[3.1.x] Fixed CVE-2021-3281 -- Fixed potential directory-traversal via archive.extract().

Thanks Florian Apolloner, Shai Berger, and Simon Charette for reviews.

Thanks Wang Baohua for the report.

Backport of 05413afa8c18cdb978fcdf470e09f7a12b234a23 from master.

1 files changed, 14 insertions, 3 deletions

diff --git a/django/utils/archive.py b/django/utils/archive.py
index 235809f2ad..d5a0cf0446 100644
--- a/django/utils/archive.py
+++ b/django/utils/archive.py
@@ -27,6 +27,8 @@ import stat
 import tarfile
 import zipfile
 
+from django.core.exceptions import SuspiciousOperation
+
 
 class ArchiveException(Exception):
     """
@@ -133,6 +135,13 @@ class BaseArchive:
                 return False
         return True
 
+    def target_filename(self, to_path, name):
+        target_path = os.path.abspath(to_path)
+        filename = os.path.abspath(os.path.join(target_path, name))
+        if not filename.startswith(target_path):
+            raise SuspiciousOperation("Archive contains invalid path: '%s'" % name)
+        return filename
+
     def extract(self):
         raise NotImplementedError('subclasses of BaseArchive must provide an extract() method')
 
@@ -155,7 +164,7 @@ class TarArchive(BaseArchive):
             name = member.name
             if leading:
                 name = self.split_leading_dir(name)[1]
-            filename = os.path.join(to_path, name)
+            filename = self.target_filename(to_path, name)
             if member.isdir():
                 if filename:
                     os.makedirs(filename, exist_ok=True)
@@ -198,8 +207,10 @@ class ZipArchive(BaseArchive):
             info = self._archive.getinfo(name)
             if leading:
                 name = self.split_leading_dir(name)[1]
-            filename = os.path.join(to_path, name)
-            if filename.endswith(('/', '\\')):
+            if not name:
+                continue
+            filename = self.target_filename(to_path, name)
+            if name.endswith(('/', '\\')):
                 # A directory
                 os.makedirs(filename, exist_ok=True)
             else: