chef os hardening

This chef cookbook provides numerous security-related configurations, providing all-round base protection.

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os-hardening (Chef cookbook)

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Tests

Description

This cookbook provides numerous security-related configurations, providing all-round base protection.

It configures:

  • Configures package management e.g. allows only signed packages
  • Remove packages with known issues
  • Configures pam and pam_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

It will not:

  • Update system packages
  • Install security patches

Requirements

  • Chef >= 14.13.11

Platform

  • Debian 10, 11
  • Ubuntu 18.04, 20.04
  • RHEL 7, 8, 9
  • CentOS 7
  • CentOS Stream 8, 9
  • Oracle Linux 7, 8, 9
  • AlmaLinux 8, 9
  • Rocky Linux 8, 9
  • Fedora 37, 38
  • OpenSuse Leap 42
  • Amazon Linux 1, 2

Attributes

  • ['os-hardening']['components'][COMPONENT_NAME] - allows the fine control over which components should be executed via default recipe. See below for more details
  • ['os-hardening']['desktop']['enable'] = false
    true if this is a desktop system, ie Xorg, KDE/GNOME/Unity/etc
  • ['os-hardening']['network']['forwarding'] = false
    true if this system requires packet forwarding (eg Router), false otherwise
  • ['os-hardening']['network']['ipv6']['enable'] = false
  • ['os-hardening']['network']['arp']['restricted'] = true
    true if you want the behavior of announcing and replying to ARP to be restricted, false otherwise
  • ['os-hardening']['env']['extra_user_paths'] = []
    add additional paths to the user’s PATH variable (default is empty).
  • ['os-hardening']['env']['umask'] = "027"
  • ['os-hardening']['env']['root_path'] = "/"
    where root is mounted
  • ['os-hardening']['auth']['pw_max_age'] = 60
    maximum password age
  • ['os-hardening']['auth']['pw_min_age'] = 7
    minimum password age (before allowing any other password change)
  • ['os-hardening']['auth']['pw_warn_age'] = 7
    number of days before maximum password age occurs to warn of impending
    change
  • ['os-hardening']['auth']['uid_min'] = 1000
    lower bound of UIDs assigned by useradd
  • ['os-hardening']['auth']['uid_max'] = 60000
    upper bound of UIDs assigned by useradd
  • ['os-hardening']['auth']['gid_min'] = 1000
    lower bound of GIDs assigned by groupadd
  • ['os-hardening']['auth']['gid_max'] = 60000
    upper bound of GIDs assigned by groupadd
  • ['os-hardening']['auth']['retries'] = 5
    the maximum number of authentication attempts, before the account is locked for some time
  • ['os-hardening']['auth']['lockout_time'] = 600
    time in seconds that needs to pass, if the account was locked due to too many failed authentication attempts
  • ['os-hardening']['auth']['timeout'] = 60
    authentication timeout in seconds, so login will exit if this time passes
  • ['os-hardening']['auth']['allow_homeless'] = false
    true if to allow users without home to login
  • ['os-hardening']['auth']['pam']['passwdqc']['enable'] = true
    true if you want to use strong password checking in PAM using passwdqc
  • ['os-hardening']['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-hardening']['auth']['pam']['passwdqc']['template_cookbook'] = 'os-hardening'
    set to the name of the cookbook from which the template is obtained for the /usr/share/pam-configs/passwdqc file
  • ['os-hardening']['auth']['pam']['tally2']['template_cookbook'] = 'os-hardening'
    set to the name of the cookbook from which the template is obtained for the /usr/share/pam-configs/tally2 file
  • ['os-hardening']['auth']['pam']['system-auth']['template_cookbook'] = 'os-hardening'
    set to the name of the cookbook from which the template is obtained for the /etc/pam.d/system-auth-ac file
  • ['os-hardening']['security']['users']['allow'] = []
    list of things, that a user is allowed to do. May contain: change_user
  • ['os-hardening']['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-hardening']['security']['kernel']['disable_filesystems'] = ['cramfs', 'freevxfs', 'jffs2', 'hfs', 'hfsplus', 'squashfs', 'udf', 'vfat']
    list of kernel file system modules, which are blacklisted for loading (e.g. they are unused and can be disabled). Set this to [] to completely avoid this blacklisting
  • ['os-hardening']['security']['kernel']['enable_sysrq'] = false
  • ['os-hardening']['security']['kernel']['enable_core_dump'] = false
  • ['os-hardening']['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-hardening']['security']['suid_sgid']['blacklist'] = []
    a list of paths which should have their SUID/SGID bits removed
  • ['os-hardening']['security']['suid_sgid']['whitelist'] = []
    a list of paths which should not have their SUID/SGID bits altered
  • ['os-hardening']['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 Chef 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-hardening']['security']['suid_sgid']['dry_run_on_unknown'] = false
    like remove_from_unknown above, only that SUID/SGID bits aren’t removed.
    It will still search the filesystems to look for SUID/SGID bits but it will only print them in your log. This option is only ever recommended, when you first configure remove_from_unknown for SUID/SGID bits, so that you can see the files that are being changed and make adjustments to your whitelist and blacklist.
  • ['os-hardening']['security']['packages']['clean'] = true
    removes packages with known issues.
  • ['os-hardening']['security']['packages']['list'] = ['xinetd','inetd','ypserv','telnet-server','rsh-server']
    list of packages to remove, by default 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)
  • ['os-hardening']['security']['selinux_mode'] = 'unmanaged'
    set to unmanaged if you want to let selinux configuration as it is. Set to enforcing to enforce or permissive to permissive SELinux.

Controlling the included components

default.rb includes other components based on the ohai autodetection attributes of your system. E.g. do not execute selinux on non-RHEL systems. You can override this behavior and force components to be executed or not via setting attributes in node['os-hardening']['components'] on the override level. Example

# some attribute file
# do not include sysctl and auditd
override['os-hardening']['components']['sysctl'] = false
override['os-hardening']['components']['auditd'] = false

# force selinux to be included
override['os-hardening']['components']['selinux'] = true

In the current implementation different components are located in the different recipes. See the available recipes or default.rb for possible component names.

Usage

Add the recipes to the run_list, it should be last:

"recipe[os-hardening]"

Configure attributes:

"security" : {
  "kernel" : {
    "enable_module_loading" : true
  }
},

Local Testing

Local testing

Please install chef-dk, VirtualBox or VMware Workstation and Vagrant.

Linting is checked with rubocop and foodcritic:

$ chef exec rake lint
.....

Unit/spec tests are done with chefspec:

$ chef exec rake spec
.....

Integration tests are done with test-kitchen and inspec:

$ chef exec rake kitchen
.....
# or you can use the kitchen directly
$ kitchen test

CI testing of forks

You can enable testing of your fork in Travis CI. By default you will get linting, spec tests and integration tests with kitchen-dokken.

Integration tests with kitchen-dokken do not cover everything as they run in the container environment.
Full integration tests can be executed using DigitalOcean.

If you want to have full integration tests for your fork, you will have to add following environment variables in the settings of your fork:

  • DIGITALOCEAN_ACCESS_TOKEN - access token for DigitalOcean
  • CI_SSH_KEY - private part of some ssh key, available on DigitalOcean for your instances, in base64 encoded form (e.g. cat id_rsa | base64 -w0 ; echo)
  • DIGITALOCEAN_SSH_KEY_IDS - ID in DigitalOcean of CI_SSH_KEY, see this for more information

Contributors + Kudos

This cookbook is mostly based on guides by:

Thanks to all of you!!

Contributing

See contributor guideline.

License and Author

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.