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         if (p->bool_val_to_struct != NULL)
 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         if (p->bool_val_to_struct)
 178                 kfree(p->bool_val_to_struct);
 179         p->bool_val_to_struct = (struct cond_bool_datum**)
 180                 kmalloc(p->p_bools.nprim * sizeof(struct cond_bool_datum*), GFP_KERNEL);
 181         if (!p->bool_val_to_struct)
 182                 return -1;
 183         return 0;
 184 }
 185
 186 int cond_destroy_bool(void *key, void *datum, void *p)
 187 {
 188         if (key)
 189                 kfree(key);
 190         kfree(datum);
 191         return 0;
 192 }
 193
 194 int cond_index_bool(void *key, void *datum, void *datap)
 195 {
 196         struct policydb *p;
 197         struct cond_bool_datum *booldatum;
 198
 199         booldatum = datum;
 200         p = datap;
 201
 202         if (!booldatum->value || booldatum->value > p->p_bools.nprim)
 203                 return -EINVAL;
 204
 205         p->p_bool_val_to_name[booldatum->value - 1] = key;
 206         p->bool_val_to_struct[booldatum->value -1] = booldatum;
 207
 208         return 0;
 209 }
 210
 211 static int bool_isvalid(struct cond_bool_datum *b)
 212 {
 213         if (!(b->state == 0 || b->state == 1))
 214                 return 0;
 215         return 1;
 216 }
 217
 218 int cond_read_bool(struct policydb *p, struct hashtab *h, void *fp)
 219 {
 220         char *key = NULL;
 221         struct cond_bool_datum *booldatum;
 222         u32 buf[3], len;
 223         int rc;
 224
 225         booldatum = kmalloc(sizeof(struct cond_bool_datum), GFP_KERNEL);
 226         if (!booldatum)
 227                 return -1;
 228         memset(booldatum, 0, sizeof(struct cond_bool_datum));
 229
 230         rc = next_entry(buf, fp, sizeof buf);
 231         if (rc < 0)
 232                 goto err;
 233
 234         booldatum->value = le32_to_cpu(buf[0]);
 235         booldatum->state = le32_to_cpu(buf[1]);
 236
 237         if (!bool_isvalid(booldatum))
 238                 goto err;
 239
 240         len = le32_to_cpu(buf[2]);
 241
 242         key = kmalloc(len + 1, GFP_KERNEL);
 243         if (!key)
 244                 goto err;
 245         rc = next_entry(key, fp, len);
 246         if (rc < 0)
 247                 goto err;
 248         key[len] = 0;
 249         if (hashtab_insert(h, key, booldatum))
 250                 goto err;
 251
 252         return 0;
 253 err:
 254         cond_destroy_bool(key, booldatum, NULL);
 255         return -1;
 256 }
 257
 258 static int cond_read_av_list(struct policydb *p, void *fp, struct cond_av_list **ret_list,
 259                              struct cond_av_list *other)
 260 {
 261         struct cond_av_list *list, *last = NULL, *cur;
 262         struct avtab_key key;
 263         struct avtab_datum datum;
 264         struct avtab_node *node_ptr;
 265         int rc;
 266         u32 buf[1], i, len;
 267         u8 found;
 268
 269         *ret_list = NULL;
 270
 271         len = 0;
 272         rc = next_entry(buf, fp, sizeof buf);
 273         if (rc < 0)
 274                 return -1;
 275
 276         len = le32_to_cpu(buf[0]);
 277         if (len == 0) {
 278                 return 0;
 279         }
 280
 281         for (i = 0; i < len; i++) {
 282                 if (avtab_read_item(fp, &datum, &key))
 283                         goto err;
 284
 285                 /*
 286                  * For type rules we have to make certain there aren't any
 287                  * conflicting rules by searching the te_avtab and the
 288                  * cond_te_avtab.
 289                  */
 290                 if (datum.specified & AVTAB_TYPE) {
 291                         if (avtab_search(&p->te_avtab, &key, AVTAB_TYPE)) {
 292                                 printk("security: type rule already exists outside of a conditional.");
 293                                 goto err;
 294                         }
 295                         /*
 296                          * If we are reading the false list other will be a pointer to
 297                          * the true list. We can have duplicate entries if there is only
 298                          * 1 other entry and it is in our true list.
 299                          *
 300                          * If we are reading the true list (other == NULL) there shouldn't
 301                          * be any other entries.
 302                          */
 303                         if (other) {
 304                                 node_ptr = avtab_search_node(&p->te_cond_avtab, &key, AVTAB_TYPE);
 305                                 if (node_ptr) {
 306                                         if (avtab_search_node_next(node_ptr, AVTAB_TYPE)) {
 307                                                 printk("security: too many conflicting type rules.");
 308                                                 goto err;
 309                                         }
 310                                         found = 0;
 311                                         for (cur = other; cur != NULL; cur = cur->next) {
 312                                                 if (cur->node == node_ptr) {
 313                                                         found = 1;
 314                                                         break;
 315                                                 }
 316                                         }
 317                                         if (!found) {
 318                                                 printk("security: conflicting type rules.");
 319                                                 goto err;
 320                                         }
 321                                 }
 322                         } else {
 323                                 if (avtab_search(&p->te_cond_avtab, &key, AVTAB_TYPE)) {
 324                                         printk("security: conflicting type rules when adding type rule for true.");
 325                                         goto err;
 326                                 }
 327                         }
 328                 }
 329                 node_ptr = avtab_insert_nonunique(&p->te_cond_avtab, &key, &datum);
 330                 if (!node_ptr) {
 331                         printk("security: could not insert rule.");
 332                         goto err;
 333                 }
 334
 335                 list = kmalloc(sizeof(struct cond_av_list), GFP_KERNEL);
 336                 if (!list)
 337                         goto err;
 338                 memset(list, 0, sizeof(struct cond_av_list));
 339
 340                 list->node = node_ptr;
 341                 if (i == 0)
 342                         *ret_list = list;
 343                 else
 344                         last->next = list;
 345                 last = list;
 346
 347         }
 348
 349         return 0;
 350 err:
 351         cond_av_list_destroy(*ret_list);
 352         *ret_list = NULL;
 353         return -1;
 354 }
 355
 356 static int expr_isvalid(struct policydb *p, struct cond_expr *expr)
 357 {
 358         if (expr->expr_type <= 0 || expr->expr_type > COND_LAST) {
 359                 printk("security: conditional expressions uses unknown operator.\n");
 360                 return 0;
 361         }
 362
 363         if (expr->bool > p->p_bools.nprim) {
 364                 printk("security: conditional expressions uses unknown bool.\n");
 365                 return 0;
 366         }
 367         return 1;
 368 }
 369
 370 static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
 371 {
 372         u32 buf[2], len, i;
 373         int rc;
 374         struct cond_expr *expr = NULL, *last = NULL;
 375
 376         rc = next_entry(buf, fp, sizeof(u32));
 377         if (rc < 0)
 378                 return -1;
 379
 380         node->cur_state = le32_to_cpu(buf[0]);
 381
 382         len = 0;
 383         rc = next_entry(buf, fp, sizeof(u32));
 384         if (rc < 0)
 385                 return -1;
 386
 387         /* expr */
 388         len = le32_to_cpu(buf[0]);
 389
 390         for (i = 0; i < len; i++ ) {
 391                 rc = next_entry(buf, fp, sizeof(u32) * 2);
 392                 if (rc < 0)
 393                         goto err;
 394
 395                 expr = kmalloc(sizeof(struct cond_expr), GFP_KERNEL);
 396                 if (!expr) {
 397                         goto err;
 398                 }
 399                 memset(expr, 0, sizeof(struct cond_expr));
 400
 401                 expr->expr_type = le32_to_cpu(buf[0]);
 402                 expr->bool = le32_to_cpu(buf[1]);
 403
 404                 if (!expr_isvalid(p, expr)) {
 405                         kfree(expr);
 406                         goto err;
 407                 }
 408
 409                 if (i == 0) {
 410                         node->expr = expr;
 411                 } else {
 412                         last->next = expr;
 413                 }
 414                 last = expr;
 415         }
 416
 417         if (cond_read_av_list(p, fp, &node->true_list, NULL) != 0)
 418                 goto err;
 419         if (cond_read_av_list(p, fp, &node->false_list, node->true_list) != 0)
 420                 goto err;
 421         return 0;
 422 err:
 423         cond_node_destroy(node);
 424         return -1;
 425 }
 426
 427 int cond_read_list(struct policydb *p, void *fp)
 428 {
 429         struct cond_node *node, *last = NULL;
 430         u32 buf[1], i, len;
 431         int rc;
 432
 433         rc = next_entry(buf, fp, sizeof buf);
 434         if (rc < 0)
 435                 return -1;
 436
 437         len = le32_to_cpu(buf[0]);
 438
 439         for (i = 0; i < len; i++) {
 440                 node = kmalloc(sizeof(struct cond_node), GFP_KERNEL);
 441                 if (!node)
 442                         goto err;
 443                 memset(node, 0, sizeof(struct cond_node));
 444
 445                 if (cond_read_node(p, node, fp) != 0)
 446                         goto err;
 447
 448                 if (i == 0) {
 449                         p->cond_list = node;
 450                 } else {
 451                         last->next = node;
 452                 }
 453                 last = node;
 454         }
 455         return 0;
 456 err:
 457         cond_list_destroy(p->cond_list);
 458         return -1;
 459 }
 460
 461 /* Determine whether additional permissions are granted by the conditional
 462  * av table, and if so, add them to the result
 463  */
 464 void cond_compute_av(struct avtab *ctab, struct avtab_key *key, struct av_decision *avd)
 465 {
 466         struct avtab_node *node;
 467
 468         if(!ctab || !key || !avd)
 469                 return;
 470
 471         for(node = avtab_search_node(ctab, key, AVTAB_AV); node != NULL;
 472                                 node = avtab_search_node_next(node, AVTAB_AV)) {
 473                 if ( (__u32) (AVTAB_ALLOWED|AVTAB_ENABLED) ==
 474                      (node->datum.specified & (AVTAB_ALLOWED|AVTAB_ENABLED)))
 475                         avd->allowed |= avtab_allowed(&node->datum);
 476                 if ( (__u32) (AVTAB_AUDITDENY|AVTAB_ENABLED) ==
 477                      (node->datum.specified & (AVTAB_AUDITDENY|AVTAB_ENABLED)))
 478                         /* Since a '0' in an auditdeny mask represents a
 479                          * permission we do NOT want to audit (dontaudit), we use
 480                          * the '&' operand to ensure that all '0's in the mask
 481                          * are retained (much unlike the allow and auditallow cases).
 482                          */
 483                         avd->auditdeny &= avtab_auditdeny(&node->datum);
 484                 if ( (__u32) (AVTAB_AUDITALLOW|AVTAB_ENABLED) ==
 485                      (node->datum.specified & (AVTAB_AUDITALLOW|AVTAB_ENABLED)))
 486                         avd->auditallow |= avtab_auditallow(&node->datum);
 487         }
 488         return;
 489 }