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Commit9a31386

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encukoumedmundsbitdancer
authored
[3.9]gh-121284: Fix email address header folding with parsed encoded-word (GH-122754) (GH-131412)
Email generators using email.policy.default may convert an RFC 2047encoded-word to unencoded form during header refolding. In a structuredheader, this could allow 'specials' chars outside a quoted-string,leading to invalid address headers and enabling spoofing. This changeensures a parsed encoded-word that contains specials is kept as anencoded-word while the header is refolded.[Better fix from@bitdancer.](cherry picked from commit295b53d)Co-authored-by: Mike Edmunds <medmunds@gmail.com>Co-authored-by: R David Murray <rdmurray@bitdance.com>
1 parentff4e5c2 commit9a31386

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3 files changed

+37
-5
lines changed

3 files changed

+37
-5
lines changed

‎Lib/email/_header_value_parser.py

Lines changed: 5 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -1037,7 +1037,7 @@ def get_fws(value):
10371037
fws=WhiteSpaceTerminal(value[:len(value)-len(newvalue)],'fws')
10381038
returnfws,newvalue
10391039

1040-
defget_encoded_word(value):
1040+
defget_encoded_word(value,terminal_type='vtext'):
10411041
""" encoded-word = "=?" charset "?" encoding "?" encoded-text "?="
10421042
10431043
"""
@@ -1076,7 +1076,7 @@ def get_encoded_word(value):
10761076
ew.append(token)
10771077
continue
10781078
chars,*remainder=_wsp_splitter(text,1)
1079-
vtext=ValueTerminal(chars,'vtext')
1079+
vtext=ValueTerminal(chars,terminal_type)
10801080
_validate_xtext(vtext)
10811081
ew.append(vtext)
10821082
text=''.join(remainder)
@@ -1118,7 +1118,7 @@ def get_unstructured(value):
11181118
valid_ew=True
11191119
ifvalue.startswith('=?'):
11201120
try:
1121-
token,value=get_encoded_word(value)
1121+
token,value=get_encoded_word(value,'utext')
11221122
except_InvalidEwError:
11231123
valid_ew=False
11241124
excepterrors.HeaderParseError:
@@ -1147,7 +1147,7 @@ def get_unstructured(value):
11471147
# the parser to go in an infinite loop.
11481148
ifvalid_ewandrfc2047_matcher.search(tok):
11491149
tok,*remainder=value.partition('=?')
1150-
vtext=ValueTerminal(tok,'vtext')
1150+
vtext=ValueTerminal(tok,'utext')
11511151
_validate_xtext(vtext)
11521152
unstructured.append(vtext)
11531153
value=''.join(remainder)
@@ -2781,7 +2781,7 @@ def _refold_parse_tree(parse_tree, *, policy):
27812781
continue
27822782
tstr=str(part)
27832783
ifnotwant_encoding:
2784-
ifpart.token_type=='ptext':
2784+
ifpart.token_typein ('ptext','vtext'):
27852785
# Encode if tstr contains special characters.
27862786
want_encoding=notSPECIALSNL.isdisjoint(tstr)
27872787
else:

‎Lib/test/test_email/test__header_value_parser.py

Lines changed: 25 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2946,6 +2946,31 @@ def test_address_list_with_unicode_names_in_quotes(self):
29462946
'=?utf-8?q?H=C3=BCbsch?= Kaktus <beautiful@example.com>,\n'
29472947
' =?utf-8?q?bei=C3=9Ft_bei=C3=9Ft?= <biter@example.com>\n')
29482948

2949+
deftest_address_list_with_specials_in_encoded_word(self):
2950+
# An encoded-word parsed from a structured header must remain
2951+
# encoded when it contains specials. Regression for gh-121284.
2952+
policy=self.policy.clone(max_line_length=40)
2953+
cases= [
2954+
# (to, folded)
2955+
('=?utf-8?q?A_v=C3=A9ry_long_name_with=2C_comma?= <to@example.com>',
2956+
'A =?utf-8?q?v=C3=A9ry_long_name_with?=\n'
2957+
' =?utf-8?q?=2C?= comma <to@example.com>\n'),
2958+
('=?utf-8?q?This_long_name_does_not_need_encoded=2Dword?= <to@example.com>',
2959+
'This long name does not need\n'
2960+
' encoded-word <to@example.com>\n'),
2961+
('"A véry long name with, comma" <to@example.com>',
2962+
# (This isn't the best fold point, but it's not invalid.)
2963+
'A =?utf-8?q?v=C3=A9ry_long_name_with?=\n'
2964+
' =?utf-8?q?=2C?= comma <to@example.com>\n'),
2965+
('"A véry long name containing a, comma" <to@example.com>',
2966+
'A =?utf-8?q?v=C3=A9ry?= long name\n'
2967+
' containing =?utf-8?q?a=2C?= comma\n'
2968+
' <to@example.com>\n'),
2969+
]
2970+
for (to,folded)incases:
2971+
withself.subTest(to=to):
2972+
self._test(parser.get_address_list(to)[0],folded,policy=policy)
2973+
29492974
# XXX Need tests with comments on various sides of a unicode token,
29502975
# and with unicode tokens in the comments. Spaces inside the quotes
29512976
# currently don't do the right thing.
Lines changed: 7 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,7 @@
1+
Fix bug in the folding of rfc2047 encoded-words when flattening an email message
2+
using a modern email policy. Previously when an encoded-word was too long
3+
for a line, it would be decoded, split across lines, and re-encoded. But commas
4+
and other special characters in the original text could be left unencoded and
5+
unquoted. This could theoretically be used to spoof header lines using
6+
a carefully constructed encoded-word if the resulting rendered email was
7+
transmitted or re-parsed.

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