1 /* $OpenBSD: auth-options.c,v 1.62 2013/12/19 00:27:57 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
37 /* Flags set authorized_keys flags */
38 int no_port_forwarding_flag = 0;
39 int no_agent_forwarding_flag = 0;
40 int no_x11_forwarding_flag = 0;
41 int no_pty_flag = 0;
42 int no_user_rc = 0;
43 int key_is_cert_authority = 0;
44
45 /* "command=" option. */
46 char *forced_command = NULL;
47
48 /* "environment=" options. */
49 struct envstring *custom_environment = NULL;
50
51 /* "tunnel=" option. */
52 int forced_tun_device = -1;
53
54 /* "principals=" option. */
55 char *authorized_principals = NULL;
56
57 extern ServerOptions options;
58
59 void
auth_clear_options(void)60 auth_clear_options(void)
61 {
62 no_agent_forwarding_flag = 0;
63 no_port_forwarding_flag = 0;
64 no_pty_flag = 0;
65 no_x11_forwarding_flag = 0;
66 no_user_rc = 0;
67 key_is_cert_authority = 0;
68 while (custom_environment) {
69 struct envstring *ce = custom_environment;
70 custom_environment = ce->next;
71 free(ce->s);
72 free(ce);
73 }
74 if (forced_command) {
75 free(forced_command);
76 forced_command = NULL;
77 }
78 if (authorized_principals) {
79 free(authorized_principals);
80 authorized_principals = NULL;
81 }
82 forced_tun_device = -1;
83 channel_clear_permitted_opens();
84 }
85
86 /*
87 * return 1 if access is granted, 0 if not.
88 * side effect: sets key option flags
89 */
90 int
auth_parse_options(struct passwd * pw,char * opts,char * file,u_long linenum)91 auth_parse_options(struct passwd *pw, char *opts, char *file, u_long linenum)
92 {
93 const char *cp;
94 int i;
95
96 /* reset options */
97 auth_clear_options();
98
99 if (!opts)
100 return 1;
101
102 while (*opts && *opts != ' ' && *opts != '\t') {
103 cp = "cert-authority";
104 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
105 key_is_cert_authority = 1;
106 opts += strlen(cp);
107 goto next_option;
108 }
109 cp = "no-port-forwarding";
110 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
111 auth_debug_add("Port forwarding disabled.");
112 no_port_forwarding_flag = 1;
113 opts += strlen(cp);
114 goto next_option;
115 }
116 cp = "no-agent-forwarding";
117 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
118 auth_debug_add("Agent forwarding disabled.");
119 no_agent_forwarding_flag = 1;
120 opts += strlen(cp);
121 goto next_option;
122 }
123 cp = "no-X11-forwarding";
124 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
125 auth_debug_add("X11 forwarding disabled.");
126 no_x11_forwarding_flag = 1;
127 opts += strlen(cp);
128 goto next_option;
129 }
130 cp = "no-pty";
131 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
132 auth_debug_add("Pty allocation disabled.");
133 no_pty_flag = 1;
134 opts += strlen(cp);
135 goto next_option;
136 }
137 cp = "no-user-rc";
138 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
139 auth_debug_add("User rc file execution disabled.");
140 no_user_rc = 1;
141 opts += strlen(cp);
142 goto next_option;
143 }
144 cp = "command=\"";
145 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
146 opts += strlen(cp);
147 if (forced_command != NULL)
148 free(forced_command);
149 forced_command = xmalloc(strlen(opts) + 1);
150 i = 0;
151 while (*opts) {
152 if (*opts == '"')
153 break;
154 if (*opts == '\\' && opts[1] == '"') {
155 opts += 2;
156 forced_command[i++] = '"';
157 continue;
158 }
159 forced_command[i++] = *opts++;
160 }
161 if (!*opts) {
162 debug("%.100s, line %lu: missing end quote",
163 file, linenum);
164 auth_debug_add("%.100s, line %lu: missing end quote",
165 file, linenum);
166 free(forced_command);
167 forced_command = NULL;
168 goto bad_option;
169 }
170 forced_command[i] = '\0';
171 auth_debug_add("Forced command.");
172 opts++;
173 goto next_option;
174 }
175 cp = "principals=\"";
176 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
177 opts += strlen(cp);
178 if (authorized_principals != NULL)
179 free(authorized_principals);
180 authorized_principals = xmalloc(strlen(opts) + 1);
181 i = 0;
182 while (*opts) {
183 if (*opts == '"')
184 break;
185 if (*opts == '\\' && opts[1] == '"') {
186 opts += 2;
187 authorized_principals[i++] = '"';
188 continue;
189 }
190 authorized_principals[i++] = *opts++;
191 }
192 if (!*opts) {
193 debug("%.100s, line %lu: missing end quote",
194 file, linenum);
195 auth_debug_add("%.100s, line %lu: missing end quote",
196 file, linenum);
197 free(authorized_principals);
198 authorized_principals = NULL;
199 goto bad_option;
200 }
201 authorized_principals[i] = '\0';
202 auth_debug_add("principals: %.900s",
203 authorized_principals);
204 opts++;
205 goto next_option;
206 }
207 cp = "environment=\"";
208 if (options.permit_user_env &&
209 strncasecmp(opts, cp, strlen(cp)) == 0) {
210 char *s;
211 struct envstring *new_envstring;
212
213 opts += strlen(cp);
214 s = xmalloc(strlen(opts) + 1);
215 i = 0;
216 while (*opts) {
217 if (*opts == '"')
218 break;
219 if (*opts == '\\' && opts[1] == '"') {
220 opts += 2;
221 s[i++] = '"';
222 continue;
223 }
224 s[i++] = *opts++;
225 }
226 if (!*opts) {
227 debug("%.100s, line %lu: missing end quote",
228 file, linenum);
229 auth_debug_add("%.100s, line %lu: missing end quote",
230 file, linenum);
231 free(s);
232 goto bad_option;
233 }
234 s[i] = '\0';
235 auth_debug_add("Adding to environment: %.900s", s);
236 debug("Adding to environment: %.900s", s);
237 opts++;
238 new_envstring = xcalloc(1, sizeof(struct envstring));
239 new_envstring->s = s;
240 new_envstring->next = custom_environment;
241 custom_environment = new_envstring;
242 goto next_option;
243 }
244 cp = "from=\"";
245 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
246 const char *remote_ip = get_remote_ipaddr();
247 const char *remote_host = get_canonical_hostname(
248 options.use_dns);
249 char *patterns = xmalloc(strlen(opts) + 1);
250
251 opts += strlen(cp);
252 i = 0;
253 while (*opts) {
254 if (*opts == '"')
255 break;
256 if (*opts == '\\' && opts[1] == '"') {
257 opts += 2;
258 patterns[i++] = '"';
259 continue;
260 }
261 patterns[i++] = *opts++;
262 }
263 if (!*opts) {
264 debug("%.100s, line %lu: missing end quote",
265 file, linenum);
266 auth_debug_add("%.100s, line %lu: missing end quote",
267 file, linenum);
268 free(patterns);
269 goto bad_option;
270 }
271 patterns[i] = '\0';
272 opts++;
273 switch (match_host_and_ip(remote_host, remote_ip,
274 patterns)) {
275 case 1:
276 free(patterns);
277 /* Host name matches. */
278 goto next_option;
279 case -1:
280 debug("%.100s, line %lu: invalid criteria",
281 file, linenum);
282 auth_debug_add("%.100s, line %lu: "
283 "invalid criteria", file, linenum);
284 /* FALLTHROUGH */
285 case 0:
286 free(patterns);
287 logit("Authentication tried for %.100s with "
288 "correct key but not from a permitted "
289 "host (host=%.200s, ip=%.200s).",
290 pw->pw_name, remote_host, remote_ip);
291 auth_debug_add("Your host '%.200s' is not "
292 "permitted to use this key for login.",
293 remote_host);
294 break;
295 }
296 /* deny access */
297 return 0;
298 }
299 cp = "permitopen=\"";
300 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
301 char *host, *p;
302 int port;
303 char *patterns = xmalloc(strlen(opts) + 1);
304
305 opts += strlen(cp);
306 i = 0;
307 while (*opts) {
308 if (*opts == '"')
309 break;
310 if (*opts == '\\' && opts[1] == '"') {
311 opts += 2;
312 patterns[i++] = '"';
313 continue;
314 }
315 patterns[i++] = *opts++;
316 }
317 if (!*opts) {
318 debug("%.100s, line %lu: missing end quote",
319 file, linenum);
320 auth_debug_add("%.100s, line %lu: missing "
321 "end quote", file, linenum);
322 free(patterns);
323 goto bad_option;
324 }
325 patterns[i] = '\0';
326 opts++;
327 p = patterns;
328 host = hpdelim(&p);
329 if (host == NULL || strlen(host) >= NI_MAXHOST) {
330 debug("%.100s, line %lu: Bad permitopen "
331 "specification <%.100s>", file, linenum,
332 patterns);
333 auth_debug_add("%.100s, line %lu: "
334 "Bad permitopen specification", file,
335 linenum);
336 free(patterns);
337 goto bad_option;
338 }
339 host = cleanhostname(host);
340 if (p == NULL || (port = permitopen_port(p)) < 0) {
341 debug("%.100s, line %lu: Bad permitopen port "
342 "<%.100s>", file, linenum, p ? p : "");
343 auth_debug_add("%.100s, line %lu: "
344 "Bad permitopen port", file, linenum);
345 free(patterns);
346 goto bad_option;
347 }
348 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0)
349 channel_add_permitted_opens(host, port);
350 free(patterns);
351 goto next_option;
352 }
353 cp = "tunnel=\"";
354 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
355 char *tun = NULL;
356 opts += strlen(cp);
357 tun = xmalloc(strlen(opts) + 1);
358 i = 0;
359 while (*opts) {
360 if (*opts == '"')
361 break;
362 tun[i++] = *opts++;
363 }
364 if (!*opts) {
365 debug("%.100s, line %lu: missing end quote",
366 file, linenum);
367 auth_debug_add("%.100s, line %lu: missing end quote",
368 file, linenum);
369 free(tun);
370 forced_tun_device = -1;
371 goto bad_option;
372 }
373 tun[i] = '\0';
374 forced_tun_device = a2tun(tun, NULL);
375 free(tun);
376 if (forced_tun_device == SSH_TUNID_ERR) {
377 debug("%.100s, line %lu: invalid tun device",
378 file, linenum);
379 auth_debug_add("%.100s, line %lu: invalid tun device",
380 file, linenum);
381 forced_tun_device = -1;
382 goto bad_option;
383 }
384 auth_debug_add("Forced tun device: %d", forced_tun_device);
385 opts++;
386 goto next_option;
387 }
388 next_option:
389 /*
390 * Skip the comma, and move to the next option
391 * (or break out if there are no more).
392 */
393 if (!*opts)
394 fatal("Bugs in auth-options.c option processing.");
395 if (*opts == ' ' || *opts == '\t')
396 break; /* End of options. */
397 if (*opts != ',')
398 goto bad_option;
399 opts++;
400 /* Process the next option. */
401 }
402
403 /* grant access */
404 return 1;
405
406 bad_option:
407 logit("Bad options in %.100s file, line %lu: %.50s",
408 file, linenum, opts);
409 auth_debug_add("Bad options in %.100s file, line %lu: %.50s",
410 file, linenum, opts);
411
412 /* deny access */
413 return 0;
414 }
415
416 #define OPTIONS_CRITICAL 1
417 #define OPTIONS_EXTENSIONS 2
418 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)419 parse_option_list(u_char *optblob, size_t optblob_len, struct passwd *pw,
420 u_int which, int crit,
421 int *cert_no_port_forwarding_flag,
422 int *cert_no_agent_forwarding_flag,
423 int *cert_no_x11_forwarding_flag,
424 int *cert_no_pty_flag,
425 int *cert_no_user_rc,
426 char **cert_forced_command,
427 int *cert_source_address_done)
428 {
429 char *command, *allowed;
430 const char *remote_ip;
431 char *name = NULL;
432 u_char *data_blob = NULL;
433 u_int nlen, dlen, clen;
434 Buffer c, data;
435 int ret = -1, result, found;
436
437 buffer_init(&data);
438
439 /* Make copy to avoid altering original */
440 buffer_init(&c);
441 buffer_append(&c, optblob, optblob_len);
442
443 while (buffer_len(&c) > 0) {
444 if ((name = buffer_get_cstring_ret(&c, &nlen)) == NULL ||
445 (data_blob = buffer_get_string_ret(&c, &dlen)) == NULL) {
446 error("Certificate options corrupt");
447 goto out;
448 }
449 buffer_append(&data, data_blob, dlen);
450 debug3("found certificate option \"%.100s\" len %u",
451 name, dlen);
452 found = 0;
453 if ((which & OPTIONS_EXTENSIONS) != 0) {
454 if (strcmp(name, "permit-X11-forwarding") == 0) {
455 *cert_no_x11_forwarding_flag = 0;
456 found = 1;
457 } else if (strcmp(name,
458 "permit-agent-forwarding") == 0) {
459 *cert_no_agent_forwarding_flag = 0;
460 found = 1;
461 } else if (strcmp(name,
462 "permit-port-forwarding") == 0) {
463 *cert_no_port_forwarding_flag = 0;
464 found = 1;
465 } else if (strcmp(name, "permit-pty") == 0) {
466 *cert_no_pty_flag = 0;
467 found = 1;
468 } else if (strcmp(name, "permit-user-rc") == 0) {
469 *cert_no_user_rc = 0;
470 found = 1;
471 }
472 }
473 if (!found && (which & OPTIONS_CRITICAL) != 0) {
474 if (strcmp(name, "force-command") == 0) {
475 if ((command = buffer_get_cstring_ret(&data,
476 &clen)) == NULL) {
477 error("Certificate constraint \"%s\" "
478 "corrupt", name);
479 goto out;
480 }
481 if (*cert_forced_command != NULL) {
482 error("Certificate has multiple "
483 "force-command options");
484 free(command);
485 goto out;
486 }
487 *cert_forced_command = command;
488 found = 1;
489 }
490 if (strcmp(name, "source-address") == 0) {
491 if ((allowed = buffer_get_cstring_ret(&data,
492 &clen)) == NULL) {
493 error("Certificate constraint "
494 "\"%s\" corrupt", name);
495 goto out;
496 }
497 if ((*cert_source_address_done)++) {
498 error("Certificate has multiple "
499 "source-address options");
500 free(allowed);
501 goto out;
502 }
503 remote_ip = get_remote_ipaddr();
504 result = addr_match_cidr_list(remote_ip,
505 allowed);
506 free(allowed);
507 switch (result) {
508 case 1:
509 /* accepted */
510 break;
511 case 0:
512 /* no match */
513 logit("Authentication tried for %.100s "
514 "with valid certificate but not "
515 "from a permitted host "
516 "(ip=%.200s).", pw->pw_name,
517 remote_ip);
518 auth_debug_add("Your address '%.200s' "
519 "is not permitted to use this "
520 "certificate for login.",
521 remote_ip);
522 goto out;
523 case -1:
524 default:
525 error("Certificate source-address "
526 "contents invalid");
527 goto out;
528 }
529 found = 1;
530 }
531 }
532
533 if (!found) {
534 if (crit) {
535 error("Certificate critical option \"%s\" "
536 "is not supported", name);
537 goto out;
538 } else {
539 logit("Certificate extension \"%s\" "
540 "is not supported", name);
541 }
542 } else if (buffer_len(&data) != 0) {
543 error("Certificate option \"%s\" corrupt "
544 "(extra data)", name);
545 goto out;
546 }
547 buffer_clear(&data);
548 free(name);
549 free(data_blob);
550 name = NULL;
551 data_blob = NULL;
552 }
553 /* successfully parsed all options */
554 ret = 0;
555
556 out:
557 if (ret != 0 &&
558 cert_forced_command != NULL &&
559 *cert_forced_command != NULL) {
560 free(*cert_forced_command);
561 *cert_forced_command = NULL;
562 }
563 if (name != NULL)
564 free(name);
565 if (data_blob != NULL)
566 free(data_blob);
567 buffer_free(&data);
568 buffer_free(&c);
569 return ret;
570 }
571
572 /*
573 * Set options from critical certificate options. These supersede user key
574 * options so this must be called after auth_parse_options().
575 */
576 int
auth_cert_options(Key * k,struct passwd * pw)577 auth_cert_options(Key *k, struct passwd *pw)
578 {
579 int cert_no_port_forwarding_flag = 1;
580 int cert_no_agent_forwarding_flag = 1;
581 int cert_no_x11_forwarding_flag = 1;
582 int cert_no_pty_flag = 1;
583 int cert_no_user_rc = 1;
584 char *cert_forced_command = NULL;
585 int cert_source_address_done = 0;
586
587 if (key_cert_is_legacy(k)) {
588 /* All options are in the one field for v00 certs */
589 if (parse_option_list(buffer_ptr(&k->cert->critical),
590 buffer_len(&k->cert->critical), pw,
591 OPTIONS_CRITICAL|OPTIONS_EXTENSIONS, 1,
592 &cert_no_port_forwarding_flag,
593 &cert_no_agent_forwarding_flag,
594 &cert_no_x11_forwarding_flag,
595 &cert_no_pty_flag,
596 &cert_no_user_rc,
597 &cert_forced_command,
598 &cert_source_address_done) == -1)
599 return -1;
600 } else {
601 /* Separate options and extensions for v01 certs */
602 if (parse_option_list(buffer_ptr(&k->cert->critical),
603 buffer_len(&k->cert->critical), pw,
604 OPTIONS_CRITICAL, 1, NULL, NULL, NULL, NULL, NULL,
605 &cert_forced_command,
606 &cert_source_address_done) == -1)
607 return -1;
608 if (parse_option_list(buffer_ptr(&k->cert->extensions),
609 buffer_len(&k->cert->extensions), pw,
610 OPTIONS_EXTENSIONS, 1,
611 &cert_no_port_forwarding_flag,
612 &cert_no_agent_forwarding_flag,
613 &cert_no_x11_forwarding_flag,
614 &cert_no_pty_flag,
615 &cert_no_user_rc,
616 NULL, NULL) == -1)
617 return -1;
618 }
619
620 no_port_forwarding_flag |= cert_no_port_forwarding_flag;
621 no_agent_forwarding_flag |= cert_no_agent_forwarding_flag;
622 no_x11_forwarding_flag |= cert_no_x11_forwarding_flag;
623 no_pty_flag |= cert_no_pty_flag;
624 no_user_rc |= cert_no_user_rc;
625 /* CA-specified forced command supersedes key option */
626 if (cert_forced_command != NULL) {
627 if (forced_command != NULL)
628 free(forced_command);
629 forced_command = cert_forced_command;
630 }
631 return 0;
632 }
633
634