63 lines
2.6 KiB
C#
63 lines
2.6 KiB
C#
using System.Security.Cryptography;
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using System.Text;
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namespace SVSim.BattleNode.Wire;
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/// <summary>
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/// AES-256-CBC encrypt/decrypt for the node socket channel. Port of
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/// Cryptographer.EncryptRJ256ForNode / DecryptRJ256ForNode in the decompilation.
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/// Key is prepended to ciphertext (cleartext); IV is the first 16 chars of the key.
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/// </summary>
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public static class NodeCrypto
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{
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/// <summary>
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/// Generate a fresh 32-char key. 32 random hex digits, base64-encoded, truncated to 32 chars.
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/// Port of Cryptographer.generateKeyString.
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/// </summary>
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public static string GenerateKey(Func<int> randHexDigit)
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{
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var sb = new StringBuilder(32);
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for (var i = 0; i < 32; i++)
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{
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sb.Append(randHexDigit().ToString("x"));
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}
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var ascii = Encoding.ASCII.GetBytes(sb.ToString());
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return Convert.ToBase64String(ascii).Substring(0, 32);
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}
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/// <summary>Encrypt: returns key + base64(AES-256-CBC(plain)).</summary>
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public static string EncryptForNode(string plaintext, string key)
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{
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if (key.Length != 32)
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throw new ArgumentException($"Key must be exactly 32 chars, got {key.Length}", nameof(key));
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using var aes = Aes.Create();
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aes.KeySize = 256;
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aes.Mode = CipherMode.CBC;
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aes.Padding = PaddingMode.PKCS7;
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aes.Key = Encoding.UTF8.GetBytes(key);
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aes.IV = Encoding.UTF8.GetBytes(key.Substring(0, 16));
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using var encryptor = aes.CreateEncryptor();
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var plainBytes = Encoding.UTF8.GetBytes(plaintext);
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var cipherBytes = encryptor.TransformFinalBlock(plainBytes, 0, plainBytes.Length);
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return key + Convert.ToBase64String(cipherBytes);
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}
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/// <summary>Decrypt: input[0..32] is key, input[32..] is base64(ciphertext).</summary>
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public static string DecryptForNode(string encrypted)
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{
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if (encrypted.Length < 32)
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throw new ArgumentException("Encrypted blob is shorter than the 32-char key prefix", nameof(encrypted));
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var key = encrypted.Substring(0, 32);
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var cipherBytes = Convert.FromBase64String(encrypted.Substring(32));
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using var aes = Aes.Create();
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aes.KeySize = 256;
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aes.Mode = CipherMode.CBC;
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aes.Padding = PaddingMode.PKCS7;
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aes.Key = Encoding.UTF8.GetBytes(key);
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aes.IV = Encoding.UTF8.GetBytes(key.Substring(0, 16));
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using var decryptor = aes.CreateDecryptor();
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var plainBytes = decryptor.TransformFinalBlock(cipherBytes, 0, cipherBytes.Length);
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return Encoding.UTF8.GetString(plainBytes);
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}
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}
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