00351-cve-2019-20907-fix-infinite-loop-in-tarfile.patchfedora-2.7.18-5

00351 #
Avoid infinite loop when reading specially crafted TAR files using the tarfile module
(CVE-2019-20907).
See: https://bugs.python.org/issue39017

4 files changed, 10 insertions, 0 deletions

diff --git a/Lib/tarfile.py b/Lib/tarfile.py
index adf91d5..574a6bb 100644
--- a/Lib/tarfile.py
+++ b/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/Lib/test/recursion.tar b/Lib/test/recursion.tar
new file mode 100644
index 0000000..b823725
--- /dev/null
+++ b/Lib/test/recursion.tar
diff --git a/Lib/test/test_tarfile.py b/Lib/test/test_tarfile.py
index 89bd738..4592156 100644
--- a/Lib/test/test_tarfile.py
+++ b/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/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
new file mode 100644
index 0000000..ad26676
--- /dev/null
+++ b/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).