Add NPN feature detection.

OpenSSL/SSL.py

@@ -347,6 +347,21 @@ def SSLeay_version(type):
     return _ffi.string(_lib.SSLeay_version(type))
 
 
+def _requires_npn(func):
+    """
+    Wraps any function that requires NPN support in OpenSSL, ensuring that
+    NotImplementedError is raised if NPN is not present.
+    """
+    @wraps(func)
+    def wrapper(*args, **kwargs):
+        if not _lib.Cryptography_HAS_NEXTPROTONEG:
+            raise NotImplementedError("NPN not available.")
+
+        return func(*args, **kwargs)
+
+    return wrapper
+
+
 
 class Session(object):
     pass
@@ -924,6 +939,7 @@ def wrapper(ssl, alert, arg):
             self._context, self._tlsext_servername_callback)
 
 
+    @_requires_npn
     def set_npn_advertise_callback(self, callback):
         """
         Specify a callback function that will be called when offering `Next
@@ -941,6 +957,7 @@ def set_npn_advertise_callback(self, callback):
             self._context, self._npn_advertise_callback, _ffi.NULL)
 
 
+    @_requires_npn
     def set_npn_select_callback(self, callback):
         """
         Specify a callback function that will be called when a server offers
@@ -1746,6 +1763,8 @@ def get_cipher_version(self):
             version =_ffi.string(_lib.SSL_CIPHER_get_version(cipher))
             return version.decode("utf-8")
 
+
+    @_requires_npn
     def get_next_proto_negotiated(self):
         """
         Get the protocol that was negotiated by NPN.

OpenSSL/test/test_ssl.py

@@ -42,6 +42,8 @@
 from OpenSSL.SSL import (
     Context, ContextType, Session, Connection, ConnectionType, SSLeay_version)
 
+from OpenSSL._util import lib as _lib
+
 from OpenSSL.test.util import NON_ASCII, TestCase, b
 from OpenSSL.test.test_crypto import (
     cleartextCertificatePEM, cleartextPrivateKeyPEM)
@@ -1626,159 +1628,186 @@ class NextProtoNegotiationTests(TestCase, _LoopbackMixin):
     """
     Test for Next Protocol Negotiation in PyOpenSSL.
     """
-    def test_npn_success(self):
-        """
-        Tests that clients and servers that agree on the negotiated next
-        protocol can correct establish a connection, and that the agreed
-        protocol is reported by the connections.
-        """
-        advertise_args = []
-        select_args = []
-        def advertise(conn):
-            advertise_args.append((conn,))
-            return [b'http/1.1', b'spdy/2']
-        def select(conn, options):
-            select_args.append((conn, options))
-            return b'spdy/2'
-
-        server_context = Context(TLSv1_METHOD)
-        server_context.set_npn_advertise_callback(advertise)
-
-        client_context = Context(TLSv1_METHOD)
-        client_context.set_npn_select_callback(select)
-
-        # Necessary to actually accept the connection
-        server_context.use_privatekey(
-            load_privatekey(FILETYPE_PEM, server_key_pem))
-        server_context.use_certificate(
-            load_certificate(FILETYPE_PEM, server_cert_pem))
-
-        # Do a little connection to trigger the logic
-        server = Connection(server_context, None)
-        server.set_accept_state()
-
-        client = Connection(client_context, None)
-        client.set_connect_state()
-
-        self._interactInMemory(server, client)
-
-        self.assertEqual([(server,)], advertise_args)
-        self.assertEqual([(client, [b'http/1.1', b'spdy/2'])], select_args)
-
-        self.assertEqual(server.get_next_proto_negotiated(), b'spdy/2')
-        self.assertEqual(client.get_next_proto_negotiated(), b'spdy/2')
-
-
-    def test_npn_client_fail(self):
-        """
-        Tests that when clients and servers cannot agree on what protocol to
-        use next that the TLS connection does not get established.
-        """
-        advertise_args = []
-        select_args = []
-        def advertise(conn):
-            advertise_args.append((conn,))
-            return [b'http/1.1', b'spdy/2']
-        def select(conn, options):
-            select_args.append((conn, options))
-            return b''
-
-        server_context = Context(TLSv1_METHOD)
-        server_context.set_npn_advertise_callback(advertise)
-
-        client_context = Context(TLSv1_METHOD)
-        client_context.set_npn_select_callback(select)
-
-        # Necessary to actually accept the connection
-        server_context.use_privatekey(
-            load_privatekey(FILETYPE_PEM, server_key_pem))
-        server_context.use_certificate(
-            load_certificate(FILETYPE_PEM, server_cert_pem))
-
-        # Do a little connection to trigger the logic
-        server = Connection(server_context, None)
-        server.set_accept_state()
-
-        client = Connection(client_context, None)
-        client.set_connect_state()
+    if _lib.Cryptography_HAS_NEXTPROTONEG:
+        def test_npn_success(self):
+            """
+            Tests that clients and servers that agree on the negotiated next
+            protocol can correct establish a connection, and that the agreed
+            protocol is reported by the connections.
+            """
+            advertise_args = []
+            select_args = []
+            def advertise(conn):
+                advertise_args.append((conn,))
+                return [b'http/1.1', b'spdy/2']
+            def select(conn, options):
+                select_args.append((conn, options))
+                return b'spdy/2'
+
+            server_context = Context(TLSv1_METHOD)
+            server_context.set_npn_advertise_callback(advertise)
+
+            client_context = Context(TLSv1_METHOD)
+            client_context.set_npn_select_callback(select)
+
+            # Necessary to actually accept the connection
+            server_context.use_privatekey(
+                load_privatekey(FILETYPE_PEM, server_key_pem))
+            server_context.use_certificate(
+                load_certificate(FILETYPE_PEM, server_cert_pem))
+
+            # Do a little connection to trigger the logic
+            server = Connection(server_context, None)
+            server.set_accept_state()
 
-        # If the client doesn't return anything, the connection will fail.
-        self.assertRaises(Error, self._interactInMemory, server, client)
+            client = Connection(client_context, None)
+            client.set_connect_state()
 
-        self.assertEqual([(server,)], advertise_args)
-        self.assertEqual([(client, [b'http/1.1', b'spdy/2'])], select_args)
+            self._interactInMemory(server, client)
 
+            self.assertEqual([(server,)], advertise_args)
+            self.assertEqual([(client, [b'http/1.1', b'spdy/2'])], select_args)
 
-    def test_npn_select_error(self):
-        """
-        Test that we can handle exceptions in the select callback. If select
-        fails it should be fatal to the connection.
-        """
-        advertise_args = []
-        def advertise(conn):
-            advertise_args.append((conn,))
-            return [b'http/1.1', b'spdy/2']
-        def select(conn, options):
-            raise TypeError
+            self.assertEqual(server.get_next_proto_negotiated(), b'spdy/2')
+            self.assertEqual(client.get_next_proto_negotiated(), b'spdy/2')
 
-        server_context = Context(TLSv1_METHOD)
-        server_context.set_npn_advertise_callback(advertise)
 
-        client_context = Context(TLSv1_METHOD)
-        client_context.set_npn_select_callback(select)
+        def test_npn_client_fail(self):
+            """
+            Tests that when clients and servers cannot agree on what protocol
+            to use next that the TLS connection does not get established.
+            """
+            advertise_args = []
+            select_args = []
+            def advertise(conn):
+                advertise_args.append((conn,))
+                return [b'http/1.1', b'spdy/2']
+            def select(conn, options):
+                select_args.append((conn, options))
+                return b''
+
+            server_context = Context(TLSv1_METHOD)
+            server_context.set_npn_advertise_callback(advertise)
+
+            client_context = Context(TLSv1_METHOD)
+            client_context.set_npn_select_callback(select)
+
+            # Necessary to actually accept the connection
+            server_context.use_privatekey(
+                load_privatekey(FILETYPE_PEM, server_key_pem))
+            server_context.use_certificate(
+                load_certificate(FILETYPE_PEM, server_cert_pem))
+
+            # Do a little connection to trigger the logic
+            server = Connection(server_context, None)
+            server.set_accept_state()
 
-        # Necessary to actually accept the connection
-        server_context.use_privatekey(
-            load_privatekey(FILETYPE_PEM, server_key_pem))
-        server_context.use_certificate(
-            load_certificate(FILETYPE_PEM, server_cert_pem))
+            client = Connection(client_context, None)
+            client.set_connect_state()
 
-        # Do a little connection to trigger the logic
-        server = Connection(server_context, None)
-        server.set_accept_state()
+            # If the client doesn't return anything, the connection will fail.
+            self.assertRaises(Error, self._interactInMemory, server, client)
 
-        client = Connection(client_context, None)
-        client.set_connect_state()
+            self.assertEqual([(server,)], advertise_args)
+            self.assertEqual([(client, [b'http/1.1', b'spdy/2'])], select_args)
 
-        # If the callback throws an exception it should be raised here.
-        self.assertRaises(TypeError, self._interactInMemory, server, client)
-        self.assertEqual([(server,)], advertise_args)
 
+        def test_npn_select_error(self):
+            """
+            Test that we can handle exceptions in the select callback. If
+            select fails it should be fatal to the connection.
+            """
+            advertise_args = []
+            def advertise(conn):
+                advertise_args.append((conn,))
+                return [b'http/1.1', b'spdy/2']
+            def select(conn, options):
+                raise TypeError
+
+            server_context = Context(TLSv1_METHOD)
+            server_context.set_npn_advertise_callback(advertise)
+
+            client_context = Context(TLSv1_METHOD)
+            client_context.set_npn_select_callback(select)
+
+            # Necessary to actually accept the connection
+            server_context.use_privatekey(
+                load_privatekey(FILETYPE_PEM, server_key_pem))
+            server_context.use_certificate(
+                load_certificate(FILETYPE_PEM, server_cert_pem))
+
+            # Do a little connection to trigger the logic
+            server = Connection(server_context, None)
+            server.set_accept_state()
 
-    def test_npn_advertise_error(self):
-        """
-        Test that we can handle exceptions in the advertise callback. If
-        advertise fails no NPN is advertised to the client.
-        """
-        select_args = []
-        def advertise(conn):
-            raise TypeError
-        def select(conn, options):
-            select_args.append((conn, options))
-            return b''
+            client = Connection(client_context, None)
+            client.set_connect_state()
 
-        server_context = Context(TLSv1_METHOD)
-        server_context.set_npn_advertise_callback(advertise)
+            # If the callback throws an exception it should be raised here.
+            self.assertRaises(
+                TypeError, self._interactInMemory, server, client
+            )
+            self.assertEqual([(server,)], advertise_args)
 
-        client_context = Context(TLSv1_METHOD)
-        client_context.set_npn_select_callback(select)
 
-        # Necessary to actually accept the connection
-        server_context.use_privatekey(
-            load_privatekey(FILETYPE_PEM, server_key_pem))
-        server_context.use_certificate(
-            load_certificate(FILETYPE_PEM, server_cert_pem))
+        def test_npn_advertise_error(self):
+            """
+            Test that we can handle exceptions in the advertise callback. If
+            advertise fails no NPN is advertised to the client.
+            """
+            select_args = []
+            def advertise(conn):
+                raise TypeError
+            def select(conn, options):
+                select_args.append((conn, options))
+                return b''
+
+            server_context = Context(TLSv1_METHOD)
+            server_context.set_npn_advertise_callback(advertise)
+
+            client_context = Context(TLSv1_METHOD)
+            client_context.set_npn_select_callback(select)
+
+            # Necessary to actually accept the connection
+            server_context.use_privatekey(
+                load_privatekey(FILETYPE_PEM, server_key_pem))
+            server_context.use_certificate(
+                load_certificate(FILETYPE_PEM, server_cert_pem))
+
+            # Do a little connection to trigger the logic
+            server = Connection(server_context, None)
+            server.set_accept_state()
 
-        # Do a little connection to trigger the logic
-        server = Connection(server_context, None)
-        server.set_accept_state()
+            client = Connection(client_context, None)
+            client.set_connect_state()
 
-        client = Connection(client_context, None)
-        client.set_connect_state()
+            # If the client doesn't return anything, the connection will fail.
+            self.assertRaises(
+                TypeError, self._interactInMemory, server, client
+            )
+            self.assertEqual([], select_args)
 
-        # If the client doesn't return anything, the connection will fail.
-        self.assertRaises(TypeError, self._interactInMemory, server, client)
-        self.assertEqual([], select_args)
+    else:
+        # No NPN.
+        def test_npn_not_implemented(self):
+            # Test the context methods first.
+            context = Context(TLSv1_METHOD)
+            fail_methods = [
+                context.set_npn_advertise_callback,
+                context.set_npn_select_callback,
+            ]
+            for method in fail_methods:
+                self.assertRaises(
+                    NotImplementedError, method, None
+                )
+
+            # Now test a connection.
+            conn = Connection(context)
+            fail_methods = [
+                conn.get_next_proto_negotiated,
+            ]
+            for method in fail_methods:
+                self.assertRaises(NotImplementedError, method)