add support and test for chacha20 encrypt

shadowsocks/encrypt.go

@@ -2,8 +2,6 @@ package shadowsocks
 
 import (
 	"bytes"
-	"golang.org/x/crypto/blowfish"
-	"golang.org/x/crypto/cast5"
 	"crypto/aes"
 	"crypto/cipher"
 	"crypto/des"
@@ -13,6 +11,10 @@ import (
 	"encoding/binary"
 	"errors"
 	"io"
+
+	"github.com/codahale/chacha20"
+	"golang.org/x/crypto/blowfish"
+	"golang.org/x/crypto/cast5"
 )
 
 var errEmptyPassword = errors.New("empty key")
@@ -137,6 +139,10 @@ func newRC4MD5Stream(key, iv []byte, _ DecOrEnc) (cipher.Stream, error) {
 	return rc4.NewCipher(rc4key)
 }
 
+func newChaCha20Stream(key, iv []byte, _ DecOrEnc) (cipher.Stream, error) {
+	return chacha20.New(key, iv)
+}
+
 type cipherInfo struct {
 	keyLen    int
 	ivLen     int
@@ -153,6 +159,7 @@ var cipherMethod = map[string]*cipherInfo{
 	"rc4-md5":     {16, 16, newRC4MD5Stream},
 	"rc4":         {16, 0, nil},
 	"table":       {16, 0, nil},
+	"chacha20":    {32, 8, newChaCha20Stream},
 }
 
 func CheckCipherMethod(method string) error {

shadowsocks/encrypt_test.go

@@ -143,6 +143,10 @@ func TestRC4MD5(t *testing.T) {
 	testBlockCipher(t, "rc4-md5")
 }
 
+func TestChaCha20(t *testing.T) {
+	testBlockCipher(t, "chacha20")
+}
+
 var cipherKey = make([]byte, 64)
 
 func init() {
@@ -200,3 +204,8 @@ func BenchmarkRC4MD5Init(b *testing.B) {
 	ci := cipherMethod["rc4-md5"]
 	benchmarkCipherInit(b, ci)
 }
+
+func BenchmarkChaCha20Init(b *testing.B) {
+	ci := cipherMethod["chacha20"]
+	benchmarkCipherInit(b, ci)
+}