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Help configuring IPTABLES

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.

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mcainc
Asked:
mcainc
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1 Solution
 
mgonulluCommented:
http://www.cae.wisc.edu/iptables-using#examples

Maybe this will be a good memory refreshment
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fosiul01Commented:
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
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mcaincAuthor Commented:
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
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mcaincAuthor Commented:
hmm, i see some strange characters before -dport & -state... they should be the standard hyphen -
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fosiul01Commented:
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
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fosiul01Commented:
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 ??
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mcaincAuthor Commented:
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mcaincAuthor Commented:
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
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fosiul01Commented:
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
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mcaincAuthor Commented:
thanks for the help!
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