[jira] [Created] (SSHD-1050) Race condition between early exceptions and AuthFuture

["Thomas Wolf (Jira)" <ji...@apache.org>]

Thomas Wolf created SSHD-1050:
---------------------------------

             Summary: Race condition between early exceptions and AuthFuture
                 Key: SSHD-1050
                 URL: https://issues.apache.org/jira/browse/SSHD-1050
             Project: MINA SSHD
          Issue Type: Bug
    Affects Versions: 2.4.0, 2.6.0
            Reporter: Thomas Wolf


It appears that sometimes exceptions that occur early in connection setup are not reported on the AuthFuture. When that happens, AuthFuture.verify(timeout) will spend the whole timeout waiting and then report a timeout. The earlier exception is lost and nowhere to be seen.

I stumbled over this when analyzing [Eclipse bug 565394|https://bugs.eclipse.org/bugs/show_bug.cgi?id=565394].

It's not easy to reproduce, but with the below client test I can manage to make the test fail from time to time if run repeatedly. (That test uses a large preamble before the server identification to provoke an early exception. Using publickey auth instead of password auth increases the chances to get a failure. Running in a debugger increases the chances even more. It's clearly timing-related.)
{code:java}
 private String longPreamble() {
   StringBuilder b = new StringBuilder();
   for (int i = 0; i < 250; i++) {
     b.append('a');
   }
   String line = b.toString();
   b = new StringBuilder(line);
   int limit = CoreModuleProperties.MAX_IDENTIFICATION_SIZE.get(sshd)
       .orElse(Integer.valueOf(16 * 1024)).intValue();
   limit = limit / 250 + 1;
   for (int i = 0; i < limit; i++) {
     b.append(CoreModuleProperties.SERVER_EXTRA_IDENT_LINES_SEPARATOR)
         .append(line);
   }
   return b.toString();
 }

 @Test
 public void testAuthGetsNotifiedOnLongPreamble() throws Exception {
   CoreModuleProperties.SERVER_EXTRA_IDENTIFICATION_LINES.set(sshd,
       longPreamble());
   sshd.setPasswordAuthenticator(RejectAllPasswordAuthenticator.INSTANCE);
   sshd.setKeyboardInteractiveAuthenticator(KeyboardInteractiveAuthenticator.NONE);
   client.setUserAuthFactories(
       Collections.singletonList(UserAuthPublicKeyFactory.INSTANCE));
   client.start();
   try (ClientSession session =
       client.connect(getCurrentTestName(), TEST_LOCALHOST, port)
       .verify(CONNECT_TIMEOUT).getSession()) {
     KeyPairProvider keys = createTestHostKeyProvider();
     session.addPublicKeyIdentity(
         keys.loadKey(session, CommonTestSupportUtils.DEFAULT_TEST_HOST_KEY_TYPE));
     // This auth should fail because the server sends too many lines before
     // the server identification. However, the auth must not time out! There's
     // an exception raised early on when the identification is read, but
     // frequently this exception gets not reported on the auth future that
     // we are waiting on here, and then we wait for the whole timeout.
     //
     // There's a race condition somewhere. The test succeeds frequently, and is
     // hard to make fail, but if run enough times it will usually fail. Running
     // this in a debugger increases the chances of it failing.
     Throwable e = assertThrows(Throwable.class,
         () -> session.auth().verify(AUTH_TIMEOUT));
     assertFalse(e.getMessage().contains("timeout"));
     assertFalse(session.isAuthenticated());
   } finally {
     client.stop();
   }
 }
{code}
Perhaps the connect future should be fulfilled only once the initial KEX is done? OpenSSH's ConnectTimeout does include the time until after the initial KEX.



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