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Add a default-deny nftables ruleset for the fips0 mesh interface as a packaged operator asset, with a companion fips-firewall.service oneshot unit for systemd hosts. Both are shipped disabled — the baseline is an operator conffile and the unit is intentionally not enabled in postinst. Activation is an explicit one-liner: sudo systemctl enable --now fips-firewall.service This is deliberate: silently mutating host firewall state on package install is hostile across the axes that matter (collisions with existing operator nftables / Docker / OPNsense rulesets, surprise behaviour for hosts that already filter elsewhere, conversion of an explicit security decision into an invisible one). The opt-in posture preserves operator agency. The baseline closes a real default-exposure gap: any service on a mesh host bound to a wildcard address (0.0.0.0 or [::]) is reachable from every authenticated peer in the mesh by default. Identity on the mesh is the peer's npub but identity is not authorization, and the mesh is closer to a shared LAN than to the public internet. With this filter loaded, the surface is closed unless a drop-in opens it explicitly. Baseline shape: - Early-return for non-fips0 traffic (every other firewall left undisturbed) - conntrack established/related accept (replies to outbound flows) - ICMPv6 echo-request accept (ping6 reachability) - include "/etc/fips/fips.d/*.nft" — operator-supplied allowances - counter drop default The accompanying docs/fips-security.md lays out the threat model (npub-authenticated mesh is closer to a shared LAN than to the public internet — identity is not authorization), the activation workflow, drop-in extension recipes (allow inbound SSH from a specific peer fd97:.../128, allow HTTP from one /64, etc), drop visibility / debugging via the journal log rule and the drop counter, coexistence with the runtime-managed `inet fips_gateway` table, what the baseline does NOT cover (outbound, application auth, mesh handshake ACL = PR #50 / IDEA-0047 territory), and future cross-OS work (macOS PF baseline, OpenWrt fw4, gateway abstraction). Packaging: - packaging/common/fips.nft → /etc/fips/fips.nft (conffile) - packaging/debian/fips-firewall.service → /lib/systemd/system/ - docs/fips-security.md → /usr/share/doc/fips/ - postinst creates /etc/fips/fips.d/ (mode 0755) on configure - prerm stops/disables fips-firewall.service on remove/purge OpenWrt fw4 path and macOS PF baseline are deferred — separate asymmetries, separate work.
18 lines
508 B
Desktop File
18 lines
508 B
Desktop File
# Firewall is not enabled by default. Enable with: systemctl enable --now fips-firewall
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[Unit]
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Description=FIPS mesh-interface nftables baseline
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Documentation=file:///etc/fips/fips.nft file:///usr/share/doc/fips/fips-security.md
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Before=fips.service
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ConditionPathExists=/etc/fips/fips.nft
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[Service]
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Type=oneshot
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RemainAfterExit=yes
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ExecStart=/usr/sbin/nft -f /etc/fips/fips.nft
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ExecStop=-/usr/sbin/nft delete table inet fips
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StandardOutput=journal
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StandardError=journal
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[Install]
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WantedBy=multi-user.target
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