vaultwarden-deployment/caddy/Caddyfile

# Caddy config for the Vaultwarden reverse proxy.
#
# Two non-obvious things:
#
#   1. Coraza runs DetectionOnly by design (see plan). The WAF observes
#      and audit-logs; it does not block. Flipping to On would silently
#      false-positive on attachment uploads and Sends — encrypted payloads
#      look exactly like the things CRS is trained to flag.
#
#   2. /admin is matched into a 404 outside the WG subnet. Returning 404
#      (not 401/403) hides the route's existence from public scanners.
#      Vaultwarden's ADMIN_TOKEN is unset by default anyway, but this keeps
#      the panel inaccessible even if a future change re-enables it.
{
    # Required for Coraza to plug into the request pipeline before
    # reverse_proxy. See coraza-caddy README.
    order coraza_waf first
}

{$VAULT_FQDN} {
    tls {
        # googleclouddns reads the project_id from the SA JSON pointed at
        # by GOOGLE_APPLICATION_CREDENTIALS — no explicit project flag needed.
        dns googleclouddns
    }

    encode zstd gzip

    coraza_waf {
        directives `
            Include @coraza.conf-recommended
            Include @crs-setup.conf.example
            Include @owasp_crs/*.conf
            SecRuleEngine DetectionOnly
            SecAuditEngine RelevantOnly
            SecAuditLog /var/log/caddy/coraza-audit.log
            SecAuditLogParts ABIJDEFHZ
            SecAuditLogFormat JSON
        `
    }

    # /admin from a WG-subnet client → reverse proxy normally.
    @admin_from_wg {
        path /admin*
        remote_ip {$WG_SUBNET}
    }
    handle @admin_from_wg {
        reverse_proxy http://vaultwarden:8080 {
            header_up X-Real-IP {remote_host}
            header_up X-Forwarded-For {remote_host}
            header_up X-Forwarded-Proto https
        }
    }

    # /admin from anywhere else → 404 (hide route existence).
    @admin_elsewhere path /admin*
    handle @admin_elsewhere {
        respond 404
    }

    # Everything else (sync API, web vault, /notifications/hub websocket).
    handle {
        reverse_proxy http://vaultwarden:8080 {
            header_up X-Real-IP {remote_host}
            header_up X-Forwarded-For {remote_host}
            header_up X-Forwarded-Proto https
        }
    }

    log {
        output file /var/log/caddy/access.log {
            roll_size 50MiB
            roll_keep 5
            roll_keep_for 720h
        }
        format json
    }
}