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Alternative: use unveil rather than chroot+setuid #6

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Alternative: use unveil rather than chroot+setuid #6

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44 changes: 8 additions & 36 deletions minimalist.pl
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@
use Carp;
use Net::Config qw(%NetConfig);
use Net::SMTP;
use OpenBSD::Unveil;
require File::Spec;
require Digest::MD5;
require MIME::QuotedPrint;
Expand Down Expand Up @@ -197,45 +198,16 @@
$maketext = Translation::en->new() || die "Language?";


################################################################
# >>>>>>>>>>>>>>> CHROOT AND DROP PRIVILEGES <<<<<<<<<<<<<<<<< #
################################################################
#####################################################
# >>>>>>>>>>>>>>> DROP PRIVILEGES <<<<<<<<<<<<<<<<< #
#####################################################

-d $conf{directory} or die "$conf{directory} is not a directory.";

# $< and $( are real [ug]id, $> and $) are effective [ug]id
if ($> == 0 && $< != 0) {
my $uid;
my $gid = getgrnam('nogroup');
defined $gid or $gid = getgrnam('nobody');
defined $gid or die "Could not get gid of nogroup.";
if (defined $conf{user}) {
$uid = getpwnam($conf{user});
defined $uid or die "Could not get uid of $conf{user}.";
}
else { $uid = $< }

# drop group privileges
$) = "$gid $gid";
die "Error while dropping group privileges: $!" unless($) eq "$gid $gid");
POSIX::setgid($gid) or die "setgid failed: $!";;

# chroot
chroot $conf{directory} or die "Could not chroot to $conf{directory}: $!";
chdir '/' or die "Cannot chdir to / in chroot ($conf{directory}).";
$conf{directory} = '/';

# drop user privileges
POSIX::setuid($uid) or die "setuid failed: $!";

# This may be too paranoid, but check
# that privileges are really dropped permanently
POSIX::setuid(0);
POSIX::setgid(0);
my $groups = qr/^$gid( $gid)?$/;
if ($< == 0 || $> == 0 || $( !~ $groups || $) !~ $groups) {
die "Could not drop privileges permanently." }
}
unveil( $conf{directory}, "crw" ) or die "Unable to unveil: $!";
unveil() || die "Unable to lock unveil: $!";
chdir "$conf{directory}" or die "Cannot chdir to ($conf{directory}).";

@INC = ('.');

####################################################################
Expand Down