From 1b8e1008791024b79455043a8ae994c4742ec150 Mon Sep 17 00:00:00 2001
From: V2Ray <admin@v2ray.com>
Date: Sun, 15 Nov 2015 21:54:28 +0100
Subject: [PATCH] validation reader for vmess

---
 proxy/vmess/protocol/io/validation.go | 75 +++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)
 create mode 100644 proxy/vmess/protocol/io/validation.go

diff --git a/proxy/vmess/protocol/io/validation.go b/proxy/vmess/protocol/io/validation.go
new file mode 100644
index 000000000..ea47cf909
--- /dev/null
+++ b/proxy/vmess/protocol/io/validation.go
@@ -0,0 +1,75 @@
+package io
+
+import (
+	"errors"
+	"hash/fnv"
+	"io"
+
+	"github.com/v2ray/v2ray-core/common/alloc"
+	"github.com/v2ray/v2ray-core/transport"
+)
+
+var (
+	TruncatedPayload = errors.New("Truncated payload.")
+)
+
+type ValidationReader struct {
+	reader io.Reader
+	buffer *alloc.Buffer
+}
+
+func NewValidationReader(reader io.Reader) *ValidationReader {
+	return &ValidationReader{
+		reader: reader,
+		buffer: alloc.NewLargeBuffer().Clear(),
+	}
+}
+
+func (this *ValidationReader) Read(data []byte) (int, error) {
+	nBytes, err := this.reader.Read(data)
+	if err != nil {
+		return nBytes, err
+	}
+	nBytesActual := 0
+	dataActual := data[:]
+	for {
+		payload, rest, err := parsePayload(data)
+		if err != nil {
+			return nBytesActual, err
+		}
+		copy(dataActual, payload)
+		nBytesActual += len(payload)
+		dataActual = dataActual[nBytesActual:]
+		if len(rest) == 0 {
+			break
+		}
+		data = rest
+	}
+	return nBytesActual, nil
+}
+
+func parsePayload(data []byte) (payload []byte, rest []byte, err error) {
+	dataLen := len(data)
+	if dataLen < 6 {
+		err = TruncatedPayload
+		return
+	}
+	payloadLen := int(data[0])<<8 + int(data[1])
+	if dataLen < payloadLen+6 {
+		err = TruncatedPayload
+		return
+	}
+
+	payload = data[6 : 6+payloadLen]
+	rest = data[6+payloadLen:]
+
+	fnv1a := fnv.New32a()
+	fnv1a.Write(payload)
+	actualHash := fnv1a.Sum32()
+	expectedHash := uint32(data[2])<<24 + uint32(data[3])<<16 + uint32(data[4])<<8 + uint32(data[5])
+	if actualHash != expectedHash {
+		err = transport.CorruptedPacket
+		return
+	}
+	return
+}