XORSelection.1sc

//------------------------------------------------
//--- 010 Editor Script File
//
//      File: XORSelection.1sc
//   Authors: Didier Stevens
//   Version: 4.0
//   Purpose: Xors the current selection with a set of bytes, 
//            which causes the bytes to be encoded so they 
//            cannot be read by a human. Run the Xor again on 
//            the encoded selection to decode the data.
//  Category: Binary
//   History: 
//   4.0   2018-03-25 D Stevens: refactoring to handle keys with null bytes and hex keys with whitespace
//   3.1   2016-02-10 SweetScape Software: Updated header for repository submission.
//   3.0   2014-12-11 D Stevens: Added hex processing; refactoring
//   1.0   2009-05-26 D Stevens: start
//
// Source code put in public domain by Didier Stevens, no Copyright
// https://DidierStevens.com
// Use at your own risk
//------------------------------------------------

#define TITLE "XORSelection"

int HexDigitToInt(int digit)
{
    if (digit >= '0' && digit <= '9')
        return digit - '0';
    if (digit >= 'a' && digit <= 'f')
        return digit - 'a' + 10;
    if (digit >= 'A' && digit <= 'F')
        return digit - 'A' + 10;
    return -1;
}

string RemoveWhitespace(string sInput)
{
    int iIter;
    string sResult = "";

    for (iIter = 0; iIter < Strlen(sInput); iIter++)
        if (sInput[iIter] != ' ' && sInput[iIter] != '\n' && sInput[iIter] != '\r' && sInput[iIter] != '\t')
            sResult = sResult + sInput[iIter];
    return sResult;
}

void Main(void)
{
    int iIter, iStart, iSize, iKeyLength;
    string sKey;

    // Check that a file is open
    if(FileCount() == 0)
    {
        MessageBox(idOk, TITLE, "XORSelection can only be executed when a file is loaded.");
        return;
    }

    // Initializes the variables
    iSize = GetSelSize();
    iStart = GetSelStart();

    // Check that bytes were selected
    if(iSize == 0)
    {
        iSize = FileSize();
        iStart = 0;
    }

    sKey = InputString(TITLE, "Input the XOR key (start with 0x for hex)", "");
    if (sKey == "")
    {
        MessageBox(idOk, TITLE, "Please enter a valid key.");
        return;
    }
    else if (SubStr(sKey, 0, 2) == "0x")
    {
        string sHex = RemoveWhitespace(SubStr(sKey, 2));
        int iIter2;
        int iHexDigit1;
        int iHexDigit2;
    
        if (Strlen(sHex) % 2 != 0)
        {
            MessageBox(idOk, TITLE, "Please enter a valid hex value (uneven digits).");
            return;
        }
        iKeyLength = Strlen(sHex) / 2;
        if (iKeyLength == 0)
        {
            MessageBox(idOk, TITLE, "Please enter a valid hex value (no digits).");
            return;
        }
        uchar aucKey[iKeyLength];
        for (iIter2 = 0; iIter2 < Strlen(sHex); iIter2 += 2)
        {
            iHexDigit1 = HexDigitToInt(sHex[iIter2]);
            if (iHexDigit1 == -1)
            {
                MessageBox(idOk, TITLE, "Please enter a valid hex value: digit %c is not hexadecimal.", sHex[iIter2]);
                return;
            }
            iHexDigit2 = HexDigitToInt(sHex[iIter2 + 1]);
            if (iHexDigit2 == -1)
            {
                MessageBox(idOk, TITLE, "Please enter a valid hex value: digit %c is not hexadecimal.", sHex[iIter2 + 1]);
                return;
            }
            aucKey[iIter2 / 2] = iHexDigit1 * 0x10 + iHexDigit2;
        }
    }
    else
    {
        string aucKey = sKey;
        iKeyLength = Strlen(sKey);
    }
    
    // Modify the selection
    for (iIter = 0; iIter < iSize; iIter++)
        // Modify the current byte
        WriteUByte(iStart + iIter, ReadUByte(iStart + iIter) ^ aucKey[iIter % iKeyLength]);
}

Main();