From ea72bc33da6220684e51e438475acd59e10898f5 Mon Sep 17 00:00:00 2001
From: Holger Cremer <HolgerCremer@gmail.com>
Date: Tue, 16 Jan 2018 21:38:07 +0100
Subject: [PATCH] adds a dynamic part in the client id

---
 mqtt/mqtt.go  |  8 +++++---
 mqtt/utils.go | 31 +++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 3 deletions(-)
 create mode 100644 mqtt/utils.go

diff --git a/mqtt/mqtt.go b/mqtt/mqtt.go
index b8b0f83..327db1f 100644
--- a/mqtt/mqtt.go
+++ b/mqtt/mqtt.go
@@ -12,7 +12,7 @@ import (
 	log "github.com/sirupsen/logrus"
 )
 
-const CLIENT_ID = "spaceDevices2"
+const CLIENT_ID = "spaceDevicesGo"
 
 var mqttLogger = log.WithField("where", "mqtt")
 
@@ -21,6 +21,7 @@ type MqttHandler struct {
 	newDataChan  chan []byte
 	sessionTopic string
 	devicesTopic string
+
 }
 
 //func init() {
@@ -63,12 +64,13 @@ func NewMqttHandler(conf conf.MqttConf) *MqttHandler {
 	}
 	opts.SetTLSConfig(tlsConf)
 
-	opts.SetClientID(CLIENT_ID)
+	opts.SetClientID(CLIENT_ID + GenerateRandomString(4))
 	opts.SetAutoReconnect(true)
 	opts.SetKeepAlive(10 * time.Second)
 	opts.SetMaxReconnectInterval(5 * time.Minute)
 	opts.SetWill(conf.DevicesTopic, emptyPeopleAndDevices(), 0, true)
 
+
 	handler := MqttHandler{newDataChan: make(chan []byte), devicesTopic: conf.DevicesTopic, sessionTopic: conf.SessionTopic}
 	opts.SetOnConnectHandler(handler.onConnect)
 	opts.SetConnectionLostHandler(handler.onConnectionLost)
@@ -98,7 +100,7 @@ func (h *MqttHandler) SendPeopleAndDevices(data PeopleAndDevices) {
 	token := h.client.Publish(h.devicesTopic, 0, true, string(bytes))
 	ok := token.WaitTimeout(time.Duration(time.Second * 10))
 	if !ok {
-		mqttLogger.Warn("Error sending devices to:", h.devicesTopic)
+		mqttLogger.WithError(token.Error()).WithField("topic", h.devicesTopic).Warn("Error sending devices.")
 		return
 	}
 }
diff --git a/mqtt/utils.go b/mqtt/utils.go
new file mode 100644
index 0000000..8c407db
--- /dev/null
+++ b/mqtt/utils.go
@@ -0,0 +1,31 @@
+package mqtt
+
+import (
+	"crypto/rand"
+	"github.com/sirupsen/logrus"
+	"encoding/base64"
+)
+
+// https://elithrar.github.io/article/generating-secure-random-numbers-crypto-rand/
+
+// GenerateRandomBytes returns securely generated random bytes.
+// It will fail with a fatal log if the system's secure random
+// number generator fails to function correctly
+func GenerateRandomBytes(n int) []byte {
+	b := make([]byte, n)
+	if _, err := rand.Read(b); err != nil {
+		// Note that err == nil only if we read len(b) bytes.
+		logrus.Fatal("Could not read random bytes")
+	}
+
+	return b
+}
+
+// GenerateRandomString returns a URL-safe, base64 encoded
+// securely generated random string.
+// It will fail with a fatal log if the system's secure random
+// number generator fails to function correctly
+func GenerateRandomString(s int) string {
+	b := GenerateRandomBytes(s)
+	return base64.URLEncoding.EncodeToString(b)
+}