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 1.146 2001/01/07 11:28:07 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 #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 u_char session_id[16];
168 u_char *session_id2 = NULL;
169 int session_id2_len = 0;
171 /* record remote hostname or ip */
172 u_int utmp_len = MAXHOSTNAMELEN;
174 /* Prototypes for various functions defined later in this file. */
175 void do_ssh1_kex(void);
176 void do_ssh2_kex(void);
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, " -D Do not fork into daemon mode\n");
657 fprintf(stderr, " -q Quiet (no logging)\n");
658 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
659 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
660 fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n");
661 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
662 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
664 fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
665 fprintf(stderr, " -4 Use IPv4 only\n");
666 fprintf(stderr, " -6 Use IPv6 only\n");
672 * Force logging to stderr until we have loaded the private host
673 * key (unless started from inetd)
676 options.log_level == -1 ? SYSLOG_LEVEL_NOTICE : options.log_level,
677 options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
678 !silent && !inetd_flag);
680 /* Read server configuration options from the configuration file. */
681 read_server_config(&options, config_file_name);
683 /* Fill in default values for those options not explicitly set. */
684 fill_default_server_options(&options);
686 /* Check that there are no remaining arguments. */
688 fprintf(stderr, "Extra argument %s.\n", av[optind]);
692 debug("sshd version %.100s", SSH_VERSION);
694 /* load private host keys */
695 sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*));
696 for(i = 0; i < options.num_host_key_files; i++)
697 sensitive_data.host_keys[i] = NULL;
698 sensitive_data.server_key = NULL;
699 sensitive_data.ssh1_host_key = NULL;
700 sensitive_data.have_ssh1_key = 0;
701 sensitive_data.have_ssh2_key = 0;
703 for(i = 0; i < options.num_host_key_files; i++) {
704 Key *key = load_private_key_autodetect(options.host_key_files[i]);
706 error("Could not load host key: %.200s: %.100s",
707 options.host_key_files[i], strerror(errno));
712 sensitive_data.ssh1_host_key = key;
713 sensitive_data.have_ssh1_key = 1;
717 sensitive_data.have_ssh2_key = 1;
720 sensitive_data.host_keys[i] = key;
722 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
723 log("Disabling protocol version 1. Could not load host key");
724 options.protocol &= ~SSH_PROTO_1;
726 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
727 log("Disabling protocol version 2. Could not load host key");
728 options.protocol &= ~SSH_PROTO_2;
730 if (! options.protocol & (SSH_PROTO_1|SSH_PROTO_2)) {
732 fprintf(stderr, "sshd: no hostkeys available -- exiting.\n");
733 log("sshd: no hostkeys available -- exiting.\n");
737 /* Check certain values for sanity. */
738 if (options.protocol & SSH_PROTO_1) {
739 if (options.server_key_bits < 512 ||
740 options.server_key_bits > 32768) {
741 fprintf(stderr, "Bad server key size.\n");
745 * Check that server and host key lengths differ sufficiently. This
746 * is necessary to make double encryption work with rsaref. Oh, I
747 * hate software patents. I dont know if this can go? Niels
749 if (options.server_key_bits >
750 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - SSH_KEY_BITS_RESERVED &&
751 options.server_key_bits <
752 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
753 options.server_key_bits =
754 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED;
755 debug("Forcing server key to %d bits to make it differ from host key.",
756 options.server_key_bits);
760 #ifdef HAVE_SCO_PROTECTED_PW
761 (void) set_auth_parameters(ac, av);
764 /* Initialize the log (it is reinitialized below in case we forked). */
765 if (debug_flag && !inetd_flag)
767 log_init(__progname, options.log_level, options.log_facility, log_stderr);
770 * If not in debugging mode, and not started from inetd, disconnect
771 * from the controlling terminal, and fork. The original process
774 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
777 #endif /* TIOCNOTTY */
778 if (daemon(0, 0) < 0)
779 fatal("daemon() failed: %.200s", strerror(errno));
781 /* Disconnect from the controlling tty. */
783 fd = open("/dev/tty", O_RDWR | O_NOCTTY);
785 (void) ioctl(fd, TIOCNOTTY, NULL);
788 #endif /* TIOCNOTTY */
790 /* Reinitialize the log (because of the fork above). */
791 log_init(__progname, options.log_level, options.log_facility, log_stderr);
793 /* Initialize the random number generator. */
796 /* Chdir to the root directory so that the current disk can be
797 unmounted if desired. */
800 /* Start listening for a socket, unless started from inetd. */
803 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
809 * We intentionally do not close the descriptors 0, 1, and 2
810 * as our code for setting the descriptors won\'t work if
811 * ttyfd happens to be one of those.
813 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
814 if (options.protocol & SSH_PROTO_1)
815 generate_empheral_server_key();
817 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
818 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
820 if (num_listen_socks >= MAX_LISTEN_SOCKS)
821 fatal("Too many listen sockets. "
822 "Enlarge MAX_LISTEN_SOCKS");
823 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
824 ntop, sizeof(ntop), strport, sizeof(strport),
825 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
826 error("getnameinfo failed");
829 /* Create socket for listening. */
830 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
831 if (listen_sock < 0) {
832 /* kernel may not support ipv6 */
833 verbose("socket: %.100s", strerror(errno));
836 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
837 error("listen_sock O_NONBLOCK: %s", strerror(errno));
842 * Set socket options. We try to make the port
843 * reusable and have it close as fast as possible
844 * without waiting in unnecessary wait states on
847 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
848 (void *) &on, sizeof(on));
851 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
852 (void *) &linger, sizeof(linger));
854 debug("Bind to port %s on %s.", strport, ntop);
856 /* Bind the socket to the desired port. */
857 if ((bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) &&
859 error("Bind to port %s on %s failed: %.200s.",
860 strport, ntop, strerror(errno));
864 listen_socks[num_listen_socks] = listen_sock;
867 /* Start listening on the port. */
868 log("Server listening on %s port %s.", ntop, strport);
869 if (listen(listen_sock, 5) < 0)
870 fatal("listen: %.100s", strerror(errno));
873 freeaddrinfo(options.listen_addrs);
875 if (!num_listen_socks)
876 fatal("Cannot bind any address.");
880 * Record our pid in /var/run/sshd.pid to make it
881 * easier to kill the correct sshd. We don't want to
882 * do this before the bind above because the bind will
883 * fail if there already is a daemon, and this will
884 * overwrite any old pid in the file.
886 f = fopen(options.pid_file, "wb");
888 fprintf(f, "%u\n", (u_int) getpid());
892 if (options.protocol & SSH_PROTO_1) {
893 generate_empheral_server_key();
895 /* Schedule server key regeneration alarm. */
896 signal(SIGALRM, key_regeneration_alarm);
897 alarm(options.key_regeneration_time);
900 /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
901 signal(SIGHUP, sighup_handler);
903 signal(SIGTERM, sigterm_handler);
904 signal(SIGQUIT, sigterm_handler);
906 /* Arrange SIGCHLD to be caught. */
907 signal(SIGCHLD, main_sigchld_handler);
909 /* setup fd set for listen */
912 for (i = 0; i < num_listen_socks; i++)
913 if (listen_socks[i] > maxfd)
914 maxfd = listen_socks[i];
915 /* pipes connected to unauthenticated childs */
916 startup_pipes = xmalloc(options.max_startups * sizeof(int));
917 for (i = 0; i < options.max_startups; i++)
918 startup_pipes[i] = -1;
921 * Stay listening for connections until the system crashes or
922 * the daemon is killed with a signal.
929 fdsetsz = howmany(maxfd, NFDBITS) * sizeof(fd_mask);
930 fdset = (fd_set *)xmalloc(fdsetsz);
931 memset(fdset, 0, fdsetsz);
933 for (i = 0; i < num_listen_socks; i++)
934 FD_SET(listen_socks[i], fdset);
935 for (i = 0; i < options.max_startups; i++)
936 if (startup_pipes[i] != -1)
937 FD_SET(startup_pipes[i], fdset);
939 /* Wait in select until there is a connection. */
940 if (select(maxfd + 1, fdset, NULL, NULL, NULL) < 0) {
942 error("select: %.100s", strerror(errno));
945 for (i = 0; i < options.max_startups; i++)
946 if (startup_pipes[i] != -1 &&
947 FD_ISSET(startup_pipes[i], fdset)) {
949 * the read end of the pipe is ready
950 * if the child has closed the pipe
951 * after successful authentication
952 * or if the child has died
954 close(startup_pipes[i]);
955 startup_pipes[i] = -1;
958 for (i = 0; i < num_listen_socks; i++) {
959 if (!FD_ISSET(listen_socks[i], fdset))
961 fromlen = sizeof(from);
962 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
965 if (errno != EINTR && errno != EWOULDBLOCK)
966 error("accept: %.100s", strerror(errno));
969 if (fcntl(newsock, F_SETFL, 0) < 0) {
970 error("newsock del O_NONBLOCK: %s", strerror(errno));
973 if (drop_connection(startups) == 1) {
974 debug("drop connection #%d", startups);
978 if (pipe(startup_p) == -1) {
983 for (j = 0; j < options.max_startups; j++)
984 if (startup_pipes[j] == -1) {
985 startup_pipes[j] = startup_p[0];
986 if (maxfd < startup_p[0])
987 maxfd = startup_p[0];
993 * Got connection. Fork a child to handle it, unless
994 * we are in debugging mode.
998 * In debugging mode. Close the listening
999 * socket, and start processing the
1000 * connection without forking.
1002 debug("Server will not fork when running in debugging mode.");
1003 close_listen_socks();
1011 * Normal production daemon. Fork, and have
1012 * the child process the connection. The
1013 * parent continues listening.
1015 if ((pid = fork()) == 0) {
1017 * Child. Close the listening and max_startup
1018 * sockets. Start using the accepted socket.
1019 * Reinitialize logging (since our pid has
1020 * changed). We break out of the loop to handle
1023 startup_pipe = startup_p[1];
1024 for (j = 0; j < options.max_startups; j++)
1025 if (startup_pipes[j] != -1)
1026 close(startup_pipes[j]);
1027 close_listen_socks();
1030 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1035 /* Parent. Stay in the loop. */
1037 error("fork: %.100s", strerror(errno));
1039 debug("Forked child %d.", pid);
1041 close(startup_p[1]);
1043 /* Mark that the key has been used (it was "given" to the child). */
1048 /* Close the new socket (the child is now taking care of it). */
1051 /* child process check (or debug mode) */
1052 if (num_listen_socks < 0)
1057 /* This is the child processing a new connection. */
1060 * Disable the key regeneration alarm. We will not regenerate the
1061 * key since we are no longer in a position to give it to anyone. We
1062 * will not restart on SIGHUP since it no longer makes sense.
1065 signal(SIGALRM, SIG_DFL);
1066 signal(SIGHUP, SIG_DFL);
1067 signal(SIGTERM, SIG_DFL);
1068 signal(SIGQUIT, SIG_DFL);
1069 signal(SIGCHLD, SIG_DFL);
1070 signal(SIGINT, SIG_DFL);
1073 * Set socket options for the connection. We want the socket to
1074 * close as fast as possible without waiting for anything. If the
1075 * connection is not a socket, these will do nothing.
1077 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1079 linger.l_linger = 5;
1080 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
1083 * Register our connection. This turns encryption off because we do
1086 packet_set_connection(sock_in, sock_out);
1088 remote_port = get_remote_port();
1089 remote_ip = get_remote_ipaddr();
1091 /* Check whether logins are denied from this host. */
1093 /* XXX LIBWRAP noes not know about IPv6 */
1095 struct request_info req;
1097 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, NULL);
1100 if (!hosts_access(&req)) {
1105 /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
1107 #endif /* LIBWRAP */
1108 /* Log the connection. */
1109 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1112 * We don\'t want to listen forever unless the other side
1113 * successfully authenticates itself. So we set up an alarm which is
1114 * cleared after successful authentication. A limit of zero
1115 * indicates no limit. Note that we don\'t set the alarm in debugging
1116 * mode; it is just annoying to have the server exit just when you
1117 * are about to discover the bug.
1119 signal(SIGALRM, grace_alarm_handler);
1121 alarm(options.login_grace_time);
1123 sshd_exchange_identification(sock_in, sock_out);
1125 * Check that the connection comes from a privileged port.
1126 * Rhosts-Authentication only makes sense from priviledged
1127 * programs. Of course, if the intruder has root access on his local
1128 * machine, he can connect from any port. So do not use these
1129 * authentication methods from machines that you do not trust.
1131 if (remote_port >= IPPORT_RESERVED ||
1132 remote_port < IPPORT_RESERVED / 2) {
1133 debug("Rhosts Authentication disabled, "
1134 "originating port not trusted.");
1135 options.rhosts_authentication = 0;
1138 if (!packet_connection_is_ipv4() &&
1139 options.kerberos_authentication) {
1140 debug("Kerberos Authentication disabled, only available for IPv4.");
1141 options.kerberos_authentication = 0;
1145 packet_set_nonblocking();
1147 /* perform the key exchange */
1148 /* authenticate user and start session */
1151 do_authentication2();
1154 do_authentication();
1158 /* Cleanup user's ticket cache file. */
1159 if (options.kerberos_ticket_cleanup)
1163 /* The connection has been terminated. */
1164 verbose("Closing connection to %.100s", remote_ip);
1168 #endif /* USE_PAM */
1182 BIGNUM *session_key_int;
1183 u_char session_key[SSH_SESSION_KEY_LENGTH];
1185 u_int cipher_type, auth_mask, protocol_flags;
1189 * Generate check bytes that the client must send back in the user
1190 * packet in order for it to be accepted; this is used to defy ip
1191 * spoofing attacks. Note that this only works against somebody
1192 * doing IP spoofing from a remote machine; any machine on the local
1193 * network can still see outgoing packets and catch the random
1194 * cookie. This only affects rhosts authentication, and this is one
1195 * of the reasons why it is inherently insecure.
1197 for (i = 0; i < 8; i++) {
1199 rand = arc4random();
1200 cookie[i] = rand & 0xff;
1205 * Send our public key. We include in the packet 64 bits of random
1206 * data that must be matched in the reply in order to prevent IP
1209 packet_start(SSH_SMSG_PUBLIC_KEY);
1210 for (i = 0; i < 8; i++)
1211 packet_put_char(cookie[i]);
1213 /* Store our public server RSA key. */
1214 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1215 packet_put_bignum(sensitive_data.server_key->rsa->e);
1216 packet_put_bignum(sensitive_data.server_key->rsa->n);
1218 /* Store our public host RSA key. */
1219 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1220 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1221 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1223 /* Put protocol flags. */
1224 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1226 /* Declare which ciphers we support. */
1227 packet_put_int(cipher_mask_ssh1(0));
1229 /* Declare supported authentication types. */
1231 if (options.rhosts_authentication)
1232 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1233 if (options.rhosts_rsa_authentication)
1234 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1235 if (options.rsa_authentication)
1236 auth_mask |= 1 << SSH_AUTH_RSA;
1238 if (options.kerberos_authentication)
1239 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1242 if (options.kerberos_tgt_passing)
1243 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1244 if (options.afs_token_passing)
1245 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1248 if (options.skey_authentication == 1)
1249 auth_mask |= 1 << SSH_AUTH_TIS;
1251 if (options.password_authentication)
1252 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1253 packet_put_int(auth_mask);
1255 /* Send the packet and wait for it to be sent. */
1257 packet_write_wait();
1259 debug("Sent %d bit server key and %d bit host key.",
1260 BN_num_bits(sensitive_data.server_key->rsa->n),
1261 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1263 /* Read clients reply (cipher type and session key). */
1264 packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1266 /* Get cipher type and check whether we accept this. */
1267 cipher_type = packet_get_char();
1269 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1270 packet_disconnect("Warning: client selects unsupported cipher.");
1272 /* Get check bytes from the packet. These must match those we
1273 sent earlier with the public key packet. */
1274 for (i = 0; i < 8; i++)
1275 if (cookie[i] != packet_get_char())
1276 packet_disconnect("IP Spoofing check bytes do not match.");
1278 debug("Encryption type: %.200s", cipher_name(cipher_type));
1280 /* Get the encrypted integer. */
1281 session_key_int = BN_new();
1282 packet_get_bignum(session_key_int, &slen);
1284 protocol_flags = packet_get_int();
1285 packet_set_protocol_flags(protocol_flags);
1287 packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1290 * Decrypt it using our private server key and private host key (key
1291 * with larger modulus first).
1293 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1294 /* Private key has bigger modulus. */
1295 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1296 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1297 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1298 get_remote_ipaddr(),
1299 BN_num_bits(sensitive_data.server_key->rsa->n),
1300 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1301 SSH_KEY_BITS_RESERVED);
1303 rsa_private_decrypt(session_key_int, session_key_int,
1304 sensitive_data.server_key->rsa);
1305 rsa_private_decrypt(session_key_int, session_key_int,
1306 sensitive_data.ssh1_host_key->rsa);
1308 /* Host key has bigger modulus (or they are equal). */
1309 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1310 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1311 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1312 get_remote_ipaddr(),
1313 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1314 BN_num_bits(sensitive_data.server_key->rsa->n),
1315 SSH_KEY_BITS_RESERVED);
1317 rsa_private_decrypt(session_key_int, session_key_int,
1318 sensitive_data.ssh1_host_key->rsa);
1319 rsa_private_decrypt(session_key_int, session_key_int,
1320 sensitive_data.server_key->rsa);
1323 compute_session_id(session_id, cookie,
1324 sensitive_data.ssh1_host_key->rsa->n,
1325 sensitive_data.server_key->rsa->n);
1327 /* Destroy the private and public keys. They will no longer be needed. */
1328 destroy_sensitive_data();
1331 * Extract session key from the decrypted integer. The key is in the
1332 * least significant 256 bits of the integer; the first byte of the
1333 * key is in the highest bits.
1335 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1336 len = BN_num_bytes(session_key_int);
1337 if (len < 0 || len > sizeof(session_key))
1338 fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d",
1339 get_remote_ipaddr(),
1340 len, sizeof(session_key));
1341 memset(session_key, 0, sizeof(session_key));
1342 BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len);
1344 /* Destroy the decrypted integer. It is no longer needed. */
1345 BN_clear_free(session_key_int);
1347 /* Xor the first 16 bytes of the session key with the session id. */
1348 for (i = 0; i < 16; i++)
1349 session_key[i] ^= session_id[i];
1351 /* Set the session key. From this on all communications will be encrypted. */
1352 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1354 /* Destroy our copy of the session key. It is no longer needed. */
1355 memset(session_key, 0, sizeof(session_key));
1357 debug("Received session key; encryption turned on.");
1359 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1360 packet_start(SSH_SMSG_SUCCESS);
1362 packet_write_wait();
1366 * SSH2 key exchange: diffie-hellman-group1-sha1
1371 Buffer *server_kexinit;
1372 Buffer *client_kexinit;
1376 char *cprop[PROPOSAL_MAX];
1380 if (options.ciphers != NULL) {
1381 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1382 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1384 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
1386 server_kexinit = kex_init(myproposal);
1387 client_kexinit = xmalloc(sizeof(*client_kexinit));
1388 buffer_init(client_kexinit);
1390 /* algorithm negotiation */
1391 kex_exchange_kexinit(server_kexinit, client_kexinit, cprop);
1392 kex = kex_choose_conf(cprop, myproposal, 1);
1393 for (i = 0; i < PROPOSAL_MAX; i++)
1396 switch (kex->kex_type) {
1398 ssh_dh1_server(kex, client_kexinit, server_kexinit);
1401 ssh_dhgex_server(kex, client_kexinit, server_kexinit);
1404 fatal("Unsupported key exchange %d", kex->kex_type);
1407 debug("send SSH2_MSG_NEWKEYS.");
1408 packet_start(SSH2_MSG_NEWKEYS);
1410 packet_write_wait();
1411 debug("done: send SSH2_MSG_NEWKEYS.");
1413 debug("Wait SSH2_MSG_NEWKEYS.");
1414 packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS);
1415 debug("GOT SSH2_MSG_NEWKEYS.");
1418 /* send 1st encrypted/maced/compressed message */
1419 packet_start(SSH2_MSG_IGNORE);
1420 packet_put_cstring("markus");
1422 packet_write_wait();
1425 debug("done: KEX2.");
1432 /* diffie-hellman-group1-sha1 */
1435 ssh_dh1_server(Kex *kex, Buffer *client_kexinit, Buffer *server_kexinit)
1440 int payload_len, dlen;
1442 u_char *signature = NULL;
1443 u_char *server_host_key_blob = NULL;
1448 BIGNUM *shared_secret = 0;
1450 BIGNUM *dh_client_pub = 0;
1453 hostkey = get_hostkey_by_type(kex->hostkey_type);
1454 if (hostkey == NULL)
1455 fatal("Unsupported hostkey type %d", kex->hostkey_type);
1458 /* generate DH key */
1459 dh = dh_new_group1(); /* XXX depends on 'kex' */
1462 debug("Wait SSH2_MSG_KEXDH_INIT.");
1463 packet_read_expect(&payload_len, SSH2_MSG_KEXDH_INIT);
1466 dh_client_pub = BN_new();
1467 if (dh_client_pub == NULL)
1468 fatal("dh_client_pub == NULL");
1469 packet_get_bignum2(dh_client_pub, &dlen);
1472 fprintf(stderr, "\ndh_client_pub= ");
1473 BN_print_fp(stderr, dh_client_pub);
1474 fprintf(stderr, "\n");
1475 debug("bits %d", BN_num_bits(dh_client_pub));
1479 fprintf(stderr, "\np= ");
1480 BN_print_fp(stderr, dh->p);
1481 fprintf(stderr, "\ng= ");
1483 fprintf(stderr, "\npub= ");
1484 BN_print_fp(stderr, dh->pub_key);
1485 fprintf(stderr, "\n");
1486 DHparams_print_fp(stderr, dh);
1488 if (!dh_pub_is_valid(dh, dh_client_pub))
1489 packet_disconnect("bad client public DH value");
1492 kbuf = xmalloc(klen);
1493 kout = DH_compute_key(kbuf, dh_client_pub, dh);
1496 debug("shared secret: len %d/%d", klen, kout);
1497 fprintf(stderr, "shared secret == ");
1498 for (i = 0; i< kout; i++)
1499 fprintf(stderr, "%02x", (kbuf[i])&0xff);
1500 fprintf(stderr, "\n");
1502 shared_secret = BN_new();
1504 BN_bin2bn(kbuf, kout, shared_secret);
1505 memset(kbuf, 0, klen);
1508 /* XXX precompute? */
1509 key_to_blob(hostkey, &server_host_key_blob, &sbloblen);
1511 /* calc H */ /* XXX depends on 'kex' */
1513 client_version_string,
1514 server_version_string,
1515 buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1516 buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1517 (char *)server_host_key_blob, sbloblen,
1522 buffer_free(client_kexinit);
1523 buffer_free(server_kexinit);
1524 xfree(client_kexinit);
1525 xfree(server_kexinit);
1527 fprintf(stderr, "hash == ");
1528 for (i = 0; i< 20; i++)
1529 fprintf(stderr, "%02x", (hash[i])&0xff);
1530 fprintf(stderr, "\n");
1532 /* save session id := H */
1533 /* XXX hashlen depends on KEX */
1534 session_id2_len = 20;
1535 session_id2 = xmalloc(session_id2_len);
1536 memcpy(session_id2, hash, session_id2_len);
1539 /* XXX hashlen depends on KEX */
1540 key_sign(hostkey, &signature, &slen, hash, 20);
1542 destroy_sensitive_data();
1544 /* send server hostkey, DH pubkey 'f' and singed H */
1545 packet_start(SSH2_MSG_KEXDH_REPLY);
1546 packet_put_string((char *)server_host_key_blob, sbloblen);
1547 packet_put_bignum2(dh->pub_key); /* f */
1548 packet_put_string((char *)signature, slen);
1551 xfree(server_host_key_blob);
1552 packet_write_wait();
1554 kex_derive_keys(kex, hash, shared_secret);
1555 packet_set_kex(kex);
1557 /* have keys, free DH */
1561 /* diffie-hellman-group-exchange-sha1 */
1564 ssh_dhgex_server(Kex *kex, Buffer *client_kexinit, Buffer *server_kexinit)
1569 int payload_len, dlen;
1571 u_char *signature = NULL;
1572 u_char *server_host_key_blob = NULL;
1577 BIGNUM *shared_secret = 0;
1579 BIGNUM *dh_client_pub = 0;
1582 hostkey = get_hostkey_by_type(kex->hostkey_type);
1583 if (hostkey == NULL)
1584 fatal("Unsupported hostkey type %d", kex->hostkey_type);
1587 debug("Wait SSH2_MSG_KEX_DH_GEX_REQUEST.");
1588 packet_read_expect(&payload_len, SSH2_MSG_KEX_DH_GEX_REQUEST);
1589 nbits = packet_get_int();
1590 dh = choose_dh(nbits);
1592 debug("Sending SSH2_MSG_KEX_DH_GEX_GROUP.");
1593 packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
1594 packet_put_bignum2(dh->p);
1595 packet_put_bignum2(dh->g);
1597 packet_write_wait();
1599 /* Compute our exchange value in parallel with the client */
1603 debug("Wait SSH2_MSG_KEX_DH_GEX_INIT.");
1604 packet_read_expect(&payload_len, SSH2_MSG_KEX_DH_GEX_INIT);
1607 dh_client_pub = BN_new();
1608 if (dh_client_pub == NULL)
1609 fatal("dh_client_pub == NULL");
1610 packet_get_bignum2(dh_client_pub, &dlen);
1613 fprintf(stderr, "\ndh_client_pub= ");
1614 BN_print_fp(stderr, dh_client_pub);
1615 fprintf(stderr, "\n");
1616 debug("bits %d", BN_num_bits(dh_client_pub));
1620 fprintf(stderr, "\np= ");
1621 BN_print_fp(stderr, dh->p);
1622 fprintf(stderr, "\ng= ");
1624 fprintf(stderr, "\npub= ");
1625 BN_print_fp(stderr, dh->pub_key);
1626 fprintf(stderr, "\n");
1627 DHparams_print_fp(stderr, dh);
1629 if (!dh_pub_is_valid(dh, dh_client_pub))
1630 packet_disconnect("bad client public DH value");
1633 kbuf = xmalloc(klen);
1634 kout = DH_compute_key(kbuf, dh_client_pub, dh);
1637 debug("shared secret: len %d/%d", klen, kout);
1638 fprintf(stderr, "shared secret == ");
1639 for (i = 0; i< kout; i++)
1640 fprintf(stderr, "%02x", (kbuf[i])&0xff);
1641 fprintf(stderr, "\n");
1643 shared_secret = BN_new();
1645 BN_bin2bn(kbuf, kout, shared_secret);
1646 memset(kbuf, 0, klen);
1649 /* XXX precompute? */
1650 key_to_blob(hostkey, &server_host_key_blob, &sbloblen);
1652 /* calc H */ /* XXX depends on 'kex' */
1653 hash = kex_hash_gex(
1654 client_version_string,
1655 server_version_string,
1656 buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1657 buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1658 (char *)server_host_key_blob, sbloblen,
1659 nbits, dh->p, dh->g,
1664 buffer_free(client_kexinit);
1665 buffer_free(server_kexinit);
1666 xfree(client_kexinit);
1667 xfree(server_kexinit);
1669 fprintf(stderr, "hash == ");
1670 for (i = 0; i< 20; i++)
1671 fprintf(stderr, "%02x", (hash[i])&0xff);
1672 fprintf(stderr, "\n");
1674 /* save session id := H */
1675 /* XXX hashlen depends on KEX */
1676 session_id2_len = 20;
1677 session_id2 = xmalloc(session_id2_len);
1678 memcpy(session_id2, hash, session_id2_len);
1681 /* XXX hashlen depends on KEX */
1682 key_sign(hostkey, &signature, &slen, hash, 20);
1684 destroy_sensitive_data();
1686 /* send server hostkey, DH pubkey 'f' and singed H */
1687 packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
1688 packet_put_string((char *)server_host_key_blob, sbloblen);
1689 packet_put_bignum2(dh->pub_key); /* f */
1690 packet_put_string((char *)signature, slen);
1693 xfree(server_host_key_blob);
1694 packet_write_wait();
1696 kex_derive_keys(kex, hash, shared_secret);
1697 packet_set_kex(kex);
1699 /* have keys, free DH */