add ssr

shadowstream/cipher.go

@@ -0,0 +1,113 @@
+package shadowstream
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/md5"
+	"crypto/rc4"
+	"strconv"
+
+	"golang.org/x/crypto/chacha20"
+)
+
+// Cipher generates a pair of stream ciphers for encryption and decryption.
+type Cipher interface {
+	IVSize() int
+	Encrypter(iv []byte) cipher.Stream
+	Decrypter(iv []byte) cipher.Stream
+}
+
+type KeySizeError int
+
+func (e KeySizeError) Error() string {
+	return "key size error: need " + strconv.Itoa(int(e)) + " bytes"
+}
+
+// CTR mode
+type ctrStream struct{ cipher.Block }
+
+func (b *ctrStream) IVSize() int                       { return b.BlockSize() }
+func (b *ctrStream) Decrypter(iv []byte) cipher.Stream { return b.Encrypter(iv) }
+func (b *ctrStream) Encrypter(iv []byte) cipher.Stream { return cipher.NewCTR(b, iv) }
+
+func AESCTR(key []byte) (Cipher, error) {
+	blk, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	return &ctrStream{blk}, nil
+}
+
+// CFB mode
+type cfbStream struct{ cipher.Block }
+
+func (b *cfbStream) IVSize() int                       { return b.BlockSize() }
+func (b *cfbStream) Decrypter(iv []byte) cipher.Stream { return cipher.NewCFBDecrypter(b, iv) }
+func (b *cfbStream) Encrypter(iv []byte) cipher.Stream { return cipher.NewCFBEncrypter(b, iv) }
+
+func AESCFB(key []byte) (Cipher, error) {
+	blk, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, err
+	}
+	return &cfbStream{blk}, nil
+}
+
+// IETF-variant of chacha20
+type chacha20ietfkey []byte
+
+func (k chacha20ietfkey) IVSize() int                       { return chacha20.NonceSize }
+func (k chacha20ietfkey) Decrypter(iv []byte) cipher.Stream { return k.Encrypter(iv) }
+func (k chacha20ietfkey) Encrypter(iv []byte) cipher.Stream {
+	ciph, err := chacha20.NewUnauthenticatedCipher(k, iv)
+	if err != nil {
+		panic(err) // should never happen
+	}
+	return ciph
+}
+
+func Chacha20IETF(key []byte) (Cipher, error) {
+	if len(key) != chacha20.KeySize {
+		return nil, KeySizeError(chacha20.KeySize)
+	}
+	return chacha20ietfkey(key), nil
+}
+
+type xchacha20key []byte
+
+func (k xchacha20key) IVSize() int                       { return chacha20.NonceSizeX }
+func (k xchacha20key) Decrypter(iv []byte) cipher.Stream { return k.Encrypter(iv) }
+func (k xchacha20key) Encrypter(iv []byte) cipher.Stream {
+	ciph, err := chacha20.NewUnauthenticatedCipher(k, iv)
+	if err != nil {
+		panic(err) // should never happen
+	}
+	return ciph
+}
+
+func Xchacha20(key []byte) (Cipher, error) {
+	if len(key) != chacha20.KeySize {
+		return nil, KeySizeError(chacha20.KeySize)
+	}
+	return xchacha20key(key), nil
+}
+
+type rc4Md5Key []byte
+
+func (k rc4Md5Key) IVSize() int {
+	return 16
+}
+func (k rc4Md5Key) Encrypter(iv []byte) cipher.Stream {
+	h := md5.New()
+	h.Write([]byte(k))
+	h.Write(iv)
+	rc4key := h.Sum(nil)
+	c, _ := rc4.NewCipher(rc4key)
+	return c
+}
+func (k rc4Md5Key) Decrypter(iv []byte) cipher.Stream {
+	return k.Encrypter(iv)
+}
+func RC4MD5(key []byte) (Cipher, error) {
+	return rc4Md5Key(key), nil
+}

shadowstream/packet.go

@@ -0,0 +1,80 @@
+package shadowstream
+
+import (
+	"crypto/rand"
+	"errors"
+	"io"
+	"net"
+	"sync"
+)
+
+// ErrShortPacket means the packet is too short to be a valid encrypted packet.
+var ErrShortPacket = errors.New("short packet")
+
+// Pack encrypts plaintext using stream cipher s and a random IV.
+// Returns a slice of dst containing random IV and ciphertext.
+// Ensure len(dst) >= s.IVSize() + len(plaintext).
+func Pack(dst, plaintext []byte, s Cipher) ([]byte, error) {
+	if len(dst) < s.IVSize()+len(plaintext) {
+		return nil, io.ErrShortBuffer
+	}
+	iv := dst[:s.IVSize()]
+	_, err := rand.Read(iv)
+	if err != nil {
+		return nil, err
+	}
+	s.Encrypter(iv).XORKeyStream(dst[len(iv):], plaintext)
+	return dst[:len(iv)+len(plaintext)], nil
+}
+
+// Unpack decrypts pkt using stream cipher s.
+// Returns a slice of dst containing decrypted plaintext.
+func Unpack(dst, pkt []byte, s Cipher) ([]byte, error) {
+	if len(pkt) < s.IVSize() {
+		return nil, ErrShortPacket
+	}
+	if len(dst) < len(pkt)-s.IVSize() {
+		return nil, io.ErrShortBuffer
+	}
+	iv := pkt[:s.IVSize()]
+	s.Decrypter(iv).XORKeyStream(dst, pkt[len(iv):])
+	return dst[:len(pkt)-len(iv)], nil
+}
+
+type PacketConn struct {
+	net.PacketConn
+	Cipher
+}
+
+// NewPacketConn wraps a net.PacketConn with stream cipher encryption/decryption.
+func NewPacketConn(c net.PacketConn, ciph Cipher) *PacketConn {
+	return &PacketConn{PacketConn: c, Cipher: ciph}
+}
+
+const maxPacketSize = 64 * 1024
+
+var bufPool = sync.Pool{New: func() any { return make([]byte, maxPacketSize) }}
+
+func (c *PacketConn) WriteTo(b []byte, addr net.Addr) (int, error) {
+	buf := bufPool.Get().([]byte)
+	defer bufPool.Put(buf)
+	buf, err := Pack(buf, b, c.Cipher)
+	if err != nil {
+		return 0, err
+	}
+	_, err = c.PacketConn.WriteTo(buf, addr)
+	return len(b), err
+}
+
+func (c *PacketConn) ReadFrom(b []byte) (int, net.Addr, error) {
+	n, addr, err := c.PacketConn.ReadFrom(b)
+	if err != nil {
+		return n, addr, err
+	}
+	bb, err := Unpack(b[c.IVSize():], b[:n], c.Cipher)
+	if err != nil {
+		return n, addr, err
+	}
+	copy(b, bb)
+	return len(bb), addr, err
+}

shadowstream/stream.go

@@ -0,0 +1,197 @@
+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
+}