From 79a9536bc5533e1159be7c571892d06cd5e9f980 Mon Sep 17 00:00:00 2001
From: iamdjones <7071112+iamdjones@users.noreply.github.com>
Date: Wed, 18 Dec 2024 20:10:30 -0600
Subject: [PATCH] add check for host rewrite to DynamicMiddleware (js plugin)

---
 gateway/mw_js_plugin.go      | 33 ++++++++++++--
 gateway/mw_js_plugin_test.go | 88 ++++++++++++++++++++++++++++++++++++
 2 files changed, 117 insertions(+), 4 deletions(-)

diff --git a/gateway/mw_js_plugin.go b/gateway/mw_js_plugin.go
index e7bfc470c5c..6b98a81d7a7 100644
--- a/gateway/mw_js_plugin.go
+++ b/gateway/mw_js_plugin.go
@@ -16,6 +16,7 @@ import (
 	"time"
 
 	"github.com/TykTechnologies/tyk/apidef"
+	"github.com/TykTechnologies/tyk/ctx"
 
 	"github.com/robertkrimen/otto"
 	_ "github.com/robertkrimen/otto/underscore"
@@ -243,10 +244,7 @@ func (d *DynamicMiddleware) ProcessRequest(w http.ResponseWriter, r *http.Reques
 	// make sure request's body can be re-read again
 	nopCloseRequestBody(r)
 
-	r.URL, err = url.Parse(newRequestData.Request.URL)
-	if err != nil {
-		return nil, http.StatusOK
-	}
+	d.SetUrlAndCheckHostRewrite(newRequestData.Request.URL, r)
 
 	ignoreCanonical := d.Gw.GetConfig().IgnoreCanonicalMIMEHeaderKey
 	// Delete and set headers
@@ -323,6 +321,33 @@ func mapStrsToIfaces(m map[string]string) map[string]interface{} {
 	return m2
 }
 
+func (d *DynamicMiddleware) SetUrlAndCheckHostRewrite(newTarget string, r *http.Request) error {
+
+	// During looping target can be API name
+	// Need make it compatible with URL parser
+	if strings.HasPrefix(newTarget, LoopScheme) {
+		newTarget = LoopHostRE.ReplaceAllStringFunc(newTarget, func(match string) string {
+			host := strings.TrimPrefix(match, LoopScheme+"://")
+			return LoopingUrl(host)
+		})
+	}
+
+	newAsURL, errParseNew := url.Parse(newTarget)
+	if errParseNew != nil {
+		return errParseNew
+	}
+
+	if shouldRewriteHost(r.URL, newAsURL) {
+		log.Debug("Detected a host rewrite in pattern!")
+		d.Spec.URLRewriteEnabled = true
+		setCtxValue(r, ctx.RetainHost, true)
+	}
+
+	r.URL = newAsURL
+
+	return nil
+}
+
 // --- Utility functions during startup to ensure a sane VM is present for each API Def ----
 
 type JSVM struct {
diff --git a/gateway/mw_js_plugin_test.go b/gateway/mw_js_plugin_test.go
index f9cfce13840..9fcd2e79bbe 100644
--- a/gateway/mw_js_plugin_test.go
+++ b/gateway/mw_js_plugin_test.go
@@ -1049,3 +1049,91 @@ func testJSVM_Auth(t *testing.T, hashKeys bool) {
 		},
 	}...)
 }
+
+func TestDynamicMiddleware_SetUrlAndCheckHostRewrite(t *testing.T) {
+	ts := StartTest(nil)
+	defer ts.Close()
+
+	type args struct {
+		oldPath   string
+		newTarget string
+	}
+
+	tests := []struct {
+		name          string
+		args          args
+		errExpected   bool
+		retainHostVal interface{}
+	}{
+		{
+			name: "no host rewrite",
+			args: args{
+				oldPath:   "/hello",
+				newTarget: "/status",
+			},
+			errExpected:   false,
+			retainHostVal: nil,
+		},
+		{
+			name: "invalid new path",
+			args: args{
+				oldPath:   "/hello",
+				newTarget: "http:// example.com/status",
+			},
+			errExpected:   true,
+			retainHostVal: nil,
+		},
+		{
+			name: "host rewrite",
+			args: args{
+				oldPath:   "/hello",
+				newTarget: "http://example.com/status",
+			},
+			errExpected:   false,
+			retainHostVal: true,
+		},
+		{
+			name: "scheme in oldPath - host rewrite",
+			args: args{
+				oldPath:   "http://tyk-gateway/hello",
+				newTarget: "http://example.com/status",
+			},
+			errExpected:   false,
+			retainHostVal: true,
+		},
+		{
+			name: "scheme in oldPath - no host rewrite",
+			args: args{
+				oldPath:   "http://tyk-gateway/hello",
+				newTarget: "/status",
+			},
+			errExpected:   false,
+			retainHostVal: nil,
+		},
+		{
+			name: "same host for new and old URL",
+			args: args{
+				oldPath:   "http://tyk-gateway/hello",
+				newTarget: "http://tyk-gateway/status",
+			},
+			errExpected:   false,
+			retainHostVal: nil,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			ts := StartTest(nil)
+			defer ts.Close()
+
+			m := &DynamicMiddleware{
+				BaseMiddleware: &BaseMiddleware{
+					Spec: &APISpec{APIDefinition: &apidef.APIDefinition{}},
+					Gw:   ts.Gw,
+				}}
+			r := httptest.NewRequest("GET", tt.args.oldPath, nil)
+			err := m.SetUrlAndCheckHostRewrite(tt.args.newTarget, r)
+			assert.Equal(t, tt.errExpected, err != nil)
+			assert.Equal(t, tt.retainHostVal, r.Context().Value(ctx.RetainHost))
+		})
+	}
+}