Plumb MojoReplaceHandleWithReducedRights() out.

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

Index: mojo/public/c/system/tests/handle_unittest.cc
diff --git a/mojo/public/c/system/tests/handle_unittest.cc b/mojo/public/c/system/tests/handle_unittest.cc
index 685fd82b6d85ae61d580360940081b33228e3bdc..0de5748b49b24eea4b53a85e58e57a67e8d5ef22 100644
--- a/mojo/public/c/system/tests/handle_unittest.cc
+++ b/mojo/public/c/system/tests/handle_unittest.cc
@@ -8,32 +8,109 @@
 // handles.
 
 #include "mojo/public/c/system/handle.h"
+#include "mojo/public/c/system/message_pipe.h"
 #include "mojo/public/c/system/result.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace {
 
+const MojoHandleRights kDefaultMessagePipeHandleRights =
+    MOJO_HANDLE_RIGHT_TRANSFER | MOJO_HANDLE_RIGHT_READ |
+    MOJO_HANDLE_RIGHT_WRITE | MOJO_HANDLE_RIGHT_GET_OPTIONS |
+    MOJO_HANDLE_RIGHT_SET_OPTIONS;
+
 TEST(HandleTest, InvalidHandle) {
-  // Close:
+  // MojoClose:
   EXPECT_EQ(MOJO_RESULT_INVALID_ARGUMENT, MojoClose(MOJO_HANDLE_INVALID));
 
-  // GetRights:
+  // MojoGetRights:
   MojoHandleRights rights = MOJO_HANDLE_RIGHT_NONE;
   EXPECT_EQ(MOJO_RESULT_INVALID_ARGUMENT,
             MojoGetRights(MOJO_HANDLE_INVALID, &rights));
 
-  // DuplicateHandleWithReducedRights:
+  // MojoReplaceHandleWithReducedRights:
+  MojoHandle replacement_handle = MOJO_HANDLE_INVALID;
+  EXPECT_EQ(
+      MOJO_RESULT_INVALID_ARGUMENT,
+      MojoReplaceHandleWithReducedRights(
+          MOJO_HANDLE_INVALID, MOJO_HANDLE_RIGHT_NONE, &replacement_handle));
+
+  // MojoDuplicateHandleWithReducedRights:
   MojoHandle new_handle = MOJO_HANDLE_INVALID;
   EXPECT_EQ(MOJO_RESULT_INVALID_ARGUMENT,
             MojoDuplicateHandleWithReducedRights(
                 MOJO_HANDLE_INVALID, MOJO_HANDLE_RIGHT_DUPLICATE, &new_handle));
   EXPECT_EQ(MOJO_HANDLE_INVALID, new_handle);
 
-  // DuplicateHandle:
+  // MojoDuplicateHandle:
   new_handle = MOJO_HANDLE_INVALID;
   EXPECT_EQ(MOJO_RESULT_INVALID_ARGUMENT,
             MojoDuplicateHandle(MOJO_HANDLE_INVALID, &new_handle));
   EXPECT_EQ(MOJO_HANDLE_INVALID, new_handle);
 }
 
+// |MojoReplaceHandleWithReducedRights()| is not handle-type specific, so we'll
+// test it here, even though it requires actually creating/using a specific
+// handle type.
+TEST(HandleTest, ReplaceHandleWithReducedRights) {
+  MojoHandle h0 = MOJO_HANDLE_INVALID;
+  MojoHandle h1 = MOJO_HANDLE_INVALID;
+  // That |MojoCreateMessagePipe()| works correctly is checked in
+  // |MessagePipeTest|.
+  EXPECT_EQ(MOJO_RESULT_OK, MojoCreateMessagePipe(nullptr, &h0, &h1));
+
+  // Still check the rights on one of the handles, just to make sure that
+  // |kDefaultMessagePipeHandleRights| stays in sync with reality.
+  MojoHandleRights rights = MOJO_HANDLE_RIGHT_NONE;
+  EXPECT_EQ(MOJO_RESULT_OK, MojoGetRights(h0, &rights));
+  EXPECT_EQ(kDefaultMessagePipeHandleRights, rights);
+
+  // First try replacing without reducing rights.
+  MojoHandle h0r0 = MOJO_HANDLE_INVALID;
+  EXPECT_EQ(MOJO_RESULT_OK, MojoReplaceHandleWithReducedRights(
+                                h0, MOJO_HANDLE_RIGHT_NONE, &h0r0));
+  EXPECT_NE(h0r0, MOJO_HANDLE_INVALID);
+  // Not guaranteed, but we depend on handle values not being reused eagerly.
+  EXPECT_NE(h0r0, h0);
+  EXPECT_NE(h0r0, h1);  // |h0r0| should definitely not be the same as |h1|.
+  // |h0| should be dead, so this should fail.
+  EXPECT_EQ(MOJO_RESULT_INVALID_ARGUMENT, MojoClose(h0));
+
+  // Check that the rights remain the same.
+  rights = MOJO_HANDLE_RIGHT_NONE;
+  EXPECT_EQ(MOJO_RESULT_OK, MojoGetRights(h0r0, &rights));
+  EXPECT_EQ(kDefaultMessagePipeHandleRights, rights);
+
+  // Make sure the replacement handle is still usable.
+  char x = 'x';
+  EXPECT_EQ(MOJO_RESULT_OK, MojoWriteMessage(h0r0, &x, 1u, nullptr, 0,
+                                             MOJO_WRITE_MESSAGE_FLAG_NONE));
+
+  // Try replacing, but removing a couple of rights.
+  MojoHandle h0r1 = MOJO_HANDLE_INVALID;
+  constexpr MojoHandleRights kRightsToRemove =
+      MOJO_HANDLE_RIGHT_TRANSFER | MOJO_HANDLE_RIGHT_WRITE;
+  EXPECT_EQ(MOJO_RESULT_OK,
+            MojoReplaceHandleWithReducedRights(h0r0, kRightsToRemove, &h0r1));
+  EXPECT_NE(h0r1, MOJO_HANDLE_INVALID);
+  // Not guaranteed, but we depend on handle values not being reused eagerly.
+  EXPECT_NE(h0r1, h0r0);
+  EXPECT_NE(h0r1, h1);  // |h0r1| should definitely not be the same as |h1|.
+  // |h0r0| should be dead, so this should fail.
+  EXPECT_EQ(MOJO_RESULT_INVALID_ARGUMENT, MojoClose(h0r0));
+
+  // Check that |h0r1| has the expected rights.
+  rights = MOJO_HANDLE_RIGHT_NONE;
+  EXPECT_EQ(MOJO_RESULT_OK, MojoGetRights(h0r1, &rights));
+  EXPECT_EQ(kDefaultMessagePipeHandleRights & ~kRightsToRemove, rights);
+
+  // Make sure that the rights are actually correctly enforced.
+  EXPECT_EQ(
+      MOJO_RESULT_PERMISSION_DENIED,
+      MojoWriteMessage(h0r1, &x, 1u, nullptr, 0, MOJO_WRITE_MESSAGE_FLAG_NONE));
+
+  EXPECT_EQ(MOJO_RESULT_OK, MojoClose(h0r1));
+  EXPECT_EQ(MOJO_RESULT_OK, MojoClose(h1));
+}
+
 }  // namespace