Blackhole outbound: Add customizable response data support (#6713)

https://github.com/XTLS/Xray-core/pull/6711#issuecomment-5508683394

---------

Co-authored-by: Raaad1on <djilyawhite@gmail.com>

proxy/blackhole/blackhole_test.go

@@ -1,12 +1,15 @@
 package blackhole_test
 
 import (
+	"bufio"
+	"bytes"
 	"context"
+	"crypto/rand"
+	"net/http"
 	"testing"
 
 	"github.com/xtls/xray-core/common"
 	"github.com/xtls/xray-core/common/buf"
-	"github.com/xtls/xray-core/common/serial"
 	"github.com/xtls/xray-core/common/session"
 	"github.com/xtls/xray-core/proxy/blackhole"
 	"github.com/xtls/xray-core/transport"
@@ -16,27 +19,58 @@ import (
 func TestBlackholeHTTPResponse(t *testing.T) {
 	ctx := session.ContextWithOutbounds(context.Background(), []*session.Outbound{{}})
 	handler, err := blackhole.New(ctx, &blackhole.Config{
-		Response: serial.ToTypedMessage(&blackhole.HTTPResponse{}),
+		Response: &blackhole.Response{Type: "http"},
 	})
 	common.Must(err)
 
 	reader, writer := pipe.New(pipe.WithoutSizeLimit())
 
-	var mb buf.MultiBuffer
-	var rerr error
+	dataCh := make(chan buf.MultiBuffer, 1)
 	go func() {
-		b, e := reader.ReadMultiBuffer()
-		mb = b
-		rerr = e
+		mb := common.Must2(reader.ReadMultiBuffer())
+		dataCh <- mb
 	}()
-
 	link := transport.Link{
 		Reader: reader,
 		Writer: writer,
 	}
 	common.Must(handler.Process(ctx, &link, nil))
-	common.Must(rerr)
-	if mb.IsEmpty() {
-		t.Error("expect http response, but nothing")
+	mb := <-dataCh
+	data := make([]byte, mb.Len())
+	mb.Copy(data)
+	resp := common.Must2(http.ReadResponse(bufio.NewReader(bytes.NewBuffer(data)), nil))
+	if resp.StatusCode != 403 {
+		t.Errorf("expected 403 response, got %d", resp.StatusCode)
+	}
+}
+
+func TestBlackholeCustomResponse(t *testing.T) {
+	ctx := session.ContextWithOutbounds(context.Background(), []*session.Outbound{{}})
+	// slightly bigger than a buffer
+	expected := make([]byte, buf.Size+1000)
+	if _, err := rand.Read(expected); err != nil {
+		t.Fatal(err)
+	}
+	handler, err := blackhole.New(ctx, &blackhole.Config{
+		Response: &blackhole.Response{
+			Type:               "custom",
+			CustomResponseData: expected,
+		},
+	})
+	common.Must(err)
+
+	reader, writer := pipe.New(pipe.WithoutSizeLimit())
+	var actual buf.MultiBuffer
+	var rerr error
+	go func() {
+		actual, rerr = reader.ReadMultiBuffer()
+	}()
+
+	link := transport.Link{Reader: reader, Writer: writer}
+	common.Must(handler.Process(ctx, &link, nil))
+	common.Must(rerr)
+
+	if actual.String() != string(expected) {
+		t.Errorf("custom response mismatch")
 	}
 }