os-hardening (Ansible Role)
Description
This role provides numerous security-related configurations, providing all-round base protection. It is intended to be compliant with the DevSec Linux Baseline.
It configures:
- Configures package management e.g. allows only signed packages
- Remove packages with known issues
- Configures
pam
andpam_limits
module - Shadow password suite configuration
- Configures system path permissions
- Disable core dumps via soft limits
- Restrict root Logins to System Console
- Set SUIDs
- Configures kernel parameters via sysctl
- Install and configure auditd
It will not:
- Update system packages
- Install security patches
Requirements
- Ansible 2.5.0
Warning
If you're using inspec to test your machines after applying this role, please make sure to add the connecting user to the os_ignore_users
-variable.
Otherwise inspec will fail. For more information, see issue #124.
Variables
Name | Default Value | Description |
---|---|---|
os_desktop_enable |
false | true if this is a desktop system, ie Xorg, KDE/GNOME/Unity/etc |
os_env_extra_user_paths |
[] | add additional paths to the user's PATH variable (default is empty). |
os_env_umask |
027 | set default permissions for new files to 750 |
os_auth_pw_max_age |
60 | maximum password age (set to 99999 to effectively disable it) |
os_auth_pw_min_age |
7 | minimum password age (before allowing any other password change) |
os_auth_retries |
5 | the maximum number of authentication attempts, before the account is locked for some time |
os_auth_lockout_time |
600 | time in seconds that needs to pass, if the account was locked due to too many failed authentication attempts |
os_auth_timeout |
60 | authentication timeout in seconds, so login will exit if this time passes |
os_auth_allow_homeless |
false | true if to allow users without home to login |
os_auth_pam_passwdqc_enable |
true | true if you want to use strong password checking in PAM using passwdqc |
os_auth_pam_passwdqc_options |
"min=disabled,disabled,16,12,8" | set to any option line (as a string) that you want to pass to passwdqc |
os_security_users_allow |
[] | list of things, that a user is allowed to do. May contain change_user . |
os_security_kernel_enable_module_loading |
true | true if you want to allowed to change kernel modules once the system is running (eg modprobe , rmmod ) |
os_security_kernel_enable_core_dump |
false | kernel is crashing or otherwise misbehaving and a kernel core dump is created |
os_security_suid_sgid_enforce |
true | true if you want to reduce SUID/SGID bits. There is already a list of items which are searched for configured, but you can also add your own |
os_security_suid_sgid_blacklist |
[] | a list of paths which should have their SUID/SGID bits removed |
os_security_suid_sgid_whitelist |
[] | a list of paths which should not have their SUID/SGID bits altered |
os_security_suid_sgid_remove_from_unknown |
false | true if you want to remove SUID/SGID bits from any file, that is not explicitly configured in a blacklist . This will make every Ansible-run search through the mounted filesystems looking for SUID/SGID bits that are not configured in the default and user blacklist. If it finds an SUID/SGID bit, it will be removed, unless this file is in your whitelist . |
os_security_packages_clean' |
true | removes packages with known issues. See section packages. |
ufw_manage_defaults |
true | true means apply all settings with ufw_ prefix |
ufw_ipt_sysctl |
'' | by default it disables IPT_SYSCTL in /etc/default/ufw. If you want to overwrite /etc/sysctl.conf values using ufw - set it to your sysctl dictionary, for example /etc/ufw/sysctl.conf |
ufw_default_input_policy |
DROP | set default input policy of ufw to DROP |
ufw_default_output_policy |
ACCEPT | set default output policy of ufw to ACCEPT |
ufw_default_forward_policy |
DROP | set default forward policy of ufw to DROP |
os_auditd_enabled |
true | Set to false to disable installing and configuring auditd. |
Packages
We remove the following packages:
- xinetd (NSA, Chapter 3.2.1)
- inetd (NSA, Chapter 3.2.1)
- tftp-server (NSA, Chapter 3.2.5)
- ypserv (NSA, Chapter 3.2.4)
- telnet-server (NSA, Chapter 3.2.2)
- rsh-server (NSA, Chapter 3.2.3)
- prelink (open-scap)
Disabled filesystems
We disable the following filesystems, because they're most likely not used:
- "cramfs"
- "freevxfs"
- "jffs2"
- "hfs"
- "hfsplus"
- "squashfs"
- "udf"
- "vfat" # only if uefi is not in use
To prevent some of the filesystems from being disabled, add them to the os_filesystem_whitelist
variable.
Example Playbook
- hosts: localhost
roles:
- dev-sec.os-hardening
Changing sysctl variables
If you want to override sysctl-variables, you can use the sysctl_overwrite
variable (in older versions you had to override the whole sysctl_dict
).
So for example if you want to change the IPv4 traffic forwarding variable to 1
, do it like this:
- hosts: localhost
roles:
- dev-sec.os-hardening
vars:
sysctl_overwrite:
# Enable IPv4 traffic forwarding.
net.ipv4.ip_forward: 1
Alternatively you can change Ansible's hash-behaviour to merge
, then you only have to overwrite the single hash you need to. But please be aware that changing the hash-behaviour changes it for all your playbooks and is not recommended by Ansible.
Local Testing
The preferred way of locally testing the role is to use Docker. You will have to install Docker on your system. See Get started for a Docker package suitable to for your system.
You can also use vagrant and Virtualbox or VMWare to run tests locally. You will have to install Virtualbox and Vagrant on your system. See Vagrant Downloads for a vagrant package suitable for your system. For all our tests we use test-kitchen
. If you are not familiar with test-kitchen
please have a look at their guide.
Next install test-kitchen:
# Install dependencies
gem install bundler
bundle install
Testing with Docker
# fast test on one machine
bundle exec kitchen test default-ubuntu-1404
# test on all machines
bundle exec kitchen test
# for development
bundle exec kitchen create default-ubuntu-1404
bundle exec kitchen converge default-ubuntu-1404
Testing with Virtualbox
# fast test on one machine
KITCHEN_YAML=".kitchen.vagrant.yml" bundle exec kitchen test default-ubuntu-1404
# test on all machines
KITCHEN_YAML=".kitchen.vagrant.yml" bundle exec kitchen test
# for development
KITCHEN_YAML=".kitchen.vagrant.yml" bundle exec kitchen create default-ubuntu-1404
KITCHEN_YAML=".kitchen.vagrant.yml" bundle exec kitchen converge default-ubuntu-1404
For more information see test-kitchen
Contributors + Kudos
...
This role is mostly based on guides by:
- Arch Linux wiki, Sysctl hardening
- NSA: Guide to the Secure Configuration of Red Hat Enterprise Linux 5
- Ubuntu Security/Features
- Deutsche Telekom, Group IT Security, Security Requirements (German)
Thanks to all of you!
Contributing
License and Author
- Author:: Sebastian Gumprich
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.