src/entropy.h

   1 /*
   2  * Copyright (c) 2000-2004 Apple Computer, Inc. All Rights Reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
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  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25
  26
  27 //
  28 // yarrowseed - periodical to collect and seed entropy into /dev/random
  29 //
  30 #ifndef _H_ENTROPY
  31 #define _H_ENTROPY
  32
  33 #include <security_utilities/machserver.h>
  34 #include <security_utilities/timeflow.h>
  35 #include <security_utilities/devrandom.h>
  36
  37 using namespace Security;
  38 using MachPlusPlus::MachServer;
  39
  40
  41 //
  42 // A (one-off) timer object that manages system entropy
  43 //
  44 class EntropyManager : public MachServer::Timer, private DevRandomGenerator {
  45     // all the parameters you ever (should) want to change :-)
  46     static const int collectInterval = 600; // collect every 10 minutes
  47     static const int updateInterval = 3600; // update file every hour
  48     static const int timingsToCollect = 40; // how many timings?
  49
  50 public:
  51         EntropyManager(MachPlusPlus::MachServer &srv, const char *entropyFile);
  52
  53         void action();
  54
  55         MachPlusPlus::MachServer        &server;                // to which we do setTimer()
  56
  57 private:
  58     string mEntropyFilePath;                    // absolute path to entropy file
  59     Time::Absolute mNextUpdate;                 // next time for entropy file update
  60
  61     void collectEntropy();                              // collect system timings and seed RNG
  62     void updateEntropyFile();                   // update entropy file from RNG if it's time
  63
  64     static const size_t entropyFileSize = 20;   // bytes (effectively one SHA-1 worth)
  65 };
  66
  67 #endif //_H_ENTROPY