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 1.142 2000/12/20 19:37:22 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, " -q Quiet (no logging)\n");
657 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
658 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
659 fprintf(stderr, " -g seconds Grace period for authentication (default: 300)\n");
660 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
661 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
663 fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
664 fprintf(stderr, " -4 Use IPv4 only\n");
665 fprintf(stderr, " -6 Use IPv6 only\n");
671 * Force logging to stderr until we have loaded the private host
672 * key (unless started from inetd)
675 options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
676 options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
677 !silent && !inetd_flag);
679 /* Read server configuration options from the configuration file. */
680 read_server_config(&options, config_file_name);
682 /* Fill in default values for those options not explicitly set. */
683 fill_default_server_options(&options);
685 /* Check that there are no remaining arguments. */
687 fprintf(stderr, "Extra argument %s.\n", av[optind]);
691 debug("sshd version %.100s", SSH_VERSION);
693 /* load private host keys */
694 sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*));
695 for(i = 0; i < options.num_host_key_files; i++)
696 sensitive_data.host_keys[i] = NULL;
697 sensitive_data.server_key = NULL;
698 sensitive_data.ssh1_host_key = NULL;
699 sensitive_data.have_ssh1_key = 0;
700 sensitive_data.have_ssh2_key = 0;
702 for(i = 0; i < options.num_host_key_files; i++) {
703 Key *key = load_private_key_autodetect(options.host_key_files[i]);
705 error("Could not load host key: %.200s: %.100s",
706 options.host_key_files[i], strerror(errno));
711 sensitive_data.ssh1_host_key = key;
712 sensitive_data.have_ssh1_key = 1;
716 sensitive_data.have_ssh2_key = 1;
719 sensitive_data.host_keys[i] = key;
721 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
722 log("Disabling protocol version 1. Could not load host key");
723 options.protocol &= ~SSH_PROTO_1;
725 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
726 log("Disabling protocol version 2. Could not load host key");
727 options.protocol &= ~SSH_PROTO_2;
729 if (! options.protocol & (SSH_PROTO_1|SSH_PROTO_2)) {
731 fprintf(stderr, "sshd: no hostkeys available -- exiting.\n");
732 log("sshd: no hostkeys available -- exiting.\n");
736 /* Check certain values for sanity. */
737 if (options.protocol & SSH_PROTO_1) {
738 if (options.server_key_bits < 512 ||
739 options.server_key_bits > 32768) {
740 fprintf(stderr, "Bad server key size.\n");
744 * Check that server and host key lengths differ sufficiently. This
745 * is necessary to make double encryption work with rsaref. Oh, I
746 * hate software patents. I dont know if this can go? Niels
748 if (options.server_key_bits >
749 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - SSH_KEY_BITS_RESERVED &&
750 options.server_key_bits <
751 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
752 options.server_key_bits =
753 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED;
754 debug("Forcing server key to %d bits to make it differ from host key.",
755 options.server_key_bits);
759 #ifdef HAVE_SCO_PROTECTED_PW
760 (void) set_auth_parameters(ac, av);
763 /* Initialize the log (it is reinitialized below in case we forked). */
764 if (debug_flag && !inetd_flag)
766 log_init(__progname, options.log_level, options.log_facility, log_stderr);
769 * If not in debugging mode, and not started from inetd, disconnect
770 * from the controlling terminal, and fork. The original process
773 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
776 #endif /* TIOCNOTTY */
777 if (daemon(0, 0) < 0)
778 fatal("daemon() failed: %.200s", strerror(errno));
780 /* Disconnect from the controlling tty. */
782 fd = open("/dev/tty", O_RDWR | O_NOCTTY);
784 (void) ioctl(fd, TIOCNOTTY, NULL);
787 #endif /* TIOCNOTTY */
789 /* Reinitialize the log (because of the fork above). */
790 log_init(__progname, options.log_level, options.log_facility, log_stderr);
792 /* Initialize the random number generator. */
795 /* Chdir to the root directory so that the current disk can be
796 unmounted if desired. */
799 /* Start listening for a socket, unless started from inetd. */
802 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
808 * We intentionally do not close the descriptors 0, 1, and 2
809 * as our code for setting the descriptors won\'t work if
810 * ttyfd happens to be one of those.
812 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
813 if (options.protocol & SSH_PROTO_1)
814 generate_empheral_server_key();
816 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
817 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
819 if (num_listen_socks >= MAX_LISTEN_SOCKS)
820 fatal("Too many listen sockets. "
821 "Enlarge MAX_LISTEN_SOCKS");
822 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
823 ntop, sizeof(ntop), strport, sizeof(strport),
824 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
825 error("getnameinfo failed");
828 /* Create socket for listening. */
829 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
830 if (listen_sock < 0) {
831 /* kernel may not support ipv6 */
832 verbose("socket: %.100s", strerror(errno));
835 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
836 error("listen_sock O_NONBLOCK: %s", strerror(errno));
841 * Set socket options. We try to make the port
842 * reusable and have it close as fast as possible
843 * without waiting in unnecessary wait states on
846 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
847 (void *) &on, sizeof(on));
850 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
851 (void *) &linger, sizeof(linger));
853 debug("Bind to port %s on %s.", strport, ntop);
855 /* Bind the socket to the desired port. */
856 if ((bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) &&
858 error("Bind to port %s on %s failed: %.200s.",
859 strport, ntop, strerror(errno));
863 listen_socks[num_listen_socks] = listen_sock;
866 /* Start listening on the port. */
867 log("Server listening on %s port %s.", ntop, strport);
868 if (listen(listen_sock, 5) < 0)
869 fatal("listen: %.100s", strerror(errno));
872 freeaddrinfo(options.listen_addrs);
874 if (!num_listen_socks)
875 fatal("Cannot bind any address.");
879 * Record our pid in /var/run/sshd.pid to make it
880 * easier to kill the correct sshd. We don't want to
881 * do this before the bind above because the bind will
882 * fail if there already is a daemon, and this will
883 * overwrite any old pid in the file.
885 f = fopen(options.pid_file, "wb");
887 fprintf(f, "%u\n", (u_int) getpid());
891 if (options.protocol & SSH_PROTO_1) {
892 generate_empheral_server_key();
894 /* Schedule server key regeneration alarm. */
895 signal(SIGALRM, key_regeneration_alarm);
896 alarm(options.key_regeneration_time);
899 /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
900 signal(SIGHUP, sighup_handler);
902 signal(SIGTERM, sigterm_handler);
903 signal(SIGQUIT, sigterm_handler);
905 /* Arrange SIGCHLD to be caught. */
906 signal(SIGCHLD, main_sigchld_handler);
908 /* setup fd set for listen */
911 for (i = 0; i < num_listen_socks; i++)
912 if (listen_socks[i] > maxfd)
913 maxfd = listen_socks[i];
914 /* pipes connected to unauthenticated childs */
915 startup_pipes = xmalloc(options.max_startups * sizeof(int));
916 for (i = 0; i < options.max_startups; i++)
917 startup_pipes[i] = -1;
920 * Stay listening for connections until the system crashes or
921 * the daemon is killed with a signal.
928 fdsetsz = howmany(maxfd, NFDBITS) * sizeof(fd_mask);
929 fdset = (fd_set *)xmalloc(fdsetsz);
930 memset(fdset, 0, fdsetsz);
932 for (i = 0; i < num_listen_socks; i++)
933 FD_SET(listen_socks[i], fdset);
934 for (i = 0; i < options.max_startups; i++)
935 if (startup_pipes[i] != -1)
936 FD_SET(startup_pipes[i], fdset);
938 /* Wait in select until there is a connection. */
939 if (select(maxfd + 1, fdset, NULL, NULL, NULL) < 0) {
941 error("select: %.100s", strerror(errno));
944 for (i = 0; i < options.max_startups; i++)
945 if (startup_pipes[i] != -1 &&
946 FD_ISSET(startup_pipes[i], fdset)) {
948 * the read end of the pipe is ready
949 * if the child has closed the pipe
950 * after successfull authentication
951 * or if the child has died
953 close(startup_pipes[i]);
954 startup_pipes[i] = -1;
957 for (i = 0; i < num_listen_socks; i++) {
958 if (!FD_ISSET(listen_socks[i], fdset))
960 fromlen = sizeof(from);
961 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
964 if (errno != EINTR && errno != EWOULDBLOCK)
965 error("accept: %.100s", strerror(errno));
968 if (fcntl(newsock, F_SETFL, 0) < 0) {
969 error("newsock del O_NONBLOCK: %s", strerror(errno));
972 if (drop_connection(startups) == 1) {
973 debug("drop connection #%d", startups);
977 if (pipe(startup_p) == -1) {
982 for (j = 0; j < options.max_startups; j++)
983 if (startup_pipes[j] == -1) {
984 startup_pipes[j] = startup_p[0];
985 if (maxfd < startup_p[0])
986 maxfd = startup_p[0];
992 * Got connection. Fork a child to handle it, unless
993 * we are in debugging mode.
997 * In debugging mode. Close the listening
998 * socket, and start processing the
999 * connection without forking.
1001 debug("Server will not fork when running in debugging mode.");
1002 close_listen_socks();
1010 * Normal production daemon. Fork, and have
1011 * the child process the connection. The
1012 * parent continues listening.
1014 if ((pid = fork()) == 0) {
1016 * Child. Close the listening and max_startup
1017 * sockets. Start using the accepted socket.
1018 * Reinitialize logging (since our pid has
1019 * changed). We break out of the loop to handle
1022 startup_pipe = startup_p[1];
1023 for (j = 0; j < options.max_startups; j++)
1024 if (startup_pipes[j] != -1)
1025 close(startup_pipes[j]);
1026 close_listen_socks();
1029 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1034 /* Parent. Stay in the loop. */
1036 error("fork: %.100s", strerror(errno));
1038 debug("Forked child %d.", pid);
1040 close(startup_p[1]);
1042 /* Mark that the key has been used (it was "given" to the child). */
1047 /* Close the new socket (the child is now taking care of it). */
1050 /* child process check (or debug mode) */
1051 if (num_listen_socks < 0)
1056 /* This is the child processing a new connection. */
1059 * Disable the key regeneration alarm. We will not regenerate the
1060 * key since we are no longer in a position to give it to anyone. We
1061 * will not restart on SIGHUP since it no longer makes sense.
1064 signal(SIGALRM, SIG_DFL);
1065 signal(SIGHUP, SIG_DFL);
1066 signal(SIGTERM, SIG_DFL);
1067 signal(SIGQUIT, SIG_DFL);
1068 signal(SIGCHLD, SIG_DFL);
1069 signal(SIGINT, SIG_DFL);
1072 * Set socket options for the connection. We want the socket to
1073 * close as fast as possible without waiting for anything. If the
1074 * connection is not a socket, these will do nothing.
1076 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1078 linger.l_linger = 5;
1079 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
1082 * Register our connection. This turns encryption off because we do
1085 packet_set_connection(sock_in, sock_out);
1087 remote_port = get_remote_port();
1088 remote_ip = get_remote_ipaddr();
1090 /* Check whether logins are denied from this host. */
1092 /* XXX LIBWRAP noes not know about IPv6 */
1094 struct request_info req;
1096 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, NULL);
1099 if (!hosts_access(&req)) {
1104 /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
1106 #endif /* LIBWRAP */
1107 /* Log the connection. */
1108 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1111 * We don\'t want to listen forever unless the other side
1112 * successfully authenticates itself. So we set up an alarm which is
1113 * cleared after successful authentication. A limit of zero
1114 * indicates no limit. Note that we don\'t set the alarm in debugging
1115 * mode; it is just annoying to have the server exit just when you
1116 * are about to discover the bug.
1118 signal(SIGALRM, grace_alarm_handler);
1120 alarm(options.login_grace_time);
1122 sshd_exchange_identification(sock_in, sock_out);
1124 * Check that the connection comes from a privileged port.
1125 * Rhosts-Authentication only makes sense from priviledged
1126 * programs. Of course, if the intruder has root access on his local
1127 * machine, he can connect from any port. So do not use these
1128 * authentication methods from machines that you do not trust.
1130 if (remote_port >= IPPORT_RESERVED ||
1131 remote_port < IPPORT_RESERVED / 2) {
1132 debug("Rhosts Authentication disabled, "
1133 "originating port not trusted.");
1134 options.rhosts_authentication = 0;
1137 if (!packet_connection_is_ipv4() &&
1138 options.kerberos_authentication) {
1139 debug("Kerberos Authentication disabled, only available for IPv4.");
1140 options.kerberos_authentication = 0;
1144 packet_set_nonblocking();
1146 /* perform the key exchange */
1147 /* authenticate user and start session */
1150 do_authentication2();
1153 do_authentication();
1157 /* Cleanup user's ticket cache file. */
1158 if (options.kerberos_ticket_cleanup)
1162 /* The connection has been terminated. */
1163 verbose("Closing connection to %.100s", remote_ip);
1167 #endif /* USE_PAM */
1181 BIGNUM *session_key_int;
1182 u_char session_key[SSH_SESSION_KEY_LENGTH];
1184 u_int cipher_type, auth_mask, protocol_flags;
1188 * Generate check bytes that the client must send back in the user
1189 * packet in order for it to be accepted; this is used to defy ip
1190 * spoofing attacks. Note that this only works against somebody
1191 * doing IP spoofing from a remote machine; any machine on the local
1192 * network can still see outgoing packets and catch the random
1193 * cookie. This only affects rhosts authentication, and this is one
1194 * of the reasons why it is inherently insecure.
1196 for (i = 0; i < 8; i++) {
1198 rand = arc4random();
1199 cookie[i] = rand & 0xff;
1204 * Send our public key. We include in the packet 64 bits of random
1205 * data that must be matched in the reply in order to prevent IP
1208 packet_start(SSH_SMSG_PUBLIC_KEY);
1209 for (i = 0; i < 8; i++)
1210 packet_put_char(cookie[i]);
1212 /* Store our public server RSA key. */
1213 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1214 packet_put_bignum(sensitive_data.server_key->rsa->e);
1215 packet_put_bignum(sensitive_data.server_key->rsa->n);
1217 /* Store our public host RSA key. */
1218 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1219 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1220 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1222 /* Put protocol flags. */
1223 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1225 /* Declare which ciphers we support. */
1226 packet_put_int(cipher_mask_ssh1(0));
1228 /* Declare supported authentication types. */
1230 if (options.rhosts_authentication)
1231 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1232 if (options.rhosts_rsa_authentication)
1233 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1234 if (options.rsa_authentication)
1235 auth_mask |= 1 << SSH_AUTH_RSA;
1237 if (options.kerberos_authentication)
1238 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1241 if (options.kerberos_tgt_passing)
1242 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1243 if (options.afs_token_passing)
1244 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1247 if (options.skey_authentication == 1)
1248 auth_mask |= 1 << SSH_AUTH_TIS;
1250 if (options.password_authentication)
1251 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1252 packet_put_int(auth_mask);
1254 /* Send the packet and wait for it to be sent. */
1256 packet_write_wait();
1258 debug("Sent %d bit server key and %d bit host key.",
1259 BN_num_bits(sensitive_data.server_key->rsa->n),
1260 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1262 /* Read clients reply (cipher type and session key). */
1263 packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1265 /* Get cipher type and check whether we accept this. */
1266 cipher_type = packet_get_char();
1268 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1269 packet_disconnect("Warning: client selects unsupported cipher.");
1271 /* Get check bytes from the packet. These must match those we
1272 sent earlier with the public key packet. */
1273 for (i = 0; i < 8; i++)
1274 if (cookie[i] != packet_get_char())
1275 packet_disconnect("IP Spoofing check bytes do not match.");
1277 debug("Encryption type: %.200s", cipher_name(cipher_type));
1279 /* Get the encrypted integer. */
1280 session_key_int = BN_new();
1281 packet_get_bignum(session_key_int, &slen);
1283 protocol_flags = packet_get_int();
1284 packet_set_protocol_flags(protocol_flags);
1286 packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1289 * Decrypt it using our private server key and private host key (key
1290 * with larger modulus first).
1292 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1293 /* Private key has bigger modulus. */
1294 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1295 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1296 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1297 get_remote_ipaddr(),
1298 BN_num_bits(sensitive_data.server_key->rsa->n),
1299 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1300 SSH_KEY_BITS_RESERVED);
1302 rsa_private_decrypt(session_key_int, session_key_int,
1303 sensitive_data.server_key->rsa);
1304 rsa_private_decrypt(session_key_int, session_key_int,
1305 sensitive_data.ssh1_host_key->rsa);
1307 /* Host key has bigger modulus (or they are equal). */
1308 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1309 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1310 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1311 get_remote_ipaddr(),
1312 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1313 BN_num_bits(sensitive_data.server_key->rsa->n),
1314 SSH_KEY_BITS_RESERVED);
1316 rsa_private_decrypt(session_key_int, session_key_int,
1317 sensitive_data.ssh1_host_key->rsa);
1318 rsa_private_decrypt(session_key_int, session_key_int,
1319 sensitive_data.server_key->rsa);
1322 compute_session_id(session_id, cookie,
1323 sensitive_data.ssh1_host_key->rsa->n,
1324 sensitive_data.server_key->rsa->n);
1326 /* Destroy the private and public keys. They will no longer be needed. */
1327 destroy_sensitive_data();
1330 * Extract session key from the decrypted integer. The key is in the
1331 * least significant 256 bits of the integer; the first byte of the
1332 * key is in the highest bits.
1334 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1335 len = BN_num_bytes(session_key_int);
1336 if (len < 0 || len > sizeof(session_key))
1337 fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d",
1338 get_remote_ipaddr(),
1339 len, sizeof(session_key));
1340 memset(session_key, 0, sizeof(session_key));
1341 BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len);
1343 /* Destroy the decrypted integer. It is no longer needed. */
1344 BN_clear_free(session_key_int);
1346 /* Xor the first 16 bytes of the session key with the session id. */
1347 for (i = 0; i < 16; i++)
1348 session_key[i] ^= session_id[i];
1350 /* Set the session key. From this on all communications will be encrypted. */
1351 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1353 /* Destroy our copy of the session key. It is no longer needed. */
1354 memset(session_key, 0, sizeof(session_key));
1356 debug("Received session key; encryption turned on.");
1358 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1359 packet_start(SSH_SMSG_SUCCESS);
1361 packet_write_wait();
1365 * SSH2 key exchange: diffie-hellman-group1-sha1
1370 Buffer *server_kexinit;
1371 Buffer *client_kexinit;
1375 char *cprop[PROPOSAL_MAX];
1379 if (options.ciphers != NULL) {
1380 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1381 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1383 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
1385 server_kexinit = kex_init(myproposal);
1386 client_kexinit = xmalloc(sizeof(*client_kexinit));
1387 buffer_init(client_kexinit);
1389 /* algorithm negotiation */
1390 kex_exchange_kexinit(server_kexinit, client_kexinit, cprop);
1391 kex = kex_choose_conf(cprop, myproposal, 1);
1392 for (i = 0; i < PROPOSAL_MAX; i++)
1395 switch (kex->kex_type) {
1397 ssh_dh1_server(kex, client_kexinit, server_kexinit);
1400 ssh_dhgex_server(kex, client_kexinit, server_kexinit);
1403 fatal("Unsupported key exchange %d", kex->kex_type);
1406 debug("send SSH2_MSG_NEWKEYS.");
1407 packet_start(SSH2_MSG_NEWKEYS);
1409 packet_write_wait();
1410 debug("done: send SSH2_MSG_NEWKEYS.");
1412 debug("Wait SSH2_MSG_NEWKEYS.");
1413 packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS);
1414 debug("GOT SSH2_MSG_NEWKEYS.");
1417 /* send 1st encrypted/maced/compressed message */
1418 packet_start(SSH2_MSG_IGNORE);
1419 packet_put_cstring("markus");
1421 packet_write_wait();
1424 debug("done: KEX2.");
1431 /* diffie-hellman-group1-sha1 */
1434 ssh_dh1_server(Kex *kex, Buffer *client_kexinit, Buffer *server_kexinit)
1439 int payload_len, dlen;
1441 u_char *signature = NULL;
1442 u_char *server_host_key_blob = NULL;
1447 BIGNUM *shared_secret = 0;
1449 BIGNUM *dh_client_pub = 0;
1452 hostkey = get_hostkey_by_type(kex->hostkey_type);
1453 if (hostkey == NULL)
1454 fatal("Unsupported hostkey type %d", kex->hostkey_type);
1457 /* generate DH key */
1458 dh = dh_new_group1(); /* XXX depends on 'kex' */
1461 debug("Wait SSH2_MSG_KEXDH_INIT.");
1462 packet_read_expect(&payload_len, SSH2_MSG_KEXDH_INIT);
1465 dh_client_pub = BN_new();
1466 if (dh_client_pub == NULL)
1467 fatal("dh_client_pub == NULL");
1468 packet_get_bignum2(dh_client_pub, &dlen);
1471 fprintf(stderr, "\ndh_client_pub= ");
1472 BN_print_fp(stderr, dh_client_pub);
1473 fprintf(stderr, "\n");
1474 debug("bits %d", BN_num_bits(dh_client_pub));
1478 fprintf(stderr, "\np= ");
1479 BN_print_fp(stderr, dh->p);
1480 fprintf(stderr, "\ng= ");
1482 fprintf(stderr, "\npub= ");
1483 BN_print_fp(stderr, dh->pub_key);
1484 fprintf(stderr, "\n");
1485 DHparams_print_fp(stderr, dh);
1487 if (!dh_pub_is_valid(dh, dh_client_pub))
1488 packet_disconnect("bad client public DH value");
1491 kbuf = xmalloc(klen);
1492 kout = DH_compute_key(kbuf, dh_client_pub, dh);
1495 debug("shared secret: len %d/%d", klen, kout);
1496 fprintf(stderr, "shared secret == ");
1497 for (i = 0; i< kout; i++)
1498 fprintf(stderr, "%02x", (kbuf[i])&0xff);
1499 fprintf(stderr, "\n");
1501 shared_secret = BN_new();
1503 BN_bin2bn(kbuf, kout, shared_secret);
1504 memset(kbuf, 0, klen);
1507 /* XXX precompute? */
1508 key_to_blob(hostkey, &server_host_key_blob, &sbloblen);
1510 /* calc H */ /* XXX depends on 'kex' */
1512 client_version_string,
1513 server_version_string,
1514 buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1515 buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1516 (char *)server_host_key_blob, sbloblen,
1521 buffer_free(client_kexinit);
1522 buffer_free(server_kexinit);
1523 xfree(client_kexinit);
1524 xfree(server_kexinit);
1526 fprintf(stderr, "hash == ");
1527 for (i = 0; i< 20; i++)
1528 fprintf(stderr, "%02x", (hash[i])&0xff);
1529 fprintf(stderr, "\n");
1531 /* save session id := H */
1532 /* XXX hashlen depends on KEX */
1533 session_id2_len = 20;
1534 session_id2 = xmalloc(session_id2_len);
1535 memcpy(session_id2, hash, session_id2_len);
1538 /* XXX hashlen depends on KEX */
1539 key_sign(hostkey, &signature, &slen, hash, 20);
1541 destroy_sensitive_data();
1543 /* send server hostkey, DH pubkey 'f' and singed H */
1544 packet_start(SSH2_MSG_KEXDH_REPLY);
1545 packet_put_string((char *)server_host_key_blob, sbloblen);
1546 packet_put_bignum2(dh->pub_key); /* f */
1547 packet_put_string((char *)signature, slen);
1550 xfree(server_host_key_blob);
1551 packet_write_wait();
1553 kex_derive_keys(kex, hash, shared_secret);
1554 packet_set_kex(kex);
1556 /* have keys, free DH */
1560 /* diffie-hellman-group-exchange-sha1 */
1563 ssh_dhgex_server(Kex *kex, Buffer *client_kexinit, Buffer *server_kexinit)
1568 int payload_len, dlen;
1570 u_char *signature = NULL;
1571 u_char *server_host_key_blob = NULL;
1576 BIGNUM *shared_secret = 0;
1578 BIGNUM *dh_client_pub = 0;
1581 hostkey = get_hostkey_by_type(kex->hostkey_type);
1582 if (hostkey == NULL)
1583 fatal("Unsupported hostkey type %d", kex->hostkey_type);
1586 debug("Wait SSH2_MSG_KEX_DH_GEX_REQUEST.");
1587 packet_read_expect(&payload_len, SSH2_MSG_KEX_DH_GEX_REQUEST);
1588 nbits = packet_get_int();
1589 dh = choose_dh(nbits);
1591 debug("Sending SSH2_MSG_KEX_DH_GEX_GROUP.");
1592 packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
1593 packet_put_bignum2(dh->p);
1594 packet_put_bignum2(dh->g);
1596 packet_write_wait();
1598 /* Compute our exchange value in parallel with the client */
1602 debug("Wait SSH2_MSG_KEX_DH_GEX_INIT.");
1603 packet_read_expect(&payload_len, SSH2_MSG_KEX_DH_GEX_INIT);
1606 dh_client_pub = BN_new();
1607 if (dh_client_pub == NULL)
1608 fatal("dh_client_pub == NULL");
1609 packet_get_bignum2(dh_client_pub, &dlen);
1612 fprintf(stderr, "\ndh_client_pub= ");
1613 BN_print_fp(stderr, dh_client_pub);
1614 fprintf(stderr, "\n");
1615 debug("bits %d", BN_num_bits(dh_client_pub));
1619 fprintf(stderr, "\np= ");
1620 BN_print_fp(stderr, dh->p);
1621 fprintf(stderr, "\ng= ");
1623 fprintf(stderr, "\npub= ");
1624 BN_print_fp(stderr, dh->pub_key);
1625 fprintf(stderr, "\n");
1626 DHparams_print_fp(stderr, dh);
1628 if (!dh_pub_is_valid(dh, dh_client_pub))
1629 packet_disconnect("bad client public DH value");
1632 kbuf = xmalloc(klen);
1633 kout = DH_compute_key(kbuf, dh_client_pub, dh);
1636 debug("shared secret: len %d/%d", klen, kout);
1637 fprintf(stderr, "shared secret == ");
1638 for (i = 0; i< kout; i++)
1639 fprintf(stderr, "%02x", (kbuf[i])&0xff);
1640 fprintf(stderr, "\n");
1642 shared_secret = BN_new();
1644 BN_bin2bn(kbuf, kout, shared_secret);
1645 memset(kbuf, 0, klen);
1648 /* XXX precompute? */
1649 key_to_blob(hostkey, &server_host_key_blob, &sbloblen);
1651 /* calc H */ /* XXX depends on 'kex' */
1652 hash = kex_hash_gex(
1653 client_version_string,
1654 server_version_string,
1655 buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1656 buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1657 (char *)server_host_key_blob, sbloblen,
1658 nbits, dh->p, dh->g,
1663 buffer_free(client_kexinit);
1664 buffer_free(server_kexinit);
1665 xfree(client_kexinit);
1666 xfree(server_kexinit);
1668 fprintf(stderr, "hash == ");
1669 for (i = 0; i< 20; i++)
1670 fprintf(stderr, "%02x", (hash[i])&0xff);
1671 fprintf(stderr, "\n");
1673 /* save session id := H */
1674 /* XXX hashlen depends on KEX */
1675 session_id2_len = 20;
1676 session_id2 = xmalloc(session_id2_len);
1677 memcpy(session_id2, hash, session_id2_len);
1680 /* XXX hashlen depends on KEX */
1681 key_sign(hostkey, &signature, &slen, hash, 20);
1683 destroy_sensitive_data();
1685 /* send server hostkey, DH pubkey 'f' and singed H */
1686 packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
1687 packet_put_string((char *)server_host_key_blob, sbloblen);
1688 packet_put_bignum2(dh->pub_key); /* f */
1689 packet_put_string((char *)signature, slen);
1692 xfree(server_host_key_blob);
1693 packet_write_wait();
1695 kex_derive_keys(kex, hash, shared_secret);
1696 packet_set_kex(kex);
1698 /* have keys, free DH */