如何在 .Net Core 中使用单个 HttpClient 实例针对不同请求发送不同的客户端证书？

Question

HttpClient 的推荐是reuse a single instance。但从 API 看来，添加证书的方式似乎是在实例上，而不是每个请求。如果我们添加两个证书，我们如何确保“cert 1”只发送到“one.somedomain.com”？

//A handler is how you add client certs (is there any other way?)
var _clientHandler = new HttpClientHandler();

//Add multiple certs
_clientHandler.ClientCertificates.Add(cert1);
_clientHandler.ClientCertificates.Add(cert2);
_clientHandler.ClientCertificateOptions = ClientCertificateOption.Manual;


//Pretend this is our long-living HttpClient
var client = new HttpClient(_clientHandler);

//Now if we make a post request, will both certs be used?
using (HttpResponseMessage response = _client.PostAsync("https://one.somedomain.com", content).Result)
{
    //...elided...
 }

Answer 1

对不起。年底工作量大。 你可以尝试实现这样的东西：

public class CustomHttpHandler : HttpClientHandler
{
    private readonly Dictionary<string, X509Certificate> _certMap;

    public CustomHttpHandler():base()
    {
        _certMap = new Dictionary<string, X509Certificate>() { { "server1name", new X509Certificate("cert1") }, { "server2name", new X509Certificate("cert2") } };
    }

    protected override async Task<HttpResponseMessage> SendAsync(
            HttpRequestMessage request,
            CancellationToken cancellationToken)
    {
        string serverName = request.RequestUri.Host;
        if (ClientCertificates.Contains(_certMap[serverName]))
        {
            try
            {
                var response = await base.SendAsync(request, cancellationToken);
                return response;
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                Console.ReadKey();
                throw;
            }
        }
        else
        {
            ClientCertificates.Clear();
            ClientCertificates.Add(_certMap[serverName]);

            try
            {
                var response = await base.SendAsync(request, cancellationToken);
                return response;
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                Console.ReadKey();
                throw;
            }
        }
    }
}

只是一个想法，没有经过测试。 或者，您也可以在 RequestMessage 实例中使用 Headers 集合。 本文涵盖主题：https://damienbod.com/2019/09/07/using-certificate-authentication-with-ihttpclientfactory-and-httpclient/

Answer 2

这是建议，但是，您可以使用“使用”语句。

一旦 HttpClient 是 IDisposable，你应该使用类似的东西

using(var client = new HttpClient(_clientHandler))
{
    //Your code here
}