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stream.go
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stream.go
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package ss2022
import (
"bytes"
"crypto/cipher"
"crypto/rand"
"encoding/binary"
"errors"
"io"
"github.com/database64128/shadowsocks-go/zerocopy"
)
const MaxPayloadSize = 0xFFFF
// ShadowStreamHeadroom is the headroom required by an encrypted Shadowsocks stream.
//
// Front is the size of an encrypted length chunk.
// Rear is the size of an AEAD tag.
var ShadowStreamHeadroom = zerocopy.Headroom{
Front: 2 + 16,
Rear: 16,
}
// ShadowStreamReaderInfo contains information about a [ShadowStreamReader].
var ShadowStreamReaderInfo = zerocopy.ReaderInfo{
Headroom: ShadowStreamHeadroom,
MinPayloadBufferSizePerRead: MaxPayloadSize,
}
// ShadowStreamWriterInfo contains information about a [ShadowStreamWriter].
var ShadowStreamWriterInfo = zerocopy.WriterInfo{
Headroom: ShadowStreamHeadroom,
MaxPayloadSizePerWrite: MaxPayloadSize,
}
var (
ErrZeroLengthChunk = errors.New("length in length chunk is zero")
ErrFirstRead = errors.New("failed to read fixed-length header in one read call")
ErrRepeatedSalt = errors.New("detected replay: repeated salt")
)
var ErrUnsafeStreamPrefixMismatch = errors.New("unsafe stream prefix mismatch")
// ShadowStreamServerReadWriter implements Shadowsocks stream server.
type ShadowStreamServerReadWriter struct {
*ShadowStreamReader
*ShadowStreamWriter
rawRW zerocopy.DirectReadWriteCloser
cipherConfig UserCipherConfig
requestSalt []byte
unsafeResponseStreamPrefix []byte
}
// WriteZeroCopy implements the Writer WriteZeroCopy method.
func (rw *ShadowStreamServerReadWriter) WriteZeroCopy(b []byte, payloadStart, payloadLen int) (int, error) {
if rw.ShadowStreamWriter == nil { // first write
urspLen := len(rw.unsafeResponseStreamPrefix)
saltLen := len(rw.cipherConfig.PSK)
responseHeaderStart := urspLen + saltLen
responseHeaderEnd := responseHeaderStart + TCPRequestFixedLengthHeaderLength + saltLen
payloadBufStart := responseHeaderEnd + 16
bufferLen := payloadBufStart + payloadLen + 16
hb := make([]byte, bufferLen)
ursp := hb[:urspLen]
salt := hb[urspLen:responseHeaderStart]
responseHeader := hb[responseHeaderStart:responseHeaderEnd]
// Write unsafe response stream prefix.
copy(ursp, rw.unsafeResponseStreamPrefix)
// Random salt.
_, err := rand.Read(salt)
if err != nil {
return 0, err
}
// Write response header.
WriteTCPResponseHeader(responseHeader, rw.requestSalt, uint16(payloadLen))
// Create AEAD cipher.
shadowStreamCipher, err := rw.cipherConfig.ShadowStreamCipher(salt)
if err != nil {
return 0, err
}
// Create writer.
rw.ShadowStreamWriter = &ShadowStreamWriter{
writer: rw.rawRW,
ssc: shadowStreamCipher,
}
// Seal response header.
shadowStreamCipher.EncryptInPlace(responseHeader)
// Seal payload.
dst := hb[payloadBufStart:]
plaintext := b[payloadStart : payloadStart+payloadLen]
shadowStreamCipher.EncryptTo(dst, plaintext)
// Write out.
_, err = rw.rawRW.Write(hb)
if err != nil {
return 0, err
}
return payloadLen, nil
}
return rw.ShadowStreamWriter.WriteZeroCopy(b, payloadStart, payloadLen)
}
// CloseRead implements the ReadWriter CloseRead method.
func (rw *ShadowStreamServerReadWriter) CloseRead() error {
return rw.rawRW.CloseRead()
}
// CloseWrite implements the ReadWriter CloseWrite method.
func (rw *ShadowStreamServerReadWriter) CloseWrite() error {
return rw.rawRW.CloseWrite()
}
// Close implements the ReadWriter Close method.
func (rw *ShadowStreamServerReadWriter) Close() error {
return rw.rawRW.Close()
}
// ShadowStreamClientReadWriter implements Shadowsocks stream client.
type ShadowStreamClientReadWriter struct {
*ShadowStreamReader
*ShadowStreamWriter
rawRW zerocopy.DirectReadWriteCloser
cipherConfig *ClientCipherConfig
requestSalt []byte
unsafeResponseStreamPrefix []byte
}
// ReadZeroCopy implements the Reader ReadZeroCopy method.
func (rw *ShadowStreamClientReadWriter) ReadZeroCopy(b []byte, payloadBufStart, payloadBufLen int) (int, error) {
if rw.ShadowStreamReader == nil { // first read
urspLen := len(rw.unsafeResponseStreamPrefix)
saltLen := len(rw.cipherConfig.PSK)
fixedLengthHeaderStart := urspLen + saltLen
bufferLen := fixedLengthHeaderStart + TCPRequestFixedLengthHeaderLength + saltLen + 16
hb := make([]byte, bufferLen)
// Read response header.
n, err := rw.rawRW.Read(hb)
if err != nil {
return 0, err
}
if n < bufferLen {
return 0, &HeaderError[int]{ErrFirstRead, bufferLen, n}
}
// Check unsafe response stream prefix.
ursp := hb[:urspLen]
if !bytes.Equal(ursp, rw.unsafeResponseStreamPrefix) {
return 0, &HeaderError[[]byte]{ErrUnsafeStreamPrefixMismatch, rw.unsafeResponseStreamPrefix, ursp}
}
// Derive key and create cipher.
salt := hb[urspLen:fixedLengthHeaderStart]
ciphertext := hb[fixedLengthHeaderStart:]
shadowStreamCipher, err := rw.cipherConfig.ShadowStreamCipher(salt)
if err != nil {
return 0, err
}
// Create reader.
rw.ShadowStreamReader = &ShadowStreamReader{
reader: rw.rawRW,
ssc: shadowStreamCipher,
}
// AEAD open.
plaintext, err := shadowStreamCipher.DecryptInPlace(ciphertext)
if err != nil {
return 0, err
}
// Parse response header.
n, err = ParseTCPResponseHeader(plaintext, rw.requestSalt)
if err != nil {
return 0, err
}
payloadBuf := b[payloadBufStart : payloadBufStart+n+16]
// Read payload chunk.
_, err = io.ReadFull(rw.rawRW, payloadBuf)
if err != nil {
return 0, err
}
// AEAD open.
_, err = shadowStreamCipher.DecryptInPlace(payloadBuf)
if err != nil {
return 0, err
}
return n, nil
}
return rw.ShadowStreamReader.ReadZeroCopy(b, payloadBufStart, payloadBufLen)
}
// CloseRead implements the ReadWriter CloseRead method.
func (rw *ShadowStreamClientReadWriter) CloseRead() error {
return rw.rawRW.CloseRead()
}
// CloseWrite implements the ReadWriter CloseWrite method.
func (rw *ShadowStreamClientReadWriter) CloseWrite() error {
return rw.rawRW.CloseWrite()
}
// Close implements the ReadWriter Close method.
func (rw *ShadowStreamClientReadWriter) Close() error {
return rw.rawRW.Close()
}
// ShadowStreamWriter wraps an io.WriteCloser and feeds an encrypted Shadowsocks stream to it.
//
// Wire format:
//
// +------------------------+---------------------------+
// | encrypted length chunk | encrypted payload chunk |
// +------------------------+---------------------------+
// | 2B length + 16B tag | variable length + 16B tag |
// +------------------------+---------------------------+
type ShadowStreamWriter struct {
writer io.WriteCloser
ssc *ShadowStreamCipher
}
// WriterInfo implements the Writer WriterInfo method.
func (w *ShadowStreamWriter) WriterInfo() zerocopy.WriterInfo {
return ShadowStreamWriterInfo
}
// WriteZeroCopy implements the Writer WriteZeroCopy method.
func (w *ShadowStreamWriter) WriteZeroCopy(b []byte, payloadStart, payloadLen int) (payloadWritten int, err error) {
overhead := w.ssc.Overhead()
lengthStart := payloadStart - overhead - 2
lengthBuf := b[lengthStart : lengthStart+2]
payloadBuf := b[payloadStart : payloadStart+payloadLen]
payloadTagEnd := payloadStart + payloadLen + overhead
chunksBuf := b[lengthStart:payloadTagEnd]
// Write length.
binary.BigEndian.PutUint16(lengthBuf, uint16(payloadLen))
// Seal length chunk.
w.ssc.EncryptInPlace(lengthBuf)
// Seal payload chunk.
w.ssc.EncryptInPlace(payloadBuf)
// Write to wrapped writer.
_, err = w.writer.Write(chunksBuf)
if err != nil {
return
}
payloadWritten = payloadLen
return
}
// ShadowStreamReader wraps an io.ReadCloser and reads from it as an encrypted Shadowsocks stream.
type ShadowStreamReader struct {
reader io.ReadCloser
ssc *ShadowStreamCipher
}
// ReaderInfo implements the Reader ReaderInfo method.
func (r *ShadowStreamReader) ReaderInfo() zerocopy.ReaderInfo {
return ShadowStreamReaderInfo
}
// ReadZeroCopy implements the Reader ReadZeroCopy method.
func (r *ShadowStreamReader) ReadZeroCopy(b []byte, payloadBufStart, payloadBufLen int) (payloadLen int, err error) {
overhead := r.ssc.Overhead()
sealedLengthChunkStart := payloadBufStart - overhead - 2
sealedLengthChunkBuf := b[sealedLengthChunkStart:payloadBufStart]
// Read sealed length chunk.
_, err = io.ReadFull(r.reader, sealedLengthChunkBuf)
if err != nil {
return
}
// Open sealed length chunk.
_, err = r.ssc.DecryptInPlace(sealedLengthChunkBuf)
if err != nil {
return
}
// Validate length.
payloadLen = int(binary.BigEndian.Uint16(sealedLengthChunkBuf))
if payloadLen == 0 {
err = ErrZeroLengthChunk
return
}
// Read sealed payload chunk.
sealedPayloadChunkBuf := b[payloadBufStart : payloadBufStart+payloadLen+overhead]
_, err = io.ReadFull(r.reader, sealedPayloadChunkBuf)
if err != nil {
payloadLen = 0
return
}
// Open sealed payload chunk.
_, err = r.ssc.DecryptInPlace(sealedPayloadChunkBuf)
if err != nil {
payloadLen = 0
}
return
}
// ShadowStreamCipher wraps an AEAD cipher and provides methods that transparently increments
// the nonce after each AEAD operation.
type ShadowStreamCipher struct {
aead cipher.AEAD
nonce []byte
}
// NewShadowStreamCipher wraps the given AEAD cipher into a new ShadowStreamCipher.
func NewShadowStreamCipher(aead cipher.AEAD) *ShadowStreamCipher {
return &ShadowStreamCipher{
aead: aead,
nonce: make([]byte, aead.NonceSize()),
}
}
// Overhead returns the tag size of the AEAD cipher.
func (c *ShadowStreamCipher) Overhead() int {
return c.aead.Overhead()
}
// EncryptInPlace encrypts and authenticates plaintext in-place.
func (c *ShadowStreamCipher) EncryptInPlace(plaintext []byte) (ciphertext []byte) {
ciphertext = c.aead.Seal(plaintext[:0], c.nonce, plaintext, nil)
increment(c.nonce)
return
}
// EncryptTo encrypts and authenticates the plaintext and saves the ciphertext to dst.
func (c *ShadowStreamCipher) EncryptTo(dst, plaintext []byte) (ciphertext []byte) {
ciphertext = c.aead.Seal(dst[:0], c.nonce, plaintext, nil)
increment(c.nonce)
return
}
// DecryptInplace decrypts and authenticates ciphertext in-place.
func (c *ShadowStreamCipher) DecryptInPlace(ciphertext []byte) (plaintext []byte, err error) {
plaintext, err = c.aead.Open(ciphertext[:0], c.nonce, ciphertext, nil)
if err == nil {
increment(c.nonce)
}
return
}
// DecryptTo decrypts and authenticates the ciphertext and saves the plaintext to dst.
func (c *ShadowStreamCipher) DecryptTo(dst, ciphertext []byte) (plaintext []byte, err error) {
plaintext, err = c.aead.Open(dst[:0], c.nonce, ciphertext, nil)
if err == nil {
increment(c.nonce)
}
return
}
// increment increments a little-endian unsigned integer b.
func increment(b []byte) {
for i := range b {
b[i]++
if b[i] != 0 {
return
}
}
}