fix(ssr): reach obfs conn through the buffered reader wrapper

protocol/shadowsocks_stream/ssr_cipher_test.go

@@ -0,0 +1,73 @@
+package shadowsocks_stream
+
+import (
+	"io"
+	"net"
+	"testing"
+	"time"
+
+	"github.com/daeuniverse/outbound/ciphers"
+	"github.com/daeuniverse/outbound/netproxy"
+)
+
+// obfsStub stands in for transport/shadowsocksr/obfs.Conn: it records the
+// cipher and address length handed down by the shadowsocks stream layer.
+type obfsStub struct {
+	netproxy.Conn
+	cipher  *ciphers.StreamCipher
+	addrLen int
+}
+
+func (o *obfsStub) SetCipher(cipher *ciphers.StreamCipher) { o.cipher = cipher }
+func (o *obfsStub) SetAddrLen(addrLen int)                 { o.addrLen = addrLen }
+
+type discardConn struct{ net.Conn }
+
+func (discardConn) Read(p []byte) (int, error)      { return 0, io.EOF }
+func (discardConn) Write(p []byte) (int, error)     { return len(p), nil }
+func (discardConn) Close() error                    { return nil }
+func (discardConn) SetDeadline(time.Time) error     { return nil }
+func (discardConn) SetReadDeadline(time.Time) error { return nil }
+func (discardConn) SetWriteDeadline(t time.Time) error {
+	return nil
+}
+
+func newStubChain(t *testing.T, wrap bool) (*TcpConn, *obfsStub) {
+	t.Helper()
+	cipher, err := ciphers.NewStreamCipher("aes-256-cfb", "p@ssw0rd")
+	if err != nil {
+		t.Fatal(err)
+	}
+	stub := &obfsStub{Conn: discardConn{}}
+	var under netproxy.Conn = stub
+	if wrap {
+		under = netproxy.NewBufferedReaderConn(stub, 0)
+	}
+	return NewTcpConn(under, cipher), stub
+}
+
+func TestSSRObfsReceivesCipherWithoutWrapper(t *testing.T) {
+	conn, stub := newStubChain(t, false)
+	if _, err := conn.Write([]byte("hello")); err != nil {
+		t.Fatal(err)
+	}
+	if stub.cipher == nil {
+		t.Fatal("obfs conn did not receive the cipher")
+	}
+	if stub.addrLen != len("hello") {
+		t.Fatalf("addrLen = %d, want %d", stub.addrLen, len("hello"))
+	}
+}
+
+func TestSSRObfsReceivesCipherThroughBufferedReaderConn(t *testing.T) {
+	conn, stub := newStubChain(t, true)
+	if _, err := conn.Write([]byte("hello")); err != nil {
+		t.Fatal(err)
+	}
+	if stub.cipher == nil {
+		t.Fatal("obfs conn behind BufferedReaderConn did not receive the cipher")
+	}
+	if stub.addrLen != len("hello") {
+		t.Fatalf("addrLen = %d, want %d", stub.addrLen, len("hello"))
+	}
+}

protocol/shadowsocks_stream/tcp_conn.go

@@ -24,6 +24,17 @@ func NewTcpConn(c netproxy.Conn, cipher *ciphers.StreamCipher) *TcpConn {
 	}
 }
 
+// unwrapConn peels transparent wrappers such as netproxy.BufferedReaderConn so
+// that SSR obfs conns stay reachable by the type assertions below.
+func unwrapConn(c netproxy.Conn) netproxy.Conn {
+	if ic, ok := c.(interface{ IntrinsicConn() netproxy.Conn }); ok {
+		if inner := ic.IntrinsicConn(); inner != nil {
+			return inner
+		}
+	}
+	return c
+}
+
 func (c *TcpConn) Read(b []byte) (n int, err error) {
 	if !c.cipher.DecryptInited() {
 		buf := b
@@ -82,12 +93,13 @@ func (c *TcpConn) Write(b []byte) (n int, err error) {
 		b = buf
 
 		// For SSR obfs.
-		if innerConn, ok := c.Conn.(interface {
+		obfsConn := unwrapConn(c.Conn)
+		if innerConn, ok := obfsConn.(interface {
 			SetCipher(cipher *ciphers.StreamCipher)
 		}); ok {
 			innerConn.SetCipher(c.cipher)
 		}
-		if innerConn, ok := c.Conn.(interface {
+		if innerConn, ok := obfsConn.(interface {
 			SetAddrLen(addrLen int)
 		}); ok {
 			innerConn.SetAddrLen(lenToWrite)