#!/bin/bash

# Remediation is applicable only in certain platforms
if dpkg-query --show --showformat='${db:Status-Status}\n' 'nftables' 2>/dev/null | grep -q installed; then

#Name of the table
var_nftables_table='filter'

#Familiy of the table 
var_nftables_family='inet'

#Name(s) of base chain
var_nftables_base_chain_names='input,forward,output'

#Type(s) of base chain
var_nftables_base_chain_types='filter,filter,filter'

# Hooks for base chain
var_nftables_base_chain_hooks='input,forward,output'

#Priority
var_nftables_base_chain_priorities='0,0,0'

#Policy 
var_nftables_base_chain_policies='accept,accept,accept'


#Transfer some of strings to arrays
IFS="," read -r -a  names <<< "$var_nftables_base_chain_names"
IFS="," read -r -a  types <<< "$var_nftables_base_chain_types"
IFS="," read -r -a  hooks <<< "$var_nftables_base_chain_hooks"
IFS="," read -r -a  priorities <<< "$var_nftables_base_chain_priorities"
IFS="," read -r -a  policies <<< "$var_nftables_base_chain_policies"

my_cmd="nft list tables | grep '$var_nftables_family $var_nftables_table'"
eval IS_TABLE_EXIST=\$\($my_cmd\)
if [ -z "$IS_TABLE_EXIST" ]
then
  # We create a table and add chains to it 
  nft create table "$var_nftables_family" "$var_nftables_table"
  num_of_chains=${#names[@]}
  for ((i=0; i < num_of_chains; i++))
  do
   chain_to_add="add chain $var_nftables_family $var_nftables_table ${names[$i]} { type ${types[$i]} hook ${hooks[$i]} priority ${priorities[$i]} ; policy ${policies[$i]} ; }"
   my_cmd="nft '$chain_to_add'"
   eval $my_cmd
  done    
else
  # We add missing chains to the existing table
  num_of_chains=${#names[@]}
  for ((i=0; i < num_of_chains; i++))
  do
    IS_CHAIN_EXIST=$(nft list table "$var_nftables_family" "$var_nftables_table" | grep "hook ${hooks[$i]}")
    if [ -z "$IS_CHAIN_EXIST" ]
      then
        chain_to_add="add chain '$var_nftables_family' '$var_nftables_table' ${names[$i]} { type ${types[$i]} hook ${hooks[$i]} priority ${priorities[$i]} ; policy ${policies[$i]} ; }"
        my_cmd="nft '$chain_to_add'"
        eval $my_cmd
    fi
  done 
fi

else
    >&2 echo 'Remediation is not applicable, nothing was done'
fi

- name: Gather the package facts
  package_facts:
    manager: auto
  tags:
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy
  - set_nftables_base_chain
- name: XCCDF Value var_nftables_table # promote to variable
  set_fact:
    var_nftables_table: !!str filter
  tags:
    - always
- name: XCCDF Value var_nftables_family # promote to variable
  set_fact:
    var_nftables_family: !!str inet
  tags:
    - always
- name: XCCDF Value var_nftables_base_chain_names # promote to variable
  set_fact:
    var_nftables_base_chain_names: !!str input,forward,output
  tags:
    - always
- name: XCCDF Value var_nftables_base_chain_types # promote to variable
  set_fact:
    var_nftables_base_chain_types: !!str filter,filter,filter
  tags:
    - always
- name: XCCDF Value var_nftables_base_chain_hooks # promote to variable
  set_fact:
    var_nftables_base_chain_hooks: !!str input,forward,output
  tags:
    - always
- name: XCCDF Value var_nftables_base_chain_priorities # promote to variable
  set_fact:
    var_nftables_base_chain_priorities: !!str 0,0,0
  tags:
    - always
- name: XCCDF Value var_nftables_base_chain_policies # promote to variable
  set_fact:
    var_nftables_base_chain_policies: !!str accept,accept,accept
  tags:
    - always

- name: Ensure Base Chains Exist for Nftables - Check Existence of Nftables Table
  ansible.builtin.shell: nft list tables | grep '{{ var_nftables_family }} {{ var_nftables_table
    }}'
  register: existing_nftables
  changed_when: false
  failed_when: false
  when: '"nftables" in ansible_facts.packages'
  tags:
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy
  - set_nftables_base_chain

- name: Ensure Base Chains Exist for Nftables - Set NFTables Table
  ansible.builtin.command: nft create table {{ var_nftables_family }} {{ var_nftables_table
    }}
  when:
  - '"nftables" in ansible_facts.packages'
  - existing_nftables is not skipped and existing_nftables.rc > 0
  tags:
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy
  - set_nftables_base_chain

- name: Ensure Base Chains Exist for Nftables - Add Base Chains
  ansible.builtin.command: nft 'add chain {{ var_nftables_family }} {{ var_nftables_table
    }} {{ item.0 }} { type {{ item.1 }} hook {{ item.2 }} priority {{ item.3 }} ;
    policy {{ item.4 }} ; }'
  with_together:
  - '{{ var_nftables_base_chain_names.split(",") }}'
  - '{{ var_nftables_base_chain_types.split(",") }}'
  - '{{ var_nftables_base_chain_hooks.split(",") }}'
  - '{{ var_nftables_base_chain_priorities.split(",") }}'
  - '{{ var_nftables_base_chain_policies.split(",") }}'
  when: '"nftables" in ansible_facts.packages'
  tags:
  - low_complexity
  - low_disruption
  - medium_severity
  - no_reboot_needed
  - restrict_strategy
  - set_nftables_base_chain