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 1.228 2002/02/27 21:23:13 stevesk Exp $");
45 #include <openssl/dh.h>
46 #include <openssl/bn.h>
47 #include <openssl/md5.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 static volatile sig_atomic_t key_do_regen = 0;
174 /* This is set to true when a signal is received. */
175 static volatile sig_atomic_t received_sighup = 0;
176 static volatile sig_atomic_t 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 /* options.max_startup sized array of fd ints */
189 int *startup_pipes = NULL;
190 int startup_pipe; /* in child */
192 /* Prototypes for various functions defined later in this file. */
193 void destroy_sensitive_data(void);
195 static void do_ssh1_kex(void);
196 static void do_ssh2_kex(void);
199 * Close all listening sockets
202 close_listen_socks(void)
205 for (i = 0; i < num_listen_socks; i++)
206 close(listen_socks[i]);
207 num_listen_socks = -1;
211 close_startup_pipes(void)
215 for (i = 0; i < options.max_startups; i++)
216 if (startup_pipes[i] != -1)
217 close(startup_pipes[i]);
221 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
222 * the effect is to reread the configuration file (and to regenerate
226 sighup_handler(int sig)
228 int save_errno = errno;
231 signal(SIGHUP, sighup_handler);
236 * Called from the main program after receiving SIGHUP.
237 * Restarts the server.
242 log("Received SIGHUP; restarting.");
243 close_listen_socks();
244 close_startup_pipes();
245 execv(saved_argv[0], saved_argv);
246 log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], strerror(errno));
251 * Generic signal handler for terminating signals in the master daemon.
254 sigterm_handler(int sig)
256 received_sigterm = sig;
260 * SIGCHLD handler. This is called whenever a child dies. This will then
261 * reap any zombies left by exited children.
264 main_sigchld_handler(int sig)
266 int save_errno = errno;
269 while (waitpid(-1, &status, WNOHANG) > 0)
272 signal(SIGCHLD, main_sigchld_handler);
277 * Signal handler for the alarm after the login grace period has expired.
280 grace_alarm_handler(int sig)
282 /* XXX no idea how fix this signal handler */
284 /* Close the connection. */
287 /* Log error and exit. */
288 fatal("Timeout before authentication for %s.", get_remote_ipaddr());
292 * Signal handler for the key regeneration alarm. Note that this
293 * alarm only occurs in the daemon waiting for connections, and it does not
294 * do anything with the private key or random state before forking.
295 * Thus there should be no concurrency control/asynchronous execution
299 generate_ephemeral_server_key(void)
304 verbose("Generating %s%d bit RSA key.",
305 sensitive_data.server_key ? "new " : "", options.server_key_bits);
306 if (sensitive_data.server_key != NULL)
307 key_free(sensitive_data.server_key);
308 sensitive_data.server_key = key_generate(KEY_RSA1,
309 options.server_key_bits);
310 verbose("RSA key generation complete.");
312 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
315 sensitive_data.ssh1_cookie[i] = rand & 0xff;
322 key_regeneration_alarm(int sig)
324 int save_errno = errno;
325 signal(SIGALRM, SIG_DFL);
331 sshd_exchange_identification(int sock_in, int sock_out)
334 int remote_major, remote_minor;
337 char buf[256]; /* Must not be larger than remote_version. */
338 char remote_version[256]; /* Must be at least as big as buf. */
340 if ((options.protocol & SSH_PROTO_1) &&
341 (options.protocol & SSH_PROTO_2)) {
342 major = PROTOCOL_MAJOR_1;
344 } else if (options.protocol & SSH_PROTO_2) {
345 major = PROTOCOL_MAJOR_2;
346 minor = PROTOCOL_MINOR_2;
348 major = PROTOCOL_MAJOR_1;
349 minor = PROTOCOL_MINOR_1;
351 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
352 server_version_string = xstrdup(buf);
354 if (client_version_string == NULL) {
355 /* Send our protocol version identification. */
356 if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
357 != strlen(server_version_string)) {
358 log("Could not write ident string to %s", get_remote_ipaddr());
362 /* Read other side's version identification. */
363 memset(buf, 0, sizeof(buf));
364 for (i = 0; i < sizeof(buf) - 1; i++) {
365 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
366 log("Did not receive identification string from %s",
367 get_remote_ipaddr());
370 if (buf[i] == '\r') {
372 /* Kludge for F-Secure Macintosh < 1.0.2 */
374 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
378 if (buf[i] == '\n') {
383 buf[sizeof(buf) - 1] = 0;
384 client_version_string = xstrdup(buf);
388 * Check that the versions match. In future this might accept
389 * several versions and set appropriate flags to handle them.
391 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
392 &remote_major, &remote_minor, remote_version) != 3) {
393 s = "Protocol mismatch.\n";
394 (void) atomicio(write, sock_out, s, strlen(s));
397 log("Bad protocol version identification '%.100s' from %s",
398 client_version_string, get_remote_ipaddr());
401 debug("Client protocol version %d.%d; client software version %.100s",
402 remote_major, remote_minor, remote_version);
404 compat_datafellows(remote_version);
406 if (datafellows & SSH_BUG_SCANNER) {
407 log("scanned from %s with %s. Don't panic.",
408 get_remote_ipaddr(), client_version_string);
413 switch (remote_major) {
415 if (remote_minor == 99) {
416 if (options.protocol & SSH_PROTO_2)
422 if (!(options.protocol & SSH_PROTO_1)) {
426 if (remote_minor < 3) {
427 packet_disconnect("Your ssh version is too old and "
428 "is no longer supported. Please install a newer version.");
429 } else if (remote_minor == 3) {
430 /* note that this disables agent-forwarding */
435 if (options.protocol & SSH_PROTO_2) {
444 chop(server_version_string);
445 debug("Local version string %.200s", server_version_string);
448 s = "Protocol major versions differ.\n";
449 (void) atomicio(write, sock_out, s, strlen(s));
452 log("Protocol major versions differ for %s: %.200s vs. %.200s",
454 server_version_string, client_version_string);
460 /* Destroy the host and server keys. They will no longer be needed. */
462 destroy_sensitive_data(void)
466 if (sensitive_data.server_key) {
467 key_free(sensitive_data.server_key);
468 sensitive_data.server_key = NULL;
470 for (i = 0; i < options.num_host_key_files; i++) {
471 if (sensitive_data.host_keys[i]) {
472 key_free(sensitive_data.host_keys[i]);
473 sensitive_data.host_keys[i] = NULL;
476 sensitive_data.ssh1_host_key = NULL;
477 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
481 list_hostkey_types(void)
488 for (i = 0; i < options.num_host_key_files; i++) {
489 Key *key = sensitive_data.host_keys[i];
495 if (buffer_len(&b) > 0)
496 buffer_append(&b, ",", 1);
497 p = key_ssh_name(key);
498 buffer_append(&b, p, strlen(p));
502 buffer_append(&b, "\0", 1);
503 p = xstrdup(buffer_ptr(&b));
505 debug("list_hostkey_types: %s", p);
510 get_hostkey_by_type(int type)
513 for (i = 0; i < options.num_host_key_files; i++) {
514 Key *key = sensitive_data.host_keys[i];
515 if (key != NULL && key->type == type)
522 * returns 1 if connection should be dropped, 0 otherwise.
523 * dropping starts at connection #max_startups_begin with a probability
524 * of (max_startups_rate/100). the probability increases linearly until
525 * all connections are dropped for startups > max_startups
528 drop_connection(int startups)
532 if (startups < options.max_startups_begin)
534 if (startups >= options.max_startups)
536 if (options.max_startups_rate == 100)
539 p = 100 - options.max_startups_rate;
540 p *= startups - options.max_startups_begin;
541 p /= (double) (options.max_startups - options.max_startups_begin);
542 p += options.max_startups_rate;
544 r = arc4random() / (double) UINT_MAX;
546 debug("drop_connection: p %g, r %g", p, r);
547 return (r < p) ? 1 : 0;
553 fprintf(stderr, "sshd version %s\n", SSH_VERSION);
554 fprintf(stderr, "Usage: %s [options]\n", __progname);
555 fprintf(stderr, "Options:\n");
556 fprintf(stderr, " -f file Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE);
557 fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n");
558 fprintf(stderr, " -i Started from inetd\n");
559 fprintf(stderr, " -D Do not fork into daemon mode\n");
560 fprintf(stderr, " -t Only test configuration file and keys\n");
561 fprintf(stderr, " -q Quiet (no logging)\n");
562 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
563 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
564 fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n");
565 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
566 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
567 _PATH_HOST_KEY_FILE);
568 fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
569 fprintf(stderr, " -4 Use IPv4 only\n");
570 fprintf(stderr, " -6 Use IPv6 only\n");
571 fprintf(stderr, " -o option Process the option as if it was read from a configuration file.\n");
576 * Main program for the daemon.
579 main(int ac, char **av)
583 int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
587 struct sockaddr_storage from;
588 const char *remote_ip;
591 struct linger linger;
593 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
594 int listen_sock, maxfd;
598 int ret, key_used = 0;
600 __progname = get_progname(av[0]);
607 /* Initialize configuration options to their default values. */
608 initialize_server_options(&options);
610 /* Parse command-line arguments. */
611 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:o:dDeiqtQ46")) != -1) {
620 config_file_name = optarg;
623 if (0 == debug_flag) {
625 options.log_level = SYSLOG_LEVEL_DEBUG1;
626 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
629 fprintf(stderr, "Too high debugging level.\n");
646 options.log_level = SYSLOG_LEVEL_QUIET;
649 options.server_key_bits = atoi(optarg);
652 options.ports_from_cmdline = 1;
653 if (options.num_ports >= MAX_PORTS) {
654 fprintf(stderr, "too many ports.\n");
657 options.ports[options.num_ports++] = a2port(optarg);
658 if (options.ports[options.num_ports-1] == 0) {
659 fprintf(stderr, "Bad port number.\n");
664 if ((options.login_grace_time = convtime(optarg)) == -1) {
665 fprintf(stderr, "Invalid login grace time.\n");
670 if ((options.key_regeneration_time = convtime(optarg)) == -1) {
671 fprintf(stderr, "Invalid key regeneration interval.\n");
676 if (options.num_host_key_files >= MAX_HOSTKEYS) {
677 fprintf(stderr, "too many host keys.\n");
680 options.host_key_files[options.num_host_key_files++] = optarg;
683 client_version_string = optarg;
684 /* only makes sense with inetd_flag, i.e. no listen() */
691 utmp_len = atoi(optarg);
694 if (process_server_config_line(&options, optarg,
695 "command-line", 0) != 0)
704 SSLeay_add_all_algorithms();
705 channel_set_af(IPv4or6);
708 * Force logging to stderr until we have loaded the private host
709 * key (unless started from inetd)
712 options.log_level == SYSLOG_LEVEL_NOT_SET ?
713 SYSLOG_LEVEL_INFO : options.log_level,
714 options.log_facility == SYSLOG_FACILITY_NOT_SET ?
715 SYSLOG_FACILITY_AUTH : options.log_facility,
719 /* Cray can define user privs drop all prives now!
720 * Not needed on PRIV_SU systems!
727 /* Read server configuration options from the configuration file. */
728 read_server_config(&options, config_file_name);
730 /* Fill in default values for those options not explicitly set. */
731 fill_default_server_options(&options);
733 /* Check that there are no remaining arguments. */
735 fprintf(stderr, "Extra argument %s.\n", av[optind]);
739 debug("sshd version %.100s", SSH_VERSION);
741 /* load private host keys */
742 sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*));
743 for (i = 0; i < options.num_host_key_files; i++)
744 sensitive_data.host_keys[i] = NULL;
745 sensitive_data.server_key = NULL;
746 sensitive_data.ssh1_host_key = NULL;
747 sensitive_data.have_ssh1_key = 0;
748 sensitive_data.have_ssh2_key = 0;
750 for (i = 0; i < options.num_host_key_files; i++) {
751 key = key_load_private(options.host_key_files[i], "", NULL);
752 sensitive_data.host_keys[i] = key;
754 error("Could not load host key: %s",
755 options.host_key_files[i]);
756 sensitive_data.host_keys[i] = NULL;
761 sensitive_data.ssh1_host_key = key;
762 sensitive_data.have_ssh1_key = 1;
766 sensitive_data.have_ssh2_key = 1;
769 debug("private host key: #%d type %d %s", i, key->type,
772 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
773 log("Disabling protocol version 1. Could not load host key");
774 options.protocol &= ~SSH_PROTO_1;
776 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
777 log("Disabling protocol version 2. Could not load host key");
778 options.protocol &= ~SSH_PROTO_2;
780 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
781 log("sshd: no hostkeys available -- exiting.");
785 /* Check certain values for sanity. */
786 if (options.protocol & SSH_PROTO_1) {
787 if (options.server_key_bits < 512 ||
788 options.server_key_bits > 32768) {
789 fprintf(stderr, "Bad server key size.\n");
793 * Check that server and host key lengths differ sufficiently. This
794 * is necessary to make double encryption work with rsaref. Oh, I
795 * hate software patents. I dont know if this can go? Niels
797 if (options.server_key_bits >
798 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - SSH_KEY_BITS_RESERVED &&
799 options.server_key_bits <
800 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
801 options.server_key_bits =
802 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED;
803 debug("Forcing server key to %d bits to make it differ from host key.",
804 options.server_key_bits);
808 /* Configuration looks good, so exit if in test mode. */
812 #ifdef HAVE_SCO_PROTECTED_PW
813 (void) set_auth_parameters(ac, av);
816 /* Initialize the log (it is reinitialized below in case we forked). */
817 if (debug_flag && !inetd_flag)
819 log_init(__progname, options.log_level, options.log_facility, log_stderr);
822 * If not in debugging mode, and not started from inetd, disconnect
823 * from the controlling terminal, and fork. The original process
826 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
829 #endif /* TIOCNOTTY */
830 if (daemon(0, 0) < 0)
831 fatal("daemon() failed: %.200s", strerror(errno));
833 /* Disconnect from the controlling tty. */
835 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
837 (void) ioctl(fd, TIOCNOTTY, NULL);
840 #endif /* TIOCNOTTY */
842 /* Reinitialize the log (because of the fork above). */
843 log_init(__progname, options.log_level, options.log_facility, log_stderr);
845 /* Initialize the random number generator. */
848 /* Chdir to the root directory so that the current disk can be
849 unmounted if desired. */
853 signal(SIGPIPE, SIG_IGN);
855 /* Start listening for a socket, unless started from inetd. */
858 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
864 * We intentionally do not close the descriptors 0, 1, and 2
865 * as our code for setting the descriptors won\'t work if
866 * ttyfd happens to be one of those.
868 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
869 if (options.protocol & SSH_PROTO_1)
870 generate_ephemeral_server_key();
872 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
873 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
875 if (num_listen_socks >= MAX_LISTEN_SOCKS)
876 fatal("Too many listen sockets. "
877 "Enlarge MAX_LISTEN_SOCKS");
878 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
879 ntop, sizeof(ntop), strport, sizeof(strport),
880 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
881 error("getnameinfo failed");
884 /* Create socket for listening. */
885 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
886 if (listen_sock < 0) {
887 /* kernel may not support ipv6 */
888 verbose("socket: %.100s", strerror(errno));
891 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
892 error("listen_sock O_NONBLOCK: %s", strerror(errno));
897 * Set socket options. We try to make the port
898 * reusable and have it close as fast as possible
899 * without waiting in unnecessary wait states on
902 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
906 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
907 &linger, sizeof(linger));
909 debug("Bind to port %s on %s.", strport, ntop);
911 /* Bind the socket to the desired port. */
912 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
914 error("Bind to port %s on %s failed: %.200s.",
915 strport, ntop, strerror(errno));
919 listen_socks[num_listen_socks] = listen_sock;
922 /* Start listening on the port. */
923 log("Server listening on %s port %s.", ntop, strport);
924 if (listen(listen_sock, 5) < 0)
925 fatal("listen: %.100s", strerror(errno));
928 freeaddrinfo(options.listen_addrs);
930 if (!num_listen_socks)
931 fatal("Cannot bind any address.");
933 if (options.protocol & SSH_PROTO_1)
934 generate_ephemeral_server_key();
937 * Arrange to restart on SIGHUP. The handler needs
940 signal(SIGHUP, sighup_handler);
942 signal(SIGTERM, sigterm_handler);
943 signal(SIGQUIT, sigterm_handler);
945 /* Arrange SIGCHLD to be caught. */
946 signal(SIGCHLD, main_sigchld_handler);
948 /* Write out the pid file after the sigterm handler is setup */
951 * Record our pid in /var/run/sshd.pid to make it
952 * easier to kill the correct sshd. We don't want to
953 * do this before the bind above because the bind will
954 * fail if there already is a daemon, and this will
955 * overwrite any old pid in the file.
957 f = fopen(options.pid_file, "wb");
959 fprintf(f, "%u\n", (u_int) getpid());
964 /* setup fd set for listen */
967 for (i = 0; i < num_listen_socks; i++)
968 if (listen_socks[i] > maxfd)
969 maxfd = listen_socks[i];
970 /* pipes connected to unauthenticated childs */
971 startup_pipes = xmalloc(options.max_startups * sizeof(int));
972 for (i = 0; i < options.max_startups; i++)
973 startup_pipes[i] = -1;
976 * Stay listening for connections until the system crashes or
977 * the daemon is killed with a signal.
984 fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
985 fdset = (fd_set *)xmalloc(fdsetsz);
986 memset(fdset, 0, fdsetsz);
988 for (i = 0; i < num_listen_socks; i++)
989 FD_SET(listen_socks[i], fdset);
990 for (i = 0; i < options.max_startups; i++)
991 if (startup_pipes[i] != -1)
992 FD_SET(startup_pipes[i], fdset);
994 /* Wait in select until there is a connection. */
995 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
996 if (ret < 0 && errno != EINTR)
997 error("select: %.100s", strerror(errno));
998 if (received_sigterm) {
999 log("Received signal %d; terminating.",
1000 (int) received_sigterm);
1001 close_listen_socks();
1002 unlink(options.pid_file);
1005 if (key_used && key_do_regen) {
1006 generate_ephemeral_server_key();
1013 for (i = 0; i < options.max_startups; i++)
1014 if (startup_pipes[i] != -1 &&
1015 FD_ISSET(startup_pipes[i], fdset)) {
1017 * the read end of the pipe is ready
1018 * if the child has closed the pipe
1019 * after successful authentication
1020 * or if the child has died
1022 close(startup_pipes[i]);
1023 startup_pipes[i] = -1;
1026 for (i = 0; i < num_listen_socks; i++) {
1027 if (!FD_ISSET(listen_socks[i], fdset))
1029 fromlen = sizeof(from);
1030 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
1033 if (errno != EINTR && errno != EWOULDBLOCK)
1034 error("accept: %.100s", strerror(errno));
1037 if (fcntl(newsock, F_SETFL, 0) < 0) {
1038 error("newsock del O_NONBLOCK: %s", strerror(errno));
1042 if (drop_connection(startups) == 1) {
1043 debug("drop connection #%d", startups);
1047 if (pipe(startup_p) == -1) {
1052 for (j = 0; j < options.max_startups; j++)
1053 if (startup_pipes[j] == -1) {
1054 startup_pipes[j] = startup_p[0];
1055 if (maxfd < startup_p[0])
1056 maxfd = startup_p[0];
1062 * Got connection. Fork a child to handle it, unless
1063 * we are in debugging mode.
1067 * In debugging mode. Close the listening
1068 * socket, and start processing the
1069 * connection without forking.
1071 debug("Server will not fork when running in debugging mode.");
1072 close_listen_socks();
1080 * Normal production daemon. Fork, and have
1081 * the child process the connection. The
1082 * parent continues listening.
1084 if ((pid = fork()) == 0) {
1086 * Child. Close the listening and max_startup
1087 * sockets. Start using the accepted socket.
1088 * Reinitialize logging (since our pid has
1089 * changed). We break out of the loop to handle
1092 startup_pipe = startup_p[1];
1093 close_startup_pipes();
1094 close_listen_socks();
1097 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1102 /* Parent. Stay in the loop. */
1104 error("fork: %.100s", strerror(errno));
1106 debug("Forked child %d.", pid);
1108 close(startup_p[1]);
1110 /* Mark that the key has been used (it was "given" to the child). */
1111 if ((options.protocol & SSH_PROTO_1) &&
1113 /* Schedule server key regeneration alarm. */
1114 signal(SIGALRM, key_regeneration_alarm);
1115 alarm(options.key_regeneration_time);
1121 /* Close the new socket (the child is now taking care of it). */
1124 /* child process check (or debug mode) */
1125 if (num_listen_socks < 0)
1130 /* This is the child processing a new connection. */
1133 * Disable the key regeneration alarm. We will not regenerate the
1134 * key since we are no longer in a position to give it to anyone. We
1135 * will not restart on SIGHUP since it no longer makes sense.
1138 signal(SIGALRM, SIG_DFL);
1139 signal(SIGHUP, SIG_DFL);
1140 signal(SIGTERM, SIG_DFL);
1141 signal(SIGQUIT, SIG_DFL);
1142 signal(SIGCHLD, SIG_DFL);
1143 signal(SIGINT, SIG_DFL);
1146 * Set socket options for the connection. We want the socket to
1147 * close as fast as possible without waiting for anything. If the
1148 * connection is not a socket, these will do nothing.
1150 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1152 linger.l_linger = 5;
1153 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, &linger, sizeof(linger));
1155 /* Set keepalives if requested. */
1156 if (options.keepalives &&
1157 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on,
1159 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1162 * Register our connection. This turns encryption off because we do
1165 packet_set_connection(sock_in, sock_out);
1167 remote_port = get_remote_port();
1168 remote_ip = get_remote_ipaddr();
1171 /* Check whether logins are denied from this host. */
1173 struct request_info req;
1175 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
1178 if (!hosts_access(&req)) {
1179 debug("Connection refused by tcp wrapper");
1182 fatal("libwrap refuse returns");
1185 #endif /* LIBWRAP */
1187 /* Log the connection. */
1188 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1191 * We don\'t want to listen forever unless the other side
1192 * successfully authenticates itself. So we set up an alarm which is
1193 * cleared after successful authentication. A limit of zero
1194 * indicates no limit. Note that we don\'t set the alarm in debugging
1195 * mode; it is just annoying to have the server exit just when you
1196 * are about to discover the bug.
1198 signal(SIGALRM, grace_alarm_handler);
1200 alarm(options.login_grace_time);
1202 sshd_exchange_identification(sock_in, sock_out);
1204 * Check that the connection comes from a privileged port.
1205 * Rhosts-Authentication only makes sense from priviledged
1206 * programs. Of course, if the intruder has root access on his local
1207 * machine, he can connect from any port. So do not use these
1208 * authentication methods from machines that you do not trust.
1210 if (options.rhosts_authentication &&
1211 (remote_port >= IPPORT_RESERVED ||
1212 remote_port < IPPORT_RESERVED / 2)) {
1213 debug("Rhosts Authentication disabled, "
1214 "originating port %d not trusted.", remote_port);
1215 options.rhosts_authentication = 0;
1217 #if defined(KRB4) && !defined(KRB5)
1218 if (!packet_connection_is_ipv4() &&
1219 options.kerberos_authentication) {
1220 debug("Kerberos Authentication disabled, only available for IPv4.");
1221 options.kerberos_authentication = 0;
1223 #endif /* KRB4 && !KRB5 */
1225 /* If machine has AFS, set process authentication group. */
1232 packet_set_nonblocking();
1234 /* perform the key exchange */
1235 /* authenticate user and start session */
1238 do_authentication2();
1241 do_authentication();
1243 /* The connection has been terminated. */
1244 verbose("Closing connection to %.100s", remote_ip);
1248 #endif /* USE_PAM */
1262 BIGNUM *session_key_int;
1263 u_char session_key[SSH_SESSION_KEY_LENGTH];
1265 u_int cipher_type, auth_mask, protocol_flags;
1269 * Generate check bytes that the client must send back in the user
1270 * packet in order for it to be accepted; this is used to defy ip
1271 * spoofing attacks. Note that this only works against somebody
1272 * doing IP spoofing from a remote machine; any machine on the local
1273 * network can still see outgoing packets and catch the random
1274 * cookie. This only affects rhosts authentication, and this is one
1275 * of the reasons why it is inherently insecure.
1277 for (i = 0; i < 8; i++) {
1279 rand = arc4random();
1280 cookie[i] = rand & 0xff;
1285 * Send our public key. We include in the packet 64 bits of random
1286 * data that must be matched in the reply in order to prevent IP
1289 packet_start(SSH_SMSG_PUBLIC_KEY);
1290 for (i = 0; i < 8; i++)
1291 packet_put_char(cookie[i]);
1293 /* Store our public server RSA key. */
1294 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1295 packet_put_bignum(sensitive_data.server_key->rsa->e);
1296 packet_put_bignum(sensitive_data.server_key->rsa->n);
1298 /* Store our public host RSA key. */
1299 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1300 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1301 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1303 /* Put protocol flags. */
1304 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1306 /* Declare which ciphers we support. */
1307 packet_put_int(cipher_mask_ssh1(0));
1309 /* Declare supported authentication types. */
1311 if (options.rhosts_authentication)
1312 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1313 if (options.rhosts_rsa_authentication)
1314 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1315 if (options.rsa_authentication)
1316 auth_mask |= 1 << SSH_AUTH_RSA;
1317 #if defined(KRB4) || defined(KRB5)
1318 if (options.kerberos_authentication)
1319 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1321 #if defined(AFS) || defined(KRB5)
1322 if (options.kerberos_tgt_passing)
1323 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1326 if (options.afs_token_passing)
1327 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1329 if (options.challenge_response_authentication == 1)
1330 auth_mask |= 1 << SSH_AUTH_TIS;
1331 if (options.password_authentication)
1332 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1333 packet_put_int(auth_mask);
1335 /* Send the packet and wait for it to be sent. */
1337 packet_write_wait();
1339 debug("Sent %d bit server key and %d bit host key.",
1340 BN_num_bits(sensitive_data.server_key->rsa->n),
1341 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1343 /* Read clients reply (cipher type and session key). */
1344 packet_read_expect(SSH_CMSG_SESSION_KEY);
1346 /* Get cipher type and check whether we accept this. */
1347 cipher_type = packet_get_char();
1349 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1350 packet_disconnect("Warning: client selects unsupported cipher.");
1352 /* Get check bytes from the packet. These must match those we
1353 sent earlier with the public key packet. */
1354 for (i = 0; i < 8; i++)
1355 if (cookie[i] != packet_get_char())
1356 packet_disconnect("IP Spoofing check bytes do not match.");
1358 debug("Encryption type: %.200s", cipher_name(cipher_type));
1360 /* Get the encrypted integer. */
1361 if ((session_key_int = BN_new()) == NULL)
1362 fatal("do_ssh1_kex: BN_new failed");
1363 packet_get_bignum(session_key_int);
1365 protocol_flags = packet_get_int();
1366 packet_set_protocol_flags(protocol_flags);
1370 * Decrypt it using our private server key and private host key (key
1371 * with larger modulus first).
1373 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1374 /* Server key has bigger modulus. */
1375 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1376 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1377 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1378 get_remote_ipaddr(),
1379 BN_num_bits(sensitive_data.server_key->rsa->n),
1380 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1381 SSH_KEY_BITS_RESERVED);
1383 if (rsa_private_decrypt(session_key_int, session_key_int,
1384 sensitive_data.server_key->rsa) <= 0)
1386 if (rsa_private_decrypt(session_key_int, session_key_int,
1387 sensitive_data.ssh1_host_key->rsa) <= 0)
1390 /* Host key has bigger modulus (or they are equal). */
1391 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1392 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1393 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1394 get_remote_ipaddr(),
1395 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1396 BN_num_bits(sensitive_data.server_key->rsa->n),
1397 SSH_KEY_BITS_RESERVED);
1399 if (rsa_private_decrypt(session_key_int, session_key_int,
1400 sensitive_data.ssh1_host_key->rsa) < 0)
1402 if (rsa_private_decrypt(session_key_int, session_key_int,
1403 sensitive_data.server_key->rsa) < 0)
1407 * Extract session key from the decrypted integer. The key is in the
1408 * least significant 256 bits of the integer; the first byte of the
1409 * key is in the highest bits.
1412 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1413 len = BN_num_bytes(session_key_int);
1414 if (len < 0 || len > sizeof(session_key)) {
1415 error("do_connection: bad session key len from %s: "
1416 "session_key_int %d > sizeof(session_key) %lu",
1417 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
1420 memset(session_key, 0, sizeof(session_key));
1421 BN_bn2bin(session_key_int,
1422 session_key + sizeof(session_key) - len);
1424 compute_session_id(session_id, cookie,
1425 sensitive_data.ssh1_host_key->rsa->n,
1426 sensitive_data.server_key->rsa->n);
1428 * Xor the first 16 bytes of the session key with the
1431 for (i = 0; i < 16; i++)
1432 session_key[i] ^= session_id[i];
1436 int bytes = BN_num_bytes(session_key_int);
1437 u_char *buf = xmalloc(bytes);
1440 log("do_connection: generating a fake encryption key");
1441 BN_bn2bin(session_key_int, buf);
1443 MD5_Update(&md, buf, bytes);
1444 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1445 MD5_Final(session_key, &md);
1447 MD5_Update(&md, session_key, 16);
1448 MD5_Update(&md, buf, bytes);
1449 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1450 MD5_Final(session_key + 16, &md);
1451 memset(buf, 0, bytes);
1453 for (i = 0; i < 16; i++)
1454 session_id[i] = session_key[i] ^ session_key[i + 16];
1456 /* Destroy the private and public keys. They will no longer be needed. */
1457 destroy_sensitive_data();
1459 /* Destroy the decrypted integer. It is no longer needed. */
1460 BN_clear_free(session_key_int);
1462 /* Set the session key. From this on all communications will be encrypted. */
1463 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1465 /* Destroy our copy of the session key. It is no longer needed. */
1466 memset(session_key, 0, sizeof(session_key));
1468 debug("Received session key; encryption turned on.");
1470 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1471 packet_start(SSH_SMSG_SUCCESS);
1473 packet_write_wait();
1477 * SSH2 key exchange: diffie-hellman-group1-sha1
1484 if (options.ciphers != NULL) {
1485 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1486 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1488 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1489 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
1490 myproposal[PROPOSAL_ENC_ALGS_STOC] =
1491 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
1493 if (options.macs != NULL) {
1494 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
1495 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
1497 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
1499 /* start key exchange */
1500 kex = kex_setup(myproposal);
1502 kex->client_version_string=client_version_string;
1503 kex->server_version_string=server_version_string;
1504 kex->load_host_key=&get_hostkey_by_type;
1508 dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
1510 session_id2 = kex->session_id;
1511 session_id2_len = kex->session_id_len;
1514 /* send 1st encrypted/maced/compressed message */
1515 packet_start(SSH2_MSG_IGNORE);
1516 packet_put_cstring("markus");
1518 packet_write_wait();