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 indirsync;
  52 };
  53
  54 struct aclread_private {
  55         bool enabled;
  56 };
  57
  58 static void aclread_mark_inaccesslible(struct ldb_message_element *el) {
  59         el->flags |= LDB_FLAG_INTERNAL_INACCESSIBLE_ATTRIBUTE;
  60 }
  61
  62 static bool aclread_is_inaccessible(struct ldb_message_element *el) {
  63         return el->flags & LDB_FLAG_INTERNAL_INACCESSIBLE_ATTRIBUTE;
  64 }
  65
  66 static int aclread_callback(struct ldb_request *req, struct ldb_reply *ares)
  67 {
  68         struct ldb_context *ldb;
  69         struct aclread_context *ac;
  70         struct ldb_message *ret_msg;
  71         struct ldb_message *msg;
  72         int ret, num_of_attrs = 0;
  73         unsigned int i, k = 0;
  74         struct security_descriptor *sd;
  75         struct dom_sid *sid = NULL;
  76         TALLOC_CTX *tmp_ctx;
  77         uint32_t instanceType;
  78
  79         ac = talloc_get_type(req->context, struct aclread_context);
  80         ldb = ldb_module_get_ctx(ac->module);
  81         if (!ares) {
  82                 return ldb_module_done(ac->req, NULL, NULL, LDB_ERR_OPERATIONS_ERROR );
  83         }
  84         if (ares->error != LDB_SUCCESS) {
  85                 return ldb_module_done(ac->req, ares->controls,
  86                                        ares->response, ares->error);
  87         }
  88         tmp_ctx = talloc_new(ac);
  89         switch (ares->type) {
  90         case LDB_REPLY_ENTRY:
  91                 msg = ares->message;
  92                 ret = dsdb_get_sd_from_ldb_message(ldb, tmp_ctx, msg, &sd);
  93                 if (ret != LDB_SUCCESS || sd == NULL ) {
  94                         ldb_debug_set(ldb, LDB_DEBUG_FATAL,
  95                                       "acl_read: cannot get descriptor of %s\n",
  96                                       ldb_dn_get_linearized(msg->dn));
  97                         ret = LDB_ERR_OPERATIONS_ERROR;
  98                         goto fail;
  99                 }
 100                 sid = samdb_result_dom_sid(tmp_ctx, msg, "objectSid");
 101                 /* get the object instance type */
 102                 instanceType = ldb_msg_find_attr_as_uint(msg,
 103                                                          "instanceType", 0);
 104                 if (!ldb_dn_is_null(msg->dn) && !(instanceType & INSTANCE_TYPE_IS_NC_HEAD))
 105                 {
 106                         /* the object has a parent, so we have to check for visibility */
 107                         struct ldb_dn *parent_dn = ldb_dn_get_parent(tmp_ctx, msg->dn);
 108
 109                         ret = dsdb_module_check_access_on_dn(ac->module,
 110                                                              tmp_ctx,
 111                                                              parent_dn,
 112                                                              SEC_ADS_LIST,
 113                                                              NULL, req);
 114                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 115                                 talloc_free(tmp_ctx);
 116                                 return LDB_SUCCESS;
 117                         } else if (ret != LDB_SUCCESS) {
 118                                 ldb_debug_set(ldb, LDB_DEBUG_FATAL,
 119                                               "acl_read: %s check parent %s - %s\n",
 120                                               ldb_dn_get_linearized(msg->dn),
 121                                               ldb_strerror(ret),
 122                                               ldb_errstring(ldb));
 123                                 goto fail;
 124                         }
 125                 }
 126                 /* for every element in the message check RP */
 127                 for (i=0; i < msg->num_elements; i++) {
 128                         const struct dsdb_attribute *attr;
 129                         bool is_sd, is_objectsid, is_instancetype;
 130                         uint32_t access_mask;
 131                         attr = dsdb_attribute_by_lDAPDisplayName(ac->schema,
 132                                                                  msg->elements[i].name);
 133                         if (!attr) {
 134                                 ldb_debug_set(ldb, LDB_DEBUG_FATAL,
 135                                               "acl_read: %s cannot find attr[%s] in of schema\n",
 136                                               ldb_dn_get_linearized(msg->dn),
 137                                               msg->elements[i].name);
 138                                 ret = LDB_ERR_OPERATIONS_ERROR;
 139                                 goto fail;
 140                         }
 141                         is_sd = ldb_attr_cmp("nTSecurityDescriptor",
 142                                               msg->elements[i].name) == 0;
 143                         is_objectsid = ldb_attr_cmp("objectSid",
 144                                                     msg->elements[i].name) == 0;
 145                         is_instancetype = ldb_attr_cmp("instanceType",
 146                                                        msg->elements[i].name) == 0;
 147                         /* these attributes were added to perform access checks and must be removed */
 148                         if (is_objectsid && ac->added_objectSid) {
 149                                 aclread_mark_inaccesslible(&msg->elements[i]);
 150                                 continue;
 151                         }
 152                         if (is_instancetype && ac->added_instanceType) {
 153                                 aclread_mark_inaccesslible(&msg->elements[i]);
 154                                 continue;
 155                         }
 156                         if (is_sd && ac->added_nTSecurityDescriptor) {
 157                                 aclread_mark_inaccesslible(&msg->elements[i]);
 158                                 continue;
 159                         }
 160                         /* nTSecurityDescriptor is a special case */
 161                         if (is_sd) {
 162                                 access_mask = 0;
 163
 164                                 if (ac->sd_flags & (SECINFO_OWNER|SECINFO_GROUP)) {
 165                                         access_mask |= SEC_STD_READ_CONTROL;
 166                                 }
 167                                 if (ac->sd_flags & SECINFO_DACL) {
 168                                         access_mask |= SEC_STD_READ_CONTROL;
 169                                 }
 170                                 if (ac->sd_flags & SECINFO_SACL) {
 171                                         access_mask |= SEC_FLAG_SYSTEM_SECURITY;
 172                                 }
 173                         } else {
 174                                 access_mask = SEC_ADS_READ_PROP;
 175                         }
 176
 177                         if (attr->searchFlags & SEARCH_FLAG_CONFIDENTIAL) {
 178                                 access_mask |= SEC_ADS_CONTROL_ACCESS;
 179                         }
 180
 181                         if (access_mask == 0) {
 182                                 aclread_mark_inaccesslible(&msg->elements[i]);
 183                                 continue;
 184                         }
 185
 186                         ret = acl_check_access_on_attribute(ac->module,
 187                                                             tmp_ctx,
 188                                                             sd,
 189                                                             sid,
 190                                                             access_mask,
 191                                                             attr);
 192
 193                         /*
 194                          * Dirsync control needs the replpropertymetadata attribute
 195                          * so return it as it will be removed by the control
 196                          * in anycase.
 197                          */
 198                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 199                                 if (!ac->indirsync) {
 200                                         /*
 201                                          * do not return this entry if attribute is
 202                                          * part of the search filter
 203                                          */
 204                                         if (dsdb_attr_in_parse_tree(ac->req->op.search.tree,
 205                                                                 msg->elements[i].name)) {
 206                                                 talloc_free(tmp_ctx);
 207                                                 return LDB_SUCCESS;
 208                                         }
 209                                         aclread_mark_inaccesslible(&msg->elements[i]);
 210                                 } else {
 211                                         /*
 212                                          * We are doing dirysnc answers
 213                                          * and the object shouldn't be returned (normally)
 214                                          * but we will return it without replPropertyMetaData
 215                                          * so that the dirysync module will do what is needed
 216                                          * (remove the object if it is not deleted, or return
 217                                          * just the objectGUID if it's deleted).
 218                                          */
 219                                         if (dsdb_attr_in_parse_tree(ac->req->op.search.tree,
 220                                                                 msg->elements[i].name)) {
 221                                                 ldb_msg_remove_attr(msg, "replPropertyMetaData");
 222                                                 break;
 223                                         } else {
 224                                                 aclread_mark_inaccesslible(&msg->elements[i]);
 225                                         }
 226                                 }
 227                         } else if (ret != LDB_SUCCESS) {
 228                                 ldb_debug_set(ldb, LDB_DEBUG_FATAL,
 229                                               "acl_read: %s check attr[%s] gives %s - %s\n",
 230                                               ldb_dn_get_linearized(msg->dn),
 231                                               msg->elements[i].name,
 232                                               ldb_strerror(ret),
 233                                               ldb_errstring(ldb));
 234                                 goto fail;
 235                         }
 236                 }
 237                 for (i=0; i < msg->num_elements; i++) {
 238                         if (!aclread_is_inaccessible(&msg->elements[i])) {
 239                                 num_of_attrs++;
 240                         }
 241                 }
 242                 /*create a new message to return*/
 243                 ret_msg = ldb_msg_new(ac->req);
 244                 ret_msg->dn = msg->dn;
 245                 talloc_steal(ret_msg, msg->dn);
 246                 ret_msg->num_elements = num_of_attrs;
 247                 if (num_of_attrs > 0) {
 248                         ret_msg->elements = talloc_array(ret_msg,
 249                                                          struct ldb_message_element,
 250                                                          num_of_attrs);
 251                         if (ret_msg->elements == NULL) {
 252                                 return ldb_oom(ldb);
 253                         }
 254                         for (i=0; i < msg->num_elements; i++) {
 255                                 bool to_remove = aclread_is_inaccessible(&msg->elements[i]);
 256                                 if (!to_remove) {
 257                                         ret_msg->elements[k] = msg->elements[i];
 258                                         talloc_steal(ret_msg->elements, msg->elements[i].name);
 259                                         talloc_steal(ret_msg->elements, msg->elements[i].values);
 260                                         k++;
 261                                 }
 262                         }
 263                         /*
 264                          * This should not be needed, but some modules
 265                          * may allocate values on the wrong context...
 266                          */
 267                         talloc_steal(ret_msg->elements, msg);
 268                 } else {
 269                         ret_msg->elements = NULL;
 270                 }
 271                 talloc_free(tmp_ctx);
 272
 273                 return ldb_module_send_entry(ac->req, ret_msg, ares->controls);
 274         case LDB_REPLY_REFERRAL:
 275                 return ldb_module_send_referral(ac->req, ares->referral);
 276         case LDB_REPLY_DONE:
 277                 return ldb_module_done(ac->req, ares->controls,
 278                                         ares->response, LDB_SUCCESS);
 279
 280         }
 281         return LDB_SUCCESS;
 282 fail:
 283         talloc_free(tmp_ctx);
 284         return ldb_module_done(ac->req, NULL, NULL, ret);
 285 }
 286
 287
 288 static int aclread_search(struct ldb_module *module, struct ldb_request *req)
 289 {
 290         struct ldb_context *ldb;
 291         int ret;
 292         struct aclread_context *ac;
 293         struct ldb_request *down_req;
 294         struct ldb_control *as_system = ldb_request_get_control(req, LDB_CONTROL_AS_SYSTEM_OID);
 295         uint32_t flags = ldb_req_get_custom_flags(req);
 296         struct ldb_result *res;
 297         struct aclread_private *p;
 298         bool need_sd = false;
 299         bool explicit_sd_flags = false;
 300         bool is_untrusted = ldb_req_is_untrusted(req);
 301         static const char * const _all_attrs[] = { "*", NULL };
 302         bool all_attrs = false;
 303         const char * const *attrs = NULL;
 304         uint32_t instanceType;
 305         static const char *acl_attrs[] = {
 306                 "instanceType",
 307                 NULL
 308         };
 309
 310         ldb = ldb_module_get_ctx(module);
 311         p = talloc_get_type(ldb_module_get_private(module), struct aclread_private);
 312
 313         /* skip access checks if we are system or system control is supplied
 314          * or this is not LDAP server request */
 315         if (!p || !p->enabled ||
 316             dsdb_module_am_system(module)
 317             || as_system || !is_untrusted) {
 318                 return ldb_next_request(module, req);
 319         }
 320         /* no checks on special dn */
 321         if (ldb_dn_is_special(req->op.search.base)) {
 322                 return ldb_next_request(module, req);
 323         }
 324
 325         /* check accessibility of base */
 326         if (!ldb_dn_is_null(req->op.search.base)) {
 327                 ret = dsdb_module_search_dn(module, req, &res, req->op.search.base,
 328                                             acl_attrs,
 329                                             DSDB_FLAG_NEXT_MODULE |
 330                                             DSDB_FLAG_AS_SYSTEM |
 331                                             DSDB_SEARCH_SHOW_RECYCLED,
 332                                             req);
 333                 if (ret != LDB_SUCCESS) {
 334                         return ldb_error(ldb, ret,
 335                                         "acl_read: Error retrieving instanceType for base.");
 336                 }
 337                 instanceType = ldb_msg_find_attr_as_uint(res->msgs[0],
 338                                                         "instanceType", 0);
 339                 if (instanceType != 0 && !(instanceType & INSTANCE_TYPE_IS_NC_HEAD))
 340                 {
 341                         /* the object has a parent, so we have to check for visibility */
 342                         struct ldb_dn *parent_dn = ldb_dn_get_parent(req, req->op.search.base);
 343                         ret = dsdb_module_check_access_on_dn(module,
 344                                                              req,
 345                                                              parent_dn,
 346                                                              SEC_ADS_LIST,
 347                                                              NULL, req);
 348                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 349                                 return ldb_module_done(req, NULL, NULL, LDB_ERR_NO_SUCH_OBJECT);
 350                         } else if (ret != LDB_SUCCESS) {
 351                                 return ldb_module_done(req, NULL, NULL, ret);
 352                         }
 353                 }
 354         }
 355         ac = talloc_zero(req, struct aclread_context);
 356         if (ac == NULL) {
 357                 return ldb_oom(ldb);
 358         }
 359         ac->module = module;
 360         ac->req = req;
 361         ac->schema = dsdb_get_schema(ldb, req);
 362         if (flags & DSDB_ACL_CHECKS_DIRSYNC_FLAG) {
 363                 ac->indirsync = true;
 364         } else {
 365                 ac->indirsync = false;
 366         }
 367         if (!ac->schema) {
 368                 return ldb_operr(ldb);
 369         }
 370
 371         attrs = req->op.search.attrs;
 372         if (attrs == NULL) {
 373                 all_attrs = true;
 374                 attrs = _all_attrs;
 375         } else if (attrs[0] == NULL) {
 376                 all_attrs = true;
 377                 attrs = _all_attrs;
 378         } else if (ldb_attr_in_list(attrs, "*")) {
 379                 all_attrs = true;
 380         }
 381
 382         /*
 383          * In theory we should also check for the SD control but control verification is
 384          * expensive so we'd better had the ntsecuritydescriptor to the list of
 385          * searched attribute and then remove it !
 386          */
 387         ac->sd_flags = dsdb_request_sd_flags(ac->req, &explicit_sd_flags);
 388
 389         if (ldb_attr_in_list(attrs, "nTSecurityDescriptor")) {
 390                 need_sd = false;
 391         } else if (explicit_sd_flags && all_attrs) {
 392                 need_sd = false;
 393         } else {
 394                 need_sd = true;
 395         }
 396
 397         if (!all_attrs) {
 398                 if (!ldb_attr_in_list(attrs, "instanceType")) {
 399                         attrs = ldb_attr_list_copy_add(ac, attrs, "instanceType");
 400                         if (attrs == NULL) {
 401                                 return ldb_oom(ldb);
 402                         }
 403                         ac->added_instanceType = true;
 404                 }
 405                 if (!ldb_attr_in_list(req->op.search.attrs, "objectSid")) {
 406                         attrs = ldb_attr_list_copy_add(ac, attrs, "objectSid");
 407                         if (attrs == NULL) {
 408                                 return ldb_oom(ldb);
 409                         }
 410                         ac->added_objectSid = true;
 411                 }
 412         }
 413
 414         if (need_sd) {
 415                 attrs = ldb_attr_list_copy_add(ac, attrs, "nTSecurityDescriptor");
 416                 if (attrs == NULL) {
 417                         return ldb_oom(ldb);
 418                 }
 419                 ac->added_nTSecurityDescriptor = true;
 420         }
 421
 422         ac->attrs = req->op.search.attrs;
 423         ret = ldb_build_search_req_ex(&down_req,
 424                                       ldb, ac,
 425                                       req->op.search.base,
 426                                       req->op.search.scope,
 427                                       req->op.search.tree,
 428                                       attrs,
 429                                       req->controls,
 430                                       ac, aclread_callback,
 431                                       req);
 432
 433         if (ret != LDB_SUCCESS) {
 434                 return LDB_ERR_OPERATIONS_ERROR;
 435         }
 436
 437         return ldb_next_request(module, down_req);
 438 }
 439
 440 static int aclread_init(struct ldb_module *module)
 441 {
 442         struct ldb_context *ldb = ldb_module_get_ctx(module);
 443         struct aclread_private *p = talloc_zero(module, struct aclread_private);
 444         if (p == NULL) {
 445                 return ldb_module_oom(module);
 446         }
 447         p->enabled = lpcfg_parm_bool(ldb_get_opaque(ldb, "loadparm"), NULL, "acl", "search", true);
 448         ldb_module_set_private(module, p);
 449         return ldb_next_init(module);
 450 }
 451
 452 static const struct ldb_module_ops ldb_aclread_module_ops = {
 453         .name              = "aclread",
 454         .search            = aclread_search,
 455         .init_context      = aclread_init
 456 };
 457
 458 int ldb_aclread_module_init(const char *version)
 459 {
 460         LDB_MODULE_CHECK_VERSION(version);
 461         return ldb_register_module(&ldb_aclread_module_ops);
 462 }