lib/ldb-samba/ldb_matching_rules.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3
   4    ldb database library - Extended match rules
   5
   6    Copyright (C) 2014 Samuel Cabrero <samuelcabrero@kernevil.me>
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20 */
  21
  22 #include "includes.h"
  23 #include <ldb_module.h>
  24 #include "dsdb/samdb/samdb.h"
  25 #include "ldb_matching_rules.h"
  26
  27 static int ldb_eval_transitive_filter_helper(TALLOC_CTX *mem_ctx,
  28                                              struct ldb_context *ldb,
  29                                              const char *attr,
  30                                              const struct dsdb_dn *dn_to_match,
  31                                              const char *dn_oid,
  32                                              struct dsdb_dn *to_visit,
  33                                              struct dsdb_dn **visited,
  34                                              unsigned int *visited_count,
  35                                              bool *matched)
  36 {
  37         TALLOC_CTX *tmp_ctx;
  38         int ret, i, j;
  39         struct ldb_result *res;
  40         struct ldb_message *msg;
  41         struct ldb_message_element *el;
  42         const char *attrs[] = { attr, NULL };
  43
  44         tmp_ctx = talloc_new(mem_ctx);
  45         if (tmp_ctx == NULL) {
  46                 return LDB_ERR_OPERATIONS_ERROR;
  47         }
  48
  49         /*
  50          * Fetch the entry to_visit
  51          *
  52          * NOTE: This is a new LDB search from the TOP of the module
  53          * stack.  This means that this search runs the whole stack
  54          * from top to bottom.
  55          *
  56          * This may seem to be in-efficient, but it is also the only
  57          * way to ensure that the ACLs for this search are applied
  58          * correctly.
  59          *
  60          * Note also that we don't have the original request
  61          * here, so we can not apply controls or timeouts here.
  62          */
  63         ret = dsdb_search_dn(ldb, tmp_ctx, &res, to_visit->dn, attrs, 0);
  64         if (ret != LDB_SUCCESS) {
  65                 talloc_free(tmp_ctx);
  66                 return ret;
  67         }
  68         if (res->count != 1) {
  69                 talloc_free(tmp_ctx);
  70                 return LDB_ERR_OPERATIONS_ERROR;
  71         }
  72         msg = res->msgs[0];
  73
  74         /* Fetch the attribute to match from the entry being visited */
  75         el = ldb_msg_find_element(msg, attr);
  76         if (el == NULL) {
  77                 /* This entry does not have the attribute to match */
  78                 talloc_free(tmp_ctx);
  79                 *matched = false;
  80                 return LDB_SUCCESS;
  81         }
  82
  83         /*
  84          * If the value to match is present in the attribute values of the
  85          * current entry being visited, set matched to true and return OK
  86          */
  87         for (i=0; i<el->num_values; i++) {
  88                 struct dsdb_dn *dn;
  89                 dn = dsdb_dn_parse(tmp_ctx, ldb, &el->values[i], dn_oid);
  90                 if (dn == NULL) {
  91                         talloc_free(tmp_ctx);
  92                         *matched = false;
  93                         return LDB_ERR_INVALID_DN_SYNTAX;
  94                 }
  95
  96                 if (ldb_dn_compare(dn_to_match->dn, dn->dn) == 0) {
  97                         talloc_free(tmp_ctx);
  98                         *matched = true;
  99                         return LDB_SUCCESS;
 100                 }
 101         }
 102
 103         /*
 104          * If arrived here, the value to match is not in the values of the
 105          * entry being visited. Add the entry being visited (to_visit)
 106          * to the visited array. The array is (re)allocated in the parent
 107          * memory context.
 108          */
 109         if (visited == NULL) {
 110                 visited = talloc_array(mem_ctx, struct dsdb_dn *, 1);
 111                 if (visited == NULL) {
 112                         talloc_free(tmp_ctx);
 113                         return LDB_ERR_OPERATIONS_ERROR;
 114                 }
 115                 visited[0] = to_visit;
 116                 (*visited_count) = 1;
 117         } else {
 118                 visited = talloc_realloc(mem_ctx, visited, struct dsdb_dn *,
 119                                          (*visited_count) + 1);
 120                 if (visited == NULL) {
 121                         talloc_free(tmp_ctx);
 122                         return LDB_ERR_OPERATIONS_ERROR;
 123                 }
 124                 visited[(*visited_count)] = to_visit;
 125                 (*visited_count)++;
 126         }
 127
 128         /*
 129          * steal to_visit into visited array context, as it has to live until
 130          * the array is freed.
 131          */
 132         talloc_steal(visited, to_visit);
 133
 134         /*
 135          * Iterate over the values of the attribute of the entry being
 136          * visited (to_visit) and follow them, calling this function
 137          * recursively.
 138          * If the value is in the visited array, skip it.
 139          * Otherwise, follow the link and visit it.
 140          */
 141         for (i=0; i<el->num_values; i++) {
 142                 struct dsdb_dn *next_to_visit;
 143                 bool skip = false;
 144
 145                 next_to_visit = dsdb_dn_parse(tmp_ctx, ldb, &el->values[i], dn_oid);
 146                 if (next_to_visit == NULL) {
 147                         talloc_free(tmp_ctx);
 148                         *matched = false;
 149                         return LDB_ERR_INVALID_DN_SYNTAX;
 150                 }
 151
 152                 /*
 153                  * If the value is already in the visited array, skip it.
 154                  * Note the last element of the array is ignored because it is
 155                  * the current entry DN.
 156                  */
 157                 for (j=0; j < (*visited_count) - 1; j++) {
 158                         struct dsdb_dn *visited_dn = visited[j];
 159                         if (ldb_dn_compare(visited_dn->dn,
 160                                            next_to_visit->dn) == 0) {
 161                                 skip = true;
 162                                 break;
 163                         }
 164                 }
 165                 if (skip) {
 166                         talloc_free(next_to_visit);
 167                         continue;
 168                 }
 169
 170                 /* If the value is not in the visited array, evaluate it */
 171                 ret = ldb_eval_transitive_filter_helper(tmp_ctx, ldb, attr,
 172                                                         dn_to_match, dn_oid,
 173                                                         next_to_visit,
 174                                                         visited, visited_count,
 175                                                         matched);
 176                 if (ret != LDB_SUCCESS) {
 177                         talloc_free(tmp_ctx);
 178                         return ret;
 179                 }
 180                 if (*matched) {
 181                         talloc_free(tmp_ctx);
 182                         return LDB_SUCCESS;
 183                 }
 184         }
 185
 186         talloc_free(tmp_ctx);
 187         *matched = false;
 188         return LDB_SUCCESS;
 189 }
 190
 191 /*
 192  * This function parses the linked attribute value to match, whose syntax
 193  * will be one of the different DN syntaxes, into a ldb_dn struct.
 194  */
 195 static int ldb_eval_transitive_filter(TALLOC_CTX *mem_ctx,
 196                                       struct ldb_context *ldb,
 197                                       const char *attr,
 198                                       const struct ldb_val *value_to_match,
 199                                       struct dsdb_dn *current_object_dn,
 200                                       bool *matched)
 201 {
 202         const struct dsdb_schema *schema;
 203         const struct dsdb_attribute *schema_attr;
 204         struct dsdb_dn *dn_to_match;
 205         const char *dn_oid;
 206         unsigned int count;
 207
 208         schema = dsdb_get_schema(ldb, mem_ctx);
 209         if (schema == NULL) {
 210                 return LDB_ERR_OPERATIONS_ERROR;
 211         }
 212
 213         schema_attr = dsdb_attribute_by_lDAPDisplayName(schema, attr);
 214         if (schema_attr == NULL) {
 215                 return LDB_ERR_NO_SUCH_ATTRIBUTE;
 216         }
 217
 218         /* This is the DN syntax of the attribute being matched */
 219         dn_oid = schema_attr->syntax->ldap_oid;
 220
 221         /*
 222          * Build a ldb_dn struct holding the value to match, which is the
 223          * value entered in the search filter
 224          */
 225         dn_to_match = dsdb_dn_parse(mem_ctx, ldb, value_to_match, dn_oid);
 226         if (dn_to_match == NULL) {
 227                 *matched = false;
 228                 return LDB_ERR_INVALID_DN_SYNTAX;
 229         }
 230
 231         return ldb_eval_transitive_filter_helper(mem_ctx, ldb, attr,
 232                                                  dn_to_match, dn_oid,
 233                                                  current_object_dn,
 234                                                  NULL, &count, matched);
 235 }
 236
 237 /*
 238  * This rule provides recursive search of a link attribute
 239  *
 240  * Documented in [MS-ADTS] section 3.1.1.3.4.4.3 LDAP_MATCHING_RULE_TRANSITIVE_EVAL
 241  * This allows a search filter such as:
 242  *
 243  * member:1.2.840.113556.1.4.1941:=cn=user,cn=users,dc=samba,dc=example,dc=com
 244  *
 245  * This searches not only the member attribute, but also any member
 246  * attributes that point at an object with this member in them.  All the
 247  * various DN syntax types are supported, not just plain DNs.
 248  *
 249  */
 250 static int ldb_comparator_trans(struct ldb_context *ldb,
 251                                 const char *oid,
 252                                 const struct ldb_message *msg,
 253                                 const char *attribute_to_match,
 254                                 const struct ldb_val *value_to_match,
 255                                 bool *matched)
 256 {
 257         const struct dsdb_schema *schema;
 258         const struct dsdb_attribute *schema_attr;
 259         struct ldb_dn *msg_dn;
 260         struct dsdb_dn *dsdb_msg_dn;
 261         TALLOC_CTX *tmp_ctx;
 262         int ret;
 263
 264         tmp_ctx = talloc_new(ldb);
 265         if (tmp_ctx == NULL) {
 266                 return LDB_ERR_OPERATIONS_ERROR;
 267         }
 268
 269         /*
 270          * If the target attribute to match is not a linked attribute, then
 271          * the filter evaluates to undefined
 272          */
 273         schema = dsdb_get_schema(ldb, tmp_ctx);
 274         if (schema == NULL) {
 275                 talloc_free(tmp_ctx);
 276                 return LDB_ERR_OPERATIONS_ERROR;
 277         }
 278
 279         schema_attr = dsdb_attribute_by_lDAPDisplayName(schema, attribute_to_match);
 280         if (schema_attr == NULL) {
 281                 talloc_free(tmp_ctx);
 282                 return LDB_ERR_NO_SUCH_ATTRIBUTE;
 283         }
 284
 285         /*
 286          * This extended match filter is only valid for linked attributes,
 287          * following the MS definition (the schema attribute has a linkID
 288          * defined). See dochelp request 114111212024789 on cifs-protocols
 289          * mailing list.
 290          */
 291         if (schema_attr->linkID == 0) {
 292                 talloc_free(tmp_ctx);
 293                 return LDB_ERR_INAPPROPRIATE_MATCHING;
 294         }
 295
 296         /* Duplicate original msg dn as the msg must not be modified */
 297         msg_dn = ldb_dn_copy(tmp_ctx, msg->dn);
 298         if (msg_dn == NULL) {
 299                 talloc_free(tmp_ctx);
 300                 return LDB_ERR_OPERATIONS_ERROR;
 301         }
 302
 303         /*
 304          * Build a dsdb dn from the message copied DN, which should be a plain
 305          * DN syntax.
 306          */
 307         dsdb_msg_dn = dsdb_dn_construct(tmp_ctx, msg_dn, data_blob_null,
 308                                         LDB_SYNTAX_DN);
 309         if (dsdb_msg_dn == NULL) {
 310                 *matched = false;
 311                 return LDB_ERR_INVALID_DN_SYNTAX;
 312         }
 313
 314         ret = ldb_eval_transitive_filter(tmp_ctx, ldb,
 315                                          attribute_to_match,
 316                                          value_to_match,
 317                                          dsdb_msg_dn, matched);
 318         talloc_free(tmp_ctx);
 319         return ret;
 320 }
 321
 322
 323 int ldb_register_samba_matching_rules(struct ldb_context *ldb)
 324 {
 325         struct ldb_extended_match_rule *transitive_eval;
 326         int ret;
 327
 328         transitive_eval = talloc_zero(ldb, struct ldb_extended_match_rule);
 329         transitive_eval->oid = SAMBA_LDAP_MATCH_RULE_TRANSITIVE_EVAL;
 330         transitive_eval->callback = ldb_comparator_trans;
 331         ret = ldb_register_extended_match_rule(ldb, transitive_eval);
 332         if (ret != LDB_SUCCESS) {
 333                 talloc_free(transitive_eval);
 334                 return ret;
 335         }
 336
 337         return LDB_SUCCESS;
 338 }