mojo/public/cpp/bindings/lib/message_header_validator.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "mojo/public/cpp/bindings/lib/message_header_validator.h"
   6
   7 #include "mojo/public/cpp/bindings/lib/bindings_serialization.h"
   8 #include "mojo/public/cpp/bindings/lib/bounds_checker.h"
   9 #include "mojo/public/cpp/bindings/lib/validation_errors.h"
  10
  11 namespace mojo {
  12 namespace internal {
  13 namespace {
  14
  15 bool IsValidMessageHeader(const MessageHeader* header) {
  16   // NOTE: Our goal is to preserve support for future extension of the message
  17   // header. If we encounter fields we do not understand, we must ignore them.
  18
  19   // Extra validation of the struct header:
  20   if (header->num_fields == 2) {
  21     if (header->num_bytes != sizeof(MessageHeader)) {
  22       ReportValidationError(VALIDATION_ERROR_UNEXPECTED_STRUCT_HEADER);
  23       return false;
  24     }
  25   } else if (header->num_fields == 3) {
  26     if (header->num_bytes != sizeof(MessageHeaderWithRequestID)) {
  27       ReportValidationError(VALIDATION_ERROR_UNEXPECTED_STRUCT_HEADER);
  28       return false;
  29     }
  30   } else if (header->num_fields > 3) {
  31     if (header->num_bytes < sizeof(MessageHeaderWithRequestID)) {
  32       ReportValidationError(VALIDATION_ERROR_UNEXPECTED_STRUCT_HEADER);
  33       return false;
  34     }
  35   }
  36
  37   // Validate flags (allow unknown bits):
  38
  39   // These flags require a RequestID.
  40   if (header->num_fields < 3 &&
  41         ((header->flags & kMessageExpectsResponse) ||
  42          (header->flags & kMessageIsResponse))) {
  43     ReportValidationError(VALIDATION_ERROR_MESSAGE_HEADER_MISSING_REQUEST_ID);
  44     return false;
  45   }
  46
  47   // These flags are mutually exclusive.
  48   if ((header->flags & kMessageExpectsResponse) &&
  49       (header->flags & kMessageIsResponse)) {
  50     ReportValidationError(
  51         VALIDATION_ERROR_MESSAGE_HEADER_INVALID_FLAG_COMBINATION);
  52     return false;
  53   }
  54
  55   return true;
  56 }
  57
  58 }  // namespace
  59
  60 MessageHeaderValidator::MessageHeaderValidator(MessageReceiver* sink)
  61     : MessageFilter(sink) {
  62 }
  63
  64 bool MessageHeaderValidator::Accept(Message* message) {
  65   // Pass 0 as number of handles because we don't expect any in the header, even
  66   // if |message| contains handles.
  67   BoundsChecker bounds_checker(message->data(), message->data_num_bytes(), 0);
  68
  69   if (!ValidateStructHeader(message->data(), sizeof(MessageHeader), 2,
  70                             &bounds_checker)) {
  71     return false;
  72   }
  73
  74   if (!IsValidMessageHeader(message->header()))
  75     return false;
  76
  77   return sink_->Accept(message);
  78 }
  79
  80 }  // namespace internal
  81 }  // namespace mojo