/
stream.go
197 lines (169 loc) · 3.55 KB
/
stream.go
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package shadowstream
import (
"crypto/cipher"
"crypto/rand"
"io"
"net"
)
const bufSize = 2048
type Writer struct {
io.Writer
cipher.Stream
buf [bufSize]byte
}
// NewWriter wraps an io.Writer with stream cipher encryption.
func NewWriter(w io.Writer, s cipher.Stream) *Writer { return &Writer{Writer: w, Stream: s} }
func (w *Writer) Write(p []byte) (n int, err error) {
buf := w.buf[:]
for nw := 0; n < len(p) && err == nil; n += nw {
end := n + len(buf)
if end > len(p) {
end = len(p)
}
w.XORKeyStream(buf, p[n:end])
nw, err = w.Writer.Write(buf[:end-n])
}
return
}
func (w *Writer) ReadFrom(r io.Reader) (n int64, err error) {
buf := w.buf[:]
for {
nr, er := r.Read(buf)
n += int64(nr)
b := buf[:nr]
w.XORKeyStream(b, b)
if _, err = w.Writer.Write(b); err != nil {
return
}
if er != nil {
if er != io.EOF { // ignore EOF as per io.ReaderFrom contract
err = er
}
return
}
}
}
type Reader struct {
io.Reader
cipher.Stream
buf [bufSize]byte
}
// NewReader wraps an io.Reader with stream cipher decryption.
func NewReader(r io.Reader, s cipher.Stream) *Reader { return &Reader{Reader: r, Stream: s} }
func (r *Reader) Read(p []byte) (n int, err error) {
n, err = r.Reader.Read(p)
if err != nil {
return 0, err
}
r.XORKeyStream(p, p[:n])
return
}
func (r *Reader) WriteTo(w io.Writer) (n int64, err error) {
buf := r.buf[:]
for {
nr, er := r.Reader.Read(buf)
if nr > 0 {
r.XORKeyStream(buf, buf[:nr])
nw, ew := w.Write(buf[:nr])
n += int64(nw)
if ew != nil {
err = ew
return
}
}
if er != nil {
if er != io.EOF { // ignore EOF as per io.Copy contract (using src.WriteTo shortcut)
err = er
}
return
}
}
}
// A Conn represents a Shadowsocks connection. It implements the net.Conn interface.
type Conn struct {
net.Conn
Cipher
r *Reader
w *Writer
readIV []byte
writeIV []byte
}
// NewConn wraps a stream-oriented net.Conn with stream cipher encryption/decryption.
func NewConn(c net.Conn, ciph Cipher) *Conn { return &Conn{Conn: c, Cipher: ciph} }
func (c *Conn) initReader() error {
if c.r == nil {
iv, err := c.ObtainReadIV()
if err != nil {
return err
}
c.r = NewReader(c.Conn, c.Decrypter(iv))
}
return nil
}
func (c *Conn) Read(b []byte) (int, error) {
if c.r == nil {
if err := c.initReader(); err != nil {
return 0, err
}
}
return c.r.Read(b)
}
func (c *Conn) WriteTo(w io.Writer) (int64, error) {
if c.r == nil {
if err := c.initReader(); err != nil {
return 0, err
}
}
return c.r.WriteTo(w)
}
func (c *Conn) initWriter() error {
if c.w == nil {
iv, err := c.ObtainWriteIV()
if err != nil {
return err
}
if _, err := c.Conn.Write(iv); err != nil {
return err
}
c.w = NewWriter(c.Conn, c.Encrypter(iv))
}
return nil
}
func (c *Conn) Write(b []byte) (int, error) {
if c.w == nil {
if err := c.initWriter(); err != nil {
return 0, err
}
}
return c.w.Write(b)
}
func (c *Conn) ReadFrom(r io.Reader) (int64, error) {
if c.w == nil {
if err := c.initWriter(); err != nil {
return 0, err
}
}
return c.w.ReadFrom(r)
}
func (c *Conn) ObtainWriteIV() ([]byte, error) {
if len(c.writeIV) == c.IVSize() {
return c.writeIV, nil
}
iv := make([]byte, c.IVSize())
if _, err := rand.Read(iv); err != nil {
return nil, err
}
c.writeIV = iv
return iv, nil
}
func (c *Conn) ObtainReadIV() ([]byte, error) {
if len(c.readIV) == c.IVSize() {
return c.readIV, nil
}
iv := make([]byte, c.IVSize())
if _, err := io.ReadFull(c.Conn, iv); err != nil {
return nil, err
}
c.readIV = iv
return iv, nil
}