security/selinux/ss/conditional.c

   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 <asm/semaphore.h>
  15 #include <linux/slab.h>
  16
  17 #include "security.h"
  18 #include "conditional.h"
  19
  20 /*
  21  * cond_evaluate_expr evaluates a conditional expr
  22  * in reverse polish notation. It returns true (1), false (0),
  23  * or undefined (-1). Undefined occurs when the expression
  24  * exceeds the stack depth of COND_EXPR_MAXDEPTH.
  25  */
  26 static int cond_evaluate_expr(struct policydb *p, struct cond_expr *expr)
  27 {
  28
  29         struct cond_expr *cur;
  30         int s[COND_EXPR_MAXDEPTH];
  31         int sp = -1;
  32
  33         for (cur = expr; cur != NULL; cur = cur->next) {
  34                 switch (cur->expr_type) {
  35                 case COND_BOOL:
  36                         if (sp == (COND_EXPR_MAXDEPTH - 1))
  37                                 return -1;
  38                         sp++;
  39                         s[sp] = p->bool_val_to_struct[cur->bool - 1]->state;
  40                         break;
  41                 case COND_NOT:
  42                         if (sp < 0)
  43                                 return -1;
  44                         s[sp] = !s[sp];
  45                         break;
  46                 case COND_OR:
  47                         if (sp < 1)
  48                                 return -1;
  49                         sp--;
  50                         s[sp] |= s[sp + 1];
  51                         break;
  52                 case COND_AND:
  53                         if (sp < 1)
  54                                 return -1;
  55                         sp--;
  56                         s[sp] &= s[sp + 1];
  57                         break;
  58                 case COND_XOR:
  59                         if (sp < 1)
  60                                 return -1;
  61                         sp--;
  62                         s[sp] ^= s[sp + 1];
  63                         break;
  64                 case COND_EQ:
  65                         if (sp < 1)
  66                                 return -1;
  67                         sp--;
  68                         s[sp] = (s[sp] == s[sp + 1]);
  69                         break;
  70                 case COND_NEQ:
  71                         if (sp < 1)
  72                                 return -1;
  73                         sp--;
  74                         s[sp] = (s[sp] != s[sp + 1]);
  75                         break;
  76                 default:
  77                         return -1;
  78                 }
  79         }
  80         return s[0];
  81 }
  82
  83 /*
  84  * evaluate_cond_node evaluates the conditional stored in
  85  * a struct cond_node and if the result is different than the
  86  * current state of the node it sets the rules in the true/false
  87  * list appropriately. If the result of the expression is undefined
  88  * all of the rules are disabled for safety.
  89  */
  90 int evaluate_cond_node(struct policydb *p, struct cond_node *node)
  91 {
  92         int new_state;
  93         struct cond_av_list* cur;
  94
  95         new_state = cond_evaluate_expr(p, node->expr);
  96         if (new_state != node->cur_state) {
  97                 node->cur_state = new_state;
  98                 if (new_state == -1)
  99                         printk(KERN_ERR "security: expression result was undefined - disabling all rules.\n");
 100                 /* turn the rules on or off */
 101                 for (cur = node->true_list; cur != NULL; cur = cur->next) {
 102                         if (new_state <= 0) {
 103                                 cur->node->datum.specified &= ~AVTAB_ENABLED;
 104                         } else {
 105                                 cur->node->datum.specified |= AVTAB_ENABLED;
 106                         }
 107                 }
 108
 109                 for (cur = node->false_list; cur != NULL; cur = cur->next) {
 110                         /* -1 or 1 */
 111                         if (new_state) {
 112                                 cur->node->datum.specified &= ~AVTAB_ENABLED;
 113                         } else {
 114                                 cur->node->datum.specified |= AVTAB_ENABLED;
 115                         }
 116                 }
 117         }
 118         return 0;
 119 }
 120
 121 int cond_policydb_init(struct policydb *p)
 122 {
 123         p->bool_val_to_struct = NULL;
 124         p->cond_list = NULL;
 125         if (avtab_init(&p->te_cond_avtab))
 126                 return -1;
 127
 128         return 0;
 129 }
 130
 131 static void cond_av_list_destroy(struct cond_av_list *list)
 132 {
 133         struct cond_av_list *cur, *next;
 134         for (cur = list; cur != NULL; cur = next) {
 135                 next = cur->next;
 136                 /* the avtab_ptr_t node is destroy by the avtab */
 137                 kfree(cur);
 138         }
 139 }
 140
 141 static void cond_node_destroy(struct cond_node *node)
 142 {
 143         struct cond_expr *cur_expr, *next_expr;
 144
 145         for (cur_expr = node->expr; cur_expr != NULL; cur_expr = next_expr) {
 146                 next_expr = cur_expr->next;
 147                 kfree(cur_expr);
 148         }
 149         cond_av_list_destroy(node->true_list);
 150         cond_av_list_destroy(node->false_list);
 151         kfree(node);
 152 }
 153
 154 static void cond_list_destroy(struct cond_node *list)
 155 {
 156         struct cond_node *next, *cur;
 157
 158         if (list == NULL)
 159                 return;
 160
 161         for (cur = list; cur != NULL; cur = next) {
 162                 next = cur->next;
 163                 cond_node_destroy(cur);
 164         }
 165 }
 166
 167 void cond_policydb_destroy(struct policydb *p)
 168 {
 169         kfree(p->bool_val_to_struct);
 170         avtab_destroy(&p->te_cond_avtab);
 171         cond_list_destroy(p->cond_list);
 172 }
 173
 174 int cond_init_bool_indexes(struct policydb *p)
 175 {
 176         kfree(p->bool_val_to_struct);
 177         p->bool_val_to_struct = (struct cond_bool_datum**)
 178                 kmalloc(p->p_bools.nprim * sizeof(struct cond_bool_datum*), GFP_KERNEL);
 179         if (!p->bool_val_to_struct)
 180                 return -1;
 181         return 0;
 182 }
 183
 184 int cond_destroy_bool(void *key, void *datum, void *p)
 185 {
 186         kfree(key);
 187         kfree(datum);
 188         return 0;
 189 }
 190
 191 int cond_index_bool(void *key, void *datum, void *datap)
 192 {
 193         struct policydb *p;
 194         struct cond_bool_datum *booldatum;
 195
 196         booldatum = datum;
 197         p = datap;
 198
 199         if (!booldatum->value || booldatum->value > p->p_bools.nprim)
 200                 return -EINVAL;
 201
 202         p->p_bool_val_to_name[booldatum->value - 1] = key;
 203         p->bool_val_to_struct[booldatum->value -1] = booldatum;
 204
 205         return 0;
 206 }
 207
 208 static int bool_isvalid(struct cond_bool_datum *b)
 209 {
 210         if (!(b->state == 0 || b->state == 1))
 211                 return 0;
 212         return 1;
 213 }
 214
 215 int cond_read_bool(struct policydb *p, struct hashtab *h, void *fp)
 216 {
 217         char *key = NULL;
 218         struct cond_bool_datum *booldatum;
 219         u32 buf[3], len;
 220         int rc;
 221
 222         booldatum = kmalloc(sizeof(struct cond_bool_datum), GFP_KERNEL);
 223         if (!booldatum)
 224                 return -1;
 225         memset(booldatum, 0, sizeof(struct cond_bool_datum));
 226
 227         rc = next_entry(buf, fp, sizeof buf);
 228         if (rc < 0)
 229                 goto err;
 230
 231         booldatum->value = le32_to_cpu(buf[0]);
 232         booldatum->state = le32_to_cpu(buf[1]);
 233
 234         if (!bool_isvalid(booldatum))
 235                 goto err;
 236
 237         len = le32_to_cpu(buf[2]);
 238
 239         key = kmalloc(len + 1, GFP_KERNEL);
 240         if (!key)
 241                 goto err;
 242         rc = next_entry(key, fp, len);
 243         if (rc < 0)
 244                 goto err;
 245         key[len] = 0;
 246         if (hashtab_insert(h, key, booldatum))
 247                 goto err;
 248
 249         return 0;
 250 err:
 251         cond_destroy_bool(key, booldatum, NULL);
 252         return -1;
 253 }
 254
 255 static int cond_read_av_list(struct policydb *p, void *fp, struct cond_av_list **ret_list,
 256                              struct cond_av_list *other)
 257 {
 258         struct cond_av_list *list, *last = NULL, *cur;
 259         struct avtab_key key;
 260         struct avtab_datum datum;
 261         struct avtab_node *node_ptr;
 262         int rc;
 263         u32 buf[1], i, len;
 264         u8 found;
 265
 266         *ret_list = NULL;
 267
 268         len = 0;
 269         rc = next_entry(buf, fp, sizeof buf);
 270         if (rc < 0)
 271                 return -1;
 272
 273         len = le32_to_cpu(buf[0]);
 274         if (len == 0) {
 275                 return 0;
 276         }
 277
 278         for (i = 0; i < len; i++) {
 279                 if (avtab_read_item(fp, &datum, &key))
 280                         goto err;
 281
 282                 /*
 283                  * For type rules we have to make certain there aren't any
 284                  * conflicting rules by searching the te_avtab and the
 285                  * cond_te_avtab.
 286                  */
 287                 if (datum.specified & AVTAB_TYPE) {
 288                         if (avtab_search(&p->te_avtab, &key, AVTAB_TYPE)) {
 289                                 printk("security: type rule already exists outside of a conditional.");
 290                                 goto err;
 291                         }
 292                         /*
 293                          * If we are reading the false list other will be a pointer to
 294                          * the true list. We can have duplicate entries if there is only
 295                          * 1 other entry and it is in our true list.
 296                          *
 297                          * If we are reading the true list (other == NULL) there shouldn't
 298                          * be any other entries.
 299                          */
 300                         if (other) {
 301                                 node_ptr = avtab_search_node(&p->te_cond_avtab, &key, AVTAB_TYPE);
 302                                 if (node_ptr) {
 303                                         if (avtab_search_node_next(node_ptr, AVTAB_TYPE)) {
 304                                                 printk("security: too many conflicting type rules.");
 305                                                 goto err;
 306                                         }
 307                                         found = 0;
 308                                         for (cur = other; cur != NULL; cur = cur->next) {
 309                                                 if (cur->node == node_ptr) {
 310                                                         found = 1;
 311                                                         break;
 312                                                 }
 313                                         }
 314                                         if (!found) {
 315                                                 printk("security: conflicting type rules.");
 316                                                 goto err;
 317                                         }
 318                                 }
 319                         } else {
 320                                 if (avtab_search(&p->te_cond_avtab, &key, AVTAB_TYPE)) {
 321                                         printk("security: conflicting type rules when adding type rule for true.");
 322                                         goto err;
 323                                 }
 324                         }
 325                 }
 326                 node_ptr = avtab_insert_nonunique(&p->te_cond_avtab, &key, &datum);
 327                 if (!node_ptr) {
 328                         printk("security: could not insert rule.");
 329                         goto err;
 330                 }
 331
 332                 list = kmalloc(sizeof(struct cond_av_list), GFP_KERNEL);
 333                 if (!list)
 334                         goto err;
 335                 memset(list, 0, sizeof(struct cond_av_list));
 336
 337                 list->node = node_ptr;
 338                 if (i == 0)
 339                         *ret_list = list;
 340                 else
 341                         last->next = list;
 342                 last = list;
 343
 344         }
 345
 346         return 0;
 347 err:
 348         cond_av_list_destroy(*ret_list);
 349         *ret_list = NULL;
 350         return -1;
 351 }
 352
 353 static int expr_isvalid(struct policydb *p, struct cond_expr *expr)
 354 {
 355         if (expr->expr_type <= 0 || expr->expr_type > COND_LAST) {
 356                 printk("security: conditional expressions uses unknown operator.\n");
 357                 return 0;
 358         }
 359
 360         if (expr->bool > p->p_bools.nprim) {
 361                 printk("security: conditional expressions uses unknown bool.\n");
 362                 return 0;
 363         }
 364         return 1;
 365 }
 366
 367 static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
 368 {
 369         u32 buf[2], len, i;
 370         int rc;
 371         struct cond_expr *expr = NULL, *last = NULL;
 372
 373         rc = next_entry(buf, fp, sizeof(u32));
 374         if (rc < 0)
 375                 return -1;
 376
 377         node->cur_state = le32_to_cpu(buf[0]);
 378
 379         len = 0;
 380         rc = next_entry(buf, fp, sizeof(u32));
 381         if (rc < 0)
 382                 return -1;
 383
 384         /* expr */
 385         len = le32_to_cpu(buf[0]);
 386
 387         for (i = 0; i < len; i++ ) {
 388                 rc = next_entry(buf, fp, sizeof(u32) * 2);
 389                 if (rc < 0)
 390                         goto err;
 391
 392                 expr = kmalloc(sizeof(struct cond_expr), GFP_KERNEL);
 393                 if (!expr) {
 394                         goto err;
 395                 }
 396                 memset(expr, 0, sizeof(struct cond_expr));
 397
 398                 expr->expr_type = le32_to_cpu(buf[0]);
 399                 expr->bool = le32_to_cpu(buf[1]);
 400
 401                 if (!expr_isvalid(p, expr)) {
 402                         kfree(expr);
 403                         goto err;
 404                 }
 405
 406                 if (i == 0) {
 407                         node->expr = expr;
 408                 } else {
 409                         last->next = expr;
 410                 }
 411                 last = expr;
 412         }
 413
 414         if (cond_read_av_list(p, fp, &node->true_list, NULL) != 0)
 415                 goto err;
 416         if (cond_read_av_list(p, fp, &node->false_list, node->true_list) != 0)
 417                 goto err;
 418         return 0;
 419 err:
 420         cond_node_destroy(node);
 421         return -1;
 422 }
 423
 424 int cond_read_list(struct policydb *p, void *fp)
 425 {
 426         struct cond_node *node, *last = NULL;
 427         u32 buf[1], i, len;
 428         int rc;
 429
 430         rc = next_entry(buf, fp, sizeof buf);
 431         if (rc < 0)
 432                 return -1;
 433
 434         len = le32_to_cpu(buf[0]);
 435
 436         for (i = 0; i < len; i++) {
 437                 node = kmalloc(sizeof(struct cond_node), GFP_KERNEL);
 438                 if (!node)
 439                         goto err;
 440                 memset(node, 0, sizeof(struct cond_node));
 441
 442                 if (cond_read_node(p, node, fp) != 0)
 443                         goto err;
 444
 445                 if (i == 0) {
 446                         p->cond_list = node;
 447                 } else {
 448                         last->next = node;
 449                 }
 450                 last = node;
 451         }
 452         return 0;
 453 err:
 454         cond_list_destroy(p->cond_list);
 455         return -1;
 456 }
 457
 458 /* Determine whether additional permissions are granted by the conditional
 459  * av table, and if so, add them to the result
 460  */
 461 void cond_compute_av(struct avtab *ctab, struct avtab_key *key, struct av_decision *avd)
 462 {
 463         struct avtab_node *node;
 464
 465         if(!ctab || !key || !avd)
 466                 return;
 467
 468         for(node = avtab_search_node(ctab, key, AVTAB_AV); node != NULL;
 469                                 node = avtab_search_node_next(node, AVTAB_AV)) {
 470                 if ( (__u32) (AVTAB_ALLOWED|AVTAB_ENABLED) ==
 471                      (node->datum.specified & (AVTAB_ALLOWED|AVTAB_ENABLED)))
 472                         avd->allowed |= avtab_allowed(&node->datum);
 473                 if ( (__u32) (AVTAB_AUDITDENY|AVTAB_ENABLED) ==
 474                      (node->datum.specified & (AVTAB_AUDITDENY|AVTAB_ENABLED)))
 475                         /* Since a '0' in an auditdeny mask represents a
 476                          * permission we do NOT want to audit (dontaudit), we use
 477                          * the '&' operand to ensure that all '0's in the mask
 478                          * are retained (much unlike the allow and auditallow cases).
 479                          */
 480                         avd->auditdeny &= avtab_auditdeny(&node->datum);
 481                 if ( (__u32) (AVTAB_AUDITALLOW|AVTAB_ENABLED) ==
 482                      (node->datum.specified & (AVTAB_AUDITALLOW|AVTAB_ENABLED)))
 483                         avd->auditallow |= avtab_auditallow(&node->datum);
 484         }
 485         return;
 486 }