source/dsdb/samdb/ldb_modules/kludge_acl.c

   1 /*
   2    ldb database library
   3
   4    Copyright (C) Andrew Bartlett 2005
   5    Copyright (C) Simo Sorce 2006
   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 kludge ACL module
  25  *
  26  *  Description: Simple module to enforce a simple form of access
  27  *               control, sufficient for securing a default Samba4
  28  *               installation.
  29  *
  30  *  Author: Andrew Bartlett
  31  */
  32
  33 #include "includes.h"
  34 #include "ldb/include/ldb.h"
  35 #include "ldb/include/ldb_errors.h"
  36 #include "ldb/include/ldb_private.h"
  37 #include "auth/auth.h"
  38 #include "libcli/security/security.h"
  39 #include "dsdb/samdb/samdb.h"
  40
  41 /* Kludge ACL rules:
  42  *
  43  * - System can read passwords
  44  * - Administrators can write anything
  45  * - Users can read anything that is not a password
  46  *
  47  */
  48
  49 enum user_is {
  50         ANONYMOUS,
  51         USER,
  52         ADMINISTRATOR,
  53         SYSTEM
  54 };
  55
  56 struct kludge_private_data {
  57         const char **password_attrs;
  58 };
  59
  60 static enum user_is what_is_user(struct ldb_module *module)
  61 {
  62         struct auth_session_info *session_info
  63                 = ldb_get_opaque(module->ldb, "sessionInfo");
  64         if (!session_info) {
  65                 return ANONYMOUS;
  66         }
  67
  68         if (security_token_is_system(session_info->security_token)) {
  69                 return SYSTEM;
  70         }
  71
  72         if (security_token_is_anonymous(session_info->security_token)) {
  73                 return ANONYMOUS;
  74         }
  75
  76         if (security_token_has_builtin_administrators(session_info->security_token)) {
  77                 return ADMINISTRATOR;
  78         }
  79
  80         if (security_token_has_nt_authenticated_users(session_info->security_token)) {
  81                 return USER;
  82         }
  83
  84         return ANONYMOUS;
  85 }
  86
  87 static const char *user_name(TALLOC_CTX *mem_ctx, struct ldb_module *module)
  88 {
  89         struct auth_session_info *session_info
  90                 = ldb_get_opaque(module->ldb, "sessionInfo");
  91         if (!session_info) {
  92                 return "UNKNOWN (NULL)";
  93         }
  94
  95         return talloc_asprintf(mem_ctx, "%s\\%s",
  96                                session_info->server_info->domain_name,
  97                                session_info->server_info->account_name);
  98 }
  99
 100 /* search */
 101 struct kludge_acl_context {
 102
 103         struct ldb_module *module;
 104         void *up_context;
 105         int (*up_callback)(struct ldb_context *, void *, struct ldb_reply *);
 106
 107         enum user_is user_type;
 108         bool allowedAttributes;
 109         bool allowedAttributesEffective;
 110         bool allowedChildClasses;
 111         bool allowedChildClassesEffective;
 112         const char **attrs;
 113 };
 114
 115 /* read all objectClasses */
 116
 117 static int kludge_acl_allowedAttributes(struct ldb_context *ldb, struct ldb_message *msg,
 118                                         const char *attrName)
 119 {
 120         struct ldb_message_element *oc_el;
 121         struct ldb_message_element *allowedAttributes;
 122         const struct dsdb_schema *schema = dsdb_get_schema(ldb);
 123         const struct dsdb_class *class;
 124         int i, j, ret;
 125         /* Must remove any existing attribute, or else confusion reins */
 126         ldb_msg_remove_attr(msg, attrName);
 127         ret = ldb_msg_add_empty(msg, attrName, 0, &allowedAttributes);
 128         if (ret != LDB_SUCCESS) {
 129                 return ret;
 130         }
 131
 132         /* To ensure that oc_el is valid, we must look for it after
 133            we alter the element array in ldb_msg_add_empty() */
 134         oc_el = ldb_msg_find_element(msg, "objectClass");
 135
 136         for (i=0; oc_el && i < oc_el->num_values; i++) {
 137                 class = dsdb_class_by_lDAPDisplayName(schema, (const char *)oc_el->values[i].data);
 138                 if (!class) {
 139                         /* We don't know this class?  what is going on? */
 140                         continue;
 141                 }
 142
 143                 for (j=0; class->mayContain && class->mayContain[j]; j++) {
 144                         ldb_msg_add_string(msg, attrName, class->mayContain[j]);
 145                 }
 146                 for (j=0; class->mustContain && class->mustContain[j]; j++) {
 147                         ldb_msg_add_string(msg, attrName, class->mustContain[j]);
 148                 }
 149                 for (j=0; class->systemMayContain && class->systemMayContain[j]; j++) {
 150                         ldb_msg_add_string(msg, attrName, class->systemMayContain[j]);
 151                 }
 152                 for (j=0; class->systemMustContain && class->systemMustContain[j]; j++) {
 153                         ldb_msg_add_string(msg, attrName, class->systemMustContain[j]);
 154                 }
 155         }
 156
 157         if (allowedAttributes->num_values > 1) {
 158                 qsort(allowedAttributes->values,
 159                       allowedAttributes->num_values,
 160                       sizeof(*allowedAttributes->values),
 161                       (comparison_fn_t)data_blob_cmp);
 162
 163                 for (i=1 ; i < allowedAttributes->num_values; i++) {
 164                         struct ldb_val *val1 = &allowedAttributes->values[i-1];
 165                         struct ldb_val *val2 = &allowedAttributes->values[i];
 166                         if (data_blob_cmp(val1, val2) == 0) {
 167                                 memmove(val1, val2, (allowedAttributes->num_values - i) * sizeof( struct ldb_val));
 168                                 allowedAttributes->num_values--;
 169                                 i--;
 170                         }
 171                 }
 172         }
 173
 174         return 0;
 175
 176 }
 177 /* read all objectClasses */
 178
 179 static int kludge_acl_childClasses(struct ldb_context *ldb, struct ldb_message *msg,
 180                                    const char *attrName)
 181 {
 182         struct ldb_message_element *oc_el;
 183         struct ldb_message_element *allowedClasses;
 184         const struct dsdb_schema *schema = dsdb_get_schema(ldb);
 185         const struct dsdb_class *class;
 186         int i, j, ret;
 187         /* Must remove any existing attribute, or else confusion reins */
 188         ldb_msg_remove_attr(msg, attrName);
 189         ret = ldb_msg_add_empty(msg, attrName, 0, &allowedClasses);
 190         if (ret != LDB_SUCCESS) {
 191                 return ret;
 192         }
 193
 194         /* To ensure that oc_el is valid, we must look for it after
 195            we alter the element array in ldb_msg_add_empty() */
 196         oc_el = ldb_msg_find_element(msg, "objectClass");
 197
 198         for (i=0; oc_el && i < oc_el->num_values; i++) {
 199                 class = dsdb_class_by_lDAPDisplayName(schema, (const char *)oc_el->values[i].data);
 200                 if (!class) {
 201                         /* We don't know this class?  what is going on? */
 202                         continue;
 203                 }
 204
 205                 for (j=0; class->possibleInferiors && class->possibleInferiors[j]; j++) {
 206                         ldb_msg_add_string(msg, attrName, class->possibleInferiors[j]);
 207                 }
 208         }
 209
 210         if (allowedClasses->num_values > 1) {
 211                 qsort(allowedClasses->values,
 212                       allowedClasses->num_values,
 213                       sizeof(*allowedClasses->values),
 214                       (comparison_fn_t)data_blob_cmp);
 215
 216                 for (i=1 ; i < allowedClasses->num_values; i++) {
 217                         struct ldb_val *val1 = &allowedClasses->values[i-1];
 218                         struct ldb_val *val2 = &allowedClasses->values[i];
 219                         if (data_blob_cmp(val1, val2) == 0) {
 220                                 memmove(val1, val2, (allowedClasses->num_values - i) * sizeof( struct ldb_val));
 221                                 allowedClasses->num_values--;
 222                                 i--;
 223                         }
 224                 }
 225         }
 226
 227         return 0;
 228
 229 }
 230
 231 /* find all attributes allowed by all these objectClasses */
 232
 233 static int kludge_acl_callback(struct ldb_context *ldb, void *context, struct ldb_reply *ares)
 234 {
 235         struct kludge_acl_context *ac;
 236         struct kludge_private_data *data;
 237         int i, ret;
 238
 239         ac = talloc_get_type(context, struct kludge_acl_context);
 240         data = talloc_get_type(ac->module->private_data, struct kludge_private_data);
 241
 242         if (ares->type != LDB_REPLY_ENTRY) {
 243                 return ac->up_callback(ldb, ac->up_context, ares);
 244         }
 245
 246         if (ac->allowedAttributes) {
 247                 ret = kludge_acl_allowedAttributes(ldb, ares->message, "allowedAttributes");
 248                 if (ret != LDB_SUCCESS) {
 249                         return ret;
 250
 251                 }
 252         }
 253         if (ac->allowedChildClasses) {
 254                 ret = kludge_acl_childClasses(ldb, ares->message, "allowedChildClasses");
 255                 if (ret != LDB_SUCCESS) {
 256                         return ret;
 257                 }
 258         }
 259
 260         if (data && data->password_attrs) /* if we are not initialized just get through */
 261         {
 262                 switch (ac->user_type) {
 263                 case SYSTEM:
 264                 case ADMINISTRATOR:
 265                         if (ac->allowedAttributesEffective) {
 266                                 ret = kludge_acl_allowedAttributes(ldb, ares->message, "allowedAttributesEffective");
 267                                 if (ret != LDB_SUCCESS) {
 268                                         return ret;
 269                                 }
 270                         }
 271                         if (ac->allowedChildClassesEffective) {
 272                                 ret = kludge_acl_childClasses(ldb, ares->message, "allowedChildClassesEffective");
 273                                 if (ret != LDB_SUCCESS) {
 274                                         return ret;
 275                                 }
 276                         }
 277                         break;
 278                 default:
 279                         /* remove password attributes */
 280                         for (i = 0; data->password_attrs[i]; i++) {
 281                                 ldb_msg_remove_attr(ares->message, data->password_attrs[i]);
 282                         }
 283                 }
 284         }
 285
 286         if ((ac->allowedAttributes || ac->allowedAttributesEffective
 287              || ac->allowedChildClasses || ac->allowedChildClassesEffective) &&
 288             (!ldb_attr_in_list(ac->attrs, "objectClass") &&
 289              !ldb_attr_in_list(ac->attrs, "*"))) {
 290                 ldb_msg_remove_attr(ares->message, "objectClass");
 291         }
 292
 293         return ac->up_callback(ldb, ac->up_context, ares);
 294 }
 295
 296 static int kludge_acl_search(struct ldb_module *module, struct ldb_request *req)
 297 {
 298         struct kludge_acl_context *ac;
 299         struct ldb_request *down_req;
 300         struct kludge_private_data *data;
 301         int ret, i;
 302
 303         req->handle = NULL;
 304
 305         ac = talloc(req, struct kludge_acl_context);
 306         if (ac == NULL) {
 307                 return LDB_ERR_OPERATIONS_ERROR;
 308         }
 309
 310         data = talloc_get_type(module->private_data, struct kludge_private_data);
 311
 312         ac->module = module;
 313         ac->up_context = req->context;
 314         ac->up_callback = req->callback;
 315         ac->user_type = what_is_user(module);
 316         ac->attrs = req->op.search.attrs;
 317
 318         down_req = talloc_zero(req, struct ldb_request);
 319         if (down_req == NULL) {
 320                 return LDB_ERR_OPERATIONS_ERROR;
 321         }
 322
 323         down_req->operation = req->operation;
 324         down_req->op.search.base = req->op.search.base;
 325         down_req->op.search.scope = req->op.search.scope;
 326         down_req->op.search.tree = req->op.search.tree;
 327         down_req->op.search.attrs = req->op.search.attrs;
 328
 329         ac->allowedAttributes = ldb_attr_in_list(req->op.search.attrs, "allowedAttributes");
 330
 331         ac->allowedAttributesEffective = ldb_attr_in_list(req->op.search.attrs, "allowedAttributesEffective");
 332
 333         ac->allowedChildClasses = ldb_attr_in_list(req->op.search.attrs, "allowedChildClasses");
 334
 335         ac->allowedChildClassesEffective = ldb_attr_in_list(req->op.search.attrs, "allowedChildClassesEffective");
 336
 337         if (ac->allowedAttributes || ac->allowedAttributesEffective || ac->allowedChildClasses || ac->allowedChildClassesEffective) {
 338                 down_req->op.search.attrs
 339                         = ldb_attr_list_copy_add(down_req, down_req->op.search.attrs, "objectClass");
 340         }
 341
 342         /*  FIXME: I hink we should copy the tree and keep the original
 343          *  unmodified. SSS */
 344         /* replace any attributes in the parse tree that are private,
 345            so we don't allow a search for 'sambaPassword=penguin',
 346            just as we would not allow that attribute to be returned */
 347         switch (ac->user_type) {
 348         case SYSTEM:
 349                 break;
 350         default:
 351                 /* remove password attributes */
 352                 for (i = 0; data && data->password_attrs && data->password_attrs[i]; i++) {
 353                         ldb_parse_tree_attr_replace(down_req->op.search.tree,
 354                                                     data->password_attrs[i],
 355                                                     "kludgeACLredactedattribute");
 356                 }
 357         }
 358
 359         down_req->controls = req->controls;
 360
 361         down_req->context = ac;
 362         down_req->callback = kludge_acl_callback;
 363         ldb_set_timeout_from_prev_req(module->ldb, req, down_req);
 364
 365         /* perform the search */
 366         ret = ldb_next_request(module, down_req);
 367
 368         /* do not free down_req as the call results may be linked to it,
 369          * it will be freed when the upper level request get freed */
 370         if (ret == LDB_SUCCESS) {
 371                 req->handle = down_req->handle;
 372         }
 373
 374         return ret;
 375 }
 376
 377 /* ANY change type */
 378 static int kludge_acl_change(struct ldb_module *module, struct ldb_request *req)
 379 {
 380         enum user_is user_type = what_is_user(module);
 381         switch (user_type) {
 382         case SYSTEM:
 383         case ADMINISTRATOR:
 384                 return ldb_next_request(module, req);
 385         default:
 386                 ldb_asprintf_errstring(module->ldb,
 387                                        "kludge_acl_change: "
 388                                        "attempted database modify not permitted. "
 389                                        "User %s is not SYSTEM or an administrator",
 390                                        user_name(req, module));
 391                 return LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS;
 392         }
 393 }
 394
 395 static int kludge_acl_init(struct ldb_module *module)
 396 {
 397         int ret, i;
 398         TALLOC_CTX *mem_ctx = talloc_new(module);
 399         static const char *attrs[] = { "passwordAttribute", NULL };
 400         struct ldb_result *res;
 401         struct ldb_message *msg;
 402         struct ldb_message_element *password_attributes;
 403
 404         struct kludge_private_data *data;
 405
 406         data = talloc(module, struct kludge_private_data);
 407         if (data == NULL) {
 408                 return LDB_ERR_OPERATIONS_ERROR;
 409         }
 410
 411         data->password_attrs = NULL;
 412         module->private_data = data;
 413
 414         if (!mem_ctx) {
 415                 return LDB_ERR_OPERATIONS_ERROR;
 416         }
 417
 418         ret = ldb_search(module->ldb, ldb_dn_new(mem_ctx, module->ldb, "@KLUDGEACL"),
 419                          LDB_SCOPE_BASE,
 420                          NULL, attrs,
 421                          &res);
 422         if (ret != LDB_SUCCESS) {
 423                 goto done;
 424         }
 425         talloc_steal(mem_ctx, res);
 426         if (res->count == 0) {
 427                 goto done;
 428         }
 429
 430         if (res->count > 1) {
 431                 talloc_free(mem_ctx);
 432                 return LDB_ERR_CONSTRAINT_VIOLATION;
 433         }
 434
 435         msg = res->msgs[0];
 436
 437         password_attributes = ldb_msg_find_element(msg, "passwordAttribute");
 438         if (!password_attributes) {
 439                 goto done;
 440         }
 441         data->password_attrs = talloc_array(data, const char *, password_attributes->num_values + 1);
 442         if (!data->password_attrs) {
 443                 talloc_free(mem_ctx);
 444                 return LDB_ERR_OPERATIONS_ERROR;
 445         }
 446         for (i=0; i < password_attributes->num_values; i++) {
 447                 data->password_attrs[i] = (const char *)password_attributes->values[i].data;
 448                 talloc_steal(data->password_attrs, password_attributes->values[i].data);
 449         }
 450         data->password_attrs[i] = NULL;
 451
 452 done:
 453         talloc_free(mem_ctx);
 454         return ldb_next_init(module);
 455 }
 456
 457 static const struct ldb_module_ops kludge_acl_ops = {
 458         .name              = "kludge_acl",
 459         .search            = kludge_acl_search,
 460         .add               = kludge_acl_change,
 461         .modify            = kludge_acl_change,
 462         .del               = kludge_acl_change,
 463         .rename            = kludge_acl_change,
 464         .extended          = kludge_acl_change,
 465         .init_context      = kludge_acl_init
 466 };
 467
 468 int ldb_kludge_acl_init(void)
 469 {
 470         return ldb_register_module(&kludge_acl_ops);
 471 }