package shadowsocks import ( "bytes" "crypto/hmac" "crypto/sha1" "errors" "io" "v2ray.com/core/common/alloc" "v2ray.com/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 (v *Authenticator) Authenticate(auth []byte, data []byte) []byte { hasher := hmac.New(sha1.New, v.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, iv...) newKey = append(newKey, key...) 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 = serial.IntToBytes(chunkId, newKey) chunkId++ return newKey } } type ChunkReader struct { reader io.Reader auth *Authenticator } func NewChunkReader(reader io.Reader, auth *Authenticator) *ChunkReader { return &ChunkReader{ reader: reader, auth: auth, } } func (v *ChunkReader) Release() { v.reader = nil v.auth = nil } func (v *ChunkReader) Read() (*alloc.Buffer, error) { buffer := alloc.NewBuffer() if _, err := io.ReadFull(v.reader, buffer.Value[:2]); err != nil { buffer.Release() return nil, err } // There is a potential buffer overflow here. Large buffer is 64K bytes, // while uin16 + 10 will be more than that length := serial.BytesToUint16(buffer.Value[:2]) + AuthSize if length > alloc.BufferSize { // Theoretically the size of a chunk is 64K, but most Shadowsocks implementations used <4K buffer. buffer.Release() buffer = alloc.NewLocalBuffer(int(length) + 128) } if _, err := io.ReadFull(v.reader, buffer.Value[:length]); err != nil { buffer.Release() return nil, err } buffer.Slice(0, int(length)) authBytes := buffer.Value[:AuthSize] payload := buffer.Value[AuthSize:] actualAuthBytes := v.auth.Authenticate(nil, payload) if !bytes.Equal(authBytes, actualAuthBytes) { buffer.Release() return nil, errors.New("Shadowsocks|AuthenticationReader: Invalid auth.") } buffer.SliceFrom(AuthSize) return buffer, nil } type ChunkWriter struct { writer io.Writer auth *Authenticator } func NewChunkWriter(writer io.Writer, auth *Authenticator) *ChunkWriter { return &ChunkWriter{ writer: writer, auth: auth, } } func (v *ChunkWriter) Release() { v.writer = nil v.auth = nil } func (v *ChunkWriter) Write(payload *alloc.Buffer) error { totalLength := payload.Len() payload.SliceBack(AuthSize) v.auth.Authenticate(payload.Value[:0], payload.Value[AuthSize:]) payload.PrependUint16(uint16(totalLength)) _, err := v.writer.Write(payload.Bytes()) return err }