71 lines
2.8 KiB
Diff
71 lines
2.8 KiB
Diff
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From 24d7b67eac89f94e11003424bcf0d8f7b72222a8 Mon Sep 17 00:00:00 2001
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From: Illia Volochii <illia.volochii@gmail.com>
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Date: Fri, 5 Dec 2025 16:41:33 +0200
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Subject: [PATCH] Merge commit from fork
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* Add a hard-coded limit for the decompression chain
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* Reuse new list
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---
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changelog/GHSA-gm62-xv2j-4w53.security.rst | 4 ++++
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src/urllib3/response.py | 12 +++++++++++-
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test/test_response.py | 10 ++++++++++
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3 files changed, 25 insertions(+), 1 deletion(-)
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create mode 100644 changelog/GHSA-gm62-xv2j-4w53.security.rst
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Index: urllib3-1.26.20/changelog/GHSA-gm62-xv2j-4w53.security.rst
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===================================================================
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--- /dev/null
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+++ urllib3-1.26.20/changelog/GHSA-gm62-xv2j-4w53.security.rst
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@@ -0,0 +1,4 @@
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+Fixed a security issue where an attacker could compose an HTTP response with
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+virtually unlimited links in the ``Content-Encoding`` header, potentially
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+leading to a denial of service (DoS) attack by exhausting system resources
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+during decoding. The number of allowed chained encodings is now limited to 5.
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Index: urllib3-1.26.20/src/urllib3/response.py
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===================================================================
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--- urllib3-1.26.20.orig/src/urllib3/response.py
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+++ urllib3-1.26.20/src/urllib3/response.py
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@@ -225,8 +225,18 @@ class MultiDecoder(object):
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they were applied.
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"""
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- def __init__(self, modes):
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- self._decoders = [_get_decoder(m.strip()) for m in modes.split(",")]
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+ # Maximum allowed number of chained HTTP encodings in the
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+ # Content-Encoding header.
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+ max_decode_links = 5
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+
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+ def __init__(self, modes: str) -> None:
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+ encodings = [m.strip() for m in modes.split(",")]
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+ if len(encodings) > self.max_decode_links:
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+ raise DecodeError(
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+ "Too many content encodings in the chain: "
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+ f"{len(encodings)} > {self.max_decode_links}"
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+ )
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+ self._decoders = [_get_decoder(e) for e in encodings]
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def flush(self):
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return self._decoders[0].flush()
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Index: urllib3-1.26.20/test/test_response.py
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===================================================================
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--- urllib3-1.26.20.orig/test/test_response.py
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+++ urllib3-1.26.20/test/test_response.py
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@@ -477,6 +477,16 @@ class TestResponse(object):
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assert r.data == b"foo"
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+ def test_read_multi_decoding_too_many_links(self):
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+ fp = BytesIO(b"foo")
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+ with pytest.raises(
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+ DecodeError, match="Too many content encodings in the chain: 6 > 5"
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+ ):
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+ HTTPResponse(
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+ fp,
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+ headers={"content-encoding": "gzip, deflate, br, zstd, gzip, deflate"},
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+ )
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+
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def test_body_blob(self):
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resp = HTTPResponse(b"foo")
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assert resp.data == b"foo"
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