How to control host from docker container?
For example, how to execute copied to host bash script?
This answer is just a more detailed version of Bradford Medeiros's solution, which for me as well turned out to be the best answer, so credit goes to him.
In his answer, he explains WHAT to do (named pipes) but not exactly HOW to do it.
I have to admit I didn't know what named pipes were when I read his solution. So I struggled to implement it (while it's actually very simple), but I did succeed.
So the point of my answer is just detailing the commands you need to run in order to get it working, but again, credit goes to him.
PART 1 - Testing the named pipe concept without docker
On the main host, chose the folder where you want to put your named pipe file, for instance /path/to/pipe/ and a pipe name, for instance mypipe, and then run:
mkfifo /path/to/pipe/mypipe
The pipe is created.
Type
ls -l /path/to/pipe/mypipe
And check the access rights start with "p", such as
prw-r--r-- 1 root root 0 mypipe
Now run:
tail -f /path/to/pipe/mypipe
The terminal is now waiting for data to be sent into this pipe
Now open another terminal window.
And then run:
echo "hello world" > /path/to/pipe/mypipe
Check the first terminal (the one with tail -f), it should display "hello world"
PART 2 - Run commands through the pipe
On the host container, instead of running tail -f which just outputs whatever is sent as input, run this command that will execute it as commands:
eval "$(cat /path/to/pipe/mypipe)"
Then, from the other terminal, try running:
echo "ls -l" > /path/to/pipe/mypipe
Go back to the first terminal and you should see the result of the ls -l command.
PART 3 - Make it listen forever
You may have noticed that in the previous part, right after ls -l output is displayed, it stops listening for commands.
Instead of eval "$(cat /path/to/pipe/mypipe)", run:
while true; do eval "$(cat /path/to/pipe/mypipe)"; done
(you can nohup that)
Now you can send unlimited number of commands one after the other, they will all be executed, not just the first one.
PART 4 - Make it work even when reboot happens
The only caveat is if the host has to reboot, the "while" loop will stop working.
To handle reboot, here what I've done:
Put the while true; do eval "$(cat /path/to/pipe/mypipe)"; done in a file called execpipe.sh with #!/bin/bash header
Don't forget to chmod +x it
Add it to crontab by running
crontab -e
And then adding
#reboot /path/to/execpipe.sh
At this point, test it: reboot your server, and when it's back up, echo some commands into the pipe and check if they are executed.
Of course, you aren't able to see the output of commands, so ls -l won't help, but touch somefile will help.
Another option is to modify the script to put the output in a file, such as:
while true; do eval "$(cat /path/to/pipe/mypipe)" &> /somepath/output.txt; done
Now you can run ls -l and the output (both stdout and stderr using &> in bash) should be in output.txt.
PART 5 - Make it work with docker
If you are using both docker compose and dockerfile like I do, here is what I've done:
Let's assume you want to mount the mypipe's parent folder as /hostpipe in your container
Add this:
VOLUME /hostpipe
in your dockerfile in order to create a mount point
Then add this:
volumes:
- /path/to/pipe:/hostpipe
in your docker compose file in order to mount /path/to/pipe as /hostpipe
Restart your docker containers.
PART 6 - Testing
Exec into your docker container:
docker exec -it <container> bash
Go into the mount folder and check you can see the pipe:
cd /hostpipe && ls -l
Now try running a command from within the container:
echo "touch this_file_was_created_on_main_host_from_a_container.txt" > /hostpipe/mypipe
And it should work!
WARNING: If you have an OSX (Mac OS) host and a Linux container, it won't work (explanation here https://stackoverflow.com/a/43474708/10018801 and issue here https://github.com/docker/for-mac/issues/483 ) because the pipe implementation is not the same, so what you write into the pipe from Linux can be read only by a Linux and what you write into the pipe from Mac OS can be read only by a Mac OS (this sentence might not be very accurate, but just be aware that a cross-platform issue exists).
For instance, when I run my docker setup in DEV from my Mac OS computer, the named pipe as explained above does not work. But in staging and production, I have Linux host and Linux containers, and it works perfectly.
PART 7 - Example from Node.JS container
Here is how I send a command from my Node.JS container to the main host and retrieve the output:
const pipePath = "/hostpipe/mypipe"
const outputPath = "/hostpipe/output.txt"
const commandToRun = "pwd && ls-l"
console.log("delete previous output")
if (fs.existsSync(outputPath)) fs.unlinkSync(outputPath)
console.log("writing to pipe...")
const wstream = fs.createWriteStream(pipePath)
wstream.write(commandToRun)
wstream.close()
console.log("waiting for output.txt...") //there are better ways to do that than setInterval
let timeout = 10000 //stop waiting after 10 seconds (something might be wrong)
const timeoutStart = Date.now()
const myLoop = setInterval(function () {
if (Date.now() - timeoutStart > timeout) {
clearInterval(myLoop);
console.log("timed out")
} else {
//if output.txt exists, read it
if (fs.existsSync(outputPath)) {
clearInterval(myLoop);
const data = fs.readFileSync(outputPath).toString()
if (fs.existsSync(outputPath)) fs.unlinkSync(outputPath) //delete the output file
console.log(data) //log the output of the command
}
}
}, 300);
Use a named pipe.
On the host OS, create a script to loop and read commands, and then you call eval on that.
Have the docker container read to that named pipe.
To be able to access the pipe, you need to mount it via a volume.
This is similar to the SSH mechanism (or a similar socket-based method), but restricts you properly to the host device, which is probably better. Plus you don't have to be passing around authentication information.
My only warning is to be cautious about why you are doing this. It's totally something to do if you want to create a method to self-upgrade with user input or whatever, but you probably don't want to call a command to get some config data, as the proper way would be to pass that in as args/volume into docker. Also, be cautious about the fact that you are evaling, so just give the permission model a thought.
Some of the other answers such as running a script. Under a volume won't work generically since they won't have access to the full system resources, but it might be more appropriate depending on your usage.
The solution I use is to connect to the host over SSH and execute the command like this:
ssh -l ${USERNAME} ${HOSTNAME} "${SCRIPT}"
UPDATE
As this answer keeps getting up votes, I would like to remind (and highly recommend), that the account which is being used to invoke the script should be an account with no permissions at all, but only executing that script as sudo (that can be done from sudoers file).
UPDATE: Named Pipes
The solution I suggested above was only the one I used while I was relatively new to Docker. Now in 2021 take a look on the answers that talk about Named Pipes. This seems to be a better solution.
However, nobody there mentioned anything about security. The script that will evaluate the commands sent through the pipe (the script that calls eval) must actually not use eval for the whole pipe output, but to handle specific cases and call the required commands according to the text sent, otherwise any command that can do anything can be sent through the pipe.
That REALLY depends on what you need that bash script to do!
For example, if the bash script just echoes some output, you could just do
docker run --rm -v $(pwd)/mybashscript.sh:/mybashscript.sh ubuntu bash /mybashscript.sh
Another possibility is that you want the bash script to install some software- say the script to install docker-compose. you could do something like
docker run --rm -v /usr/bin:/usr/bin --privileged -v $(pwd)/mybashscript.sh:/mybashscript.sh ubuntu bash /mybashscript.sh
But at this point you're really getting into having to know intimately what the script is doing to allow the specific permissions it needs on your host from inside the container.
My laziness led me to find the easiest solution that wasn't published as an answer here.
It is based on the great article by luc juggery.
All you need to do in order to gain a full shell to your linux host from within your docker container is:
docker run --privileged --pid=host -it alpine:3.8 \
nsenter -t 1 -m -u -n -i sh
Explanation:
--privileged : grants additional permissions to the container, it allows the container to gain access to the devices of the host (/dev)
--pid=host : allows the containers to use the processes tree of the Docker host (the VM in which the Docker daemon is running)
nsenter utility: allows to run a process in existing namespaces (the building blocks that provide isolation to containers)
nsenter (-t 1 -m -u -n -i sh) allows to run the process sh in the same isolation context as the process with PID 1.
The whole command will then provide an interactive sh shell in the VM
This setup has major security implications and should be used with cautions (if any).
Write a simple server python server listening on a port (say 8080), bind the port -p 8080:8080 with the container, make a HTTP request to localhost:8080 to ask the python server running shell scripts with popen, run a curl or writing code to make a HTTP request curl -d '{"foo":"bar"}' localhost:8080
#!/usr/bin/python
from BaseHTTPServer import BaseHTTPRequestHandler,HTTPServer
import subprocess
import json
PORT_NUMBER = 8080
# This class will handles any incoming request from
# the browser
class myHandler(BaseHTTPRequestHandler):
def do_POST(self):
content_len = int(self.headers.getheader('content-length'))
post_body = self.rfile.read(content_len)
self.send_response(200)
self.end_headers()
data = json.loads(post_body)
# Use the post data
cmd = "your shell cmd"
p = subprocess.Popen(cmd, stdout=subprocess.PIPE, shell=True)
p_status = p.wait()
(output, err) = p.communicate()
print "Command output : ", output
print "Command exit status/return code : ", p_status
self.wfile.write(cmd + "\n")
return
try:
# Create a web server and define the handler to manage the
# incoming request
server = HTTPServer(('', PORT_NUMBER), myHandler)
print 'Started httpserver on port ' , PORT_NUMBER
# Wait forever for incoming http requests
server.serve_forever()
except KeyboardInterrupt:
print '^C received, shutting down the web server'
server.socket.close()
If you are not worried about security and you're simply looking to start a docker container on the host from within another docker container like the OP, you can share the docker server running on the host with the docker container by sharing it's listen socket.
Please see https://docs.docker.com/engine/security/security/#docker-daemon-attack-surface and see if your personal risk tolerance allows this for this particular application.
You can do this by adding the following volume args to your start command
docker run -v /var/run/docker.sock:/var/run/docker.sock ...
or by sharing /var/run/docker.sock within your docker compose file like this:
version: '3'
services:
ci:
command: ...
image: ...
volumes:
- /var/run/docker.sock:/var/run/docker.sock
When you run the docker start command within your docker container,
the docker server running on your host will see the request and provision the sibling container.
credit: http://jpetazzo.github.io/2015/09/03/do-not-use-docker-in-docker-for-ci/
As Marcus reminds, docker is basically process isolation. Starting with docker 1.8, you can copy files both ways between the host and the container, see the doc of docker cp
https://docs.docker.com/reference/commandline/cp/
Once a file is copied, you can run it locally
docker run --detach-keys="ctrl-p" -it -v /:/mnt/rootdir --name testing busybox
# chroot /mnt/rootdir
#
I have a simple approach.
Step 1: Mount /var/run/docker.sock:/var/run/docker.sock (So you will be able to execute docker commands inside your container)
Step 2: Execute this below inside your container. The key part here is (--network host as this will execute from host context)
docker run -i --rm --network host -v /opt/test.sh:/test.sh alpine:3.7
sh /test.sh
test.sh should contain the some commands (ifconfig, netstat etc...) whatever you need.
Now you will be able to get host context output.
You can use the pipe concept, but use a file on the host and fswatch to accomplish the goal to execute a script on the host machine from a docker container. Like so (Use at your own risk):
#! /bin/bash
touch .command_pipe
chmod +x .command_pipe
# Use fswatch to execute a command on the host machine and log result
fswatch -o --event Updated .command_pipe | \
xargs -n1 -I "{}" .command_pipe >> .command_pipe_log &
docker run -it --rm \
--name alpine \
-w /home/test \
-v $PWD/.command_pipe:/dev/command_pipe \
alpine:3.7 sh
rm -rf .command_pipe
kill %1
In this example, inside the container send commands to /dev/command_pipe, like so:
/home/test # echo 'docker network create test2.network.com' > /dev/command_pipe
On the host, you can check if the network was created:
$ docker network ls | grep test2
8e029ec83afe test2.network.com bridge local
In my scenario I just ssh login the host (via host ip) within a container and then I can do anything I want to the host machine
I found answers using named pipes awesome. But I was wondering if there is a way to get the output of the executed command.
The solution is to create two named pipes:
mkfifo /path/to/pipe/exec_in
mkfifo /path/to/pipe/exec_out
Then, the solution using a loop, as suggested by #Vincent, would become:
# on the host
while true; do eval "$(cat exec_in)" > exec_out; done
And then on the docker container, we can execute the command and get the output using:
# on the container
echo "ls -l" > /path/to/pipe/exec_in
cat /path/to/pipe/exec_out
If anyone interested, my need was to use a failover IP on the host from the container, I created this simple ruby method:
def fifo_exec(cmd)
exec_in = '/path/to/pipe/exec_in'
exec_out = '/path/to/pipe/exec_out'
%x[ echo #{cmd} > #{exec_in} ]
%x[ cat #{exec_out} ]
end
# example
fifo_exec "curl https://ip4.seeip.org"
Depending on the situation, this could be a helpful resource.
This uses a job queue (Celery) that can be run on the host, commands/data could be passed to this through Redis (or rabbitmq). In the example below, this is occurring in a django application (which is commonly dockerized).
https://www.codingforentrepreneurs.com/blog/celery-redis-django/
To expand on user2915097's response:
The idea of isolation is to be able to restrict what an application/process/container (whatever your angle at this is) can do to the host system very clearly. Hence, being able to copy and execute a file would really break the whole concept.
Yes. But it's sometimes necessary.
No. That's not the case, or Docker is not the right thing to use. What you should do is declare a clear interface for what you want to do (e.g. updating a host config), and write a minimal client/server to do exactly that and nothing more. Generally, however, this doesn't seem to be very desirable. In many cases, you should simply rethink your approach and eradicate that need. Docker came into an existence when basically everything was a service that was reachable using some protocol. I can't think of any proper usecase of a Docker container getting the rights to execute arbitrary stuff on the host.
I am trying to spawn processes to a remote node. The code resembles the answer I have found
here
if __name__ == "__main__":
from pathos.pp import ParallelPythonPool as Pool
def sleepy_squared(x):
from time import sleep
sleep(1.0)
import socket
print(socket.gethostname())
return x**2
p = Pool(8, servers=('151.49.140.246:1234',))
# use an asynchronous parallel map
x = [1,2,3,4,5,6,7,8,9]
res = p.amap(sleepy_squared, x)
print(res.get())
The problem is that when I run this code, pathos keeps running on my local machine ignoring the servers attribute. I would like the function to run only on the remote server (or crash if not available).
In order to configure the server I'm launching the file ppserver.py (found in the Scripts folder in the Anaconda installation). I have tried launching it with multiple configurations
python ppserver.py -d
python ppserver.py -i 127.0.0.1 -p 1234 -d
python ppserver.py -i 151.49.140.246 -p 1234 -b 255.255.255.0 -d
(the last one doesn't even work)
I can't understand honestly if the problem is with the configuration server side (the server is listening though) or the client side (servers are ignored) or both.
I want to run an HTML file in localhost:8080, I'm using the command:
python3 -m http.server
Problem is when I try to open localhost:8080 it downloads the HTML file instead of displaying it.
Problem is when I try to open localhost:8080 it downloads the HTML file instead of displaying it.
You want to open http://localhost:8000 instead.
When you use the command you mentioned, python3 -m http.server, it defaults to port 8000, as explained in its startup output:
$ python3 -m http.server
Serving HTTP on 0.0.0.0 port 8000 (http://0.0.0.0:8000/) ...
We don't know what different server you have running on port 8080, but apparently it doesn't put Content-type: text/html in its output headers.
viewing webserver http headers
It's easy to view those headers, e.g. with wget use the -S switch.
You need to add an option that'll put your website on port 8080 because the http.server command defaults to port 8000.
You can do this using:
python3 -m http.server 8080
Then when you go to 0.0.0.0:8080 it should show you your webpage instead of a download prompt.
Also, you might have another instance of http.server running on port 8080.
You can find the PID of this task using:
ps -A | grep "python3"
Which should show something that looks like this:
Then you could kill it using:
kill <PID-FOR-PYTHON3-INSTANCE>
Or in my case the task that's running on port 8080 is:
kill 6856
Or, if you don't mind, just kill all Python3 tasks using:
killall python3
Which in my case would kill both Python3 tasks.
WARNING: be very, VERY careful before running the killall command, because this command will NOT save your work.
UPDATE: that blurry section in the picture is my username, I wasn't sure if it would be against the rules to include it.
Good luck.
I'm trying to open Tcpdump to capture UDP packets from a Python script. Here is my code:
os.system("tcpdump -i wlp2s0 -n dst 8.8.8.8 -w decryptedpackets.pcap &")
testfile = urllib.URLopener()
s = socket(AF_INET, SOCK_DGRAM)
host = "8.8.8.8"
port = 5000
buf = 1024
addr = (host, port)
s.connect((host, port))
f = open("file.txt", "rb")
data = f.read(buf)
while (data):
if (s.sendto(data, addr)):
print "sending ..."
data = f.read(buf)
I am able to capture the packets (pcap file has content) if I manually execute this command in shell:
tcpdump -i wlp2s0 -n dst 8.8.8.8 -w decryptedpackets.pcap &
However, If I use os.system() I can't capture the packets. ( When I open the pcap file, I find it empty)
I have verified and found that there is a process that gets created when the Python script is executed:
root 10092 0.0 0.0 17856 1772 pts/19 S 10:25 0:00
tcpdump -i wlp2s0 -n dst 8.8.8.8 -w decryptedpackets.pcap
Also, I'm running this as a sudo user to avoid any permission problems.
Any suggestions what could be causing this problem ?
From python documentation.
os.system(command) Execute the command (a string) in a subshell. This
is implemented by calling the Standard C function system(), and has
the same limitations. Changes to sys.stdin, etc. are not reflected in
the environment of the executed command.
On Unix, the return value is the exit status of the process encoded in
the format specified for wait(). Note that POSIX does not specify the
meaning of the return value of the C system() function, so the return
value of the Python function is system-dependent.
On Windows, the return value is that returned by the system shell
after running command, given by the Windows environment variable
COMSPEC: on command.com systems (Windows 95, 98 and ME) this is always
0; on cmd.exe systems (Windows NT, 2000 and XP) this is the exit
status of the command run; on systems using a non-native shell,
consult your shell documentation.
The subprocess module provides more powerful facilities for spawning
new processes and retrieving their results; using that module is
preferable to using this function. See the Replacing Older Functions
with the subprocess Module section in the subprocess documentation for
some helpful recipes.
I think that os.system returns immediately and the script keeps going, there's no problem with the code but you probably need to create a separate thread and call os.system with the tcp-dump since I believe that it is returning immediately.
did you use the -w switch too when running from the command line instead of the script? If not your problem might be buffering and you should have a look at the -U option. Apart from that the -w switch should be used before the capture expression, i.e. the expression should be the last thing. In summary: tcpdump -i wlp2s0 -n -w out.pcap -U dst 8.8.8.8
– Steffen Ullrich
Having a server that has to handle lots of TCP-requests from gprs-modules I think it is handy to set up something to protect this server from multiple requests from certain ip's.
Now I want to make something(within python) that will check how much times a certain ip tries to connect and if this exceeds a given amount of tries this ip will be blocked for a given amount of time (or forever).
I am wondering if there are libraries present to do this, or how I should tackle this problem in my code.
Don't tackle this from your code - this is what a firewall is designed to do.
Using iptables its trivial:
iptables -I INPUT -p tcp --dport $PORT -i eth0 -m state --state NEW -m recent --set
iptables -I INPUT -p tcp --dport $PORT -i eth0 -m state --state NEW -m recent --update --seconds 600 --hitcount 2 -j DROP
The above means "drop anything that makes more than 2 connection attempts in 10 minutes at port $PORT"
If you decide you do want to handle this in code, you don't need a separate library (although using one will probably be more efficient), you can add something like the following to your connection handler:
from collections import defaultdict, deque
from datetime import datetime
floodlog = defaultdict(deque)
def checkForFlood(clientIP):
"""check if how many times clientIP has connected within TIMELIMIT, and block if more than MAX_CONNECTEIONS_PER_TIMELIMIT"""
now = datetime.now()
clientFloodLog = floodlog[clientIP]
clientFloodLog.append(now)
if len(clientFloodLog) > MAX_CONNECTIONS_PER_TIMELIMIT:
earliestLoggedConenction = clientFloodLog.popleft()
if now - earliestLoggedConnection < TIMELIMIT:
blockIP(clientIP)
As Burhan Khalid said. You don't want to try this in your code. It's not very performant and that's what firewalls are made for.
iptables -I INPUT -p tcp --dport $PORT -i eth0 -m state --state NEW -m recent --set
iptables -I INPUT -p tcp --dport $PORT -i eth0 -m state --state NEW -m recent --update --seconds 600 --hitcount 2 -j DROP
This example is very usefull but not very handy. The problem is that you're also limiting good/trusted connections.
You need to be more flexible. On a linux-based OS you can use fail2ban. It's a very handy tool to prevent your services of bruteforce attacks by using dynamic iptables rules. On Debian/Ubuntu you can install it by using apt-get. If you're on CentOS you need to use a third party repository.
Log every connection into a logfile:
[Jun 3 03:52:23] server [pid]: Connect from 1.2.3.4
[Jun 3 03:52:23] server [pid]: Failed password for $USER from 1.2.3.4 port $DST
[Jun 3 03:52:23] server [pid]: Connect from 2.3.4.5
[Jun 3 03:52:23] server [pid]: Successful login from 2.3.4.5
Now monitor this file with fail2ban and define a regex to difference between successful and failed logins. Tell fail2ban how long it should block the IP for you and if you would like to get an email notification.
The documentation is very good so have a look onto here how you have to configure fail2ban to monitor your logile: fail2ban docu
You don't have to watch only for failed logins. You can also try to watch out for portscans. And the biggest win: don't only secure your application. Safe also your SSH, HTTP, etc logins for beeing bruteforced! ;)
For a pure Python solution, I think you could reuse something I developed for the same problem, but for the client point of view: avoiding to issue more than 'x tries per sec' to a service provider.
The code is available on GitHub: you can probably reuse most of it, but you'll need to replace the time.sleep call for your 'blacklisting' mechanism.