Enforce/require MOJO_HANDLE_RIGHT_TRANSFER in sending handles via MojoWriteMessage().

mojo/public/c/system/tests/core_unittest.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file tests the C API.
 
 #include <string.h>
 
 #include "mojo/public/c/system/buffer.h"
 #include "mojo/public/c/system/data_pipe.h"
@@ skipping 719 matching lines @@
             rights);
   // Trying to duplicate |h2| should fail.
   MojoHandle h3 = MOJO_HANDLE_INVALID;
   EXPECT_EQ(MOJO_RESULT_PERMISSION_DENIED, MojoDuplicateHandle(h2, &h3));
   EXPECT_EQ(MOJO_HANDLE_INVALID, h3);
 
   EXPECT_EQ(MOJO_RESULT_OK, MojoClose(h1));
   EXPECT_EQ(MOJO_RESULT_OK, MojoClose(h2));
 }
 
+TEST(CoreTest, MessagePipeChecksTransferRight) {
+  MojoHandle h0 = MOJO_HANDLE_INVALID;
+  MojoHandle h1 = MOJO_HANDLE_INVALID;
+  EXPECT_EQ(MOJO_RESULT_OK, MojoCreateMessagePipe(nullptr, &h0, &h1));
+
+  // Create a shared buffer (which is transferrable and duplicatable).
+  MojoHandle h_transferrable = MOJO_HANDLE_INVALID;
+  EXPECT_EQ(MOJO_RESULT_OK,
+            MojoCreateSharedBuffer(nullptr, 100, &h_transferrable));
+
+  // Make a non-transferrable duplicate handle.
+  MojoHandle h_not_transferrable = MOJO_HANDLE_INVALID;
+  EXPECT_EQ(MOJO_RESULT_OK, MojoDuplicateHandleWithReducedRights(
+                                h_transferrable, MOJO_HANDLE_RIGHT_TRANSFER,
+                                &h_not_transferrable));
+
+  // |h_transferrable| can be transferred.
+  EXPECT_EQ(MOJO_RESULT_OK, MojoWriteMessage(h0, nullptr, 0u, &h_transferrable,
+                                             1u, MOJO_WRITE_MESSAGE_FLAG_NONE));
+
+  // |h_not_transferrable| can be transferred.
+  EXPECT_EQ(MOJO_RESULT_PERMISSION_DENIED,
+            MojoWriteMessage(h0, nullptr, 0u, &h_not_transferrable, 1u,
+                             MOJO_WRITE_MESSAGE_FLAG_NONE));
+
+  EXPECT_EQ(MOJO_RESULT_OK, MojoClose(h0));
+  EXPECT_EQ(MOJO_RESULT_OK, MojoClose(h1));
+  EXPECT_EQ(MOJO_RESULT_OK, MojoClose(h_not_transferrable));
+}
+
 // This checks that things actually work in C (not C++).
 TEST(CoreTest, MinimalCTest) {
   const char* failure = MinimalCTest();
   EXPECT_FALSE(failure) << failure;
 }
 
 TEST(CoreTest, MinimalCppTest) {
   const char* failure = MinimalCppTest();
   EXPECT_FALSE(failure) << failure;
 }
 
 // TODO(vtl): Add multi-threaded tests.
 
 }  // namespace
 }  // namespace mojo