breach/breacher/ssh.go

package breacher

import (
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net"
	"os"
	"strconv"
	"strings"

	"github.com/spf13/cobra"
	"golang.org/x/crypto/ssh"
	"golang.org/x/crypto/ssh/agent"
)

var (
	sPasswd string
	sKey    string
)

func init() {
	sshCmd.Flags().StringVarP(&sPasswd, "password", "p", "", "login using password")
	sshCmd.Flags().StringVarP(&sKey, "keyfile", "i", "", "login keyfile (path/to/file)")
}

var sshCmd = &cobra.Command{
	Use:   "tunnel [from address] [to address] [user@host:port]",
	Short: "ssh tunneling to access remote services",
	Long: `ssh tunneling to access remote services
ex.
breacher tunnel :8080 host:80 user@example.com -p paswd
breacher tunnel :8080 :80 user@example.com -i ~/.ssh/id_rsa
breacher tunnel :8080 kumoly.io:443 user@example.com
`,
	Args: cobra.ExactArgs(3),
	Run: func(cmd *cobra.Command, args []string) {
		localHost, localPortStr, err := net.SplitHostPort(args[0])
		if err != nil {
			log.Fatalln(err)
		}
		remoteHost, remotePortStr, err := net.SplitHostPort(args[1])
		if err != nil {
			log.Fatalln(err)
		}
		localPort, err := strconv.Atoi(localPortStr)
		if err != nil {
			log.Fatalln(err)
		}
		remotePort, err := strconv.Atoi(remotePortStr)
		if err != nil {
			log.Fatalln(err)
		}
		if localHost == "" {
			localHost = "0.0.0.0"
		}
		if remoteHost == "" {
			remoteHost = "localhost"
		}
		split := strings.Split(args[2], "@")
		if len(split) != 2 {
			log.Fatalln("ssh host name not valid")
		}
		usr := split[0]
		sshHost := "localhost"
		sshPort := 22
		if !strings.Contains(split[1], ":") {
			sshHost = split[1]
		} else {
			sshPortStr := ""
			sshHost, sshPortStr, err = net.SplitHostPort(split[1])
			if err != nil {
				log.Fatalln(err)
			}
			if sshHost == "" {
				log.Fatalln("no ssh host")
			}
			if sshPortStr != "" {
				sshPort, err = strconv.Atoi(sshPortStr)
				if err != nil {
					log.Fatalln(err)
				}
			}
		}
		var auth ssh.AuthMethod
		if sPasswd != "" {
			auth = ssh.Password(sPasswd)
		} else if sKey != "" {
			auth = PrivateKeyFile(sKey)
		} else {
			auth = SSHAgent()
		}
		st := NewSSHTunnel(
			&Endpoint{localHost, localPort, ""},
			&Endpoint{remoteHost, remotePort, ""},
			&Endpoint{sshHost, sshPort, usr},
			auth,
		)

		log.Fatalln(st.Start())
	},
}

type Endpoint struct {
	Host string
	Port int
	User string
}

func (endpoint *Endpoint) String() string {
	return fmt.Sprintf("%s:%d", endpoint.Host, endpoint.Port)
}

type SSHTunnel struct {
	Local    *Endpoint
	Server   *Endpoint
	Remote   *Endpoint
	Config   *ssh.ClientConfig
	Conns    []net.Conn
	SvrConns []*ssh.Client
	isOpen   bool
	close    chan interface{}
}

func newConnectionWaiter(listener net.Listener, c chan net.Conn) {
	conn, err := listener.Accept()
	if err != nil {
		fmt.Println(err)
		return
	}
	c <- conn
}

func (tunnel *SSHTunnel) Start() error {
	listener, err := net.Listen("tcp", tunnel.Local.String())
	if err != nil {
		return err
	}
	tunnel.isOpen = true
	tunnel.Local.Port = listener.Addr().(*net.TCPAddr).Port

	for {
		if !tunnel.isOpen {
			break
		}

		c := make(chan net.Conn)
		go newConnectionWaiter(listener, c)
		log.Println("listening for new connections...")

		select {
		case <-tunnel.close:
			log.Println("close signal received, closing...")
			tunnel.isOpen = false
		case conn := <-c:
			tunnel.Conns = append(tunnel.Conns, conn)
			log.Println("accepted connection")
			go tunnel.forward(conn)
		}
	}
	var total int
	total = len(tunnel.Conns)
	for i, conn := range tunnel.Conns {
		log.Printf("closing the netConn (%d of %d)\n", i+1, total)
		err := conn.Close()
		if err != nil {
			log.Println(err.Error())
		}
	}
	total = len(tunnel.SvrConns)
	for i, conn := range tunnel.SvrConns {
		log.Printf("closing the serverConn (%d of %d)\n", i+1, total)
		err := conn.Close()
		if err != nil {
			log.Println(err.Error())
		}
	}
	err = listener.Close()
	if err != nil {
		return err
	}
	log.Println("tunnel closed")
	return nil
}

func (tunnel *SSHTunnel) forward(localConn net.Conn) {
	serverConn, err := ssh.Dial("tcp", tunnel.Server.String(), tunnel.Config)
	if err != nil {
		log.Printf("server dial error: %s\n", err)
		return
	}
	log.Printf("connected to %s (1 of 2)\n", tunnel.Server.String())
	tunnel.SvrConns = append(tunnel.SvrConns, serverConn)

	remoteConn, err := serverConn.Dial("tcp", tunnel.Remote.String())
	if err != nil {
		log.Printf("remote dial error: %s\n", err)
		return
	}
	tunnel.Conns = append(tunnel.Conns, remoteConn)
	log.Printf("connected to %s (2 of 2)\n", tunnel.Remote.String())
	copyConn := func(writer, reader net.Conn) {
		_, err := io.Copy(writer, reader)
		if err != nil {
			log.Printf("io.Copy error: %s\n", err)
		}
	}
	go copyConn(localConn, remoteConn)
	go copyConn(remoteConn, localConn)

}

func (tunnel *SSHTunnel) Close() {
	tunnel.close <- struct{}{}
}

// NewSSHTunnel creates a new single-use tunnel. Supplying "0" for localport will use a random port.
func NewSSHTunnel(from, to, server *Endpoint, auth ssh.AuthMethod) *SSHTunnel {
	if server.Port == 0 {
		server.Port = 22
	}

	sshTunnel := &SSHTunnel{
		Config: &ssh.ClientConfig{
			User: server.User,
			Auth: []ssh.AuthMethod{auth},
			HostKeyCallback: func(hostname string, remote net.Addr, key ssh.PublicKey) error {
				// Always accept key.
				return nil
			},
		},
		Local:  from,
		Server: server,
		Remote: to,
		close:  make(chan interface{}),
	}

	return sshTunnel
}

func PrivateKeyFile(file string) ssh.AuthMethod {
	buffer, err := ioutil.ReadFile(file)
	if err != nil {
		return nil
	}

	key, err := ssh.ParsePrivateKey(buffer)
	if err != nil {
		return nil
	}

	return ssh.PublicKeys(key)
}

func SSHAgent() ssh.AuthMethod {
	if sshAgent, err := net.Dial("unix", os.Getenv("SSH_AUTH_SOCK")); err == nil {
		return ssh.PublicKeysCallback(agent.NewClient(sshAgent).Signers)
	}
	return nil
}