Scope#
Raspberry is exposed to the internet for my backup solution. I want to enable ipv6 access only and enable access only from my home computer.Steps:
- register your home computer (Windows) at a dyndns service to provide the current ipv6, see dynv6.com
- Windows: create windows batch script to update dynv6
- Windows schedule script to run each time the PC is booted, see "Aufgabenplanung" (task scheduler)
- Raspberry: create and set iptables ruleset
- Raspberry: use python script to query the current ipv6 from dynv6 (Windows) and replace in iptables ruleset
- Raspberry: schedule the ipv6 update in firewall (ip6tables)
2. Windows batch script to update dynv6 service#
REM update_dynv6.bat
REM set utf-8
chcp 65001
echo off
set domain=<your.domain.here>
set token=<youtTokenHere>
echo ---- check and update local ipv6 address at dynv6.com for %domain% ----
rem ping -n 1 -6 %domain%
for /F "tokens=3" %%i in ('"ping -n 1 -6 %domain% | findstr Antwort"') do set dynv6_ipv6=%%i
rem cut last colon, example 2a02:5a0:4110:f590:29f6:40ba:51b4:b4da:
set dynv6_ipv6=%dynv6_ipv6:~0,-1%
echo dynv6 ipv6= %dynv6_ipv6%
rem ipconfig
rem echo ---------- extracting Temporäre IPv6-Adresse ----------
for /F "tokens=9" %%i in ('"ipconfig | findstr Temp | findstr 2a02"') do set local_ipv6=%%i
echo local ipv6= %local_ipv6%
if %local_ipv6% == %dynv6_ipv6% (
echo ipv6 at dynv6 is up to date, update skipped
) else (
set url="https://dynv6.com/api/update?hostname=%domain%^&token=%token%&ipv6=%ipv6%"
ECHO updating IPv6
curl "%url%"
)
echo:
echo done
pause
iptables#
Commands#
> ls -la /usr/sbin/ip* # list all commands, there are many > iptables* # for ipv4 (in debian busters = nft) > ip6tables* # for ipv6 (in debian busters = nft) > iptables-legacy # former ones, not nft > iptables-nft # directly use nftNotes:
- all iptables commands (for ipv4) have an ip6tabbles* equivalent (for ipv6)
- see info on nft
> who -u # get all sessions with ip and pid > sudo netstat -pantW # list network connections, p=programs,a=all,n=IPs,t=tcp,W=wide(not truncate IP address) > ip a # list all ips > sudo ip6tables -L -v # list all ipv6 rules > sudo ip6tables -n -v --line-numbers -L # list all ipv6 rules with numeric IPs and rule number
Syntax#
see docu
> sudo iptables -L -v > sudo iptables -n -v --line-numbers -L > sudo service iptables start # activate firewalling > sudo service ip6tables start > sudo chkconfig iptables on # enable after reboot > sudo chkconfig ip6tables on
iptables [-t <table-name>] <command> <chain-name> <parameter-1> <option-1> <parameter-n> <option-n>
- table-name
- like [filter, nat, mangle, raw, security], if omitted we use "filter"
- command
- -F : flush current chain or all if omitted
- -X : deletes a user-specified chain or all if omitted
- -Z : zeros the byte and packet counters in all chains
- -A : apppend a rule at the end
- -I : inserts at a specified position (similar to replace -R), wihtout position at the top
- -P : a policy is a fall back and is used after all rules have passede** you can enable certain special addresses earlier
- -L : list all rules
- chain-name
- INPUT, FORWARD, OUTPUT (as listed with > iptables -L)
- you may invent new chain names, but this seems not to be common (command -N)
- parameter-1 (filter)
- -s : source filter (address[/mask][...])
- -d : destination filter
- -p : protocoll filter like [icmp, tcp, udp, all] or those in /etc/protocols, if omitted ALL protocols are considered
- with -p tcp you can use --dport for destination port filter, any number
- with -p udp you can use --dport for destination port and --sport as source port filter
- ports can be also a range like 3000:3200 (all from 3000 to 3200)
- with -p icmp you can use --icmp-type
- -i : interface like [eth0, lo, ppp0], without name ALL interfaces are used
- -j : jump to [ACCEPT, DROP, QUEUE, RETURN] (or others added with modules)
- -m : adds a comment when listing the rules, syntax >-m comment --comment "My comments here"<
- option-1 (target)
- [ACCEPT, DROP, QUEUE, RETURN] (or others added with modules)
- option-n (listing options)
- -v : verbose output
- -n : displays IP addresses and port numbers in numeric format instead of hostname/network service
- notes
- the first three commands are usually used to create a fresh ruleset in a script
- in the chain list and then drop all other later
4. my general ruleset#
#!/bin/bash # MARKUS #SOURCE=2a02:5a0:4110:f590:fdd3:3e99:a137:852c SOURCE=:: # ipv4 ------------------------------------ # Flush all rules and delete all chains for a clean startup iptables -F iptables -X iptables -Z # Zero out all counters # drop all ipv4 traffic, we want to use ipv6 only iptables -A INPUT -s 1.1.1.1 -j ACCEPT iptables -A OUTPUT -d 1.1.1.1 -j ACCEPT iptables -A INPUT -s 8.8.8.8 -j ACCEPT iptables -A OUTPUT -d 8.8.8.8 -j ACCEPT iptables -A INPUT -i lo -j ACCEPT iptables -A OUTPUT -o lo -j ACCEPT iptables -A INPUT -j DROP iptables -A FORWARD -j DROP iptables -A OUTPUT -j DROP # ipv6 ------------------------------------ # Flush all rules and delete all chains for a clean startup ip6tables -F ip6tables -X ip6tables -Z # drop all ipv6 traffic, except EbelStube # do not limit to --dport 22, because the source has random ports (?) # add first to enabel replacing 1. rule later ip6tables -A INPUT -s $SOURCE -j ACCEPT ip6tables -A OUTPUT -d $SOURCE -j ACCEPT # allow ipv6 local loopback ip6tables -A INPUT -i lo -j ACCEPT ip6tables -A OUTPUT -o lo -j ACCEPT # drop everthing else ip6tables -P FORWARD DROP # as policy generally ip6tables -A INPUT -j DROP ip6tables -A OUTPUT -j DROP # update first ip6tables rules and enable my computer python update_ip6tables.py
Python#
- package "python3-iptables" manages legacy ones only, docu1, docu2
- package "python3-nftables" manages nft tables, docu
- alternatively you can use subprocess.run to call the original system commands
5. subprocess#
import socket # determine ipv6
import subprocess
tupel = socket.getaddrinfo('your.pc.com', None, socket.AF_INET6)
# tupel like [(<AddressFamily.AF_INET6: 23>, 0, 0, '', ('2a02:5a0:4110:f590:4670:d3e6:f2bc:ee', 8384, 0, 0))]
print("tupel=", tupel)
ipv6=tupel[0][4][0]
print("ipv6=", ipv6)
subprocess.run(["/usr/sbin/ip6tables", "-R", "INPUT", "1", "-s", ipv6, "-j", "ACCEPT"])
subprocess.run(["/usr/sbin/ip6tables", "-R", "OUTPUT", "1", "-d", ipv6, "-j", "ACCEPT"])
6. Schedule script with crontab#
Run every 15 minutes
*/15 * * * mon /home/markus/yourscript.sh