SSH terminal in a webapp using ASP.NET

Question

Hello I creating a webapp that has a working SSH terminal similar to Putty. I'm using SSH Library as a means of handling the ssh stream. However there is a problem. I can log into a Cisco 2950 and type in commands but it comes out jumbled and in one line. Also when I try "conf t" it gets into the configuration terminal but then you can't do anything and this pops up "Line has invalid autocommand "?".

Here is the code I have so far:

This is the SSH.cs that interacts with the library.

public class SSH
{
    public string cmdInput { get; set; }

    public string SSHConnect()
    {
        var PasswordConnection = new PasswordAuthenticationMethod("username", "password");
        var KeyboardInteractive = new KeyboardInteractiveAuthenticationMethod("username");
        // jmccarthy is the username
        var connectionInfo = new ConnectionInfo("10.56.1.2", 22, "username", PasswordConnection, KeyboardInteractive);
        var ssh = new SshClient(connectionInfo);

        ssh.Connect();
        var cmd = ssh.CreateCommand(cmdInput);
        var asynch = cmd.BeginExecute(delegate(IAsyncResult ar)
        {
            //Console.WriteLine("Finished.");
        }, null);

        var reader = new StreamReader(cmd.OutputStream);
        var myData = "";

        while (!asynch.IsCompleted)
        {
            var result = reader.ReadToEnd();
            if (string.IsNullOrEmpty(result))
                continue;
            myData = result;
        }

        cmd.EndExecute(asynch);
        return myData;
    } 
}

This the code in the .aspx.cs that displays the code on the web page.

protected void CMD(object sender, EventArgs e)
    {
        SSH s = new SSH();

        s.cmdInput = input.Text;

        output.Text = s.SSHConnect();
    }

Any help would be appreciated.

BateTech · Accepted Answer · 2014-03-28 20:54:29Z

7

From looking through the test cases in the code for the SSH.NET library, you can use the RunCommand method instead of CreateCommand, which will synchronously process the command. I also added a using block for the SshClient ssh object since it implements iDisposable. Remember to call Disconnect as well so you don't get stuck with open connections.

Also the SshCommand.Result property (used in the command.Result call below), encapsulates the logic to pull the results from the OutputSteam, and uses this._session.ConnectionInfo.Encoding to read the OutputStream using the proper encoding. This should help with the jumbled lines you were receiving.

Here is an example:

    public string SSHConnect() {
        var PasswordConnection = new PasswordAuthenticationMethod("username", "password");
        var KeyboardInteractive = new KeyboardInteractiveAuthenticationMethod("username");
        string myData = null;

        var connectionInfo = new ConnectionInfo("10.56.1.2", 22, "username", PasswordConnection, KeyboardInteractive);

        using (SshClient ssh = new SshClient(connectionInfo)){
            ssh.Connect();
            var command = ssh.RunCommand(cmdInput);
            myData = command.Result;
            ssh.Disconnect();
        }

        return myData;
    }

edited Mar 28, 2014 at 20:54

answered Mar 28, 2014 at 20:43

BateTech

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7 Comments

ValMangul Over a year ago

Thanks dude, There is one issue still in that when I enter "conf t", to get into the configuration terminal, it gets in but when I type the command "interface fastethernet 0/1" to a configure the first port it gives me a "Line has invalid autocommand 'interface fastEthernet 0/1'".

BateTech Over a year ago

That issue is that web requests are stateless by nature, so if you send a conf t command with one request, and then send another command interface fastethernet 0/1, then those are executing against two different instances of 2 different SshClient objects.

BateTech Over a year ago

@user3325399 This sounds like a good candidate for using .NET 4.5 WebSockets and/or SignalR to keep a persistent connection open between the server and client. Then you can open your SshClient connection on the server, keep it open and pass data back and forth from the client (web browser) and server in real time. I have not personally used SignalR before, but the demos I've seen look really cool. Check out asp.net/signalr/videos/getting-started/signalr-and-web-sockets and asp.net/signalr

BateTech Over a year ago

What is the anticipated user base for this app? If it is just you (or you and a few members of your team), then it might be easier to make this a WinForms app, where you do not have to worry about maintaining the connections and state across multiple users.

BateTech Over a year ago

In that case you will need to be able to maintain the connected SshClient objects per user if they have any commands that depend on the previous command. SingalR is one option, and from what I understand of it, would allow you to know when a client connection is broken and cleanup the server objects accordingly. Static server side classes or session to manage the objects are another options.

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