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ota.go
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ota.go
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package shadowsocks
import (
"bytes"
"crypto/hmac"
"crypto/sha1"
"encoding/binary"
"io"
"v2ray.com/core/common"
"v2ray.com/core/common/buf"
"v2ray.com/core/common/bytespool"
"v2ray.com/core/common/serial"
)
const (
// AuthSize is the number of extra bytes for Shadowsocks OTA.
AuthSize = 10
)
type KeyGenerator func() []byte
type Authenticator struct {
key KeyGenerator
}
func NewAuthenticator(keygen KeyGenerator) *Authenticator {
return &Authenticator{
key: keygen,
}
}
func (v *Authenticator) Authenticate(data []byte, dest []byte) {
hasher := hmac.New(sha1.New, v.key())
common.Must2(hasher.Write(data))
res := hasher.Sum(nil)
copy(dest, 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 := uint32(0)
return func() []byte {
newKey := make([]byte, len(iv)+4)
copy(newKey, iv)
binary.BigEndian.PutUint32(newKey[len(iv):], chunkID)
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) ReadMultiBuffer() (buf.MultiBuffer, error) {
size, err := serial.ReadUint16(v.reader)
if err != nil {
return nil, newError("failed to read size").Base(err)
}
size += AuthSize
buffer := bytespool.Alloc(int32(size))
defer bytespool.Free(buffer)
if _, err := io.ReadFull(v.reader, buffer[:size]); err != nil {
return nil, err
}
authBytes := buffer[:AuthSize]
payload := buffer[AuthSize:size]
actualAuthBytes := make([]byte, AuthSize)
v.auth.Authenticate(payload, actualAuthBytes)
if !bytes.Equal(authBytes, actualAuthBytes) {
return nil, newError("invalid auth")
}
mb := buf.MergeBytes(nil, payload)
return mb, nil
}
type ChunkWriter struct {
writer io.Writer
auth *Authenticator
buffer []byte
}
func NewChunkWriter(writer io.Writer, auth *Authenticator) *ChunkWriter {
return &ChunkWriter{
writer: writer,
auth: auth,
buffer: make([]byte, 32*1024),
}
}
// WriteMultiBuffer implements buf.Writer.
func (w *ChunkWriter) WriteMultiBuffer(mb buf.MultiBuffer) error {
defer buf.ReleaseMulti(mb)
for {
mb, payloadLen := buf.SplitBytes(mb, w.buffer[2+AuthSize:])
binary.BigEndian.PutUint16(w.buffer, uint16(payloadLen))
w.auth.Authenticate(w.buffer[2+AuthSize:2+AuthSize+payloadLen], w.buffer[2:])
if err := buf.WriteAllBytes(w.writer, w.buffer[:2+AuthSize+payloadLen]); err != nil {
return err
}
if mb.IsEmpty() {
break
}
}
return nil
}