#28047: Fix calculation of base64 line length.

This is buggy in the old email code as well, but it doesn't affect anything
there because only the default line length is ever used there.

4 files changed, 40 insertions, 7 deletions

diff --git a/Lib/email/contentmanager.py b/Lib/email/contentmanager.py
index d3636529b6..b98ce27184 100644
--- a/Lib/email/contentmanager.py
+++ b/Lib/email/contentmanager.py
@@ -126,12 +126,13 @@ def _finalize_set(msg, disposition, filename, cid, params):
             msg.set_param(key, value)
 
 
-# XXX: This is a cleaned-up version of base64mime.body_encode.  It would
-# be nice to drop both this and quoprimime.body_encode in favor of
-# enhanced binascii routines that accepted a max_line_length parameter.
+# XXX: This is a cleaned-up version of base64mime.body_encode (including a bug
+# fix in the calculation of unencoded_bytes_per_line).  It would be nice to
+# drop both this and quoprimime.body_encode in favor of enhanced binascii
+# routines that accepted a max_line_length parameter.
 def _encode_base64(data, max_line_length):
     encoded_lines = []
-    unencoded_bytes_per_line = max_line_length * 3 // 4
+    unencoded_bytes_per_line = max_line_length // 4 * 3
     for i in range(0, len(data), unencoded_bytes_per_line):
         thisline = data[i:i+unencoded_bytes_per_line]
         encoded_lines.append(binascii.b2a_base64(thisline).decode('ascii'))
diff --git a/Lib/test/test_email/__init__.py b/Lib/test/test_email/__init__.py
index d2f7d31934..d4a03ee071 100644
--- a/Lib/test/test_email/__init__.py
+++ b/Lib/test/test_email/__init__.py
@@ -121,6 +121,10 @@ def parameterize(cls):
     Note: if and only if the generated test name is a valid identifier can it
     be used to select the test individually from the unittest command line.
 
+    The values in the params dict can be a single value, a tuple, or a
+    dict.  If a single value of a tuple, it is passed to the test function
+    as positional arguments.  If a dict, it is a passed via **kw.
+
     """
     paramdicts = {}
     testers = collections.defaultdict(list)
@@ -149,8 +153,12 @@ def parameterize(cls):
             if name.startswith(paramsname):
                 testnameroot = 'test_' + name[len(paramsname):]
                 for paramname, params in paramsdict.items():
-                    test = (lambda self, name=name, params=params:
-                                    getattr(self, name)(*params))
+                    if hasattr(params, 'keys'):
+                        test = (lambda self, name=name, params=params:
+                                    getattr(self, name)(**params))
+                    else:
+                        test = (lambda self, name=name, params=params:
+                                        getattr(self, name)(*params))
                     testname = testnameroot + '_' + paramname
                     test.__name__ = testname
                     testfuncs[testname] = test
diff --git a/Lib/test/test_email/test_inversion.py b/Lib/test/test_email/test_inversion.py
index f36e33d431..8e8d67641b 100644
--- a/Lib/test/test_email/test_inversion.py
+++ b/Lib/test/test_email/test_inversion.py
@@ -7,6 +7,7 @@ producing RFC valid messages.
 import io
 import unittest
 from email import policy, message_from_bytes
+from email.message import EmailMessage
 from email.generator import BytesGenerator
 from test.test_email import TestEmailBase, parameterize
 
@@ -23,7 +24,10 @@ def dedent(bstr):
 
 
 @parameterize
-class TestInversion(TestEmailBase, unittest.TestCase):
+class TestInversion(TestEmailBase):
+
+    policy = policy.default
+    message = EmailMessage
 
     def msg_as_input(self, msg):
         m = message_from_bytes(msg, policy=policy.SMTP)
@@ -44,6 +48,23 @@ class TestInversion(TestEmailBase, unittest.TestCase):
 
             }
 
+    payload_params = {
+        'plain_text': dict(payload='This is a test\n'*20),
+        'base64_text': dict(payload=(('xy a'*40+'\n')*5), cte='base64'),
+        'qp_text': dict(payload=(('xy a'*40+'\n')*5), cte='quoted-printable'),
+        }
+
+    def payload_as_body(self, payload, **kw):
+        msg = self._make_message()
+        msg['From'] = 'foo'
+        msg['To'] = 'bar'
+        msg['Subject'] = 'payload round trip test'
+        msg.set_content(payload, **kw)
+        b = bytes(msg)
+        msg2 = message_from_bytes(b, policy=self.policy)
+        self.assertEqual(bytes(msg2), b)
+        self.assertEqual(msg2.get_content(), payload)
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/Misc/NEWS b/Misc/NEWS
index 1922432e0d..86d499b29f 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -62,6 +62,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #28047: Fixed calculation of line length used for the base64 CTE
+  in the new email policies.
+
 - Issue #27445: Don't pass str(_charset) to MIMEText.set_payload().
   Patch by Claude Paroz.