1 /* $OpenBSD: sshd.c,v 1.364 2008/07/10 18:08:11 markus 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"
57 #include "openbsd-compat/sys-queue.h"
75 #include <openssl/dh.h>
76 #include <openssl/bn.h>
77 #include <openssl/md5.h>
78 #include <openssl/rand.h>
79 #include "openbsd-compat/openssl-compat.h"
81 #ifdef HAVE_SECUREWARE
82 #include <sys/security.h>
102 #include "myproposal.h"
103 #include "authfile.h"
104 #include "pathnames.h"
105 #include "atomicio.h"
106 #include "canohost.h"
107 #include "hostfile.h"
111 #include "dispatch.h"
112 #include "channels.h"
114 #include "monitor_mm.h"
119 #include "monitor_wrap.h"
120 #include "monitor_fdpass.h"
135 #define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1)
136 #define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2)
137 #define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3)
138 #define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4)
143 extern char *__progname;
145 /* Server configuration options. */
146 ServerOptions options;
148 /* Name of the server configuration file. */
149 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
152 * Debug mode flag. This can be set on the command line. If debug
153 * mode is enabled, extra debugging output will be sent to the system
154 * log, the daemon will not go to background, and will exit after processing
155 * the first connection.
159 /* Flag indicating that the daemon should only test the configuration and keys. */
162 /* Flag indicating that the daemon is being started from inetd. */
165 /* Flag indicating that sshd should not detach and become a daemon. */
166 int no_daemon_flag = 0;
168 /* debug goes to stderr unless inetd_flag is set */
171 /* Saved arguments to main(). */
176 int rexeced_flag = 0;
182 * The sockets that the server is listening; this is used in the SIGHUP
185 #define MAX_LISTEN_SOCKS 16
186 int listen_socks[MAX_LISTEN_SOCKS];
187 int num_listen_socks = 0;
190 * the client's version string, passed by sshd2 in compat mode. if != NULL,
191 * sshd will skip the version-number exchange
193 char *client_version_string = NULL;
194 char *server_version_string = NULL;
196 /* for rekeying XXX fixme */
200 * Any really sensitive data in the application is contained in this
201 * structure. The idea is that this structure could be locked into memory so
202 * that the pages do not get written into swap. However, there are some
203 * problems. The private key contains BIGNUMs, and we do not (in principle)
204 * have access to the internals of them, and locking just the structure is
205 * not very useful. Currently, memory locking is not implemented.
208 Key *server_key; /* ephemeral server key */
209 Key *ssh1_host_key; /* ssh1 host key */
210 Key **host_keys; /* all private host keys */
213 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
217 * Flag indicating whether the RSA server key needs to be regenerated.
218 * Is set in the SIGALRM handler and cleared when the key is regenerated.
220 static volatile sig_atomic_t key_do_regen = 0;
222 /* This is set to true when a signal is received. */
223 static volatile sig_atomic_t received_sighup = 0;
224 static volatile sig_atomic_t received_sigterm = 0;
226 /* session identifier, used by RSA-auth */
227 u_char session_id[16];
230 u_char *session_id2 = NULL;
231 u_int session_id2_len = 0;
233 /* record remote hostname or ip */
234 u_int utmp_len = MAXHOSTNAMELEN;
236 /* options.max_startup sized array of fd ints */
237 int *startup_pipes = NULL;
238 int startup_pipe; /* in child */
240 /* variables used for privilege separation */
241 int use_privsep = -1;
242 struct monitor *pmonitor = NULL;
244 /* global authentication context */
245 Authctxt *the_authctxt = NULL;
247 /* sshd_config buffer */
250 /* message to be displayed after login */
253 /* Unprivileged user */
254 struct passwd *privsep_pw = NULL;
256 /* Prototypes for various functions defined later in this file. */
257 void destroy_sensitive_data(void);
258 void demote_sensitive_data(void);
260 static void do_ssh1_kex(void);
261 static void do_ssh2_kex(void);
264 * Close all listening sockets
267 close_listen_socks(void)
271 for (i = 0; i < num_listen_socks; i++)
272 close(listen_socks[i]);
273 num_listen_socks = -1;
277 close_startup_pipes(void)
282 for (i = 0; i < options.max_startups; i++)
283 if (startup_pipes[i] != -1)
284 close(startup_pipes[i]);
288 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
289 * the effect is to reread the configuration file (and to regenerate
295 sighup_handler(int sig)
297 int save_errno = errno;
300 signal(SIGHUP, sighup_handler);
305 * Called from the main program after receiving SIGHUP.
306 * Restarts the server.
311 logit("Received SIGHUP; restarting.");
312 close_listen_socks();
313 close_startup_pipes();
314 alarm(0); /* alarm timer persists across exec */
315 execv(saved_argv[0], saved_argv);
316 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
322 * Generic signal handler for terminating signals in the master daemon.
326 sigterm_handler(int sig)
328 received_sigterm = sig;
332 * SIGCHLD handler. This is called whenever a child dies. This will then
333 * reap any zombies left by exited children.
337 main_sigchld_handler(int sig)
339 int save_errno = errno;
343 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
344 (pid < 0 && errno == EINTR))
347 signal(SIGCHLD, main_sigchld_handler);
352 * Signal handler for the alarm after the login grace period has expired.
356 grace_alarm_handler(int sig)
358 if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0)
359 kill(pmonitor->m_pid, SIGALRM);
361 /* Log error and exit. */
362 sigdie("Timeout before authentication for %s", get_remote_ipaddr());
366 * Signal handler for the key regeneration alarm. Note that this
367 * alarm only occurs in the daemon waiting for connections, and it does not
368 * do anything with the private key or random state before forking.
369 * Thus there should be no concurrency control/asynchronous execution
373 generate_ephemeral_server_key(void)
375 verbose("Generating %s%d bit RSA key.",
376 sensitive_data.server_key ? "new " : "", options.server_key_bits);
377 if (sensitive_data.server_key != NULL)
378 key_free(sensitive_data.server_key);
379 sensitive_data.server_key = key_generate(KEY_RSA1,
380 options.server_key_bits);
381 verbose("RSA key generation complete.");
383 arc4random_buf(sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
389 key_regeneration_alarm(int sig)
391 int save_errno = errno;
393 signal(SIGALRM, SIG_DFL);
399 sshd_exchange_identification(int sock_in, int sock_out)
403 int remote_major, remote_minor;
405 char *s, *newline = "\n";
406 char buf[256]; /* Must not be larger than remote_version. */
407 char remote_version[256]; /* Must be at least as big as buf. */
409 if ((options.protocol & SSH_PROTO_1) &&
410 (options.protocol & SSH_PROTO_2)) {
411 major = PROTOCOL_MAJOR_1;
413 } else if (options.protocol & SSH_PROTO_2) {
414 major = PROTOCOL_MAJOR_2;
415 minor = PROTOCOL_MINOR_2;
418 major = PROTOCOL_MAJOR_1;
419 minor = PROTOCOL_MINOR_1;
421 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s", major, minor,
422 SSH_RELEASE, newline);
423 server_version_string = xstrdup(buf);
425 /* Send our protocol version identification. */
426 if (atomicio(vwrite, sock_out, server_version_string,
427 strlen(server_version_string))
428 != strlen(server_version_string)) {
429 logit("Could not write ident string to %s", get_remote_ipaddr());
433 /* Read other sides version identification. */
434 memset(buf, 0, sizeof(buf));
435 for (i = 0; i < sizeof(buf) - 1; i++) {
436 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
437 logit("Did not receive identification string from %s",
438 get_remote_ipaddr());
441 if (buf[i] == '\r') {
443 /* Kludge for F-Secure Macintosh < 1.0.2 */
445 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
449 if (buf[i] == '\n') {
454 buf[sizeof(buf) - 1] = 0;
455 client_version_string = xstrdup(buf);
458 * Check that the versions match. In future this might accept
459 * several versions and set appropriate flags to handle them.
461 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
462 &remote_major, &remote_minor, remote_version) != 3) {
463 s = "Protocol mismatch.\n";
464 (void) atomicio(vwrite, sock_out, s, strlen(s));
467 logit("Bad protocol version identification '%.100s' from %s",
468 client_version_string, get_remote_ipaddr());
471 debug("Client protocol version %d.%d; client software version %.100s",
472 remote_major, remote_minor, remote_version);
473 logit("SSH: Server;Ltype: Version;Remote: %s-%d;Protocol: %d.%d;Client: %.100s",
474 get_remote_ipaddr(), get_remote_port(),
475 remote_major, remote_minor, remote_version);
477 compat_datafellows(remote_version);
479 if (datafellows & SSH_BUG_PROBE) {
480 logit("probed from %s with %s. Don't panic.",
481 get_remote_ipaddr(), client_version_string);
485 if (datafellows & SSH_BUG_SCANNER) {
486 logit("scanned from %s with %s. Don't panic.",
487 get_remote_ipaddr(), client_version_string);
492 switch (remote_major) {
494 if (remote_minor == 99) {
495 if (options.protocol & SSH_PROTO_2)
501 if (!(options.protocol & SSH_PROTO_1)) {
505 if (remote_minor < 3) {
506 packet_disconnect("Your ssh version is too old and "
507 "is no longer supported. Please install a newer version.");
508 } else if (remote_minor == 3) {
509 /* note that this disables agent-forwarding */
514 if (options.protocol & SSH_PROTO_2) {
523 chop(server_version_string);
524 debug("Local version string %.200s", server_version_string);
527 s = "Protocol major versions differ.\n";
528 (void) atomicio(vwrite, sock_out, s, strlen(s));
531 logit("Protocol major versions differ for %s: %.200s vs. %.200s",
533 server_version_string, client_version_string);
538 /* Destroy the host and server keys. They will no longer be needed. */
540 destroy_sensitive_data(void)
544 if (sensitive_data.server_key) {
545 key_free(sensitive_data.server_key);
546 sensitive_data.server_key = NULL;
548 for (i = 0; i < options.num_host_key_files; i++) {
549 if (sensitive_data.host_keys[i]) {
550 key_free(sensitive_data.host_keys[i]);
551 sensitive_data.host_keys[i] = NULL;
554 sensitive_data.ssh1_host_key = NULL;
555 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
558 /* Demote private to public keys for network child */
560 demote_sensitive_data(void)
565 if (sensitive_data.server_key) {
566 tmp = key_demote(sensitive_data.server_key);
567 key_free(sensitive_data.server_key);
568 sensitive_data.server_key = tmp;
571 for (i = 0; i < options.num_host_key_files; i++) {
572 if (sensitive_data.host_keys[i]) {
573 tmp = key_demote(sensitive_data.host_keys[i]);
574 key_free(sensitive_data.host_keys[i]);
575 sensitive_data.host_keys[i] = tmp;
576 if (tmp->type == KEY_RSA1)
577 sensitive_data.ssh1_host_key = tmp;
581 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */
585 privsep_preauth_child(void)
590 /* Enable challenge-response authentication for privilege separation */
591 privsep_challenge_enable();
594 arc4random_buf(rnd, sizeof(rnd));
595 RAND_seed(rnd, sizeof(rnd));
597 /* Demote the private keys to public keys. */
598 demote_sensitive_data();
600 /* Change our root directory */
601 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
602 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
604 if (chdir("/") == -1)
605 fatal("chdir(\"/\"): %s", strerror(errno));
607 /* Drop our privileges */
608 debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid,
609 (u_int)privsep_pw->pw_gid);
611 /* XXX not ready, too heavy after chroot */
612 do_setusercontext(privsep_pw);
614 gidset[0] = privsep_pw->pw_gid;
615 if (setgroups(1, gidset) < 0)
616 fatal("setgroups: %.100s", strerror(errno));
617 permanently_set_uid(privsep_pw);
622 privsep_preauth(Authctxt *authctxt)
627 /* Set up unprivileged child process to deal with network data */
628 pmonitor = monitor_init();
629 /* Store a pointer to the kex for later rekeying */
630 pmonitor->m_pkex = &xxx_kex;
634 fatal("fork of unprivileged child failed");
635 } else if (pid != 0) {
636 debug2("Network child is on pid %ld", (long)pid);
638 close(pmonitor->m_recvfd);
639 pmonitor->m_pid = pid;
640 monitor_child_preauth(authctxt, pmonitor);
641 close(pmonitor->m_sendfd);
644 monitor_sync(pmonitor);
646 /* Wait for the child's exit status */
647 while (waitpid(pid, &status, 0) < 0)
654 close(pmonitor->m_sendfd);
656 /* Demote the child */
657 if (getuid() == 0 || geteuid() == 0)
658 privsep_preauth_child();
659 setproctitle("%s", "[net]");
665 privsep_postauth(Authctxt *authctxt)
669 #ifdef DISABLE_FD_PASSING
672 if (authctxt->pw->pw_uid == 0 || options.use_login) {
674 /* File descriptor passing is broken or root login */
679 /* New socket pair */
680 monitor_reinit(pmonitor);
682 pmonitor->m_pid = fork();
683 if (pmonitor->m_pid == -1)
684 fatal("fork of unprivileged child failed");
685 else if (pmonitor->m_pid != 0) {
686 verbose("User child is on pid %ld", (long)pmonitor->m_pid);
687 close(pmonitor->m_recvfd);
688 buffer_clear(&loginmsg);
689 monitor_child_postauth(pmonitor);
695 close(pmonitor->m_sendfd);
697 /* Demote the private keys to public keys. */
698 demote_sensitive_data();
701 arc4random_buf(rnd, sizeof(rnd));
702 RAND_seed(rnd, sizeof(rnd));
704 /* Drop privileges */
705 do_setusercontext(authctxt->pw);
708 /* It is safe now to apply the key state */
709 monitor_apply_keystate(pmonitor);
712 * Tell the packet layer that authentication was successful, since
713 * this information is not part of the key state.
715 packet_set_authenticated();
719 list_hostkey_types(void)
727 for (i = 0; i < options.num_host_key_files; i++) {
728 Key *key = sensitive_data.host_keys[i];
734 if (buffer_len(&b) > 0)
735 buffer_append(&b, ",", 1);
736 p = key_ssh_name(key);
737 buffer_append(&b, p, strlen(p));
741 buffer_append(&b, "\0", 1);
742 ret = xstrdup(buffer_ptr(&b));
744 debug("list_hostkey_types: %s", ret);
749 get_hostkey_by_type(int type)
753 for (i = 0; i < options.num_host_key_files; i++) {
754 Key *key = sensitive_data.host_keys[i];
755 if (key != NULL && key->type == type)
762 get_hostkey_by_index(int ind)
764 if (ind < 0 || ind >= options.num_host_key_files)
766 return (sensitive_data.host_keys[ind]);
770 get_hostkey_index(Key *key)
774 for (i = 0; i < options.num_host_key_files; i++) {
775 if (key == sensitive_data.host_keys[i])
782 * returns 1 if connection should be dropped, 0 otherwise.
783 * dropping starts at connection #max_startups_begin with a probability
784 * of (max_startups_rate/100). the probability increases linearly until
785 * all connections are dropped for startups > max_startups
788 drop_connection(int startups)
792 if (startups < options.max_startups_begin)
794 if (startups >= options.max_startups)
796 if (options.max_startups_rate == 100)
799 p = 100 - options.max_startups_rate;
800 p *= startups - options.max_startups_begin;
801 p /= options.max_startups - options.max_startups_begin;
802 p += options.max_startups_rate;
803 r = arc4random_uniform(100);
805 debug("drop_connection: p %d, r %d", p, r);
806 return (r < p) ? 1 : 0;
812 fprintf(stderr, "%s, %s\n",
813 SSH_RELEASE, SSLeay_version(SSLEAY_VERSION));
815 "usage: sshd [-46DdeiqTt] [-b bits] [-C connection_spec] [-f config_file]\n"
816 " [-g login_grace_time] [-h host_key_file] [-k key_gen_time]\n"
817 " [-o option] [-p port] [-u len]\n"
823 send_rexec_state(int fd, Buffer *conf)
827 debug3("%s: entering fd = %d config len %d", __func__, fd,
831 * Protocol from reexec master to child:
832 * string configuration
833 * u_int ephemeral_key_follows
834 * bignum e (only if ephemeral_key_follows == 1)
840 * string rngseed (only if OpenSSL is not self-seeded)
843 buffer_put_cstring(&m, buffer_ptr(conf));
845 if (sensitive_data.server_key != NULL &&
846 sensitive_data.server_key->type == KEY_RSA1) {
847 buffer_put_int(&m, 1);
848 buffer_put_bignum(&m, sensitive_data.server_key->rsa->e);
849 buffer_put_bignum(&m, sensitive_data.server_key->rsa->n);
850 buffer_put_bignum(&m, sensitive_data.server_key->rsa->d);
851 buffer_put_bignum(&m, sensitive_data.server_key->rsa->iqmp);
852 buffer_put_bignum(&m, sensitive_data.server_key->rsa->p);
853 buffer_put_bignum(&m, sensitive_data.server_key->rsa->q);
855 buffer_put_int(&m, 0);
857 #ifndef OPENSSL_PRNG_ONLY
858 rexec_send_rng_seed(&m);
861 if (ssh_msg_send(fd, 0, &m) == -1)
862 fatal("%s: ssh_msg_send failed", __func__);
866 debug3("%s: done", __func__);
870 recv_rexec_state(int fd, Buffer *conf)
876 debug3("%s: entering fd = %d", __func__, fd);
880 if (ssh_msg_recv(fd, &m) == -1)
881 fatal("%s: ssh_msg_recv failed", __func__);
882 if (buffer_get_char(&m) != 0)
883 fatal("%s: rexec version mismatch", __func__);
885 cp = buffer_get_string(&m, &len);
887 buffer_append(conf, cp, len + 1);
890 if (buffer_get_int(&m)) {
891 if (sensitive_data.server_key != NULL)
892 key_free(sensitive_data.server_key);
893 sensitive_data.server_key = key_new_private(KEY_RSA1);
894 buffer_get_bignum(&m, sensitive_data.server_key->rsa->e);
895 buffer_get_bignum(&m, sensitive_data.server_key->rsa->n);
896 buffer_get_bignum(&m, sensitive_data.server_key->rsa->d);
897 buffer_get_bignum(&m, sensitive_data.server_key->rsa->iqmp);
898 buffer_get_bignum(&m, sensitive_data.server_key->rsa->p);
899 buffer_get_bignum(&m, sensitive_data.server_key->rsa->q);
900 rsa_generate_additional_parameters(
901 sensitive_data.server_key->rsa);
904 #ifndef OPENSSL_PRNG_ONLY
905 rexec_recv_rng_seed(&m);
910 debug3("%s: done", __func__);
913 /* Accept a connection from inetd */
915 server_accept_inetd(int *sock_in, int *sock_out)
921 close(REEXEC_CONFIG_PASS_FD);
922 *sock_in = *sock_out = dup(STDIN_FILENO);
924 startup_pipe = dup(REEXEC_STARTUP_PIPE_FD);
925 close(REEXEC_STARTUP_PIPE_FD);
928 *sock_in = dup(STDIN_FILENO);
929 *sock_out = dup(STDOUT_FILENO);
932 * We intentionally do not close the descriptors 0, 1, and 2
933 * as our code for setting the descriptors won't work if
934 * ttyfd happens to be one of those.
936 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
937 dup2(fd, STDIN_FILENO);
938 dup2(fd, STDOUT_FILENO);
939 if (fd > STDOUT_FILENO)
942 debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out);
946 * Listen for TCP connections
951 int ret, listen_sock, on = 1;
953 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
955 int socksizelen = sizeof(int);
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 getsockopt(listen_sock, SOL_SOCKET, SO_RCVBUF,
1003 &socksize, &socksizelen);
1004 debug("Server TCP RWIN socket size: %d", socksize);
1005 debug("HPN Buffer Size: %d", options.hpn_buffer_size);
1007 /* Bind the socket to the desired port. */
1008 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1009 error("Bind to port %s on %s failed: %.200s.",
1010 strport, ntop, strerror(errno));
1014 listen_socks[num_listen_socks] = listen_sock;
1017 /* Start listening on the port. */
1018 if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0)
1019 fatal("listen on [%s]:%s: %.100s",
1020 ntop, strport, strerror(errno));
1021 logit("Server listening on %s port %s.", ntop, strport);
1023 freeaddrinfo(options.listen_addrs);
1025 if (!num_listen_socks)
1026 fatal("Cannot bind any address.");
1030 * The main TCP accept loop. Note that, for the non-debug case, returns
1031 * from this function are in a forked subprocess.
1034 server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
1037 int i, j, ret, maxfd;
1038 int key_used = 0, startups = 0;
1039 int startup_p[2] = { -1 , -1 };
1040 struct sockaddr_storage from;
1044 /* setup fd set for accept */
1047 for (i = 0; i < num_listen_socks; i++)
1048 if (listen_socks[i] > maxfd)
1049 maxfd = listen_socks[i];
1050 /* pipes connected to unauthenticated childs */
1051 startup_pipes = xcalloc(options.max_startups, sizeof(int));
1052 for (i = 0; i < options.max_startups; i++)
1053 startup_pipes[i] = -1;
1056 * Stay listening for connections until the system crashes or
1057 * the daemon is killed with a signal.
1060 if (received_sighup)
1064 fdset = (fd_set *)xcalloc(howmany(maxfd + 1, NFDBITS),
1067 for (i = 0; i < num_listen_socks; i++)
1068 FD_SET(listen_socks[i], fdset);
1069 for (i = 0; i < options.max_startups; i++)
1070 if (startup_pipes[i] != -1)
1071 FD_SET(startup_pipes[i], fdset);
1073 /* Wait in select until there is a connection. */
1074 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
1075 if (ret < 0 && errno != EINTR)
1076 error("select: %.100s", strerror(errno));
1077 if (received_sigterm) {
1078 logit("Received signal %d; terminating.",
1079 (int) received_sigterm);
1080 close_listen_socks();
1081 unlink(options.pid_file);
1084 if (key_used && key_do_regen) {
1085 generate_ephemeral_server_key();
1092 for (i = 0; i < options.max_startups; i++)
1093 if (startup_pipes[i] != -1 &&
1094 FD_ISSET(startup_pipes[i], fdset)) {
1096 * the read end of the pipe is ready
1097 * if the child has closed the pipe
1098 * after successful authentication
1099 * or if the child has died
1101 close(startup_pipes[i]);
1102 startup_pipes[i] = -1;
1105 for (i = 0; i < num_listen_socks; i++) {
1106 if (!FD_ISSET(listen_socks[i], fdset))
1108 fromlen = sizeof(from);
1109 *newsock = accept(listen_socks[i],
1110 (struct sockaddr *)&from, &fromlen);
1112 if (errno != EINTR && errno != EAGAIN &&
1113 errno != EWOULDBLOCK)
1114 error("accept: %.100s", strerror(errno));
1117 if (unset_nonblock(*newsock) == -1) {
1121 if (drop_connection(startups) == 1) {
1122 debug("drop connection #%d", startups);
1126 if (pipe(startup_p) == -1) {
1131 if (rexec_flag && socketpair(AF_UNIX,
1132 SOCK_STREAM, 0, config_s) == -1) {
1133 error("reexec socketpair: %s",
1136 close(startup_p[0]);
1137 close(startup_p[1]);
1141 for (j = 0; j < options.max_startups; j++)
1142 if (startup_pipes[j] == -1) {
1143 startup_pipes[j] = startup_p[0];
1144 if (maxfd < startup_p[0])
1145 maxfd = startup_p[0];
1151 * Got connection. Fork a child to handle it, unless
1152 * we are in debugging mode.
1156 * In debugging mode. Close the listening
1157 * socket, and start processing the
1158 * connection without forking.
1160 debug("Server will not fork when running in debugging mode.");
1161 close_listen_socks();
1162 *sock_in = *newsock;
1163 *sock_out = *newsock;
1164 close(startup_p[0]);
1165 close(startup_p[1]);
1169 send_rexec_state(config_s[0],
1177 * Normal production daemon. Fork, and have
1178 * the child process the connection. The
1179 * parent continues listening.
1181 platform_pre_fork();
1182 if ((pid = fork()) == 0) {
1184 * Child. Close the listening and
1185 * max_startup sockets. Start using
1186 * the accepted socket. Reinitialize
1187 * logging (since our pid has changed).
1188 * We break out of the loop to handle
1191 platform_post_fork_child();
1192 startup_pipe = startup_p[1];
1193 close_startup_pipes();
1194 close_listen_socks();
1195 *sock_in = *newsock;
1196 *sock_out = *newsock;
1197 log_init(__progname,
1199 options.log_facility,
1206 /* Parent. Stay in the loop. */
1207 platform_post_fork_parent(pid);
1209 error("fork: %.100s", strerror(errno));
1211 debug("Forked child %ld.", (long)pid);
1213 close(startup_p[1]);
1216 send_rexec_state(config_s[0], &cfg);
1222 * Mark that the key has been used (it
1223 * was "given" to the child).
1225 if ((options.protocol & SSH_PROTO_1) &&
1227 /* Schedule server key regeneration alarm. */
1228 signal(SIGALRM, key_regeneration_alarm);
1229 alarm(options.key_regeneration_time);
1236 * Ensure that our random state differs
1237 * from that of the child
1242 /* child process check (or debug mode) */
1243 if (num_listen_socks < 0)
1250 * Main program for the daemon.
1253 main(int ac, char **av)
1255 extern char *optarg;
1258 int sock_in = -1, sock_out = -1, newsock = -1;
1259 const char *remote_ip;
1260 char *test_user = NULL, *test_host = NULL, *test_addr = NULL;
1262 char *line, *p, *cp;
1263 int config_s[2] = { -1 , -1 };
1264 u_int64_t ibytes, obytes;
1269 #ifdef HAVE_SECUREWARE
1270 (void)set_auth_parameters(ac, av);
1272 __progname = ssh_get_progname(av[0]);
1275 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
1278 saved_argv = xcalloc(ac + 1, sizeof(*saved_argv));
1279 for (i = 0; i < ac; i++)
1280 saved_argv[i] = xstrdup(av[i]);
1281 saved_argv[i] = NULL;
1283 #ifndef HAVE_SETPROCTITLE
1284 /* Prepare for later setproctitle emulation */
1285 compat_init_setproctitle(ac, av);
1289 if (geteuid() == 0 && setgroups(0, NULL) == -1)
1290 debug("setgroups(): %.200s", strerror(errno));
1292 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
1295 /* Initialize configuration options to their default values. */
1296 initialize_server_options(&options);
1298 /* Parse command-line arguments. */
1299 while ((opt = getopt(ac, av, "f:p:b:k:h:g:u:o:C:dDeiqrtQRT46")) != -1) {
1302 options.address_family = AF_INET;
1305 options.address_family = AF_INET6;
1308 config_file_name = optarg;
1311 if (debug_flag == 0) {
1313 options.log_level = SYSLOG_LEVEL_DEBUG1;
1314 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
1315 options.log_level++;
1337 options.log_level = SYSLOG_LEVEL_QUIET;
1340 options.server_key_bits = (int)strtonum(optarg, 256,
1344 options.ports_from_cmdline = 1;
1345 if (options.num_ports >= MAX_PORTS) {
1346 fprintf(stderr, "too many ports.\n");
1349 options.ports[options.num_ports++] = a2port(optarg);
1350 if (options.ports[options.num_ports-1] == 0) {
1351 fprintf(stderr, "Bad port number.\n");
1356 if ((options.login_grace_time = convtime(optarg)) == -1) {
1357 fprintf(stderr, "Invalid login grace time.\n");
1362 if ((options.key_regeneration_time = convtime(optarg)) == -1) {
1363 fprintf(stderr, "Invalid key regeneration interval.\n");
1368 if (options.num_host_key_files >= MAX_HOSTKEYS) {
1369 fprintf(stderr, "too many host keys.\n");
1372 options.host_key_files[options.num_host_key_files++] = optarg;
1382 while ((p = strsep(&cp, ",")) && *p != '\0') {
1383 if (strncmp(p, "addr=", 5) == 0)
1384 test_addr = xstrdup(p + 5);
1385 else if (strncmp(p, "host=", 5) == 0)
1386 test_host = xstrdup(p + 5);
1387 else if (strncmp(p, "user=", 5) == 0)
1388 test_user = xstrdup(p + 5);
1390 fprintf(stderr, "Invalid test "
1391 "mode specification %s\n", p);
1397 utmp_len = (u_int)strtonum(optarg, 0, MAXHOSTNAMELEN+1, NULL);
1398 if (utmp_len > MAXHOSTNAMELEN) {
1399 fprintf(stderr, "Invalid utmp length.\n");
1404 line = xstrdup(optarg);
1405 if (process_server_config_line(&options, line,
1406 "command-line", 0, NULL, NULL, NULL, NULL) != 0)
1416 if (rexeced_flag || inetd_flag)
1418 if (!test_flag && (rexec_flag && (av[0] == NULL || *av[0] != '/')))
1419 fatal("sshd re-exec requires execution with an absolute path");
1421 closefrom(REEXEC_MIN_FREE_FD);
1423 closefrom(REEXEC_DEVCRYPTO_RESERVED_FD);
1425 SSLeay_add_all_algorithms();
1428 * Force logging to stderr until we have loaded the private host
1429 * key (unless started from inetd)
1431 log_init(__progname,
1432 options.log_level == SYSLOG_LEVEL_NOT_SET ?
1433 SYSLOG_LEVEL_INFO : options.log_level,
1434 options.log_facility == SYSLOG_FACILITY_NOT_SET ?
1435 SYSLOG_FACILITY_AUTH : options.log_facility,
1436 log_stderr || !inetd_flag);
1439 * Unset KRB5CCNAME, otherwise the user's session may inherit it from
1440 * root's environment
1442 if (getenv("KRB5CCNAME") != NULL)
1443 unsetenv("KRB5CCNAME");
1446 /* Cray can define user privs drop all privs now!
1447 * Not needed on PRIV_SU systems!
1452 sensitive_data.server_key = NULL;
1453 sensitive_data.ssh1_host_key = NULL;
1454 sensitive_data.have_ssh1_key = 0;
1455 sensitive_data.have_ssh2_key = 0;
1458 * If we're doing an extended config test, make sure we have all of
1459 * the parameters we need. If we're not doing an extended test,
1460 * do not silently ignore connection test params.
1462 if (test_flag >= 2 &&
1463 (test_user != NULL || test_host != NULL || test_addr != NULL)
1464 && (test_user == NULL || test_host == NULL || test_addr == NULL))
1465 fatal("user, host and addr are all required when testing "
1467 if (test_flag < 2 && (test_user != NULL || test_host != NULL ||
1469 fatal("Config test connection parameter (-C) provided without "
1472 /* Fetch our configuration */
1475 recv_rexec_state(REEXEC_CONFIG_PASS_FD, &cfg);
1477 load_server_config(config_file_name, &cfg);
1479 parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name,
1480 &cfg, NULL, NULL, NULL);
1484 /* Fill in default values for those options not explicitly set. */
1485 fill_default_server_options(&options);
1487 /* challenge-response is implemented via keyboard interactive */
1488 if (options.challenge_response_authentication)
1489 options.kbd_interactive_authentication = 1;
1491 /* set default channel AF */
1492 channel_set_af(options.address_family);
1494 /* Check that there are no remaining arguments. */
1496 fprintf(stderr, "Extra argument %s.\n", av[optind]);
1500 debug("sshd version %.100s", SSH_RELEASE);
1502 /* Store privilege separation user for later use if required. */
1503 if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) {
1504 if (use_privsep || options.kerberos_authentication)
1505 fatal("Privilege separation user %s does not exist",
1508 memset(privsep_pw->pw_passwd, 0, strlen(privsep_pw->pw_passwd));
1509 privsep_pw = pwcopy(privsep_pw);
1510 xfree(privsep_pw->pw_passwd);
1511 privsep_pw->pw_passwd = xstrdup("*");
1515 /* load private host keys */
1516 sensitive_data.host_keys = xcalloc(options.num_host_key_files,
1518 for (i = 0; i < options.num_host_key_files; i++)
1519 sensitive_data.host_keys[i] = NULL;
1521 for (i = 0; i < options.num_host_key_files; i++) {
1522 key = key_load_private(options.host_key_files[i], "", NULL);
1523 sensitive_data.host_keys[i] = key;
1525 error("Could not load host key: %s",
1526 options.host_key_files[i]);
1527 sensitive_data.host_keys[i] = NULL;
1530 switch (key->type) {
1532 sensitive_data.ssh1_host_key = key;
1533 sensitive_data.have_ssh1_key = 1;
1537 sensitive_data.have_ssh2_key = 1;
1540 debug("private host key: #%d type %d %s", i, key->type,
1543 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
1544 logit("Disabling protocol version 1. Could not load host key");
1545 options.protocol &= ~SSH_PROTO_1;
1547 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
1548 logit("Disabling protocol version 2. Could not load host key");
1549 options.protocol &= ~SSH_PROTO_2;
1551 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
1552 logit("sshd: no hostkeys available -- exiting.");
1556 /* Check certain values for sanity. */
1557 if (options.protocol & SSH_PROTO_1) {
1558 if (options.server_key_bits < 512 ||
1559 options.server_key_bits > 32768) {
1560 fprintf(stderr, "Bad server key size.\n");
1564 * Check that server and host key lengths differ sufficiently. This
1565 * is necessary to make double encryption work with rsaref. Oh, I
1566 * hate software patents. I dont know if this can go? Niels
1568 if (options.server_key_bits >
1569 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) -
1570 SSH_KEY_BITS_RESERVED && options.server_key_bits <
1571 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1572 SSH_KEY_BITS_RESERVED) {
1573 options.server_key_bits =
1574 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1575 SSH_KEY_BITS_RESERVED;
1576 debug("Forcing server key to %d bits to make it differ from host key.",
1577 options.server_key_bits);
1584 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) ||
1585 (S_ISDIR(st.st_mode) == 0))
1586 fatal("Missing privilege separation directory: %s",
1587 _PATH_PRIVSEP_CHROOT_DIR);
1590 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
1591 (st.st_uid != getuid () ||
1592 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0))
1594 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)
1596 fatal("%s must be owned by root and not group or "
1597 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR);
1600 if (test_flag > 1) {
1601 if (test_user != NULL && test_addr != NULL && test_host != NULL)
1602 parse_server_match_config(&options, test_user,
1603 test_host, test_addr);
1604 dump_config(&options);
1607 /* Configuration looks good, so exit if in test mode. */
1612 * Clear out any supplemental groups we may have inherited. This
1613 * prevents inadvertent creation of files with bad modes (in the
1614 * portable version at least, it's certainly possible for PAM
1615 * to create a file, and we can't control the code in every
1616 * module which might be used).
1618 if (setgroups(0, NULL) < 0)
1619 debug("setgroups() failed: %.200s", strerror(errno));
1622 rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *));
1623 for (i = 0; i < rexec_argc; i++) {
1624 debug("rexec_argv[%d]='%s'", i, saved_argv[i]);
1625 rexec_argv[i] = saved_argv[i];
1627 rexec_argv[rexec_argc] = "-R";
1628 rexec_argv[rexec_argc + 1] = NULL;
1631 /* Ensure that umask disallows at least group and world write */
1632 new_umask = umask(0077) | 0022;
1633 (void) umask(new_umask);
1635 /* Initialize the log (it is reinitialized below in case we forked). */
1636 if (debug_flag && (!inetd_flag || rexeced_flag))
1638 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1641 * If not in debugging mode, and not started from inetd, disconnect
1642 * from the controlling terminal, and fork. The original process
1645 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
1648 #endif /* TIOCNOTTY */
1649 if (daemon(0, 0) < 0)
1650 fatal("daemon() failed: %.200s", strerror(errno));
1652 /* Disconnect from the controlling tty. */
1654 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
1656 (void) ioctl(fd, TIOCNOTTY, NULL);
1659 #endif /* TIOCNOTTY */
1661 /* Reinitialize the log (because of the fork above). */
1662 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1664 /* Initialize the random number generator. */
1667 /* Chdir to the root directory so that the current disk can be
1668 unmounted if desired. */
1671 /* ignore SIGPIPE */
1672 signal(SIGPIPE, SIG_IGN);
1674 /* Get a connection, either from inetd or a listening TCP socket */
1676 server_accept_inetd(&sock_in, &sock_out);
1680 if (options.protocol & SSH_PROTO_1)
1681 generate_ephemeral_server_key();
1683 signal(SIGHUP, sighup_handler);
1684 signal(SIGCHLD, main_sigchld_handler);
1685 signal(SIGTERM, sigterm_handler);
1686 signal(SIGQUIT, sigterm_handler);
1689 * Write out the pid file after the sigterm handler
1690 * is setup and the listen sockets are bound
1693 FILE *f = fopen(options.pid_file, "w");
1696 error("Couldn't create pid file \"%s\": %s",
1697 options.pid_file, strerror(errno));
1699 fprintf(f, "%ld\n", (long) getpid());
1704 /* Accept a connection and return in a forked child */
1705 server_accept_loop(&sock_in, &sock_out,
1706 &newsock, config_s);
1709 /* This is the child processing a new connection. */
1710 setproctitle("%s", "[accepted]");
1713 * Create a new session and process group since the 4.4BSD
1714 * setlogin() affects the entire process group. We don't
1715 * want the child to be able to affect the parent.
1717 #if !defined(SSHD_ACQUIRES_CTTY)
1719 * If setsid is called, on some platforms sshd will later acquire a
1720 * controlling terminal which will result in "could not set
1721 * controlling tty" errors.
1723 if (!debug_flag && !inetd_flag && setsid() < 0)
1724 error("setsid: %.100s", strerror(errno));
1730 debug("rexec start in %d out %d newsock %d pipe %d sock %d",
1731 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
1732 dup2(newsock, STDIN_FILENO);
1733 dup2(STDIN_FILENO, STDOUT_FILENO);
1734 if (startup_pipe == -1)
1735 close(REEXEC_STARTUP_PIPE_FD);
1737 dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD);
1739 dup2(config_s[1], REEXEC_CONFIG_PASS_FD);
1741 if (startup_pipe != -1)
1742 close(startup_pipe);
1744 execv(rexec_argv[0], rexec_argv);
1746 /* Reexec has failed, fall back and continue */
1747 error("rexec of %s failed: %s", rexec_argv[0], strerror(errno));
1748 recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL);
1749 log_init(__progname, options.log_level,
1750 options.log_facility, log_stderr);
1753 startup_pipe = REEXEC_STARTUP_PIPE_FD;
1755 close(REEXEC_CONFIG_PASS_FD);
1756 newsock = sock_out = sock_in = dup(STDIN_FILENO);
1757 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
1758 dup2(fd, STDIN_FILENO);
1759 dup2(fd, STDOUT_FILENO);
1760 if (fd > STDERR_FILENO)
1763 debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d",
1764 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
1768 * Disable the key regeneration alarm. We will not regenerate the
1769 * key since we are no longer in a position to give it to anyone. We
1770 * will not restart on SIGHUP since it no longer makes sense.
1773 signal(SIGALRM, SIG_DFL);
1774 signal(SIGHUP, SIG_DFL);
1775 signal(SIGTERM, SIG_DFL);
1776 signal(SIGQUIT, SIG_DFL);
1777 signal(SIGCHLD, SIG_DFL);
1778 signal(SIGINT, SIG_DFL);
1781 * Register our connection. This turns encryption off because we do
1784 packet_set_connection(sock_in, sock_out);
1785 packet_set_server();
1787 /* Set SO_KEEPALIVE if requested. */
1788 if (options.tcp_keep_alive && packet_connection_is_on_socket() &&
1789 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) < 0)
1790 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1792 if ((remote_port = get_remote_port()) < 0) {
1793 debug("get_remote_port failed");
1798 * We use get_canonical_hostname with usedns = 0 instead of
1799 * get_remote_ipaddr here so IP options will be checked.
1801 (void) get_canonical_hostname(0);
1803 * The rest of the code depends on the fact that
1804 * get_remote_ipaddr() caches the remote ip, even if
1805 * the socket goes away.
1807 remote_ip = get_remote_ipaddr();
1809 #ifdef SSH_AUDIT_EVENTS
1810 audit_connection_from(remote_ip, remote_port);
1813 allow_severity = options.log_facility|LOG_INFO;
1814 deny_severity = options.log_facility|LOG_WARNING;
1815 /* Check whether logins are denied from this host. */
1816 if (packet_connection_is_on_socket()) {
1817 struct request_info req;
1819 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
1822 if (!hosts_access(&req)) {
1823 debug("Connection refused by tcp wrapper");
1826 fatal("libwrap refuse returns");
1829 #endif /* LIBWRAP */
1831 /* Log the connection. */
1832 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1834 /* set the HPN options for the child */
1835 channel_set_hpn(options.hpn_disabled, options.hpn_buffer_size);
1838 * We don't want to listen forever unless the other side
1839 * successfully authenticates itself. So we set up an alarm which is
1840 * cleared after successful authentication. A limit of zero
1841 * indicates no limit. Note that we don't set the alarm in debugging
1842 * mode; it is just annoying to have the server exit just when you
1843 * are about to discover the bug.
1845 signal(SIGALRM, grace_alarm_handler);
1847 alarm(options.login_grace_time);
1849 sshd_exchange_identification(sock_in, sock_out);
1851 /* In inetd mode, generate ephemeral key only for proto 1 connections */
1852 if (!compat20 && inetd_flag && sensitive_data.server_key == NULL)
1853 generate_ephemeral_server_key();
1855 packet_set_nonblocking();
1857 /* allocate authentication context */
1858 authctxt = xcalloc(1, sizeof(*authctxt));
1860 authctxt->loginmsg = &loginmsg;
1862 /* XXX global for cleanup, access from other modules */
1863 the_authctxt = authctxt;
1865 /* prepare buffer to collect messages to display to user after login */
1866 buffer_init(&loginmsg);
1869 if (privsep_preauth(authctxt) == 1)
1872 /* perform the key exchange */
1873 /* authenticate user and start session */
1876 do_authentication2(authctxt);
1879 do_authentication(authctxt);
1882 * If we use privilege separation, the unprivileged child transfers
1883 * the current keystate and exits
1886 mm_send_keystate(pmonitor);
1892 * Cancel the alarm we set to limit the time taken for
1896 signal(SIGALRM, SIG_DFL);
1897 authctxt->authenticated = 1;
1898 if (startup_pipe != -1) {
1899 close(startup_pipe);
1903 #ifdef SSH_AUDIT_EVENTS
1904 audit_event(SSH_AUTH_SUCCESS);
1908 if (options.gss_authentication) {
1909 temporarily_use_uid(authctxt->pw);
1910 ssh_gssapi_storecreds();
1915 if (options.use_pam) {
1922 * In privilege separation, we fork another child and prepare
1923 * file descriptor passing.
1926 privsep_postauth(authctxt);
1927 /* the monitor process [priv] will not return */
1929 destroy_sensitive_data();
1932 packet_set_timeout(options.client_alive_interval,
1933 options.client_alive_count_max);
1935 /* Start session. */
1936 do_authenticated(authctxt);
1938 /* The connection has been terminated. */
1939 packet_get_state(MODE_IN, NULL, NULL, NULL, &ibytes);
1940 packet_get_state(MODE_OUT, NULL, NULL, NULL, &obytes);
1941 verbose("Transferred: sent %llu, received %llu bytes", obytes, ibytes);
1943 verbose("Closing connection to %.500s port %d", remote_ip, remote_port);
1946 if (options.use_pam)
1948 #endif /* USE_PAM */
1950 #ifdef SSH_AUDIT_EVENTS
1951 PRIVSEP(audit_event(SSH_CONNECTION_CLOSE));
1963 * Decrypt session_key_int using our private server key and private host key
1964 * (key with larger modulus first).
1967 ssh1_session_key(BIGNUM *session_key_int)
1971 if (BN_cmp(sensitive_data.server_key->rsa->n,
1972 sensitive_data.ssh1_host_key->rsa->n) > 0) {
1973 /* Server key has bigger modulus. */
1974 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1975 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1976 SSH_KEY_BITS_RESERVED) {
1977 fatal("do_connection: %s: "
1978 "server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1979 get_remote_ipaddr(),
1980 BN_num_bits(sensitive_data.server_key->rsa->n),
1981 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1982 SSH_KEY_BITS_RESERVED);
1984 if (rsa_private_decrypt(session_key_int, session_key_int,
1985 sensitive_data.server_key->rsa) <= 0)
1987 if (rsa_private_decrypt(session_key_int, session_key_int,
1988 sensitive_data.ssh1_host_key->rsa) <= 0)
1991 /* Host key has bigger modulus (or they are equal). */
1992 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1993 BN_num_bits(sensitive_data.server_key->rsa->n) +
1994 SSH_KEY_BITS_RESERVED) {
1995 fatal("do_connection: %s: "
1996 "host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1997 get_remote_ipaddr(),
1998 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1999 BN_num_bits(sensitive_data.server_key->rsa->n),
2000 SSH_KEY_BITS_RESERVED);
2002 if (rsa_private_decrypt(session_key_int, session_key_int,
2003 sensitive_data.ssh1_host_key->rsa) < 0)
2005 if (rsa_private_decrypt(session_key_int, session_key_int,
2006 sensitive_data.server_key->rsa) < 0)
2019 BIGNUM *session_key_int;
2020 u_char session_key[SSH_SESSION_KEY_LENGTH];
2022 u_int cipher_type, auth_mask, protocol_flags;
2025 * Generate check bytes that the client must send back in the user
2026 * packet in order for it to be accepted; this is used to defy ip
2027 * spoofing attacks. Note that this only works against somebody
2028 * doing IP spoofing from a remote machine; any machine on the local
2029 * network can still see outgoing packets and catch the random
2030 * cookie. This only affects rhosts authentication, and this is one
2031 * of the reasons why it is inherently insecure.
2033 arc4random_buf(cookie, sizeof(cookie));
2036 * Send our public key. We include in the packet 64 bits of random
2037 * data that must be matched in the reply in order to prevent IP
2040 packet_start(SSH_SMSG_PUBLIC_KEY);
2041 for (i = 0; i < 8; i++)
2042 packet_put_char(cookie[i]);
2044 /* Store our public server RSA key. */
2045 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
2046 packet_put_bignum(sensitive_data.server_key->rsa->e);
2047 packet_put_bignum(sensitive_data.server_key->rsa->n);
2049 /* Store our public host RSA key. */
2050 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
2051 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
2052 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
2054 /* Put protocol flags. */
2055 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
2057 /* Declare which ciphers we support. */
2058 packet_put_int(cipher_mask_ssh1(0));
2060 /* Declare supported authentication types. */
2062 if (options.rhosts_rsa_authentication)
2063 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
2064 if (options.rsa_authentication)
2065 auth_mask |= 1 << SSH_AUTH_RSA;
2066 if (options.challenge_response_authentication == 1)
2067 auth_mask |= 1 << SSH_AUTH_TIS;
2068 if (options.password_authentication)
2069 auth_mask |= 1 << SSH_AUTH_PASSWORD;
2070 packet_put_int(auth_mask);
2072 /* Send the packet and wait for it to be sent. */
2074 packet_write_wait();
2076 debug("Sent %d bit server key and %d bit host key.",
2077 BN_num_bits(sensitive_data.server_key->rsa->n),
2078 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
2080 /* Read clients reply (cipher type and session key). */
2081 packet_read_expect(SSH_CMSG_SESSION_KEY);
2083 /* Get cipher type and check whether we accept this. */
2084 cipher_type = packet_get_char();
2086 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
2087 packet_disconnect("Warning: client selects unsupported cipher.");
2089 /* Get check bytes from the packet. These must match those we
2090 sent earlier with the public key packet. */
2091 for (i = 0; i < 8; i++)
2092 if (cookie[i] != packet_get_char())
2093 packet_disconnect("IP Spoofing check bytes do not match.");
2095 debug("Encryption type: %.200s", cipher_name(cipher_type));
2097 /* Get the encrypted integer. */
2098 if ((session_key_int = BN_new()) == NULL)
2099 fatal("do_ssh1_kex: BN_new failed");
2100 packet_get_bignum(session_key_int);
2102 protocol_flags = packet_get_int();
2103 packet_set_protocol_flags(protocol_flags);
2106 /* Decrypt session_key_int using host/server keys */
2107 rsafail = PRIVSEP(ssh1_session_key(session_key_int));
2110 * Extract session key from the decrypted integer. The key is in the
2111 * least significant 256 bits of the integer; the first byte of the
2112 * key is in the highest bits.
2115 (void) BN_mask_bits(session_key_int, sizeof(session_key) * 8);
2116 len = BN_num_bytes(session_key_int);
2117 if (len < 0 || (u_int)len > sizeof(session_key)) {
2118 error("do_ssh1_kex: bad session key len from %s: "
2119 "session_key_int %d > sizeof(session_key) %lu",
2120 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
2123 memset(session_key, 0, sizeof(session_key));
2124 BN_bn2bin(session_key_int,
2125 session_key + sizeof(session_key) - len);
2127 derive_ssh1_session_id(
2128 sensitive_data.ssh1_host_key->rsa->n,
2129 sensitive_data.server_key->rsa->n,
2130 cookie, session_id);
2132 * Xor the first 16 bytes of the session key with the
2135 for (i = 0; i < 16; i++)
2136 session_key[i] ^= session_id[i];
2140 int bytes = BN_num_bytes(session_key_int);
2141 u_char *buf = xmalloc(bytes);
2144 logit("do_connection: generating a fake encryption key");
2145 BN_bn2bin(session_key_int, buf);
2147 MD5_Update(&md, buf, bytes);
2148 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
2149 MD5_Final(session_key, &md);
2151 MD5_Update(&md, session_key, 16);
2152 MD5_Update(&md, buf, bytes);
2153 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
2154 MD5_Final(session_key + 16, &md);
2155 memset(buf, 0, bytes);
2157 for (i = 0; i < 16; i++)
2158 session_id[i] = session_key[i] ^ session_key[i + 16];
2160 /* Destroy the private and public keys. No longer. */
2161 destroy_sensitive_data();
2164 mm_ssh1_session_id(session_id);
2166 /* Destroy the decrypted integer. It is no longer needed. */
2167 BN_clear_free(session_key_int);
2169 /* Set the session key. From this on all communications will be encrypted. */
2170 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
2172 /* Destroy our copy of the session key. It is no longer needed. */
2173 memset(session_key, 0, sizeof(session_key));
2175 debug("Received session key; encryption turned on.");
2177 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */
2178 packet_start(SSH_SMSG_SUCCESS);
2180 packet_write_wait();
2184 * SSH2 key exchange: diffie-hellman-group1-sha1
2192 debug ("MYFLAG IS %d", myflag);
2193 if (options.ciphers != NULL) {
2194 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2195 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
2196 } else if (options.none_enabled == 1) {
2197 debug ("WARNING: None cipher enabled");
2198 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2199 myproposal[PROPOSAL_ENC_ALGS_STOC] = KEX_ENCRYPT_INCLUDE_NONE;
2201 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2202 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
2203 myproposal[PROPOSAL_ENC_ALGS_STOC] =
2204 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
2206 if (options.macs != NULL) {
2207 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
2208 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
2210 if (options.compression == COMP_NONE) {
2211 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2212 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
2213 } else if (options.compression == COMP_DELAYED) {
2214 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2215 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com";
2218 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
2220 /* start key exchange */
2221 kex = kex_setup(myproposal);
2222 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
2223 kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
2224 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
2225 kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
2227 kex->client_version_string=client_version_string;
2228 kex->server_version_string=server_version_string;
2229 kex->load_host_key=&get_hostkey_by_type;
2230 kex->host_key_index=&get_hostkey_index;
2234 dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
2236 session_id2 = kex->session_id;
2237 session_id2_len = kex->session_id_len;
2240 /* send 1st encrypted/maced/compressed message */
2241 packet_start(SSH2_MSG_IGNORE);
2242 packet_put_cstring("markus");
2244 packet_write_wait();
2249 /* server specific fatal cleanup */
2254 do_cleanup(the_authctxt);
2255 #ifdef SSH_AUDIT_EVENTS
2256 /* done after do_cleanup so it can cancel the PAM auth 'thread' */
2257 if (!use_privsep || mm_is_monitor())
2258 audit_event(SSH_CONNECTION_ABANDON);