bpo-39259: nntplib.NNTP/NNTP_SSL now reject timeout = 0 (GH-17936)

nntplib.NNTP and nntplib.NNTP_SSL now raise a ValueError
if the given timeout for their constructor is zero to
prevent the creation of a non-blocking socket.

2 files changed, 6 insertions, 0 deletions

diff --git a/Lib/nntplib.py b/Lib/nntplib.py
index 0ab5185..8951203 100644
--- a/Lib/nntplib.py
+++ b/Lib/nntplib.py
@@ -1056,6 +1056,8 @@ class NNTP(_NNTPBase):
             raise
 
     def _create_socket(self, timeout):
+        if timeout is not None and not timeout:
+            raise ValueError('Non-blocking socket (timeout=0) is not supported')
         sys.audit("nntplib.connect", self, self.host, self.port)
         return socket.create_connection((self.host, self.port), timeout)
 
diff --git a/Lib/test/test_nntplib.py b/Lib/test/test_nntplib.py
index 88c54f4..fdd76f9 100644
--- a/Lib/test/test_nntplib.py
+++ b/Lib/test/test_nntplib.py
@@ -258,6 +258,10 @@ class NetworkedNNTPTestsMixin:
             # value
             setattr(cls, name, wrap_meth(meth))
 
+    def test_timeout(self):
+        with self.assertRaises(ValueError):
+            self.NNTP_CLASS(self.NNTP_HOST, timeout=0, usenetrc=False)
+
     def test_with_statement(self):
         def is_connected():
             if not hasattr(server, 'file'):