hmac.cpp

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

#include "pch.h"

#ifndef CRYPTOPP_IMPORTS

#include "hmac.h"

NAMESPACE_BEGIN(CryptoPP)

void HMAC_Base::UncheckedSetKey(const byte *userKey, unsigned int keylength, const NameValuePairs &)
{
    AssertValidKeyLength(keylength);

    Restart();

    HashTransformation &hash = AccessHash();
    unsigned int blockSize = hash.BlockSize();

    if (!blockSize)
        throw InvalidArgument("HMAC: can only be used with a block-based hash function");

    m_buf.resize(2*AccessHash().BlockSize() + AccessHash().DigestSize());

    if (keylength <= blockSize)
        memcpy(AccessIpad(), userKey, keylength);
    else
    {
        AccessHash().CalculateDigest(AccessIpad(), userKey, keylength);
        keylength = hash.DigestSize();
    }

    CRYPTOPP_ASSERT(keylength <= blockSize);
    memset(AccessIpad()+keylength, 0, blockSize-keylength);

    for (unsigned int i=0; i<blockSize; i++)
    {
        AccessOpad()[i] = AccessIpad()[i] ^ 0x5c;
        AccessIpad()[i] ^= 0x36;
    }
}

void HMAC_Base::KeyInnerHash()
{
    CRYPTOPP_ASSERT(!m_innerHashKeyed);
    HashTransformation &hash = AccessHash();
    hash.Update(AccessIpad(), hash.BlockSize());
    m_innerHashKeyed = true;
}

void HMAC_Base::Restart()
{
    if (m_innerHashKeyed)
    {
        AccessHash().Restart();
        m_innerHashKeyed = false;
    }
}

void HMAC_Base::Update(const byte *input, size_t length)
{
    if (!m_innerHashKeyed)
        KeyInnerHash();
    AccessHash().Update(input, length);
}

void HMAC_Base::TruncatedFinal(byte *mac, size_t size)
{
    ThrowIfInvalidTruncatedSize(size);

    HashTransformation &hash = AccessHash();

    if (!m_innerHashKeyed)
        KeyInnerHash();
    hash.Final(AccessInnerHash());

    hash.Update(AccessOpad(), hash.BlockSize());
    hash.Update(AccessInnerHash(), hash.DigestSize());
    hash.TruncatedFinal(mac, size);

    m_innerHashKeyed = false;
}

NAMESPACE_END

#endif