transx/tscipher/cipher.go

package tscipher

import (
	"bytes"
	"errors"
	"github.com/TransX/log"
	"github.com/TransX/utils"
	"net"
)

var StartMark = []byte("#2v!") //should be constant
var EndMark = []byte("_=1z")   //should be constant

type Cipher interface {
	Decrypt(data []byte) (decrypted []byte, err error)
	Encrypt(data []byte) (encryped []byte, err error)
}

type Carrier struct {
	Conn   net.Conn
	Cipher Cipher
	Cache  []byte
}

func NewCipher(cipherName string) (cipher Cipher) {
	if cipherName == "default" {
		return NewChaCha()
	}
	if cipherName == "AES" {
		return NewAES()
	}
	if cipherName == "XOR" {
		return NewXOR([]byte("fasdfasdf!3297!jfsl12*&!HHHFds"))
	}
	return nil //TODO:临时这样处理
}

func WrapPackage(data []byte) []byte { //把要加密传输的数据打包成一定的格式，避免发送了100自己，只收到90字节的问题。
	sizeOfData := len(data)
	binSize := utils.Int2binary(sizeOfData, 10)
	header := append(append(StartMark, binSize...), EndMark...)
	//加密
	key := []byte("hahahehe~-1!")
	cipheredHeader := make([]byte, len(header))
	for i, v := range header {
		cipheredHeader[i] = v ^ key[i%len(key)]
	}
	return append(cipheredHeader, data...)
}

func UnwrapPackage(pacakge []byte) (packageSize int, data []byte, err error) {
	//前14个字节是header
	cipheredHeader := pacakge[:18]
	header := make([]byte, len(cipheredHeader))
	key := []byte("hahahehe~-1!")
	for i, v := range cipheredHeader {
		header[i] = v ^ key[i%len(key)]
	}
	start := header[:4]
	end := header[14:]
	binSize := header[4:14]
	if bytes.Compare(start, StartMark) == 0 && bytes.Compare(end, EndMark) == 0 {
		packageSize = utils.Binary2Int(binSize)
		data = pacakge[18:]
		err = nil
	} else {
		packageSize = 0
		data = pacakge
		err = errors.New("not a package")
	}
	return

}

func SendData(carrier *Carrier, nByte int) (n int, err error) {
	if len(carrier.Cache) < nByte {
		log.Panic("Cache of send is too small")
	}
	if carrier.Cipher == nil {
		n, err = carrier.Conn.Write(carrier.Cache[:nByte])
		return
	}
	encrypedByte, err := carrier.Cipher.Encrypt(carrier.Cache[:nByte])
	if err != nil {
		n = 0
		return
	}
	//打包
	wraped := WrapPackage(encrypedByte[:nByte])
	n, err = carrier.Conn.Write(wraped)
	copy(carrier.Cache, encrypedByte[:nByte]) // in case of debugging
	return
}

func SendData2(carrier *Carrier, nByte int) (n int, err error) {
	n, err = carrier.Conn.Write(carrier.Cache[:nByte])
	if err != nil {
		return
	}
	return
}

func ReceiveData(carrier *Carrier) (n int, err error) {
	n, err = carrier.Conn.Read(carrier.Cache)
	if err != nil {
		n = 0
		return
	}
	if carrier.Cipher == nil {
		return
	}
	//解包
	wrapedPackage := carrier.Cache[:n]
	packageSize, data, err := UnwrapPackage(wrapedPackage)
	realData := make([]byte, 0, packageSize)
	// log.Info("packageSize %d data size %d", packageSize, len(data))
	if err == nil && packageSize == len(data) { //读到的是一个完整的包
		realData = data
		log.Debug("read a complete package")
	} else {
		gotSize := len(data)
		for {
			n, err = carrier.Conn.Read(carrier.Cache)
			if err != nil {
				n = 0
				return
			}
			wrapedPackage = carrier.Cache[:n]
			log.Debug("got partial package size %d from %s", n, carrier.Conn.RemoteAddr().String())
			_, data, err = UnwrapPackage(wrapedPackage)
			if err == nil {
				n = 0
				err = errors.New("partial package lost")
				return
			}
			gotSize += len(data)
			realData = append(realData, data...)
			if gotSize == packageSize {
				log.Debug("got enough:. packageSize %d, real size %d. not include header", packageSize, gotSize)
				n = gotSize
				break
			}
		}

	}
	decrypted, err := carrier.Cipher.Decrypt(realData)
	if err != nil {
		n = 0
		return
	}
	// n = len(decrypted)
	copy(carrier.Cache, decrypted)
	return
}

func ReceiveData2(carrier *Carrier) (n int, err error) {
	n, err = carrier.Conn.Read(carrier.Cache)
	if err != nil {
		n = 0
		return
	}
	return
}