execgate.py

import ast

class GateSecurityError(Exception): pass

class GatedNodeVisitor(ast.NodeVisitor):
 def visit_Attribute(self, node):
 if('__' in node.attr):
 raise GateSecurityError("Attempting to access private attribute")

def gated_compile(source, filename='<unknown>', mode='exec'):
 code_node = ast.parse(source, filename, mode)
 GatedNodeVisitor().visit(code_node)
 return compile(code_node, filename, mode)

def gated_exec_eval(source, globals={}, locals={}, mode='exec'):
 if globals is None:
 globals = { '__builtins__': {} }
 if globals.get('__builtins__', None) is None:
 globals['__builtins__'] = {}
 if mode is 'exec':
 return exec(gated_compile(source, '<string>', mode), globals, locals)
 elif mode is 'eval':
 return eval(gated_compile(source, '<string>', mode), globals, locals)
 else:
 raise GatedEvalException('invalid mode {}'.format(mode))

def gated_exec(source, globals={}, locals={}):
 gated_exec_eval(source, globals, locals)

def gated_eval(source, globals={}, locals={}):
 return gated_exec_eval(source, globals, locals, 'eval')