entropy.h   [plain text]

/*
 * Copyright (c) 2000-2001 Apple Computer, Inc. All Rights Reserved.
 * 
 * The contents of this file constitute Original Code as defined in and are
 * subject to the Apple Public Source License Version 1.2 (the 'License').
 * You may not use this file except in compliance with the License. Please obtain
 * a copy of the License at http://www.apple.com/publicsource and read it before
 * using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS
 * OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, INCLUDING WITHOUT
 * LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. Please see the License for the
 * specific language governing rights and limitations under the License.
 */


//
// yarrowseed - periodical to collect and seed entropy into /dev/random
//
#ifndef _H_ENTROPY
#define _H_ENTROPY

#include <Security/machserver.h>
#include <Security/timeflow.h>
#include <Security/devrandom.h>

using namespace Security;
using MachPlusPlus::MachServer;


//
// A (one-off) timer object that manages system entropy
//
class EntropyManager : public MachServer::Timer, private DevRandomGenerator {
    // all the parameters you ever (should) want to change :-)
    static const int collectInterval = 600; // collect every 10 minutes
    static const int updateInterval = 3600; // update file every hour
    static const int timingsToCollect = 40; // how many timings?

public:
	EntropyManager(MachPlusPlus::MachServer &srv, const char *entropyFile);
		
	void action();
    
	MachPlusPlus::MachServer	&server;		// to which we do setTimer()
    
private:
    string mEntropyFilePath;			// absolute path to entropy file
    Time::Absolute mNextUpdate;			// next time for entropy file update
    
    void collectEntropy();				// collect system timings and seed RNG
    void updateEntropyFile();			// update entropy file from RNG if it's time
    
    static const size_t entropyFileSize = 20;	// bytes (effectively one SHA-1 worth)
};

#endif //_H_ENTROPY