From 0d8fe6ceabf6c8939b562c10f225805fddec9b48 Mon Sep 17 00:00:00 2001
From: ffa500 <hubertus.hohl@siemens.com>
Date: Wed, 15 Feb 2023 13:10:26 +0100
Subject: [PATCH] fix: correct decoding of packets including Properties
 exceeding 127 bytes in length

---
 packets/packets.go         | 14 +++++++-------
 packets/properties.go      | 19 ++++++++++---------
 packets/properties_test.go |  2 +-
 3 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/packets/packets.go b/packets/packets.go
index 7ce992b3..36125d73 100644
--- a/packets/packets.go
+++ b/packets/packets.go
@@ -383,7 +383,7 @@ func (pk *Packet) ConnectDecode(buf []byte) error {
 		if err != nil {
 			return fmt.Errorf("%s: %w", err, ErrMalformedProperties)
 		}
-		offset += n + 1
+		offset += n
 	}
 
 	pk.Connect.ClientIdentifier, offset, err = decodeString(buf, offset) //[MQTT-3.1.3-1] [MQTT-3.1.3-2] [MQTT-3.1.3-3] [MQTT-3.1.3-4]
@@ -397,7 +397,7 @@ func (pk *Packet) ConnectDecode(buf []byte) error {
 			if err != nil {
 				return ErrMalformedWillProperties
 			}
-			offset += n + 1
+			offset += n
 		}
 
 		pk.Connect.WillTopic, offset, err = decodeString(buf, offset)
@@ -644,7 +644,7 @@ func (pk *Packet) PublishDecode(buf []byte) error {
 			return fmt.Errorf("%s: %w", err, ErrMalformedProperties)
 		}
 
-		offset += n + 1
+		offset += n
 	}
 
 	pk.Payload = buf[offset:]
@@ -861,7 +861,7 @@ func (pk *Packet) SubackDecode(buf []byte) error {
 		if err != nil {
 			return fmt.Errorf("%s: %w", err, ErrMalformedProperties)
 		}
-		offset += n + 1
+		offset += n
 	}
 
 	pk.ReasonCodes = buf[offset:]
@@ -918,7 +918,7 @@ func (pk *Packet) SubscribeDecode(buf []byte) error {
 		if err != nil {
 			return fmt.Errorf("%s: %w", err, ErrMalformedProperties)
 		}
-		offset += n + 1
+		offset += n
 	}
 
 	var filter string
@@ -1014,7 +1014,7 @@ func (pk *Packet) UnsubackDecode(buf []byte) error {
 			return fmt.Errorf("%s: %w", err, ErrMalformedProperties)
 		}
 
-		offset += n + 1
+		offset += n
 
 		pk.ReasonCodes = buf[offset:]
 	}
@@ -1066,7 +1066,7 @@ func (pk *Packet) UnsubscribeDecode(buf []byte) error {
 		if err != nil {
 			return fmt.Errorf("%s: %w", err, ErrMalformedProperties)
 		}
-		offset += n + 1
+		offset += n
 	}
 
 	var filter string
diff --git a/packets/properties.go b/packets/properties.go
index 5405bcf2..6c8d56b1 100644
--- a/packets/properties.go
+++ b/packets/properties.go
@@ -366,13 +366,14 @@ func (p *Properties) Decode(pk byte, b *bytes.Buffer) (n int, err error) {
 		return 0, nil
 	}
 
-	n, _, err = DecodeLength(b)
+	var bu int
+	n, bu, err = DecodeLength(b)
 	if err != nil {
-		return n, err
+		return n + bu, err
 	}
 
 	if n == 0 {
-		return n, nil
+		return n + bu, nil
 	}
 
 	bt := b.Bytes()
@@ -380,11 +381,11 @@ func (p *Properties) Decode(pk byte, b *bytes.Buffer) (n int, err error) {
 	for offset := 0; offset < n; {
 		k, offset, err = decodeByte(bt, offset)
 		if err != nil {
-			return n, err
+			return n + bu, err
 		}
 
 		if _, ok := validPacketProperties[k][pk]; !ok {
-			return n, fmt.Errorf("property type %v not valid for packet type %v: %w", k, pk, ErrProtocolViolationUnsupportedProperty)
+			return n + bu, fmt.Errorf("property type %v not valid for packet type %v: %w", k, pk, ErrProtocolViolationUnsupportedProperty)
 		}
 
 		switch k {
@@ -406,7 +407,7 @@ func (p *Properties) Decode(pk byte, b *bytes.Buffer) (n int, err error) {
 
 			n, bu, err := DecodeLength(bytes.NewBuffer(bt[offset:]))
 			if err != nil {
-				return n, err
+				return n + bu, err
 			}
 			p.SubscriptionIdentifier = append(p.SubscriptionIdentifier, n)
 			offset += bu
@@ -452,7 +453,7 @@ func (p *Properties) Decode(pk byte, b *bytes.Buffer) (n int, err error) {
 			var k, v string
 			k, offset, err = decodeString(bt, offset)
 			if err != nil {
-				return n, err
+				return n + bu, err
 			}
 			v, offset, err = decodeString(bt, offset)
 			p.User = append(p.User, UserProperty{Key: k, Val: v})
@@ -470,9 +471,9 @@ func (p *Properties) Decode(pk byte, b *bytes.Buffer) (n int, err error) {
 		}
 
 		if err != nil {
-			return n, err
+			return n + bu, err
 		}
 	}
 
-	return n, nil
+	return n + bu, nil
 }
diff --git a/packets/properties_test.go b/packets/properties_test.go
index 672530e0..d10445f0 100644
--- a/packets/properties_test.go
+++ b/packets/properties_test.go
@@ -250,7 +250,7 @@ func TestDecodeProperties(t *testing.T) {
 	props := new(Properties)
 	n, err := props.Decode(Reserved, b)
 	require.NoError(t, err)
-	require.Equal(t, 172, n)
+	require.Equal(t, 172 + 2, n)
 	require.EqualValues(t, propertiesStruct, *props)
 }