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DISCUSSION [email protected] 3 participants 3 messages Feb 3, 2005

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[email protected]

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#0 lore raw

Hello,
My server is Mandrake 10.1
eth0 is WAN with static IP connected to 512k DSL
eth1 is LAN.

Basically I want clients to able to :

1. send and recieve mails

2. browse the net through squid

3. Use MSN or Yahoo

My iptables config is as follows :

# Generated by iptables-save v1.2.9 on Thu Oct 21 05:32:36 2004 *nat
:OUTPUT ACCEPT [0:0]
:PREROUTING ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]
-A POSTROUTING -o eth0 -j MASQUERADE
COMMIT
# Completed on Thu Oct 21 05:32:36 2004
# Generated by iptables-save v1.2.9 on Thu Oct 21 05:32:36 2004 *mangle
:PREROUTING ACCEPT [32056:3889577]
:INPUT ACCEPT [32010:3885659]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [31637:4617585]
:POSTROUTING ACCEPT [31639:4618071]
COMMIT
# Completed on Thu Oct 21 05:32:36 2004
# Generated by iptables-save v1.2.9 on Thu Oct 21 05:32:36 2004 *filter
:FORWARD DROP [0:0]
:INPUT DROP [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -j ACCEPT
-A INPUT -s 127.0.0.1 -j ACCEPT
-A INPUT -p tcp -m tcp -i eth1 --dport 3128 -j ACCEPT
-A INPUT -p udp -m udp -i eth1 --dport 3128 --sport 80 -j ACCEPT -A INPUT -s 62.0.0.0/255.0.0.0 -i eth0 -j REJECT
-A INPUT -p tcp -m tcp -s 217.81.0.0/255.255.0.0 -i eth0 -j REJECT -A INPUT -i eth0 -j DROP
-A INPUT -p tcp -m tcp -i eth1 --sport 80 -j DROP
-A INPUT -m state -i eth1 --state ESTABLISHED,RELATED -j ACCEPT -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
-A FORWARD -i eth1 -o eth0 -p tcp --syn --sport 1024 --dport 25 -j ACCEPT -A FORWARD -i eth1 -o eth0 -p tcp --syn --sport 1024 --dport 110 -j ACCEPT COMMIT
# Completed on Thu Oct 21 05:32:36 2004

Please feel free to comment and correct.

Thanks

Varun

#1 lore raw
Quoted 28 lines · On Thu, 2005-02-03 at 09:58 +0500, [email protected] wrote:

Hello,
My server is Mandrake 10.1
eth0 is WAN with static IP connected to 512k DSL
eth1 is LAN.

Basically I want clients to able to :

1. send and recieve mails

2. browse the net through squid

3. Use MSN or Yahoo

My iptables config is as follows :

# Generated by iptables-save v1.2.9 on Thu Oct 21 05:32:36 2004 *nat
:OUTPUT ACCEPT [0:0]
:PREROUTING ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]
-A POSTROUTING -o eth0 -j MASQUERADE
COMMIT
# Completed on Thu Oct 21 05:32:36 2004
# Generated by iptables-save v1.2.9 on Thu Oct 21 05:32:36 2004 *mangle
:PREROUTING ACCEPT [32056:3889577]
:INPUT ACCEPT [32010:3885659]

Quoted 8 lines

:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [31637:4617585]
:POSTROUTING ACCEPT [31639:4618071]
COMMIT
# Completed on Thu Oct 21 05:32:36 2004
# Generated by iptables-save v1.2.9 on Thu Oct 21 05:32:36 2004 *filter
:FORWARD DROP [0:0]

good

Quoted 1 line

:INPUT DROP [0:0]

good

Quoted 3 lines

:OUTPUT ACCEPT [0:0]

-A INPUT -j ACCEPT

You are accepting every packet

Quoted 1 line

-A INPUT -s 127.0.0.1 -j ACCEPT

rule unreachable

Quoted 1 line

-A INPUT -p tcp -m tcp -i eth1 --dport 3128 -j ACCEPT

rule unreachable

Review

Quoted 6 lines
(quoted diff) +0 -6
-A INPUT -p udp -m udp -i eth1 --dport 3128 --sport 80 -j ACCEPT
-A INPUT -s 62.0.0.0/255.0.0.0 -i eth0 -j REJECT
-A INPUT -p tcp -m tcp -s 217.81.0.0/255.255.0.0 -i eth0 -j REJECT
-A INPUT -i eth0 -j DROP
-A INPUT -p tcp -m tcp -i eth1 --sport 80 -j DROP
-A INPUT -m state -i eth1 --state ESTABLISHED,RELATED -j ACCEPT

all rule unreachable

Quoted 4 lines
(quoted diff) +0 -3
-A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
-A FORWARD -i eth1 -o eth0 -p tcp --syn --sport 1024 --dport 25 -j ACCEPT
-A FORWARD -i eth1 -o eth0 -p tcp --syn --sport 1024 --dport 110 -j ACCEPT

COMMIT

You should IPTables-HowTo.

MOhammad

Quoted 11 lines

# Completed on Thu Oct 21 05:32:36 2004

Please feel free to comment and correct.

Thanks

Varun

#2 lore raw
In reply to [email protected]
Quoted 8 lines · On Wed, 2005-02-02 at 23:58, [email protected] wrote:

Hello,
My server is Mandrake 10.1
eth0 is WAN with static IP connected to 512k DSL
eth1 is LAN.

Basically I want clients to able to :

1. send and recieve mails

internal users sending mail:

  iptables -A FORWARD -i eth1 -o eth0 -p tcp --syn \
    --sport 1024: --dport 25 -j ACCEPT

internal users receiving mail via pop3:

  iptables -A FORWARD -i eth1 -o eth0 -p tcp --syn \
    --sport 1024: --dport 110 -j ACCEPT
Quoted 1 line

2. browse the net through squid

internal users connecting to squid:

  iptables -A INPUT -i eth1 -p tcp --syn \
    --sport 1024: --dport 3128 -j ACCEPT

squid proxy fetching content from the internet:

  iptables -A OUTPUT -p udp \
    --sport 1024: --dport 53 -j ACCEPT

  iptables -A OUTPUT -o eth0 -p tcp --syn \
    -m owner --uid-owner squid \
    --sport 1024: --dport 80 -j ACCEPT
Quoted 1 line

3. Use MSN or Yahoo

msn:

  iptables -A FORWARD -i eth1 -o eth0 -p tcp --syn \
    --sport 1024: --dport 1863 -j ACCEPT

yahoo:

  iptables -A FORWARD -i eth1 -o eth0 -p tcp --syn \
    --sport 1024: --dport 5050 -j ACCEPT
Quoted 17 lines

My iptables config is as follows :

# Generated by iptables-save v1.2.9 on Thu Oct 21 05:32:36 2004 *nat
:OUTPUT ACCEPT [0:0]
:PREROUTING ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]
-A POSTROUTING -o eth0 -j MASQUERADE
COMMIT
# Completed on Thu Oct 21 05:32:36 2004
# Generated by iptables-save v1.2.9 on Thu Oct 21 05:32:36 2004 *mangle
:PREROUTING ACCEPT [32056:3889577]
:INPUT ACCEPT [32010:3885659]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [31637:4617585]
:POSTROUTING ACCEPT [31639:4618071]

Quoted 8 lines

COMMIT
# Completed on Thu Oct 21 05:32:36 2004
# Generated by iptables-save v1.2.9 on Thu Oct 21 05:32:36 2004 *filter
:FORWARD DROP [0:0]
:INPUT DROP [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -j ACCEPT

every INPUT rule after this is ignored, as you have just accepted all packets,

Review

Quoted 9 lines
(quoted diff) +0 -9
-A INPUT -s 127.0.0.1 -j ACCEPT
-A INPUT -p tcp -m tcp -i eth1 --dport 3128 -j ACCEPT
-A INPUT -p udp -m udp -i eth1 --dport 3128 --sport 80 -j ACCEPT
-A INPUT -s 62.0.0.0/255.0.0.0 -i eth0 -j REJECT
-A INPUT -p tcp -m tcp -s 217.81.0.0/255.255.0.0 -i eth0 -j REJECT
-A INPUT -i eth0 -j DROP
-A INPUT -p tcp -m tcp -i eth1 --sport 80 -j DROP
-A INPUT -m state -i eth1 --state ESTABLISHED,RELATED -j ACCEPT
-A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT

excellent.

Review

Quoted 2 lines
(quoted diff) +0 -2
-A FORWARD -i eth1 -o eth0 -p tcp --syn --sport 1024 --dport 25 -j ACCEPT
-A FORWARD -i eth1 -o eth0 -p tcp --syn --sport 1024 --dport 110 -j ACCEPT

those rules will only match packets that have a source port of exactly 1024--which won't be many packets. i think you mean "1024:"

-j

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