feat(seat-device): entry links in the device authorization answer (E-1)

lib/seat-device/contract.test.ts

@@ -28,6 +28,7 @@ import {
   readSeatDeviceTrustedProxyHops,
   resolveSeatDeviceTrustedSource,
   seatDeviceCredentialExpiresAt,
+  seatDeviceEntryLinks,
   seatDeviceHashesEqual,
   seatDeviceIdentity,
   seatDevicePreviousAccessExpiresAt,
@@ -249,6 +250,26 @@ describe("seat device request validation", () => {
     expect(parseSeatDeviceRevokeRequest({ refreshToken, reason: "device_logout", extra: 1 })).toEqual({ ok: false, code: "invalid_input" });
   });
 
+  it("builds entry links from the given origin only; activation follows its own switch; no sign-up link", () => {
+    const origin = "https://seat.example.test";
+    expect(seatDeviceEntryLinks(origin, {})).toEqual({ signIn: `${origin}/login`, activateMember: null, signUp: null });
+    expect(seatDeviceEntryLinks(origin, { HELM_AUTH_MEMBER_ACTIVATION_ENABLED: "true" })).toEqual({
+      signIn: `${origin}/login`,
+      activateMember: `${origin}/activate-member`,
+      signUp: null,
+    });
+    // Only the exact "true" opens the activation page (it answers 404 otherwise).
+    for (const value of ["false", "TRUE", "1", "", undefined]) {
+      expect(seatDeviceEntryLinks(origin, { HELM_AUTH_MEMBER_ACTIVATION_ENABLED: value }).activateMember).toBeNull();
+    }
+    // The origin passed in is the only source: APP_URL itself is not re-read here.
+    expect(seatDeviceEntryLinks(origin, { ...on, APP_URL: "https://other.example.test" })).toEqual({
+      signIn: `${origin}/login`,
+      activateMember: null,
+      signUp: null,
+    });
+  });
+
   it("normalizes pairing codes in lookup and decision bodies", () => {
     expect(parseSeatDeviceRequest(SEAT_DEVICE_LOOKUP_REQUEST_SCHEMA, { pairingCode: "bcdf-ghjk" })).toEqual({ ok: true, value: { pairingCode: "BCDFGHJK" } });
     expect(parseSeatDeviceRequest(SEAT_DEVICE_LOOKUP_REQUEST_SCHEMA, { pairingCode: "BCDF-GHJA" }).ok).toBe(false);

lib/seat-device/contract.ts

@@ -23,6 +23,9 @@ export type SeatDeviceClientType = (typeof SEAT_DEVICE_CLIENT_TYPES)[number];
 export const SEAT_DEVICE_PUBLIC_AUTH_BASE_PATH = "/api/public-auth/seat-device";
 // The verification URL never carries the pairing code: the member types it.
 export const SEAT_DEVICE_VERIFICATION_PATH = "/device";
+// Existing Core pages the client may point a member to (server design §8).
+export const SEAT_DEVICE_SIGN_IN_PATH = "/login";
+export const SEAT_DEVICE_ACTIVATE_MEMBER_PATH = "/activate-member";
 
 export const SEAT_DEVICE_REQUEST_TTL_SECONDS = 600;
 export const SEAT_DEVICE_POLL_INTERVAL_SECONDS = 5;
@@ -242,6 +245,28 @@ export function isSeatDeviceWorkspaceEnabled(
   }
 }
 
+export type SeatDeviceEntryLinks = {
+  signIn: string;
+  activateMember: string | null;
+  signUp: string | null;
+};
+
+// Entry links in the authorization answer (server design §8.3), for the
+// client's guidance text. `origin` is the already resolved APP_URL origin
+// (https outside local development), never anything from the request.
+// activateMember is null while its page answers 404. signUp stays null:
+// Core has no sign-up page and no sign-up address is configured.
+export function seatDeviceEntryLinks(
+  origin: string,
+  env: Readonly<Record<string, string | undefined>> = process.env,
+): SeatDeviceEntryLinks {
+  return {
+    signIn: `${origin}${SEAT_DEVICE_SIGN_IN_PATH}`,
+    activateMember: env.HELM_AUTH_MEMBER_ACTIVATION_ENABLED === "true" ? `${origin}${SEAT_DEVICE_ACTIVATE_MEMBER_PATH}` : null,
+    signUp: null,
+  };
+}
+
 // Number of proxies in front of the app that append to x-forwarded-for. Any
 // value other than a small non-negative integer means 0: source untrusted.
 export function readSeatDeviceTrustedProxyHops(

lib/seat-device/device-routes.ts

@@ -29,6 +29,7 @@ import {
   parseSeatDeviceRevokeRequest,
   readSeatDeviceTrustedProxyHops,
   resolveSeatDeviceTrustedSource,
+  seatDeviceEntryLinks,
   type SeatDeviceErrorCode,
 } from "@/lib/seat-device/contract";
 import {
@@ -118,7 +119,7 @@ const OPERATIONS: Record<SeatDeviceOperation, (request: Request) => Promise<Resp
     const input = rejectOnParse(parseSeatDeviceAuthorizationRequest(await readJson(request)));
     const grant = await requestSeatDeviceAuthorization({ ...input, source: trustedSource(request) });
     // The member types the pairing code; the URL never carries it.
-    return ok({ ...grant, verificationUrl: `${origin}${SEAT_DEVICE_VERIFICATION_PATH}` });
+    return ok({ ...grant, verificationUrl: `${origin}${SEAT_DEVICE_VERIFICATION_PATH}`, entryLinks: seatDeviceEntryLinks(origin) });
   },
   async cancel(request) {
     const input = rejectOnParse(parseSeatDeviceRequest(SEAT_DEVICE_POLL_REQUEST_SCHEMA, await readJson(request)));

lib/seat-device/seat-device-routes.mysql.test.ts

@@ -2,7 +2,7 @@
 // The five D1 device endpoints (design v0.3 §4.2, §15) through their real
 // route handlers and the real store on an isolated MySQL database: answer
 // shapes, the code map with its HTTP statuses, no-store on every answer,
-// Retry-After on every 429 and 503, the verification URL (APP_URL only, no
+// Retry-After on every 429 and 503, the verification URL and entry links (APP_URL only, no
 // code), and a log probe that no token or pairing code reaches a log line.
 //
 //   SEAT_DEVICE_DATABASE_URL=<disposable db> DATABASE_URL=<same>
@@ -160,7 +160,7 @@ describeMysql("seat device endpoints on MySQL", () => {
   async function authorize(source = freshSource()) {
     const answer = await post("authorize", DEVICE, source);
     expect(answer.status).toBe(200);
-    return { grant: answer.body as Grant & { verificationUrl: string }, source };
+    return { grant: answer.body as Grant & { verificationUrl: string; entryLinks: unknown }, source };
   }
 
   // A claimed device of a fresh member, from a trusted source.
@@ -185,6 +185,8 @@ describeMysql("seat device endpoints on MySQL", () => {
     vi.stubEnv("HELM_SEAT_DEVICE_AUTH_ENABLED", "true");
     vi.stubEnv("HELM_SEAT_DEVICE_TRUSTED_PROXY_HOPS", "1");
     vi.stubEnv("APP_URL", APP_ORIGIN);
+    // The activation page (and so its entry link) is off unless a test opens it.
+    vi.stubEnv("HELM_AUTH_MEMBER_ACTIVATION_ENABLED", undefined);
     for (const method of CONSOLE_METHODS) {
       const original = console[method].bind(console);
       vi.spyOn(console, method).mockImplementation((...args: unknown[]) => {
@@ -209,9 +211,11 @@ describeMysql("seat device endpoints on MySQL", () => {
   it("authorizes with a URL built from APP_URL only, never carrying the code, and keeps the trusted source", async () => {
     nextDay();
     const { grant, source } = await authorize();
-    expect(Object.keys(grant).sort()).toEqual(["expiresInSeconds", "intervalSeconds", "pairingCode", "pollToken", "requestId", "verificationUrl"]);
+    expect(Object.keys(grant).sort()).toEqual(["entryLinks", "expiresInSeconds", "intervalSeconds", "pairingCode", "pollToken", "requestId", "verificationUrl"]);
     expect(grant).toMatchObject({ expiresInSeconds: 600, intervalSeconds: 5 });
     expect(grant.verificationUrl).toBe(`${APP_ORIGIN}/device`);
+    // post() sends a hostile Host, x-forwarded-host and an http forwarded proto.
+    expect(grant.entryLinks).toEqual({ signIn: `${APP_ORIGIN}/login`, activateMember: null, signUp: null });
     const url = new URL(grant.verificationUrl);
     expect(url.search + url.hash).toBe("");
     expect(grant.verificationUrl).not.toContain(grant.pairingCode.replace("-", ""));
@@ -222,13 +226,29 @@ describeMysql("seat device endpoints on MySQL", () => {
     expect(row.pollTokenHash).toBe(hashSeatDeviceToken(grant.pollToken));
   });
 
+  it("offers the activation link only while the activation page is on, and takes no address from the client", async () => {
+    nextDay();
+    vi.stubEnv("HELM_AUTH_MEMBER_ACTIVATION_ENABLED", "true");
+    try {
+      const { grant } = await authorize();
+      expect(grant.entryLinks).toEqual({ signIn: `${APP_ORIGIN}/login`, activateMember: `${APP_ORIGIN}/activate-member`, signUp: null });
+    } finally {
+      vi.stubEnv("HELM_AUTH_MEMBER_ACTIVATION_ENABLED", undefined);
+    }
+    // A client cannot steer the links: any address field is an unknown field.
+    for (const extra of [{ entryLinks: { signUp: "https://phish.example" } }, { signUpUrl: "https://phish.example" }, { verificationUrl: "https://phish.example/device" }]) {
+      expect(only(await post("authorize", { ...DEVICE, ...extra }, freshSource()))).toEqual({ status: 400, body: errorOf("invalid_input") });
+    }
+  });
+
   it("resolves the public origin before storing anything", async () => {
     nextDay();
     const before = await db.seatDeviceAuthorization.count();
     vi.stubEnv("NODE_ENV", "production");
     vi.stubEnv("APP_URL", "http://plain-http.example.test");
     try {
-      expect(await post("authorize", DEVICE, freshSource())).toMatchObject({ status: 503, body: errorOf("temporarily_unavailable") });
+      // Fail closed: no link of any kind leaves with a non-https origin.
+      expect(only(await post("authorize", DEVICE, freshSource()))).toEqual({ status: 503, body: errorOf("temporarily_unavailable") });
     } finally {
       vi.stubEnv("NODE_ENV", "test");
       vi.stubEnv("APP_URL", APP_ORIGIN);