modes.cpp

// modes.cpp - originally written and placed in the public domain by Wei Dai
 
#include "pch.h"
 
#ifndef CRYPTOPP_IMPORTS
 
#include "modes.h"
#include "strciphr.h"
#include "misc.h"
 
#if defined(CRYPTOPP_DEBUG)
#include "des.h"
#endif
 
NAMESPACE_BEGIN(CryptoPP)
 
#if defined(CRYPTOPP_DEBUG) && !defined(CRYPTOPP_DOXYGEN_PROCESSING)
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 CipherModeBase::ResizeBuffers()
{
    m_register.New(m_cipher->BlockSize());
}
 
void CFB_ModePolicy::Iterate(byte *output, const byte *input, CipherDir dir, size_t iterationCount)
{
    CRYPTOPP_ASSERT(input); CRYPTOPP_ASSERT(output);
    CRYPTOPP_ASSERT(m_cipher->IsForwardTransformation());
    CRYPTOPP_ASSERT(m_register.size() == BlockSize());
    CRYPTOPP_ASSERT(m_temp.size() == BlockSize());
    CRYPTOPP_ASSERT(iterationCount > 0);
 
    const unsigned int s = BlockSize();
    if (dir == ENCRYPTION)
    {
        m_cipher->ProcessAndXorBlock(m_register, input, output);
        if (iterationCount > 1)
            m_cipher->AdvancedProcessBlocks(output, PtrAdd(input,s), PtrAdd(output,s), (iterationCount-1)*s, 0);
        std::memcpy(m_register, PtrAdd(output,(iterationCount-1)*s), s);
    }
    else
    {
        // make copy first in case of in-place decryption
        std::memcpy(m_temp, PtrAdd(input,(iterationCount-1)*s), s);
        if (iterationCount > 1)
            m_cipher->AdvancedProcessBlocks(input, PtrAdd(input,s), PtrAdd(output,s), (iterationCount-1)*s, BlockTransformation::BT_ReverseDirection);
        m_cipher->ProcessAndXorBlock(m_register, input, output);
        std::memcpy(m_register, m_temp, s);
    }
}
 
void CFB_ModePolicy::TransformRegister()
{
    CRYPTOPP_ASSERT(m_cipher->IsForwardTransformation());
    CRYPTOPP_ASSERT(m_register.size() == BlockSize());
    CRYPTOPP_ASSERT(m_temp.size() == BlockSize());
 
    const ptrdiff_t updateSize = BlockSize()-m_feedbackSize;
    m_cipher->ProcessBlock(m_register, m_temp);
    memmove_s(m_register, m_register.size(), PtrAdd(m_register.begin(),m_feedbackSize), updateSize);
    memcpy_s(PtrAdd(m_register.begin(),updateSize), m_register.size()-updateSize, m_temp, m_feedbackSize);
}
 
void CFB_ModePolicy::CipherResynchronize(const byte *iv, size_t length)
{
    CRYPTOPP_ASSERT(length == BlockSize());
    CRYPTOPP_ASSERT(m_register.size() == BlockSize());
 
    CopyOrZero(m_register, m_register.size(), iv, length);
    TransformRegister();
}
 
void CFB_ModePolicy::SetFeedbackSize(unsigned int feedbackSize)
{
    CRYPTOPP_ASSERT(feedbackSize <= BlockSize());
    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());
}
 
byte* CFB_ModePolicy::GetRegisterBegin()
{
    CRYPTOPP_ASSERT(!m_register.empty());
    CRYPTOPP_ASSERT(BlockSize() >= m_feedbackSize);
    return PtrAdd(m_register.begin(), BlockSize() - m_feedbackSize);
}
 
void OFB_ModePolicy::WriteKeystream(byte *keystreamBuffer, size_t iterationCount)
{
    CRYPTOPP_ASSERT(m_cipher->IsForwardTransformation());
    CRYPTOPP_ASSERT(m_register.size() == BlockSize());
    CRYPTOPP_ASSERT(iterationCount > 0);
 
    const unsigned int s = BlockSize();
    m_cipher->ProcessBlock(m_register, keystreamBuffer);
    if (iterationCount > 1)
        m_cipher->AdvancedProcessBlocks(keystreamBuffer, NULLPTR, PtrAdd(keystreamBuffer, s), s*(iterationCount-1), 0);
    std::memcpy(m_register, PtrAdd(keystreamBuffer, (iterationCount-1)*s), s);
}
 
void OFB_ModePolicy::CipherResynchronize(byte *keystreamBuffer, const byte *iv, size_t length)
{
    CRYPTOPP_UNUSED(keystreamBuffer), CRYPTOPP_UNUSED(length);
    CRYPTOPP_ASSERT(m_register.size() == BlockSize());
    CRYPTOPP_ASSERT(length == BlockSize());
 
    CopyOrZero(m_register, m_register.size(), 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 & 0xff);
        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)
{
    CRYPTOPP_ASSERT(output);
    // CRYPTOPP_ASSERT(input);  // input is sometimes NULL
    CRYPTOPP_ASSERT(m_cipher->IsForwardTransformation());
    CRYPTOPP_ASSERT(m_counterArray.size() == BlockSize());
    CRYPTOPP_UNUSED(operation);
 
    const size_t s = BlockSize();
 
    while (iterationCount)
    {
        const byte lsb = m_counterArray[s-1];
        const size_t blocks = UnsignedMin(iterationCount, 256u-lsb);
        const size_t outIncrement = output ? blocks*s : 0;
        const size_t inIncrement = input ? blocks*s : 0;
 
        m_cipher->AdvancedProcessBlocks(m_counterArray, input, output, blocks*s, BlockTransformation::BT_InBlockIsCounter|BlockTransformation::BT_AllowParallel);
        if ((m_counterArray[s-1] = static_cast<byte>(lsb + blocks)) == 0)
            IncrementCounterBy256();
 
        output = PtrAdd(output, outIncrement);
        input = PtrAdd(input, inIncrement);
        iterationCount -= blocks;
    }
}
 
void CTR_ModePolicy::CipherResynchronize(byte *keystreamBuffer, const byte *iv, size_t length)
{
    CRYPTOPP_UNUSED(keystreamBuffer), CRYPTOPP_UNUSED(length);
    CRYPTOPP_ASSERT(m_register.size() == BlockSize());
    CRYPTOPP_ASSERT(length == BlockSize());
 
    CopyOrZero(m_register, m_register.size(), iv, length);
    m_counterArray.Assign(m_register.begin(), m_register.size());
}
 
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 BlockOrientedCipherModeBase::ResizeBuffers()
{
    CipherModeBase::ResizeBuffers();
    m_buffer.New(BlockSize());
}
 
void ECB_OneWay::ProcessData(byte *outString, const byte *inString, size_t length)
{
    CRYPTOPP_ASSERT(length%BlockSize()==0);
    m_cipher->AdvancedProcessBlocks(inString, NULLPTR, outString, length, BlockTransformation::BT_AllowParallel);
}
 
void CBC_Encryption::ProcessData(byte *outString, const byte *inString, size_t length)
{
    CRYPTOPP_ASSERT(length%BlockSize()==0);
    CRYPTOPP_ASSERT(m_register.size() == BlockSize());
    if (!length) return;
 
    const unsigned int blockSize = BlockSize();
    m_cipher->AdvancedProcessBlocks(inString, m_register, outString, blockSize, BlockTransformation::BT_XorInput);
    if (length > blockSize)
        m_cipher->AdvancedProcessBlocks(PtrAdd(inString,blockSize), outString, PtrAdd(outString,blockSize), length-blockSize, BlockTransformation::BT_XorInput);
    std::memcpy(m_register, PtrAdd(outString, length - blockSize), blockSize);
}
 
size_t CBC_CTS_Encryption::ProcessLastBlock(byte *outString, size_t outLength, const byte *inString, size_t inLength)
{
    CRYPTOPP_UNUSED(outLength);
    const size_t used = inLength;
    const unsigned int blockSize = BlockSize();
 
    if (inLength <= blockSize)
    {
        if (!m_stolenIV)
            throw InvalidArgument("CBC_Encryption: message is too short for ciphertext stealing");
 
        // steal from IV
        std::memcpy(outString, m_register, inLength);
        outString = m_stolenIV;
    }
    else
    {
        // steal from next to last block
        xorbuf(m_register, inString, blockSize);
        m_cipher->ProcessBlock(m_register);
        inString = PtrAdd(inString, blockSize);
        inLength -= blockSize;
        std::memcpy(PtrAdd(outString, blockSize), m_register, inLength);
    }
 
    // output last full ciphertext block
    xorbuf(m_register, inString, inLength);
    m_cipher->ProcessBlock(m_register);
    std::memcpy(outString, m_register, blockSize);
 
    return used;
}
 
void CBC_Decryption::ResizeBuffers()
{
    BlockOrientedCipherModeBase::ResizeBuffers();
    m_temp.New(BlockSize());
}
 
void CBC_Decryption::ProcessData(byte *outString, const byte *inString, size_t length)
{
    CRYPTOPP_ASSERT(length%BlockSize()==0);
    if (!length) {return;}
 
    // save copy now in case of in-place decryption
    const unsigned int blockSize = BlockSize();
    std::memcpy(m_temp, PtrAdd(inString, length-blockSize), blockSize);
    if (length > blockSize)
        m_cipher->AdvancedProcessBlocks(PtrAdd(inString,blockSize), inString, PtrAdd(outString,blockSize), length-blockSize, BlockTransformation::BT_ReverseDirection|BlockTransformation::BT_AllowParallel);
    m_cipher->ProcessAndXorBlock(inString, m_register, outString);
    m_register.swap(m_temp);
}
 
size_t CBC_CTS_Decryption::ProcessLastBlock(byte *outString, size_t outLength, const byte *inString, size_t inLength)
{
    CRYPTOPP_UNUSED(outLength);
    const byte *pn1, *pn2;
    const size_t used = inLength;
    const bool stealIV = inLength <= BlockSize();
    const unsigned int blockSize = BlockSize();
 
    if (stealIV)
    {
        pn1 = inString;
        pn2 = m_register;
    }
    else
    {
        pn1 = PtrAdd(inString, blockSize);
        pn2 = inString;
        inLength -= blockSize;
    }
 
    // decrypt last partial plaintext block
    std::memcpy(m_temp, pn2, blockSize);
    m_cipher->ProcessBlock(m_temp);
    xorbuf(m_temp, pn1, inLength);
 
    if (stealIV)
    {
        std::memcpy(outString, m_temp, inLength);
    }
    else
    {
        std::memcpy(PtrAdd(outString, blockSize), m_temp, inLength);
        // decrypt next to last plaintext block
        std::memcpy(m_temp, pn1, inLength);
        m_cipher->ProcessBlock(m_temp);
        xorbuf(outString, m_temp, m_register, blockSize);
    }
 
    return used;
}
 
NAMESPACE_END
 
#endif