Renci.SshNet.Common.SshConnectionException: An established connection was aborted by the server

[harsh288]

I 'm using Rencii package and it used to work however when I do List Directory which has got more than 2000 files, that is where it's breaking and giving established connection was aborted.

using System;
using System.Collections.Generic;
using System.IO;
using Renci.SshNet;
namespace worship_sync
{
class Program
{
static void Main(string[] args)
{
const string host = "******";
const string username = "****";
const string password = "vagrant";
const string workingdirectory = "*****";
const string uploadfile = #"******";
Console.WriteLine("Creating client and connecting");
using (SftpClient client = new SftpClient(host, 8822, username, password))
{
client.Connect();
Console.WriteLine("Connected to {0}", host);
client.ChangeDirectory(workingdirectory);
Console.WriteLine("Changed directory to {0}", workingdirectory);
var listDirectory = client.ListDirectory(workingdirectory); // ERROR
Console.WriteLine("Listing directory:");
foreach (var fi in listDirectory)
{
Console.WriteLine(" - " + fi.Name);
}   
}
}
}
}

AND I got this error when I am runing my code: Unhandled Exception: Renci.SshNet.Common.SshConnectionException: An established connection was aborted by the server.

[biocoder-frodo]

Is it breaking because it takes too long, or are you traversing into a folder where you do not have access permissions? Your server admin should be able to tell you what is causing the aborted connection or change the timeout limit.
How long does it take for the server to produce the same list of files in an interactive SSH session (Putty?)

[csxcode]

I have the same problem, could you solve it?

[ecocarlisle]

We have been experiencing the same issue. Any update would be great.

Uncaught exception [Renci.SshNet.Common.SshConnectionException: An established connection was aborted by the server.]
at Renci.SshNet.SubsystemSession.WaitOnHandle(WaitHandle waitHandle, Int32 millisecondsTimeout)
at Renci.SshNet.Sftp.SftpSession.RequestRealPath(String path, Boolean nullOnError)
at Renci.SshNet.Sftp.SftpSession.GetCanonicalPath(String path)
at Renci.SshNet.SftpClient.InternalUploadFile(Stream input, String path, Flags flags, SftpUploadAsyncResult asyncResult, Action`1 uploadCallback)

[csxcode]

Anyone?

[drieseng]

@csxcode Can you consult the server logs to find out why the SSH server closed the connection?

[erhan0]

We have been experiencing the same issue on connect....is there an update to this?

[drieseng]

@erhan0 if no one bothers to check server logs, or provide access to a system that allows me to reproduce the problems ... then no, no update from my end.

[biocoder-frodo]

To the people asking for updates, have you tried running your code in Visual Studio in Debug mode?
You should see plenty SshNet.Logging debug messages in the Output pane (Show output from: Debug) if you have a debug build of the library attached to your solution. Please see here https://github.com/sshnet/SSH.NET/wiki/Troubleshooting-SSH.NET
e.g.

'SynoDuplicateFolders.exe' (CLR v4.0.30319: SynoDuplicateFolders.exe): Loaded 'D:\github\SynoDuplicateFolders\SynoDuplicateFolders\bin\Debug\Renci.SshNet.dll'. Symbols loaded.
Exception thrown: 'Renci.SshNet.Common.SshPassPhraseNullOrEmptyException' in Renci.SshNet.dll
SshNet.Logging Verbose: 3 : Initiating connection to 'diskstation:22'.
SshNet.Logging Verbose: 3 : Server version '2.0' on 'OpenSSH_7.4'.
SshNet.Logging Verbose: 4 : [] Received message 'KeyExchangeInitMessage' from server: 'SSH_MSG_KEXINIT'.

[Carcinogen72]

Hi there, here is a bit of auth.log, the last line seems to be the problem. If you would like access then send me your public key.

Aug 9 11:21:10 crsserver sshd[20806]: Accepted publickey for clientdata from 192.168.2.111 port 57507 ssh2: RSA SHA256:-
Aug 9 11:21:10 crsserver sshd[20806]: pam_unix(sshd:session): session opened for user clientdata by (uid=0)
Aug 9 11:21:10 crsserver systemd-logind[786]: New session 61 of user clientdata.
Aug 9 11:22:10 crsserver sshd[20806]: pam_unix(sshd:session): session closed for user clientdata
Aug 9 11:22:10 crsserver systemd-logind[786]: Removed session 61.
Aug 9 11:29:36 crsserver sshd[20929]: fatal: mm_answer_moduli: bad parameters: 2048 2048 1024

I'm using the same key to ssh in through the terminal as I'm using in code.

Anson

[drieseng]

@Carcinogen72 Your issue appears to be unrelated to the issue. If you have a way to us to reproduce this issue (you can contact me privately to share connection info), please open a new issue.

[julianperrott]

This may not help you but it may help someone with a similar issue. We are using a 2016 version which is experiencing these errors:

• An established connection was aborted by the server.
• An existing connection was forcibly closed by the remote host

This was caused by being blocked by Cisco Meraki Intrusion detection. The particular rules which were triggered were:

• Buffer overflow in sshd in OpenSSH 2.3.1 through 3.3 may allow remote attackers to execute arbitrary code via a large number of responses during challenge response authentication when OpenBSD is using PAM modules with interactive keyboard authentication (PAMAuthenticationViaKbdInt).

• Integer overflow in sshd in OpenSSH 2.9.9 through 3.3 allows remote attackers to execute arbitrary code during challenge response authentication (ChallengeResponseAuthentication) when OpenSSH is using SKEY or BSD_AUTH authentication.

[dchiranjib]

Using the latest version (2021.10.2) and still getting the same error. Can't find any details on the server side too. I have failed on both an on-prem and a k8s environment. Can anyone shade some light? Thanks

[drieseng]

@dchiranjib Do you happen to have a server (or specific docker image) that I can use to reproduce this issue against?

[dchiranjib]

@drieseng unfortunately I can't share those details, but I can explain how I am trying to connect. I am using a host, port 22, username, password, a proxy host in the middle, port number of the proxy, and using Socks5 method.

I tried with both ConnectionInfo with Password authentication and PasswordConnectionInfo, then tried with object of both SftpClient and SSHClient, but ended up with the same outcome, failing while calling Connect method.

Uncaught exception [Renci.SshNet.Common.SshConnectionException: An established connection was aborted by the server.]

Checked the IP's that my organization is exposing and they are already whitelisted by the sFTP server.

[RPJack]

Hi everyone, i just encountered the same problem in my case, there are a few code and the logs are as follows:

authMethods.Add(new PasswordAuthenticationMethod(userName, password));
var connInfo = new ConnectionInfo(host, Convert.ToInt32(port), userName, authMethods.ToArray());
using (var sftpClient = new SftpClient(connInfo))
              {
                  sftpClient.Connect();
                  await SFTPDownload(sftpClient);
              }

client error log:
Renci.SshNet.Common.SshConnectionException: An established connection was aborted by the server.\n at Renci.SshNet.Session.WaitOnHandle(WaitHandle waitHandle, TimeSpan timeout)\n at Renci.SshNet.Session.WaitOnHandle(WaitHandle waitHandle)\n at Renci.SshNet.Session.Connect()\n at Renci.SshNet.BaseClient.CreateAndConnectSession()\n at Renci.SshNet.BaseClient.Connect()

server error log:
ERRORS KEX_FAILURE Message="no matching host key type found" Kex=ssh-ed25519,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-rsa,ssh-dss SourceIP=xxx.xxx.xxx.xxx

By the way, i used the same information connect success by openssh-client, but it can't be correct result by my code which using Renci.SshNet. @drieseng Can you help me to check the Renci.SshNet's ssh version different openssh-client