Don't crash diaspora retrieve_diaspora_webfinger on XRD parse error

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## [unreleased]
+
+### Fixes
+* Don't crash `federation.utils.diaspora.retrieve_diaspora_webfinger` if XRD parse raises an `xml.parsers.expat.ExpatError`.
+
 ## [0.9.1] - 2016-12-10
 
 ### Fixes

federation/tests/utils/test_diaspora.py

@@ -1,4 +1,5 @@
 # -*- coding: utf-8 -*-
+import xml
 from unittest.mock import patch, Mock
 from urllib.parse import quote
 
@@ -69,6 +70,17 @@ class TestRetrieveDiasporaWebfinger(object):
         mock_fetch.assert_called_with("https://localhost/webfinger?q=%s" % quote("bob@localhost"))
         assert document == None
 
+    @patch("federation.utils.diaspora.fetch_document", return_value=("document", None, None))
+    @patch("federation.utils.diaspora.retrieve_diaspora_host_meta", return_value=None)
+    @patch("federation.utils.diaspora.XRD.parse_xrd", side_effect=xml.parsers.expat.ExpatError)
+    def test_returns_none_on_xrd_parse_exception(self, mock_parse, mock_retrieve, mock_fetch):
+        mock_retrieve.return_value = DiasporaHostMeta(
+            webfinger_host="https://localhost"
+        ).xrd
+        document = retrieve_diaspora_webfinger("bob@localhost")
+        mock_parse.assert_called_once_with("document")
+        assert document == None
+
 
 class TestRetrieveDiasporaHostMeta(object):
     @patch("federation.utils.diaspora.XRD.parse_xrd")

federation/utils/diaspora.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 import logging
+import xml
 from urllib.parse import quote
 
 from lxml import html
@@ -42,7 +43,10 @@ def retrieve_diaspora_webfinger(handle):
     document, code, exception = fetch_document(url)
     if exception:
         return None
-    xrd = XRD.parse_xrd(document)
+    try:
+        xrd = XRD.parse_xrd(document)
+    except xml.parsers.expat.ExpatError:
+        return None
     return xrd