Penetration Testing mailing list archives
Re: Any way to automatically change arbitrary headers of IP packets on-the-fly?
From: João Paulo Caldas Campello <protecao () gmail com>
Date: Fri, 15 Apr 2005 20:12:24 -0300
On 4/14/05, Valdis.Kletnieks () vt edu <Valdis.Kletnieks () vt edu> wrote:
Currently, iptables doesn't seem to support that, probably to keep you from shooting yourself in the foot. Consider for example how fast the kernel will fold up if you change that first nybble of the packet from an x'4' to an x'6' without changing the rest of the packet to match. Suddenly, that sk_buff is a lot too short.. ;)
Yeah, maybe, who knows :P Well, I've did some searching last days and found a couple ways to achieve what I've described in my email. One is using "DIVERT sockets" and other is the use of the "-j QUEUE" target of iptables/netfilter. Both approaches are similar: you match a packet using iptables to flush them to userspace, where you can mangle the entire packet as you like and send it back to iptables, who will put it again onto the stack. The "-j QUEUE" approach is manipulated through the "libipq" API: - netfilter can feed userspace using IPQUEUE: * http://www.crhc.uiuc.edu/~grier/projects/libipq.html - Perl: * http://www.intercode.com.au/jmorris/perlipq/ - Python: * http://woozle.org/~neale/src/ipqueue/ As you can see, there's already libraries written in Perl and Python to query IPQUEUE, so the effort of writing userspace code to deal with IP packets wiil be much more easier. That's it =) Cheers, João Paulo.
Current thread:
- Any way to automatically change arbitrary headers of IP packets on-the-fly? João Paulo Caldas Campello (Apr 12)
- Re: Any way to automatically change arbitrary headers of IP packets on-the-fly? Lynx (Apr 13)
- Re: Any way to automatically change arbitrary headers of IP packets on-the-fly? Vladimir Parkhaev (Apr 13)
- Re: Any way to automatically change arbitrary headers of IP packets on-the-fly? Kary Rogers (Apr 13)
- Re: Any way to automatically change arbitrary headers of IP packets on-the-fly? João Paulo Caldas Campello (Apr 17)
- <Possible follow-ups>
- Re: Any way to automatically change arbitrary headers of IP packets on-the-fly? Sebastian Muñiz (Apr 13)
- Re: Any way to automatically change arbitrary headers of IP packets on-the-fly? Foundation Linux (Apr 13)
- Re: Any way to automatically change arbitrary headers of IP packets on-the-fly? João Paulo Caldas Campello (Apr 17)