119 lines
5.4 KiB
Diff
119 lines
5.4 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: "Miss Islington (bot)"
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<31488909+miss-islington@users.noreply.github.com>
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Date: Mon, 7 Nov 2022 19:22:14 -0800
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Subject: [PATCH]
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00394-cve-2022-45061-cpu-denial-of-service-via-inefficient-idna-decoder.patch
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00394 #
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gh-98433: Fix quadratic time idna decoding.
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There was an unnecessary quadratic loop in idna decoding. This restores
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the behavior to linear.
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Backported from python3.
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(cherry picked from commit a6f6c3a3d6f2b580f2d87885c9b8a9350ad7bf15)
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Co-authored-by: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>
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Co-authored-by: Gregory P. Smith <greg@krypto.org>
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---
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Lib/encodings/idna.py | 32 +++++++++----------
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Lib/test/test_codecs.py | 6 ++++
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...2-11-04-09-29-36.gh-issue-98433.l76c5G.rst | 6 ++++
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3 files changed, 27 insertions(+), 17 deletions(-)
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create mode 100644 Misc/NEWS.d/next/Security/2022-11-04-09-29-36.gh-issue-98433.l76c5G.rst
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diff --git a/Lib/encodings/idna.py b/Lib/encodings/idna.py
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index ea90d67142f..2ce798cf47e 100644
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--- a/Lib/encodings/idna.py
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+++ b/Lib/encodings/idna.py
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@@ -39,23 +39,21 @@ def nameprep(label):
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# Check bidi
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RandAL = map(stringprep.in_table_d1, label)
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- for c in RandAL:
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- if c:
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- # There is a RandAL char in the string. Must perform further
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- # 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
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- # 2) If a string contains any RandALCat character, the string
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- # MUST NOT contain any LCat character.
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- if filter(stringprep.in_table_d2, label):
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- raise UnicodeError("Violation of BIDI requirement 2")
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-
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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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+ if any(RandAL):
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+ # There is a RandAL char in the string. Must perform further
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+ # 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
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+ # 2) If a string contains any RandALCat character, the string
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+ # MUST NOT contain any LCat character.
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+ 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
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diff --git a/Lib/test/test_codecs.py b/Lib/test/test_codecs.py
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index 0ec8bf5a4b4..76428e1794a 100644
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--- a/Lib/test/test_codecs.py
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+++ b/Lib/test/test_codecs.py
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@@ -1318,6 +1318,12 @@ class IDNACodecTest(unittest.TestCase):
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self.assertEqual(u"pyth\xf6n.org".encode("idna"), "xn--pythn-mua.org")
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self.assertEqual(u"pyth\xf6n.org.".encode("idna"), "xn--pythn-mua.org.")
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+ def test_builtin_decode_length_limit(self):
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+ with self.assertRaisesRegexp(UnicodeError, "too long"):
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+ (b"xn--016c"+b"a"*1100).decode("idna")
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+ with self.assertRaisesRegexp(UnicodeError, "too long"):
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+ (b"xn--016c"+b"a"*70).decode("idna")
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+
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def test_stream(self):
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import StringIO
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r = codecs.getreader("idna")(StringIO.StringIO("abc"))
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diff --git a/Misc/NEWS.d/next/Security/2022-11-04-09-29-36.gh-issue-98433.l76c5G.rst b/Misc/NEWS.d/next/Security/2022-11-04-09-29-36.gh-issue-98433.l76c5G.rst
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new file mode 100644
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index 00000000000..5185fac2e29
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--- /dev/null
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+++ b/Misc/NEWS.d/next/Security/2022-11-04-09-29-36.gh-issue-98433.l76c5G.rst
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@@ -0,0 +1,6 @@
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+The IDNA codec decoder used on DNS hostnames by :mod:`socket` or :mod:`asyncio`
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+related name resolution functions no longer involves a quadratic algorithm.
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+This prevents a potential CPU denial of service if an out-of-spec excessive
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+length hostname involving bidirectional characters were decoded. Some protocols
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+such as :mod:`urllib` http ``3xx`` redirects potentially allow for an attacker
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+to supply such a name.
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diff -urNp a/Lib/encodings/idna.py b/Lib/encodings/idna.py
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--- a/Lib/encodings/idna.py 2023-02-16 08:58:06.884171667 +0100
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+++ b/Lib/encodings/idna.py 2023-02-16 08:59:31.931296399 +0100
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@@ -101,6 +101,16 @@ def ToASCII(label):
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raise UnicodeError("label empty or too long")
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def ToUnicode(label):
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+ 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
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+ # 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
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+ # 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, str):
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pure_ascii = True
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