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 /* Ported to Xen 3.0, George Coker, <gscoker@alpha.ncsc.mil> */
11 
12 #include <asm/byteorder.h>
13 #include <xen/lib.h>
14 #include <xen/types.h>
15 #include <xen/errno.h>
16 #include <xen/string.h>
17 #include <xen/spinlock.h>
18 #include <xen/xmalloc.h>
19 
20 #include "security.h"
21 #include "conditional.h"
22 
23 /*
24  * cond_evaluate_expr evaluates a conditional expr
25  * in reverse polish notation. It returns true (1), false (0),
26  * or undefined (-1). Undefined occurs when the expression
27  * exceeds the stack depth of COND_EXPR_MAXDEPTH.
28  */
cond_evaluate_expr(struct policydb * p,struct cond_expr * expr)29 static int cond_evaluate_expr(struct policydb *p, struct cond_expr *expr)
30 {
31     struct cond_expr *cur;
32     int s[COND_EXPR_MAXDEPTH];
33     int sp = -1;
34 
35     for ( cur = expr; cur != NULL; cur = cur->next )
36     {
37         switch ( cur->expr_type )
38         {
39             case COND_BOOL:
40                 if ( sp == (COND_EXPR_MAXDEPTH - 1) )
41                     return -1;
42                 sp++;
43                 s[sp] = p->bool_val_to_struct[cur->bool_val - 1]->state;
44             break;
45             case COND_NOT:
46                 if ( sp < 0 )
47                     return -1;
48                 s[sp] = !s[sp];
49             break;
50             case COND_OR:
51                 if ( sp < 1 )
52                     return -1;
53                 sp--;
54                 s[sp] |= s[sp + 1];
55             break;
56             case COND_AND:
57                 if ( sp < 1 )
58                     return -1;
59                 sp--;
60                 s[sp] &= s[sp + 1];
61             break;
62           case COND_XOR:
63                 if ( sp < 1 )
64                     return -1;
65                sp--;
66                 s[sp] ^= s[sp + 1];
67                break;
68             case COND_EQ:
69                 if ( sp < 1 )
70                     return -1;
71                 sp--;
72                 s[sp] = (s[sp] == s[sp + 1]);
73             break;
74             case COND_NEQ:
75                 if ( sp < 1 )
76                     return -1;
77                 sp--;
78                 s[sp] = (s[sp] != s[sp + 1]);
79             break;
80             default:
81                 return -1;
82         }
83     }
84     return s[0];
85 }
86 
87 /*
88  * evaluate_cond_node evaluates the conditional stored in
89  * a struct cond_node and if the result is different than the
90  * current state of the node it sets the rules in the true/false
91  * list appropriately. If the result of the expression is undefined
92  * all of the rules are disabled for safety.
93  */
evaluate_cond_node(struct policydb * p,struct cond_node * node)94 int evaluate_cond_node(struct policydb *p, struct cond_node *node)
95 {
96     int new_state;
97     struct cond_av_list* cur;
98 
99     new_state = cond_evaluate_expr(p, node->expr);
100     if ( new_state != node->cur_state )
101     {
102         node->cur_state = new_state;
103         if ( new_state == -1 )
104             printk(KERN_ERR "Flask: expression result was undefined - disabling all rules.\n");
105         /* turn the rules on or off */
106         for ( cur = node->true_list; cur != NULL; cur = cur->next )
107         {
108             if ( new_state <= 0 )
109                 cur->node->key.specified &= ~AVTAB_ENABLED;
110             else
111                 cur->node->key.specified |= AVTAB_ENABLED;
112         }
113 
114         for ( cur = node->false_list; cur != NULL; cur = cur->next )
115         {
116             /* -1 or 1 */
117             if ( new_state )
118                 cur->node->key.specified &= ~AVTAB_ENABLED;
119             else
120                 cur->node->key.specified |= AVTAB_ENABLED;
121         }
122     }
123     return 0;
124 }
125 
cond_policydb_init(struct policydb * p)126 int cond_policydb_init(struct policydb *p)
127 {
128     p->bool_val_to_struct = NULL;
129     p->cond_list = NULL;
130     if ( avtab_init(&p->te_cond_avtab) )
131         return -1;
132 
133     return 0;
134 }
135 
cond_av_list_destroy(struct cond_av_list * list)136 static void cond_av_list_destroy(struct cond_av_list *list)
137 {
138     struct cond_av_list *cur, *next;
139     for ( cur = list; cur != NULL; cur = next )
140     {
141         next = cur->next;
142         /* the avtab_ptr_t node is destroy by the avtab */
143         xfree(cur);
144     }
145 }
146 
cond_node_destroy(struct cond_node * node)147 static void cond_node_destroy(struct cond_node *node)
148 {
149     struct cond_expr *cur_expr, *next_expr;
150 
151     for ( cur_expr = node->expr; cur_expr != NULL; cur_expr = next_expr )
152     {
153         next_expr = cur_expr->next;
154         xfree(cur_expr);
155     }
156     cond_av_list_destroy(node->true_list);
157     cond_av_list_destroy(node->false_list);
158     xfree(node);
159 }
160 
cond_list_destroy(struct cond_node * list)161 static void cond_list_destroy(struct cond_node *list)
162 {
163     struct cond_node *next, *cur;
164 
165     if ( list == NULL )
166         return;
167 
168     for ( cur = list; cur != NULL; cur = next )
169     {
170         next = cur->next;
171         cond_node_destroy(cur);
172     }
173 }
174 
cond_policydb_destroy(struct policydb * p)175 void cond_policydb_destroy(struct policydb *p)
176 {
177     xfree(p->bool_val_to_struct);
178     avtab_destroy(&p->te_cond_avtab);
179     cond_list_destroy(p->cond_list);
180 }
181 
cond_init_bool_indexes(struct policydb * p)182 int cond_init_bool_indexes(struct policydb *p)
183 {
184     xfree(p->bool_val_to_struct);
185     p->bool_val_to_struct = (struct cond_bool_datum**)
186         xmalloc_array(struct cond_bool_datum*, p->p_bools.nprim);
187     if ( !p->bool_val_to_struct )
188         return -1;
189     return 0;
190 }
191 
cond_destroy_bool(void * key,void * datum,void * p)192 int cond_destroy_bool(void *key, void *datum, void *p)
193 {
194     xfree(key);
195     xfree(datum);
196     return 0;
197 }
198 
cond_index_bool(void * key,void * datum,void * datap)199 int cond_index_bool(void *key, void *datum, void *datap)
200 {
201     struct policydb *p;
202     struct cond_bool_datum *booldatum;
203 
204     booldatum = datum;
205     p = datap;
206 
207     if ( !booldatum->value || booldatum->value > p->p_bools.nprim )
208         return -EINVAL;
209 
210     p->p_bool_val_to_name[booldatum->value - 1] = key;
211     p->bool_val_to_struct[booldatum->value -1] = booldatum;
212 
213     return 0;
214 }
215 
bool_isvalid(struct cond_bool_datum * b)216 static int bool_isvalid(struct cond_bool_datum *b)
217 {
218     if ( !(b->state == 0 || b->state == 1) )
219         return 0;
220     return 1;
221 }
222 
cond_read_bool(struct policydb * p,struct hashtab * h,void * fp)223 int cond_read_bool(struct policydb *p, struct hashtab *h, void *fp)
224 {
225     char *key = NULL;
226     struct cond_bool_datum *booldatum;
227     __le32 buf[3];
228     u32 len;
229     int rc;
230 
231     booldatum = xzalloc(struct cond_bool_datum);
232     if ( !booldatum )
233         return -1;
234 
235     rc = next_entry(buf, fp, sizeof buf);
236     if ( rc < 0 )
237         goto err;
238 
239     booldatum->value = le32_to_cpu(buf[0]);
240     booldatum->state = le32_to_cpu(buf[1]);
241 
242     if ( !bool_isvalid(booldatum) )
243         goto err;
244 
245     len = le32_to_cpu(buf[2]);
246 
247     key = xmalloc_array(char, len + 1);
248     if ( !key )
249         goto err;
250     rc = next_entry(key, fp, len);
251     if ( rc < 0 )
252         goto err;
253     key[len] = 0;
254     if ( hashtab_insert(h, key, booldatum) )
255         goto err;
256 
257     return 0;
258 err:
259     cond_destroy_bool(key, booldatum, NULL);
260     return -1;
261 }
262 
263 struct cond_insertf_data
264 {
265     struct policydb *p;
266     struct cond_av_list *other;
267     struct cond_av_list *head;
268     struct cond_av_list *tail;
269 };
270 
cond_insertf(struct avtab * a,struct avtab_key * k,struct avtab_datum * d,void * ptr)271 static int cond_insertf(struct avtab *a, struct avtab_key *k,
272                                             struct avtab_datum *d, void *ptr)
273 {
274     struct cond_insertf_data *data = ptr;
275     struct policydb *p = data->p;
276     struct cond_av_list *other = data->other, *list, *cur;
277     struct avtab_node *node_ptr;
278     u8 found;
279 
280     /*
281      * For type rules we have to make certain there aren't any
282      * conflicting rules by searching the te_avtab and the
283      * cond_te_avtab.
284      */
285     if ( k->specified & AVTAB_TYPE )
286     {
287         if ( avtab_search(&p->te_avtab, k) )
288         {
289             printk("Flask: type rule already exists outside of a "
290                                                                 "conditional.");
291             goto err;
292         }
293         /*
294          * If we are reading the false list other will be a pointer to
295          * the true list. We can have duplicate entries if there is only
296          * 1 other entry and it is in our true list.
297          *
298          * If we are reading the true list (other == NULL) there shouldn't
299          * be any other entries.
300          */
301         if ( other )
302         {
303             node_ptr = avtab_search_node(&p->te_cond_avtab, k);
304             if ( node_ptr )
305             {
306                 if ( avtab_search_node_next(node_ptr, k->specified) )
307                 {
308                     printk("Flask: too many conflicting type rules.");
309                     goto err;
310                 }
311                 found = 0;
312                 for ( cur = other; cur != NULL; cur = cur->next )
313                 {
314                     if ( cur->node == node_ptr )
315                     {
316                         found = 1;
317                         break;
318                     }
319                 }
320                 if ( !found )
321                 {
322                     printk("Flask: conflicting type rules.\n");
323                     goto err;
324                 }
325             }
326         }
327         else
328         {
329             if ( avtab_search(&p->te_cond_avtab, k) )
330             {
331                 printk("Flask: conflicting type rules when adding type rule "
332                                                                 "for true.\n");
333                 goto err;
334             }
335         }
336     }
337 
338     node_ptr = avtab_insert_nonunique(&p->te_cond_avtab, k, d);
339     if ( !node_ptr )
340     {
341         printk("Flask: could not insert rule.");
342         goto err;
343     }
344 
345     list = xzalloc(struct cond_av_list);
346     if ( !list )
347         goto err;
348 
349     list->node = node_ptr;
350     if ( !data->head )
351         data->head = list;
352     else
353         data->tail->next = list;
354     data->tail = list;
355     return 0;
356 
357 err:
358     cond_av_list_destroy(data->head);
359     data->head = NULL;
360     return -1;
361 }
362 
cond_read_av_list(struct policydb * p,void * fp,struct cond_av_list ** ret_list,struct cond_av_list * other)363 static int cond_read_av_list(struct policydb *p, void *fp,
364                     struct cond_av_list **ret_list, struct cond_av_list *other)
365 {
366     int i, rc;
367     __le32 buf[1];
368     u32 len;
369     struct cond_insertf_data data;
370 
371     *ret_list = NULL;
372 
373     len = 0;
374     rc = next_entry(buf, fp, sizeof(u32));
375     if ( rc < 0 )
376         return -1;
377 
378     len = le32_to_cpu(buf[0]);
379     if ( len == 0 )
380     {
381         return 0;
382     }
383 
384     data.p = p;
385     data.other = other;
386     data.head = NULL;
387     data.tail = NULL;
388     for ( i = 0; i < len; i++ )
389     {
390         rc = avtab_read_item(&p->te_cond_avtab, fp, p, cond_insertf, &data);
391         if ( rc )
392             return rc;
393     }
394 
395     *ret_list = data.head;
396     return 0;
397 }
398 
expr_isvalid(struct policydb * p,struct cond_expr * expr)399 static int expr_isvalid(struct policydb *p, struct cond_expr *expr)
400 {
401     if ( expr->expr_type <= 0 || expr->expr_type > COND_LAST )
402     {
403         printk("Flask: conditional expressions uses unknown operator.\n");
404         return 0;
405     }
406 
407     if ( expr->bool_val > p->p_bools.nprim )
408     {
409         printk("Flask: conditional expressions uses unknown bool.\n");
410         return 0;
411     }
412     return 1;
413 }
414 
cond_read_node(struct policydb * p,struct cond_node * node,void * fp)415 static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
416 {
417     __le32 buf[2];
418     u32 len, i;
419     int rc;
420     struct cond_expr *expr = NULL, *last = NULL;
421 
422     rc = next_entry(buf, fp, sizeof(u32));
423     if ( rc < 0 )
424         return -1;
425 
426     node->cur_state = le32_to_cpu(buf[0]);
427 
428     len = 0;
429     rc = next_entry(buf, fp, sizeof(u32));
430     if ( rc < 0 )
431         return -1;
432 
433     /* expr */
434     len = le32_to_cpu(buf[0]);
435 
436     for ( i = 0; i < len; i++ )
437     {
438         rc = next_entry(buf, fp, sizeof(u32) * 2);
439         if ( rc < 0 )
440             goto err;
441 
442         expr = xzalloc(struct cond_expr);
443         if ( !expr )
444             goto err;
445 
446         expr->expr_type = le32_to_cpu(buf[0]);
447         expr->bool_val = le32_to_cpu(buf[1]);
448 
449         if ( !expr_isvalid(p, expr) )
450         {
451             xfree(expr);
452             goto err;
453         }
454 
455         if ( i == 0 )
456             node->expr = expr;
457         else
458             last->next = expr;
459 
460         last = expr;
461     }
462 
463     if ( cond_read_av_list(p, fp, &node->true_list, NULL) != 0 )
464         goto err;
465     if ( cond_read_av_list(p, fp, &node->false_list, node->true_list) != 0 )
466         goto err;
467     return 0;
468 err:
469     cond_node_destroy(node);
470     return -1;
471 }
472 
cond_read_list(struct policydb * p,void * fp)473 int cond_read_list(struct policydb *p, void *fp)
474 {
475     struct cond_node *node, *last = NULL;
476     __le32 buf[1];
477     u32 i, len;
478     int rc;
479 
480     rc = next_entry(buf, fp, sizeof buf);
481     if ( rc < 0 )
482         return -1;
483 
484     len = le32_to_cpu(buf[0]);
485 
486     rc = avtab_alloc(&(p->te_cond_avtab), p->te_avtab.nel);
487     if ( rc )
488       goto err;
489 
490     for ( i = 0; i < len; i++ )
491     {
492         node = xzalloc(struct cond_node);
493         if ( !node )
494             goto err;
495 
496         if ( cond_read_node(p, node, fp) != 0 )
497             goto err;
498 
499         if ( i == 0 )
500             p->cond_list = node;
501         else
502             last->next = node;
503 
504         last = node;
505     }
506     return 0;
507 err:
508     cond_list_destroy(p->cond_list);
509     p->cond_list = NULL;
510     return -1;
511 }
512 
513 /* Determine whether additional permissions are granted by the conditional
514  * av table, and if so, add them to the result
515  */
cond_compute_av(struct avtab * ctab,struct avtab_key * key,struct av_decision * avd)516 void cond_compute_av(struct avtab *ctab, struct avtab_key *key,
517                                                         struct av_decision *avd)
518 {
519     struct avtab_node *node;
520 
521     if( !ctab || !key || !avd )
522         return;
523 
524     for( node = avtab_search_node(ctab, key); node != NULL;
525                 node = avtab_search_node_next(node, key->specified) )
526     {
527         if ( (u16) (AVTAB_ALLOWED|AVTAB_ENABLED) ==
528              (node->key.specified & (AVTAB_ALLOWED|AVTAB_ENABLED)) )
529             avd->allowed |= node->datum.data;
530         if ( (u16) (AVTAB_AUDITDENY|AVTAB_ENABLED) ==
531              (node->key.specified & (AVTAB_AUDITDENY|AVTAB_ENABLED)) )
532             /* Since a '0' in an auditdeny mask represents a
533              * permission we do NOT want to audit (dontaudit), we use
534              * the '&' operand to ensure that all '0's in the mask
535              * are retained (much unlike the allow and auditallow cases).
536              */
537             avd->auditdeny &= node->datum.data;
538         if ( (u16) (AVTAB_AUDITALLOW|AVTAB_ENABLED) ==
539              (node->key.specified & (AVTAB_AUDITALLOW|AVTAB_ENABLED)) )
540             avd->auditallow |= node->datum.data;
541     }
542     return;
543 }
544