#!/usr/bin/python
# -*- coding: utf-8 -*-

# (c) 2015, Linus Unnebäck <linus@folkdatorn.se>
#
# This file is part of Ansible
#
# This module is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This software is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this software.  If not, see <http://www.gnu.org/licenses/>.

# import module snippets
from ansible.module_utils.basic import *

BINS = dict(
    ipv4='iptables',
    ipv6='ip6tables',
)

DOCUMENTATION = '''
---
module: iptables
short_description: Modify the systems iptables
requirements: []
version_added: "2.0"
author: Linus Unnebäck (@LinusU) <linus@folkdatorn.se>
description: Iptables is used to set up, maintain, and inspect the tables of IP packet filter rules in the Linux kernel. This module does not handle the saving and/or loading of rules, but rather only manipulates the current rules that are present in memory. This is the same as the behaviour of the "iptables" and "ip6tables" command which this module uses internally.
notes:
  - This module just deals with individual rules. If you need advanced chaining of rules the recommended way is to template the iptables restore file.
options:
  table:
    description: This option specifies the packet matching table which the command should operate on. If the kernel is configured with automatic module loading, an attempt will be made to load the appropriate module for that table if it is not already there.
    required: false
    default: filter
    choices: [ "filter", "nat", "mangle", "raw", "security" ]
  state:
    description: Wheter the rule should be absent or present.
    required: false
    default: present
    choices: [ "present", "absent" ]
  ip_version:
    description: Which version of the IP protocol this rule should apply to.
    required: false
    default: ipv4
    choices: [ "ipv4", "ipv6" ]
  chain:
    description: Chain to operate on. This option can either be the name of a user defined chain or any of the builtin chains: "INPUT", "FORWARD", "OUTPUT", "PREROUTING", "POSTROUTING", "SECMARK", "CONNSECMARK"
    required: true
  protocol:
    description: The protocol of the rule or of the packet to check. The specified protocol can be one of tcp, udp, udplite, icmp, esp, ah, sctp or the special keyword "all", or it can be a numeric value, representing one of these protocols or a different one. A protocol name from /etc/protocols is also allowed. A "!" argument before the protocol inverts the test. The number zero is equivalent to all. "all" will match with all protocols and is taken as default when this option is omitted.
    required: false
  source:
    description: Source specification. Address can be either a network name, a hostname, a network IP address (with /mask), or a plain IP address. Hostnames will be resolved once only, before the rule is submitted to the kernel. Please note that specifying any name to be resolved with a remote query such as DNS is a really bad idea. The mask can be either a network mask or a plain number, specifying the number of 1's at the left side of the network mask. Thus, a mask of 24 is equivalent to 255.255.255.0. A "!" argument before the address specification inverts the sense of the address.Source specification. Address can be either a network name, a hostname, a network IP address (with /mask), or a plain IP address. Hostnames will be resolved once only, before the rule is submitted to the kernel. Please note that specifying any name to be resolved with a remote query such as DNS is a really bad idea. The mask can be either a network mask or a plain number, specifying the number of 1's at the left side of the network mask. Thus, a mask of 24 is equivalent to 255.255.255.0. A "!" argument before the address specification inverts the sense of the address.
    required: false
  destination:
    description: Destination specification. Address can be either a network name, a hostname, a network IP address (with /mask), or a plain IP address. Hostnames will be resolved once only, before the rule is submitted to the kernel. Please note that specifying any name to be resolved with a remote query such as DNS is a really bad idea. The mask can be either a network mask or a plain number, specifying the number of 1's at the left side of the network mask. Thus, a mask of 24 is equivalent to 255.255.255.0. A "!" argument before the address specification inverts the sense of the address.Source specification. Address can be either a network name, a hostname, a network IP address (with /mask), or a plain IP address. Hostnames will be resolved once only, before the rule is submitted to the kernel. Please note that specifying any name to be resolved with a remote query such as DNS is a really bad idea. The mask can be either a network mask or a plain number, specifying the number of 1's at the left side of the network mask. Thus, a mask of 24 is equivalent to 255.255.255.0. A "!" argument before the address specification inverts the sense of the address.
    required: false
  match:
    description: Specifies a match to use, that is, an extension module that tests for a specific property. The set of matches make up the condition under which a target is invoked. Matches are evaluated first to last if specified as an array and work in short-circuit fashion, i.e. if one extension yields false, evaluation will stop.
    required: false
  jump:
    description: This specifies the target of the rule; i.e., what to do if the packet matches it. The target can be a user-defined chain (other than the one this rule is in), one of the special builtin targets which decide the fate of the packet immediately, or an extension (see EXTENSIONS below). If this option is omitted in a rule (and the goto paramater is not used), then matching the rule will have no effect on the packet's fate, but the counters on the rule will be incremented.
    required: false
  goto:
    description: This specifies that the processing should continue in a user specified chain. Unlike the jump argument return will not continue processing in this chain but instead in the chain that called us via jump.
    required: false
  in_interface:
    description: Name of an interface via which a packet was received (only for packets entering the INPUT, FORWARD and PREROUTING chains). When the "!" argument is used before the interface name, the sense is inverted. If the interface name ends in a "+", then any interface which begins with this name will match. If this option is omitted, any interface name will match.
    required: false
  out_interface:
    description: Name of an interface via which a packet is going to be sent (for packets entering the FORWARD, OUTPUT and POSTROUTING chains). When the "!" argument is used before the interface name, the sense is inverted. If the interface name ends in a "+", then any interface which begins with this name will match. If this option is omitted, any interface name will match.
    required: false
  fragment:
    description: This means that the rule only refers to second and further fragments of fragmented packets. Since there is no way to tell the source or destination ports of such a packet (or ICMP type), such a packet will not match any rules which specify them. When the "!" argument precedes fragment argument, the rule will only match head fragments, or unfragmented packets.
    required: false
  set_counters:
    description: This enables the administrator to initialize the packet and byte counters of a rule (during INSERT, APPEND, REPLACE operations).
    required: false
  source_port:
    description: Source port or port range specification. This can either be a service name or a port number. An inclusive range can also be specified, using the format first:last. If the first port is omitted, "0" is assumed; if the last is omitted, "65535" is assumed. If the first port is greater than the second one they will be swapped.
    required: false
  destination_port:
    description: Destination port or port range specification. This can either be a service name or a port number. An inclusive range can also be specified, using the format first:last. If the first port is omitted, "0" is assumed; if the last is omitted, "65535" is assumed. If the first port is greater than the second one they will be swapped.
    required: false
  to_ports:
    description: This specifies a destination port or range of ports to use: without this, the destination port is never altered. This is only valid if the rule also specifies one of the following protocols: tcp, udp, dccp or sctp.
    required: false
'''

EXAMPLES = '''
# Block specific IP
- iptables: chain=INPUT source=8.8.8.8 jump=DROP
  become: yes

# Forward port 80 to 8600
- iptables: table=nat chain=PREROUTING in_interface=eth0 protocol=tcp match=tcp destination_port=80 jump=REDIRECT to_ports=8600
  become: yes
'''


def append_param(rule, param, flag, is_list):
    if is_list:
        for item in param:
            append_param(rule, item, flag, False)
    else:
        if param is not None:
            rule.extend([flag, param])


def construct_rule(params):
    rule = []
    append_param(rule, params['protocol'], '-p', False)
    append_param(rule, params['source'], '-s', False)
    append_param(rule, params['destination'], '-d', False)
    append_param(rule, params['match'], '-m', True)
    append_param(rule, params['jump'], '-j', False)
    append_param(rule, params['goto'], '-g', False)
    append_param(rule, params['in_interface'], '-i', False)
    append_param(rule, params['out_interface'], '-o', False)
    append_param(rule, params['fragment'], '-f', False)
    append_param(rule, params['set_counters'], '-c', False)
    append_param(rule, params['source_port'], '--source-port', False)
    append_param(rule, params['destination_port'], '--destination-port', False)
    append_param(rule, params['to_ports'], '--to-ports', False)
    return rule


def push_arguments(iptables_path, action, params):
    cmd = [iptables_path]
    cmd.extend(['-t', params['table']])
    cmd.extend([action, params['chain']])
    cmd.extend(construct_rule(params))
    return cmd


def check_present(iptables_path, module, params):
    cmd = push_arguments(iptables_path, '-C', params)
    rc, _, __ = module.run_command(cmd, check_rc=False)
    return (rc == 0)


def append_rule(iptables_path, module, params):
    cmd = push_arguments(iptables_path, '-A', params)
    module.run_command(cmd, check_rc=True)


def remove_rule(iptables_path, module, params):
    cmd = push_arguments(iptables_path, '-D', params)
    module.run_command(cmd, check_rc=True)


def main():
    module = AnsibleModule(
        supports_check_mode=True,
        argument_spec=dict(
            table=dict(required=False, default='filter', choices=['filter', 'nat', 'mangle', 'raw', 'security']),
            state=dict(required=False, default='present', choices=['present', 'absent']),
            ip_version=dict(required=False, default='ipv4', choices=['ipv4', 'ipv6']),
            chain=dict(required=True, default=None, type='str'),
            protocol=dict(required=False, default=None, type='str'),
            source=dict(required=False, default=None, type='str'),
            destination=dict(required=False, default=None, type='str'),
            match=dict(required=False, default=[], type='list'),
            jump=dict(required=False, default=None, type='str'),
            goto=dict(required=False, default=None, type='str'),
            in_interface=dict(required=False, default=None, type='str'),
            out_interface=dict(required=False, default=None, type='str'),
            fragment=dict(required=False, default=None, type='str'),
            set_counters=dict(required=False, default=None, type='str'),
            source_port=dict(required=False, default=None, type='str'),
            destination_port=dict(required=False, default=None, type='str'),
            to_ports=dict(required=False, default=None, type='str'),
        ),
    )
    args = dict(
        changed=False,
        failed=False,
        ip_version=module.params['ip_version'],
        table=module.params['table'],
        chain=module.params['chain'],
        rule=' '.join(construct_rule(module.params)),
        state=module.params['state'],
    )
    ip_version = module.params['ip_version']
    iptables_path = module.get_bin_path(BINS[ip_version], True)
    rule_is_present = check_present(iptables_path, module, module.params)
    should_be_present = (args['state'] == 'present')

    # Check if target is up to date
    args['changed'] = (rule_is_present != should_be_present)

    # Check only; don't modify
    if module.check_mode:
        module.exit_json(changed=args['changed'])

    # Target is already up to date
    if args['changed'] == False:
        module.exit_json(**args)

    if should_be_present:
        append_rule(iptables_path, module, module.params)
    else:
        remove_rule(iptables_path, module, module.params)

    module.exit_json(**args)

if __name__ == '__main__':
    main()