Upload a file to a remote EC2 server through a NAT bastion gateway over SSH using JSch. Allows tunneling from A -> B, A -> C, A -> D, etc.

jschAWSConnect.groovy

@Grab(group='com.jcraft', module='jsch', version='0.1.49')

import com.jcraft.jsch.*

//--------------------------  CONFIG ------------------------//
def gatewayServer = "ec2-gateway"
def gatewayUsername = "ec2-user"
def gatewayKeyPath = "/javadev/scripts/gateway.pem"        
def gatewayPassword = ""

//all hosts that will be connected to through the gateway
def hosts = ["10.x.x.x", "10.x.x.x"]
def username = "ubuntu"
//key file takes precedent over password, assumes same used on all servers
def keyPath = "/javadev/scripts/web.pem"        
def password = ""

//delay between running commands on each host server (in ms)
int delay = 10 * 1000

//command to run on each server in 'hosts' list
String command = "whoami;hostname";
//--------------------------  ACTION ------------------------//

JSch jsch=new JSch();
if (gatewayKeyPath)
    jsch.addIdentity(gatewayKeyPath);
if (keyPath)10
    jsch.addIdentity(keyPath);
jsch.setConfig("StrictHostKeyChecking", "no");

//establish connection to gateway server
Session gatewaySession=jsch.getSession(gatewayUsername, gatewayServer, 22);
if (!gatewayKeyPath)
    gatewaySession.setPassword(gatewayPassword);
gatewaySession.connect();
println "Gateway session established to $gatewayUsername@$gatewayServer"

//get sessions to each host through the gateway
int count = 0
List sessions = []
for (def host : hosts){
    int assinged_port = gatewaySession.setPortForwardingL(0, host, 22);
    println "portforwarding: localhost:${assinged_port} -> ${host}:22"
    
    Session tunnelSession = jsch.getSession(username, "127.0.0.1", assinged_port)
    if (!keyPath)
        tunnelSession.setPassword(password)
    tunnelSession.setHostKeyAlias(host)
    tunnelSession.connect()
    sessions << tunnelSession
    
    println "The session has been established to $username@$host"
}

//run commands on each session to remote host
int hostSize = hosts.size()
for (def session : sessions){
    Channel channel = session.openChannel("exec");
    channel.setCommand(command);
    channel.setErrStream(System.err);
    channel.connect();
    
    InputStream input = channel.getInputStream();
    //start reading the input from the executed commands on the shell
    byte[] tmp = new byte[1024];
    while (true) {
        while (input.available() > 0) {
            int i = input.read(tmp, 0, 1024);
            if (i < 0) break;
            print(new String(tmp, 0, i));
        }
        if (channel.isClosed()){
            println("exit-status: " + channel.getExitStatus());
            break;
        }
        sleep(1000);
    }
    channel.disconnect();
    
    //wait between connecting to each host
    if ((++count) < hostSize && hostSize > 1){
        sleep(delay)
    }
}

sessions*.disconnect()
gatewaySession.disconnect()