Feature: add ssr support (#805)

* Refactor ssr stream cipher to expose iv and key

References:
https://github.com/Dreamacro/go-shadowsocks2
https://github.com/sh4d0wfiend/go-shadowsocksr2

* Implement ssr obfs

Reference:
https://github.com/mzz2017/shadowsocksR

* Implement ssr protocol

References:
https://github.com/mzz2017/shadowsocksR
https://github.com/shadowsocksRb/shadowsocksr-libev
https://github.com/shadowsocksr-backup/shadowsocksr

adapters/outbound/parser.go

@@ -24,6 +24,13 @@ func ParseProxy(mapping map[string]interface{}) (C.Proxy, error) {
 			break
 		}
 		proxy, err = NewShadowSocks(*ssOption)
+	case "ssr":
+		ssrOption := &ShadowSocksROption{}
+		err = decoder.Decode(mapping, ssrOption)
+		if err != nil {
+			break
+		}
+		proxy, err = NewShadowSocksR(*ssrOption)
 	case "socks5":
 		socksOption := &Socks5Option{}
 		err = decoder.Decode(mapping, socksOption)

adapters/outbound/shadowsocksr.go

@@ -0,0 +1,134 @@
+package outbound
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net"
+	"strconv"
+
+	"github.com/Dreamacro/clash/component/dialer"
+	"github.com/Dreamacro/clash/component/ssr/obfs"
+	"github.com/Dreamacro/clash/component/ssr/protocol"
+	C "github.com/Dreamacro/clash/constant"
+	"github.com/Dreamacro/go-shadowsocks2/core"
+	"github.com/Dreamacro/go-shadowsocks2/shadowstream"
+)
+
+type ShadowSocksR struct {
+	*Base
+	cipher   *core.StreamCipher
+	obfs     obfs.Obfs
+	protocol protocol.Protocol
+}
+
+type ShadowSocksROption struct {
+	Name          string `proxy:"name"`
+	Server        string `proxy:"server"`
+	Port          int    `proxy:"port"`
+	Password      string `proxy:"password"`
+	Cipher        string `proxy:"cipher"`
+	Obfs          string `proxy:"obfs"`
+	ObfsParam     string `proxy:"obfs-param,omitempty"`
+	Protocol      string `proxy:"protocol"`
+	ProtocolParam string `proxy:"protocol-param,omitempty"`
+	UDP           bool   `proxy:"udp,omitempty"`
+}
+
+func (ssr *ShadowSocksR) StreamConn(c net.Conn, metadata *C.Metadata) (net.Conn, error) {
+	c = obfs.NewConn(c, ssr.obfs)
+	c = ssr.cipher.StreamConn(c)
+	conn, ok := c.(*shadowstream.Conn)
+	if !ok {
+		return nil, fmt.Errorf("invalid connection type")
+	}
+	iv, err := conn.ObtainWriteIV()
+	if err != nil {
+		return nil, err
+	}
+	c = protocol.NewConn(c, ssr.protocol, iv)
+	_, err = c.Write(serializesSocksAddr(metadata))
+	return c, err
+}
+
+func (ssr *ShadowSocksR) DialContext(ctx context.Context, metadata *C.Metadata) (C.Conn, error) {
+	c, err := dialer.DialContext(ctx, "tcp", ssr.addr)
+	if err != nil {
+		return nil, fmt.Errorf("%s connect error: %w", ssr.addr, err)
+	}
+	tcpKeepAlive(c)
+
+	c, err = ssr.StreamConn(c, metadata)
+	return NewConn(c, ssr), err
+}
+
+func (ssr *ShadowSocksR) DialUDP(metadata *C.Metadata) (C.PacketConn, error) {
+	pc, err := dialer.ListenPacket("udp", "")
+	if err != nil {
+		return nil, err
+	}
+
+	addr, err := resolveUDPAddr("udp", ssr.addr)
+	if err != nil {
+		return nil, err
+	}
+
+	pc = ssr.cipher.PacketConn(pc)
+	pc = protocol.NewPacketConn(pc, ssr.protocol)
+	return newPacketConn(&ssPacketConn{PacketConn: pc, rAddr: addr}, ssr), nil
+}
+
+func (ssr *ShadowSocksR) MarshalJSON() ([]byte, error) {
+	return json.Marshal(map[string]string{
+		"type": ssr.Type().String(),
+	})
+}
+
+func NewShadowSocksR(option ShadowSocksROption) (*ShadowSocksR, error) {
+	addr := net.JoinHostPort(option.Server, strconv.Itoa(option.Port))
+	cipher := option.Cipher
+	password := option.Password
+	coreCiph, err := core.PickCipher(cipher, nil, password)
+	if err != nil {
+		return nil, fmt.Errorf("ssr %s initialize cipher error: %w", addr, err)
+	}
+	ciph, ok := coreCiph.(*core.StreamCipher)
+	if !ok {
+		return nil, fmt.Errorf("%s is not a supported stream cipher in ssr", cipher)
+	}
+
+	obfs, err := obfs.PickObfs(option.Obfs, &obfs.Base{
+		IVSize:  ciph.IVSize(),
+		Key:     ciph.Key,
+		HeadLen: 30,
+		Host:    option.Server,
+		Port:    option.Port,
+		Param:   option.ObfsParam,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("ssr %s initialize obfs error: %w", addr, err)
+	}
+
+	protocol, err := protocol.PickProtocol(option.Protocol, &protocol.Base{
+		IV:     nil,
+		Key:    ciph.Key,
+		TCPMss: 1460,
+		Param:  option.ProtocolParam,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("ssr %s initialize protocol error: %w", addr, err)
+	}
+	protocol.SetOverhead(obfs.GetObfsOverhead() + protocol.GetProtocolOverhead())
+
+	return &ShadowSocksR{
+		Base: &Base{
+			name: option.Name,
+			addr: addr,
+			tp:   C.ShadowsocksR,
+			udp:  option.UDP,
+		},
+		cipher:   ciph,
+		obfs:     obfs,
+		protocol: protocol,
+	}, nil
+}