Fix: incorrect scheme on proxy.Do (#1762)

middleware/proxy/proxy.go

@@ -1,6 +1,7 @@
 package proxy
 
 import (
+	"bytes"
 	"crypto/tls"
 	"fmt"
 	"net/url"
@@ -121,10 +122,25 @@ func Do(c *fiber.Ctx, addr string) error {
 	req := c.Request()
 	res := c.Response()
 	req.SetRequestURI(addr)
+	// NOTE: if req.isTLS is true, SetRequestURI keeps the scheme as https.
+	// issue reference:
+	// https://github.com/gofiber/fiber/issues/1762
+	if scheme := getScheme(utils.UnsafeBytes(addr)); len(scheme) > 0 {
+		req.URI().SetSchemeBytes(scheme)
+	}
+
 	req.Header.Del(fiber.HeaderConnection)
 	if err := client.Do(req, res); err != nil {
 		return err
 	}
 	res.Header.Del(fiber.HeaderConnection)
 	return nil
 }
+
+func getScheme(uri []byte) []byte {
+	i := bytes.IndexByte(uri, '/')
+	if i < 1 || uri[i-1] != ':' || i == len(uri)-1 || uri[i+1] != '/' {
+		return nil
+	}
+	return uri[:i-1]
+}

middleware/proxy/proxy_test.go

@@ -122,6 +122,40 @@ func Test_Proxy_Balancer_WithTlsConfig(t *testing.T) {
 	utils.AssertEqual(t, "tls balancer", body)
 }
 
+// go test -run Test_Proxy_Forward_WithTlsConfig_To_Http
+func Test_Proxy_Forward_WithTlsConfig_To_Http(t *testing.T) {
+	t.Parallel()
+
+	_, targetAddr := createProxyTestServer(func(c *fiber.Ctx) error {
+		return c.SendString("hello from target")
+	}, t)
+
+	proxyServerTLSConf, _, err := tlstest.GetTLSConfigs()
+	utils.AssertEqual(t, nil, err)
+
+	proxyServerLn, err := net.Listen(fiber.NetworkTCP4, "127.0.0.1:0")
+	utils.AssertEqual(t, nil, err)
+
+	proxyServerLn = tls.NewListener(proxyServerLn, proxyServerTLSConf)
+
+	app := fiber.New(fiber.Config{DisableStartupMessage: true})
+
+	proxyAddr := proxyServerLn.Addr().String()
+
+	app.Use(Forward("http://" + targetAddr))
+
+	go func() { utils.AssertEqual(t, nil, app.Listener(proxyServerLn)) }()
+
+	code, body, errs := fiber.Get("https://" + proxyAddr).
+		InsecureSkipVerify().
+		Timeout(5 * time.Second).
+		String()
+
+	utils.AssertEqual(t, 0, len(errs))
+	utils.AssertEqual(t, fiber.StatusOK, code)
+	utils.AssertEqual(t, "hello from target", body)
+}
+
 // go test -run Test_Proxy_Forward
 func Test_Proxy_Forward(t *testing.T) {
 	t.Parallel()