (i = 0; i < num_listen_socks; i++)
202 close(listen_socks[i]);
203 num_listen_socks = -1;
207 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
208 * the effect is to reread the configuration file (and to regenerate
212 sighup_handler(int sig)
215 signal(SIGHUP, sighup_handler);
219 * Called from the main program after receiving SIGHUP.
220 * Restarts the server.
225 log("Received SIGHUP; restarting.");
226 close_listen_socks();
227 execv(saved_argv[0], saved_argv);
228 log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], strerror(errno));
233 * Generic signal handler for terminating signals in the master daemon.
236 sigterm_handler(int sig)
238 received_sigterm = sig;
242 * SIGCHLD handler. This is called whenever a child dies. This will then
243 * reap any zombies left by exited children.
246 main_sigchld_handler(int sig)
248 int save_errno = errno;
251 while (waitpid(-1, &status, WNOHANG) > 0)
254 signal(SIGCHLD, main_sigchld_handler);
259 * Signal handler for the alarm after the login grace period has expired.
262 grace_alarm_handler(int sig)
264 /* XXX no idea how fix this signal handler */
266 /* Close the connection. */
269 /* Log error and exit. */
270 fatal("Timeout before authentication for %s.", get_remote_ipaddr());
274 * Signal handler for the key regeneration alarm. Note that this
275 * alarm only occurs in the daemon waiting for connections, and it does not
276 * do anything with the private key or random state before forking.
277 * Thus there should be no concurrency control/asynchronous execution
281 generate_ephemeral_server_key(void)
286 verbose("Generating %s%d bit RSA key.",
287 sensitive_data.server_key ? "new " : "", options.server_key_bits);
288 if (sensitive_data.server_key != NULL)
289 key_free(sensitive_data.server_key);
290 sensitive_data.server_key = key_generate(KEY_RSA1,
291 options.server_key_bits);
292 verbose("RSA key generation complete.");
294 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
297 sensitive_data.ssh1_cookie[i] = rand & 0xff;
304 key_regeneration_alarm(int sig)
306 int save_errno = errno;
307 signal(SIGALRM, SIG_DFL);
313 sshd_exchange_identification(int sock_in, int sock_out)
316 int remote_major, remote_minor;
319 char buf[256]; /* Must not be larger than remote_version. */
320 char remote_version[256]; /* Must be at least as big as buf. */
322 if ((options.protocol & SSH_PROTO_1) &&
323 (options.protocol & SSH_PROTO_2)) {
324 major = PROTOCOL_MAJOR_1;
326 } else if (options.protocol & SSH_PROTO_2) {
327 major = PROTOCOL_MAJOR_2;
328 minor = PROTOCOL_MINOR_2;
330 major = PROTOCOL_MAJOR_1;
331 minor = PROTOCOL_MINOR_1;
333 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
334 server_version_string = xstrdup(buf);
336 if (client_version_string == NULL) {
337 /* Send our protocol version identification. */
338 if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
339 != strlen(server_version_string)) {
340 log("Could not write ident string to %s", get_remote_ipaddr());
344 /* Read other side's version identification. */
345 memset(buf, 0, sizeof(buf));
346 for (i = 0; i < sizeof(buf) - 1; i++) {
347 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
348 log("Did not receive identification string from %s",
349 get_remote_ipaddr());
352 if (buf[i] == '\r') {
354 /* Kludge for F-Secure Macintosh < 1.0.2 */
356 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
360 if (buf[i] == '\n') {
365 buf[sizeof(buf) - 1] = 0;
366 client_version_string = xstrdup(buf);
370 * Check that the versions match. In future this might accept
371 * several versions and set appropriate flags to handle them.
373 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
374 &remote_major, &remote_minor, remote_version) != 3) {
375 s = "Protocol mismatch.\n";
376 (void) atomicio(write, sock_out, s, strlen(s));
379 log("Bad protocol version identification '%.100s' from %s",
380 client_version_string, get_remote_ipaddr());
383 debug("Client protocol version %d.%d; client software version %.100s",
384 remote_major, remote_minor, remote_version);
386 compat_datafellows(remote_version);
388 if (datafellows & SSH_BUG_SCANNER) {
389 log("scanned from %s with %s. Don't panic.",
390 get_remote_ipaddr(), client_version_string);
395 switch(remote_major) {
397 if (remote_minor == 99) {
398 if (options.protocol & SSH_PROTO_2)
404 if (!(options.protocol & SSH_PROTO_1)) {
408 if (remote_minor < 3) {
409 packet_disconnect("Your ssh version is too old and "
410 "is no longer supported. Please install a newer version.");
411 } else if (remote_minor == 3) {
412 /* note that this disables agent-forwarding */
417 if (options.protocol & SSH_PROTO_2) {
426 chop(server_version_string);
427 debug("Local version string %.200s", server_version_string);
430 s = "Protocol major versions differ.\n";
431 (void) atomicio(write, sock_out, s, strlen(s));
434 log("Protocol major versions differ for %s: %.200s vs. %.200s",
436 server_version_string, client_version_string);
442 /* Destroy the host and server keys. They will no longer be needed. */
444 destroy_sensitive_data(void)
448 if (sensitive_data.server_key) {
449 key_free(sensitive_data.server_key);
450 sensitive_data.server_key = NULL;
452 for(i = 0; i < options.num_host_key_files; i++) {
453 if (sensitive_data.host_keys[i]) {
454 key_free(sensitive_data.host_keys[i]);
455 sensitive_data.host_keys[i] = NULL;
458 sensitive_data.ssh1_host_key = NULL;
459 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
463 list_hostkey_types(void)
465 static char buf[1024];
468 for(i = 0; i < options.num_host_key_files; i++) {
469 Key *key = sensitive_data.host_keys[i];
475 strlcat(buf, key_ssh_name(key), sizeof buf);
476 strlcat(buf, ",", sizeof buf);
481 if (i > 0 && buf[i-1] == ',')
483 debug("list_hostkey_types: %s", buf);
488 get_hostkey_by_type(int type)
491 for(i = 0; i < options.num_host_key_files; i++) {
492 Key *key = sensitive_data.host_keys[i];
493 if (key != NULL && key->type == type)
500 * returns 1 if connection should be dropped, 0 otherwise.
501 * dropping starts at connection #max_startups_begin with a probability
502 * of (max_startups_rate/100). the probability increases linearly until
503 * all connections are dropped for startups > max_startups
506 drop_connection(int startups)
510 if (startups < options.max_startups_begin)
512 if (startups >= options.max_startups)
514 if (options.max_startups_rate == 100)
517 p = 100 - options.max_startups_rate;
518 p *= startups - options.max_startups_begin;
519 p /= (double) (options.max_startups - options.max_startups_begin);
520 p += options.max_startups_rate;
522 r = arc4random() / (double) UINT_MAX;
524 debug("drop_connection: p %g, r %g", p, r);
525 return (r < p) ? 1 : 0;
528 int *startup_pipes = NULL; /* options.max_startup sized array of fd ints */
529 int startup_pipe; /* in child */
532 * Main program for the daemon.
535 main(int ac, char **av)
539 int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
543 struct sockaddr_storage from;
544 const char *remote_ip;
547 struct linger linger;
549 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
550 int listen_sock, maxfd;
554 int ret, key_used = 0;
556 __progname = get_progname(av[0]);
563 /* Initialize configuration options to their default values. */
564 initialize_server_options(&options);
566 /* Parse command-line arguments. */
567 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:dDeiqtQ46")) != -1) {
576 config_file_name = optarg;
579 if (0 == debug_flag) {
581 options.log_level = SYSLOG_LEVEL_DEBUG1;
582 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
585 fprintf(stderr, "Too high debugging level.\n");
602 options.log_level = SYSLOG_LEVEL_QUIET;
605 options.server_key_bits = atoi(optarg);
608 options.ports_from_cmdline = 1;
609 if (options.num_ports >= MAX_PORTS) {
610 fprintf(stderr, "too many ports.\n");
613 options.ports[options.num_ports++] = a2port(optarg);
614 if (options.ports[options.num_ports-1] == 0) {
615 fprintf(stderr, "Bad port number.\n");
620 if ((options.login_grace_time = convtime(optarg)) == -1) {
621 fprintf(stderr, "Invalid login grace time.\n");
626 if ((options.key_regeneration_time = convtime(optarg)) == -1) {
627 fprintf(stderr, "Invalid key regeneration interval.\n");
632 if (options.num_host_key_files >= MAX_HOSTKEYS) {
633 fprintf(stderr, "too many host keys.\n");
636 options.host_key_files[options.num_host_key_files++] = optarg;
639 client_version_string = optarg;
640 /* only makes sense with inetd_flag, i.e. no listen() */
647 utmp_len = atoi(optarg);
651 fprintf(stderr, "sshd version %s\n", SSH_VERSION);
652 fprintf(stderr, "Usage: %s [options]\n", __progname);
653 fprintf(stderr, "Options:\n");
654 fprintf(stderr, " -f file Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE);
655 fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n");
656 fprintf(stderr, " -i Started from inetd\n");
657 fprintf(stderr, " -D Do not fork into daemon mode\n");
658 fprintf(stderr, " -t Only test configuration file and keys\n");
659 fprintf(stderr, " -q Quiet (no logging)\n");
660 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
661 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
662 fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n");
663 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
664 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
665 _PATH_HOST_KEY_FILE);
666 fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
667 fprintf(stderr, " -4 Use IPv4 only\n");
668 fprintf(stderr, " -6 Use IPv6 only\n");
672 SSLeay_add_all_algorithms();
673 channel_set_af(IPv4or6);
676 * Force logging to stderr until we have loaded the private host
677 * key (unless started from inetd)
680 options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
681 options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
685 /* Cray can define user privs drop all prives now!
686 * Not needed on PRIV_SU systems!
693 /* Read server configuration options from the configuration file. */
694 read_server_config(&options, config_file_name);
696 /* Fill in default values for those options not explicitly set. */
697 fill_default_server_options(&options);
699 /* Check that there are no remaining arguments. */
701 fprintf(stderr, "Extra argument %s.\n", av[optind]);
705 debug("sshd version %.100s", SSH_VERSION);
707 /* load private host keys */
708 sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*));
709 for(i = 0; i < options.num_host_key_files; i++)
710 sensitive_data.host_keys[i] = NULL;
711 sensitive_data.server_key = NULL;
712 sensitive_data.ssh1_host_key = NULL;
713 sensitive_data.have_ssh1_key = 0;
714 sensitive_data.have_ssh2_key = 0;
716 for(i = 0; i < options.num_host_key_files; i++) {
717 key = key_load_private(options.host_key_files[i], "", NULL);
718 sensitive_data.host_keys[i] = key;
720 error("Could not load host key: %s",
721 options.host_key_files[i]);
722 sensitive_data.host_keys[i] = NULL;
727 sensitive_data.ssh1_host_key = key;
728 sensitive_data.have_ssh1_key = 1;
732 sensitive_data.have_ssh2_key = 1;
735 debug("private host key: #%d type %d %s", i, key->type,
738 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
739 log("Disabling protocol version 1. Could not load host key");
740 options.protocol &= ~SSH_PROTO_1;
742 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
743 log("Disabling protocol version 2. Could not load host key");
744 options.protocol &= ~SSH_PROTO_2;
746 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
747 log("sshd: no hostkeys available -- exiting.");
751 /* Check certain values for sanity. */
752 if (options.protocol & SSH_PROTO_1) {
753 if (options.server_key_bits < 512 ||
754 options.server_key_bits > 32768) {
755 fprintf(stderr, "Bad server key size.\n");
759 * Check that server and host key lengths differ sufficiently. This
760 * is necessary to make double encryption work with rsaref. Oh, I
761 * hate software patents. I dont know if this can go? Niels
763 if (options.server_key_bits >
764 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - SSH_KEY_BITS_RESERVED &&
765 options.server_key_bits <
766 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
767 options.server_key_bits =
768 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED;
769 debug("Forcing server key to %d bits to make it differ from host key.",
770 options.server_key_bits);
774 /* Configuration looks good, so exit if in test mode. */
778 #ifdef HAVE_SCO_PROTECTED_PW
779 (void) set_auth_parameters(ac, av);
782 /* Initialize the log (it is reinitialized below in case we forked). */
783 if (debug_flag && !inetd_flag)
785 log_init(__progname, options.log_level, options.log_facility, log_stderr);
788 * If not in debugging mode, and not started from inetd, disconnect
789 * from the controlling terminal, and fork. The original process
792 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
795 #endif /* TIOCNOTTY */
796 if (daemon(0, 0) < 0)
797 fatal("daemon() failed: %.200s", strerror(errno));
799 /* Disconnect from the controlling tty. */
801 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
803 (void) ioctl(fd, TIOCNOTTY, NULL);
806 #endif /* TIOCNOTTY */
808 /* Reinitialize the log (because of the fork above). */
809 log_init(__progname, options.log_level, options.log_facility, log_stderr);
811 /* Initialize the random number generator. */
814 /* Chdir to the root directory so that the current disk can be
815 unmounted if desired. */
819 signal(SIGPIPE, SIG_IGN);
821 /* Start listening for a socket, unless started from inetd. */
824 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
830 * We intentionally do not close the descriptors 0, 1, and 2
831 * as our code for setting the descriptors won\'t work if
832 * ttyfd happens to be one of those.
834 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
835 if (options.protocol & SSH_PROTO_1)
836 generate_ephemeral_server_key();
838 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
839 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
841 if (num_listen_socks >= MAX_LISTEN_SOCKS)
842 fatal("Too many listen sockets. "
843 "Enlarge MAX_LISTEN_SOCKS");
844 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
845 ntop, sizeof(ntop), strport, sizeof(strport),
846 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
847 error("getnameinfo failed");
850 /* Create socket for listening. */
851 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
852 if (listen_sock < 0) {
853 /* kernel may not support ipv6 */
854 verbose("socket: %.100s", strerror(errno));
857 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
858 error("listen_sock O_NONBLOCK: %s", strerror(errno));
863 * Set socket options. We try to make the port
864 * reusable and have it close as fast as possible
865 * without waiting in unnecessary wait states on
868 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
869 (void *) &on, sizeof(on));
872 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
873 (void *) &linger, sizeof(linger));
875 debug("Bind to port %s on %s.", strport, ntop);
877 /* Bind the socket to the desired port. */
878 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
880 error("Bind to port %s on %s failed: %.200s.",
881 strport, ntop, strerror(errno));
885 listen_socks[num_listen_socks] = listen_sock;
888 /* Start listening on the port. */
889 log("Server listening on %s port %s.", ntop, strport);
890 if (listen(listen_sock, 5) < 0)
891 fatal("listen: %.100s", strerror(errno));
894 freeaddrinfo(options.listen_addrs);
896 if (!num_listen_socks)
897 fatal("Cannot bind any address.");
899 if (options.protocol & SSH_PROTO_1)
900 generate_ephemeral_server_key();
903 * Arrange to restart on SIGHUP. The handler needs
906 signal(SIGHUP, sighup_handler);
908 signal(SIGTERM, sigterm_handler);
909 signal(SIGQUIT, sigterm_handler);
911 /* Arrange SIGCHLD to be caught. */
912 signal(SIGCHLD, main_sigchld_handler);
914 /* Write out the pid file after the sigterm handler is setup */
917 * Record our pid in /var/run/sshd.pid to make it
918 * easier to kill the correct sshd. We don't want to
919 * do this before the bind above because the bind will
920 * fail if there already is a daemon, and this will
921 * overwrite any old pid in the file.
923 f = fopen(options.pid_file, "wb");
925 fprintf(f, "%u\n", (u_int) getpid());
930 /* setup fd set for listen */
933 for (i = 0; i < num_listen_socks; i++)
934 if (listen_socks[i] > maxfd)
935 maxfd = listen_socks[i];
936 /* pipes connected to unauthenticated childs */
937 startup_pipes = xmalloc(options.max_startups * sizeof(int));
938 for (i = 0; i < options.max_startups; i++)
939 startup_pipes[i] = -1;
942 * Stay listening for connections until the system crashes or
943 * the daemon is killed with a signal.
950 fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
951 fdset = (fd_set *)xmalloc(fdsetsz);
952 memset(fdset, 0, fdsetsz);
954 for (i = 0; i < num_listen_socks; i++)
955 FD_SET(listen_socks[i], fdset);
956 for (i = 0; i < options.max_startups; i++)
957 if (startup_pipes[i] != -1)
958 FD_SET(startup_pipes[i], fdset);
960 /* Wait in select until there is a connection. */
961 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
962 if (ret < 0 && errno != EINTR)
963 error("select: %.100s", strerror(errno));
964 if (received_sigterm) {
965 log("Received signal %d; terminating.",
967 close_listen_socks();
968 unlink(options.pid_file);
971 if (key_used && key_do_regen) {
972 generate_ephemeral_server_key();
979 for (i = 0; i < options.max_startups; i++)
980 if (startup_pipes[i] != -1 &&
981 FD_ISSET(startup_pipes[i], fdset)) {
983 * the read end of the pipe is ready
984 * if the child has closed the pipe
985 * after successful authentication
986 * or if the child has died
988 close(startup_pipes[i]);
989 startup_pipes[i] = -1;
992 for (i = 0; i < num_listen_socks; i++) {
993 if (!FD_ISSET(listen_socks[i], fdset))
995 fromlen = sizeof(from);
996 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
999 if (errno != EINTR && errno != EWOULDBLOCK)
1000 error("accept: %.100s", strerror(errno));
1003 if (fcntl(newsock, F_SETFL, 0) < 0) {
1004 error("newsock del O_NONBLOCK: %s", strerror(errno));
1007 if (drop_connection(startups) == 1) {
1008 debug("drop connection #%d", startups);
1012 if (pipe(startup_p) == -1) {
1017 for (j = 0; j < options.max_startups; j++)
1018 if (startup_pipes[j] == -1) {
1019 startup_pipes[j] = startup_p[0];
1020 if (maxfd < startup_p[0])
1021 maxfd = startup_p[0];
1027 * Got connection. Fork a child to handle it, unless
1028 * we are in debugging mode.
1032 * In debugging mode. Close the listening
1033 * socket, and start processing the
1034 * connection without forking.
1036 debug("Server will not fork when running in debugging mode.");
1037 close_listen_socks();
1045 * Normal production daemon. Fork, and have
1046 * the child process the connection. The
1047 * parent continues listening.
1049 if ((pid = fork()) == 0) {
1051 * Child. Close the listening and max_startup
1052 * sockets. Start using the accepted socket.
1053 * Reinitialize logging (since our pid has
1054 * changed). We break out of the loop to handle
1057 startup_pipe = startup_p[1];
1058 for (j = 0; j < options.max_startups; j++)
1059 if (startup_pipes[j] != -1)
1060 close(startup_pipes[j]);
1061 close_listen_socks();
1064 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1069 /* Parent. Stay in the loop. */
1071 error("fork: %.100s", strerror(errno));
1073 debug("Forked child %d.", pid);
1075 close(startup_p[1]);
1077 /* Mark that the key has been used (it was "given" to the child). */
1078 if ((options.protocol & SSH_PROTO_1) &&
1080 /* Schedule server key regeneration alarm. */
1081 signal(SIGALRM, key_regeneration_alarm);
1082 alarm(options.key_regeneration_time);
1088 /* Close the new socket (the child is now taking care of it). */
1091 /* child process check (or debug mode) */
1092 if (num_listen_socks < 0)
1097 /* This is the child processing a new connection. */
1100 * Disable the key regeneration alarm. We will not regenerate the
1101 * key since we are no longer in a position to give it to anyone. We
1102 * will not restart on SIGHUP since it no longer makes sense.
1105 signal(SIGALRM, SIG_DFL);
1106 signal(SIGHUP, SIG_DFL);
1107 signal(SIGTERM, SIG_DFL);
1108 signal(SIGQUIT, SIG_DFL);
1109 signal(SIGCHLD, SIG_DFL);
1110 signal(SIGINT, SIG_DFL);
1113 * Set socket options for the connection. We want the socket to
1114 * close as fast as possible without waiting for anything. If the
1115 * connection is not a socket, these will do nothing.
1117 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1119 linger.l_linger = 5;
1120 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
1122 /* Set keepalives if requested. */
1123 if (options.keepalives &&
1124 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
1126 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1129 * Register our connection. This turns encryption off because we do
1132 packet_set_connection(sock_in, sock_out);
1134 remote_port = get_remote_port();
1135 remote_ip = get_remote_ipaddr();
1138 /* Check whether logins are denied from this host. */
1140 struct request_info req;
1142 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
1145 if (!hosts_access(&req)) {
1146 debug("Connection refused by tcp wrapper");
1149 fatal("libwrap refuse returns");
1152 #endif /* LIBWRAP */
1154 /* Log the connection. */
1155 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1158 * We don\'t want to listen forever unless the other side
1159 * successfully authenticates itself. So we set up an alarm which is
1160 * cleared after successful authentication. A limit of zero
1161 * indicates no limit. Note that we don\'t set the alarm in debugging
1162 * mode; it is just annoying to have the server exit just when you
1163 * are about to discover the bug.
1165 signal(SIGALRM, grace_alarm_handler);
1167 alarm(options.login_grace_time);
1169 sshd_exchange_identification(sock_in, sock_out);
1171 * Check that the connection comes from a privileged port.
1172 * Rhosts-Authentication only makes sense from priviledged
1173 * programs. Of course, if the intruder has root access on his local
1174 * machine, he can connect from any port. So do not use these
1175 * authentication methods from machines that you do not trust.
1177 if (remote_port >= IPPORT_RESERVED ||
1178 remote_port < IPPORT_RESERVED / 2) {
1179 debug("Rhosts Authentication disabled, "
1180 "originating port %d not trusted.", remote_port);
1181 options.rhosts_authentication = 0;
1183 #if defined(KRB4) && !defined(KRB5)
1184 if (!packet_connection_is_ipv4() &&
1185 options.kerberos_authentication) {
1186 debug("Kerberos Authentication disabled, only available for IPv4.");
1187 options.kerberos_authentication = 0;
1189 #endif /* KRB4 && !KRB5 */
1191 /* If machine has AFS, set process authentication group. */
1198 packet_set_nonblocking();
1200 /* perform the key exchange */
1201 /* authenticate user and start session */
1204 do_authentication2();
1207 do_authentication();
1209 /* The connection has been terminated. */
1210 verbose("Closing connection to %.100s", remote_ip);
1214 #endif /* USE_PAM */
1229 BIGNUM *session_key_int;
1230 u_char session_key[SSH_SESSION_KEY_LENGTH];
1232 u_int cipher_type, auth_mask, protocol_flags;
1236 * Generate check bytes that the client must send back in the user
1237 * packet in order for it to be accepted; this is used to defy ip
1238 * spoofing attacks. Note that this only works against somebody
1239 * doing IP spoofing from a remote machine; any machine on the local
1240 * network can still see outgoing packets and catch the random
1241 * cookie. This only affects rhosts authentication, and this is one
1242 * of the reasons why it is inherently insecure.
1244 for (i = 0; i < 8; i++) {
1246 rand = arc4random();
1247 cookie[i] = rand & 0xff;
1252 * Send our public key. We include in the packet 64 bits of random
1253 * data that must be matched in the reply in order to prevent IP
1256 packet_start(SSH_SMSG_PUBLIC_KEY);
1257 for (i = 0; i < 8; i++)
1258 packet_put_char(cookie[i]);
1260 /* Store our public server RSA key. */
1261 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1262 packet_put_bignum(sensitive_data.server_key->rsa->e);
1263 packet_put_bignum(sensitive_data.server_key->rsa->n);
1265 /* Store our public host RSA key. */
1266 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1267 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1268 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1270 /* Put protocol flags. */
1271 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1273 /* Declare which ciphers we support. */
1274 packet_put_int(cipher_mask_ssh1(0));
1276 /* Declare supported authentication types. */
1278 if (options.rhosts_authentication)
1279 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1280 if (options.rhosts_rsa_authentication)
1281 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1282 if (options.rsa_authentication)
1283 auth_mask |= 1 << SSH_AUTH_RSA;
1284 #if defined(KRB4) || defined(KRB5)
1285 if (options.kerberos_authentication)
1286 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1288 #if defined(AFS) || defined(KRB5)
1289 if (options.kerberos_tgt_passing)
1290 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1293 if (options.afs_token_passing)
1294 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1296 if (options.challenge_response_authentication == 1)
1297 auth_mask |= 1 << SSH_AUTH_TIS;
1298 if (options.password_authentication)
1299 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1300 packet_put_int(auth_mask);
1302 /* Send the packet and wait for it to be sent. */
1304 packet_write_wait();
1306 debug("Sent %d bit server key and %d bit host key.",
1307 BN_num_bits(sensitive_data.server_key->rsa->n),
1308 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1310 /* Read clients reply (cipher type and session key). */
1311 packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1313 /* Get cipher type and check whether we accept this. */
1314 cipher_type = packet_get_char();
1316 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1317 packet_disconnect("Warning: client selects unsupported cipher.");
1319 /* Get check bytes from the packet. These must match those we
1320 sent earlier with the public key packet. */
1321 for (i = 0; i < 8; i++)
1322 if (cookie[i] != packet_get_char())
1323 packet_disconnect("IP Spoofing check bytes do not match.");
1325 debug("Encryption type: %.200s", cipher_name(cipher_type));
1327 /* Get the encrypted integer. */
1328 session_key_int = BN_new();
1329 packet_get_bignum(session_key_int, &slen);
1331 protocol_flags = packet_get_int();
1332 packet_set_protocol_flags(protocol_flags);
1334 packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1337 * Decrypt it using our private server key and private host key (key
1338 * with larger modulus first).
1340 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1341 /* Server key has bigger modulus. */
1342 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1343 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1344 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1345 get_remote_ipaddr(),
1346 BN_num_bits(sensitive_data.server_key->rsa->n),
1347 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1348 SSH_KEY_BITS_RESERVED);
1350 if (rsa_private_decrypt(session_key_int, session_key_int,
1351 sensitive_data.server_key->rsa) <= 0)
1353 if (rsa_private_decrypt(session_key_int, session_key_int,
1354 sensitive_data.ssh1_host_key->rsa) <= 0)
1357 /* Host key has bigger modulus (or they are equal). */
1358 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1359 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1360 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1361 get_remote_ipaddr(),
1362 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1363 BN_num_bits(sensitive_data.server_key->rsa->n),
1364 SSH_KEY_BITS_RESERVED);
1366 if (rsa_private_decrypt(session_key_int, session_key_int,
1367 sensitive_data.ssh1_host_key->rsa) < 0)
1369 if (rsa_private_decrypt(session_key_int, session_key_int,
1370 sensitive_data.server_key->rsa) < 0)
1374 * Extract session key from the decrypted integer. The key is in the
1375 * least significant 256 bits of the integer; the first byte of the
1376 * key is in the highest bits.
1379 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1380 len = BN_num_bytes(session_key_int);
1381 if (len < 0 || len > sizeof(session_key)) {
1382 error("do_connection: bad session key len from %s: "
1383 "session_key_int %d > sizeof(session_key) %lu",
1384 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
1387 memset(session_key, 0, sizeof(session_key));
1388 BN_bn2bin(session_key_int,
1389 session_key + sizeof(session_key) - len);
1391 compute_session_id(session_id, cookie,
1392 sensitive_data.ssh1_host_key->rsa->n,
1393 sensitive_data.server_key->rsa->n);
1395 * Xor the first 16 bytes of the session key with the
1398 for (i = 0; i < 16; i++)
1399 session_key[i] ^= session_id[i];
1403 int bytes = BN_num_bytes(session_key_int);
1404 char *buf = xmalloc(bytes);
1407 log("do_connection: generating a fake encryption key");
1408 BN_bn2bin(session_key_int, buf);
1410 MD5_Update(&md, buf, bytes);
1411 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1412 MD5_Final(session_key, &md);
1414 MD5_Update(&md, session_key, 16);
1415 MD5_Update(&md, buf, bytes);
1416 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1417 MD5_Final(session_key + 16, &md);
1418 memset(buf, 0, bytes);
1420 for (i = 0; i < 16; i++)
1421 session_id[i] = session_key[i] ^ session_key[i + 16];
1423 /* Destroy the private and public keys. They will no longer be needed. */
1424 destroy_sensitive_data();
1426 /* Destroy the decrypted integer. It is no longer needed. */
1427 BN_clear_free(session_key_int);
1429 /* Set the session key. From this on all communications will be encrypted. */
1430 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1432 /* Destroy our copy of the session key. It is no longer needed. */
1433 memset(session_key, 0, sizeof(session_key));
1435 debug("Received session key; encryption turned on.");
1437 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1438 packet_start(SSH_SMSG_SUCCESS);
1440 packet_write_wait();
1444 * SSH2 key exchange: diffie-hellman-group1-sha1
1451 if (options.ciphers != NULL) {
1452 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1453 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1455 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1456 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
1457 myproposal[PROPOSAL_ENC_ALGS_STOC] =
1458 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
1460 if (options.macs != NULL) {
1461 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
1462 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
1464 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
1466 /* start key exchange */
1467 kex = kex_setup(myproposal);
1469 kex->client_version_string=client_version_string;
1470 kex->server_version_string=server_version_string;
1471 kex->load_host_key=&get_hostkey_by_type;
1475 dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
1477 session_id2 = kex->session_id;
1478 session_id2_len = kex->session_id_len;
1481 /* send 1st encrypted/maced/compressed message */
1482 packet_start(SSH2_MSG_IGNORE);
1483 packet_put_cstring("markus");
1485 packet_write_wait();