s4-dsdb Reorganise and clarify the LSA objectClass check (forbidden on LDAP)

This arranged the check to avoid talloc_strdup() (the schema pointers
are constant, and can be relied upon), and checks the untrusted bit
first (it is faster), before the ldb_attr_cmp().

The strcmp() here was valid, if unusual, because the ldapDisplayName
values are already in the correct case, but strcasecmp() is more
correct, as for the small extra cost, we avoid a difficult to diagnose
bug later.

Andrew Bartlett

Signed-off-by: Matthias Dieter Wallnöfer <mdw@samba.org>

1 files changed, 28 insertions, 15 deletions

diff --git a/source4/dsdb/samdb/ldb_modules/objectclass.c b/source4/dsdb/samdb/ldb_modules/objectclass.c
index 0eceaefce4a..66e6e393eab 100644
--- a/source4/dsdb/samdb/ldb_modules/objectclass.c
+++ b/source4/dsdb/samdb/ldb_modules/objectclass.c
@@ -368,7 +368,6 @@ static int objectclass_add(struct ldb_module *module, struct ldb_request *req)
 	struct oc_context *ac;
 	struct ldb_dn *parent_dn;
 	const struct ldb_val *val;
-	char *value;
 	int ret;
 	static const char * const parent_attrs[] = { "objectClass", NULL };
 
@@ -566,25 +565,39 @@ static int objectclass_do_add(struct oc_context *ac)
 
 		/* Move from the linked list back into an ldb msg */
 		for (current = sorted; current; current = current->next) {
-			value = talloc_strdup(msg,
-					      current->objectclass->lDAPDisplayName);
-			if (value == NULL) {
-				talloc_free(mem_ctx);
-				return ldb_module_oom(ac->module);
-			}
-
-			/* LSA-specific objectclasses per default not allowed */
-			if (((strcmp(value, "secret") == 0) ||
-			     (strcmp(value, "trustedDomain") == 0)) &&
-			    ldb_req_is_untrusted(ac->req)) {
+			const char *objectclass_name = current->objectclass->lDAPDisplayName;
+
+			/* LSA-specific objectclasses per default not
+			 * allowed to be created over LDAP, so we need
+			 * to tell if this connection is LDAP (ie
+			 * marked as untrusted), and if the client is
+			 * adding these particular objectClass values
+			 * we must reject */
+
+			/* Hongwei Sun from Microsoft explians:
+			   The constraint in 3.1.1.5.2.2 MS-ADTS means that the TDO
+			   cannot be added through LDAP interface, instead it can only be
+			   created through LSA Policy API.  This is also explained in
+			   7.1.6.9.7 MS-ADTS as follows:
+
+			   "Despite being replicated normally between peer DCs in a domain,
+			   the process of creating or manipulating TDOs is specifically
+			   restricted to the LSA Policy APIs, as detailed in [MS-LSAD] section
+			   3.1.1.5. Unlike other objects in the DS, TDOs may not be created or
+			   manipulated by client machines over the LDAPv3 transport."
+			*/
+
+			if (ldb_req_is_untrusted(ac->req) &&
+			    ((strcasecmp(objectclass_name, "secret") == 0) ||
+			     (strcasecmp(objectclass_name, "trustedDomain") == 0))) {
 				ldb_asprintf_errstring(ldb,
-						       "objectclass: object class '%s' is LSA-specific, rejecting creation of '%s'!",
-						       value,
+						       "objectclass: object class '%s' is LSA-specific, rejecting creation of '%s' over LDAP!",
+						       objectclass_name,
 						       ldb_dn_get_linearized(msg->dn));
 				return LDB_ERR_UNWILLING_TO_PERFORM;
 			}
 
-			ret = ldb_msg_add_string(msg, "objectClass", value);
+			ret = ldb_msg_add_string(msg, "objectClass", objectclass_name);
 			if (ret != LDB_SUCCESS) {
 				ldb_set_errstring(ldb,
 						  "objectclass: could not re-add sorted "