| From 064ec20bf7a181ba5fa961aaa12973812aa6ca5d Mon Sep 17 00:00:00 2001 |
| From: "Miss Islington (bot)" |
| <31488909+miss-islington@users.noreply.github.com> |
| Date: Mon, 7 Nov 2022 18:57:10 -0800 |
| Subject: [PATCH] [3.11] gh-98433: Fix quadratic time idna decoding. (GH-99092) |
| (GH-99222) |
| |
| There was an unnecessary quadratic loop in idna decoding. This restores |
| the behavior to linear. |
| |
| (cherry picked from commit d315722564927c7202dd6e111dc79eaf14240b0d) |
| |
| (cherry picked from commit a6f6c3a3d6f2b580f2d87885c9b8a9350ad7bf15) |
| |
| Co-authored-by: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> |
| Co-authored-by: Gregory P. Smith <greg@krypto.org> |
| --- |
| Lib/encodings/idna.py | 32 +++++++++---------- |
| Lib/test/test_codecs.py | 6 ++++ |
| ...2-11-04-09-29-36.gh-issue-98433.l76c5G.rst | 6 ++++ |
| 3 files changed, 27 insertions(+), 17 deletions(-) |
| create mode 100644 Misc/NEWS.d/next/Security/2022-11-04-09-29-36.gh-issue-98433.l76c5G.rst |
| |
| diff --git a/Lib/encodings/idna.py b/Lib/encodings/idna.py |
| index ea4058512fe3..bf98f513366b 100644 |
| --- a/Lib/encodings/idna.py |
| +++ b/Lib/encodings/idna.py |
| @@ -39,23 +39,21 @@ def nameprep(label): |
| |
| # Check bidi |
| RandAL = [stringprep.in_table_d1(x) for x in label] |
| - for c in RandAL: |
| - if c: |
| - # There is a RandAL char in the string. Must perform further |
| - # tests: |
| - # 1) The characters in section 5.8 MUST be prohibited. |
| - # This is table C.8, which was already checked |
| - # 2) If a string contains any RandALCat character, the string |
| - # MUST NOT contain any LCat character. |
| - if any(stringprep.in_table_d2(x) for x in label): |
| - raise UnicodeError("Violation of BIDI requirement 2") |
| - |
| - # 3) If a string contains any RandALCat character, a |
| - # RandALCat character MUST be the first character of the |
| - # string, and a RandALCat character MUST be the last |
| - # character of the string. |
| - if not RandAL[0] or not RandAL[-1]: |
| - raise UnicodeError("Violation of BIDI requirement 3") |
| + if any(RandAL): |
| + # There is a RandAL char in the string. Must perform further |
| + # tests: |
| + # 1) The characters in section 5.8 MUST be prohibited. |
| + # This is table C.8, which was already checked |
| + # 2) If a string contains any RandALCat character, the string |
| + # MUST NOT contain any LCat character. |
| + if any(stringprep.in_table_d2(x) for x in label): |
| + raise UnicodeError("Violation of BIDI requirement 2") |
| + # 3) If a string contains any RandALCat character, a |
| + # RandALCat character MUST be the first character of the |
| + # string, and a RandALCat character MUST be the last |
| + # character of the string. |
| + if not RandAL[0] or not RandAL[-1]: |
| + raise UnicodeError("Violation of BIDI requirement 3") |
| |
| return label |
| |
| diff --git a/Lib/test/test_codecs.py b/Lib/test/test_codecs.py |
| index d1faf0126c1e..37ade7d80d02 100644 |
| --- a/Lib/test/test_codecs.py |
| +++ b/Lib/test/test_codecs.py |
| @@ -1532,6 +1532,12 @@ def test_builtin_encode(self): |
| self.assertEqual("pyth\xf6n.org".encode("idna"), b"xn--pythn-mua.org") |
| self.assertEqual("pyth\xf6n.org.".encode("idna"), b"xn--pythn-mua.org.") |
| |
| + def test_builtin_decode_length_limit(self): |
| + 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") |
| + |
| def test_stream(self): |
| r = codecs.getreader("idna")(io.BytesIO(b"abc")) |
| r.read(3) |
| 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 |
| new file mode 100644 |
| index 000000000000..5185fac2e29d |
| --- /dev/null |
| +++ b/Misc/NEWS.d/next/Security/2022-11-04-09-29-36.gh-issue-98433.l76c5G.rst |
| @@ -0,0 +1,6 @@ |
| +The IDNA codec decoder used on DNS hostnames by :mod:`socket` or :mod:`asyncio` |
| +related name resolution functions no longer involves a quadratic algorithm. |
| +This prevents a potential CPU denial of service if an out-of-spec excessive |
| +length hostname involving bidirectional characters were decoded. Some protocols |
| +such as :mod:`urllib` http ``3xx`` redirects potentially allow for an attacker |
| +to supply such a name. |