+45
-17
lines changedFilter options
+45
-17
lines changed Original file line number Diff line number Diff line change
@@ -39,23 +39,21 @@ def nameprep(label):
39 39 40 40
# Check bidi
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RandAL = [stringprep.in_table_d1(x) for x in label]
42 -
for c in RandAL:
43 -
if c:
44 -
# There is a RandAL char in the string. Must perform further
45 -
# tests:
46 -
# 1) The characters in section 5.8 MUST be prohibited.
47 -
# This is table C.8, which was already checked
48 -
# 2) If a string contains any RandALCat character, the string
49 -
# MUST NOT contain any LCat character.
50 -
if any(stringprep.in_table_d2(x) for x in label):
51 -
raise UnicodeError("Violation of BIDI requirement 2")
52 - 53 -
# 3) If a string contains any RandALCat character, a
54 -
# RandALCat character MUST be the first character of the
55 -
# string, and a RandALCat character MUST be the last
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# character of the string.
57 -
if not RandAL[0] or not RandAL[-1]:
58 -
raise UnicodeError("Violation of BIDI requirement 3")
42 +
if any(RandAL):
43 +
# There is a RandAL char in the string. Must perform further
44 +
# tests:
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# 1) The characters in section 5.8 MUST be prohibited.
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# This is table C.8, which was already checked
47 +
# 2) If a string contains any RandALCat character, the string
48 +
# MUST NOT contain any LCat character.
49 +
if any(stringprep.in_table_d2(x) for x in label):
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raise UnicodeError("Violation of BIDI requirement 2")
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# 3) If a string contains any RandALCat character, a
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# RandALCat character MUST be the first character of the
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# string, and a RandALCat character MUST be the last
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# character of the string.
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if not RandAL[0] or not RandAL[-1]:
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raise UnicodeError("Violation of BIDI requirement 3")
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return label
61 59
@@ -103,6 +101,16 @@ def ToASCII(label):
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raise UnicodeError("label empty or too long")
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def ToUnicode(label):
104 +
if len(label) > 1024:
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# Protection from https://github.com/python/cpython/issues/98433.
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# https://datatracker.ietf.org/doc/html/rfc5894#section-6
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# doesn't specify a label size limit prior to NAMEPREP. But having
108 +
# one makes practical sense.
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# This leaves ample room for nameprep() to remove Nothing characters
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# per https://www.rfc-editor.org/rfc/rfc3454#section-3.1 while still
111 +
# preventing us from wasting time decoding a big thing that'll just
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# hit the actual <= 63 length limit in Step 6.
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raise UnicodeError("label way too long")
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# Step 1: Check for ASCII
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if isinstance(label, bytes):
108 116
pure_ascii = True
@@ -1552,6 +1552,12 @@ def test_builtin_encode(self):
1552 1552
self.assertEqual("pyth\xf6n.org".encode("idna"), b"xn--pythn-mua.org")
1553 1553
self.assertEqual("pyth\xf6n.org.".encode("idna"), b"xn--pythn-mua.org.")
1554 1554 1555 +
def test_builtin_decode_length_limit(self):
1556 +
with self.assertRaisesRegex(UnicodeError, "way too long"):
1557 +
(b"xn--016c"+b"a"*1100).decode("idna")
1558 +
with self.assertRaisesRegex(UnicodeError, "too long"):
1559 +
(b"xn--016c"+b"a"*70).decode("idna")
1560 + 1555 1561
def test_stream(self):
1556 1562
r = codecs.getreader("idna")(io.BytesIO(b"abc"))
1557 1563
r.read(3)
@@ -0,0 +1,14 @@
1 +
The IDNA codec decoder used on DNS hostnames by :mod:`socket` or :mod:`asyncio`
2 +
related name resolution functions no longer involves a quadratic algorithm.
3 +
This prevents a potential CPU denial of service if an out-of-spec excessive
4 +
length hostname involving bidirectional characters were decoded. Some protocols
5 +
such as :mod:`urllib` http ``3xx`` redirects potentially allow for an attacker
6 +
to supply such a name.
7 + 8 +
Individual labels within an IDNA encoded DNS name will now raise an error early
9 +
during IDNA decoding if they are longer than 1024 unicode characters given that
10 +
each decoded DNS label must be 63 or fewer characters and the entire decoded
11 +
DNS name is limited to 255. Only an application presenting a hostname or label
12 +
consisting primarily of :rfc:`3454` section 3.1 "Nothing" characters to be
13 +
removed would run into of this new limit. See also :rfc:`5894` section 6 and
14 +
:rfc:`3491`.
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