kernel/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
 164         if (!l->sens || l->sens > p->p_levels.nprim)
 165                 return 0;
 166         levdatum = hashtab_search(p->p_levels.table,
 167                                   sym_name(p, SYM_LEVELS, l->sens - 1));
 168         if (!levdatum)
 169                 return 0;
 170
 171         /*
 172          * Return 1 iff all the bits set in l->cat are also be set in
 173          * levdatum->level->cat and no bit in l->cat is larger than
 174          * p->p_cats.nprim.
 175          */
 176         return ebitmap_contains(&levdatum->level->cat, &l->cat,
 177                                 p->p_cats.nprim);
 178 }
 179
 180 int mls_range_isvalid(struct policydb *p, struct mls_range *r)
 181 {
 182         return (mls_level_isvalid(p, &r->level[0]) &&
 183                 mls_level_isvalid(p, &r->level[1]) &&
 184                 mls_level_dom(&r->level[1], &r->level[0]));
 185 }
 186
 187 /*
 188  * Return 1 if the MLS fields in the security context
 189  * structure `c' are valid.  Return 0 otherwise.
 190  */
 191 int mls_context_isvalid(struct policydb *p, struct context *c)
 192 {
 193         struct user_datum *usrdatum;
 194
 195         if (!p->mls_enabled)
 196                 return 1;
 197
 198         if (!mls_range_isvalid(p, &c->range))
 199                 return 0;
 200
 201         if (c->role == OBJECT_R_VAL)
 202                 return 1;
 203
 204         /*
 205          * User must be authorized for the MLS range.
 206          */
 207         if (!c->user || c->user > p->p_users.nprim)
 208                 return 0;
 209         usrdatum = p->user_val_to_struct[c->user - 1];
 210         if (!mls_range_contains(usrdatum->range, c->range))
 211                 return 0; /* user may not be associated with range */
 212
 213         return 1;
 214 }
 215
 216 /*
 217  * Set the MLS fields in the security context structure
 218  * `context' based on the string representation in
 219  * the string `*scontext'.  Update `*scontext' to
 220  * point to the end of the string representation of
 221  * the MLS fields.
 222  *
 223  * This function modifies the string in place, inserting
 224  * NULL characters to terminate the MLS fields.
 225  *
 226  * If a def_sid is provided and no MLS field is present,
 227  * copy the MLS field of the associated default context.
 228  * Used for upgraded to MLS systems where objects may lack
 229  * MLS fields.
 230  *
 231  * Policy read-lock must be held for sidtab lookup.
 232  *
 233  */
 234 int mls_context_to_sid(struct policydb *pol,
 235                        char oldc,
 236                        char **scontext,
 237                        struct context *context,
 238                        struct sidtab *s,
 239                        u32 def_sid)
 240 {
 241
 242         char delim;
 243         char *scontextp, *p, *rngptr;
 244         struct level_datum *levdatum;
 245         struct cat_datum *catdatum, *rngdatum;
 246         int l, rc = -EINVAL;
 247
 248         if (!pol->mls_enabled) {
 249                 if (def_sid != SECSID_NULL && oldc)
 250                         *scontext += strlen(*scontext) + 1;
 251                 return 0;
 252         }
 253
 254         /*
 255          * No MLS component to the security context, try and map to
 256          * default if provided.
 257          */
 258         if (!oldc) {
 259                 struct context *defcon;
 260
 261                 if (def_sid == SECSID_NULL)
 262                         goto out;
 263
 264                 defcon = sidtab_search(s, def_sid);
 265                 if (!defcon)
 266                         goto out;
 267
 268                 rc = mls_context_cpy(context, defcon);
 269                 goto out;
 270         }
 271
 272         /* Extract low sensitivity. */
 273         scontextp = p = *scontext;
 274         while (*p && *p != ':' && *p != '-')
 275                 p++;
 276
 277         delim = *p;
 278         if (delim != '\0')
 279                 *p++ = '\0';
 280
 281         for (l = 0; l < 2; l++) {
 282                 levdatum = hashtab_search(pol->p_levels.table, scontextp);
 283                 if (!levdatum) {
 284                         rc = -EINVAL;
 285                         goto out;
 286                 }
 287
 288                 context->range.level[l].sens = levdatum->level->sens;
 289
 290                 if (delim == ':') {
 291                         /* Extract category set. */
 292                         while (1) {
 293                                 scontextp = p;
 294                                 while (*p && *p != ',' && *p != '-')
 295                                         p++;
 296                                 delim = *p;
 297                                 if (delim != '\0')
 298                                         *p++ = '\0';
 299
 300                                 /* Separate into range if exists */
 301                                 rngptr = strchr(scontextp, '.');
 302                                 if (rngptr != NULL) {
 303                                         /* Remove '.' */
 304                                         *rngptr++ = '\0';
 305                                 }
 306
 307                                 catdatum = hashtab_search(pol->p_cats.table,
 308                                                           scontextp);
 309                                 if (!catdatum) {
 310                                         rc = -EINVAL;
 311                                         goto out;
 312                                 }
 313
 314                                 rc = ebitmap_set_bit(&context->range.level[l].cat,
 315                                                      catdatum->value - 1, 1);
 316                                 if (rc)
 317                                         goto out;
 318
 319                                 /* If range, set all categories in range */
 320                                 if (rngptr) {
 321                                         int i;
 322
 323                                         rngdatum = hashtab_search(pol->p_cats.table, rngptr);
 324                                         if (!rngdatum) {
 325                                                 rc = -EINVAL;
 326                                                 goto out;
 327                                         }
 328
 329                                         if (catdatum->value >= rngdatum->value) {
 330                                                 rc = -EINVAL;
 331                                                 goto out;
 332                                         }
 333
 334                                         for (i = catdatum->value; i < rngdatum->value; i++) {
 335                                                 rc = ebitmap_set_bit(&context->range.level[l].cat, i, 1);
 336                                                 if (rc)
 337                                                         goto out;
 338                                         }
 339                                 }
 340
 341                                 if (delim != ',')
 342                                         break;
 343                         }
 344                 }
 345                 if (delim == '-') {
 346                         /* Extract high sensitivity. */
 347                         scontextp = p;
 348                         while (*p && *p != ':')
 349                                 p++;
 350
 351                         delim = *p;
 352                         if (delim != '\0')
 353                                 *p++ = '\0';
 354                 } else
 355                         break;
 356         }
 357
 358         if (l == 0) {
 359                 context->range.level[1].sens = context->range.level[0].sens;
 360                 rc = ebitmap_cpy(&context->range.level[1].cat,
 361                                  &context->range.level[0].cat);
 362                 if (rc)
 363                         goto out;
 364         }
 365         *scontext = ++p;
 366         rc = 0;
 367 out:
 368         return rc;
 369 }
 370
 371 /*
 372  * Set the MLS fields in the security context structure
 373  * `context' based on the string representation in
 374  * the string `str'.  This function will allocate temporary memory with the
 375  * given constraints of gfp_mask.
 376  */
 377 int mls_from_string(char *str, struct context *context, gfp_t gfp_mask)
 378 {
 379         char *tmpstr, *freestr;
 380         int rc;
 381
 382         if (!policydb.mls_enabled)
 383                 return -EINVAL;
 384
 385         /* we need freestr because mls_context_to_sid will change
 386            the value of tmpstr */
 387         tmpstr = freestr = kstrdup(str, gfp_mask);
 388         if (!tmpstr) {
 389                 rc = -ENOMEM;
 390         } else {
 391                 rc = mls_context_to_sid(&policydb, ':', &tmpstr, context,
 392                                         NULL, SECSID_NULL);
 393                 kfree(freestr);
 394         }
 395
 396         return rc;
 397 }
 398
 399 /*
 400  * Copies the MLS range `range' into `context'.
 401  */
 402 int mls_range_set(struct context *context,
 403                                 struct mls_range *range)
 404 {
 405         int l, rc = 0;
 406
 407         /* Copy the MLS range into the  context */
 408         for (l = 0; l < 2; l++) {
 409                 context->range.level[l].sens = range->level[l].sens;
 410                 rc = ebitmap_cpy(&context->range.level[l].cat,
 411                                  &range->level[l].cat);
 412                 if (rc)
 413                         break;
 414         }
 415
 416         return rc;
 417 }
 418
 419 int mls_setup_user_range(struct context *fromcon, struct user_datum *user,
 420                          struct context *usercon)
 421 {
 422         if (policydb.mls_enabled) {
 423                 struct mls_level *fromcon_sen = &(fromcon->range.level[0]);
 424                 struct mls_level *fromcon_clr = &(fromcon->range.level[1]);
 425                 struct mls_level *user_low = &(user->range.level[0]);
 426                 struct mls_level *user_clr = &(user->range.level[1]);
 427                 struct mls_level *user_def = &(user->dfltlevel);
 428                 struct mls_level *usercon_sen = &(usercon->range.level[0]);
 429                 struct mls_level *usercon_clr = &(usercon->range.level[1]);
 430
 431                 /* Honor the user's default level if we can */
 432                 if (mls_level_between(user_def, fromcon_sen, fromcon_clr))
 433                         *usercon_sen = *user_def;
 434                 else if (mls_level_between(fromcon_sen, user_def, user_clr))
 435                         *usercon_sen = *fromcon_sen;
 436                 else if (mls_level_between(fromcon_clr, user_low, user_def))
 437                         *usercon_sen = *user_low;
 438                 else
 439                         return -EINVAL;
 440
 441                 /* Lower the clearance of available contexts
 442                    if the clearance of "fromcon" is lower than
 443                    that of the user's default clearance (but
 444                    only if the "fromcon" clearance dominates
 445                    the user's computed sensitivity level) */
 446                 if (mls_level_dom(user_clr, fromcon_clr))
 447                         *usercon_clr = *fromcon_clr;
 448                 else if (mls_level_dom(fromcon_clr, user_clr))
 449                         *usercon_clr = *user_clr;
 450                 else
 451                         return -EINVAL;
 452         }
 453
 454         return 0;
 455 }
 456
 457 /*
 458  * Convert the MLS fields in the security context
 459  * structure `c' from the values specified in the
 460  * policy `oldp' to the values specified in the policy `newp'.
 461  */
 462 int mls_convert_context(struct policydb *oldp,
 463                         struct policydb *newp,
 464                         struct context *c)
 465 {
 466         struct level_datum *levdatum;
 467         struct cat_datum *catdatum;
 468         struct ebitmap bitmap;
 469         struct ebitmap_node *node;
 470         int l, i;
 471
 472         if (!policydb.mls_enabled)
 473                 return 0;
 474
 475         for (l = 0; l < 2; l++) {
 476                 levdatum = hashtab_search(newp->p_levels.table,
 477                                           sym_name(oldp, SYM_LEVELS,
 478                                                    c->range.level[l].sens - 1));
 479
 480                 if (!levdatum)
 481                         return -EINVAL;
 482                 c->range.level[l].sens = levdatum->level->sens;
 483
 484                 ebitmap_init(&bitmap);
 485                 ebitmap_for_each_positive_bit(&c->range.level[l].cat, node, i) {
 486                         int rc;
 487
 488                         catdatum = hashtab_search(newp->p_cats.table,
 489                                                   sym_name(oldp, SYM_CATS, i));
 490                         if (!catdatum)
 491                                 return -EINVAL;
 492                         rc = ebitmap_set_bit(&bitmap, catdatum->value - 1, 1);
 493                         if (rc)
 494                                 return rc;
 495
 496                         cond_resched();
 497                 }
 498                 ebitmap_destroy(&c->range.level[l].cat);
 499                 c->range.level[l].cat = bitmap;
 500         }
 501
 502         return 0;
 503 }
 504
 505 int mls_compute_sid(struct context *scontext,
 506                     struct context *tcontext,
 507                     u16 tclass,
 508                     u32 specified,
 509                     struct context *newcontext,
 510                     bool sock)
 511 {
 512         struct range_trans rtr;
 513         struct mls_range *r;
 514         struct class_datum *cladatum;
 515         int default_range = 0;
 516
 517         if (!policydb.mls_enabled)
 518                 return 0;
 519
 520         switch (specified) {
 521         case AVTAB_TRANSITION:
 522                 /* Look for a range transition rule. */
 523                 rtr.source_type = scontext->type;
 524                 rtr.target_type = tcontext->type;
 525                 rtr.target_class = tclass;
 526                 r = hashtab_search(policydb.range_tr, &rtr);
 527                 if (r)
 528                         return mls_range_set(newcontext, r);
 529
 530                 if (tclass && tclass <= policydb.p_classes.nprim) {
 531                         cladatum = policydb.class_val_to_struct[tclass - 1];
 532                         if (cladatum)
 533                                 default_range = cladatum->default_range;
 534                 }
 535
 536                 switch (default_range) {
 537                 case DEFAULT_SOURCE_LOW:
 538                         return mls_context_cpy_low(newcontext, scontext);
 539                 case DEFAULT_SOURCE_HIGH:
 540                         return mls_context_cpy_high(newcontext, scontext);
 541                 case DEFAULT_SOURCE_LOW_HIGH:
 542                         return mls_context_cpy(newcontext, scontext);
 543                 case DEFAULT_TARGET_LOW:
 544                         return mls_context_cpy_low(newcontext, tcontext);
 545                 case DEFAULT_TARGET_HIGH:
 546                         return mls_context_cpy_high(newcontext, tcontext);
 547                 case DEFAULT_TARGET_LOW_HIGH:
 548                         return mls_context_cpy(newcontext, tcontext);
 549                 }
 550
 551                 /* Fallthrough */
 552         case AVTAB_CHANGE:
 553                 if ((tclass == policydb.process_class) || (sock == true))
 554                         /* Use the process MLS attributes. */
 555                         return mls_context_cpy(newcontext, scontext);
 556                 else
 557                         /* Use the process effective MLS attributes. */
 558                         return mls_context_cpy_low(newcontext, scontext);
 559         case AVTAB_MEMBER:
 560                 /* Use the process effective MLS attributes. */
 561                 return mls_context_cpy_low(newcontext, scontext);
 562
 563         /* fall through */
 564         }
 565         return -EINVAL;
 566 }
 567
 568 #ifdef CONFIG_NETLABEL
 569 /**
 570  * mls_export_netlbl_lvl - Export the MLS sensitivity levels to NetLabel
 571  * @context: the security context
 572  * @secattr: the NetLabel security attributes
 573  *
 574  * Description:
 575  * Given the security context copy the low MLS sensitivity level into the
 576  * NetLabel MLS sensitivity level field.
 577  *
 578  */
 579 void mls_export_netlbl_lvl(struct context *context,
 580                            struct netlbl_lsm_secattr *secattr)
 581 {
 582         if (!policydb.mls_enabled)
 583                 return;
 584
 585         secattr->attr.mls.lvl = context->range.level[0].sens - 1;
 586         secattr->flags |= NETLBL_SECATTR_MLS_LVL;
 587 }
 588
 589 /**
 590  * mls_import_netlbl_lvl - Import the NetLabel MLS sensitivity levels
 591  * @context: the security context
 592  * @secattr: the NetLabel security attributes
 593  *
 594  * Description:
 595  * Given the security context and the NetLabel security attributes, copy the
 596  * NetLabel MLS sensitivity level into the context.
 597  *
 598  */
 599 void mls_import_netlbl_lvl(struct context *context,
 600                            struct netlbl_lsm_secattr *secattr)
 601 {
 602         if (!policydb.mls_enabled)
 603                 return;
 604
 605         context->range.level[0].sens = secattr->attr.mls.lvl + 1;
 606         context->range.level[1].sens = context->range.level[0].sens;
 607 }
 608
 609 /**
 610  * mls_export_netlbl_cat - Export the MLS categories to NetLabel
 611  * @context: the security context
 612  * @secattr: the NetLabel security attributes
 613  *
 614  * Description:
 615  * Given the security context copy the low MLS categories into the NetLabel
 616  * MLS category field.  Returns zero on success, negative values on failure.
 617  *
 618  */
 619 int mls_export_netlbl_cat(struct context *context,
 620                           struct netlbl_lsm_secattr *secattr)
 621 {
 622         int rc;
 623
 624         if (!policydb.mls_enabled)
 625                 return 0;
 626
 627         rc = ebitmap_netlbl_export(&context->range.level[0].cat,
 628                                    &secattr->attr.mls.cat);
 629         if (rc == 0 && secattr->attr.mls.cat != NULL)
 630                 secattr->flags |= NETLBL_SECATTR_MLS_CAT;
 631
 632         return rc;
 633 }
 634
 635 /**
 636  * mls_import_netlbl_cat - Import the MLS categories from NetLabel
 637  * @context: the security context
 638  * @secattr: the NetLabel security attributes
 639  *
 640  * Description:
 641  * Copy the NetLabel security attributes into the SELinux context; since the
 642  * NetLabel security attribute only contains a single MLS category use it for
 643  * both the low and high categories of the context.  Returns zero on success,
 644  * negative values on failure.
 645  *
 646  */
 647 int mls_import_netlbl_cat(struct context *context,
 648                           struct netlbl_lsm_secattr *secattr)
 649 {
 650         int rc;
 651
 652         if (!policydb.mls_enabled)
 653                 return 0;
 654
 655         rc = ebitmap_netlbl_import(&context->range.level[0].cat,
 656                                    secattr->attr.mls.cat);
 657         if (rc)
 658                 goto import_netlbl_cat_failure;
 659         memcpy(&context->range.level[1].cat, &context->range.level[0].cat,
 660                sizeof(context->range.level[0].cat));
 661
 662         return 0;
 663
 664 import_netlbl_cat_failure:
 665         ebitmap_destroy(&context->range.level[0].cat);
 666         return rc;
 667 }
 668 #endif /* CONFIG_NETLABEL */