fix(detector): detect local alias subscript replay

kernelguard.py

@@ -2459,6 +2459,84 @@ def _has_ver(expr: ast.AST | None) -> bool:
                 ),
             }]
 
+        # Fourth pass: replay through a local alias to captured state.
+        #
+        # Pattern: values = _state.__dict__
+        #          if values: return values["x"]
+        #          values["x"] = data.clone()
+        params = {
+            arg.arg
+            for args in (node.args.posonlyargs, node.args.args, node.args.kwonlyargs)
+            for arg in args
+        }
+        if node.args.vararg is not None:
+            params.add(node.args.vararg.arg)
+        if node.args.kwarg is not None:
+            params.add(node.args.kwarg.arg)
+
+        global_names = {
+            name
+            for stmt in node.body
+            if isinstance(stmt, ast.Global)
+            for name in stmt.names
+        }
+        local_names = {
+            target.id
+            for stmt in node.body
+            if isinstance(stmt, (ast.Assign, ast.AnnAssign, ast.AugAssign))
+            for target in (
+                stmt.targets if isinstance(stmt, ast.Assign)
+                else [stmt.target]
+            )
+            if isinstance(target, ast.Name) and target.id not in global_names
+        }
+        captured = _expr_names(node) - params - local_names
+
+        alias_sources: dict[str, str] = {}
+        mutated_aliases: set[str] = set()
+        for child in ast.walk(node):
+            if not isinstance(child, ast.Assign):
+                continue
+            if (len(child.targets) == 1
+                    and isinstance(child.targets[0], ast.Name)
+                    and isinstance(child.value, (ast.Attribute, ast.Subscript))):
+                source = _ast_root_name(child.value)
+                if source in captured:
+                    alias_sources[child.targets[0].id] = source
+            for target in child.targets:
+                if isinstance(target, ast.Subscript):
+                    target_root = _ast_root_name(target)
+                    if target_root in alias_sources:
+                        mutated_aliases.add(target_root)
+
+        if mutated_aliases:
+            for child in ast.walk(node):
+                if not isinstance(child, ast.If):
+                    continue
+                if _body_has_calls(child.body):
+                    continue
+                if _expr_names(child.test) & params:
+                    continue
+                if not (_expr_names(child.test) & mutated_aliases):
+                    continue
+                if not any(
+                    isinstance(stmt, ast.Return)
+                    and stmt.value is not None
+                    and isinstance(stmt.value, ast.Subscript)
+                    and _ast_root_name(stmt.value) in mutated_aliases
+                    for stmt in child.body
+                ):
+                    continue
+
+                return [{
+                    "pattern": "LAST_CALL_REPLAY",
+                    "severity": "critical",
+                    "evidence": (
+                        f"{entrypoint_name} returns from a local alias to "
+                        "captured state mutated by the entrypoint"
+                    ),
+                }]
+
     return []