83 lines
3.3 KiB
C#
83 lines
3.3 KiB
C#
using System;
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using System.IO;
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using System.Linq;
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namespace AssetStudio
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{
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public static class OPFPUtils
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{
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private static readonly string BaseFolder = "BundleResources";
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private static readonly string[] V0_Prefixes = { "UI/", "Atlas/", "UITexture/" };
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private static readonly string[] V1_Prefixes = { "DynamicAtlas/", "Atlas/Skill", "Atlas/PlayerTitle", "UITexture/HeroCardEP12", "UITexture/HeroCardEP13" };
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public static void Decrypt(Span<byte> data, string path)
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{
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Logger.Verbose($"Attempting to decrypt block with OPFP encryption...");
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if (IsEncryptionBundle(path, out var key, out var version))
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{
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switch (version)
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{
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case 0:
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data[0] ^= key;
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for (int i = 1; i < data.Length; i++)
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{
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data[i] ^= data[i - 1];
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}
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break;
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case 1:
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for (int i = 1; i < data.Length; i++)
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{
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var idx = (i + data.Length + key * key) % (i + 1);
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(data[i], data[idx]) = (data[idx], data[i]);
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data[i] ^= key;
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data[idx] ^= key;
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}
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break;
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}
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}
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}
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private static bool IsEncryptionBundle(string path, out byte key, out int version)
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{
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if (IsFixedPath(path, out var relativePath))
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{
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if (V1_Prefixes.Any(prefix => relativePath.StartsWith(prefix, StringComparison.OrdinalIgnoreCase)))
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{
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Logger.Verbose("Path matches with V1 prefixes, generatring key...");
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key = (byte)Path.GetFileName(relativePath).Length;
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version = 1;
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Logger.Verbose($"version: {version}, key: {key}");
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return true;
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}
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else if (V0_Prefixes.Any(prefix => relativePath.StartsWith(prefix, StringComparison.OrdinalIgnoreCase)))
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{
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Logger.Verbose("Path matches with V2 prefixes, generatring key...");
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key = (byte)relativePath.Length;
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version = 0;
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Logger.Verbose($"version: {version}, key: {key}");
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return true;
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}
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}
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Logger.Verbose($"Unknown encryption type");
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key = 0x00;
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version = 0;
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return false;
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}
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private static bool IsFixedPath(string path, out string fixedPath)
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{
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Logger.Verbose($"Fixing path before checking...");
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var dirs = path.Split(Path.DirectorySeparatorChar);
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if (dirs.Contains(BaseFolder))
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{
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var idx = Array.IndexOf(dirs, BaseFolder);
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Logger.Verbose($"Seperator found at index {idx}");
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fixedPath = string.Join(Path.DirectorySeparatorChar, dirs[(idx+1)..]).Replace("\\", "/");
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return true;
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}
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Logger.Verbose($"Unknown path");
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fixedPath = string.Empty;
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return false;
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}
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}
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}
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