11-04-2016
Openvpn nat and iptables
good day good people
hi
first to tell that firewall and vpn is working as expected, but I notice something strange.
I have host system 11.11.11.11(local ip) firewall is blocking everything except port to vpn.
I have vpn on virtualized system 22.22.22.22 (CentOS both host and virtual). They are behind MikroTik router and then to my ISP router. This is a home setup I'm just experimenting.
PREROUTING 11.11.11.11:1194 to 22.22.22.22:1194 all other is blocked by iptables.
POSTROUTING 22.22.22.22 to 11.11.11.11
I noticed with Wireshark from host 11.11.11.11 that while I'm connected to vpn from another pc that 11.11.11.11 is connecting to ip addresses of websites I visit while in same time is connected to vpn. like:
11.11.11.11 XX.XX.XX public ip
11.11.11.11 tcp udp sites i visit
but 11.11.11.11 is unnecessarily making connections to website ip addresses. She cannot make the reqests because DNS and ports for that are blocked. So this is because postrouting command my best guess. Can this somehow be disabled? First this is a security issue, second its unnecessary.
Someone told me that this is because NAT setup. but I believe that this can be disabled somehow, I didn't find solution yet so maybe someone know how.
thanks
Moderator's Comments:
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We had to correct a lot of spelling errors. Please put more effort into using proper english
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Last edited by Scrutinizer; 11-05-2016 at 04:48 AM..
Reason: Spelling
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LEARN ABOUT DEBIAN
pyroman
PYROMAN(8) System Manager's Manual PYROMAN(8)
NAME
pyroman - a firewall configuration utility
SYNOPSIS
pyroman
[ -hvnspP ] [ -r RULESDIR ] [ -t SECONDS ]
[ --help ] [ --version ] [ --safe ] [ --no-act ]
[ --print ] [ --print-verbose ] [ --rules=RULESDIR ]
[ --timeout=SECONDS ] [ safe ]
DESCRIPTION
pyroman is a firewall configuration utility.
It will compile a set of configuration files to iptables statements to setup IP packet filtering for you.
While it is not necessary for operating and using Pyroman, you should have understood how IP, TCP, UDP, ICMP and the other commonly used
Internet protocols work and interact. You should also have understood the basics of iptables in order to make use of the full
functionality.
pyroman does not try to hide all the iptables complexity from you, but tries to provide you with a convenient way of managing a complex
networks firewall. For this it offers a compact syntax to add new firewall rules, while still exposing access to add arbitrary iptables
rules.
OPTIONS
-r RULESDIR,--rules=RULES
Load the rules from directory RULESDIR instead of the default directory (usually /etc/pyroman )
-t SECONDS,--timeout=SECONDS
Wait SECONDS seconds after applying the changes for the user to type OK to confirm he can still access the firewall. This implies
--safe but allows you to use a different timeout.
-h, --help
Print a summary of the command line options and exit.
-V, --version
Print the version number of pyroman and exit.
-s, --safe, safe
When the firewall was committed, wait 30 seconds for the user to type OK to confirm, that he can still access the firewall (i.e. the
network connection wasn't blocked by the firewall). Otherwise, the firewall changes will be undone, and the firewall will be
restored to the previous state. Use the --timeout=SECONDS option to change the timeout.
-n, --no-act
Don't actually run iptables. This can be used to check if pyroman accepts the configuration files.
-p, --print
Instead of running iptables, output the generated rules.
-P, --print-verbose
Instead of running iptables, output the generated rules. Each statement will have one comment line explaining how this rules was
generated. This will usually include the filename and line number, and is useful for debugging.
CONFIGURATION
Configuration of pyroman consists of a number of files in the directory /etc/pyroman. These files are in python syntax, although you do
not need to be a python programmer to use these rules. There is only a small number of statements you need to know:
add_host
Define a new host or network
add_interface
Define a new interface (group)
add_service
Add a new service alias (note that you can always use e.g. www/tcp to reference the www tcp service as defined in /etc/services)
add_nat
Define a new NAT (Network Address Translation) rule
allow Allow a service, client, server combination
reject Reject access for this service, client, server combination
drop Drop packets for this service, client, server combination
add_rule
Add a rule for this service, client, server and target combination
iptables
Add an arbitrary iptables statement to be executed at beginning
iptables_end
Add an arbitrary iptables statement to be executed at the end
Detailed parameters for these functions can be looked up by caling
cd /usr/share/pyroman
pydoc ./commands.py
BUGS
None known as of pyroman-0.4 release
AUTHOR
pyroman was written by Erich Schubert <erich@debian.org>
SEE ALSO
iptables(8), iptables-restore(8) iptables-load(8)
PYROMAN(8)