authenc.cpp

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

#include "pch.h"

#ifndef CRYPTOPP_IMPORTS

#include "authenc.h"

NAMESPACE_BEGIN(CryptoPP)

void AuthenticatedSymmetricCipherBase::AuthenticateData(const byte *input, size_t len)
{
        unsigned int blockSize = AuthenticationBlockSize();
        unsigned int &num = m_bufferedDataLength;
        byte* data = m_buffer.begin();

        if (num != 0)   // process left over data
        {
                if (num+len >= blockSize)
                {
                        memcpy(data+num, input, blockSize-num);
                        AuthenticateBlocks(data, blockSize);
                        input += (blockSize-num);
                        len -= (blockSize-num);
                        num = 0;
                        // drop through and do the rest
                }
                else
                {
                        memcpy(data+num, input, len);
                        num += (unsigned int)len;
                        return;
                }
        }

        // now process the input data in blocks of blockSize bytes and save the leftovers to m_data
        if (len >= blockSize)
        {
                size_t leftOver = AuthenticateBlocks(input, len);
                input += (len - leftOver);
                len = leftOver;
        }

        memcpy(data, input, len);
        num = (unsigned int)len;
}

void AuthenticatedSymmetricCipherBase::SetKey(const byte *userKey, size_t keylength, const NameValuePairs &params)
{
        m_bufferedDataLength = 0;
        m_state = State_Start;

        SetKeyWithoutResync(userKey, keylength, params);
        m_state = State_KeySet;

        size_t length;
        const byte *iv = GetIVAndThrowIfInvalid(params, length);
        if (iv)
                Resynchronize(iv, (int)length);
}

void AuthenticatedSymmetricCipherBase::Resynchronize(const byte *iv, int length)
{
        if (m_state < State_KeySet)
                throw BadState(AlgorithmName(), "Resynchronize", "key is set");

        m_bufferedDataLength = 0;
        m_totalHeaderLength = m_totalMessageLength = m_totalFooterLength = 0;
        m_state = State_KeySet;

        Resync(iv, this->ThrowIfInvalidIVLength(length));
        m_state = State_IVSet;
}

void AuthenticatedSymmetricCipherBase::Update(const byte *input, size_t length)
{
        if (length == 0)
                return;

        switch (m_state)
        {
        case State_Start:
        case State_KeySet:
                throw BadState(AlgorithmName(), "Update", "setting key and IV");
        case State_IVSet:
                AuthenticateData(input, length);
                m_totalHeaderLength += length;
                break;
        case State_AuthUntransformed:
        case State_AuthTransformed:
                AuthenticateLastConfidentialBlock();
                m_bufferedDataLength = 0;
                m_state = State_AuthFooter;
                // fall through
        case State_AuthFooter:
                AuthenticateData(input, length);
                m_totalFooterLength += length;
                break;
        default:
                assert(false);
        }
}

void AuthenticatedSymmetricCipherBase::ProcessData(byte *outString, const byte *inString, size_t length)
{
        m_totalMessageLength += length;
        if (m_state >= State_IVSet && m_totalMessageLength > MaxMessageLength())
                throw InvalidArgument(AlgorithmName() + ": message length exceeds maximum");

reswitch:
        switch (m_state)
        {
        case State_Start:
        case State_KeySet:
                throw BadState(AlgorithmName(), "ProcessData", "setting key and IV");
        case State_AuthFooter:
                throw BadState(AlgorithmName(), "ProcessData was called after footer input has started");
        case State_IVSet:
                AuthenticateLastHeaderBlock();
                m_bufferedDataLength = 0;
                m_state = AuthenticationIsOnPlaintext()==IsForwardTransformation() ? State_AuthUntransformed : State_AuthTransformed;
                goto reswitch;
        case State_AuthUntransformed:
                AuthenticateData(inString, length);
                AccessSymmetricCipher().ProcessData(outString, inString, length);
                break;
        case State_AuthTransformed:
                AccessSymmetricCipher().ProcessData(outString, inString, length);
                AuthenticateData(outString, length);
                break;
        default:
                assert(false);
        }
}

void AuthenticatedSymmetricCipherBase::TruncatedFinal(byte *mac, size_t macSize)
{
        if (m_totalHeaderLength > MaxHeaderLength())
                throw InvalidArgument(AlgorithmName() + ": header length of " + IntToString(m_totalHeaderLength) + " exceeds the maximum of " + IntToString(MaxHeaderLength()));

        if (m_totalFooterLength > MaxFooterLength())
        {
                if (MaxFooterLength() == 0)
                        throw InvalidArgument(AlgorithmName() + ": additional authenticated data (AAD) cannot be input after data to be encrypted or decrypted");
                else
                        throw InvalidArgument(AlgorithmName() + ": footer length of " + IntToString(m_totalFooterLength) + " exceeds the maximum of " + IntToString(MaxFooterLength()));
        }

        switch (m_state)
        {
        case State_Start:
        case State_KeySet:
                throw BadState(AlgorithmName(), "TruncatedFinal", "setting key and IV");

        case State_IVSet:
                AuthenticateLastHeaderBlock();
                m_bufferedDataLength = 0;
                // fall through

        case State_AuthUntransformed:
        case State_AuthTransformed:
                AuthenticateLastConfidentialBlock();
                m_bufferedDataLength = 0;
                // fall through

        case State_AuthFooter:
                AuthenticateLastFooterBlock(mac, macSize);
                m_bufferedDataLength = 0;
                break;

        default:
                assert(false);
        }

        m_state = State_KeySet;
}

NAMESPACE_END

#endif

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