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:
18 * Privilege Separation:
20 * Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved.
21 * Copyright (c) 2002 Niels Provos. All rights reserved.
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
26 * 1. Redistributions of source code must retain the above copyright
27 * notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 * notice, this list of conditions and the following disclaimer in the
30 * documentation and/or other materials provided with the distribution.
32 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
33 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
34 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
35 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
36 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
37 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
38 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
39 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
40 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
41 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
45 RCSID("$OpenBSD: sshd.c,v 1.323 2006/02/20 17:19:54 stevesk Exp $");
47 #include <sys/types.h>
48 #ifdef HAVE_SYS_STAT_H
49 # include <sys/stat.h>
51 #include <sys/ioctl.h>
57 #include <openssl/dh.h>
58 #include <openssl/bn.h>
59 #include <openssl/md5.h>
60 #include <openssl/rand.h>
61 #ifdef HAVE_SECUREWARE
62 #include <sys/security.h>
83 #include "myproposal.h"
85 #include "pathnames.h"
94 #include "monitor_mm.h"
96 #include "monitor_wrap.h"
97 #include "monitor_fdpass.h"
102 int allow_severity = LOG_INFO;
103 int deny_severity = LOG_WARNING;
111 #define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1)
112 #define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2)
113 #define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3)
114 #define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4)
116 extern char *__progname;
118 /* Server configuration options. */
119 ServerOptions options;
121 /* Name of the server configuration file. */
122 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
125 * Debug mode flag. This can be set on the command line. If debug
126 * mode is enabled, extra debugging output will be sent to the system
127 * log, the daemon will not go to background, and will exit after processing
128 * the first connection.
132 /* Flag indicating that the daemon should only test the configuration and keys. */
135 /* Flag indicating that the daemon is being started from inetd. */
138 /* Flag indicating that sshd should not detach and become a daemon. */
139 int no_daemon_flag = 0;
141 /* debug goes to stderr unless inetd_flag is set */
144 /* Saved arguments to main(). */
149 int rexeced_flag = 0;
155 * The sockets that the server is listening; this is used in the SIGHUP
158 #define MAX_LISTEN_SOCKS 16
159 int listen_socks[MAX_LISTEN_SOCKS];
160 int num_listen_socks = 0;
163 * the client's version string, passed by sshd2 in compat mode. if != NULL,
164 * sshd will skip the version-number exchange
166 char *client_version_string = NULL;
167 char *server_version_string = NULL;
169 /* for rekeying XXX fixme */
173 * Any really sensitive data in the application is contained in this
174 * structure. The idea is that this structure could be locked into memory so
175 * that the pages do not get written into swap. However, there are some
176 * problems. The private key contains BIGNUMs, and we do not (in principle)
177 * have access to the internals of them, and locking just the structure is
178 * not very useful. Currently, memory locking is not implemented.
181 Key *server_key; /* ephemeral server key */
182 Key *ssh1_host_key; /* ssh1 host key */
183 Key **host_keys; /* all private host keys */
186 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
190 * Flag indicating whether the RSA server key needs to be regenerated.
191 * Is set in the SIGALRM handler and cleared when the key is regenerated.
193 static volatile sig_atomic_t key_do_regen = 0;
195 /* This is set to true when a signal is received. */
196 static volatile sig_atomic_t received_sighup = 0;
197 static volatile sig_atomic_t received_sigterm = 0;
199 /* session identifier, used by RSA-auth */
200 u_char session_id[16];
203 u_char *session_id2 = NULL;
204 u_int session_id2_len = 0;
206 /* record remote hostname or ip */
207 u_int utmp_len = MAXHOSTNAMELEN;
209 /* options.max_startup sized array of fd ints */
210 int *startup_pipes = NULL;
211 int startup_pipe; /* in child */
213 /* variables used for privilege separation */
215 struct monitor *pmonitor = NULL;
217 /* global authentication context */
218 Authctxt *the_authctxt = NULL;
220 /* message to be displayed after login */
223 /* Prototypes for various functions defined later in this file. */
224 void destroy_sensitive_data(void);
225 void demote_sensitive_data(void);
227 static void do_ssh1_kex(void);
228 static void do_ssh2_kex(void);
231 * Close all listening sockets
234 close_listen_socks(void)
238 for (i = 0; i < num_listen_socks; i++)
239 close(listen_socks[i]);
240 num_listen_socks = -1;
244 close_startup_pipes(void)
249 for (i = 0; i < options.max_startups; i++)
250 if (startup_pipes[i] != -1)
251 close(startup_pipes[i]);
255 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
256 * the effect is to reread the configuration file (and to regenerate
260 sighup_handler(int sig)
262 int save_errno = errno;
265 signal(SIGHUP, sighup_handler);
270 * Called from the main program after receiving SIGHUP.
271 * Restarts the server.
276 logit("Received SIGHUP; restarting.");
277 close_listen_socks();
278 close_startup_pipes();
279 execv(saved_argv[0], saved_argv);
280 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
286 * Generic signal handler for terminating signals in the master daemon.
289 sigterm_handler(int sig)
291 received_sigterm = sig;
295 * SIGCHLD handler. This is called whenever a child dies. This will then
296 * reap any zombies left by exited children.
299 main_sigchld_handler(int sig)
301 int save_errno = errno;
305 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
306 (pid < 0 && errno == EINTR))
309 signal(SIGCHLD, main_sigchld_handler);
314 * Signal handler for the alarm after the login grace period has expired.
317 grace_alarm_handler(int sig)
319 /* XXX no idea how fix this signal handler */
321 if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0)
322 kill(pmonitor->m_pid, SIGALRM);
324 /* Log error and exit. */
325 fatal("Timeout before authentication for %s", get_remote_ipaddr());
329 * Signal handler for the key regeneration alarm. Note that this
330 * alarm only occurs in the daemon waiting for connections, and it does not
331 * do anything with the private key or random state before forking.
332 * Thus there should be no concurrency control/asynchronous execution
336 generate_ephemeral_server_key(void)
341 verbose("Generating %s%d bit RSA key.",
342 sensitive_data.server_key ? "new " : "", options.server_key_bits);
343 if (sensitive_data.server_key != NULL)
344 key_free(sensitive_data.server_key);
345 sensitive_data.server_key = key_generate(KEY_RSA1,
346 options.server_key_bits);
347 verbose("RSA key generation complete.");
349 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
352 sensitive_data.ssh1_cookie[i] = rnd & 0xff;
359 key_regeneration_alarm(int sig)
361 int save_errno = errno;
363 signal(SIGALRM, SIG_DFL);
369 sshd_exchange_identification(int sock_in, int sock_out)
373 int remote_major, remote_minor;
376 char buf[256]; /* Must not be larger than remote_version. */
377 char remote_version[256]; /* Must be at least as big as buf. */
379 if ((options.protocol & SSH_PROTO_1) &&
380 (options.protocol & SSH_PROTO_2)) {
381 major = PROTOCOL_MAJOR_1;
383 } else if (options.protocol & SSH_PROTO_2) {
384 major = PROTOCOL_MAJOR_2;
385 minor = PROTOCOL_MINOR_2;
387 major = PROTOCOL_MAJOR_1;
388 minor = PROTOCOL_MINOR_1;
390 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
391 server_version_string = xstrdup(buf);
393 /* Send our protocol version identification. */
394 if (atomicio(vwrite, sock_out, server_version_string,
395 strlen(server_version_string))
396 != strlen(server_version_string)) {
397 logit("Could not write ident string to %s", get_remote_ipaddr());
401 /* Read other sides version identification. */
402 memset(buf, 0, sizeof(buf));
403 for (i = 0; i < sizeof(buf) - 1; i++) {
404 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
405 logit("Did not receive identification string from %s",
406 get_remote_ipaddr());
409 if (buf[i] == '\r') {
411 /* Kludge for F-Secure Macintosh < 1.0.2 */
413 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
417 if (buf[i] == '\n') {
422 buf[sizeof(buf) - 1] = 0;
423 client_version_string = xstrdup(buf);
426 * Check that the versions match. In future this might accept
427 * several versions and set appropriate flags to handle them.
429 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
430 &remote_major, &remote_minor, remote_version) != 3) {
431 s = "Protocol mismatch.\n";
432 (void) atomicio(vwrite, sock_out, s, strlen(s));
435 logit("Bad protocol version identification '%.100s' from %s",
436 client_version_string, get_remote_ipaddr());
439 debug("Client protocol version %d.%d; client software version %.100s",
440 remote_major, remote_minor, remote_version);
442 compat_datafellows(remote_version);
444 if (datafellows & SSH_BUG_PROBE) {
445 logit("probed from %s with %s. Don't panic.",
446 get_remote_ipaddr(), client_version_string);
450 if (datafellows & SSH_BUG_SCANNER) {
451 logit("scanned from %s with %s. Don't panic.",
452 get_remote_ipaddr(), client_version_string);
457 switch (remote_major) {
459 if (remote_minor == 99) {
460 if (options.protocol & SSH_PROTO_2)
466 if (!(options.protocol & SSH_PROTO_1)) {
470 if (remote_minor < 3) {
471 packet_disconnect("Your ssh version is too old and "
472 "is no longer supported. Please install a newer version.");
473 } else if (remote_minor == 3) {
474 /* note that this disables agent-forwarding */
479 if (options.protocol & SSH_PROTO_2) {
488 chop(server_version_string);
489 debug("Local version string %.200s", server_version_string);
492 s = "Protocol major versions differ.\n";
493 (void) atomicio(vwrite, sock_out, s, strlen(s));
496 logit("Protocol major versions differ for %s: %.200s vs. %.200s",
498 server_version_string, client_version_string);
503 /* Destroy the host and server keys. They will no longer be needed. */
505 destroy_sensitive_data(void)
509 if (sensitive_data.server_key) {
510 key_free(sensitive_data.server_key);
511 sensitive_data.server_key = NULL;
513 for (i = 0; i < options.num_host_key_files; i++) {
514 if (sensitive_data.host_keys[i]) {
515 key_free(sensitive_data.host_keys[i]);
516 sensitive_data.host_keys[i] = NULL;
519 sensitive_data.ssh1_host_key = NULL;
520 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
523 /* Demote private to public keys for network child */
525 demote_sensitive_data(void)
530 if (sensitive_data.server_key) {
531 tmp = key_demote(sensitive_data.server_key);
532 key_free(sensitive_data.server_key);
533 sensitive_data.server_key = tmp;
536 for (i = 0; i < options.num_host_key_files; i++) {
537 if (sensitive_data.host_keys[i]) {
538 tmp = key_demote(sensitive_data.host_keys[i]);
539 key_free(sensitive_data.host_keys[i]);
540 sensitive_data.host_keys[i] = tmp;
541 if (tmp->type == KEY_RSA1)
542 sensitive_data.ssh1_host_key = tmp;
546 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */
550 privsep_preauth_child(void)
557 /* Enable challenge-response authentication for privilege separation */
558 privsep_challenge_enable();
560 for (i = 0; i < 256; i++)
561 rnd[i] = arc4random();
562 RAND_seed(rnd, sizeof(rnd));
564 /* Demote the private keys to public keys. */
565 demote_sensitive_data();
567 if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
568 fatal("Privilege separation user %s does not exist",
570 memset(pw->pw_passwd, 0, strlen(pw->pw_passwd));
573 /* Change our root directory */
574 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
575 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
577 if (chdir("/") == -1)
578 fatal("chdir(\"/\"): %s", strerror(errno));
580 /* Drop our privileges */
581 debug3("privsep user:group %u:%u", (u_int)pw->pw_uid,
584 /* XXX not ready, too heavy after chroot */
585 do_setusercontext(pw);
587 gidset[0] = pw->pw_gid;
588 if (setgroups(1, gidset) < 0)
589 fatal("setgroups: %.100s", strerror(errno));
590 permanently_set_uid(pw);
595 privsep_preauth(Authctxt *authctxt)
600 /* Set up unprivileged child process to deal with network data */
601 pmonitor = monitor_init();
602 /* Store a pointer to the kex for later rekeying */
603 pmonitor->m_pkex = &xxx_kex;
607 fatal("fork of unprivileged child failed");
608 } else if (pid != 0) {
609 debug2("Network child is on pid %ld", (long)pid);
611 close(pmonitor->m_recvfd);
612 pmonitor->m_pid = pid;
613 monitor_child_preauth(authctxt, pmonitor);
614 close(pmonitor->m_sendfd);
617 monitor_sync(pmonitor);
619 /* Wait for the child's exit status */
620 while (waitpid(pid, &status, 0) < 0)
627 close(pmonitor->m_sendfd);
629 /* Demote the child */
630 if (getuid() == 0 || geteuid() == 0)
631 privsep_preauth_child();
632 setproctitle("%s", "[net]");
638 privsep_postauth(Authctxt *authctxt)
640 #ifdef DISABLE_FD_PASSING
643 if (authctxt->pw->pw_uid == 0 || options.use_login) {
645 /* File descriptor passing is broken or root login */
650 /* New socket pair */
651 monitor_reinit(pmonitor);
653 pmonitor->m_pid = fork();
654 if (pmonitor->m_pid == -1)
655 fatal("fork of unprivileged child failed");
656 else if (pmonitor->m_pid != 0) {
657 debug2("User child is on pid %ld", (long)pmonitor->m_pid);
658 close(pmonitor->m_recvfd);
659 buffer_clear(&loginmsg);
660 monitor_child_postauth(pmonitor);
666 close(pmonitor->m_sendfd);
668 /* Demote the private keys to public keys. */
669 demote_sensitive_data();
671 /* Drop privileges */
672 do_setusercontext(authctxt->pw);
675 /* It is safe now to apply the key state */
676 monitor_apply_keystate(pmonitor);
679 * Tell the packet layer that authentication was successful, since
680 * this information is not part of the key state.
682 packet_set_authenticated();
686 list_hostkey_types(void)
694 for (i = 0; i < options.num_host_key_files; i++) {
695 Key *key = sensitive_data.host_keys[i];
701 if (buffer_len(&b) > 0)
702 buffer_append(&b, ",", 1);
703 p = key_ssh_name(key);
704 buffer_append(&b, p, strlen(p));
708 buffer_append(&b, "\0", 1);
709 ret = xstrdup(buffer_ptr(&b));
711 debug("list_hostkey_types: %s", ret);
716 get_hostkey_by_type(int type)
720 for (i = 0; i < options.num_host_key_files; i++) {
721 Key *key = sensitive_data.host_keys[i];
722 if (key != NULL && key->type == type)
729 get_hostkey_by_index(int ind)
731 if (ind < 0 || ind >= options.num_host_key_files)
733 return (sensitive_data.host_keys[ind]);
737 get_hostkey_index(Key *key)
741 for (i = 0; i < options.num_host_key_files; i++) {
742 if (key == sensitive_data.host_keys[i])
749 * returns 1 if connection should be dropped, 0 otherwise.
750 * dropping starts at connection #max_startups_begin with a probability
751 * of (max_startups_rate/100). the probability increases linearly until
752 * all connections are dropped for startups > max_startups
755 drop_connection(int startups)
759 if (startups < options.max_startups_begin)
761 if (startups >= options.max_startups)
763 if (options.max_startups_rate == 100)
766 p = 100 - options.max_startups_rate;
767 p *= startups - options.max_startups_begin;
768 p /= options.max_startups - options.max_startups_begin;
769 p += options.max_startups_rate;
770 r = arc4random() % 100;
772 debug("drop_connection: p %d, r %d", p, r);
773 return (r < p) ? 1 : 0;
779 fprintf(stderr, "%s, %s\n",
780 SSH_RELEASE, SSLeay_version(SSLEAY_VERSION));
782 "usage: sshd [-46Ddeiqt] [-b bits] [-f config_file] [-g login_grace_time]\n"
783 " [-h host_key_file] [-k key_gen_time] [-o option] [-p port] [-u len]\n"
789 send_rexec_state(int fd, Buffer *conf)
793 debug3("%s: entering fd = %d config len %d", __func__, fd,
797 * Protocol from reexec master to child:
798 * string configuration
799 * u_int ephemeral_key_follows
800 * bignum e (only if ephemeral_key_follows == 1)
806 * string rngseed (only if OpenSSL is not self-seeded)
809 buffer_put_cstring(&m, buffer_ptr(conf));
811 if (sensitive_data.server_key != NULL &&
812 sensitive_data.server_key->type == KEY_RSA1) {
813 buffer_put_int(&m, 1);
814 buffer_put_bignum(&m, sensitive_data.server_key->rsa->e);
815 buffer_put_bignum(&m, sensitive_data.server_key->rsa->n);
816 buffer_put_bignum(&m, sensitive_data.server_key->rsa->d);
817 buffer_put_bignum(&m, sensitive_data.server_key->rsa->iqmp);
818 buffer_put_bignum(&m, sensitive_data.server_key->rsa->p);
819 buffer_put_bignum(&m, sensitive_data.server_key->rsa->q);
821 buffer_put_int(&m, 0);
823 #ifndef OPENSSL_PRNG_ONLY
824 rexec_send_rng_seed(&m);
827 if (ssh_msg_send(fd, 0, &m) == -1)
828 fatal("%s: ssh_msg_send failed", __func__);
832 debug3("%s: done", __func__);
836 recv_rexec_state(int fd, Buffer *conf)
842 debug3("%s: entering fd = %d", __func__, fd);
846 if (ssh_msg_recv(fd, &m) == -1)
847 fatal("%s: ssh_msg_recv failed", __func__);
848 if (buffer_get_char(&m) != 0)
849 fatal("%s: rexec version mismatch", __func__);
851 cp = buffer_get_string(&m, &len);
853 buffer_append(conf, cp, len + 1);
856 if (buffer_get_int(&m)) {
857 if (sensitive_data.server_key != NULL)
858 key_free(sensitive_data.server_key);
859 sensitive_data.server_key = key_new_private(KEY_RSA1);
860 buffer_get_bignum(&m, sensitive_data.server_key->rsa->e);
861 buffer_get_bignum(&m, sensitive_data.server_key->rsa->n);
862 buffer_get_bignum(&m, sensitive_data.server_key->rsa->d);
863 buffer_get_bignum(&m, sensitive_data.server_key->rsa->iqmp);
864 buffer_get_bignum(&m, sensitive_data.server_key->rsa->p);
865 buffer_get_bignum(&m, sensitive_data.server_key->rsa->q);
866 rsa_generate_additional_parameters(
867 sensitive_data.server_key->rsa);
870 #ifndef OPENSSL_PRNG_ONLY
871 rexec_recv_rng_seed(&m);
876 debug3("%s: done", __func__);
880 * Main program for the daemon.
883 main(int ac, char **av)
887 int opt, j, i, fdsetsz, on = 1;
888 int sock_in = -1, sock_out = -1, newsock = -1;
892 struct sockaddr_storage from;
893 const char *remote_ip;
897 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
899 int listen_sock, maxfd;
900 int startup_p[2] = { -1 , -1 }, config_s[2] = { -1 , -1 };
904 int ret, key_used = 0;
907 #ifdef HAVE_SECUREWARE
908 (void)set_auth_parameters(ac, av);
910 __progname = ssh_get_progname(av[0]);
913 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
916 saved_argv = xmalloc(sizeof(*saved_argv) * (ac + 1));
917 for (i = 0; i < ac; i++)
918 saved_argv[i] = xstrdup(av[i]);
919 saved_argv[i] = NULL;
921 #ifndef HAVE_SETPROCTITLE
922 /* Prepare for later setproctitle emulation */
923 compat_init_setproctitle(ac, av);
927 if (geteuid() == 0 && setgroups(0, NULL) == -1)
928 debug("setgroups(): %.200s", strerror(errno));
930 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
933 /* Initialize configuration options to their default values. */
934 initialize_server_options(&options);
936 /* Parse command-line arguments. */
937 while ((opt = getopt(ac, av, "f:p:b:k:h:g:u:o:dDeiqrtQR46")) != -1) {
940 options.address_family = AF_INET;
943 options.address_family = AF_INET6;
946 config_file_name = optarg;
949 if (debug_flag == 0) {
951 options.log_level = SYSLOG_LEVEL_DEBUG1;
952 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
975 options.log_level = SYSLOG_LEVEL_QUIET;
978 options.server_key_bits = atoi(optarg);
981 options.ports_from_cmdline = 1;
982 if (options.num_ports >= MAX_PORTS) {
983 fprintf(stderr, "too many ports.\n");
986 options.ports[options.num_ports++] = a2port(optarg);
987 if (options.ports[options.num_ports-1] == 0) {
988 fprintf(stderr, "Bad port number.\n");
993 if ((options.login_grace_time = convtime(optarg)) == -1) {
994 fprintf(stderr, "Invalid login grace time.\n");
999 if ((options.key_regeneration_time = convtime(optarg)) == -1) {
1000 fprintf(stderr, "Invalid key regeneration interval.\n");
1005 if (options.num_host_key_files >= MAX_HOSTKEYS) {
1006 fprintf(stderr, "too many host keys.\n");
1009 options.host_key_files[options.num_host_key_files++] = optarg;
1015 utmp_len = atoi(optarg);
1016 if (utmp_len > MAXHOSTNAMELEN) {
1017 fprintf(stderr, "Invalid utmp length.\n");
1022 line = xstrdup(optarg);
1023 if (process_server_config_line(&options, line,
1024 "command-line", 0) != 0)
1034 if (rexeced_flag || inetd_flag)
1036 if (rexec_flag && (av[0] == NULL || *av[0] != '/'))
1037 fatal("sshd re-exec requires execution with an absolute path");
1039 closefrom(REEXEC_MIN_FREE_FD);
1041 closefrom(REEXEC_DEVCRYPTO_RESERVED_FD);
1043 SSLeay_add_all_algorithms();
1046 * Force logging to stderr until we have loaded the private host
1047 * key (unless started from inetd)
1049 log_init(__progname,
1050 options.log_level == SYSLOG_LEVEL_NOT_SET ?
1051 SYSLOG_LEVEL_INFO : options.log_level,
1052 options.log_facility == SYSLOG_FACILITY_NOT_SET ?
1053 SYSLOG_FACILITY_AUTH : options.log_facility,
1054 log_stderr || !inetd_flag);
1057 * Unset KRB5CCNAME, otherwise the user's session may inherit it from
1058 * root's environment
1060 if (getenv("KRB5CCNAME") != NULL)
1061 unsetenv("KRB5CCNAME");
1064 /* Cray can define user privs drop all privs now!
1065 * Not needed on PRIV_SU systems!
1070 sensitive_data.server_key = NULL;
1071 sensitive_data.ssh1_host_key = NULL;
1072 sensitive_data.have_ssh1_key = 0;
1073 sensitive_data.have_ssh2_key = 0;
1075 /* Fetch our configuration */
1078 recv_rexec_state(REEXEC_CONFIG_PASS_FD, &cfg);
1080 load_server_config(config_file_name, &cfg);
1082 parse_server_config(&options,
1083 rexeced_flag ? "rexec" : config_file_name, &cfg);
1090 /* Fill in default values for those options not explicitly set. */
1091 fill_default_server_options(&options);
1093 /* set default channel AF */
1094 channel_set_af(options.address_family);
1096 /* Check that there are no remaining arguments. */
1098 fprintf(stderr, "Extra argument %s.\n", av[optind]);
1102 debug("sshd version %.100s", SSH_RELEASE);
1104 /* load private host keys */
1105 sensitive_data.host_keys = xmalloc(options.num_host_key_files *
1107 for (i = 0; i < options.num_host_key_files; i++)
1108 sensitive_data.host_keys[i] = NULL;
1110 for (i = 0; i < options.num_host_key_files; i++) {
1111 key = key_load_private(options.host_key_files[i], "", NULL);
1112 sensitive_data.host_keys[i] = key;
1114 error("Could not load host key: %s",
1115 options.host_key_files[i]);
1116 sensitive_data.host_keys[i] = NULL;
1119 switch (key->type) {
1121 sensitive_data.ssh1_host_key = key;
1122 sensitive_data.have_ssh1_key = 1;
1126 sensitive_data.have_ssh2_key = 1;
1129 debug("private host key: #%d type %d %s", i, key->type,
1132 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
1133 logit("Disabling protocol version 1. Could not load host key");
1134 options.protocol &= ~SSH_PROTO_1;
1136 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
1137 logit("Disabling protocol version 2. Could not load host key");
1138 options.protocol &= ~SSH_PROTO_2;
1140 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
1141 logit("sshd: no hostkeys available -- exiting.");
1145 /* Check certain values for sanity. */
1146 if (options.protocol & SSH_PROTO_1) {
1147 if (options.server_key_bits < 512 ||
1148 options.server_key_bits > 32768) {
1149 fprintf(stderr, "Bad server key size.\n");
1153 * Check that server and host key lengths differ sufficiently. This
1154 * is necessary to make double encryption work with rsaref. Oh, I
1155 * hate software patents. I dont know if this can go? Niels
1157 if (options.server_key_bits >
1158 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) -
1159 SSH_KEY_BITS_RESERVED && options.server_key_bits <
1160 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1161 SSH_KEY_BITS_RESERVED) {
1162 options.server_key_bits =
1163 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1164 SSH_KEY_BITS_RESERVED;
1165 debug("Forcing server key to %d bits to make it differ from host key.",
1166 options.server_key_bits);
1174 if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
1175 fatal("Privilege separation user %s does not exist",
1177 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) ||
1178 (S_ISDIR(st.st_mode) == 0))
1179 fatal("Missing privilege separation directory: %s",
1180 _PATH_PRIVSEP_CHROOT_DIR);
1183 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
1184 (st.st_uid != getuid () ||
1185 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0))
1187 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)
1189 fatal("%s must be owned by root and not group or "
1190 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR);
1193 /* Configuration looks good, so exit if in test mode. */
1198 * Clear out any supplemental groups we may have inherited. This
1199 * prevents inadvertent creation of files with bad modes (in the
1200 * portable version at least, it's certainly possible for PAM
1201 * to create a file, and we can't control the code in every
1202 * module which might be used).
1204 if (setgroups(0, NULL) < 0)
1205 debug("setgroups() failed: %.200s", strerror(errno));
1208 rexec_argv = xmalloc(sizeof(char *) * (rexec_argc + 2));
1209 for (i = 0; i < rexec_argc; i++) {
1210 debug("rexec_argv[%d]='%s'", i, saved_argv[i]);
1211 rexec_argv[i] = saved_argv[i];
1213 rexec_argv[rexec_argc] = "-R";
1214 rexec_argv[rexec_argc + 1] = NULL;
1217 /* Initialize the log (it is reinitialized below in case we forked). */
1218 if (debug_flag && (!inetd_flag || rexeced_flag))
1220 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1223 * If not in debugging mode, and not started from inetd, disconnect
1224 * from the controlling terminal, and fork. The original process
1227 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
1230 #endif /* TIOCNOTTY */
1231 if (daemon(0, 0) < 0)
1232 fatal("daemon() failed: %.200s", strerror(errno));
1234 /* Disconnect from the controlling tty. */
1236 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
1238 (void) ioctl(fd, TIOCNOTTY, NULL);
1241 #endif /* TIOCNOTTY */
1243 /* Reinitialize the log (because of the fork above). */
1244 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1246 /* Initialize the random number generator. */
1249 /* Chdir to the root directory so that the current disk can be
1250 unmounted if desired. */
1253 /* ignore SIGPIPE */
1254 signal(SIGPIPE, SIG_IGN);
1256 /* Start listening for a socket, unless started from inetd. */
1262 close(REEXEC_CONFIG_PASS_FD);
1263 sock_in = sock_out = dup(STDIN_FILENO);
1265 startup_pipe = dup(REEXEC_STARTUP_PIPE_FD);
1266 close(REEXEC_STARTUP_PIPE_FD);
1269 sock_in = dup(STDIN_FILENO);
1270 sock_out = dup(STDOUT_FILENO);
1273 * We intentionally do not close the descriptors 0, 1, and 2
1274 * as our code for setting the descriptors won't work if
1275 * ttyfd happens to be one of those.
1277 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
1278 dup2(fd, STDIN_FILENO);
1279 dup2(fd, STDOUT_FILENO);
1280 if (fd > STDOUT_FILENO)
1283 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
1284 if ((options.protocol & SSH_PROTO_1) &&
1285 sensitive_data.server_key == NULL)
1286 generate_ephemeral_server_key();
1288 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
1289 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
1291 if (num_listen_socks >= MAX_LISTEN_SOCKS)
1292 fatal("Too many listen sockets. "
1293 "Enlarge MAX_LISTEN_SOCKS");
1294 if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen,
1295 ntop, sizeof(ntop), strport, sizeof(strport),
1296 NI_NUMERICHOST|NI_NUMERICSERV)) != 0) {
1297 error("getnameinfo failed: %.100s",
1298 (ret != EAI_SYSTEM) ? gai_strerror(ret) :
1302 /* Create socket for listening. */
1303 listen_sock = socket(ai->ai_family, ai->ai_socktype,
1305 if (listen_sock < 0) {
1306 /* kernel may not support ipv6 */
1307 verbose("socket: %.100s", strerror(errno));
1310 if (set_nonblock(listen_sock) == -1) {
1315 * Set socket options.
1316 * Allow local port reuse in TIME_WAIT.
1318 if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
1319 &on, sizeof(on)) == -1)
1320 error("setsockopt SO_REUSEADDR: %s", strerror(errno));
1322 debug("Bind to port %s on %s.", strport, ntop);
1324 /* Bind the socket to the desired port. */
1325 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1327 error("Bind to port %s on %s failed: %.200s.",
1328 strport, ntop, strerror(errno));
1332 listen_socks[num_listen_socks] = listen_sock;
1335 /* Start listening on the port. */
1336 logit("Server listening on %s port %s.", ntop, strport);
1337 if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0)
1338 fatal("listen: %.100s", strerror(errno));
1341 freeaddrinfo(options.listen_addrs);
1343 if (!num_listen_socks)
1344 fatal("Cannot bind any address.");
1346 if (options.protocol & SSH_PROTO_1)
1347 generate_ephemeral_server_key();
1350 * Arrange to restart on SIGHUP. The handler needs
1353 signal(SIGHUP, sighup_handler);
1355 signal(SIGTERM, sigterm_handler);
1356 signal(SIGQUIT, sigterm_handler);
1358 /* Arrange SIGCHLD to be caught. */
1359 signal(SIGCHLD, main_sigchld_handler);
1361 /* Write out the pid file after the sigterm handler is setup */
1364 * Record our pid in /var/run/sshd.pid to make it
1365 * easier to kill the correct sshd. We don't want to
1366 * do this before the bind above because the bind will
1367 * fail if there already is a daemon, and this will
1368 * overwrite any old pid in the file.
1370 f = fopen(options.pid_file, "wb");
1372 error("Couldn't create pid file \"%s\": %s",
1373 options.pid_file, strerror(errno));
1375 fprintf(f, "%ld\n", (long) getpid());
1380 /* setup fd set for listen */
1383 for (i = 0; i < num_listen_socks; i++)
1384 if (listen_socks[i] > maxfd)
1385 maxfd = listen_socks[i];
1386 /* pipes connected to unauthenticated childs */
1387 startup_pipes = xmalloc(options.max_startups * sizeof(int));
1388 for (i = 0; i < options.max_startups; i++)
1389 startup_pipes[i] = -1;
1392 * Stay listening for connections until the system crashes or
1393 * the daemon is killed with a signal.
1396 if (received_sighup)
1400 fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
1401 fdset = (fd_set *)xmalloc(fdsetsz);
1402 memset(fdset, 0, fdsetsz);
1404 for (i = 0; i < num_listen_socks; i++)
1405 FD_SET(listen_socks[i], fdset);
1406 for (i = 0; i < options.max_startups; i++)
1407 if (startup_pipes[i] != -1)
1408 FD_SET(startup_pipes[i], fdset);
1410 /* Wait in select until there is a connection. */
1411 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
1412 if (ret < 0 && errno != EINTR)
1413 error("select: %.100s", strerror(errno));
1414 if (received_sigterm) {
1415 logit("Received signal %d; terminating.",
1416 (int) received_sigterm);
1417 close_listen_socks();
1418 unlink(options.pid_file);
1421 if (key_used && key_do_regen) {
1422 generate_ephemeral_server_key();
1429 for (i = 0; i < options.max_startups; i++)
1430 if (startup_pipes[i] != -1 &&
1431 FD_ISSET(startup_pipes[i], fdset)) {
1433 * the read end of the pipe is ready
1434 * if the child has closed the pipe
1435 * after successful authentication
1436 * or if the child has died
1438 close(startup_pipes[i]);
1439 startup_pipes[i] = -1;
1442 for (i = 0; i < num_listen_socks; i++) {
1443 if (!FD_ISSET(listen_socks[i], fdset))
1445 fromlen = sizeof(from);
1446 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
1449 if (errno != EINTR && errno != EWOULDBLOCK)
1450 error("accept: %.100s", strerror(errno));
1453 if (unset_nonblock(newsock) == -1) {
1457 if (drop_connection(startups) == 1) {
1458 debug("drop connection #%d", startups);
1462 if (pipe(startup_p) == -1) {
1467 if (rexec_flag && socketpair(AF_UNIX,
1468 SOCK_STREAM, 0, config_s) == -1) {
1469 error("reexec socketpair: %s",
1472 close(startup_p[0]);
1473 close(startup_p[1]);
1477 for (j = 0; j < options.max_startups; j++)
1478 if (startup_pipes[j] == -1) {
1479 startup_pipes[j] = startup_p[0];
1480 if (maxfd < startup_p[0])
1481 maxfd = startup_p[0];
1487 * Got connection. Fork a child to handle it, unless
1488 * we are in debugging mode.
1492 * In debugging mode. Close the listening
1493 * socket, and start processing the
1494 * connection without forking.
1496 debug("Server will not fork when running in debugging mode.");
1497 close_listen_socks();
1500 close(startup_p[0]);
1501 close(startup_p[1]);
1505 send_rexec_state(config_s[0],
1512 * Normal production daemon. Fork, and have
1513 * the child process the connection. The
1514 * parent continues listening.
1516 if ((pid = fork()) == 0) {
1518 * Child. Close the listening and max_startup
1519 * sockets. Start using the accepted socket.
1520 * Reinitialize logging (since our pid has
1521 * changed). We break out of the loop to handle
1524 startup_pipe = startup_p[1];
1525 close_startup_pipes();
1526 close_listen_socks();
1529 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1536 /* Parent. Stay in the loop. */
1538 error("fork: %.100s", strerror(errno));
1540 debug("Forked child %ld.", (long)pid);
1542 close(startup_p[1]);
1545 send_rexec_state(config_s[0], &cfg);
1550 /* Mark that the key has been used (it was "given" to the child). */
1551 if ((options.protocol & SSH_PROTO_1) &&
1553 /* Schedule server key regeneration alarm. */
1554 signal(SIGALRM, key_regeneration_alarm);
1555 alarm(options.key_regeneration_time);
1561 /* Close the new socket (the child is now taking care of it). */
1564 /* child process check (or debug mode) */
1565 if (num_listen_socks < 0)
1570 /* This is the child processing a new connection. */
1571 setproctitle("%s", "[accepted]");
1574 * Create a new session and process group since the 4.4BSD
1575 * setlogin() affects the entire process group. We don't
1576 * want the child to be able to affect the parent.
1578 #if !defined(SSHD_ACQUIRES_CTTY)
1580 * If setsid is called, on some platforms sshd will later acquire a
1581 * controlling terminal which will result in "could not set
1582 * controlling tty" errors.
1584 if (!debug_flag && !inetd_flag && setsid() < 0)
1585 error("setsid: %.100s", strerror(errno));
1591 debug("rexec start in %d out %d newsock %d pipe %d sock %d",
1592 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
1593 dup2(newsock, STDIN_FILENO);
1594 dup2(STDIN_FILENO, STDOUT_FILENO);
1595 if (startup_pipe == -1)
1596 close(REEXEC_STARTUP_PIPE_FD);
1598 dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD);
1600 dup2(config_s[1], REEXEC_CONFIG_PASS_FD);
1602 if (startup_pipe != -1)
1603 close(startup_pipe);
1605 execv(rexec_argv[0], rexec_argv);
1607 /* Reexec has failed, fall back and continue */
1608 error("rexec of %s failed: %s", rexec_argv[0], strerror(errno));
1609 recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL);
1610 log_init(__progname, options.log_level,
1611 options.log_facility, log_stderr);
1614 startup_pipe = REEXEC_STARTUP_PIPE_FD;
1616 close(REEXEC_CONFIG_PASS_FD);
1617 newsock = sock_out = sock_in = dup(STDIN_FILENO);
1618 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
1619 dup2(fd, STDIN_FILENO);
1620 dup2(fd, STDOUT_FILENO);
1621 if (fd > STDERR_FILENO)
1624 debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d",
1625 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
1629 * Disable the key regeneration alarm. We will not regenerate the
1630 * key since we are no longer in a position to give it to anyone. We
1631 * will not restart on SIGHUP since it no longer makes sense.
1634 signal(SIGALRM, SIG_DFL);
1635 signal(SIGHUP, SIG_DFL);
1636 signal(SIGTERM, SIG_DFL);
1637 signal(SIGQUIT, SIG_DFL);
1638 signal(SIGCHLD, SIG_DFL);
1639 signal(SIGINT, SIG_DFL);
1642 * Register our connection. This turns encryption off because we do
1645 packet_set_connection(sock_in, sock_out);
1646 packet_set_server();
1648 /* Set SO_KEEPALIVE if requested. */
1649 if (options.tcp_keep_alive && packet_connection_is_on_socket() &&
1650 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) < 0)
1651 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1653 if ((remote_port = get_remote_port()) < 0) {
1654 debug("get_remote_port failed");
1659 * We use get_canonical_hostname with usedns = 0 instead of
1660 * get_remote_ipaddr here so IP options will be checked.
1662 remote_ip = get_canonical_hostname(0);
1664 #ifdef SSH_AUDIT_EVENTS
1665 audit_connection_from(remote_ip, remote_port);
1668 /* Check whether logins are denied from this host. */
1669 if (packet_connection_is_on_socket()) {
1670 struct request_info req;
1672 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
1675 if (!hosts_access(&req)) {
1676 debug("Connection refused by tcp wrapper");
1679 fatal("libwrap refuse returns");
1682 #endif /* LIBWRAP */
1684 /* Log the connection. */
1685 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1688 * We don't want to listen forever unless the other side
1689 * successfully authenticates itself. So we set up an alarm which is
1690 * cleared after successful authentication. A limit of zero
1691 * indicates no limit. Note that we don't set the alarm in debugging
1692 * mode; it is just annoying to have the server exit just when you
1693 * are about to discover the bug.
1695 signal(SIGALRM, grace_alarm_handler);
1697 alarm(options.login_grace_time);
1699 sshd_exchange_identification(sock_in, sock_out);
1701 packet_set_nonblocking();
1703 /* allocate authentication context */
1704 authctxt = xmalloc(sizeof(*authctxt));
1705 memset(authctxt, 0, sizeof(*authctxt));
1707 authctxt->loginmsg = &loginmsg;
1709 /* XXX global for cleanup, access from other modules */
1710 the_authctxt = authctxt;
1712 /* prepare buffer to collect messages to display to user after login */
1713 buffer_init(&loginmsg);
1716 if (privsep_preauth(authctxt) == 1)
1719 /* perform the key exchange */
1720 /* authenticate user and start session */
1723 do_authentication2(authctxt);
1726 do_authentication(authctxt);
1729 * If we use privilege separation, the unprivileged child transfers
1730 * the current keystate and exits
1733 mm_send_keystate(pmonitor);
1739 * Cancel the alarm we set to limit the time taken for
1743 signal(SIGALRM, SIG_DFL);
1744 if (startup_pipe != -1) {
1745 close(startup_pipe);
1749 #ifdef SSH_AUDIT_EVENTS
1750 audit_event(SSH_AUTH_SUCCESS);
1754 * In privilege separation, we fork another child and prepare
1755 * file descriptor passing.
1758 privsep_postauth(authctxt);
1759 /* the monitor process [priv] will not return */
1761 destroy_sensitive_data();
1764 /* Start session. */
1765 do_authenticated(authctxt);
1767 /* The connection has been terminated. */
1768 verbose("Closing connection to %.100s", remote_ip);
1771 if (options.use_pam)
1773 #endif /* USE_PAM */
1775 #ifdef SSH_AUDIT_EVENTS
1776 PRIVSEP(audit_event(SSH_CONNECTION_CLOSE));
1788 * Decrypt session_key_int using our private server key and private host key
1789 * (key with larger modulus first).
1792 ssh1_session_key(BIGNUM *session_key_int)
1796 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1797 /* Server key has bigger modulus. */
1798 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1799 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1800 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1801 get_remote_ipaddr(),
1802 BN_num_bits(sensitive_data.server_key->rsa->n),
1803 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1804 SSH_KEY_BITS_RESERVED);
1806 if (rsa_private_decrypt(session_key_int, session_key_int,
1807 sensitive_data.server_key->rsa) <= 0)
1809 if (rsa_private_decrypt(session_key_int, session_key_int,
1810 sensitive_data.ssh1_host_key->rsa) <= 0)
1813 /* Host key has bigger modulus (or they are equal). */
1814 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1815 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1816 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1817 get_remote_ipaddr(),
1818 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1819 BN_num_bits(sensitive_data.server_key->rsa->n),
1820 SSH_KEY_BITS_RESERVED);
1822 if (rsa_private_decrypt(session_key_int, session_key_int,
1823 sensitive_data.ssh1_host_key->rsa) < 0)
1825 if (rsa_private_decrypt(session_key_int, session_key_int,
1826 sensitive_data.server_key->rsa) < 0)
1839 BIGNUM *session_key_int;
1840 u_char session_key[SSH_SESSION_KEY_LENGTH];
1842 u_int cipher_type, auth_mask, protocol_flags;
1846 * Generate check bytes that the client must send back in the user
1847 * packet in order for it to be accepted; this is used to defy ip
1848 * spoofing attacks. Note that this only works against somebody
1849 * doing IP spoofing from a remote machine; any machine on the local
1850 * network can still see outgoing packets and catch the random
1851 * cookie. This only affects rhosts authentication, and this is one
1852 * of the reasons why it is inherently insecure.
1854 for (i = 0; i < 8; i++) {
1857 cookie[i] = rnd & 0xff;
1862 * Send our public key. We include in the packet 64 bits of random
1863 * data that must be matched in the reply in order to prevent IP
1866 packet_start(SSH_SMSG_PUBLIC_KEY);
1867 for (i = 0; i < 8; i++)
1868 packet_put_char(cookie[i]);
1870 /* Store our public server RSA key. */
1871 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1872 packet_put_bignum(sensitive_data.server_key->rsa->e);
1873 packet_put_bignum(sensitive_data.server_key->rsa->n);
1875 /* Store our public host RSA key. */
1876 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1877 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1878 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1880 /* Put protocol flags. */
1881 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1883 /* Declare which ciphers we support. */
1884 packet_put_int(cipher_mask_ssh1(0));
1886 /* Declare supported authentication types. */
1888 if (options.rhosts_rsa_authentication)
1889 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1890 if (options.rsa_authentication)
1891 auth_mask |= 1 << SSH_AUTH_RSA;
1892 if (options.challenge_response_authentication == 1)
1893 auth_mask |= 1 << SSH_AUTH_TIS;
1894 if (options.password_authentication)
1895 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1896 packet_put_int(auth_mask);
1898 /* Send the packet and wait for it to be sent. */
1900 packet_write_wait();
1902 debug("Sent %d bit server key and %d bit host key.",
1903 BN_num_bits(sensitive_data.server_key->rsa->n),
1904 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1906 /* Read clients reply (cipher type and session key). */
1907 packet_read_expect(SSH_CMSG_SESSION_KEY);
1909 /* Get cipher type and check whether we accept this. */
1910 cipher_type = packet_get_char();
1912 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1913 packet_disconnect("Warning: client selects unsupported cipher.");
1915 /* Get check bytes from the packet. These must match those we
1916 sent earlier with the public key packet. */
1917 for (i = 0; i < 8; i++)
1918 if (cookie[i] != packet_get_char())
1919 packet_disconnect("IP Spoofing check bytes do not match.");
1921 debug("Encryption type: %.200s", cipher_name(cipher_type));
1923 /* Get the encrypted integer. */
1924 if ((session_key_int = BN_new()) == NULL)
1925 fatal("do_ssh1_kex: BN_new failed");
1926 packet_get_bignum(session_key_int);
1928 protocol_flags = packet_get_int();
1929 packet_set_protocol_flags(protocol_flags);
1932 /* Decrypt session_key_int using host/server keys */
1933 rsafail = PRIVSEP(ssh1_session_key(session_key_int));
1936 * Extract session key from the decrypted integer. The key is in the
1937 * least significant 256 bits of the integer; the first byte of the
1938 * key is in the highest bits.
1941 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1942 len = BN_num_bytes(session_key_int);
1943 if (len < 0 || (u_int)len > sizeof(session_key)) {
1944 error("do_connection: bad session key len from %s: "
1945 "session_key_int %d > sizeof(session_key) %lu",
1946 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
1949 memset(session_key, 0, sizeof(session_key));
1950 BN_bn2bin(session_key_int,
1951 session_key + sizeof(session_key) - len);
1953 derive_ssh1_session_id(
1954 sensitive_data.ssh1_host_key->rsa->n,
1955 sensitive_data.server_key->rsa->n,
1956 cookie, session_id);
1958 * Xor the first 16 bytes of the session key with the
1961 for (i = 0; i < 16; i++)
1962 session_key[i] ^= session_id[i];
1966 int bytes = BN_num_bytes(session_key_int);
1967 u_char *buf = xmalloc(bytes);
1970 logit("do_connection: generating a fake encryption key");
1971 BN_bn2bin(session_key_int, buf);
1973 MD5_Update(&md, buf, bytes);
1974 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1975 MD5_Final(session_key, &md);
1977 MD5_Update(&md, session_key, 16);
1978 MD5_Update(&md, buf, bytes);
1979 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1980 MD5_Final(session_key + 16, &md);
1981 memset(buf, 0, bytes);
1983 for (i = 0; i < 16; i++)
1984 session_id[i] = session_key[i] ^ session_key[i + 16];
1986 /* Destroy the private and public keys. No longer. */
1987 destroy_sensitive_data();
1990 mm_ssh1_session_id(session_id);
1992 /* Destroy the decrypted integer. It is no longer needed. */
1993 BN_clear_free(session_key_int);
1995 /* Set the session key. From this on all communications will be encrypted. */
1996 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1998 /* Destroy our copy of the session key. It is no longer needed. */
1999 memset(session_key, 0, sizeof(session_key));
2001 debug("Received session key; encryption turned on.");
2003 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */
2004 packet_start(SSH_SMSG_SUCCESS);
2006 packet_write_wait();
2010 * SSH2 key exchange: diffie-hellman-group1-sha1
2017 if (options.ciphers != NULL) {
2018 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2019 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
2021 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2022 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
2023 myproposal[PROPOSAL_ENC_ALGS_STOC] =
2024 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
2026 if (options.macs != NULL) {
2027 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
2028 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
2030 if (options.compression == COMP_NONE) {
2031 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2032 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
2033 } else if (options.compression == COMP_DELAYED) {
2034 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2035 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com";
2038 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
2040 /* start key exchange */
2041 kex = kex_setup(myproposal);
2042 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
2043 kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
2044 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
2046 kex->client_version_string=client_version_string;
2047 kex->server_version_string=server_version_string;
2048 kex->load_host_key=&get_hostkey_by_type;
2049 kex->host_key_index=&get_hostkey_index;
2053 dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
2055 session_id2 = kex->session_id;
2056 session_id2_len = kex->session_id_len;
2059 /* send 1st encrypted/maced/compressed message */
2060 packet_start(SSH2_MSG_IGNORE);
2061 packet_put_cstring("markus");
2063 packet_write_wait();
2068 /* server specific fatal cleanup */
2073 do_cleanup(the_authctxt);
2074 #ifdef SSH_AUDIT_EVENTS
2075 /* done after do_cleanup so it can cancel the PAM auth 'thread' */
2076 if (!use_privsep || mm_is_monitor())
2077 audit_event(SSH_CONNECTION_ABANDON);