switch back and forth from root to a user

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  • djurdjura
    New Member
    • Aug 2010
    • 3
    #1

    switch back and forth from root to a user

    Hi there,

    I looked around and couldn't find an answer to this question (and I'm now wondering is there is one :-)

    I have a piece of code in which I need to switch from root to a particular user, run the command as this user and would like to return to root. I don't want to use, if possible at all, "su".

    Here is the snippet code that is run as root initially:
    Code:
    import os
try:
  if os.name == 'posix':
    import pwd
    pw  = pwd.getpwnam(user)
    uid = pw.pw_uid
    os.setuid(uid)
except:
    return 1 # Error
finally:
  # Put back root user...
  os.setuid(0)
    As you can imagine, you can't set back to root (setuid(0)) - running as 'user' at this point.

    Thanks in advance for any help.

    D.
    Last edited by bvdet; Aug 31 '10, 06:53 PM. Reason: Add code tags
    Tags: python. setuid, root
    • djurdjura
      New Member
      • Aug 2010
      • 3
      #2
      Oops! Correcting indentation:

      Code:
      import os
try:
  if os.name == 'posix':
    import pwd

    pw = pwd.getpwnam(user)
    uid = pw.pw_uid
    os.setuid(uid)
else:
    # Do something useful here
except:
  return 1 # Error
finally:
  # Put back root user...
  os.setuid(0)
      Last edited by djurdjura; Aug 31 '10, 06:29 PM. Reason: Inedentation still not correct :-(

        Comment

        • dwblas
          Recognized Expert Contributor
          • May 2008
          • 626
          #3
          Hopefully, no OS will let you do that. su and sudo are there to limit escalation of privileges, and are the only way that you can do this AFAIK.

            Comment

            • djurdjura
              New Member
              • Aug 2010
              • 3
              #4
              May be I wasn't clear enough. The script runs as root all the time. I just need to run the few steps as a given user and get back to root. Theses steps involve populating a cron tab. I'm looking for the best way of doing that. An idea that I was thinking of was to do this in a separate thread, then this approach isn't Posix compliant and I'm not sure if the whole process doesn't get the same UID (the script runs under Solaris).

              Any other ideas?

                Comment

                • dwblas
                  Recognized Expert Contributor
                  • May 2008
                  • 626
                  #5
                  Theses steps involve populating a cron tab
                  It is as simple as changing the permissions of cron to the user's (it never is). I tried multiprocessing (on Linux) and it appears to work. I am not a fan of setuid so know very little about it.
                  Code:
                  import os
import pwd
import time
from multiprocessing import Process

class TestClass():

    def test_f(self, user):
       try:
           if os.name == 'posix':
 
               pw = pwd.getpwnam(user)
               uid = pw.pw_uid
               os.setuid(uid)
               print "setuid successful", pw

               ##--- create file as test of permissions
               fp = open("./test_user", "w")
               fp.write("test user\n")
               fp.close()
       except:
           return 1 # Error

if __name__ == '__main__':
    CT=TestClass()
    p = Process(target=CT.test_f, args=('user name',))
    p.start()

    ## sleep for 5 seconds to simulate processing and terminate
    time.sleep(5.0)
    p.terminate()

    ##--- create file as test of permissions
    fp = open("./test_root", "w")
    fp.write("test root\n")
    fp.close()

                    Comment

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