Re: [PATCH] firewall: Accept traffic on loopback interface if source and destination are within 127.0.0.0/8 only

[Michael Tremer <michael.tremer@ipfire.org>]

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Hello,

This is indeed *very* unlikely, but I am okay with this patch being accepted.

Acked-by: Michael Tremer <michael.tremer(a)ipfire.org>

Best,
-Michael

> On 13 May 2020, at 21:21, Peter Müller <peter.mueller(a)ipfire.org> wrote:
> 
> This ensures traffic on the loopback interface matches the IPv4
> loopback characteristics (source and destination are within 127.0.0.0/8)
> and prevents any damage in the unlikely case of non-loopback traffic
> being injected/emitted (in)to the loopback interface.
> 
> Cc: Arne Fitzenreiter <arne.fitzenreiter(a)ipfire.org>
> Cc: Michael Tremer <michael.tremer(a)ipfire.org>
> Signed-off-by: Peter Müller <peter.mueller(a)ipfire.org>
> ---
> src/initscripts/system/firewall | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/src/initscripts/system/firewall b/src/initscripts/system/firewall
> index 00512d9fa..409aaf7a9 100644
> --- a/src/initscripts/system/firewall
> +++ b/src/initscripts/system/firewall
> @@ -219,10 +219,10 @@ iptables_init() {
> 	iptables -A INPUT -j ICMPINPUT
> 	iptables -A ICMPINPUT -p icmp --icmp-type 8 -j ACCEPT
> 
> -	# Accept everything on loopback
> +	# Accept everything on loopback if both source and destination are within 127.0.0.0/8
> 	iptables -N LOOPBACK
> -	iptables -A LOOPBACK -i lo -j ACCEPT
> -	iptables -A LOOPBACK -o lo -j ACCEPT
> +	iptables -A LOOPBACK -i lo -s 127.0.0.0/8 -d 127.0.0.0/8 -j ACCEPT
> +	iptables -A LOOPBACK -o lo -s 127.0.0.0/8 -d 127.0.0.0/8 -j ACCEPT
> 
> 	# Filter all packets with loopback addresses on non-loopback interfaces.
> 	iptables -A LOOPBACK -s 127.0.0.0/8 -j DROP
> -- 
> 2.26.1