Secure Copy File from remote server via scp and os module in Python

Question

I'm pretty new to Python and programming. I'm trying to copy a file between two computers via a python script. However the code

os.system("ssh " + hostname + " scp " + filepath + " " + user + "@" + localhost + ":" cwd)

won't work. I think it needs a password, as descriped in How to copy a file to a remote server in Python using SCP or SSH?. I didn't get any error logs, the file just won't show in my current working directory.

However every other command with os.system("ssh " + hostname + "command") or os.popen("ssh " + hostname + "command") does work. -> command = e.g. ls

When I try ssh hostname scp file user@local:directory in the commandline it works without entering a password.

I tried to combine os.popen commands with getpass and pxssh module to establish a ssh connection to the remote server and use it to send commands directly (I only tested it for an easy command):

import pxssh
import getpass

ssh = pxssh.pxssh()
ssh.force_password = True
hostname = raw_input("Hostname: ")
user = raw_input("Username: ")
password = getpass.getpass("Password: ")
ssh.login(hostname, user, password)
test = os.popen("hostname")
print test

But I'm not able to put commands through to the remote server (print test shows, that hostname = local and not the remote server), however I'm sure, the conection is established. I thought it would be easier to establish a connection than always use "ssh " + hostname in the bash commands. I also tried some of the workarounds in How to copy a file to a remote server in Python using SCP or SSH?, but I must admit due to lack of expirience I didn't get them to work.

Thanks a lot for helping me.

Solution

I think the easiest (to avoid having to enter a password) and most secure way to go about this is to first set public/private key authentication. Once that is done, and you can log in to the remote system by doing ssh user@hostname, the following bash command would do the trick:

scp some/complete/path/to/file user@remote_system:some/remote/path

The corresponding Python code would be:

import subprocess

filepath = "some/complete/path/to/file"
hostname = "user@remote_system"
remote_path = "some/remote/path"

subprocess.call(['scp', filepath, ':'.join([hostname,remote_path])])