Stop for good when the server says device_removed (GRYT-1555)

src/mls/deliveryService.fake.ts

@@ -57,6 +57,10 @@ export class FakeDeliveryService {
   scope: IdentityScope;
   conversations = new Map<string, string[]>();
   devices = new Map<string, string[]>();
+  /** Ids their owner removed, as `${serverUserId}:${deviceId}`. Anything naming one is refused (GRYT-1555). */
+  removed = new Set<string>();
+  /** Every call that named a device, in order, by device id. */
+  callsBy = new Map<string, string[]>();
   /** When each device id first published, as `mls:devices` reports it. */
   deviceAddedAt = new Map<string, string>();
   keyPackages: KeyPackageRow[] = [];
@@ -210,6 +214,7 @@ export class FakeDeliveryService {
         await tick();
         if (!this.isDevice(me, deviceId)) return fail("unknown_device", "Publish KeyPackages from this device first.");
         this.devices.set(me, (this.devices.get(me) ?? []).filter((d) => d !== deviceId));
+        this.removed.add(`${me}:${deviceId}`);
         this.keyPackages = this.keyPackages.filter((k) => !(k.serverUserId === me && k.deviceId === deviceId));
         this.welcomes = this.welcomes.filter((w) => !(w.serverUserId === me && w.deviceId === deviceId));
         this.push(this.peopleSharing(me), (d) => d.handleDevicesChanged({ serverUserId: me }));
@@ -308,6 +313,14 @@ export class FakeDeliveryService {
     for (const [name, method] of Object.entries(methods) as [string, (req: unknown) => Promise<unknown>][]) {
       guarded[name] = async (req) => {
         this.checkParts(socket, name, req);
+        const deviceId = (req as { deviceId?: unknown })?.deviceId;
+        if (typeof deviceId === "string") {
+          this.callsBy.set(deviceId, [...(this.callsBy.get(deviceId) ?? []), name]);
+          if (this.removed.has(`${me}:${deviceId}`)) {
+            await tick();
+            return fail("device_removed", "You removed this device from encrypted messages here.");
+          }
+        }
         const reply = await method(req);
         this.checkParts(socket, name, reply);
         return reply;

src/mls/dmDriver.test.ts

@@ -43,10 +43,16 @@ function pinStore(people: string[], withPersonKey: string[]) {
   return { store, pinPerson };
 }
 
-type DeviceOptions = { seed?: Uint8Array; capability?: MlsServerCapability | null; unpinned?: string[] };
+type DeviceOptions = {
+  seed?: Uint8Array;
+  capability?: MlsServerCapability | null;
+  unpinned?: string[];
+  store?: MemoryMlsStore;
+};
 
 function device(fake: FakeDeliveryService, who: string, name: string, opts: DeviceOptions = {}) {
-  const store = new MemoryMlsStore();
+  const store = opts.store ?? new MemoryMlsStore();
+  const removed: number[] = [];
   const messages: MlsDecryptedMessage[] = [];
   const lost: { conversationId: string; reason: string }[] = [];
   const undecryptable: { conversationId: string; seq: number; reason: string }[] = [];
@@ -73,12 +79,13 @@ function device(fake: FakeDeliveryService, who: string, name: string, opts: Devi
       onMessage: (m) => void messages.push(m),
       onGroupLost: (i) => void lost.push(i),
       onUndecryptable: (i) => void undecryptable.push(i),
+      onDeviceRemoved: () => void removed.push(Date.now()),
     },
     newDevice: () => createMlsDevice({ seed, scope: SCOPE, deviceName: name }),
   });
   socket.driver = driver;
   const texts = () => messages.map((m) => `${m.senderServerUserId}: ${new TextDecoder().decode(m.plaintext)}`);
-  return { driver, store, messages, lost, undecryptable, seen, socket, texts, pinPerson: pins.pinPerson };
+  return { driver, store, messages, lost, undecryptable, removed, seen, socket, texts, pinPerson: pins.pinPerson };
 }
 
 /* A package for `d` made as if the clock said `at`, put first in line for its device. */
@@ -279,6 +286,41 @@ describe("MLS DM driver", () => {
     assert.equal(fake.groups.get(dm)!.log.at(-1)!.senderDeviceId, laptop.store.device!.deviceId);
   });
 
+  it("stops a stolen phone for good once it's removed, online or on reconnect (GRYT-1555)", async () => {
+    const fake = new FakeDeliveryService(SCOPE);
+    const dm = fake.dm("kari", "ola");
+    const laptop = device(fake, "kari", "laptop");
+    const phone = device(fake, "kari", "phone");
+    const ola = device(fake, "ola", "phone");
+    for (const d of [laptop, phone, ola]) await d.driver.start();
+    await laptop.driver.send(dm, "ola", text("before"));
+    await fake.settle();
+    const phoneId = phone.store.device!.deviceId;
+
+    // Removed while it's online: the devices push is how it finds out.
+    await laptop.driver.removeOwnDevice(phoneId);
+    await fake.settle();
+    assert.equal(phone.removed.length, 1);
+    assert.deepEqual(phone.lost, [{ conversationId: dm, reason: "removed" }]);
+
+    // The same driver asks nothing more of the server.
+    const called = fake.callsBy.get(phoneId)!.length;
+    await assert.rejects(phone.driver.start(), { code: "device_removed" });
+    assert.equal(fake.callsBy.get(phoneId)!.length, called);
+
+    // Reconnecting with its state still there gets one refused sync, and never publishes.
+    const reconnected = device(fake, "kari", "phone", { store: phone.store });
+    await assert.rejects(reconnected.driver.start(), { code: "device_removed" });
+    assert.equal(reconnected.removed.length, 1);
+    assert.deepEqual(fake.callsBy.get(phoneId)!.slice(called), ["sync"]);
+
+    await ola.driver.send(dm, "kari", text("after"));
+    await fake.settle();
+    assert.deepEqual(laptop.texts(), ["ola: after"]);
+    assert.deepEqual(phone.texts(), ["kari: before"]);
+    assert.deepEqual(fake.welcomes.filter((w) => w.deviceId === phoneId), [], "and nobody adds it back");
+  });
+
   it("lists your own devices with the names their certificates carry", async () => {
     const fake = new FakeDeliveryService(SCOPE);
     const dm = fake.dm("kari", "ola");

src/mls/dmDriver.ts

@@ -34,6 +34,8 @@ import type {
   MlsLogEntry,
   MlsOwnDevice,
   MlsRefusal,
+  MlsReply,
+  MlsTransport,
   MlsWelcomeDelivery,
 } from "./interfaces.js";
 
@@ -59,7 +61,8 @@ export type MlsDriverErrorCode =
   | "unexpected_member"
   | "peer_unverified"
   | "too_many_attachments"
-  | "commit_retries";
+  | "commit_retries"
+  | "device_removed";
 
 export class MlsDriverError extends Error {
   code: MlsDriverErrorCode;
@@ -116,7 +119,40 @@ interface Open {
 }
 
 export function createMlsDmDriver(options: MlsDmDriverOptions): MlsDmDriver {
-  const { transport, store, pins, events, serverUserId: self, capability } = options;
+  const { store, pins, events, serverUserId: self, capability } = options;
+
+  /* Once the server says `device_removed`, nothing goes to it again from this driver:
+     no sync, and above all no publish that could register this device back. */
+  let removed = false;
+  const removedError = (r?: MlsRefusal) =>
+    new MlsDriverError("device_removed", "This device was removed from encrypted messages on this server.", r);
+  function stopOnRemoval<Req, Res extends object>(call: (req: Req) => Promise<MlsReply<Res>>) {
+    return async (req: Req): Promise<MlsReply<Res>> => {
+      if (removed) throw removedError();
+      const r = await call(req);
+      if (!r.ok && r.error === "device_removed") {
+        if (!removed) {
+          removed = true;
+          events.onDeviceRemoved?.();
+        }
+        throw removedError(r);
+      }
+      return r;
+    };
+  }
+  const raw = options.transport;
+  const transport: MlsTransport = {
+    publishKeyPackages: stopOnRemoval((req) => raw.publishKeyPackages(req)),
+    claimKeyPackages: stopOnRemoval((req) => raw.claimKeyPackages(req)),
+    listDevices: stopOnRemoval((req) => raw.listDevices(req)),
+    removeDevice: stopOnRemoval((req) => raw.removeDevice(req)),
+    createGroup: stopOnRemoval((req) => raw.createGroup(req)),
+    commit: stopOnRemoval((req) => raw.commit(req)),
+    send: stopOnRemoval((req) => raw.send(req)),
+    fetchLog: stopOnRemoval((req) => raw.fetchLog(req)),
+    sync: stopOnRemoval((req) => raw.sync(req)),
+    ackWelcomes: stopOnRemoval((req) => raw.ackWelcomes(req)),
+  };
   const scope = asIdentityScope(options.scope);
   const trusts = new Map<string, MlsTrust>();
   /** What the engine asks about every leaf: is it somebody in this conversation, by pin. */
@@ -617,6 +653,8 @@ export function createMlsDmDriver(options: MlsDmDriverOptions): MlsDmDriver {
   /** Adds wait for the next send; a device that's gone is removed straight away. */
   async function handleDevicesChanged(push: { serverUserId: string }): Promise<void> {
     reconciled.clear();
+    // One of yours changed, and it may be this one: a sync is how the server says so.
+    if (push.serverUserId === self && registered) await transport.sync({ deviceId: (await ownDevice()).deviceId });
     for (const rec of await store.listGroups()) {
       await run(rec.conversationId, async () => {
         const open = await load(rec.conversationId);

src/mls/interfaces.ts

@@ -225,6 +225,11 @@ export interface MlsDmEvents {
   /** This device is out of the group: removed, or its state couldn't keep up. */
   onGroupLost?(info: { conversationId: string; reason: "removed" | "out_of_sync" | "gap" }): void;
   onJoined?(info: { conversationId: string; groupId: string }): void;
+  /**
+   * The server says this device was removed here (`device_removed`). The driver has stopped for
+   * good. Wipe this server's MLS state, and don't make a new device until the person asks.
+   */
+  onDeviceRemoved?(): void;
 }
 
 /** Decision 4, per DM. `refused` never falls back to version 1. */