bpo-44888: Add ssl.OP_LEGACY_SERVER_CONNECT

Doc/library/ssl.rst

@@ -920,6 +920,16 @@ Constants
 
  .. versionadded:: 3.10
 
+.. data:: OP_LEGACY_SERVER_CONNECT
+
+ Allow legacy insecure renegotiation between OpenSSL and unpatched servers
+ only.
+
+ This option is only available with OpenSSL 0.9.8m and later, and is disabled
+ in default context since OpenSSL 3.0.0.
+
+ .. versionadded:: 3.11
+
 .. data:: HAS_ALPN
 
  Whether the OpenSSL library has built-in support for the *Application-Layer

Lib/test/test_ssl.py

@@ -157,6 +157,7 @@ def data_file(*name):
 OP_CIPHER_SERVER_PREFERENCE = getattr(ssl, "OP_CIPHER_SERVER_PREFERENCE", 0)
 OP_ENABLE_MIDDLEBOX_COMPAT = getattr(ssl, "OP_ENABLE_MIDDLEBOX_COMPAT", 0)
 OP_IGNORE_UNEXPECTED_EOF = getattr(ssl, "OP_IGNORE_UNEXPECTED_EOF", 0)
+OP_LEGACY_SERVER_CONNECT = getattr(ssl, "OP_LEGACY_SERVER_CONNECT", 0)
 
 # Ubuntu has patched OpenSSL and changed behavior of security level 2
 # see https://bugs.python.org/issue41561#msg389003
@@ -1191,6 +1192,9 @@ def test_options(self):
  ctx.options = 0
  # Ubuntu has OP_NO_SSLv3 forced on by default
  self.assertEqual(0, ctx.options & ~ssl.OP_NO_SSLv3)
+ # 0.9.8m or later
+ if ssl.OPENSSL_VERSION_INFO >= (0, 9, 8, 13, 15):
+ self.assertNotEqual(OP_LEGACY_SERVER_CONNECT, 0)
 
  def test_verify_mode_protocol(self):
  with warnings_helper.check_warnings():
@@ -1681,6 +1685,12 @@ def _assert_context_options(self, ctx):
  if OP_CIPHER_SERVER_PREFERENCE != 0:
  self.assertEqual(ctx.options & OP_CIPHER_SERVER_PREFERENCE,
  OP_CIPHER_SERVER_PREFERENCE)
+ if OP_LEGACY_SERVER_CONNECT != 0:
+ if IS_OPENSSL_3_0_0:
+ self.assertEqual(ctx.options & OP_LEGACY_SERVER_CONNECT, 0)
+ else:
+ self.assertEqual(ctx.options & OP_LEGACY_SERVER_CONNECT,
+ OP_LEGACY_SERVER_CONNECT)
 
  def test_create_default_context(self):
  ctx = ssl.create_default_context()
@@ -4073,6 +4083,18 @@ def test_compression_disabled(self):
  sni_name=hostname)
  self.assertIs(stats['compression'], None)
 
+ @unittest.skipUnless(hasattr(ssl, 'OP_LEGACY_SERVER_CONNECT'),
+ "ssl.OP_LEGACY_SERVER_CONNECT needed for this test")
+ def test_legacy_server_connect(self):
+ client_context, server_context, hostname = testing_context()
+ if IS_OPENSSL_3_0_0:
+ client_context.options |= ssl.OP_LEGACY_SERVER_CONNECT
+ else:
+ client_context.options &= ~ssl.OP_LEGACY_SERVER_CONNECT
+ stats = server_params_test(client_context, server_context,
+ chatty=True, connectionchatty=True,
+ sni_name=hostname)
+
  @unittest.skipIf(Py_DEBUG_WIN32, "Avoid mixing debug/release CRT on Windows")
  def test_dh_params(self):
  # Check we can get a connection with ephemeral Diffie-Hellman

Misc/NEWS.d/next/Library/2021-08-18-05-14-36.bpo-44888.kpmYjl.rst

@@ -0,0 +1 @@
+Add :data:`ssl.OP_LEGACY_SERVER_CONNECT`

Modules/_ssl.c

@@ -5890,6 +5890,10 @@ sslmodule_init_constants(PyObject *m)
  PyModule_AddIntConstant(m, "OP_IGNORE_UNEXPECTED_EOF",
  SSL_OP_IGNORE_UNEXPECTED_EOF);
 #endif
+#ifdef SSL_OP_LEGACY_SERVER_CONNECT
+ PyModule_AddIntConstant(m, "OP_LEGACY_SERVER_CONNECT",
+ SSL_OP_LEGACY_SERVER_CONNECT);
+#endif
 
 #ifdef X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT
  PyModule_AddIntConstant(m, "HOSTFLAG_ALWAYS_CHECK_SUBJECT",