Masah on winter boots

In reference to your question, there is a slight difference in the necessary requirements for masah on boots to be valid and the requirements for salah in boots to be valid. 

            For masah to be valid upon any footwear, it must be thick enough to keep out water and securely cover the whole foot including the ankle.  It must be free of holes while being able to withstand walking at least one mile.  If any boots meet these requirements and are free of impurities, then it would be permissible to perform masah on them.  

            As for offering salah in such boots, it should be noted that it is a necessary component of sajdah that the toes touch the ground.  If there is a gap between the toes and the end of the boot (as is customary in most boots), then the toes will not be touching the ground whilst in sajdah thus making the salah invalid. However, if this is not the case or one is able to bend the boot in such a manner that part of his foot would be reaching the ground while performing sajdah, the salah would be valid and this would be permissible.