1 /* $OpenBSD: auth-options.c,v 1.68 2015/07/03 03:43:18 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
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 (strncasecmp(opts, cp, strlen(cp)) == 0) {
213 char *s;
214 struct envstring *new_envstring;
215
216 opts += strlen(cp);
217 s = xmalloc(strlen(opts) + 1);
218 i = 0;
219 while (*opts) {
220 if (*opts == '"')
221 break;
222 if (*opts == '\\' && opts[1] == '"') {
223 opts += 2;
224 s[i++] = '"';
225 continue;
226 }
227 s[i++] = *opts++;
228 }
229 if (!*opts) {
230 debug("%.100s, line %lu: missing end quote",
231 file, linenum);
232 auth_debug_add("%.100s, line %lu: missing end quote",
233 file, linenum);
234 free(s);
235 goto bad_option;
236 }
237 s[i] = '\0';
238 opts++;
239 if (options.permit_user_env) {
240 auth_debug_add("Adding to environment: "
241 "%.900s", s);
242 debug("Adding to environment: %.900s", s);
243 new_envstring = xcalloc(1,
244 sizeof(*new_envstring));
245 new_envstring->s = s;
246 new_envstring->next = custom_environment;
247 custom_environment = new_envstring;
248 s = NULL;
249 }
250 free(s);
251 goto next_option;
252 }
253 cp = "from=\"";
254 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
255 const char *remote_ip = get_remote_ipaddr();
256 const char *remote_host = get_canonical_hostname(
257 options.use_dns);
258 char *patterns = xmalloc(strlen(opts) + 1);
259
260 opts += strlen(cp);
261 i = 0;
262 while (*opts) {
263 if (*opts == '"')
264 break;
265 if (*opts == '\\' && opts[1] == '"') {
266 opts += 2;
267 patterns[i++] = '"';
268 continue;
269 }
270 patterns[i++] = *opts++;
271 }
272 if (!*opts) {
273 debug("%.100s, line %lu: missing end quote",
274 file, linenum);
275 auth_debug_add("%.100s, line %lu: missing end quote",
276 file, linenum);
277 free(patterns);
278 goto bad_option;
279 }
280 patterns[i] = '\0';
281 opts++;
282 switch (match_host_and_ip(remote_host, remote_ip,
283 patterns)) {
284 case 1:
285 free(patterns);
286 /* Host name matches. */
287 goto next_option;
288 case -1:
289 debug("%.100s, line %lu: invalid criteria",
290 file, linenum);
291 auth_debug_add("%.100s, line %lu: "
292 "invalid criteria", file, linenum);
293 /* FALLTHROUGH */
294 case 0:
295 free(patterns);
296 logit("Authentication tried for %.100s with "
297 "correct key but not from a permitted "
298 "host (host=%.200s, ip=%.200s).",
299 pw->pw_name, remote_host, remote_ip);
300 auth_debug_add("Your host '%.200s' is not "
301 "permitted to use this key for login.",
302 remote_host);
303 break;
304 }
305 /* deny access */
306 return 0;
307 }
308 cp = "permitopen=\"";
309 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
310 char *host, *p;
311 int port;
312 char *patterns = xmalloc(strlen(opts) + 1);
313
314 opts += strlen(cp);
315 i = 0;
316 while (*opts) {
317 if (*opts == '"')
318 break;
319 if (*opts == '\\' && opts[1] == '"') {
320 opts += 2;
321 patterns[i++] = '"';
322 continue;
323 }
324 patterns[i++] = *opts++;
325 }
326 if (!*opts) {
327 debug("%.100s, line %lu: missing end quote",
328 file, linenum);
329 auth_debug_add("%.100s, line %lu: missing "
330 "end quote", file, linenum);
331 free(patterns);
332 goto bad_option;
333 }
334 patterns[i] = '\0';
335 opts++;
336 p = patterns;
337 /* XXX - add streamlocal support */
338 host = hpdelim(&p);
339 if (host == NULL || strlen(host) >= NI_MAXHOST) {
340 debug("%.100s, line %lu: Bad permitopen "
341 "specification <%.100s>", file, linenum,
342 patterns);
343 auth_debug_add("%.100s, line %lu: "
344 "Bad permitopen specification", file,
345 linenum);
346 free(patterns);
347 goto bad_option;
348 }
349 host = cleanhostname(host);
350 if (p == NULL || (port = permitopen_port(p)) < 0) {
351 debug("%.100s, line %lu: Bad permitopen port "
352 "<%.100s>", file, linenum, p ? p : "");
353 auth_debug_add("%.100s, line %lu: "
354 "Bad permitopen port", file, linenum);
355 free(patterns);
356 goto bad_option;
357 }
358 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0)
359 channel_add_permitted_opens(host, port);
360 free(patterns);
361 goto next_option;
362 }
363 cp = "tunnel=\"";
364 if (strncasecmp(opts, cp, strlen(cp)) == 0) {
365 char *tun = NULL;
366 opts += strlen(cp);
367 tun = xmalloc(strlen(opts) + 1);
368 i = 0;
369 while (*opts) {
370 if (*opts == '"')
371 break;
372 tun[i++] = *opts++;
373 }
374 if (!*opts) {
375 debug("%.100s, line %lu: missing end quote",
376 file, linenum);
377 auth_debug_add("%.100s, line %lu: missing end quote",
378 file, linenum);
379 free(tun);
380 forced_tun_device = -1;
381 goto bad_option;
382 }
383 tun[i] = '\0';
384 forced_tun_device = a2tun(tun, NULL);
385 free(tun);
386 if (forced_tun_device == SSH_TUNID_ERR) {
387 debug("%.100s, line %lu: invalid tun device",
388 file, linenum);
389 auth_debug_add("%.100s, line %lu: invalid tun device",
390 file, linenum);
391 forced_tun_device = -1;
392 goto bad_option;
393 }
394 auth_debug_add("Forced tun device: %d", forced_tun_device);
395 opts++;
396 goto next_option;
397 }
398 next_option:
399 /*
400 * Skip the comma, and move to the next option
401 * (or break out if there are no more).
402 */
403 if (!*opts)
404 fatal("Bugs in auth-options.c option processing.");
405 if (*opts == ' ' || *opts == '\t')
406 break; /* End of options. */
407 if (*opts != ',')
408 goto bad_option;
409 opts++;
410 /* Process the next option. */
411 }
412
413 /* grant access */
414 return 1;
415
416 bad_option:
417 logit("Bad options in %.100s file, line %lu: %.50s",
418 file, linenum, opts);
419 auth_debug_add("Bad options in %.100s file, line %lu: %.50s",
420 file, linenum, opts);
421
422 /* deny access */
423 return 0;
424 }
425
426 #define OPTIONS_CRITICAL 1
427 #define OPTIONS_EXTENSIONS 2
428 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)429 parse_option_list(struct sshbuf *oblob, struct passwd *pw,
430 u_int which, int crit,
431 int *cert_no_port_forwarding_flag,
432 int *cert_no_agent_forwarding_flag,
433 int *cert_no_x11_forwarding_flag,
434 int *cert_no_pty_flag,
435 int *cert_no_user_rc,
436 char **cert_forced_command,
437 int *cert_source_address_done)
438 {
439 char *command, *allowed;
440 const char *remote_ip;
441 char *name = NULL;
442 struct sshbuf *c = NULL, *data = NULL;
443 int r, ret = -1, result, found;
444
445 if ((c = sshbuf_fromb(oblob)) == NULL) {
446 error("%s: sshbuf_fromb failed", __func__);
447 goto out;
448 }
449
450 while (sshbuf_len(c) > 0) {
451 sshbuf_free(data);
452 data = NULL;
453 if ((r = sshbuf_get_cstring(c, &name, NULL)) != 0 ||
454 (r = sshbuf_froms(c, &data)) != 0) {
455 error("Unable to parse certificate options: %s",
456 ssh_err(r));
457 goto out;
458 }
459 debug3("found certificate option \"%.100s\" len %zu",
460 name, sshbuf_len(data));
461 found = 0;
462 if ((which & OPTIONS_EXTENSIONS) != 0) {
463 if (strcmp(name, "permit-X11-forwarding") == 0) {
464 *cert_no_x11_forwarding_flag = 0;
465 found = 1;
466 } else if (strcmp(name,
467 "permit-agent-forwarding") == 0) {
468 *cert_no_agent_forwarding_flag = 0;
469 found = 1;
470 } else if (strcmp(name,
471 "permit-port-forwarding") == 0) {
472 *cert_no_port_forwarding_flag = 0;
473 found = 1;
474 } else if (strcmp(name, "permit-pty") == 0) {
475 *cert_no_pty_flag = 0;
476 found = 1;
477 } else if (strcmp(name, "permit-user-rc") == 0) {
478 *cert_no_user_rc = 0;
479 found = 1;
480 }
481 }
482 if (!found && (which & OPTIONS_CRITICAL) != 0) {
483 if (strcmp(name, "force-command") == 0) {
484 if ((r = sshbuf_get_cstring(data, &command,
485 NULL)) != 0) {
486 error("Unable to parse \"%s\" "
487 "section: %s", name, ssh_err(r));
488 goto out;
489 }
490 if (*cert_forced_command != NULL) {
491 error("Certificate has multiple "
492 "force-command options");
493 free(command);
494 goto out;
495 }
496 *cert_forced_command = command;
497 found = 1;
498 }
499 if (strcmp(name, "source-address") == 0) {
500 if ((r = sshbuf_get_cstring(data, &allowed,
501 NULL)) != 0) {
502 error("Unable to parse \"%s\" "
503 "section: %s", name, ssh_err(r));
504 goto out;
505 }
506 if ((*cert_source_address_done)++) {
507 error("Certificate has multiple "
508 "source-address options");
509 free(allowed);
510 goto out;
511 }
512 remote_ip = get_remote_ipaddr();
513 result = addr_match_cidr_list(remote_ip,
514 allowed);
515 free(allowed);
516 switch (result) {
517 case 1:
518 /* accepted */
519 break;
520 case 0:
521 /* no match */
522 logit("Authentication tried for %.100s "
523 "with valid certificate but not "
524 "from a permitted host "
525 "(ip=%.200s).", pw->pw_name,
526 remote_ip);
527 auth_debug_add("Your address '%.200s' "
528 "is not permitted to use this "
529 "certificate for login.",
530 remote_ip);
531 goto out;
532 case -1:
533 default:
534 error("Certificate source-address "
535 "contents invalid");
536 goto out;
537 }
538 found = 1;
539 }
540 }
541
542 if (!found) {
543 if (crit) {
544 error("Certificate critical option \"%s\" "
545 "is not supported", name);
546 goto out;
547 } else {
548 logit("Certificate extension \"%s\" "
549 "is not supported", name);
550 }
551 } else if (sshbuf_len(data) != 0) {
552 error("Certificate option \"%s\" corrupt "
553 "(extra data)", name);
554 goto out;
555 }
556 free(name);
557 name = NULL;
558 }
559 /* successfully parsed all options */
560 ret = 0;
561
562 out:
563 if (ret != 0 &&
564 cert_forced_command != NULL &&
565 *cert_forced_command != NULL) {
566 free(*cert_forced_command);
567 *cert_forced_command = NULL;
568 }
569 if (name != NULL)
570 free(name);
571 sshbuf_free(data);
572 sshbuf_free(c);
573 return ret;
574 }
575
576 /*
577 * Set options from critical certificate options. These supersede user key
578 * options so this must be called after auth_parse_options().
579 */
580 int
auth_cert_options(struct sshkey * k,struct passwd * pw)581 auth_cert_options(struct sshkey *k, struct passwd *pw)
582 {
583 int cert_no_port_forwarding_flag = 1;
584 int cert_no_agent_forwarding_flag = 1;
585 int cert_no_x11_forwarding_flag = 1;
586 int cert_no_pty_flag = 1;
587 int cert_no_user_rc = 1;
588 char *cert_forced_command = NULL;
589 int cert_source_address_done = 0;
590
591 /* Separate options and extensions for v01 certs */
592 if (parse_option_list(k->cert->critical, pw,
593 OPTIONS_CRITICAL, 1, NULL, NULL, NULL, NULL, NULL,
594 &cert_forced_command,
595 &cert_source_address_done) == -1)
596 return -1;
597 if (parse_option_list(k->cert->extensions, pw,
598 OPTIONS_EXTENSIONS, 0,
599 &cert_no_port_forwarding_flag,
600 &cert_no_agent_forwarding_flag,
601 &cert_no_x11_forwarding_flag,
602 &cert_no_pty_flag,
603 &cert_no_user_rc,
604 NULL, NULL) == -1)
605 return -1;
606
607 no_port_forwarding_flag |= cert_no_port_forwarding_flag;
608 no_agent_forwarding_flag |= cert_no_agent_forwarding_flag;
609 no_x11_forwarding_flag |= cert_no_x11_forwarding_flag;
610 no_pty_flag |= cert_no_pty_flag;
611 no_user_rc |= cert_no_user_rc;
612 /* CA-specified forced command supersedes key option */
613 if (cert_forced_command != NULL) {
614 if (forced_command != NULL)
615 free(forced_command);
616 forced_command = cert_forced_command;
617 }
618 return 0;
619 }
620
621