gh-116931: Add fileobj parameter check for Tarfile.addfile (GH-117988)

Tarfile.addfile now throws an ValueError when the user passes
in a non-zero size tarinfo but does not provide a fileobj,
instead of writing an incomplete entry.

1 files changed, 7 insertions, 4 deletions

diff --git a/Lib/tarfile.py b/Lib/tarfile.py
index 149b1c3..78bb10c 100755
--- a/Lib/tarfile.py
+++ b/Lib/tarfile.py
@@ -2214,13 +2214,16 @@ class TarFile(object):
             self.addfile(tarinfo)
 
     def addfile(self, tarinfo, fileobj=None):
-        """Add the TarInfo object `tarinfo' to the archive. If `fileobj' is
-           given, it should be a binary file, and tarinfo.size bytes are read
-           from it and added to the archive. You can create TarInfo objects
-           directly, or by using gettarinfo().
+        """Add the TarInfo object `tarinfo' to the archive. If `tarinfo' represents
+           a non zero-size regular file, the `fileobj' argument should be a binary file,
+           and tarinfo.size bytes are read from it and added to the archive.
+           You can create TarInfo objects directly, or by using gettarinfo().
         """
         self._check("awx")
 
+        if fileobj is None and tarinfo.isreg() and tarinfo.size != 0:
+            raise ValueError("fileobj not provided for non zero-size regular file")
+
         tarinfo = copy.copy(tarinfo)
 
         buf = tarinfo.tobuf(self.format, self.encoding, self.errors)