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