1 /* $OpenBSD: sshd.c,v 1.333 2006/07/06 16:03:53 stevesk Exp $ */
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 * This program is the ssh daemon. It listens for connections from clients,
7 * and performs authentication, executes use commands or shell, and forwards
8 * information to/from the application to the user client over an encrypted
9 * connection. This can also handle forwarding of X11, TCP/IP, and
10 * authentication agent connections.
12 * As far as I am concerned, the code I have written for this software
13 * can be used freely for any purpose. Any derived versions of this
14 * software must be clearly marked as such, and if the derived work is
15 * incompatible with the protocol description in the RFC file, it must be
16 * called by a name other than "ssh" or "Secure Shell".
18 * SSH2 implementation:
19 * Privilege Separation:
21 * Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved.
22 * Copyright (c) 2002 Niels Provos. All rights reserved.
24 * Redistribution and use in source and binary forms, with or without
25 * modification, are permitted provided that the following conditions
27 * 1. Redistributions of source code must retain the above copyright
28 * notice, this list of conditions and the following disclaimer.
29 * 2. Redistributions in binary form must reproduce the above copyright
30 * notice, this list of conditions and the following disclaimer in the
31 * documentation and/or other materials provided with the distribution.
33 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
34 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
35 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
36 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
37 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
38 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
39 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
40 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
41 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
42 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
47 #include <sys/types.h>
48 #ifdef HAVE_SYS_STAT_H
49 # include <sys/stat.h>
51 #include <sys/ioctl.h>
60 #include <openssl/dh.h>
61 #include <openssl/bn.h>
62 #include <openssl/md5.h>
63 #include <openssl/rand.h>
64 #ifdef HAVE_SECUREWARE
65 #include <sys/security.h>
86 #include "myproposal.h"
88 #include "pathnames.h"
97 #include "monitor_mm.h"
99 #include "monitor_wrap.h"
100 #include "monitor_fdpass.h"
106 int allow_severity = LOG_INFO;
107 int deny_severity = LOG_WARNING;
115 #define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1)
116 #define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2)
117 #define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3)
118 #define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4)
120 extern char *__progname;
122 /* Server configuration options. */
123 ServerOptions options;
125 /* Name of the server configuration file. */
126 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
129 * Debug mode flag. This can be set on the command line. If debug
130 * mode is enabled, extra debugging output will be sent to the system
131 * log, the daemon will not go to background, and will exit after processing
132 * the first connection.
136 /* Flag indicating that the daemon should only test the configuration and keys. */
139 /* Flag indicating that the daemon is being started from inetd. */
142 /* Flag indicating that sshd should not detach and become a daemon. */
143 int no_daemon_flag = 0;
145 /* debug goes to stderr unless inetd_flag is set */
148 /* Saved arguments to main(). */
153 int rexeced_flag = 0;
159 * The sockets that the server is listening; this is used in the SIGHUP
162 #define MAX_LISTEN_SOCKS 16
163 int listen_socks[MAX_LISTEN_SOCKS];
164 int num_listen_socks = 0;
167 * the client's version string, passed by sshd2 in compat mode. if != NULL,
168 * sshd will skip the version-number exchange
170 char *client_version_string = NULL;
171 char *server_version_string = NULL;
173 /* for rekeying XXX fixme */
177 * Any really sensitive data in the application is contained in this
178 * structure. The idea is that this structure could be locked into memory so
179 * that the pages do not get written into swap. However, there are some
180 * problems. The private key contains BIGNUMs, and we do not (in principle)
181 * have access to the internals of them, and locking just the structure is
182 * not very useful. Currently, memory locking is not implemented.
185 Key *server_key; /* ephemeral server key */
186 Key *ssh1_host_key; /* ssh1 host key */
187 Key **host_keys; /* all private host keys */
190 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
194 * Flag indicating whether the RSA server key needs to be regenerated.
195 * Is set in the SIGALRM handler and cleared when the key is regenerated.
197 static volatile sig_atomic_t key_do_regen = 0;
199 /* This is set to true when a signal is received. */
200 static volatile sig_atomic_t received_sighup = 0;
201 static volatile sig_atomic_t received_sigterm = 0;
203 /* session identifier, used by RSA-auth */
204 u_char session_id[16];
207 u_char *session_id2 = NULL;
208 u_int session_id2_len = 0;
210 /* record remote hostname or ip */
211 u_int utmp_len = MAXHOSTNAMELEN;
213 /* options.max_startup sized array of fd ints */
214 int *startup_pipes = NULL;
215 int startup_pipe; /* in child */
217 /* variables used for privilege separation */
219 struct monitor *pmonitor = NULL;
221 /* global authentication context */
222 Authctxt *the_authctxt = NULL;
224 /* message to be displayed after login */
227 /* Prototypes for various functions defined later in this file. */
228 void destroy_sensitive_data(void);
229 void demote_sensitive_data(void);
231 static void do_ssh1_kex(void);
232 static void do_ssh2_kex(void);
235 * Close all listening sockets
238 close_listen_socks(void)
242 for (i = 0; i < num_listen_socks; i++)
243 close(listen_socks[i]);
244 num_listen_socks = -1;
248 close_startup_pipes(void)
253 for (i = 0; i < options.max_startups; i++)
254 if (startup_pipes[i] != -1)
255 close(startup_pipes[i]);
259 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
260 * the effect is to reread the configuration file (and to regenerate
266 sighup_handler(int sig)
268 int save_errno = errno;
271 signal(SIGHUP, sighup_handler);
276 * Called from the main program after receiving SIGHUP.
277 * Restarts the server.
282 logit("Received SIGHUP; restarting.");
283 close_listen_socks();
284 close_startup_pipes();
285 execv(saved_argv[0], saved_argv);
286 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
292 * Generic signal handler for terminating signals in the master daemon.
296 sigterm_handler(int sig)
298 received_sigterm = sig;
302 * SIGCHLD handler. This is called whenever a child dies. This will then
303 * reap any zombies left by exited children.
307 main_sigchld_handler(int sig)
309 int save_errno = errno;
313 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
314 (pid < 0 && errno == EINTR))
317 signal(SIGCHLD, main_sigchld_handler);
322 * Signal handler for the alarm after the login grace period has expired.
326 grace_alarm_handler(int sig)
328 /* XXX no idea how fix this signal handler */
330 if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0)
331 kill(pmonitor->m_pid, SIGALRM);
333 /* Log error and exit. */
334 fatal("Timeout before authentication for %s", get_remote_ipaddr());
338 * Signal handler for the key regeneration alarm. Note that this
339 * alarm only occurs in the daemon waiting for connections, and it does not
340 * do anything with the private key or random state before forking.
341 * Thus there should be no concurrency control/asynchronous execution
345 generate_ephemeral_server_key(void)
350 verbose("Generating %s%d bit RSA key.",
351 sensitive_data.server_key ? "new " : "", options.server_key_bits);
352 if (sensitive_data.server_key != NULL)
353 key_free(sensitive_data.server_key);
354 sensitive_data.server_key = key_generate(KEY_RSA1,
355 options.server_key_bits);
356 verbose("RSA key generation complete.");
358 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
361 sensitive_data.ssh1_cookie[i] = rnd & 0xff;
369 key_regeneration_alarm(int sig)
371 int save_errno = errno;
373 signal(SIGALRM, SIG_DFL);
379 sshd_exchange_identification(int sock_in, int sock_out)
383 int remote_major, remote_minor;
386 char buf[256]; /* Must not be larger than remote_version. */
387 char remote_version[256]; /* Must be at least as big as buf. */
389 if ((options.protocol & SSH_PROTO_1) &&
390 (options.protocol & SSH_PROTO_2)) {
391 major = PROTOCOL_MAJOR_1;
393 } else if (options.protocol & SSH_PROTO_2) {
394 major = PROTOCOL_MAJOR_2;
395 minor = PROTOCOL_MINOR_2;
397 major = PROTOCOL_MAJOR_1;
398 minor = PROTOCOL_MINOR_1;
400 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
401 server_version_string = xstrdup(buf);
403 /* Send our protocol version identification. */
404 if (atomicio(vwrite, sock_out, server_version_string,
405 strlen(server_version_string))
406 != strlen(server_version_string)) {
407 logit("Could not write ident string to %s", get_remote_ipaddr());
411 /* Read other sides version identification. */
412 memset(buf, 0, sizeof(buf));
413 for (i = 0; i < sizeof(buf) - 1; i++) {
414 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
415 logit("Did not receive identification string from %s",
416 get_remote_ipaddr());
419 if (buf[i] == '\r') {
421 /* Kludge for F-Secure Macintosh < 1.0.2 */
423 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
427 if (buf[i] == '\n') {
432 buf[sizeof(buf) - 1] = 0;
433 client_version_string = xstrdup(buf);
436 * Check that the versions match. In future this might accept
437 * several versions and set appropriate flags to handle them.
439 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
440 &remote_major, &remote_minor, remote_version) != 3) {
441 s = "Protocol mismatch.\n";
442 (void) atomicio(vwrite, sock_out, s, strlen(s));
445 logit("Bad protocol version identification '%.100s' from %s",
446 client_version_string, get_remote_ipaddr());
449 debug("Client protocol version %d.%d; client software version %.100s",
450 remote_major, remote_minor, remote_version);
452 compat_datafellows(remote_version);
454 if (datafellows & SSH_BUG_PROBE) {
455 logit("probed from %s with %s. Don't panic.",
456 get_remote_ipaddr(), client_version_string);
460 if (datafellows & SSH_BUG_SCANNER) {
461 logit("scanned from %s with %s. Don't panic.",
462 get_remote_ipaddr(), client_version_string);
467 switch (remote_major) {
469 if (remote_minor == 99) {
470 if (options.protocol & SSH_PROTO_2)
476 if (!(options.protocol & SSH_PROTO_1)) {
480 if (remote_minor < 3) {
481 packet_disconnect("Your ssh version is too old and "
482 "is no longer supported. Please install a newer version.");
483 } else if (remote_minor == 3) {
484 /* note that this disables agent-forwarding */
489 if (options.protocol & SSH_PROTO_2) {
498 chop(server_version_string);
499 debug("Local version string %.200s", server_version_string);
502 s = "Protocol major versions differ.\n";
503 (void) atomicio(vwrite, sock_out, s, strlen(s));
506 logit("Protocol major versions differ for %s: %.200s vs. %.200s",
508 server_version_string, client_version_string);
513 /* Destroy the host and server keys. They will no longer be needed. */
515 destroy_sensitive_data(void)
519 if (sensitive_data.server_key) {
520 key_free(sensitive_data.server_key);
521 sensitive_data.server_key = NULL;
523 for (i = 0; i < options.num_host_key_files; i++) {
524 if (sensitive_data.host_keys[i]) {
525 key_free(sensitive_data.host_keys[i]);
526 sensitive_data.host_keys[i] = NULL;
529 sensitive_data.ssh1_host_key = NULL;
530 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
533 /* Demote private to public keys for network child */
535 demote_sensitive_data(void)
540 if (sensitive_data.server_key) {
541 tmp = key_demote(sensitive_data.server_key);
542 key_free(sensitive_data.server_key);
543 sensitive_data.server_key = tmp;
546 for (i = 0; i < options.num_host_key_files; i++) {
547 if (sensitive_data.host_keys[i]) {
548 tmp = key_demote(sensitive_data.host_keys[i]);
549 key_free(sensitive_data.host_keys[i]);
550 sensitive_data.host_keys[i] = tmp;
551 if (tmp->type == KEY_RSA1)
552 sensitive_data.ssh1_host_key = tmp;
556 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */
560 privsep_preauth_child(void)
567 /* Enable challenge-response authentication for privilege separation */
568 privsep_challenge_enable();
570 for (i = 0; i < 256; i++)
571 rnd[i] = arc4random();
572 RAND_seed(rnd, sizeof(rnd));
574 /* Demote the private keys to public keys. */
575 demote_sensitive_data();
577 if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
578 fatal("Privilege separation user %s does not exist",
580 memset(pw->pw_passwd, 0, strlen(pw->pw_passwd));
583 /* Change our root directory */
584 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
585 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
587 if (chdir("/") == -1)
588 fatal("chdir(\"/\"): %s", strerror(errno));
590 /* Drop our privileges */
591 debug3("privsep user:group %u:%u", (u_int)pw->pw_uid,
594 /* XXX not ready, too heavy after chroot */
595 do_setusercontext(pw);
597 gidset[0] = pw->pw_gid;
598 if (setgroups(1, gidset) < 0)
599 fatal("setgroups: %.100s", strerror(errno));
600 permanently_set_uid(pw);
605 privsep_preauth(Authctxt *authctxt)
610 /* Set up unprivileged child process to deal with network data */
611 pmonitor = monitor_init();
612 /* Store a pointer to the kex for later rekeying */
613 pmonitor->m_pkex = &xxx_kex;
617 fatal("fork of unprivileged child failed");
618 } else if (pid != 0) {
619 debug2("Network child is on pid %ld", (long)pid);
621 close(pmonitor->m_recvfd);
622 pmonitor->m_pid = pid;
623 monitor_child_preauth(authctxt, pmonitor);
624 close(pmonitor->m_sendfd);
627 monitor_sync(pmonitor);
629 /* Wait for the child's exit status */
630 while (waitpid(pid, &status, 0) < 0)
637 close(pmonitor->m_sendfd);
639 /* Demote the child */
640 if (getuid() == 0 || geteuid() == 0)
641 privsep_preauth_child();
642 setproctitle("%s", "[net]");
648 privsep_postauth(Authctxt *authctxt)
650 #ifdef DISABLE_FD_PASSING
653 if (authctxt->pw->pw_uid == 0 || options.use_login) {
655 /* File descriptor passing is broken or root login */
660 /* New socket pair */
661 monitor_reinit(pmonitor);
663 pmonitor->m_pid = fork();
664 if (pmonitor->m_pid == -1)
665 fatal("fork of unprivileged child failed");
666 else if (pmonitor->m_pid != 0) {
667 debug2("User child is on pid %ld", (long)pmonitor->m_pid);
668 close(pmonitor->m_recvfd);
669 buffer_clear(&loginmsg);
670 monitor_child_postauth(pmonitor);
676 close(pmonitor->m_sendfd);
678 /* Demote the private keys to public keys. */
679 demote_sensitive_data();
681 /* Drop privileges */
682 do_setusercontext(authctxt->pw);
685 /* It is safe now to apply the key state */
686 monitor_apply_keystate(pmonitor);
689 * Tell the packet layer that authentication was successful, since
690 * this information is not part of the key state.
692 packet_set_authenticated();
696 list_hostkey_types(void)
704 for (i = 0; i < options.num_host_key_files; i++) {
705 Key *key = sensitive_data.host_keys[i];
711 if (buffer_len(&b) > 0)
712 buffer_append(&b, ",", 1);
713 p = key_ssh_name(key);
714 buffer_append(&b, p, strlen(p));
718 buffer_append(&b, "\0", 1);
719 ret = xstrdup(buffer_ptr(&b));
721 debug("list_hostkey_types: %s", ret);
726 get_hostkey_by_type(int type)
730 for (i = 0; i < options.num_host_key_files; i++) {
731 Key *key = sensitive_data.host_keys[i];
732 if (key != NULL && key->type == type)
739 get_hostkey_by_index(int ind)
741 if (ind < 0 || ind >= options.num_host_key_files)
743 return (sensitive_data.host_keys[ind]);
747 get_hostkey_index(Key *key)
751 for (i = 0; i < options.num_host_key_files; i++) {
752 if (key == sensitive_data.host_keys[i])
759 * returns 1 if connection should be dropped, 0 otherwise.
760 * dropping starts at connection #max_startups_begin with a probability
761 * of (max_startups_rate/100). the probability increases linearly until
762 * all connections are dropped for startups > max_startups
765 drop_connection(int startups)
769 if (startups < options.max_startups_begin)
771 if (startups >= options.max_startups)
773 if (options.max_startups_rate == 100)
776 p = 100 - options.max_startups_rate;
777 p *= startups - options.max_startups_begin;
778 p /= options.max_startups - options.max_startups_begin;
779 p += options.max_startups_rate;
780 r = arc4random() % 100;
782 debug("drop_connection: p %d, r %d", p, r);
783 return (r < p) ? 1 : 0;
789 fprintf(stderr, "%s, %s\n",
790 SSH_RELEASE, SSLeay_version(SSLEAY_VERSION));
792 "usage: sshd [-46Ddeiqt] [-b bits] [-f config_file] [-g login_grace_time]\n"
793 " [-h host_key_file] [-k key_gen_time] [-o option] [-p port] [-u len]\n"
799 send_rexec_state(int fd, Buffer *conf)
803 debug3("%s: entering fd = %d config len %d", __func__, fd,
807 * Protocol from reexec master to child:
808 * string configuration
809 * u_int ephemeral_key_follows
810 * bignum e (only if ephemeral_key_follows == 1)
816 * string rngseed (only if OpenSSL is not self-seeded)
819 buffer_put_cstring(&m, buffer_ptr(conf));
821 if (sensitive_data.server_key != NULL &&
822 sensitive_data.server_key->type == KEY_RSA1) {
823 buffer_put_int(&m, 1);
824 buffer_put_bignum(&m, sensitive_data.server_key->rsa->e);
825 buffer_put_bignum(&m, sensitive_data.server_key->rsa->n);
826 buffer_put_bignum(&m, sensitive_data.server_key->rsa->d);
827 buffer_put_bignum(&m, sensitive_data.server_key->rsa->iqmp);
828 buffer_put_bignum(&m, sensitive_data.server_key->rsa->p);
829 buffer_put_bignum(&m, sensitive_data.server_key->rsa->q);
831 buffer_put_int(&m, 0);
833 #ifndef OPENSSL_PRNG_ONLY
834 rexec_send_rng_seed(&m);
837 if (ssh_msg_send(fd, 0, &m) == -1)
838 fatal("%s: ssh_msg_send failed", __func__);
842 debug3("%s: done", __func__);
846 recv_rexec_state(int fd, Buffer *conf)
852 debug3("%s: entering fd = %d", __func__, fd);
856 if (ssh_msg_recv(fd, &m) == -1)
857 fatal("%s: ssh_msg_recv failed", __func__);
858 if (buffer_get_char(&m) != 0)
859 fatal("%s: rexec version mismatch", __func__);
861 cp = buffer_get_string(&m, &len);
863 buffer_append(conf, cp, len + 1);
866 if (buffer_get_int(&m)) {
867 if (sensitive_data.server_key != NULL)
868 key_free(sensitive_data.server_key);
869 sensitive_data.server_key = key_new_private(KEY_RSA1);
870 buffer_get_bignum(&m, sensitive_data.server_key->rsa->e);
871 buffer_get_bignum(&m, sensitive_data.server_key->rsa->n);
872 buffer_get_bignum(&m, sensitive_data.server_key->rsa->d);
873 buffer_get_bignum(&m, sensitive_data.server_key->rsa->iqmp);
874 buffer_get_bignum(&m, sensitive_data.server_key->rsa->p);
875 buffer_get_bignum(&m, sensitive_data.server_key->rsa->q);
876 rsa_generate_additional_parameters(
877 sensitive_data.server_key->rsa);
880 #ifndef OPENSSL_PRNG_ONLY
881 rexec_recv_rng_seed(&m);
886 debug3("%s: done", __func__);
890 * Main program for the daemon.
893 main(int ac, char **av)
897 int opt, j, i, on = 1;
898 int sock_in = -1, sock_out = -1, newsock = -1;
902 struct sockaddr_storage from;
903 const char *remote_ip;
907 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
909 int listen_sock, maxfd;
910 int startup_p[2] = { -1 , -1 }, config_s[2] = { -1 , -1 };
914 int ret, key_used = 0;
917 #ifdef HAVE_SECUREWARE
918 (void)set_auth_parameters(ac, av);
920 __progname = ssh_get_progname(av[0]);
923 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
926 saved_argv = xcalloc(ac + 1, sizeof(*saved_argv));
927 for (i = 0; i < ac; i++)
928 saved_argv[i] = xstrdup(av[i]);
929 saved_argv[i] = NULL;
931 #ifndef HAVE_SETPROCTITLE
932 /* Prepare for later setproctitle emulation */
933 compat_init_setproctitle(ac, av);
937 if (geteuid() == 0 && setgroups(0, NULL) == -1)
938 debug("setgroups(): %.200s", strerror(errno));
940 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
943 /* Initialize configuration options to their default values. */
944 initialize_server_options(&options);
946 /* Parse command-line arguments. */
947 while ((opt = getopt(ac, av, "f:p:b:k:h:g:u:o:dDeiqrtQR46")) != -1) {
950 options.address_family = AF_INET;
953 options.address_family = AF_INET6;
956 config_file_name = optarg;
959 if (debug_flag == 0) {
961 options.log_level = SYSLOG_LEVEL_DEBUG1;
962 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
985 options.log_level = SYSLOG_LEVEL_QUIET;
988 options.server_key_bits = (int)strtonum(optarg, 256,
992 options.ports_from_cmdline = 1;
993 if (options.num_ports >= MAX_PORTS) {
994 fprintf(stderr, "too many ports.\n");
997 options.ports[options.num_ports++] = a2port(optarg);
998 if (options.ports[options.num_ports-1] == 0) {
999 fprintf(stderr, "Bad port number.\n");
1004 if ((options.login_grace_time = convtime(optarg)) == -1) {
1005 fprintf(stderr, "Invalid login grace time.\n");
1010 if ((options.key_regeneration_time = convtime(optarg)) == -1) {
1011 fprintf(stderr, "Invalid key regeneration interval.\n");
1016 if (options.num_host_key_files >= MAX_HOSTKEYS) {
1017 fprintf(stderr, "too many host keys.\n");
1020 options.host_key_files[options.num_host_key_files++] = optarg;
1026 utmp_len = (u_int)strtonum(optarg, 0, MAXHOSTNAMELEN+1, NULL);
1027 if (utmp_len > MAXHOSTNAMELEN) {
1028 fprintf(stderr, "Invalid utmp length.\n");
1033 line = xstrdup(optarg);
1034 if (process_server_config_line(&options, line,
1035 "command-line", 0) != 0)
1045 if (rexeced_flag || inetd_flag)
1047 if (rexec_flag && (av[0] == NULL || *av[0] != '/'))
1048 fatal("sshd re-exec requires execution with an absolute path");
1050 closefrom(REEXEC_MIN_FREE_FD);
1052 closefrom(REEXEC_DEVCRYPTO_RESERVED_FD);
1054 SSLeay_add_all_algorithms();
1057 * Force logging to stderr until we have loaded the private host
1058 * key (unless started from inetd)
1060 log_init(__progname,
1061 options.log_level == SYSLOG_LEVEL_NOT_SET ?
1062 SYSLOG_LEVEL_INFO : options.log_level,
1063 options.log_facility == SYSLOG_FACILITY_NOT_SET ?
1064 SYSLOG_FACILITY_AUTH : options.log_facility,
1065 log_stderr || !inetd_flag);
1068 * Unset KRB5CCNAME, otherwise the user's session may inherit it from
1069 * root's environment
1071 if (getenv("KRB5CCNAME") != NULL)
1072 unsetenv("KRB5CCNAME");
1075 /* Cray can define user privs drop all privs now!
1076 * Not needed on PRIV_SU systems!
1081 sensitive_data.server_key = NULL;
1082 sensitive_data.ssh1_host_key = NULL;
1083 sensitive_data.have_ssh1_key = 0;
1084 sensitive_data.have_ssh2_key = 0;
1086 /* Fetch our configuration */
1089 recv_rexec_state(REEXEC_CONFIG_PASS_FD, &cfg);
1091 load_server_config(config_file_name, &cfg);
1093 parse_server_config(&options,
1094 rexeced_flag ? "rexec" : config_file_name, &cfg);
1101 /* Fill in default values for those options not explicitly set. */
1102 fill_default_server_options(&options);
1104 /* set default channel AF */
1105 channel_set_af(options.address_family);
1107 /* Check that there are no remaining arguments. */
1109 fprintf(stderr, "Extra argument %s.\n", av[optind]);
1113 debug("sshd version %.100s", SSH_RELEASE);
1115 /* load private host keys */
1116 sensitive_data.host_keys = xcalloc(options.num_host_key_files,
1118 for (i = 0; i < options.num_host_key_files; i++)
1119 sensitive_data.host_keys[i] = NULL;
1121 for (i = 0; i < options.num_host_key_files; i++) {
1122 key = key_load_private(options.host_key_files[i], "", NULL);
1123 sensitive_data.host_keys[i] = key;
1125 error("Could not load host key: %s",
1126 options.host_key_files[i]);
1127 sensitive_data.host_keys[i] = NULL;
1130 switch (key->type) {
1132 sensitive_data.ssh1_host_key = key;
1133 sensitive_data.have_ssh1_key = 1;
1137 sensitive_data.have_ssh2_key = 1;
1140 debug("private host key: #%d type %d %s", i, key->type,
1143 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
1144 logit("Disabling protocol version 1. Could not load host key");
1145 options.protocol &= ~SSH_PROTO_1;
1147 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
1148 logit("Disabling protocol version 2. Could not load host key");
1149 options.protocol &= ~SSH_PROTO_2;
1151 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
1152 logit("sshd: no hostkeys available -- exiting.");
1156 /* Check certain values for sanity. */
1157 if (options.protocol & SSH_PROTO_1) {
1158 if (options.server_key_bits < 512 ||
1159 options.server_key_bits > 32768) {
1160 fprintf(stderr, "Bad server key size.\n");
1164 * Check that server and host key lengths differ sufficiently. This
1165 * is necessary to make double encryption work with rsaref. Oh, I
1166 * hate software patents. I dont know if this can go? Niels
1168 if (options.server_key_bits >
1169 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) -
1170 SSH_KEY_BITS_RESERVED && options.server_key_bits <
1171 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1172 SSH_KEY_BITS_RESERVED) {
1173 options.server_key_bits =
1174 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1175 SSH_KEY_BITS_RESERVED;
1176 debug("Forcing server key to %d bits to make it differ from host key.",
1177 options.server_key_bits);
1184 if (getpwnam(SSH_PRIVSEP_USER) == NULL)
1185 fatal("Privilege separation user %s does not exist",
1187 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) ||
1188 (S_ISDIR(st.st_mode) == 0))
1189 fatal("Missing privilege separation directory: %s",
1190 _PATH_PRIVSEP_CHROOT_DIR);
1193 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
1194 (st.st_uid != getuid () ||
1195 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0))
1197 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)
1199 fatal("%s must be owned by root and not group or "
1200 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR);
1203 /* Configuration looks good, so exit if in test mode. */
1208 * Clear out any supplemental groups we may have inherited. This
1209 * prevents inadvertent creation of files with bad modes (in the
1210 * portable version at least, it's certainly possible for PAM
1211 * to create a file, and we can't control the code in every
1212 * module which might be used).
1214 if (setgroups(0, NULL) < 0)
1215 debug("setgroups() failed: %.200s", strerror(errno));
1218 rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *));
1219 for (i = 0; i < rexec_argc; i++) {
1220 debug("rexec_argv[%d]='%s'", i, saved_argv[i]);
1221 rexec_argv[i] = saved_argv[i];
1223 rexec_argv[rexec_argc] = "-R";
1224 rexec_argv[rexec_argc + 1] = NULL;
1227 /* Initialize the log (it is reinitialized below in case we forked). */
1228 if (debug_flag && (!inetd_flag || rexeced_flag))
1230 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1233 * If not in debugging mode, and not started from inetd, disconnect
1234 * from the controlling terminal, and fork. The original process
1237 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
1240 #endif /* TIOCNOTTY */
1241 if (daemon(0, 0) < 0)
1242 fatal("daemon() failed: %.200s", strerror(errno));
1244 /* Disconnect from the controlling tty. */
1246 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
1248 (void) ioctl(fd, TIOCNOTTY, NULL);
1251 #endif /* TIOCNOTTY */
1253 /* Reinitialize the log (because of the fork above). */
1254 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1256 /* Initialize the random number generator. */
1259 /* Chdir to the root directory so that the current disk can be
1260 unmounted if desired. */
1263 /* ignore SIGPIPE */
1264 signal(SIGPIPE, SIG_IGN);
1266 /* Start listening for a socket, unless started from inetd. */
1272 close(REEXEC_CONFIG_PASS_FD);
1273 sock_in = sock_out = dup(STDIN_FILENO);
1275 startup_pipe = dup(REEXEC_STARTUP_PIPE_FD);
1276 close(REEXEC_STARTUP_PIPE_FD);
1279 sock_in = dup(STDIN_FILENO);
1280 sock_out = dup(STDOUT_FILENO);
1283 * We intentionally do not close the descriptors 0, 1, and 2
1284 * as our code for setting the descriptors won't work if
1285 * ttyfd happens to be one of those.
1287 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
1288 dup2(fd, STDIN_FILENO);
1289 dup2(fd, STDOUT_FILENO);
1290 if (fd > STDOUT_FILENO)
1293 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
1294 if ((options.protocol & SSH_PROTO_1) &&
1295 sensitive_data.server_key == NULL)
1296 generate_ephemeral_server_key();
1298 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
1299 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
1301 if (num_listen_socks >= MAX_LISTEN_SOCKS)
1302 fatal("Too many listen sockets. "
1303 "Enlarge MAX_LISTEN_SOCKS");
1304 if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen,
1305 ntop, sizeof(ntop), strport, sizeof(strport),
1306 NI_NUMERICHOST|NI_NUMERICSERV)) != 0) {
1307 error("getnameinfo failed: %.100s",
1308 (ret != EAI_SYSTEM) ? gai_strerror(ret) :
1312 /* Create socket for listening. */
1313 listen_sock = socket(ai->ai_family, ai->ai_socktype,
1315 if (listen_sock < 0) {
1316 /* kernel may not support ipv6 */
1317 verbose("socket: %.100s", strerror(errno));
1320 if (set_nonblock(listen_sock) == -1) {
1325 * Set socket options.
1326 * Allow local port reuse in TIME_WAIT.
1328 if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
1329 &on, sizeof(on)) == -1)
1330 error("setsockopt SO_REUSEADDR: %s", strerror(errno));
1332 debug("Bind to port %s on %s.", strport, ntop);
1334 /* Bind the socket to the desired port. */
1335 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1337 error("Bind to port %s on %s failed: %.200s.",
1338 strport, ntop, strerror(errno));
1342 listen_socks[num_listen_socks] = listen_sock;
1345 /* Start listening on the port. */
1346 if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0)
1347 fatal("listen on [%s]:%s: %.100s",
1348 ntop, strport, strerror(errno));
1349 logit("Server listening on %s port %s.", ntop, strport);
1351 freeaddrinfo(options.listen_addrs);
1353 if (!num_listen_socks)
1354 fatal("Cannot bind any address.");
1356 if (options.protocol & SSH_PROTO_1)
1357 generate_ephemeral_server_key();
1360 * Arrange to restart on SIGHUP. The handler needs
1363 signal(SIGHUP, sighup_handler);
1365 signal(SIGTERM, sigterm_handler);
1366 signal(SIGQUIT, sigterm_handler);
1368 /* Arrange SIGCHLD to be caught. */
1369 signal(SIGCHLD, main_sigchld_handler);
1371 /* Write out the pid file after the sigterm handler is setup */
1374 * Record our pid in /var/run/sshd.pid to make it
1375 * easier to kill the correct sshd. We don't want to
1376 * do this before the bind above because the bind will
1377 * fail if there already is a daemon, and this will
1378 * overwrite any old pid in the file.
1380 f = fopen(options.pid_file, "wb");
1382 error("Couldn't create pid file \"%s\": %s",
1383 options.pid_file, strerror(errno));
1385 fprintf(f, "%ld\n", (long) getpid());
1390 /* setup fd set for listen */
1393 for (i = 0; i < num_listen_socks; i++)
1394 if (listen_socks[i] > maxfd)
1395 maxfd = listen_socks[i];
1396 /* pipes connected to unauthenticated childs */
1397 startup_pipes = xcalloc(options.max_startups, sizeof(int));
1398 for (i = 0; i < options.max_startups; i++)
1399 startup_pipes[i] = -1;
1402 * Stay listening for connections until the system crashes or
1403 * the daemon is killed with a signal.
1406 if (received_sighup)
1410 fdset = (fd_set *)xcalloc(howmany(maxfd + 1, NFDBITS),
1413 for (i = 0; i < num_listen_socks; i++)
1414 FD_SET(listen_socks[i], fdset);
1415 for (i = 0; i < options.max_startups; i++)
1416 if (startup_pipes[i] != -1)
1417 FD_SET(startup_pipes[i], fdset);
1419 /* Wait in select until there is a connection. */
1420 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
1421 if (ret < 0 && errno != EINTR)
1422 error("select: %.100s", strerror(errno));
1423 if (received_sigterm) {
1424 logit("Received signal %d; terminating.",
1425 (int) received_sigterm);
1426 close_listen_socks();
1427 unlink(options.pid_file);
1430 if (key_used && key_do_regen) {
1431 generate_ephemeral_server_key();
1438 for (i = 0; i < options.max_startups; i++)
1439 if (startup_pipes[i] != -1 &&
1440 FD_ISSET(startup_pipes[i], fdset)) {
1442 * the read end of the pipe is ready
1443 * if the child has closed the pipe
1444 * after successful authentication
1445 * or if the child has died
1447 close(startup_pipes[i]);
1448 startup_pipes[i] = -1;
1451 for (i = 0; i < num_listen_socks; i++) {
1452 if (!FD_ISSET(listen_socks[i], fdset))
1454 fromlen = sizeof(from);
1455 newsock = accept(listen_socks[i],
1456 (struct sockaddr *)&from, &fromlen);
1458 if (errno != EINTR && errno != EWOULDBLOCK)
1459 error("accept: %.100s", strerror(errno));
1462 if (unset_nonblock(newsock) == -1) {
1466 if (drop_connection(startups) == 1) {
1467 debug("drop connection #%d", startups);
1471 if (pipe(startup_p) == -1) {
1476 if (rexec_flag && socketpair(AF_UNIX,
1477 SOCK_STREAM, 0, config_s) == -1) {
1478 error("reexec socketpair: %s",
1481 close(startup_p[0]);
1482 close(startup_p[1]);
1486 for (j = 0; j < options.max_startups; j++)
1487 if (startup_pipes[j] == -1) {
1488 startup_pipes[j] = startup_p[0];
1489 if (maxfd < startup_p[0])
1490 maxfd = startup_p[0];
1496 * Got connection. Fork a child to handle it, unless
1497 * we are in debugging mode.
1501 * In debugging mode. Close the listening
1502 * socket, and start processing the
1503 * connection without forking.
1505 debug("Server will not fork when running in debugging mode.");
1506 close_listen_socks();
1509 close(startup_p[0]);
1510 close(startup_p[1]);
1514 send_rexec_state(config_s[0],
1521 * Normal production daemon. Fork, and have
1522 * the child process the connection. The
1523 * parent continues listening.
1525 if ((pid = fork()) == 0) {
1527 * Child. Close the listening and
1528 * max_startup sockets. Start using
1529 * the accepted socket. Reinitialize
1530 * logging (since our pid has changed).
1531 * We break out of the loop to handle
1534 startup_pipe = startup_p[1];
1535 close_startup_pipes();
1536 close_listen_socks();
1539 log_init(__progname,
1541 options.log_facility,
1549 /* Parent. Stay in the loop. */
1551 error("fork: %.100s", strerror(errno));
1553 debug("Forked child %ld.", (long)pid);
1555 close(startup_p[1]);
1558 send_rexec_state(config_s[0], &cfg);
1564 * Mark that the key has been used (it
1565 * was "given" to the child).
1567 if ((options.protocol & SSH_PROTO_1) &&
1569 /* Schedule server key regeneration alarm. */
1570 signal(SIGALRM, key_regeneration_alarm);
1571 alarm(options.key_regeneration_time);
1578 /* child process check (or debug mode) */
1579 if (num_listen_socks < 0)
1584 /* This is the child processing a new connection. */
1585 setproctitle("%s", "[accepted]");
1588 * Create a new session and process group since the 4.4BSD
1589 * setlogin() affects the entire process group. We don't
1590 * want the child to be able to affect the parent.
1592 #if !defined(SSHD_ACQUIRES_CTTY)
1594 * If setsid is called, on some platforms sshd will later acquire a
1595 * controlling terminal which will result in "could not set
1596 * controlling tty" errors.
1598 if (!debug_flag && !inetd_flag && setsid() < 0)
1599 error("setsid: %.100s", strerror(errno));
1605 debug("rexec start in %d out %d newsock %d pipe %d sock %d",
1606 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
1607 dup2(newsock, STDIN_FILENO);
1608 dup2(STDIN_FILENO, STDOUT_FILENO);
1609 if (startup_pipe == -1)
1610 close(REEXEC_STARTUP_PIPE_FD);
1612 dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD);
1614 dup2(config_s[1], REEXEC_CONFIG_PASS_FD);
1616 if (startup_pipe != -1)
1617 close(startup_pipe);
1619 execv(rexec_argv[0], rexec_argv);
1621 /* Reexec has failed, fall back and continue */
1622 error("rexec of %s failed: %s", rexec_argv[0], strerror(errno));
1623 recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL);
1624 log_init(__progname, options.log_level,
1625 options.log_facility, log_stderr);
1628 startup_pipe = REEXEC_STARTUP_PIPE_FD;
1630 close(REEXEC_CONFIG_PASS_FD);
1631 newsock = sock_out = sock_in = dup(STDIN_FILENO);
1632 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
1633 dup2(fd, STDIN_FILENO);
1634 dup2(fd, STDOUT_FILENO);
1635 if (fd > STDERR_FILENO)
1638 debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d",
1639 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
1643 * Disable the key regeneration alarm. We will not regenerate the
1644 * key since we are no longer in a position to give it to anyone. We
1645 * will not restart on SIGHUP since it no longer makes sense.
1648 signal(SIGALRM, SIG_DFL);
1649 signal(SIGHUP, SIG_DFL);
1650 signal(SIGTERM, SIG_DFL);
1651 signal(SIGQUIT, SIG_DFL);
1652 signal(SIGCHLD, SIG_DFL);
1653 signal(SIGINT, SIG_DFL);
1656 * Register our connection. This turns encryption off because we do
1659 packet_set_connection(sock_in, sock_out);
1660 packet_set_server();
1662 /* Set SO_KEEPALIVE if requested. */
1663 if (options.tcp_keep_alive && packet_connection_is_on_socket() &&
1664 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) < 0)
1665 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1667 if ((remote_port = get_remote_port()) < 0) {
1668 debug("get_remote_port failed");
1673 * We use get_canonical_hostname with usedns = 0 instead of
1674 * get_remote_ipaddr here so IP options will be checked.
1676 (void) get_canonical_hostname(0);
1678 * The rest of the code depends on the fact that
1679 * get_remote_ipaddr() caches the remote ip, even if
1680 * the socket goes away.
1682 remote_ip = get_remote_ipaddr();
1684 #ifdef SSH_AUDIT_EVENTS
1685 audit_connection_from(remote_ip, remote_port);
1688 /* Check whether logins are denied from this host. */
1689 if (packet_connection_is_on_socket()) {
1690 struct request_info req;
1692 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
1695 if (!hosts_access(&req)) {
1696 debug("Connection refused by tcp wrapper");
1699 fatal("libwrap refuse returns");
1702 #endif /* LIBWRAP */
1704 /* Log the connection. */
1705 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1708 * We don't want to listen forever unless the other side
1709 * successfully authenticates itself. So we set up an alarm which is
1710 * cleared after successful authentication. A limit of zero
1711 * indicates no limit. Note that we don't set the alarm in debugging
1712 * mode; it is just annoying to have the server exit just when you
1713 * are about to discover the bug.
1715 signal(SIGALRM, grace_alarm_handler);
1717 alarm(options.login_grace_time);
1719 sshd_exchange_identification(sock_in, sock_out);
1721 packet_set_nonblocking();
1723 /* allocate authentication context */
1724 authctxt = xcalloc(1, sizeof(*authctxt));
1726 authctxt->loginmsg = &loginmsg;
1728 /* XXX global for cleanup, access from other modules */
1729 the_authctxt = authctxt;
1731 /* prepare buffer to collect messages to display to user after login */
1732 buffer_init(&loginmsg);
1735 if (privsep_preauth(authctxt) == 1)
1738 /* perform the key exchange */
1739 /* authenticate user and start session */
1742 do_authentication2(authctxt);
1745 do_authentication(authctxt);
1748 * If we use privilege separation, the unprivileged child transfers
1749 * the current keystate and exits
1752 mm_send_keystate(pmonitor);
1758 * Cancel the alarm we set to limit the time taken for
1762 signal(SIGALRM, SIG_DFL);
1763 if (startup_pipe != -1) {
1764 close(startup_pipe);
1768 #ifdef SSH_AUDIT_EVENTS
1769 audit_event(SSH_AUTH_SUCCESS);
1773 * In privilege separation, we fork another child and prepare
1774 * file descriptor passing.
1777 privsep_postauth(authctxt);
1778 /* the monitor process [priv] will not return */
1780 destroy_sensitive_data();
1783 /* Start session. */
1784 do_authenticated(authctxt);
1786 /* The connection has been terminated. */
1787 verbose("Closing connection to %.100s", remote_ip);
1790 if (options.use_pam)
1792 #endif /* USE_PAM */
1794 #ifdef SSH_AUDIT_EVENTS
1795 PRIVSEP(audit_event(SSH_CONNECTION_CLOSE));
1807 * Decrypt session_key_int using our private server key and private host key
1808 * (key with larger modulus first).
1811 ssh1_session_key(BIGNUM *session_key_int)
1815 if (BN_cmp(sensitive_data.server_key->rsa->n,
1816 sensitive_data.ssh1_host_key->rsa->n) > 0) {
1817 /* Server key has bigger modulus. */
1818 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1819 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1820 SSH_KEY_BITS_RESERVED) {
1821 fatal("do_connection: %s: "
1822 "server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1823 get_remote_ipaddr(),
1824 BN_num_bits(sensitive_data.server_key->rsa->n),
1825 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1826 SSH_KEY_BITS_RESERVED);
1828 if (rsa_private_decrypt(session_key_int, session_key_int,
1829 sensitive_data.server_key->rsa) <= 0)
1831 if (rsa_private_decrypt(session_key_int, session_key_int,
1832 sensitive_data.ssh1_host_key->rsa) <= 0)
1835 /* Host key has bigger modulus (or they are equal). */
1836 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1837 BN_num_bits(sensitive_data.server_key->rsa->n) +
1838 SSH_KEY_BITS_RESERVED) {
1839 fatal("do_connection: %s: "
1840 "host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1841 get_remote_ipaddr(),
1842 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1843 BN_num_bits(sensitive_data.server_key->rsa->n),
1844 SSH_KEY_BITS_RESERVED);
1846 if (rsa_private_decrypt(session_key_int, session_key_int,
1847 sensitive_data.ssh1_host_key->rsa) < 0)
1849 if (rsa_private_decrypt(session_key_int, session_key_int,
1850 sensitive_data.server_key->rsa) < 0)
1863 BIGNUM *session_key_int;
1864 u_char session_key[SSH_SESSION_KEY_LENGTH];
1866 u_int cipher_type, auth_mask, protocol_flags;
1870 * Generate check bytes that the client must send back in the user
1871 * packet in order for it to be accepted; this is used to defy ip
1872 * spoofing attacks. Note that this only works against somebody
1873 * doing IP spoofing from a remote machine; any machine on the local
1874 * network can still see outgoing packets and catch the random
1875 * cookie. This only affects rhosts authentication, and this is one
1876 * of the reasons why it is inherently insecure.
1878 for (i = 0; i < 8; i++) {
1881 cookie[i] = rnd & 0xff;
1886 * Send our public key. We include in the packet 64 bits of random
1887 * data that must be matched in the reply in order to prevent IP
1890 packet_start(SSH_SMSG_PUBLIC_KEY);
1891 for (i = 0; i < 8; i++)
1892 packet_put_char(cookie[i]);
1894 /* Store our public server RSA key. */
1895 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1896 packet_put_bignum(sensitive_data.server_key->rsa->e);
1897 packet_put_bignum(sensitive_data.server_key->rsa->n);
1899 /* Store our public host RSA key. */
1900 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1901 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1902 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1904 /* Put protocol flags. */
1905 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1907 /* Declare which ciphers we support. */
1908 packet_put_int(cipher_mask_ssh1(0));
1910 /* Declare supported authentication types. */
1912 if (options.rhosts_rsa_authentication)
1913 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1914 if (options.rsa_authentication)
1915 auth_mask |= 1 << SSH_AUTH_RSA;
1916 if (options.challenge_response_authentication == 1)
1917 auth_mask |= 1 << SSH_AUTH_TIS;
1918 if (options.password_authentication)
1919 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1920 packet_put_int(auth_mask);
1922 /* Send the packet and wait for it to be sent. */
1924 packet_write_wait();
1926 debug("Sent %d bit server key and %d bit host key.",
1927 BN_num_bits(sensitive_data.server_key->rsa->n),
1928 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1930 /* Read clients reply (cipher type and session key). */
1931 packet_read_expect(SSH_CMSG_SESSION_KEY);
1933 /* Get cipher type and check whether we accept this. */
1934 cipher_type = packet_get_char();
1936 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1937 packet_disconnect("Warning: client selects unsupported cipher.");
1939 /* Get check bytes from the packet. These must match those we
1940 sent earlier with the public key packet. */
1941 for (i = 0; i < 8; i++)
1942 if (cookie[i] != packet_get_char())
1943 packet_disconnect("IP Spoofing check bytes do not match.");
1945 debug("Encryption type: %.200s", cipher_name(cipher_type));
1947 /* Get the encrypted integer. */
1948 if ((session_key_int = BN_new()) == NULL)
1949 fatal("do_ssh1_kex: BN_new failed");
1950 packet_get_bignum(session_key_int);
1952 protocol_flags = packet_get_int();
1953 packet_set_protocol_flags(protocol_flags);
1956 /* Decrypt session_key_int using host/server keys */
1957 rsafail = PRIVSEP(ssh1_session_key(session_key_int));
1960 * Extract session key from the decrypted integer. The key is in the
1961 * least significant 256 bits of the integer; the first byte of the
1962 * key is in the highest bits.
1965 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1966 len = BN_num_bytes(session_key_int);
1967 if (len < 0 || (u_int)len > sizeof(session_key)) {
1968 error("do_connection: bad session key len from %s: "
1969 "session_key_int %d > sizeof(session_key) %lu",
1970 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
1973 memset(session_key, 0, sizeof(session_key));
1974 BN_bn2bin(session_key_int,
1975 session_key + sizeof(session_key) - len);
1977 derive_ssh1_session_id(
1978 sensitive_data.ssh1_host_key->rsa->n,
1979 sensitive_data.server_key->rsa->n,
1980 cookie, session_id);
1982 * Xor the first 16 bytes of the session key with the
1985 for (i = 0; i < 16; i++)
1986 session_key[i] ^= session_id[i];
1990 int bytes = BN_num_bytes(session_key_int);
1991 u_char *buf = xmalloc(bytes);
1994 logit("do_connection: generating a fake encryption key");
1995 BN_bn2bin(session_key_int, buf);
1997 MD5_Update(&md, buf, bytes);
1998 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1999 MD5_Final(session_key, &md);
2001 MD5_Update(&md, session_key, 16);
2002 MD5_Update(&md, buf, bytes);
2003 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
2004 MD5_Final(session_key + 16, &md);
2005 memset(buf, 0, bytes);
2007 for (i = 0; i < 16; i++)
2008 session_id[i] = session_key[i] ^ session_key[i + 16];
2010 /* Destroy the private and public keys. No longer. */
2011 destroy_sensitive_data();
2014 mm_ssh1_session_id(session_id);
2016 /* Destroy the decrypted integer. It is no longer needed. */
2017 BN_clear_free(session_key_int);
2019 /* Set the session key. From this on all communications will be encrypted. */
2020 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
2022 /* Destroy our copy of the session key. It is no longer needed. */
2023 memset(session_key, 0, sizeof(session_key));
2025 debug("Received session key; encryption turned on.");
2027 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */
2028 packet_start(SSH_SMSG_SUCCESS);
2030 packet_write_wait();
2034 * SSH2 key exchange: diffie-hellman-group1-sha1
2041 if (options.ciphers != NULL) {
2042 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2043 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
2045 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2046 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
2047 myproposal[PROPOSAL_ENC_ALGS_STOC] =
2048 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
2050 if (options.macs != NULL) {
2051 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
2052 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
2054 if (options.compression == COMP_NONE) {
2055 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2056 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
2057 } else if (options.compression == COMP_DELAYED) {
2058 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2059 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com";
2062 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
2064 /* start key exchange */
2065 kex = kex_setup(myproposal);
2066 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
2067 kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
2068 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
2069 kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
2071 kex->client_version_string=client_version_string;
2072 kex->server_version_string=server_version_string;
2073 kex->load_host_key=&get_hostkey_by_type;
2074 kex->host_key_index=&get_hostkey_index;
2078 dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
2080 session_id2 = kex->session_id;
2081 session_id2_len = kex->session_id_len;
2084 /* send 1st encrypted/maced/compressed message */
2085 packet_start(SSH2_MSG_IGNORE);
2086 packet_put_cstring("markus");
2088 packet_write_wait();
2093 /* server specific fatal cleanup */
2098 do_cleanup(the_authctxt);
2099 #ifdef SSH_AUDIT_EVENTS
2100 /* done after do_cleanup so it can cancel the PAM auth 'thread' */
2101 if (!use_privsep || mm_is_monitor())
2102 audit_event(SSH_CONNECTION_ABANDON);