既然您提到了守护程序,我可以得出结论,您正在运行于类Unix操作系统上。这很重要,因为如何执行此操作取决于操作系统类型。这个答案适用 仅 于 ,包括Linux和Mac OS X.
subprocess.Popen将使用fork / exec模型来使用您的preexec_fn。这等效于按此顺序调用os.fork(),preexec_fn()(在子进程中)和os.exec()(在子进程中)。由于os.setuid,os.setgid和preexec_fn仅在Unix上受支持,因此该解决方案不能移植到其他类型的操作系统上。
以下代码是一个脚本(Python 2.4+),演示了如何执行此操作:
import os
import pwd
import subprocess
import sys
def main(my_args=None):
if my_args is None: my_args = sys.argv[1:]
user_name, cwd = my_args[:2]
args = my_args[2:]
pw_record = pwd.getpwnam(user_name)
user_name = pw_record.pw_name
user_home_dir = pw_record.pw_dir
user_uid = pw_record.pw_uid
user_gid = pw_record.pw_gid
env = os.environ.copy()
env[ 'HOME' ] = user_home_dir
env[ 'LOGNAME' ] = user_name
env[ 'PWD' ] = cwd
env[ 'USER' ] = user_name
report_ids('starting ' + str(args))
process = subprocess.Popen(
args, preexec_fn=demote(user_uid, user_gid), cwd=cwd, env=env
)
result = process.wait()
report_ids('finished ' + str(args))
print 'result', result
def demote(user_uid, user_gid):
def result():
report_ids('starting demotion')
os.setgid(user_gid)
os.setuid(user_uid)
report_ids('finished demotion')
return result
def report_ids(msg):
print 'uid, gid = %d, %d; %s' % (os.getuid(), os.getgid(), msg)
if __name__ == '__main__':
main()
您可以像这样调用此脚本:
以root身份启动…
(hale)/tmp/demo$ sudo bash --norc
(root)/tmp/demo$ ls -l
total 8
drwxr-xr-x 2 hale wheel 68 May 17 16:26 inner
-rw-r--r-- 1 hale staff 1836 May 17 15:25 test-child.py
成为非root用户的子进程…
(root)/tmp/demo$ python test-child.py hale inner /bin/bash --norc
uid, gid = 0, 0; starting ['/bin/bash', '--norc']
uid, gid = 0, 0; starting demotion
uid, gid = 501, 20; finished demotion
(hale)/tmp/demo/inner$ pwd
/tmp/demo/inner
(hale)/tmp/demo/inner$ whoami
hale
当子进程退出时,我们返回到父进程的根目录…
(hale)/tmp/demo/inner$ exit
exit
uid, gid = 0, 0; finished ['/bin/bash', '--norc']
result 0
(root)/tmp/demo$ pwd
/tmp/demo
(root)/tmp/demo$ whoami
root
,让父进程等待子进程退出只是出于 演示目的 。我这样做是为了使父母和孩子可以共享一个终端。守护程序将没有终端,并且很少等待子进程退出。