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 1.200 2001/06/23 15:12:21 itojun 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 is being started from inetd. */
119 /* Flag indicating that sshd should not detach and become a daemon. */
120 int no_daemon_flag = 0;
122 /* debug goes to stderr unless inetd_flag is set */
125 /* Saved arguments to main(). */
130 * The sockets that the server is listening; this is used in the SIGHUP
133 #define MAX_LISTEN_SOCKS 16
134 int listen_socks[MAX_LISTEN_SOCKS];
135 int num_listen_socks = 0;
138 * the client's version string, passed by sshd2 in compat mode. if != NULL,
139 * sshd will skip the version-number exchange
141 char *client_version_string = NULL;
142 char *server_version_string = NULL;
144 /* for rekeying XXX fixme */
148 * Any really sensitive data in the application is contained in this
149 * structure. The idea is that this structure could be locked into memory so
150 * that the pages do not get written into swap. However, there are some
151 * problems. The private key contains BIGNUMs, and we do not (in principle)
152 * have access to the internals of them, and locking just the structure is
153 * not very useful. Currently, memory locking is not implemented.
156 Key *server_key; /* ephemeral server key */
157 Key *ssh1_host_key; /* ssh1 host key */
158 Key **host_keys; /* all private host keys */
161 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
165 * Flag indicating whether the RSA server key needs to be regenerated.
166 * Is set in the SIGALRM handler and cleared when the key is regenerated.
168 int key_do_regen = 0;
170 /* This is set to true when a signal is received. */
171 int received_sighup = 0;
172 int received_sigterm = 0;
174 /* session identifier, used by RSA-auth */
175 u_char session_id[16];
178 u_char *session_id2 = NULL;
179 int session_id2_len = 0;
181 /* record remote hostname or ip */
182 u_int utmp_len = MAXHOSTNAMELEN;
184 /* Prototypes for various functions defined later in this file. */
185 void destroy_sensitive_data(void);
187 static void do_ssh1_kex(void);
188 static void do_ssh2_kex(void);
191 * Close all listening sockets
194 close_listen_socks(void)
197 for (i = 0; i < num_listen_socks; i++)
198 close(listen_socks[i]);
199 num_listen_socks = -1;
203 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
204 * the effect is to reread the configuration file (and to regenerate
208 sighup_handler(int sig)
211 signal(SIGHUP, sighup_handler);
215 * Called from the main program after receiving SIGHUP.
216 * Restarts the server.
221 log("Received SIGHUP; restarting.");
222 close_listen_socks();
223 execv(saved_argv[0], saved_argv);
224 log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], strerror(errno));
229 * Generic signal handler for terminating signals in the master daemon.
232 sigterm_handler(int sig)
234 received_sigterm = sig;
238 * SIGCHLD handler. This is called whenever a child dies. This will then
239 * reap any zombies left by exited children.
242 main_sigchld_handler(int sig)
244 int save_errno = errno;
247 while (waitpid(-1, &status, WNOHANG) > 0)
250 signal(SIGCHLD, main_sigchld_handler);
255 * Signal handler for the alarm after the login grace period has expired.
258 grace_alarm_handler(int sig)
260 /* XXX no idea how fix this signal handler */
262 /* Close the connection. */
265 /* Log error and exit. */
266 fatal("Timeout before authentication for %s.", get_remote_ipaddr());
270 * Signal handler for the key regeneration alarm. Note that this
271 * alarm only occurs in the daemon waiting for connections, and it does not
272 * do anything with the private key or random state before forking.
273 * Thus there should be no concurrency control/asynchronous execution
277 generate_ephemeral_server_key(void)
282 verbose("Generating %s%d bit RSA key.",
283 sensitive_data.server_key ? "new " : "", options.server_key_bits);
284 if (sensitive_data.server_key != NULL)
285 key_free(sensitive_data.server_key);
286 sensitive_data.server_key = key_generate(KEY_RSA1,
287 options.server_key_bits);
288 verbose("RSA key generation complete.");
290 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
293 sensitive_data.ssh1_cookie[i] = rand & 0xff;
300 key_regeneration_alarm(int sig)
302 int save_errno = errno;
303 signal(SIGALRM, SIG_DFL);
309 sshd_exchange_identification(int sock_in, int sock_out)
312 int remote_major, remote_minor;
315 char buf[256]; /* Must not be larger than remote_version. */
316 char remote_version[256]; /* Must be at least as big as buf. */
318 if ((options.protocol & SSH_PROTO_1) &&
319 (options.protocol & SSH_PROTO_2)) {
320 major = PROTOCOL_MAJOR_1;
322 } else if (options.protocol & SSH_PROTO_2) {
323 major = PROTOCOL_MAJOR_2;
324 minor = PROTOCOL_MINOR_2;
326 major = PROTOCOL_MAJOR_1;
327 minor = PROTOCOL_MINOR_1;
329 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
330 server_version_string = xstrdup(buf);
332 if (client_version_string == NULL) {
333 /* Send our protocol version identification. */
334 if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
335 != strlen(server_version_string)) {
336 log("Could not write ident string to %s.", get_remote_ipaddr());
340 /* Read other side's version identification. */
341 memset(buf, 0, sizeof(buf));
342 for (i = 0; i < sizeof(buf) - 1; i++) {
343 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
344 log("Did not receive identification string from %s.",
345 get_remote_ipaddr());
348 if (buf[i] == '\r') {
350 /* Kludge for F-Secure Macintosh < 1.0.2 */
352 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
356 if (buf[i] == '\n') {
361 buf[sizeof(buf) - 1] = 0;
362 client_version_string = xstrdup(buf);
366 * Check that the versions match. In future this might accept
367 * several versions and set appropriate flags to handle them.
369 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
370 &remote_major, &remote_minor, remote_version) != 3) {
371 s = "Protocol mismatch.\n";
372 (void) atomicio(write, sock_out, s, strlen(s));
375 log("Bad protocol version identification '%.100s' from %s",
376 client_version_string, get_remote_ipaddr());
379 debug("Client protocol version %d.%d; client software version %.100s",
380 remote_major, remote_minor, remote_version);
382 compat_datafellows(remote_version);
384 if (datafellows & SSH_BUG_SCANNER) {
385 log("scanned from %s with %s. Don't panic.",
386 get_remote_ipaddr(), client_version_string);
391 switch(remote_major) {
393 if (remote_minor == 99) {
394 if (options.protocol & SSH_PROTO_2)
400 if (!(options.protocol & SSH_PROTO_1)) {
404 if (remote_minor < 3) {
405 packet_disconnect("Your ssh version is too old and "
406 "is no longer supported. Please install a newer version.");
407 } else if (remote_minor == 3) {
408 /* note that this disables agent-forwarding */
413 if (options.protocol & SSH_PROTO_2) {
422 chop(server_version_string);
423 debug("Local version string %.200s", server_version_string);
426 s = "Protocol major versions differ.\n";
427 (void) atomicio(write, sock_out, s, strlen(s));
430 log("Protocol major versions differ for %s: %.200s vs. %.200s",
432 server_version_string, client_version_string);
438 /* Destroy the host and server keys. They will no longer be needed. */
440 destroy_sensitive_data(void)
444 if (sensitive_data.server_key) {
445 key_free(sensitive_data.server_key);
446 sensitive_data.server_key = NULL;
448 for(i = 0; i < options.num_host_key_files; i++) {
449 if (sensitive_data.host_keys[i]) {
450 key_free(sensitive_data.host_keys[i]);
451 sensitive_data.host_keys[i] = NULL;
454 sensitive_data.ssh1_host_key = NULL;
455 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
459 list_hostkey_types(void)
461 static char buf[1024];
464 for(i = 0; i < options.num_host_key_files; i++) {
465 Key *key = sensitive_data.host_keys[i];
471 strlcat(buf, key_ssh_name(key), sizeof buf);
472 strlcat(buf, ",", sizeof buf);
477 if (i > 0 && buf[i-1] == ',')
479 debug("list_hostkey_types: %s", buf);
484 get_hostkey_by_type(int type)
487 for(i = 0; i < options.num_host_key_files; i++) {
488 Key *key = sensitive_data.host_keys[i];
489 if (key != NULL && key->type == type)
496 * returns 1 if connection should be dropped, 0 otherwise.
497 * dropping starts at connection #max_startups_begin with a probability
498 * of (max_startups_rate/100). the probability increases linearly until
499 * all connections are dropped for startups > max_startups
502 drop_connection(int startups)
506 if (startups < options.max_startups_begin)
508 if (startups >= options.max_startups)
510 if (options.max_startups_rate == 100)
513 p = 100 - options.max_startups_rate;
514 p *= startups - options.max_startups_begin;
515 p /= (double) (options.max_startups - options.max_startups_begin);
516 p += options.max_startups_rate;
518 r = arc4random() / (double) UINT_MAX;
520 debug("drop_connection: p %g, r %g", p, r);
521 return (r < p) ? 1 : 0;
524 int *startup_pipes = NULL; /* options.max_startup sized array of fd ints */
525 int startup_pipe; /* in child */
528 * Main program for the daemon.
531 main(int ac, char **av)
535 int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
539 struct sockaddr_storage from;
540 const char *remote_ip;
543 struct linger linger;
545 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
546 int listen_sock, maxfd;
550 int ret, key_used = 0;
552 __progname = get_progname(av[0]);
559 /* Initialize configuration options to their default values. */
560 initialize_server_options(&options);
562 /* Parse command-line arguments. */
563 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:dDeiqQ46")) != -1) {
572 config_file_name = optarg;
575 if (0 == debug_flag) {
577 options.log_level = SYSLOG_LEVEL_DEBUG1;
578 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
581 fprintf(stderr, "Too high debugging level.\n");
598 options.log_level = SYSLOG_LEVEL_QUIET;
601 options.server_key_bits = atoi(optarg);
604 options.ports_from_cmdline = 1;
605 if (options.num_ports >= MAX_PORTS) {
606 fprintf(stderr, "too many ports.\n");
609 options.ports[options.num_ports++] = a2port(optarg);
610 if (options.ports[options.num_ports-1] == 0) {
611 fprintf(stderr, "Bad port number.\n");
616 if ((options.login_grace_time = convtime(optarg)) == -1) {
617 fprintf(stderr, "Invalid login grace time.\n");
622 if ((options.key_regeneration_time = convtime(optarg)) == -1) {
623 fprintf(stderr, "Invalid key regeneration interval.\n");
628 if (options.num_host_key_files >= MAX_HOSTKEYS) {
629 fprintf(stderr, "too many host keys.\n");
632 options.host_key_files[options.num_host_key_files++] = optarg;
635 client_version_string = optarg;
636 /* only makes sense with inetd_flag, i.e. no listen() */
640 utmp_len = atoi(optarg);
644 fprintf(stderr, "sshd version %s\n", SSH_VERSION);
645 fprintf(stderr, "Usage: %s [options]\n", __progname);
646 fprintf(stderr, "Options:\n");
647 fprintf(stderr, " -f file Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE);
648 fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n");
649 fprintf(stderr, " -i Started from inetd\n");
650 fprintf(stderr, " -D Do not fork into daemon mode\n");
651 fprintf(stderr, " -q Quiet (no logging)\n");
652 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
653 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
654 fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n");
655 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
656 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
657 _PATH_HOST_KEY_FILE);
658 fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
659 fprintf(stderr, " -4 Use IPv4 only\n");
660 fprintf(stderr, " -6 Use IPv6 only\n");
664 SSLeay_add_all_algorithms();
667 * Force logging to stderr until we have loaded the private host
668 * key (unless started from inetd)
671 options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
672 options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
677 /* Read server configuration options from the configuration file. */
678 read_server_config(&options, config_file_name);
680 /* Fill in default values for those options not explicitly set. */
681 fill_default_server_options(&options);
683 /* Check that there are no remaining arguments. */
685 fprintf(stderr, "Extra argument %s.\n", av[optind]);
689 debug("sshd version %.100s", SSH_VERSION);
691 /* load private host keys */
692 sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*));
693 for(i = 0; i < options.num_host_key_files; i++)
694 sensitive_data.host_keys[i] = NULL;
695 sensitive_data.server_key = NULL;
696 sensitive_data.ssh1_host_key = NULL;
697 sensitive_data.have_ssh1_key = 0;
698 sensitive_data.have_ssh2_key = 0;
700 for(i = 0; i < options.num_host_key_files; i++) {
701 key = key_load_private(options.host_key_files[i], "", NULL);
702 sensitive_data.host_keys[i] = key;
704 error("Could not load host key: %s",
705 options.host_key_files[i]);
706 sensitive_data.host_keys[i] = NULL;
711 sensitive_data.ssh1_host_key = key;
712 sensitive_data.have_ssh1_key = 1;
716 sensitive_data.have_ssh2_key = 1;
719 debug("private host key: #%d type %d %s", i, key->type,
722 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
723 log("Disabling protocol version 1. Could not load host key");
724 options.protocol &= ~SSH_PROTO_1;
726 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
727 log("Disabling protocol version 2. Could not load host key");
728 options.protocol &= ~SSH_PROTO_2;
730 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
731 log("sshd: no hostkeys available -- exiting.");
735 /* Check certain values for sanity. */
736 if (options.protocol & SSH_PROTO_1) {
737 if (options.server_key_bits < 512 ||
738 options.server_key_bits > 32768) {
739 fprintf(stderr, "Bad server key size.\n");
743 * Check that server and host key lengths differ sufficiently. This
744 * is necessary to make double encryption work with rsaref. Oh, I
745 * hate software patents. I dont know if this can go? Niels
747 if (options.server_key_bits >
748 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - SSH_KEY_BITS_RESERVED &&
749 options.server_key_bits <
750 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
751 options.server_key_bits =
752 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED;
753 debug("Forcing server key to %d bits to make it differ from host key.",
754 options.server_key_bits);
758 #ifdef HAVE_SCO_PROTECTED_PW
759 (void) set_auth_parameters(ac, av);
762 /* Initialize the log (it is reinitialized below in case we forked). */
763 if (debug_flag && !inetd_flag)
765 log_init(__progname, options.log_level, options.log_facility, log_stderr);
768 * If not in debugging mode, and not started from inetd, disconnect
769 * from the controlling terminal, and fork. The original process
772 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
775 #endif /* TIOCNOTTY */
776 if (daemon(0, 0) < 0)
777 fatal("daemon() failed: %.200s", strerror(errno));
779 /* Disconnect from the controlling tty. */
781 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
783 (void) ioctl(fd, TIOCNOTTY, NULL);
786 #endif /* TIOCNOTTY */
788 /* Reinitialize the log (because of the fork above). */
789 log_init(__progname, options.log_level, options.log_facility, log_stderr);
791 /* Initialize the random number generator. */
794 /* Chdir to the root directory so that the current disk can be
795 unmounted if desired. */
799 signal(SIGPIPE, SIG_IGN);
801 /* Start listening for a socket, unless started from inetd. */
804 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
810 * We intentionally do not close the descriptors 0, 1, and 2
811 * as our code for setting the descriptors won\'t work if
812 * ttyfd happens to be one of those.
814 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
815 if (options.protocol & SSH_PROTO_1)
816 generate_ephemeral_server_key();
818 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
819 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
821 if (num_listen_socks >= MAX_LISTEN_SOCKS)
822 fatal("Too many listen sockets. "
823 "Enlarge MAX_LISTEN_SOCKS");
824 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
825 ntop, sizeof(ntop), strport, sizeof(strport),
826 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
827 error("getnameinfo failed");
830 /* Create socket for listening. */
831 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
832 if (listen_sock < 0) {
833 /* kernel may not support ipv6 */
834 verbose("socket: %.100s", strerror(errno));
837 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
838 error("listen_sock O_NONBLOCK: %s", strerror(errno));
843 * Set socket options. We try to make the port
844 * reusable and have it close as fast as possible
845 * without waiting in unnecessary wait states on
848 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
849 (void *) &on, sizeof(on));
852 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
853 (void *) &linger, sizeof(linger));
855 debug("Bind to port %s on %s.", strport, ntop);
857 /* Bind the socket to the desired port. */
858 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
860 error("Bind to port %s on %s failed: %.200s.",
861 strport, ntop, strerror(errno));
865 listen_socks[num_listen_socks] = listen_sock;
868 /* Start listening on the port. */
869 log("Server listening on %s port %s.", ntop, strport);
870 if (listen(listen_sock, 5) < 0)
871 fatal("listen: %.100s", strerror(errno));
874 freeaddrinfo(options.listen_addrs);
876 if (!num_listen_socks)
877 fatal("Cannot bind any address.");
881 * Record our pid in /var/run/sshd.pid to make it
882 * easier to kill the correct sshd. We don't want to
883 * do this before the bind above because the bind will
884 * fail if there already is a daemon, and this will
885 * overwrite any old pid in the file.
887 f = fopen(options.pid_file, "wb");
889 fprintf(f, "%u\n", (u_int) getpid());
893 if (options.protocol & SSH_PROTO_1)
894 generate_ephemeral_server_key();
896 /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
897 signal(SIGHUP, sighup_handler);
899 signal(SIGTERM, sigterm_handler);
900 signal(SIGQUIT, sigterm_handler);
902 /* Arrange SIGCHLD to be caught. */
903 signal(SIGCHLD, main_sigchld_handler);
905 /* setup fd set for listen */
908 for (i = 0; i < num_listen_socks; i++)
909 if (listen_socks[i] > maxfd)
910 maxfd = listen_socks[i];
911 /* pipes connected to unauthenticated childs */
912 startup_pipes = xmalloc(options.max_startups * sizeof(int));
913 for (i = 0; i < options.max_startups; i++)
914 startup_pipes[i] = -1;
917 * Stay listening for connections until the system crashes or
918 * the daemon is killed with a signal.
925 fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
926 fdset = (fd_set *)xmalloc(fdsetsz);
927 memset(fdset, 0, fdsetsz);
929 for (i = 0; i < num_listen_socks; i++)
930 FD_SET(listen_socks[i], fdset);
931 for (i = 0; i < options.max_startups; i++)
932 if (startup_pipes[i] != -1)
933 FD_SET(startup_pipes[i], fdset);
935 /* Wait in select until there is a connection. */
936 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
937 if (ret < 0 && errno != EINTR)
938 error("select: %.100s", strerror(errno));
939 if (received_sigterm) {
940 log("Received signal %d; terminating.",
942 close_listen_socks();
943 unlink(options.pid_file);
946 if (key_used && key_do_regen) {
947 generate_ephemeral_server_key();
954 for (i = 0; i < options.max_startups; i++)
955 if (startup_pipes[i] != -1 &&
956 FD_ISSET(startup_pipes[i], fdset)) {
958 * the read end of the pipe is ready
959 * if the child has closed the pipe
960 * after successful authentication
961 * or if the child has died
963 close(startup_pipes[i]);
964 startup_pipes[i] = -1;
967 for (i = 0; i < num_listen_socks; i++) {
968 if (!FD_ISSET(listen_socks[i], fdset))
970 fromlen = sizeof(from);
971 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
974 if (errno != EINTR && errno != EWOULDBLOCK)
975 error("accept: %.100s", strerror(errno));
978 if (fcntl(newsock, F_SETFL, 0) < 0) {
979 error("newsock del O_NONBLOCK: %s", strerror(errno));
982 if (drop_connection(startups) == 1) {
983 debug("drop connection #%d", startups);
987 if (pipe(startup_p) == -1) {
992 for (j = 0; j < options.max_startups; j++)
993 if (startup_pipes[j] == -1) {
994 startup_pipes[j] = startup_p[0];
995 if (maxfd < startup_p[0])
996 maxfd = startup_p[0];
1002 * Got connection. Fork a child to handle it, unless
1003 * we are in debugging mode.
1007 * In debugging mode. Close the listening
1008 * socket, and start processing the
1009 * connection without forking.
1011 debug("Server will not fork when running in debugging mode.");
1012 close_listen_socks();
1020 * Normal production daemon. Fork, and have
1021 * the child process the connection. The
1022 * parent continues listening.
1024 if ((pid = fork()) == 0) {
1026 * Child. Close the listening and max_startup
1027 * sockets. Start using the accepted socket.
1028 * Reinitialize logging (since our pid has
1029 * changed). We break out of the loop to handle
1032 startup_pipe = startup_p[1];
1033 for (j = 0; j < options.max_startups; j++)
1034 if (startup_pipes[j] != -1)
1035 close(startup_pipes[j]);
1036 close_listen_socks();
1039 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1044 /* Parent. Stay in the loop. */
1046 error("fork: %.100s", strerror(errno));
1048 debug("Forked child %d.", pid);
1050 close(startup_p[1]);
1052 /* Mark that the key has been used (it was "given" to the child). */
1053 if ((options.protocol & SSH_PROTO_1) &&
1055 /* Schedule server key regeneration alarm. */
1056 signal(SIGALRM, key_regeneration_alarm);
1057 alarm(options.key_regeneration_time);
1063 /* Close the new socket (the child is now taking care of it). */
1066 /* child process check (or debug mode) */
1067 if (num_listen_socks < 0)
1072 /* This is the child processing a new connection. */
1075 * Disable the key regeneration alarm. We will not regenerate the
1076 * key since we are no longer in a position to give it to anyone. We
1077 * will not restart on SIGHUP since it no longer makes sense.
1080 signal(SIGALRM, SIG_DFL);
1081 signal(SIGHUP, SIG_DFL);
1082 signal(SIGTERM, SIG_DFL);
1083 signal(SIGQUIT, SIG_DFL);
1084 signal(SIGCHLD, SIG_DFL);
1085 signal(SIGINT, SIG_DFL);
1088 * Set socket options for the connection. We want the socket to
1089 * close as fast as possible without waiting for anything. If the
1090 * connection is not a socket, these will do nothing.
1092 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1094 linger.l_linger = 5;
1095 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
1097 /* Set keepalives if requested. */
1098 if (options.keepalives &&
1099 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
1101 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1104 * Register our connection. This turns encryption off because we do
1107 packet_set_connection(sock_in, sock_out);
1109 remote_port = get_remote_port();
1110 remote_ip = get_remote_ipaddr();
1112 /* Check whether logins are denied from this host. */
1114 /* XXX LIBWRAP noes not know about IPv6 */
1116 struct request_info req;
1118 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, NULL);
1121 if (!hosts_access(&req)) {
1126 /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
1128 #endif /* LIBWRAP */
1129 /* Log the connection. */
1130 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1133 * We don\'t want to listen forever unless the other side
1134 * successfully authenticates itself. So we set up an alarm which is
1135 * cleared after successful authentication. A limit of zero
1136 * indicates no limit. Note that we don\'t set the alarm in debugging
1137 * mode; it is just annoying to have the server exit just when you
1138 * are about to discover the bug.
1140 signal(SIGALRM, grace_alarm_handler);
1142 alarm(options.login_grace_time);
1144 sshd_exchange_identification(sock_in, sock_out);
1146 * Check that the connection comes from a privileged port.
1147 * Rhosts-Authentication only makes sense from priviledged
1148 * programs. Of course, if the intruder has root access on his local
1149 * machine, he can connect from any port. So do not use these
1150 * authentication methods from machines that you do not trust.
1152 if (remote_port >= IPPORT_RESERVED ||
1153 remote_port < IPPORT_RESERVED / 2) {
1154 debug("Rhosts Authentication disabled, "
1155 "originating port not trusted.");
1156 options.rhosts_authentication = 0;
1159 if (!packet_connection_is_ipv4() &&
1160 options.kerberos_authentication) {
1161 debug("Kerberos Authentication disabled, only available for IPv4.");
1162 options.kerberos_authentication = 0;
1166 /* If machine has AFS, set process authentication group. */
1173 packet_set_nonblocking();
1175 /* perform the key exchange */
1176 /* authenticate user and start session */
1179 do_authentication2();
1182 do_authentication();
1186 /* Cleanup user's ticket cache file. */
1187 if (options.kerberos_ticket_cleanup)
1191 /* The connection has been terminated. */
1192 verbose("Closing connection to %.100s", remote_ip);
1196 #endif /* USE_PAM */
1211 BIGNUM *session_key_int;
1212 u_char session_key[SSH_SESSION_KEY_LENGTH];
1214 u_int cipher_type, auth_mask, protocol_flags;
1218 * Generate check bytes that the client must send back in the user
1219 * packet in order for it to be accepted; this is used to defy ip
1220 * spoofing attacks. Note that this only works against somebody
1221 * doing IP spoofing from a remote machine; any machine on the local
1222 * network can still see outgoing packets and catch the random
1223 * cookie. This only affects rhosts authentication, and this is one
1224 * of the reasons why it is inherently insecure.
1226 for (i = 0; i < 8; i++) {
1228 rand = arc4random();
1229 cookie[i] = rand & 0xff;
1234 * Send our public key. We include in the packet 64 bits of random
1235 * data that must be matched in the reply in order to prevent IP
1238 packet_start(SSH_SMSG_PUBLIC_KEY);
1239 for (i = 0; i < 8; i++)
1240 packet_put_char(cookie[i]);
1242 /* Store our public server RSA key. */
1243 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1244 packet_put_bignum(sensitive_data.server_key->rsa->e);
1245 packet_put_bignum(sensitive_data.server_key->rsa->n);
1247 /* Store our public host RSA key. */
1248 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1249 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1250 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1252 /* Put protocol flags. */
1253 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1255 /* Declare which ciphers we support. */
1256 packet_put_int(cipher_mask_ssh1(0));
1258 /* Declare supported authentication types. */
1260 if (options.rhosts_authentication)
1261 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1262 if (options.rhosts_rsa_authentication)
1263 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1264 if (options.rsa_authentication)
1265 auth_mask |= 1 << SSH_AUTH_RSA;
1267 if (options.kerberos_authentication)
1268 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1271 if (options.kerberos_tgt_passing)
1272 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1273 if (options.afs_token_passing)
1274 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1276 if (options.challenge_response_authentication == 1)
1277 auth_mask |= 1 << SSH_AUTH_TIS;
1278 if (options.password_authentication)
1279 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1280 packet_put_int(auth_mask);
1282 /* Send the packet and wait for it to be sent. */
1284 packet_write_wait();
1286 debug("Sent %d bit server key and %d bit host key.",
1287 BN_num_bits(sensitive_data.server_key->rsa->n),
1288 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1290 /* Read clients reply (cipher type and session key). */
1291 packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1293 /* Get cipher type and check whether we accept this. */
1294 cipher_type = packet_get_char();
1296 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1297 packet_disconnect("Warning: client selects unsupported cipher.");
1299 /* Get check bytes from the packet. These must match those we
1300 sent earlier with the public key packet. */
1301 for (i = 0; i < 8; i++)
1302 if (cookie[i] != packet_get_char())
1303 packet_disconnect("IP Spoofing check bytes do not match.");
1305 debug("Encryption type: %.200s", cipher_name(cipher_type));
1307 /* Get the encrypted integer. */
1308 session_key_int = BN_new();
1309 packet_get_bignum(session_key_int, &slen);
1311 protocol_flags = packet_get_int();
1312 packet_set_protocol_flags(protocol_flags);
1314 packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1317 * Decrypt it using our private server key and private host key (key
1318 * with larger modulus first).
1320 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1321 /* Server key has bigger modulus. */
1322 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1323 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1324 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1325 get_remote_ipaddr(),
1326 BN_num_bits(sensitive_data.server_key->rsa->n),
1327 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1328 SSH_KEY_BITS_RESERVED);
1330 if (rsa_private_decrypt(session_key_int, session_key_int,
1331 sensitive_data.server_key->rsa) <= 0)
1333 if (rsa_private_decrypt(session_key_int, session_key_int,
1334 sensitive_data.ssh1_host_key->rsa) <= 0)
1337 /* Host key has bigger modulus (or they are equal). */
1338 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1339 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1340 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1341 get_remote_ipaddr(),
1342 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1343 BN_num_bits(sensitive_data.server_key->rsa->n),
1344 SSH_KEY_BITS_RESERVED);
1346 if (rsa_private_decrypt(session_key_int, session_key_int,
1347 sensitive_data.ssh1_host_key->rsa) < 0)
1349 if (rsa_private_decrypt(session_key_int, session_key_int,
1350 sensitive_data.server_key->rsa) < 0)
1354 * Extract session key from the decrypted integer. The key is in the
1355 * least significant 256 bits of the integer; the first byte of the
1356 * key is in the highest bits.
1359 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1360 len = BN_num_bytes(session_key_int);
1361 if (len < 0 || len > sizeof(session_key)) {
1362 error("do_connection: bad session key len from %s: "
1363 "session_key_int %d > sizeof(session_key) %lu",
1364 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
1367 memset(session_key, 0, sizeof(session_key));
1368 BN_bn2bin(session_key_int,
1369 session_key + sizeof(session_key) - len);
1371 compute_session_id(session_id, cookie,
1372 sensitive_data.ssh1_host_key->rsa->n,
1373 sensitive_data.server_key->rsa->n);
1375 * Xor the first 16 bytes of the session key with the
1378 for (i = 0; i < 16; i++)
1379 session_key[i] ^= session_id[i];
1383 int bytes = BN_num_bytes(session_key_int);
1384 char *buf = xmalloc(bytes);
1387 log("do_connection: generating a fake encryption key");
1388 BN_bn2bin(session_key_int, buf);
1390 MD5_Update(&md, buf, bytes);
1391 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1392 MD5_Final(session_key, &md);
1394 MD5_Update(&md, session_key, 16);
1395 MD5_Update(&md, buf, bytes);
1396 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1397 MD5_Final(session_key + 16, &md);
1398 memset(buf, 0, bytes);
1400 for (i = 0; i < 16; i++)
1401 session_id[i] = session_key[i] ^ session_key[i + 16];
1403 /* Destroy the private and public keys. They will no longer be needed. */
1404 destroy_sensitive_data();
1406 /* Destroy the decrypted integer. It is no longer needed. */
1407 BN_clear_free(session_key_int);
1409 /* Set the session key. From this on all communications will be encrypted. */
1410 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1412 /* Destroy our copy of the session key. It is no longer needed. */
1413 memset(session_key, 0, sizeof(session_key));
1415 debug("Received session key; encryption turned on.");
1417 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1418 packet_start(SSH_SMSG_SUCCESS);
1420 packet_write_wait();
1424 * SSH2 key exchange: diffie-hellman-group1-sha1
1431 if (options.ciphers != NULL) {
1432 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1433 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1435 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1436 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
1437 myproposal[PROPOSAL_ENC_ALGS_STOC] =
1438 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
1440 if (options.macs != NULL) {
1441 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
1442 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
1444 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
1446 /* start key exchange */
1447 kex = kex_setup(myproposal);
1449 kex->client_version_string=client_version_string;
1450 kex->server_version_string=server_version_string;
1451 kex->load_host_key=&get_hostkey_by_type;
1455 dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
1457 session_id2 = kex->session_id;
1458 session_id2_len = kex->session_id_len;
1461 /* send 1st encrypted/maced/compressed message */
1462 packet_start(SSH2_MSG_IGNORE);
1463 packet_put_cstring("markus");
1465 packet_write_wait();