/// <summary>
/// Runs Reverse SSH Tunnel, using command: "ssh -NvR bindAddress:remoteAccessPort:localSideHost:localSidePort user@remoteHost
/// </summary>
/// <param name="bindAddress">
/// By default, the listening socket on the server will be bound to the loopback interface only.
/// This may be overridden by specifying a bind_address.
/// An empty bind_address, or the address '*', indicates that the remote socket should listen on all interfaces.
/// Specifying a remote bind_address will only succeed if the server's GatewayPorts option is enabled.
/// </param>
/// <returns></returns>
public bool Start(string bindAddress = DEFAULT_BIND_ADDRESS)
{
if (bindAddress == DEFAULT_BIND_ADDRESS && !IsHostChanged)
{
LastStartedCommandSSH = DefaultSSHCommand;
}
else
{
LastStartedCommandSSH = CreateCommandString(SSH_FORMAT_STRING, bindAddress, RemoteHost.Port, LocalSideHost.IP, LocalSideHost.Port, RemoteHost.User, RemoteHost.IP);
}
_SSHProcess = new BashProcess(LastStartedCommandSSH);
_SSHProcess.StandardOutputStringReceived += _SSHProcess_StandardOutputStringReceived;
_SSHProcess.StandardErrorStringReceived += _SSHProcess_StandardOutputStringReceived;
IsTunnelEstablished = _SSHProcess.RunNewProcess(true, true, true);
return(IsTunnelEstablished);
}
/// <summary>
/// Finds old processes used by last command and kill them
/// </summary>
/// <returns>Current tunnel connection type</returns>
public async Task <(TunnelConnectionState, string)> CheckAndKillOldProcesses()
{
try
{
if (await CheckConnectionType() != TunnelConnectionState.NoConnection)
{
List <int> PIDs = BashProcess.FindPIDs(LastStartedCommandSSH ?? DefaultSSHCommand);
foreach (int pid in PIDs)
{
BashProcess.KillProcess(pid);
}
}
return(await CheckConnectionType(), null);
}
catch (TunnelEstablishedException ex)
{
return(TunnelConnectionState.StoppedWithoutChecking, ex.Message);
}
}
/// <summary>
/// Checking connection type (local/remote) / state (connected/disconnected)
/// (To execute this method, device must be ssh authorised_host (ssh can't ask for password))
/// </summary>
/// <returns>Tunnel connection state or throws TunnelUnknownConnectionStateException when netstat has no result.</returns>
/// <exception cref="TunnelUnknownConnectionStateException">When netstat on remote device (command executed via SSH) returns null/whitespace (no netstatResult)
/// or when regexp match for netstat result, finds other address (than `0.0.0.0`/`127.0.0.1`) using tunnel's port.</exception>
public async Task <TunnelConnectionState> CheckConnectionType()
{
string netstatLocalAddress = null;
BashProcess netstatProcess = new BashProcess($"ssh {RemoteHost.User}@{RemoteHost.IP} netstat -tlnp")
{
SubscribeStandardOutput = false
};
string netstatResult = await netstatProcess.RunNewProcessAndReadStdOutputAsync();
if (!string.IsNullOrWhiteSpace(netstatResult))
{
Regex regex = new Regex($@"[0-255].[0-255].[0-255].[0-255](?=:{RemoteHost.Port})");
Match match = regex.Match(netstatResult);
if (match.Success)
{
netstatLocalAddress = match.Groups[0].Value;
}
switch (netstatLocalAddress)
{
case "0.0.0.0":
IsTunnelEstablished = true;
return(TunnelConnectionState.RemoteConnection);
case "127.0.0.1":
IsTunnelEstablished = true;
return(TunnelConnectionState.LocalConnection);
case null: // No match for regexp pattern - it means, no connection established
IsTunnelEstablished = false;
return(TunnelConnectionState.NoConnection);
default:
throw new TunnelUnknownConnectionStateException($"Unknown Tunnel Connection State: {netstatLocalAddress}");
}
}
throw new TunnelUnknownConnectionStateException("Unknown Tunnel Connection State: no netstatResult");
}
