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 1.199 2001/06/04 23:07:21 markus Exp $");
45 #include <openssl/dh.h>
46 #include <openssl/bn.h>
47 #include <openssl/hmac.h>
66 #include "myproposal.h"
68 #include "pathnames.h"
78 int allow_severity = LOG_INFO;
79 int deny_severity = LOG_WARNING;
86 #ifdef HAVE___PROGNAME
87 extern char *__progname;
92 /* Server configuration options. */
93 ServerOptions options;
95 /* Name of the server configuration file. */
96 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
99 * Flag indicating whether IPv4 or IPv6. This can be set on the command line.
100 * Default value is AF_UNSPEC means both IPv4 and IPv6.
103 int IPv4or6 = AF_INET;
105 int IPv4or6 = AF_UNSPEC;
109 * Debug mode flag. This can be set on the command line. If debug
110 * mode is enabled, extra debugging output will be sent to the system
111 * log, the daemon will not go to background, and will exit after processing
112 * the first connection.
116 /* Flag indicating that the daemon is being started from inetd. */
119 /* Flag indicating that sshd should not detach and become a daemon. */
120 int no_daemon_flag = 0;
122 /* debug goes to stderr unless inetd_flag is set */
125 /* Saved arguments to main(). */
130 * The sockets that the server is listening; this is used in the SIGHUP
133 #define MAX_LISTEN_SOCKS 16
134 int listen_socks[MAX_LISTEN_SOCKS];
135 int num_listen_socks = 0;
138 * the client's version string, passed by sshd2 in compat mode. if != NULL,
139 * sshd will skip the version-number exchange
141 char *client_version_string = NULL;
142 char *server_version_string = NULL;
144 /* for rekeying XXX fixme */
148 * Any really sensitive data in the application is contained in this
149 * structure. The idea is that this structure could be locked into memory so
150 * that the pages do not get written into swap. However, there are some
151 * problems. The private key contains BIGNUMs, and we do not (in principle)
152 * have access to the internals of them, and locking just the structure is
153 * not very useful. Currently, memory locking is not implemented.
156 Key *server_key; /* ephemeral server key */
157 Key *ssh1_host_key; /* ssh1 host key */
158 Key **host_keys; /* all private host keys */
161 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
165 * Flag indicating whether the RSA server key needs to be regenerated.
166 * Is set in the SIGALRM handler and cleared when the key is regenerated.
168 int key_do_regen = 0;
170 /* This is set to true when a signal is received. */
171 int received_sighup = 0;
172 int received_sigterm = 0;
174 /* session identifier, used by RSA-auth */
175 u_char session_id[16];
178 u_char *session_id2 = NULL;
179 int session_id2_len = 0;
181 /* record remote hostname or ip */
182 u_int utmp_len = MAXHOSTNAMELEN;
184 /* Prototypes for various functions defined later in this file. */
185 void do_ssh1_kex(void);
186 void do_ssh2_kex(void);
188 void ssh_dh1_server(Kex *, Buffer *_kexinit, Buffer *);
189 void ssh_dhgex_server(Kex *, Buffer *_kexinit, Buffer *);
192 * Close all listening sockets
195 close_listen_socks(void)
198 for (i = 0; i < num_listen_socks; i++)
199 close(listen_socks[i]);
200 num_listen_socks = -1;
204 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
205 * the effect is to reread the configuration file (and to regenerate
209 sighup_handler(int sig)
212 signal(SIGHUP, sighup_handler);
216 * Called from the main program after receiving SIGHUP.
217 * Restarts the server.
222 log("Received SIGHUP; restarting.");
223 close_listen_socks();
224 execv(saved_argv[0], saved_argv);
225 log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], strerror(errno));
230 * Generic signal handler for terminating signals in the master daemon.
233 sigterm_handler(int sig)
235 received_sigterm = sig;
239 * SIGCHLD handler. This is called whenever a child dies. This will then
240 * reap any zombies left by exited children.
243 main_sigchld_handler(int sig)
245 int save_errno = errno;
248 while (waitpid(-1, &status, WNOHANG) > 0)
251 signal(SIGCHLD, main_sigchld_handler);
256 * Signal handler for the alarm after the login grace period has expired.
259 grace_alarm_handler(int sig)
261 /* XXX no idea how fix this signal handler */
263 /* Close the connection. */
266 /* Log error and exit. */
267 fatal("Timeout before authentication for %s.", get_remote_ipaddr());
271 * Signal handler for the key regeneration alarm. Note that this
272 * alarm only occurs in the daemon waiting for connections, and it does not
273 * do anything with the private key or random state before forking.
274 * Thus there should be no concurrency control/asynchronous execution
278 generate_ephemeral_server_key(void)
283 verbose("Generating %s%d bit RSA key.",
284 sensitive_data.server_key ? "new " : "", options.server_key_bits);
285 if (sensitive_data.server_key != NULL)
286 key_free(sensitive_data.server_key);
287 sensitive_data.server_key = key_generate(KEY_RSA1,
288 options.server_key_bits);
289 verbose("RSA key generation complete.");
291 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
294 sensitive_data.ssh1_cookie[i] = rand & 0xff;
301 key_regeneration_alarm(int sig)
303 int save_errno = errno;
304 signal(SIGALRM, SIG_DFL);
310 sshd_exchange_identification(int sock_in, int sock_out)
313 int remote_major, remote_minor;
316 char buf[256]; /* Must not be larger than remote_version. */
317 char remote_version[256]; /* Must be at least as big as buf. */
319 if ((options.protocol & SSH_PROTO_1) &&
320 (options.protocol & SSH_PROTO_2)) {
321 major = PROTOCOL_MAJOR_1;
323 } else if (options.protocol & SSH_PROTO_2) {
324 major = PROTOCOL_MAJOR_2;
325 minor = PROTOCOL_MINOR_2;
327 major = PROTOCOL_MAJOR_1;
328 minor = PROTOCOL_MINOR_1;
330 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
331 server_version_string = xstrdup(buf);
333 if (client_version_string == NULL) {
334 /* Send our protocol version identification. */
335 if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
336 != strlen(server_version_string)) {
337 log("Could not write ident string to %s.", get_remote_ipaddr());
341 /* Read other side's version identification. */
342 memset(buf, 0, sizeof(buf));
343 for (i = 0; i < sizeof(buf) - 1; i++) {
344 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
345 log("Did not receive identification string from %s.",
346 get_remote_ipaddr());
349 if (buf[i] == '\r') {
351 /* Kludge for F-Secure Macintosh < 1.0.2 */
353 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
357 if (buf[i] == '\n') {
362 buf[sizeof(buf) - 1] = 0;
363 client_version_string = xstrdup(buf);
367 * Check that the versions match. In future this might accept
368 * several versions and set appropriate flags to handle them.
370 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
371 &remote_major, &remote_minor, remote_version) != 3) {
372 s = "Protocol mismatch.\n";
373 (void) atomicio(write, sock_out, s, strlen(s));
376 log("Bad protocol version identification '%.100s' from %s",
377 client_version_string, get_remote_ipaddr());
380 debug("Client protocol version %d.%d; client software version %.100s",
381 remote_major, remote_minor, remote_version);
383 compat_datafellows(remote_version);
385 if (datafellows & SSH_BUG_SCANNER) {
386 log("scanned from %s with %s. Don't panic.",
387 get_remote_ipaddr(), client_version_string);
392 switch(remote_major) {
394 if (remote_minor == 99) {
395 if (options.protocol & SSH_PROTO_2)
401 if (!(options.protocol & SSH_PROTO_1)) {
405 if (remote_minor < 3) {
406 packet_disconnect("Your ssh version is too old and "
407 "is no longer supported. Please install a newer version.");
408 } else if (remote_minor == 3) {
409 /* note that this disables agent-forwarding */
414 if (options.protocol & SSH_PROTO_2) {
423 chop(server_version_string);
424 debug("Local version string %.200s", server_version_string);
427 s = "Protocol major versions differ.\n";
428 (void) atomicio(write, sock_out, s, strlen(s));
431 log("Protocol major versions differ for %s: %.200s vs. %.200s",
433 server_version_string, client_version_string);
439 /* Destroy the host and server keys. They will no longer be needed. */
441 destroy_sensitive_data(void)
445 if (sensitive_data.server_key) {
446 key_free(sensitive_data.server_key);
447 sensitive_data.server_key = NULL;
449 for(i = 0; i < options.num_host_key_files; i++) {
450 if (sensitive_data.host_keys[i]) {
451 key_free(sensitive_data.host_keys[i]);
452 sensitive_data.host_keys[i] = NULL;
455 sensitive_data.ssh1_host_key = NULL;
456 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
460 list_hostkey_types(void)
462 static char buf[1024];
465 for(i = 0; i < options.num_host_key_files; i++) {
466 Key *key = sensitive_data.host_keys[i];
472 strlcat(buf, key_ssh_name(key), sizeof buf);
473 strlcat(buf, ",", sizeof buf);
478 if (i > 0 && buf[i-1] == ',')
480 debug("list_hostkey_types: %s", buf);
485 get_hostkey_by_type(int type)
488 for(i = 0; i < options.num_host_key_files; i++) {
489 Key *key = sensitive_data.host_keys[i];
490 if (key != NULL && key->type == type)
497 * returns 1 if connection should be dropped, 0 otherwise.
498 * dropping starts at connection #max_startups_begin with a probability
499 * of (max_startups_rate/100). the probability increases linearly until
500 * all connections are dropped for startups > max_startups
503 drop_connection(int startups)
507 if (startups < options.max_startups_begin)
509 if (startups >= options.max_startups)
511 if (options.max_startups_rate == 100)
514 p = 100 - options.max_startups_rate;
515 p *= startups - options.max_startups_begin;
516 p /= (double) (options.max_startups - options.max_startups_begin);
517 p += options.max_startups_rate;
519 r = arc4random() / (double) UINT_MAX;
521 debug("drop_connection: p %g, r %g", p, r);
522 return (r < p) ? 1 : 0;
525 int *startup_pipes = NULL; /* options.max_startup sized array of fd ints */
526 int startup_pipe; /* in child */
529 * Main program for the daemon.
532 main(int ac, char **av)
536 int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
540 struct sockaddr_storage from;
541 const char *remote_ip;
544 struct linger linger;
546 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
547 int listen_sock, maxfd;
551 int ret, key_used = 0;
553 __progname = get_progname(av[0]);
560 /* Initialize configuration options to their default values. */
561 initialize_server_options(&options);
563 /* Parse command-line arguments. */
564 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:dDeiqQ46")) != -1) {
573 config_file_name = optarg;
576 if (0 == debug_flag) {
578 options.log_level = SYSLOG_LEVEL_DEBUG1;
579 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
582 fprintf(stderr, "Too high debugging level.\n");
599 options.log_level = SYSLOG_LEVEL_QUIET;
602 options.server_key_bits = atoi(optarg);
605 options.ports_from_cmdline = 1;
606 if (options.num_ports >= MAX_PORTS) {
607 fprintf(stderr, "too many ports.\n");
610 options.ports[options.num_ports++] = a2port(optarg);
611 if (options.ports[options.num_ports-1] == 0) {
612 fprintf(stderr, "Bad port number.\n");
617 if ((options.login_grace_time = convtime(optarg)) == -1) {
618 fprintf(stderr, "Invalid login grace time.\n");
623 if ((options.key_regeneration_time = convtime(optarg)) == -1) {
624 fprintf(stderr, "Invalid key regeneration interval.\n");
629 if (options.num_host_key_files >= MAX_HOSTKEYS) {
630 fprintf(stderr, "too many host keys.\n");
633 options.host_key_files[options.num_host_key_files++] = optarg;
636 client_version_string = optarg;
637 /* only makes sense with inetd_flag, i.e. no listen() */
641 utmp_len = atoi(optarg);
645 fprintf(stderr, "sshd version %s\n", SSH_VERSION);
646 fprintf(stderr, "Usage: %s [options]\n", __progname);
647 fprintf(stderr, "Options:\n");
648 fprintf(stderr, " -f file Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE);
649 fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n");
650 fprintf(stderr, " -i Started from inetd\n");
651 fprintf(stderr, " -D Do not fork into daemon mode\n");
652 fprintf(stderr, " -q Quiet (no logging)\n");
653 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
654 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
655 fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n");
656 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
657 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
658 _PATH_HOST_KEY_FILE);
659 fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
660 fprintf(stderr, " -4 Use IPv4 only\n");
661 fprintf(stderr, " -6 Use IPv6 only\n");
665 SSLeay_add_all_algorithms();
668 * Force logging to stderr until we have loaded the private host
669 * key (unless started from inetd)
672 options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
673 options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
678 /* Read server configuration options from the configuration file. */
679 read_server_config(&options, config_file_name);
681 /* Fill in default values for those options not explicitly set. */
682 fill_default_server_options(&options);
684 /* Check that there are no remaining arguments. */
686 fprintf(stderr, "Extra argument %s.\n", av[optind]);
690 debug("sshd version %.100s", SSH_VERSION);
692 /* load private host keys */
693 sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*));
694 for(i = 0; i < options.num_host_key_files; i++)
695 sensitive_data.host_keys[i] = NULL;
696 sensitive_data.server_key = NULL;
697 sensitive_data.ssh1_host_key = NULL;
698 sensitive_data.have_ssh1_key = 0;
699 sensitive_data.have_ssh2_key = 0;
701 for(i = 0; i < options.num_host_key_files; i++) {
702 key = key_load_private(options.host_key_files[i], "", NULL);
703 sensitive_data.host_keys[i] = key;
705 error("Could not load host key: %s",
706 options.host_key_files[i]);
707 sensitive_data.host_keys[i] = NULL;
712 sensitive_data.ssh1_host_key = key;
713 sensitive_data.have_ssh1_key = 1;
717 sensitive_data.have_ssh2_key = 1;
720 debug("private host key: #%d type %d %s", i, key->type,
723 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
724 log("Disabling protocol version 1. Could not load host key");
725 options.protocol &= ~SSH_PROTO_1;
727 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
728 log("Disabling protocol version 2. Could not load host key");
729 options.protocol &= ~SSH_PROTO_2;
731 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
732 log("sshd: no hostkeys available -- exiting.");
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(_PATH_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. */
800 signal(SIGPIPE, SIG_IGN);
802 /* Start listening for a socket, unless started from inetd. */
805 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
811 * We intentionally do not close the descriptors 0, 1, and 2
812 * as our code for setting the descriptors won\'t work if
813 * ttyfd happens to be one of those.
815 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
816 if (options.protocol & SSH_PROTO_1)
817 generate_ephemeral_server_key();
819 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
820 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
822 if (num_listen_socks >= MAX_LISTEN_SOCKS)
823 fatal("Too many listen sockets. "
824 "Enlarge MAX_LISTEN_SOCKS");
825 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
826 ntop, sizeof(ntop), strport, sizeof(strport),
827 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
828 error("getnameinfo failed");
831 /* Create socket for listening. */
832 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
833 if (listen_sock < 0) {
834 /* kernel may not support ipv6 */
835 verbose("socket: %.100s", strerror(errno));
838 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
839 error("listen_sock O_NONBLOCK: %s", strerror(errno));
844 * Set socket options. We try to make the port
845 * reusable and have it close as fast as possible
846 * without waiting in unnecessary wait states on
849 setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
850 (void *) &on, sizeof(on));
853 setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
854 (void *) &linger, sizeof(linger));
856 debug("Bind to port %s on %s.", strport, ntop);
858 /* Bind the socket to the desired port. */
859 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
861 error("Bind to port %s on %s failed: %.200s.",
862 strport, ntop, strerror(errno));
866 listen_socks[num_listen_socks] = listen_sock;
869 /* Start listening on the port. */
870 log("Server listening on %s port %s.", ntop, strport);
871 if (listen(listen_sock, 5) < 0)
872 fatal("listen: %.100s", strerror(errno));
875 freeaddrinfo(options.listen_addrs);
877 if (!num_listen_socks)
878 fatal("Cannot bind any address.");
882 * Record our pid in /var/run/sshd.pid to make it
883 * easier to kill the correct sshd. We don't want to
884 * do this before the bind above because the bind will
885 * fail if there already is a daemon, and this will
886 * overwrite any old pid in the file.
888 f = fopen(options.pid_file, "wb");
890 fprintf(f, "%u\n", (u_int) getpid());
894 if (options.protocol & SSH_PROTO_1)
895 generate_ephemeral_server_key();
897 /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
898 signal(SIGHUP, sighup_handler);
900 signal(SIGTERM, sigterm_handler);
901 signal(SIGQUIT, sigterm_handler);
903 /* Arrange SIGCHLD to be caught. */
904 signal(SIGCHLD, main_sigchld_handler);
906 /* setup fd set for listen */
909 for (i = 0; i < num_listen_socks; i++)
910 if (listen_socks[i] > maxfd)
911 maxfd = listen_socks[i];
912 /* pipes connected to unauthenticated childs */
913 startup_pipes = xmalloc(options.max_startups * sizeof(int));
914 for (i = 0; i < options.max_startups; i++)
915 startup_pipes[i] = -1;
918 * Stay listening for connections until the system crashes or
919 * the daemon is killed with a signal.
926 fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
927 fdset = (fd_set *)xmalloc(fdsetsz);
928 memset(fdset, 0, fdsetsz);
930 for (i = 0; i < num_listen_socks; i++)
931 FD_SET(listen_socks[i], fdset);
932 for (i = 0; i < options.max_startups; i++)
933 if (startup_pipes[i] != -1)
934 FD_SET(startup_pipes[i], fdset);
936 /* Wait in select until there is a connection. */
937 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
938 if (ret < 0 && errno != EINTR)
939 error("select: %.100s", strerror(errno));
940 if (received_sigterm) {
941 log("Received signal %d; terminating.",
943 close_listen_socks();
944 unlink(options.pid_file);
947 if (key_used && key_do_regen) {
948 generate_ephemeral_server_key();
955 for (i = 0; i < options.max_startups; i++)
956 if (startup_pipes[i] != -1 &&
957 FD_ISSET(startup_pipes[i], fdset)) {
959 * the read end of the pipe is ready
960 * if the child has closed the pipe
961 * after successful authentication
962 * or if the child has died
964 close(startup_pipes[i]);
965 startup_pipes[i] = -1;
968 for (i = 0; i < num_listen_socks; i++) {
969 if (!FD_ISSET(listen_socks[i], fdset))
971 fromlen = sizeof(from);
972 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
975 if (errno != EINTR && errno != EWOULDBLOCK)
976 error("accept: %.100s", strerror(errno));
979 if (fcntl(newsock, F_SETFL, 0) < 0) {
980 error("newsock del O_NONBLOCK: %s", strerror(errno));
983 if (drop_connection(startups) == 1) {
984 debug("drop connection #%d", startups);
988 if (pipe(startup_p) == -1) {
993 for (j = 0; j < options.max_startups; j++)
994 if (startup_pipes[j] == -1) {
995 startup_pipes[j] = startup_p[0];
996 if (maxfd < startup_p[0])
997 maxfd = startup_p[0];
1003 * Got connection. Fork a child to handle it, unless
1004 * we are in debugging mode.
1008 * In debugging mode. Close the listening
1009 * socket, and start processing the
1010 * connection without forking.
1012 debug("Server will not fork when running in debugging mode.");
1013 close_listen_socks();
1021 * Normal production daemon. Fork, and have
1022 * the child process the connection. The
1023 * parent continues listening.
1025 if ((pid = fork()) == 0) {
1027 * Child. Close the listening and max_startup
1028 * sockets. Start using the accepted socket.
1029 * Reinitialize logging (since our pid has
1030 * changed). We break out of the loop to handle
1033 startup_pipe = startup_p[1];
1034 for (j = 0; j < options.max_startups; j++)
1035 if (startup_pipes[j] != -1)
1036 close(startup_pipes[j]);
1037 close_listen_socks();
1040 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1045 /* Parent. Stay in the loop. */
1047 error("fork: %.100s", strerror(errno));
1049 debug("Forked child %d.", pid);
1051 close(startup_p[1]);
1053 /* Mark that the key has been used (it was "given" to the child). */
1054 if ((options.protocol & SSH_PROTO_1) &&
1056 /* Schedule server key regeneration alarm. */
1057 signal(SIGALRM, key_regeneration_alarm);
1058 alarm(options.key_regeneration_time);
1064 /* Close the new socket (the child is now taking care of it). */
1067 /* child process check (or debug mode) */
1068 if (num_listen_socks < 0)
1073 /* This is the child processing a new connection. */
1076 * Disable the key regeneration alarm. We will not regenerate the
1077 * key since we are no longer in a position to give it to anyone. We
1078 * will not restart on SIGHUP since it no longer makes sense.
1081 signal(SIGALRM, SIG_DFL);
1082 signal(SIGHUP, SIG_DFL);
1083 signal(SIGTERM, SIG_DFL);
1084 signal(SIGQUIT, SIG_DFL);
1085 signal(SIGCHLD, SIG_DFL);
1086 signal(SIGINT, SIG_DFL);
1089 * Set socket options for the connection. We want the socket to
1090 * close as fast as possible without waiting for anything. If the
1091 * connection is not a socket, these will do nothing.
1093 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1095 linger.l_linger = 5;
1096 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
1098 /* Set keepalives if requested. */
1099 if (options.keepalives &&
1100 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
1102 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1105 * Register our connection. This turns encryption off because we do
1108 packet_set_connection(sock_in, sock_out);
1110 remote_port = get_remote_port();
1111 remote_ip = get_remote_ipaddr();
1113 /* Check whether logins are denied from this host. */
1115 /* XXX LIBWRAP noes not know about IPv6 */
1117 struct request_info req;
1119 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, NULL);
1122 if (!hosts_access(&req)) {
1127 /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
1129 #endif /* LIBWRAP */
1130 /* Log the connection. */
1131 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1134 * We don\'t want to listen forever unless the other side
1135 * successfully authenticates itself. So we set up an alarm which is
1136 * cleared after successful authentication. A limit of zero
1137 * indicates no limit. Note that we don\'t set the alarm in debugging
1138 * mode; it is just annoying to have the server exit just when you
1139 * are about to discover the bug.
1141 signal(SIGALRM, grace_alarm_handler);
1143 alarm(options.login_grace_time);
1145 sshd_exchange_identification(sock_in, sock_out);
1147 * Check that the connection comes from a privileged port.
1148 * Rhosts-Authentication only makes sense from priviledged
1149 * programs. Of course, if the intruder has root access on his local
1150 * machine, he can connect from any port. So do not use these
1151 * authentication methods from machines that you do not trust.
1153 if (remote_port >= IPPORT_RESERVED ||
1154 remote_port < IPPORT_RESERVED / 2) {
1155 debug("Rhosts Authentication disabled, "
1156 "originating port not trusted.");
1157 options.rhosts_authentication = 0;
1160 if (!packet_connection_is_ipv4() &&
1161 options.kerberos_authentication) {
1162 debug("Kerberos Authentication disabled, only available for IPv4.");
1163 options.kerberos_authentication = 0;
1167 /* If machine has AFS, set process authentication group. */
1174 packet_set_nonblocking();
1176 /* perform the key exchange */
1177 /* authenticate user and start session */
1180 do_authentication2();
1183 do_authentication();
1187 /* Cleanup user's ticket cache file. */
1188 if (options.kerberos_ticket_cleanup)
1192 /* The connection has been terminated. */
1193 verbose("Closing connection to %.100s", remote_ip);
1197 #endif /* USE_PAM */
1212 BIGNUM *session_key_int;
1213 u_char session_key[SSH_SESSION_KEY_LENGTH];
1215 u_int cipher_type, auth_mask, protocol_flags;
1219 * Generate check bytes that the client must send back in the user
1220 * packet in order for it to be accepted; this is used to defy ip
1221 * spoofing attacks. Note that this only works against somebody
1222 * doing IP spoofing from a remote machine; any machine on the local
1223 * network can still see outgoing packets and catch the random
1224 * cookie. This only affects rhosts authentication, and this is one
1225 * of the reasons why it is inherently insecure.
1227 for (i = 0; i < 8; i++) {
1229 rand = arc4random();
1230 cookie[i] = rand & 0xff;
1235 * Send our public key. We include in the packet 64 bits of random
1236 * data that must be matched in the reply in order to prevent IP
1239 packet_start(SSH_SMSG_PUBLIC_KEY);
1240 for (i = 0; i < 8; i++)
1241 packet_put_char(cookie[i]);
1243 /* Store our public server RSA key. */
1244 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1245 packet_put_bignum(sensitive_data.server_key->rsa->e);
1246 packet_put_bignum(sensitive_data.server_key->rsa->n);
1248 /* Store our public host RSA key. */
1249 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1250 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1251 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1253 /* Put protocol flags. */
1254 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1256 /* Declare which ciphers we support. */
1257 packet_put_int(cipher_mask_ssh1(0));
1259 /* Declare supported authentication types. */
1261 if (options.rhosts_authentication)
1262 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1263 if (options.rhosts_rsa_authentication)
1264 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1265 if (options.rsa_authentication)
1266 auth_mask |= 1 << SSH_AUTH_RSA;
1268 if (options.kerberos_authentication)
1269 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1272 if (options.kerberos_tgt_passing)
1273 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1274 if (options.afs_token_passing)
1275 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1277 if (options.challenge_response_authentication == 1)
1278 auth_mask |= 1 << SSH_AUTH_TIS;
1279 if (options.password_authentication)
1280 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1281 packet_put_int(auth_mask);
1283 /* Send the packet and wait for it to be sent. */
1285 packet_write_wait();
1287 debug("Sent %d bit server key and %d bit host key.",
1288 BN_num_bits(sensitive_data.server_key->rsa->n),
1289 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1291 /* Read clients reply (cipher type and session key). */
1292 packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1294 /* Get cipher type and check whether we accept this. */
1295 cipher_type = packet_get_char();
1297 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1298 packet_disconnect("Warning: client selects unsupported cipher.");
1300 /* Get check bytes from the packet. These must match those we
1301 sent earlier with the public key packet. */
1302 for (i = 0; i < 8; i++)
1303 if (cookie[i] != packet_get_char())
1304 packet_disconnect("IP Spoofing check bytes do not match.");
1306 debug("Encryption type: %.200s", cipher_name(cipher_type));
1308 /* Get the encrypted integer. */
1309 session_key_int = BN_new();
1310 packet_get_bignum(session_key_int, &slen);
1312 protocol_flags = packet_get_int();
1313 packet_set_protocol_flags(protocol_flags);
1315 packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1318 * Decrypt it using our private server key and private host key (key
1319 * with larger modulus first).
1321 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1322 /* Server key has bigger modulus. */
1323 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1324 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1325 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1326 get_remote_ipaddr(),
1327 BN_num_bits(sensitive_data.server_key->rsa->n),
1328 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1329 SSH_KEY_BITS_RESERVED);
1331 if (rsa_private_decrypt(session_key_int, session_key_int,
1332 sensitive_data.server_key->rsa) <= 0)
1334 if (rsa_private_decrypt(session_key_int, session_key_int,
1335 sensitive_data.ssh1_host_key->rsa) <= 0)
1338 /* Host key has bigger modulus (or they are equal). */
1339 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1340 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1341 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1342 get_remote_ipaddr(),
1343 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1344 BN_num_bits(sensitive_data.server_key->rsa->n),
1345 SSH_KEY_BITS_RESERVED);
1347 if (rsa_private_decrypt(session_key_int, session_key_int,
1348 sensitive_data.ssh1_host_key->rsa) < 0)
1350 if (rsa_private_decrypt(session_key_int, session_key_int,
1351 sensitive_data.server_key->rsa) < 0)
1355 * Extract session key from the decrypted integer. The key is in the
1356 * least significant 256 bits of the integer; the first byte of the
1357 * key is in the highest bits.
1360 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1361 len = BN_num_bytes(session_key_int);
1362 if (len < 0 || len > sizeof(session_key)) {
1363 error("do_connection: bad session key len from %s: "
1364 "session_key_int %d > sizeof(session_key) %lu",
1365 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
1368 memset(session_key, 0, sizeof(session_key));
1369 BN_bn2bin(session_key_int,
1370 session_key + sizeof(session_key) - len);
1372 compute_session_id(session_id, cookie,
1373 sensitive_data.ssh1_host_key->rsa->n,
1374 sensitive_data.server_key->rsa->n);
1376 * Xor the first 16 bytes of the session key with the
1379 for (i = 0; i < 16; i++)
1380 session_key[i] ^= session_id[i];
1384 int bytes = BN_num_bytes(session_key_int);
1385 char *buf = xmalloc(bytes);
1388 log("do_connection: generating a fake encryption key");
1389 BN_bn2bin(session_key_int, buf);
1391 MD5_Update(&md, buf, bytes);
1392 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1393 MD5_Final(session_key, &md);
1395 MD5_Update(&md, session_key, 16);
1396 MD5_Update(&md, buf, bytes);
1397 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1398 MD5_Final(session_key + 16, &md);
1399 memset(buf, 0, bytes);
1401 for (i = 0; i < 16; i++)
1402 session_id[i] = session_key[i] ^ session_key[i + 16];
1404 /* Destroy the private and public keys. They will no longer be needed. */
1405 destroy_sensitive_data();
1407 /* Destroy the decrypted integer. It is no longer needed. */
1408 BN_clear_free(session_key_int);
1410 /* Set the session key. From this on all communications will be encrypted. */
1411 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1413 /* Destroy our copy of the session key. It is no longer needed. */
1414 memset(session_key, 0, sizeof(session_key));
1416 debug("Received session key; encryption turned on.");
1418 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1419 packet_start(SSH_SMSG_SUCCESS);
1421 packet_write_wait();
1425 * SSH2 key exchange: diffie-hellman-group1-sha1
1432 if (options.ciphers != NULL) {
1433 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1434 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1436 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1437 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
1438 myproposal[PROPOSAL_ENC_ALGS_STOC] =
1439 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
1441 if (options.macs != NULL) {
1442 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
1443 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
1445 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
1447 /* start key exchange */
1448 kex = kex_setup(myproposal);
1450 kex->client_version_string=client_version_string;
1451 kex->server_version_string=server_version_string;
1452 kex->load_host_key=&get_hostkey_by_type;
1456 dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
1458 session_id2 = kex->session_id;
1459 session_id2_len = kex->session_id_len;
1462 /* send 1st encrypted/maced/compressed message */
1463 packet_start(SSH2_MSG_IGNORE);
1464 packet_put_cstring("markus");
1466 packet_write_wait();