1 // Copyright (c) 2012 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 #ifndef DBUS_FILE_DESCRIPTOR_H_ 6 #define DBUS_FILE_DESCRIPTOR_H_ 7 8 #include <memory> 9 10 #include "base/macros.h" 11 #include "dbus/dbus_export.h" 12 13 namespace dbus { 14 15 // FileDescriptor is a type used to encapsulate D-Bus file descriptors 16 // and to follow the RAII idiom appropiate for use with message operations 17 // where the descriptor might be easily leaked. To guard against this the 18 // descriptor is closed when an instance is destroyed if it is owned. 19 // Ownership is asserted only when PutValue is used and TakeValue can be 20 // used to take ownership. 21 // 22 // For example, in the following 23 // FileDescriptor fd; 24 // if (!reader->PopString(&name) || 25 // !reader->PopFileDescriptor(&fd) || 26 // !reader->PopUint32(&flags)) { 27 // the descriptor in fd will be closed if the PopUint32 fails. But 28 // writer.AppendFileDescriptor(dbus::FileDescriptor(1)); 29 // will not automatically close "1" because it is not owned. 30 // 31 // Descriptors must be validated before marshalling in a D-Bus message 32 // or using them after unmarshalling. We disallow descriptors to a 33 // directory to reduce the security risks. Splitting out validation 34 // also allows the caller to do this work on the File thread to conform 35 // with i/o restrictions. 36 class CHROME_DBUS_EXPORT FileDescriptor { 37 public: 38 // This provides a simple way to pass around file descriptors since they must 39 // be closed on a thread that is allowed to perform I/O. 40 struct Deleter { 41 void CHROME_DBUS_EXPORT operator()(FileDescriptor* fd); 42 }; 43 44 // Permits initialization without a value for passing to 45 // dbus::MessageReader::PopFileDescriptor to fill in and from int values. FileDescriptor()46 FileDescriptor() : value_(-1), owner_(false), valid_(false) {} FileDescriptor(int value)47 explicit FileDescriptor(int value) : value_(value), owner_(false), 48 valid_(false) {} 49 50 FileDescriptor(FileDescriptor&& other); 51 52 virtual ~FileDescriptor(); 53 54 FileDescriptor& operator=(FileDescriptor&& other); 55 56 // Retrieves value as an int without affecting ownership. 57 int value() const; 58 59 // Retrieves whether or not the descriptor is ok to send/receive. is_valid()60 int is_valid() const { return valid_; } 61 62 // Sets the value and assign ownership. PutValue(int value)63 void PutValue(int value) { 64 value_ = value; 65 owner_ = true; 66 valid_ = false; 67 } 68 69 // Takes the value and ownership. 70 int TakeValue(); 71 72 // Checks (and records) validity of the file descriptor. 73 // We disallow directories to avoid potential sandbox escapes. 74 // Note this call must be made on a thread where file i/o is allowed. 75 void CheckValidity(); 76 77 private: 78 void Swap(FileDescriptor* other); 79 80 int value_; 81 bool owner_; 82 bool valid_; 83 84 DISALLOW_COPY_AND_ASSIGN(FileDescriptor); 85 }; 86 87 using ScopedFileDescriptor = 88 std::unique_ptr<FileDescriptor, FileDescriptor::Deleter>; 89 90 } // namespace dbus 91 92 #endif // DBUS_FILE_DESCRIPTOR_H_ 93