recipe-496746.py 文件源码

def safe_eval(code, context = {}, timeout_secs = 5):
    """
    Validate source code and make sure it contains no unauthorized
    expression/statements as configured via 'unallowed_ast_nodes' and
    'unallowed_builtins'. By default this means that code is not
    allowed import modules or access dangerous builtins like 'open' or
    'eval'. If code is considered 'safe' it will be executed via
    'exec' using 'context' as the global environment. More details on
    how code is executed can be found in the Python Reference Manual
    section 6.14 (ignore the remark on '__builtins__'). The 'context'
    enviroment is also validated and is not allowed to contain modules
    or builtins. The following exception will be raised on errors:

      if 'context' contains unallowed objects = 
        SafeEvalContextException

      if code is didn't validate and is considered 'unsafe' = 
        SafeEvalCodeException

      if code did not execute within the given timelimit =
        SafeEvalTimeoutException
    """   
    ctx_errkeys, ctx_errors = [], []
    for (key, obj) in context.items():
        if inspect.isbuiltin(obj):
            ctx_errkeys.append(key)
            ctx_errors.append("key '%s' : unallowed builtin %s" % (key, obj))
        if inspect.ismodule(obj):
            ctx_errkeys.append(key)
            ctx_errors.append("key '%s' : unallowed module %s" % (key, obj))

    if ctx_errors:
        raise SafeEvalContextException(ctx_errkeys, ctx_errors)

    ast = compiler.parse(code)
    checker = SafeEvalVisitor()

    if checker.walk(ast):
        exec_timed(code, context, timeout_secs)
    else:
        raise SafeEvalCodeException(code, checker.errors)

#----------------------------------------------------------------------
# Basic tests.
#----------------------------------------------------------------------