Allow client only 1 connect per 20 seconds

Allow client only 1 connect per 20 seconds

[Adem]

How would you code this rule in iptables:

If anybody tries to do more than 1 connection to port 8191
within 20 seconds, regardless of the protocol, then DROP 
it and ignore any further connect attempts on that port
from that source for 20 seconds.

Re: Allow client only 1 connect per 20 seconds

[Adem]

"Adem" wrote:
>
> How would you code this rule in iptables:
> 
> If anybody tries to do more than 1 connection to port 8191
> within 20 seconds, regardless of the protocol, then DROP 
> it and ignore any further connect attempts on that port
> from that source for 20 seconds.

The following should work, but it somehow doesn't work in iptables v1.4.1.1:
 ...
  # if anybody from the list WATCHLIST, and in the last 20 sec, tries to do new connect attempts then DROP them!
  /sbin/iptables -A INPUT --match recent --name WATCHLIST --rcheck --seconds 20 -j DROP

  # accept client at port 8191 (all protocols) and register in WATCHLIST
  # BUG: if "-p XXX" is left out or if instead "-p all" is used then the rule gets eliminated!
  /sbin/iptables -A INPUT -p all --dport 8191 --match recent --name WATCHLIST --set -j DROP
 ...

It works only if "-p tcp" is specified.
Isn't that a bug in iptables?

Re: Allow client only 1 connect per 20 seconds

[Matt Zagrabelny]

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On Tue, 2008-11-25 at 21:07 +0100, Adem wrote:
> "Adem" wrote:
> >
> > How would you code this rule in iptables:
> > 
> > If anybody tries to do more than 1 connection to port 8191
> > within 20 seconds, regardless of the protocol, then DROP 
> > it and ignore any further connect attempts on that port
> > from that source for 20 seconds.
> 
> The following should work, but it somehow doesn't work in iptables v1.4.1.1:
>  ...
>   # if anybody from the list WATCHLIST, and in the last 20 sec, tries to do new connect attempts then DROP them!
>   /sbin/iptables -A INPUT --match recent --name WATCHLIST --rcheck --seconds 20 -j DROP
> 
>   # accept client at port 8191 (all protocols) and register in WATCHLIST
>   # BUG: if "-p XXX" is left out or if instead "-p all" is used then the rule gets eliminated!
>   /sbin/iptables -A INPUT -p all --dport 8191 --match recent --name WATCHLIST --set -j DROP
>  ...
> 
> It works only if "-p tcp" is specified.

From the man page:

These extensions can be used if ‘--protocol tcp’ is specified.
These extensions can be used if ‘--protocol udp’ is specified.

Hence, these extensions cannot be used with '--protocol all'.
So, it looks like you will need to double the number of rules you have.

> Isn't that a bug in iptables?

Doesn't look like it.

-- 
Matt Zagrabelny - mzagrabe@d.umn.edu - (218) 726 8844
University of Minnesota Duluth
Information Technology Systems & Services
PGP key 1024D/84E22DA2 2005-11-07
Fingerprint: 78F9 18B3 EF58 56F5 FC85  C5CA 53E7 887F 84E2 2DA2

He is not a fool who gives up what he cannot keep to gain what he cannot
lose.
-Jim Elliot

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Re: Allow client only 1 connect per 20 seconds

[Matt Zagrabelny]

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On Tue, 2008-11-25 at 19:38 +0100, Adem wrote:
> How would you code this rule in iptables:
> 
> If anybody tries to do more than 1 connection to port 8191
> within 20 seconds, regardless of the protocol, then DROP 
> it and ignore any further connect attempts on that port
> from that source for 20 seconds.

NOTE: this is completely untested:

iptables -A INPUT -p tcp --dport 8191 --match state --state
ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -p tcp --dport 8191 --match state --state NEW --match
recent --name THROTTLE --set
iptables -A INPUT -p tcp --dport 8191 --match state --state NEW --match
recent --name THROTTLE --update --seconds 20 --hitcount 2 --rttl -j DROP

Same rules for '-p udp'.

Cheers,

-- 
Matt Zagrabelny - mzagrabe@d.umn.edu - (218) 726 8844
University of Minnesota Duluth
Information Technology Systems & Services
PGP key 1024D/84E22DA2 2005-11-07
Fingerprint: 78F9 18B3 EF58 56F5 FC85  C5CA 53E7 887F 84E2 2DA2

He is not a fool who gives up what he cannot keep to gain what he cannot
lose.
-Jim Elliot

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Re: Allow client only 1 connect per 20 seconds

[Paul Evans]

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On Tue, 25 Nov 2008 21:07:13 +0100
"Adem" <for-gmane@alicewho.com> wrote:

> It works only if "-p tcp" is specified.
> Isn't that a bug in iptables?

Port numbers only make sense in some higher-level protocols built on
top of IP, such as TCP and UDP. What would the "port number" be of an
ICMP packet, or an AH or ESP IPsec header, or any of these other
ideas..?

-- 
Paul Evans <paul@mxtelecom.com>
Tel: +44 (0) 845 666 7778
Fax: +44 (0) 870 163 4694
http://www.mxtelecom.com

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