Merged revisions 87873 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/branches/py3k

........
  r87873 | r.david.murray | 2011-01-08 21:35:24 -0500 (Sat, 08 Jan 2011) | 12 lines

  #5871: protect against header injection attacks.

  This makes Header.encode throw a HeaderParseError if it winds up
  formatting a header such that a continuation line has no leading
  whitespace and looks like a header.  Since Header accepts values
  containing newlines and preserves them (and this is by design), without
  this fix any program that took user input (say, a subject in a web form)
  and passed it to the email package as a header was vulnerable to header
  injection attacks.  (As far as we know this has never been exploited.)

  Thanks to Jakub Wilk for reporting this vulnerability.
........

Lib/email/test/test_email.py

@@ -540,6 +540,19 @@ class TestMessageAPI(TestEmailBase):
             msg['Content-Disposition'])
 
 
+    # Issue 5871: reject an attempt to embed a header inside a header value
+    # (header injection attack).
+    def test_embeded_header_via_Header_rejected(self):
+        msg = Message()
+        msg['Dummy'] = Header('dummy\nX-Injected-Header: test')
+        self.assertRaises(errors.HeaderParseError, msg.as_string)
+
+    def test_embeded_header_via_string_rejected(self):
+        msg = Message()
+        msg['Dummy'] = 'dummy\nX-Injected-Header: test'
+        self.assertRaises(errors.HeaderParseError, msg.as_string)
+
+
 # Test the email.encoders module
 class TestEncoders(unittest.TestCase):
     def test_encode_empty_payload(self):