lib_unity_purchase/Runtime/Security/Obfuscator.cs

38 lines
1.7 KiB
C#

using System;
using System.Linq;
using System.Collections.Generic;
namespace UnityEngine.Purchasing.Security
{
/// <summary>
/// This class will deobfuscate the tangled signature used for client-side receipt validation obfuscation.
/// </summary>
public static class Obfuscator
{
/// <summary>
/// Deobfucscates tangle data.
/// </summary>
/// <param name="data"> The Apple or GooglePlay public key data to be deobfuscated. </param>
/// <param name="order"> The array of the order of the data slices used to obfuscate the data when the tangle files were originally generated. </param>
/// <param name="key"> The encryption key to deobfuscate the tangled data at runtime, previously generated with the tangle file. </param>
/// <returns>The deobfucated public key</returns>
public static byte[] DeObfuscate(byte[] data, int[] order, int key)
{
var res = new byte[data.Length];
int slices = data.Length / 20 + 1;
bool hasRemainder = data.Length % 20 != 0;
Array.Copy(data, res, data.Length);
for (int i = order.Length - 1; i >= 0; i--)
{
var j = order[i];
int sliceSize = (hasRemainder && j == slices - 1) ? (data.Length % 20) : 20;
var tmp = res.Skip(i * 20).Take(sliceSize).ToArray(); // tmp = res[i*20 .. slice]
Array.Copy(res, j * 20, res, i * 20, sliceSize); // res[i] = res[j*20 .. slice]
Array.Copy(tmp, 0, res, j * 20, sliceSize); // res[j] = tmp
}
return res.Select(x => (byte)(x ^ key)).ToArray();
}
}
}