1 /* $OpenBSD: sshd.c,v 1.355 2008/02/14 13:10:31 mbalmer 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 #include <sys/ioctl.h>
49 #include <sys/socket.h>
50 #ifdef HAVE_SYS_STAT_H
51 # include <sys/stat.h>
53 #ifdef HAVE_SYS_TIME_H
54 # include <sys/time.h>
56 #include "openbsd-compat/sys-tree.h"
74 #include <openssl/dh.h>
75 #include <openssl/bn.h>
76 #include <openssl/md5.h>
77 #include <openssl/rand.h>
78 #include "openbsd-compat/openssl-compat.h"
80 #ifdef HAVE_SECUREWARE
81 #include <sys/security.h>
101 #include "myproposal.h"
102 #include "authfile.h"
103 #include "pathnames.h"
104 #include "atomicio.h"
105 #include "canohost.h"
106 #include "hostfile.h"
110 #include "dispatch.h"
111 #include "channels.h"
113 #include "monitor_mm.h"
118 #include "monitor_wrap.h"
119 #include "monitor_fdpass.h"
134 #define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1)
135 #define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2)
136 #define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3)
137 #define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4)
139 extern char *__progname;
141 /* Server configuration options. */
142 ServerOptions options;
144 /* Name of the server configuration file. */
145 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
148 * Debug mode flag. This can be set on the command line. If debug
149 * mode is enabled, extra debugging output will be sent to the system
150 * log, the daemon will not go to background, and will exit after processing
151 * the first connection.
155 /* Flag indicating that the daemon should only test the configuration and keys. */
158 /* Flag indicating that the daemon is being started from inetd. */
161 /* Flag indicating that sshd should not detach and become a daemon. */
162 int no_daemon_flag = 0;
164 /* debug goes to stderr unless inetd_flag is set */
167 /* Saved arguments to main(). */
172 int rexeced_flag = 0;
178 * The sockets that the server is listening; this is used in the SIGHUP
181 #define MAX_LISTEN_SOCKS 16
182 int listen_socks[MAX_LISTEN_SOCKS];
183 int num_listen_socks = 0;
186 * the client's version string, passed by sshd2 in compat mode. if != NULL,
187 * sshd will skip the version-number exchange
189 char *client_version_string = NULL;
190 char *server_version_string = NULL;
192 /* for rekeying XXX fixme */
196 * Any really sensitive data in the application is contained in this
197 * structure. The idea is that this structure could be locked into memory so
198 * that the pages do not get written into swap. However, there are some
199 * problems. The private key contains BIGNUMs, and we do not (in principle)
200 * have access to the internals of them, and locking just the structure is
201 * not very useful. Currently, memory locking is not implemented.
204 Key *server_key; /* ephemeral server key */
205 Key *ssh1_host_key; /* ssh1 host key */
206 Key **host_keys; /* all private host keys */
209 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
213 * Flag indicating whether the RSA server key needs to be regenerated.
214 * Is set in the SIGALRM handler and cleared when the key is regenerated.
216 static volatile sig_atomic_t key_do_regen = 0;
218 /* This is set to true when a signal is received. */
219 static volatile sig_atomic_t received_sighup = 0;
220 static volatile sig_atomic_t received_sigterm = 0;
222 /* session identifier, used by RSA-auth */
223 u_char session_id[16];
226 u_char *session_id2 = NULL;
227 u_int session_id2_len = 0;
229 /* record remote hostname or ip */
230 u_int utmp_len = MAXHOSTNAMELEN;
232 /* options.max_startup sized array of fd ints */
233 int *startup_pipes = NULL;
234 int startup_pipe; /* in child */
236 /* variables used for privilege separation */
237 int use_privsep = -1;
238 struct monitor *pmonitor = NULL;
240 /* global authentication context */
241 Authctxt *the_authctxt = NULL;
243 /* sshd_config buffer */
246 /* message to be displayed after login */
249 /* Unprivileged user */
250 struct passwd *privsep_pw = NULL;
252 /* Prototypes for various functions defined later in this file. */
253 void destroy_sensitive_data(void);
254 void demote_sensitive_data(void);
256 static void do_ssh1_kex(void);
257 static void do_ssh2_kex(void);
260 * Close all listening sockets
263 close_listen_socks(void)
267 for (i = 0; i < num_listen_socks; i++)
268 close(listen_socks[i]);
269 num_listen_socks = -1;
273 close_startup_pipes(void)
278 for (i = 0; i < options.max_startups; i++)
279 if (startup_pipes[i] != -1)
280 close(startup_pipes[i]);
284 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
285 * the effect is to reread the configuration file (and to regenerate
291 sighup_handler(int sig)
293 int save_errno = errno;
296 signal(SIGHUP, sighup_handler);
301 * Called from the main program after receiving SIGHUP.
302 * Restarts the server.
307 logit("Received SIGHUP; restarting.");
308 close_listen_socks();
309 close_startup_pipes();
310 alarm(0); /* alarm timer persists across exec */
311 execv(saved_argv[0], saved_argv);
312 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
318 * Generic signal handler for terminating signals in the master daemon.
322 sigterm_handler(int sig)
324 received_sigterm = sig;
328 * SIGCHLD handler. This is called whenever a child dies. This will then
329 * reap any zombies left by exited children.
333 main_sigchld_handler(int sig)
335 int save_errno = errno;
339 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
340 (pid < 0 && errno == EINTR))
343 signal(SIGCHLD, main_sigchld_handler);
348 * Signal handler for the alarm after the login grace period has expired.
352 grace_alarm_handler(int sig)
354 if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0)
355 kill(pmonitor->m_pid, SIGALRM);
357 /* Log error and exit. */
358 sigdie("Timeout before authentication for %s", get_remote_ipaddr());
362 * Signal handler for the key regeneration alarm. Note that this
363 * alarm only occurs in the daemon waiting for connections, and it does not
364 * do anything with the private key or random state before forking.
365 * Thus there should be no concurrency control/asynchronous execution
369 generate_ephemeral_server_key(void)
374 verbose("Generating %s%d bit RSA key.",
375 sensitive_data.server_key ? "new " : "", options.server_key_bits);
376 if (sensitive_data.server_key != NULL)
377 key_free(sensitive_data.server_key);
378 sensitive_data.server_key = key_generate(KEY_RSA1,
379 options.server_key_bits);
380 verbose("RSA key generation complete.");
382 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
385 sensitive_data.ssh1_cookie[i] = rnd & 0xff;
393 key_regeneration_alarm(int sig)
395 int save_errno = errno;
397 signal(SIGALRM, SIG_DFL);
403 sshd_exchange_identification(int sock_in, int sock_out)
407 int remote_major, remote_minor;
410 char buf[256]; /* Must not be larger than remote_version. */
411 char remote_version[256]; /* Must be at least as big as buf. */
413 if ((options.protocol & SSH_PROTO_1) &&
414 (options.protocol & SSH_PROTO_2)) {
415 major = PROTOCOL_MAJOR_1;
417 } else if (options.protocol & SSH_PROTO_2) {
418 major = PROTOCOL_MAJOR_2;
419 minor = PROTOCOL_MINOR_2;
421 major = PROTOCOL_MAJOR_1;
422 minor = PROTOCOL_MINOR_1;
424 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
425 server_version_string = xstrdup(buf);
427 /* Send our protocol version identification. */
428 if (atomicio(vwrite, sock_out, server_version_string,
429 strlen(server_version_string))
430 != strlen(server_version_string)) {
431 logit("Could not write ident string to %s", get_remote_ipaddr());
435 /* Read other sides version identification. */
436 memset(buf, 0, sizeof(buf));
437 for (i = 0; i < sizeof(buf) - 1; i++) {
438 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
439 logit("Did not receive identification string from %s",
440 get_remote_ipaddr());
443 if (buf[i] == '\r') {
445 /* Kludge for F-Secure Macintosh < 1.0.2 */
447 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
451 if (buf[i] == '\n') {
456 buf[sizeof(buf) - 1] = 0;
457 client_version_string = xstrdup(buf);
460 * Check that the versions match. In future this might accept
461 * several versions and set appropriate flags to handle them.
463 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
464 &remote_major, &remote_minor, remote_version) != 3) {
465 s = "Protocol mismatch.\n";
466 (void) atomicio(vwrite, sock_out, s, strlen(s));
469 logit("Bad protocol version identification '%.100s' from %s",
470 client_version_string, get_remote_ipaddr());
473 debug("Client protocol version %d.%d; client software version %.100s",
474 remote_major, remote_minor, remote_version);
476 compat_datafellows(remote_version);
478 if (datafellows & SSH_BUG_PROBE) {
479 logit("probed from %s with %s. Don't panic.",
480 get_remote_ipaddr(), client_version_string);
484 if (datafellows & SSH_BUG_SCANNER) {
485 logit("scanned from %s with %s. Don't panic.",
486 get_remote_ipaddr(), client_version_string);
491 switch (remote_major) {
493 if (remote_minor == 99) {
494 if (options.protocol & SSH_PROTO_2)
500 if (!(options.protocol & SSH_PROTO_1)) {
504 if (remote_minor < 3) {
505 packet_disconnect("Your ssh version is too old and "
506 "is no longer supported. Please install a newer version.");
507 } else if (remote_minor == 3) {
508 /* note that this disables agent-forwarding */
513 if (options.protocol & SSH_PROTO_2) {
522 chop(server_version_string);
523 debug("Local version string %.200s", server_version_string);
526 s = "Protocol major versions differ.\n";
527 (void) atomicio(vwrite, sock_out, s, strlen(s));
530 logit("Protocol major versions differ for %s: %.200s vs. %.200s",
532 server_version_string, client_version_string);
537 /* Destroy the host and server keys. They will no longer be needed. */
539 destroy_sensitive_data(void)
543 if (sensitive_data.server_key) {
544 key_free(sensitive_data.server_key);
545 sensitive_data.server_key = NULL;
547 for (i = 0; i < options.num_host_key_files; i++) {
548 if (sensitive_data.host_keys[i]) {
549 key_free(sensitive_data.host_keys[i]);
550 sensitive_data.host_keys[i] = NULL;
553 sensitive_data.ssh1_host_key = NULL;
554 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
557 /* Demote private to public keys for network child */
559 demote_sensitive_data(void)
564 if (sensitive_data.server_key) {
565 tmp = key_demote(sensitive_data.server_key);
566 key_free(sensitive_data.server_key);
567 sensitive_data.server_key = tmp;
570 for (i = 0; i < options.num_host_key_files; i++) {
571 if (sensitive_data.host_keys[i]) {
572 tmp = key_demote(sensitive_data.host_keys[i]);
573 key_free(sensitive_data.host_keys[i]);
574 sensitive_data.host_keys[i] = tmp;
575 if (tmp->type == KEY_RSA1)
576 sensitive_data.ssh1_host_key = tmp;
580 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */
584 privsep_preauth_child(void)
590 /* Enable challenge-response authentication for privilege separation */
591 privsep_challenge_enable();
594 for (i = 0; i < 256; i++)
595 rnd[i] = arc4random();
596 RAND_seed(rnd, sizeof(rnd));
598 /* Demote the private keys to public keys. */
599 demote_sensitive_data();
601 /* Change our root directory */
602 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
603 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
605 if (chdir("/") == -1)
606 fatal("chdir(\"/\"): %s", strerror(errno));
608 /* Drop our privileges */
609 debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid,
610 (u_int)privsep_pw->pw_gid);
612 /* XXX not ready, too heavy after chroot */
613 do_setusercontext(privsep_pw);
615 gidset[0] = privsep_pw->pw_gid;
616 if (setgroups(1, gidset) < 0)
617 fatal("setgroups: %.100s", strerror(errno));
618 permanently_set_uid(privsep_pw);
623 privsep_preauth(Authctxt *authctxt)
628 /* Set up unprivileged child process to deal with network data */
629 pmonitor = monitor_init();
630 /* Store a pointer to the kex for later rekeying */
631 pmonitor->m_pkex = &xxx_kex;
635 fatal("fork of unprivileged child failed");
636 } else if (pid != 0) {
637 debug2("Network child is on pid %ld", (long)pid);
639 close(pmonitor->m_recvfd);
640 pmonitor->m_pid = pid;
641 monitor_child_preauth(authctxt, pmonitor);
642 close(pmonitor->m_sendfd);
645 monitor_sync(pmonitor);
647 /* Wait for the child's exit status */
648 while (waitpid(pid, &status, 0) < 0)
655 close(pmonitor->m_sendfd);
657 /* Demote the child */
658 if (getuid() == 0 || geteuid() == 0)
659 privsep_preauth_child();
660 setproctitle("%s", "[net]");
666 privsep_postauth(Authctxt *authctxt)
671 #ifdef DISABLE_FD_PASSING
674 if (authctxt->pw->pw_uid == 0 || options.use_login) {
676 /* File descriptor passing is broken or root login */
681 /* New socket pair */
682 monitor_reinit(pmonitor);
684 pmonitor->m_pid = fork();
685 if (pmonitor->m_pid == -1)
686 fatal("fork of unprivileged child failed");
687 else if (pmonitor->m_pid != 0) {
688 debug2("User child is on pid %ld", (long)pmonitor->m_pid);
689 close(pmonitor->m_recvfd);
690 buffer_clear(&loginmsg);
691 monitor_child_postauth(pmonitor);
697 close(pmonitor->m_sendfd);
699 /* Demote the private keys to public keys. */
700 demote_sensitive_data();
703 for (i = 0; i < 256; i++)
704 rnd[i] = arc4random();
705 RAND_seed(rnd, sizeof(rnd));
707 /* Drop privileges */
708 do_setusercontext(authctxt->pw);
711 /* It is safe now to apply the key state */
712 monitor_apply_keystate(pmonitor);
715 * Tell the packet layer that authentication was successful, since
716 * this information is not part of the key state.
718 packet_set_authenticated();
722 list_hostkey_types(void)
730 for (i = 0; i < options.num_host_key_files; i++) {
731 Key *key = sensitive_data.host_keys[i];
737 if (buffer_len(&b) > 0)
738 buffer_append(&b, ",", 1);
739 p = key_ssh_name(key);
740 buffer_append(&b, p, strlen(p));
744 buffer_append(&b, "\0", 1);
745 ret = xstrdup(buffer_ptr(&b));
747 debug("list_hostkey_types: %s", ret);
752 get_hostkey_by_type(int type)
756 for (i = 0; i < options.num_host_key_files; i++) {
757 Key *key = sensitive_data.host_keys[i];
758 if (key != NULL && key->type == type)
765 get_hostkey_by_index(int ind)
767 if (ind < 0 || ind >= options.num_host_key_files)
769 return (sensitive_data.host_keys[ind]);
773 get_hostkey_index(Key *key)
777 for (i = 0; i < options.num_host_key_files; i++) {
778 if (key == sensitive_data.host_keys[i])
785 * returns 1 if connection should be dropped, 0 otherwise.
786 * dropping starts at connection #max_startups_begin with a probability
787 * of (max_startups_rate/100). the probability increases linearly until
788 * all connections are dropped for startups > max_startups
791 drop_connection(int startups)
795 if (startups < options.max_startups_begin)
797 if (startups >= options.max_startups)
799 if (options.max_startups_rate == 100)
802 p = 100 - options.max_startups_rate;
803 p *= startups - options.max_startups_begin;
804 p /= options.max_startups - options.max_startups_begin;
805 p += options.max_startups_rate;
806 r = arc4random() % 100;
808 debug("drop_connection: p %d, r %d", p, r);
809 return (r < p) ? 1 : 0;
815 fprintf(stderr, "%s, %s\n",
816 SSH_RELEASE, SSLeay_version(SSLEAY_VERSION));
818 "usage: sshd [-46Ddeiqt] [-b bits] [-f config_file] [-g login_grace_time]\n"
819 " [-h host_key_file] [-k key_gen_time] [-o option] [-p port] [-u len]\n"
825 send_rexec_state(int fd, Buffer *conf)
829 debug3("%s: entering fd = %d config len %d", __func__, fd,
833 * Protocol from reexec master to child:
834 * string configuration
835 * u_int ephemeral_key_follows
836 * bignum e (only if ephemeral_key_follows == 1)
842 * string rngseed (only if OpenSSL is not self-seeded)
845 buffer_put_cstring(&m, buffer_ptr(conf));
847 if (sensitive_data.server_key != NULL &&
848 sensitive_data.server_key->type == KEY_RSA1) {
849 buffer_put_int(&m, 1);
850 buffer_put_bignum(&m, sensitive_data.server_key->rsa->e);
851 buffer_put_bignum(&m, sensitive_data.server_key->rsa->n);
852 buffer_put_bignum(&m, sensitive_data.server_key->rsa->d);
853 buffer_put_bignum(&m, sensitive_data.server_key->rsa->iqmp);
854 buffer_put_bignum(&m, sensitive_data.server_key->rsa->p);
855 buffer_put_bignum(&m, sensitive_data.server_key->rsa->q);
857 buffer_put_int(&m, 0);
859 #ifndef OPENSSL_PRNG_ONLY
860 rexec_send_rng_seed(&m);
863 if (ssh_msg_send(fd, 0, &m) == -1)
864 fatal("%s: ssh_msg_send failed", __func__);
868 debug3("%s: done", __func__);
872 recv_rexec_state(int fd, Buffer *conf)
878 debug3("%s: entering fd = %d", __func__, fd);
882 if (ssh_msg_recv(fd, &m) == -1)
883 fatal("%s: ssh_msg_recv failed", __func__);
884 if (buffer_get_char(&m) != 0)
885 fatal("%s: rexec version mismatch", __func__);
887 cp = buffer_get_string(&m, &len);
889 buffer_append(conf, cp, len + 1);
892 if (buffer_get_int(&m)) {
893 if (sensitive_data.server_key != NULL)
894 key_free(sensitive_data.server_key);
895 sensitive_data.server_key = key_new_private(KEY_RSA1);
896 buffer_get_bignum(&m, sensitive_data.server_key->rsa->e);
897 buffer_get_bignum(&m, sensitive_data.server_key->rsa->n);
898 buffer_get_bignum(&m, sensitive_data.server_key->rsa->d);
899 buffer_get_bignum(&m, sensitive_data.server_key->rsa->iqmp);
900 buffer_get_bignum(&m, sensitive_data.server_key->rsa->p);
901 buffer_get_bignum(&m, sensitive_data.server_key->rsa->q);
902 rsa_generate_additional_parameters(
903 sensitive_data.server_key->rsa);
906 #ifndef OPENSSL_PRNG_ONLY
907 rexec_recv_rng_seed(&m);
912 debug3("%s: done", __func__);
915 /* Accept a connection from inetd */
917 server_accept_inetd(int *sock_in, int *sock_out)
923 close(REEXEC_CONFIG_PASS_FD);
924 *sock_in = *sock_out = dup(STDIN_FILENO);
926 startup_pipe = dup(REEXEC_STARTUP_PIPE_FD);
927 close(REEXEC_STARTUP_PIPE_FD);
930 *sock_in = dup(STDIN_FILENO);
931 *sock_out = dup(STDOUT_FILENO);
934 * We intentionally do not close the descriptors 0, 1, and 2
935 * as our code for setting the descriptors won't work if
936 * ttyfd happens to be one of those.
938 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
939 dup2(fd, STDIN_FILENO);
940 dup2(fd, STDOUT_FILENO);
941 if (fd > STDOUT_FILENO)
944 debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out);
948 * Listen for TCP connections
953 int ret, listen_sock, on = 1;
955 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
957 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
958 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
960 if (num_listen_socks >= MAX_LISTEN_SOCKS)
961 fatal("Too many listen sockets. "
962 "Enlarge MAX_LISTEN_SOCKS");
963 if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen,
964 ntop, sizeof(ntop), strport, sizeof(strport),
965 NI_NUMERICHOST|NI_NUMERICSERV)) != 0) {
966 error("getnameinfo failed: %.100s",
967 ssh_gai_strerror(ret));
970 /* Create socket for listening. */
971 listen_sock = socket(ai->ai_family, ai->ai_socktype,
973 if (listen_sock < 0) {
974 /* kernel may not support ipv6 */
975 verbose("socket: %.100s", strerror(errno));
978 if (set_nonblock(listen_sock) == -1) {
983 * Set socket options.
984 * Allow local port reuse in TIME_WAIT.
986 if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
987 &on, sizeof(on)) == -1)
988 error("setsockopt SO_REUSEADDR: %s", strerror(errno));
991 /* Only communicate in IPv6 over AF_INET6 sockets. */
992 if (ai->ai_family == AF_INET6) {
993 if (setsockopt(listen_sock, IPPROTO_IPV6, IPV6_V6ONLY,
994 &on, sizeof(on)) == -1)
995 error("setsockopt IPV6_V6ONLY: %s",
1000 debug("Bind to port %s on %s.", strport, ntop);
1002 /* Bind the socket to the desired port. */
1003 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1004 error("Bind to port %s on %s failed: %.200s.",
1005 strport, ntop, strerror(errno));
1009 listen_socks[num_listen_socks] = listen_sock;
1012 /* Start listening on the port. */
1013 if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0)
1014 fatal("listen on [%s]:%s: %.100s",
1015 ntop, strport, strerror(errno));
1016 logit("Server listening on %s port %s.", ntop, strport);
1018 freeaddrinfo(options.listen_addrs);
1020 if (!num_listen_socks)
1021 fatal("Cannot bind any address.");
1025 * The main TCP accept loop. Note that, for the non-debug case, returns
1026 * from this function are in a forked subprocess.
1029 server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
1032 int i, j, ret, maxfd;
1033 int key_used = 0, startups = 0;
1034 int startup_p[2] = { -1 , -1 };
1035 struct sockaddr_storage from;
1039 /* setup fd set for accept */
1042 for (i = 0; i < num_listen_socks; i++)
1043 if (listen_socks[i] > maxfd)
1044 maxfd = listen_socks[i];
1045 /* pipes connected to unauthenticated childs */
1046 startup_pipes = xcalloc(options.max_startups, sizeof(int));
1047 for (i = 0; i < options.max_startups; i++)
1048 startup_pipes[i] = -1;
1051 * Stay listening for connections until the system crashes or
1052 * the daemon is killed with a signal.
1055 if (received_sighup)
1059 fdset = (fd_set *)xcalloc(howmany(maxfd + 1, NFDBITS),
1062 for (i = 0; i < num_listen_socks; i++)
1063 FD_SET(listen_socks[i], fdset);
1064 for (i = 0; i < options.max_startups; i++)
1065 if (startup_pipes[i] != -1)
1066 FD_SET(startup_pipes[i], fdset);
1068 /* Wait in select until there is a connection. */
1069 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
1070 if (ret < 0 && errno != EINTR)
1071 error("select: %.100s", strerror(errno));
1072 if (received_sigterm) {
1073 logit("Received signal %d; terminating.",
1074 (int) received_sigterm);
1075 close_listen_socks();
1076 unlink(options.pid_file);
1079 if (key_used && key_do_regen) {
1080 generate_ephemeral_server_key();
1087 for (i = 0; i < options.max_startups; i++)
1088 if (startup_pipes[i] != -1 &&
1089 FD_ISSET(startup_pipes[i], fdset)) {
1091 * the read end of the pipe is ready
1092 * if the child has closed the pipe
1093 * after successful authentication
1094 * or if the child has died
1096 close(startup_pipes[i]);
1097 startup_pipes[i] = -1;
1100 for (i = 0; i < num_listen_socks; i++) {
1101 if (!FD_ISSET(listen_socks[i], fdset))
1103 fromlen = sizeof(from);
1104 *newsock = accept(listen_socks[i],
1105 (struct sockaddr *)&from, &fromlen);
1107 if (errno != EINTR && errno != EWOULDBLOCK)
1108 error("accept: %.100s", strerror(errno));
1111 if (unset_nonblock(*newsock) == -1) {
1115 if (drop_connection(startups) == 1) {
1116 debug("drop connection #%d", startups);
1120 if (pipe(startup_p) == -1) {
1125 if (rexec_flag && socketpair(AF_UNIX,
1126 SOCK_STREAM, 0, config_s) == -1) {
1127 error("reexec socketpair: %s",
1130 close(startup_p[0]);
1131 close(startup_p[1]);
1135 for (j = 0; j < options.max_startups; j++)
1136 if (startup_pipes[j] == -1) {
1137 startup_pipes[j] = startup_p[0];
1138 if (maxfd < startup_p[0])
1139 maxfd = startup_p[0];
1145 * Got connection. Fork a child to handle it, unless
1146 * we are in debugging mode.
1150 * In debugging mode. Close the listening
1151 * socket, and start processing the
1152 * connection without forking.
1154 debug("Server will not fork when running in debugging mode.");
1155 close_listen_socks();
1156 *sock_in = *newsock;
1157 *sock_out = *newsock;
1158 close(startup_p[0]);
1159 close(startup_p[1]);
1163 send_rexec_state(config_s[0],
1171 * Normal production daemon. Fork, and have
1172 * the child process the connection. The
1173 * parent continues listening.
1175 platform_pre_fork();
1176 if ((pid = fork()) == 0) {
1178 * Child. Close the listening and
1179 * max_startup sockets. Start using
1180 * the accepted socket. Reinitialize
1181 * logging (since our pid has changed).
1182 * We break out of the loop to handle
1185 platform_post_fork_child();
1186 startup_pipe = startup_p[1];
1187 close_startup_pipes();
1188 close_listen_socks();
1189 *sock_in = *newsock;
1190 *sock_out = *newsock;
1191 log_init(__progname,
1193 options.log_facility,
1200 /* Parent. Stay in the loop. */
1201 platform_post_fork_parent(pid);
1203 error("fork: %.100s", strerror(errno));
1205 debug("Forked child %ld.", (long)pid);
1207 close(startup_p[1]);
1210 send_rexec_state(config_s[0], &cfg);
1216 * Mark that the key has been used (it
1217 * was "given" to the child).
1219 if ((options.protocol & SSH_PROTO_1) &&
1221 /* Schedule server key regeneration alarm. */
1222 signal(SIGALRM, key_regeneration_alarm);
1223 alarm(options.key_regeneration_time);
1230 * Ensure that our random state differs
1231 * from that of the child
1236 /* child process check (or debug mode) */
1237 if (num_listen_socks < 0)
1244 * Main program for the daemon.
1247 main(int ac, char **av)
1249 extern char *optarg;
1252 int sock_in = -1, sock_out = -1, newsock = -1;
1253 const char *remote_ip;
1256 int config_s[2] = { -1 , -1 };
1260 #ifdef HAVE_SECUREWARE
1261 (void)set_auth_parameters(ac, av);
1263 __progname = ssh_get_progname(av[0]);
1266 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
1269 saved_argv = xcalloc(ac + 1, sizeof(*saved_argv));
1270 for (i = 0; i < ac; i++)
1271 saved_argv[i] = xstrdup(av[i]);
1272 saved_argv[i] = NULL;
1274 #ifndef HAVE_SETPROCTITLE
1275 /* Prepare for later setproctitle emulation */
1276 compat_init_setproctitle(ac, av);
1280 if (geteuid() == 0 && setgroups(0, NULL) == -1)
1281 debug("setgroups(): %.200s", strerror(errno));
1283 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
1286 /* Initialize configuration options to their default values. */
1287 initialize_server_options(&options);
1289 /* Parse command-line arguments. */
1290 while ((opt = getopt(ac, av, "f:p:b:k:h:g:u:o:dDeiqrtQR46")) != -1) {
1293 options.address_family = AF_INET;
1296 options.address_family = AF_INET6;
1299 config_file_name = optarg;
1302 if (debug_flag == 0) {
1304 options.log_level = SYSLOG_LEVEL_DEBUG1;
1305 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
1306 options.log_level++;
1328 options.log_level = SYSLOG_LEVEL_QUIET;
1331 options.server_key_bits = (int)strtonum(optarg, 256,
1335 options.ports_from_cmdline = 1;
1336 if (options.num_ports >= MAX_PORTS) {
1337 fprintf(stderr, "too many ports.\n");
1340 options.ports[options.num_ports++] = a2port(optarg);
1341 if (options.ports[options.num_ports-1] == 0) {
1342 fprintf(stderr, "Bad port number.\n");
1347 if ((options.login_grace_time = convtime(optarg)) == -1) {
1348 fprintf(stderr, "Invalid login grace time.\n");
1353 if ((options.key_regeneration_time = convtime(optarg)) == -1) {
1354 fprintf(stderr, "Invalid key regeneration interval.\n");
1359 if (options.num_host_key_files >= MAX_HOSTKEYS) {
1360 fprintf(stderr, "too many host keys.\n");
1363 options.host_key_files[options.num_host_key_files++] = optarg;
1369 utmp_len = (u_int)strtonum(optarg, 0, MAXHOSTNAMELEN+1, NULL);
1370 if (utmp_len > MAXHOSTNAMELEN) {
1371 fprintf(stderr, "Invalid utmp length.\n");
1376 line = xstrdup(optarg);
1377 if (process_server_config_line(&options, line,
1378 "command-line", 0, NULL, NULL, NULL, NULL) != 0)
1388 if (rexeced_flag || inetd_flag)
1390 if (!test_flag && (rexec_flag && (av[0] == NULL || *av[0] != '/')))
1391 fatal("sshd re-exec requires execution with an absolute path");
1393 closefrom(REEXEC_MIN_FREE_FD);
1395 closefrom(REEXEC_DEVCRYPTO_RESERVED_FD);
1397 SSLeay_add_all_algorithms();
1400 * Force logging to stderr until we have loaded the private host
1401 * key (unless started from inetd)
1403 log_init(__progname,
1404 options.log_level == SYSLOG_LEVEL_NOT_SET ?
1405 SYSLOG_LEVEL_INFO : options.log_level,
1406 options.log_facility == SYSLOG_FACILITY_NOT_SET ?
1407 SYSLOG_FACILITY_AUTH : options.log_facility,
1408 log_stderr || !inetd_flag);
1411 * Unset KRB5CCNAME, otherwise the user's session may inherit it from
1412 * root's environment
1414 if (getenv("KRB5CCNAME") != NULL)
1415 unsetenv("KRB5CCNAME");
1418 /* Cray can define user privs drop all privs now!
1419 * Not needed on PRIV_SU systems!
1424 sensitive_data.server_key = NULL;
1425 sensitive_data.ssh1_host_key = NULL;
1426 sensitive_data.have_ssh1_key = 0;
1427 sensitive_data.have_ssh2_key = 0;
1429 /* Fetch our configuration */
1432 recv_rexec_state(REEXEC_CONFIG_PASS_FD, &cfg);
1434 load_server_config(config_file_name, &cfg);
1436 parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name,
1437 &cfg, NULL, NULL, NULL);
1441 /* Fill in default values for those options not explicitly set. */
1442 fill_default_server_options(&options);
1444 /* challenge-response is implemented via keyboard interactive */
1445 if (options.challenge_response_authentication)
1446 options.kbd_interactive_authentication = 1;
1448 /* set default channel AF */
1449 channel_set_af(options.address_family);
1451 /* Check that there are no remaining arguments. */
1453 fprintf(stderr, "Extra argument %s.\n", av[optind]);
1457 debug("sshd version %.100s", SSH_RELEASE);
1459 /* Store privilege separation user for later use if required. */
1460 if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) {
1461 if (use_privsep || options.kerberos_authentication)
1462 fatal("Privilege separation user %s does not exist",
1465 memset(privsep_pw->pw_passwd, 0, strlen(privsep_pw->pw_passwd));
1466 privsep_pw = pwcopy(privsep_pw);
1467 xfree(privsep_pw->pw_passwd);
1468 privsep_pw->pw_passwd = xstrdup("*");
1472 /* load private host keys */
1473 sensitive_data.host_keys = xcalloc(options.num_host_key_files,
1475 for (i = 0; i < options.num_host_key_files; i++)
1476 sensitive_data.host_keys[i] = NULL;
1478 for (i = 0; i < options.num_host_key_files; i++) {
1479 key = key_load_private(options.host_key_files[i], "", NULL);
1480 sensitive_data.host_keys[i] = key;
1482 error("Could not load host key: %s",
1483 options.host_key_files[i]);
1484 sensitive_data.host_keys[i] = NULL;
1487 switch (key->type) {
1489 sensitive_data.ssh1_host_key = key;
1490 sensitive_data.have_ssh1_key = 1;
1494 sensitive_data.have_ssh2_key = 1;
1497 debug("private host key: #%d type %d %s", i, key->type,
1500 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
1501 logit("Disabling protocol version 1. Could not load host key");
1502 options.protocol &= ~SSH_PROTO_1;
1504 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
1505 logit("Disabling protocol version 2. Could not load host key");
1506 options.protocol &= ~SSH_PROTO_2;
1508 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
1509 logit("sshd: no hostkeys available -- exiting.");
1513 /* Check certain values for sanity. */
1514 if (options.protocol & SSH_PROTO_1) {
1515 if (options.server_key_bits < 512 ||
1516 options.server_key_bits > 32768) {
1517 fprintf(stderr, "Bad server key size.\n");
1521 * Check that server and host key lengths differ sufficiently. This
1522 * is necessary to make double encryption work with rsaref. Oh, I
1523 * hate software patents. I dont know if this can go? Niels
1525 if (options.server_key_bits >
1526 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) -
1527 SSH_KEY_BITS_RESERVED && options.server_key_bits <
1528 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1529 SSH_KEY_BITS_RESERVED) {
1530 options.server_key_bits =
1531 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1532 SSH_KEY_BITS_RESERVED;
1533 debug("Forcing server key to %d bits to make it differ from host key.",
1534 options.server_key_bits);
1541 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) ||
1542 (S_ISDIR(st.st_mode) == 0))
1543 fatal("Missing privilege separation directory: %s",
1544 _PATH_PRIVSEP_CHROOT_DIR);
1547 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
1548 (st.st_uid != getuid () ||
1549 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0))
1551 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)
1553 fatal("%s must be owned by root and not group or "
1554 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR);
1557 /* Configuration looks good, so exit if in test mode. */
1562 * Clear out any supplemental groups we may have inherited. This
1563 * prevents inadvertent creation of files with bad modes (in the
1564 * portable version at least, it's certainly possible for PAM
1565 * to create a file, and we can't control the code in every
1566 * module which might be used).
1568 if (setgroups(0, NULL) < 0)
1569 debug("setgroups() failed: %.200s", strerror(errno));
1572 rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *));
1573 for (i = 0; i < rexec_argc; i++) {
1574 debug("rexec_argv[%d]='%s'", i, saved_argv[i]);
1575 rexec_argv[i] = saved_argv[i];
1577 rexec_argv[rexec_argc] = "-R";
1578 rexec_argv[rexec_argc + 1] = NULL;
1581 /* Initialize the log (it is reinitialized below in case we forked). */
1582 if (debug_flag && (!inetd_flag || rexeced_flag))
1584 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1587 * If not in debugging mode, and not started from inetd, disconnect
1588 * from the controlling terminal, and fork. The original process
1591 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
1594 #endif /* TIOCNOTTY */
1595 if (daemon(0, 0) < 0)
1596 fatal("daemon() failed: %.200s", strerror(errno));
1598 /* Disconnect from the controlling tty. */
1600 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
1602 (void) ioctl(fd, TIOCNOTTY, NULL);
1605 #endif /* TIOCNOTTY */
1607 /* Reinitialize the log (because of the fork above). */
1608 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1610 /* Initialize the random number generator. */
1613 /* Chdir to the root directory so that the current disk can be
1614 unmounted if desired. */
1617 /* ignore SIGPIPE */
1618 signal(SIGPIPE, SIG_IGN);
1620 /* Get a connection, either from inetd or a listening TCP socket */
1622 server_accept_inetd(&sock_in, &sock_out);
1626 if (options.protocol & SSH_PROTO_1)
1627 generate_ephemeral_server_key();
1629 signal(SIGHUP, sighup_handler);
1630 signal(SIGCHLD, main_sigchld_handler);
1631 signal(SIGTERM, sigterm_handler);
1632 signal(SIGQUIT, sigterm_handler);
1635 * Write out the pid file after the sigterm handler
1636 * is setup and the listen sockets are bound
1639 FILE *f = fopen(options.pid_file, "w");
1642 error("Couldn't create pid file \"%s\": %s",
1643 options.pid_file, strerror(errno));
1645 fprintf(f, "%ld\n", (long) getpid());
1650 /* Accept a connection and return in a forked child */
1651 server_accept_loop(&sock_in, &sock_out,
1652 &newsock, config_s);
1655 /* This is the child processing a new connection. */
1656 setproctitle("%s", "[accepted]");
1659 * Create a new session and process group since the 4.4BSD
1660 * setlogin() affects the entire process group. We don't
1661 * want the child to be able to affect the parent.
1663 #if !defined(SSHD_ACQUIRES_CTTY)
1665 * If setsid is called, on some platforms sshd will later acquire a
1666 * controlling terminal which will result in "could not set
1667 * controlling tty" errors.
1669 if (!debug_flag && !inetd_flag && setsid() < 0)
1670 error("setsid: %.100s", strerror(errno));
1676 debug("rexec start in %d out %d newsock %d pipe %d sock %d",
1677 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
1678 dup2(newsock, STDIN_FILENO);
1679 dup2(STDIN_FILENO, STDOUT_FILENO);
1680 if (startup_pipe == -1)
1681 close(REEXEC_STARTUP_PIPE_FD);
1683 dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD);
1685 dup2(config_s[1], REEXEC_CONFIG_PASS_FD);
1687 if (startup_pipe != -1)
1688 close(startup_pipe);
1690 execv(rexec_argv[0], rexec_argv);
1692 /* Reexec has failed, fall back and continue */
1693 error("rexec of %s failed: %s", rexec_argv[0], strerror(errno));
1694 recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL);
1695 log_init(__progname, options.log_level,
1696 options.log_facility, log_stderr);
1699 startup_pipe = REEXEC_STARTUP_PIPE_FD;
1701 close(REEXEC_CONFIG_PASS_FD);
1702 newsock = sock_out = sock_in = dup(STDIN_FILENO);
1703 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
1704 dup2(fd, STDIN_FILENO);
1705 dup2(fd, STDOUT_FILENO);
1706 if (fd > STDERR_FILENO)
1709 debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d",
1710 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
1714 * Disable the key regeneration alarm. We will not regenerate the
1715 * key since we are no longer in a position to give it to anyone. We
1716 * will not restart on SIGHUP since it no longer makes sense.
1719 signal(SIGALRM, SIG_DFL);
1720 signal(SIGHUP, SIG_DFL);
1721 signal(SIGTERM, SIG_DFL);
1722 signal(SIGQUIT, SIG_DFL);
1723 signal(SIGCHLD, SIG_DFL);
1724 signal(SIGINT, SIG_DFL);
1727 * Register our connection. This turns encryption off because we do
1730 packet_set_connection(sock_in, sock_out);
1731 packet_set_server();
1733 /* Set SO_KEEPALIVE if requested. */
1734 if (options.tcp_keep_alive && packet_connection_is_on_socket() &&
1735 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) < 0)
1736 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1738 if ((remote_port = get_remote_port()) < 0) {
1739 debug("get_remote_port failed");
1744 * We use get_canonical_hostname with usedns = 0 instead of
1745 * get_remote_ipaddr here so IP options will be checked.
1747 (void) get_canonical_hostname(0);
1749 * The rest of the code depends on the fact that
1750 * get_remote_ipaddr() caches the remote ip, even if
1751 * the socket goes away.
1753 remote_ip = get_remote_ipaddr();
1755 #ifdef SSH_AUDIT_EVENTS
1756 audit_connection_from(remote_ip, remote_port);
1759 allow_severity = options.log_facility|LOG_INFO;
1760 deny_severity = options.log_facility|LOG_WARNING;
1761 /* Check whether logins are denied from this host. */
1762 if (packet_connection_is_on_socket()) {
1763 struct request_info req;
1765 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
1768 if (!hosts_access(&req)) {
1769 debug("Connection refused by tcp wrapper");
1772 fatal("libwrap refuse returns");
1775 #endif /* LIBWRAP */
1777 /* Log the connection. */
1778 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1781 * We don't want to listen forever unless the other side
1782 * successfully authenticates itself. So we set up an alarm which is
1783 * cleared after successful authentication. A limit of zero
1784 * indicates no limit. Note that we don't set the alarm in debugging
1785 * mode; it is just annoying to have the server exit just when you
1786 * are about to discover the bug.
1788 signal(SIGALRM, grace_alarm_handler);
1790 alarm(options.login_grace_time);
1792 sshd_exchange_identification(sock_in, sock_out);
1794 /* In inetd mode, generate ephemeral key only for proto 1 connections */
1795 if (!compat20 && inetd_flag && sensitive_data.server_key == NULL)
1796 generate_ephemeral_server_key();
1798 packet_set_nonblocking();
1800 /* allocate authentication context */
1801 authctxt = xcalloc(1, sizeof(*authctxt));
1803 authctxt->loginmsg = &loginmsg;
1805 /* XXX global for cleanup, access from other modules */
1806 the_authctxt = authctxt;
1808 /* prepare buffer to collect messages to display to user after login */
1809 buffer_init(&loginmsg);
1812 if (privsep_preauth(authctxt) == 1)
1815 /* perform the key exchange */
1816 /* authenticate user and start session */
1819 do_authentication2(authctxt);
1822 do_authentication(authctxt);
1825 * If we use privilege separation, the unprivileged child transfers
1826 * the current keystate and exits
1829 mm_send_keystate(pmonitor);
1835 * Cancel the alarm we set to limit the time taken for
1839 signal(SIGALRM, SIG_DFL);
1840 authctxt->authenticated = 1;
1841 if (startup_pipe != -1) {
1842 close(startup_pipe);
1846 #ifdef SSH_AUDIT_EVENTS
1847 audit_event(SSH_AUTH_SUCCESS);
1851 if (options.gss_authentication) {
1852 temporarily_use_uid(authctxt->pw);
1853 ssh_gssapi_storecreds();
1858 if (options.use_pam) {
1865 * In privilege separation, we fork another child and prepare
1866 * file descriptor passing.
1869 privsep_postauth(authctxt);
1870 /* the monitor process [priv] will not return */
1872 destroy_sensitive_data();
1875 /* Start session. */
1876 do_authenticated(authctxt);
1878 /* The connection has been terminated. */
1879 verbose("Closing connection to %.100s", remote_ip);
1882 if (options.use_pam)
1884 #endif /* USE_PAM */
1886 #ifdef SSH_AUDIT_EVENTS
1887 PRIVSEP(audit_event(SSH_CONNECTION_CLOSE));
1899 * Decrypt session_key_int using our private server key and private host key
1900 * (key with larger modulus first).
1903 ssh1_session_key(BIGNUM *session_key_int)
1907 if (BN_cmp(sensitive_data.server_key->rsa->n,
1908 sensitive_data.ssh1_host_key->rsa->n) > 0) {
1909 /* Server key has bigger modulus. */
1910 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1911 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1912 SSH_KEY_BITS_RESERVED) {
1913 fatal("do_connection: %s: "
1914 "server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1915 get_remote_ipaddr(),
1916 BN_num_bits(sensitive_data.server_key->rsa->n),
1917 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1918 SSH_KEY_BITS_RESERVED);
1920 if (rsa_private_decrypt(session_key_int, session_key_int,
1921 sensitive_data.server_key->rsa) <= 0)
1923 if (rsa_private_decrypt(session_key_int, session_key_int,
1924 sensitive_data.ssh1_host_key->rsa) <= 0)
1927 /* Host key has bigger modulus (or they are equal). */
1928 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1929 BN_num_bits(sensitive_data.server_key->rsa->n) +
1930 SSH_KEY_BITS_RESERVED) {
1931 fatal("do_connection: %s: "
1932 "host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1933 get_remote_ipaddr(),
1934 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1935 BN_num_bits(sensitive_data.server_key->rsa->n),
1936 SSH_KEY_BITS_RESERVED);
1938 if (rsa_private_decrypt(session_key_int, session_key_int,
1939 sensitive_data.ssh1_host_key->rsa) < 0)
1941 if (rsa_private_decrypt(session_key_int, session_key_int,
1942 sensitive_data.server_key->rsa) < 0)
1955 BIGNUM *session_key_int;
1956 u_char session_key[SSH_SESSION_KEY_LENGTH];
1958 u_int cipher_type, auth_mask, protocol_flags;
1962 * Generate check bytes that the client must send back in the user
1963 * packet in order for it to be accepted; this is used to defy ip
1964 * spoofing attacks. Note that this only works against somebody
1965 * doing IP spoofing from a remote machine; any machine on the local
1966 * network can still see outgoing packets and catch the random
1967 * cookie. This only affects rhosts authentication, and this is one
1968 * of the reasons why it is inherently insecure.
1970 for (i = 0; i < 8; i++) {
1973 cookie[i] = rnd & 0xff;
1978 * Send our public key. We include in the packet 64 bits of random
1979 * data that must be matched in the reply in order to prevent IP
1982 packet_start(SSH_SMSG_PUBLIC_KEY);
1983 for (i = 0; i < 8; i++)
1984 packet_put_char(cookie[i]);
1986 /* Store our public server RSA key. */
1987 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1988 packet_put_bignum(sensitive_data.server_key->rsa->e);
1989 packet_put_bignum(sensitive_data.server_key->rsa->n);
1991 /* Store our public host RSA key. */
1992 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1993 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1994 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1996 /* Put protocol flags. */
1997 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1999 /* Declare which ciphers we support. */
2000 packet_put_int(cipher_mask_ssh1(0));
2002 /* Declare supported authentication types. */
2004 if (options.rhosts_rsa_authentication)
2005 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
2006 if (options.rsa_authentication)
2007 auth_mask |= 1 << SSH_AUTH_RSA;
2008 if (options.challenge_response_authentication == 1)
2009 auth_mask |= 1 << SSH_AUTH_TIS;
2010 if (options.password_authentication)
2011 auth_mask |= 1 << SSH_AUTH_PASSWORD;
2012 packet_put_int(auth_mask);
2014 /* Send the packet and wait for it to be sent. */
2016 packet_write_wait();
2018 debug("Sent %d bit server key and %d bit host key.",
2019 BN_num_bits(sensitive_data.server_key->rsa->n),
2020 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
2022 /* Read clients reply (cipher type and session key). */
2023 packet_read_expect(SSH_CMSG_SESSION_KEY);
2025 /* Get cipher type and check whether we accept this. */
2026 cipher_type = packet_get_char();
2028 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
2029 packet_disconnect("Warning: client selects unsupported cipher.");
2031 /* Get check bytes from the packet. These must match those we
2032 sent earlier with the public key packet. */
2033 for (i = 0; i < 8; i++)
2034 if (cookie[i] != packet_get_char())
2035 packet_disconnect("IP Spoofing check bytes do not match.");
2037 debug("Encryption type: %.200s", cipher_name(cipher_type));
2039 /* Get the encrypted integer. */
2040 if ((session_key_int = BN_new()) == NULL)
2041 fatal("do_ssh1_kex: BN_new failed");
2042 packet_get_bignum(session_key_int);
2044 protocol_flags = packet_get_int();
2045 packet_set_protocol_flags(protocol_flags);
2048 /* Decrypt session_key_int using host/server keys */
2049 rsafail = PRIVSEP(ssh1_session_key(session_key_int));
2052 * Extract session key from the decrypted integer. The key is in the
2053 * least significant 256 bits of the integer; the first byte of the
2054 * key is in the highest bits.
2057 (void) BN_mask_bits(session_key_int, sizeof(session_key) * 8);
2058 len = BN_num_bytes(session_key_int);
2059 if (len < 0 || (u_int)len > sizeof(session_key)) {
2060 error("do_ssh1_kex: bad session key len from %s: "
2061 "session_key_int %d > sizeof(session_key) %lu",
2062 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
2065 memset(session_key, 0, sizeof(session_key));
2066 BN_bn2bin(session_key_int,
2067 session_key + sizeof(session_key) - len);
2069 derive_ssh1_session_id(
2070 sensitive_data.ssh1_host_key->rsa->n,
2071 sensitive_data.server_key->rsa->n,
2072 cookie, session_id);
2074 * Xor the first 16 bytes of the session key with the
2077 for (i = 0; i < 16; i++)
2078 session_key[i] ^= session_id[i];
2082 int bytes = BN_num_bytes(session_key_int);
2083 u_char *buf = xmalloc(bytes);
2086 logit("do_connection: generating a fake encryption key");
2087 BN_bn2bin(session_key_int, buf);
2089 MD5_Update(&md, buf, bytes);
2090 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
2091 MD5_Final(session_key, &md);
2093 MD5_Update(&md, session_key, 16);
2094 MD5_Update(&md, buf, bytes);
2095 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
2096 MD5_Final(session_key + 16, &md);
2097 memset(buf, 0, bytes);
2099 for (i = 0; i < 16; i++)
2100 session_id[i] = session_key[i] ^ session_key[i + 16];
2102 /* Destroy the private and public keys. No longer. */
2103 destroy_sensitive_data();
2106 mm_ssh1_session_id(session_id);
2108 /* Destroy the decrypted integer. It is no longer needed. */
2109 BN_clear_free(session_key_int);
2111 /* Set the session key. From this on all communications will be encrypted. */
2112 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
2114 /* Destroy our copy of the session key. It is no longer needed. */
2115 memset(session_key, 0, sizeof(session_key));
2117 debug("Received session key; encryption turned on.");
2119 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */
2120 packet_start(SSH_SMSG_SUCCESS);
2122 packet_write_wait();
2126 * SSH2 key exchange: diffie-hellman-group1-sha1
2133 if (options.ciphers != NULL) {
2134 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2135 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
2137 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2138 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
2139 myproposal[PROPOSAL_ENC_ALGS_STOC] =
2140 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
2142 if (options.macs != NULL) {
2143 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
2144 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
2146 if (options.compression == COMP_NONE) {
2147 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2148 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
2149 } else if (options.compression == COMP_DELAYED) {
2150 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2151 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com";
2154 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
2156 /* start key exchange */
2157 kex = kex_setup(myproposal);
2158 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
2159 kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
2160 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
2161 kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
2163 kex->client_version_string=client_version_string;
2164 kex->server_version_string=server_version_string;
2165 kex->load_host_key=&get_hostkey_by_type;
2166 kex->host_key_index=&get_hostkey_index;
2170 dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
2172 session_id2 = kex->session_id;
2173 session_id2_len = kex->session_id_len;
2176 /* send 1st encrypted/maced/compressed message */
2177 packet_start(SSH2_MSG_IGNORE);
2178 packet_put_cstring("markus");
2180 packet_write_wait();
2185 /* server specific fatal cleanup */
2190 do_cleanup(the_authctxt);
2191 #ifdef SSH_AUDIT_EVENTS
2192 /* done after do_cleanup so it can cancel the PAM auth 'thread' */
2193 if (!use_privsep || mm_is_monitor())
2194 audit_event(SSH_CONNECTION_ABANDON);