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 #include "services.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; 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 "SELinux: expression result was undefined - disabling all rules.\n");
 100                 /* turn the rules on or off */
 101                 for (cur = node->true_list; cur; 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                 for (cur = node->false_list; cur; cur = cur->next) {
 109                         /* -1 or 1 */
 110                         if (new_state)
 111                                 cur->node->key.specified &= ~AVTAB_ENABLED;
 112                         else
 113                                 cur->node->key.specified |= AVTAB_ENABLED;
 114                 }
 115         }
 116         return 0;
 117 }
 118
 119 int cond_policydb_init(struct policydb *p)
 120 {
 121         int rc;
 122
 123         p->bool_val_to_struct = NULL;
 124         p->cond_list = NULL;
 125
 126         rc = avtab_init(&p->te_cond_avtab);
 127         if (rc)
 128                 return rc;
 129
 130         return 0;
 131 }
 132
 133 static void cond_av_list_destroy(struct cond_av_list *list)
 134 {
 135         struct cond_av_list *cur, *next;
 136         for (cur = list; cur; cur = next) {
 137                 next = cur->next;
 138                 /* the avtab_ptr_t node is destroy by the avtab */
 139                 kfree(cur);
 140         }
 141 }
 142
 143 static void cond_node_destroy(struct cond_node *node)
 144 {
 145         struct cond_expr *cur_expr, *next_expr;
 146
 147         for (cur_expr = node->expr; cur_expr; cur_expr = next_expr) {
 148                 next_expr = cur_expr->next;
 149                 kfree(cur_expr);
 150         }
 151         cond_av_list_destroy(node->true_list);
 152         cond_av_list_destroy(node->false_list);
 153         kfree(node);
 154 }
 155
 156 static void cond_list_destroy(struct cond_node *list)
 157 {
 158         struct cond_node *next, *cur;
 159
 160         if (list == NULL)
 161                 return;
 162
 163         for (cur = list; cur; cur = next) {
 164                 next = cur->next;
 165                 cond_node_destroy(cur);
 166         }
 167 }
 168
 169 void cond_policydb_destroy(struct policydb *p)
 170 {
 171         kfree(p->bool_val_to_struct);
 172         avtab_destroy(&p->te_cond_avtab);
 173         cond_list_destroy(p->cond_list);
 174 }
 175
 176 int cond_init_bool_indexes(struct policydb *p)
 177 {
 178         kfree(p->bool_val_to_struct);
 179         p->bool_val_to_struct = kmalloc_array(p->p_bools.nprim,
 180                                               sizeof(*p->bool_val_to_struct),
 181                                               GFP_KERNEL);
 182         if (!p->bool_val_to_struct)
 183                 return -ENOMEM;
 184         return 0;
 185 }
 186
 187 int cond_destroy_bool(void *key, void *datum, void *p)
 188 {
 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         struct flex_array *fa;
 199
 200         booldatum = datum;
 201         p = datap;
 202
 203         if (!booldatum->value || booldatum->value > p->p_bools.nprim)
 204                 return -EINVAL;
 205
 206         fa = p->sym_val_to_name[SYM_BOOLS];
 207         if (flex_array_put_ptr(fa, booldatum->value - 1, key,
 208                                GFP_KERNEL | __GFP_ZERO))
 209                 BUG();
 210         p->bool_val_to_struct[booldatum->value - 1] = booldatum;
 211
 212         return 0;
 213 }
 214
 215 static int bool_isvalid(struct cond_bool_datum *b)
 216 {
 217         if (!(b->state == 0 || b->state == 1))
 218                 return 0;
 219         return 1;
 220 }
 221
 222 int cond_read_bool(struct policydb *p, struct hashtab *h, void *fp)
 223 {
 224         char *key = NULL;
 225         struct cond_bool_datum *booldatum;
 226         __le32 buf[3];
 227         u32 len;
 228         int rc;
 229
 230         booldatum = kzalloc(sizeof(*booldatum), GFP_KERNEL);
 231         if (!booldatum)
 232                 return -ENOMEM;
 233
 234         rc = next_entry(buf, fp, sizeof buf);
 235         if (rc)
 236                 goto err;
 237
 238         booldatum->value = le32_to_cpu(buf[0]);
 239         booldatum->state = le32_to_cpu(buf[1]);
 240
 241         rc = -EINVAL;
 242         if (!bool_isvalid(booldatum))
 243                 goto err;
 244
 245         len = le32_to_cpu(buf[2]);
 246         if (((len == 0) || (len == (u32)-1)))
 247                 goto err;
 248
 249         rc = -ENOMEM;
 250         key = kmalloc(len + 1, GFP_KERNEL);
 251         if (!key)
 252                 goto err;
 253         rc = next_entry(key, fp, len);
 254         if (rc)
 255                 goto err;
 256         key[len] = '\0';
 257         rc = hashtab_insert(h, key, booldatum);
 258         if (rc)
 259                 goto err;
 260
 261         return 0;
 262 err:
 263         cond_destroy_bool(key, booldatum, NULL);
 264         return rc;
 265 }
 266
 267 struct cond_insertf_data {
 268         struct policydb *p;
 269         struct cond_av_list *other;
 270         struct cond_av_list *head;
 271         struct cond_av_list *tail;
 272 };
 273
 274 static int cond_insertf(struct avtab *a, struct avtab_key *k, struct avtab_datum *d, void *ptr)
 275 {
 276         struct cond_insertf_data *data = ptr;
 277         struct policydb *p = data->p;
 278         struct cond_av_list *other = data->other, *list, *cur;
 279         struct avtab_node *node_ptr;
 280         u8 found;
 281         int rc = -EINVAL;
 282
 283         /*
 284          * For type rules we have to make certain there aren't any
 285          * conflicting rules by searching the te_avtab and the
 286          * cond_te_avtab.
 287          */
 288         if (k->specified & AVTAB_TYPE) {
 289                 if (avtab_search(&p->te_avtab, k)) {
 290                         printk(KERN_ERR "SELinux: type rule already exists outside of a conditional.\n");
 291                         goto err;
 292                 }
 293                 /*
 294                  * If we are reading the false list other will be a pointer to
 295                  * the true list. We can have duplicate entries if there is only
 296                  * 1 other entry and it is in our true list.
 297                  *
 298                  * If we are reading the true list (other == NULL) there shouldn't
 299                  * be any other entries.
 300                  */
 301                 if (other) {
 302                         node_ptr = avtab_search_node(&p->te_cond_avtab, k);
 303                         if (node_ptr) {
 304                                 if (avtab_search_node_next(node_ptr, k->specified)) {
 305                                         printk(KERN_ERR "SELinux: too many conflicting type rules.\n");
 306                                         goto err;
 307                                 }
 308                                 found = 0;
 309                                 for (cur = other; cur; cur = cur->next) {
 310                                         if (cur->node == node_ptr) {
 311                                                 found = 1;
 312                                                 break;
 313                                         }
 314                                 }
 315                                 if (!found) {
 316                                         printk(KERN_ERR "SELinux: conflicting type rules.\n");
 317                                         goto err;
 318                                 }
 319                         }
 320                 } else {
 321                         if (avtab_search(&p->te_cond_avtab, k)) {
 322                                 printk(KERN_ERR "SELinux: conflicting type rules when adding type rule for true.\n");
 323                                 goto err;
 324                         }
 325                 }
 326         }
 327
 328         node_ptr = avtab_insert_nonunique(&p->te_cond_avtab, k, d);
 329         if (!node_ptr) {
 330                 printk(KERN_ERR "SELinux: could not insert rule.\n");
 331                 rc = -ENOMEM;
 332                 goto err;
 333         }
 334
 335         list = kzalloc(sizeof(*list), GFP_KERNEL);
 336         if (!list) {
 337                 rc = -ENOMEM;
 338                 goto err;
 339         }
 340
 341         list->node = node_ptr;
 342         if (!data->head)
 343                 data->head = list;
 344         else
 345                 data->tail->next = list;
 346         data->tail = list;
 347         return 0;
 348
 349 err:
 350         cond_av_list_destroy(data->head);
 351         data->head = NULL;
 352         return rc;
 353 }
 354
 355 static int cond_read_av_list(struct policydb *p, void *fp, struct cond_av_list **ret_list, struct cond_av_list *other)
 356 {
 357         int i, rc;
 358         __le32 buf[1];
 359         u32 len;
 360         struct cond_insertf_data data;
 361
 362         *ret_list = NULL;
 363
 364         rc = next_entry(buf, fp, sizeof(u32));
 365         if (rc)
 366                 return rc;
 367
 368         len = le32_to_cpu(buf[0]);
 369         if (len == 0)
 370                 return 0;
 371
 372         data.p = p;
 373         data.other = other;
 374         data.head = NULL;
 375         data.tail = NULL;
 376         for (i = 0; i < len; i++) {
 377                 rc = avtab_read_item(&p->te_cond_avtab, fp, p, cond_insertf,
 378                                      &data);
 379                 if (rc)
 380                         return rc;
 381         }
 382
 383         *ret_list = data.head;
 384         return 0;
 385 }
 386
 387 static int expr_isvalid(struct policydb *p, struct cond_expr *expr)
 388 {
 389         if (expr->expr_type <= 0 || expr->expr_type > COND_LAST) {
 390                 printk(KERN_ERR "SELinux: conditional expressions uses unknown operator.\n");
 391                 return 0;
 392         }
 393
 394         if (expr->bool > p->p_bools.nprim) {
 395                 printk(KERN_ERR "SELinux: conditional expressions uses unknown bool.\n");
 396                 return 0;
 397         }
 398         return 1;
 399 }
 400
 401 static int cond_read_node(struct policydb *p, struct cond_node *node, void *fp)
 402 {
 403         __le32 buf[2];
 404         u32 len, i;
 405         int rc;
 406         struct cond_expr *expr = NULL, *last = NULL;
 407
 408         rc = next_entry(buf, fp, sizeof(u32) * 2);
 409         if (rc)
 410                 goto err;
 411
 412         node->cur_state = le32_to_cpu(buf[0]);
 413
 414         /* expr */
 415         len = le32_to_cpu(buf[1]);
 416
 417         for (i = 0; i < len; i++) {
 418                 rc = next_entry(buf, fp, sizeof(u32) * 2);
 419                 if (rc)
 420                         goto err;
 421
 422                 rc = -ENOMEM;
 423                 expr = kzalloc(sizeof(*expr), GFP_KERNEL);
 424                 if (!expr)
 425                         goto err;
 426
 427                 expr->expr_type = le32_to_cpu(buf[0]);
 428                 expr->bool = le32_to_cpu(buf[1]);
 429
 430                 if (!expr_isvalid(p, expr)) {
 431                         rc = -EINVAL;
 432                         kfree(expr);
 433                         goto err;
 434                 }
 435
 436                 if (i == 0)
 437                         node->expr = expr;
 438                 else
 439                         last->next = expr;
 440                 last = expr;
 441         }
 442
 443         rc = cond_read_av_list(p, fp, &node->true_list, NULL);
 444         if (rc)
 445                 goto err;
 446         rc = cond_read_av_list(p, fp, &node->false_list, node->true_list);
 447         if (rc)
 448                 goto err;
 449         return 0;
 450 err:
 451         cond_node_destroy(node);
 452         return rc;
 453 }
 454
 455 int cond_read_list(struct policydb *p, void *fp)
 456 {
 457         struct cond_node *node, *last = NULL;
 458         __le32 buf[1];
 459         u32 i, len;
 460         int rc;
 461
 462         rc = next_entry(buf, fp, sizeof buf);
 463         if (rc)
 464                 return rc;
 465
 466         len = le32_to_cpu(buf[0]);
 467
 468         rc = avtab_alloc(&(p->te_cond_avtab), p->te_avtab.nel);
 469         if (rc)
 470                 goto err;
 471
 472         for (i = 0; i < len; i++) {
 473                 rc = -ENOMEM;
 474                 node = kzalloc(sizeof(*node), GFP_KERNEL);
 475                 if (!node)
 476                         goto err;
 477
 478                 rc = cond_read_node(p, node, fp);
 479                 if (rc)
 480                         goto err;
 481
 482                 if (i == 0)
 483                         p->cond_list = node;
 484                 else
 485                         last->next = node;
 486                 last = node;
 487         }
 488         return 0;
 489 err:
 490         cond_list_destroy(p->cond_list);
 491         p->cond_list = NULL;
 492         return rc;
 493 }
 494
 495 int cond_write_bool(void *vkey, void *datum, void *ptr)
 496 {
 497         char *key = vkey;
 498         struct cond_bool_datum *booldatum = datum;
 499         struct policy_data *pd = ptr;
 500         void *fp = pd->fp;
 501         __le32 buf[3];
 502         u32 len;
 503         int rc;
 504
 505         len = strlen(key);
 506         buf[0] = cpu_to_le32(booldatum->value);
 507         buf[1] = cpu_to_le32(booldatum->state);
 508         buf[2] = cpu_to_le32(len);
 509         rc = put_entry(buf, sizeof(u32), 3, fp);
 510         if (rc)
 511                 return rc;
 512         rc = put_entry(key, 1, len, fp);
 513         if (rc)
 514                 return rc;
 515         return 0;
 516 }
 517
 518 /*
 519  * cond_write_cond_av_list doesn't write out the av_list nodes.
 520  * Instead it writes out the key/value pairs from the avtab. This
 521  * is necessary because there is no way to uniquely identifying rules
 522  * in the avtab so it is not possible to associate individual rules
 523  * in the avtab with a conditional without saving them as part of
 524  * the conditional. This means that the avtab with the conditional
 525  * rules will not be saved but will be rebuilt on policy load.
 526  */
 527 static int cond_write_av_list(struct policydb *p,
 528                               struct cond_av_list *list, struct policy_file *fp)
 529 {
 530         __le32 buf[1];
 531         struct cond_av_list *cur_list;
 532         u32 len;
 533         int rc;
 534
 535         len = 0;
 536         for (cur_list = list; cur_list != NULL; cur_list = cur_list->next)
 537                 len++;
 538
 539         buf[0] = cpu_to_le32(len);
 540         rc = put_entry(buf, sizeof(u32), 1, fp);
 541         if (rc)
 542                 return rc;
 543
 544         if (len == 0)
 545                 return 0;
 546
 547         for (cur_list = list; cur_list != NULL; cur_list = cur_list->next) {
 548                 rc = avtab_write_item(p, cur_list->node, fp);
 549                 if (rc)
 550                         return rc;
 551         }
 552
 553         return 0;
 554 }
 555
 556 static int cond_write_node(struct policydb *p, struct cond_node *node,
 557                     struct policy_file *fp)
 558 {
 559         struct cond_expr *cur_expr;
 560         __le32 buf[2];
 561         int rc;
 562         u32 len = 0;
 563
 564         buf[0] = cpu_to_le32(node->cur_state);
 565         rc = put_entry(buf, sizeof(u32), 1, fp);
 566         if (rc)
 567                 return rc;
 568
 569         for (cur_expr = node->expr; cur_expr != NULL; cur_expr = cur_expr->next)
 570                 len++;
 571
 572         buf[0] = cpu_to_le32(len);
 573         rc = put_entry(buf, sizeof(u32), 1, fp);
 574         if (rc)
 575                 return rc;
 576
 577         for (cur_expr = node->expr; cur_expr != NULL; cur_expr = cur_expr->next) {
 578                 buf[0] = cpu_to_le32(cur_expr->expr_type);
 579                 buf[1] = cpu_to_le32(cur_expr->bool);
 580                 rc = put_entry(buf, sizeof(u32), 2, fp);
 581                 if (rc)
 582                         return rc;
 583         }
 584
 585         rc = cond_write_av_list(p, node->true_list, fp);
 586         if (rc)
 587                 return rc;
 588         rc = cond_write_av_list(p, node->false_list, fp);
 589         if (rc)
 590                 return rc;
 591
 592         return 0;
 593 }
 594
 595 int cond_write_list(struct policydb *p, struct cond_node *list, void *fp)
 596 {
 597         struct cond_node *cur;
 598         u32 len;
 599         __le32 buf[1];
 600         int rc;
 601
 602         len = 0;
 603         for (cur = list; cur != NULL; cur = cur->next)
 604                 len++;
 605         buf[0] = cpu_to_le32(len);
 606         rc = put_entry(buf, sizeof(u32), 1, fp);
 607         if (rc)
 608                 return rc;
 609
 610         for (cur = list; cur != NULL; cur = cur->next) {
 611                 rc = cond_write_node(p, cur, fp);
 612                 if (rc)
 613                         return rc;
 614         }
 615
 616         return 0;
 617 }
 618
 619 void cond_compute_xperms(struct avtab *ctab, struct avtab_key *key,
 620                 struct extended_perms_decision *xpermd)
 621 {
 622         struct avtab_node *node;
 623
 624         if (!ctab || !key || !xpermd)
 625                 return;
 626
 627         for (node = avtab_search_node(ctab, key); node;
 628                         node = avtab_search_node_next(node, key->specified)) {
 629                 if (node->key.specified & AVTAB_ENABLED)
 630                         services_compute_xperms_decision(xpermd, node);
 631         }
 632         return;
 633
 634 }
 635 /* Determine whether additional permissions are granted by the conditional
 636  * av table, and if so, add them to the result
 637  */
 638 void cond_compute_av(struct avtab *ctab, struct avtab_key *key,
 639                 struct av_decision *avd, struct extended_perms *xperms)
 640 {
 641         struct avtab_node *node;
 642
 643         if (!ctab || !key || !avd)
 644                 return;
 645
 646         for (node = avtab_search_node(ctab, key); node;
 647                                 node = avtab_search_node_next(node, key->specified)) {
 648                 if ((u16)(AVTAB_ALLOWED|AVTAB_ENABLED) ==
 649                     (node->key.specified & (AVTAB_ALLOWED|AVTAB_ENABLED)))
 650                         avd->allowed |= node->datum.u.data;
 651                 if ((u16)(AVTAB_AUDITDENY|AVTAB_ENABLED) ==
 652                     (node->key.specified & (AVTAB_AUDITDENY|AVTAB_ENABLED)))
 653                         /* Since a '0' in an auditdeny mask represents a
 654                          * permission we do NOT want to audit (dontaudit), we use
 655                          * the '&' operand to ensure that all '0's in the mask
 656                          * are retained (much unlike the allow and auditallow cases).
 657                          */
 658                         avd->auditdeny &= node->datum.u.data;
 659                 if ((u16)(AVTAB_AUDITALLOW|AVTAB_ENABLED) ==
 660                     (node->key.specified & (AVTAB_AUDITALLOW|AVTAB_ENABLED)))
 661                         avd->auditallow |= node->datum.u.data;
 662                 if (xperms && (node->key.specified & AVTAB_ENABLED) &&
 663                                 (node->key.specified & AVTAB_XPERMS))
 664                         services_compute_xperms_drivers(xperms, node);
 665         }
 666 }