Is the story true about Khabbab ibn al-Aratt being tortured with fire and it being extinguished by the fat from his back, and is this considered a miracle?

It has been authentically established that Khabbab ibn al-Aratt was afflicted, and the scars of torture remained on his back. Umar used to say to Khabbab, "Come closer, for no one is more deserving of this sitting place than you, except for Ammar." And Khabbab would show him the marks on his back from the torture inflicted by the polytheists. Al-Bukhari narrated from Khabbab his saying: "We complained to the Messenger of Allah, peace and blessings be upon him, and said: 'Will you not seek help for us? Will you not pray for us?'"

There is also a narration by Abu Nu'aym in Al-Hilyah from Al-Sha'bi who said: "Umar asked Bilal about what he suffered from the polytheists, and Khabbab said: 'O Commander of the Faithful, look at my back!' Umar said: 'I have never seen anything like this day!' He said: 'They lit a fire for me, and nothing extinguished it but the fat from my back.'" This narration has a断 (interruption) in its chain of transmission because Al-Sha'bi would send narrations from Umar.