Merge pull request #108 from PlaidWeb/feature/93-relmeauth

Add support for RelMeAuth, sort of

authl/__init__.py

@@ -70,19 +70,17 @@ def get_handler_for_url(self, url: str) -> typing.Tuple[typing.Optional[handlers
         :returns: a tuple of ``(handler, hander_id, profile_url)``.
 
         """
+        # pylint:disable=too-many-return-statements
 
         url = url.strip()
-
-        # If webfinger detects profiles for this address, try all of those first
-        for profile in webfinger.get_profiles(url):
-            LOGGER.debug("Checking profile %s", profile)
-            resp = self.get_handler_for_url(profile)
-            if resp[0]:
-                return resp
-
         if not url:
             return None, '', ''
 
+        # check webfinger profiles
+        resp = self.check_profiles(webfinger.get_profiles(url))
+        if resp and resp[0]:
+            return resp
+
         by_url = self._match_url(url)
         if by_url[0]:
             return by_url
@@ -104,13 +102,28 @@ def get_handler_for_url(self, url: str) -> typing.Tuple[typing.Optional[handlers
                     LOGGER.debug("%s response matches %s", profile, handler)
                     return handler, hid, request.url
 
+            # check for RelMeAuth candidates
+            resp = self.check_profiles(utils.extract_rel('me', profile, soup, request.links))
+            if resp and resp[0]:
+                return resp
+
         LOGGER.debug("No handler found for URL %s", url)
         return None, '', ''
 
     def get_handler_by_id(self, handler_id):
         """ Get the handler with the given ID, for a transaction in progress. """
         return self._handlers.get(handler_id)
 
+    def check_profiles(self, profiles) -> typing.Tuple[typing.Optional[handlers.Handler], str, str]:
+        """ Given a list of profile URLs, check them for a handle-able identity """
+        for profile in profiles:
+            LOGGER.debug("Checking profile %s", profile)
+            resp = self.get_handler_for_url(profile)
+            if resp and resp[0]:
+                return resp
+
+        return None, '', ''
+
     @property
     def handlers(self):
         """ Provides a list of all of the registered handlers. """

authl/utils.py

@@ -100,3 +100,19 @@ def pkce_challenge(verifier: str, method: str = 'S256') -> str:
         return encoded.decode().strip('=')
 
     raise ValueError(f'Unknown PKCE method {method}')
+
+
+def extract_rel(rel: str, base_url, content, links) -> typing.Set[str]:
+    """ Given a parsed page/response, extract all of the URLs that match a particular link rel """
+    result: typing.Set[str] = set()
+
+    if links and rel in links:
+        LOGGER.debug("%s: Found %s link header: %s", base_url, rel, links[rel]['url'])
+        result.add(links[rel]['url'])
+
+    if content:
+        for link in content.find_all(('link', 'a'), rel=rel):
+            LOGGER.debug("%s: Found %s link tag: %s", base_url, rel, link.get('href'))
+            result.add(urllib.parse.urljoin(base_url, link.get('href')))
+
+    return result

tests/test_main.py

@@ -158,3 +158,32 @@ def test_scheme_fallback(requests_mock):
         'http://foo/bar') == (handler_http, 'insecure', 'http://foo/bar')
     assert instance.get_handler_for_url('foo/bar') == (handler_https, 'secure', 'https://foo/bar')
     assert instance.get_handler_for_url('example://foo') == (None, '', '')
+
+
+def test_relme_auth(requests_mock):
+    """ test RelMeAuth profile support """
+    handler_1 = UrlHandler('test://foo', 'a')
+    handler_2 = UrlHandler('https://social.example/bob', 'b')
+    instance = Authl([handler_1, handler_2])
+
+    requests_mock.get('https://foo-link.example/', text='<link rel="me" href="test://foo">')
+    requests_mock.get('https://foo-a.example/', text='<a rel="me" href="test://foo">')
+    requests_mock.get('https://header.example/', headers={'Link': '<test://foo>; rel="me"'})
+
+    requests_mock.get('https://social.example/relative-link', text='<link rel="me" href="bob">')
+    requests_mock.get('https://social.example/relative-a', text='<a rel="me" href="bob">')
+    requests_mock.get('https://multiple.example/', text='''
+        <link rel="me" href="test://bar">
+        <link rel="me" href="test://baz">
+        <a href="https://social.example/bob" rel="me">
+        ''')
+
+    for url in ('https://foo-link.example/',
+                'https://foo-a.example',
+                'https://header.example'):
+        assert instance.get_handler_for_url(url) == (handler_1, 'a', 'test://foo')
+
+    for url in ('https://social.example/relative-link',
+                'https://social.example/relative-a',
+                'https://multiple.example/'):
+        assert instance.get_handler_for_url(url) == (handler_2, 'b', 'https://social.example/bob')