From: Pablo Neira Ayuso <pablo@netfilter.org>
To: Florian Westphal <fw@strlen.de>
Cc: netfilter-devel@vger.kernel.org, eric@garver.life, phil@nwl.cc,
kadlec@netfilter.org
Subject: Re: [PATCH RFC 2/2] netfilter: nf_nat: don't allow source ports that shadow local port
Date: Mon, 4 Oct 2021 12:16:46 +0200 [thread overview]
Message-ID: <YVrUjttDagSNWnWT@salvia> (raw)
In-Reply-To: <20211001132128.GG2935@breakpoint.cc>
On Fri, Oct 01, 2021 at 03:21:28PM +0200, Florian Westphal wrote:
> Florian Westphal <fw@strlen.de> wrote:
> > PoC, incomplete -- ipv4 udp only.
> >
> > Ipv6 support needs help from ipv6 indirection infra.
> >
> > Also lacks direction support: the check should only be done
> > for nf_conn objects created by externally generated packets.
>
> Alternate fix idea:
>
> 1. store skb->skb_iif in nf_conn.
>
> This means locally vs. remote-generated nf_conn can be identified
> via ct->skb_iff != 0.
>
> 2. For "remote" case, force following behaviour:
> check that sport > dport and sport > 1024.
>
> OTOH, this isn't transparent to users and might cause issues
> with very very old "credential passing" applications that insist
> on using privileged port range (< 1024) :-/
Can't this be just expressed through ruleset? I mean, conditionally
masquerade depending on whether the packet is locally generated or
not, for remove for sport > 1024 range.
next prev parent reply other threads:[~2021-10-04 10:16 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-23 13:12 [PATCH nf 0/1.5 RFC] netfilter: nat: source port shadowing Florian Westphal
2021-09-23 13:12 ` [PATCH nf 1/2] selftests: nft_nat: add udp hole punch test case Florian Westphal
2021-10-11 23:42 ` Pablo Neira Ayuso
2021-09-23 13:12 ` [PATCH RFC 2/2] netfilter: nf_nat: don't allow source ports that shadow local port Florian Westphal
2021-10-01 13:21 ` Florian Westphal
2021-10-04 10:16 ` Pablo Neira Ayuso [this message]
2021-10-04 10:41 ` Florian Westphal
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