main.go

/**
* Filename: main.go
* Description: the PortForward main entry point
*   It supports tcp/udp protocol layer traffic forwarding, forward/reverse
*   creation of forwarding links, and multi-level cascading use.
* Author: knownsec404
* Time: 2020.09.02
*/

package main

import (
    "errors"
    "fmt"
    "os"
    "strings"
)

const VERSION string = "version: 0.5.0(build-20201022)"

/**********************************************************************
* @Function: main()
* @Description: the PortForward entry point, parse command-line argument
* @Parameter: nil
* @Return: nil
**********************************************************************/
func main() {
    if len(os.Args) != 4 {
        usage()
        return
    }
    proto := os.Args[1]
    sock1 := os.Args[2]
    sock2 := os.Args[3]

    // parse and check argument
    protocol := PORTFORWARD_PROTO_TCP
    if strings.ToUpper(proto) == "TCP" {
        protocol = PORTFORWARD_PROTO_TCP
    } else if strings.ToUpper(proto) == "UDP" {
        protocol = PORTFORWARD_PROTO_UDP
    } else {
        fmt.Printf("unknown protocol [%s]\n", proto)
        return
    }

    m1, a1, err := parseSock(sock1)
    if err != nil {
        fmt.Println(err)
        return
    }
    m2, a2, err := parseSock(sock2)
    if err != nil {
        fmt.Println(err)
        return
    }

    // launch
    args := Args{
        Protocol:   protocol,
        Method1:    m1,
        Addr1:      a1,
        Method2:    m2,
        Addr2:      a2,
    }
    Launch(args)
}


/**********************************************************************
* @Function: parseSock(sock string) (uint8, string, error)
* @Description: parse and check sock string
* @Parameter: sock string, the sock string from command-line
* @Return: (uint8, string, error), the method, address and error
**********************************************************************/
func parseSock(sock string) (uint8, string, error) {
    // split "method" and "address"
    items := strings.SplitN(sock, ":", 2)
    if len(items) != 2 {
        return PORTFORWARD_SOCK_NIL, "",
               errors.New("host format must [method:address:port]")
    }

    method := items[0]
    address := items[1]
    // check the method field
    if strings.ToUpper(method) == "LISTEN" {
        return PORTFORWARD_SOCK_LISTEN, address, nil
    } else if strings.ToUpper(method) == "CONN" {
        return PORTFORWARD_SOCK_CONN, address, nil
    } else {
        errmsg := fmt.Sprintf("unknown method [%s]", method)
        return PORTFORWARD_SOCK_NIL, "", errors.New(errmsg)
    }
}


/**********************************************************************
* @Function: usage()
* @Description: the PortForward usage
* @Parameter: nil
* @Return: nil
**********************************************************************/
func usage() {
    fmt.Println("Usage:")
    fmt.Println("  ./portforward [proto] [sock1] [sock2]")
    fmt.Println("Option:")
    fmt.Println("  proto      the port forward with protocol(tcp/udp)")
    fmt.Println("  sock       format: [method:address:port]")
    fmt.Println("  method     the sock mode(listen/conn)")
    fmt.Println("Example:")
    fmt.Println("  tcp conn:192.168.1.1:3389 conn:192.168.1.10:23333")
    fmt.Println("  udp listen:192.168.1.3:5353 conn:8.8.8.8:53")
    fmt.Println("  tcp listen:[fe80::1%lo0]:8888 conn:[fe80::1%lo0]:7777")
    fmt.Println()
    fmt.Println(VERSION)
}