ext-cryptopp/randpool.cpp

// randpool.cpp - written and placed in the public domain by Wei Dai
// RandomPool used to follow the design of randpool in PGP 2.6.x,
// but as of version 5.5 it has been redesigned to reduce the risk
// of reusing random numbers after state rollback (which may occur
// when running in a virtual machine like VMware).

#include "pch.h"

#ifndef CRYPTOPP_IMPORTS

#include "randpool.h"
#include "aes.h"
#include "sha.h"
#include "hrtimer.h"
#include <time.h>

NAMESPACE_BEGIN(CryptoPP)

RandomPool::RandomPool()
	: m_pCipher(new AES::Encryption), m_keySet(false)
{
	memset(m_key, 0, m_key.SizeInBytes());
	memset(m_seed, 0, m_seed.SizeInBytes());
}

void RandomPool::IncorporateEntropy(const byte *input, size_t length)
{
	SHA256 hash;
	hash.Update(m_key, 32);
	hash.Update(input, length);
	hash.Final(m_key);
	m_keySet = false;
}

void RandomPool::GenerateIntoBufferedTransformation(BufferedTransformation &target, const std::string &channel, lword size)
{
	if (size > 0)
	{
		if (!m_keySet)
			m_pCipher->SetKey(m_key, 32);

		Timer timer;
		TimerWord tw = timer.GetCurrentTimerValue();
		CRYPTOPP_COMPILE_ASSERT(sizeof(tw) <= 16);
		*(TimerWord *)m_seed.data() += tw;

		time_t t = time(NULL);
		CRYPTOPP_COMPILE_ASSERT(sizeof(t) <= 8);
		
		// UBsan finding: signed integer overflow: 1876017710 + 1446085457 cannot be represented in type 'long int'
		// *(time_t *)(m_seed.data()+8) += t;
		assert(m_seed.size() >= 16);
		word64 tt1, tt2 = (word64)t;
		memcpy(&tt1, m_seed.data()+8, 8);
		memcpy(m_seed.data()+8, &(tt2 += tt1), 8);
		
		// Wipe the intermediates
		*((volatile TimerWord*)&tw) = 0;
		*((volatile word64*)&tt1) = 0;
		*((volatile word64*)&tt2) = 0;

		do
		{
			m_pCipher->ProcessBlock(m_seed);
			size_t len = UnsignedMin(16, size);
			target.ChannelPut(channel, m_seed, len);
			size -= len;
		} while (size > 0);
	}
}

NAMESPACE_END

#endif