Fix rclone hang

src/classes/SshConnectionHandler.ts

@@ -105,9 +105,13 @@ export class SshConnectionHandler {
   ): void => {
     logger.verbose('SSH request for a new session');
     const session = accept();
-    const sessionHandler = new SshSessionHandler(this.authSession?.authToken ?? '');
+    const sessionHandler = new SshSessionHandler(
+      session,
+      this.authSession?.authToken ?? '',
+    );
     session.on('sftp', sessionHandler.onSftp);
     session.on('close', sessionHandler.onClose);
+    session.on('eof', sessionHandler.onEof);
   };
 
   /**

src/classes/SshSessionHandler.ts

@@ -1,11 +1,20 @@
 import { logger } from '../logger';
 import { SftpSessionHandler } from './SftpSessionHandler';
-import type { SFTPWrapper } from 'ssh2';
+import type {
+  Session,
+  SFTPWrapper,
+} from 'ssh2';
 
 export class SshSessionHandler {
   private readonly authToken: string;
 
-  public constructor(authToken: string) {
+  private readonly session: Session;
+
+  public constructor(
+    session: Session,
+    authToken: string,
+  ) {
+    this.session = session;
     this.authToken = authToken;
   }
 
@@ -50,4 +59,20 @@ export class SshSessionHandler {
   public onClose = (): void => {
     logger.verbose('SSH session closed');
   };
+
+  public onEof = (): void => {
+    // This addresses a bug in the ssh2 library where EOF is not properly
+    // handled for sftp connections.
+    // An upstream PR that would fix the behavior: https://github.com/mscdex/ssh2/pull/1111
+    // And some context from our own debugging: https://github.com/PermanentOrg/sftp-service/issues/45
+    //
+    // The solution here is not ideal, as it is accessing an undocumented attribute that
+    // doesn't exist in TypeScript.  As a result I need to disable typescript checks.
+    //
+    // Once upstream makes that patch this entire handler should become completely unnecessary
+    //
+    // !!BEWARE: THERE BE DRAGONS HERE!!
+    // @ts-expect-error because `_channel` is private / isn't actually documented.
+    this.session._channel.end(); // eslint-disable-line max-len, no-underscore-dangle, @typescript-eslint/no-unsafe-call, @typescript-eslint/no-unsafe-member-access
+  };
 }