Get Windows Product Key

WinProdKey.cpp

#include <windows.h>
#include <iostream>
#include <vector>
#include <string>

static constexpr const int start = 52;
static const std::string digits = "BCDFGHJKMPQRTVWXY2346789";

// The Microsoft Windows product key is hidden in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion, 
// which is base24-encoded & encrypted in a binary string.
// Decoding routines are provided by the WinProdKeyFinder project (github.com/mrpeardotnet/WinProdKeyFinder), 
// ported to C++11.
static std::string DecodeKeyFor7AndLower(const ::BYTE *bytes)
{
    if (!bytes)
        return std::string();
    
    static constexpr const int end = start + 15;
    static constexpr const int decodeLength  =   29;
    static constexpr int decodeStringLength = 15;

    std::string chars;
    chars.resize(decodeLength + 1);

    ::byte hexPid[end - start + 1];

    for (int i = start; i <= end; ++i)
        hexPid[i - start] = bytes[i];
    
    for (int i = decodeLength - 1; i >= 0; i--)
    {
        if ((i + 1) % 6 == 0)
            chars[i] = '-';
        else
        {
            int digitMapIndex = 0;
            for (int j = decodeStringLength - 1; j >= 0; j--)
            {
                int byteValue = (digitMapIndex << 8) | hexPid[j];
                hexPid[j] = (::byte) (byteValue / 24);
                digitMapIndex = byteValue % 24;
                chars[i] = digits[digitMapIndex];
            }
        }
    }

    return chars;
}

static std::string DecodeKeyFor8AndHigher(/* const */ ::BYTE *bytes)
{
    if (!bytes)
        return std::string();

    std::string chars = {};
    bytes[66] = (byte)((bytes[66] & 0xf7) | (1 & 2) * 4);
    
    int last = 0;
    for (int i = 24; i >= 0; i--)
    {
        int current = 0;
        for (int j = 14; j >= 0; j--)
        {
            current = current*256;
            current = bytes[j + start] + current;
            bytes[j + start] = (byte)(current/24);
            current = current%24;
            last = current;
        }
        chars = digits[current] + chars;
    }

    chars = chars.substr(1, last) + "N" + chars.substr(last + 1, chars.size() - (last + 1));

    for (auto i = 5; i < chars.size(); i += 6)
        chars.insert(i, "-");

    return chars;
}

// Recupera la chiave di Windows dalla Registry Key "DigitalProductId"
std::string GetWindowsProductKey()
{
    // Legge la chiave dal registro
    HKEY hKey;
    const char* subKey = "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion";
    if (RegOpenKeyExA(HKEY_LOCAL_MACHINE, subKey, 0, KEY_READ | KEY_WOW64_64KEY, &hKey) != ERROR_SUCCESS)
    {
        return "";
    }

    DWORD sizeNeeded = 0;
    if (RegQueryValueExA(hKey, "DigitalProductId", nullptr, nullptr, nullptr, &sizeNeeded) != ERROR_SUCCESS)
    {
        RegCloseKey(hKey);
        return "";
    }

    std::vector<BYTE> digitalProductId(sizeNeeded);
    if (RegQueryValueExA(hKey, "DigitalProductId", nullptr, nullptr, digitalProductId.data(), &sizeNeeded) != ERROR_SUCCESS)
    {
        RegCloseKey(hKey);
        return "";
    }
    RegCloseKey(hKey);
    
    // Verifica versione Windows
    bool isWin8AndHigher = (digitalProductId.data()[66] >> 3) & 1;

    // Esegue la decodifica in base alla versione
    if (isWin8AndHigher)
    {
        return DecodeKeyFor8AndHigher(digitalProductId.data());
    }
    else
    {
        return DecodeKeyFor7AndLower(digitalProductId.data());
    }
}

int main()
{
    std::string productKey = GetWindowsProductKey();
    if (!productKey.empty()) {
        std::cout << "Product Key: " << productKey << std::endl;
    } else {
        std::cout << "Impossibile recuperare il product key." << std::endl;
    }
    return 0;
}