Dailydave mailing list archives
Re: Google Apps Engine
From: "Aidan Thornton" <makosoft () googlemail com>
Date: Sat, 12 Apr 2008 09:09:09 +0100
On 4/11/08, Lutz Böhne <lboehne () damogran de> wrote:
Even those could easily be sanitized by just some fun with function pointers. >>> open=lambda *x: "no" >>> open('/etc/passwd') 'no'Unless there are other ways to find these functions: >>> __builtins__.__dict__["open"]( '/etc/passwd') <open file '/etc/passwd', mode 'r' at 0xb7dac7b8> or even: >>> open=lambda *x: "no" >>> open('/etc/passwd') 'no' >>> del open >>> open('/etc/passwd') <open file '/etc/passwd', mode 'r' at 0xb7db44a0> Python is fun, there are so many ways to have it do what you want ;) It might be possible to remove these functions like this: >>> del __builtins__.__dict__["open"] >>> open('/etc/passwd') Traceback (most recent call last): File "<stdin>", line 1, in <module> NameError: name 'open' is not defined [...] But i don't know whether that'd get rid of all problems. Best regards, Lutz
Hi, The quick answer is no, it wouldn't be enough. For example, try type(sys.stdin)('/etc/passwd') or the equivalent sys.stdin.__class__('/etc/passwd'). Also, as http://mail.python.org/pipermail/python-dev/2006-July/067291.html points out, file can be obtained from object.__subclasses__(). (object itself can be found by working up the inheritance tree from any new-style class - say, a string - using __bases__) Python's powerful introspection support and lack of data hiding make doing any sort of meaningful sandboxing within the language itself very difficult. There used to be a bundled module called rexec to do this (via a combination of hooks into the interpreter and built-in support), but it was depreciated due to security issues. They might be doing something similar - it seems to strip what functions from native-code modules can be imported to some safe whitelist (and load all modules written in Python within the sandbox). Aidan _______________________________________________ Dailydave mailing list Dailydave () lists immunitysec com http://lists.immunitysec.com/mailman/listinfo/dailydave
Current thread:
- Google Apps Engine Dave Aitel (Apr 08)
- Re: Google Apps Engine jf (Apr 08)
- Re: Google Apps Engine Jeremy Kelley (Apr 08)
- Re: Google Apps Engine jf (Apr 08)
- Re: Google Apps Engine Lutz Böhne (Apr 11)
- Re: Google Apps Engine Jeremy Kelley (Apr 11)
- Re: Google Apps Engine Aidan Thornton (Apr 12)
- Re: Google Apps Engine Thomas Ptacek (Apr 13)