1 /* Authors: Karl MacMillan <kmacmillan@tresys.com>
2  *          Frank Mayer <mayerf@tresys.com>
3  *
4  * Copyright (C) 2003 - 2004 Tresys Technology, LLC
5  *	This program is free software; you can redistribute it and/or modify
6  *  	it under the terms of the GNU General Public License as published by
7  *	the Free Software Foundation, version 2.
8  */
9 
10 #include <linux/kernel.h>
11 #include <linux/errno.h>
12 #include <linux/string.h>
13 #include <linux/spinlock.h>
14 #include <asm/semaphore.h>
15 #include <linux/slab.h>
16 
17 #include "security.h"
18 #include "conditional.h"
19 
20 /*
21  * cond_evaluate_expr evaluates a conditional expr
22  * in reverse polish notation. It returns true (1), false (0),
23  * or undefined (-1). Undefined occurs when the expression
24  * exceeds the stack depth of COND_EXPR_MAXDEPTH.
25  */
26 static int cond_evaluate_expr(struct policydb *p, struct cond_expr *expr)
27 {
28 
29 	struct cond_expr *cur;
30 	int s[COND_EXPR_MAXDEPTH];
31 	int sp = -1;
32 
33 	for (cur = expr; cur != NULL; cur = cur->next) {
34 		switch (cur->expr_type) {
35 		case COND_BOOL:
36 			if (sp == (COND_EXPR_MAXDEPTH - 1))
37 				return -1;
38 			sp++;
39 			s[sp] = p->bool_val_to_struct[cur->bool - 1]->state;
40 			break;
41 		case COND_NOT:
42 			if (sp < 0)
43 				return -1;
44 			s[sp] = !s[sp];
45 			break;
46 		case COND_OR:
47 			if (sp < 1)
48 				return -1;
49 			sp--;
50 			s[sp] |= s[sp + 1];
51 			break;
52 		case COND_AND:
53 			if (sp < 1)
54 				return -1;
55 			sp--;
56 			s[sp] &= s[sp + 1];
57 			break;
58 		case COND_XOR:
59 			if (sp < 1)
60 				return -1;
61 			sp--;
62 			s[sp] ^= s[sp + 1];
63 			break;
64 		case COND_EQ:
65 			if (sp < 1)
66 				return -1;
67 			sp--;
68 			s[sp] = (s[sp] == s[sp + 1]);
69 			break;
70 		case COND_NEQ:
71 			if (sp < 1)
72 				return -1;
73 			sp--;
74 			s[sp] = (s[sp] != s[sp + 1]);
75 			break;
76 		default:
77 			return -1;
78 		}
79 	}
80 	return s[0];
81 }
82 
83 /*
84  * evaluate_cond_node evaluates the conditional stored in
85  * a struct cond_node and if the result is different than the
86  * current state of the node it sets the rules in the true/false
87  * list appropriately. If the result of the expression is undefined
88  * all of the rules are disabled for safety.
89  */
90 int evaluate_cond_node(struct policydb *p, struct cond_node *node)
91 {
92 	int new_state;
93 	struct cond_av_list* cur;
94 
95 	new_state = cond_evaluate_expr(p, node->expr);
96 	if (new_state != node->cur_state) {
97 		node->cur_state = new_state;
98 		if (new_state == -1)
99 			printk(KERN_ERR "security: expression result was undefined - disabling all rules.\n");
100 		/* turn the rules on or off */
101 		for (cur = node->true_list; cur != NULL; cur = cur->next) {
102 			if (new_state <= 0) {
103 				cur->node->key.specified &= ~AVTAB_ENABLED;
104 			} else {
105 				cur->node->key.specified |= AVTAB_ENABLED;
106 			}
107 		}
108 
109 		for (cur = node->false_list; cur != NULL; cur = cur->next) {
110 			/* -1 or 1 */
111 			if (new_state) {
112 				cur->node->key.specified &= ~AVTAB_ENABLED;
113 			} else {
114 				cur->node->key.specified |= AVTAB_ENABLED;
115 			}
116 		}
117 	}
118 	return 0;
119 }
120 
121 int cond_policydb_init(struct policydb *p)
122 {
123 	p->bool_val_to_struct = NULL;
124 	p->cond_list = NULL;
125 	if (avtab_init(&p->te_cond_avtab))
126 		return -1;
127 
128 	return 0;
129 }
130 
131 static void cond_av_list_destroy(struct cond_av_list *list)
132 {
133 	struct cond_av_list *cur, *next;
134 	for (cur = list; cur != NULL; cur = next) {
135 		next = cur->next;
136 		/* the avtab_ptr_t node is destroy by the avtab */
137 		kfree(cur);
138 	}
139 }
140 
141 static void cond_node_destroy(struct cond_node *node)
142 {
143 	struct cond_expr *cur_expr, *next_expr;
144 
145 	for (cur_expr = node->expr; cur_expr != NULL; cur_expr = next_expr) {
146 		next_expr = cur_expr->next;
147 		kfree(cur_expr);
148 	}
149 	cond_av_list_destroy(node->true_list);
150 	cond_av_list_destroy(node->false_list);
151 	kfree(node);
152 }
153 
154 static void cond_list_destroy(struct cond_node *list)
155 {
156 	struct cond_node *next, *cur;
157 
158 	if (list == NULL)
159 		return;
160 
161 	for (cur = list; cur != NULL; cur = next) {
162 		next = cur->next;
163 		cond_node_destroy(cur);
164 	}
165 }
166 
167 void cond_policydb_destroy(struct policydb *p)
168 {
169 	kfree(p->bool_val_to_struct);
170 	avtab_destroy(&p->te_cond_avtab);
171 	cond_list_destroy(p->cond_list);
172 }
173 
174 int cond_init_bool_indexes(struct policydb *p)
175 {
176 	kfree(p->bool_val_to_struct);
177 	p->bool_val_to_struct = (struct cond_bool_datum**)
178 		kmalloc(p->p_bools.nprim * sizeof(struct cond_bool_datum*), GFP_KERNEL);
179 	if (!p->bool_val_to_struct)
180 		return -1;
181 	return 0;
182 }
183 
184 int cond_destroy_bool(void *key, void *datum, void *p)
185 {
186 	kfree(key);
187 	kfree(datum);
188 	return 0;
189 }
190 
191 int cond_index_bool(void *key, void *datum, void *datap)
192 {
193 	struct policydb *p;
194 	struct cond_bool_datum *booldatum;
195 
196 	booldatum = datum;
197 	p = datap;
198 
199 	if (!booldatum->value || booldatum->value > p->p_bools.nprim)
200 		return -EINVAL;
201 
202 	p->p_bool_val_to_name[booldatum->value - 1] = key;
203 	p->bool_val_to_struct[booldatum->value -1] = booldatum;
204 
205 	return 0;
206 }
207 
208 static int bool_isvalid(struct cond_bool_datum *b)
209 {
210 	if (!(b->state == 0 || b->state == 1))
211 		return 0;
212 	return 1;
213 }
214 
215 int cond_read_bool(struct policydb *p, struct hashtab *h, void *fp)
216 {
217 	char *key = NULL;
218 	struct cond_bool_datum *booldatum;
219 	__le32 buf[3];
220 	u32 len;
221 	int rc;
222 
223 	booldatum = kzalloc(sizeof(struct cond_bool_datum), GFP_KERNEL);
224 	if (!booldatum)
225 		return -1;
226 
227 	rc = next_entry(buf, fp, sizeof buf);
228 	if (rc < 0)
229 		goto err;
230 
231 	booldatum->value = le32_to_cpu(buf[0]);
232 	booldatum->state = le32_to_cpu(buf[1]);
233 
234 	if (!bool_isvalid(booldatum))
235 		goto err;
236 
237 	len = le32_to_cpu(buf[2]);
238 
239 	key = kmalloc(len + 1, GFP_KERNEL);
240 	if (!key)
241 		goto err;
242 	rc = next_entry(key, fp, len);
243 	if (rc < 0)
244 		goto err;
245 	key[len] = 0;
246 	if (hashtab_insert(h, key, booldatum))
247 		goto err;
248 
249 	return 0;
250 err:
251 	cond_destroy_bool(key, booldatum, NULL);
252 	return -1;
253 }
254 
255 struct cond_insertf_data
256 {
257 	struct policydb *p;
258 	struct cond_av_list *other;
259 	struct cond_av_list *head;
260 	struct cond_av_list *tail;
261 };
262 
263 static int cond_insertf(struct avtab *a, struct avtab_key *k, struct avtab_datum *d, void *ptr)
264 {
265 	struct cond_insertf_data *data = ptr;
266 	struct policydb *p = data->p;
267 	struct cond_av_list *other = data->other, *list, *cur;
268 	struct avtab_node *node_ptr;
269 	u8 found;
270 
271 
272 	/*
273 	 * For type rules we have to make certain there aren't any
274 	 * conflicting rules by searching the te_avtab and the
275 	 * cond_te_avtab.
276 	 */
277 	if (k->specified & AVTAB_TYPE) {
278 		if (avtab_search(&p->te_avtab, k)) {
279 			printk("security: type rule already exists outside of a conditional.");
280 			goto err;
281 		}
282 		/*
283 		 * If we are reading the false list other will be a pointer to
284 		 * the true list. We can have duplicate entries if there is only
285 		 * 1 other entry and it is in our true list.
286 		 *
287 		 * If we are reading the true list (other == NULL) there shouldn't
288 		 * be any other entries.
289 		 */
290 		if (other) {
291 			node_ptr = avtab_search_node(&p->te_cond_avtab, k);
292 			if (node_ptr) {
293 				if (avtab_search_node_next(node_ptr, k->specified)) {
294 					printk("security: too many conflicting type rules.");
295 					goto err;
296 				}
297 				found = 0;
298 				for (cur = other; cur != NULL; cur = cur->next) {
299 					if (cur->node == node_ptr) {
300 						found = 1;
301 						break;
302 					}
303 				}
304 				if (!found) {
305 					printk("security: conflicting type rules.\n");
306 					goto err;
307 				}
308 			}
309 		} else {
310 			if (avtab_search(&p->te_cond_avtab, k)) {
311 				printk("security: conflicting type rules when adding type rule for true.\n");
312 				goto err;
313 			}
314 		}
315 	}
316 
317 	node_ptr = avtab_insert_nonunique(&p->te_cond_avtab, k, d);
318 	if (!node_ptr) {
319 		printk("security: could not insert rule.");
320 		goto err;
321 	}
322 
323 	list = kzalloc(sizeof(struct cond_av_list), GFP_KERNEL);
324 	if (!list)
325 		goto err;
326 
327 	list->node = node_ptr;
328 	if (!data->head)
329 		data->head = list;
330 	else
331 		data->tail->next = list;
332 	data->tail = list;
333 	return 0;
334 
335 err:
336 	cond_av_list_destroy(data->head);
337 	data->head = NULL;
338 	return -1;
339 }
340 
341 static int cond_read_av_list(struct policydb *p, void *fp, struct cond_av_list **ret_list, struct cond_av_list *other)
342 {
343 	int i, rc;
344 	__le32 buf[1];
345 	u32 len;
346 	struct cond_insertf_data data;
347 
348 	*ret_list = NULL;
349 
350 	len = 0;
351 	rc = next_entry(buf, fp, sizeof(u32));
352 	if (rc < 0)
353 		return -1;
354 
355 	len = le32_to_cpu(buf[0]);
356 	if (len == 0) {
357 		return 0;
358 	}
359 
360 	data.p = p;
361 	data.other = other;
362 	data.head = NULL;
363 	data.tail = NULL;
364 	for (i = 0; i < len; i++) {
365 		rc = avtab_read_item(fp, p->policyvers, &p->te_cond_avtab, cond_insertf, &data);
366 		if (rc)
367 			return rc;
368 
369 	}
370 
371 	*ret_list = data.head;
372 	return 0;
373 }
374 
375 static int expr_isvalid(struct policydb *p, struct cond_expr *expr)
376 {
377 	if (expr->expr_type <= 0 || expr->expr_type > COND_LAST) {
378 		printk("security: conditional expressions uses unknown operator.\n");
379 		return 0;
380 	}
381 
382 	if (expr->bool > p->p_bools.nprim) {
383 		printk("security: conditional expressions uses unknown bool.\n");
384 		return 0;
385 	}
386 	return 1;
387 }
388 
389 static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
390 {
391 	__le32 buf[2];
392 	u32 len, i;
393 	int rc;
394 	struct cond_expr *expr = NULL, *last = NULL;
395 
396 	rc = next_entry(buf, fp, sizeof(u32));
397 	if (rc < 0)
398 		return -1;
399 
400 	node->cur_state = le32_to_cpu(buf[0]);
401 
402 	len = 0;
403 	rc = next_entry(buf, fp, sizeof(u32));
404 	if (rc < 0)
405 		return -1;
406 
407 	/* expr */
408 	len = le32_to_cpu(buf[0]);
409 
410 	for (i = 0; i < len; i++ ) {
411 		rc = next_entry(buf, fp, sizeof(u32) * 2);
412 		if (rc < 0)
413 			goto err;
414 
415 		expr = kzalloc(sizeof(struct cond_expr), GFP_KERNEL);
416 		if (!expr) {
417 			goto err;
418 		}
419 
420 		expr->expr_type = le32_to_cpu(buf[0]);
421 		expr->bool = le32_to_cpu(buf[1]);
422 
423 		if (!expr_isvalid(p, expr)) {
424 			kfree(expr);
425 			goto err;
426 		}
427 
428 		if (i == 0) {
429 			node->expr = expr;
430 		} else {
431 			last->next = expr;
432 		}
433 		last = expr;
434 	}
435 
436 	if (cond_read_av_list(p, fp, &node->true_list, NULL) != 0)
437 		goto err;
438 	if (cond_read_av_list(p, fp, &node->false_list, node->true_list) != 0)
439 		goto err;
440 	return 0;
441 err:
442 	cond_node_destroy(node);
443 	return -1;
444 }
445 
446 int cond_read_list(struct policydb *p, void *fp)
447 {
448 	struct cond_node *node, *last = NULL;
449 	__le32 buf[1];
450 	u32 i, len;
451 	int rc;
452 
453 	rc = next_entry(buf, fp, sizeof buf);
454 	if (rc < 0)
455 		return -1;
456 
457 	len = le32_to_cpu(buf[0]);
458 
459 	for (i = 0; i < len; i++) {
460 		node = kzalloc(sizeof(struct cond_node), GFP_KERNEL);
461 		if (!node)
462 			goto err;
463 
464 		if (cond_read_node(p, node, fp) != 0)
465 			goto err;
466 
467 		if (i == 0) {
468 			p->cond_list = node;
469 		} else {
470 			last->next = node;
471 		}
472 		last = node;
473 	}
474 	return 0;
475 err:
476 	cond_list_destroy(p->cond_list);
477 	p->cond_list = NULL;
478 	return -1;
479 }
480 
481 /* Determine whether additional permissions are granted by the conditional
482  * av table, and if so, add them to the result
483  */
484 void cond_compute_av(struct avtab *ctab, struct avtab_key *key, struct av_decision *avd)
485 {
486 	struct avtab_node *node;
487 
488 	if(!ctab || !key || !avd)
489 		return;
490 
491 	for(node = avtab_search_node(ctab, key); node != NULL;
492 				node = avtab_search_node_next(node, key->specified)) {
493 		if ( (u16) (AVTAB_ALLOWED|AVTAB_ENABLED) ==
494 		     (node->key.specified & (AVTAB_ALLOWED|AVTAB_ENABLED)))
495 			avd->allowed |= node->datum.data;
496 		if ( (u16) (AVTAB_AUDITDENY|AVTAB_ENABLED) ==
497 		     (node->key.specified & (AVTAB_AUDITDENY|AVTAB_ENABLED)))
498 			/* Since a '0' in an auditdeny mask represents a
499 			 * permission we do NOT want to audit (dontaudit), we use
500 			 * the '&' operand to ensure that all '0's in the mask
501 			 * are retained (much unlike the allow and auditallow cases).
502 			 */
503 			avd->auditdeny &= node->datum.data;
504 		if ( (u16) (AVTAB_AUDITALLOW|AVTAB_ENABLED) ==
505 		     (node->key.specified & (AVTAB_AUDITALLOW|AVTAB_ENABLED)))
506 			avd->auditallow |= node->datum.data;
507 	}
508 	return;
509 }
510