10000 [3.11] gh-98433: Fix quadratic time idna decoding. (GH-99092) by miss-islington · Pull Request #99222 · python/cpython · GitHub
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[3.11] gh-98433: Fix quadratic time idna decoding. (GH-99092) #99222

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Merged
merged 3 commits into from
Nov 8, 2022
Merged

[3.11] gh-98433: Fix quadratic time idna decoding. (GH-99092) #99222

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3a692f2
gh-98433: Fix quadratic time idna decoding. (GH-99092)
gpshead Nov 8, 2022
72ea7f8
Remove the upfront length check in the backports.
gpshead Nov 8, 2022
f047396
drop mention of the new length check from NEWS
gpshead Nov 8, 2022
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Remove the upfront length check in the backports. 
While I don't think anyone should have reasonable code depending on
unbounded strings full of Nothing characters to silently be removed
during idna decoding... this is the conservative choice for a bugfix
backport.
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@gpshead
gpshead committed Nov 8, 2022
commit 72ea7f80c7b9defcf8fbac8d01cf1c856f751440
10 changes: 0 additions & 10 deletions Lib/encodings/idna.py
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Expand Up @@ -101,16 +101,6 @@ def ToASCII(label):
raise UnicodeError("label empty or too long")

def ToUnicode(label):
if len(label) > 1024:
# Protection from https://github.com/python/cpython/issues/98433.
# https://datatracker.ietf.org/doc/html/rfc5894#section-6
# doesn't specify a label size limit prior to NAMEPREP. But having
# one makes practical sense.
# This leaves ample room for nameprep() to remove Nothing characters
# per https://www.rfc-editor.org/rfc/rfc3454#section-3.1 while still
# preventing us from wasting time decoding a big thing that'll just
# hit the actual <= 63 length limit in Step 6.
raise UnicodeError("label way too long")
# Step 1: Check for ASCII
if isinstance(label, bytes):
pure_ascii = True
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2 changes: 1 addition & 1 deletion Lib/test/test_codecs.py
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Expand Up @@ -1554,7 +1554,7 @@ def test_builtin_encode(self):
self.assertEqual("pyth\xf6n.org.".encode("idna"), b"xn--pythn-mua.org.")

def test_builtin_decode_length_limit(self):
with self.assertRaisesRegex(UnicodeError, "way too long"):
with self.assertRaisesRegex(UnicodeError, "too long"):
(b"xn--016c"+b"a"*1100).decode("idna")
with self.assertRaisesRegex(UnicodeError, "too long"):
(b"xn--016c"+b"a"*70).decode("idna")
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