SecurityServer/entropy.h

   1 /*
   2  * Copyright (c) 2000-2001 Apple Computer, Inc. All Rights Reserved.
   3  *
   4  * The contents of this file constitute Original Code as defined in and are
   5  * subject to the Apple Public Source License Version 1.2 (the 'License').
   6  * You may not use this file except in compliance with the License. Please obtain
   7  * a copy of the License at http://www.apple.com/publicsource and read it before
   8  * using this file.
   9  *
  10  * This Original Code and all software distributed under the License are
  11  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS
  12  * OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, INCLUDING WITHOUT
  13  * LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
  14  * PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. Please see the License for the
  15  * specific language governing rights and limitations under the License.
  16  */
  17
  18
  19 //
  20 // yarrowseed - periodical to collect and seed entropy into /dev/random
  21 //
  22 #ifndef _H_ENTROPY
  23 #define _H_ENTROPY
  24
  25 #include <Security/machserver.h>
  26 #include <Security/timeflow.h>
  27 #include <Security/devrandom.h>
  28
  29 using namespace Security;
  30 using MachPlusPlus::MachServer;
  31
  32
  33 //
  34 // A (one-off) timer object that manages system entropy
  35 //
  36 class EntropyManager : public MachServer::Timer, private DevRandomGenerator {
  37     // all the parameters you ever (should) want to change :-)
  38     static const int collectInterval = 600; // collect every 10 minutes
  39     static const int updateInterval = 3600; // update file every hour
  40     static const int timingsToCollect = 40; // how many timings?
  41
  42 public:
  43         EntropyManager(MachPlusPlus::MachServer &srv, const char *entropyFile);
  44
  45         void action();
  46
  47         MachPlusPlus::MachServer        &server;                // to which we do setTimer()
  48
  49 private:
  50     string mEntropyFilePath;                    // absolute path to entropy file
  51     Time::Absolute mNextUpdate;                 // next time for entropy file update
  52
  53     void collectEntropy();                              // collect system timings and seed RNG
  54     void updateEntropyFile();                   // update entropy file from RNG if it's time
  55
  56     static const size_t entropyFileSize = 20;   // bytes (effectively one SHA-1 worth)
  57 };
  58
  59 #endif //_H_ENTROPY