ResourceHelper: Directly decrypt PSP assets

Switches from an XOR blob to directly decrypting the data as we stream it in.

Refresh.GameServer/Importing/ImageImporter.cs

@@ -80,7 +80,7 @@ public void ImportAsset(GameAsset asset, IDataStore dataStore)
                 break;
             case GameAssetType.Mip: {
                 byte[] rawData = dataStore.GetDataFromStore(asset.IsPSP ? "psp/" + asset.AssetHash : asset.AssetHash);
-                byte[] data = ResourceHelper.PspDecrypt(rawData, this._pspKey.Value);
+                byte[] data = ResourceHelper.PspDecrypt(rawData, this.PSPKey.Value);
 
                 using MemoryStream dataStream = new(data);
 

Refresh.GameServer/Importing/Importer.cs

@@ -1,6 +1,7 @@
 using System.Buffers.Binary;
 using System.Diagnostics;
 using System.Runtime.CompilerServices;
+using System.Security.Cryptography;
 using System.Text;
 using Bunkum.Core;
 using NotEnoughLogs;
@@ -14,7 +15,7 @@ public abstract class Importer
 {
     private readonly Logger _logger;
     protected readonly Stopwatch Stopwatch;
-    protected readonly Lazy<byte[]?> _pspKey;
+    protected readonly Lazy<byte[]?> PSPKey;
 
     protected Importer(Logger? logger = null)
     {
@@ -26,11 +27,20 @@ protected Importer(Logger? logger = null)
         this._logger = logger;
         this.Stopwatch = new Stopwatch();
 
-        this._pspKey = new(() =>
+        this.PSPKey = new(() =>
         {
             try
             {
-                return File.ReadAllBytes("keys/psp");
+                //Read the key
+                byte[] key = File.ReadAllBytes("keys/psp");
+
+                //If the hash matches, return the read key
+                if (SHA1.HashData(key).AsSpan().SequenceEqual(new byte[] { 0x12, 0xb5, 0xa8, 0xb5, 0x91, 0x55, 0x24, 0x96, 0x00, 0xdf, 0x0e, 0x33, 0xf9, 0xc5, 0xa8, 0x76, 0xc1, 0x85, 0x43, 0xfe })) 
+                    return key;
+
+                //If the hash does not match, log an error and return null
+                this._logger.LogError(BunkumCategory.Digest, "PSP key failed to validate! Correct hash is 12b5a8b59155249600df0e33f9c5a876c18543fe");
+                return null;
             }
             catch(Exception e)
             {
@@ -126,7 +136,7 @@ private static bool IsPspTga(ReadOnlySpan<byte> data)
     private bool IsMip(Span<byte> rawData)
     {
         //If we dont have a key, then we cant determine the data type
-        if (this._pspKey.Value == null) return false;
+        if (this.PSPKey.Value == null) return false;
 
         //Data less than this size isn't encrypted(?) and all Mip files uploaded to the server will be encrypted
         //See https://github.com/ennuo/lbparc/blob/16ad36aa7f4eae2f7b406829e604082750f16fe1/tools/toggle.js#L33
@@ -135,7 +145,7 @@ private bool IsMip(Span<byte> rawData)
         try
         {
             //Decrypt the data
-            ReadOnlySpan<byte> data = ResourceHelper.PspDecrypt(rawData, this._pspKey.Value);
+            ReadOnlySpan<byte> data = ResourceHelper.PspDecrypt(rawData, this.PSPKey.Value);
 
             uint clutOffset = BinaryPrimitives.ReadUInt32LittleEndian(data[..4]);
             uint width = BinaryPrimitives.ReadUInt32LittleEndian(data[4..8]);

Refresh.GameServer/Refresh.GameServer.csproj

@@ -6,7 +6,6 @@
         <Nullable>enable</Nullable>
         <Configurations>Debug;Release;DebugLocalBunkum</Configurations>
         <Platforms>AnyCPU</Platforms>
-        <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     </PropertyGroup>
 
     <PropertyGroup Condition=" '$(Configuration)' == 'DebugLocalBunkum' ">
@@ -66,6 +65,7 @@
       <PackageReference Include="BCrypt.Net-Next" Version="4.0.3" />
       <PackageReference Include="CommandLineParser" Version="2.9.1" />
       <PackageReference Include="Discord.Net.Webhook" Version="3.13.0" />
+      <PackageReference Include="FastAes" Version="1.0.1" />
       <PackageReference Include="IronCompress" Version="1.5.1" />
       <PackageReference Include="MailKit" Version="4.3.0" />
       <PackageReference Include="NPTicket" Version="3.1.0" />

Refresh.GameServer/Resources/ResourceHelper.cs

@@ -1,10 +1,9 @@
 using System.Buffers;
 using System.Buffers.Binary;
-using System.Numerics;
 using System.Reflection;
 using System.Security.Cryptography;
+using FastAes;
 using IronCompress;
-using Microsoft.Toolkit.HighPerformance;
 
 namespace Refresh.GameServer.Resources;
 
@@ -15,61 +14,10 @@ public static Stream StreamFromResource(string name)
         Assembly assembly = Assembly.GetExecutingAssembly();
         return assembly.GetManifestResourceStream(name)!;
     }
-
-    private static unsafe void XorVectorized(Span<byte> rawData, ReadOnlySpan<byte> key)
-    {
-        fixed (byte* dataPtr = rawData)
-        {
-            //Get the misalignment of the data
-            int misalignment = (int)((nint)dataPtr % sizeof(nint));
-
-            Span<byte> data = new(dataPtr, rawData.Length);
-
-            if (misalignment != 0)
-            {
-                //XOR the data before the aligned data
-                XorScalar(data[..misalignment], key);
-            }
-
-            //Get the span of data which is aligned to word boundaries
-            Span<byte> alignedData = data[misalignment..];
-
-            //Get a Vector<byte> of the data, offset by the misalignment, making this data byte-aligned
-            Span<Vector<byte>> alignedDataVec = alignedData.Cast<byte, Vector<byte>>();
-            //Get a Vector<byte> of the key, offset by the misalignment
-            ReadOnlySpan<Vector<byte>> keyVec = key[misalignment..].Cast<byte, Vector<byte>>();
-
-            //Iterate over every item in the data vector
-            for (int i = 0; i < alignedDataVec.Length; i++) 
-                //XOR it with the key
-                alignedDataVec[i] ^= keyVec[i];
-
-            //Get the amount of bytes which are left over
-            int leftoverCount = data.Length - (alignedDataVec.Length * Vector<byte>.Count * sizeof(byte)) - misalignment;
-
-            //If theres no leftover bytes, return out
-            if (leftoverCount <= 0) return;
-
-            //Get the start index of the leftover bytes
-            int leftoverOffset = data.Length - leftoverCount;
-            //Slice the data to only have the leftover data
-            Span<byte> leftover = data[leftoverOffset..];
-
-            XorScalar(leftover, key[leftoverOffset..]);
-        }
-    }
-
-    private static void XorScalar(Span<byte> data, ReadOnlySpan<byte> key)
-    {
-        //Iterate over all bytes
-        for (int i = 0; i < data.Length; i++) 
-            //Iterate over all data, and XOR it with the key
-            data[i] ^= key[i];
-    }
 
     private static readonly ThreadLocal<Iron> Iron = new(() => new Iron(ArrayPool<byte>.Shared));
 
-    private static void Encrypt(Span<byte> data, ReadOnlySpan<byte> key)
+    private static void Encrypt(ReadOnlySpan<byte> data, ReadOnlySpan<byte> key)
     {
         throw new NotImplementedException(); //TODO
     }
@@ -82,9 +30,13 @@ private static void Encrypt(Span<byte> data, ReadOnlySpan<byte> key)
     /// <returns>The decrypted data.</returns>
     public static byte[] PspDecrypt(Span<byte> data, ReadOnlySpan<byte> key)
     {
-        //XOR the data
-        Xor(data, key);
+        byte[] initialCounter = new byte[16];
+        key[..8].CopyTo(initialCounter);
 
+        //Decrypt the data
+        AesCtr ctr = new(key, initialCounter);
+        ctr.DecryptBytes(data, data);
+
         //Get the data buffer
         Span<byte> buf = data[..^0x19];
         //Get the info of the file
@@ -98,28 +50,12 @@ public static byte[] PspDecrypt(Span<byte> data, ReadOnlySpan<byte> key)
         if (!signature.SequenceEqual(MD5.HashData(data[..^0x10]))) throw new InvalidDataException("Encrypted PSP asset hash does not match signature, likely corrupt");
 
         //If the data is not compressed, just return a copy of the raw buffer
-        if (info[0x4] != 1)
-        {
-            Xor(data, key);
-            return buf.ToArray();
-        }
+        if (info[0x4] != 1) return buf.ToArray();
 
         //Decompress the data
         using IronCompressResult decompressed = Iron.Value!.Decompress(Codec.LZO, buf, (int)len);
 
-        Xor(data, key);
-
         //Return a copy of the decompressed data
         return decompressed.AsSpan().ToArray();
     }
-
-    public static void Xor(Span<byte> data, ReadOnlySpan<byte> key)
-    {
-        if (key.Length < data.Length) throw new ArgumentException("Key must be as long or longer than the data!", nameof(key));
-
-        if (Vector<byte>.IsSupported && data.Length >= Vector<byte>.Count * sizeof(byte))
-            XorVectorized(data, key);
-        else
-            XorScalar(data, key);
-    }
 }