第一次命中API时，“请求已中止:无法创建SSL/TLS安全通道”

Question

我正在尝试从Web API使用客户端的Web服务，下面是我们当前用来绕过SSL证书的代码

ServicePointManager.ServerCertificateValidationCallback += (发送者，证书，链，sslPolicyErrors) => true；

它工作得很好，直到他们禁用了TLS 1.0和TLS 1.1。现在，我们添加了以下代码，以便使用TLS 1.2进行客户端和服务器连接

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12；发送方+= (发送方，证书，链，sslPolicyErrors) => true；

现在我看到“请求已中止:无法创建SSL/TLS安全通道”。只有当我第一次点击API时才会出错，如果我连续点击API就会得到结果，如果我等待了一分钟左右，第一次也会出现同样的错误。

Answer 1

在创建发出请求之前，需要设置安全协议类型。所以这就是：

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

应出现在此之前：

HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);

因此，如果您看到它在后续请求上起作用，可能是您设置协议太晚了。

Answer 2

以下代码可用于帮助解决此问题。

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls;
ServicePointManager.ServerCertificateValidationCallback += ValidateServerCertificate;

...

private static bool ValidateServerCertificate(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors sslPolicyErrors)
{
    // If the certificate is a valid, signed certificate, return true to short circuit any add'l processing.
    if (sslPolicyErrors == SslPolicyErrors.None)
    {
        return true;
    }
    else
    {
        // cast cert as v2 in order to expose thumbprint prop - if needed
        var requestCertificate = (X509Certificate2)certificate;

        // init string builder for creating a long log entry
        var logEntry = new StringBuilder();

        // capture initial info for the log entry
        logEntry.AppendFormat("SSL Policy Error(s): {0} - Cert Issuer: {1} - SubjectName: {2}",
           sslPolicyErrors.ToString(),
           requestCertificate.Issuer,
           requestCertificate.SubjectName.Name);

        // check for other error types as needed
        if (sslPolicyErrors == SslPolicyErrors.RemoteCertificateChainErrors) //Root CA problem
        {
            // check chain status and log
            if (chain != null && chain.ChainStatus != null)
            {
                // check errors in chain and add to log entry
                foreach (var chainStatus in chain.ChainStatus)
                {
                    logEntry.AppendFormat("|Chain Status: {0} - {1}", chainStatus.Status.ToString(), chainStatus.StatusInformation.Trim());
                }
            }
        }

        // replace with your logger
        MyLogger.Info(logEntry.ToString().Trim());
    }

    return false;
}

Answer 3

对于运行.NET版本4的用户，他们可以使用下面的

ServicePointManager.SecurityProtocol = CType(768, SecurityProtocolType) Or CType(3072,SecurityProtocolType)
ServicePointManager.Expect100Continue = True