Jean-Paul Calderone <exar...@divmod.com> wrote:
> On Wed, 11 Feb 2009 09:31:56 -0600, Nick Craig-Wood <n...@craig-wood.com>
> wrote:
> >r0g <aioe....@technicalbloke.com> wrote:
> >> I'm writing a linux remastering script in python where I need to chroot
> >> into a folder, run some system commands and then come out and do some
> >> tidying up, un-mounting proc & sys etc.
> >>
> >> I got in there with os.chroot() and I tried using that to get back out
> >> but that didn't work so... is my script trapped in there forever now or
> >> is there an un-hacky way to escape?
> >
> >No!
>
> If you still have root in the chroot (and you need root to get in there, so
> it's not implausible that you will), then you can get out. Googling for
> "escape chroot" turns up lots of hits. This page contains a fairly simple,
> explicit description of how to get out of a chroot:
>
> http://www.bpfh.net/simes/computing/chroot-break.html
>
> See the bulleted list in the "Breaking chroot()" section. Since you also
> control the process before the chroot happens, breaking out is even simpler
> in your case (just open / before you chroot in the first place). forking
> before doing the chroot may still be a good idea, but it's not the only
> solution.
I admit it can be done, but I'm not sure it isn't hacky!
#!/usr/bin/python
"""
Enter a chroot and escape again
Run as root
"""
import os
import sys
def ls(path):
"""List the path"""
print "Directory listing of %r" % path
for f in os.listdir(path):
print ">>", f
def main():
if len(sys.argv) < 2:
print >>sys.stderr, "Need directory to chroot to as an argument"
raise SystemExit(1)
chroot_dir = sys.argv[1]
print "Opening root"
root = os.open("/", os.O_RDONLY)
print "Before chroot"
ls("/")
print "Chrooting to %r" % chroot_dir
os.chroot(chroot_dir)
ls("/")
print "Breaking the chroot"
os.fchdir(root)
for i in range(100):
os.chdir("..")
os.chroot(".")
ls("/")
os.close(root)
if __name__ == "__main__":
main()
I ran this
$ mkdir chroot_test
$ touch chroot_test/in_the_chroot
$ sudo ./chroot_test.py chroot_test
And it produced this
Opening root
Before chroot
Directory listing of '/'
>> lost+found
>> home
>> bin
>> boot
>> proc
>> dev
>> etc
[snip]
Chrooting to 'chroot_test'
Directory listing of '/'
>> in_the_chroot
Breaking the chroot
Directory listing of '/'
>> lost+found
>> home
>> bin
>> boot
>> proc
>> dev
>> etc
[snip]
--
Nick Craig-Wood <n...@craig-wood.com> -- http://www.craig-wood.com/nick
--
http://mail.python.org/mailman/listinfo/python-list
