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 1.203 2001/07/26 17:18:22 stevesk Exp $");
45 #include <openssl/dh.h>
46 #include <openssl/bn.h>
47 #include <openssl/hmac.h>
66 #include "myproposal.h"
68 #include "pathnames.h"
78 int allow_severity = LOG_INFO;
79 int deny_severity = LOG_WARNING;
86 #ifdef HAVE___PROGNAME
87 extern char *__progname;
92 /* Server configuration options. */
93 ServerOptions options;
95 /* Name of the server configuration file. */
96 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
99 * Flag indicating whether IPv4 or IPv6. This can be set on the command line.
100 * Default value is AF_UNSPEC means both IPv4 and IPv6.
103 int IPv4or6 = AF_INET;
105 int IPv4or6 = AF_UNSPEC;
109 * Debug mode flag. This can be set on the command line. If debug
110 * mode is enabled, extra debugging output will be sent to the system
111 * log, the daemon will not go to background, and will exit after processing
112 * the first connection.
116 /* Flag indicating that the daemon should only test the configuration and keys. */
119 /* Flag indicating that the daemon is being started from inetd. */
122 /* Flag indicating that sshd should not detach and become a daemon. */
123 int no_daemon_flag = 0;
125 /* debug goes to stderr unless inetd_flag is set */
128 /* Saved arguments to main(). */
133 * The sockets that the server is listening; this is used in the SIGHUP
136 #define MAX_LISTEN_SOCKS 16
137 int listen_socks[MAX_LISTEN_SOCKS];
138 int num_listen_socks = 0;
141 * the client's version string, passed by sshd2 in compat mode. if != NULL,
142 * sshd will skip the version-number exchange
144 char *client_version_string = NULL;
145 char *server_version_string = NULL;
147 /* for rekeying XXX fixme */
151 * Any really sensitive data in the application is contained in this
152 * structure. The idea is that this structure could be locked into memory so
153 * that the pages do not get written into swap. However, there are some
154 * problems. The private key contains BIGNUMs, and we do not (in principle)
155 * have access to the internals of them, and locking just the structure is
156 * not very useful. Currently, memory locking is not implemented.
159 Key *server_key; /* ephemeral server key */
160 Key *ssh1_host_key; /* ssh1 host key */
161 Key **host_keys; /* all private host keys */
164 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
168 * Flag indicating whether the RSA server key needs to be regenerated.
169 * Is set in the SIGALRM handler and cleared when the key is regenerated.
171 int key_do_regen = 0;
173 /* This is set to true when a signal is received. */
174 int received_sighup = 0;
175 int received_sigterm = 0;
177 /* session identifier, used by RSA-auth */
178 u_char session_id[16];
181 u_char *session_id2 = NULL;
182 int session_id2_len = 0;
184 /* record remote hostname or ip */
185 u_int utmp_len = MAXHOSTNAMELEN;
187 /* Prototypes for various functions defined later in this file. */
188 void destroy_sensitive_data(void);
190 static void do_ssh1_kex(void);
191 static void do_ssh2_kex(void);
194 * Close all listening sockets
197 close_listen_socks(void)
200 for (i = 0; i < num_listen_socks; i++)
201 close(listen_socks[i]);
202 num_listen_socks = -1;
206 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
207 * the effect is to reread the configuration file (and to regenerate
211 sighup_handler(int sig)
214 signal(SIGHUP, sighup_handler);
218 * Called from the main program after receiving SIGHUP.
219 * Restarts the server.
224 log("Received SIGHUP; restarting.");
225 close_listen_socks();
226 execv(saved_argv[0], saved_argv);
227 log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], strerror(errno));
232 * Generic signal handler for terminating signals in the master daemon.
235 sigterm_handler(int sig)
237 received_sigterm = sig;
241 * SIGCHLD handler. This is called whenever a child dies. This will then
242 * reap any zombies left by exited children.
245 main_sigchld_handler(int sig)
247 int save_errno = errno;
250 while (waitpid(-1, &status, WNOHANG) > 0)
253 signal(SIGCHLD, main_sigchld_handler);
258 * Signal handler for the alarm after the login grace period has expired.
261 grace_alarm_handler(int sig)
263 /* XXX no idea how fix this signal handler */
265 /* Close the connection. */
268 /* Log error and exit. */
269 fatal("Timeout before authentication for %s.", get_remote_ipaddr());
273 * Signal handler for the key regeneration alarm. Note that this
274 * alarm only occurs in the daemon waiting for connections, and it does not
275 * do anything with the private key or random state before forking.
276 * Thus there should be no concurrency control/asynchronous execution
280 generate_ephemeral_server_key(void)
285 verbose("Generating %s%d bit RSA key.",
286 sensitive_data.server_key ? "new " : "", options.server_key_bits);
287 if (sensitive_data.server_key != NULL)
288 key_free(sensitive_data.server_key);
289 sensitive_data.server_key = key_generate(KEY_RSA1,
290 options.server_key_bits);
291 verbose("RSA key generation complete.");
293 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
296 sensitive_data.ssh1_cookie[i] = rand & 0xff;
303 key_regeneration_alarm(int sig)
305 int save_errno = errno;
306 signal(SIGALRM, SIG_DFL);
312 sshd_exchange_identification(int sock_in, int sock_out)
315 int remote_major, remote_minor;
318 char buf[256]; /* Must not be larger than remote_version. */
319 char remote_version[256]; /* Must be at least as big as buf. */
321 if ((options.protocol & SSH_PROTO_1) &&
322 (options.protocol & SSH_PROTO_2)) {
323 major = PROTOCOL_MAJOR_1;
325 } else if (options.protocol & SSH_PROTO_2) {
326 major = PROTOCOL_MAJOR_2;
327 minor = PROTOCOL_MINOR_2;
329 major = PROTOCOL_MAJOR_1;
330 minor = PROTOCOL_MINOR_1;
332 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
333 server_version_string = xstrdup(buf);
335 if (client_version_string == NULL) {
336 /* Send our protocol version identification. */
337 if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
338 != strlen(server_version_string)) {
339 log("Could not write ident string to %s.", get_remote_ipaddr());
343 /* Read other side's version identification. */
344 memset(buf, 0, sizeof(buf));
345 for (i = 0; i < sizeof(buf) - 1; i++) {
346 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
347 log("Did not receive identification string from %s.",
348 get_remote_ipaddr());
351 if (buf[i] == '\r') {
353 /* Kludge for F-Secure Macintosh < 1.0.2 */
355 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
359 if (buf[i] == '\n') {
364 buf[sizeof(buf) - 1] = 0;
365 client_version_string = xstrdup(buf);
369 * Check that the versions match. In future this might accept
370 * several versions and set appropriate flags to handle them.
372 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
373 &remote_major, &remote_minor, remote_version) != 3) {
374 s = "Protocol mismatch.\n";
375 (void) atomicio(write, sock_out, s, strlen(s));
378 log("Bad protocol version identification '%.100s' from %s",
379 client_version_string, get_remote_ipaddr());
382 debug("Client protocol version %d.%d; client software version %.100s",
383 remote_major, remote_minor, remote_version);
385 compat_datafellows(remote_version);
387 if (datafellows & SSH_BUG_SCANNER) {
388 log("scanned from %s with %s. Don't panic.",
389 get_remote_ipaddr(), client_version_string);
394 switch(remote_major) {
396 if (remote_minor == 99) {
397 if (options.protocol & SSH_PROTO_2)
403 if (!(options.protocol & SSH_PROTO_1)) {
407 if (remote_minor < 3) {
408 packet_disconnect("Your ssh version is too old and "
409 "is no longer supported. Please install a newer version.");
410 } else if (remote_minor == 3) {
411 /* note that this disables agent-forwarding */
416 if (options.protocol & SSH_PROTO_2) {
425 chop(server_version_string);
426 debug("Local version string %.200s", server_version_string);
429 s = "Protocol major versions differ.\n";
430 (void) atomicio(write, sock_out, s, strlen(s));
433 log("Protocol major versions differ for %s: %.200s vs. %.200s",
435 server_version_string, client_version_string);
441 /* Destroy the host and server keys. They will no longer be needed. */
443 destroy_sensitive_data(void)
447 if (sensitive_data.server_key) {
448 key_free(sensitive_data.server_key);
449 sensitive_data.server_key = NULL;
451 for(i = 0; i < options.num_host_key_files; i++) {
452 if (sensitive_data.host_keys[i]) {
453 key_free(sensitive_data.host_keys[i]);
454 sensitive_data.host_keys[i] = NULL;
457 sensitive_data.ssh1_host_key = NULL;
458 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
462 list_hostkey_types(void)
464 static char buf[1024];
467 for(i = 0; i < options.num_host_key_files; i++) {
468 Key *key = sensitive_data.host_keys[i];
474 strlcat(buf, key_ssh_name(key), sizeof buf);
475 strlcat(buf, ",", sizeof buf);
480 if (i > 0 && buf[i-1] == ',')
482 debug("list_hostkey_types: %s", buf);
487 get_hostkey_by_type(int type)
490 for(i = 0; i < options.num_host_key_files; i++) {
491 Key *key = sensitive_data.host_keys[i];
492 if (key != NULL && key->type == type)
499 * returns 1 if connection should be dropped, 0 otherwise.
500 * dropping starts at connection #max_startups_begin with a probability
501 * of (max_startups_rate/100). the probability increases linearly until
502 * all connections are dropped for startups > max_startups
505 drop_connection(int startups)
509 if (startups < options.max_startups_begin)
511 if (startups >= options.max_startups)
513 if (options.max_startups_rate == 100)
516 p = 100 - options.max_startups_rate;
517 p *= startups - options.max_startups_begin;
518 p /= (double) (options.max_startups - options.max_startups_begin);
519 p += options.max_startups_rate;
521 r = arc4random() / (double) UINT_MAX;
523 debug("drop_connection: p %g, r %g", p, r);
524 return (r < p) ? 1 : 0;
527 int *startup_pipes = NULL; /* options.max_startup sized array of fd ints */
528 int startup_pipe; /* in child */
531 * Main program for the daemon.
534 main(int ac, char **av)
538 int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
542 struct sockaddr_storage from;
543 const char *remote_ip;
546 struct linger linger;
548 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
549 int listen_sock, maxfd;
553 int ret, key_used = 0;
555 __progname = get_progname(av[0]);
562 /* Initialize configuration options to their default values. */
563 initialize_server_options(&options);
565 /* Parse command-line arguments. */
566 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:dDeiqtQ46")) != -1) {
575 config_file_name = optarg;
578 if (0 == debug_flag) {
580 options.log_level = SYSLOG_LEVEL_DEBUG1;
581 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
584 fprintf(stderr, "Too high debugging level.\n");
601 options.log_level = SYSLOG_LEVEL_QUIET;
604 options.server_key_bits = atoi(optarg);
607 options.ports_from_cmdline = 1;
608 if (options.num_ports >= MAX_PORTS) {
609 fprintf(stderr, "too many ports.\n");
612 options.ports[options.num_ports++] = a2port(optarg);
613 if (options.ports[options.num_ports-1] == 0) {
614 fprintf(stderr, "Bad port number.\n");
619 if ((options.login_grace_time = convtime(optarg)) == -1) {
620 fprintf(stderr, "Invalid login grace time.\n");
625 if ((options.key_regeneration_time = convtime(optarg)) == -1) {
626 fprintf(stderr, "Invalid key regeneration interval.\n");
631 if (options.num_host_key_files >= MAX_HOSTKEYS) {
632 fprintf(stderr, "too many host keys.\n");
635 options.host_key_files[options.num_host_key_files++] = optarg;
638 client_version_string = optarg;
639 /* only makes sense with inetd_flag, i.e. no listen() */
646 utmp_len = atoi(optarg);
650 fprintf(stderr, "sshd version %s\n", SSH_VERSION);
651 fprintf(stderr, "Usage: %s [options]\n", __progname);
652 fprintf(stderr, "Options:\n");
653 fprintf(stderr, " -f file Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE);
654 fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n");
655 fprintf(stderr, " -i Started from inetd\n");
656 fprintf(stderr, " -D Do not fork into daemon mode\n");
657 fprintf(stderr, " -t Only test configuration file and keys\n");
658 fprintf(stderr, " -q Quiet (no logging)\n");
659 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
660 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
661 fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n");
662 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
663 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
664 _PATH_HOST_KEY_FILE);
665 fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
666 fprintf(stderr, " -4 Use IPv4 only\n");
667 fprintf(stderr, " -6 Use IPv6 only\n");
671 SSLeay_add_all_algorithms();
674 * Force logging to stderr until we have loaded the private host
675 * key (unless started from inetd)
678 options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
679 options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
683 /* Cray can define user privs drop all prives now!
684 * Not needed on PRIV_SU systems!
691 /* Read server configuration options from the configuration file. */
692 read_server_config(&options, config_file_name);
694 /* Fill in default values for those options not explicitly set. */
695 fill_default_server_options(&options);
697 /* Check that there are no remaining arguments. */
699 fprintf(stderr, "Extra argument %s.\n", av[optind]);
703 debug("sshd version %.100s", SSH_VERSION);
705 /* load private host keys */
706 sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*));
707 for(i = 0; i < options.num_host_key_files; i++)
708 sensitive_data.host_keys[i] = NULL;
709 sensitive_data.server_key = NULL;
710 sensitive_data.ssh1_host_key = NULL;
711 sensitive_data.have_ssh1_key = 0;
712 sensitive_data.have_ssh2_key = 0;
714 for(i = 0; i < options.num_host_key_files; i++) {
715 key = key_load_private(options.host_key_files[i], "", NULL);
716 sensitive_data.host_keys[i] = key;
718 error("Could not load host key: %s",
719 options.host_key_files[i]);
720 sensitive_data.host_keys[i] = NULL;
725 sensitive_data.ssh1_host_key = key;
726 sensitive_data.have_ssh1_key = 1;
730 sensitive_data.have_ssh2_key = 1;
733 debug("private host key: #%d type %d %s", i, key->type,
736 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
737 log("Disabling protocol version 1. Could not load host key");
738 options.protocol &= ~SSH_PROTO_1;
740 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
741 log("Disabling protocol version 2. Could not load host key");
742 options.protocol &= ~SSH_PROTO_2;
744 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
745 log("sshd: no hostkeys available -- exiting.");
749 /* Check certain values for sanity. */
750 if (options.protocol & SSH_PROTO_1) {
751 if (options.server_key_bits < 512 ||
752 options.server_key_bits > 32768) {
753 fprintf(stderr, "Bad server key size.\n");
757 * Check that server and host key lengths differ sufficiently. This
758 * is necessary to make double encryption work with rsaref. Oh, I
759 * hate software patents. I dont know if this can go? Niels
761 if (options.server_key_bits >
762 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - SSH_KEY_BITS_RESERVED &&
763 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 debug("Forcing server key to %d bits to make it differ from host key.",
768 options.server_key_bits);
772 /* Configuration looks good, so exit if in test mode. */
776 #ifdef HAVE_SCO_PROTECTED_PW
777 (void) set_auth_parameters(ac, av);
780 /* Initialize the log (it is reinitialized below in case we forked). */
781 if (debug_flag && !inetd_flag)
783 log_init(__progname, options.log_level, options.log_facility, log_stderr);
786 * If not in debugging mode, and not started from inetd, disconnect
787 * from the controlling terminal, and fork. The original process
790 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
793 #endif /* TIOCNOTTY */
794 if (daemon(0, 0) < 0)
795 fatal("daemon() failed: %.200s", strerror(errno));
797 /* Disconnect from the controlling tty. */
799 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
801 (void) ioctl(fd, TIOCNOTTY, NULL);
804 #endif /* TIOCNOTTY */
806 /* Reinitialize the log (because of the fork above). */
807 log_init(__progname, options.log_level, options.log_facility, log_stderr);
809 /* Initialize the random number generator. */
812 /* Chdir to the root directory so that the current disk can be
813 unmounted if desired. */
817 signal(SIGPIPE, SIG_IGN);
819 /* Start listening for a socket, unless started from inetd. */
822 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
828 * We intentionally do not close the descriptors 0, 1, and 2
829 * as our code for setting the descriptors won\'t work if
830 * ttyfd happens to be one of those.
832 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
833 if (options.protocol & SSH_PROTO_1)
834 generate_ephemeral_server_key();
836 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
837 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
839 if (num_listen_socks >= MAX_LISTEN_SOCKS)
840 fatal("Too many listen sockets. "
841 "Enlarge MAX_LISTEN_SOCKS");
842 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
843 ntop, sizeof(ntop), strport, sizeof(strport),
844 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
845 error("getnameinfo failed");
848 /* Create socket for listening. */
849 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
850 if (listen_sock < 0) {
851 /* kernel may not support ipv6 */
852 verbose("socket: %.100s", strerror(errno));
855 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
856 error("listen_sock O_NONBLOCK: %s", strerror(errno));
861 * Set socket options. We try to make the port
862 * reusable and have it close as fast as possible
863 * without waiting in unnecessary wait states on
866 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
867 (void *) &on, sizeof(on));
870 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
871 (void *) &linger, sizeof(linger));
873 debug("Bind to port %s on %s.", strport, ntop);
875 /* Bind the socket to the desired port. */
876 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
878 error("Bind to port %s on %s failed: %.200s.",
879 strport, ntop, strerror(errno));
883 listen_socks[num_listen_socks] = listen_sock;
886 /* Start listening on the port. */
887 log("Server listening on %s port %s.", ntop, strport);
888 if (listen(listen_sock, 5) < 0)
889 fatal("listen: %.100s", strerror(errno));
892 freeaddrinfo(options.listen_addrs);
894 if (!num_listen_socks)
895 fatal("Cannot bind any address.");
897 if (options.protocol & SSH_PROTO_1)
898 generate_ephemeral_server_key();
901 * Arrange to restart on SIGHUP. The handler needs
904 signal(SIGHUP, sighup_handler);
906 signal(SIGTERM, sigterm_handler);
907 signal(SIGQUIT, sigterm_handler);
909 /* Arrange SIGCHLD to be caught. */
910 signal(SIGCHLD, main_sigchld_handler);
912 /* Write out the pid file after the sigterm handler is setup */
915 * Record our pid in /var/run/sshd.pid to make it
916 * easier to kill the correct sshd. We don't want to
917 * do this before the bind above because the bind will
918 * fail if there already is a daemon, and this will
919 * overwrite any old pid in the file.
921 f = fopen(options.pid_file, "wb");
923 fprintf(f, "%u\n", (u_int) getpid());
928 /* setup fd set for listen */
931 for (i = 0; i < num_listen_socks; i++)
932 if (listen_socks[i] > maxfd)
933 maxfd = listen_socks[i];
934 /* pipes connected to unauthenticated childs */
935 startup_pipes = xmalloc(options.max_startups * sizeof(int));
936 for (i = 0; i < options.max_startups; i++)
937 startup_pipes[i] = -1;
940 * Stay listening for connections until the system crashes or
941 * the daemon is killed with a signal.
948 fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
949 fdset = (fd_set *)xmalloc(fdsetsz);
950 memset(fdset, 0, fdsetsz);
952 for (i = 0; i < num_listen_socks; i++)
953 FD_SET(listen_socks[i], fdset);
954 for (i = 0; i < options.max_startups; i++)
955 if (startup_pipes[i] != -1)
956 FD_SET(startup_pipes[i], fdset);
958 /* Wait in select until there is a connection. */
959 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
960 if (ret < 0 && errno != EINTR)
961 error("select: %.100s", strerror(errno));
962 if (received_sigterm) {
963 log("Received signal %d; terminating.",
965 close_listen_socks();
966 unlink(options.pid_file);
969 if (key_used && key_do_regen) {
970 generate_ephemeral_server_key();
977 for (i = 0; i < options.max_startups; i++)
978 if (startup_pipes[i] != -1 &&
979 FD_ISSET(startup_pipes[i], fdset)) {
981 * the read end of the pipe is ready
982 * if the child has closed the pipe
983 * after successful authentication
984 * or if the child has died
986 close(startup_pipes[i]);
987 startup_pipes[i] = -1;
990 for (i = 0; i < num_listen_socks; i++) {
991 if (!FD_ISSET(listen_socks[i], fdset))
993 fromlen = sizeof(from);
994 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
997 if (errno != EINTR && errno != EWOULDBLOCK)
998 error("accept: %.100s", strerror(errno));
1001 if (fcntl(newsock, F_SETFL, 0) < 0) {
1002 error("newsock del O_NONBLOCK: %s", strerror(errno));
1005 if (drop_connection(startups) == 1) {
1006 debug("drop connection #%d", startups);
1010 if (pipe(startup_p) == -1) {
1015 for (j = 0; j < options.max_startups; j++)
1016 if (startup_pipes[j] == -1) {
1017 startup_pipes[j] = startup_p[0];
1018 if (maxfd < startup_p[0])
1019 maxfd = startup_p[0];
1025 * Got connection. Fork a child to handle it, unless
1026 * we are in debugging mode.
1030 * In debugging mode. Close the listening
1031 * socket, and start processing the
1032 * connection without forking.
1034 debug("Server will not fork when running in debugging mode.");
1035 close_listen_socks();
1043 * Normal production daemon. Fork, and have
1044 * the child process the connection. The
1045 * parent continues listening.
1047 if ((pid = fork()) == 0) {
1049 * Child. Close the listening and max_startup
1050 * sockets. Start using the accepted socket.
1051 * Reinitialize logging (since our pid has
1052 * changed). We break out of the loop to handle
1055 startup_pipe = startup_p[1];
1056 for (j = 0; j < options.max_startups; j++)
1057 if (startup_pipes[j] != -1)
1058 close(startup_pipes[j]);
1059 close_listen_socks();
1062 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1067 /* Parent. Stay in the loop. */
1069 error("fork: %.100s", strerror(errno));
1071 debug("Forked child %d.", pid);
1073 close(startup_p[1]);
1075 /* Mark that the key has been used (it was "given" to the child). */
1076 if ((options.protocol & SSH_PROTO_1) &&
1078 /* Schedule server key regeneration alarm. */
1079 signal(SIGALRM, key_regeneration_alarm);
1080 alarm(options.key_regeneration_time);
1086 /* Close the new socket (the child is now taking care of it). */
1089 /* child process check (or debug mode) */
1090 if (num_listen_socks < 0)
1095 /* This is the child processing a new connection. */
1098 * Disable the key regeneration alarm. We will not regenerate the
1099 * key since we are no longer in a position to give it to anyone. We
1100 * will not restart on SIGHUP since it no longer makes sense.
1103 signal(SIGALRM, SIG_DFL);
1104 signal(SIGHUP, SIG_DFL);
1105 signal(SIGTERM, SIG_DFL);
1106 signal(SIGQUIT, SIG_DFL);
1107 signal(SIGCHLD, SIG_DFL);
1108 signal(SIGINT, SIG_DFL);
1111 * Set socket options for the connection. We want the socket to
1112 * close as fast as possible without waiting for anything. If the
1113 * connection is not a socket, these will do nothing.
1115 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1117 linger.l_linger = 5;
1118 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
1120 /* Set keepalives if requested. */
1121 if (options.keepalives &&
1122 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
1124 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1127 * Register our connection. This turns encryption off because we do
1130 packet_set_connection(sock_in, sock_out);
1132 remote_port = get_remote_port();
1133 remote_ip = get_remote_ipaddr();
1135 /* Check whether logins are denied from this host. */
1137 /* XXX LIBWRAP noes not know about IPv6 */
1139 struct request_info req;
1141 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, NULL);
1144 if (!hosts_access(&req)) {
1149 /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
1151 #endif /* LIBWRAP */
1152 /* Log the connection. */
1153 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1156 * We don\'t want to listen forever unless the other side
1157 * successfully authenticates itself. So we set up an alarm which is
1158 * cleared after successful authentication. A limit of zero
1159 * indicates no limit. Note that we don\'t set the alarm in debugging
1160 * mode; it is just annoying to have the server exit just when you
1161 * are about to discover the bug.
1163 signal(SIGALRM, grace_alarm_handler);
1165 alarm(options.login_grace_time);
1167 sshd_exchange_identification(sock_in, sock_out);
1169 * Check that the connection comes from a privileged port.
1170 * Rhosts-Authentication only makes sense from priviledged
1171 * programs. Of course, if the intruder has root access on his local
1172 * machine, he can connect from any port. So do not use these
1173 * authentication methods from machines that you do not trust.
1175 if (remote_port >= IPPORT_RESERVED ||
1176 remote_port < IPPORT_RESERVED / 2) {
1177 debug("Rhosts Authentication disabled, "
1178 "originating port not trusted.");
1179 options.rhosts_authentication = 0;
1181 #if defined(KRB4) && !defined(KRB5)
1182 if (!packet_connection_is_ipv4() &&
1183 options.kerberos_authentication) {
1184 debug("Kerberos Authentication disabled, only available for IPv4.");
1185 options.kerberos_authentication = 0;
1187 #endif /* KRB4 && !KRB5 */
1189 /* If machine has AFS, set process authentication group. */
1196 packet_set_nonblocking();
1198 /* perform the key exchange */
1199 /* authenticate user and start session */
1202 do_authentication2();
1205 do_authentication();
1207 /* The connection has been terminated. */
1208 verbose("Closing connection to %.100s", remote_ip);
1212 #endif /* USE_PAM */
1227 BIGNUM *session_key_int;
1228 u_char session_key[SSH_SESSION_KEY_LENGTH];
1230 u_int cipher_type, auth_mask, protocol_flags;
1234 * Generate check bytes that the client must send back in the user
1235 * packet in order for it to be accepted; this is used to defy ip
1236 * spoofing attacks. Note that this only works against somebody
1237 * doing IP spoofing from a remote machine; any machine on the local
1238 * network can still see outgoing packets and catch the random
1239 * cookie. This only affects rhosts authentication, and this is one
1240 * of the reasons why it is inherently insecure.
1242 for (i = 0; i < 8; i++) {
1244 rand = arc4random();
1245 cookie[i] = rand & 0xff;
1250 * Send our public key. We include in the packet 64 bits of random
1251 * data that must be matched in the reply in order to prevent IP
1254 packet_start(SSH_SMSG_PUBLIC_KEY);
1255 for (i = 0; i < 8; i++)
1256 packet_put_char(cookie[i]);
1258 /* Store our public server RSA key. */
1259 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1260 packet_put_bignum(sensitive_data.server_key->rsa->e);
1261 packet_put_bignum(sensitive_data.server_key->rsa->n);
1263 /* Store our public host RSA key. */
1264 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1265 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1266 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1268 /* Put protocol flags. */
1269 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1271 /* Declare which ciphers we support. */
1272 packet_put_int(cipher_mask_ssh1(0));
1274 /* Declare supported authentication types. */
1276 if (options.rhosts_authentication)
1277 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1278 if (options.rhosts_rsa_authentication)
1279 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1280 if (options.rsa_authentication)
1281 auth_mask |= 1 << SSH_AUTH_RSA;
1282 #if defined(KRB4) || defined(KRB5)
1283 if (options.kerberos_authentication)
1284 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1286 #if defined(AFS) || defined(KRB5)
1287 if (options.kerberos_tgt_passing)
1288 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1291 if (options.afs_token_passing)
1292 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1294 if (options.challenge_response_authentication == 1)
1295 auth_mask |= 1 << SSH_AUTH_TIS;
1296 if (options.password_authentication)
1297 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1298 packet_put_int(auth_mask);
1300 /* Send the packet and wait for it to be sent. */
1302 packet_write_wait();
1304 debug("Sent %d bit server key and %d bit host key.",
1305 BN_num_bits(sensitive_data.server_key->rsa->n),
1306 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1308 /* Read clients reply (cipher type and session key). */
1309 packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1311 /* Get cipher type and check whether we accept this. */
1312 cipher_type = packet_get_char();
1314 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1315 packet_disconnect("Warning: client selects unsupported cipher.");
1317 /* Get check bytes from the packet. These must match those we
1318 sent earlier with the public key packet. */
1319 for (i = 0; i < 8; i++)
1320 if (cookie[i] != packet_get_char())
1321 packet_disconnect("IP Spoofing check bytes do not match.");
1323 debug("Encryption type: %.200s", cipher_name(cipher_type));
1325 /* Get the encrypted integer. */
1326 session_key_int = BN_new();
1327 packet_get_bignum(session_key_int, &slen);
1329 protocol_flags = packet_get_int();
1330 packet_set_protocol_flags(protocol_flags);
1332 packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1335 * Decrypt it using our private server key and private host key (key
1336 * with larger modulus first).
1338 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1339 /* Server key has bigger modulus. */
1340 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1341 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1342 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1343 get_remote_ipaddr(),
1344 BN_num_bits(sensitive_data.server_key->rsa->n),
1345 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1346 SSH_KEY_BITS_RESERVED);
1348 if (rsa_private_decrypt(session_key_int, session_key_int,
1349 sensitive_data.server_key->rsa) <= 0)
1351 if (rsa_private_decrypt(session_key_int, session_key_int,
1352 sensitive_data.ssh1_host_key->rsa) <= 0)
1355 /* Host key has bigger modulus (or they are equal). */
1356 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1357 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1358 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1359 get_remote_ipaddr(),
1360 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1361 BN_num_bits(sensitive_data.server_key->rsa->n),
1362 SSH_KEY_BITS_RESERVED);
1364 if (rsa_private_decrypt(session_key_int, session_key_int,
1365 sensitive_data.ssh1_host_key->rsa) < 0)
1367 if (rsa_private_decrypt(session_key_int, session_key_int,
1368 sensitive_data.server_key->rsa) < 0)
1372 * Extract session key from the decrypted integer. The key is in the
1373 * least significant 256 bits of the integer; the first byte of the
1374 * key is in the highest bits.
1377 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1378 len = BN_num_bytes(session_key_int);
1379 if (len < 0 || len > sizeof(session_key)) {
1380 error("do_connection: bad session key len from %s: "
1381 "session_key_int %d > sizeof(session_key) %lu",
1382 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
1385 memset(session_key, 0, sizeof(session_key));
1386 BN_bn2bin(session_key_int,
1387 session_key + sizeof(session_key) - len);
1389 compute_session_id(session_id, cookie,
1390 sensitive_data.ssh1_host_key->rsa->n,
1391 sensitive_data.server_key->rsa->n);
1393 * Xor the first 16 bytes of the session key with the
1396 for (i = 0; i < 16; i++)
1397 session_key[i] ^= session_id[i];
1401 int bytes = BN_num_bytes(session_key_int);
1402 char *buf = xmalloc(bytes);
1405 log("do_connection: generating a fake encryption key");
1406 BN_bn2bin(session_key_int, buf);
1408 MD5_Update(&md, buf, bytes);
1409 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1410 MD5_Final(session_key, &md);
1412 MD5_Update(&md, session_key, 16);
1413 MD5_Update(&md, buf, bytes);
1414 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1415 MD5_Final(session_key + 16, &md);
1416 memset(buf, 0, bytes);
1418 for (i = 0; i < 16; i++)
1419 session_id[i] = session_key[i] ^ session_key[i + 16];
1421 /* Destroy the private and public keys. They will no longer be needed. */
1422 destroy_sensitive_data();
1424 /* Destroy the decrypted integer. It is no longer needed. */
1425 BN_clear_free(session_key_int);
1427 /* Set the session key. From this on all communications will be encrypted. */
1428 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1430 /* Destroy our copy of the session key. It is no longer needed. */
1431 memset(session_key, 0, sizeof(session_key));
1433 debug("Received session key; encryption turned on.");
1435 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1436 packet_start(SSH_SMSG_SUCCESS);
1438 packet_write_wait();
1442 * SSH2 key exchange: diffie-hellman-group1-sha1
1449 if (options.ciphers != NULL) {
1450 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1451 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1453 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1454 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
1455 myproposal[PROPOSAL_ENC_ALGS_STOC] =
1456 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
1458 if (options.macs != NULL) {
1459 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
1460 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
1462 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
1464 /* start key exchange */
1465 kex = kex_setup(myproposal);
1467 kex->client_version_string=client_version_string;
1468 kex->server_version_string=server_version_string;
1469 kex->load_host_key=&get_hostkey_by_type;
1473 dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
1475 session_id2 = kex->session_id;
1476 session_id2_len = kex->session_id_len;
1479 /* send 1st encrypted/maced/compressed message */
1480 packet_start(SSH2_MSG_IGNORE);
1481 packet_put_cstring("markus");
1483 packet_write_wait();