sysdirs="
  /bin
  /etc
  /lib
  /sbin
  /usr
"

# Remove world-writable permissions.
# This breaks apps that need to write to /tmp,
# such as ssh-agent.
find / -xdev -type d -perm +0002 -exec chmod o-w {} +
find / -xdev -type f -perm +0002 -exec chmod o-w {} +

# Ensure system dirs are owned by root and not writable by anybody else.
find $sysdirs -xdev -type d \
  -exec chown root:root {} \; \
  -exec chmod 0755 {} \;

#!/bin/sh
set -x
set -e
#
# Docker build calls this script to harden the image during build.
#
# NOTE: To build on CircleCI, you must take care to keep the `find`
# command out of the /proc filesystem to avoid errors like:
#
#    find: /proc/tty/driver: Permission denied
#    lxc-start: The container failed to start.
#    lxc-start: Additional information can be obtained by \
#        setting the --logfile and --logpriority options.

# Remove existing crontabs, if any.
rm -fr /var/spool/cron
rm -fr /etc/crontabs
rm -fr /etc/periodic

# Remove all but a handful of admin commands.
find /sbin /usr/sbin ! -type d \
  -a ! -name exim \
  -a ! -name nologin \
  -delete

# Remove world-writable permissions.
# This breaks apps that need to write to /tmp,
# such as ssh-agent.
find / -xdev -type d -perm +0002 -exec chmod o-w {} +
find / -xdev -type f -perm +0002 -exec chmod o-w {} +

# Remove unnecessary user accounts, including root.
sed -i -r '/^(mail)/!d' /etc/group
sed -i -r '/^(mail)/!d' /etc/passwd

# Remove interactive login shell for everybody but user.
sed -i -r 's#^(.*):[^:]*$#\1:/sbin/nologin#' /etc/passwd

sysdirs="
  /bin
  /etc
  /lib
  /sbin
  /usr
"

# Remove apk configs.
find $sysdirs -xdev -regex '.*apk.*' -exec rm -fr {} +

# Remove crufty...
#   /etc/shadow-
#   /etc/passwd-
#   /etc/group-
find $sysdirs -xdev -type f -regex '.*-$' -exec rm -f {} +

# Ensure system dirs are owned by root and not writable by anybody else.
find $sysdirs -xdev -type d \
  -exec chown root:root {} \; \
  -exec chmod 0755 {} \;

# Remove suid bit from exim.
chmod u-s /usr/sbin/exim

# Remove all suid files.
find $sysdirs -xdev -type f -a -perm +4000 -delete

# Remove other programs that could be dangerous.
find $sysdirs -xdev \( \
  -name hexdump -o \
  -name chgrp -o \
  -name chmod -o \
  -name chown -o \
  -name ln -o \
  -name od -o \
  -name strings -o \
  -name su \
  \) -delete

# Remove init scripts since we do not use them.
rm -fr /etc/init.d
rm -fr /lib/rc
rm -fr /etc/conf.d
rm -fr /etc/inittab
rm -fr /etc/runlevels
rm -fr /etc/rc.conf

# Remove kernel tunables since we do not need them.
rm -fr /etc/sysctl*
rm -fr /etc/modprobe.d
rm -fr /etc/modules
rm -fr /etc/mdev.conf
rm -fr /etc/acpi

# Remove root homedir since we do not need it.
rm -fr /root

# Remove fstab since we do not need it.
rm -f /etc/fstab

# Remove broken symlinks (because we removed the targets above).
find $sysdirs -xdev -type l -exec test ! -e {} \; -delete