| // Copyright 2019 The Fuchsia Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "src/lib/fidl_codec/message_decoder.h" |
| |
| #include <lib/syslog/cpp/macros.h> |
| |
| #include <ostream> |
| #include <sstream> |
| |
| #include <rapidjson/stringbuffer.h> |
| #include <rapidjson/writer.h> |
| |
| #include "src/lib/fidl_codec/library_loader.h" |
| #include "src/lib/fidl_codec/status.h" |
| #include "src/lib/fidl_codec/wire_object.h" |
| #include "src/lib/fidl_codec/wire_parser.h" |
| #include "src/lib/fidl_codec/wire_types.h" |
| |
| namespace fidl_codec { |
| |
| std::string DocumentToString(rapidjson::Document* document); |
| |
| bool DecodedMessage::DecodeMessage(MessageDecoderDispatcher* dispatcher, uint64_t process_koid, |
| zx_handle_t handle, const uint8_t* bytes, uint32_t num_bytes, |
| const zx_handle_disposition_t* handles, uint32_t num_handles, |
| SyscallFidlType type, std::ostream& error_stream) { |
| if ((bytes == nullptr) || (num_bytes < sizeof(fidl_message_header_t))) { |
| error_stream << "not enough data for message\n"; |
| return false; |
| } |
| |
| header_ = reinterpret_cast<const fidl_message_header_t*>(bytes); |
| txid_ = header_->txid; |
| ordinal_ = header_->ordinal; |
| |
| // Handle the epitaph header explicitly. |
| if (ordinal_ == kFidlOrdinalEpitaph) { |
| if (num_bytes < sizeof(fidl_epitaph)) { |
| error_stream << "not enough data for epitaph\n"; |
| return false; |
| } |
| switch (type) { |
| case SyscallFidlType::kOutputRequest: |
| case SyscallFidlType::kOutputMessage: |
| received_ = false; |
| break; |
| case SyscallFidlType::kInputResponse: |
| case SyscallFidlType::kInputMessage: |
| received_ = true; |
| break; |
| } |
| auto epitaph = reinterpret_cast<const fidl_epitaph_t*>(header_); |
| epitaph_error_ = epitaph->error; |
| return true; |
| } |
| |
| if ((dispatcher == nullptr) || (dispatcher->loader() == nullptr)) { |
| return false; |
| } |
| |
| const std::vector<const InterfaceMethod*>* methods = dispatcher->loader()->GetByOrdinal(ordinal_); |
| if (methods == nullptr || methods->empty()) { |
| error_stream << "Protocol method with ordinal 0x" << std::hex << header_->ordinal |
| << " not found\n"; |
| return false; |
| } |
| |
| method_ = (*methods)[0]; |
| |
| matched_request_ = DecodeRequest(method_, bytes, num_bytes, handles, num_handles, |
| &decoded_request_, request_error_stream_); |
| matched_response_ = DecodeResponse(method_, bytes, num_bytes, handles, num_handles, |
| &decoded_response_, response_error_stream_); |
| |
| direction_ = dispatcher->ComputeDirection(process_koid, handle, type, method_, |
| matched_request_ != matched_response_); |
| switch (type) { |
| case SyscallFidlType::kOutputMessage: |
| if (direction_ == Direction::kClient) { |
| is_request_ = true; |
| } |
| received_ = false; |
| break; |
| case SyscallFidlType::kInputMessage: |
| if (direction_ == Direction::kServer) { |
| is_request_ = true; |
| } |
| received_ = true; |
| break; |
| case SyscallFidlType::kOutputRequest: |
| is_request_ = true; |
| received_ = false; |
| break; |
| case SyscallFidlType::kInputResponse: |
| received_ = true; |
| break; |
| } |
| if (direction_ != Direction::kUnknown) { |
| if ((is_request_ && !matched_request_) || (!is_request_ && !matched_response_)) { |
| if ((is_request_ && matched_response_) || (!is_request_ && matched_request_)) { |
| if ((type == SyscallFidlType::kOutputRequest) || |
| (type == SyscallFidlType::kInputResponse)) { |
| // We know the direction: we can't be wrong => we haven't been able to decode the message. |
| // However, we can still display something. |
| return true; |
| } |
| // The first determination seems to be wrong. That is, we are expecting |
| // a request but only a response has been successfully decoded or we are |
| // expecting a response but only a request has been successfully |
| // decoded. |
| // Invert the deduction which should now be the right one. |
| dispatcher->UpdateDirection( |
| process_koid, handle, |
| (direction_ == Direction::kClient) ? Direction::kServer : Direction::kClient); |
| is_request_ = !is_request_; |
| } |
| } |
| } |
| return true; |
| } |
| |
| Direction MessageDecoderDispatcher::ComputeDirection(uint64_t process_koid, zx_handle_t handle, |
| SyscallFidlType type, |
| const InterfaceMethod* method, |
| bool only_one_valid) { |
| auto handle_direction = handle_directions_.find(std::make_tuple(handle, process_koid)); |
| if (handle_direction != handle_directions_.end()) { |
| return handle_direction->second; |
| } |
| // This is the first read or write we intercept for this handle/koid. If we |
| // launched the process, we suppose we intercepted the very first read or |
| // write. |
| // If this is not an event (which would mean method->request() is null), a |
| // write means that we are watching a client (a client starts by writing a |
| // request) and a read means that we are watching a server (a server starts |
| // by reading the first client request). |
| // If we attached to a running process, we can only determine correctly if |
| // we are watching a client or a server if we have only one matched_request |
| // or one matched_response. |
| if (IsLaunchedProcess(process_koid) || only_one_valid) { |
| // We launched the process or exactly one of request and response are |
| // valid => we can determine the direction. |
| switch (type) { |
| case SyscallFidlType::kOutputMessage: |
| handle_directions_[std::make_tuple(handle, process_koid)] = |
| (method->request() != nullptr) ? Direction::kClient : Direction::kServer; |
| break; |
| case SyscallFidlType::kInputMessage: |
| handle_directions_[std::make_tuple(handle, process_koid)] = |
| (method->request() != nullptr) ? Direction::kServer : Direction::kClient; |
| break; |
| case SyscallFidlType::kOutputRequest: |
| case SyscallFidlType::kInputResponse: |
| handle_directions_[std::make_tuple(handle, process_koid)] = Direction::kClient; |
| } |
| return handle_directions_[std::make_tuple(handle, process_koid)]; |
| } |
| return Direction::kUnknown; |
| } |
| |
| MessageDecoder::MessageDecoder(const uint8_t* bytes, uint64_t num_bytes, |
| const zx_handle_disposition_t* handles, uint32_t num_handles, |
| std::ostream& error_stream) |
| : num_bytes_(num_bytes), |
| start_byte_pos_(bytes), |
| end_handle_pos_(handles + num_handles), |
| handle_pos_(handles), |
| error_stream_(error_stream) {} |
| |
| MessageDecoder::MessageDecoder(MessageDecoder* container, uint64_t offset, uint64_t num_bytes, |
| uint64_t num_handles) |
| : absolute_offset_(container->absolute_offset() + offset), |
| num_bytes_(num_bytes), |
| start_byte_pos_(container->start_byte_pos_ + offset), |
| end_handle_pos_(container->handle_pos_ + num_handles), |
| handle_pos_(container->handle_pos_), |
| error_stream_(container->error_stream_) { |
| container->handle_pos_ += num_handles; |
| } |
| |
| std::unique_ptr<StructValue> MessageDecoder::DecodeMessage(const Struct& message_format) { |
| // Set the offset for the next object (just after this one). |
| SkipObject(message_format.size()); |
| // Decode the message. |
| std::unique_ptr<StructValue> message = DecodeStruct(message_format, 0); |
| // It's an error if we didn't use all the bytes in the buffer. |
| if (next_object_offset_ != num_bytes_) { |
| AddError() << "Message not fully decoded (decoded=" << next_object_offset_ |
| << ", size=" << num_bytes_ << ")\n"; |
| } |
| // It's an error if we didn't use all the handles in the buffer. |
| if (GetRemainingHandles() != 0) { |
| AddError() << "Message not fully decoded (remain " << GetRemainingHandles() << " handles)\n"; |
| } |
| return message; |
| } |
| |
| std::unique_ptr<Value> MessageDecoder::DecodeValue(const Type* type) { |
| if (type == nullptr) { |
| return nullptr; |
| } |
| // Set the offset for the next object (just after this one). |
| SkipObject(type->InlineSize()); |
| // Decode the envelope. |
| std::unique_ptr<Value> result = type->Decode(this, 0); |
| // It's an error if we didn't use all the bytes in the buffer. |
| if (next_object_offset_ != num_bytes_) { |
| AddError() << "Message envelope not fully decoded (decoded=" << next_object_offset_ |
| << ", size=" << num_bytes_ << ")\n"; |
| } |
| // It's an error if we didn't use all the handles in the buffer. |
| if (GetRemainingHandles() != 0) { |
| AddError() << "Message envelope not fully decoded (remain " << GetRemainingHandles() |
| << " handles)\n"; |
| } |
| return result; |
| } |
| |
| std::unique_ptr<StructValue> MessageDecoder::DecodeStruct(const Struct& struct_definition, |
| uint64_t offset) { |
| std::unique_ptr<StructValue> result = std::make_unique<StructValue>(struct_definition); |
| for (const auto& member : struct_definition.members()) { |
| std::unique_ptr<Value> value = member->type()->Decode(this, offset + member->offset()); |
| result->AddField(member.get(), std::move(value)); |
| } |
| return result; |
| } |
| |
| bool MessageDecoder::DecodeNullableHeader(uint64_t offset, uint64_t size, bool* is_null, |
| uint64_t* nullable_offset) { |
| uintptr_t data; |
| if (!GetValueAt(offset, &data)) { |
| return false; |
| } |
| |
| if (data == FIDL_ALLOC_ABSENT) { |
| *is_null = true; |
| *nullable_offset = 0; |
| return true; |
| } |
| if (data != FIDL_ALLOC_PRESENT) { |
| AddError() << std::hex << (absolute_offset() + offset) << std::dec << ": Invalid value <" |
| << std::hex << data << std::dec << "> for nullable\n"; |
| return false; |
| } |
| *is_null = false; |
| *nullable_offset = next_object_offset(); |
| // Set the offset for the next object (just after this one). |
| SkipObject(size); |
| return true; |
| } |
| |
| std::unique_ptr<Value> MessageDecoder::DecodeEnvelope(uint64_t offset, const Type* type) { |
| FX_DCHECK(type != nullptr); |
| uint32_t envelope_bytes; |
| GetValueAt(offset, &envelope_bytes); |
| offset += sizeof(envelope_bytes); |
| uint32_t envelope_handles; |
| GetValueAt(offset, &envelope_handles); |
| offset += sizeof(envelope_handles); |
| bool is_null; |
| uint64_t nullable_offset; |
| if (!DecodeNullableHeader(offset, envelope_bytes, &is_null, &nullable_offset)) { |
| return std::make_unique<InvalidValue>(); |
| } |
| if (is_null) { |
| if (envelope_bytes != 0) { |
| AddError() << std::hex << (absolute_offset() + offset) << std::dec |
| << ": Null envelope shouldn't have bytes\n"; |
| } |
| if (envelope_handles != 0) { |
| AddError() << std::hex << (absolute_offset() + offset) << std::dec |
| << ": Null envelope shouldn't have handles\n"; |
| } |
| return std::make_unique<NullValue>(); |
| } |
| if (envelope_bytes > num_bytes() - nullable_offset) { |
| AddError() << std::hex << (absolute_offset() + nullable_offset) << std::dec |
| << ": Not enough data to decode an envelope\n"; |
| return std::make_unique<InvalidValue>(); |
| } |
| if (envelope_handles > GetRemainingHandles()) { |
| AddError() << std::hex << (absolute_offset() + nullable_offset) << std::dec |
| << ": Not enough handles to decode an envelope\n"; |
| return std::make_unique<InvalidValue>(); |
| } |
| MessageDecoder envelope_decoder(this, nullable_offset, envelope_bytes, envelope_handles); |
| return envelope_decoder.DecodeValue(type); |
| } |
| |
| bool MessageDecoder::CheckNullEnvelope(uint64_t offset) { |
| uint32_t envelope_bytes; |
| GetValueAt(offset, &envelope_bytes); |
| offset += sizeof(envelope_bytes); |
| uint32_t envelope_handles; |
| GetValueAt(offset, &envelope_handles); |
| offset += sizeof(envelope_handles); |
| bool is_null; |
| uint64_t nullable_offset; |
| if (!DecodeNullableHeader(offset, envelope_bytes, &is_null, &nullable_offset)) { |
| return false; |
| } |
| if (!is_null) { |
| AddError() << std::hex << (absolute_offset() + offset) << std::dec |
| << ": Expecting null envelope\n"; |
| return false; |
| } |
| if (envelope_bytes != 0) { |
| AddError() << std::hex << (absolute_offset() + offset) << std::dec |
| << ": Null envelope shouldn't have bytes\n"; |
| return false; |
| } |
| if (envelope_handles != 0) { |
| AddError() << std::hex << (absolute_offset() + offset) << std::dec |
| << ": Null envelope shouldn't have handles\n"; |
| return false; |
| } |
| return true; |
| } |
| |
| void MessageDecoder::SkipEnvelope(uint64_t offset) { |
| uint32_t envelope_bytes; |
| GetValueAt(offset, &envelope_bytes); |
| offset += sizeof(envelope_bytes); |
| uint32_t envelope_handles; |
| GetValueAt(offset, &envelope_handles); |
| offset += sizeof(envelope_handles); |
| bool is_null; |
| uint64_t nullable_offset; |
| if (!DecodeNullableHeader(offset, envelope_bytes, &is_null, &nullable_offset)) { |
| return; |
| } |
| if (is_null) { |
| if (envelope_bytes != 0) { |
| AddError() << std::hex << (absolute_offset() + offset) << std::dec |
| << ": Null envelope shouldn't have bytes\n"; |
| } |
| if (envelope_handles != 0) { |
| AddError() << std::hex << (absolute_offset() + offset) << std::dec |
| << ": Null envelope shouldn't have handles\n"; |
| } |
| return; |
| } |
| if (envelope_bytes > num_bytes() - nullable_offset) { |
| AddError() << std::hex << (absolute_offset() + nullable_offset) << std::dec |
| << ": Not enough data to decode an envelope\n"; |
| return; |
| } |
| if (envelope_handles > GetRemainingHandles()) { |
| AddError() << std::hex << (absolute_offset() + nullable_offset) << std::dec |
| << ": Not enough handles to decode an envelope\n"; |
| return; |
| } |
| } |
| |
| } // namespace fidl_codec |
