Blame SOURCES/00351-avoid-infinite-loop-in-the-tarfile-module.patch

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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: Wed, 15 Jul 2020 05:36:36 -0700
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Subject: [PATCH] 00351: Avoid infinite loop in the tarfile module
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Avoid infinite loop when reading specially crafted TAR files using the tarfile module
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(CVE-2019-20907).
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Fixed upstream: https://bugs.python.org/issue39017
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---
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 Lib/tarfile.py                                    |   2 ++
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 Lib/test/recursion.tar                            | Bin 0 -> 516 bytes
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 Lib/test/test_tarfile.py                          |   7 +++++++
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 .../2020-07-12-22-16-58.bpo-39017.x3Cg-9.rst      |   1 +
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 4 files changed, 10 insertions(+)
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 create mode 100644 Lib/test/recursion.tar
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 create mode 100644 Misc/NEWS.d/next/Library/2020-07-12-22-16-58.bpo-39017.x3Cg-9.rst
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diff --git a/Lib/tarfile.py b/Lib/tarfile.py
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index 62d22150f5..2ea47978ff 100755
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--- a/Lib/tarfile.py
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+++ b/Lib/tarfile.py
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@@ -1231,6 +1231,8 @@ class TarInfo(object):
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             length, keyword = match.groups()
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             length = int(length)
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+            if length == 0:
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+                raise InvalidHeaderError("invalid header")
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             value = buf[match.end(2) + 1:match.start(1) + length - 1]
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             # Normally, we could just use "utf-8" as the encoding and "strict"
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diff --git a/Lib/test/recursion.tar b/Lib/test/recursion.tar
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new file mode 100644
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index 0000000000000000000000000000000000000000..b8237251964983f54ed1966297e887636cd0c5f4
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GIT binary patch
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literal 516
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zcmYdFPRz+kEn=W0Fn}74P8%Xw3X=l~85kIuo0>8xq$A1Gm}!7)KUsFc41m#O8A5+e
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I1_}|j06>QaCIA2c
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literal 0
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HcmV?d00001
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diff --git a/Lib/test/test_tarfile.py b/Lib/test/test_tarfile.py
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index 4cd7d5370f..573be812ea 100644
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--- a/Lib/test/test_tarfile.py
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+++ b/Lib/test/test_tarfile.py
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@@ -395,6 +395,13 @@ class CommonReadTest(ReadTest):
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                 with self.assertRaisesRegex(tarfile.ReadError, "unexpected end of data"):
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                     tar.extractfile(t).read()
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+    def test_length_zero_header(self):
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+        # bpo-39017 (CVE-2019-20907): reading a zero-length header should fail
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+        # with an exception
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+        with self.assertRaisesRegex(tarfile.ReadError, "file could not be opened successfully"):
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+            with tarfile.open(support.findfile('recursion.tar')) as tar:
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+                pass
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+
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 class MiscReadTestBase(CommonReadTest):
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     def requires_name_attribute(self):
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         pass
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diff --git a/Misc/NEWS.d/next/Library/2020-07-12-22-16-58.bpo-39017.x3Cg-9.rst b/Misc/NEWS.d/next/Library/2020-07-12-22-16-58.bpo-39017.x3Cg-9.rst
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new file mode 100644
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index 0000000000..ad26676f8b
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--- /dev/null
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+++ b/Misc/NEWS.d/next/Library/2020-07-12-22-16-58.bpo-39017.x3Cg-9.rst
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@@ -0,0 +1 @@
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+Avoid infinite loop when reading specially crafted TAR files using the tarfile module (CVE-2019-20907).