feat(NODE-5233)!: prevent session from one client from being used on another

src/mongo_client.ts

@@ -597,7 +597,14 @@ export class MongoClient extends TypedEventEmitter<MongoClientEvents> {
     return client.connect();
   }
 
-  /** Starts a new session on the server */
+  /**
+   * Creates a new ClientSession. When using the returned session in an operation
+   * a corresponding ServerSession will be created.
+   *
+   * @remarks
+   * A ClientSession instance may only be passed to operations being performed on the same
+   * MongoClient it was started from.
+   */
   startSession(options?: ClientSessionOptions): ClientSession {
     const session = new ClientSession(
       this,

src/operations/execute_operation.ts

@@ -7,6 +7,7 @@ import {
   MongoError,
   MongoErrorLabel,
   MongoExpiredSessionError,
+  MongoInvalidArgumentError,
   MongoNetworkError,
   MongoNotConnectedError,
   MongoRuntimeError,
@@ -118,6 +119,8 @@ async function executeOperationAsync<
     throw new MongoExpiredSessionError('Use of expired sessions is not permitted');
   } else if (session.snapshotEnabled && !topology.capabilities.supportsSnapshotReads) {
     throw new MongoCompatibilityError('Snapshot reads require MongoDB 5.0 or later');
+  } else if (session.client !== client) {
+    throw new MongoInvalidArgumentError('ClientSession must be from the same MongoClient');
   }
 
   const readPreference = operation.readPreference ?? ReadPreference.primary;

test/integration/sessions/sessions.prose.test.ts

@@ -6,11 +6,64 @@ import {
   type Collection,
   type CommandStartedEvent,
   MongoClient,
-  MongoDriverError
+  MongoDriverError,
+  MongoInvalidArgumentError
 } from '../../mongodb';
 import { sleep } from '../../tools/utils';
 
 describe('Sessions Prose Tests', () => {
+  describe('5. Session argument is for the right client', () => {
+    let client1: MongoClient;
+    let client2: MongoClient;
+    beforeEach(async function () {
+      client1 = this.configuration.newClient();
+      client2 = this.configuration.newClient();
+    });
+
+    afterEach(async function () {
+      await client1?.close();
+      await client2?.close();
+    });
+
+    /**
+     * Steps:
+     * - Create client1 and client2
+     * - Get database from client1
+     * - Get collection from database
+     * - Start session from client2
+     * - Call collection.insertOne(session,...)
+     * - Assert that an error was reported because session was not started from client1
+     *
+     * This validation lives in our executeOperation layer so it applies universally.
+     * A find and an insert provide enough coverage, we determined we do not need to enumerate every possible operation.
+     */
+    context(
+      'when session is started from a different client than operation is being run on',
+      () => {
+        it('insertOne operation throws a MongoInvalidArgumentError', async () => {
+          const db = client1.db();
+          const collection = db.collection('test');
+          const session = client2.startSession();
+          const error = await collection.insertOne({}, { session }).catch(error => error);
+          expect(error).to.be.instanceOf(MongoInvalidArgumentError);
+          expect(error).to.match(/ClientSession must be from the same MongoClient/i);
+        });
+
+        it('find operation throws a MongoInvalidArgumentError', async () => {
+          const db = client1.db();
+          const collection = db.collection('test');
+          const session = client2.startSession();
+          const error = await collection
+            .find({}, { session })
+            .toArray()
+            .catch(error => error);
+          expect(error).to.be.instanceOf(MongoInvalidArgumentError);
+          expect(error).to.match(/ClientSession must be from the same MongoClient/i);
+        });
+      }
+    );
+  });
+
   describe('14. Implicit sessions only allocate their server session after a successful connection checkout', () => {
     let client: MongoClient;
     let testCollection: Collection<{ _id: number; a?: number }>;

test/integration/sessions/sessions.test.ts

@@ -1,4 +1,5 @@
 import { expect } from 'chai';
+import { MongoClient as LegacyMongoClient } from 'mongodb-legacy';
 
 import type { CommandStartedEvent, CommandSucceededEvent, MongoClient } from '../../mongodb';
 import { LEGACY_HELLO_COMMAND, MongoServerError } from '../../mongodb';
@@ -422,4 +423,31 @@ describe('Sessions Spec', function () {
       expect(new Set(events.map(ev => ev.command.lsid.id.toString('hex'))).size).to.equal(2);
     });
   });
+
+  context('when using a LegacyMongoClient', () => {
+    let legacyClient;
+    beforeEach(async function () {
+      const options = this.configuration.serverApi
+        ? { serverApi: this.configuration.serverApi }
+        : {};
+      legacyClient = new LegacyMongoClient(this.configuration.url(), options);
+    });
+
+    afterEach(async function () {
+      await legacyClient?.close();
+    });
+
+    it('insertOne accepts session started by legacy client', async () => {
+      const db = legacyClient.db();
+      const collection = db.collection('test');
+      const session = legacyClient.startSession();
+      const error = await collection.insertOne({}, { session }).catch(error => error);
+      expect(error).to.not.be.instanceOf(Error);
+    });
+
+    it('session returned by legacy startSession has reference to legacyClient', async () => {
+      const session = legacyClient.startSession();
+      expect(session).to.have.property('client', legacyClient);
+    });
+  });
 });

test/tools/runner/config.ts

@@ -7,6 +7,7 @@ import {
   type AuthMechanism,
   HostAddress,
   MongoClient,
+  type ServerApi,
   TopologyType,
   type WriteConcernSettings
 } from '../../mongodb';
@@ -71,7 +72,7 @@ export class TestConfiguration {
     auth?: { username: string; password: string; authSource?: string };
     proxyURIParams?: ProxyParams;
   };
-  serverApi: string;
+  serverApi: ServerApi;
 
   constructor(uri: string, context: Record<string, any>) {
     const url = new ConnectionString(uri);