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