commit f3232294ee695492f43d424cc6969d018d49861d
author Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> Wed Jul 15 05:30:33 2020 -0700
committer GitHub <noreply@github.com> Wed Jul 15 05:30:33 2020 -0700
tree bc2a7128a5a8f258eb926ec785aa04caf367050d
parent 805874a9f1c3840bd4f61f9b6a7a7eebae7bae8e

[3.9] bpo-39017: Avoid infinite loop in the tarfile module (GH-21454) (GH-21482)



Avoid infinite loop when reading specially crafted TAR files using the tarfile module
(CVE-2019-20907).
(cherry picked from commit 5a8d121a1f3ef5ad7c105ee378cc79a3eac0c7d4)


Co-authored-by: Rishi <rishi_devan@mail.com>

Automerge-Triggered-By: @encukou

Lib/tarfile.py

diff --git a/Lib/tarfile.py b/Lib/tarfile.py
index e2b6053..6769066 100755
--- a/Lib/tarfile.py
+++ b/Lib/tarfile.py
@@ -1249,6 +1249,8 @@
 
             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"