linux-kernel - Re: [PATCH net v5 2/2] net: netfilter: Fix port selection of FTP for NF_NAT_RANGE_PROTO

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Date:   Mon, 20 Sep 2021 09:23:05 +0200
From:   Florian Westphal <fw@...len.de>
To:     Cole Dishington <Cole.Dishington@...iedtelesis.co.nz>
Cc:     pablo@...filter.org, kadlec@...filter.org, fw@...len.de,
        davem@...emloft.net, kuba@...nel.org, shuah@...nel.org,
        linux-kernel@...r.kernel.org, netfilter-devel@...r.kernel.org,
        coreteam@...filter.org, netdev@...r.kernel.org,
        Anthony Lineham <anthony.lineham@...iedtelesis.co.nz>,
        Scott Parlane <scott.parlane@...iedtelesis.co.nz>,
        Blair Steven <blair.steven@...iedtelesis.co.nz>
Subject: Re: [PATCH net v5 2/2] net: netfilter: Fix port selection of FTP for
 NF_NAT_RANGE_PROTO_SPECIFIED

Cole Dishington <Cole.Dishington@...iedtelesis.co.nz> wrote:
> FTP port selection ignores specified port ranges (with iptables
> masquerade --to-ports) when creating an expectation, based on
> FTP commands PORT or PASV, for the data connection.
> 
> For masquerading, this issue allows an FTP client to use unassigned
> source ports for their data connection (in both the PORT and PASV
> cases). This can cause problems in setups that allocate different
> masquerade port ranges for each client.
> 
> The proposed fix involves storing a port range (on nf_conn_nat) to:
> - Fix FTP PORT data connections using the stored port range to select a
>   port number in nf_conntrack_ftp.
> - Fix FTP PASV data connections using the stored port range to specify a
>   port range on source port in nf_nat_helper if the FTP PORT/PASV packet
>   comes from the client.

Looks much simpler now, thanks.

Acked-by: Florian Westphal <fw@...len.de>