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
 106                         ret = dsdb_module_check_access_on_dn(ac->module,
 107                                                              tmp_ctx,
 108                                                              parent_dn,
 109                                                              SEC_ADS_LIST,
 110                                                              NULL, req);
 111                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 112                                 talloc_free(tmp_ctx);
 113                                 return LDB_SUCCESS;
 114                         } else if (ret != LDB_SUCCESS) {
 115                                 goto fail;
 116                         }
 117                 }
 118                 /* for every element in the message check RP */
 119                 for (i=0; i < msg->num_elements; i++) {
 120                         const struct dsdb_attribute *attr;
 121                         bool is_sd, is_objectsid, is_instancetype;
 122                         uint32_t access_mask;
 123                         attr = dsdb_attribute_by_lDAPDisplayName(ac->schema,
 124                                                                  msg->elements[i].name);
 125                         if (!attr) {
 126                                 DEBUG(2, ("acl_read: cannot find attribute %s in schema\n",
 127                                            msg->elements[i].name));
 128                                 ret = LDB_ERR_OPERATIONS_ERROR;
 129                                 goto fail;
 130                         }
 131                         is_sd = ldb_attr_cmp("nTSecurityDescriptor",
 132                                               msg->elements[i].name) == 0;
 133                         is_objectsid = ldb_attr_cmp("objectSid",
 134                                                     msg->elements[i].name) == 0;
 135                         is_instancetype = ldb_attr_cmp("instanceType",
 136                                                        msg->elements[i].name) == 0;
 137                         /* these attributes were added to perform access checks and must be removed */
 138                         if (is_objectsid && ac->object_sid) {
 139                                 aclread_mark_inaccesslible(&msg->elements[i]);
 140                                 continue;
 141                         }
 142                         if (is_instancetype && ac->instance_type) {
 143                                 aclread_mark_inaccesslible(&msg->elements[i]);
 144                                 continue;
 145                         }
 146                         if (is_sd && ac->sd) {
 147                                 aclread_mark_inaccesslible(&msg->elements[i]);
 148                                 continue;
 149                         }
 150                         /* nTSecurityDescriptor is a special case */
 151                         if (is_sd) {
 152                                 access_mask = SEC_FLAG_SYSTEM_SECURITY|SEC_STD_READ_CONTROL;
 153                         } else {
 154                                 access_mask = SEC_ADS_READ_PROP;
 155                         }
 156
 157                         if (attr->searchFlags & SEARCH_FLAG_CONFIDENTIAL) {
 158                                 access_mask |= SEC_ADS_CONTROL_ACCESS;
 159                         }
 160
 161                         ret = acl_check_access_on_attribute(ac->module,
 162                                                             tmp_ctx,
 163                                                             sd,
 164                                                             sid,
 165                                                             access_mask,
 166                                                             attr);
 167
 168                         /*
 169                          * Dirsync control needs the replpropertymetadata attribute
 170                          * so return it as it will be removed by the control
 171                          * in anycase.
 172                          */
 173                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 174                                 if (!ac->indirsync) {
 175                                         /*
 176                                          * do not return this entry if attribute is
 177                                          * part of the search filter
 178                                          */
 179                                         if (dsdb_attr_in_parse_tree(ac->req->op.search.tree,
 180                                                                 msg->elements[i].name)) {
 181                                                 talloc_free(tmp_ctx);
 182                                                 return LDB_SUCCESS;
 183                                         }
 184                                         aclread_mark_inaccesslible(&msg->elements[i]);
 185                                 } else {
 186                                         /*
 187                                          * We are doing dirysnc answers
 188                                          * and the object shouldn't be returned (normally)
 189                                          * but we will return it without replPropertyMetaData
 190                                          * so that the dirysync module will do what is needed
 191                                          * (remove the object if it is not deleted, or return
 192                                          * just the objectGUID if it's deleted).
 193                                          */
 194                                         if (dsdb_attr_in_parse_tree(ac->req->op.search.tree,
 195                                                                 msg->elements[i].name)) {
 196                                                 ldb_msg_remove_attr(msg, "replPropertyMetaData");
 197                                                 break;
 198                                         } else {
 199                                                 aclread_mark_inaccesslible(&msg->elements[i]);
 200                                         }
 201                                 }
 202                         } else if (ret != LDB_SUCCESS) {
 203                                 goto fail;
 204                         }
 205                 }
 206                 for (i=0; i < msg->num_elements; i++) {
 207                         if (!aclread_is_inaccessible(&msg->elements[i])) {
 208                                 num_of_attrs++;
 209                         }
 210                 }
 211                 /*create a new message to return*/
 212                 ret_msg = ldb_msg_new(ac->req);
 213                 ret_msg->dn = msg->dn;
 214                 talloc_steal(ret_msg, msg->dn);
 215                 ret_msg->num_elements = num_of_attrs;
 216                 if (num_of_attrs > 0) {
 217                         ret_msg->elements = talloc_array(ret_msg,
 218                                                          struct ldb_message_element,
 219                                                          num_of_attrs);
 220                         if (ret_msg->elements == NULL) {
 221                                 return ldb_oom(ldb);
 222                         }
 223                         for (i=0; i < msg->num_elements; i++) {
 224                                 bool to_remove = aclread_is_inaccessible(&msg->elements[i]);
 225                                 if (!to_remove) {
 226                                         ret_msg->elements[k] = msg->elements[i];
 227                                         talloc_steal(ret_msg->elements, msg->elements[i].name);
 228                                         talloc_steal(ret_msg->elements, msg->elements[i].values);
 229                                         k++;
 230                                 }
 231                         }
 232                 } else {
 233                         ret_msg->elements = NULL;
 234                 }
 235                 talloc_free(tmp_ctx);
 236
 237                 return ldb_module_send_entry(ac->req, ret_msg, ares->controls);
 238         case LDB_REPLY_REFERRAL:
 239                 return ldb_module_send_referral(ac->req, ares->referral);
 240         case LDB_REPLY_DONE:
 241                 return ldb_module_done(ac->req, ares->controls,
 242                                         ares->response, LDB_SUCCESS);
 243
 244         }
 245         return LDB_SUCCESS;
 246 fail:
 247         talloc_free(tmp_ctx);
 248         return ldb_module_done(ac->req, NULL, NULL, ret);
 249 }
 250
 251
 252 static int aclread_search(struct ldb_module *module, struct ldb_request *req)
 253 {
 254         struct ldb_context *ldb;
 255         int ret;
 256         struct aclread_context *ac;
 257         struct ldb_request *down_req;
 258         struct ldb_control *as_system = ldb_request_get_control(req, LDB_CONTROL_AS_SYSTEM_OID);
 259         uint32_t flags = ldb_req_get_custom_flags(req);
 260         struct ldb_result *res;
 261         struct aclread_private *p;
 262         bool is_untrusted = ldb_req_is_untrusted(req);
 263         const char * const *attrs = NULL;
 264         uint32_t instanceType;
 265         static const char *acl_attrs[] = {
 266                 "instanceType",
 267                 NULL
 268         };
 269
 270         ldb = ldb_module_get_ctx(module);
 271         p = talloc_get_type(ldb_module_get_private(module), struct aclread_private);
 272
 273         /* skip access checks if we are system or system control is supplied
 274          * or this is not LDAP server request */
 275         if (!p || !p->enabled ||
 276             dsdb_module_am_system(module)
 277             || as_system || !is_untrusted) {
 278                 return ldb_next_request(module, req);
 279         }
 280         /* no checks on special dn */
 281         if (ldb_dn_is_special(req->op.search.base)) {
 282                 return ldb_next_request(module, req);
 283         }
 284
 285         /* check accessibility of base */
 286         if (!ldb_dn_is_null(req->op.search.base)) {
 287                 ret = dsdb_module_search_dn(module, req, &res, req->op.search.base,
 288                                             acl_attrs,
 289                                             DSDB_FLAG_NEXT_MODULE |
 290                                             DSDB_FLAG_AS_SYSTEM |
 291                                             DSDB_SEARCH_SHOW_RECYCLED,
 292                                             req);
 293                 if (ret != LDB_SUCCESS) {
 294                         return ldb_error(ldb, ret,
 295                                         "acl_read: Error retrieving instanceType for base.");
 296                 }
 297                 instanceType = ldb_msg_find_attr_as_uint(res->msgs[0],
 298                                                         "instanceType", 0);
 299                 if (instanceType != 0 && !(instanceType & INSTANCE_TYPE_IS_NC_HEAD))
 300                 {
 301                         /* the object has a parent, so we have to check for visibility */
 302                         struct ldb_dn *parent_dn = ldb_dn_get_parent(req, req->op.search.base);
 303                         ret = dsdb_module_check_access_on_dn(module,
 304                                                              req,
 305                                                              parent_dn,
 306                                                              SEC_ADS_LIST,
 307                                                              NULL, req);
 308                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 309                                 return ldb_module_done(req, NULL, NULL, LDB_ERR_NO_SUCH_OBJECT);
 310                         } else if (ret != LDB_SUCCESS) {
 311                                 return ldb_module_done(req, NULL, NULL, ret);
 312                         }
 313                 }
 314         }
 315         ac = talloc_zero(req, struct aclread_context);
 316         if (ac == NULL) {
 317                 return ldb_oom(ldb);
 318         }
 319         ac->module = module;
 320         ac->req = req;
 321         ac->schema = dsdb_get_schema(ldb, req);
 322         if (flags & DSDB_ACL_CHECKS_DIRSYNC_FLAG) {
 323                 ac->indirsync = true;
 324         } else {
 325                 ac->indirsync = false;
 326         }
 327         if (!ac->schema) {
 328                 return ldb_operr(ldb);
 329         }
 330         /*
 331          * In theory we should also check for the SD control but control verification is
 332          * expensive so we'd better had the ntsecuritydescriptor to the list of
 333          * searched attribute and then remove it !
 334          */
 335         ac->sd = !(ldb_attr_in_list(req->op.search.attrs, "nTSecurityDescriptor"));
 336         if (req->op.search.attrs && !ldb_attr_in_list(req->op.search.attrs, "*")) {
 337                 if (!ldb_attr_in_list(req->op.search.attrs, "instanceType")) {
 338                         ac->instance_type = true;
 339                         attrs = ldb_attr_list_copy_add(ac, req->op.search.attrs, "instanceType");
 340                 } else {
 341                         attrs = req->op.search.attrs;
 342                 }
 343                 if (!ldb_attr_in_list(req->op.search.attrs, "objectSid")) {
 344                         ac->object_sid = true;
 345                         attrs = ldb_attr_list_copy_add(ac, attrs, "objectSid");
 346                 }
 347         }
 348
 349         if (ac->sd) {
 350                 /* avoid replacing all attributes with nTSecurityDescriptor
 351                  * if attribute list is empty */
 352                 if (!attrs) {
 353                         attrs = ldb_attr_list_copy_add(ac, req->op.search.attrs, "*");
 354                 }
 355                 attrs = ldb_attr_list_copy_add(ac, attrs, "nTSecurityDescriptor");
 356         }
 357         ac->attrs = req->op.search.attrs;
 358         ret = ldb_build_search_req_ex(&down_req,
 359                                       ldb, ac,
 360                                       req->op.search.base,
 361                                       req->op.search.scope,
 362                                       req->op.search.tree,
 363                                       attrs,
 364                                       req->controls,
 365                                       ac, aclread_callback,
 366                                       req);
 367
 368         if (ret != LDB_SUCCESS) {
 369                 return LDB_ERR_OPERATIONS_ERROR;
 370         }
 371
 372         return ldb_next_request(module, down_req);
 373 }
 374
 375 static int aclread_init(struct ldb_module *module)
 376 {
 377         struct ldb_context *ldb = ldb_module_get_ctx(module);
 378         struct aclread_private *p = talloc_zero(module, struct aclread_private);
 379         if (p == NULL) {
 380                 return ldb_module_oom(module);
 381         }
 382         p->enabled = lpcfg_parm_bool(ldb_get_opaque(ldb, "loadparm"), NULL, "acl", "search", false);
 383         ldb_module_set_private(module, p);
 384         return ldb_next_init(module);
 385 }
 386
 387 static const struct ldb_module_ops ldb_aclread_module_ops = {
 388         .name              = "aclread",
 389         .search            = aclread_search,
 390         .init_context      = aclread_init
 391 };
 392
 393 int ldb_aclread_module_init(const char *version)
 394 {
 395         LDB_MODULE_CHECK_VERSION(version);
 396         return ldb_register_module(&ldb_aclread_module_ops);
 397 }