modes.cpp

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

#include "pch.h"

#ifndef CRYPTOPP_IMPORTS

#include "modes.h"

#ifndef NDEBUG
#include "des.h"
#endif

NAMESPACE_BEGIN(CryptoPP)

#ifndef NDEBUG
void Modes_TestInstantiations()
{
        CFB_Mode<DES>::Encryption m0;
        CFB_Mode<DES>::Decryption m1;
        OFB_Mode<DES>::Encryption m2;
        CTR_Mode<DES>::Encryption m3;
        ECB_Mode<DES>::Encryption m4;
        CBC_Mode<DES>::Encryption m5;
}
#endif

void CFB_ModePolicy::Iterate(byte *output, const byte *input, CipherDir dir, size_t iterationCount)
{
        assert(m_cipher->IsForwardTransformation());    // CFB mode needs the "encrypt" direction of the underlying block cipher, even to decrypt
        assert(m_feedbackSize == BlockSize());

        unsigned int s = BlockSize();
        if (dir == ENCRYPTION)
        {
                m_cipher->ProcessAndXorBlock(m_register, input, output);
                m_cipher->AdvancedProcessBlocks(output, input+s, output+s, (iterationCount-1)*s, 0);
                memcpy(m_register, output+(iterationCount-1)*s, s);
        }
        else
        {
                memcpy(m_temp, input+(iterationCount-1)*s, s);  // make copy first in case of in-place decryption
                m_cipher->AdvancedProcessBlocks(input, input+s, output+s, (iterationCount-1)*s, BlockTransformation::BT_ReverseDirection);
                m_cipher->ProcessAndXorBlock(m_register, input, output);
                memcpy(m_register, m_temp, s);
        }
}

void CFB_ModePolicy::TransformRegister()
{
        assert(m_cipher->IsForwardTransformation());    // CFB mode needs the "encrypt" direction of the underlying block cipher, even to decrypt
        m_cipher->ProcessBlock(m_register, m_temp);
        unsigned int updateSize = BlockSize()-m_feedbackSize;
        memmove_s(m_register, m_register.size(), m_register+m_feedbackSize, updateSize);
        memcpy_s(m_register+updateSize, m_register.size()-updateSize, m_temp, m_feedbackSize);
}

void CFB_ModePolicy::CipherResynchronize(const byte *iv, size_t length)
{
        assert(length == BlockSize());
        CopyOrZero(m_register, iv, length);
        TransformRegister();
}

void CFB_ModePolicy::SetFeedbackSize(unsigned int feedbackSize)
{
        if (feedbackSize > BlockSize())
                throw InvalidArgument("CFB_Mode: invalid feedback size");
        m_feedbackSize = feedbackSize ? feedbackSize : BlockSize();
}

void CFB_ModePolicy::ResizeBuffers()
{
        CipherModeBase::ResizeBuffers();
        m_temp.New(BlockSize());
}

void OFB_ModePolicy::WriteKeystream(byte *keystreamBuffer, size_t iterationCount)
{
        assert(m_cipher->IsForwardTransformation());    // OFB mode needs the "encrypt" direction of the underlying block cipher, even to decrypt
        unsigned int s = BlockSize();
        m_cipher->ProcessBlock(m_register, keystreamBuffer);
        if (iterationCount > 1)
                m_cipher->AdvancedProcessBlocks(keystreamBuffer, NULL, keystreamBuffer+s, s*(iterationCount-1), 0);
        memcpy(m_register, keystreamBuffer+s*(iterationCount-1), s);
}

void OFB_ModePolicy::CipherResynchronize(byte *keystreamBuffer, const byte *iv, size_t length)
{
        assert(length == BlockSize());
        CopyOrZero(m_register, iv, length);
}

void CTR_ModePolicy::SeekToIteration(lword iterationCount)
{
        int carry=0;
        for (int i=BlockSize()-1; i>=0; i--)
        {
                unsigned int sum = m_register[i] + byte(iterationCount) + carry;
                m_counterArray[i] = (byte) sum;
                carry = sum >> 8;
                iterationCount >>= 8;
        }
}

void CTR_ModePolicy::IncrementCounterBy256()
{
        IncrementCounterByOne(m_counterArray, BlockSize()-1);
}

void CTR_ModePolicy::OperateKeystream(KeystreamOperation operation, byte *output, const byte *input, size_t iterationCount)
{
        assert(m_cipher->IsForwardTransformation());    // CTR mode needs the "encrypt" direction of the underlying block cipher, even to decrypt
        unsigned int s = BlockSize();
        unsigned int inputIncrement = input ? s : 0;

        while (iterationCount)
        {
                byte lsb = m_counterArray[s-1];
                size_t blocks = UnsignedMin(iterationCount, 256U-lsb);
                m_cipher->AdvancedProcessBlocks(m_counterArray, input, output, blocks*s, BlockTransformation::BT_InBlockIsCounter|BlockTransformation::BT_AllowParallel);
                if ((m_counterArray[s-1] = lsb + (byte)blocks) == 0)
                        IncrementCounterBy256();

                output += blocks*s;
                input += blocks*inputIncrement;
                iterationCount -= blocks;
        }
}

void CTR_ModePolicy::CipherResynchronize(byte *keystreamBuffer, const byte *iv, size_t length)
{
        assert(length == BlockSize());
        CopyOrZero(m_register, iv, length);
        m_counterArray = m_register;
}

void BlockOrientedCipherModeBase::UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs &params)
{
        m_cipher->SetKey(key, length, params);
        ResizeBuffers();
        if (IsResynchronizable())
        {
                size_t ivLength;
                const byte *iv = GetIVAndThrowIfInvalid(params, ivLength);
                Resynchronize(iv, (int)ivLength);
        }
}

void ECB_OneWay::ProcessData(byte *outString, const byte *inString, size_t length)
{
        assert(length%BlockSize()==0);
        m_cipher->AdvancedProcessBlocks(inString, NULL, outString, length, BlockTransformation::BT_AllowParallel);
}

void CBC_Encryption::ProcessData(byte *outString, const byte *inString, size_t length)
{
        if (!length)
                return;
        assert(length%BlockSize()==0);

        unsigned int blockSize = BlockSize();
        m_cipher->AdvancedProcessBlocks(inString, m_register, outString, blockSize, BlockTransformation::BT_XorInput);
        if (length > blockSize)
                m_cipher->AdvancedProcessBlocks(inString+blockSize, outString, outString+blockSize, length-blockSize, BlockTransformation::BT_XorInput);
        memcpy(m_register, outString + length - blockSize, blockSize);
}

void CBC_CTS_Encryption::ProcessLastBlock(byte *outString, const byte *inString, size_t length)
{
        if (length <= BlockSize())
        {
                if (!m_stolenIV)
                        throw InvalidArgument("CBC_Encryption: message is too short for ciphertext stealing");

                // steal from IV
                memcpy(outString, m_register, length);
                outString = m_stolenIV;
        }
        else
        {
                // steal from next to last block
                xorbuf(m_register, inString, BlockSize());
                m_cipher->ProcessBlock(m_register);
                inString += BlockSize();
                length -= BlockSize();
                memcpy(outString+BlockSize(), m_register, length);
        }

        // output last full ciphertext block
        xorbuf(m_register, inString, length);
        m_cipher->ProcessBlock(m_register);
        memcpy(outString, m_register, BlockSize());
}

void CBC_Decryption::ProcessData(byte *outString, const byte *inString, size_t length)
{
        if (!length)
                return;
        assert(length%BlockSize()==0);

        unsigned int blockSize = BlockSize();
        memcpy(m_temp, inString+length-blockSize, blockSize);   // save copy now in case of in-place decryption
        if (length > blockSize)
                m_cipher->AdvancedProcessBlocks(inString+blockSize, inString, outString+blockSize, length-blockSize, BlockTransformation::BT_ReverseDirection|BlockTransformation::BT_AllowParallel);
        m_cipher->ProcessAndXorBlock(inString, m_register, outString);
        m_register.swap(m_temp);
}

void CBC_CTS_Decryption::ProcessLastBlock(byte *outString, const byte *inString, size_t length)
{
        const byte *pn, *pn1;
        bool stealIV = length <= BlockSize();

        if (stealIV)
        {
                pn = inString;
                pn1 = m_register;
        }
        else
        {
                pn = inString + BlockSize();
                pn1 = inString;
                length -= BlockSize();
        }

        // decrypt last partial plaintext block
        memcpy(m_temp, pn1, BlockSize());
        m_cipher->ProcessBlock(m_temp);
        xorbuf(m_temp, pn, length);

        if (stealIV)
                memcpy(outString, m_temp, length);
        else
        {
                memcpy(outString+BlockSize(), m_temp, length);
                // decrypt next to last plaintext block
                memcpy(m_temp, pn, length);
                m_cipher->ProcessBlock(m_temp);
                xorbuf(outString, m_temp, m_register, BlockSize());
        }
}

NAMESPACE_END

#endif