Solved

Help configuring IPTABLES

Posted on 2008-10-21
10
313 Views
Last Modified: 2013-12-16
I need some assistance configuring IPTABLES (haven't done it in ages).

I want to restrict all incoming connections on any port to "trusted" IPs.

I will have a local squid server running & want to make sure it isnt wide open... also some other services that I want to filter this way as well.

0
Comment
Question by:mcainc
  • 5
  • 4
10 Comments
 
LVL 9

Expert Comment

by:mgonullu
Comment Utility
http://www.cae.wisc.edu/iptables-using#examples

Maybe this will be a good memory refreshment
0
 
LVL 29

Expert Comment

by:fosiul01
Comment Utility
the tutorial mgonullu provided its quite good

basicaly,

start of with block every port ( incomming port)

iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -P FORWARD DROP
then open one by one as you go and as you need

iptables -A INPUT  -p tcp --dport 22 -j ACCEPT    (ssh)

iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT


http://www.cyberciti.biz/tips/linux-iptables-6-how-to-block-outgoing-access-to-selectedspecific-ip-address.html
http://www.cyberciti.biz/tips/linux-iptables-4-block-all-incoming-traffic-but-allow-ssh.html
0
 

Author Comment

by:mcainc
Comment Utility
i've been reading a bit and would like to know if this is valid, i want to allow ssh access & ftp access to my home ip ("ip.ip.ip.ip")

i'm not concerned with blocking the outgoing packets from the server, only preventing what is allowed in

before i run this i want to make sure it is accurate so i dont lock myself out!


# flushing rules

iptables -F
iptables -X

# blocking all ports

iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -P FORWARD DROP

# allowing loopback unrestricted access

iptables -A INPUT -i lo
iptables -A OUTPUT -o lo

# allowing trusted ips appropriate access

iptables -A INPUT -s ip.ip.ip.ip -j ACCEPT
iptables -A OUTPUT -d ip.ip.ip.ip -j ACCEPT

# allow incoming ssh

iptables -A INPUT -p tcp dport 22 -m state state NEW -j ACCEPT

# allow incoming ftp

iptables -A INPUT -p tcp dport 21 -m state state NEW -j ACCEPT

# nothing else gets into this box

iptables -A INPUT -j DROP
0
 

Author Comment

by:mcainc
Comment Utility
hmm, i see some strange characters before -dport & -state... they should be the standard hyphen -
0
 
LVL 29

Expert Comment

by:fosiul01
Comment Utility
its seems alright to me
but if you see, you system is resonding slowly to ssh connection to be established
then just add this 2 rules

iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
0
Get up to 2TB FREE CLOUD per backup license!

An exclusive Black Friday offer just for Expert Exchange audience! Buy any of our top-rated backup solutions & get up to 2TB free cloud per system! Perform local & cloud backup in the same step, and restore instantly—anytime, anywhere. Grab this deal now before it disappears!

 
LVL 29

Expert Comment

by:fosiul01
Comment Utility
I always use this command  to allow any port to come

iptables -A INPUT  -p tcp --dport 22 -j ACCEPT    (ssh)

but you have used this
iptables -A INPUT -p tcp dport 22 -m state state NEW -j ACCEPT


" -m state state " from which reference you got this one ??
0
 

Author Comment

by:mcainc
Comment Utility
0
 

Author Comment

by:mcainc
Comment Utility
if i am specifying trusted ip addresses to only be able to access the system, is it even necessary to block ports?

it seems pointless because the ips are trusted... so can this all just be simplified by

# flushing rules

iptables -F
iptables -X

# blocking all ports

iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -P FORWARD DROP

# allowing loopback unrestricted access

iptables -A INPUT -i lo
iptables -A OUTPUT -o lo

# allowing trusted ips appropriate access

iptables -A INPUT -s ip.ip.ip.ip -j ACCEPT
iptables -A OUTPUT -d ip.ip.ip.ip -j ACCEPT

# optimizing

iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# nothing else gets into this box

iptables -A INPUT -j DROP
0
 
LVL 29

Accepted Solution

by:
fosiul01 earned 500 total points
Comment Utility
yes its finej
iptables -F
iptables -X

# blocking all ports

iptables -P INPUT DROP
iptables -P OUTPUT DROP
iptables -P FORWARD DROP

# allowing loopback unrestricted access

iptables -A INPUT -i lo
iptables -A OUTPUT -o lo

# allowing trusted ips appropriate access

iptables -A INPUT -s ip.ip.ip.ip -j ACCEPT
iptables -A OUTPUT -d ip.ip.ip.ip -j ACCEPT

# optimizing

iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT

# nothing else gets into this box

iptables -A INPUT -j DROP


you just have to add the port such as 22, 80(web site) to allow to your box

thats it
how are you adding this rule ??
just add by hand, one by one command, then test it, if you are happy
then

service iptables save

it will automaticaly save all rules in iptables
0
 

Author Closing Comment

by:mcainc
Comment Utility
thanks for the help!
0

Featured Post

How your wiki can always stay up-to-date

Quip doubles as a “living” wiki and a project management tool that evolves with your organization. As you finish projects in Quip, the work remains, easily accessible to all team members, new and old.
- Increase transparency
- Onboard new hires faster
- Access from mobile/offline

Join & Write a Comment

These are on the increase and getting more common these days. Users who use the Google search engine may complain of having their search redirected to unwanted sites, regardless of what browser is used. This happens when the system is infected with…
If you have a server on collocation with the super-fast CPU, that doesn't mean that you get it running at full power. Here is a preamble. When doing inventory of Linux servers, that I'm administering, I've found that some of them are running on l…
Learn several ways to interact with files and get file information from the bash shell. ls lists the contents of a directory: Using the -a flag displays hidden files: Using the -l flag formats the output in a long list: The file command gives us mor…
This demo shows you how to set up the containerized NetScaler CPX with NetScaler Management and Analytics System in a non-routable Mesos/Marathon environment for use with Micro-Services applications.

763 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

10 Experts available now in Live!

Get 1:1 Help Now