城狐社鼠　

◎ 城狐社鼠 chénghú-shèshǔ

[take advantage of one‘s or sb. else‘s power to do evils;the evildoes are like foxes in the city and rats in the temple] 要掏挖狐狸恐怕毁坏城池,要熏死老鼠恐怕烧灼社庙。比喻凭藉某种势力的庇护而作恶的人