ccm.cpp

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

#include "pch.h"

#ifndef CRYPTOPP_IMPORTS

#include "ccm.h"

NAMESPACE_BEGIN(CryptoPP)

void CCM_Base::SetKeyWithoutResync(const byte *userKey, size_t keylength, const NameValuePairs &params)
{
        BlockCipher &blockCipher = AccessBlockCipher();

        blockCipher.SetKey(userKey, keylength, params);

        if (blockCipher.BlockSize() != REQUIRED_BLOCKSIZE)
                throw InvalidArgument(AlgorithmName() + ": block size of underlying block cipher is not 16");

        m_digestSize = params.GetIntValueWithDefault(Name::DigestSize(), DefaultDigestSize());
        if (m_digestSize % 2 > 0 || m_digestSize < 4 || m_digestSize > 16)
                throw InvalidArgument(AlgorithmName() + ": DigestSize must be 4, 6, 8, 10, 12, 14, or 16");

        m_buffer.Grow(2*REQUIRED_BLOCKSIZE);
        m_L = 8;
}

void CCM_Base::Resync(const byte *iv, size_t len)
{
        BlockCipher &cipher = AccessBlockCipher();

        m_L = REQUIRED_BLOCKSIZE-1-(int)len;
        assert(m_L >= 2);
        if (m_L > 8)
                m_L = 8;

        m_buffer[0] = byte(m_L-1);      // flag
        memcpy(m_buffer+1, iv, len);
        memset(m_buffer+1+len, 0, REQUIRED_BLOCKSIZE-1-len);

        if (m_state >= State_IVSet)
                m_ctr.Resynchronize(m_buffer, REQUIRED_BLOCKSIZE);
        else
                m_ctr.SetCipherWithIV(cipher, m_buffer);

        m_ctr.Seek(REQUIRED_BLOCKSIZE);
        m_aadLength = 0; 
        m_messageLength = 0;
}

void CCM_Base::UncheckedSpecifyDataLengths(lword headerLength, lword messageLength, lword footerLength)
{
        if (m_state != State_IVSet)
                throw BadState(AlgorithmName(), "SpecifyDataLengths", "or after State_IVSet");

        m_aadLength = headerLength; 
        m_messageLength = messageLength;

        byte *cbcBuffer = CBC_Buffer();
        const BlockCipher &cipher = GetBlockCipher();

        cbcBuffer[0] = byte(64*(headerLength>0) + 8*((m_digestSize-2)/2) + (m_L-1));    // flag
        PutWord<word64>(true, BIG_ENDIAN_ORDER, cbcBuffer+REQUIRED_BLOCKSIZE-8, m_messageLength);
        memcpy(cbcBuffer+1, m_buffer+1, REQUIRED_BLOCKSIZE-1-m_L);
        cipher.ProcessBlock(cbcBuffer);

        if (headerLength>0)
        {
                assert(m_bufferedDataLength == 0);

                if (headerLength < ((1<<16) - (1<<8)))
                {
                        PutWord<word16>(true, BIG_ENDIAN_ORDER, m_buffer, (word16)headerLength);
                        m_bufferedDataLength = 2;
                }
                else if (headerLength < (W64LIT(1)<<32))
                {
                        m_buffer[0] = 0xff;
                        m_buffer[1] = 0xfe;
                        PutWord<word32>(false, BIG_ENDIAN_ORDER, m_buffer+2, (word32)headerLength);
                        m_bufferedDataLength = 6;
                }
                else
                {
                        m_buffer[0] = 0xff;
                        m_buffer[1] = 0xff;
                        PutWord<word64>(false, BIG_ENDIAN_ORDER, m_buffer+2, headerLength);
                        m_bufferedDataLength = 10;
                }
        }
}

size_t CCM_Base::AuthenticateBlocks(const byte *data, size_t len)
{
        byte *cbcBuffer = CBC_Buffer();
        const BlockCipher &cipher = GetBlockCipher();
        return cipher.AdvancedProcessBlocks(cbcBuffer, data, cbcBuffer, len, BlockTransformation::BT_DontIncrementInOutPointers|BlockTransformation::BT_XorInput);
}

void CCM_Base::AuthenticateLastHeaderBlock()
{
        byte *cbcBuffer = CBC_Buffer();
        const BlockCipher &cipher = GetBlockCipher();

        if (m_aadLength != m_totalHeaderLength)
                throw InvalidArgument(AlgorithmName() + ": header length doesn't match that given in SpecifyDataLengths");

        if (m_bufferedDataLength > 0)
        {
                xorbuf(cbcBuffer, m_buffer, m_bufferedDataLength);
                cipher.ProcessBlock(cbcBuffer);
                m_bufferedDataLength = 0;
        }
}

void CCM_Base::AuthenticateLastConfidentialBlock()
{
        byte *cbcBuffer = CBC_Buffer();
        const BlockCipher &cipher = GetBlockCipher();

        if (m_messageLength != m_totalMessageLength)
                throw InvalidArgument(AlgorithmName() + ": message length doesn't match that given in SpecifyDataLengths");

        if (m_bufferedDataLength > 0)
        {
                xorbuf(cbcBuffer, m_buffer, m_bufferedDataLength);
                cipher.ProcessBlock(cbcBuffer);
                m_bufferedDataLength = 0;
        }
}

void CCM_Base::AuthenticateLastFooterBlock(byte *mac, size_t macSize)
{
        m_ctr.Seek(0);
        m_ctr.ProcessData(mac, CBC_Buffer(), macSize);
}

NAMESPACE_END

#endif