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

[Matthias Fischer <matthias.fischer@ipfire.org>]

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Hi,

perhaps its only me, but after applying this patch for testing purposes
I don't see any (redirected) urlfilter block pages anymore.

Only the firewall logs are telling me:

...
REJECT_INPUT lo TCP 192.168.100.254 53464 192.168.100.254 81
...

I had to build a new "Incoming Firewall Access" rule (INPUTFW) allowing
TCP traffic from (e.g.) 192.168.100.254/32 to GREEN (192.168.100.254) to
TCP port 81 to see a block page again...

Only me?

Best,
Matthias

On 14.05.2020 12:36, Michael Tremer wrote:
> 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
>