- messages. On local transports, the sender credentials are attached
- by the kernel and cannot be manipulated by userspace. By default,
- no sender credentials are attached.</para>
+ messages. Specifically, implicit sender credentials on messages
+ are only fully supported on kdbus transports, and dbus1 only
+ supports <constant>SD_BUS_CREDS_UNIQUE_NAME</constant>. The sender
+ credentials are attached by the kernel and cannot be manipulated
+ by userspace, and are thus suitable for authorization
+ decisions. By default, only
+ <constant>SD_BUS_CREDS_WELL_KNOWN_NAMES</constant> and
+ <constant>SD_BUS_CREDS_UNIQUE_NAME</constant> are enabled. In
+ fact, these two credential fields are always sent along and cannot
+ be turned off.</para>