gh-155327: Guard SSLSocket chain methods after TLS teardown

get_verified_chain() and get_unverified_chain() accessed self._sslobj without
the guard used by the other query methods, raising AttributeError after
unwrap(). Return an empty list instead.

Author: tonghuaroot

Lib/ssl.py

@@ -1183,6 +1183,9 @@ def getpeercert(self, binary_form=False):
 
     @_sslcopydoc
     def get_verified_chain(self):
+        self._checkClosed()
+        if self._sslobj is None:
+            return []
         chain = self._sslobj.get_verified_chain()
 
         if chain is None:
@@ -1192,6 +1195,9 @@ def get_verified_chain(self):
 
     @_sslcopydoc
     def get_unverified_chain(self):
+        self._checkClosed()
+        if self._sslobj is None:
+            return []
         chain = self._sslobj.get_unverified_chain()
 
         if chain is None:

Lib/test/test_ssl.py

@@ -5435,6 +5435,24 @@ def test_certificate_chain(self):
                 self.assertEqual(ee, uvc[0])
                 self.assertNotEqual(ee, ca)
 
+    def test_chain_methods_after_unwrap(self):
+        # The chain methods must not crash once the TLS layer is torn down;
+        # like the other query methods they return an empty list when
+        # _sslobj is gone.
+        client_context, server_context, hostname = testing_context()
+        server = ThreadedEchoServer(context=server_context, chatty=False)
+        with server:
+            with client_context.wrap_socket(
+                socket.socket(),
+                server_hostname=hostname
+            ) as s:
+                s.connect((HOST, server.port))
+                self.assertGreater(len(s.get_verified_chain()), 0)
+                s.unwrap()
+                self.assertIsNone(s._sslobj)
+                self.assertEqual(s.get_verified_chain(), [])
+                self.assertEqual(s.get_unverified_chain(), [])
+
     def test_internal_chain_server(self):
         client_context, server_context, hostname = testing_context()
         client_context.load_cert_chain(SIGNED_CERTFILE)

Misc/NEWS.d/next/Library/2026-08-07-20-17-21.gh-issue-155327.Ss5Wq8.rst

@@ -0,0 +1,4 @@
+Fix ``ssl.SSLSocket.get_verified_chain()`` and
+``ssl.SSLSocket.get_unverified_chain()`` to return an empty list instead of
+raising :exc:`AttributeError` when called after the socket's TLS layer has been
+shut down. Patch by tonghuaroot.