From 1fa6ef2bc7cee1c8e088dd8b397d9b2d54036dbc Mon Sep 17 00:00:00 2001 From: Rajarishi Devarajan Date: Sun, 12 Jul 2020 23:47:42 +0200 Subject: [PATCH 1/4] bpo-39017 Fix infinite loop in the tarfile module Add a check for length = 0 in the _proc_pax function to avoid running into an infinite loop --- Lib/tarfile.py | 2 ++ Lib/test/recursion.tar | Bin 0 -> 516 bytes Lib/test/test_tarfile.py | 5 +++++ 3 files changed, 7 insertions(+) create mode 100644 Lib/test/recursion.tar diff --git a/Lib/tarfile.py b/Lib/tarfile.py index e2b60532f693d..6769066cabd6f 100755 --- a/Lib/tarfile.py +++ b/Lib/tarfile.py @@ -1249,6 +1249,8 @@ def _proc_pax(self, tarfile): 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] # Normally, we could just use "utf-8" as the encoding and "strict" diff --git a/Lib/test/recursion.tar b/Lib/test/recursion.tar new file mode 100644 index 0000000000000000000000000000000000000000..b8237251964983f54ed1966297e887636cd0c5f4 GIT binary patch literal 516 zcmYdFPRz+kEn=W0Fn}74P8%Xw3X=l~85kIuo0>8xq$A1Gm}!7)KUsFc41m#O8A5+e I1_}|j06>QaCIA2c literal 0 HcmV?d00001 diff --git a/Lib/test/test_tarfile.py b/Lib/test/test_tarfile.py index d60d35b5be04a..1f31a8f700766 100644 --- a/Lib/test/test_tarfile.py +++ b/Lib/test/test_tarfile.py @@ -429,6 +429,11 @@ def test_premature_end_of_archive(self): with self.assertRaisesRegex(tarfile.ReadError, "unexpected end of data"): tar.extractfile(t).read() + def test_length_zero_header(self): + with self.assertRaisesRegex(tarfile.ReadError, "file could not be opened successfully"): + with tarfile.open(support.findfile('recursion.tar')) as tar: + tar.getmembers() + class MiscReadTestBase(CommonReadTest): def requires_name_attribute(self): pass From c43a5afcf9cc2dab2410c35632f66e055a938c02 Mon Sep 17 00:00:00 2001 From: "blurb-it[bot]" <43283697+blurb-it[bot]@users.noreply.github.com> Date: Sun, 12 Jul 2020 22:16:59 +0000 Subject: [PATCH 2/4] =?UTF-8?q?=F0=9F=93=9C=F0=9F=A4=96=20Added=20by=20blu?= =?UTF-8?q?rb=5Fit.?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- .../NEWS.d/next/Library/2020-07-12-22-16-58.bpo-39017.x3Cg-9.rst | 1 + 1 file changed, 1 insertion(+) create mode 100644 Misc/NEWS.d/next/Library/2020-07-12-22-16-58.bpo-39017.x3Cg-9.rst 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 0000000000000..10d98f759ac87 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2020-07-12-22-16-58.bpo-39017.x3Cg-9.rst @@ -0,0 +1 @@ +Add check for length = 0 to avoid infinite loop inside _proc_pax function in tarfile module \ No newline at end of file From 5f7b94574db21086dc2693210a975def7cc058e3 Mon Sep 17 00:00:00 2001 From: Rishi Date: Tue, 14 Jul 2020 12:39:14 +0200 Subject: [PATCH 3/4] Apply suggestions from code review Add relevant CVE number in inline comments Co-authored-by: Petr Viktorin --- Lib/test/test_tarfile.py | 2 ++ .../next/Library/2020-07-12-22-16-58.bpo-39017.x3Cg-9.rst | 2 +- 2 files changed, 3 insertions(+), 1 deletion(-) diff --git a/Lib/test/test_tarfile.py b/Lib/test/test_tarfile.py index 1f31a8f700766..827ffaf3273b3 100644 --- a/Lib/test/test_tarfile.py +++ b/Lib/test/test_tarfile.py @@ -430,6 +430,8 @@ def test_premature_end_of_archive(self): tar.extractfile(t).read() def test_length_zero_header(self): + # bpo-39017 (CVE-2019-20907): reading a zero-length header should fail + # with an exception with self.assertRaisesRegex(tarfile.ReadError, "file could not be opened successfully"): with tarfile.open(support.findfile('recursion.tar')) as tar: tar.getmembers() 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 index 10d98f759ac87..ad26676f8b856 100644 --- 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 @@ -1 +1 @@ -Add check for length = 0 to avoid infinite loop inside _proc_pax function in tarfile module \ No newline at end of file +Avoid infinite loop when reading specially crafted TAR files using the tarfile module (CVE-2019-20907). From 54084a8beef62fa0ac443618be2352f67f2bb8c3 Mon Sep 17 00:00:00 2001 From: rishi93 Date: Tue, 14 Jul 2020 12:45:48 +0200 Subject: [PATCH 4/4] bpo-39017: Fix infinite loop in the tarfile module Replace code that is never called with pass in tarfile testcase --- Lib/test/test_tarfile.py | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/Lib/test/test_tarfile.py b/Lib/test/test_tarfile.py index 827ffaf3273b3..3ddeb97f5268f 100644 --- a/Lib/test/test_tarfile.py +++ b/Lib/test/test_tarfile.py @@ -434,7 +434,7 @@ def test_length_zero_header(self): # with an exception with self.assertRaisesRegex(tarfile.ReadError, "file could not be opened successfully"): with tarfile.open(support.findfile('recursion.tar')) as tar: - tar.getmembers() + pass class MiscReadTestBase(CommonReadTest): def requires_name_attribute(self):