fix: 校验加固（嵌套敏感键/naive时间防御）

- _depth_ok 与敏感键扫描合并为单次递归 _walk_props，dict 所有层级键均过
  _SENSITIVE（此前嵌套键不扫描，utm 白名单内可夹带敏感键）
- occurred_at 为 naive datetime 时返回 invalid_occurred_at（原为 TypeError 500）
- 删除未使用的 timedelta 导入
- 深度超限即停止下探，10 万层嵌套不爆栈

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

server/tracker/services/validation.py

@@ -1,6 +1,6 @@
 import json
 import re
-from datetime import datetime, timedelta
+from datetime import datetime
 from urllib.parse import parse_qsl, urlencode, urlparse
 from django.utils import timezone
 from tracker import constants as C
@@ -15,14 +15,28 @@ def sanitize_url(url: str) -> str:
             if not _URL_DROP_KEY.fullmatch(k)]
     return p._replace(query=urlencode(kept)).geturl()
 
-def _depth_ok(v, depth=0) -> bool:
+def _walk_props(v, depth=0):
+    """单次递归同时做深度检查与敏感键扫描（dict 所有层级的键都过 _SENSITIVE）。
+    返回 (depth_ok, sensitive_hit)。深度超限即停止下探，防恶意深嵌套递归爆栈。"""
     if depth > C.MAX_PROP_DEPTH:
-        return False
+        return False, False
     if isinstance(v, dict):
-        return all(_depth_ok(x, depth + 1) for x in v.values())
+        depth_ok, sens = True, False
+        for k, x in v.items():
+            if _SENSITIVE.search(str(k)):
+                sens = True
+            d, s = _walk_props(x, depth + 1)
+            depth_ok = depth_ok and d
+            sens = sens or s
+        return depth_ok, sens
     if isinstance(v, list):
-        return all(_depth_ok(x, depth + 1) for x in v)
+        depth_ok, sens = True, False
-    return True
+        for x in v:
+            d, s = _walk_props(x, depth + 1)
+            depth_ok = depth_ok and d
+            sens = sens or s
+        return depth_ok, sens
+    return True, False
 
 def validate_event(ev) -> str | None:
     """返回 None 表示通过；否则返回拒绝原因码。类型/白名单/体积/深度全在此守门。"""
@@ -39,20 +53,22 @@ def validate_event(ev) -> str | None:
     occ = ev.get("occurred_at")
     if not isinstance(occ, datetime):
         return "invalid_occurred_at"
+    if timezone.is_naive(occ):
+        return "invalid_occurred_at"
     skew = (timezone.now() - occ).total_seconds()
     if abs(skew) > C.CLOCK_SKEW_REJECT_SEC:
         return "occurred_at_out_of_window"
     props = ev.get("properties") or {}
     if not isinstance(props, dict) or len(props) > C.MAX_PROP_KEYS:
         return "properties_invalid"
-    # 敏感键扫描必须先于属性白名单：白名单内无任何键命中敏感模式，
+    # 敏感键扫描（含嵌套层级）先于属性白名单：白名单内无任何键命中敏感模式，
     # 若放在白名单之后，sensitive_field 将不可达（见 test_sensitive_property_rejected）。
-    for k in props:
+    depth_ok, sensitive_hit = _walk_props(props)
-        if _SENSITIVE.search(str(k)):
+    if sensitive_hit:
-            return "sensitive_field"
+        return "sensitive_field"
     if not set(props) <= C.EVENT_PROP_WHITELIST.get(ev["event_name"], set()):
         return "property_not_allowed"
-    if not _depth_ok(props):
+    if not depth_ok:
         return "properties_depth"
     if len(json.dumps(props, ensure_ascii=False, default=str)) > C.MAX_PROP_JSON_BYTES:
         return "properties_too_large"

server/tracker/tests/test_validation.py

@@ -40,3 +40,10 @@ def test_sanitize_url_drops_sensitive_params():
     u = sanitize_url("/p?email=a@b.com&token=x&id=3&utm_source=google&monkey=1")
     assert "email=" not in u and "token=" not in u and "utm_source=google" in u
     assert "monkey=1" in u          # fullmatch：含 key 子串的正常参数不误伤
+
+def test_nested_sensitive_key_rejected():
+    r = validate_event(_ev(properties={"utm": {"utm_a": 1, "user_password": "x"}}))
+    assert "sensitive" in r         # utm 在 page_view 白名单内，嵌套敏感键仍须命中
+
+def test_naive_datetime_rejected():
+    assert validate_event(_ev(occurred_at=NOW.replace(tzinfo=None))) == "invalid_occurred_at"