From 6f6771aa1deecd39405991d9ae4e69d4d93b1e5f Mon Sep 17 00:00:00 2001
From: Tao <mail@steadytao.com>
Date: Sun, 29 Mar 2026 03:10:34 +1000
Subject: [PATCH] rewrite: skip query rename when source key is absent (#7599)

---
 modules/caddyhttp/rewrite/rewrite.go      |  9 +++-
 modules/caddyhttp/rewrite/rewrite_test.go | 50 +++++++++++++++++++++++
 2 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/modules/caddyhttp/rewrite/rewrite.go b/modules/caddyhttp/rewrite/rewrite.go
index ca5f63bac..ba2ea5407 100644
--- a/modules/caddyhttp/rewrite/rewrite.go
+++ b/modules/caddyhttp/rewrite/rewrite.go
@@ -529,7 +529,14 @@ func (q *queryOps) do(r *http.Request, repl *caddy.Replacer) {
 		if key == "" || val == "" {
 			continue
 		}
-		query[val] = query[key]
+		if key == val {
+			continue
+		}
+		originalValues, ok := query[key]
+		if !ok {
+			continue
+		}
+		query[val] = originalValues
 		delete(query, key)
 	}
 
diff --git a/modules/caddyhttp/rewrite/rewrite_test.go b/modules/caddyhttp/rewrite/rewrite_test.go
index c3b4c1f6c..602e31084 100644
--- a/modules/caddyhttp/rewrite/rewrite_test.go
+++ b/modules/caddyhttp/rewrite/rewrite_test.go
@@ -16,6 +16,7 @@ package rewrite
 
 import (
 	"net/http"
+	"reflect"
 	"regexp"
 	"testing"
 
@@ -397,6 +398,55 @@ func TestRewrite(t *testing.T) {
 	}
 }
 
+func TestQueryOpsRenameNoOpCases(t *testing.T) {
+	repl := caddy.NewReplacer()
+
+	for i, tc := range []struct {
+		input  *http.Request
+		expect map[string][]string
+		ops    *queryOps
+	}{
+		{
+			ops: &queryOps{
+				Rename: []queryOpsArguments{{Key: "ID", Val: "id"}},
+			},
+			input:  newRequest(t, "GET", "/?page=test&id=5&test=100"),
+			expect: map[string][]string{"id": {"5"}, "page": {"test"}, "test": {"100"}},
+		},
+		{
+			ops: &queryOps{
+				Rename: []queryOpsArguments{{Key: "id", Val: "id"}},
+			},
+			input:  newRequest(t, "GET", "/?page=test&id=5&test=100"),
+			expect: map[string][]string{"id": {"5"}, "page": {"test"}, "test": {"100"}},
+		},
+		{
+			ops: &queryOps{
+				Rename: []queryOpsArguments{{Key: "ID", Val: "id"}},
+			},
+			input:  newRequest(t, "GET", "/?page=test&ID=5&test=100"),
+			expect: map[string][]string{"id": {"5"}, "page": {"test"}, "test": {"100"}},
+		},
+		{
+			ops: &queryOps{
+				Rename: []queryOpsArguments{{Key: "ID", Val: "id"}},
+			},
+			input:  newRequest(t, "GET", "/?page=test&ID=5&id=7&test=100"),
+			expect: map[string][]string{"id": {"5"}, "page": {"test"}, "test": {"100"}},
+		},
+	} {
+		repl.Set("http.request.uri", tc.input.RequestURI)
+		repl.Set("http.request.uri.path", tc.input.URL.Path)
+		repl.Set("http.request.uri.query", tc.input.URL.RawQuery)
+
+		tc.ops.do(tc.input, repl)
+
+		if actual := tc.input.URL.Query(); !reflect.DeepEqual(tc.expect, map[string][]string(actual)) {
+			t.Errorf("Test %d: Expected query=%v but got %v", i, tc.expect, actual)
+		}
+	}
+}
+
 func newRequest(t *testing.T, method, uri string) *http.Request {
 	req, err := http.NewRequest(method, uri, nil)
 	if err != nil {