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 1.196 2001/05/18 14:13:29 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 SIGHUP is received. */
171 int received_sighup = 0;
173 /* session identifier, used by RSA-auth */
174 u_char session_id[16];
177 u_char *session_id2 = NULL;
178 int session_id2_len = 0;
180 /* record remote hostname or ip */
181 u_int utmp_len = MAXHOSTNAMELEN;
183 /* Prototypes for various functions defined later in this file. */
184 void do_ssh1_kex(void);
185 void do_ssh2_kex(void);
187 void ssh_dh1_server(Kex *, Buffer *_kexinit, Buffer *);
188 void ssh_dhgex_server(Kex *, Buffer *_kexinit, Buffer *);
191 * Close all listening sockets
194 close_listen_socks(void)
197 for (i = 0; i < num_listen_socks; i++)
198 close(listen_socks[i]);
199 num_listen_socks = -1;
203 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
204 * the effect is to reread the configuration file (and to regenerate
208 sighup_handler(int sig)
211 signal(SIGHUP, sighup_handler);
215 * Called from the main program after receiving SIGHUP.
216 * Restarts the server.
221 log("Received SIGHUP; restarting.");
222 close_listen_socks();
223 execv(saved_argv[0], saved_argv);
224 log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], strerror(errno));
229 * Generic signal handler for terminating signals in the master daemon.
230 * These close the listen socket; not closing it seems to cause "Address
231 * already in use" problems on some machines, which is inconvenient.
234 sigterm_handler(int sig)
236 log("Received signal %d; terminating.", sig);
237 close_listen_socks();
238 unlink(options.pid_file);
243 * SIGCHLD handler. This is called whenever a child dies. This will then
244 * reap any zombies left by exited c.
247 main_sigchld_handler(int sig)
249 int save_errno = errno;
252 while (waitpid(-1, &status, WNOHANG) > 0)
255 signal(SIGCHLD, main_sigchld_handler);
260 * Signal handler for the alarm after the login grace period has expired.
263 grace_alarm_handler(int sig)
265 /* Close the connection. */
268 /* Log error and exit. */
269 fatal("Timeout before authentication for %s.", get_remote_ipaddr());
273 * Signal handler for the key regeneration alarm. Note that this
274 * alarm only occurs in the daemon waiting for connections, and it does not
275 * do anything with the private key or random state before forking.
276 * Thus there should be no concurrency control/asynchronous execution
280 generate_ephemeral_server_key(void)
285 verbose("Generating %s%d bit RSA key.",
286 sensitive_data.server_key ? "new " : "", options.server_key_bits);
287 if (sensitive_data.server_key != NULL)
288 key_free(sensitive_data.server_key);
289 sensitive_data.server_key = key_generate(KEY_RSA1,
290 options.server_key_bits);
291 verbose("RSA key generation complete.");
293 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
296 sensitive_data.ssh1_cookie[i] = rand & 0xff;
303 key_regeneration_alarm(int sig)
305 int save_errno = errno;
306 signal(SIGALRM, SIG_DFL);
312 sshd_exchange_identification(int sock_in, int sock_out)
315 int remote_major, remote_minor;
318 char buf[256]; /* Must not be larger than remote_version. */
319 char remote_version[256]; /* Must be at least as big as buf. */
321 if ((options.protocol & SSH_PROTO_1) &&
322 (options.protocol & SSH_PROTO_2)) {
323 major = PROTOCOL_MAJOR_1;
325 } else if (options.protocol & SSH_PROTO_2) {
326 major = PROTOCOL_MAJOR_2;
327 minor = PROTOCOL_MINOR_2;
329 major = PROTOCOL_MAJOR_1;
330 minor = PROTOCOL_MINOR_1;
332 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
333 server_version_string = xstrdup(buf);
335 if (client_version_string == NULL) {
336 /* Send our protocol version identification. */
337 if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
338 != strlen(server_version_string)) {
339 log("Could not write ident string to %s.", get_remote_ipaddr());
343 /* Read other side's version identification. */
344 memset(buf, 0, sizeof(buf));
345 for (i = 0; i < sizeof(buf) - 1; i++) {
346 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
347 log("Did not receive identification string from %s.",
348 get_remote_ipaddr());
351 if (buf[i] == '\r') {
353 /* Kludge for F-Secure Macintosh < 1.0.2 */
355 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
359 if (buf[i] == '\n') {
364 buf[sizeof(buf) - 1] = 0;
365 client_version_string = xstrdup(buf);
369 * Check that the versions match. In future this might accept
370 * several versions and set appropriate flags to handle them.
372 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
373 &remote_major, &remote_minor, remote_version) != 3) {
374 s = "Protocol mismatch.\n";
375 (void) atomicio(write, sock_out, s, strlen(s));
378 log("Bad protocol version identification '%.100s' from %s",
379 client_version_string, get_remote_ipaddr());
382 debug("Client protocol version %d.%d; client software version %.100s",
383 remote_major, remote_minor, remote_version);
385 compat_datafellows(remote_version);
387 if (datafellows & SSH_BUG_SCANNER) {
388 log("scanned from %s with %s. Don't panic.",
389 get_remote_ipaddr(), client_version_string);
394 switch(remote_major) {
396 if (remote_minor == 99) {
397 if (options.protocol & SSH_PROTO_2)
403 if (!(options.protocol & SSH_PROTO_1)) {
407 if (remote_minor < 3) {
408 packet_disconnect("Your ssh version is too old and "
409 "is no longer supported. Please install a newer version.");
410 } else if (remote_minor == 3) {
411 /* note that this disables agent-forwarding */
416 if (options.protocol & SSH_PROTO_2) {
425 chop(server_version_string);
426 debug("Local version string %.200s", server_version_string);
429 s = "Protocol major versions differ.\n";
430 (void) atomicio(write, sock_out, s, strlen(s));
433 log("Protocol major versions differ for %s: %.200s vs. %.200s",
435 server_version_string, client_version_string);
439 packet_set_ssh2_format();
443 /* Destroy the host and server keys. They will no longer be needed. */
445 destroy_sensitive_data(void)
449 if (sensitive_data.server_key) {
450 key_free(sensitive_data.server_key);
451 sensitive_data.server_key = NULL;
453 for(i = 0; i < options.num_host_key_files; i++) {
454 if (sensitive_data.host_keys[i]) {
455 key_free(sensitive_data.host_keys[i]);
456 sensitive_data.host_keys[i] = NULL;
459 sensitive_data.ssh1_host_key = NULL;
460 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
464 list_hostkey_types(void)
466 static char buf[1024];
469 for(i = 0; i < options.num_host_key_files; i++) {
470 Key *key = sensitive_data.host_keys[i];
476 strlcat(buf, key_ssh_name(key), sizeof buf);
477 strlcat(buf, ",", sizeof buf);
482 if (i > 0 && buf[i-1] == ',')
484 debug("list_hostkey_types: %s", buf);
489 get_hostkey_by_type(int type)
492 for(i = 0; i < options.num_host_key_files; i++) {
493 Key *key = sensitive_data.host_keys[i];
494 if (key != NULL && key->type == type)
501 * returns 1 if connection should be dropped, 0 otherwise.
502 * dropping starts at connection #max_startups_begin with a probability
503 * of (max_startups_rate/100). the probability increases linearly until
504 * all connections are dropped for startups > max_startups
507 drop_connection(int startups)
511 if (startups < options.max_startups_begin)
513 if (startups >= options.max_startups)
515 if (options.max_startups_rate == 100)
518 p = 100 - options.max_startups_rate;
519 p *= startups - options.max_startups_begin;
520 p /= (double) (options.max_startups - options.max_startups_begin);
521 p += options.max_startups_rate;
523 r = arc4random() / (double) UINT_MAX;
525 debug("drop_connection: p %g, r %g", p, r);
526 return (r < p) ? 1 : 0;
529 int *startup_pipes = NULL; /* options.max_startup sized array of fd ints */
530 int startup_pipe; /* in child */
533 * Main program for the daemon.
536 main(int ac, char **av)
540 int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
544 struct sockaddr_storage from;
545 const char *remote_ip;
548 struct linger linger;
550 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
551 int listen_sock, maxfd;
555 int ret, key_used = 0;
557 __progname = get_progname(av[0]);
564 /* Initialize configuration options to their default values. */
565 initialize_server_options(&options);
567 /* Parse command-line arguments. */
568 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:dDeiqQ46")) != -1) {
577 config_file_name = optarg;
580 if (0 == debug_flag) {
582 options.log_level = SYSLOG_LEVEL_DEBUG1;
583 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
586 fprintf(stderr, "Too high debugging level.\n");
603 options.log_level = SYSLOG_LEVEL_QUIET;
606 options.server_key_bits = atoi(optarg);
609 options.ports_from_cmdline = 1;
610 if (options.num_ports >= MAX_PORTS) {
611 fprintf(stderr, "too many ports.\n");
614 options.ports[options.num_ports++] = a2port(optarg);
615 if (options.ports[options.num_ports-1] == 0) {
616 fprintf(stderr, "Bad port number.\n");
621 options.login_grace_time = atoi(optarg);
624 options.key_regeneration_time = atoi(optarg);
627 if (options.num_host_key_files >= MAX_HOSTKEYS) {
628 fprintf(stderr, "too many host keys.\n");
631 options.host_key_files[options.num_host_key_files++] = optarg;
634 client_version_string = optarg;
635 /* only makes sense with inetd_flag, i.e. no listen() */
639 utmp_len = atoi(optarg);
643 fprintf(stderr, "sshd version %s\n", SSH_VERSION);
644 fprintf(stderr, "Usage: %s [options]\n", __progname);
645 fprintf(stderr, "Options:\n");
646 fprintf(stderr, " -f file Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE);
647 fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n");
648 fprintf(stderr, " -i Started from inetd\n");
649 fprintf(stderr, " -D Do not fork into daemon mode\n");
650 fprintf(stderr, " -q Quiet (no logging)\n");
651 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
652 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
653 fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n");
654 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
655 fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
656 _PATH_HOST_KEY_FILE);
657 fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
658 fprintf(stderr, " -4 Use IPv4 only\n");
659 fprintf(stderr, " -6 Use IPv6 only\n");
663 SSLeay_add_all_algorithms();
666 * Force logging to stderr until we have loaded the private host
667 * key (unless started from inetd)
670 options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
671 options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
676 /* Read server configuration options from the configuration file. */
677 read_server_config(&options, config_file_name);
679 /* Fill in default values for those options not explicitly set. */
680 fill_default_server_options(&options);
682 /* Check that there are no remaining arguments. */
684 fprintf(stderr, "Extra argument %s.\n", av[optind]);
688 debug("sshd version %.100s", SSH_VERSION);
690 /* load private host keys */
691 sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*));
692 for(i = 0; i < options.num_host_key_files; i++)
693 sensitive_data.host_keys[i] = NULL;
694 sensitive_data.server_key = NULL;
695 sensitive_data.ssh1_host_key = NULL;
696 sensitive_data.have_ssh1_key = 0;
697 sensitive_data.have_ssh2_key = 0;
699 for(i = 0; i < options.num_host_key_files; i++) {
700 key = key_load_private(options.host_key_files[i], "", NULL);
701 sensitive_data.host_keys[i] = key;
703 error("Could not load host key: %s",
704 options.host_key_files[i]);
705 sensitive_data.host_keys[i] = NULL;
710 sensitive_data.ssh1_host_key = key;
711 sensitive_data.have_ssh1_key = 1;
715 sensitive_data.have_ssh2_key = 1;
718 debug("private host key: #%d type %d %s", i, key->type,
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))) {
730 log("sshd: no hostkeys available -- exiting.");
734 /* Check certain values for sanity. */
735 if (options.protocol & SSH_PROTO_1) {
736 if (options.server_key_bits < 512 ||
737 options.server_key_bits > 32768) {
738 fprintf(stderr, "Bad server key size.\n");
742 * Check that server and host key lengths differ sufficiently. This
743 * is necessary to make double encryption work with rsaref. Oh, I
744 * hate software patents. I dont know if this can go? Niels
746 if (options.server_key_bits >
747 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - SSH_KEY_BITS_RESERVED &&
748 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 debug("Forcing server key to %d bits to make it differ from host key.",
753 options.server_key_bits);
757 #ifdef HAVE_SCO_PROTECTED_PW
758 (void) set_auth_parameters(ac, av);
761 /* Initialize the log (it is reinitialized below in case we forked). */
762 if (debug_flag && !inetd_flag)
764 log_init(__progname, options.log_level, options.log_facility, log_stderr);
767 * If not in debugging mode, and not started from inetd, disconnect
768 * from the controlling terminal, and fork. The original process
771 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
774 #endif /* TIOCNOTTY */
775 if (daemon(0, 0) < 0)
776 fatal("daemon() failed: %.200s", strerror(errno));
778 /* Disconnect from the controlling tty. */
780 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
782 (void) ioctl(fd, TIOCNOTTY, NULL);
785 #endif /* TIOCNOTTY */
787 /* Reinitialize the log (because of the fork above). */
788 log_init(__progname, options.log_level, options.log_facility, log_stderr);
790 /* Initialize the random number generator. */
793 /* Chdir to the root directory so that the current disk can be
794 unmounted if desired. */
798 signal(SIGPIPE, SIG_IGN);
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_ephemeral_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_ephemeral_server_key();
895 /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
896 signal(SIGHUP, sighup_handler);
898 signal(SIGTERM, sigterm_handler);
899 signal(SIGQUIT, sigterm_handler);
901 /* Arrange SIGCHLD to be caught. */
902 signal(SIGCHLD, main_sigchld_handler);
904 /* setup fd set for listen */
907 for (i = 0; i < num_listen_socks; i++)
908 if (listen_socks[i] > maxfd)
909 maxfd = listen_socks[i];
910 /* pipes connected to unauthenticated childs */
911 startup_pipes = xmalloc(options.max_startups * sizeof(int));
912 for (i = 0; i < options.max_startups; i++)
913 startup_pipes[i] = -1;
916 * Stay listening for connections until the system crashes or
917 * the daemon is killed with a signal.
924 fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
925 fdset = (fd_set *)xmalloc(fdsetsz);
926 memset(fdset, 0, fdsetsz);
928 for (i = 0; i < num_listen_socks; i++)
929 FD_SET(listen_socks[i], fdset);
930 for (i = 0; i < options.max_startups; i++)
931 if (startup_pipes[i] != -1)
932 FD_SET(startup_pipes[i], fdset);
934 /* Wait in select until there is a connection. */
935 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
936 if (ret < 0 && errno != EINTR)
937 error("select: %.100s", strerror(errno));
938 if (key_used && key_do_regen) {
939 generate_ephemeral_server_key();
946 for (i = 0; i < options.max_startups; i++)
947 if (startup_pipes[i] != -1 &&
948 FD_ISSET(startup_pipes[i], fdset)) {
950 * the read end of the pipe is ready
951 * if the child has closed the pipe
952 * after successful authentication
953 * or if the child has died
955 close(startup_pipes[i]);
956 startup_pipes[i] = -1;
959 for (i = 0; i < num_listen_socks; i++) {
960 if (!FD_ISSET(listen_socks[i], fdset))
962 fromlen = sizeof(from);
963 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
966 if (errno != EINTR && errno != EWOULDBLOCK)
967 error("accept: %.100s", strerror(errno));
970 if (fcntl(newsock, F_SETFL, 0) < 0) {
971 error("newsock del O_NONBLOCK: %s", strerror(errno));
974 if (drop_connection(startups) == 1) {
975 debug("drop connection #%d", startups);
979 if (pipe(startup_p) == -1) {
984 for (j = 0; j < options.max_startups; j++)
985 if (startup_pipes[j] == -1) {
986 startup_pipes[j] = startup_p[0];
987 if (maxfd < startup_p[0])
988 maxfd = startup_p[0];
994 * Got connection. Fork a child to handle it, unless
995 * we are in debugging mode.
999 * In debugging mode. Close the listening
1000 * socket, and start processing the
1001 * connection without forking.
1003 debug("Server will not fork when running in debugging mode.");
1004 close_listen_socks();
1012 * Normal production daemon. Fork, and have
1013 * the child process the connection. The
1014 * parent continues listening.
1016 if ((pid = fork()) == 0) {
1018 * Child. Close the listening and max_startup
1019 * sockets. Start using the accepted socket.
1020 * Reinitialize logging (since our pid has
1021 * changed). We break out of the loop to handle
1024 startup_pipe = startup_p[1];
1025 for (j = 0; j < options.max_startups; j++)
1026 if (startup_pipes[j] != -1)
1027 close(startup_pipes[j]);
1028 close_listen_socks();
1031 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1036 /* Parent. Stay in the loop. */
1038 error("fork: %.100s", strerror(errno));
1040 debug("Forked child %d.", pid);
1042 close(startup_p[1]);
1044 /* Mark that the key has been used (it was "given" to the child). */
1045 if ((options.protocol & SSH_PROTO_1) &&
1047 /* Schedule server key regeneration alarm. */
1048 signal(SIGALRM, key_regeneration_alarm);
1049 alarm(options.key_regeneration_time);
1055 /* Close the new socket (the child is now taking care of it). */
1058 /* child process check (or debug mode) */
1059 if (num_listen_socks < 0)
1064 /* This is the child processing a new connection. */
1067 * Disable the key regeneration alarm. We will not regenerate the
1068 * key since we are no longer in a position to give it to anyone. We
1069 * will not restart on SIGHUP since it no longer makes sense.
1072 signal(SIGALRM, SIG_DFL);
1073 signal(SIGHUP, SIG_DFL);
1074 signal(SIGTERM, SIG_DFL);
1075 signal(SIGQUIT, SIG_DFL);
1076 signal(SIGCHLD, SIG_DFL);
1077 signal(SIGINT, SIG_DFL);
1080 * Set socket options for the connection. We want the socket to
1081 * close as fast as possible without waiting for anything. If the
1082 * connection is not a socket, these will do nothing.
1084 /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1086 linger.l_linger = 5;
1087 setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
1089 /* Set keepalives if requested. */
1090 if (options.keepalives &&
1091 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
1093 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1096 * Register our connection. This turns encryption off because we do
1099 packet_set_connection(sock_in, sock_out);
1101 remote_port = get_remote_port();
1102 remote_ip = get_remote_ipaddr();
1104 /* Check whether logins are denied from this host. */
1106 /* XXX LIBWRAP noes not know about IPv6 */
1108 struct request_info req;
1110 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, NULL);
1113 if (!hosts_access(&req)) {
1118 /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
1120 #endif /* LIBWRAP */
1121 /* Log the connection. */
1122 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1125 * We don\'t want to listen forever unless the other side
1126 * successfully authenticates itself. So we set up an alarm which is
1127 * cleared after successful authentication. A limit of zero
1128 * indicates no limit. Note that we don\'t set the alarm in debugging
1129 * mode; it is just annoying to have the server exit just when you
1130 * are about to discover the bug.
1132 signal(SIGALRM, grace_alarm_handler);
1134 alarm(options.login_grace_time);
1136 sshd_exchange_identification(sock_in, sock_out);
1138 * Check that the connection comes from a privileged port.
1139 * Rhosts-Authentication only makes sense from priviledged
1140 * programs. Of course, if the intruder has root access on his local
1141 * machine, he can connect from any port. So do not use these
1142 * authentication methods from machines that you do not trust.
1144 if (remote_port >= IPPORT_RESERVED ||
1145 remote_port < IPPORT_RESERVED / 2) {
1146 debug("Rhosts Authentication disabled, "
1147 "originating port not trusted.");
1148 options.rhosts_authentication = 0;
1151 if (!packet_connection_is_ipv4() &&
1152 options.kerberos_authentication) {
1153 debug("Kerberos Authentication disabled, only available for IPv4.");
1154 options.kerberos_authentication = 0;
1158 /* If machine has AFS, set process authentication group. */
1165 packet_set_nonblocking();
1167 /* perform the key exchange */
1168 /* authenticate user and start session */
1171 do_authentication2();
1174 do_authentication();
1178 /* Cleanup user's ticket cache file. */
1179 if (options.kerberos_ticket_cleanup)
1183 /* The connection has been terminated. */
1184 verbose("Closing connection to %.100s", remote_ip);
1188 #endif /* USE_PAM */
1203 BIGNUM *session_key_int;
1204 u_char session_key[SSH_SESSION_KEY_LENGTH];
1206 u_int cipher_type, auth_mask, protocol_flags;
1210 * Generate check bytes that the client must send back in the user
1211 * packet in order for it to be accepted; this is used to defy ip
1212 * spoofing attacks. Note that this only works against somebody
1213 * doing IP spoofing from a remote machine; any machine on the local
1214 * network can still see outgoing packets and catch the random
1215 * cookie. This only affects rhosts authentication, and this is one
1216 * of the reasons why it is inherently insecure.
1218 for (i = 0; i < 8; i++) {
1220 rand = arc4random();
1221 cookie[i] = rand & 0xff;
1226 * Send our public key. We include in the packet 64 bits of random
1227 * data that must be matched in the reply in order to prevent IP
1230 packet_start(SSH_SMSG_PUBLIC_KEY);
1231 for (i = 0; i < 8; i++)
1232 packet_put_char(cookie[i]);
1234 /* Store our public server RSA key. */
1235 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1236 packet_put_bignum(sensitive_data.server_key->rsa->e);
1237 packet_put_bignum(sensitive_data.server_key->rsa->n);
1239 /* Store our public host RSA key. */
1240 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1241 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1242 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1244 /* Put protocol flags. */
1245 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1247 /* Declare which ciphers we support. */
1248 packet_put_int(cipher_mask_ssh1(0));
1250 /* Declare supported authentication types. */
1252 if (options.rhosts_authentication)
1253 auth_mask |= 1 << SSH_AUTH_RHOSTS;
1254 if (options.rhosts_rsa_authentication)
1255 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1256 if (options.rsa_authentication)
1257 auth_mask |= 1 << SSH_AUTH_RSA;
1259 if (options.kerberos_authentication)
1260 auth_mask |= 1 << SSH_AUTH_KERBEROS;
1263 if (options.kerberos_tgt_passing)
1264 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1265 if (options.afs_token_passing)
1266 auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1268 if (options.challenge_response_authentication == 1)
1269 auth_mask |= 1 << SSH_AUTH_TIS;
1270 if (options.password_authentication)
1271 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1272 packet_put_int(auth_mask);
1274 /* Send the packet and wait for it to be sent. */
1276 packet_write_wait();
1278 debug("Sent %d bit server key and %d bit host key.",
1279 BN_num_bits(sensitive_data.server_key->rsa->n),
1280 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1282 /* Read clients reply (cipher type and session key). */
1283 packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1285 /* Get cipher type and check whether we accept this. */
1286 cipher_type = packet_get_char();
1288 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1289 packet_disconnect("Warning: client selects unsupported cipher.");
1291 /* Get check bytes from the packet. These must match those we
1292 sent earlier with the public key packet. */
1293 for (i = 0; i < 8; i++)
1294 if (cookie[i] != packet_get_char())
1295 packet_disconnect("IP Spoofing check bytes do not match.");
1297 debug("Encryption type: %.200s", cipher_name(cipher_type));
1299 /* Get the encrypted integer. */
1300 session_key_int = BN_new();
1301 packet_get_bignum(session_key_int, &slen);
1303 protocol_flags = packet_get_int();
1304 packet_set_protocol_flags(protocol_flags);
1306 packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1309 * Decrypt it using our private server key and private host key (key
1310 * with larger modulus first).
1312 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1313 /* Server key has bigger modulus. */
1314 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1315 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1316 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1317 get_remote_ipaddr(),
1318 BN_num_bits(sensitive_data.server_key->rsa->n),
1319 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1320 SSH_KEY_BITS_RESERVED);
1322 if (rsa_private_decrypt(session_key_int, session_key_int,
1323 sensitive_data.server_key->rsa) <= 0)
1325 if (rsa_private_decrypt(session_key_int, session_key_int,
1326 sensitive_data.ssh1_host_key->rsa) <= 0)
1329 /* Host key has bigger modulus (or they are equal). */
1330 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1331 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1332 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1333 get_remote_ipaddr(),
1334 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1335 BN_num_bits(sensitive_data.server_key->rsa->n),
1336 SSH_KEY_BITS_RESERVED);
1338 if (rsa_private_decrypt(session_key_int, session_key_int,
1339 sensitive_data.ssh1_host_key->rsa) < 0)
1341 if (rsa_private_decrypt(session_key_int, session_key_int,
1342 sensitive_data.server_key->rsa) < 0)
1346 * Extract session key from the decrypted integer. The key is in the
1347 * least significant 256 bits of the integer; the first byte of the
1348 * key is in the highest bits.
1351 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1352 len = BN_num_bytes(session_key_int);
1353 if (len < 0 || len > sizeof(session_key)) {
1354 error("do_connection: bad session key len from %s: "
1355 "session_key_int %d > sizeof(session_key) %lu",
1356 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
1359 memset(session_key, 0, sizeof(session_key));
1360 BN_bn2bin(session_key_int,
1361 session_key + sizeof(session_key) - len);
1363 compute_session_id(session_id, cookie,
1364 sensitive_data.ssh1_host_key->rsa->n,
1365 sensitive_data.server_key->rsa->n);
1367 * Xor the first 16 bytes of the session key with the
1370 for (i = 0; i < 16; i++)
1371 session_key[i] ^= session_id[i];
1375 int bytes = BN_num_bytes(session_key_int);
1376 char *buf = xmalloc(bytes);
1379 log("do_connection: generating a fake encryption key");
1380 BN_bn2bin(session_key_int, buf);
1382 MD5_Update(&md, buf, bytes);
1383 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1384 MD5_Final(session_key, &md);
1386 MD5_Update(&md, session_key, 16);
1387 MD5_Update(&md, buf, bytes);
1388 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1389 MD5_Final(session_key + 16, &md);
1390 memset(buf, 0, bytes);
1392 for (i = 0; i < 16; i++)
1393 session_id[i] = session_key[i] ^ session_key[i + 16];
1395 /* Destroy the private and public keys. They will no longer be needed. */
1396 destroy_sensitive_data();
1398 /* Destroy the decrypted integer. It is no longer needed. */
1399 BN_clear_free(session_key_int);
1401 /* Set the session key. From this on all communications will be encrypted. */
1402 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1404 /* Destroy our copy of the session key. It is no longer needed. */
1405 memset(session_key, 0, sizeof(session_key));
1407 debug("Received session key; encryption turned on.");
1409 /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1410 packet_start(SSH_SMSG_SUCCESS);
1412 packet_write_wait();
1416 * SSH2 key exchange: diffie-hellman-group1-sha1
1423 if (options.ciphers != NULL) {
1424 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1425 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1427 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1428 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
1429 myproposal[PROPOSAL_ENC_ALGS_STOC] =
1430 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
1432 if (options.macs != NULL) {
1433 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
1434 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
1436 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
1438 /* start key exchange */
1439 kex = kex_setup(myproposal);
1441 kex->client_version_string=client_version_string;
1442 kex->server_version_string=server_version_string;
1443 kex->load_host_key=&get_hostkey_by_type;
1447 dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
1449 session_id2 = kex->session_id;
1450 session_id2_len = kex->session_id_len;
1453 /* send 1st encrypted/maced/compressed message */
1454 packet_start(SSH2_MSG_IGNORE);
1455 packet_put_cstring("markus");
1457 packet_write_wait();