Creating Import Hooks

Steven D'Aprano steven at REMOVE.THIS.cybersource.com.au
Thu Feb 18 09:57:01 CET 2010


On Thu, 18 Feb 2010 00:03:51 -0800, Jonathan Gardner wrote:

> On Feb 17, 10:48 pm, Sreejith K <sreejith... at gmail.com> wrote:
>> Hi everyone,
>>
>> I need to implement custom import hooks for an application
>> (http://www.python.org/dev/peps/pep-0302/). I want to restrict an
>> application to import certain modules (say socket module). Google app
>> engine is using a module hook to do this (HardenedModulesHook in
>> google/ appengine/tools/dev_appserver.py). But I want to allow that
>> application to use an sdk module (custom) which imports and uses socket
>> module. But the module hook restricts the access by sdk. Finding out,
>> which file is importing a module give a solution?? ie. If the
>> application is importing socket module, I want to restrict it. But if
>> the sdk module is importing socket I want to allow it. Is there any way
>> I can do this ?
>>
>> Application
>> ========
>> import sdk
>> import socket               # I dont want to allow this (need to raise
>> ImportError)
>>
>> SDK
>> ====
>> import socket               # need to allow this
> 
> 
> SDK
> ===
> import socket
> 
> App
> ===
> import SDK
> import sys
> socket = sys.modules['socket']


I'm not sure, but I think Sreejith wants to prohibit imports from the App 
layer while allowing them from the SDK layer, not work around a 
prohibition in the SDK layer.

In other words, he wants the import hook to do something like this:

if module is socket and the caller is not SKD:
    prohibit
else
    allow



I could be wrong of course.



-- 
Steven



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