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.
48 #include <sys/types.h>
49 #include <sys/ioctl.h>
50 #include <sys/socket.h>
51 #ifdef HAVE_SYS_STAT_H
52 # include <sys/stat.h>
54 #ifdef HAVE_SYS_TIME_H
55 # include <sys/time.h>
57 #include "openbsd-compat/sys-tree.h"
58 #include "openbsd-compat/sys-queue.h"
77 #include <openssl/dh.h>
78 #include <openssl/bn.h>
79 #include <openssl/md5.h>
80 #include <openssl/rand.h>
81 #include "openbsd-compat/openssl-compat.h"
83 #ifdef HAVE_SECUREWARE
84 #include <sys/security.h>
90 #if defined(GSSAPI) && defined(HAVE_GSSAPI_H)
92 #elif defined(GSSAPI) && defined(HAVE_GSSAPI_GSSAPI_H)
93 #include <gssapi/gssapi.h>
106 #include "servconf.h"
113 #include "myproposal.h"
114 #include "authfile.h"
115 #include "pathnames.h"
116 #include "atomicio.h"
117 #include "canohost.h"
118 #include "hostfile.h"
122 #include "dispatch.h"
123 #include "channels.h"
125 #include "monitor_mm.h"
130 #include "monitor_wrap.h"
145 #define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1)
146 #define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2)
147 #define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3)
148 #define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4)
150 extern char *__progname;
152 /* Server configuration options. */
153 ServerOptions options;
155 /* Name of the server configuration file. */
156 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
159 * Debug mode flag. This can be set on the command line. If debug
160 * mode is enabled, extra debugging output will be sent to the system
161 * log, the daemon will not go to background, and will exit after processing
162 * the first connection.
166 /* Flag indicating that the daemon should only test the configuration and keys. */
169 /* Flag indicating that the daemon is being started from inetd. */
172 /* Flag indicating that sshd should not detach and become a daemon. */
173 int no_daemon_flag = 0;
175 /* debug goes to stderr unless inetd_flag is set */
178 /* Saved arguments to main(). */
183 int rexeced_flag = 0;
189 * The sockets that the server is listening; this is used in the SIGHUP
192 #define MAX_LISTEN_SOCKS 16
193 int listen_socks[MAX_LISTEN_SOCKS];
194 int num_listen_socks = 0;
197 * the client's version string, passed by sshd2 in compat mode. if != NULL,
198 * sshd will skip the version-number exchange
200 char *client_version_string = NULL;
201 char *server_version_string = NULL;
203 /* for rekeying XXX fixme */
207 * Any really sensitive data in the application is contained in this
208 * structure. The idea is that this structure could be locked into memory so
209 * that the pages do not get written into swap. However, there are some
210 * problems. The private key contains BIGNUMs, and we do not (in principle)
211 * have access to the internals of them, and locking just the structure is
212 * not very useful. Currently, memory locking is not implemented.
215 Key *server_key; /* ephemeral server key */
216 Key *ssh1_host_key; /* ssh1 host key */
217 Key **host_keys; /* all private host keys */
220 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
224 * Flag indicating whether the RSA server key needs to be regenerated.
225 * Is set in the SIGALRM handler and cleared when the key is regenerated.
227 static volatile sig_atomic_t key_do_regen = 0;
229 /* This is set to true when a signal is received. */
230 static volatile sig_atomic_t received_sighup = 0;
231 static volatile sig_atomic_t received_sigterm = 0;
233 /* session identifier, used by RSA-auth */
234 u_char session_id[16];
237 u_char *session_id2 = NULL;
238 u_int session_id2_len = 0;
240 /* record remote hostname or ip */
241 u_int utmp_len = UT_HOSTSIZE;
243 /* options.max_startup sized array of fd ints */
244 int *startup_pipes = NULL;
245 int startup_pipe; /* in child */
247 /* variables used for privilege separation */
248 int use_privsep = -1;
249 struct monitor *pmonitor = NULL;
251 /* global authentication context */
252 Authctxt *the_authctxt = NULL;
254 /* sshd_config buffer */
257 /* message to be displayed after login */
260 /* Unprivileged user */
261 struct passwd *privsep_pw = NULL;
263 /* Prototypes for various functions defined later in this file. */
264 void destroy_sensitive_data(void);
265 void demote_sensitive_data(void);
267 static void do_ssh1_kex(void);
268 static void do_ssh2_kex(void);
271 * Close all listening sockets
274 close_listen_socks(void)
278 for (i = 0; i < num_listen_socks; i++)
279 close(listen_socks[i]);
280 num_listen_socks = -1;
284 close_startup_pipes(void)
289 for (i = 0; i < options.max_startups; i++)
290 if (startup_pipes[i] != -1)
291 close(startup_pipes[i]);
295 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
296 * the effect is to reread the configuration file (and to regenerate
302 sighup_handler(int sig)
304 int save_errno = errno;
307 signal(SIGHUP, sighup_handler);
312 * Called from the main program after receiving SIGHUP.
313 * Restarts the server.
318 logit("Received SIGHUP; restarting.");
319 close_listen_socks();
320 close_startup_pipes();
321 alarm(0); /* alarm timer persists across exec */
322 execv(saved_argv[0], saved_argv);
323 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
329 * Generic signal handler for terminating signals in the master daemon.
333 sigterm_handler(int sig)
335 received_sigterm = sig;
339 * SIGCHLD handler. This is called whenever a child dies. This will then
340 * reap any zombies left by exited children.
344 main_sigchld_handler(int sig)
346 int save_errno = errno;
350 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
351 (pid < 0 && errno == EINTR))
354 signal(SIGCHLD, main_sigchld_handler);
359 * Signal handler for the alarm after the login grace period has expired.
363 grace_alarm_handler(int sig)
365 if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0)
366 kill(pmonitor->m_pid, SIGALRM);
368 /* Log error and exit. */
369 sigdie("Timeout before authentication for %s", get_remote_ipaddr());
373 * Signal handler for the key regeneration alarm. Note that this
374 * alarm only occurs in the daemon waiting for connections, and it does not
375 * do anything with the private key or random state before forking.
376 * Thus there should be no concurrency control/asynchronous execution
380 generate_ephemeral_server_key(void)
382 verbose("Generating %s%d bit RSA key.",
383 sensitive_data.server_key ? "new " : "", options.server_key_bits);
384 if (sensitive_data.server_key != NULL)
385 key_free(sensitive_data.server_key);
386 sensitive_data.server_key = key_generate(KEY_RSA1,
387 options.server_key_bits);
388 verbose("RSA key generation complete.");
390 arc4random_buf(sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
396 key_regeneration_alarm(int sig)
398 int save_errno = errno;
400 signal(SIGALRM, SIG_DFL);
406 sshd_exchange_identification(int sock_in, int sock_out)
410 int remote_major, remote_minor;
412 char *s, *newline = "\n";
413 char buf[256]; /* Must not be larger than remote_version. */
414 char remote_version[256]; /* Must be at least as big as buf. */
416 if ((options.protocol & SSH_PROTO_1) &&
417 (options.protocol & SSH_PROTO_2)) {
418 major = PROTOCOL_MAJOR_1;
420 } else if (options.protocol & SSH_PROTO_2) {
421 major = PROTOCOL_MAJOR_2;
422 minor = PROTOCOL_MINOR_2;
425 major = PROTOCOL_MAJOR_1;
426 minor = PROTOCOL_MINOR_1;
428 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s", major, minor,
429 SSH_VERSION, newline);
430 server_version_string = xstrdup(buf);
432 /* Send our protocol version identification. */
433 if (atomicio(vwrite, sock_out, server_version_string,
434 strlen(server_version_string))
435 != strlen(server_version_string)) {
436 logit("Could not write ident string to %s", get_remote_ipaddr());
440 /* Read other sides version identification. */
441 memset(buf, 0, sizeof(buf));
442 for (i = 0; i < sizeof(buf) - 1; i++) {
443 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
444 logit("Did not receive identification string from %s",
445 get_remote_ipaddr());
448 if (buf[i] == '\r') {
450 /* Kludge for F-Secure Macintosh < 1.0.2 */
452 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
456 if (buf[i] == '\n') {
461 buf[sizeof(buf) - 1] = 0;
462 client_version_string = xstrdup(buf);
465 * Check that the versions match. In future this might accept
466 * several versions and set appropriate flags to handle them.
468 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
469 &remote_major, &remote_minor, remote_version) != 3) {
470 s = "Protocol mismatch.\n";
471 (void) atomicio(vwrite, sock_out, s, strlen(s));
474 logit("Bad protocol version identification '%.100s' from %s",
475 client_version_string, get_remote_ipaddr());
478 debug("Client protocol version %d.%d; client software version %.100s",
479 remote_major, remote_minor, remote_version);
481 compat_datafellows(remote_version);
483 if (datafellows & SSH_BUG_PROBE) {
484 logit("probed from %s with %s. Don't panic.",
485 get_remote_ipaddr(), client_version_string);
489 if (datafellows & SSH_BUG_SCANNER) {
490 logit("scanned from %s with %s. Don't panic.",
491 get_remote_ipaddr(), client_version_string);
496 switch (remote_major) {
498 if (remote_minor == 99) {
499 if (options.protocol & SSH_PROTO_2)
505 if (!(options.protocol & SSH_PROTO_1)) {
509 if (remote_minor < 3) {
510 packet_disconnect("Your ssh version is too old and "
511 "is no longer supported. Please install a newer version.");
512 } else if (remote_minor == 3) {
513 /* note that this disables agent-forwarding */
518 if (options.protocol & SSH_PROTO_2) {
527 chop(server_version_string);
528 debug("Local version string %.200s", server_version_string);
531 s = "Protocol major versions differ.\n";
532 (void) atomicio(vwrite, sock_out, s, strlen(s));
535 logit("Protocol major versions differ for %s: %.200s vs. %.200s",
537 server_version_string, client_version_string);
542 /* Destroy the host and server keys. They will no longer be needed. */
544 destroy_sensitive_data(void)
548 if (sensitive_data.server_key) {
549 key_free(sensitive_data.server_key);
550 sensitive_data.server_key = NULL;
552 for (i = 0; i < options.num_host_key_files; i++) {
553 if (sensitive_data.host_keys[i]) {
554 key_free(sensitive_data.host_keys[i]);
555 sensitive_data.host_keys[i] = NULL;
558 sensitive_data.ssh1_host_key = NULL;
559 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
562 /* Demote private to public keys for network child */
564 demote_sensitive_data(void)
569 if (sensitive_data.server_key) {
570 tmp = key_demote(sensitive_data.server_key);
571 key_free(sensitive_data.server_key);
572 sensitive_data.server_key = tmp;
575 for (i = 0; i < options.num_host_key_files; i++) {
576 if (sensitive_data.host_keys[i]) {
577 tmp = key_demote(sensitive_data.host_keys[i]);
578 key_free(sensitive_data.host_keys[i]);
579 sensitive_data.host_keys[i] = tmp;
580 if (tmp->type == KEY_RSA1)
581 sensitive_data.ssh1_host_key = tmp;
585 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */
589 privsep_preauth_child(void)
594 /* Enable challenge-response authentication for privilege separation */
595 privsep_challenge_enable();
598 arc4random_buf(rnd, sizeof(rnd));
599 RAND_seed(rnd, sizeof(rnd));
601 /* Demote the private keys to public keys. */
602 demote_sensitive_data();
604 /* Change our root directory */
605 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
606 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
608 if (chdir("/") == -1)
609 fatal("chdir(\"/\"): %s", strerror(errno));
611 /* Drop our privileges */
612 debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid,
613 (u_int)privsep_pw->pw_gid);
615 /* XXX not ready, too heavy after chroot */
616 do_setusercontext(privsep_pw);
618 gidset[0] = privsep_pw->pw_gid;
619 if (setgroups(1, gidset) < 0)
620 fatal("setgroups: %.100s", strerror(errno));
621 permanently_set_uid(privsep_pw);
626 privsep_preauth(Authctxt *authctxt)
631 /* Set up unprivileged child process to deal with network data */
632 pmonitor = monitor_init();
633 /* Store a pointer to the kex for later rekeying */
634 pmonitor->m_pkex = &xxx_kex;
638 fatal("fork of unprivileged child failed");
639 } else if (pid != 0) {
640 debug2("Network child is on pid %ld", (long)pid);
642 close(pmonitor->m_recvfd);
643 pmonitor->m_pid = pid;
644 monitor_child_preauth(authctxt, pmonitor);
645 close(pmonitor->m_sendfd);
648 monitor_sync(pmonitor);
650 /* Wait for the child's exit status */
651 while (waitpid(pid, &status, 0) < 0)
658 close(pmonitor->m_sendfd);
660 /* Demote the child */
661 if (getuid() == 0 || geteuid() == 0)
662 privsep_preauth_child();
663 setproctitle("%s", "[net]");
669 privsep_postauth(Authctxt *authctxt)
673 #ifdef DISABLE_FD_PASSING
676 if (authctxt->pw->pw_uid == 0 || options.use_login) {
678 /* File descriptor passing is broken or root login */
683 /* New socket pair */
684 monitor_reinit(pmonitor);
686 pmonitor->m_pid = fork();
687 if (pmonitor->m_pid == -1)
688 fatal("fork of unprivileged child failed");
689 else if (pmonitor->m_pid != 0) {
690 verbose("User child is on pid %ld", (long)pmonitor->m_pid);
691 close(pmonitor->m_recvfd);
692 buffer_clear(&loginmsg);
693 monitor_child_postauth(pmonitor);
699 close(pmonitor->m_sendfd);
701 /* Demote the private keys to public keys. */
702 demote_sensitive_data();
705 arc4random_buf(rnd, sizeof(rnd));
706 RAND_seed(rnd, sizeof(rnd));
708 /* Drop privileges */
709 do_setusercontext(authctxt->pw);
712 /* It is safe now to apply the key state */
713 monitor_apply_keystate(pmonitor);
716 * Tell the packet layer that authentication was successful, since
717 * this information is not part of the key state.
719 packet_set_authenticated();
723 list_hostkey_types(void)
731 for (i = 0; i < options.num_host_key_files; i++) {
732 Key *key = sensitive_data.host_keys[i];
738 if (buffer_len(&b) > 0)
739 buffer_append(&b, ",", 1);
740 p = key_ssh_name(key);
741 buffer_append(&b, p, strlen(p));
745 buffer_append(&b, "\0", 1);
746 ret = xstrdup(buffer_ptr(&b));
748 debug("list_hostkey_types: %s", ret);
753 get_hostkey_by_type(int type)
757 for (i = 0; i < options.num_host_key_files; i++) {
758 Key *key = sensitive_data.host_keys[i];
759 if (key != NULL && key->type == type)
766 get_hostkey_by_index(int ind)
768 if (ind < 0 || ind >= options.num_host_key_files)
770 return (sensitive_data.host_keys[ind]);
774 get_hostkey_index(Key *key)
778 for (i = 0; i < options.num_host_key_files; i++) {
779 if (key == sensitive_data.host_keys[i])
786 * returns 1 if connection should be dropped, 0 otherwise.
787 * dropping starts at connection #max_startups_begin with a probability
788 * of (max_startups_rate/100). the probability increases linearly until
789 * all connections are dropped for startups > max_startups
792 drop_connection(int startups)
796 if (startups < options.max_startups_begin)
798 if (startups >= options.max_startups)
800 if (options.max_startups_rate == 100)
803 p = 100 - options.max_startups_rate;
804 p *= startups - options.max_startups_begin;
805 p /= options.max_startups - options.max_startups_begin;
806 p += options.max_startups_rate;
807 r = arc4random_uniform(100);
809 debug("drop_connection: p %d, r %d", p, r);
810 return (r < p) ? 1 : 0;
816 fprintf(stderr, "%s, %s\n",
817 SSH_RELEASE, SSLeay_version(SSLEAY_VERSION));
819 "usage: sshd [-46DdeiqTt] [-b bits] [-C connection_spec] [-f config_file]\n"
820 " [-g login_grace_time] [-h host_key_file] [-k key_gen_time]\n"
821 " [-o option] [-p port] [-u len]\n"
827 send_rexec_state(int fd, Buffer *conf)
831 debug3("%s: entering fd = %d config len %d", __func__, fd,
835 * Protocol from reexec master to child:
836 * string configuration
837 * u_int ephemeral_key_follows
838 * bignum e (only if ephemeral_key_follows == 1)
844 * string rngseed (only if OpenSSL is not self-seeded)
847 buffer_put_cstring(&m, buffer_ptr(conf));
849 if (sensitive_data.server_key != NULL &&
850 sensitive_data.server_key->type == KEY_RSA1) {
851 buffer_put_int(&m, 1);
852 buffer_put_bignum(&m, sensitive_data.server_key->rsa->e);
853 buffer_put_bignum(&m, sensitive_data.server_key->rsa->n);
854 buffer_put_bignum(&m, sensitive_data.server_key->rsa->d);
855 buffer_put_bignum(&m, sensitive_data.server_key->rsa->iqmp);
856 buffer_put_bignum(&m, sensitive_data.server_key->rsa->p);
857 buffer_put_bignum(&m, sensitive_data.server_key->rsa->q);
859 buffer_put_int(&m, 0);
861 #ifndef OPENSSL_PRNG_ONLY
862 rexec_send_rng_seed(&m);
865 if (ssh_msg_send(fd, 0, &m) == -1)
866 fatal("%s: ssh_msg_send failed", __func__);
870 debug3("%s: done", __func__);
874 recv_rexec_state(int fd, Buffer *conf)
880 debug3("%s: entering fd = %d", __func__, fd);
884 if (ssh_msg_recv(fd, &m) == -1)
885 fatal("%s: ssh_msg_recv failed", __func__);
886 if (buffer_get_char(&m) != 0)
887 fatal("%s: rexec version mismatch", __func__);
889 cp = buffer_get_string(&m, &len);
891 buffer_append(conf, cp, len + 1);
894 if (buffer_get_int(&m)) {
895 if (sensitive_data.server_key != NULL)
896 key_free(sensitive_data.server_key);
897 sensitive_data.server_key = key_new_private(KEY_RSA1);
898 buffer_get_bignum(&m, sensitive_data.server_key->rsa->e);
899 buffer_get_bignum(&m, sensitive_data.server_key->rsa->n);
900 buffer_get_bignum(&m, sensitive_data.server_key->rsa->d);
901 buffer_get_bignum(&m, sensitive_data.server_key->rsa->iqmp);
902 buffer_get_bignum(&m, sensitive_data.server_key->rsa->p);
903 buffer_get_bignum(&m, sensitive_data.server_key->rsa->q);
904 rsa_generate_additional_parameters(
905 sensitive_data.server_key->rsa);
908 #ifndef OPENSSL_PRNG_ONLY
909 rexec_recv_rng_seed(&m);
914 debug3("%s: done", __func__);
917 /* Accept a connection from inetd */
919 server_accept_inetd(int *sock_in, int *sock_out)
925 close(REEXEC_CONFIG_PASS_FD);
926 *sock_in = *sock_out = dup(STDIN_FILENO);
928 startup_pipe = dup(REEXEC_STARTUP_PIPE_FD);
929 close(REEXEC_STARTUP_PIPE_FD);
932 *sock_in = dup(STDIN_FILENO);
933 *sock_out = dup(STDOUT_FILENO);
936 * We intentionally do not close the descriptors 0, 1, and 2
937 * as our code for setting the descriptors won't work if
938 * ttyfd happens to be one of those.
940 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
941 dup2(fd, STDIN_FILENO);
942 dup2(fd, STDOUT_FILENO);
943 if (fd > STDOUT_FILENO)
946 debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out);
950 * Listen for TCP connections
955 int ret, listen_sock, on = 1;
957 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
959 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
960 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
962 if (num_listen_socks >= MAX_LISTEN_SOCKS)
963 fatal("Too many listen sockets. "
964 "Enlarge MAX_LISTEN_SOCKS");
965 if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen,
966 ntop, sizeof(ntop), strport, sizeof(strport),
967 NI_NUMERICHOST|NI_NUMERICSERV)) != 0) {
968 error("getnameinfo failed: %.100s",
969 ssh_gai_strerror(ret));
972 /* Create socket for listening. */
973 listen_sock = socket(ai->ai_family, ai->ai_socktype,
975 if (listen_sock < 0) {
976 /* kernel may not support ipv6 */
977 verbose("socket: %.100s", strerror(errno));
980 if (set_nonblock(listen_sock) == -1) {
985 * Set socket options.
986 * Allow local port reuse in TIME_WAIT.
988 if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
989 &on, sizeof(on)) == -1)
990 error("setsockopt SO_REUSEADDR: %s", strerror(errno));
993 /* Only communicate in IPv6 over AF_INET6 sockets. */
994 if (ai->ai_family == AF_INET6) {
995 if (setsockopt(listen_sock, IPPROTO_IPV6, IPV6_V6ONLY,
996 &on, sizeof(on)) == -1)
997 error("setsockopt IPV6_V6ONLY: %s",
1002 debug("Bind to port %s on %s.", strport, ntop);
1004 /* Bind the socket to the desired port. */
1005 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1006 error("Bind to port %s on %s failed: %.200s.",
1007 strport, ntop, strerror(errno));
1011 listen_socks[num_listen_socks] = listen_sock;
1014 /* Start listening on the port. */
1015 if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0)
1016 fatal("listen on [%s]:%s: %.100s",
1017 ntop, strport, strerror(errno));
1018 logit("Server listening on %s port %s.", ntop, strport);
1020 freeaddrinfo(options.listen_addrs);
1022 if (!num_listen_socks)
1023 fatal("Cannot bind any address.");
1027 * The main TCP accept loop. Note that, for the non-debug case, returns
1028 * from this function are in a forked subprocess.
1031 server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
1034 int i, j, ret, maxfd;
1035 int key_used = 0, startups = 0;
1036 int startup_p[2] = { -1 , -1 };
1037 struct sockaddr_storage from;
1041 /* setup fd set for accept */
1044 for (i = 0; i < num_listen_socks; i++)
1045 if (listen_socks[i] > maxfd)
1046 maxfd = listen_socks[i];
1047 /* pipes connected to unauthenticated childs */
1048 startup_pipes = xcalloc(options.max_startups, sizeof(int));
1049 for (i = 0; i < options.max_startups; i++)
1050 startup_pipes[i] = -1;
1053 * Stay listening for connections until the system crashes or
1054 * the daemon is killed with a signal.
1057 if (received_sighup)
1061 fdset = (fd_set *)xcalloc(howmany(maxfd + 1, NFDBITS),
1064 for (i = 0; i < num_listen_socks; i++)
1065 FD_SET(listen_socks[i], fdset);
1066 for (i = 0; i < options.max_startups; i++)
1067 if (startup_pipes[i] != -1)
1068 FD_SET(startup_pipes[i], fdset);
1070 /* Wait in select until there is a connection. */
1071 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
1072 if (ret < 0 && errno != EINTR)
1073 error("select: %.100s", strerror(errno));
1074 if (received_sigterm) {
1075 logit("Received signal %d; terminating.",
1076 (int) received_sigterm);
1077 close_listen_socks();
1078 unlink(options.pid_file);
1081 if (key_used && key_do_regen) {
1082 generate_ephemeral_server_key();
1089 for (i = 0; i < options.max_startups; i++)
1090 if (startup_pipes[i] != -1 &&
1091 FD_ISSET(startup_pipes[i], fdset)) {
1093 * the read end of the pipe is ready
1094 * if the child has closed the pipe
1095 * after successful authentication
1096 * or if the child has died
1098 close(startup_pipes[i]);
1099 startup_pipes[i] = -1;
1102 for (i = 0; i < num_listen_socks; i++) {
1103 if (!FD_ISSET(listen_socks[i], fdset))
1105 fromlen = sizeof(from);
1106 *newsock = accept(listen_socks[i],
1107 (struct sockaddr *)&from, &fromlen);
1109 if (errno != EINTR && errno != EAGAIN &&
1110 errno != EWOULDBLOCK)
1111 error("accept: %.100s", strerror(errno));
1114 if (unset_nonblock(*newsock) == -1) {
1118 if (drop_connection(startups) == 1) {
1119 debug("drop connection #%d", startups);
1123 if (pipe(startup_p) == -1) {
1128 if (rexec_flag && socketpair(AF_UNIX,
1129 SOCK_STREAM, 0, config_s) == -1) {
1130 error("reexec socketpair: %s",
1133 close(startup_p[0]);
1134 close(startup_p[1]);
1138 for (j = 0; j < options.max_startups; j++)
1139 if (startup_pipes[j] == -1) {
1140 startup_pipes[j] = startup_p[0];
1141 if (maxfd < startup_p[0])
1142 maxfd = startup_p[0];
1148 * Got connection. Fork a child to handle it, unless
1149 * we are in debugging mode.
1153 * In debugging mode. Close the listening
1154 * socket, and start processing the
1155 * connection without forking.
1157 debug("Server will not fork when running in debugging mode.");
1158 close_listen_socks();
1159 *sock_in = *newsock;
1160 *sock_out = *newsock;
1161 close(startup_p[0]);
1162 close(startup_p[1]);
1166 send_rexec_state(config_s[0],
1174 * Normal production daemon. Fork, and have
1175 * the child process the connection. The
1176 * parent continues listening.
1178 platform_pre_fork();
1179 if ((pid = fork()) == 0) {
1181 * Child. Close the listening and
1182 * max_startup sockets. Start using
1183 * the accepted socket. Reinitialize
1184 * logging (since our pid has changed).
1185 * We break out of the loop to handle
1188 platform_post_fork_child();
1189 startup_pipe = startup_p[1];
1190 close_startup_pipes();
1191 close_listen_socks();
1192 *sock_in = *newsock;
1193 *sock_out = *newsock;
1194 log_init(__progname,
1196 options.log_facility,
1203 /* Parent. Stay in the loop. */
1204 platform_post_fork_parent(pid);
1206 error("fork: %.100s", strerror(errno));
1208 debug("Forked child %ld.", (long)pid);
1210 close(startup_p[1]);
1213 send_rexec_state(config_s[0], &cfg);
1219 * Mark that the key has been used (it
1220 * was "given" to the child).
1222 if ((options.protocol & SSH_PROTO_1) &&
1224 /* Schedule server key regeneration alarm. */
1225 signal(SIGALRM, key_regeneration_alarm);
1226 alarm(options.key_regeneration_time);
1233 * Ensure that our random state differs
1234 * from that of the child
1239 /* child process check (or debug mode) */
1240 if (num_listen_socks < 0)
1247 * Main program for the daemon.
1250 main(int ac, char **av)
1252 extern char *optarg;
1255 int sock_in = -1, sock_out = -1, newsock = -1;
1256 const char *remote_ip;
1257 char *test_user = NULL, *test_host = NULL, *test_addr = NULL;
1259 char *line, *p, *cp;
1260 int config_s[2] = { -1 , -1 };
1261 u_int64_t ibytes, obytes;
1266 #ifdef HAVE_SECUREWARE
1267 (void)set_auth_parameters(ac, av);
1269 __progname = ssh_get_progname(av[0]);
1272 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
1275 saved_argv = xcalloc(ac + 1, sizeof(*saved_argv));
1276 for (i = 0; i < ac; i++)
1277 saved_argv[i] = xstrdup(av[i]);
1278 saved_argv[i] = NULL;
1280 #ifndef HAVE_SETPROCTITLE
1281 /* Prepare for later setproctitle emulation */
1282 compat_init_setproctitle(ac, av);
1286 if (geteuid() == 0 && setgroups(0, NULL) == -1)
1287 debug("setgroups(): %.200s", strerror(errno));
1289 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
1292 /* Initialize configuration options to their default values. */
1293 initialize_server_options(&options);
1295 /* Parse command-line arguments. */
1296 while ((opt = getopt(ac, av, "f:p:b:k:h:g:u:o:C:dDeiqrtQRT46")) != -1) {
1299 options.address_family = AF_INET;
1302 options.address_family = AF_INET6;
1305 config_file_name = optarg;
1308 if (debug_flag == 0) {
1310 options.log_level = SYSLOG_LEVEL_DEBUG1;
1311 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
1312 options.log_level++;
1334 options.log_level = SYSLOG_LEVEL_QUIET;
1337 options.server_key_bits = (int)strtonum(optarg, 256,
1341 options.ports_from_cmdline = 1;
1342 if (options.num_ports >= MAX_PORTS) {
1343 fprintf(stderr, "too many ports.\n");
1346 options.ports[options.num_ports++] = a2port(optarg);
1347 if (options.ports[options.num_ports-1] <= 0) {
1348 fprintf(stderr, "Bad port number.\n");
1353 if ((options.login_grace_time = convtime(optarg)) == -1) {
1354 fprintf(stderr, "Invalid login grace time.\n");
1359 if ((options.key_regeneration_time = convtime(optarg)) == -1) {
1360 fprintf(stderr, "Invalid key regeneration interval.\n");
1365 if (options.num_host_key_files >= MAX_HOSTKEYS) {
1366 fprintf(stderr, "too many host keys.\n");
1369 options.host_key_files[options.num_host_key_files++] = optarg;
1379 while ((p = strsep(&cp, ",")) && *p != '\0') {
1380 if (strncmp(p, "addr=", 5) == 0)
1381 test_addr = xstrdup(p + 5);
1382 else if (strncmp(p, "host=", 5) == 0)
1383 test_host = xstrdup(p + 5);
1384 else if (strncmp(p, "user=", 5) == 0)
1385 test_user = xstrdup(p + 5);
1387 fprintf(stderr, "Invalid test "
1388 "mode specification %s\n", p);
1394 utmp_len = (u_int)strtonum(optarg, 0, MAXHOSTNAMELEN+1, NULL);
1395 if (utmp_len > MAXHOSTNAMELEN) {
1396 fprintf(stderr, "Invalid utmp length.\n");
1401 line = xstrdup(optarg);
1402 if (process_server_config_line(&options, line,
1403 "command-line", 0, NULL, NULL, NULL, NULL) != 0)
1413 if (rexeced_flag || inetd_flag)
1415 if (!test_flag && (rexec_flag && (av[0] == NULL || *av[0] != '/')))
1416 fatal("sshd re-exec requires execution with an absolute path");
1418 closefrom(REEXEC_MIN_FREE_FD);
1420 closefrom(REEXEC_DEVCRYPTO_RESERVED_FD);
1422 SSLeay_add_all_algorithms();
1425 * Force logging to stderr until we have loaded the private host
1426 * key (unless started from inetd)
1428 log_init(__progname,
1429 options.log_level == SYSLOG_LEVEL_NOT_SET ?
1430 SYSLOG_LEVEL_INFO : options.log_level,
1431 options.log_facility == SYSLOG_FACILITY_NOT_SET ?
1432 SYSLOG_FACILITY_AUTH : options.log_facility,
1433 log_stderr || !inetd_flag);
1436 * Unset KRB5CCNAME, otherwise the user's session may inherit it from
1437 * root's environment
1439 if (getenv("KRB5CCNAME") != NULL)
1440 unsetenv("KRB5CCNAME");
1443 /* Cray can define user privs drop all privs now!
1444 * Not needed on PRIV_SU systems!
1449 sensitive_data.server_key = NULL;
1450 sensitive_data.ssh1_host_key = NULL;
1451 sensitive_data.have_ssh1_key = 0;
1452 sensitive_data.have_ssh2_key = 0;
1455 * If we're doing an extended config test, make sure we have all of
1456 * the parameters we need. If we're not doing an extended test,
1457 * do not silently ignore connection test params.
1459 if (test_flag >= 2 &&
1460 (test_user != NULL || test_host != NULL || test_addr != NULL)
1461 && (test_user == NULL || test_host == NULL || test_addr == NULL))
1462 fatal("user, host and addr are all required when testing "
1464 if (test_flag < 2 && (test_user != NULL || test_host != NULL ||
1466 fatal("Config test connection parameter (-C) provided without "
1469 /* Fetch our configuration */
1472 recv_rexec_state(REEXEC_CONFIG_PASS_FD, &cfg);
1474 load_server_config(config_file_name, &cfg);
1476 parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name,
1477 &cfg, NULL, NULL, NULL);
1481 /* Fill in default values for those options not explicitly set. */
1482 fill_default_server_options(&options);
1484 /* challenge-response is implemented via keyboard interactive */
1485 if (options.challenge_response_authentication)
1486 options.kbd_interactive_authentication = 1;
1488 /* set default channel AF */
1489 channel_set_af(options.address_family);
1491 /* Check that there are no remaining arguments. */
1493 fprintf(stderr, "Extra argument %s.\n", av[optind]);
1497 debug("sshd version %.100s", SSH_RELEASE);
1499 /* Store privilege separation user for later use if required. */
1500 if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) {
1501 if (use_privsep || options.kerberos_authentication)
1502 fatal("Privilege separation user %s does not exist",
1505 memset(privsep_pw->pw_passwd, 0, strlen(privsep_pw->pw_passwd));
1506 privsep_pw = pwcopy(privsep_pw);
1507 xfree(privsep_pw->pw_passwd);
1508 privsep_pw->pw_passwd = xstrdup("*");
1512 /* load private host keys */
1513 sensitive_data.host_keys = xcalloc(options.num_host_key_files,
1515 for (i = 0; i < options.num_host_key_files; i++)
1516 sensitive_data.host_keys[i] = NULL;
1518 for (i = 0; i < options.num_host_key_files; i++) {
1519 key = key_load_private(options.host_key_files[i], "", NULL);
1520 sensitive_data.host_keys[i] = key;
1522 error("Could not load host key: %s",
1523 options.host_key_files[i]);
1524 sensitive_data.host_keys[i] = NULL;
1527 switch (key->type) {
1529 sensitive_data.ssh1_host_key = key;
1530 sensitive_data.have_ssh1_key = 1;
1534 sensitive_data.have_ssh2_key = 1;
1537 debug("private host key: #%d type %d %s", i, key->type,
1540 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
1541 logit("Disabling protocol version 1. Could not load host key");
1542 options.protocol &= ~SSH_PROTO_1;
1544 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
1545 logit("Disabling protocol version 2. Could not load host key");
1546 options.protocol &= ~SSH_PROTO_2;
1548 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
1549 logit("sshd: no hostkeys available -- exiting.");
1553 /* Check certain values for sanity. */
1554 if (options.protocol & SSH_PROTO_1) {
1555 if (options.server_key_bits < 512 ||
1556 options.server_key_bits > 32768) {
1557 fprintf(stderr, "Bad server key size.\n");
1561 * Check that server and host key lengths differ sufficiently. This
1562 * is necessary to make double encryption work with rsaref. Oh, I
1563 * hate software patents. I dont know if this can go? Niels
1565 if (options.server_key_bits >
1566 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) -
1567 SSH_KEY_BITS_RESERVED && options.server_key_bits <
1568 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1569 SSH_KEY_BITS_RESERVED) {
1570 options.server_key_bits =
1571 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1572 SSH_KEY_BITS_RESERVED;
1573 debug("Forcing server key to %d bits to make it differ from host key.",
1574 options.server_key_bits);
1581 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) ||
1582 (S_ISDIR(st.st_mode) == 0))
1583 fatal("Missing privilege separation directory: %s",
1584 _PATH_PRIVSEP_CHROOT_DIR);
1587 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
1588 (st.st_uid != getuid () ||
1589 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0))
1591 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)
1593 fatal("%s must be owned by root and not group or "
1594 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR);
1597 if (test_flag > 1) {
1598 if (test_user != NULL && test_addr != NULL && test_host != NULL)
1599 parse_server_match_config(&options, test_user,
1600 test_host, test_addr);
1601 dump_config(&options);
1604 /* Configuration looks good, so exit if in test mode. */
1609 * Clear out any supplemental groups we may have inherited. This
1610 * prevents inadvertent creation of files with bad modes (in the
1611 * portable version at least, it's certainly possible for PAM
1612 * to create a file, and we can't control the code in every
1613 * module which might be used).
1615 if (setgroups(0, NULL) < 0)
1616 debug("setgroups() failed: %.200s", strerror(errno));
1619 rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *));
1620 for (i = 0; i < rexec_argc; i++) {
1621 debug("rexec_argv[%d]='%s'", i, saved_argv[i]);
1622 rexec_argv[i] = saved_argv[i];
1624 rexec_argv[rexec_argc] = "-R";
1625 rexec_argv[rexec_argc + 1] = NULL;
1628 /* Ensure that umask disallows at least group and world write */
1629 new_umask = umask(0077) | 0022;
1630 (void) umask(new_umask);
1632 /* Initialize the log (it is reinitialized below in case we forked). */
1633 if (debug_flag && (!inetd_flag || rexeced_flag))
1635 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1638 * If not in debugging mode, and not started from inetd, disconnect
1639 * from the controlling terminal, and fork. The original process
1642 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
1645 #endif /* TIOCNOTTY */
1646 if (daemon(0, 0) < 0)
1647 fatal("daemon() failed: %.200s", strerror(errno));
1649 /* Disconnect from the controlling tty. */
1651 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
1653 (void) ioctl(fd, TIOCNOTTY, NULL);
1656 #endif /* TIOCNOTTY */
1658 /* Reinitialize the log (because of the fork above). */
1659 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1661 /* Initialize the random number generator. */
1664 /* Chdir to the root directory so that the current disk can be
1665 unmounted if desired. */
1668 /* ignore SIGPIPE */
1669 signal(SIGPIPE, SIG_IGN);
1671 /* Get a connection, either from inetd or a listening TCP socket */
1673 server_accept_inetd(&sock_in, &sock_out);
1677 if (options.protocol & SSH_PROTO_1)
1678 generate_ephemeral_server_key();
1680 signal(SIGHUP, sighup_handler);
1681 signal(SIGCHLD, main_sigchld_handler);
1682 signal(SIGTERM, sigterm_handler);
1683 signal(SIGQUIT, sigterm_handler);
1686 * Write out the pid file after the sigterm handler
1687 * is setup and the listen sockets are bound
1690 FILE *f = fopen(options.pid_file, "w");
1693 error("Couldn't create pid file \"%s\": %s",
1694 options.pid_file, strerror(errno));
1696 fprintf(f, "%ld\n", (long) getpid());
1701 /* Accept a connection and return in a forked child */
1702 server_accept_loop(&sock_in, &sock_out,
1703 &newsock, config_s);
1706 /* This is the child processing a new connection. */
1707 setproctitle("%s", "[accepted]");
1710 * Create a new session and process group since the 4.4BSD
1711 * setlogin() affects the entire process group. We don't
1712 * want the child to be able to affect the parent.
1714 #if !defined(SSHD_ACQUIRES_CTTY)
1716 * If setsid is called, on some platforms sshd will later acquire a
1717 * controlling terminal which will result in "could not set
1718 * controlling tty" errors.
1720 if (!debug_flag && !inetd_flag && setsid() < 0)
1721 error("setsid: %.100s", strerror(errno));
1727 debug("rexec start in %d out %d newsock %d pipe %d sock %d",
1728 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
1729 dup2(newsock, STDIN_FILENO);
1730 dup2(STDIN_FILENO, STDOUT_FILENO);
1731 if (startup_pipe == -1)
1732 close(REEXEC_STARTUP_PIPE_FD);
1734 dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD);
1736 dup2(config_s[1], REEXEC_CONFIG_PASS_FD);
1738 if (startup_pipe != -1)
1739 close(startup_pipe);
1741 execv(rexec_argv[0], rexec_argv);
1743 /* Reexec has failed, fall back and continue */
1744 error("rexec of %s failed: %s", rexec_argv[0], strerror(errno));
1745 recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL);
1746 log_init(__progname, options.log_level,
1747 options.log_facility, log_stderr);
1750 startup_pipe = REEXEC_STARTUP_PIPE_FD;
1752 close(REEXEC_CONFIG_PASS_FD);
1753 newsock = sock_out = sock_in = dup(STDIN_FILENO);
1754 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
1755 dup2(fd, STDIN_FILENO);
1756 dup2(fd, STDOUT_FILENO);
1757 if (fd > STDERR_FILENO)
1760 debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d",
1761 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
1765 * Disable the key regeneration alarm. We will not regenerate the
1766 * key since we are no longer in a position to give it to anyone. We
1767 * will not restart on SIGHUP since it no longer makes sense.
1770 signal(SIGALRM, SIG_DFL);
1771 signal(SIGHUP, SIG_DFL);
1772 signal(SIGTERM, SIG_DFL);
1773 signal(SIGQUIT, SIG_DFL);
1774 signal(SIGCHLD, SIG_DFL);
1775 signal(SIGINT, SIG_DFL);
1779 * Initialize the resolver. This may not happen automatically
1780 * before privsep chroot().
1782 if ((_res.options & RES_INIT) == 0) {
1783 debug("res_init()");
1788 * Force GSS-API to parse its configuration and load any
1789 * mechanism plugins.
1793 OM_uint32 minor_status;
1794 gss_indicate_mechs(&minor_status, &mechs);
1795 gss_release_oid_set(&minor_status, &mechs);
1801 * Register our connection. This turns encryption off because we do
1804 packet_set_connection(sock_in, sock_out);
1805 packet_set_server();
1807 /* Set SO_KEEPALIVE if requested. */
1808 if (options.tcp_keep_alive && packet_connection_is_on_socket() &&
1809 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) < 0)
1810 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1812 if ((remote_port = get_remote_port()) < 0) {
1813 debug("get_remote_port failed");
1818 * We use get_canonical_hostname with usedns = 0 instead of
1819 * get_remote_ipaddr here so IP options will be checked.
1821 (void) get_canonical_hostname(0);
1823 * The rest of the code depends on the fact that
1824 * get_remote_ipaddr() caches the remote ip, even if
1825 * the socket goes away.
1827 remote_ip = get_remote_ipaddr();
1829 #ifdef SSH_AUDIT_EVENTS
1830 audit_connection_from(remote_ip, remote_port);
1833 allow_severity = options.log_facility|LOG_INFO;
1834 deny_severity = options.log_facility|LOG_WARNING;
1835 /* Check whether logins are denied from this host. */
1836 if (packet_connection_is_on_socket()) {
1837 struct request_info req;
1839 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
1842 if (!hosts_access(&req)) {
1843 debug("Connection refused by tcp wrapper");
1846 fatal("libwrap refuse returns");
1849 #endif /* LIBWRAP */
1851 /* Log the connection. */
1852 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1855 * We don't want to listen forever unless the other side
1856 * successfully authenticates itself. So we set up an alarm which is
1857 * cleared after successful authentication. A limit of zero
1858 * indicates no limit. Note that we don't set the alarm in debugging
1859 * mode; it is just annoying to have the server exit just when you
1860 * are about to discover the bug.
1862 signal(SIGALRM, grace_alarm_handler);
1864 alarm(options.login_grace_time);
1866 sshd_exchange_identification(sock_in, sock_out);
1868 /* In inetd mode, generate ephemeral key only for proto 1 connections */
1869 if (!compat20 && inetd_flag && sensitive_data.server_key == NULL)
1870 generate_ephemeral_server_key();
1872 packet_set_nonblocking();
1874 /* allocate authentication context */
1875 authctxt = xcalloc(1, sizeof(*authctxt));
1877 authctxt->loginmsg = &loginmsg;
1879 /* XXX global for cleanup, access from other modules */
1880 the_authctxt = authctxt;
1882 /* prepare buffer to collect messages to display to user after login */
1883 buffer_init(&loginmsg);
1886 if (privsep_preauth(authctxt) == 1)
1889 /* perform the key exchange */
1890 /* authenticate user and start session */
1893 do_authentication2(authctxt);
1896 do_authentication(authctxt);
1899 * If we use privilege separation, the unprivileged child transfers
1900 * the current keystate and exits
1903 mm_send_keystate(pmonitor);
1909 * Cancel the alarm we set to limit the time taken for
1913 signal(SIGALRM, SIG_DFL);
1914 authctxt->authenticated = 1;
1915 if (startup_pipe != -1) {
1916 close(startup_pipe);
1920 #ifdef SSH_AUDIT_EVENTS
1921 audit_event(SSH_AUTH_SUCCESS);
1925 if (options.gss_authentication) {
1926 temporarily_use_uid(authctxt->pw);
1927 ssh_gssapi_storecreds();
1932 if (options.use_pam) {
1939 * In privilege separation, we fork another child and prepare
1940 * file descriptor passing.
1943 privsep_postauth(authctxt);
1944 /* the monitor process [priv] will not return */
1946 destroy_sensitive_data();
1949 packet_set_timeout(options.client_alive_interval,
1950 options.client_alive_count_max);
1952 /* Start session. */
1953 do_authenticated(authctxt);
1955 /* The connection has been terminated. */
1956 packet_get_state(MODE_IN, NULL, NULL, NULL, &ibytes);
1957 packet_get_state(MODE_OUT, NULL, NULL, NULL, &obytes);
1958 verbose("Transferred: sent %llu, received %llu bytes", obytes, ibytes);
1960 verbose("Closing connection to %.500s port %d", remote_ip, remote_port);
1963 if (options.use_pam)
1965 #endif /* USE_PAM */
1967 #ifdef SSH_AUDIT_EVENTS
1968 PRIVSEP(audit_event(SSH_CONNECTION_CLOSE));
1980 * Decrypt session_key_int using our private server key and private host key
1981 * (key with larger modulus first).
1984 ssh1_session_key(BIGNUM *session_key_int)
1988 if (BN_cmp(sensitive_data.server_key->rsa->n,
1989 sensitive_data.ssh1_host_key->rsa->n) > 0) {
1990 /* Server key has bigger modulus. */
1991 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1992 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1993 SSH_KEY_BITS_RESERVED) {
1994 fatal("do_connection: %s: "
1995 "server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1996 get_remote_ipaddr(),
1997 BN_num_bits(sensitive_data.server_key->rsa->n),
1998 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1999 SSH_KEY_BITS_RESERVED);
2001 if (rsa_private_decrypt(session_key_int, session_key_int,
2002 sensitive_data.server_key->rsa) <= 0)
2004 if (rsa_private_decrypt(session_key_int, session_key_int,
2005 sensitive_data.ssh1_host_key->rsa) <= 0)
2008 /* Host key has bigger modulus (or they are equal). */
2009 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
2010 BN_num_bits(sensitive_data.server_key->rsa->n) +
2011 SSH_KEY_BITS_RESERVED) {
2012 fatal("do_connection: %s: "
2013 "host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
2014 get_remote_ipaddr(),
2015 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
2016 BN_num_bits(sensitive_data.server_key->rsa->n),
2017 SSH_KEY_BITS_RESERVED);
2019 if (rsa_private_decrypt(session_key_int, session_key_int,
2020 sensitive_data.ssh1_host_key->rsa) < 0)
2022 if (rsa_private_decrypt(session_key_int, session_key_int,
2023 sensitive_data.server_key->rsa) < 0)
2036 BIGNUM *session_key_int;
2037 u_char session_key[SSH_SESSION_KEY_LENGTH];
2039 u_int cipher_type, auth_mask, protocol_flags;
2042 * Generate check bytes that the client must send back in the user
2043 * packet in order for it to be accepted; this is used to defy ip
2044 * spoofing attacks. Note that this only works against somebody
2045 * doing IP spoofing from a remote machine; any machine on the local
2046 * network can still see outgoing packets and catch the random
2047 * cookie. This only affects rhosts authentication, and this is one
2048 * of the reasons why it is inherently insecure.
2050 arc4random_buf(cookie, sizeof(cookie));
2053 * Send our public key. We include in the packet 64 bits of random
2054 * data that must be matched in the reply in order to prevent IP
2057 packet_start(SSH_SMSG_PUBLIC_KEY);
2058 for (i = 0; i < 8; i++)
2059 packet_put_char(cookie[i]);
2061 /* Store our public server RSA key. */
2062 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
2063 packet_put_bignum(sensitive_data.server_key->rsa->e);
2064 packet_put_bignum(sensitive_data.server_key->rsa->n);
2066 /* Store our public host RSA key. */
2067 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
2068 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
2069 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
2071 /* Put protocol flags. */
2072 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
2074 /* Declare which ciphers we support. */
2075 packet_put_int(cipher_mask_ssh1(0));
2077 /* Declare supported authentication types. */
2079 if (options.rhosts_rsa_authentication)
2080 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
2081 if (options.rsa_authentication)
2082 auth_mask |= 1 << SSH_AUTH_RSA;
2083 if (options.challenge_response_authentication == 1)
2084 auth_mask |= 1 << SSH_AUTH_TIS;
2085 if (options.password_authentication)
2086 auth_mask |= 1 << SSH_AUTH_PASSWORD;
2087 packet_put_int(auth_mask);
2089 /* Send the packet and wait for it to be sent. */
2091 packet_write_wait();
2093 debug("Sent %d bit server key and %d bit host key.",
2094 BN_num_bits(sensitive_data.server_key->rsa->n),
2095 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
2097 /* Read clients reply (cipher type and session key). */
2098 packet_read_expect(SSH_CMSG_SESSION_KEY);
2100 /* Get cipher type and check whether we accept this. */
2101 cipher_type = packet_get_char();
2103 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
2104 packet_disconnect("Warning: client selects unsupported cipher.");
2106 /* Get check bytes from the packet. These must match those we
2107 sent earlier with the public key packet. */
2108 for (i = 0; i < 8; i++)
2109 if (cookie[i] != packet_get_char())
2110 packet_disconnect("IP Spoofing check bytes do not match.");
2112 debug("Encryption type: %.200s", cipher_name(cipher_type));
2114 /* Get the encrypted integer. */
2115 if ((session_key_int = BN_new()) == NULL)
2116 fatal("do_ssh1_kex: BN_new failed");
2117 packet_get_bignum(session_key_int);
2119 protocol_flags = packet_get_int();
2120 packet_set_protocol_flags(protocol_flags);
2123 /* Decrypt session_key_int using host/server keys */
2124 rsafail = PRIVSEP(ssh1_session_key(session_key_int));
2127 * Extract session key from the decrypted integer. The key is in the
2128 * least significant 256 bits of the integer; the first byte of the
2129 * key is in the highest bits.
2132 (void) BN_mask_bits(session_key_int, sizeof(session_key) * 8);
2133 len = BN_num_bytes(session_key_int);
2134 if (len < 0 || (u_int)len > sizeof(session_key)) {
2135 error("do_ssh1_kex: bad session key len from %s: "
2136 "session_key_int %d > sizeof(session_key) %lu",
2137 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
2140 memset(session_key, 0, sizeof(session_key));
2141 BN_bn2bin(session_key_int,
2142 session_key + sizeof(session_key) - len);
2144 derive_ssh1_session_id(
2145 sensitive_data.ssh1_host_key->rsa->n,
2146 sensitive_data.server_key->rsa->n,
2147 cookie, session_id);
2149 * Xor the first 16 bytes of the session key with the
2152 for (i = 0; i < 16; i++)
2153 session_key[i] ^= session_id[i];
2157 int bytes = BN_num_bytes(session_key_int);
2158 u_char *buf = xmalloc(bytes);
2161 logit("do_connection: generating a fake encryption key");
2162 BN_bn2bin(session_key_int, buf);
2164 MD5_Update(&md, buf, bytes);
2165 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
2166 MD5_Final(session_key, &md);
2168 MD5_Update(&md, session_key, 16);
2169 MD5_Update(&md, buf, bytes);
2170 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
2171 MD5_Final(session_key + 16, &md);
2172 memset(buf, 0, bytes);
2174 for (i = 0; i < 16; i++)
2175 session_id[i] = session_key[i] ^ session_key[i + 16];
2177 /* Destroy the private and public keys. No longer. */
2178 destroy_sensitive_data();
2181 mm_ssh1_session_id(session_id);
2183 /* Destroy the decrypted integer. It is no longer needed. */
2184 BN_clear_free(session_key_int);
2186 /* Set the session key. From this on all communications will be encrypted. */
2187 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
2189 /* Destroy our copy of the session key. It is no longer needed. */
2190 memset(session_key, 0, sizeof(session_key));
2192 debug("Received session key; encryption turned on.");
2194 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */
2195 packet_start(SSH_SMSG_SUCCESS);
2197 packet_write_wait();
2201 * SSH2 key exchange: diffie-hellman-group1-sha1
2208 if (options.ciphers != NULL) {
2209 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2210 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
2212 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2213 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
2214 myproposal[PROPOSAL_ENC_ALGS_STOC] =
2215 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
2217 if (options.macs != NULL) {
2218 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
2219 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
2221 if (options.compression == COMP_NONE) {
2222 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2223 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
2224 } else if (options.compression == COMP_DELAYED) {
2225 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2226 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com";
2229 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
2231 /* start key exchange */
2232 kex = kex_setup(myproposal);
2233 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
2234 kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
2235 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
2236 kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
2238 kex->client_version_string=client_version_string;
2239 kex->server_version_string=server_version_string;
2240 kex->load_host_key=&get_hostkey_by_type;
2241 kex->host_key_index=&get_hostkey_index;
2245 dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
2247 session_id2 = kex->session_id;
2248 session_id2_len = kex->session_id_len;
2251 /* send 1st encrypted/maced/compressed message */
2252 packet_start(SSH2_MSG_IGNORE);
2253 packet_put_cstring("markus");
2255 packet_write_wait();
2260 /* server specific fatal cleanup */
2265 do_cleanup(the_authctxt);
2266 #ifdef SSH_AUDIT_EVENTS
2267 /* done after do_cleanup so it can cancel the PAM auth 'thread' */
2268 if (!use_privsep || mm_is_monitor())
2269 audit_event(SSH_CONNECTION_ABANDON);