fix(cookie): dynamically calculate parent wildcard domain (.atyg.org) to prevent host-scoping redirect loop

server/auth-session.ts

@@ -9,6 +9,26 @@ export interface AuthenticatedUser {
   username: string;
 }
 
+/**
+ * Calculates the wildcard parent cookie domain (e.g. auth.atyg.org -> .atyg.org)
+ * to ensure cookies are sent to all subdomains (ed-droid.atyg.org, grafana.atyg.org, etc.).
+ */
+export function getCookieDomain(customRpId?: string): string | undefined {
+  const envDomain = Deno.env.get("COOKIE_DOMAIN");
+  if (envDomain) {
+    return envDomain.startsWith(".") ? envDomain : `.${envDomain}`;
+  }
+  const targetId = customRpId || Deno.env.get("RP_ID") || "";
+  if (!targetId || !targetId.includes(".") || targetId === "localhost") {
+    return undefined;
+  }
+  const parts = targetId.split(".").filter(Boolean);
+  if (parts.length >= 2) {
+    return `.${parts.slice(-2).join(".")}`;
+  }
+  return `.${targetId}`;
+}
+
 /**
  * Helper to get authenticated user from session cookie.
  * Checks Valkey cache first, with automatic PostgreSQL sessions table fallback.

server/main.test.ts

@@ -418,3 +418,13 @@ Deno.test("WebAuthn - /api/login/challenge handles username for PRF", async () =
     sqlWrapper.sql = originalSql;
   }
 });
+
+Deno.test("Cookie Domain Scoping - getCookieDomain derives wildcard parent domain", async () => {
+  const { getCookieDomain } = await import("./auth-session.ts");
+
+  assertEquals(getCookieDomain("auth.atyg.org"), ".atyg.org");
+  assertEquals(getCookieDomain("ed-droid.atyg.org"), ".atyg.org");
+  assertEquals(getCookieDomain("atyg.org"), ".atyg.org");
+  assertEquals(getCookieDomain("localhost"), undefined);
+  assertEquals(getCookieDomain(""), undefined);
+});

server/main.ts

@@ -48,6 +48,22 @@ const origin = Deno.env.get("ORIGIN") ||
   (import.meta.main ? undefined : "http://localhost");
 const requireHardwareToken = Deno.env.get("REQUIRE_HARDWARE_TOKEN") === "true";
 
+export function getCookieDomain(customRpId?: string): string | undefined {
+  const envDomain = Deno.env.get("COOKIE_DOMAIN");
+  if (envDomain) {
+    return envDomain.startsWith(".") ? envDomain : `.${envDomain}`;
+  }
+  const targetId = customRpId || Deno.env.get("RP_ID") || "";
+  if (!targetId || !targetId.includes(".") || targetId === "localhost") {
+    return undefined;
+  }
+  const parts = targetId.split(".").filter(Boolean);
+  if (parts.length >= 2) {
+    return `.${parts.slice(-2).join(".")}`;
+  }
+  return `.${targetId}`;
+}
+
 if (!rpID || !origin) {
   throw new Error(
     "Missing critical environment variables: RP_ID and ORIGIN must be set.",
@@ -544,8 +560,7 @@ app.post("/api/register/verify", async (c) => {
       maxAge: 0,
     });
 
-    const cookieDomain = Deno.env.get("COOKIE_DOMAIN") ||
-      (rpID && rpID.includes(".") ? `.${rpID}` : undefined);
+    const cookieDomain = getCookieDomain(rpID);
     if (cookieDomain) {
       deleteCookie(c, "session_id", { domain: cookieDomain, path: "/" });
     }
@@ -735,8 +750,7 @@ app.post("/api/login/verify", async (c) => {
     }
   }
 
-  const cookieDomain = Deno.env.get("COOKIE_DOMAIN") ||
-    (rpID && rpID.includes(".") ? `.${rpID}` : undefined);
+  const cookieDomain = getCookieDomain(rpID);
 
   // Clear any existing host-scoped cookie to prevent domain duplication
   deleteCookie(c, "session_id", { path: "/" });
@@ -2080,8 +2094,7 @@ app.post("/api/revoke", async (c) => {
     // ignore
   }
 
-  const cookieDomain = Deno.env.get("COOKIE_DOMAIN") ||
-    (rpID && rpID.includes(".") ? `.${rpID}` : undefined);
+  const cookieDomain = getCookieDomain(rpID);
 
   if (cookieDomain) {
     deleteCookie(c, "session_id", {

ui/mod.ts

@@ -3,7 +3,11 @@ import { serveStatic } from "jsr:@hono/hono@4/deno";
 import { deleteCookie, getCookie } from "jsr:@hono/hono@4/cookie";
 import { sql } from "../server/db.ts";
 import { valkey } from "../server/valkey.ts";
-import { getAuthenticatedUser, isGlobalAdmin } from "../server/auth-session.ts";
+import {
+  getAuthenticatedUser,
+  getCookieDomain,
+  isGlobalAdmin,
+} from "../server/auth-session.ts";
 import { LoginPage } from "./components/LoginPage.tsx";
 import { RegisterPage } from "./components/RegisterPage.tsx";
 import { SessionsPage } from "./components/SessionsPage.tsx";
@@ -37,8 +41,7 @@ uiApp.get("/logout", async (c) => {
   }
 
   const rpID = Deno.env.get("RP_ID") || "";
-  const cookieDomain = Deno.env.get("COOKIE_DOMAIN") ||
-    (rpID.includes(".") ? `.${rpID}` : undefined);
+  const cookieDomain = getCookieDomain(rpID);
 
   if (cookieDomain) {
     deleteCookie(c, "session_id", {