C# could not create ssl/tls secure channel (Restsharp)-CodePudding

I'm currently trying to connect to an api but I am getting this error: could not create ssl/tls secure channel

The request works when its made through Postman, same endpoint, same certificate and everything, but when I am making the request through restsharp it stops with the SSL/TLS error

I've tried forcing the security protocol to TLS12 with the code: ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

Also tried to remove the certificate validation with ServicePointManager.ServerCertificateValidationCallback = delegate { return true; }; And some other variations of this code.

Tried to disable it on the client as well, with no success either client.RemoteCertificateValidationCallback = (sender, certificate, chain, sslPolicyErrors) => true;

So I am currently trying to use Wireshark to get some more information. From what i could understand, it isn't an issue with the cipher suite, since it passes the "Client Hello" and "Server Hello" and it stops on the "Certificate Request, Server Hello Done".

Wireshark 1

The errors that appear on the image also appear when I make the request with Postman.

It stops on this line when it receives a RST flag with the ACK.

Wireshark 2

Does anyone have any idea on why it isn't working?

Also it's worth mentioning that I used the same code many times before to call other api's and they seem to work fine. Just this one that I can't make work no matter what I try. I don't have access to the servers since its a third-party api.

Any help on this matter is appreciated.

Edit: To add the code that i use to make the api call and some more info that was asked

ServicePointManager.Expect100Continue = true;
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12 | SecurityProtocolType.Tls11;
ServicePointManager.ServerCertificateValidationCallback  = (sender, certificateReturn, chainReturn, sslPolicyErrors) => true;

var client = new RestClient(api);
client.Timeout = -1;

//Add Certificate
X509Certificate2 cert = null;
if (GCONTABANCO.SelectCERTIFICADO(IDCONTABANCO, ref cert, ref MSG) == false) { return false; }
client.ClientCertificates = new X509CertificateCollection();
client.ClientCertificates.Add(cert);
var request = new RestRequest(Method.POST);
request.AddHeader("Accept", "application/json");
request.AddHeader("Content-Type", "application/x-www-form-urlencoded");
request.AddParameter("grant_type", "client_credentials");
request.AddParameter("client_id", clientId);
request.AddParameter("client_secret", clientSecret);
request.AddParameter("scope", "extrato.read boleto-cobranca.read boleto-cobranca.write");
IRestResponse response = client.Execute(request);

I'm using .net framework 4.5.2, i tried updating to 4.7 but the error persisted and currently i can't update the version because its a big system and can't risk breaking it

Windows build number: 21H1 (10.0.19043)

CodePudding user response：

So i managed to fix the issue with the help from their IT architect, i'll leave the answer here in case someone runs into the same issue in the future.

Since they had a lot of certificates being sent through the connection, it was going over the limit allowed and closing the connection, so i had to change the limit to be able to connect to the server. In C# it has to be changed on the regedit.

To do so i had to:

Open regedit.
Go to: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Messaging
Then add a MessageLimitClient DWORD value.
Set the value to 65536.
Restart the machine.

After doing that and testing again the connection was successful.