globrand.h

伯克利做的SFTP安全文件传输协议

// globrand.h
// defines a global random pool, such that all modules can both
//   (1) get strong random values, and
//   (2) add entropy with it is available
// copyright SafeTP Development Group, Inc., 2000  Terms of use are as specified in license.txt

#ifndef __GLOBRAND_H
#define __GLOBRAND_H

#include "randpool.h"      // RandomPool
#include "datablok.h"      // DataBlock


// random generator with added security because it hashes everything on
// the way out; this was an idea I had originally, but decided to actually
// implement it after reading "Cryptanalytic Attacks on Pseudorandom
// Number Generators" by Kelsey, Schneier, Wagner, and Hall, available
// at counterpane.com
class HashedRandomPool : public RandomNumberGenerator {
private:     // data
  // pool I'm improving
  RandomPool basePool;                   // internal random pool

  // output hashing state
  enum { BUFSIZE = 20 };                 // should be equal to SHA::DIGESTSIZE
  byte outBuffer[BUFSIZE];               // bytes ready to output
  int outPtr;                            // next byte to output

  // state, so we can warn on failure to seed
  bool notSeeded;

private:     // funcs
  // set state so next GetByte() triggers a refill of output buffer
  void forceRehash();

public:      // funcs
  HashedRandomPool();

  // RandomNumberGenerator interface
  byte GetByte();

  // entropy-adding interface, similar to RandomPool's
  void Put(byte const *bytes, int length);

  // seed saving and loading (not guaranteed to save or
  // restore the exact state, but guaranteed to retain
  // entropy across save/load)
  DataBlock getSeed();
  void seed(DataBlock const &seed);
};


// the pool
// sm: I'm commenting this out to hide the name externally, since
// all access needs to be protected by the lock; all of the public
// entry points below take responsibility for protecting accesses
//extern HashedRandomPool globalRandomPool;

// there places we want to access the pool directly; this class can be
// instantiated in those places, and will automatically lock/unlock
// the pool
class GlobalRandomPool {
public:
  GlobalRandomPool();           // lock
  ~GlobalRandomPool();          // unlock

  HashedRandomPool &pool();     // access the pool
};


// read seed from persistent state
void readRandomSeed(bool complain = true);
  // if complain is true, we will print a warning message if
  // the random seed file is missing

// simple existence check
bool isRandomSeedThere();

// save seed to persistent state
void saveRandomSeed();


// add entropy based on time and other queryable stats
void addEntropy();

// add whatever entropy is available from some value
void addEntropy(long value);


// occasionally-convenient interface
DataBlock getRandomBytes(int bytes);

#endif // __GLOBRAND_H