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                                 rngptr = strchr(scontextp, '.');
 309                                 if (rngptr != NULL) {
 310                                         /* Remove '.' */
 311                                         *rngptr++ = 0;
 312                                 }
 313
 314                                 catdatum = hashtab_search(policydb.p_cats.table,
 315                                                           scontextp);
 316                                 if (!catdatum) {
 317                                         rc = -EINVAL;
 318                                         goto out;
 319                                 }
 320
 321                                 rc = ebitmap_set_bit(&context->range.level[l].cat,
 322                                                      catdatum->value - 1, 1);
 323                                 if (rc)
 324                                         goto out;
 325
 326                                 /* If range, set all categories in range */
 327                                 if (rngptr) {
 328                                         int i;
 329
 330                                         rngdatum = hashtab_search(policydb.p_cats.table, rngptr);
 331                                         if (!rngdatum) {
 332                                                 rc = -EINVAL;
 333                                                 goto out;
 334                                         }
 335
 336                                         if (catdatum->value >= rngdatum->value) {
 337                                                 rc = -EINVAL;
 338                                                 goto out;
 339                                         }
 340
 341                                         for (i = catdatum->value; i < rngdatum->value; i++) {
 342                                                 rc = ebitmap_set_bit(&context->range.level[l].cat, i, 1);
 343                                                 if (rc)
 344                                                         goto out;
 345                                         }
 346                                 }
 347
 348                                 if (delim != ',')
 349                                         break;
 350                         }
 351                 }
 352                 if (delim == '-') {
 353                         /* Extract high sensitivity. */
 354                         scontextp = p;
 355                         while (*p && *p != ':')
 356                                 p++;
 357
 358                         delim = *p;
 359                         if (delim != 0)
 360                                 *p++ = 0;
 361                 } else
 362                         break;
 363         }
 364
 365         if (l == 0) {
 366                 context->range.level[1].sens = context->range.level[0].sens;
 367                 rc = ebitmap_cpy(&context->range.level[1].cat,
 368                                  &context->range.level[0].cat);
 369                 if (rc)
 370                         goto out;
 371         }
 372         *scontext = ++p;
 373         rc = 0;
 374 out:
 375         return rc;
 376 }
 377
 378 /*
 379  * Set the MLS fields in the security context structure
 380  * `context' based on the string representation in
 381  * the string `str'.  This function will allocate temporary memory with the
 382  * given constraints of gfp_mask.
 383  */
 384 int mls_from_string(char *str, struct context *context, gfp_t gfp_mask)
 385 {
 386         char *tmpstr, *freestr;
 387         int rc;
 388
 389         if (!selinux_mls_enabled)
 390                 return -EINVAL;
 391
 392         /* we need freestr because mls_context_to_sid will change
 393            the value of tmpstr */
 394         tmpstr = freestr = kstrdup(str, gfp_mask);
 395         if (!tmpstr) {
 396                 rc = -ENOMEM;
 397         } else {
 398                 rc = mls_context_to_sid(':', &tmpstr, context,
 399                                         NULL, SECSID_NULL);
 400                 kfree(freestr);
 401         }
 402
 403         return rc;
 404 }
 405
 406 /*
 407  * Copies the MLS range `range' into `context'.
 408  */
 409 static inline int mls_range_set(struct context *context,
 410                                 struct mls_range *range)
 411 {
 412         int l, rc = 0;
 413
 414         /* Copy the MLS range into the  context */
 415         for (l = 0; l < 2; l++) {
 416                 context->range.level[l].sens = range->level[l].sens;
 417                 rc = ebitmap_cpy(&context->range.level[l].cat,
 418                                  &range->level[l].cat);
 419                 if (rc)
 420                         break;
 421         }
 422
 423         return rc;
 424 }
 425
 426 int mls_setup_user_range(struct context *fromcon, struct user_datum *user,
 427                          struct context *usercon)
 428 {
 429         if (selinux_mls_enabled) {
 430                 struct mls_level *fromcon_sen = &(fromcon->range.level[0]);
 431                 struct mls_level *fromcon_clr = &(fromcon->range.level[1]);
 432                 struct mls_level *user_low = &(user->range.level[0]);
 433                 struct mls_level *user_clr = &(user->range.level[1]);
 434                 struct mls_level *user_def = &(user->dfltlevel);
 435                 struct mls_level *usercon_sen = &(usercon->range.level[0]);
 436                 struct mls_level *usercon_clr = &(usercon->range.level[1]);
 437
 438                 /* Honor the user's default level if we can */
 439                 if (mls_level_between(user_def, fromcon_sen, fromcon_clr)) {
 440                         *usercon_sen = *user_def;
 441                 } else if (mls_level_between(fromcon_sen, user_def, user_clr)) {
 442                         *usercon_sen = *fromcon_sen;
 443                 } else if (mls_level_between(fromcon_clr, user_low, user_def)) {
 444                         *usercon_sen = *user_low;
 445                 } else
 446                         return -EINVAL;
 447
 448                 /* Lower the clearance of available contexts
 449                    if the clearance of "fromcon" is lower than
 450                    that of the user's default clearance (but
 451                    only if the "fromcon" clearance dominates
 452                    the user's computed sensitivity level) */
 453                 if (mls_level_dom(user_clr, fromcon_clr))
 454                         *usercon_clr = *fromcon_clr;
 455                 else if (mls_level_dom(fromcon_clr, user_clr))
 456                         *usercon_clr = *user_clr;
 457                 else
 458                         return -EINVAL;
 459         }
 460
 461         return 0;
 462 }
 463
 464 /*
 465  * Convert the MLS fields in the security context
 466  * structure `c' from the values specified in the
 467  * policy `oldp' to the values specified in the policy `newp'.
 468  */
 469 int mls_convert_context(struct policydb *oldp,
 470                         struct policydb *newp,
 471                         struct context *c)
 472 {
 473         struct level_datum *levdatum;
 474         struct cat_datum *catdatum;
 475         struct ebitmap bitmap;
 476         struct ebitmap_node *node;
 477         int l, i;
 478
 479         if (!selinux_mls_enabled)
 480                 return 0;
 481
 482         for (l = 0; l < 2; l++) {
 483                 levdatum = hashtab_search(newp->p_levels.table,
 484                         oldp->p_sens_val_to_name[c->range.level[l].sens - 1]);
 485
 486                 if (!levdatum)
 487                         return -EINVAL;
 488                 c->range.level[l].sens = levdatum->level->sens;
 489
 490                 ebitmap_init(&bitmap);
 491                 ebitmap_for_each_positive_bit(&c->range.level[l].cat, node, i) {
 492                         int rc;
 493
 494                         catdatum = hashtab_search(newp->p_cats.table,
 495                                                   oldp->p_cat_val_to_name[i]);
 496                         if (!catdatum)
 497                                 return -EINVAL;
 498                         rc = ebitmap_set_bit(&bitmap, catdatum->value - 1, 1);
 499                         if (rc)
 500                                 return rc;
 501                 }
 502                 ebitmap_destroy(&c->range.level[l].cat);
 503                 c->range.level[l].cat = bitmap;
 504         }
 505
 506         return 0;
 507 }
 508
 509 int mls_compute_sid(struct context *scontext,
 510                     struct context *tcontext,
 511                     u16 tclass,
 512                     u32 specified,
 513                     struct context *newcontext)
 514 {
 515         struct range_trans *rtr;
 516
 517         if (!selinux_mls_enabled)
 518                 return 0;
 519
 520         switch (specified) {
 521         case AVTAB_TRANSITION:
 522                 /* Look for a range transition rule. */
 523                 for (rtr = policydb.range_tr; rtr; rtr = rtr->next) {
 524                         if (rtr->source_type == scontext->type &&
 525                             rtr->target_type == tcontext->type &&
 526                             rtr->target_class == tclass) {
 527                                 /* Set the range from the rule */
 528                                 return mls_range_set(newcontext,
 529                                                      &rtr->target_range);
 530                         }
 531                 }
 532                 /* Fallthrough */
 533         case AVTAB_CHANGE:
 534                 if (tclass == SECCLASS_PROCESS)
 535                         /* Use the process MLS attributes. */
 536                         return mls_context_cpy(newcontext, scontext);
 537                 else
 538                         /* Use the process effective MLS attributes. */
 539                         return mls_context_cpy_low(newcontext, scontext);
 540         case AVTAB_MEMBER:
 541                 /* Use the process effective MLS attributes. */
 542                 return mls_context_cpy_low(newcontext, scontext);
 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->attr.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->attr.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->attr.mls.cat);
 610         if (rc == 0 && secattr->attr.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->attr.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 */