53 lines
2.1 KiB
C#
53 lines
2.1 KiB
C#
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using System;
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using System.Collections.Generic;
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using System.Linq;
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namespace UnityEditor.Purchasing
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{
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/// <summary>
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/// This class will generate the tangled signature used for client-side receipt validation obfuscation.
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/// </summary>
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public static class TangleObfuscator
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{
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/// <summary>
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/// An Exception thrown when the tangle order array provided is invalid or shorter than the number of data slices made.
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/// </summary>
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public class InvalidOrderArray : Exception { }
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/// <summary>
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/// Generates the obfucscation tangle data.
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/// </summary>
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/// <param name="data"> The Apple or GooglePlay public key data to be obfuscated. </param>
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/// <param name="order"> The array, passed by reference, of order of the data slices used to obfuscate the data with. </param>
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/// <param name="rkey"> Outputs the encryption key to deobfuscate the tangled data at runtime </param>
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/// <returns>The obfucated public key</returns>
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public static byte[] Obfuscate(byte[] data, int[] order, out int rkey)
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{
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var rnd = new Random();
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var key = rnd.Next(2, 255);
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var res = new byte[data.Length];
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var slices = data.Length / 20 + 1;
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if (order == null || order.Length < slices)
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{
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throw new InvalidOrderArray();
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}
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Array.Copy(data, res, data.Length);
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for (var i = 0; i < slices - 1; i++)
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{
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var j = rnd.Next(i, slices - 1);
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order[i] = j;
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var sliceSize = 20; // prob should be configurable
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var tmp = res.Skip(i * 20).Take(sliceSize).ToArray(); // tmp = res[i*20 .. slice]
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Array.Copy(res, j * 20, res, i * 20, sliceSize); // res[i] = res[j*20 .. slice]
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Array.Copy(tmp, 0, res, j * 20, sliceSize); // res[j] = tmp
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}
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order[slices - 1] = slices - 1;
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rkey = key;
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return res.Select(x => (byte)(x ^ key)).ToArray();
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}
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}
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}
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