以子之矛，攻子之盾 [－－－－－－－－－]

Jyutping ji5 zi2 zi1 maau4 , gung1 zi2 zi1 teon5
Pinyin yǐ zǐ zhī máo , gōng zǐ zhī dùn

Definitions (CC-CEDICT)
  1. lit. use sb's spear to attack his shield (idiom, derived from Han Feizi 韓非子|韩非子); turning a weapon against its owner
  2. fig. to attack an opponent using his own devices
  3. hoist with his own petard