Is this hadith about a seven year treaty betweent the Romans and Imam Mahdi authentic?

An anti-Islamic website references a hadith while trying to correlate the Mahdi to the biblical Antichrist but gives no indication whether it's even authentic or not. Can anyone confirm the health of this hadith, and whether the given interpretation is valid? Al-Mahdi’s Treaty With Romans According to various Islamic theological sources, al-Mahdi is said to be one who will initiate Islam’s fourth and final treaty between the “Romans” and the Muslims. Al-Mahdi will make this treaty for a period of seven years! In a Hadith, Prophet Muhammad (pbuh) said: > قال رسول الله صلى الله عليه وسلم: سيكون بينكم وبين الروم أربع هدن، تقوم الرابعة على يد رجل من أهل هرقل يدوم سبع سنين . فقال له رجل من عبد القيس يقال له المستورد بن خيلان: يا رسول الله، من إمام الناس يومئذ؟ قال: من ولد أربعين سنة كأن وجهه كوكب دري، في خده الأيمن خال أسود، عليه عباءتان قعوايتان، كأنه من رجال بني إسرائيل، يملك عشرين سنة يستخرج الكنوز، ويفتح مدائن الشرك > > Thr Prophet said: “There will be four peace agreements between you and the Romans. The fourth will be at the hand of a person who will be from the progeny of Heraclius and will be upheld for seven years.“ > >The people asked, “O Prophet Muhammad (peace be upon him), who will be the Imam (leader) of the people at that time?” > > The Prophet said: “He will be from my progeny and will be forty years of age. His face will shine like a star, he will have a black mole on his right cheek, he will wear two cloaks, as if he was a man from the Bani Israel. He shall rule for twenty years and shall uncover treasures and conquer the cities of the polytheists.” > > *([Tabarani](https://shamela.ws/book/1733/9251) , as related by Hadrat Abu Umamah)*.