security: harden traefik auth flow — fix header spoofing, TLS leak, DERP rate-limit

- Auth-proxy fallback now sets ALL X-authentik-* headers (username, uid,
  email, name, groups) to prevent client-supplied header spoofing when
  Authentik is down. Previously only username was set, allowing a malicious
  client to inject fake X-authentik-groups.
- Catch-all IngressRoute restricted to *.viktorbarzin.me only. Non-matching
  domains no longer get the wildcard cert served (TLS info leak).
- Added rate-limit and CrowdSec middleware to catch-all IngressRoute.
- Added rate-limit middleware to Headscale DERP IngressRoute.
- Rotated auth-proxy basicAuth credentials (bcrypt cost 5 → 12, admin → emergency-admin).
- Created Authentik brute-force reputation policy (threshold -5, IP+username).

stacks/headscale/modules/headscale/main.tf

@@ -324,11 +324,17 @@ resource "kubernetes_manifest" "derp_ingress_route" {
           name = kubernetes_service.headscale.metadata[0].name
           port = 8080
         }]
-        # Only retry middleware — no CrowdSec, rate limit, anti-AI, error pages
-        middlewares = [{
-          name      = "retry"
-          namespace = "traefik"
-        }]
+        # Minimal middleware — retry + rate-limit. No CrowdSec/anti-AI (DERP is a relay protocol)
+        middlewares = [
+          {
+            name      = "retry"
+            namespace = "traefik"
+          },
+          {
+            name      = "rate-limit"
+            namespace = "traefik"
+          },
+        ]
       }]
       tls = {
         secretName = var.tls_secret_name

stacks/traefik/modules/traefik/error-pages.tf

@@ -158,7 +158,9 @@ resource "kubernetes_manifest" "tlsstore_default" {
   depends_on = [helm_release.traefik, module.tls_secret]
 }
 
-# Catch-all IngressRoute — serves 404 for unknown hosts (lowest priority)
+# Catch-all IngressRoute — serves 404 for unmatched *.viktorbarzin.me hosts (lowest priority)
+# Only matches *.viktorbarzin.me — non-viktorbarzin.me domains get TLS rejection (no matching router)
+# This prevents leaking the wildcard cert to attackers who point arbitrary domains at our IP
 resource "kubernetes_manifest" "ingressroute_catchall" {
   manifest = {
     apiVersion = "traefik.io/v1alpha1"
@@ -170,9 +172,13 @@ resource "kubernetes_manifest" "ingressroute_catchall" {
     spec = {
       entryPoints = ["websecure"]
       routes = [{
-        match    = "HostRegexp(`.+`)"
+        match    = "HostRegexp(`^(.+\\.)?viktorbarzin\\.me$`)"
         kind     = "Rule"
         priority = 1
+        middlewares = [
+          { name = "rate-limit", namespace = kubernetes_namespace.traefik.metadata[0].name },
+          { name = "crowdsec", namespace = kubernetes_namespace.traefik.metadata[0].name },
+        ]
         services = [{
           name      = "error-pages"
           namespace = kubernetes_namespace.traefik.metadata[0].name

stacks/traefik/modules/traefik/main.tf

@@ -494,9 +494,17 @@ resource "kubernetes_config_map" "auth_proxy_config" {
           location @fallback_auth {
               auth_basic "Emergency Access";
               auth_basic_user_file /etc/nginx/htpasswd;
+              # Set ALL X-authentik-* headers to prevent client-supplied header spoofing.
+              # Without this, a client could inject fake X-authentik-groups and backends
+              # that trust these headers would grant elevated access.
               add_header X-authentik-username $remote_user always;
+              add_header X-authentik-uid "" always;
+              add_header X-authentik-email "" always;
+              add_header X-authentik-name "" always;
+              add_header X-authentik-groups "" always;
               add_header X-Auth-Fallback "true" always;
-              return 200;
+              root /usr/share/nginx/fallback;
+              try_files /ok =403;
           }
 
           location /outpost.goauthentik.io/ {
@@ -518,6 +526,17 @@ resource "kubernetes_config_map" "auth_proxy_config" {
   }
 }
 
+resource "kubernetes_config_map" "auth_proxy_fallback" {
+  metadata {
+    name      = "auth-proxy-fallback"
+    namespace = kubernetes_namespace.traefik.metadata[0].name
+  }
+
+  data = {
+    "ok" = "authenticated"
+  }
+}
+
 resource "kubernetes_deployment" "auth_proxy" {
   metadata {
     name      = "auth-proxy"
@@ -577,6 +596,11 @@ resource "kubernetes_deployment" "auth_proxy" {
             sub_path   = "htpasswd"
             read_only  = true
           }
+          volume_mount {
+            name       = "fallback"
+            mount_path = "/usr/share/nginx/fallback"
+            read_only  = true
+          }
 
           liveness_probe {
             http_get {
@@ -618,6 +642,12 @@ resource "kubernetes_deployment" "auth_proxy" {
             secret_name = kubernetes_secret.auth_proxy_htpasswd.metadata[0].name
           }
         }
+        volume {
+          name = "fallback"
+          config_map {
+            name = kubernetes_config_map.auth_proxy_fallback.metadata[0].name
+          }
+        }
       }
     }
   }