This is true, all the Koran states regarding a womans dress code is that she must dress modestly. In fact there is a verse about not covering up the identity of females ...
[33.59] O Prophet! say to your wives and your daughters and the women of the believers that they let down upon them their over-garments; this will be more proper, that they may be known, and thus they will not be given trouble; and Allah is Forgiving, Merciful.