From 0dab17ea851827fcee44e3ff1ea4767689148a63 Mon Sep 17 00:00:00 2001
From: MrMelon54 <github@mrmelon54.com>
Date: Wed, 30 Aug 2023 11:34:53 +0100
Subject: [PATCH] Add internal loop detection

---
 servers/https.go | 5 +++++
 target/route.go  | 9 +++++++++
 2 files changed, 14 insertions(+)

diff --git a/servers/https.go b/servers/https.go
index 269906e..7a9af86 100644
--- a/servers/https.go
+++ b/servers/https.go
@@ -73,6 +73,11 @@ func setupRateLimiter(rateLimit uint64, next http.Handler) http.Handler {
 
 func setupFaviconMiddleware(fav *favicons.Favicons, next http.Handler) http.Handler {
 	return http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
+		if req.Header.Get("X-Violet-Loop-Detect") == "1" {
+			rw.WriteHeader(http.StatusLoopDetected)
+			_, _ = rw.Write([]byte("Detected a routing loop\n"))
+			return
+		}
 		if req.Header.Get("X-Violet-Raw-Favicon") != "1" {
 			switch req.URL.Path {
 			case "/favicon.svg", "/favicon.png", "/favicon.ico":
diff --git a/target/route.go b/target/route.go
index c887cf3..ba557ef 100644
--- a/target/route.go
+++ b/target/route.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"github.com/1f349/violet/proxy"
 	"github.com/1f349/violet/utils"
+	"github.com/google/uuid"
 	websocket2 "github.com/gorilla/websocket"
 	"github.com/rs/cors"
 	"golang.org/x/net/http/httpguts"
@@ -155,6 +156,8 @@ func (r Route) internalServeHTTP(rw http.ResponseWriter, req *http.Request) {
 		return
 	}
 
+	req2.Header.Set("X-Violet-Loop-Detect", "1")
+
 	// serve request with reverse proxy
 	var resp *http.Response
 	if r.HasFlag(FlagIgnoreCert) {
@@ -167,6 +170,12 @@ func (r Route) internalServeHTTP(rw http.ResponseWriter, req *http.Request) {
 		utils.RespondVioletError(rw, http.StatusBadGateway, "error receiving internal round trip response")
 		return
 	}
+	if resp.StatusCode == http.StatusLoopDetected {
+		u := uuid.New()
+		log.Printf("[ServeRoute::ServeHTTP()] Loop Detected: %s %s '%s' -> '%s'\n", u, req.Method, req.URL.String(), req2.URL.String())
+		utils.RespondVioletError(rw, http.StatusLoopDetected, "error loop detected: "+u.String())
+		return
+	}
 
 	// copy headers and status code
 	copyHeader(rw.Header(), resp.Header)