Python, Subprocess call into a input field

Question

Im trying to change the password with python on a router with a linux OS. The problem is im stuck in the input field which i've to complete with return.

My code looks like this:

root_password_bytes = subprocess.check_output(["pwgen", "-1", "32"])
root_password = root_password_bytes.decode('utf-8')

#root_password = subprocess.check_output(["pwgen", "-1", "32"])
#print(f'printing root passwd: {root_password}')

# Try 1: with decode and no quotation marks
subprocess.call([f"ssh [email protected] printf {root_password}\n{root_password}\n | passwd"], shell=True)
# error: Syntax error: "|" unexpected

# Try 2: with decode and with quotation marks
subprocess.call([f"ssh [email protected] printf '{root_password}\n{root_password}\n' | passwd"], shell=True)
# error: it tries to execute the command on my machine and not on the router

# Try 3: WITHOUT decode and no quotation marks
#subprocess.call([f"ssh [email protected] printf {root_password}\n{root_password}\n | passwd"], shell=True)
# error: Syntax error: "|" unexpected

# Try 4: WITHOUT decode and with quotation marks
#subprocess.call([f"ssh [email protected] printf '{root_password}\n{root_password}' | passwd"], shell=True)
# error: it tries to execute the command on my machine and not on the router
# passwd: Bearbeitungssfehler des Legitimierungszeichens

# Try 5: Without passwd as var
subprocess.call([f"ssh [email protected] echo 'onetwothree\nonetwothree\n' | passwd"], shell=True)
# error: it tries to execute the command on my machine and not on the router
# passwd: Bearbeitungssfehler des Legitimierungszeichens
subprocess.call([f"ssh [email protected] 'printf onetwothree\n' | passwd"], shell=True)

# Try 6: different quotation marks most success it types the first password in
# but after using new-line (\n) the pipe will be unexpected
subprocess.call([f"ssh [email protected] 'printf onetwothree123 | passwd'"], shell=True)
# so this will not work
subprocess.call([f"ssh [email protected] 'printf onetwothree123\nonetwothree123\n | passwd'"], shell=True)

eagr · Accepted Answer · 2022-06-24 12:18:59Z

2

You run 2 different and unrelated sub processes, they don't share input/output. You should either use communicate() to send characters to the running process (also see examples at the bottom of the doc).

Or, you can modify the command to contain the password so you don't have to communicate with it: ssh root@ip "echo 123 | passwd --stdin root"

answered Jun 24, 2022 at 12:18

eagr

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2 Comments

gubwan Over a year ago

i have edited the code at the 1. post

eagr Over a year ago

you missed the --stdin, also notice the quotes "" around the echo | passwd

gubwan · Accepted Answer · 2022-07-01 12:36:41Z

0

I now use the following solution

    root_password_bytes = subprocess.check_output(["pwgen", "-1", "32"])
    root_password = root_password_bytes.decode('utf-8')

    cmds = [
        f' rm -f /etc/dropbear/authorized_keys\n',
        f' printf "{root_password}{root_password}" | passwd\n',
        f' reboot'
    ]

    proc = subprocess.Popen(["ssh", "[email protected]"], stdin=subprocess.PIPE)
    for cmd in cmds:
        proc.stdin.write(f'{cmd}'.encode())
    proc.stdin.flush()
    proc.stdin.close()
    proc.wait()

edited Jul 1, 2022 at 12:36

answered Jul 1, 2022 at 11:09

gubwan

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1 Comment

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