Change to sudo user within a python script

问题:

I have a problem. I am writing a piece of software, which is required to perform an operation which requires the user to be in sudo mode. running 'sudo python filename.py' isn't an option, which leads me to my question. Is there a way of changing to sudo half way through a python script, security isn't an issue as the user will know the sudo password the program should run in the following way to illustrate the issue

1. program running as normal user
2. ...... performing operations
3. user enters sudo password
4. user changed to sudo
5. sub program requiring sudo permission is run
6. on trigger even (end of sub program) user becomes normal user again
7. ...... performing operations

My problem lies in step 3, any pointers or frameworks you could suggest would be of great help.

Cheers

Chris

回答1:

Use Tcl and Expect, plus subprocess to elevate yourself. So basically it's like this:

sudo.tcl

spawn sudo
expect {
    "Password:" {
        send "password"
    }
}

sudo.py

import subprocess
subprocess.call(['tclsh', 'sudo.tcl'])

And then run sudo.py.

回答2:

It is better to run as little of the program as possible with elevated privileges. You can run the small part that needs more privilege via the subprocess.call() function, e.g.

import subprocess
returncode = subprocess.call(["/usr/bin/sudo", "/usr/bin/id"])

回答3:

Don't try and make yourself sudo just check if you are and error if your not

class NotSudo(Exception):
    pass

if os.getuid() != 0:
    raise NotSudo("This program is not run as sudo or elevated this it will not work")

回答4:

I've recently dealt with this problem while making a system installation script. To switch to superuser permissions, I used subprocess.call() with 'sudo':

#!/usr/bin/python

import subprocess
import shlex
import getpass

print "This script was called by: " + getpass.getuser()

print "Now do something as 'root'..."
subprocess.call(shlex.split('sudo id -nu'))

print "Now switch back to the calling user: " + getpass.getuser()

Note that you need to use shlex.split() to make your command usable for subprocess.call(). If you want to use the output from a command, you can use subprocess.check_output(). There is also a package called 'sh' (http://amoffat.github.com/sh/) that you can use for this purpose.

回答5:

If you are able to encapsulate just the necessary functionality requiring elevated privileges in a separate executable, you could use the setuid bit on the executable program, and call it from your user-level python script.

In this way, only the activity in the setuid-executable run as root, however executing this does NOT require sudo, i.e., root privileges. Only creating/modifying the setuid-executable requires sudo.

There are a few security implications, such as ensuring that your setuid executable program properly sanitizes any user input (e.g., parameters), so that it cannot be tricked into doing something it should not (confused deputy problem).

ref: http://en.wikipedia.org/wiki/Setuid#setuid_on_executables

edit: setuid only seems to work for compiled executables (binaries), and not interpreted scripts, so you may need to use a compiled setuid wrapper.

回答6:

You can use setuid to set the users uid. But for obvious security reasons you can only do this if you are root (or the program has suid root rights). Both of these are probably a bad idea.

In this case you need to sudo rights to run a specific program. In that case just sub to "sudo theprogram" instead.

回答7:

import subprocess
subprocess.check_output("sudo -i -u " + str(username) + " ls -l", shell=True).decode("utf-8").strip()

回答8:

Are you talking about having the user input password half way through your execution? raw_input() can take a user input from console, but it will not mask the password.

>>>> y = raw_input()
somehting
>>> y
'somehting'