Add sea decryption

distribution/changelog.txt

@@ -13,6 +13,7 @@
 - Feature: [#11788] Command to extract images from a .DAT file.
 - Feature: [#11959] Hacked go-kart tracks can now use 2x2 bends, 3x3 bends and S-bends.
 - Feature: [#12090] Boosters for the Wooden Roller Coaster (if the "Show all track pieces" cheat is enabled).
+- Feature: [#12184] .sea (RCT Classic) scenario files can now be imported.
 - Change: [#11209] Warn when user is running OpenRCT2 through Wine.
 - Change: [#11358] Switch copy and paste button positions in tile inspector.
 - Change: [#11449] Remove complete circuit requirement from Air Powered Vertical Coaster (for RCT1 parity).

src/openrct2-ui/windows/LoadSave.cpp

@@ -150,7 +150,7 @@ static std::vector<LoadSaveListItem> _listItems;
 static char _directory[MAX_PATH];
 static char _shortenedDirectory[MAX_PATH];
 static char _parentDirectory[MAX_PATH];
-static char _extension[32];
+static char _extension[256];
 static char _defaultName[MAX_PATH];
 static int32_t _type;
 
@@ -218,10 +218,10 @@ static const char* getFilterPatternByType(const int32_t type, const bool isSave)
     switch (type & 0x0E)
     {
         case LOADSAVETYPE_GAME:
-            return isSave ? "*.sv6" : "*.sv6;*.sc6;*.sc4;*.sv4;*.sv7";
+            return isSave ? "*.sv6" : "*.sv6;*.sc6;*.sc4;*.sv4;*.sv7;*.sea;";
 
         case LOADSAVETYPE_LANDSCAPE:
-            return isSave ? "*.sc6" : "*.sc6;*.sv6;*.sc4;*.sv4;*.sv7";
+            return isSave ? "*.sc6" : "*.sc6;*.sv6;*.sc4;*.sv4;*.sv7;*.sea;";
 
         case LOADSAVETYPE_SCENARIO:
             return "*.sc6";

src/openrct2/Context.cpp

@@ -541,8 +541,17 @@ namespace OpenRCT2
             log_verbose("Context::LoadParkFromFile(%s)", path.c_str());
             try
             {
-                auto fs = FileStream(path, FILE_MODE_OPEN);
-                return LoadParkFromStream(&fs, path, loadTitleScreenOnFail);
+                if (String::Equals(Path::GetExtension(path), ".sea", true))
+                {
+                    auto data = DecryptSea(fs::u8path(path));
+                    auto ms = MemoryStream(data.data(), data.size(), MEMORY_ACCESS::READ);
+                    return LoadParkFromStream(&ms, path, loadTitleScreenOnFail);
+                }
+                else
+                {
+                    auto fs = FileStream(path, FILE_MODE_OPEN);
+                    return LoadParkFromStream(&fs, path, loadTitleScreenOnFail);
+                }
             }
             catch (const std::exception& e)
             {

src/openrct2/libopenrct2.vcxproj

@@ -629,6 +629,7 @@
     <ClCompile Include="rct1\Tables.cpp" />
     <ClCompile Include="rct2\S6Exporter.cpp" />
     <ClCompile Include="rct2\S6Importer.cpp" />
+    <ClCompile Include="rct2\SeaDecrypt.cpp" />
     <ClCompile Include="rct2\T6Exporter.cpp" />
     <ClCompile Include="rct2\T6Importer.cpp" />
     <ClCompile Include="ReplayManager.cpp" />

src/openrct2/rct2/RCT2.h

@@ -10,11 +10,14 @@
 #pragma once
 
 #include "../common.h"
+#include "../core/FileSystem.hpp"
 #include "../object/Object.h"
 #include "../rct12/RCT12.h"
 #include "../ride/RideRatings.h"
 #include "../ride/Vehicle.h"
 
+#include <vector>
+
 constexpr const uint8_t RCT2_MAX_STAFF = 200;
 constexpr const uint8_t RCT2_MAX_BANNERS_IN_PARK = 250;
 constexpr const uint8_t RCT2_MAX_VEHICLES_PER_RIDE = 31;
@@ -760,3 +763,5 @@ struct RCT2RideRatingCalculationData
 assert_struct_size(RCT2RideRatingCalculationData, 76);
 
 #pragma pack(pop)
+
+std::vector<uint8_t> DecryptSea(const fs::path& path);

src/openrct2/rct2/SeaDecrypt.cpp

@@ -0,0 +1,109 @@
+/*****************************************************************************
+ * Copyright (c) 2014-2020 OpenRCT2 developers
+ *
+ * For a complete list of all authors, please refer to contributors.md
+ * Interested in contributing? Visit https://github.com/OpenRCT2/OpenRCT2
+ *
+ * OpenRCT2 is licensed under the GNU General Public License version 3.
+ *****************************************************************************/
+
+#include "../common.h"
+#include "../core/File.h"
+#include "../core/Path.hpp"
+#include "RCT2.h"
+
+#include <cstdint>
+#include <memory>
+#include <string_view>
+
+constexpr int32_t MASK_SIZE = 0x1000;
+
+struct EncryptionKey
+{
+    uint32_t Seed0{};
+    uint32_t Seed1{};
+};
+
+static EncryptionKey GetEncryptionKey(const std::string_view& fileName)
+{
+    auto fileNameLen = static_cast<int32_t>(fileName.size());
+    uint32_t s0 = 0;
+    for (int i = fileNameLen - 1; i >= 0; i--)
+    {
+        s0 = (s0 + (s0 << 5)) ^ fileName[i];
+    }
+
+    uint32_t s1 = 0;
+    for (int i = 0; i < fileNameLen; i++)
+    {
+        s1 = (s1 + (s1 << 5)) ^ fileName[i];
+    }
+
+    return EncryptionKey{ s0, s1 };
+}
+
+static std::unique_ptr<uint8_t[]> CreateMask(const EncryptionKey& key)
+{
+    auto result = std::make_unique<uint8_t[]>(MASK_SIZE);
+    auto dst8 = result.get();
+    uint32_t seed0 = key.Seed0;
+    uint32_t seed1 = key.Seed1;
+    int32_t i = MASK_SIZE;
+    while (i > 0)
+    {
+        uint32_t s0 = seed0;
+        uint32_t s1 = seed1 ^ 0xF7654321;
+        seed0 = rol32(s1, 25) + s0;
+        seed1 = rol32(s0, 29);
+        *dst8++ = (s0 >> 3) & 0xFF;
+        if (i >= 2)
+        {
+            *dst8++ = (s0 >> 11) & 0xFF;
+            if (i >= 3)
+            {
+                *dst8++ = (s0 >> 19) & 0xFF;
+                if (i >= 4)
+                {
+                    *dst8++ = (seed1 >> 24) & 0xFF;
+                    i -= 4;
+                }
+            }
+        }
+    }
+    return result;
+}
+
+static void Decrypt(std::vector<uint8_t>& data, const EncryptionKey& key)
+{
+    auto mask = CreateMask(key);
+    const uint8_t* mask8 = (const uint8_t*)mask.get();
+
+    uint32_t b = 0;
+    uint32_t c = 0;
+    for (size_t i = 0; i < data.size(); i++)
+    {
+        auto a = b % MASK_SIZE;
+        c = c % MASK_SIZE;
+        b = (a + 1) % MASK_SIZE;
+
+        data[i] = (((data[i] - mask8[b]) ^ mask8[c]) + mask8[a]) & 0xFF;
+
+        c += 3;
+        b = a + 7;
+    }
+}
+
+std::vector<uint8_t> DecryptSea(const fs::path& path)
+{
+    auto key = GetEncryptionKey(path.filename().u8string());
+    auto data = File::ReadAllBytes(path.u8string());
+
+    // Last 4 bytes is the checksum
+    size_t inputSize = data.size() - 4;
+    uint32_t checksum;
+    std::memcpy(&checksum, data.data() + inputSize, sizeof(checksum));
+    data.resize(inputSize);
+
+    Decrypt(data, key);
+    return data;
+}