🔒️ security(server): 业务接口保护开关与存活探针

- access_key 改用 subtle.ConstantTimeCompare 常量时间比较，防时序攻击
- 新增 server.protect_all 配置：开启后业务接口（/search、/content 等）也要求访问密钥
- 代理路由（/audio/proxy/、/manga/image/）不参与保护，其 URL 由服务端生成不含 key
- 新增 /healthz 存活探针（不校验密钥，供容器/反代使用）
- openapi.yaml 补 /healthz 定义，Unauthorized 描述说明 protect_all 行为
- 新增 3 个测试：保护开关放行、healthz、错误响应行为

internal/handlers/common.go

@@ -1,6 +1,7 @@
 package handlers
 
 import (
+	"crypto/subtle"
 	"encoding/json"
 	"fanqie/internal/config"
 	"fanqie/internal/fqapi"
@@ -122,19 +123,33 @@ func RequireAccessKey(handler http.HandlerFunc) http.HandlerFunc {
 			key = r.Header.Get("X-Access-Key")
 		}
 		
-		// 验证密钥
-		if key != cfg.Server.AccessKey {
+		// 验证密钥（常量时间比较，防时序攻击）
+		if subtle.ConstantTimeCompare([]byte(key), []byte(cfg.Server.AccessKey)) != 1 {
 			w.Header().Set("Content-Type", "application/json; charset=utf-8")
 			w.WriteHeader(http.StatusUnauthorized)
 			fmt.Fprintf(w, `{"code": -1, "msg": "访问被拒绝：无效的访问密钥"}`)
 			return
 		}
-		
+
 		// 验证通过，继续处理请求
 		handler(w, r)
 	}
 }
 
+// OptionalAccessKey 业务接口保护（仅 server.protect_all 开启时校验）
+func OptionalAccessKey(handler http.HandlerFunc) http.HandlerFunc {
+	cfg := config.GetAppConfig()
+	if cfg == nil || !cfg.Server.ProtectAll {
+		return handler
+	}
+	return RequireAccessKey(handler)
+}
+
+// HandleHealth 存活探针（供容器/反向代理使用）
+func HandleHealth(w http.ResponseWriter, r *http.Request) {
+	fmt.Fprint(w, "ok")
+}
+
 // HandleMain 主页处理
 func HandleMain(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Type", "application/json; charset=utf-8")

internal/handlers/error_response_test.go

@@ -2,6 +2,7 @@ package handlers
 
 import (
 	"encoding/json"
+	"net/http"
 	"net/http/httptest"
 	"testing"
 )
@@ -40,3 +41,22 @@ func TestHandleDetailMissingParam(t *testing.T) {
 		t.Errorf("缺参应返回 400, got %d, body: %s", w.Code, w.Body.String())
 	}
 }
+
+// TestOptionalAccessKeyDisabled protect_all 未启用（或配置未加载）时直接放行
+func TestOptionalAccessKeyDisabled(t *testing.T) {
+	called := false
+	h := OptionalAccessKey(func(w http.ResponseWriter, r *http.Request) { called = true })
+	h(httptest.NewRecorder(), httptest.NewRequest("GET", "/search?query=x", nil))
+	if !called {
+		t.Error("protect_all 未启用时应直接放行")
+	}
+}
+
+// TestHandleHealth 存活探针返回 200 ok
+func TestHandleHealth(t *testing.T) {
+	w := httptest.NewRecorder()
+	HandleHealth(w, httptest.NewRequest("GET", "/healthz", nil))
+	if w.Code != 200 || w.Body.String() != "ok" {
+		t.Errorf("应返回 200 ok, got %d %q", w.Code, w.Body.String())
+	}
+}