1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Implementation of the multi-level security (MLS) policy.
4 *
5 * Author : Stephen Smalley, <stephen.smalley.work@gmail.com>
6 */
7
8 /*
9 * Updated: Trusted Computer Solutions, Inc. <dgoeddel@trustedcs.com>
10 * Support for enhanced MLS infrastructure.
11 * Copyright (C) 2004-2006 Trusted Computer Solutions, Inc.
12 *
13 * Updated: Hewlett-Packard <paul@paul-moore.com>
14 * Added support to import/export the MLS label from NetLabel
15 * Copyright (C) Hewlett-Packard Development Company, L.P., 2006
16 */
17
18 #include <linux/kernel.h>
19 #include <linux/slab.h>
20 #include <linux/string.h>
21 #include <linux/errno.h>
22 #include <net/netlabel.h>
23 #include "sidtab.h"
24 #include "mls.h"
25 #include "policydb.h"
26 #include "services.h"
27
28 /*
29 * Return the length in bytes for the MLS fields of the
30 * security context string representation of `context'.
31 */
32 int mls_compute_context_len(struct policydb *p, struct context *context)
33 {
34 int i, l, len, head, prev;
35 char *nm;
36 struct ebitmap *e;
37 struct ebitmap_node *node;
38
39 if (!p->mls_enabled)
40 return 0;
41
42 len = 1; /* for the beginning ":" */
43 for (l = 0; l < 2; l++) {
44 u32 index_sens = context->range.level[l].sens;
45 len += strlen(sym_name(p, SYM_LEVELS, index_sens - 1));
46
47 /* categories */
48 head = -2;
49 prev = -2;
50 e = &context->range.level[l].cat;
51 ebitmap_for_each_positive_bit(e, node, i)
52 {
53 if (i - prev > 1) {
54 /* one or more negative bits are skipped */
55 if (head != prev) {
56 nm = sym_name(p, SYM_CATS, prev);
57 len += strlen(nm) + 1;
58 }
59 nm = sym_name(p, SYM_CATS, i);
60 len += strlen(nm) + 1;
61 head = i;
62 }
63 prev = i;
64 }
65 if (prev != head) {
66 nm = sym_name(p, SYM_CATS, prev);
67 len += strlen(nm) + 1;
68 }
69 if (l == 0) {
70 if (mls_level_eq(&context->range.level[0],
71 &context->range.level[1]))
72 break;
73 else
74 len++;
75 }
76 }
77
78 return len;
79 }
80
81 /*
82 * Write the security context string representation of
83 * the MLS fields of `context' into the string `*scontext'.
84 * Update `*scontext' to point to the end of the MLS fields.
85 */
86 void mls_sid_to_context(struct policydb *p, struct context *context,
87 char **scontext)
88 {
89 char *scontextp, *nm;
90 int i, l, head, prev;
91 struct ebitmap *e;
92 struct ebitmap_node *node;
93
94 if (!p->mls_enabled)
95 return;
96
97 scontextp = *scontext;
98
99 *scontextp = ':';
100 scontextp++;
101
102 for (l = 0; l < 2; l++) {
103 strcpy(scontextp, sym_name(p, SYM_LEVELS,
104 context->range.level[l].sens - 1));
105 scontextp += strlen(scontextp);
106
107 /* categories */
108 head = -2;
109 prev = -2;
110 e = &context->range.level[l].cat;
111 ebitmap_for_each_positive_bit(e, node, i)
112 {
113 if (i - prev > 1) {
114 /* one or more negative bits are skipped */
115 if (prev != head) {
116 if (prev - head > 1)
117 *scontextp++ = '.';
118 else
119 *scontextp++ = ',';
120 nm = sym_name(p, SYM_CATS, prev);
121 strcpy(scontextp, nm);
122 scontextp += strlen(nm);
123 }
124 if (prev < 0)
125 *scontextp++ = ':';
126 else
127 *scontextp++ = ',';
128 nm = sym_name(p, SYM_CATS, i);
129 strcpy(scontextp, nm);
130 scontextp += strlen(nm);
131 head = i;
132 }
133 prev = i;
134 }
135
136 if (prev != head) {
137 if (prev - head > 1)
138 *scontextp++ = '.';
139 else
140 *scontextp++ = ',';
141 nm = sym_name(p, SYM_CATS, prev);
142 strcpy(scontextp, nm);
143 scontextp += strlen(nm);
144 }
145
146 if (l == 0) {
147 if (mls_level_eq(&context->range.level[0],
148 &context->range.level[1]))
149 break;
150 else
151 *scontextp++ = '-';
152 }
153 }
154
155 *scontext = scontextp;
156 }
157
158 int mls_level_isvalid(struct policydb *p, struct mls_level *l)
159 {
160 struct level_datum *levdatum;
161
162 if (!l->sens || l->sens > p->p_levels.nprim)
163 return 0;
164 levdatum = symtab_search(&p->p_levels,
165 sym_name(p, SYM_LEVELS, l->sens - 1));
166 if (!levdatum)
167 return 0;
168
169 /*
170 * Return 1 iff all the bits set in l->cat are also be set in
171 * levdatum->level->cat and no bit in l->cat is larger than
172 * p->p_cats.nprim.
173 */
174 return ebitmap_contains(&levdatum->level->cat, &l->cat,
175 p->p_cats.nprim);
176 }
177
178 int mls_range_isvalid(struct policydb *p, struct mls_range *r)
179 {
180 return (mls_level_isvalid(p, &r->level[0]) &&
181 mls_level_isvalid(p, &r->level[1]) &&
182 mls_level_dom(&r->level[1], &r->level[0]));
183 }
184
185 /*
186 * Return 1 if the MLS fields in the security context
187 * structure `c' are valid. Return 0 otherwise.
188 */
189 int mls_context_isvalid(struct policydb *p, struct context *c)
190 {
191 struct user_datum *usrdatum;
192
193 if (!p->mls_enabled)
194 return 1;
195
196 if (!mls_range_isvalid(p, &c->range))
197 return 0;
198
199 if (c->role == OBJECT_R_VAL)
200 return 1;
201
202 /*
203 * User must be authorized for the MLS range.
204 */
205 if (!c->user || c->user > p->p_users.nprim)
206 return 0;
207 usrdatum = p->user_val_to_struct[c->user - 1];
208 if (!mls_range_contains(usrdatum->range, c->range))
209 return 0; /* user may not be associated with range */
210
211 return 1;
212 }
213
214 /*
215 * Set the MLS fields in the security context structure
216 * `context' based on the string representation in
217 * the string `scontext'.
218 *
219 * This function modifies the string in place, inserting
220 * NULL characters to terminate the MLS fields.
221 *
222 * If a def_sid is provided and no MLS field is present,
223 * copy the MLS field of the associated default context.
224 * Used for upgraded to MLS systems where objects may lack
225 * MLS fields.
226 *
227 * Policy read-lock must be held for sidtab lookup.
228 *
229 */
230 int mls_context_to_sid(struct policydb *pol, char oldc, char *scontext,
231 struct context *context, struct sidtab *s, u32 def_sid)
232 {
233 char *sensitivity, *cur_cat, *next_cat, *rngptr;
234 struct level_datum *levdatum;
235 struct cat_datum *catdatum, *rngdatum;
236 u32 i;
237 int l, rc;
238 char *rangep[2];
239
240 if (!pol->mls_enabled) {
241 /*
242 * With no MLS, only return -EINVAL if there is a MLS field
243 * and it did not come from an xattr.
244 */
245 if (oldc && def_sid == SECSID_NULL)
246 return -EINVAL;
247 return 0;
248 }
249
250 /*
251 * No MLS component to the security context, try and map to
252 * default if provided.
253 */
254 if (!oldc) {
255 struct context *defcon;
256
257 if (def_sid == SECSID_NULL)
258 return -EINVAL;
259
260 defcon = sidtab_search(s, def_sid);
261 if (!defcon)
262 return -EINVAL;
263
264 return mls_context_cpy(context, defcon);
265 }
266
267 /*
268 * If we're dealing with a range, figure out where the two parts
269 * of the range begin.
270 */
271 rangep[0] = scontext;
272 rangep[1] = strchr(scontext, '-');
273 if (rangep[1]) {
274 rangep[1][0] = '\0';
275 rangep[1]++;
276 }
277
278 /* For each part of the range: */
279 for (l = 0; l < 2; l++) {
280 /* Split sensitivity and category set. */
281 sensitivity = rangep[l];
282 if (sensitivity == NULL)
283 break;
284 next_cat = strchr(sensitivity, ':');
285 if (next_cat)
286 *(next_cat++) = '\0';
287
288 /* Parse sensitivity. */
289 levdatum = symtab_search(&pol->p_levels, sensitivity);
290 if (!levdatum)
291 return -EINVAL;
292 context->range.level[l].sens = levdatum->level->sens;
293
294 /* Extract category set. */
295 while (next_cat != NULL) {
296 cur_cat = next_cat;
297 next_cat = strchr(next_cat, ',');
298 if (next_cat != NULL)
299 *(next_cat++) = '\0';
300
301 /* Separate into range if exists */
302 rngptr = strchr(cur_cat, '.');
303 if (rngptr != NULL) {
304 /* Remove '.' */
305 *rngptr++ = '\0';
306 }
307
308 catdatum = symtab_search(&pol->p_cats, cur_cat);
309 if (!catdatum)
310 return -EINVAL;
311
312 rc = ebitmap_set_bit(&context->range.level[l].cat,
313 catdatum->value - 1, 1);
314 if (rc)
315 return rc;
316
317 /* If range, set all categories in range */
318 if (rngptr == NULL)
319 continue;
320
321 rngdatum = symtab_search(&pol->p_cats, rngptr);
322 if (!rngdatum)
323 return -EINVAL;
324
325 if (catdatum->value >= rngdatum->value)
326 return -EINVAL;
327
328 for (i = catdatum->value; i < rngdatum->value; i++) {
329 rc = ebitmap_set_bit(
330 &context->range.level[l].cat, i, 1);
331 if (rc)
332 return rc;
333 }
334 }
335 }
336
337 /* If we didn't see a '-', the range start is also the range end. */
338 if (rangep[1] == NULL) {
339 context->range.level[1].sens = context->range.level[0].sens;
340 rc = ebitmap_cpy(&context->range.level[1].cat,
341 &context->range.level[0].cat);
342 if (rc)
343 return rc;
344 }
345
346 return 0;
347 }
348
349 /*
350 * Set the MLS fields in the security context structure
351 * `context' based on the string representation in
352 * the string `str'. This function will allocate temporary memory with the
353 * given constraints of gfp_mask.
354 */
355 int mls_from_string(struct policydb *p, char *str, struct context *context,
356 gfp_t gfp_mask)
357 {
358 char *tmpstr;
359 int rc;
360
361 if (!p->mls_enabled)
362 return -EINVAL;
363
364 tmpstr = kstrdup(str, gfp_mask);
365 if (!tmpstr) {
366 rc = -ENOMEM;
367 } else {
368 rc = mls_context_to_sid(p, ':', tmpstr, context, NULL,
369 SECSID_NULL);
370 kfree(tmpstr);
371 }
372
373 return rc;
374 }
375
376 /*
377 * Copies the MLS range `range' into `context'.
378 */
379 int mls_range_set(struct context *context, struct mls_range *range)
380 {
381 int l, rc = 0;
382
383 /* Copy the MLS range into the context */
384 for (l = 0; l < 2; l++) {
385 context->range.level[l].sens = range->level[l].sens;
386 rc = ebitmap_cpy(&context->range.level[l].cat,
387 &range->level[l].cat);
388 if (rc)
389 break;
390 }
391
392 return rc;
393 }
394
395 int mls_setup_user_range(struct policydb *p, struct context *fromcon,
396 struct user_datum *user, struct context *usercon)
397 {
398 if (p->mls_enabled) {
399 struct mls_level *fromcon_sen = &(fromcon->range.level[0]);
400 struct mls_level *fromcon_clr = &(fromcon->range.level[1]);
401 struct mls_level *user_low = &(user->range.level[0]);
402 struct mls_level *user_clr = &(user->range.level[1]);
403 struct mls_level *user_def = &(user->dfltlevel);
404 struct mls_level *usercon_sen = &(usercon->range.level[0]);
405 struct mls_level *usercon_clr = &(usercon->range.level[1]);
406
407 /* Honor the user's default level if we can */
408 if (mls_level_between(user_def, fromcon_sen, fromcon_clr))
409 *usercon_sen = *user_def;
410 else if (mls_level_between(fromcon_sen, user_def, user_clr))
411 *usercon_sen = *fromcon_sen;
412 else if (mls_level_between(fromcon_clr, user_low, user_def))
413 *usercon_sen = *user_low;
414 else
415 return -EINVAL;
416
417 /* Lower the clearance of available contexts
418 if the clearance of "fromcon" is lower than
419 that of the user's default clearance (but
420 only if the "fromcon" clearance dominates
421 the user's computed sensitivity level) */
422 if (mls_level_dom(user_clr, fromcon_clr))
423 *usercon_clr = *fromcon_clr;
424 else if (mls_level_dom(fromcon_clr, user_clr))
425 *usercon_clr = *user_clr;
426 else
427 return -EINVAL;
428 }
429
430 return 0;
431 }
432
433 /*
434 * Convert the MLS fields in the security context
435 * structure `oldc' from the values specified in the
436 * policy `oldp' to the values specified in the policy `newp',
437 * storing the resulting context in `newc'.
438 */
439 int mls_convert_context(struct policydb *oldp, struct policydb *newp,
440 struct context *oldc, struct context *newc)
441 {
442 struct level_datum *levdatum;
443 struct cat_datum *catdatum;
444 struct ebitmap_node *node;
445 u32 i;
446 int l;
447
448 if (!oldp->mls_enabled || !newp->mls_enabled)
449 return 0;
450
451 for (l = 0; l < 2; l++) {
452 char *name = sym_name(oldp, SYM_LEVELS,
453 oldc->range.level[l].sens - 1);
454
455 levdatum = symtab_search(&newp->p_levels, name);
456
457 if (!levdatum)
458 return -EINVAL;
459 newc->range.level[l].sens = levdatum->level->sens;
460
461 ebitmap_for_each_positive_bit(&oldc->range.level[l].cat, node,
462 i)
463 {
464 int rc;
465
466 catdatum = symtab_search(&newp->p_cats,
467 sym_name(oldp, SYM_CATS, i));
468 if (!catdatum)
469 return -EINVAL;
470 rc = ebitmap_set_bit(&newc->range.level[l].cat,
471 catdatum->value - 1, 1);
472 if (rc)
473 return rc;
474 }
475 }
476
477 return 0;
478 }
479
480 int mls_compute_sid(struct policydb *p, struct context *scontext,
481 struct context *tcontext, u16 tclass, u32 specified,
482 struct context *newcontext, bool sock)
483 {
484 struct range_trans rtr;
485 struct mls_range *r;
486 struct class_datum *cladatum;
487 char default_range = 0;
488
489 if (!p->mls_enabled)
490 return 0;
491
492 switch (specified) {
493 case AVTAB_TRANSITION:
494 /* Look for a range transition rule. */
495 rtr.source_type = scontext->type;
496 rtr.target_type = tcontext->type;
497 rtr.target_class = tclass;
498 r = policydb_rangetr_search(p, &rtr);
499 if (r)
500 return mls_range_set(newcontext, r);
501
502 if (tclass && tclass <= p->p_classes.nprim) {
503 cladatum = p->class_val_to_struct[tclass - 1];
504 if (cladatum)
505 default_range = cladatum->default_range;
506 }
507
508 switch (default_range) {
509 case DEFAULT_SOURCE_LOW:
510 return mls_context_cpy_low(newcontext, scontext);
511 case DEFAULT_SOURCE_HIGH:
512 return mls_context_cpy_high(newcontext, scontext);
513 case DEFAULT_SOURCE_LOW_HIGH:
514 return mls_context_cpy(newcontext, scontext);
515 case DEFAULT_TARGET_LOW:
516 return mls_context_cpy_low(newcontext, tcontext);
517 case DEFAULT_TARGET_HIGH:
518 return mls_context_cpy_high(newcontext, tcontext);
519 case DEFAULT_TARGET_LOW_HIGH:
520 return mls_context_cpy(newcontext, tcontext);
521 case DEFAULT_GLBLUB:
522 return mls_context_glblub(newcontext, scontext,
523 tcontext);
524 }
525
526 fallthrough;
527 case AVTAB_CHANGE:
528 if ((tclass == p->process_class) || sock)
529 /* Use the process MLS attributes. */
530 return mls_context_cpy(newcontext, scontext);
531 else
532 /* Use the process effective MLS attributes. */
533 return mls_context_cpy_low(newcontext, scontext);
534 case AVTAB_MEMBER:
535 /* Use the process effective MLS attributes. */
536 return mls_context_cpy_low(newcontext, scontext);
537 }
538 return -EINVAL;
539 }
540
541 #ifdef CONFIG_NETLABEL
542 /**
543 * mls_export_netlbl_lvl - Export the MLS sensitivity levels to NetLabel
544 * @p: the policy
545 * @context: the security context
546 * @secattr: the NetLabel security attributes
547 *
548 * Description:
549 * Given the security context copy the low MLS sensitivity level into the
550 * NetLabel MLS sensitivity level field.
551 *
552 */
553 void mls_export_netlbl_lvl(struct policydb *p, struct context *context,
554 struct netlbl_lsm_secattr *secattr)
555 {
556 if (!p->mls_enabled)
557 return;
558
559 secattr->attr.mls.lvl = context->range.level[0].sens - 1;
560 secattr->flags |= NETLBL_SECATTR_MLS_LVL;
561 }
562
563 /**
564 * mls_import_netlbl_lvl - Import the NetLabel MLS sensitivity levels
565 * @p: the policy
566 * @context: the security context
567 * @secattr: the NetLabel security attributes
568 *
569 * Description:
570 * Given the security context and the NetLabel security attributes, copy the
571 * NetLabel MLS sensitivity level into the context.
572 *
573 */
574 void mls_import_netlbl_lvl(struct policydb *p, struct context *context,
575 struct netlbl_lsm_secattr *secattr)
576 {
577 if (!p->mls_enabled)
578 return;
579
580 context->range.level[0].sens = secattr->attr.mls.lvl + 1;
581 context->range.level[1].sens = context->range.level[0].sens;
582 }
583
584 /**
585 * mls_export_netlbl_cat - Export the MLS categories to NetLabel
586 * @p: the policy
587 * @context: the security context
588 * @secattr: the NetLabel security attributes
589 *
590 * Description:
591 * Given the security context copy the low MLS categories into the NetLabel
592 * MLS category field. Returns zero on success, negative values on failure.
593 *
594 */
595 int mls_export_netlbl_cat(struct policydb *p, struct context *context,
596 struct netlbl_lsm_secattr *secattr)
597 {
598 int rc;
599
600 if (!p->mls_enabled)
601 return 0;
602
603 rc = ebitmap_netlbl_export(&context->range.level[0].cat,
604 &secattr->attr.mls.cat);
605 if (rc == 0 && secattr->attr.mls.cat != NULL)
606 secattr->flags |= NETLBL_SECATTR_MLS_CAT;
607
608 return rc;
609 }
610
611 /**
612 * mls_import_netlbl_cat - Import the MLS categories from NetLabel
613 * @p: the policy
614 * @context: the security context
615 * @secattr: the NetLabel security attributes
616 *
617 * Description:
618 * Copy the NetLabel security attributes into the SELinux context; since the
619 * NetLabel security attribute only contains a single MLS category use it for
620 * both the low and high categories of the context. Returns zero on success,
621 * negative values on failure.
622 *
623 */
624 int mls_import_netlbl_cat(struct policydb *p, struct context *context,
625 struct netlbl_lsm_secattr *secattr)
626 {
627 int rc;
628
629 if (!p->mls_enabled)
630 return 0;
631
632 rc = ebitmap_netlbl_import(&context->range.level[0].cat,
633 secattr->attr.mls.cat);
634 if (rc)
635 goto import_netlbl_cat_failure;
636 memcpy(&context->range.level[1].cat, &context->range.level[0].cat,
637 sizeof(context->range.level[0].cat));
638
639 return 0;
640
641 import_netlbl_cat_failure:
642 ebitmap_destroy(&context->range.level[0].cat);
643 return rc;
644 }
645 #endif /* CONFIG_NETLABEL */
646
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