cookies: Make over18 cookie not IP-hashed.

The over18 cookie's IP hashing behavior is of dubious use and is not at
all compatible with efficient CDN caching.

r2/r2/controllers/post.py

@@ -143,10 +143,7 @@ class PostController(ApiController):
                 c.user.pref_over_18 = True
                 c.user._commit()
             else:
-                ip_hash = hashlib.sha1(request.ip).hexdigest()
-                domain = g.domain if not c.frameless_cname else None
-                c.cookies.add('over18', ip_hash,
-                              domain = domain)
+                c.cookies.add("over18", "1")
             return self.redirect(dest)
         else:
             return self.redirect('/')

r2/r2/controllers/reddit_base.py

@@ -319,8 +319,10 @@ def over18():
     else:
         if 'over18' in c.cookies:
             cookie = c.cookies['over18'].value
-            if cookie == sha1(request.ip).hexdigest():
+            if cookie == "1":
                 return True
+            else:
+                c.cookies["over18"] = Cookie(value="", expires=DELETE)
 
 def set_obey_over18():
     "querystring parameter for API to obey over18 filtering rules"