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         int rc;
 121
 122         p->bool_val_to_struct = NULL;
 123         p->cond_list = NULL;
 124
 125         rc = avtab_init(&p->te_cond_avtab);
 126         if (rc)
 127                 return rc;
 128
 129         return 0;
 130 }
 131
 132 static void cond_av_list_destroy(struct cond_av_list *list)
 133 {
 134         struct cond_av_list *cur, *next;
 135         for (cur = list; cur; cur = next) {
 136                 next = cur->next;
 137                 /* the avtab_ptr_t node is destroy by the avtab */
 138                 kfree(cur);
 139         }
 140 }
 141
 142 static void cond_node_destroy(struct cond_node *node)
 143 {
 144         struct cond_expr *cur_expr, *next_expr;
 145
 146         for (cur_expr = node->expr; cur_expr; cur_expr = next_expr) {
 147                 next_expr = cur_expr->next;
 148                 kfree(cur_expr);
 149         }
 150         cond_av_list_destroy(node->true_list);
 151         cond_av_list_destroy(node->false_list);
 152         kfree(node);
 153 }
 154
 155 static void cond_list_destroy(struct cond_node *list)
 156 {
 157         struct cond_node *next, *cur;
 158
 159         if (list == NULL)
 160                 return;
 161
 162         for (cur = list; cur; cur = next) {
 163                 next = cur->next;
 164                 cond_node_destroy(cur);
 165         }
 166 }
 167
 168 void cond_policydb_destroy(struct policydb *p)
 169 {
 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         kfree(p->bool_val_to_struct);
 178         p->bool_val_to_struct =
 179                 kmalloc(p->p_bools.nprim * sizeof(struct cond_bool_datum *), GFP_KERNEL);
 180         if (!p->bool_val_to_struct)
 181                 return -ENOMEM;
 182         return 0;
 183 }
 184
 185 int cond_destroy_bool(void *key, void *datum, void *p)
 186 {
 187         kfree(key);
 188         kfree(datum);
 189         return 0;
 190 }
 191
 192 int cond_index_bool(void *key, void *datum, void *datap)
 193 {
 194         struct policydb *p;
 195         struct cond_bool_datum *booldatum;
 196         struct flex_array *fa;
 197
 198         booldatum = datum;
 199         p = datap;
 200
 201         if (!booldatum->value || booldatum->value > p->p_bools.nprim)
 202                 return -EINVAL;
 203
 204         fa = p->sym_val_to_name[SYM_BOOLS];
 205         if (flex_array_put_ptr(fa, booldatum->value - 1, key,
 206                                GFP_KERNEL | __GFP_ZERO))
 207                 BUG();
 208         p->bool_val_to_struct[booldatum->value - 1] = booldatum;
 209
 210         return 0;
 211 }
 212
 213 static int bool_isvalid(struct cond_bool_datum *b)
 214 {
 215         if (!(b->state == 0 || b->state == 1))
 216                 return 0;
 217         return 1;
 218 }
 219
 220 int cond_read_bool(struct policydb *p, struct hashtab *h, void *fp)
 221 {
 222         char *key = NULL;
 223         struct cond_bool_datum *booldatum;
 224         __le32 buf[3];
 225         u32 len;
 226         int rc;
 227
 228         booldatum = kzalloc(sizeof(struct cond_bool_datum), GFP_KERNEL);
 229         if (!booldatum)
 230                 return -ENOMEM;
 231
 232         rc = next_entry(buf, fp, sizeof buf);
 233         if (rc)
 234                 goto err;
 235
 236         booldatum->value = le32_to_cpu(buf[0]);
 237         booldatum->state = le32_to_cpu(buf[1]);
 238
 239         rc = -EINVAL;
 240         if (!bool_isvalid(booldatum))
 241                 goto err;
 242
 243         len = le32_to_cpu(buf[2]);
 244
 245         rc = -ENOMEM;
 246         key = kmalloc(len + 1, GFP_KERNEL);
 247         if (!key)
 248                 goto err;
 249         rc = next_entry(key, fp, len);
 250         if (rc)
 251                 goto err;
 252         key[len] = '\0';
 253         rc = hashtab_insert(h, key, booldatum);
 254         if (rc)
 255                 goto err;
 256
 257         return 0;
 258 err:
 259         cond_destroy_bool(key, booldatum, NULL);
 260         return rc;
 261 }
 262
 263 struct cond_insertf_data {
 264         struct policydb *p;
 265         struct cond_av_list *other;
 266         struct cond_av_list *head;
 267         struct cond_av_list *tail;
 268 };
 269
 270 static int cond_insertf(struct avtab *a, struct avtab_key *k, struct avtab_datum *d, void *ptr)
 271 {
 272         struct cond_insertf_data *data = ptr;
 273         struct policydb *p = data->p;
 274         struct cond_av_list *other = data->other, *list, *cur;
 275         struct avtab_node *node_ptr;
 276         u8 found;
 277         int rc = -EINVAL;
 278
 279         /*
 280          * For type rules we have to make certain there aren't any
 281          * conflicting rules by searching the te_avtab and the
 282          * cond_te_avtab.
 283          */
 284         if (k->specified & AVTAB_TYPE) {
 285                 if (avtab_search(&p->te_avtab, k)) {
 286                         printk(KERN_ERR "SELinux: type rule already exists outside of a conditional.\n");
 287                         goto err;
 288                 }
 289                 /*
 290                  * If we are reading the false list other will be a pointer to
 291                  * the true list. We can have duplicate entries if there is only
 292                  * 1 other entry and it is in our true list.
 293                  *
 294                  * If we are reading the true list (other == NULL) there shouldn't
 295                  * be any other entries.
 296                  */
 297                 if (other) {
 298                         node_ptr = avtab_search_node(&p->te_cond_avtab, k);
 299                         if (node_ptr) {
 300                                 if (avtab_search_node_next(node_ptr, k->specified)) {
 301                                         printk(KERN_ERR "SELinux: too many conflicting type rules.\n");
 302                                         goto err;
 303                                 }
 304                                 found = 0;
 305                                 for (cur = other; cur; cur = cur->next) {
 306                                         if (cur->node == node_ptr) {
 307                                                 found = 1;
 308                                                 break;
 309                                         }
 310                                 }
 311                                 if (!found) {
 312                                         printk(KERN_ERR "SELinux: conflicting type rules.\n");
 313                                         goto err;
 314                                 }
 315                         }
 316                 } else {
 317                         if (avtab_search(&p->te_cond_avtab, k)) {
 318                                 printk(KERN_ERR "SELinux: conflicting type rules when adding type rule for true.\n");
 319                                 goto err;
 320                         }
 321                 }
 322         }
 323
 324         node_ptr = avtab_insert_nonunique(&p->te_cond_avtab, k, d);
 325         if (!node_ptr) {
 326                 printk(KERN_ERR "SELinux: could not insert rule.\n");
 327                 rc = -ENOMEM;
 328                 goto err;
 329         }
 330
 331         list = kzalloc(sizeof(struct cond_av_list), GFP_KERNEL);
 332         if (!list) {
 333                 rc = -ENOMEM;
 334                 goto err;
 335         }
 336
 337         list->node = node_ptr;
 338         if (!data->head)
 339                 data->head = list;
 340         else
 341                 data->tail->next = list;
 342         data->tail = list;
 343         return 0;
 344
 345 err:
 346         cond_av_list_destroy(data->head);
 347         data->head = NULL;
 348         return rc;
 349 }
 350
 351 static int cond_read_av_list(struct policydb *p, void *fp, struct cond_av_list **ret_list, struct cond_av_list *other)
 352 {
 353         int i, rc;
 354         __le32 buf[1];
 355         u32 len;
 356         struct cond_insertf_data data;
 357
 358         *ret_list = NULL;
 359
 360         len = 0;
 361         rc = next_entry(buf, fp, sizeof(u32));
 362         if (rc)
 363                 return rc;
 364
 365         len = le32_to_cpu(buf[0]);
 366         if (len == 0)
 367                 return 0;
 368
 369         data.p = p;
 370         data.other = other;
 371         data.head = NULL;
 372         data.tail = NULL;
 373         for (i = 0; i < len; i++) {
 374                 rc = avtab_read_item(&p->te_cond_avtab, fp, p, cond_insertf,
 375                                      &data);
 376                 if (rc)
 377                         return rc;
 378         }
 379
 380         *ret_list = data.head;
 381         return 0;
 382 }
 383
 384 static int expr_isvalid(struct policydb *p, struct cond_expr *expr)
 385 {
 386         if (expr->expr_type <= 0 || expr->expr_type > COND_LAST) {
 387                 printk(KERN_ERR "SELinux: conditional expressions uses unknown operator.\n");
 388                 return 0;
 389         }
 390
 391         if (expr->bool > p->p_bools.nprim) {
 392                 printk(KERN_ERR "SELinux: conditional expressions uses unknown bool.\n");
 393                 return 0;
 394         }
 395         return 1;
 396 }
 397
 398 static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
 399 {
 400         __le32 buf[2];
 401         u32 len, i;
 402         int rc;
 403         struct cond_expr *expr = NULL, *last = NULL;
 404
 405         rc = next_entry(buf, fp, sizeof(u32));
 406         if (rc)
 407                 return rc;
 408
 409         node->cur_state = le32_to_cpu(buf[0]);
 410
 411         len = 0;
 412         rc = next_entry(buf, fp, sizeof(u32));
 413         if (rc)
 414                 return rc;
 415
 416         /* expr */
 417         len = le32_to_cpu(buf[0]);
 418
 419         for (i = 0; i < len; i++) {
 420                 rc = next_entry(buf, fp, sizeof(u32) * 2);
 421                 if (rc)
 422                         goto err;
 423
 424                 rc = -ENOMEM;
 425                 expr = kzalloc(sizeof(struct cond_expr), GFP_KERNEL);
 426                 if (!expr)
 427                         goto err;
 428
 429                 expr->expr_type = le32_to_cpu(buf[0]);
 430                 expr->bool = le32_to_cpu(buf[1]);
 431
 432                 if (!expr_isvalid(p, expr)) {
 433                         rc = -EINVAL;
 434                         kfree(expr);
 435                         goto err;
 436                 }
 437
 438                 if (i == 0)
 439                         node->expr = expr;
 440                 else
 441                         last->next = expr;
 442                 last = expr;
 443         }
 444
 445         rc = cond_read_av_list(p, fp, &node->true_list, NULL);
 446         if (rc)
 447                 goto err;
 448         rc = cond_read_av_list(p, fp, &node->false_list, node->true_list);
 449         if (rc)
 450                 goto err;
 451         return 0;
 452 err:
 453         cond_node_destroy(node);
 454         return rc;
 455 }
 456
 457 int cond_read_list(struct policydb *p, void *fp)
 458 {
 459         struct cond_node *node, *last = NULL;
 460         __le32 buf[1];
 461         u32 i, len;
 462         int rc;
 463
 464         rc = next_entry(buf, fp, sizeof buf);
 465         if (rc)
 466                 return rc;
 467
 468         len = le32_to_cpu(buf[0]);
 469
 470         rc = avtab_alloc(&(p->te_cond_avtab), p->te_avtab.nel);
 471         if (rc)
 472                 goto err;
 473
 474         for (i = 0; i < len; i++) {
 475                 rc = -ENOMEM;
 476                 node = kzalloc(sizeof(struct cond_node), GFP_KERNEL);
 477                 if (!node)
 478                         goto err;
 479
 480                 rc = cond_read_node(p, node, fp);
 481                 if (rc)
 482                         goto err;
 483
 484                 if (i == 0)
 485                         p->cond_list = node;
 486                 else
 487                         last->next = node;
 488                 last = node;
 489         }
 490         return 0;
 491 err:
 492         cond_list_destroy(p->cond_list);
 493         p->cond_list = NULL;
 494         return rc;
 495 }
 496
 497 int cond_write_bool(void *vkey, void *datum, void *ptr)
 498 {
 499         char *key = vkey;
 500         struct cond_bool_datum *booldatum = datum;
 501         struct policy_data *pd = ptr;
 502         void *fp = pd->fp;
 503         __le32 buf[3];
 504         u32 len;
 505         int rc;
 506
 507         len = strlen(key);
 508         buf[0] = cpu_to_le32(booldatum->value);
 509         buf[1] = cpu_to_le32(booldatum->state);
 510         buf[2] = cpu_to_le32(len);
 511         rc = put_entry(buf, sizeof(u32), 3, fp);
 512         if (rc)
 513                 return rc;
 514         rc = put_entry(key, 1, len, fp);
 515         if (rc)
 516                 return rc;
 517         return 0;
 518 }
 519
 520 /*
 521  * cond_write_cond_av_list doesn't write out the av_list nodes.
 522  * Instead it writes out the key/value pairs from the avtab. This
 523  * is necessary because there is no way to uniquely identifying rules
 524  * in the avtab so it is not possible to associate individual rules
 525  * in the avtab with a conditional without saving them as part of
 526  * the conditional. This means that the avtab with the conditional
 527  * rules will not be saved but will be rebuilt on policy load.
 528  */
 529 static int cond_write_av_list(struct policydb *p,
 530                               struct cond_av_list *list, struct policy_file *fp)
 531 {
 532         __le32 buf[1];
 533         struct cond_av_list *cur_list;
 534         u32 len;
 535         int rc;
 536
 537         len = 0;
 538         for (cur_list = list; cur_list != NULL; cur_list = cur_list->next)
 539                 len++;
 540
 541         buf[0] = cpu_to_le32(len);
 542         rc = put_entry(buf, sizeof(u32), 1, fp);
 543         if (rc)
 544                 return rc;
 545
 546         if (len == 0)
 547                 return 0;
 548
 549         for (cur_list = list; cur_list != NULL; cur_list = cur_list->next) {
 550                 rc = avtab_write_item(p, cur_list->node, fp);
 551                 if (rc)
 552                         return rc;
 553         }
 554
 555         return 0;
 556 }
 557
 558 static int cond_write_node(struct policydb *p, struct cond_node *node,
 559                     struct policy_file *fp)
 560 {
 561         struct cond_expr *cur_expr;
 562         __le32 buf[2];
 563         int rc;
 564         u32 len = 0;
 565
 566         buf[0] = cpu_to_le32(node->cur_state);
 567         rc = put_entry(buf, sizeof(u32), 1, fp);
 568         if (rc)
 569                 return rc;
 570
 571         for (cur_expr = node->expr; cur_expr != NULL; cur_expr = cur_expr->next)
 572                 len++;
 573
 574         buf[0] = cpu_to_le32(len);
 575         rc = put_entry(buf, sizeof(u32), 1, fp);
 576         if (rc)
 577                 return rc;
 578
 579         for (cur_expr = node->expr; cur_expr != NULL; cur_expr = cur_expr->next) {
 580                 buf[0] = cpu_to_le32(cur_expr->expr_type);
 581                 buf[1] = cpu_to_le32(cur_expr->bool);
 582                 rc = put_entry(buf, sizeof(u32), 2, fp);
 583                 if (rc)
 584                         return rc;
 585         }
 586
 587         rc = cond_write_av_list(p, node->true_list, fp);
 588         if (rc)
 589                 return rc;
 590         rc = cond_write_av_list(p, node->false_list, fp);
 591         if (rc)
 592                 return rc;
 593
 594         return 0;
 595 }
 596
 597 int cond_write_list(struct policydb *p, struct cond_node *list, void *fp)
 598 {
 599         struct cond_node *cur;
 600         u32 len;
 601         __le32 buf[1];
 602         int rc;
 603
 604         len = 0;
 605         for (cur = list; cur != NULL; cur = cur->next)
 606                 len++;
 607         buf[0] = cpu_to_le32(len);
 608         rc = put_entry(buf, sizeof(u32), 1, fp);
 609         if (rc)
 610                 return rc;
 611
 612         for (cur = list; cur != NULL; cur = cur->next) {
 613                 rc = cond_write_node(p, cur, fp);
 614                 if (rc)
 615                         return rc;
 616         }
 617
 618         return 0;
 619 }
 620 /* Determine whether additional permissions are granted by the conditional
 621  * av table, and if so, add them to the result
 622  */
 623 void cond_compute_av(struct avtab *ctab, struct avtab_key *key, struct av_decision *avd)
 624 {
 625         struct avtab_node *node;
 626
 627         if (!ctab || !key || !avd)
 628                 return;
 629
 630         for (node = avtab_search_node(ctab, key); node;
 631                                 node = avtab_search_node_next(node, key->specified)) {
 632                 if ((u16)(AVTAB_ALLOWED|AVTAB_ENABLED) ==
 633                     (node->key.specified & (AVTAB_ALLOWED|AVTAB_ENABLED)))
 634                         avd->allowed |= node->datum.data;
 635                 if ((u16)(AVTAB_AUDITDENY|AVTAB_ENABLED) ==
 636                     (node->key.specified & (AVTAB_AUDITDENY|AVTAB_ENABLED)))
 637                         /* Since a '0' in an auditdeny mask represents a
 638                          * permission we do NOT want to audit (dontaudit), we use
 639                          * the '&' operand to ensure that all '0's in the mask
 640                          * are retained (much unlike the allow and auditallow cases).
 641                          */
 642                         avd->auditdeny &= node->datum.data;
 643                 if ((u16)(AVTAB_AUDITALLOW|AVTAB_ENABLED) ==
 644                     (node->key.specified & (AVTAB_AUDITALLOW|AVTAB_ENABLED)))
 645                         avd->auditallow |= node->datum.data;
 646         }
 647         return;
 648 }