Develop Reference

Connecting to user dbus as root

If we open a python interpreter normally and enter the following:
import dbus
bus = dbus.SessionBus()
bus.list_names()
We see all the services on the user's session dbus. Now suppose we wanted to do some root-only things in the same script to determine information to pass through dbus, so we run the interpreter with sudo python and run the same thing, we only see a short list of items on the root user's session dbus, and attempting to connect to anything that was on the user dbus with get_object produces a not found error accordingly.
So far I've tried inserting
import os
os.seteuid(int(os.environ['SUDO_UID']))
But this only makes SessionBus() give a org.freedesktop.DBus.Error.NoReply so this is probably nonsense. Is there a way to connect to a user's dbus service as a super user, with the python dbus bindings?

I have little knowledge about DBus, but that question got me curious.
TL;DR: Use dbus.bus.BusConnection with the socket address for the target user and seteuid for gaining access.
First question: What socket does DBus connect to for the session bus?
$ cat list_bus.py
import dbus
print(dbus.SessionBus().list_names())
$ strace -o list_bus.trace python3 list_bus.py
$ grep ^connect list_bus.trace
connect(3, {sa_family=AF_UNIX, sun_path="/run/user/1000/bus"}, 20) = 0
Maybe it relies on environment variables for this? Gotcha!
$ env|grep /run/user/1000/bus
DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/1000/bus
Stracing the behaviour from the root account it appears that it does not know the address to connect to. Googling for the variable name got me to the D-Bus Specification, section "Well-known Message Bus Instances".
Second question: Can we connect directly to the socket without having the D-Bus library guess the right address? The dbus-python tutorial states:
For special purposes, you might use a non-default Bus, or a connection which isn’t a Bus at all, using some new API added in dbus-python 0.81.0.
Looking at the changelog, this appears to refer to these:
Bus has a superclass dbus.bus.BusConnection (a connection to a bus daemon, but without the shared-connection semantics or any deprecated API) for the benefit of those wanting to subclass bus daemon connections
Let's try this out:
$ python3
Python 3.9.2 (default, Feb 28 2021, 17:03:44)
>>> from dbus.bus import BusConnection
>>> len(BusConnection("unix:path=/run/user/1000/bus").list_names())
145
How about root access?
# python3
>>> from dbus.bus import BusConnection
>>> len(BusConnection("unix:path=/run/user/1000/bus").list_names())
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python3/dist-packages/dbus/bus.py", line 124, in __new__
bus = cls._new_for_bus(address_or_type, mainloop=mainloop)
dbus.exceptions.DBusException: org.freedesktop.DBus.Error.NoReply: Did not
receive a reply. Possible causes include: the remote application did not send
a reply, the message bus security policy blocked the reply, the reply timeout
expired, or the network connection was broken.
>>> import os
>>> os.seteuid(1000)
>>> len(BusConnection("unix:path=/run/user/1000/bus").list_names())
143
So this answers the question: Use BusConnection instead of SessionBus and specify the address explicitly, combined with seteuid to gain access.
Bonus: Connect as root without seteuid
Still I'd like to know if it is possible
to access the bus directly as root user, without resorting to seteuid. After
a few search queries, I found a systemd ticket
with this remark:
dbus-daemon is the component enforcing access ... (but you can drop an xml policy file in, to make it so).
This led me to an askubuntu question discussing how to modify the site local session bus policy.
Just to play with it, I ran this in one terminal:
$ cp /usr/share/dbus-1/session.conf session.conf
$ (edit session.conf to modify the include for local customization)
$ diff /usr/share/dbus-1/session.conf session.conf
50c50
< <include ignore_missing="yes">/etc/dbus-1/session-local.conf</include>
---
> <include ignore_missing="yes">session-local.conf</include>
$ cat > session-local.conf
<busconfig>
<policy context="mandatory">
<allow user="root"/>
</policy>
</busconfig>
$ dbus-daemon --config-file session.conf --print-address
unix:abstract=/tmp/dbus-j0r67hLIuh,guid=d100052e45d06f248242109262325b98
$ dbus-daemon --config-file session.conf --print-address
unix:abstract=/tmp/dbus-j0r67hLIuh,guid=d100052e45d06f248242109262325b98
In another terminal, I can not attach to this bus as a root user:
# python3
Python 3.9.2 (default, Feb 28 2021, 17:03:44)
>>> from dbus.bus import BusConnection
>>> address = "unix:abstract=/tmp/dbus-j0r67hLIuh,guid=d100052e45d06f248242109262325b98"
>>> BusConnection(address).list_names()
dbus.Array([dbus.String('org.freedesktop.DBus'), dbus.String(':1.0')], signature=dbus.Signature('s'))
This should also enable accessing all session busses on the system, when installing session-local.conf globally:
# cp session-local.conf /etc/dbus-1/session-local.conf
# kill -HUP 1865 # reload config of my users session dbus-daemon
# python3
>>> from dbus.bus import BusConnection
>>> len(BusConnection("unix:path=/run/user/1000/bus").list_names())
143
And it works - now root can connect to any session bus without resorting to seteuid. Don't forget to
# rm /etc/dbus-1/session-local.conf
if your root user does not need this power.

Bluehorn's answer helped me. I figured I'd share my solution. I'm only a few months into learning Python (coming from just shell scripting) so if this is really wrong and just happens to work on my system please let me know.
These are parts from a daemon I wrote to monitor CPU temps and control the fan speeds in Linux so it needs root permissions. Not sure how well it would work if ran as a regular user when multiple users are logged in. I'm guessing it wouldn't...
import os, pwd
from dbus import SessionBus, Interface
from dbus.bus import BusConnection
# Subclassing dbus.Interface because why not
class Dbus(Interface):
def __init__(self, uid):
method = 'org.freedesktop.Notifications'
path = '/' + method.replace('.', '/')
if os.getuid() == uid:
obj = SessionBus().get_object( method, path )
else:
os.seteuid(uid)
obj = BusConnection( "unix:path=/run/user/" + str(uid) + "/bus" )
obj.get_object( method, path )
super().__init__(obj, method)
# Did this so my notifications would work
# when running as root or non root
class DbusNotificationHandler:
app_icon = r"/path/to/my/apps/icon.png"
name = "MacFanD"
def __init__(self):
loggedIn, users = [ os.getlogin() ], []
for login in pwd.getpwall():
if login.pw_name in loggedIn:
users.append( login.pw_uid )
self.users = []
for i in users:
self.users.append( Dbus(i) )
def notification(self, msg, mtype=None):
if not isinstance(msg, list) or len(msg) < 2:
raise TypeError("Expecting a list of 2 for 'msg' parameter")
hint = {}
if mtype == 'temp':
icon = 'dialog-warning'
hint['urgency'] = 2
db_id = 498237618
timeout = 0
elif mtype == 'warn':
icon = 'dialog-warning'
hint['urgency'] = 2
db_id = 0
timeout = 5000
else:
icon = self.app_icon
hint['urgency'] = 1
db_id = 0
timeout = 5000
for db in self.users:
db.Notify( self.name, db_id, icon, msg[0], msg[1:], [], hint, timeout )
handler = DbusNotificationHandler()
notify = handler.notification
msg = [ "Daemon Started", "Daemon is now running - %s"%os.getpid() ]
notify(msg)
temp = "95 Celsius"
msg = [ "High Temp Warning", "CPU temperature has reached %s"%temp ]
notify(msg, 'warn')

You can set DBUS_SESSION_BUS_ADDRESS environment variable to choose the dbus session you want to connect to.
Incorrect permissions (i.e., missing the seteuid) causes an immediate NoReply, and not defining DBUS_SESSION_BUS_ADDRESS responded with Using X11 for dbus-daemon autolaunch was disabled at compile time, set your DBUS_SESSION_BUS_ADDRESS instead.
Here's the test code I used:
import os
import dbus
# become user
uid = os.environ["SUDO_UID"]
print(f"I'm {os.geteuid()}, becoming {uid}")
os.seteuid(int(uid))
# set the dbus address
os.environ["DBUS_SESSION_BUS_ADDRESS"] = f"unix:path=/run/user/{uid}/bus"
bus = dbus.SessionBus()
print(bus.list_names())
# I'm 0, becoming 1000
# dbus.Array([dbus.String('org.freedesktop.DBus'), dbus.String('org.fr .. <snip>

fabric 2 traffic generation with non-blocking commands

I need to run some tests with a traffic generator that has different client and server commands. I would like to roll this into a fabric2 script which executes the traffic generation commands while cd'd into /root.
I have public-key authentication on the iperf machines. How can I run this traffic generation test under fabric2?

This was a little interesting to get running because the fabric2 docs don't include much information about run() arguments... you need to look at the invoke Runner.run() documentation to see all fabric run() keywords.
The key to making iperf work in this case was setting pty=True and asynchronous=True when I run the iperf server commands. If I did not run the iperf server as asynchronous, it would block execution of the iperf client command.
# Save this script as run_iperf.py and run with "python run_iperf.py"
from getpass import getuser
import os
#from fabric import Config, SerialGroup, ThreadingGroup, exceptions, runners
#from fabric.exceptions import GroupException
from fabric import Connection
server_vm = "10.1.0.1"
client_vm = "10.2.0.1"
# This matters because my user .ssh/id_rsa.pub is authorized on the remote sytems
assert getuser()=="mpenning"
hosts = list()
conn1 = Connection(host=client_vm, user="root",
connect_kwargs={"key_filename": os.path.expanduser("~/.ssh/id_rsa")})
conn2 = Connection(host=server_vm, user="root",
connect_kwargs={"key_filename": os.path.expanduser("~/.ssh/id_rsa")})
hosts.append(conn1)
hosts.append(conn2)
iperf_udp_client_cmd = "nice -19 iperf3 --plus-more-client-commands"
iperf_udp_server_cmd = "nice -19 iperf3 --plus-more-server-commands"
# ThreadingGroup is optional for this use case, but the iperf commands
# definitely require pty and asynchronous (server-side)...
# ThreadingGroup() is required for concurrent fabric commands.
#
# Uncomment below to use ThreadingGroup()...
# t_hosts = ThreadingGroup.from_connections(hosts)
#
# also ref invoke Runner.run() for more run() args:
# -> https://github.com/pyinvoke/invoke/blob/master/invoke/runners.py
with conn2.cd("/root"):
conn2.run(iperf_udp_server_cmd, pty=True, asynchronous=True, disown=False, echo=True)
with conn1.cd("/root"):
conn1.run("sleep 1;%s" % iperf_udp_client_cmd, pty=True, asynchronous=False, echo=True)
This script was loosely based-on this answer:
https://stackoverflow.com/a/53763786/667301

Pass open connection between two different python programs

Pass open connection between two different python programs
Here is my use case..
I want to connect to ssh server ( network / linux/ windows) and open the connection.
And have another python program continue to use open session from step 1 and provide user inputs (commands )
The reason programs have to be separate is the caller is going to orchestrate these programs into a graphical process flow inside a designer workflow e.g mistral.

CAN I PASS THE HANDLE OF WHATEVER? NO (I'm pretty sure at least)
... why not just pass the credentials and let it open connection?
or basically your first program would have to run some sort of server, that listens for commands and forwards them up the tree ... something like this i guess
one way of passing information between two applications might be to have a flask server running on one and the other calls the flask endpoints (you dont have to use flask ... theres many ways to do this)
import argparse
import requests
from flask import Flask,request
def prog_1():
''' manage some open connection '''
my_open_thing = OpenConnection(stuff)
app = flask.Flask("__main__")
#app.route("/execute"):
def execute_command():
if request.form.get("CMD",None):
my_open_thing.send(request.form['CMD'])
return my_open_thing.recv().to_string()
app.run(port=23123)
def prog_2():
'''interact with other thing'''
while 1:
cmd = input("CMD:")
if cmd in ["quit","q"]:
break
print(requests.post("http://localhost:23123/execute",{"CMD":cmd}).content)
if __name__ == "__main__":
parser = argparse.ArgumentParser()
parser.add_argument('TYPE',choices=['manager','client'],help="Serve the connection, or use the manager")
parser.parse_args()
if parser.TYPE == "manager":
prog_1()
else:
prog_2()

Multiple server login using Putty with Pywinauto python script

How to logged in to multiple server using pywinauto application? I am using below program for access putty and run the command, This is work for single server when i have defined like
app = Application ().Start (cmd_line = 'C:\Program Files\PuTTY\putty.exe -ssh user#10.55.167.4')
But while i am passing with for loop to do the same task for another server it does not work.
from pywinauto.application import Application
import time
server = [ "10.55.167.4", "10.56.127.23" ]
for inser in server:
print(inser)
app = Application ().Start (cmd_line = 'C:\Program Files\PuTTY\putty.exe -ssh user#inser')
putty = app.PuTTY
putty.Wait ('ready')
time.sleep (1)
putty.TypeKeys ("aq#wer")
putty.TypeKeys ("{ENTER}")
putty.TypeKeys ("ls")
putty.TypeKeys ("{ENTER}")

pywinauto is a Python module to automatize graphical user interface (GUI) operations for example to simulate mouse clicking and everything else humans used to do on GUIs to interact with the computer. SSH is a remote access protocol designed primarily for command line and having excellent programmatic support in Python. Putty is a little GUI tool to manage SSH and Telnet connections. Although, based on quick check, I think it is possible to read the console output (you mean in cmd.com?) by pywinauto, I think your approach is unnecessarily complicated: you don't need to use a GUI tool designed for human interaction to access a protocol with excellent command line and programmatic library support. I suggest you to use paramiko which gives a very simple and convenient interface to SSH:
import paramiko
def ssh_connect(server, **kwargs):
client = paramiko.client.SSHClient()
client.load_system_host_keys()
# note: here you can give other paremeters
# like user, port, password, key file, etc.
# also you can wrap the call below into
# try/except, you can expect many kinds of
# errors here, if the address is unreachable,
# times out, authentication fails, etc.
client.connect(server, **kwargs)
return client
servers = ['10.55.167.4', '10.56.127.23']
# connect to all servers
clients = dict((server, ssh_connect(server)) for server in servers)
# execute commands on the servers by the clients, 2 examples:
stdin, stdout, stderr = clients['10.55.167.4'].exec_command('pwd')
print(stdout.read())
# b'/home/denes\n'
stdin, stdout, stderr = clients['10.56.127.23'].exec_command('rm foobar')
print(stderr.read())
# b"rm: cannot remove 'foobar': No such file or directory\n"
# once you finished close the connections
_ = [cl.close() for cl in clients.values()]

How to wrap a zeromq bind socket in a twisted application service?

I am using txzmq and twisted to build a listener service that will process some data through a push-pull pattern. Here's a working code:
from txzmq import ZmqFactory, ZmqEndpoint, ZmqPullConnection
from twisted.internet import reactor
zf = ZmqFactory()
endpoint = ZmqEndpoint('bind', 'tcp://*:5050')
def onPull(data):
# do something with data
puller = ZmqPullConnection(zf, endpoint)
puller.onPull = onPull
reactor.run()
My question is - how can I wrap this code in a twisted application service? That is, how to wrap this into a specific service (e.g. MyService) that I can later run with:
from twisted.application.service import Application
application = Application('My listener')
service = MyService(bind_address='*', port=5050)
service.setServiceParent(application)
with the twistd runner?

IService defines what it means to be a service. Service is a base class that is often helpful when implementing a new service.
Just move your ZMQ initialization code into a startService method of an object that implements IService, perhaps a subclass of Service. If you want to do proper cleanup too, then add some cleanup code to the stopService method of that class.