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 1.139 2000/12/15 17:30:14 provos Exp $");
57 #include <openssl/dh.h>
58 #include <openssl/bn.h>
59 #include <openssl/hmac.h>
61 #include <openssl/dsa.h>
62 #include <openssl/rsa.h>
67 #include "myproposal.h"
73 int allow_severity = LOG_INFO;
74 int deny_severity = LOG_WARNING;
81 #ifdef HAVE___PROGNAME
82 extern char *__progname;
87 /* Server configuration options. */
88 ServerOptions options;
90 /* Name of the server configuration file. */
91 char *config_file_name = SERVER_CONFIG_FILE;
94 * Flag indicating whether IPv4 or IPv6. This can be set on the command line.
95 * Default value is AF_UNSPEC means both IPv4 and IPv6.
98 int IPv4or6 = AF_INET;
100 int IPv4or6 = AF_UNSPEC;
104 * Debug mode flag. This can be set on the command line. If debug
105 * mode is enabled, extra debugging output will be sent to the system
106 * log, the daemon will not go to background, and will exit after processing
107 * the first connection.
111 /* Flag indicating that the daemon is being started from inetd. */
114 /* Flag indicating that sshd should not detach and become a daemon. */
115 int no_daemon_flag = 0;
117 /* debug goes to stderr unless inetd_flag is set */
120 /* Saved arguments to main(). */
125 * The sockets that the server is listening; this is used in the SIGHUP
128 #define MAX_LISTEN_SOCKS 16
129 int listen_socks[MAX_LISTEN_SOCKS];
130 int num_listen_socks = 0;
133 * the client's version string, passed by sshd2 in compat mode. if != NULL,
134 * sshd will skip the version-number exchange
136 char *client_version_string = NULL;
137 char *server_version_string = NULL;
140 * Any really sensitive data in the application is contained in this
141 * structure. The idea is that this structure could be locked into memory so
142 * that the pages do not get written into swap. However, there are some
143 * problems. The private key contains BIGNUMs, and we do not (in principle)
144 * have access to the internals of them, and locking just the structure is
145 * not very useful. Currently, memory locking is not implemented.
148 Key *server_key; /* empheral server key */
149 Key *ssh1_host_key; /* ssh1 host key */
150 Key **host_keys; /* all private host keys */
156 * Flag indicating whether the current session key has been used. This flag
157 * is set whenever the key is used, and cleared when the key is regenerated.
161 /* This is set to true when SIGHUP is received. */
162 int received_sighup = 0;
164 /* session identifier, used by RSA-auth */
165 unsigned char session_id[16];
168 unsigned char *session_id2 = NULL;
169 int session_id2_len = 0;
171 /* record remote hostname or ip */
172 unsigned int utmp_len = MAXHOSTNAMELEN;
174 /* Prototypes for various functions defined later in this file. */
178 void ssh_dh1_server(Kex *, Buffer *_kexinit, Buffer *);
179 void ssh_dhgex_server(Kex *, Buffer *_kexinit, Buffer *);
182 * Close all listening sockets
185 close_listen_socks(void)
188 for (i = 0; i < num_listen_socks; i++)
189 close(listen_socks[i]);
190 num_listen_socks = -1;
194 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
195 * the effect is to reread the configuration file (and to regenerate
199 sighup_handler(int sig)
202 signal(SIGHUP, sighup_handler);
206 * Called from the main program after receiving SIGHUP.
207 * Restarts the server.
212 log("Received SIGHUP; restarting.");
213 close_listen_socks();
214 execv(saved_argv[0], saved_argv);
215 log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], strerror(errno));
220 * Generic signal handler for terminating signals in the master daemon.
221 * These close the listen socket; not closing it seems to cause "Address
222 * already in use" problems on some machines, which is inconvenient.
225 sigterm_handler(int sig)
227 log("Received signal %d; terminating.", sig);
228 close_listen_socks();
229 unlink(options.pid_file);
234 * SIGCHLD handler. This is called whenever a child dies. This will then
235 * reap any zombies left by exited c.
238 main_sigchld_handler(int sig)
240 int save_errno = errno;
243 while (waitpid(-1, &status, WNOHANG) > 0)
246 signal(SIGCHLD, main_sigchld_handler);
251 * Signal handler for the alarm after the login grace period has expired.
254 grace_alarm_handler(int sig)
256 /* Close the connection. */
259 /* Log error and exit. */
260 fatal("Timeout before authentication for %s.", get_remote_ipaddr());
264 * Signal handler for the key regeneration alarm. Note that this
265 * alarm only occurs in the daemon waiting for connections, and it does not
266 * do anything with the private key or random state before forking.
267 * Thus there should be no concurrency control/asynchronous execution
270 /* XXX do we really want this work to be done in a signal handler ? -m */
272 generate_empheral_server_key(void)
274 log("Generating %s%d bit RSA key.", sensitive_data.server_key ? "new " : "",
275 options.server_key_bits);
276 if (sensitive_data.server_key != NULL)
277 key_free(sensitive_data.server_key);
278 sensitive_data.server_key = key_generate(KEY_RSA1, options.server_key_bits);
280 log("RSA key generation complete.");
283 key_regeneration_alarm(int sig)
285 int save_errno = errno;
287 /* Check if we should generate a new key. */
289 /* This should really be done in the background. */
290 generate_empheral_server_key();
293 /* Reschedule the alarm. */
294 signal(SIGALRM, key_regeneration_alarm);
295 alarm(options.key_regeneration_time);
300 sshd_exchange_identification(int sock_in, int sock_out)
303 int remote_major, remote_minor;
306 char buf[256]; /* Must not be larger than remote_version. */
307 char remote_version[256]; /* Must be at least as big as buf. */
309 if ((options.protocol & SSH_PROTO_1) &&
310 (options.protocol & SSH_PROTO_2)) {
311 major = PROTOCOL_MAJOR_1;
313 } else if (options.protocol & SSH_PROTO_2) {
314 major = PROTOCOL_MAJOR_2;
315 minor = PROTOCOL_MINOR_2;
317 major = PROTOCOL_MAJOR_1;
318 minor = PROTOCOL_MINOR_1;
320 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
321 server_version_string = xstrdup(buf);
323 if (client_version_string == NULL) {
324 /* Send our protocol version identification. */
325 if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
326 != strlen(server_version_string)) {
327 log("Could not write ident string to %s.", get_remote_ipaddr());
331 /* Read other side\'s version identification. */
332 for (i = 0; i < sizeof(buf) - 1; i++) {
333 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
334 log("Did not receive ident string from %s.", get_remote_ipaddr());
337 if (buf[i] == '\r') {
340 /* Kludge for F-Secure Macintosh < 1.0.2 */
342 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
346 if (buf[i] == '\n') {
352 buf[sizeof(buf) - 1] = 0;
353 client_version_string = xstrdup(buf);
357 * Check that the versions match. In future this might accept
358 * several versions and set appropriate flags to handle them.
360 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
361 &remote_major, &remote_minor, remote_version) != 3) {
362 s = "Protocol mismatch.\n";
363 (void) atomicio(write, sock_out, s, strlen(s));
366 log("Bad protocol version identification '%.100s' from %s",
367 client_version_string, get_remote_ipaddr());
370 debug("Client protocol version %d.%d; client software version %.100s",
371 remote_major, remote_minor, remote_version);
373 compat_datafellows(remote_version);
376 switch(remote_major) {
378 if (remote_minor == 99) {
379 if (options.protocol & SSH_PROTO_2)
385 if (!(options.protocol & SSH_PROTO_1)) {
389 if (remote_minor < 3) {
390 packet_disconnect("Your ssh version is too old and "
391 "is no longer supported. Please install a newer version.");
392 } else if (remote_minor == 3) {
393 /* note that this disables agent-forwarding */
398 if (options.protocol & SSH_PROTO_2) {
407 chop(server_version_string);
408 chop(client_version_string);
409 debug("Local version string %.200s", server_version_string);
412 s = "Protocol major versions differ.\n";
413 (void) atomicio(write, sock_out, s, strlen(s));
416 log("Protocol major versions differ for %s: %.200s vs. %.200s",
418 server_version_string, client_version_string);
422 packet_set_ssh2_format();
426 /* Destroy the host and server keys. They will no longer be needed. */
428 destroy_sensitive_data(void)
432 if (sensitive_data.server_key) {
433 key_free(sensitive_data.server_key);
434 sensitive_data.server_key = NULL;
436 for(i = 0; i < options.num_host_key_files; i++) {
437 if (sensitive_data.host_keys[i]) {
438 key_free(sensitive_data.host_keys[i]);
439 sensitive_data.host_keys[i] = NULL;
442 sensitive_data.ssh1_host_key = NULL;
445 load_private_key_autodetect(const char *filename)
449 Key *public, *private;
451 if (stat(filename, &st) < 0) {
456 * try to load the public key. right now this only works for RSA1,
457 * since SSH2 keys are fully encrypted
460 public = key_new(type);
461 if (!load_public_key(filename, public, NULL)) {
462 /* ok, so we will assume this is 'some' key */
467 /* Ok, try key with empty passphrase */
468 private = key_new(type);
469 if (load_private_key(filename, "", private, NULL)) {
470 debug("load_private_key_autodetect: type %d %s",
471 private->type, key_type(private));
479 list_hostkey_types(void)
481 static char buf[1024];
484 for(i = 0; i < options.num_host_key_files; i++) {
485 Key *key = sensitive_data.host_keys[i];
491 strlcat(buf, key_ssh_name(key), sizeof buf);
492 strlcat(buf, ",", sizeof buf);
497 if (i > 0 && buf[i-1] == ',')
499 debug("list_hostkey_types: %s", buf);
504 get_hostkey_by_type(int type)
507 for(i = 0; i < options.num_host_key_files; i++) {
508 Key *key = sensitive_data.host_keys[i];
509 if (key != NULL && key->type == type)
516 * returns 1 if connection should be dropped, 0 otherwise.
517 * dropping starts at connection #max_startups_begin with a probability
518 * of (max_startups_rate/100). the probability increases linearly until
519 * all connections are dropped for startups > max_startups
522 drop_connection(int startups)
526 if (startups < options.max_startups_begin)
528 if (startups >= options.max_startups)
530 if (options.max_startups_rate == 100)
533 p = 100 - options.max_startups_rate;
534 p *= startups - options.max_startups_begin;
535 p /= (double) (options.max_startups - options.max_startups_begin);
536 p += options.max_startups_rate;
538 r = arc4random() / (double) UINT_MAX;
540 debug("drop_connection: p %g, r %g", p, r);
541 return (r < p) ? 1 : 0;
544 int *startup_pipes = NULL; /* options.max_startup sized array of fd ints */
545 int startup_pipe; /* in child */
548 * Main program for the daemon.
551 main(int ac, char **av)
555 int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
560 struct sockaddr_storage from;
561 const char *remote_ip;
564 struct linger linger;
566 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
567 int listen_sock, maxfd;
571 __progname = get_progname(av[0]);
578 /* Initialize configuration options to their default values. */
579 initialize_server_options(&options);
581 /* Parse command-line arguments. */
582 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:dDiqQ46")) != EOF) {
591 config_file_name = optarg;
594 if (0 == debug_flag) {
596 options.log_level = SYSLOG_LEVEL_DEBUG1;
597 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
600 fprintf(stderr, "Too high debugging level.\n");
614 options.log_level = SYSLOG_LEVEL_QUIET;
617 options.server_key_bits = atoi(optarg);
620 options.ports_from_cmdline = 1;
621 if (options.num_ports >= MAX_PORTS) {
622 fprintf(stderr, "too many ports.\n");
625 options.ports[options.num_ports++] = atoi(optarg);
628 options.login_grace_time = atoi(optarg);
631 options.key_regeneration_time = atoi(optarg);
634 if (options.num_host_key_files >= MAX_HOSTKEYS) {
635 fprintf(stderr, "too many host keys.\n");
638 options.host_key_files[options.num_host_key_files++] = optarg;
641 client_version_string = optarg;
642 /* 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", 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, " -q Quiet (no logging)\n");
657 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
658 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
659 fprintf(stderr, " -g seconds Grace period for authentication (default: 300)\n");
660 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
661 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
663 fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
664 fprintf(stderr, " -4 Use IPv4 only\n");
665 fprintf(stderr, " -6 Use IPv6 only\n");
671 * Force logging to stderr until we have loaded the private host
672 * key (unless started from inetd)
675 options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
676 options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
677 !silent && !inetd_flag);
679 /* Read server configuration options from the configuration file. */
680 read_server_config(&options, config_file_name);
682 /* Fill in default values for those options not explicitly set. */
683 fill_default_server_options(&options);
685 /* Check that there are no remaining arguments. */
687 fprintf(stderr, "Extra argument %s.\n", av[optind]);
691 debug("sshd version %.100s", SSH_VERSION);
693 /* load private host keys */
694 sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*));
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_key_autodetect(options.host_key_files[i]);
703 error("Could not load host key: %.200s: %.100s",
704 options.host_key_files[i], strerror(errno));
709 sensitive_data.ssh1_host_key = key;
710 sensitive_data.have_ssh1_key = 1;
714 sensitive_data.have_ssh2_key = 1;
717 sensitive_data.host_keys[i] = key;
719 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
720 log("Disabling protocol version 1. Could not load host key");
721 options.protocol &= ~SSH_PROTO_1;
723 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
724 log("Disabling protocol version 2. Could not load host key");
725 options.protocol &= ~SSH_PROTO_2;
727 if (! options.protocol & (SSH_PROTO_1|SSH_PROTO_2)) {
729 fprintf(stderr, "sshd: no hostkeys available -- exiting.\n");
730 log("sshd: no hostkeys available -- exiting.\n");
734 /* Check certain values for sanity. */
735 if (options.protocol & SSH_PROTO_1) {
736 if (options.server_key_bits < 512 ||
737 options.server_key_bits > 32768) {
738 fprintf(stderr, "Bad server key size.\n");
742 * Check that server and host key lengths differ sufficiently. This
743 * is necessary to make double encryption work with rsaref. Oh, I
744 * hate software patents. I dont know if this can go? Niels
746 if (options.server_key_bits >
747 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - SSH_KEY_BITS_RESERVED &&
748 options.server_key_bits <
749 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
750 options.server_key_bits =
751 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED;
752 debug("Forcing server key to %d bits to make it differ from host key.",
753 options.server_key_bits);
757 #ifdef HAVE_SCO_PROTECTED_PW
758 (void) set_auth_parameters(ac, av);
761 /* Initialize the log (it is reinitialized below in case we forked). */
762 if (debug_flag && !inetd_flag)
764 log_init(__progname, options.log_level, options.log_facility, log_stderr);
767 * If not in debugging mode, and not started from inetd, disconnect
768 * from the controlling terminal, and fork. The original process
771 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
774 #endif /* TIOCNOTTY */
775 if (daemon(0, 0) < 0)
776 fatal("daemon() failed: %.200s", strerror(errno));
778 /* Disconnect from the controlling tty. */
780 fd = open("/dev/tty", O_RDWR | O_NOCTTY);
782 (void) ioctl(fd, TIOCNOTTY, NULL);
785 #endif /* TIOCNOTTY */
787 /* Reinitialize the log (because of the fork above). */
788 log_init(__progname, options.log_level, options.log_facility, log_stderr);
790 /* Initialize the random number generator. */
793 /* Chdir to the root directory so that the current disk can be
794 unmounted if desired. */
797 /* Start listening for a socket, unless started from inetd. */
800 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
806 * We intentionally do not close the descriptors 0, 1, and 2
807 * as our code for setting the descriptors won\'t work if
808 * ttyfd happens to be one of those.
810 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
811 if (options.protocol & SSH_PROTO_1)
812 generate_empheral_server_key();
814 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
815 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
817 if (num_listen_socks >= MAX_LISTEN_SOCKS)
818 fatal("Too many listen sockets. "
819 "Enlarge MAX_LISTEN_SOCKS");
820 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
821 ntop, sizeof(ntop), strport, sizeof(strport),
822 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
823 error("getnameinfo failed");
826 /* Create socket for listening. */
827 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
828 if (listen_sock < 0) {
829 /* kernel may not support ipv6 */
830 verbose("socket: %.100s", strerror(errno));
833 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
834 error("listen_sock O_NONBLOCK: %s", strerror(errno));
839 * Set socket options. We try to make the port
840 * reusable and have it close as fast as possible
841 * without waiting in unnecessary wait states on
844 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
845 (void *) &on, sizeof(on));
848 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
849 (void *) &linger, sizeof(linger));
851 debug("Bind to port %s on %s.", strport, ntop);
853 /* Bind the socket to the desired port. */
854 if ((bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) &&
856 error("Bind to port %s on %s failed: %.200s.",
857 strport, ntop, strerror(errno));
861 listen_socks[num_listen_socks] = listen_sock;
864 /* Start listening on the port. */
865 log("Server listening on %s port %s.", ntop, strport);
866 if (listen(listen_sock, 5) < 0)
867 fatal("listen: %.100s", strerror(errno));
870 freeaddrinfo(options.listen_addrs);
872 if (!num_listen_socks)
873 fatal("Cannot bind any address.");
877 * Record our pid in /var/run/sshd.pid to make it
878 * easier to kill the correct sshd. We don't want to
879 * do this before the bind above because the bind will
880 * fail if there already is a daemon, and this will
881 * overwrite any old pid in the file.
883 f = fopen(options.pid_file, "wb");
885 fprintf(f, "%u\n", (unsigned int) getpid());
889 if (options.protocol & SSH_PROTO_1) {
890 generate_empheral_server_key();
892 /* Schedule server key regeneration alarm. */
893 signal(SIGALRM, key_regeneration_alarm);
894 alarm(options.key_regeneration_time);
897 /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
898 signal(SIGHUP, sighup_handler);
900 signal(SIGTERM, sigterm_handler);
901 signal(SIGQUIT, sigterm_handler);
903 /* Arrange SIGCHLD to be caught. */
904 signal(SIGCHLD, main_sigchld_handler);
906 /* setup fd set for listen */
909 for (i = 0; i < num_listen_socks; i++)
910 if (listen_socks[i] > maxfd)
911 maxfd = listen_socks[i];
912 /* pipes connected to unauthenticated childs */
913 startup_pipes = xmalloc(options.max_startups * sizeof(int));
914 for (i = 0; i < options.max_startups; i++)
915 startup_pipes[i] = -1;
918 * Stay listening for connections until the system crashes or
919 * the daemon is killed with a signal.
926 fdsetsz = howmany(maxfd, NFDBITS) * sizeof(fd_mask);
927 fdset = (fd_set *)xmalloc(fdsetsz);
928 memset(fdset, 0, fdsetsz);
930 for (i = 0; i < num_listen_socks; i++)
931 FD_SET(listen_socks[i], fdset);
932 for (i = 0; i < options.max_startups; i++)
933 if (startup_pipes[i] != -1)
934 FD_SET(startup_pipes[i], fdset);
936 /* Wait in select until there is a connection. */
937 if (select(maxfd + 1, fdset, NULL, NULL, NULL) < 0) {
939 error("select: %.100s", strerror(errno));
942 for (i = 0; i < options.max_startups; i++)
943 if (startup_pipes[i] != -1 &&
944 FD_ISSET(startup_pipes[i], fdset)) {
946 * the read end of the pipe is ready
947 * if the child has closed the pipe
948 * after successfull authentication
949 * or if the child has died
951 close(startup_pipes[i]);
952 startup_pipes[i] = -1;
955 for (i = 0; i < num_listen_socks; i++) {
956 if (!FD_ISSET(listen_socks[i], fdset))
958 fromlen = sizeof(from);
959 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
962 if (errno != EINTR && errno != EWOULDBLOCK)
963 error("accept: %.100s", strerror(errno));
966 if (fcntl(newsock, F_SETFL, 0) < 0) {
967 error("newsock del O_NONBLOCK: %s", strerror(errno));
970 if (drop_connection(startups) == 1) {
971 debug("drop connection #%d", startups);
975 if (pipe(startup_p) == -1) {
980 for (j = 0; j < options.max_startups; j++)
981 if (startup_pipes[j] == -1) {
982 startup_pipes[j] = startup_p[0];
983 if (maxfd < startup_p[0])
984 maxfd = startup_p[0];
990 * Got connection. Fork a child to handle it, unless
991 * we are in debugging mode.
995 * In debugging mode. Close the listening
996 * socket, and start processing the
997 * connection without forking.
999 debug("Server will not fork when running in debugging mode.");
1000 close_listen_socks();
1008 * Normal production daemon. Fork, and have
1009 * the child process the connection. The
1010 * parent continues listening.
1012 if ((pid = fork()) == 0) {
1014 * Child. Close the listening and max_startup
1015 * sockets. Start using the accepted socket.
1016 * Reinitialize logging (since our pid has
1017 * changed). We break out of the loop to handle
1020 startup_pipe = startup_p[1];
1021 for (j = 0; j < options.max_startups; j++)
1022 if (startup_pipes[j] != -1)
1023 close(startup_pipes[j]);
1024 close_listen_socks();
1027 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1032 /* Parent. Stay in the loop. */
1034 error("fork: %.100s", strerror(errno));
1036 debug("Forked child %d.", pid);
1038 close(startup_p[1]);
1040 /* Mark that the key has been used (it was "given" to the child). */
1045 /* Close the new socket (the child is now taking care of it). */
1048 /* child process check (or debug mode) */
1049 if (num_listen_socks < 0)
1054 /* This is the child processing a new connection. */
1057 * Disable the key regeneration alarm. We will not regenerate the
1058 * key since we are no longer in a position to give it to anyone. We
1059 * will not restart on SIGHUP since it no longer makes sense.
1062 signal(SIGALRM, SIG_DFL);
1063 signal(SIGHUP, SIG_DFL);
1064 signal(SIGTERM, SIG_DFL);
1065 signal(SIGQUIT, SIG_DFL);
1066 signal(SIGCHLD, SIG_DFL);
1067 signal(SIGINT, SIG_DFL);
1070 * Set socket options for the connection. We want the socket to
1071 * close as fast as possible without waiting for anything. If the
1072 * connection is not a socket, these will do nothing.
1074 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1076 linger.l_linger = 5;
1077 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
1080 * Register our connection. This turns encryption off because we do
1083 packet_set_connection(sock_in, sock_out);
1085 remote_port = get_remote_port();
1086 remote_ip = get_remote_ipaddr();
1088 /* Check whether logins are denied from this host. */
1090 /* XXX LIBWRAP noes not know about IPv6 */
1092 struct request_info req;
1094 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, NULL);
1097 if (!hosts_access(&req)) {
1102 /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
1104 #endif /* LIBWRAP */
1105 /* Log the connection. */
1106 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1109 * We don\'t want to listen forever unless the other side
1110 * successfully authenticates itself. So we set up an alarm which is
1111 * cleared after successful authentication. A limit of zero
1112 * indicates no limit. Note that we don\'t set the alarm in debugging
1113 * mode; it is just annoying to have the server exit just when you
1114 * are about to discover the bug.
1116 signal(SIGALRM, grace_alarm_handler);
1118 alarm(options.login_grace_time);
1120 sshd_exchange_identification(sock_in, sock_out);
1122 * Check that the connection comes from a privileged port.
1123 * Rhosts-Authentication only makes sense from priviledged
1124 * programs. Of course, if the intruder has root access on his local
1125 * machine, he can connect from any port. So do not use these
1126 * authentication methods from machines that you do not trust.
1128 if (remote_port >= IPPORT_RESERVED ||
1129 remote_port < IPPORT_RESERVED / 2) {
1130 debug("Rhosts Authentication disabled, "
1131 "originating port not trusted.");
1132 options.rhosts_authentication = 0;
1135 if (!packet_connection_is_ipv4() &&
1136 options.kerberos_authentication) {
1137 debug("Kerberos Authentication disabled, only available for IPv4.");
1138 options.kerberos_authentication = 0;
1142 packet_set_nonblocking();
1144 /* perform the key exchange */
1145 /* authenticate user and start session */
1148 do_authentication2();
1151 do_authentication();
1155 /* Cleanup user's ticket cache file. */
1156 if (options.kerberos_ticket_cleanup)
1160 /* The connection has been terminated. */
1161 verbose("Closing connection to %.100s", remote_ip);
1165 #endif /* USE_PAM */
1179 BIGNUM *session_key_int;
1180 unsigned char session_key[SSH_SESSION_KEY_LENGTH];
1181 unsigned char cookie[8];
1182 unsigned int cipher_type, auth_mask, protocol_flags;
1186 * Generate check bytes that the client must send back in the user
1187 * packet in order for it to be accepted; this is used to defy ip
1188 * spoofing attacks. Note that this only works against somebody
1189 * doing IP spoofing from a remote machine; any machine on the local
1190 * network can still see outgoing packets and catch the random
1191 * cookie. This only affects rhosts authentication, and this is one
1192 * of the reasons why it is inherently insecure.
1194 for (i = 0; i < 8; i++) {
1196 rand = arc4random();
1197 cookie[i] = rand & 0xff;
1202 * Send our public key. We include in the packet 64 bits of random
1203 * data that must be matched in the reply in order to prevent IP
1206 packet_start(SSH_SMSG_PUBLIC_KEY);
1207 for (i = 0; i < 8; i++)
1208 packet_put_char(cookie[i]);
1210 /* Store our public server RSA key. */
1211 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1212 packet_put_bignum(sensitive_data.server_key->rsa->e);
1213 packet_put_bignum(sensitive_data.server_key->rsa->n);
1215 /* Store our public host RSA key. */
1216 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1217 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1218 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1220 /* Put protocol flags. */
1221 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1223 /* Declare which ciphers we support. */
1224 packet_put_int(cipher_mask_ssh1(0));
1226 /* Declare supported authentication types. */
1228 if (options.rhosts_authentication)
1229 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1230 if (options.rhosts_rsa_authentication)
1231 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1232 if (options.rsa_authentication)
1233 auth_mask |= 1 << SSH_AUTH_RSA;
1235 if (options.kerberos_authentication)
1236 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1239 if (options.kerberos_tgt_passing)
1240 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1241 if (options.afs_token_passing)
1242 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1245 if (options.skey_authentication == 1)
1246 auth_mask |= 1 << SSH_AUTH_TIS;
1248 if (options.password_authentication)
1249 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1250 packet_put_int(auth_mask);
1252 /* Send the packet and wait for it to be sent. */
1254 packet_write_wait();
1256 debug("Sent %d bit server key and %d bit host key.",
1257 BN_num_bits(sensitive_data.server_key->rsa->n),
1258 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1260 /* Read clients reply (cipher type and session key). */
1261 packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1263 /* Get cipher type and check whether we accept this. */
1264 cipher_type = packet_get_char();
1266 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1267 packet_disconnect("Warning: client selects unsupported cipher.");
1269 /* Get check bytes from the packet. These must match those we
1270 sent earlier with the public key packet. */
1271 for (i = 0; i < 8; i++)
1272 if (cookie[i] != packet_get_char())
1273 packet_disconnect("IP Spoofing check bytes do not match.");
1275 debug("Encryption type: %.200s", cipher_name(cipher_type));
1277 /* Get the encrypted integer. */
1278 session_key_int = BN_new();
1279 packet_get_bignum(session_key_int, &slen);
1281 protocol_flags = packet_get_int();
1282 packet_set_protocol_flags(protocol_flags);
1284 packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1287 * Decrypt it using our private server key and private host key (key
1288 * with larger modulus first).
1290 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1291 /* Private key has bigger modulus. */
1292 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1293 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1294 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1295 get_remote_ipaddr(),
1296 BN_num_bits(sensitive_data.server_key->rsa->n),
1297 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1298 SSH_KEY_BITS_RESERVED);
1300 rsa_private_decrypt(session_key_int, session_key_int,
1301 sensitive_data.server_key->rsa);
1302 rsa_private_decrypt(session_key_int, session_key_int,
1303 sensitive_data.ssh1_host_key->rsa);
1305 /* Host key has bigger modulus (or they are equal). */
1306 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1307 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1308 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1309 get_remote_ipaddr(),
1310 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1311 BN_num_bits(sensitive_data.server_key->rsa->n),
1312 SSH_KEY_BITS_RESERVED);
1314 rsa_private_decrypt(session_key_int, session_key_int,
1315 sensitive_data.ssh1_host_key->rsa);
1316 rsa_private_decrypt(session_key_int, session_key_int,
1317 sensitive_data.server_key->rsa);
1320 compute_session_id(session_id, cookie,
1321 sensitive_data.ssh1_host_key->rsa->n,
1322 sensitive_data.server_key->rsa->n);
1324 /* Destroy the private and public keys. They will no longer be needed. */
1325 destroy_sensitive_data();
1328 * Extract session key from the decrypted integer. The key is in the
1329 * least significant 256 bits of the integer; the first byte of the
1330 * key is in the highest bits.
1332 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1333 len = BN_num_bytes(session_key_int);
1334 if (len < 0 || len > sizeof(session_key))
1335 fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d",
1336 get_remote_ipaddr(),
1337 len, sizeof(session_key));
1338 memset(session_key, 0, sizeof(session_key));
1339 BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len);
1341 /* Destroy the decrypted integer. It is no longer needed. */
1342 BN_clear_free(session_key_int);
1344 /* Xor the first 16 bytes of the session key with the session id. */
1345 for (i = 0; i < 16; i++)
1346 session_key[i] ^= session_id[i];
1348 /* Set the session key. From this on all communications will be encrypted. */
1349 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1351 /* Destroy our copy of the session key. It is no longer needed. */
1352 memset(session_key, 0, sizeof(session_key));
1354 debug("Received session key; encryption turned on.");
1356 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1357 packet_start(SSH_SMSG_SUCCESS);
1359 packet_write_wait();
1363 * SSH2 key exchange: diffie-hellman-group1-sha1
1368 Buffer *server_kexinit;
1369 Buffer *client_kexinit;
1373 char *cprop[PROPOSAL_MAX];
1377 if (options.ciphers != NULL) {
1378 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1379 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1381 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
1383 server_kexinit = kex_init(myproposal);
1384 client_kexinit = xmalloc(sizeof(*client_kexinit));
1385 buffer_init(client_kexinit);
1387 /* algorithm negotiation */
1388 kex_exchange_kexinit(server_kexinit, client_kexinit, cprop);
1389 kex = kex_choose_conf(cprop, myproposal, 1);
1390 for (i = 0; i < PROPOSAL_MAX; i++)
1393 switch (kex->kex_type) {
1395 ssh_dh1_server(kex, client_kexinit, server_kexinit);
1398 ssh_dhgex_server(kex, client_kexinit, server_kexinit);
1401 fatal("Unsupported key exchange %d", kex->kex_type);
1404 debug("send SSH2_MSG_NEWKEYS.");
1405 packet_start(SSH2_MSG_NEWKEYS);
1407 packet_write_wait();
1408 debug("done: send SSH2_MSG_NEWKEYS.");
1410 debug("Wait SSH2_MSG_NEWKEYS.");
1411 packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS);
1412 debug("GOT SSH2_MSG_NEWKEYS.");
1415 /* send 1st encrypted/maced/compressed message */
1416 packet_start(SSH2_MSG_IGNORE);
1417 packet_put_cstring("markus");
1419 packet_write_wait();
1422 debug("done: KEX2.");
1429 /* diffie-hellman-group1-sha1 */
1432 ssh_dh1_server(Kex *kex, Buffer *client_kexinit, Buffer *server_kexinit)
1437 int payload_len, dlen;
1439 unsigned char *signature = NULL;
1440 unsigned char *server_host_key_blob = NULL;
1441 unsigned int sbloblen;
1442 unsigned int klen, kout;
1443 unsigned char *kbuf;
1444 unsigned char *hash;
1445 BIGNUM *shared_secret = 0;
1447 BIGNUM *dh_client_pub = 0;
1450 hostkey = get_hostkey_by_type(kex->hostkey_type);
1451 if (hostkey == NULL)
1452 fatal("Unsupported hostkey type %d", kex->hostkey_type);
1455 /* generate DH key */
1456 dh = dh_new_group1(); /* XXX depends on 'kex' */
1459 debug("Wait SSH2_MSG_KEXDH_INIT.");
1460 packet_read_expect(&payload_len, SSH2_MSG_KEXDH_INIT);
1463 dh_client_pub = BN_new();
1464 if (dh_client_pub == NULL)
1465 fatal("dh_client_pub == NULL");
1466 packet_get_bignum2(dh_client_pub, &dlen);
1469 fprintf(stderr, "\ndh_client_pub= ");
1470 BN_print_fp(stderr, dh_client_pub);
1471 fprintf(stderr, "\n");
1472 debug("bits %d", BN_num_bits(dh_client_pub));
1476 fprintf(stderr, "\np= ");
1477 BN_print_fp(stderr, dh->p);
1478 fprintf(stderr, "\ng= ");
1480 fprintf(stderr, "\npub= ");
1481 BN_print_fp(stderr, dh->pub_key);
1482 fprintf(stderr, "\n");
1483 DHparams_print_fp(stderr, dh);
1485 if (!dh_pub_is_valid(dh, dh_client_pub))
1486 packet_disconnect("bad client public DH value");
1489 kbuf = xmalloc(klen);
1490 kout = DH_compute_key(kbuf, dh_client_pub, dh);
1493 debug("shared secret: len %d/%d", klen, kout);
1494 fprintf(stderr, "shared secret == ");
1495 for (i = 0; i< kout; i++)
1496 fprintf(stderr, "%02x", (kbuf[i])&0xff);
1497 fprintf(stderr, "\n");
1499 shared_secret = BN_new();
1501 BN_bin2bn(kbuf, kout, shared_secret);
1502 memset(kbuf, 0, klen);
1505 /* XXX precompute? */
1506 key_to_blob(hostkey, &server_host_key_blob, &sbloblen);
1508 /* calc H */ /* XXX depends on 'kex' */
1510 client_version_string,
1511 server_version_string,
1512 buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1513 buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1514 (char *)server_host_key_blob, sbloblen,
1519 buffer_free(client_kexinit);
1520 buffer_free(server_kexinit);
1521 xfree(client_kexinit);
1522 xfree(server_kexinit);
1524 fprintf(stderr, "hash == ");
1525 for (i = 0; i< 20; i++)
1526 fprintf(stderr, "%02x", (hash[i])&0xff);
1527 fprintf(stderr, "\n");
1529 /* save session id := H */
1530 /* XXX hashlen depends on KEX */
1531 session_id2_len = 20;
1532 session_id2 = xmalloc(session_id2_len);
1533 memcpy(session_id2, hash, session_id2_len);
1536 /* XXX hashlen depends on KEX */
1537 key_sign(hostkey, &signature, &slen, hash, 20);
1539 destroy_sensitive_data();
1541 /* send server hostkey, DH pubkey 'f' and singed H */
1542 packet_start(SSH2_MSG_KEXDH_REPLY);
1543 packet_put_string((char *)server_host_key_blob, sbloblen);
1544 packet_put_bignum2(dh->pub_key); /* f */
1545 packet_put_string((char *)signature, slen);
1548 xfree(server_host_key_blob);
1549 packet_write_wait();
1551 kex_derive_keys(kex, hash, shared_secret);
1552 packet_set_kex(kex);
1554 /* have keys, free DH */
1558 /* diffie-hellman-group-exchange-sha1 */
1561 ssh_dhgex_server(Kex *kex, Buffer *client_kexinit, Buffer *server_kexinit)
1566 int payload_len, dlen;
1568 unsigned char *signature = NULL;
1569 unsigned char *server_host_key_blob = NULL;
1570 unsigned int sbloblen;
1571 unsigned int klen, kout;
1572 unsigned char *kbuf;
1573 unsigned char *hash;
1574 BIGNUM *shared_secret = 0;
1576 BIGNUM *dh_client_pub = 0;
1579 hostkey = get_hostkey_by_type(kex->hostkey_type);
1580 if (hostkey == NULL)
1581 fatal("Unsupported hostkey type %d", kex->hostkey_type);
1584 debug("Wait SSH2_MSG_KEX_DH_GEX_REQUEST.");
1585 packet_read_expect(&payload_len, SSH2_MSG_KEX_DH_GEX_REQUEST);
1586 nbits = packet_get_int();
1587 dh = choose_dh(nbits);
1589 debug("Sending SSH2_MSG_KEX_DH_GEX_GROUP.");
1590 packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
1591 packet_put_bignum2(dh->p);
1592 packet_put_bignum2(dh->g);
1594 packet_write_wait();
1596 /* Compute our exchange value in parallel with the client */
1600 debug("Wait SSH2_MSG_KEX_DH_GEX_INIT.");
1601 packet_read_expect(&payload_len, SSH2_MSG_KEX_DH_GEX_INIT);
1604 dh_client_pub = BN_new();
1605 if (dh_client_pub == NULL)
1606 fatal("dh_client_pub == NULL");
1607 packet_get_bignum2(dh_client_pub, &dlen);
1610 fprintf(stderr, "\ndh_client_pub= ");
1611 BN_print_fp(stderr, dh_client_pub);
1612 fprintf(stderr, "\n");
1613 debug("bits %d", BN_num_bits(dh_client_pub));
1617 fprintf(stderr, "\np= ");
1618 BN_print_fp(stderr, dh->p);
1619 fprintf(stderr, "\ng= ");
1621 fprintf(stderr, "\npub= ");
1622 BN_print_fp(stderr, dh->pub_key);
1623 fprintf(stderr, "\n");
1624 DHparams_print_fp(stderr, dh);
1626 if (!dh_pub_is_valid(dh, dh_client_pub))
1627 packet_disconnect("bad client public DH value");
1630 kbuf = xmalloc(klen);
1631 kout = DH_compute_key(kbuf, dh_client_pub, dh);
1634 debug("shared secret: len %d/%d", klen, kout);
1635 fprintf(stderr, "shared secret == ");
1636 for (i = 0; i< kout; i++)
1637 fprintf(stderr, "%02x", (kbuf[i])&0xff);
1638 fprintf(stderr, "\n");
1640 shared_secret = BN_new();
1642 BN_bin2bn(kbuf, kout, shared_secret);
1643 memset(kbuf, 0, klen);
1646 /* XXX precompute? */
1647 key_to_blob(hostkey, &server_host_key_blob, &sbloblen);
1649 /* calc H */ /* XXX depends on 'kex' */
1650 hash = kex_hash_gex(
1651 client_version_string,
1652 server_version_string,
1653 buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1654 buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1655 (char *)server_host_key_blob, sbloblen,
1656 nbits, dh->p, dh->g,
1661 buffer_free(client_kexinit);
1662 buffer_free(server_kexinit);
1663 xfree(client_kexinit);
1664 xfree(server_kexinit);
1666 fprintf(stderr, "hash == ");
1667 for (i = 0; i< 20; i++)
1668 fprintf(stderr, "%02x", (hash[i])&0xff);
1669 fprintf(stderr, "\n");
1671 /* save session id := H */
1672 /* XXX hashlen depends on KEX */
1673 session_id2_len = 20;
1674 session_id2 = xmalloc(session_id2_len);
1675 memcpy(session_id2, hash, session_id2_len);
1678 /* XXX hashlen depends on KEX */
1679 key_sign(hostkey, &signature, &slen, hash, 20);
1681 destroy_sensitive_data();
1683 /* send server hostkey, DH pubkey 'f' and singed H */
1684 packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
1685 packet_put_string((char *)server_host_key_blob, sbloblen);
1686 packet_put_bignum2(dh->pub_key); /* f */
1687 packet_put_string((char *)signature, slen);
1690 xfree(server_host_key_blob);
1691 packet_write_wait();
1693 kex_derive_keys(kex, hash, shared_secret);
1694 packet_set_kex(kex);
1696 /* have keys, free DH */