1 /* $OpenBSD: auth-options.c,v 1.54 2010/12/24 21:41:48 djm Exp $ */
2 /*
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * All rights reserved
6 * As far as I am concerned, the code I have written for this software
7 * can be used freely for any purpose. Any derived versions of this
8 * software must be clearly marked as such, and if the derived work is
9 * incompatible with the protocol description in the RFC file, it must be
10 * called by a name other than "ssh" or "Secure Shell".
11 */
12
13 #include "includes.h"
14
15 #include <sys/types.h>
16
17 #include <netdb.h>
18 #include <pwd.h>
19 #include <string.h>
20 #include <stdio.h>
21 #include <stdarg.h>
22
23 #include "openbsd-compat/sys-queue.h"
24 #include "xmalloc.h"
25 #include "match.h"
26 #include "log.h"
27 #include "canohost.h"
28 #include "buffer.h"
29 #include "channels.h"
30 #include "servconf.h"
31 #include "misc.h"
32 #include "key.h"
33 #include "auth-options.h"
34 #include "hostfile.h"
35 #include "auth.h"
36 #ifdef GSSAPI
37 #include "ssh-gss.h"
38 #endif
39 #include "monitor_wrap.h"
40
41 /* Flags set authorized_keys flags */
42 int no_port_forwarding_flag = 0;
43 int no_agent_forwarding_flag = 0;
44 int no_x11_forwarding_flag = 0;
45 int no_pty_flag = 0;
46 int no_user_rc = 0;
47 int key_is_cert_authority = 0;
48
49 /* "command=" option. */
50 char *forced_command = NULL;
51
52 /* "environment=" options. */
53 struct envstring *custom_environment = NULL;
54
55 /* "tunnel=" option. */
56 int forced_tun_device = -1;
57
58 /* "principals=" option. */
59 char *authorized_principals = NULL;
60
61 extern ServerOptions options;
62
63 void
auth_clear_options(void)64 auth_clear_options(void)
65 {
66 no_agent_forwarding_flag = 0;
67 no_port_forwarding_flag = 0;
68 no_pty_flag = 0;
69 no_x11_forwarding_flag = 0;
70 no_user_rc = 0;
71 key_is_cert_authority = 0;
72 while (custom_environment) {
73 struct envstring *ce = custom_environment;
74 custom_environment = ce->next;
75 xfree(ce->s);
76 xfree(ce);
77 }
78 if (forced_command) {
79 xfree(forced_command);
80 forced_command = NULL;
81 }
82 if (authorized_principals) {
83 xfree(authorized_principals);
84 authorized_principals = NULL;
85 }
86 forced_tun_device = -1;
87 channel_clear_permitted_opens();
88 }
89
90 /*
91 * return 1 if access is granted, 0 if not.
92 * side effect: sets key option flags
93 */
94 int
auth_parse_options(struct passwd * pw,char * opts,char * file,u_long linenum)95 auth_parse_options(struct passwd *pw, char *opts, char *file, u_long linenum)
96 {
97 const char *cp;
98 int i;
99
100 /* reset options */
101 auth_clear_options();
102
103 if (!opts)
104 return 1;
105
106 while (*opts && *opts != ' ' && *opts != '\t') {
107 cp = "cert-authority";
108 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
109 key_is_cert_authority = 1;
110 opts += strlen(cp);
111 goto next_option;
112 }
113 cp = "no-port-forwarding";
114 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
115 auth_debug_add("Port forwarding disabled.");
116 no_port_forwarding_flag = 1;
117 opts += strlen(cp);
118 goto next_option;
119 }
120 cp = "no-agent-forwarding";
121 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
122 auth_debug_add("Agent forwarding disabled.");
123 no_agent_forwarding_flag = 1;
124 opts += strlen(cp);
125 goto next_option;
126 }
127 cp = "no-X11-forwarding";
128 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
129 auth_debug_add("X11 forwarding disabled.");
130 no_x11_forwarding_flag = 1;
131 opts += strlen(cp);
132 goto next_option;
133 }
134 cp = "no-pty";
135 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
136 auth_debug_add("Pty allocation disabled.");
137 no_pty_flag = 1;
138 opts += strlen(cp);
139 goto next_option;
140 }
141 cp = "no-user-rc";
142 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
143 auth_debug_add("User rc file execution disabled.");
144 no_user_rc = 1;
145 opts += strlen(cp);
146 goto next_option;
147 }
148 cp = "command=\"";
149 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
150 opts += strlen(cp);
151 if (forced_command != NULL)
152 xfree(forced_command);
153 forced_command = xmalloc(strlen(opts) + 1);
154 i = 0;
155 while (*opts) {
156 if (*opts == '"')
157 break;
158 if (*opts == '\\' && opts[1] == '"') {
159 opts += 2;
160 forced_command[i++] = '"';
161 continue;
162 }
163 forced_command[i++] = *opts++;
164 }
165 if (!*opts) {
166 debug("%.100s, line %lu: missing end quote",
167 file, linenum);
168 auth_debug_add("%.100s, line %lu: missing end quote",
169 file, linenum);
170 xfree(forced_command);
171 forced_command = NULL;
172 goto bad_option;
173 }
174 forced_command[i] = '\0';
175 auth_debug_add("Forced command.");
176 opts++;
177 goto next_option;
178 }
179 cp = "principals=\"";
180 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
181 opts += strlen(cp);
182 if (authorized_principals != NULL)
183 xfree(authorized_principals);
184 authorized_principals = xmalloc(strlen(opts) + 1);
185 i = 0;
186 while (*opts) {
187 if (*opts == '"')
188 break;
189 if (*opts == '\\' && opts[1] == '"') {
190 opts += 2;
191 authorized_principals[i++] = '"';
192 continue;
193 }
194 authorized_principals[i++] = *opts++;
195 }
196 if (!*opts) {
197 debug("%.100s, line %lu: missing end quote",
198 file, linenum);
199 auth_debug_add("%.100s, line %lu: missing end quote",
200 file, linenum);
201 xfree(authorized_principals);
202 authorized_principals = NULL;
203 goto bad_option;
204 }
205 authorized_principals[i] = '\0';
206 auth_debug_add("principals: %.900s",
207 authorized_principals);
208 opts++;
209 goto next_option;
210 }
211 cp = "environment=\"";
212 if (options.permit_user_env &&
213 strncasecmp(opts, cp, strlen(cp)) == 0) {
214 char *s;
215 struct envstring *new_envstring;
216
217 opts += strlen(cp);
218 s = xmalloc(strlen(opts) + 1);
219 i = 0;
220 while (*opts) {
221 if (*opts == '"')
222 break;
223 if (*opts == '\\' && opts[1] == '"') {
224 opts += 2;
225 s[i++] = '"';
226 continue;
227 }
228 s[i++] = *opts++;
229 }
230 if (!*opts) {
231 debug("%.100s, line %lu: missing end quote",
232 file, linenum);
233 auth_debug_add("%.100s, line %lu: missing end quote",
234 file, linenum);
235 xfree(s);
236 goto bad_option;
237 }
238 s[i] = '\0';
239 auth_debug_add("Adding to environment: %.900s", s);
240 debug("Adding to environment: %.900s", s);
241 opts++;
242 new_envstring = xmalloc(sizeof(struct envstring));
243 new_envstring->s = s;
244 new_envstring->next = custom_environment;
245 custom_environment = new_envstring;
246 goto next_option;
247 }
248 cp = "from=\"";
249 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
250 const char *remote_ip = get_remote_ipaddr();
251 const char *remote_host = get_canonical_hostname(
252 options.use_dns);
253 char *patterns = xmalloc(strlen(opts) + 1);
254
255 opts += strlen(cp);
256 i = 0;
257 while (*opts) {
258 if (*opts == '"')
259 break;
260 if (*opts == '\\' && opts[1] == '"') {
261 opts += 2;
262 patterns[i++] = '"';
263 continue;
264 }
265 patterns[i++] = *opts++;
266 }
267 if (!*opts) {
268 debug("%.100s, line %lu: missing end quote",
269 file, linenum);
270 auth_debug_add("%.100s, line %lu: missing end quote",
271 file, linenum);
272 xfree(patterns);
273 goto bad_option;
274 }
275 patterns[i] = '\0';
276 opts++;
277 switch (match_host_and_ip(remote_host, remote_ip,
278 patterns)) {
279 case 1:
280 xfree(patterns);
281 /* Host name matches. */
282 goto next_option;
283 case -1:
284 debug("%.100s, line %lu: invalid criteria",
285 file, linenum);
286 auth_debug_add("%.100s, line %lu: "
287 "invalid criteria", file, linenum);
288 /* FALLTHROUGH */
289 case 0:
290 xfree(patterns);
291 logit("Authentication tried for %.100s with "
292 "correct key but not from a permitted "
293 "host (host=%.200s, ip=%.200s).",
294 pw->pw_name, remote_host, remote_ip);
295 auth_debug_add("Your host '%.200s' is not "
296 "permitted to use this key for login.",
297 remote_host);
298 break;
299 }
300 /* deny access */
301 return 0;
302 }
303 cp = "permitopen=\"";
304 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
305 char *host, *p;
306 int port;
307 char *patterns = xmalloc(strlen(opts) + 1);
308
309 opts += strlen(cp);
310 i = 0;
311 while (*opts) {
312 if (*opts == '"')
313 break;
314 if (*opts == '\\' && opts[1] == '"') {
315 opts += 2;
316 patterns[i++] = '"';
317 continue;
318 }
319 patterns[i++] = *opts++;
320 }
321 if (!*opts) {
322 debug("%.100s, line %lu: missing end quote",
323 file, linenum);
324 auth_debug_add("%.100s, line %lu: missing "
325 "end quote", file, linenum);
326 xfree(patterns);
327 goto bad_option;
328 }
329 patterns[i] = '\0';
330 opts++;
331 p = patterns;
332 host = hpdelim(&p);
333 if (host == NULL || strlen(host) >= NI_MAXHOST) {
334 debug("%.100s, line %lu: Bad permitopen "
335 "specification <%.100s>", file, linenum,
336 patterns);
337 auth_debug_add("%.100s, line %lu: "
338 "Bad permitopen specification", file,
339 linenum);
340 xfree(patterns);
341 goto bad_option;
342 }
343 host = cleanhostname(host);
344 if (p == NULL || (port = a2port(p)) <= 0) {
345 debug("%.100s, line %lu: Bad permitopen port "
346 "<%.100s>", file, linenum, p ? p : "");
347 auth_debug_add("%.100s, line %lu: "
348 "Bad permitopen port", file, linenum);
349 xfree(patterns);
350 goto bad_option;
351 }
352 if (options.allow_tcp_forwarding)
353 channel_add_permitted_opens(host, port);
354 xfree(patterns);
355 goto next_option;
356 }
357 cp = "tunnel=\"";
358 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
359 char *tun = NULL;
360 opts += strlen(cp);
361 tun = xmalloc(strlen(opts) + 1);
362 i = 0;
363 while (*opts) {
364 if (*opts == '"')
365 break;
366 tun[i++] = *opts++;
367 }
368 if (!*opts) {
369 debug("%.100s, line %lu: missing end quote",
370 file, linenum);
371 auth_debug_add("%.100s, line %lu: missing end quote",
372 file, linenum);
373 xfree(tun);
374 forced_tun_device = -1;
375 goto bad_option;
376 }
377 tun[i] = '\0';
378 forced_tun_device = a2tun(tun, NULL);
379 xfree(tun);
380 if (forced_tun_device == SSH_TUNID_ERR) {
381 debug("%.100s, line %lu: invalid tun device",
382 file, linenum);
383 auth_debug_add("%.100s, line %lu: invalid tun device",
384 file, linenum);
385 forced_tun_device = -1;
386 goto bad_option;
387 }
388 auth_debug_add("Forced tun device: %d", forced_tun_device);
389 opts++;
390 goto next_option;
391 }
392 next_option:
393 /*
394 * Skip the comma, and move to the next option
395 * (or break out if there are no more).
396 */
397 if (!*opts)
398 fatal("Bugs in auth-options.c option processing.");
399 if (*opts == ' ' || *opts == '\t')
400 break; /* End of options. */
401 if (*opts != ',')
402 goto bad_option;
403 opts++;
404 /* Process the next option. */
405 }
406
407 /* grant access */
408 return 1;
409
410 bad_option:
411 logit("Bad options in %.100s file, line %lu: %.50s",
412 file, linenum, opts);
413 auth_debug_add("Bad options in %.100s file, line %lu: %.50s",
414 file, linenum, opts);
415
416 /* deny access */
417 return 0;
418 }
419
420 #define OPTIONS_CRITICAL 1
421 #define OPTIONS_EXTENSIONS 2
422 static int
parse_option_list(u_char * optblob,size_t optblob_len,struct passwd * pw,u_int which,int crit,int * cert_no_port_forwarding_flag,int * cert_no_agent_forwarding_flag,int * cert_no_x11_forwarding_flag,int * cert_no_pty_flag,int * cert_no_user_rc,char ** cert_forced_command,int * cert_source_address_done)423 parse_option_list(u_char *optblob, size_t optblob_len, struct passwd *pw,
424 u_int which, int crit,
425 int *cert_no_port_forwarding_flag,
426 int *cert_no_agent_forwarding_flag,
427 int *cert_no_x11_forwarding_flag,
428 int *cert_no_pty_flag,
429 int *cert_no_user_rc,
430 char **cert_forced_command,
431 int *cert_source_address_done)
432 {
433 char *command, *allowed;
434 const char *remote_ip;
435 u_char *name = NULL, *data_blob = NULL;
436 u_int nlen, dlen, clen;
437 Buffer c, data;
438 int ret = -1, found;
439
440 buffer_init(&data);
441
442 /* Make copy to avoid altering original */
443 buffer_init(&c);
444 buffer_append(&c, optblob, optblob_len);
445
446 while (buffer_len(&c) > 0) {
447 if ((name = buffer_get_cstring_ret(&c, &nlen)) == NULL ||
448 (data_blob = buffer_get_string_ret(&c, &dlen)) == NULL) {
449 error("Certificate options corrupt");
450 goto out;
451 }
452 buffer_append(&data, data_blob, dlen);
453 debug3("found certificate option \"%.100s\" len %u",
454 name, dlen);
455 if (strlen(name) != nlen) {
456 error("Certificate constraint name contains \\0");
457 goto out;
458 }
459 found = 0;
460 if ((which & OPTIONS_EXTENSIONS) != 0) {
461 if (strcmp(name, "permit-X11-forwarding") == 0) {
462 *cert_no_x11_forwarding_flag = 0;
463 found = 1;
464 } else if (strcmp(name,
465 "permit-agent-forwarding") == 0) {
466 *cert_no_agent_forwarding_flag = 0;
467 found = 1;
468 } else if (strcmp(name,
469 "permit-port-forwarding") == 0) {
470 *cert_no_port_forwarding_flag = 0;
471 found = 1;
472 } else if (strcmp(name, "permit-pty") == 0) {
473 *cert_no_pty_flag = 0;
474 found = 1;
475 } else if (strcmp(name, "permit-user-rc") == 0) {
476 *cert_no_user_rc = 0;
477 found = 1;
478 }
479 }
480 if (!found && (which & OPTIONS_CRITICAL) != 0) {
481 if (strcmp(name, "force-command") == 0) {
482 if ((command = buffer_get_cstring_ret(&data,
483 &clen)) == NULL) {
484 error("Certificate constraint \"%s\" "
485 "corrupt", name);
486 goto out;
487 }
488 if (strlen(command) != clen) {
489 error("force-command constraint "
490 "contains \\0");
491 goto out;
492 }
493 if (*cert_forced_command != NULL) {
494 error("Certificate has multiple "
495 "force-command options");
496 xfree(command);
497 goto out;
498 }
499 *cert_forced_command = command;
500 found = 1;
501 }
502 if (strcmp(name, "source-address") == 0) {
503 if ((allowed = buffer_get_cstring_ret(&data,
504 &clen)) == NULL) {
505 error("Certificate constraint "
506 "\"%s\" corrupt", name);
507 goto out;
508 }
509 if (strlen(allowed) != clen) {
510 error("source-address constraint "
511 "contains \\0");
512 goto out;
513 }
514 if ((*cert_source_address_done)++) {
515 error("Certificate has multiple "
516 "source-address options");
517 xfree(allowed);
518 goto out;
519 }
520 remote_ip = get_remote_ipaddr();
521 switch (addr_match_cidr_list(remote_ip,
522 allowed)) {
523 case 1:
524 /* accepted */
525 xfree(allowed);
526 break;
527 case 0:
528 /* no match */
529 logit("Authentication tried for %.100s "
530 "with valid certificate but not "
531 "from a permitted host "
532 "(ip=%.200s).", pw->pw_name,
533 remote_ip);
534 auth_debug_add("Your address '%.200s' "
535 "is not permitted to use this "
536 "certificate for login.",
537 remote_ip);
538 xfree(allowed);
539 goto out;
540 case -1:
541 error("Certificate source-address "
542 "contents invalid");
543 xfree(allowed);
544 goto out;
545 }
546 found = 1;
547 }
548 }
549
550 if (!found) {
551 if (crit) {
552 error("Certificate critical option \"%s\" "
553 "is not supported", name);
554 goto out;
555 } else {
556 logit("Certificate extension \"%s\" "
557 "is not supported", name);
558 }
559 } else if (buffer_len(&data) != 0) {
560 error("Certificate option \"%s\" corrupt "
561 "(extra data)", name);
562 goto out;
563 }
564 buffer_clear(&data);
565 xfree(name);
566 xfree(data_blob);
567 name = data_blob = NULL;
568 }
569 /* successfully parsed all options */
570 ret = 0;
571
572 out:
573 if (ret != 0 &&
574 cert_forced_command != NULL &&
575 *cert_forced_command != NULL) {
576 xfree(*cert_forced_command);
577 *cert_forced_command = NULL;
578 }
579 if (name != NULL)
580 xfree(name);
581 if (data_blob != NULL)
582 xfree(data_blob);
583 buffer_free(&data);
584 buffer_free(&c);
585 return ret;
586 }
587
588 /*
589 * Set options from critical certificate options. These supersede user key
590 * options so this must be called after auth_parse_options().
591 */
592 int
auth_cert_options(Key * k,struct passwd * pw)593 auth_cert_options(Key *k, struct passwd *pw)
594 {
595 int cert_no_port_forwarding_flag = 1;
596 int cert_no_agent_forwarding_flag = 1;
597 int cert_no_x11_forwarding_flag = 1;
598 int cert_no_pty_flag = 1;
599 int cert_no_user_rc = 1;
600 char *cert_forced_command = NULL;
601 int cert_source_address_done = 0;
602
603 if (key_cert_is_legacy(k)) {
604 /* All options are in the one field for v00 certs */
605 if (parse_option_list(buffer_ptr(&k->cert->critical),
606 buffer_len(&k->cert->critical), pw,
607 OPTIONS_CRITICAL|OPTIONS_EXTENSIONS, 1,
608 &cert_no_port_forwarding_flag,
609 &cert_no_agent_forwarding_flag,
610 &cert_no_x11_forwarding_flag,
611 &cert_no_pty_flag,
612 &cert_no_user_rc,
613 &cert_forced_command,
614 &cert_source_address_done) == -1)
615 return -1;
616 } else {
617 /* Separate options and extensions for v01 certs */
618 if (parse_option_list(buffer_ptr(&k->cert->critical),
619 buffer_len(&k->cert->critical), pw,
620 OPTIONS_CRITICAL, 1, NULL, NULL, NULL, NULL, NULL,
621 &cert_forced_command,
622 &cert_source_address_done) == -1)
623 return -1;
624 if (parse_option_list(buffer_ptr(&k->cert->extensions),
625 buffer_len(&k->cert->extensions), pw,
626 OPTIONS_EXTENSIONS, 1,
627 &cert_no_port_forwarding_flag,
628 &cert_no_agent_forwarding_flag,
629 &cert_no_x11_forwarding_flag,
630 &cert_no_pty_flag,
631 &cert_no_user_rc,
632 NULL, NULL) == -1)
633 return -1;
634 }
635
636 no_port_forwarding_flag |= cert_no_port_forwarding_flag;
637 no_agent_forwarding_flag |= cert_no_agent_forwarding_flag;
638 no_x11_forwarding_flag |= cert_no_x11_forwarding_flag;
639 no_pty_flag |= cert_no_pty_flag;
640 no_user_rc |= cert_no_user_rc;
641 /* CA-specified forced command supersedes key option */
642 if (cert_forced_command != NULL) {
643 if (forced_command != NULL)
644 xfree(forced_command);
645 forced_command = cert_forced_command;
646 }
647 return 0;
648 }
649
650