ccm.cpp

// ccm.cpp - originally 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;
    CRYPTOPP_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)
    {
        CRYPTOPP_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