mirror of https://github.com/OpenRCT2/OpenRCT2.git
99 lines
2.5 KiB
C++
99 lines
2.5 KiB
C++
/*****************************************************************************
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* Copyright (c) 2014-2020 OpenRCT2 developers
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*
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* For a complete list of all authors, please refer to contributors.md
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* Interested in contributing? Visit https://github.com/OpenRCT2/OpenRCT2
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*
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* OpenRCT2 is licensed under the GNU General Public License version 3.
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*****************************************************************************/
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#include "../common.h"
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#include "../core/File.h"
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#include "../core/Numerics.hpp"
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#include "../core/Path.hpp"
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#include "RCT2.h"
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#include <cstdint>
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#include <cstring>
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#include <memory>
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#include <string_view>
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constexpr int32_t MASK_SIZE = 0x1000;
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struct EncryptionKey
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{
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uint32_t Seed0{};
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uint32_t Seed1{};
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};
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static EncryptionKey GetEncryptionKey(std::string_view fileName)
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{
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auto fileNameLen = static_cast<int32_t>(fileName.size());
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uint32_t s0 = 0;
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for (int i = fileNameLen - 1; i >= 0; i--)
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{
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s0 = (s0 + (s0 << 5)) ^ fileName[i];
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}
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uint32_t s1 = 0;
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for (int i = 0; i < fileNameLen; i++)
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{
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s1 = (s1 + (s1 << 5)) ^ fileName[i];
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}
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return EncryptionKey{ s0, s1 };
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}
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static std::vector<uint8_t> CreateMask(const EncryptionKey& key)
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{
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std::vector<uint8_t> result;
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result.resize(MASK_SIZE);
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uint32_t seed0 = key.Seed0;
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uint32_t seed1 = key.Seed1;
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for (size_t i = 0; i < MASK_SIZE; i += 4)
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{
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uint32_t s0 = seed0;
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uint32_t s1 = seed1 ^ 0xF7654321;
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seed0 = Numerics::rol32(s1, 25) + s0;
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seed1 = Numerics::rol32(s0, 29);
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result[i + 0] = (s0 >> 3) & 0xFF;
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result[i + 1] = (s0 >> 11) & 0xFF;
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result[i + 2] = (s0 >> 19) & 0xFF;
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result[i + 3] = (seed1 >> 24) & 0xFF;
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}
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return result;
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}
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static void Decrypt(std::vector<uint8_t>& data, const EncryptionKey& key)
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{
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auto mask = CreateMask(key);
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uint32_t b = 0;
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uint32_t c = 0;
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for (size_t i = 0; i < data.size(); i++)
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{
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auto a = b % MASK_SIZE;
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c = c % MASK_SIZE;
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b = (a + 1) % MASK_SIZE;
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data[i] = (((data[i] - mask[b]) ^ mask[c]) + mask[a]) & 0xFF;
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c += 3;
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b = a + 7;
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}
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}
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std::vector<uint8_t> DecryptSea(const fs::path& path)
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{
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auto key = GetEncryptionKey(path.filename().u8string());
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auto data = File::ReadAllBytes(path.u8string());
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// Last 4 bytes is the checksum
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size_t inputSize = data.size() - 4;
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uint32_t checksum;
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std::memcpy(&checksum, data.data() + inputSize, sizeof(checksum));
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data.resize(inputSize);
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Decrypt(data, key);
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return data;
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}
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