Measured follow-up to the AppSec section. Virtual patching blocks 7 of 41
probes with near-zero false positives; the OWASP CRS raises that to 27 of 41
but, at default paranoia, blocks six legitimate workflows (git push, Forgejo
issues and file contents, Outline documents, ntfy publish, n8n webhooks).
crowdsec/appsec-rules/crs-route-exclusions.yaml disables the SecLang/Coraza
engine (ctl:ruleEngine=Off) for exactly those application routes, matched by
host + URI, so virtual patching still runs there. crowdsec/appsec-configs/
appsec-tuned.yaml wires it in before the CRS rule. Measured with tuning: zero
false positives, still 27 of 41 blocked on non-excluded routes, about +2 ms
per request, ~15-40 MB more RAM.
Trap: RemoveInBandRuleByName in a pre_eval hook does not disable CRS (it is
SecLang, not a native rule); ctl:ruleEngine in phase 1 is the working lever,
and the exclusion rule must be listed before the CRS rule.
The stack runs vpatch+generic by default (zero false positives, no per-app
tuning). The CRS recipe ships as a documented opt-in in crowdsec/README.md.
Measured on the demo box against the same 24h of real traffic.
Episode 12 (detection, blocklist, firewall):
- crowdsec/ with install notes and the traps: port 8080 clash, empty first
blocklist pull, replay forensic-mode dropping events (FIFO workaround),
ssh-time-based-bf shipping remediation:false, the AppSec collections that
refuse to start without extra rules.
- firewall bouncer in nftables mode (input + forward), which blocks
Docker-published ports and survives ufw reload; iptables/DOCKER-USER does not.
- HARDENING.md episode 12 section with the numbers: fail2ban 4 banned IPs vs
CrowdSec 23 detected / 1 blocked, blocklist overlap 50% of IPs but 19% of
attempts, and the mode=normal blind spot for key-only root attempts.
Episode 13 (AppSec WAF):
- caddy/Dockerfile now builds the CrowdSec bouncer and AppSec handler alongside
rate-limit, pinned to v0.14.1.
- Caddyfile imports a crowdsec snippet (bouncer + appsec) on every site except
vpn; compose passes CROWDSEC_BOUNCER_KEY and host.docker.internal.
- Measured: virtual patching blocks known CVEs only (7 of 41 probes, near-zero
false positives); OWASP CRS raises that to 27 of 41 but breaks git push and
wiki editing at default paranoia. Default stays vpatch+generic.
fail2ban config unchanged. No secrets or real domains/IPs in tracked files.
