2 files changed, 20 insertions, 1 deletions

diff --git a/src/mailman/handlers/cook_headers.py b/src/mailman/handlers/cook_headers.py
index 297155d90..f43e3ad5a 100644
--- a/src/mailman/handlers/cook_headers.py
+++ b/src/mailman/handlers/cook_headers.py
@@ -18,6 +18,7 @@
 """Cook a message's headers."""
 
 import re
+import logging
 
 from email.header import Header
 from email.utils import formataddr, getaddresses, parseaddr
@@ -28,6 +29,7 @@ from mailman.interfaces.mailinglist import Personalization, ReplyToMunging
 from mailman.version import VERSION
 from zope.interface import implementer
 
+log = logging.getLogger('mailman.error')
 
 COMMASPACE = ', '
 MAXLINELEN = 78
@@ -42,6 +44,8 @@ def uheader(mlist, s, header_name=None, continuation_ws='\t', maxlinelen=None):
     there is and the charset is us-ascii then we use iso-8859-1 instead.  If
     the string is ascii only we use 'us-ascii' if another charset is
     specified.
+
+    If the header contains a newline, truncate it (see GL#273).
     """
     charset = mlist.preferred_language.charset
     if NONASCII.search(s):
@@ -51,6 +55,10 @@ def uheader(mlist, s, header_name=None, continuation_ws='\t', maxlinelen=None):
     else:
         # there is no non-ascii so ...
         charset = 'us-ascii'
+    if '\n' in s:
+        s = '{} [...]'.format(s.split('\n')[0])
+        log.warning('Header {} contains a newline, truncating it.'.format(
+                    header_name, s))
     return Header(s, charset, maxlinelen, header_name, continuation_ws)
 
 
diff --git a/src/mailman/handlers/tests/test_cook_headers.py b/src/mailman/handlers/tests/test_cook_headers.py
index fad3f49d9..f9def6ca8 100644
--- a/src/mailman/handlers/tests/test_cook_headers.py
+++ b/src/mailman/handlers/tests/test_cook_headers.py
@@ -23,7 +23,7 @@ from mailman.app.lifecycle import create_list
 from mailman.handlers import cook_headers
 from mailman.interfaces.member import DeliveryMode
 from mailman.testing.helpers import (
-    get_queue_messages, make_digest_messages, subscribe)
+    get_queue_messages, LogFileMark, make_digest_messages, subscribe)
 from mailman.testing.layers import ConfigLayer
 
 
@@ -50,3 +50,14 @@ class TestCookHeaders(unittest.TestCase):
             except AttributeError as error:
                 # LP: #1130696 would raise an AttributeError on .sender
                 self.fail(error)
+
+    def test_uheader_multiline(self):
+        # Multiline headers should be truncated (GL#273).
+        mark = LogFileMark('mailman.error')
+        header = cook_headers.uheader(
+            self._mlist, 'A multiline\ndescription', 'X-Header')
+        self.assertEqual(
+            header.encode(), 'A multiline [...]')
+        log_messages = mark.read()
+        self.assertIn(
+            'Header X-Header contains a newline, truncating it', log_messages)