src/entropy.h

   1 /*
   2  * Copyright (c) 2000-2004 Apple Computer, Inc. All Rights Reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24
  25 //
  26 // entropy - periodical to collect and seed entropy into /dev/random
  27 //
  28 #ifndef _H_ENTROPY
  29 #define _H_ENTROPY
  30
  31 #include <security_utilities/machserver.h>
  32 #include <security_utilities/timeflow.h>
  33 #include <security_utilities/devrandom.h>
  34
  35 using namespace Security;
  36 using MachPlusPlus::MachServer;
  37
  38
  39 //
  40 // A (one-off) timer object that manages system entropy
  41 //
  42 class EntropyManager : public MachServer::Timer, private DevRandomGenerator {
  43     // all the parameters you ever (should) want to change :-)
  44     static const int collectInterval = 600; // collect every 10 minutes
  45     static const int updateInterval = 3600; // update file every hour
  46     static const int timingsToCollect = 40; // how many timings?
  47
  48 public:
  49         EntropyManager(MachPlusPlus::MachServer &srv, const char *entropyFile);
  50
  51         void action();
  52
  53         MachPlusPlus::MachServer        &server;                // to which we do setTimer()
  54
  55 private:
  56     string mEntropyFilePath;                    // absolute path to entropy file
  57     Time::Absolute mNextUpdate;                 // next time for entropy file update
  58
  59     void collectEntropy();                              // collect system timings and seed RNG
  60     void updateEntropyFile();                   // update entropy file from RNG if it's time
  61
  62     static const size_t entropyFileSize = 20;   // bytes (effectively one SHA-1 worth)
  63 };
  64
  65 #endif //_H_ENTROPY