xref: /linux/security/selinux/ss/avtab.c (revision d5859510d35d8e7d63fed5169f1775317f40fb03) 
1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3  * Implementation of the access vector table type.
4  *
5  * Author : Stephen Smalley, <stephen.smalley.work@gmail.com>
6  */
7 
8 /* Updated: Frank Mayer <mayerf@tresys.com> and
9  *          Karl MacMillan <kmacmillan@tresys.com>
10  *          Added conditional policy language extensions
11  *          Copyright (C) 2003 Tresys Technology, LLC
12  *
13  * Updated: Yuichi Nakamura <ynakam@hitachisoft.jp>
14  *          Tuned number of hash slots for avtab to reduce memory usage
15  */
16 
17 #include <linux/bitops.h>
18 #include <linux/kernel.h>
19 #include <linux/slab.h>
20 #include <linux/errno.h>
21 #include "avtab.h"
22 #include "policydb.h"
23 
24 static struct kmem_cache *avtab_node_cachep __ro_after_init;
25 static struct kmem_cache *avtab_xperms_cachep __ro_after_init;
26 
27 /* Based on MurmurHash3, written by Austin Appleby and placed in the
28  * public domain.
29  */
30 static inline u32 avtab_hash(const struct avtab_key *keyp, u32 mask)
31 {
32 	static const u32 c1 = 0xcc9e2d51;
33 	static const u32 c2 = 0x1b873593;
34 	static const u32 r1 = 15;
35 	static const u32 r2 = 13;
36 	static const u32 m = 5;
37 	static const u32 n = 0xe6546b64;
38 
39 	u32 hash = 0;
40 
41 #define mix(input)                                         \
42 	do {                                               \
43 		u32 v = input;                             \
44 		v *= c1;                                   \
45 		v = (v << r1) | (v >> (32 - r1));          \
46 		v *= c2;                                   \
47 		hash ^= v;                                 \
48 		hash = (hash << r2) | (hash >> (32 - r2)); \
49 		hash = hash * m + n;                       \
50 	} while (0)
51 
52 	mix(keyp->target_class);
53 	mix(keyp->target_type);
54 	mix(keyp->source_type);
55 
56 #undef mix
57 
58 	hash ^= hash >> 16;
59 	hash *= 0x85ebca6b;
60 	hash ^= hash >> 13;
61 	hash *= 0xc2b2ae35;
62 	hash ^= hash >> 16;
63 
64 	return hash & mask;
65 }
66 
67 static struct avtab_node *avtab_insert_node(struct avtab *h,
68 					    struct avtab_node **dst,
69 					    const struct avtab_key *key,
70 					    const struct avtab_datum *datum)
71 {
72 	struct avtab_node *newnode;
73 	struct avtab_extended_perms *xperms;
74 	newnode = kmem_cache_zalloc(avtab_node_cachep, GFP_KERNEL);
75 	if (newnode == NULL)
76 		return NULL;
77 	newnode->key = *key;
78 
79 	if (key->specified & AVTAB_XPERMS) {
80 		xperms = kmem_cache_zalloc(avtab_xperms_cachep, GFP_KERNEL);
81 		if (xperms == NULL) {
82 			kmem_cache_free(avtab_node_cachep, newnode);
83 			return NULL;
84 		}
85 		*xperms = *(datum->u.xperms);
86 		newnode->datum.u.xperms = xperms;
87 	} else {
88 		newnode->datum.u.data = datum->u.data;
89 	}
90 
91 	newnode->next = *dst;
92 	*dst = newnode;
93 
94 	h->nel++;
95 	return newnode;
96 }
97 
98 static int avtab_node_cmp(const struct avtab_key *key1,
99 			  const struct avtab_key *key2)
100 {
101 	u16 specified = key1->specified & ~(AVTAB_ENABLED | AVTAB_ENABLED_OLD);
102 
103 	if (key1->source_type == key2->source_type &&
104 	    key1->target_type == key2->target_type &&
105 	    key1->target_class == key2->target_class &&
106 	    (specified & key2->specified))
107 		return 0;
108 	if (key1->source_type < key2->source_type)
109 		return -1;
110 	if (key1->source_type == key2->source_type &&
111 	    key1->target_type < key2->target_type)
112 		return -1;
113 	if (key1->source_type == key2->source_type &&
114 	    key1->target_type == key2->target_type &&
115 	    key1->target_class < key2->target_class)
116 		return -1;
117 	return 1;
118 }
119 
120 static int avtab_insert(struct avtab *h, const struct avtab_key *key,
121 			const struct avtab_datum *datum)
122 {
123 	u32 hvalue;
124 	struct avtab_node *prev, *cur, *newnode;
125 	int cmp;
126 
127 	if (!h || !h->nslot || h->nel == U32_MAX)
128 		return -EINVAL;
129 
130 	hvalue = avtab_hash(key, h->mask);
131 	for (prev = NULL, cur = h->htable[hvalue]; cur;
132 	     prev = cur, cur = cur->next) {
133 		cmp = avtab_node_cmp(key, &cur->key);
134 		/* extended perms may not be unique */
135 		if (cmp == 0 && !(key->specified & AVTAB_XPERMS))
136 			return -EEXIST;
137 		if (cmp <= 0)
138 			break;
139 	}
140 
141 	newnode = avtab_insert_node(h, prev ? &prev->next : &h->htable[hvalue],
142 				    key, datum);
143 	if (!newnode)
144 		return -ENOMEM;
145 
146 	return 0;
147 }
148 
149 /* Unlike avtab_insert(), this function allow multiple insertions of the same
150  * key/specified mask into the table, as needed by the conditional avtab.
151  * It also returns a pointer to the node inserted.
152  */
153 struct avtab_node *avtab_insert_nonunique(struct avtab *h,
154 					  const struct avtab_key *key,
155 					  const struct avtab_datum *datum)
156 {
157 	u32 hvalue;
158 	struct avtab_node *prev, *cur;
159 	int cmp;
160 
161 	if (!h || !h->nslot || h->nel == U32_MAX)
162 		return NULL;
163 	hvalue = avtab_hash(key, h->mask);
164 	for (prev = NULL, cur = h->htable[hvalue]; cur;
165 	     prev = cur, cur = cur->next) {
166 		cmp = avtab_node_cmp(key, &cur->key);
167 		if (cmp <= 0)
168 			break;
169 	}
170 	return avtab_insert_node(h, prev ? &prev->next : &h->htable[hvalue],
171 				 key, datum);
172 }
173 
174 /* This search function returns a node pointer, and can be used in
175  * conjunction with avtab_search_next_node()
176  */
177 struct avtab_node *avtab_search_node(struct avtab *h,
178 				     const struct avtab_key *key)
179 {
180 	u32 hvalue;
181 	struct avtab_node *cur;
182 	int cmp;
183 
184 	if (!h || !h->nslot)
185 		return NULL;
186 
187 	hvalue = avtab_hash(key, h->mask);
188 	for (cur = h->htable[hvalue]; cur; cur = cur->next) {
189 		cmp = avtab_node_cmp(key, &cur->key);
190 		if (cmp == 0)
191 			return cur;
192 		if (cmp < 0)
193 			break;
194 	}
195 	return NULL;
196 }
197 
198 struct avtab_node *avtab_search_node_next(struct avtab_node *node,
199 					  u16 specified)
200 {
201 	struct avtab_key tmp_key;
202 	struct avtab_node *cur;
203 	int cmp;
204 
205 	if (!node)
206 		return NULL;
207 	tmp_key = node->key;
208 	tmp_key.specified = specified;
209 	for (cur = node->next; cur; cur = cur->next) {
210 		cmp = avtab_node_cmp(&tmp_key, &cur->key);
211 		if (cmp == 0)
212 			return cur;
213 		if (cmp < 0)
214 			break;
215 	}
216 	return NULL;
217 }
218 
219 void avtab_destroy(struct avtab *h)
220 {
221 	u32 i;
222 	struct avtab_node *cur, *temp;
223 
224 	if (!h)
225 		return;
226 
227 	for (i = 0; i < h->nslot; i++) {
228 		cur = h->htable[i];
229 		while (cur) {
230 			temp = cur;
231 			cur = cur->next;
232 			if (temp->key.specified & AVTAB_XPERMS)
233 				kmem_cache_free(avtab_xperms_cachep,
234 						temp->datum.u.xperms);
235 			kmem_cache_free(avtab_node_cachep, temp);
236 		}
237 	}
238 	kvfree(h->htable);
239 	h->htable = NULL;
240 	h->nel = 0;
241 	h->nslot = 0;
242 	h->mask = 0;
243 }
244 
245 void avtab_init(struct avtab *h)
246 {
247 	h->htable = NULL;
248 	h->nel = 0;
249 	h->nslot = 0;
250 	h->mask = 0;
251 }
252 
253 static int avtab_alloc_common(struct avtab *h, u32 nslot)
254 {
255 	if (!nslot)
256 		return 0;
257 
258 	h->htable = kvcalloc(nslot, sizeof(void *), GFP_KERNEL);
259 	if (!h->htable)
260 		return -ENOMEM;
261 
262 	h->nslot = nslot;
263 	h->mask = nslot - 1;
264 	return 0;
265 }
266 
267 int avtab_alloc(struct avtab *h, u32 nrules)
268 {
269 	int rc;
270 	u32 nslot = 0;
271 
272 	if (nrules != 0) {
273 		nslot = nrules > 3 ? rounddown_pow_of_two(nrules / 2) : 2;
274 		if (nslot > MAX_AVTAB_HASH_BUCKETS)
275 			nslot = MAX_AVTAB_HASH_BUCKETS;
276 
277 		rc = avtab_alloc_common(h, nslot);
278 		if (rc)
279 			return rc;
280 	}
281 
282 	pr_debug("SELinux: %d avtab hash slots, %d rules.\n", nslot, nrules);
283 	return 0;
284 }
285 
286 int avtab_alloc_dup(struct avtab *new, const struct avtab *orig)
287 {
288 	return avtab_alloc_common(new, orig->nslot);
289 }
290 
291 #ifdef CONFIG_SECURITY_SELINUX_DEBUG
292 void avtab_hash_eval(struct avtab *h, const char *tag)
293 {
294 	u32 i, chain_len, slots_used, max_chain_len;
295 	unsigned long long chain2_len_sum;
296 	struct avtab_node *cur;
297 
298 	slots_used = 0;
299 	max_chain_len = 0;
300 	chain2_len_sum = 0;
301 	for (i = 0; i < h->nslot; i++) {
302 		cur = h->htable[i];
303 		if (cur) {
304 			slots_used++;
305 			chain_len = 0;
306 			while (cur) {
307 				chain_len++;
308 				cur = cur->next;
309 			}
310 
311 			if (chain_len > max_chain_len)
312 				max_chain_len = chain_len;
313 			chain2_len_sum +=
314 				(unsigned long long)chain_len * chain_len;
315 		}
316 	}
317 
318 	pr_debug("SELinux: %s:  %d entries and %d/%d buckets used, "
319 		 "longest chain length %d, sum of chain length^2 %llu\n",
320 		 tag, h->nel, slots_used, h->nslot, max_chain_len,
321 		 chain2_len_sum);
322 }
323 #endif /* CONFIG_SECURITY_SELINUX_DEBUG */
324 
325 /* clang-format off */
326 static const uint16_t spec_order[] = {
327 	AVTAB_ALLOWED,
328 	AVTAB_AUDITDENY,
329 	AVTAB_AUDITALLOW,
330 	AVTAB_TRANSITION,
331 	AVTAB_CHANGE,
332 	AVTAB_MEMBER,
333 	AVTAB_XPERMS_ALLOWED,
334 	AVTAB_XPERMS_AUDITALLOW,
335 	AVTAB_XPERMS_DONTAUDIT
336 };
337 /* clang-format on */
338 
339 int avtab_read_item(struct avtab *a, void *fp, struct policydb *pol,
340 		    int (*insertf)(struct avtab *a, const struct avtab_key *k,
341 				   const struct avtab_datum *d, void *p),
342 		    void *p)
343 {
344 	__le16 buf16[4];
345 	u16 enabled;
346 	u32 items, items2, val, i;
347 	struct avtab_key key;
348 	struct avtab_datum datum;
349 	struct avtab_extended_perms xperms;
350 	__le32 buf32[ARRAY_SIZE(xperms.perms.p)];
351 	int rc;
352 	unsigned int set, vers = pol->policyvers;
353 
354 	memset(&key, 0, sizeof(struct avtab_key));
355 	memset(&datum, 0, sizeof(struct avtab_datum));
356 
357 	if (vers < POLICYDB_VERSION_AVTAB) {
358 		rc = next_entry(buf32, fp, sizeof(u32));
359 		if (rc) {
360 			pr_err("SELinux: avtab: truncated entry\n");
361 			return rc;
362 		}
363 		items2 = le32_to_cpu(buf32[0]);
364 		if (items2 > ARRAY_SIZE(buf32)) {
365 			pr_err("SELinux: avtab: entry overflow\n");
366 			return -EINVAL;
367 		}
368 		rc = next_entry(buf32, fp, sizeof(u32) * items2);
369 		if (rc) {
370 			pr_err("SELinux: avtab: truncated entry\n");
371 			return rc;
372 		}
373 		items = 0;
374 
375 		val = le32_to_cpu(buf32[items++]);
376 		key.source_type = (u16)val;
377 		if (key.source_type != val) {
378 			pr_err("SELinux: avtab: truncated source type\n");
379 			return -EINVAL;
380 		}
381 		val = le32_to_cpu(buf32[items++]);
382 		key.target_type = (u16)val;
383 		if (key.target_type != val) {
384 			pr_err("SELinux: avtab: truncated target type\n");
385 			return -EINVAL;
386 		}
387 		val = le32_to_cpu(buf32[items++]);
388 		key.target_class = (u16)val;
389 		if (key.target_class != val) {
390 			pr_err("SELinux: avtab: truncated target class\n");
391 			return -EINVAL;
392 		}
393 
394 		val = le32_to_cpu(buf32[items++]);
395 		enabled = (val & AVTAB_ENABLED_OLD) ? AVTAB_ENABLED : 0;
396 
397 		if (!(val & (AVTAB_AV | AVTAB_TYPE))) {
398 			pr_err("SELinux: avtab: null entry\n");
399 			return -EINVAL;
400 		}
401 		if ((val & AVTAB_AV) && (val & AVTAB_TYPE)) {
402 			pr_err("SELinux: avtab: entry has both access vectors and types\n");
403 			return -EINVAL;
404 		}
405 		if (val & AVTAB_XPERMS) {
406 			pr_err("SELinux: avtab: entry has extended permissions\n");
407 			return -EINVAL;
408 		}
409 
410 		for (i = 0; i < ARRAY_SIZE(spec_order); i++) {
411 			if (val & spec_order[i]) {
412 				key.specified = spec_order[i] | enabled;
413 				datum.u.data = le32_to_cpu(buf32[items++]);
414 				rc = insertf(a, &key, &datum, p);
415 				if (rc)
416 					return rc;
417 			}
418 		}
419 
420 		if (items != items2) {
421 			pr_err("SELinux: avtab: entry only had %d items, expected %d\n",
422 			       items2, items);
423 			return -EINVAL;
424 		}
425 		return 0;
426 	}
427 
428 	rc = next_entry(buf16, fp, sizeof(u16) * 4);
429 	if (rc) {
430 		pr_err("SELinux: avtab: truncated entry\n");
431 		return rc;
432 	}
433 
434 	items = 0;
435 	key.source_type = le16_to_cpu(buf16[items++]);
436 	key.target_type = le16_to_cpu(buf16[items++]);
437 	key.target_class = le16_to_cpu(buf16[items++]);
438 	key.specified = le16_to_cpu(buf16[items++]);
439 
440 	if (!policydb_type_isvalid(pol, key.source_type) ||
441 	    !policydb_type_isvalid(pol, key.target_type) ||
442 	    !policydb_class_isvalid(pol, key.target_class)) {
443 		pr_err("SELinux: avtab: invalid type or class\n");
444 		return -EINVAL;
445 	}
446 
447 	set = hweight16(key.specified & (AVTAB_XPERMS | AVTAB_TYPE | AVTAB_AV));
448 	if (!set || set > 1) {
449 		pr_err("SELinux:  avtab:  more than one specifier\n");
450 		return -EINVAL;
451 	}
452 
453 	if ((vers < POLICYDB_VERSION_XPERMS_IOCTL) &&
454 	    (key.specified & AVTAB_XPERMS)) {
455 		pr_err("SELinux:  avtab:  policy version %u does not "
456 		       "support extended permissions rules and one "
457 		       "was specified\n",
458 		       vers);
459 		return -EINVAL;
460 	} else if (key.specified & AVTAB_XPERMS) {
461 		memset(&xperms, 0, sizeof(struct avtab_extended_perms));
462 		rc = next_entry(&xperms.specified, fp, sizeof(u8));
463 		if (rc) {
464 			pr_err("SELinux: avtab: truncated entry\n");
465 			return rc;
466 		}
467 		rc = next_entry(&xperms.driver, fp, sizeof(u8));
468 		if (rc) {
469 			pr_err("SELinux: avtab: truncated entry\n");
470 			return rc;
471 		}
472 		rc = next_entry(buf32, fp,
473 				sizeof(u32) * ARRAY_SIZE(xperms.perms.p));
474 		if (rc) {
475 			pr_err("SELinux: avtab: truncated entry\n");
476 			return rc;
477 		}
478 		for (i = 0; i < ARRAY_SIZE(xperms.perms.p); i++)
479 			xperms.perms.p[i] = le32_to_cpu(buf32[i]);
480 		datum.u.xperms = &xperms;
481 	} else {
482 		rc = next_entry(buf32, fp, sizeof(u32));
483 		if (rc) {
484 			pr_err("SELinux: avtab: truncated entry\n");
485 			return rc;
486 		}
487 		datum.u.data = le32_to_cpu(*buf32);
488 	}
489 	if ((key.specified & AVTAB_TYPE) &&
490 	    !policydb_type_isvalid(pol, datum.u.data)) {
491 		pr_err("SELinux: avtab: invalid type\n");
492 		return -EINVAL;
493 	}
494 	return insertf(a, &key, &datum, p);
495 }
496 
497 static int avtab_insertf(struct avtab *a, const struct avtab_key *k,
498 			 const struct avtab_datum *d, void *p)
499 {
500 	return avtab_insert(a, k, d);
501 }
502 
503 int avtab_read(struct avtab *a, void *fp, struct policydb *pol)
504 {
505 	int rc;
506 	__le32 buf[1];
507 	u32 nel, i;
508 
509 	rc = next_entry(buf, fp, sizeof(u32));
510 	if (rc < 0) {
511 		pr_err("SELinux: avtab: truncated table\n");
512 		goto bad;
513 	}
514 	nel = le32_to_cpu(buf[0]);
515 	if (!nel) {
516 		pr_err("SELinux: avtab: table is empty\n");
517 		rc = -EINVAL;
518 		goto bad;
519 	}
520 
521 	rc = avtab_alloc(a, nel);
522 	if (rc)
523 		goto bad;
524 
525 	for (i = 0; i < nel; i++) {
526 		rc = avtab_read_item(a, fp, pol, avtab_insertf, NULL);
527 		if (rc) {
528 			if (rc == -ENOMEM)
529 				pr_err("SELinux: avtab: out of memory\n");
530 			else if (rc == -EEXIST)
531 				pr_err("SELinux: avtab: duplicate entry\n");
532 
533 			goto bad;
534 		}
535 	}
536 
537 	rc = 0;
538 out:
539 	return rc;
540 
541 bad:
542 	avtab_destroy(a);
543 	goto out;
544 }
545 
546 int avtab_write_item(struct policydb *p, const struct avtab_node *cur, void *fp)
547 {
548 	__le16 buf16[4];
549 	__le32 buf32[ARRAY_SIZE(cur->datum.u.xperms->perms.p)];
550 	int rc;
551 	unsigned int i;
552 
553 	buf16[0] = cpu_to_le16(cur->key.source_type);
554 	buf16[1] = cpu_to_le16(cur->key.target_type);
555 	buf16[2] = cpu_to_le16(cur->key.target_class);
556 	buf16[3] = cpu_to_le16(cur->key.specified);
557 	rc = put_entry(buf16, sizeof(u16), 4, fp);
558 	if (rc)
559 		return rc;
560 
561 	if (cur->key.specified & AVTAB_XPERMS) {
562 		rc = put_entry(&cur->datum.u.xperms->specified, sizeof(u8), 1,
563 			       fp);
564 		if (rc)
565 			return rc;
566 		rc = put_entry(&cur->datum.u.xperms->driver, sizeof(u8), 1, fp);
567 		if (rc)
568 			return rc;
569 		for (i = 0; i < ARRAY_SIZE(cur->datum.u.xperms->perms.p); i++)
570 			buf32[i] = cpu_to_le32(cur->datum.u.xperms->perms.p[i]);
571 		rc = put_entry(buf32, sizeof(u32),
572 			       ARRAY_SIZE(cur->datum.u.xperms->perms.p), fp);
573 	} else {
574 		buf32[0] = cpu_to_le32(cur->datum.u.data);
575 		rc = put_entry(buf32, sizeof(u32), 1, fp);
576 	}
577 	if (rc)
578 		return rc;
579 	return 0;
580 }
581 
582 int avtab_write(struct policydb *p, struct avtab *a, void *fp)
583 {
584 	u32 i;
585 	int rc = 0;
586 	struct avtab_node *cur;
587 	__le32 buf[1];
588 
589 	buf[0] = cpu_to_le32(a->nel);
590 	rc = put_entry(buf, sizeof(u32), 1, fp);
591 	if (rc)
592 		return rc;
593 
594 	for (i = 0; i < a->nslot; i++) {
595 		for (cur = a->htable[i]; cur; cur = cur->next) {
596 			rc = avtab_write_item(p, cur, fp);
597 			if (rc)
598 				return rc;
599 		}
600 	}
601 
602 	return rc;
603 }
604 
605 void __init avtab_cache_init(void)
606 {
607 	avtab_node_cachep = kmem_cache_create(
608 		"avtab_node", sizeof(struct avtab_node), 0, SLAB_PANIC, NULL);
609 	avtab_xperms_cachep = kmem_cache_create(
610 		"avtab_extended_perms", sizeof(struct avtab_extended_perms), 0,
611 		SLAB_PANIC, NULL);
612 }
613