fix: 采集接口 origin urlsplit/finalize_response 信封/CL 防御

审查三项必修：
1. Origin host 提取改 urlsplit（封堵 https://evil.com/?x=https://www.a.com
   类查询串绕过）；"null" Origin 视为无 host 走 allow_no_origin；
   Referer 回显死逻辑一并清理，ACAO 只回显真正的 Origin 头。
2. finalize_response 统一钩子：429/ParseError 等 DRF 异常响应补 ACAO +
   {code,data,message} 信封（浏览器 SDK 需读错误体，误判网络错误重试会
   打爆限流器）；删 post/_deny/options 三处临时加头代码。
3. Content-Length isdecimal 防御（"abc" → 400 非 500；isdigit 放过 "²"
   而 int("²") 仍崩，isdecimal 与 int() 可解析集精确对齐）。

锁定测试 ×4：429 信封+ACAO / 坏 JSON 信封+ACAO / 查询串绕过 403 / 畸形 CL 400。

Co-Authored-By: Claude Code <noreply@anthropic.com>

server/tracker/api/collect.py

@@ -1,5 +1,6 @@
 import json
 from datetime import datetime, timezone as dt_tz
+from urllib.parse import urlsplit
 from rest_framework.views import APIView
 from rest_framework.response import Response
 from rest_framework.permissions import AllowAny
@@ -40,14 +41,16 @@ class CollectBatchView(APIView):
     authentication_classes = []
 
     def post(self, request):
-        origin = request.headers.get("Origin") or request.headers.get("Referer") or ""
-        if int(request.headers.get("Content-Length") or 0) > 262144:
+        origin = request.headers.get("Origin") or ""
+        cl = request.headers.get("Content-Length") or "0"
+        if not cl.isdecimal() or int(cl) > 262144:   # isdecimal：isdigit 放过 "²"（int 仍崩），isdecimal 与 int() 精确对齐
             return self._deny(400, "payload_too_large")   # 应用层兜底（nginx 另设 client_max_body_size）
         site = self._match_site(request)
         if site is None or not site.is_active:
             return self._deny(403, "not_allowed")         # 三种拒绝统一 reason，防 site_id 枚举探测
-        host = (origin.split("//")[-1].split("/")[0].split(":")[0].lower()
-                if origin else "")
+        # urlsplit 提取 host：split("//")[-1] 会被查询串里的白名单 URL 绕过；
+        # "null" Origin（隐私上下文/沙箱 iframe）视为无 host，走 allow_no_origin 分支
+        host = (urlsplit(origin).hostname or "").lower() if origin and origin != "null" else ""
         if host and host not in [d.lower() for d in site.domains]:
             return self._deny(403, "not_allowed")
         if not host and not site.allow_no_origin:
@@ -63,22 +66,31 @@ class CollectBatchView(APIView):
             return self._deny(400, "invalid_payload")
         ip = self._client_ip(request)
         r = ingest_batch(site, payload, ip, request.headers.get("User-Agent", ""))
-        resp = Response({"code": 200,
+        return Response({"code": 200,
             "data": {"accepted": r["accepted"], "duplicated": r["duplicated"]},
             "message": "ok"})
-        if origin:   # 成功分支回显 ACAO（SDK fetch 需读响应）
-            resp["Access-Control-Allow-Origin"] = origin
-            resp["Access-Control-Allow-Headers"] = "content-type"
+
+    def options(self, request):   # 预检兜底（SDK text/plain 简单请求通常不触发）；ACAO 由 finalize_response 统一补
+        resp = Response(status=200)
+        resp["Access-Control-Allow-Methods"] = "POST, OPTIONS"
+        resp["Access-Control-Allow-Headers"] = "content-type"
         return resp
 
-    def options(self, request):   # 预检兜底（SDK text/plain 简单请求通常不触发）
-        origin = request.headers.get("Origin") or ""
-        resp = Response(status=200)
-        if origin:
-            resp["Access-Control-Allow-Origin"] = origin
-            resp["Access-Control-Allow-Methods"] = "POST, OPTIONS"
-            resp["Access-Control-Allow-Headers"] = "content-type"
-        return resp
+    def finalize_response(self, request, response, *args, **kwargs):
+        """统一收口：ACAO 回显 + 错误信封。
+
+        429/ParseError 等由 DRF 异常处理器产出的响应（无 ACAO、body 是 {detail}）在这里补齐——
+        否则浏览器 SDK 跨域读不到错误体会误判网络错误而重试，限流时反而打爆限流器。
+        dispatch 对 initial() 抛出的 Throttled/ParseError 同样走 finalize_response，此钩子全覆盖。
+        """
+        response = super().finalize_response(request, response, *args, **kwargs)
+        origin = request.headers.get("Origin")
+        if origin and "Access-Control-Allow-Origin" not in response:   # 只回显真正的 Origin 头
+            response["Access-Control-Allow-Origin"] = origin
+        if response.status_code >= 400 and isinstance(response.data, dict) and "detail" in response.data:
+            response.data = {"code": response.status_code, "data": None,
+                             "message": response.data["detail"]}
+        return response
 
     def _match_site(self, request):
         sid = (request.data or {}).get("site_id") if isinstance(request.data, dict) else None
@@ -94,8 +106,4 @@ class CollectBatchView(APIView):
         return ip
 
     def _deny(self, code, reason):
-        resp = Response({"code": code, "data": None, "message": reason}, status=code)
-        origin = self.request.headers.get("Origin")
-        if origin:   # 拒绝也要回 ACAO，否则浏览器读不到错误体、SDK 误判为网络错误走重试
-            resp["Access-Control-Allow-Origin"] = origin
-        return resp
+        return Response({"code": code, "data": None, "message": reason}, status=code)   # ACAO/信封由 finalize_response 统一补