conditional.c

  1/* SPDX-License-Identifier: GPL-2.0-only */
  2/* Authors: Karl MacMillan <kmacmillan@tresys.com>
  3 *	    Frank Mayer <mayerf@tresys.com>
  4 *          Copyright (C) 2003 - 2004 Tresys Technology, LLC
  5 */
  6
  7#include <linux/kernel.h>
  8#include <linux/errno.h>
  9#include <linux/string.h>
 10#include <linux/spinlock.h>
 11#include <linux/slab.h>
 12
 13#include "security.h"
 14#include "conditional.h"
 15#include "services.h"
 16
 17/*
 18 * cond_evaluate_expr evaluates a conditional expr
 19 * in reverse polish notation. It returns true (1), false (0),
 20 * or undefined (-1). Undefined occurs when the expression
 21 * exceeds the stack depth of COND_EXPR_MAXDEPTH.
 22 */
 23static int cond_evaluate_expr(struct policydb *p, struct cond_expr *expr)
 24{
 25	u32 i;
 26	int s[COND_EXPR_MAXDEPTH];
 27	int sp = -1;
 28
 29	if (expr->len == 0)
 30		return -1;
 31
 32	for (i = 0; i < expr->len; i++) {
 33		struct cond_expr_node *node = &expr->nodes[i];
 34
 35		switch (node->expr_type) {
 36		case COND_BOOL:
 37			if (sp == (COND_EXPR_MAXDEPTH - 1))
 38				return -1;
 39			sp++;
 40			s[sp] = p->bool_val_to_struct[node->boolean - 1]->state;
 41			break;
 42		case COND_NOT:
 43			if (sp < 0)
 44				return -1;
 45			s[sp] = !s[sp];
 46			break;
 47		case COND_OR:
 48			if (sp < 1)
 49				return -1;
 50			sp--;
 51			s[sp] |= s[sp + 1];
 52			break;
 53		case COND_AND:
 54			if (sp < 1)
 55				return -1;
 56			sp--;
 57			s[sp] &= s[sp + 1];
 58			break;
 59		case COND_XOR:
 60			if (sp < 1)
 61				return -1;
 62			sp--;
 63			s[sp] ^= s[sp + 1];
 64			break;
 65		case COND_EQ:
 66			if (sp < 1)
 67				return -1;
 68			sp--;
 69			s[sp] = (s[sp] == s[sp + 1]);
 70			break;
 71		case COND_NEQ:
 72			if (sp < 1)
 73				return -1;
 74			sp--;
 75			s[sp] = (s[sp] != s[sp + 1]);
 76			break;
 77		default:
 78			return -1;
 79		}
 80	}
 81	return s[0];
 82}
 83
 84/*
 85 * evaluate_cond_node evaluates the conditional stored in
 86 * a struct cond_node and if the result is different than the
 87 * current state of the node it sets the rules in the true/false
 88 * list appropriately. If the result of the expression is undefined
 89 * all of the rules are disabled for safety.
 90 */
 91static void evaluate_cond_node(struct policydb *p, struct cond_node *node)
 92{
 93	struct avtab_node *avnode;
 94	int new_state;
 95	u32 i;
 96
 97	new_state = cond_evaluate_expr(p, &node->expr);
 98	if (new_state != node->cur_state) {
 99		node->cur_state = new_state;
100		if (new_state == -1)
101			pr_err("SELinux: expression result was undefined - disabling all rules.\n");
102		/* turn the rules on or off */
103		for (i = 0; i < node->true_list.len; i++) {
104			avnode = node->true_list.nodes[i];
105			if (new_state <= 0)
106				avnode->key.specified &= ~AVTAB_ENABLED;
107			else
108				avnode->key.specified |= AVTAB_ENABLED;
109		}
110
111		for (i = 0; i < node->false_list.len; i++) {
112			avnode = node->false_list.nodes[i];
113			/* -1 or 1 */
114			if (new_state)
115				avnode->key.specified &= ~AVTAB_ENABLED;
116			else
117				avnode->key.specified |= AVTAB_ENABLED;
118		}
119	}
120}
121
122void evaluate_cond_nodes(struct policydb *p)
123{
124	u32 i;
125
126	for (i = 0; i < p->cond_list_len; i++)
127		evaluate_cond_node(p, &p->cond_list[i]);
128}
129
130void cond_policydb_init(struct policydb *p)
131{
132	p->bool_val_to_struct = NULL;
133	p->cond_list = NULL;
134	p->cond_list_len = 0;
135
136	avtab_init(&p->te_cond_avtab);
137}
138
139static void cond_node_destroy(struct cond_node *node)
140{
141	kfree(node->expr.nodes);
142	/* the avtab_ptr_t nodes are destroyed by the avtab */
143	kfree(node->true_list.nodes);
144	kfree(node->false_list.nodes);
145}
146
147static void cond_list_destroy(struct policydb *p)
148{
149	u32 i;
150
151	for (i = 0; i < p->cond_list_len; i++)
152		cond_node_destroy(&p->cond_list[i]);
153	kfree(p->cond_list);
154	p->cond_list = NULL;
155	p->cond_list_len = 0;
156}
157
158void cond_policydb_destroy(struct policydb *p)
159{
160	kfree(p->bool_val_to_struct);
161	avtab_destroy(&p->te_cond_avtab);
162	cond_list_destroy(p);
163}
164
165int cond_init_bool_indexes(struct policydb *p)
166{
167	kfree(p->bool_val_to_struct);
168	p->bool_val_to_struct = kmalloc_array(
169		p->p_bools.nprim, sizeof(*p->bool_val_to_struct), GFP_KERNEL);
170	if (!p->bool_val_to_struct)
171		return -ENOMEM;
172
173	avtab_hash_eval(&p->te_cond_avtab, "conditional_rules");
174
175	return 0;
176}
177
178int cond_destroy_bool(void *key, void *datum, void *p)
179{
180	kfree(key);
181	kfree(datum);
182	return 0;
183}
184
185int cond_index_bool(void *key, void *datum, void *datap)
186{
187	struct policydb *p;
188	struct cond_bool_datum *booldatum;
189
190	booldatum = datum;
191	p = datap;
192
193	if (!booldatum->value || booldatum->value > p->p_bools.nprim)
194		return -EINVAL;
195
196	p->sym_val_to_name[SYM_BOOLS][booldatum->value - 1] = key;
197	p->bool_val_to_struct[booldatum->value - 1] = booldatum;
198
199	return 0;
200}
201
202static int bool_isvalid(struct cond_bool_datum *b)
203{
204	if (!(b->state == 0 || b->state == 1))
205		return 0;
206	return 1;
207}
208
209int cond_read_bool(struct policydb *p, struct symtab *s, struct policy_file *fp)
210{
211	char *key = NULL;
212	struct cond_bool_datum *booldatum;
213	__le32 buf[3];
214	u32 len;
215	int rc;
216
217	booldatum = kzalloc(sizeof(*booldatum), GFP_KERNEL);
218	if (!booldatum)
219		return -ENOMEM;
220
221	rc = next_entry(buf, fp, sizeof(buf));
222	if (rc)
223		goto err;
224
225	booldatum->value = le32_to_cpu(buf[0]);
226	booldatum->state = le32_to_cpu(buf[1]);
227
228	rc = -EINVAL;
229	if (!bool_isvalid(booldatum))
230		goto err;
231
232	len = le32_to_cpu(buf[2]);
233
234	rc = str_read(&key, GFP_KERNEL, fp, len);
235	if (rc)
236		goto err;
237
238	rc = symtab_insert(s, key, booldatum);
239	if (rc)
240		goto err;
241
242	return 0;
243err:
244	cond_destroy_bool(key, booldatum, NULL);
245	return rc;
246}
247
248struct cond_insertf_data {
249	struct policydb *p;
250	struct avtab_node **dst;
251	struct cond_av_list *other;
252};
253
254static int cond_insertf(struct avtab *a, const struct avtab_key *k,
255			const struct avtab_datum *d, void *ptr)
256{
257	struct cond_insertf_data *data = ptr;
258	struct policydb *p = data->p;
259	struct cond_av_list *other = data->other;
260	struct avtab_node *node_ptr;
261	u32 i;
262	bool found;
263
264	/*
265	 * For type rules we have to make certain there aren't any
266	 * conflicting rules by searching the te_avtab and the
267	 * cond_te_avtab.
268	 */
269	if (k->specified & AVTAB_TYPE) {
270		if (avtab_search_node(&p->te_avtab, k)) {
271			pr_err("SELinux: type rule already exists outside of a conditional.\n");
272			return -EINVAL;
273		}
274		/*
275		 * If we are reading the false list other will be a pointer to
276		 * the true list. We can have duplicate entries if there is only
277		 * 1 other entry and it is in our true list.
278		 *
279		 * If we are reading the true list (other == NULL) there shouldn't
280		 * be any other entries.
281		 */
282		if (other) {
283			node_ptr = avtab_search_node(&p->te_cond_avtab, k);
284			if (node_ptr) {
285				if (avtab_search_node_next(node_ptr,
286							   k->specified)) {
287					pr_err("SELinux: too many conflicting type rules.\n");
288					return -EINVAL;
289				}
290				found = false;
291				for (i = 0; i < other->len; i++) {
292					if (other->nodes[i] == node_ptr) {
293						found = true;
294						break;
295					}
296				}
297				if (!found) {
298					pr_err("SELinux: conflicting type rules.\n");
299					return -EINVAL;
300				}
301			}
302		} else {
303			if (avtab_search_node(&p->te_cond_avtab, k)) {
304				pr_err("SELinux: conflicting type rules when adding type rule for true.\n");
305				return -EINVAL;
306			}
307		}
308	}
309
310	node_ptr = avtab_insert_nonunique(&p->te_cond_avtab, k, d);
311	if (!node_ptr) {
312		pr_err("SELinux: could not insert rule.\n");
313		return -ENOMEM;
314	}
315
316	*data->dst = node_ptr;
317	return 0;
318}
319
320static int cond_read_av_list(struct policydb *p, struct policy_file *fp,
321			     struct cond_av_list *list,
322			     struct cond_av_list *other)
323{
324	int rc;
325	__le32 buf[1];
326	u32 i, len;
327	struct cond_insertf_data data;
328
329	rc = next_entry(buf, fp, sizeof(u32));
330	if (rc)
331		return rc;
332
333	len = le32_to_cpu(buf[0]);
334	if (len == 0)
335		return 0;
336
337	list->nodes = kcalloc(len, sizeof(*list->nodes), GFP_KERNEL);
338	if (!list->nodes)
339		return -ENOMEM;
340
341	data.p = p;
342	data.other = other;
343	for (i = 0; i < len; i++) {
344		data.dst = &list->nodes[i];
345		rc = avtab_read_item(&p->te_cond_avtab, fp, p, cond_insertf,
346				     &data, true);
347		if (rc) {
348			kfree(list->nodes);
349			list->nodes = NULL;
350			return rc;
351		}
352	}
353
354	list->len = len;
355	return 0;
356}
357
358static int expr_node_isvalid(struct policydb *p, struct cond_expr_node *expr)
359{
360	if (expr->expr_type <= 0 || expr->expr_type > COND_LAST) {
361		pr_err("SELinux: conditional expressions uses unknown operator.\n");
362		return 0;
363	}
364
365	if (expr->boolean > p->p_bools.nprim) {
366		pr_err("SELinux: conditional expressions uses unknown bool.\n");
367		return 0;
368	}
369	return 1;
370}
371
372static int cond_read_node(struct policydb *p, struct cond_node *node, struct policy_file *fp)
373{
374	__le32 buf[2];
375	u32 i, len;
376	int rc;
377
378	rc = next_entry(buf, fp, sizeof(u32) * 2);
379	if (rc)
380		return rc;
381
382	node->cur_state = le32_to_cpu(buf[0]);
383
384	/* expr */
385	len = le32_to_cpu(buf[1]);
386	node->expr.nodes = kcalloc(len, sizeof(*node->expr.nodes), GFP_KERNEL);
387	if (!node->expr.nodes)
388		return -ENOMEM;
389
390	node->expr.len = len;
391
392	for (i = 0; i < len; i++) {
393		struct cond_expr_node *expr = &node->expr.nodes[i];
394
395		rc = next_entry(buf, fp, sizeof(u32) * 2);
396		if (rc)
397			return rc;
398
399		expr->expr_type = le32_to_cpu(buf[0]);
400		expr->boolean = le32_to_cpu(buf[1]);
401
402		if (!expr_node_isvalid(p, expr))
403			return -EINVAL;
404	}
405
406	rc = cond_read_av_list(p, fp, &node->true_list, NULL);
407	if (rc)
408		return rc;
409	return cond_read_av_list(p, fp, &node->false_list, &node->true_list);
410}
411
412int cond_read_list(struct policydb *p, struct policy_file *fp)
413{
414	__le32 buf[1];
415	u32 i, len;
416	int rc;
417
418	rc = next_entry(buf, fp, sizeof(buf));
419	if (rc)
420		return rc;
421
422	len = le32_to_cpu(buf[0]);
423
424	p->cond_list = kcalloc(len, sizeof(*p->cond_list), GFP_KERNEL);
425	if (!p->cond_list)
426		return -ENOMEM;
427
428	rc = avtab_alloc(&(p->te_cond_avtab), p->te_avtab.nel);
429	if (rc)
430		goto err;
431
432	p->cond_list_len = len;
433
434	for (i = 0; i < len; i++) {
435		rc = cond_read_node(p, &p->cond_list[i], fp);
436		if (rc)
437			goto err;
438	}
439	return 0;
440err:
441	cond_list_destroy(p);
442	return rc;
443}
444
445int cond_write_bool(void *vkey, void *datum, void *ptr)
446{
447	char *key = vkey;
448	struct cond_bool_datum *booldatum = datum;
449	struct policy_data *pd = ptr;
450	struct policy_file *fp = pd->fp;
451	__le32 buf[3];
452	u32 len;
453	int rc;
454
455	len = strlen(key);
456	buf[0] = cpu_to_le32(booldatum->value);
457	buf[1] = cpu_to_le32(booldatum->state);
458	buf[2] = cpu_to_le32(len);
459	rc = put_entry(buf, sizeof(u32), 3, fp);
460	if (rc)
461		return rc;
462	rc = put_entry(key, 1, len, fp);
463	if (rc)
464		return rc;
465	return 0;
466}
467
468/*
469 * cond_write_cond_av_list doesn't write out the av_list nodes.
470 * Instead it writes out the key/value pairs from the avtab. This
471 * is necessary because there is no way to uniquely identifying rules
472 * in the avtab so it is not possible to associate individual rules
473 * in the avtab with a conditional without saving them as part of
474 * the conditional. This means that the avtab with the conditional
475 * rules will not be saved but will be rebuilt on policy load.
476 */
477static int cond_write_av_list(struct policydb *p, struct cond_av_list *list,
478			      struct policy_file *fp)
479{
480	__le32 buf[1];
481	u32 i;
482	int rc;
483
484	buf[0] = cpu_to_le32(list->len);
485	rc = put_entry(buf, sizeof(u32), 1, fp);
486	if (rc)
487		return rc;
488
489	for (i = 0; i < list->len; i++) {
490		rc = avtab_write_item(p, list->nodes[i], fp);
491		if (rc)
492			return rc;
493	}
494
495	return 0;
496}
497
498static int cond_write_node(struct policydb *p, struct cond_node *node,
499			   struct policy_file *fp)
500{
501	__le32 buf[2];
502	int rc;
503	u32 i;
504
505	buf[0] = cpu_to_le32(node->cur_state);
506	rc = put_entry(buf, sizeof(u32), 1, fp);
507	if (rc)
508		return rc;
509
510	buf[0] = cpu_to_le32(node->expr.len);
511	rc = put_entry(buf, sizeof(u32), 1, fp);
512	if (rc)
513		return rc;
514
515	for (i = 0; i < node->expr.len; i++) {
516		buf[0] = cpu_to_le32(node->expr.nodes[i].expr_type);
517		buf[1] = cpu_to_le32(node->expr.nodes[i].boolean);
518		rc = put_entry(buf, sizeof(u32), 2, fp);
519		if (rc)
520			return rc;
521	}
522
523	rc = cond_write_av_list(p, &node->true_list, fp);
524	if (rc)
525		return rc;
526	rc = cond_write_av_list(p, &node->false_list, fp);
527	if (rc)
528		return rc;
529
530	return 0;
531}
532
533int cond_write_list(struct policydb *p, struct policy_file *fp)
534{
535	u32 i;
536	__le32 buf[1];
537	int rc;
538
539	buf[0] = cpu_to_le32(p->cond_list_len);
540	rc = put_entry(buf, sizeof(u32), 1, fp);
541	if (rc)
542		return rc;
543
544	for (i = 0; i < p->cond_list_len; i++) {
545		rc = cond_write_node(p, &p->cond_list[i], fp);
546		if (rc)
547			return rc;
548	}
549
550	return 0;
551}
552
553void cond_compute_xperms(struct avtab *ctab, struct avtab_key *key,
554			 struct extended_perms_decision *xpermd)
555{
556	struct avtab_node *node;
557
558	if (!ctab || !key || !xpermd)
559		return;
560
561	for (node = avtab_search_node(ctab, key); node;
562	     node = avtab_search_node_next(node, key->specified)) {
563		if (node->key.specified & AVTAB_ENABLED)
564			services_compute_xperms_decision(xpermd, node);
565	}
566}
567/* Determine whether additional permissions are granted by the conditional
568 * av table, and if so, add them to the result
569 */
570void cond_compute_av(struct avtab *ctab, struct avtab_key *key,
571		     struct av_decision *avd, struct extended_perms *xperms)
572{
573	struct avtab_node *node;
574
575	if (!ctab || !key || !avd)
576		return;
577
578	for (node = avtab_search_node(ctab, key); node;
579	     node = avtab_search_node_next(node, key->specified)) {
580		if ((u16)(AVTAB_ALLOWED | AVTAB_ENABLED) ==
581		    (node->key.specified & (AVTAB_ALLOWED | AVTAB_ENABLED)))
582			avd->allowed |= node->datum.u.data;
583		if ((u16)(AVTAB_AUDITDENY | AVTAB_ENABLED) ==
584		    (node->key.specified & (AVTAB_AUDITDENY | AVTAB_ENABLED)))
585			/* Since a '0' in an auditdeny mask represents a
586			 * permission we do NOT want to audit (dontaudit), we use
587			 * the '&' operand to ensure that all '0's in the mask
588			 * are retained (much unlike the allow and auditallow cases).
589			 */
590			avd->auditdeny &= node->datum.u.data;
591		if ((u16)(AVTAB_AUDITALLOW | AVTAB_ENABLED) ==
592		    (node->key.specified & (AVTAB_AUDITALLOW | AVTAB_ENABLED)))
593			avd->auditallow |= node->datum.u.data;
594		if (xperms && (node->key.specified & AVTAB_ENABLED) &&
595		    (node->key.specified & AVTAB_XPERMS))
596			services_compute_xperms_drivers(xperms, node);
597	}
598}
599
600static int cond_dup_av_list(struct cond_av_list *new,
601			    const struct cond_av_list *orig,
602			    struct avtab *avtab)
603{
604	u32 i;
605
606	memset(new, 0, sizeof(*new));
607
608	new->nodes = kcalloc(orig->len, sizeof(*new->nodes), GFP_KERNEL);
609	if (!new->nodes)
610		return -ENOMEM;
611
612	for (i = 0; i < orig->len; i++) {
613		new->nodes[i] = avtab_insert_nonunique(
614			avtab, &orig->nodes[i]->key, &orig->nodes[i]->datum);
615		if (!new->nodes[i])
616			return -ENOMEM;
617		new->len++;
618	}
619
620	return 0;
621}
622
623static int duplicate_policydb_cond_list(struct policydb *newp,
624					const struct policydb *origp)
625{
626	int rc;
627	u32 i;
628
629	rc = avtab_alloc_dup(&newp->te_cond_avtab, &origp->te_cond_avtab);
630	if (rc)
631		return rc;
632
633	newp->cond_list_len = 0;
634	newp->cond_list = kcalloc(origp->cond_list_len,
635				  sizeof(*newp->cond_list), GFP_KERNEL);
636	if (!newp->cond_list)
637		goto error;
638
639	for (i = 0; i < origp->cond_list_len; i++) {
640		struct cond_node *newn = &newp->cond_list[i];
641		const struct cond_node *orign = &origp->cond_list[i];
642
643		newp->cond_list_len++;
644
645		newn->cur_state = orign->cur_state;
646		newn->expr.nodes =
647			kmemdup(orign->expr.nodes,
648				orign->expr.len * sizeof(*orign->expr.nodes),
649				GFP_KERNEL);
650		if (!newn->expr.nodes)
651			goto error;
652
653		newn->expr.len = orign->expr.len;
654
655		rc = cond_dup_av_list(&newn->true_list, &orign->true_list,
656				      &newp->te_cond_avtab);
657		if (rc)
658			goto error;
659
660		rc = cond_dup_av_list(&newn->false_list, &orign->false_list,
661				      &newp->te_cond_avtab);
662		if (rc)
663			goto error;
664	}
665
666	return 0;
667
668error:
669	avtab_destroy(&newp->te_cond_avtab);
670	cond_list_destroy(newp);
671	return -ENOMEM;
672}
673
674static int cond_bools_destroy(void *key, void *datum, void *args)
675{
676	/* key was not copied so no need to free here */
677	kfree(datum);
678	return 0;
679}
680
681static int cond_bools_copy(struct hashtab_node *new,
682			   const struct hashtab_node *orig, void *args)
683{
684	struct cond_bool_datum *datum;
685
686	datum = kmemdup(orig->datum, sizeof(struct cond_bool_datum),
687			GFP_KERNEL);
688	if (!datum)
689		return -ENOMEM;
690
691	new->key = orig->key; /* No need to copy, never modified */
692	new->datum = datum;
693	return 0;
694}
695
696static int cond_bools_index(void *key, void *datum, void *args)
697{
698	struct cond_bool_datum *booldatum, **cond_bool_array;
699
700	booldatum = datum;
701	cond_bool_array = args;
702	cond_bool_array[booldatum->value - 1] = booldatum;
703
704	return 0;
705}
706
707static int duplicate_policydb_bools(struct policydb *newdb,
708				    const struct policydb *orig)
709{
710	struct cond_bool_datum **cond_bool_array;
711	int rc;
712
713	cond_bool_array = kmalloc_array(orig->p_bools.nprim,
714					sizeof(*orig->bool_val_to_struct),
715					GFP_KERNEL);
716	if (!cond_bool_array)
717		return -ENOMEM;
718
719	rc = hashtab_duplicate(&newdb->p_bools.table, &orig->p_bools.table,
720			       cond_bools_copy, cond_bools_destroy, NULL);
721	if (rc) {
722		kfree(cond_bool_array);
723		return -ENOMEM;
724	}
725
726	hashtab_map(&newdb->p_bools.table, cond_bools_index, cond_bool_array);
727	newdb->bool_val_to_struct = cond_bool_array;
728
729	newdb->p_bools.nprim = orig->p_bools.nprim;
730
731	return 0;
732}
733
734void cond_policydb_destroy_dup(struct policydb *p)
735{
736	hashtab_map(&p->p_bools.table, cond_bools_destroy, NULL);
737	hashtab_destroy(&p->p_bools.table);
738	cond_policydb_destroy(p);
739}
740
741int cond_policydb_dup(struct policydb *new, const struct policydb *orig)
742{
743	cond_policydb_init(new);
744
745	if (duplicate_policydb_bools(new, orig))
746		return -ENOMEM;
747
748	if (duplicate_policydb_cond_list(new, orig)) {
749		cond_policydb_destroy_dup(new);
750		return -ENOMEM;
751	}
752
753	return 0;
754}