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 IsValidMessageHeader(const MessageHeader * header)15bool 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 MessageHeaderValidator(MessageReceiver * sink)60MessageHeaderValidator::MessageHeaderValidator(MessageReceiver* sink) 61 : MessageFilter(sink) { 62 } 63 Accept(Message * message)64bool 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 82