Correct case-folding of permanent URLs

Fixes #87

authl/utils.py

@@ -3,6 +3,7 @@
 import logging
 import os.path
 import typing
+import urllib.parse
 
 import requests
 
@@ -46,14 +47,19 @@ def permanent_url(response: requests.Response) -> str:
     """ Given a requests.Response object, determine what the permanent URL
     for it is from the response history """
 
+    def normalize(url):
+        # normalize the netloc to lowercase
+        parsed = urllib.parse.urlparse(url)
+        return urllib.parse.urlunparse(parsed._replace(netloc=parsed.netloc.lower()))
+
     for item in response.history:
         if item.status_code in (301, 308):
             # permanent redirect means we continue on to the next URL in the
             # redirection change
             continue
         # Any other status code is assumed to be a temporary redirect, so this
         # is the last permanent URL
-        return item.url
+        return normalize(item.url)
 
     # Last history item was a permanent redirect, or there was no history
-    return response.url
+    return normalize(response.url)

tests/test_utils.py

@@ -47,6 +47,10 @@ def test_permanent_url(requests_mock):
     req = requests.get('https://make-secure.example/final')
     assert utils.permanent_url(req) == 'https://make-secure.example/final'
 
+    # correct case folding
+    req = requests.get('Https://Make-SecuRE.Example/final')
+    assert utils.permanent_url(req) == 'https://make-secure.example/final'
+
     # ensure 308 redirect works too
     requests_mock.get('http://perm-308.example', status_code=308,
                       headers={'Location': 'https://make-secure.example/308'})