由于以下错误消息，我们无法使用WebRequest连接到HTTPS服务器:
请求被中止:无法创建SSL/TLS安全通道。
我们知道服务器没有有效的HTTPS证书，但为了绕过这个问题，我们使用下面的代码，我们从另一个StackOverflow帖子:
private void Somewhere() {
ServicePointManager.ServerCertificateValidationCallback += new RemoteCertificateValidationCallback(AlwaysGoodCertificate);
}
private static bool AlwaysGoodCertificate(object sender, X509Certificate certificate, X509Chain chain, SslPolicyErrors policyErrors) {
return true;
}
问题是服务器从未验证证书，并出现上述错误而失败。有人知道我该怎么做吗?
我应该提到的是，我和一个同事几周前进行了测试，它运行得很好，与我上面写的类似。我们发现的唯一“主要区别”是，我用的是Windows 7，而他用的是Windows XP。这会改变什么吗?
After days of pulling what hair I have left out, we solved the problem. I tried everything suggested on this post and nothing worked for me. For us, we had a basic .Net Framework 4.8 console app running on a customers Windows VM. The on-premise server we were communicating with required that SSL Certificate Validation was turned off. One of our guys discovered that the server required we were using TLS 1.0 and on the registry settings of the VM, TLS 1.0 was disabled. Once we enabled that, it worked. I also needed to added the following two lines as mentioned many times above:
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls;
ServicePointManager.ServerCertificateValidationCallback = delegate { return true; };
在我的例子中，当一个Windows服务试图连接到一个web服务时，我遇到了这个问题。在Windows事件中，我终于找到了一个错误代码。
事件ID 36888(通道)被引发:
The following fatal alert was generated: 40. The internal error state is 808.
最后，它与Windows热修复有关。在我的例子中是KB3172605和KB3177186
vmware论坛提出的解决方案是在windows中添加一个注册表项。添加以下注册表后，所有工作正常。
[HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ \控制SecurityProviders \ SCHANNEL \ KeyExchangeAlgorithms \ diffie - hellman)
“ClientMinKeyBitLength”= dword: 00000200
显然，这与客户端https握手中缺失的值有关。
列出你的Windows HotFix:
wmic qfe list
解决方案线程:
https://communities.vmware.com/message/2604912#2604912
希望对大家有所帮助。
我们在Windows Server 2012R2客户端中遇到了同样的问题。
错误40表示客户端和服务器不同意使用密码套件。
在大多数情况下，服务器需要客户端无法识别的密码套件。
如果你不能修改服务器设置，解决方案是将那些“缺失”的密码套件添加到客户端:
First, go to SSLLabs SSL Labs
Enter the url of the site/api you are having problem to connect
Wait a few minutes until the test is completed
Go to 'Cipher Suites' section and read very carefully TLS 1.3 / TLS 1.2
There you will find the Cipher Suites accepted by the server
Now in your windows server, go to Regedit
Open the Key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Cryptography\Configuration\Local\SSL
There you will find 2 folders: 00010002 -->TLS 1.2 and 00010003 --> TLS 1.3
Now, edit the Functions key, and add the suites required by the server
In our case, we needed to Add TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 to 00010002 folder
确保ServicePointManager设置是在创建HttpWebRequest之前完成的，否则它将无法工作。
工作原理:
ServicePointManager.Expect100Continue = true;
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls
| SecurityProtocolType.Tls11
| SecurityProtocolType.Tls12
| SecurityProtocolType.Ssl3;
HttpWebRequest request = (HttpWebRequest)WebRequest.Create("https://google.com/api/")
失败:
HttpWebRequest request = (HttpWebRequest)WebRequest.Create("https://google.com/api/")
ServicePointManager.Expect100Continue = true;
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls
| SecurityProtocolType.Tls11
| SecurityProtocolType.Tls12
| SecurityProtocolType.Ssl3;
我终于找到了答案(我没有注明我的来源，但它来自一次搜索);
虽然代码在Windows XP中工作，但在Windows 7中，你必须在开头添加这个:
// using System.Net;
ServicePointManager.Expect100Continue = true;
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
// Use SecurityProtocolType.Ssl3 if needed for compatibility reasons
现在，它工作得很完美。
齿顶高
Robin French提到过;如果你在配置PayPal时遇到了这个问题，请注意从2018年12月3日开始他们将不支持SSL3。您需要使用TLS。这是关于它的Paypal页面。
