2 * Author: Tatu Ylonen <ylo@cs.hut.fi>
3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * This program is the ssh daemon. It listens for connections from clients,
6 * and performs authentication, executes use commands or shell, and forwards
7 * information to/from the application to the user client over an encrypted
8 * connection. This can also handle forwarding of X11, TCP/IP, and
9 * authentication agent connections.
11 * As far as I am concerned, the code I have written for this software
12 * can be used freely for any purpose. Any derived versions of this
13 * software must be clearly marked as such, and if the derived work is
14 * incompatible with the protocol description in the RFC file, it must be
15 * called by a name other than "ssh" or "Secure Shell".
17 * SSH2 implementation:
18 * Privilege Separation:
20 * Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved.
21 * Copyright (c) 2002 Niels Provos. All rights reserved.
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
26 * 1. Redistributions of source code must retain the above copyright
27 * notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 * notice, this list of conditions and the following disclaimer in the
30 * documentation and/or other materials provided with the distribution.
32 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
33 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
34 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
35 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
36 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
37 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
38 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
39 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
40 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
41 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
45 RCSID("$OpenBSD: sshd.c,v 1.293 2004/06/14 01:44:39 djm Exp $");
47 #include <openssl/dh.h>
48 #include <openssl/bn.h>
49 #include <openssl/md5.h>
50 #include <openssl/rand.h>
51 #ifdef HAVE_SECUREWARE
52 #include <sys/security.h>
72 #include "myproposal.h"
74 #include "pathnames.h"
82 #include "monitor_mm.h"
84 #include "monitor_wrap.h"
85 #include "monitor_fdpass.h"
90 int allow_severity = LOG_INFO;
91 int deny_severity = LOG_WARNING;
98 #ifdef HAVE___PROGNAME
99 extern char *__progname;
104 /* Server configuration options. */
105 ServerOptions options;
107 /* Name of the server configuration file. */
108 char *config_file_name = _PATH_SERVER_CONFIG_FILE;
111 * Flag indicating whether IPv4 or IPv6. This can be set on the command line.
112 * Default value is AF_UNSPEC means both IPv4 and IPv6.
114 int IPv4or6 = AF_UNSPEC;
117 * Debug mode flag. This can be set on the command line. If debug
118 * mode is enabled, extra debugging output will be sent to the system
119 * log, the daemon will not go to background, and will exit after processing
120 * the first connection.
124 /* Flag indicating that the daemon should only test the configuration and keys. */
127 /* Flag indicating that the daemon is being started from inetd. */
130 /* Flag indicating that sshd should not detach and become a daemon. */
131 int no_daemon_flag = 0;
133 /* debug goes to stderr unless inetd_flag is set */
136 /* Saved arguments to main(). */
141 * The sockets that the server is listening; this is used in the SIGHUP
144 #define MAX_LISTEN_SOCKS 16
145 int listen_socks[MAX_LISTEN_SOCKS];
146 int num_listen_socks = 0;
149 * the client's version string, passed by sshd2 in compat mode. if != NULL,
150 * sshd will skip the version-number exchange
152 char *client_version_string = NULL;
153 char *server_version_string = NULL;
155 /* for rekeying XXX fixme */
159 * Any really sensitive data in the application is contained in this
160 * structure. The idea is that this structure could be locked into memory so
161 * that the pages do not get written into swap. However, there are some
162 * problems. The private key contains BIGNUMs, and we do not (in principle)
163 * have access to the internals of them, and locking just the structure is
164 * not very useful. Currently, memory locking is not implemented.
167 Key *server_key; /* ephemeral server key */
168 Key *ssh1_host_key; /* ssh1 host key */
169 Key **host_keys; /* all private host keys */
172 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
176 * Flag indicating whether the RSA server key needs to be regenerated.
177 * Is set in the SIGALRM handler and cleared when the key is regenerated.
179 static volatile sig_atomic_t key_do_regen = 0;
181 /* This is set to true when a signal is received. */
182 static volatile sig_atomic_t received_sighup = 0;
183 static volatile sig_atomic_t received_sigterm = 0;
185 /* session identifier, used by RSA-auth */
186 u_char session_id[16];
189 u_char *session_id2 = NULL;
190 u_int session_id2_len = 0;
192 /* record remote hostname or ip */
193 u_int utmp_len = MAXHOSTNAMELEN;
195 /* options.max_startup sized array of fd ints */
196 int *startup_pipes = NULL;
197 int startup_pipe; /* in child */
199 /* variables used for privilege separation */
201 struct monitor *pmonitor = NULL;
203 /* message to be displayed after login */
206 /* global authentication context */
207 Authctxt *the_authctxt = NULL;
209 /* Prototypes for various functions defined later in this file. */
210 void destroy_sensitive_data(void);
211 void demote_sensitive_data(void);
213 static void do_ssh1_kex(void);
214 static void do_ssh2_kex(void);
217 * Close all listening sockets
220 close_listen_socks(void)
224 for (i = 0; i < num_listen_socks; i++)
225 close(listen_socks[i]);
226 num_listen_socks = -1;
230 close_startup_pipes(void)
235 for (i = 0; i < options.max_startups; i++)
236 if (startup_pipes[i] != -1)
237 close(startup_pipes[i]);
241 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
242 * the effect is to reread the configuration file (and to regenerate
246 sighup_handler(int sig)
248 int save_errno = errno;
251 signal(SIGHUP, sighup_handler);
256 * Called from the main program after receiving SIGHUP.
257 * Restarts the server.
262 logit("Received SIGHUP; restarting.");
263 close_listen_socks();
264 close_startup_pipes();
265 execv(saved_argv[0], saved_argv);
266 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0],
272 * Generic signal handler for terminating signals in the master daemon.
275 sigterm_handler(int sig)
277 received_sigterm = sig;
281 * SIGCHLD handler. This is called whenever a child dies. This will then
282 * reap any zombies left by exited children.
285 main_sigchld_handler(int sig)
287 int save_errno = errno;
291 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
292 (pid < 0 && errno == EINTR))
295 signal(SIGCHLD, main_sigchld_handler);
300 * Signal handler for the alarm after the login grace period has expired.
303 grace_alarm_handler(int sig)
305 /* XXX no idea how fix this signal handler */
307 if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0)
308 kill(pmonitor->m_pid, SIGALRM);
310 /* Log error and exit. */
311 fatal("Timeout before authentication for %s", get_remote_ipaddr());
315 * Signal handler for the key regeneration alarm. Note that this
316 * alarm only occurs in the daemon waiting for connections, and it does not
317 * do anything with the private key or random state before forking.
318 * Thus there should be no concurrency control/asynchronous execution
322 generate_ephemeral_server_key(void)
327 verbose("Generating %s%d bit RSA key.",
328 sensitive_data.server_key ? "new " : "", options.server_key_bits);
329 if (sensitive_data.server_key != NULL)
330 key_free(sensitive_data.server_key);
331 sensitive_data.server_key = key_generate(KEY_RSA1,
332 options.server_key_bits);
333 verbose("RSA key generation complete.");
335 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
338 sensitive_data.ssh1_cookie[i] = rnd & 0xff;
345 key_regeneration_alarm(int sig)
347 int save_errno = errno;
349 signal(SIGALRM, SIG_DFL);
355 sshd_exchange_identification(int sock_in, int sock_out)
358 int remote_major, remote_minor;
361 char buf[256]; /* Must not be larger than remote_version. */
362 char remote_version[256]; /* Must be at least as big as buf. */
364 if ((options.protocol & SSH_PROTO_1) &&
365 (options.protocol & SSH_PROTO_2)) {
366 major = PROTOCOL_MAJOR_1;
368 } else if (options.protocol & SSH_PROTO_2) {
369 major = PROTOCOL_MAJOR_2;
370 minor = PROTOCOL_MINOR_2;
372 major = PROTOCOL_MAJOR_1;
373 minor = PROTOCOL_MINOR_1;
375 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
376 server_version_string = xstrdup(buf);
378 /* Send our protocol version identification. */
379 if (atomicio(vwrite, sock_out, server_version_string,
380 strlen(server_version_string))
381 != strlen(server_version_string)) {
382 logit("Could not write ident string to %s", get_remote_ipaddr());
386 /* Read other sides version identification. */
387 memset(buf, 0, sizeof(buf));
388 for (i = 0; i < sizeof(buf) - 1; i++) {
389 if (atomicio(read, sock_in, &buf[i], 1) != 1) {
390 logit("Did not receive identification string from %s",
391 get_remote_ipaddr());
394 if (buf[i] == '\r') {
396 /* Kludge for F-Secure Macintosh < 1.0.2 */
398 strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
402 if (buf[i] == '\n') {
407 buf[sizeof(buf) - 1] = 0;
408 client_version_string = xstrdup(buf);
411 * Check that the versions match. In future this might accept
412 * several versions and set appropriate flags to handle them.
414 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
415 &remote_major, &remote_minor, remote_version) != 3) {
416 s = "Protocol mismatch.\n";
417 (void) atomicio(vwrite, sock_out, s, strlen(s));
420 logit("Bad protocol version identification '%.100s' from %s",
421 client_version_string, get_remote_ipaddr());
424 debug("Client protocol version %d.%d; client software version %.100s",
425 remote_major, remote_minor, remote_version);
427 compat_datafellows(remote_version);
429 if (datafellows & SSH_BUG_PROBE) {
430 logit("probed from %s with %s. Don't panic.",
431 get_remote_ipaddr(), client_version_string);
435 if (datafellows & SSH_BUG_SCANNER) {
436 logit("scanned from %s with %s. Don't panic.",
437 get_remote_ipaddr(), client_version_string);
442 switch (remote_major) {
444 if (remote_minor == 99) {
445 if (options.protocol & SSH_PROTO_2)
451 if (!(options.protocol & SSH_PROTO_1)) {
455 if (remote_minor < 3) {
456 packet_disconnect("Your ssh version is too old and "
457 "is no longer supported. Please install a newer version.");
458 } else if (remote_minor == 3) {
459 /* note that this disables agent-forwarding */
464 if (options.protocol & SSH_PROTO_2) {
473 chop(server_version_string);
474 debug("Local version string %.200s", server_version_string);
477 s = "Protocol major versions differ.\n";
478 (void) atomicio(vwrite, sock_out, s, strlen(s));
481 logit("Protocol major versions differ for %s: %.200s vs. %.200s",
483 server_version_string, client_version_string);
488 /* Destroy the host and server keys. They will no longer be needed. */
490 destroy_sensitive_data(void)
494 if (sensitive_data.server_key) {
495 key_free(sensitive_data.server_key);
496 sensitive_data.server_key = NULL;
498 for (i = 0; i < options.num_host_key_files; i++) {
499 if (sensitive_data.host_keys[i]) {
500 key_free(sensitive_data.host_keys[i]);
501 sensitive_data.host_keys[i] = NULL;
504 sensitive_data.ssh1_host_key = NULL;
505 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
508 /* Demote private to public keys for network child */
510 demote_sensitive_data(void)
515 if (sensitive_data.server_key) {
516 tmp = key_demote(sensitive_data.server_key);
517 key_free(sensitive_data.server_key);
518 sensitive_data.server_key = tmp;
521 for (i = 0; i < options.num_host_key_files; i++) {
522 if (sensitive_data.host_keys[i]) {
523 tmp = key_demote(sensitive_data.host_keys[i]);
524 key_free(sensitive_data.host_keys[i]);
525 sensitive_data.host_keys[i] = tmp;
526 if (tmp->type == KEY_RSA1)
527 sensitive_data.ssh1_host_key = tmp;
531 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */
535 privsep_preauth_child(void)
542 /* Enable challenge-response authentication for privilege separation */
543 privsep_challenge_enable();
545 for (i = 0; i < 256; i++)
546 rnd[i] = arc4random();
547 RAND_seed(rnd, sizeof(rnd));
549 /* Demote the private keys to public keys. */
550 demote_sensitive_data();
552 if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
553 fatal("Privilege separation user %s does not exist",
555 memset(pw->pw_passwd, 0, strlen(pw->pw_passwd));
558 /* Change our root directory */
559 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
560 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
562 if (chdir("/") == -1)
563 fatal("chdir(\"/\"): %s", strerror(errno));
565 /* Drop our privileges */
566 debug3("privsep user:group %u:%u", (u_int)pw->pw_uid,
569 /* XXX not ready, too heavy after chroot */
570 do_setusercontext(pw);
572 gidset[0] = pw->pw_gid;
573 if (setgroups(1, gidset) < 0)
574 fatal("setgroups: %.100s", strerror(errno));
575 permanently_set_uid(pw);
580 privsep_preauth(Authctxt *authctxt)
585 /* Set up unprivileged child process to deal with network data */
586 pmonitor = monitor_init();
587 /* Store a pointer to the kex for later rekeying */
588 pmonitor->m_pkex = &xxx_kex;
592 fatal("fork of unprivileged child failed");
593 } else if (pid != 0) {
594 debug2("Network child is on pid %ld", (long)pid);
596 close(pmonitor->m_recvfd);
597 pmonitor->m_pid = pid;
598 monitor_child_preauth(authctxt, pmonitor);
599 close(pmonitor->m_sendfd);
602 monitor_sync(pmonitor);
604 /* Wait for the child's exit status */
605 while (waitpid(pid, &status, 0) < 0)
612 close(pmonitor->m_sendfd);
614 /* Demote the child */
615 if (getuid() == 0 || geteuid() == 0)
616 privsep_preauth_child();
617 setproctitle("%s", "[net]");
623 privsep_postauth(Authctxt *authctxt)
625 #ifdef DISABLE_FD_PASSING
628 if (authctxt->pw->pw_uid == 0 || options.use_login) {
630 /* File descriptor passing is broken or root login */
631 monitor_apply_keystate(pmonitor);
636 /* Authentication complete */
638 if (startup_pipe != -1) {
643 /* New socket pair */
644 monitor_reinit(pmonitor);
646 pmonitor->m_pid = fork();
647 if (pmonitor->m_pid == -1)
648 fatal("fork of unprivileged child failed");
649 else if (pmonitor->m_pid != 0) {
650 debug2("User child is on pid %ld", (long)pmonitor->m_pid);
651 close(pmonitor->m_recvfd);
652 monitor_child_postauth(pmonitor);
658 close(pmonitor->m_sendfd);
660 /* Demote the private keys to public keys. */
661 demote_sensitive_data();
663 /* Drop privileges */
664 do_setusercontext(authctxt->pw);
666 /* It is safe now to apply the key state */
667 monitor_apply_keystate(pmonitor);
671 list_hostkey_types(void)
679 for (i = 0; i < options.num_host_key_files; i++) {
680 Key *key = sensitive_data.host_keys[i];
686 if (buffer_len(&b) > 0)
687 buffer_append(&b, ",", 1);
688 p = key_ssh_name(key);
689 buffer_append(&b, p, strlen(p));
693 buffer_append(&b, "\0", 1);
694 ret = xstrdup(buffer_ptr(&b));
696 debug("list_hostkey_types: %s", ret);
701 get_hostkey_by_type(int type)
705 for (i = 0; i < options.num_host_key_files; i++) {
706 Key *key = sensitive_data.host_keys[i];
707 if (key != NULL && key->type == type)
714 get_hostkey_by_index(int ind)
716 if (ind < 0 || ind >= options.num_host_key_files)
718 return (sensitive_data.host_keys[ind]);
722 get_hostkey_index(Key *key)
726 for (i = 0; i < options.num_host_key_files; i++) {
727 if (key == sensitive_data.host_keys[i])
734 * returns 1 if connection should be dropped, 0 otherwise.
735 * dropping starts at connection #max_startups_begin with a probability
736 * of (max_startups_rate/100). the probability increases linearly until
737 * all connections are dropped for startups > max_startups
740 drop_connection(int startups)
744 if (startups < options.max_startups_begin)
746 if (startups >= options.max_startups)
748 if (options.max_startups_rate == 100)
751 p = 100 - options.max_startups_rate;
752 p *= startups - options.max_startups_begin;
753 p /= (double) (options.max_startups - options.max_startups_begin);
754 p += options.max_startups_rate;
756 r = arc4random() / (double) UINT_MAX;
758 debug("drop_connection: p %g, r %g", p, r);
759 return (r < p) ? 1 : 0;
765 fprintf(stderr, "%s, %s\n",
766 SSH_VERSION, SSLeay_version(SSLEAY_VERSION));
768 "usage: sshd [-46Ddeiqt] [-b bits] [-f config_file] [-g login_grace_time]\n"
769 " [-h host_key_file] [-k key_gen_time] [-o option] [-p port] [-u len]\n"
775 * Main program for the daemon.
778 main(int ac, char **av)
782 int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
786 struct sockaddr_storage from;
787 const char *remote_ip;
791 char ntop[NI_MAXHOST], strport[NI_MAXSERV];
793 int listen_sock, maxfd;
798 int ret, key_used = 0;
800 #ifdef HAVE_SECUREWARE
801 (void)set_auth_parameters(ac, av);
803 __progname = ssh_get_progname(av[0]);
806 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */
808 saved_argv = xmalloc(sizeof(*saved_argv) * (ac + 1));
809 for (i = 0; i < ac; i++)
810 saved_argv[i] = xstrdup(av[i]);
811 saved_argv[i] = NULL;
813 #ifndef HAVE_SETPROCTITLE
814 /* Prepare for later setproctitle emulation */
815 compat_init_setproctitle(ac, av);
819 if (geteuid() == 0 && setgroups(0, NULL) == -1)
820 debug("setgroups(): %.200s", strerror(errno));
822 /* Initialize configuration options to their default values. */
823 initialize_server_options(&options);
825 /* Parse command-line arguments. */
826 while ((opt = getopt(ac, av, "f:p:b:k:h:g:u:o:dDeiqtQ46")) != -1) {
835 config_file_name = optarg;
838 if (debug_flag == 0) {
840 options.log_level = SYSLOG_LEVEL_DEBUG1;
841 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3)
857 options.log_level = SYSLOG_LEVEL_QUIET;
860 options.server_key_bits = atoi(optarg);
863 options.ports_from_cmdline = 1;
864 if (options.num_ports >= MAX_PORTS) {
865 fprintf(stderr, "too many ports.\n");
868 options.ports[options.num_ports++] = a2port(optarg);
869 if (options.ports[options.num_ports-1] == 0) {
870 fprintf(stderr, "Bad port number.\n");
875 if ((options.login_grace_time = convtime(optarg)) == -1) {
876 fprintf(stderr, "Invalid login grace time.\n");
881 if ((options.key_regeneration_time = convtime(optarg)) == -1) {
882 fprintf(stderr, "Invalid key regeneration interval.\n");
887 if (options.num_host_key_files >= MAX_HOSTKEYS) {
888 fprintf(stderr, "too many host keys.\n");
891 options.host_key_files[options.num_host_key_files++] = optarg;
897 utmp_len = atoi(optarg);
898 if (utmp_len > MAXHOSTNAMELEN) {
899 fprintf(stderr, "Invalid utmp length.\n");
904 line = xstrdup(optarg);
905 if (process_server_config_line(&options, line,
906 "command-line", 0) != 0)
916 SSLeay_add_all_algorithms();
917 channel_set_af(IPv4or6);
920 * Force logging to stderr until we have loaded the private host
921 * key (unless started from inetd)
924 options.log_level == SYSLOG_LEVEL_NOT_SET ?
925 SYSLOG_LEVEL_INFO : options.log_level,
926 options.log_facility == SYSLOG_FACILITY_NOT_SET ?
927 SYSLOG_FACILITY_AUTH : options.log_facility,
928 log_stderr || !inetd_flag);
932 * Unset KRB5CCNAME, otherwise the user's session may inherit it from
935 unsetenv("KRB5CCNAME");
938 /* Cray can define user privs drop all privs now!
939 * Not needed on PRIV_SU systems!
946 /* Read server configuration options from the configuration file. */
947 read_server_config(&options, config_file_name);
949 /* Fill in default values for those options not explicitly set. */
950 fill_default_server_options(&options);
952 /* Check that there are no remaining arguments. */
954 fprintf(stderr, "Extra argument %s.\n", av[optind]);
958 debug("sshd version %.100s", SSH_VERSION);
960 /* load private host keys */
961 sensitive_data.host_keys = xmalloc(options.num_host_key_files *
963 for (i = 0; i < options.num_host_key_files; i++)
964 sensitive_data.host_keys[i] = NULL;
965 sensitive_data.server_key = NULL;
966 sensitive_data.ssh1_host_key = NULL;
967 sensitive_data.have_ssh1_key = 0;
968 sensitive_data.have_ssh2_key = 0;
970 for (i = 0; i < options.num_host_key_files; i++) {
971 key = key_load_private(options.host_key_files[i], "", NULL);
972 sensitive_data.host_keys[i] = key;
974 error("Could not load host key: %s",
975 options.host_key_files[i]);
976 sensitive_data.host_keys[i] = NULL;
981 sensitive_data.ssh1_host_key = key;
982 sensitive_data.have_ssh1_key = 1;
986 sensitive_data.have_ssh2_key = 1;
989 debug("private host key: #%d type %d %s", i, key->type,
992 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
993 logit("Disabling protocol version 1. Could not load host key");
994 options.protocol &= ~SSH_PROTO_1;
996 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
997 logit("Disabling protocol version 2. Could not load host key");
998 options.protocol &= ~SSH_PROTO_2;
1000 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
1001 logit("sshd: no hostkeys available -- exiting.");
1005 /* Check certain values for sanity. */
1006 if (options.protocol & SSH_PROTO_1) {
1007 if (options.server_key_bits < 512 ||
1008 options.server_key_bits > 32768) {
1009 fprintf(stderr, "Bad server key size.\n");
1013 * Check that server and host key lengths differ sufficiently. This
1014 * is necessary to make double encryption work with rsaref. Oh, I
1015 * hate software patents. I dont know if this can go? Niels
1017 if (options.server_key_bits >
1018 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) -
1019 SSH_KEY_BITS_RESERVED && options.server_key_bits <
1020 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1021 SSH_KEY_BITS_RESERVED) {
1022 options.server_key_bits =
1023 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) +
1024 SSH_KEY_BITS_RESERVED;
1025 debug("Forcing server key to %d bits to make it differ from host key.",
1026 options.server_key_bits);
1034 if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
1035 fatal("Privilege separation user %s does not exist",
1037 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) ||
1038 (S_ISDIR(st.st_mode) == 0))
1039 fatal("Missing privilege separation directory: %s",
1040 _PATH_PRIVSEP_CHROOT_DIR);
1043 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) &&
1044 (st.st_uid != getuid () ||
1045 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0))
1047 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)
1049 fatal("%s must be owned by root and not group or "
1050 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR);
1053 /* Configuration looks good, so exit if in test mode. */
1058 * Clear out any supplemental groups we may have inherited. This
1059 * prevents inadvertent creation of files with bad modes (in the
1060 * portable version at least, it's certainly possible for PAM
1061 * to create a file, and we can't control the code in every
1062 * module which might be used).
1064 if (setgroups(0, NULL) < 0)
1065 debug("setgroups() failed: %.200s", strerror(errno));
1067 /* Initialize the log (it is reinitialized below in case we forked). */
1068 if (debug_flag && !inetd_flag)
1070 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1073 * If not in debugging mode, and not started from inetd, disconnect
1074 * from the controlling terminal, and fork. The original process
1077 if (!(debug_flag || inetd_flag || no_daemon_flag)) {
1080 #endif /* TIOCNOTTY */
1081 if (daemon(0, 0) < 0)
1082 fatal("daemon() failed: %.200s", strerror(errno));
1084 /* Disconnect from the controlling tty. */
1086 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
1088 (void) ioctl(fd, TIOCNOTTY, NULL);
1091 #endif /* TIOCNOTTY */
1093 /* Reinitialize the log (because of the fork above). */
1094 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1096 /* Initialize the random number generator. */
1099 /* Chdir to the root directory so that the current disk can be
1100 unmounted if desired. */
1103 /* ignore SIGPIPE */
1104 signal(SIGPIPE, SIG_IGN);
1106 /* Start listening for a socket, unless started from inetd. */
1109 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
1115 * We intentionally do not close the descriptors 0, 1, and 2
1116 * as our code for setting the descriptors won\'t work if
1117 * ttyfd happens to be one of those.
1119 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
1120 if (options.protocol & SSH_PROTO_1)
1121 generate_ephemeral_server_key();
1123 for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
1124 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
1126 if (num_listen_socks >= MAX_LISTEN_SOCKS)
1127 fatal("Too many listen sockets. "
1128 "Enlarge MAX_LISTEN_SOCKS");
1129 if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
1130 ntop, sizeof(ntop), strport, sizeof(strport),
1131 NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
1132 error("getnameinfo failed");
1135 /* Create socket for listening. */
1136 listen_sock = socket(ai->ai_family, ai->ai_socktype,
1138 if (listen_sock < 0) {
1139 /* kernel may not support ipv6 */
1140 verbose("socket: %.100s", strerror(errno));
1143 if (set_nonblock(listen_sock) == -1) {
1148 * Set socket options.
1149 * Allow local port reuse in TIME_WAIT.
1151 if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
1152 &on, sizeof(on)) == -1)
1153 error("setsockopt SO_REUSEADDR: %s", strerror(errno));
1155 debug("Bind to port %s on %s.", strport, ntop);
1157 /* Bind the socket to the desired port. */
1158 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1160 error("Bind to port %s on %s failed: %.200s.",
1161 strport, ntop, strerror(errno));
1165 listen_socks[num_listen_socks] = listen_sock;
1168 /* Start listening on the port. */
1169 logit("Server listening on %s port %s.", ntop, strport);
1170 if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0)
1171 fatal("listen: %.100s", strerror(errno));
1174 freeaddrinfo(options.listen_addrs);
1176 if (!num_listen_socks)
1177 fatal("Cannot bind any address.");
1179 if (options.protocol & SSH_PROTO_1)
1180 generate_ephemeral_server_key();
1183 * Arrange to restart on SIGHUP. The handler needs
1186 signal(SIGHUP, sighup_handler);
1188 signal(SIGTERM, sigterm_handler);
1189 signal(SIGQUIT, sigterm_handler);
1191 /* Arrange SIGCHLD to be caught. */
1192 signal(SIGCHLD, main_sigchld_handler);
1194 /* Write out the pid file after the sigterm handler is setup */
1197 * Record our pid in /var/run/sshd.pid to make it
1198 * easier to kill the correct sshd. We don't want to
1199 * do this before the bind above because the bind will
1200 * fail if there already is a daemon, and this will
1201 * overwrite any old pid in the file.
1203 f = fopen(options.pid_file, "wb");
1205 error("Couldn't create pid file \"%s\": %s",
1206 options.pid_file, strerror(errno));
1208 fprintf(f, "%ld\n", (long) getpid());
1213 /* setup fd set for listen */
1216 for (i = 0; i < num_listen_socks; i++)
1217 if (listen_socks[i] > maxfd)
1218 maxfd = listen_socks[i];
1219 /* pipes connected to unauthenticated childs */
1220 startup_pipes = xmalloc(options.max_startups * sizeof(int));
1221 for (i = 0; i < options.max_startups; i++)
1222 startup_pipes[i] = -1;
1225 * Stay listening for connections until the system crashes or
1226 * the daemon is killed with a signal.
1229 if (received_sighup)
1233 fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
1234 fdset = (fd_set *)xmalloc(fdsetsz);
1235 memset(fdset, 0, fdsetsz);
1237 for (i = 0; i < num_listen_socks; i++)
1238 FD_SET(listen_socks[i], fdset);
1239 for (i = 0; i < options.max_startups; i++)
1240 if (startup_pipes[i] != -1)
1241 FD_SET(startup_pipes[i], fdset);
1243 /* Wait in select until there is a connection. */
1244 ret = select(maxfd+1, fdset, NULL, NULL, NULL);
1245 if (ret < 0 && errno != EINTR)
1246 error("select: %.100s", strerror(errno));
1247 if (received_sigterm) {
1248 logit("Received signal %d; terminating.",
1249 (int) received_sigterm);
1250 close_listen_socks();
1251 unlink(options.pid_file);
1254 if (key_used && key_do_regen) {
1255 generate_ephemeral_server_key();
1262 for (i = 0; i < options.max_startups; i++)
1263 if (startup_pipes[i] != -1 &&
1264 FD_ISSET(startup_pipes[i], fdset)) {
1266 * the read end of the pipe is ready
1267 * if the child has closed the pipe
1268 * after successful authentication
1269 * or if the child has died
1271 close(startup_pipes[i]);
1272 startup_pipes[i] = -1;
1275 for (i = 0; i < num_listen_socks; i++) {
1276 if (!FD_ISSET(listen_socks[i], fdset))
1278 fromlen = sizeof(from);
1279 newsock = accept(listen_socks[i], (struct sockaddr *)&from,
1282 if (errno != EINTR && errno != EWOULDBLOCK)
1283 error("accept: %.100s", strerror(errno));
1286 if (unset_nonblock(newsock) == -1) {
1290 if (drop_connection(startups) == 1) {
1291 debug("drop connection #%d", startups);
1295 if (pipe(startup_p) == -1) {
1300 for (j = 0; j < options.max_startups; j++)
1301 if (startup_pipes[j] == -1) {
1302 startup_pipes[j] = startup_p[0];
1303 if (maxfd < startup_p[0])
1304 maxfd = startup_p[0];
1310 * Got connection. Fork a child to handle it, unless
1311 * we are in debugging mode.
1315 * In debugging mode. Close the listening
1316 * socket, and start processing the
1317 * connection without forking.
1319 debug("Server will not fork when running in debugging mode.");
1320 close_listen_socks();
1328 * Normal production daemon. Fork, and have
1329 * the child process the connection. The
1330 * parent continues listening.
1332 if ((pid = fork()) == 0) {
1334 * Child. Close the listening and max_startup
1335 * sockets. Start using the accepted socket.
1336 * Reinitialize logging (since our pid has
1337 * changed). We break out of the loop to handle
1340 startup_pipe = startup_p[1];
1341 close_startup_pipes();
1342 close_listen_socks();
1345 log_init(__progname, options.log_level, options.log_facility, log_stderr);
1350 /* Parent. Stay in the loop. */
1352 error("fork: %.100s", strerror(errno));
1354 debug("Forked child %ld.", (long)pid);
1356 close(startup_p[1]);
1358 /* Mark that the key has been used (it was "given" to the child). */
1359 if ((options.protocol & SSH_PROTO_1) &&
1361 /* Schedule server key regeneration alarm. */
1362 signal(SIGALRM, key_regeneration_alarm);
1363 alarm(options.key_regeneration_time);
1369 /* Close the new socket (the child is now taking care of it). */
1372 /* child process check (or debug mode) */
1373 if (num_listen_socks < 0)
1378 /* This is the child processing a new connection. */
1379 setproctitle("%s", "[accepted]");
1382 * Create a new session and process group since the 4.4BSD
1383 * setlogin() affects the entire process group. We don't
1384 * want the child to be able to affect the parent.
1386 #if !defined(SSHD_ACQUIRES_CTTY)
1388 * If setsid is called, on some platforms sshd will later acquire a
1389 * controlling terminal which will result in "could not set
1390 * controlling tty" errors.
1392 if (!debug_flag && !inetd_flag && setsid() < 0)
1393 error("setsid: %.100s", strerror(errno));
1397 * Disable the key regeneration alarm. We will not regenerate the
1398 * key since we are no longer in a position to give it to anyone. We
1399 * will not restart on SIGHUP since it no longer makes sense.
1402 signal(SIGALRM, SIG_DFL);
1403 signal(SIGHUP, SIG_DFL);
1404 signal(SIGTERM, SIG_DFL);
1405 signal(SIGQUIT, SIG_DFL);
1406 signal(SIGCHLD, SIG_DFL);
1407 signal(SIGINT, SIG_DFL);
1409 /* Set SO_KEEPALIVE if requested. */
1410 if (options.tcp_keep_alive &&
1411 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on,
1413 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1416 * Register our connection. This turns encryption off because we do
1419 packet_set_connection(sock_in, sock_out);
1421 remote_port = get_remote_port();
1422 remote_ip = get_remote_ipaddr();
1425 /* Check whether logins are denied from this host. */
1427 struct request_info req;
1429 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
1432 if (!hosts_access(&req)) {
1433 debug("Connection refused by tcp wrapper");
1436 fatal("libwrap refuse returns");
1439 #endif /* LIBWRAP */
1441 /* Log the connection. */
1442 verbose("Connection from %.500s port %d", remote_ip, remote_port);
1445 * We don\'t want to listen forever unless the other side
1446 * successfully authenticates itself. So we set up an alarm which is
1447 * cleared after successful authentication. A limit of zero
1448 * indicates no limit. Note that we don\'t set the alarm in debugging
1449 * mode; it is just annoying to have the server exit just when you
1450 * are about to discover the bug.
1452 signal(SIGALRM, grace_alarm_handler);
1454 alarm(options.login_grace_time);
1456 sshd_exchange_identification(sock_in, sock_out);
1458 packet_set_nonblocking();
1460 /* prepare buffers to collect authentication messages */
1461 buffer_init(&loginmsg);
1463 /* allocate authentication context */
1464 authctxt = xmalloc(sizeof(*authctxt));
1465 memset(authctxt, 0, sizeof(*authctxt));
1467 /* XXX global for cleanup, access from other modules */
1468 the_authctxt = authctxt;
1471 if (privsep_preauth(authctxt) == 1)
1474 /* perform the key exchange */
1475 /* authenticate user and start session */
1478 do_authentication2(authctxt);
1481 do_authentication(authctxt);
1484 * If we use privilege separation, the unprivileged child transfers
1485 * the current keystate and exits
1488 mm_send_keystate(pmonitor);
1494 * In privilege separation, we fork another child and prepare
1495 * file descriptor passing.
1498 privsep_postauth(authctxt);
1499 /* the monitor process [priv] will not return */
1501 destroy_sensitive_data();
1504 /* Start session. */
1505 do_authenticated(authctxt);
1507 /* The connection has been terminated. */
1508 verbose("Closing connection to %.100s", remote_ip);
1511 if (options.use_pam)
1513 #endif /* USE_PAM */
1524 * Decrypt session_key_int using our private server key and private host key
1525 * (key with larger modulus first).
1528 ssh1_session_key(BIGNUM *session_key_int)
1532 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1533 /* Server key has bigger modulus. */
1534 if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1535 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1536 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1537 get_remote_ipaddr(),
1538 BN_num_bits(sensitive_data.server_key->rsa->n),
1539 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1540 SSH_KEY_BITS_RESERVED);
1542 if (rsa_private_decrypt(session_key_int, session_key_int,
1543 sensitive_data.server_key->rsa) <= 0)
1545 if (rsa_private_decrypt(session_key_int, session_key_int,
1546 sensitive_data.ssh1_host_key->rsa) <= 0)
1549 /* Host key has bigger modulus (or they are equal). */
1550 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1551 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1552 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1553 get_remote_ipaddr(),
1554 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1555 BN_num_bits(sensitive_data.server_key->rsa->n),
1556 SSH_KEY_BITS_RESERVED);
1558 if (rsa_private_decrypt(session_key_int, session_key_int,
1559 sensitive_data.ssh1_host_key->rsa) < 0)
1561 if (rsa_private_decrypt(session_key_int, session_key_int,
1562 sensitive_data.server_key->rsa) < 0)
1575 BIGNUM *session_key_int;
1576 u_char session_key[SSH_SESSION_KEY_LENGTH];
1578 u_int cipher_type, auth_mask, protocol_flags;
1582 * Generate check bytes that the client must send back in the user
1583 * packet in order for it to be accepted; this is used to defy ip
1584 * spoofing attacks. Note that this only works against somebody
1585 * doing IP spoofing from a remote machine; any machine on the local
1586 * network can still see outgoing packets and catch the random
1587 * cookie. This only affects rhosts authentication, and this is one
1588 * of the reasons why it is inherently insecure.
1590 for (i = 0; i < 8; i++) {
1593 cookie[i] = rnd & 0xff;
1598 * Send our public key. We include in the packet 64 bits of random
1599 * data that must be matched in the reply in order to prevent IP
1602 packet_start(SSH_SMSG_PUBLIC_KEY);
1603 for (i = 0; i < 8; i++)
1604 packet_put_char(cookie[i]);
1606 /* Store our public server RSA key. */
1607 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1608 packet_put_bignum(sensitive_data.server_key->rsa->e);
1609 packet_put_bignum(sensitive_data.server_key->rsa->n);
1611 /* Store our public host RSA key. */
1612 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1613 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1614 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1616 /* Put protocol flags. */
1617 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1619 /* Declare which ciphers we support. */
1620 packet_put_int(cipher_mask_ssh1(0));
1622 /* Declare supported authentication types. */
1624 if (options.rhosts_rsa_authentication)
1625 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1626 if (options.rsa_authentication)
1627 auth_mask |= 1 << SSH_AUTH_RSA;
1628 if (options.challenge_response_authentication == 1)
1629 auth_mask |= 1 << SSH_AUTH_TIS;
1630 if (options.password_authentication)
1631 auth_mask |= 1 << SSH_AUTH_PASSWORD;
1632 packet_put_int(auth_mask);
1634 /* Send the packet and wait for it to be sent. */
1636 packet_write_wait();
1638 debug("Sent %d bit server key and %d bit host key.",
1639 BN_num_bits(sensitive_data.server_key->rsa->n),
1640 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1642 /* Read clients reply (cipher type and session key). */
1643 packet_read_expect(SSH_CMSG_SESSION_KEY);
1645 /* Get cipher type and check whether we accept this. */
1646 cipher_type = packet_get_char();
1648 if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1649 packet_disconnect("Warning: client selects unsupported cipher.");
1651 /* Get check bytes from the packet. These must match those we
1652 sent earlier with the public key packet. */
1653 for (i = 0; i < 8; i++)
1654 if (cookie[i] != packet_get_char())
1655 packet_disconnect("IP Spoofing check bytes do not match.");
1657 debug("Encryption type: %.200s", cipher_name(cipher_type));
1659 /* Get the encrypted integer. */
1660 if ((session_key_int = BN_new()) == NULL)
1661 fatal("do_ssh1_kex: BN_new failed");
1662 packet_get_bignum(session_key_int);
1664 protocol_flags = packet_get_int();
1665 packet_set_protocol_flags(protocol_flags);
1668 /* Decrypt session_key_int using host/server keys */
1669 rsafail = PRIVSEP(ssh1_session_key(session_key_int));
1672 * Extract session key from the decrypted integer. The key is in the
1673 * least significant 256 bits of the integer; the first byte of the
1674 * key is in the highest bits.
1677 BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1678 len = BN_num_bytes(session_key_int);
1679 if (len < 0 || len > sizeof(session_key)) {
1680 error("do_connection: bad session key len from %s: "
1681 "session_key_int %d > sizeof(session_key) %lu",
1682 get_remote_ipaddr(), len, (u_long)sizeof(session_key));
1685 memset(session_key, 0, sizeof(session_key));
1686 BN_bn2bin(session_key_int,
1687 session_key + sizeof(session_key) - len);
1689 derive_ssh1_session_id(
1690 sensitive_data.ssh1_host_key->rsa->n,
1691 sensitive_data.server_key->rsa->n,
1692 cookie, session_id);
1694 * Xor the first 16 bytes of the session key with the
1697 for (i = 0; i < 16; i++)
1698 session_key[i] ^= session_id[i];
1702 int bytes = BN_num_bytes(session_key_int);
1703 u_char *buf = xmalloc(bytes);
1706 logit("do_connection: generating a fake encryption key");
1707 BN_bn2bin(session_key_int, buf);
1709 MD5_Update(&md, buf, bytes);
1710 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1711 MD5_Final(session_key, &md);
1713 MD5_Update(&md, session_key, 16);
1714 MD5_Update(&md, buf, bytes);
1715 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1716 MD5_Final(session_key + 16, &md);
1717 memset(buf, 0, bytes);
1719 for (i = 0; i < 16; i++)
1720 session_id[i] = session_key[i] ^ session_key[i + 16];
1722 /* Destroy the private and public keys. No longer. */
1723 destroy_sensitive_data();
1726 mm_ssh1_session_id(session_id);
1728 /* Destroy the decrypted integer. It is no longer needed. */
1729 BN_clear_free(session_key_int);
1731 /* Set the session key. From this on all communications will be encrypted. */
1732 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1734 /* Destroy our copy of the session key. It is no longer needed. */
1735 memset(session_key, 0, sizeof(session_key));
1737 debug("Received session key; encryption turned on.");
1739 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */
1740 packet_start(SSH_SMSG_SUCCESS);
1742 packet_write_wait();
1746 * SSH2 key exchange: diffie-hellman-group1-sha1
1753 if (options.ciphers != NULL) {
1754 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1755 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1757 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1758 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
1759 myproposal[PROPOSAL_ENC_ALGS_STOC] =
1760 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
1762 if (options.macs != NULL) {
1763 myproposal[PROPOSAL_MAC_ALGS_CTOS] =
1764 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
1766 if (!options.compression) {
1767 myproposal[PROPOSAL_COMP_ALGS_CTOS] =
1768 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
1770 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
1772 /* start key exchange */
1773 kex = kex_setup(myproposal);
1774 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
1775 kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
1776 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
1778 kex->client_version_string=client_version_string;
1779 kex->server_version_string=server_version_string;
1780 kex->load_host_key=&get_hostkey_by_type;
1781 kex->host_key_index=&get_hostkey_index;
1785 dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
1787 session_id2 = kex->session_id;
1788 session_id2_len = kex->session_id_len;
1791 /* send 1st encrypted/maced/compressed message */
1792 packet_start(SSH2_MSG_IGNORE);
1793 packet_put_cstring("markus");
1795 packet_write_wait();
1800 /* server specific fatal cleanup */
1805 do_cleanup(the_authctxt);