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 /*
 Copyright (c) 2011, Andre Somers
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are met:
     * Redistributions of source code must retain the above copyright
       notice, this list of conditions and the following disclaimer.
     * Redistributions in binary form must reproduce the above copyright
       notice, this list of conditions and the following disclaimer in the
       documentation and/or other materials provided with the distribution.
     * Neither the name of the Rathenau Instituut, Andre Somers nor the
       names of its contributors may be used to endorse or promote products
       derived from this software without specific prior written permission.
 
 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 DISCLAIMED. IN NO EVENT SHALL ANDRE SOMERS BE LIABLE FOR ANY
 DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 #include "o0simplecrypt.h"
 #include <QByteArray>
 #include <QtDebug>
 #include <QtGlobal>
 #include <QDateTime>
 #include <QCryptographicHash>
 #include <QDataStream>
 #include <QIODevice>
 
 O0SimpleCrypt::O0SimpleCrypt():
     m_key(0),
     m_compressionMode(CompressionAuto),
     m_protectionMode(ProtectionChecksum),
     m_lastError(ErrorNoError)
 {
 #if (QT_VERSION < QT_VERSION_CHECK(5, 15, 0))
     qsrand(uint(QDateTime::currentMSecsSinceEpoch() & 0xFFFF));
 #else
     m_rand.seed(uint(QDateTime::currentMSecsSinceEpoch() & 0xFFFF));
 #endif
 }
 
 O0SimpleCrypt::O0SimpleCrypt(quint64 key):
     m_key(key),
     m_compressionMode(CompressionAuto),
     m_protectionMode(ProtectionChecksum),
     m_lastError(ErrorNoError)
 {
 #if (QT_VERSION < QT_VERSION_CHECK(5, 15, 0))
     qsrand(uint(QDateTime::currentMSecsSinceEpoch() & 0xFFFF));
 #else
     m_rand.seed(uint(QDateTime::currentMSecsSinceEpoch() & 0xFFFF));
 #endif
     splitKey();
 }
 
 void O0SimpleCrypt::setKey(quint64 key)
 {
     m_key = key;
     splitKey();
 }
 
 void O0SimpleCrypt::splitKey()
 {
     m_keyParts.clear();
     m_keyParts.resize(8);
     for (int i=0;i<8;i++) {
         quint64 part = m_key;
         for (int j=i; j>0; j--)
             part = part >> 8;
         part = part & 0xff;
         m_keyParts[i] = static_cast<char>(part);
     }
 }
 
 QByteArray O0SimpleCrypt::encryptToByteArray(const QString& plaintext)
 {
     QByteArray plaintextArray = plaintext.toUtf8();
     return encryptToByteArray(plaintextArray);
 }
 
 QByteArray O0SimpleCrypt::encryptToByteArray(QByteArray plaintext)
 {
     if (m_keyParts.isEmpty()) {
         qWarning() << "No key set.";
         m_lastError = ErrorNoKeySet;
         return QByteArray();
     }
 
 
     QByteArray ba = plaintext;
 
     CryptoFlags flags = CryptoFlagNone;
     if (m_compressionMode == CompressionAlways) {
         ba = qCompress(ba, 9); //maximum compression
         flags |= CryptoFlagCompression;
     } else if (m_compressionMode == CompressionAuto) {
         QByteArray compressed = qCompress(ba, 9);
         if (compressed.count() < ba.count()) {
             ba = compressed;
             flags |= CryptoFlagCompression;
         }
     }
 
     QByteArray integrityProtection;
     if (m_protectionMode == ProtectionChecksum) {
         flags |= CryptoFlagChecksum;
         QDataStream s(&integrityProtection, QIODevice::WriteOnly);
 #if QT_VERSION >= 0x060000
         s << qChecksum(QByteArrayView(ba));
 #else
         s << qChecksum(ba.constData(), ba.length());
 #endif
     } else if (m_protectionMode == ProtectionHash) {
         flags |= CryptoFlagHash;
         QCryptographicHash hash(QCryptographicHash::Sha1);
         hash.addData(ba);
 
         integrityProtection += hash.result();
     }
 
     //prepend a random char to the string
 #if (QT_VERSION < QT_VERSION_CHECK(5, 15, 0))
     char randomChar = char(qrand() & 0xFF);
 #else
     char randomChar = char(m_rand.generate() & 0xFF);
 #endif
     ba = randomChar + integrityProtection + ba;
 
     int pos(0);
     char lastChar(0);
 
     int cnt = ba.count();
 
     while (pos < cnt) {
         ba[pos] = ba.at(pos) ^ m_keyParts.at(pos % 8) ^ lastChar;
         lastChar = ba.at(pos);
         ++pos;
     }
 
     QByteArray resultArray;
     resultArray.append(char(0x03));  //version for future updates to algorithm
     resultArray.append(char(flags)); //encryption flags
     resultArray.append(ba);
 
     m_lastError = ErrorNoError;
     return resultArray;
 }
 
 QString O0SimpleCrypt::encryptToString(const QString& plaintext)
 {
     QByteArray plaintextArray = plaintext.toUtf8();
     QByteArray cypher = encryptToByteArray(plaintextArray);
     QString cypherString = QString::fromLatin1(cypher.toBase64());
     return cypherString;
 }
 
 QString O0SimpleCrypt::encryptToString(QByteArray plaintext)
 {
     QByteArray cypher = encryptToByteArray(plaintext);
     QString cypherString = QString::fromLatin1(cypher.toBase64());
     return cypherString;
 }
 
 QString O0SimpleCrypt::decryptToString(const QString &cyphertext)
 {
     QByteArray cyphertextArray = QByteArray::fromBase64(cyphertext.toLatin1());
     QByteArray plaintextArray = decryptToByteArray(cyphertextArray);
     QString plaintext = QString::fromUtf8(plaintextArray, plaintextArray.size());
 
     return plaintext;
 }
 
 QString O0SimpleCrypt::decryptToString(QByteArray cypher)
 {
     QByteArray ba = decryptToByteArray(cypher);
     QString plaintext = QString::fromUtf8(ba, ba.size());
 
     return plaintext;
 }
 
 QByteArray O0SimpleCrypt::decryptToByteArray(const QString& cyphertext)
 {
     QByteArray cyphertextArray = QByteArray::fromBase64(cyphertext.toLatin1());
     QByteArray ba = decryptToByteArray(cyphertextArray);
 
     return ba;
 }
 
 QByteArray O0SimpleCrypt::decryptToByteArray(QByteArray cypher)
 {
     if (m_keyParts.isEmpty()) {
         qWarning() << "No key set.";
         m_lastError = ErrorNoKeySet;
         return QByteArray();
     }
 
     if (!cypher.length()) {
         m_lastError = ErrorUnknownVersion;
         return QByteArray();
     }
 
     QByteArray ba = cypher;
 
     char version = ba.at(0);
 
     if (version !=3) {  //we only work with version 3
         m_lastError = ErrorUnknownVersion;
         qWarning() << "Invalid version or not a cyphertext.";
         return QByteArray();
     }
 
     CryptoFlags flags = CryptoFlags(ba.at(1));
 
     ba = ba.mid(2);
     int pos(0);
     int cnt(ba.count());
     char lastChar = 0;
 
     while (pos < cnt) {
         char currentChar = ba[pos];
         ba[pos] = ba.at(pos) ^ lastChar ^ m_keyParts.at(pos % 8);
         lastChar = currentChar;
         ++pos;
     }
 
     ba = ba.mid(1); //chop off the random number at the start
 
     bool integrityOk(true);
     if (flags.testFlag(CryptoFlagChecksum)) {
         if (ba.length() < 2) {
             m_lastError = ErrorIntegrityFailed;
             return QByteArray();
         }
         quint16 storedChecksum;
         {
             QDataStream s(&ba, QIODevice::ReadOnly);
             s >> storedChecksum;
         }
         ba = ba.mid(2);
 #if QT_VERSION >= 0x060000
         quint16 checksum = qChecksum(QByteArrayView(ba));
 #else
         quint16 checksum = qChecksum(ba.constData(), ba.length());
 #endif
         integrityOk = (checksum == storedChecksum);
     } else if (flags.testFlag(CryptoFlagHash)) {
         if (ba.length() < 20) {
             m_lastError = ErrorIntegrityFailed;
             return QByteArray();
         }
         QByteArray storedHash = ba.left(20);
         ba = ba.mid(20);
         QCryptographicHash hash(QCryptographicHash::Sha1);
         hash.addData(ba);
         integrityOk = (hash.result() == storedHash);
     }
 
     if (!integrityOk) {
         m_lastError = ErrorIntegrityFailed;
         return QByteArray();
     }
 
     if (flags.testFlag(CryptoFlagCompression))
         ba = qUncompress(ba);
 
     m_lastError = ErrorNoError;
     return ba;
 }