1 /* $OpenBSD: sshd.c,v 1.375 2010/04/16 01:47:26 djm 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"
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)
140 extern char *__progname;
142 /* Server configuration options. */
143 ServerOptions options;
145 /* Name of the server configuration file. */
146 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
149 * Debug mode flag. This can be set on the command line. If debug
150 * mode is enabled, extra debugging output will be sent to the system
151 * log, the daemon will not go to background, and will exit after processing
152 * the first connection.
156 /* Flag indicating that the daemon should only test the configuration and keys. */
159 /* Flag indicating that the daemon is being started from inetd. */
162 /* Flag indicating that sshd should not detach and become a daemon. */
163 int no_daemon_flag = 0;
165 /* debug goes to stderr unless inetd_flag is set */
168 /* Saved arguments to main(). */
173 int rexeced_flag = 0;
179 * The sockets that the server is listening; this is used in the SIGHUP
182 #define MAX_LISTEN_SOCKS 16
183 int listen_socks[MAX_LISTEN_SOCKS];
184 int num_listen_socks = 0;
187 * the client's version string, passed by sshd2 in compat mode. if != NULL,
188 * sshd will skip the version-number exchange
190 char *client_version_string = NULL;
191 char *server_version_string = NULL;
193 /* for rekeying XXX fixme */
197 * Any really sensitive data in the application is contained in this
198 * structure. The idea is that this structure could be locked into memory so
199 * that the pages do not get written into swap. However, there are some
200 * problems. The private key contains BIGNUMs, and we do not (in principle)
201 * have access to the internals of them, and locking just the structure is
202 * not very useful. Currently, memory locking is not implemented.
205 Key *server_key; /* ephemeral server key */
206 Key *ssh1_host_key; /* ssh1 host key */
207 Key **host_keys; /* all private host keys */
208 Key **host_certificates; /* all public host certificates */
211 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
215 * Flag indicating whether the RSA server key needs to be regenerated.
216 * Is set in the SIGALRM handler and cleared when the key is regenerated.
218 static volatile sig_atomic_t key_do_regen = 0;
220 /* This is set to true when a signal is received. */
221 static volatile sig_atomic_t received_sighup = 0;
222 static volatile sig_atomic_t received_sigterm = 0;
224 /* session identifier, used by RSA-auth */
225 u_char session_id[16];
228 u_char *session_id2 = NULL;
229 u_int session_id2_len = 0;
231 /* record remote hostname or ip */
232 u_int utmp_len = MAXHOSTNAMELEN;
234 /* options.max_startup sized array of fd ints */
235 int *startup_pipes = NULL;
236 int startup_pipe; /* in child */
238 /* variables used for privilege separation */
239 int use_privsep = -1;
240 struct monitor *pmonitor = NULL;
242 /* global authentication context */
243 Authctxt *the_authctxt = NULL;
245 /* sshd_config buffer */
248 /* message to be displayed after login */
251 /* Unprivileged user */
252 struct passwd *privsep_pw = NULL;
254 /* Prototypes for various functions defined later in this file. */
255 void destroy_sensitive_data(void);
256 void demote_sensitive_data(void);
258 static void do_ssh1_kex(void);
259 static void do_ssh2_kex(void);
262 * Close all listening sockets
265 close_listen_socks(void)
269 for (i = 0; i < num_listen_socks; i++)
270 close(listen_socks[i]);
271 num_listen_socks = -1;
275 close_startup_pipes(void)
280 for (i = 0; i < options.max_startups; i++)
281 if (startup_pipes[i] != -1)
282 close(startup_pipes[i]);
286 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
287 * the effect is to reread the configuration file (and to regenerate
293 sighup_handler(int sig)
295 int save_errno = errno;
298 signal(SIGHUP, sighup_handler);
303 * Called from the main program after receiving SIGHUP.
304 * Restarts the server.
309 logit("Received SIGHUP; restarting.");
310 close_listen_socks();
311 close_startup_pipes();
312 alarm(0); /* alarm timer persists across exec */
313 signal(SIGHUP, SIG_IGN); /* will be restored after exec */
314 execv(saved_argv[0], saved_argv);
315 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
321 * Generic signal handler for terminating signals in the master daemon.
325 sigterm_handler(int sig)
327 received_sigterm = sig;
331 * SIGCHLD handler. This is called whenever a child dies. This will then
332 * reap any zombies left by exited children.
336 main_sigchld_handler(int sig)
338 int save_errno = errno;
342 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
343 (pid < 0 && errno == EINTR))
346 signal(SIGCHLD, main_sigchld_handler);
351 * Signal handler for the alarm after the login grace period has expired.
355 grace_alarm_handler(int sig)
357 if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0)
358 kill(pmonitor->m_pid, SIGALRM);
360 /* Log error and exit. */
361 sigdie("Timeout before authentication for %s", get_remote_ipaddr());
365 * Signal handler for the key regeneration alarm. Note that this
366 * alarm only occurs in the daemon waiting for connections, and it does not
367 * do anything with the private key or random state before forking.
368 * Thus there should be no concurrency control/asynchronous execution
372 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 arc4random_buf(sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
388 key_regeneration_alarm(int sig)
390 int save_errno = errno;
392 signal(SIGALRM, SIG_DFL);
398 sshd_exchange_identification(int sock_in, int sock_out)
402 int remote_major, remote_minor;
404 char *s, *newline = "\n";
405 char buf[256]; /* Must not be larger than remote_version. */
406 char remote_version[256]; /* Must be at least as big as buf. */
408 if ((options.protocol & SSH_PROTO_1) &&
409 (options.protocol & SSH_PROTO_2)) {
410 major = PROTOCOL_MAJOR_1;
412 } else if (options.protocol & SSH_PROTO_2) {
413 major = PROTOCOL_MAJOR_2;
414 minor = PROTOCOL_MINOR_2;
417 major = PROTOCOL_MAJOR_1;
418 minor = PROTOCOL_MINOR_1;
420 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s", major, minor,
421 SSH_VERSION, newline);
422 server_version_string = xstrdup(buf);
424 /* Send our protocol version identification. */
425 if (roaming_atomicio(vwrite, sock_out, server_version_string,
426 strlen(server_version_string))
427 != strlen(server_version_string)) {
428 logit("Could not write ident string to %s", get_remote_ipaddr());
432 /* Read other sides version identification. */
433 memset(buf, 0, sizeof(buf));
434 for (i = 0; i < sizeof(buf) - 1; i++) {
435 if (roaming_atomicio(read, sock_in, &buf[i], 1) != 1) {
436 logit("Did not receive identification string from %s",
437 get_remote_ipaddr());
440 if (buf[i] == '\r') {
442 /* Kludge for F-Secure Macintosh < 1.0.2 */
444 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
448 if (buf[i] == '\n') {
453 buf[sizeof(buf) - 1] = 0;
454 client_version_string = xstrdup(buf);
457 * Check that the versions match. In future this might accept
458 * several versions and set appropriate flags to handle them.
460 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
461 &remote_major, &remote_minor, remote_version) != 3) {
462 s = "Protocol mismatch.\n";
463 (void) atomicio(vwrite, sock_out, s, strlen(s));
466 logit("Bad protocol version identification '%.100s' from %s",
467 client_version_string, get_remote_ipaddr());
470 debug("Client protocol version %d.%d; client software version %.100s",
471 remote_major, remote_minor, remote_version);
473 compat_datafellows(remote_version);
475 if (datafellows & SSH_BUG_PROBE) {
476 logit("probed from %s with %s. Don't panic.",
477 get_remote_ipaddr(), client_version_string);
481 if (datafellows & SSH_BUG_SCANNER) {
482 logit("scanned from %s with %s. Don't panic.",
483 get_remote_ipaddr(), client_version_string);
488 switch (remote_major) {
490 if (remote_minor == 99) {
491 if (options.protocol & SSH_PROTO_2)
497 if (!(options.protocol & SSH_PROTO_1)) {
501 if (remote_minor < 3) {
502 packet_disconnect("Your ssh version is too old and "
503 "is no longer supported. Please install a newer version.");
504 } else if (remote_minor == 3) {
505 /* note that this disables agent-forwarding */
510 if (options.protocol & SSH_PROTO_2) {
519 chop(server_version_string);
520 debug("Local version string %.200s", server_version_string);
523 s = "Protocol major versions differ.\n";
524 (void) atomicio(vwrite, sock_out, s, strlen(s));
527 logit("Protocol major versions differ for %s: %.200s vs. %.200s",
529 server_version_string, client_version_string);
534 /* Destroy the host and server keys. They will no longer be needed. */
536 destroy_sensitive_data(void)
540 if (sensitive_data.server_key) {
541 key_free(sensitive_data.server_key);
542 sensitive_data.server_key = NULL;
544 for (i = 0; i < options.num_host_key_files; i++) {
545 if (sensitive_data.host_keys[i]) {
546 key_free(sensitive_data.host_keys[i]);
547 sensitive_data.host_keys[i] = NULL;
549 if (sensitive_data.host_certificates[i]) {
550 key_free(sensitive_data.host_certificates[i]);
551 sensitive_data.host_certificates[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;
579 /* Certs do not need demotion */
582 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */
586 privsep_preauth_child(void)
591 /* Enable challenge-response authentication for privilege separation */
592 privsep_challenge_enable();
595 arc4random_buf(rnd, sizeof(rnd));
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)
670 #ifdef DISABLE_FD_PASSING
673 if (authctxt->pw->pw_uid == 0 || options.use_login) {
675 /* File descriptor passing is broken or root login */
680 /* New socket pair */
681 monitor_reinit(pmonitor);
683 pmonitor->m_pid = fork();
684 if (pmonitor->m_pid == -1)
685 fatal("fork of unprivileged child failed");
686 else if (pmonitor->m_pid != 0) {
687 verbose("User child is on pid %ld", (long)pmonitor->m_pid);
688 close(pmonitor->m_recvfd);
689 buffer_clear(&loginmsg);
690 monitor_child_postauth(pmonitor);
696 close(pmonitor->m_sendfd);
698 /* Demote the private keys to public keys. */
699 demote_sensitive_data();
702 arc4random_buf(rnd, sizeof(rnd));
703 RAND_seed(rnd, sizeof(rnd));
705 /* Drop privileges */
706 do_setusercontext(authctxt->pw);
709 /* It is safe now to apply the key state */
710 monitor_apply_keystate(pmonitor);
713 * Tell the packet layer that authentication was successful, since
714 * this information is not part of the key state.
716 packet_set_authenticated();
720 list_hostkey_types(void)
729 for (i = 0; i < options.num_host_key_files; i++) {
730 key = sensitive_data.host_keys[i];
736 if (buffer_len(&b) > 0)
737 buffer_append(&b, ",", 1);
738 p = key_ssh_name(key);
739 buffer_append(&b, p, strlen(p));
742 /* If the private key has a cert peer, then list that too */
743 key = sensitive_data.host_certificates[i];
747 case KEY_RSA_CERT_V00:
748 case KEY_DSA_CERT_V00:
751 if (buffer_len(&b) > 0)
752 buffer_append(&b, ",", 1);
753 p = key_ssh_name(key);
754 buffer_append(&b, p, strlen(p));
758 buffer_append(&b, "\0", 1);
759 ret = xstrdup(buffer_ptr(&b));
761 debug("list_hostkey_types: %s", ret);
766 get_hostkey_by_type(int type, int need_private)
771 for (i = 0; i < options.num_host_key_files; i++) {
773 case KEY_RSA_CERT_V00:
774 case KEY_DSA_CERT_V00:
777 key = sensitive_data.host_certificates[i];
780 key = sensitive_data.host_keys[i];
783 if (key != NULL && key->type == type)
784 return need_private ?
785 sensitive_data.host_keys[i] : key;
791 get_hostkey_public_by_type(int type)
793 return get_hostkey_by_type(type, 0);
797 get_hostkey_private_by_type(int type)
799 return get_hostkey_by_type(type, 1);
803 get_hostkey_by_index(int ind)
805 if (ind < 0 || ind >= options.num_host_key_files)
807 return (sensitive_data.host_keys[ind]);
811 get_hostkey_index(Key *key)
815 for (i = 0; i < options.num_host_key_files; i++) {
816 if (key_is_cert(key)) {
817 if (key == sensitive_data.host_certificates[i])
820 if (key == sensitive_data.host_keys[i])
828 * returns 1 if connection should be dropped, 0 otherwise.
829 * dropping starts at connection #max_startups_begin with a probability
830 * of (max_startups_rate/100). the probability increases linearly until
831 * all connections are dropped for startups > max_startups
834 drop_connection(int startups)
838 if (startups < options.max_startups_begin)
840 if (startups >= options.max_startups)
842 if (options.max_startups_rate == 100)
845 p = 100 - options.max_startups_rate;
846 p *= startups - options.max_startups_begin;
847 p /= options.max_startups - options.max_startups_begin;
848 p += options.max_startups_rate;
849 r = arc4random_uniform(100);
851 debug("drop_connection: p %d, r %d", p, r);
852 return (r < p) ? 1 : 0;
858 fprintf(stderr, "%s, %s\n",
859 SSH_RELEASE, SSLeay_version(SSLEAY_VERSION));
861 "usage: sshd [-46DdeiqTt] [-b bits] [-C connection_spec] [-c host_cert_file]\n"
862 " [-f config_file] [-g login_grace_time] [-h host_key_file]\n"
863 " [-k key_gen_time] [-o option] [-p port] [-u len]\n"
869 send_rexec_state(int fd, Buffer *conf)
873 debug3("%s: entering fd = %d config len %d", __func__, fd,
877 * Protocol from reexec master to child:
878 * string configuration
879 * u_int ephemeral_key_follows
880 * bignum e (only if ephemeral_key_follows == 1)
886 * string rngseed (only if OpenSSL is not self-seeded)
889 buffer_put_cstring(&m, buffer_ptr(conf));
891 if (sensitive_data.server_key != NULL &&
892 sensitive_data.server_key->type == KEY_RSA1) {
893 buffer_put_int(&m, 1);
894 buffer_put_bignum(&m, sensitive_data.server_key->rsa->e);
895 buffer_put_bignum(&m, sensitive_data.server_key->rsa->n);
896 buffer_put_bignum(&m, sensitive_data.server_key->rsa->d);
897 buffer_put_bignum(&m, sensitive_data.server_key->rsa->iqmp);
898 buffer_put_bignum(&m, sensitive_data.server_key->rsa->p);
899 buffer_put_bignum(&m, sensitive_data.server_key->rsa->q);
901 buffer_put_int(&m, 0);
903 #ifndef OPENSSL_PRNG_ONLY
904 rexec_send_rng_seed(&m);
907 if (ssh_msg_send(fd, 0, &m) == -1)
908 fatal("%s: ssh_msg_send failed", __func__);
912 debug3("%s: done", __func__);
916 recv_rexec_state(int fd, Buffer *conf)
922 debug3("%s: entering fd = %d", __func__, fd);
926 if (ssh_msg_recv(fd, &m) == -1)
927 fatal("%s: ssh_msg_recv failed", __func__);
928 if (buffer_get_char(&m) != 0)
929 fatal("%s: rexec version mismatch", __func__);
931 cp = buffer_get_string(&m, &len);
933 buffer_append(conf, cp, len + 1);
936 if (buffer_get_int(&m)) {
937 if (sensitive_data.server_key != NULL)
938 key_free(sensitive_data.server_key);
939 sensitive_data.server_key = key_new_private(KEY_RSA1);
940 buffer_get_bignum(&m, sensitive_data.server_key->rsa->e);
941 buffer_get_bignum(&m, sensitive_data.server_key->rsa->n);
942 buffer_get_bignum(&m, sensitive_data.server_key->rsa->d);
943 buffer_get_bignum(&m, sensitive_data.server_key->rsa->iqmp);
944 buffer_get_bignum(&m, sensitive_data.server_key->rsa->p);
945 buffer_get_bignum(&m, sensitive_data.server_key->rsa->q);
946 rsa_generate_additional_parameters(
947 sensitive_data.server_key->rsa);
950 #ifndef OPENSSL_PRNG_ONLY
951 rexec_recv_rng_seed(&m);
956 debug3("%s: done", __func__);
959 /* Accept a connection from inetd */
961 server_accept_inetd(int *sock_in, int *sock_out)
967 close(REEXEC_CONFIG_PASS_FD);
968 *sock_in = *sock_out = dup(STDIN_FILENO);
970 startup_pipe = dup(REEXEC_STARTUP_PIPE_FD);
971 close(REEXEC_STARTUP_PIPE_FD);
974 *sock_in = dup(STDIN_FILENO);
975 *sock_out = dup(STDOUT_FILENO);
978 * We intentionally do not close the descriptors 0, 1, and 2
979 * as our code for setting the descriptors won't work if
980 * ttyfd happens to be one of those.
982 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
983 dup2(fd, STDIN_FILENO);
984 dup2(fd, STDOUT_FILENO);
985 if (fd > STDOUT_FILENO)
988 debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out);
992 * Listen for TCP connections
997 int ret, listen_sock, on = 1;
999 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
1001 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
1002 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
1004 if (num_listen_socks >= MAX_LISTEN_SOCKS)
1005 fatal("Too many listen sockets. "
1006 "Enlarge MAX_LISTEN_SOCKS");
1007 if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen,
1008 ntop, sizeof(ntop), strport, sizeof(strport),
1009 NI_NUMERICHOST|NI_NUMERICSERV)) != 0) {
1010 error("getnameinfo failed: %.100s",
1011 ssh_gai_strerror(ret));
1014 /* Create socket for listening. */
1015 listen_sock = socket(ai->ai_family, ai->ai_socktype,
1017 if (listen_sock < 0) {
1018 /* kernel may not support ipv6 */
1019 verbose("socket: %.100s", strerror(errno));
1022 if (set_nonblock(listen_sock) == -1) {
1027 * Set socket options.
1028 * Allow local port reuse in TIME_WAIT.
1030 if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
1031 &on, sizeof(on)) == -1)
1032 error("setsockopt SO_REUSEADDR: %s", strerror(errno));
1034 /* Only communicate in IPv6 over AF_INET6 sockets. */
1035 if (ai->ai_family == AF_INET6)
1036 sock_set_v6only(listen_sock);
1038 debug("Bind to port %s on %s.", strport, ntop);
1040 /* Bind the socket to the desired port. */
1041 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1042 error("Bind to port %s on %s failed: %.200s.",
1043 strport, ntop, strerror(errno));
1047 listen_socks[num_listen_socks] = listen_sock;
1050 /* Start listening on the port. */
1051 if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0)
1052 fatal("listen on [%s]:%s: %.100s",
1053 ntop, strport, strerror(errno));
1054 logit("Server listening on %s port %s.", ntop, strport);
1056 freeaddrinfo(options.listen_addrs);
1058 if (!num_listen_socks)
1059 fatal("Cannot bind any address.");
1063 * The main TCP accept loop. Note that, for the non-debug case, returns
1064 * from this function are in a forked subprocess.
1067 server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
1070 int i, j, ret, maxfd;
1071 int key_used = 0, startups = 0;
1072 int startup_p[2] = { -1 , -1 };
1073 struct sockaddr_storage from;
1077 /* setup fd set for accept */
1080 for (i = 0; i < num_listen_socks; i++)
1081 if (listen_socks[i] > maxfd)
1082 maxfd = listen_socks[i];
1083 /* pipes connected to unauthenticated childs */
1084 startup_pipes = xcalloc(options.max_startups, sizeof(int));
1085 for (i = 0; i < options.max_startups; i++)
1086 startup_pipes[i] = -1;
1089 * Stay listening for connections until the system crashes or
1090 * the daemon is killed with a signal.
1093 if (received_sighup)
1097 fdset = (fd_set *)xcalloc(howmany(maxfd + 1, NFDBITS),
1100 for (i = 0; i < num_listen_socks; i++)
1101 FD_SET(listen_socks[i], fdset);
1102 for (i = 0; i < options.max_startups; i++)
1103 if (startup_pipes[i] != -1)
1104 FD_SET(startup_pipes[i], fdset);
1106 /* Wait in select until there is a connection. */
1107 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
1108 if (ret < 0 && errno != EINTR)
1109 error("select: %.100s", strerror(errno));
1110 if (received_sigterm) {
1111 logit("Received signal %d; terminating.",
1112 (int) received_sigterm);
1113 close_listen_socks();
1114 unlink(options.pid_file);
1117 if (key_used && key_do_regen) {
1118 generate_ephemeral_server_key();
1125 for (i = 0; i < options.max_startups; i++)
1126 if (startup_pipes[i] != -1 &&
1127 FD_ISSET(startup_pipes[i], fdset)) {
1129 * the read end of the pipe is ready
1130 * if the child has closed the pipe
1131 * after successful authentication
1132 * or if the child has died
1134 close(startup_pipes[i]);
1135 startup_pipes[i] = -1;
1138 for (i = 0; i < num_listen_socks; i++) {
1139 if (!FD_ISSET(listen_socks[i], fdset))
1141 fromlen = sizeof(from);
1142 *newsock = accept(listen_socks[i],
1143 (struct sockaddr *)&from, &fromlen);
1145 if (errno != EINTR && errno != EAGAIN &&
1146 errno != EWOULDBLOCK)
1147 error("accept: %.100s", strerror(errno));
1150 if (unset_nonblock(*newsock) == -1) {
1154 if (drop_connection(startups) == 1) {
1155 debug("drop connection #%d", startups);
1159 if (pipe(startup_p) == -1) {
1164 if (rexec_flag && socketpair(AF_UNIX,
1165 SOCK_STREAM, 0, config_s) == -1) {
1166 error("reexec socketpair: %s",
1169 close(startup_p[0]);
1170 close(startup_p[1]);
1174 for (j = 0; j < options.max_startups; j++)
1175 if (startup_pipes[j] == -1) {
1176 startup_pipes[j] = startup_p[0];
1177 if (maxfd < startup_p[0])
1178 maxfd = startup_p[0];
1184 * Got connection. Fork a child to handle it, unless
1185 * we are in debugging mode.
1189 * In debugging mode. Close the listening
1190 * socket, and start processing the
1191 * connection without forking.
1193 debug("Server will not fork when running in debugging mode.");
1194 close_listen_socks();
1195 *sock_in = *newsock;
1196 *sock_out = *newsock;
1197 close(startup_p[0]);
1198 close(startup_p[1]);
1202 send_rexec_state(config_s[0],
1210 * Normal production daemon. Fork, and have
1211 * the child process the connection. The
1212 * parent continues listening.
1214 platform_pre_fork();
1215 if ((pid = fork()) == 0) {
1217 * Child. Close the listening and
1218 * max_startup sockets. Start using
1219 * the accepted socket. Reinitialize
1220 * logging (since our pid has changed).
1221 * We break out of the loop to handle
1224 platform_post_fork_child();
1225 startup_pipe = startup_p[1];
1226 close_startup_pipes();
1227 close_listen_socks();
1228 *sock_in = *newsock;
1229 *sock_out = *newsock;
1230 log_init(__progname,
1232 options.log_facility,
1239 /* Parent. Stay in the loop. */
1240 platform_post_fork_parent(pid);
1242 error("fork: %.100s", strerror(errno));
1244 debug("Forked child %ld.", (long)pid);
1246 close(startup_p[1]);
1249 send_rexec_state(config_s[0], &cfg);
1255 * Mark that the key has been used (it
1256 * was "given" to the child).
1258 if ((options.protocol & SSH_PROTO_1) &&
1260 /* Schedule server key regeneration alarm. */
1261 signal(SIGALRM, key_regeneration_alarm);
1262 alarm(options.key_regeneration_time);
1269 * Ensure that our random state differs
1270 * from that of the child
1275 /* child process check (or debug mode) */
1276 if (num_listen_socks < 0)
1283 * Main program for the daemon.
1286 main(int ac, char **av)
1288 extern char *optarg;
1290 int opt, i, j, on = 1;
1291 int sock_in = -1, sock_out = -1, newsock = -1;
1292 const char *remote_ip;
1293 char *test_user = NULL, *test_host = NULL, *test_addr = NULL;
1295 char *line, *p, *cp;
1296 int config_s[2] = { -1 , -1 };
1297 u_int64_t ibytes, obytes;
1302 #ifdef HAVE_SECUREWARE
1303 (void)set_auth_parameters(ac, av);
1305 __progname = ssh_get_progname(av[0]);
1308 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
1311 saved_argv = xcalloc(ac + 1, sizeof(*saved_argv));
1312 for (i = 0; i < ac; i++)
1313 saved_argv[i] = xstrdup(av[i]);
1314 saved_argv[i] = NULL;
1316 #ifndef HAVE_SETPROCTITLE
1317 /* Prepare for later setproctitle emulation */
1318 compat_init_setproctitle(ac, av);
1322 if (geteuid() == 0 && setgroups(0, NULL) == -1)
1323 debug("setgroups(): %.200s", strerror(errno));
1325 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
1328 /* Initialize configuration options to their default values. */
1329 initialize_server_options(&options);
1331 /* Parse command-line arguments. */
1332 while ((opt = getopt(ac, av, "f:p:b:k:h:g:u:o:C:dDeiqrtQRT46")) != -1) {
1335 options.address_family = AF_INET;
1338 options.address_family = AF_INET6;
1341 config_file_name = optarg;
1344 if (options.num_host_cert_files >= MAX_HOSTCERTS) {
1345 fprintf(stderr, "too many host certificates.\n");
1348 options.host_cert_files[options.num_host_cert_files++] =
1349 derelativise_path(optarg);
1352 if (debug_flag == 0) {
1354 options.log_level = SYSLOG_LEVEL_DEBUG1;
1355 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
1356 options.log_level++;
1378 options.log_level = SYSLOG_LEVEL_QUIET;
1381 options.server_key_bits = (int)strtonum(optarg, 256,
1385 options.ports_from_cmdline = 1;
1386 if (options.num_ports >= MAX_PORTS) {
1387 fprintf(stderr, "too many ports.\n");
1390 options.ports[options.num_ports++] = a2port(optarg);
1391 if (options.ports[options.num_ports-1] <= 0) {
1392 fprintf(stderr, "Bad port number.\n");
1397 if ((options.login_grace_time = convtime(optarg)) == -1) {
1398 fprintf(stderr, "Invalid login grace time.\n");
1403 if ((options.key_regeneration_time = convtime(optarg)) == -1) {
1404 fprintf(stderr, "Invalid key regeneration interval.\n");
1409 if (options.num_host_key_files >= MAX_HOSTKEYS) {
1410 fprintf(stderr, "too many host keys.\n");
1413 options.host_key_files[options.num_host_key_files++] =
1414 derelativise_path(optarg);
1424 while ((p = strsep(&cp, ",")) && *p != '\0') {
1425 if (strncmp(p, "addr=", 5) == 0)
1426 test_addr = xstrdup(p + 5);
1427 else if (strncmp(p, "host=", 5) == 0)
1428 test_host = xstrdup(p + 5);
1429 else if (strncmp(p, "user=", 5) == 0)
1430 test_user = xstrdup(p + 5);
1432 fprintf(stderr, "Invalid test "
1433 "mode specification %s\n", p);
1439 utmp_len = (u_int)strtonum(optarg, 0, MAXHOSTNAMELEN+1, NULL);
1440 if (utmp_len > MAXHOSTNAMELEN) {
1441 fprintf(stderr, "Invalid utmp length.\n");
1446 line = xstrdup(optarg);
1447 if (process_server_config_line(&options, line,
1448 "command-line", 0, NULL, NULL, NULL, NULL) != 0)
1458 if (rexeced_flag || inetd_flag)
1460 if (!test_flag && (rexec_flag && (av[0] == NULL || *av[0] != '/')))
1461 fatal("sshd re-exec requires execution with an absolute path");
1463 closefrom(REEXEC_MIN_FREE_FD);
1465 closefrom(REEXEC_DEVCRYPTO_RESERVED_FD);
1467 SSLeay_add_all_algorithms();
1470 * Force logging to stderr until we have loaded the private host
1471 * key (unless started from inetd)
1473 log_init(__progname,
1474 options.log_level == SYSLOG_LEVEL_NOT_SET ?
1475 SYSLOG_LEVEL_INFO : options.log_level,
1476 options.log_facility == SYSLOG_FACILITY_NOT_SET ?
1477 SYSLOG_FACILITY_AUTH : options.log_facility,
1478 log_stderr || !inetd_flag);
1481 * Unset KRB5CCNAME, otherwise the user's session may inherit it from
1482 * root's environment
1484 if (getenv("KRB5CCNAME") != NULL)
1485 unsetenv("KRB5CCNAME");
1488 /* Cray can define user privs drop all privs now!
1489 * Not needed on PRIV_SU systems!
1494 sensitive_data.server_key = NULL;
1495 sensitive_data.ssh1_host_key = NULL;
1496 sensitive_data.have_ssh1_key = 0;
1497 sensitive_data.have_ssh2_key = 0;
1500 * If we're doing an extended config test, make sure we have all of
1501 * the parameters we need. If we're not doing an extended test,
1502 * do not silently ignore connection test params.
1504 if (test_flag >= 2 &&
1505 (test_user != NULL || test_host != NULL || test_addr != NULL)
1506 && (test_user == NULL || test_host == NULL || test_addr == NULL))
1507 fatal("user, host and addr are all required when testing "
1509 if (test_flag < 2 && (test_user != NULL || test_host != NULL ||
1511 fatal("Config test connection parameter (-C) provided without "
1514 /* Fetch our configuration */
1517 recv_rexec_state(REEXEC_CONFIG_PASS_FD, &cfg);
1519 load_server_config(config_file_name, &cfg);
1521 parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name,
1522 &cfg, NULL, NULL, NULL);
1526 /* Fill in default values for those options not explicitly set. */
1527 fill_default_server_options(&options);
1529 /* challenge-response is implemented via keyboard interactive */
1530 if (options.challenge_response_authentication)
1531 options.kbd_interactive_authentication = 1;
1533 /* set default channel AF */
1534 channel_set_af(options.address_family);
1536 /* Check that there are no remaining arguments. */
1538 fprintf(stderr, "Extra argument %s.\n", av[optind]);
1542 debug("sshd version %.100s", SSH_RELEASE);
1544 /* Store privilege separation user for later use if required. */
1545 if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) {
1546 if (use_privsep || options.kerberos_authentication)
1547 fatal("Privilege separation user %s does not exist",
1550 memset(privsep_pw->pw_passwd, 0, strlen(privsep_pw->pw_passwd));
1551 privsep_pw = pwcopy(privsep_pw);
1552 xfree(privsep_pw->pw_passwd);
1553 privsep_pw->pw_passwd = xstrdup("*");
1557 /* load private host keys */
1558 sensitive_data.host_keys = xcalloc(options.num_host_key_files,
1560 for (i = 0; i < options.num_host_key_files; i++)
1561 sensitive_data.host_keys[i] = NULL;
1563 for (i = 0; i < options.num_host_key_files; i++) {
1564 key = key_load_private(options.host_key_files[i], "", NULL);
1565 sensitive_data.host_keys[i] = key;
1567 error("Could not load host key: %s",
1568 options.host_key_files[i]);
1569 sensitive_data.host_keys[i] = NULL;
1572 switch (key->type) {
1574 sensitive_data.ssh1_host_key = key;
1575 sensitive_data.have_ssh1_key = 1;
1579 sensitive_data.have_ssh2_key = 1;
1582 debug("private host key: #%d type %d %s", i, key->type,
1585 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
1586 logit("Disabling protocol version 1. Could not load host key");
1587 options.protocol &= ~SSH_PROTO_1;
1589 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
1590 logit("Disabling protocol version 2. Could not load host key");
1591 options.protocol &= ~SSH_PROTO_2;
1593 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
1594 logit("sshd: no hostkeys available -- exiting.");
1599 * Load certificates. They are stored in an array at identical
1600 * indices to the public keys that they relate to.
1602 sensitive_data.host_certificates = xcalloc(options.num_host_key_files,
1604 for (i = 0; i < options.num_host_key_files; i++)
1605 sensitive_data.host_certificates[i] = NULL;
1607 for (i = 0; i < options.num_host_cert_files; i++) {
1608 key = key_load_public(options.host_cert_files[i], NULL);
1610 error("Could not load host certificate: %s",
1611 options.host_cert_files[i]);
1614 if (!key_is_cert(key)) {
1615 error("Certificate file is not a certificate: %s",
1616 options.host_cert_files[i]);
1620 /* Find matching private key */
1621 for (j = 0; j < options.num_host_key_files; j++) {
1622 if (key_equal_public(key,
1623 sensitive_data.host_keys[j])) {
1624 sensitive_data.host_certificates[j] = key;
1628 if (j >= options.num_host_key_files) {
1629 error("No matching private key for certificate: %s",
1630 options.host_cert_files[i]);
1634 sensitive_data.host_certificates[j] = key;
1635 debug("host certificate: #%d type %d %s", j, key->type,
1638 /* Check certain values for sanity. */
1639 if (options.protocol & SSH_PROTO_1) {
1640 if (options.server_key_bits < 512 ||
1641 options.server_key_bits > 32768) {
1642 fprintf(stderr, "Bad server key size.\n");
1646 * Check that server and host key lengths differ sufficiently. This
1647 * is necessary to make double encryption work with rsaref. Oh, I
1648 * hate software patents. I dont know if this can go? Niels
1650 if (options.server_key_bits >
1651 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) -
1652 SSH_KEY_BITS_RESERVED && options.server_key_bits <
1653 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1654 SSH_KEY_BITS_RESERVED) {
1655 options.server_key_bits =
1656 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1657 SSH_KEY_BITS_RESERVED;
1658 debug("Forcing server key to %d bits to make it differ from host key.",
1659 options.server_key_bits);
1666 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) ||
1667 (S_ISDIR(st.st_mode) == 0))
1668 fatal("Missing privilege separation directory: %s",
1669 _PATH_PRIVSEP_CHROOT_DIR);
1672 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
1673 (st.st_uid != getuid () ||
1674 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0))
1676 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)
1678 fatal("%s must be owned by root and not group or "
1679 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR);
1682 if (test_flag > 1) {
1683 if (test_user != NULL && test_addr != NULL && test_host != NULL)
1684 parse_server_match_config(&options, test_user,
1685 test_host, test_addr);
1686 dump_config(&options);
1689 /* Configuration looks good, so exit if in test mode. */
1694 * Clear out any supplemental groups we may have inherited. This
1695 * prevents inadvertent creation of files with bad modes (in the
1696 * portable version at least, it's certainly possible for PAM
1697 * to create a file, and we can't control the code in every
1698 * module which might be used).
1700 if (setgroups(0, NULL) < 0)
1701 debug("setgroups() failed: %.200s", strerror(errno));
1704 rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *));
1705 for (i = 0; i < rexec_argc; i++) {
1706 debug("rexec_argv[%d]='%s'", i, saved_argv[i]);
1707 rexec_argv[i] = saved_argv[i];
1709 rexec_argv[rexec_argc] = "-R";
1710 rexec_argv[rexec_argc + 1] = NULL;
1713 /* Ensure that umask disallows at least group and world write */
1714 new_umask = umask(0077) | 0022;
1715 (void) umask(new_umask);
1717 /* Initialize the log (it is reinitialized below in case we forked). */
1718 if (debug_flag && (!inetd_flag || rexeced_flag))
1720 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1723 * If not in debugging mode, and not started from inetd, disconnect
1724 * from the controlling terminal, and fork. The original process
1727 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
1730 #endif /* TIOCNOTTY */
1731 if (daemon(0, 0) < 0)
1732 fatal("daemon() failed: %.200s", strerror(errno));
1734 /* Disconnect from the controlling tty. */
1736 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
1738 (void) ioctl(fd, TIOCNOTTY, NULL);
1741 #endif /* TIOCNOTTY */
1743 /* Reinitialize the log (because of the fork above). */
1744 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1746 /* Initialize the random number generator. */
1749 /* Chdir to the root directory so that the current disk can be
1750 unmounted if desired. */
1753 /* ignore SIGPIPE */
1754 signal(SIGPIPE, SIG_IGN);
1756 /* Get a connection, either from inetd or a listening TCP socket */
1758 server_accept_inetd(&sock_in, &sock_out);
1760 platform_pre_listen();
1763 if (options.protocol & SSH_PROTO_1)
1764 generate_ephemeral_server_key();
1766 signal(SIGHUP, sighup_handler);
1767 signal(SIGCHLD, main_sigchld_handler);
1768 signal(SIGTERM, sigterm_handler);
1769 signal(SIGQUIT, sigterm_handler);
1772 * Write out the pid file after the sigterm handler
1773 * is setup and the listen sockets are bound
1776 FILE *f = fopen(options.pid_file, "w");
1779 error("Couldn't create pid file \"%s\": %s",
1780 options.pid_file, strerror(errno));
1782 fprintf(f, "%ld\n", (long) getpid());
1787 /* Accept a connection and return in a forked child */
1788 server_accept_loop(&sock_in, &sock_out,
1789 &newsock, config_s);
1792 /* This is the child processing a new connection. */
1793 setproctitle("%s", "[accepted]");
1796 * Create a new session and process group since the 4.4BSD
1797 * setlogin() affects the entire process group. We don't
1798 * want the child to be able to affect the parent.
1800 #if !defined(SSHD_ACQUIRES_CTTY)
1802 * If setsid is called, on some platforms sshd will later acquire a
1803 * controlling terminal which will result in "could not set
1804 * controlling tty" errors.
1806 if (!debug_flag && !inetd_flag && setsid() < 0)
1807 error("setsid: %.100s", strerror(errno));
1813 debug("rexec start in %d out %d newsock %d pipe %d sock %d",
1814 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
1815 dup2(newsock, STDIN_FILENO);
1816 dup2(STDIN_FILENO, STDOUT_FILENO);
1817 if (startup_pipe == -1)
1818 close(REEXEC_STARTUP_PIPE_FD);
1820 dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD);
1822 dup2(config_s[1], REEXEC_CONFIG_PASS_FD);
1824 if (startup_pipe != -1)
1825 close(startup_pipe);
1827 execv(rexec_argv[0], rexec_argv);
1829 /* Reexec has failed, fall back and continue */
1830 error("rexec of %s failed: %s", rexec_argv[0], strerror(errno));
1831 recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL);
1832 log_init(__progname, options.log_level,
1833 options.log_facility, log_stderr);
1836 startup_pipe = REEXEC_STARTUP_PIPE_FD;
1838 close(REEXEC_CONFIG_PASS_FD);
1839 newsock = sock_out = sock_in = dup(STDIN_FILENO);
1840 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
1841 dup2(fd, STDIN_FILENO);
1842 dup2(fd, STDOUT_FILENO);
1843 if (fd > STDERR_FILENO)
1846 debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d",
1847 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
1850 /* Executed child processes don't need these. */
1851 fcntl(sock_out, F_SETFD, FD_CLOEXEC);
1852 fcntl(sock_in, F_SETFD, FD_CLOEXEC);
1855 * Disable the key regeneration alarm. We will not regenerate the
1856 * key since we are no longer in a position to give it to anyone. We
1857 * will not restart on SIGHUP since it no longer makes sense.
1860 signal(SIGALRM, SIG_DFL);
1861 signal(SIGHUP, SIG_DFL);
1862 signal(SIGTERM, SIG_DFL);
1863 signal(SIGQUIT, SIG_DFL);
1864 signal(SIGCHLD, SIG_DFL);
1865 signal(SIGINT, SIG_DFL);
1868 * Register our connection. This turns encryption off because we do
1871 packet_set_connection(sock_in, sock_out);
1872 packet_set_server();
1874 /* Set SO_KEEPALIVE if requested. */
1875 if (options.tcp_keep_alive && packet_connection_is_on_socket() &&
1876 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) < 0)
1877 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1879 if ((remote_port = get_remote_port()) < 0) {
1880 debug("get_remote_port failed");
1885 * We use get_canonical_hostname with usedns = 0 instead of
1886 * get_remote_ipaddr here so IP options will be checked.
1888 (void) get_canonical_hostname(0);
1890 * The rest of the code depends on the fact that
1891 * get_remote_ipaddr() caches the remote ip, even if
1892 * the socket goes away.
1894 remote_ip = get_remote_ipaddr();
1896 #ifdef SSH_AUDIT_EVENTS
1897 audit_connection_from(remote_ip, remote_port);
1900 allow_severity = options.log_facility|LOG_INFO;
1901 deny_severity = options.log_facility|LOG_WARNING;
1902 /* Check whether logins are denied from this host. */
1903 if (packet_connection_is_on_socket()) {
1904 struct request_info req;
1906 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
1909 if (!hosts_access(&req)) {
1910 debug("Connection refused by tcp wrapper");
1913 fatal("libwrap refuse returns");
1916 #endif /* LIBWRAP */
1918 /* Log the connection. */
1919 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1922 * We don't want to listen forever unless the other side
1923 * successfully authenticates itself. So we set up an alarm which is
1924 * cleared after successful authentication. A limit of zero
1925 * indicates no limit. Note that we don't set the alarm in debugging
1926 * mode; it is just annoying to have the server exit just when you
1927 * are about to discover the bug.
1929 signal(SIGALRM, grace_alarm_handler);
1931 alarm(options.login_grace_time);
1933 sshd_exchange_identification(sock_in, sock_out);
1935 /* In inetd mode, generate ephemeral key only for proto 1 connections */
1936 if (!compat20 && inetd_flag && sensitive_data.server_key == NULL)
1937 generate_ephemeral_server_key();
1939 packet_set_nonblocking();
1941 /* allocate authentication context */
1942 authctxt = xcalloc(1, sizeof(*authctxt));
1944 authctxt->loginmsg = &loginmsg;
1946 /* XXX global for cleanup, access from other modules */
1947 the_authctxt = authctxt;
1949 /* prepare buffer to collect messages to display to user after login */
1950 buffer_init(&loginmsg);
1954 if (privsep_preauth(authctxt) == 1)
1957 /* perform the key exchange */
1958 /* authenticate user and start session */
1961 do_authentication2(authctxt);
1964 do_authentication(authctxt);
1967 * If we use privilege separation, the unprivileged child transfers
1968 * the current keystate and exits
1971 mm_send_keystate(pmonitor);
1977 * Cancel the alarm we set to limit the time taken for
1981 signal(SIGALRM, SIG_DFL);
1982 authctxt->authenticated = 1;
1983 if (startup_pipe != -1) {
1984 close(startup_pipe);
1988 #ifdef SSH_AUDIT_EVENTS
1989 audit_event(SSH_AUTH_SUCCESS);
1993 if (options.gss_authentication) {
1994 temporarily_use_uid(authctxt->pw);
1995 ssh_gssapi_storecreds();
2000 if (options.use_pam) {
2007 * In privilege separation, we fork another child and prepare
2008 * file descriptor passing.
2011 privsep_postauth(authctxt);
2012 /* the monitor process [priv] will not return */
2014 destroy_sensitive_data();
2017 packet_set_timeout(options.client_alive_interval,
2018 options.client_alive_count_max);
2020 /* Start session. */
2021 do_authenticated(authctxt);
2023 /* The connection has been terminated. */
2024 packet_get_state(MODE_IN, NULL, NULL, NULL, &ibytes);
2025 packet_get_state(MODE_OUT, NULL, NULL, NULL, &obytes);
2026 verbose("Transferred: sent %llu, received %llu bytes", obytes, ibytes);
2028 verbose("Closing connection to %.500s port %d", remote_ip, remote_port);
2031 if (options.use_pam)
2033 #endif /* USE_PAM */
2035 #ifdef SSH_AUDIT_EVENTS
2036 PRIVSEP(audit_event(SSH_CONNECTION_CLOSE));
2048 * Decrypt session_key_int using our private server key and private host key
2049 * (key with larger modulus first).
2052 ssh1_session_key(BIGNUM *session_key_int)
2056 if (BN_cmp(sensitive_data.server_key->rsa->n,
2057 sensitive_data.ssh1_host_key->rsa->n) > 0) {
2058 /* Server key has bigger modulus. */
2059 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
2060 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
2061 SSH_KEY_BITS_RESERVED) {
2062 fatal("do_connection: %s: "
2063 "server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
2064 get_remote_ipaddr(),
2065 BN_num_bits(sensitive_data.server_key->rsa->n),
2066 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
2067 SSH_KEY_BITS_RESERVED);
2069 if (rsa_private_decrypt(session_key_int, session_key_int,
2070 sensitive_data.server_key->rsa) <= 0)
2072 if (rsa_private_decrypt(session_key_int, session_key_int,
2073 sensitive_data.ssh1_host_key->rsa) <= 0)
2076 /* Host key has bigger modulus (or they are equal). */
2077 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
2078 BN_num_bits(sensitive_data.server_key->rsa->n) +
2079 SSH_KEY_BITS_RESERVED) {
2080 fatal("do_connection: %s: "
2081 "host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
2082 get_remote_ipaddr(),
2083 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
2084 BN_num_bits(sensitive_data.server_key->rsa->n),
2085 SSH_KEY_BITS_RESERVED);
2087 if (rsa_private_decrypt(session_key_int, session_key_int,
2088 sensitive_data.ssh1_host_key->rsa) < 0)
2090 if (rsa_private_decrypt(session_key_int, session_key_int,
2091 sensitive_data.server_key->rsa) < 0)
2104 BIGNUM *session_key_int;
2105 u_char session_key[SSH_SESSION_KEY_LENGTH];
2107 u_int cipher_type, auth_mask, protocol_flags;
2110 * Generate check bytes that the client must send back in the user
2111 * packet in order for it to be accepted; this is used to defy ip
2112 * spoofing attacks. Note that this only works against somebody
2113 * doing IP spoofing from a remote machine; any machine on the local
2114 * network can still see outgoing packets and catch the random
2115 * cookie. This only affects rhosts authentication, and this is one
2116 * of the reasons why it is inherently insecure.
2118 arc4random_buf(cookie, sizeof(cookie));
2121 * Send our public key. We include in the packet 64 bits of random
2122 * data that must be matched in the reply in order to prevent IP
2125 packet_start(SSH_SMSG_PUBLIC_KEY);
2126 for (i = 0; i < 8; i++)
2127 packet_put_char(cookie[i]);
2129 /* Store our public server RSA key. */
2130 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
2131 packet_put_bignum(sensitive_data.server_key->rsa->e);
2132 packet_put_bignum(sensitive_data.server_key->rsa->n);
2134 /* Store our public host RSA key. */
2135 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
2136 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
2137 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
2139 /* Put protocol flags. */
2140 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
2142 /* Declare which ciphers we support. */
2143 packet_put_int(cipher_mask_ssh1(0));
2145 /* Declare supported authentication types. */
2147 if (options.rhosts_rsa_authentication)
2148 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
2149 if (options.rsa_authentication)
2150 auth_mask |= 1 << SSH_AUTH_RSA;
2151 if (options.challenge_response_authentication == 1)
2152 auth_mask |= 1 << SSH_AUTH_TIS;
2153 if (options.password_authentication)
2154 auth_mask |= 1 << SSH_AUTH_PASSWORD;
2155 packet_put_int(auth_mask);
2157 /* Send the packet and wait for it to be sent. */
2159 packet_write_wait();
2161 debug("Sent %d bit server key and %d bit host key.",
2162 BN_num_bits(sensitive_data.server_key->rsa->n),
2163 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
2165 /* Read clients reply (cipher type and session key). */
2166 packet_read_expect(SSH_CMSG_SESSION_KEY);
2168 /* Get cipher type and check whether we accept this. */
2169 cipher_type = packet_get_char();
2171 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
2172 packet_disconnect("Warning: client selects unsupported cipher.");
2174 /* Get check bytes from the packet. These must match those we
2175 sent earlier with the public key packet. */
2176 for (i = 0; i < 8; i++)
2177 if (cookie[i] != packet_get_char())
2178 packet_disconnect("IP Spoofing check bytes do not match.");
2180 debug("Encryption type: %.200s", cipher_name(cipher_type));
2182 /* Get the encrypted integer. */
2183 if ((session_key_int = BN_new()) == NULL)
2184 fatal("do_ssh1_kex: BN_new failed");
2185 packet_get_bignum(session_key_int);
2187 protocol_flags = packet_get_int();
2188 packet_set_protocol_flags(protocol_flags);
2191 /* Decrypt session_key_int using host/server keys */
2192 rsafail = PRIVSEP(ssh1_session_key(session_key_int));
2195 * Extract session key from the decrypted integer. The key is in the
2196 * least significant 256 bits of the integer; the first byte of the
2197 * key is in the highest bits.
2200 (void) BN_mask_bits(session_key_int, sizeof(session_key) * 8);
2201 len = BN_num_bytes(session_key_int);
2202 if (len < 0 || (u_int)len > sizeof(session_key)) {
2203 error("do_ssh1_kex: bad session key len from %s: "
2204 "session_key_int %d > sizeof(session_key) %lu",
2205 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
2208 memset(session_key, 0, sizeof(session_key));
2209 BN_bn2bin(session_key_int,
2210 session_key + sizeof(session_key) - len);
2212 derive_ssh1_session_id(
2213 sensitive_data.ssh1_host_key->rsa->n,
2214 sensitive_data.server_key->rsa->n,
2215 cookie, session_id);
2217 * Xor the first 16 bytes of the session key with the
2220 for (i = 0; i < 16; i++)
2221 session_key[i] ^= session_id[i];
2225 int bytes = BN_num_bytes(session_key_int);
2226 u_char *buf = xmalloc(bytes);
2229 logit("do_connection: generating a fake encryption key");
2230 BN_bn2bin(session_key_int, buf);
2232 MD5_Update(&md, buf, bytes);
2233 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
2234 MD5_Final(session_key, &md);
2236 MD5_Update(&md, session_key, 16);
2237 MD5_Update(&md, buf, bytes);
2238 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
2239 MD5_Final(session_key + 16, &md);
2240 memset(buf, 0, bytes);
2242 for (i = 0; i < 16; i++)
2243 session_id[i] = session_key[i] ^ session_key[i + 16];
2245 /* Destroy the private and public keys. No longer. */
2246 destroy_sensitive_data();
2249 mm_ssh1_session_id(session_id);
2251 /* Destroy the decrypted integer. It is no longer needed. */
2252 BN_clear_free(session_key_int);
2254 /* Set the session key. From this on all communications will be encrypted. */
2255 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
2257 /* Destroy our copy of the session key. It is no longer needed. */
2258 memset(session_key, 0, sizeof(session_key));
2260 debug("Received session key; encryption turned on.");
2262 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */
2263 packet_start(SSH_SMSG_SUCCESS);
2265 packet_write_wait();
2269 * SSH2 key exchange: diffie-hellman-group1-sha1
2276 if (options.ciphers != NULL) {
2277 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2278 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
2280 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2281 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
2282 myproposal[PROPOSAL_ENC_ALGS_STOC] =
2283 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
2285 if (options.macs != NULL) {
2286 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
2287 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
2289 if (options.compression == COMP_NONE) {
2290 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2291 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
2292 } else if (options.compression == COMP_DELAYED) {
2293 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2294 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com";
2297 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
2299 /* start key exchange */
2300 kex = kex_setup(myproposal);
2301 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
2302 kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
2303 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
2304 kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
2306 kex->client_version_string=client_version_string;
2307 kex->server_version_string=server_version_string;
2308 kex->load_host_public_key=&get_hostkey_public_by_type;
2309 kex->load_host_private_key=&get_hostkey_private_by_type;
2310 kex->host_key_index=&get_hostkey_index;
2314 dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
2316 session_id2 = kex->session_id;
2317 session_id2_len = kex->session_id_len;
2320 /* send 1st encrypted/maced/compressed message */
2321 packet_start(SSH2_MSG_IGNORE);
2322 packet_put_cstring("markus");
2324 packet_write_wait();
2329 /* server specific fatal cleanup */
2334 do_cleanup(the_authctxt);
2335 #ifdef SSH_AUDIT_EVENTS
2336 /* done after do_cleanup so it can cancel the PAM auth 'thread' */
2337 if (!use_privsep || mm_is_monitor())
2338 audit_event(SSH_CONNECTION_ABANDON);