bpo-35907, CVE-2019-9948: urllib rejects local_file:// scheme (GH-13474) (GH-13505)

CVE-2019-9948: Avoid file reading as disallowing the unnecessary URL
scheme in URLopener().open() and URLopener().retrieve()
of urllib.request.

Co-Authored-By: SH <[email protected]>
(cherry picked from commit 0c2b6a3)

Author: vstinner

Lib/test/test_urllib.py

@@ -16,6 +16,7 @@
     ssl = None
 import sys
 import tempfile
+import warnings
 from nturl2path import url2pathname, pathname2url
 
 from base64 import b64encode
@@ -1463,6 +1464,23 @@ def open_spam(self, url):
                 "spam://c:|windows%/:=&?~#+!$,;'@()*[]|/path/"),
                 "//c:|windows%/:=&?~#+!$,;'@()*[]|/path/")
 
+    def test_local_file_open(self):
+        # bpo-35907, CVE-2019-9948: urllib must reject local_file:// scheme
+        class DummyURLopener(urllib.request.URLopener):
+            def open_local_file(self, url):
+                return url
+
+        with warnings.catch_warnings(record=True):
+            warnings.simplefilter("ignore", DeprecationWarning)
+
+            for url in ('local_file://example', 'local-file://example'):
+                self.assertRaises(OSError, urllib.request.urlopen, url)
+                self.assertRaises(OSError, urllib.request.URLopener().open, url)
+                self.assertRaises(OSError, urllib.request.URLopener().retrieve, url)
+                self.assertRaises(OSError, DummyURLopener().open, url)
+                self.assertRaises(OSError, DummyURLopener().retrieve, url)
+
+
 # Just commented them out.
 # Can't really tell why keep failing in windows and sparc.
 # Everywhere else they work ok, but on those machines, sometimes

Lib/urllib/request.py

@@ -1746,7 +1746,7 @@ def open(self, fullurl, data=None):
         name = 'open_' + urltype
         self.type = urltype
         name = name.replace('-', '_')
-        if not hasattr(self, name):
+        if not hasattr(self, name) or name == 'open_local_file':
             if proxy:
                 return self.open_unknown_proxy(proxy, fullurl, data)
             else:

Misc/NEWS.d/next/Security/2019-05-21-23-20-18.bpo-35907.NC_zNK.rst

@@ -0,0 +1,2 @@
+CVE-2019-9948: Avoid file reading as disallowing the unnecessary URL scheme in
+``URLopener().open()`` and ``URLopener().retrieve()`` of :mod:`urllib.request`.