C# 对接卡密验证

// C# 卡密验证客户端（.NET Standard 2.0+）
using System;
using System.Net.Http;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;

public class KamiClient
{
    private readonly string _baseUrl;
    private readonly string _app;
    private readonly string _signKey;

    public KamiClient(string userName, string app, string signKey)
    {
        _baseUrl = $"https://www.keyt.cn/kami/{userName}/check.php";
        _app = app;
        _signKey = signKey;
    }

    private string Md5(string input)
    {
        using var md5 = MD5.Create();
        var bytes = Encoding.UTF8.GetBytes(input);
        var hash = md5.ComputeHash(bytes);
        return BitConverter.ToString(hash).Replace("-", "").ToLower();
    }

    private string VerifyResponse(string raw)
    {
        if (!raw.Contains("|sign=")) return null;
        var parts = raw.Split(new[] { "|sign=" }, StringSplitOptions.None);
        var body = parts[0];
        var sign = parts[1];

        var localSign = Md5(body + _signKey);
        if (localSign != sign) return null;

        var lastPipe = body.LastIndexOf('|');
        if (lastPipe == -1) return null;
        var tsStr = body.Substring(lastPipe + 1);
        if (!long.TryParse(tsStr, out var ts)) return null;
        var nowTs = DateTimeOffset.UtcNow.ToUnixTimeSeconds();
        if (Math.Abs(nowTs - ts) > 120) return null;

        return body.Substring(0, lastPipe);
    }

    public async Task<string> VerifyCardAsync(string card, string mac)
    {
        var url = $"{_baseUrl}?card={card}&mac={mac}&app={_app}&heart=1&t={DateTimeOffset.UtcNow.ToUnixTimeSeconds()}";
        using var client = new HttpClient();
        var resp = await client.GetStringAsync(url);
        return VerifyResponse(resp);
    }
}