Is it permissible to attend Christian holidays and congratulate them on them?

It is impermissible to attend the festivals of the polytheists, by agreement of the people of knowledge. The jurists of the four schools of thought have explicitly stated this. It is reported from Umar ibn al-Khattab, may Allah be pleased with him, that he said: "Do not enter upon the polytheists in their churches on the day of their festival, for displeasure descends upon them," and "Avoid the enemies of Allah during their festivals." It is also reported from Abdullah ibn Amr that he said: "Whoever passes through the lands of the non-Arabs and celebrates their Nawruz and Mahrajan and imitates them until he dies in that state, he will be resurrected with them on the Day of Resurrection."