randpool.cpp

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// The algorithm in this module comes from PGP's randpool.c

#include "randpool.h"
#include "mdc.h"
#include "md5.h"
#include "modes.h"
#include <assert.h>

typedef MDC<MD5> RandomPoolCipher;

RandomPool::RandomPool(unsigned int poolSize)
    : pool(poolSize), key(RandomPoolCipher::KEYLENGTH)
{
    assert(poolSize > key.size);

    addPos=0;
    getPos=poolSize;
    memset(pool, 0, poolSize);
    memset(key, 0, key.size);
}

void RandomPool::Stir()
{
//  add these lines to be compatible with PGP's randpool.c
//  byteReverse((word32 *)pool.ptr, (word32 *)pool.ptr, pool.size);
    for (int i=0; i<2; i++)
    {
        RandomPoolCipher cipher(key);
        CFBEncryption cfb(cipher, pool+pool.size-cipher.BlockSize());
        cfb.ProcessString(pool, pool.size);
        memcpy(key, pool, key.size);
    }
//  byteReverse((word32 *)pool.ptr, (word32 *)pool.ptr, pool.size);

	addPos = 0;
	getPos = key.size;
}

void RandomPool::Put(byte inByte)
{
    if (addPos == pool.size)
        Stir();

    pool[addPos++] ^= inByte;
    getPos = pool.size; // Force stir on get
}

void RandomPool::Put(const byte *inString, unsigned int length)
{
	unsigned t;

	while (length > (t = pool.size - addPos))
    {
		xorbuf(pool+addPos, inString, t);
		inString += t;
		length -= t;
		Stir();
	}

	if (length)
    {
		xorbuf(pool+addPos, inString, length);
		addPos += length;
		getPos = pool.size; // Force stir on get
	}
}

int RandomPool::Get(byte &outByte)
{
	if (getPos == pool.size)
		Stir();

	outByte = pool[getPos++];
    return 1;
}

unsigned int RandomPool::Get(byte *outString, unsigned int getMax)
{
	unsigned t;
    unsigned int length = getMax;

	while (length > (t = pool.size - getPos))
    {
		memcpy(outString, pool+getPos, t);
		outString += t;
		length -= t;
		Stir();
	}

	if (length)
    {
		memcpy(outString, pool+getPos, length);
		getPos += length;
	}
    return getMax;
}