From 260f21b8c8bd3fe0bdfaf623564c127a2216291f Mon Sep 17 00:00:00 2001
From: t0rchwo0d <huiseong.seo@linecorp.com>
Date: Fri, 17 Feb 2023 12:46:00 +0900
Subject: [PATCH] Fix #3500 Add escape logic for header

---
 gin.go         |  9 ++++++---
 routes_test.go | 38 +++++++++++++++++++++++++++++++++-----
 2 files changed, 39 insertions(+), 8 deletions(-)

diff --git a/gin.go b/gin.go
index 32dae2497f..f95e5dda54 100644
--- a/gin.go
+++ b/gin.go
@@ -9,9 +9,9 @@ import (
 	"html/template"
 	"net"
 	"net/http"
-	"net/url"
 	"os"
 	"path"
+	"regexp"
 	"strings"
 	"sync"
 
@@ -41,6 +41,9 @@ var defaultTrustedCIDRs = []*net.IPNet{
 	},
 }
 
+var regSafePrefix = regexp.MustCompile("[^a-zA-Z0-9/-]+")
+var regRemoveRepeatedChar = regexp.MustCompile("/{2,}")
+
 // HandlerFunc defines the handler used by gin middleware as return value.
 type HandlerFunc func(*Context)
 
@@ -669,8 +672,8 @@ func redirectTrailingSlash(c *Context) {
 	req := c.Request
 	p := req.URL.Path
 	if prefix := path.Clean(c.Request.Header.Get("X-Forwarded-Prefix")); prefix != "." {
-		prefix = url.QueryEscape(prefix)
-		prefix = strings.ReplaceAll(prefix, "%2F", "/")
+		prefix = regSafePrefix.ReplaceAllString(prefix, "")
+		prefix = regRemoveRepeatedChar.ReplaceAllString(prefix, "/")
 
 		p = prefix + "/" + req.URL.Path
 	}
diff --git a/routes_test.go b/routes_test.go
index 5310caec25..ecca21a8fb 100644
--- a/routes_test.go
+++ b/routes_test.go
@@ -185,16 +185,44 @@ func TestRouteRedirectTrailingSlash(t *testing.T) {
 	w = PerformRequest(router, http.MethodGet, "/path2/", header{Key: "X-Forwarded-Prefix", Value: "/api/"})
 	assert.Equal(t, 200, w.Code)
 
-	w = PerformRequest(router, http.MethodGet, "/path/", header{Key: "X-Forwarded-Prefix", Value: "../../bug#?"})
-	assert.Equal(t, "../../../bug%2523%253F/path", w.Header().Get("Location"))
+	w = PerformRequest(router, http.MethodGet, "/path/", header{Key: "X-Forwarded-Prefix", Value: "../../api#?"})
+	assert.Equal(t, "/api/path", w.Header().Get("Location"))
+	assert.Equal(t, 301, w.Code)
+
+	w = PerformRequest(router, http.MethodGet, "/path/", header{Key: "X-Forwarded-Prefix", Value: "../../api"})
+	assert.Equal(t, "/api/path", w.Header().Get("Location"))
+	assert.Equal(t, 301, w.Code)
+
+	w = PerformRequest(router, http.MethodGet, "/path2", header{Key: "X-Forwarded-Prefix", Value: "../../api"})
+	assert.Equal(t, "/api/path2/", w.Header().Get("Location"))
+	assert.Equal(t, 301, w.Code)
+
+	w = PerformRequest(router, http.MethodGet, "/path2", header{Key: "X-Forwarded-Prefix", Value: "/../../api"})
+	assert.Equal(t, "/api/path2/", w.Header().Get("Location"))
+	assert.Equal(t, 301, w.Code)
+
+	w = PerformRequest(router, http.MethodGet, "/path/", header{Key: "X-Forwarded-Prefix", Value: "api/../../"})
+	assert.Equal(t, "//path", w.Header().Get("Location"))
+	assert.Equal(t, 301, w.Code)
+
+	w = PerformRequest(router, http.MethodGet, "/path2", header{Key: "X-Forwarded-Prefix", Value: "../../gin-gonic.com"})
+	assert.Equal(t, "/gin-goniccom/path2/", w.Header().Get("Location"))
+	assert.Equal(t, 301, w.Code)
+
+	w = PerformRequest(router, http.MethodGet, "/path2", header{Key: "X-Forwarded-Prefix", Value: "/../../gin-gonic.com"})
+	assert.Equal(t, "/gin-goniccom/path2/", w.Header().Get("Location"))
 	assert.Equal(t, 301, w.Code)
 
 	w = PerformRequest(router, http.MethodGet, "/path/", header{Key: "X-Forwarded-Prefix", Value: "https://gin-gonic.com/#"})
-	assert.Equal(t, "https%3A/gin-gonic.com/%23/https%253A/gin-gonic.com/%2523/path", w.Header().Get("Location"))
+	assert.Equal(t, "https/gin-goniccom/https/gin-goniccom/path", w.Header().Get("Location"))
+	assert.Equal(t, 301, w.Code)
+
+	w = PerformRequest(router, http.MethodGet, "/path/", header{Key: "X-Forwarded-Prefix", Value: "#api"})
+	assert.Equal(t, "api/api/path", w.Header().Get("Location"))
 	assert.Equal(t, 301, w.Code)
 
-	w = PerformRequest(router, http.MethodGet, "/path/", header{Key: "X-Forwarded-Prefix", Value: "#bug"})
-	assert.Equal(t, "%23bug/%2523bug/path", w.Header().Get("Location"))
+	w = PerformRequest(router, http.MethodGet, "/path/", header{Key: "X-Forwarded-Prefix", Value: "/nor-mal/#?a=1"})
+	assert.Equal(t, "/nor-mal/a1/path", w.Header().Get("Location"))
 	assert.Equal(t, 301, w.Code)
 
 	router.RedirectTrailingSlash = false