Docker Traefik ModSecurity Setup

jeserga edited on Jul 8, 2025.

Setting up ModSecurity will proxy all requests to Vaultwarden through a Web Application Firewall (WAF). This might help mitigate unknown vulnerabilities in Vaultwarden by filtering suspicious requests (like injection attempts).

Pre-Reqs

Setup with Docker + Traefik 2.0 as reverse proxy
Fail2Ban properly set up (see this tutorial)
This is only tested on Debian (but should work on similar systems like Ubuntu or Raspbian)

Installation

bash

touch /opt/docker/waf-rules/REQUEST-900-EXCLUSION-RULES-BEFORE-CRS.conf && touch /opt/docker/waf-rules/RESPONSE-999-EXCLUSION-RULES-AFTER-CRS.conf

/opt/docker/docker-compose.yml

services:
  traefik:
    image: traefik:latest
    container_name: traefik
    command:
      - --providers.docker=true
      - --providers.docker.exposedByDefault=false
      - --entrypoints.web.address=:80
      - --entrypoints.websecure.address=:443
      - --certificatesresolvers.myresolver.acme.tlschallenge=true
      - --certificatesresolvers.myresolver.acme.email=you@domain.tld
      - --certificatesresolvers.myresolver.acme.storage=acme.json
      - --certificatesresolvers.myresolver.acme.storage=/letsencrypt/acme.json
    restart: unless-stopped
    ports:
      - 80:80
      - 443:443
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
      - /opt/docker/le:/letsencrypt

  waf:
    image: owasp/modsecurity-crs:apache
    container_name: waf
    environment:
      PARANOIA: 1
      ANOMALY_INBOUND: 10
      ANOMALY_OUTBOUND: 5
      PROXY: 1
      REMOTEIP_INT_PROXY: "172.20.0.1/16"
      BACKEND: "http://vaultwarden:80"
      BACKEND_WS: "ws://vaultwarden:80/notifications/hub"
      ERRORLOG: "/var/log/waf/waf.log"
      PROXY_ERROR_OVERRIDE: "off"
    volumes:
     - /opt/docker/waf:/var/log/waf
     - /opt/docker/waf-rules/REQUEST-900-EXCLUSION-RULES-BEFORE-CRS.conf:/etc/modsecurity.d/owasp-crs/rules/REQUEST-900-EXCLUSION-RULES-BEFORE-CRS.conf
     - /opt/docker/waf-rules/RESPONSE-999-EXCLUSION-RULES-AFTER-CRS.conf:/etc/modsecurity.d/owasp-crs/rules/RESPONSE-999-EXCLUSION-RULES-AFTER-CRS.conf
    labels:
      - traefik.enable=true
      - traefik.http.middlewares.redirect-https.redirectScheme.scheme=https
      - traefik.http.middlewares.redirect-https.redirectScheme.permanent=true
      - traefik.http.routers.vw-ui-https.rule=Host(`sub.domain.tld`)
      - traefik.http.routers.vw-ui-https.entrypoints=websecure
      - traefik.http.routers.vw-ui-https.tls=true
      - traefik.http.routers.vw-ui-https.service=vw-ui
      - traefik.http.routers.vw-ui-http.rule=Host(`sub.domain.tld`)
      - traefik.http.routers.vw-ui-http.entrypoints=web
      - traefik.http.routers.vw-ui-http.middlewares=redirect-https
      - traefik.http.routers.vw-ui-http.service=vw-ui
      - traefik.http.services.vw-ui.loadbalancer.server.port=80
      - traefik.http.routers.vw-websocket-https.rule=Host(`sub.domain.tld`) && Path(`/notifications/hub`)
      - traefik.http.routers.vw-websocket-https.entrypoints=websecure
      - traefik.http.routers.vw-websocket-https.tls=true
      - traefik.http.routers.vw-websocket-https.service=vw-websocket
      - traefik.http.routers.vw-websocket-http.rule=Host(`sub.domain.tld`) && Path(`/notifications/hub`)
      - traefik.http.routers.vw-websocket-http.entrypoints=web
      - traefik.http.routers.vw-websocket-http.middlewares=redirect-https
      - traefik.http.routers.vw-websocket-http.service=vw-websocket
      - traefik.http.services.vw-websocket.loadbalancer.server.port=3012

  vaultwarden:
    image: vaultwarden/server:latest
    container_name: vaultwarden
    restart: unless-stopped
    environment:
      WEBSOCKET_ENABLED: "true"
      SENDS_ALLOWED: "true"
      PASSWORD_ITERATIONS: 500000
      SIGNUPS_ALLOWED: "true"
      SIGNUPS_VERIFY: "true"
      SIGNUPS_DOMAINS_WHITELIST: "yourdomain.tld"
      ADMIN_TOKEN: "some random string" #generate with openssl rand
      DOMAIN: "domain host name"
      SMTP_HOST: "smtp server"
      SMTP_FROM: "sender email e.g: you@domain.tld"
      SMTP_FROM_NAME: "sender name"
      SMTP_SECURITY: "starttls"
      SMTP_PORT: 587
      SMTP_USERNAME: "smtp username"
      SMTP_PASSWORD: "smtp password"
      SMTP_TIMEOUT: 15
      LOG_FILE: "/data/vaultwarden.log"
      LOG_LEVEL: "warn"
      EXTENDED_LOGGING: "true"
      TZ: "your time zone"
    volumes:
      - /opt/docker/vaultwarden:/data

networks:
  default:
    driver: bridge
    ipam:
      driver: default
      config:
      - subnet: 172.20.0.1/16

/etc/fail2ban/filter.d/waf.conf

[INCLUDES]
before = common.conf

[Definition]
failregex = ^.*\[client <ADDR>\] ModSecurity: Access denied with code 403 .*$
ignoreregex =

/etc/fail2ban/jail.d/waf.conf

[waf]
enabled = true
port = 80,443
filter = waf
action = iptables-allports[name=waf, chain=FORWARD]
logpath = /opt/docker/waf/waf.log
maxretry = 1
bantime = 14400
findtime = 14400

Note

Integrating Fail2Ban with ModSecurity will slow / deter further exploitation / exploration by adversaries. This is setup to ban on the first ModSecurity intervention.

In order to increase the aggressivity of ModSecurity increase PARANOIA (read more here) and or decrease ANOMALY_INBOUND (read more).

Prepare yourself to tune ModSecurity HEAVILY with PARANOIA >2 in order to get the UI barely working without disabling many rules.

The following files will enable you to tune ModSecurity (tutorial)

/opt/docker/waf-rules/REQUEST-900-EXCLUSION-RULES-BEFORE-CRS.conf
/opt/docker/waf-rules/RESPONSE-999-EXCLUSION-RULES-AFTER-CRS.conf

☁️ Food for thought ☁️

If your data is so sensitive that you are considering PARANOIA > 1, then consider hosting Vaultwarden not on a public endpoint and limit access to the host itself via a firewall and grant user access only via a VPN connection. Keep in mind that this does not mitigate insider threats which are often underestimated, so keep that in mind!