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Linux/security/selinux/ss/mls.c

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  1 /*
  2  * Implementation of the multi-level security (MLS) policy.
  3  *
  4  * Author : Stephen Smalley, <sds@epoch.ncsc.mil>
  5  */
  6 /*
  7  * Updated: Trusted Computer Solutions, Inc. <dgoeddel@trustedcs.com>
  8  *
  9  *      Support for enhanced MLS infrastructure.
 10  *
 11  * Copyright (C) 2004-2006 Trusted Computer Solutions, Inc.
 12  */
 13 /*
 14  * Updated: Hewlett-Packard <paul@paul-moore.com>
 15  *
 16  *      Added support to import/export the MLS label from NetLabel
 17  *
 18  * (c) Copyright Hewlett-Packard Development Company, L.P., 2006
 19  */
 20 
 21 #include <linux/kernel.h>
 22 #include <linux/slab.h>
 23 #include <linux/string.h>
 24 #include <linux/errno.h>
 25 #include <net/netlabel.h>
 26 #include "sidtab.h"
 27 #include "mls.h"
 28 #include "policydb.h"
 29 #include "services.h"
 30 
 31 /*
 32  * Return the length in bytes for the MLS fields of the
 33  * security context string representation of `context'.
 34  */
 35 int mls_compute_context_len(struct context *context)
 36 {
 37         int i, l, len, head, prev;
 38         char *nm;
 39         struct ebitmap *e;
 40         struct ebitmap_node *node;
 41 
 42         if (!policydb.mls_enabled)
 43                 return 0;
 44 
 45         len = 1; /* for the beginning ":" */
 46         for (l = 0; l < 2; l++) {
 47                 int index_sens = context->range.level[l].sens;
 48                 len += strlen(sym_name(&policydb, SYM_LEVELS, index_sens - 1));
 49 
 50                 /* categories */
 51                 head = -2;
 52                 prev = -2;
 53                 e = &context->range.level[l].cat;
 54                 ebitmap_for_each_positive_bit(e, node, i) {
 55                         if (i - prev > 1) {
 56                                 /* one or more negative bits are skipped */
 57                                 if (head != prev) {
 58                                         nm = sym_name(&policydb, SYM_CATS, prev);
 59                                         len += strlen(nm) + 1;
 60                                 }
 61                                 nm = sym_name(&policydb, SYM_CATS, i);
 62                                 len += strlen(nm) + 1;
 63                                 head = i;
 64                         }
 65                         prev = i;
 66                 }
 67                 if (prev != head) {
 68                         nm = sym_name(&policydb, SYM_CATS, prev);
 69                         len += strlen(nm) + 1;
 70                 }
 71                 if (l == 0) {
 72                         if (mls_level_eq(&context->range.level[0],
 73                                          &context->range.level[1]))
 74                                 break;
 75                         else
 76                                 len++;
 77                 }
 78         }
 79 
 80         return len;
 81 }
 82 
 83 /*
 84  * Write the security context string representation of
 85  * the MLS fields of `context' into the string `*scontext'.
 86  * Update `*scontext' to point to the end of the MLS fields.
 87  */
 88 void mls_sid_to_context(struct context *context,
 89                         char **scontext)
 90 {
 91         char *scontextp, *nm;
 92         int i, l, head, prev;
 93         struct ebitmap *e;
 94         struct ebitmap_node *node;
 95 
 96         if (!policydb.mls_enabled)
 97                 return;
 98 
 99         scontextp = *scontext;
100 
101         *scontextp = ':';
102         scontextp++;
103 
104         for (l = 0; l < 2; l++) {
105                 strcpy(scontextp, sym_name(&policydb, SYM_LEVELS,
106                                            context->range.level[l].sens - 1));
107                 scontextp += strlen(scontextp);
108 
109                 /* categories */
110                 head = -2;
111                 prev = -2;
112                 e = &context->range.level[l].cat;
113                 ebitmap_for_each_positive_bit(e, node, i) {
114                         if (i - prev > 1) {
115                                 /* one or more negative bits are skipped */
116                                 if (prev != head) {
117                                         if (prev - head > 1)
118                                                 *scontextp++ = '.';
119                                         else
120                                                 *scontextp++ = ',';
121                                         nm = sym_name(&policydb, SYM_CATS, prev);
122                                         strcpy(scontextp, nm);
123                                         scontextp += strlen(nm);
124                                 }
125                                 if (prev < 0)
126                                         *scontextp++ = ':';
127                                 else
128                                         *scontextp++ = ',';
129                                 nm = sym_name(&policydb, SYM_CATS, i);
130                                 strcpy(scontextp, nm);
131                                 scontextp += strlen(nm);
132                                 head = i;
133                         }
134                         prev = i;
135                 }
136 
137                 if (prev != head) {
138                         if (prev - head > 1)
139                                 *scontextp++ = '.';
140                         else
141                                 *scontextp++ = ',';
142                         nm = sym_name(&policydb, SYM_CATS, prev);
143                         strcpy(scontextp, nm);
144                         scontextp += strlen(nm);
145                 }
146 
147                 if (l == 0) {
148                         if (mls_level_eq(&context->range.level[0],
149                                          &context->range.level[1]))
150                                 break;
151                         else
152                                 *scontextp++ = '-';
153                 }
154         }
155 
156         *scontext = scontextp;
157         return;
158 }
159 
160 int mls_level_isvalid(struct policydb *p, struct mls_level *l)
161 {
162         struct level_datum *levdatum;
163 
164         if (!l->sens || l->sens > p->p_levels.nprim)
165                 return 0;
166         levdatum = hashtab_search(p->p_levels.table,
167                                   sym_name(p, SYM_LEVELS, l->sens - 1));
168         if (!levdatum)
169                 return 0;
170 
171         /*
172          * Return 1 iff all the bits set in l->cat are also be set in
173          * levdatum->level->cat and no bit in l->cat is larger than
174          * p->p_cats.nprim.
175          */
176         return ebitmap_contains(&levdatum->level->cat, &l->cat,
177                                 p->p_cats.nprim);
178 }
179 
180 int mls_range_isvalid(struct policydb *p, struct mls_range *r)
181 {
182         return (mls_level_isvalid(p, &r->level[0]) &&
183                 mls_level_isvalid(p, &r->level[1]) &&
184                 mls_level_dom(&r->level[1], &r->level[0]));
185 }
186 
187 /*
188  * Return 1 if the MLS fields in the security context
189  * structure `c' are valid.  Return 0 otherwise.
190  */
191 int mls_context_isvalid(struct policydb *p, struct context *c)
192 {
193         struct user_datum *usrdatum;
194 
195         if (!p->mls_enabled)
196                 return 1;
197 
198         if (!mls_range_isvalid(p, &c->range))
199                 return 0;
200 
201         if (c->role == OBJECT_R_VAL)
202                 return 1;
203 
204         /*
205          * User must be authorized for the MLS range.
206          */
207         if (!c->user || c->user > p->p_users.nprim)
208                 return 0;
209         usrdatum = p->user_val_to_struct[c->user - 1];
210         if (!mls_range_contains(usrdatum->range, c->range))
211                 return 0; /* user may not be associated with range */
212 
213         return 1;
214 }
215 
216 /*
217  * Set the MLS fields in the security context structure
218  * `context' based on the string representation in
219  * the string `*scontext'.  Update `*scontext' to
220  * point to the end of the string representation of
221  * the MLS fields.
222  *
223  * This function modifies the string in place, inserting
224  * NULL characters to terminate the MLS fields.
225  *
226  * If a def_sid is provided and no MLS field is present,
227  * copy the MLS field of the associated default context.
228  * Used for upgraded to MLS systems where objects may lack
229  * MLS fields.
230  *
231  * Policy read-lock must be held for sidtab lookup.
232  *
233  */
234 int mls_context_to_sid(struct policydb *pol,
235                        char oldc,
236                        char **scontext,
237                        struct context *context,
238                        struct sidtab *s,
239                        u32 def_sid)
240 {
241 
242         char delim;
243         char *scontextp, *p, *rngptr;
244         struct level_datum *levdatum;
245         struct cat_datum *catdatum, *rngdatum;
246         int l, rc = -EINVAL;
247 
248         if (!pol->mls_enabled) {
249                 if (def_sid != SECSID_NULL && oldc)
250                         *scontext += strlen(*scontext) + 1;
251                 return 0;
252         }
253 
254         /*
255          * No MLS component to the security context, try and map to
256          * default if provided.
257          */
258         if (!oldc) {
259                 struct context *defcon;
260 
261                 if (def_sid == SECSID_NULL)
262                         goto out;
263 
264                 defcon = sidtab_search(s, def_sid);
265                 if (!defcon)
266                         goto out;
267 
268                 rc = mls_context_cpy(context, defcon);
269                 goto out;
270         }
271 
272         /* Extract low sensitivity. */
273         scontextp = p = *scontext;
274         while (*p && *p != ':' && *p != '-')
275                 p++;
276 
277         delim = *p;
278         if (delim != '\0')
279                 *p++ = '\0';
280 
281         for (l = 0; l < 2; l++) {
282                 levdatum = hashtab_search(pol->p_levels.table, scontextp);
283                 if (!levdatum) {
284                         rc = -EINVAL;
285                         goto out;
286                 }
287 
288                 context->range.level[l].sens = levdatum->level->sens;
289 
290                 if (delim == ':') {
291                         /* Extract category set. */
292                         while (1) {
293                                 scontextp = p;
294                                 while (*p && *p != ',' && *p != '-')
295                                         p++;
296                                 delim = *p;
297                                 if (delim != '\0')
298                                         *p++ = '\0';
299 
300                                 /* Separate into range if exists */
301                                 rngptr = strchr(scontextp, '.');
302                                 if (rngptr != NULL) {
303                                         /* Remove '.' */
304                                         *rngptr++ = '\0';
305                                 }
306 
307                                 catdatum = hashtab_search(pol->p_cats.table,
308                                                           scontextp);
309                                 if (!catdatum) {
310                                         rc = -EINVAL;
311                                         goto out;
312                                 }
313 
314                                 rc = ebitmap_set_bit(&context->range.level[l].cat,
315                                                      catdatum->value - 1, 1);
316                                 if (rc)
317                                         goto out;
318 
319                                 /* If range, set all categories in range */
320                                 if (rngptr) {
321                                         int i;
322 
323                                         rngdatum = hashtab_search(pol->p_cats.table, rngptr);
324                                         if (!rngdatum) {
325                                                 rc = -EINVAL;
326                                                 goto out;
327                                         }
328 
329                                         if (catdatum->value >= rngdatum->value) {
330                                                 rc = -EINVAL;
331                                                 goto out;
332                                         }
333 
334                                         for (i = catdatum->value; i < rngdatum->value; i++) {
335                                                 rc = ebitmap_set_bit(&context->range.level[l].cat, i, 1);
336                                                 if (rc)
337                                                         goto out;
338                                         }
339                                 }
340 
341                                 if (delim != ',')
342                                         break;
343                         }
344                 }
345                 if (delim == '-') {
346                         /* Extract high sensitivity. */
347                         scontextp = p;
348                         while (*p && *p != ':')
349                                 p++;
350 
351                         delim = *p;
352                         if (delim != '\0')
353                                 *p++ = '\0';
354                 } else
355                         break;
356         }
357 
358         if (l == 0) {
359                 context->range.level[1].sens = context->range.level[0].sens;
360                 rc = ebitmap_cpy(&context->range.level[1].cat,
361                                  &context->range.level[0].cat);
362                 if (rc)
363                         goto out;
364         }
365         *scontext = ++p;
366         rc = 0;
367 out:
368         return rc;
369 }
370 
371 /*
372  * Set the MLS fields in the security context structure
373  * `context' based on the string representation in
374  * the string `str'.  This function will allocate temporary memory with the
375  * given constraints of gfp_mask.
376  */
377 int mls_from_string(char *str, struct context *context, gfp_t gfp_mask)
378 {
379         char *tmpstr, *freestr;
380         int rc;
381 
382         if (!policydb.mls_enabled)
383                 return -EINVAL;
384 
385         /* we need freestr because mls_context_to_sid will change
386            the value of tmpstr */
387         tmpstr = freestr = kstrdup(str, gfp_mask);
388         if (!tmpstr) {
389                 rc = -ENOMEM;
390         } else {
391                 rc = mls_context_to_sid(&policydb, ':', &tmpstr, context,
392                                         NULL, SECSID_NULL);
393                 kfree(freestr);
394         }
395 
396         return rc;
397 }
398 
399 /*
400  * Copies the MLS range `range' into `context'.
401  */
402 int mls_range_set(struct context *context,
403                                 struct mls_range *range)
404 {
405         int l, rc = 0;
406 
407         /* Copy the MLS range into the  context */
408         for (l = 0; l < 2; l++) {
409                 context->range.level[l].sens = range->level[l].sens;
410                 rc = ebitmap_cpy(&context->range.level[l].cat,
411                                  &range->level[l].cat);
412                 if (rc)
413                         break;
414         }
415 
416         return rc;
417 }
418 
419 int mls_setup_user_range(struct context *fromcon, struct user_datum *user,
420                          struct context *usercon)
421 {
422         if (policydb.mls_enabled) {
423                 struct mls_level *fromcon_sen = &(fromcon->range.level[0]);
424                 struct mls_level *fromcon_clr = &(fromcon->range.level[1]);
425                 struct mls_level *user_low = &(user->range.level[0]);
426                 struct mls_level *user_clr = &(user->range.level[1]);
427                 struct mls_level *user_def = &(user->dfltlevel);
428                 struct mls_level *usercon_sen = &(usercon->range.level[0]);
429                 struct mls_level *usercon_clr = &(usercon->range.level[1]);
430 
431                 /* Honor the user's default level if we can */
432                 if (mls_level_between(user_def, fromcon_sen, fromcon_clr))
433                         *usercon_sen = *user_def;
434                 else if (mls_level_between(fromcon_sen, user_def, user_clr))
435                         *usercon_sen = *fromcon_sen;
436                 else if (mls_level_between(fromcon_clr, user_low, user_def))
437                         *usercon_sen = *user_low;
438                 else
439                         return -EINVAL;
440 
441                 /* Lower the clearance of available contexts
442                    if the clearance of "fromcon" is lower than
443                    that of the user's default clearance (but
444                    only if the "fromcon" clearance dominates
445                    the user's computed sensitivity level) */
446                 if (mls_level_dom(user_clr, fromcon_clr))
447                         *usercon_clr = *fromcon_clr;
448                 else if (mls_level_dom(fromcon_clr, user_clr))
449                         *usercon_clr = *user_clr;
450                 else
451                         return -EINVAL;
452         }
453 
454         return 0;
455 }
456 
457 /*
458  * Convert the MLS fields in the security context
459  * structure `c' from the values specified in the
460  * policy `oldp' to the values specified in the policy `newp'.
461  */
462 int mls_convert_context(struct policydb *oldp,
463                         struct policydb *newp,
464                         struct context *c)
465 {
466         struct level_datum *levdatum;
467         struct cat_datum *catdatum;
468         struct ebitmap bitmap;
469         struct ebitmap_node *node;
470         int l, i;
471 
472         if (!policydb.mls_enabled)
473                 return 0;
474 
475         for (l = 0; l < 2; l++) {
476                 levdatum = hashtab_search(newp->p_levels.table,
477                                           sym_name(oldp, SYM_LEVELS,
478                                                    c->range.level[l].sens - 1));
479 
480                 if (!levdatum)
481                         return -EINVAL;
482                 c->range.level[l].sens = levdatum->level->sens;
483 
484                 ebitmap_init(&bitmap);
485                 ebitmap_for_each_positive_bit(&c->range.level[l].cat, node, i) {
486                         int rc;
487 
488                         catdatum = hashtab_search(newp->p_cats.table,
489                                                   sym_name(oldp, SYM_CATS, i));
490                         if (!catdatum)
491                                 return -EINVAL;
492                         rc = ebitmap_set_bit(&bitmap, catdatum->value - 1, 1);
493                         if (rc)
494                                 return rc;
495                 }
496                 ebitmap_destroy(&c->range.level[l].cat);
497                 c->range.level[l].cat = bitmap;
498         }
499 
500         return 0;
501 }
502 
503 int mls_compute_sid(struct context *scontext,
504                     struct context *tcontext,
505                     u16 tclass,
506                     u32 specified,
507                     struct context *newcontext,
508                     bool sock)
509 {
510         struct range_trans rtr;
511         struct mls_range *r;
512         struct class_datum *cladatum;
513         int default_range = 0;
514 
515         if (!policydb.mls_enabled)
516                 return 0;
517 
518         switch (specified) {
519         case AVTAB_TRANSITION:
520                 /* Look for a range transition rule. */
521                 rtr.source_type = scontext->type;
522                 rtr.target_type = tcontext->type;
523                 rtr.target_class = tclass;
524                 r = hashtab_search(policydb.range_tr, &rtr);
525                 if (r)
526                         return mls_range_set(newcontext, r);
527 
528                 if (tclass && tclass <= policydb.p_classes.nprim) {
529                         cladatum = policydb.class_val_to_struct[tclass - 1];
530                         if (cladatum)
531                                 default_range = cladatum->default_range;
532                 }
533 
534                 switch (default_range) {
535                 case DEFAULT_SOURCE_LOW:
536                         return mls_context_cpy_low(newcontext, scontext);
537                 case DEFAULT_SOURCE_HIGH:
538                         return mls_context_cpy_high(newcontext, scontext);
539                 case DEFAULT_SOURCE_LOW_HIGH:
540                         return mls_context_cpy(newcontext, scontext);
541                 case DEFAULT_TARGET_LOW:
542                         return mls_context_cpy_low(newcontext, tcontext);
543                 case DEFAULT_TARGET_HIGH:
544                         return mls_context_cpy_high(newcontext, tcontext);
545                 case DEFAULT_TARGET_LOW_HIGH:
546                         return mls_context_cpy(newcontext, tcontext);
547                 }
548 
549                 /* Fallthrough */
550         case AVTAB_CHANGE:
551                 if ((tclass == policydb.process_class) || (sock == true))
552                         /* Use the process MLS attributes. */
553                         return mls_context_cpy(newcontext, scontext);
554                 else
555                         /* Use the process effective MLS attributes. */
556                         return mls_context_cpy_low(newcontext, scontext);
557         case AVTAB_MEMBER:
558                 /* Use the process effective MLS attributes. */
559                 return mls_context_cpy_low(newcontext, scontext);
560 
561         /* fall through */
562         }
563         return -EINVAL;
564 }
565 
566 #ifdef CONFIG_NETLABEL
567 /**
568  * mls_export_netlbl_lvl - Export the MLS sensitivity levels to NetLabel
569  * @context: the security context
570  * @secattr: the NetLabel security attributes
571  *
572  * Description:
573  * Given the security context copy the low MLS sensitivity level into the
574  * NetLabel MLS sensitivity level field.
575  *
576  */
577 void mls_export_netlbl_lvl(struct context *context,
578                            struct netlbl_lsm_secattr *secattr)
579 {
580         if (!policydb.mls_enabled)
581                 return;
582 
583         secattr->attr.mls.lvl = context->range.level[0].sens - 1;
584         secattr->flags |= NETLBL_SECATTR_MLS_LVL;
585 }
586 
587 /**
588  * mls_import_netlbl_lvl - Import the NetLabel MLS sensitivity levels
589  * @context: the security context
590  * @secattr: the NetLabel security attributes
591  *
592  * Description:
593  * Given the security context and the NetLabel security attributes, copy the
594  * NetLabel MLS sensitivity level into the context.
595  *
596  */
597 void mls_import_netlbl_lvl(struct context *context,
598                            struct netlbl_lsm_secattr *secattr)
599 {
600         if (!policydb.mls_enabled)
601                 return;
602 
603         context->range.level[0].sens = secattr->attr.mls.lvl + 1;
604         context->range.level[1].sens = context->range.level[0].sens;
605 }
606 
607 /**
608  * mls_export_netlbl_cat - Export the MLS categories to NetLabel
609  * @context: the security context
610  * @secattr: the NetLabel security attributes
611  *
612  * Description:
613  * Given the security context copy the low MLS categories into the NetLabel
614  * MLS category field.  Returns zero on success, negative values on failure.
615  *
616  */
617 int mls_export_netlbl_cat(struct context *context,
618                           struct netlbl_lsm_secattr *secattr)
619 {
620         int rc;
621 
622         if (!policydb.mls_enabled)
623                 return 0;
624 
625         rc = ebitmap_netlbl_export(&context->range.level[0].cat,
626                                    &secattr->attr.mls.cat);
627         if (rc == 0 && secattr->attr.mls.cat != NULL)
628                 secattr->flags |= NETLBL_SECATTR_MLS_CAT;
629 
630         return rc;
631 }
632 
633 /**
634  * mls_import_netlbl_cat - Import the MLS categories from NetLabel
635  * @context: the security context
636  * @secattr: the NetLabel security attributes
637  *
638  * Description:
639  * Copy the NetLabel security attributes into the SELinux context; since the
640  * NetLabel security attribute only contains a single MLS category use it for
641  * both the low and high categories of the context.  Returns zero on success,
642  * negative values on failure.
643  *
644  */
645 int mls_import_netlbl_cat(struct context *context,
646                           struct netlbl_lsm_secattr *secattr)
647 {
648         int rc;
649 
650         if (!policydb.mls_enabled)
651                 return 0;
652 
653         rc = ebitmap_netlbl_import(&context->range.level[0].cat,
654                                    secattr->attr.mls.cat);
655         if (rc != 0)
656                 goto import_netlbl_cat_failure;
657 
658         rc = ebitmap_cpy(&context->range.level[1].cat,
659                          &context->range.level[0].cat);
660         if (rc != 0)
661                 goto import_netlbl_cat_failure;
662 
663         return 0;
664 
665 import_netlbl_cat_failure:
666         ebitmap_destroy(&context->range.level[0].cat);
667         ebitmap_destroy(&context->range.level[1].cat);
668         return rc;
669 }
670 #endif /* CONFIG_NETLABEL */
671 

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