func Hop(through *ssh.Client, toaddr string, c *ssh.ClientConfig) (*ssh.Client, error) {
hopconn, err := through.Dial("tcp", toaddr)
if err != nil {
return nil, err
}
conn, chans, reqs, err := ssh.NewClientConn(hopconn, toaddr, c)
if err != nil {
return nil, err
}
return ssh.NewClient(conn, chans, reqs), nil
}
// Start port forwarding for the given SSH client:
func loop(sshClient *ssh.Client, localToRemote, remoteToLocal []PortForward) {
done := make(chan bool, 1)
// Intercept termination signals:
sigc := make(chan os.Signal, 1)
signal.Notify(sigc, os.Interrupt, os.Kill, syscall.SIGTERM, syscall.SIGQUIT)
go func() {
sig := <-sigc
log.Printf("Caught signal: %s\n", sig)
done <- true
}()
// Forward all the local-to-remote ports:
for _, fwd := range localToRemote {
// Set up forwarding addresses:
localAddr := fwd.LocalAddr
remoteAddr := fwd.RemoteAddr
log.Printf("Forwarding connections from local %s to remote %s\n", localAddr, remoteAddr)
go func() {
localListener, err := net.Listen("tcp", localAddr)
if err != nil {
log.Printf("unable to listen: %s\n", err)
done <- true
return
}
defer localListener.Close()
log.Printf("Listening...\n")
// Begin accepting new connections from the SSH tunnel:
for {
// Accept a new local connection:
local, err := localListener.Accept()
if err != nil {
log.Printf("Accept: %s\n", err)
break
}
logContext := local.RemoteAddr().String()
log.Printf("%s: Accepted local connection.\n", logContext)
// Connect to the remote RDP service:
remote, err := sshClient.Dial("tcp", remoteAddr)
if err != nil {
log.Printf("%s: Unable to connect via SSH: %s\n", logContext, err)
local.Close()
continue
}
defer remote.Close()
// Start forwarding data back 'n forth:
go forward(local, remote, logContext)
}
}()
}
// Forward all remote-to-local ports:
for _, fwd := range remoteToLocal {
// Set up forwarding addresses:
localAddr := fwd.LocalAddr
remoteAddr := fwd.RemoteAddr
// Resolve local address:
var err error
localTCPAddr, err := net.ResolveTCPAddr("tcp", localAddr)
if err != nil {
log.Printf("unable to resolve local address: %s\n", err)
done <- true
return
}
log.Printf("Forwarding connections from remote %s to local %s\n", remoteAddr, localAddr)
go func() {
// Request the remote side to open a port for forwarding:
l, err := sshClient.Listen("tcp", remoteAddr)
if err != nil {
log.Printf("unable to register tcp forward: %s\n", err)
return
}
log.Printf("Listening...\n")
defer l.Close()
// Begin accepting new connections from the SSH tunnel:
for {
// Accept a new remote connection from SSH:
remote, err := l.Accept()
if err != nil {
log.Printf("Accept: %s\n", err)
done <- true
break
}
logContext := remote.RemoteAddr().String()
log.Printf("%s: Accepted new SSH tunnel connection.\n", logContext)
// Connect to the local RDP service:
local, err := net.DialTCP("tcp", nil, localTCPAddr)
if err != nil {
log.Printf("%s: Could not open local connection to: %s\n", logContext, localTCPAddr)
remote.Close()
continue
}
// Start forwarding data back 'n forth:
go forward(local, remote, logContext)
}
}()
}
<-done
}
