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using System;
using XenAdmin.Core;
using XenAPI;
using XenAdmin.Diagnostics.Problems;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography.X509Certificates;
using XenAdmin.Diagnostics.Hotfixing;
using XenAdmin.Diagnostics.Problems.HostProblem;

namespace XenAdmin.Diagnostics.Checks
{
    class CertificateKeyLengthCheck : HostPostLivenessCheck
    {
        private readonly bool _manualUpgrade;
        private readonly Dictionary<string, string> _installMethodConfig;

        public CertificateKeyLengthCheck(Host coordinator, bool manualUpgrade = false, Dictionary<string, string> installMethodConfig = null)
            : base(coordinator)
        {
            _manualUpgrade = manualUpgrade;
            _installMethodConfig = installMethodConfig;
        }

        protected override Problem RunHostCheck()
        {
            //post-stockholm uses stunnel 5.60 which requires certificate key length
            //equal to or greater than 2048 bytes; yangtze uses stunnel 5.56

            if (!IsShortCertificateKey())
                return null;

            if (!_manualUpgrade)
            {
                var hotfix = HotfixFactory.Hotfix(Host);
                if (hotfix != null && hotfix.ShouldBeAppliedTo(Host))
                    return new HostDoesNotHaveHotfixWarning(this, Host);
            }

            string upgradePlatformVersion = null;

            if (_installMethodConfig != null)
                Host.TryGetUpgradeVersion(Host, _installMethodConfig, out upgradePlatformVersion, out _);

            // we don't know the upgrade version, so add warning
            // (this is the case of the manual upgrade or when the rpu plugin doesn't have the function)
            if (string.IsNullOrEmpty(upgradePlatformVersion))
                return new CertificateKeyLengthWarningUrl(this, Host);

            if (Helpers.CloudOrGreater(upgradePlatformVersion))
                return new CertificateKeyLengthProblem(this, Host);

            return null;
        }

        private bool IsShortCertificateKey()
        {
            var session = Host.Connection?.Session;
            if (session == null)
                return false;

            var certificate = Host.get_server_certificate(session, Host.opaque_ref);

            var lines = certificate.Split('\n').ToList();
            if (lines.Count > 0)
                lines.RemoveAt(0); //remove BEGIN CERTIFICATE header
            if (lines.Count > 0)
                lines.RemoveAt(lines.Count - 1); //remove END CERTIFICATE footer

            certificate = string.Join("\n", lines);

            try
            {
                byte[] bytes = Convert.FromBase64String(certificate);
                var x509Cert = new X509Certificate2(bytes);
                return x509Cert.PublicKey.Key.KeySize < 2048;
            }
            catch
            {
                return false;
            }
        }

        public override string Description => Messages.CERTIFICATE_KEY_LENGTH_CHECK_DESCRIPTION;
    }
}