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1 | /* | |
2 | * Author: Tatu Ylonen <ylo@cs.hut.fi> | |
3 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
4 | * All rights reserved | |
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. | |
10 | * | |
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". | |
16 | * | |
17 | * SSH2 implementation: | |
18 | * | |
19 | * Copyright (c) 2000 Markus Friedl. All rights reserved. | |
20 | * | |
21 | * Redistribution and use in source and binary forms, with or without | |
22 | * modification, are permitted provided that the following conditions | |
23 | * are met: | |
24 | * 1. Redistributions of source code must retain the above copyright | |
25 | * notice, this list of conditions and the following disclaimer. | |
26 | * 2. Redistributions in binary form must reproduce the above copyright | |
27 | * notice, this list of conditions and the following disclaimer in the | |
28 | * documentation and/or other materials provided with the distribution. | |
29 | * | |
30 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR | |
31 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
32 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
33 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, | |
34 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
35 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
36 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
37 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
38 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
39 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
40 | */ | |
41 | ||
42 | #include "includes.h" | |
43 | RCSID("$OpenBSD: sshd.c,v 1.195 2001/04/15 16:58:03 markus Exp $"); | |
44 | ||
45 | #include <openssl/dh.h> | |
46 | #include <openssl/bn.h> | |
47 | #include <openssl/hmac.h> | |
48 | ||
49 | #include "ssh.h" | |
50 | #include "ssh1.h" | |
51 | #include "ssh2.h" | |
52 | #include "xmalloc.h" | |
53 | #include "rsa.h" | |
54 | #include "sshpty.h" | |
55 | #include "packet.h" | |
56 | #include "mpaux.h" | |
57 | #include "log.h" | |
58 | #include "servconf.h" | |
59 | #include "uidswap.h" | |
60 | #include "compat.h" | |
61 | #include "buffer.h" | |
62 | #include "cipher.h" | |
63 | #include "kex.h" | |
64 | #include "key.h" | |
65 | #include "dh.h" | |
66 | #include "myproposal.h" | |
67 | #include "authfile.h" | |
68 | #include "pathnames.h" | |
69 | #include "atomicio.h" | |
70 | #include "canohost.h" | |
71 | #include "auth.h" | |
72 | #include "misc.h" | |
73 | #include "dispatch.h" | |
74 | ||
75 | #ifdef LIBWRAP | |
76 | #include <tcpd.h> | |
77 | #include <syslog.h> | |
78 | int allow_severity = LOG_INFO; | |
79 | int deny_severity = LOG_WARNING; | |
80 | #endif /* LIBWRAP */ | |
81 | ||
82 | #ifndef O_NOCTTY | |
83 | #define O_NOCTTY 0 | |
84 | #endif | |
85 | ||
86 | #ifdef HAVE___PROGNAME | |
87 | extern char *__progname; | |
88 | #else | |
89 | char *__progname; | |
90 | #endif | |
91 | ||
92 | /* Server configuration options. */ | |
93 | ServerOptions options; | |
94 | ||
95 | /* Name of the server configuration file. */ | |
96 | char *config_file_name = _PATH_SERVER_CONFIG_FILE; | |
97 | ||
98 | /* | |
99 | * Flag indicating whether IPv4 or IPv6. This can be set on the command line. | |
100 | * Default value is AF_UNSPEC means both IPv4 and IPv6. | |
101 | */ | |
102 | #ifdef IPV4_DEFAULT | |
103 | int IPv4or6 = AF_INET; | |
104 | #else | |
105 | int IPv4or6 = AF_UNSPEC; | |
106 | #endif | |
107 | ||
108 | /* | |
109 | * Debug mode flag. This can be set on the command line. If debug | |
110 | * mode is enabled, extra debugging output will be sent to the system | |
111 | * log, the daemon will not go to background, and will exit after processing | |
112 | * the first connection. | |
113 | */ | |
114 | int debug_flag = 0; | |
115 | ||
116 | /* Flag indicating that the daemon is being started from inetd. */ | |
117 | int inetd_flag = 0; | |
118 | ||
119 | /* Flag indicating that sshd should not detach and become a daemon. */ | |
120 | int no_daemon_flag = 0; | |
121 | ||
122 | /* debug goes to stderr unless inetd_flag is set */ | |
123 | int log_stderr = 0; | |
124 | ||
125 | /* Saved arguments to main(). */ | |
126 | char **saved_argv; | |
127 | int saved_argc; | |
128 | ||
129 | /* | |
130 | * The sockets that the server is listening; this is used in the SIGHUP | |
131 | * signal handler. | |
132 | */ | |
133 | #define MAX_LISTEN_SOCKS 16 | |
134 | int listen_socks[MAX_LISTEN_SOCKS]; | |
135 | int num_listen_socks = 0; | |
136 | ||
137 | /* | |
138 | * the client's version string, passed by sshd2 in compat mode. if != NULL, | |
139 | * sshd will skip the version-number exchange | |
140 | */ | |
141 | char *client_version_string = NULL; | |
142 | char *server_version_string = NULL; | |
143 | ||
144 | /* for rekeying XXX fixme */ | |
145 | Kex *xxx_kex; | |
146 | ||
147 | /* | |
148 | * Any really sensitive data in the application is contained in this | |
149 | * structure. The idea is that this structure could be locked into memory so | |
150 | * that the pages do not get written into swap. However, there are some | |
151 | * problems. The private key contains BIGNUMs, and we do not (in principle) | |
152 | * have access to the internals of them, and locking just the structure is | |
153 | * not very useful. Currently, memory locking is not implemented. | |
154 | */ | |
155 | struct { | |
156 | Key *server_key; /* ephemeral server key */ | |
157 | Key *ssh1_host_key; /* ssh1 host key */ | |
158 | Key **host_keys; /* all private host keys */ | |
159 | int have_ssh1_key; | |
160 | int have_ssh2_key; | |
161 | u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH]; | |
162 | } sensitive_data; | |
163 | ||
164 | /* | |
165 | * Flag indicating whether the RSA server key needs to be regenerated. | |
166 | * Is set in the SIGALRM handler and cleared when the key is regenerated. | |
167 | */ | |
168 | int key_do_regen = 0; | |
169 | ||
170 | /* This is set to true when SIGHUP is received. */ | |
171 | int received_sighup = 0; | |
172 | ||
173 | /* session identifier, used by RSA-auth */ | |
174 | u_char session_id[16]; | |
175 | ||
176 | /* same for ssh2 */ | |
177 | u_char *session_id2 = NULL; | |
178 | int session_id2_len = 0; | |
179 | ||
180 | /* record remote hostname or ip */ | |
181 | u_int utmp_len = MAXHOSTNAMELEN; | |
182 | ||
183 | /* Prototypes for various functions defined later in this file. */ | |
184 | void do_ssh1_kex(void); | |
185 | void do_ssh2_kex(void); | |
186 | ||
187 | void ssh_dh1_server(Kex *, Buffer *_kexinit, Buffer *); | |
188 | void ssh_dhgex_server(Kex *, Buffer *_kexinit, Buffer *); | |
189 | ||
190 | /* | |
191 | * Close all listening sockets | |
192 | */ | |
193 | void | |
194 | close_listen_socks(void) | |
195 | { | |
196 | int i; | |
197 | for (i = 0; i < num_listen_socks; i++) | |
198 | close(listen_socks[i]); | |
199 | num_listen_socks = -1; | |
200 | } | |
201 | ||
202 | /* | |
203 | * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; | |
204 | * the effect is to reread the configuration file (and to regenerate | |
205 | * the server key). | |
206 | */ | |
207 | void | |
208 | sighup_handler(int sig) | |
209 | { | |
210 | received_sighup = 1; | |
211 | signal(SIGHUP, sighup_handler); | |
212 | } | |
213 | ||
214 | /* | |
215 | * Called from the main program after receiving SIGHUP. | |
216 | * Restarts the server. | |
217 | */ | |
218 | void | |
219 | sighup_restart(void) | |
220 | { | |
221 | log("Received SIGHUP; restarting."); | |
222 | close_listen_socks(); | |
223 | execv(saved_argv[0], saved_argv); | |
224 | log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], strerror(errno)); | |
225 | exit(1); | |
226 | } | |
227 | ||
228 | /* | |
229 | * Generic signal handler for terminating signals in the master daemon. | |
230 | * These close the listen socket; not closing it seems to cause "Address | |
231 | * already in use" problems on some machines, which is inconvenient. | |
232 | */ | |
233 | void | |
234 | sigterm_handler(int sig) | |
235 | { | |
236 | log("Received signal %d; terminating.", sig); | |
237 | close_listen_socks(); | |
238 | unlink(options.pid_file); | |
239 | exit(255); | |
240 | } | |
241 | ||
242 | /* | |
243 | * SIGCHLD handler. This is called whenever a child dies. This will then | |
244 | * reap any zombies left by exited c. | |
245 | */ | |
246 | void | |
247 | main_sigchld_handler(int sig) | |
248 | { | |
249 | int save_errno = errno; | |
250 | int status; | |
251 | ||
252 | while (waitpid(-1, &status, WNOHANG) > 0) | |
253 | ; | |
254 | ||
255 | signal(SIGCHLD, main_sigchld_handler); | |
256 | errno = save_errno; | |
257 | } | |
258 | ||
259 | /* | |
260 | * Signal handler for the alarm after the login grace period has expired. | |
261 | */ | |
262 | void | |
263 | grace_alarm_handler(int sig) | |
264 | { | |
265 | /* Close the connection. */ | |
266 | packet_close(); | |
267 | ||
268 | /* Log error and exit. */ | |
269 | fatal("Timeout before authentication for %s.", get_remote_ipaddr()); | |
270 | } | |
271 | ||
272 | /* | |
273 | * Signal handler for the key regeneration alarm. Note that this | |
274 | * alarm only occurs in the daemon waiting for connections, and it does not | |
275 | * do anything with the private key or random state before forking. | |
276 | * Thus there should be no concurrency control/asynchronous execution | |
277 | * problems. | |
278 | */ | |
279 | void | |
280 | generate_ephemeral_server_key(void) | |
281 | { | |
282 | u_int32_t rand = 0; | |
283 | int i; | |
284 | ||
285 | verbose("Generating %s%d bit RSA key.", | |
286 | sensitive_data.server_key ? "new " : "", options.server_key_bits); | |
287 | if (sensitive_data.server_key != NULL) | |
288 | key_free(sensitive_data.server_key); | |
289 | sensitive_data.server_key = key_generate(KEY_RSA1, | |
290 | options.server_key_bits); | |
291 | verbose("RSA key generation complete."); | |
292 | ||
293 | for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { | |
294 | if (i % 4 == 0) | |
295 | rand = arc4random(); | |
296 | sensitive_data.ssh1_cookie[i] = rand & 0xff; | |
297 | rand >>= 8; | |
298 | } | |
299 | arc4random_stir(); | |
300 | } | |
301 | ||
302 | void | |
303 | key_regeneration_alarm(int sig) | |
304 | { | |
305 | int save_errno = errno; | |
306 | signal(SIGALRM, SIG_DFL); | |
307 | errno = save_errno; | |
308 | key_do_regen = 1; | |
309 | } | |
310 | ||
311 | void | |
312 | sshd_exchange_identification(int sock_in, int sock_out) | |
313 | { | |
314 | int i, mismatch; | |
315 | int remote_major, remote_minor; | |
316 | int major, minor; | |
317 | char *s; | |
318 | char buf[256]; /* Must not be larger than remote_version. */ | |
319 | char remote_version[256]; /* Must be at least as big as buf. */ | |
320 | ||
321 | if ((options.protocol & SSH_PROTO_1) && | |
322 | (options.protocol & SSH_PROTO_2)) { | |
323 | major = PROTOCOL_MAJOR_1; | |
324 | minor = 99; | |
325 | } else if (options.protocol & SSH_PROTO_2) { | |
326 | major = PROTOCOL_MAJOR_2; | |
327 | minor = PROTOCOL_MINOR_2; | |
328 | } else { | |
329 | major = PROTOCOL_MAJOR_1; | |
330 | minor = PROTOCOL_MINOR_1; | |
331 | } | |
332 | snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION); | |
333 | server_version_string = xstrdup(buf); | |
334 | ||
335 | if (client_version_string == NULL) { | |
336 | /* Send our protocol version identification. */ | |
337 | if (atomicio(write, sock_out, server_version_string, strlen(server_version_string)) | |
338 | != strlen(server_version_string)) { | |
339 | log("Could not write ident string to %s.", get_remote_ipaddr()); | |
340 | fatal_cleanup(); | |
341 | } | |
342 | ||
343 | /* Read other side's version identification. */ | |
344 | memset(buf, 0, sizeof(buf)); | |
345 | for (i = 0; i < sizeof(buf) - 1; i++) { | |
346 | if (atomicio(read, sock_in, &buf[i], 1) != 1) { | |
347 | log("Did not receive identification string from %s.", | |
348 | get_remote_ipaddr()); | |
349 | fatal_cleanup(); | |
350 | } | |
351 | if (buf[i] == '\r') { | |
352 | buf[i] = 0; | |
353 | /* Kludge for F-Secure Macintosh < 1.0.2 */ | |
354 | if (i == 12 && | |
355 | strncmp(buf, "SSH-1.5-W1.0", 12) == 0) | |
356 | break; | |
357 | continue; | |
358 | } | |
359 | if (buf[i] == '\n') { | |
360 | buf[i] = 0; | |
361 | break; | |
362 | } | |
363 | } | |
364 | buf[sizeof(buf) - 1] = 0; | |
365 | client_version_string = xstrdup(buf); | |
366 | } | |
367 | ||
368 | /* | |
369 | * Check that the versions match. In future this might accept | |
370 | * several versions and set appropriate flags to handle them. | |
371 | */ | |
372 | if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n", | |
373 | &remote_major, &remote_minor, remote_version) != 3) { | |
374 | s = "Protocol mismatch.\n"; | |
375 | (void) atomicio(write, sock_out, s, strlen(s)); | |
376 | close(sock_in); | |
377 | close(sock_out); | |
378 | log("Bad protocol version identification '%.100s' from %s", | |
379 | client_version_string, get_remote_ipaddr()); | |
380 | fatal_cleanup(); | |
381 | } | |
382 | debug("Client protocol version %d.%d; client software version %.100s", | |
383 | remote_major, remote_minor, remote_version); | |
384 | ||
385 | compat_datafellows(remote_version); | |
386 | ||
387 | if (datafellows & SSH_BUG_SCANNER) { | |
388 | log("scanned from %s with %s. Don't panic.", | |
389 | get_remote_ipaddr(), client_version_string); | |
390 | fatal_cleanup(); | |
391 | } | |
392 | ||
393 | mismatch = 0; | |
394 | switch(remote_major) { | |
395 | case 1: | |
396 | if (remote_minor == 99) { | |
397 | if (options.protocol & SSH_PROTO_2) | |
398 | enable_compat20(); | |
399 | else | |
400 | mismatch = 1; | |
401 | break; | |
402 | } | |
403 | if (!(options.protocol & SSH_PROTO_1)) { | |
404 | mismatch = 1; | |
405 | break; | |
406 | } | |
407 | if (remote_minor < 3) { | |
408 | packet_disconnect("Your ssh version is too old and " | |
409 | "is no longer supported. Please install a newer version."); | |
410 | } else if (remote_minor == 3) { | |
411 | /* note that this disables agent-forwarding */ | |
412 | enable_compat13(); | |
413 | } | |
414 | break; | |
415 | case 2: | |
416 | if (options.protocol & SSH_PROTO_2) { | |
417 | enable_compat20(); | |
418 | break; | |
419 | } | |
420 | /* FALLTHROUGH */ | |
421 | default: | |
422 | mismatch = 1; | |
423 | break; | |
424 | } | |
425 | chop(server_version_string); | |
426 | debug("Local version string %.200s", server_version_string); | |
427 | ||
428 | if (mismatch) { | |
429 | s = "Protocol major versions differ.\n"; | |
430 | (void) atomicio(write, sock_out, s, strlen(s)); | |
431 | close(sock_in); | |
432 | close(sock_out); | |
433 | log("Protocol major versions differ for %s: %.200s vs. %.200s", | |
434 | get_remote_ipaddr(), | |
435 | server_version_string, client_version_string); | |
436 | fatal_cleanup(); | |
437 | } | |
438 | if (compat20) | |
439 | packet_set_ssh2_format(); | |
440 | } | |
441 | ||
442 | ||
443 | /* Destroy the host and server keys. They will no longer be needed. */ | |
444 | void | |
445 | destroy_sensitive_data(void) | |
446 | { | |
447 | int i; | |
448 | ||
449 | if (sensitive_data.server_key) { | |
450 | key_free(sensitive_data.server_key); | |
451 | sensitive_data.server_key = NULL; | |
452 | } | |
453 | for(i = 0; i < options.num_host_key_files; i++) { | |
454 | if (sensitive_data.host_keys[i]) { | |
455 | key_free(sensitive_data.host_keys[i]); | |
456 | sensitive_data.host_keys[i] = NULL; | |
457 | } | |
458 | } | |
459 | sensitive_data.ssh1_host_key = NULL; | |
460 | memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH); | |
461 | } | |
462 | ||
463 | char * | |
464 | list_hostkey_types(void) | |
465 | { | |
466 | static char buf[1024]; | |
467 | int i; | |
468 | buf[0] = '\0'; | |
469 | for(i = 0; i < options.num_host_key_files; i++) { | |
470 | Key *key = sensitive_data.host_keys[i]; | |
471 | if (key == NULL) | |
472 | continue; | |
473 | switch(key->type) { | |
474 | case KEY_RSA: | |
475 | case KEY_DSA: | |
476 | strlcat(buf, key_ssh_name(key), sizeof buf); | |
477 | strlcat(buf, ",", sizeof buf); | |
478 | break; | |
479 | } | |
480 | } | |
481 | i = strlen(buf); | |
482 | if (i > 0 && buf[i-1] == ',') | |
483 | buf[i-1] = '\0'; | |
484 | debug("list_hostkey_types: %s", buf); | |
485 | return buf; | |
486 | } | |
487 | ||
488 | Key * | |
489 | get_hostkey_by_type(int type) | |
490 | { | |
491 | int i; | |
492 | for(i = 0; i < options.num_host_key_files; i++) { | |
493 | Key *key = sensitive_data.host_keys[i]; | |
494 | if (key != NULL && key->type == type) | |
495 | return key; | |
496 | } | |
497 | return NULL; | |
498 | } | |
499 | ||
500 | /* | |
501 | * returns 1 if connection should be dropped, 0 otherwise. | |
502 | * dropping starts at connection #max_startups_begin with a probability | |
503 | * of (max_startups_rate/100). the probability increases linearly until | |
504 | * all connections are dropped for startups > max_startups | |
505 | */ | |
506 | int | |
507 | drop_connection(int startups) | |
508 | { | |
509 | double p, r; | |
510 | ||
511 | if (startups < options.max_startups_begin) | |
512 | return 0; | |
513 | if (startups >= options.max_startups) | |
514 | return 1; | |
515 | if (options.max_startups_rate == 100) | |
516 | return 1; | |
517 | ||
518 | p = 100 - options.max_startups_rate; | |
519 | p *= startups - options.max_startups_begin; | |
520 | p /= (double) (options.max_startups - options.max_startups_begin); | |
521 | p += options.max_startups_rate; | |
522 | p /= 100.0; | |
523 | r = arc4random() / (double) UINT_MAX; | |
524 | ||
525 | debug("drop_connection: p %g, r %g", p, r); | |
526 | return (r < p) ? 1 : 0; | |
527 | } | |
528 | ||
529 | int *startup_pipes = NULL; /* options.max_startup sized array of fd ints */ | |
530 | int startup_pipe; /* in child */ | |
531 | ||
532 | /* | |
533 | * Main program for the daemon. | |
534 | */ | |
535 | int | |
536 | main(int ac, char **av) | |
537 | { | |
538 | extern char *optarg; | |
539 | extern int optind; | |
540 | int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1; | |
541 | pid_t pid; | |
542 | socklen_t fromlen; | |
543 | fd_set *fdset; | |
544 | struct sockaddr_storage from; | |
545 | const char *remote_ip; | |
546 | int remote_port; | |
547 | FILE *f; | |
548 | struct linger linger; | |
549 | struct addrinfo *ai; | |
550 | char ntop[NI_MAXHOST], strport[NI_MAXSERV]; | |
551 | int listen_sock, maxfd; | |
552 | int startup_p[2]; | |
553 | int startups = 0; | |
554 | Key *key; | |
555 | int ret, key_used = 0; | |
556 | ||
557 | __progname = get_progname(av[0]); | |
558 | init_rng(); | |
559 | ||
560 | /* Save argv. */ | |
561 | saved_argc = ac; | |
562 | saved_argv = av; | |
563 | ||
564 | /* Initialize configuration options to their default values. */ | |
565 | initialize_server_options(&options); | |
566 | ||
567 | /* Parse command-line arguments. */ | |
568 | while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:dDeiqQ46")) != -1) { | |
569 | switch (opt) { | |
570 | case '4': | |
571 | IPv4or6 = AF_INET; | |
572 | break; | |
573 | case '6': | |
574 | IPv4or6 = AF_INET6; | |
575 | break; | |
576 | case 'f': | |
577 | config_file_name = optarg; | |
578 | break; | |
579 | case 'd': | |
580 | if (0 == debug_flag) { | |
581 | debug_flag = 1; | |
582 | options.log_level = SYSLOG_LEVEL_DEBUG1; | |
583 | } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) { | |
584 | options.log_level++; | |
585 | } else { | |
586 | fprintf(stderr, "Too high debugging level.\n"); | |
587 | exit(1); | |
588 | } | |
589 | break; | |
590 | case 'D': | |
591 | no_daemon_flag = 1; | |
592 | break; | |
593 | case 'e': | |
594 | log_stderr = 1; | |
595 | break; | |
596 | case 'i': | |
597 | inetd_flag = 1; | |
598 | break; | |
599 | case 'Q': | |
600 | /* ignored */ | |
601 | break; | |
602 | case 'q': | |
603 | options.log_level = SYSLOG_LEVEL_QUIET; | |
604 | break; | |
605 | case 'b': | |
606 | options.server_key_bits = atoi(optarg); | |
607 | break; | |
608 | case 'p': | |
609 | options.ports_from_cmdline = 1; | |
610 | if (options.num_ports >= MAX_PORTS) { | |
611 | fprintf(stderr, "too many ports.\n"); | |
612 | exit(1); | |
613 | } | |
614 | options.ports[options.num_ports++] = a2port(optarg); | |
615 | if (options.ports[options.num_ports-1] == 0) { | |
616 | fprintf(stderr, "Bad port number.\n"); | |
617 | exit(1); | |
618 | } | |
619 | break; | |
620 | case 'g': | |
621 | options.login_grace_time = atoi(optarg); | |
622 | break; | |
623 | case 'k': | |
624 | options.key_regeneration_time = atoi(optarg); | |
625 | break; | |
626 | case 'h': | |
627 | if (options.num_host_key_files >= MAX_HOSTKEYS) { | |
628 | fprintf(stderr, "too many host keys.\n"); | |
629 | exit(1); | |
630 | } | |
631 | options.host_key_files[options.num_host_key_files++] = optarg; | |
632 | break; | |
633 | case 'V': | |
634 | client_version_string = optarg; | |
635 | /* only makes sense with inetd_flag, i.e. no listen() */ | |
636 | inetd_flag = 1; | |
637 | break; | |
638 | case 'u': | |
639 | utmp_len = atoi(optarg); | |
640 | break; | |
641 | case '?': | |
642 | default: | |
643 | fprintf(stderr, "sshd version %s\n", SSH_VERSION); | |
644 | fprintf(stderr, "Usage: %s [options]\n", __progname); | |
645 | fprintf(stderr, "Options:\n"); | |
646 | fprintf(stderr, " -f file Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE); | |
647 | fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n"); | |
648 | fprintf(stderr, " -i Started from inetd\n"); | |
649 | fprintf(stderr, " -D Do not fork into daemon mode\n"); | |
650 | fprintf(stderr, " -q Quiet (no logging)\n"); | |
651 | fprintf(stderr, " -p port Listen on the specified port (default: 22)\n"); | |
652 | fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n"); | |
653 | fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n"); | |
654 | fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n"); | |
655 | fprintf(stderr, " -h file File from which to read host key (default: %s)\n", | |
656 | _PATH_HOST_KEY_FILE); | |
657 | fprintf(stderr, " -u len Maximum hostname length for utmp recording\n"); | |
658 | fprintf(stderr, " -4 Use IPv4 only\n"); | |
659 | fprintf(stderr, " -6 Use IPv6 only\n"); | |
660 | exit(1); | |
661 | } | |
662 | } | |
663 | SSLeay_add_all_algorithms(); | |
664 | ||
665 | /* | |
666 | * Force logging to stderr until we have loaded the private host | |
667 | * key (unless started from inetd) | |
668 | */ | |
669 | log_init(__progname, | |
670 | options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level, | |
671 | options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility, | |
672 | !inetd_flag); | |
673 | ||
674 | seed_rng(); | |
675 | ||
676 | /* Read server configuration options from the configuration file. */ | |
677 | read_server_config(&options, config_file_name); | |
678 | ||
679 | /* Fill in default values for those options not explicitly set. */ | |
680 | fill_default_server_options(&options); | |
681 | ||
682 | /* Check that there are no remaining arguments. */ | |
683 | if (optind < ac) { | |
684 | fprintf(stderr, "Extra argument %s.\n", av[optind]); | |
685 | exit(1); | |
686 | } | |
687 | ||
688 | debug("sshd version %.100s", SSH_VERSION); | |
689 | ||
690 | /* load private host keys */ | |
691 | sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*)); | |
692 | for(i = 0; i < options.num_host_key_files; i++) | |
693 | sensitive_data.host_keys[i] = NULL; | |
694 | sensitive_data.server_key = NULL; | |
695 | sensitive_data.ssh1_host_key = NULL; | |
696 | sensitive_data.have_ssh1_key = 0; | |
697 | sensitive_data.have_ssh2_key = 0; | |
698 | ||
699 | for(i = 0; i < options.num_host_key_files; i++) { | |
700 | key = key_load_private(options.host_key_files[i], "", NULL); | |
701 | sensitive_data.host_keys[i] = key; | |
702 | if (key == NULL) { | |
703 | error("Could not load host key: %s", | |
704 | options.host_key_files[i]); | |
705 | sensitive_data.host_keys[i] = NULL; | |
706 | continue; | |
707 | } | |
708 | switch(key->type){ | |
709 | case KEY_RSA1: | |
710 | sensitive_data.ssh1_host_key = key; | |
711 | sensitive_data.have_ssh1_key = 1; | |
712 | break; | |
713 | case KEY_RSA: | |
714 | case KEY_DSA: | |
715 | sensitive_data.have_ssh2_key = 1; | |
716 | break; | |
717 | } | |
718 | debug("private host key: #%d type %d %s", i, key->type, | |
719 | key_type(key)); | |
720 | } | |
721 | if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) { | |
722 | log("Disabling protocol version 1. Could not load host key"); | |
723 | options.protocol &= ~SSH_PROTO_1; | |
724 | } | |
725 | if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) { | |
726 | log("Disabling protocol version 2. Could not load host key"); | |
727 | options.protocol &= ~SSH_PROTO_2; | |
728 | } | |
729 | if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) { | |
730 | log("sshd: no hostkeys available -- exiting."); | |
731 | exit(1); | |
732 | } | |
733 | ||
734 | /* Check certain values for sanity. */ | |
735 | if (options.protocol & SSH_PROTO_1) { | |
736 | if (options.server_key_bits < 512 || | |
737 | options.server_key_bits > 32768) { | |
738 | fprintf(stderr, "Bad server key size.\n"); | |
739 | exit(1); | |
740 | } | |
741 | /* | |
742 | * Check that server and host key lengths differ sufficiently. This | |
743 | * is necessary to make double encryption work with rsaref. Oh, I | |
744 | * hate software patents. I dont know if this can go? Niels | |
745 | */ | |
746 | if (options.server_key_bits > | |
747 | BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - SSH_KEY_BITS_RESERVED && | |
748 | options.server_key_bits < | |
749 | BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) { | |
750 | options.server_key_bits = | |
751 | BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED; | |
752 | debug("Forcing server key to %d bits to make it differ from host key.", | |
753 | options.server_key_bits); | |
754 | } | |
755 | } | |
756 | ||
757 | #ifdef HAVE_SCO_PROTECTED_PW | |
758 | (void) set_auth_parameters(ac, av); | |
759 | #endif | |
760 | ||
761 | /* Initialize the log (it is reinitialized below in case we forked). */ | |
762 | if (debug_flag && !inetd_flag) | |
763 | log_stderr = 1; | |
764 | log_init(__progname, options.log_level, options.log_facility, log_stderr); | |
765 | ||
766 | /* | |
767 | * If not in debugging mode, and not started from inetd, disconnect | |
768 | * from the controlling terminal, and fork. The original process | |
769 | * exits. | |
770 | */ | |
771 | if (!(debug_flag || inetd_flag || no_daemon_flag)) { | |
772 | #ifdef TIOCNOTTY | |
773 | int fd; | |
774 | #endif /* TIOCNOTTY */ | |
775 | if (daemon(0, 0) < 0) | |
776 | fatal("daemon() failed: %.200s", strerror(errno)); | |
777 | ||
778 | /* Disconnect from the controlling tty. */ | |
779 | #ifdef TIOCNOTTY | |
780 | fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); | |
781 | if (fd >= 0) { | |
782 | (void) ioctl(fd, TIOCNOTTY, NULL); | |
783 | close(fd); | |
784 | } | |
785 | #endif /* TIOCNOTTY */ | |
786 | } | |
787 | /* Reinitialize the log (because of the fork above). */ | |
788 | log_init(__progname, options.log_level, options.log_facility, log_stderr); | |
789 | ||
790 | /* Initialize the random number generator. */ | |
791 | arc4random_stir(); | |
792 | ||
793 | /* Chdir to the root directory so that the current disk can be | |
794 | unmounted if desired. */ | |
795 | chdir("/"); | |
796 | ||
797 | /* ignore SIGPIPE */ | |
798 | signal(SIGPIPE, SIG_IGN); | |
799 | ||
800 | /* Start listening for a socket, unless started from inetd. */ | |
801 | if (inetd_flag) { | |
802 | int s1; | |
803 | s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */ | |
804 | dup(s1); | |
805 | sock_in = dup(0); | |
806 | sock_out = dup(1); | |
807 | startup_pipe = -1; | |
808 | /* | |
809 | * We intentionally do not close the descriptors 0, 1, and 2 | |
810 | * as our code for setting the descriptors won\'t work if | |
811 | * ttyfd happens to be one of those. | |
812 | */ | |
813 | debug("inetd sockets after dupping: %d, %d", sock_in, sock_out); | |
814 | if (options.protocol & SSH_PROTO_1) | |
815 | generate_ephemeral_server_key(); | |
816 | } else { | |
817 | for (ai = options.listen_addrs; ai; ai = ai->ai_next) { | |
818 | if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) | |
819 | continue; | |
820 | if (num_listen_socks >= MAX_LISTEN_SOCKS) | |
821 | fatal("Too many listen sockets. " | |
822 | "Enlarge MAX_LISTEN_SOCKS"); | |
823 | if (getnameinfo(ai->ai_addr, ai->ai_addrlen, | |
824 | ntop, sizeof(ntop), strport, sizeof(strport), | |
825 | NI_NUMERICHOST|NI_NUMERICSERV) != 0) { | |
826 | error("getnameinfo failed"); | |
827 | continue; | |
828 | } | |
829 | /* Create socket for listening. */ | |
830 | listen_sock = socket(ai->ai_family, SOCK_STREAM, 0); | |
831 | if (listen_sock < 0) { | |
832 | /* kernel may not support ipv6 */ | |
833 | verbose("socket: %.100s", strerror(errno)); | |
834 | continue; | |
835 | } | |
836 | if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) { | |
837 | error("listen_sock O_NONBLOCK: %s", strerror(errno)); | |
838 | close(listen_sock); | |
839 | continue; | |
840 | } | |
841 | /* | |
842 | * Set socket options. We try to make the port | |
843 | * reusable and have it close as fast as possible | |
844 | * without waiting in unnecessary wait states on | |
845 | * close. | |
846 | */ | |
847 | setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, | |
848 | (void *) &on, sizeof(on)); | |
849 | linger.l_onoff = 1; | |
850 | linger.l_linger = 5; | |
851 | setsockopt(listen_sock, SOL_SOCKET, SO_LINGER, | |
852 | (void *) &linger, sizeof(linger)); | |
853 | ||
854 | debug("Bind to port %s on %s.", strport, ntop); | |
855 | ||
856 | /* Bind the socket to the desired port. */ | |
857 | if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) { | |
858 | if (!ai->ai_next) | |
859 | error("Bind to port %s on %s failed: %.200s.", | |
860 | strport, ntop, strerror(errno)); | |
861 | close(listen_sock); | |
862 | continue; | |
863 | } | |
864 | listen_socks[num_listen_socks] = listen_sock; | |
865 | num_listen_socks++; | |
866 | ||
867 | /* Start listening on the port. */ | |
868 | log("Server listening on %s port %s.", ntop, strport); | |
869 | if (listen(listen_sock, 5) < 0) | |
870 | fatal("listen: %.100s", strerror(errno)); | |
871 | ||
872 | } | |
873 | freeaddrinfo(options.listen_addrs); | |
874 | ||
875 | if (!num_listen_socks) | |
876 | fatal("Cannot bind any address."); | |
877 | ||
878 | if (!debug_flag) { | |
879 | /* | |
880 | * Record our pid in /var/run/sshd.pid to make it | |
881 | * easier to kill the correct sshd. We don't want to | |
882 | * do this before the bind above because the bind will | |
883 | * fail if there already is a daemon, and this will | |
884 | * overwrite any old pid in the file. | |
885 | */ | |
886 | f = fopen(options.pid_file, "wb"); | |
887 | if (f) { | |
888 | fprintf(f, "%u\n", (u_int) getpid()); | |
889 | fclose(f); | |
890 | } | |
891 | } | |
892 | if (options.protocol & SSH_PROTO_1) | |
893 | generate_ephemeral_server_key(); | |
894 | ||
895 | /* Arrange to restart on SIGHUP. The handler needs listen_sock. */ | |
896 | signal(SIGHUP, sighup_handler); | |
897 | ||
898 | signal(SIGTERM, sigterm_handler); | |
899 | signal(SIGQUIT, sigterm_handler); | |
900 | ||
901 | /* Arrange SIGCHLD to be caught. */ | |
902 | signal(SIGCHLD, main_sigchld_handler); | |
903 | ||
904 | /* setup fd set for listen */ | |
905 | fdset = NULL; | |
906 | maxfd = 0; | |
907 | for (i = 0; i < num_listen_socks; i++) | |
908 | if (listen_socks[i] > maxfd) | |
909 | maxfd = listen_socks[i]; | |
910 | /* pipes connected to unauthenticated childs */ | |
911 | startup_pipes = xmalloc(options.max_startups * sizeof(int)); | |
912 | for (i = 0; i < options.max_startups; i++) | |
913 | startup_pipes[i] = -1; | |
914 | ||
915 | /* | |
916 | * Stay listening for connections until the system crashes or | |
917 | * the daemon is killed with a signal. | |
918 | */ | |
919 | for (;;) { | |
920 | if (received_sighup) | |
921 | sighup_restart(); | |
922 | if (fdset != NULL) | |
923 | xfree(fdset); | |
924 | fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask); | |
925 | fdset = (fd_set *)xmalloc(fdsetsz); | |
926 | memset(fdset, 0, fdsetsz); | |
927 | ||
928 | for (i = 0; i < num_listen_socks; i++) | |
929 | FD_SET(listen_socks[i], fdset); | |
930 | for (i = 0; i < options.max_startups; i++) | |
931 | if (startup_pipes[i] != -1) | |
932 | FD_SET(startup_pipes[i], fdset); | |
933 | ||
934 | /* Wait in select until there is a connection. */ | |
935 | ret = select(maxfd+1, fdset, NULL, NULL, NULL); | |
936 | if (ret < 0 && errno != EINTR) | |
937 | error("select: %.100s", strerror(errno)); | |
938 | if (key_used && key_do_regen) { | |
939 | generate_ephemeral_server_key(); | |
940 | key_used = 0; | |
941 | key_do_regen = 0; | |
942 | } | |
943 | if (ret < 0) | |
944 | continue; | |
945 | ||
946 | for (i = 0; i < options.max_startups; i++) | |
947 | if (startup_pipes[i] != -1 && | |
948 | FD_ISSET(startup_pipes[i], fdset)) { | |
949 | /* | |
950 | * the read end of the pipe is ready | |
951 | * if the child has closed the pipe | |
952 | * after successful authentication | |
953 | * or if the child has died | |
954 | */ | |
955 | close(startup_pipes[i]); | |
956 | startup_pipes[i] = -1; | |
957 | startups--; | |
958 | } | |
959 | for (i = 0; i < num_listen_socks; i++) { | |
960 | if (!FD_ISSET(listen_socks[i], fdset)) | |
961 | continue; | |
962 | fromlen = sizeof(from); | |
963 | newsock = accept(listen_socks[i], (struct sockaddr *)&from, | |
964 | &fromlen); | |
965 | if (newsock < 0) { | |
966 | if (errno != EINTR && errno != EWOULDBLOCK) | |
967 | error("accept: %.100s", strerror(errno)); | |
968 | continue; | |
969 | } | |
970 | if (fcntl(newsock, F_SETFL, 0) < 0) { | |
971 | error("newsock del O_NONBLOCK: %s", strerror(errno)); | |
972 | continue; | |
973 | } | |
974 | if (drop_connection(startups) == 1) { | |
975 | debug("drop connection #%d", startups); | |
976 | close(newsock); | |
977 | continue; | |
978 | } | |
979 | if (pipe(startup_p) == -1) { | |
980 | close(newsock); | |
981 | continue; | |
982 | } | |
983 | ||
984 | for (j = 0; j < options.max_startups; j++) | |
985 | if (startup_pipes[j] == -1) { | |
986 | startup_pipes[j] = startup_p[0]; | |
987 | if (maxfd < startup_p[0]) | |
988 | maxfd = startup_p[0]; | |
989 | startups++; | |
990 | break; | |
991 | } | |
992 | ||
993 | /* | |
994 | * Got connection. Fork a child to handle it, unless | |
995 | * we are in debugging mode. | |
996 | */ | |
997 | if (debug_flag) { | |
998 | /* | |
999 | * In debugging mode. Close the listening | |
1000 | * socket, and start processing the | |
1001 | * connection without forking. | |
1002 | */ | |
1003 | debug("Server will not fork when running in debugging mode."); | |
1004 | close_listen_socks(); | |
1005 | sock_in = newsock; | |
1006 | sock_out = newsock; | |
1007 | startup_pipe = -1; | |
1008 | pid = getpid(); | |
1009 | break; | |
1010 | } else { | |
1011 | /* | |
1012 | * Normal production daemon. Fork, and have | |
1013 | * the child process the connection. The | |
1014 | * parent continues listening. | |
1015 | */ | |
1016 | if ((pid = fork()) == 0) { | |
1017 | /* | |
1018 | * Child. Close the listening and max_startup | |
1019 | * sockets. Start using the accepted socket. | |
1020 | * Reinitialize logging (since our pid has | |
1021 | * changed). We break out of the loop to handle | |
1022 | * the connection. | |
1023 | */ | |
1024 | startup_pipe = startup_p[1]; | |
1025 | for (j = 0; j < options.max_startups; j++) | |
1026 | if (startup_pipes[j] != -1) | |
1027 | close(startup_pipes[j]); | |
1028 | close_listen_socks(); | |
1029 | sock_in = newsock; | |
1030 | sock_out = newsock; | |
1031 | log_init(__progname, options.log_level, options.log_facility, log_stderr); | |
1032 | break; | |
1033 | } | |
1034 | } | |
1035 | ||
1036 | /* Parent. Stay in the loop. */ | |
1037 | if (pid < 0) | |
1038 | error("fork: %.100s", strerror(errno)); | |
1039 | else | |
1040 | debug("Forked child %d.", pid); | |
1041 | ||
1042 | close(startup_p[1]); | |
1043 | ||
1044 | /* Mark that the key has been used (it was "given" to the child). */ | |
1045 | if ((options.protocol & SSH_PROTO_1) && | |
1046 | key_used == 0) { | |
1047 | /* Schedule server key regeneration alarm. */ | |
1048 | signal(SIGALRM, key_regeneration_alarm); | |
1049 | alarm(options.key_regeneration_time); | |
1050 | key_used = 1; | |
1051 | } | |
1052 | ||
1053 | arc4random_stir(); | |
1054 | ||
1055 | /* Close the new socket (the child is now taking care of it). */ | |
1056 | close(newsock); | |
1057 | } | |
1058 | /* child process check (or debug mode) */ | |
1059 | if (num_listen_socks < 0) | |
1060 | break; | |
1061 | } | |
1062 | } | |
1063 | ||
1064 | /* This is the child processing a new connection. */ | |
1065 | ||
1066 | /* | |
1067 | * Disable the key regeneration alarm. We will not regenerate the | |
1068 | * key since we are no longer in a position to give it to anyone. We | |
1069 | * will not restart on SIGHUP since it no longer makes sense. | |
1070 | */ | |
1071 | alarm(0); | |
1072 | signal(SIGALRM, SIG_DFL); | |
1073 | signal(SIGHUP, SIG_DFL); | |
1074 | signal(SIGTERM, SIG_DFL); | |
1075 | signal(SIGQUIT, SIG_DFL); | |
1076 | signal(SIGCHLD, SIG_DFL); | |
1077 | signal(SIGINT, SIG_DFL); | |
1078 | ||
1079 | /* | |
1080 | * Set socket options for the connection. We want the socket to | |
1081 | * close as fast as possible without waiting for anything. If the | |
1082 | * connection is not a socket, these will do nothing. | |
1083 | */ | |
1084 | /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */ | |
1085 | linger.l_onoff = 1; | |
1086 | linger.l_linger = 5; | |
1087 | setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger)); | |
1088 | ||
1089 | /* Set keepalives if requested. */ | |
1090 | if (options.keepalives && | |
1091 | setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, | |
1092 | sizeof(on)) < 0) | |
1093 | error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); | |
1094 | ||
1095 | /* | |
1096 | * Register our connection. This turns encryption off because we do | |
1097 | * not have a key. | |
1098 | */ | |
1099 | packet_set_connection(sock_in, sock_out); | |
1100 | ||
1101 | remote_port = get_remote_port(); | |
1102 | remote_ip = get_remote_ipaddr(); | |
1103 | ||
1104 | /* Check whether logins are denied from this host. */ | |
1105 | #ifdef LIBWRAP | |
1106 | /* XXX LIBWRAP noes not know about IPv6 */ | |
1107 | { | |
1108 | struct request_info req; | |
1109 | ||
1110 | request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, NULL); | |
1111 | fromhost(&req); | |
1112 | ||
1113 | if (!hosts_access(&req)) { | |
1114 | refuse(&req); | |
1115 | close(sock_in); | |
1116 | close(sock_out); | |
1117 | } | |
1118 | /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */ | |
1119 | } | |
1120 | #endif /* LIBWRAP */ | |
1121 | /* Log the connection. */ | |
1122 | verbose("Connection from %.500s port %d", remote_ip, remote_port); | |
1123 | ||
1124 | /* | |
1125 | * We don\'t want to listen forever unless the other side | |
1126 | * successfully authenticates itself. So we set up an alarm which is | |
1127 | * cleared after successful authentication. A limit of zero | |
1128 | * indicates no limit. Note that we don\'t set the alarm in debugging | |
1129 | * mode; it is just annoying to have the server exit just when you | |
1130 | * are about to discover the bug. | |
1131 | */ | |
1132 | signal(SIGALRM, grace_alarm_handler); | |
1133 | if (!debug_flag) | |
1134 | alarm(options.login_grace_time); | |
1135 | ||
1136 | sshd_exchange_identification(sock_in, sock_out); | |
1137 | /* | |
1138 | * Check that the connection comes from a privileged port. | |
1139 | * Rhosts-Authentication only makes sense from priviledged | |
1140 | * programs. Of course, if the intruder has root access on his local | |
1141 | * machine, he can connect from any port. So do not use these | |
1142 | * authentication methods from machines that you do not trust. | |
1143 | */ | |
1144 | if (remote_port >= IPPORT_RESERVED || | |
1145 | remote_port < IPPORT_RESERVED / 2) { | |
1146 | debug("Rhosts Authentication disabled, " | |
1147 | "originating port not trusted."); | |
1148 | options.rhosts_authentication = 0; | |
1149 | } | |
1150 | #ifdef KRB4 | |
1151 | if (!packet_connection_is_ipv4() && | |
1152 | options.kerberos_authentication) { | |
1153 | debug("Kerberos Authentication disabled, only available for IPv4."); | |
1154 | options.kerberos_authentication = 0; | |
1155 | } | |
1156 | #endif /* KRB4 */ | |
1157 | #ifdef AFS | |
1158 | /* If machine has AFS, set process authentication group. */ | |
1159 | if (k_hasafs()) { | |
1160 | k_setpag(); | |
1161 | k_unlog(); | |
1162 | } | |
1163 | #endif /* AFS */ | |
1164 | ||
1165 | packet_set_nonblocking(); | |
1166 | ||
1167 | /* perform the key exchange */ | |
1168 | /* authenticate user and start session */ | |
1169 | if (compat20) { | |
1170 | do_ssh2_kex(); | |
1171 | do_authentication2(); | |
1172 | } else { | |
1173 | do_ssh1_kex(); | |
1174 | do_authentication(); | |
1175 | } | |
1176 | ||
1177 | #ifdef KRB4 | |
1178 | /* Cleanup user's ticket cache file. */ | |
1179 | if (options.kerberos_ticket_cleanup) | |
1180 | (void) dest_tkt(); | |
1181 | #endif /* KRB4 */ | |
1182 | ||
1183 | /* The connection has been terminated. */ | |
1184 | verbose("Closing connection to %.100s", remote_ip); | |
1185 | ||
1186 | #ifdef USE_PAM | |
1187 | finish_pam(); | |
1188 | #endif /* USE_PAM */ | |
1189 | ||
1190 | packet_close(); | |
1191 | exit(0); | |
1192 | } | |
1193 | ||
1194 | /* | |
1195 | * SSH1 key exchange | |
1196 | */ | |
1197 | void | |
1198 | do_ssh1_kex(void) | |
1199 | { | |
1200 | int i, len; | |
1201 | int plen, slen; | |
1202 | int rsafail = 0; | |
1203 | BIGNUM *session_key_int; | |
1204 | u_char session_key[SSH_SESSION_KEY_LENGTH]; | |
1205 | u_char cookie[8]; | |
1206 | u_int cipher_type, auth_mask, protocol_flags; | |
1207 | u_int32_t rand = 0; | |
1208 | ||
1209 | /* | |
1210 | * Generate check bytes that the client must send back in the user | |
1211 | * packet in order for it to be accepted; this is used to defy ip | |
1212 | * spoofing attacks. Note that this only works against somebody | |
1213 | * doing IP spoofing from a remote machine; any machine on the local | |
1214 | * network can still see outgoing packets and catch the random | |
1215 | * cookie. This only affects rhosts authentication, and this is one | |
1216 | * of the reasons why it is inherently insecure. | |
1217 | */ | |
1218 | for (i = 0; i < 8; i++) { | |
1219 | if (i % 4 == 0) | |
1220 | rand = arc4random(); | |
1221 | cookie[i] = rand & 0xff; | |
1222 | rand >>= 8; | |
1223 | } | |
1224 | ||
1225 | /* | |
1226 | * Send our public key. We include in the packet 64 bits of random | |
1227 | * data that must be matched in the reply in order to prevent IP | |
1228 | * spoofing. | |
1229 | */ | |
1230 | packet_start(SSH_SMSG_PUBLIC_KEY); | |
1231 | for (i = 0; i < 8; i++) | |
1232 | packet_put_char(cookie[i]); | |
1233 | ||
1234 | /* Store our public server RSA key. */ | |
1235 | packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n)); | |
1236 | packet_put_bignum(sensitive_data.server_key->rsa->e); | |
1237 | packet_put_bignum(sensitive_data.server_key->rsa->n); | |
1238 | ||
1239 | /* Store our public host RSA key. */ | |
1240 | packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); | |
1241 | packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e); | |
1242 | packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n); | |
1243 | ||
1244 | /* Put protocol flags. */ | |
1245 | packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN); | |
1246 | ||
1247 | /* Declare which ciphers we support. */ | |
1248 | packet_put_int(cipher_mask_ssh1(0)); | |
1249 | ||
1250 | /* Declare supported authentication types. */ | |
1251 | auth_mask = 0; | |
1252 | if (options.rhosts_authentication) | |
1253 | auth_mask |= 1 << SSH_AUTH_RHOSTS; | |
1254 | if (options.rhosts_rsa_authentication) | |
1255 | auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA; | |
1256 | if (options.rsa_authentication) | |
1257 | auth_mask |= 1 << SSH_AUTH_RSA; | |
1258 | #ifdef KRB4 | |
1259 | if (options.kerberos_authentication) | |
1260 | auth_mask |= 1 << SSH_AUTH_KERBEROS; | |
1261 | #endif | |
1262 | #ifdef AFS | |
1263 | if (options.kerberos_tgt_passing) | |
1264 | auth_mask |= 1 << SSH_PASS_KERBEROS_TGT; | |
1265 | if (options.afs_token_passing) | |
1266 | auth_mask |= 1 << SSH_PASS_AFS_TOKEN; | |
1267 | #endif | |
1268 | if (options.challenge_reponse_authentication == 1) | |
1269 | auth_mask |= 1 << SSH_AUTH_TIS; | |
1270 | if (options.password_authentication) | |
1271 | auth_mask |= 1 << SSH_AUTH_PASSWORD; | |
1272 | packet_put_int(auth_mask); | |
1273 | ||
1274 | /* Send the packet and wait for it to be sent. */ | |
1275 | packet_send(); | |
1276 | packet_write_wait(); | |
1277 | ||
1278 | debug("Sent %d bit server key and %d bit host key.", | |
1279 | BN_num_bits(sensitive_data.server_key->rsa->n), | |
1280 | BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); | |
1281 | ||
1282 | /* Read clients reply (cipher type and session key). */ | |
1283 | packet_read_expect(&plen, SSH_CMSG_SESSION_KEY); | |
1284 | ||
1285 | /* Get cipher type and check whether we accept this. */ | |
1286 | cipher_type = packet_get_char(); | |
1287 | ||
1288 | if (!(cipher_mask_ssh1(0) & (1 << cipher_type))) | |
1289 | packet_disconnect("Warning: client selects unsupported cipher."); | |
1290 | ||
1291 | /* Get check bytes from the packet. These must match those we | |
1292 | sent earlier with the public key packet. */ | |
1293 | for (i = 0; i < 8; i++) | |
1294 | if (cookie[i] != packet_get_char()) | |
1295 | packet_disconnect("IP Spoofing check bytes do not match."); | |
1296 | ||
1297 | debug("Encryption type: %.200s", cipher_name(cipher_type)); | |
1298 | ||
1299 | /* Get the encrypted integer. */ | |
1300 | session_key_int = BN_new(); | |
1301 | packet_get_bignum(session_key_int, &slen); | |
1302 | ||
1303 | protocol_flags = packet_get_int(); | |
1304 | packet_set_protocol_flags(protocol_flags); | |
1305 | ||
1306 | packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY); | |
1307 | ||
1308 | /* | |
1309 | * Decrypt it using our private server key and private host key (key | |
1310 | * with larger modulus first). | |
1311 | */ | |
1312 | if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) { | |
1313 | /* Server key has bigger modulus. */ | |
1314 | if (BN_num_bits(sensitive_data.server_key->rsa->n) < | |
1315 | BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) { | |
1316 | fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d", | |
1317 | get_remote_ipaddr(), | |
1318 | BN_num_bits(sensitive_data.server_key->rsa->n), | |
1319 | BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), | |
1320 | SSH_KEY_BITS_RESERVED); | |
1321 | } | |
1322 | if (rsa_private_decrypt(session_key_int, session_key_int, | |
1323 | sensitive_data.server_key->rsa) <= 0) | |
1324 | rsafail++; | |
1325 | if (rsa_private_decrypt(session_key_int, session_key_int, | |
1326 | sensitive_data.ssh1_host_key->rsa) <= 0) | |
1327 | rsafail++; | |
1328 | } else { | |
1329 | /* Host key has bigger modulus (or they are equal). */ | |
1330 | if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) < | |
1331 | BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) { | |
1332 | fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d", | |
1333 | get_remote_ipaddr(), | |
1334 | BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), | |
1335 | BN_num_bits(sensitive_data.server_key->rsa->n), | |
1336 | SSH_KEY_BITS_RESERVED); | |
1337 | } | |
1338 | if (rsa_private_decrypt(session_key_int, session_key_int, | |
1339 | sensitive_data.ssh1_host_key->rsa) < 0) | |
1340 | rsafail++; | |
1341 | if (rsa_private_decrypt(session_key_int, session_key_int, | |
1342 | sensitive_data.server_key->rsa) < 0) | |
1343 | rsafail++; | |
1344 | } | |
1345 | /* | |
1346 | * Extract session key from the decrypted integer. The key is in the | |
1347 | * least significant 256 bits of the integer; the first byte of the | |
1348 | * key is in the highest bits. | |
1349 | */ | |
1350 | if (!rsafail) { | |
1351 | BN_mask_bits(session_key_int, sizeof(session_key) * 8); | |
1352 | len = BN_num_bytes(session_key_int); | |
1353 | if (len < 0 || len > sizeof(session_key)) { | |
1354 | error("do_connection: bad session key len from %s: " | |
1355 | "session_key_int %d > sizeof(session_key) %lu", | |
1356 | get_remote_ipaddr(), len, (u_long)sizeof(session_key)); | |
1357 | rsafail++; | |
1358 | } else { | |
1359 | memset(session_key, 0, sizeof(session_key)); | |
1360 | BN_bn2bin(session_key_int, | |
1361 | session_key + sizeof(session_key) - len); | |
1362 | ||
1363 | compute_session_id(session_id, cookie, | |
1364 | sensitive_data.ssh1_host_key->rsa->n, | |
1365 | sensitive_data.server_key->rsa->n); | |
1366 | /* | |
1367 | * Xor the first 16 bytes of the session key with the | |
1368 | * session id. | |
1369 | */ | |
1370 | for (i = 0; i < 16; i++) | |
1371 | session_key[i] ^= session_id[i]; | |
1372 | } | |
1373 | } | |
1374 | if (rsafail) { | |
1375 | int bytes = BN_num_bytes(session_key_int); | |
1376 | char *buf = xmalloc(bytes); | |
1377 | MD5_CTX md; | |
1378 | ||
1379 | log("do_connection: generating a fake encryption key"); | |
1380 | BN_bn2bin(session_key_int, buf); | |
1381 | MD5_Init(&md); | |
1382 | MD5_Update(&md, buf, bytes); | |
1383 | MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); | |
1384 | MD5_Final(session_key, &md); | |
1385 | MD5_Init(&md); | |
1386 | MD5_Update(&md, session_key, 16); | |
1387 | MD5_Update(&md, buf, bytes); | |
1388 | MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); | |
1389 | MD5_Final(session_key + 16, &md); | |
1390 | memset(buf, 0, bytes); | |
1391 | xfree(buf); | |
1392 | for (i = 0; i < 16; i++) | |
1393 | session_id[i] = session_key[i] ^ session_key[i + 16]; | |
1394 | } | |
1395 | /* Destroy the private and public keys. They will no longer be needed. */ | |
1396 | destroy_sensitive_data(); | |
1397 | ||
1398 | /* Destroy the decrypted integer. It is no longer needed. */ | |
1399 | BN_clear_free(session_key_int); | |
1400 | ||
1401 | /* Set the session key. From this on all communications will be encrypted. */ | |
1402 | packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type); | |
1403 | ||
1404 | /* Destroy our copy of the session key. It is no longer needed. */ | |
1405 | memset(session_key, 0, sizeof(session_key)); | |
1406 | ||
1407 | debug("Received session key; encryption turned on."); | |
1408 | ||
1409 | /* Send an acknowledgement packet. Note that this packet is sent encrypted. */ | |
1410 | packet_start(SSH_SMSG_SUCCESS); | |
1411 | packet_send(); | |
1412 | packet_write_wait(); | |
1413 | } | |
1414 | ||
1415 | /* | |
1416 | * SSH2 key exchange: diffie-hellman-group1-sha1 | |
1417 | */ | |
1418 | void | |
1419 | do_ssh2_kex(void) | |
1420 | { | |
1421 | Kex *kex; | |
1422 | ||
1423 | if (options.ciphers != NULL) { | |
1424 | myproposal[PROPOSAL_ENC_ALGS_CTOS] = | |
1425 | myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; | |
1426 | } | |
1427 | myproposal[PROPOSAL_ENC_ALGS_CTOS] = | |
1428 | compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]); | |
1429 | myproposal[PROPOSAL_ENC_ALGS_STOC] = | |
1430 | compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]); | |
1431 | ||
1432 | if (options.macs != NULL) { | |
1433 | myproposal[PROPOSAL_MAC_ALGS_CTOS] = | |
1434 | myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs; | |
1435 | } | |
1436 | myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types(); | |
1437 | ||
1438 | /* start key exchange */ | |
1439 | kex = kex_setup(myproposal); | |
1440 | kex->server = 1; | |
1441 | kex->client_version_string=client_version_string; | |
1442 | kex->server_version_string=server_version_string; | |
1443 | kex->load_host_key=&get_hostkey_by_type; | |
1444 | ||
1445 | xxx_kex = kex; | |
1446 | ||
1447 | dispatch_run(DISPATCH_BLOCK, &kex->done, kex); | |
1448 | ||
1449 | session_id2 = kex->session_id; | |
1450 | session_id2_len = kex->session_id_len; | |
1451 | ||
1452 | #ifdef DEBUG_KEXDH | |
1453 | /* send 1st encrypted/maced/compressed message */ | |
1454 | packet_start(SSH2_MSG_IGNORE); | |
1455 | packet_put_cstring("markus"); | |
1456 | packet_send(); | |
1457 | packet_write_wait(); | |
1458 | #endif | |
1459 | debug("KEX done"); | |
1460 | } |