feat(crowdsec): firewall bouncer on the NetBird proxy hosts

Enforces the decisions the in-cluster CrowdSec already detects, at the point
where public traffic actually enters. These hosts terminate TLS for every
*.renner.uno name, so a drop here never reaches the mesh, the relay or the
cluster. Detection stays where it is: the reverse-proxy produces no parseable
access log and has no collection, while Traefik has a working one, and every
scenario in use needs HTTP detail that does not exist at this layer.

Deployed in dry-run. It pulls decisions and logs what it would block without
creating a single nftables rule. The first bouncer to arm anywhere enforces
~24k CAPI decisions at once on the only external entry path, so the
false-positive window has to come before the enforcement rather than after it.
Arming is flipping crowdsec_bouncer_mode per host.

The static release tarball, not a package. The AUR package
crowdsec-firewall-bouncer-nftables depends on `crowdsec` and would pull the
whole Security Engine onto hosts that need only the bouncer; the group is
mixed (proxy-1 Arch, VPS-1 Debian); and the AUR would be a pattern this repo
does not otherwise have. The tarball is the same artefact the AUR package
downloads, pinned by version and sha256, and only the binary is unpacked —
the install/upgrade/uninstall scripts beside it manage systemd and config
themselves, which would leave two owners for the same files.

retry_initial_connect is set, and it is not cosmetic. Without it the process
exits when the LAPI is unreachable at startup, and since a clean shutdown
deletes the nftables tables, the systemd restart loop would leave the host
with no blocklist at all until the first successful connect. The flag exists
in the code but not in the shipped example config.

nftables_hooks covers input and forward. input is the traffic this exists for,
because the reverse-proxy is host-networked and owns :443. forward covers the
bridge-networked http-redirect sidecar, whose packets never traverse INPUT —
the same Docker bridge that showed up as 172.18.0.3 in the Traefik access log.

Prometheus is enabled but bound to loopback. These hosts are public and have
no metrics collection path today; opening :60601 to the internet to gain a
scrape target is the wrong trade.

No CA file: Traefik serves Let's Encrypt for crowdsec.renner.uno, and
ca_cert_path is added to the system pool rather than replacing it.

Rollback is `systemctl stop` — a clean stop deletes both tables by itself.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.woodpecker/deploy-netbird-proxy.yml

@@ -7,6 +7,8 @@ when:
       # install-netbird-proxy.yml also applies the netbird-proxy-watchdog role,
       # so changes to it must redeploy this host too.
       - "ansible/roles/netbird-proxy-watchdog/**"
+      # install-netbird-proxy.yml also applies the edge bouncer.
+      - "ansible/roles/crowdsec-edge-bouncer/**"
       - "ansible/plays/install-netbird-proxy.yml"
       - ".woodpecker/deploy-netbird-proxy.yml"
   - event: deployment

ansible/plays/install-netbird-proxy.yml

@@ -26,3 +26,7 @@
     - docker-install
     - netbird-proxy
     - netbird-proxy-watchdog
+    # Enforces the cluster's CrowdSec decisions here, where public traffic
+    # enters. Deployed in dry-run: it logs what it would block and creates no
+    # nftables rules until crowdsec_bouncer_mode is flipped per host.
+    - crowdsec-edge-bouncer

ansible/roles/crowdsec-edge-bouncer/defaults/main.yml

@@ -0,0 +1,47 @@
+---
+# CrowdSec firewall bouncer on the NetBird proxy hosts.
+#
+# Enforces the decisions the in-cluster CrowdSec already detects, at the point
+# where public traffic actually enters: these hosts terminate TLS for every
+# *.renner.uno name. A drop here never reaches the mesh, the relay or the
+# cluster.
+#
+# Detection stays in the cluster. The reverse-proxy produces no parseable
+# access log and there is no CrowdSec collection for it, while Traefik has a
+# working one — and every scenario in use needs HTTP detail (paths, status
+# codes, user agents) that does not exist at this layer.
+
+# Pinned. A release tarball URL is immutable, and this checksum is of the
+# amd64 asset for exactly this tag.
+crowdsec_bouncer_version: v0.0.36
+crowdsec_bouncer_sha256: f86e4b72693549d99f40a9402abefb894108f047a3fbe6e72fada25ee17ce88b
+
+# The LAPI over the public path these hosts already serve, see
+# kubernetes/infrastructure/crowdsec/lapi-ingress.yaml. The proxies cannot
+# reach it over the mesh: the reverse-proxy container runs non-root, so its
+# embedded NetBird client terminates the tunnel in userspace and the tunnel
+# belongs to that process rather than to the host netns.
+#
+# No ca_cert_path: Traefik serves a Let's Encrypt certificate for this name,
+# and the bouncer adds ca_cert_path to the system pool rather than replacing
+# it — the system pool already trusts LE.
+crowdsec_bouncer_api_url: https://crowdsec.renner.uno/
+crowdsec_bouncer_api_key: "{{ vault_crowdsec_edge_bouncer_key }}"
+
+# STARTS INERT, and that is the point.
+#
+# dry-run pulls decisions and logs what it would block without creating a
+# single nftables rule. The first bouncer to arm anywhere enforces ~24k CAPI
+# decisions at once on the only external entry path, so the false-positive
+# window has to come before the enforcement, not after it. Flip to `nftables`
+# one host at a time once the log looks right.
+crowdsec_bouncer_mode: dry-run
+
+crowdsec_bouncer_update_frequency: 10s
+crowdsec_bouncer_log_level: info
+
+# Bound to loopback deliberately. These hosts are public and have no metrics
+# collection path at all today — opening :60601 to the internet to gain a
+# scrape target is the wrong trade. Revisit when host metrics exist.
+crowdsec_bouncer_metrics_listen: 127.0.0.1
+crowdsec_bouncer_metrics_port: 60601

ansible/roles/crowdsec-edge-bouncer/handlers/main.yml

@@ -0,0 +1,10 @@
+---
+# A restart drops both nftables tables and rebuilds them from the next
+# successful LAPI pull, so there is a short window with no blocklist. That is
+# the documented behaviour of a clean shutdown, not a defect — and it is why
+# retry_initial_connect matters.
+- name: Restart crowdsec firewall bouncer
+  ansible.builtin.systemd:
+    name: crowdsec-firewall-bouncer.service
+    state: restarted
+    daemon_reload: true

ansible/roles/crowdsec-edge-bouncer/tasks/main.yml

@@ -0,0 +1,84 @@
+---
+# See defaults/main.yml for why this exists and why it starts inert.
+#
+# The static release tarball, not a distribution package: the AUR package
+# `crowdsec-firewall-bouncer-nftables` depends on `crowdsec` and would pull the
+# whole Security Engine onto hosts that only need the bouncer, the group is
+# mixed (proxy-1 Arch, VPS-1 Debian), and the AUR would be a new pattern this
+# repo does not otherwise have. The tarball is the same artefact the AUR
+# package downloads.
+
+- name: Ensure nftables is present (the enforcing backend)
+  ansible.builtin.package:
+    name: nftables
+    state: present
+
+- name: Ensure the bouncer config directory exists
+  ansible.builtin.file:
+    path: /etc/crowdsec/bouncers
+    state: directory
+    mode: "0755"
+
+- name: Fetch the pinned bouncer release
+  ansible.builtin.get_url:
+    url: >-
+      https://github.com/crowdsecurity/cs-firewall-bouncer/releases/download/{{
+      crowdsec_bouncer_version }}/crowdsec-firewall-bouncer-linux-amd64.tgz
+    dest: /opt/crowdsec-firewall-bouncer-{{ crowdsec_bouncer_version }}.tgz
+    checksum: sha256:{{ crowdsec_bouncer_sha256 }}
+    mode: "0644"
+
+# Only the binary. The tarball also carries install.sh / upgrade.sh /
+# uninstall.sh, which manage systemd and config themselves — that is this
+# role's job, and letting them run would leave two owners for the same files.
+- name: Unpack the bouncer binary
+  ansible.builtin.unarchive:
+    src: /opt/crowdsec-firewall-bouncer-{{ crowdsec_bouncer_version }}.tgz
+    dest: /opt
+    remote_src: true
+    include:
+      - crowdsec-firewall-bouncer-{{ crowdsec_bouncer_version }}/crowdsec-firewall-bouncer
+    creates: /opt/crowdsec-firewall-bouncer-{{ crowdsec_bouncer_version }}/crowdsec-firewall-bouncer
+
+- name: Install the bouncer binary
+  ansible.builtin.copy:
+    src: /opt/crowdsec-firewall-bouncer-{{ crowdsec_bouncer_version }}/crowdsec-firewall-bouncer
+    dest: /usr/local/bin/crowdsec-firewall-bouncer
+    remote_src: true
+    mode: "0755"
+  notify: Restart crowdsec firewall bouncer
+
+# 0600: this file carries the LAPI key.
+- name: Deploy the bouncer configuration
+  ansible.builtin.template:
+    src: crowdsec-firewall-bouncer.yaml.j2
+    dest: /etc/crowdsec/bouncers/crowdsec-firewall-bouncer.yaml
+    mode: "0600"
+  notify: Restart crowdsec firewall bouncer
+
+- name: Deploy the bouncer systemd unit
+  ansible.builtin.template:
+    src: crowdsec-firewall-bouncer.service.j2
+    dest: /etc/systemd/system/crowdsec-firewall-bouncer.service
+    mode: "0644"
+  notify: Restart crowdsec firewall bouncer
+
+- name: Enable and start the bouncer
+  ansible.builtin.systemd:
+    name: crowdsec-firewall-bouncer.service
+    enabled: true
+    state: started
+    daemon_reload: true
+
+- name: Report how to read it
+  ansible.builtin.debug:
+    msg: |
+      crowdsec-firewall-bouncer deployed in mode "{{ crowdsec_bouncer_mode }}".
+
+      What it would block:  journalctl -u crowdsec-firewall-bouncer -f
+      What it does block:   nft list table ip crowdsec ; nft list table ip6 crowdsec6
+      Metrics:              curl -s {{ crowdsec_bouncer_metrics_listen }}:{{ crowdsec_bouncer_metrics_port }}/metrics
+
+      Rollback: systemctl stop crowdsec-firewall-bouncer. A clean stop deletes
+      both nftables tables by itself. Only after a kill -9 do they need
+      removing by hand: nft delete table ip crowdsec ; nft delete table ip6 crowdsec6

ansible/roles/crowdsec-edge-bouncer/templates/crowdsec-firewall-bouncer.service.j2

@@ -0,0 +1,24 @@
+# Managed by Ansible (crowdsec-edge-bouncer role) — do not edit.
+#
+# Upstream's shipped unit orders itself After=crowdsec.service. There is no
+# local Security Engine on these hosts — the LAPI is in the cluster — so that
+# dependency is dropped; nss-lookup instead, because api_url is a public name
+# that has to resolve before the first connect.
+[Unit]
+Description=CrowdSec firewall bouncer (edge enforcement for the NetBird proxy)
+After=network-online.target nss-lookup.target
+Wants=network-online.target
+
+[Service]
+Type=notify
+# -t validates the config and exits non-zero on a bad one, so a broken config
+# fails the start instead of taking the running rules down with it.
+ExecStartPre=/usr/local/bin/crowdsec-firewall-bouncer -c /etc/crowdsec/bouncers/crowdsec-firewall-bouncer.yaml -t
+ExecStart=/usr/local/bin/crowdsec-firewall-bouncer -c /etc/crowdsec/bouncers/crowdsec-firewall-bouncer.yaml
+Restart=always
+RestartSec=10
+LimitNOFILE=65536
+KillMode=mixed
+
+[Install]
+WantedBy=multi-user.target

ansible/roles/crowdsec-edge-bouncer/templates/crowdsec-firewall-bouncer.yaml.j2

@@ -0,0 +1,55 @@
+# Managed by Ansible (crowdsec-edge-bouncer role) — do not edit.
+mode: {{ crowdsec_bouncer_mode }}
+update_frequency: {{ crowdsec_bouncer_update_frequency }}
+
+# stdout, so journald owns the log and there is no second rotation policy to
+# keep in sync. The shipped example writes to /var/log; that only matters for
+# hosts without journald.
+log_mode: stdout
+log_level: {{ crowdsec_bouncer_log_level }}
+
+api_url: {{ crowdsec_bouncer_api_url }}
+api_key: {{ crowdsec_bouncer_api_key }}
+
+# Without this the process EXITS when the LAPI is unreachable at startup —
+# there is no retry on the first connect. And because a clean shutdown deletes
+# the nftables tables, the systemd restart loop would leave the host with no
+# blocklist at all until the first successful connect. Present in the code,
+# absent from the shipped example config.
+retry_initial_connect: true
+
+disable_ipv4: false
+disable_ipv6: false
+deny_action: DROP
+
+supported_decisions_types:
+  - ban
+
+# Separate tables per family; the bouncer never touches an existing table or
+# chain, and never sets a chain policy. Priority -10 puts it ahead of anything
+# at the default filter priority.
+nftables:
+  ipv4:
+    enabled: true
+    set-only: false
+    table: crowdsec
+    chain: crowdsec-chain
+    priority: -10
+  ipv6:
+    enabled: true
+    set-only: false
+    table: crowdsec6
+    chain: crowdsec6-chain
+    priority: -10
+
+# input is the traffic this exists for: the reverse-proxy is host-networked and
+# owns :443, so its packets traverse INPUT. forward covers the bridge-networked
+# http-redirect sidecar, whose packets never do.
+nftables_hooks:
+  - input
+  - forward
+
+prometheus:
+  enabled: true
+  listen_addr: {{ crowdsec_bouncer_metrics_listen }}
+  listen_port: {{ crowdsec_bouncer_metrics_port }}