🐛 Ensure the configure requests CA bundle is used

Replaced IDP metadata fetching via urllib with requests.

Projects making use of requests/self-certifi set up the CA bundle
to wire up additional trusted root CAs, which are picked up by
requests, so this should also work properly.

Upstream issue: SAML-Toolkits#403
Open Forms issue: open-formulieren/open-forms#4079

src/onelogin/saml2/idp_metadata_parser.py

@@ -7,12 +7,7 @@
 
 from copy import deepcopy
 
-try:
-    import urllib.request as urllib2
-except ImportError:
-    import urllib2
-
-import ssl
+import requests
 
 from onelogin.saml2.constants import OneLogin_Saml2_Constants
 from onelogin.saml2.xml_utils import OneLogin_Saml2_XML
@@ -46,16 +41,12 @@ def get_metadata(cls, url, validate_cert=True, timeout=None, headers=None):
         """
         valid = False
 
-        request = urllib2.Request(url, headers=headers or {})
-
-        if validate_cert:
-            response = urllib2.urlopen(request, timeout=timeout)
-        else:
-            ctx = ssl.create_default_context()
-            ctx.check_hostname = False
-            ctx.verify_mode = ssl.CERT_NONE
-            response = urllib2.urlopen(request, context=ctx, timeout=timeout)
-        xml = response.read()
+        # MAYKIN: use requests to retrieve the metadata, so the CA bundle configured for
+        # requests can be used and self-signed/private root certificates still continue
+        # to work.
+        response = requests.get(url, headers=headers, verify=validate_cert, timeout=timeout)
+        response.raise_for_status()
+        xml = response.content
 
         if xml:
             try:

tests/src/OneLogin/saml2_tests/idp_metadata_parser_test.py

@@ -1,15 +1,10 @@
 # -*- coding: utf-8 -*-
 
-
-try:
-    from urllib.error import URLError
-except ImportError:
-    from urllib2 import URLError
-
 from copy import deepcopy
 import json
 from os.path import dirname, join, exists
 from lxml.etree import XMLSyntaxError
+from requests import RequestException
 import unittest
 
 from onelogin.saml2.idp_metadata_parser import OneLogin_Saml2_IdPMetadataParser
@@ -51,7 +46,7 @@ def testGetMetadata(self):
         try:
             data = OneLogin_Saml2_IdPMetadataParser.get_metadata('https://idp.testshib.org/idp/shibboleth')
             self.assertTrue(data is not None and data is not {})
-        except URLError:
+        except RequestException:
             pass
 
     def testGetMetadataWithHeaders(self):
@@ -69,7 +64,7 @@ def testParseRemote(self):
 
         try:
             data = OneLogin_Saml2_IdPMetadataParser.parse_remote('https://idp.testshib.org/idp/shibboleth')
-        except URLError:
+        except RequestException:
             xml = self.file_contents(join(self.data_path, 'metadata', 'testshib-providers.xml'))
             data = OneLogin_Saml2_IdPMetadataParser.parse(xml)
 
@@ -172,7 +167,7 @@ def test_parse_testshib_required_binding_sso_redirect(self):
         try:
             xmldoc = OneLogin_Saml2_IdPMetadataParser.get_metadata(
                 'https://idp.testshib.org/idp/shibboleth')
-        except URLError:
+        except RequestException:
             xmldoc = self.file_contents(join(self.data_path, 'metadata', 'testshib-providers.xml'))
 
         # Parse, require SSO REDIRECT binding, implicitly.
@@ -215,7 +210,7 @@ def test_parse_testshib_required_binding_sso_post(self):
         try:
             xmldoc = OneLogin_Saml2_IdPMetadataParser.get_metadata(
                 'https://idp.testshib.org/idp/shibboleth')
-        except URLError:
+        except RequestException:
             xmldoc = self.file_contents(join(self.data_path, 'metadata', 'testshib-providers.xml'))
 
         # Parse, require POST binding.