security/selinux/ss/mls.c

   1 /*
   2  * Implementation of the multi-level security (MLS) policy.
   3  *
   4  * Author : Stephen Smalley, <sds@epoch.ncsc.mil>
   5  */
   6 /*
   7  * Updated: Trusted Computer Solutions, Inc. <dgoeddel@trustedcs.com>
   8  *
   9  *      Support for enhanced MLS infrastructure.
  10  *
  11  * Copyright (C) 2004-2006 Trusted Computer Solutions, Inc.
  12  */
  13 /*
  14  * Updated: Hewlett-Packard <paul.moore@hp.com>
  15  *
  16  *      Added support to import/export the MLS label from NetLabel
  17  *
  18  * (c) Copyright Hewlett-Packard Development Company, L.P., 2006
  19  */
  20
  21 #include <linux/kernel.h>
  22 #include <linux/slab.h>
  23 #include <linux/string.h>
  24 #include <linux/errno.h>
  25 #include <net/netlabel.h>
  26 #include "sidtab.h"
  27 #include "mls.h"
  28 #include "policydb.h"
  29 #include "services.h"
  30
  31 /*
  32  * Return the length in bytes for the MLS fields of the
  33  * security context string representation of `context'.
  34  */
  35 int mls_compute_context_len(struct context * context)
  36 {
  37         int i, l, len, head, prev;
  38         char *nm;
  39         struct ebitmap *e;
  40         struct ebitmap_node *node;
  41
  42         if (!selinux_mls_enabled)
  43                 return 0;
  44
  45         len = 1; /* for the beginning ":" */
  46         for (l = 0; l < 2; l++) {
  47                 int index_sens = context->range.level[l].sens;
  48                 len += strlen(policydb.p_sens_val_to_name[index_sens - 1]);
  49
  50                 /* categories */
  51                 head = -2;
  52                 prev = -2;
  53                 e = &context->range.level[l].cat;
  54                 ebitmap_for_each_positive_bit(e, node, i) {
  55                         if (i - prev > 1) {
  56                                 /* one or more negative bits are skipped */
  57                                 if (head != prev) {
  58                                         nm = policydb.p_cat_val_to_name[prev];
  59                                         len += strlen(nm) + 1;
  60                                 }
  61                                 nm = policydb.p_cat_val_to_name[i];
  62                                 len += strlen(nm) + 1;
  63                                 head = i;
  64                         }
  65                         prev = i;
  66                 }
  67                 if (prev != head) {
  68                         nm = policydb.p_cat_val_to_name[prev];
  69                         len += strlen(nm) + 1;
  70                 }
  71                 if (l == 0) {
  72                         if (mls_level_eq(&context->range.level[0],
  73                                          &context->range.level[1]))
  74                                 break;
  75                         else
  76                                 len++;
  77                 }
  78         }
  79
  80         return len;
  81 }
  82
  83 /*
  84  * Write the security context string representation of
  85  * the MLS fields of `context' into the string `*scontext'.
  86  * Update `*scontext' to point to the end of the MLS fields.
  87  */
  88 void mls_sid_to_context(struct context *context,
  89                         char **scontext)
  90 {
  91         char *scontextp, *nm;
  92         int i, l, head, prev;
  93         struct ebitmap *e;
  94         struct ebitmap_node *node;
  95
  96         if (!selinux_mls_enabled)
  97                 return;
  98
  99         scontextp = *scontext;
 100
 101         *scontextp = ':';
 102         scontextp++;
 103
 104         for (l = 0; l < 2; l++) {
 105                 strcpy(scontextp,
 106                        policydb.p_sens_val_to_name[context->range.level[l].sens - 1]);
 107                 scontextp += strlen(scontextp);
 108
 109                 /* categories */
 110                 head = -2;
 111                 prev = -2;
 112                 e = &context->range.level[l].cat;
 113                 ebitmap_for_each_positive_bit(e, node, i) {
 114                         if (i - prev > 1) {
 115                                 /* one or more negative bits are skipped */
 116                                 if (prev != head) {
 117                                         if (prev - head > 1)
 118                                                 *scontextp++ = '.';
 119                                         else
 120                                                 *scontextp++ = ',';
 121                                         nm = policydb.p_cat_val_to_name[prev];
 122                                         strcpy(scontextp, nm);
 123                                         scontextp += strlen(nm);
 124                                 }
 125                                 if (prev < 0)
 126                                         *scontextp++ = ':';
 127                                 else
 128                                         *scontextp++ = ',';
 129                                 nm = policydb.p_cat_val_to_name[i];
 130                                 strcpy(scontextp, nm);
 131                                 scontextp += strlen(nm);
 132                                 head = i;
 133                         }
 134                         prev = i;
 135                 }
 136
 137                 if (prev != head) {
 138                         if (prev - head > 1)
 139                                 *scontextp++ = '.';
 140                         else
 141                                 *scontextp++ = ',';
 142                         nm = policydb.p_cat_val_to_name[prev];
 143                         strcpy(scontextp, nm);
 144                         scontextp += strlen(nm);
 145                 }
 146
 147                 if (l == 0) {
 148                         if (mls_level_eq(&context->range.level[0],
 149                                          &context->range.level[1]))
 150                                 break;
 151                         else
 152                                 *scontextp++ = '-';
 153                 }
 154         }
 155
 156         *scontext = scontextp;
 157         return;
 158 }
 159
 160 int mls_level_isvalid(struct policydb *p, struct mls_level *l)
 161 {
 162         struct level_datum *levdatum;
 163         struct ebitmap_node *node;
 164         int i;
 165
 166         if (!l->sens || l->sens > p->p_levels.nprim)
 167                 return 0;
 168         levdatum = hashtab_search(p->p_levels.table,
 169                                   p->p_sens_val_to_name[l->sens - 1]);
 170         if (!levdatum)
 171                 return 0;
 172
 173         ebitmap_for_each_positive_bit(&l->cat, node, i) {
 174                 if (i > p->p_cats.nprim)
 175                         return 0;
 176                 if (!ebitmap_get_bit(&levdatum->level->cat, i)) {
 177                         /*
 178                          * Category may not be associated with
 179                          * sensitivity.
 180                          */
 181                         return 0;
 182                 }
 183         }
 184
 185         return 1;
 186 }
 187
 188 int mls_range_isvalid(struct policydb *p, struct mls_range *r)
 189 {
 190         return (mls_level_isvalid(p, &r->level[0]) &&
 191                 mls_level_isvalid(p, &r->level[1]) &&
 192                 mls_level_dom(&r->level[1], &r->level[0]));
 193 }
 194
 195 /*
 196  * Return 1 if the MLS fields in the security context
 197  * structure `c' are valid.  Return 0 otherwise.
 198  */
 199 int mls_context_isvalid(struct policydb *p, struct context *c)
 200 {
 201         struct user_datum *usrdatum;
 202
 203         if (!selinux_mls_enabled)
 204                 return 1;
 205
 206         if (!mls_range_isvalid(p, &c->range))
 207                 return 0;
 208
 209         if (c->role == OBJECT_R_VAL)
 210                 return 1;
 211
 212         /*
 213          * User must be authorized for the MLS range.
 214          */
 215         if (!c->user || c->user > p->p_users.nprim)
 216                 return 0;
 217         usrdatum = p->user_val_to_struct[c->user - 1];
 218         if (!mls_range_contains(usrdatum->range, c->range))
 219                 return 0; /* user may not be associated with range */
 220
 221         return 1;
 222 }
 223
 224 /*
 225  * Set the MLS fields in the security context structure
 226  * `context' based on the string representation in
 227  * the string `*scontext'.  Update `*scontext' to
 228  * point to the end of the string representation of
 229  * the MLS fields.
 230  *
 231  * This function modifies the string in place, inserting
 232  * NULL characters to terminate the MLS fields.
 233  *
 234  * If a def_sid is provided and no MLS field is present,
 235  * copy the MLS field of the associated default context.
 236  * Used for upgraded to MLS systems where objects may lack
 237  * MLS fields.
 238  *
 239  * Policy read-lock must be held for sidtab lookup.
 240  *
 241  */
 242 int mls_context_to_sid(char oldc,
 243                        char **scontext,
 244                        struct context *context,
 245                        struct sidtab *s,
 246                        u32 def_sid)
 247 {
 248
 249         char delim;
 250         char *scontextp, *p, *rngptr;
 251         struct level_datum *levdatum;
 252         struct cat_datum *catdatum, *rngdatum;
 253         int l, rc = -EINVAL;
 254
 255         if (!selinux_mls_enabled) {
 256                 if (def_sid != SECSID_NULL && oldc)
 257                         *scontext += strlen(*scontext)+1;
 258                 return 0;
 259         }
 260
 261         /*
 262          * No MLS component to the security context, try and map to
 263          * default if provided.
 264          */
 265         if (!oldc) {
 266                 struct context *defcon;
 267
 268                 if (def_sid == SECSID_NULL)
 269                         goto out;
 270
 271                 defcon = sidtab_search(s, def_sid);
 272                 if (!defcon)
 273                         goto out;
 274
 275                 rc = mls_context_cpy(context, defcon);
 276                 goto out;
 277         }
 278
 279         /* Extract low sensitivity. */
 280         scontextp = p = *scontext;
 281         while (*p && *p != ':' && *p != '-')
 282                 p++;
 283
 284         delim = *p;
 285         if (delim != 0)
 286                 *p++ = 0;
 287
 288         for (l = 0; l < 2; l++) {
 289                 levdatum = hashtab_search(policydb.p_levels.table, scontextp);
 290                 if (!levdatum) {
 291                         rc = -EINVAL;
 292                         goto out;
 293                 }
 294
 295                 context->range.level[l].sens = levdatum->level->sens;
 296
 297                 if (delim == ':') {
 298                         /* Extract category set. */
 299                         while (1) {
 300                                 scontextp = p;
 301                                 while (*p && *p != ',' && *p != '-')
 302                                         p++;
 303                                 delim = *p;
 304                                 if (delim != 0)
 305                                         *p++ = 0;
 306
 307                                 /* Separate into range if exists */
 308                                 if ((rngptr = strchr(scontextp, '.')) != NULL) {
 309                                         /* Remove '.' */
 310                                         *rngptr++ = 0;
 311                                 }
 312
 313                                 catdatum = hashtab_search(policydb.p_cats.table,
 314                                                           scontextp);
 315                                 if (!catdatum) {
 316                                         rc = -EINVAL;
 317                                         goto out;
 318                                 }
 319
 320                                 rc = ebitmap_set_bit(&context->range.level[l].cat,
 321                                                      catdatum->value - 1, 1);
 322                                 if (rc)
 323                                         goto out;
 324
 325                                 /* If range, set all categories in range */
 326                                 if (rngptr) {
 327                                         int i;
 328
 329                                         rngdatum = hashtab_search(policydb.p_cats.table, rngptr);
 330                                         if (!rngdatum) {
 331                                                 rc = -EINVAL;
 332                                                 goto out;
 333                                         }
 334
 335                                         if (catdatum->value >= rngdatum->value) {
 336                                                 rc = -EINVAL;
 337                                                 goto out;
 338                                         }
 339
 340                                         for (i = catdatum->value; i < rngdatum->value; i++) {
 341                                                 rc = ebitmap_set_bit(&context->range.level[l].cat, i, 1);
 342                                                 if (rc)
 343                                                         goto out;
 344                                         }
 345                                 }
 346
 347                                 if (delim != ',')
 348                                         break;
 349                         }
 350                 }
 351                 if (delim == '-') {
 352                         /* Extract high sensitivity. */
 353                         scontextp = p;
 354                         while (*p && *p != ':')
 355                                 p++;
 356
 357                         delim = *p;
 358                         if (delim != 0)
 359                                 *p++ = 0;
 360                 } else
 361                         break;
 362         }
 363
 364         if (l == 0) {
 365                 context->range.level[1].sens = context->range.level[0].sens;
 366                 rc = ebitmap_cpy(&context->range.level[1].cat,
 367                                  &context->range.level[0].cat);
 368                 if (rc)
 369                         goto out;
 370         }
 371         *scontext = ++p;
 372         rc = 0;
 373 out:
 374         return rc;
 375 }
 376
 377 /*
 378  * Set the MLS fields in the security context structure
 379  * `context' based on the string representation in
 380  * the string `str'.  This function will allocate temporary memory with the
 381  * given constraints of gfp_mask.
 382  */
 383 int mls_from_string(char *str, struct context *context, gfp_t gfp_mask)
 384 {
 385         char *tmpstr, *freestr;
 386         int rc;
 387
 388         if (!selinux_mls_enabled)
 389                 return -EINVAL;
 390
 391         /* we need freestr because mls_context_to_sid will change
 392            the value of tmpstr */
 393         tmpstr = freestr = kstrdup(str, gfp_mask);
 394         if (!tmpstr) {
 395                 rc = -ENOMEM;
 396         } else {
 397                 rc = mls_context_to_sid(':', &tmpstr, context,
 398                                         NULL, SECSID_NULL);
 399                 kfree(freestr);
 400         }
 401
 402         return rc;
 403 }
 404
 405 /*
 406  * Copies the MLS range `range' into `context'.
 407  */
 408 static inline int mls_range_set(struct context *context,
 409                                 struct mls_range *range)
 410 {
 411         int l, rc = 0;
 412
 413         /* Copy the MLS range into the  context */
 414         for (l = 0; l < 2; l++) {
 415                 context->range.level[l].sens = range->level[l].sens;
 416                 rc = ebitmap_cpy(&context->range.level[l].cat,
 417                                  &range->level[l].cat);
 418                 if (rc)
 419                         break;
 420         }
 421
 422         return rc;
 423 }
 424
 425 int mls_setup_user_range(struct context *fromcon, struct user_datum *user,
 426                          struct context *usercon)
 427 {
 428         if (selinux_mls_enabled) {
 429                 struct mls_level *fromcon_sen = &(fromcon->range.level[0]);
 430                 struct mls_level *fromcon_clr = &(fromcon->range.level[1]);
 431                 struct mls_level *user_low = &(user->range.level[0]);
 432                 struct mls_level *user_clr = &(user->range.level[1]);
 433                 struct mls_level *user_def = &(user->dfltlevel);
 434                 struct mls_level *usercon_sen = &(usercon->range.level[0]);
 435                 struct mls_level *usercon_clr = &(usercon->range.level[1]);
 436
 437                 /* Honor the user's default level if we can */
 438                 if (mls_level_between(user_def, fromcon_sen, fromcon_clr)) {
 439                         *usercon_sen = *user_def;
 440                 } else if (mls_level_between(fromcon_sen, user_def, user_clr)) {
 441                         *usercon_sen = *fromcon_sen;
 442                 } else if (mls_level_between(fromcon_clr, user_low, user_def)) {
 443                         *usercon_sen = *user_low;
 444                 } else
 445                         return -EINVAL;
 446
 447                 /* Lower the clearance of available contexts
 448                    if the clearance of "fromcon" is lower than
 449                    that of the user's default clearance (but
 450                    only if the "fromcon" clearance dominates
 451                    the user's computed sensitivity level) */
 452                 if (mls_level_dom(user_clr, fromcon_clr)) {
 453                         *usercon_clr = *fromcon_clr;
 454                 } else if (mls_level_dom(fromcon_clr, user_clr)) {
 455                         *usercon_clr = *user_clr;
 456                 } else
 457                         return -EINVAL;
 458         }
 459
 460         return 0;
 461 }
 462
 463 /*
 464  * Convert the MLS fields in the security context
 465  * structure `c' from the values specified in the
 466  * policy `oldp' to the values specified in the policy `newp'.
 467  */
 468 int mls_convert_context(struct policydb *oldp,
 469                         struct policydb *newp,
 470                         struct context *c)
 471 {
 472         struct level_datum *levdatum;
 473         struct cat_datum *catdatum;
 474         struct ebitmap bitmap;
 475         struct ebitmap_node *node;
 476         int l, i;
 477
 478         if (!selinux_mls_enabled)
 479                 return 0;
 480
 481         for (l = 0; l < 2; l++) {
 482                 levdatum = hashtab_search(newp->p_levels.table,
 483                         oldp->p_sens_val_to_name[c->range.level[l].sens - 1]);
 484
 485                 if (!levdatum)
 486                         return -EINVAL;
 487                 c->range.level[l].sens = levdatum->level->sens;
 488
 489                 ebitmap_init(&bitmap);
 490                 ebitmap_for_each_positive_bit(&c->range.level[l].cat, node, i) {
 491                         int rc;
 492
 493                         catdatum = hashtab_search(newp->p_cats.table,
 494                                                   oldp->p_cat_val_to_name[i]);
 495                         if (!catdatum)
 496                                 return -EINVAL;
 497                         rc = ebitmap_set_bit(&bitmap, catdatum->value - 1, 1);
 498                         if (rc)
 499                                 return rc;
 500                 }
 501                 ebitmap_destroy(&c->range.level[l].cat);
 502                 c->range.level[l].cat = bitmap;
 503         }
 504
 505         return 0;
 506 }
 507
 508 int mls_compute_sid(struct context *scontext,
 509                     struct context *tcontext,
 510                     u16 tclass,
 511                     u32 specified,
 512                     struct context *newcontext)
 513 {
 514         struct range_trans *rtr;
 515
 516         if (!selinux_mls_enabled)
 517                 return 0;
 518
 519         switch (specified) {
 520         case AVTAB_TRANSITION:
 521                 /* Look for a range transition rule. */
 522                 for (rtr = policydb.range_tr; rtr; rtr = rtr->next) {
 523                         if (rtr->source_type == scontext->type &&
 524                             rtr->target_type == tcontext->type &&
 525                             rtr->target_class == tclass) {
 526                                 /* Set the range from the rule */
 527                                 return mls_range_set(newcontext,
 528                                                      &rtr->target_range);
 529                         }
 530                 }
 531                 /* Fallthrough */
 532         case AVTAB_CHANGE:
 533                 if (tclass == SECCLASS_PROCESS)
 534                         /* Use the process MLS attributes. */
 535                         return mls_context_cpy(newcontext, scontext);
 536                 else
 537                         /* Use the process effective MLS attributes. */
 538                         return mls_context_cpy_low(newcontext, scontext);
 539         case AVTAB_MEMBER:
 540                 /* Use the process effective MLS attributes. */
 541                 return mls_context_cpy_low(newcontext, scontext);
 542         default:
 543                 return -EINVAL;
 544         }
 545         return -EINVAL;
 546 }
 547
 548 #ifdef CONFIG_NETLABEL
 549 /**
 550  * mls_export_netlbl_lvl - Export the MLS sensitivity levels to NetLabel
 551  * @context: the security context
 552  * @secattr: the NetLabel security attributes
 553  *
 554  * Description:
 555  * Given the security context copy the low MLS sensitivity level into the
 556  * NetLabel MLS sensitivity level field.
 557  *
 558  */
 559 void mls_export_netlbl_lvl(struct context *context,
 560                            struct netlbl_lsm_secattr *secattr)
 561 {
 562         if (!selinux_mls_enabled)
 563                 return;
 564
 565         secattr->attr.mls.lvl = context->range.level[0].sens - 1;
 566         secattr->flags |= NETLBL_SECATTR_MLS_LVL;
 567 }
 568
 569 /**
 570  * mls_import_netlbl_lvl - Import the NetLabel MLS sensitivity levels
 571  * @context: the security context
 572  * @secattr: the NetLabel security attributes
 573  *
 574  * Description:
 575  * Given the security context and the NetLabel security attributes, copy the
 576  * NetLabel MLS sensitivity level into the context.
 577  *
 578  */
 579 void mls_import_netlbl_lvl(struct context *context,
 580                            struct netlbl_lsm_secattr *secattr)
 581 {
 582         if (!selinux_mls_enabled)
 583                 return;
 584
 585         context->range.level[0].sens = secattr->attr.mls.lvl + 1;
 586         context->range.level[1].sens = context->range.level[0].sens;
 587 }
 588
 589 /**
 590  * mls_export_netlbl_cat - Export the MLS categories to NetLabel
 591  * @context: the security context
 592  * @secattr: the NetLabel security attributes
 593  *
 594  * Description:
 595  * Given the security context copy the low MLS categories into the NetLabel
 596  * MLS category field.  Returns zero on success, negative values on failure.
 597  *
 598  */
 599 int mls_export_netlbl_cat(struct context *context,
 600                           struct netlbl_lsm_secattr *secattr)
 601 {
 602         int rc;
 603
 604         if (!selinux_mls_enabled)
 605                 return 0;
 606
 607         rc = ebitmap_netlbl_export(&context->range.level[0].cat,
 608                                    &secattr->attr.mls.cat);
 609         if (rc == 0 && secattr->attr.mls.cat != NULL)
 610                 secattr->flags |= NETLBL_SECATTR_MLS_CAT;
 611
 612         return rc;
 613 }
 614
 615 /**
 616  * mls_import_netlbl_cat - Import the MLS categories from NetLabel
 617  * @context: the security context
 618  * @secattr: the NetLabel security attributes
 619  *
 620  * Description:
 621  * Copy the NetLabel security attributes into the SELinux context; since the
 622  * NetLabel security attribute only contains a single MLS category use it for
 623  * both the low and high categories of the context.  Returns zero on success,
 624  * negative values on failure.
 625  *
 626  */
 627 int mls_import_netlbl_cat(struct context *context,
 628                           struct netlbl_lsm_secattr *secattr)
 629 {
 630         int rc;
 631
 632         if (!selinux_mls_enabled)
 633                 return 0;
 634
 635         rc = ebitmap_netlbl_import(&context->range.level[0].cat,
 636                                    secattr->attr.mls.cat);
 637         if (rc != 0)
 638                 goto import_netlbl_cat_failure;
 639
 640         rc = ebitmap_cpy(&context->range.level[1].cat,
 641                          &context->range.level[0].cat);
 642         if (rc != 0)
 643                 goto import_netlbl_cat_failure;
 644
 645         return 0;
 646
 647 import_netlbl_cat_failure:
 648         ebitmap_destroy(&context->range.level[0].cat);
 649         ebitmap_destroy(&context->range.level[1].cat);
 650         return rc;
 651 }
 652 #endif /* CONFIG_NETLABEL */