1/*
  2 * Copyright (C) 2007 Casey Schaufler <casey@schaufler-ca.com>
  3 *
  4 *      This program is free software; you can redistribute it and/or modify
  5 *      it under the terms of the GNU General Public License as published by
  6 *      the Free Software Foundation, version 2.
  7 *
  8 * Author:
  9 *      Casey Schaufler <casey@schaufler-ca.com>
 10 *
 11 */
 12
 13#include <linux/types.h>
 14#include <linux/slab.h>
 15#include <linux/fs.h>
 16#include <linux/sched.h>
 17#include "smack.h"
 18
 19struct smack_known smack_known_huh = {
 20	.smk_known	= "?",
 21	.smk_secid	= 2,
 22};
 23
 24struct smack_known smack_known_hat = {
 25	.smk_known	= "^",
 26	.smk_secid	= 3,
 27};
 28
 29struct smack_known smack_known_star = {
 30	.smk_known	= "*",
 31	.smk_secid	= 4,
 32};
 33
 34struct smack_known smack_known_floor = {
 35	.smk_known	= "_",
 36	.smk_secid	= 5,
 37};
 38
 39struct smack_known smack_known_invalid = {
 40	.smk_known	= "",
 41	.smk_secid	= 6,
 42};
 43
 44struct smack_known smack_known_web = {
 45	.smk_known	= "@",
 46	.smk_secid	= 7,
 47};
 48
 49LIST_HEAD(smack_known_list);
 50
 51/*
 52 * The initial value needs to be bigger than any of the
 53 * known values above.
 54 */
 55static u32 smack_next_secid = 10;
 56
 57/*
 58 * what events do we log
 59 * can be overwritten at run-time by /smack/logging
 60 */
 61int log_policy = SMACK_AUDIT_DENIED;
 62
 63/**
 64 * smk_access_entry - look up matching access rule
 65 * @subject_label: a pointer to the subject's Smack label
 66 * @object_label: a pointer to the object's Smack label
 67 * @rule_list: the list of rules to search
 68 *
 69 * This function looks up the subject/object pair in the
 70 * access rule list and returns the access mode. If no
 71 * entry is found returns -ENOENT.
 72 *
 73 * NOTE:
 74 *
 75 * Earlier versions of this function allowed for labels that
 76 * were not on the label list. This was done to allow for
 77 * labels to come over the network that had never been seen
 78 * before on this host. Unless the receiving socket has the
 79 * star label this will always result in a failure check. The
 80 * star labeled socket case is now handled in the networking
 81 * hooks so there is no case where the label is not on the
 82 * label list. Checking to see if the address of two labels
 83 * is the same is now a reliable test.
 84 *
 85 * Do the object check first because that is more
 86 * likely to differ.
 87 */
 88int smk_access_entry(char *subject_label, char *object_label,
 89			struct list_head *rule_list)
 90{
 91	int may = -ENOENT;
 92	struct smack_rule *srp;
 93
 94	list_for_each_entry_rcu(srp, rule_list, list) {
 95		if (srp->smk_object == object_label &&
 96		    srp->smk_subject == subject_label) {
 97			may = srp->smk_access;
 98			break;
 99		}
100	}
101
102	return may;
103}
104
105/**
106 * smk_access - determine if a subject has a specific access to an object
107 * @subject_label: a pointer to the subject's Smack label
108 * @object_label: a pointer to the object's Smack label
109 * @request: the access requested, in "MAY" format
110 * @a : a pointer to the audit data
111 *
112 * This function looks up the subject/object pair in the
113 * access rule list and returns 0 if the access is permitted,
114 * non zero otherwise.
115 *
116 * Smack labels are shared on smack_list
117 */
118int smk_access(char *subject_label, char *object_label, int request,
119	       struct smk_audit_info *a)
120{
121	struct smack_known *skp;
122	int may = MAY_NOT;
123	int rc = 0;
124
125	/*
126	 * Hardcoded comparisons.
127	 *
128	 * A star subject can't access any object.
129	 */
130	if (subject_label == smack_known_star.smk_known) {
131		rc = -EACCES;
132		goto out_audit;
133	}
134	/*
135	 * An internet object can be accessed by any subject.
136	 * Tasks cannot be assigned the internet label.
137	 * An internet subject can access any object.
138	 */
139	if (object_label == smack_known_web.smk_known ||
140	    subject_label == smack_known_web.smk_known)
141		goto out_audit;
142	/*
143	 * A star object can be accessed by any subject.
144	 */
145	if (object_label == smack_known_star.smk_known)
146		goto out_audit;
147	/*
148	 * An object can be accessed in any way by a subject
149	 * with the same label.
150	 */
151	if (subject_label == object_label)
152		goto out_audit;
153	/*
154	 * A hat subject can read any object.
155	 * A floor object can be read by any subject.
156	 */
157	if ((request & MAY_ANYREAD) == request) {
158		if (object_label == smack_known_floor.smk_known)
159			goto out_audit;
160		if (subject_label == smack_known_hat.smk_known)
161			goto out_audit;
162	}
163	/*
164	 * Beyond here an explicit relationship is required.
165	 * If the requested access is contained in the available
166	 * access (e.g. read is included in readwrite) it's
167	 * good. A negative response from smk_access_entry()
168	 * indicates there is no entry for this pair.
169	 */
170	skp = smk_find_entry(subject_label);
171	rcu_read_lock();
172	may = smk_access_entry(subject_label, object_label, &skp->smk_rules);
173	rcu_read_unlock();
174
175	if (may > 0 && (request & may) == request)
176		goto out_audit;
177
178	rc = -EACCES;
179out_audit:
180#ifdef CONFIG_AUDIT
181	if (a)
182		smack_log(subject_label, object_label, request, rc, a);
183#endif
184	return rc;
185}
186
187/**
188 * smk_curacc - determine if current has a specific access to an object
189 * @obj_label: a pointer to the object's Smack label
190 * @mode: the access requested, in "MAY" format
191 * @a : common audit data
192 *
193 * This function checks the current subject label/object label pair
194 * in the access rule list and returns 0 if the access is permitted,
195 * non zero otherwise. It allows that current may have the capability
196 * to override the rules.
197 */
198int smk_curacc(char *obj_label, u32 mode, struct smk_audit_info *a)
199{
200	struct task_smack *tsp = current_security();
201	char *sp = smk_of_task(tsp);
202	int may;
203	int rc;
204
205	/*
206	 * Check the global rule list
207	 */
208	rc = smk_access(sp, obj_label, mode, NULL);
209	if (rc == 0) {
210		/*
211		 * If there is an entry in the task's rule list
212		 * it can further restrict access.
213		 */
214		may = smk_access_entry(sp, obj_label, &tsp->smk_rules);
215		if (may < 0)
216			goto out_audit;
217		if ((mode & may) == mode)
218			goto out_audit;
219		rc = -EACCES;
220	}
221
222	/*
223	 * Return if a specific label has been designated as the
224	 * only one that gets privilege and current does not
225	 * have that label.
226	 */
227	if (smack_onlycap != NULL && smack_onlycap != sp)
228		goto out_audit;
229
230	if (capable(CAP_MAC_OVERRIDE))
231		rc = 0;
232
233out_audit:
234#ifdef CONFIG_AUDIT
235	if (a)
236		smack_log(sp, obj_label, mode, rc, a);
237#endif
238	return rc;
239}
240
241#ifdef CONFIG_AUDIT
242/**
243 * smack_str_from_perm : helper to transalate an int to a
244 * readable string
245 * @string : the string to fill
246 * @access : the int
247 *
248 */
249static inline void smack_str_from_perm(char *string, int access)
250{
251	int i = 0;
252	if (access & MAY_READ)
253		string[i++] = 'r';
254	if (access & MAY_WRITE)
255		string[i++] = 'w';
256	if (access & MAY_EXEC)
257		string[i++] = 'x';
258	if (access & MAY_APPEND)
259		string[i++] = 'a';
260	string[i] = '\0';
261}
262/**
263 * smack_log_callback - SMACK specific information
264 * will be called by generic audit code
265 * @ab : the audit_buffer
266 * @a  : audit_data
267 *
268 */
269static void smack_log_callback(struct audit_buffer *ab, void *a)
270{
271	struct common_audit_data *ad = a;
272	struct smack_audit_data *sad = ad->smack_audit_data;
273	audit_log_format(ab, "lsm=SMACK fn=%s action=%s",
274			 ad->smack_audit_data->function,
275			 sad->result ? "denied" : "granted");
276	audit_log_format(ab, " subject=");
277	audit_log_untrustedstring(ab, sad->subject);
278	audit_log_format(ab, " object=");
279	audit_log_untrustedstring(ab, sad->object);
280	audit_log_format(ab, " requested=%s", sad->request);
281}
282
283/**
284 *  smack_log - Audit the granting or denial of permissions.
285 *  @subject_label : smack label of the requester
286 *  @object_label  : smack label of the object being accessed
287 *  @request: requested permissions
288 *  @result: result from smk_access
289 *  @a:  auxiliary audit data
290 *
291 * Audit the granting or denial of permissions in accordance
292 * with the policy.
293 */
294void smack_log(char *subject_label, char *object_label, int request,
295	       int result, struct smk_audit_info *ad)
296{
297	char request_buffer[SMK_NUM_ACCESS_TYPE + 1];
298	struct smack_audit_data *sad;
299	struct common_audit_data *a = &ad->a;
300
301	/* check if we have to log the current event */
302	if (result != 0 && (log_policy & SMACK_AUDIT_DENIED) == 0)
303		return;
304	if (result == 0 && (log_policy & SMACK_AUDIT_ACCEPT) == 0)
305		return;
306
307	sad = a->smack_audit_data;
308
309	if (sad->function == NULL)
310		sad->function = "unknown";
311
312	/* end preparing the audit data */
313	smack_str_from_perm(request_buffer, request);
314	sad->subject = subject_label;
315	sad->object  = object_label;
316	sad->request = request_buffer;
317	sad->result  = result;
318
319	common_lsm_audit(a, smack_log_callback, NULL);
320}
321#else /* #ifdef CONFIG_AUDIT */
322void smack_log(char *subject_label, char *object_label, int request,
323               int result, struct smk_audit_info *ad)
324{
325}
326#endif
327
328DEFINE_MUTEX(smack_known_lock);
329
330/**
331 * smk_find_entry - find a label on the list, return the list entry
332 * @string: a text string that might be a Smack label
333 *
334 * Returns a pointer to the entry in the label list that
335 * matches the passed string.
336 */
337struct smack_known *smk_find_entry(const char *string)
338{
339	struct smack_known *skp;
340
341	list_for_each_entry_rcu(skp, &smack_known_list, list) {
342		if (strcmp(skp->smk_known, string) == 0)
343			return skp;
344	}
345
346	return NULL;
347}
348
349/**
350 * smk_parse_smack - parse smack label from a text string
351 * @string: a text string that might contain a Smack label
352 * @len: the maximum size, or zero if it is NULL terminated.
353 *
354 * Returns a pointer to the clean label, or NULL
355 */
356char *smk_parse_smack(const char *string, int len)
357{
358	char *smack;
359	int i;
360
361	if (len <= 0)
362		len = strlen(string) + 1;
363
364	/*
365	 * Reserve a leading '-' as an indicator that
366	 * this isn't a label, but an option to interfaces
367	 * including /smack/cipso and /smack/cipso2
368	 */
369	if (string[0] == '-')
370		return NULL;
371
372	for (i = 0; i < len; i++)
373		if (string[i] > '~' || string[i] <= ' ' || string[i] == '/' ||
374		    string[i] == '"' || string[i] == '\\' || string[i] == '\'')
375			break;
376
377	if (i == 0 || i >= SMK_LONGLABEL)
378		return NULL;
379
380	smack = kzalloc(i + 1, GFP_KERNEL);
381	if (smack != NULL) {
382		strncpy(smack, string, i + 1);
383		smack[i] = '\0';
384	}
385	return smack;
386}
387
388/**
389 * smk_netlbl_mls - convert a catset to netlabel mls categories
390 * @catset: the Smack categories
391 * @sap: where to put the netlabel categories
392 *
393 * Allocates and fills attr.mls
394 * Returns 0 on success, error code on failure.
395 */
396int smk_netlbl_mls(int level, char *catset, struct netlbl_lsm_secattr *sap,
397			int len)
398{
399	unsigned char *cp;
400	unsigned char m;
401	int cat;
402	int rc;
403	int byte;
404
405	sap->flags |= NETLBL_SECATTR_MLS_CAT;
406	sap->attr.mls.lvl = level;
407	sap->attr.mls.cat = netlbl_secattr_catmap_alloc(GFP_ATOMIC);
408	sap->attr.mls.cat->startbit = 0;
409
410	for (cat = 1, cp = catset, byte = 0; byte < len; cp++, byte++)
411		for (m = 0x80; m != 0; m >>= 1, cat++) {
412			if ((m & *cp) == 0)
413				continue;
414			rc = netlbl_secattr_catmap_setbit(sap->attr.mls.cat,
415							  cat, GFP_ATOMIC);
416			if (rc < 0) {
417				netlbl_secattr_catmap_free(sap->attr.mls.cat);
418				return rc;
419			}
420		}
421
422	return 0;
423}
424
425/**
426 * smk_import_entry - import a label, return the list entry
427 * @string: a text string that might be a Smack label
428 * @len: the maximum size, or zero if it is NULL terminated.
429 *
430 * Returns a pointer to the entry in the label list that
431 * matches the passed string, adding it if necessary.
432 */
433struct smack_known *smk_import_entry(const char *string, int len)
434{
435	struct smack_known *skp;
436	char *smack;
437	int slen;
438	int rc;
439
440	smack = smk_parse_smack(string, len);
441	if (smack == NULL)
442		return NULL;
443
444	mutex_lock(&smack_known_lock);
445
446	skp = smk_find_entry(smack);
447	if (skp != NULL)
448		goto freeout;
449
450	skp = kzalloc(sizeof(*skp), GFP_KERNEL);
451	if (skp == NULL)
452		goto freeout;
453
454	skp->smk_known = smack;
455	skp->smk_secid = smack_next_secid++;
456	skp->smk_netlabel.domain = skp->smk_known;
457	skp->smk_netlabel.flags =
458		NETLBL_SECATTR_DOMAIN | NETLBL_SECATTR_MLS_LVL;
459	/*
460	 * If direct labeling works use it.
461	 * Otherwise use mapped labeling.
462	 */
463	slen = strlen(smack);
464	if (slen < SMK_CIPSOLEN)
465		rc = smk_netlbl_mls(smack_cipso_direct, skp->smk_known,
466			       &skp->smk_netlabel, slen);
467	else
468		rc = smk_netlbl_mls(smack_cipso_mapped, (char *)&skp->smk_secid,
469			       &skp->smk_netlabel, sizeof(skp->smk_secid));
470
471	if (rc >= 0) {
472		INIT_LIST_HEAD(&skp->smk_rules);
473		mutex_init(&skp->smk_rules_lock);
474		/*
475		 * Make sure that the entry is actually
476		 * filled before putting it on the list.
477		 */
478		list_add_rcu(&skp->list, &smack_known_list);
479		goto unlockout;
480	}
481	/*
482	 * smk_netlbl_mls failed.
483	 */
484	kfree(skp);
485	skp = NULL;
486freeout:
487	kfree(smack);
488unlockout:
489	mutex_unlock(&smack_known_lock);
490
491	return skp;
492}
493
494/**
495 * smk_import - import a smack label
496 * @string: a text string that might be a Smack label
497 * @len: the maximum size, or zero if it is NULL terminated.
498 *
499 * Returns a pointer to the label in the label list that
500 * matches the passed string, adding it if necessary.
501 */
502char *smk_import(const char *string, int len)
503{
504	struct smack_known *skp;
505
506	/* labels cannot begin with a '-' */
507	if (string[0] == '-')
508		return NULL;
509	skp = smk_import_entry(string, len);
510	if (skp == NULL)
511		return NULL;
512	return skp->smk_known;
513}
514
515/**
516 * smack_from_secid - find the Smack label associated with a secid
517 * @secid: an integer that might be associated with a Smack label
518 *
519 * Returns a pointer to the appropriate Smack label if there is one,
520 * otherwise a pointer to the invalid Smack label.
521 */
522char *smack_from_secid(const u32 secid)
523{
524	struct smack_known *skp;
525
526	rcu_read_lock();
527	list_for_each_entry_rcu(skp, &smack_known_list, list) {
528		if (skp->smk_secid == secid) {
529			rcu_read_unlock();
530			return skp->smk_known;
531		}
532	}
533
534	/*
535	 * If we got this far someone asked for the translation
536	 * of a secid that is not on the list.
537	 */
538	rcu_read_unlock();
539	return smack_known_invalid.smk_known;
540}
541
542/**
543 * smack_to_secid - find the secid associated with a Smack label
544 * @smack: the Smack label
545 *
546 * Returns the appropriate secid if there is one,
547 * otherwise 0
548 */
549u32 smack_to_secid(const char *smack)
550{
551	struct smack_known *skp = smk_find_entry(smack);
552
553	if (skp == NULL)
554		return 0;
555	return skp->smk_secid;
556}