CVE-2022-32745 s4/dsdb/util: Use correct value for loop count limit

Currently, we can crash the server by sending a large number of values
of a specific attribute (such as sAMAccountName) spread across a few
message elements. If val_count is larger than the total number of
elements, we get an access beyond the elements array.

Similarly, we can include unrelated message elements prior to the
message elements of the attribute in question, so that not all of the
attribute's values are copied into the returned elements values array.
This can cause the server to access uninitialised data, likely resulting
in a crash or unexpected behaviour.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15008

Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz>

diff --git a/source4/dsdb/samdb/ldb_modules/util.c b/source4/dsdb/samdb/ldb_modules/util.c
index 405febf0b3d0dff8bb4facf691234d0a87d0acc6..14947746837557dc70b2339461c70a4a3eb1ac0f 100644 (file)
--- a/source4/dsdb/samdb/ldb_modules/util.c
+++ b/source4/dsdb/samdb/ldb_modules/util.c
@@ -1546,7 +1546,7 @@ int dsdb_get_expected_new_values(TALLOC_CTX *mem_ctx,
 
        v = _el->values;
 
-       for (i = 0; i < val_count; i++) {
+       for (i = 0; i < msg->num_elements; i++) {
                if (ldb_attr_cmp(msg->elements[i].name, attr_name) == 0) {
                        if ((operation == LDB_MODIFY) &&
                            (LDB_FLAG_MOD_TYPE(msg->elements[i].flags)