annotations/Azaion.Common/Security.cs

using System.Security.Cryptography;
using System.Text;
using Newtonsoft.Json;

namespace Azaion.Common;

public class Security
{
    private static string GenDefaultKey()
    {
        var date = DateTime.UtcNow;
        return $"sAzaion_default_dfvkjhg_{date:yyyy}-{date:MM}_{date:dd}_{date:HH}_key";
    }
    
    public static string Encrypt<T>(T model, string? key = null) where T : class
    {
        var json = JsonConvert.SerializeObject(model);
        var inputBytes = Encoding.UTF8.GetBytes(json);
        
        var keyBytes = SHA256.HashData(Encoding.UTF8.GetBytes(key ?? GenDefaultKey()));
        var iv = RandomNumberGenerator.GetBytes(16);

        using var aes = Aes.Create();
        aes.Key = keyBytes;
        aes.IV = iv;
        aes.Mode = CipherMode.CFB;
        aes.Padding = PaddingMode.ISO10126;
        
        using var encryptor = aes.CreateEncryptor();
        var ciphertext = encryptor.TransformFinalBlock(inputBytes, 0, inputBytes.Length);
        
        var result = new byte[iv.Length + ciphertext.Length];
        iv.CopyTo(result, 0);
        ciphertext.CopyTo(result, iv.Length);

        return Convert.ToBase64String(result);
    }
    
    public static T Decrypt<T>(string encryptedData, string? key = null) where T : class
    {
        var ciphertextWithIv = Convert.FromBase64String(encryptedData);
        var keyBytes = SHA256.HashData(Encoding.UTF8.GetBytes(key ?? GenDefaultKey()));
        
        var iv = ciphertextWithIv[..16];
        var ciphertext = ciphertextWithIv[16..];
        
        using var aes = Aes.Create();
        aes.Key = keyBytes;
        aes.IV = iv;
        aes.Mode = CipherMode.CFB;
        aes.Padding = PaddingMode.ISO10126;
        
        using var decryptor = aes.CreateDecryptor();
        var plaintext = decryptor.TransformFinalBlock(ciphertext, 0, ciphertext.Length);

        var json = Encoding.UTF8.GetString(plaintext);
        return JsonConvert.DeserializeObject<T>(json)!;
    }
}