fix(security): harden connector ingress parser paths

connector/platforms/feishu_webhook.py

@@ -123,10 +123,9 @@ def _make_json_response(web_mod, data: Dict[str, Any], *, status: int = 200):
     )
 
 
-def _safe_external_error_code(default: str, exc: Exception) -> str:
-    raw = str(exc or "").strip()
-    if raw and len(raw) <= 64 and raw.replace("_", "").replace("-", "").isalnum():
-        return raw
+def _safe_external_error_code(default: str, _exc: Exception) -> str:
+    # IMPORTANT: keep Feishu external failures constant. Returning exception-
+    # derived codes/text here reopens the residual CodeQL stack-trace finding.
     return default
 
 

connector/platforms/slack_webhook.py

@@ -97,10 +97,9 @@ def _make_redirect_response(web_mod, url: str):
     return _CompatResponse(status=302, text=url)
 
 
-def _safe_external_error_text(default: str, exc: Exception) -> str:
-    raw = str(exc or "").strip()
-    if raw and len(raw) <= 64 and raw.replace("_", "").replace("-", "").isalnum():
-        return raw
+def _safe_external_error_text(default: str, _exc: Exception) -> str:
+    # IMPORTANT: keep Slack external failures constant. Even "short safe-looking"
+    # exception text remains scanner-tainted and can re-expose internal detail.
     return default
 
 

connector/platforms/wechat_webhook.py

@@ -32,6 +32,9 @@ import time
 from typing import Optional
 from xml.etree import ElementTree as ET
 
+from defusedxml import ElementTree as DefusedET
+from defusedxml.common import DefusedXmlException
+
 from ..config import ConnectorConfig
 from ..contract import CommandRequest, CommandResponse
 from ..router import CommandRouter
@@ -272,10 +275,10 @@ def parse_wechat_xml(raw: bytes) -> dict:
         raise XMLBudgetExceeded("DTD/entity declarations are not allowed")
 
     try:
-        parser = ET.XMLParser()
-        parser.feed(raw.decode("utf-8"))
-        root = parser.close()
-    except (ET.ParseError, UnicodeDecodeError) as e:
+        # IMPORTANT: keep defusedxml here. Reverting to the stdlib parser path
+        # reopens the residual CodeQL xml-bomb finding on this ingress seam.
+        root = DefusedET.fromstring(raw.decode("utf-8"))
+    except (ET.ParseError, DefusedXmlException, UnicodeDecodeError) as e:
         raise XMLBudgetExceeded(f"XML parse error: {e}") from e
 
     # Depth check — WeChat envelopes are <xml><Tag>val</Tag></xml>, depth=2

pyproject.toml

@@ -6,8 +6,9 @@ license = {text = "MIT"}
 readme = "README.md"
 requires-python = ">=3.10"
 
-# S57: cryptography is required for Fernet AEAD secrets-at-rest encryption
-dependencies = ["cryptography>=41.0"]
+# S57: cryptography is required for Fernet AEAD secrets-at-rest encryption.
+# S85: defusedxml is required for scanner-recognized fail-closed WeChat XML parsing.
+dependencies = ["cryptography>=41.0", "defusedxml>=0.7.1"]
 
 [project.optional-dependencies]
 # WeChat AES encrypted ingress mode (R82) — lazy-imported, only needed when encrypt_type=aes