From ab0bf1867d9946c1fac57e8ec2bdff1ad07aff33 Mon Sep 17 00:00:00 2001 From: Guilhem Moulin Date: Mon, 18 May 2020 01:15:43 +0200 Subject: Firewall: Use `meta secpath exists` to match xfrm associations. Marking incoming ESP packets and matching decapsulated packets doesn't work with NAT traverslate (UDP encapsulation aka MOBIKE). --- roles/common/templates/etc/nftables.conf.j2 | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) diff --git a/roles/common/templates/etc/nftables.conf.j2 b/roles/common/templates/etc/nftables.conf.j2 index 3104a4a..2261994 100755 --- a/roles/common/templates/etc/nftables.conf.j2 +++ b/roles/common/templates/etc/nftables.conf.j2 @@ -56,13 +56,15 @@ table inet filter { iif lo accept - # XXX Bullseye: this is a hack for the lack of reqid matches in - # nftables: we mark the esp packet and accept after decapsulation + # XXX Bullseye: this is a rather crude match as nftables 0.9.0 lacks support for ipsec expressions + # to match match inbound resp. outbound policies and source resp. destination tunnel addresses. # https://serverfault.com/questions/971735/how-to-match-reqid-in-nftables # https://blog.fraggod.net/2016/09/25/nftables-re-injected-ipsec-matching-without-xt_policy.html - define IPsec.mark = 0x220 - meta l4proto esp mark set mark | $IPsec.mark accept - ip saddr 172.16.0.0/24 ip daddr {{ ipsec[inventory_hostname_short] }} mark & $IPsec.mark == $IPsec.mark accept + # (We can't use marks to match post-ESP decapsulation here because that doesn't work well with UDP + # encapsulation.) + meta l4proto esp accept + # ipsec in ip saddr {{ ipsec_subnet }} ip daddr {{ ipsec[inventory_hostname_short] }} accept + ip saddr {{ ipsec_subnet }} ip daddr {{ ipsec[inventory_hostname_short] }} meta secpath exists accept # rate-limiting is done directly by the kernel (net.ipv4.icmp_{ratelimit,ratemask} runtime options) icmp type { echo-reply, echo-request, destination-unreachable } counter accept @@ -104,11 +106,12 @@ table inet filter { oif lo accept - # XXX Bullseye: unlike for input we can't use marks here, - # because by the time we see a packet to 172.16.0.0/24 we don't - # know if it'll be encapsulated + # XXX Bullseye: unlike for input we can't use marks or test for + # secpath existence here, because by the time we see a packet to + # 172.16.0.0/24 we don't know if it'll be encapsulated meta l4proto esp accept - ip saddr {{ ipsec[inventory_hostname_short] }} ip daddr 172.16.0.0/24 accept + # ipsec out ip saddr {{ ipsec[inventory_hostname_short] }} ip daddr {{ ipsec_subnet }} accept + ip saddr {{ ipsec[inventory_hostname_short] }} ip daddr {{ ipsec_subnet }} accept meta l4proto { icmp, icmpv6 } accept -- cgit v1.2.3