I\'m having problems with changing a Linux user\'s password from python. I\'ve tried so many things, but I couldn\'t manage to solve the issue, here is the sample of things
I ran accross the same problem today and I wrote a simple wrapper around subprocess
to call the passwd
command and feed stdin
with the new password. This code is not fool proof and only works when running as root which does not prompt for the old password.
import subprocess
from time import sleep
PASSWD_CMD='/usr/bin/passwd'
def set_password(user, password):
cmd = [PASSWD_CMD, user]
p = subprocess.Popen(cmd, stdin=subprocess.PIPE)
p.stdin.write(u'%(p)s\n%(p)s\n' % { 'p': password })
p.stdin.flush()
# Give `passwd` cmd 1 second to finish and kill it otherwise.
for x in range(0, 10):
if p.poll() is not None:
break
sleep(0.1)
else:
p.terminate()
sleep(1)
p.kill()
raise RuntimeError('Setting password failed. '
'`passwd` process did not terminate.')
if p.returncode != 0:
raise RuntimeError('`passwd` failed: %d' % p.returncode)
If you need the output of passwd you can also pass stdout=subprocess.PIPE
to the Popen
call and read from it. In my case I was only interested if the operation succeeded or not so I simply skipped that part.
Security consideration: Do not use something like echo -n 'password\npassword\n | passwd username'
as this will make the password visible in the process list.
Since you seam to want to be using sudo passwd <username>
I would recommend adding a new line to your /etc/sudoers
(use visudo
for that!)
some_user ALL = NOPASSWD: /usr/bin/passwd
Sudo will not ask for the password for some_user
and the script will run as expected.
Alternatively simply add an extra p.stdin.write(u'%s\n' % SUDO_PASSWORD)
line. That way sudo
will receive the user password first and then passwd
receives the new user password.
As mentioned before passing passwords on the command line is not very secure unfortunately. Additionally something like "--stdin
" for passwd
is not available on every passwd
implementation. Therefor here is a more secure version using chpasswd
:
def setPassword(userName:str, password:str):
p = subprocess.Popen([ "/usr/sbin/chpasswd" ], universal_newlines=True, shell=False, stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
(stdout, stderr) = p.communicate(userName + ":" + password + "\n")
assert p.wait() == 0
if stdout or stderr:
raise Exception("Error encountered changing the password!")
Explanation:
With subprocess.Popen
we launch an instance of chpasswd
. We pipe the user name and password to an instance of chpasswd
. chpasswd
will then change the password using the settings defined for the current operating system. chpasswd
will remain completely silent if no error occurred. Therefor the code above will raise an exception if any kind of error occurred (without having a closer look to the actual error).
usermod-based version:
#!/usr/bin/env python
from crypt import crypt
from getpass import getpass
from subprocess import Popen, PIPE
sudo_password_callback = lambda: sudo_password # getpass("[sudo] password: ")
username, username_newpassword = 'testaccount', '$2&J|5ty)*X?9+KqODA)7'
# passwd has no `--stdin` on my system, so `usermod` is used instead
# hash password for `usermod`
try:
hashed = crypt(username_newpassword) # use the strongest available method
except TypeError: # Python < 3.3
p = Popen(["mkpasswd", "-m", "sha-512", "-s"], stdin=PIPE, stdout=PIPE,
universal_newlines=True)
hashed = p.communicate(username_newpassword)[0][:-1] # chop '\n'
assert p.wait() == 0
assert hashed == crypt(username_newpassword, hashed)
# change password
p = Popen(['sudo', '-S', # read sudo password from the pipe
# XXX: hashed is visible to other users
'usermod', '-p', hashed, username],
stdin=PIPE, universal_newlines=True)
p.communicate(sudo_password_callback() + '\n')
assert p.wait() == 0
For those that --stdin isn't an option:
import subprocess
cmd = "bash -c \"echo -e 'NewPassword\\nNewPassword' | passwd root\""
subprocess.check_call(cmd, shell=True)
The user you are running this as must have sudo permission to run the passwd
command without a password.
>>> from subprocess import Popen
>>> proc = Popen(['/usr/bin/sudo', '/usr/bin/passwd', 'test', '--stdin'])
>>> proc.communicate('newpassword')
Try using the '--stdin' option to the passwd command in your pipes. To quote from the man page:
--stdin This option is used to indicate that passwd should read the new password from standard input, which can be a pipe.
Another option, if your Linux has the usermod command, as root (or via sudo) you can explicitly set the (encrypted) password using the '-p' option.