c# - System.Net.HttpWebRequest.GetResponse() 错误 "ResponceSystem.Net.WebException: The request was aborted: Could not create SSL/TLS secure channel"

Question

Dotnet 应用程序是使用 dotnet 4.5 构建的。在一些系统上，我们在连接到最近对 SSL 进行了一些更改的 Web 服务器时遇到此错误。

Web 服务器仅 TLS 1.2 https://drive.google.com/open?id=1Z0S-MWugDZdQrIy3BnquooB0ZX7veIVT

客户端代码。

WebRequest webRequest = WebRequest.Create(strUrl);
webRequest.ContentType = "application/x-www-form-urlencoded";
webRequest.Method = "Get";
if (strUrl.StartsWith("HTTPS", StringComparison.OrdinalIgnoreCase)) ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12 | SecurityProtocolType.Tls | SecurityProtocolType.Ssl3;
using (WebResponse webResponse = webRequest.GetResponse())
{
    if (webResponse == null) return blnResult;
    using (StreamReader sr = new StreamReader(webResponse.GetResponseStream()))
    {
       strSuccess = sr.ReadToEnd().Trim();
       blnResult = true;
    }
}

只要我用框架 4.6.2 编译它，它就可以工作。

为什么它在少数具有相同 4.5 编译 EXE 的系统上工作，而在少数系统上需要使用 4.6.2 编译？

WebClient 类适用于 4.5 版本的 dotnet 框架。只有 WebRequest 不工作。

Answer 1

初始化WebRequest对象前需要先设置安全协议(protocol)。

if (strUrl.StartsWith("HTTPS", StringComparison.OrdinalIgnoreCase)) ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12 | SecurityProtocolType.Tls | SecurityProtocolType.Ssl3;

WebRequest webRequest = WebRequest.Create(strUrl);
webRequest.ContentType = "application/x-www-form-urlencoded";
webRequest.Method = "Get";

using (WebResponse webResponse = webRequest.GetResponse())
{
    if (webResponse == null) return blnResult;
    using (StreamReader sr = new StreamReader(webResponse.GetResponseStream()))
    {
       strSuccess = sr.ReadToEnd().Trim();
       blnResult = true;
    }
}