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