From 5ba4da0da676647fd972fe4282cdd1c1f9e110c4 Mon Sep 17 00:00:00 2001
From: Rishi <rishi_devan@mail.com>
Date: Wed, 15 Jul 2020 13:51:00 +0200
Subject: [PATCH] 00351-cve-2019-20907-fix-infinite-loop-in-tarfile.patch

00351 #
Avoid infinite loop when reading specially crafted TAR files using the tarfile module
(CVE-2019-20907).
See: https://bugs.python.org/issue39017
---
 Python/Lib/tarfile.py                                      | 2 ++
 Python/Lib/test/test_tarfile.py                            | 7 +++++++
 .../next/Library/2020-07-12-22-16-58.bpo-39017.x3Cg-9.rst  | 1 +
 3 files changed, 10 insertions(+)
 create mode 100644 Python/Misc/NEWS.d/next/Library/2020-07-12-22-16-58.bpo-39017.x3Cg-9.rst

diff --git a/Python/Lib/tarfile.py b/Python/Lib/tarfile.py
index adf91d53..574a6bb2 100644
--- a/Python/Lib/tarfile.py
+++ b/Python/Lib/tarfile.py
@@ -1400,6 +1400,8 @@ class TarInfo(object):
 
             length, keyword = match.groups()
             length = int(length)
+            if length == 0:
+                raise InvalidHeaderError("invalid header")
             value = buf[match.end(2) + 1:match.start(1) + length - 1]
 
             keyword = keyword.decode("utf8")
diff --git a/Python/Lib/test/test_tarfile.py b/Python/Lib/test/test_tarfile.py
index 89bd738a..45921562 100644
--- a/Python/Lib/test/test_tarfile.py
+++ b/Python/Lib/test/test_tarfile.py
@@ -325,6 +325,13 @@ class CommonReadTest(ReadTest):
 class MiscReadTest(CommonReadTest):
     taropen = tarfile.TarFile.taropen
 
+    def test_length_zero_header(self):
+        # bpo-39017 (CVE-2019-20907): reading a zero-length header should fail
+        # with an exception
+        with self.assertRaisesRegexp(tarfile.ReadError, "file could not be opened successfully"):
+            with tarfile.open(support.findfile('recursion.tar')) as tar:
+                pass
+
     def test_no_name_argument(self):
         with open(self.tarname, "rb") as fobj:
             tar = tarfile.open(fileobj=fobj, mode=self.mode)
diff --git a/Python/Misc/NEWS.d/next/Library/2020-07-12-22-16-58.bpo-39017.x3Cg-9.rst b/Python/Misc/NEWS.d/next/Library/2020-07-12-22-16-58.bpo-39017.x3Cg-9.rst
new file mode 100644
index 00000000..ad26676f
--- /dev/null
+++ b/Python/Misc/NEWS.d/next/Library/2020-07-12-22-16-58.bpo-39017.x3Cg-9.rst
@@ -0,0 +1 @@
+Avoid infinite loop when reading specially crafted TAR files using the tarfile module (CVE-2019-20907).
-- 
2.25.4