auth-options.c revision 295367 
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 */
42int no_port_forwarding_flag = 0;
43int no_agent_forwarding_flag = 0;
44int no_x11_forwarding_flag = 0;
45int no_pty_flag = 0;
46int no_user_rc = 0;
47int key_is_cert_authority = 0;
48
49/* "command=" option. */
50char *forced_command = NULL;
51
52/* "environment=" options. */
53struct envstring *custom_environment = NULL;
54
55/* "tunnel=" option. */
56int forced_tun_device = -1;
57
58/* "principals=" option. */
59char *authorized_principals = NULL;
60
61extern ServerOptions options;
62
63void
64auth_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 */
94int
95auth_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		}
398next_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
416bad_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
428static int
429parse_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 */
580int
581auth_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