From: Jacek Tomasiak <jtomasiak@arista.com>
To: netfilter@vger.kernel.org
Subject: Matching on protocols inside IPv6 IPSec AH (legacy vs nft)
Date: Thu, 22 Jun 2023 15:25:44 +0200 [thread overview]
Message-ID: <CAPEBPyMNe5dPTC9Dwp888M5RR-2ThC7ZtuaQPxNG+5VqbJinsQ@mail.gmail.com> (raw)
Hello,
I'm working on migrating from legacy iptables to iptables-nft and I encountered
a change in behaviour in handling the IPSec AH protocol.
With following two ipv6 rules:
-A INPUT -p ipv6-icmp --icmpv6-type echo-request -j ACCEPT
-A INPUT -m ipv6header --header ah --soft -j ACCEPT
After sending packets with following scapy code:
# ping6 without AH
pck = IPv6()/ICMPv6EchoRequest()
send(pck)
# ping6 with AH
sa = SecurityAssociation(AH, spi=0)
apck = sa.encrypt(pck)
send(apck)
I get this from ip6tables-nft -vS:
-P INPUT ACCEPT -c 0 0
-P FORWARD ACCEPT -c 0 0
-P OUTPUT ACCEPT -c 0 0
-A INPUT -p ipv6-icmp -m icmp6 --icmpv6-type 128 -c 1 48 -j ACCEPT
-A INPUT -m ipv6header --header ah --soft -c 1 64 -j ACCEPT
Hovewer, with ip6tables-legacy -vS:
-P INPUT ACCEPT -c 1 48
-P FORWARD ACCEPT -c 0 0
-P OUTPUT ACCEPT -c 1 48
-A INPUT -p ipv6-icmp -m icmp6 --icmpv6-type 128 -c 2 112 -j ACCEPT
-A INPUT -m ipv6header --header ah --soft -c 0 0 -j ACCEPT
My main concern is that in the nft version the AH rule matches one of the ICMP
packets even though the ICMP rule is higher up on the list.
I tried to debug this and it seems to be related to this change:
https://github.com/torvalds/linux/commit/568af6de058cb2b0c5b98d98ffcf37cdc6bc38a7
IIUC, this "stop ipv6_find_hdr on AH" is not a regression but intended behavior.
Now the question: is there some way to define rules which will match
the same way
as it works in iptables-legacy? That is, look at the inner protocol
and not stop on
AH?
Best Regards,
Jacek Tomasiak
next reply other threads:[~2023-06-22 13:25 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-22 13:25 Jacek Tomasiak [this message]
2023-06-22 22:00 ` Matching on protocols inside IPv6 IPSec AH (legacy vs nft) Pablo Neira Ayuso
2023-06-26 12:06 ` Jacek Tomasiak
2023-07-07 7:28 ` Pablo Neira Ayuso
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