If I am not wrong, you are looking for these files (below screenshots)
Open CMS.zip file at location /modules/_protected/CMS/
Open Util folder and you will see Login.aspx and Logout.aspx
I am not sure what you are trying to acheive. But hope this will be helpful.
I am looking for the default/standard login and logout functionality/code/templates of episerver. Where can I find them?
I looked in the episerver alloy demo website but could not find anything meaningful there.