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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 | |
5 | * Created: Fri Mar 17 17:09:28 1995 ylo | |
6 | * This program is the ssh daemon. It listens for connections from clients, and | |
7 | * performs authentication, executes use commands or shell, and forwards | |
8 | * information to/from the application to the user client over an encrypted | |
9 | * connection. This can also handle forwarding of X11, TCP/IP, and authentication | |
10 | * agent connections. | |
e78a59f5 | 11 | * |
12 | * SSH2 implementation, | |
13 | * Copyright (c) 2000 Markus Friedl. All rights reserved. | |
5260325f | 14 | */ |
8efc0c15 | 15 | |
16 | #include "includes.h" | |
e5a0294f | 17 | RCSID("$OpenBSD: sshd.c,v 1.119 2000/06/22 16:32:27 markus Exp $"); |
8efc0c15 | 18 | |
19 | #include "xmalloc.h" | |
20 | #include "rsa.h" | |
21 | #include "ssh.h" | |
22 | #include "pty.h" | |
23 | #include "packet.h" | |
8efc0c15 | 24 | #include "cipher.h" |
25 | #include "mpaux.h" | |
26 | #include "servconf.h" | |
27 | #include "uidswap.h" | |
28 | #include "compat.h" | |
7368a6c8 | 29 | #include "buffer.h" |
30 | ||
e78a59f5 | 31 | #include "ssh2.h" |
35484284 | 32 | #include <openssl/dh.h> |
33 | #include <openssl/bn.h> | |
34 | #include <openssl/hmac.h> | |
e78a59f5 | 35 | #include "kex.h" |
35484284 | 36 | #include <openssl/dsa.h> |
37 | #include <openssl/rsa.h> | |
7368a6c8 | 38 | #include "key.h" |
e78a59f5 | 39 | #include "dsa.h" |
7368a6c8 | 40 | |
41 | #include "auth.h" | |
e78a59f5 | 42 | #include "myproposal.h" |
a306f2dd | 43 | #include "authfile.h" |
8efc0c15 | 44 | |
45 | #ifdef LIBWRAP | |
46 | #include <tcpd.h> | |
47 | #include <syslog.h> | |
48 | int allow_severity = LOG_INFO; | |
49 | int deny_severity = LOG_WARNING; | |
50 | #endif /* LIBWRAP */ | |
51 | ||
52 | #ifndef O_NOCTTY | |
53 | #define O_NOCTTY 0 | |
54 | #endif | |
55 | ||
8efc0c15 | 56 | /* Server configuration options. */ |
57 | ServerOptions options; | |
58 | ||
59 | /* Name of the server configuration file. */ | |
60 | char *config_file_name = SERVER_CONFIG_FILE; | |
61 | ||
6ae2364d | 62 | /* |
48e671d5 | 63 | * Flag indicating whether IPv4 or IPv6. This can be set on the command line. |
64 | * Default value is AF_UNSPEC means both IPv4 and IPv6. | |
65 | */ | |
59e76f33 | 66 | #ifdef IPV4_DEFAULT |
67 | int IPv4or6 = AF_INET; | |
68 | #else | |
48e671d5 | 69 | int IPv4or6 = AF_UNSPEC; |
59e76f33 | 70 | #endif |
48e671d5 | 71 | |
5260325f | 72 | /* |
73 | * Debug mode flag. This can be set on the command line. If debug | |
74 | * mode is enabled, extra debugging output will be sent to the system | |
75 | * log, the daemon will not go to background, and will exit after processing | |
76 | * the first connection. | |
77 | */ | |
8efc0c15 | 78 | int debug_flag = 0; |
79 | ||
80 | /* Flag indicating that the daemon is being started from inetd. */ | |
81 | int inetd_flag = 0; | |
82 | ||
6a17f9c2 | 83 | /* debug goes to stderr unless inetd_flag is set */ |
84 | int log_stderr = 0; | |
85 | ||
8efc0c15 | 86 | /* argv[0] without path. */ |
87 | char *av0; | |
88 | ||
89 | /* Saved arguments to main(). */ | |
90 | char **saved_argv; | |
4d33e531 | 91 | int saved_argc; |
8efc0c15 | 92 | |
aa3378df | 93 | /* |
48e671d5 | 94 | * The sockets that the server is listening; this is used in the SIGHUP |
95 | * signal handler. | |
aa3378df | 96 | */ |
48e671d5 | 97 | #define MAX_LISTEN_SOCKS 16 |
98 | int listen_socks[MAX_LISTEN_SOCKS]; | |
99 | int num_listen_socks = 0; | |
8efc0c15 | 100 | |
aa3378df | 101 | /* |
102 | * the client's version string, passed by sshd2 in compat mode. if != NULL, | |
103 | * sshd will skip the version-number exchange | |
104 | */ | |
5260325f | 105 | char *client_version_string = NULL; |
7368a6c8 | 106 | char *server_version_string = NULL; |
8efc0c15 | 107 | |
aa3378df | 108 | /* |
109 | * Any really sensitive data in the application is contained in this | |
110 | * structure. The idea is that this structure could be locked into memory so | |
111 | * that the pages do not get written into swap. However, there are some | |
112 | * problems. The private key contains BIGNUMs, and we do not (in principle) | |
113 | * have access to the internals of them, and locking just the structure is | |
114 | * not very useful. Currently, memory locking is not implemented. | |
115 | */ | |
5260325f | 116 | struct { |
a306f2dd | 117 | RSA *private_key; /* Private part of empheral server key. */ |
5260325f | 118 | RSA *host_key; /* Private part of host key. */ |
a306f2dd | 119 | Key *dsa_host_key; /* Private DSA host key. */ |
8efc0c15 | 120 | } sensitive_data; |
121 | ||
aa3378df | 122 | /* |
123 | * Flag indicating whether the current session key has been used. This flag | |
124 | * is set whenever the key is used, and cleared when the key is regenerated. | |
125 | */ | |
8efc0c15 | 126 | int key_used = 0; |
127 | ||
128 | /* This is set to true when SIGHUP is received. */ | |
129 | int received_sighup = 0; | |
130 | ||
131 | /* Public side of the server key. This value is regenerated regularly with | |
132 | the private key. */ | |
133 | RSA *public_key; | |
134 | ||
7368a6c8 | 135 | /* session identifier, used by RSA-auth */ |
136 | unsigned char session_id[16]; | |
e7c0f9d5 | 137 | |
a306f2dd | 138 | /* same for ssh2 */ |
139 | unsigned char *session_id2 = NULL; | |
140 | int session_id2_len = 0; | |
141 | ||
7368a6c8 | 142 | /* Prototypes for various functions defined later in this file. */ |
143 | void do_ssh1_kex(); | |
e78a59f5 | 144 | void do_ssh2_kex(); |
c8d54615 | 145 | |
48e671d5 | 146 | /* |
147 | * Close all listening sockets | |
148 | */ | |
149 | void | |
150 | close_listen_socks(void) | |
151 | { | |
152 | int i; | |
153 | for (i = 0; i < num_listen_socks; i++) | |
154 | close(listen_socks[i]); | |
155 | num_listen_socks = -1; | |
156 | } | |
157 | ||
5260325f | 158 | /* |
159 | * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; | |
160 | * the effect is to reread the configuration file (and to regenerate | |
161 | * the server key). | |
162 | */ | |
6ae2364d | 163 | void |
5260325f | 164 | sighup_handler(int sig) |
8efc0c15 | 165 | { |
5260325f | 166 | received_sighup = 1; |
167 | signal(SIGHUP, sighup_handler); | |
8efc0c15 | 168 | } |
169 | ||
5260325f | 170 | /* |
171 | * Called from the main program after receiving SIGHUP. | |
172 | * Restarts the server. | |
173 | */ | |
6ae2364d | 174 | void |
5260325f | 175 | sighup_restart() |
8efc0c15 | 176 | { |
5260325f | 177 | log("Received SIGHUP; restarting."); |
48e671d5 | 178 | close_listen_socks(); |
5260325f | 179 | execv(saved_argv[0], saved_argv); |
180 | log("RESTART FAILED: av0='%s', error: %s.", av0, strerror(errno)); | |
181 | exit(1); | |
8efc0c15 | 182 | } |
183 | ||
5260325f | 184 | /* |
185 | * Generic signal handler for terminating signals in the master daemon. | |
186 | * These close the listen socket; not closing it seems to cause "Address | |
187 | * already in use" problems on some machines, which is inconvenient. | |
188 | */ | |
6ae2364d | 189 | void |
5260325f | 190 | sigterm_handler(int sig) |
8efc0c15 | 191 | { |
5260325f | 192 | log("Received signal %d; terminating.", sig); |
48e671d5 | 193 | close_listen_socks(); |
0fbe8c74 | 194 | unlink(options.pid_file); |
5260325f | 195 | exit(255); |
8efc0c15 | 196 | } |
197 | ||
5260325f | 198 | /* |
199 | * SIGCHLD handler. This is called whenever a child dies. This will then | |
200 | * reap any zombies left by exited c. | |
201 | */ | |
6ae2364d | 202 | void |
5260325f | 203 | main_sigchld_handler(int sig) |
8efc0c15 | 204 | { |
5260325f | 205 | int save_errno = errno; |
206 | int status; | |
5ad13cd7 | 207 | |
5260325f | 208 | while (waitpid(-1, &status, WNOHANG) > 0) |
209 | ; | |
5ad13cd7 | 210 | |
5260325f | 211 | signal(SIGCHLD, main_sigchld_handler); |
212 | errno = save_errno; | |
8efc0c15 | 213 | } |
214 | ||
5260325f | 215 | /* |
216 | * Signal handler for the alarm after the login grace period has expired. | |
217 | */ | |
6ae2364d | 218 | void |
5260325f | 219 | grace_alarm_handler(int sig) |
8efc0c15 | 220 | { |
5260325f | 221 | /* Close the connection. */ |
222 | packet_close(); | |
8efc0c15 | 223 | |
5260325f | 224 | /* Log error and exit. */ |
225 | fatal("Timeout before authentication for %s.", get_remote_ipaddr()); | |
226 | } | |
8efc0c15 | 227 | |
5260325f | 228 | /* |
229 | * Signal handler for the key regeneration alarm. Note that this | |
230 | * alarm only occurs in the daemon waiting for connections, and it does not | |
231 | * do anything with the private key or random state before forking. | |
232 | * Thus there should be no concurrency control/asynchronous execution | |
233 | * problems. | |
234 | */ | |
a306f2dd | 235 | /* XXX do we really want this work to be done in a signal handler ? -m */ |
6ae2364d | 236 | void |
5260325f | 237 | key_regeneration_alarm(int sig) |
238 | { | |
239 | int save_errno = errno; | |
240 | ||
241 | /* Check if we should generate a new key. */ | |
242 | if (key_used) { | |
243 | /* This should really be done in the background. */ | |
244 | log("Generating new %d bit RSA key.", options.server_key_bits); | |
245 | ||
246 | if (sensitive_data.private_key != NULL) | |
247 | RSA_free(sensitive_data.private_key); | |
248 | sensitive_data.private_key = RSA_new(); | |
249 | ||
250 | if (public_key != NULL) | |
251 | RSA_free(public_key); | |
252 | public_key = RSA_new(); | |
253 | ||
254 | rsa_generate_key(sensitive_data.private_key, public_key, | |
255 | options.server_key_bits); | |
256 | arc4random_stir(); | |
257 | key_used = 0; | |
258 | log("RSA key generation complete."); | |
259 | } | |
260 | /* Reschedule the alarm. */ | |
261 | signal(SIGALRM, key_regeneration_alarm); | |
262 | alarm(options.key_regeneration_time); | |
263 | errno = save_errno; | |
264 | } | |
8efc0c15 | 265 | |
7368a6c8 | 266 | void |
267 | sshd_exchange_identification(int sock_in, int sock_out) | |
268 | { | |
a8be9f80 | 269 | int i, mismatch; |
7368a6c8 | 270 | int remote_major, remote_minor; |
a8be9f80 | 271 | int major, minor; |
7368a6c8 | 272 | char *s; |
273 | char buf[256]; /* Must not be larger than remote_version. */ | |
274 | char remote_version[256]; /* Must be at least as big as buf. */ | |
275 | ||
a8be9f80 | 276 | if ((options.protocol & SSH_PROTO_1) && |
277 | (options.protocol & SSH_PROTO_2)) { | |
278 | major = PROTOCOL_MAJOR_1; | |
279 | minor = 99; | |
280 | } else if (options.protocol & SSH_PROTO_2) { | |
281 | major = PROTOCOL_MAJOR_2; | |
282 | minor = PROTOCOL_MINOR_2; | |
283 | } else { | |
284 | major = PROTOCOL_MAJOR_1; | |
285 | minor = PROTOCOL_MINOR_1; | |
286 | } | |
287 | snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION); | |
7368a6c8 | 288 | server_version_string = xstrdup(buf); |
289 | ||
290 | if (client_version_string == NULL) { | |
291 | /* Send our protocol version identification. */ | |
292 | if (atomicio(write, sock_out, server_version_string, strlen(server_version_string)) | |
293 | != strlen(server_version_string)) { | |
294 | log("Could not write ident string to %s.", get_remote_ipaddr()); | |
295 | fatal_cleanup(); | |
296 | } | |
297 | ||
298 | /* Read other side\'s version identification. */ | |
299 | for (i = 0; i < sizeof(buf) - 1; i++) { | |
e5a0294f | 300 | if (atomicio(read, sock_in, &buf[i], 1) != 1) { |
7368a6c8 | 301 | log("Did not receive ident string from %s.", get_remote_ipaddr()); |
302 | fatal_cleanup(); | |
303 | } | |
304 | if (buf[i] == '\r') { | |
305 | buf[i] = '\n'; | |
306 | buf[i + 1] = 0; | |
307 | continue; | |
7368a6c8 | 308 | } |
309 | if (buf[i] == '\n') { | |
310 | /* buf[i] == '\n' */ | |
311 | buf[i + 1] = 0; | |
312 | break; | |
313 | } | |
314 | } | |
315 | buf[sizeof(buf) - 1] = 0; | |
316 | client_version_string = xstrdup(buf); | |
317 | } | |
318 | ||
319 | /* | |
320 | * Check that the versions match. In future this might accept | |
321 | * several versions and set appropriate flags to handle them. | |
322 | */ | |
323 | if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n", | |
324 | &remote_major, &remote_minor, remote_version) != 3) { | |
6ae2364d | 325 | s = "Protocol mismatch.\n"; |
7368a6c8 | 326 | (void) atomicio(write, sock_out, s, strlen(s)); |
327 | close(sock_in); | |
328 | close(sock_out); | |
329 | log("Bad protocol version identification '%.100s' from %s", | |
330 | client_version_string, get_remote_ipaddr()); | |
331 | fatal_cleanup(); | |
332 | } | |
333 | debug("Client protocol version %d.%d; client software version %.100s", | |
334 | remote_major, remote_minor, remote_version); | |
335 | ||
e78a59f5 | 336 | compat_datafellows(remote_version); |
337 | ||
a8be9f80 | 338 | mismatch = 0; |
7368a6c8 | 339 | switch(remote_major) { |
340 | case 1: | |
a306f2dd | 341 | if (remote_minor == 99) { |
342 | if (options.protocol & SSH_PROTO_2) | |
343 | enable_compat20(); | |
344 | else | |
345 | mismatch = 1; | |
346 | break; | |
347 | } | |
a8be9f80 | 348 | if (!(options.protocol & SSH_PROTO_1)) { |
349 | mismatch = 1; | |
350 | break; | |
351 | } | |
7368a6c8 | 352 | if (remote_minor < 3) { |
353 | packet_disconnect("Your ssh version is too old and" | |
354 | "is no longer supported. Please install a newer version."); | |
355 | } else if (remote_minor == 3) { | |
356 | /* note that this disables agent-forwarding */ | |
357 | enable_compat13(); | |
358 | } | |
a8be9f80 | 359 | break; |
e78a59f5 | 360 | case 2: |
a8be9f80 | 361 | if (options.protocol & SSH_PROTO_2) { |
e78a59f5 | 362 | enable_compat20(); |
363 | break; | |
364 | } | |
365 | /* FALLTHROUGH */ | |
6ae2364d | 366 | default: |
a8be9f80 | 367 | mismatch = 1; |
368 | break; | |
369 | } | |
370 | chop(server_version_string); | |
371 | chop(client_version_string); | |
372 | debug("Local version string %.200s", server_version_string); | |
373 | ||
374 | if (mismatch) { | |
7368a6c8 | 375 | s = "Protocol major versions differ.\n"; |
376 | (void) atomicio(write, sock_out, s, strlen(s)); | |
377 | close(sock_in); | |
378 | close(sock_out); | |
a8be9f80 | 379 | log("Protocol major versions differ for %s: %.200s vs. %.200s", |
380 | get_remote_ipaddr(), | |
381 | server_version_string, client_version_string); | |
7368a6c8 | 382 | fatal_cleanup(); |
7368a6c8 | 383 | } |
a306f2dd | 384 | if (compat20) |
385 | packet_set_ssh2_format(); | |
386 | } | |
387 | ||
388 | ||
389 | void | |
390 | destroy_sensitive_data(void) | |
391 | { | |
392 | /* Destroy the private and public keys. They will no longer be needed. */ | |
afa5ee68 | 393 | if (public_key) |
394 | RSA_free(public_key); | |
395 | if (sensitive_data.private_key) | |
396 | RSA_free(sensitive_data.private_key); | |
397 | if (sensitive_data.host_key) | |
398 | RSA_free(sensitive_data.host_key); | |
a306f2dd | 399 | if (sensitive_data.dsa_host_key != NULL) |
400 | key_free(sensitive_data.dsa_host_key); | |
7368a6c8 | 401 | } |
402 | ||
5260325f | 403 | /* |
404 | * Main program for the daemon. | |
405 | */ | |
8efc0c15 | 406 | int |
407 | main(int ac, char **av) | |
408 | { | |
5260325f | 409 | extern char *optarg; |
410 | extern int optind; | |
9da5c3c9 | 411 | int opt, sock_in = 0, sock_out = 0, newsock, i, fdsetsz, on = 1; |
412 | pid_t pid; | |
48e671d5 | 413 | socklen_t fromlen; |
a306f2dd | 414 | int silent = 0; |
48e671d5 | 415 | fd_set *fdset; |
416 | struct sockaddr_storage from; | |
5260325f | 417 | const char *remote_ip; |
418 | int remote_port; | |
5260325f | 419 | FILE *f; |
420 | struct linger linger; | |
48e671d5 | 421 | struct addrinfo *ai; |
422 | char ntop[NI_MAXHOST], strport[NI_MAXSERV]; | |
423 | int listen_sock, maxfd; | |
5260325f | 424 | |
264dce47 | 425 | init_rng(); |
426 | ||
5260325f | 427 | /* Save argv[0]. */ |
4d33e531 | 428 | saved_argc = ac; |
5260325f | 429 | saved_argv = av; |
430 | if (strchr(av[0], '/')) | |
431 | av0 = strrchr(av[0], '/') + 1; | |
432 | else | |
433 | av0 = av[0]; | |
434 | ||
435 | /* Initialize configuration options to their default values. */ | |
436 | initialize_server_options(&options); | |
437 | ||
438 | /* Parse command-line arguments. */ | |
a8be9f80 | 439 | while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:diqQ46")) != EOF) { |
5260325f | 440 | switch (opt) { |
48e671d5 | 441 | case '4': |
442 | IPv4or6 = AF_INET; | |
443 | break; | |
444 | case '6': | |
445 | IPv4or6 = AF_INET6; | |
446 | break; | |
5260325f | 447 | case 'f': |
448 | config_file_name = optarg; | |
449 | break; | |
450 | case 'd': | |
451 | debug_flag = 1; | |
452 | options.log_level = SYSLOG_LEVEL_DEBUG; | |
453 | break; | |
454 | case 'i': | |
455 | inetd_flag = 1; | |
456 | break; | |
457 | case 'Q': | |
a306f2dd | 458 | silent = 1; |
5260325f | 459 | break; |
460 | case 'q': | |
461 | options.log_level = SYSLOG_LEVEL_QUIET; | |
462 | break; | |
463 | case 'b': | |
464 | options.server_key_bits = atoi(optarg); | |
465 | break; | |
466 | case 'p': | |
48e671d5 | 467 | options.ports_from_cmdline = 1; |
468 | if (options.num_ports >= MAX_PORTS) | |
469 | fatal("too many ports.\n"); | |
470 | options.ports[options.num_ports++] = atoi(optarg); | |
5260325f | 471 | break; |
472 | case 'g': | |
473 | options.login_grace_time = atoi(optarg); | |
474 | break; | |
475 | case 'k': | |
476 | options.key_regeneration_time = atoi(optarg); | |
477 | break; | |
478 | case 'h': | |
479 | options.host_key_file = optarg; | |
480 | break; | |
481 | case 'V': | |
482 | client_version_string = optarg; | |
483 | /* only makes sense with inetd_flag, i.e. no listen() */ | |
484 | inetd_flag = 1; | |
485 | break; | |
486 | case '?': | |
487 | default: | |
488 | fprintf(stderr, "sshd version %s\n", SSH_VERSION); | |
489 | fprintf(stderr, "Usage: %s [options]\n", av0); | |
490 | fprintf(stderr, "Options:\n"); | |
aa3378df | 491 | fprintf(stderr, " -f file Configuration file (default %s)\n", SERVER_CONFIG_FILE); |
5260325f | 492 | fprintf(stderr, " -d Debugging mode\n"); |
493 | fprintf(stderr, " -i Started from inetd\n"); | |
494 | fprintf(stderr, " -q Quiet (no logging)\n"); | |
495 | fprintf(stderr, " -p port Listen on the specified port (default: 22)\n"); | |
496 | fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n"); | |
497 | fprintf(stderr, " -g seconds Grace period for authentication (default: 300)\n"); | |
498 | fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n"); | |
499 | fprintf(stderr, " -h file File from which to read host key (default: %s)\n", | |
48e671d5 | 500 | HOST_KEY_FILE); |
501 | fprintf(stderr, " -4 Use IPv4 only\n"); | |
502 | fprintf(stderr, " -6 Use IPv6 only\n"); | |
5260325f | 503 | exit(1); |
504 | } | |
505 | } | |
506 | ||
48e671d5 | 507 | /* |
508 | * Force logging to stderr until we have loaded the private host | |
509 | * key (unless started from inetd) | |
510 | */ | |
511 | log_init(av0, | |
512 | options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level, | |
513 | options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility, | |
a306f2dd | 514 | !silent && !inetd_flag); |
48e671d5 | 515 | |
5260325f | 516 | /* Read server configuration options from the configuration file. */ |
517 | read_server_config(&options, config_file_name); | |
518 | ||
519 | /* Fill in default values for those options not explicitly set. */ | |
520 | fill_default_server_options(&options); | |
521 | ||
5260325f | 522 | /* Check that there are no remaining arguments. */ |
523 | if (optind < ac) { | |
524 | fprintf(stderr, "Extra argument %s.\n", av[optind]); | |
525 | exit(1); | |
8efc0c15 | 526 | } |
5260325f | 527 | |
528 | debug("sshd version %.100s", SSH_VERSION); | |
529 | ||
a306f2dd | 530 | sensitive_data.dsa_host_key = NULL; |
531 | sensitive_data.host_key = NULL; | |
532 | ||
533 | /* check if RSA support exists */ | |
534 | if ((options.protocol & SSH_PROTO_1) && | |
535 | rsa_alive() == 0) { | |
536 | log("no RSA support in libssl and libcrypto. See ssl(8)"); | |
537 | log("Disabling protocol version 1"); | |
538 | options.protocol &= ~SSH_PROTO_1; | |
539 | } | |
540 | /* Load the RSA/DSA host key. It must have empty passphrase. */ | |
541 | if (options.protocol & SSH_PROTO_1) { | |
542 | Key k; | |
543 | sensitive_data.host_key = RSA_new(); | |
544 | k.type = KEY_RSA; | |
545 | k.rsa = sensitive_data.host_key; | |
546 | errno = 0; | |
547 | if (!load_private_key(options.host_key_file, "", &k, NULL)) { | |
548 | error("Could not load host key: %.200s: %.100s", | |
549 | options.host_key_file, strerror(errno)); | |
550 | log("Disabling protocol version 1"); | |
551 | options.protocol &= ~SSH_PROTO_1; | |
552 | } | |
553 | k.rsa = NULL; | |
554 | } | |
555 | if (options.protocol & SSH_PROTO_2) { | |
556 | sensitive_data.dsa_host_key = key_new(KEY_DSA); | |
1d1ffb87 | 557 | if (!load_private_key(options.host_dsa_key_file, "", sensitive_data.dsa_host_key, NULL)) { |
558 | ||
559 | error("Could not load DSA host key: %.200s", options.host_dsa_key_file); | |
a306f2dd | 560 | log("Disabling protocol version 2"); |
561 | options.protocol &= ~SSH_PROTO_2; | |
562 | } | |
563 | } | |
564 | if (! options.protocol & (SSH_PROTO_1|SSH_PROTO_2)) { | |
565 | if (silent == 0) | |
566 | fprintf(stderr, "sshd: no hostkeys available -- exiting.\n"); | |
567 | log("sshd: no hostkeys available -- exiting.\n"); | |
5260325f | 568 | exit(1); |
569 | } | |
5260325f | 570 | |
a306f2dd | 571 | /* Check certain values for sanity. */ |
572 | if (options.protocol & SSH_PROTO_1) { | |
573 | if (options.server_key_bits < 512 || | |
574 | options.server_key_bits > 32768) { | |
575 | fprintf(stderr, "Bad server key size.\n"); | |
576 | exit(1); | |
577 | } | |
578 | /* | |
579 | * Check that server and host key lengths differ sufficiently. This | |
580 | * is necessary to make double encryption work with rsaref. Oh, I | |
581 | * hate software patents. I dont know if this can go? Niels | |
582 | */ | |
583 | if (options.server_key_bits > | |
584 | BN_num_bits(sensitive_data.host_key->n) - SSH_KEY_BITS_RESERVED && | |
585 | options.server_key_bits < | |
586 | BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) { | |
587 | options.server_key_bits = | |
588 | BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED; | |
589 | debug("Forcing server key to %d bits to make it differ from host key.", | |
590 | options.server_key_bits); | |
591 | } | |
592 | } | |
593 | ||
594 | /* Initialize the log (it is reinitialized below in case we forked). */ | |
5260325f | 595 | if (debug_flag && !inetd_flag) |
596 | log_stderr = 1; | |
597 | log_init(av0, options.log_level, options.log_facility, log_stderr); | |
598 | ||
a306f2dd | 599 | /* |
600 | * If not in debugging mode, and not started from inetd, disconnect | |
601 | * from the controlling terminal, and fork. The original process | |
602 | * exits. | |
603 | */ | |
5260325f | 604 | if (!debug_flag && !inetd_flag) { |
8efc0c15 | 605 | #ifdef TIOCNOTTY |
5260325f | 606 | int fd; |
8efc0c15 | 607 | #endif /* TIOCNOTTY */ |
5260325f | 608 | if (daemon(0, 0) < 0) |
609 | fatal("daemon() failed: %.200s", strerror(errno)); | |
610 | ||
611 | /* Disconnect from the controlling tty. */ | |
8efc0c15 | 612 | #ifdef TIOCNOTTY |
5260325f | 613 | fd = open("/dev/tty", O_RDWR | O_NOCTTY); |
614 | if (fd >= 0) { | |
615 | (void) ioctl(fd, TIOCNOTTY, NULL); | |
616 | close(fd); | |
617 | } | |
8efc0c15 | 618 | #endif /* TIOCNOTTY */ |
8efc0c15 | 619 | } |
5260325f | 620 | /* Reinitialize the log (because of the fork above). */ |
621 | log_init(av0, options.log_level, options.log_facility, log_stderr); | |
622 | ||
5260325f | 623 | /* Do not display messages to stdout in RSA code. */ |
624 | rsa_set_verbose(0); | |
625 | ||
626 | /* Initialize the random number generator. */ | |
627 | arc4random_stir(); | |
628 | ||
629 | /* Chdir to the root directory so that the current disk can be | |
630 | unmounted if desired. */ | |
631 | chdir("/"); | |
632 | ||
5260325f | 633 | /* Start listening for a socket, unless started from inetd. */ |
634 | if (inetd_flag) { | |
635 | int s1, s2; | |
636 | s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */ | |
637 | s2 = dup(s1); | |
638 | sock_in = dup(0); | |
639 | sock_out = dup(1); | |
a306f2dd | 640 | /* |
641 | * We intentionally do not close the descriptors 0, 1, and 2 | |
642 | * as our code for setting the descriptors won\'t work if | |
643 | * ttyfd happens to be one of those. | |
644 | */ | |
5260325f | 645 | debug("inetd sockets after dupping: %d, %d", sock_in, sock_out); |
646 | ||
a306f2dd | 647 | if (options.protocol & SSH_PROTO_1) { |
648 | public_key = RSA_new(); | |
649 | sensitive_data.private_key = RSA_new(); | |
650 | log("Generating %d bit RSA key.", options.server_key_bits); | |
651 | rsa_generate_key(sensitive_data.private_key, public_key, | |
652 | options.server_key_bits); | |
653 | arc4random_stir(); | |
654 | log("RSA key generation complete."); | |
655 | } | |
5260325f | 656 | } else { |
48e671d5 | 657 | for (ai = options.listen_addrs; ai; ai = ai->ai_next) { |
658 | if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) | |
659 | continue; | |
660 | if (num_listen_socks >= MAX_LISTEN_SOCKS) | |
661 | fatal("Too many listen sockets. " | |
662 | "Enlarge MAX_LISTEN_SOCKS"); | |
663 | if (getnameinfo(ai->ai_addr, ai->ai_addrlen, | |
664 | ntop, sizeof(ntop), strport, sizeof(strport), | |
665 | NI_NUMERICHOST|NI_NUMERICSERV) != 0) { | |
666 | error("getnameinfo failed"); | |
667 | continue; | |
668 | } | |
669 | /* Create socket for listening. */ | |
670 | listen_sock = socket(ai->ai_family, SOCK_STREAM, 0); | |
671 | if (listen_sock < 0) { | |
672 | /* kernel may not support ipv6 */ | |
673 | verbose("socket: %.100s", strerror(errno)); | |
674 | continue; | |
675 | } | |
676 | if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) { | |
677 | error("listen_sock O_NONBLOCK: %s", strerror(errno)); | |
678 | close(listen_sock); | |
679 | continue; | |
680 | } | |
681 | /* | |
682 | * Set socket options. We try to make the port | |
683 | * reusable and have it close as fast as possible | |
684 | * without waiting in unnecessary wait states on | |
685 | * close. | |
686 | */ | |
687 | setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, | |
688 | (void *) &on, sizeof(on)); | |
689 | linger.l_onoff = 1; | |
690 | linger.l_linger = 5; | |
691 | setsockopt(listen_sock, SOL_SOCKET, SO_LINGER, | |
692 | (void *) &linger, sizeof(linger)); | |
693 | ||
694 | debug("Bind to port %s on %s.", strport, ntop); | |
695 | ||
696 | /* Bind the socket to the desired port. */ | |
16218745 | 697 | if ((bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) && |
698 | (!ai->ai_next)) { | |
48e671d5 | 699 | error("Bind to port %s on %s failed: %.200s.", |
700 | strport, ntop, strerror(errno)); | |
701 | close(listen_sock); | |
702 | continue; | |
703 | } | |
704 | listen_socks[num_listen_socks] = listen_sock; | |
705 | num_listen_socks++; | |
706 | ||
707 | /* Start listening on the port. */ | |
708 | log("Server listening on %s port %s.", ntop, strport); | |
709 | if (listen(listen_sock, 5) < 0) | |
710 | fatal("listen: %.100s", strerror(errno)); | |
711 | ||
5260325f | 712 | } |
48e671d5 | 713 | freeaddrinfo(options.listen_addrs); |
714 | ||
715 | if (!num_listen_socks) | |
716 | fatal("Cannot bind any address."); | |
717 | ||
5260325f | 718 | if (!debug_flag) { |
aa3378df | 719 | /* |
720 | * Record our pid in /etc/sshd_pid to make it easier | |
721 | * to kill the correct sshd. We don\'t want to do | |
722 | * this before the bind above because the bind will | |
723 | * fail if there already is a daemon, and this will | |
724 | * overwrite any old pid in the file. | |
725 | */ | |
0fbe8c74 | 726 | f = fopen(options.pid_file, "w"); |
5260325f | 727 | if (f) { |
728 | fprintf(f, "%u\n", (unsigned int) getpid()); | |
729 | fclose(f); | |
730 | } | |
8efc0c15 | 731 | } |
a306f2dd | 732 | if (options.protocol & SSH_PROTO_1) { |
733 | public_key = RSA_new(); | |
734 | sensitive_data.private_key = RSA_new(); | |
8efc0c15 | 735 | |
a306f2dd | 736 | log("Generating %d bit RSA key.", options.server_key_bits); |
737 | rsa_generate_key(sensitive_data.private_key, public_key, | |
738 | options.server_key_bits); | |
739 | arc4random_stir(); | |
740 | log("RSA key generation complete."); | |
5260325f | 741 | |
a306f2dd | 742 | /* Schedule server key regeneration alarm. */ |
743 | signal(SIGALRM, key_regeneration_alarm); | |
744 | alarm(options.key_regeneration_time); | |
745 | } | |
5260325f | 746 | |
747 | /* Arrange to restart on SIGHUP. The handler needs listen_sock. */ | |
748 | signal(SIGHUP, sighup_handler); | |
749 | signal(SIGTERM, sigterm_handler); | |
750 | signal(SIGQUIT, sigterm_handler); | |
751 | ||
752 | /* Arrange SIGCHLD to be caught. */ | |
753 | signal(SIGCHLD, main_sigchld_handler); | |
754 | ||
48e671d5 | 755 | /* setup fd set for listen */ |
756 | maxfd = 0; | |
757 | for (i = 0; i < num_listen_socks; i++) | |
758 | if (listen_socks[i] > maxfd) | |
759 | maxfd = listen_socks[i]; | |
6ae2364d | 760 | fdsetsz = howmany(maxfd, NFDBITS) * sizeof(fd_mask); |
761 | fdset = (fd_set *)xmalloc(fdsetsz); | |
48e671d5 | 762 | |
aa3378df | 763 | /* |
764 | * Stay listening for connections until the system crashes or | |
765 | * the daemon is killed with a signal. | |
766 | */ | |
5260325f | 767 | for (;;) { |
768 | if (received_sighup) | |
769 | sighup_restart(); | |
48e671d5 | 770 | /* Wait in select until there is a connection. */ |
771 | memset(fdset, 0, fdsetsz); | |
772 | for (i = 0; i < num_listen_socks; i++) | |
773 | FD_SET(listen_socks[i], fdset); | |
774 | if (select(maxfd + 1, fdset, NULL, NULL, NULL) < 0) { | |
775 | if (errno != EINTR) | |
776 | error("select: %.100s", strerror(errno)); | |
2d86a6cc | 777 | continue; |
48e671d5 | 778 | } |
779 | for (i = 0; i < num_listen_socks; i++) { | |
780 | if (!FD_ISSET(listen_socks[i], fdset)) | |
5260325f | 781 | continue; |
48e671d5 | 782 | fromlen = sizeof(from); |
783 | newsock = accept(listen_socks[i], (struct sockaddr *)&from, | |
784 | &fromlen); | |
785 | if (newsock < 0) { | |
786 | if (errno != EINTR && errno != EWOULDBLOCK) | |
787 | error("accept: %.100s", strerror(errno)); | |
788 | continue; | |
789 | } | |
790 | if (fcntl(newsock, F_SETFL, 0) < 0) { | |
791 | error("newsock del O_NONBLOCK: %s", strerror(errno)); | |
5260325f | 792 | continue; |
793 | } | |
aa3378df | 794 | /* |
795 | * Got connection. Fork a child to handle it, unless | |
796 | * we are in debugging mode. | |
797 | */ | |
5260325f | 798 | if (debug_flag) { |
aa3378df | 799 | /* |
800 | * In debugging mode. Close the listening | |
801 | * socket, and start processing the | |
802 | * connection without forking. | |
803 | */ | |
5260325f | 804 | debug("Server will not fork when running in debugging mode."); |
48e671d5 | 805 | close_listen_socks(); |
5260325f | 806 | sock_in = newsock; |
807 | sock_out = newsock; | |
808 | pid = getpid(); | |
809 | break; | |
810 | } else { | |
aa3378df | 811 | /* |
812 | * Normal production daemon. Fork, and have | |
813 | * the child process the connection. The | |
814 | * parent continues listening. | |
815 | */ | |
5260325f | 816 | if ((pid = fork()) == 0) { |
aa3378df | 817 | /* |
818 | * Child. Close the listening socket, and start using the | |
819 | * accepted socket. Reinitialize logging (since our pid has | |
820 | * changed). We break out of the loop to handle the connection. | |
821 | */ | |
48e671d5 | 822 | close_listen_socks(); |
5260325f | 823 | sock_in = newsock; |
824 | sock_out = newsock; | |
825 | log_init(av0, options.log_level, options.log_facility, log_stderr); | |
826 | break; | |
827 | } | |
828 | } | |
829 | ||
830 | /* Parent. Stay in the loop. */ | |
831 | if (pid < 0) | |
832 | error("fork: %.100s", strerror(errno)); | |
833 | else | |
834 | debug("Forked child %d.", pid); | |
835 | ||
836 | /* Mark that the key has been used (it was "given" to the child). */ | |
837 | key_used = 1; | |
838 | ||
839 | arc4random_stir(); | |
840 | ||
841 | /* Close the new socket (the child is now taking care of it). */ | |
842 | close(newsock); | |
48e671d5 | 843 | } /* for (i = 0; i < num_listen_socks; i++) */ |
844 | /* child process check (or debug mode) */ | |
845 | if (num_listen_socks < 0) | |
846 | break; | |
5260325f | 847 | } |
848 | } | |
8efc0c15 | 849 | |
5260325f | 850 | /* This is the child processing a new connection. */ |
851 | ||
aa3378df | 852 | /* |
853 | * Disable the key regeneration alarm. We will not regenerate the | |
854 | * key since we are no longer in a position to give it to anyone. We | |
855 | * will not restart on SIGHUP since it no longer makes sense. | |
856 | */ | |
5260325f | 857 | alarm(0); |
858 | signal(SIGALRM, SIG_DFL); | |
859 | signal(SIGHUP, SIG_DFL); | |
860 | signal(SIGTERM, SIG_DFL); | |
861 | signal(SIGQUIT, SIG_DFL); | |
862 | signal(SIGCHLD, SIG_DFL); | |
863 | ||
aa3378df | 864 | /* |
865 | * Set socket options for the connection. We want the socket to | |
866 | * close as fast as possible without waiting for anything. If the | |
867 | * connection is not a socket, these will do nothing. | |
868 | */ | |
869 | /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */ | |
5260325f | 870 | linger.l_onoff = 1; |
871 | linger.l_linger = 5; | |
872 | setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger)); | |
873 | ||
aa3378df | 874 | /* |
875 | * Register our connection. This turns encryption off because we do | |
876 | * not have a key. | |
877 | */ | |
5260325f | 878 | packet_set_connection(sock_in, sock_out); |
879 | ||
880 | remote_port = get_remote_port(); | |
881 | remote_ip = get_remote_ipaddr(); | |
882 | ||
883 | /* Check whether logins are denied from this host. */ | |
884 | #ifdef LIBWRAP | |
48e671d5 | 885 | /* XXX LIBWRAP noes not know about IPv6 */ |
5260325f | 886 | { |
887 | struct request_info req; | |
8efc0c15 | 888 | |
5260325f | 889 | request_init(&req, RQ_DAEMON, av0, RQ_FILE, sock_in, NULL); |
890 | fromhost(&req); | |
8efc0c15 | 891 | |
5260325f | 892 | if (!hosts_access(&req)) { |
893 | close(sock_in); | |
894 | close(sock_out); | |
895 | refuse(&req); | |
896 | } | |
48e671d5 | 897 | /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */ |
8efc0c15 | 898 | } |
48e671d5 | 899 | #endif /* LIBWRAP */ |
5260325f | 900 | /* Log the connection. */ |
901 | verbose("Connection from %.500s port %d", remote_ip, remote_port); | |
8efc0c15 | 902 | |
aa3378df | 903 | /* |
904 | * We don\'t want to listen forever unless the other side | |
905 | * successfully authenticates itself. So we set up an alarm which is | |
906 | * cleared after successful authentication. A limit of zero | |
907 | * indicates no limit. Note that we don\'t set the alarm in debugging | |
908 | * mode; it is just annoying to have the server exit just when you | |
909 | * are about to discover the bug. | |
910 | */ | |
5260325f | 911 | signal(SIGALRM, grace_alarm_handler); |
912 | if (!debug_flag) | |
913 | alarm(options.login_grace_time); | |
914 | ||
7368a6c8 | 915 | sshd_exchange_identification(sock_in, sock_out); |
aa3378df | 916 | /* |
917 | * Check that the connection comes from a privileged port. Rhosts- | |
918 | * and Rhosts-RSA-Authentication only make sense from priviledged | |
919 | * programs. Of course, if the intruder has root access on his local | |
920 | * machine, he can connect from any port. So do not use these | |
921 | * authentication methods from machines that you do not trust. | |
922 | */ | |
5260325f | 923 | if (remote_port >= IPPORT_RESERVED || |
924 | remote_port < IPPORT_RESERVED / 2) { | |
925 | options.rhosts_authentication = 0; | |
926 | options.rhosts_rsa_authentication = 0; | |
927 | } | |
48e671d5 | 928 | #ifdef KRB4 |
929 | if (!packet_connection_is_ipv4() && | |
930 | options.kerberos_authentication) { | |
931 | debug("Kerberos Authentication disabled, only available for IPv4."); | |
932 | options.kerberos_authentication = 0; | |
933 | } | |
934 | #endif /* KRB4 */ | |
935 | ||
5260325f | 936 | packet_set_nonblocking(); |
937 | ||
7b2ea3a1 | 938 | /* perform the key exchange */ |
7b2ea3a1 | 939 | /* authenticate user and start session */ |
e78a59f5 | 940 | if (compat20) { |
941 | do_ssh2_kex(); | |
942 | do_authentication2(); | |
943 | } else { | |
944 | do_ssh1_kex(); | |
945 | do_authentication(); | |
946 | } | |
8efc0c15 | 947 | |
948 | #ifdef KRB4 | |
5260325f | 949 | /* Cleanup user's ticket cache file. */ |
950 | if (options.kerberos_ticket_cleanup) | |
951 | (void) dest_tkt(); | |
8efc0c15 | 952 | #endif /* KRB4 */ |
953 | ||
5260325f | 954 | /* The connection has been terminated. */ |
955 | verbose("Closing connection to %.100s", remote_ip); | |
8efc0c15 | 956 | |
d94aa2ae | 957 | #ifdef USE_PAM |
a5c9cd31 | 958 | finish_pam(); |
d94aa2ae | 959 | #endif /* USE_PAM */ |
8efc0c15 | 960 | |
5260325f | 961 | packet_close(); |
962 | exit(0); | |
963 | } | |
8efc0c15 | 964 | |
5260325f | 965 | /* |
7b2ea3a1 | 966 | * SSH1 key exchange |
5260325f | 967 | */ |
e7c0f9d5 | 968 | void |
7368a6c8 | 969 | do_ssh1_kex() |
8efc0c15 | 970 | { |
5260325f | 971 | int i, len; |
7b2ea3a1 | 972 | int plen, slen; |
5260325f | 973 | BIGNUM *session_key_int; |
974 | unsigned char session_key[SSH_SESSION_KEY_LENGTH]; | |
7b2ea3a1 | 975 | unsigned char cookie[8]; |
5260325f | 976 | unsigned int cipher_type, auth_mask, protocol_flags; |
5260325f | 977 | u_int32_t rand = 0; |
978 | ||
aa3378df | 979 | /* |
980 | * Generate check bytes that the client must send back in the user | |
981 | * packet in order for it to be accepted; this is used to defy ip | |
982 | * spoofing attacks. Note that this only works against somebody | |
983 | * doing IP spoofing from a remote machine; any machine on the local | |
984 | * network can still see outgoing packets and catch the random | |
985 | * cookie. This only affects rhosts authentication, and this is one | |
986 | * of the reasons why it is inherently insecure. | |
987 | */ | |
5260325f | 988 | for (i = 0; i < 8; i++) { |
989 | if (i % 4 == 0) | |
990 | rand = arc4random(); | |
7b2ea3a1 | 991 | cookie[i] = rand & 0xff; |
5260325f | 992 | rand >>= 8; |
993 | } | |
994 | ||
aa3378df | 995 | /* |
996 | * Send our public key. We include in the packet 64 bits of random | |
997 | * data that must be matched in the reply in order to prevent IP | |
998 | * spoofing. | |
999 | */ | |
5260325f | 1000 | packet_start(SSH_SMSG_PUBLIC_KEY); |
1001 | for (i = 0; i < 8; i++) | |
7b2ea3a1 | 1002 | packet_put_char(cookie[i]); |
5260325f | 1003 | |
1004 | /* Store our public server RSA key. */ | |
1005 | packet_put_int(BN_num_bits(public_key->n)); | |
1006 | packet_put_bignum(public_key->e); | |
1007 | packet_put_bignum(public_key->n); | |
1008 | ||
1009 | /* Store our public host RSA key. */ | |
1010 | packet_put_int(BN_num_bits(sensitive_data.host_key->n)); | |
1011 | packet_put_bignum(sensitive_data.host_key->e); | |
1012 | packet_put_bignum(sensitive_data.host_key->n); | |
1013 | ||
1014 | /* Put protocol flags. */ | |
1015 | packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN); | |
1016 | ||
1017 | /* Declare which ciphers we support. */ | |
8ce64345 | 1018 | packet_put_int(cipher_mask1()); |
5260325f | 1019 | |
1020 | /* Declare supported authentication types. */ | |
1021 | auth_mask = 0; | |
1022 | if (options.rhosts_authentication) | |
1023 | auth_mask |= 1 << SSH_AUTH_RHOSTS; | |
1024 | if (options.rhosts_rsa_authentication) | |
1025 | auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA; | |
1026 | if (options.rsa_authentication) | |
1027 | auth_mask |= 1 << SSH_AUTH_RSA; | |
8efc0c15 | 1028 | #ifdef KRB4 |
5260325f | 1029 | if (options.kerberos_authentication) |
1030 | auth_mask |= 1 << SSH_AUTH_KERBEROS; | |
8efc0c15 | 1031 | #endif |
1032 | #ifdef AFS | |
5260325f | 1033 | if (options.kerberos_tgt_passing) |
1034 | auth_mask |= 1 << SSH_PASS_KERBEROS_TGT; | |
1035 | if (options.afs_token_passing) | |
1036 | auth_mask |= 1 << SSH_PASS_AFS_TOKEN; | |
8efc0c15 | 1037 | #endif |
5260325f | 1038 | #ifdef SKEY |
1039 | if (options.skey_authentication == 1) | |
1040 | auth_mask |= 1 << SSH_AUTH_TIS; | |
1041 | #endif | |
1042 | if (options.password_authentication) | |
1043 | auth_mask |= 1 << SSH_AUTH_PASSWORD; | |
1044 | packet_put_int(auth_mask); | |
1045 | ||
1046 | /* Send the packet and wait for it to be sent. */ | |
1047 | packet_send(); | |
1048 | packet_write_wait(); | |
1049 | ||
1050 | debug("Sent %d bit public key and %d bit host key.", | |
1051 | BN_num_bits(public_key->n), BN_num_bits(sensitive_data.host_key->n)); | |
1052 | ||
1053 | /* Read clients reply (cipher type and session key). */ | |
1054 | packet_read_expect(&plen, SSH_CMSG_SESSION_KEY); | |
1055 | ||
2d86a6cc | 1056 | /* Get cipher type and check whether we accept this. */ |
5260325f | 1057 | cipher_type = packet_get_char(); |
1058 | ||
6ae2364d | 1059 | if (!(cipher_mask() & (1 << cipher_type))) |
2d86a6cc | 1060 | packet_disconnect("Warning: client selects unsupported cipher."); |
1061 | ||
5260325f | 1062 | /* Get check bytes from the packet. These must match those we |
1063 | sent earlier with the public key packet. */ | |
1064 | for (i = 0; i < 8; i++) | |
7b2ea3a1 | 1065 | if (cookie[i] != packet_get_char()) |
5260325f | 1066 | packet_disconnect("IP Spoofing check bytes do not match."); |
1067 | ||
1068 | debug("Encryption type: %.200s", cipher_name(cipher_type)); | |
1069 | ||
1070 | /* Get the encrypted integer. */ | |
1071 | session_key_int = BN_new(); | |
1072 | packet_get_bignum(session_key_int, &slen); | |
1073 | ||
5260325f | 1074 | protocol_flags = packet_get_int(); |
1075 | packet_set_protocol_flags(protocol_flags); | |
1076 | ||
1077 | packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY); | |
1078 | ||
aa3378df | 1079 | /* |
1080 | * Decrypt it using our private server key and private host key (key | |
1081 | * with larger modulus first). | |
1082 | */ | |
5260325f | 1083 | if (BN_cmp(sensitive_data.private_key->n, sensitive_data.host_key->n) > 0) { |
1084 | /* Private key has bigger modulus. */ | |
1085 | if (BN_num_bits(sensitive_data.private_key->n) < | |
1086 | BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED) { | |
1087 | fatal("do_connection: %s: private_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d", | |
1088 | get_remote_ipaddr(), | |
1089 | BN_num_bits(sensitive_data.private_key->n), | |
1090 | BN_num_bits(sensitive_data.host_key->n), | |
1091 | SSH_KEY_BITS_RESERVED); | |
1092 | } | |
1093 | rsa_private_decrypt(session_key_int, session_key_int, | |
1094 | sensitive_data.private_key); | |
1095 | rsa_private_decrypt(session_key_int, session_key_int, | |
1096 | sensitive_data.host_key); | |
1097 | } else { | |
1098 | /* Host key has bigger modulus (or they are equal). */ | |
1099 | if (BN_num_bits(sensitive_data.host_key->n) < | |
1100 | BN_num_bits(sensitive_data.private_key->n) + SSH_KEY_BITS_RESERVED) { | |
1101 | fatal("do_connection: %s: host_key %d < private_key %d + SSH_KEY_BITS_RESERVED %d", | |
1102 | get_remote_ipaddr(), | |
1103 | BN_num_bits(sensitive_data.host_key->n), | |
1104 | BN_num_bits(sensitive_data.private_key->n), | |
1105 | SSH_KEY_BITS_RESERVED); | |
1106 | } | |
1107 | rsa_private_decrypt(session_key_int, session_key_int, | |
1108 | sensitive_data.host_key); | |
1109 | rsa_private_decrypt(session_key_int, session_key_int, | |
1110 | sensitive_data.private_key); | |
1111 | } | |
1112 | ||
7b2ea3a1 | 1113 | compute_session_id(session_id, cookie, |
5260325f | 1114 | sensitive_data.host_key->n, |
1115 | sensitive_data.private_key->n); | |
1116 | ||
7b2ea3a1 | 1117 | /* Destroy the private and public keys. They will no longer be needed. */ |
a306f2dd | 1118 | destroy_sensitive_data(); |
7b2ea3a1 | 1119 | |
aa3378df | 1120 | /* |
1121 | * Extract session key from the decrypted integer. The key is in the | |
1122 | * least significant 256 bits of the integer; the first byte of the | |
1123 | * key is in the highest bits. | |
1124 | */ | |
5260325f | 1125 | BN_mask_bits(session_key_int, sizeof(session_key) * 8); |
1126 | len = BN_num_bytes(session_key_int); | |
1127 | if (len < 0 || len > sizeof(session_key)) | |
1128 | fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d", | |
1129 | get_remote_ipaddr(), | |
1130 | len, sizeof(session_key)); | |
1131 | memset(session_key, 0, sizeof(session_key)); | |
1132 | BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len); | |
1133 | ||
7b2ea3a1 | 1134 | /* Destroy the decrypted integer. It is no longer needed. */ |
1135 | BN_clear_free(session_key_int); | |
1136 | ||
5260325f | 1137 | /* Xor the first 16 bytes of the session key with the session id. */ |
1138 | for (i = 0; i < 16; i++) | |
1139 | session_key[i] ^= session_id[i]; | |
1140 | ||
5260325f | 1141 | /* Set the session key. From this on all communications will be encrypted. */ |
1142 | packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type); | |
1143 | ||
1144 | /* Destroy our copy of the session key. It is no longer needed. */ | |
1145 | memset(session_key, 0, sizeof(session_key)); | |
1146 | ||
1147 | debug("Received session key; encryption turned on."); | |
1148 | ||
1149 | /* Send an acknowledgement packet. Note that this packet is sent encrypted. */ | |
1150 | packet_start(SSH_SMSG_SUCCESS); | |
1151 | packet_send(); | |
1152 | packet_write_wait(); | |
5260325f | 1153 | } |
e78a59f5 | 1154 | |
1155 | /* | |
1156 | * SSH2 key exchange: diffie-hellman-group1-sha1 | |
1157 | */ | |
1158 | void | |
1159 | do_ssh2_kex() | |
1160 | { | |
1161 | Buffer *server_kexinit; | |
1162 | Buffer *client_kexinit; | |
1163 | int payload_len, dlen; | |
1164 | int slen; | |
1165 | unsigned int klen, kout; | |
e78a59f5 | 1166 | unsigned char *signature = NULL; |
1167 | unsigned char *server_host_key_blob = NULL; | |
1168 | unsigned int sbloblen; | |
1169 | DH *dh; | |
1170 | BIGNUM *dh_client_pub = 0; | |
1171 | BIGNUM *shared_secret = 0; | |
1172 | int i; | |
1173 | unsigned char *kbuf; | |
1174 | unsigned char *hash; | |
1175 | Kex *kex; | |
e78a59f5 | 1176 | char *cprop[PROPOSAL_MAX]; |
e78a59f5 | 1177 | |
1178 | /* KEXINIT */ | |
1179 | ||
a8be9f80 | 1180 | if (options.ciphers != NULL) { |
6ae2364d | 1181 | myproposal[PROPOSAL_ENC_ALGS_CTOS] = |
a8be9f80 | 1182 | myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; |
1183 | } | |
71276795 | 1184 | server_kexinit = kex_init(myproposal); |
e78a59f5 | 1185 | client_kexinit = xmalloc(sizeof(*client_kexinit)); |
1186 | buffer_init(client_kexinit); | |
e78a59f5 | 1187 | |
71276795 | 1188 | /* algorithm negotiation */ |
1189 | kex_exchange_kexinit(server_kexinit, client_kexinit, cprop); | |
1190 | kex = kex_choose_conf(cprop, myproposal, 1); | |
1191 | for (i = 0; i < PROPOSAL_MAX; i++) | |
1192 | xfree(cprop[i]); | |
e78a59f5 | 1193 | |
1194 | /* KEXDH */ | |
1195 | ||
1196 | debug("Wait SSH2_MSG_KEXDH_INIT."); | |
1197 | packet_read_expect(&payload_len, SSH2_MSG_KEXDH_INIT); | |
1198 | ||
1199 | /* key, cert */ | |
1200 | dh_client_pub = BN_new(); | |
1201 | if (dh_client_pub == NULL) | |
1202 | fatal("dh_client_pub == NULL"); | |
1203 | packet_get_bignum2(dh_client_pub, &dlen); | |
1204 | ||
1205 | #ifdef DEBUG_KEXDH | |
1206 | fprintf(stderr, "\ndh_client_pub= "); | |
1207 | bignum_print(dh_client_pub); | |
1208 | fprintf(stderr, "\n"); | |
1209 | debug("bits %d", BN_num_bits(dh_client_pub)); | |
1210 | #endif | |
1211 | ||
1212 | /* generate DH key */ | |
a8be9f80 | 1213 | dh = dh_new_group1(); /* XXX depends on 'kex' */ |
e78a59f5 | 1214 | |
1215 | #ifdef DEBUG_KEXDH | |
1216 | fprintf(stderr, "\np= "); | |
1217 | bignum_print(dh->p); | |
1218 | fprintf(stderr, "\ng= "); | |
1219 | bignum_print(dh->g); | |
1220 | fprintf(stderr, "\npub= "); | |
1221 | bignum_print(dh->pub_key); | |
1222 | fprintf(stderr, "\n"); | |
1223 | #endif | |
a8be9f80 | 1224 | if (!dh_pub_is_valid(dh, dh_client_pub)) |
1225 | packet_disconnect("bad client public DH value"); | |
e78a59f5 | 1226 | |
1227 | klen = DH_size(dh); | |
1228 | kbuf = xmalloc(klen); | |
1229 | kout = DH_compute_key(kbuf, dh_client_pub, dh); | |
1230 | ||
1231 | #ifdef DEBUG_KEXDH | |
1232 | debug("shared secret: len %d/%d", klen, kout); | |
1233 | fprintf(stderr, "shared secret == "); | |
1234 | for (i = 0; i< kout; i++) | |
1235 | fprintf(stderr, "%02x", (kbuf[i])&0xff); | |
1236 | fprintf(stderr, "\n"); | |
1237 | #endif | |
1238 | shared_secret = BN_new(); | |
1239 | ||
1240 | BN_bin2bn(kbuf, kout, shared_secret); | |
1241 | memset(kbuf, 0, klen); | |
1242 | xfree(kbuf); | |
1243 | ||
a306f2dd | 1244 | /* XXX precompute? */ |
1245 | dsa_make_key_blob(sensitive_data.dsa_host_key, &server_host_key_blob, &sbloblen); | |
e78a59f5 | 1246 | |
1247 | /* calc H */ /* XXX depends on 'kex' */ | |
1248 | hash = kex_hash( | |
1249 | client_version_string, | |
1250 | server_version_string, | |
1251 | buffer_ptr(client_kexinit), buffer_len(client_kexinit), | |
1252 | buffer_ptr(server_kexinit), buffer_len(server_kexinit), | |
1253 | (char *)server_host_key_blob, sbloblen, | |
1254 | dh_client_pub, | |
1255 | dh->pub_key, | |
1256 | shared_secret | |
1257 | ); | |
1258 | buffer_free(client_kexinit); | |
1259 | buffer_free(server_kexinit); | |
1260 | xfree(client_kexinit); | |
1261 | xfree(server_kexinit); | |
1262 | #ifdef DEBUG_KEXDH | |
6ae2364d | 1263 | fprintf(stderr, "hash == "); |
1264 | for (i = 0; i< 20; i++) | |
1265 | fprintf(stderr, "%02x", (hash[i])&0xff); | |
1266 | fprintf(stderr, "\n"); | |
e78a59f5 | 1267 | #endif |
a306f2dd | 1268 | /* save session id := H */ |
1269 | /* XXX hashlen depends on KEX */ | |
1270 | session_id2_len = 20; | |
1271 | session_id2 = xmalloc(session_id2_len); | |
1272 | memcpy(session_id2, hash, session_id2_len); | |
1273 | ||
e78a59f5 | 1274 | /* sign H */ |
a306f2dd | 1275 | /* XXX hashlen depends on KEX */ |
1276 | dsa_sign(sensitive_data.dsa_host_key, &signature, &slen, hash, 20); | |
1277 | ||
1278 | destroy_sensitive_data(); | |
e78a59f5 | 1279 | |
1280 | /* send server hostkey, DH pubkey 'f' and singed H */ | |
1281 | packet_start(SSH2_MSG_KEXDH_REPLY); | |
1282 | packet_put_string((char *)server_host_key_blob, sbloblen); | |
1d1ffb87 | 1283 | packet_put_bignum2(dh->pub_key); /* f */ |
e78a59f5 | 1284 | packet_put_string((char *)signature, slen); |
1285 | packet_send(); | |
d6f24e45 | 1286 | xfree(signature); |
a306f2dd | 1287 | xfree(server_host_key_blob); |
e78a59f5 | 1288 | packet_write_wait(); |
1289 | ||
1290 | kex_derive_keys(kex, hash, shared_secret); | |
1291 | packet_set_kex(kex); | |
1292 | ||
1293 | /* have keys, free DH */ | |
1294 | DH_free(dh); | |
1295 | ||
1296 | debug("send SSH2_MSG_NEWKEYS."); | |
1297 | packet_start(SSH2_MSG_NEWKEYS); | |
1298 | packet_send(); | |
1299 | packet_write_wait(); | |
1300 | debug("done: send SSH2_MSG_NEWKEYS."); | |
1301 | ||
1302 | debug("Wait SSH2_MSG_NEWKEYS."); | |
1303 | packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS); | |
1304 | debug("GOT SSH2_MSG_NEWKEYS."); | |
1305 | ||
a8be9f80 | 1306 | #ifdef DEBUG_KEXDH |
e78a59f5 | 1307 | /* send 1st encrypted/maced/compressed message */ |
1308 | packet_start(SSH2_MSG_IGNORE); | |
1309 | packet_put_cstring("markus"); | |
1310 | packet_send(); | |
1311 | packet_write_wait(); | |
a8be9f80 | 1312 | #endif |
e78a59f5 | 1313 | debug("done: KEX2."); |
1314 | } |