source4/dsdb/samdb/ldb_modules/acl_read.c

   1 /*
   2   ldb database library
   3
   4   Copyright (C) Simo Sorce 2006-2008
   5   Copyright (C) Nadezhda Ivanova 2010
   6
   7   This program is free software; you can redistribute it and/or modify
   8   it under the terms of the GNU General Public License as published by
   9   the Free Software Foundation; either version 3 of the License, or
  10   (at your option) any later version.
  11
  12   This program is distributed in the hope that it will be useful,
  13   but WITHOUT ANY WARRANTY; without even the implied warranty of
  14   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15   GNU General Public License for more details.
  16
  17   You should have received a copy of the GNU General Public License
  18   along with this program.  If not, see <http://www.gnu.org/licenses/>.
  19 */
  20
  21 /*
  22  *  Name: ldb
  23  *
  24  *  Component: ldb ACL Read module
  25  *
  26  *  Description: Module that performs authorisation access checks on read requests
  27  *               Only DACL checks implemented at this point
  28  *
  29  *  Author: Nadezhda Ivanova
  30  */
  31
  32 #include "includes.h"
  33 #include "ldb_module.h"
  34 #include "auth/auth.h"
  35 #include "libcli/security/security.h"
  36 #include "dsdb/samdb/samdb.h"
  37 #include "librpc/gen_ndr/ndr_security.h"
  38 #include "param/param.h"
  39 #include "dsdb/samdb/ldb_modules/util.h"
  40
  41
  42 struct aclread_context {
  43         struct ldb_module *module;
  44         struct ldb_request *req;
  45         const char * const *attrs;
  46         const struct dsdb_schema *schema;
  47         uint32_t sd_flags;
  48         bool added_nTSecurityDescriptor;
  49         bool added_instanceType;
  50         bool added_objectSid;
  51         bool added_objectClass;
  52         bool indirsync;
  53 };
  54
  55 struct aclread_private {
  56         bool enabled;
  57 };
  58
  59 static void aclread_mark_inaccesslible(struct ldb_message_element *el) {
  60         el->flags |= LDB_FLAG_INTERNAL_INACCESSIBLE_ATTRIBUTE;
  61 }
  62
  63 static bool aclread_is_inaccessible(struct ldb_message_element *el) {
  64         return el->flags & LDB_FLAG_INTERNAL_INACCESSIBLE_ATTRIBUTE;
  65 }
  66
  67 static int aclread_callback(struct ldb_request *req, struct ldb_reply *ares)
  68 {
  69         struct ldb_context *ldb;
  70         struct aclread_context *ac;
  71         struct ldb_message *ret_msg;
  72         struct ldb_message *msg;
  73         int ret, num_of_attrs = 0;
  74         unsigned int i, k = 0;
  75         struct security_descriptor *sd;
  76         struct dom_sid *sid = NULL;
  77         TALLOC_CTX *tmp_ctx;
  78         uint32_t instanceType;
  79         const struct dsdb_class *objectclass;
  80
  81         ac = talloc_get_type(req->context, struct aclread_context);
  82         ldb = ldb_module_get_ctx(ac->module);
  83         if (!ares) {
  84                 return ldb_module_done(ac->req, NULL, NULL, LDB_ERR_OPERATIONS_ERROR );
  85         }
  86         if (ares->error != LDB_SUCCESS) {
  87                 return ldb_module_done(ac->req, ares->controls,
  88                                        ares->response, ares->error);
  89         }
  90         tmp_ctx = talloc_new(ac);
  91         switch (ares->type) {
  92         case LDB_REPLY_ENTRY:
  93                 msg = ares->message;
  94                 ret = dsdb_get_sd_from_ldb_message(ldb, tmp_ctx, msg, &sd);
  95                 if (ret != LDB_SUCCESS || sd == NULL ) {
  96                         ldb_debug_set(ldb, LDB_DEBUG_FATAL,
  97                                       "acl_read: cannot get descriptor of %s\n",
  98                                       ldb_dn_get_linearized(msg->dn));
  99                         ret = LDB_ERR_OPERATIONS_ERROR;
 100                         goto fail;
 101                 }
 102                 /*
 103                  * Get the most specific structural object class for the ACL check
 104                  */
 105                 objectclass = dsdb_get_structural_oc_from_msg(ac->schema, msg);
 106                 if (objectclass == NULL) {
 107                         ldb_asprintf_errstring(ldb, "acl_read: Failed to find a structural class for %s",
 108                                                ldb_dn_get_linearized(msg->dn));
 109                         ret = LDB_ERR_OPERATIONS_ERROR;
 110                         goto fail;
 111                 }
 112
 113                 sid = samdb_result_dom_sid(tmp_ctx, msg, "objectSid");
 114                 /* get the object instance type */
 115                 instanceType = ldb_msg_find_attr_as_uint(msg,
 116                                                          "instanceType", 0);
 117                 if (!ldb_dn_is_null(msg->dn) && !(instanceType & INSTANCE_TYPE_IS_NC_HEAD))
 118                 {
 119                         /* the object has a parent, so we have to check for visibility */
 120                         struct ldb_dn *parent_dn = ldb_dn_get_parent(tmp_ctx, msg->dn);
 121
 122                         ret = dsdb_module_check_access_on_dn(ac->module,
 123                                                              tmp_ctx,
 124                                                              parent_dn,
 125                                                              SEC_ADS_LIST,
 126                                                              NULL, req);
 127                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 128                                 talloc_free(tmp_ctx);
 129                                 return LDB_SUCCESS;
 130                         } else if (ret != LDB_SUCCESS) {
 131                                 ldb_debug_set(ldb, LDB_DEBUG_FATAL,
 132                                               "acl_read: %s check parent %s - %s\n",
 133                                               ldb_dn_get_linearized(msg->dn),
 134                                               ldb_strerror(ret),
 135                                               ldb_errstring(ldb));
 136                                 goto fail;
 137                         }
 138                 }
 139
 140                 /* for every element in the message check RP */
 141                 for (i=0; i < msg->num_elements; i++) {
 142                         const struct dsdb_attribute *attr;
 143                         bool is_sd, is_objectsid, is_instancetype, is_objectclass;
 144                         uint32_t access_mask;
 145                         attr = dsdb_attribute_by_lDAPDisplayName(ac->schema,
 146                                                                  msg->elements[i].name);
 147                         if (!attr) {
 148                                 ldb_debug_set(ldb, LDB_DEBUG_FATAL,
 149                                               "acl_read: %s cannot find attr[%s] in of schema\n",
 150                                               ldb_dn_get_linearized(msg->dn),
 151                                               msg->elements[i].name);
 152                                 ret = LDB_ERR_OPERATIONS_ERROR;
 153                                 goto fail;
 154                         }
 155                         is_sd = ldb_attr_cmp("nTSecurityDescriptor",
 156                                               msg->elements[i].name) == 0;
 157                         is_objectsid = ldb_attr_cmp("objectSid",
 158                                                     msg->elements[i].name) == 0;
 159                         is_instancetype = ldb_attr_cmp("instanceType",
 160                                                        msg->elements[i].name) == 0;
 161                         is_objectclass = ldb_attr_cmp("objectClass",
 162                                                       msg->elements[i].name) == 0;
 163                         /* these attributes were added to perform access checks and must be removed */
 164                         if (is_objectsid && ac->added_objectSid) {
 165                                 aclread_mark_inaccesslible(&msg->elements[i]);
 166                                 continue;
 167                         }
 168                         if (is_instancetype && ac->added_instanceType) {
 169                                 aclread_mark_inaccesslible(&msg->elements[i]);
 170                                 continue;
 171                         }
 172                         if (is_objectclass && ac->added_objectClass) {
 173                                 aclread_mark_inaccesslible(&msg->elements[i]);
 174                                 continue;
 175                         }
 176                         if (is_sd && ac->added_nTSecurityDescriptor) {
 177                                 aclread_mark_inaccesslible(&msg->elements[i]);
 178                                 continue;
 179                         }
 180                         /* nTSecurityDescriptor is a special case */
 181                         if (is_sd) {
 182                                 access_mask = 0;
 183
 184                                 if (ac->sd_flags & (SECINFO_OWNER|SECINFO_GROUP)) {
 185                                         access_mask |= SEC_STD_READ_CONTROL;
 186                                 }
 187                                 if (ac->sd_flags & SECINFO_DACL) {
 188                                         access_mask |= SEC_STD_READ_CONTROL;
 189                                 }
 190                                 if (ac->sd_flags & SECINFO_SACL) {
 191                                         access_mask |= SEC_FLAG_SYSTEM_SECURITY;
 192                                 }
 193                         } else {
 194                                 access_mask = SEC_ADS_READ_PROP;
 195                         }
 196
 197                         if (attr->searchFlags & SEARCH_FLAG_CONFIDENTIAL) {
 198                                 access_mask |= SEC_ADS_CONTROL_ACCESS;
 199                         }
 200
 201                         if (access_mask == 0) {
 202                                 aclread_mark_inaccesslible(&msg->elements[i]);
 203                                 continue;
 204                         }
 205
 206                         ret = acl_check_access_on_attribute(ac->module,
 207                                                             tmp_ctx,
 208                                                             sd,
 209                                                             sid,
 210                                                             access_mask,
 211                                                             attr,
 212                                                             objectclass);
 213
 214                         /*
 215                          * Dirsync control needs the replpropertymetadata attribute
 216                          * so return it as it will be removed by the control
 217                          * in anycase.
 218                          */
 219                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 220                                 if (!ac->indirsync) {
 221                                         /*
 222                                          * do not return this entry if attribute is
 223                                          * part of the search filter
 224                                          */
 225                                         if (dsdb_attr_in_parse_tree(ac->req->op.search.tree,
 226                                                                 msg->elements[i].name)) {
 227                                                 talloc_free(tmp_ctx);
 228                                                 return LDB_SUCCESS;
 229                                         }
 230                                         aclread_mark_inaccesslible(&msg->elements[i]);
 231                                 } else {
 232                                         /*
 233                                          * We are doing dirysnc answers
 234                                          * and the object shouldn't be returned (normally)
 235                                          * but we will return it without replPropertyMetaData
 236                                          * so that the dirysync module will do what is needed
 237                                          * (remove the object if it is not deleted, or return
 238                                          * just the objectGUID if it's deleted).
 239                                          */
 240                                         if (dsdb_attr_in_parse_tree(ac->req->op.search.tree,
 241                                                                 msg->elements[i].name)) {
 242                                                 ldb_msg_remove_attr(msg, "replPropertyMetaData");
 243                                                 break;
 244                                         } else {
 245                                                 aclread_mark_inaccesslible(&msg->elements[i]);
 246                                         }
 247                                 }
 248                         } else if (ret != LDB_SUCCESS) {
 249                                 ldb_debug_set(ldb, LDB_DEBUG_FATAL,
 250                                               "acl_read: %s check attr[%s] gives %s - %s\n",
 251                                               ldb_dn_get_linearized(msg->dn),
 252                                               msg->elements[i].name,
 253                                               ldb_strerror(ret),
 254                                               ldb_errstring(ldb));
 255                                 goto fail;
 256                         }
 257                 }
 258                 for (i=0; i < msg->num_elements; i++) {
 259                         if (!aclread_is_inaccessible(&msg->elements[i])) {
 260                                 num_of_attrs++;
 261                         }
 262                 }
 263                 /*create a new message to return*/
 264                 ret_msg = ldb_msg_new(ac->req);
 265                 ret_msg->dn = msg->dn;
 266                 talloc_steal(ret_msg, msg->dn);
 267                 ret_msg->num_elements = num_of_attrs;
 268                 if (num_of_attrs > 0) {
 269                         ret_msg->elements = talloc_array(ret_msg,
 270                                                          struct ldb_message_element,
 271                                                          num_of_attrs);
 272                         if (ret_msg->elements == NULL) {
 273                                 return ldb_oom(ldb);
 274                         }
 275                         for (i=0; i < msg->num_elements; i++) {
 276                                 bool to_remove = aclread_is_inaccessible(&msg->elements[i]);
 277                                 if (!to_remove) {
 278                                         ret_msg->elements[k] = msg->elements[i];
 279                                         talloc_steal(ret_msg->elements, msg->elements[i].name);
 280                                         talloc_steal(ret_msg->elements, msg->elements[i].values);
 281                                         k++;
 282                                 }
 283                         }
 284                         /*
 285                          * This should not be needed, but some modules
 286                          * may allocate values on the wrong context...
 287                          */
 288                         talloc_steal(ret_msg->elements, msg);
 289                 } else {
 290                         ret_msg->elements = NULL;
 291                 }
 292                 talloc_free(tmp_ctx);
 293
 294                 return ldb_module_send_entry(ac->req, ret_msg, ares->controls);
 295         case LDB_REPLY_REFERRAL:
 296                 return ldb_module_send_referral(ac->req, ares->referral);
 297         case LDB_REPLY_DONE:
 298                 return ldb_module_done(ac->req, ares->controls,
 299                                         ares->response, LDB_SUCCESS);
 300
 301         }
 302         return LDB_SUCCESS;
 303 fail:
 304         talloc_free(tmp_ctx);
 305         return ldb_module_done(ac->req, NULL, NULL, ret);
 306 }
 307
 308
 309 static int aclread_search(struct ldb_module *module, struct ldb_request *req)
 310 {
 311         struct ldb_context *ldb;
 312         int ret;
 313         struct aclread_context *ac;
 314         struct ldb_request *down_req;
 315         struct ldb_control *as_system = ldb_request_get_control(req, LDB_CONTROL_AS_SYSTEM_OID);
 316         uint32_t flags = ldb_req_get_custom_flags(req);
 317         struct ldb_result *res;
 318         struct aclread_private *p;
 319         bool need_sd = false;
 320         bool explicit_sd_flags = false;
 321         bool is_untrusted = ldb_req_is_untrusted(req);
 322         static const char * const _all_attrs[] = { "*", NULL };
 323         bool all_attrs = false;
 324         const char * const *attrs = NULL;
 325         uint32_t instanceType;
 326         static const char *acl_attrs[] = {
 327                 "instanceType",
 328                 NULL
 329         };
 330
 331         ldb = ldb_module_get_ctx(module);
 332         p = talloc_get_type(ldb_module_get_private(module), struct aclread_private);
 333
 334         /* skip access checks if we are system or system control is supplied
 335          * or this is not LDAP server request */
 336         if (!p || !p->enabled ||
 337             dsdb_module_am_system(module)
 338             || as_system || !is_untrusted) {
 339                 return ldb_next_request(module, req);
 340         }
 341         /* no checks on special dn */
 342         if (ldb_dn_is_special(req->op.search.base)) {
 343                 return ldb_next_request(module, req);
 344         }
 345
 346         /* check accessibility of base */
 347         if (!ldb_dn_is_null(req->op.search.base)) {
 348                 ret = dsdb_module_search_dn(module, req, &res, req->op.search.base,
 349                                             acl_attrs,
 350                                             DSDB_FLAG_NEXT_MODULE |
 351                                             DSDB_FLAG_AS_SYSTEM |
 352                                             DSDB_SEARCH_SHOW_RECYCLED,
 353                                             req);
 354                 if (ret != LDB_SUCCESS) {
 355                         return ldb_error(ldb, ret,
 356                                         "acl_read: Error retrieving instanceType for base.");
 357                 }
 358                 instanceType = ldb_msg_find_attr_as_uint(res->msgs[0],
 359                                                         "instanceType", 0);
 360                 if (instanceType != 0 && !(instanceType & INSTANCE_TYPE_IS_NC_HEAD))
 361                 {
 362                         /* the object has a parent, so we have to check for visibility */
 363                         struct ldb_dn *parent_dn = ldb_dn_get_parent(req, req->op.search.base);
 364                         ret = dsdb_module_check_access_on_dn(module,
 365                                                              req,
 366                                                              parent_dn,
 367                                                              SEC_ADS_LIST,
 368                                                              NULL, req);
 369                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 370                                 return ldb_module_done(req, NULL, NULL, LDB_ERR_NO_SUCH_OBJECT);
 371                         } else if (ret != LDB_SUCCESS) {
 372                                 return ldb_module_done(req, NULL, NULL, ret);
 373                         }
 374                 }
 375         }
 376         ac = talloc_zero(req, struct aclread_context);
 377         if (ac == NULL) {
 378                 return ldb_oom(ldb);
 379         }
 380         ac->module = module;
 381         ac->req = req;
 382         ac->schema = dsdb_get_schema(ldb, req);
 383         if (flags & DSDB_ACL_CHECKS_DIRSYNC_FLAG) {
 384                 ac->indirsync = true;
 385         } else {
 386                 ac->indirsync = false;
 387         }
 388         if (!ac->schema) {
 389                 return ldb_operr(ldb);
 390         }
 391
 392         attrs = req->op.search.attrs;
 393         if (attrs == NULL) {
 394                 all_attrs = true;
 395                 attrs = _all_attrs;
 396         } else if (attrs[0] == NULL) {
 397                 all_attrs = true;
 398                 attrs = _all_attrs;
 399         } else if (ldb_attr_in_list(attrs, "*")) {
 400                 all_attrs = true;
 401         }
 402
 403         /*
 404          * In theory we should also check for the SD control but control verification is
 405          * expensive so we'd better had the ntsecuritydescriptor to the list of
 406          * searched attribute and then remove it !
 407          */
 408         ac->sd_flags = dsdb_request_sd_flags(ac->req, &explicit_sd_flags);
 409
 410         if (ldb_attr_in_list(attrs, "nTSecurityDescriptor")) {
 411                 need_sd = false;
 412         } else if (explicit_sd_flags && all_attrs) {
 413                 need_sd = false;
 414         } else {
 415                 need_sd = true;
 416         }
 417
 418         if (!all_attrs) {
 419                 if (!ldb_attr_in_list(attrs, "instanceType")) {
 420                         attrs = ldb_attr_list_copy_add(ac, attrs, "instanceType");
 421                         if (attrs == NULL) {
 422                                 return ldb_oom(ldb);
 423                         }
 424                         ac->added_instanceType = true;
 425                 }
 426                 if (!ldb_attr_in_list(req->op.search.attrs, "objectSid")) {
 427                         attrs = ldb_attr_list_copy_add(ac, attrs, "objectSid");
 428                         if (attrs == NULL) {
 429                                 return ldb_oom(ldb);
 430                         }
 431                         ac->added_objectSid = true;
 432                 }
 433                 if (!ldb_attr_in_list(req->op.search.attrs, "objectClass")) {
 434                         attrs = ldb_attr_list_copy_add(ac, attrs, "objectClass");
 435                         if (attrs == NULL) {
 436                                 return ldb_oom(ldb);
 437                         }
 438                         ac->added_objectClass = true;
 439                 }
 440         }
 441
 442         if (need_sd) {
 443                 attrs = ldb_attr_list_copy_add(ac, attrs, "nTSecurityDescriptor");
 444                 if (attrs == NULL) {
 445                         return ldb_oom(ldb);
 446                 }
 447                 ac->added_nTSecurityDescriptor = true;
 448         }
 449
 450         ac->attrs = req->op.search.attrs;
 451         ret = ldb_build_search_req_ex(&down_req,
 452                                       ldb, ac,
 453                                       req->op.search.base,
 454                                       req->op.search.scope,
 455                                       req->op.search.tree,
 456                                       attrs,
 457                                       req->controls,
 458                                       ac, aclread_callback,
 459                                       req);
 460
 461         if (ret != LDB_SUCCESS) {
 462                 return LDB_ERR_OPERATIONS_ERROR;
 463         }
 464
 465         return ldb_next_request(module, down_req);
 466 }
 467
 468 static int aclread_init(struct ldb_module *module)
 469 {
 470         struct ldb_context *ldb = ldb_module_get_ctx(module);
 471         struct aclread_private *p = talloc_zero(module, struct aclread_private);
 472         if (p == NULL) {
 473                 return ldb_module_oom(module);
 474         }
 475         p->enabled = lpcfg_parm_bool(ldb_get_opaque(ldb, "loadparm"), NULL, "acl", "search", true);
 476         ldb_module_set_private(module, p);
 477         return ldb_next_init(module);
 478 }
 479
 480 static const struct ldb_module_ops ldb_aclread_module_ops = {
 481         .name              = "aclread",
 482         .search            = aclread_search,
 483         .init_context      = aclread_init
 484 };
 485
 486 int ldb_aclread_module_init(const char *version)
 487 {
 488         LDB_MODULE_CHECK_VERSION(version);
 489         return ldb_register_module(&ldb_aclread_module_ops);
 490 }