1 /* $OpenBSD: sshd.c,v 1.366 2009/01/22 10:02:34 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"
122 #ifdef USE_SECURITY_SESSION_API
123 #include <Security/AuthSession.h>
138 #define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1)
139 #define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2)
140 #define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3)
141 #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_VERSION, 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);
474 compat_datafellows(remote_version);
476 if (datafellows & SSH_BUG_PROBE) {
477 logit("probed from %s with %s. Don't panic.",
478 get_remote_ipaddr(), client_version_string);
482 if (datafellows & SSH_BUG_SCANNER) {
483 logit("scanned from %s with %s. Don't panic.",
484 get_remote_ipaddr(), client_version_string);
489 switch (remote_major) {
491 if (remote_minor == 99) {
492 if (options.protocol & SSH_PROTO_2)
498 if (!(options.protocol & SSH_PROTO_1)) {
502 if (remote_minor < 3) {
503 packet_disconnect("Your ssh version is too old and "
504 "is no longer supported. Please install a newer version.");
505 } else if (remote_minor == 3) {
506 /* note that this disables agent-forwarding */
511 if (options.protocol & SSH_PROTO_2) {
520 chop(server_version_string);
521 debug("Local version string %.200s", server_version_string);
524 s = "Protocol major versions differ.\n";
525 (void) atomicio(vwrite, sock_out, s, strlen(s));
528 logit("Protocol major versions differ for %s: %.200s vs. %.200s",
530 server_version_string, client_version_string);
535 /* Destroy the host and server keys. They will no longer be needed. */
537 destroy_sensitive_data(void)
541 if (sensitive_data.server_key) {
542 key_free(sensitive_data.server_key);
543 sensitive_data.server_key = NULL;
545 for (i = 0; i < options.num_host_key_files; i++) {
546 if (sensitive_data.host_keys[i]) {
547 key_free(sensitive_data.host_keys[i]);
548 sensitive_data.host_keys[i] = NULL;
551 sensitive_data.ssh1_host_key = NULL;
552 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
555 /* Demote private to public keys for network child */
557 demote_sensitive_data(void)
562 if (sensitive_data.server_key) {
563 tmp = key_demote(sensitive_data.server_key);
564 key_free(sensitive_data.server_key);
565 sensitive_data.server_key = tmp;
568 for (i = 0; i < options.num_host_key_files; i++) {
569 if (sensitive_data.host_keys[i]) {
570 tmp = key_demote(sensitive_data.host_keys[i]);
571 key_free(sensitive_data.host_keys[i]);
572 sensitive_data.host_keys[i] = tmp;
573 if (tmp->type == KEY_RSA1)
574 sensitive_data.ssh1_host_key = tmp;
578 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */
582 privsep_preauth_child(void)
587 /* Enable challenge-response authentication for privilege separation */
588 privsep_challenge_enable();
591 arc4random_buf(rnd, sizeof(rnd));
592 RAND_seed(rnd, sizeof(rnd));
594 /* Demote the private keys to public keys. */
595 demote_sensitive_data();
597 /* Change our root directory */
598 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
599 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
601 if (chdir("/") == -1)
602 fatal("chdir(\"/\"): %s", strerror(errno));
604 /* Drop our privileges */
605 debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid,
606 (u_int)privsep_pw->pw_gid);
608 /* XXX not ready, too heavy after chroot */
609 do_setusercontext(privsep_pw);
611 gidset[0] = privsep_pw->pw_gid;
612 if (setgroups(1, gidset) < 0)
613 fatal("setgroups: %.100s", strerror(errno));
614 permanently_set_uid(privsep_pw);
619 privsep_preauth(Authctxt *authctxt)
624 /* Set up unprivileged child process to deal with network data */
625 pmonitor = monitor_init();
626 /* Store a pointer to the kex for later rekeying */
627 pmonitor->m_pkex = &xxx_kex;
631 fatal("fork of unprivileged child failed");
632 } else if (pid != 0) {
633 debug2("Network child is on pid %ld", (long)pid);
635 close(pmonitor->m_recvfd);
636 pmonitor->m_pid = pid;
637 monitor_child_preauth(authctxt, pmonitor);
638 close(pmonitor->m_sendfd);
641 monitor_sync(pmonitor);
643 /* Wait for the child's exit status */
644 while (waitpid(pid, &status, 0) < 0)
651 close(pmonitor->m_sendfd);
653 /* Demote the child */
654 if (getuid() == 0 || geteuid() == 0)
655 privsep_preauth_child();
656 setproctitle("%s", "[net]");
662 privsep_postauth(Authctxt *authctxt)
666 #ifdef DISABLE_FD_PASSING
669 if (authctxt->pw->pw_uid == 0 || options.use_login) {
671 /* File descriptor passing is broken or root login */
676 /* New socket pair */
677 monitor_reinit(pmonitor);
679 pmonitor->m_pid = fork();
680 if (pmonitor->m_pid == -1)
681 fatal("fork of unprivileged child failed");
682 else if (pmonitor->m_pid != 0) {
683 verbose("User child is on pid %ld", (long)pmonitor->m_pid);
684 close(pmonitor->m_recvfd);
685 buffer_clear(&loginmsg);
686 monitor_child_postauth(pmonitor);
692 close(pmonitor->m_sendfd);
694 /* Demote the private keys to public keys. */
695 demote_sensitive_data();
698 arc4random_buf(rnd, sizeof(rnd));
699 RAND_seed(rnd, sizeof(rnd));
701 /* Drop privileges */
702 do_setusercontext(authctxt->pw);
705 /* It is safe now to apply the key state */
706 monitor_apply_keystate(pmonitor);
709 * Tell the packet layer that authentication was successful, since
710 * this information is not part of the key state.
712 packet_set_authenticated();
716 list_hostkey_types(void)
724 for (i = 0; i < options.num_host_key_files; i++) {
725 Key *key = sensitive_data.host_keys[i];
731 if (buffer_len(&b) > 0)
732 buffer_append(&b, ",", 1);
733 p = key_ssh_name(key);
734 buffer_append(&b, p, strlen(p));
738 buffer_append(&b, "\0", 1);
739 ret = xstrdup(buffer_ptr(&b));
741 debug("list_hostkey_types: %s", ret);
746 get_hostkey_by_type(int type)
750 for (i = 0; i < options.num_host_key_files; i++) {
751 Key *key = sensitive_data.host_keys[i];
752 if (key != NULL && key->type == type)
759 get_hostkey_by_index(int ind)
761 if (ind < 0 || ind >= options.num_host_key_files)
763 return (sensitive_data.host_keys[ind]);
767 get_hostkey_index(Key *key)
771 for (i = 0; i < options.num_host_key_files; i++) {
772 if (key == sensitive_data.host_keys[i])
779 * returns 1 if connection should be dropped, 0 otherwise.
780 * dropping starts at connection #max_startups_begin with a probability
781 * of (max_startups_rate/100). the probability increases linearly until
782 * all connections are dropped for startups > max_startups
785 drop_connection(int startups)
789 if (startups < options.max_startups_begin)
791 if (startups >= options.max_startups)
793 if (options.max_startups_rate == 100)
796 p = 100 - options.max_startups_rate;
797 p *= startups - options.max_startups_begin;
798 p /= options.max_startups - options.max_startups_begin;
799 p += options.max_startups_rate;
800 r = arc4random_uniform(100);
802 debug("drop_connection: p %d, r %d", p, r);
803 return (r < p) ? 1 : 0;
809 fprintf(stderr, "%s, %s\n",
810 SSH_RELEASE, SSLeay_version(SSLEAY_VERSION));
812 "usage: sshd [-46DdeiqTt] [-b bits] [-C connection_spec] [-f config_file]\n"
813 " [-g login_grace_time] [-h host_key_file] [-k key_gen_time]\n"
814 " [-o option] [-p port] [-u len]\n"
820 send_rexec_state(int fd, Buffer *conf)
824 debug3("%s: entering fd = %d config len %d", __func__, fd,
828 * Protocol from reexec master to child:
829 * string configuration
830 * u_int ephemeral_key_follows
831 * bignum e (only if ephemeral_key_follows == 1)
837 * string rngseed (only if OpenSSL is not self-seeded)
840 buffer_put_cstring(&m, buffer_ptr(conf));
842 if (sensitive_data.server_key != NULL &&
843 sensitive_data.server_key->type == KEY_RSA1) {
844 buffer_put_int(&m, 1);
845 buffer_put_bignum(&m, sensitive_data.server_key->rsa->e);
846 buffer_put_bignum(&m, sensitive_data.server_key->rsa->n);
847 buffer_put_bignum(&m, sensitive_data.server_key->rsa->d);
848 buffer_put_bignum(&m, sensitive_data.server_key->rsa->iqmp);
849 buffer_put_bignum(&m, sensitive_data.server_key->rsa->p);
850 buffer_put_bignum(&m, sensitive_data.server_key->rsa->q);
852 buffer_put_int(&m, 0);
854 #ifndef OPENSSL_PRNG_ONLY
855 rexec_send_rng_seed(&m);
858 if (ssh_msg_send(fd, 0, &m) == -1)
859 fatal("%s: ssh_msg_send failed", __func__);
863 debug3("%s: done", __func__);
867 recv_rexec_state(int fd, Buffer *conf)
873 debug3("%s: entering fd = %d", __func__, fd);
877 if (ssh_msg_recv(fd, &m) == -1)
878 fatal("%s: ssh_msg_recv failed", __func__);
879 if (buffer_get_char(&m) != 0)
880 fatal("%s: rexec version mismatch", __func__);
882 cp = buffer_get_string(&m, &len);
884 buffer_append(conf, cp, len + 1);
887 if (buffer_get_int(&m)) {
888 if (sensitive_data.server_key != NULL)
889 key_free(sensitive_data.server_key);
890 sensitive_data.server_key = key_new_private(KEY_RSA1);
891 buffer_get_bignum(&m, sensitive_data.server_key->rsa->e);
892 buffer_get_bignum(&m, sensitive_data.server_key->rsa->n);
893 buffer_get_bignum(&m, sensitive_data.server_key->rsa->d);
894 buffer_get_bignum(&m, sensitive_data.server_key->rsa->iqmp);
895 buffer_get_bignum(&m, sensitive_data.server_key->rsa->p);
896 buffer_get_bignum(&m, sensitive_data.server_key->rsa->q);
897 rsa_generate_additional_parameters(
898 sensitive_data.server_key->rsa);
901 #ifndef OPENSSL_PRNG_ONLY
902 rexec_recv_rng_seed(&m);
907 debug3("%s: done", __func__);
910 /* Accept a connection from inetd */
912 server_accept_inetd(int *sock_in, int *sock_out)
918 close(REEXEC_CONFIG_PASS_FD);
919 *sock_in = *sock_out = dup(STDIN_FILENO);
921 startup_pipe = dup(REEXEC_STARTUP_PIPE_FD);
922 close(REEXEC_STARTUP_PIPE_FD);
925 *sock_in = dup(STDIN_FILENO);
926 *sock_out = dup(STDOUT_FILENO);
929 * We intentionally do not close the descriptors 0, 1, and 2
930 * as our code for setting the descriptors won't work if
931 * ttyfd happens to be one of those.
933 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
934 dup2(fd, STDIN_FILENO);
935 dup2(fd, STDOUT_FILENO);
936 if (fd > STDOUT_FILENO)
939 debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out);
943 * Listen for TCP connections
948 int ret, listen_sock, on = 1;
950 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
952 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
953 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
955 if (num_listen_socks >= MAX_LISTEN_SOCKS)
956 fatal("Too many listen sockets. "
957 "Enlarge MAX_LISTEN_SOCKS");
958 if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen,
959 ntop, sizeof(ntop), strport, sizeof(strport),
960 NI_NUMERICHOST|NI_NUMERICSERV)) != 0) {
961 error("getnameinfo failed: %.100s",
962 ssh_gai_strerror(ret));
965 /* Create socket for listening. */
966 listen_sock = socket(ai->ai_family, ai->ai_socktype,
968 if (listen_sock < 0) {
969 /* kernel may not support ipv6 */
970 verbose("socket: %.100s", strerror(errno));
973 if (set_nonblock(listen_sock) == -1) {
978 * Set socket options.
979 * Allow local port reuse in TIME_WAIT.
981 if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
982 &on, sizeof(on)) == -1)
983 error("setsockopt SO_REUSEADDR: %s", strerror(errno));
986 /* Only communicate in IPv6 over AF_INET6 sockets. */
987 if (ai->ai_family == AF_INET6) {
988 if (setsockopt(listen_sock, IPPROTO_IPV6, IPV6_V6ONLY,
989 &on, sizeof(on)) == -1)
990 error("setsockopt IPV6_V6ONLY: %s",
995 debug("Bind to port %s on %s.", strport, ntop);
997 /* Bind the socket to the desired port. */
998 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
999 error("Bind to port %s on %s failed: %.200s.",
1000 strport, ntop, strerror(errno));
1004 listen_socks[num_listen_socks] = listen_sock;
1007 /* Start listening on the port. */
1008 if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0)
1009 fatal("listen on [%s]:%s: %.100s",
1010 ntop, strport, strerror(errno));
1011 logit("Server listening on %s port %s.", ntop, strport);
1013 freeaddrinfo(options.listen_addrs);
1015 if (!num_listen_socks)
1016 fatal("Cannot bind any address.");
1020 * The main TCP accept loop. Note that, for the non-debug case, returns
1021 * from this function are in a forked subprocess.
1024 server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
1027 int i, j, ret, maxfd;
1028 int key_used = 0, startups = 0;
1029 int startup_p[2] = { -1 , -1 };
1030 struct sockaddr_storage from;
1034 /* setup fd set for accept */
1037 for (i = 0; i < num_listen_socks; i++)
1038 if (listen_socks[i] > maxfd)
1039 maxfd = listen_socks[i];
1040 /* pipes connected to unauthenticated childs */
1041 startup_pipes = xcalloc(options.max_startups, sizeof(int));
1042 for (i = 0; i < options.max_startups; i++)
1043 startup_pipes[i] = -1;
1046 * Stay listening for connections until the system crashes or
1047 * the daemon is killed with a signal.
1050 if (received_sighup)
1054 fdset = (fd_set *)xcalloc(howmany(maxfd + 1, NFDBITS),
1057 for (i = 0; i < num_listen_socks; i++)
1058 FD_SET(listen_socks[i], fdset);
1059 for (i = 0; i < options.max_startups; i++)
1060 if (startup_pipes[i] != -1)
1061 FD_SET(startup_pipes[i], fdset);
1063 /* Wait in select until there is a connection. */
1064 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
1065 if (ret < 0 && errno != EINTR)
1066 error("select: %.100s", strerror(errno));
1067 if (received_sigterm) {
1068 logit("Received signal %d; terminating.",
1069 (int) received_sigterm);
1070 close_listen_socks();
1071 unlink(options.pid_file);
1074 if (key_used && key_do_regen) {
1075 generate_ephemeral_server_key();
1082 for (i = 0; i < options.max_startups; i++)
1083 if (startup_pipes[i] != -1 &&
1084 FD_ISSET(startup_pipes[i], fdset)) {
1086 * the read end of the pipe is ready
1087 * if the child has closed the pipe
1088 * after successful authentication
1089 * or if the child has died
1091 close(startup_pipes[i]);
1092 startup_pipes[i] = -1;
1095 for (i = 0; i < num_listen_socks; i++) {
1096 if (!FD_ISSET(listen_socks[i], fdset))
1098 fromlen = sizeof(from);
1099 *newsock = accept(listen_socks[i],
1100 (struct sockaddr *)&from, &fromlen);
1102 if (errno != EINTR && errno != EAGAIN &&
1103 errno != EWOULDBLOCK)
1104 error("accept: %.100s", strerror(errno));
1107 if (unset_nonblock(*newsock) == -1) {
1111 if (drop_connection(startups) == 1) {
1112 debug("drop connection #%d", startups);
1116 if (pipe(startup_p) == -1) {
1121 if (rexec_flag && socketpair(AF_UNIX,
1122 SOCK_STREAM, 0, config_s) == -1) {
1123 error("reexec socketpair: %s",
1126 close(startup_p[0]);
1127 close(startup_p[1]);
1131 for (j = 0; j < options.max_startups; j++)
1132 if (startup_pipes[j] == -1) {
1133 startup_pipes[j] = startup_p[0];
1134 if (maxfd < startup_p[0])
1135 maxfd = startup_p[0];
1141 * Got connection. Fork a child to handle it, unless
1142 * we are in debugging mode.
1146 * In debugging mode. Close the listening
1147 * socket, and start processing the
1148 * connection without forking.
1150 debug("Server will not fork when running in debugging mode.");
1151 close_listen_socks();
1152 *sock_in = *newsock;
1153 *sock_out = *newsock;
1154 close(startup_p[0]);
1155 close(startup_p[1]);
1159 send_rexec_state(config_s[0],
1167 * Normal production daemon. Fork, and have
1168 * the child process the connection. The
1169 * parent continues listening.
1171 platform_pre_fork();
1172 if ((pid = fork()) == 0) {
1174 * Child. Close the listening and
1175 * max_startup sockets. Start using
1176 * the accepted socket. Reinitialize
1177 * logging (since our pid has changed).
1178 * We break out of the loop to handle
1181 platform_post_fork_child();
1182 startup_pipe = startup_p[1];
1183 close_startup_pipes();
1184 close_listen_socks();
1185 *sock_in = *newsock;
1186 *sock_out = *newsock;
1187 log_init(__progname,
1189 options.log_facility,
1196 /* Parent. Stay in the loop. */
1197 platform_post_fork_parent(pid);
1199 error("fork: %.100s", strerror(errno));
1201 debug("Forked child %ld.", (long)pid);
1203 close(startup_p[1]);
1206 send_rexec_state(config_s[0], &cfg);
1212 * Mark that the key has been used (it
1213 * was "given" to the child).
1215 if ((options.protocol & SSH_PROTO_1) &&
1217 /* Schedule server key regeneration alarm. */
1218 signal(SIGALRM, key_regeneration_alarm);
1219 alarm(options.key_regeneration_time);
1226 * Ensure that our random state differs
1227 * from that of the child
1232 /* child process check (or debug mode) */
1233 if (num_listen_socks < 0)
1240 * Main program for the daemon.
1243 main(int ac, char **av)
1245 extern char *optarg;
1248 int sock_in = -1, sock_out = -1, newsock = -1;
1249 const char *remote_ip;
1250 char *test_user = NULL, *test_host = NULL, *test_addr = NULL;
1252 char *line, *p, *cp;
1253 int config_s[2] = { -1 , -1 };
1254 u_int64_t ibytes, obytes;
1259 #ifdef HAVE_SECUREWARE
1260 (void)set_auth_parameters(ac, av);
1262 __progname = ssh_get_progname(av[0]);
1265 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
1268 saved_argv = xcalloc(ac + 1, sizeof(*saved_argv));
1269 for (i = 0; i < ac; i++)
1270 saved_argv[i] = xstrdup(av[i]);
1271 saved_argv[i] = NULL;
1273 #ifndef HAVE_SETPROCTITLE
1274 /* Prepare for later setproctitle emulation */
1275 compat_init_setproctitle(ac, av);
1279 if (geteuid() == 0 && setgroups(0, NULL) == -1)
1280 debug("setgroups(): %.200s", strerror(errno));
1282 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
1285 /* Initialize configuration options to their default values. */
1286 initialize_server_options(&options);
1288 /* Parse command-line arguments. */
1289 while ((opt = getopt(ac, av, "f:p:b:k:h:g:u:o:C:dDeiqrtQRT46")) != -1) {
1292 options.address_family = AF_INET;
1295 options.address_family = AF_INET6;
1298 config_file_name = optarg;
1301 if (debug_flag == 0) {
1303 options.log_level = SYSLOG_LEVEL_DEBUG1;
1304 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
1305 options.log_level++;
1327 options.log_level = SYSLOG_LEVEL_QUIET;
1330 options.server_key_bits = (int)strtonum(optarg, 256,
1334 options.ports_from_cmdline = 1;
1335 if (options.num_ports >= MAX_PORTS) {
1336 fprintf(stderr, "too many ports.\n");
1339 options.ports[options.num_ports++] = a2port(optarg);
1340 if (options.ports[options.num_ports-1] <= 0) {
1341 fprintf(stderr, "Bad port number.\n");
1346 if ((options.login_grace_time = convtime(optarg)) == -1) {
1347 fprintf(stderr, "Invalid login grace time.\n");
1352 if ((options.key_regeneration_time = convtime(optarg)) == -1) {
1353 fprintf(stderr, "Invalid key regeneration interval.\n");
1358 if (options.num_host_key_files >= MAX_HOSTKEYS) {
1359 fprintf(stderr, "too many host keys.\n");
1362 options.host_key_files[options.num_host_key_files++] = optarg;
1372 while ((p = strsep(&cp, ",")) && *p != '\0') {
1373 if (strncmp(p, "addr=", 5) == 0)
1374 test_addr = xstrdup(p + 5);
1375 else if (strncmp(p, "host=", 5) == 0)
1376 test_host = xstrdup(p + 5);
1377 else if (strncmp(p, "user=", 5) == 0)
1378 test_user = xstrdup(p + 5);
1380 fprintf(stderr, "Invalid test "
1381 "mode specification %s\n", p);
1387 utmp_len = (u_int)strtonum(optarg, 0, MAXHOSTNAMELEN+1, NULL);
1388 if (utmp_len > MAXHOSTNAMELEN) {
1389 fprintf(stderr, "Invalid utmp length.\n");
1394 line = xstrdup(optarg);
1395 if (process_server_config_line(&options, line,
1396 "command-line", 0, NULL, NULL, NULL, NULL) != 0)
1406 if (rexeced_flag || inetd_flag)
1408 if (!test_flag && (rexec_flag && (av[0] == NULL || *av[0] != '/')))
1409 fatal("sshd re-exec requires execution with an absolute path");
1411 closefrom(REEXEC_MIN_FREE_FD);
1413 closefrom(REEXEC_DEVCRYPTO_RESERVED_FD);
1415 SSLeay_add_all_algorithms();
1418 * Force logging to stderr until we have loaded the private host
1419 * key (unless started from inetd)
1421 log_init(__progname,
1422 options.log_level == SYSLOG_LEVEL_NOT_SET ?
1423 SYSLOG_LEVEL_INFO : options.log_level,
1424 options.log_facility == SYSLOG_FACILITY_NOT_SET ?
1425 SYSLOG_FACILITY_AUTH : options.log_facility,
1426 log_stderr || !inetd_flag);
1429 * Unset KRB5CCNAME, otherwise the user's session may inherit it from
1430 * root's environment
1432 if (getenv("KRB5CCNAME") != NULL)
1433 unsetenv("KRB5CCNAME");
1436 /* Cray can define user privs drop all privs now!
1437 * Not needed on PRIV_SU systems!
1442 sensitive_data.server_key = NULL;
1443 sensitive_data.ssh1_host_key = NULL;
1444 sensitive_data.have_ssh1_key = 0;
1445 sensitive_data.have_ssh2_key = 0;
1448 * If we're doing an extended config test, make sure we have all of
1449 * the parameters we need. If we're not doing an extended test,
1450 * do not silently ignore connection test params.
1452 if (test_flag >= 2 &&
1453 (test_user != NULL || test_host != NULL || test_addr != NULL)
1454 && (test_user == NULL || test_host == NULL || test_addr == NULL))
1455 fatal("user, host and addr are all required when testing "
1457 if (test_flag < 2 && (test_user != NULL || test_host != NULL ||
1459 fatal("Config test connection parameter (-C) provided without "
1462 /* Fetch our configuration */
1465 recv_rexec_state(REEXEC_CONFIG_PASS_FD, &cfg);
1467 load_server_config(config_file_name, &cfg);
1469 parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name,
1470 &cfg, NULL, NULL, NULL);
1474 /* Fill in default values for those options not explicitly set. */
1475 fill_default_server_options(&options);
1477 /* challenge-response is implemented via keyboard interactive */
1478 if (options.challenge_response_authentication)
1479 options.kbd_interactive_authentication = 1;
1481 /* set default channel AF */
1482 channel_set_af(options.address_family);
1484 /* Check that there are no remaining arguments. */
1486 fprintf(stderr, "Extra argument %s.\n", av[optind]);
1490 debug("sshd version %.100s", SSH_RELEASE);
1492 /* Store privilege separation user for later use if required. */
1493 if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) {
1494 if (use_privsep || options.kerberos_authentication)
1495 fatal("Privilege separation user %s does not exist",
1498 memset(privsep_pw->pw_passwd, 0, strlen(privsep_pw->pw_passwd));
1499 privsep_pw = pwcopy(privsep_pw);
1500 xfree(privsep_pw->pw_passwd);
1501 privsep_pw->pw_passwd = xstrdup("*");
1505 /* load private host keys */
1506 sensitive_data.host_keys = xcalloc(options.num_host_key_files,
1508 for (i = 0; i < options.num_host_key_files; i++)
1509 sensitive_data.host_keys[i] = NULL;
1511 for (i = 0; i < options.num_host_key_files; i++) {
1512 key = key_load_private(options.host_key_files[i], "", NULL);
1513 sensitive_data.host_keys[i] = key;
1515 error("Could not load host key: %s",
1516 options.host_key_files[i]);
1517 sensitive_data.host_keys[i] = NULL;
1520 switch (key->type) {
1522 sensitive_data.ssh1_host_key = key;
1523 sensitive_data.have_ssh1_key = 1;
1527 sensitive_data.have_ssh2_key = 1;
1530 debug("private host key: #%d type %d %s", i, key->type,
1533 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
1534 logit("Disabling protocol version 1. Could not load host key");
1535 options.protocol &= ~SSH_PROTO_1;
1538 /* The GSSAPI key exchange can run without a host key */
1539 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
1540 logit("Disabling protocol version 2. Could not load host key");
1541 options.protocol &= ~SSH_PROTO_2;
1544 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
1545 logit("sshd: no hostkeys available -- exiting.");
1549 /* Check certain values for sanity. */
1550 if (options.protocol & SSH_PROTO_1) {
1551 if (options.server_key_bits < 512 ||
1552 options.server_key_bits > 32768) {
1553 fprintf(stderr, "Bad server key size.\n");
1557 * Check that server and host key lengths differ sufficiently. This
1558 * is necessary to make double encryption work with rsaref. Oh, I
1559 * hate software patents. I dont know if this can go? Niels
1561 if (options.server_key_bits >
1562 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) -
1563 SSH_KEY_BITS_RESERVED && options.server_key_bits <
1564 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1565 SSH_KEY_BITS_RESERVED) {
1566 options.server_key_bits =
1567 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1568 SSH_KEY_BITS_RESERVED;
1569 debug("Forcing server key to %d bits to make it differ from host key.",
1570 options.server_key_bits);
1577 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) ||
1578 (S_ISDIR(st.st_mode) == 0))
1579 fatal("Missing privilege separation directory: %s",
1580 _PATH_PRIVSEP_CHROOT_DIR);
1583 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
1584 (st.st_uid != getuid () ||
1585 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0))
1587 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)
1589 fatal("%s must be owned by root and not group or "
1590 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR);
1593 if (test_flag > 1) {
1594 if (test_user != NULL && test_addr != NULL && test_host != NULL)
1595 parse_server_match_config(&options, test_user,
1596 test_host, test_addr);
1597 dump_config(&options);
1600 /* Configuration looks good, so exit if in test mode. */
1605 * Clear out any supplemental groups we may have inherited. This
1606 * prevents inadvertent creation of files with bad modes (in the
1607 * portable version at least, it's certainly possible for PAM
1608 * to create a file, and we can't control the code in every
1609 * module which might be used).
1611 if (setgroups(0, NULL) < 0)
1612 debug("setgroups() failed: %.200s", strerror(errno));
1615 rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *));
1616 for (i = 0; i < rexec_argc; i++) {
1617 debug("rexec_argv[%d]='%s'", i, saved_argv[i]);
1618 rexec_argv[i] = saved_argv[i];
1620 rexec_argv[rexec_argc] = "-R";
1621 rexec_argv[rexec_argc + 1] = NULL;
1624 /* Ensure that umask disallows at least group and world write */
1625 new_umask = umask(0077) | 0022;
1626 (void) umask(new_umask);
1628 /* Initialize the log (it is reinitialized below in case we forked). */
1629 if (debug_flag && (!inetd_flag || rexeced_flag))
1631 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1634 * If not in debugging mode, and not started from inetd, disconnect
1635 * from the controlling terminal, and fork. The original process
1638 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
1641 #endif /* TIOCNOTTY */
1642 if (daemon(0, 0) < 0)
1643 fatal("daemon() failed: %.200s", strerror(errno));
1645 /* Disconnect from the controlling tty. */
1647 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
1649 (void) ioctl(fd, TIOCNOTTY, NULL);
1652 #endif /* TIOCNOTTY */
1654 /* Reinitialize the log (because of the fork above). */
1655 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1657 /* Initialize the random number generator. */
1660 /* Chdir to the root directory so that the current disk can be
1661 unmounted if desired. */
1664 /* ignore SIGPIPE */
1665 signal(SIGPIPE, SIG_IGN);
1667 /* Get a connection, either from inetd or a listening TCP socket */
1669 server_accept_inetd(&sock_in, &sock_out);
1673 if (options.protocol & SSH_PROTO_1)
1674 generate_ephemeral_server_key();
1676 signal(SIGHUP, sighup_handler);
1677 signal(SIGCHLD, main_sigchld_handler);
1678 signal(SIGTERM, sigterm_handler);
1679 signal(SIGQUIT, sigterm_handler);
1682 * Write out the pid file after the sigterm handler
1683 * is setup and the listen sockets are bound
1686 FILE *f = fopen(options.pid_file, "w");
1689 error("Couldn't create pid file \"%s\": %s",
1690 options.pid_file, strerror(errno));
1692 fprintf(f, "%ld\n", (long) getpid());
1697 /* Accept a connection and return in a forked child */
1698 server_accept_loop(&sock_in, &sock_out,
1699 &newsock, config_s);
1702 /* This is the child processing a new connection. */
1703 setproctitle("%s", "[accepted]");
1706 * Create a new session and process group since the 4.4BSD
1707 * setlogin() affects the entire process group. We don't
1708 * want the child to be able to affect the parent.
1710 #if !defined(SSHD_ACQUIRES_CTTY)
1712 * If setsid is called, on some platforms sshd will later acquire a
1713 * controlling terminal which will result in "could not set
1714 * controlling tty" errors.
1716 if (!debug_flag && !inetd_flag && setsid() < 0)
1717 error("setsid: %.100s", strerror(errno));
1723 debug("rexec start in %d out %d newsock %d pipe %d sock %d",
1724 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
1725 dup2(newsock, STDIN_FILENO);
1726 dup2(STDIN_FILENO, STDOUT_FILENO);
1727 if (startup_pipe == -1)
1728 close(REEXEC_STARTUP_PIPE_FD);
1730 dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD);
1732 dup2(config_s[1], REEXEC_CONFIG_PASS_FD);
1734 if (startup_pipe != -1)
1735 close(startup_pipe);
1737 execv(rexec_argv[0], rexec_argv);
1739 /* Reexec has failed, fall back and continue */
1740 error("rexec of %s failed: %s", rexec_argv[0], strerror(errno));
1741 recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL);
1742 log_init(__progname, options.log_level,
1743 options.log_facility, log_stderr);
1746 startup_pipe = REEXEC_STARTUP_PIPE_FD;
1748 close(REEXEC_CONFIG_PASS_FD);
1749 newsock = sock_out = sock_in = dup(STDIN_FILENO);
1750 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
1751 dup2(fd, STDIN_FILENO);
1752 dup2(fd, STDOUT_FILENO);
1753 if (fd > STDERR_FILENO)
1756 debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d",
1757 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
1761 * Disable the key regeneration alarm. We will not regenerate the
1762 * key since we are no longer in a position to give it to anyone. We
1763 * will not restart on SIGHUP since it no longer makes sense.
1766 signal(SIGALRM, SIG_DFL);
1767 signal(SIGHUP, SIG_DFL);
1768 signal(SIGTERM, SIG_DFL);
1769 signal(SIGQUIT, SIG_DFL);
1770 signal(SIGCHLD, SIG_DFL);
1771 signal(SIGINT, SIG_DFL);
1774 * Register our connection. This turns encryption off because we do
1777 packet_set_connection(sock_in, sock_out);
1778 packet_set_server();
1780 /* Set SO_KEEPALIVE if requested. */
1781 if (options.tcp_keep_alive && packet_connection_is_on_socket() &&
1782 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) < 0)
1783 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1785 if ((remote_port = get_remote_port()) < 0) {
1786 debug("get_remote_port failed");
1791 * We use get_canonical_hostname with usedns = 0 instead of
1792 * get_remote_ipaddr here so IP options will be checked.
1794 (void) get_canonical_hostname(0);
1796 * The rest of the code depends on the fact that
1797 * get_remote_ipaddr() caches the remote ip, even if
1798 * the socket goes away.
1800 remote_ip = get_remote_ipaddr();
1802 #ifdef SSH_AUDIT_EVENTS
1803 audit_connection_from(remote_ip, remote_port);
1806 allow_severity = options.log_facility|LOG_INFO;
1807 deny_severity = options.log_facility|LOG_WARNING;
1808 /* Check whether logins are denied from this host. */
1809 if (packet_connection_is_on_socket()) {
1810 struct request_info req;
1812 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
1815 if (!hosts_access(&req)) {
1816 debug("Connection refused by tcp wrapper");
1819 fatal("libwrap refuse returns");
1822 #endif /* LIBWRAP */
1824 /* Log the connection. */
1825 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1827 #ifdef USE_SECURITY_SESSION_API
1829 * Create a new security session for use by the new user login if
1830 * the current session is the root session or we are not launched
1831 * by inetd (eg: debugging mode or server mode). We do not
1832 * necessarily need to create a session if we are launched from
1833 * inetd because Panther xinetd will create a session for us.
1835 * The only case where this logic will fail is if there is an
1836 * inetd running in a non-root session which is not creating
1837 * new sessions for us. Then all the users will end up in the
1838 * same session (bad).
1840 * When the client exits, the session will be destroyed for us
1843 * We must create the session before any credentials are stored
1844 * (including AFS pags, which happens a few lines below).
1848 SecuritySessionId sid = 0;
1849 SessionAttributeBits sattrs = 0;
1851 err = SessionGetInfo(callerSecuritySession, &sid, &sattrs);
1853 error("SessionGetInfo() failed with error %.8X",
1856 debug("Current Session ID is %.8X / Session Attributes are %.8X",
1857 (unsigned) sid, (unsigned) sattrs);
1859 if (inetd_flag && !(sattrs & sessionIsRoot))
1860 debug("Running in inetd mode in a non-root session... "
1861 "assuming inetd created the session for us.");
1863 debug("Creating new security session...");
1864 err = SessionCreate(0, sessionHasTTY | sessionIsRemote);
1866 error("SessionCreate() failed with error %.8X",
1869 err = SessionGetInfo(callerSecuritySession, &sid,
1872 error("SessionGetInfo() failed with error %.8X",
1875 debug("New Session ID is %.8X / Session Attributes are %.8X",
1876 (unsigned) sid, (unsigned) sattrs);
1882 * We don't want to listen forever unless the other side
1883 * successfully authenticates itself. So we set up an alarm which is
1884 * cleared after successful authentication. A limit of zero
1885 * indicates no limit. Note that we don't set the alarm in debugging
1886 * mode; it is just annoying to have the server exit just when you
1887 * are about to discover the bug.
1889 signal(SIGALRM, grace_alarm_handler);
1891 alarm(options.login_grace_time);
1893 sshd_exchange_identification(sock_in, sock_out);
1895 /* In inetd mode, generate ephemeral key only for proto 1 connections */
1896 if (!compat20 && inetd_flag && sensitive_data.server_key == NULL)
1897 generate_ephemeral_server_key();
1899 packet_set_nonblocking();
1901 /* allocate authentication context */
1902 authctxt = xcalloc(1, sizeof(*authctxt));
1904 authctxt->loginmsg = &loginmsg;
1906 /* XXX global for cleanup, access from other modules */
1907 the_authctxt = authctxt;
1909 /* prepare buffer to collect messages to display to user after login */
1910 buffer_init(&loginmsg);
1913 if (privsep_preauth(authctxt) == 1)
1916 /* perform the key exchange */
1917 /* authenticate user and start session */
1920 do_authentication2(authctxt);
1923 do_authentication(authctxt);
1926 * If we use privilege separation, the unprivileged child transfers
1927 * the current keystate and exits
1930 mm_send_keystate(pmonitor);
1936 * Cancel the alarm we set to limit the time taken for
1940 signal(SIGALRM, SIG_DFL);
1941 authctxt->authenticated = 1;
1942 if (startup_pipe != -1) {
1943 close(startup_pipe);
1947 #ifdef SSH_AUDIT_EVENTS
1948 audit_event(SSH_AUTH_SUCCESS);
1952 if (options.gss_authentication) {
1953 temporarily_use_uid(authctxt->pw);
1954 ssh_gssapi_storecreds();
1959 if (options.use_pam) {
1966 * In privilege separation, we fork another child and prepare
1967 * file descriptor passing.
1970 privsep_postauth(authctxt);
1971 /* the monitor process [priv] will not return */
1973 destroy_sensitive_data();
1976 packet_set_timeout(options.client_alive_interval,
1977 options.client_alive_count_max);
1979 /* Start session. */
1980 do_authenticated(authctxt);
1982 /* The connection has been terminated. */
1983 packet_get_state(MODE_IN, NULL, NULL, NULL, &ibytes);
1984 packet_get_state(MODE_OUT, NULL, NULL, NULL, &obytes);
1985 verbose("Transferred: sent %llu, received %llu bytes", obytes, ibytes);
1987 verbose("Closing connection to %.500s port %d", remote_ip, remote_port);
1990 if (options.use_pam)
1992 #endif /* USE_PAM */
1994 #ifdef SSH_AUDIT_EVENTS
1995 PRIVSEP(audit_event(SSH_CONNECTION_CLOSE));
2007 * Decrypt session_key_int using our private server key and private host key
2008 * (key with larger modulus first).
2011 ssh1_session_key(BIGNUM *session_key_int)
2015 if (BN_cmp(sensitive_data.server_key->rsa->n,
2016 sensitive_data.ssh1_host_key->rsa->n) > 0) {
2017 /* Server key has bigger modulus. */
2018 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
2019 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
2020 SSH_KEY_BITS_RESERVED) {
2021 fatal("do_connection: %s: "
2022 "server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
2023 get_remote_ipaddr(),
2024 BN_num_bits(sensitive_data.server_key->rsa->n),
2025 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
2026 SSH_KEY_BITS_RESERVED);
2028 if (rsa_private_decrypt(session_key_int, session_key_int,
2029 sensitive_data.server_key->rsa) <= 0)
2031 if (rsa_private_decrypt(session_key_int, session_key_int,
2032 sensitive_data.ssh1_host_key->rsa) <= 0)
2035 /* Host key has bigger modulus (or they are equal). */
2036 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
2037 BN_num_bits(sensitive_data.server_key->rsa->n) +
2038 SSH_KEY_BITS_RESERVED) {
2039 fatal("do_connection: %s: "
2040 "host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
2041 get_remote_ipaddr(),
2042 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
2043 BN_num_bits(sensitive_data.server_key->rsa->n),
2044 SSH_KEY_BITS_RESERVED);
2046 if (rsa_private_decrypt(session_key_int, session_key_int,
2047 sensitive_data.ssh1_host_key->rsa) < 0)
2049 if (rsa_private_decrypt(session_key_int, session_key_int,
2050 sensitive_data.server_key->rsa) < 0)
2063 BIGNUM *session_key_int;
2064 u_char session_key[SSH_SESSION_KEY_LENGTH];
2066 u_int cipher_type, auth_mask, protocol_flags;
2069 * Generate check bytes that the client must send back in the user
2070 * packet in order for it to be accepted; this is used to defy ip
2071 * spoofing attacks. Note that this only works against somebody
2072 * doing IP spoofing from a remote machine; any machine on the local
2073 * network can still see outgoing packets and catch the random
2074 * cookie. This only affects rhosts authentication, and this is one
2075 * of the reasons why it is inherently insecure.
2077 arc4random_buf(cookie, sizeof(cookie));
2080 * Send our public key. We include in the packet 64 bits of random
2081 * data that must be matched in the reply in order to prevent IP
2084 packet_start(SSH_SMSG_PUBLIC_KEY);
2085 for (i = 0; i < 8; i++)
2086 packet_put_char(cookie[i]);
2088 /* Store our public server RSA key. */
2089 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
2090 packet_put_bignum(sensitive_data.server_key->rsa->e);
2091 packet_put_bignum(sensitive_data.server_key->rsa->n);
2093 /* Store our public host RSA key. */
2094 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
2095 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
2096 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
2098 /* Put protocol flags. */
2099 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
2101 /* Declare which ciphers we support. */
2102 packet_put_int(cipher_mask_ssh1(0));
2104 /* Declare supported authentication types. */
2106 if (options.rhosts_rsa_authentication)
2107 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
2108 if (options.rsa_authentication)
2109 auth_mask |= 1 << SSH_AUTH_RSA;
2110 if (options.challenge_response_authentication == 1)
2111 auth_mask |= 1 << SSH_AUTH_TIS;
2112 if (options.password_authentication)
2113 auth_mask |= 1 << SSH_AUTH_PASSWORD;
2114 packet_put_int(auth_mask);
2116 /* Send the packet and wait for it to be sent. */
2118 packet_write_wait();
2120 debug("Sent %d bit server key and %d bit host key.",
2121 BN_num_bits(sensitive_data.server_key->rsa->n),
2122 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
2124 /* Read clients reply (cipher type and session key). */
2125 packet_read_expect(SSH_CMSG_SESSION_KEY);
2127 /* Get cipher type and check whether we accept this. */
2128 cipher_type = packet_get_char();
2130 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
2131 packet_disconnect("Warning: client selects unsupported cipher.");
2133 /* Get check bytes from the packet. These must match those we
2134 sent earlier with the public key packet. */
2135 for (i = 0; i < 8; i++)
2136 if (cookie[i] != packet_get_char())
2137 packet_disconnect("IP Spoofing check bytes do not match.");
2139 debug("Encryption type: %.200s", cipher_name(cipher_type));
2141 /* Get the encrypted integer. */
2142 if ((session_key_int = BN_new()) == NULL)
2143 fatal("do_ssh1_kex: BN_new failed");
2144 packet_get_bignum(session_key_int);
2146 protocol_flags = packet_get_int();
2147 packet_set_protocol_flags(protocol_flags);
2150 /* Decrypt session_key_int using host/server keys */
2151 rsafail = PRIVSEP(ssh1_session_key(session_key_int));
2154 * Extract session key from the decrypted integer. The key is in the
2155 * least significant 256 bits of the integer; the first byte of the
2156 * key is in the highest bits.
2159 (void) BN_mask_bits(session_key_int, sizeof(session_key) * 8);
2160 len = BN_num_bytes(session_key_int);
2161 if (len < 0 || (u_int)len > sizeof(session_key)) {
2162 error("do_ssh1_kex: bad session key len from %s: "
2163 "session_key_int %d > sizeof(session_key) %lu",
2164 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
2167 memset(session_key, 0, sizeof(session_key));
2168 BN_bn2bin(session_key_int,
2169 session_key + sizeof(session_key) - len);
2171 derive_ssh1_session_id(
2172 sensitive_data.ssh1_host_key->rsa->n,
2173 sensitive_data.server_key->rsa->n,
2174 cookie, session_id);
2176 * Xor the first 16 bytes of the session key with the
2179 for (i = 0; i < 16; i++)
2180 session_key[i] ^= session_id[i];
2184 int bytes = BN_num_bytes(session_key_int);
2185 u_char *buf = xmalloc(bytes);
2188 logit("do_connection: generating a fake encryption key");
2189 BN_bn2bin(session_key_int, buf);
2191 MD5_Update(&md, buf, bytes);
2192 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
2193 MD5_Final(session_key, &md);
2195 MD5_Update(&md, session_key, 16);
2196 MD5_Update(&md, buf, bytes);
2197 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
2198 MD5_Final(session_key + 16, &md);
2199 memset(buf, 0, bytes);
2201 for (i = 0; i < 16; i++)
2202 session_id[i] = session_key[i] ^ session_key[i + 16];
2204 /* Destroy the private and public keys. No longer. */
2205 destroy_sensitive_data();
2208 mm_ssh1_session_id(session_id);
2210 /* Destroy the decrypted integer. It is no longer needed. */
2211 BN_clear_free(session_key_int);
2213 /* Set the session key. From this on all communications will be encrypted. */
2214 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
2216 /* Destroy our copy of the session key. It is no longer needed. */
2217 memset(session_key, 0, sizeof(session_key));
2219 debug("Received session key; encryption turned on.");
2221 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */
2222 packet_start(SSH_SMSG_SUCCESS);
2224 packet_write_wait();
2228 * SSH2 key exchange: diffie-hellman-group1-sha1
2235 if (options.ciphers != NULL) {
2236 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2237 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
2239 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2240 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
2241 myproposal[PROPOSAL_ENC_ALGS_STOC] =
2242 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
2244 if (options.macs != NULL) {
2245 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
2246 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
2248 if (options.compression == COMP_NONE) {
2249 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2250 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
2251 } else if (options.compression == COMP_DELAYED) {
2252 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2253 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com";
2256 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
2262 char *newstr = NULL;
2263 orig = myproposal[PROPOSAL_KEX_ALGS];
2266 * If we don't have a host key, then there's no point advertising
2267 * the other key exchange algorithms
2270 if (strlen(myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS]) == 0)
2273 if (options.gss_keyex)
2274 gss = ssh_gssapi_server_mechanisms();
2279 xasprintf(&newstr, "%s,%s", gss, orig);
2286 * If we've got GSSAPI mechanisms, then we've got the 'null' host
2287 * key alg, but we can't tell people about it unless its the only
2288 * host key algorithm we support
2290 if (gss && (strlen(myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS])) == 0)
2291 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = "null";
2294 myproposal[PROPOSAL_KEX_ALGS] = newstr;
2296 fatal("No supported key exchange algorithms");
2300 /* start key exchange */
2301 kex = kex_setup(myproposal);
2302 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
2303 kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
2304 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
2305 kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
2307 if (options.gss_keyex) {
2308 kex->kex[KEX_GSS_GRP1_SHA1] = kexgss_server;
2309 kex->kex[KEX_GSS_GRP14_SHA1] = kexgss_server;
2310 kex->kex[KEX_GSS_GEX_SHA1] = kexgss_server;
2314 kex->client_version_string=client_version_string;
2315 kex->server_version_string=server_version_string;
2316 kex->load_host_key=&get_hostkey_by_type;
2317 kex->host_key_index=&get_hostkey_index;
2321 dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
2323 session_id2 = kex->session_id;
2324 session_id2_len = kex->session_id_len;
2327 /* send 1st encrypted/maced/compressed message */
2328 packet_start(SSH2_MSG_IGNORE);
2329 packet_put_cstring("markus");
2331 packet_write_wait();
2336 /* server specific fatal cleanup */
2341 do_cleanup(the_authctxt);
2342 #ifdef SSH_AUDIT_EVENTS
2343 /* done after do_cleanup so it can cancel the PAM auth 'thread' */
2344 if (!use_privsep || mm_is_monitor())
2345 audit_event(SSH_CONNECTION_ABANDON);