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 1.134 2000/11/12 19:50:38 markus 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 /* Server configuration options. */
82 ServerOptions options;
84 /* Name of the server configuration file. */
85 char *config_file_name = SERVER_CONFIG_FILE;
88 * Flag indicating whether IPv4 or IPv6. This can be set on the command line.
89 * Default value is AF_UNSPEC means both IPv4 and IPv6.
92 int IPv4or6 = AF_INET;
94 int IPv4or6 = AF_UNSPEC;
98 * Debug mode flag. This can be set on the command line. If debug
99 * mode is enabled, extra debugging output will be sent to the system
100 * log, the daemon will not go to background, and will exit after processing
101 * the first connection.
105 /* Flag indicating that the daemon is being started from inetd. */
108 /* debug goes to stderr unless inetd_flag is set */
111 /* argv[0] without path. */
114 /* Saved arguments to main(). */
119 * The sockets that the server is listening; this is used in the SIGHUP
122 #define MAX_LISTEN_SOCKS 16
123 int listen_socks[MAX_LISTEN_SOCKS];
124 int num_listen_socks = 0;
127 * the client's version string, passed by sshd2 in compat mode. if != NULL,
128 * sshd will skip the version-number exchange
130 char *client_version_string = NULL;
131 char *server_version_string = NULL;
134 * Any really sensitive data in the application is contained in this
135 * structure. The idea is that this structure could be locked into memory so
136 * that the pages do not get written into swap. However, there are some
137 * problems. The private key contains BIGNUMs, and we do not (in principle)
138 * have access to the internals of them, and locking just the structure is
139 * not very useful. Currently, memory locking is not implemented.
142 Key *server_key; /* empheral server key */
143 Key *ssh1_host_key; /* ssh1 host key */
144 Key **host_keys; /* all private host keys */
150 * Flag indicating whether the current session key has been used. This flag
151 * is set whenever the key is used, and cleared when the key is regenerated.
155 /* This is set to true when SIGHUP is received. */
156 int received_sighup = 0;
158 /* session identifier, used by RSA-auth */
159 unsigned char session_id[16];
162 unsigned char *session_id2 = NULL;
163 int session_id2_len = 0;
165 /* record remote hostname or ip */
166 unsigned int utmp_len = MAXHOSTNAMELEN;
168 /* Prototypes for various functions defined later in this file. */
172 void ssh_dh1_server(Kex *, Buffer *_kexinit, Buffer *);
173 void ssh_dhgex_server(Kex *, Buffer *_kexinit, Buffer *);
176 * Close all listening sockets
179 close_listen_socks(void)
182 for (i = 0; i < num_listen_socks; i++)
183 close(listen_socks[i]);
184 num_listen_socks = -1;
188 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
189 * the effect is to reread the configuration file (and to regenerate
193 sighup_handler(int sig)
196 signal(SIGHUP, sighup_handler);
200 * Called from the main program after receiving SIGHUP.
201 * Restarts the server.
206 log("Received SIGHUP; restarting.");
207 close_listen_socks();
208 execv(saved_argv[0], saved_argv);
209 log("RESTART FAILED: av0='%s', error: %s.", av0, strerror(errno));
214 * Generic signal handler for terminating signals in the master daemon.
215 * These close the listen socket; not closing it seems to cause "Address
216 * already in use" problems on some machines, which is inconvenient.
219 sigterm_handler(int sig)
221 log("Received signal %d; terminating.", sig);
222 close_listen_socks();
223 unlink(options.pid_file);
228 * SIGCHLD handler. This is called whenever a child dies. This will then
229 * reap any zombies left by exited c.
232 main_sigchld_handler(int sig)
234 int save_errno = errno;
237 while (waitpid(-1, &status, WNOHANG) > 0)
240 signal(SIGCHLD, main_sigchld_handler);
245 * Signal handler for the alarm after the login grace period has expired.
248 grace_alarm_handler(int sig)
250 /* Close the connection. */
253 /* Log error and exit. */
254 fatal("Timeout before authentication for %s.", get_remote_ipaddr());
258 * Signal handler for the key regeneration alarm. Note that this
259 * alarm only occurs in the daemon waiting for connections, and it does not
260 * do anything with the private key or random state before forking.
261 * Thus there should be no concurrency control/asynchronous execution
264 /* XXX do we really want this work to be done in a signal handler ? -m */
266 generate_empheral_server_key(void)
268 log("Generating %s%d bit RSA key.", sensitive_data.server_key ? "new " : "",
269 options.server_key_bits);
270 if (sensitive_data.server_key != NULL)
271 key_free(sensitive_data.server_key);
272 sensitive_data.server_key = key_generate(KEY_RSA1, options.server_key_bits);
274 log("RSA key generation complete.");
277 key_regeneration_alarm(int sig)
279 int save_errno = errno;
281 /* Check if we should generate a new key. */
283 /* This should really be done in the background. */
284 generate_empheral_server_key();
287 /* Reschedule the alarm. */
288 signal(SIGALRM, key_regeneration_alarm);
289 alarm(options.key_regeneration_time);
294 sshd_exchange_identification(int sock_in, int sock_out)
297 int remote_major, remote_minor;
300 char buf[256]; /* Must not be larger than remote_version. */
301 char remote_version[256]; /* Must be at least as big as buf. */
303 if ((options.protocol & SSH_PROTO_1) &&
304 (options.protocol & SSH_PROTO_2)) {
305 major = PROTOCOL_MAJOR_1;
307 } else if (options.protocol & SSH_PROTO_2) {
308 major = PROTOCOL_MAJOR_2;
309 minor = PROTOCOL_MINOR_2;
311 major = PROTOCOL_MAJOR_1;
312 minor = PROTOCOL_MINOR_1;
314 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
315 server_version_string = xstrdup(buf);
317 if (client_version_string == NULL) {
318 /* Send our protocol version identification. */
319 if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
320 != strlen(server_version_string)) {
321 log("Could not write ident string to %s.", get_remote_ipaddr());
325 /* Read other side\'s version identification. */
326 for (i = 0; i < sizeof(buf) - 1; i++) {
327 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
328 log("Did not receive ident string from %s.", get_remote_ipaddr());
331 if (buf[i] == '\r') {
334 /* Kludge for F-Secure Macintosh < 1.0.2 */
336 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
340 if (buf[i] == '\n') {
346 buf[sizeof(buf) - 1] = 0;
347 client_version_string = xstrdup(buf);
351 * Check that the versions match. In future this might accept
352 * several versions and set appropriate flags to handle them.
354 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
355 &remote_major, &remote_minor, remote_version) != 3) {
356 s = "Protocol mismatch.\n";
357 (void) atomicio(write, sock_out, s, strlen(s));
360 log("Bad protocol version identification '%.100s' from %s",
361 client_version_string, get_remote_ipaddr());
364 debug("Client protocol version %d.%d; client software version %.100s",
365 remote_major, remote_minor, remote_version);
367 compat_datafellows(remote_version);
370 switch(remote_major) {
372 if (remote_minor == 99) {
373 if (options.protocol & SSH_PROTO_2)
379 if (!(options.protocol & SSH_PROTO_1)) {
383 if (remote_minor < 3) {
384 packet_disconnect("Your ssh version is too old and "
385 "is no longer supported. Please install a newer version.");
386 } else if (remote_minor == 3) {
387 /* note that this disables agent-forwarding */
392 if (options.protocol & SSH_PROTO_2) {
401 chop(server_version_string);
402 chop(client_version_string);
403 debug("Local version string %.200s", server_version_string);
406 s = "Protocol major versions differ.\n";
407 (void) atomicio(write, sock_out, s, strlen(s));
410 log("Protocol major versions differ for %s: %.200s vs. %.200s",
412 server_version_string, client_version_string);
416 packet_set_ssh2_format();
420 /* Destroy the host and server keys. They will no longer be needed. */
422 destroy_sensitive_data(void)
426 if (sensitive_data.server_key) {
427 key_free(sensitive_data.server_key);
428 sensitive_data.server_key = NULL;
430 for(i = 0; i < options.num_host_key_files; i++) {
431 if (sensitive_data.host_keys[i]) {
432 key_free(sensitive_data.host_keys[i]);
433 sensitive_data.host_keys[i] = NULL;
436 sensitive_data.ssh1_host_key = NULL;
439 load_private_key_autodetect(const char *filename)
443 Key *public, *private;
445 if (stat(filename, &st) < 0) {
450 * try to load the public key. right now this only works for RSA1,
451 * since SSH2 keys are fully encrypted
454 public = key_new(type);
455 if (!load_public_key(filename, public, NULL)) {
456 /* ok, so we will assume this is 'some' key */
461 /* Ok, try key with empty passphrase */
462 private = key_new(type);
463 if (load_private_key(filename, "", private, NULL)) {
464 debug("load_private_key_autodetect: type %d %s",
465 private->type, key_type(private));
473 list_hostkey_types(void)
475 static char buf[1024];
478 for(i = 0; i < options.num_host_key_files; i++) {
479 Key *key = sensitive_data.host_keys[i];
485 strlcat(buf, key_ssh_name(key), sizeof buf);
486 strlcat(buf, ",", sizeof buf);
491 if (i > 0 && buf[i-1] == ',')
493 debug("list_hostkey_types: %s", buf);
498 get_hostkey_by_type(int type)
501 for(i = 0; i < options.num_host_key_files; i++) {
502 Key *key = sensitive_data.host_keys[i];
503 if (key != NULL && key->type == type)
510 * returns 1 if connection should be dropped, 0 otherwise.
511 * dropping starts at connection #max_startups_begin with a probability
512 * of (max_startups_rate/100). the probability increases linearly until
513 * all connections are dropped for startups > max_startups
516 drop_connection(int startups)
520 if (startups < options.max_startups_begin)
522 if (startups >= options.max_startups)
524 if (options.max_startups_rate == 100)
527 p = 100 - options.max_startups_rate;
528 p *= startups - options.max_startups_begin;
529 p /= (double) (options.max_startups - options.max_startups_begin);
530 p += options.max_startups_rate;
532 r = arc4random() / (double) UINT_MAX;
534 debug("drop_connection: p %g, r %g", p, r);
535 return (r < p) ? 1 : 0;
538 int *startup_pipes = NULL; /* options.max_startup sized array of fd ints */
539 int startup_pipe; /* in child */
542 * Main program for the daemon.
545 main(int ac, char **av)
549 int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
554 struct sockaddr_storage from;
555 const char *remote_ip;
558 struct linger linger;
560 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
561 int listen_sock, maxfd;
570 if (strchr(av[0], '/'))
571 av0 = strrchr(av[0], '/') + 1;
575 /* Initialize configuration options to their default values. */
576 initialize_server_options(&options);
578 /* Parse command-line arguments. */
579 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:diqQ46")) != EOF) {
588 config_file_name = optarg;
591 if (0 == debug_flag) {
593 options.log_level = SYSLOG_LEVEL_DEBUG1;
594 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
597 fprintf(stderr, "Too high debugging level.\n");
608 options.log_level = SYSLOG_LEVEL_QUIET;
611 options.server_key_bits = atoi(optarg);
614 options.ports_from_cmdline = 1;
615 if (options.num_ports >= MAX_PORTS) {
616 fprintf(stderr, "too many ports.\n");
619 options.ports[options.num_ports++] = atoi(optarg);
622 options.login_grace_time = atoi(optarg);
625 options.key_regeneration_time = atoi(optarg);
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", av0);
646 fprintf(stderr, "Options:\n");
647 fprintf(stderr, " -f file Configuration file (default %s)\n", 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, " -q Quiet (no logging)\n");
651 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
652 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
653 fprintf(stderr, " -g seconds Grace period for authentication (default: 300)\n");
654 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
655 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
657 fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
658 fprintf(stderr, " -4 Use IPv4 only\n");
659 fprintf(stderr, " -6 Use IPv6 only\n");
665 * Force logging to stderr until we have loaded the private host
666 * key (unless started from inetd)
669 options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
670 options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
671 !silent && !inetd_flag);
673 /* Read server configuration options from the configuration file. */
674 read_server_config(&options, config_file_name);
676 /* Fill in default values for those options not explicitly set. */
677 fill_default_server_options(&options);
679 /* Check that there are no remaining arguments. */
681 fprintf(stderr, "Extra argument %s.\n", av[optind]);
685 debug("sshd version %.100s", SSH_VERSION);
687 /* load private host keys */
688 sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*));
689 sensitive_data.server_key = NULL;
690 sensitive_data.ssh1_host_key = NULL;
691 sensitive_data.have_ssh1_key = 0;
692 sensitive_data.have_ssh2_key = 0;
694 for(i = 0; i < options.num_host_key_files; i++) {
695 Key *key = load_private_key_autodetect(options.host_key_files[i]);
697 error("Could not load host key: %.200s: %.100s",
698 options.host_key_files[i], strerror(errno));
703 sensitive_data.ssh1_host_key = key;
704 sensitive_data.have_ssh1_key = 1;
708 sensitive_data.have_ssh2_key = 1;
711 sensitive_data.host_keys[i] = key;
713 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
714 log("Disabling protocol version 1. Could not load host key");
715 options.protocol &= ~SSH_PROTO_1;
717 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
718 log("Disabling protocol version 2. Could not load host key");
719 options.protocol &= ~SSH_PROTO_2;
721 if (! options.protocol & (SSH_PROTO_1|SSH_PROTO_2)) {
723 fprintf(stderr, "sshd: no hostkeys available -- exiting.\n");
724 log("sshd: no hostkeys available -- exiting.\n");
728 /* Check certain values for sanity. */
729 if (options.protocol & SSH_PROTO_1) {
730 if (options.server_key_bits < 512 ||
731 options.server_key_bits > 32768) {
732 fprintf(stderr, "Bad server key size.\n");
736 * Check that server and host key lengths differ sufficiently. This
737 * is necessary to make double encryption work with rsaref. Oh, I
738 * hate software patents. I dont know if this can go? Niels
740 if (options.server_key_bits >
741 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - SSH_KEY_BITS_RESERVED &&
742 options.server_key_bits <
743 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
744 options.server_key_bits =
745 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED;
746 debug("Forcing server key to %d bits to make it differ from host key.",
747 options.server_key_bits);
751 #ifdef HAVE_SCO_PROTECTED_PW
752 (void) set_auth_parameters(ac, av);
755 /* Initialize the log (it is reinitialized below in case we forked). */
756 if (debug_flag && !inetd_flag)
758 log_init(av0, options.log_level, options.log_facility, log_stderr);
761 * If not in debugging mode, and not started from inetd, disconnect
762 * from the controlling terminal, and fork. The original process
765 if (!debug_flag && !inetd_flag) {
768 #endif /* TIOCNOTTY */
769 if (daemon(0, 0) < 0)
770 fatal("daemon() failed: %.200s", strerror(errno));
772 /* Disconnect from the controlling tty. */
774 fd = open("/dev/tty", O_RDWR | O_NOCTTY);
776 (void) ioctl(fd, TIOCNOTTY, NULL);
779 #endif /* TIOCNOTTY */
781 /* Reinitialize the log (because of the fork above). */
782 log_init(av0, options.log_level, options.log_facility, log_stderr);
784 /* Initialize the random number generator. */
787 /* Chdir to the root directory so that the current disk can be
788 unmounted if desired. */
791 /* Start listening for a socket, unless started from inetd. */
794 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
800 * We intentionally do not close the descriptors 0, 1, and 2
801 * as our code for setting the descriptors won\'t work if
802 * ttyfd happens to be one of those.
804 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
805 if (options.protocol & SSH_PROTO_1)
806 generate_empheral_server_key();
808 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
809 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
811 if (num_listen_socks >= MAX_LISTEN_SOCKS)
812 fatal("Too many listen sockets. "
813 "Enlarge MAX_LISTEN_SOCKS");
814 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
815 ntop, sizeof(ntop), strport, sizeof(strport),
816 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
817 error("getnameinfo failed");
820 /* Create socket for listening. */
821 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
822 if (listen_sock < 0) {
823 /* kernel may not support ipv6 */
824 verbose("socket: %.100s", strerror(errno));
827 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
828 error("listen_sock O_NONBLOCK: %s", strerror(errno));
833 * Set socket options. We try to make the port
834 * reusable and have it close as fast as possible
835 * without waiting in unnecessary wait states on
838 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
839 (void *) &on, sizeof(on));
842 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
843 (void *) &linger, sizeof(linger));
845 debug("Bind to port %s on %s.", strport, ntop);
847 /* Bind the socket to the desired port. */
848 if ((bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) &&
850 error("Bind to port %s on %s failed: %.200s.",
851 strport, ntop, strerror(errno));
855 listen_socks[num_listen_socks] = listen_sock;
858 /* Start listening on the port. */
859 log("Server listening on %s port %s.", ntop, strport);
860 if (listen(listen_sock, 5) < 0)
861 fatal("listen: %.100s", strerror(errno));
864 freeaddrinfo(options.listen_addrs);
866 if (!num_listen_socks)
867 fatal("Cannot bind any address.");
871 * Record our pid in /etc/sshd_pid to make it easier
872 * to kill the correct sshd. We don\'t want to do
873 * this before the bind above because the bind will
874 * fail if there already is a daemon, and this will
875 * overwrite any old pid in the file.
877 f = fopen(options.pid_file, "wb");
879 fprintf(f, "%u\n", (unsigned int) getpid());
883 if (options.protocol & SSH_PROTO_1) {
884 generate_empheral_server_key();
886 /* Schedule server key regeneration alarm. */
887 signal(SIGALRM, key_regeneration_alarm);
888 alarm(options.key_regeneration_time);
891 /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
892 signal(SIGHUP, sighup_handler);
894 signal(SIGTERM, sigterm_handler);
895 signal(SIGQUIT, sigterm_handler);
897 /* Arrange SIGCHLD to be caught. */
898 signal(SIGCHLD, main_sigchld_handler);
900 /* setup fd set for listen */
903 for (i = 0; i < num_listen_socks; i++)
904 if (listen_socks[i] > maxfd)
905 maxfd = listen_socks[i];
906 /* pipes connected to unauthenticated childs */
907 startup_pipes = xmalloc(options.max_startups * sizeof(int));
908 for (i = 0; i < options.max_startups; i++)
909 startup_pipes[i] = -1;
912 * Stay listening for connections until the system crashes or
913 * the daemon is killed with a signal.
920 fdsetsz = howmany(maxfd, NFDBITS) * sizeof(fd_mask);
921 fdset = (fd_set *)xmalloc(fdsetsz);
922 memset(fdset, 0, fdsetsz);
924 for (i = 0; i < num_listen_socks; i++)
925 FD_SET(listen_socks[i], fdset);
926 for (i = 0; i < options.max_startups; i++)
927 if (startup_pipes[i] != -1)
928 FD_SET(startup_pipes[i], fdset);
930 /* Wait in select until there is a connection. */
931 if (select(maxfd + 1, fdset, NULL, NULL, NULL) < 0) {
933 error("select: %.100s", strerror(errno));
936 for (i = 0; i < options.max_startups; i++)
937 if (startup_pipes[i] != -1 &&
938 FD_ISSET(startup_pipes[i], fdset)) {
940 * the read end of the pipe is ready
941 * if the child has closed the pipe
942 * after successfull authentication
943 * or if the child has died
945 close(startup_pipes[i]);
946 startup_pipes[i] = -1;
949 for (i = 0; i < num_listen_socks; i++) {
950 if (!FD_ISSET(listen_socks[i], fdset))
952 fromlen = sizeof(from);
953 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
956 if (errno != EINTR && errno != EWOULDBLOCK)
957 error("accept: %.100s", strerror(errno));
960 if (fcntl(newsock, F_SETFL, 0) < 0) {
961 error("newsock del O_NONBLOCK: %s", strerror(errno));
964 if (drop_connection(startups) == 1) {
965 debug("drop connection #%d", startups);
969 if (pipe(startup_p) == -1) {
974 for (j = 0; j < options.max_startups; j++)
975 if (startup_pipes[j] == -1) {
976 startup_pipes[j] = startup_p[0];
977 if (maxfd < startup_p[0])
978 maxfd = startup_p[0];
984 * Got connection. Fork a child to handle it, unless
985 * we are in debugging mode.
989 * In debugging mode. Close the listening
990 * socket, and start processing the
991 * connection without forking.
993 debug("Server will not fork when running in debugging mode.");
994 close_listen_socks();
1002 * Normal production daemon. Fork, and have
1003 * the child process the connection. The
1004 * parent continues listening.
1006 if ((pid = fork()) == 0) {
1008 * Child. Close the listening and max_startup
1009 * sockets. Start using the accepted socket.
1010 * Reinitialize logging (since our pid has
1011 * changed). We break out of the loop to handle
1014 startup_pipe = startup_p[1];
1015 for (j = 0; j < options.max_startups; j++)
1016 if (startup_pipes[j] != -1)
1017 close(startup_pipes[j]);
1018 close_listen_socks();
1021 log_init(av0, options.log_level, options.log_facility, log_stderr);
1026 /* Parent. Stay in the loop. */
1028 error("fork: %.100s", strerror(errno));
1030 debug("Forked child %d.", pid);
1032 close(startup_p[1]);
1034 /* Mark that the key has been used (it was "given" to the child). */
1039 /* Close the new socket (the child is now taking care of it). */
1042 /* child process check (or debug mode) */
1043 if (num_listen_socks < 0)
1048 /* This is the child processing a new connection. */
1051 * Disable the key regeneration alarm. We will not regenerate the
1052 * key since we are no longer in a position to give it to anyone. We
1053 * will not restart on SIGHUP since it no longer makes sense.
1056 signal(SIGALRM, SIG_DFL);
1057 signal(SIGHUP, SIG_DFL);
1058 signal(SIGTERM, SIG_DFL);
1059 signal(SIGQUIT, SIG_DFL);
1060 signal(SIGCHLD, SIG_DFL);
1061 signal(SIGINT, SIG_DFL);
1064 * Set socket options for the connection. We want the socket to
1065 * close as fast as possible without waiting for anything. If the
1066 * connection is not a socket, these will do nothing.
1068 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1070 linger.l_linger = 5;
1071 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
1074 * Register our connection. This turns encryption off because we do
1077 packet_set_connection(sock_in, sock_out);
1079 remote_port = get_remote_port();
1080 remote_ip = get_remote_ipaddr();
1082 /* Check whether logins are denied from this host. */
1084 /* XXX LIBWRAP noes not know about IPv6 */
1086 struct request_info req;
1088 request_init(&req, RQ_DAEMON, av0, RQ_FILE, sock_in, NULL);
1091 if (!hosts_access(&req)) {
1096 /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
1098 #endif /* LIBWRAP */
1099 /* Log the connection. */
1100 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1103 * We don\'t want to listen forever unless the other side
1104 * successfully authenticates itself. So we set up an alarm which is
1105 * cleared after successful authentication. A limit of zero
1106 * indicates no limit. Note that we don\'t set the alarm in debugging
1107 * mode; it is just annoying to have the server exit just when you
1108 * are about to discover the bug.
1110 signal(SIGALRM, grace_alarm_handler);
1112 alarm(options.login_grace_time);
1114 sshd_exchange_identification(sock_in, sock_out);
1116 * Check that the connection comes from a privileged port. Rhosts-
1117 * and Rhosts-RSA-Authentication only make sense from priviledged
1118 * programs. Of course, if the intruder has root access on his local
1119 * machine, he can connect from any port. So do not use these
1120 * authentication methods from machines that you do not trust.
1122 if (remote_port >= IPPORT_RESERVED ||
1123 remote_port < IPPORT_RESERVED / 2) {
1124 debug("Rhosts Authentication methods disabled, "
1125 "originating port not trusted.");
1126 options.rhosts_authentication = 0;
1127 options.rhosts_rsa_authentication = 0;
1130 if (!packet_connection_is_ipv4() &&
1131 options.kerberos_authentication) {
1132 debug("Kerberos Authentication disabled, only available for IPv4.");
1133 options.kerberos_authentication = 0;
1137 packet_set_nonblocking();
1139 /* perform the key exchange */
1140 /* authenticate user and start session */
1143 do_authentication2();
1146 do_authentication();
1150 /* Cleanup user's ticket cache file. */
1151 if (options.kerberos_ticket_cleanup)
1155 /* The connection has been terminated. */
1156 verbose("Closing connection to %.100s", remote_ip);
1160 #endif /* USE_PAM */
1174 BIGNUM *session_key_int;
1175 unsigned char session_key[SSH_SESSION_KEY_LENGTH];
1176 unsigned char cookie[8];
1177 unsigned int cipher_type, auth_mask, protocol_flags;
1181 * Generate check bytes that the client must send back in the user
1182 * packet in order for it to be accepted; this is used to defy ip
1183 * spoofing attacks. Note that this only works against somebody
1184 * doing IP spoofing from a remote machine; any machine on the local
1185 * network can still see outgoing packets and catch the random
1186 * cookie. This only affects rhosts authentication, and this is one
1187 * of the reasons why it is inherently insecure.
1189 for (i = 0; i < 8; i++) {
1191 rand = arc4random();
1192 cookie[i] = rand & 0xff;
1197 * Send our public key. We include in the packet 64 bits of random
1198 * data that must be matched in the reply in order to prevent IP
1201 packet_start(SSH_SMSG_PUBLIC_KEY);
1202 for (i = 0; i < 8; i++)
1203 packet_put_char(cookie[i]);
1205 /* Store our public server RSA key. */
1206 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1207 packet_put_bignum(sensitive_data.server_key->rsa->e);
1208 packet_put_bignum(sensitive_data.server_key->rsa->n);
1210 /* Store our public host RSA key. */
1211 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1212 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1213 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1215 /* Put protocol flags. */
1216 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1218 /* Declare which ciphers we support. */
1219 packet_put_int(cipher_mask_ssh1(0));
1221 /* Declare supported authentication types. */
1223 if (options.rhosts_authentication)
1224 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1225 if (options.rhosts_rsa_authentication)
1226 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1227 if (options.rsa_authentication)
1228 auth_mask |= 1 << SSH_AUTH_RSA;
1230 if (options.kerberos_authentication)
1231 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1234 if (options.kerberos_tgt_passing)
1235 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1236 if (options.afs_token_passing)
1237 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1240 if (options.skey_authentication == 1)
1241 auth_mask |= 1 << SSH_AUTH_TIS;
1243 if (options.password_authentication)
1244 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1245 packet_put_int(auth_mask);
1247 /* Send the packet and wait for it to be sent. */
1249 packet_write_wait();
1251 debug("Sent %d bit server key and %d bit host key.",
1252 BN_num_bits(sensitive_data.server_key->rsa->n),
1253 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1255 /* Read clients reply (cipher type and session key). */
1256 packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1258 /* Get cipher type and check whether we accept this. */
1259 cipher_type = packet_get_char();
1261 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1262 packet_disconnect("Warning: client selects unsupported cipher.");
1264 /* Get check bytes from the packet. These must match those we
1265 sent earlier with the public key packet. */
1266 for (i = 0; i < 8; i++)
1267 if (cookie[i] != packet_get_char())
1268 packet_disconnect("IP Spoofing check bytes do not match.");
1270 debug("Encryption type: %.200s", cipher_name(cipher_type));
1272 /* Get the encrypted integer. */
1273 session_key_int = BN_new();
1274 packet_get_bignum(session_key_int, &slen);
1276 protocol_flags = packet_get_int();
1277 packet_set_protocol_flags(protocol_flags);
1279 packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1282 * Decrypt it using our private server key and private host key (key
1283 * with larger modulus first).
1285 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1286 /* Private key has bigger modulus. */
1287 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1288 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1289 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1290 get_remote_ipaddr(),
1291 BN_num_bits(sensitive_data.server_key->rsa->n),
1292 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1293 SSH_KEY_BITS_RESERVED);
1295 rsa_private_decrypt(session_key_int, session_key_int,
1296 sensitive_data.server_key->rsa);
1297 rsa_private_decrypt(session_key_int, session_key_int,
1298 sensitive_data.ssh1_host_key->rsa);
1300 /* Host key has bigger modulus (or they are equal). */
1301 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1302 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1303 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1304 get_remote_ipaddr(),
1305 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1306 BN_num_bits(sensitive_data.server_key->rsa->n),
1307 SSH_KEY_BITS_RESERVED);
1309 rsa_private_decrypt(session_key_int, session_key_int,
1310 sensitive_data.ssh1_host_key->rsa);
1311 rsa_private_decrypt(session_key_int, session_key_int,
1312 sensitive_data.server_key->rsa);
1315 compute_session_id(session_id, cookie,
1316 sensitive_data.ssh1_host_key->rsa->n,
1317 sensitive_data.server_key->rsa->n);
1319 /* Destroy the private and public keys. They will no longer be needed. */
1320 destroy_sensitive_data();
1323 * Extract session key from the decrypted integer. The key is in the
1324 * least significant 256 bits of the integer; the first byte of the
1325 * key is in the highest bits.
1327 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1328 len = BN_num_bytes(session_key_int);
1329 if (len < 0 || len > sizeof(session_key))
1330 fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d",
1331 get_remote_ipaddr(),
1332 len, sizeof(session_key));
1333 memset(session_key, 0, sizeof(session_key));
1334 BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len);
1336 /* Destroy the decrypted integer. It is no longer needed. */
1337 BN_clear_free(session_key_int);
1339 /* Xor the first 16 bytes of the session key with the session id. */
1340 for (i = 0; i < 16; i++)
1341 session_key[i] ^= session_id[i];
1343 /* Set the session key. From this on all communications will be encrypted. */
1344 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1346 /* Destroy our copy of the session key. It is no longer needed. */
1347 memset(session_key, 0, sizeof(session_key));
1349 debug("Received session key; encryption turned on.");
1351 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1352 packet_start(SSH_SMSG_SUCCESS);
1354 packet_write_wait();
1358 * SSH2 key exchange: diffie-hellman-group1-sha1
1363 Buffer *server_kexinit;
1364 Buffer *client_kexinit;
1368 char *cprop[PROPOSAL_MAX];
1372 if (options.ciphers != NULL) {
1373 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1374 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1376 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
1378 server_kexinit = kex_init(myproposal);
1379 client_kexinit = xmalloc(sizeof(*client_kexinit));
1380 buffer_init(client_kexinit);
1382 /* algorithm negotiation */
1383 kex_exchange_kexinit(server_kexinit, client_kexinit, cprop);
1384 kex = kex_choose_conf(cprop, myproposal, 1);
1385 for (i = 0; i < PROPOSAL_MAX; i++)
1388 switch (kex->kex_type) {
1390 ssh_dh1_server(kex, client_kexinit, server_kexinit);
1393 ssh_dhgex_server(kex, client_kexinit, server_kexinit);
1396 fatal("Unsupported key exchange %d", kex->kex_type);
1399 debug("send SSH2_MSG_NEWKEYS.");
1400 packet_start(SSH2_MSG_NEWKEYS);
1402 packet_write_wait();
1403 debug("done: send SSH2_MSG_NEWKEYS.");
1405 debug("Wait SSH2_MSG_NEWKEYS.");
1406 packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS);
1407 debug("GOT SSH2_MSG_NEWKEYS.");
1410 /* send 1st encrypted/maced/compressed message */
1411 packet_start(SSH2_MSG_IGNORE);
1412 packet_put_cstring("markus");
1414 packet_write_wait();
1417 debug("done: KEX2.");
1424 /* diffie-hellman-group1-sha1 */
1427 ssh_dh1_server(Kex *kex, Buffer *client_kexinit, Buffer *server_kexinit)
1432 int payload_len, dlen;
1434 unsigned char *signature = NULL;
1435 unsigned char *server_host_key_blob = NULL;
1436 unsigned int sbloblen;
1437 unsigned int klen, kout;
1438 unsigned char *kbuf;
1439 unsigned char *hash;
1440 BIGNUM *shared_secret = 0;
1442 BIGNUM *dh_client_pub = 0;
1445 hostkey = get_hostkey_by_type(kex->hostkey_type);
1446 if (hostkey == NULL)
1447 fatal("Unsupported hostkey type %d", kex->hostkey_type);
1450 debug("Wait SSH2_MSG_KEXDH_INIT.");
1451 packet_read_expect(&payload_len, SSH2_MSG_KEXDH_INIT);
1454 dh_client_pub = BN_new();
1455 if (dh_client_pub == NULL)
1456 fatal("dh_client_pub == NULL");
1457 packet_get_bignum2(dh_client_pub, &dlen);
1460 fprintf(stderr, "\ndh_client_pub= ");
1461 BN_print_fp(stderr, dh_client_pub);
1462 fprintf(stderr, "\n");
1463 debug("bits %d", BN_num_bits(dh_client_pub));
1466 /* generate DH key */
1467 dh = dh_new_group1(); /* XXX depends on 'kex' */
1470 fprintf(stderr, "\np= ");
1471 BN_print_fp(stderr, dh->p);
1472 fprintf(stderr, "\ng= ");
1474 fprintf(stderr, "\npub= ");
1475 BN_print_fp(stderr, dh->pub_key);
1476 fprintf(stderr, "\n");
1477 DHparams_print_fp(stderr, dh);
1479 if (!dh_pub_is_valid(dh, dh_client_pub))
1480 packet_disconnect("bad client public DH value");
1483 kbuf = xmalloc(klen);
1484 kout = DH_compute_key(kbuf, dh_client_pub, dh);
1487 debug("shared secret: len %d/%d", klen, kout);
1488 fprintf(stderr, "shared secret == ");
1489 for (i = 0; i< kout; i++)
1490 fprintf(stderr, "%02x", (kbuf[i])&0xff);
1491 fprintf(stderr, "\n");
1493 shared_secret = BN_new();
1495 BN_bin2bn(kbuf, kout, shared_secret);
1496 memset(kbuf, 0, klen);
1499 /* XXX precompute? */
1500 key_to_blob(hostkey, &server_host_key_blob, &sbloblen);
1502 /* calc H */ /* XXX depends on 'kex' */
1504 client_version_string,
1505 server_version_string,
1506 buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1507 buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1508 (char *)server_host_key_blob, sbloblen,
1513 buffer_free(client_kexinit);
1514 buffer_free(server_kexinit);
1515 xfree(client_kexinit);
1516 xfree(server_kexinit);
1518 fprintf(stderr, "hash == ");
1519 for (i = 0; i< 20; i++)
1520 fprintf(stderr, "%02x", (hash[i])&0xff);
1521 fprintf(stderr, "\n");
1523 /* save session id := H */
1524 /* XXX hashlen depends on KEX */
1525 session_id2_len = 20;
1526 session_id2 = xmalloc(session_id2_len);
1527 memcpy(session_id2, hash, session_id2_len);
1530 /* XXX hashlen depends on KEX */
1531 key_sign(hostkey, &signature, &slen, hash, 20);
1533 destroy_sensitive_data();
1535 /* send server hostkey, DH pubkey 'f' and singed H */
1536 packet_start(SSH2_MSG_KEXDH_REPLY);
1537 packet_put_string((char *)server_host_key_blob, sbloblen);
1538 packet_put_bignum2(dh->pub_key); /* f */
1539 packet_put_string((char *)signature, slen);
1542 xfree(server_host_key_blob);
1543 packet_write_wait();
1545 kex_derive_keys(kex, hash, shared_secret);
1546 packet_set_kex(kex);
1548 /* have keys, free DH */
1552 /* diffie-hellman-group-exchange-sha1 */
1555 ssh_dhgex_server(Kex *kex, Buffer *client_kexinit, Buffer *server_kexinit)
1560 int payload_len, dlen;
1562 unsigned char *signature = NULL;
1563 unsigned char *server_host_key_blob = NULL;
1564 unsigned int sbloblen;
1565 unsigned int klen, kout;
1566 unsigned char *kbuf;
1567 unsigned char *hash;
1568 BIGNUM *shared_secret = 0;
1570 BIGNUM *dh_client_pub = 0;
1573 hostkey = get_hostkey_by_type(kex->hostkey_type);
1574 if (hostkey == NULL)
1575 fatal("Unsupported hostkey type %d", kex->hostkey_type);
1578 debug("Wait SSH2_MSG_KEX_DH_GEX_REQUEST.");
1579 packet_read_expect(&payload_len, SSH2_MSG_KEX_DH_GEX_REQUEST);
1580 nbits = packet_get_int();
1581 dh = choose_dh(nbits);
1583 debug("Sending SSH2_MSG_KEX_DH_GEX_GROUP.");
1584 packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
1585 packet_put_bignum2(dh->p);
1586 packet_put_bignum2(dh->g);
1588 packet_write_wait();
1590 debug("Wait SSH2_MSG_KEX_DH_GEX_INIT.");
1591 packet_read_expect(&payload_len, SSH2_MSG_KEX_DH_GEX_INIT);
1594 dh_client_pub = BN_new();
1595 if (dh_client_pub == NULL)
1596 fatal("dh_client_pub == NULL");
1597 packet_get_bignum2(dh_client_pub, &dlen);
1600 fprintf(stderr, "\ndh_client_pub= ");
1601 BN_print_fp(stderr, dh_client_pub);
1602 fprintf(stderr, "\n");
1603 debug("bits %d", BN_num_bits(dh_client_pub));
1607 fprintf(stderr, "\np= ");
1608 BN_print_fp(stderr, dh->p);
1609 fprintf(stderr, "\ng= ");
1611 fprintf(stderr, "\npub= ");
1612 BN_print_fp(stderr, dh->pub_key);
1613 fprintf(stderr, "\n");
1614 DHparams_print_fp(stderr, dh);
1616 if (!dh_pub_is_valid(dh, dh_client_pub))
1617 packet_disconnect("bad client public DH value");
1620 kbuf = xmalloc(klen);
1621 kout = DH_compute_key(kbuf, dh_client_pub, dh);
1624 debug("shared secret: len %d/%d", klen, kout);
1625 fprintf(stderr, "shared secret == ");
1626 for (i = 0; i< kout; i++)
1627 fprintf(stderr, "%02x", (kbuf[i])&0xff);
1628 fprintf(stderr, "\n");
1630 shared_secret = BN_new();
1632 BN_bin2bn(kbuf, kout, shared_secret);
1633 memset(kbuf, 0, klen);
1636 /* XXX precompute? */
1637 key_to_blob(hostkey, &server_host_key_blob, &sbloblen);
1639 /* calc H */ /* XXX depends on 'kex' */
1640 hash = kex_hash_gex(
1641 client_version_string,
1642 server_version_string,
1643 buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1644 buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1645 (char *)server_host_key_blob, sbloblen,
1646 nbits, dh->p, dh->g,
1651 buffer_free(client_kexinit);
1652 buffer_free(server_kexinit);
1653 xfree(client_kexinit);
1654 xfree(server_kexinit);
1656 fprintf(stderr, "hash == ");
1657 for (i = 0; i< 20; i++)
1658 fprintf(stderr, "%02x", (hash[i])&0xff);
1659 fprintf(stderr, "\n");
1661 /* save session id := H */
1662 /* XXX hashlen depends on KEX */
1663 session_id2_len = 20;
1664 session_id2 = xmalloc(session_id2_len);
1665 memcpy(session_id2, hash, session_id2_len);
1668 /* XXX hashlen depends on KEX */
1669 key_sign(hostkey, &signature, &slen, hash, 20);
1671 destroy_sensitive_data();
1673 /* send server hostkey, DH pubkey 'f' and singed H */
1674 packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
1675 packet_put_string((char *)server_host_key_blob, sbloblen);
1676 packet_put_bignum2(dh->pub_key); /* f */
1677 packet_put_string((char *)signature, slen);
1680 xfree(server_host_key_blob);
1681 packet_write_wait();
1683 kex_derive_keys(kex, hash, shared_secret);
1684 packet_set_kex(kex);
1686 /* have keys, free DH */