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 sd;
  49         bool instance_type;
  50         bool object_sid;
  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                         DEBUG(10, ("acl_read: cannot get descriptor\n"));
  95                         ret = LDB_ERR_OPERATIONS_ERROR;
  96                         goto fail;
  97                 }
  98                 sid = samdb_result_dom_sid(tmp_ctx, msg, "objectSid");
  99                 /* get the object instance type */
 100                 instanceType = ldb_msg_find_attr_as_uint(msg,
 101                                                          "instanceType", 0);
 102                 if (!ldb_dn_is_null(msg->dn) && !(instanceType & INSTANCE_TYPE_IS_NC_HEAD))
 103                 {
 104                         /* the object has a parent, so we have to check for visibility */
 105                         struct ldb_dn *parent_dn = ldb_dn_get_parent(tmp_ctx, msg->dn);
 106
 107                         ret = dsdb_module_check_access_on_dn(ac->module,
 108                                                              tmp_ctx,
 109                                                              parent_dn,
 110                                                              SEC_ADS_LIST,
 111                                                              NULL, req);
 112                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 113                                 talloc_free(tmp_ctx);
 114                                 return LDB_SUCCESS;
 115                         } else if (ret != LDB_SUCCESS) {
 116                                 goto fail;
 117                         }
 118                 }
 119                 /* for every element in the message check RP */
 120                 for (i=0; i < msg->num_elements; i++) {
 121                         const struct dsdb_attribute *attr;
 122                         bool is_sd, is_objectsid, is_instancetype;
 123                         uint32_t access_mask;
 124                         attr = dsdb_attribute_by_lDAPDisplayName(ac->schema,
 125                                                                  msg->elements[i].name);
 126                         if (!attr) {
 127                                 DEBUG(2, ("acl_read: cannot find attribute %s in schema\n",
 128                                            msg->elements[i].name));
 129                                 ret = LDB_ERR_OPERATIONS_ERROR;
 130                                 goto fail;
 131                         }
 132                         is_sd = ldb_attr_cmp("nTSecurityDescriptor",
 133                                               msg->elements[i].name) == 0;
 134                         is_objectsid = ldb_attr_cmp("objectSid",
 135                                                     msg->elements[i].name) == 0;
 136                         is_instancetype = ldb_attr_cmp("instanceType",
 137                                                        msg->elements[i].name) == 0;
 138                         /* these attributes were added to perform access checks and must be removed */
 139                         if (is_objectsid && ac->object_sid) {
 140                                 aclread_mark_inaccesslible(&msg->elements[i]);
 141                                 continue;
 142                         }
 143                         if (is_instancetype && ac->instance_type) {
 144                                 aclread_mark_inaccesslible(&msg->elements[i]);
 145                                 continue;
 146                         }
 147                         if (is_sd && ac->sd) {
 148                                 aclread_mark_inaccesslible(&msg->elements[i]);
 149                                 continue;
 150                         }
 151                         /* nTSecurityDescriptor is a special case */
 152                         if (is_sd) {
 153                                 access_mask = 0;
 154
 155                                 if (ac->sd_flags & (SECINFO_OWNER|SECINFO_GROUP)) {
 156                                         access_mask |= SEC_STD_READ_CONTROL;
 157                                 }
 158                                 if (ac->sd_flags & SECINFO_DACL) {
 159                                         access_mask |= SEC_STD_READ_CONTROL;
 160                                 }
 161                                 if (ac->sd_flags & SECINFO_SACL) {
 162                                         access_mask |= SEC_FLAG_SYSTEM_SECURITY;
 163                                 }
 164                         } else {
 165                                 access_mask = SEC_ADS_READ_PROP;
 166                         }
 167
 168                         if (attr->searchFlags & SEARCH_FLAG_CONFIDENTIAL) {
 169                                 access_mask |= SEC_ADS_CONTROL_ACCESS;
 170                         }
 171
 172                         if (access_mask == 0) {
 173                                 aclread_mark_inaccesslible(&msg->elements[i]);
 174                                 continue;
 175                         }
 176
 177                         ret = acl_check_access_on_attribute(ac->module,
 178                                                             tmp_ctx,
 179                                                             sd,
 180                                                             sid,
 181                                                             access_mask,
 182                                                             attr);
 183
 184                         /*
 185                          * Dirsync control needs the replpropertymetadata attribute
 186                          * so return it as it will be removed by the control
 187                          * in anycase.
 188                          */
 189                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 190                                 if (!ac->indirsync) {
 191                                         /*
 192                                          * do not return this entry if attribute is
 193                                          * part of the search filter
 194                                          */
 195                                         if (dsdb_attr_in_parse_tree(ac->req->op.search.tree,
 196                                                                 msg->elements[i].name)) {
 197                                                 talloc_free(tmp_ctx);
 198                                                 return LDB_SUCCESS;
 199                                         }
 200                                         aclread_mark_inaccesslible(&msg->elements[i]);
 201                                 } else {
 202                                         /*
 203                                          * We are doing dirysnc answers
 204                                          * and the object shouldn't be returned (normally)
 205                                          * but we will return it without replPropertyMetaData
 206                                          * so that the dirysync module will do what is needed
 207                                          * (remove the object if it is not deleted, or return
 208                                          * just the objectGUID if it's deleted).
 209                                          */
 210                                         if (dsdb_attr_in_parse_tree(ac->req->op.search.tree,
 211                                                                 msg->elements[i].name)) {
 212                                                 ldb_msg_remove_attr(msg, "replPropertyMetaData");
 213                                                 break;
 214                                         } else {
 215                                                 aclread_mark_inaccesslible(&msg->elements[i]);
 216                                         }
 217                                 }
 218                         } else if (ret != LDB_SUCCESS) {
 219                                 goto fail;
 220                         }
 221                 }
 222                 for (i=0; i < msg->num_elements; i++) {
 223                         if (!aclread_is_inaccessible(&msg->elements[i])) {
 224                                 num_of_attrs++;
 225                         }
 226                 }
 227                 /*create a new message to return*/
 228                 ret_msg = ldb_msg_new(ac->req);
 229                 ret_msg->dn = msg->dn;
 230                 talloc_steal(ret_msg, msg->dn);
 231                 ret_msg->num_elements = num_of_attrs;
 232                 if (num_of_attrs > 0) {
 233                         ret_msg->elements = talloc_array(ret_msg,
 234                                                          struct ldb_message_element,
 235                                                          num_of_attrs);
 236                         if (ret_msg->elements == NULL) {
 237                                 return ldb_oom(ldb);
 238                         }
 239                         for (i=0; i < msg->num_elements; i++) {
 240                                 bool to_remove = aclread_is_inaccessible(&msg->elements[i]);
 241                                 if (!to_remove) {
 242                                         ret_msg->elements[k] = msg->elements[i];
 243                                         talloc_steal(ret_msg->elements, msg->elements[i].name);
 244                                         talloc_steal(ret_msg->elements, msg->elements[i].values);
 245                                         k++;
 246                                 }
 247                         }
 248                         /*
 249                          * This should not be needed, but some modules
 250                          * may allocate values on the wrong context...
 251                          */
 252                         talloc_steal(ret_msg->elements, msg);
 253                 } else {
 254                         ret_msg->elements = NULL;
 255                 }
 256                 talloc_free(tmp_ctx);
 257
 258                 return ldb_module_send_entry(ac->req, ret_msg, ares->controls);
 259         case LDB_REPLY_REFERRAL:
 260                 return ldb_module_send_referral(ac->req, ares->referral);
 261         case LDB_REPLY_DONE:
 262                 return ldb_module_done(ac->req, ares->controls,
 263                                         ares->response, LDB_SUCCESS);
 264
 265         }
 266         return LDB_SUCCESS;
 267 fail:
 268         talloc_free(tmp_ctx);
 269         return ldb_module_done(ac->req, NULL, NULL, ret);
 270 }
 271
 272
 273 static int aclread_search(struct ldb_module *module, struct ldb_request *req)
 274 {
 275         struct ldb_context *ldb;
 276         int ret;
 277         struct aclread_context *ac;
 278         struct ldb_request *down_req;
 279         struct ldb_control *as_system = ldb_request_get_control(req, LDB_CONTROL_AS_SYSTEM_OID);
 280         uint32_t flags = ldb_req_get_custom_flags(req);
 281         struct ldb_result *res;
 282         struct aclread_private *p;
 283         bool is_untrusted = ldb_req_is_untrusted(req);
 284         const char * const *attrs = NULL;
 285         uint32_t instanceType;
 286         static const char *acl_attrs[] = {
 287                 "instanceType",
 288                 NULL
 289         };
 290
 291         ldb = ldb_module_get_ctx(module);
 292         p = talloc_get_type(ldb_module_get_private(module), struct aclread_private);
 293
 294         /* skip access checks if we are system or system control is supplied
 295          * or this is not LDAP server request */
 296         if (!p || !p->enabled ||
 297             dsdb_module_am_system(module)
 298             || as_system || !is_untrusted) {
 299                 return ldb_next_request(module, req);
 300         }
 301         /* no checks on special dn */
 302         if (ldb_dn_is_special(req->op.search.base)) {
 303                 return ldb_next_request(module, req);
 304         }
 305
 306         /* check accessibility of base */
 307         if (!ldb_dn_is_null(req->op.search.base)) {
 308                 ret = dsdb_module_search_dn(module, req, &res, req->op.search.base,
 309                                             acl_attrs,
 310                                             DSDB_FLAG_NEXT_MODULE |
 311                                             DSDB_FLAG_AS_SYSTEM |
 312                                             DSDB_SEARCH_SHOW_RECYCLED,
 313                                             req);
 314                 if (ret != LDB_SUCCESS) {
 315                         return ldb_error(ldb, ret,
 316                                         "acl_read: Error retrieving instanceType for base.");
 317                 }
 318                 instanceType = ldb_msg_find_attr_as_uint(res->msgs[0],
 319                                                         "instanceType", 0);
 320                 if (instanceType != 0 && !(instanceType & INSTANCE_TYPE_IS_NC_HEAD))
 321                 {
 322                         /* the object has a parent, so we have to check for visibility */
 323                         struct ldb_dn *parent_dn = ldb_dn_get_parent(req, req->op.search.base);
 324                         ret = dsdb_module_check_access_on_dn(module,
 325                                                              req,
 326                                                              parent_dn,
 327                                                              SEC_ADS_LIST,
 328                                                              NULL, req);
 329                         if (ret == LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS) {
 330                                 return ldb_module_done(req, NULL, NULL, LDB_ERR_NO_SUCH_OBJECT);
 331                         } else if (ret != LDB_SUCCESS) {
 332                                 return ldb_module_done(req, NULL, NULL, ret);
 333                         }
 334                 }
 335         }
 336         ac = talloc_zero(req, struct aclread_context);
 337         if (ac == NULL) {
 338                 return ldb_oom(ldb);
 339         }
 340         ac->module = module;
 341         ac->req = req;
 342         ac->schema = dsdb_get_schema(ldb, req);
 343         if (flags & DSDB_ACL_CHECKS_DIRSYNC_FLAG) {
 344                 ac->indirsync = true;
 345         } else {
 346                 ac->indirsync = false;
 347         }
 348         if (!ac->schema) {
 349                 return ldb_operr(ldb);
 350         }
 351         /*
 352          * In theory we should also check for the SD control but control verification is
 353          * expensive so we'd better had the ntsecuritydescriptor to the list of
 354          * searched attribute and then remove it !
 355          */
 356         ac->sd_flags = dsdb_request_sd_flags(ac->req, NULL);
 357
 358         ac->sd = !(ldb_attr_in_list(req->op.search.attrs, "nTSecurityDescriptor"));
 359         if (req->op.search.attrs && !ldb_attr_in_list(req->op.search.attrs, "*")) {
 360                 if (!ldb_attr_in_list(req->op.search.attrs, "instanceType")) {
 361                         ac->instance_type = true;
 362                         attrs = ldb_attr_list_copy_add(ac, req->op.search.attrs, "instanceType");
 363                 } else {
 364                         attrs = req->op.search.attrs;
 365                 }
 366                 if (!ldb_attr_in_list(req->op.search.attrs, "objectSid")) {
 367                         ac->object_sid = true;
 368                         attrs = ldb_attr_list_copy_add(ac, attrs, "objectSid");
 369                 }
 370         }
 371
 372         if (ac->sd) {
 373                 /* avoid replacing all attributes with nTSecurityDescriptor
 374                  * if attribute list is empty */
 375                 if (!attrs) {
 376                         attrs = ldb_attr_list_copy_add(ac, req->op.search.attrs, "*");
 377                 }
 378                 attrs = ldb_attr_list_copy_add(ac, attrs, "nTSecurityDescriptor");
 379         }
 380         ac->attrs = req->op.search.attrs;
 381         ret = ldb_build_search_req_ex(&down_req,
 382                                       ldb, ac,
 383                                       req->op.search.base,
 384                                       req->op.search.scope,
 385                                       req->op.search.tree,
 386                                       attrs,
 387                                       req->controls,
 388                                       ac, aclread_callback,
 389                                       req);
 390
 391         if (ret != LDB_SUCCESS) {
 392                 return LDB_ERR_OPERATIONS_ERROR;
 393         }
 394
 395         return ldb_next_request(module, down_req);
 396 }
 397
 398 static int aclread_init(struct ldb_module *module)
 399 {
 400         struct ldb_context *ldb = ldb_module_get_ctx(module);
 401         struct aclread_private *p = talloc_zero(module, struct aclread_private);
 402         if (p == NULL) {
 403                 return ldb_module_oom(module);
 404         }
 405         p->enabled = lpcfg_parm_bool(ldb_get_opaque(ldb, "loadparm"), NULL, "acl", "search", true);
 406         ldb_module_set_private(module, p);
 407         return ldb_next_init(module);
 408 }
 409
 410 static const struct ldb_module_ops ldb_aclread_module_ops = {
 411         .name              = "aclread",
 412         .search            = aclread_search,
 413         .init_context      = aclread_init
 414 };
 415
 416 int ldb_aclread_module_init(const char *version)
 417 {
 418         LDB_MODULE_CHECK_VERSION(version);
 419         return ldb_register_module(&ldb_aclread_module_ops);
 420 }