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285
Assets/ClientSDK/Encryption.cs
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285
Assets/ClientSDK/Encryption.cs
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using System;
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using System.IO;
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using System.Security.Cryptography;
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using System.Text;
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namespace GeoSus.Client
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{
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// Klientská strana šifrování - generuje session key, šifruje RSA, AES-CBC session
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// Používá AES-CBC místo AES-GCM pro kompatibilitu s Unity
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public class ClientEncryption : IDisposable
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{
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private byte[] _sessionKey;
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private byte[] _sessionIv;
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private long _nonceCounter;
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private readonly object _lock = new object();
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// Kontrola, zda je session key nastaven
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public bool HasSessionKey => _sessionKey != null && _sessionIv != null;
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// Generuje nový session key a IV
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public void GenerateSessionKey()
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{
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_sessionKey = new byte[32]; // AES-256
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_sessionIv = new byte[16]; // CBC IV (16 bytes)
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using (var rng = RandomNumberGenerator.Create())
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{
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rng.GetBytes(_sessionKey);
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rng.GetBytes(_sessionIv);
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}
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}
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public byte[] SessionKey => _sessionKey ?? throw new InvalidOperationException("Session key not generated");
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public byte[] SessionIV => _sessionIv ?? throw new InvalidOperationException("Session IV not generated");
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// Zašifruje session key pomocí RSA public key serveru
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public (string EncryptedKey, string EncryptedIV) EncryptSessionKeyForServer(string rsaPublicKeyPem)
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{
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if (_sessionKey == null || _sessionIv == null)
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throw new InvalidOperationException("Session key not generated");
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using (var rsa = RSA.Create())
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{
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// Parse PEM - extrahuj Base64 obsah
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var pemLines = rsaPublicKeyPem.Split('\n');
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var base64 = new StringBuilder();
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foreach (var line in pemLines)
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{
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var trimmed = line.Trim();
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if (!trimmed.StartsWith("-----") && !string.IsNullOrEmpty(trimmed))
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{
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base64.Append(trimmed);
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}
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}
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var keyBytes = Convert.FromBase64String(base64.ToString());
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// Unity kompatibilní import - parsujeme SubjectPublicKeyInfo ručně
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ImportSubjectPublicKeyInfoManual(rsa, keyBytes);
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// Používáme OaepSHA1 pro Unity kompatibilitu (OaepSHA256 není podporován)
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var encryptedKey = rsa.Encrypt(_sessionKey, RSAEncryptionPadding.OaepSHA1);
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var encryptedIv = rsa.Encrypt(_sessionIv, RSAEncryptionPadding.OaepSHA1);
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return (Convert.ToBase64String(encryptedKey), Convert.ToBase64String(encryptedIv));
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}
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}
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// Ručně parsuje SubjectPublicKeyInfo (DER) a importuje RSA klíč - Unity kompatibilní
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private static void ImportSubjectPublicKeyInfoManual(RSA rsa, byte[] subjectPublicKeyInfo)
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{
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// SubjectPublicKeyInfo ::= SEQUENCE {
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// algorithm AlgorithmIdentifier,
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// subjectPublicKey BIT STRING }
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// RSAPublicKey ::= SEQUENCE { modulus INTEGER, publicExponent INTEGER }
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int index = 0;
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// Outer SEQUENCE
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if (subjectPublicKeyInfo[index++] != 0x30)
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throw new InvalidOperationException("Invalid SubjectPublicKeyInfo");
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ReadLength(subjectPublicKeyInfo, ref index);
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// AlgorithmIdentifier SEQUENCE - skip it
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if (subjectPublicKeyInfo[index++] != 0x30)
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throw new InvalidOperationException("Invalid AlgorithmIdentifier");
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int algLen = ReadLength(subjectPublicKeyInfo, ref index);
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index += algLen;
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// BIT STRING containing RSAPublicKey
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if (subjectPublicKeyInfo[index++] != 0x03)
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throw new InvalidOperationException("Invalid BIT STRING");
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ReadLength(subjectPublicKeyInfo, ref index);
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index++; // Skip unused bits byte (should be 0)
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// RSAPublicKey SEQUENCE
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if (subjectPublicKeyInfo[index++] != 0x30)
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throw new InvalidOperationException("Invalid RSAPublicKey");
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ReadLength(subjectPublicKeyInfo, ref index);
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// Modulus INTEGER
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byte[] modulus = ReadInteger(subjectPublicKeyInfo, ref index);
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// Exponent INTEGER
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byte[] exponent = ReadInteger(subjectPublicKeyInfo, ref index);
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var parameters = new RSAParameters
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{
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Modulus = modulus,
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Exponent = exponent
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};
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rsa.ImportParameters(parameters);
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}
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private static int ReadLength(byte[] data, ref int index)
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{
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int length = data[index++];
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if ((length & 0x80) != 0)
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{
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int numBytes = length & 0x7F;
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length = 0;
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for (int i = 0; i < numBytes; i++)
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{
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length = (length << 8) | data[index++];
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}
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}
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return length;
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}
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private static byte[] ReadInteger(byte[] data, ref int index)
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{
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if (data[index++] != 0x02)
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throw new InvalidOperationException("Expected INTEGER");
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int length = ReadLength(data, ref index);
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// Skip leading zero if present (used for positive sign in DER)
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int originalLength = length;
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int start = index;
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if (length > 1 && data[start] == 0x00)
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{
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start++;
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length--;
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}
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byte[] result = new byte[length];
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Buffer.BlockCopy(data, start, result, 0, length);
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index += originalLength;
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return result;
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}
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// Šifruje zprávu pomocí AES-256-CBC s HMAC
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public byte[] Encrypt(byte[] plaintext)
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{
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if (_sessionKey == null || _sessionIv == null)
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throw new InvalidOperationException("Session key not set");
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lock (_lock)
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{
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// Generuj unikátní IV pro tuto zprávu
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var iv = GetNextIV();
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using (var aes = Aes.Create())
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{
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aes.Key = _sessionKey;
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aes.IV = iv;
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aes.Mode = CipherMode.CBC;
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aes.Padding = PaddingMode.PKCS7;
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byte[] ciphertext;
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using (var encryptor = aes.CreateEncryptor())
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using (var ms = new MemoryStream())
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{
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using (var cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
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{
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cs.Write(plaintext, 0, plaintext.Length);
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}
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ciphertext = ms.ToArray();
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}
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// Compute HMAC pro integritu
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byte[] hmac;
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using (var hmacSha = new HMACSHA256(_sessionKey))
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{
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var toSign = new byte[iv.Length + ciphertext.Length];
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Buffer.BlockCopy(iv, 0, toSign, 0, iv.Length);
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Buffer.BlockCopy(ciphertext, 0, toSign, iv.Length, ciphertext.Length);
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hmac = hmacSha.ComputeHash(toSign);
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}
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// Výstup: [16 bytes IV][32 bytes HMAC][ciphertext]
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var result = new byte[16 + 32 + ciphertext.Length];
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Buffer.BlockCopy(iv, 0, result, 0, 16);
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Buffer.BlockCopy(hmac, 0, result, 16, 32);
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Buffer.BlockCopy(ciphertext, 0, result, 48, ciphertext.Length);
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return result;
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}
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}
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}
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// Dešifruje zprávu pomocí AES-256-CBC s HMAC ověřením
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public byte[] Decrypt(byte[] encrypted)
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{
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if (_sessionKey == null)
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throw new InvalidOperationException("Session key not set");
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if (encrypted.Length < 48) return null;
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try
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{
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var iv = new byte[16];
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var hmac = new byte[32];
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var ciphertext = new byte[encrypted.Length - 48];
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Buffer.BlockCopy(encrypted, 0, iv, 0, 16);
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Buffer.BlockCopy(encrypted, 16, hmac, 0, 32);
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Buffer.BlockCopy(encrypted, 48, ciphertext, 0, ciphertext.Length);
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// Ověř HMAC
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byte[] expectedHmac;
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using (var hmacSha = new HMACSHA256(_sessionKey))
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{
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var toVerify = new byte[iv.Length + ciphertext.Length];
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Buffer.BlockCopy(iv, 0, toVerify, 0, iv.Length);
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Buffer.BlockCopy(ciphertext, 0, toVerify, iv.Length, ciphertext.Length);
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expectedHmac = hmacSha.ComputeHash(toVerify);
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}
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// Constant-time compare
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var diff = 0;
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for (int i = 0; i < 32; i++)
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{
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diff |= hmac[i] ^ expectedHmac[i];
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}
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if (diff != 0) return null; // HMAC mismatch
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using (var aes = Aes.Create())
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{
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aes.Key = _sessionKey;
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aes.IV = iv;
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aes.Mode = CipherMode.CBC;
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aes.Padding = PaddingMode.PKCS7;
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using (var decryptor = aes.CreateDecryptor())
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using (var ms = new MemoryStream(ciphertext))
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using (var cs = new CryptoStream(ms, decryptor, CryptoStreamMode.Read))
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using (var output = new MemoryStream())
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{
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cs.CopyTo(output);
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return output.ToArray();
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}
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}
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}
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catch (CryptographicException)
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{
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return null;
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}
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}
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private byte[] GetNextIV()
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{
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if (_sessionIv == null)
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throw new InvalidOperationException("Session IV not set");
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var iv = new byte[16];
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Buffer.BlockCopy(_sessionIv, 0, iv, 0, 8);
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var counter = System.Threading.Interlocked.Increment(ref _nonceCounter);
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var counterBytes = BitConverter.GetBytes(counter);
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Buffer.BlockCopy(counterBytes, 0, iv, 8, 8);
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return iv;
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}
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public void Dispose()
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{
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if (_sessionKey != null)
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{
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Array.Clear(_sessionKey, 0, _sessionKey.Length);
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_sessionKey = null;
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}
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}
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}
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}
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