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         bool sd;
  48         bool instance_type;
  49         bool object_sid;
  50         bool indirsync;
  51 };
  52
  53 struct aclread_private {
  54         bool enabled;
  55 };
  56
  57 static void aclread_mark_inaccesslible(struct ldb_message_element *el) {
  58          el->flags |= LDB_FLAG_INTERNAL_INACCESSIBLE_ATTRIBUTE;
  59 }
  60
  61 static bool aclread_is_inaccessible(struct ldb_message_element *el) {
  62         return el->flags & LDB_FLAG_INTERNAL_INACCESSIBLE_ATTRIBUTE;
  63 }
  64
  65 static int aclread_callback(struct ldb_request *req, struct ldb_reply *ares)
  66 {
  67          struct ldb_context *ldb;
  68          struct aclread_context *ac;
  69          struct ldb_message *ret_msg;
  70          struct ldb_message *msg;
  71          int ret, num_of_attrs = 0;
  72          unsigned int i, k = 0;
  73          struct security_descriptor *sd;
  74          struct dom_sid *sid = NULL;
  75          TALLOC_CTX *tmp_ctx;
  76          uint32_t instanceType;
  77
  78          ac = talloc_get_type(req->context, struct aclread_context);
  79          ldb = ldb_module_get_ctx(ac->module);
  80          if (!ares) {
  81                  return ldb_module_done(ac->req, NULL, NULL, LDB_ERR_OPERATIONS_ERROR );
  82          }
  83          if (ares->error != LDB_SUCCESS) {
  84                  return ldb_module_done(ac->req, ares->controls,
  85                                         ares->response, ares->error);
  86          }
  87          tmp_ctx = talloc_new(ac);
  88          switch (ares->type) {
  89          case LDB_REPLY_ENTRY:
  90                  msg = ares->message;
  91                  ret = dsdb_get_sd_from_ldb_message(ldb, tmp_ctx, msg, &sd);
  92                  if (ret != LDB_SUCCESS || sd == NULL ) {
  93                          DEBUG(10, ("acl_read: cannot get descriptor\n"));
  94                          ret = LDB_ERR_OPERATIONS_ERROR;
  95                          goto fail;
  96                  }
  97                  sid = samdb_result_dom_sid(tmp_ctx, msg, "objectSid");
  98                  /* get the object instance type */
  99                  instanceType = ldb_msg_find_attr_as_uint(msg,
 100                                                          "instanceType", 0);
 101                  if (!ldb_dn_is_null(msg->dn) && !(instanceType & INSTANCE_TYPE_IS_NC_HEAD))
 102                  {
 103                         /* the object has a parent, so we have to check for visibility */
 104                         struct ldb_dn *parent_dn = ldb_dn_get_parent(tmp_ctx, msg->dn);
 105                         ret = dsdb_module_check_access_on_dn(ac->module,
 106                                                              tmp_ctx,
 107                                                              parent_dn,
 108                                                              SEC_ADS_LIST,
 109                                                              NULL, req);
 110                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 111                                 talloc_free(tmp_ctx);
 112                                 return LDB_SUCCESS;
 113                         } else if (ret != LDB_SUCCESS) {
 114                                 goto fail;
 115                         }
 116                  }
 117                  /* for every element in the message check RP */
 118                  for (i=0; i < msg->num_elements; i++) {
 119                          const struct dsdb_attribute *attr;
 120                          bool is_sd, is_objectsid, is_instancetype;
 121                          uint32_t access_mask;
 122                          attr =  dsdb_attribute_by_lDAPDisplayName(ac->schema,
 123                                                                    msg->elements[i].name);
 124                          if (!attr) {
 125                                  DEBUG(2, ("acl_read: cannot find attribute %s in schema\n",
 126                                            msg->elements[i].name));
 127                                  ret = LDB_ERR_OPERATIONS_ERROR;
 128                                  goto fail;
 129                          }
 130                          is_sd = ldb_attr_cmp("nTSecurityDescriptor",
 131                                               msg->elements[i].name) == 0;
 132                          is_objectsid = ldb_attr_cmp("objectSid",
 133                                                      msg->elements[i].name) == 0;
 134                          is_instancetype = ldb_attr_cmp("instanceType",
 135                                                         msg->elements[i].name) == 0;
 136                          /* these attributes were added to perform access checks and must be removed */
 137                          if (is_objectsid && ac->object_sid) {
 138                                  aclread_mark_inaccesslible(&msg->elements[i]);
 139                                  continue;
 140                          }
 141                          if (is_instancetype && ac->instance_type) {
 142                                  aclread_mark_inaccesslible(&msg->elements[i]);
 143                                  continue;
 144                          }
 145                          if (is_sd && ac->sd) {
 146                                  aclread_mark_inaccesslible(&msg->elements[i]);
 147                                  continue;
 148                          }
 149                          /* nTSecurityDescriptor is a special case */
 150                          if (is_sd) {
 151                                  access_mask = SEC_FLAG_SYSTEM_SECURITY|SEC_STD_READ_CONTROL;
 152                          } else {
 153                                  access_mask = SEC_ADS_READ_PROP;
 154                          }
 155                          ret = acl_check_access_on_attribute(ac->module,
 156                                                              tmp_ctx,
 157                                                              sd,
 158                                                              sid,
 159                                                              access_mask,
 160                                                              attr);
 161
 162                         /*
 163                          * Dirsync control needs the replpropertymetadata attribute
 164                          * so return it as it will be removed by the control
 165                          * in anycase.
 166                          */
 167                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 168                                 if (!ac->indirsync) {
 169                                         /* do not return this entry if attribute is
 170                                         part of the search filter */
 171                                         if (dsdb_attr_in_parse_tree(ac->req->op.search.tree,
 172                                                                 msg->elements[i].name)) {
 173                                                 talloc_free(tmp_ctx);
 174                                                 return LDB_SUCCESS;
 175                                         }
 176                                         aclread_mark_inaccesslible(&msg->elements[i]);
 177                                 } else {
 178                                         /*
 179                                          * We are doing dirysnc answers
 180                                          * and the object shouldn't be returned (normally)
 181                                          * but we will return it without replPropertyMetaData
 182                                          * so that the dirysync module will do what is needed
 183                                          * (remove the object if it is not deleted, or return
 184                                          * just the objectGUID if it's deleted).
 185                                          */
 186                                         if (dsdb_attr_in_parse_tree(ac->req->op.search.tree,
 187                                                                 msg->elements[i].name)) {
 188                                                 ldb_msg_remove_attr(msg, "replPropertyMetaData");
 189                                                 break;
 190                                         } else {
 191                                                 aclread_mark_inaccesslible(&msg->elements[i]);
 192                                         }
 193                                 }
 194                         } else if (ret != LDB_SUCCESS) {
 195                                 goto fail;
 196                         }
 197                  }
 198                  for (i=0; i < msg->num_elements; i++) {
 199                          if (!aclread_is_inaccessible(&msg->elements[i])) {
 200                                  num_of_attrs++;
 201                          }
 202                  }
 203                  /*create a new message to return*/
 204                  ret_msg = ldb_msg_new(ac->req);
 205                  ret_msg->dn = msg->dn;
 206                  talloc_steal(ret_msg, msg->dn);
 207                  ret_msg->num_elements = num_of_attrs;
 208                  if (num_of_attrs > 0) {
 209                          ret_msg->elements = talloc_array(ret_msg,
 210                                                           struct ldb_message_element,
 211                                                           num_of_attrs);
 212                          if (ret_msg->elements == NULL) {
 213                                  return ldb_oom(ldb);
 214                          }
 215                          for (i=0; i < msg->num_elements; i++) {
 216                                  bool to_remove = aclread_is_inaccessible(&msg->elements[i]);
 217                                  if (!to_remove) {
 218                                          ret_msg->elements[k] = msg->elements[i];
 219                                          talloc_steal(ret_msg->elements, msg->elements[i].name);
 220                                          talloc_steal(ret_msg->elements, msg->elements[i].values);
 221                                          k++;
 222                                  }
 223                          }
 224                  } else {
 225                          ret_msg->elements = NULL;
 226                  }
 227                  talloc_free(tmp_ctx);
 228
 229                  return ldb_module_send_entry(ac->req, ret_msg, ares->controls);
 230          case LDB_REPLY_REFERRAL:
 231                  return ldb_module_send_referral(ac->req, ares->referral);
 232          case LDB_REPLY_DONE:
 233                  return ldb_module_done(ac->req, ares->controls,
 234                                         ares->response, LDB_SUCCESS);
 235
 236          }
 237          return LDB_SUCCESS;
 238 fail:
 239          talloc_free(tmp_ctx);
 240          return ldb_module_done(ac->req, NULL, NULL, ret);
 241 }
 242
 243
 244 static int aclread_search(struct ldb_module *module, struct ldb_request *req)
 245 {
 246         struct ldb_context *ldb;
 247         int ret;
 248         struct aclread_context *ac;
 249         struct ldb_request *down_req;
 250         struct ldb_control *as_system = ldb_request_get_control(req, LDB_CONTROL_AS_SYSTEM_OID);
 251         uint32_t flags = ldb_req_get_custom_flags(req);
 252         struct ldb_result *res;
 253         struct aclread_private *p;
 254         bool is_untrusted = ldb_req_is_untrusted(req);
 255         const char * const *attrs = NULL;
 256         uint32_t instanceType;
 257         static const char *acl_attrs[] = {
 258                  "instanceType",
 259                  NULL
 260         };
 261
 262         ldb = ldb_module_get_ctx(module);
 263         p = talloc_get_type(ldb_module_get_private(module), struct aclread_private);
 264
 265         /* skip access checks if we are system or system control is supplied
 266          * or this is not LDAP server request */
 267         if (!p || !p->enabled ||
 268             dsdb_module_am_system(module)
 269             || as_system || !is_untrusted) {
 270                 return ldb_next_request(module, req);
 271         }
 272         /* no checks on special dn */
 273         if (ldb_dn_is_special(req->op.search.base)) {
 274                 return ldb_next_request(module, req);
 275         }
 276
 277         /* check accessibility of base */
 278         if (!ldb_dn_is_null(req->op.search.base)) {
 279                 ret = dsdb_module_search_dn(module, req, &res, req->op.search.base,
 280                                             acl_attrs,
 281                                             DSDB_FLAG_NEXT_MODULE |
 282                                             DSDB_SEARCH_SHOW_DELETED, req);
 283                 if (ret != LDB_SUCCESS) {
 284                         return ldb_error(ldb, ret,
 285                                          "acl_read: Error retrieving instanceType for base.");
 286                 }
 287                 instanceType = ldb_msg_find_attr_as_uint(res->msgs[0],
 288                                                          "instanceType", 0);
 289                 if (instanceType != 0 && !(instanceType & INSTANCE_TYPE_IS_NC_HEAD))
 290                 {
 291                         /* the object has a parent, so we have to check for visibility */
 292                         struct ldb_dn *parent_dn = ldb_dn_get_parent(req, req->op.search.base);
 293                         ret = dsdb_module_check_access_on_dn(module,
 294                                                              req,
 295                                                              parent_dn,
 296                                                              SEC_ADS_LIST,
 297                                                              NULL, req);
 298                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 299                                 return ldb_module_done(req, NULL, NULL, LDB_ERR_NO_SUCH_OBJECT);
 300                         } else if (ret != LDB_SUCCESS) {
 301                                 return ldb_module_done(req, NULL, NULL, ret);
 302                         }
 303                 }
 304         }
 305         ac = talloc_zero(req, struct aclread_context);
 306         if (ac == NULL) {
 307                 return ldb_oom(ldb);
 308         }
 309         ac->module = module;
 310         ac->req = req;
 311         ac->schema = dsdb_get_schema(ldb, req);
 312         if (flags & DSDB_ACL_CHECKS_DIRSYNC_FLAG) {
 313                 ac->indirsync = true;
 314         } else {
 315                 ac->indirsync = false;
 316         }
 317         if (!ac->schema) {
 318                 return ldb_operr(ldb);
 319         }
 320         /*
 321          * In theory we should also check for the SD control but control verification is
 322          * expensive so we'd better had the ntsecuritydescriptor to the list of
 323          * searched attribute and then remove it !
 324          */
 325         ac->sd = !(ldb_attr_in_list(req->op.search.attrs, "nTSecurityDescriptor"));
 326         if (req->op.search.attrs && !ldb_attr_in_list(req->op.search.attrs, "*")) {
 327                 if (!ldb_attr_in_list(req->op.search.attrs, "instanceType")) {
 328                         ac->instance_type = true;
 329                         attrs = ldb_attr_list_copy_add(ac, req->op.search.attrs, "instanceType");
 330                 } else {
 331                         attrs = req->op.search.attrs;
 332                 }
 333                 if (!ldb_attr_in_list(req->op.search.attrs, "objectSid")) {
 334                         ac->object_sid = true;
 335                         attrs = ldb_attr_list_copy_add(ac, attrs, "objectSid");
 336                 }
 337         }
 338
 339         if (ac->sd) {
 340                 /* avoid replacing all attributes with nTSecurityDescriptor
 341                  * if attribute list is empty */
 342                 if (!attrs) {
 343                         attrs = ldb_attr_list_copy_add(ac, req->op.search.attrs, "*");
 344                 }
 345                 attrs = ldb_attr_list_copy_add(ac, attrs, "nTSecurityDescriptor");
 346         }
 347         ac->attrs = req->op.search.attrs;
 348         ret = ldb_build_search_req_ex(&down_req,
 349                                       ldb, ac,
 350                                       req->op.search.base,
 351                                       req->op.search.scope,
 352                                       req->op.search.tree,
 353                                       attrs,
 354                                       req->controls,
 355                                       ac, aclread_callback,
 356                                       req);
 357
 358         if (ret != LDB_SUCCESS) {
 359                 return LDB_ERR_OPERATIONS_ERROR;
 360         }
 361
 362         return ldb_next_request(module, down_req);
 363 }
 364
 365 static int aclread_init(struct ldb_module *module)
 366 {
 367         struct ldb_context *ldb = ldb_module_get_ctx(module);
 368         struct aclread_private *p = talloc_zero(module, struct aclread_private);
 369         if (p == NULL) {
 370                 return ldb_module_oom(module);
 371         }
 372         p->enabled = lpcfg_parm_bool(ldb_get_opaque(ldb, "loadparm"), NULL, "acl", "search", false);
 373         ldb_module_set_private(module, p);
 374         return ldb_next_init(module);
 375 }
 376
 377 static const struct ldb_module_ops ldb_aclread_module_ops = {
 378         .name              = "aclread",
 379         .search            = aclread_search,
 380         .init_context      = aclread_init
 381 };
 382
 383 int ldb_aclread_module_init(const char *version)
 384 {
 385         LDB_MODULE_CHECK_VERSION(version);
 386         return ldb_register_module(&ldb_aclread_module_ops);
 387 }