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@paul-moore.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 (!policydb.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(sym_name(&policydb, SYM_LEVELS, 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 = sym_name(&policydb, SYM_CATS, prev);
  59                                         len += strlen(nm) + 1;
  60                                 }
  61                                 nm = sym_name(&policydb, SYM_CATS, i);
  62                                 len += strlen(nm) + 1;
  63                                 head = i;
  64                         }
  65                         prev = i;
  66                 }
  67                 if (prev != head) {
  68                         nm = sym_name(&policydb, SYM_CATS, 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 (!policydb.mls_enabled)
  97                 return;
  98
  99         scontextp = *scontext;
 100
 101         *scontextp = ':';
 102         scontextp++;
 103
 104         for (l = 0; l < 2; l++) {
 105                 strcpy(scontextp, sym_name(&policydb, SYM_LEVELS,
 106                                            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 = sym_name(&policydb, SYM_CATS, prev);
 122                                         strcpy(scontextp, nm);
 123                                         scontextp += strlen(nm);
 124                                 }
 125                                 if (prev < 0)
 126                                         *scontextp++ = ':';
 127                                 else
 128                                         *scontextp++ = ',';
 129                                 nm = sym_name(&policydb, SYM_CATS, 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 = sym_name(&policydb, SYM_CATS, 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                                   sym_name(p, SYM_LEVELS, 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 (!p->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(struct policydb *pol,
 243                        char oldc,
 244                        char **scontext,
 245                        struct context *context,
 246                        struct sidtab *s,
 247                        u32 def_sid)
 248 {
 249
 250         char delim;
 251         char *scontextp, *p, *rngptr;
 252         struct level_datum *levdatum;
 253         struct cat_datum *catdatum, *rngdatum;
 254         int l, rc = -EINVAL;
 255
 256         if (!pol->mls_enabled) {
 257                 if (def_sid != SECSID_NULL && oldc)
 258                         *scontext += strlen(*scontext) + 1;
 259                 return 0;
 260         }
 261
 262         /*
 263          * No MLS component to the security context, try and map to
 264          * default if provided.
 265          */
 266         if (!oldc) {
 267                 struct context *defcon;
 268
 269                 if (def_sid == SECSID_NULL)
 270                         goto out;
 271
 272                 defcon = sidtab_search(s, def_sid);
 273                 if (!defcon)
 274                         goto out;
 275
 276                 rc = mls_context_cpy(context, defcon);
 277                 goto out;
 278         }
 279
 280         /* Extract low sensitivity. */
 281         scontextp = p = *scontext;
 282         while (*p && *p != ':' && *p != '-')
 283                 p++;
 284
 285         delim = *p;
 286         if (delim != '\0')
 287                 *p++ = '\0';
 288
 289         for (l = 0; l < 2; l++) {
 290                 levdatum = hashtab_search(pol->p_levels.table, scontextp);
 291                 if (!levdatum) {
 292                         rc = -EINVAL;
 293                         goto out;
 294                 }
 295
 296                 context->range.level[l].sens = levdatum->level->sens;
 297
 298                 if (delim == ':') {
 299                         /* Extract category set. */
 300                         while (1) {
 301                                 scontextp = p;
 302                                 while (*p && *p != ',' && *p != '-')
 303                                         p++;
 304                                 delim = *p;
 305                                 if (delim != '\0')
 306                                         *p++ = '\0';
 307
 308                                 /* Separate into range if exists */
 309                                 rngptr = strchr(scontextp, '.');
 310                                 if (rngptr != NULL) {
 311                                         /* Remove '.' */
 312                                         *rngptr++ = '\0';
 313                                 }
 314
 315                                 catdatum = hashtab_search(pol->p_cats.table,
 316                                                           scontextp);
 317                                 if (!catdatum) {
 318                                         rc = -EINVAL;
 319                                         goto out;
 320                                 }
 321
 322                                 rc = ebitmap_set_bit(&context->range.level[l].cat,
 323                                                      catdatum->value - 1, 1);
 324                                 if (rc)
 325                                         goto out;
 326
 327                                 /* If range, set all categories in range */
 328                                 if (rngptr) {
 329                                         int i;
 330
 331                                         rngdatum = hashtab_search(pol->p_cats.table, rngptr);
 332                                         if (!rngdatum) {
 333                                                 rc = -EINVAL;
 334                                                 goto out;
 335                                         }
 336
 337                                         if (catdatum->value >= rngdatum->value) {
 338                                                 rc = -EINVAL;
 339                                                 goto out;
 340                                         }
 341
 342                                         for (i = catdatum->value; i < rngdatum->value; i++) {
 343                                                 rc = ebitmap_set_bit(&context->range.level[l].cat, i, 1);
 344                                                 if (rc)
 345                                                         goto out;
 346                                         }
 347                                 }
 348
 349                                 if (delim != ',')
 350                                         break;
 351                         }
 352                 }
 353                 if (delim == '-') {
 354                         /* Extract high sensitivity. */
 355                         scontextp = p;
 356                         while (*p && *p != ':')
 357                                 p++;
 358
 359                         delim = *p;
 360                         if (delim != '\0')
 361                                 *p++ = '\0';
 362                 } else
 363                         break;
 364         }
 365
 366         if (l == 0) {
 367                 context->range.level[1].sens = context->range.level[0].sens;
 368                 rc = ebitmap_cpy(&context->range.level[1].cat,
 369                                  &context->range.level[0].cat);
 370                 if (rc)
 371                         goto out;
 372         }
 373         *scontext = ++p;
 374         rc = 0;
 375 out:
 376         return rc;
 377 }
 378
 379 /*
 380  * Set the MLS fields in the security context structure
 381  * `context' based on the string representation in
 382  * the string `str'.  This function will allocate temporary memory with the
 383  * given constraints of gfp_mask.
 384  */
 385 int mls_from_string(char *str, struct context *context, gfp_t gfp_mask)
 386 {
 387         char *tmpstr, *freestr;
 388         int rc;
 389
 390         if (!policydb.mls_enabled)
 391                 return -EINVAL;
 392
 393         /* we need freestr because mls_context_to_sid will change
 394            the value of tmpstr */
 395         tmpstr = freestr = kstrdup(str, gfp_mask);
 396         if (!tmpstr) {
 397                 rc = -ENOMEM;
 398         } else {
 399                 rc = mls_context_to_sid(&policydb, ':', &tmpstr, context,
 400                                         NULL, SECSID_NULL);
 401                 kfree(freestr);
 402         }
 403
 404         return rc;
 405 }
 406
 407 /*
 408  * Copies the MLS range `range' into `context'.
 409  */
 410 int mls_range_set(struct context *context,
 411                                 struct mls_range *range)
 412 {
 413         int l, rc = 0;
 414
 415         /* Copy the MLS range into the  context */
 416         for (l = 0; l < 2; l++) {
 417                 context->range.level[l].sens = range->level[l].sens;
 418                 rc = ebitmap_cpy(&context->range.level[l].cat,
 419                                  &range->level[l].cat);
 420                 if (rc)
 421                         break;
 422         }
 423
 424         return rc;
 425 }
 426
 427 int mls_setup_user_range(struct context *fromcon, struct user_datum *user,
 428                          struct context *usercon)
 429 {
 430         if (policydb.mls_enabled) {
 431                 struct mls_level *fromcon_sen = &(fromcon->range.level[0]);
 432                 struct mls_level *fromcon_clr = &(fromcon->range.level[1]);
 433                 struct mls_level *user_low = &(user->range.level[0]);
 434                 struct mls_level *user_clr = &(user->range.level[1]);
 435                 struct mls_level *user_def = &(user->dfltlevel);
 436                 struct mls_level *usercon_sen = &(usercon->range.level[0]);
 437                 struct mls_level *usercon_clr = &(usercon->range.level[1]);
 438
 439                 /* Honor the user's default level if we can */
 440                 if (mls_level_between(user_def, fromcon_sen, fromcon_clr))
 441                         *usercon_sen = *user_def;
 442                 else if (mls_level_between(fromcon_sen, user_def, user_clr))
 443                         *usercon_sen = *fromcon_sen;
 444                 else if (mls_level_between(fromcon_clr, user_low, user_def))
 445                         *usercon_sen = *user_low;
 446                 else
 447                         return -EINVAL;
 448
 449                 /* Lower the clearance of available contexts
 450                    if the clearance of "fromcon" is lower than
 451                    that of the user's default clearance (but
 452                    only if the "fromcon" clearance dominates
 453                    the user's computed sensitivity level) */
 454                 if (mls_level_dom(user_clr, fromcon_clr))
 455                         *usercon_clr = *fromcon_clr;
 456                 else if (mls_level_dom(fromcon_clr, user_clr))
 457                         *usercon_clr = *user_clr;
 458                 else
 459                         return -EINVAL;
 460         }
 461
 462         return 0;
 463 }
 464
 465 /*
 466  * Convert the MLS fields in the security context
 467  * structure `c' from the values specified in the
 468  * policy `oldp' to the values specified in the policy `newp'.
 469  */
 470 int mls_convert_context(struct policydb *oldp,
 471                         struct policydb *newp,
 472                         struct context *c)
 473 {
 474         struct level_datum *levdatum;
 475         struct cat_datum *catdatum;
 476         struct ebitmap bitmap;
 477         struct ebitmap_node *node;
 478         int l, i;
 479
 480         if (!policydb.mls_enabled)
 481                 return 0;
 482
 483         for (l = 0; l < 2; l++) {
 484                 levdatum = hashtab_search(newp->p_levels.table,
 485                                           sym_name(oldp, SYM_LEVELS,
 486                                                    c->range.level[l].sens - 1));
 487
 488                 if (!levdatum)
 489                         return -EINVAL;
 490                 c->range.level[l].sens = levdatum->level->sens;
 491
 492                 ebitmap_init(&bitmap);
 493                 ebitmap_for_each_positive_bit(&c->range.level[l].cat, node, i) {
 494                         int rc;
 495
 496                         catdatum = hashtab_search(newp->p_cats.table,
 497                                                   sym_name(oldp, SYM_CATS, i));
 498                         if (!catdatum)
 499                                 return -EINVAL;
 500                         rc = ebitmap_set_bit(&bitmap, catdatum->value - 1, 1);
 501                         if (rc)
 502                                 return rc;
 503                 }
 504                 ebitmap_destroy(&c->range.level[l].cat);
 505                 c->range.level[l].cat = bitmap;
 506         }
 507
 508         return 0;
 509 }
 510
 511 int mls_compute_sid(struct context *scontext,
 512                     struct context *tcontext,
 513                     u16 tclass,
 514                     u32 specified,
 515                     struct context *newcontext,
 516                     bool sock)
 517 {
 518         struct range_trans rtr;
 519         struct mls_range *r;
 520         struct class_datum *cladatum;
 521         int default_range = 0;
 522
 523         if (!policydb.mls_enabled)
 524                 return 0;
 525
 526         switch (specified) {
 527         case AVTAB_TRANSITION:
 528                 /* Look for a range transition rule. */
 529                 rtr.source_type = scontext->type;
 530                 rtr.target_type = tcontext->type;
 531                 rtr.target_class = tclass;
 532                 r = hashtab_search(policydb.range_tr, &rtr);
 533                 if (r)
 534                         return mls_range_set(newcontext, r);
 535
 536                 if (tclass && tclass <= policydb.p_classes.nprim) {
 537                         cladatum = policydb.class_val_to_struct[tclass - 1];
 538                         if (cladatum)
 539                                 default_range = cladatum->default_range;
 540                 }
 541
 542                 switch (default_range) {
 543                 case DEFAULT_SOURCE_LOW:
 544                         return mls_context_cpy_low(newcontext, scontext);
 545                 case DEFAULT_SOURCE_HIGH:
 546                         return mls_context_cpy_high(newcontext, scontext);
 547                 case DEFAULT_SOURCE_LOW_HIGH:
 548                         return mls_context_cpy(newcontext, scontext);
 549                 case DEFAULT_TARGET_LOW:
 550                         return mls_context_cpy_low(newcontext, tcontext);
 551                 case DEFAULT_TARGET_HIGH:
 552                         return mls_context_cpy_high(newcontext, tcontext);
 553                 case DEFAULT_TARGET_LOW_HIGH:
 554                         return mls_context_cpy(newcontext, tcontext);
 555                 }
 556
 557                 /* Fallthrough */
 558         case AVTAB_CHANGE:
 559                 if ((tclass == policydb.process_class) || (sock == true))
 560                         /* Use the process MLS attributes. */
 561                         return mls_context_cpy(newcontext, scontext);
 562                 else
 563                         /* Use the process effective MLS attributes. */
 564                         return mls_context_cpy_low(newcontext, scontext);
 565         case AVTAB_MEMBER:
 566                 /* Use the process effective MLS attributes. */
 567                 return mls_context_cpy_low(newcontext, scontext);
 568
 569         /* fall through */
 570         }
 571         return -EINVAL;
 572 }
 573
 574 #ifdef CONFIG_NETLABEL
 575 /**
 576  * mls_export_netlbl_lvl - Export the MLS sensitivity levels to NetLabel
 577  * @context: the security context
 578  * @secattr: the NetLabel security attributes
 579  *
 580  * Description:
 581  * Given the security context copy the low MLS sensitivity level into the
 582  * NetLabel MLS sensitivity level field.
 583  *
 584  */
 585 void mls_export_netlbl_lvl(struct context *context,
 586                            struct netlbl_lsm_secattr *secattr)
 587 {
 588         if (!policydb.mls_enabled)
 589                 return;
 590
 591         secattr->attr.mls.lvl = context->range.level[0].sens - 1;
 592         secattr->flags |= NETLBL_SECATTR_MLS_LVL;
 593 }
 594
 595 /**
 596  * mls_import_netlbl_lvl - Import the NetLabel MLS sensitivity levels
 597  * @context: the security context
 598  * @secattr: the NetLabel security attributes
 599  *
 600  * Description:
 601  * Given the security context and the NetLabel security attributes, copy the
 602  * NetLabel MLS sensitivity level into the context.
 603  *
 604  */
 605 void mls_import_netlbl_lvl(struct context *context,
 606                            struct netlbl_lsm_secattr *secattr)
 607 {
 608         if (!policydb.mls_enabled)
 609                 return;
 610
 611         context->range.level[0].sens = secattr->attr.mls.lvl + 1;
 612         context->range.level[1].sens = context->range.level[0].sens;
 613 }
 614
 615 /**
 616  * mls_export_netlbl_cat - Export the MLS categories to NetLabel
 617  * @context: the security context
 618  * @secattr: the NetLabel security attributes
 619  *
 620  * Description:
 621  * Given the security context copy the low MLS categories into the NetLabel
 622  * MLS category field.  Returns zero on success, negative values on failure.
 623  *
 624  */
 625 int mls_export_netlbl_cat(struct context *context,
 626                           struct netlbl_lsm_secattr *secattr)
 627 {
 628         int rc;
 629
 630         if (!policydb.mls_enabled)
 631                 return 0;
 632
 633         rc = ebitmap_netlbl_export(&context->range.level[0].cat,
 634                                    &secattr->attr.mls.cat);
 635         if (rc == 0 && secattr->attr.mls.cat != NULL)
 636                 secattr->flags |= NETLBL_SECATTR_MLS_CAT;
 637
 638         return rc;
 639 }
 640
 641 /**
 642  * mls_import_netlbl_cat - Import the MLS categories from NetLabel
 643  * @context: the security context
 644  * @secattr: the NetLabel security attributes
 645  *
 646  * Description:
 647  * Copy the NetLabel security attributes into the SELinux context; since the
 648  * NetLabel security attribute only contains a single MLS category use it for
 649  * both the low and high categories of the context.  Returns zero on success,
 650  * negative values on failure.
 651  *
 652  */
 653 int mls_import_netlbl_cat(struct context *context,
 654                           struct netlbl_lsm_secattr *secattr)
 655 {
 656         int rc;
 657
 658         if (!policydb.mls_enabled)
 659                 return 0;
 660
 661         rc = ebitmap_netlbl_import(&context->range.level[0].cat,
 662                                    secattr->attr.mls.cat);
 663         if (rc != 0)
 664                 goto import_netlbl_cat_failure;
 665
 666         rc = ebitmap_cpy(&context->range.level[1].cat,
 667                          &context->range.level[0].cat);
 668         if (rc != 0)
 669                 goto import_netlbl_cat_failure;
 670
 671         return 0;
 672
 673 import_netlbl_cat_failure:
 674         ebitmap_destroy(&context->range.level[0].cat);
 675         ebitmap_destroy(&context->range.level[1].cat);
 676         return rc;
 677 }
 678 #endif /* CONFIG_NETLABEL */