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Bug #10886

NAT64 allows to bypass pfBlockerNG IPv4 feed list

Added by Viktor Gurov about 2 months ago. Updated 7 days ago.

Status:
Closed
Priority:
Normal
Assignee:
-
Category:
pfBlockerNG
Target version:
-
Start date:
09/09/2020
Due date:
% Done:

0%

Estimated time:
Affected Version:
Affected Architecture:

Description

If NAT64 is used, the firewall first checks the rules and then translates IPv6 to IPv4.
In this case, if IPv4 feeds are used, they can be easily bypassed using the NAT64 representation.

Example:
pfBlockerNG PRI1 feed contains 1.1.1.1 address,
user can bypass it using NAT64 representation address: 64:ff9b::0101:0101

Solution:
add global pfBlockerNG options:
'Convert IPv4 addresses to NAT64 representations' - checkbox
'NAT64 prefix' - default 64:ff9b::/96 prefix

NAT64 feature: #2358

see also ipfw(8):

net.inet.ip.fw.nat64_direct_output: 0
         Controls the output method    used by    ipfw_nat64 module:

         0         A packet is handled by ipfw twice.     First time an origi-
             nal packet    is handled by ipfw and consumed    by ipfw_nat64
             translator.  Then translated packet is queued via netisr
             to    input processing again.

         1         A packet is handled by ipfw only once, and    after transla-
             tion it will be pushed directly to    outgoing interface.

History

#1 Updated by Rick Coats 18 days ago

I don't know if this is possible, but a more intuitive solution is to have a "interface" for NAT64 (non-intuitively it is ipv4), like is currently done for OpenVPN. This would give user flexibility to write firewall rules for it.

Otherwise, wouldn't this will cause the tables in pfblocker to more than double in size?

When I have used NAT64 (external device) with pfsense, I found that you do have to watch out for "bypassed" traffic via firewall rules.

#2 Updated by Viktor Gurov 7 days ago

  • Status changed from New to Closed

All good, no needs to change pfBlockerNG

https://github.com/pfsense/pfsense/pull/4405#issuecomment-708721849:

you need PF firewall rules that match the result AFTER translation (similar to how NAT44 works) or else it will drop it.
Please make sure that works to pass traffic for you. I.E. NAT64 64:ff9b::/96 -> 10.0.6.0/24 you need a accept source net 
10.0.6.0/24 on the IPv6 side and accept source net 64:ff9b::/96 on the IPv4 side.

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