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 <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         p->bool_val_to_struct = NULL;
 121         p->cond_list = NULL;
 122         if (avtab_init(&p->te_cond_avtab))
 123                 return -1;
 124
 125         return 0;
 126 }
 127
 128 static void cond_av_list_destroy(struct cond_av_list *list)
 129 {
 130         struct cond_av_list *cur, *next;
 131         for (cur = list; cur; cur = next) {
 132                 next = cur->next;
 133                 /* the avtab_ptr_t node is destroy by the avtab */
 134                 kfree(cur);
 135         }
 136 }
 137
 138 static void cond_node_destroy(struct cond_node *node)
 139 {
 140         struct cond_expr *cur_expr, *next_expr;
 141
 142         for (cur_expr = node->expr; cur_expr; cur_expr = next_expr) {
 143                 next_expr = cur_expr->next;
 144                 kfree(cur_expr);
 145         }
 146         cond_av_list_destroy(node->true_list);
 147         cond_av_list_destroy(node->false_list);
 148         kfree(node);
 149 }
 150
 151 static void cond_list_destroy(struct cond_node *list)
 152 {
 153         struct cond_node *next, *cur;
 154
 155         if (list == NULL)
 156                 return;
 157
 158         for (cur = list; cur; cur = next) {
 159                 next = cur->next;
 160                 cond_node_destroy(cur);
 161         }
 162 }
 163
 164 void cond_policydb_destroy(struct policydb *p)
 165 {
 166         kfree(p->bool_val_to_struct);
 167         avtab_destroy(&p->te_cond_avtab);
 168         cond_list_destroy(p->cond_list);
 169 }
 170
 171 int cond_init_bool_indexes(struct policydb *p)
 172 {
 173         kfree(p->bool_val_to_struct);
 174         p->bool_val_to_struct = (struct cond_bool_datum **)
 175                 kmalloc(p->p_bools.nprim * sizeof(struct cond_bool_datum *), GFP_KERNEL);
 176         if (!p->bool_val_to_struct)
 177                 return -1;
 178         return 0;
 179 }
 180
 181 int cond_destroy_bool(void *key, void *datum, void *p)
 182 {
 183         kfree(key);
 184         kfree(datum);
 185         return 0;
 186 }
 187
 188 int cond_index_bool(void *key, void *datum, void *datap)
 189 {
 190         struct policydb *p;
 191         struct cond_bool_datum *booldatum;
 192
 193         booldatum = datum;
 194         p = datap;
 195
 196         if (!booldatum->value || booldatum->value > p->p_bools.nprim)
 197                 return -EINVAL;
 198
 199         p->p_bool_val_to_name[booldatum->value - 1] = key;
 200         p->bool_val_to_struct[booldatum->value - 1] = booldatum;
 201
 202         return 0;
 203 }
 204
 205 static int bool_isvalid(struct cond_bool_datum *b)
 206 {
 207         if (!(b->state == 0 || b->state == 1))
 208                 return 0;
 209         return 1;
 210 }
 211
 212 int cond_read_bool(struct policydb *p, struct hashtab *h, void *fp)
 213 {
 214         char *key = NULL;
 215         struct cond_bool_datum *booldatum;
 216         __le32 buf[3];
 217         u32 len;
 218         int rc;
 219
 220         booldatum = kzalloc(sizeof(struct cond_bool_datum), GFP_KERNEL);
 221         if (!booldatum)
 222                 return -1;
 223
 224         rc = next_entry(buf, fp, sizeof buf);
 225         if (rc < 0)
 226                 goto err;
 227
 228         booldatum->value = le32_to_cpu(buf[0]);
 229         booldatum->state = le32_to_cpu(buf[1]);
 230
 231         if (!bool_isvalid(booldatum))
 232                 goto err;
 233
 234         len = le32_to_cpu(buf[2]);
 235
 236         key = kmalloc(len + 1, GFP_KERNEL);
 237         if (!key)
 238                 goto err;
 239         rc = next_entry(key, fp, len);
 240         if (rc < 0)
 241                 goto err;
 242         key[len] = '\0';
 243         if (hashtab_insert(h, key, booldatum))
 244                 goto err;
 245
 246         return 0;
 247 err:
 248         cond_destroy_bool(key, booldatum, NULL);
 249         return -1;
 250 }
 251
 252 struct cond_insertf_data {
 253         struct policydb *p;
 254         struct cond_av_list *other;
 255         struct cond_av_list *head;
 256         struct cond_av_list *tail;
 257 };
 258
 259 static int cond_insertf(struct avtab *a, struct avtab_key *k, struct avtab_datum *d, void *ptr)
 260 {
 261         struct cond_insertf_data *data = ptr;
 262         struct policydb *p = data->p;
 263         struct cond_av_list *other = data->other, *list, *cur;
 264         struct avtab_node *node_ptr;
 265         u8 found;
 266         int rc = -EINVAL;
 267
 268         /*
 269          * For type rules we have to make certain there aren't any
 270          * conflicting rules by searching the te_avtab and the
 271          * cond_te_avtab.
 272          */
 273         if (k->specified & AVTAB_TYPE) {
 274                 if (avtab_search(&p->te_avtab, k)) {
 275                         printk(KERN_ERR "SELinux: type rule already exists outside of a conditional.\n");
 276                         goto err;
 277                 }
 278                 /*
 279                  * If we are reading the false list other will be a pointer to
 280                  * the true list. We can have duplicate entries if there is only
 281                  * 1 other entry and it is in our true list.
 282                  *
 283                  * If we are reading the true list (other == NULL) there shouldn't
 284                  * be any other entries.
 285                  */
 286                 if (other) {
 287                         node_ptr = avtab_search_node(&p->te_cond_avtab, k);
 288                         if (node_ptr) {
 289                                 if (avtab_search_node_next(node_ptr, k->specified)) {
 290                                         printk(KERN_ERR "SELinux: too many conflicting type rules.\n");
 291                                         goto err;
 292                                 }
 293                                 found = 0;
 294                                 for (cur = other; cur; cur = cur->next) {
 295                                         if (cur->node == node_ptr) {
 296                                                 found = 1;
 297                                                 break;
 298                                         }
 299                                 }
 300                                 if (!found) {
 301                                         printk(KERN_ERR "SELinux: conflicting type rules.\n");
 302                                         goto err;
 303                                 }
 304                         }
 305                 } else {
 306                         if (avtab_search(&p->te_cond_avtab, k)) {
 307                                 printk(KERN_ERR "SELinux: conflicting type rules when adding type rule for true.\n");
 308                                 goto err;
 309                         }
 310                 }
 311         }
 312
 313         node_ptr = avtab_insert_nonunique(&p->te_cond_avtab, k, d);
 314         if (!node_ptr) {
 315                 printk(KERN_ERR "SELinux: could not insert rule.\n");
 316                 rc = -ENOMEM;
 317                 goto err;
 318         }
 319
 320         list = kzalloc(sizeof(struct cond_av_list), GFP_KERNEL);
 321         if (!list) {
 322                 rc = -ENOMEM;
 323                 goto err;
 324         }
 325
 326         list->node = node_ptr;
 327         if (!data->head)
 328                 data->head = list;
 329         else
 330                 data->tail->next = list;
 331         data->tail = list;
 332         return 0;
 333
 334 err:
 335         cond_av_list_destroy(data->head);
 336         data->head = NULL;
 337         return rc;
 338 }
 339
 340 static int cond_read_av_list(struct policydb *p, void *fp, struct cond_av_list **ret_list, struct cond_av_list *other)
 341 {
 342         int i, rc;
 343         __le32 buf[1];
 344         u32 len;
 345         struct cond_insertf_data data;
 346
 347         *ret_list = NULL;
 348
 349         len = 0;
 350         rc = next_entry(buf, fp, sizeof(u32));
 351         if (rc)
 352                 return rc;
 353
 354         len = le32_to_cpu(buf[0]);
 355         if (len == 0)
 356                 return 0;
 357
 358         data.p = p;
 359         data.other = other;
 360         data.head = NULL;
 361         data.tail = NULL;
 362         for (i = 0; i < len; i++) {
 363                 rc = avtab_read_item(&p->te_cond_avtab, fp, p, cond_insertf,
 364                                      &data);
 365                 if (rc)
 366                         return rc;
 367         }
 368
 369         *ret_list = data.head;
 370         return 0;
 371 }
 372
 373 static int expr_isvalid(struct policydb *p, struct cond_expr *expr)
 374 {
 375         if (expr->expr_type <= 0 || expr->expr_type > COND_LAST) {
 376                 printk(KERN_ERR "SELinux: conditional expressions uses unknown operator.\n");
 377                 return 0;
 378         }
 379
 380         if (expr->bool > p->p_bools.nprim) {
 381                 printk(KERN_ERR "SELinux: conditional expressions uses unknown bool.\n");
 382                 return 0;
 383         }
 384         return 1;
 385 }
 386
 387 static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
 388 {
 389         __le32 buf[2];
 390         u32 len, i;
 391         int rc;
 392         struct cond_expr *expr = NULL, *last = NULL;
 393
 394         rc = next_entry(buf, fp, sizeof(u32));
 395         if (rc < 0)
 396                 return -1;
 397
 398         node->cur_state = le32_to_cpu(buf[0]);
 399
 400         len = 0;
 401         rc = next_entry(buf, fp, sizeof(u32));
 402         if (rc < 0)
 403                 return -1;
 404
 405         /* expr */
 406         len = le32_to_cpu(buf[0]);
 407
 408         for (i = 0; i < len; i++) {
 409                 rc = next_entry(buf, fp, sizeof(u32) * 2);
 410                 if (rc < 0)
 411                         goto err;
 412
 413                 expr = kzalloc(sizeof(struct cond_expr), GFP_KERNEL);
 414                 if (!expr)
 415                         goto err;
 416
 417                 expr->expr_type = le32_to_cpu(buf[0]);
 418                 expr->bool = le32_to_cpu(buf[1]);
 419
 420                 if (!expr_isvalid(p, expr)) {
 421                         kfree(expr);
 422                         goto err;
 423                 }
 424
 425                 if (i == 0)
 426                         node->expr = expr;
 427                 else
 428                         last->next = expr;
 429                 last = expr;
 430         }
 431
 432         if (cond_read_av_list(p, fp, &node->true_list, NULL) != 0)
 433                 goto err;
 434         if (cond_read_av_list(p, fp, &node->false_list, node->true_list) != 0)
 435                 goto err;
 436         return 0;
 437 err:
 438         cond_node_destroy(node);
 439         return -1;
 440 }
 441
 442 int cond_read_list(struct policydb *p, void *fp)
 443 {
 444         struct cond_node *node, *last = NULL;
 445         __le32 buf[1];
 446         u32 i, len;
 447         int rc;
 448
 449         rc = next_entry(buf, fp, sizeof buf);
 450         if (rc)
 451                 return rc;
 452
 453         len = le32_to_cpu(buf[0]);
 454
 455         rc = avtab_alloc(&(p->te_cond_avtab), p->te_avtab.nel);
 456         if (rc)
 457                 goto err;
 458
 459         for (i = 0; i < len; i++) {
 460                 rc = -ENOMEM;
 461                 node = kzalloc(sizeof(struct cond_node), GFP_KERNEL);
 462                 if (!node)
 463                         goto err;
 464
 465                 rc = cond_read_node(p, node, fp);
 466                 if (rc)
 467                         goto err;
 468
 469                 if (i == 0)
 470                         p->cond_list = node;
 471                 else
 472                         last->next = node;
 473                 last = node;
 474         }
 475         return 0;
 476 err:
 477         cond_list_destroy(p->cond_list);
 478         p->cond_list = NULL;
 479         return rc;
 480 }
 481
 482 /* Determine whether additional permissions are granted by the conditional
 483  * av table, and if so, add them to the result
 484  */
 485 void cond_compute_av(struct avtab *ctab, struct avtab_key *key, struct av_decision *avd)
 486 {
 487         struct avtab_node *node;
 488
 489         if (!ctab || !key || !avd)
 490                 return;
 491
 492         for (node = avtab_search_node(ctab, key); node;
 493                                 node = avtab_search_node_next(node, key->specified)) {
 494                 if ((u16)(AVTAB_ALLOWED|AVTAB_ENABLED) ==
 495                     (node->key.specified & (AVTAB_ALLOWED|AVTAB_ENABLED)))
 496                         avd->allowed |= node->datum.data;
 497                 if ((u16)(AVTAB_AUDITDENY|AVTAB_ENABLED) ==
 498                     (node->key.specified & (AVTAB_AUDITDENY|AVTAB_ENABLED)))
 499                         /* Since a '0' in an auditdeny mask represents a
 500                          * permission we do NOT want to audit (dontaudit), we use
 501                          * the '&' operand to ensure that all '0's in the mask
 502                          * are retained (much unlike the allow and auditallow cases).
 503                          */
 504                         avd->auditdeny &= node->datum.data;
 505                 if ((u16)(AVTAB_AUDITALLOW|AVTAB_ENABLED) ==
 506                     (node->key.specified & (AVTAB_AUDITALLOW|AVTAB_ENABLED)))
 507                         avd->auditallow |= node->datum.data;
 508         }
 509         return;
 510 }