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) 2004-2005 Trusted Computer Solutions, Inc.
  12  */
  13
  14 #include <linux/kernel.h>
  15 #include <linux/slab.h>
  16 #include <linux/string.h>
  17 #include <linux/errno.h>
  18 #include "sidtab.h"
  19 #include "mls.h"
  20 #include "policydb.h"
  21 #include "services.h"
  22
  23 /*
  24  * Return the length in bytes for the MLS fields of the
  25  * security context string representation of `context'.
  26  */
  27 int mls_compute_context_len(struct context * context)
  28 {
  29         int i, l, len, range;
  30         struct ebitmap_node *node;
  31
  32         if (!selinux_mls_enabled)
  33                 return 0;
  34
  35         len = 1; /* for the beginning ":" */
  36         for (l = 0; l < 2; l++) {
  37                 range = 0;
  38                 len += strlen(policydb.p_sens_val_to_name[context->range.level[l].sens - 1]);
  39
  40                 ebitmap_for_each_bit(&context->range.level[l].cat, node, i) {
  41                         if (ebitmap_node_get_bit(node, i)) {
  42                                 if (range) {
  43                                         range++;
  44                                         continue;
  45                                 }
  46
  47                                 len += strlen(policydb.p_cat_val_to_name[i]) + 1;
  48                                 range++;
  49                         } else {
  50                                 if (range > 1)
  51                                         len += strlen(policydb.p_cat_val_to_name[i - 1]) + 1;
  52                                 range = 0;
  53                         }
  54                 }
  55                 /* Handle case where last category is the end of range */
  56                 if (range > 1)
  57                         len += strlen(policydb.p_cat_val_to_name[i - 1]) + 1;
  58
  59                 if (l == 0) {
  60                         if (mls_level_eq(&context->range.level[0],
  61                                          &context->range.level[1]))
  62                                 break;
  63                         else
  64                                 len++;
  65                 }
  66         }
  67
  68         return len;
  69 }
  70
  71 /*
  72  * Write the security context string representation of
  73  * the MLS fields of `context' into the string `*scontext'.
  74  * Update `*scontext' to point to the end of the MLS fields.
  75  */
  76 void mls_sid_to_context(struct context *context,
  77                         char **scontext)
  78 {
  79         char *scontextp;
  80         int i, l, range, wrote_sep;
  81         struct ebitmap_node *node;
  82
  83         if (!selinux_mls_enabled)
  84                 return;
  85
  86         scontextp = *scontext;
  87
  88         *scontextp = ':';
  89         scontextp++;
  90
  91         for (l = 0; l < 2; l++) {
  92                 range = 0;
  93                 wrote_sep = 0;
  94                 strcpy(scontextp,
  95                        policydb.p_sens_val_to_name[context->range.level[l].sens - 1]);
  96                 scontextp += strlen(policydb.p_sens_val_to_name[context->range.level[l].sens - 1]);
  97
  98                 /* categories */
  99                 ebitmap_for_each_bit(&context->range.level[l].cat, node, i) {
 100                         if (ebitmap_node_get_bit(node, i)) {
 101                                 if (range) {
 102                                         range++;
 103                                         continue;
 104                                 }
 105
 106                                 if (!wrote_sep) {
 107                                         *scontextp++ = ':';
 108                                         wrote_sep = 1;
 109                                 } else
 110                                         *scontextp++ = ',';
 111                                 strcpy(scontextp, policydb.p_cat_val_to_name[i]);
 112                                 scontextp += strlen(policydb.p_cat_val_to_name[i]);
 113                                 range++;
 114                         } else {
 115                                 if (range > 1) {
 116                                         if (range > 2)
 117                                                 *scontextp++ = '.';
 118                                         else
 119                                                 *scontextp++ = ',';
 120
 121                                         strcpy(scontextp, policydb.p_cat_val_to_name[i - 1]);
 122                                         scontextp += strlen(policydb.p_cat_val_to_name[i - 1]);
 123                                 }
 124                                 range = 0;
 125                         }
 126                 }
 127
 128                 /* Handle case where last category is the end of range */
 129                 if (range > 1) {
 130                         if (range > 2)
 131                                 *scontextp++ = '.';
 132                         else
 133                                 *scontextp++ = ',';
 134
 135                         strcpy(scontextp, policydb.p_cat_val_to_name[i - 1]);
 136                         scontextp += strlen(policydb.p_cat_val_to_name[i - 1]);
 137                 }
 138
 139                 if (l == 0) {
 140                         if (mls_level_eq(&context->range.level[0],
 141                                          &context->range.level[1]))
 142                                 break;
 143                         else {
 144                                 *scontextp = '-';
 145                                 scontextp++;
 146                         }
 147                 }
 148         }
 149
 150         *scontext = scontextp;
 151         return;
 152 }
 153
 154 /*
 155  * Return 1 if the MLS fields in the security context
 156  * structure `c' are valid.  Return 0 otherwise.
 157  */
 158 int mls_context_isvalid(struct policydb *p, struct context *c)
 159 {
 160         struct level_datum *levdatum;
 161         struct user_datum *usrdatum;
 162         struct ebitmap_node *node;
 163         int i, l;
 164
 165         if (!selinux_mls_enabled)
 166                 return 1;
 167
 168         /*
 169          * MLS range validity checks: high must dominate low, low level must
 170          * be valid (category set <-> sensitivity check), and high level must
 171          * be valid (category set <-> sensitivity check)
 172          */
 173         if (!mls_level_dom(&c->range.level[1], &c->range.level[0]))
 174                 /* High does not dominate low. */
 175                 return 0;
 176
 177         for (l = 0; l < 2; l++) {
 178                 if (!c->range.level[l].sens || c->range.level[l].sens > p->p_levels.nprim)
 179                         return 0;
 180                 levdatum = hashtab_search(p->p_levels.table,
 181                         p->p_sens_val_to_name[c->range.level[l].sens - 1]);
 182                 if (!levdatum)
 183                         return 0;
 184
 185                 ebitmap_for_each_bit(&c->range.level[l].cat, node, i) {
 186                         if (ebitmap_node_get_bit(node, i)) {
 187                                 if (i > p->p_cats.nprim)
 188                                         return 0;
 189                                 if (!ebitmap_get_bit(&levdatum->level->cat, i))
 190                                         /*
 191                                          * Category may not be associated with
 192                                          * sensitivity in low level.
 193                                          */
 194                                         return 0;
 195                         }
 196                 }
 197         }
 198
 199         if (c->role == OBJECT_R_VAL)
 200                 return 1;
 201
 202         /*
 203          * User must be authorized for the MLS range.
 204          */
 205         if (!c->user || c->user > p->p_users.nprim)
 206                 return 0;
 207         usrdatum = p->user_val_to_struct[c->user - 1];
 208         if (!mls_range_contains(usrdatum->range, c->range))
 209                 return 0; /* user may not be associated with range */
 210
 211         return 1;
 212 }
 213
 214 /*
 215  * Copies the MLS range from `src' into `dst'.
 216  */
 217 static inline int mls_copy_context(struct context *dst,
 218                                    struct context *src)
 219 {
 220         int l, rc = 0;
 221
 222         /* Copy the MLS range from the source context */
 223         for (l = 0; l < 2; l++) {
 224                 dst->range.level[l].sens = src->range.level[l].sens;
 225                 rc = ebitmap_cpy(&dst->range.level[l].cat,
 226                                  &src->range.level[l].cat);
 227                 if (rc)
 228                         break;
 229         }
 230
 231         return rc;
 232 }
 233
 234 /*
 235  * Set the MLS fields in the security context structure
 236  * `context' based on the string representation in
 237  * the string `*scontext'.  Update `*scontext' to
 238  * point to the end of the string representation of
 239  * the MLS fields.
 240  *
 241  * This function modifies the string in place, inserting
 242  * NULL characters to terminate the MLS fields.
 243  *
 244  * If a def_sid is provided and no MLS field is present,
 245  * copy the MLS field of the associated default context.
 246  * Used for upgraded to MLS systems where objects may lack
 247  * MLS fields.
 248  *
 249  * Policy read-lock must be held for sidtab lookup.
 250  *
 251  */
 252 int mls_context_to_sid(char oldc,
 253                        char **scontext,
 254                        struct context *context,
 255                        struct sidtab *s,
 256                        u32 def_sid)
 257 {
 258
 259         char delim;
 260         char *scontextp, *p, *rngptr;
 261         struct level_datum *levdatum;
 262         struct cat_datum *catdatum, *rngdatum;
 263         int l, rc = -EINVAL;
 264
 265         if (!selinux_mls_enabled) {
 266                 if (def_sid != SECSID_NULL && oldc)
 267                         *scontext += strlen(*scontext);
 268                 return 0;
 269         }
 270
 271         /*
 272          * No MLS component to the security context, try and map to
 273          * default if provided.
 274          */
 275         if (!oldc) {
 276                 struct context *defcon;
 277
 278                 if (def_sid == SECSID_NULL)
 279                         goto out;
 280
 281                 defcon = sidtab_search(s, def_sid);
 282                 if (!defcon)
 283                         goto out;
 284
 285                 rc = mls_copy_context(context, defcon);
 286                 goto out;
 287         }
 288
 289         /* Extract low sensitivity. */
 290         scontextp = p = *scontext;
 291         while (*p && *p != ':' && *p != '-')
 292                 p++;
 293
 294         delim = *p;
 295         if (delim != 0)
 296                 *p++ = 0;
 297
 298         for (l = 0; l < 2; l++) {
 299                 levdatum = hashtab_search(policydb.p_levels.table, scontextp);
 300                 if (!levdatum) {
 301                         rc = -EINVAL;
 302                         goto out;
 303                 }
 304
 305                 context->range.level[l].sens = levdatum->level->sens;
 306
 307                 if (delim == ':') {
 308                         /* Extract category set. */
 309                         while (1) {
 310                                 scontextp = p;
 311                                 while (*p && *p != ',' && *p != '-')
 312                                         p++;
 313                                 delim = *p;
 314                                 if (delim != 0)
 315                                         *p++ = 0;
 316
 317                                 /* Separate into range if exists */
 318                                 if ((rngptr = strchr(scontextp, '.')) != NULL) {
 319                                         /* Remove '.' */
 320                                         *rngptr++ = 0;
 321                                 }
 322
 323                                 catdatum = hashtab_search(policydb.p_cats.table,
 324                                                           scontextp);
 325                                 if (!catdatum) {
 326                                         rc = -EINVAL;
 327                                         goto out;
 328                                 }
 329
 330                                 rc = ebitmap_set_bit(&context->range.level[l].cat,
 331                                                      catdatum->value - 1, 1);
 332                                 if (rc)
 333                                         goto out;
 334
 335                                 /* If range, set all categories in range */
 336                                 if (rngptr) {
 337                                         int i;
 338
 339                                         rngdatum = hashtab_search(policydb.p_cats.table, rngptr);
 340                                         if (!rngdatum) {
 341                                                 rc = -EINVAL;
 342                                                 goto out;
 343                                         }
 344
 345                                         if (catdatum->value >= rngdatum->value) {
 346                                                 rc = -EINVAL;
 347                                                 goto out;
 348                                         }
 349
 350                                         for (i = catdatum->value; i < rngdatum->value; i++) {
 351                                                 rc = ebitmap_set_bit(&context->range.level[l].cat, i, 1);
 352                                                 if (rc)
 353                                                         goto out;
 354                                         }
 355                                 }
 356
 357                                 if (delim != ',')
 358                                         break;
 359                         }
 360                 }
 361                 if (delim == '-') {
 362                         /* Extract high sensitivity. */
 363                         scontextp = p;
 364                         while (*p && *p != ':')
 365                                 p++;
 366
 367                         delim = *p;
 368                         if (delim != 0)
 369                                 *p++ = 0;
 370                 } else
 371                         break;
 372         }
 373
 374         if (l == 0) {
 375                 context->range.level[1].sens = context->range.level[0].sens;
 376                 rc = ebitmap_cpy(&context->range.level[1].cat,
 377                                  &context->range.level[0].cat);
 378                 if (rc)
 379                         goto out;
 380         }
 381         *scontext = ++p;
 382         rc = 0;
 383 out:
 384         return rc;
 385 }
 386
 387 /*
 388  * Copies the effective MLS range from `src' into `dst'.
 389  */
 390 static inline int mls_scopy_context(struct context *dst,
 391                                     struct context *src)
 392 {
 393         int l, rc = 0;
 394
 395         /* Copy the MLS range from the source context */
 396         for (l = 0; l < 2; l++) {
 397                 dst->range.level[l].sens = src->range.level[0].sens;
 398                 rc = ebitmap_cpy(&dst->range.level[l].cat,
 399                                  &src->range.level[0].cat);
 400                 if (rc)
 401                         break;
 402         }
 403
 404         return rc;
 405 }
 406
 407 /*
 408  * Copies the MLS range `range' into `context'.
 409  */
 410 static inline 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 (selinux_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 (!selinux_mls_enabled)
 481                 return 0;
 482
 483         for (l = 0; l < 2; l++) {
 484                 levdatum = hashtab_search(newp->p_levels.table,
 485                         oldp->p_sens_val_to_name[c->range.level[l].sens - 1]);
 486
 487                 if (!levdatum)
 488                         return -EINVAL;
 489                 c->range.level[l].sens = levdatum->level->sens;
 490
 491                 ebitmap_init(&bitmap);
 492                 ebitmap_for_each_bit(&c->range.level[l].cat, node, i) {
 493                         if (ebitmap_node_get_bit(node, i)) {
 494                                 int rc;
 495
 496                                 catdatum = hashtab_search(newp->p_cats.table,
 497                                                 oldp->p_cat_val_to_name[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                 }
 505                 ebitmap_destroy(&c->range.level[l].cat);
 506                 c->range.level[l].cat = bitmap;
 507         }
 508
 509         return 0;
 510 }
 511
 512 int mls_compute_sid(struct context *scontext,
 513                     struct context *tcontext,
 514                     u16 tclass,
 515                     u32 specified,
 516                     struct context *newcontext)
 517 {
 518         if (!selinux_mls_enabled)
 519                 return 0;
 520
 521         switch (specified) {
 522         case AVTAB_TRANSITION:
 523                 if (tclass == SECCLASS_PROCESS) {
 524                         struct range_trans *rangetr;
 525                         /* Look for a range transition rule. */
 526                         for (rangetr = policydb.range_tr; rangetr;
 527                              rangetr = rangetr->next) {
 528                                 if (rangetr->dom == scontext->type &&
 529                                     rangetr->type == tcontext->type) {
 530                                         /* Set the range from the rule */
 531                                         return mls_range_set(newcontext,
 532                                                              &rangetr->range);
 533                                 }
 534                         }
 535                 }
 536                 /* Fallthrough */
 537         case AVTAB_CHANGE:
 538                 if (tclass == SECCLASS_PROCESS)
 539                         /* Use the process MLS attributes. */
 540                         return mls_copy_context(newcontext, scontext);
 541                 else
 542                         /* Use the process effective MLS attributes. */
 543                         return mls_scopy_context(newcontext, scontext);
 544         case AVTAB_MEMBER:
 545                 /* Only polyinstantiate the MLS attributes if
 546                    the type is being polyinstantiated */
 547                 if (newcontext->type != tcontext->type) {
 548                         /* Use the process effective MLS attributes. */
 549                         return mls_scopy_context(newcontext, scontext);
 550                 } else {
 551                         /* Use the related object MLS attributes. */
 552                         return mls_copy_context(newcontext, tcontext);
 553                 }
 554         default:
 555                 return -EINVAL;
 556         }
 557         return -EINVAL;
 558 }
 559