Develop Reference

How to implement execCommand of Twisted SSH server for use with fabric?

I implemented a Twisted SSH server to test a component that uses fabric to run commands on a remote machine via SSH. I have found this example but I don't understand how I have to implement the execCommand method to be compatible with fabric. Here is my implementation of the SSH server:
from pathlib import Path
from twisted.conch import avatar, recvline
from twisted.conch.insults import insults
from twisted.conch.interfaces import ISession
from twisted.conch.ssh import factory, keys, session
from twisted.cred import checkers, portal
from twisted.internet import reactor
from zope.interface import implementer
SSH_KEYS_FOLDER = Path(__file__).parent.parent / "resources" / "ssh_keys"
#implementer(ISession)
class SSHDemoAvatar(avatar.ConchUser):
def __init__(self, username: str):
avatar.ConchUser.__init__(self)
self.username = username
self.channelLookup.update({b"session": session.SSHSession})
def openShell(self, protocol):
pass
def getPty(self, terminal, windowSize, attrs):
return None
def execCommand(self, protocol: session.SSHSessionProcessProtocol, cmd: bytes):
protocol.write("Some text to return")
protocol.session.conn.sendEOF(protocol.session)
def eofReceived(self):
pass
def closed(self):
pass
#implementer(portal.IRealm)
class SSHDemoRealm(object):
def requestAvatar(self, avatarId, _, *interfaces):
return interfaces[0], SSHDemoAvatar(avatarId), lambda: None
def getRSAKeys():
with open(SSH_KEYS_FOLDER / "ssh_key") as private_key_file:
private_key = keys.Key.fromString(data=private_key_file.read())
with open(SSH_KEYS_FOLDER / "ssh_key.pub") as public_key_file:
public_key = keys.Key.fromString(data=public_key_file.read())
return public_key, private_key
if __name__ == "__main__":
sshFactory = factory.SSHFactory()
sshFactory.portal = portal.Portal(SSHDemoRealm())
users = {
"admin": b"aaa",
"guest": b"bbb",
}
sshFactory.portal.registerChecker(checkers.InMemoryUsernamePasswordDatabaseDontUse(**users))
pubKey, privKey = getRSAKeys()
sshFactory.publicKeys = {b"ssh-rsa": pubKey}
sshFactory.privateKeys = {b"ssh-rsa": privKey}
reactor.listenTCP(22222, sshFactory)
reactor.run()
Trying to execute a command via fabric yields the following output:
[paramiko.transport ][INFO ] Connected (version 2.0, client Twisted_22.4.0)
[paramiko.transport ][INFO ] Authentication (password) successful!
Some text to return
This looks promising but the program execution hangs after this line. Do I have to close the connection from the server side after executing the command? How do I implement that properly?

In a traditional UNIX server, it's still the server's responsibility to close the connection if it was told to execute a command. It's up to the server's discretion where and how to do this.
I believe you just want to change protocol.session.conn.sendEOF(protocol.session) to protocol.loseConnection(). I apologize for not testing this myself to be sure, setting up an environment to properly test a full-size conch setup like this is a bit tedious (and the example isn't self-contained, requiring key generation and moduli, etc)

Creating and logging into a linux virtual machine in automation with python

I currently have a working python script that SSHs into a remote Linux machine and executes commands on that machine. I'm using paramiko to handle ssh connectivity. Here is the code in action, executing an hostname -s command:
blade = '192.168.1.15'
username='root'
password=''
# now, connect
try:
client = paramiko.SSHClient()
client.load_system_host_keys()
client.set_missing_host_key_policy(paramiko.WarningPolicy())
print '*** Connecting...'
client.connect(blade, 22, username, password)
# print hostname for verification
stdin, stdout, stderr = client.exec_command('hostname --short')
print stdout.readlines()
except Exception, e:
print '*** Caught exception: %s: %s' % (e.__class__, e)
traceback.print_exc()
try:
client.close()
except:
pass
sys.exit(1)
This works fine, but what I'm actually trying to do is more complicated. What I would actually like to do is SSH into that same Linux machine, as I did above, but then create a temporary virtual machine on it, and execute a command on that virtual machine. Here is my (nonworking) attempt:
blade='192.168.1.15'
username='root'
password=''
# now, connect
try:
# client = paramiko.SSHClient()
client.load_system_host_keys()
client.set_missing_host_key_policy(paramiko.WarningPolicy())
print '*** Connecting...'
client.connect(blade, 22, username, password)
# create VM, log in, and print hostname for verification
stdin, stdout, stderr = client.exec_command('sudo kvm -m 1024 -drive file=/var/lib/libvirt/images/oa4-vm$
time.sleep(60) #delay to allow VM to initialize
stdin.write(username + '\n') #log into VM
stdin.write(password + '\n') #log into VM
stdin, stdout, stderr = client.exec_command('hostname --short')
print stdout.readlines()
except Exception, e:
print '*** Caught exception: %s: %s' % (e.__class__, e)
traceback.print_exc()
try:
client.close()
except:
pass
sys.exit(1)
When I run this, I get the following:
joe#computer:~$ python automata.py
*** Connecting...
/home/joe/.local/lib/python2.7/site-packages/paramiko/client.py:95: UserWarning: Unknown ssh-rsa host key for 192.168.1.15: 25f6a84613a635f6bcb5cceae2c2b435
(key.get_name(), hostname, hexlify(key.get_fingerprint())))
*** Caught exception: <class 'socket.error'>: Socket is closed
Traceback (most recent call last):
File "automata.py", line 32, in function1
stdin.write(username + '\n') #log into VM
File "/home/joe/.local/lib/python2.7/site-packages/paramiko/file.py", line 314, in write
self._write_all(data)
File "/home/joe/.local/lib/python2.7/site-packages/paramiko/file.py", line 439, in _write_all
count = self._write(data)
File "/home/joe/.local/lib/python2.7/site-packages/paramiko/channel.py", line 1263, in _write
self.channel.sendall(data)
File "/home/joe/.local/lib/python2.7/site-packages/paramiko/channel.py", line 796, in sendall
raise socket.error('Socket is closed')
error: Socket is closed
I'm not sure how to interpret this error -- "socket is closed" makes me think the SSH connection is terminating one I try to create the VM. Does anyone have any pointers?
update
I'm attempting to use the pexpect wrapper and having trouble getting it to interact with the un/pw prompt. I'm testing the process by ssh'ing into a remote machine and running a test.py script which prompts me for a username, then saves the username in a text file. Here is my fab file:
env.hosts = ['hostname']
env.user = 'userame'
env.password = 'password'
def vm_create():
run("python test.py")
And the contents of test.py on the remote machine are:
#! /usr/bin/env python
uname = raw_input("Enter Username: ")
f = open('output.txt','w')
f.write(uname + "\n")
f.close
So, I can execute "fab vm_create" on the local machine and it successfully establishes the SSH connection and prompts me for the username, as defined by test.py. However, if I execute a third python file on my local machine with the pexpect wrapper, like this:
import pexpect
child = pexpect.spawn('fab vm_create')
child.expect ('Enter Username: ')
child.sendline ('password')
Nothing seems to happen. I get no errors, and no output.txt is created on the remote machine. Am I using pexpect incorrectly?

As much as I love paramiko, this may be better suited to using Fabric.
Here's a sample fabfile.py:
from fabric.api import run
from fabric.api import sudo
from fabric.api import env
env.user = 'root'
env.password = ''
env.host = ='192.168.1.15'
def vm_up():
sudo("kvm -m 1024 -drive file=/var/lib/libvirt/images/oa4-vm$...")
run("hostname --short")
To then run this, use
$ fab vm_up
If you don't set the host and password in the fabfile itself (rightly so), then you can set these at the command line:
$ fab -H 192.168.1.15 -p PASSWORD vm_up
However, your kvm line is still expecting input. To send input (and wait for the expected prompts), write another script that uses pexpect to call fab:
child = pexpect.spawn('fab vm_up')
child.expect('username:') # Put this in the format you're expecting
child.send('root')

use fabric http://docs.fabfile.org/en/1.8/
Fabric is a Python (2.5 or higher) library and command-line tool for streamlining the use of SSH for application deployment or systems administration tasks
from fabric.api import run
def host_name():
run('hostname -s')

Python run mutiple ssh commands in the same session

My goal is to connect to SSH with python and authenticate which i can do with Paramiko or Fabric. But i would like to keep the session open after each execution and read the input/output. With paramiko i can only run 1 command before the session is closed and i am asked to authenticate again and the session hangs. And since fabric is using the paramiko library its giving me the same issue. For example if my directory structure is like this
-home
--myfolder1
--myfolder2
I would like to execute the below commands without having to re-authenticate because the sessions closes.
(make connection)
run cmd: 'pwd'
output: /home
run cmd: 'cd myfolder2'
run cmd: 'pwd'
output: /home/myfolder2
Is this possible with any module that is out there right now? Could it be made from scratch with native python? And also is this just not possible...?
Edit Added code. Without the new open_session it closes and i cannot run any command. After running the first command with this i will be prompted again to authenticate and it creates an infinite loop.
Edit2 If it closes after each command then there is no way this will work at all correct?
edit3 If i run this on a different server and exec_command with the paramikio.SSHClient it wont ask me to reauthenticate but if i 'cd somedir' and then 'pwd' it will output that i am back in the root directory of where i created.
class connect:
newconnection = ''
def __init__(self,username,password):
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
try:
ssh.connect('someserver', username=username,password=password,port=22,timeout=5)
except:
print "Count not connect"
sys.exit()
self.newconnection = ssh
def con(self):
return self.newconnection
#This will create the connection
sshconnection = connect('someuser','somepassword').con()
while True:
cmd = raw_input("Command to run: ")
if cmd == "":
break
try:
transport = sshconnection.get_transport()
transport.set_keepalive(999999)
chan = transport.open_session()
chan.settimeout(3)
chan.setblocking(0)
except:
print "Failed to open a channel"
chan.get_exception()
sys.exit()
print "running '%s'" % cmd
stdout_data = []
stderr_data = []
pprint.pprint(chan)
nbytes = 4096
chan.settimeout(5)
chan.get_pty()
chan.exec_command(cmd)
while True:
print "Inside loop " , chan.exit_status_ready()
time.sleep(1.2)
if chan.recv_ready():
print "First if"
stdout_data.append(chan.recv(nbytes))
if chan.recv_stderr_ready():
print "Recv Ready"
stderr_data.append(chan.recv_stderr(nbytes))
if chan.exit_status_ready():
print "Breaking"
break
print 'exit status: ', chan.recv_exit_status()
print ''.join(stdout_data)

This is possible by using the normal modules when you can concatenate the commands into one. Try
pwd ; cd myfolder2 ; pwd
as command. This should work but quickly becomes tedious when you have more complex commands which need arguments and horrible when the arguments contain spaces. The next step then is to copy a script with all the commands to the remote side and tell ssh to execute said script.
Another problem of this approach is that SSH doesn't return until all commands have executed.
Alternatively, you could build a "command server", i.e. a simple TCP server that listens for incoming connections and executes commands sent to it. It's pretty simple to write but also pretty insecure. Again, the solution is to turn the server into a (Python) script which reads commands from stdin and start that script remotely via SSH and then send commands.

Pexpect - silence ssh connection output

I'm using a simple pexpect script to ssh to a remote machine and grab a value returned by a command.
Is there any way, pexpect or sshwise I can use to ignore the unix greeting?
That is, from
child = pexpect.spawn('/usr/bin/ssh %s#%s' % (rem_user, host))
child.expect('[pP]assword: ', timeout=5)
child.sendline(spass)
child.expect([pexpect.TIMEOUT, prompt])
child.before = '0'
child.sendline ('%s' % cmd2exec)
child.expect([pexpect.EOF, prompt])
# Collected data processing
result = child.before
# logon to the machine returns a lot of garbage, the returned executed command is at the 57th position
print result.split('\r\n') [57]
result = result.split('\r\n') [57]
How can I simply get the returned value, ignoring,
the "Last successful login" and "(c)Copyright" stuff
and without having to concern with the value correct position?
Thanks !

If you have access to the server to which you are logging in, you can try creating a file named .hushlogin in the home directory. The presence of this file silences the standard MOTD greeting and similar stuff.
Alternatively, try ssh -T, which will disable terminal allocation entirely; you won't get a shell prompt, but you may still issue commands and read the response.
There is also a similar thread on ServerFault which may be of some use to you.

If the command isn't interactive, you can just run ssh HOST COMMAND to run the command without all the login excitement happening at all. If the command is interactive, you can frequently use the ssh -t option (ssh -t HOST COMMAND) to force pseudo-tty allocation and trick the remote process to think that it's running attached to a TTY.

I have used paramiko to automate ssh connection and I have found it useful. It can deal with greetings and silent execution.
http://www.lag.net/paramiko/

Hey there you kann kill all that noise by using the sys module and a small class:
class StreamToLogger(object):
"""
Fake file-like stream object that redirects writes to a logger instance.
"""
def __init__(self, logger, log_level=logging.INFO):
self.logger = logger
self.log_level = log_level
self.linebuf = ''
def write(self, buf):
for line in buf.rstrip().splitlines():
self.logger.log(self.log_level, line.rstrip())
#Mak
stdout_logger = logging.getLogger('STDOUT')
sl = StreamToLogger(stdout_logger, logging.INFO)
sys.stdout = sl
stderr_logger = logging.getLogger('STDERR')
sl = StreamToLogger(stderr_logger, logging.ERROR)
sys.stderr = sl
Can't remember where i found that snippet but it works for me :)

SCP a tar file using pexpect

I am using ssh to log into a camera, scp a tarball over to it and extract files from the tarbal and then run the script. I am having problems with Pexpect, though. Pexpect times out when the tarball is being copied over. It seem's not to wait until it is done. And then it start's doing the same thing with the untar command, The code I have is below:
ssh_newkey = 'Are you sure you want to continue connecting'
copy = pexpect.spawn('ssh service#10.10.10.10')
i=copy.expect([ssh_newkey,'password:',pexpect.EOF])
if i==0:
copy.sendline('yes')
i=copy.expect([ssh_newkey,'password:',pexpect.EOF])
if i==1:
copy.sendline("service")
print 'Password Accepted'
copy.expect('service#user:')
copy.sendline('su - root')
i=copy.expect('Password:')
copy.sendline('root')
i=copy.expect('#')
copy.sendline('cd /tmp')
i=copy.expect("#")
copy.sendline('scp user#20.20.20.20:/home/user/tarfile.tar.gz .')
i=copy.expect([ssh_newkey,'password:',pexpect.EOF])
if i==0:
copy.sendline('yes')
i=copy.expect([ssh_newkey,'password:',pexpect.EOF])
else:
pass
copy.sendline('userpwd')
i=copy.expect('#')
copy.sendline('tar -zxvf tarfile.tar.gz bin/installer.sh')
i=copy.expect("#")
copy.sendline("setsid /tmp/bin/installer.sh /tmp/tarfile.tar.gz > /dev/null 2>&1 &")
elif i==2:
print "I either got key or connection timeout"
else:
pass
Can anyone help find a solution for this?
Thanks

I'm not sure if this is correct, but I'd try setting the timeout to None:
copy = pexpect.spawn('ssh service#10.10.10.10', timeout=None)
According to the source code, pexpect seems to not check the timeout when it's set to None.
Anyway, the reason I'm answering this even though I'm not sure whether it solves your problem is that I wanted to recommend using paramiko instead. I had good experience using it for communication over SSH in the past.

Is there a reason your using pexpect or even paramiko?
if you setup a public/private key then you can just use as a single example:
command = "scp user#20.20.20.20:/home/user/tarfile.tar.gz"
split_command = shlex.split(command)
subprocess.call(split_command)
Then as per the suggestion above use paramiko to send commands.
you can use the keyfile for that as well:
The following class method will give you a persistent session (although it is untested):
#!/usr/bin/python
# -*- coding: utf-8 -*-
from __future__ import print_function
import os
from paramiko import SSHClient, AutoAddPolicy, AuthenticationException, RSAKey
from subprocess import call
class CommsSuite(object):
def __init__(self):
self.ssh_client = SSHClient()
#--------------------------------------
def _session_send(command):
"""
Use to send commands over ssh in a 'interactive_session'
Verifies session is present
If the interactive_session is not present then print the failed command.
This may be updated to raise an error,
which would probably make more sense.
#param command: the command to send across as a string
::TODO:: consider raise exception here as failed
session will most likely be fatal.
"""
if self.session.send_ready():
self.session.send("%s\n" % command)
else:
print("Session cannot send %s" % command)
#--------------------------------------
def _get_persistent_session(_timeout = 5):
"""
connect to the host and establish an interactive session.
#param _timeout: sets the timout to prevent blocking.
"""
privatekeyfile = os.path.expanduser('~/.ssh/id_rsa')#this must point to your keyfile
private_key = RSAKey.from_private_key_file(privatekeyfile)
self.ssh_client.set_missing_host_key_policy(AutoAddPolicy())
self.ssh_client.connect(hostname,
username = <username>,
pkey = private_key,
timeout = _timeout)
self.transport = self.ssh_client.get_transport()
self.session = self.transport.open_session()
self.session.exec_command("bash -s")
_get_persistent_session()
# build a comma seperated list of commands here as a string "[a,b,c]"
commands = ["tar -zxvf tarfile.tar.gz bin/installer.sh", "setsid /tmp/bin/installer.sh /tmp/tarfile.tar.gz > /dev/null 2>&1"]
# then run the list of commands
if len(commands) > 0:
for command in commands:
_session_send(command)
self.session.close()#close the session when done
CommsSuite()