prs/prs.services/CertificateManager.cs

using InABox.Core;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using System.Timers;
using Timer = System.Timers.Timer;

namespace PRSServices;

public enum CertificateStatus
{
    Valid,
    Expired,
    NotFound,
    Error
}

public class CertificateManager
{
    public string? CertificateFile { get; set; }
    private X509Certificate2? Certificate;
    private Timer? CertificateRefreshTimer;
    private Timer? CertificateHaltTimer;

    public delegate void UpdateCertificateEvent(X509Certificate2 certificate);
    public event UpdateCertificateEvent? UpdateCertificate;

    public delegate void CertificateExpiringEvent(DateTime expiry);
    public event CertificateExpiringEvent? CertificateExpiring;

    public delegate void CertificateExpiredEvent();
    public event CertificateExpiredEvent? CertificateExpired;

    public CertificateManager(string? filename = null)
    {
        CertificateFile = filename;
    }

    public void SetFile(string certificateFile)
    {
        CertificateFile = certificateFile;
    }

    public void SetCertificate(X509Certificate2 certificate)
    {
        Certificate = certificate;
    }

    public void Clear()
    {
        Certificate = null;
    }

    public void Stop()
    {
        CertificateRefreshTimer?.Stop();

        CertificateHaltTimer?.Dispose();
        CertificateHaltTimer = null;
    }

    public X509Certificate2? GetCertificate()
    {
        GetCertificate(out var certificate);
        return certificate;
    }

    public CertificateStatus CheckCertificate()
    {
        return GetCertificate(out var certificate);
    }

    public CertificateStatus GetCertificate(out X509Certificate2? certificate)
    {
        if(Certificate != null)
        {
            certificate = Certificate;
            return CertificateStatus.Valid;
        }
        certificate = null;
        CertificateStatus status;
        if (File.Exists(CertificateFile))
        {
            try
            {
                certificate = new X509Certificate2(CertificateFile);
                if (certificate.NotAfter > DateTime.Now)
                {
                    Certificate = certificate;
                    status = CertificateStatus.Valid;
                }
                else
                {
                    status = CertificateStatus.Expired;
                    certificate = null;
                }
            }
            catch (Exception)
            {
                status = CertificateStatus.Error;
            }
        }
        else
        {
            status = CertificateStatus.NotFound;
        }
        if(certificate is not null)
        {
            if (CertificateRefreshTimer == null)
            {
                CertificateRefreshTimer = new Timer(1000 * 60 * 60 * 24);
                CertificateRefreshTimer.Elapsed += CertificateTimer_Elapsed;
                CertificateRefreshTimer.AutoReset = true;
            }
            CertificateRefreshTimer.Start();
        }
        return status;
    }

    #region Certificate Management

    private void CertificateTimer_Elapsed(object? sender, ElapsedEventArgs e)
    {
        if (Certificate is not null)
        {
            X509Certificate2? cert = null;
            if (File.Exists(CertificateFile))
            {
                cert = new X509Certificate2(CertificateFile);
            }

            if (cert != null && cert.NotAfter > Certificate.NotAfter && cert.NotAfter > DateTime.Now)
            {
                Certificate = cert;
                UpdateCertificate?.Invoke(cert);
            }

            var expiry = Certificate.NotAfter;
            var untilExpiry = expiry - DateTime.Now;
            if (untilExpiry.TotalDays <= 7)
            {
                CertificateExpiring?.Invoke(expiry);
                if (untilExpiry.TotalDays <= 1)
                {
                    CertificateRefreshTimer?.Stop();

                    CertificateHaltTimer = new Timer(untilExpiry.TotalMilliseconds);
                    CertificateHaltTimer.Elapsed += HTTPS_Halt_Elapsed;
                    CertificateHaltTimer.AutoReset = false;
                    CertificateHaltTimer.Start();
                }
            }
        }
    }

    /// <summary>
    /// Restarts listener in HTTP mode
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void HTTPS_Halt_Elapsed(object? sender, ElapsedEventArgs e)
    {
        CertificateHaltTimer?.Dispose();
        CertificateHaltTimer = null;

        CertificateExpired?.Invoke();
    }

    #endregion
}