“请求被中止：无法创建 SSL/TLS 安全通道”第一次点击 API 时

Question

我正在尝试从 Web API 使用客户端的 Web 服务，以下是我们目前用来绕过 SSL 证书的代码

ServicePointManager.ServerCertificateValidationCallback += (sender, cert, chain, sslPolicyErrors) => true;

它运行良好，直到他们最终禁用了 TLS 1.0 和 TLS 1.1。现在我们添加了以下代码以使用 TLS 1.2 进行客户端服务器连接

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12; ServicePointManager.ServerCertificateValidationCallback += (sender, cert, chain, sslPolicyErrors) => true;

现在我收到“请求已中止：无法创建 SSL/TLS 安全通道。” 仅当我第一次点击 API 时出错，然后如果我连续点击 API 就会得到结果，如果我等待一分钟左右的时间，再次仅第一次出现相同的错误。

Answer 1

需要在创建发布请求之前设置安全协议类型。所以这：

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

应该出现在此之前：

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

因此，如果您看到它对后续请求起作用，则可能是您设置协议太晚了。

Answer 2

以下代码可用于帮助解决该问题。

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;
}