bpo-15795: Preserve permissions on UNIX (based/like) systems

Lib/zipfile.py

@@ -1677,14 +1677,24 @@ def _extract_member(self, member, targetpath, pwd):
         if upperdirs and not os.path.exists(upperdirs):
             os.makedirs(upperdirs)
 
+        # Extract the member
         if member.is_dir():
             if not os.path.isdir(targetpath):
                 os.mkdir(targetpath)
-            return targetpath
-
-        with self.open(member, pwd=pwd) as source, \
-             open(targetpath, "wb") as target:
-            shutil.copyfileobj(source, target)
+        else:
+            with self.open(member, pwd=pwd) as source, \
+                 open(targetpath, "wb") as target:
+                shutil.copyfileobj(source, target)
+
+        # Preserve the permissions if we're on a posix system and the create_system was UNIX
+        # In the zip specification create_system 3 is UNIX
+        # See https://pkware.cachefly.net/webdocs/casestudies/APPNOTE.TXT CHAPTER 4.4.2.2
+        zip_create_system_unix = 3
+        if member.create_system == zip_create_system_unix and os.name == "posix":
+            # The first 16 bits contain the UNIX permission attributes
+            # See https://stackoverflow.com/a/46837272
+            attr = member.external_attr >> 16
+            os.chmod(targetpath, attr)
 
         return targetpath
 

Misc/NEWS.d/next/Library/2020-03-03-13-50-37.bpo-15795.qQkxN0.rst

@@ -0,0 +1 @@
+Preserve permissions when extracting zip files on POSIX systems. Only do so if the zip file was created on a Unix-like system.