Validate incoming JS Message Headers

mojo/public/js/bindings/validator.js

Index: mojo/public/js/bindings/validator.js
diff --git a/mojo/public/js/bindings/validator.js b/mojo/public/js/bindings/validator.js
new file mode 100644
index 0000000000000000000000000000000000000000..19aee8fd50c41bfd2da93a25d639dae806f7299f
--- /dev/null
+++ b/mojo/public/js/bindings/validator.js
@@ -0,0 +1,59 @@
+// Copyright 2014 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.
+
+define("mojo/public/js/bindings/validator", [

[abarth-chromium, 2014/07/22 03:51:00]

No need to name the module.  The module loader will imply the name from the
path.

[hansmuller, 2014/07/22 15:49:07]

OK.

+  "mojo/public/js/bindings/codec",
+  ], function(codec) {
+
+  var ValidationError = (function() {
+    var errorEnum = {};
+    function defineError(name) {
+      errorEnum[name] = "VALIDATION_ERROR_" + name;
+    }

[abarth-chromium, 2014/07/22 03:51:00]

Normally we'd just make this an anonymous function in the forEach call

+    ["NONE",

[abarth-chromium, 2014/07/22 03:51:00]

Blank line after [

+     "MISALIGNED_OBJECT",
+     "ILLEGAL_MEMORY_RANGE",
+     "UNEXPECTED_STRUCT_HEADER",
+     "UNEXPECTED_ARRAY_HEADER",
+     "ILLEGAL_HANDLE",
+     "ILLEGAL_POINTER",
+     "MESSAGE_HEADER_INVALID_FLAG_COMBINATION",
+     "MESSAGE_HEADER_MISSING_REQUEST_ID"

[abarth-chromium, 2014/07/22 03:51:00]

Missing , at the end of this line.

+    ].forEach(defineError);
+    return errorEnum;
+  })();

[abarth-chromium, 2014/07/22 03:51:00]

Why not just write out the code?  It seems unnecessary to do all this work at
module load time.

[hansmuller, 2014/07/22 15:49:07]

Sorry, I got carried away. I'll write out the constants (which should address
the other comments about this enum.

+
+  function validateMessageHeader(message) {
+    if (message.byteLength() < codec.kMessageHeaderSize)
+      return ValidationError.ILLEGAL_MEMORY_RANGE;
+
+    var numBytes = message.getHeaderNumBytes();
+    var numFields = message.getHeaderNumFields();
+
+    if (message.byteLength() < numBytes)
+      return ValidationError.ILLEGAL_MEMORY_RANGE;
+
+    if (!((numFields == 2 && numBytes == codec.kMessageHeaderSize) ||
+          (numFields == 3 &&
+           numBytes == codec.kMessageWithRequestIDHeaderSize)))
+      return ValidationError.UNEXPECTED_STRUCT_HEADER;
+
+    var flags = message.getHeaderFlags();
+    var expectsResponse = flags & codec.kMessageExpectsResponse;
+    var isResponse = flags & codec.kMessageIsResponse;
+
+    if (numFields == 2 && (expectsResponse || isResponse))
+      return ValidationError.MESSAGE_HEADER_MISSING_REQUEST_ID;
+
+    if (isResponse && expectsResponse)
+      return ValidationError.MESSAGE_HEADER_INVALID_FLAG_COMBINATION;
+
+    return ValidationError.NONE;
+  }
+
+  var exports = {};
+  exports.ValidationError = ValidationError;
+  exports.validateMessageHeader = validateMessageHeader;
+  return exports;
+});