#3196: if needed pad a short base64 encoded word before trying to decode.
The RFCs encourage following Postel's law: be liberal in what you accept.
So if someone forgot to pad the base64 encoded word payload to an
even four bytes, we add the padding before handing it to base64mime.decode.
Previously, missing padding resulted in a HeaderParseError.
Patch by Jason Williams.
diff --git a/Lib/email/header.py b/Lib/email/header.py
index c924d3a..89c1391 100644
--- a/Lib/email/header.py
+++ b/Lib/email/header.py
@@ -94,6 +94,9 @@
word = email.quoprimime.header_decode(encoded_string)
decoded_words.append((word, charset))
elif encoding == 'b':
+ paderr = len(encoded_string) % 4 # Postel's law: add missing padding
+ if paderr:
+ encoded_string += '==='[:4 - paderr]
try:
word = email.base64mime.decode(encoded_string)
except binascii.Error:
diff --git a/Lib/email/test/test_email.py b/Lib/email/test/test_email.py
index 09f51df..c311469 100644
--- a/Lib/email/test/test_email.py
+++ b/Lib/email/test/test_email.py
@@ -1649,6 +1649,15 @@
(b'rg', None), (b'\xe5', 'iso-8859-1'),
(b'sbord', None)])
+ def test_rfc2047_B_bad_padding(self):
+ s = '=?iso-8859-1?B?%s?='
+ data = [ # only test complete bytes
+ ('dm==', b'v'), ('dm=', b'v'), ('dm', b'v'),
+ ('dmk=', b'vi'), ('dmk', b'vi')
+ ]
+ for q, a in data:
+ dh = decode_header(s % q)
+ self.assertEqual(dh, [(a, 'iso-8859-1')])
# Test the MIMEMessage class
@@ -3176,7 +3185,7 @@
def test_broken_base64_header(self):
raises = self.assertRaises
- s = 'Subject: =?EUC-KR?B?CSixpLDtKSC/7Liuvsax4iC6uLmwMcijIKHaILzSwd/H0SC8+LCjwLsgv7W/+Mj3IQ?='
+ s = 'Subject: =?EUC-KR?B?CSixpLDtKSC/7Liuvsax4iC6uLmwMcijIKHaILzSwd/H0SC8+LCjwLsgv7W/+Mj3I ?='
raises(errors.HeaderParseError, decode_header, s)
diff --git a/Misc/ACKS b/Misc/ACKS
index 0347f67..75c3ae7 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -854,6 +854,7 @@
Gerry Wiener
Frank Wierzbicki
Bryce "Zooko" Wilcox-O'Hearn
+Jason Williams
John Williams
Sue Williams
Gerald S. Williams
diff --git a/Misc/NEWS b/Misc/NEWS
index a523b8f..dcf2b62 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -37,6 +37,9 @@
Library
-------
+- Issue #3196: email header decoding is now forgiving if an RFC2047
+ encoded word encoded in base64 is lacking padding.
+
- Issue #9444: Argparse now uses the first element of prefix_chars as
the option character for the added 'h/help' option if prefix_chars
does not contain a '-', instead of raising an error.