iterhash.cpp

// iterhash.cpp - originally written and placed in the public domain by Wei Dai

#ifndef __GNUC__
#define CRYPTOPP_MANUALLY_INSTANTIATE_TEMPLATES
#endif

#include "iterhash.h"
#include "misc.h"
#include "cpu.h"

NAMESPACE_BEGIN(CryptoPP)

template <class T, class BASE> void IteratedHashBase<T, BASE>::Update(const byte *input, size_t len)
{
    HashWordType oldCountLo = m_countLo, oldCountHi = m_countHi;
    if ((m_countLo = oldCountLo + HashWordType(len)) < oldCountLo)
        m_countHi++;             // carry from low to high
    m_countHi += (HashWordType)SafeRightShift<8*sizeof(HashWordType)>(len);
    if (m_countHi < oldCountHi || SafeRightShift<2*8*sizeof(HashWordType)>(len) != 0)
        throw HashInputTooLong(this->AlgorithmName());

    const unsigned int blockSize = this->BlockSize();
    unsigned int num = ModPowerOf2(oldCountLo, blockSize);

    T* dataBuf = this->DataBuf();
    byte* data = (byte *)dataBuf;
    CRYPTOPP_ASSERT(dataBuf && data);

    if (num != 0)   // process left over data
    {
        if (num+len >= blockSize)
        {
            if (data && input) {memcpy(data+num, input, blockSize-num);}
            HashBlock(dataBuf);
            input += (blockSize-num);
            len -= (blockSize-num);
            num = 0;
            // drop through and do the rest
        }
        else
        {
            if (data && input && len) {memcpy(data+num, input, len);}
            return;
        }
    }

    // now process the input data in blocks of blockSize bytes and save the leftovers to m_data
    if (len >= blockSize)
    {
        if (input == data)
        {
            CRYPTOPP_ASSERT(len == blockSize);
            HashBlock(dataBuf);
            return;
        }
        else if (IsAligned<T>(input))
        {
            size_t leftOver = HashMultipleBlocks((T *)(void*)input, len);
            input += (len - leftOver);
            len = leftOver;
        }
        else
            do
            {   // copy input first if it's not aligned correctly
                if (data && input) memcpy(data, input, blockSize);
                HashBlock(dataBuf);
                input+=blockSize;
                len-=blockSize;
            } while (len >= blockSize);
    }

    if (data && input && len && data != input)
        memcpy(data, input, len);
}

template <class T, class BASE> byte * IteratedHashBase<T, BASE>::CreateUpdateSpace(size_t &size)
{
    unsigned int blockSize = this->BlockSize();
    unsigned int num = ModPowerOf2(m_countLo, blockSize);
    size = blockSize - num;
    return (byte *)DataBuf() + num;
}

template <class T, class BASE> size_t IteratedHashBase<T, BASE>::HashMultipleBlocks(const T *input, size_t length)
{
    unsigned int blockSize = this->BlockSize();
    bool noReverse = NativeByteOrderIs(this->GetByteOrder());
    T* dataBuf = this->DataBuf();
    do
    {
        if (noReverse)
            this->HashEndianCorrectedBlock(input);
        else
        {
            ByteReverse(dataBuf, input, this->BlockSize());
            this->HashEndianCorrectedBlock(dataBuf);
        }

        input += blockSize/sizeof(T);
        length -= blockSize;
    }
    while (length >= blockSize);
    return length;
}

template <class T, class BASE> void IteratedHashBase<T, BASE>::PadLastBlock(unsigned int lastBlockSize, byte padFirst)
{
    unsigned int blockSize = this->BlockSize();
    unsigned int num = ModPowerOf2(m_countLo, blockSize);
    T* dataBuf = this->DataBuf();
    byte* data = (byte *)dataBuf;
    data[num++] = padFirst;
    if (num <= lastBlockSize)
        memset(data+num, 0, lastBlockSize-num);
    else
    {
        memset(data+num, 0, blockSize-num);
        HashBlock(dataBuf);
        memset(data, 0, lastBlockSize);
    }
}

template <class T, class BASE> void IteratedHashBase<T, BASE>::Restart()
{
    m_countLo = m_countHi = 0;
    Init();
}

template <class T, class BASE> void IteratedHashBase<T, BASE>::TruncatedFinal(byte *digest, size_t size)
{
    this->ThrowIfInvalidTruncatedSize(size);

    T* dataBuf = this->DataBuf();
    T* stateBuf = this->StateBuf();
    unsigned int blockSize = this->BlockSize();
    ByteOrder order = this->GetByteOrder();

    PadLastBlock(blockSize - 2*sizeof(HashWordType));
    dataBuf[blockSize/sizeof(T)-2+order] = ConditionalByteReverse(order, this->GetBitCountLo());
    dataBuf[blockSize/sizeof(T)-1-order] = ConditionalByteReverse(order, this->GetBitCountHi());

    HashBlock(dataBuf);

    if (IsAligned<HashWordType>(digest) && size%sizeof(HashWordType)==0)
        ConditionalByteReverse<HashWordType>(order, (HashWordType *)(void*)digest, stateBuf, size);
    else
    {
        ConditionalByteReverse<HashWordType>(order, stateBuf, stateBuf, this->DigestSize());
        memcpy(digest, stateBuf, size);
    }

    this->Restart();        // reinit for next use
}

#ifdef __GNUC__
    template class IteratedHashBase<word64, HashTransformation>;
    template class IteratedHashBase<word64, MessageAuthenticationCode>;

    template class IteratedHashBase<word32, HashTransformation>;
    template class IteratedHashBase<word32, MessageAuthenticationCode>;
#endif

NAMESPACE_END