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8efc0c15 | 1 | /* |
2 | ||
3 | ssh.c | |
4 | ||
5 | Author: Tatu Ylonen <ylo@cs.hut.fi> | |
6 | ||
7 | Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
8 | All rights reserved | |
9 | ||
10 | Created: Sat Mar 18 16:36:11 1995 ylo | |
11 | ||
12 | Ssh client program. This program can be used to log into a remote machine. | |
13 | The software supports strong authentication, encryption, and forwarding | |
14 | of X11, TCP/IP, and authentication connections. | |
15 | ||
16 | Modified to work with SSL by Niels Provos <provos@citi.umich.edu> in Canada. | |
17 | ||
18 | */ | |
19 | ||
20 | #include "includes.h" | |
21 | RCSID("$Id$"); | |
22 | ||
23 | #include "xmalloc.h" | |
24 | #include "ssh.h" | |
25 | #include "packet.h" | |
26 | #include "buffer.h" | |
27 | #include "authfd.h" | |
28 | #include "readconf.h" | |
29 | #include "uidswap.h" | |
30 | ||
31 | /* Flag indicating whether debug mode is on. This can be set on the | |
32 | command line. */ | |
33 | int debug_flag = 0; | |
34 | ||
35 | /* Flag indicating whether quiet mode is on. */ | |
36 | int quiet_flag = 0; | |
37 | ||
38 | /* Flag indicating whether to allocate a pseudo tty. This can be set on the | |
39 | command line, and is automatically set if no command is given on the command | |
40 | line. */ | |
41 | int tty_flag = 0; | |
42 | ||
43 | /* Flag indicating that nothing should be read from stdin. This can be set | |
44 | on the command line. */ | |
45 | int stdin_null_flag = 0; | |
46 | ||
47 | /* Flag indicating that ssh should fork after authentication. This is useful | |
48 | so that the pasphrase can be entered manually, and then ssh goes to the | |
49 | background. */ | |
50 | int fork_after_authentication_flag = 0; | |
51 | ||
52 | /* General data structure for command line options and options configurable | |
53 | in configuration files. See readconf.h. */ | |
54 | Options options; | |
55 | ||
56 | /* Name of the host we are connecting to. This is the name given on the | |
57 | command line, or the HostName specified for the user-supplied name | |
58 | in a configuration file. */ | |
59 | char *host; | |
60 | ||
61 | /* socket address the host resolves to */ | |
62 | struct sockaddr_in hostaddr; | |
63 | ||
64 | /* Flag to indicate that we have received a window change signal which has | |
65 | not yet been processed. This will cause a message indicating the new | |
66 | window size to be sent to the server a little later. This is volatile | |
67 | because this is updated in a signal handler. */ | |
68 | volatile int received_window_change_signal = 0; | |
69 | ||
70 | /* Value of argv[0] (set in the main program). */ | |
71 | char *av0; | |
72 | ||
73 | /* Flag indicating whether we have a valid host private key loaded. */ | |
74 | int host_private_key_loaded = 0; | |
75 | ||
76 | /* Host private key. */ | |
77 | RSA *host_private_key = NULL; | |
78 | ||
79 | /* Original real UID. */ | |
80 | uid_t original_real_uid; | |
81 | ||
82 | /* Prints a help message to the user. This function never returns. */ | |
83 | ||
84 | void | |
85 | usage() | |
86 | { | |
87 | fprintf(stderr, "Usage: %s [options] host [command]\n", av0); | |
88 | fprintf(stderr, "Options:\n"); | |
89 | fprintf(stderr, " -l user Log in using this user name.\n"); | |
90 | fprintf(stderr, " -n Redirect input from /dev/null.\n"); | |
91 | fprintf(stderr, " -a Disable authentication agent forwarding.\n"); | |
92 | #ifdef AFS | |
93 | fprintf(stderr, " -k Disable Kerberos ticket and AFS token forwarding.\n"); | |
94 | #endif /* AFS */ | |
95 | fprintf(stderr, " -x Disable X11 connection forwarding.\n"); | |
96 | fprintf(stderr, " -i file Identity for RSA authentication (default: ~/.ssh/identity).\n"); | |
97 | fprintf(stderr, " -t Tty; allocate a tty even if command is given.\n"); | |
98 | fprintf(stderr, " -v Verbose; display verbose debugging messages.\n"); | |
99 | fprintf(stderr, " -V Display version number only.\n"); | |
100 | fprintf(stderr, " -P Don't allocate a privileged port.\n"); | |
101 | fprintf(stderr, " -q Quiet; don't display any warning messages.\n"); | |
102 | fprintf(stderr, " -f Fork into background after authentication.\n"); | |
103 | fprintf(stderr, " -e char Set escape character; ``none'' = disable (default: ~).\n"); | |
104 | ||
105 | fprintf(stderr, " -c cipher Select encryption algorithm: " | |
106 | "``3des'', " | |
107 | "``blowfish''\n"); | |
108 | fprintf(stderr, " -p port Connect to this port. Server must be on the same port.\n"); | |
109 | fprintf(stderr, " -L listen-port:host:port Forward local port to remote address\n"); | |
110 | fprintf(stderr, " -R listen-port:host:port Forward remote port to local address\n"); | |
111 | fprintf(stderr, " These cause %s to listen for connections on a port, and\n", av0); | |
112 | fprintf(stderr, " forward them to the other side by connecting to host:port.\n"); | |
113 | fprintf(stderr, " -C Enable compression.\n"); | |
114 | fprintf(stderr, " -g Allow remote hosts to connect to forwarded ports.\n"); | |
115 | fprintf(stderr, " -o 'option' Process the option as if it was read from a configuration file.\n"); | |
116 | exit(1); | |
117 | } | |
118 | ||
119 | /* Connects to the given host using rsh (or prints an error message and exits | |
120 | if rsh is not available). This function never returns. */ | |
121 | ||
122 | void | |
123 | rsh_connect(char *host, char *user, Buffer *command) | |
124 | { | |
125 | char *args[10]; | |
126 | int i; | |
127 | ||
128 | log("Using rsh. WARNING: Connection will not be encrypted."); | |
129 | /* Build argument list for rsh. */ | |
130 | i = 0; | |
131 | args[i++] = _PATH_RSH; | |
132 | args[i++] = host; /* may have to come after user on some systems */ | |
133 | if (user) | |
134 | { | |
135 | args[i++] = "-l"; | |
136 | args[i++] = user; | |
137 | } | |
138 | if (buffer_len(command) > 0) | |
139 | { | |
140 | buffer_append(command, "\0", 1); | |
141 | args[i++] = buffer_ptr(command); | |
142 | } | |
143 | args[i++] = NULL; | |
144 | if (debug_flag) | |
145 | { | |
146 | for (i = 0; args[i]; i++) | |
147 | { | |
148 | if (i != 0) | |
149 | fprintf(stderr, " "); | |
150 | fprintf(stderr, "%s", args[i]); | |
151 | } | |
152 | fprintf(stderr, "\n"); | |
153 | } | |
154 | execv(_PATH_RSH, args); | |
155 | perror(_PATH_RSH); | |
156 | exit(1); | |
157 | } | |
158 | ||
159 | /* Main program for the ssh client. */ | |
160 | ||
161 | uid_t original_real_uid; | |
162 | ||
163 | int | |
164 | main(int ac, char **av) | |
165 | { | |
166 | int i, opt, optind, type, exit_status, ok, fwd_port, fwd_host_port, authfd; | |
167 | char *optarg, *cp, buf[256]; | |
168 | Buffer command; | |
169 | struct winsize ws; | |
170 | struct stat st; | |
171 | struct passwd *pw, pwcopy; | |
172 | int interactive = 0, dummy; | |
173 | uid_t original_effective_uid; | |
174 | int plen; | |
175 | ||
176 | /* Save the original real uid. It will be needed later (uid-swapping may | |
177 | clobber the real uid). */ | |
178 | original_real_uid = getuid(); | |
179 | original_effective_uid = geteuid(); | |
180 | ||
181 | /* If we are installed setuid root be careful to not drop core. */ | |
182 | if (original_real_uid != original_effective_uid) | |
183 | { | |
184 | struct rlimit rlim; | |
185 | rlim.rlim_cur = rlim.rlim_max = 0; | |
186 | if (setrlimit(RLIMIT_CORE, &rlim) < 0) | |
187 | fatal("setrlimit failed: %.100s", strerror(errno)); | |
188 | } | |
189 | ||
190 | /* Use uid-swapping to give up root privileges for the duration of option | |
191 | processing. We will re-instantiate the rights when we are ready to | |
192 | create the privileged port, and will permanently drop them when the | |
193 | port has been created (actually, when the connection has been made, as | |
194 | we may need to create the port several times). */ | |
195 | temporarily_use_uid(original_real_uid); | |
196 | ||
197 | /* Set our umask to something reasonable, as some files are created with | |
198 | the default umask. This will make them world-readable but writable | |
199 | only by the owner, which is ok for all files for which we don't set | |
200 | the modes explicitly. */ | |
201 | umask(022); | |
202 | ||
203 | /* Save our own name. */ | |
204 | av0 = av[0]; | |
205 | ||
206 | /* Initialize option structure to indicate that no values have been set. */ | |
207 | initialize_options(&options); | |
208 | ||
209 | /* Parse command-line arguments. */ | |
210 | host = NULL; | |
211 | ||
212 | /* If program name is not one of the standard names, use it as host name. */ | |
213 | if (strchr(av0, '/')) | |
214 | cp = strrchr(av0, '/') + 1; | |
215 | else | |
216 | cp = av0; | |
217 | if (strcmp(cp, "rsh") != 0 && strcmp(cp, "ssh") != 0 && | |
218 | strcmp(cp, "rlogin") != 0 && strcmp(cp, "slogin") != 0) | |
219 | host = cp; | |
220 | ||
221 | for (optind = 1; optind < ac; optind++) | |
222 | { | |
223 | if (av[optind][0] != '-') | |
224 | { | |
225 | if (host) | |
226 | break; | |
227 | if ((cp = strchr(av[optind], '@'))) { | |
228 | options.user = av[optind]; | |
229 | *cp = '\0'; | |
230 | host = ++cp; | |
231 | } | |
232 | else | |
233 | host = av[optind]; | |
234 | continue; | |
235 | } | |
236 | opt = av[optind][1]; | |
237 | if (!opt) | |
238 | usage(); | |
239 | if (strchr("eilcpLRo", opt)) /* options with arguments */ | |
240 | { | |
241 | optarg = av[optind] + 2; | |
242 | if (strcmp(optarg, "") == 0) | |
243 | { | |
244 | if (optind >= ac - 1) | |
245 | usage(); | |
246 | optarg = av[++optind]; | |
247 | } | |
248 | } | |
249 | else | |
250 | { | |
251 | if (av[optind][2]) | |
252 | usage(); | |
253 | optarg = NULL; | |
254 | } | |
255 | switch (opt) | |
256 | { | |
257 | case 'n': | |
258 | stdin_null_flag = 1; | |
259 | break; | |
260 | ||
261 | case 'f': | |
262 | fork_after_authentication_flag = 1; | |
263 | stdin_null_flag = 1; | |
264 | break; | |
265 | ||
266 | case 'x': | |
267 | options.forward_x11 = 0; | |
268 | break; | |
269 | ||
270 | case 'X': | |
271 | options.forward_x11 = 1; | |
272 | break; | |
273 | ||
274 | case 'g': | |
275 | options.gateway_ports = 1; | |
276 | break; | |
277 | ||
278 | case 'P': | |
279 | options.use_privileged_port = 0; | |
280 | break; | |
281 | ||
282 | case 'a': | |
283 | options.forward_agent = 0; | |
284 | break; | |
285 | #ifdef AFS | |
286 | case 'k': | |
287 | options.kerberos_tgt_passing = 0; | |
288 | options.afs_token_passing = 0; | |
289 | break; | |
290 | #endif | |
291 | case 'i': | |
292 | if (stat(optarg, &st) < 0) | |
293 | { | |
294 | fprintf(stderr, "Warning: Identity file %s does not exist.\n", | |
295 | optarg); | |
296 | break; | |
297 | } | |
298 | if (options.num_identity_files >= SSH_MAX_IDENTITY_FILES) | |
299 | fatal("Too many identity files specified (max %d)", | |
300 | SSH_MAX_IDENTITY_FILES); | |
301 | options.identity_files[options.num_identity_files++] = | |
302 | xstrdup(optarg); | |
303 | break; | |
304 | ||
305 | case 't': | |
306 | tty_flag = 1; | |
307 | break; | |
308 | ||
309 | case 'v': | |
310 | case 'V': | |
311 | debug_flag = 1; | |
312 | fprintf(stderr, "SSH Version %s, protocol version %d.%d.\n", | |
313 | SSH_VERSION, PROTOCOL_MAJOR, PROTOCOL_MINOR); | |
314 | fprintf(stderr, "Compiled with SSL.\n"); | |
315 | if (opt == 'V') | |
316 | exit(0); | |
317 | break; | |
318 | ||
319 | case 'q': | |
320 | quiet_flag = 1; | |
321 | break; | |
322 | ||
323 | case 'e': | |
324 | if (optarg[0] == '^' && optarg[2] == 0 && | |
325 | (unsigned char)optarg[1] >= 64 && (unsigned char)optarg[1] < 128) | |
326 | options.escape_char = (unsigned char)optarg[1] & 31; | |
327 | else | |
328 | if (strlen(optarg) == 1) | |
329 | options.escape_char = (unsigned char)optarg[0]; | |
330 | else | |
331 | if (strcmp(optarg, "none") == 0) | |
332 | options.escape_char = -2; | |
333 | else | |
334 | { | |
335 | fprintf(stderr, "Bad escape character '%s'.\n", optarg); | |
336 | exit(1); | |
337 | } | |
338 | break; | |
339 | ||
340 | case 'c': | |
341 | options.cipher = cipher_number(optarg); | |
342 | if (options.cipher == -1) | |
343 | { | |
344 | fprintf(stderr, "Unknown cipher type '%s'\n", optarg); | |
345 | exit(1); | |
346 | } | |
347 | break; | |
348 | ||
349 | case 'p': | |
350 | options.port = atoi(optarg); | |
351 | if (options.port < 1 || options.port > 65535) | |
352 | { | |
353 | fprintf(stderr, "Bad port %s.\n", optarg); | |
354 | exit(1); | |
355 | } | |
356 | break; | |
357 | ||
358 | case 'l': | |
359 | options.user = optarg; | |
360 | break; | |
361 | ||
362 | case 'R': | |
363 | if (sscanf(optarg, "%d:%255[^:]:%d", &fwd_port, buf, | |
364 | &fwd_host_port) != 3) | |
365 | { | |
366 | fprintf(stderr, "Bad forwarding specification '%s'.\n", optarg); | |
367 | usage(); | |
368 | /*NOTREACHED*/ | |
369 | } | |
370 | add_remote_forward(&options, fwd_port, buf, fwd_host_port); | |
371 | break; | |
372 | ||
373 | case 'L': | |
374 | if (sscanf(optarg, "%d:%255[^:]:%d", &fwd_port, buf, | |
375 | &fwd_host_port) != 3) | |
376 | { | |
377 | fprintf(stderr, "Bad forwarding specification '%s'.\n", optarg); | |
378 | usage(); | |
379 | /*NOTREACHED*/ | |
380 | } | |
381 | add_local_forward(&options, fwd_port, buf, fwd_host_port); | |
382 | break; | |
383 | ||
384 | case 'C': | |
385 | options.compression = 1; | |
386 | break; | |
387 | ||
388 | case 'o': | |
389 | dummy = 1; | |
390 | process_config_line(&options, host ? host : "", optarg, | |
391 | "command-line", 0, &dummy); | |
392 | break; | |
393 | ||
394 | default: | |
395 | usage(); | |
396 | } | |
397 | } | |
398 | ||
399 | /* Check that we got a host name. */ | |
400 | if (!host) | |
401 | usage(); | |
402 | ||
403 | /* check if RSA support exists */ | |
404 | if (rsa_alive() == 0) { | |
405 | extern char *__progname; | |
406 | ||
407 | fprintf(stderr, | |
408 | "%s: no RSA support in libssl and libcrypto. See ssl(8).\n", | |
409 | __progname); | |
410 | exit(1); | |
411 | } | |
412 | ||
413 | /* Initialize the command to execute on remote host. */ | |
414 | buffer_init(&command); | |
415 | ||
416 | /* Save the command to execute on the remote host in a buffer. There is | |
417 | no limit on the length of the command, except by the maximum packet | |
418 | size. Also sets the tty flag if there is no command. */ | |
419 | if (optind == ac) | |
420 | { | |
421 | /* No command specified - execute shell on a tty. */ | |
422 | tty_flag = 1; | |
423 | } | |
424 | else | |
425 | { | |
426 | /* A command has been specified. Store it into the buffer. */ | |
427 | for (i = optind; i < ac; i++) | |
428 | { | |
429 | if (i > optind) | |
430 | buffer_append(&command, " ", 1); | |
431 | buffer_append(&command, av[i], strlen(av[i])); | |
432 | } | |
433 | } | |
434 | ||
435 | /* Cannot fork to background if no command. */ | |
436 | if (fork_after_authentication_flag && buffer_len(&command) == 0) | |
437 | fatal("Cannot fork into background without a command to execute."); | |
438 | ||
439 | /* Allocate a tty by default if no command specified. */ | |
440 | if (buffer_len(&command) == 0) | |
441 | tty_flag = 1; | |
442 | ||
443 | /* Do not allocate a tty if stdin is not a tty. */ | |
444 | if (!isatty(fileno(stdin))) | |
445 | { | |
446 | if (tty_flag) | |
447 | fprintf(stderr, "Pseudo-terminal will not be allocated because stdin is not a terminal.\n"); | |
448 | tty_flag = 0; | |
449 | } | |
450 | ||
451 | /* Get user data. */ | |
452 | pw = getpwuid(original_real_uid); | |
453 | if (!pw) | |
454 | { | |
455 | fprintf(stderr, "You don't exist, go away!\n"); | |
456 | exit(1); | |
457 | } | |
458 | ||
459 | /* Take a copy of the returned structure. */ | |
460 | memset(&pwcopy, 0, sizeof(pwcopy)); | |
461 | pwcopy.pw_name = xstrdup(pw->pw_name); | |
462 | pwcopy.pw_passwd = xstrdup(pw->pw_passwd); | |
463 | pwcopy.pw_uid = pw->pw_uid; | |
464 | pwcopy.pw_gid = pw->pw_gid; | |
465 | pwcopy.pw_dir = xstrdup(pw->pw_dir); | |
466 | pwcopy.pw_shell = xstrdup(pw->pw_shell); | |
467 | pw = &pwcopy; | |
468 | ||
469 | /* Initialize "log" output. Since we are the client all output actually | |
470 | goes to the terminal. */ | |
471 | log_init(av[0], 1, debug_flag, quiet_flag, SYSLOG_FACILITY_USER); | |
472 | ||
473 | /* Read per-user configuration file. */ | |
474 | snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir, SSH_USER_CONFFILE); | |
475 | read_config_file(buf, host, &options); | |
476 | ||
477 | /* Read systemwide configuration file. */ | |
478 | read_config_file(HOST_CONFIG_FILE, host, &options); | |
479 | ||
480 | /* Fill configuration defaults. */ | |
481 | fill_default_options(&options); | |
482 | if (options.user == NULL) | |
483 | options.user = xstrdup(pw->pw_name); | |
484 | ||
485 | if (options.hostname != NULL) | |
486 | host = options.hostname; | |
487 | ||
488 | /* Find canonic host name. */ | |
489 | if (strchr(host, '.') == 0) | |
490 | { | |
491 | struct hostent *hp = gethostbyname(host); | |
492 | if (hp != 0) | |
493 | { | |
494 | if (strchr(hp->h_name, '.') != 0) | |
495 | host = xstrdup(hp->h_name); | |
496 | else if (hp->h_aliases != 0 | |
497 | && hp->h_aliases[0] != 0 | |
498 | && strchr(hp->h_aliases[0], '.') != 0) | |
499 | host = xstrdup(hp->h_aliases[0]); | |
500 | } | |
501 | } | |
502 | ||
503 | /* Disable rhosts authentication if not running as root. */ | |
504 | if (original_effective_uid != 0) | |
505 | { | |
506 | options.rhosts_authentication = 0; | |
507 | options.rhosts_rsa_authentication = 0; | |
508 | } | |
509 | ||
510 | /* If using rsh has been selected, exec it now (without trying anything | |
511 | else). Note that we must release privileges first. */ | |
512 | if (options.use_rsh) | |
513 | { | |
514 | /* Restore our superuser privileges. This must be done before | |
515 | permanently setting the uid. */ | |
516 | restore_uid(); | |
517 | ||
518 | /* Switch to the original uid permanently. */ | |
519 | permanently_set_uid(original_real_uid); | |
520 | ||
521 | /* Execute rsh. */ | |
522 | rsh_connect(host, options.user, &command); | |
523 | fatal("rsh_connect returned"); | |
524 | } | |
525 | ||
526 | /* Restore our superuser privileges. */ | |
527 | restore_uid(); | |
528 | ||
529 | /* Open a connection to the remote host. This needs root privileges if | |
530 | rhosts_{rsa_}authentication is true. */ | |
531 | ||
532 | if (!options.use_privileged_port) | |
533 | { | |
534 | options.rhosts_authentication = 0; | |
535 | options.rhosts_rsa_authentication = 0; | |
536 | } | |
537 | ||
538 | ok = ssh_connect(host, &hostaddr, options.port, options.connection_attempts, | |
539 | !options.rhosts_authentication && | |
540 | !options.rhosts_rsa_authentication, | |
541 | original_real_uid, options.proxy_command); | |
542 | ||
543 | /* If we successfully made the connection, load the host private key in | |
544 | case we will need it later for combined rsa-rhosts authentication. | |
545 | This must be done before releasing extra privileges, because the file | |
546 | is only readable by root. */ | |
547 | if (ok) | |
548 | { | |
549 | host_private_key = RSA_new(); | |
550 | if (load_private_key(HOST_KEY_FILE, "", host_private_key, NULL)) | |
551 | host_private_key_loaded = 1; | |
552 | } | |
553 | ||
554 | /* Get rid of any extra privileges that we may have. We will no longer need | |
555 | them. Also, extra privileges could make it very hard to read identity | |
556 | files and other non-world-readable files from the user's home directory | |
557 | if it happens to be on a NFS volume where root is mapped to nobody. */ | |
558 | permanently_set_uid(original_real_uid); | |
559 | ||
560 | /* Now that we are back to our own permissions, create ~/.ssh directory | |
561 | if it doesn\'t already exist. */ | |
562 | snprintf(buf, sizeof buf, "%.100s/%.100s", pw->pw_dir, SSH_USER_DIR); | |
563 | if (stat(buf, &st) < 0) | |
564 | if (mkdir(buf, 0755) < 0) | |
565 | error("Could not create directory '%.200s'.", buf); | |
566 | ||
567 | /* Check if the connection failed, and try "rsh" if appropriate. */ | |
568 | if (!ok) | |
569 | { | |
570 | if (options.port != 0) | |
571 | log("Secure connection to %.100s on port %d refused%.100s.", | |
572 | host, options.port, | |
573 | options.fallback_to_rsh ? "; reverting to insecure method" : ""); | |
574 | else | |
575 | log("Secure connection to %.100s refused%.100s.", host, | |
576 | options.fallback_to_rsh ? "; reverting to insecure method" : ""); | |
577 | ||
578 | if (options.fallback_to_rsh) | |
579 | { | |
580 | rsh_connect(host, options.user, &command); | |
581 | fatal("rsh_connect returned"); | |
582 | } | |
583 | exit(1); | |
584 | } | |
585 | ||
586 | /* Expand ~ in options.identity_files. */ | |
587 | for (i = 0; i < options.num_identity_files; i++) | |
588 | options.identity_files[i] = | |
589 | tilde_expand_filename(options.identity_files[i], original_real_uid); | |
590 | ||
591 | /* Expand ~ in known host file names. */ | |
592 | options.system_hostfile = tilde_expand_filename(options.system_hostfile, | |
593 | original_real_uid); | |
594 | options.user_hostfile = tilde_expand_filename(options.user_hostfile, | |
595 | original_real_uid); | |
596 | ||
597 | /* Log into the remote system. This never returns if the login fails. */ | |
598 | ssh_login(host_private_key_loaded, host_private_key, | |
599 | host, &hostaddr, &options, original_real_uid); | |
600 | ||
601 | /* We no longer need the host private key. Clear it now. */ | |
602 | if (host_private_key_loaded) | |
603 | RSA_free(host_private_key); /* Destroys contents safely */ | |
604 | ||
605 | /* Close connection cleanly after attack. */ | |
606 | cipher_attack_detected = packet_disconnect; | |
607 | ||
608 | /* If requested, fork and let ssh continue in the background. */ | |
609 | if (fork_after_authentication_flag) | |
610 | { | |
611 | int ret = fork(); | |
612 | if (ret == -1) | |
613 | fatal("fork failed: %.100s", strerror(errno)); | |
614 | if (ret != 0) | |
615 | exit(0); | |
616 | setsid(); | |
617 | } | |
618 | ||
619 | /* Enable compression if requested. */ | |
620 | if (options.compression) | |
621 | { | |
622 | debug("Requesting compression at level %d.", options.compression_level); | |
623 | ||
624 | if (options.compression_level < 1 || options.compression_level > 9) | |
625 | fatal("Compression level must be from 1 (fast) to 9 (slow, best)."); | |
626 | ||
627 | /* Send the request. */ | |
628 | packet_start(SSH_CMSG_REQUEST_COMPRESSION); | |
629 | packet_put_int(options.compression_level); | |
630 | packet_send(); | |
631 | packet_write_wait(); | |
632 | type = packet_read(&plen); | |
633 | if (type == SSH_SMSG_SUCCESS) | |
634 | packet_start_compression(options.compression_level); | |
635 | else if (type == SSH_SMSG_FAILURE) | |
636 | log("Warning: Remote host refused compression."); | |
637 | else | |
638 | packet_disconnect("Protocol error waiting for compression response."); | |
639 | } | |
640 | ||
641 | /* Allocate a pseudo tty if appropriate. */ | |
642 | if (tty_flag) | |
643 | { | |
644 | debug("Requesting pty."); | |
645 | ||
646 | /* Start the packet. */ | |
647 | packet_start(SSH_CMSG_REQUEST_PTY); | |
648 | ||
649 | /* Store TERM in the packet. There is no limit on the length of the | |
650 | string. */ | |
651 | cp = getenv("TERM"); | |
652 | if (!cp) | |
653 | cp = ""; | |
654 | packet_put_string(cp, strlen(cp)); | |
655 | ||
656 | /* Store window size in the packet. */ | |
657 | if (ioctl(fileno(stdin), TIOCGWINSZ, &ws) < 0) | |
658 | memset(&ws, 0, sizeof(ws)); | |
659 | packet_put_int(ws.ws_row); | |
660 | packet_put_int(ws.ws_col); | |
661 | packet_put_int(ws.ws_xpixel); | |
662 | packet_put_int(ws.ws_ypixel); | |
663 | ||
664 | /* Store tty modes in the packet. */ | |
665 | tty_make_modes(fileno(stdin)); | |
666 | ||
667 | /* Send the packet, and wait for it to leave. */ | |
668 | packet_send(); | |
669 | packet_write_wait(); | |
670 | ||
671 | /* Read response from the server. */ | |
672 | type = packet_read(&plen); | |
673 | if (type == SSH_SMSG_SUCCESS) | |
674 | interactive = 1; | |
675 | else if (type == SSH_SMSG_FAILURE) | |
676 | log("Warning: Remote host failed or refused to allocate a pseudo tty."); | |
677 | else | |
678 | packet_disconnect("Protocol error waiting for pty request response."); | |
679 | } | |
680 | ||
681 | /* Request X11 forwarding if enabled and DISPLAY is set. */ | |
682 | if (options.forward_x11 && getenv("DISPLAY") != NULL) | |
683 | { | |
684 | char line[512], proto[512], data[512]; | |
685 | FILE *f; | |
686 | int forwarded = 0, got_data = 0, i; | |
687 | ||
688 | #ifdef XAUTH_PATH | |
689 | /* Try to get Xauthority information for the display. */ | |
690 | snprintf(line, sizeof line, "%.100s list %.200s 2>/dev/null", | |
691 | XAUTH_PATH, getenv("DISPLAY")); | |
692 | f = popen(line, "r"); | |
693 | if (f && fgets(line, sizeof(line), f) && | |
694 | sscanf(line, "%*s %s %s", proto, data) == 2) | |
695 | got_data = 1; | |
696 | if (f) | |
697 | pclose(f); | |
698 | #endif /* XAUTH_PATH */ | |
699 | /* If we didn't get authentication data, just make up some data. The | |
700 | forwarding code will check the validity of the response anyway, and | |
701 | substitute this data. The X11 server, however, will ignore this | |
702 | fake data and use whatever authentication mechanisms it was using | |
703 | otherwise for the local connection. */ | |
704 | if (!got_data) | |
705 | { | |
706 | u_int32_t rand = 0; | |
707 | ||
708 | strlcpy(proto, "MIT-MAGIC-COOKIE-1", sizeof proto); | |
709 | for (i = 0; i < 16; i++) { | |
710 | if (i % 4 == 0) | |
711 | rand = arc4random(); | |
712 | snprintf(data + 2 * i, sizeof data - 2 * i, "%02x", rand & 0xff); | |
713 | rand >>= 8; | |
714 | } | |
715 | } | |
716 | ||
717 | /* Got local authentication reasonable information. Request forwarding | |
718 | with authentication spoofing. */ | |
719 | debug("Requesting X11 forwarding with authentication spoofing."); | |
720 | x11_request_forwarding_with_spoofing(proto, data); | |
721 | ||
722 | /* Read response from the server. */ | |
723 | type = packet_read(&plen); | |
724 | if (type == SSH_SMSG_SUCCESS) | |
725 | { | |
726 | forwarded = 1; | |
727 | interactive = 1; | |
728 | } | |
729 | else if (type == SSH_SMSG_FAILURE) | |
730 | log("Warning: Remote host denied X11 forwarding."); | |
731 | else | |
732 | packet_disconnect("Protocol error waiting for X11 forwarding"); | |
733 | } | |
734 | ||
735 | /* Tell the packet module whether this is an interactive session. */ | |
736 | packet_set_interactive(interactive, options.keepalives); | |
737 | ||
738 | /* Clear agent forwarding if we don\'t have an agent. */ | |
739 | authfd = ssh_get_authentication_socket(); | |
740 | if (authfd < 0) | |
741 | options.forward_agent = 0; | |
742 | else | |
743 | ssh_close_authentication_socket(authfd); | |
744 | ||
745 | /* Request authentication agent forwarding if appropriate. */ | |
746 | if (options.forward_agent) | |
747 | { | |
748 | debug("Requesting authentication agent forwarding."); | |
749 | auth_request_forwarding(); | |
750 | ||
751 | /* Read response from the server. */ | |
752 | type = packet_read(&plen); | |
753 | packet_integrity_check(plen, 0, type); | |
754 | if (type != SSH_SMSG_SUCCESS) | |
755 | log("Warning: Remote host denied authentication agent forwarding."); | |
756 | } | |
757 | ||
758 | /* Initiate local TCP/IP port forwardings. */ | |
759 | for (i = 0; i < options.num_local_forwards; i++) | |
760 | { | |
761 | debug("Connections to local port %d forwarded to remote address %.200s:%d", | |
762 | options.local_forwards[i].port, options.local_forwards[i].host, | |
763 | options.local_forwards[i].host_port); | |
764 | channel_request_local_forwarding(options.local_forwards[i].port, | |
765 | options.local_forwards[i].host, | |
766 | options.local_forwards[i].host_port); | |
767 | } | |
768 | ||
769 | /* Initiate remote TCP/IP port forwardings. */ | |
770 | for (i = 0; i < options.num_remote_forwards; i++) | |
771 | { | |
772 | debug("Connections to remote port %d forwarded to local address %.200s:%d", | |
773 | options.remote_forwards[i].port, options.remote_forwards[i].host, | |
774 | options.remote_forwards[i].host_port); | |
775 | channel_request_remote_forwarding(options.remote_forwards[i].port, | |
776 | options.remote_forwards[i].host, | |
777 | options.remote_forwards[i].host_port); | |
778 | } | |
779 | ||
780 | /* If a command was specified on the command line, execute the command now. | |
781 | Otherwise request the server to start a shell. */ | |
782 | if (buffer_len(&command) > 0) | |
783 | { | |
784 | int len = buffer_len(&command); | |
785 | if (len > 900) | |
786 | len = 900; | |
787 | debug("Sending command: %.*s", len, buffer_ptr(&command)); | |
788 | packet_start(SSH_CMSG_EXEC_CMD); | |
789 | packet_put_string(buffer_ptr(&command), buffer_len(&command)); | |
790 | packet_send(); | |
791 | packet_write_wait(); | |
792 | } | |
793 | else | |
794 | { | |
795 | debug("Requesting shell."); | |
796 | packet_start(SSH_CMSG_EXEC_SHELL); | |
797 | packet_send(); | |
798 | packet_write_wait(); | |
799 | } | |
800 | ||
801 | /* Enter the interactive session. */ | |
802 | exit_status = client_loop(tty_flag, tty_flag ? options.escape_char : -1); | |
803 | ||
804 | /* Close the connection to the remote host. */ | |
805 | packet_close(); | |
806 | ||
807 | /* Exit with the status returned by the program on the remote side. */ | |
808 | exit(exit_status); | |
809 | } |