On Fri, Nov 15, 2013 at 6:56 PM, Trent Nelson <tr...@snakebite.org> wrote: > On Tue, Nov 12, 2013 at 01:16:55PM -0800, Victor Stinner wrote: >> pysandbox cannot be used in practice >> ==================================== >> >> To protect the untrusted namespace, pysandbox installs a lot of >> different protections. Because of all these protections, it becomes >> hard to write Python code. Basic features like "del dict[key]" are >> denied. Passing an object to a sandbox is not possible to sandbox, >> pysandbox is unable to proxify arbitary objects. >> >> For something more complex than evaluating "1+(2*3)", pysandbox cannot >> be used in practice, because of all these protections. Individual >> protections cannot be disabled, all protections are required to get a >> secure sandbox. > > This sounds a lot like the work I initially did with PyParallel to > try and intercept/prevent parallel threads mutating main-thread > objects. > > I ended up arriving at a much better solution by just relying on > memory protection; main thread pages are set read-only prior to > parallel threads being able to run. If a parallel thread attempts > to mutate a main thread object; a SEH is raised (SIGSEV on POSIX), > which I catch in the ceval loop and convert into an exception. > > See slide 138 of this: > https://speakerdeck.com/trent/pyparallel-how-we-removed-the-gil-and-exploited-all-cores-1 > > I'm wondering if this sort of an approach (which worked surprisingly > well) could be leveraged to also provide a sandbox environment? The > goals are the same: robust protection against mutation of memory > allocated outside of the sandbox. > > (I'm purely talking about memory mutation; haven't thought about how > that could be extended to prevent file system interaction as well.) > > > Trent. > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > https://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > https://mail.python.org/mailman/options/python-dev/fijall%40gmail.com
Trent, you should read the mail more carefully. Notably the same issues that make it impossible to create a sandbox make it impossible to create pyparaller really work. Being read-only is absolutely not enough - you can read some internal structures in inconsistent state that lead to crashes and/or very unexpected behavior even without modifying anything. PS. We really did a lot of work analyzing how STM-pypy can lead to conflicts and/or inconsistent behavior. Cheers, fijal _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
