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 /*
 161  * Return 1 if the MLS fields in the security context
 162  * structure `c' are valid.  Return 0 otherwise.
 163  */
 164 int mls_context_isvalid(struct policydb *p, struct context *c)
 165 {
 166         struct level_datum *levdatum;
 167         struct user_datum *usrdatum;
 168         struct ebitmap_node *node;
 169         int i, l;
 170
 171         if (!selinux_mls_enabled)
 172                 return 1;
 173
 174         /*
 175          * MLS range validity checks: high must dominate low, low level must
 176          * be valid (category set <-> sensitivity check), and high level must
 177          * be valid (category set <-> sensitivity check)
 178          */
 179         if (!mls_level_dom(&c->range.level[1], &c->range.level[0]))
 180                 /* High does not dominate low. */
 181                 return 0;
 182
 183         for (l = 0; l < 2; l++) {
 184                 if (!c->range.level[l].sens || c->range.level[l].sens > p->p_levels.nprim)
 185                         return 0;
 186                 levdatum = hashtab_search(p->p_levels.table,
 187                         p->p_sens_val_to_name[c->range.level[l].sens - 1]);
 188                 if (!levdatum)
 189                         return 0;
 190
 191                 ebitmap_for_each_positive_bit(&c->range.level[l].cat, node, i) {
 192                         if (i > p->p_cats.nprim)
 193                                 return 0;
 194                         if (!ebitmap_get_bit(&levdatum->level->cat, i))
 195                                 /*
 196                                  * Category may not be associated with
 197                                  * sensitivity in low level.
 198                                  */
 199                                 return 0;
 200                 }
 201         }
 202
 203         if (c->role == OBJECT_R_VAL)
 204                 return 1;
 205
 206         /*
 207          * User must be authorized for the MLS range.
 208          */
 209         if (!c->user || c->user > p->p_users.nprim)
 210                 return 0;
 211         usrdatum = p->user_val_to_struct[c->user - 1];
 212         if (!mls_range_contains(usrdatum->range, c->range))
 213                 return 0; /* user may not be associated with range */
 214
 215         return 1;
 216 }
 217
 218 /*
 219  * Set the MLS fields in the security context structure
 220  * `context' based on the string representation in
 221  * the string `*scontext'.  Update `*scontext' to
 222  * point to the end of the string representation of
 223  * the MLS fields.
 224  *
 225  * This function modifies the string in place, inserting
 226  * NULL characters to terminate the MLS fields.
 227  *
 228  * If a def_sid is provided and no MLS field is present,
 229  * copy the MLS field of the associated default context.
 230  * Used for upgraded to MLS systems where objects may lack
 231  * MLS fields.
 232  *
 233  * Policy read-lock must be held for sidtab lookup.
 234  *
 235  */
 236 int mls_context_to_sid(char oldc,
 237                        char **scontext,
 238                        struct context *context,
 239                        struct sidtab *s,
 240                        u32 def_sid)
 241 {
 242
 243         char delim;
 244         char *scontextp, *p, *rngptr;
 245         struct level_datum *levdatum;
 246         struct cat_datum *catdatum, *rngdatum;
 247         int l, rc = -EINVAL;
 248
 249         if (!selinux_mls_enabled) {
 250                 if (def_sid != SECSID_NULL && oldc)
 251                         *scontext += strlen(*scontext)+1;
 252                 return 0;
 253         }
 254
 255         /*
 256          * No MLS component to the security context, try and map to
 257          * default if provided.
 258          */
 259         if (!oldc) {
 260                 struct context *defcon;
 261
 262                 if (def_sid == SECSID_NULL)
 263                         goto out;
 264
 265                 defcon = sidtab_search(s, def_sid);
 266                 if (!defcon)
 267                         goto out;
 268
 269                 rc = mls_context_cpy(context, defcon);
 270                 goto out;
 271         }
 272
 273         /* Extract low sensitivity. */
 274         scontextp = p = *scontext;
 275         while (*p && *p != ':' && *p != '-')
 276                 p++;
 277
 278         delim = *p;
 279         if (delim != 0)
 280                 *p++ = 0;
 281
 282         for (l = 0; l < 2; l++) {
 283                 levdatum = hashtab_search(policydb.p_levels.table, scontextp);
 284                 if (!levdatum) {
 285                         rc = -EINVAL;
 286                         goto out;
 287                 }
 288
 289                 context->range.level[l].sens = levdatum->level->sens;
 290
 291                 if (delim == ':') {
 292                         /* Extract category set. */
 293                         while (1) {
 294                                 scontextp = p;
 295                                 while (*p && *p != ',' && *p != '-')
 296                                         p++;
 297                                 delim = *p;
 298                                 if (delim != 0)
 299                                         *p++ = 0;
 300
 301                                 /* Separate into range if exists */
 302                                 if ((rngptr = strchr(scontextp, '.')) != NULL) {
 303                                         /* Remove '.' */
 304                                         *rngptr++ = 0;
 305                                 }
 306
 307                                 catdatum = hashtab_search(policydb.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(policydb.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 (!selinux_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(':', &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 static inline 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 (selinux_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 (!selinux_mls_enabled)
 473                 return 0;
 474
 475         for (l = 0; l < 2; l++) {
 476                 levdatum = hashtab_search(newp->p_levels.table,
 477                         oldp->p_sens_val_to_name[c->range.level[l].sens - 1]);
 478
 479                 if (!levdatum)
 480                         return -EINVAL;
 481                 c->range.level[l].sens = levdatum->level->sens;
 482
 483                 ebitmap_init(&bitmap);
 484                 ebitmap_for_each_positive_bit(&c->range.level[l].cat, node, i) {
 485                         int rc;
 486
 487                         catdatum = hashtab_search(newp->p_cats.table,
 488                                                   oldp->p_cat_val_to_name[i]);
 489                         if (!catdatum)
 490                                 return -EINVAL;
 491                         rc = ebitmap_set_bit(&bitmap, catdatum->value - 1, 1);
 492                         if (rc)
 493                                 return rc;
 494                 }
 495                 ebitmap_destroy(&c->range.level[l].cat);
 496                 c->range.level[l].cat = bitmap;
 497         }
 498
 499         return 0;
 500 }
 501
 502 int mls_compute_sid(struct context *scontext,
 503                     struct context *tcontext,
 504                     u16 tclass,
 505                     u32 specified,
 506                     struct context *newcontext)
 507 {
 508         struct range_trans *rtr;
 509
 510         if (!selinux_mls_enabled)
 511                 return 0;
 512
 513         switch (specified) {
 514         case AVTAB_TRANSITION:
 515                 /* Look for a range transition rule. */
 516                 for (rtr = policydb.range_tr; rtr; rtr = rtr->next) {
 517                         if (rtr->source_type == scontext->type &&
 518                             rtr->target_type == tcontext->type &&
 519                             rtr->target_class == tclass) {
 520                                 /* Set the range from the rule */
 521                                 return mls_range_set(newcontext,
 522                                                      &rtr->target_range);
 523                         }
 524                 }
 525                 /* Fallthrough */
 526         case AVTAB_CHANGE:
 527                 if (tclass == SECCLASS_PROCESS)
 528                         /* Use the process MLS attributes. */
 529                         return mls_context_cpy(newcontext, scontext);
 530                 else
 531                         /* Use the process effective MLS attributes. */
 532                         return mls_context_cpy_low(newcontext, scontext);
 533         case AVTAB_MEMBER:
 534                 /* Only polyinstantiate the MLS attributes if
 535                    the type is being polyinstantiated */
 536                 if (newcontext->type != tcontext->type) {
 537                         /* Use the process effective MLS attributes. */
 538                         return mls_context_cpy_low(newcontext, scontext);
 539                 } else {
 540                         /* Use the related object MLS attributes. */
 541                         return mls_context_cpy(newcontext, tcontext);
 542                 }
 543         default:
 544                 return -EINVAL;
 545         }
 546         return -EINVAL;
 547 }
 548
 549 #ifdef CONFIG_NETLABEL
 550 /**
 551  * mls_export_netlbl_lvl - Export the MLS sensitivity levels to NetLabel
 552  * @context: the security context
 553  * @secattr: the NetLabel security attributes
 554  *
 555  * Description:
 556  * Given the security context copy the low MLS sensitivity level into the
 557  * NetLabel MLS sensitivity level field.
 558  *
 559  */
 560 void mls_export_netlbl_lvl(struct context *context,
 561                            struct netlbl_lsm_secattr *secattr)
 562 {
 563         if (!selinux_mls_enabled)
 564                 return;
 565
 566         secattr->mls_lvl = context->range.level[0].sens - 1;
 567         secattr->flags |= NETLBL_SECATTR_MLS_LVL;
 568 }
 569
 570 /**
 571  * mls_import_netlbl_lvl - Import the NetLabel MLS sensitivity levels
 572  * @context: the security context
 573  * @secattr: the NetLabel security attributes
 574  *
 575  * Description:
 576  * Given the security context and the NetLabel security attributes, copy the
 577  * NetLabel MLS sensitivity level into the context.
 578  *
 579  */
 580 void mls_import_netlbl_lvl(struct context *context,
 581                            struct netlbl_lsm_secattr *secattr)
 582 {
 583         if (!selinux_mls_enabled)
 584                 return;
 585
 586         context->range.level[0].sens = secattr->mls_lvl + 1;
 587         context->range.level[1].sens = context->range.level[0].sens;
 588 }
 589
 590 /**
 591  * mls_export_netlbl_cat - Export the MLS categories to NetLabel
 592  * @context: the security context
 593  * @secattr: the NetLabel security attributes
 594  *
 595  * Description:
 596  * Given the security context copy the low MLS categories into the NetLabel
 597  * MLS category field.  Returns zero on success, negative values on failure.
 598  *
 599  */
 600 int mls_export_netlbl_cat(struct context *context,
 601                           struct netlbl_lsm_secattr *secattr)
 602 {
 603         int rc;
 604
 605         if (!selinux_mls_enabled)
 606                 return 0;
 607
 608         rc = ebitmap_netlbl_export(&context->range.level[0].cat,
 609                                    &secattr->mls_cat);
 610         if (rc == 0 && secattr->mls_cat != NULL)
 611                 secattr->flags |= NETLBL_SECATTR_MLS_CAT;
 612
 613         return rc;
 614 }
 615
 616 /**
 617  * mls_import_netlbl_cat - Import the MLS categories from NetLabel
 618  * @context: the security context
 619  * @secattr: the NetLabel security attributes
 620  *
 621  * Description:
 622  * Copy the NetLabel security attributes into the SELinux context; since the
 623  * NetLabel security attribute only contains a single MLS category use it for
 624  * both the low and high categories of the context.  Returns zero on success,
 625  * negative values on failure.
 626  *
 627  */
 628 int mls_import_netlbl_cat(struct context *context,
 629                           struct netlbl_lsm_secattr *secattr)
 630 {
 631         int rc;
 632
 633         if (!selinux_mls_enabled)
 634                 return 0;
 635
 636         rc = ebitmap_netlbl_import(&context->range.level[0].cat,
 637                                    secattr->mls_cat);
 638         if (rc != 0)
 639                 goto import_netlbl_cat_failure;
 640
 641         rc = ebitmap_cpy(&context->range.level[1].cat,
 642                          &context->range.level[0].cat);
 643         if (rc != 0)
 644                 goto import_netlbl_cat_failure;
 645
 646         return 0;
 647
 648 import_netlbl_cat_failure:
 649         ebitmap_destroy(&context->range.level[0].cat);
 650         ebitmap_destroy(&context->range.level[1].cat);
 651         return rc;
 652 }
 653 #endif /* CONFIG_NETLABEL */