Automate scp file transfer - between Synology DS and a dd-wrt router

Question

Summary: I'm looking to set-up a bash script to transfer a single file from a Synology DS to a dd-wrt router (Netgear WNR3500Lv1).

The problem: router only allows me to write in the /tmp folder, which is erased after reboot. Instead of checking if the router rebooted, I would like to just push the file ("hosts") to it automatically every morning.

The solution that did not work: Similar question was asked before (Automate scp file transfer using a shell script), however none of the answers work for me. The shell in Synology DS does not have required commands: expect, spawn, interact or sshpass. It does have rsync, but the router does not have it.

The solution with SSH keys does not work for me either, because I can't write anything permanently to the router -> so after reboot the setup is gone.

Question: is there a way to add the required commands to DS shell? Or perhaps a simpler way to accomplish this - so that it can happen automatically without prompting for password?

Answer 1

The code below works with python 3 :

import os
def run():
    print('Start script')
    pid, fd = os.forkpty()
    if pid==0:
        os.system('scp ...')
    while True:
        data = os.read(fd,1024)
        print (data)
        if "password:".encode() in data:
            os.write(fd,"YOUR-PASSWORD\n".encode())
run()

Answer 2

It looks like this is not possible with the limited linux bash of Synology DSM. However, it turns out scp can be automated using Python.

I have combined code from this question: How to scp in python?, with the script from this thread: https://unix.stackexchange.com/questions/276336/automatically-enter-ssh-password-without-using-ssh-key-expect-sshpass-or-p, and then automated it using this guide: https://forum.synology.com/enu/viewtopic.php?t=141745

As a result, I have the following Python script:

import os
def run():
    pid, fd = os.forkpty()
    if pid==0:
        os.system('scp "%s" "%s:%s"' % ('myfile.txt', 'user@domain.com', 'path') )
    while True:
        data = os.read(fd,1024)
        print data
        if "password:" in data:    # ssh prompt
            os.write(fd,"mypassword\n")
        elif "100%" in data:  # upload done
            os.write(fd,"echo hello\n")
            os.write(fd,"echo bye\n")
            os.write(fd,"exit\n")
            os.close(fd)

run()

This does the job, however, it always exits with OSError: [Errno 9] Bad file descriptor.