mod_python.publisher index.py exposes underscore prefixed variables

• Key: MODPYTHON-34
• Type: Bug
• Status: Closed
• Resolution: Fixed
• Priority: Critical
• Assignee: Nicolas Lehuen
• Reporter: Graham Dumpleton
• Component/s: publisher
• Affects Version/s: 3.1.4
• Fix Version/s: 3.2.7

Description

If index.py is used with mod_python.publisher, all underscore prefixed
variables are actually visible and not hidden as they should. This could
result in exposure of login/passwd information stored in __auth__ as a
dictionary, plus any other private data in underscore prefixed variables.

See following exchange from mailing list. This may require a security
fix release.

You have found a bug in mod_python.publisher. It shouldn't be visible,
but the code which handles defaulting to "index.py" doesn't reapply the
rule which stops access to "_" variables.

Ie., early in code in publisher.py, it has a check:

    # if any part of the path begins with "_", abort
    if func_path[0] == '_' or func_path.count("._"):
        raise apache.SERVER_RETURN, apache.HTTP_NOT_FOUND

After that point though it has:

    try:
        module = apache.import_module(module_name,
                                      autoreload=autoreload,
                                      log=log,
                                      path=[path])
    except ImportError:
        et, ev, etb = sys.exc_info()
        # try again, using default module, perhaps this is a
        # /directory/function (as opposed to /directory/module/function)
        func_path = module_name
        module_name = "index"
        try:
            module = apache.import_module(module_name,
                                          autoreload=autoreload,
                                          log=log,
                                          path=[path])
        except ImportError:
            # raise the original exception
            raise et, ev, etb

Note how it resets the value of func_path. After that the code goes on
to reolve the object, but the new func_path has skipped the check.

I believe the fix would be for the "_" check to be after the import and
not before.

The only workaround you would have in the short term is not to use
an "index.py" file and always name it something different.

This is actually a security hole because any __auth__ stuff would
be visible and thus people could work out login/passwd. This may
require another security fix release of mod_python. :-(

Graham



Jan Huelsbergen wrote ..
> Hi,
>
> The mod_python.publisher documentation states at
> http://modpython.org/live/current/doc-html/hand-pub-alg-trav.html that
> if
> "Any of the traversed object's names begin with an underscore ("_")."
> they are not accsessable through the web, yet, when I put a
> _foo = 'bar'
> in my index.py, http://my.site/_foo returns 'bar'.
>
> Am I missinterpreting the documentation?
> How to protect a variable from outside access?
>
> TIA

Comments

[Nicolas Lehuen]

This is not a security hole, as resolve_object re-checks for underscore. It would make more sense to put the check for underscore after the import, but as it is totally redundant, so we might as well remove it. What do you think ?

[Graham Dumpleton]

If the latest version of resolve_object() you have been working on checks for this then fine,
but in 3.1.4 it doesn't check for underscores and thus it is still a security problem in the
currently released version out there.

[Nicolas Lehuen]

OK this definitively has been fixed in 3.2.0 beta.