complete implementation of shadowsocks ota

proxy/shadowsocks/ota.go

@@ -0,0 +1,55 @@
+package shadowsocks
+
+import (
+	"crypto/hmac"
+	"crypto/sha1"
+
+	"github.com/v2ray/v2ray-core/common/serial"
+)
+
+const (
+	AuthSize = 10
+)
+
+type KeyGenerator func() []byte
+
+type Authenticator struct {
+	key KeyGenerator
+}
+
+func NewAuthenticator(keygen KeyGenerator) *Authenticator {
+	return &Authenticator{
+		key: keygen,
+	}
+}
+
+func (this *Authenticator) AuthSize() int {
+	return AuthSize
+}
+
+func (this *Authenticator) Authenticate(auth []byte, data []byte) []byte {
+	hasher := hmac.New(sha1.New, this.key())
+	hasher.Write(data)
+	res := hasher.Sum(nil)
+	return append(auth, res[:AuthSize]...)
+}
+
+func HeaderKeyGenerator(key []byte, iv []byte) func() []byte {
+	return func() []byte {
+		newKey := make([]byte, 0, len(key)+len(iv))
+		newKey = append(newKey, key...)
+		newKey = append(newKey, iv...)
+		return newKey
+	}
+}
+
+func ChunkKeyGenerator(iv []byte) func() []byte {
+	chunkId := 0
+	return func() []byte {
+		newKey := make([]byte, 0, len(iv)+4)
+		newKey = append(newKey, iv...)
+		newKey = append(newKey, serial.IntLiteral(chunkId).Bytes()...)
+		chunkId++
+		return newKey
+	}
+}