[PATCH] Send bad forward_zone packets to verdict_from_zone

dsmtngoat at gmail.com dsmtngoat at gmail.com
Wed Sep 28 08:31:26 PDT 2022

From: Gordon Maclean <dsmtngoat at gmail.com>

Received forward packets which fail acceptance tests are finally handled by a <verdict>_to_<zone> chain
where <verdict> is typically "drop" or "reject".  This "_to_" chain only matches packets destined
for the interface, and so does not match packets destined for interfaces other than where they were received.

As a result the final resolution depends on the default policy for the forward chain, which for a
reasonably configured router is "drop" or "reject", so this is unlikely to be a security hole,
This does not match what the user has configured as the resolution of forward packets received
for the zone.  Also, if the user has enabled logging of failed packets, these packets will not be logged.

This patch may also result in failues in firewall4/tests. That has not been investigated.
 root/usr/share/firewall4/templates/ruleset.uc | 2 +-
 root/usr/share/ucode/fw4.uc                   | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/root/usr/share/firewall4/templates/ruleset.uc b/root/usr/share/firewall4/templates/ruleset.uc
index eaa1f04..daef252 100644
--- a/root/usr/share/firewall4/templates/ruleset.uc
+++ b/root/usr/share/firewall4/templates/ruleset.uc
@@ -239,7 +239,7 @@ table inet fw4 {
 		ct status dnat accept comment "!fw4: Accept port forwards"
 {%  endif %}
 {%  fw4.includes('chain-append', `forward_${zone.name}`) %}
-		jump {{ zone.forward }}_to_{{ zone.name }}
+		jump {{ zone.forward }}_from_{{ zone.name }}
 {%  if (zone.dflags.helper): %}
diff --git a/root/usr/share/ucode/fw4.uc b/root/usr/share/ucode/fw4.uc
index 29ae053..a6c1ae5 100644
--- a/root/usr/share/ucode/fw4.uc
+++ b/root/usr/share/ucode/fw4.uc
@@ -2113,6 +2113,7 @@ return {
 		zone.sflags = {};
 		zone.sflags[zone.input] = true;
+		zone.sflags[zone.forward] = true;
 		zone.dflags = {};
 		zone.dflags[zone.output] = true;

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