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sysctl.rb
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sysctl.rb
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# encoding: utf-8
#
# Cookbook Name: os-hardening
# Recipe: sysctl
#
# Copyright 2012, Dominik Richter
# Copyright 2014, Deutsche Telekom AG
#
# 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.
#
# default attributes
# We can not set this kind of defaults in the attribute files
# as we react on value of other attributes
# https://github.com/dev-sec/chef-ssh-hardening/issues/140#issuecomment-267779720
# Only enable IP traffic forwarding, if required.
node.default['sysctl']['params']['net']['ipv4']['ip_forward'] =
node['os-hardening']['network']['forwarding'] ? 1 : 0
node.default['sysctl']['params']['net']['ipv6']['conf']['all']['forwarding'] =
node['os-hardening']['network']['ipv6']['enable'] && node['os-hardening']['network']['forwarding'] ? 1 : 0
# Disable or Enable IPv6 as it is needed.
node.default['sysctl']['params']['net']['ipv6']['conf']['all']['disable_ipv6'] =
node['os-hardening']['network']['ipv6']['enable'] ? 0 : 1
# Define different modes for sending replies in response to received ARP requests that resolve local target IP addresses:
#
# * **0** - (default): reply for any local target IP address, configured on
# any interface
# * **1** - reply only if the target IP address is local address configured
# on the incoming interface
# * **2** - reply only if the target IP address is local address configured
# on the incoming interface and both with the sender's IP address are
# part from same subnet on this interface
# * **3** - do not reply for local addresses configured with scope host, only
# resolutions for global and link addresses are replied
# * **4-7** - reserved
# * **8** - do not reply for all local addresses
node.default['sysctl']['params']['net']['ipv4']['conf']['all']['arp_ignore'] =
node['os-hardening']['network']['arp']['restricted'] ? 1 : 0
# Define different restriction levels for announcing the local source IP
# address from IP packets in ARP requests sent on interface:
#
# * **0** - (default) Use any local address, configured on any interface
# * **1** - Try to avoid local addresses that are not in the target's subnet
# for this interface. This mode is useful when target hosts reachable
# via this interface require the source IP address in ARP requests to
# be part of their logical network configured on the receiving
# interface. When we generate the request we will check all our
# subnets that include the target IP and will preserve the source
# address if it is from such subnet. If there is no such subnet we
# select source address according to the rules for level 2.
# * **2** - Always use the best local address for this target. In this mode
# we ignore the source address in the IP packet and try to select
# local address that we prefer for talks with the target host. Such
# local address is selected by looking for primary IP addresses on
# all our subnets on the outgoing interface that include the target
# IP address. If no suitable local address is found we select the
# first local address we have on the outgoing interface or on all
# other interfaces, with the hope we will receive reply for our
# request and even sometimes no matter the source IP address we
# announce.
#
node.default['sysctl']['params']['net']['ipv4']['conf']['all']['arp_announce'] =
node['os-hardening']['network']['arp']['restricted'] ? 2 : 0
# This setting controls how the kernel behaves towards module changes at
# runtime. Setting to 1 will disable module loading at runtime.
# Setting it to 0 is actually never supported.
unless node['os-hardening']['security']['kernel']['enable_module_loading']
node.default['sysctl']['params']['kernel']['modules_disabled'] = 1
end
# Magic Sysrq should be disabled, but can also be set to a safe value if so
# desired for physical machines. It can allow a safe reboot if the system hangs
# and is a 'cleaner' alternative to hitting the reset button.
# The following values are permitted:
#
# * **0** - disable sysrq
# * **1** - enable sysrq completely
# * **>1** - bitmask of enabled sysrq functions:
# * **2** - control of console logging level
# * **4** - control of keyboard (SAK, unraw)
# * **8** - debugging dumps of processes etc.
# * **16** - sync command
# * **32** - remount read-only
# * **64** - signalling of processes (term, kill, oom-kill)
# * **128** - reboot/poweroff
# * **256** - nicing of all RT tasks
node.default['sysctl']['params']['kernel']['sysrq'] =
node['os-hardening']['security']['kernel']['enable_sysrq'] ? node['os-hardening']['security']['kernel']['secure_sysrq'] : 0
# Prevent core dumps with SUID. These are usually only needed by developers and
# may contain sensitive information.
node.default['sysctl']['params']['fs']['suid_dumpable'] =
node['os-hardening']['security']['kernel']['enable_core_dump'] ? 2 : 0
# include sysctl recipe and set /etc/sysctl.d/99-chef-attributes.conf
include_recipe 'sysctl::apply'
# try to determine the real cpu vendor
begin
cpu_vendor = node['cpu']['0']['vendor_id'].
sub(/^.*GenuineIntel.*$/, 'intel').
sub(/^.*AuthenticAMD.*$/, 'amd')
node.default['os-hardening']['security']['cpu_vendor'] = cpu_vendor
rescue
log 'WARNING: Could not properly determine the cpu vendor. Fallback to intel cpu.' do
level :warn
end
end
# protect sysctl.conf
file '/etc/sysctl.conf' do
mode 0440
owner 'root'
group 'root'
end
# NSA 2.2.4.1 Set Daemon umask
# do config for rhel-family
case node['platform_family']
when 'rhel', 'fedora'
template '/etc/sysconfig/init' do
source 'rhel_sysconfig_init.erb'
mode 0544
owner 'root'
group 'root'
variables(
prompt: node['os-hardening']['security']['init']['prompt'],
single: node['os-hardening']['security']['init']['single']
)
end
end
# do initramfs config for ubuntu and debian
case node['platform_family']
when 'debian'
# rebuild initramfs with starting pack of modules,
# if module loading at runtime is disabled
unless node['os-hardening']['security']['kernel']['enable_module_loading']
template '/etc/initramfs-tools/modules' do
source 'modules.erb'
mode 0440
owner 'root'
group 'root'
variables(
x86_64: !(node['kernel']['machine'] =~ /x86_64/).nil?,
cpuVendor: node['os-hardening']['security']['cpu_vendor']
)
end
execute 'update-initramfs' do
command 'update-initramfs -u'
action :run
end
end
end