safe_eval fix (#57188)

* just dont pass locals

 - also fix globals
 - added tests

* fixed tests

lib/ansible/template/__init__.py

@@ -543,7 +543,7 @@ class Templar:
                                 # if this looks like a dictionary or list, convert it to such using the safe_eval method
                                 if (result.startswith("{") and not result.startswith(self.environment.variable_start_string)) or \
                                         result.startswith("[") or result in ("True", "False"):
-                                    eval_results = safe_eval(result, locals=self._available_variables, include_exceptions=True)
+                                    eval_results = safe_eval(result, include_exceptions=True)
                                     if eval_results[1] is None:
                                         result = eval_results[0]
                                         if unsafe:

lib/ansible/template/safe_eval.py

@@ -42,10 +42,14 @@ def safe_eval(expr, locals=None, include_exceptions=False):
 
     # define certain JSON types
     # eg. JSON booleans are unknown to python eval()
-    JSON_TYPES = {
+    OUR_GLOBALS = {
+        '__builtins__': {},  # avoid global builtins as per eval docs
         'false': False,
         'null': None,
         'true': True,
+        # also add back some builtins we do need
+        'True': True,
+        'False': False,
     }
 
     # this is the whitelist of AST nodes we are going to
@@ -138,7 +142,7 @@ def safe_eval(expr, locals=None, include_exceptions=False):
         # Note: passing our own globals and locals here constrains what
         # callables (and other identifiers) are recognized.  this is in
         # addition to the filtering of builtins done in CleansingNodeVisitor
-        result = eval(compiled, JSON_TYPES, dict(locals))
+        result = eval(compiled, OUR_GLOBALS, dict(locals))
 
         if include_exceptions:
             return (result, None)