aspnetcore/src/Microsoft.AspNetCore.Server.IISIntegration/ForwardedTlsConnectionFeature.cs

// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Security.Cryptography.X509Certificates;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http.Features;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Primitives;

namespace Microsoft.AspNetCore.Server.IISIntegration
{
    internal class ForwardedTlsConnectionFeature : ITlsConnectionFeature
    {
        private StringValues _header;
        private X509Certificate2 _certificate;
        private ILogger _logger;

        public ForwardedTlsConnectionFeature(ILogger logger, StringValues header)
        {
            _logger = logger;
            _header = header;
        }

        public X509Certificate2 ClientCertificate
        {
            get
            {
                if (_certificate == null && _header != StringValues.Empty)
                {
                    try
                    {
                        var bytes = Convert.FromBase64String(_header);
                        _certificate = new X509Certificate2(bytes);
                    }
                    catch (Exception ex)
                    {
                        _logger.LogWarning(0, ex, "Failed to read the client certificate.");
                    }
                }
                return _certificate;
            }
            set
            {
                _certificate = value;
                _header = StringValues.Empty;
            }
        }

        public Task<X509Certificate2> GetClientCertificateAsync(CancellationToken cancellationToken)
        {
            return Task.FromResult(ClientCertificate);
        }
    }
}