Add a server_host_override to stub creation

This optional value should only be passed in tests.

src/python/src/grpc/_adapter/_c_test.py

@@ -70,7 +70,8 @@ class _CTest(unittest.TestCase):
   def testChannel(self):
     _c.init()
 
-    channel = _c.Channel('test host:12345', None)
+    channel = _c.Channel(
+        'test host:12345', None, server_host_override='ignored')
     del channel
 
     _c.shut_down()

src/python/src/grpc/_adapter/_channel.c

@@ -42,19 +42,35 @@
 static int pygrpc_channel_init(Channel *self, PyObject *args, PyObject *kwds) {
   const char *hostport;
   PyObject *client_credentials;
-  static char *kwlist[] = {"hostport", "client_credentials", NULL};
+  char *server_host_override = NULL;
+  static char *kwlist[] = {"hostport", "client_credentials",
+                           "server_host_override", NULL};
+  grpc_arg server_host_override_arg;
+  grpc_channel_args channel_args;
 
-  if (!(PyArg_ParseTupleAndKeywords(args, kwds, "sO:Channel", kwlist,
-                                    &hostport, &client_credentials))) {
+  if (!(PyArg_ParseTupleAndKeywords(args, kwds, "sO|z:Channel", kwlist,
+                                    &hostport, &client_credentials,
+                                    &server_host_override))) {
     return -1;
   }
   if (client_credentials == Py_None) {
     self->c_channel = grpc_channel_create(hostport, NULL);
     return 0;
   } else {
-    self->c_channel = grpc_secure_channel_create(
-        ((ClientCredentials *)client_credentials)->c_client_credentials,
-        hostport, NULL);
+    if (server_host_override == NULL) {
+      self->c_channel = grpc_secure_channel_create(
+	  ((ClientCredentials *)client_credentials)->c_client_credentials,
+          hostport, NULL);
+    } else {
+      server_host_override_arg.type = GRPC_ARG_STRING;
+      server_host_override_arg.key = GRPC_SSL_TARGET_NAME_OVERRIDE_ARG;
+      server_host_override_arg.value.string = server_host_override;
+      channel_args.num_args = 1;
+      channel_args.args = &server_host_override_arg;
+      self->c_channel = grpc_secure_channel_create(
+          ((ClientCredentials *)client_credentials)->c_client_credentials,
+          hostport, &channel_args);
+    }
     return 0;
   }
 }

src/python/src/grpc/_adapter/rear.py

@@ -93,7 +93,8 @@ class RearLink(ticket_interfaces.RearLink, activated.Activated):
 
   def __init__(
       self, host, port, pool, request_serializers, response_deserializers,
-      secure, root_certificates, private_key, certificate_chain):
+      secure, root_certificates, private_key, certificate_chain,
+      server_host_override=None):
     """Constructor.
 
     Args:
@@ -111,6 +112,8 @@ class RearLink(ticket_interfaces.RearLink, activated.Activated):
         key should be used.
       certificate_chain: The PEM-encoded certificate chain to use or None if
         no certificate chain should be used.
+      server_host_override: (For testing only) the target name used for SSL
+        host name checking.
     """
     self._condition = threading.Condition()
     self._host = host
@@ -132,6 +135,7 @@ class RearLink(ticket_interfaces.RearLink, activated.Activated):
     self._root_certificates = root_certificates
     self._private_key = private_key
     self._certificate_chain = certificate_chain
+    self._server_host_override = server_host_override
 
   def _on_write_event(self, operation_id, event, rpc_state):
     if event.write_accepted:
@@ -327,7 +331,8 @@ class RearLink(ticket_interfaces.RearLink, activated.Activated):
     with self._condition:
       self._completion_queue = _low.CompletionQueue()
       self._channel = _low.Channel(
-          '%s:%d' % (self._host, self._port), self._client_credentials)
+          '%s:%d' % (self._host, self._port), self._client_credentials,
+          server_host_override=self._server_host_override)
     return self
 
   def _stop(self):
@@ -388,7 +393,8 @@ class _ActivatedRearLink(ticket_interfaces.RearLink, activated.Activated):
 
   def __init__(
       self, host, port, request_serializers, response_deserializers, secure,
-      root_certificates, private_key, certificate_chain):
+      root_certificates, private_key, certificate_chain,
+      server_host_override=None):
     self._host = host
     self._port = port
     self._request_serializers = request_serializers
@@ -397,6 +403,7 @@ class _ActivatedRearLink(ticket_interfaces.RearLink, activated.Activated):
     self._root_certificates = root_certificates
     self._private_key = private_key
     self._certificate_chain = certificate_chain
+    self._server_host_override = server_host_override
 
     self._lock = threading.Lock()
     self._pool = None
@@ -415,7 +422,8 @@ class _ActivatedRearLink(ticket_interfaces.RearLink, activated.Activated):
       self._rear_link = RearLink(
           self._host, self._port, self._pool, self._request_serializers,
           self._response_deserializers, self._secure, self._root_certificates,
-          self._private_key, self._certificate_chain)
+          self._private_key, self._certificate_chain,
+          server_host_override=self._server_host_override)
       self._rear_link.join_fore_link(self._fore_link)
       self._rear_link.start()
     return self
@@ -477,7 +485,7 @@ def activated_rear_link(
 
 def secure_activated_rear_link(
     host, port, request_serializers, response_deserializers, root_certificates,
-    private_key, certificate_chain):
+    private_key, certificate_chain, server_host_override=None):
   """Creates a RearLink that is also an activated.Activated.
 
   The returned object is only valid for use between calls to its start and stop
@@ -496,7 +504,10 @@ def secure_activated_rear_link(
       should be used.
     certificate_chain: The PEM-encoded certificate chain to use or None if no
       certificate chain should be used.
+    server_host_override: (For testing only) the target name used for SSL
+      host name checking.
   """
   return _ActivatedRearLink(
       host, port, request_serializers, response_deserializers, True,
-      root_certificates, private_key, certificate_chain)
+      root_certificates, private_key, certificate_chain,
+      server_host_override=server_host_override)

src/python/src/grpc/early_adopter/implementations.py

@@ -125,7 +125,8 @@ def insecure_stub(methods, host, port):
 
 
 def secure_stub(
-    methods, host, port, root_certificates, private_key, certificate_chain):
+    methods, host, port, root_certificates, private_key, certificate_chain,
+    server_host_override=None):
   """Constructs an insecure interfaces.Stub.
 
   Args:
@@ -140,6 +141,8 @@ def secure_stub(
       should be used.
     certificate_chain: The PEM-encoded certificate chain to use or None if no
       certificate chain should be used.
+    server_host_override: (For testing only) the target name used for SSL
+      host name checking.
 
   Returns:
     An interfaces.Stub affording RPC invocation.
@@ -148,7 +151,7 @@ def secure_stub(
   activated_rear_link = _rear.secure_activated_rear_link(
       host, port, breakdown.request_serializers,
       breakdown.response_deserializers, root_certificates, private_key,
-      certificate_chain)
+      certificate_chain, server_host_override=server_host_override)
   return _build_stub(breakdown, activated_rear_link)