Initial attempt at decoding Wi-fi Plaza gamestats blobs

gts/gts.csproj

@@ -89,6 +89,7 @@
     <Compile Include="BattleVideo.aspx.designer.cs">
       <DependentUpon>BattleVideo.aspx</DependentUpon>
     </Compile>
+    <Compile Include="src\GamestatsSessionPlat.cs" />
     <Compile Include="src\HeaderColour.cs" />
     <Compile Include="test\BoxUp.aspx.cs">
       <DependentUpon>BoxUp.aspx</DependentUpon>

gts/src/GamestatsSessionPlat.cs

@@ -0,0 +1,68 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Web;
+using System.Security.Cryptography;
+using System.IO;
+using System.Net;
+
+namespace PkmnFoundations.GTS
+{
+    public class GamestatsSessionPlat : GtsSessionBase
+    {
+        public GamestatsSessionPlat(int pid, String url)
+            : base(pid, url)
+        {
+            Hash = ComputeHash(Token);
+        }
+
+        public static String ComputeHash(String token)
+        {
+            // todo: add unit tests with some wiresharked examples.
+
+            if (m_sha1 == null) m_sha1 = SHA1.Create();
+
+            String longToken = "uLMOGEiiJogofchScpXb" + token;
+
+            byte[] data = new byte[longToken.Length];
+            MemoryStream stream = new MemoryStream(data);
+            StreamWriter writer = new StreamWriter(stream);
+            writer.Write(longToken); // fixme: this throws an OutOfBoundsException if the passed token contains non-ascii.
+            writer.Flush();
+
+            return m_sha1.ComputeHash(data).ToHexStringLower();
+        }
+
+        /// <summary>
+        /// Decrypts the NDS &data= querystring into readable binary data.
+        /// The PID (little endian) is left at the start of the output
+        /// but the (unencrypted) checksum is removed.
+        /// </summary>
+        public static byte[] DecryptData(String data)
+        {
+            byte[] data2 = FromUrlSafeBase64String(data);
+            if (data2.Length < 4) throw new FormatException("Data must contain at least 4 bytes.");
+
+            byte[] data3 = new byte[data2.Length - 4];
+            int checksum = BitConverter.ToInt32(data2, 0);
+            checksum = IPAddress.NetworkToHostOrder(checksum); // endian flip
+            checksum ^= 0x5b440000;
+            int rand = checksum | (checksum << 16);
+
+            // todo: prune first 8 bytes, pass pid to this function to validate
+            for (int pos = 0; pos < data3.Length; pos++)
+            {
+                rand = DecryptRNG(rand);
+                data3[pos] = (byte)(data2[pos + 4] ^ (byte)(rand >> 16));
+            }
+
+            int checkedsum = 0;
+            foreach (byte b in data3)
+                checkedsum += b;
+
+            if (checkedsum != checksum) throw new FormatException("Data checksum is incorrect.");
+
+            return data3;
+        }
+    }
+}

gts/test/Decode.aspx

@@ -17,6 +17,11 @@
     <div class="code">
     <asp:Literal ID="litDecoded" runat="server" />
     </div>
+    <asp:PlaceHolder ID="phChecksum" Visible="false" runat="server">
+    <p>
+    Checksum: <asp:Literal ID="litChecksum" runat="server" />
+    </p>
+    </asp:PlaceHolder>
     </div>
     </asp:PlaceHolder>
 </form>

gts/test/Decode.aspx.cs

@@ -5,6 +5,7 @@ using System.Web;
 using System.Web.UI;
 using System.Web.UI.WebControls;
 using System.Text;
+using System.Net;
 
 namespace PkmnFoundations.GTS.debug
 {
@@ -13,12 +14,14 @@ namespace PkmnFoundations.GTS.debug
         protected void Page_Load(object sender, EventArgs e)
         {
             litMessage.Text = "";
+            litChecksum.Text = "";
         }
 
         protected void btnDecode_Click(object sender, EventArgs e)
         {
             byte[] data = null;
             phDecoded.Visible = false;
+            phChecksum.Visible = false;
 
             try
             {
@@ -38,16 +41,49 @@ namespace PkmnFoundations.GTS.debug
             {
             }
 
+            if (data == null) try
+            {
+                data = GamestatsSessionPlat.DecryptData(txtData.Text);
+                litGeneration.Text = "Platinum";
+            }
+            catch (FormatException)
+            {
+            }
+
+            if (data == null)
+            {
+                data = DecryptData(txtData.Text);
+
+                int checkedsum = 0;
+                foreach (byte b in data)
+                    checkedsum += b;
+
+                litGeneration.Text = "";
+                litChecksum.Text = checkedsum.ToString();
+                phChecksum.Visible = true;
+            }
+
             if (data == null)
             {
                 litMessage.Text = "<p class=\"errorMessage\">Data is not formatted correctly.</p>";
-                return;
             }
 
             litDecoded.Text = RenderHex(data.ToHexStringLower());
             phDecoded.Visible = true;
         }
 
+        public static byte[] DecryptData(String data)
+        {
+            byte[] data2 = GtsSessionBase.FromUrlSafeBase64String(data);
+            if (data2.Length < 12) throw new FormatException("Data must contain at least 12 bytes.");
+
+            int checksum = BitConverter.ToInt32(data2, 0);
+            checksum = IPAddress.NetworkToHostOrder(checksum); // endian flip
+            //checksum ^= 0x2db842b2;
+
+            return data2;
+        }
+
         private String RenderHex(String hex)
         {
             StringBuilder builder = new StringBuilder();

gts/test/Decode.aspx.designer.cs

@@ -74,5 +74,23 @@ namespace PkmnFoundations.GTS.debug {
         /// To modify move field declaration from designer file to code-behind file.
         /// </remarks>
         protected global::System.Web.UI.WebControls.Literal litDecoded;
+        
+        /// <summary>
+        /// phChecksum control.
+        /// </summary>
+        /// <remarks>
+        /// Auto-generated field.
+        /// To modify move field declaration from designer file to code-behind file.
+        /// </remarks>
+        protected global::System.Web.UI.WebControls.PlaceHolder phChecksum;
+        
+        /// <summary>
+        /// litChecksum control.
+        /// </summary>
+        /// <remarks>
+        /// Auto-generated field.
+        /// To modify move field declaration from designer file to code-behind file.
+        /// </remarks>
+        protected global::System.Web.UI.WebControls.Literal litChecksum;
     }
 }