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 1.132 2000/10/13 18:34:46 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>
68 #include "myproposal.h"
74 int allow_severity = LOG_INFO;
75 int deny_severity = LOG_WARNING;
82 /* Server configuration options. */
83 ServerOptions options;
85 /* Name of the server configuration file. */
86 char *config_file_name = SERVER_CONFIG_FILE;
89 * Flag indicating whether IPv4 or IPv6. This can be set on the command line.
90 * Default value is AF_UNSPEC means both IPv4 and IPv6.
93 int IPv4or6 = AF_INET;
95 int IPv4or6 = AF_UNSPEC;
99 * Debug mode flag. This can be set on the command line. If debug
100 * mode is enabled, extra debugging output will be sent to the system
101 * log, the daemon will not go to background, and will exit after processing
102 * the first connection.
106 /* Flag indicating that the daemon is being started from inetd. */
109 /* debug goes to stderr unless inetd_flag is set */
112 /* argv[0] without path. */
115 /* Saved arguments to main(). */
120 * The sockets that the server is listening; this is used in the SIGHUP
123 #define MAX_LISTEN_SOCKS 16
124 int listen_socks[MAX_LISTEN_SOCKS];
125 int num_listen_socks = 0;
128 * the client's version string, passed by sshd2 in compat mode. if != NULL,
129 * sshd will skip the version-number exchange
131 char *client_version_string = NULL;
132 char *server_version_string = NULL;
135 * Any really sensitive data in the application is contained in this
136 * structure. The idea is that this structure could be locked into memory so
137 * that the pages do not get written into swap. However, there are some
138 * problems. The private key contains BIGNUMs, and we do not (in principle)
139 * have access to the internals of them, and locking just the structure is
140 * not very useful. Currently, memory locking is not implemented.
143 RSA *private_key; /* Private part of empheral server key. */
144 RSA *host_key; /* Private part of host key. */
145 Key *dsa_host_key; /* Private DSA host key. */
149 * Flag indicating whether the current session key has been used. This flag
150 * is set whenever the key is used, and cleared when the key is regenerated.
154 /* This is set to true when SIGHUP is received. */
155 int received_sighup = 0;
157 /* Public side of the server key. This value is regenerated regularly with
161 /* session identifier, used by RSA-auth */
162 unsigned char session_id[16];
165 unsigned char *session_id2 = NULL;
166 int session_id2_len = 0;
168 /* record remote hostname or ip */
169 unsigned int utmp_len = MAXHOSTNAMELEN;
171 /* Prototypes for various functions defined later in this file. */
175 void ssh_dh1_server(Kex *, Buffer *_kexinit, Buffer *);
176 void ssh_dhgex_server(Kex *, Buffer *_kexinit, Buffer *);
179 * Close all listening sockets
182 close_listen_socks(void)
185 for (i = 0; i < num_listen_socks; i++)
186 close(listen_socks[i]);
187 num_listen_socks = -1;
191 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
192 * the effect is to reread the configuration file (and to regenerate
196 sighup_handler(int sig)
199 signal(SIGHUP, sighup_handler);
203 * Called from the main program after receiving SIGHUP.
204 * Restarts the server.
209 log("Received SIGHUP; restarting.");
210 close_listen_socks();
211 execv(saved_argv[0], saved_argv);
212 log("RESTART FAILED: av0='%s', error: %s.", av0, strerror(errno));
217 * Generic signal handler for terminating signals in the master daemon.
218 * These close the listen socket; not closing it seems to cause "Address
219 * already in use" problems on some machines, which is inconvenient.
222 sigterm_handler(int sig)
224 log("Received signal %d; terminating.", sig);
225 close_listen_socks();
226 unlink(options.pid_file);
231 * SIGCHLD handler. This is called whenever a child dies. This will then
232 * reap any zombies left by exited c.
235 main_sigchld_handler(int sig)
237 int save_errno = errno;
240 while (waitpid(-1, &status, WNOHANG) > 0)
243 signal(SIGCHLD, main_sigchld_handler);
248 * Signal handler for the alarm after the login grace period has expired.
251 grace_alarm_handler(int sig)
253 /* Close the connection. */
256 /* Log error and exit. */
257 fatal("Timeout before authentication for %s.", get_remote_ipaddr());
261 * Signal handler for the key regeneration alarm. Note that this
262 * alarm only occurs in the daemon waiting for connections, and it does not
263 * do anything with the private key or random state before forking.
264 * Thus there should be no concurrency control/asynchronous execution
267 /* XXX do we really want this work to be done in a signal handler ? -m */
269 key_regeneration_alarm(int sig)
271 int save_errno = errno;
273 /* Check if we should generate a new key. */
275 /* This should really be done in the background. */
276 log("Generating new %d bit RSA key.", options.server_key_bits);
278 if (sensitive_data.private_key != NULL)
279 RSA_free(sensitive_data.private_key);
280 sensitive_data.private_key = RSA_new();
282 if (public_key != NULL)
283 RSA_free(public_key);
284 public_key = RSA_new();
286 rsa_generate_key(sensitive_data.private_key, public_key,
287 options.server_key_bits);
290 log("RSA key generation complete.");
292 /* Reschedule the alarm. */
293 signal(SIGALRM, key_regeneration_alarm);
294 alarm(options.key_regeneration_time);
299 sshd_exchange_identification(int sock_in, int sock_out)
302 int remote_major, remote_minor;
305 char buf[256]; /* Must not be larger than remote_version. */
306 char remote_version[256]; /* Must be at least as big as buf. */
308 if ((options.protocol & SSH_PROTO_1) &&
309 (options.protocol & SSH_PROTO_2)) {
310 major = PROTOCOL_MAJOR_1;
312 } else if (options.protocol & SSH_PROTO_2) {
313 major = PROTOCOL_MAJOR_2;
314 minor = PROTOCOL_MINOR_2;
316 major = PROTOCOL_MAJOR_1;
317 minor = PROTOCOL_MINOR_1;
319 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
320 server_version_string = xstrdup(buf);
322 if (client_version_string == NULL) {
323 /* Send our protocol version identification. */
324 if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
325 != strlen(server_version_string)) {
326 log("Could not write ident string to %s.", get_remote_ipaddr());
330 /* Read other side\'s version identification. */
331 for (i = 0; i < sizeof(buf) - 1; i++) {
332 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
333 log("Did not receive ident string from %s.", get_remote_ipaddr());
336 if (buf[i] == '\r') {
339 /* Kludge for F-Secure Macintosh < 1.0.2 */
341 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
345 if (buf[i] == '\n') {
351 buf[sizeof(buf) - 1] = 0;
352 client_version_string = xstrdup(buf);
356 * Check that the versions match. In future this might accept
357 * several versions and set appropriate flags to handle them.
359 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
360 &remote_major, &remote_minor, remote_version) != 3) {
361 s = "Protocol mismatch.\n";
362 (void) atomicio(write, sock_out, s, strlen(s));
365 log("Bad protocol version identification '%.100s' from %s",
366 client_version_string, get_remote_ipaddr());
369 debug("Client protocol version %d.%d; client software version %.100s",
370 remote_major, remote_minor, remote_version);
372 compat_datafellows(remote_version);
375 switch(remote_major) {
377 if (remote_minor == 99) {
378 if (options.protocol & SSH_PROTO_2)
384 if (!(options.protocol & SSH_PROTO_1)) {
388 if (remote_minor < 3) {
389 packet_disconnect("Your ssh version is too old and "
390 "is no longer supported. Please install a newer version.");
391 } else if (remote_minor == 3) {
392 /* note that this disables agent-forwarding */
397 if (options.protocol & SSH_PROTO_2) {
406 chop(server_version_string);
407 chop(client_version_string);
408 debug("Local version string %.200s", server_version_string);
411 s = "Protocol major versions differ.\n";
412 (void) atomicio(write, sock_out, s, strlen(s));
415 log("Protocol major versions differ for %s: %.200s vs. %.200s",
417 server_version_string, client_version_string);
421 packet_set_ssh2_format();
426 destroy_sensitive_data(void)
428 /* Destroy the private and public keys. They will no longer be needed. */
430 RSA_free(public_key);
431 if (sensitive_data.private_key)
432 RSA_free(sensitive_data.private_key);
433 if (sensitive_data.host_key)
434 RSA_free(sensitive_data.host_key);
435 if (sensitive_data.dsa_host_key != NULL)
436 key_free(sensitive_data.dsa_host_key);
440 * returns 1 if connection should be dropped, 0 otherwise.
441 * dropping starts at connection #max_startups_begin with a probability
442 * of (max_startups_rate/100). the probability increases linearly until
443 * all connections are dropped for startups > max_startups
446 drop_connection(int startups)
450 if (startups < options.max_startups_begin)
452 if (startups >= options.max_startups)
454 if (options.max_startups_rate == 100)
457 p = 100 - options.max_startups_rate;
458 p *= startups - options.max_startups_begin;
459 p /= (double) (options.max_startups - options.max_startups_begin);
460 p += options.max_startups_rate;
462 r = arc4random() / (double) UINT_MAX;
464 debug("drop_connection: p %g, r %g", p, r);
465 return (r < p) ? 1 : 0;
468 int *startup_pipes = NULL; /* options.max_startup sized array of fd ints */
469 int startup_pipe; /* in child */
472 * Main program for the daemon.
475 main(int ac, char **av)
479 int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
484 struct sockaddr_storage from;
485 const char *remote_ip;
488 struct linger linger;
490 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
491 int listen_sock, maxfd;
500 if (strchr(av[0], '/'))
501 av0 = strrchr(av[0], '/') + 1;
505 /* Initialize configuration options to their default values. */
506 initialize_server_options(&options);
508 /* Parse command-line arguments. */
509 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:diqQ46")) != EOF) {
518 config_file_name = optarg;
521 if (0 == debug_flag) {
523 options.log_level = SYSLOG_LEVEL_DEBUG1;
524 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
527 fprintf(stderr, "Too high debugging level.\n");
538 options.log_level = SYSLOG_LEVEL_QUIET;
541 options.server_key_bits = atoi(optarg);
544 options.ports_from_cmdline = 1;
545 if (options.num_ports >= MAX_PORTS) {
546 fprintf(stderr, "too many ports.\n");
549 options.ports[options.num_ports++] = atoi(optarg);
552 options.login_grace_time = atoi(optarg);
555 options.key_regeneration_time = atoi(optarg);
558 options.host_key_file = optarg;
561 client_version_string = optarg;
562 /* only makes sense with inetd_flag, i.e. no listen() */
566 utmp_len = atoi(optarg);
570 fprintf(stderr, "sshd version %s\n", SSH_VERSION);
571 fprintf(stderr, "Usage: %s [options]\n", av0);
572 fprintf(stderr, "Options:\n");
573 fprintf(stderr, " -f file Configuration file (default %s)\n", SERVER_CONFIG_FILE);
574 fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n");
575 fprintf(stderr, " -i Started from inetd\n");
576 fprintf(stderr, " -q Quiet (no logging)\n");
577 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
578 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
579 fprintf(stderr, " -g seconds Grace period for authentication (default: 300)\n");
580 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
581 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
583 fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
584 fprintf(stderr, " -4 Use IPv4 only\n");
585 fprintf(stderr, " -6 Use IPv6 only\n");
591 * Force logging to stderr until we have loaded the private host
592 * key (unless started from inetd)
595 options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
596 options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
597 !silent && !inetd_flag);
599 /* Read server configuration options from the configuration file. */
600 read_server_config(&options, config_file_name);
602 /* Fill in default values for those options not explicitly set. */
603 fill_default_server_options(&options);
605 /* Check that there are no remaining arguments. */
607 fprintf(stderr, "Extra argument %s.\n", av[optind]);
611 debug("sshd version %.100s", SSH_VERSION);
613 sensitive_data.dsa_host_key = NULL;
614 sensitive_data.host_key = NULL;
616 /* check if RSA support exists */
617 if ((options.protocol & SSH_PROTO_1) &&
619 log("no RSA support in libssl and libcrypto. See ssl(8)");
620 log("Disabling protocol version 1");
621 options.protocol &= ~SSH_PROTO_1;
623 /* Load the RSA/DSA host key. It must have empty passphrase. */
624 if (options.protocol & SSH_PROTO_1) {
626 sensitive_data.host_key = RSA_new();
628 k.rsa = sensitive_data.host_key;
630 if (!load_private_key(options.host_key_file, "", &k, NULL)) {
631 error("Could not load host key: %.200s: %.100s",
632 options.host_key_file, strerror(errno));
633 log("Disabling protocol version 1");
634 options.protocol &= ~SSH_PROTO_1;
638 if (options.protocol & SSH_PROTO_2) {
639 sensitive_data.dsa_host_key = key_new(KEY_DSA);
640 if (!load_private_key(options.host_dsa_key_file, "", sensitive_data.dsa_host_key, NULL)) {
642 error("Could not load DSA host key: %.200s", options.host_dsa_key_file);
643 log("Disabling protocol version 2");
644 options.protocol &= ~SSH_PROTO_2;
647 if (! options.protocol & (SSH_PROTO_1|SSH_PROTO_2)) {
649 fprintf(stderr, "sshd: no hostkeys available -- exiting.\n");
650 log("sshd: no hostkeys available -- exiting.\n");
654 /* Check certain values for sanity. */
655 if (options.protocol & SSH_PROTO_1) {
656 if (options.server_key_bits < 512 ||
657 options.server_key_bits > 32768) {
658 fprintf(stderr, "Bad server key size.\n");
662 * Check that server and host key lengths differ sufficiently. This
663 * is necessary to make double encryption work with rsaref. Oh, I
664 * hate software patents. I dont know if this can go? Niels
666 if (options.server_key_bits >
667 BN_num_bits(sensitive_data.host_key->n) - SSH_KEY_BITS_RESERVED &&
668 options.server_key_bits <
669 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
670 options.server_key_bits =
671 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED;
672 debug("Forcing server key to %d bits to make it differ from host key.",
673 options.server_key_bits);
677 #ifdef HAVE_SCO_PROTECTED_PW
678 (void) set_auth_parameters(ac, av);
681 /* Initialize the log (it is reinitialized below in case we forked). */
682 if (debug_flag && !inetd_flag)
684 log_init(av0, options.log_level, options.log_facility, log_stderr);
687 * If not in debugging mode, and not started from inetd, disconnect
688 * from the controlling terminal, and fork. The original process
691 if (!debug_flag && !inetd_flag) {
694 #endif /* TIOCNOTTY */
695 if (daemon(0, 0) < 0)
696 fatal("daemon() failed: %.200s", strerror(errno));
698 /* Disconnect from the controlling tty. */
700 fd = open("/dev/tty", O_RDWR | O_NOCTTY);
702 (void) ioctl(fd, TIOCNOTTY, NULL);
705 #endif /* TIOCNOTTY */
707 /* Reinitialize the log (because of the fork above). */
708 log_init(av0, options.log_level, options.log_facility, log_stderr);
710 /* Do not display messages to stdout in RSA code. */
713 /* Initialize the random number generator. */
716 /* Chdir to the root directory so that the current disk can be
717 unmounted if desired. */
720 /* Start listening for a socket, unless started from inetd. */
723 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
729 * We intentionally do not close the descriptors 0, 1, and 2
730 * as our code for setting the descriptors won\'t work if
731 * ttyfd happens to be one of those.
733 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
735 if (options.protocol & SSH_PROTO_1) {
736 public_key = RSA_new();
737 sensitive_data.private_key = RSA_new();
738 log("Generating %d bit RSA key.", options.server_key_bits);
739 rsa_generate_key(sensitive_data.private_key, public_key,
740 options.server_key_bits);
742 log("RSA key generation complete.");
745 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
746 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
748 if (num_listen_socks >= MAX_LISTEN_SOCKS)
749 fatal("Too many listen sockets. "
750 "Enlarge MAX_LISTEN_SOCKS");
751 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
752 ntop, sizeof(ntop), strport, sizeof(strport),
753 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
754 error("getnameinfo failed");
757 /* Create socket for listening. */
758 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
759 if (listen_sock < 0) {
760 /* kernel may not support ipv6 */
761 verbose("socket: %.100s", strerror(errno));
764 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
765 error("listen_sock O_NONBLOCK: %s", strerror(errno));
770 * Set socket options. We try to make the port
771 * reusable and have it close as fast as possible
772 * without waiting in unnecessary wait states on
775 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
776 (void *) &on, sizeof(on));
779 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
780 (void *) &linger, sizeof(linger));
782 debug("Bind to port %s on %s.", strport, ntop);
784 /* Bind the socket to the desired port. */
785 if ((bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) &&
787 error("Bind to port %s on %s failed: %.200s.",
788 strport, ntop, strerror(errno));
792 listen_socks[num_listen_socks] = listen_sock;
795 /* Start listening on the port. */
796 log("Server listening on %s port %s.", ntop, strport);
797 if (listen(listen_sock, 5) < 0)
798 fatal("listen: %.100s", strerror(errno));
801 freeaddrinfo(options.listen_addrs);
803 if (!num_listen_socks)
804 fatal("Cannot bind any address.");
808 * Record our pid in /etc/sshd_pid to make it easier
809 * to kill the correct sshd. We don\'t want to do
810 * this before the bind above because the bind will
811 * fail if there already is a daemon, and this will
812 * overwrite any old pid in the file.
814 f = fopen(options.pid_file, "wb");
816 fprintf(f, "%u\n", (unsigned int) getpid());
820 if (options.protocol & SSH_PROTO_1) {
821 public_key = RSA_new();
822 sensitive_data.private_key = RSA_new();
824 log("Generating %d bit RSA key.", options.server_key_bits);
825 rsa_generate_key(sensitive_data.private_key, public_key,
826 options.server_key_bits);
828 log("RSA key generation complete.");
830 /* Schedule server key regeneration alarm. */
831 signal(SIGALRM, key_regeneration_alarm);
832 alarm(options.key_regeneration_time);
835 /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
836 signal(SIGHUP, sighup_handler);
838 signal(SIGTERM, sigterm_handler);
839 signal(SIGQUIT, sigterm_handler);
841 /* Arrange SIGCHLD to be caught. */
842 signal(SIGCHLD, main_sigchld_handler);
844 /* setup fd set for listen */
847 for (i = 0; i < num_listen_socks; i++)
848 if (listen_socks[i] > maxfd)
849 maxfd = listen_socks[i];
850 /* pipes connected to unauthenticated childs */
851 startup_pipes = xmalloc(options.max_startups * sizeof(int));
852 for (i = 0; i < options.max_startups; i++)
853 startup_pipes[i] = -1;
856 * Stay listening for connections until the system crashes or
857 * the daemon is killed with a signal.
864 fdsetsz = howmany(maxfd, NFDBITS) * sizeof(fd_mask);
865 fdset = (fd_set *)xmalloc(fdsetsz);
866 memset(fdset, 0, fdsetsz);
868 for (i = 0; i < num_listen_socks; i++)
869 FD_SET(listen_socks[i], fdset);
870 for (i = 0; i < options.max_startups; i++)
871 if (startup_pipes[i] != -1)
872 FD_SET(startup_pipes[i], fdset);
874 /* Wait in select until there is a connection. */
875 if (select(maxfd + 1, fdset, NULL, NULL, NULL) < 0) {
877 error("select: %.100s", strerror(errno));
880 for (i = 0; i < options.max_startups; i++)
881 if (startup_pipes[i] != -1 &&
882 FD_ISSET(startup_pipes[i], fdset)) {
884 * the read end of the pipe is ready
885 * if the child has closed the pipe
886 * after successfull authentication
887 * or if the child has died
889 close(startup_pipes[i]);
890 startup_pipes[i] = -1;
893 for (i = 0; i < num_listen_socks; i++) {
894 if (!FD_ISSET(listen_socks[i], fdset))
896 fromlen = sizeof(from);
897 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
900 if (errno != EINTR && errno != EWOULDBLOCK)
901 error("accept: %.100s", strerror(errno));
904 if (fcntl(newsock, F_SETFL, 0) < 0) {
905 error("newsock del O_NONBLOCK: %s", strerror(errno));
908 if (drop_connection(startups) == 1) {
909 debug("drop connection #%d", startups);
913 if (pipe(startup_p) == -1) {
918 for (j = 0; j < options.max_startups; j++)
919 if (startup_pipes[j] == -1) {
920 startup_pipes[j] = startup_p[0];
921 if (maxfd < startup_p[0])
922 maxfd = startup_p[0];
928 * Got connection. Fork a child to handle it, unless
929 * we are in debugging mode.
933 * In debugging mode. Close the listening
934 * socket, and start processing the
935 * connection without forking.
937 debug("Server will not fork when running in debugging mode.");
938 close_listen_socks();
946 * Normal production daemon. Fork, and have
947 * the child process the connection. The
948 * parent continues listening.
950 if ((pid = fork()) == 0) {
952 * Child. Close the listening and max_startup
953 * sockets. Start using the accepted socket.
954 * Reinitialize logging (since our pid has
955 * changed). We break out of the loop to handle
958 startup_pipe = startup_p[1];
959 for (j = 0; j < options.max_startups; j++)
960 if (startup_pipes[j] != -1)
961 close(startup_pipes[j]);
962 close_listen_socks();
965 log_init(av0, options.log_level, options.log_facility, log_stderr);
970 /* Parent. Stay in the loop. */
972 error("fork: %.100s", strerror(errno));
974 debug("Forked child %d.", pid);
978 /* Mark that the key has been used (it was "given" to the child). */
983 /* Close the new socket (the child is now taking care of it). */
986 /* child process check (or debug mode) */
987 if (num_listen_socks < 0)
992 /* This is the child processing a new connection. */
995 * Disable the key regeneration alarm. We will not regenerate the
996 * key since we are no longer in a position to give it to anyone. We
997 * will not restart on SIGHUP since it no longer makes sense.
1000 signal(SIGALRM, SIG_DFL);
1001 signal(SIGHUP, SIG_DFL);
1002 signal(SIGTERM, SIG_DFL);
1003 signal(SIGQUIT, SIG_DFL);
1004 signal(SIGCHLD, SIG_DFL);
1005 signal(SIGINT, SIG_DFL);
1008 * Set socket options for the connection. We want the socket to
1009 * close as fast as possible without waiting for anything. If the
1010 * connection is not a socket, these will do nothing.
1012 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1014 linger.l_linger = 5;
1015 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
1018 * Register our connection. This turns encryption off because we do
1021 packet_set_connection(sock_in, sock_out);
1023 remote_port = get_remote_port();
1024 remote_ip = get_remote_ipaddr();
1026 /* Check whether logins are denied from this host. */
1028 /* XXX LIBWRAP noes not know about IPv6 */
1030 struct request_info req;
1032 request_init(&req, RQ_DAEMON, av0, RQ_FILE, sock_in, NULL);
1035 if (!hosts_access(&req)) {
1040 /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
1042 #endif /* LIBWRAP */
1043 /* Log the connection. */
1044 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1047 * We don\'t want to listen forever unless the other side
1048 * successfully authenticates itself. So we set up an alarm which is
1049 * cleared after successful authentication. A limit of zero
1050 * indicates no limit. Note that we don\'t set the alarm in debugging
1051 * mode; it is just annoying to have the server exit just when you
1052 * are about to discover the bug.
1054 signal(SIGALRM, grace_alarm_handler);
1056 alarm(options.login_grace_time);
1058 sshd_exchange_identification(sock_in, sock_out);
1060 * Check that the connection comes from a privileged port. Rhosts-
1061 * and Rhosts-RSA-Authentication only make sense from priviledged
1062 * programs. Of course, if the intruder has root access on his local
1063 * machine, he can connect from any port. So do not use these
1064 * authentication methods from machines that you do not trust.
1066 if (remote_port >= IPPORT_RESERVED ||
1067 remote_port < IPPORT_RESERVED / 2) {
1068 options.rhosts_authentication = 0;
1069 options.rhosts_rsa_authentication = 0;
1072 if (!packet_connection_is_ipv4() &&
1073 options.kerberos_authentication) {
1074 debug("Kerberos Authentication disabled, only available for IPv4.");
1075 options.kerberos_authentication = 0;
1079 packet_set_nonblocking();
1081 /* perform the key exchange */
1082 /* authenticate user and start session */
1085 do_authentication2();
1088 do_authentication();
1092 /* Cleanup user's ticket cache file. */
1093 if (options.kerberos_ticket_cleanup)
1097 /* The connection has been terminated. */
1098 verbose("Closing connection to %.100s", remote_ip);
1102 #endif /* USE_PAM */
1116 BIGNUM *session_key_int;
1117 unsigned char session_key[SSH_SESSION_KEY_LENGTH];
1118 unsigned char cookie[8];
1119 unsigned int cipher_type, auth_mask, protocol_flags;
1123 * Generate check bytes that the client must send back in the user
1124 * packet in order for it to be accepted; this is used to defy ip
1125 * spoofing attacks. Note that this only works against somebody
1126 * doing IP spoofing from a remote machine; any machine on the local
1127 * network can still see outgoing packets and catch the random
1128 * cookie. This only affects rhosts authentication, and this is one
1129 * of the reasons why it is inherently insecure.
1131 for (i = 0; i < 8; i++) {
1133 rand = arc4random();
1134 cookie[i] = rand & 0xff;
1139 * Send our public key. We include in the packet 64 bits of random
1140 * data that must be matched in the reply in order to prevent IP
1143 packet_start(SSH_SMSG_PUBLIC_KEY);
1144 for (i = 0; i < 8; i++)
1145 packet_put_char(cookie[i]);
1147 /* Store our public server RSA key. */
1148 packet_put_int(BN_num_bits(public_key->n));
1149 packet_put_bignum(public_key->e);
1150 packet_put_bignum(public_key->n);
1152 /* Store our public host RSA key. */
1153 packet_put_int(BN_num_bits(sensitive_data.host_key->n));
1154 packet_put_bignum(sensitive_data.host_key->e);
1155 packet_put_bignum(sensitive_data.host_key->n);
1157 /* Put protocol flags. */
1158 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1160 /* Declare which ciphers we support. */
1161 packet_put_int(cipher_mask_ssh1(0));
1163 /* Declare supported authentication types. */
1165 if (options.rhosts_authentication)
1166 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1167 if (options.rhosts_rsa_authentication)
1168 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1169 if (options.rsa_authentication)
1170 auth_mask |= 1 << SSH_AUTH_RSA;
1172 if (options.kerberos_authentication)
1173 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1176 if (options.kerberos_tgt_passing)
1177 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1178 if (options.afs_token_passing)
1179 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1182 if (options.skey_authentication == 1)
1183 auth_mask |= 1 << SSH_AUTH_TIS;
1185 if (options.password_authentication)
1186 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1187 packet_put_int(auth_mask);
1189 /* Send the packet and wait for it to be sent. */
1191 packet_write_wait();
1193 debug("Sent %d bit public key and %d bit host key.",
1194 BN_num_bits(public_key->n), BN_num_bits(sensitive_data.host_key->n));
1196 /* Read clients reply (cipher type and session key). */
1197 packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1199 /* Get cipher type and check whether we accept this. */
1200 cipher_type = packet_get_char();
1202 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1203 packet_disconnect("Warning: client selects unsupported cipher.");
1205 /* Get check bytes from the packet. These must match those we
1206 sent earlier with the public key packet. */
1207 for (i = 0; i < 8; i++)
1208 if (cookie[i] != packet_get_char())
1209 packet_disconnect("IP Spoofing check bytes do not match.");
1211 debug("Encryption type: %.200s", cipher_name(cipher_type));
1213 /* Get the encrypted integer. */
1214 session_key_int = BN_new();
1215 packet_get_bignum(session_key_int, &slen);
1217 protocol_flags = packet_get_int();
1218 packet_set_protocol_flags(protocol_flags);
1220 packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1223 * Decrypt it using our private server key and private host key (key
1224 * with larger modulus first).
1226 if (BN_cmp(sensitive_data.private_key->n, sensitive_data.host_key->n) > 0) {
1227 /* Private key has bigger modulus. */
1228 if (BN_num_bits(sensitive_data.private_key->n) <
1229 BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) {
1230 fatal("do_connection: %s: private_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1231 get_remote_ipaddr(),
1232 BN_num_bits(sensitive_data.private_key->n),
1233 BN_num_bits(sensitive_data.host_key->n),
1234 SSH_KEY_BITS_RESERVED);
1236 rsa_private_decrypt(session_key_int, session_key_int,
1237 sensitive_data.private_key);
1238 rsa_private_decrypt(session_key_int, session_key_int,
1239 sensitive_data.host_key);
1241 /* Host key has bigger modulus (or they are equal). */
1242 if (BN_num_bits(sensitive_data.host_key->n) <
1243 BN_num_bits(sensitive_data.private_key->n) + SSH_KEY_BITS_RESERVED) {
1244 fatal("do_connection: %s: host_key %d < private_key %d + SSH_KEY_BITS_RESERVED %d",
1245 get_remote_ipaddr(),
1246 BN_num_bits(sensitive_data.host_key->n),
1247 BN_num_bits(sensitive_data.private_key->n),
1248 SSH_KEY_BITS_RESERVED);
1250 rsa_private_decrypt(session_key_int, session_key_int,
1251 sensitive_data.host_key);
1252 rsa_private_decrypt(session_key_int, session_key_int,
1253 sensitive_data.private_key);
1256 compute_session_id(session_id, cookie,
1257 sensitive_data.host_key->n,
1258 sensitive_data.private_key->n);
1260 /* Destroy the private and public keys. They will no longer be needed. */
1261 destroy_sensitive_data();
1264 * Extract session key from the decrypted integer. The key is in the
1265 * least significant 256 bits of the integer; the first byte of the
1266 * key is in the highest bits.
1268 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1269 len = BN_num_bytes(session_key_int);
1270 if (len < 0 || len > sizeof(session_key))
1271 fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d",
1272 get_remote_ipaddr(),
1273 len, (int) sizeof(session_key));
1274 memset(session_key, 0, sizeof(session_key));
1275 BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len);
1277 /* Destroy the decrypted integer. It is no longer needed. */
1278 BN_clear_free(session_key_int);
1280 /* Xor the first 16 bytes of the session key with the session id. */
1281 for (i = 0; i < 16; i++)
1282 session_key[i] ^= session_id[i];
1284 /* Set the session key. From this on all communications will be encrypted. */
1285 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1287 /* Destroy our copy of the session key. It is no longer needed. */
1288 memset(session_key, 0, sizeof(session_key));
1290 debug("Received session key; encryption turned on.");
1292 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1293 packet_start(SSH_SMSG_SUCCESS);
1295 packet_write_wait();
1299 * SSH2 key exchange: diffie-hellman-group1-sha1
1304 Buffer *server_kexinit;
1305 Buffer *client_kexinit;
1309 char *cprop[PROPOSAL_MAX];
1313 if (options.ciphers != NULL) {
1314 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1315 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1317 server_kexinit = kex_init(myproposal);
1318 client_kexinit = xmalloc(sizeof(*client_kexinit));
1319 buffer_init(client_kexinit);
1321 /* algorithm negotiation */
1322 kex_exchange_kexinit(server_kexinit, client_kexinit, cprop);
1323 kex = kex_choose_conf(cprop, myproposal, 1);
1324 for (i = 0; i < PROPOSAL_MAX; i++)
1327 switch (kex->kex_type) {
1329 ssh_dh1_server(kex, client_kexinit, server_kexinit);
1332 ssh_dhgex_server(kex, client_kexinit, server_kexinit);
1335 fatal("Unsupported key exchange %d", kex->kex_type);
1338 debug("send SSH2_MSG_NEWKEYS.");
1339 packet_start(SSH2_MSG_NEWKEYS);
1341 packet_write_wait();
1342 debug("done: send SSH2_MSG_NEWKEYS.");
1344 debug("Wait SSH2_MSG_NEWKEYS.");
1345 packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS);
1346 debug("GOT SSH2_MSG_NEWKEYS.");
1349 /* send 1st encrypted/maced/compressed message */
1350 packet_start(SSH2_MSG_IGNORE);
1351 packet_put_cstring("markus");
1353 packet_write_wait();
1356 debug("done: KEX2.");
1363 /* diffie-hellman-group1-sha1 */
1366 ssh_dh1_server(Kex *kex, Buffer *client_kexinit, Buffer *server_kexinit)
1371 int payload_len, dlen;
1373 unsigned char *signature = NULL;
1374 unsigned char *server_host_key_blob = NULL;
1375 unsigned int sbloblen;
1376 unsigned int klen, kout;
1377 unsigned char *kbuf;
1378 unsigned char *hash;
1379 BIGNUM *shared_secret = 0;
1381 BIGNUM *dh_client_pub = 0;
1384 debug("Wait SSH2_MSG_KEXDH_INIT.");
1385 packet_read_expect(&payload_len, SSH2_MSG_KEXDH_INIT);
1388 dh_client_pub = BN_new();
1389 if (dh_client_pub == NULL)
1390 fatal("dh_client_pub == NULL");
1391 packet_get_bignum2(dh_client_pub, &dlen);
1394 fprintf(stderr, "\ndh_client_pub= ");
1395 BN_print_fp(stderr, dh_client_pub);
1396 fprintf(stderr, "\n");
1397 debug("bits %d", BN_num_bits(dh_client_pub));
1400 /* generate DH key */
1401 dh = dh_new_group1(); /* XXX depends on 'kex' */
1404 fprintf(stderr, "\np= ");
1405 BN_print_fp(stderr, dh->p);
1406 fprintf(stderr, "\ng= ");
1408 fprintf(stderr, "\npub= ");
1409 BN_print_fp(stderr, dh->pub_key);
1410 fprintf(stderr, "\n");
1411 DHparams_print_fp(stderr, dh);
1413 if (!dh_pub_is_valid(dh, dh_client_pub))
1414 packet_disconnect("bad client public DH value");
1417 kbuf = xmalloc(klen);
1418 kout = DH_compute_key(kbuf, dh_client_pub, dh);
1421 debug("shared secret: len %d/%d", klen, kout);
1422 fprintf(stderr, "shared secret == ");
1423 for (i = 0; i< kout; i++)
1424 fprintf(stderr, "%02x", (kbuf[i])&0xff);
1425 fprintf(stderr, "\n");
1427 shared_secret = BN_new();
1429 BN_bin2bn(kbuf, kout, shared_secret);
1430 memset(kbuf, 0, klen);
1433 /* XXX precompute? */
1434 dsa_make_key_blob(sensitive_data.dsa_host_key,
1435 &server_host_key_blob, &sbloblen);
1437 /* calc H */ /* XXX depends on 'kex' */
1439 client_version_string,
1440 server_version_string,
1441 buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1442 buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1443 (char *)server_host_key_blob, sbloblen,
1448 buffer_free(client_kexinit);
1449 buffer_free(server_kexinit);
1450 xfree(client_kexinit);
1451 xfree(server_kexinit);
1453 fprintf(stderr, "hash == ");
1454 for (i = 0; i< 20; i++)
1455 fprintf(stderr, "%02x", (hash[i])&0xff);
1456 fprintf(stderr, "\n");
1458 /* save session id := H */
1459 /* XXX hashlen depends on KEX */
1460 session_id2_len = 20;
1461 session_id2 = xmalloc(session_id2_len);
1462 memcpy(session_id2, hash, session_id2_len);
1465 /* XXX hashlen depends on KEX */
1466 dsa_sign(sensitive_data.dsa_host_key, &signature, &slen, hash, 20);
1468 destroy_sensitive_data();
1470 /* send server hostkey, DH pubkey 'f' and singed H */
1471 packet_start(SSH2_MSG_KEXDH_REPLY);
1472 packet_put_string((char *)server_host_key_blob, sbloblen);
1473 packet_put_bignum2(dh->pub_key); /* f */
1474 packet_put_string((char *)signature, slen);
1477 xfree(server_host_key_blob);
1478 packet_write_wait();
1480 kex_derive_keys(kex, hash, shared_secret);
1481 packet_set_kex(kex);
1483 /* have keys, free DH */
1487 /* diffie-hellman-group-exchange-sha1 */
1490 ssh_dhgex_server(Kex *kex, Buffer *client_kexinit, Buffer *server_kexinit)
1495 int payload_len, dlen;
1497 unsigned char *signature = NULL;
1498 unsigned char *server_host_key_blob = NULL;
1499 unsigned int sbloblen;
1500 unsigned int klen, kout;
1501 unsigned char *kbuf;
1502 unsigned char *hash;
1503 BIGNUM *shared_secret = 0;
1505 BIGNUM *dh_client_pub = 0;
1508 debug("Wait SSH2_MSG_KEX_DH_GEX_REQUEST.");
1509 packet_read_expect(&payload_len, SSH2_MSG_KEX_DH_GEX_REQUEST);
1510 nbits = packet_get_int();
1511 dh = choose_dh(nbits);
1513 debug("Sending SSH2_MSG_KEX_DH_GEX_GROUP.");
1514 packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
1515 packet_put_bignum2(dh->p);
1516 packet_put_bignum2(dh->g);
1518 packet_write_wait();
1520 debug("Wait SSH2_MSG_KEX_DH_GEX_INIT.");
1521 packet_read_expect(&payload_len, SSH2_MSG_KEX_DH_GEX_INIT);
1524 dh_client_pub = BN_new();
1525 if (dh_client_pub == NULL)
1526 fatal("dh_client_pub == NULL");
1527 packet_get_bignum2(dh_client_pub, &dlen);
1530 fprintf(stderr, "\ndh_client_pub= ");
1531 BN_print_fp(stderr, dh_client_pub);
1532 fprintf(stderr, "\n");
1533 debug("bits %d", BN_num_bits(dh_client_pub));
1537 fprintf(stderr, "\np= ");
1538 BN_print_fp(stderr, dh->p);
1539 fprintf(stderr, "\ng= ");
1541 fprintf(stderr, "\npub= ");
1542 BN_print_fp(stderr, dh->pub_key);
1543 fprintf(stderr, "\n");
1544 DHparams_print_fp(stderr, dh);
1546 if (!dh_pub_is_valid(dh, dh_client_pub))
1547 packet_disconnect("bad client public DH value");
1550 kbuf = xmalloc(klen);
1551 kout = DH_compute_key(kbuf, dh_client_pub, dh);
1554 debug("shared secret: len %d/%d", klen, kout);
1555 fprintf(stderr, "shared secret == ");
1556 for (i = 0; i< kout; i++)
1557 fprintf(stderr, "%02x", (kbuf[i])&0xff);
1558 fprintf(stderr, "\n");
1560 shared_secret = BN_new();
1562 BN_bin2bn(kbuf, kout, shared_secret);
1563 memset(kbuf, 0, klen);
1566 /* XXX precompute? */
1567 dsa_make_key_blob(sensitive_data.dsa_host_key,
1568 &server_host_key_blob, &sbloblen);
1570 /* calc H */ /* XXX depends on 'kex' */
1571 hash = kex_hash_gex(
1572 client_version_string,
1573 server_version_string,
1574 buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1575 buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1576 (char *)server_host_key_blob, sbloblen,
1577 nbits, dh->p, dh->g,
1582 buffer_free(client_kexinit);
1583 buffer_free(server_kexinit);
1584 xfree(client_kexinit);
1585 xfree(server_kexinit);
1587 fprintf(stderr, "hash == ");
1588 for (i = 0; i< 20; i++)
1589 fprintf(stderr, "%02x", (hash[i])&0xff);
1590 fprintf(stderr, "\n");
1592 /* save session id := H */
1593 /* XXX hashlen depends on KEX */
1594 session_id2_len = 20;
1595 session_id2 = xmalloc(session_id2_len);
1596 memcpy(session_id2, hash, session_id2_len);
1599 /* XXX hashlen depends on KEX */
1600 dsa_sign(sensitive_data.dsa_host_key, &signature, &slen, hash, 20);
1602 destroy_sensitive_data();
1604 /* send server hostkey, DH pubkey 'f' and singed H */
1605 packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
1606 packet_put_string((char *)server_host_key_blob, sbloblen);
1607 packet_put_bignum2(dh->pub_key); /* f */
1608 packet_put_string((char *)signature, slen);
1611 xfree(server_host_key_blob);
1612 packet_write_wait();
1614 kex_derive_keys(kex, hash, shared_secret);
1615 packet_set_kex(kex);
1617 /* have keys, free DH */