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->key.specified &= ~AVTAB_ENABLED;
 104                         } else {
 105                                 cur->node->key.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->key.specified &= ~AVTAB_ENABLED;
 113                         } else {
 114                                 cur->node->key.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         __le32 buf[3];
 220         u32 len;
 221         int rc;
 222
 223         booldatum = kzalloc(sizeof(struct cond_bool_datum), GFP_KERNEL);
 224         if (!booldatum)
 225                 return -1;
 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 struct cond_insertf_data
 256 {
 257         struct policydb *p;
 258         struct cond_av_list *other;
 259         struct cond_av_list *head;
 260         struct cond_av_list *tail;
 261 };
 262
 263 static int cond_insertf(struct avtab *a, struct avtab_key *k, struct avtab_datum *d, void *ptr)
 264 {
 265         struct cond_insertf_data *data = ptr;
 266         struct policydb *p = data->p;
 267         struct cond_av_list *other = data->other, *list, *cur;
 268         struct avtab_node *node_ptr;
 269         u8 found;
 270
 271
 272         /*
 273          * For type rules we have to make certain there aren't any
 274          * conflicting rules by searching the te_avtab and the
 275          * cond_te_avtab.
 276          */
 277         if (k->specified & AVTAB_TYPE) {
 278                 if (avtab_search(&p->te_avtab, k)) {
 279                         printk("security: type rule already exists outside of a conditional.");
 280                         goto err;
 281                 }
 282                 /*
 283                  * If we are reading the false list other will be a pointer to
 284                  * the true list. We can have duplicate entries if there is only
 285                  * 1 other entry and it is in our true list.
 286                  *
 287                  * If we are reading the true list (other == NULL) there shouldn't
 288                  * be any other entries.
 289                  */
 290                 if (other) {
 291                         node_ptr = avtab_search_node(&p->te_cond_avtab, k);
 292                         if (node_ptr) {
 293                                 if (avtab_search_node_next(node_ptr, k->specified)) {
 294                                         printk("security: too many conflicting type rules.");
 295                                         goto err;
 296                                 }
 297                                 found = 0;
 298                                 for (cur = other; cur != NULL; cur = cur->next) {
 299                                         if (cur->node == node_ptr) {
 300                                                 found = 1;
 301                                                 break;
 302                                         }
 303                                 }
 304                                 if (!found) {
 305                                         printk("security: conflicting type rules.\n");
 306                                         goto err;
 307                                 }
 308                         }
 309                 } else {
 310                         if (avtab_search(&p->te_cond_avtab, k)) {
 311                                 printk("security: conflicting type rules when adding type rule for true.\n");
 312                                 goto err;
 313                         }
 314                 }
 315         }
 316
 317         node_ptr = avtab_insert_nonunique(&p->te_cond_avtab, k, d);
 318         if (!node_ptr) {
 319                 printk("security: could not insert rule.");
 320                 goto err;
 321         }
 322
 323         list = kzalloc(sizeof(struct cond_av_list), GFP_KERNEL);
 324         if (!list)
 325                 goto err;
 326
 327         list->node = node_ptr;
 328         if (!data->head)
 329                 data->head = list;
 330         else
 331                 data->tail->next = list;
 332         data->tail = list;
 333         return 0;
 334
 335 err:
 336         cond_av_list_destroy(data->head);
 337         data->head = NULL;
 338         return -1;
 339 }
 340
 341 static int cond_read_av_list(struct policydb *p, void *fp, struct cond_av_list **ret_list, struct cond_av_list *other)
 342 {
 343         int i, rc;
 344         __le32 buf[1];
 345         u32 len;
 346         struct cond_insertf_data data;
 347
 348         *ret_list = NULL;
 349
 350         len = 0;
 351         rc = next_entry(buf, fp, sizeof(u32));
 352         if (rc < 0)
 353                 return -1;
 354
 355         len = le32_to_cpu(buf[0]);
 356         if (len == 0) {
 357                 return 0;
 358         }
 359
 360         data.p = p;
 361         data.other = other;
 362         data.head = NULL;
 363         data.tail = NULL;
 364         for (i = 0; i < len; i++) {
 365                 rc = avtab_read_item(&p->te_cond_avtab, fp, p, cond_insertf,
 366                                      &data);
 367                 if (rc)
 368                         return rc;
 369
 370         }
 371
 372         *ret_list = data.head;
 373         return 0;
 374 }
 375
 376 static int expr_isvalid(struct policydb *p, struct cond_expr *expr)
 377 {
 378         if (expr->expr_type <= 0 || expr->expr_type > COND_LAST) {
 379                 printk("security: conditional expressions uses unknown operator.\n");
 380                 return 0;
 381         }
 382
 383         if (expr->bool > p->p_bools.nprim) {
 384                 printk("security: conditional expressions uses unknown bool.\n");
 385                 return 0;
 386         }
 387         return 1;
 388 }
 389
 390 static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
 391 {
 392         __le32 buf[2];
 393         u32 len, i;
 394         int rc;
 395         struct cond_expr *expr = NULL, *last = NULL;
 396
 397         rc = next_entry(buf, fp, sizeof(u32));
 398         if (rc < 0)
 399                 return -1;
 400
 401         node->cur_state = le32_to_cpu(buf[0]);
 402
 403         len = 0;
 404         rc = next_entry(buf, fp, sizeof(u32));
 405         if (rc < 0)
 406                 return -1;
 407
 408         /* expr */
 409         len = le32_to_cpu(buf[0]);
 410
 411         for (i = 0; i < len; i++ ) {
 412                 rc = next_entry(buf, fp, sizeof(u32) * 2);
 413                 if (rc < 0)
 414                         goto err;
 415
 416                 expr = kzalloc(sizeof(struct cond_expr), GFP_KERNEL);
 417                 if (!expr) {
 418                         goto err;
 419                 }
 420
 421                 expr->expr_type = le32_to_cpu(buf[0]);
 422                 expr->bool = le32_to_cpu(buf[1]);
 423
 424                 if (!expr_isvalid(p, expr)) {
 425                         kfree(expr);
 426                         goto err;
 427                 }
 428
 429                 if (i == 0) {
 430                         node->expr = expr;
 431                 } else {
 432                         last->next = expr;
 433                 }
 434                 last = expr;
 435         }
 436
 437         if (cond_read_av_list(p, fp, &node->true_list, NULL) != 0)
 438                 goto err;
 439         if (cond_read_av_list(p, fp, &node->false_list, node->true_list) != 0)
 440                 goto err;
 441         return 0;
 442 err:
 443         cond_node_destroy(node);
 444         return -1;
 445 }
 446
 447 int cond_read_list(struct policydb *p, void *fp)
 448 {
 449         struct cond_node *node, *last = NULL;
 450         __le32 buf[1];
 451         u32 i, len;
 452         int rc;
 453
 454         rc = next_entry(buf, fp, sizeof buf);
 455         if (rc < 0)
 456                 return -1;
 457
 458         len = le32_to_cpu(buf[0]);
 459
 460         rc = avtab_alloc(&(p->te_cond_avtab), p->te_avtab.nel);
 461         if (rc)
 462                 goto err;
 463
 464         for (i = 0; i < len; i++) {
 465                 node = kzalloc(sizeof(struct cond_node), GFP_KERNEL);
 466                 if (!node)
 467                         goto err;
 468
 469                 if (cond_read_node(p, node, fp) != 0)
 470                         goto err;
 471
 472                 if (i == 0) {
 473                         p->cond_list = node;
 474                 } else {
 475                         last->next = node;
 476                 }
 477                 last = node;
 478         }
 479         return 0;
 480 err:
 481         cond_list_destroy(p->cond_list);
 482         p->cond_list = NULL;
 483         return -1;
 484 }
 485
 486 /* Determine whether additional permissions are granted by the conditional
 487  * av table, and if so, add them to the result
 488  */
 489 void cond_compute_av(struct avtab *ctab, struct avtab_key *key, struct av_decision *avd)
 490 {
 491         struct avtab_node *node;
 492
 493         if(!ctab || !key || !avd)
 494                 return;
 495
 496         for(node = avtab_search_node(ctab, key); node != NULL;
 497                                 node = avtab_search_node_next(node, key->specified)) {
 498                 if ( (u16) (AVTAB_ALLOWED|AVTAB_ENABLED) ==
 499                      (node->key.specified & (AVTAB_ALLOWED|AVTAB_ENABLED)))
 500                         avd->allowed |= node->datum.data;
 501                 if ( (u16) (AVTAB_AUDITDENY|AVTAB_ENABLED) ==
 502                      (node->key.specified & (AVTAB_AUDITDENY|AVTAB_ENABLED)))
 503                         /* Since a '0' in an auditdeny mask represents a
 504                          * permission we do NOT want to audit (dontaudit), we use
 505                          * the '&' operand to ensure that all '0's in the mask
 506                          * are retained (much unlike the allow and auditallow cases).
 507                          */
 508                         avd->auditdeny &= node->datum.data;
 509                 if ( (u16) (AVTAB_AUDITALLOW|AVTAB_ENABLED) ==
 510                      (node->key.specified & (AVTAB_AUDITALLOW|AVTAB_ENABLED)))
 511                         avd->auditallow |= node->datum.data;
 512         }
 513         return;
 514 }