1 /* $OpenBSD: sshd.c,v 1.355 2008/02/14 13:10:31 mbalmer Exp $ */
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 * This program is the ssh daemon. It listens for connections from clients,
7 * and performs authentication, executes use commands or shell, and forwards
8 * information to/from the application to the user client over an encrypted
9 * connection. This can also handle forwarding of X11, TCP/IP, and
10 * authentication agent connections.
12 * As far as I am concerned, the code I have written for this software
13 * can be used freely for any purpose. Any derived versions of this
14 * software must be clearly marked as such, and if the derived work is
15 * incompatible with the protocol description in the RFC file, it must be
16 * called by a name other than "ssh" or "Secure Shell".
18 * SSH2 implementation:
19 * Privilege Separation:
21 * Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved.
22 * Copyright (c) 2002 Niels Provos. All rights reserved.
24 * Redistribution and use in source and binary forms, with or without
25 * modification, are permitted provided that the following conditions
27 * 1. Redistributions of source code must retain the above copyright
28 * notice, this list of conditions and the following disclaimer.
29 * 2. Redistributions in binary form must reproduce the above copyright
30 * notice, this list of conditions and the following disclaimer in the
31 * documentation and/or other materials provided with the distribution.
33 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
34 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
35 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
36 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
37 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
38 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
39 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
40 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
41 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
42 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
47 #include <sys/types.h>
48 #include <sys/ioctl.h>
49 #include <sys/socket.h>
50 #ifdef HAVE_SYS_STAT_H
51 # include <sys/stat.h>
53 #ifdef HAVE_SYS_TIME_H
54 # include <sys/time.h>
56 #include "openbsd-compat/sys-tree.h"
74 #include <openssl/dh.h>
75 #include <openssl/bn.h>
76 #include <openssl/md5.h>
77 #include <openssl/rand.h>
78 #include "openbsd-compat/openssl-compat.h"
80 #ifdef HAVE_SECUREWARE
81 #include <sys/security.h>
101 #include "myproposal.h"
102 #include "authfile.h"
103 #include "pathnames.h"
104 #include "atomicio.h"
105 #include "canohost.h"
106 #include "hostfile.h"
110 #include "dispatch.h"
111 #include "channels.h"
113 #include "monitor_mm.h"
118 #include "monitor_wrap.h"
119 #include "monitor_fdpass.h"
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)
146 extern char *__progname;
148 /* Server configuration options. */
149 ServerOptions options;
151 /* Name of the server configuration file. */
152 char *config_file_name;
155 * Debug mode flag. This can be set on the command line. If debug
156 * mode is enabled, extra debugging output will be sent to the system
157 * log, the daemon will not go to background, and will exit after processing
158 * the first connection.
162 /* Flag indicating that the daemon should only test the configuration and keys. */
165 /* Flag indicating that the daemon is being started from inetd. */
168 /* Flag indicating that sshd should not detach and become a daemon. */
169 int no_daemon_flag = 0;
171 /* debug goes to stderr unless inetd_flag is set */
174 /* Saved arguments to main(). */
179 int rexeced_flag = 0;
185 * The sockets that the server is listening; this is used in the SIGHUP
188 #define MAX_LISTEN_SOCKS 16
189 int listen_socks[MAX_LISTEN_SOCKS];
190 int num_listen_socks = 0;
193 * the client's version string, passed by sshd2 in compat mode. if != NULL,
194 * sshd will skip the version-number exchange
196 char *client_version_string = NULL;
197 char *server_version_string = NULL;
199 /* for rekeying XXX fixme */
203 * Any really sensitive data in the application is contained in this
204 * structure. The idea is that this structure could be locked into memory so
205 * that the pages do not get written into swap. However, there are some
206 * problems. The private key contains BIGNUMs, and we do not (in principle)
207 * have access to the internals of them, and locking just the structure is
208 * not very useful. Currently, memory locking is not implemented.
211 Key *server_key; /* ephemeral server key */
212 Key *ssh1_host_key; /* ssh1 host key */
213 Key **host_keys; /* all private host keys */
216 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
220 * Flag indicating whether the RSA server key needs to be regenerated.
221 * Is set in the SIGALRM handler and cleared when the key is regenerated.
223 static volatile sig_atomic_t key_do_regen = 0;
225 /* This is set to true when a signal is received. */
226 static volatile sig_atomic_t received_sighup = 0;
227 static volatile sig_atomic_t received_sigterm = 0;
229 /* session identifier, used by RSA-auth */
230 u_char session_id[16];
233 u_char *session_id2 = NULL;
234 u_int session_id2_len = 0;
236 /* record remote hostname or ip */
237 u_int utmp_len = MAXHOSTNAMELEN;
239 /* options.max_startup sized array of fd ints */
240 int *startup_pipes = NULL;
241 int startup_pipe; /* in child */
243 /* variables used for privilege separation */
244 int use_privsep = -1;
245 struct monitor *pmonitor = NULL;
247 /* global authentication context */
248 Authctxt *the_authctxt = NULL;
250 /* sshd_config buffer */
253 /* message to be displayed after login */
256 /* Unprivileged user */
257 struct passwd *privsep_pw = NULL;
259 /* Prototypes for various functions defined later in this file. */
260 void destroy_sensitive_data(void);
261 void demote_sensitive_data(void);
263 static void do_ssh1_kex(void);
264 static void do_ssh2_kex(void);
267 * Close all listening sockets
270 close_listen_socks(void)
274 for (i = 0; i < num_listen_socks; i++)
275 close(listen_socks[i]);
276 num_listen_socks = -1;
280 close_startup_pipes(void)
285 for (i = 0; i < options.max_startups; i++)
286 if (startup_pipes[i] != -1)
287 close(startup_pipes[i]);
291 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
292 * the effect is to reread the configuration file (and to regenerate
298 sighup_handler(int sig)
300 int save_errno = errno;
303 signal(SIGHUP, sighup_handler);
308 * Called from the main program after receiving SIGHUP.
309 * Restarts the server.
314 logit("Received SIGHUP; restarting.");
315 close_listen_socks();
316 close_startup_pipes();
317 alarm(0); /* alarm timer persists across exec */
318 execv(saved_argv[0], saved_argv);
319 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
325 * Generic signal handler for terminating signals in the master daemon.
329 sigterm_handler(int sig)
331 received_sigterm = sig;
335 * SIGCHLD handler. This is called whenever a child dies. This will then
336 * reap any zombies left by exited children.
340 main_sigchld_handler(int sig)
342 int save_errno = errno;
346 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
347 (pid < 0 && errno == EINTR))
350 signal(SIGCHLD, main_sigchld_handler);
355 * Signal handler for the alarm after the login grace period has expired.
359 grace_alarm_handler(int sig)
361 if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0)
362 kill(pmonitor->m_pid, SIGALRM);
364 /* Log error and exit. */
365 sigdie("Timeout before authentication for %s", get_remote_ipaddr());
369 * Signal handler for the key regeneration alarm. Note that this
370 * alarm only occurs in the daemon waiting for connections, and it does not
371 * do anything with the private key or random state before forking.
372 * Thus there should be no concurrency control/asynchronous execution
376 generate_ephemeral_server_key(void)
381 verbose("Generating %s%d bit RSA key.",
382 sensitive_data.server_key ? "new " : "", options.server_key_bits);
383 if (sensitive_data.server_key != NULL)
384 key_free(sensitive_data.server_key);
385 sensitive_data.server_key = key_generate(KEY_RSA1,
386 options.server_key_bits);
387 verbose("RSA key generation complete.");
389 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
392 sensitive_data.ssh1_cookie[i] = rnd & 0xff;
400 key_regeneration_alarm(int sig)
402 int save_errno = errno;
404 signal(SIGALRM, SIG_DFL);
410 sshd_exchange_identification(int sock_in, int sock_out)
414 int remote_major, remote_minor;
417 char buf[256]; /* Must not be larger than remote_version. */
418 char remote_version[256]; /* Must be at least as big as buf. */
420 if ((options.protocol & SSH_PROTO_1) &&
421 (options.protocol & SSH_PROTO_2)) {
422 major = PROTOCOL_MAJOR_1;
424 } else if (options.protocol & SSH_PROTO_2) {
425 major = PROTOCOL_MAJOR_2;
426 minor = PROTOCOL_MINOR_2;
428 major = PROTOCOL_MAJOR_1;
429 minor = PROTOCOL_MINOR_1;
431 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_RELEASE);
432 server_version_string = xstrdup(buf);
434 /* Send our protocol version identification. */
435 if (atomicio(vwrite, sock_out, server_version_string,
436 strlen(server_version_string))
437 != strlen(server_version_string)) {
438 logit("Could not write ident string to %s", get_remote_ipaddr());
442 /* Read other sides version identification. */
443 memset(buf, 0, sizeof(buf));
444 for (i = 0; i < sizeof(buf) - 1; i++) {
445 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
446 logit("Did not receive identification string from %s",
447 get_remote_ipaddr());
450 if (buf[i] == '\r') {
452 /* Kludge for F-Secure Macintosh < 1.0.2 */
454 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
458 if (buf[i] == '\n') {
463 buf[sizeof(buf) - 1] = 0;
464 client_version_string = xstrdup(buf);
467 * Check that the versions match. In future this might accept
468 * several versions and set appropriate flags to handle them.
470 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
471 &remote_major, &remote_minor, remote_version) != 3) {
472 s = "Protocol mismatch.\n";
473 (void) atomicio(vwrite, sock_out, s, strlen(s));
476 logit("Bad protocol version identification '%.100s' from %s",
477 client_version_string, get_remote_ipaddr());
480 debug("Client protocol version %d.%d; client software version %.100s",
481 remote_major, remote_minor, remote_version);
482 logit("SSH: Server;Ltype: Version;Remote: %s-%d;Protocol: %d.%d;Client: %.100s",
483 get_remote_ipaddr(), get_remote_port(),
484 remote_major, remote_minor, remote_version);
486 compat_datafellows(remote_version);
488 if (datafellows & SSH_BUG_PROBE) {
489 logit("probed from %s with %s. Don't panic.",
490 get_remote_ipaddr(), client_version_string);
494 if (datafellows & SSH_BUG_SCANNER) {
495 logit("scanned from %s with %s. Don't panic.",
496 get_remote_ipaddr(), client_version_string);
501 switch (remote_major) {
503 if (remote_minor == 99) {
504 if (options.protocol & SSH_PROTO_2)
510 if (!(options.protocol & SSH_PROTO_1)) {
514 if (remote_minor < 3) {
515 packet_disconnect("Your ssh version is too old and "
516 "is no longer supported. Please install a newer version.");
517 } else if (remote_minor == 3) {
518 /* note that this disables agent-forwarding */
523 if (options.protocol & SSH_PROTO_2) {
532 chop(server_version_string);
533 debug("Local version string %.200s", server_version_string);
536 s = "Protocol major versions differ.\n";
537 (void) atomicio(vwrite, sock_out, s, strlen(s));
540 logit("Protocol major versions differ for %s: %.200s vs. %.200s",
542 server_version_string, client_version_string);
547 /* Destroy the host and server keys. They will no longer be needed. */
549 destroy_sensitive_data(void)
553 if (sensitive_data.server_key) {
554 key_free(sensitive_data.server_key);
555 sensitive_data.server_key = NULL;
557 for (i = 0; i < options.num_host_key_files; i++) {
558 if (sensitive_data.host_keys[i]) {
559 key_free(sensitive_data.host_keys[i]);
560 sensitive_data.host_keys[i] = NULL;
563 sensitive_data.ssh1_host_key = NULL;
564 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
567 /* Demote private to public keys for network child */
569 demote_sensitive_data(void)
574 if (sensitive_data.server_key) {
575 tmp = key_demote(sensitive_data.server_key);
576 key_free(sensitive_data.server_key);
577 sensitive_data.server_key = tmp;
580 for (i = 0; i < options.num_host_key_files; i++) {
581 if (sensitive_data.host_keys[i]) {
582 tmp = key_demote(sensitive_data.host_keys[i]);
583 key_free(sensitive_data.host_keys[i]);
584 sensitive_data.host_keys[i] = tmp;
585 if (tmp->type == KEY_RSA1)
586 sensitive_data.ssh1_host_key = tmp;
590 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */
594 privsep_preauth_child(void)
600 /* Enable challenge-response authentication for privilege separation */
601 privsep_challenge_enable();
604 for (i = 0; i < 256; i++)
605 rnd[i] = arc4random();
606 RAND_seed(rnd, sizeof(rnd));
608 /* Demote the private keys to public keys. */
609 demote_sensitive_data();
611 /* Change our root directory */
612 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
613 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
615 if (chdir("/") == -1)
616 fatal("chdir(\"/\"): %s", strerror(errno));
618 /* Drop our privileges */
619 debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid,
620 (u_int)privsep_pw->pw_gid);
622 /* XXX not ready, too heavy after chroot */
623 do_setusercontext(privsep_pw);
625 gidset[0] = privsep_pw->pw_gid;
626 if (setgroups(1, gidset) < 0)
627 fatal("setgroups: %.100s", strerror(errno));
628 permanently_set_uid(privsep_pw);
633 privsep_preauth(Authctxt *authctxt)
638 /* Set up unprivileged child process to deal with network data */
639 pmonitor = monitor_init();
640 /* Store a pointer to the kex for later rekeying */
641 pmonitor->m_pkex = &xxx_kex;
645 fatal("fork of unprivileged child failed");
646 } else if (pid != 0) {
647 debug2("Network child is on pid %ld", (long)pid);
649 close(pmonitor->m_recvfd);
650 pmonitor->m_pid = pid;
651 monitor_child_preauth(authctxt, pmonitor);
652 close(pmonitor->m_sendfd);
655 monitor_sync(pmonitor);
657 /* Wait for the child's exit status */
658 while (waitpid(pid, &status, 0) < 0)
665 close(pmonitor->m_sendfd);
667 /* Demote the child */
668 if (getuid() == 0 || geteuid() == 0)
669 privsep_preauth_child();
670 setproctitle("%s", "[net]");
676 privsep_postauth(Authctxt *authctxt)
681 #ifdef DISABLE_FD_PASSING
684 if (authctxt->pw->pw_uid == 0 || options.use_login) {
686 /* File descriptor passing is broken or root login */
691 /* New socket pair */
692 monitor_reinit(pmonitor);
694 pmonitor->m_pid = fork();
695 if (pmonitor->m_pid == -1)
696 fatal("fork of unprivileged child failed");
697 else if (pmonitor->m_pid != 0) {
698 debug2("User child is on pid %ld", (long)pmonitor->m_pid);
699 close(pmonitor->m_recvfd);
700 buffer_clear(&loginmsg);
701 monitor_child_postauth(pmonitor);
707 close(pmonitor->m_sendfd);
709 /* Demote the private keys to public keys. */
710 demote_sensitive_data();
713 for (i = 0; i < 256; i++)
714 rnd[i] = arc4random();
715 RAND_seed(rnd, sizeof(rnd));
717 /* Drop privileges */
718 do_setusercontext(authctxt->pw);
721 /* It is safe now to apply the key state */
722 monitor_apply_keystate(pmonitor);
725 * Tell the packet layer that authentication was successful, since
726 * this information is not part of the key state.
728 packet_set_authenticated();
732 list_hostkey_types(void)
740 for (i = 0; i < options.num_host_key_files; i++) {
741 Key *key = sensitive_data.host_keys[i];
747 if (buffer_len(&b) > 0)
748 buffer_append(&b, ",", 1);
749 p = key_ssh_name(key);
750 buffer_append(&b, p, strlen(p));
754 buffer_append(&b, "\0", 1);
755 ret = xstrdup(buffer_ptr(&b));
757 debug("list_hostkey_types: %s", ret);
762 get_hostkey_by_type(int type)
766 for (i = 0; i < options.num_host_key_files; i++) {
767 Key *key = sensitive_data.host_keys[i];
768 if (key != NULL && key->type == type)
775 get_hostkey_by_index(int ind)
777 if (ind < 0 || ind >= options.num_host_key_files)
779 return (sensitive_data.host_keys[ind]);
783 get_hostkey_index(Key *key)
787 for (i = 0; i < options.num_host_key_files; i++) {
788 if (key == sensitive_data.host_keys[i])
795 * returns 1 if connection should be dropped, 0 otherwise.
796 * dropping starts at connection #max_startups_begin with a probability
797 * of (max_startups_rate/100). the probability increases linearly until
798 * all connections are dropped for startups > max_startups
801 drop_connection(int startups)
805 if (startups < options.max_startups_begin)
807 if (startups >= options.max_startups)
809 if (options.max_startups_rate == 100)
812 p = 100 - options.max_startups_rate;
813 p *= startups - options.max_startups_begin;
814 p /= options.max_startups - options.max_startups_begin;
815 p += options.max_startups_rate;
816 r = arc4random() % 100;
818 debug("drop_connection: p %d, r %d", p, r);
819 return (r < p) ? 1 : 0;
825 fprintf(stderr, "%s, %s\n",
826 SSH_RELEASE, SSLeay_version(SSLEAY_VERSION));
828 "usage: sshd [-46Ddeiqt] [-b bits] [-f config_file] [-g login_grace_time]\n"
829 " [-h host_key_file] [-k key_gen_time] [-o option] [-p port] [-u len]\n"
835 send_rexec_state(int fd, Buffer *conf)
839 debug3("%s: entering fd = %d config len %d", __func__, fd,
843 * Protocol from reexec master to child:
844 * string configuration
845 * u_int ephemeral_key_follows
846 * bignum e (only if ephemeral_key_follows == 1)
852 * string rngseed (only if OpenSSL is not self-seeded)
855 buffer_put_cstring(&m, buffer_ptr(conf));
857 if (sensitive_data.server_key != NULL &&
858 sensitive_data.server_key->type == KEY_RSA1) {
859 buffer_put_int(&m, 1);
860 buffer_put_bignum(&m, sensitive_data.server_key->rsa->e);
861 buffer_put_bignum(&m, sensitive_data.server_key->rsa->n);
862 buffer_put_bignum(&m, sensitive_data.server_key->rsa->d);
863 buffer_put_bignum(&m, sensitive_data.server_key->rsa->iqmp);
864 buffer_put_bignum(&m, sensitive_data.server_key->rsa->p);
865 buffer_put_bignum(&m, sensitive_data.server_key->rsa->q);
867 buffer_put_int(&m, 0);
869 #ifndef OPENSSL_PRNG_ONLY
870 rexec_send_rng_seed(&m);
873 if (ssh_msg_send(fd, 0, &m) == -1)
874 fatal("%s: ssh_msg_send failed", __func__);
878 debug3("%s: done", __func__);
882 recv_rexec_state(int fd, Buffer *conf)
888 debug3("%s: entering fd = %d", __func__, fd);
892 if (ssh_msg_recv(fd, &m) == -1)
893 fatal("%s: ssh_msg_recv failed", __func__);
894 if (buffer_get_char(&m) != 0)
895 fatal("%s: rexec version mismatch", __func__);
897 cp = buffer_get_string(&m, &len);
899 buffer_append(conf, cp, len + 1);
902 if (buffer_get_int(&m)) {
903 if (sensitive_data.server_key != NULL)
904 key_free(sensitive_data.server_key);
905 sensitive_data.server_key = key_new_private(KEY_RSA1);
906 buffer_get_bignum(&m, sensitive_data.server_key->rsa->e);
907 buffer_get_bignum(&m, sensitive_data.server_key->rsa->n);
908 buffer_get_bignum(&m, sensitive_data.server_key->rsa->d);
909 buffer_get_bignum(&m, sensitive_data.server_key->rsa->iqmp);
910 buffer_get_bignum(&m, sensitive_data.server_key->rsa->p);
911 buffer_get_bignum(&m, sensitive_data.server_key->rsa->q);
912 rsa_generate_additional_parameters(
913 sensitive_data.server_key->rsa);
916 #ifndef OPENSSL_PRNG_ONLY
917 rexec_recv_rng_seed(&m);
922 debug3("%s: done", __func__);
925 /* Accept a connection from inetd */
927 server_accept_inetd(int *sock_in, int *sock_out)
933 close(REEXEC_CONFIG_PASS_FD);
934 *sock_in = *sock_out = dup(STDIN_FILENO);
936 startup_pipe = dup(REEXEC_STARTUP_PIPE_FD);
937 close(REEXEC_STARTUP_PIPE_FD);
940 *sock_in = dup(STDIN_FILENO);
941 *sock_out = dup(STDOUT_FILENO);
944 * We intentionally do not close the descriptors 0, 1, and 2
945 * as our code for setting the descriptors won't work if
946 * ttyfd happens to be one of those.
948 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
949 dup2(fd, STDIN_FILENO);
950 dup2(fd, STDOUT_FILENO);
951 if (fd > STDOUT_FILENO)
954 debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out);
958 * Listen for TCP connections
963 int ret, listen_sock, on = 1;
965 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
967 int socksizelen = sizeof(int);
969 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
970 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
972 if (num_listen_socks >= MAX_LISTEN_SOCKS)
973 fatal("Too many listen sockets. "
974 "Enlarge MAX_LISTEN_SOCKS");
975 if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen,
976 ntop, sizeof(ntop), strport, sizeof(strport),
977 NI_NUMERICHOST|NI_NUMERICSERV)) != 0) {
978 error("getnameinfo failed: %.100s",
979 ssh_gai_strerror(ret));
982 /* Create socket for listening. */
983 listen_sock = socket(ai->ai_family, ai->ai_socktype,
985 if (listen_sock < 0) {
986 /* kernel may not support ipv6 */
987 verbose("socket: %.100s", strerror(errno));
990 if (set_nonblock(listen_sock) == -1) {
995 * Set socket options.
996 * Allow local port reuse in TIME_WAIT.
998 if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
999 &on, sizeof(on)) == -1)
1000 error("setsockopt SO_REUSEADDR: %s", strerror(errno));
1003 /* Only communicate in IPv6 over AF_INET6 sockets. */
1004 if (ai->ai_family == AF_INET6) {
1005 if (setsockopt(listen_sock, IPPROTO_IPV6, IPV6_V6ONLY,
1006 &on, sizeof(on)) == -1)
1007 error("setsockopt IPV6_V6ONLY: %s",
1012 debug("Bind to port %s on %s.", strport, ntop);
1014 getsockopt(listen_sock, SOL_SOCKET, SO_RCVBUF,
1015 &socksize, &socksizelen);
1016 debug("Server TCP RWIN socket size: %d", socksize);
1017 debug("HPN Buffer Size: %d", options.hpn_buffer_size);
1019 /* Bind the socket to the desired port. */
1020 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1021 error("Bind to port %s on %s failed: %.200s.",
1022 strport, ntop, strerror(errno));
1026 listen_socks[num_listen_socks] = listen_sock;
1029 /* Start listening on the port. */
1030 if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0)
1031 fatal("listen on [%s]:%s: %.100s",
1032 ntop, strport, strerror(errno));
1033 logit("Server listening on %s port %s.", ntop, strport);
1035 freeaddrinfo(options.listen_addrs);
1037 if (!num_listen_socks)
1038 fatal("Cannot bind any address.");
1042 * The main TCP accept loop. Note that, for the non-debug case, returns
1043 * from this function are in a forked subprocess.
1046 server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s)
1049 int i, j, ret, maxfd;
1050 int key_used = 0, startups = 0;
1051 int startup_p[2] = { -1 , -1 };
1052 struct sockaddr_storage from;
1056 /* setup fd set for accept */
1059 for (i = 0; i < num_listen_socks; i++)
1060 if (listen_socks[i] > maxfd)
1061 maxfd = listen_socks[i];
1062 /* pipes connected to unauthenticated childs */
1063 startup_pipes = xcalloc(options.max_startups, sizeof(int));
1064 for (i = 0; i < options.max_startups; i++)
1065 startup_pipes[i] = -1;
1068 * Stay listening for connections until the system crashes or
1069 * the daemon is killed with a signal.
1072 if (received_sighup)
1076 fdset = (fd_set *)xcalloc(howmany(maxfd + 1, NFDBITS),
1079 for (i = 0; i < num_listen_socks; i++)
1080 FD_SET(listen_socks[i], fdset);
1081 for (i = 0; i < options.max_startups; i++)
1082 if (startup_pipes[i] != -1)
1083 FD_SET(startup_pipes[i], fdset);
1085 /* Wait in select until there is a connection. */
1086 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
1087 if (ret < 0 && errno != EINTR)
1088 error("select: %.100s", strerror(errno));
1089 if (received_sigterm) {
1090 logit("Received signal %d; terminating.",
1091 (int) received_sigterm);
1092 close_listen_socks();
1093 unlink(options.pid_file);
1096 if (key_used && key_do_regen) {
1097 generate_ephemeral_server_key();
1104 for (i = 0; i < options.max_startups; i++)
1105 if (startup_pipes[i] != -1 &&
1106 FD_ISSET(startup_pipes[i], fdset)) {
1108 * the read end of the pipe is ready
1109 * if the child has closed the pipe
1110 * after successful authentication
1111 * or if the child has died
1113 close(startup_pipes[i]);
1114 startup_pipes[i] = -1;
1117 for (i = 0; i < num_listen_socks; i++) {
1118 if (!FD_ISSET(listen_socks[i], fdset))
1120 fromlen = sizeof(from);
1121 *newsock = accept(listen_socks[i],
1122 (struct sockaddr *)&from, &fromlen);
1124 if (errno != EINTR && errno != EWOULDBLOCK)
1125 error("accept: %.100s", strerror(errno));
1128 if (unset_nonblock(*newsock) == -1) {
1132 if (drop_connection(startups) == 1) {
1133 debug("drop connection #%d", startups);
1137 if (pipe(startup_p) == -1) {
1142 if (rexec_flag && socketpair(AF_UNIX,
1143 SOCK_STREAM, 0, config_s) == -1) {
1144 error("reexec socketpair: %s",
1147 close(startup_p[0]);
1148 close(startup_p[1]);
1152 for (j = 0; j < options.max_startups; j++)
1153 if (startup_pipes[j] == -1) {
1154 startup_pipes[j] = startup_p[0];
1155 if (maxfd < startup_p[0])
1156 maxfd = startup_p[0];
1162 * Got connection. Fork a child to handle it, unless
1163 * we are in debugging mode.
1167 * In debugging mode. Close the listening
1168 * socket, and start processing the
1169 * connection without forking.
1171 debug("Server will not fork when running in debugging mode.");
1172 close_listen_socks();
1173 *sock_in = *newsock;
1174 *sock_out = *newsock;
1175 close(startup_p[0]);
1176 close(startup_p[1]);
1180 send_rexec_state(config_s[0],
1188 * Normal production daemon. Fork, and have
1189 * the child process the connection. The
1190 * parent continues listening.
1192 platform_pre_fork();
1193 if ((pid = fork()) == 0) {
1195 * Child. Close the listening and
1196 * max_startup sockets. Start using
1197 * the accepted socket. Reinitialize
1198 * logging (since our pid has changed).
1199 * We break out of the loop to handle
1202 platform_post_fork_child();
1203 startup_pipe = startup_p[1];
1204 close_startup_pipes();
1205 close_listen_socks();
1206 *sock_in = *newsock;
1207 *sock_out = *newsock;
1208 log_init(__progname,
1210 options.log_facility,
1217 /* Parent. Stay in the loop. */
1218 platform_post_fork_parent(pid);
1220 error("fork: %.100s", strerror(errno));
1222 debug("Forked child %ld.", (long)pid);
1224 close(startup_p[1]);
1227 send_rexec_state(config_s[0], &cfg);
1233 * Mark that the key has been used (it
1234 * was "given" to the child).
1236 if ((options.protocol & SSH_PROTO_1) &&
1238 /* Schedule server key regeneration alarm. */
1239 signal(SIGALRM, key_regeneration_alarm);
1240 alarm(options.key_regeneration_time);
1247 * Ensure that our random state differs
1248 * from that of the child
1253 /* child process check (or debug mode) */
1254 if (num_listen_socks < 0)
1261 * Main program for the daemon.
1264 main(int ac, char **av)
1266 extern char *optarg;
1269 int sock_in = -1, sock_out = -1, newsock = -1;
1270 const char *remote_ip;
1273 int config_s[2] = { -1 , -1 };
1277 #ifdef HAVE_SECUREWARE
1278 (void)set_auth_parameters(ac, av);
1280 __progname = ssh_get_progname(av[0]);
1282 config_file_name = _PATH_SERVER_CONFIG_FILE;
1285 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
1288 saved_argv = xcalloc(ac + 1, sizeof(*saved_argv));
1289 for (i = 0; i < ac; i++)
1290 saved_argv[i] = xstrdup(av[i]);
1291 saved_argv[i] = NULL;
1293 #ifndef HAVE_SETPROCTITLE
1294 /* Prepare for later setproctitle emulation */
1295 compat_init_setproctitle(ac, av);
1299 if (geteuid() == 0 && setgroups(0, NULL) == -1)
1300 debug("setgroups(): %.200s", strerror(errno));
1302 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
1305 /* Initialize configuration options to their default values. */
1306 initialize_server_options(&options);
1308 /* Parse command-line arguments. */
1309 while ((opt = getopt(ac, av, "f:p:b:k:h:g:u:o:dDeiqrtQR46")) != -1) {
1312 options.address_family = AF_INET;
1315 options.address_family = AF_INET6;
1318 config_file_name = optarg;
1321 if (debug_flag == 0) {
1323 options.log_level = SYSLOG_LEVEL_DEBUG1;
1324 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
1325 options.log_level++;
1347 options.log_level = SYSLOG_LEVEL_QUIET;
1350 options.server_key_bits = (int)strtonum(optarg, 256,
1354 options.ports_from_cmdline = 1;
1355 if (options.num_ports >= MAX_PORTS) {
1356 fprintf(stderr, "too many ports.\n");
1359 options.ports[options.num_ports++] = a2port(optarg);
1360 if (options.ports[options.num_ports-1] == 0) {
1361 fprintf(stderr, "Bad port number.\n");
1366 if ((options.login_grace_time = convtime(optarg)) == -1) {
1367 fprintf(stderr, "Invalid login grace time.\n");
1372 if ((options.key_regeneration_time = convtime(optarg)) == -1) {
1373 fprintf(stderr, "Invalid key regeneration interval.\n");
1378 if (options.num_host_key_files >= MAX_HOSTKEYS) {
1379 fprintf(stderr, "too many host keys.\n");
1382 options.host_key_files[options.num_host_key_files++] = optarg;
1388 utmp_len = (u_int)strtonum(optarg, 0, MAXHOSTNAMELEN+1, NULL);
1389 if (utmp_len > MAXHOSTNAMELEN) {
1390 fprintf(stderr, "Invalid utmp length.\n");
1395 line = xstrdup(optarg);
1396 if (process_server_config_line(&options, line,
1397 "command-line", 0, NULL, NULL, NULL, NULL) != 0)
1407 if (rexeced_flag || inetd_flag)
1409 if (!test_flag && (rexec_flag && (av[0] == NULL || *av[0] != '/')))
1410 fatal("sshd re-exec requires execution with an absolute path");
1412 closefrom(REEXEC_MIN_FREE_FD);
1414 closefrom(REEXEC_DEVCRYPTO_RESERVED_FD);
1416 SSLeay_add_all_algorithms();
1419 * Force logging to stderr until we have loaded the private host
1420 * key (unless started from inetd)
1422 log_init(__progname,
1423 options.log_level == SYSLOG_LEVEL_NOT_SET ?
1424 SYSLOG_LEVEL_INFO : options.log_level,
1425 options.log_facility == SYSLOG_FACILITY_NOT_SET ?
1426 SYSLOG_FACILITY_AUTH : options.log_facility,
1427 log_stderr || !inetd_flag);
1430 * Unset KRB5CCNAME, otherwise the user's session may inherit it from
1431 * root's environment
1433 if (getenv("KRB5CCNAME") != NULL)
1434 unsetenv("KRB5CCNAME");
1437 /* Cray can define user privs drop all privs now!
1438 * Not needed on PRIV_SU systems!
1443 sensitive_data.server_key = NULL;
1444 sensitive_data.ssh1_host_key = NULL;
1445 sensitive_data.have_ssh1_key = 0;
1446 sensitive_data.have_ssh2_key = 0;
1448 /* Fetch our configuration */
1451 recv_rexec_state(REEXEC_CONFIG_PASS_FD, &cfg);
1453 load_server_config(config_file_name, &cfg);
1455 parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name,
1456 &cfg, NULL, NULL, NULL);
1460 /* Fill in default values for those options not explicitly set. */
1461 fill_default_server_options(&options);
1463 /* challenge-response is implemented via keyboard interactive */
1464 if (options.challenge_response_authentication)
1465 options.kbd_interactive_authentication = 1;
1467 /* set default channel AF */
1468 channel_set_af(options.address_family);
1470 /* Check that there are no remaining arguments. */
1472 fprintf(stderr, "Extra argument %s.\n", av[optind]);
1476 debug("sshd version %.100s", SSH_RELEASE);
1478 /* Store privilege separation user for later use if required. */
1479 if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) {
1480 if (use_privsep || options.kerberos_authentication)
1481 fatal("Privilege separation user %s does not exist",
1484 memset(privsep_pw->pw_passwd, 0, strlen(privsep_pw->pw_passwd));
1485 privsep_pw = pwcopy(privsep_pw);
1486 xfree(privsep_pw->pw_passwd);
1487 privsep_pw->pw_passwd = xstrdup("*");
1491 /* load private host keys */
1492 sensitive_data.host_keys = xcalloc(options.num_host_key_files,
1494 for (i = 0; i < options.num_host_key_files; i++)
1495 sensitive_data.host_keys[i] = NULL;
1497 for (i = 0; i < options.num_host_key_files; i++) {
1498 key = key_load_private(options.host_key_files[i], "", NULL);
1499 sensitive_data.host_keys[i] = key;
1501 error("Could not load host key: %s",
1502 options.host_key_files[i]);
1503 sensitive_data.host_keys[i] = NULL;
1506 switch (key->type) {
1508 sensitive_data.ssh1_host_key = key;
1509 sensitive_data.have_ssh1_key = 1;
1513 sensitive_data.have_ssh2_key = 1;
1516 debug("private host key: #%d type %d %s", i, key->type,
1519 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
1520 logit("Disabling protocol version 1. Could not load host key");
1521 options.protocol &= ~SSH_PROTO_1;
1524 /* The GSSAPI key exchange can run without a host key */
1525 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
1526 logit("Disabling protocol version 2. Could not load host key");
1527 options.protocol &= ~SSH_PROTO_2;
1530 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
1531 logit("sshd: no hostkeys available -- exiting.");
1535 /* Check certain values for sanity. */
1536 if (options.protocol & SSH_PROTO_1) {
1537 if (options.server_key_bits < 512 ||
1538 options.server_key_bits > 32768) {
1539 fprintf(stderr, "Bad server key size.\n");
1543 * Check that server and host key lengths differ sufficiently. This
1544 * is necessary to make double encryption work with rsaref. Oh, I
1545 * hate software patents. I dont know if this can go? Niels
1547 if (options.server_key_bits >
1548 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) -
1549 SSH_KEY_BITS_RESERVED && options.server_key_bits <
1550 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1551 SSH_KEY_BITS_RESERVED) {
1552 options.server_key_bits =
1553 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1554 SSH_KEY_BITS_RESERVED;
1555 debug("Forcing server key to %d bits to make it differ from host key.",
1556 options.server_key_bits);
1563 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) ||
1564 (S_ISDIR(st.st_mode) == 0))
1565 fatal("Missing privilege separation directory: %s",
1566 _PATH_PRIVSEP_CHROOT_DIR);
1569 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
1570 (st.st_uid != getuid () ||
1571 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0))
1573 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)
1575 fatal("%s must be owned by root and not group or "
1576 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR);
1579 /* Configuration looks good, so exit if in test mode. */
1584 * Clear out any supplemental groups we may have inherited. This
1585 * prevents inadvertent creation of files with bad modes (in the
1586 * portable version at least, it's certainly possible for PAM
1587 * to create a file, and we can't control the code in every
1588 * module which might be used).
1590 if (setgroups(0, NULL) < 0)
1591 debug("setgroups() failed: %.200s", strerror(errno));
1594 rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *));
1595 for (i = 0; i < rexec_argc; i++) {
1596 debug("rexec_argv[%d]='%s'", i, saved_argv[i]);
1597 rexec_argv[i] = saved_argv[i];
1599 rexec_argv[rexec_argc] = "-R";
1600 rexec_argv[rexec_argc + 1] = NULL;
1603 /* Initialize the log (it is reinitialized below in case we forked). */
1604 if (debug_flag && (!inetd_flag || rexeced_flag))
1606 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1609 * If not in debugging mode, and not started from inetd, disconnect
1610 * from the controlling terminal, and fork. The original process
1613 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
1616 #endif /* TIOCNOTTY */
1617 if (daemon(0, 0) < 0)
1618 fatal("daemon() failed: %.200s", strerror(errno));
1620 /* Disconnect from the controlling tty. */
1622 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
1624 (void) ioctl(fd, TIOCNOTTY, NULL);
1627 #endif /* TIOCNOTTY */
1629 /* Reinitialize the log (because of the fork above). */
1630 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1632 /* Initialize the random number generator. */
1635 /* Chdir to the root directory so that the current disk can be
1636 unmounted if desired. */
1639 /* ignore SIGPIPE */
1640 signal(SIGPIPE, SIG_IGN);
1642 /* Get a connection, either from inetd or a listening TCP socket */
1644 server_accept_inetd(&sock_in, &sock_out);
1648 if (options.protocol & SSH_PROTO_1)
1649 generate_ephemeral_server_key();
1651 signal(SIGHUP, sighup_handler);
1652 signal(SIGCHLD, main_sigchld_handler);
1653 signal(SIGTERM, sigterm_handler);
1654 signal(SIGQUIT, sigterm_handler);
1657 * Write out the pid file after the sigterm handler
1658 * is setup and the listen sockets are bound
1661 FILE *f = fopen(options.pid_file, "w");
1664 error("Couldn't create pid file \"%s\": %s",
1665 options.pid_file, strerror(errno));
1667 fprintf(f, "%ld\n", (long) getpid());
1672 /* Accept a connection and return in a forked child */
1673 server_accept_loop(&sock_in, &sock_out,
1674 &newsock, config_s);
1677 /* This is the child processing a new connection. */
1678 setproctitle("%s", "[accepted]");
1681 * Create a new session and process group since the 4.4BSD
1682 * setlogin() affects the entire process group. We don't
1683 * want the child to be able to affect the parent.
1685 #if !defined(SSHD_ACQUIRES_CTTY)
1687 * If setsid is called, on some platforms sshd will later acquire a
1688 * controlling terminal which will result in "could not set
1689 * controlling tty" errors.
1691 if (!debug_flag && !inetd_flag && setsid() < 0)
1692 error("setsid: %.100s", strerror(errno));
1698 debug("rexec start in %d out %d newsock %d pipe %d sock %d",
1699 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
1700 dup2(newsock, STDIN_FILENO);
1701 dup2(STDIN_FILENO, STDOUT_FILENO);
1702 if (startup_pipe == -1)
1703 close(REEXEC_STARTUP_PIPE_FD);
1705 dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD);
1707 dup2(config_s[1], REEXEC_CONFIG_PASS_FD);
1709 if (startup_pipe != -1)
1710 close(startup_pipe);
1712 execv(rexec_argv[0], rexec_argv);
1714 /* Reexec has failed, fall back and continue */
1715 error("rexec of %s failed: %s", rexec_argv[0], strerror(errno));
1716 recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL);
1717 log_init(__progname, options.log_level,
1718 options.log_facility, log_stderr);
1721 startup_pipe = REEXEC_STARTUP_PIPE_FD;
1723 close(REEXEC_CONFIG_PASS_FD);
1724 newsock = sock_out = sock_in = dup(STDIN_FILENO);
1725 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
1726 dup2(fd, STDIN_FILENO);
1727 dup2(fd, STDOUT_FILENO);
1728 if (fd > STDERR_FILENO)
1731 debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d",
1732 sock_in, sock_out, newsock, startup_pipe, config_s[0]);
1736 * Disable the key regeneration alarm. We will not regenerate the
1737 * key since we are no longer in a position to give it to anyone. We
1738 * will not restart on SIGHUP since it no longer makes sense.
1741 signal(SIGALRM, SIG_DFL);
1742 signal(SIGHUP, SIG_DFL);
1743 signal(SIGTERM, SIG_DFL);
1744 signal(SIGQUIT, SIG_DFL);
1745 signal(SIGCHLD, SIG_DFL);
1746 signal(SIGINT, SIG_DFL);
1749 * Register our connection. This turns encryption off because we do
1752 packet_set_connection(sock_in, sock_out);
1753 packet_set_server();
1755 /* Set SO_KEEPALIVE if requested. */
1756 if (options.tcp_keep_alive && packet_connection_is_on_socket() &&
1757 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) < 0)
1758 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1760 if ((remote_port = get_remote_port()) < 0) {
1761 debug("get_remote_port failed");
1766 * We use get_canonical_hostname with usedns = 0 instead of
1767 * get_remote_ipaddr here so IP options will be checked.
1769 (void) get_canonical_hostname(0);
1771 * The rest of the code depends on the fact that
1772 * get_remote_ipaddr() caches the remote ip, even if
1773 * the socket goes away.
1775 remote_ip = get_remote_ipaddr();
1777 #ifdef SSH_AUDIT_EVENTS
1778 audit_connection_from(remote_ip, remote_port);
1781 allow_severity = options.log_facility|LOG_INFO;
1782 deny_severity = options.log_facility|LOG_WARNING;
1783 /* Check whether logins are denied from this host. */
1784 if (packet_connection_is_on_socket()) {
1785 struct request_info req;
1787 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
1790 if (!hosts_access(&req)) {
1791 debug("Connection refused by tcp wrapper");
1794 fatal("libwrap refuse returns");
1797 #endif /* LIBWRAP */
1799 /* Log the connection. */
1800 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1802 #ifdef USE_SECURITY_SESSION_API
1804 * Create a new security session for use by the new user login if
1805 * the current session is the root session or we are not launched
1806 * by inetd (eg: debugging mode or server mode). We do not
1807 * necessarily need to create a session if we are launched from
1808 * inetd because Panther xinetd will create a session for us.
1810 * The only case where this logic will fail is if there is an
1811 * inetd running in a non-root session which is not creating
1812 * new sessions for us. Then all the users will end up in the
1813 * same session (bad).
1815 * When the client exits, the session will be destroyed for us
1818 * We must create the session before any credentials are stored
1819 * (including AFS pags, which happens a few lines below).
1823 SecuritySessionId sid = 0;
1824 SessionAttributeBits sattrs = 0;
1826 err = SessionGetInfo(callerSecuritySession, &sid, &sattrs);
1828 error("SessionGetInfo() failed with error %.8X",
1831 debug("Current Session ID is %.8X / Session Attributes are %.8X",
1832 (unsigned) sid, (unsigned) sattrs);
1834 if (inetd_flag && !(sattrs & sessionIsRoot))
1835 debug("Running in inetd mode in a non-root session... "
1836 "assuming inetd created the session for us.");
1838 debug("Creating new security session...");
1839 err = SessionCreate(0, sessionHasTTY | sessionIsRemote);
1841 error("SessionCreate() failed with error %.8X",
1844 err = SessionGetInfo(callerSecuritySession, &sid,
1847 error("SessionGetInfo() failed with error %.8X",
1850 debug("New Session ID is %.8X / Session Attributes are %.8X",
1851 (unsigned) sid, (unsigned) sattrs);
1857 * We don't want to listen forever unless the other side
1858 * successfully authenticates itself. So we set up an alarm which is
1859 * cleared after successful authentication. A limit of zero
1860 * indicates no limit. Note that we don't set the alarm in debugging
1861 * mode; it is just annoying to have the server exit just when you
1862 * are about to discover the bug.
1864 signal(SIGALRM, grace_alarm_handler);
1866 alarm(options.login_grace_time);
1868 sshd_exchange_identification(sock_in, sock_out);
1869 #if defined(AFS_KRB5)
1870 /* If machine has AFS, set process authentication group. */
1875 #endif /* AFS || AFS_KRB5 */
1877 /* In inetd mode, generate ephemeral key only for proto 1 connections */
1878 if (!compat20 && inetd_flag && sensitive_data.server_key == NULL)
1879 generate_ephemeral_server_key();
1881 packet_set_nonblocking();
1883 /* allocate authentication context */
1884 authctxt = xcalloc(1, sizeof(*authctxt));
1886 authctxt->loginmsg = &loginmsg;
1888 /* XXX global for cleanup, access from other modules */
1889 the_authctxt = authctxt;
1891 /* prepare buffer to collect messages to display to user after login */
1892 buffer_init(&loginmsg);
1895 if (privsep_preauth(authctxt) == 1)
1898 /* perform the key exchange */
1899 /* authenticate user and start session */
1902 do_authentication2(authctxt);
1905 do_authentication(authctxt);
1908 * If we use privilege separation, the unprivileged child transfers
1909 * the current keystate and exits
1912 mm_send_keystate(pmonitor);
1918 * Cancel the alarm we set to limit the time taken for
1922 signal(SIGALRM, SIG_DFL);
1923 authctxt->authenticated = 1;
1924 if (startup_pipe != -1) {
1925 close(startup_pipe);
1929 #ifdef SSH_AUDIT_EVENTS
1930 audit_event(SSH_AUTH_SUCCESS);
1934 if (options.gss_authentication) {
1935 temporarily_use_uid(authctxt->pw);
1936 ssh_gssapi_storecreds();
1941 if (options.use_pam) {
1948 * In privilege separation, we fork another child and prepare
1949 * file descriptor passing.
1952 privsep_postauth(authctxt);
1953 /* the monitor process [priv] will not return */
1955 destroy_sensitive_data();
1958 /* Start session. */
1959 do_authenticated(authctxt);
1961 /* The connection has been terminated. */
1962 verbose("Closing connection to %.100s", remote_ip);
1965 if (options.use_pam)
1967 #endif /* USE_PAM */
1969 #ifdef SSH_AUDIT_EVENTS
1970 PRIVSEP(audit_event(SSH_CONNECTION_CLOSE));
1982 * Decrypt session_key_int using our private server key and private host key
1983 * (key with larger modulus first).
1986 ssh1_session_key(BIGNUM *session_key_int)
1990 if (BN_cmp(sensitive_data.server_key->rsa->n,
1991 sensitive_data.ssh1_host_key->rsa->n) > 0) {
1992 /* Server key has bigger modulus. */
1993 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1994 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1995 SSH_KEY_BITS_RESERVED) {
1996 fatal("do_connection: %s: "
1997 "server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1998 get_remote_ipaddr(),
1999 BN_num_bits(sensitive_data.server_key->rsa->n),
2000 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
2001 SSH_KEY_BITS_RESERVED);
2003 if (rsa_private_decrypt(session_key_int, session_key_int,
2004 sensitive_data.server_key->rsa) <= 0)
2006 if (rsa_private_decrypt(session_key_int, session_key_int,
2007 sensitive_data.ssh1_host_key->rsa) <= 0)
2010 /* Host key has bigger modulus (or they are equal). */
2011 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
2012 BN_num_bits(sensitive_data.server_key->rsa->n) +
2013 SSH_KEY_BITS_RESERVED) {
2014 fatal("do_connection: %s: "
2015 "host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
2016 get_remote_ipaddr(),
2017 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
2018 BN_num_bits(sensitive_data.server_key->rsa->n),
2019 SSH_KEY_BITS_RESERVED);
2021 if (rsa_private_decrypt(session_key_int, session_key_int,
2022 sensitive_data.ssh1_host_key->rsa) < 0)
2024 if (rsa_private_decrypt(session_key_int, session_key_int,
2025 sensitive_data.server_key->rsa) < 0)
2038 BIGNUM *session_key_int;
2039 u_char session_key[SSH_SESSION_KEY_LENGTH];
2041 u_int cipher_type, auth_mask, protocol_flags;
2045 * Generate check bytes that the client must send back in the user
2046 * packet in order for it to be accepted; this is used to defy ip
2047 * spoofing attacks. Note that this only works against somebody
2048 * doing IP spoofing from a remote machine; any machine on the local
2049 * network can still see outgoing packets and catch the random
2050 * cookie. This only affects rhosts authentication, and this is one
2051 * of the reasons why it is inherently insecure.
2053 for (i = 0; i < 8; i++) {
2056 cookie[i] = rnd & 0xff;
2061 * Send our public key. We include in the packet 64 bits of random
2062 * data that must be matched in the reply in order to prevent IP
2065 packet_start(SSH_SMSG_PUBLIC_KEY);
2066 for (i = 0; i < 8; i++)
2067 packet_put_char(cookie[i]);
2069 /* Store our public server RSA key. */
2070 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
2071 packet_put_bignum(sensitive_data.server_key->rsa->e);
2072 packet_put_bignum(sensitive_data.server_key->rsa->n);
2074 /* Store our public host RSA key. */
2075 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
2076 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
2077 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
2079 /* Put protocol flags. */
2080 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
2082 /* Declare which ciphers we support. */
2083 packet_put_int(cipher_mask_ssh1(0));
2085 /* Declare supported authentication types. */
2087 if (options.rhosts_rsa_authentication)
2088 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
2089 if (options.rsa_authentication)
2090 auth_mask |= 1 << SSH_AUTH_RSA;
2091 if (options.challenge_response_authentication == 1)
2092 auth_mask |= 1 << SSH_AUTH_TIS;
2093 if (options.password_authentication)
2094 auth_mask |= 1 << SSH_AUTH_PASSWORD;
2095 packet_put_int(auth_mask);
2097 /* Send the packet and wait for it to be sent. */
2099 packet_write_wait();
2101 debug("Sent %d bit server key and %d bit host key.",
2102 BN_num_bits(sensitive_data.server_key->rsa->n),
2103 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
2105 /* Read clients reply (cipher type and session key). */
2106 packet_read_expect(SSH_CMSG_SESSION_KEY);
2108 /* Get cipher type and check whether we accept this. */
2109 cipher_type = packet_get_char();
2111 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
2112 packet_disconnect("Warning: client selects unsupported cipher.");
2114 /* Get check bytes from the packet. These must match those we
2115 sent earlier with the public key packet. */
2116 for (i = 0; i < 8; i++)
2117 if (cookie[i] != packet_get_char())
2118 packet_disconnect("IP Spoofing check bytes do not match.");
2120 debug("Encryption type: %.200s", cipher_name(cipher_type));
2122 /* Get the encrypted integer. */
2123 if ((session_key_int = BN_new()) == NULL)
2124 fatal("do_ssh1_kex: BN_new failed");
2125 packet_get_bignum(session_key_int);
2127 protocol_flags = packet_get_int();
2128 packet_set_protocol_flags(protocol_flags);
2131 /* Decrypt session_key_int using host/server keys */
2132 rsafail = PRIVSEP(ssh1_session_key(session_key_int));
2135 * Extract session key from the decrypted integer. The key is in the
2136 * least significant 256 bits of the integer; the first byte of the
2137 * key is in the highest bits.
2140 (void) BN_mask_bits(session_key_int, sizeof(session_key) * 8);
2141 len = BN_num_bytes(session_key_int);
2142 if (len < 0 || (u_int)len > sizeof(session_key)) {
2143 error("do_ssh1_kex: bad session key len from %s: "
2144 "session_key_int %d > sizeof(session_key) %lu",
2145 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
2148 memset(session_key, 0, sizeof(session_key));
2149 BN_bn2bin(session_key_int,
2150 session_key + sizeof(session_key) - len);
2152 derive_ssh1_session_id(
2153 sensitive_data.ssh1_host_key->rsa->n,
2154 sensitive_data.server_key->rsa->n,
2155 cookie, session_id);
2157 * Xor the first 16 bytes of the session key with the
2160 for (i = 0; i < 16; i++)
2161 session_key[i] ^= session_id[i];
2165 int bytes = BN_num_bytes(session_key_int);
2166 u_char *buf = xmalloc(bytes);
2169 logit("do_connection: generating a fake encryption key");
2170 BN_bn2bin(session_key_int, buf);
2172 MD5_Update(&md, buf, bytes);
2173 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
2174 MD5_Final(session_key, &md);
2176 MD5_Update(&md, session_key, 16);
2177 MD5_Update(&md, buf, bytes);
2178 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
2179 MD5_Final(session_key + 16, &md);
2180 memset(buf, 0, bytes);
2182 for (i = 0; i < 16; i++)
2183 session_id[i] = session_key[i] ^ session_key[i + 16];
2185 /* Destroy the private and public keys. No longer. */
2186 destroy_sensitive_data();
2189 mm_ssh1_session_id(session_id);
2191 /* Destroy the decrypted integer. It is no longer needed. */
2192 BN_clear_free(session_key_int);
2194 /* Set the session key. From this on all communications will be encrypted. */
2195 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
2197 /* Destroy our copy of the session key. It is no longer needed. */
2198 memset(session_key, 0, sizeof(session_key));
2200 debug("Received session key; encryption turned on.");
2202 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */
2203 packet_start(SSH_SMSG_SUCCESS);
2205 packet_write_wait();
2209 * SSH2 key exchange: diffie-hellman-group1-sha1
2217 debug ("MYFLAG IS %d", myflag);
2218 if (options.ciphers != NULL) {
2219 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2220 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
2221 } else if (options.none_enabled == 1) {
2222 debug ("WARNING: None cipher enabled");
2223 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2224 myproposal[PROPOSAL_ENC_ALGS_STOC] = KEX_ENCRYPT_INCLUDE_NONE;
2226 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
2227 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
2228 myproposal[PROPOSAL_ENC_ALGS_STOC] =
2229 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
2231 if (options.macs != NULL) {
2232 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
2233 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
2235 if (options.compression == COMP_NONE) {
2236 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2237 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
2238 } else if (options.compression == COMP_DELAYED) {
2239 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
2240 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com";
2243 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
2249 char *newstr = NULL;
2250 orig = myproposal[PROPOSAL_KEX_ALGS];
2253 * If we don't have a host key, then there's no point advertising
2254 * the other key exchange algorithms
2257 if (strlen(myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS]) == 0)
2260 if (options.gss_keyex)
2261 gss = ssh_gssapi_server_mechanisms();
2266 xasprintf(&newstr, "%s,%s", gss, orig);
2273 * If we've got GSSAPI mechanisms, then we've got the 'null' host
2274 * key alg, but we can't tell people about it unless its the only
2275 * host key algorithm we support
2277 if (gss && (strlen(myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS])) == 0)
2278 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = "null";
2281 myproposal[PROPOSAL_KEX_ALGS] = newstr;
2283 fatal("No supported key exchange algorithms");
2287 /* start key exchange */
2288 /* start key exchange */
2289 kex = kex_setup(myproposal);
2290 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
2291 kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
2292 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
2293 kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
2295 kex->kex[KEX_GSS_GRP1_SHA1] = kexgss_server;
2296 kex->kex[KEX_GSS_GRP14_SHA1] = kexgss_server;
2297 kex->kex[KEX_GSS_GEX_SHA1] = kexgss_server;
2300 kex->client_version_string=client_version_string;
2301 kex->server_version_string=server_version_string;
2302 kex->load_host_key=&get_hostkey_by_type;
2303 kex->host_key_index=&get_hostkey_index;
2307 dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
2309 session_id2 = kex->session_id;
2310 session_id2_len = kex->session_id_len;
2313 /* send 1st encrypted/maced/compressed message */
2314 packet_start(SSH2_MSG_IGNORE);
2315 packet_put_cstring("markus");
2317 packet_write_wait();
2322 /* server specific fatal cleanup */
2327 do_cleanup(the_authctxt);
2328 #ifdef SSH_AUDIT_EVENTS
2329 /* done after do_cleanup so it can cancel the PAM auth 'thread' */
2330 if (!use_privsep || mm_is_monitor())
2331 audit_event(SSH_CONNECTION_ABANDON);