Free Electrons

Embedded Linux Experts

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
/*
 * Implementation of the multi-level security (MLS) policy.
 *
 * Author : Stephen Smalley, <sds@epoch.ncsc.mil>
 */
/*
 * Updated: Trusted Computer Solutions, Inc. <dgoeddel@trustedcs.com>
 *
 *	Support for enhanced MLS infrastructure.
 *
 * Copyright (C) 2004-2006 Trusted Computer Solutions, Inc.
 */
/*
 * Updated: Hewlett-Packard <paul@paul-moore.com>
 *
 *      Added support to import/export the MLS label from NetLabel
 *
 * (c) Copyright Hewlett-Packard Development Company, L.P., 2006
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <net/netlabel.h>
#include "sidtab.h"
#include "mls.h"
#include "policydb.h"
#include "services.h"

/*
 * Return the length in bytes for the MLS fields of the
 * security context string representation of `context'.
 */
int mls_compute_context_len(struct context *context)
{
	int i, l, len, head, prev;
	char *nm;
	struct ebitmap *e;
	struct ebitmap_node *node;

	if (!policydb.mls_enabled)
		return 0;

	len = 1; /* for the beginning ":" */
	for (l = 0; l < 2; l++) {
		int index_sens = context->range.level[l].sens;
		len += strlen(sym_name(&policydb, SYM_LEVELS, index_sens - 1));

		/* categories */
		head = -2;
		prev = -2;
		e = &context->range.level[l].cat;
		ebitmap_for_each_positive_bit(e, node, i) {
			if (i - prev > 1) {
				/* one or more negative bits are skipped */
				if (head != prev) {
					nm = sym_name(&policydb, SYM_CATS, prev);
					len += strlen(nm) + 1;
				}
				nm = sym_name(&policydb, SYM_CATS, i);
				len += strlen(nm) + 1;
				head = i;
			}
			prev = i;
		}
		if (prev != head) {
			nm = sym_name(&policydb, SYM_CATS, prev);
			len += strlen(nm) + 1;
		}
		if (l == 0) {
			if (mls_level_eq(&context->range.level[0],
					 &context->range.level[1]))
				break;
			else
				len++;
		}
	}

	return len;
}

/*
 * Write the security context string representation of
 * the MLS fields of `context' into the string `*scontext'.
 * Update `*scontext' to point to the end of the MLS fields.
 */
void mls_sid_to_context(struct context *context,
			char **scontext)
{
	char *scontextp, *nm;
	int i, l, head, prev;
	struct ebitmap *e;
	struct ebitmap_node *node;

	if (!policydb.mls_enabled)
		return;

	scontextp = *scontext;

	*scontextp = ':';
	scontextp++;

	for (l = 0; l < 2; l++) {
		strcpy(scontextp, sym_name(&policydb, SYM_LEVELS,
					   context->range.level[l].sens - 1));
		scontextp += strlen(scontextp);

		/* categories */
		head = -2;
		prev = -2;
		e = &context->range.level[l].cat;
		ebitmap_for_each_positive_bit(e, node, i) {
			if (i - prev > 1) {
				/* one or more negative bits are skipped */
				if (prev != head) {
					if (prev - head > 1)
						*scontextp++ = '.';
					else
						*scontextp++ = ',';
					nm = sym_name(&policydb, SYM_CATS, prev);
					strcpy(scontextp, nm);
					scontextp += strlen(nm);
				}
				if (prev < 0)
					*scontextp++ = ':';
				else
					*scontextp++ = ',';
				nm = sym_name(&policydb, SYM_CATS, i);
				strcpy(scontextp, nm);
				scontextp += strlen(nm);
				head = i;
			}
			prev = i;
		}

		if (prev != head) {
			if (prev - head > 1)
				*scontextp++ = '.';
			else
				*scontextp++ = ',';
			nm = sym_name(&policydb, SYM_CATS, prev);
			strcpy(scontextp, nm);
			scontextp += strlen(nm);
		}

		if (l == 0) {
			if (mls_level_eq(&context->range.level[0],
					 &context->range.level[1]))
				break;
			else
				*scontextp++ = '-';
		}
	}

	*scontext = scontextp;
	return;
}

int mls_level_isvalid(struct policydb *p, struct mls_level *l)
{
	struct level_datum *levdatum;
	struct ebitmap_node *node;
	int i;

	if (!l->sens || l->sens > p->p_levels.nprim)
		return 0;
	levdatum = hashtab_search(p->p_levels.table,
				  sym_name(p, SYM_LEVELS, l->sens - 1));
	if (!levdatum)
		return 0;

	ebitmap_for_each_positive_bit(&l->cat, node, i) {
		if (i > p->p_cats.nprim)
			return 0;
		if (!ebitmap_get_bit(&levdatum->level->cat, i)) {
			/*
			 * Category may not be associated with
			 * sensitivity.
			 */
			return 0;
		}
	}

	return 1;
}

int mls_range_isvalid(struct policydb *p, struct mls_range *r)
{
	return (mls_level_isvalid(p, &r->level[0]) &&
		mls_level_isvalid(p, &r->level[1]) &&
		mls_level_dom(&r->level[1], &r->level[0]));
}

/*
 * Return 1 if the MLS fields in the security context
 * structure `c' are valid.  Return 0 otherwise.
 */
int mls_context_isvalid(struct policydb *p, struct context *c)
{
	struct user_datum *usrdatum;

	if (!p->mls_enabled)
		return 1;

	if (!mls_range_isvalid(p, &c->range))
		return 0;

	if (c->role == OBJECT_R_VAL)
		return 1;

	/*
	 * User must be authorized for the MLS range.
	 */
	if (!c->user || c->user > p->p_users.nprim)
		return 0;
	usrdatum = p->user_val_to_struct[c->user - 1];
	if (!mls_range_contains(usrdatum->range, c->range))
		return 0; /* user may not be associated with range */

	return 1;
}

/*
 * Set the MLS fields in the security context structure
 * `context' based on the string representation in
 * the string `*scontext'.  Update `*scontext' to
 * point to the end of the string representation of
 * the MLS fields.
 *
 * This function modifies the string in place, inserting
 * NULL characters to terminate the MLS fields.
 *
 * If a def_sid is provided and no MLS field is present,
 * copy the MLS field of the associated default context.
 * Used for upgraded to MLS systems where objects may lack
 * MLS fields.
 *
 * Policy read-lock must be held for sidtab lookup.
 *
 */
int mls_context_to_sid(struct policydb *pol,
		       char oldc,
		       char **scontext,
		       struct context *context,
		       struct sidtab *s,
		       u32 def_sid)
{

	char delim;
	char *scontextp, *p, *rngptr;
	struct level_datum *levdatum;
	struct cat_datum *catdatum, *rngdatum;
	int l, rc = -EINVAL;

	if (!pol->mls_enabled) {
		if (def_sid != SECSID_NULL && oldc)
			*scontext += strlen(*scontext) + 1;
		return 0;
	}

	/*
	 * No MLS component to the security context, try and map to
	 * default if provided.
	 */
	if (!oldc) {
		struct context *defcon;

		if (def_sid == SECSID_NULL)
			goto out;

		defcon = sidtab_search(s, def_sid);
		if (!defcon)
			goto out;

		rc = mls_context_cpy(context, defcon);
		goto out;
	}

	/* Extract low sensitivity. */
	scontextp = p = *scontext;
	while (*p && *p != ':' && *p != '-')
		p++;

	delim = *p;
	if (delim != '\0')
		*p++ = '\0';

	for (l = 0; l < 2; l++) {
		levdatum = hashtab_search(pol->p_levels.table, scontextp);
		if (!levdatum) {
			rc = -EINVAL;
			goto out;
		}

		context->range.level[l].sens = levdatum->level->sens;

		if (delim == ':') {
			/* Extract category set. */
			while (1) {
				scontextp = p;
				while (*p && *p != ',' && *p != '-')
					p++;
				delim = *p;
				if (delim != '\0')
					*p++ = '\0';

				/* Separate into range if exists */
				rngptr = strchr(scontextp, '.');
				if (rngptr != NULL) {
					/* Remove '.' */
					*rngptr++ = '\0';
				}

				catdatum = hashtab_search(pol->p_cats.table,
							  scontextp);
				if (!catdatum) {
					rc = -EINVAL;
					goto out;
				}

				rc = ebitmap_set_bit(&context->range.level[l].cat,
						     catdatum->value - 1, 1);
				if (rc)
					goto out;

				/* If range, set all categories in range */
				if (rngptr) {
					int i;

					rngdatum = hashtab_search(pol->p_cats.table, rngptr);
					if (!rngdatum) {
						rc = -EINVAL;
						goto out;
					}

					if (catdatum->value >= rngdatum->value) {
						rc = -EINVAL;
						goto out;
					}

					for (i = catdatum->value; i < rngdatum->value; i++) {
						rc = ebitmap_set_bit(&context->range.level[l].cat, i, 1);
						if (rc)
							goto out;
					}
				}

				if (delim != ',')
					break;
			}
		}
		if (delim == '-') {
			/* Extract high sensitivity. */
			scontextp = p;
			while (*p && *p != ':')
				p++;

			delim = *p;
			if (delim != '\0')
				*p++ = '\0';
		} else
			break;
	}

	if (l == 0) {
		context->range.level[1].sens = context->range.level[0].sens;
		rc = ebitmap_cpy(&context->range.level[1].cat,
				 &context->range.level[0].cat);
		if (rc)
			goto out;
	}
	*scontext = ++p;
	rc = 0;
out:
	return rc;
}

/*
 * Set the MLS fields in the security context structure
 * `context' based on the string representation in
 * the string `str'.  This function will allocate temporary memory with the
 * given constraints of gfp_mask.
 */
int mls_from_string(char *str, struct context *context, gfp_t gfp_mask)
{
	char *tmpstr, *freestr;
	int rc;

	if (!policydb.mls_enabled)
		return -EINVAL;

	/* we need freestr because mls_context_to_sid will change
	   the value of tmpstr */
	tmpstr = freestr = kstrdup(str, gfp_mask);
	if (!tmpstr) {
		rc = -ENOMEM;
	} else {
		rc = mls_context_to_sid(&policydb, ':', &tmpstr, context,
					NULL, SECSID_NULL);
		kfree(freestr);
	}

	return rc;
}

/*
 * Copies the MLS range `range' into `context'.
 */
int mls_range_set(struct context *context,
				struct mls_range *range)
{
	int l, rc = 0;

	/* Copy the MLS range into the  context */
	for (l = 0; l < 2; l++) {
		context->range.level[l].sens = range->level[l].sens;
		rc = ebitmap_cpy(&context->range.level[l].cat,
				 &range->level[l].cat);
		if (rc)
			break;
	}

	return rc;
}

int mls_setup_user_range(struct context *fromcon, struct user_datum *user,
			 struct context *usercon)
{
	if (policydb.mls_enabled) {
		struct mls_level *fromcon_sen = &(fromcon->range.level[0]);
		struct mls_level *fromcon_clr = &(fromcon->range.level[1]);
		struct mls_level *user_low = &(user->range.level[0]);
		struct mls_level *user_clr = &(user->range.level[1]);
		struct mls_level *user_def = &(user->dfltlevel);
		struct mls_level *usercon_sen = &(usercon->range.level[0]);
		struct mls_level *usercon_clr = &(usercon->range.level[1]);

		/* Honor the user's default level if we can */
		if (mls_level_between(user_def, fromcon_sen, fromcon_clr))
			*usercon_sen = *user_def;
		else if (mls_level_between(fromcon_sen, user_def, user_clr))
			*usercon_sen = *fromcon_sen;
		else if (mls_level_between(fromcon_clr, user_low, user_def))
			*usercon_sen = *user_low;
		else
			return -EINVAL;

		/* Lower the clearance of available contexts
		   if the clearance of "fromcon" is lower than
		   that of the user's default clearance (but
		   only if the "fromcon" clearance dominates
		   the user's computed sensitivity level) */
		if (mls_level_dom(user_clr, fromcon_clr))
			*usercon_clr = *fromcon_clr;
		else if (mls_level_dom(fromcon_clr, user_clr))
			*usercon_clr = *user_clr;
		else
			return -EINVAL;
	}

	return 0;
}

/*
 * Convert the MLS fields in the security context
 * structure `c' from the values specified in the
 * policy `oldp' to the values specified in the policy `newp'.
 */
int mls_convert_context(struct policydb *oldp,
			struct policydb *newp,
			struct context *c)
{
	struct level_datum *levdatum;
	struct cat_datum *catdatum;
	struct ebitmap bitmap;
	struct ebitmap_node *node;
	int l, i;

	if (!policydb.mls_enabled)
		return 0;

	for (l = 0; l < 2; l++) {
		levdatum = hashtab_search(newp->p_levels.table,
					  sym_name(oldp, SYM_LEVELS,
						   c->range.level[l].sens - 1));

		if (!levdatum)
			return -EINVAL;
		c->range.level[l].sens = levdatum->level->sens;

		ebitmap_init(&bitmap);
		ebitmap_for_each_positive_bit(&c->range.level[l].cat, node, i) {
			int rc;

			catdatum = hashtab_search(newp->p_cats.table,
						  sym_name(oldp, SYM_CATS, i));
			if (!catdatum)
				return -EINVAL;
			rc = ebitmap_set_bit(&bitmap, catdatum->value - 1, 1);
			if (rc)
				return rc;
		}
		ebitmap_destroy(&c->range.level[l].cat);
		c->range.level[l].cat = bitmap;
	}

	return 0;
}

int mls_compute_sid(struct context *scontext,
		    struct context *tcontext,
		    u16 tclass,
		    u32 specified,
		    struct context *newcontext,
		    bool sock)
{
	struct range_trans rtr;
	struct mls_range *r;

	if (!policydb.mls_enabled)
		return 0;

	switch (specified) {
	case AVTAB_TRANSITION:
		/* Look for a range transition rule. */
		rtr.source_type = scontext->type;
		rtr.target_type = tcontext->type;
		rtr.target_class = tclass;
		r = hashtab_search(policydb.range_tr, &rtr);
		if (r)
			return mls_range_set(newcontext, r);
		/* Fallthrough */
	case AVTAB_CHANGE:
		if ((tclass == policydb.process_class) || (sock == true))
			/* Use the process MLS attributes. */
			return mls_context_cpy(newcontext, scontext);
		else
			/* Use the process effective MLS attributes. */
			return mls_context_cpy_low(newcontext, scontext);
	case AVTAB_MEMBER:
		/* Use the process effective MLS attributes. */
		return mls_context_cpy_low(newcontext, scontext);

	/* fall through */
	}
	return -EINVAL;
}

#ifdef CONFIG_NETLABEL
/**
 * mls_export_netlbl_lvl - Export the MLS sensitivity levels to NetLabel
 * @context: the security context
 * @secattr: the NetLabel security attributes
 *
 * Description:
 * Given the security context copy the low MLS sensitivity level into the
 * NetLabel MLS sensitivity level field.
 *
 */
void mls_export_netlbl_lvl(struct context *context,
			   struct netlbl_lsm_secattr *secattr)
{
	if (!policydb.mls_enabled)
		return;

	secattr->attr.mls.lvl = context->range.level[0].sens - 1;
	secattr->flags |= NETLBL_SECATTR_MLS_LVL;
}

/**
 * mls_import_netlbl_lvl - Import the NetLabel MLS sensitivity levels
 * @context: the security context
 * @secattr: the NetLabel security attributes
 *
 * Description:
 * Given the security context and the NetLabel security attributes, copy the
 * NetLabel MLS sensitivity level into the context.
 *
 */
void mls_import_netlbl_lvl(struct context *context,
			   struct netlbl_lsm_secattr *secattr)
{
	if (!policydb.mls_enabled)
		return;

	context->range.level[0].sens = secattr->attr.mls.lvl + 1;
	context->range.level[1].sens = context->range.level[0].sens;
}

/**
 * mls_export_netlbl_cat - Export the MLS categories to NetLabel
 * @context: the security context
 * @secattr: the NetLabel security attributes
 *
 * Description:
 * Given the security context copy the low MLS categories into the NetLabel
 * MLS category field.  Returns zero on success, negative values on failure.
 *
 */
int mls_export_netlbl_cat(struct context *context,
			  struct netlbl_lsm_secattr *secattr)
{
	int rc;

	if (!policydb.mls_enabled)
		return 0;

	rc = ebitmap_netlbl_export(&context->range.level[0].cat,
				   &secattr->attr.mls.cat);
	if (rc == 0 && secattr->attr.mls.cat != NULL)
		secattr->flags |= NETLBL_SECATTR_MLS_CAT;

	return rc;
}

/**
 * mls_import_netlbl_cat - Import the MLS categories from NetLabel
 * @context: the security context
 * @secattr: the NetLabel security attributes
 *
 * Description:
 * Copy the NetLabel security attributes into the SELinux context; since the
 * NetLabel security attribute only contains a single MLS category use it for
 * both the low and high categories of the context.  Returns zero on success,
 * negative values on failure.
 *
 */
int mls_import_netlbl_cat(struct context *context,
			  struct netlbl_lsm_secattr *secattr)
{
	int rc;

	if (!policydb.mls_enabled)
		return 0;

	rc = ebitmap_netlbl_import(&context->range.level[0].cat,
				   secattr->attr.mls.cat);
	if (rc != 0)
		goto import_netlbl_cat_failure;

	rc = ebitmap_cpy(&context->range.level[1].cat,
			 &context->range.level[0].cat);
	if (rc != 0)
		goto import_netlbl_cat_failure;

	return 0;

import_netlbl_cat_failure:
	ebitmap_destroy(&context->range.level[0].cat);
	ebitmap_destroy(&context->range.level[1].cat);
	return rc;
}
#endif /* CONFIG_NETLABEL */