source4/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         const char **attrs;
 111 };
 112
 113 /* read all objectClasses */
 114
 115 static int kludge_acl_allowedAttributes(struct ldb_context *ldb, struct ldb_message *msg,
 116                                                          const char *attrName)
 117 {
 118         struct ldb_message_element *oc_el;
 119         struct ldb_message_element *allowedAttributes;
 120         const struct dsdb_schema *schema = dsdb_get_schema(ldb);
 121         const struct dsdb_class *class;
 122         int i, j, ret;
 123         ret = ldb_msg_add_empty(msg, attrName, 0, &allowedAttributes);
 124         if (ret != LDB_SUCCESS) {
 125                 return ret;
 126         }
 127
 128         /* To ensure that oc_el is valid, we must look for it after
 129            we alter the element array in ldb_msg_add_empty() */
 130         oc_el = ldb_msg_find_element(msg, "objectClass");
 131
 132         for (i=0; i < oc_el->num_values; i++) {
 133                 class = dsdb_class_by_lDAPDisplayName(schema, (const char *)oc_el->values[i].data);
 134                 if (!class) {
 135                         /* We don't know this class?  what is going on? */
 136                         continue;
 137                 }
 138                 for (j=0; class->mayContain && class->mayContain[j]; j++) {
 139                         ldb_msg_add_string(msg, attrName, class->mayContain[j]);
 140                 }
 141                 for (j=0; class->mustContain && class->mustContain[j]; j++) {
 142                         ldb_msg_add_string(msg, attrName, class->mustContain[j]);
 143                 }
 144                 for (j=0; class->systemMayContain && class->systemMayContain[j]; j++) {
 145                         ldb_msg_add_string(msg, attrName, class->systemMayContain[j]);
 146                 }
 147                 for (j=0; class->systemMustContain && class->systemMustContain[j]; j++) {
 148                         ldb_msg_add_string(msg, attrName, class->systemMustContain[j]);
 149                 }
 150         }
 151
 152         if (allowedAttributes->num_values > 1) {
 153                 qsort(allowedAttributes->values,
 154                       allowedAttributes->num_values,
 155                       sizeof(*allowedAttributes->values),
 156                       (comparison_fn_t)data_blob_cmp);
 157
 158                 for (i=1 ; i < allowedAttributes->num_values; i++) {
 159                         struct ldb_val *val1 = &allowedAttributes->values[i-1];
 160                         struct ldb_val *val2 = &allowedAttributes->values[i];
 161                         if (data_blob_cmp(val1, val2) == 0) {
 162                                 memmove(val1, val2, (allowedAttributes->num_values - i) * sizeof( struct ldb_val));
 163                                 allowedAttributes->num_values--;
 164                                 i--;
 165                         }
 166                 }
 167         }
 168
 169         return 0;
 170
 171 }
 172
 173 /* find all attributes allowed by all these objectClasses */
 174
 175 static int kludge_acl_callback(struct ldb_context *ldb, void *context, struct ldb_reply *ares)
 176 {
 177         struct kludge_acl_context *ac;
 178         struct kludge_private_data *data;
 179         int i, ret;
 180
 181         if (!context || !ares) {
 182                 ldb_set_errstring(ldb, "NULL Context or Result in callback");
 183                 goto error;
 184         }
 185
 186         ac = talloc_get_type(context, struct kludge_acl_context);
 187         data = talloc_get_type(ac->module->private_data, struct kludge_private_data);
 188
 189         if (ares->type != LDB_REPLY_ENTRY) {
 190                 return ac->up_callback(ldb, ac->up_context, ares);
 191         }
 192
 193         if (ac->allowedAttributes) {
 194                 ret = kludge_acl_allowedAttributes(ldb, ares->message, "allowedAttributes");
 195                 if (ret != LDB_SUCCESS) {
 196                         return ret;
 197                 }
 198         }
 199
 200         if (data && data->password_attrs) /* if we are not initialized just get through */
 201         {
 202                 switch (ac->user_type) {
 203                 case SYSTEM:
 204                 case ADMINISTRATOR:
 205                         if (ac->allowedAttributesEffective) {
 206                                 ret = kludge_acl_allowedAttributes(ldb, ares->message, "allowedAttributesEffective");
 207                                 if (ret != LDB_SUCCESS) {
 208                                         return ret;
 209                                 }
 210                         }
 211                         break;
 212                 default:
 213                         /* remove password attributes */
 214                         for (i = 0; data->password_attrs[i]; i++) {
 215                                 ldb_msg_remove_attr(ares->message, data->password_attrs[i]);
 216                         }
 217                 }
 218         }
 219
 220         if ((ac->allowedAttributes || ac->allowedAttributesEffective) &&
 221             (!ldb_attr_in_list(ac->attrs, "objectClass") &&
 222              !ldb_attr_in_list(ac->attrs, "*"))) {
 223                 ldb_msg_remove_attr(ares->message, "objectClass");
 224         }
 225
 226         return ac->up_callback(ldb, ac->up_context, ares);
 227
 228 error:
 229         talloc_free(ares);
 230         return LDB_ERR_OPERATIONS_ERROR;
 231 }
 232
 233 static int kludge_acl_search(struct ldb_module *module, struct ldb_request *req)
 234 {
 235         struct kludge_acl_context *ac;
 236         struct ldb_request *down_req;
 237         struct kludge_private_data *data;
 238         int ret, i;
 239
 240         req->handle = NULL;
 241
 242         ac = talloc(req, struct kludge_acl_context);
 243         if (ac == NULL) {
 244                 return LDB_ERR_OPERATIONS_ERROR;
 245         }
 246
 247         data = talloc_get_type(module->private_data, struct kludge_private_data);
 248
 249         ac->module = module;
 250         ac->up_context = req->context;
 251         ac->up_callback = req->callback;
 252         ac->user_type = what_is_user(module);
 253         ac->attrs = req->op.search.attrs;
 254
 255         down_req = talloc_zero(req, struct ldb_request);
 256         if (down_req == NULL) {
 257                 return LDB_ERR_OPERATIONS_ERROR;
 258         }
 259
 260         down_req->operation = req->operation;
 261         down_req->op.search.base = req->op.search.base;
 262         down_req->op.search.scope = req->op.search.scope;
 263         down_req->op.search.tree = req->op.search.tree;
 264         down_req->op.search.attrs = req->op.search.attrs;
 265
 266         ac->allowedAttributes = ldb_attr_in_list(req->op.search.attrs, "allowedAttributes");
 267
 268         ac->allowedAttributesEffective = ldb_attr_in_list(req->op.search.attrs, "allowedAttributesEffective");
 269
 270         if (ac->allowedAttributes || ac->allowedAttributesEffective) {
 271                 down_req->op.search.attrs
 272                         = ldb_attr_list_copy_add(down_req, down_req->op.search.attrs, "objectClass");
 273         }
 274
 275         /*  FIXME: I hink we should copy the tree and keep the original
 276          *  unmodified. SSS */
 277         /* replace any attributes in the parse tree that are private,
 278            so we don't allow a search for 'sambaPassword=penguin',
 279            just as we would not allow that attribute to be returned */
 280         switch (ac->user_type) {
 281         case SYSTEM:
 282                 break;
 283         default:
 284                 /* remove password attributes */
 285                 for (i = 0; data && data->password_attrs && data->password_attrs[i]; i++) {
 286                         ldb_parse_tree_attr_replace(down_req->op.search.tree,
 287                                                     data->password_attrs[i],
 288                                                     "kludgeACLredactedattribute");
 289                 }
 290         }
 291
 292         down_req->controls = req->controls;
 293
 294         down_req->context = ac;
 295         down_req->callback = kludge_acl_callback;
 296         ldb_set_timeout_from_prev_req(module->ldb, req, down_req);
 297
 298         /* perform the search */
 299         ret = ldb_next_request(module, down_req);
 300
 301         /* do not free down_req as the call results may be linked to it,
 302          * it will be freed when the upper level request get freed */
 303         if (ret == LDB_SUCCESS) {
 304                 req->handle = down_req->handle;
 305         }
 306
 307         return ret;
 308 }
 309
 310 /* ANY change type */
 311 static int kludge_acl_change(struct ldb_module *module, struct ldb_request *req)
 312 {
 313         enum user_is user_type = what_is_user(module);
 314         switch (user_type) {
 315         case SYSTEM:
 316         case ADMINISTRATOR:
 317                 return ldb_next_request(module, req);
 318         default:
 319                 ldb_asprintf_errstring(module->ldb,
 320                                        "kludge_acl_change: "
 321                                        "attempted database modify not permitted. "
 322                                        "User %s is not SYSTEM or an administrator",
 323                                        user_name(req, module));
 324                 return LDB_ERR_INSUFFICIENT_ACCESS_RIGHTS;
 325         }
 326 }
 327
 328 static int kludge_acl_init(struct ldb_module *module)
 329 {
 330         int ret, i;
 331         TALLOC_CTX *mem_ctx = talloc_new(module);
 332         static const char *attrs[] = { "passwordAttribute", NULL };
 333         struct ldb_result *res;
 334         struct ldb_message *msg;
 335         struct ldb_message_element *password_attributes;
 336
 337         struct kludge_private_data *data;
 338
 339         data = talloc(module, struct kludge_private_data);
 340         if (data == NULL) {
 341                 return LDB_ERR_OPERATIONS_ERROR;
 342         }
 343
 344         data->password_attrs = NULL;
 345         module->private_data = data;
 346
 347         if (!mem_ctx) {
 348                 return LDB_ERR_OPERATIONS_ERROR;
 349         }
 350
 351         ret = ldb_search(module->ldb, ldb_dn_new(mem_ctx, module->ldb, "@KLUDGEACL"),
 352                          LDB_SCOPE_BASE,
 353                          NULL, attrs,
 354                          &res);
 355         if (ret != LDB_SUCCESS) {
 356                 goto done;
 357         }
 358         talloc_steal(mem_ctx, res);
 359         if (res->count == 0) {
 360                 goto done;
 361         }
 362
 363         if (res->count > 1) {
 364                 talloc_free(mem_ctx);
 365                 return LDB_ERR_CONSTRAINT_VIOLATION;
 366         }
 367
 368         msg = res->msgs[0];
 369
 370         password_attributes = ldb_msg_find_element(msg, "passwordAttribute");
 371         if (!password_attributes) {
 372                 goto done;
 373         }
 374         data->password_attrs = talloc_array(data, const char *, password_attributes->num_values + 1);
 375         if (!data->password_attrs) {
 376                 talloc_free(mem_ctx);
 377                 return LDB_ERR_OPERATIONS_ERROR;
 378         }
 379         for (i=0; i < password_attributes->num_values; i++) {
 380                 data->password_attrs[i] = (const char *)password_attributes->values[i].data;
 381                 talloc_steal(data->password_attrs, password_attributes->values[i].data);
 382         }
 383         data->password_attrs[i] = NULL;
 384
 385 done:
 386         talloc_free(mem_ctx);
 387         return ldb_next_init(module);
 388 }
 389
 390 static const struct ldb_module_ops kludge_acl_ops = {
 391         .name              = "kludge_acl",
 392         .search            = kludge_acl_search,
 393         .add               = kludge_acl_change,
 394         .modify            = kludge_acl_change,
 395         .del               = kludge_acl_change,
 396         .rename            = kludge_acl_change,
 397         .extended          = kludge_acl_change,
 398         .init_context      = kludge_acl_init
 399 };
 400
 401 int ldb_kludge_acl_init(void)
 402 {
 403         return ldb_register_module(&kludge_acl_ops);
 404 }