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) {
  96                         ldb_debug_set(ldb, LDB_DEBUG_FATAL,
  97                                       "acl_read: cannot get descriptor of %s: %s\n",
  98                                       ldb_dn_get_linearized(msg->dn), ldb_strerror(ret));
  99                         ret = LDB_ERR_OPERATIONS_ERROR;
 100                         goto fail;
 101                 } else if (sd == NULL) {
 102                         ldb_debug_set(ldb, LDB_DEBUG_FATAL,
 103                                       "acl_read: cannot get descriptor of %s (attribute not found)\n",
 104                                       ldb_dn_get_linearized(msg->dn));
 105                         ret = LDB_ERR_OPERATIONS_ERROR;
 106                         goto fail;
 107                 }
 108                 /*
 109                  * Get the most specific structural object class for the ACL check
 110                  */
 111                 objectclass = dsdb_get_structural_oc_from_msg(ac->schema, msg);
 112                 if (objectclass == NULL) {
 113                         ldb_asprintf_errstring(ldb, "acl_read: Failed to find a structural class for %s",
 114                                                ldb_dn_get_linearized(msg->dn));
 115                         ret = LDB_ERR_OPERATIONS_ERROR;
 116                         goto fail;
 117                 }
 118
 119                 sid = samdb_result_dom_sid(tmp_ctx, msg, "objectSid");
 120                 /* get the object instance type */
 121                 instanceType = ldb_msg_find_attr_as_uint(msg,
 122                                                          "instanceType", 0);
 123                 if (!ldb_dn_is_null(msg->dn) && !(instanceType & INSTANCE_TYPE_IS_NC_HEAD))
 124                 {
 125                         /* the object has a parent, so we have to check for visibility */
 126                         struct ldb_dn *parent_dn = ldb_dn_get_parent(tmp_ctx, msg->dn);
 127
 128                         ret = dsdb_module_check_access_on_dn(ac->module,
 129                                                              tmp_ctx,
 130                                                              parent_dn,
 131                                                              SEC_ADS_LIST,
 132                                                              NULL, req);
 133                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 134                                 talloc_free(tmp_ctx);
 135                                 return LDB_SUCCESS;
 136                         } else if (ret != LDB_SUCCESS) {
 137                                 ldb_debug_set(ldb, LDB_DEBUG_FATAL,
 138                                               "acl_read: %s check parent %s - %s\n",
 139                                               ldb_dn_get_linearized(msg->dn),
 140                                               ldb_strerror(ret),
 141                                               ldb_errstring(ldb));
 142                                 goto fail;
 143                         }
 144                 }
 145
 146                 /* for every element in the message check RP */
 147                 for (i=0; i < msg->num_elements; i++) {
 148                         const struct dsdb_attribute *attr;
 149                         bool is_sd, is_objectsid, is_instancetype, is_objectclass;
 150                         uint32_t access_mask;
 151                         attr = dsdb_attribute_by_lDAPDisplayName(ac->schema,
 152                                                                  msg->elements[i].name);
 153                         if (!attr) {
 154                                 ldb_debug_set(ldb, LDB_DEBUG_FATAL,
 155                                               "acl_read: %s cannot find attr[%s] in of schema\n",
 156                                               ldb_dn_get_linearized(msg->dn),
 157                                               msg->elements[i].name);
 158                                 ret = LDB_ERR_OPERATIONS_ERROR;
 159                                 goto fail;
 160                         }
 161                         is_sd = ldb_attr_cmp("nTSecurityDescriptor",
 162                                               msg->elements[i].name) == 0;
 163                         is_objectsid = ldb_attr_cmp("objectSid",
 164                                                     msg->elements[i].name) == 0;
 165                         is_instancetype = ldb_attr_cmp("instanceType",
 166                                                        msg->elements[i].name) == 0;
 167                         is_objectclass = ldb_attr_cmp("objectClass",
 168                                                       msg->elements[i].name) == 0;
 169                         /* these attributes were added to perform access checks and must be removed */
 170                         if (is_objectsid && ac->added_objectSid) {
 171                                 aclread_mark_inaccesslible(&msg->elements[i]);
 172                                 continue;
 173                         }
 174                         if (is_instancetype && ac->added_instanceType) {
 175                                 aclread_mark_inaccesslible(&msg->elements[i]);
 176                                 continue;
 177                         }
 178                         if (is_objectclass && ac->added_objectClass) {
 179                                 aclread_mark_inaccesslible(&msg->elements[i]);
 180                                 continue;
 181                         }
 182                         if (is_sd && ac->added_nTSecurityDescriptor) {
 183                                 aclread_mark_inaccesslible(&msg->elements[i]);
 184                                 continue;
 185                         }
 186                         /* nTSecurityDescriptor is a special case */
 187                         if (is_sd) {
 188                                 access_mask = 0;
 189
 190                                 if (ac->sd_flags & (SECINFO_OWNER|SECINFO_GROUP)) {
 191                                         access_mask |= SEC_STD_READ_CONTROL;
 192                                 }
 193                                 if (ac->sd_flags & SECINFO_DACL) {
 194                                         access_mask |= SEC_STD_READ_CONTROL;
 195                                 }
 196                                 if (ac->sd_flags & SECINFO_SACL) {
 197                                         access_mask |= SEC_FLAG_SYSTEM_SECURITY;
 198                                 }
 199                         } else {
 200                                 access_mask = SEC_ADS_READ_PROP;
 201                         }
 202
 203                         if (attr->searchFlags & SEARCH_FLAG_CONFIDENTIAL) {
 204                                 access_mask |= SEC_ADS_CONTROL_ACCESS;
 205                         }
 206
 207                         if (access_mask == 0) {
 208                                 aclread_mark_inaccesslible(&msg->elements[i]);
 209                                 continue;
 210                         }
 211
 212                         ret = acl_check_access_on_attribute(ac->module,
 213                                                             tmp_ctx,
 214                                                             sd,
 215                                                             sid,
 216                                                             access_mask,
 217                                                             attr,
 218                                                             objectclass);
 219
 220                         /*
 221                          * Dirsync control needs the replpropertymetadata attribute
 222                          * so return it as it will be removed by the control
 223                          * in anycase.
 224                          */
 225                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 226                                 if (!ac->indirsync) {
 227                                         /*
 228                                          * do not return this entry if attribute is
 229                                          * part of the search filter
 230                                          */
 231                                         if (dsdb_attr_in_parse_tree(ac->req->op.search.tree,
 232                                                                 msg->elements[i].name)) {
 233                                                 talloc_free(tmp_ctx);
 234                                                 return LDB_SUCCESS;
 235                                         }
 236                                         aclread_mark_inaccesslible(&msg->elements[i]);
 237                                 } else {
 238                                         /*
 239                                          * We are doing dirysnc answers
 240                                          * and the object shouldn't be returned (normally)
 241                                          * but we will return it without replPropertyMetaData
 242                                          * so that the dirysync module will do what is needed
 243                                          * (remove the object if it is not deleted, or return
 244                                          * just the objectGUID if it's deleted).
 245                                          */
 246                                         if (dsdb_attr_in_parse_tree(ac->req->op.search.tree,
 247                                                                 msg->elements[i].name)) {
 248                                                 ldb_msg_remove_attr(msg, "replPropertyMetaData");
 249                                                 break;
 250                                         } else {
 251                                                 aclread_mark_inaccesslible(&msg->elements[i]);
 252                                         }
 253                                 }
 254                         } else if (ret != LDB_SUCCESS) {
 255                                 ldb_debug_set(ldb, LDB_DEBUG_FATAL,
 256                                               "acl_read: %s check attr[%s] gives %s - %s\n",
 257                                               ldb_dn_get_linearized(msg->dn),
 258                                               msg->elements[i].name,
 259                                               ldb_strerror(ret),
 260                                               ldb_errstring(ldb));
 261                                 goto fail;
 262                         }
 263                 }
 264                 for (i=0; i < msg->num_elements; i++) {
 265                         if (!aclread_is_inaccessible(&msg->elements[i])) {
 266                                 num_of_attrs++;
 267                         }
 268                 }
 269                 /*create a new message to return*/
 270                 ret_msg = ldb_msg_new(ac->req);
 271                 ret_msg->dn = msg->dn;
 272                 talloc_steal(ret_msg, msg->dn);
 273                 ret_msg->num_elements = num_of_attrs;
 274                 if (num_of_attrs > 0) {
 275                         ret_msg->elements = talloc_array(ret_msg,
 276                                                          struct ldb_message_element,
 277                                                          num_of_attrs);
 278                         if (ret_msg->elements == NULL) {
 279                                 return ldb_oom(ldb);
 280                         }
 281                         for (i=0; i < msg->num_elements; i++) {
 282                                 bool to_remove = aclread_is_inaccessible(&msg->elements[i]);
 283                                 if (!to_remove) {
 284                                         ret_msg->elements[k] = msg->elements[i];
 285                                         talloc_steal(ret_msg->elements, msg->elements[i].name);
 286                                         talloc_steal(ret_msg->elements, msg->elements[i].values);
 287                                         k++;
 288                                 }
 289                         }
 290                         /*
 291                          * This should not be needed, but some modules
 292                          * may allocate values on the wrong context...
 293                          */
 294                         talloc_steal(ret_msg->elements, msg);
 295                 } else {
 296                         ret_msg->elements = NULL;
 297                 }
 298                 talloc_free(tmp_ctx);
 299
 300                 return ldb_module_send_entry(ac->req, ret_msg, ares->controls);
 301         case LDB_REPLY_REFERRAL:
 302                 return ldb_module_send_referral(ac->req, ares->referral);
 303         case LDB_REPLY_DONE:
 304                 return ldb_module_done(ac->req, ares->controls,
 305                                         ares->response, LDB_SUCCESS);
 306
 307         }
 308         return LDB_SUCCESS;
 309 fail:
 310         talloc_free(tmp_ctx);
 311         return ldb_module_done(ac->req, NULL, NULL, ret);
 312 }
 313
 314
 315 static int aclread_search(struct ldb_module *module, struct ldb_request *req)
 316 {
 317         struct ldb_context *ldb;
 318         int ret;
 319         struct aclread_context *ac;
 320         struct ldb_request *down_req;
 321         struct ldb_control *as_system = ldb_request_get_control(req, LDB_CONTROL_AS_SYSTEM_OID);
 322         uint32_t flags = ldb_req_get_custom_flags(req);
 323         struct ldb_result *res;
 324         struct aclread_private *p;
 325         bool need_sd = false;
 326         bool explicit_sd_flags = false;
 327         bool is_untrusted = ldb_req_is_untrusted(req);
 328         static const char * const _all_attrs[] = { "*", NULL };
 329         bool all_attrs = false;
 330         const char * const *attrs = NULL;
 331         uint32_t instanceType;
 332         static const char *acl_attrs[] = {
 333                 "instanceType",
 334                 NULL
 335         };
 336
 337         ldb = ldb_module_get_ctx(module);
 338         p = talloc_get_type(ldb_module_get_private(module), struct aclread_private);
 339
 340         /* skip access checks if we are system or system control is supplied
 341          * or this is not LDAP server request */
 342         if (!p || !p->enabled ||
 343             dsdb_module_am_system(module)
 344             || as_system || !is_untrusted) {
 345                 return ldb_next_request(module, req);
 346         }
 347         /* no checks on special dn */
 348         if (ldb_dn_is_special(req->op.search.base)) {
 349                 return ldb_next_request(module, req);
 350         }
 351
 352         /* check accessibility of base */
 353         if (!ldb_dn_is_null(req->op.search.base)) {
 354                 ret = dsdb_module_search_dn(module, req, &res, req->op.search.base,
 355                                             acl_attrs,
 356                                             DSDB_FLAG_NEXT_MODULE |
 357                                             DSDB_FLAG_AS_SYSTEM |
 358                                             DSDB_SEARCH_SHOW_RECYCLED,
 359                                             req);
 360                 if (ret != LDB_SUCCESS) {
 361                         return ldb_error(ldb, ret,
 362                                         "acl_read: Error retrieving instanceType for base.");
 363                 }
 364                 instanceType = ldb_msg_find_attr_as_uint(res->msgs[0],
 365                                                         "instanceType", 0);
 366                 if (instanceType != 0 && !(instanceType & INSTANCE_TYPE_IS_NC_HEAD))
 367                 {
 368                         /* the object has a parent, so we have to check for visibility */
 369                         struct ldb_dn *parent_dn = ldb_dn_get_parent(req, req->op.search.base);
 370                         ret = dsdb_module_check_access_on_dn(module,
 371                                                              req,
 372                                                              parent_dn,
 373                                                              SEC_ADS_LIST,
 374                                                              NULL, req);
 375                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 376                                 return ldb_module_done(req, NULL, NULL, LDB_ERR_NO_SUCH_OBJECT);
 377                         } else if (ret != LDB_SUCCESS) {
 378                                 return ldb_module_done(req, NULL, NULL, ret);
 379                         }
 380                 }
 381         }
 382         ac = talloc_zero(req, struct aclread_context);
 383         if (ac == NULL) {
 384                 return ldb_oom(ldb);
 385         }
 386         ac->module = module;
 387         ac->req = req;
 388         ac->schema = dsdb_get_schema(ldb, req);
 389         if (flags & DSDB_ACL_CHECKS_DIRSYNC_FLAG) {
 390                 ac->indirsync = true;
 391         } else {
 392                 ac->indirsync = false;
 393         }
 394         if (!ac->schema) {
 395                 return ldb_operr(ldb);
 396         }
 397
 398         attrs = req->op.search.attrs;
 399         if (attrs == NULL) {
 400                 all_attrs = true;
 401                 attrs = _all_attrs;
 402         } else if (attrs[0] == NULL) {
 403                 all_attrs = true;
 404                 attrs = _all_attrs;
 405         } else if (ldb_attr_in_list(attrs, "*")) {
 406                 all_attrs = true;
 407         }
 408
 409         /*
 410          * In theory we should also check for the SD control but control verification is
 411          * expensive so we'd better had the ntsecuritydescriptor to the list of
 412          * searched attribute and then remove it !
 413          */
 414         ac->sd_flags = dsdb_request_sd_flags(ac->req, &explicit_sd_flags);
 415
 416         if (ldb_attr_in_list(attrs, "nTSecurityDescriptor")) {
 417                 need_sd = false;
 418         } else if (explicit_sd_flags && all_attrs) {
 419                 need_sd = false;
 420         } else {
 421                 need_sd = true;
 422         }
 423
 424         if (!all_attrs) {
 425                 if (!ldb_attr_in_list(attrs, "instanceType")) {
 426                         attrs = ldb_attr_list_copy_add(ac, attrs, "instanceType");
 427                         if (attrs == NULL) {
 428                                 return ldb_oom(ldb);
 429                         }
 430                         ac->added_instanceType = true;
 431                 }
 432                 if (!ldb_attr_in_list(req->op.search.attrs, "objectSid")) {
 433                         attrs = ldb_attr_list_copy_add(ac, attrs, "objectSid");
 434                         if (attrs == NULL) {
 435                                 return ldb_oom(ldb);
 436                         }
 437                         ac->added_objectSid = true;
 438                 }
 439                 if (!ldb_attr_in_list(req->op.search.attrs, "objectClass")) {
 440                         attrs = ldb_attr_list_copy_add(ac, attrs, "objectClass");
 441                         if (attrs == NULL) {
 442                                 return ldb_oom(ldb);
 443                         }
 444                         ac->added_objectClass = true;
 445                 }
 446         }
 447
 448         if (need_sd) {
 449                 attrs = ldb_attr_list_copy_add(ac, attrs, "nTSecurityDescriptor");
 450                 if (attrs == NULL) {
 451                         return ldb_oom(ldb);
 452                 }
 453                 ac->added_nTSecurityDescriptor = true;
 454         }
 455
 456         ac->attrs = req->op.search.attrs;
 457         ret = ldb_build_search_req_ex(&down_req,
 458                                       ldb, ac,
 459                                       req->op.search.base,
 460                                       req->op.search.scope,
 461                                       req->op.search.tree,
 462                                       attrs,
 463                                       req->controls,
 464                                       ac, aclread_callback,
 465                                       req);
 466
 467         if (ret != LDB_SUCCESS) {
 468                 return LDB_ERR_OPERATIONS_ERROR;
 469         }
 470
 471         return ldb_next_request(module, down_req);
 472 }
 473
 474 static int aclread_init(struct ldb_module *module)
 475 {
 476         struct ldb_context *ldb = ldb_module_get_ctx(module);
 477         struct aclread_private *p = talloc_zero(module, struct aclread_private);
 478         if (p == NULL) {
 479                 return ldb_module_oom(module);
 480         }
 481         p->enabled = lpcfg_parm_bool(ldb_get_opaque(ldb, "loadparm"), NULL, "acl", "search", true);
 482         ldb_module_set_private(module, p);
 483         return ldb_next_init(module);
 484 }
 485
 486 static const struct ldb_module_ops ldb_aclread_module_ops = {
 487         .name              = "aclread",
 488         .search            = aclread_search,
 489         .init_context      = aclread_init
 490 };
 491
 492 int ldb_aclread_module_init(const char *version)
 493 {
 494         LDB_MODULE_CHECK_VERSION(version);
 495         return ldb_register_module(&ldb_aclread_module_ops);
 496 }