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|
#!/bin/sh
set -e
# Make a simple chroot for vsftpd and scp.
# Note that for the base chroot this attempts to use read-only bind
# mounts. These will be silently readable on older kernels. If
# you're using this for anything except simple testing then PLEASE
# TEST the chroot's security!
usage ()
{
cat <<EOF
usage: $0 { create | destroy } chroot_dir
$0 mount src_dir dst_dir
$0 umount dst_dir
EOF
exit 1
}
[ $# -ge 1 ] || usage
action="$1"
shift
case "$action" in
create|destroy|umount)
:
;;
mount)
[ $# -ge 2 ] || usage
;;
*)
usage
esac
do_mount ()
{
_src="$1"
_dst="$2"
if [ -f "$_dst" ] ; then
return 0
fi
if [ -f "$_src" ] ; then
mkdir -vp $(dirname "$_dst")
touch "$_dst"
else
mkdir -vp "$_dst"
fi
mount -v --bind "$_src" "$_dst"
}
do_umount ()
{
_dst="$1"
_out=$(awk "\$2 == \"$_dst\" {print \$2}" /proc/mounts)
if [ -n "$_out" ] ; then
_is_file=false
if [ -f "$_dst" ] ; then
_is_file=true
fi
umount -v "$_dst"
if $_is_file ; then
rm -vf "$_dst"
rmdir --ignore-fail-on-non-empty -vp $(dirname "$_dst")
else
rmdir --ignore-fail-on-non-empty -vp "$_dst"
fi
fi
}
first_ro_mount=true
can_remount_ro=true
do_mount_ro ()
{
_src="$1"
_dst="$2"
if [ -f "$_dst" ] ; then
return 0
fi
do_mount "$_src" "$_dst"
if $first_ro_mount ; then
if ! mount -v -o remount,ro "$_dst"; then
cat <<EOF
Unable to remount $_dst read-only. Won't try this again.
WARNING: Your chroot may be less secure than you think!
EOF
can_remount_ro=false
else
if f=$(mktemp -p "$_dst" >/dev/null 2>&1) ; then
rm -f "$f"
cat <<EOF
WARNING: Bind mounts don't really look to be read-only!
EOF
fi
fi
else
if $can_remount_ro ; then
mount -v -o remount,ro "$_dst"
fi
fi
first_ro_mount=false
}
sftp_server=""
for d in /usr/libexec/openssh /usr/lib/openssh ; do
f="$d/sftp-server"
if [ -x "$f" ] ; then
sftp_server="$f"
break
fi
done
if [ -z "$sftp_server" ] ; then
echo "$0: error - could not find location of sftp_server"
exit 2
fi
case $(uname -m) in
x86_64)
lib="lib64"
;;
*)
lib="lib"
esac
mounts="\
/usr/$lib \
/$lib \
/etc/nsswitch.conf \
/etc/resolv.conf \
$sftp_server \
/usr/bin/scp \
"
do_create ()
{
chroot_dir="$1"
mkdir -p "$chroot_dir"
fake="${chroot_dir}/.mkchroot"
touch "$fake"
ls -l "$fake"
d="$chroot_dir/dev"
mkdir -vp "$d"
cp -va /dev/null /dev/zero "$d/"
for s in $mounts ; do
f="$chroot_dir$s"
do_mount_ro "$s" "$f"
done
d="$chroot_dir/etc/passwd"
touch "$d"
ls -l "$d"
}
do_destroy ()
{
chroot_dir="$1"
rm -vf "$chroot_dir/etc/passwd"
for i in "null" "zero" ; do
rm -vf "$chroot_dir/dev/$i"
done
rmdir -v "$chroot_dir/dev"
# Reverse the list 1st.
rmounts=
for s in $mounts ; do
rmounts="$s${rmounts:+ }${rmounts}"
done
for s in $rmounts ; do
do_umount "${chroot_dir}$s"
done
fake="${chroot_dir}/.mkchroot"
rm -vf "$fake"
rmdir -v "$chroot_dir"
}
"do_$action" "$@"
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