117 lines
3.6 KiB
C#
117 lines
3.6 KiB
C#
using System;
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using System.Security.Cryptography;
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using System.Text;
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public static class BoardAuthentication
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{
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private const int _blockSizeBytes = 16;
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private const int _hexBlockLength = _blockSizeBytes * 2;
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private static readonly byte[] _aesObfuscatedKey =
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{
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0x69, 0x40, 0xC7, 0x0E, 0xF2, 0xC7, 0x45, 0x70,
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0x72, 0xCD, 0x28, 0x58, 0x99, 0x8F, 0x73, 0xA8,
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0x5F, 0x5F, 0xED, 0xB4, 0xC1, 0x62, 0xB4, 0x24,
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0xAC, 0xD7, 0xA3, 0xD6, 0xD8, 0x0B, 0x50, 0x37
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};
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public static string CreateChallengeHex()
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{
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byte[] challenge = new byte[_blockSizeBytes];
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using RandomNumberGenerator generator = RandomNumberGenerator.Create();
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generator.GetBytes(challenge);
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return ToHex(challenge);
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}
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public static string EncryptHexBlock(string plainHex)
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{
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byte[] plain = ParseHexBlock(plainHex);
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using Aes aes = Aes.Create();
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aes.KeySize = 256;
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aes.BlockSize = 128;
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aes.Mode = CipherMode.ECB;
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aes.Padding = PaddingMode.None;
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aes.Key = (byte[])_aesObfuscatedKey.Clone();
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using ICryptoTransform encryptor = aes.CreateEncryptor();
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byte[] encrypted = encryptor.TransformFinalBlock(plain, 0, plain.Length);
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return ToHex(encrypted);
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}
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public static bool TryExtractHexPayload(string line, string prefix, out string payload)
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{
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payload = null;
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if (string.IsNullOrEmpty(line)
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|| string.IsNullOrEmpty(prefix)
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|| line.Length != prefix.Length + _hexBlockLength
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|| !line.StartsWith(prefix, StringComparison.Ordinal))
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return false;
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string candidate = line.Substring(prefix.Length);
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for (int i = 0; i < candidate.Length; i++)
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{
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if (!IsHexCharacter(candidate[i]))
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return false;
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}
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payload = candidate.ToUpperInvariant();
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return true;
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}
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public static bool ValidateEncryptedResponse(string challengeHex, string responseHex)
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{
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if (!TryNormalizeHexBlock(responseHex, out string normalizedResponse))
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return false;
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string expectedResponse = EncryptHexBlock(challengeHex);
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int difference = 0;
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for (int i = 0; i < expectedResponse.Length; i++)
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difference |= expectedResponse[i] ^ normalizedResponse[i];
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return difference == 0;
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}
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private static byte[] ParseHexBlock(string value)
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{
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if (!TryNormalizeHexBlock(value, out string normalized))
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throw new ArgumentException($"Ожидался HEX-блок длиной {_hexBlockLength} символа.", nameof(value));
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byte[] bytes = new byte[_blockSizeBytes];
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for (int i = 0; i < bytes.Length; i++)
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bytes[i] = Convert.ToByte(normalized.Substring(i * 2, 2), 16);
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return bytes;
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}
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private static bool TryNormalizeHexBlock(string value, out string normalized)
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{
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normalized = null;
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if (string.IsNullOrEmpty(value) || value.Length != _hexBlockLength)
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return false;
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for (int i = 0; i < value.Length; i++)
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{
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if (!IsHexCharacter(value[i]))
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return false;
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}
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normalized = value.ToUpperInvariant();
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return true;
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}
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private static bool IsHexCharacter(char value)
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=> value >= '0' && value <= '9'
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|| value >= 'A' && value <= 'F'
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|| value >= 'a' && value <= 'f';
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private static string ToHex(byte[] bytes)
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{
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StringBuilder builder = new(bytes.Length * 2);
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for (int i = 0; i < bytes.Length; i++)
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builder.Append(bytes[i].ToString("X2"));
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return builder.ToString();
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}
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}
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