1 /* $OpenBSD: auth-options.c,v 1.65 2015/01/14 10:30:34 markus 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
25 #include "key.h" /* XXX for typedef */
26 #include "buffer.h" /* XXX for typedef */
27 #include "xmalloc.h"
28 #include "match.h"
29 #include "ssherr.h"
30 #include "log.h"
31 #include "canohost.h"
32 #include "sshbuf.h"
33 #include "misc.h"
34 #include "channels.h"
35 #include "servconf.h"
36 #include "sshkey.h"
37 #include "auth-options.h"
38 #include "hostfile.h"
39 #include "auth.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 free(ce->s);
76 free(ce);
77 }
78 if (forced_command) {
79 free(forced_command);
80 forced_command = NULL;
81 }
82 if (authorized_principals) {
83 free(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 free(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 free(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 free(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 free(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 free(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 = xcalloc(1, 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 free(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 free(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 free(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 free(patterns);
327 goto bad_option;
328 }
329 patterns[i] = '\0';
330 opts++;
331 p = patterns;
332 /* XXX - add streamlocal support */
333 host = hpdelim(&p);
334 if (host == NULL || strlen(host) >= NI_MAXHOST) {
335 debug("%.100s, line %lu: Bad permitopen "
336 "specification <%.100s>", file, linenum,
337 patterns);
338 auth_debug_add("%.100s, line %lu: "
339 "Bad permitopen specification", file,
340 linenum);
341 free(patterns);
342 goto bad_option;
343 }
344 host = cleanhostname(host);
345 if (p == NULL || (port = permitopen_port(p)) < 0) {
346 debug("%.100s, line %lu: Bad permitopen port "
347 "<%.100s>", file, linenum, p ? p : "");
348 auth_debug_add("%.100s, line %lu: "
349 "Bad permitopen port", file, linenum);
350 free(patterns);
351 goto bad_option;
352 }
353 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0)
354 channel_add_permitted_opens(host, port);
355 free(patterns);
356 goto next_option;
357 }
358 cp = "tunnel=\"";
359 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
360 char *tun = NULL;
361 opts += strlen(cp);
362 tun = xmalloc(strlen(opts) + 1);
363 i = 0;
364 while (*opts) {
365 if (*opts == '"')
366 break;
367 tun[i++] = *opts++;
368 }
369 if (!*opts) {
370 debug("%.100s, line %lu: missing end quote",
371 file, linenum);
372 auth_debug_add("%.100s, line %lu: missing end quote",
373 file, linenum);
374 free(tun);
375 forced_tun_device = -1;
376 goto bad_option;
377 }
378 tun[i] = '\0';
379 forced_tun_device = a2tun(tun, NULL);
380 free(tun);
381 if (forced_tun_device == SSH_TUNID_ERR) {
382 debug("%.100s, line %lu: invalid tun device",
383 file, linenum);
384 auth_debug_add("%.100s, line %lu: invalid tun device",
385 file, linenum);
386 forced_tun_device = -1;
387 goto bad_option;
388 }
389 auth_debug_add("Forced tun device: %d", forced_tun_device);
390 opts++;
391 goto next_option;
392 }
393 next_option:
394 /*
395 * Skip the comma, and move to the next option
396 * (or break out if there are no more).
397 */
398 if (!*opts)
399 fatal("Bugs in auth-options.c option processing.");
400 if (*opts == ' ' || *opts == '\t')
401 break; /* End of options. */
402 if (*opts != ',')
403 goto bad_option;
404 opts++;
405 /* Process the next option. */
406 }
407
408 /* grant access */
409 return 1;
410
411 bad_option:
412 logit("Bad options in %.100s file, line %lu: %.50s",
413 file, linenum, opts);
414 auth_debug_add("Bad options in %.100s file, line %lu: %.50s",
415 file, linenum, opts);
416
417 /* deny access */
418 return 0;
419 }
420
421 #define OPTIONS_CRITICAL 1
422 #define OPTIONS_EXTENSIONS 2
423 static int
parse_option_list(struct sshbuf * oblob,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)424 parse_option_list(struct sshbuf *oblob, struct passwd *pw,
425 u_int which, int crit,
426 int *cert_no_port_forwarding_flag,
427 int *cert_no_agent_forwarding_flag,
428 int *cert_no_x11_forwarding_flag,
429 int *cert_no_pty_flag,
430 int *cert_no_user_rc,
431 char **cert_forced_command,
432 int *cert_source_address_done)
433 {
434 char *command, *allowed;
435 const char *remote_ip;
436 char *name = NULL;
437 struct sshbuf *c = NULL, *data = NULL;
438 int r, ret = -1, result, found;
439
440 if ((c = sshbuf_fromb(oblob)) == NULL) {
441 error("%s: sshbuf_fromb failed", __func__);
442 goto out;
443 }
444
445 while (sshbuf_len(c) > 0) {
446 sshbuf_free(data);
447 data = NULL;
448 if ((r = sshbuf_get_cstring(c, &name, NULL)) != 0 ||
449 (r = sshbuf_froms(c, &data)) != 0) {
450 error("Unable to parse certificate options: %s",
451 ssh_err(r));
452 goto out;
453 }
454 debug3("found certificate option \"%.100s\" len %zu",
455 name, sshbuf_len(data));
456 found = 0;
457 if ((which & OPTIONS_EXTENSIONS) != 0) {
458 if (strcmp(name, "permit-X11-forwarding") == 0) {
459 *cert_no_x11_forwarding_flag = 0;
460 found = 1;
461 } else if (strcmp(name,
462 "permit-agent-forwarding") == 0) {
463 *cert_no_agent_forwarding_flag = 0;
464 found = 1;
465 } else if (strcmp(name,
466 "permit-port-forwarding") == 0) {
467 *cert_no_port_forwarding_flag = 0;
468 found = 1;
469 } else if (strcmp(name, "permit-pty") == 0) {
470 *cert_no_pty_flag = 0;
471 found = 1;
472 } else if (strcmp(name, "permit-user-rc") == 0) {
473 *cert_no_user_rc = 0;
474 found = 1;
475 }
476 }
477 if (!found && (which & OPTIONS_CRITICAL) != 0) {
478 if (strcmp(name, "force-command") == 0) {
479 if ((r = sshbuf_get_cstring(data, &command,
480 NULL)) != 0) {
481 error("Unable to parse \"%s\" "
482 "section: %s", name, ssh_err(r));
483 goto out;
484 }
485 if (*cert_forced_command != NULL) {
486 error("Certificate has multiple "
487 "force-command options");
488 free(command);
489 goto out;
490 }
491 *cert_forced_command = command;
492 found = 1;
493 }
494 if (strcmp(name, "source-address") == 0) {
495 if ((r = sshbuf_get_cstring(data, &allowed,
496 NULL)) != 0) {
497 error("Unable to parse \"%s\" "
498 "section: %s", name, ssh_err(r));
499 goto out;
500 }
501 if ((*cert_source_address_done)++) {
502 error("Certificate has multiple "
503 "source-address options");
504 free(allowed);
505 goto out;
506 }
507 remote_ip = get_remote_ipaddr();
508 result = addr_match_cidr_list(remote_ip,
509 allowed);
510 free(allowed);
511 switch (result) {
512 case 1:
513 /* accepted */
514 break;
515 case 0:
516 /* no match */
517 logit("Authentication tried for %.100s "
518 "with valid certificate but not "
519 "from a permitted host "
520 "(ip=%.200s).", pw->pw_name,
521 remote_ip);
522 auth_debug_add("Your address '%.200s' "
523 "is not permitted to use this "
524 "certificate for login.",
525 remote_ip);
526 goto out;
527 case -1:
528 default:
529 error("Certificate source-address "
530 "contents invalid");
531 goto out;
532 }
533 found = 1;
534 }
535 }
536
537 if (!found) {
538 if (crit) {
539 error("Certificate critical option \"%s\" "
540 "is not supported", name);
541 goto out;
542 } else {
543 logit("Certificate extension \"%s\" "
544 "is not supported", name);
545 }
546 } else if (sshbuf_len(data) != 0) {
547 error("Certificate option \"%s\" corrupt "
548 "(extra data)", name);
549 goto out;
550 }
551 free(name);
552 name = NULL;
553 }
554 /* successfully parsed all options */
555 ret = 0;
556
557 out:
558 if (ret != 0 &&
559 cert_forced_command != NULL &&
560 *cert_forced_command != NULL) {
561 free(*cert_forced_command);
562 *cert_forced_command = NULL;
563 }
564 if (name != NULL)
565 free(name);
566 sshbuf_free(data);
567 sshbuf_free(c);
568 return ret;
569 }
570
571 /*
572 * Set options from critical certificate options. These supersede user key
573 * options so this must be called after auth_parse_options().
574 */
575 int
auth_cert_options(struct sshkey * k,struct passwd * pw)576 auth_cert_options(struct sshkey *k, struct passwd *pw)
577 {
578 int cert_no_port_forwarding_flag = 1;
579 int cert_no_agent_forwarding_flag = 1;
580 int cert_no_x11_forwarding_flag = 1;
581 int cert_no_pty_flag = 1;
582 int cert_no_user_rc = 1;
583 char *cert_forced_command = NULL;
584 int cert_source_address_done = 0;
585
586 if (sshkey_cert_is_legacy(k)) {
587 /* All options are in the one field for v00 certs */
588 if (parse_option_list(k->cert->critical, pw,
589 OPTIONS_CRITICAL|OPTIONS_EXTENSIONS, 1,
590 &cert_no_port_forwarding_flag,
591 &cert_no_agent_forwarding_flag,
592 &cert_no_x11_forwarding_flag,
593 &cert_no_pty_flag,
594 &cert_no_user_rc,
595 &cert_forced_command,
596 &cert_source_address_done) == -1)
597 return -1;
598 } else {
599 /* Separate options and extensions for v01 certs */
600 if (parse_option_list(k->cert->critical, pw,
601 OPTIONS_CRITICAL, 1, NULL, NULL, NULL, NULL, NULL,
602 &cert_forced_command,
603 &cert_source_address_done) == -1)
604 return -1;
605 if (parse_option_list(k->cert->extensions, pw,
606 OPTIONS_EXTENSIONS, 1,
607 &cert_no_port_forwarding_flag,
608 &cert_no_agent_forwarding_flag,
609 &cert_no_x11_forwarding_flag,
610 &cert_no_pty_flag,
611 &cert_no_user_rc,
612 NULL, NULL) == -1)
613 return -1;
614 }
615
616 no_port_forwarding_flag |= cert_no_port_forwarding_flag;
617 no_agent_forwarding_flag |= cert_no_agent_forwarding_flag;
618 no_x11_forwarding_flag |= cert_no_x11_forwarding_flag;
619 no_pty_flag |= cert_no_pty_flag;
620 no_user_rc |= cert_no_user_rc;
621 /* CA-specified forced command supersedes key option */
622 if (cert_forced_command != NULL) {
623 if (forced_command != NULL)
624 free(forced_command);
625 forced_command = cert_forced_command;
626 }
627 return 0;
628 }
629
630