Multi-factor authentication (password and key) with Paramiko

Question

I've got the following code:

import paramiko
policy = paramiko.client.WarningPolicy()
client = paramiko.client.SSHClient()
client.set_missing_host_key_policy(policy)
username = '...'
password = '...'
file_path = '...'
pkey = paramiko.RSAKey.from_private_key_file(file_path)
client.connect('...', username=username, password=password, pkey=key)
sftp = client.open_sftp() 

From the docs, it seems like it should work. Everything works successfully, but when the code hits client.open_sftp it bombs with a SSHException: Unable to open channel. and the transport (from client.get_transport) is active but not authenticated. I'm also having trouble enabling debug logging for this (I'm trying logging.getLogger('paramiko').setLevel(logging.DEBUG) without success.)

Any ideas on where I can start to debug this very vague error message?

Answer 1

Sorry for the late response but this problem was really hard to find any information on so i wanted to post a solution for anyone else stuck on this issue.

After pulling my hair out trying to solve this I found a solution thanks to some code posted by Doug Ellwanger and Daniel Brownridge. The problem seems to be caused by the way the multi-factor authentication is handled using more of an interactive style.

import paramiko
import threading

... 

username = '...'
password = '...'
file_path = '...'
pkey = paramiko.RSAKey.from_private_key_file(file_path)
sftpClient = multifactor_auth('...', 22, username, pkey, password)

...

def multifactor_auth_sftp_client(host, port, username, key, password):
    #Create an SSH transport configured to the host
    transport = paramiko.Transport((host, port))
    #Negotiate an SSH2 session
    transport.connect()
    #Attempt authenticating using a private key
    transport.auth_publickey(username, key)
    #Create an event for password auth
    password_auth_event = threading.Event()
    #Create password auth handler from transport
    password_auth_handler = paramiko.auth_handler.AuthHandler(transport)
    #Set transport auth_handler to password handler
    transport.auth_handler = password_auth_handler
    #Aquire lock on transport
    transport.lock.acquire()
    #Register the password auth event with handler
    password_auth_handler.auth_event = password_auth_event
    #Set the auth handler method to 'password'
    password_auth_handler.auth_method = 'password'
    #Set auth handler username
    password_auth_handler.username = username
    #Set auth handler password
    password_auth_handler.password = password
    #Create an SSH user auth message
    userauth_message = paramiko.message.Message()
    userauth_message.add_string('ssh-userauth')
    userauth_message.rewind()
    #Make the password auth attempt
    password_auth_handler._parse_service_accept(userauth_message)
    #Release lock on transport
    transport.lock.release()
    #Wait for password auth response
    password_auth_handler.wait_for_response(password_auth_event)
    #Create an open SFTP client channel
    return transport.open_sftp_client()

I hope this helps, it worked for my project.