Rust

SSH Tunnel Static (Fixed-Destination) Port Forwarding

Demonstrates fixed-destination port forwarding with the DestHostname, DestPort, ListenBindIpAddress, and ListenPort properties. Every local connection accepted by the listener is forwarded to the same fixed destination through the SSH server.

Background: This is the classic ssh -L scenario: expose a single remote service — a database, an internal web app — at a local port. Binding the listener to 127.0.0.1 keeps the tunnel private to the local machine, whereas 0.0.0.0 would let other hosts route through it. Passing 0 to BeginAccepting lets the OS pick a free port, which ListenPort then reports — handy when a fixed port might already be in use.

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// Demonstrates fixed-destination (static) port forwarding with the SshTunnel properties
// DestHostname, DestPort, ListenBindIpAddress, and ListenPort.
// 
// Every local connection accepted by the listener is forwarded to the same fixed destination
// through the SSH server.

let tunnel = chilkat::SshTunnel::new();

// The fixed destination that accepted connections are forwarded to.
tunnel.set_dest_hostname("db.internal.example.com");
tunnel.set_dest_port(5432);

// Bind the listener to loopback so only local processes can use the tunnel.  Use "0.0.0.0" to
// accept connections from other machines (less secure).
tunnel.set_listen_bind_ip_address("127.0.0.1");

let ssh_port = 22;
if tunnel.connect("ssh.example.com", ssh_port).is_err() {
    println!("{}", tunnel.last_error_text());
    return;
}

// Normally you would not hard-code the password in source.  You should instead obtain it
// from an interactive prompt, environment variable, or a secrets vault.
let password = "mySshPassword".to_string();

if tunnel.authenticate_pw("mySshLogin", &password).is_err() {
    println!("{}", tunnel.last_error_text());
    return;
}

// Pass 0 to let the operating system choose an available port.  After BeginAccepting succeeds,
// ListenPort contains the actual port that was bound.
if tunnel.begin_accepting(0).is_err() {
    println!("{}", tunnel.last_error_text());
    return;
}

println!("Listening on 127.0.0.1 port {}", tunnel.listen_port());

// Applications now connect to 127.0.0.1:ListenPort as if it were the database server.

let wait_for_thread_exit = true;
if tunnel.close_tunnel(wait_for_thread_exit).is_err() {
    println!("{}", tunnel.last_error_text());
    return;
}