////////////////////////////////////////////////////////////////////////////////
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// This source file is part of the ZipArchive library source distribution and
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// is Copyrighted 2000 - 2011 by Artpol Software - Tadeusz Dracz
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License
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// as published by the Free Software Foundation; either version 2
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// of the License, or (at your option) any later version.
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//
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// For the licensing details refer to the License.txt file.
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//
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// Web Site: http://www.artpol-software.com
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////////////////////////////////////////////////////////////////////////////////
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#include "stdafx.h"
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#include "ZipCrc32Cryptograph.h"
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bool CZipCrc32Cryptograph::InitDecode(CZipAutoBuffer& password, CZipFileHeader& currentFile, CZipStorage& storage, bool ignoreCheck)
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{
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CryptInitKeys(password);
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CZipAutoBuffer buf(ZIPARCHIVE_ENCR_HEADER_LEN);
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storage.Read(buf, ZIPARCHIVE_ENCR_HEADER_LEN, false);
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BYTE b = 0;
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for (int i = 0; i < ZIPARCHIVE_ENCR_HEADER_LEN; i++)
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{
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b = buf[i]; // only temporary
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CryptDecode((char&)b);
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}
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// check the last byte
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return ignoreCheck || (currentFile.IsDataDescriptor() ?
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(BYTE(currentFile.m_uModTime >> 8) == b) : (BYTE(currentFile.m_uCrc32 >> 24) == b));
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}
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void CZipCrc32Cryptograph::InitEncode(CZipAutoBuffer& password, CZipFileHeader& currentFile, CZipStorage& storage)
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{
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CZipAutoBuffer buf(ZIPARCHIVE_ENCR_HEADER_LEN);
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// use pseudo-crc since we don't know it yet
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CryptInitKeys(password);
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srand(UINT(time(NULL)));
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// generate pseudo-random sequence
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char c;
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char* buffer = (char*)buf;
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for (int i = 0; i < ZIPARCHIVE_ENCR_HEADER_LEN - 2; i++)
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{
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int t1 = rand();
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c = (char)((t1 >> 6) & 0xFF);
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if (!c)
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c = (char)(t1 & 0xFF);
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CryptEncode(c);
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buffer[i] = c;
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}
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int iCrc = (int)currentFile.m_uModTime << 16;
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c = (char)((iCrc >> 16) & 0xFF);
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CryptEncode(c);
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buffer[ZIPARCHIVE_ENCR_HEADER_LEN - 2] = c;
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c = (char)((iCrc >> 24) & 0xFF);
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CryptEncode(c);
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buffer[ZIPARCHIVE_ENCR_HEADER_LEN - 1] = c;
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storage.Write(buf, ZIPARCHIVE_ENCR_HEADER_LEN, false);
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currentFile.m_uComprSize += ZIPARCHIVE_ENCR_HEADER_LEN;
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}
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void CZipCrc32Cryptograph::CryptInitKeys(CZipAutoBuffer& password)
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{
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m_keys[0] = 305419896L;
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m_keys[1] = 591751049L;
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m_keys[2] = 878082192L;
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for (DWORD i = 0; i < password.GetSize(); i++)
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CryptUpdateKeys(password[i]);
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}
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void CZipCrc32Cryptograph::CryptUpdateKeys(char c)
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{
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m_keys[0] = CryptCRC32(m_keys[0], c);
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m_keys[1] += m_keys[0] & 0xff;
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m_keys[1] = m_keys[1] * 134775813L + 1;
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c = char(m_keys[1] >> 24);
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m_keys[2] = CryptCRC32(m_keys[2], c);
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}
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