fix(proxy): keep JSON nulls as null in audit log values (#46577)

LiteLLM_AuditLogs masked before_value and updated_values with
SensitiveDataMasker.mask_dict, which stringifies every non-native leaf, so a
null in the change was stored as the string "None" (or "" under a key-named
field). Walk audit values with mask_credentials_in_payload instead, injecting
the existing {"key"} masker so the masked format and scope stay the same.

litellm/litellm_core_utils/sensitive_data_masker.py

@@ -168,7 +168,7 @@ def mask_sensitive_structure(data: object) -> object:
     return _error_masker.mask(data)
 
 
-def mask_credentials_in_payload(data: object) -> object:
+def mask_credentials_in_payload(data: object, masker: SensitiveDataMasker = _default_masker) -> object:
     """Return a copy of ``data`` where string values under sensitive-named keys
     are masked but every other value (``None``, ``int``, ``float``, ``bool``,
     ``bytes``, ``datetime``, tuples, sets, typed objects) is preserved by
@@ -189,18 +189,19 @@ def mask_credentials_in_payload(data: object) -> object:
     Sensitive-key detection is delegated to the shared
     :class:`SensitiveDataMasker` so pattern updates stay in one place.
     """
-    return _PayloadWalker().walk(data, key_is_sensitive=False, depth=0)
+    return _PayloadWalker(masker).walk(data, key_is_sensitive=False, depth=0)
 
 
 @dataclass(frozen=True, slots=True)
 class _PayloadWalker:
+    masker: SensitiveDataMasker = _default_masker
     _memo: dict[tuple[int, bool], tuple[object, object]] = field(  # mutable-ok: memo of one walk, pins each keyed node
         default_factory=dict
     )
 
     def walk(self, node: object, key_is_sensitive: bool, depth: int) -> object:
         if not isinstance(node, (Mapping, list, tuple, BaseModel)):
-            return _default_masker.mask_value(node) if key_is_sensitive and isinstance(node, str) and node else node
+            return self.masker.mask_value(node) if key_is_sensitive and isinstance(node, str) and node else node
         if depth >= DEFAULT_MAX_RECURSE_DEPTH_SENSITIVE_DATA_MASKER:
             return REDACTED
         memo_key: Final = (id(node), key_is_sensitive and not isinstance(node, Mapping))
@@ -218,7 +219,7 @@ class _PayloadWalker:
         if isinstance(node, BaseModel):
             return self.walk(node.model_dump(), key_is_sensitive, depth)
         if isinstance(node, Mapping):
-            return {k: self.walk(v, _default_masker.is_sensitive_key(k), depth + 1) for k, v in node.items()}
+            return {k: self.walk(v, self.masker.is_sensitive_key(k), depth + 1) for k, v in node.items()}
         if isinstance(node, tuple):
             return tuple(self.walk(item, key_is_sensitive, depth + 1) for item in node)
         return [self.walk(item, key_is_sensitive, depth + 1) for item in node]

litellm/proxy/_types.py

@@ -3359,14 +3359,14 @@ class LiteLLM_AuditLogs(LiteLLMPydanticObjectBase):
 
     @model_validator(mode="after")
     def mask_api_keys(self):
-        from litellm.litellm_core_utils.sensitive_data_masker import SensitiveDataMasker
+        from litellm.litellm_core_utils.sensitive_data_masker import SensitiveDataMasker, mask_credentials_in_payload
 
         masker: Final = SensitiveDataMasker(sensitive_patterns={"key"})
 
         if self.before_value is not None:
-            self.before_value = json.dumps(masker.mask(self.before_value), default=str)
+            self.before_value = json.dumps(mask_credentials_in_payload(self.before_value, masker), default=str)
         if self.updated_values is not None:
-            self.updated_values = json.dumps(masker.mask(self.updated_values), default=str)
+            self.updated_values = json.dumps(mask_credentials_in_payload(self.updated_values, masker), default=str)
 
         return self
 

tests/unit/proxy/test__types.py

@@ -249,17 +249,32 @@ def test_an_audit_log_does_not_store_the_key_it_recorded_a_change_to(field):
 
 @pytest.mark.parametrize("field", ("before_value", "updated_values"))
 def test_an_audit_log_keeps_the_non_secret_fields_it_recorded(field):
-    sent = {"key": SECRET, "max_budget": 50, "models": ["gpt-4o"]}
+    sent = {"key": SECRET, "token": "88dc28d0f030c55ed4ab", "max_budget": 50, "models": ["gpt-4o"]}
 
     log = _audit_log(**{field: json.dumps(sent)})
 
     assert json.loads(getattr(log, field)) == {
         "key": SECRET_MASKED,
+        "token": "88dc28d0f030c55ed4ab",
         "max_budget": 50,
         "models": ["gpt-4o"],
     }
 
 
+@pytest.mark.parametrize("field", ("before_value", "updated_values"))
+def test_an_audit_log_stores_null_values_as_null(field):
+    sent = {
+        "key": SECRET,
+        "key_alias": None,
+        "metadata": {"ignored_until": None},
+        "tags": ["prod", None, {"owner": None}],
+    }
+
+    log = _audit_log(**{field: json.dumps(sent)})
+
+    assert json.loads(getattr(log, field)) == {**sent, "key": SECRET_MASKED}
+
+
 @pytest.mark.parametrize("field", ("before_value", "updated_values"))
 def test_an_audit_log_stores_a_list_of_changes_as_json_text_with_keys_masked(field):
     sent = [{"id": "no_redis", "key": SECRET}, {"id": "detailed_debug"}]