[3.12] gh-98188: Fix EmailMessage.get_payload to decode data when CTE value has extra text (GH-127547)

Lib/email/message.py

@@ -286,8 +286,12 @@ def get_payload(self, i=None, decode=False):
         if i is not None and not isinstance(self._payload, list):
             raise TypeError('Expected list, got %s' % type(self._payload))
         payload = self._payload
-        # cte might be a Header, so for now stringify it.
-        cte = str(self.get('content-transfer-encoding', '')).lower()
+        cte = self.get('content-transfer-encoding', '')
+        if hasattr(cte, 'cte'):
+            cte = cte.cte
+        else:
+            # cte might be a Header, so for now stringify it.
+            cte = str(cte).strip().lower()
         # payload may be bytes here.
         if not decode:
             if isinstance(payload, str) and utils._has_surrogates(payload):

Lib/test/test_email/test_email.py

@@ -810,6 +810,16 @@ def test_unicode_body_defaults_to_utf8_encoding(self):
             w4kgdGVzdGFiYwo=
             """))
 
+    def test_string_payload_with_base64_cte(self):
+        msg = email.message_from_string(textwrap.dedent("""\
+        Content-Transfer-Encoding: base64
+
+        SGVsbG8uIFRlc3Rpbmc=
+        """), policy=email.policy.default)
+        self.assertEqual(msg.get_payload(decode=True), b"Hello. Testing")
+        self.assertDefectsEqual(msg['content-transfer-encoding'].defects, [])
+
+
 
 # Test the email.encoders module
 class TestEncoders(unittest.TestCase):
@@ -2352,6 +2362,40 @@ def test_missing_header_body_separator(self):
         self.assertDefectsEqual(msg.defects,
                                 [errors.MissingHeaderBodySeparatorDefect])
 
+    def test_string_payload_with_extra_space_after_cte(self):
+        # https://github.com/python/cpython/issues/98188
+        cte = "base64 "
+        msg = email.message_from_string(textwrap.dedent(f"""\
+        Content-Transfer-Encoding: {cte}
+
+        SGVsbG8uIFRlc3Rpbmc=
+        """), policy=email.policy.default)
+        self.assertEqual(msg.get_payload(decode=True), b"Hello. Testing")
+        self.assertDefectsEqual(msg['content-transfer-encoding'].defects, [])
+
+    def test_string_payload_with_extra_text_after_cte(self):
+        msg = email.message_from_string(textwrap.dedent("""\
+        Content-Transfer-Encoding: base64 some text
+
+        SGVsbG8uIFRlc3Rpbmc=
+        """), policy=email.policy.default)
+        self.assertEqual(msg.get_payload(decode=True), b"Hello. Testing")
+        cte = msg['content-transfer-encoding']
+        self.assertDefectsEqual(cte.defects, [email.errors.InvalidHeaderDefect])
+
+    def test_string_payload_with_extra_space_after_cte_compat32(self):
+        cte = "base64 "
+        msg = email.message_from_string(textwrap.dedent(f"""\
+        Content-Transfer-Encoding: {cte}
+
+        SGVsbG8uIFRlc3Rpbmc=
+        """), policy=email.policy.compat32)
+        pasted_cte = msg['content-transfer-encoding']
+        self.assertEqual(pasted_cte, cte)
+        self.assertEqual(msg.get_payload(decode=True), b"Hello. Testing")
+        self.assertDefectsEqual(msg.defects, [])
+
+
 
 # Test RFC 2047 header encoding and decoding
 class TestRFC2047(TestEmailBase):

Lib/test/test_email/test_headerregistry.py

@@ -838,6 +838,11 @@ def cte_as_value(self,
             '7bit',
             [errors.InvalidHeaderDefect]),
 
+        'extra_space_after_cte': (
+            'base64 ',
+            'base64',
+            []),
+
     }
 
 

Misc/ACKS

@@ -1112,6 +1112,7 @@ Gregor Lingl
 Everett Lipman
 Mirko Liss
 Alexander Liu
+Hui Liu
 Yuan Liu
 Nick Lockwood
 Stephanie Lockwood

Misc/NEWS.d/next/Library/2024-12-03-14-45-16.gh-issue-98188.GX9i2b.rst

@@ -0,0 +1,3 @@
+Fix an issue in :meth:`email.message.Message.get_payload` where data
+cannot be decoded if the Content Transfer Encoding mechanism contains
+trailing whitespaces or additional junk text. Patch by Hui Liu.