wire: use maxprotocol message len on msg reject

wire/message.go

@@ -23,8 +23,16 @@ const MessageHeaderSize = 24
 const CommandSize = 12
 
 // MaxMessagePayload is the maximum bytes a message can be regardless of other
-// individual limits imposed by messages themselves.
-const MaxMessagePayload = (1024 * 1024 * 4) // 4MB
+// individual limits imposed by messages themselves. This is used as a
+// serialization bound for all contexts (disk, RPC, network, etc.).
+const MaxMessagePayload = (1024 * 1024 * 32) // 32MiB
+
+// MaxProtocolMessageLength is the maximum length of an incoming/outgoing p2p
+// protocol message. This is separate from MaxMessagePayload which is used as a
+// general serialization bound. No current valid p2p message exceeds 4MB.
+// This mirrors Bitcoin Core's MAX_PROTOCOL_MESSAGE_LENGTH introduced in
+// bitcoin/bitcoin#5843.
+const MaxProtocolMessageLength = (4 * 1000 * 1000) // ~4MB
 
 // Commands used in bitcoin message headers which describe the type of message.
 const (
@@ -398,11 +406,11 @@ func WriteV2MessageN(w io.Writer, msg Message, pver uint32,
 	payload := bw.Bytes()
 	lenp := len(payload)
 
-	// Enforce maximum overall message payload.
-	if lenp > MaxMessagePayload {
+	// Enforce maximum protocol message payload.
+	if lenp > MaxProtocolMessageLength {
 		str := fmt.Sprintf("message payload is too large - encoded "+
 			"%d bytes, but maximum message payload is %d bytes",
-			lenp, MaxMessagePayload)
+			lenp, MaxProtocolMessageLength)
 		return totalBytes, messageError("WriteMessage", str)
 	}
 
@@ -453,11 +461,11 @@ func WriteMessageWithEncodingN(w io.Writer, msg Message, pver uint32,
 	payload := bw.Bytes()
 	lenp := len(payload)
 
-	// Enforce maximum overall message payload.
-	if lenp > MaxMessagePayload {
+	// Enforce maximum protocol message payload.
+	if lenp > MaxProtocolMessageLength {
 		str := fmt.Sprintf("message payload is too large - encoded "+
 			"%d bytes, but maximum message payload is %d bytes",
-			lenp, MaxMessagePayload)
+			lenp, MaxProtocolMessageLength)
 		return totalBytes, messageError("WriteMessage", str)
 	}
 
@@ -506,7 +514,8 @@ func ReadV2MessageN(plaintext []byte, pver uint32, enc MessageEncoding) (
 	Message, []byte, error) {
 
 	if len(plaintext) == 0 {
-		return nil, nil, fmt.Errorf("invalid plaintext length")
+		return nil, nil, messageError("ReadV2MessageN",
+			"invalid plaintext length")
 	}
 
 	var msgCmd string
@@ -515,7 +524,8 @@ func ReadV2MessageN(plaintext []byte, pver uint32, enc MessageEncoding) (
 	// message this is.
 	if plaintext[0] == 0x00 {
 		if len(plaintext) < CommandSize+1 {
-			return nil, nil, fmt.Errorf("invalid plaintext length")
+			return nil, nil, messageError("ReadV2MessageN",
+				"invalid plaintext length")
 		}
 
 		// Slice off the first 0x00 and the trailing 0x00 bytes.
@@ -537,9 +547,21 @@ func ReadV2MessageN(plaintext []byte, pver uint32, enc MessageEncoding) (
 		return nil, nil, err
 	}
 
+	// Enforce maximum protocol message payload.
+	if len(plaintext) > MaxProtocolMessageLength {
+		str := fmt.Sprintf("message payload is too large - "+
+			"%d bytes, but max message payload is %d bytes",
+			len(plaintext), MaxProtocolMessageLength)
+		return nil, nil, messageError("ReadV2MessageN", str)
+	}
+
+	// Check for maximum length based on the message type.
 	mpl := msg.MaxPayloadLength(pver)
 	if len(plaintext) > int(mpl) {
-		return nil, nil, fmt.Errorf("payload exceeds max length")
+		str := fmt.Sprintf("payload exceeds max length - "+
+			"%d bytes, but max payload size for messages of "+
+			"type [%v] is %v.", len(plaintext), msgCmd, mpl)
+		return nil, nil, messageError("ReadV2MessageN", str)
 	}
 
 	buf := bytes.NewBuffer(plaintext)
@@ -599,11 +621,11 @@ func readMessageWithEncodingNInternal(r io.Reader, pver uint32,
 	hdr *messageHeader, btcnet BitcoinNet, enc MessageEncoding,
 	totalBytes int) (int, Message, []byte, error) {
 
-	// Enforce maximum message payload.
-	if hdr.length > MaxMessagePayload {
+	// Enforce maximum protocol message payload.
+	if hdr.length > MaxProtocolMessageLength {
 		str := fmt.Sprintf("message payload is too large - header "+
 			"indicates %d bytes, but max message payload is %d "+
-			"bytes.", hdr.length, MaxMessagePayload)
+			"bytes.", hdr.length, MaxProtocolMessageLength)
 		return totalBytes, nil, nil, messageError("ReadMessage", str)
 
 	}

wire/message_test.go

@@ -203,7 +203,7 @@ func TestReadMessageWireErrors(t *testing.T) {
 
 	// Wire encoded bytes for a message that exceeds max overall message
 	// length.
-	mpl := uint32(MaxMessagePayload)
+	mpl := uint32(MaxProtocolMessageLength)
 	exceedMaxPayloadBytes := makeHeader(btcnet, "getaddr", mpl+1, 0)
 
 	// Wire encoded bytes for a command which is invalid utf-8.
@@ -392,7 +392,7 @@ func TestWriteMessageWireErrors(t *testing.T) {
 	encodeErrMsg := &fakeMessage{forceEncodeErr: true}
 
 	// Fake message that has payload which exceeds max overall message size.
-	exceedOverallPayload := make([]byte, MaxMessagePayload+1)
+	exceedOverallPayload := make([]byte, MaxProtocolMessageLength+1)
 	exceedOverallPayloadErrMsg := &fakeMessage{payload: exceedOverallPayload}
 
 	// Fake message that has payload which exceeds max allowed per message.

wire/msgreject.go

@@ -175,7 +175,7 @@ func (msg *MsgReject) MaxPayloadLength(pver uint32) uint32 {
 		// Unfortunately the bitcoin protocol does not enforce a sane
 		// limit on the length of the reason, so the max payload is the
 		// overall maximum message payload.
-		plen = MaxMessagePayload
+		plen = MaxProtocolMessageLength
 	}
 
 	return plen

wire/msgreject_test.go

@@ -77,7 +77,7 @@ func TestRejectLatest(t *testing.T) {
 	}
 
 	// Ensure max payload is expected value for latest protocol version.
-	wantPayload := uint32(MaxMessagePayload)
+	wantPayload := uint32(MaxProtocolMessageLength)
 	maxPayload := msg.MaxPayloadLength(pver)
 	if maxPayload != wantPayload {
 		t.Errorf("MaxPayloadLength: wrong max payload length for "+