bpo-30835: email: Fix AttributeError when parsing invalid CTE (GH-13598)
* bpo-30835: email: Fix AttributeError when parsing invalid Content-Transfer-Encoding
Parsing an email containing a multipart Content-Type, along with a
Content-Transfer-Encoding containing an invalid (non-ASCII-decodable) byte
will fail. email.feedparser.FeedParser._parsegen() gets the header and
attempts to convert it to lowercase before comparing it with the accepted
encodings, but as the header contains an invalid byte, it's returned as a
Header object rather than a str.
Cast the Content-Transfer-Encoding header to a str to avoid this.
Found using the AFL fuzzer.
Reported-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Andrew Donnellan <andrew@donnellan.id.au>
* Add email and NEWS entry for the bugfix.
(cherry picked from commit aa79707262f893428665ef45b5e879129abca4aa)
Co-authored-by: Abhilash Raj <maxking@users.noreply.github.com>
diff --git a/Lib/email/feedparser.py b/Lib/email/feedparser.py
index 7c07ca8..97d3f51 100644
--- a/Lib/email/feedparser.py
+++ b/Lib/email/feedparser.py
@@ -320,7 +320,7 @@
self._cur.set_payload(EMPTYSTRING.join(lines))
return
# Make sure a valid content type was specified per RFC 2045:6.4.
- if (self._cur.get('content-transfer-encoding', '8bit').lower()
+ if (str(self._cur.get('content-transfer-encoding', '8bit')).lower()
not in ('7bit', '8bit', 'binary')):
defect = errors.InvalidMultipartContentTransferEncodingDefect()
self.policy.handle_defect(self._cur, defect)
diff --git a/Lib/test/test_email/test_email.py b/Lib/test/test_email/test_email.py
index dfb3be8..c29cc56 100644
--- a/Lib/test/test_email/test_email.py
+++ b/Lib/test/test_email/test_email.py
@@ -1466,6 +1466,15 @@
g.flatten(msg)
self.assertEqual(b.getvalue(), source + b'>From R\xc3\xb6lli\n')
+ def test_mutltipart_with_bad_bytes_in_cte(self):
+ # bpo30835
+ source = textwrap.dedent("""\
+ From: aperson@example.com
+ Content-Type: multipart/mixed; boundary="1"
+ Content-Transfer-Encoding: \xc8
+ """).encode('utf-8')
+ msg = email.message_from_bytes(source)
+
# Test the basic MIMEAudio class
class TestMIMEAudio(unittest.TestCase):
diff --git a/Misc/NEWS.d/next/Library/2019-05-27-15-29-46.bpo-30835.3FoaWH.rst b/Misc/NEWS.d/next/Library/2019-05-27-15-29-46.bpo-30835.3FoaWH.rst
new file mode 100644
index 0000000..019321d
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-05-27-15-29-46.bpo-30835.3FoaWH.rst
@@ -0,0 +1,3 @@
+Fixed a bug in email parsing where a message with invalid bytes in
+content-transfer-encoding of a multipart message can cause an AttributeError.
+Patch by Andrew Donnellan.