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139 lines
3.0 KiB
139 lines
3.0 KiB
package shadowsocks
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import (
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"bytes"
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"crypto/hmac"
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"crypto/sha1"
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"io"
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"v2ray.com/core/common/buf"
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"v2ray.com/core/common/serial"
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)
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const (
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// AuthSize is the number of extra bytes for Shadowsocks OTA.
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AuthSize = 10
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)
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type KeyGenerator func() []byte
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type Authenticator struct {
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key KeyGenerator
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}
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func NewAuthenticator(keygen KeyGenerator) *Authenticator {
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return &Authenticator{
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key: keygen,
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}
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}
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func (v *Authenticator) Authenticate(data []byte) buf.Supplier {
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hasher := hmac.New(sha1.New, v.key())
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hasher.Write(data)
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res := hasher.Sum(nil)
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return func(b []byte) (int, error) {
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return copy(b, res[:AuthSize]), nil
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}
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}
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func HeaderKeyGenerator(key []byte, iv []byte) func() []byte {
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return func() []byte {
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newKey := make([]byte, 0, len(key)+len(iv))
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newKey = append(newKey, iv...)
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newKey = append(newKey, key...)
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return newKey
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}
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}
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func ChunkKeyGenerator(iv []byte) func() []byte {
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chunkID := 0
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return func() []byte {
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newKey := make([]byte, 0, len(iv)+4)
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newKey = append(newKey, iv...)
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newKey = serial.IntToBytes(chunkID, newKey)
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chunkID++
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return newKey
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}
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}
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type ChunkReader struct {
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reader io.Reader
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auth *Authenticator
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}
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func NewChunkReader(reader io.Reader, auth *Authenticator) *ChunkReader {
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return &ChunkReader{
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reader: reader,
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auth: auth,
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}
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}
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func (v *ChunkReader) Read() (buf.MultiBuffer, error) {
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buffer := buf.New()
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if err := buffer.AppendSupplier(buf.ReadFullFrom(v.reader, 2)); err != nil {
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buffer.Release()
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return nil, err
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}
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// There is a potential buffer overflow here. Large buffer is 64K bytes,
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// while uin16 + 10 will be more than that
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length := serial.BytesToUint16(buffer.BytesTo(2)) + AuthSize
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if length > buf.Size {
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// Theoretically the size of a chunk is 64K, but most Shadowsocks implementations used <4K buffer.
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buffer.Release()
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buffer = buf.NewLocal(int(length) + 128)
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}
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buffer.Clear()
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if err := buffer.AppendSupplier(buf.ReadFullFrom(v.reader, int(length))); err != nil {
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buffer.Release()
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return nil, err
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}
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authBytes := buffer.BytesTo(AuthSize)
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payload := buffer.BytesFrom(AuthSize)
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actualAuthBytes := make([]byte, AuthSize)
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v.auth.Authenticate(payload)(actualAuthBytes)
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if !bytes.Equal(authBytes, actualAuthBytes) {
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buffer.Release()
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return nil, newError("invalid auth")
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}
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buffer.SliceFrom(AuthSize)
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return buf.NewMultiBufferValue(buffer), nil
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}
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type ChunkWriter struct {
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writer io.Writer
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auth *Authenticator
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buffer []byte
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}
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func NewChunkWriter(writer io.Writer, auth *Authenticator) *ChunkWriter {
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return &ChunkWriter{
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writer: writer,
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auth: auth,
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buffer: make([]byte, 32*1024),
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}
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}
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func (w *ChunkWriter) Write(mb buf.MultiBuffer) error {
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defer mb.Release()
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for {
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payloadLen, err := mb.Read(w.buffer[2+AuthSize:])
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if err != nil {
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return err
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}
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serial.Uint16ToBytes(uint16(payloadLen), w.buffer[:0])
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w.auth.Authenticate(w.buffer[2+AuthSize : 2+AuthSize+payloadLen])(w.buffer[2:])
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if _, err := w.writer.Write(w.buffer[:2+AuthSize+payloadLen]); err != nil {
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return err
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}
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if mb.IsEmpty() {
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break
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}
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}
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return nil
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}
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