KEX negotiation failed using curve25519-sha256

With the develop branch, I’ve already ran a few times into a KEX failure:

Renci.SshNet.Common.SshConnectionException: Key exchange negotiation failed. at Renci.SshNet.Session.WaitOnHandle(WaitHandle waitHandle, TimeSpan timeout) at Renci.SshNet.Session.Connect() at Renci.SshNet.BaseClient.CreateAndConnectSession() at Renci.SshNet.BaseClient.Connect()

I’m testing again OpenSSH 8.0p1 (Ubuntu 19.10 Desktop).

The following simple code fragment should allow you to reproduce this issue:

using Renci.SshNet;
using System;
using System.Linq;
using System.Threading.Tasks;

class ConnectDisconnect
{
    private static void Main(string[] args)
    {
        if (args.Length != 3)
        {
            Console.Error.WriteLine("Please specify the host name, user name and password.");
            return;
        }

        var hostName = args[0];
        var userName = args[1];
        var password = args[2];

        var tasks = Enumerable.Range(1, 10).Select(y =>
            {
                return Task.Factory.StartNew(() =>
                    {
                        for (var i = 0; i < 500; i++)
                        {
                            using (SftpClient client = new SftpClient(args[0], userName, password))
                            {
                                client.Connect();
                                Console.Write(".");
                            }
                        }
                    });
            }).ToArray();

        Task.WaitAll(tasks);
    }
}

Note: It could take a while for this issue to reproduce.

[drieseng]

I’ve fixed my changes, and up to now I’ve not been able to reproduce this issue again. I’ll commit the fix tomorrow.

[drieseng]

@darinkes No problem, I can admit my mistakes. Like I always say: “I’ve made many mistakes, but I’m not married”. My gf doesn’t always appreciate this. Not sure why.