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TOMOYO Linux Cross Reference
Linux/security/selinux/ss/conditional.c

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  1 /* Authors: Karl MacMillan <kmacmillan@tresys.com>
  2  *          Frank Mayer <mayerf@tresys.com>
  3  *
  4  * Copyright (C) 2003 - 2004 Tresys Technology, LLC
  5  *      This program is free software; you can redistribute it and/or modify
  6  *      it under the terms of the GNU General Public License as published by
  7  *      the Free Software Foundation, version 2.
  8  */
  9 
 10 #include <linux/kernel.h>
 11 #include <linux/errno.h>
 12 #include <linux/string.h>
 13 #include <linux/spinlock.h>
 14 #include <linux/slab.h>
 15 
 16 #include "security.h"
 17 #include "conditional.h"
 18 
 19 /*
 20  * cond_evaluate_expr evaluates a conditional expr
 21  * in reverse polish notation. It returns true (1), false (0),
 22  * or undefined (-1). Undefined occurs when the expression
 23  * exceeds the stack depth of COND_EXPR_MAXDEPTH.
 24  */
 25 static int cond_evaluate_expr(struct policydb *p, struct cond_expr *expr)
 26 {
 27 
 28         struct cond_expr *cur;
 29         int s[COND_EXPR_MAXDEPTH];
 30         int sp = -1;
 31 
 32         for (cur = expr; cur; cur = cur->next) {
 33                 switch (cur->expr_type) {
 34                 case COND_BOOL:
 35                         if (sp == (COND_EXPR_MAXDEPTH - 1))
 36                                 return -1;
 37                         sp++;
 38                         s[sp] = p->bool_val_to_struct[cur->bool - 1]->state;
 39                         break;
 40                 case COND_NOT:
 41                         if (sp < 0)
 42                                 return -1;
 43                         s[sp] = !s[sp];
 44                         break;
 45                 case COND_OR:
 46                         if (sp < 1)
 47                                 return -1;
 48                         sp--;
 49                         s[sp] |= s[sp + 1];
 50                         break;
 51                 case COND_AND:
 52                         if (sp < 1)
 53                                 return -1;
 54                         sp--;
 55                         s[sp] &= s[sp + 1];
 56                         break;
 57                 case COND_XOR:
 58                         if (sp < 1)
 59                                 return -1;
 60                         sp--;
 61                         s[sp] ^= s[sp + 1];
 62                         break;
 63                 case COND_EQ:
 64                         if (sp < 1)
 65                                 return -1;
 66                         sp--;
 67                         s[sp] = (s[sp] == s[sp + 1]);
 68                         break;
 69                 case COND_NEQ:
 70                         if (sp < 1)
 71                                 return -1;
 72                         sp--;
 73                         s[sp] = (s[sp] != s[sp + 1]);
 74                         break;
 75                 default:
 76                         return -1;
 77                 }
 78         }
 79         return s[0];
 80 }
 81 
 82 /*
 83  * evaluate_cond_node evaluates the conditional stored in
 84  * a struct cond_node and if the result is different than the
 85  * current state of the node it sets the rules in the true/false
 86  * list appropriately. If the result of the expression is undefined
 87  * all of the rules are disabled for safety.
 88  */
 89 int evaluate_cond_node(struct policydb *p, struct cond_node *node)
 90 {
 91         int new_state;
 92         struct cond_av_list *cur;
 93 
 94         new_state = cond_evaluate_expr(p, node->expr);
 95         if (new_state != node->cur_state) {
 96                 node->cur_state = new_state;
 97                 if (new_state == -1)
 98                         printk(KERN_ERR "SELinux: expression result was undefined - disabling all rules.\n");
 99                 /* turn the rules on or off */
100                 for (cur = node->true_list; cur; cur = cur->next) {
101                         if (new_state <= 0)
102                                 cur->node->key.specified &= ~AVTAB_ENABLED;
103                         else
104                                 cur->node->key.specified |= AVTAB_ENABLED;
105                 }
106 
107                 for (cur = node->false_list; cur; cur = cur->next) {
108                         /* -1 or 1 */
109                         if (new_state)
110                                 cur->node->key.specified &= ~AVTAB_ENABLED;
111                         else
112                                 cur->node->key.specified |= AVTAB_ENABLED;
113                 }
114         }
115         return 0;
116 }
117 
118 int cond_policydb_init(struct policydb *p)
119 {
120         int rc;
121 
122         p->bool_val_to_struct = NULL;
123         p->cond_list = NULL;
124 
125         rc = avtab_init(&p->te_cond_avtab);
126         if (rc)
127                 return rc;
128 
129         return 0;
130 }
131 
132 static void cond_av_list_destroy(struct cond_av_list *list)
133 {
134         struct cond_av_list *cur, *next;
135         for (cur = list; cur; cur = next) {
136                 next = cur->next;
137                 /* the avtab_ptr_t node is destroy by the avtab */
138                 kfree(cur);
139         }
140 }
141 
142 static void cond_node_destroy(struct cond_node *node)
143 {
144         struct cond_expr *cur_expr, *next_expr;
145 
146         for (cur_expr = node->expr; cur_expr; cur_expr = next_expr) {
147                 next_expr = cur_expr->next;
148                 kfree(cur_expr);
149         }
150         cond_av_list_destroy(node->true_list);
151         cond_av_list_destroy(node->false_list);
152         kfree(node);
153 }
154 
155 static void cond_list_destroy(struct cond_node *list)
156 {
157         struct cond_node *next, *cur;
158 
159         if (list == NULL)
160                 return;
161 
162         for (cur = list; cur; cur = next) {
163                 next = cur->next;
164                 cond_node_destroy(cur);
165         }
166 }
167 
168 void cond_policydb_destroy(struct policydb *p)
169 {
170         kfree(p->bool_val_to_struct);
171         avtab_destroy(&p->te_cond_avtab);
172         cond_list_destroy(p->cond_list);
173 }
174 
175 int cond_init_bool_indexes(struct policydb *p)
176 {
177         kfree(p->bool_val_to_struct);
178         p->bool_val_to_struct =
179                 kmalloc(p->p_bools.nprim * sizeof(struct cond_bool_datum *), GFP_KERNEL);
180         if (!p->bool_val_to_struct)
181                 return -ENOMEM;
182         return 0;
183 }
184 
185 int cond_destroy_bool(void *key, void *datum, void *p)
186 {
187         kfree(key);
188         kfree(datum);
189         return 0;
190 }
191 
192 int cond_index_bool(void *key, void *datum, void *datap)
193 {
194         struct policydb *p;
195         struct cond_bool_datum *booldatum;
196         struct flex_array *fa;
197 
198         booldatum = datum;
199         p = datap;
200 
201         if (!booldatum->value || booldatum->value > p->p_bools.nprim)
202                 return -EINVAL;
203 
204         fa = p->sym_val_to_name[SYM_BOOLS];
205         if (flex_array_put_ptr(fa, booldatum->value - 1, key,
206                                GFP_KERNEL | __GFP_ZERO))
207                 BUG();
208         p->bool_val_to_struct[booldatum->value - 1] = booldatum;
209 
210         return 0;
211 }
212 
213 static int bool_isvalid(struct cond_bool_datum *b)
214 {
215         if (!(b->state == 0 || b->state == 1))
216                 return 0;
217         return 1;
218 }
219 
220 int cond_read_bool(struct policydb *p, struct hashtab *h, void *fp)
221 {
222         char *key = NULL;
223         struct cond_bool_datum *booldatum;
224         __le32 buf[3];
225         u32 len;
226         int rc;
227 
228         booldatum = kzalloc(sizeof(struct cond_bool_datum), GFP_KERNEL);
229         if (!booldatum)
230                 return -ENOMEM;
231 
232         rc = next_entry(buf, fp, sizeof buf);
233         if (rc)
234                 goto err;
235 
236         booldatum->value = le32_to_cpu(buf[0]);
237         booldatum->state = le32_to_cpu(buf[1]);
238 
239         rc = -EINVAL;
240         if (!bool_isvalid(booldatum))
241                 goto err;
242 
243         len = le32_to_cpu(buf[2]);
244 
245         rc = -ENOMEM;
246         key = kmalloc(len + 1, GFP_KERNEL);
247         if (!key)
248                 goto err;
249         rc = next_entry(key, fp, len);
250         if (rc)
251                 goto err;
252         key[len] = '\0';
253         rc = hashtab_insert(h, key, booldatum);
254         if (rc)
255                 goto err;
256 
257         return 0;
258 err:
259         cond_destroy_bool(key, booldatum, NULL);
260         return rc;
261 }
262 
263 struct cond_insertf_data {
264         struct policydb *p;
265         struct cond_av_list *other;
266         struct cond_av_list *head;
267         struct cond_av_list *tail;
268 };
269 
270 static int cond_insertf(struct avtab *a, struct avtab_key *k, struct avtab_datum *d, void *ptr)
271 {
272         struct cond_insertf_data *data = ptr;
273         struct policydb *p = data->p;
274         struct cond_av_list *other = data->other, *list, *cur;
275         struct avtab_node *node_ptr;
276         u8 found;
277         int rc = -EINVAL;
278 
279         /*
280          * For type rules we have to make certain there aren't any
281          * conflicting rules by searching the te_avtab and the
282          * cond_te_avtab.
283          */
284         if (k->specified & AVTAB_TYPE) {
285                 if (avtab_search(&p->te_avtab, k)) {
286                         printk(KERN_ERR "SELinux: type rule already exists outside of a conditional.\n");
287                         goto err;
288                 }
289                 /*
290                  * If we are reading the false list other will be a pointer to
291                  * the true list. We can have duplicate entries if there is only
292                  * 1 other entry and it is in our true list.
293                  *
294                  * If we are reading the true list (other == NULL) there shouldn't
295                  * be any other entries.
296                  */
297                 if (other) {
298                         node_ptr = avtab_search_node(&p->te_cond_avtab, k);
299                         if (node_ptr) {
300                                 if (avtab_search_node_next(node_ptr, k->specified)) {
301                                         printk(KERN_ERR "SELinux: too many conflicting type rules.\n");
302                                         goto err;
303                                 }
304                                 found = 0;
305                                 for (cur = other; cur; cur = cur->next) {
306                                         if (cur->node == node_ptr) {
307                                                 found = 1;
308                                                 break;
309                                         }
310                                 }
311                                 if (!found) {
312                                         printk(KERN_ERR "SELinux: conflicting type rules.\n");
313                                         goto err;
314                                 }
315                         }
316                 } else {
317                         if (avtab_search(&p->te_cond_avtab, k)) {
318                                 printk(KERN_ERR "SELinux: conflicting type rules when adding type rule for true.\n");
319                                 goto err;
320                         }
321                 }
322         }
323 
324         node_ptr = avtab_insert_nonunique(&p->te_cond_avtab, k, d);
325         if (!node_ptr) {
326                 printk(KERN_ERR "SELinux: could not insert rule.\n");
327                 rc = -ENOMEM;
328                 goto err;
329         }
330 
331         list = kzalloc(sizeof(struct cond_av_list), GFP_KERNEL);
332         if (!list) {
333                 rc = -ENOMEM;
334                 goto err;
335         }
336 
337         list->node = node_ptr;
338         if (!data->head)
339                 data->head = list;
340         else
341                 data->tail->next = list;
342         data->tail = list;
343         return 0;
344 
345 err:
346         cond_av_list_destroy(data->head);
347         data->head = NULL;
348         return rc;
349 }
350 
351 static int cond_read_av_list(struct policydb *p, void *fp, struct cond_av_list **ret_list, struct cond_av_list *other)
352 {
353         int i, rc;
354         __le32 buf[1];
355         u32 len;
356         struct cond_insertf_data data;
357 
358         *ret_list = NULL;
359 
360         len = 0;
361         rc = next_entry(buf, fp, sizeof(u32));
362         if (rc)
363                 return rc;
364 
365         len = le32_to_cpu(buf[0]);
366         if (len == 0)
367                 return 0;
368 
369         data.p = p;
370         data.other = other;
371         data.head = NULL;
372         data.tail = NULL;
373         for (i = 0; i < len; i++) {
374                 rc = avtab_read_item(&p->te_cond_avtab, fp, p, cond_insertf,
375                                      &data);
376                 if (rc)
377                         return rc;
378         }
379 
380         *ret_list = data.head;
381         return 0;
382 }
383 
384 static int expr_isvalid(struct policydb *p, struct cond_expr *expr)
385 {
386         if (expr->expr_type <= 0 || expr->expr_type > COND_LAST) {
387                 printk(KERN_ERR "SELinux: conditional expressions uses unknown operator.\n");
388                 return 0;
389         }
390 
391         if (expr->bool > p->p_bools.nprim) {
392                 printk(KERN_ERR "SELinux: conditional expressions uses unknown bool.\n");
393                 return 0;
394         }
395         return 1;
396 }
397 
398 static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
399 {
400         __le32 buf[2];
401         u32 len, i;
402         int rc;
403         struct cond_expr *expr = NULL, *last = NULL;
404 
405         rc = next_entry(buf, fp, sizeof(u32));
406         if (rc)
407                 return rc;
408 
409         node->cur_state = le32_to_cpu(buf[0]);
410 
411         len = 0;
412         rc = next_entry(buf, fp, sizeof(u32));
413         if (rc)
414                 return rc;
415 
416         /* expr */
417         len = le32_to_cpu(buf[0]);
418 
419         for (i = 0; i < len; i++) {
420                 rc = next_entry(buf, fp, sizeof(u32) * 2);
421                 if (rc)
422                         goto err;
423 
424                 rc = -ENOMEM;
425                 expr = kzalloc(sizeof(struct cond_expr), GFP_KERNEL);
426                 if (!expr)
427                         goto err;
428 
429                 expr->expr_type = le32_to_cpu(buf[0]);
430                 expr->bool = le32_to_cpu(buf[1]);
431 
432                 if (!expr_isvalid(p, expr)) {
433                         rc = -EINVAL;
434                         kfree(expr);
435                         goto err;
436                 }
437 
438                 if (i == 0)
439                         node->expr = expr;
440                 else
441                         last->next = expr;
442                 last = expr;
443         }
444 
445         rc = cond_read_av_list(p, fp, &node->true_list, NULL);
446         if (rc)
447                 goto err;
448         rc = cond_read_av_list(p, fp, &node->false_list, node->true_list);
449         if (rc)
450                 goto err;
451         return 0;
452 err:
453         cond_node_destroy(node);
454         return rc;
455 }
456 
457 int cond_read_list(struct policydb *p, void *fp)
458 {
459         struct cond_node *node, *last = NULL;
460         __le32 buf[1];
461         u32 i, len;
462         int rc;
463 
464         rc = next_entry(buf, fp, sizeof buf);
465         if (rc)
466                 return rc;
467 
468         len = le32_to_cpu(buf[0]);
469 
470         rc = avtab_alloc(&(p->te_cond_avtab), p->te_avtab.nel);
471         if (rc)
472                 goto err;
473 
474         for (i = 0; i < len; i++) {
475                 rc = -ENOMEM;
476                 node = kzalloc(sizeof(struct cond_node), GFP_KERNEL);
477                 if (!node)
478                         goto err;
479 
480                 rc = cond_read_node(p, node, fp);
481                 if (rc)
482                         goto err;
483 
484                 if (i == 0)
485                         p->cond_list = node;
486                 else
487                         last->next = node;
488                 last = node;
489         }
490         return 0;
491 err:
492         cond_list_destroy(p->cond_list);
493         p->cond_list = NULL;
494         return rc;
495 }
496 
497 int cond_write_bool(void *vkey, void *datum, void *ptr)
498 {
499         char *key = vkey;
500         struct cond_bool_datum *booldatum = datum;
501         struct policy_data *pd = ptr;
502         void *fp = pd->fp;
503         __le32 buf[3];
504         u32 len;
505         int rc;
506 
507         len = strlen(key);
508         buf[0] = cpu_to_le32(booldatum->value);
509         buf[1] = cpu_to_le32(booldatum->state);
510         buf[2] = cpu_to_le32(len);
511         rc = put_entry(buf, sizeof(u32), 3, fp);
512         if (rc)
513                 return rc;
514         rc = put_entry(key, 1, len, fp);
515         if (rc)
516                 return rc;
517         return 0;
518 }
519 
520 /*
521  * cond_write_cond_av_list doesn't write out the av_list nodes.
522  * Instead it writes out the key/value pairs from the avtab. This
523  * is necessary because there is no way to uniquely identifying rules
524  * in the avtab so it is not possible to associate individual rules
525  * in the avtab with a conditional without saving them as part of
526  * the conditional. This means that the avtab with the conditional
527  * rules will not be saved but will be rebuilt on policy load.
528  */
529 static int cond_write_av_list(struct policydb *p,
530                               struct cond_av_list *list, struct policy_file *fp)
531 {
532         __le32 buf[1];
533         struct cond_av_list *cur_list;
534         u32 len;
535         int rc;
536 
537         len = 0;
538         for (cur_list = list; cur_list != NULL; cur_list = cur_list->next)
539                 len++;
540 
541         buf[0] = cpu_to_le32(len);
542         rc = put_entry(buf, sizeof(u32), 1, fp);
543         if (rc)
544                 return rc;
545 
546         if (len == 0)
547                 return 0;
548 
549         for (cur_list = list; cur_list != NULL; cur_list = cur_list->next) {
550                 rc = avtab_write_item(p, cur_list->node, fp);
551                 if (rc)
552                         return rc;
553         }
554 
555         return 0;
556 }
557 
558 static int cond_write_node(struct policydb *p, struct cond_node *node,
559                     struct policy_file *fp)
560 {
561         struct cond_expr *cur_expr;
562         __le32 buf[2];
563         int rc;
564         u32 len = 0;
565 
566         buf[0] = cpu_to_le32(node->cur_state);
567         rc = put_entry(buf, sizeof(u32), 1, fp);
568         if (rc)
569                 return rc;
570 
571         for (cur_expr = node->expr; cur_expr != NULL; cur_expr = cur_expr->next)
572                 len++;
573 
574         buf[0] = cpu_to_le32(len);
575         rc = put_entry(buf, sizeof(u32), 1, fp);
576         if (rc)
577                 return rc;
578 
579         for (cur_expr = node->expr; cur_expr != NULL; cur_expr = cur_expr->next) {
580                 buf[0] = cpu_to_le32(cur_expr->expr_type);
581                 buf[1] = cpu_to_le32(cur_expr->bool);
582                 rc = put_entry(buf, sizeof(u32), 2, fp);
583                 if (rc)
584                         return rc;
585         }
586 
587         rc = cond_write_av_list(p, node->true_list, fp);
588         if (rc)
589                 return rc;
590         rc = cond_write_av_list(p, node->false_list, fp);
591         if (rc)
592                 return rc;
593 
594         return 0;
595 }
596 
597 int cond_write_list(struct policydb *p, struct cond_node *list, void *fp)
598 {
599         struct cond_node *cur;
600         u32 len;
601         __le32 buf[1];
602         int rc;
603 
604         len = 0;
605         for (cur = list; cur != NULL; cur = cur->next)
606                 len++;
607         buf[0] = cpu_to_le32(len);
608         rc = put_entry(buf, sizeof(u32), 1, fp);
609         if (rc)
610                 return rc;
611 
612         for (cur = list; cur != NULL; cur = cur->next) {
613                 rc = cond_write_node(p, cur, fp);
614                 if (rc)
615                         return rc;
616         }
617 
618         return 0;
619 }
620 /* Determine whether additional permissions are granted by the conditional
621  * av table, and if so, add them to the result
622  */
623 void cond_compute_av(struct avtab *ctab, struct avtab_key *key, struct av_decision *avd)
624 {
625         struct avtab_node *node;
626 
627         if (!ctab || !key || !avd)
628                 return;
629 
630         for (node = avtab_search_node(ctab, key); node;
631                                 node = avtab_search_node_next(node, key->specified)) {
632                 if ((u16)(AVTAB_ALLOWED|AVTAB_ENABLED) ==
633                     (node->key.specified & (AVTAB_ALLOWED|AVTAB_ENABLED)))
634                         avd->allowed |= node->datum.data;
635                 if ((u16)(AVTAB_AUDITDENY|AVTAB_ENABLED) ==
636                     (node->key.specified & (AVTAB_AUDITDENY|AVTAB_ENABLED)))
637                         /* Since a '' in an auditdeny mask represents a
638                          * permission we do NOT want to audit (dontaudit), we use
639                          * the '&' operand to ensure that all ''s in the mask
640                          * are retained (much unlike the allow and auditallow cases).
641                          */
642                         avd->auditdeny &= node->datum.data;
643                 if ((u16)(AVTAB_AUDITALLOW|AVTAB_ENABLED) ==
644                     (node->key.specified & (AVTAB_AUDITALLOW|AVTAB_ENABLED)))
645                         avd->auditallow |= node->datum.data;
646         }
647         return;
648 }
649 

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