Have you ever wanted to quickly execute certain commands in your Linux machine ? or you want to routinely execute some lines of code in your server to automate stuff ? In this tutorial, you will learn how you can write a simple Python script to execute BASH commands in your Linux machine.
RELATED: How to Brute-Force SSH Servers in Python.
We will be using paramiko library, let's install it:
pip3 install paramiko
Defining some connection credentials:
import paramiko hostname = "192.168.1.101" username = "test" password = "abc123"
In the above code, I've defined the hostname, username and password, this is my local Linux box, you need to edit these variables for your case, or you may want to make command line argument parsing using argparse module as we usually do in such tasks.
Note that, it isn't safe to connect to SSH using credentials like that, you can configure your SSH listener daemon to only accept public authentication key, instead of using a password. However, for demonstration purposes, we will be using a password.
Now let's create a list of commands you wish to execute on that remote machine:
commands = [ "pwd", "id", "uname -a", "df -h" ]
In this case, just simple commands that outputs some useful information about the operating system.
The below code is responsible for initiating the SSH client and connecting to the server:
# initialize the SSH client client = paramiko.SSHClient() # add to known hosts client.set_missing_host_key_policy(paramiko.AutoAddPolicy()) try: client.connect(hostname=hostname, username=username, password=password) except: print("[!] Cannot connect to the SSH Server") exit()
Now let's iterate over commands we just defined and execute them one by one:
# execute the commands for command in commands: print("="*50, command, "="*50) stdin, stdout, stderr = client.exec_command(command) print(stdout.read().decode()) err = stderr.read().decode() if err: print(err)
Here is my results:
================================================== pwd ================================================== /home/test ================================================== id ================================================== uid=1000(test) gid=0(root) groups=0(root),27(sudo) ================================================== uname -a ================================================== Linux rockikz 4.17.0-kali1-amd64 #1 SMP Debian 4.17.8-1kali1 (2018-07-24) x86_64 GNU/Linux ================================================== df -h ================================================== Filesystem Size Used Avail Use% Mounted on udev 1.9G 0 1.9G 0% /dev tmpfs 392M 6.2M 386M 2% /run /dev/sda1 452G 410G 19G 96% / tmpfs 2.0G 0 2.0G 0% /dev/shm tmpfs 5.0M 0 5.0M 0% /run/lock tmpfs 2.0G 0 2.0G 0% /sys/fs/cgroup tmpfs 392M 12K 392M 1% /run/user/131 tmpfs 392M 0 392M 0% /run/user/1000
Awesome, these commands were executed successfully on my Linux machine !
Now that you know how you can execute commands one by one, let's dive a little bit deeper and execute entire BASH (.sh) scripts.
Consider this BASH script (named "script.sh"):
cd Desktop mkdir test_folder cd test_folder echo "$PATH" > path.txt
After the SSH connection, instead of iterating for commands, now we read the content of this script and execute it:
# read the BASH script content from the file bash_script = open("script.sh").read() # execute the BASH script stdin, stdout, stderr = client.exec_command(bash_script) # read the standard output and print it print(stdout.read().decode()) # print errors if there are any err = stderr.read().decode() if err: print(err) # close the connection client.close()
exec_command() method executes the script and returns standard input, standard output and standard error respectively, we will read from stdout and stderr if there are any, and then we close the SSH connection.
After the execution of the above code, a new file test_folder was created in Desktop and got a text file inside that contain the global $PATH variable:
As you can see, this is useful for many scenarios, for example, you may want to manage your servers only with executing Python scripts remotely, you can anything you want ! Let us know what you did with this in the comments below !
And by the way, If you want to run more complex jobs on a remote server you might want to look into Ansible instead.
Feel free to edit the code as you wish, for example, you may want to parse command line arguments with argparse.
READ ALSO: How to Create a Reverse Shell in Python.
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