v2 auth-ledger issue with Paho

[bkupidura]

Im investigeting new (v2) auth-ledger hook, but i believe that there is some issue there.

Looks like golang-paho is not receiving ErrBadUsernameOrPassword packet when auth is failing on broker side.

Simple code to reproduce:

package t

import (
	"log"

	"github.com/mochi-co/mqtt/v2"
	"github.com/mochi-co/mqtt/v2/hooks/auth"
	"github.com/mochi-co/mqtt/v2/listeners"
)

func New() (*mqtt.Server, error) {
	mqttServer := mqtt.New(&mqtt.Options{})

	if err := mqttServer.AddHook(new(auth.Hook), &auth.Options{
		Ledger: &auth.Ledger{
			Auth: auth.AuthRules{
				{Username: "test", Password: "test"},
			},
		},
	}); err != nil {
		return nil, err
	}

	listener := listeners.NewTCP("tcp", ":1883", nil)

	if err := mqttServer.AddListener(listener); err != nil {
		return nil, err
	}

	go func() {
		if err := mqttServer.Serve(); err != nil {
			log.Fatalf("mqttServer.Serve worker died: %s", err)
		}
	}()

	return mqttServer, nil
}

package t

import (
	"errors"
	"testing"

	paho "github.com/eclipse/paho.mqtt.golang"
	"github.com/stretchr/testify/require"
)

func TestNew(t *testing.T) {
	b, err := New()
	require.Nil(t, err)

	mqttClient := paho.NewClient(paho.NewClientOptions().
		AddBroker("127.0.0.1:1883").
		SetUsername("wrong-username").
		SetPassword("wrong-password").
		SetAutoReconnect(false).
		SetConnectRetry(false))

	token := mqttClient.Connect()
	token.Wait()

	require.Equal(t, errors.New("bad user name or password"), token.Error())

	b.Close()
}

I would expect that paho ConnectToken will return error, but it looks like from paho perspective connection was successfull.

4:28PM INF added hook hook=auth-ledger
4:28PM INF loaded auth rules acl=0 authentication=1 hook=auth-ledger
4:28PM INF attached listener address=:1883 id=tcp protocol=tcp
4:28PM INF mochi mqtt starting version=2.1.1
4:28PM INF mochi mqtt server started
4:28PM INF client failed authentication check hook=auth-ledger remote=127.0.0.1:60562 username=wrong-username
4:28PM WRN error="bad username or password" listener=tcp
4:28PM INF client failed authentication check hook=auth-ledger remote=127.0.0.1:60563 username=wrong-username
4:28PM WRN error="bad username or password" listener=tcp
--- FAIL: TestNew (0.01s)
    main_test.go:25:
        	Error Trace:	main_test.go:25
        	Error:      	Not equal:
        	            	expected: *errors.errorString(&errors.errorString{s:"bad user name or password"})
        	            	actual  : <nil>(<nil>)
        	Test:       	TestNew
FAIL
exit status 1
FAIL	t	0.539s

[mochi-co]

Hi @bkupidura - Thank you for finding and raising this issue!
I looked into this and it's because MQTT v3 has a different specification for the (very few) Connack return codes it provides. In this case the broker was sending the error correctly, but the byte value was incorrect for v3.

I have put together a v5 to v3 code map which seems to fix this issue, and is released in v2.1.4. Give it a try and see if it works as you would expect.

[bkupidura]

@mochi-co can confirm, new version works as expected! Thanks!