Basic Mojo message header validation for JavaScript.

mojo/public/js/bindings/validator.js

+// 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", [
+  "mojo/public/js/bindings/codec",
+  ], function(codec) {
+
+  var ValidationError = {
+    NONE: 'VALIDATION_ERROR_NONE',
+    MISALIGNED_OBJECT: 'VALIDATION_ERROR_MISALIGNED_OBJECT',
+    ILLEGAL_MEMORY_RANGE: 'VALIDATION_ERROR_ILLEGAL_MEMORY_RANGE',
+    UNEXPECTED_STRUCT_HEADER: 'VALIDATION_ERROR_UNEXPECTED_STRUCT_HEADER',
+    UNEXPECTED_ARRAY_HEADER: 'VALIDATION_ERROR_UNEXPECTED_ARRAY_HEADER',
+    ILLEGAL_HANDLE: 'VALIDATION_ERROR_ILLEGAL_HANDLE',
+    ILLEGAL_POINTER: 'VALIDATION_ERROR_ILLEGAL_POINTER',
+    MESSAGE_HEADER_INVALID_FLAG_COMBINATION:
+        'VALIDATION_ERROR_MESSAGE_HEADER_INVALID_FLAG_COMBINATION',
+    MESSAGE_HEADER_MISSING_REQUEST_ID:
+        'VALIDATION_ERROR_MESSAGE_HEADER_MISSING_REQUEST_ID'
+  };
+
+  function Validator(message, offset) {
+    this.message = message;
+    this.offset = offset;
+  }
+
+  Object.defineProperty(Validator.prototype, "offsetLimit", {
+    get: function() { return this.message.buffer.byteLength; }
+  });
+
+  Validator.prototype.claimMemory = function(numBytes) {
+    if (numBytes < 0 || this.offset + numBytes > this.offsetLimit)
+      return false;
+    this.offset += numBytes;
+    return true;
+  }
+
+  Validator.prototype.validateStructHeader =
+      function(offset, minNumBytes, minNumFields) {
+    if (!codec.isAligned(offset))
+      return ValidationError.MISALIGNED_OBJECT;
+
+    if (offset + codec.kStructHeaderSize > this.offsetLimit)
+      return ValidationError.ILLEGAL_MEMORY_RANGE;
+
+    var numBytes = this.message.buffer.getUint32(offset);
+    var numFields = this.message.buffer.getUint32(offset + 4);
+
+    if (numBytes < minNumBytes || numFields < minNumFields)
+      return ValidationError.UNEXPECTED_STRUCT_HEADER;
+
+    if (!this.claimMemory(numBytes))
+      return ValidationError.ILLEGAL_MEMORY_RANGE;
+
+    return ValidationError.NONE;
+  }
+
+  Validator.prototype.validateMessageHeader = function() {
+    var numBytes = this.message.getHeaderNumBytes();
+    var numFields = this.message.getHeaderNumFields();
+
+    var validNumFieldsAndNumBytes =
+      (numFields == 2 && numBytes == codec.kMessageHeaderSize) ||

[Matt Perry, 2014/07/28 23:59:03]

indent += 2

[hansmuller, 2014/07/29 00:10:42]

Done.

+      (numFields == 3 && numBytes == codec.kMessageWithRequestIDHeaderSize);
+    if (!validNumFieldsAndNumBytes)
+      return ValidationError.UNEXPECTED_STRUCT_HEADER;
+
+    var expectsResponse = this.message.expectsResponse();
+    var isResponse = this.message.isResponse();
+
+    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;
+  }
+
+  Validator.prototype.validateMessage = function() {
+    var err = this.validateStructHeader(0, codec.kStructHeaderSize, 2);
+    if (err != ValidationError.NONE)
+      return err;
+
+    return this.validateMessageHeader();
+  }
+
+  var exports = {};
+  exports.ValidationError = ValidationError;
+  exports.Validator = Validator;
+  return exports;
+});