selinux: allow MLS->non-MLS and vice versa upon policy reload
[linux-2.6.git] / security / selinux / ss / mls.c
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.moore@hp.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(policydb.p_sens_val_to_name[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 = policydb.p_cat_val_to_name[prev];
59                                         len += strlen(nm) + 1;
60                                 }
61                                 nm = policydb.p_cat_val_to_name[i];
62                                 len += strlen(nm) + 1;
63                                 head = i;
64                         }
65                         prev = i;
66                 }
67                 if (prev != head) {
68                         nm = policydb.p_cat_val_to_name[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,
106                        policydb.p_sens_val_to_name[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 = policydb.p_cat_val_to_name[prev];
122                                         strcpy(scontextp, nm);
123                                         scontextp += strlen(nm);
124                                 }
125                                 if (prev < 0)
126                                         *scontextp++ = ':';
127                                 else
128                                         *scontextp++ = ',';
129                                 nm = policydb.p_cat_val_to_name[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 = policydb.p_cat_val_to_name[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         struct ebitmap_node *node;
164         int i;
165
166         if (!l->sens || l->sens > p->p_levels.nprim)
167                 return 0;
168         levdatum = hashtab_search(p->p_levels.table,
169                                   p->p_sens_val_to_name[l->sens - 1]);
170         if (!levdatum)
171                 return 0;
172
173         ebitmap_for_each_positive_bit(&l->cat, node, i) {
174                 if (i > p->p_cats.nprim)
175                         return 0;
176                 if (!ebitmap_get_bit(&levdatum->level->cat, i)) {
177                         /*
178                          * Category may not be associated with
179                          * sensitivity.
180                          */
181                         return 0;
182                 }
183         }
184
185         return 1;
186 }
187
188 int mls_range_isvalid(struct policydb *p, struct mls_range *r)
189 {
190         return (mls_level_isvalid(p, &r->level[0]) &&
191                 mls_level_isvalid(p, &r->level[1]) &&
192                 mls_level_dom(&r->level[1], &r->level[0]));
193 }
194
195 /*
196  * Return 1 if the MLS fields in the security context
197  * structure `c' are valid.  Return 0 otherwise.
198  */
199 int mls_context_isvalid(struct policydb *p, struct context *c)
200 {
201         struct user_datum *usrdatum;
202
203         if (!p->mls_enabled)
204                 return 1;
205
206         if (!mls_range_isvalid(p, &c->range))
207                 return 0;
208
209         if (c->role == OBJECT_R_VAL)
210                 return 1;
211
212         /*
213          * User must be authorized for the MLS range.
214          */
215         if (!c->user || c->user > p->p_users.nprim)
216                 return 0;
217         usrdatum = p->user_val_to_struct[c->user - 1];
218         if (!mls_range_contains(usrdatum->range, c->range))
219                 return 0; /* user may not be associated with range */
220
221         return 1;
222 }
223
224 /*
225  * Set the MLS fields in the security context structure
226  * `context' based on the string representation in
227  * the string `*scontext'.  Update `*scontext' to
228  * point to the end of the string representation of
229  * the MLS fields.
230  *
231  * This function modifies the string in place, inserting
232  * NULL characters to terminate the MLS fields.
233  *
234  * If a def_sid is provided and no MLS field is present,
235  * copy the MLS field of the associated default context.
236  * Used for upgraded to MLS systems where objects may lack
237  * MLS fields.
238  *
239  * Policy read-lock must be held for sidtab lookup.
240  *
241  */
242 int mls_context_to_sid(struct policydb *pol,
243                        char oldc,
244                        char **scontext,
245                        struct context *context,
246                        struct sidtab *s,
247                        u32 def_sid)
248 {
249
250         char delim;
251         char *scontextp, *p, *rngptr;
252         struct level_datum *levdatum;
253         struct cat_datum *catdatum, *rngdatum;
254         int l, rc = -EINVAL;
255
256         if (!pol->mls_enabled) {
257                 if (def_sid != SECSID_NULL && oldc)
258                         *scontext += strlen(*scontext)+1;
259                 return 0;
260         }
261
262         /*
263          * No MLS component to the security context, try and map to
264          * default if provided.
265          */
266         if (!oldc) {
267                 struct context *defcon;
268
269                 if (def_sid == SECSID_NULL)
270                         goto out;
271
272                 defcon = sidtab_search(s, def_sid);
273                 if (!defcon)
274                         goto out;
275
276                 rc = mls_context_cpy(context, defcon);
277                 goto out;
278         }
279
280         /* Extract low sensitivity. */
281         scontextp = p = *scontext;
282         while (*p && *p != ':' && *p != '-')
283                 p++;
284
285         delim = *p;
286         if (delim != '\0')
287                 *p++ = '\0';
288
289         for (l = 0; l < 2; l++) {
290                 levdatum = hashtab_search(pol->p_levels.table, scontextp);
291                 if (!levdatum) {
292                         rc = -EINVAL;
293                         goto out;
294                 }
295
296                 context->range.level[l].sens = levdatum->level->sens;
297
298                 if (delim == ':') {
299                         /* Extract category set. */
300                         while (1) {
301                                 scontextp = p;
302                                 while (*p && *p != ',' && *p != '-')
303                                         p++;
304                                 delim = *p;
305                                 if (delim != '\0')
306                                         *p++ = '\0';
307
308                                 /* Separate into range if exists */
309                                 rngptr = strchr(scontextp, '.');
310                                 if (rngptr != NULL) {
311                                         /* Remove '.' */
312                                         *rngptr++ = '\0';
313                                 }
314
315                                 catdatum = hashtab_search(pol->p_cats.table,
316                                                           scontextp);
317                                 if (!catdatum) {
318                                         rc = -EINVAL;
319                                         goto out;
320                                 }
321
322                                 rc = ebitmap_set_bit(&context->range.level[l].cat,
323                                                      catdatum->value - 1, 1);
324                                 if (rc)
325                                         goto out;
326
327                                 /* If range, set all categories in range */
328                                 if (rngptr) {
329                                         int i;
330
331                                         rngdatum = hashtab_search(pol->p_cats.table, rngptr);
332                                         if (!rngdatum) {
333                                                 rc = -EINVAL;
334                                                 goto out;
335                                         }
336
337                                         if (catdatum->value >= rngdatum->value) {
338                                                 rc = -EINVAL;
339                                                 goto out;
340                                         }
341
342                                         for (i = catdatum->value; i < rngdatum->value; i++) {
343                                                 rc = ebitmap_set_bit(&context->range.level[l].cat, i, 1);
344                                                 if (rc)
345                                                         goto out;
346                                         }
347                                 }
348
349                                 if (delim != ',')
350                                         break;
351                         }
352                 }
353                 if (delim == '-') {
354                         /* Extract high sensitivity. */
355                         scontextp = p;
356                         while (*p && *p != ':')
357                                 p++;
358
359                         delim = *p;
360                         if (delim != '\0')
361                                 *p++ = '\0';
362                 } else
363                         break;
364         }
365
366         if (l == 0) {
367                 context->range.level[1].sens = context->range.level[0].sens;
368                 rc = ebitmap_cpy(&context->range.level[1].cat,
369                                  &context->range.level[0].cat);
370                 if (rc)
371                         goto out;
372         }
373         *scontext = ++p;
374         rc = 0;
375 out:
376         return rc;
377 }
378
379 /*
380  * Set the MLS fields in the security context structure
381  * `context' based on the string representation in
382  * the string `str'.  This function will allocate temporary memory with the
383  * given constraints of gfp_mask.
384  */
385 int mls_from_string(char *str, struct context *context, gfp_t gfp_mask)
386 {
387         char *tmpstr, *freestr;
388         int rc;
389
390         if (!policydb.mls_enabled)
391                 return -EINVAL;
392
393         /* we need freestr because mls_context_to_sid will change
394            the value of tmpstr */
395         tmpstr = freestr = kstrdup(str, gfp_mask);
396         if (!tmpstr) {
397                 rc = -ENOMEM;
398         } else {
399                 rc = mls_context_to_sid(&policydb, ':', &tmpstr, context,
400                                         NULL, SECSID_NULL);
401                 kfree(freestr);
402         }
403
404         return rc;
405 }
406
407 /*
408  * Copies the MLS range `range' into `context'.
409  */
410 int mls_range_set(struct context *context,
411                                 struct mls_range *range)
412 {
413         int l, rc = 0;
414
415         /* Copy the MLS range into the  context */
416         for (l = 0; l < 2; l++) {
417                 context->range.level[l].sens = range->level[l].sens;
418                 rc = ebitmap_cpy(&context->range.level[l].cat,
419                                  &range->level[l].cat);
420                 if (rc)
421                         break;
422         }
423
424         return rc;
425 }
426
427 int mls_setup_user_range(struct context *fromcon, struct user_datum *user,
428                          struct context *usercon)
429 {
430         if (policydb.mls_enabled) {
431                 struct mls_level *fromcon_sen = &(fromcon->range.level[0]);
432                 struct mls_level *fromcon_clr = &(fromcon->range.level[1]);
433                 struct mls_level *user_low = &(user->range.level[0]);
434                 struct mls_level *user_clr = &(user->range.level[1]);
435                 struct mls_level *user_def = &(user->dfltlevel);
436                 struct mls_level *usercon_sen = &(usercon->range.level[0]);
437                 struct mls_level *usercon_clr = &(usercon->range.level[1]);
438
439                 /* Honor the user's default level if we can */
440                 if (mls_level_between(user_def, fromcon_sen, fromcon_clr))
441                         *usercon_sen = *user_def;
442                 else if (mls_level_between(fromcon_sen, user_def, user_clr))
443                         *usercon_sen = *fromcon_sen;
444                 else if (mls_level_between(fromcon_clr, user_low, user_def))
445                         *usercon_sen = *user_low;
446                 else
447                         return -EINVAL;
448
449                 /* Lower the clearance of available contexts
450                    if the clearance of "fromcon" is lower than
451                    that of the user's default clearance (but
452                    only if the "fromcon" clearance dominates
453                    the user's computed sensitivity level) */
454                 if (mls_level_dom(user_clr, fromcon_clr))
455                         *usercon_clr = *fromcon_clr;
456                 else if (mls_level_dom(fromcon_clr, user_clr))
457                         *usercon_clr = *user_clr;
458                 else
459                         return -EINVAL;
460         }
461
462         return 0;
463 }
464
465 /*
466  * Convert the MLS fields in the security context
467  * structure `c' from the values specified in the
468  * policy `oldp' to the values specified in the policy `newp'.
469  */
470 int mls_convert_context(struct policydb *oldp,
471                         struct policydb *newp,
472                         struct context *c)
473 {
474         struct level_datum *levdatum;
475         struct cat_datum *catdatum;
476         struct ebitmap bitmap;
477         struct ebitmap_node *node;
478         int l, i;
479
480         if (!policydb.mls_enabled)
481                 return 0;
482
483         for (l = 0; l < 2; l++) {
484                 levdatum = hashtab_search(newp->p_levels.table,
485                         oldp->p_sens_val_to_name[c->range.level[l].sens - 1]);
486
487                 if (!levdatum)
488                         return -EINVAL;
489                 c->range.level[l].sens = levdatum->level->sens;
490
491                 ebitmap_init(&bitmap);
492                 ebitmap_for_each_positive_bit(&c->range.level[l].cat, node, i) {
493                         int rc;
494
495                         catdatum = hashtab_search(newp->p_cats.table,
496                                                   oldp->p_cat_val_to_name[i]);
497                         if (!catdatum)
498                                 return -EINVAL;
499                         rc = ebitmap_set_bit(&bitmap, catdatum->value - 1, 1);
500                         if (rc)
501                                 return rc;
502                 }
503                 ebitmap_destroy(&c->range.level[l].cat);
504                 c->range.level[l].cat = bitmap;
505         }
506
507         return 0;
508 }
509
510 int mls_compute_sid(struct context *scontext,
511                     struct context *tcontext,
512                     u16 tclass,
513                     u32 specified,
514                     struct context *newcontext)
515 {
516         struct range_trans rtr;
517         struct mls_range *r;
518
519         if (!policydb.mls_enabled)
520                 return 0;
521
522         switch (specified) {
523         case AVTAB_TRANSITION:
524                 /* Look for a range transition rule. */
525                 rtr.source_type = scontext->type;
526                 rtr.target_type = tcontext->type;
527                 rtr.target_class = tclass;
528                 r = hashtab_search(policydb.range_tr, &rtr);
529                 if (r)
530                         return mls_range_set(newcontext, r);
531                 /* Fallthrough */
532         case AVTAB_CHANGE:
533                 if (tclass == policydb.process_class)
534                         /* Use the process MLS attributes. */
535                         return mls_context_cpy(newcontext, scontext);
536                 else
537                         /* Use the process effective MLS attributes. */
538                         return mls_context_cpy_low(newcontext, scontext);
539         case AVTAB_MEMBER:
540                 /* Use the process effective MLS attributes. */
541                 return mls_context_cpy_low(newcontext, scontext);
542
543         /* fall through */
544         }
545         return -EINVAL;
546 }
547
548 #ifdef CONFIG_NETLABEL
549 /**
550  * mls_export_netlbl_lvl - Export the MLS sensitivity levels to NetLabel
551  * @context: the security context
552  * @secattr: the NetLabel security attributes
553  *
554  * Description:
555  * Given the security context copy the low MLS sensitivity level into the
556  * NetLabel MLS sensitivity level field.
557  *
558  */
559 void mls_export_netlbl_lvl(struct context *context,
560                            struct netlbl_lsm_secattr *secattr)
561 {
562         if (!policydb.mls_enabled)
563                 return;
564
565         secattr->attr.mls.lvl = context->range.level[0].sens - 1;
566         secattr->flags |= NETLBL_SECATTR_MLS_LVL;
567 }
568
569 /**
570  * mls_import_netlbl_lvl - Import the NetLabel MLS sensitivity levels
571  * @context: the security context
572  * @secattr: the NetLabel security attributes
573  *
574  * Description:
575  * Given the security context and the NetLabel security attributes, copy the
576  * NetLabel MLS sensitivity level into the context.
577  *
578  */
579 void mls_import_netlbl_lvl(struct context *context,
580                            struct netlbl_lsm_secattr *secattr)
581 {
582         if (!policydb.mls_enabled)
583                 return;
584
585         context->range.level[0].sens = secattr->attr.mls.lvl + 1;
586         context->range.level[1].sens = context->range.level[0].sens;
587 }
588
589 /**
590  * mls_export_netlbl_cat - Export the MLS categories to NetLabel
591  * @context: the security context
592  * @secattr: the NetLabel security attributes
593  *
594  * Description:
595  * Given the security context copy the low MLS categories into the NetLabel
596  * MLS category field.  Returns zero on success, negative values on failure.
597  *
598  */
599 int mls_export_netlbl_cat(struct context *context,
600                           struct netlbl_lsm_secattr *secattr)
601 {
602         int rc;
603
604         if (!policydb.mls_enabled)
605                 return 0;
606
607         rc = ebitmap_netlbl_export(&context->range.level[0].cat,
608                                    &secattr->attr.mls.cat);
609         if (rc == 0 && secattr->attr.mls.cat != NULL)
610                 secattr->flags |= NETLBL_SECATTR_MLS_CAT;
611
612         return rc;
613 }
614
615 /**
616  * mls_import_netlbl_cat - Import the MLS categories from NetLabel
617  * @context: the security context
618  * @secattr: the NetLabel security attributes
619  *
620  * Description:
621  * Copy the NetLabel security attributes into the SELinux context; since the
622  * NetLabel security attribute only contains a single MLS category use it for
623  * both the low and high categories of the context.  Returns zero on success,
624  * negative values on failure.
625  *
626  */
627 int mls_import_netlbl_cat(struct context *context,
628                           struct netlbl_lsm_secattr *secattr)
629 {
630         int rc;
631
632         if (!policydb.mls_enabled)
633                 return 0;
634
635         rc = ebitmap_netlbl_import(&context->range.level[0].cat,
636                                    secattr->attr.mls.cat);
637         if (rc != 0)
638                 goto import_netlbl_cat_failure;
639
640         rc = ebitmap_cpy(&context->range.level[1].cat,
641                          &context->range.level[0].cat);
642         if (rc != 0)
643                 goto import_netlbl_cat_failure;
644
645         return 0;
646
647 import_netlbl_cat_failure:
648         ebitmap_destroy(&context->range.level[0].cat);
649         ebitmap_destroy(&context->range.level[1].cat);
650         return rc;
651 }
652 #endif /* CONFIG_NETLABEL */