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1 | /* $OpenBSD: sshd.c,v 1.356 2008/04/13 00:22:17 djm Exp $ */ | |
2 | /* | |
3 | * Author: Tatu Ylonen <ylo@cs.hut.fi> | |
4 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
5 | * All rights reserved | |
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. | |
11 | * | |
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". | |
17 | * | |
18 | * SSH2 implementation: | |
19 | * Privilege Separation: | |
20 | * | |
21 | * Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved. | |
22 | * Copyright (c) 2002 Niels Provos. All rights reserved. | |
23 | * | |
24 | * Redistribution and use in source and binary forms, with or without | |
25 | * modification, are permitted provided that the following conditions | |
26 | * are met: | |
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. | |
32 | * | |
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. | |
43 | */ | |
44 | ||
45 | #include "includes.h" | |
46 | ||
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> | |
52 | #endif | |
53 | #ifdef HAVE_SYS_TIME_H | |
54 | # include <sys/time.h> | |
55 | #endif | |
56 | #include "openbsd-compat/sys-tree.h" | |
57 | #include <sys/wait.h> | |
58 | ||
59 | #include <errno.h> | |
60 | #include <fcntl.h> | |
61 | #include <netdb.h> | |
62 | #ifdef HAVE_PATHS_H | |
63 | #include <paths.h> | |
64 | #endif | |
65 | #include <grp.h> | |
66 | #include <pwd.h> | |
67 | #include <signal.h> | |
68 | #include <stdarg.h> | |
69 | #include <stdio.h> | |
70 | #include <stdlib.h> | |
71 | #include <string.h> | |
72 | #include <unistd.h> | |
73 | ||
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" | |
79 | ||
80 | #ifdef HAVE_SECUREWARE | |
81 | #include <sys/security.h> | |
82 | #include <prot.h> | |
83 | #endif | |
84 | ||
85 | #include "xmalloc.h" | |
86 | #include "ssh.h" | |
87 | #include "ssh1.h" | |
88 | #include "ssh2.h" | |
89 | #include "rsa.h" | |
90 | #include "sshpty.h" | |
91 | #include "packet.h" | |
92 | #include "log.h" | |
93 | #include "buffer.h" | |
94 | #include "servconf.h" | |
95 | #include "uidswap.h" | |
96 | #include "compat.h" | |
97 | #include "cipher.h" | |
98 | #include "key.h" | |
99 | #include "kex.h" | |
100 | #include "dh.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" | |
107 | #include "auth.h" | |
108 | #include "misc.h" | |
109 | #include "msg.h" | |
110 | #include "dispatch.h" | |
111 | #include "channels.h" | |
112 | #include "session.h" | |
113 | #include "monitor_mm.h" | |
114 | #include "monitor.h" | |
115 | #ifdef GSSAPI | |
116 | #include "ssh-gss.h" | |
117 | #endif | |
118 | #include "monitor_wrap.h" | |
119 | #include "monitor_fdpass.h" | |
120 | #include "version.h" | |
121 | ||
122 | #ifdef LIBWRAP | |
123 | #include <tcpd.h> | |
124 | #include <syslog.h> | |
125 | int allow_severity; | |
126 | int deny_severity; | |
127 | #endif /* LIBWRAP */ | |
128 | ||
129 | #ifndef O_NOCTTY | |
130 | #define O_NOCTTY 0 | |
131 | #endif | |
132 | ||
133 | /* Re-exec fds */ | |
134 | #define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1) | |
135 | #define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2) | |
136 | #define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3) | |
137 | #define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4) | |
138 | ||
139 | extern char *__progname; | |
140 | ||
141 | /* Server configuration options. */ | |
142 | ServerOptions options; | |
143 | ||
144 | /* Name of the server configuration file. */ | |
145 | char *config_file_name = _PATH_SERVER_CONFIG_FILE; | |
146 | ||
147 | /* | |
148 | * Debug mode flag. This can be set on the command line. If debug | |
149 | * mode is enabled, extra debugging output will be sent to the system | |
150 | * log, the daemon will not go to background, and will exit after processing | |
151 | * the first connection. | |
152 | */ | |
153 | int debug_flag = 0; | |
154 | ||
155 | /* Flag indicating that the daemon should only test the configuration and keys. */ | |
156 | int test_flag = 0; | |
157 | ||
158 | /* Flag indicating that the daemon is being started from inetd. */ | |
159 | int inetd_flag = 0; | |
160 | ||
161 | /* Flag indicating that sshd should not detach and become a daemon. */ | |
162 | int no_daemon_flag = 0; | |
163 | ||
164 | /* debug goes to stderr unless inetd_flag is set */ | |
165 | int log_stderr = 0; | |
166 | ||
167 | /* Saved arguments to main(). */ | |
168 | char **saved_argv; | |
169 | int saved_argc; | |
170 | ||
171 | /* re-exec */ | |
172 | int rexeced_flag = 0; | |
173 | int rexec_flag = 1; | |
174 | int rexec_argc = 0; | |
175 | char **rexec_argv; | |
176 | ||
177 | /* | |
178 | * The sockets that the server is listening; this is used in the SIGHUP | |
179 | * signal handler. | |
180 | */ | |
181 | #define MAX_LISTEN_SOCKS 16 | |
182 | int listen_socks[MAX_LISTEN_SOCKS]; | |
183 | int num_listen_socks = 0; | |
184 | ||
185 | /* | |
186 | * the client's version string, passed by sshd2 in compat mode. if != NULL, | |
187 | * sshd will skip the version-number exchange | |
188 | */ | |
189 | char *client_version_string = NULL; | |
190 | char *server_version_string = NULL; | |
191 | ||
192 | /* for rekeying XXX fixme */ | |
193 | Kex *xxx_kex; | |
194 | ||
195 | /* | |
196 | * Any really sensitive data in the application is contained in this | |
197 | * structure. The idea is that this structure could be locked into memory so | |
198 | * that the pages do not get written into swap. However, there are some | |
199 | * problems. The private key contains BIGNUMs, and we do not (in principle) | |
200 | * have access to the internals of them, and locking just the structure is | |
201 | * not very useful. Currently, memory locking is not implemented. | |
202 | */ | |
203 | struct { | |
204 | Key *server_key; /* ephemeral server key */ | |
205 | Key *ssh1_host_key; /* ssh1 host key */ | |
206 | Key **host_keys; /* all private host keys */ | |
207 | int have_ssh1_key; | |
208 | int have_ssh2_key; | |
209 | u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH]; | |
210 | } sensitive_data; | |
211 | ||
212 | /* | |
213 | * Flag indicating whether the RSA server key needs to be regenerated. | |
214 | * Is set in the SIGALRM handler and cleared when the key is regenerated. | |
215 | */ | |
216 | static volatile sig_atomic_t key_do_regen = 0; | |
217 | ||
218 | /* This is set to true when a signal is received. */ | |
219 | static volatile sig_atomic_t received_sighup = 0; | |
220 | static volatile sig_atomic_t received_sigterm = 0; | |
221 | ||
222 | /* session identifier, used by RSA-auth */ | |
223 | u_char session_id[16]; | |
224 | ||
225 | /* same for ssh2 */ | |
226 | u_char *session_id2 = NULL; | |
227 | u_int session_id2_len = 0; | |
228 | ||
229 | /* record remote hostname or ip */ | |
230 | u_int utmp_len = MAXHOSTNAMELEN; | |
231 | ||
232 | /* options.max_startup sized array of fd ints */ | |
233 | int *startup_pipes = NULL; | |
234 | int startup_pipe; /* in child */ | |
235 | ||
236 | /* variables used for privilege separation */ | |
237 | int use_privsep = -1; | |
238 | struct monitor *pmonitor = NULL; | |
239 | ||
240 | /* global authentication context */ | |
241 | Authctxt *the_authctxt = NULL; | |
242 | ||
243 | /* sshd_config buffer */ | |
244 | Buffer cfg; | |
245 | ||
246 | /* message to be displayed after login */ | |
247 | Buffer loginmsg; | |
248 | ||
249 | /* Unprivileged user */ | |
250 | struct passwd *privsep_pw = NULL; | |
251 | ||
252 | /* Prototypes for various functions defined later in this file. */ | |
253 | void destroy_sensitive_data(void); | |
254 | void demote_sensitive_data(void); | |
255 | ||
256 | static void do_ssh1_kex(void); | |
257 | static void do_ssh2_kex(void); | |
258 | ||
259 | /* | |
260 | * Close all listening sockets | |
261 | */ | |
262 | static void | |
263 | close_listen_socks(void) | |
264 | { | |
265 | int i; | |
266 | ||
267 | for (i = 0; i < num_listen_socks; i++) | |
268 | close(listen_socks[i]); | |
269 | num_listen_socks = -1; | |
270 | } | |
271 | ||
272 | static void | |
273 | close_startup_pipes(void) | |
274 | { | |
275 | int i; | |
276 | ||
277 | if (startup_pipes) | |
278 | for (i = 0; i < options.max_startups; i++) | |
279 | if (startup_pipes[i] != -1) | |
280 | close(startup_pipes[i]); | |
281 | } | |
282 | ||
283 | /* | |
284 | * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; | |
285 | * the effect is to reread the configuration file (and to regenerate | |
286 | * the server key). | |
287 | */ | |
288 | ||
289 | /*ARGSUSED*/ | |
290 | static void | |
291 | sighup_handler(int sig) | |
292 | { | |
293 | int save_errno = errno; | |
294 | ||
295 | received_sighup = 1; | |
296 | signal(SIGHUP, sighup_handler); | |
297 | errno = save_errno; | |
298 | } | |
299 | ||
300 | /* | |
301 | * Called from the main program after receiving SIGHUP. | |
302 | * Restarts the server. | |
303 | */ | |
304 | static void | |
305 | sighup_restart(void) | |
306 | { | |
307 | logit("Received SIGHUP; restarting."); | |
308 | close_listen_socks(); | |
309 | close_startup_pipes(); | |
310 | alarm(0); /* alarm timer persists across exec */ | |
311 | execv(saved_argv[0], saved_argv); | |
312 | logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], | |
313 | strerror(errno)); | |
314 | exit(1); | |
315 | } | |
316 | ||
317 | /* | |
318 | * Generic signal handler for terminating signals in the master daemon. | |
319 | */ | |
320 | /*ARGSUSED*/ | |
321 | static void | |
322 | sigterm_handler(int sig) | |
323 | { | |
324 | received_sigterm = sig; | |
325 | } | |
326 | ||
327 | /* | |
328 | * SIGCHLD handler. This is called whenever a child dies. This will then | |
329 | * reap any zombies left by exited children. | |
330 | */ | |
331 | /*ARGSUSED*/ | |
332 | static void | |
333 | main_sigchld_handler(int sig) | |
334 | { | |
335 | int save_errno = errno; | |
336 | pid_t pid; | |
337 | int status; | |
338 | ||
339 | while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || | |
340 | (pid < 0 && errno == EINTR)) | |
341 | ; | |
342 | ||
343 | signal(SIGCHLD, main_sigchld_handler); | |
344 | errno = save_errno; | |
345 | } | |
346 | ||
347 | /* | |
348 | * Signal handler for the alarm after the login grace period has expired. | |
349 | */ | |
350 | /*ARGSUSED*/ | |
351 | static void | |
352 | grace_alarm_handler(int sig) | |
353 | { | |
354 | if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0) | |
355 | kill(pmonitor->m_pid, SIGALRM); | |
356 | ||
357 | /* Log error and exit. */ | |
358 | sigdie("Timeout before authentication for %s", get_remote_ipaddr()); | |
359 | } | |
360 | ||
361 | /* | |
362 | * Signal handler for the key regeneration alarm. Note that this | |
363 | * alarm only occurs in the daemon waiting for connections, and it does not | |
364 | * do anything with the private key or random state before forking. | |
365 | * Thus there should be no concurrency control/asynchronous execution | |
366 | * problems. | |
367 | */ | |
368 | static void | |
369 | generate_ephemeral_server_key(void) | |
370 | { | |
371 | verbose("Generating %s%d bit RSA key.", | |
372 | sensitive_data.server_key ? "new " : "", options.server_key_bits); | |
373 | if (sensitive_data.server_key != NULL) | |
374 | key_free(sensitive_data.server_key); | |
375 | sensitive_data.server_key = key_generate(KEY_RSA1, | |
376 | options.server_key_bits); | |
377 | verbose("RSA key generation complete."); | |
378 | ||
379 | arc4random_buf(sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); | |
380 | arc4random_stir(); | |
381 | } | |
382 | ||
383 | /*ARGSUSED*/ | |
384 | static void | |
385 | key_regeneration_alarm(int sig) | |
386 | { | |
387 | int save_errno = errno; | |
388 | ||
389 | signal(SIGALRM, SIG_DFL); | |
390 | errno = save_errno; | |
391 | key_do_regen = 1; | |
392 | } | |
393 | ||
394 | static void | |
395 | sshd_exchange_identification(int sock_in, int sock_out) | |
396 | { | |
397 | u_int i; | |
398 | int mismatch; | |
399 | int remote_major, remote_minor; | |
400 | int major, minor; | |
401 | char *s; | |
402 | char buf[256]; /* Must not be larger than remote_version. */ | |
403 | char remote_version[256]; /* Must be at least as big as buf. */ | |
404 | ||
405 | if ((options.protocol & SSH_PROTO_1) && | |
406 | (options.protocol & SSH_PROTO_2)) { | |
407 | major = PROTOCOL_MAJOR_1; | |
408 | minor = 99; | |
409 | } else if (options.protocol & SSH_PROTO_2) { | |
410 | major = PROTOCOL_MAJOR_2; | |
411 | minor = PROTOCOL_MINOR_2; | |
412 | } else { | |
413 | major = PROTOCOL_MAJOR_1; | |
414 | minor = PROTOCOL_MINOR_1; | |
415 | } | |
416 | snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION); | |
417 | server_version_string = xstrdup(buf); | |
418 | ||
419 | /* Send our protocol version identification. */ | |
420 | if (atomicio(vwrite, sock_out, server_version_string, | |
421 | strlen(server_version_string)) | |
422 | != strlen(server_version_string)) { | |
423 | logit("Could not write ident string to %s", get_remote_ipaddr()); | |
424 | cleanup_exit(255); | |
425 | } | |
426 | ||
427 | /* Read other sides version identification. */ | |
428 | memset(buf, 0, sizeof(buf)); | |
429 | for (i = 0; i < sizeof(buf) - 1; i++) { | |
430 | if (atomicio(read, sock_in, &buf[i], 1) != 1) { | |
431 | logit("Did not receive identification string from %s", | |
432 | get_remote_ipaddr()); | |
433 | cleanup_exit(255); | |
434 | } | |
435 | if (buf[i] == '\r') { | |
436 | buf[i] = 0; | |
437 | /* Kludge for F-Secure Macintosh < 1.0.2 */ | |
438 | if (i == 12 && | |
439 | strncmp(buf, "SSH-1.5-W1.0", 12) == 0) | |
440 | break; | |
441 | continue; | |
442 | } | |
443 | if (buf[i] == '\n') { | |
444 | buf[i] = 0; | |
445 | break; | |
446 | } | |
447 | } | |
448 | buf[sizeof(buf) - 1] = 0; | |
449 | client_version_string = xstrdup(buf); | |
450 | ||
451 | /* | |
452 | * Check that the versions match. In future this might accept | |
453 | * several versions and set appropriate flags to handle them. | |
454 | */ | |
455 | if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n", | |
456 | &remote_major, &remote_minor, remote_version) != 3) { | |
457 | s = "Protocol mismatch.\n"; | |
458 | (void) atomicio(vwrite, sock_out, s, strlen(s)); | |
459 | close(sock_in); | |
460 | close(sock_out); | |
461 | logit("Bad protocol version identification '%.100s' from %s", | |
462 | client_version_string, get_remote_ipaddr()); | |
463 | cleanup_exit(255); | |
464 | } | |
465 | debug("Client protocol version %d.%d; client software version %.100s", | |
466 | remote_major, remote_minor, remote_version); | |
467 | ||
468 | compat_datafellows(remote_version); | |
469 | ||
470 | if (datafellows & SSH_BUG_PROBE) { | |
471 | logit("probed from %s with %s. Don't panic.", | |
472 | get_remote_ipaddr(), client_version_string); | |
473 | cleanup_exit(255); | |
474 | } | |
475 | ||
476 | if (datafellows & SSH_BUG_SCANNER) { | |
477 | logit("scanned from %s with %s. Don't panic.", | |
478 | get_remote_ipaddr(), client_version_string); | |
479 | cleanup_exit(255); | |
480 | } | |
481 | ||
482 | mismatch = 0; | |
483 | switch (remote_major) { | |
484 | case 1: | |
485 | if (remote_minor == 99) { | |
486 | if (options.protocol & SSH_PROTO_2) | |
487 | enable_compat20(); | |
488 | else | |
489 | mismatch = 1; | |
490 | break; | |
491 | } | |
492 | if (!(options.protocol & SSH_PROTO_1)) { | |
493 | mismatch = 1; | |
494 | break; | |
495 | } | |
496 | if (remote_minor < 3) { | |
497 | packet_disconnect("Your ssh version is too old and " | |
498 | "is no longer supported. Please install a newer version."); | |
499 | } else if (remote_minor == 3) { | |
500 | /* note that this disables agent-forwarding */ | |
501 | enable_compat13(); | |
502 | } | |
503 | break; | |
504 | case 2: | |
505 | if (options.protocol & SSH_PROTO_2) { | |
506 | enable_compat20(); | |
507 | break; | |
508 | } | |
509 | /* FALLTHROUGH */ | |
510 | default: | |
511 | mismatch = 1; | |
512 | break; | |
513 | } | |
514 | chop(server_version_string); | |
515 | debug("Local version string %.200s", server_version_string); | |
516 | ||
517 | if (mismatch) { | |
518 | s = "Protocol major versions differ.\n"; | |
519 | (void) atomicio(vwrite, sock_out, s, strlen(s)); | |
520 | close(sock_in); | |
521 | close(sock_out); | |
522 | logit("Protocol major versions differ for %s: %.200s vs. %.200s", | |
523 | get_remote_ipaddr(), | |
524 | server_version_string, client_version_string); | |
525 | cleanup_exit(255); | |
526 | } | |
527 | } | |
528 | ||
529 | /* Destroy the host and server keys. They will no longer be needed. */ | |
530 | void | |
531 | destroy_sensitive_data(void) | |
532 | { | |
533 | int i; | |
534 | ||
535 | if (sensitive_data.server_key) { | |
536 | key_free(sensitive_data.server_key); | |
537 | sensitive_data.server_key = NULL; | |
538 | } | |
539 | for (i = 0; i < options.num_host_key_files; i++) { | |
540 | if (sensitive_data.host_keys[i]) { | |
541 | key_free(sensitive_data.host_keys[i]); | |
542 | sensitive_data.host_keys[i] = NULL; | |
543 | } | |
544 | } | |
545 | sensitive_data.ssh1_host_key = NULL; | |
546 | memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH); | |
547 | } | |
548 | ||
549 | /* Demote private to public keys for network child */ | |
550 | void | |
551 | demote_sensitive_data(void) | |
552 | { | |
553 | Key *tmp; | |
554 | int i; | |
555 | ||
556 | if (sensitive_data.server_key) { | |
557 | tmp = key_demote(sensitive_data.server_key); | |
558 | key_free(sensitive_data.server_key); | |
559 | sensitive_data.server_key = tmp; | |
560 | } | |
561 | ||
562 | for (i = 0; i < options.num_host_key_files; i++) { | |
563 | if (sensitive_data.host_keys[i]) { | |
564 | tmp = key_demote(sensitive_data.host_keys[i]); | |
565 | key_free(sensitive_data.host_keys[i]); | |
566 | sensitive_data.host_keys[i] = tmp; | |
567 | if (tmp->type == KEY_RSA1) | |
568 | sensitive_data.ssh1_host_key = tmp; | |
569 | } | |
570 | } | |
571 | ||
572 | /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */ | |
573 | } | |
574 | ||
575 | static void | |
576 | privsep_preauth_child(void) | |
577 | { | |
578 | u_int32_t rnd[256]; | |
579 | gid_t gidset[1]; | |
580 | ||
581 | /* Enable challenge-response authentication for privilege separation */ | |
582 | privsep_challenge_enable(); | |
583 | ||
584 | arc4random_stir(); | |
585 | arc4random_buf(rnd, sizeof(rnd)); | |
586 | RAND_seed(rnd, sizeof(rnd)); | |
587 | ||
588 | /* Demote the private keys to public keys. */ | |
589 | demote_sensitive_data(); | |
590 | ||
591 | /* Change our root directory */ | |
592 | if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1) | |
593 | fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR, | |
594 | strerror(errno)); | |
595 | if (chdir("/") == -1) | |
596 | fatal("chdir(\"/\"): %s", strerror(errno)); | |
597 | ||
598 | /* Drop our privileges */ | |
599 | debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid, | |
600 | (u_int)privsep_pw->pw_gid); | |
601 | #if 0 | |
602 | /* XXX not ready, too heavy after chroot */ | |
603 | do_setusercontext(privsep_pw); | |
604 | #else | |
605 | gidset[0] = privsep_pw->pw_gid; | |
606 | if (setgroups(1, gidset) < 0) | |
607 | fatal("setgroups: %.100s", strerror(errno)); | |
608 | permanently_set_uid(privsep_pw); | |
609 | #endif | |
610 | } | |
611 | ||
612 | static int | |
613 | privsep_preauth(Authctxt *authctxt) | |
614 | { | |
615 | int status; | |
616 | pid_t pid; | |
617 | ||
618 | /* Set up unprivileged child process to deal with network data */ | |
619 | pmonitor = monitor_init(); | |
620 | /* Store a pointer to the kex for later rekeying */ | |
621 | pmonitor->m_pkex = &xxx_kex; | |
622 | ||
623 | pid = fork(); | |
624 | if (pid == -1) { | |
625 | fatal("fork of unprivileged child failed"); | |
626 | } else if (pid != 0) { | |
627 | debug2("Network child is on pid %ld", (long)pid); | |
628 | ||
629 | close(pmonitor->m_recvfd); | |
630 | pmonitor->m_pid = pid; | |
631 | monitor_child_preauth(authctxt, pmonitor); | |
632 | close(pmonitor->m_sendfd); | |
633 | ||
634 | /* Sync memory */ | |
635 | monitor_sync(pmonitor); | |
636 | ||
637 | /* Wait for the child's exit status */ | |
638 | while (waitpid(pid, &status, 0) < 0) | |
639 | if (errno != EINTR) | |
640 | break; | |
641 | return (1); | |
642 | } else { | |
643 | /* child */ | |
644 | ||
645 | close(pmonitor->m_sendfd); | |
646 | ||
647 | /* Demote the child */ | |
648 | if (getuid() == 0 || geteuid() == 0) | |
649 | privsep_preauth_child(); | |
650 | setproctitle("%s", "[net]"); | |
651 | } | |
652 | return (0); | |
653 | } | |
654 | ||
655 | static void | |
656 | privsep_postauth(Authctxt *authctxt) | |
657 | { | |
658 | u_int32_t rnd[256]; | |
659 | ||
660 | #ifdef DISABLE_FD_PASSING | |
661 | if (1) { | |
662 | #else | |
663 | if (authctxt->pw->pw_uid == 0 || options.use_login) { | |
664 | #endif | |
665 | /* File descriptor passing is broken or root login */ | |
666 | use_privsep = 0; | |
667 | goto skip; | |
668 | } | |
669 | ||
670 | /* New socket pair */ | |
671 | monitor_reinit(pmonitor); | |
672 | ||
673 | pmonitor->m_pid = fork(); | |
674 | if (pmonitor->m_pid == -1) | |
675 | fatal("fork of unprivileged child failed"); | |
676 | else if (pmonitor->m_pid != 0) { | |
677 | debug2("User child is on pid %ld", (long)pmonitor->m_pid); | |
678 | close(pmonitor->m_recvfd); | |
679 | buffer_clear(&loginmsg); | |
680 | monitor_child_postauth(pmonitor); | |
681 | ||
682 | /* NEVERREACHED */ | |
683 | exit(0); | |
684 | } | |
685 | ||
686 | close(pmonitor->m_sendfd); | |
687 | ||
688 | /* Demote the private keys to public keys. */ | |
689 | demote_sensitive_data(); | |
690 | ||
691 | arc4random_stir(); | |
692 | arc4random_buf(rnd, sizeof(rnd)); | |
693 | RAND_seed(rnd, sizeof(rnd)); | |
694 | ||
695 | /* Drop privileges */ | |
696 | do_setusercontext(authctxt->pw); | |
697 | ||
698 | skip: | |
699 | /* It is safe now to apply the key state */ | |
700 | monitor_apply_keystate(pmonitor); | |
701 | ||
702 | /* | |
703 | * Tell the packet layer that authentication was successful, since | |
704 | * this information is not part of the key state. | |
705 | */ | |
706 | packet_set_authenticated(); | |
707 | } | |
708 | ||
709 | static char * | |
710 | list_hostkey_types(void) | |
711 | { | |
712 | Buffer b; | |
713 | const char *p; | |
714 | char *ret; | |
715 | int i; | |
716 | ||
717 | buffer_init(&b); | |
718 | for (i = 0; i < options.num_host_key_files; i++) { | |
719 | Key *key = sensitive_data.host_keys[i]; | |
720 | if (key == NULL) | |
721 | continue; | |
722 | switch (key->type) { | |
723 | case KEY_RSA: | |
724 | case KEY_DSA: | |
725 | if (buffer_len(&b) > 0) | |
726 | buffer_append(&b, ",", 1); | |
727 | p = key_ssh_name(key); | |
728 | buffer_append(&b, p, strlen(p)); | |
729 | break; | |
730 | } | |
731 | } | |
732 | buffer_append(&b, "\0", 1); | |
733 | ret = xstrdup(buffer_ptr(&b)); | |
734 | buffer_free(&b); | |
735 | debug("list_hostkey_types: %s", ret); | |
736 | return ret; | |
737 | } | |
738 | ||
739 | Key * | |
740 | get_hostkey_by_type(int type) | |
741 | { | |
742 | int i; | |
743 | ||
744 | for (i = 0; i < options.num_host_key_files; i++) { | |
745 | Key *key = sensitive_data.host_keys[i]; | |
746 | if (key != NULL && key->type == type) | |
747 | return key; | |
748 | } | |
749 | return NULL; | |
750 | } | |
751 | ||
752 | Key * | |
753 | get_hostkey_by_index(int ind) | |
754 | { | |
755 | if (ind < 0 || ind >= options.num_host_key_files) | |
756 | return (NULL); | |
757 | return (sensitive_data.host_keys[ind]); | |
758 | } | |
759 | ||
760 | int | |
761 | get_hostkey_index(Key *key) | |
762 | { | |
763 | int i; | |
764 | ||
765 | for (i = 0; i < options.num_host_key_files; i++) { | |
766 | if (key == sensitive_data.host_keys[i]) | |
767 | return (i); | |
768 | } | |
769 | return (-1); | |
770 | } | |
771 | ||
772 | /* | |
773 | * returns 1 if connection should be dropped, 0 otherwise. | |
774 | * dropping starts at connection #max_startups_begin with a probability | |
775 | * of (max_startups_rate/100). the probability increases linearly until | |
776 | * all connections are dropped for startups > max_startups | |
777 | */ | |
778 | static int | |
779 | drop_connection(int startups) | |
780 | { | |
781 | int p, r; | |
782 | ||
783 | if (startups < options.max_startups_begin) | |
784 | return 0; | |
785 | if (startups >= options.max_startups) | |
786 | return 1; | |
787 | if (options.max_startups_rate == 100) | |
788 | return 1; | |
789 | ||
790 | p = 100 - options.max_startups_rate; | |
791 | p *= startups - options.max_startups_begin; | |
792 | p /= options.max_startups - options.max_startups_begin; | |
793 | p += options.max_startups_rate; | |
794 | r = arc4random_uniform(100); | |
795 | ||
796 | debug("drop_connection: p %d, r %d", p, r); | |
797 | return (r < p) ? 1 : 0; | |
798 | } | |
799 | ||
800 | static void | |
801 | usage(void) | |
802 | { | |
803 | fprintf(stderr, "%s, %s\n", | |
804 | SSH_RELEASE, SSLeay_version(SSLEAY_VERSION)); | |
805 | fprintf(stderr, | |
806 | "usage: sshd [-46Ddeiqt] [-b bits] [-f config_file] [-g login_grace_time]\n" | |
807 | " [-h host_key_file] [-k key_gen_time] [-o option] [-p port] [-u len]\n" | |
808 | ); | |
809 | exit(1); | |
810 | } | |
811 | ||
812 | static void | |
813 | send_rexec_state(int fd, Buffer *conf) | |
814 | { | |
815 | Buffer m; | |
816 | ||
817 | debug3("%s: entering fd = %d config len %d", __func__, fd, | |
818 | buffer_len(conf)); | |
819 | ||
820 | /* | |
821 | * Protocol from reexec master to child: | |
822 | * string configuration | |
823 | * u_int ephemeral_key_follows | |
824 | * bignum e (only if ephemeral_key_follows == 1) | |
825 | * bignum n " | |
826 | * bignum d " | |
827 | * bignum iqmp " | |
828 | * bignum p " | |
829 | * bignum q " | |
830 | * string rngseed (only if OpenSSL is not self-seeded) | |
831 | */ | |
832 | buffer_init(&m); | |
833 | buffer_put_cstring(&m, buffer_ptr(conf)); | |
834 | ||
835 | if (sensitive_data.server_key != NULL && | |
836 | sensitive_data.server_key->type == KEY_RSA1) { | |
837 | buffer_put_int(&m, 1); | |
838 | buffer_put_bignum(&m, sensitive_data.server_key->rsa->e); | |
839 | buffer_put_bignum(&m, sensitive_data.server_key->rsa->n); | |
840 | buffer_put_bignum(&m, sensitive_data.server_key->rsa->d); | |
841 | buffer_put_bignum(&m, sensitive_data.server_key->rsa->iqmp); | |
842 | buffer_put_bignum(&m, sensitive_data.server_key->rsa->p); | |
843 | buffer_put_bignum(&m, sensitive_data.server_key->rsa->q); | |
844 | } else | |
845 | buffer_put_int(&m, 0); | |
846 | ||
847 | #ifndef OPENSSL_PRNG_ONLY | |
848 | rexec_send_rng_seed(&m); | |
849 | #endif | |
850 | ||
851 | if (ssh_msg_send(fd, 0, &m) == -1) | |
852 | fatal("%s: ssh_msg_send failed", __func__); | |
853 | ||
854 | buffer_free(&m); | |
855 | ||
856 | debug3("%s: done", __func__); | |
857 | } | |
858 | ||
859 | static void | |
860 | recv_rexec_state(int fd, Buffer *conf) | |
861 | { | |
862 | Buffer m; | |
863 | char *cp; | |
864 | u_int len; | |
865 | ||
866 | debug3("%s: entering fd = %d", __func__, fd); | |
867 | ||
868 | buffer_init(&m); | |
869 | ||
870 | if (ssh_msg_recv(fd, &m) == -1) | |
871 | fatal("%s: ssh_msg_recv failed", __func__); | |
872 | if (buffer_get_char(&m) != 0) | |
873 | fatal("%s: rexec version mismatch", __func__); | |
874 | ||
875 | cp = buffer_get_string(&m, &len); | |
876 | if (conf != NULL) | |
877 | buffer_append(conf, cp, len + 1); | |
878 | xfree(cp); | |
879 | ||
880 | if (buffer_get_int(&m)) { | |
881 | if (sensitive_data.server_key != NULL) | |
882 | key_free(sensitive_data.server_key); | |
883 | sensitive_data.server_key = key_new_private(KEY_RSA1); | |
884 | buffer_get_bignum(&m, sensitive_data.server_key->rsa->e); | |
885 | buffer_get_bignum(&m, sensitive_data.server_key->rsa->n); | |
886 | buffer_get_bignum(&m, sensitive_data.server_key->rsa->d); | |
887 | buffer_get_bignum(&m, sensitive_data.server_key->rsa->iqmp); | |
888 | buffer_get_bignum(&m, sensitive_data.server_key->rsa->p); | |
889 | buffer_get_bignum(&m, sensitive_data.server_key->rsa->q); | |
890 | rsa_generate_additional_parameters( | |
891 | sensitive_data.server_key->rsa); | |
892 | } | |
893 | ||
894 | #ifndef OPENSSL_PRNG_ONLY | |
895 | rexec_recv_rng_seed(&m); | |
896 | #endif | |
897 | ||
898 | buffer_free(&m); | |
899 | ||
900 | debug3("%s: done", __func__); | |
901 | } | |
902 | ||
903 | /* Accept a connection from inetd */ | |
904 | static void | |
905 | server_accept_inetd(int *sock_in, int *sock_out) | |
906 | { | |
907 | int fd; | |
908 | ||
909 | startup_pipe = -1; | |
910 | if (rexeced_flag) { | |
911 | close(REEXEC_CONFIG_PASS_FD); | |
912 | *sock_in = *sock_out = dup(STDIN_FILENO); | |
913 | if (!debug_flag) { | |
914 | startup_pipe = dup(REEXEC_STARTUP_PIPE_FD); | |
915 | close(REEXEC_STARTUP_PIPE_FD); | |
916 | } | |
917 | } else { | |
918 | *sock_in = dup(STDIN_FILENO); | |
919 | *sock_out = dup(STDOUT_FILENO); | |
920 | } | |
921 | /* | |
922 | * We intentionally do not close the descriptors 0, 1, and 2 | |
923 | * as our code for setting the descriptors won't work if | |
924 | * ttyfd happens to be one of those. | |
925 | */ | |
926 | if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) { | |
927 | dup2(fd, STDIN_FILENO); | |
928 | dup2(fd, STDOUT_FILENO); | |
929 | if (fd > STDOUT_FILENO) | |
930 | close(fd); | |
931 | } | |
932 | debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out); | |
933 | } | |
934 | ||
935 | /* | |
936 | * Listen for TCP connections | |
937 | */ | |
938 | static void | |
939 | server_listen(void) | |
940 | { | |
941 | int ret, listen_sock, on = 1; | |
942 | struct addrinfo *ai; | |
943 | char ntop[NI_MAXHOST], strport[NI_MAXSERV]; | |
944 | ||
945 | for (ai = options.listen_addrs; ai; ai = ai->ai_next) { | |
946 | if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) | |
947 | continue; | |
948 | if (num_listen_socks >= MAX_LISTEN_SOCKS) | |
949 | fatal("Too many listen sockets. " | |
950 | "Enlarge MAX_LISTEN_SOCKS"); | |
951 | if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen, | |
952 | ntop, sizeof(ntop), strport, sizeof(strport), | |
953 | NI_NUMERICHOST|NI_NUMERICSERV)) != 0) { | |
954 | error("getnameinfo failed: %.100s", | |
955 | ssh_gai_strerror(ret)); | |
956 | continue; | |
957 | } | |
958 | /* Create socket for listening. */ | |
959 | listen_sock = socket(ai->ai_family, ai->ai_socktype, | |
960 | ai->ai_protocol); | |
961 | if (listen_sock < 0) { | |
962 | /* kernel may not support ipv6 */ | |
963 | verbose("socket: %.100s", strerror(errno)); | |
964 | continue; | |
965 | } | |
966 | if (set_nonblock(listen_sock) == -1) { | |
967 | close(listen_sock); | |
968 | continue; | |
969 | } | |
970 | /* | |
971 | * Set socket options. | |
972 | * Allow local port reuse in TIME_WAIT. | |
973 | */ | |
974 | if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, | |
975 | &on, sizeof(on)) == -1) | |
976 | error("setsockopt SO_REUSEADDR: %s", strerror(errno)); | |
977 | ||
978 | #ifdef IPV6_V6ONLY | |
979 | /* Only communicate in IPv6 over AF_INET6 sockets. */ | |
980 | if (ai->ai_family == AF_INET6) { | |
981 | if (setsockopt(listen_sock, IPPROTO_IPV6, IPV6_V6ONLY, | |
982 | &on, sizeof(on)) == -1) | |
983 | error("setsockopt IPV6_V6ONLY: %s", | |
984 | strerror(errno)); | |
985 | } | |
986 | #endif | |
987 | ||
988 | debug("Bind to port %s on %s.", strport, ntop); | |
989 | ||
990 | /* Bind the socket to the desired port. */ | |
991 | if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) { | |
992 | error("Bind to port %s on %s failed: %.200s.", | |
993 | strport, ntop, strerror(errno)); | |
994 | close(listen_sock); | |
995 | continue; | |
996 | } | |
997 | listen_socks[num_listen_socks] = listen_sock; | |
998 | num_listen_socks++; | |
999 | ||
1000 | /* Start listening on the port. */ | |
1001 | if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0) | |
1002 | fatal("listen on [%s]:%s: %.100s", | |
1003 | ntop, strport, strerror(errno)); | |
1004 | logit("Server listening on %s port %s.", ntop, strport); | |
1005 | } | |
1006 | freeaddrinfo(options.listen_addrs); | |
1007 | ||
1008 | if (!num_listen_socks) | |
1009 | fatal("Cannot bind any address."); | |
1010 | } | |
1011 | ||
1012 | /* | |
1013 | * The main TCP accept loop. Note that, for the non-debug case, returns | |
1014 | * from this function are in a forked subprocess. | |
1015 | */ | |
1016 | static void | |
1017 | server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s) | |
1018 | { | |
1019 | fd_set *fdset; | |
1020 | int i, j, ret, maxfd; | |
1021 | int key_used = 0, startups = 0; | |
1022 | int startup_p[2] = { -1 , -1 }; | |
1023 | struct sockaddr_storage from; | |
1024 | socklen_t fromlen; | |
1025 | pid_t pid; | |
1026 | ||
1027 | /* setup fd set for accept */ | |
1028 | fdset = NULL; | |
1029 | maxfd = 0; | |
1030 | for (i = 0; i < num_listen_socks; i++) | |
1031 | if (listen_socks[i] > maxfd) | |
1032 | maxfd = listen_socks[i]; | |
1033 | /* pipes connected to unauthenticated childs */ | |
1034 | startup_pipes = xcalloc(options.max_startups, sizeof(int)); | |
1035 | for (i = 0; i < options.max_startups; i++) | |
1036 | startup_pipes[i] = -1; | |
1037 | ||
1038 | /* | |
1039 | * Stay listening for connections until the system crashes or | |
1040 | * the daemon is killed with a signal. | |
1041 | */ | |
1042 | for (;;) { | |
1043 | if (received_sighup) | |
1044 | sighup_restart(); | |
1045 | if (fdset != NULL) | |
1046 | xfree(fdset); | |
1047 | fdset = (fd_set *)xcalloc(howmany(maxfd + 1, NFDBITS), | |
1048 | sizeof(fd_mask)); | |
1049 | ||
1050 | for (i = 0; i < num_listen_socks; i++) | |
1051 | FD_SET(listen_socks[i], fdset); | |
1052 | for (i = 0; i < options.max_startups; i++) | |
1053 | if (startup_pipes[i] != -1) | |
1054 | FD_SET(startup_pipes[i], fdset); | |
1055 | ||
1056 | /* Wait in select until there is a connection. */ | |
1057 | ret = select(maxfd+1, fdset, NULL, NULL, NULL); | |
1058 | if (ret < 0 && errno != EINTR) | |
1059 | error("select: %.100s", strerror(errno)); | |
1060 | if (received_sigterm) { | |
1061 | logit("Received signal %d; terminating.", | |
1062 | (int) received_sigterm); | |
1063 | close_listen_socks(); | |
1064 | unlink(options.pid_file); | |
1065 | exit(255); | |
1066 | } | |
1067 | if (key_used && key_do_regen) { | |
1068 | generate_ephemeral_server_key(); | |
1069 | key_used = 0; | |
1070 | key_do_regen = 0; | |
1071 | } | |
1072 | if (ret < 0) | |
1073 | continue; | |
1074 | ||
1075 | for (i = 0; i < options.max_startups; i++) | |
1076 | if (startup_pipes[i] != -1 && | |
1077 | FD_ISSET(startup_pipes[i], fdset)) { | |
1078 | /* | |
1079 | * the read end of the pipe is ready | |
1080 | * if the child has closed the pipe | |
1081 | * after successful authentication | |
1082 | * or if the child has died | |
1083 | */ | |
1084 | close(startup_pipes[i]); | |
1085 | startup_pipes[i] = -1; | |
1086 | startups--; | |
1087 | } | |
1088 | for (i = 0; i < num_listen_socks; i++) { | |
1089 | if (!FD_ISSET(listen_socks[i], fdset)) | |
1090 | continue; | |
1091 | fromlen = sizeof(from); | |
1092 | *newsock = accept(listen_socks[i], | |
1093 | (struct sockaddr *)&from, &fromlen); | |
1094 | if (*newsock < 0) { | |
1095 | if (errno != EINTR && errno != EWOULDBLOCK) | |
1096 | error("accept: %.100s", strerror(errno)); | |
1097 | continue; | |
1098 | } | |
1099 | if (unset_nonblock(*newsock) == -1) { | |
1100 | close(*newsock); | |
1101 | continue; | |
1102 | } | |
1103 | if (drop_connection(startups) == 1) { | |
1104 | debug("drop connection #%d", startups); | |
1105 | close(*newsock); | |
1106 | continue; | |
1107 | } | |
1108 | if (pipe(startup_p) == -1) { | |
1109 | close(*newsock); | |
1110 | continue; | |
1111 | } | |
1112 | ||
1113 | if (rexec_flag && socketpair(AF_UNIX, | |
1114 | SOCK_STREAM, 0, config_s) == -1) { | |
1115 | error("reexec socketpair: %s", | |
1116 | strerror(errno)); | |
1117 | close(*newsock); | |
1118 | close(startup_p[0]); | |
1119 | close(startup_p[1]); | |
1120 | continue; | |
1121 | } | |
1122 | ||
1123 | for (j = 0; j < options.max_startups; j++) | |
1124 | if (startup_pipes[j] == -1) { | |
1125 | startup_pipes[j] = startup_p[0]; | |
1126 | if (maxfd < startup_p[0]) | |
1127 | maxfd = startup_p[0]; | |
1128 | startups++; | |
1129 | break; | |
1130 | } | |
1131 | ||
1132 | /* | |
1133 | * Got connection. Fork a child to handle it, unless | |
1134 | * we are in debugging mode. | |
1135 | */ | |
1136 | if (debug_flag) { | |
1137 | /* | |
1138 | * In debugging mode. Close the listening | |
1139 | * socket, and start processing the | |
1140 | * connection without forking. | |
1141 | */ | |
1142 | debug("Server will not fork when running in debugging mode."); | |
1143 | close_listen_socks(); | |
1144 | *sock_in = *newsock; | |
1145 | *sock_out = *newsock; | |
1146 | close(startup_p[0]); | |
1147 | close(startup_p[1]); | |
1148 | startup_pipe = -1; | |
1149 | pid = getpid(); | |
1150 | if (rexec_flag) { | |
1151 | send_rexec_state(config_s[0], | |
1152 | &cfg); | |
1153 | close(config_s[0]); | |
1154 | } | |
1155 | break; | |
1156 | } | |
1157 | ||
1158 | /* | |
1159 | * Normal production daemon. Fork, and have | |
1160 | * the child process the connection. The | |
1161 | * parent continues listening. | |
1162 | */ | |
1163 | platform_pre_fork(); | |
1164 | if ((pid = fork()) == 0) { | |
1165 | /* | |
1166 | * Child. Close the listening and | |
1167 | * max_startup sockets. Start using | |
1168 | * the accepted socket. Reinitialize | |
1169 | * logging (since our pid has changed). | |
1170 | * We break out of the loop to handle | |
1171 | * the connection. | |
1172 | */ | |
1173 | platform_post_fork_child(); | |
1174 | startup_pipe = startup_p[1]; | |
1175 | close_startup_pipes(); | |
1176 | close_listen_socks(); | |
1177 | *sock_in = *newsock; | |
1178 | *sock_out = *newsock; | |
1179 | log_init(__progname, | |
1180 | options.log_level, | |
1181 | options.log_facility, | |
1182 | log_stderr); | |
1183 | if (rexec_flag) | |
1184 | close(config_s[0]); | |
1185 | break; | |
1186 | } | |
1187 | ||
1188 | /* Parent. Stay in the loop. */ | |
1189 | platform_post_fork_parent(pid); | |
1190 | if (pid < 0) | |
1191 | error("fork: %.100s", strerror(errno)); | |
1192 | else | |
1193 | debug("Forked child %ld.", (long)pid); | |
1194 | ||
1195 | close(startup_p[1]); | |
1196 | ||
1197 | if (rexec_flag) { | |
1198 | send_rexec_state(config_s[0], &cfg); | |
1199 | close(config_s[0]); | |
1200 | close(config_s[1]); | |
1201 | } | |
1202 | ||
1203 | /* | |
1204 | * Mark that the key has been used (it | |
1205 | * was "given" to the child). | |
1206 | */ | |
1207 | if ((options.protocol & SSH_PROTO_1) && | |
1208 | key_used == 0) { | |
1209 | /* Schedule server key regeneration alarm. */ | |
1210 | signal(SIGALRM, key_regeneration_alarm); | |
1211 | alarm(options.key_regeneration_time); | |
1212 | key_used = 1; | |
1213 | } | |
1214 | ||
1215 | close(*newsock); | |
1216 | ||
1217 | /* | |
1218 | * Ensure that our random state differs | |
1219 | * from that of the child | |
1220 | */ | |
1221 | arc4random_stir(); | |
1222 | } | |
1223 | ||
1224 | /* child process check (or debug mode) */ | |
1225 | if (num_listen_socks < 0) | |
1226 | break; | |
1227 | } | |
1228 | } | |
1229 | ||
1230 | ||
1231 | /* | |
1232 | * Main program for the daemon. | |
1233 | */ | |
1234 | int | |
1235 | main(int ac, char **av) | |
1236 | { | |
1237 | extern char *optarg; | |
1238 | extern int optind; | |
1239 | int opt, i, on = 1; | |
1240 | int sock_in = -1, sock_out = -1, newsock = -1; | |
1241 | const char *remote_ip; | |
1242 | int remote_port; | |
1243 | char *line; | |
1244 | int config_s[2] = { -1 , -1 }; | |
1245 | Key *key; | |
1246 | Authctxt *authctxt; | |
1247 | ||
1248 | #ifdef HAVE_SECUREWARE | |
1249 | (void)set_auth_parameters(ac, av); | |
1250 | #endif | |
1251 | __progname = ssh_get_progname(av[0]); | |
1252 | init_rng(); | |
1253 | ||
1254 | /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */ | |
1255 | saved_argc = ac; | |
1256 | rexec_argc = ac; | |
1257 | saved_argv = xcalloc(ac + 1, sizeof(*saved_argv)); | |
1258 | for (i = 0; i < ac; i++) | |
1259 | saved_argv[i] = xstrdup(av[i]); | |
1260 | saved_argv[i] = NULL; | |
1261 | ||
1262 | #ifndef HAVE_SETPROCTITLE | |
1263 | /* Prepare for later setproctitle emulation */ | |
1264 | compat_init_setproctitle(ac, av); | |
1265 | av = saved_argv; | |
1266 | #endif | |
1267 | ||
1268 | if (geteuid() == 0 && setgroups(0, NULL) == -1) | |
1269 | debug("setgroups(): %.200s", strerror(errno)); | |
1270 | ||
1271 | /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ | |
1272 | sanitise_stdfd(); | |
1273 | ||
1274 | /* Initialize configuration options to their default values. */ | |
1275 | initialize_server_options(&options); | |
1276 | ||
1277 | /* Parse command-line arguments. */ | |
1278 | while ((opt = getopt(ac, av, "f:p:b:k:h:g:u:o:dDeiqrtQR46")) != -1) { | |
1279 | switch (opt) { | |
1280 | case '4': | |
1281 | options.address_family = AF_INET; | |
1282 | break; | |
1283 | case '6': | |
1284 | options.address_family = AF_INET6; | |
1285 | break; | |
1286 | case 'f': | |
1287 | config_file_name = optarg; | |
1288 | break; | |
1289 | case 'd': | |
1290 | if (debug_flag == 0) { | |
1291 | debug_flag = 1; | |
1292 | options.log_level = SYSLOG_LEVEL_DEBUG1; | |
1293 | } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) | |
1294 | options.log_level++; | |
1295 | break; | |
1296 | case 'D': | |
1297 | no_daemon_flag = 1; | |
1298 | break; | |
1299 | case 'e': | |
1300 | log_stderr = 1; | |
1301 | break; | |
1302 | case 'i': | |
1303 | inetd_flag = 1; | |
1304 | break; | |
1305 | case 'r': | |
1306 | rexec_flag = 0; | |
1307 | break; | |
1308 | case 'R': | |
1309 | rexeced_flag = 1; | |
1310 | inetd_flag = 1; | |
1311 | break; | |
1312 | case 'Q': | |
1313 | /* ignored */ | |
1314 | break; | |
1315 | case 'q': | |
1316 | options.log_level = SYSLOG_LEVEL_QUIET; | |
1317 | break; | |
1318 | case 'b': | |
1319 | options.server_key_bits = (int)strtonum(optarg, 256, | |
1320 | 32768, NULL); | |
1321 | break; | |
1322 | case 'p': | |
1323 | options.ports_from_cmdline = 1; | |
1324 | if (options.num_ports >= MAX_PORTS) { | |
1325 | fprintf(stderr, "too many ports.\n"); | |
1326 | exit(1); | |
1327 | } | |
1328 | options.ports[options.num_ports++] = a2port(optarg); | |
1329 | if (options.ports[options.num_ports-1] == 0) { | |
1330 | fprintf(stderr, "Bad port number.\n"); | |
1331 | exit(1); | |
1332 | } | |
1333 | break; | |
1334 | case 'g': | |
1335 | if ((options.login_grace_time = convtime(optarg)) == -1) { | |
1336 | fprintf(stderr, "Invalid login grace time.\n"); | |
1337 | exit(1); | |
1338 | } | |
1339 | break; | |
1340 | case 'k': | |
1341 | if ((options.key_regeneration_time = convtime(optarg)) == -1) { | |
1342 | fprintf(stderr, "Invalid key regeneration interval.\n"); | |
1343 | exit(1); | |
1344 | } | |
1345 | break; | |
1346 | case 'h': | |
1347 | if (options.num_host_key_files >= MAX_HOSTKEYS) { | |
1348 | fprintf(stderr, "too many host keys.\n"); | |
1349 | exit(1); | |
1350 | } | |
1351 | options.host_key_files[options.num_host_key_files++] = optarg; | |
1352 | break; | |
1353 | case 't': | |
1354 | test_flag = 1; | |
1355 | break; | |
1356 | case 'u': | |
1357 | utmp_len = (u_int)strtonum(optarg, 0, MAXHOSTNAMELEN+1, NULL); | |
1358 | if (utmp_len > MAXHOSTNAMELEN) { | |
1359 | fprintf(stderr, "Invalid utmp length.\n"); | |
1360 | exit(1); | |
1361 | } | |
1362 | break; | |
1363 | case 'o': | |
1364 | line = xstrdup(optarg); | |
1365 | if (process_server_config_line(&options, line, | |
1366 | "command-line", 0, NULL, NULL, NULL, NULL) != 0) | |
1367 | exit(1); | |
1368 | xfree(line); | |
1369 | break; | |
1370 | case '?': | |
1371 | default: | |
1372 | usage(); | |
1373 | break; | |
1374 | } | |
1375 | } | |
1376 | if (rexeced_flag || inetd_flag) | |
1377 | rexec_flag = 0; | |
1378 | if (!test_flag && (rexec_flag && (av[0] == NULL || *av[0] != '/'))) | |
1379 | fatal("sshd re-exec requires execution with an absolute path"); | |
1380 | if (rexeced_flag) | |
1381 | closefrom(REEXEC_MIN_FREE_FD); | |
1382 | else | |
1383 | closefrom(REEXEC_DEVCRYPTO_RESERVED_FD); | |
1384 | ||
1385 | SSLeay_add_all_algorithms(); | |
1386 | ||
1387 | /* | |
1388 | * Force logging to stderr until we have loaded the private host | |
1389 | * key (unless started from inetd) | |
1390 | */ | |
1391 | log_init(__progname, | |
1392 | options.log_level == SYSLOG_LEVEL_NOT_SET ? | |
1393 | SYSLOG_LEVEL_INFO : options.log_level, | |
1394 | options.log_facility == SYSLOG_FACILITY_NOT_SET ? | |
1395 | SYSLOG_FACILITY_AUTH : options.log_facility, | |
1396 | log_stderr || !inetd_flag); | |
1397 | ||
1398 | /* | |
1399 | * Unset KRB5CCNAME, otherwise the user's session may inherit it from | |
1400 | * root's environment | |
1401 | */ | |
1402 | if (getenv("KRB5CCNAME") != NULL) | |
1403 | unsetenv("KRB5CCNAME"); | |
1404 | ||
1405 | #ifdef _UNICOS | |
1406 | /* Cray can define user privs drop all privs now! | |
1407 | * Not needed on PRIV_SU systems! | |
1408 | */ | |
1409 | drop_cray_privs(); | |
1410 | #endif | |
1411 | ||
1412 | sensitive_data.server_key = NULL; | |
1413 | sensitive_data.ssh1_host_key = NULL; | |
1414 | sensitive_data.have_ssh1_key = 0; | |
1415 | sensitive_data.have_ssh2_key = 0; | |
1416 | ||
1417 | /* Fetch our configuration */ | |
1418 | buffer_init(&cfg); | |
1419 | if (rexeced_flag) | |
1420 | recv_rexec_state(REEXEC_CONFIG_PASS_FD, &cfg); | |
1421 | else | |
1422 | load_server_config(config_file_name, &cfg); | |
1423 | ||
1424 | parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name, | |
1425 | &cfg, NULL, NULL, NULL); | |
1426 | ||
1427 | seed_rng(); | |
1428 | ||
1429 | /* Fill in default values for those options not explicitly set. */ | |
1430 | fill_default_server_options(&options); | |
1431 | ||
1432 | /* challenge-response is implemented via keyboard interactive */ | |
1433 | if (options.challenge_response_authentication) | |
1434 | options.kbd_interactive_authentication = 1; | |
1435 | ||
1436 | /* set default channel AF */ | |
1437 | channel_set_af(options.address_family); | |
1438 | ||
1439 | /* Check that there are no remaining arguments. */ | |
1440 | if (optind < ac) { | |
1441 | fprintf(stderr, "Extra argument %s.\n", av[optind]); | |
1442 | exit(1); | |
1443 | } | |
1444 | ||
1445 | debug("sshd version %.100s", SSH_RELEASE); | |
1446 | ||
1447 | /* Store privilege separation user for later use if required. */ | |
1448 | if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) { | |
1449 | if (use_privsep || options.kerberos_authentication) | |
1450 | fatal("Privilege separation user %s does not exist", | |
1451 | SSH_PRIVSEP_USER); | |
1452 | } else { | |
1453 | memset(privsep_pw->pw_passwd, 0, strlen(privsep_pw->pw_passwd)); | |
1454 | privsep_pw = pwcopy(privsep_pw); | |
1455 | xfree(privsep_pw->pw_passwd); | |
1456 | privsep_pw->pw_passwd = xstrdup("*"); | |
1457 | } | |
1458 | endpwent(); | |
1459 | ||
1460 | /* load private host keys */ | |
1461 | sensitive_data.host_keys = xcalloc(options.num_host_key_files, | |
1462 | sizeof(Key *)); | |
1463 | for (i = 0; i < options.num_host_key_files; i++) | |
1464 | sensitive_data.host_keys[i] = NULL; | |
1465 | ||
1466 | for (i = 0; i < options.num_host_key_files; i++) { | |
1467 | key = key_load_private(options.host_key_files[i], "", NULL); | |
1468 | sensitive_data.host_keys[i] = key; | |
1469 | if (key == NULL) { | |
1470 | error("Could not load host key: %s", | |
1471 | options.host_key_files[i]); | |
1472 | sensitive_data.host_keys[i] = NULL; | |
1473 | continue; | |
1474 | } | |
1475 | switch (key->type) { | |
1476 | case KEY_RSA1: | |
1477 | sensitive_data.ssh1_host_key = key; | |
1478 | sensitive_data.have_ssh1_key = 1; | |
1479 | break; | |
1480 | case KEY_RSA: | |
1481 | case KEY_DSA: | |
1482 | sensitive_data.have_ssh2_key = 1; | |
1483 | break; | |
1484 | } | |
1485 | debug("private host key: #%d type %d %s", i, key->type, | |
1486 | key_type(key)); | |
1487 | } | |
1488 | if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) { | |
1489 | logit("Disabling protocol version 1. Could not load host key"); | |
1490 | options.protocol &= ~SSH_PROTO_1; | |
1491 | } | |
1492 | if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) { | |
1493 | logit("Disabling protocol version 2. Could not load host key"); | |
1494 | options.protocol &= ~SSH_PROTO_2; | |
1495 | } | |
1496 | if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) { | |
1497 | logit("sshd: no hostkeys available -- exiting."); | |
1498 | exit(1); | |
1499 | } | |
1500 | ||
1501 | /* Check certain values for sanity. */ | |
1502 | if (options.protocol & SSH_PROTO_1) { | |
1503 | if (options.server_key_bits < 512 || | |
1504 | options.server_key_bits > 32768) { | |
1505 | fprintf(stderr, "Bad server key size.\n"); | |
1506 | exit(1); | |
1507 | } | |
1508 | /* | |
1509 | * Check that server and host key lengths differ sufficiently. This | |
1510 | * is necessary to make double encryption work with rsaref. Oh, I | |
1511 | * hate software patents. I dont know if this can go? Niels | |
1512 | */ | |
1513 | if (options.server_key_bits > | |
1514 | BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - | |
1515 | SSH_KEY_BITS_RESERVED && options.server_key_bits < | |
1516 | BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + | |
1517 | SSH_KEY_BITS_RESERVED) { | |
1518 | options.server_key_bits = | |
1519 | BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + | |
1520 | SSH_KEY_BITS_RESERVED; | |
1521 | debug("Forcing server key to %d bits to make it differ from host key.", | |
1522 | options.server_key_bits); | |
1523 | } | |
1524 | } | |
1525 | ||
1526 | if (use_privsep) { | |
1527 | struct stat st; | |
1528 | ||
1529 | if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) || | |
1530 | (S_ISDIR(st.st_mode) == 0)) | |
1531 | fatal("Missing privilege separation directory: %s", | |
1532 | _PATH_PRIVSEP_CHROOT_DIR); | |
1533 | ||
1534 | #ifdef HAVE_CYGWIN | |
1535 | if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) && | |
1536 | (st.st_uid != getuid () || | |
1537 | (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)) | |
1538 | #else | |
1539 | if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0) | |
1540 | #endif | |
1541 | fatal("%s must be owned by root and not group or " | |
1542 | "world-writable.", _PATH_PRIVSEP_CHROOT_DIR); | |
1543 | } | |
1544 | ||
1545 | /* Configuration looks good, so exit if in test mode. */ | |
1546 | if (test_flag) | |
1547 | exit(0); | |
1548 | ||
1549 | /* | |
1550 | * Clear out any supplemental groups we may have inherited. This | |
1551 | * prevents inadvertent creation of files with bad modes (in the | |
1552 | * portable version at least, it's certainly possible for PAM | |
1553 | * to create a file, and we can't control the code in every | |
1554 | * module which might be used). | |
1555 | */ | |
1556 | if (setgroups(0, NULL) < 0) | |
1557 | debug("setgroups() failed: %.200s", strerror(errno)); | |
1558 | ||
1559 | if (rexec_flag) { | |
1560 | rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *)); | |
1561 | for (i = 0; i < rexec_argc; i++) { | |
1562 | debug("rexec_argv[%d]='%s'", i, saved_argv[i]); | |
1563 | rexec_argv[i] = saved_argv[i]; | |
1564 | } | |
1565 | rexec_argv[rexec_argc] = "-R"; | |
1566 | rexec_argv[rexec_argc + 1] = NULL; | |
1567 | } | |
1568 | ||
1569 | /* Initialize the log (it is reinitialized below in case we forked). */ | |
1570 | if (debug_flag && (!inetd_flag || rexeced_flag)) | |
1571 | log_stderr = 1; | |
1572 | log_init(__progname, options.log_level, options.log_facility, log_stderr); | |
1573 | ||
1574 | /* | |
1575 | * If not in debugging mode, and not started from inetd, disconnect | |
1576 | * from the controlling terminal, and fork. The original process | |
1577 | * exits. | |
1578 | */ | |
1579 | if (!(debug_flag || inetd_flag || no_daemon_flag)) { | |
1580 | #ifdef TIOCNOTTY | |
1581 | int fd; | |
1582 | #endif /* TIOCNOTTY */ | |
1583 | if (daemon(0, 0) < 0) | |
1584 | fatal("daemon() failed: %.200s", strerror(errno)); | |
1585 | ||
1586 | /* Disconnect from the controlling tty. */ | |
1587 | #ifdef TIOCNOTTY | |
1588 | fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); | |
1589 | if (fd >= 0) { | |
1590 | (void) ioctl(fd, TIOCNOTTY, NULL); | |
1591 | close(fd); | |
1592 | } | |
1593 | #endif /* TIOCNOTTY */ | |
1594 | } | |
1595 | /* Reinitialize the log (because of the fork above). */ | |
1596 | log_init(__progname, options.log_level, options.log_facility, log_stderr); | |
1597 | ||
1598 | /* Initialize the random number generator. */ | |
1599 | arc4random_stir(); | |
1600 | ||
1601 | /* Chdir to the root directory so that the current disk can be | |
1602 | unmounted if desired. */ | |
1603 | chdir("/"); | |
1604 | ||
1605 | /* ignore SIGPIPE */ | |
1606 | signal(SIGPIPE, SIG_IGN); | |
1607 | ||
1608 | /* Get a connection, either from inetd or a listening TCP socket */ | |
1609 | if (inetd_flag) { | |
1610 | server_accept_inetd(&sock_in, &sock_out); | |
1611 | } else { | |
1612 | server_listen(); | |
1613 | ||
1614 | if (options.protocol & SSH_PROTO_1) | |
1615 | generate_ephemeral_server_key(); | |
1616 | ||
1617 | signal(SIGHUP, sighup_handler); | |
1618 | signal(SIGCHLD, main_sigchld_handler); | |
1619 | signal(SIGTERM, sigterm_handler); | |
1620 | signal(SIGQUIT, sigterm_handler); | |
1621 | ||
1622 | /* | |
1623 | * Write out the pid file after the sigterm handler | |
1624 | * is setup and the listen sockets are bound | |
1625 | */ | |
1626 | if (!debug_flag) { | |
1627 | FILE *f = fopen(options.pid_file, "w"); | |
1628 | ||
1629 | if (f == NULL) { | |
1630 | error("Couldn't create pid file \"%s\": %s", | |
1631 | options.pid_file, strerror(errno)); | |
1632 | } else { | |
1633 | fprintf(f, "%ld\n", (long) getpid()); | |
1634 | fclose(f); | |
1635 | } | |
1636 | } | |
1637 | ||
1638 | /* Accept a connection and return in a forked child */ | |
1639 | server_accept_loop(&sock_in, &sock_out, | |
1640 | &newsock, config_s); | |
1641 | } | |
1642 | ||
1643 | /* This is the child processing a new connection. */ | |
1644 | setproctitle("%s", "[accepted]"); | |
1645 | ||
1646 | /* | |
1647 | * Create a new session and process group since the 4.4BSD | |
1648 | * setlogin() affects the entire process group. We don't | |
1649 | * want the child to be able to affect the parent. | |
1650 | */ | |
1651 | #if !defined(SSHD_ACQUIRES_CTTY) | |
1652 | /* | |
1653 | * If setsid is called, on some platforms sshd will later acquire a | |
1654 | * controlling terminal which will result in "could not set | |
1655 | * controlling tty" errors. | |
1656 | */ | |
1657 | if (!debug_flag && !inetd_flag && setsid() < 0) | |
1658 | error("setsid: %.100s", strerror(errno)); | |
1659 | #endif | |
1660 | ||
1661 | if (rexec_flag) { | |
1662 | int fd; | |
1663 | ||
1664 | debug("rexec start in %d out %d newsock %d pipe %d sock %d", | |
1665 | sock_in, sock_out, newsock, startup_pipe, config_s[0]); | |
1666 | dup2(newsock, STDIN_FILENO); | |
1667 | dup2(STDIN_FILENO, STDOUT_FILENO); | |
1668 | if (startup_pipe == -1) | |
1669 | close(REEXEC_STARTUP_PIPE_FD); | |
1670 | else | |
1671 | dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD); | |
1672 | ||
1673 | dup2(config_s[1], REEXEC_CONFIG_PASS_FD); | |
1674 | close(config_s[1]); | |
1675 | if (startup_pipe != -1) | |
1676 | close(startup_pipe); | |
1677 | ||
1678 | execv(rexec_argv[0], rexec_argv); | |
1679 | ||
1680 | /* Reexec has failed, fall back and continue */ | |
1681 | error("rexec of %s failed: %s", rexec_argv[0], strerror(errno)); | |
1682 | recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL); | |
1683 | log_init(__progname, options.log_level, | |
1684 | options.log_facility, log_stderr); | |
1685 | ||
1686 | /* Clean up fds */ | |
1687 | startup_pipe = REEXEC_STARTUP_PIPE_FD; | |
1688 | close(config_s[1]); | |
1689 | close(REEXEC_CONFIG_PASS_FD); | |
1690 | newsock = sock_out = sock_in = dup(STDIN_FILENO); | |
1691 | if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) { | |
1692 | dup2(fd, STDIN_FILENO); | |
1693 | dup2(fd, STDOUT_FILENO); | |
1694 | if (fd > STDERR_FILENO) | |
1695 | close(fd); | |
1696 | } | |
1697 | debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d", | |
1698 | sock_in, sock_out, newsock, startup_pipe, config_s[0]); | |
1699 | } | |
1700 | ||
1701 | /* | |
1702 | * Disable the key regeneration alarm. We will not regenerate the | |
1703 | * key since we are no longer in a position to give it to anyone. We | |
1704 | * will not restart on SIGHUP since it no longer makes sense. | |
1705 | */ | |
1706 | alarm(0); | |
1707 | signal(SIGALRM, SIG_DFL); | |
1708 | signal(SIGHUP, SIG_DFL); | |
1709 | signal(SIGTERM, SIG_DFL); | |
1710 | signal(SIGQUIT, SIG_DFL); | |
1711 | signal(SIGCHLD, SIG_DFL); | |
1712 | signal(SIGINT, SIG_DFL); | |
1713 | ||
1714 | /* | |
1715 | * Register our connection. This turns encryption off because we do | |
1716 | * not have a key. | |
1717 | */ | |
1718 | packet_set_connection(sock_in, sock_out); | |
1719 | packet_set_server(); | |
1720 | ||
1721 | /* Set SO_KEEPALIVE if requested. */ | |
1722 | if (options.tcp_keep_alive && packet_connection_is_on_socket() && | |
1723 | setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) < 0) | |
1724 | error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); | |
1725 | ||
1726 | if ((remote_port = get_remote_port()) < 0) { | |
1727 | debug("get_remote_port failed"); | |
1728 | cleanup_exit(255); | |
1729 | } | |
1730 | ||
1731 | /* | |
1732 | * We use get_canonical_hostname with usedns = 0 instead of | |
1733 | * get_remote_ipaddr here so IP options will be checked. | |
1734 | */ | |
1735 | (void) get_canonical_hostname(0); | |
1736 | /* | |
1737 | * The rest of the code depends on the fact that | |
1738 | * get_remote_ipaddr() caches the remote ip, even if | |
1739 | * the socket goes away. | |
1740 | */ | |
1741 | remote_ip = get_remote_ipaddr(); | |
1742 | ||
1743 | #ifdef SSH_AUDIT_EVENTS | |
1744 | audit_connection_from(remote_ip, remote_port); | |
1745 | #endif | |
1746 | #ifdef LIBWRAP | |
1747 | allow_severity = options.log_facility|LOG_INFO; | |
1748 | deny_severity = options.log_facility|LOG_WARNING; | |
1749 | /* Check whether logins are denied from this host. */ | |
1750 | if (packet_connection_is_on_socket()) { | |
1751 | struct request_info req; | |
1752 | ||
1753 | request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0); | |
1754 | fromhost(&req); | |
1755 | ||
1756 | if (!hosts_access(&req)) { | |
1757 | debug("Connection refused by tcp wrapper"); | |
1758 | refuse(&req); | |
1759 | /* NOTREACHED */ | |
1760 | fatal("libwrap refuse returns"); | |
1761 | } | |
1762 | } | |
1763 | #endif /* LIBWRAP */ | |
1764 | ||
1765 | /* Log the connection. */ | |
1766 | verbose("Connection from %.500s port %d", remote_ip, remote_port); | |
1767 | ||
1768 | /* | |
1769 | * We don't want to listen forever unless the other side | |
1770 | * successfully authenticates itself. So we set up an alarm which is | |
1771 | * cleared after successful authentication. A limit of zero | |
1772 | * indicates no limit. Note that we don't set the alarm in debugging | |
1773 | * mode; it is just annoying to have the server exit just when you | |
1774 | * are about to discover the bug. | |
1775 | */ | |
1776 | signal(SIGALRM, grace_alarm_handler); | |
1777 | if (!debug_flag) | |
1778 | alarm(options.login_grace_time); | |
1779 | ||
1780 | sshd_exchange_identification(sock_in, sock_out); | |
1781 | ||
1782 | /* In inetd mode, generate ephemeral key only for proto 1 connections */ | |
1783 | if (!compat20 && inetd_flag && sensitive_data.server_key == NULL) | |
1784 | generate_ephemeral_server_key(); | |
1785 | ||
1786 | packet_set_nonblocking(); | |
1787 | ||
1788 | /* allocate authentication context */ | |
1789 | authctxt = xcalloc(1, sizeof(*authctxt)); | |
1790 | ||
1791 | authctxt->loginmsg = &loginmsg; | |
1792 | ||
1793 | /* XXX global for cleanup, access from other modules */ | |
1794 | the_authctxt = authctxt; | |
1795 | ||
1796 | /* prepare buffer to collect messages to display to user after login */ | |
1797 | buffer_init(&loginmsg); | |
1798 | ||
1799 | if (use_privsep) | |
1800 | if (privsep_preauth(authctxt) == 1) | |
1801 | goto authenticated; | |
1802 | ||
1803 | /* perform the key exchange */ | |
1804 | /* authenticate user and start session */ | |
1805 | if (compat20) { | |
1806 | do_ssh2_kex(); | |
1807 | do_authentication2(authctxt); | |
1808 | } else { | |
1809 | do_ssh1_kex(); | |
1810 | do_authentication(authctxt); | |
1811 | } | |
1812 | /* | |
1813 | * If we use privilege separation, the unprivileged child transfers | |
1814 | * the current keystate and exits | |
1815 | */ | |
1816 | if (use_privsep) { | |
1817 | mm_send_keystate(pmonitor); | |
1818 | exit(0); | |
1819 | } | |
1820 | ||
1821 | authenticated: | |
1822 | /* | |
1823 | * Cancel the alarm we set to limit the time taken for | |
1824 | * authentication. | |
1825 | */ | |
1826 | alarm(0); | |
1827 | signal(SIGALRM, SIG_DFL); | |
1828 | authctxt->authenticated = 1; | |
1829 | if (startup_pipe != -1) { | |
1830 | close(startup_pipe); | |
1831 | startup_pipe = -1; | |
1832 | } | |
1833 | ||
1834 | #ifdef SSH_AUDIT_EVENTS | |
1835 | audit_event(SSH_AUTH_SUCCESS); | |
1836 | #endif | |
1837 | ||
1838 | #ifdef GSSAPI | |
1839 | if (options.gss_authentication) { | |
1840 | temporarily_use_uid(authctxt->pw); | |
1841 | ssh_gssapi_storecreds(); | |
1842 | restore_uid(); | |
1843 | } | |
1844 | #endif | |
1845 | #ifdef USE_PAM | |
1846 | if (options.use_pam) { | |
1847 | do_pam_setcred(1); | |
1848 | do_pam_session(); | |
1849 | } | |
1850 | #endif | |
1851 | ||
1852 | /* | |
1853 | * In privilege separation, we fork another child and prepare | |
1854 | * file descriptor passing. | |
1855 | */ | |
1856 | if (use_privsep) { | |
1857 | privsep_postauth(authctxt); | |
1858 | /* the monitor process [priv] will not return */ | |
1859 | if (!compat20) | |
1860 | destroy_sensitive_data(); | |
1861 | } | |
1862 | ||
1863 | /* Start session. */ | |
1864 | do_authenticated(authctxt); | |
1865 | ||
1866 | /* The connection has been terminated. */ | |
1867 | verbose("Closing connection to %.100s", remote_ip); | |
1868 | ||
1869 | #ifdef USE_PAM | |
1870 | if (options.use_pam) | |
1871 | finish_pam(); | |
1872 | #endif /* USE_PAM */ | |
1873 | ||
1874 | #ifdef SSH_AUDIT_EVENTS | |
1875 | PRIVSEP(audit_event(SSH_CONNECTION_CLOSE)); | |
1876 | #endif | |
1877 | ||
1878 | packet_close(); | |
1879 | ||
1880 | if (use_privsep) | |
1881 | mm_terminate(); | |
1882 | ||
1883 | exit(0); | |
1884 | } | |
1885 | ||
1886 | /* | |
1887 | * Decrypt session_key_int using our private server key and private host key | |
1888 | * (key with larger modulus first). | |
1889 | */ | |
1890 | int | |
1891 | ssh1_session_key(BIGNUM *session_key_int) | |
1892 | { | |
1893 | int rsafail = 0; | |
1894 | ||
1895 | if (BN_cmp(sensitive_data.server_key->rsa->n, | |
1896 | sensitive_data.ssh1_host_key->rsa->n) > 0) { | |
1897 | /* Server key has bigger modulus. */ | |
1898 | if (BN_num_bits(sensitive_data.server_key->rsa->n) < | |
1899 | BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + | |
1900 | SSH_KEY_BITS_RESERVED) { | |
1901 | fatal("do_connection: %s: " | |
1902 | "server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d", | |
1903 | get_remote_ipaddr(), | |
1904 | BN_num_bits(sensitive_data.server_key->rsa->n), | |
1905 | BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), | |
1906 | SSH_KEY_BITS_RESERVED); | |
1907 | } | |
1908 | if (rsa_private_decrypt(session_key_int, session_key_int, | |
1909 | sensitive_data.server_key->rsa) <= 0) | |
1910 | rsafail++; | |
1911 | if (rsa_private_decrypt(session_key_int, session_key_int, | |
1912 | sensitive_data.ssh1_host_key->rsa) <= 0) | |
1913 | rsafail++; | |
1914 | } else { | |
1915 | /* Host key has bigger modulus (or they are equal). */ | |
1916 | if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) < | |
1917 | BN_num_bits(sensitive_data.server_key->rsa->n) + | |
1918 | SSH_KEY_BITS_RESERVED) { | |
1919 | fatal("do_connection: %s: " | |
1920 | "host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d", | |
1921 | get_remote_ipaddr(), | |
1922 | BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), | |
1923 | BN_num_bits(sensitive_data.server_key->rsa->n), | |
1924 | SSH_KEY_BITS_RESERVED); | |
1925 | } | |
1926 | if (rsa_private_decrypt(session_key_int, session_key_int, | |
1927 | sensitive_data.ssh1_host_key->rsa) < 0) | |
1928 | rsafail++; | |
1929 | if (rsa_private_decrypt(session_key_int, session_key_int, | |
1930 | sensitive_data.server_key->rsa) < 0) | |
1931 | rsafail++; | |
1932 | } | |
1933 | return (rsafail); | |
1934 | } | |
1935 | /* | |
1936 | * SSH1 key exchange | |
1937 | */ | |
1938 | static void | |
1939 | do_ssh1_kex(void) | |
1940 | { | |
1941 | int i, len; | |
1942 | int rsafail = 0; | |
1943 | BIGNUM *session_key_int; | |
1944 | u_char session_key[SSH_SESSION_KEY_LENGTH]; | |
1945 | u_char cookie[8]; | |
1946 | u_int cipher_type, auth_mask, protocol_flags; | |
1947 | ||
1948 | /* | |
1949 | * Generate check bytes that the client must send back in the user | |
1950 | * packet in order for it to be accepted; this is used to defy ip | |
1951 | * spoofing attacks. Note that this only works against somebody | |
1952 | * doing IP spoofing from a remote machine; any machine on the local | |
1953 | * network can still see outgoing packets and catch the random | |
1954 | * cookie. This only affects rhosts authentication, and this is one | |
1955 | * of the reasons why it is inherently insecure. | |
1956 | */ | |
1957 | arc4random_buf(cookie, sizeof(cookie)); | |
1958 | ||
1959 | /* | |
1960 | * Send our public key. We include in the packet 64 bits of random | |
1961 | * data that must be matched in the reply in order to prevent IP | |
1962 | * spoofing. | |
1963 | */ | |
1964 | packet_start(SSH_SMSG_PUBLIC_KEY); | |
1965 | for (i = 0; i < 8; i++) | |
1966 | packet_put_char(cookie[i]); | |
1967 | ||
1968 | /* Store our public server RSA key. */ | |
1969 | packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n)); | |
1970 | packet_put_bignum(sensitive_data.server_key->rsa->e); | |
1971 | packet_put_bignum(sensitive_data.server_key->rsa->n); | |
1972 | ||
1973 | /* Store our public host RSA key. */ | |
1974 | packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); | |
1975 | packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e); | |
1976 | packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n); | |
1977 | ||
1978 | /* Put protocol flags. */ | |
1979 | packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN); | |
1980 | ||
1981 | /* Declare which ciphers we support. */ | |
1982 | packet_put_int(cipher_mask_ssh1(0)); | |
1983 | ||
1984 | /* Declare supported authentication types. */ | |
1985 | auth_mask = 0; | |
1986 | if (options.rhosts_rsa_authentication) | |
1987 | auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA; | |
1988 | if (options.rsa_authentication) | |
1989 | auth_mask |= 1 << SSH_AUTH_RSA; | |
1990 | if (options.challenge_response_authentication == 1) | |
1991 | auth_mask |= 1 << SSH_AUTH_TIS; | |
1992 | if (options.password_authentication) | |
1993 | auth_mask |= 1 << SSH_AUTH_PASSWORD; | |
1994 | packet_put_int(auth_mask); | |
1995 | ||
1996 | /* Send the packet and wait for it to be sent. */ | |
1997 | packet_send(); | |
1998 | packet_write_wait(); | |
1999 | ||
2000 | debug("Sent %d bit server key and %d bit host key.", | |
2001 | BN_num_bits(sensitive_data.server_key->rsa->n), | |
2002 | BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); | |
2003 | ||
2004 | /* Read clients reply (cipher type and session key). */ | |
2005 | packet_read_expect(SSH_CMSG_SESSION_KEY); | |
2006 | ||
2007 | /* Get cipher type and check whether we accept this. */ | |
2008 | cipher_type = packet_get_char(); | |
2009 | ||
2010 | if (!(cipher_mask_ssh1(0) & (1 << cipher_type))) | |
2011 | packet_disconnect("Warning: client selects unsupported cipher."); | |
2012 | ||
2013 | /* Get check bytes from the packet. These must match those we | |
2014 | sent earlier with the public key packet. */ | |
2015 | for (i = 0; i < 8; i++) | |
2016 | if (cookie[i] != packet_get_char()) | |
2017 | packet_disconnect("IP Spoofing check bytes do not match."); | |
2018 | ||
2019 | debug("Encryption type: %.200s", cipher_name(cipher_type)); | |
2020 | ||
2021 | /* Get the encrypted integer. */ | |
2022 | if ((session_key_int = BN_new()) == NULL) | |
2023 | fatal("do_ssh1_kex: BN_new failed"); | |
2024 | packet_get_bignum(session_key_int); | |
2025 | ||
2026 | protocol_flags = packet_get_int(); | |
2027 | packet_set_protocol_flags(protocol_flags); | |
2028 | packet_check_eom(); | |
2029 | ||
2030 | /* Decrypt session_key_int using host/server keys */ | |
2031 | rsafail = PRIVSEP(ssh1_session_key(session_key_int)); | |
2032 | ||
2033 | /* | |
2034 | * Extract session key from the decrypted integer. The key is in the | |
2035 | * least significant 256 bits of the integer; the first byte of the | |
2036 | * key is in the highest bits. | |
2037 | */ | |
2038 | if (!rsafail) { | |
2039 | (void) BN_mask_bits(session_key_int, sizeof(session_key) * 8); | |
2040 | len = BN_num_bytes(session_key_int); | |
2041 | if (len < 0 || (u_int)len > sizeof(session_key)) { | |
2042 | error("do_ssh1_kex: bad session key len from %s: " | |
2043 | "session_key_int %d > sizeof(session_key) %lu", | |
2044 | get_remote_ipaddr(), len, (u_long)sizeof(session_key)); | |
2045 | rsafail++; | |
2046 | } else { | |
2047 | memset(session_key, 0, sizeof(session_key)); | |
2048 | BN_bn2bin(session_key_int, | |
2049 | session_key + sizeof(session_key) - len); | |
2050 | ||
2051 | derive_ssh1_session_id( | |
2052 | sensitive_data.ssh1_host_key->rsa->n, | |
2053 | sensitive_data.server_key->rsa->n, | |
2054 | cookie, session_id); | |
2055 | /* | |
2056 | * Xor the first 16 bytes of the session key with the | |
2057 | * session id. | |
2058 | */ | |
2059 | for (i = 0; i < 16; i++) | |
2060 | session_key[i] ^= session_id[i]; | |
2061 | } | |
2062 | } | |
2063 | if (rsafail) { | |
2064 | int bytes = BN_num_bytes(session_key_int); | |
2065 | u_char *buf = xmalloc(bytes); | |
2066 | MD5_CTX md; | |
2067 | ||
2068 | logit("do_connection: generating a fake encryption key"); | |
2069 | BN_bn2bin(session_key_int, buf); | |
2070 | MD5_Init(&md); | |
2071 | MD5_Update(&md, buf, bytes); | |
2072 | MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); | |
2073 | MD5_Final(session_key, &md); | |
2074 | MD5_Init(&md); | |
2075 | MD5_Update(&md, session_key, 16); | |
2076 | MD5_Update(&md, buf, bytes); | |
2077 | MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); | |
2078 | MD5_Final(session_key + 16, &md); | |
2079 | memset(buf, 0, bytes); | |
2080 | xfree(buf); | |
2081 | for (i = 0; i < 16; i++) | |
2082 | session_id[i] = session_key[i] ^ session_key[i + 16]; | |
2083 | } | |
2084 | /* Destroy the private and public keys. No longer. */ | |
2085 | destroy_sensitive_data(); | |
2086 | ||
2087 | if (use_privsep) | |
2088 | mm_ssh1_session_id(session_id); | |
2089 | ||
2090 | /* Destroy the decrypted integer. It is no longer needed. */ | |
2091 | BN_clear_free(session_key_int); | |
2092 | ||
2093 | /* Set the session key. From this on all communications will be encrypted. */ | |
2094 | packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type); | |
2095 | ||
2096 | /* Destroy our copy of the session key. It is no longer needed. */ | |
2097 | memset(session_key, 0, sizeof(session_key)); | |
2098 | ||
2099 | debug("Received session key; encryption turned on."); | |
2100 | ||
2101 | /* Send an acknowledgment packet. Note that this packet is sent encrypted. */ | |
2102 | packet_start(SSH_SMSG_SUCCESS); | |
2103 | packet_send(); | |
2104 | packet_write_wait(); | |
2105 | } | |
2106 | ||
2107 | /* | |
2108 | * SSH2 key exchange: diffie-hellman-group1-sha1 | |
2109 | */ | |
2110 | static void | |
2111 | do_ssh2_kex(void) | |
2112 | { | |
2113 | Kex *kex; | |
2114 | ||
2115 | if (options.ciphers != NULL) { | |
2116 | myproposal[PROPOSAL_ENC_ALGS_CTOS] = | |
2117 | myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; | |
2118 | } | |
2119 | myproposal[PROPOSAL_ENC_ALGS_CTOS] = | |
2120 | compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]); | |
2121 | myproposal[PROPOSAL_ENC_ALGS_STOC] = | |
2122 | compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]); | |
2123 | ||
2124 | if (options.macs != NULL) { | |
2125 | myproposal[PROPOSAL_MAC_ALGS_CTOS] = | |
2126 | myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs; | |
2127 | } | |
2128 | if (options.compression == COMP_NONE) { | |
2129 | myproposal[PROPOSAL_COMP_ALGS_CTOS] = | |
2130 | myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; | |
2131 | } else if (options.compression == COMP_DELAYED) { | |
2132 | myproposal[PROPOSAL_COMP_ALGS_CTOS] = | |
2133 | myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com"; | |
2134 | } | |
2135 | ||
2136 | myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types(); | |
2137 | ||
2138 | /* start key exchange */ | |
2139 | kex = kex_setup(myproposal); | |
2140 | kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server; | |
2141 | kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server; | |
2142 | kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; | |
2143 | kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; | |
2144 | kex->server = 1; | |
2145 | kex->client_version_string=client_version_string; | |
2146 | kex->server_version_string=server_version_string; | |
2147 | kex->load_host_key=&get_hostkey_by_type; | |
2148 | kex->host_key_index=&get_hostkey_index; | |
2149 | ||
2150 | xxx_kex = kex; | |
2151 | ||
2152 | dispatch_run(DISPATCH_BLOCK, &kex->done, kex); | |
2153 | ||
2154 | session_id2 = kex->session_id; | |
2155 | session_id2_len = kex->session_id_len; | |
2156 | ||
2157 | #ifdef DEBUG_KEXDH | |
2158 | /* send 1st encrypted/maced/compressed message */ | |
2159 | packet_start(SSH2_MSG_IGNORE); | |
2160 | packet_put_cstring("markus"); | |
2161 | packet_send(); | |
2162 | packet_write_wait(); | |
2163 | #endif | |
2164 | debug("KEX done"); | |
2165 | } | |
2166 | ||
2167 | /* server specific fatal cleanup */ | |
2168 | void | |
2169 | cleanup_exit(int i) | |
2170 | { | |
2171 | if (the_authctxt) | |
2172 | do_cleanup(the_authctxt); | |
2173 | #ifdef SSH_AUDIT_EVENTS | |
2174 | /* done after do_cleanup so it can cancel the PAM auth 'thread' */ | |
2175 | if (!use_privsep || mm_is_monitor()) | |
2176 | audit_event(SSH_CONNECTION_ABANDON); | |
2177 | #endif | |
2178 | _exit(i); | |
2179 | } |