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#!/usr/bin/env perl

use strict;
use warnings;

use File::Temp qw/tempdir/;

my @cmd = ("/bin/sh");

# running as root to chroot
if ($> != 0) {
    die "This must be run as root\n";
}

if (@ARGV) {
    @cmd = @ARGV;
}

my $jaildir = tempdir(DIR => "/");
(my $jaildir_rel_root = $jaildir) =~ s/.//;

chmod 0755, $jaildir or die "chmod failed: $!";
chdir "/" or die "chdir to / failed: $!";
chroot $jaildir or die "chroot to jail failed: $!";
rmdir $jaildir_rel_root or warn "failed to clean $jaildir: $!";

my $ino = 0;
while (1) {
    my @st = stat ".";
    if (!@st) {
        die "stat failed: $!";
    }
    my $cur_ino = $st[1];
    if ($cur_ino == $ino) {
        last;
    }
    $ino = $cur_ino;
    chdir ".." or die "chdir to .. failed: $!";
}

chroot "." or die "chroot to . failed: $!";

exec { $cmd[0] } @cmd or die "exec failure: $!";

__END__