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                                                              &objectclass->schemaIDGUID,
 127                                                              req);
 128                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 129                                 talloc_free(tmp_ctx);
 130                                 return LDB_SUCCESS;
 131                         } else if (ret != LDB_SUCCESS) {
 132                                 ldb_debug_set(ldb, LDB_DEBUG_FATAL,
 133                                               "acl_read: %s check parent %s - %s\n",
 134                                               ldb_dn_get_linearized(msg->dn),
 135                                               ldb_strerror(ret),
 136                                               ldb_errstring(ldb));
 137                                 goto fail;
 138                         }
 139                 }
 140
 141                 /* for every element in the message check RP */
 142                 for (i=0; i < msg->num_elements; i++) {
 143                         const struct dsdb_attribute *attr;
 144                         bool is_sd, is_objectsid, is_instancetype, is_objectclass;
 145                         uint32_t access_mask;
 146                         attr = dsdb_attribute_by_lDAPDisplayName(ac->schema,
 147                                                                  msg->elements[i].name);
 148                         if (!attr) {
 149                                 ldb_debug_set(ldb, LDB_DEBUG_FATAL,
 150                                               "acl_read: %s cannot find attr[%s] in of schema\n",
 151                                               ldb_dn_get_linearized(msg->dn),
 152                                               msg->elements[i].name);
 153                                 ret = LDB_ERR_OPERATIONS_ERROR;
 154                                 goto fail;
 155                         }
 156                         is_sd = ldb_attr_cmp("nTSecurityDescriptor",
 157                                               msg->elements[i].name) == 0;
 158                         is_objectsid = ldb_attr_cmp("objectSid",
 159                                                     msg->elements[i].name) == 0;
 160                         is_instancetype = ldb_attr_cmp("instanceType",
 161                                                        msg->elements[i].name) == 0;
 162                         is_objectclass = ldb_attr_cmp("objectClass",
 163                                                       msg->elements[i].name) == 0;
 164                         /* these attributes were added to perform access checks and must be removed */
 165                         if (is_objectsid && ac->added_objectSid) {
 166                                 aclread_mark_inaccesslible(&msg->elements[i]);
 167                                 continue;
 168                         }
 169                         if (is_instancetype && ac->added_instanceType) {
 170                                 aclread_mark_inaccesslible(&msg->elements[i]);
 171                                 continue;
 172                         }
 173                         if (is_objectclass && ac->added_objectClass) {
 174                                 aclread_mark_inaccesslible(&msg->elements[i]);
 175                                 continue;
 176                         }
 177                         if (is_sd && ac->added_nTSecurityDescriptor) {
 178                                 aclread_mark_inaccesslible(&msg->elements[i]);
 179                                 continue;
 180                         }
 181                         /* nTSecurityDescriptor is a special case */
 182                         if (is_sd) {
 183                                 access_mask = 0;
 184
 185                                 if (ac->sd_flags & (SECINFO_OWNER|SECINFO_GROUP)) {
 186                                         access_mask |= SEC_STD_READ_CONTROL;
 187                                 }
 188                                 if (ac->sd_flags & SECINFO_DACL) {
 189                                         access_mask |= SEC_STD_READ_CONTROL;
 190                                 }
 191                                 if (ac->sd_flags & SECINFO_SACL) {
 192                                         access_mask |= SEC_FLAG_SYSTEM_SECURITY;
 193                                 }
 194                         } else {
 195                                 access_mask = SEC_ADS_READ_PROP;
 196                         }
 197
 198                         if (attr->searchFlags & SEARCH_FLAG_CONFIDENTIAL) {
 199                                 access_mask |= SEC_ADS_CONTROL_ACCESS;
 200                         }
 201
 202                         if (access_mask == 0) {
 203                                 aclread_mark_inaccesslible(&msg->elements[i]);
 204                                 continue;
 205                         }
 206
 207                         ret = acl_check_access_on_attribute(ac->module,
 208                                                             tmp_ctx,
 209                                                             sd,
 210                                                             sid,
 211                                                             access_mask,
 212                                                             attr,
 213                                                             objectclass);
 214
 215                         /*
 216                          * Dirsync control needs the replpropertymetadata attribute
 217                          * so return it as it will be removed by the control
 218                          * in anycase.
 219                          */
 220                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 221                                 if (!ac->indirsync) {
 222                                         /*
 223                                          * do not return this entry if attribute is
 224                                          * part of the search filter
 225                                          */
 226                                         if (dsdb_attr_in_parse_tree(ac->req->op.search.tree,
 227                                                                 msg->elements[i].name)) {
 228                                                 talloc_free(tmp_ctx);
 229                                                 return LDB_SUCCESS;
 230                                         }
 231                                         aclread_mark_inaccesslible(&msg->elements[i]);
 232                                 } else {
 233                                         /*
 234                                          * We are doing dirysnc answers
 235                                          * and the object shouldn't be returned (normally)
 236                                          * but we will return it without replPropertyMetaData
 237                                          * so that the dirysync module will do what is needed
 238                                          * (remove the object if it is not deleted, or return
 239                                          * just the objectGUID if it's deleted).
 240                                          */
 241                                         if (dsdb_attr_in_parse_tree(ac->req->op.search.tree,
 242                                                                 msg->elements[i].name)) {
 243                                                 ldb_msg_remove_attr(msg, "replPropertyMetaData");
 244                                                 break;
 245                                         } else {
 246                                                 aclread_mark_inaccesslible(&msg->elements[i]);
 247                                         }
 248                                 }
 249                         } else if (ret != LDB_SUCCESS) {
 250                                 ldb_debug_set(ldb, LDB_DEBUG_FATAL,
 251                                               "acl_read: %s check attr[%s] gives %s - %s\n",
 252                                               ldb_dn_get_linearized(msg->dn),
 253                                               msg->elements[i].name,
 254                                               ldb_strerror(ret),
 255                                               ldb_errstring(ldb));
 256                                 goto fail;
 257                         }
 258                 }
 259                 for (i=0; i < msg->num_elements; i++) {
 260                         if (!aclread_is_inaccessible(&msg->elements[i])) {
 261                                 num_of_attrs++;
 262                         }
 263                 }
 264                 /*create a new message to return*/
 265                 ret_msg = ldb_msg_new(ac->req);
 266                 ret_msg->dn = msg->dn;
 267                 talloc_steal(ret_msg, msg->dn);
 268                 ret_msg->num_elements = num_of_attrs;
 269                 if (num_of_attrs > 0) {
 270                         ret_msg->elements = talloc_array(ret_msg,
 271                                                          struct ldb_message_element,
 272                                                          num_of_attrs);
 273                         if (ret_msg->elements == NULL) {
 274                                 return ldb_oom(ldb);
 275                         }
 276                         for (i=0; i < msg->num_elements; i++) {
 277                                 bool to_remove = aclread_is_inaccessible(&msg->elements[i]);
 278                                 if (!to_remove) {
 279                                         ret_msg->elements[k] = msg->elements[i];
 280                                         talloc_steal(ret_msg->elements, msg->elements[i].name);
 281                                         talloc_steal(ret_msg->elements, msg->elements[i].values);
 282                                         k++;
 283                                 }
 284                         }
 285                         /*
 286                          * This should not be needed, but some modules
 287                          * may allocate values on the wrong context...
 288                          */
 289                         talloc_steal(ret_msg->elements, msg);
 290                 } else {
 291                         ret_msg->elements = NULL;
 292                 }
 293                 talloc_free(tmp_ctx);
 294
 295                 return ldb_module_send_entry(ac->req, ret_msg, ares->controls);
 296         case LDB_REPLY_REFERRAL:
 297                 return ldb_module_send_referral(ac->req, ares->referral);
 298         case LDB_REPLY_DONE:
 299                 return ldb_module_done(ac->req, ares->controls,
 300                                         ares->response, LDB_SUCCESS);
 301
 302         }
 303         return LDB_SUCCESS;
 304 fail:
 305         talloc_free(tmp_ctx);
 306         return ldb_module_done(ac->req, NULL, NULL, ret);
 307 }
 308
 309
 310 static int aclread_search(struct ldb_module *module, struct ldb_request *req)
 311 {
 312         struct ldb_context *ldb;
 313         int ret;
 314         struct aclread_context *ac;
 315         struct ldb_request *down_req;
 316         struct ldb_control *as_system = ldb_request_get_control(req, LDB_CONTROL_AS_SYSTEM_OID);
 317         uint32_t flags = ldb_req_get_custom_flags(req);
 318         struct ldb_result *res;
 319         struct aclread_private *p;
 320         bool need_sd = false;
 321         bool explicit_sd_flags = false;
 322         bool is_untrusted = ldb_req_is_untrusted(req);
 323         static const char * const _all_attrs[] = { "*", NULL };
 324         bool all_attrs = false;
 325         const char * const *attrs = NULL;
 326         uint32_t instanceType;
 327         static const char *acl_attrs[] = {
 328                 "instanceType",
 329                 NULL
 330         };
 331
 332         ldb = ldb_module_get_ctx(module);
 333         p = talloc_get_type(ldb_module_get_private(module), struct aclread_private);
 334
 335         /* skip access checks if we are system or system control is supplied
 336          * or this is not LDAP server request */
 337         if (!p || !p->enabled ||
 338             dsdb_module_am_system(module)
 339             || as_system || !is_untrusted) {
 340                 return ldb_next_request(module, req);
 341         }
 342         /* no checks on special dn */
 343         if (ldb_dn_is_special(req->op.search.base)) {
 344                 return ldb_next_request(module, req);
 345         }
 346
 347         /* check accessibility of base */
 348         if (!ldb_dn_is_null(req->op.search.base)) {
 349                 ret = dsdb_module_search_dn(module, req, &res, req->op.search.base,
 350                                             acl_attrs,
 351                                             DSDB_FLAG_NEXT_MODULE |
 352                                             DSDB_FLAG_AS_SYSTEM |
 353                                             DSDB_SEARCH_SHOW_RECYCLED,
 354                                             req);
 355                 if (ret != LDB_SUCCESS) {
 356                         return ldb_error(ldb, ret,
 357                                         "acl_read: Error retrieving instanceType for base.");
 358                 }
 359                 instanceType = ldb_msg_find_attr_as_uint(res->msgs[0],
 360                                                         "instanceType", 0);
 361                 if (instanceType != 0 && !(instanceType & INSTANCE_TYPE_IS_NC_HEAD))
 362                 {
 363                         /* the object has a parent, so we have to check for visibility */
 364                         struct ldb_dn *parent_dn = ldb_dn_get_parent(req, req->op.search.base);
 365                         ret = dsdb_module_check_access_on_dn(module,
 366                                                              req,
 367                                                              parent_dn,
 368                                                              SEC_ADS_LIST,
 369                                                              NULL, req);
 370                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 371                                 return ldb_module_done(req, NULL, NULL, LDB_ERR_NO_SUCH_OBJECT);
 372                         } else if (ret != LDB_SUCCESS) {
 373                                 return ldb_module_done(req, NULL, NULL, ret);
 374                         }
 375                 }
 376         }
 377         ac = talloc_zero(req, struct aclread_context);
 378         if (ac == NULL) {
 379                 return ldb_oom(ldb);
 380         }
 381         ac->module = module;
 382         ac->req = req;
 383         ac->schema = dsdb_get_schema(ldb, req);
 384         if (flags & DSDB_ACL_CHECKS_DIRSYNC_FLAG) {
 385                 ac->indirsync = true;
 386         } else {
 387                 ac->indirsync = false;
 388         }
 389         if (!ac->schema) {
 390                 return ldb_operr(ldb);
 391         }
 392
 393         attrs = req->op.search.attrs;
 394         if (attrs == NULL) {
 395                 all_attrs = true;
 396                 attrs = _all_attrs;
 397         } else if (attrs[0] == NULL) {
 398                 all_attrs = true;
 399                 attrs = _all_attrs;
 400         } else if (ldb_attr_in_list(attrs, "*")) {
 401                 all_attrs = true;
 402         }
 403
 404         /*
 405          * In theory we should also check for the SD control but control verification is
 406          * expensive so we'd better had the ntsecuritydescriptor to the list of
 407          * searched attribute and then remove it !
 408          */
 409         ac->sd_flags = dsdb_request_sd_flags(ac->req, &explicit_sd_flags);
 410
 411         if (ldb_attr_in_list(attrs, "nTSecurityDescriptor")) {
 412                 need_sd = false;
 413         } else if (explicit_sd_flags && all_attrs) {
 414                 need_sd = false;
 415         } else {
 416                 need_sd = true;
 417         }
 418
 419         if (!all_attrs) {
 420                 if (!ldb_attr_in_list(attrs, "instanceType")) {
 421                         attrs = ldb_attr_list_copy_add(ac, attrs, "instanceType");
 422                         if (attrs == NULL) {
 423                                 return ldb_oom(ldb);
 424                         }
 425                         ac->added_instanceType = true;
 426                 }
 427                 if (!ldb_attr_in_list(req->op.search.attrs, "objectSid")) {
 428                         attrs = ldb_attr_list_copy_add(ac, attrs, "objectSid");
 429                         if (attrs == NULL) {
 430                                 return ldb_oom(ldb);
 431                         }
 432                         ac->added_objectSid = true;
 433                 }
 434                 if (!ldb_attr_in_list(req->op.search.attrs, "objectClass")) {
 435                         attrs = ldb_attr_list_copy_add(ac, attrs, "objectClass");
 436                         if (attrs == NULL) {
 437                                 return ldb_oom(ldb);
 438                         }
 439                         ac->added_objectClass = true;
 440                 }
 441         }
 442
 443         if (need_sd) {
 444                 attrs = ldb_attr_list_copy_add(ac, attrs, "nTSecurityDescriptor");
 445                 if (attrs == NULL) {
 446                         return ldb_oom(ldb);
 447                 }
 448                 ac->added_nTSecurityDescriptor = true;
 449         }
 450
 451         ac->attrs = req->op.search.attrs;
 452         ret = ldb_build_search_req_ex(&down_req,
 453                                       ldb, ac,
 454                                       req->op.search.base,
 455                                       req->op.search.scope,
 456                                       req->op.search.tree,
 457                                       attrs,
 458                                       req->controls,
 459                                       ac, aclread_callback,
 460                                       req);
 461
 462         if (ret != LDB_SUCCESS) {
 463                 return LDB_ERR_OPERATIONS_ERROR;
 464         }
 465
 466         return ldb_next_request(module, down_req);
 467 }
 468
 469 static int aclread_init(struct ldb_module *module)
 470 {
 471         struct ldb_context *ldb = ldb_module_get_ctx(module);
 472         struct aclread_private *p = talloc_zero(module, struct aclread_private);
 473         if (p == NULL) {
 474                 return ldb_module_oom(module);
 475         }
 476         p->enabled = lpcfg_parm_bool(ldb_get_opaque(ldb, "loadparm"), NULL, "acl", "search", true);
 477         ldb_module_set_private(module, p);
 478         return ldb_next_init(module);
 479 }
 480
 481 static const struct ldb_module_ops ldb_aclread_module_ops = {
 482         .name              = "aclread",
 483         .search            = aclread_search,
 484         .init_context      = aclread_init
 485 };
 486
 487 int ldb_aclread_module_init(const char *version)
 488 {
 489         LDB_MODULE_CHECK_VERSION(version);
 490         return ldb_register_module(&ldb_aclread_module_ops);
 491 }