Codechef asks permissions on each login

Whenever my app logins a user using Codechef oAuth, code chef asks for permission every time even if the person has already given the permissions before.
Is this the default behaviour or there is some error in my implementation ?

@vaibhavthakkar, store access token once user authorises your app. The life time of an access token is one hour. You can use refresh tokens to get new access tokens after that.