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8efc0c15 | 1 | /* |
5260325f | 2 | * Author: Tatu Ylonen <ylo@cs.hut.fi> |
3 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
4 | * All rights reserved | |
bcbf86ec | 5 | * This program is the ssh daemon. It listens for connections from clients, |
6 | * and performs authentication, executes use commands or shell, and forwards | |
5260325f | 7 | * information to/from the application to the user client over an encrypted |
bcbf86ec | 8 | * connection. This can also handle forwarding of X11, TCP/IP, and |
9 | * authentication agent connections. | |
e78a59f5 | 10 | * |
bcbf86ec | 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. | |
5260325f | 40 | */ |
8efc0c15 | 41 | |
42 | #include "includes.h" | |
bcbf86ec | 43 | RCSID("$OpenBSD: sshd.c,v 1.127 2000/09/12 20:53:10 markus Exp $"); |
8efc0c15 | 44 | |
45 | #include "xmalloc.h" | |
46 | #include "rsa.h" | |
47 | #include "ssh.h" | |
48 | #include "pty.h" | |
49 | #include "packet.h" | |
8efc0c15 | 50 | #include "cipher.h" |
51 | #include "mpaux.h" | |
52 | #include "servconf.h" | |
53 | #include "uidswap.h" | |
54 | #include "compat.h" | |
7368a6c8 | 55 | #include "buffer.h" |
56 | ||
e78a59f5 | 57 | #include "ssh2.h" |
35484284 | 58 | #include <openssl/dh.h> |
59 | #include <openssl/bn.h> | |
60 | #include <openssl/hmac.h> | |
e78a59f5 | 61 | #include "kex.h" |
35484284 | 62 | #include <openssl/dsa.h> |
63 | #include <openssl/rsa.h> | |
7368a6c8 | 64 | #include "key.h" |
e78a59f5 | 65 | #include "dsa.h" |
7368a6c8 | 66 | |
67 | #include "auth.h" | |
e78a59f5 | 68 | #include "myproposal.h" |
a306f2dd | 69 | #include "authfile.h" |
8efc0c15 | 70 | |
71 | #ifdef LIBWRAP | |
72 | #include <tcpd.h> | |
73 | #include <syslog.h> | |
74 | int allow_severity = LOG_INFO; | |
75 | int deny_severity = LOG_WARNING; | |
76 | #endif /* LIBWRAP */ | |
77 | ||
78 | #ifndef O_NOCTTY | |
79 | #define O_NOCTTY 0 | |
80 | #endif | |
81 | ||
8efc0c15 | 82 | /* Server configuration options. */ |
83 | ServerOptions options; | |
84 | ||
85 | /* Name of the server configuration file. */ | |
86 | char *config_file_name = SERVER_CONFIG_FILE; | |
87 | ||
6ae2364d | 88 | /* |
48e671d5 | 89 | * Flag indicating whether IPv4 or IPv6. This can be set on the command line. |
90 | * Default value is AF_UNSPEC means both IPv4 and IPv6. | |
91 | */ | |
59e76f33 | 92 | #ifdef IPV4_DEFAULT |
93 | int IPv4or6 = AF_INET; | |
94 | #else | |
48e671d5 | 95 | int IPv4or6 = AF_UNSPEC; |
59e76f33 | 96 | #endif |
48e671d5 | 97 | |
5260325f | 98 | /* |
99 | * Debug mode flag. This can be set on the command line. If debug | |
100 | * mode is enabled, extra debugging output will be sent to the system | |
101 | * log, the daemon will not go to background, and will exit after processing | |
102 | * the first connection. | |
103 | */ | |
8efc0c15 | 104 | int debug_flag = 0; |
105 | ||
106 | /* Flag indicating that the daemon is being started from inetd. */ | |
107 | int inetd_flag = 0; | |
108 | ||
6a17f9c2 | 109 | /* debug goes to stderr unless inetd_flag is set */ |
110 | int log_stderr = 0; | |
111 | ||
8efc0c15 | 112 | /* argv[0] without path. */ |
113 | char *av0; | |
114 | ||
115 | /* Saved arguments to main(). */ | |
116 | char **saved_argv; | |
4d33e531 | 117 | int saved_argc; |
8efc0c15 | 118 | |
aa3378df | 119 | /* |
48e671d5 | 120 | * The sockets that the server is listening; this is used in the SIGHUP |
121 | * signal handler. | |
aa3378df | 122 | */ |
48e671d5 | 123 | #define MAX_LISTEN_SOCKS 16 |
124 | int listen_socks[MAX_LISTEN_SOCKS]; | |
125 | int num_listen_socks = 0; | |
8efc0c15 | 126 | |
aa3378df | 127 | /* |
128 | * the client's version string, passed by sshd2 in compat mode. if != NULL, | |
129 | * sshd will skip the version-number exchange | |
130 | */ | |
5260325f | 131 | char *client_version_string = NULL; |
7368a6c8 | 132 | char *server_version_string = NULL; |
8efc0c15 | 133 | |
aa3378df | 134 | /* |
135 | * Any really sensitive data in the application is contained in this | |
136 | * structure. The idea is that this structure could be locked into memory so | |
137 | * that the pages do not get written into swap. However, there are some | |
138 | * problems. The private key contains BIGNUMs, and we do not (in principle) | |
139 | * have access to the internals of them, and locking just the structure is | |
140 | * not very useful. Currently, memory locking is not implemented. | |
141 | */ | |
5260325f | 142 | struct { |
a306f2dd | 143 | RSA *private_key; /* Private part of empheral server key. */ |
5260325f | 144 | RSA *host_key; /* Private part of host key. */ |
a306f2dd | 145 | Key *dsa_host_key; /* Private DSA host key. */ |
8efc0c15 | 146 | } sensitive_data; |
147 | ||
aa3378df | 148 | /* |
149 | * Flag indicating whether the current session key has been used. This flag | |
150 | * is set whenever the key is used, and cleared when the key is regenerated. | |
151 | */ | |
8efc0c15 | 152 | int key_used = 0; |
153 | ||
154 | /* This is set to true when SIGHUP is received. */ | |
155 | int received_sighup = 0; | |
156 | ||
157 | /* Public side of the server key. This value is regenerated regularly with | |
158 | the private key. */ | |
159 | RSA *public_key; | |
160 | ||
7368a6c8 | 161 | /* session identifier, used by RSA-auth */ |
162 | unsigned char session_id[16]; | |
e7c0f9d5 | 163 | |
a306f2dd | 164 | /* same for ssh2 */ |
165 | unsigned char *session_id2 = NULL; | |
166 | int session_id2_len = 0; | |
167 | ||
c345cf9d | 168 | /* record remote hostname or ip */ |
169 | unsigned int utmp_len = MAXHOSTNAMELEN; | |
170 | ||
7368a6c8 | 171 | /* Prototypes for various functions defined later in this file. */ |
172 | void do_ssh1_kex(); | |
e78a59f5 | 173 | void do_ssh2_kex(); |
c8d54615 | 174 | |
48e671d5 | 175 | /* |
176 | * Close all listening sockets | |
177 | */ | |
178 | void | |
179 | close_listen_socks(void) | |
180 | { | |
181 | int i; | |
182 | for (i = 0; i < num_listen_socks; i++) | |
183 | close(listen_socks[i]); | |
184 | num_listen_socks = -1; | |
185 | } | |
186 | ||
5260325f | 187 | /* |
188 | * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; | |
189 | * the effect is to reread the configuration file (and to regenerate | |
190 | * the server key). | |
191 | */ | |
6ae2364d | 192 | void |
5260325f | 193 | sighup_handler(int sig) |
8efc0c15 | 194 | { |
5260325f | 195 | received_sighup = 1; |
196 | signal(SIGHUP, sighup_handler); | |
8efc0c15 | 197 | } |
198 | ||
5260325f | 199 | /* |
200 | * Called from the main program after receiving SIGHUP. | |
201 | * Restarts the server. | |
202 | */ | |
6ae2364d | 203 | void |
5260325f | 204 | sighup_restart() |
8efc0c15 | 205 | { |
5260325f | 206 | log("Received SIGHUP; restarting."); |
48e671d5 | 207 | close_listen_socks(); |
5260325f | 208 | execv(saved_argv[0], saved_argv); |
209 | log("RESTART FAILED: av0='%s', error: %s.", av0, strerror(errno)); | |
210 | exit(1); | |
8efc0c15 | 211 | } |
212 | ||
5260325f | 213 | /* |
214 | * Generic signal handler for terminating signals in the master daemon. | |
215 | * These close the listen socket; not closing it seems to cause "Address | |
216 | * already in use" problems on some machines, which is inconvenient. | |
217 | */ | |
6ae2364d | 218 | void |
5260325f | 219 | sigterm_handler(int sig) |
8efc0c15 | 220 | { |
5260325f | 221 | log("Received signal %d; terminating.", sig); |
48e671d5 | 222 | close_listen_socks(); |
0fbe8c74 | 223 | unlink(options.pid_file); |
5260325f | 224 | exit(255); |
8efc0c15 | 225 | } |
226 | ||
5260325f | 227 | /* |
228 | * SIGCHLD handler. This is called whenever a child dies. This will then | |
229 | * reap any zombies left by exited c. | |
230 | */ | |
6ae2364d | 231 | void |
5260325f | 232 | main_sigchld_handler(int sig) |
8efc0c15 | 233 | { |
5260325f | 234 | int save_errno = errno; |
235 | int status; | |
5ad13cd7 | 236 | |
5260325f | 237 | while (waitpid(-1, &status, WNOHANG) > 0) |
238 | ; | |
5ad13cd7 | 239 | |
5260325f | 240 | signal(SIGCHLD, main_sigchld_handler); |
241 | errno = save_errno; | |
8efc0c15 | 242 | } |
243 | ||
5260325f | 244 | /* |
245 | * Signal handler for the alarm after the login grace period has expired. | |
246 | */ | |
6ae2364d | 247 | void |
5260325f | 248 | grace_alarm_handler(int sig) |
8efc0c15 | 249 | { |
5260325f | 250 | /* Close the connection. */ |
251 | packet_close(); | |
8efc0c15 | 252 | |
5260325f | 253 | /* Log error and exit. */ |
254 | fatal("Timeout before authentication for %s.", get_remote_ipaddr()); | |
255 | } | |
8efc0c15 | 256 | |
5260325f | 257 | /* |
258 | * Signal handler for the key regeneration alarm. Note that this | |
259 | * alarm only occurs in the daemon waiting for connections, and it does not | |
260 | * do anything with the private key or random state before forking. | |
261 | * Thus there should be no concurrency control/asynchronous execution | |
262 | * problems. | |
263 | */ | |
a306f2dd | 264 | /* XXX do we really want this work to be done in a signal handler ? -m */ |
6ae2364d | 265 | void |
5260325f | 266 | key_regeneration_alarm(int sig) |
267 | { | |
268 | int save_errno = errno; | |
269 | ||
270 | /* Check if we should generate a new key. */ | |
271 | if (key_used) { | |
272 | /* This should really be done in the background. */ | |
273 | log("Generating new %d bit RSA key.", options.server_key_bits); | |
274 | ||
275 | if (sensitive_data.private_key != NULL) | |
276 | RSA_free(sensitive_data.private_key); | |
277 | sensitive_data.private_key = RSA_new(); | |
278 | ||
279 | if (public_key != NULL) | |
280 | RSA_free(public_key); | |
281 | public_key = RSA_new(); | |
282 | ||
283 | rsa_generate_key(sensitive_data.private_key, public_key, | |
284 | options.server_key_bits); | |
285 | arc4random_stir(); | |
286 | key_used = 0; | |
287 | log("RSA key generation complete."); | |
288 | } | |
289 | /* Reschedule the alarm. */ | |
290 | signal(SIGALRM, key_regeneration_alarm); | |
291 | alarm(options.key_regeneration_time); | |
292 | errno = save_errno; | |
293 | } | |
8efc0c15 | 294 | |
7368a6c8 | 295 | void |
296 | sshd_exchange_identification(int sock_in, int sock_out) | |
297 | { | |
a8be9f80 | 298 | int i, mismatch; |
7368a6c8 | 299 | int remote_major, remote_minor; |
a8be9f80 | 300 | int major, minor; |
7368a6c8 | 301 | char *s; |
302 | char buf[256]; /* Must not be larger than remote_version. */ | |
303 | char remote_version[256]; /* Must be at least as big as buf. */ | |
304 | ||
a8be9f80 | 305 | if ((options.protocol & SSH_PROTO_1) && |
306 | (options.protocol & SSH_PROTO_2)) { | |
307 | major = PROTOCOL_MAJOR_1; | |
308 | minor = 99; | |
309 | } else if (options.protocol & SSH_PROTO_2) { | |
310 | major = PROTOCOL_MAJOR_2; | |
311 | minor = PROTOCOL_MINOR_2; | |
312 | } else { | |
313 | major = PROTOCOL_MAJOR_1; | |
314 | minor = PROTOCOL_MINOR_1; | |
315 | } | |
316 | snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION); | |
7368a6c8 | 317 | server_version_string = xstrdup(buf); |
318 | ||
319 | if (client_version_string == NULL) { | |
320 | /* Send our protocol version identification. */ | |
321 | if (atomicio(write, sock_out, server_version_string, strlen(server_version_string)) | |
322 | != strlen(server_version_string)) { | |
323 | log("Could not write ident string to %s.", get_remote_ipaddr()); | |
324 | fatal_cleanup(); | |
325 | } | |
326 | ||
327 | /* Read other side\'s version identification. */ | |
328 | for (i = 0; i < sizeof(buf) - 1; i++) { | |
e5a0294f | 329 | if (atomicio(read, sock_in, &buf[i], 1) != 1) { |
7368a6c8 | 330 | log("Did not receive ident string from %s.", get_remote_ipaddr()); |
331 | fatal_cleanup(); | |
332 | } | |
333 | if (buf[i] == '\r') { | |
334 | buf[i] = '\n'; | |
335 | buf[i + 1] = 0; | |
336 | continue; | |
7368a6c8 | 337 | } |
338 | if (buf[i] == '\n') { | |
339 | /* buf[i] == '\n' */ | |
340 | buf[i + 1] = 0; | |
341 | break; | |
342 | } | |
343 | } | |
344 | buf[sizeof(buf) - 1] = 0; | |
345 | client_version_string = xstrdup(buf); | |
346 | } | |
347 | ||
348 | /* | |
349 | * Check that the versions match. In future this might accept | |
350 | * several versions and set appropriate flags to handle them. | |
351 | */ | |
352 | if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n", | |
353 | &remote_major, &remote_minor, remote_version) != 3) { | |
6ae2364d | 354 | s = "Protocol mismatch.\n"; |
7368a6c8 | 355 | (void) atomicio(write, sock_out, s, strlen(s)); |
356 | close(sock_in); | |
357 | close(sock_out); | |
358 | log("Bad protocol version identification '%.100s' from %s", | |
359 | client_version_string, get_remote_ipaddr()); | |
360 | fatal_cleanup(); | |
361 | } | |
362 | debug("Client protocol version %d.%d; client software version %.100s", | |
363 | remote_major, remote_minor, remote_version); | |
364 | ||
e78a59f5 | 365 | compat_datafellows(remote_version); |
366 | ||
a8be9f80 | 367 | mismatch = 0; |
7368a6c8 | 368 | switch(remote_major) { |
369 | case 1: | |
a306f2dd | 370 | if (remote_minor == 99) { |
371 | if (options.protocol & SSH_PROTO_2) | |
372 | enable_compat20(); | |
373 | else | |
374 | mismatch = 1; | |
375 | break; | |
376 | } | |
a8be9f80 | 377 | if (!(options.protocol & SSH_PROTO_1)) { |
378 | mismatch = 1; | |
379 | break; | |
380 | } | |
7368a6c8 | 381 | if (remote_minor < 3) { |
089fbbd2 | 382 | packet_disconnect("Your ssh version is too old and " |
7368a6c8 | 383 | "is no longer supported. Please install a newer version."); |
384 | } else if (remote_minor == 3) { | |
385 | /* note that this disables agent-forwarding */ | |
386 | enable_compat13(); | |
387 | } | |
a8be9f80 | 388 | break; |
e78a59f5 | 389 | case 2: |
a8be9f80 | 390 | if (options.protocol & SSH_PROTO_2) { |
e78a59f5 | 391 | enable_compat20(); |
392 | break; | |
393 | } | |
394 | /* FALLTHROUGH */ | |
6ae2364d | 395 | default: |
a8be9f80 | 396 | mismatch = 1; |
397 | break; | |
398 | } | |
399 | chop(server_version_string); | |
400 | chop(client_version_string); | |
401 | debug("Local version string %.200s", server_version_string); | |
402 | ||
403 | if (mismatch) { | |
7368a6c8 | 404 | s = "Protocol major versions differ.\n"; |
405 | (void) atomicio(write, sock_out, s, strlen(s)); | |
406 | close(sock_in); | |
407 | close(sock_out); | |
a8be9f80 | 408 | log("Protocol major versions differ for %s: %.200s vs. %.200s", |
409 | get_remote_ipaddr(), | |
410 | server_version_string, client_version_string); | |
7368a6c8 | 411 | fatal_cleanup(); |
7368a6c8 | 412 | } |
a306f2dd | 413 | if (compat20) |
414 | packet_set_ssh2_format(); | |
415 | } | |
416 | ||
417 | ||
418 | void | |
419 | destroy_sensitive_data(void) | |
420 | { | |
421 | /* Destroy the private and public keys. They will no longer be needed. */ | |
afa5ee68 | 422 | if (public_key) |
423 | RSA_free(public_key); | |
424 | if (sensitive_data.private_key) | |
425 | RSA_free(sensitive_data.private_key); | |
426 | if (sensitive_data.host_key) | |
427 | RSA_free(sensitive_data.host_key); | |
a306f2dd | 428 | if (sensitive_data.dsa_host_key != NULL) |
429 | key_free(sensitive_data.dsa_host_key); | |
7368a6c8 | 430 | } |
431 | ||
c345cf9d | 432 | /* |
433 | * returns 1 if connection should be dropped, 0 otherwise. | |
434 | * dropping starts at connection #max_startups_begin with a probability | |
435 | * of (max_startups_rate/100). the probability increases linearly until | |
436 | * all connections are dropped for startups > max_startups | |
437 | */ | |
438 | int | |
439 | drop_connection(int startups) | |
440 | { | |
441 | double p, r; | |
442 | ||
443 | if (startups < options.max_startups_begin) | |
444 | return 0; | |
445 | if (startups >= options.max_startups) | |
446 | return 1; | |
447 | if (options.max_startups_rate == 100) | |
448 | return 1; | |
449 | ||
450 | p = 100 - options.max_startups_rate; | |
451 | p *= startups - options.max_startups_begin; | |
452 | p /= (double) (options.max_startups - options.max_startups_begin); | |
453 | p += options.max_startups_rate; | |
454 | p /= 100.0; | |
455 | r = arc4random() / (double) UINT_MAX; | |
456 | ||
457 | debug("drop_connection: p %g, r %g", p, r); | |
458 | return (r < p) ? 1 : 0; | |
459 | } | |
460 | ||
089fbbd2 | 461 | int *startup_pipes = NULL; /* options.max_startup sized array of fd ints */ |
462 | int startup_pipe; /* in child */ | |
463 | ||
5260325f | 464 | /* |
465 | * Main program for the daemon. | |
466 | */ | |
8efc0c15 | 467 | int |
468 | main(int ac, char **av) | |
469 | { | |
5260325f | 470 | extern char *optarg; |
471 | extern int optind; | |
089fbbd2 | 472 | int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1; |
9da5c3c9 | 473 | pid_t pid; |
48e671d5 | 474 | socklen_t fromlen; |
a306f2dd | 475 | int silent = 0; |
48e671d5 | 476 | fd_set *fdset; |
477 | struct sockaddr_storage from; | |
5260325f | 478 | const char *remote_ip; |
479 | int remote_port; | |
5260325f | 480 | FILE *f; |
481 | struct linger linger; | |
48e671d5 | 482 | struct addrinfo *ai; |
483 | char ntop[NI_MAXHOST], strport[NI_MAXSERV]; | |
484 | int listen_sock, maxfd; | |
089fbbd2 | 485 | int startup_p[2]; |
486 | int startups = 0; | |
5260325f | 487 | |
264dce47 | 488 | init_rng(); |
489 | ||
5260325f | 490 | /* Save argv[0]. */ |
4d33e531 | 491 | saved_argc = ac; |
5260325f | 492 | saved_argv = av; |
493 | if (strchr(av[0], '/')) | |
494 | av0 = strrchr(av[0], '/') + 1; | |
495 | else | |
496 | av0 = av[0]; | |
497 | ||
498 | /* Initialize configuration options to their default values. */ | |
499 | initialize_server_options(&options); | |
500 | ||
501 | /* Parse command-line arguments. */ | |
c345cf9d | 502 | while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:diqQ46")) != EOF) { |
5260325f | 503 | switch (opt) { |
48e671d5 | 504 | case '4': |
505 | IPv4or6 = AF_INET; | |
506 | break; | |
507 | case '6': | |
508 | IPv4or6 = AF_INET6; | |
509 | break; | |
5260325f | 510 | case 'f': |
511 | config_file_name = optarg; | |
512 | break; | |
513 | case 'd': | |
bcbf86ec | 514 | if (0 == debug_flag) { |
515 | debug_flag = 1; | |
516 | options.log_level = SYSLOG_LEVEL_DEBUG1; | |
517 | } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) { | |
518 | options.log_level++; | |
519 | } else { | |
520 | fprintf(stderr, "Too high debugging level.\n"); | |
521 | exit(1); | |
522 | } | |
5260325f | 523 | break; |
524 | case 'i': | |
525 | inetd_flag = 1; | |
526 | break; | |
527 | case 'Q': | |
a306f2dd | 528 | silent = 1; |
5260325f | 529 | break; |
530 | case 'q': | |
531 | options.log_level = SYSLOG_LEVEL_QUIET; | |
532 | break; | |
533 | case 'b': | |
534 | options.server_key_bits = atoi(optarg); | |
535 | break; | |
536 | case 'p': | |
48e671d5 | 537 | options.ports_from_cmdline = 1; |
bcbf86ec | 538 | if (options.num_ports >= MAX_PORTS) { |
539 | fprintf(stderr, "too many ports.\n"); | |
540 | exit(1); | |
541 | } | |
48e671d5 | 542 | options.ports[options.num_ports++] = atoi(optarg); |
5260325f | 543 | break; |
544 | case 'g': | |
545 | options.login_grace_time = atoi(optarg); | |
546 | break; | |
547 | case 'k': | |
548 | options.key_regeneration_time = atoi(optarg); | |
549 | break; | |
550 | case 'h': | |
551 | options.host_key_file = optarg; | |
552 | break; | |
553 | case 'V': | |
554 | client_version_string = optarg; | |
555 | /* only makes sense with inetd_flag, i.e. no listen() */ | |
556 | inetd_flag = 1; | |
557 | break; | |
c345cf9d | 558 | case 'u': |
559 | utmp_len = atoi(optarg); | |
560 | break; | |
5260325f | 561 | case '?': |
562 | default: | |
563 | fprintf(stderr, "sshd version %s\n", SSH_VERSION); | |
564 | fprintf(stderr, "Usage: %s [options]\n", av0); | |
565 | fprintf(stderr, "Options:\n"); | |
aa3378df | 566 | fprintf(stderr, " -f file Configuration file (default %s)\n", SERVER_CONFIG_FILE); |
bcbf86ec | 567 | fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n"); |
5260325f | 568 | fprintf(stderr, " -i Started from inetd\n"); |
569 | fprintf(stderr, " -q Quiet (no logging)\n"); | |
570 | fprintf(stderr, " -p port Listen on the specified port (default: 22)\n"); | |
571 | fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n"); | |
572 | fprintf(stderr, " -g seconds Grace period for authentication (default: 300)\n"); | |
573 | fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n"); | |
574 | fprintf(stderr, " -h file File from which to read host key (default: %s)\n", | |
48e671d5 | 575 | HOST_KEY_FILE); |
c345cf9d | 576 | fprintf(stderr, " -u len Maximum hostname length for utmp recording\n"); |
48e671d5 | 577 | fprintf(stderr, " -4 Use IPv4 only\n"); |
578 | fprintf(stderr, " -6 Use IPv6 only\n"); | |
5260325f | 579 | exit(1); |
580 | } | |
581 | } | |
582 | ||
48e671d5 | 583 | /* |
584 | * Force logging to stderr until we have loaded the private host | |
585 | * key (unless started from inetd) | |
586 | */ | |
587 | log_init(av0, | |
588 | options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level, | |
589 | options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility, | |
a306f2dd | 590 | !silent && !inetd_flag); |
48e671d5 | 591 | |
5260325f | 592 | /* Read server configuration options from the configuration file. */ |
593 | read_server_config(&options, config_file_name); | |
594 | ||
595 | /* Fill in default values for those options not explicitly set. */ | |
596 | fill_default_server_options(&options); | |
597 | ||
5260325f | 598 | /* Check that there are no remaining arguments. */ |
599 | if (optind < ac) { | |
600 | fprintf(stderr, "Extra argument %s.\n", av[optind]); | |
601 | exit(1); | |
8efc0c15 | 602 | } |
5260325f | 603 | |
604 | debug("sshd version %.100s", SSH_VERSION); | |
605 | ||
a306f2dd | 606 | sensitive_data.dsa_host_key = NULL; |
607 | sensitive_data.host_key = NULL; | |
608 | ||
609 | /* check if RSA support exists */ | |
610 | if ((options.protocol & SSH_PROTO_1) && | |
611 | rsa_alive() == 0) { | |
612 | log("no RSA support in libssl and libcrypto. See ssl(8)"); | |
613 | log("Disabling protocol version 1"); | |
614 | options.protocol &= ~SSH_PROTO_1; | |
615 | } | |
616 | /* Load the RSA/DSA host key. It must have empty passphrase. */ | |
617 | if (options.protocol & SSH_PROTO_1) { | |
618 | Key k; | |
619 | sensitive_data.host_key = RSA_new(); | |
620 | k.type = KEY_RSA; | |
621 | k.rsa = sensitive_data.host_key; | |
622 | errno = 0; | |
623 | if (!load_private_key(options.host_key_file, "", &k, NULL)) { | |
624 | error("Could not load host key: %.200s: %.100s", | |
625 | options.host_key_file, strerror(errno)); | |
626 | log("Disabling protocol version 1"); | |
627 | options.protocol &= ~SSH_PROTO_1; | |
628 | } | |
629 | k.rsa = NULL; | |
630 | } | |
631 | if (options.protocol & SSH_PROTO_2) { | |
632 | sensitive_data.dsa_host_key = key_new(KEY_DSA); | |
1d1ffb87 | 633 | if (!load_private_key(options.host_dsa_key_file, "", sensitive_data.dsa_host_key, NULL)) { |
634 | ||
635 | error("Could not load DSA host key: %.200s", options.host_dsa_key_file); | |
a306f2dd | 636 | log("Disabling protocol version 2"); |
637 | options.protocol &= ~SSH_PROTO_2; | |
638 | } | |
639 | } | |
640 | if (! options.protocol & (SSH_PROTO_1|SSH_PROTO_2)) { | |
641 | if (silent == 0) | |
642 | fprintf(stderr, "sshd: no hostkeys available -- exiting.\n"); | |
643 | log("sshd: no hostkeys available -- exiting.\n"); | |
5260325f | 644 | exit(1); |
645 | } | |
5260325f | 646 | |
a306f2dd | 647 | /* Check certain values for sanity. */ |
648 | if (options.protocol & SSH_PROTO_1) { | |
649 | if (options.server_key_bits < 512 || | |
650 | options.server_key_bits > 32768) { | |
651 | fprintf(stderr, "Bad server key size.\n"); | |
652 | exit(1); | |
653 | } | |
654 | /* | |
655 | * Check that server and host key lengths differ sufficiently. This | |
656 | * is necessary to make double encryption work with rsaref. Oh, I | |
657 | * hate software patents. I dont know if this can go? Niels | |
658 | */ | |
659 | if (options.server_key_bits > | |
660 | BN_num_bits(sensitive_data.host_key->n) - SSH_KEY_BITS_RESERVED && | |
661 | options.server_key_bits < | |
662 | BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) { | |
663 | options.server_key_bits = | |
664 | BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED; | |
665 | debug("Forcing server key to %d bits to make it differ from host key.", | |
666 | options.server_key_bits); | |
667 | } | |
668 | } | |
669 | ||
670 | /* Initialize the log (it is reinitialized below in case we forked). */ | |
5260325f | 671 | if (debug_flag && !inetd_flag) |
672 | log_stderr = 1; | |
673 | log_init(av0, options.log_level, options.log_facility, log_stderr); | |
674 | ||
a306f2dd | 675 | /* |
676 | * If not in debugging mode, and not started from inetd, disconnect | |
677 | * from the controlling terminal, and fork. The original process | |
678 | * exits. | |
679 | */ | |
5260325f | 680 | if (!debug_flag && !inetd_flag) { |
8efc0c15 | 681 | #ifdef TIOCNOTTY |
5260325f | 682 | int fd; |
8efc0c15 | 683 | #endif /* TIOCNOTTY */ |
5260325f | 684 | if (daemon(0, 0) < 0) |
685 | fatal("daemon() failed: %.200s", strerror(errno)); | |
686 | ||
687 | /* Disconnect from the controlling tty. */ | |
8efc0c15 | 688 | #ifdef TIOCNOTTY |
5260325f | 689 | fd = open("/dev/tty", O_RDWR | O_NOCTTY); |
690 | if (fd >= 0) { | |
691 | (void) ioctl(fd, TIOCNOTTY, NULL); | |
692 | close(fd); | |
693 | } | |
8efc0c15 | 694 | #endif /* TIOCNOTTY */ |
8efc0c15 | 695 | } |
5260325f | 696 | /* Reinitialize the log (because of the fork above). */ |
697 | log_init(av0, options.log_level, options.log_facility, log_stderr); | |
698 | ||
5260325f | 699 | /* Do not display messages to stdout in RSA code. */ |
700 | rsa_set_verbose(0); | |
701 | ||
702 | /* Initialize the random number generator. */ | |
703 | arc4random_stir(); | |
704 | ||
705 | /* Chdir to the root directory so that the current disk can be | |
706 | unmounted if desired. */ | |
707 | chdir("/"); | |
708 | ||
5260325f | 709 | /* Start listening for a socket, unless started from inetd. */ |
710 | if (inetd_flag) { | |
711 | int s1, s2; | |
712 | s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */ | |
713 | s2 = dup(s1); | |
714 | sock_in = dup(0); | |
715 | sock_out = dup(1); | |
4c8722d9 | 716 | startup_pipe = -1; |
a306f2dd | 717 | /* |
718 | * We intentionally do not close the descriptors 0, 1, and 2 | |
719 | * as our code for setting the descriptors won\'t work if | |
720 | * ttyfd happens to be one of those. | |
721 | */ | |
5260325f | 722 | debug("inetd sockets after dupping: %d, %d", sock_in, sock_out); |
723 | ||
a306f2dd | 724 | if (options.protocol & SSH_PROTO_1) { |
725 | public_key = RSA_new(); | |
726 | sensitive_data.private_key = RSA_new(); | |
727 | log("Generating %d bit RSA key.", options.server_key_bits); | |
728 | rsa_generate_key(sensitive_data.private_key, public_key, | |
729 | options.server_key_bits); | |
730 | arc4random_stir(); | |
731 | log("RSA key generation complete."); | |
732 | } | |
5260325f | 733 | } else { |
48e671d5 | 734 | for (ai = options.listen_addrs; ai; ai = ai->ai_next) { |
735 | if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) | |
736 | continue; | |
737 | if (num_listen_socks >= MAX_LISTEN_SOCKS) | |
738 | fatal("Too many listen sockets. " | |
739 | "Enlarge MAX_LISTEN_SOCKS"); | |
740 | if (getnameinfo(ai->ai_addr, ai->ai_addrlen, | |
741 | ntop, sizeof(ntop), strport, sizeof(strport), | |
742 | NI_NUMERICHOST|NI_NUMERICSERV) != 0) { | |
743 | error("getnameinfo failed"); | |
744 | continue; | |
745 | } | |
746 | /* Create socket for listening. */ | |
747 | listen_sock = socket(ai->ai_family, SOCK_STREAM, 0); | |
748 | if (listen_sock < 0) { | |
749 | /* kernel may not support ipv6 */ | |
750 | verbose("socket: %.100s", strerror(errno)); | |
751 | continue; | |
752 | } | |
753 | if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) { | |
754 | error("listen_sock O_NONBLOCK: %s", strerror(errno)); | |
755 | close(listen_sock); | |
756 | continue; | |
757 | } | |
758 | /* | |
759 | * Set socket options. We try to make the port | |
760 | * reusable and have it close as fast as possible | |
761 | * without waiting in unnecessary wait states on | |
762 | * close. | |
763 | */ | |
764 | setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, | |
765 | (void *) &on, sizeof(on)); | |
766 | linger.l_onoff = 1; | |
767 | linger.l_linger = 5; | |
768 | setsockopt(listen_sock, SOL_SOCKET, SO_LINGER, | |
769 | (void *) &linger, sizeof(linger)); | |
770 | ||
771 | debug("Bind to port %s on %s.", strport, ntop); | |
772 | ||
773 | /* Bind the socket to the desired port. */ | |
16218745 | 774 | if ((bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) && |
775 | (!ai->ai_next)) { | |
48e671d5 | 776 | error("Bind to port %s on %s failed: %.200s.", |
777 | strport, ntop, strerror(errno)); | |
778 | close(listen_sock); | |
779 | continue; | |
780 | } | |
781 | listen_socks[num_listen_socks] = listen_sock; | |
782 | num_listen_socks++; | |
783 | ||
784 | /* Start listening on the port. */ | |
785 | log("Server listening on %s port %s.", ntop, strport); | |
786 | if (listen(listen_sock, 5) < 0) | |
787 | fatal("listen: %.100s", strerror(errno)); | |
788 | ||
5260325f | 789 | } |
48e671d5 | 790 | freeaddrinfo(options.listen_addrs); |
791 | ||
792 | if (!num_listen_socks) | |
793 | fatal("Cannot bind any address."); | |
794 | ||
5260325f | 795 | if (!debug_flag) { |
aa3378df | 796 | /* |
797 | * Record our pid in /etc/sshd_pid to make it easier | |
798 | * to kill the correct sshd. We don\'t want to do | |
799 | * this before the bind above because the bind will | |
800 | * fail if there already is a daemon, and this will | |
801 | * overwrite any old pid in the file. | |
802 | */ | |
3c62e7eb | 803 | f = fopen(options.pid_file, "wb"); |
5260325f | 804 | if (f) { |
805 | fprintf(f, "%u\n", (unsigned int) getpid()); | |
806 | fclose(f); | |
807 | } | |
8efc0c15 | 808 | } |
a306f2dd | 809 | if (options.protocol & SSH_PROTO_1) { |
810 | public_key = RSA_new(); | |
811 | sensitive_data.private_key = RSA_new(); | |
8efc0c15 | 812 | |
a306f2dd | 813 | log("Generating %d bit RSA key.", options.server_key_bits); |
814 | rsa_generate_key(sensitive_data.private_key, public_key, | |
815 | options.server_key_bits); | |
816 | arc4random_stir(); | |
817 | log("RSA key generation complete."); | |
5260325f | 818 | |
a306f2dd | 819 | /* Schedule server key regeneration alarm. */ |
820 | signal(SIGALRM, key_regeneration_alarm); | |
821 | alarm(options.key_regeneration_time); | |
822 | } | |
5260325f | 823 | |
824 | /* Arrange to restart on SIGHUP. The handler needs listen_sock. */ | |
825 | signal(SIGHUP, sighup_handler); | |
089fbbd2 | 826 | |
5260325f | 827 | signal(SIGTERM, sigterm_handler); |
828 | signal(SIGQUIT, sigterm_handler); | |
829 | ||
830 | /* Arrange SIGCHLD to be caught. */ | |
831 | signal(SIGCHLD, main_sigchld_handler); | |
832 | ||
48e671d5 | 833 | /* setup fd set for listen */ |
089fbbd2 | 834 | fdset = NULL; |
48e671d5 | 835 | maxfd = 0; |
836 | for (i = 0; i < num_listen_socks; i++) | |
837 | if (listen_socks[i] > maxfd) | |
838 | maxfd = listen_socks[i]; | |
089fbbd2 | 839 | /* pipes connected to unauthenticated childs */ |
840 | startup_pipes = xmalloc(options.max_startups * sizeof(int)); | |
841 | for (i = 0; i < options.max_startups; i++) | |
842 | startup_pipes[i] = -1; | |
48e671d5 | 843 | |
aa3378df | 844 | /* |
845 | * Stay listening for connections until the system crashes or | |
846 | * the daemon is killed with a signal. | |
847 | */ | |
5260325f | 848 | for (;;) { |
849 | if (received_sighup) | |
850 | sighup_restart(); | |
089fbbd2 | 851 | if (fdset != NULL) |
852 | xfree(fdset); | |
853 | fdsetsz = howmany(maxfd, NFDBITS) * sizeof(fd_mask); | |
854 | fdset = (fd_set *)xmalloc(fdsetsz); | |
48e671d5 | 855 | memset(fdset, 0, fdsetsz); |
089fbbd2 | 856 | |
48e671d5 | 857 | for (i = 0; i < num_listen_socks; i++) |
858 | FD_SET(listen_socks[i], fdset); | |
089fbbd2 | 859 | for (i = 0; i < options.max_startups; i++) |
860 | if (startup_pipes[i] != -1) | |
861 | FD_SET(startup_pipes[i], fdset); | |
862 | ||
863 | /* Wait in select until there is a connection. */ | |
48e671d5 | 864 | if (select(maxfd + 1, fdset, NULL, NULL, NULL) < 0) { |
865 | if (errno != EINTR) | |
866 | error("select: %.100s", strerror(errno)); | |
2d86a6cc | 867 | continue; |
48e671d5 | 868 | } |
089fbbd2 | 869 | for (i = 0; i < options.max_startups; i++) |
870 | if (startup_pipes[i] != -1 && | |
871 | FD_ISSET(startup_pipes[i], fdset)) { | |
872 | /* | |
873 | * the read end of the pipe is ready | |
874 | * if the child has closed the pipe | |
875 | * after successfull authentication | |
876 | * or if the child has died | |
877 | */ | |
878 | close(startup_pipes[i]); | |
879 | startup_pipes[i] = -1; | |
880 | startups--; | |
881 | } | |
48e671d5 | 882 | for (i = 0; i < num_listen_socks; i++) { |
883 | if (!FD_ISSET(listen_socks[i], fdset)) | |
5260325f | 884 | continue; |
089fbbd2 | 885 | fromlen = sizeof(from); |
886 | newsock = accept(listen_socks[i], (struct sockaddr *)&from, | |
887 | &fromlen); | |
888 | if (newsock < 0) { | |
889 | if (errno != EINTR && errno != EWOULDBLOCK) | |
890 | error("accept: %.100s", strerror(errno)); | |
891 | continue; | |
892 | } | |
893 | if (fcntl(newsock, F_SETFL, 0) < 0) { | |
894 | error("newsock del O_NONBLOCK: %s", strerror(errno)); | |
895 | continue; | |
896 | } | |
c345cf9d | 897 | if (drop_connection(startups) == 1) { |
898 | debug("drop connection #%d", startups); | |
089fbbd2 | 899 | close(newsock); |
900 | continue; | |
901 | } | |
902 | if (pipe(startup_p) == -1) { | |
903 | close(newsock); | |
904 | continue; | |
905 | } | |
906 | ||
907 | for (j = 0; j < options.max_startups; j++) | |
908 | if (startup_pipes[j] == -1) { | |
909 | startup_pipes[j] = startup_p[0]; | |
910 | if (maxfd < startup_p[0]) | |
911 | maxfd = startup_p[0]; | |
912 | startups++; | |
913 | break; | |
914 | } | |
915 | ||
aa3378df | 916 | /* |
089fbbd2 | 917 | * Got connection. Fork a child to handle it, unless |
918 | * we are in debugging mode. | |
aa3378df | 919 | */ |
089fbbd2 | 920 | if (debug_flag) { |
aa3378df | 921 | /* |
089fbbd2 | 922 | * In debugging mode. Close the listening |
923 | * socket, and start processing the | |
924 | * connection without forking. | |
aa3378df | 925 | */ |
089fbbd2 | 926 | debug("Server will not fork when running in debugging mode."); |
48e671d5 | 927 | close_listen_socks(); |
5260325f | 928 | sock_in = newsock; |
929 | sock_out = newsock; | |
5540ea9b | 930 | startup_pipe = -1; |
3f7a7e4a | 931 | pid = getpid(); |
5260325f | 932 | break; |
089fbbd2 | 933 | } else { |
934 | /* | |
935 | * Normal production daemon. Fork, and have | |
936 | * the child process the connection. The | |
937 | * parent continues listening. | |
938 | */ | |
939 | if ((pid = fork()) == 0) { | |
940 | /* | |
941 | * Child. Close the listening and max_startup | |
942 | * sockets. Start using the accepted socket. | |
943 | * Reinitialize logging (since our pid has | |
944 | * changed). We break out of the loop to handle | |
945 | * the connection. | |
946 | */ | |
947 | startup_pipe = startup_p[1]; | |
948 | for (j = 0; j < options.max_startups; j++) | |
949 | if (startup_pipes[j] != -1) | |
950 | close(startup_pipes[j]); | |
951 | close_listen_socks(); | |
952 | sock_in = newsock; | |
953 | sock_out = newsock; | |
954 | log_init(av0, options.log_level, options.log_facility, log_stderr); | |
955 | break; | |
956 | } | |
5260325f | 957 | } |
5260325f | 958 | |
089fbbd2 | 959 | /* Parent. Stay in the loop. */ |
960 | if (pid < 0) | |
961 | error("fork: %.100s", strerror(errno)); | |
962 | else | |
963 | debug("Forked child %d.", pid); | |
5260325f | 964 | |
089fbbd2 | 965 | close(startup_p[1]); |
5260325f | 966 | |
089fbbd2 | 967 | /* Mark that the key has been used (it was "given" to the child). */ |
968 | key_used = 1; | |
5260325f | 969 | |
089fbbd2 | 970 | arc4random_stir(); |
971 | ||
972 | /* Close the new socket (the child is now taking care of it). */ | |
973 | close(newsock); | |
974 | } | |
48e671d5 | 975 | /* child process check (or debug mode) */ |
976 | if (num_listen_socks < 0) | |
977 | break; | |
5260325f | 978 | } |
979 | } | |
8efc0c15 | 980 | |
5260325f | 981 | /* This is the child processing a new connection. */ |
982 | ||
aa3378df | 983 | /* |
984 | * Disable the key regeneration alarm. We will not regenerate the | |
985 | * key since we are no longer in a position to give it to anyone. We | |
986 | * will not restart on SIGHUP since it no longer makes sense. | |
987 | */ | |
5260325f | 988 | alarm(0); |
989 | signal(SIGALRM, SIG_DFL); | |
990 | signal(SIGHUP, SIG_DFL); | |
991 | signal(SIGTERM, SIG_DFL); | |
992 | signal(SIGQUIT, SIG_DFL); | |
993 | signal(SIGCHLD, SIG_DFL); | |
9aaf9be4 | 994 | signal(SIGINT, SIG_DFL); |
5260325f | 995 | |
aa3378df | 996 | /* |
997 | * Set socket options for the connection. We want the socket to | |
998 | * close as fast as possible without waiting for anything. If the | |
999 | * connection is not a socket, these will do nothing. | |
1000 | */ | |
1001 | /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */ | |
5260325f | 1002 | linger.l_onoff = 1; |
1003 | linger.l_linger = 5; | |
1004 | setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger)); | |
1005 | ||
aa3378df | 1006 | /* |
1007 | * Register our connection. This turns encryption off because we do | |
1008 | * not have a key. | |
1009 | */ | |
5260325f | 1010 | packet_set_connection(sock_in, sock_out); |
1011 | ||
1012 | remote_port = get_remote_port(); | |
1013 | remote_ip = get_remote_ipaddr(); | |
1014 | ||
1015 | /* Check whether logins are denied from this host. */ | |
1016 | #ifdef LIBWRAP | |
48e671d5 | 1017 | /* XXX LIBWRAP noes not know about IPv6 */ |
5260325f | 1018 | { |
1019 | struct request_info req; | |
8efc0c15 | 1020 | |
5260325f | 1021 | request_init(&req, RQ_DAEMON, av0, RQ_FILE, sock_in, NULL); |
1022 | fromhost(&req); | |
8efc0c15 | 1023 | |
5260325f | 1024 | if (!hosts_access(&req)) { |
1025 | close(sock_in); | |
1026 | close(sock_out); | |
1027 | refuse(&req); | |
1028 | } | |
48e671d5 | 1029 | /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */ |
8efc0c15 | 1030 | } |
48e671d5 | 1031 | #endif /* LIBWRAP */ |
5260325f | 1032 | /* Log the connection. */ |
1033 | verbose("Connection from %.500s port %d", remote_ip, remote_port); | |
8efc0c15 | 1034 | |
aa3378df | 1035 | /* |
1036 | * We don\'t want to listen forever unless the other side | |
1037 | * successfully authenticates itself. So we set up an alarm which is | |
1038 | * cleared after successful authentication. A limit of zero | |
1039 | * indicates no limit. Note that we don\'t set the alarm in debugging | |
1040 | * mode; it is just annoying to have the server exit just when you | |
1041 | * are about to discover the bug. | |
1042 | */ | |
5260325f | 1043 | signal(SIGALRM, grace_alarm_handler); |
1044 | if (!debug_flag) | |
1045 | alarm(options.login_grace_time); | |
1046 | ||
7368a6c8 | 1047 | sshd_exchange_identification(sock_in, sock_out); |
aa3378df | 1048 | /* |
1049 | * Check that the connection comes from a privileged port. Rhosts- | |
1050 | * and Rhosts-RSA-Authentication only make sense from priviledged | |
1051 | * programs. Of course, if the intruder has root access on his local | |
1052 | * machine, he can connect from any port. So do not use these | |
1053 | * authentication methods from machines that you do not trust. | |
1054 | */ | |
5260325f | 1055 | if (remote_port >= IPPORT_RESERVED || |
1056 | remote_port < IPPORT_RESERVED / 2) { | |
1057 | options.rhosts_authentication = 0; | |
1058 | options.rhosts_rsa_authentication = 0; | |
1059 | } | |
48e671d5 | 1060 | #ifdef KRB4 |
1061 | if (!packet_connection_is_ipv4() && | |
1062 | options.kerberos_authentication) { | |
1063 | debug("Kerberos Authentication disabled, only available for IPv4."); | |
1064 | options.kerberos_authentication = 0; | |
1065 | } | |
1066 | #endif /* KRB4 */ | |
1067 | ||
5260325f | 1068 | packet_set_nonblocking(); |
1069 | ||
7b2ea3a1 | 1070 | /* perform the key exchange */ |
7b2ea3a1 | 1071 | /* authenticate user and start session */ |
e78a59f5 | 1072 | if (compat20) { |
1073 | do_ssh2_kex(); | |
1074 | do_authentication2(); | |
1075 | } else { | |
1076 | do_ssh1_kex(); | |
1077 | do_authentication(); | |
1078 | } | |
8efc0c15 | 1079 | |
1080 | #ifdef KRB4 | |
5260325f | 1081 | /* Cleanup user's ticket cache file. */ |
1082 | if (options.kerberos_ticket_cleanup) | |
1083 | (void) dest_tkt(); | |
8efc0c15 | 1084 | #endif /* KRB4 */ |
1085 | ||
5260325f | 1086 | /* The connection has been terminated. */ |
1087 | verbose("Closing connection to %.100s", remote_ip); | |
8efc0c15 | 1088 | |
d94aa2ae | 1089 | #ifdef USE_PAM |
a5c9cd31 | 1090 | finish_pam(); |
d94aa2ae | 1091 | #endif /* USE_PAM */ |
8efc0c15 | 1092 | |
5260325f | 1093 | packet_close(); |
1094 | exit(0); | |
1095 | } | |
8efc0c15 | 1096 | |
5260325f | 1097 | /* |
7b2ea3a1 | 1098 | * SSH1 key exchange |
5260325f | 1099 | */ |
e7c0f9d5 | 1100 | void |
7368a6c8 | 1101 | do_ssh1_kex() |
8efc0c15 | 1102 | { |
5260325f | 1103 | int i, len; |
7b2ea3a1 | 1104 | int plen, slen; |
5260325f | 1105 | BIGNUM *session_key_int; |
1106 | unsigned char session_key[SSH_SESSION_KEY_LENGTH]; | |
7b2ea3a1 | 1107 | unsigned char cookie[8]; |
5260325f | 1108 | unsigned int cipher_type, auth_mask, protocol_flags; |
5260325f | 1109 | u_int32_t rand = 0; |
1110 | ||
aa3378df | 1111 | /* |
1112 | * Generate check bytes that the client must send back in the user | |
1113 | * packet in order for it to be accepted; this is used to defy ip | |
1114 | * spoofing attacks. Note that this only works against somebody | |
1115 | * doing IP spoofing from a remote machine; any machine on the local | |
1116 | * network can still see outgoing packets and catch the random | |
1117 | * cookie. This only affects rhosts authentication, and this is one | |
1118 | * of the reasons why it is inherently insecure. | |
1119 | */ | |
5260325f | 1120 | for (i = 0; i < 8; i++) { |
1121 | if (i % 4 == 0) | |
1122 | rand = arc4random(); | |
7b2ea3a1 | 1123 | cookie[i] = rand & 0xff; |
5260325f | 1124 | rand >>= 8; |
1125 | } | |
1126 | ||
aa3378df | 1127 | /* |
1128 | * Send our public key. We include in the packet 64 bits of random | |
1129 | * data that must be matched in the reply in order to prevent IP | |
1130 | * spoofing. | |
1131 | */ | |
5260325f | 1132 | packet_start(SSH_SMSG_PUBLIC_KEY); |
1133 | for (i = 0; i < 8; i++) | |
7b2ea3a1 | 1134 | packet_put_char(cookie[i]); |
5260325f | 1135 | |
1136 | /* Store our public server RSA key. */ | |
1137 | packet_put_int(BN_num_bits(public_key->n)); | |
1138 | packet_put_bignum(public_key->e); | |
1139 | packet_put_bignum(public_key->n); | |
1140 | ||
1141 | /* Store our public host RSA key. */ | |
1142 | packet_put_int(BN_num_bits(sensitive_data.host_key->n)); | |
1143 | packet_put_bignum(sensitive_data.host_key->e); | |
1144 | packet_put_bignum(sensitive_data.host_key->n); | |
1145 | ||
1146 | /* Put protocol flags. */ | |
1147 | packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN); | |
1148 | ||
1149 | /* Declare which ciphers we support. */ | |
8ce64345 | 1150 | packet_put_int(cipher_mask1()); |
5260325f | 1151 | |
1152 | /* Declare supported authentication types. */ | |
1153 | auth_mask = 0; | |
1154 | if (options.rhosts_authentication) | |
1155 | auth_mask |= 1 << SSH_AUTH_RHOSTS; | |
1156 | if (options.rhosts_rsa_authentication) | |
1157 | auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA; | |
1158 | if (options.rsa_authentication) | |
1159 | auth_mask |= 1 << SSH_AUTH_RSA; | |
8efc0c15 | 1160 | #ifdef KRB4 |
5260325f | 1161 | if (options.kerberos_authentication) |
1162 | auth_mask |= 1 << SSH_AUTH_KERBEROS; | |
8efc0c15 | 1163 | #endif |
1164 | #ifdef AFS | |
5260325f | 1165 | if (options.kerberos_tgt_passing) |
1166 | auth_mask |= 1 << SSH_PASS_KERBEROS_TGT; | |
1167 | if (options.afs_token_passing) | |
1168 | auth_mask |= 1 << SSH_PASS_AFS_TOKEN; | |
8efc0c15 | 1169 | #endif |
5260325f | 1170 | #ifdef SKEY |
1171 | if (options.skey_authentication == 1) | |
1172 | auth_mask |= 1 << SSH_AUTH_TIS; | |
1173 | #endif | |
1174 | if (options.password_authentication) | |
1175 | auth_mask |= 1 << SSH_AUTH_PASSWORD; | |
1176 | packet_put_int(auth_mask); | |
1177 | ||
1178 | /* Send the packet and wait for it to be sent. */ | |
1179 | packet_send(); | |
1180 | packet_write_wait(); | |
1181 | ||
1182 | debug("Sent %d bit public key and %d bit host key.", | |
1183 | BN_num_bits(public_key->n), BN_num_bits(sensitive_data.host_key->n)); | |
1184 | ||
1185 | /* Read clients reply (cipher type and session key). */ | |
1186 | packet_read_expect(&plen, SSH_CMSG_SESSION_KEY); | |
1187 | ||
2d86a6cc | 1188 | /* Get cipher type and check whether we accept this. */ |
5260325f | 1189 | cipher_type = packet_get_char(); |
1190 | ||
6ae2364d | 1191 | if (!(cipher_mask() & (1 << cipher_type))) |
2d86a6cc | 1192 | packet_disconnect("Warning: client selects unsupported cipher."); |
1193 | ||
5260325f | 1194 | /* Get check bytes from the packet. These must match those we |
1195 | sent earlier with the public key packet. */ | |
1196 | for (i = 0; i < 8; i++) | |
7b2ea3a1 | 1197 | if (cookie[i] != packet_get_char()) |
5260325f | 1198 | packet_disconnect("IP Spoofing check bytes do not match."); |
1199 | ||
1200 | debug("Encryption type: %.200s", cipher_name(cipher_type)); | |
1201 | ||
1202 | /* Get the encrypted integer. */ | |
1203 | session_key_int = BN_new(); | |
1204 | packet_get_bignum(session_key_int, &slen); | |
1205 | ||
5260325f | 1206 | protocol_flags = packet_get_int(); |
1207 | packet_set_protocol_flags(protocol_flags); | |
1208 | ||
1209 | packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY); | |
1210 | ||
aa3378df | 1211 | /* |
1212 | * Decrypt it using our private server key and private host key (key | |
1213 | * with larger modulus first). | |
1214 | */ | |
5260325f | 1215 | if (BN_cmp(sensitive_data.private_key->n, sensitive_data.host_key->n) > 0) { |
1216 | /* Private key has bigger modulus. */ | |
1217 | if (BN_num_bits(sensitive_data.private_key->n) < | |
1218 | BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) { | |
1219 | fatal("do_connection: %s: private_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d", | |
1220 | get_remote_ipaddr(), | |
1221 | BN_num_bits(sensitive_data.private_key->n), | |
1222 | BN_num_bits(sensitive_data.host_key->n), | |
1223 | SSH_KEY_BITS_RESERVED); | |
1224 | } | |
1225 | rsa_private_decrypt(session_key_int, session_key_int, | |
1226 | sensitive_data.private_key); | |
1227 | rsa_private_decrypt(session_key_int, session_key_int, | |
1228 | sensitive_data.host_key); | |
1229 | } else { | |
1230 | /* Host key has bigger modulus (or they are equal). */ | |
1231 | if (BN_num_bits(sensitive_data.host_key->n) < | |
1232 | BN_num_bits(sensitive_data.private_key->n) + SSH_KEY_BITS_RESERVED) { | |
1233 | fatal("do_connection: %s: host_key %d < private_key %d + SSH_KEY_BITS_RESERVED %d", | |
1234 | get_remote_ipaddr(), | |
1235 | BN_num_bits(sensitive_data.host_key->n), | |
1236 | BN_num_bits(sensitive_data.private_key->n), | |
1237 | SSH_KEY_BITS_RESERVED); | |
1238 | } | |
1239 | rsa_private_decrypt(session_key_int, session_key_int, | |
1240 | sensitive_data.host_key); | |
1241 | rsa_private_decrypt(session_key_int, session_key_int, | |
1242 | sensitive_data.private_key); | |
1243 | } | |
1244 | ||
7b2ea3a1 | 1245 | compute_session_id(session_id, cookie, |
5260325f | 1246 | sensitive_data.host_key->n, |
1247 | sensitive_data.private_key->n); | |
1248 | ||
7b2ea3a1 | 1249 | /* Destroy the private and public keys. They will no longer be needed. */ |
a306f2dd | 1250 | destroy_sensitive_data(); |
7b2ea3a1 | 1251 | |
aa3378df | 1252 | /* |
1253 | * Extract session key from the decrypted integer. The key is in the | |
1254 | * least significant 256 bits of the integer; the first byte of the | |
1255 | * key is in the highest bits. | |
1256 | */ | |
5260325f | 1257 | BN_mask_bits(session_key_int, sizeof(session_key) * 8); |
1258 | len = BN_num_bytes(session_key_int); | |
1259 | if (len < 0 || len > sizeof(session_key)) | |
1260 | fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d", | |
1261 | get_remote_ipaddr(), | |
1262 | len, sizeof(session_key)); | |
1263 | memset(session_key, 0, sizeof(session_key)); | |
1264 | BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len); | |
1265 | ||
7b2ea3a1 | 1266 | /* Destroy the decrypted integer. It is no longer needed. */ |
1267 | BN_clear_free(session_key_int); | |
1268 | ||
5260325f | 1269 | /* Xor the first 16 bytes of the session key with the session id. */ |
1270 | for (i = 0; i < 16; i++) | |
1271 | session_key[i] ^= session_id[i]; | |
1272 | ||
5260325f | 1273 | /* Set the session key. From this on all communications will be encrypted. */ |
1274 | packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type); | |
1275 | ||
1276 | /* Destroy our copy of the session key. It is no longer needed. */ | |
1277 | memset(session_key, 0, sizeof(session_key)); | |
1278 | ||
1279 | debug("Received session key; encryption turned on."); | |
1280 | ||
1281 | /* Send an acknowledgement packet. Note that this packet is sent encrypted. */ | |
1282 | packet_start(SSH_SMSG_SUCCESS); | |
1283 | packet_send(); | |
1284 | packet_write_wait(); | |
5260325f | 1285 | } |
e78a59f5 | 1286 | |
1287 | /* | |
1288 | * SSH2 key exchange: diffie-hellman-group1-sha1 | |
1289 | */ | |
1290 | void | |
1291 | do_ssh2_kex() | |
1292 | { | |
1293 | Buffer *server_kexinit; | |
1294 | Buffer *client_kexinit; | |
1295 | int payload_len, dlen; | |
1296 | int slen; | |
1297 | unsigned int klen, kout; | |
e78a59f5 | 1298 | unsigned char *signature = NULL; |
1299 | unsigned char *server_host_key_blob = NULL; | |
1300 | unsigned int sbloblen; | |
1301 | DH *dh; | |
1302 | BIGNUM *dh_client_pub = 0; | |
1303 | BIGNUM *shared_secret = 0; | |
1304 | int i; | |
1305 | unsigned char *kbuf; | |
1306 | unsigned char *hash; | |
1307 | Kex *kex; | |
e78a59f5 | 1308 | char *cprop[PROPOSAL_MAX]; |
e78a59f5 | 1309 | |
1310 | /* KEXINIT */ | |
1311 | ||
a8be9f80 | 1312 | if (options.ciphers != NULL) { |
6ae2364d | 1313 | myproposal[PROPOSAL_ENC_ALGS_CTOS] = |
a8be9f80 | 1314 | myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; |
1315 | } | |
71276795 | 1316 | server_kexinit = kex_init(myproposal); |
e78a59f5 | 1317 | client_kexinit = xmalloc(sizeof(*client_kexinit)); |
1318 | buffer_init(client_kexinit); | |
e78a59f5 | 1319 | |
71276795 | 1320 | /* algorithm negotiation */ |
1321 | kex_exchange_kexinit(server_kexinit, client_kexinit, cprop); | |
1322 | kex = kex_choose_conf(cprop, myproposal, 1); | |
1323 | for (i = 0; i < PROPOSAL_MAX; i++) | |
1324 | xfree(cprop[i]); | |
e78a59f5 | 1325 | |
1326 | /* KEXDH */ | |
1327 | ||
1328 | debug("Wait SSH2_MSG_KEXDH_INIT."); | |
1329 | packet_read_expect(&payload_len, SSH2_MSG_KEXDH_INIT); | |
1330 | ||
1331 | /* key, cert */ | |
1332 | dh_client_pub = BN_new(); | |
1333 | if (dh_client_pub == NULL) | |
1334 | fatal("dh_client_pub == NULL"); | |
1335 | packet_get_bignum2(dh_client_pub, &dlen); | |
1336 | ||
1337 | #ifdef DEBUG_KEXDH | |
1338 | fprintf(stderr, "\ndh_client_pub= "); | |
1339 | bignum_print(dh_client_pub); | |
1340 | fprintf(stderr, "\n"); | |
1341 | debug("bits %d", BN_num_bits(dh_client_pub)); | |
1342 | #endif | |
1343 | ||
1344 | /* generate DH key */ | |
a8be9f80 | 1345 | dh = dh_new_group1(); /* XXX depends on 'kex' */ |
e78a59f5 | 1346 | |
1347 | #ifdef DEBUG_KEXDH | |
1348 | fprintf(stderr, "\np= "); | |
1349 | bignum_print(dh->p); | |
1350 | fprintf(stderr, "\ng= "); | |
1351 | bignum_print(dh->g); | |
1352 | fprintf(stderr, "\npub= "); | |
1353 | bignum_print(dh->pub_key); | |
1354 | fprintf(stderr, "\n"); | |
1355 | #endif | |
a8be9f80 | 1356 | if (!dh_pub_is_valid(dh, dh_client_pub)) |
1357 | packet_disconnect("bad client public DH value"); | |
e78a59f5 | 1358 | |
1359 | klen = DH_size(dh); | |
1360 | kbuf = xmalloc(klen); | |
1361 | kout = DH_compute_key(kbuf, dh_client_pub, dh); | |
1362 | ||
1363 | #ifdef DEBUG_KEXDH | |
1364 | debug("shared secret: len %d/%d", klen, kout); | |
1365 | fprintf(stderr, "shared secret == "); | |
1366 | for (i = 0; i< kout; i++) | |
1367 | fprintf(stderr, "%02x", (kbuf[i])&0xff); | |
1368 | fprintf(stderr, "\n"); | |
1369 | #endif | |
1370 | shared_secret = BN_new(); | |
1371 | ||
1372 | BN_bin2bn(kbuf, kout, shared_secret); | |
1373 | memset(kbuf, 0, klen); | |
1374 | xfree(kbuf); | |
1375 | ||
a306f2dd | 1376 | /* XXX precompute? */ |
1377 | dsa_make_key_blob(sensitive_data.dsa_host_key, &server_host_key_blob, &sbloblen); | |
e78a59f5 | 1378 | |
1379 | /* calc H */ /* XXX depends on 'kex' */ | |
1380 | hash = kex_hash( | |
1381 | client_version_string, | |
1382 | server_version_string, | |
1383 | buffer_ptr(client_kexinit), buffer_len(client_kexinit), | |
1384 | buffer_ptr(server_kexinit), buffer_len(server_kexinit), | |
1385 | (char *)server_host_key_blob, sbloblen, | |
1386 | dh_client_pub, | |
1387 | dh->pub_key, | |
1388 | shared_secret | |
1389 | ); | |
1390 | buffer_free(client_kexinit); | |
1391 | buffer_free(server_kexinit); | |
1392 | xfree(client_kexinit); | |
1393 | xfree(server_kexinit); | |
1394 | #ifdef DEBUG_KEXDH | |
6ae2364d | 1395 | fprintf(stderr, "hash == "); |
1396 | for (i = 0; i< 20; i++) | |
1397 | fprintf(stderr, "%02x", (hash[i])&0xff); | |
1398 | fprintf(stderr, "\n"); | |
e78a59f5 | 1399 | #endif |
a306f2dd | 1400 | /* save session id := H */ |
1401 | /* XXX hashlen depends on KEX */ | |
1402 | session_id2_len = 20; | |
1403 | session_id2 = xmalloc(session_id2_len); | |
1404 | memcpy(session_id2, hash, session_id2_len); | |
1405 | ||
e78a59f5 | 1406 | /* sign H */ |
a306f2dd | 1407 | /* XXX hashlen depends on KEX */ |
1408 | dsa_sign(sensitive_data.dsa_host_key, &signature, &slen, hash, 20); | |
1409 | ||
1410 | destroy_sensitive_data(); | |
e78a59f5 | 1411 | |
1412 | /* send server hostkey, DH pubkey 'f' and singed H */ | |
1413 | packet_start(SSH2_MSG_KEXDH_REPLY); | |
1414 | packet_put_string((char *)server_host_key_blob, sbloblen); | |
1d1ffb87 | 1415 | packet_put_bignum2(dh->pub_key); /* f */ |
e78a59f5 | 1416 | packet_put_string((char *)signature, slen); |
1417 | packet_send(); | |
d6f24e45 | 1418 | xfree(signature); |
a306f2dd | 1419 | xfree(server_host_key_blob); |
e78a59f5 | 1420 | packet_write_wait(); |
1421 | ||
1422 | kex_derive_keys(kex, hash, shared_secret); | |
1423 | packet_set_kex(kex); | |
1424 | ||
1425 | /* have keys, free DH */ | |
1426 | DH_free(dh); | |
1427 | ||
1428 | debug("send SSH2_MSG_NEWKEYS."); | |
1429 | packet_start(SSH2_MSG_NEWKEYS); | |
1430 | packet_send(); | |
1431 | packet_write_wait(); | |
1432 | debug("done: send SSH2_MSG_NEWKEYS."); | |
1433 | ||
1434 | debug("Wait SSH2_MSG_NEWKEYS."); | |
1435 | packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS); | |
1436 | debug("GOT SSH2_MSG_NEWKEYS."); | |
1437 | ||
a8be9f80 | 1438 | #ifdef DEBUG_KEXDH |
e78a59f5 | 1439 | /* send 1st encrypted/maced/compressed message */ |
1440 | packet_start(SSH2_MSG_IGNORE); | |
1441 | packet_put_cstring("markus"); | |
1442 | packet_send(); | |
1443 | packet_write_wait(); | |
a8be9f80 | 1444 | #endif |
e78a59f5 | 1445 | debug("done: KEX2."); |
1446 | } |